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• 1.
COMSATS Univ Islamabad, Pakistan; Hubei Univ, Peoples R China.
COMSATS Univ Islamabad, Pakistan. Univ Calif Los Angeles, CA 90095 USA. COMSATS Univ Islamabad, Pakistan. COMSATS Univ Islamabad, Pakistan. COMSATS Univ Islamabad, Pakistan; Hubei Univ, Peoples R China. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering. COMSATS Univ Islamabad, Pakistan.
Effect of sintering temperature on properties of LiNiCuZn-Oxide: a potential anode for solid oxide fuel cell2019In: MATERIALS RESEARCH EXPRESS, ISSN 2053-1591, Vol. 6, no 10, article id 105505Article in journal (Refereed)

Crystal structure and surface morphology play vital role in the performance of Solid Oxide Fuel cells (SOFCs) anode. Sufficient electrocatalytic activity and high conductivity are the key requirements for anode to enhance the electrochemical capability. In current work, sintering temperature effects are investigated on the properties of advanced LiNiCuZn-Oxide based electrode for solid oxide fuel cells (SOFCs). The powders were prepared by simple solid-state reaction method was followed by sintering at different temperatures (700 degrees C-1200 degrees C). Moreover, various characterization techniques have been employed to investigate the sintering temperatures effects on the crystallite size, morphology, particle size, energy band gap and absorption peaks. The energy gap (Eg) was observed to increase from 2.94 eV to 3.32 eV and dc conductivity decreased from 9.084 Scm(-1) to 0.46 Scm(-1) by increasing sintering temperature from 700 degrees C to 1200 degrees C. Additionally, the best fuel cell performance of 0.90 Wcm(-2) was achieved for LiNiCuZn-Oxide sintered at 700 degrees C using H-2/air as a fuel and oxidant and it decreased to 0.17 Wcm(-2) for powders sintered at 1200 degrees C. Based on these results, we can conclude that 700 degrees C is the best optimum temperature for these chemical compositions, where all parameters of electrode are as per SOFCs requirement.

• 2.
COMSATS Univ Islamabad, Pakistan; Univ Okara, Pakistan.
Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering. COMSATS Univ Islamabad, Pakistan. King Saud Univ, Saudi Arabia; Univ Calif Los Angeles, CA 90095 USA. COMSATS Univ Islamabad, Pakistan. COMSATS Univ Islamabad, Pakistan. COMSATS Univ Islamabad, Pakistan. Univ Okara, Pakistan. Loughborough Univ, England.
Promising electrochemical study of titanate based anodes in direct carbon fuel cell using walnut and almond shells biochar fuel2019In: Journal of Power Sources, ISSN 0378-7753, E-ISSN 1873-2755, Vol. 434, article id 126679Article in journal (Refereed)

The direct carbon fuel cell (DCFC) is an efficient device that converts the carbon fuel directly into electricity with 100% theoretical efficiency contrary to practical efficiency around 60%. In this paper four perovskite anode materials La0.4Sr0.6M0.09Ti0.91O3-delta (M = Ni, Fe, Co, Zn) have been prepared using sol-gel technique to measure the performance of the device using solid fuel. These materials have shown reasonable stability and conductivity at 700 degrees C. Further structural analysis of as-prepared anode material using XRD technique reveals a single cubic perovskite structure with average crystallite size roughly 47 nm. Walnut and almond shells biochar have also been examined as a fuel in DCFC at the temperature range 400-700 degrees C. In addition, Elemental analysis of walnut and almond shells has shown high carbon content and low nitrogen and sulfur contents in the obtained biochar. Subsequently, the superior stability of as-prepared anode materials is evident by thermogravimetric analysis in pure N-2 gas atmosphere. Conversely, the LSFT anode has shown the highest electronic conductivity of 7.53Scm(-1) at 700 degrees C. The obtained power density for LSFTO3-delta composite anode mixed in sub-bituminous coal, walnut and almond shells biochar is of 68, 55, 48 mWcm(-2) respectively. A significant improvement in performance of DCFC (78 mWcm(-2)) was achieved.

• 3.
Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering. Department of Electrical and Computer Engineering, University of Nebraska-Lincoln, USA. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering. Department of Electrical and Computer Engineering, University of Nebraska-Lincoln, USA / Department of Physics and Optical Science, University of North Carolina at Charlotte, USA. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering. Department of Electrical and Computer Engineering, University of Nebraska-Lincoln, USA. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
Cavity-enhanced optical Hall effect in epitaxial graphene detected at terahertz frequencies2017In: Applied Surface Science, ISSN 0169-4332, E-ISSN 1873-5584, Vol. 421, p. 357-360Article in journal (Refereed)

Cavity-enhanced optical Hall effect at terahertz (THz) frequencies is employed to determine the free charge carrier properties in epitaxial graphene (EG) with different number of layers grown by high-temperature sublimation on 4H-SiC(0001). We find that one monolayer (ML) EG possesses p-type conductivity with a free hole concentration in the low 1012 cmï¿œï¿œï¿œ2 range and a free hole mobility parameter as high as 1550 cm2/Vs. We also find that 6 ML EG shows n-type doping behavior with a much lower free electron mobility parameter of 470 cm2/Vs and an order of magnitude higher free electron density in the low 1013 cmï¿œï¿œï¿œ2 range. The observed differences are discussed. The cavity-enhanced THz optical Hall effect is demonstrated to be an excellent tool for contactless access to the type of free charge carriers and their properties in two-dimensional materials such as EG.

• 4.
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
• 5.
Nanjing University, Peoples R China; Nanjing University, Peoples R China; Nanjing University of Science and Technology, Peoples R China.
Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, The Institute of Technology. Nanjing University, Peoples R China; Nanjing University, Peoples R China. Nanjing University, Peoples R China; Nanjing University, Peoples R China. Nanjing University, Peoples R China; Nanjing University, Peoples R China. Nanjing University, Peoples R China; Nanjing University, Peoples R China. Nanjing University, Peoples R China; Nanjing University, Peoples R China. Nanjing University, Peoples R China; Nanjing University, Peoples R China. Nanjing University, Peoples R China; Nanjing University, Peoples R China. Nanjing University, Peoples R China; Nanjing University, Peoples R China. Nanjing University, Peoples R China; Nanjing University, Peoples R China. Nanjing University, Peoples R China; Nanjing University, Peoples R China. Nanjing University, Peoples R China; Nanjing University, Peoples R China.
Room-temperature multiferroic properties in NiBi2O42010In: Europhysics letters, ISSN 0295-5075, E-ISSN 1286-4854, Vol. 89, no 2, article id 27004Article in journal (Refereed)

Magnetism and ferroelectricity at room temperature are observed in the NiBi2O4 ceramics. Both the time reversal and the inversion symmetry of the structure (space group F-43m) are broken. The saturation magnetization is 0.028 emu/g and the saturation polarization 2P(s) similar to 4.0 mu C/cm(2). NiBi2O4 also shows other room-temperature multiferroic properties, e. g. the piezoelectric coefficient (d(33)), the polarized dielectric character, the magneto-dielectric response and the magnetoelectric effect. Copyright (C) EPLA, 2010

