Surface Coating of Submicron Particles by Fluidized/Moving Bed-CVD

Research Project

Project/Area Number	06555224
Research Category	Grant-in-Aid for Developmental Scientific Research (B)
Allocation Type	Single-year Grants
Research Field	化学工学一般
Research Institution	HOKKAIDO UNIVERSITY
Principal Investigator	SHINOHARA Kunio Hokkaido Univ., Fac. of Eng., Pro.Inst., 工学部, 教授 (60001294)
Co-Investigator(Kenkyū-buntansha)	TUTUMI Katsuo Kawasaki Heavy Ind., Tech Development, Leeder, 技術開発本部, 係長大山恭史北海道工業技術研究所, 資源エネルギー基礎工学部, 通商産業技官 TAKEUCHI Hiroshi Hokkaido Ind. Res. Inst., Energy Resource, Tech Res., 資源エネルギー基礎工学部, 主任研究官 CHIBA Sigeo Hokkaido Ind. Res. Inst., Env. Material, Chief, 極限環境材料部, 室長 KONDO Kazuo Hokkaido Univ., Fac. of Eng., Pro.Inst., 工学部, 助手 (50250478) 堤香津雄川崎重工業株式会社, 技術開発本部, (研究開発担当)係長
Project Period (FY)	1994 – 1995
Project Status	Completed (Fiscal Year 1995)
Budget Amount *help	¥6,000,000 (Direct Cost: ¥6,000,000) Fiscal Year 1995: ¥1,000,000 (Direct Cost: ¥1,000,000) Fiscal Year 1994: ¥5,000,000 (Direct Cost: ¥5,000,000)
Keywords	Fine Particle / CVD / Coating / Moving Bed / Fluidized Bed / Agglomeration / Aluminium Nitride / 表面改質
Research Abstract	For the purpose of mass-production process of surface-coated submicron particles, reactor designs and operational conditions were investigated for Si_3N_4 particles coated with AlN by CVD method. The seed particles were agglomerated with a screen to enhance flowability without binder. Firstly, a fluidized bed was used with a suspended draft tube below which AlCl_3 gas was supplied to submerge the agglomerates. They were overflown to the annular region to react with NH_3 gas. The contact time was controlled with circulation inside the bed. But, the product blocked the distributor during operation, so improvements were made in vain shortly. Secondly, a moving bed in counter-current was adopted without any distributor. The residence time of the agglomerates was adjusted with an orifice at the ractor bottom. Though the deposit amount was a little with single pass, the continuous operation becomes possible with proper design of the inside structure to yield a large reaction zone and small pressure drop. As a result, the agglomerate shape did not change substantially with SEM,AlN defraction line was recognized with XRD,and Al was deposited inside the agglomerate with EPMA.Higher concentration of reaction gas, higher temperature and longer reaction time produced higher coating ratio of AlN,but lower temperature and smaller agglomerate were preferable to its uniform distribution. These are obtained due to combined effects of reactio rate and diffusion rate with temperature and of diffusion distance. Thus, a core shell model based on the first order reaction rate was developed to analyze the axial change in apparent coating ratio, and then a diffusion-control model inside a porous agglomerate was introduced to describe the radial distribution of the deposit.