Nanometallocarbosilanes： Synthesis, Physicochemical Properties and Structure

Highly efficient synthesis methods have been developed and characteristics of nanometallocarbosilanes molecular structure were studied by the research team of GNIIChTEOS (State Research Institute for Chemistry and Technology of Organoelement Compounds). Nanometallocarbosilanes were synthesized by thermal co-condensation of oligocarbosilanes and alkyl amides of refractory metals. Initial, intermediate and final products of side reactions were characterized by 1 H, 13 C, 29 Si NMR (nuclear magnetic resonance), IR (infra-red) spectroscopy, GPC (gel-penetrating chromatography), TGA (thermal gravimetric analysis), TEM (transmission electron microscopy), SEM (scanning electron microscopy), RES (X-ray phase analysis) and elemental analysis. The proposed synthesis method of nanometallocarbosilanes was found to produce fusable soluble organosilicon oligomers with homogeneous distribution of nanoscale (10-20 nm) metal particles in the oligomer matrix. A computational model of the group and elemental composition of nanometallocarbosilanes was developed; it was shown that they are molecular globules of near-spherical shape and rigid polycyclic structure. Thermochemical treatment of nanometallocarbosilanes leads to SiC-nanoceramics (a high yield of up to 75-80 mass%) modified by metal nanoparticles (20-30 nm) contributing to its stabilization. The application of preceramic oxygen-free nanometallocarbosilanes will make it possible to advance in solving the problem of ceramic composite materials with long-term resistance at temperatures above 1,500 °C in oxidizing environments.