• 6.
Linköping University, Department of Science and Technology. Linköping University, Faculty of Science & Engineering.
Linköping University, Department of Science and Technology. Linköping University, Faculty of Science & Engineering. Department of Material Engineering, University of Toulon, FR-83041 Toulon, France . Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering. Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering. Linköping University, Faculty of Science & Engineering. Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering. Linköping University, Department of Science and Technology, Physics and Electronics. Linköping University, Faculty of Science & Engineering. Linköping University, Department of Science and Technology, Physics and Electronics. Linköping University, Faculty of Science & Engineering. Linköping University, Department of Science and Technology, Physics and Electronics. Linköping University, Faculty of Science & Engineering.
Low-temperature growth of polyethylene glycol-doped BiZn2VO6 nanocompounds with enhanced photoelectrochemical properties2017In: Journal of Materials Chemistry A, ISSN 2050-7488, Vol. 5, no 3, p. 1112-1119Article in journal (Refereed)

We demonstrate scalable, low-cost and low-temperature (<100 °C) aqueous chemical growth of bismuth–zinc vanadate (BiZn2VO6) nanocompounds by BiVO4 growth on ZnO nanobelts (NBs). The nanocompounds were further doped with polyethylene glycol (PEG) to tune the electronic structure of the materials, as a means to lower the charge carrier recombination rate. The chemical composition, morphology, and detailed nanostructure of the BiZn2VO6 nanocompounds were characterized. They exhibit rice-like morphology, are highly dense on the substrate and possess a good crystalline quality. Photoelectrochemical characterization in 0.1 M lithium perchlorate in carbonate propylene shows that BiZn2VO6 nanocompounds are highly suitable as anodes for solar-driven photoelectrochemical applications, providing significantly better performance than with only ZnO NBs. This performance could be attributed to the heterogeneous catalysis effect at nanocompound and ZnO NB interfaces, which have enhanced the electron transfer process on the electrode surface. Furthermore, the charge collection efficiency could be significantly improved through PEG doping of nanocompounds. The photocurrent density of PEG-doped BiZn2VO6 nanocompounds reached values of 2 mA cm−2 at 1.23 V (vs. Ag/AgCl), over 60% larger than that of undoped BiZn2VO6 nanocompounds. Photoluminescence emission experiments confirmed that PEG plays a crucial role in lowering the charge carrier recombination rate. The presented BiZn2VO6 nanocompounds are shown to provide highly competitive performance compared with other state-of-the art photoelectrodes.

• 7.
Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
Atom Probe Tomography of Hard Nitride and Boride Thin Films2019Doctoral thesis, comprehensive summary (Other academic)

Hard ceramic thin films, including TiSiN, ZrAlN, ZrB2, and ZrTaB2, with applications for wear-resistant coatings, have been studied using atom probe tomography and correlated with several other analytical techniques, including X-ray diffraction, electron microscopy, and elastic recoil detection analysis. Outstanding obstacles for quantitative atom probe tomography of ceramic thin films have been surmounted.

Mass spectral overlaps in TiSiN, which make 28Si indistinguishable from 14N, was resolved by isotopic substitution with 15N, and the nanostructural distribution of elements was thus revealed in 3-D, which enabled the identification of additional structural elements within the nanostructured Ti0.81Si0.1915N film. Improvements to the growth model of TiSiN by cathodic arc deposition was suggested.

A self-organized nanolabyrinthine structure of ZrAlN, consisting of standing lamellae of fcc-ZrN and hexagonal AlN, was investigated with focus on the onset and limits of the self-organization. The local crystallographic orientational relationships were (001)ZrN || (0001)AlN and <110>ZrN || <2-1-10>AlN. Close to the MgO substrates, a smooth transition region was formed, going from segregated and disordered to the self-organized nanolabyrinthine structure. With increased growth temperature, coarse (111)-oriented ZrN grains occasionally precipitated and locally replaced the nanolabyrinthine structure. Significant local magnification effects rendered the Zr and N signals unusable, thereby inhibiting quantitative compositional analysis of the constituent phases, but the nanostructure was resolved using the Al signal.

Ceramic materials are often affected by correlated evaporation, which can result in losses due to the detector dead-time/space. A compositional correction procedure was suggested, tested against an established procedure, and applied to ZrB2. The correction was found to be less dependent on the isotope abundances and background correction compared to the established procedure. While losses due to dead-time/space occur in atom probe tomography of all materials, the correlative field evaporation behavior of ceramics significantly increases the compositional error. The evaporation behavior of ZrB2 was therefore thoroughly investigated and evidence of preferential retention, correlated evaporation, and inhomogeneous field distributions at a low-index pole was presented. The high mass resolution, relatively low multiple events percentage, and quality of the co-evaporation correlation data was partly attributed to the crystal structure and film orientation, which promoted a layer-by-layer field evaporation.

The evaporation behavior of the related ZrTaB2 films was found to be similar to that of ZrB2. The distribution of Ta in relation to Zr was investigated, showing that the column boundaries were both metal- and Ta-rich, and that there was a significant amount of Ta in solid solution within the columns.

In addition, an instrumental artefact previously not described in atom probe tomography was found in several of the materials investigated in this thesis. The artefact consists of high-density lines along the analysis direction, which cannot be related to pole artefacts. The detection system of the atom probe was identified as the cause, because the artefact patterns on detector histograms coincided with the structure of the microchannel plate. Inconsistencies in the internal boundaries of the microchannel plate multifibers from the manufacturing process can influence the signal to the detector and locally increase the detection efficiency in a pattern characteristic to the microchannel plate in question.

Altogether, this thesis shows that atom probe tomography of nitride and boride thin films is burdened by several artefacts and distortions, but that relevant material outcomes can nevertheless be achieved by informed choices of film isotopic constituents and analytical parameters, exclusion of heavily distorted regions (such as pole artefacts), and the use of compositional correction procedures when applicable.

1. Resolving Mass Spectral Overlaps in Atom Probe Tomography by Isotopic Substitutions: Case of TiSi15N
Open this publication in new window or tab >>Resolving Mass Spectral Overlaps in Atom Probe Tomography by Isotopic Substitutions: Case of TiSi15N
2018 (English)In: Ultramicroscopy, ISSN 0304-3991, E-ISSN 1879-2723, Vol. 184, p. 51-60Article in journal (Refereed) Published
##### Abstract [en]

Mass spectral overlaps in atom probe tomography (APT) analyses of complex compounds typically limit the identification of elements and microstructural analysis of a material. This study concerns the TiSiN system, chosen because of severe mass-to-charge-state ratio overlaps of the 14N+ and 28Si2+ peaks as well as the 14N$\tiny\frac{+}{2}$ and 28Si2+ peaks. By substituting 14N with 15N, mass spectrum peaks generated by ions composed of one or more N atoms will be shifted toward higher mass-to-charge-state ratios, thereby enabling the separation of N from the predominant Si isotope. We thus resolve thermodynamically driven Si segregation on the nanometer scale in cubic phase Ti1-xSix15N thin films for Si contents 0.08 ≤ x ≤ 0.19 by APT, as corroborated by transmission electron microscopy. The APT analysis yields a composition determination that is in good agreement with energy dispersive X-ray spectroscopy and elastic recoil detection analyses. Additionally, a method for determining good voxel sizes for visualizing small-scale fluctuations is presented and demonstrated for the TiSiN system.

