Optically selective SiC-based nanocomposite objects derived from titanium and boron-modified polycarbosilanes

Herein, we introduce a bottom-up material design approach of optically selective SiC-based nanocomposite objects. Precursors have been firstly synthesized by reaction of allylhydridopolycarbosilane with titanium and boron complexes before a pyrolysis at 1000 degrees C in flowing argon to deliver single-phase amorphous Si-Ti-C-N(B, H) ceramics. The later was then heat-treated up to 1800 degrees C under argon. Relatively dense nanocomposites made of TiCxN1-x (0 <= x <= 1) nanocrystals homogeneously formed in situ in a SiCxN4-x-type phases (0 <= x <= 4) have been isolated after heat-treatment at 1400 degrees C. Above 1400 degrees C, our experimental data showed a continuous evolution of carbon and nitrogen contents up to 1800 degrees C due to carbothermal reduction reactions forming carbide phases while releasing nitrogen-containing species. Thus, heat-treatment at 1800 degrees C led to porous and fully crystallized TiC(N)/SiC(B) nanocomposites that displayed a maximal optical selectivity of 1.67 measured at room temperature; a value significantly increased compared to the SiC(B) counterpart.