Fabrication and properties of dense silicon carbide ceramic via gel-casting and gas silicon infiltration

Abstract

The dense Silicon Carbide (SiC) ceramics are fabricated by means of gel-casting and gas silicon infiltration (GSI) using carbon black and α-SiC as raw materials. We have successfully introduced a new initiator AIBA which is very suitable to aqueous gel-casting system containing carbon black, overcoming the problems posed by the conventionally used initiator. We have investigated the influences of the monomer acrylamide (AM) content, the ratio of the monomer to crosslinking agent AM/MBAM content, the particle size distribution and the solid content on the mechanical and structural properties of samples. The result show that, the linear shrinkage of the green body can be reduced to 1.0% and its bending strength can reach 59.2 MPa at the optimized gel-casting process that has an AM content of 25 wt.%, an AM to MBAM ratio of 12, a SiC particle distribution of 3/2 and a solid content of 60 vol.%. After the GSI process, the bending strength and elastic modulus of the final products from such green bodies can reach 245 MPa and 220 GPa respectively. The study highlights that the combined application of the gel-casting and the GSI processes can produce high-quality silicon carbide ceramics that are suitable in the space optical applications.

Damage development during flexural loading of a 5-directional braided C/C-SiC composite, characterized by X-ray tomography and digital volume correlation

“…There are currently no published data for the tensile elastic moduli of these GSI and PIP composites, but there are data for composites with similar constituents; the tensile modulus of T300 carbon fiber is ~230 GPa [41] and the typical modulus of SiC produced by the GSI process is ~200 GPa [42]. In a two-dimensional LSI-fabricated C-SiC composite with 40% fiber content, the highest tensile modulus was 145 GPa; lower values were attributed to the effects of thermal residual stresses [11].…”

In situ Observation of Compression Damage in a Three-Dimensional Braided Carbon Fiber Reinforced Carbon and Silicon Carbide (C/C-SiC) Ceramic Composite

“…That is beyond the scope of this work, but a simple consideration may be done. The high longitudinal compressive modulus (~160 GPa) is due to the axial stiffness of the fibers and continuous ceramic matrix, although a simple Voigt model suggests that this is still relatively low compared to the expected Young’s moduli (Miyagawa et al, 2006) of the T300 fiber (~230 GPa), and typical properties (~200 GPa) of SiC produced by the GSI process (Huang et al, 2016). However, the longitudinal modulus reduces with compression (Fig.…”

Si/SiC optical coatings for C/SiC composites via gel-casting and gas silicon infiltration: Effects of carbon black content

“…The pre-coating was fabricated by gel-casting [16] . Firstly, AM and MBAM were dissolved in deionized water to form a solution, AM and MABM took 25wt.% and 2wt.% in water respectively.…”

“…Meanwhile, the gas silicon infiltration (GSI) method which serves as sintering process of the C/SiC composites is also used in the preparation of the coating, due to its short preparation period, low sintering temperature, minimum sintering shrinkage and low cost [14,15] . In our previous works [16] , the process optimization of GC-GSI have already been carried out.…”