Fabrication of the composite by ultra high-pressure sintering

3 Fabrication of the composite by ultra high-pressure sintering 

14 Schematic diagram of the cross-sectional view of a high-pressure anvil. 

XRD was performed on the compaction surface, cross section and crushed powder of the specimen. The XRD profiles shown in Fig. 14.15(b) reveal the (200) reflection that does not appear in the pristine Cgo phase. The relatively strong intensity of the (220) reflection may be due to the 110 preferred orientation along the compact direction, probably caused by the (111) 110 slip system that allows considerable deformation of the Cgo crystals. The XRD chart in Fig. 14.15(b) indicates that the matrix phase can be indexed as the fee structure with a lattice constant a = 1.31 nm. The lattice constant decreases by approximately 8% relative to that of the pristine Cgo (a = 1.42 nm) and is approximately equal to the minimum value (a 1.32nm) reported by Takahashi et al. In this specimen, an endothermic peak at approximately 563 K has been confirmed by differential thermal analysis. These results suggest that the h-Cgo phase, a Cgo phase that is subjected to high pressure, can be regarded as a polymerised Cgo phase. 

15 X-ray diffraction chart obtained using monochromated Cu ka for (a) pristine Cso, (b) compaction surface, (c) cross section and (d) crushed powder. 

16 High-resolution TEM image of a polymerised Cgo crystal and the electron diffraction pattern. 

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