Surface Modification of Graphite Particles Coated by Atomic Layer Deposition and Advances in Ceramic Composites

Graphite particles have been coated with Al2O3 via atomic layer deposition. Alumina content was measured via inductively coupled plasma spectrometry (ICP), LECO combustion analysis, and thermogravimetric analysis (TGA). While alumina was present, adherence was limited, and nonconformal films were deposited on the graphite particles. Coatings produced changes in particle interactions and dispersability. These changes were observed via sedimentation rates of particle suspensions in water, Zeta potential values, and particle size distributions. Alumina-Graphite composites were sintered using coated and uncoated particles. Differences in bulk thermal properties are ascribed to enhanced dispersability of the coated particles in presintered powder mixtures. EDS mapping of the sintered composites confirms the enhanced dispersion of the coated graphite particles. Particle coating through atomic layer deposition provides a means to improve particle dispersion with low material loadings. It has been shown that changes in particle interaction characteristics can be achieved even without uniform and conformal coatings. These particle interaction changes can result in sintered composites with enhanced thermal properties.