Sintering Behavior of Nanocrystalline Silicon Carbide Using a Plasma Pressure Compaction System: Master Sintering Curve Analysis

Abstract

Nanostructured ceramics offer significant improvements in properties over corresponding materials with larger grain sizes on the order of tens to hundreds of micrometers. Silicon carbide (SiC) samples with grain sizes on the order of 100 nm can result in improved strength, chemical resistance, thermal stability, and tailored electrical resistivity. In this study, nanocrystalline SiC was processed in a plasma pressure compaction (P 2 C) system at a temperature of 1973 K (1700°C) that was much lower than the temperatures reported for other sintering techniques. Microstructure of the resulting samples was studied and the hardness and the fracture toughness were measured. The grain sizes were on the order of 700 nm, the hardness between 22 and 24 GPa, and the toughness between 5 and 6.5 MPaAEm 1/2 . The master sintering curve (MSC) analysis was used to model the densification behavior of SiC powder sintered by the P 2 C method. The apparent activation energies for three different pressures of 10, 30, and 50 MPa were obtained to be 1666, 1034, and 1162 kJ/mol, respectively. Although densification occurs via diffusion, the activation energies were higher than those associated with self-diffusion in SiC (between 570 and 920 kJ/mol). A validation study of the MSC was also conducted and the variation in observed density from the density predicted by the MSC was found to range from 1 to 10 pct.

Microstructural and Mechanical Properties of Al2O3 and Al2O3/TiB2 Ceramics Consolidated by Plasma Pressure Compaction

“…No sintering aids or other additives, except for the titanium diboride used on purpose, were employed. During the compaction, a direct current was applied simultaneously to the external pressure of 20 MPa ( Ref 24,34). The consolidation time was ten minutes and prevents grain growth.…”

Review of Net Shape Fabrication of Thermally Conducting Ceramics

“…The retarded grain growth with pressure reported by Bothara (Fig. 13) [105] in plasma compacted SiC can thus be used for high hardness applications. On the other hand, grain growth reported in pressureless sintered AlN (Fig.…”

“…-SiC sintering at 1700 C for 60 min via plasma pressure compaction with an external pressure of (a) 10 MPa, (b) 30 MPa, and (c) 50 MPa (courtesy of Bothara[105]). …”

Kissinger-Style Kinetic Analysis for Sintering Dilatometry Data

“…The benefit of the MSC method is that it is independent of geometric factors of the powder, and dilatometry experiments are low cost and easy to perform. This method has therefore been applied to many systems [7][8][9][10][11][12][13][14][15] . However, there is one major assumption that limits the utility of the MSC approach, namely, that it assumes that the entire sintering process is dominated by a single kinetics, characterized by a single activation energy [5,16] .…”