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• 1.
Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, The Institute of Technology.
Phase Stability and Elasticity of TiAlN2011In: Materials, ISSN 1996-1944, E-ISSN 1996-1944, Vol. 4, no 9, p. 1599-1618Article in journal (Refereed)

We review results of recent combined theoretical and experimental studies of Ti1−xAlxN, an archetypical alloy system material for hard-coating applications. Theoretical simulations of lattice parameters, mixing enthalpies, and elastic properties are presented. Calculated phase diagrams at ambient pressure, as well as at pressure of 10 GPa, show a wide miscibility gap and broad region of compositions and temperatures where the spinodal decomposition takes place. The strong dependence of the elastic properties and sound wave anisotropy on the Al-content offers detailed understanding of the spinodal decomposition and age hardening in Ti1−xAlxN alloy films and multilayers. TiAlN/TiN multilayers can further improve the hardness and thermal stability compared to TiAlN since they offer means to influence the kinetics of the favorable spinodal decomposition and suppress the detrimental transformation to w-AlN. Here, we show that a 100 degree improvement in terms of w-AlN suppression can be achieved, which is of importance when the coating is used as a protective coating on metal cutting inserts.

• 2.
Linköping University, Department of Physics, Chemistry and Biology, Molecular Surface Physics and Nano Science. Linköping University, Faculty of Science & Engineering.
A simple polyol-free synthesis route to Gd2O3 nanoparticles for MRI applications: an experimental and theoretical study2012In: Journal of nanoparticle research, ISSN 1388-0764, E-ISSN 1572-896X, Vol. 14, no 8Article in journal (Refereed)

Chelated gadolinium ions, e. g., GdDTPA, are today used clinically as contrast agents for magnetic resonance imaging (MRI). An attractive alternative contrast agent is composed of gadolinium oxide nanoparticles as they have shown to provide enhanced contrast and, in principle, more straightforward molecular capping possibilities. In this study, we report a new, simple, and polyol-free way of synthesizing 4-5-nm-sized Gd2O3 nanoparticles at room temperature, with high stability and water solubility. The nanoparticles induce high-proton relaxivity compared to Gd-DTPA showing r(1) and r(2) values almost as high as those for free Gd3+ ions in water. The Gd2O3 nanoparticles are capped with acetate and carbonate groups, as shown with infrared spectroscopy, near-edge X-ray absorption spectroscopy, X-ray photoelectron spectroscopy and combined thermogravimetric and mass spectroscopy analysis. Interpretation of infrared spectroscopy data is corroborated by extensive quantum chemical calculations. This nanomaterial is easily prepared and has promising properties to function as a core in a future contrast agent for MRI.

• 3.
Linköping University, Department of Physics, Chemistry and Biology, Molecular Surface Physics and Nano Science. Linköping University, Faculty of Science & Engineering.
Linköping University, Department of Physics, Chemistry and Biology, Nanostructured Materials. Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Computational Physics. Linköping University, The Institute of Technology. Division of Solid State Physics, Department of Engineering Sciences, Uppsala University, Uppsala, Sweden. Linköping University, Department of Physics, Chemistry and Biology, Computational Physics. Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Molecular Surface Physics and Nano Science. Linköping University, Faculty of Science & Engineering.
One-step synthesis of sub 5 nm sized manganese oxide based nanoparticles2013Manuscript (preprint) (Other academic)

Sub 5 nm sized manganese oxide nanoparticles; MnOx (1 ≤ x ≤ 2), were synthesized via a short time room temperature synthesis route. The nanoparticles are crystalline, spherically shaped and in the size range of 2-4 nm as shown by transmission electron microscopy studies. Selected area electron diffraction patterns were collected and their appearance indicated that the nanoparticle cores are composed of MnO. Also, co-existence of the (II) and (III) oxidation states at the nanoparticle surface was verified by results achieved from infrared spectroscopy and X-ray photoelectron spectroscopy. These measurements also supported presence of a minor amount of acetate groups as well as a negligible fraction of carbonate groups at the nanoparticle surfaces. The interpretation of the IR spectra was confirmed by quantum chemical calculations using the high spin manganese nanoparticle Mn12O12(OAc)16(H2O)4, as a model system for the MnOx nanoparticle surface. Bulk MnO and Mn2O3 are known to be antiferromagnetic. The magnetic properties are however somewhat dependent of the crystallite size and changes when scaling down to the nanoregion. The MnOx (1 ≤ x ≤ 2) nanoparticles investigated in this work show a superparamagnetic behavior with a blocking temperature of approximately 12 K proven by means of SQUID measurements. The relaxivities of the nanoparticles and the Mn(OAc)2 precursors were studied with a bench top NMR analyzer verifying nanoparticle r1 and r2 of 0.5 and 6 mMs-1 respectively. The r1 relaxivity is lower than what is earlier reported for Gd based contrast agent, but improvements are expected by further surface modification, due to increased rotational time and higher water dispersability.

• 4.
Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics . Linköping University, The Institute of Technology.
Linköping University, Department of Physics, Chemistry and Biology, Nanostructured Materials . Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics . Linköping University, The Institute of Technology.
Pressure enhancement of the isostructural cubic decomposition in Ti1−xAlxN2009In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 95, no 181906Article in journal (Refereed)

The influence of pressure on the phase stabilities of Ti1−xAlxN solid solutions has been studied using first principles calculations. We find that the application of hydrostatic pressure enhances the tendency for isostructural decomposition, including spinodal decomposition. The effect originates in the gradual pressure stabilization of cubic AlN with respect to the wurtzite structure and an increased isostructural cubic mixing enthalpy with increased pressure. The influence is sufficiently strong in the composition-temperature interval corresponding to a shoulder of the spinodal line that it could impact the stability of the material at pressures achievable in the tool-work piece contact during cutting operations

• 5. Almer, J
Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Nanostructured Materials .
Microstructure and thermal stability of arc-evaporated Cr-C-N coatings2004In: PHILOSOPHICAL MAGAZINE, ISSN 1478-6443, Vol. 84, no 7, p. 611-630Article in journal (Refereed)

The role of C incorporation in the microstructure and thermal stability of arc-evaporated Cr-C-N coatings is explored via reactive growth in a mixed C2H4-N-2 environment. C is found to react more readily than N at both the Cr cathode and the coating surfaces, so that a C2H4-to-N-2 flow ratio of only 1% yields a C-to-N ratio of approximately 10% within the coatings. The as-deposited microstructures consist primarily of the delta-Cr(C, N) phase and possess high compressive residual stresses, which decrease with increasing C content. Post-deposition annealing up to 700degreesC results in depletion of lattice defects, and concomitant reductions in stress and coating hardness, together with phase transformations which suggest metastable phase formation during growth. Apparent activation energies for this lattice defect are found to be in the range expected for bulk diffusion of N and C (2.4-2.8 eV). The results suggest that inclusion of small amounts of C in this system offers the ability to reduce internal stresses while maintaining defect-related hardness increases, permitting growth of thicker and thus more wear-resistant coatings.

• 6.
Drexel University.
Los Alamos National Laboratory. University of Pennsylvania. University of Delaware. Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Nanostructured Materials . Linköping University, The Institute of Technology.
On the Stability of Mg Nanograins to Coarsening after Repeated Melting2009In: NANO LETTERS, ISSN 1530-6984, Vol. 9, no 8, p. 3082-3086Article in journal (Refereed)

Herein we report on the extraordinary thermal stability of similar to 35 nm Mg-nanograins that constitute the matrix of a Ti2AlC-Mg composite that has previously been shown to have excellent mechanical properties. The microstructure is so stable that heating the composite three times to 700 degrees C, which is 50 degrees C over the melting point of Mg, not only resulted in the repeated melting of the Mg, but surprisingly and within the resolution of our differential scanning calorimeter, did not lead to any coarsening. The reduction in the Mg melting point due to the nanograins was similar to 50 degrees C. X-ray diffraction and neutron spectroscopy results suggest that thin, amorphous, and/or poorly crystallized rutile, anatase, and/or magnesia layers separate the Mg nanograins and prevent them from coarsening. Clearly that layer is thin enough, and thus mechanically robust enough, to survive the melting and solidification stresses encountered during cycling. Annealing in hydrogen at 250 degrees C for 20 h, also did not seem to alter the grain size significantly.

• 7.
Luleå University of Technology.
Monash University. Linköping University, Department of Physics, Chemistry and Biology, Nanostructured Materials. Linköping University, The Institute of Technology.
Synthesis and phase development in the Ct-Al-N system2009In: Ceramic Engineering and Science Proceedings, vol 29, no 2, 2009, Vol. 29, no 2, p. 3-12Conference paper (Refereed)

The ternary nitride system Cr-Al-N has been investigated by sintering different powder compositions. The powder compositions belong to four groups, AIN- + Cr-powder (5 compositions between 20-90 molar% AlN), Al- + Cr 2N-powder (5 compositions between 15-80 molar% Cr2N), AlN-+ Cr2N-powder (50- and 90 molar% Cr2N) and Al- + Cr-powder. The powders were dry mixed and pressed into pellets by uniaxial pressing followed by cold isostatic pressing (ClP). Sintering took place in a graphite lined reaction bonding furnace under nitrogen atmosphere at three different temperatures, 1350C, 1500C and 1800C and in an alumina tube furnace in order to avoid access to carbon. Holding times were varied, from 2 hours up to 72 hours. The phase development was evaluated by thermal analysis and XRD. CrAlN was formed at 1350C but decomposed at higher temperatures. Both pure Al and Cr-powder were prone to react with carbon in the graphite furnace. Thermal analysis showed a sublimation of Cr2N at temperatures around 1050C and nitridation of pure Al-powder between 680-750C and of pure Cr-powder between 610-1080C. Samples with pure Al-powder showed a very large expansion due to melting of aluminium in combination with nitridation. AIN was found to be more stable than Cr 2N at higher temperatures and longer holding times. The mixtures of Al-+Cr-powder produced an intermediate Al-Cr-phase.

• 8.
Budapest University of Technology and Economy.
Research Group of the Hungarian Academy of Sciences. Budapest University of Technology and Economy. University of the Witwatersrand. Linköping University, Department of Physics, Chemistry and Biology, Nanostructured Materials . Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Nanostructured Materials . Linköping University, The Institute of Technology.
Ab initio density-functional supercell calculations of hydrogen defects in cubic SiC2001In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 63, no 245202Article in journal (Refereed)

Based on ab initio density-functional calculations in supercells of 3C-SiC, the stable configurations of hydrogen and dihydrogen defects have been established. The calculated formation energies are used to give semiquantitative estimates for the concentration of hydrogen in SiC after chemical vapor deposition, low temperature H-plasma anneal, or heat treatment in high temperature hydrogen gas. Vibration frequencies, spin distributions, and occupation levels were also calculated in order to facilitate spectroscopic identification of these defects. (V+nH) complexes are suggested as the origin of some of the signals assigned earlier to pure vacancies. Qualitative extrapolation of our results to hexagonal polytypes explains observed electrical passivation effects of hydrogen.

• 9.
Linköping University, Department of Physics, Chemistry and Biology, Nanostructured Materials. Linköping University, The Institute of Technology.
Royal Institute Technology, Sweden. Linköping University, Department of Physics, Chemistry and Biology, Nanostructured Materials. Linköping University, The Institute of Technology.
Phase-field modelling of spinodal decomposition in TiAlN including the effect of metal vacancies2015In: Scripta Materialia, ISSN 1359-6462, E-ISSN 1872-8456, Vol. 95, p. 42-45Article in journal (Refereed)

Using a CALPHAD approach together with a Cahn-Hilliard model, we describe the microstructure evolution in cubic Ti1-xAlxN including vacancies on the metal sublattice. Our results show that vacancy content has a pronounced effect on the decomposition kinetics. Furthermore, vacancies show a strong tendency to segregate to the coherent AlN-TiN interface regions. We illustrate how vacancies anneal to grain boundaries, and finally, we compare our prediction to experimental differential scanning calorimetry data and attribute the second peak in the thermogram to vacancy depletion.

• 10. Buy this publication >>
Linköping University, Department of Physics, Chemistry and Biology, Nanostructured Materials. Linköping University, Faculty of Science & Engineering.
Mesoporous material systems for catalysis and drug delivery2018Doctoral thesis, comprehensive summary (Other academic)

Hybrid material systems possess multi-functional properties which make them intriguing for the materials science community since very early dates. However, it is not straightforward to produce such material systems. A smart and efficient approach is necessary to extract the desired properties of each component under the desired conditions. This study evolved to its last form primarily around this notion, where the development of a hybrid material is the core of the work. This hybrid material is then further explored for two different applications in the catalysis and drug delivery fields.

