Effect of Liquid Phase Sintering on Microstructure and Mechanical Properties of Yb₂O₃‐AlN Containing SiC‐Based Ceramics

Abstract

A series of silicon carbide‐based ceramics with different sintering additives were liquid‐phase sintered to high densities. Yb2O3 in combination with AlN was used as the additive, instead of the commonly used Y2O3–AlN, to improve the refractoriness of the secondary phase. Thermo‐chemical decomposition of AlN was sufficiently suppressed with the use of nitrogen overpressure and reasonable weight loss was achieved in the different additive containing SiC ceramics without a reactive powder bed. Use of the heavier rare‐earth element modified the liquid phase formed during sintering and reduced the phase transformation controlled grain growth rate, compared with Y2O3 doped materials. It also permitted microstructure tailoring through post‐sintering heat treatments in nitrogen. Materials with self‐reinforced microstructures, formed as a result of anisotropic grain growth, were obtained. Improved fracture toughness (4.5–5 MPa/m1/2) and good flexural strength retention up to 1400°C were also observed.

Sintering Behavior of Nanocrystalline Silicon Carbide Using a Plasma Pressure Compaction System: Master Sintering Curve Analysis

“…Thus, it was concluded that P 2 C can be used for the fabrication of nanocrystalline SiC samples with excellent hardness and fracture toughness. [34][35][36][37][38] are comparable to the values obtained for the SiC samples sintered in the P 2 C in the current work. Some of the processing conditions used are also given to show that SiC can be sintered in the P 2 C at much lower temperatures than reported in the literature for other processes such as gas-pressure-assisted sintering (GPS), pressureless sintering, and HP.…”

“…These were similar to those reported in the literature for SiC prepared by various methods such as pressureless sintering and HP at much higher temperatures between 2073 K and 2273 K (1800°C and 2000°C). [34][35][36][37][38] A comparison of various literature studies with the current work is shown in Figure 13. The reduced time and temperature in the P 2 C process led to increased process efficiency.…”

“…Fig. 12 [34,35,37,38,[40][41][42][43] and this is depicted in Figure 15. Note that Vassan and Sto¨ver reported the toughness of 2.8 to 4.2 MPaAEm 1/2 for SiC samples prepared by HIP at high pressure of 350 MPa and temperature of 1773 K to 1923 K (1500°C to 1650°C) from SiC powder with particle size less than 20 nm.…”

“…Table I. [34,35,37,38,[40][41][42][43] in the literature for different processing methods such as HP and GPS is compared to the SiC samples prepared in the P 2 C in this work. It should be noted that though most of the data were obtained by the IF method, Hidaka et al used the single edge V-notch beam method and Cao et al used the disk-shaped compact tension specimen method for measuring the toughness of their samples.…”

Mechanical properties of SiC ceramics sintered with RE2O3 (RE: Sc, Lu, Y) and AlN additives

“…3. Among the investigated systems, the toughness was the lowest (3.54 MPa.m [8,20,24,25]. From the morphology of fracture surfaces, the absence of significant toughening mechanisms in SCSc caused it to have the lowest toughness.…”