A Solvothermal Approach for the Preparation of Nanostructured Carbide and Boride Ultra-High-Temperature Ceramics

The use of a solvothermal process for the synthesis of tantalum carbide (TaC) and lanthanum hexaboride (LaB₆) powders in fused-quartz test tubes is reported in order to demonstrate the synthesis of these powders using thermal and chemical ignition techniques and to prove that the process is of a self-propagating high-temperature synthesis type, obviating the need for an autoclave. X-ray powder diffraction showed phase pure powders with crystallite sizes of 25 and ∼80 nm, while dynamic light scattering showed average particle sizes of 97 and ∼130 nm, for TaC and LaB₆, respectively. The data demonstrates that the powders have a very low level of agglomeration. Scanning electron microscopy shows that the TaC powders have a spherical morphology, while the LaB₆ powders have a mixture of cubic and spherical morphologies.