A nanoassembly was established around a mesoporous silica support. SBA-15 was picked as this support among the other mesoporous silica due to its well-defined pore structure and accessible pore volume. The silica framework was doped with Zr atoms and the pores were partly infiltrated with Cu nanoparticles resulting in a hybrid material with tunable properties. SBA-15 was synthesized by a sol-gel method where a micellar solution was employed as a template for the silica framework. To achieve the doped version, a Zr precursor was added to the synthesis solution. The effects of different synthesis conditions, such as the synthesis catalyst (F-or a Cl-salt) and the Si source (tetraethyl orthosilicate (TEOS) or sodium metasilicate (SMS)) on the characteristics of the final material were investigated. It was observed that these changes in the synthesis conditions yielded different particle morphology, pore size (11-15 nm), and specific surface area (400-700 m2/g). Cu nanoparticles (NPs) were grown in the (Zr-)SBA-15 support using infiltration (Inf) or evaporation induced wetness impregnation (EIWI) methods. The infiltration method is based on functionalizing the (Zr-)SBA-15 support surfaces before the Cu ion attachment whereas EIWI is based on slow evaporation of the liquid from the (Zr-)SBA-15 - Cu aqueous suspension. Both methods are designed to yield preferential growth of Cu NPs in the pores with a diameter smaller than 10 nm and in oxidized form. However, depending on the loading method used, different chemical states of the final material were achieved, i.e. Zr content and porous network properties are different.

Cu-Zr-SBA-15 nanoassemblies produced under various synthesis conditions were used for the catalytic conversion of CO2into valuable fuels such as methanol and dimethyl ether (DME). The effect of different chemical states of the catalyst arising from variations in the synthesis parameters was investigated. It was found that the Si precursor (TEOS or SMS) had a considerable impact on the overall performance of the catalyst whereas the Cu loading method (Inf or EIWI) changed the catalytic selectivity between DME and methanol. The activity of the catalyst was further investigated in a time-evolution study where the accumulation of each product in the gas phase and the molecular groups attached to the catalyst surface were recorded over time. Accordingly, thermodynamic equilibrium was achieved on the 14th day of the reaction under 250°C and 33 bar. The resulting total CO2conversion was 24%, which is the thermodynamically highest possible conversion, according to theoretical calculations. It was also concluded from the experimental results that, DME is formed by a combination of two methoxy surface groups. Additionally, the formation of DME boosts the total CO2conversion to fuels, which otherwise is limited to 9.5%.

The design of Cu-Zr-SBA-15 was also investigated for drug delivery applications, due to its potential as a biomaterial, e.g., a filler in dental composites, and the antibacterial properties of Cu. Also, the bioactivity of SiO2and ZrO2was considered to be an advantage. With this aim, Cu infiltrated Zr doped SBA-15 material was prepared by using TEOS as the silica precursor and the Inf-method to grow Cu NPs. The performance of the final material as a drug delivery vehicle was tested by an in-vitro delivery study with chlorhexidine digluconate.The nanoassemblies show a drug loading capacity of 25-40% [mg drug / mg (drug+carrier)]. The drug release was determined to be composed of two steps. First, a burst release of the drug molecules that are loosely held in the voids of the mesoporous carrier followed by the diffusion of the drug molecules that are attached to the carrier surface. The presence of Zr and Cu limits the burst release and beneficially slows down the drug release process.

The effect of pore properties of SBA-15 was explored in a study where the antibiotic doxycycline hyclate was loaded in SBA-15 materials with different pore sizes. It was observed that the pore size is directly proportional to the drug loading capacity [mg drug / mg (drug+carrier)] and the released drug percentage (the released drug amount/total amount of loaded drug). The drug release was fast due to its weak interactions with the SBA-15 materials.

In summary, this work demonstrates the multifunctional character of a smart-tailored nanoassembly which gives valuable insights for two distinct applications in catalysis and drug delivery.

1. Synthesis of a Cu-infiltrated Zr-doped SBA-15 catalyst for CO2 hydrogenation into methanol and dimethyl ethert
Open this publication in new window or tab >>Synthesis of a Cu-infiltrated Zr-doped SBA-15 catalyst for CO2 hydrogenation into methanol and dimethyl ethert
2017 (English)In: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 19, no 29, p. 19139-19149Article in journal (Refereed) Published
##### Abstract [en]

A catalytically active nanoassembly comprising Cu-nanoparticles grown on integrated and active supports (large pore Zr-doped mesoporous SBA-15 silica) has been synthesized and used to promote CO2 hydrogenation. The doped mesoporous material was synthesized using a sal-gel method, in which the pore size was tuned between 11 and 15 nm while maintaining a specific surface area of about 700 m(2) g (1). The subsequent Cu nanoparticle growth was achieved by an infiltration process involving attachment of different functional groups on the external and internal surfaces of the mesoporous structure such that 7-10 nm sized Cu nanoparticles grew preferentially inside the pores. Chemisorption showed improved absorption of both CO2 and H-2 for the assembly compared to pure SBA-15 and 15% of the total CO2 was converted to methanol and dimethyl ether at 250 degrees C and 33 bar.

##### Place, publisher, year, edition, pages
ROYAL SOC CHEMISTRY, 2017
##### National Category
Materials Chemistry
##### Identifiers
urn:nbn:se:liu:diva-139804 (URN)10.1039/c7cp03037a (DOI)000406334300033 ()28702581 (PubMedID)
##### Note

Funding Agencies|EUs Erasmus-Mundus program; Swedish Research Council; Swedish Government Strategic Research Area in Materials Science on Functional Materials at Linkoping University [SFO-Mat-LiU 11 2009-00971]; Knut och Alice Wallenbergs Foundation [KAW 2012.0083]

Available from: 2017-08-17 Created: 2017-08-17 Last updated: 2018-04-16
2. Time evolution of the CO2 hydrogenation to fuels over Cu-Zr-SBA-15 catalysts
Open this publication in new window or tab >>Time evolution of the CO2 hydrogenation to fuels over Cu-Zr-SBA-15 catalysts
2018 (English)In: Journal of Catalysis, ISSN 0021-9517, E-ISSN 1090-2694, Vol. 362, p. 55-64Article in journal (Refereed) Published
##### Abstract [en]

Time evolution of catalytic CO2 hydrogenation to methanol and dimethyl ether (DME) has been investigated in a high-temperature high-pressure reaction chamber where products accumulate over time. The employed catalysts are based on a nano-assembly composed of Cu nanoparticles infiltrated into a Zr doped SiOx mesoporous framework (SBA-15): Cu-Zr-SBA-15. The CO2 conversion was recorded as a function of time by gas chromatography-mass spectrometry (GC-MS) and the molecular activity on the catalyst’s surface was examined by diffuse reflectance in-situ Fourier transform infrared spectroscopy (DRIFTS). The experimental results showed that after 14 days a CO2 conversion of 25% to methanol and DME was reached when a DME selective catalyst was used which was also illustrated by thermodynamic equilibrium calculations. With higher Zr content in the catalyst, greater selectivity for methanol and a total 9.5% conversion to methanol and DME was observed, yielding also CO as an additional product. The time evolution profiles indicated that DME is formed directly from methoxy groups in this reaction system. Both DME and methanol selective systems show the thermodynamically highest possible conversion.

##### Keywords
Cu-Zr-SBA-15, CO2 hydrogenation, Catalysis, Time evolution, Thermodynamics, Methanol, Dimethyl ether
##### National Category
Nano Technology Physical Chemistry
##### Identifiers
urn:nbn:se:liu:diva-147297 (URN)10.1016/j.jcat.2018.03.023 (DOI)000432770900007 ()
##### Note

Funding agencies: EUs Erasmus-Mundus program (The European School of Materials Doctoral Programme - DocMASE); Knut och Alice Wallenbergs Foundation [KAW 2012.0083]; Swedish Government Strategic Research Area (SFO Mat LiU) [2009 00971]; Swedish Energy Agency [42022-1]

Available from: 2018-04-16 Created: 2018-04-16 Last updated: 2018-06-14Bibliographically approved
• 11.
Linköping University, Department of Physics, Chemistry and Biology, Nanostructured Materials. Linköping University, Faculty of Science & Engineering.
Linköping University, Department of Physics, Chemistry and Biology, Chemistry. Linköping University, Faculty of Science & Engineering. Linköping University, Department of Physics, Chemistry and Biology, Nanostructured Materials. Linköping University, Faculty of Science & Engineering. Linköping University, Department of Physics, Chemistry and Biology, Chemistry. Linköping University, Faculty of Science & Engineering. Linköping University, Department of Physics, Chemistry and Biology, Nanostructured Materials. Linköping University, Faculty of Science & Engineering.
Time evolution of the CO2 hydrogenation to fuels over Cu-Zr-SBA-15 catalysts2018In: Journal of Catalysis, ISSN 0021-9517, E-ISSN 1090-2694, Vol. 362, p. 55-64Article in journal (Refereed)

Time evolution of catalytic CO2 hydrogenation to methanol and dimethyl ether (DME) has been investigated in a high-temperature high-pressure reaction chamber where products accumulate over time. The employed catalysts are based on a nano-assembly composed of Cu nanoparticles infiltrated into a Zr doped SiOx mesoporous framework (SBA-15): Cu-Zr-SBA-15. The CO2 conversion was recorded as a function of time by gas chromatography-mass spectrometry (GC-MS) and the molecular activity on the catalyst’s surface was examined by diffuse reflectance in-situ Fourier transform infrared spectroscopy (DRIFTS). The experimental results showed that after 14 days a CO2 conversion of 25% to methanol and DME was reached when a DME selective catalyst was used which was also illustrated by thermodynamic equilibrium calculations. With higher Zr content in the catalyst, greater selectivity for methanol and a total 9.5% conversion to methanol and DME was observed, yielding also CO as an additional product. The time evolution profiles indicated that DME is formed directly from methoxy groups in this reaction system. Both DME and methanol selective systems show the thermodynamically highest possible conversion.

• 12.
Linköping University, Department of Physics, Chemistry and Biology, Nanostructured Materials. Linköping University, Faculty of Science & Engineering.
Linköping University, Department of Physics, Chemistry and Biology, Plasma and Coating Physics. Linköping University, Faculty of Science & Engineering. Linköping University, Department of Physics, Chemistry and Biology, Nanostructured Materials. Linköping University, Faculty of Science & Engineering. Lund Univ, Sweden. Linköping University, Department of Physics, Chemistry and Biology, Nanostructured Materials. Linköping University, Faculty of Science & Engineering. Linköping University, Department of Physics, Chemistry and Biology, Nanostructured Materials. Linköping University, Faculty of Science & Engineering.
Impact of the morphological and chemical properties of copper-zirconium-SBA-15 catalysts on the conversion and selectivity in carbon dioxide hydrogenation2019In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 546, p. 163-173Article in journal (Refereed)

A hybrid catalyst consisting of Zr-doped mesoporous silica (Zr-SBA-15) supports with intergrown Cu nanoparticles was used to study the effects of a catalysts chemical states on CO2 hydrogenation. The chemical state of the catalyst was altered by using tetraethyl orthosilicate (TEOS) or sodium metasilicate (SMS) as the silica precursor in the synthesis of the Zr-SBA-15 framework, and infiltration (Inf) or evaporation induced wetness impregnation (EIWI) as the Cu loading method. As a result, the silica precursor mainly affects the activity of the catalyst whereas the Cu loading method alters the selectivity of the products. TEOS materials exhibit a higher catalytic activity compared to SMS materials due to different Zr dispersion and bonding to the silica matrix. EIWI catalysts display selectivity for methanol formation, while the Inf ones enable methanol conversion to DME. This is correlated to a higher Zr content and lower Cu oxidation states of EIWI prepared catalysts. (C) 2019 Elsevier Inc. All rights reserved.

• 13.
Linköping University, Department of Physics, Chemistry and Biology, Nanostructured Materials. Linköping University, Faculty of Science & Engineering.
Linköping University, Department of Physics, Chemistry and Biology, Nanostructured Materials. Linköping University, Faculty of Science & Engineering. Linköping University, Department of Physics, Chemistry and Biology, Chemistry. Linköping University, Faculty of Science & Engineering. Linköping University, Department of Physics, Chemistry and Biology, Plasma and Coating Physics. Linköping University, Faculty of Science & Engineering. Linköping University, Department of Physics, Chemistry and Biology, Nanostructured Materials. Linköping University, Faculty of Science & Engineering. Linköping University, Department of Physics, Chemistry and Biology, Nanostructured Materials. Linköping University, Faculty of Science & Engineering.
Synthesis of a Cu-infiltrated Zr-doped SBA-15 catalyst for CO2 hydrogenation into methanol and dimethyl ethert2017In: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 19, no 29, p. 19139-19149Article in journal (Refereed)

A catalytically active nanoassembly comprising Cu-nanoparticles grown on integrated and active supports (large pore Zr-doped mesoporous SBA-15 silica) has been synthesized and used to promote CO2 hydrogenation. The doped mesoporous material was synthesized using a sal-gel method, in which the pore size was tuned between 11 and 15 nm while maintaining a specific surface area of about 700 m(2) g (1). The subsequent Cu nanoparticle growth was achieved by an infiltration process involving attachment of different functional groups on the external and internal surfaces of the mesoporous structure such that 7-10 nm sized Cu nanoparticles grew preferentially inside the pores. Chemisorption showed improved absorption of both CO2 and H-2 for the assembly compared to pure SBA-15 and 15% of the total CO2 was converted to methanol and dimethyl ether at 250 degrees C and 33 bar.

• 14.
Linköping University, Department of Physics, Chemistry and Biology, Nanostructured Materials . Linköping University, The Institute of Technology.
Synthesis of Mesoporous Silica and their Use as Templates for Metal and Metal Oxide Nanoparticles2011Doctoral thesis, comprehensive summary (Other academic)

This thesis covers the synthesis and characterization of two types of mesoporous silica, SBA-15 silica with two-dimensional hexagonal arrangement, and SBA-16 silica with three-dimensional cubic arrangement. The obtained mesoporous materials were then used as hard templates for synthesizing of different types of nanostructures.

