含硼石墨中甲烷的热解吸行为研究

THERMAL DESORPTION BEHAVIORS OF METHANE IN BORON DOPER GRAPHITE

研究了含硼石墨ＧＢ１１０（１０ｗｔ．％Ｂ）甲烷（ＣＨ４）的热解吸谱，发现甲烷的解吸谱主要由３个峰构成，估算出了ＣＨ４不同峰值的解吸激活能。为了弄清含硼石墨中甲烷的形成与解吸机理，分别对高纯石墨ＩＳＯ８８０Ｕ和Ｂ４Ｃ涂层进行了热解吸实验，同时对材料的微观结构进行了分析。经过比较，表明甲烷在含硼石墨中的形成与解吸有３个过程：氢离子注入导致甲烷沿气孔内壁形成，并通过石墨内部的微通道向表面自由扩散；被石墨中Ｂ４Ｃ析出物所俘获的氢原子与Ｂ４Ｃ化合物中的碳原子反应，从而生成甲烷并解吸出来；以及石墨晶格俘获的氢原子与碳原子化学反应产生的甲烷，通过体扩散过程解吸。其中前后两个过程起主导作用。

The thermal desorption spectra of methane in boron doped graphite GB110(10wt% B) were measured, three peaks of CH 4 were found and the desorption activation energies corresponding to these peaks were estimated. In order to make clear the mechanism of methane formation and release in boron doped graphite, the thermal desorption spectra of high purity graphite ISO880U and B 4C coating were studied, and the microstructure of these carbon materials was also analyzed. Comparing with the thermal desorption spectra of these three kinds of carbon materials, the results show that there are three processes existed in the thermal desorption of methane in boron doped graphite:(1) Methane forms at the internal pore surface and freely diffuses through the internal channel of the graphite. (2) Methane forms by the chemical reaction between the hydrogen atoms trapped in B 4C precipitates and the carbon atoms from B 4C compounds. (3) Methane forms in the matrix lattices and desorbs by bulk diffusion. (1) and (3) are the prominent processes.