Carmen Carney

Development of transparent polycrystalline beta-silicon carbide

Transparent beta-SiC is of great interest because its high strength, low coefficient of thermal expansion, very high thermal conductivity, and cubic crystal structure give it a very high thermal shock resistance. A transparent, polycrystalline beta-SiC window will find applications in armor, hypersonic missiles, and thermal control for thin disc lasers. SiC is currently available as either small transparent vapor grown disks or larger opaque shapes. Neither of which are useful in window applications. We are developing sintering technology to enable transparent SiC ceramics. This involves developing procedures to make high purity powders and studying their densification behavior. We have been successful in demonstrating transparency in thin sections using Field Assisted Sintering Technology (FAST). This paper will discuss the reaction mechanisms in the formation of beta-SiC powder and its sintering behavior in producing transparent ceramics.

Densification and Microhardness of Spark Plasma Sintered ZrB2+SiC Nano-Composites

Ultra-High-Temperature Ceramics (UHTCs) such as ZrB2 and HfB2 with incorporation of SiC nanofiller are useful as structural materials for applications in propulsion and thermal protection systems such as turbine-engine hot section components, leading edge of hypersonic vehicles, where extremely high heat fluxes generate very high temperatures and steep temperature gradients [1]. Spark plasma sintering (SPS) technique is used for densifying the UHTCs under the influence of uniaxial pressure and pulsed direct current [2]. Here, we study the densification, grain growth, and microhardness of ZrB2 nanocomposites with 15% and 20% SiC consolidated using SPS.