In the first part, the effects of some synthesis parameters on the morphology and texture properties of the mesoporous silica have been studied. By varying the synthesis temperature solid spheres of SBA-16 with different sizes were synthesized and by additions of heptane as a swelling agent, SBA-16 in a hollow-sphere morphology with a large pore size was obtained. In the case of SBA-15, dispersed rods were synthesized in the presence of heptane and NH4F in a low-temperature synthesis. The length of the rods was varied by changing the concentration of HCl, and the pore size was tuned by changing the hydrothermal treatment time and temperature. Furthermore, the reaction time was decreased with a well-retained pore size and morphology. This work has resulted in SBA-15 rods with large pore sizes for this morphology.

In the second part, SBA-15 and SBA-16 silica were used to synthesize different nanostructured materials such as metal and metal oxide nanoparticles. In fact, most of the work in this part is focused on the use of mesoporous silica as hard templates for synthesis of different types of nanoparticles. The synthesis of these nanoparticles was carried out by infiltration of a suitable precursor in the pores of the silica template. The mesoporous frameworks act as molds controlling the size and the final shape of the formed nanostructures. Subsequent dissolution of the silica templates by NaOH resulted in e.g., monodispersed zirconia, hematite, and cobalt nanoparticles with narrow size distributions.

Functionalization of the SBA-15 surfaces was carried out in the synthesis of cobalt nanoparticles. This functionalization plays a crucial role on the infiltration and reaction of the reagents in the pores of the silica. By functionalization of the external surface, a highly hydrophobic surface was achieved, which proved to be sufficient to avoid formation of large cobalt particles outside the silica channels, while the internal functionalization enhances the attraction of cobalt ions to the silica pores, and as a result the nanoparticles grew inside these pores.

1. Influence of synthesis temperature on morphology of SBA-16 mesoporous materials with a three-dimensional pore system
Open this publication in new window or tab >>Influence of synthesis temperature on morphology of SBA-16 mesoporous materials with a three-dimensional pore system
2010 (English)In: Microporous and Mesoporous Materials, ISSN 1387-1811, E-ISSN 1873-3093, Vol. 129, p. 106-111Article in journal (Refereed) Published
##### Abstract [en]

Spherical particles of mesoporous silica SBA-16 with cubic Im3m structure were synthesized at low pH using Pluronic F127 as template and TEOS as silica source. The diameter of the spherical particles can be controlled in the range of 0.5–8 μm by varying synthesis temperature from 1 °C up to 40 °C. A sharp transition from large particle sizes at approximately 20 °C to smaller ones is observed when the temperature is increased. It is suggested that this morphology transition is due to a change in hydrolysis and condensation rate of the silica source and as a result the assembly of F127 micelles will differ. The SBA-16 samples were characterized using powder X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and nitrogen adsorption techniques.

##### Keywords
SBA-16; Spherical particles; Synthesis temperature; Morphology; F127
##### National Category
Other Engineering and Technologies not elsewhere specified
##### Identifiers
urn:nbn:se:liu:diva-52757 (URN)10.1016/j.micromeso.2009.09.004 (DOI)000273862900014 ()
##### Note
Original Publication: Mohamed A. Ballem, José M. Córdoba and Magnus Odén, Influence of synthesis temperature on morphology of SBA-16 mesoporous materials with a three-dimensional pore system, 2010, Microporous and Mesoporous Materials, (129), 106-111. http://dx.doi.org/10.1016/j.micromeso.2009.09.004 Copyright: Elsevier Science B.V., Amsterdam. http://www.elsevier.com/ Available from: 2010-02-02 Created: 2010-01-12 Last updated: 2017-12-12Bibliographically approved
2. Synthesis of hollow silica spheres SBA-16 with large-pore diameter
Open this publication in new window or tab >>Synthesis of hollow silica spheres SBA-16 with large-pore diameter
2011 (English)In: Materials letters (General ed.), ISSN 0167-577X, E-ISSN 1873-4979, Vol. 65, no 7, p. 1066-1068Article in journal (Refereed) Published
##### Abstract [en]

Hollow silica SBA-16 spheres with cubic ordered mesoporous shells were synthesized by an emulsion-templating method, using Pluronic F127 as a structure-directing agent. tetraethyl orthosilicateas as a silica source and heptane as a cosolvent in the presence of NH4F. The size of these spheres is in the range of 10 to 30 mu m. The shell is about 700 nm thick and consists of large pores, similar to 9 nm in diameter, arranged in a cubic order. After calcination, the spheres maintain their mesoporosity and show a high surface area of 822 m(2)/g. The formation mechanism of the silica hollow spheres is discussed.

##### Place, publisher, year, edition, pages
Elsevier Science B.V., Amsterdam., 2011
##### Keywords
Mesoporous silica, SBA-16, Hollow spheres, Large pore, F127
##### National Category
Engineering and Technology
##### Identifiers
urn:nbn:se:liu:diva-67554 (URN)10.1016/j.matlet.2011.01.035 (DOI)000289021700002 ()
Available from: 2011-04-18 Created: 2011-04-18 Last updated: 2017-12-11Bibliographically approved
3. Rapid Synthesis of SBA-15 Rods with Variable Lengths, Widths, and Tunable Large Pores
Open this publication in new window or tab >>Rapid Synthesis of SBA-15 Rods with Variable Lengths, Widths, and Tunable Large Pores
2011 (English)In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 27, no 8, p. 4994-4999Article in journal (Refereed) Published
##### Abstract [en]

Dispersed SBA-15 rods have been synthesized with varying lengths, widths, and pore sizes in a low-temperature synthesis in the presence of heptane and NH4F. The pore size of the material can systematically be varied between 11 and 17 nm using different hydrothermal treatment times And/or temperatures. The particle length (400-600 nm) and width (100-400 nm) were tuned by varying the HCl concentration. All the synthesized materials possess a large surface area of 400-600 m(2)/g And a pore volume of 1.05-1.30 cm(3). A, mechanism for the effect of the HCl concentration on the particle morphology is suggested. Furthermore, it is shown that the reaction time an be decreased to 1 h, with well-retained pore size and morphology. This work has resulted in SBA-15 rods with the largest pore size reported for this morphology.

##### Place, publisher, year, edition, pages
ACS American Chemical Society, 2011
##### National Category
Engineering and Technology
##### Identifiers
urn:nbn:se:liu:diva-67831 (URN)10.1021/la104864d (DOI)000289321000091 ()
Available from: 2011-04-29 Created: 2011-04-29 Last updated: 2017-12-11Bibliographically approved
4. Mesoporous silica templated zirconia nanoparticles
Open this publication in new window or tab >>Mesoporous silica templated zirconia nanoparticles
2011 (English)In: Journal of nanoparticle research, ISSN 1388-0764, E-ISSN 1572-896X, Vol. 13, no 7, p. 2743-2748Article in journal (Refereed) Published
##### Abstract [en]

Nanoparticles of zirconium oxide (ZrO2)were synthesized by infiltration of a zirconia precursor(ZrOCl28H2O) into a SBA-15 mesoporous silicamold using a wet-impregnation technique. X-raydiffractometry and high-resolution transmission electronmicroscopy show formation of stable ZrO2nanoparticles inside the silica pores after a thermaltreatment at 550 C. Subsequent leaching out of thesilica template by NaOH resulted in well-dispersedZrO2 nanoparticles with an average diameter of*4 nm. The formed single crystal nanoparticles arefaceted with 110 surfaces termination suggesting it tobe the preferred growth orientation. A growth modelof these nanoparticles is also suggested.

##### Keywords
Zirconia - Nanoparticles - Mesoporous silica - Wet-impregnation - Metal oxide - Synthesis - Nanomanufacturing
##### National Category
Natural Sciences
##### Identifiers
urn:nbn:se:liu:diva-63058 (URN)10.1007/s11051-010-0160-7 (DOI)
Available from: 2010-12-09 Created: 2010-12-09 Last updated: 2017-12-11Bibliographically approved
5. Low Temperature Nanocasting of Ultrafine Hematite Nanoparticles using Mesoporous Silica Molds
Open this publication in new window or tab >>Low Temperature Nanocasting of Ultrafine Hematite Nanoparticles using Mesoporous Silica Molds
2012 (English)In: Powder Technology, ISSN 0032-5910, E-ISSN 1873-328X, Vol. 217, p. 269-273Article in journal (Refereed) Published
##### Abstract [en]

Iron oxide (α-Fe2O3) nanoparticles with very small size, high crystallinity, and narrow size distribution were synthesized by infiltration of Fe(NO3)3.9H2O as an oxide precursor into mesoporous silica (SBA-15 and SBA-16) molds using a wetimpregnation technique. High resolution transmission electron microscopy shows that during the hydrothermal treatment of the precursor at 140 °C for 2 days, stable α-Fe2O3 nanoparticles inside the silica pores are formed. Subsequent leaching out of the silica template by NaOH resulted in well dispersed nanoparticles with an average diameter of ~ 4 nm.

##### Place, publisher, year, edition, pages
Elsevier, 2012
##### Keywords
α-Fe2O3, Nanoparticles, Nanocasting, Mesoporous silica, SBA-15, SBA-16
##### National Category
Natural Sciences
##### Identifiers
urn:nbn:se:liu:diva-67915 (URN)10.1016/j.powtec.2011.10.037 (DOI)000301159500034 ()
Available from: 2011-05-02 Created: 2011-05-02 Last updated: 2017-12-11
6. Synthesis of homogeneously dispersed cobalt nanoparticles in the pores of functionalized SBA-15 silica
Open this publication in new window or tab >>Synthesis of homogeneously dispersed cobalt nanoparticles in the pores of functionalized SBA-15 silica
2012 (English)In: Powder Technology, ISSN 0032-5910, E-ISSN 1873-328X, Vol. 221, no S1, p. 359-364Article in journal (Refereed) Published
##### Abstract [en]

Cobalt nanoparticles were prepared at room temperature by reducing cobalt sulfate heptahydrate with sodium borohydride and using functionalized SBA-15 mesoporous silica as a hard template. It was found that both external and internal fuctionalization of silica walls play a crucial role on the infiltration and reaction of the reagents in the silica framework. Subsequent heat treatment of the impregnated silica at 500 °C in air or nitrogen atmospheres leads to growth of crystals of the deposited cobalt and formation of cobalt and cobalt oxide nanoparticles, respectively. Dissolution of the silica template by NaOH resulted in well dispersed Co and Co3O4 nanoparticles ranging in size from 2 to 4 nm. The functionalization of the silica was studied by FTIR, N2-physisorption, and thermogravimetric techniques and the obtained nanoparticles were characterized by XRD, TEM and EDX analysis.

##### Place, publisher, year, edition, pages
Elsevier, 2012
##### Keywords
Functionalization; Cobalt; Cobalt oxide; Nanoparticles; SBA-15 silica; Sodium borohydride
##### National Category
Natural Sciences
##### Identifiers
urn:nbn:se:liu:diva-67917 (URN)10.1016/j.powtec.2012.01.025 (DOI)000303222300046 ()
##### Note
funding agencies|Swedish International Development Cooperation Agency, Sida||Available from: 2011-05-02 Created: 2011-05-02 Last updated: 2017-12-11Bibliographically approved
7. Growth of Gd2O3 nanoparticles inside mesoporous silica frameworks
Open this publication in new window or tab >>Growth of Gd2O3 nanoparticles inside mesoporous silica frameworks
2013 (English)In: Microporous and Mesoporous Materials, ISSN 1387-1811, E-ISSN 1873-3093, Vol. 168, p. 221-224Article in journal (Refereed) Published
##### Abstract [en]

Gadolinium oxide (Gd2O3) nanoparticles with very small size, and narrow size distribution were synthesized by infiltration of Gd(NO3)3.6H2O as an oxide precursor into the pores of SBA-15 mesoporous silica using a wet-impregnation technique. High resolution transmission electron microscopy and X-ray diffraction show that during the hydrothermal treatment of the precursor at 550 °C, gadolinium oxide nanoparticles inside the silica pores are formed. Subsequent dissolution of the silica template by NaOH resulted in well dispersed nanoparticles with an average diameter of 3.6 ± 0.9 nm.

##### Place, publisher, year, edition, pages
Elsevier, 2013
##### Keywords
Gd2O3; Nanoparticles; Nanocasting; Mesoporous silica; SBA-15
##### National Category
Natural Sciences
##### Identifiers
urn:nbn:se:liu:diva-67918 (URN)10.1016/j.micromeso.2012.10.009 (DOI)000313839800030 ()
##### Note

At the time of the defence, this publication was an unsubmitted manuscript

Available from: 2011-05-02 Created: 2011-05-02 Last updated: 2017-12-11Bibliographically approved
• 15.
Linköping University, Department of Physics, Chemistry and Biology, Nanostructured Materials . Linköping University, The Institute of Technology.
Linköping University, Department of Physics, Chemistry and Biology, Nanostructured Materials . Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Nanostructured Materials . Linköping University, The Institute of Technology.
Influence of synthesis temperature on morphology of SBA-16 mesoporous materials with a three-dimensional pore system2010In: Microporous and Mesoporous Materials, ISSN 1387-1811, E-ISSN 1873-3093, Vol. 129, p. 106-111Article in journal (Refereed)

Spherical particles of mesoporous silica SBA-16 with cubic Im3m structure were synthesized at low pH using Pluronic F127 as template and TEOS as silica source. The diameter of the spherical particles can be controlled in the range of 0.5–8 μm by varying synthesis temperature from 1 °C up to 40 °C. A sharp transition from large particle sizes at approximately 20 °C to smaller ones is observed when the temperature is increased. It is suggested that this morphology transition is due to a change in hydrolysis and condensation rate of the silica source and as a result the assembly of F127 micelles will differ. The SBA-16 samples were characterized using powder X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and nitrogen adsorption techniques.

