镁-镍合金催化剂制备及纳米碳管生长模式研究

采用多元醇法制备镁-镍合金纳米粉末,并以此为催化剂制备纳米碳管,利用比表面和孔径分布测定仪、X射线衍射仪和透射电镜,研究镁-镍合金催化剂的性能和纳米碳管的生长模式。结果表明:Mg∶Ni值对镁-镍合金催化剂特性影响较大,其中Mg∶Ni为1的催化剂颗粒比表面积较大且平均粒径较小;聚乙烯吡咯烷酮(PVP)用量增大,有利于提高催化剂颗粒的比表面积、减小平均粒径,但用量过大不利于Mg2Ni合成。在以镁-镍合金为催化剂制备碳纳米管的过程中,首先在催化剂表面形成碳膜,随后形成的碳膜将前期形成的碳膜及催化剂颗粒向外推挤,催化剂颗粒移动后遗留下中空隧道,最终形成碳管,由于纳米碳管尖端的催化剂颗粒反应后失去催化活性,碳管的生长动力主要来自碳管根部。

Preparation of Mg-Ni alloy catalyst and growth mode of CNTs

Mg-Ni alloy nano-powder was prepared by polyol method and used as catalyst to prepare carbon nanotubes(CNTs).The performance of Mg-Ni alloy catalyst was studied by measurement of specific surface area and pore size distribution and XRD.The growth process of CNTs was studied by TEM.The results shown that the change of Mg∶Ni value greatly affected the performances of Mg-Ni alloy catalysts,and the catalyst particles with Mg∶Ni value of 1 had larger specific surface area and smaller average particle size.The increase of the amount of PVP was beneficial to increase the specific surface area of the catalyst particles and reduced the average particle size,but the excessive amount was not conducive to the synthesis of Mg2Ni.In the process of preparing CNTs by using Mg-Ni alloy as catalyst,a carbon film was first formed on the surface of the catalyst,and then the formed carbon film pushed the carbon film and catalyst particles formed in the early stage outward,and the hollow tunnel was left after the catalyst particles move.Finally,a carbon tube was formed.Since the catalyst particles at the tip of CNTs losed catalytic activity after reaction,the growth dynamics of CNTs mainly came from the roots of the carbon tubes.