The c-axis texturing of seeded Si3N4 with β-Si3N4 whiskers by slip casting in a rotating magnetic field

X. W. Zhu, Y. Sakka, T. S. Suzuki, T. Uchikoshi, S. Kikkawa

Research output: Contribution to journalArticle

39 Citations (Scopus)

Abstract

The c-axis texture development in seeded Si3N4 with β-Si3N4 whiskers by slip casting in a rotating magnetic field was investigated by powder X-ray diffraction, scanning electron microscopy and thermal anisotropy evaluation, including the effects of magnetic flux density, suspension rheological properties and rotational speed. By increasing the magnetic flux density from 1 to 12 T, the c-axis orientation of β-Si3N4 whiskers is achieved in the well-dispersed 30 vol.% suspension but hindered in the flocculated 40 vol.% suspension. The degree of orientation tends to decrease with increasing rotational speed from 5 to 30 rpm. The green body shows no density gradient but nonuniform orientation of β-Si3N4 whiskers regardless of the rotational speed, resulting in the similar nonuniform texture in the sintered body. The nonuniform texture is featured in three major layers: lower surface, inner region and upper surface, corresponding to the lower, higher and lower c-axis orientation, respectively. The resultant c-axis textured Si3N4 exhibits thermal anisotropy as high as 55%, slightly lower than the intrinsic thermal anisotropy (62%) of β-Si3N4. A theoretical analysis is performed to help understand the key factors affecting the orientation of β-Si3N4 whiskers by slip casting in the rotating magnetic field. The formation mechanisms of the nonuniform texture were discussed.

Original languageEnglish
Pages (from-to)146-161
Number of pages16
JournalActa Materialia
Volume58
Issue number1
DOIs
Publication statusPublished - 2010 Jan 1

Keywords

  • Rotating magnetic field
  • Silicon nitride
  • Slip casting
  • Texture
  • Thermal conductivity

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Ceramics and Composites
  • Polymers and Plastics
  • Metals and Alloys

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