liu.seSearch for publications in DiVA
Change search
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • oxford
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf
The effects on pore size and particle morphology of heptane additions to the synthesis of mesoporous silica SBA-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.ORCID iD: 0000-0002-2286-5588
2010 (English)In: Microporous and Mesoporous Materials, ISSN 1387-1811, E-ISSN 1873-3093, Vol. 133, no 01-Mar, 66-74 p.Article 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. Vol. 133, no 01-Mar, 66-74 p.
Keyword [en]
SBA-15; Morphology; Heptane; H2O2; Sheet
National Category
Engineering and Technology
Identifiers
URN: urn:nbn:se:liu:diva-58290DOI: 10.1016/j.micromeso.2010.04.016ISI: 000279061000009OAI: oai:DiVA.org:liu-58290DiVA: diva2:337906
Available from: 2010-08-10 Created: 2010-08-09 Last updated: 2017-12-12
In thesis
1. Controlling the Pore Size and Morphology of Mesoporous Silica
Open this publication in new window or tab >>Controlling the Pore Size and Morphology of Mesoporous Silica
2010 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

Mesoporous silica with a hexagonally ordered pore structure (SBA-15) has been synthesized. Through variations in the synthesis conditions several morphologies, such as fibers, sheets and separate rods, have been realized. Furthermore, additions of heptane and NH4F make it possible to synthesize SBA-15 with pores as large as 18 nm in the sheet morphology. Mechanisms for the formation of different morphologies have been suggested. In the case of fibers and sheets, the amount of heptane present during the synthesis determines the final morphology. For low concentrations, the heptane enters the micelles and increases the pore size while the particles (crystallites) attaches to each other end to end. When the heptane concentration increases, the heptane droplets increase in size, and above a critical droplet size the crystallites attach with one short end towards the droplet, forming the sheet morphology. The crystallites can also be separated. This is the case of the rod morphology. The separation is performed by shortening the stirring time and increasing the HCl concentration. The increased amount of HCl increases the hydration rate of the silica precursor, which can be used to control the thickness and length of the rods. Furthermore, the reaction time has been decreased from 20 h for all morphologies to less than 4 hours. The materials have been characterized with nitrogen sorption, electron microscopy and x-ray diffraction. Also, thermogravimetric analysis and fourier transformed infrared spectroscopy have been used for studying the removal of surfactants.

Place, publisher, year, edition, pages
Linköping: Linköping University Electronic Press, 2010. 67 p.
Series
Linköping Studies in Science and Technology. Thesis, ISSN 0280-7971 ; 1451
National Category
Natural Sciences
Identifiers
urn:nbn:se:liu:diva-70405 (URN)LIU-TEK-LIC-2010:22 (Local ID)978-91-7393-305-6 (ISBN)LIU-TEK-LIC-2010:22 (Archive number)LIU-TEK-LIC-2010:22 (OAI)
Presentation
2011-11-03, Planck, Fysikuset, Campus Valla, Linköpings universitet, Linköping, 10:15 (Swedish)
Opponent
Supervisors
Available from: 2011-09-06 Created: 2011-09-06 Last updated: 2013-10-02Bibliographically approved
2. Mesoporous Building Blocks: Synthesis and Characterization of Mesoporous Silica Particles and Films
Open this publication in new window or tab >>Mesoporous Building Blocks: Synthesis and Characterization of Mesoporous Silica Particles and Films
2013 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

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.

Place, publisher, year, edition, pages
Linköping: Linköping University Electronic Press, 2013. 82 p.
Series
Linköping Studies in Science and Technology. Dissertations, ISSN 0345-7524 ; 1542
National Category
Natural Sciences
Identifiers
urn:nbn:se:liu:diva-99858 (URN)10.3384/diss.diva-99858 (DOI)978-91-7519-516-2 (ISBN)
Public defence
2013-11-15, Visionen, Hus B, Campus Valla, Linköpings universitet, Linköping, 13:15 (English)
Opponent
Supervisors
Available from: 2013-10-22 Created: 2013-10-22 Last updated: 2013-10-22Bibliographically approved

Open Access in DiVA

No full text

Other links

Publisher's full text

Authority records BETA

Johansson, EmmaCordoba Gallego, Jose ManuelOdén, Magnus

Search in DiVA

By author/editor
Johansson, EmmaCordoba Gallego, Jose ManuelOdén, Magnus
By organisation
Nanostructured MaterialsThe Institute of Technology
In the same journal
Microporous and Mesoporous Materials
Engineering and Technology

Search outside of DiVA

GoogleGoogle Scholar

doi
urn-nbn

Altmetric score

doi
urn-nbn
Total: 613 hits
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • oxford
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf