Papers by Keyword: C_f/SiC Composites

Abstract: Abstract. This paper investigated the Cf/SiC ceramic matrix composites. By utilizing different interfacial treatment processes to prepare carbon-fiber preform, the preform was then densified by infiltration and pyrolysis(PIP) with polycarbosilan/xylene solution as precursor, and the Cf/SiC ceramic matrix composite specimens were fabricated. Mechanical tests such as bending test and fracture toughness were performed for Cf/SiC samples. The results show that the interfacial bonding strength in the sample with high-temperature treatment process was improved due to removing surface sizing. The samples which were treated up to 1400°C exhibited the highest three-point flexural strength, up to 595MPa; The samples which were treated up to 1400°C and deposited by pyrolytic carbon(PyC) coating shows the highest fracture toughness value which was 20.70MPa•m1/2.

Abstract: Using polycarbosilane(PCS) as precursor materials, 2.5D、3D3d、3D4d、3D5d braided structure Cf/SiC composites were prepared by Precursor Infiltration and Pyrolysis (PIP). The result showed that different braided structure Cf/SiC composites had dissimilar change tendency of density and porosity. The braided structure and pore position influenced mechanical properties of Cf/SiC composites obviously. 2.5D Cf/SiC composites had the lowest mechanical properties compared others braided structure via PIP process, 3D5d Cf/SiC composites had the highest mechanical properties for the bending strength reached 334MPa, modulus 99.5GPa. Furthermore, the microstructure and properties of different braided structure Cf/SiC composites has been investigated by means of SEM.

Abstract: The conversion of the liquid polycabosilane (LPCS) into silicon carbide was investigated by IR, XRD, which indicated the feasibility of the transition from LPCS to SiC ceramics above 900°C. The FTIR spectra and XRD Pattern of the C_f/SiC composites show that the matrix deposited at 1200°C has silicon carbide structure with the crystallite size of β-SiC phase of about 41 nm, while the SiC phase is amorphous at 900°C. The carbon fiber reinforced silicon carbide composites (C_f/SiC) were hereby prepared at 900°C and 1200°C, through chemical liquid-vapor deposition (CLVD) process using LPCS as precursor. Flexural strength of 224 MPa for C_f/SiC specimen with density of 1.81g·cm^-3 was obtained after being prepared at 1200°C for 30 minutes. The load-deflection curve has shown that the fracture behavior of the C_f/SiC composites is a typical non-brittleness. The results indicate that the CLVD process has a great advantage and prospect to prepare C_f/SiC composites in future.

Abstract: PAN and Pitch short carbon fiber-reinforced SiC matrix composites were fabricated by using a melting infiltration technique. The microstructure of the composites was characterized by scanning electron microscopy. The flexural strength of the composites was measured at room and high temperatures. The thermal conducitivity of the composites were evaluated. Effects of fibers on mechanical properties and thermal conductivity were assessed. The experimental results showed that the silicification of fibers during siliconizing was prevented due to the presence of barrier layer on the surface of fiber. Also, flexural strength and thermal conductivity depended on fibers used and content of fibers.

Abstract: Continuous carbon fiber-reinforced silicon carbide (Cf/SiC) composite was fabricated by hot-pressing, via liquid phase sintering. Sintering conditions strongly affect the densification process, and therefore dominate the mechanical properties and fracture behavior. The composites under the lower sintering temperature behaves less densified matrix and it demonstrates a relatively weak fiber/matrix bonding allowing the longer fibers pull-out. Increasing sintering temperature could accelerate the densified matrix and make fiber/matrix bonding stronger. In this case, the shorter fibers pull-out was predominant fracture behavior and it could improve mechanical properties.