Preparation Of Carbon Nanotubes On Carbon Fibers By CVD Method And The Mechanism Research

With the progress of science and technology, the composites have been used in everywalk of life in our society. And the carbon fiber (CF) reinforced composite materials arewidely used in aerospace and other sophisticated scientific fields as a high performancestructural material in recent years. The carbon nanotubes (CNTs) which possess aspects ofexcellent performances, can be used to prepare more excellent nano-materials with in situreinforced CF. In this paper, the CNTs were in situ grown on CFs surface by chemical vapordeposition (CVD) method with propylene and acetylene as carbon source, and Ni as catalyst.The effects of CVD parameters and Ni catalysts on growth of CNTs were investigated, andthe growth mechanism of CNTs was analysed.1) The method of electroplating was adopted to deposit Ni catalyst on CFs. The effect ofelectroplating time on Ni coating was studied and the morphology, growth pattern and growthof Ni coating were analysed. In our results, the catalyst particles with a appropriate size wereuniformly coated on CFs surface for5to10min of electroplating time. The catalyst particlescatalytic cracking of propylene and acetylene could obtain CNTs on CFs surface with a betteractivity.2) The catalyst particles played an important role in the process of growth of CNTs.During the process of electroplating, Ni grew with the Frank-van der Merwe (F-M) model.Firstly, the nano-Ni particles deposited on the CF surface where energy was suitable, forminginto small crystallites. Then, with the time prolonged, the Ni particles gradually increased andgathered to form into island grains. The special surface morphology of CFs after pretreatmentinduced the Ni particles to develop into dendrites that played an important role in the growthof CNTs.3) CNTs were synthesized on CFs by CVD method with propylene and acetylene ascarbon source, respectively. The effects of Ni catalysts, deposition temperature and reactiontime on growth of CNTs were investigated. When propylene as carbon source,5min forelectroplating, on condition of propylene flow rate of30sccm, hydrogen gas flow rate of200sccm and nitrogen flow rate of400sccm, growth time of4h, some perfect CNTs weregrew on CFs by controlling growth temperature at900℃.When acetylene as carbon source,oncondition of acetylene flow rate of30sccm,hydrogen gas flow rate of400sccm and nitrogenflow rate of400sccm, growth time of15min, at650℃, the smoother CNTs can be obtain onCFs.4) According to the analysis of the growth mechanism of Ni catalyst particles and the effects of CVD parameters on CNTs growth, the growth mechanism model of CNTs in thispaper was presented.5) The orientated growth of CNTs on CFs was studied for the first time. The orientatedgrowth of CNTs was achieved by developing the reaction technology, utilizing airflowcontrolling and gravity of CNTs. And we obtained forest-like CNTs.