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

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.