##### Place, publisher, year, edition, pages
Elsevier, 2018
##### National Category
Physical Sciences
##### Identifiers
urn:nbn:se:liu:diva-122721 (URN)10.1016/j.ultramic.2017.08.004 (DOI)000415650200007 ()28850866 (PubMedID)
##### Note

Funding Agencies:VINN Excellence Center on Functional Nanoscale Materials (FunMat) [2007-00863]; Swedish Research Council (VR) project [2013-4018]; Swedish Government Strategic Research Area Grant in Materials Science (Grant SFO Mat-LiU) on Advanced Functional Materials [2009-00971]; Knut and Alice Wallenberg Project Isotope

Available from: 2015-11-18 Created: 2015-11-18 Last updated: 2019-08-01Bibliographically approved
2. Self-organized Nanostructuring in Zr0.64Al0.36N Thin Films Studied by Atom Probe Tomography
Open this publication in new window or tab >>Self-organized Nanostructuring in Zr0.64Al0.36N Thin Films Studied by Atom Probe Tomography
2016 (English)In: Thin Solid Films, ISSN 0040-6090, E-ISSN 1879-2731, p. 233-238Article in journal (Refereed) Published
##### Abstract [en]

We have applied atom probe tomography (apt) to analyze the selforganized structure of wear-resistant Zr0.64Al0.36N thin films grown by magnetron sputtering. Transmission electron microscopy shows that these films grow as a two-dimensional nanocomposite, consisting of interleaved lamellae in a labyrinthine structure, with a size scale of ∼ 5 nm. The structure was recovered in the Al apt signal, while the Zr and N data lacked structural information due to severe local magnification effects. The onset of the self-organized growth was observed to occur locally by nucleation, at 5-8 nm from the MgO substrate, after increasing Zr-Al compositional fluctuations. Finally, it was observed that the self-organized growth mode could be perturbed by renucleation of ZrN.

##### Place, publisher, year, edition, pages
Elsevier, 2016
##### National Category
Natural Sciences
##### Identifiers
urn:nbn:se:liu:diva-84258 (URN)10.1016/j.tsf.2016.07.034 (DOI)000381939700037 ()
##### Note

Funding agencies: VINN Excellence Center on Functional Nanoscale Materials; Swedish Research Council; Swedish Government Strategic Faculty Grant in Materials Science (SFO Mat-LiU) at Linkoping University; Swedish Governmental Agency for Innovation Systems (Vinnova) [2011-0

Vid tiden för disputationen förelåg publikationen som manuskript

Available from: 2012-10-03 Created: 2012-10-03 Last updated: 2019-08-02Bibliographically approved
3. Strategy for simultaneously increasing both hardness and toughness in ZrB2-rich Zr1-xTaxBy thin films
Open this publication in new window or tab >>Strategy for simultaneously increasing both hardness and toughness in ZrB2-rich Zr1-xTaxBy thin films
2019 (English)In: Journal of Vacuum Science & Technology. A. Vacuum, Surfaces, and Films, ISSN 0734-2101, E-ISSN 1520-8559, Vol. 37, no 3, article id 031506Article in journal (Refereed) Published
##### Abstract [en]

Refractory transition-metal diborides exhibit inherent hardness. However, this is not always sufficient to prevent failure in applications involving high mechanical and thermal stress, since hardness is typically accompanied by brittleness leading to crack formation and propagation. Toughness, the combination of hardness and ductility, is required to avoid brittle fracture. Here, the authors demonstrate a strategy for simultaneously enhancing both hardness and ductility of ZrB2-rich thin films grown in pure Ar on Al2O3(0001) and Si(001) substrates at 475 degrees C. ZrB2.4 layers are deposited by dc magnetron sputtering (DCMS) from a ZrB2 target, while Zr1-xTaxBy alloy films are grown, thus varying the B/metal ratio as a function of x, by adding pulsed high-power impulse magnetron sputtering (HiPIMS) from a Ta target to deposit Zr1-xTaxBy alloy films using hybrid Ta-HiPIMS/ZrB2-DCMS sputtering with a substrate bias synchronized to the metal-rich portion of each HiPIMS pulse. The average power P-Ta (and pulse frequency) applied to the HiPIMS Ta target is varied from 0 to 1800W (0 to 300 Hz) in increments of 600W (100 Hz). The resulting boron-to-metal ratio, y = B/(Zr+Ta), in as-deposited Zr1-xTaxBy films decreases from 2.4 to 1.5 as P-Ta is increased from 0 to 1800W, while x increases from 0 to 0.3. A combination of x-ray diffraction (XRD), glancing-angle XRD, transmission electron microscopy (TEM), analytical Z-contrast scanning TEM, electron energy-loss spectroscopy, energy-dispersive x-ray spectroscopy, x-ray photoelectron spectroscopy, and atom-probe tomography reveals that all films have the hexagonal AlB2 crystal structure with a columnar nanostructure, in which the column boundaries of layers with 0 amp;lt;= x amp;lt; 0.2 are B-rich, whereas those with x amp;gt;= 0.2 are Ta-rich. The nanostructural transition, combined with changes in average column widths, results in an similar to 20% increase in hardness, from 35 to 42 GPa, with a simultaneous increase of similar to 30% in nanoindentation toughness, from 4.0 to 5.2MPa root m. Published by the AVS.

##### Place, publisher, year, edition, pages
A V S AMER INST PHYSICS, 2019
##### National Category
Inorganic Chemistry
##### Identifiers
urn:nbn:se:liu:diva-159001 (URN)10.1116/1.5093170 (DOI)000472182400035 ()
##### Note

Funding Agencies|Swedish Research Council VR [2014-5790, 2018-03957, 642-2013-8020]; Knut and Alice Wallenbergs foundation [KAW 2015.0043]; VINNOVA [2018-04290]; Aforsk Foundation [16-359]; Carl Tryggers Stiftelse [CTS 15: 219, CTS 17: 166, CTS 14: 431]; Swedish Government Strategic Research Area in Materials Science on Functional Materials at Linkoping University (Faculty Grant SFO Mat LiU) [2009 00971]

Available from: 2019-07-19 Created: 2019-07-19 Last updated: 2019-08-01
4. Atom probe tomography field evaporation characteristics and compositional corrections of ZrB2
Open this publication in new window or tab >>Atom probe tomography field evaporation characteristics and compositional corrections of ZrB2
2019 (English)In: Materials Characterization, ISSN 1044-5803, E-ISSN 1873-4189, Vol. 156, article id 109871Article in journal (Refereed) Published
##### Abstract [en]

The microstructure of stoichiometric ZrB2.0 and B over-stoichiometric ZrB2.5 thin films has been studied using atom probe tomography (APT), X-ray diffraction, and transmission electron microscopy. Both films consist of columnar ZrB2 grains with AlB2-type crystal structure. The narrow stoichiometry range of ZrB2 results in the presence of separate disordered B-rich boundaries even in ZrB2.0. At higher average B content, specifically ZrB2.5, the formation of a continuous network around the sides of the ZrB2 columns is promoted. In addition, the APT field evaporation characteristics of ZrB2 and its influence on the measured local composition has been studied and compared to the average composition from elastic recoil detection analysis (ERDA). Differences in the measured average compositions of the two techniques are explained by the APT detector dead-time/space. A new pile-up pairs correction procedure based on co-evaporation correlation data was thus employed here for the APT data and compared with the 10B-method (the B equivalence of the 13C-method), as well as the combination of both methods. In ZrB2.0, all of the applied compositional correction methods were found to reduce the compositional difference when appropriate isotopic abundances were used. In ZrB2.5, the inhomogeneity of the film likely increased the local APT composition to such an extent that even conservative correction procedures overestimated the B content compared to the ERDA reference. The strengths of the pile-up pairs correction compared the 10B and the combined methods are higher precision, due to it being less dependent on the accuracy of estimated isotopic abundances, and that the correction itself is not dependent on careful background correction of the mass spectrum.

