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|Type:||Artigo de periódico|
|Title:||Synthesis and structural characterization of carbon-rich SiCxOy derived from a Ni-containing hybrid polymer|
|Abstract:||Carbon-rich silicon oxycarbide ceramics were obtained by controlled pyrolysis at 950, 1300 and 1500 degrees C from hybrid polymeric precursors based on poly(methylsiloxane) and divinylbenzene with different molar ratios, in the presence or absence of nickel acetate. By increasing the pyrolysis temperature changes in the local molecular structure were observed by Si-29 NMR, with the segregation of thermodynamically stable SiO2 and SiC phases, in addition to formation of graphitic carbon nanoclusters. Ceramics without Ni were amorphous at 950 degrees C, while those obtained at 1300 degrees C showed the presence of a beta-SiC phase. The presence of Ni in the polymeric precursor induced the formation of beta-SiC, cristobalite silica, graphitic carbon, metallic Ni, NiO and Ni2Si, and also reflected in denser materials. In general, the resulting ceramics without Ni did not present measurable porosity, whereas Ni-containing ceramics at 1500 degrees C showed behavior typical of mesoporous materials. (C) 2008 Elsevier Ltd. All rights reserved.|
|Editor:||Elsevier Sci Ltd|
|Appears in Collections:||Unicamp - Artigos e Outros Documentos|
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