| Fabrication of Mullite Bonded Porous SiC Ceramics
via Sol-Gel Coated Precursor |
Sanchita Baitalik, Nijhuma Kayal* and Omprakash Chakrabarti
pages: 181-185
DOI : 10.1080/0371750X.2015.1064327 |
| Abstract |
| In the present work oxide bonded porous SiC ceramics were fabricated using surface modified sol-gel mullite
coated SiC particles. The coated powder was characterized by measuring zeta potential at different pH, XRD analysis,
thermal analysis and FTIR spectroscopy. To observe the role of mullite source on the properties of final ceramics
two other sources of mullite (commercial mullite and synthesized mullite through sol-gel route) were also used.
Porous SiC ceramics were prepared by sintering powder compact of mullite coated SiC/SiC+mullite particles in air
at 1300oC for 3 h keeping the mullite content same. The morphologies, phase composition, porosity, pore size
distribution and mechanical strength of porous ceramics were examined as a function of mullite source. It was
observed that the coating of SiC particles by sol-gel mullite precursor effectively reduced the % SiC oxidation
degree from 51 to 33%. The ceramics obtained from sol-gel coated precursor had a flexural strength of ~23 MPa at
porosity of ~45 vol% and ceramics fabricated from SiC with sol-gel derived mullite powder had a flexural strength
of ~25 MPa at porosity of ~42 vol%. Microstructure observations revealed that neighbouring SiC particles were
bonded by well-developed neck consisting of needle-shaped mullite grown in a siliceous matrix.
[Keywords: Mullite, SiC coating, Morphology, Flexural strength] |
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