Surface chemistry and structure of silicon oxycarbide gels and glasses

Abstract

Abstract. In this study, the surface chemistry and structure of methyl-substituted silica gels and porous oxycarbide glasses were investigated. FTIR was used to measure the relative concentration of Si--CH3 and Si--OH as a function of the degree of methyl-substitution and the pyrolysis temperature. The gels and glasses were further heated, dehydrated or hydrated, in situ, within the FTIR spectrometer. In the temperature range of 800-850~ high surface area oxycarbide glasses were created with no detectable surface hydroxyl groups. Oxycarbide glasses synthesized in argon at 700~ displayed a weak band for surface hydroxyl groups and reversible physisorption of water, while those synthesized at 850/900~ showed a complete absence of surface hydroxyl groups and the formation of vicinal silanols upon chemisorption of water. Isolated silanols were observed upon heat treatment in vacuum. Formation of aromatic carbon species was found to correlate with the decomposition of the methyl groups. The oxycarbide surface is quite stable to densification (presumably due to elemental carbon on the pore surfaces). In the absence of oxygen, porous silicon oxycarbide glass powders maintain surface areas >200 m2/g at 1200~ However, oxidizing species in the atmosphere deplete the aromatic carbon species, and the glasses lose surface area.

Metalorganic chemical vapor deposition of mesoporous SiTiOC nanostructured thin films

“…These peaks appear stronger and broader in case of using hydrogen gas with high possibility to form -OH group at the surface of the produced films than other gases. Other research groups [21,22] have shown that when materials containing silicon oxycarbide (Si\O\C) exposure to the ambient condition the numbers of Si\OH groups increased. Accordingly, the broadening of the peaks with the usage of hydrogen gas indicated that the film contained much amount of SiOC than films produced in the presence of other gases.…”

Relationship between surface structure and morphology of Fe3O4/silica composite nanospheres and nucleic acid extraction

“…Recently, different synthesis methods have been developed to control surface structure and morphology of silica. These methods include changing catalyst pH value [3], using nonionic surfactant Igepal CA-720 [4], using different silica sources to change the silanol groups' quantity [5], changing reaction temperature [4,6] or using solvents of different polarity as silica aging solvents [7].…”

“…Recently, different synthesis methods have been developed to control surface structure and morphology of silica. These methods include changing catalyst pH value [3], using nonionic surfactant Igepal CA-720 [4], using different silica sources to change the silanol groups' quantity [5], changing reaction temperature [4,6] or using solvents of different polarity as silica aging solvents [7].To enhance nucleic acid extraction efficiency, especially for automated extraction procedures, it is necessary to investigate the effect of surface structure and morphology of Fe 3 O 4 /silica composite nanospheres on nucleic acid extraction. In this study, we focused on the synthesis of Fe 3 O 4 /silica composite nanospheres with different surface structure and morphology via modified Stö ber methods, and their effect on nucleic acid extraction.…”

Si–O–C nanotubes from pyrolyzing polycarbosilane in a mesoporous template

“…Silicon oxycarbide, a carbon containing silicate, has been synthesized as tetrahedral network of Si-O and Si-C [34,35], carbon-dispersed black glass [34] and porous glass [36]. The Si-O-C has a wide range of applications such as structural materials [37], reinforcement materials [38] and catalyst support [39]. Si-O-C has been prepared as bulk [40], foams [37] and fibers [38,41,42].…”