Hot Isostatically Pressed SiC‐AIN Powder Mixtures: Effect of Milling on Solid‐Solution Formation and Related Properties

Abstract

Powder mixtures with nominal compositions of 75 mol% SiC and 25 mol% AlN as well as 50 mol% SiC and 50 mol% AlN were prepared by ball milling for 1-300 h and subsequently sintered to full density by hot isostatic pressing (HIPing) at 1850°C under a pressure of 200 MPa. Microstructures and properties of the HIP-sintered SiC-AlN powder mixtures were investigated with special attention to the effect of ball milling on the formation of SiC-AlN solid solutions. Extensive ball milling facilitated effectively the formation of solid solutions by improvement in mixing homogeneity and pulverization of the SiC and AlN powders. Thermal conductivity of the HIP-sintered SiC-AlN powder mixtures decreased remarkably with ball-milling time, mainly because of the enhanced formation of solid solutions. Mechanical properties-such as strength, fracture toughness, and microhardness-were dependent on the microstructural homogeneity and the grain refinement resulting from the formation of solid solutions.

Two‐Step Carbothermal Synthesis of AlN–SiC Solid Solution Powder Using Combustion Synthesized Precursor

“…An increase in the contact area among the particles always shortens the diffusion paths of reactants. The previous studies have also indicated that the higher contact area among reactants as well as the finer reactant particles leads to the lower transformation temperature of AlN and SiC into AlN–SiCss …”

Preparation of Aluminum Nitride–Silicon Carbide Nanocomposite Powder by the Nitridation of Aluminum Silicon Carbide

“…Previously, Li et al 2 found sluggish interdiffusion between AlN and SiC and stressed some requirements for forming the solid solution with a homogeneous composition, i.e., small starting particle size (e.g., below 0.5 m at 1850°C) and thorough mixing of the starting powder. These requirements are met by the present technique.…”

“…These AlN-SiC ceramics form a solid solution over a wide chemical compositional range, 1 which is rather rare for non-oxide ceramics with strong covalent bonds. 2 The homogeneous formation of solid solution helps enhance the mechanical properties, chiefly due to the restriction of excessive grain growth. For example, the formation of homogeneous solid solution increases flexural strength and fracture toughness of the ceramics up to 1 GPa at 65-75 mass% of SiC and 4.5-5 MPa⅐m 1/2 at 90 mass% SiC, respectively, 3,4 whereas that of poor solid solution shows lower mechanical strengths.…”

“…Generally, AlN-SiC ceramics have often been prepared using mechanically mixed powders. [1][2][3][4][5] Although this mixing technique is very simple and easily controls the composition of the powder, the chemical compositions in the resulting ceramics tend to be inhomogeneous locally, due to the difficulty in "thorough" mixing. To achieve the homogeneous chemical composition in the AlN-SiC powder, some techniques have been proposed, e.g., the pyrolysis of organometallic precursor, 6 the carbothermal reduction and nitridation of oxide powders, 7,8 and self-propagating combustion.…”

The effect of in situ synthesized AlN on densification of SiC ceramics by pressureless sintering

“…It was reported that AlN could form solid solution with SiC and affected the structural stability of SiC [12]. Some researchers have revealed that SiC with the addition of AlN could be preferably sintered by hot pressing [13][14][15] or spark plasma sintering [11] or hot isostatic pressing [16], and densification in such system was frequently explained by AlN going into solid solution in SiC in a large proportion. As for pressureless sintering with AlN, Malinge et al [17] found that the added AlN had almost no influences on the density of SiC ceramics which contain boron carbide and carbon.…”