仿壁虎碳纳米管阵列制备及黏附性能研究
发布时间：2018-11-21 14:43
【摘要】：碳纳米管阵列(VACNTs)以其优异的力学、电学、热学性能以及对极端环境的适应性,成为仿壁虎干黏附极具潜力的材料,在爬壁机器人领域体现出重要的应用价值。本文针对目前VACNTs可控制备存在的问题,设计了具有不同缓冲层和催化剂厚度的生长基底,并调节了化学气相沉积工艺过程中的氢气预处理时间,氢气浓度,沉积时间和反应压力等,以探究这些因素对制备的VACNTs的形貌结构、缺陷程度、纯度质量及黏附性能的影响,为实现其可控制备建立方法和理解上的基础。本文的主要成果和结论如下:1.支撑层和催化剂层的厚度对VACNTs的生长状况有显著的影响。Fe层的厚度直接决定形成的催化剂Fe颗粒的分布状况,进一步影响以此为模板生长的VACNTs的形貌结构。多孔结构的Al_2O_3使还原后的Fe进入其空隙分散成均匀分布的颗粒,过厚的Al_2O_3层增大了Fe颗粒的扩散损耗。而比Al_2O_3层更加致密的SiO_2层有效阻断了Fe颗粒的扩散损耗。2.通过调节预处理阶段和沉积阶段的氢气浓度,可以控制VACNTs的生长速率实现快速生长。AFM观察表明,预处理阶段适宜浓度的氢气将催化剂Fe膜还原到具有催化活性的金属状态并形成均匀分布的Fe颗粒。实验中以SiO_2/Al_2O_3/Fe=300nm/15nm/1nm的生长基底,在25%的氢气浓度下制备的VACNTs高度达到949μm,生长速率为23.72μm/min。拉曼光谱表明,该条件下生长的VACNTs呈现较高的石墨化结晶程度,具有相对最佳的纯度和质量。3.本文提出了反应气氛中氢气浓度对VACNTs黏附性能的影响机理:当氢气比例过低(0%~5%)时,VACNTs生长高度较低,不足以适应目标表面形成大面积的线接触。而当氢气比例过高(25%~35%)时,多余的氢气改变了催化剂的晶相,从具有催化活性的FeC_3转变为体心立方(BCC)Fe,使生长的VACNTs缺陷程度更高而石墨化结晶程度较差。实验中以SiO_2/Al_2O_3/Fe=300nm/20nm/2nm的生长基底,在15%的氢气浓度下制备的VACNTs在黏附测试中表现出优良的黏附性能,宏观切向黏附力达到32N/cm2,是壁虎脚掌的3.2倍。
[Abstract]:Because of its excellent mechanical, electrical, thermal properties and adaptability to extreme environments, carbon nanotube array (VACNTs) has become a potential material for dry adhesion of Gecko, and has shown great application value in the field of wall-climbing robot. Aiming at the existing problems of controllable preparation of VACNTs, the growth substrate with different buffer layer and catalyst thickness was designed, and the pretreatment time and concentration of hydrogen in the process of chemical vapor deposition were adjusted. The deposition time and reaction pressure were used to investigate the influence of these factors on the morphology, defect degree, purity quality and adhesion property of the prepared VACNTs. The main results and conclusions are as follows: 1. The thickness of the supporting layer and the catalyst layer has a significant effect on the growth of VACNTs. The thickness of the Fe layer directly determines the distribution of the formed catalyst Fe particles, and further influences the morphology and structure of the VACNTs grown on the template. Al_2O_3 with porous structure makes the reduced Fe into its pore space to disperse into uniformly distributed particles, and the excessive thickness of Al_2O_3 layer increases the diffusion loss of Fe particles. SiO_2 layer, which is denser than Al_2O_3 layer, effectively blocks the diffusion loss of Fe particles. 2. The growth rate of VACNTs can be controlled by adjusting the concentration of hydrogen in pretreatment stage and deposition stage. The Fe membrane of the catalyst was reduced to a metal state with catalytic activity by hydrogen at a suitable concentration in the pretreatment stage and a uniform distribution of Fe particles was formed. In the experiment, the growth rate of SiO_2/Al_2O_3/Fe=300nm/15nm/1nm was 23.72 渭 m / min and the height of VACNTs was 949 渭 m at 25% hydrogen concentration. The Raman spectra show that the VACNTs grown under this condition has a relatively high degree of graphitization and crystallization, and has the best purity and quality of 3. 3%. The mechanism of the effect of hydrogen concentration in the reaction atmosphere on the adhesion properties of VACNTs is presented. When the hydrogen ratio is too low (0%), the growth height of VACNTs is low, which is not enough to adapt to the formation of large area linear contact on the target surface. When the hydrogen ratio is too high (25%), the excess hydrogen changes the crystalline phase of the catalyst, from the catalytic activity of FeC_3 to the bulk centered cubic (BCC) Fe,), resulting in higher degree of defect of VACNTs growth and less degree of graphitization crystallization. In the experiment, the VACNTs prepared on the growth substrate of SiO_2/Al_2O_3/Fe=300nm/20nm/2nm with 15% hydrogen concentration showed excellent adhesion performance in the adhesion test. The macroscopic tangential adhesion force reached 32N / cm ~ 2. 3.2 times the gecko's soles.
