Processing of silica bonded porous SiC preform for metallic composites

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 MgAl 2 O 4 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 Al 4 C 3 interfacial reaction product.

Effects of SiC whisker addition on mechanical, thermal, and permeability properties of porous silica‐bonded SiC ceramics

“…reported that the flexural strength of porous silica‐bonded SiC ceramics prepared by infiltration method decreased from ∼47.9 to ∼29.5 MPa as the porosity increased from 26.1% to 35.6%. Many other researchers have also reported the same trend in porous silica‐bonded SiC ceramics 34,35,39–41 . In summary, the mechanical strength of porous SiC ceramics decreases with an increase in porosity. Effect of porosity on thermal conductivity: Kim et al 34 .…”

“…One approach that provides economic advantages due to the application of low sintering temperature (<1450°C) while enhancing necking between SiC particles is the oxidation bonding technique 34–37 . The oxidation bonding method entails the preparation of an SiC powder‐template body followed by sintering the green body in air to promote bonding of SiC particles by in situ oxidation‐derived SiO 2 34–41 . SiO 2 as bonding phase provides a beneficial effect in reducing the temperature required to make necking between particles and facilitating partial densification of SiC strut 14,15,38,41 .…”

“…SiO 2 as bonding phase provides a beneficial effect in reducing the temperature required to make necking between particles and facilitating partial densification of SiC strut 14,15,38,41 . Furthermore, by controlling the sintering temperature and template content, the mechanical and thermal properties of porous silica‐bonded SiC ceramics can be adjusted to some extent 34,37,39,41 …”

Effects of Composite Sintering Additives: Al(OH)3+Y2O3+CaF2 on the Performance of Porous Mullite Oxide-Bonded SiC Ceramics

“…Recently, oxide bonding sintering attracts more and more attention because it enables porous SiC ceramics to be sintered at a temperature lower than 1600 ℃, which dramatically reduces the fabrication cost. The first oxide bonding phase studied is silica (SiO2) in the cristobalite phase and/or amorphous form at room temperature [7,20,21].…”

Microstructures and Properties of Porous Liquid-Phase-Sintered SiC Ceramic by Hot Press Sintering

“…Thanks to the partial sintering and a tiny bit of oxide additions, the densification of sintered bodies is inadequate, and then pores are successfully formed [23]. Earlier studies about porous L-SiC ceramics have mostly focused on the types of additions such as silica [24,25], alumina [21], yttria [26], silicon nitride [27], mullite [28,29,30], glass frit, cordierite [31], CeO 2 [16], V 2 O 5 [32], and so on. They have summarized the effects of starting powders, additive amount, and sintering temperature on the microstructure of porous L-SiC ceramics, which were all prepared by pressureless sintering.…”