Study on Fluidization Characteristics and Coating Performance of Micro-Nano Particles in a Vibration Fluidized Atomic Layer Deposition Reactor

Atomic layer deposition can achieve precise control of the surface of micro-nano particles in the sub-nanometer or even smaller scale. However, it is difficult to achieve the modification of a large number of micro-nano particles in the traditional static atomic layer deposition reactor. In order to solve this problem, a vibration fluidized atomic layer deposition reactor with an inner diameter of 26 mm and a height of 350 mm was built in this paper to realize the batch and precise modification of micro-nano particles. Micro-nano particles are easy to agglomerate and difficult to fluidize. In order to achieve uniform deposition, it is necessary to realize the uniform fluidization of micro-nano particles first. In this paper, TiO₂ and SiO₂ particles with a particle size of 20 nm and resin particles with a particle size of 600 μm were selected to study their fluidization behavior in our home-made vibration fluidized bed reactor. When the initial bed height was 15 mm, due to the difference of viscous force between the agglomerates, TiO₂ had higher bed pressure drop and lower bed expansion rate than SiO₂ during the fluidization, which showed agglomerate bubbling fluidization, and SiO₂ bed pressure drop was low, bed expansion rate was high, SiO₂ showed agglomerate particulate fluidization. The SiO₂ particle tracer fluidization experiments show that during fluidization nanoparticle agglomerates are in a dynamic change of rupture and aggregation. Vibration can reduce the channeling and agglomeration in the fluidization process of nanoparticles, promote the breakup of agglomerates, reduce the minimum fluidization velocity of particles, and help to improve the gas-solid contact efficiency. In order to test the coating performance of the home-made atomic layer deposition reactor on nanoparticles, under the optimal fluidization conditions, at 80 ℃ using TiCl₄ and H₂O as precursors, deposition dense and uniform amorphous TiO₂ film on TiO₂ nanoparticles.The amorphous TiO₂ film can suppress the photocatalytic activity and improve the weatherability of TiO₂ pigment. After 30 cycles, the thickness of amorphous TiO₂ film is about 3. 11 nm, and its photocatalytic activity is about 90% lower than that of anatase TiO₂, and the photocatalytic activity suppression is remarkable. It is shown that a home-made vibration fluidized atomic layer deposition reactor can achieve precise modification of micro-nano particles with good application prospects.