Verissimo C, Aguiar M R, Moshkalev S A
Center for Semiconductor Components-CCS, State University of Campinas-UNICAMP, Campinas, SFP CEP 13083-870, Brazil.
J Nanosci Nanotechnol. 2009 Jul;9(7):4459-66. doi: 10.1166/jnn.2009.m77.
Multi-walled carbon nanotubes and other carbon nanostructures have been grown using catalytic thermal chemical vapor deposition method in a horizontal tubular quartz furnace at atmospheric pressure. The mechanisms of nanotubes/nanofibers nucleation and growth are analyzed. A new model explaining the nanotube nucleation as a specific instability occurring on the catalyst particle surface supersaturated with carbon is presented. It is also shown that an axially symmetric instability, giving rise to the nanotube nucleation, is developed when certain critical conditions such as temperature, supersaturation and catalyst volume are achieved. For smaller temperatures, another mechanism of carbon segregation from supersaturated catalyst particles has been observed. In this case, flat rather than tubular graphitic layers are formed. These findings are important for better understanding and control of the synthesis of different carbon nanoforms using chemical vapor deposition.
多壁碳纳米管和其他碳纳米结构已通过催化热化学气相沉积法在常压下的卧式管状石英炉中生长。分析了纳米管/纳米纤维的成核和生长机制。提出了一种新模型，将纳米管成核解释为在碳过饱和的催化剂颗粒表面发生的特定不稳定性。研究还表明，当达到温度、过饱和度和催化剂体积等特定临界条件时，会产生导致纳米管成核的轴对称不稳定性。对于较低温度，观察到了过饱和催化剂颗粒中碳偏析的另一种机制。在这种情况下，形成的是扁平而非管状的石墨层。这些发现对于更好地理解和控制利用化学气相沉积合成不同碳纳米形态具有重要意义。
