Thermal conductivity of precursor derived Si–B–C–N ceramic foams using Metroxylon sagu as sacrificial template

• Published in: Ceramics international 2015-01, Vol.41 (1), p.1163-1170
• Main Authors: Kousaalya, Adhimoolam Bakthavachalam, Kumar, Ravi, Sridhar, B.T.N.
• Format: Article
• Language: English
• Subjects: B. Porosity; C. Thermal conductivity; Natural starch; Si–B–C–N foam
• ISSN: 0272-8842; 1873-3956
• DOI: 10.1016/j.ceramint.2014.09.044

Thermolysis of as-cast polyorganoborosilazane resulted in the formation of porous monolith of Si–B–C–N ceramic. However the addition of varying amounts of Metroxylon sagu (30–60wt%) to polyorganoborosilazane, on thermolysis, resulted in Si–B–C–N foams. Thermo-gravimetric analysis of M. sagu revealed complete decomposition at 850°C. Spark plasma sintering of Si–B–C–N was carried out at 1600°C at a pressure of 30MPa for 5min in vacuum to obtain highly dense compacts. The obtained Si–B–C–N foam was found to be amorphous while the SPS-processed samples were observed to be highly crystalline. The geometrical density of the foam was found to vary from 0.4 to 0.25g/cm3 with increase in sago content along with the presence of both closed and open cells. The thermal conductivity of the foam and SPS-processed samples showed varying trends with increasing temperature due to the amorphous and crystalline nature of the samplesrespectively.