##### Place, publisher, year, edition, pages
Elsevier, 2019
##### Keywords
Atom probe tomography (APT), Zirconium diboride (ZrB), Field evaporation characteristics of borides, Elastic recoil detection analysis (ERDA), Compositional correction procedures, Transition metal diborides
##### National Category
Physical Sciences
##### Identifiers
urn:nbn:se:liu:diva-160356 (URN)10.1016/j.matchar.2019.109871 (DOI)
Available from: 2019-09-19 Created: 2019-09-19 Last updated: 2019-09-20Bibliographically approved
• 8.
Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering. Drexel University, PA 19104 USA.
University of Poitiers, France. National Academic Science Ukrain, Ukraine. National Academic Science Ukrain, Ukraine. Nucl Research Centre Negev, Israel. Drexel University, PA 19104 USA. University of Poitiers, France.
Structure and thermal expansion of (Cr-x,V1-x)(n+1)AlCn phases measured by X-ray diffraction2017In: Journal of the European Ceramic Society, ISSN 0955-2219, E-ISSN 1873-619X, Vol. 37, no 1, p. 15-21Article in journal (Refereed)

MAX phases in the (Crx,V1-x)(n+1)AlCn,system were synthesized by reactive sintering or hot isostatic pressing of elemental powders at temperatures between 1400 degrees C and 1600 degrees C. For n=1, a complete range (0 amp;lt;= x amp;lt;= 1) of solid solutions was found; for n=2 and 3 the solubility ranges were 0.25 amp;lt;= x amp;lt;= 0.75 and 0 amp;lt;= x amp;lt;= 0.5, respectively. Powder X-ray diffraction revealed that the lattice parameters of all (Cr-x,V1-x)(n+1)AlCn solid solutions followed Vegards law. The thermal expansion coefficients of the various compounds were determined from Rietveld refinements of X-Ray patterns obtained at temperatures between ambient and 800 degrees C. For the n=1 and 3 phases the thermal expansion coefficients were almost isotropic; those for the n=2, however, were quite anisotropic with the expansion along the a-axis being significantly larger than along the c-axis. As a general trend, vanadium rich compounds have smaller thermal expansion coefficients than their Cr-rich counterparts. (C) 2016 Elsevier Ltd. All rights reserved.

• 9.
Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology. Lawrence Berkeley National Laboratory, Berkeley, California, USA. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
High-Resolution Raman and Luminescence Spectroscopy of Isotope-Pure (SiC)-Si-28-C-12, Natural and C-13 - Enriched 4H-SIC2014In: Silicon Carbide and Related Materials 2013, PTS 1 AND 2, Trans Tech Publications Inc., 2014, Vol. 778-780, p. 471-474Conference paper (Refereed)

The optical properties of isotope-pure (SiC)-Si-28-C-12, natural SiC and enriched with C-13 isotope samples of the 4H polytype are studied by means of Raman and photoluminescence spectroscopies. The phonon energies of the Raman active phonons at the Gamma point and the phonons at the M point of the Brillouin zone are experimentally determined. The excitonic bandgaps of the samples are accurately derived using tunable laser excitation and the phonon energies obtained from the photoluminescence spectra. Qualitative comparison with previously reported results on isotope-controlled Si is presented.

• 10.
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. Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology. Argonne National Laboratory, Illinois, USA. Linköping University, Department of Physics, Chemistry and Biology, Nanostructured Materials. Linköping University, The Institute of Technology. Seco Tools AB, Fagersta, Sweden. Linköping University, Department of Physics, Chemistry and Biology, Nanostructured Materials. Linköping University, The Institute of Technology.
Early stage spinodal decomposition and microstructure evolution in TiAlN: A combined in-situ SAXS and phase field studyManuscript (preprint) (Other academic)

This paper describes in detail the microstructure and phase evolution in Ti0.33Al0.67N and Ti0.50Al0.50N coatings during isothermal annealing, studied by in-situ small angle x-ray scattering (SAXS), in combination with phase field simulations. We show that the isostructural spinodal decomposition occurs in two stages. During the initial stage, the phase segregation proceeds with a constant size of AlN- and TiN-rich domains with an experimentally measured radius of ~0.7 nm for 5 and 20 min at 900 and 850 °C respectively in the Ti0.50Al0.50N alloy. The length of  the initial stage depends on temperature as well as metal composition, and is shorter for the higher Al-content  coating. After the initial stage, the coherent cubic AlN- and TiN-rich domains coarsen. The coarsening process is kinetically limited by diffusion, which allowed us to estimate the diffusivity and activation energies of the metals to 1.4·10-7 m2s-1 and 3.14 eV at-1 respectively.

• 11.
Luleå Tekniska Universitet.
Samband mellan tjockleken hos PVD-skikt och förslitningsbeteendet vid svarvning2008Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis

This project has as main goal to study the influence of the coating thickness, deposited by arc-PVD- technology, on the wear resistance of coated cemented carbide inserts in three different turning operations. An additional effort has also been made to develop a new test method for evaluating flank wear resistance. Three different coating types (Coating A, Coating B and Coating C) have been studied in three distinctive thicknesses (2, 4 and 6 μ m) for each type. For two of the coating types (Coating A and B) special studies has been done with the thickest coating, creating two additional coating versions of the thickest coating, by changing various deposition parameters, with the aim to enhance the cohesive properties of the coating and lower the residual stresses at the cutting edge. The results show increased crater wear resistance with increased coating thickness for all coating types, but the amount of increase changes with coating type (Coating A>B>C). Flaking wear resistance decreased with increased coating thickness for all coating types. Further the high temperature version of Coating A, showed a significant increase in the flaking wear resistance compared to the standard version of Coating A. The flank wear test showed an increased resistance with thicker coatings in all cases except for the 6 μ m version of Coating C. The flank wear resistance of the most flank wear resistant coatings (Coating B, C) was also successfully examined in a new developed test method. The method suppressed excessive crater wear on the rake face and presented a high abrasive wear rate on the flank and some flaking on the rake face. The amount of flaking is judged not to influence the testing of the flank wear resistance. For all the tested coatings in the new test an increase in the coating thickness resulted in better flank wear resistance.