• 16.
Linköping University, Department of Physics, Chemistry and Biology, Nanostructured Materials . Linköping University, The Institute of Technology.
Linköping University, Department of Physics, Chemistry and Biology, Nanostructured Materials . Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Nanostructured Materials . Linköping University, The Institute of Technology.
Mesoporous silica templated zirconia nanoparticles2011In: Journal of nanoparticle research, ISSN 1388-0764, E-ISSN 1572-896X, Vol. 13, no 7, p. 2743-2748Article in journal (Refereed)

Nanoparticles of zirconium oxide (ZrO2)were synthesized by infiltration of a zirconia precursor(ZrOCl28H2O) into a SBA-15 mesoporous silicamold using a wet-impregnation technique. X-raydiffractometry and high-resolution transmission electronmicroscopy show formation of stable ZrO2nanoparticles inside the silica pores after a thermaltreatment at 550 C. Subsequent leaching out of thesilica template by NaOH resulted in well-dispersedZrO2 nanoparticles with an average diameter of*4 nm. The formed single crystal nanoparticles arefaceted with 110 surfaces termination suggesting it tobe the preferred growth orientation. A growth modelof these nanoparticles is also suggested.

• 17.
Linköping University, Department of Physics, Chemistry and Biology, Nanostructured Materials. Linköping University, The Institute of Technology.
Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Applied Physics. Linköping University, Department of Physics, Chemistry and Biology, Nanostructured Materials. Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Nanostructured Materials. Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Nanostructured Materials. Linköping University, The Institute of Technology.
Low Temperature Nanocasting of Ultrafine Hematite Nanoparticles using Mesoporous Silica Molds2012In: Powder Technology, ISSN 0032-5910, E-ISSN 1873-328X, Vol. 217, p. 269-273Article in journal (Refereed)

Iron oxide (α-Fe2O3) nanoparticles with very small size, high crystallinity, and narrow size distribution were synthesized by infiltration of Fe(NO3)3.9H2O as an oxide precursor into mesoporous silica (SBA-15 and SBA-16) molds using a wetimpregnation technique. High resolution transmission electron microscopy shows that during the hydrothermal treatment of the precursor at 140 °C for 2 days, stable α-Fe2O3 nanoparticles inside the silica pores are formed. Subsequent leaching out of the silica template by NaOH resulted in well dispersed nanoparticles with an average diameter of ~ 4 nm.

• 18.
Linköping University, Department of Physics, Chemistry and Biology, Nanostructured Materials. Linköping University, The Institute of Technology.
Linköping University, Department of Physics, Chemistry and Biology, Nanostructured Materials. Linköping University, The Institute of Technology. Uppsala Unversity, Sweden. Linköping University, Department of Physics, Chemistry and Biology, Chemistry. Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Nanostructured Materials. Linköping University, The Institute of Technology.
Growth of Gd2O3 nanoparticles inside mesoporous silica frameworks2013In: Microporous and Mesoporous Materials, ISSN 1387-1811, E-ISSN 1873-3093, Vol. 168, p. 221-224Article in journal (Refereed)

Gadolinium oxide (Gd2O3) nanoparticles with very small size, and narrow size distribution were synthesized by infiltration of Gd(NO3)3.6H2O as an oxide precursor into the pores of SBA-15 mesoporous silica using a wet-impregnation technique. High resolution transmission electron microscopy and X-ray diffraction show that during the hydrothermal treatment of the precursor at 550 °C, gadolinium oxide nanoparticles inside the silica pores are formed. Subsequent dissolution of the silica template by NaOH resulted in well dispersed nanoparticles with an average diameter of 3.6 ± 0.9 nm.

• 19.
Linköping University, Department of Physics, Chemistry and Biology, Nanostructured Materials . Linköping University, The Institute of Technology.
Linköping University, Department of Physics, Chemistry and Biology, Nanostructured Materials . Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Nanostructured Materials . Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Nanostructured Materials . Linköping University, The Institute of Technology.
Synthesis of hollow silica spheres SBA-16 with large-pore diameter2011In: Materials letters (General ed.), ISSN 0167-577X, E-ISSN 1873-4979, Vol. 65, no 7, p. 1066-1068Article in journal (Refereed)

Hollow silica SBA-16 spheres with cubic ordered mesoporous shells were synthesized by an emulsion-templating method, using Pluronic F127 as a structure-directing agent. tetraethyl orthosilicateas as a silica source and heptane as a cosolvent in the presence of NH4F. The size of these spheres is in the range of 10 to 30 mu m. The shell is about 700 nm thick and consists of large pores, similar to 9 nm in diameter, arranged in a cubic order. After calcination, the spheres maintain their mesoporosity and show a high surface area of 822 m(2)/g. The formation mechanism of the silica hollow spheres is discussed.

• 20.
Saarland Univ, Germany.
Saarland Univ, Germany. Linköping University, Department of Physics, Chemistry and Biology, Nanostructured Materials. Linköping University, Faculty of Science & Engineering. Saarland Univ, Germany.
Phase Selective Sample Preparation of Al-Si alloys for Atom Probe Tomography2019In: Praktische metallographie, ISSN 0032-678X, E-ISSN 2195-8599, Vol. 56, no 2, p. 76-90Article in journal (Refereed)

We present how the conventional focused ion beam (FIB) lift-out method can be modified to obtain phase selective specimens for atom probe tomography (APT). The modified method combines selective deep etching with site-specific lift-out using a micromanipulator in a FIB/SEM workstation. This method is used for phase-selective sample preparation in alloys with complex microstructures such as the coral- and plate-like silicon structures in the eutectic phase of Al-Si castings. The method proves to be both, practical and robust, with a high success rate of high-quality phase-specific APT specimens.

• 21. Buy this publication >>
Linköping University, Department of Physics, Chemistry and Biology, Nanostructured Materials. Linköping University, Faculty of Science & Engineering. Department of Material Science, Saarland University, Saarbrücken, Germany.
Eutectic Modification of Al-Si casting alloys2019Doctoral thesis, comprehensive summary (Other academic)

Aluminum alloys with silicon as the major alloying element are the most widely used aluminum casting alloys. The eutectic phase in these alloys is formed by hard and brittle silicon plates in an aluminum matrix. Such silicon plates can act as crack propagation paths deteriorating the toughness of the material. To enhance ductility, silicon can be modified to a coral-like microstructure by addition of a modifying agent. Amongst the elements proposed as modifiers, only strontium, sodium and europium induce a plate-tocoral transition, while others such as ytterbium, only refine the silicon plates. The exact mechanism for the remarkable plate-to-coral change, and the reason why certain elements only refine the structure, is still not completely understood.

In this investigation, atom probe tomography and transmission electron microscopy were used to analyze and compare the crystal structure and the distribution of solute atoms in silicon at the atomic level. An unmodified alloy and alloys modified by strontium, sodium, europium and ytterbium were studied. Elements inducing silicon plate-to-coral transition were found to contain nanometer sized clusters at the defects in silicon with stoichiometries corresponding to compounds formed at the ternary eutectic reaction of each system. In contrast, the addition of ytterbium, that only refines the silicon plates, is unable to form clusters in silicon. We propose that the formation of ternary compound clusters AlSiNa, Al2Si2Sr and Al2Si2Eu at the silicon / liquid interface during solidification restrict silicon growth. The formation of clusters on silicon facets create growth steps and increase growth direction diversity. The incorporation of clusters in silicon explains the high density of crystallographic defects and the structural modification from plates to corals.

The parallel lattice plane-normals 011Si // 0001Al2Si2Eu, 011Si // 6$\tiny\overline{7}$10Al2Si2Eu and 111Si // 6$\tiny\overline{7}$10Al2Si2Eu were found between Al2Si2Eu and silicon, and absent between Al2Si2Yb and silicon. We propose a favorable heterogeneous formation of Al2Si2Eu on silicon. The misfit between 011Si and 0002Al2Si2X interplanar spacings shows a consistent trend with the potency of modification for several elements such as strontium, sodium, europium, calcium, barium, ytterbium and yttrium.

1. Comparison of segregations formed in unmodified and Sr-modified Al-Si alloys studied by atom probe tomography and transmission electron microscopy
Open this publication in new window or tab >>Comparison of segregations formed in unmodified and Sr-modified Al-Si alloys studied by atom probe tomography and transmission electron microscopy
2014 (English)In: Journal of Alloys and Compounds, ISSN 0925-8388, E-ISSN 1873-4669, Vol. 611, p. 410-421Article in journal (Refereed) Published
##### Abstract [en]

The mechanical properties of Al-7 wt.% Si can be enhanced by structural modifications of its eutectic phase. Addition of low concentrations of certain elements, in this case 150 wt-ppm Sr, is enough to cause a transition from a coarse plate-like Si structure to a finer coralline one. To fully understand the operating mechanism of this modification, the composition of the eutectic Si phase in unmodified and Sr-modified alloys was analysed and compared by atom probe tomography and (scanning) transmission electron microscopy. The unmodified alloy showed nanometre sized Al-segregations decorating defects, while the Sr-modified sample presented three types of Al-Sr segregations: (1) rod-like segregations that promote smoothening of the Al-Si boundaries in the eutectic phase, (2) particle-like segregations comparable to the ones seen in the unmodified alloy, and (3) planar segregations favouring the formation of twin boundaries. Al and Sr solubilities in Si after solidification were determined to be 430 +/- 160 at-ppm and 40 +/- 10 at-ppm, respectively. Sr predominantly segregates to the Si phase confirming its importance in the modification of the eutectic growth.

##### Place, publisher, year, edition, pages
Elsevier, 2014
##### Keywords
Aluminium-silicon alloys; Strontium modification; Atom probe tomography; Transmission electron microscopy; Microstructure
##### National Category
Physical Sciences
##### Identifiers
urn:nbn:se:liu:diva-109356 (URN)10.1016/j.jallcom.2014.05.121 (DOI)000338932400064 ()
Available from: 2014-08-15 Created: 2014-08-15 Last updated: 2020-03-19Bibliographically approved
2. Cluster formation at the Si/liquid interface in Sr and Na modified Al-Si alloys
Open this publication in new window or tab >>Cluster formation at the Si/liquid interface in Sr and Na modified Al-Si alloys
2016 (English)In: Scripta Materialia, ISSN 1359-6462, E-ISSN 1872-8456, Vol. 117, p. 16-19Article in journal (Refereed) Published
##### Abstract [en]

Atom probe tomography was used to compare Na and Sr modified Al-Si hypoeutectic alloys. Both Na and Sr promote the formation of nanometre-sized clusters in the Si eutectic phase. Compositional analyses of the clusters show an Al:Sr ratio of 2.92 +/- 0.46 and an Al:Na ratio of 1.07 +/- 0.23. It is proposed that SrAl2Si2 and NaAlSi clusters are formed at the Si/liquid interface and take part in the modification process by altering the eutectic Si growth.

##### Place, publisher, year, edition, pages
PERGAMON-ELSEVIER SCIENCE LTD, 2016
##### Keywords
Eutectic solidification; Atom probe tomography; Aluminium alloys; Eutectic modification; Transmission electron microscopy
##### National Category
Physical Sciences
##### Identifiers
urn:nbn:se:liu:diva-127548 (URN)10.1016/j.scriptamat.2016.02.018 (DOI)000373547500004 ()
##### Note

Funding Agencies|German Federal Ministry of Economics and Technology [AiF 17204 N]; European Regional Development Fund (AME-Lab) [C/4-EFRE-13/2009/Br]; German Research Foundation (DFG); Federal State Government of Saarland [INST 256/298-1 FUGG]; Erasmus Mundus Doctoral Programme DocMASE of the European Commission [FPA 2011-0020]; VINNOVA Strategic Faculty Grant VINNMER Marie Curie Chair [2011-03464]; Major International (Regional) Joint Research Project from China [51420105005]

Available from: 2016-05-04 Created: 2016-05-03 Last updated: 2020-03-19
3. Eutectic modification by ternary compound cluster formation in Al-Si alloys
Open this publication in new window or tab >>Eutectic modification by ternary compound cluster formation in Al-Si alloys
2019 (English)In: Scientific Reports, ISSN 2045-2322, E-ISSN 2045-2322, Vol. 9, article id 5506Article in journal (Refereed) Published
##### Abstract [en]

Al-alloys with Si as the main alloying element constitute the vast majority of Al castings used commercially today. The eutectic Si microstructure in these alloys can be modified from plate-like to coral-like by the addition of a small amount of a third element to improve ductility and toughness. In this investigation the effects of Eu and Yb are studied and their influence on the microstructure is compared to further understand this modification. The two elements impact the alloy differently, where Eu modifies Si into a coral-like structure while Yb does not. Atom probe tomography shows that Eu is present within the Si phase in the form of ternary compound Al2Si2Eu clusters, while Yb is absent in the Si phase. This indicates that the presence of ternary compound clusters within Si is a necessary condition for the formation of a coral-like structure. A crystallographic orientation relationship between Si and the Al2Si2Eu phase was found, where the following plane normals are parallel: 011(Si) //0001(Al2Si2Eu), 111(Si)//6 (7) over bar 10(Al2Si2Eu) and 011(Si)//6 (7) over bar 10(Al2Si2Eu). No crystallographic relationship was found between Si and Al2Si2Yb. The heterogeneous formation of coherent Al2Si2Eu clusters inside the Si-phase is suggested to trigger the modification of the microstructure.

