弱氧化輔助的碳納米管陣列的制備工藝研究
發(fā)布時(shí)間：2018-10-20 10:25
【摘要】：壁虎優(yōu)異的爬壁性能來(lái)源于其腳掌的精細(xì)結(jié)構(gòu),設(shè)計(jì)并制備這種具有優(yōu)異黏附性能的仿壁虎剛毛對(duì)爬壁機(jī)器人等具有非常重要的意義。碳納米管具有優(yōu)異的力學(xué)、光學(xué)和熱學(xué)性能等,其尺寸可達(dá)納米級(jí)別,成為仿壁虎剛毛的熱門材料。本文通過(guò)化學(xué)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?jī)?nèi)容如下:(1)在常壓環(huán)境下,通過(guò)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(zhì)量,顯著影響碳納米管陣列的質(zhì)量;沉積時(shí)間越長(zhǎng),碳納米管生長(zhǎng)的越高,但是存在限值,并且時(shí)間越長(zhǎng)雜質(zhì)和缺陷也會(huì)越多。(2)催化劑對(duì)碳納米管陣列的生長(zhǎng)起決定性的作用。本文以Fe作為主要的催化劑,因?yàn)镕e對(duì)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(nèi)能夠快速轉(zhuǎn)移并飽和析出生長(zhǎng)碳納米管。以SiO2/Al2O3為支撐層,Al2O3的多孔狀結(jié)構(gòu)能夠讓鐵顆粒的分布均勻,優(yōu)化熔融狀態(tài)下細(xì)小致密的鐵顆粒形成,但Al2O3層過(guò)厚則容易造成更多的催化劑擴(kuò)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(chǔ)上通過(guò)鼓泡工藝在碳納米管的生長(zhǎng)過(guò)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(wú)定形碳,增強(qiáng)催化劑的活性,使碳納米管能夠更長(zhǎng)時(shí)間的生長(zhǎng)。通過(guò)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(zhǎng),使其長(zhǎng)得更高,缺陷更少;但是過(guò)多的水由于刻蝕作用強(qiáng)而導(dǎo)致碳納米管無(wú)法生長(zhǎng),因此30 sccm水蒸氣(Ar)最為適中。(4)通過(guò)黏附力測(cè)試裝置對(duì)聚合物PVS和碳納米管陣列干黏附材料進(jìn)行黏附性能測(cè)試。測(cè)試結(jié)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(qiáng)的黏附能力,達(dá)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(qiáng)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(xué)位授予單位】：南京航空航天大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2017
【分類號(hào)】：TQ127.11;TB383.1
本文編號(hào)：2282863
[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(xué)位授予單位】：南京航空航天大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2017
【分類號(hào)】：TQ127.11;TB383.1
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