聚酰亚胺(PI)薄膜用于光纤布拉格光栅湿度传感器的特性分析

研究了湿敏聚合物--聚酰亚胺(PI)薄膜用于光纤布拉格光栅湿度传感器的原理及应用,并对其传感特性进行了分析与测量.实验表明:镀有聚酰亚胺(PI)薄膜的光纤布拉格光栅的反射峰位置漂移量与湿度呈线性关系,容易标定,实现了对湿度的高精度测量.用这种材料制作的湿度传感器比其他类型湿度传感器性能优越.     

退火温度对纳米氧化铜湿敏性能的影响

湿度传感器在生产和生活中扮演着不容小觑的角色,越来越受到人们的广泛关注.本文利用低温液相法以氢氧化钠、过硫酸铵和铜粉为原料,成功制备出氧化铜纳米结构.运用扫描电子显微镜(SEM)、X-射线衍射仪(XRD)等技术对材料的结构与形貌进行表征,发现可以通过退火温度来调控氧化铜纳米结构的表面形貌,进一步比较研究了不同退火温度下制备的纳米氧化铜的湿敏性能.并将CuO纳米材料涂敷在电极表面制成了湿敏元件.研究结果表明,元件的湿敏特性明显与材料的退火温度密切相关,在500℃退火获得的氧化铜纳米线灵敏度最高,达到1.93×10~5;湿滞最小,几乎为零;感湿频率特性曲线的线性度好.分析认为这主要是由于,退火温度500℃时,氧化铜呈现纳米线状结构,具有更大的表面积,增加了与水分子的接触面积,进而具有更佳的湿敏特性.     

单壁碳纳米管的场发射特性研究

利用场发射显微镜(FEM)和四极质谱计分别研究了经过热处理的单壁碳纳米管的场发射图像和热处理过程中样品脱附的残气质谱.当热处理温度达到1000℃左右时得到了单壁碳纳米管的场发射像,此像可能是顶端开口的单根(16,0)锯齿形单壁碳纳米管的具有原子可分辨的场发射图像.四极质谱分析结果表明,在此温度范围W针尖晶粒间隙中有O原子和C原子释放出来.它们对单壁碳纳米管顶端的修饰是我们能观察到这些碳纳米管场发射像的可能原因. 关键词： 单壁碳纳米管(SWCNTs) 场发射显微镜(FEM) 四极质谱     

碳纳米管的纯化及其在聚乙烯醇中的分散

采用硫酸和硝酸混合酸对多壁碳纳米管(MWNTs)进行纯化,利用红外光谱(IR)、X射线衍射(XRD)对MWNTs进行了表征;聚乙烯醇/乙醇(V/V=1:1)溶液分散MWNTs,循环伏安法(CV)测试了碳纳米管/聚乙烯醇膜修饰电极的电化学性能.实验结果表明,混酸处理可以提高碳纳米管的纯度及石墨化程度,并可以在碳纳米管上引入羧基功能团;碳纳米管可以均匀地分散在聚乙烯醇/乙醇溶液中并形成稳定的悬浮液,同时碳纳米管/聚乙烯醇膜修饰电极对苯二酚具有明显电化学催化活性.     

多壁碳纳米管阵列场发射研究

研究了Ar离子束轰击及温度对多壁碳纳米管阵列场发射性能的影响.经Ar离子轰击35min后，发现阵列顶端的Fe催化剂颗粒明显减少，弯曲的顶部被轰击掉，使碳纳米管的场发射电流明显减小而场发射像无明显改变.温度的增加引起碳纳米管的场发射电流也随之增加.还研 究了在透明阳极技术中涂在阳极的荧光粉对场发射电流的影响.对同一碳纳米管阵列样品，发现涂有荧光粉的透明阳极使测量到的场发射电流大幅度减小，只是未涂荧光粉阳极电流的 1/30左右.直接用二氧化锡导电膜作阳极时，测得样品的开启场强为1.0V/μm.沉积了荧光粉的二 关键词： 多壁碳纳米管 场发射     

敏感电阻在生物生长培养环境中的应用

基于湿敏、热敏、光敏电阻实现对湿度温度和光照的控制,能适用于温度湿度光照变化范围较大或较为剧烈的环境。利用敏感电阻对环境条件敏感的特性,将环境中的信息转化为模拟信号,通过单片机处理得到环境中湿度、温度以及光照数据。对比设定阈值,设计电路通过固态继电器选择性驱动除/加湿设备和温控光照设备工作。此系统可应用于温室养殖、大棚与实验室培养等场所,为生物提供适宜可控的生长培养环境。     

