In the last few years, numerous efforts have been explored to add metal reinforcements of (nano)powders into Si3N4 to prepare metal-reinforced Si3N4-based composites using hot pressed sintering, pressureless sintering or hot isostatic pressing. However, the grain sizes of the composites are limited to the micrometer range, and the dispersion of metal particles is not homogeneous by using the above-mentioned traditional powder techniques. In recent years, polymer-derived ceramic (PDC) route is considered to be the most promising approach in fabrication of homogeneous ceramic nanocomposites with unique nanostructures by pyrolysis of suitable single-source precursors (SSPs) with low sintering temperature.
In the present lecture, the SSP synthesis, polymer-to-ceramic conversion, the microstructural evolution of final SiHf(B)N ceramics as well as densification of SiHf(B)N ceramic nanocomposites without sintering additives will be discussed. The main findings are as follows: (1) Novel SSPs are successfully synthesized via chemical reactions; (2) Additive-free bulk SiHf(B)N ceramics could be fabricated using the PDC route plus warm pressing; (3) Si3N4/X (X = HfN, Hf3N4) ceramic nanocomposites with a homogenous microstructure can be obtained by further annealing at higher temperatures. Moreover, the correlations regarding to molecular design, compositions, microstructure and properties of the SiHf(B)N ceramic nanocomposites will be highlighted, which provides new insights into the design and synthesis of metal-modified Si-based ceramic nanocomposites via the PDC approach.