Low-temperature formation of TaB₂ powder from oxides and sodium metal with concurrent generation of water glass

抄録

Tantalum borides have conventionally been produced via high-temperature solid-state reactions of the corresponding elemental raw materials. In this study, a unique chemical reaction design to add SiO₂ to the starting materials for an assist of TaB₂ formation is demonstrated. Powder mixtures of Ta₂O₅, B₂O₃, and SiO₂ were heated together with Na metal. TaB₂ was formed with concurrent generation of Na₂SiO₃ (otherwise known as water glass) in the reaction. Nearly single phase of TaB₂ powders with 50–200 nm particle sizes were obtained by by heating at a temperature range from 800 to 1000 °C followed by the successive removal of unreacted sodium and washing with ethanol and water. TaB₂ grains having a hexagonal prism morphology and sizes of several micrometers were grown in the sample heated at 1100 °C, possibly because molten Na₂SiO₃ with a melting point of 1088 °C acted as a flux.