• 12.
Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
Homo-epitaxial growth on low-angle off cut 4H-SiC substrate2014In: SILICON CARBIDE AND RELATED MATERIALS 2013, PTS 1 AND 2, Trans Tech Publications Inc., 2014, Vol. 778-780, p. 131-134Conference paper (Refereed)

The growth of 4H-SiC epilayers on 1.28 degrees off-cut substrates is reported in this study and comparison when using standard 4 degrees and 8 degrees off-cut substrates is added. Growth at high temperature is needed for the polytype stability, whereas low C/Si is requested to decrease both triangular defects density and roughness of the grown surface. An in-situ etching with Si rich ambient allows the growth of epilayers with specular surface. The formation of Si droplets can be observed on the grown surfaces when lowering the growth temperature and appears first for the high off-cut angle.

• 13.
US DOE-National Energy Technology Laboratory, Pittsburgh, PA, USA and University of Pittsburgh, USA.
Carnegie Mellon University, Pittsburgh, PA, USA . US DOE-National Energy Technology Laboratory, Pittsburgh, PA, USA and University of Pittsburgh, USA. US DOE-National Energy Technology Laboratory, Pittsburgh, PA, USA and University of Pittsburgh, USA. US DOE-National Energy Technology Laboratory, Pittsburgh, PA, USA and University of Pittsburgh, USA.
Highly stable, mesoporous mixed lanthanum–cerium oxides with tailored structure and reducibility2011In: Journal of Materials Science, ISSN 0022-2461, E-ISSN 1573-4803, Vol. 46, no 9, p. 2928-2937Article in journal (Refereed)

Pure and mixed lanthanum and cerium oxides were synthesized via a reverse microemulsion-templated route. This approach yields highly homogeneous and phase-stable mixed oxides with high surface areas across the entire range of La:Ce ratios from pure lanthana to pure ceria. Surprisingly, all mixed oxides show the fluorite crystal structure of ceria, even for lanthanum contents as high as 90%. Varying the La:Ce ratio not only allows tailoring of the oxide morphology (lattice parameter, pore structure, particle size, and surface area), but also results in a fine-tuning of the reducibility of the oxide which can be explained by the creation of oxygen vacancies in the ceria lattice upon La addition. Such finely controlled syntheses, which enable the formation of stable, homogeneous mixed oxides across the entire composition range, open the path towards functional tailoring of oxide materials, such as rational catalyst design via fine-tuning of redox activity.

• 14.
Nanjing University, Peoples R China; Chinese Academic Science, Peoples R China.
Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, The Institute of Technology. Nanjing University, Peoples R China; Chinese Academic Science, Peoples R China. Nanjing University, Peoples R China; Chinese Academic Science, Peoples R China. Nanjing University, Peoples R China; Chinese Academic Science, Peoples R China. Nanjing University, Peoples R China; Chinese Academic Science, Peoples R China.
Ferroelectric and magnetoelectric behaviors of multiferroic BiFeO3 and piezoelectric-magnetostrictive composites2008In: Journal of Electroceramics, ISSN 1385-3449, E-ISSN 1573-8663, Vol. 21, no 1-4, p. 78-84Article in journal (Refereed)

In this paper we overview our recent work on ferroelectric and magnetoelectric coupling behaviors of multiferroic doped BiFeO3 (BFO) and piezoelectric-magnetostrictive composites. Using rapid liquid sintering method we prepare single-phase BFO ceramics of excellent ferroelectric property. The BFO thin films on Pt-coated silicon wafers by pulsed laser deposition show large remnant polarization but serious ferroelectric switching fatigue. A series of piezoelectric-magnetostrictive composite structures in bulk and thin film forms are prepared and giant magnetoelectric coupling effect of them is observed. The experimentally measured results are confirmed by numerical modeling based on piezoelectric and magnetostrictive constitution equations.

• 15.
Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering. Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering. Uppsala Univ, Sweden. Linköping University, Department of Physics, Chemistry and Biology. Linköping University, Faculty of Science & Engineering. SKF Res and Technol Dev Ctr, Netherlands. Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, Faculty of Science & Engineering. Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering. Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering. Evatec AG, Switzerland. Uppsala Univ, Sweden. Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering. Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
Synthesis and characterization of (Ti1-xAlx)B2+Delta thin films from combinatorial magnetron sputtering2019In: Thin Solid Films, ISSN 0040-6090, E-ISSN 1879-2731, Vol. 669, p. 181-187Article in journal (Refereed)

(Ti1-xAlx)B2+Delta films with a lateral composition gradient of x = [0.30-0.66] and Delta = [0.07-1.22] were deposited on an Al2O3 wafer by dual magnetron sputtering at 400 degrees C from sintered TiB2 and AlB2 targets. Composition analysis indicates that higher Ti:Al ratios favor overstoichiometry in B and a reduced incorporation of O. Transmission electron microscopy reveals distinctly different microstructures of Ti- and Al-rich compositions, with formation of characteristic conical growth features for the latter along with a lower degree of crystallinity and significantly less tissue phase from B segregation at the grain boundaries. For Al-rich films, phase separation into Ti- and Al-rich diboride nanometer-size domains is observed and interpreted as surface-initiated spinodal decomposition. The hardness of the films ranges from 14 to 28 GPa, where the higher values were obtained for the Ti-rich regions of the metal boride.

The full text will be freely available from 2020-10-26 15:00
• 16.
Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
Theoretical and experimental studies of ternary and quaternary nitrides for machining and thermoelectric materials2019Doctoral thesis, comprehensive summary (Other academic)

Nitrides are used as coatings and thin films for a wide range of applications. The study and use of nitrides in the recent decades have shifted towards ternary, quaternary or even higher order (complex) nitrides. There is an interest to use ternary and quaternary nitrides for machining and thermoelectric materials, because it gives the possibility to choose composition and thereby design the materials properties. This thesis presents research results on TiAlN and and TiAlN-based coatings that are used as hard coatings for machining and on ternary scandium nitrides that are of interest for thin films for thermoelectric applications. The high-pressure high-temperature behavior of cubic TiAlN deposited on cubic boron nitride has been experimentally studied. It has been shown that the spinodal decomposition, which means decomposition into cubic domains enriched in TiN and AlN, is delayed as a result of high pressure compared to ambient pressure. No chemical interaction between coating and substrate occurs. TiZrAlN has been theoretically and experimentally studied at high temperature. The results show that the when Zr-content is decreased and the Al-content is increased the decomposition route changes from nucleation and growth to spinodal decomposition. The microstructure evolution with temperature depends on the initial composition. In the case where the decompositon starts with only spinodal decomposition the microstructure at 1100 °C consists of domains that are larger than in the case where the decomposition occurs by nucleation and growth. ScMN2 (M=V, Nb, Ta) phases have been experimentally demonstrated for M=Nb and Ta in a few studies, but have not been much investigated. In this theseis, their crystal structure, stability, elastic properties, electronic structure and thermoelectric properties have been studied. At 0 K and 0 GPa it has been shown that these three phases are thermodynamically and elastically stable. Additionally, these are narrow-bandgap semiconductors and their thermoelectric properties can be tuned by doping. Pressure has a stabilizing effect on these structures. When pressure increases from 0-150 GPa the elastic constants and moduli increases in the range 53-317 %.

