Summary Ashima Sah

This PhD thesis deals with the composite membrane system a-alumina(macroporous)/g-alumina(mesoporous)/hybrid silica (microporous). It studies the chemical modification of the surface and pores of the membrane.

Two ways have been adopted in this regard. Grafting of the intermediate layers with organochlorosilanes and in situ hydrolysis and condensation of organosilane precursors.

Detailed structural characterization of the unsupported powders and the sol has been carried out by means of adsorption techniques, particle sizing, and mass spectrometry.

The study on the powders and sols have provided valuable insights into the physical characteristics of the material like particle size of the sol, porosity of the material and pore size ranges. This information further helps in understanding transport behaviour in membranes. The multifunctional precursors in the case of grafting formed a polymerized network which imparted greater resistance to flow of solvents as well as hydrophobic character.

With the use of hybrid precursors, 1,2-bis(triethoxysilyl)ethane and methyltriethoxy silane a nano sized sol was obtained. The particle size of the sol could be tuned to meet requirements by varying parameters of the sol like hydrolysis ratio, amount of acid, the ratio of the two precursors.

It is seen that the characteristics of the sol play a role in the formation of a thin film on the supported g- alumina membrane. When the particle size of the sol was small penetration of sol particles into the underlying layers took place, which suffocated the pores. A decrease in flux and separation factors was thus observed.

The membranes have been characterized by using SEM, XPS, liquid permeation, permporometry, gas separation and pervaporation.

The hybrid membranes exhibit enhanced hydrothermal stability as they are able to operate at higher temperatures of 150 ° C, as compared to the normal working conditions of 95 ° C, for standard silica membranes, for a 97.5 % n-butanol and 2.5 % water system, in pervaporation.

Thus by fine tuning the properties of the sol we are able to monitor the characteristics of the film, and hence transport properties.

By adopting these approaches, we incorporated an organic moiety in the inorganic matrix thus moving towards hybrid inorganic- organic systems.

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Home News Events Strategic Orientations research groups Publications PhD students Education MESA+ NanoLab Starting entrepreneurs Tech Park Industrial Partners Vacancies Links Sitemap Search	Summary Ashima Sah This PhD thesis deals with the composite membrane system a-alumina(macroporous)/g-alumina(mesoporous)/hybrid silica (microporous). It studies the chemical modification of the surface and pores of the membrane. Two ways have been adopted in this regard. Grafting of the intermediate layers with organochlorosilanes and in situ hydrolysis and condensation of organosilane precursors. Detailed structural characterization of the unsupported powders and the sol has been carried out by means of adsorption techniques, particle sizing, and mass spectrometry. The study on the powders and sols have provided valuable insights into the physical characteristics of the material like particle size of the sol, porosity of the material and pore size ranges. This information further helps in understanding transport behaviour in membranes. The multifunctional precursors in the case of grafting formed a polymerized network which imparted greater resistance to flow of solvents as well as hydrophobic character. With the use of hybrid precursors, 1,2-bis(triethoxysilyl)ethane and methyltriethoxy silane a nano sized sol was obtained. The particle size of the sol could be tuned to meet requirements by varying parameters of the sol like hydrolysis ratio, amount of acid, the ratio of the two precursors. It is seen that the characteristics of the sol play a role in the formation of a thin film on the supported g- alumina membrane. When the particle size of the sol was small penetration of sol particles into the underlying layers took place, which suffocated the pores. A decrease in flux and separation factors was thus observed. The membranes have been characterized by using SEM, XPS, liquid permeation, permporometry, gas separation and pervaporation. The hybrid membranes exhibit enhanced hydrothermal stability as they are able to operate at higher temperatures of 150 ° C, as compared to the normal working conditions of 95 ° C, for standard silica membranes, for a 97.5 % n-butanol and 2.5 % water system, in pervaporation. Thus by fine tuning the properties of the sol we are able to monitor the characteristics of the film, and hence transport properties. By adopting these approaches, we incorporated an organic moiety in the inorganic matrix thus moving towards hybrid inorganic- organic systems.