碳酸钾催化制备螺旋纳米碳纤维

Preparation of helical carbon nanofibers catalyzed by potassium carbonate

关键词:  碳酸钾  螺旋纳米碳纤维  化学气相沉积法  催化裂解  生长机理 

Key words:  potassium carbonate  helical carbon nanofibers  chemical vapor deposition method  catalytic cracking  growth mechanism

摘要:

目的 螺旋纳米碳纤维制备过程中残留的催化剂会影响产物本征性能,常采用酸洗除去催化剂,但会破坏纤维的结构并增加使用成本。以水溶性盐为催化剂制备螺旋纳米碳纤维,可水洗除去催化剂得到高纯度的螺旋纳米碳纤维。方法 以K₂CO₃为催化剂、C₂H₂为碳源,采用化学气相沉积法制备螺旋纳米碳纤维,用简单的水洗除去K₂CO₃催化剂,并考查制备温度对螺旋纳米碳纤维形貌的影响。利用场发射扫描电子显微镜、透射电子显微镜和能谱仪表征螺旋纳米碳纤维的微观结构和元素组成,通过X射线衍射、拉曼光谱和傅里叶红外光谱表征螺旋纳米碳纤维的晶体结构和表面官能团。结果 在700 ℃条件下制备的产物直径约为60 nm,呈螺旋结构且形貌均匀,螺旋纳米碳纤维的碳原子呈短程有序排列,主要由C-H、C=C官能团组成；K₂CO₃催化剂在纤维中呈类似菱形对称结构,导致纤维在催化剂两侧呈手性对称生长。结论 采用化学气相沉积法制备出形貌均匀的螺旋纳米碳纤维,水洗除去表面催化剂可得到高纯度的螺旋纳米碳纤维。 

Abstract:

Objective The residual catalyst during the preparation of helical carbon nanofibers(HCNFs) can affect its intrinsic properties. Acid washing is often used to remove the catalyst in helical carbon nanofibers, but it can destroy the structure of the fiber and increase the cost of use. Helical carbon nanofibers were prepared by using water-soluble salt as catalyst, and the catalyst was removed by washing to obtain high-purity helical carbon nanofibers. Methods Helical carbon nanofibers were prepared by chemical vapor deposition using potassium carbonate as catalyst and acetylene as carbon source. The potassium carbonate catalyst was removed by simple water washing, and the effect of preparation temperature on the morphology of helical carbon nanofibers was investigated. The microstructure and elemental composition of the helical carbon nanofibers were characterized by field emission scanning electron microscopy, transmission electron microscopy and energy dispersive spectroscopy. The crystal structure and surface functional groups of the helical carbon nanofibers were characterized by X-ray diffraction, Raman spectroscopy and Fourier transform infrared spectroscopy. Results The helical carbon nanofibers prepared at 700 ℃ have a diameter of about 60 nm, a helical structure and a uniform morphology. The carbon atoms of HCNFs are arranged in a short-range order, mainly composed of C-H and C=C functional groups. The potassium carbonate catalyst has a rhombic symmetrical structure in the fiber, resulting in a chiral symmetrical growth of the fiber on both sides of the catalyst. Conclusion sHelical carbon nanofibers with uniform morphology were prepared by chemical vapor deposition. High purity helical carbon nanofibers can be obtained by washing off the surface catalyst.