Effects of heating rate on densification and grain growth during field assisted sintering of α-Al2O3 and MoSi2 powders

Two types of powders, electrically conductive MoSi2 and insulating a-Al2O3, were sintered by a field-assisted sintering technique (FAST) using heating rates from 50 8C to 700 8C/min. The Al2O3 powders were sintered to 99 pct density at 1100 8C for 2 minutes under 45 MPa pressure. For Al2O3, no exaggerated grain growth was observed and the final grain size inversely scaled with the heating rate. Such a grain growth behavior fits the literature models based on multiple transport mechanisms for constant-heating-rate sintering. The density reached by MoSi2 under similar sintering conditions was 91 pct. The grain size was independent of the heating-rate value. Specific electrical field and pressure effects are shown to contribute to enhanced densification and minimal coarsening in each material. I. INTRODUCTION TiN nanopowders, coarsening during FAST sintering resulted in a final grain size that was at least 1 order ofIN ceramic powder processing, high heating rates are magnitude less than in the conventional sintering of the often used to enhance sintering and reduce grain growth. same powders.[9] The limited coarsening observed in FASTThe essence of this concept is that fast heating rates favo