1. High temperature phase decomposition in TixZryAlzN
Open this publication in new window or tab >>High temperature phase decomposition in TixZryAlzN
2014 (English)In: AIP Advances, ISSN 2158-3226, E-ISSN 2158-3226, Vol. 4, no 12, p. 127147-1-127147-9Article in journal (Refereed) Published
##### Abstract [en]

Through a combination of theoretical and experimental observations we study the high temperature decomposition behavior of c-(TixZryAlzN) alloys. We show that for most concentrations the high formation energy of (ZrAl)N causes a strong tendency for spinodal decomposition between ZrN and AlN while other decompositions tendencies are suppressed. In addition we observe that entropic  effects due to configurational disorder favor a formation of a stable Zr-rich (TiZr)N phase with increasing temperature. Our calculations also predict that at high temperatures a Zr rich (TiZrAl)N disordered phase should become more resistant against the spinodal decomposition despite its high and positive formation energy due to the specific topology of the free energy surface at the relevant concentrations. Our experimental observations confirm this prediction by showing strong tendency towards decomposition in a Zr-poor sample while a Zr-rich alloy shows a greatly reduced decomposition rate, which is mostly attributable to binodal decomposition processes. This result highlights the importance of considering the second derivative of the free energy, in addition to its absolute value in predicting decomposition trends of thermodynamically unstable alloys.

##### Place, publisher, year, edition, pages
American Institute of Physics (AIP), 2014
##### National Category
Physical Sciences
##### Identifiers
urn:nbn:se:liu:diva-110682 (URN)10.1063/1.4905138 (DOI)000347170100078 ()
##### Note

On the day of the defence date the status of this article was Manuscript.

Available from: 2014-09-18 Created: 2014-09-18 Last updated: 2019-05-07Bibliographically approved
2. Decomposition routes and strain evolution in arc deposited TiZrAlN coatings
Open this publication in new window or tab >>Decomposition routes and strain evolution in arc deposited TiZrAlN coatings
2019 (English)In: Journal of Alloys and Compounds, ISSN 0925-8388, E-ISSN 1873-4669, Vol. 779, p. 261-269Article in journal (Refereed) Published
##### Abstract [en]

Phase, microstructure, and strain evolution during annealing of arc deposited TiZrAlN coatings are studied using in situ x-ray scattering and ex situ transmission electron microscopy. We find that the decomposition route changes from nucleation and growth of wurtzite AlN to spinodal decomposition when the Zr-content is decreased and the Al-content increases. Decomposition of Ti0.31Zr0.24Al0.45N results in homogeneously distributed wurtzite AlN grains in a cubic, dislocation-dense matrix of TiZrN consisting of domains of different chemical composition. The combination of high dislocation density, variation of chemical composition within the cubic grains, and evenly distributed wurtzite AlN grains results in high compressive strains, -1.1%, which are retained after 3 h at 1100 degrees C. In coatings with higher Zr-content, the strains relax during annealing above 900 degrees C due to grain growth and defect annihilation. (C) 2018 Elsevier B.V. All rights reserved.

##### Place, publisher, year, edition, pages
ELSEVIER SCIENCE SA, 2019
##### Keywords
Ti-Zr-Al-N; Hard coatings; Thermal stability; Strain evolution
##### National Category
Metallurgy and Metallic Materials
##### Identifiers
urn:nbn:se:liu:diva-154526 (URN)10.1016/j.jallcom.2018.11.039 (DOI)000457154700032 ()
##### Note

Funding Agencies|VINNOVA (Swedish Governmental Agency for Innovation Systems) [2016-05156]; Swedish Government Strategic Research Area (SFO Mat LiU) [2009 00971]; Swedish Research Council [2017-03813]; Rontgen-Angstrom Cluster frame grants [VR 2011-6505, VR 2017-06701]

Available from: 2019-02-20 Created: 2019-02-20 Last updated: 2019-05-07
3. Thermodynamic Stability, Thermoelectric, Elastic and Electronic Structure Properties of ScMN2-Type (M = V, Nb, Ta) Phases Studied by ab initio Calculations
Open this publication in new window or tab >>Thermodynamic Stability, Thermoelectric, Elastic and Electronic Structure Properties of ScMN2-Type (M = V, Nb, Ta) Phases Studied by ab initio Calculations
2019 (English)In: Condensed Matter, ISSN 2410-3896, Vol. 4, no 2, article id 36Article in journal (Refereed) Published
##### Abstract [en]

ScMN2-type (M = V, Nb, Ta) phases are layered materials that have been experimentally reported for M = Ta and Nb, but they have up to now not been much studied. However, based on the properties of binary ScN and its alloys, it is reasonable to expect these phases to be of relevance in a range of applications, including thermoelectrics. Here, we have used first-principles calculations to study their thermodynamic stability, elastic, thermoelectric and electronic properties. We have used density functional theory to calculate lattice parameters, the mixing enthalpy of formation and electronic density of states as well as the thermoelectric properties and elastic constants (cij), bulk (B), shear (G) and Young’s (E) modulus, which were compared with available experimental data. Our results indicate that the considered systems are thermodynamically and elastically stable and that all are semiconductors with small band gaps. All three materials display anisotropic thermoelectric properties and indicate the possibility to tune these properties by doping. In particular, ScVN2, featuring the largest band gap exhibits a particularly large and strongly doping-sensitive Seebeck coefficient.

##### Place, publisher, year, edition, pages
Basel: MDPI, 2019
##### Keywords
ScTaN2; inverse MAX phase; thermoelectric properties; density functional theory
##### National Category
Physical Sciences Condensed Matter Physics
##### Identifiers
urn:nbn:se:liu:diva-156671 (URN)10.3390/condmat4020036 (DOI)000475286700002 ()
##### Note

Funding agencies: Swedish Research Council (VR) [2016-03365]; Knut and AliceWallenberg Foundation through the Academy Fellows Program; Swedish Government Strategic Research Area in Materials Science on Functional Materials at Linkoping University [2009 00971]; European Res

Available from: 2019-05-07 Created: 2019-05-07 Last updated: 2019-07-30Bibliographically approved
4. Effects of high pressure on ScMN2-type (M = V, Nb, Ta) phases studied by density functional theory
Open this publication in new window or tab >>Effects of high pressure on ScMN2-type (M = V, Nb, Ta) phases studied by density functional theory
2019 (English)In: Results in Physics, ISSN 2211-3797, Vol. 13, article id 102293Article in journal (Refereed) Published
##### Abstract [en]

ScMN2-type (M = V, Nb, Ta) phases are layered materials that have been experimentally reported for M = Ta and Nb, but their high-pressure properties have not been studied. Here, we have used first-principles calculations to study their thermodynamic stability, elastic and electronic properties at high-pressure. We have used density functional theory to calculate the formation enthalpy relative to the competing binary phases, electronic density of states and elastic constants (c(ij)), bulk (B), shear (G) and Youngs (E) modulus as the pressure is varied from 0 to 150 GPa. Our results show that when the pressure increases from 0 to 150 GPa, elastic constants, bulk, shear and elastic moduli increase in the range 53-216% for ScTaN2, 72-286% for ScNbN2, and 61-317% for ScVN2.

