催化裂解CH4或CO制碳纳米管结构性能的谱学表征

利用TEM、HRTEM、XRD、XPS和TPO等方法对CH₄或CO催化分解生成的碳纳米管结构和性能进行了表征.结果表明,所得产物是管径15～20nm的均匀碳纳米管.其XRD谱图与石墨的相近,但特征衍射峰稍宽化,表明其长程有序度较石墨的低.由CH₄制备的碳纳米管系由多层具有类石墨片状结构的同心、等径及中空圆锥形面叠合而成,类石墨层面取向与管轴倾斜;而由CO制备的碳纳米管系由多层具有类石墨片状结构的圆柱形面围叠而成,类石墨层面取向与管轴平行.碳纳米管中C_1s的电子结合能比石墨的下降约0.5eV.TPO试验结果显示所制备的两种产物中无定形碳含量都很低,其整体结构石墨化程度较高;由CH₄制得的碳纳米管与O₂反应的起燃温度比由CO制得的约高100K.

Studies on Structure and Property of Carbon-nanotubes Formed Catalytically from Decomposition of CH4 or CO

By means of TEM, HRTEM, XRD, XPS and TPO methods, structure and properties of the carbon-nanofibers formed catalytically from decomposition of CH₄ or CO have been investigated. The TEM observation shows that these materials are even nanotubes with the outer diameters of 15～20 nm. Their XRD patterns are very close to that of graphite, but the XRD features are somewhat broadened, indicating that the degree of long-range order of these nanostructures is relatively low in comparison with that of graphite. HRTEM observation reveals that the wall of these nanotubes is constructed by many layers of carbon with graphite-like platelets in an extremely ordered arrangement, with the orientation of the conical graphite like platelets inclined to the central axis of the tube for the material produced from CH₄ and the cylindrical graphite-like platelets parallel to the tube axis for that from CO, respectively. XPS measurements show that C_1s electron binding energy in these carbon nanotubes is about 0.5 eVlower than that of graphite. The results of the O₂-TPO testing demonstrate that content of amorphous carbon in these materials is very low, and then the nanostructures are entirely graphitic in nature; the TPOresults also show that the temperature for gasification of the material produced from CH₄ is about 100 Khigher than that from CO, indicating that the former has a better oxygen-resistibility than the latter.