【摘要】：壁虎優(yōu)異的爬壁性能來源于其腳掌的精細結構,設計并制備這種具有優(yōu)異黏附性能的仿壁虎剛毛對爬壁機器人等具有非常重要的意義。碳納米管具有優(yōu)異的力學、光學和熱學性能等,其尺寸可達納米級別,成為仿壁虎剛毛的熱門材料。本文通過化學氣相沉積法可控制備了具有優(yōu)異黏附性能的碳納米管陣列,研究了其黏附特性,分析了各工藝參數(shù)的影響。具體研究內容如下:(1)在常壓環(huán)境下,通過CVD法制備了具有不同催化劑基底的碳納米管陣列,分析了各工藝參數(shù)的影響。氫氣能夠還原催化劑,優(yōu)化催化劑顆粒形貌和質量,顯著影響碳納米管陣列的質量;沉積時間越長,碳納米管生長的越高,但是存在限值,并且時間越長雜質和缺陷也會越多。(2)催化劑對碳納米管陣列的生長起決定性的作用。本文以Fe作為主要的催化劑,因為Fe對C原子有很高的溶解度能夠形成FeC3,在高溫下C原子在鐵內能夠快速轉移并飽和析出生長碳納米管。以SiO2/Al2O3為支撐層,Al2O3的多孔狀結構能夠讓鐵顆粒的分布均勻,優(yōu)化熔融狀態(tài)下細小致密的鐵顆粒形成,但Al2O3層過厚則容易造成更多的催化劑擴散損失。致密的SiO2層則能夠減少催化劑的損失。(3)在常規(guī)低壓CVD工藝的基礎上通過鼓泡工藝在碳納米管的生長過程中引入了弱氧化劑H2O。弱氧化劑能夠刻蝕催化劑周圍的無定形碳,增強催化劑的活性,使碳納米管能夠更長時間的生長。通過分析水蒸氣含量的影響我們發(fā)現(xiàn),較少的水能夠顯著改善碳納米管的生長,使其長得更高,缺陷更少;但是過多的水由于刻蝕作用強而導致碳納米管無法生長,因此30 sccm水蒸氣(Ar)最為適中。(4)通過黏附力測試裝置對聚合物PVS和碳納米管陣列干黏附材料進行黏附性能測試。測試結果表明,在低壓100 torr環(huán)境下,以SiO2/Al2O3/Fe=300 nm/20 nm/2 nm為催化劑基底,氣體流量比為H2:C2H4:Ar=177:272:734 sccm的CVD工藝制備的碳納米管陣列具有超強的黏附能力,達到32.9 N/cm2,但是其法向黏附力卻很弱。與此相反,聚合物PVS具有強的的法向黏附力,但是其切向黏附力較弱。水輔助法雖然能夠制備得到更高的碳納米管,但是其黏附性能卻大大降低。
[Abstract]:The excellent wall climbing performance of gecko comes from the fine structure of its soles. It is very important to design and fabricate the gecko bristles with excellent adhesion performance for the wall climbing robot. Carbon nanotubes (CNTs) have excellent mechanical, optical and thermal properties. In this paper, carbon nanotube arrays with excellent adhesion properties can be controlled by chemical vapor deposition. The adhesion characteristics of carbon nanotubes are studied and the effects of various technological parameters are analyzed. The main contents are as follows: (1) carbon nanotube arrays with different catalyst substrates were prepared by CVD method under atmospheric pressure, and the effects of various process parameters were analyzed. Hydrogen can reduce the catalyst, optimize the morphology and mass of catalyst particles, and significantly affect the quality of carbon nanotube arrays. The longer the deposition time, the higher the growth of carbon nanotubes, but there is a limit value. And the longer the time is, the more impurities and defects will occur. (2) Catalysts play a decisive role in the growth of carbon nanotube arrays. In this paper, Fe is used as the main catalyst, because of the high solubility of Fe to C atom, C atom can be rapidly transferred and saturated to grow carbon nanotubes (CNTs) in iron at high temperature. With SiO2/Al2O3 as the supporting layer, the porous structure of Al2O3 can make the distribution of iron particles uniform, and optimize the formation of fine and dense iron particles in the melting state, but the thickness of Al2O3 layer is easy to cause more diffusion loss of catalyst. The dense SiO2 layer can reduce the catalyst loss. (3) based on the conventional low-pressure CVD process, the weak oxidant H _ 2O was introduced into the growth process of carbon nanotubes by bubbling process. The weak oxidant can etch the amorphous carbon around the catalyst, enhance the activity of the catalyst, and make the carbon nanotubes grow for a longer time. By analyzing the effect of water vapor content, we find that less water can significantly improve the growth of carbon nanotubes, make them grow higher and have fewer defects, but too much water can cause carbon nanotubes to grow because of strong etching. Therefore, 30 sccm water vapor (Ar) is the most suitable. (4) Adhesion properties of polymer PVS and carbon nanotube array dry adhesion materials are tested by means of adhesion force test device. The results show that the carbon nanotube arrays prepared by CVD process with SiO2/Al2O3/Fe=300 nm/20 nm/2 nm as catalyst substrate and gas flow ratio of H2:C2H4:Ar=177:272:734 sccm at low pressure of 100 torr have excellent adhesion ability, up to 32.9 N / cm ~ 2, but the normal adhesion force is very weak. In contrast, polymer PVS has strong normal adhesion, but its tangential adhesion is weak. Although higher carbon nanotubes can be prepared by water assisted method, the adhesion properties of carbon nanotubes are greatly reduced.
【學位授予單位】：南京航空航天大學
【學位級別】：碩士
【學位授予年份】：2017
【分類號】：TQ127.11;TB383.1

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