##### Place, publisher, year, edition, pages
Elsevier, 2019
##### Keywords
ScTaN2; Inverse MAX phase; High pressure; Density functional theory
##### National Category
Inorganic Chemistry
##### Identifiers
urn:nbn:se:liu:diva-159276 (URN)10.1016/j.rinp.2019.102293 (DOI)000476618700182 ()
##### Note

Funding Agencies|Swedish Research Council (VR) [2016-03365]; Knut and Alice Wallenberg Foundation through the Wallenberg Academy Fellows program; Swedish Government Strategic Research Area in Materials Science on Functional Materials at Linkoping University [2009 00971]

Available from: 2019-08-07 Created: 2019-08-07 Last updated: 2019-10-16Bibliographically approved
5. The Effect of Point Defects on the Electronic Density of States of ScMN2-Type (M = V, Nb, Ta) Phases
Open this publication in new window or tab >>The Effect of Point Defects on the Electronic Density of States of ScMN2-Type (M = V, Nb, Ta) Phases
2019 (English)In: Condensed Matter, ISSN 2410-3896, Vol. 4, no 3, article id 70Article in journal (Refereed) Published
##### Abstract [en]

ScMN2-type (M = V, Nb, Ta) phases are layered materials that have been experimentally reported for M = Ta and Nb. They are narrow-bandgap semiconductors with potentially interesting thermoelectric properties. Point defects such as dopants and vacancies largely affect these properties, motivating the need to investigate these effects. In particular, asymmetric peak features in the density of states (DOS) close to the highest occupied state is expected to increase the Seebeck coefficient. Here, we used first principles calculations to study the effects of one vacancy or one C, O, or F dopant on the DOS of the ScMN2 phases. We used density functional theory to calculate formation energy and the density of states when a point defect is introduced in the structures. In the DOS, asymmetric peak features close to the highest occupied state were found as a result of having a vacancy in all three phases. Furthermore, one C dopant in ScTaN2, ScNbN2, and ScVN2 implies a shift of the highest occupied state into the valence band, while one O or F dopant causes a shift of the highest occupied state into the conduction band.

MDPI, 2019
##### National Category
Physical Sciences
##### Identifiers
urn:nbn:se:liu:diva-160948 (URN)10.3390/condmat4030070 (DOI)
Available from: 2019-10-16 Created: 2019-10-16 Last updated: 2019-10-16Bibliographically approved
• 17.
Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, Faculty of Science & Engineering.
Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, Faculty of Science & Engineering. Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, Faculty of Science & Engineering. Linköping University, Department of Management and Engineering. Linköping University, Faculty of Science & Engineering. Siemens Industrial Turbomachinery AB, Finspång.
3D Residual Stresses in Selective Laser Melted Hastelloy X2017In: Residual Stresses 2016: ICRS-10, Materials Research Proceedings 2 (2016), 2017, Vol. 2, p. 73-78Conference paper (Refereed)

3D residual stresses in as manufactured EOS NickelAlloy HX, produced by laser powder bed additive manufacturing, are analysed on the surface closest to the build-plate. Due to the severe thermal gradient produced during the melting and solidification process, profound amounts of thermal strains are generated. Which can result in unwanted geometrical distortion and effect the mechanical properties of the manufactured component. Measurements were performed using a four-circle goniometer Seifert X-ray machine, equipped with a linear sensitive detector and a Cr-tube. Evaluation of the residual stresses was conducted using sin2ψ method of the Ni {220} diffraction peak, together with material removal technique to obtain in-depth profiles. An analysis of the material is reported. The analysis reveals unwanted residual stresses, and a complicated non-uniform grain structure containing large grains with multiple low angle grain boundaries together with nano-sized grains. Grains are to a large extent, not equiaxed, but rather elongated.

• 18.
Linköping University, Department of Science and Technology. Linköping University, The Institute of Technology.
Linköping University, Department of Science and Technology. Linköping University, The Institute of Technology. Linköping University, Department of Science and Technology. 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 Science and Technology, Physics and Electronics. Linköping University, The Institute of Technology. Linköping University, Department of Science and Technology, Physics and Electronics. Linköping University, The Institute of Technology.
Nanoscale elastic modulus of single horizontal ZnO nanorod using nanoindentation experiment2012In: Nanoscale Research Letters, ISSN 1931-7573, E-ISSN 1556-276X, Vol. 7, p. 146-148Article in journal (Refereed)

We measure the elastic modulus of a single horizontal ZnO nanorod [NR] grown by a low-temperature hydrothermal chemical process on silicon substrates by performing room-temperature, direct load-controlled nanoindentation measurements. The configuration of the experiment for the single ZnO NR was achieved using a focused ion beam/scanning electron microscope dual-beam instrument. The single ZnO NR was positioned horizontally over a hole on a silicon wafer using a nanomanipulator, and both ends were bonded with platinum, defining a three-point bending configuration. The elastic modulus of the ZnO NR, extracted from the unloading curve using the well-known Oliver-Pharr method, resulted in a value of approximately 800 GPa. Also, we discuss the NR creep mechanism observed under indentation. The mechanical behavior reported in this paper will be a useful reference for the design and applications of future nanodevices.

• 19.
Drexel University.
Linköping University, Department of Physics, Chemistry and Biology, Nanostructured Materials . Linköping University, The Institute of Technology. Texas A&M University. Drexel University. Texas A&M University. 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. Drexel University.
Phase Evaluation in Al(2)O(3) Fiber-Reinforced Ti(2)AlC During Sintering in the 1300 degrees C-1500 degrees C Temperature Range2011In: Journal of The American Ceramic Society, ISSN 0002-7820, E-ISSN 1551-2916, Vol. 94, no 10, p. 3327-3334Article in journal (Refereed)

In this article, the reactivity of Ti(2)AlC powders, with 3 and 10 mu m alumina, Al(2)O(3), fibers during pressure-assisted sintering is explored. Samples were fabricated by hot-isostatic-pressing (HIPed) or hot-pressing (HPed), and characterized by X-ray diffraction, differential thermal analysis, and electron microscopy-both scanning and transmission-equipped with energy dispersive X-ray spectroscopes. Samples prepared at 1300 degrees C were fully dense, with no apparent reaction between fiber and matrix. In samples HPed to 1500 degrees C, even pure Ti(2)AlC powders dissociated to Ti(3)AlC(2) according to: 2 Ti(2)AlC = Ti(3)AlC(2) + TiAl(x) (l) + (1-x) Al (l/v), with x andlt; 1. More severe Al loss results in the formation of TiC(y). The presence of the Al(2)O(3) fibers delayed densification enough to allow most of the Al and some of the Ti to escape into the vacuum of the hot press or react with the encapsulating glass during HIPing a resulting in a more intensive dissociation of the Ti(2)AlC. Although, in principle Ti(2)AlC can be reinforced with Al(2)O(3) fibers, the processing/use temperature will have to be kept below 1500 degrees C, as, at that temperature the fibers, used here, sinter together.

