Thin films of mesoporous silica: characterization and applications

Chao, Kuei‐Hsiang; Liu, Pang-Hung; Huang, Kuo-Ying

doi:10.1016/j.crci.2005.01.004

Cited by 33 publications

(15 citation statements)

References 88 publications

(132 reference statements)

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“…After deposition of the solution onto the substrate, the ethanol evaporates and the concentration of water and surfactants increase. Hence, the surfactant concentration increases above CMC and micelles start to form on the substrate [188][189][190]. The process is illustrated in Figure 19.…”

Section: Evaporation-induced Self-assemblymentioning

confidence: 97%

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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Section: Evaporation-induced Self-assemblymentioning

confidence: 97%

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

Björk¹

2013

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“…The steeply decaying reflectivity curve is modified by several oscillations known as the Kiessig fringes. Film thickness and density can be derived from the frequency of the Kiessig fringes and θ c value [18,23] respectively. The XRR profiles of as-synthesized and UV-O 3 treated films as well as the XRR profile of dense SiO 2 film (of thickness~59 nm and density = 2.1 g/cm 3 ) are measured at ≤5% relative humidity and shown in Fig.…”

Section: Xrr Analysis Of Density and Thickness Of Filmsmentioning

confidence: 99%

“…Kr adsorption essentially reduces the uncertainty associated with equipment dead volume on the pore size distribution analysis [16]. The density and thickness of thin films on flat substrates have been measured by ellipsometry [17], X-ray reflectivity (XRR) or n&k analyzer [18]. XRR has been used to study morphology of ultra-thin films in semiconductor technology [17].…”

Section: Introductionmentioning

confidence: 99%

The effect of surfactant removal on continuous mesoporous ultra-thin silica films—A study by X-ray reflectivity, X-ray diffraction and Kr adsorption

Hsu¹,

Chao²,

Chen³

et al. 2008

Thin Solid Films

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“…Depending on the intended application, such materials exhibit a wide variability of volume fraction, shape and arrangement of pores, which in turn affects their mechanical properties (Chao et al, 2005;Ha et al, 2010;Jauffrès et al, 2011;Vanstreels et al, 2013). Understanding the relation between pore microstructure and effective mechanical properties therefore plays a key role in successfully implementing these materials in practice.…”

Section: Introductionmentioning

confidence: 99%

Homogenisation of porous thin films and perforated layers: Comparison of analytical and numerical approaches

Richter

2015

Mechanics of Materials

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Keywords:Finite element method Self-consistent method Mori-Tanaka approach Micromechanics Porous thin films Constitutive behaviour a b s t r a c tThe mechanical properties of porous thin films and perforated layers are affected by pore content, shape and arrangement. The experimental determination of the in-plane mechanical properties of such materials is challenging, yet reliable data are essential for materials development and component design. Analytical and numerical approaches therefore provide valuable, supplementary tools for evaluating the effect of porosity on the mechanical properties of such materials.The applicability of both the classical self-consistent method and the Mori-Tanaka approach to the estimation of the effective elastic properties of porous thin films and perforated layers is investigated in this paper. For generic model microstructures with various arrangements of pores, variable pore content and varying matrix Poisson's ratio, the effective elastic properties predicted by the classical self-consistent method and by the Mori-Tanaka approach are quantitatively compared with results obtained by numerical experiments. Based upon this comparison, the range of validity of both the classical self-consistent method and the Mori-Tanaka approach with regard to the different arrangements of pores investigated is defined, and the deviation to be expected if critical values of pore content or inter-pore distance are exceeded and interactions between adjacent pores are occurring is assessed.

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Thin films of mesoporous silica: characterization and applications

Cited by 33 publications

References 88 publications

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

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

The effect of surfactant removal on continuous mesoporous ultra-thin silica films—A study by X-ray reflectivity, X-ray diffraction and Kr adsorption

Homogenisation of porous thin films and perforated layers: Comparison of analytical and numerical approaches

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