Ion irradiation-induced novel microstructural change in silicon carbide nanotubes

In-situ TEM was used to observe the microstructural changes of SiC nanotubes under ion irradiation, and the results are significantly different from those of bulk SiC. The nanotubes possess better resistance against amorphization by irradiation, having a higher critical irradiation dose at room temperature. At room temperature, both the outer and inner diameters of the SiC nanotubes increase during irradiation till complete amorphization, and decrease afterwards. The lattice plane spacing of SiC crystals increases with increasing ion fluence due to the increasing disorder. At 700 degrees C, both the inner and outer diameters change very little during ion irradiation; and the lattice plane spacing decreases slightly, which is not consistent with previous studies of bulk SiC. The reason is that, in the nanotubes, the number of inherent defects that buffer the residual stress in it can be reduced. A new structure with smaller crystal segments is produced in the SiC grains of nanotubes to relieve the residual stress, instead of inducing structural defects and nanotube contraction. From these results, ion irradiation clearly induces novel microstructural changes in SiC nanotubes, due to the nanosizing and tubal configuration of the material. (C) 2018 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.