Fabrication of reaction bonded TiB2/Si/SiC composites for thermal applications

Abstract

Titanium diboride (TiB2) is an extremely hard ceramic which has excellent heat conductivity, oxidation stability, and resistance to mechanical erosion. Broader application of this material is inhibited by economic factors, particularly the cost of densifying a material with a high melting point. In this study, reaction bonded TiB2 (RB-TiB2) composites are fabricated by the reactive infiltration of molten Si into preforms of TiB2 plus carbon. Microstructure analysis indicates uniform distribution of TiB2 particles in the composites. RB-TiB2 composites with fine particles show higher flex strength and fracture toughness, while composites with larger particles have higher thermal conductivity, measured to be 120 W/(m K) at room. The coefficient of thermal expansion (CTE) of the composites is insensitive to the particle size and can be controlled in the range of 4.0-5.2 ppm/K (room temperature). RB-TiB2 shows the potential to be used for electronics thermal management applications with a combination of matching CTE, good thermal conductivity, high melting point, and attractive mechanical properties.