Paper Title:
Properties of Cubic Si3N4 Obtained by Shock Synthesis
  Abstract

The cubic γ-Si3N4 phase was synthesized by the shock technique from the hexagonal β-Si3N4 phase. The thermal stability of the γ-Si3N4 was investigated during heating in vacuum up to 1773 K. An exothermal heat effect was found at 1690 K and structural investigations revealed complete transformation of γ-Si3N4 to β-Si3N4. Corresponding heat effect value was estimated as 51.3±7.7 KJ/mol. The high-pressure-high-temperature treatment (P=13 GPa, T=1300-2300 K) was applied to γ-Si3N4 to make bulk polycrystalline non-porous samples. It was found that temperatures below 1623 K do not change content of the cubic γ-Si3N4 while temperatures above 2273 K decrease it substantially. Mechanical properties of these bulk samples were measured by acoustic wave and nanoindentation techniques. The maximum values belong to cubic γ-Si3N4: hardness 39-44 GPa, Young’s modulus 475 Gpa and bulk modulus 263 GPa. Equilibrium γ-β line position in P-T phase diagram was estimated by using data obtained in this work. The equilibrium pressure at T=300 K was estimated as P300=7.0±2.0 GPa.

  Info
Periodical
Edited by
S. Itoh and K. Hokamoto
Pages
129-134
DOI
10.4028/www.scientific.net/MSF.566.129
Citation
V.D. Blank, A.A. Deribas, N.A. Lvova, R.H. Bagramov, B.A. Kulnitsky, I.A. Perezhogin, V.M. Prokhorov, V.V. Silvestrov, A.S. Yunoschev, "Properties of Cubic Si3N4 Obtained by Shock Synthesis", Materials Science Forum, Vol. 566, pp. 129-134, 2008
Online since
November 2007
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