Properties of Boron Suboxide B13O2

We describe for the first time a method for synthesis of boron suboxide under vacuum from a B2O3 + B mixture. We show that at 1420°C, under vacuum a boron suboxide phase of composition B13O2 is formed. The product is a highly disperse powder which, according to electron microscopy and crystal optics analysis, consists of agglomerates of various sizes with single-crystal particles mainly no larger than 2 μm. We have used differential thermal analysis for the first time to study the reaction of crystalline boron with boric anhydride under vacuum and also in helium. We have shown that the temperature of onset of the reaction (B + B2O3) depends on the heating rate of the reagent mixture, and is practically independent of the reaction medium (1420°C). Compared with the original boron, the B13O2 powder has higher chemical stability in liquid reagents and thermal stability in air for isothermal and nonisothermal heating conditions. We wetted hot-pressed B13O2 samples with iron, nickel, copper, and tin melts. We have shown that B13O2 is readily wetted by iron and nickel at temperatures of 1200-1300°C, while it is practically unwetted by copper and tin at 1200°C and 900°C.