tailieunhanh - Báo cáo hóa học: " Effect of Temperature Gradient Direction in the Catalyst Nanoparticle on CNTs Growth Mode"

Tuyển tập báo cáo các nghiên cứu khoa học quốc tế ngành hóa học dành cho các bạn yêu hóa học tham khảo đề tài: Effect of Temperature Gradient Direction in the Catalyst Nanoparticle on CNTs Growth Mode | Nanoscale Res Lett 2010 5 1393-1402 DOI s11671-010-9648-4 NANO EXPRESS Effect of Temperature Gradient Direction in the Catalyst Nanoparticle on CNTs Growth Mode An-Ya Lo Shang-Bin Liu Cheng-Tzu Kuo Received 1 October 2009 Accepted 17 May 2010 Published online 26 June 2010 The Author s 2010. This article is published with open access at Abstract To improve the understanding on CNT growth modes the various processes including thermal CVD MP-CVD and ECR-CVD have been used to deposit CNTs on nanoporous SBA-15 and Si wafer substrates with C2H2 and H2 as reaction gases. The experiments to vary process parameter of AT defined as the vector quantities of temperature at catalyst top minus it at catalyst bottom were carried out to demonstrate its effect on the CNT growth mode. The TEM and TGA analyses were used to characterize their growth modes and carbon yields of the processes. The results show that AT can be used to monitor the temperature gradient direction across the catalyst nanoparticle during the growth stage of CNTs. The results also indicate that the tip-growth CNTs base-growth CNTs and onion-like carbon are generally fabricated under conditions of AT 0 0 and 0 respectively. Our proposed growth mechanisms can be successfully adopted to explain why the base- and tip-growth CNTs are common in thermal CVD and plasma-enhanced CVD processes respectively. Furthermore our experiments have also successfully demonstrated the possibility to vary AT to obtain the desired growth mode of CNTs by thermal or plasma-enhanced CVD systems for different applications. . Lo Department of Materials Science and Engineering National Chiao Tung University Hsinchu 300 Taiwan . Liu Institute of Atomic and Molecular Sciences Academia Sinica Taipei 106 Taiwan . Kuo Department of Materials Science and Engineering Ming Dao University Changhua 52345 Taiwan e-mail kuoct@ Keywords CNTs Growth mechanism Base-growth Tip-growth CVD Introduction Starting