This experimental investigation reports on the mechanical properties of nanocrystalline silicon carbide as a function of the crystallite size. Monolithic SiC samples are fabricated by controlled pyrolysis of a polymer precursor under an inert atmosphere. The degree of crystallization, and the resulting grain size, is controlled by varying the processing conditions. Subsequently, the modulus and hardness are determined using instrumented indentation. Meanwhile the microstructure is characterized using X-ray diffraction. The process yields grain sizes in the range of approx 0-12 nm. It is seen that the presence of nanocrystalline domains in amorphous SiC significantly influences the modulus and hardness. A non-linear relationship is observed with optimal mechanical properties for a grain size of 3.5 run.
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