【学位授予单位】：南京航空航天大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TQ127.11;TB383.1
本文编号：2347278
[Abstract]:Because of its excellent mechanical, electrical, thermal properties and adaptability to extreme environments, carbon nanotube array (VACNTs) has become a potential material for dry adhesion of Gecko, and has shown great application value in the field of wall-climbing robot. Aiming at the existing problems of controllable preparation of VACNTs, the growth substrate with different buffer layer and catalyst thickness was designed, and the pretreatment time and concentration of hydrogen in the process of chemical vapor deposition were adjusted. The deposition time and reaction pressure were used to investigate the influence of these factors on the morphology, defect degree, purity quality and adhesion property of the prepared VACNTs. The main results and conclusions are as follows: 1. The thickness of the supporting layer and the catalyst layer has a significant effect on the growth of VACNTs. The thickness of the Fe layer directly determines the distribution of the formed catalyst Fe particles, and further influences the morphology and structure of the VACNTs grown on the template. Al_2O_3 with porous structure makes the reduced Fe into its pore space to disperse into uniformly distributed particles, and the excessive thickness of Al_2O_3 layer increases the diffusion loss of Fe particles. SiO_2 layer, which is denser than Al_2O_3 layer, effectively blocks the diffusion loss of Fe particles. 2. The growth rate of VACNTs can be controlled by adjusting the concentration of hydrogen in pretreatment stage and deposition stage. The Fe membrane of the catalyst was reduced to a metal state with catalytic activity by hydrogen at a suitable concentration in the pretreatment stage and a uniform distribution of Fe particles was formed. In the experiment, the growth rate of SiO_2/Al_2O_3/Fe=300nm/15nm/1nm was 23.72 渭 m / min and the height of VACNTs was 949 渭 m at 25% hydrogen concentration. The Raman spectra show that the VACNTs grown under this condition has a relatively high degree of graphitization and crystallization, and has the best purity and quality of 3. 3%. The mechanism of the effect of hydrogen concentration in the reaction atmosphere on the adhesion properties of VACNTs is presented. When the hydrogen ratio is too low (0%), the growth height of VACNTs is low, which is not enough to adapt to the formation of large area linear contact on the target surface. When the hydrogen ratio is too high (25%), the excess hydrogen changes the crystalline phase of the catalyst, from the catalytic activity of FeC_3 to the bulk centered cubic (BCC) Fe,), resulting in higher degree of defect of VACNTs growth and less degree of graphitization crystallization. In the experiment, the VACNTs prepared on the growth substrate of SiO_2/Al_2O_3/Fe=300nm/20nm/2nm with 15% hydrogen concentration showed excellent adhesion performance in the adhesion test. The macroscopic tangential adhesion force reached 32N / cm ~ 2. 3.2 times the gecko's soles.
【学位授予单位】：南京航空航天大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TQ127.11;TB383.1
【参考文献】
相关期刊论文 前7条
1 李宏凯;戴振东;石爱菊;张昊;孙久荣;;大壁虎在垂直面和水平面上小跑和行走的关节角度观测[J];科学通报;2008年22期
2 张培锋;王洪光;房立金;姜勇;;一种新型爬壁机器人机构及运动学研究[J];机器人;2007年01期
3 李满天;黄博;刘国才;孙立宁;;模块化可重构履带式微小型机器人的研究[J];机器人;2006年05期
4 戴振东;孙久荣;;壁虎的运动及仿生研究进展[J];自然科学进展;2006年05期
5 张俊强;张华;万伟民;;履带式爬壁机器人磁吸附单元的磁场及运动分析[J];机器人;2006年02期
6 张厚祥,刘荣,王巍,宗光华;爬壁机器人气动位置伺服控制研究[J];北京航空航天大学学报;2004年08期
7 高学山;徐殿国;王炎;;新型壁面清洗机器人的研究与设计[J];高技术通讯;2004年04期
，本文编号：2347278
本文链接：https://www.wllwen.com/kejilunwen/huaxuehuagong/2347278.html
