Self‐Assembly and Characterization of Mesostructured Silica Films with a 3D Arrangement of Isolated Spherical Mesopores

Yu, Kaiwen; Smarsly, Bernd M.; Brinker, C.J.

doi:10.1002/adfm.200390005

Cited by 98 publications

(130 citation statements)

References 29 publications

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“…2; a decrease in the ordering of mesoporous structures can cause measurement errors when using ellipsometry and thus errors in the calculated porosity. 17,18 To maximize the thermoelectric properties of a material, the material should have high electrical conductivity and low thermal conductivity. However, these parameters are proportional to each other and are therefore difficult to manipulate independently.…”

Section: Resultsmentioning

confidence: 99%

Thermoelectric Properties of Nb-Doped Ordered Mesoporous TiO2

Jung

Seo

et al. 2011

Journal of Elec Materi

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Mesoporous materials have pores with diameters between 2 nm and 50 nm, the presence of which generally decreases the thermal conductivity of the material. By incorporating mesoporous structures into thermoelectric materials, the thermoelectric properties of these materials can be improved. Although TiO 2 is an ordinary insulator, reduced TiO 2 shows better electrical conductivity and is therefore a potential thermoelectric material. Furthermore, the addition of a dopant to TiO 2 can improve its electrical conductivity. We hypothesized that, by doping ordered mesoporous TiO 2 films with niobium, we would be able to minimize the thermal conductivity and maximize the electrical conductivity. To investigate the effects of Nb doping and a mesoporous structure on the thermoelectric characteristics of TiO 2 films, Nb-doped mesoporous films were investigated using x-ray diffraction, ellipsometry, fourpoint probe measurements, and thermal conductivity analysis. We found that Nb doping of ordered mesoporous TiO 2 films improved their thermoelectric properties.

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Section: Resultsmentioning

confidence: 99%

Thermoelectric Properties of Nb-Doped Ordered Mesoporous TiO2

Jung

Seo

et al. 2011

Journal of Elec Materi

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“…In this way the silica matrix rearranges to form a dense network without micropores. [45] When functionalized silica is used in an EISA process the same concept applies to the hydrophilic sulfonic acid groups. They will be directed to the inside of the mesochannels together with the hydrophilic polyoxyethylene groups of the surfactant to provide channels with a high density of sulfonic acid groups for increased proton conduction.…”

Section: Proton Conduction and Ion Exchange Capacitymentioning

confidence: 99%

Supported and Free‐Standing Sulfonic Acid Functionalized Mesostructured Silica Films with High Proton Conductivity

et al. 2010

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Sulfonic acid functionalized silica films with 2D-hexagonal mesostructures of various channel sizes are prepared in a one-step synthesis. A successful combination of in situ oxidation of a mercapto-functionalized silane with an evaporation induced self-assembly (EISA) process in the presence of amphiphilic block copolymers allows the formation of a highly structured material with a sulfonation degree of 33 %. Analysis of the mesostructure by a combination of XRD, grazing-incidence small-angle X-ray scattering (GI-SAXS), and TEM shows that 2D-hexagonally ordered mesostructured films are obtained by optimization of the surfactant to silica

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“…At calcination temperatures as high as 950 °C, the pores can be completely closed, leaving separated mesopores in the silica matrix [177][178][179]. The material with high closed porosity can be of interest for applications where materials with low dielectric constant are desired.…”

Section: Surfactant Removalmentioning

confidence: 99%

Mesoporous Building Blocks: Synthesis and Characterization of Mesoporous Silica Particles and Films

Björk¹

2013

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On the cover, the structure of SBA-15 is illustrated. Inside the pores SEM micrographs have been inserted showing (clockwise from the top): rods, fibers, a film consisting of rods grown on a substrate, a film consisting of platelets grafted on a substrate, short rods, and platelets. In the center the sheet morphology is presented.© Emma Björk, unless otherwise stated.ISBN: 978-91-7519-516-2 ISSN: 0345-7524 Printed by LiU-tryck, Linköping, Sweden, 2013 Research is formalized curiosity. It is poking and prying with a purposeZora Neale Hurston (1903Hurston ( -1960 i ABSTRACTCatalyst 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 NH 4 F 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 NH 4 F concentration, independent of heptane amount, and a platelet morphology can be formed. The formation time of the particles decrease with decreasing NH 4 F, 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.ii T...

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Self‐Assembly and Characterization of Mesostructured Silica Films with a 3D Arrangement of Isolated Spherical Mesopores

Cited by 98 publications

References 29 publications

Thermoelectric Properties of Nb-Doped Ordered Mesoporous TiO2

Thermoelectric Properties of Nb-Doped Ordered Mesoporous TiO2

Supported and Free‐Standing Sulfonic Acid Functionalized Mesostructured Silica Films with High Proton Conductivity

Mesoporous Building Blocks: Synthesis and Characterization of Mesoporous Silica Particles and Films

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