Nanocrystalline mesoporous metal oxides synthesized via triblock copolymer and phenolic resin

Abstract

The work presented in this thesis addressed the synthesis and characterization of nanocrystalline mesoporous metal oxides. Mesoporous metal oxides, including $CeO_2$, $ZrO_2$, $Al_2O_3$, $Y_2O_3$ and mixed oxide $CeO_2 -ZrO_2$ have been successfully synthesized via triblock copolymer and phenolic resin double template system. Inclusion of carbonization process gives the great advance in soft template method of mesoporous metal oxide synthesis. This methodology takes advantage of using micelle of surfactant template method, and it also complements the low crystallinity issue of using one organic template. The materials were obtained using organic phenol/formaldehyde or phloroglucinol/formaldehyde as carbon precursors, triblock copolymer F127 as a template and metal nitrate as inorganic metal precursor, three components were mesostructured based on the solvent evaporation-induced assembly (EISA). Homogeneously mixed phenolic resin with self assembled inorganic-micelle structure inhibits the agglomerization of metal species during heat treatment under nitrogen flow and high heat treatment gives the atomic array of metal species without structure change. Uniformly embedded carbon species is removable through heat treatment with air flow. The resultant mesoporous $CeO_2$ (~4.3 nm) materials have uniform pore structure, have high Brunauer-Emmett-Teller specific surface areas ($~140 m^2g^{-1}$) and represent nanocrystalline wall structure. In addition, $ZrO_2$ shows the low-angle diffraction peaks which indicate that mesoscopic order are preserved in sample after burning the carbon from the mesoscopically ordered carbon-zirconium composite. Our results show that double template system is the suitable for preparing the nanocrystalline mesoporous metal oxide rather than using one organic template and other synthesis methods. the silica based double template strategy was found out to be effective for preparing nanocrystalline ceria with fine porosity. Additional silica...