SiC/Si composites elaboration by capillary infiltration of molten silicon

Abstract

Infiltration of molten metal into ceramic performs without external pressure is a promising fabrication method for metal-matrix composites. Thus, this research is focused on the kinetic of capillary infiltration in the processing of Si/SiC composites. The calculation of the infiltration kinetics for a liquid in a porous material is possible by applying the modified-Washburn equation which involves the effective diameter of the pores. This equation implies a K value depending on the wetting angle, the density, the viscosity and the surface tension of the liquid at a given temperature. In this study, the main aim was to measure the K Si value of molten silicon infiltration into porous SiC at 1500°C. On this way, consolidated β-SiC powder compacts were prepared for infiltration experiments. The effects of the SiC particles presintering on the pore size were examined as they can affect molten silicon infiltration. So, the monitoring of the mass increase during hexadecane rise was used to determine the effective diameter of the pores. It was evidenced that an increase of 15.5% of the initial effective diameter occurs. Consequently, a corresponding correction has to be applied to the initial effective diameter of the siliconinfiltrated compacts. Infiltrations of pure molten silicon into SiC compacts were successfully carried out at 1500°C under high vacuum (5.10 -3 mbar) and the average value of K Si was found equal to (5.8±0.4)×10 -6 cm 5 .s.g -2 . The effect of molten silicon rise on the porosity was also considered.

Kinetics of liquid metal infiltration in TiC-SiC or SiC porous compacts

“…However, it is known from many experimental studies of such composites that, the infiltration of high melting point metals such as nickel and titanium is possible but the reactivity of these metals with SiC makes them unusable at high temperatures [8,9]. Liquid Silicon Infiltration process (LSI) is also developed to produce SiC-based composites and to realize near-net formed ceramic components but the use of these materials is limited to the melting temperature of silicon (1410°C) [10][11][12][13]. Another solution to increase the performances consists in the association of SiC with another ceramic phase.…”

Characterization of SiC ceramics with complex porosity by capillary infiltration: Part B – Filling by molten silicon at 1500 °C

“…Good wettability of the molten metal on the reinforcement is required preferably without any reactivity. This technic is also applicable to the infiltration of metals with a high melting point as nickel and titanium or silicon [13][14][15]. Liquid silicon infiltration process is developed to improve the mechanical properties of SiC composites and to realize near-net formed ceramic components [16,17].…”

“…This way commonly called LSI (Liquid Silicon Infiltration) implies a production temperature higher than the melting point of Si (1414°C). In a previous study, we examined the infiltration kinetic of molten silicon at 1500°C in porous and homogeneous SiC preforms [15]. But the infiltration mechanisms and kinetics of liquid silicon in heterogeneous SiC materials remain largely unknown, especially since chemical processes may occur at such an elevated temperature.…”

Characterization of SiC ceramics with complex porosity by capillary infiltration: Part A - Filling by hexadecane at 20 °C

“…MMC can be tailored to have superior properties such as enhanced high-temperature performance, high specific strength and stiffness, increased wear resistance, better thermal and mechanical fatigue, and creep resistance than those of unreinforced alloys. This way is also applied for the fabrication of SiC/Si composites by capillary infiltration of molten silicon into porous silicon carbide [17][18][19]. Macroporous silicon carbide is widely used in various industrial applications including filtration for gas and water, absorption, catalyst supports, concentrated solar power, thermoelectric conversion, etc [20][21].…”