Nickel-coated graphite composite particles have the excellent properties of graphite and nickel, and have important applications in electromagnetic shielding, catalysis, communications and military industries. However, the existing nickel-coated graphite composite particles have the problems of non-dense shell and uncontrollable morphology, which limits their application in the field of electromagnetic shielding and catalysis. To this end, this dissertation proposes a method based on electrostatic adsorption to control the number of nucleation sites on the surface of graphite particles, and then to prepare nickel-coated graphite composite particles with different shapes of nickel shells by simply adjusting the reaction kinetics. The method of controlling the density and morphology of the nickel shell in the nickel-coated graphite composite particles and their effects on electromagnetic properties and catalytic activity were studied. The main research results obtained are as follows:
First, based on electrostatic adsorption, the seed growth method was used to control the number of nucleation to prepare nickel-coated graphite composite particles with a dense shell. The effect of different nickel sulfate concentrations on the nucleation number on graphite particles during soaking was studied and the reasons were analyzed. Studies have shown that when the concentration of nickel sulfate is 0.76 mol·L-1, the number of nickel ions adsorbed on the graphite particles is the largest, which is beneficial to obtain more nucleation numbers to prepare continuous dense nickel-coated graphite composite particles.
Second, on the premise of not adding any surfactant and magnetic field, nano-needle and spherical particle-shaped nickel-coated graphite composite particles were prepared only by the control of chemical kinetics. The mechanism of its morphological transformation was studied. It is found that when the NaOH concentration is low, the reaction rate is low. After nucleation, in order to reduce the surface free energy of the system, the newly generated nickel crystal nucleus grows along the <110> direction with high surface free energy to generate one-dimensional nano-needle nickel; When the NaOH concentration is higher, the reaction rate is higher, the nickel crystal nucleus grows isotropically, and finally becomes spherical granular nickel film. The conductive adhesive prepared with spherical particle-shaped nickel-coated graphite composite particles as filler has a volume resistivity of 4.69 × 10-2Ω · cm and a saturation magnetization of 40.6 emu / g. It has excellent electromagnetic properties and can be used for electromagnetic shielding materials. Nano needle-shaped nickel-coated graphite composite particles have good catalytic activity and can be used to catalyze the reduction of p-nitrophenol by sodium borohydride.