Study On Micro/Nano-Particles Coating Via Atomic Layer Deposition And The Design Of Enlarged ALD Equipment

Micro/nanoparticles have been widely used in many fields such as energy,aerospace and military due to its large specific area and huge surface energy.However,the major drawback for micro/nanoparticles is its poor stability toward easy oxidation under ambient conditions,leading to the failure.Coating a barrier layer on the surface of micro/nanoparticles is a common surface modification method to improve their stability.Atomic layer deposition?ALD?is a novel method for the surface modification of micro/nanoparticles,which can precisely control the thickness and the content of coating films.In this paper,ultrathin zirconia?ZrO₂?film has been deposited on the surface of Al nanoparticles to improve its stability in hot water.And the enlarged ALD equipment for particles has been designed.The main contents of this research can be classified into two parts as followed:The ultrathin ZrO₂ film has been successfully deposited on the surface of Al nanoparticles via ALD,where a sub-nanometer coating can completely prevent the reaction between Al nanoparticles and hot water?80oC?.The percentage of metallic Al for ultrathin ZrO₂ coated Al nanoparticles can reach 82.2 wt%.The metallic Al's weight has been kept at 93.4%for ultrathin ZrO₂ coating Al nanoparticles comparing to the original Al nanoparticles.The passivation mechanism is attributed to ZrO₂ coating'structural stability and the enhanced hydrophobicity to water.The enlarged ALD equipment for micro/nanoparticles has been detail designed in this chapter.Different motion mode of particles under different expiation have been raised firstly.The simulation of single particle's motion under vibration of different frequency has been simulated by discrete element method,which verified the correction of the motion mode.And the effect of vibration frequency,amplitude magnitude and particles size distribution on the velocity and velocity distribution were studied with multi-particles as the research object.The heat transform and dissipation of the particles conveying assembly were design in detail and studied by fluid-solid coupling thermal simulation,which satisfied the high temperature condition for ALD reaction and safe temperature for piezoelectric driving motor at the same time.Al₂O₃ film growing on the surface of SiO₂ particles verified the feasibility.In the end of the chapter,the particles conveying and reaction assembly have been improved and the circulating ALD equipment and continuous ALD equipment were proposed.