摘要
以稀土合金MlNi5-1.35(CoAlMn)1.35为催化剂,C2H2为碳源,H2为还原气和载气,用CVD法合成了纯度较高的CNTs。通过用SEM,TEM,XRD及Raman等表征测试方法,研究了H2流量对合成的CNTs管径、产量、纯度、形态及石墨化程度的影响。结果表明:合金催化剂经还原后其粒径从μm级细化到了nm量级;在催化剂与C2H2反应过程中不通入H2时,催化剂上仍能生长出CNTs,但其长度短而管径粗(约97.8nm),管壁厚而粗糙;随着H2流量增大,CNTs管径先减小后增大,而其产量、纯度及石墨化程度则先提高后下降。当H2流量为50ml·min-1时,CNTs管径达最细(平均管径49.1nm);H2流量为75ml·min-1时,其产物纯度高,产量最大(4.05g·g-1催化剂),CNTs石墨化程度最高;H2流量为100ml·min-1时,CNTs管径最均匀(平均管径97.8nm)。
High-purity carbon nanotubes (CNTs) were synthesized in hydrogen ambience by CVD method by using rare earth alloy MlM 5-1.35 (CoAlMn) 1.35 as catalyst, acetylene as carbon source. The influence of hydrogen flow rate on the diameter, shape, purity, graphitization degree and output of carbon nanotubes was systematically studied by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD) and Raman technique. The results indicate that the size of MlM5 alloy particles changes from micrometer order into nanometer order during the process of hydrogen reduction. While not introducing hydrogen in the reaction of acetylene and catalyst, CNTs can also be synthesized on the catalyst. The CNTs are short and thick with average diameter of about 97.8 nm, and the wall of CNTs is also thick and rough. With increasing of hydrogen flow rate, the diameter of CNTs decreases firstly and then increases, while the output, purity, and graphitization degree first increase and then decrease. The optimized conditions are: CNTs reach their thinner diameter of 49.1 nm when hydrogen flow rate is 50 ml·min -1 ; the purity, graphitization degree, and output of CNTs reach highest and largest when hydrogen flow rate is 75 ml·min -1 . They have the most uniform tube size of 97.38 nm when hydrogen flow rate is 100 ml·min -1 .
出处
《中国稀土学报》
CAS
CSCD
北大核心
2005年第3期286-290,共5页
Journal of the Chinese Society of Rare Earths
基金
国家自然科学基金(50372013)
广东省自然科学基金(004009487
04300168)
关键词
稀土合金
催化裂解
碳纳米管
管径可控
稀土
rare earth alloy
catalytic pyrolysis
CNTs
controllable diameter
rare earths
