Research Overview
Advantage of nano- relative to micro-size diamond composites. For diamond-SiC composites this goal can be accomplished by a controlled production of nanosize silicon carbide by including nanosize diamond crystals in the manufacturing protocol. Nanostructured SiC can be also obtained from amorphous silicon. We also make hybrid composites in which micron size diamonds are embedded in nanostructured silicon carbide matrix that may also include SiC nanowires.
Accepted model of a nanograin illustrates the fact that atoms close to the surface have different environment and, thus, the interatomic distances are different (smaller or larger) than those in the bulk. Those differences have direct impact on the properties of the material. While that impact may be ignored for large grains, in nanomaterials it can be dominant.
To improve manufacturing conditions one needs to understand the reaction mechanism between diamond and silicon. We studied the reaction rates and activation energy for diamonds of various sizes.
Diffraction on nanocrystals provides information on the structure of the precursors and products. Both x-ray and neutron diffraction scattering have been employed.
Strain and dislocations in crystals have been investigated by x-ray diffraction line profile analysis. This method has been used to study pure diamond and silicon carbide powders, as well as diamond and silicon carbide phases in diamond-SiC composites.
Raman mapping has provided information on residual strain in diamond crystals in diamond composites. Distribution of stress in crystals have been evaluated for composites obtained at various manufacturing conditions and using different size diamond crystals.
Silicon carbide nanowires have been obtained by high temperature sintering. Their mechanical and physical properties are being investigated.