Research Of Adhesion And Heat Transfer Properties Of Vertically Aligned Carbon Nanotube Array

Carbon nanotube(CNT)array is a black film-like solid material in which carbon nanotubes are arranged in parallel in a direction perpendicular to the substrate.As a typical one-dimensional carbon material,carbon nanotubes have obtained a large number of research results for their excellent physical properties in the past two decades since its discovery.Due to the special structural morphology of the carbon nanotube array,the excellent micro-nano characteristics are concentrated in macroscopic array materials,possessing special mechanical and heat transfer properties,and thus in bionic adhesion,thermal interface materials,etc.There are huge potential applications.At present,achievements of carbon nanotube arrays have been made.However,there are still some differences in the results of different researches,which limits its further engineering applications.The mechanical behavior and heat transfer performance of carbon nanotube arrays still need to be further improved.In view of this,this article examines the growth method of carbon nanotube arrays,analyzes the vertical compressive mechanical properties of carbon nanotube arrays,tests and reveals the biomimetic adhesion characteristics and mechanism of carbon nanotube arrays,and develops carbon nanotube arrays-based thermal interface materials with flexible substrate which is suitable for vibration devices.This work establishes the relationship between the two fields of mechanical and heat transfer in carbon nanotube arrays and opens up new engineering applications of carbon nanotube arrays.The main research contents of this article and related research findings are as follows:Firstly,the synthesis method of carbon nanotube arrays was investigated,along with the vertical compressive mechanical behavior of carbon nanotube arrays.Chemical vapor deposition system for preparing carbon nanotube arrays was built,and the appropriate gas composition and atmosphere for preparing carbon nanotube arrays were analyzed and summarized.Carbon nanotube arrays with different array heights and densities were prepared,and microlithographic arrays of carbon nanotubes with different sizes were prepared by means of photolithographic patterning.Vertical compressive experiments were performed on the above-described different-characteristic carbon nanotube arrays to obtain vertical compressive mechanical properties.The results show that there are certain differences in the compression mechanics characteristics of different carbon nanotube arrays.High array density carbon nanotube arrays exhibit significant super-elastic properties while low density arrays exhibit shaped properties.The height of the array and the size of the patterned array pillars also have a certain influence on the compressive mechanical properties.Secondly,the gecko imitation adhesion characteristics of carbon nanotube array were studied.The influence of the preload force,the holding time and the surface properties of the material on the adhesion characteristics were analyzed.The durability and repeatability effects of adhesion were explored.At the same time,combined with the vertical compressive mechanical behavior of CNT arrays,the reasons for adhesion force are mainly caused by the deformation of the arrays.There is a close relationship between the adhesion force and the compression deformation of carbon nanotubes,and the deformation and lateral contact of carbon nanotubes are the main reason for the adhesion force,and the preload force deforms and surrenders the carbon nanotubes.At the same time,this article has developed a non-contact transient optical heat reflection technology applied to the measurement of thermal conductivity of thin film materials,including their mathematical model,using the multi-parameter fitting method to get the thermal conductivity and interface thermal conductance of the film.The system was used to measure the thermos-physical properties of flexible carbon nanotube array samples.Finally,the mechanical and heat transfer characteristics of the carbon nanotube array as a thermal interface material on the interface of the vibrational device are studied.Taking piezoelectric transformer as an a typical example,the operating characteristics of three different heat transfer structures were compared,including the relationship between temperature rise,power transfer efficiency,and the power density.The results show that piezoelectric transformers equipped with carbon nanotube array thermal interface materials achieve lower temperature rise and higher power transfer efficiency.At the same time,the thermal property parameters of the CNT arrays were measured by the optical-thermal reflection technique,and the thermal conductivity was higher than that of the traditional polymer material.In addition,the carbon nanotube array reduces the fretting friction loss of the electrode on the surface of the vibrating device.After 120 days of continuous operation tests,the piezoelectric transformer equipped with the carbon nanotube array has no obvious wear on the surface electrodes of the device,which greatly increases the lifetime of the device.Finally,a certain mechanical analysis of the wear resistance of the CNT array was performed.