Mechano-chemical Effects of One-dimensional Explosively Shocked Treatment on the Characteristics of Si₃N₄

Abstract

Direct consolidation of α- and β-Si₃N₄ is conducted by the use of one-dimensional explosively shocked treatment. The effect of shock pressure, phase and particle size distribution of a sample powder on the characteristics of explosively shocked compact is examined by the measurement with X-ray diffraction (XRD), Electron spin resonance (ESR), Infrared absorption (IR) and so forth. The following is the results induced:
1) Cracks exist in the shock compact. The apparent density and Vickers hardness increase with the increase in shock pressure. A compact of ca. 90% theoretical density is obtained.
2) Residual strain by XRD and spin density by ESR is reduced under higher shock pressure. This is considered to be attributed to the relaxation effect of high residual temperature. The shock compact of α-Si₃N₄ receives more residual strain and spin density than that of β-Si₃N₄.
3) The effect of the particle size distribution of sample powder on the characteristics of shock compact is slightly present. The shock compact of larger particle size has more residual strain.
4) Metal impurities are not found except in the surface layer of the compact.
5) The solubility of the powder grinding shock compact in 1N NaOH is higher than that of the as-received powder. This indicates that an active surface layer exists in the shock compact.
6) The tapping density of the powder grinding shock compact is much higher than that of the as-received powder.