纳米CaCO3负载过渡金属CVD法制备多壁碳纳米管的研究

以纳米碳酸钙粉体为载体,用浸渍法制备了可用于化学气相沉积(CVD)法制备碳纳米管的高产率催化剂.应用FESEM,HRTEM,TEM,XRD和激光拉曼谱对产物进行了表征.结果表明,由于纳米碳酸钙具有较大的比表面积,可高密度地承载催化剂活性组分.在碳纳米管生长初期,处于缓慢分解状态的纳米碳酸钙才能有效地起到载体作用,且反应温度为700～750℃时,碳纳米管的产率较高.Fe-Co双金属催化剂在700℃,催化生长60min后,可增重10倍,而且产物中无定形碳含量极少.纳米碳酸钙载体易于提纯,用质量分数为30%的硝酸超声提纯粗产品1h,可使纯度提高到97%,且不破坏碳纳米管结构.

Preparation of Multi-walled Carbon Nanotubes by CVD over Transition Metal Catalyst Supported on Nanocrystallite CaCO3

Multi-walled carbon nanotubes(MWNTs) were synthesized by chemical vapor deposition(CVD) over transition metal catalyst supported on nanocrystalline CaCO3. The compositions and the preparation conditions of the catalysts were studied and the nanotubes synthesized were characterized by field emission scanning electron microscopy(FESEM), transmission electron microscopy(TEM), high transmission electron microscopy(HREM), XRD and Raman spectroscopy. The results show that the high specific surface area of nanocrystallite CaCO3 has the advantage to load metal nanoparticles with a high density. The prepared Fe-Co bimetallic catalyst was the best catalyst for CNTs synthesis. An ideal condition for CNTs′ forming is 700 ℃ for 60～90 min with proper decomposition speed of nanocrystallite CaCO3 at early stages of CNTs synthesis, and the yield of CNTs with the outer diameter of 15～25 nm is 11 g MWNTs/g catalyst. The purity can reach 97% by sonication in 30% nitric acid based on thermal gravimetric analysis results. The structures of the carbon nanotubes were not damaged proved by Raman spectroscopy.