Investigation of the Microstructure of SiC-Zn Nanocomposites by Microscopic Methods: SEM, AFM and TEM

SiC-Zn nanocomposites with about 20% volume fraction of metal were fabricated by infiltration process under the pressure of 2-8 GPa and at the temperature of 400_1000oC. SiC nanopowders used in the experiments formed loosely agglomerated chains of single crystal nanoparticles. The dimension of the agglomerates was in the micrometer range, the mean grain size was up to tens of nanometers. Microstructural investigations of the nanocomposites were performed at a different resolution levels using scanning, transmission electron microscopy and atomic force microscopy techniques (SEM, TEM, AFM, respectively). SEM observations indicate a presence of nano-dispersed, uniform (on the micrometer scale) mixture of two phases. TEM observations show that distribution of SiC and Zn nanocrystallites is uniform on the nanometer scale. High-resolution TEM images demonstrate an existence of thin (on the order of tens of Angstroms) Zn layers separating SiC grains. AFM images of the mechanically polished samples show a smooth surface with the roughness on the order of the SiC grain size (10-30 nm). After ion etching of some samples the AFM topographs show surface irregularities: periodically spaced hillocks 50-100 nm in height. The size of the SiC grains remains equal to that of the initial powder crystallites. The size of the Zn grains varies in the range of 20-100 nm depending on the initial SiC grain size and the composite fabrication conditions.