• 20.
Tech Univ Denmark, Denmark; Xnovo Technol, Denmark.
Tech Univ Denmark, Denmark. Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, Faculty of Science & Engineering. ESRF, France; Univ Lyon, France. Tech Univ Denmark, Denmark.
3D characterization of partially recrystallized Al using high resolution diffraction contrast tomography2018In: Scripta Materialia, ISSN 1359-6462, E-ISSN 1872-8456, Vol. 157, p. 72-75Article in journal (Refereed)

Synchrotron diffraction contrast tomography (DCT) is for the first time used to characterize recrystallized grains in partially recrystallized Al. The positions, orientations and 3D shapes of amp;gt;900 recrystallized grains are reconstructed within a gauge volume. The results are compared with those obtained using electron backscattered diffraction based on a statistical analysis. It is found that recrystallized grains with size larger than 10 mu m, corresponding to similar to 98% of the total recrystallized volume of the sample, are well characterized by DCT. The advantages of DCT for recrystallization studies and new possibilities with DCT on new generation synchrotron sources are discussed. (C) 2018 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

• 21.
Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
Institute for Solid State Physics and Optics, Wigner Research Centre for Physics, Hungarian Academy of Sciences, Hungary. Institute for Solid State Physics and Optics, Wigner Research Centre for Physics, Hungarian Academy of Sciences, Hungary. Institute of Physics, Loránd Eötvös University, Hungary. Institute of Physics, Loránd Eötvös University, Hungary. Institute of Physics, Loránd Eötvös University, Hungary. Institute for Solid State Physics and Optics, Wigner Research Centre for Physics, Hungarian Academy of Sciences, Hungary, Department of Electronic Science and Engineering, Kyoto University, Japan. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
Identification of the negative carbon vacancy at quasi-cubic site in 4H-SiC by EPR and theoretical calculations2014In: Silicon Carbide and Related Materials 2013, PTS 1 AND 2, Trans Tech Publications Inc., 2014, Vol. 778-780, p. 285-288Conference paper (Refereed)

In freestanding n-type 4H-SiC epilayers irradiated with low-energy (250 keV) electrons at room temperature, the electron paramagnetic resonance (EPR) spectrum of the negative carbon vacancy at the hexagonal site, V-C(-)(h), and a new signal were observed. From the similarity in defect formation and the spin-Hamiltonian parameters of the two defects, the new center is suggested to be the negative C vacancy at the quasi-cubic site, V-C(-)(k). The identification is further supported by hyperfine calculations.

• 22.
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, Theoretical Physics. Linköping University, The Institute of Technology. Seco Tools AB, Fagersta, Sweden. Linköping University, Department of Physics, Chemistry and Biology, Nanostructured Materials. Linköping University, The Institute of Technology.
Microstructure evolution of TiAlN-a phase field studyManuscript (preprint) (Other academic)

In this work the phase field method has been applied to model the spinodal decomposition of TiAlN. Here we have used thermodynamic data from ab initio calculations that takes into account clustering effects, and experimental diffusivity data of TiAlN as an input to the model. The effect of alloy composition on microstructure and stresses, is studied in time and space. In addition, Young’s modulus evolution of the decomposing microstructure is reported. It was found that the microstructure changes from round AlN rich domains in a TiN matrix, to outstretched TiN rich domains in the {100} crystallographic directions in an AlN matrix, as the composition was changed from x=0.3 to x=0.75 in Ti1-xAlxN. The microstructure evolution was observed to undergo different stages. In short; first elongated structures enriched of the majority element in random directions evolve. Thereafter round AlN rich domains evolve, independent of composition studied, and a completely segregated microstructure forms that finally coarsens. The initiation, decomposition, and coarsening rate was found to increase with Al content due to the increase in driving force with Al content. Al rich domains purify fastest, independent of composition studied. The evolving compositional wavelength decreases with Al content resulting in a finer microstructure for alloys rich in Al. During decomposition high local strains and stresses develop, which reach maximum values of 6·10-3 and 12 GPa respectively.

• 23.
Nanjing University, Peoples R China.
Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, The Institute of Technology. Nanjing University, Peoples R China. Nanjing University, Peoples R China. Nanjing University, Peoples R China. Nanjing University, Peoples R China.
Effect of Pr doping on ferroelectric behaviors of Pb(Zr0.65Ti0.35)O-32008In: International Journal of Modern Physics B, ISSN 0217-9792, Vol. 22, no 13, p. 2070-2081Article in journal (Refereed)

Pr-doped Pb(Zr0.65Ti0.35)O-3 (Pb1-xPr (Zr0.65Ti0.35)(1-x)/O-4(3), PPZT) ceramic samples are prepared using conventional solid-state sintering method, and their structural, dielectric, ferroelectric, and piezoelectric properties are investigated, focusing on the effects of Pr-doping. Upon increasing Pr doping level x, a transition of the crystallographic structure from rhombohedral symmetry to tetrahedral and finally to pseudocubic symmetry is observed at x similar to 0.08. The detailed dielectric measurements present a clear indication of relaxor-like behaviors at x = 0.08, while the samples at x less than 0.08 offer slightly improved ferroelectric properties compared with pure Pb(Zr0.65Ti0.35)O-3. In spite of the dielectric relaxor behaviors induced by Pr-doping, both the ferroelectric and piezoelectric properties of PPZT are degraded at x = 0.08. The physics underlying the Pr-doping induced relaxor behaviors is then discussed.

• 24.
Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, Faculty of Science & Engineering. Department of Management and Engineering, Linköping University, Linköping, Sweden.
Högskolan Väst, Avdelningen för avverkande och additativa tillverkningsprocesser (AAT). Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, Faculty of Science & Engineering. Siemens Industrial Turbomachinery AB, Finspång, Sweden. Högskolan Väst, Avdelningen för avverkande och additativa tillverkningsprocesser (AAT). Högskolan Väst, Avdelningen för avverkande och additativa tillverkningsprocesser (AAT). Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, Faculty of Science & Engineering.
Isothermal oxidation behavior of HVAF-sprayed NiCoCrAlY coatings: Effect of surface treatment2017In: Proceedings of International Thermal Sprayed Conference (ITSC), May 7-9,Germany, 456-461 (2017), 2017, p. 456-461Conference paper (Other academic)

NiCoCrAlY coatings are widely used as bond coats for ceramic thermal barrier coatings (TBCs) andoxidation and corrosion protective overlay coatings in industrial gas turbines. High temperature oxidation behaviour of NiCoCrAlYs has a great influence on the coating performance and lifetime of TBCs. A promising route to decrease the oxidation rate of such coatings is post-coating surface modification which can facilitate formation of a uniform alumina scale with a considerably slower growth rate compared to the as-sprayed coatings. In this work, the effect of surface treatment by means of shot peening and laser surface melting (LSM) on the oxidation resistance of high velocity air-fuel (HVAF) sprayed NiCoCrAlY coatings was studied. Isothermal oxidation was carried out at 1000⁰C for 1000h. Results showed that the rough surface of as-sprayed HVAF sprayed coatings was significantly changed after shot peening and LSM treatment, with a compact and smooth appearance. After the exposure, the oxide scales formed on surface-treated NiCoCrAlY coatings showed different morphology and growth rate compared to those formed on as-sprayed coating surface. The oxidation behaviour of surface treated HVAF-sprayed NiCoCrAlY coatings were revealed and discussed.

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