High-Temperature Properties of SiC-Si3N4 Particle Composites

Abstract

Due to promising results in literature, SiC-Si3N4 particle composites in the range 0–100 percent SiC were evaluated. Focusing on high-temperature properties, mainly Y2O3 was used as sintering additive. Consolidation occurred primarily by hot-pressing, sintering tests were performed for comparison. Besides short-term properties like strength, toughness etc., long-term properties like creep and oxidation behavior were determined. Results as a function of SiC-content and microstructure were discussed with respect to materials’ performance at high temperatures and possibilities of their production on a technical scale. [S0742-4795(00)00201-5]

Ultrasonic Attenuation of Ceramic and Inorganic Materials Using the Through-Transmission Method

“…This additional E reduction may arise from low intergranular bonding between Si 3 N 4 and SiC grains. Si 3 N 4 with 20% SiC with Y 2 O 3 showed the fracture toughness of 5.2 MPa•m 0.5 , which was at 71% of that of Si 3 N 4 [64]. As noted earlier, the 20% SiC addition increased E only slightly.…”

“…For the sapphire disc used here was previously assumed to be of R-cut (the second pyramidal plane (11 02)), but it is closer to the A-cut (with prismatic (11 00) face). [55][56][57][58][59][60][61][62][63][64][65][66][67]. Agreements between nominally same materials were good; e.g., for B 4 C and WC cermet.…”

“…The translucent alumina sample has a low porosity of 2% from its density and a typical microstructure showing low void counts (Figure 10 in [65]). More recent YSZ microstructures contained few voids and larger grain sizes [64]. Such materials will be useful for studying the sources of YSZ attenuation when large enough samples become available.…”

“…As noted above, dislocation damping is also expected to be low in materials with Vickers hardness exceeding 1000. The WC and Si 3 N 4 samples had Vickers hardness of 1755 (1 kg load) and 1170 (300 g load), while B 4 C was reported to have 3200 [71] and 1430-2300 for Si 3 N 4 [64,72]. In B 4 C, sintering and hot pressing slightly decrease carbon content and also leave the intergranular amorphous phase [73].…”

“…In terms of Cij values, SiC has higher C11 and C44 than those of Si3N4 (by 25% and 46-65%), while both have similar C33. In yttria-added Si3N4 and Si3N4-20%SiC, Woetting et al[64] reported an increase in E from 316 to 324 GPa. Thus, the observed softening in Si3N4-SiC in this study needs further evaluation.…”