##### Place, publisher, year, edition, pages
NATURE PUBLISHING GROUP, 2019
##### National Category
Metallurgy and Metallic Materials
##### Identifiers
urn:nbn:se:liu:diva-156563 (URN)10.1038/s41598-019-41919-2 (DOI)000462990000048 ()30940873 (PubMedID)
##### Note

Funding Agencies|European Regional Development Fund (ERDF); DFG; Federal State Government of Saarland [INST 256/298-1 FUGG]; Erasmus Mundus Programme of the European Commission within the Doctoral Programme DocMASE; Major International (Regional) Joint Research Project from China [51420105005]; Overseas, Hong Kong, Macao Scholars Cooperative Research Fund from China [51728101]

Available from: 2019-05-15 Created: 2019-05-15 Last updated: 2020-03-19
4. Nucleation and Growth of Eutectic Si in Al-Si Alloys with Na Addition
Open this publication in new window or tab >>Nucleation and Growth of Eutectic Si in Al-Si Alloys with Na Addition
2015 (English)In: Metallurgical and Materials Transactions. A, ISSN 1073-5623, E-ISSN 1543-1940, Vol. 46, no 3, p. 1300-1311Article in journal (Refereed) Published
##### Abstract [en]

Al-5 wt pct Si-based alloys with Na additions (19 and 160 ppm) have been produced by controlled sand casting and melt spinning. Entrained droplet technique and differential scanning calorimetry were employed to investigate the nucleation behavior of eutectic Si. High-resolution transmission electron microscopy and atom probe tomography were used to investigate the distribution of Na atoms within eutectic Si and at the interfaces between eutectic Si and eutectic Al. It was found that (i) only 19 ppm Na addition results into a high undercooling (49 K (49 °C)) of the entrained eutectic droplet. However, further increasing Na addition up to 160 ppm exerts no positive effect on the nucleation of eutectic Si, instead a decreased undercooling (29 K (29 °C)) was observed. (ii) Na addition suppresses the growth of eutectic Si due to the Na segregation at the interface between eutectic Si and eutectic Al, and (iii) Na addition promotes significant multiple Si twins, which can be attributed to the proposed adsorption of Na atoms at the intersection of Si twins and along the 〈112〉Si growth direction of Si. The present investigation demonstrates, for the first time, a direct observation on the distribution of Na atoms within eutectic Si and thereby provides strong experimental supports to the well-accepted impurity-induced twinning growth mechanism and poisoning of the twin plane re-entrant edge growth mechanism.

##### National Category
Condensed Matter Physics
##### Identifiers
urn:nbn:se:liu:diva-160234 (URN)10.1007/s11661-014-2702-6 (DOI)
Available from: 2019-09-12 Created: 2019-09-12 Last updated: 2019-09-13
5. Phase Selective Sample Preparation of Al-Si alloys for Atom Probe Tomography
Open this publication in new window or tab >>Phase Selective Sample Preparation of Al-Si alloys for Atom Probe Tomography
2019 (English)In: Praktische metallographie, ISSN 0032-678X, E-ISSN 2195-8599, Vol. 56, no 2, p. 76-90Article in journal (Refereed) Published
##### Abstract [en]

We present how the conventional focused ion beam (FIB) lift-out method can be modified to obtain phase selective specimens for atom probe tomography (APT). The modified method combines selective deep etching with site-specific lift-out using a micromanipulator in a FIB/SEM workstation. This method is used for phase-selective sample preparation in alloys with complex microstructures such as the coral- and plate-like silicon structures in the eutectic phase of Al-Si castings. The method proves to be both, practical and robust, with a high success rate of high-quality phase-specific APT specimens.

##### Place, publisher, year, edition, pages
CARL HANSER VERLAG, 2019
##### National Category
Analytical Chemistry
##### Identifiers
urn:nbn:se:liu:diva-154847 (URN)10.3139/147.110557 (DOI)000458507500002 ()
##### Note

Funding Agencies|EU; DFG; Federal State Government of Saarland [INST 256/298-1 FUGG]; Erasmus Mundus Programme of the European Commission within the Doctoral Programme DocMASE

Available from: 2019-03-05 Created: 2019-03-05 Last updated: 2019-09-13
• 22.
Linköping University, Department of Physics, Chemistry and Biology, Nanostructured Materials. Linköping University, The Institute of Technology. Saarland University, Saarbrücken, Germany.
Saarland University, Saarbrücken, Germany. Linköping University, Department of Physics, Chemistry and Biology, Nanostructured Materials. Linköping University, The Institute of Technology. Saarland University, Saarbrücken, Germany. Linköping University, Department of Physics, Chemistry and Biology, Nanostructured Materials. Linköping University, The Institute of Technology. Saarland University, Saarbrücken, Germany.
Comparison of segregations formed in unmodified and Sr-modified Al-Si alloys studied by atom probe tomography and transmission electron microscopy2014In: Journal of Alloys and Compounds, ISSN 0925-8388, E-ISSN 1873-4669, Vol. 611, p. 410-421Article in journal (Refereed)

The mechanical properties of Al-7 wt.% Si can be enhanced by structural modifications of its eutectic phase. Addition of low concentrations of certain elements, in this case 150 wt-ppm Sr, is enough to cause a transition from a coarse plate-like Si structure to a finer coralline one. To fully understand the operating mechanism of this modification, the composition of the eutectic Si phase in unmodified and Sr-modified alloys was analysed and compared by atom probe tomography and (scanning) transmission electron microscopy. The unmodified alloy showed nanometre sized Al-segregations decorating defects, while the Sr-modified sample presented three types of Al-Sr segregations: (1) rod-like segregations that promote smoothening of the Al-Si boundaries in the eutectic phase, (2) particle-like segregations comparable to the ones seen in the unmodified alloy, and (3) planar segregations favouring the formation of twin boundaries. Al and Sr solubilities in Si after solidification were determined to be 430 +/- 160 at-ppm and 40 +/- 10 at-ppm, respectively. Sr predominantly segregates to the Si phase confirming its importance in the modification of the eutectic growth.

• 23.
Linköping University, Department of Physics, Chemistry and Biology. Linköping University, Faculty of Science & Engineering. University of Saarland, Germany.
University of Leoben, Austria. University of Saarland, Germany. Linköping University, Department of Physics, Chemistry and Biology, Nanostructured Materials. Linköping University, Faculty of Science & Engineering. University of Leoben, Austria. Linköping University, Department of Physics, Chemistry and Biology, Nanostructured Materials. Linköping University, Faculty of Science & Engineering. University of Saarland, Germany.
Cluster formation at the Si/liquid interface in Sr and Na modified Al-Si alloys2016In: Scripta Materialia, ISSN 1359-6462, E-ISSN 1872-8456, Vol. 117, p. 16-19Article in journal (Refereed)

Atom probe tomography was used to compare Na and Sr modified Al-Si hypoeutectic alloys. Both Na and Sr promote the formation of nanometre-sized clusters in the Si eutectic phase. Compositional analyses of the clusters show an Al:Sr ratio of 2.92 +/- 0.46 and an Al:Na ratio of 1.07 +/- 0.23. It is proposed that SrAl2Si2 and NaAlSi clusters are formed at the Si/liquid interface and take part in the modification process by altering the eutectic Si growth.

• 24.
Linköping University, Department of Physics, Chemistry and Biology, Nanostructured Materials. Linköping University, Faculty of Science & Engineering. Saarland Univ, Germany.
Saarland Univ, Germany. Saarland Univ, Germany. Univ Lorraine, France. Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering. Univ Leoben, Austria. Univ Leoben, Austria. Linköping University, Department of Physics, Chemistry and Biology, Nanostructured Materials. Linköping University, Faculty of Science & Engineering. Saarland Univ, Germany.
Eutectic modification by ternary compound cluster formation in Al-Si alloys2019In: Scientific Reports, ISSN 2045-2322, E-ISSN 2045-2322, Vol. 9, article id 5506Article in journal (Refereed)

Al-alloys with Si as the main alloying element constitute the vast majority of Al castings used commercially today. The eutectic Si microstructure in these alloys can be modified from plate-like to coral-like by the addition of a small amount of a third element to improve ductility and toughness. In this investigation the effects of Eu and Yb are studied and their influence on the microstructure is compared to further understand this modification. The two elements impact the alloy differently, where Eu modifies Si into a coral-like structure while Yb does not. Atom probe tomography shows that Eu is present within the Si phase in the form of ternary compound Al2Si2Eu clusters, while Yb is absent in the Si phase. This indicates that the presence of ternary compound clusters within Si is a necessary condition for the formation of a coral-like structure. A crystallographic orientation relationship between Si and the Al2Si2Eu phase was found, where the following plane normals are parallel: 011(Si) //0001(Al2Si2Eu), 111(Si)//6 (7) over bar 10(Al2Si2Eu) and 011(Si)//6 (7) over bar 10(Al2Si2Eu). No crystallographic relationship was found between Si and Al2Si2Yb. The heterogeneous formation of coherent Al2Si2Eu clusters inside the Si-phase is suggested to trigger the modification of the microstructure.

• 25.
Linköping University, Department of Physics, Chemistry and Biology, Nanostructured Materials. Linköping University, Faculty of Science & Engineering.
Synthesizing and Characterizing Mesoporous Silica SBA-15: A Hands On Laboratory Experiment for Undergraduates Using Various Instrumental Techniques2017In: Journal of Chemical Education, ISSN 0021-9584, E-ISSN 1938-1328, Vol. 94, no 1, p. 91-94Article in journal (Refereed)

In this laboratory experiment, students learn how to synthesize mesoporous silica of the SBA-15 type and explore how the different synthesis steps affect the final material. Mesoporous materials, especially SBA-15, are often used in the development of new methods for. drug delivery, catalysis, and separation because of the flexibility of tailoring these materials to optimize the performance in different applications. However, the synthesis of mesoporous materials is rarely introduced to undergraduate students. The material synthesis is a simple sol gel process, where small alterations in the synthesis steps can significantly change the material characteristics. The presented laboratory experiment aims to introduce undergraduate students to the synthesis of SBA-15 mesoporous silica with different pore sizes due to alterations in the hydrothermal treatment time and/ or temperature and to give students hands-on experience with important characterization tools, including physisorption, X-ray diffraction, FTIR spectroscopy, and thermogravimetric analysis, to understand the effect of hydrothermal treatment and surfactant removal. Additional synthesis parameters to study, such as surfactant removal, the silica precursor, and pore swelling agents, are also presented. The experiment has been used in teaching of both bachelors and masters students and can be adapted to various instrumental techniques, e.g., scanning electron microscopy for morphology studies, transition electron microscopy for pore structure characterization, etc.

• 26.
Linköping University, Department of Physics, Chemistry and Biology, Nanostructured Materials. Linköping University, Faculty of Science & Engineering. Univ Ulm, Germany.
Univ Ulm, Germany. Ulm Univ, Germany. Ulm Univ, Germany. Univ Ulm, Germany.
Cell adherence and drug delivery from particle based mesoporous silica films2019In: RSC Advances, ISSN 2046-2069, E-ISSN 2046-2069, Vol. 9, no 31, p. 17745-17753Article in journal (Refereed)

Spatially and temporally controlled drug delivery is important for implant and tissue engineering applications, as the efficacy and bioavailability of the drug can be enhanced, and can also allow for drugging stem cells at different stages of development. Long-term drug delivery over weeks to months is however difficult to achieve, and coating of 3D surfaces or creating patterned surfaces is a challenge using coating techniques like spin- and dip-coating. In this study, mesoporous films consisting of SBA-15 particles grown onto silicon wafers using wet processing were evaluated as a scaffold for drug delivery. Films with various particle sizes (100-900 nm) and hence thicknesses were grown onto trichloro(octadecyl)silane-functionalized silicon wafers using a direct growth method. Precise patterning of the areas for film growth could be obtained by local removal of the OTS functionalization through laser ablation. The films were incubated with the drug model 3,3 -dioctadecyloxacarbocyanine perchlorate (DiO), and murine myoblast cells (C2C12 cells) were seeded onto films with different particle sizes. Confocal laser scanning microscopy (CLSM) was used to study the cell growth, and a vinculin-mediated adherence of C2C12 cells on all films was verified. The successful loading of DiO into the films was confirmed by UV-vis and CLSM. It was observed that the drugs did not desorb from the particles during 24 hours in cell culture. During adherent growth on the films for 4 h, small amounts of DiO and separate particles were observed inside single cells. After 24 h, a larger number of particles and a strong DiO signal were recorded in the cells, indicating a particle mediated drug uptake. The vast majority of the DiO-loaded particles remained attached to the substrate also after 24 h of incubation, making the films attractive as longer-term reservoirs for drugs on e.g. medical implants.

