▎ 摘　　要

A low-cost and effective approach to large-quantity freestanding graphene sheets through selective solid-phase chemical reactions between Ni and poly-crystalline SiC powders at the temperature of 1000 degrees C was reported. High-resolution transmission electron microscopy (HRTEM) investigations indicated that single- and multi-layered graphene sheets in microns of size were obtained. The proposed mechanism for our approach shows that Ni silicides produced from the interface reactions might act as a blockade to slow down further diffusion and cystallization of precipitated carbon. The average yield of carbon reached up to 94 wt.%. Real-time measurement of the gas sensor shows graphene synthesized by taking this approach exhibited a sensible and repeatable response to hydrogen with low concentration. (C) 2012 Elsevier B.V. All rights reserved.