Development of Antioxidant Technology for Graphite Products Used in High Temperature Processes

2003 Fiscal Year Final Research Report Summary

• Project/Area Number: 12355029
• Research Category: Grant-in-Aid for Scientific Research (A)
• Allocation Type: Single-year Grants
• Section: 展開研究
• Research Field: Metal making engineering
• Research Institution: Kyushu Institute of Technology
• Principal Investigator: MUKAI Kushuhiro Kyushu Institute of Technology, Faculty of Engineering, Professor, 工学部, 教授 (60023173)
• Co-Investigator(Kenkyū-buntansha): 陶 再南 フジファインテック株式会社, 主任研究員 ; SHIROMIZU Ysironobu Fiji Finetec CO.,LTD., President [Researcher], 代表取締役社長(兼研究開発担当) ; TAO Zainan Fiji Finetec CO.,LTD., Researcher
• Project Period (FY): 2000 – 2003
• Keywords: Graphite / Anti-oxidant / Coating / Fine ceramics

Research Abstract

Stable dispersion of complex fine ceramics
A device for dispersing complex fine ceramics was developed. With this device a novel antioxidant with basic ingredients of Al_2O_3、SiO_2、 ZrO_2 SiC and ZrB_2, can disperse stably in aqueous solution. In the antioxidant suspension the solid matters can reach 35 %(w) in maximum in which 6 %(w) of non-oxides (nitrides, borides) are mixed. Because the suspension has a low viscosity of 150 mPa・s and the solid matters don't deposit or gel for one month, it can be easily applied for the impregnation in graphite materials.
Formation of fine ceramics film
A novel antioxidant with optimized composition materials and combination ratio was developed. Compare to the graphite sample impregnated with nothing and the one impregnated with former antioxidant, the oxidation ratio of the graphite sample impregnated with the new type of antioxidant decreased 66% and 50% respectively when they were heated to 1400 ℃ in air. The sintering characteristics and physical properties of the fine ceramics film are improved because of the addition of small amount of borides and carbides. To achieve better performance of the antioxidant, the nonoxides need to be added in a larger ratio. The porous graphite material was impregnated with the fine ceramics suspension, and a fine ceramics film was formed on the surface of the graphite material and as well as the surface of internal pores.
Impregnation method
Low-pressure vacuum pump is used to draw out the air in the pores of graphite electrode, then the antioxidant suspension is introduced to impregnate in the graphite material. During the impregnation of antioxidant, the viscosity of the suspension needs to be controlled less than 150 mPas to drench the graphite material thoroughly.