• 27. Buy this publication >>
Linköping University, Department of Physics, Chemistry and Biology, Nanostructured Materials. Linköping University, The Institute of Technology.
Mesoporous Building Blocks: Synthesis and Characterization of Mesoporous Silica Particles and Films2013Doctoral thesis, comprehensive summary (Other academic)

Catalyst supports, drug delivery systems, hosts for nanoparticles, and solar cells are just some examples of the wide range of exciting applications for mesoporous silica. In order to optimize the performance of a specific application, controlling the material’s morphology and pore size is crucial. For example, short and separated particles are beneficial for drug delivery systems, while for molecular sieves, the pore size is the key parameter.

In this thesis, mesoporous silica building blocks, crystallites, with hexagonally ordered cylindrical pores were synthesized, with the aim to understand how the synthesis parameters affect the particle morphology and pore size. The synthesis of the particles is performed using a sol-gel process, and in order to increase the pore size, a combination of low temperature, and additions of heptane and NH4F was used. By variations in the amounts of reagents, as well as other synthesis conditions, the particle morphology and pore size could be altered. Separated particles were also grown on or attached to substrates to form films. Also, a material with spherical pore structure was synthesized, for the first time using this method.

It was found that a variation in the heptane concentration, in combination with a long stirring time, yields a transition between fiber and sheet morphologies. Both morphologies consist of crystallites, which for the fibers are joined end to end, while for the sheets they are attached side by side such that the pores are accessible from the sheet surface. The crystallites can be separated to a rod morphology by decreasing the stirring time and tuning the HCl concentration, and it was seen that these rods are formed within 5 min of static time, even though the pore size and unit cell parameters were evolving for another 30 min. Further studies of the effects of heptane showed that the shape and mesoscopic parameters of the rods are affected by the heptane concentration, up to a value where the micelles are fully saturated with heptane. It was also observed that the particle width increases with decreasing NH4F concentration, independent of heptane amount, and a platelet morphology can be formed. The formation time of the particles decrease with decreasing NH4F, and the growth mechanism for platelets was further studied. The pore sizes for various morphologies were altered by e.g. variations in the hydrothermal treatment conditions, or the method for removing the surfactants.

The separated particles can be attached to substrates, either during the particle synthesis or by post grafting prior to calcination. The film formation during the one-pot-synthesis was studied and a formation mechanism including nucleation of elongated micelles on the substrate was suggested. During the post grafting film synthesis, the medium in which the particles are dispersed, as well as functionalization of both particle and substrate are crucial for the post grafting process. The pores are easily accessible independent of the method, even though they are aligned parallel to the substrate when the one-pot-method is used, while post grafting gives a perpendicular pore orientation.

In summary, this work aims to give an understanding for the formation of the synthesized material, and how to tune the material properties by alterations in parameter space. Successful syntheses of four different particle morphologies and two new types of films were performed, and the pore size could easily be tuned by various methods.

1. Synthesis and characterization of large mesoporous silica SBA-15 sheets with ordered accessible 18 nm pores
Open this publication in new window or tab >>Synthesis and characterization of large mesoporous silica SBA-15 sheets with ordered accessible 18 nm pores
2009 (English)In: Materials Letters, ISSN 0167-577X, Vol. 63, no 24-25, p. 2129-2131Article in journal (Refereed) Published
##### Abstract [en]

Mesoporous silica SBA-15 in the form of 10-30 μm sized sheets with unusually large ordered pores has been synthesized using heptane as a cosolvent in the presence of NH4F. The resulting morphology of 400 nm thick sheets that contain easily accessed, hexagonally arranged, 18 nm sized pores running parallel to sheet normal has not been previously reported. The material has a BET surface area of 541 m2/g, large pore volume of 1.69 cm3/g and ordered mesopore structure with a narrow pore size distribution around 18 nm. A mechanism for sheet formation based on heptane droplets acting as sites for self assembling of silica crystallites is suggested.

##### Keywords
Large pore; Mesoporous silica; SBA-15; Sheet
##### National Category
Natural Sciences
##### Identifiers
urn:nbn:se:liu:diva-21193 (URN)10.1016/j.matlet.2009.07.013 (DOI)
##### Note
Original Publication: Emma Johansson, Jose Manuel Cordoba and Magnus Odén, Synthesis and characterization of large mesoporous silica SBA-15 sheets with ordered accessible 18 nm pores, 2009, Materials Letters, (63), 24-25, 2129-2131. http://dx.doi.org/10.1016/j.matlet.2009.07.013 Copyright: Elsevier Science B.V., Amsterdam. http://www.elsevier.com/ Available from: 2009-09-30 Created: 2009-09-30 Last updated: 2013-10-22
2. Synthesis of hollow silica spheres SBA-16 with large-pore diameter
Open this publication in new window or tab >>Synthesis of hollow silica spheres SBA-16 with large-pore diameter
2011 (English)In: Materials letters (General ed.), ISSN 0167-577X, E-ISSN 1873-4979, Vol. 65, no 7, p. 1066-1068Article in journal (Refereed) Published
##### Abstract [en]

Hollow silica SBA-16 spheres with cubic ordered mesoporous shells were synthesized by an emulsion-templating method, using Pluronic F127 as a structure-directing agent. tetraethyl orthosilicateas as a silica source and heptane as a cosolvent in the presence of NH4F. The size of these spheres is in the range of 10 to 30 mu m. The shell is about 700 nm thick and consists of large pores, similar to 9 nm in diameter, arranged in a cubic order. After calcination, the spheres maintain their mesoporosity and show a high surface area of 822 m(2)/g. The formation mechanism of the silica hollow spheres is discussed.

##### Place, publisher, year, edition, pages
Elsevier Science B.V., Amsterdam., 2011
##### Keywords
Mesoporous silica, SBA-16, Hollow spheres, Large pore, F127
##### National Category
Engineering and Technology
##### Identifiers
urn:nbn:se:liu:diva-67554 (URN)10.1016/j.matlet.2011.01.035 (DOI)000289021700002 ()
Available from: 2011-04-18 Created: 2011-04-18 Last updated: 2017-12-11Bibliographically approved
3. The effects on pore size and particle morphology of heptane additions to the synthesis of mesoporous silica SBA-15
Open this publication in new window or tab >>The effects on pore size and particle morphology of heptane additions to the synthesis of mesoporous silica SBA-15
2010 (English)In: Microporous and Mesoporous Materials, ISSN 1387-1811, E-ISSN 1873-3093, Vol. 133, no 01-Mar, p. 66-74Article in journal (Refereed) Published
##### Abstract [en]

The effect of heptane on the particle morphology and pore size in the synthesis of SBA-15 is presented. Heptane in the presence of NH4F works as a pore swelling agent, resulting in 13-18 nm sized pores in 400 nm long and 200-1000 nm wide crystallites. The pores are hexagonally arranged and run through the crystallites. Increasing the heptane to P123 molar ratio changes the morphology of SBA-15 from fibers to sheets when the crystallites rearrange during the synthesis. The pore order in the sheets is controlled by changing the molar ratio of water to P123. The surface areas of these materials are 500-800 m(2)/g with pore volumes of 1.2-1.7 cm(3)/g. The sheets have accessible pores with a size of 18 nm running parallel to the sheet normal, which makes them suitable for membranes.

##### Place, publisher, year, edition, pages
Elsevier Science B.V., Amsterdam., 2010
##### Keywords
SBA-15; Morphology; Heptane; H2O2; Sheet
##### National Category
Engineering and Technology
##### Identifiers
urn:nbn:se:liu:diva-58290 (URN)10.1016/j.micromeso.2010.04.016 (DOI)000279061000009 ()
Available from: 2010-08-10 Created: 2010-08-09 Last updated: 2017-12-12
4. Rapid Synthesis of SBA-15 Rods with Variable Lengths, Widths, and Tunable Large Pores
Open this publication in new window or tab >>Rapid Synthesis of SBA-15 Rods with Variable Lengths, Widths, and Tunable Large Pores
2011 (English)In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 27, no 8, p. 4994-4999Article in journal (Refereed) Published
##### Abstract [en]

Dispersed SBA-15 rods have been synthesized with varying lengths, widths, and pore sizes in a low-temperature synthesis in the presence of heptane and NH4F. The pore size of the material can systematically be varied between 11 and 17 nm using different hydrothermal treatment times And/or temperatures. The particle length (400-600 nm) and width (100-400 nm) were tuned by varying the HCl concentration. All the synthesized materials possess a large surface area of 400-600 m(2)/g And a pore volume of 1.05-1.30 cm(3). A, mechanism for the effect of the HCl concentration on the particle morphology is suggested. Furthermore, it is shown that the reaction time an be decreased to 1 h, with well-retained pore size and morphology. This work has resulted in SBA-15 rods with the largest pore size reported for this morphology.

##### Place, publisher, year, edition, pages
ACS American Chemical Society, 2011
##### National Category
Engineering and Technology
##### Identifiers
urn:nbn:se:liu:diva-67831 (URN)10.1021/la104864d (DOI)000289321000091 ()
Available from: 2011-04-29 Created: 2011-04-29 Last updated: 2017-12-11Bibliographically approved
5. Tuning the shape of mesoporous silica particles by alterations in parameter space: from rods to platelets
Open this publication in new window or tab >>Tuning the shape of mesoporous silica particles by alterations in parameter space: from rods to platelets
2013 (English)In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 29, no 44, p. 13551-13561Article in journal (Refereed) Published
##### Abstract [en]

The knowledge of how to control the pore size and morphology of separated mesoporous silica particles is crucial for optimizing their performance in applications, such as molecular sieves and drug delivery systems. In this work, we have systematically studied the effects of various synthesis parameters to gain a deeper understanding of how particle morphologies can be altered. It was found that the morphology for isolated particles of SBA-15 type, with unusually short and wide pores, could be altered from rods to platelets by variations in the NH4F concentration. The pore length is nearly constant (similar to 300 nm) for the different morphologies, but the particle width is increasing from 200 nm to >3 mu m when decreasing the amount of NH4F, and the pore size can be tuned between 10 and 13 nm. Furthermore, other synthesis parameters such as heptane concentration, pH, silica precursor, and additions of ions have also been studied. The trend regarding particle width is independent of heptane concentration, at the same time as heptane increases the particle length up to a plateau value of similar to 500 nm. In all, parameters controlling particle width, length, and pore size have been separated in order to evaluate their function in the particle formation. Additionally, it was found that the formation time of the particles is strongly affected by the fluoride ion concentration, and a mechanism for particle formation for this system, where micelles transform from a foam, to multilamellar vesicles, and finally to cylindrical micelles, is suggested.

##### Place, publisher, year, edition, pages
American Chemical Society (ACS), 2013
##### National Category
Natural Sciences
##### Identifiers
urn:nbn:se:liu:diva-99859 (URN)10.1021/la403201v (DOI)000326711200029 ()
Available from: 2013-10-22 Created: 2013-10-22 Last updated: 2017-12-06Bibliographically approved
6. Single-pot synthesis of ordered mesoporous silica films with unique controllable morphology
Open this publication in new window or tab >>Single-pot synthesis of ordered mesoporous silica films with unique controllable morphology
2014 (English)In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 413, p. 1-7Article in journal (Refereed) Published
##### Abstract [en]

Mesoporous silica films consisting of a monolayer of separated SBA-15 particles with unusually wide and short pores grown on silicon wafers have been fabricated in a simple single-pot-synthesis, and the formation of the films has been studied. A recipe for synthesizing mesoporous silica rods with the addition of heptane and NH4F at low temperature was used and substrates were added to the synthesis solution during the reaction. The films are ∼90 nm thick, have a pore size of 10.7–13.9 nm depending on the hydrothermal treatment time and temperature, and a pore length of 200–400 nm. All pores are parallel to the substrate, open, and easy to access, making them suitable for applications such as catalyst hosts and gas separation. The growth of the films is closely correlated to the evolution of the mesoporous silica particles. Here, we have studied the time for adding substrates to the synthesis solution, the evolution of the films with time during formation, and the effect of hydrothermal treatment. It was found that the substrates should be added within 30–60 s after turning off the stirring and the films are formed within 10 min after addition to the synthesis solution. The study has yielded a new route for synthesizing mesoporous silica films with a unique morphology.

##### Place, publisher, year, edition, pages
Elsevier, 2014
##### Keywords
SBA-15; Mesoporous silica; Large pore; Films; Rods; Film growth; Particle formation
##### National Category
Natural Sciences
##### Identifiers
urn:nbn:se:liu:diva-99856 (URN)10.1016/j.jcis.2013.09.023 (DOI)000327168800001 ()
Available from: 2013-10-22 Created: 2013-10-22 Last updated: 2017-12-06Bibliographically approved
7. Grafting mesoporous silica particles to substrates: a method for synthesizing mesoporous films with cylindrical pores perpendicular to the substrate
Open this publication in new window or tab >>Grafting mesoporous silica particles to substrates: a method for synthesizing mesoporous films with cylindrical pores perpendicular to the substrate
##### Abstract [en]

A method for synthesizing mesoporous silica films with cylindrical pores perpendicular to the substrate has been developed. The films consist of SBA-15 platelets that are grafted on glass substrates. The grafting is studied in terms of parameters such as pH, substrate functionalization, salt additions, time for TEOS prehydrolysis, and calcination. The best coverage of particles on the substrate was achieved for a low pH in combination with OTS-treated glass substrate. Furthermore, the prehydrolysis time of the TEOS was found to be a key parameter in order to bind the particles to the substrate. These porous films have potential in applications such as catalysis, drug delivery, and as a template for nanoparticle or nanorod, growth.

