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采用摩尔分数1%Ni及负载少量Mo的Ni/Mo/MgO催化剂裂解甲烷合成薄壁碳纳米管。通过SEM、TEM、XRD和Raman光谱表征方法研究了碳纳米管直径和催化剂中Ni/Mo比例关系。实验发现:通过控制Ni/Mo比例可以调变催化剂颗粒大小以及活性相。TEM及XRD表征发现,随着Ni/Mo比例的降低,金属Mo相逐渐从NiMo合金相中析出。NiMo合金相对应的活性组分颗粒很小,容易催化裂解甲烷形成薄壁碳纳米管;而后析出的Mo相则主要形成了大管径厚壁的碳纳米管。当Ni/Mo比例为6时可以高选择性地获得窄分布,内径为1.3nm,外径为3.0nm的薄壁碳纳米管。Raman光谱进一步验证了碳纳米管含有较少的缺陷。薄壁碳纳米管形成的关键因素主要体现为碳在其表面的快速扩散以及小颗粒的碳纳米管催化剂活性相控制。
Carbon nanotubes were synthesized by cracking methane with Ni / Mo / MgO catalyst containing 1% Ni and a small amount of Mo. The relationship between the diameter of carbon nanotubes and the ratio of Ni / Mo in the catalyst was investigated by SEM, TEM, XRD and Raman spectroscopy. The experimental results show that the catalyst particle size and the active phase can be tuned by controlling the Ni / Mo ratio. Characterization by TEM and XRD revealed that as the Ni / Mo ratio decreased, the metal Mo gradually precipitated from the NiMo alloy phase. NiMo alloy corresponding to the active component particles is small, easy to catalyze the cracking of methane to form thin-walled carbon nanotubes; and then precipitated Mo phase is mainly the formation of large diameter thick-walled carbon nanotubes. When the Ni / Mo ratio is 6, a thin carbon nanotube having a narrow distribution, an inner diameter of 1.3 nm, and an outer diameter of 3.0 nm can be selectively obtained. Raman spectroscopy further confirmed that carbon nanotubes contain fewer defects. The key factors for the formation of thin-walled carbon nanotubes are mainly the rapid diffusion of carbon on its surface and the control of the active phase of the small-sized carbon nanotube catalyst.