Microstructure and Properties of Spark Plasma Sintered MoAlB Ceramics

Advisor: Bai Cui Molybdenum aluminum boride (MoAlB) is a ternary transition metal boride which has promising aeronautic and nuclear applications. It inheres excellent properties of the binary transitional metal borides (e.g., MoB, ZrB2) such as high melting temperature, high hardness, and thermal conductivity. Besides, MoAlB is superior to MoB because: (1) the Al element provides an oxidation resistance at high temperatures; (2) its nanolaminated structure consisting of M-B layers with alternating Al layers results in a unique damage tolerance property. In this research, polycrystalline MoAlB have been successfully synthesized and simultaneously sintered using spark plasma sintering (SPS) from molybdenum boride (MoB) and aluminum (Al) powders. The SPS conditions have been optimized to obtain bulk samples with a high purity (>98 vol.%) and a high relative density (>97%). The microstructures have been characterized by X-ray diffraction and scanning electron microscopy. The mechanical property and oxidation behavior have been studied by using the Vickers indentation method and oxidation kinetics measurements, respectively.