Periodically twinned SiC nanowires

Abstract

Twinning has been recognized to be an important microstructural defect innanoscale materials. Periodically twinned SiC nanowires were largely synthesizedby the carbothermal reduction of a carbonaceous silica xerogel prepared fromtetraethoxysilane and biphenyl with iron nitrate as an additive. The twinnedβ-SiC nanowires, with a hexagonal cross section, a diameter of 50–300 nm anda length of tens to hundreds of micrometers, feature a zigzag arrangement ofperiodically twinned segments with a rather uniform thickness along the entire growthlength. Computer simulation has been used to generate three-dimensional atomicstructures of the zigzag columnar twin structure by the stacking of hexagonal discs of{111} planes of SiC. A minimum surface energy and strain energy argument isproposed to explain the formation of periodic twins in the SiC nanowires. Thethickness of the periodic twinned segments is found to be linearly proportional to thenanowire diameter, and a constant volume model is proposed to explain the relation.