Consolidation of Nanostructured β‐SiC by Spark Plasma Sintering

Abstract

Nanostructured ␤-SiC, with crystallite size in the range of 5-20 nm in agglomerates of 50 -150 nm, was formed by reactive high-energy ball milling and consolidated to a relative density of 98% by sintering at 1700°C without the use of additives. X-ray line broadening analysis gave a crystallite size of 25 nm, while transmission electron microscopy observations showed the crystallite size to be in the range of 30 -50 nm. Evidence demonstrating the role of a disorder-order transformation in the densification process is provided by changes in the diffraction peak patterns and in the integral width with temperature. R. Riedel-contributing editorManuscript No. 10245.

Influence of sintering temperature and pressure on crystallite size and lattice defect structure in nanocrystalline SiC

“…This phenomenon can be explained by the promoting effect of temperature for the growth of crystallites. 15,16 It is interesting to note that when the crystallite size decreases, e.g., for sintering at 8 GPa and 1800°C, the planar defects have significant densities, which again supports the observed correlation between the crystallite size and the defect structure.…”

“…Statistically equivalent population of threefold and fourfold coordinated atoms has been registered in the outer layers of nanosize SiC grains. 14 The presence of partially disordered structures near the grain boundary has been postulated by Keblinski et al 15 and detected by Yakamoto et al 16 and Liao et al 17 Such structures may facilitate surface diffusion or atom rearrangement during the early stages of the sintering process. The increase of temperature causes the increase of mobility of atoms resulting in faster grain growth.…”

Consolidating and Deforming SiC Nanoceramics Via Dynamic Grain Sliding

“…[4] The densification is enhanced by the application of an external mechanical pressure, either uniaxial or isostatic. [3,5] It may be further enhanced by involving a disorder-order phase transformation, [6] by involving a suitable liquid that facilitates the solution-reprecipitation of the major phase, [7] or by allowing deformation to occur during densification, i.e. sinter forging.…”

“…[5] So far, nanoceramics of SiC, as it is generally defined as ceramics consisting of grains less than 100 nm, have been prepared both by solid-state sintering and by liquid-phase sintering of nano-powders. [3][4][5][6]8] Their record superplastic deformation strain rate is in the order of 1 × 10 -5 /s above 1600°C and of 1 × 10 -4 /s at 1700°C for solid-state sintered and liquidphase sintered SiC nanoceramics, respectively. [3,4] These deformation strain rates are far too low for the potential application of plastic forming of complex shaped ceramic components at elevated temperatures.…”

Preparation of TiB<SUB>2</SUB>&ndash;SiC Eutectic Composite by an Arc-Melted Method and Its Characterization

“…heat exchanger, metal working parts, nozzles. [1][2][3][4][5][6] However, the low fracture toughness (around 2 MPa m 1=2 ) of SiC limits its more extensive usage. Titanium boride (TiB 2 ) is also an excellent engineering material with high electrical conductivity, thermal conductivity and hardness.…”