Leucoxene concentrate as an effective source for synthesizing MAX phase high-temperature ceramic composites

Abstract

The authors have developed a three-stage technology for making dense Ti3SiC2–TiB2–(TiC)–SiC ceramic composites of a leucoxene concentrate being a product of previous treatment of titanium-containing sandstones. The first stage means the synthesis of agglomerated Ti3SiC2–TiB2–SiC powders which may significantly differ in SiC content. The synthesis proceeds by the method of the vacuum carbosilicothermic reduction of leucoxene concentrate using SiC as a reducing agent with addition of B4C as a solid boron-containing component. The second stage is etching the obtained powders with hydrofluoric acid in order to remove the by-products of silicide composition having been formed of impurities in leucoxene concentrate. At the final third stage, the purified Ti3SiC2–TiB2–(TiC)–SiC powders are hot-pressed in a graphite die under 30 MPa at a temperature of 1500-1550 °C. The end product is Ti3SiC2–TiB2–(TiC)–SiC ceramic composites with nearly absolute pore-free microstructure.