氧吸附对单壁碳纳米管的电子结构和光学性能的影响

用密度泛函理论计算了氧分子物理吸附在半导体型单壁碳纳米管的束缚能，能带结构和吸收 光谱.计算结果指出氧分子吸附在碳纳米管表面的优先位置，研究发现氧吸附对碳管的电子 输运特性和吸收光谱有着重要的影响，并对光致氧分子解吸附的现象进行了理论分析. 关键词： 单壁碳纳米管 氧物理吸附 能带结构 吸收光谱     

碳湿敏膜的非线性感湿特性和导电机理

采用羟乙基纤维素（HEC）和导电炭黑并添加山梨醇增湿剂制备碳湿敏膜,研究了膜在偏离结露区的非线性感湿特性和导电机理.扫描电镜观测到,膜中炭黑粒子形成网链状的空间导电结构;2%炭黑含量使膜的导电通路处于渗流区,膜电阻在80%RH附近对湿度有较强的非线性特性.分析I-V曲线认为,是导电网链中炭黑粒子的间距使膜电阻对湿度变化和测量电压的变化都非常敏感,非线性感湿特性与导电机理密切相关.复阻抗谱表明,碳湿敏样品在33%RH时只出现与炭黑体电阻有关的半圆弧,在80%RH时出现与炭黑粒界电 关键词： 碳湿敏膜 逾渗阈值 I-V特性')" href="#">I-V特性 复阻抗谱     

FP腔与MZI级联的三参量同时测量的光纤传感器

制作了敏感材料修饰的拉锥光纤与微腔级联的多参量光纤传感器,并用实验研究了其应变、温度和湿度特性。所提微腔由飞秒激光划线放电形成,并对其进行拉锥。传感器的反射光谱干涉峰对应变的变化敏感,实验结果表明应变灵敏度为4.8 pm/με。然而,该结构对温度与湿度均不敏感,在该结构的锥部涂覆了掺入石墨烯量子点的聚乙烯醇之后,温度和湿度的灵敏度明显提升,此时最大温度灵敏度为20.4 pm/℃,最大相对湿度灵敏度最大为14.6 pm/%。对Dip1、Dip2、Dip3进行分析,再利用三阶矩阵消除交叉敏感,能够同时测量应变、温度和湿度。     

多壁碳纳米管薄膜的压阻效应研究

对多壁碳纳米管薄膜的压阻效应进行了研究. 实验所用的多壁碳纳米管用热灯丝化学气相沉积法合成, 压阻效应用三点弯曲法测量. 研究发现: 在室温下与500微应变内, 原始的多壁碳纳米管薄膜无明显压阻效应, 而经化学修饰处理的碳纳米管膜的压阻因子最高可达120左右, 大大超过多晶硅(Si)在35°C时的压阻因子30, 并且压阻因子与制备方法密切相关. 重点讨论了多壁碳纳米管薄膜产生压阻效应的机制.     

Enhanced mechanical properties and morphological characterizations of poly(vinyl alcohol)-carbon nanotube composite films

Tensile tests were carried out on free-standing composite films of poly(vinyl alcohol) (PVA) and multiwall carbon nanotubes (MWNTs) for different loading levels. Results show that overall mechanical properties of the composite were greatly improved as compared to the neat PVA film. For PVA-based materials at significant high loading level such as 9.1 wt.% MWNTs, considerable increases in Young's modulus, tensile strength and toughness by factors of 4.5, 2.7 and 4.1, respectively, were achieved. Raman, SEM, TEM, and DSC techniques were used to evaluate the PVA/MWNTs composite system. Strong acid-modification of the pristine MWNTs and the subsequent ultrasonication processing allowed good distribution of the nanotubes in the matrix. SEM together with DSC result shows apparent good wetting of the nanotubes by the PVA matrix, which are supportive of good interfacial bonding between the modified carbon nanotubes and the hosting polymer matrix.     

