【作者】 万步勇；

【导师】 王万录；

【作者基本信息】 重庆大学 ， 凝聚态物理， 2005， 硕士

【摘要】 碳纳米管是在1991 年发现的一种新兴的一维的纳米材料,它具有中空的几何结构和螺旋手性结构,根据其手性参数和直径的不同,碳纳米管即可呈金属性又可呈现半导体的性质。由于碳纳米管特殊的结构,使其具有许多奇异的物理化学性质,有着广阔的应用前景。随着对碳纳米管理论和实验研究的不断深入,碳纳米管越来越引起科学家和研究人员的关注和重视。它可以用于分子器件、驱动器和信号处理器等器件中,特别是碳纳米管作为传感器材料,具有广阔的应用前景。本文主要对碳纳米管膜的气敏、湿敏和温差电效应进行了研究。碳纳米管膜网络中,其电阻由碳纳米管结电阻和碳纳米管本身的电阻决定。研究发现,前者与温度的关系呈正指数变化,后者与温度的关系呈负指数变化。化学修饰后的碳纳米管膜电阻主要由碳纳米管结的电阻决定。其中碳纳米管结的电阻与碳纳米管间的距离成正比。对碳纳米管膜在空气、乙醇、氨气等气体的气敏性质进行了实验研究。结果发现,碳纳米管膜在室温下就表现出较强的气敏特性。空气中,碳纳米管膜对水分子最敏感,而对CO₂、CH₄、O₂等不太灵敏。在干燥空气和湿敏为48%的空气中,碳纳米管膜的电阻变化约为18%。碳纳米管膜对乙醇气体和氨气具有较强的气敏性质,室温下,其灵敏度分别可达28%和70%。并且,其响应时间和恢复时间都较短。研究还发现,化学修饰后的碳纳米管膜相对于未经化学修饰的样品其气敏性质明显增强。并对其实验结果进行了理论分析。对碳纳米管膜的湿敏性质进行了研究。发现在水蒸气氛围中,相对于空气中,碳纳米管膜电阻变化最大可达250%,且,膜电阻的变化量与相对湿度成正比。本文对碳纳米管膜的湿敏机理进行了简要的讨论和分析。另外,对碳纳米管膜的温差电效应进行了研究,发现其温差电动势与温差成正比,碳纳米管膜的塞贝克系数在-15μv/K^-60μv/K 之间,碳纳米管膜呈n 型半导体性质。并根据其实验数据,计算出了碳纳米管膜中的费米能和电子浓度等参数。更多还原

【Abstract】 Carbon nanotube (CNT) is a new type of one-dimensional nanostructured material that was discovered in 1991, which has a cylindrical geometry structure. In terms of their chiral properties and diameters, CNTs can be either metallic or semiconducting. CNTs unique structure exhibits fantastic physical and chemical characteristics, and shows potentials in wide. With the more research efforts, CNTs attract attentions from scientists worldwide. They can be used for nanomechanical-based devices, sensors, actuators and signal processor et.al. CNTs show potentials as a sensor material. In this study, gas-sensitivity, humidity-sensitivity and thermoelectric effect of CNT films have been investigated. In the CNT films, their total resistance consists of the resistance of CNT junctions and their own resistance. It is found that the former is positive exponentially proportional to temperature, while the latter is negative exponentially proportional to temperature. The resistanc of the treated CNT films is decided by that of CNT junctions that is proportional to the distance between CNTs. The gas-sensitivity of CNT films has been studied in air、ethanol、ammonia atomsphere. It is indicated that it is at room temperature that CNT films have stronger gas-sensitivity. In air atomsphere , the CNT films have the most sensitivity to water vapour, while they are not sensitive to CO2、CH4、O2. The biggest change of resistance of CNT films is about 18% between dry air and air of 48% humidity. The CNT films are rather sensitive to ethanol and ammonia gas, the sensitivities can reach 28% and 70% in room temperature, respectively. Meanwhile, the response time and the recovery time are very short. In addition, the study shows chemical treatments have enhanced gas-sensing characteristics greatly. The results have also been discussed and analysed. Humidity-sensitivity of CNT films has been studied. It is revealed that in water vapour, the biggest change of resistance of CNT films can reach 250% comparing to that in air. And the change of resistance in CNT films is proportional to relative humidity. The humidity-sensing mechanism has been discussed and analysed briefly. The thermoelectric effect of CNT films has also been studied in this research. The study shows that the thermoelectric force is proportional to temperature difference. The Seebeck coefficience is -15μv/K~-60μv/K, which exhibits that CNT films are n-type. In addition, the parameters such as Femi energy and electron concentration in the CNT films have been calculated.更多还原