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|Type:||Artigo de periódico|
|Title:||Processing Of Monolithic Ceramic Bodies From Polysiloxane Precursor|
|Abstract:||A low temperature process for the manufacture of ceramic-body composite, with preceramic polymer as binder, has been shown to be a promising technique for the preparation of monolithic ceramic blocks in a process that excluded powder-sintering phenomena. This work reports the direct transformation of a silicone polycyclic network into silicon oxycarbide in the presence of ceramic powders, such as SiC or Si3N4, which act as inert fillers. They prevent the shrinkage usually observed during polymer pyrolysis. The preparation of ceramic bodies using a ceramic powder/polysiloxane system was achieved by hydrosilylation reaction between functional siloxane cyclic oligomers, using a transition metal catalyst (PtII) in the presence of the powder filler, at different volume fractions. In order to develop green bodies, the ceramic powder/polysiloxane mixtures were pressed and cured at 70°C for 3 hours. Afterwards, they were then pyrolysed in argon atmosphere at 1000°C, producing ceramic matrix composites SiC/SiCxO4-x and Si3N4/SiCxO4-x having no cracks. Microstructural characterization was performed by 29Si MAS NMR, suggesting a random distribution of SiC4, SiC3O, SiC2O2 and SiO4 sites in the SiCxO4-x phase. Scanning Electron Microscopy showed evidence of a homogeneous distribution of the polymer in the green bodies and in the SiCxO4-x phase after pyrolysis. Impact resistance and flexural strength performed mechanical characterization of the ceramic composites. The results highlighted the potential benefits of this strategy to produce resistant ceramic composite bodies.|
|Editor:||Trans Tech Publ, Uetikon-Zuerich, Switzerland|
|Appears in Collections:||Unicamp - Artigos e Outros Documentos|
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