Journal of the Korean Ceramic Society (한국세라믹학회지)

The Korean Ceramic Society (한국세라믹학회)
권호 표지

Sintering and Mechanical Properties of Silicon Nitride Prepared with a Low-cost Silicon Nitride Powder

저가의 $\beta$-상 분말을 사용한 질화규소의 소결 및 기계적 특성

  • 박우윤 (한국기계연구원 세라믹재료그룹) ;
  • 박동수 (한국기계연구원 세라믹재료그룹) ;
  • 김해두 (한국기계연구원 세라믹재료그룹) ;
  • 한병동 (한국기계연구원 세라믹재료그룹)
  • Published : 2001.11.01
Download PDF
⟨ Previous Next ⟩

Abstract

A refractory grade low-cost silicon nitride powder was chemically analyzed, purified, and gas pressure sintered with the sintering additives. As-received powder contained a significant amount of free-Si, 0.72 wt% of Fe, 0.5 wt% of al and 0.31 wt% of Ca. Oxygen and carbon contents of the powder were 3.3 wt% and 0.4 wt%, respectively, and it consisted of 96% of $\beta$-phase and 4% of $\alpha$-phase. After lowering the Fe content and nitriding treatment, the powder was sintered with 6 wt% yttria and 2 wt% alumina for 1 h between 1823 K and 2123 K in order to examine the sintering behavior. Fully dense samples were obtained by sintering at 2123k for 2h. For comparison, a commercially available high-grade powder was also sintered at the same time. The low-cost powder showed much slower densification rate than the high-grade powder. Fully dense sample prepared from the low-cost powder contained a number of coarse grains with a low aspect ratio, and its hardness, fracture toughness, flexural strength and thermal shock resistance were not as good as those of the sample prepared with the high-grade powder.

내화물 등급의 저가 질화규소 분말을 분석 및 가공한 후, 소결조제을 첨가하여 가스압 소결하였다. 원료분말에는 다량의 free Si가 있었으며 Fe, Al, Ca등의 불순물도 각각 0.72wt%, 0.5wt%, 0.31wt%로 다량 존재하였다. 산소와 탄소의 함량도 각각 3.3wt%와 0.4wt%로 많았으며, 96%의 $\beta$-상과 4%의 $\alpha$-상으로 구성하였다. 원료 분말을 탈철처리 및 질화처리 하여 소결조제인 6wt% yttria와 2wt% alumina를 첨가하고, 1823K-2133 K의 온도 범위에서 1시간씩 소결하여 소결거동을 조사하였다. 또, 2123K에서 2시간동안 소결하여 충분히 치밀화된 소결체를 얻었다. 비교를 위하여 상용 질화규소 분말을 같이 소결하여 소결거동과 기계적 특성 등을 조사하였다. 저가의 분말을 상용 분말보다 치밀화 속도는 늦었다. 충분히 치밀화된 저가 분말의 소결체는 낮은 aspect rtio를 갖는 조대 결정립들이 다수 존재하였으며, 경도, 파괴인성, 꺽임강도, 내열 충격성 등이 상용 분말의 소결체 보다 떨어졌다.

Keywords

References

  1. Ceram. Eng. Sci. Proc. v.20 no.4 Advanced Silicon Nitride Components: A Cost Analysis J. M. Schoenung;E. H. Kraft;D. Askin
  2. The 5th Int'l Symp. On Ceram. Mater. And Components for Engines The Progress of Ceramic Parts in Engine Applications R. Matsuda;K.Niihara(ed.);S.Hirano(ed.);S.Kanzaki(ed.);K.Komeya(ed.);K.Morinaga(ed.)
  3. J. Ceram. Soc. Jpn. v.103 no.6 Effect of Purification of β-Si₃N₄on the Strength of Sintered Matrials N. Hirosaki;Y. Okamoto;Y. Akimune;K. Isozaki;M. Mitomo
  4. Development of Silicon Nitride based Structure Ceramics KIST
  5. Am. Ceram. Bull. v.56 no.9 Determination of Phase Content of Si₃O₄by X-ray Diffraction Analysis C. P. Gazzara;D. R. Messier
  6. J. Am. Ceram. Soc. v.81 no.5 Fabrication of Si₃O₄/SiC Composite by Reaction-bonding and Gas-pressure Sintering S. Y. Lee
  7. Powder Metall. Int. v.18 Powder characteristics and sintering behavior of Si₃N₄-powders G. Woetting;G. Ziegler
  8. J. Ceram. Soc. Jpn. v.104 no.1 Influence of Phase Transformation on Densification Behavior and Grain Growth of Fine Silicon Nitride Powder H. Hirotsuru;M. Mitomo;T. Nishimura
  9. J. Ceram. Soc. Jpn. v.102 no.8 Sintering of Y₂O₃-Al₂O₃Doped β-Si₃N₄Powder and Mechanical Properties of Sintered Materials N. Hirosaki;Y. Okamoto;Y. Akimune;M. Mitomo
  10. J. Am. Ceram. Soc. v.59 no.7;8 Fracture Toughness Determinations by Indentation A. G. Evans;E. A. Charles
  11. J. Am. Ceram. Soc. v.65 no.8 Microhardness and Elastic Moduli of Si-Y-Al-O-N Glasses D. R. Messier;A. Broz
  12. Int. Metals Rev. v.1 Silicon Nitride Polyphase Systems: Fabrication, Microstructure, and Properties F. F. Lange
  13. J. Euro. Ceram. Soc. v.21 Influence of Tungsten Carbide Particles on Resistance of Alumina Materix Ceramics to Thermal Shock L. Wang;J-L. Shi;J-H. Gao;D-S. Yan