The Design Of Atomic Layer Deposition System For Powders And Surface Passivation Research Of Aluminum Nanoparticles

Atomic layer deposition(ALD)technology is an advanced technology for the preparation of nanometer thin films with characteristics such as uniform thickness,controllable deposition rate and good conformity.It has been applied in many fields,especially surface modification of micro-nano-particles.In this thesis,an atomic layer deposition system is self-designed and aluminum nanoparticles are passivated by aluminum oxide or zirconium oxide films to improve their performances in the application of reaction with hot water.The main contents of this thesis include:[1] A fluidized bed is integrated into ALD system and the fluidized bed model is simulated and verified using the Fluent.Aiming at the shortcomings that diffusion rate of precursors is undesirable in static particle bed,a fluidized bed is integrated into ALD system to disperse nanoparticles and improve the deposition rate and film quality.Design parameters(minimum fluidize velocity and bed height)are verified by Euler two-phase model.[2] A fluidized bed ALD system for powders has been designed and built,and its temperature control algorithm is also optimized.The temperature sub-system is simulated by MATLAB-Simulink.The application performances of traditional PID controller and PID with Simth Estimator are compared in both simulation and experiments.The parameters of PID with Simth Estimator are optimized and the percent overshoot of temperature system is eliminated.The stabilization time of temperature system has also been reduced.[3] Surface passivation of aluminum nanoparticles has been completed by coating thin films using the self-designed ALD system,and related failure mechanisms of the films have also been analyzed.Alumina and zirconia thin films are coated on aluminum nanoparticles,and their failure mechanisms are analyzed according to the hydrogen release by reacting with water under different temperatures.Then the minimum thickness of zirconia films at different temperature to passivate aluminum nanoparticles are optimized.