Abstract:
Porous SiC ceramics were successfully fabricated
by silica bonding of SiC compacts and porogen
burnout technique. Silica coating on SiC particle was carried
out using TEOS hydrolysis and crystallizes during the
sintering process at 1200 C, which forms a well-developed
neck growth between the SiC particles. Different
volume fractions of sodium chloride porogen were used to
obtain varied porosity content in porous SiC ceramics from
36 to 62.47 % leading to wide-ranging compressive
strength from 8.11 to 0.69 MPa. Interconnected bimodal
pores were created throughout the sample due to the burnt
out of salt and stacking of SiC particles. The pore size
distribution of porous SiC measured using mercury intrusion
porosimetry shows that average pore size due to the
salt particle is around 74–110 lm and stacking of SiC
particle result 4–10 lm. Direct squeeze infiltration method
is successfully adopted for infiltration of 6061 aluminium
molten alloy into SiC preforms with the controlled process
parameters of initial preform temperature, liquid metal
superheating, squeezed pressure and its rate of application
and die temperature. Microstructures have shown complete
infiltration of Al alloy into the pores of the SiC preform
forming Al composite with good interfacial bonding aided
by the presence of MgAl2O4 spinel. The silica coating on
SiC surface have a multifunctional role of acting as a
binder for the porous preform, enhances the wettability of
SiC particle with molten metal during infiltration and
prevention of deleterious Al4C3 interfacial reaction
product.
