Preparation,Modification And Properties Of SiC Nanosheets

In the fields of aviation,aerospace and military applitacions,higher requirements are imposed on gas sensors that can be used under extreme conditions.Due to its good stability,wide band gap and high specific surface area,two-dimensional silicon carbide nanostructures can keep good gas sensitivity under extreme conditions.In this paper,SiC nanosheets were prepared from graphene as a template by carbothermal reduction method,and modified by platinum?Pt?nanoclusters.The composition,structure,room temperature humidity sensing and high temperature gas sensing performance were investigated.Also,the sensing mechanism were studied.SiC nanosheets with a thickness of about 10 nm,high crystallinity and a specific surface area of 90.1 m² g^-1 were prepared by using silicon powder and graphene oxide as raw materials by carbothermal reduction method.The sample has a humidity sensitivity response of up to 16991 at room temperature and a response/recovery time of3 s,demonstrating excellent room temperature humidity sensing properties.The mechanism is due to the electron transfer caused by the“donor effect”between water molecules and SiC nanosheets.SiC nanosheets can also respond to ethanol,acetone,methanol and ammonia at high temperature,and the gas sensing mechanism is a typical oxygen ions adsorption effect.In order to improve the sensitivity and selectivity of SiC nanosheets,Pt nanoclusters@SiC nanosheets two-dimensional heterojunctions were constructed by chemical reduction method and impregnation method.Pt nanoclusters with a particle size of 2-4 nm were evenly distributed on the surface of SiC nanosheets.After modification,the gas sensitivity response is significantly improved,and it exhibits excellent selectivity to hydrogen.The"spill-over effect"that occurs on the Pt NCs@Si C NSs surface and the Schottky heterojunction are the causes of improved gas-sensitive response and selectivity.The wet chemical impregnation method is easy to operate,and the prepared samples possess a high Pt loading and better response/recovery performance.