"The objective is to synthesise non-oxide mesoporous materials, boron nitride (BN) and silicon carbide (SiC). These new materials will have both high thermal and chemical stabilities associated to an homogeneous mesoporosity (pore diameter 2-30 nm), periodically structured. They will find applications in catalysis, in analytical chemistry, and also in nanotechnologies. In the case of silica, the self-assembly process has led to materials with a periodical arrangement of nanopores having an homogenous size. Copo lymers triblock have been used as structurating agents for the synthesis of ordered SBA-15 mesoporous silica with an hexagonal porosity organization and with pore size up to 30 nm. Mesoporous carbons have been recently prepared by using silica as hard-templates. Sucrose, infiltrated in the channels of the porous silica, is carbonized. A mesoporous carbon is obtained after template elimination by chemical washing. To extend the field of ordered mesoporous silica to non-oxide materials, we will use this innovative exo-templating approach. Mesoporous silica will be used as hard-templates to perform the synthesis of ordered porous non-oxide materials. Infiltration of hard-templates can be performed using a liquid ceramic precursor (a borazinic or a polysilane co mpound), followed with a ceramization step. For boron nitride, the molecular precursor is the trichloroborazine, TCB (B3N3H3Cl3). For the silicon carbide, a polydimethylsilane precursor (PDMS) will be used. Various pyrolysis steps to convert precursors (TC B or PDMS) into ceramics will be studied. Characterizations of the materials will be carried out using X-ray diffraction analysis, Scanning and Transmission Electronic Microscopies, NMR, Infrared and Raman analysis. Porosity will be studied by using adsorption/desorption of nitrogen. X-ray photoelectron spectroscopy (XPS) and Rutherford Backscattering Spectrometry (RBS) will be performed to characterize BN and SiC mesoporous films."
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