##### Keywords
Mesoporous silica films, platelets, particle functionalization, substrate functionalization, pH, salt
##### National Category
Natural Sciences
##### Identifiers
urn:nbn:se:liu:diva-99857 (URN)
Available from: 2013-10-22 Created: 2013-10-22 Last updated: 2013-10-22Bibliographically approved
• 28.
Linköping University, Department of Physics, Chemistry and Biology, Nanostructured Materials. Linköping University, The Institute of Technology.
Linköping University, Department of Physics, Chemistry and Biology, Nanostructured Materials. Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Nanostructured Materials. Linköping University, The Institute of Technology.
Grafting mesoporous silica particles to substrates: a method for synthesizing mesoporous films with cylindrical pores perpendicular to the substrate2013Manuscript (preprint) (Other academic)

A method for synthesizing mesoporous silica films with cylindrical pores perpendicular to the substrate has been developed. The films consist of SBA-15 platelets that are grafted on glass substrates. The grafting is studied in terms of parameters such as pH, substrate functionalization, salt additions, time for TEOS prehydrolysis, and calcination. The best coverage of particles on the substrate was achieved for a low pH in combination with OTS-treated glass substrate. Furthermore, the prehydrolysis time of the TEOS was found to be a key parameter in order to bind the particles to the substrate. These porous films have potential in applications such as catalysis, drug delivery, and as a template for nanoparticle or nanorod, growth.

• 29.
Linköping University, Department of Physics, Chemistry and Biology, Nanostructured Materials. Linköping University, The Institute of Technology.
Linköping University, Department of Physics, Chemistry and Biology, Nanostructured Materials. Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Nanostructured Materials. Linköping University, The Institute of Technology.
Single-pot synthesis of ordered mesoporous silica films with unique controllable morphology2014In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 413, p. 1-7Article in journal (Refereed)

Mesoporous silica films consisting of a monolayer of separated SBA-15 particles with unusually wide and short pores grown on silicon wafers have been fabricated in a simple single-pot-synthesis, and the formation of the films has been studied. A recipe for synthesizing mesoporous silica rods with the addition of heptane and NH4F at low temperature was used and substrates were added to the synthesis solution during the reaction. The films are ∼90 nm thick, have a pore size of 10.7–13.9 nm depending on the hydrothermal treatment time and temperature, and a pore length of 200–400 nm. All pores are parallel to the substrate, open, and easy to access, making them suitable for applications such as catalyst hosts and gas separation. The growth of the films is closely correlated to the evolution of the mesoporous silica particles. Here, we have studied the time for adding substrates to the synthesis solution, the evolution of the films with time during formation, and the effect of hydrothermal treatment. It was found that the substrates should be added within 30–60 s after turning off the stirring and the films are formed within 10 min after addition to the synthesis solution. The study has yielded a new route for synthesizing mesoporous silica films with a unique morphology.

• 30.
Linköping University, Department of Physics, Chemistry and Biology, Nanostructured Materials. Linköping University, The Institute of Technology.
Linköping University, Department of Physics, Chemistry and Biology, Nanostructured Materials. Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Nanostructured Materials. Linköping University, The Institute of Technology.
Tuning the shape of mesoporous silica particles by alterations in parameter space: from rods to platelets2013In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 29, no 44, p. 13551-13561Article in journal (Refereed)

The knowledge of how to control the pore size and morphology of separated mesoporous silica particles is crucial for optimizing their performance in applications, such as molecular sieves and drug delivery systems. In this work, we have systematically studied the effects of various synthesis parameters to gain a deeper understanding of how particle morphologies can be altered. It was found that the morphology for isolated particles of SBA-15 type, with unusually short and wide pores, could be altered from rods to platelets by variations in the NH4F concentration. The pore length is nearly constant (similar to 300 nm) for the different morphologies, but the particle width is increasing from 200 nm to >3 mu m when decreasing the amount of NH4F, and the pore size can be tuned between 10 and 13 nm. Furthermore, other synthesis parameters such as heptane concentration, pH, silica precursor, and additions of ions have also been studied. The trend regarding particle width is independent of heptane concentration, at the same time as heptane increases the particle length up to a plateau value of similar to 500 nm. In all, parameters controlling particle width, length, and pore size have been separated in order to evaluate their function in the particle formation. Additionally, it was found that the formation time of the particles is strongly affected by the fluoride ion concentration, and a mechanism for particle formation for this system, where micelles transform from a foam, to multilamellar vesicles, and finally to cylindrical micelles, is suggested.

• 31.
Linköping University, Department of Physics, Chemistry and Biology, Nanostructured Materials. Linköping University, Faculty of Science & Engineering. University of Nacl Rio Cuarto, Argentina.
University of Nacl Rio Cuarto, Argentina. University of Nacl Rio Cuarto, Argentina. University of Nacl Rio Cuarto, Argentina. University of Nacl Rio Cuarto, Argentina. University of Nacl Rio Cuarto, Argentina; University of Nacl Rio Cuarto, Argentina. Consejo Nacl Invest Cient and Tecn, Argentina. Linköping University, Department of Physics, Chemistry and Biology, Nanostructured Materials. Linköping University, Faculty of Science & Engineering. University of Nacl Rio Cuarto, Argentina.
Mesoporous silica and carbon based catalysts for esterification and biodiesel fabrication-The effect of matrix surface composition and porosity2017In: Applied Catalysis A: General, ISSN 0926-860X, E-ISSN 1873-3875, Vol. 533, p. 49-58Article in journal (Refereed)

The effects of catalyst matrix porosity composition on the catalytic performance have been studied using sulfonated mesoporous SBA-15 silica. The matrix was sulfonated with three different methods grafting, in situ oxidation, and carbon infiltration. Additionally, unordered sulfonated mesoporous carbon, and the commercial catalysts Amberlite IR-120 and Nafion 117 were tested. The catalytic performance was evaluated in a Fischer esterification using acetic acid and ethanol, as well as in a transesterification of triglycerides (sunflower oil) and ethanol to produce biodiesel. The study shows that for long carbon chains, the effective wetting of the porous catalyst matrix by the reactants is most important for the catalytic efficiency, while for shorter carbon chain, the mass transport of the reagents trough the porous structure is more important. The catalysts were analysed using electron microscopy and physisorption. The study shows that the reactions are faster with carbon infiltrated materials than the silica materials due to a higher concentration of sulfonic groups linked to the carbon. The in situ functionalized SBA-15 is a more efficient catalyst compared to the post grafted one. All the synthesized catalysts outperform the commercial ones in both reactions in terms of conversion. (C) 2017 Elsevier B.V. All rights reserved.

• 32.
Linköping University, Department of Physics, Chemistry and Biology, Nanostructured Materials. Linköping University, Faculty of Science & Engineering. Univ Ulm, Germany.
Linköping University, Department of Physics, Chemistry and Biology, Nanostructured Materials. Linköping University, Faculty of Science & Engineering. Linköping University, Department of Physics, Chemistry and Biology, Nanostructured Materials. Linköping University, Faculty of Science & Engineering. Linköping University, Department of Physics, Chemistry and Biology, Nanostructured Materials. Linköping University, Faculty of Science & Engineering. Helmholtz Zentrum Geesthacht, Germany. Linköping University, Department of Physics, Chemistry and Biology, Nanostructured Materials. Linköping University, Faculty of Science & Engineering.
Formation of block-copolymer-templated mesoporous silica2018In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 521, p. 183-189Article in journal (Refereed)

In situ attenuated total reflectance Fourier transform infrared spectroscopy is used to monitor the chemical evolution of the mesoporous silica SBA-15 from hydrolysis of the silica precursor to final silica condensation after the particle formation. Two silica precursors, tetraethyl orthosilicate (TEOS) or sodium metasilicate (SMS) were used, and the effects of additive (heptane and NH4F) concentrations were studied. Five formation stages are identified when TEOS is used as the precursor. The fourth stage correlates with the appearance and evolution of diffraction peaks recorded using in situ small angle X-ray diffraction. Details of the formed silica matrix are observed, e.g. the ratio between six-fold cyclic silica rings and linear bonding increases with the NH4F concentration. The TEOS hydrolysis time is independent of the NH4F concentration for small amounts of heptane, but is affected by the size of the emulsion droplets when the heptane amount increases. Polymerization and condensation rates of both silica precursors are affected by the salt concentration. Materials synthesized using SMS form significantly faster compared to TEOS-materials due to the pre-hydrolysis of the precursor. The study provides detailed insights into how the composition of the synthesis solution affects the chemical evolution and micellar aggregation during formation of mesoporous silica. (C) 2018 Elsevier Inc. All rights reserved.

• 33.
Linköping University, Department of Physics, Chemistry and Biology, Plasma and Coating Physics. Linköping University, Faculty of Science & Engineering.
Linköping University, Department of Physics, Chemistry and Biology, Chemistry. Linköping University, Faculty of Science & Engineering. Linköping University, Department of Physics, Chemistry and Biology, Plasma and Coating Physics. Linköping University, Faculty of Science & Engineering. Linköping University, Department of Physics, Chemistry and Biology, Nanostructured Materials. Linköping University, Faculty of Science & Engineering. Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
Complex 3D nanocoral like structures formed by copper nanoparticle aggregation on nanostructured zinc oxide rods2016In: Materials letters (General ed.), ISSN 0167-577X, E-ISSN 1873-4979, Vol. 184, p. 127-130Article in journal (Refereed)

This paper reports a new strategy for nanoparticle surface assembly so that they form anisotropic fibril like features, consisting of particles directly attached to each other, which can extend 500 nm from the surface. The particles are both formed and deposited in a single step process enabled via the use of a pulsed plasma based technique. Using this approach, we have successfully modified zinc oxide rods, up to several hundred nanometers in diameter, with 25 nm diameter copper nanoparticles for catalytic applications. The resulting structure could be modelled using a diffusion limited aggregation based approach. This gives the material the appearance of marine coral, hence the term nanocoral. (C) 2016 Elsevier B.V. All rights reserved.

• 34.
Linköping University, Department of Physics, Chemistry and Biology, Nanostructured Materials. Linköping University, Faculty of Science & Engineering. Department of Materials Science and Engineering, D3.3 Saarland University, Saarbrücken, Germany.
Linköping University, Department of Physics, Chemistry and Biology, Nanostructured Materials. Linköping University, Faculty of Science & Engineering. Linköping University, Department of Physics, Chemistry and Biology, Nanostructured Materials. Linköping University, Faculty of Science & Engineering. Linköping University, Department of Physics, Chemistry and Biology, Nanostructured Materials. Linköping University, Faculty of Science & Engineering. Seco Tools AB, SE-737 82 Fagersta, Sweden. Seco Tools AB, SE-737 82 Fagersta, Sweden. Institute Jean Lamour, Campus ARTEM, University of Lorraine, CNRS, F-54011 Nancy, France. Sandvik Coromant, SE-126 80 Stockholm, Sweden. Department of Materials Science and Engineering, D3.3 Saarland University, D-66123 Saarbrücken, Germany. Linköping University, Department of Physics, Chemistry and Biology, Nanostructured Materials. Linköping University, Faculty of Science & Engineering.
The Effect of Cathodic Arc Guiding Magnetic Field on the Growth of (Ti0.36Al0.64)N Coatings2019In: Coatings, ISSN 2079-6412, Vol. 9, no 10, article id 660Article in journal (Refereed)

We use a modified cathodic arc deposition technique, including an electromagnetic coil that introduces a magnetic field in the vicinity of the source, to study its influence on the growth of (Ti0.36Al0.64)N coatings. By increasing the strength of the magnetic field produced by the coil, the cathode arc spots are steered toward the edge of the cathode, and the electrons are guided to an annular anode surrounding the cathode. As a result, the plasma density between the cathode and substrate decreased, which was observed as a lateral spread of the plasma plume, and a reduction of the deposition rate. Optical emission spectroscopy shows reduced intensities of all recorded plasma species when the magnetic field is increased due to a lower number of collisions resulting in excitation. We note a charge-to-mass ratio decrease of 12% when the magnetic field is increased, which is likely caused by a reduced degree of gas phase ionization, mainly through a decrease in N2 ionization. (Ti0.36Al0.64)N coatings grown at different plasma densities show considerable variations in grain size and phase composition. Two growth modes were identified, resulting in coatings with (i) a fine-grained glassy cubic and wurtzite phase mixture when deposited with a weak magnetic field, and (ii) a coarse-grained columnar cubic phase with a strong magnetic field. The latter conditions result in lower energy flux to the coating&rsquo;s growth front, which suppresses surface diffusion and favors the formation of c-(Ti,Al)N solid solutions over phase segregated c-TiN and w-AlN.

