Effect of the Whisker Amount and Orientation on Mechanical Properties of the Si$_3$N$_4$ based Composites

Si$_3$N$_4$ Whisker의 첨가량과 배열방향이 Si$_3$N$_4$ 복합 소결체의 기계적 특성에 미치는 영향

  • Kim, Chang-Won (Department of Materials Science and Engineering, Pukyong Nation National University) ;
  • Park, Dong-Soo (Ceramic Materials Group, Korea Institute of Machinery and Materials) ;
  • Park, Chan (Department of Materials Science and Engineering, Pukyong Nation National University)
  • 김창원 (부경대학교 재료공학과) ;
  • 박동수 (한국기계연구원 요업재료그룹) ;
  • 박찬 (부경대학교 재료공학과)
  • Published : 1999.01.01

Abstract

Gas pressure sintered silicon nitride based composites with 0~5wt% $\beta$-Si3N4 whiskers were prepared. The whiskers were unidirectionally oriented by a modified tape casting technqiue and green bodies with various microstructure were formed by changing stacking sequences of sheets cut from the tape. Orientations of the large elongated grains of the sample after gas pressure sintering were the same as the those of the whiskers of green body, and the sintering shrinkage and mechanical properties of sintered sample were consistent with the microstructural characteristics. In case of unidirectional samples, the sintering shrinkage normal to whisker alignment direction was larger than that parallel to the direction. The shrinkage difference inceaed as the whiskercontent increaed. As whisker content increaed, the crack length normal to and parallel to tape casting direction became shorter and larger, respectively. Although the grain size increased by th whisker addition, the flexural strength of unidirectional samples was not lower than that of smaple without the whisker. In case of crossplied and 45$^{\circ}$rotated samples, the anisotropy of mechanical preoperties disappeared.

0~5 wt%의 $\beta$-Si3N4 whisker를 첨가한 질화규소 가스압 소결체를 제작하였다. 첨가된 whisker들은 tape casting을 응용하여 tape 내에서 일방향으로 배열하였으며, 제작된 tape로부터 절취된 sheet들의 적층 과정을 변화하여 다양한 미세구조를 갖는 성형체를 제작하였다. 가스압 소결을 통하여 치밀화된 소결체의 조대결정립은 성형체의 whisker와 같은 방향성을 가졌으며, 소결수축률과 기계적 특성 등도 이러한 다양한 미세구조상의 특징과 일관된 결과를 나타내었다. Whisker를 일방향으로 배열하였을 경우, 소결수축률은 whisker 배열 방향과 평행한 방향보다 수직한 방향으로 크게 일어났을 때, whisker 함량이 증가함에 따라 수축률의 차이가 증가하였다. Indentationi crack length는 whisker 함량이 증가함에 따라 whisker 배열 방향과 수직한 방향의 균열 길이는 더 짧아졌고, 그와 평행한 방향의 균열 길이는 길어졌다. Whisker 첨가에 의해 결정립이 더 크게 성장하였으나 강도는 whisker를 첨가하지 않을을때보다 낮지 않았다. Whisker 배열 방향을 90$^{\circ}$ 및 45$^{\circ}$ 간격으로 엇갈리게 적층하였을 경우에는 특성의 이방성이 나타나지 않았다.

Keywords

References

  1. J. Am. Ceram. Soc. v.77 no.7 Microstructure Control of Silicon Nitride by Seeding with Rodlike β-Silicon Nitride Particles K. Hirao;T. Nagaoka;M.E. Brito;S. Kanzaki
  2. J. Am. Ceram. Soc. v.74 no.2 Microstructural Design of Toughened Ceramics P.F. Becher
  3. J. Ceram. Soc. Jpn. v.102 no.9 Sinterability and Fracture Toughness of β-Si₃N₄ Whisker-Added Silicon Nitride M. Andou;A. Sawaoka
  4. J. Am. Ceram. Soc. v.75 no.1 Microstructural Development During Gas-Pressure Sintering of α-Silicon Nitride M. Mitomo;S. Uenosono
  5. J. Am. Ceram. Soc. v.76 no.7 Effect of Grain Growth of β-Silicon Nitride on Strength, Weibull Modulus and Fracture Toughness N. Hirosaki;Y. Akimune;M. Mitomo
  6. J. Ceram. Soc. Jpn. v.99 no.4 Grain Size Dependence of the Fracture Toughness of Silicon Nitride Ceramics T. Kawashima;H. Okamoto;H. Yamamoto;A. Kitamura
  7. J. Ceram. Soc. Jpn. v.102 no.9 TEM Analysis of Core/Rim Structure in β-Silicon Nitride Ceramics N. Hirosaki;M. Tanimura;Y. Okamoto;Y. Akimune;M. Mitomo
  8. Ceramics: Toward the 21st Century Progress of Advanced Nitride Ceramics Research and Its Industrial Implications T.S. Yen;N.Soga(ed.);A. Kato(ed.)
  9. J. Am. Ceram. Soc. v.73 no.11 Mechanical Properties of β-Si₃N₄-Whisker/Si₃N₄-Matrix Composites J. Homeny;L.J. Neergaard
  10. J. Am. Ceram. Soc. v.75 no.10 Microstructure of an Extrued β-Silicon Nitride Whisker-Reinforced Silicon Nitride Composite D. Muscat;M.D. Pugh;R.A. Drew
  11. J. Am. Ceram. Soc. v.77 no.10 Fabrication of Oriented SiC-Whisker-Reinforced Mullite Matrix Composites by Tape Casting M. Wu;G.L. Messing
  12. J. Am. Ceram. Soc. v.79 no.9 High Thermal Conductivity in Silicon Nitride with Anisotropic Microstructure K. Hirao;K. Watari;M.E. Brito;M. Toriyama;S. Kanzaki
  13. Introduction to the Principles of Ceramic Processing James S. Reed
  14. J. Am. Ceram. Soc. v.71 no.12 Toughening Behavior in Whisker-Reinforced Ceramic Matrix Composites P.F. Becher;C.H. Hsueh;P. Angelni;T.N. Tiegs
  15. J. Am. Ceram. Soc. v.78 no.6 Processing Strategy for Producing Highly Anisotropic Silicon Nitride K. Hirao;M. Ohashi;M.E. Brito;S. Kanzaki