Study On The Weak Oxidant Assisted Carbon Nanotube Arrays Preparation Technology

The micro-nano scale beta-keratin pillars contribute to the gecko's superior climbing ability on vertical walls and even ceilings.Design and preparation of gecko-mimicking dry adhesive arrays are important for the development of wall climbing robots.Carbon nanotubes have excellent mechanical properties,optical performance and thermal performance,with diameter in nanometer level,it has become an appropriate material to prepare gecko-mimicking setae.We have controllably prepared carbon nanotube arrays with excellent adhesive properties,then studied their adhesion characteristic and analyzed the influence of various process parameters.(1)Under atmospheric pressure,carbon nanotube arrays were prepared by CVD method with different catalysts and the influence of various process parameters is analyzed.Hydrogen can reduce catalyst and optimize the morphology and quality of catalyst particles which significantly affect the quality of the carbon nanotube arrays.Carbon nanotubes grow higher with deposition time.(2)Catalysts play a determinative effect on the growth of carbon nanotube arrays.Fe is chosen as the main catalyst because of its great solubility to carbon.Carbon can move quickly in Fe particles and saturated precipitation to grow carbon nanotubes at high temperature.The Al2O3 layer with porous structure can make the iron particles in uniform distribution and optimized the formation of Fe particles to be small and dense during crystallization.(3)On the basis of low-pressure CVD process,the weak oxidant H2 O is introduced into the process of the growth of carbon nanotubes by bubbling process.Weak oxidant can etch the amorphous carbon around Fe catalyst and enhance its activity.We found that less water can significantly improve the growth of carbon nanotubes which make it grow higher.But too much water cause carbon nanotubes can't grow due to the strong etching effect,so the 30 sccm water vapor(Ar)is the most moderate.(4)The adhesion performance of three kind of bionic dry adhesive materials with different fabrication processes have been tested through adhesion force test device.Test results show that carbon nanotube arrays with super strong shear adhesion strength reached 32.9 N/cm2 can be prepared by CVD process with 100 torr pressure.On the contrary,polymer PVS has a strong normal adhesion force,but the normal adhesion force is weak.Water auxiliary method although can get higher carbon nanotubes,but its adhesion is greatly reduced.