• 35.
Linköping University, Department of Physics, Chemistry and Biology, Nanostructured Materials. Linköping University, Faculty of Science & Engineering. Univ Lorraine, France.
Linköping University, Department of Physics, Chemistry and Biology, Nanostructured Materials. Linköping University, Faculty of Science & Engineering. Saarland Univ, Germany. SECO Tools AB, Sweden. Univ Lorraine, France. Linköping University, Department of Physics, Chemistry and Biology, Plasma and Coating Physics. Linköping University, Faculty of Science & Engineering. Univ Lorraine, France. Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering. Saarland Univ, Germany. Linköping University, Department of Physics, Chemistry and Biology, Nanostructured Materials. Linköping University, Faculty of Science & Engineering.
Growth and high temperature decomposition of epitaxial metastable wurtzite (Ti1-x,Al-x)N(0001) thin films2019In: Thin Solid Films, ISSN 0040-6090, E-ISSN 1879-2731, Vol. 688, article id 137414Article in journal (Refereed)

The structure, growth, and phase stability of (Ti1-x,Al-x)N films with high Al content were investigated. (Ti1-x,Al-x)N (x= 0.63 and 0.77) thin films were grown on MgO (111) substrates at 700 degrees C using a UHV DC magnetron sputtering system. The (Ti-0.37,Al-0.63)N film is a single crystal with a cubic NaCl (B1) structure while the (T-i0.23,Al-0.77)N film only shows epitaxial growth of the same cubic phase in the first few atomic layers. With increasing film thickness, epitaxial wurtzite (B4) forms. The thin cubic layer and the wurtzite film has an orientation relationship of c-(Ti-0.23,Al-0.77)N(111)[110]parallel to w-(Ti-0.23,Al-0.77)N(0001)[11 (2) over bar0]. Continued deposition results in a gradual break-down of the epitaxial growth. It is replaced by polycrystalline growth of wurtzite columns with a high degree of 0001 texture, separated by a Tienriched cubic phase. In the as-deposited state, c-(Ti-0.27,Al-0.63)N displays a homogeneous chemical distribution while the w-(Ti-0.23,Al-0.77)N has segregated to Al- and Ti-rich domains. Annealing at 900 degrees C resulted in the spinodal decomposition of the metastable c-(Ti-0.27,Al-0.63)N film and formation of coherent elongated c-AlN and cTi-N-rich domains with an average width of 4.5 +/- 0.2 nm while the width of the domains in the w-(Ti-0.23,Al-0.77)N film only marginally increases to 2.8 +/- 0.1 nm. The slower coarsening rate of the wurtzite structure compared to cubic is indicative of a higher thermal stability.

• 36.
Linköping University, Department of Physics, Chemistry and Biology, Nanostructured Materials. Linköping University, Faculty of Science & Engineering. Univ Lorraine, France.
Linköping University, Department of Physics, Chemistry and Biology, Nanostructured Materials. Linköping University, Faculty of Science & Engineering. SECO Tools AB, Sweden. Univ Lorraine, France. Univ Lorraine, France. Linköping University, Department of Physics, Chemistry and Biology, Plasma and Coating Physics. Linköping University, Faculty of Science & Engineering. SECO Tools AB, Sweden. Linköping University, Department of Physics, Chemistry and Biology, Nanostructured Materials. Linköping University, Faculty of Science & Engineering.
The effect of nitrogen vacancies on initial wear in arc deposited (Ti-0.52,Ti- Al-0.48)N-y, (y < 1) coatings during machining2019In: Surface & Coatings Technology, ISSN 0257-8972, E-ISSN 1879-3347, Vol. 358, p. 452-460Article in journal (Refereed)

Nitrogen deficient c-(Ti0.52Al0.48)Ny, y = 0.92, y = 0.87, and y = 0.75 coatings were prepared in different N-2/Ar discharges on WC-Co inserts by reactive cathodic arc deposition. The microstructure of the y = 0.92 coating show that spinodal decomposition has occurred resulting in the formation of coherent c-TiN- and c-AIN rich domains during cutting. The y = 0.87 and y = 0.75 coatings have exhibited a delay in decomposition due to the presence of nitrogen vacancies that lowers the free energy of the system. In the decomposed structure, grain boundaries and misfit dislocations enhance the diffusion of elements from the workpiece and the substrate (e.g. Fe, Cr, and Co) into the coatings and it becomes more susceptible to crater wear. The y = 0.87 sample displays the highest crater wear resistance because of its dense grain boundaries that prevent chemical wear. The y = 0.92 sample has the best flank wear resistance because the decomposition results in age hardening. The y = 0.75 sample contains the MAX-phase Ti(2)AIN after cutting. The chemical alteration within the y = 0.75 sample and its high amount of macroparticles cause its low wear resistance. The different microstructure evolution caused by different amount of N-vacancies result in distinctive interactions between chip and coating, which also causes difference in the initial wear mechanism of the (Ti,Al)/N-y coatings.

• 37.
Linköping University, Department of Physics, Chemistry and Biology, Nanostructured Materials. Linköping University, Faculty of Science & Engineering.
Phase stability and defect structures in (Ti,Al)N hard coatings2019Doctoral thesis, comprehensive summary (Other academic)

This study highlights the role of nitrogen vacancies and defect structures in engineering hard coatings with enhanced phase stability and mechanical properties for high temperature applications. Titanium aluminum nitride (Ti,Al)N based materials in the form of thin coatings has remained as an outstanding choice for protection of metal cutting tools due to its superior oxidation resistance and high-temperature wear resistance. High-temperature spinodal decomposition of metastable (Ti,Al)N into coherent c-TiN and c-AlN nm-sized domains results in high hardness at elevated temperatures. Even higher thermal input leads to transformation of c-AlN to w-AlN, which is detrimental to the mechanical properties of the coating. One mean to delay this transformation is to introduce nitrogen vacancies.

In this thesis, I show that by combining a reduction of the overall N-content of the c-(Ti,Al)Ny (y < 1) coating with a low substrate bias voltage during cathodic arc deposition an even more pronounced delay of the c-AlN to w-AlN phase transformation is achieved. Under such condition, age hardening is retained until 1100 ˚C, which is the highest temperature reported for (Ti,Al)N films. During cutting operations, the wear mechanism of the cathodicarc-deposited c-(Ti0.52Al0.48)Ny with N-contents of y = 0.92, 0.87, and 0.75 films are influenced by the interplay of nitrogen vacancies, microstructure, and chemical reactions with the workpiece material. The y = 0.75 coating contains the highest number of macroparticles and has an inhomogeneous microstructure after machining, which lower its flank and crater wear resistance. Age hardening of the y = 0.92 sample causes its superior flank wear resistance while the dense structure of the y = 0.87 sample prevents chemical wear that results in excellent crater wear resistance.

Heteroepitaxial c-(Ti1-x,Alx)Ny (y = 0.92, 0.79, and0.67) films were grown on MgO(001) and (111) substrates using magnetron putter deposition to examine the details of their defect structures during spinodal decomposition. At 900 ˚C, the films decompose to form coherent c-AlN- and c-TiN- rich domains with elongated shape along the elastically soft <001> direction. Deformation maps show that most strains occur near the interface of the segregated domains and inside the c-TiN domains. Dislocations favorably aggregate in c-TiN rather than c-AlN because the later has stronger directionality of covalent chemical bonds. At elevated temperature, the domain size of (001) and (111)- oriented c-(Ti,Al)Ny films increases with the nitrogen content. This indicates that there is a delay in coarsening due to the presence of more N vacancies in the film.

The structural and functional properties (Ti1-x,Alx)Ny are also influenced by its Al content (x). TiN and (Ti1-x,Alx)Ny (y = 1, x = 0.63 and x = 0.77) thin films were grown on MgO(111) substrates using magnetron sputtering technique. Both TiN and Ti0.27Al0.63N films are single crystals with cubic structure. (Ti0.23,Al0.77)N film has epitaxial cubic structure only in the first few atomic layers then it transitions to an epitaxial wurtzite layer, with an orientation relationship of c-(Ti0.23,Al0.77)N(111)[1-10]ǀǀw-(Ti0.23,Al0.77)N(0001)[11-20]. The w-(Ti0.23,Al0.77)N shows phase separation of coherent nm-sized domains with varying chemical composition during growth. After annealing at high temperature, the domains in w-(Ti0.23,Al0.77)N have coarsened. The domains in w-(Ti0.23,Al0.77)N are smaller compared to the domains in c-(Ti0.27,Al0.63)N film that has undergone spinodal decomposition. The results that emerged from this thesis are of great importance in the cutting tool industry and also in the microelectronics industry, because the layers examined have properties that are well suited for diffusion barriers.

1. Enhanced thermal stability and mechanical properties of nitrogen deficient titanium aluminum nitride (Ti0.54Al0.46Ny) thin films by tuning the applied negative bias voltage
Open this publication in new window or tab >>Enhanced thermal stability and mechanical properties of nitrogen deficient titanium aluminum nitride (Ti0.54Al0.46Ny) thin films by tuning the applied negative bias voltage
2017 (English)In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 122, no 6, article id 065301Article in journal (Refereed) Published
##### Abstract [en]

Aspects on the phase stability and mechanical properties of nitrogen deficient (Ti0.54Al0.46)N-y alloys were investigated. Solid solution alloys of (Ti,Al)N were grown by cathodic arc deposition. The kinetic energy of the impinging ions was altered by varying the substrate bias voltage from -30V to -80 V. Films deposited with a high bias value of -80V showed larger lattice parameter, finer columnar structure, and higher compressive residual stress resulting in higher hardness than films biased at -30V when comparing their as-deposited states. At elevated temperatures, the presence of nitrogen vacancies and point defects (anti-sites and self-interstitials generated by the ion-bombardment during coating deposition) in (Ti0.54Al0.46)N-0.87 influence the driving force for phase separation. Highly biased nitrogen deficient films have point defects with higher stability during annealing, which cause a delay of the release of the stored lattice strain energy and then accelerates the decomposition tendencies to thermodynamically stable c-TiN and w-AlN. Low biased nitrogen deficient films have retarded phase transformation to w-AlN, which results in the prolongment of age hardening effect up to 1100 degrees C, i.e., the highest reported temperature for Ti-Al-N material system. Our study points out the role of vacancies and point defects in engineering thin films with enhanced thermal stability and mechanical properties for high temperature hard coating applications. Published by AIP Publishing.

##### Place, publisher, year, edition, pages
American Institute of Physics (AIP), 2017
##### National Category
Other Materials Engineering
##### Identifiers
urn:nbn:se:liu:diva-140514 (URN)10.1063/1.4986350 (DOI)000407742400032 ()
##### Note

Funding Agencies|European Unions Erasmus Mundus doctoral program in Materials Science and Engineering (DocMASE); Swedish Research Council [621-2012-4401]; Swedish government strategic research area grant AFM - SFO MatLiU [2009-00971]; VINNOVA [2013-02355]; DFG; federal state government of Saarland [INST 256/298-1 FUGG]; European Regional Development Fund [AME-Lab C/4-EFRE-13/2009/Br]

Available from: 2017-09-11 Created: 2017-09-11 Last updated: 2019-05-27
2. The effect of nitrogen vacancies on initial wear in arc deposited (Ti-0.52,Ti- Al-0.48)N-y, (y < 1) coatings during machining
Open this publication in new window or tab >>The effect of nitrogen vacancies on initial wear in arc deposited (Ti-0.52,Ti- Al-0.48)N-y, (y < 1) coatings during machining
2019 (English)In: Surface & Coatings Technology, ISSN 0257-8972, E-ISSN 1879-3347, Vol. 358, p. 452-460Article in journal (Refereed) Published
##### Abstract [en]

Nitrogen deficient c-(Ti0.52Al0.48)Ny, y = 0.92, y = 0.87, and y = 0.75 coatings were prepared in different N-2/Ar discharges on WC-Co inserts by reactive cathodic arc deposition. The microstructure of the y = 0.92 coating show that spinodal decomposition has occurred resulting in the formation of coherent c-TiN- and c-AIN rich domains during cutting. The y = 0.87 and y = 0.75 coatings have exhibited a delay in decomposition due to the presence of nitrogen vacancies that lowers the free energy of the system. In the decomposed structure, grain boundaries and misfit dislocations enhance the diffusion of elements from the workpiece and the substrate (e.g. Fe, Cr, and Co) into the coatings and it becomes more susceptible to crater wear. The y = 0.87 sample displays the highest crater wear resistance because of its dense grain boundaries that prevent chemical wear. The y = 0.92 sample has the best flank wear resistance because the decomposition results in age hardening. The y = 0.75 sample contains the MAX-phase Ti(2)AIN after cutting. The chemical alteration within the y = 0.75 sample and its high amount of macroparticles cause its low wear resistance. The different microstructure evolution caused by different amount of N-vacancies result in distinctive interactions between chip and coating, which also causes difference in the initial wear mechanism of the (Ti,Al)/N-y coatings.

##### Place, publisher, year, edition, pages
ELSEVIER SCIENCE SA, 2019
##### Keywords
Wear mechanism; Nitrogen vacancies; (Ti, Al)N; Spinodal decomposition; MAX-phase; Cathodic arc
##### National Category
Manufacturing, Surface and Joining Technology
##### Identifiers
urn:nbn:se:liu:diva-154689 (URN)10.1016/j.surfcoat.2018.11.062 (DOI)000456762300054 ()
##### Note

Funding Agencies|European Unions Erasmus Mundus doctoral program in Materials Science and Engineering (DocMASE); Swedish Research Council [2017-03813, 2017-06701]; Swedish government strategic research area grant AFM, LiU [2009-00971]; VINNOVA (FunMat-II project) [2016-05156]

Available from: 2019-02-28 Created: 2019-02-28 Last updated: 2019-05-27