Synthesis Of Free-standing Mesoporous Thin Film And Micro-mesoporous Composite Thin Film

Mesoporous thin film not only has the property of two-dimension extension, homogeneity and integrity, but also has the diverse mesostructure, order pore architectures, large porosities, various framework compositions, which shows great potential in the fields of separation system, catalysis, nano-device, etc., and has triggered substantial research interest from all over the world and has been greatly developed in recent years. This thesis focuses on mesoporous thin film, developed "coating-etching" process to synthesize free-standing mesoporous carbon-silica composite film. By adjusting the preparation procedure, free-standing mesoporous carbon and silica film have also been synthesized. These materials have improved that ordinary thin films are limited by the substrate and the permeability was effected by the substrate, but also provide a new idea and approach to prepare free-standing mesoporous thin film despite the traditional method-interface growth. And also from the aspect of hierarchical pore structure, a composite film of mesoporous silica film and micropore zeolite film has been successfully synthesized. Such materials obtained may have great theoretical and practical significance.In Chapter 2, a free-standing mesoporous carbon-silica composite film polymer has been synthesized via evaporation induced tri-constituent co-assembly of resol precursor, TEOS and Pluronic F127 as templates. Firstly, a Al2O3 layer was deposited on silicon wafer substrate by atomic layer deposition (ALD) method. Secondly, the mesoporous carbon-silica composite film with c2m meso-structure was prepared by spin-coating resol/TEOS/F127 solution on pre-treated silicon wafer substrate followed by carbonization in inert atmosphere, and the ratio of carbon/silica can be varied by adjusting ration of resol/TEOS in the coating solution. Thirdly, the integrity and crack-free mesoporous free-standing carbon-silica composite film was obtained by HC1 etching the Al2O3 interlayer.In Chapter 3, based on free-stand mesoporous carbon-silica film, the free-standing mesoporous carbon and mesoporous silica films can also be synthesized by slightly adjusting the preparation procedure. The free-standing carbon film was obtained by using HF instead of HC during the etching process, as the interlayer and the silica skeleton are both been removed at the same time. The surface area and pore volume of mesoporous carbon film have been largely increased for the reason that lots of defects are left after the silica component was wiped off. What’s more, free-standing mesoporous silica film can also be obtained by carbon-silica composite film on substrate further calcination in air at high temperature. In this way, the carbon component was removed and only silica skeleton was left. After HC1 etching off the interlayer, the silica film was synthesized. By TG analyzed and IR, it is further confirmed the "reinforced concrete" framework structure in carbon-silica composite film.In Chapter 4, from the view of hierarchical pore structure, the composite film of mesoporous silica and zeolite was synthesized. First the silicalite-1 zeolite film on glass or silicon wafer substrate was prepared by hydrothermal treatment. Then, the mesoporous silica film was coated onto zeolite film via spin-coating method. In this way, the obtained composite film not only has the micro-pores from zeolite, but also lots meso-pores. This material will have great potential in catalysis, water treatment, electronic chemistry etc.In Chapter 5, the whole thesis is summarized.