Synthesis Of Controllable Nanosize Ordered Mesoporous Ceramic Monolith Materials By The Template Assistive Technology

In the past few years, porous monolithic materials have attracted attention of researchers because of various applications, especially within catalysis, flow separation and chromatography. And the ordered porous materials with higher specific surface areas and uniform pore-size distribution have more research and application values. In this paper, we study the synthesis of ordered mesoporous SiC, SiOC and Al2O3 ceramic monolith materials.First, ordered mesoporous silica (SBA-15) with 2-D P6mm hexagonal symmetry was successfully prepared utilizing a triblock copolymer P123 as structure agent. And then synthesized mesoporous carbon (CMK-3) had similar microscopic structure with initial structure of mesoporous silica SBA-15 by nanocasting method. Through a series of tests showed that SBA-15 and CMK-3 templates have highly ordered, large specific surface areas and uniform pore-size distributions, which have laid a good foundation for our next experiments.Second, highly ordered mesoporous SiC and SiOC ceramic monolith materials are successfully prepared using mesoporous carbon CMK-3 as a hard template and polycarbosilane (PCS) and poly(hydromethylsiloxane) (PHMS) as starting preceramic polymers via nanocusting and simple technology of pressing to obtain cylindrical monoliths contained the polymers. The composites were carried out in a tubular furnace pyrolysis in inert atmosphere and then removed carbon template under ammonia atmosphere. The SiC-based ceramic monoliths are exactly the inverse replicas of direct template (carbon template) and possess similar structural symmetries to their mother templates, as characterized by small angle X-ray diffraction (SA-XRD), transmission electron microscope (TEM), nitrogen absorption-desorption and so on measurements. Therefore, two kinds of 2-D ordered mesoporous SiC and SiOC monolithic ceramics with high specific surface areas (>600m2/g) had successfully prepared by template casting by casting and pressing technology. The shapes of monoliths just depend on the mold, and the preparation technology is easy for industrial production.Finally, Al2O3 monoliths with hexagonal mesoporous structure are prepared by polymer gel-casting starting from well-ordered mesoporous alumina powders which were obtained using a triblock copolymer P123 as structure agent. The resulting samples keep the original shapes after introducing polymer cross-linking agents, curing at low temperature, cutting and burning off the polymer at high treatment. Monolithic products are investigated through small angle X-ray scattering (SAXS), transmission electron microscope (TEM) and nitrogen absorption-desorption measurements to exhibit ordered p6mm hexagonal mesoporosity, high specific surface areas and uniform pore-size.In this thesis, we designed and fabricated various ordered mesoporous ceramic monoliths with nanostrutures and controllable size. These materials will have highly application values to need our further more research.