Study On Preparation And Properties Of Graphite/Oxides Composite Particles

As a super refractory, nature flaky graphite has many advantages such as high thermal conductivity, high thermal shock resistance, excellent high-temperature strength, excellent machinability, high sublimation temperature and low thermal expansion coefficient. Unfortunately, the poor water wettability, low density and flaky structure of graphite surface limit its application with large quantity.Inorganic salts, such as A1(NO3)3, ZrOCl2, TiCl3, et al. was used as raw materials and corresponding hydroxides were deposited on the surface of graphite particle with heterogeneous nucleation process; composite particles of graphite/oxides were obtained after heat treatment. In this paper, preparing conditions and properties of composite particles were studied.By the analysis of coating ratio, oxidation ratio, micrograph and particlesize of composite particle, it was found out that factors such as pH value, coating temperature, concentration of premonitory matter solution mainly affect the coating layer forming. With the optimum parameter, the obtained composite particle have many changes compared with uncoated graphite, such as the increase of coating ratio, particle size and decrease of specific surface area, et al. Graphite particle surfaces are coated by a layer of oxides equably through micrograph images. In addition, the coating effect of Al2O3-coated particle is the best and much homogeneously; the effect of TiO2-coated particle is the worst and its self-nucleation was serious, while after Al2O3/ZrO2-coated, the coating on graphite surface becomes much denser.Compared with uncoated graphite, contact angle with water of all of the composite particles are much smaller and decreased gradually with the increase of the coating amount. When dispersed in water, the electric property of composite particles surface is similar to that of corresponding oxides, whileafter Al2O3/ZrO2-coated, the electric property of graphite surface was similar to that of ZrO2. In water, the apparent viscosity of composite particles is much lower than that of uncoated graphite with the same solid content; composite particles have good dispersion effect under different pH value with dispersant agent of sodium hexametahposphate. Through the analysis of TG-DTG curve, the oxidation resistance of composite particles has been greatly improved. The XRD results reveal that the oxides coated are non-crystal and XPS results reveal that it has chemical bonder with the surface of graphite particle.