Functional multi-walled carbon nanotube/polyaniline composite films as supports of platinum for formic acid electrooxidation

Embedding of carbon nanotubes in conducting polymeric matrices for various nanocomposites material is now a popular area. In this article, a concise chemical method has been described for the preparation of homogeneous nanocomposite of multi-walled carbon nanotube (MWNT)/polyaniline (PANI) by electrochemical codeposition. For this we functionalized the MWNTs via the diazotization reaction. This helped to disperse the nanotubes in aniline. The composite films were dispersed Pt by electrodeposition technique. The presence of MWNTs and platinum in the composite films was confirmed by XRD analysis and transmission electron microscopy (TEM). Four-point probe investigations revealed that the MWNT/PANI composite films exhibited a good conductivity. Cyclic voltammograms (CV) showed that Pt-modified MWNT/PANI composite films perform higher electrocatalytic activity and better long-term stability than Pt-modified pure PANI film toward formic acid oxidation. The results imply that the MWNT/PANI composite films as a promising support material improves the electrocatalytic activity for formic acid oxidation greatly.     

Preparation and Physical Properties of Carbon Nanotubes–PVA Nanocomposites

Nanocomposite materials were prepared by incorporating multiwall carbon nanotubes (MWNTs), obtained by acetylene catalytic chemical vapor deposition (CCVD) on Co/Fe‐modified MgO, within poly(vinyl alcohol) (PVA). Before incorporation, nanotubes were oxidized to obtain better compatibilization with the polymer. It has been found that the addition of COOH‐functionalized and purified MWNTs improves the mechanical response, increases the glass transition temperature, and delays the thermal oxidation of PVA. Furthermore, the PVA crystallinity seems to be enhanced by the presence of nanotubes.     

Features of the specific resistance of nanocomposite films fabricated from multiwall carbon tubes by means of a directed spinning chuck

Nanocomposite films are produced on the basis of carbon multiwalled nanotubes (MWNTs) and polymer (carbon MWNTs/polymer, 95/5 mass %). The nanocomposite is deposited in the liquid phase on a paper substrate by a directed spinning chuck. The temperature dependence of specific resistance of the obtained films along and across the nanotube orientation is studied in the range T = 20?140°C. Irreversible transitions from semiconductor-to metal-type conductivity are observed.     

Superconductivity in entirely end-bonded multiwalled carbon nanotubes

We report that entirely end-bonded multiwalled carbon nanotubes (MWNTs) can exhibit superconductivity with a transition temperature (T(c)) as high as 12 K, which is approximately 30 times greater than T(c) reported for ropes of single-walled nanotubes. We find that the emergence of this superconductivity is highly sensitive to the junction structures of the Au electrode/MWNTs. This reveals that only MWNTs with optimal numbers of electrically activated shells, which are realized by end bonding, can allow superconductivity due to intershell effects.     

Comparative study on modification of multi-walled carbon nanotubes by a hydrophilic polymer with different approaches

The multi-walled carbon nanotubes (MWNTs) modified by a hydrophilic polymer were prepared with polymerization and blending approaches. The differences of both modified MWNTs were compared by Fourier transform infrared and Raman spectroscopies, thermogravimetric analysis and transmission electron microscopy. Chemical grafting reaction had occurred between MWNTs and polyvinyl pyrrolidone (PVP) after modification with polymerization and blending approaches. Polymerization modification can graft more PVP on the surface of MWNTs compared with blending modification. Polymerization modification of MWNTs belongs to the “grafting from” mechanism, while blending modification belongs to the “grafting to” mechanism. Modified MWNTs exhibit remarkable solubility in water, ethanol and dimethyl formamide.     

Fabrication of superhydrophobic surfaces with poly(furfuryl alcohol)/multi-walled carbon nanotubes composites

Superhydrophobic films of poly(furfuryl alcohol)/multi-walled carbon nanotubes (PFA/MWNTs) composites have been obtained by using fluorocarbon-modified MWNTs (MWNT-OOCC₇F₁₅), PFA, and PTFE with a simple preparation method. The prepared films showed both high contact angle and small sliding angle for water droplets. The chemical compositions and microstructures of the resultant film surfaces were also investigated by means of infrared spectroscopy, X-ray photoelectron spectroscopy, and field emission scanning electron microscope, respectively. Both the formed multiscale roughness structures and the lower surface energy play an important role in creating the superhydrophobic surfaces of PFA/MWNTs composites.     

Multi-walled carbon nanotubes supported Cu-doped ZnO nanoparticles and their optical property

Multi-walled carbon nanotubes (MWNTs)/Cu-doped ZnO composite powders were prepared by co-precipitation method, and were characterized by X-ray diffraction, electron microscopy, fluorescence spectrum, and ultraviolet spectrum. Experimental results show that the MWNTs can be modified by Cu-doped ZnO nanoparticles with hexagonal wurtzite structure after annealed at 450?°C, and the nanoparticle size is about 15?nm. Two ultraviolet (UV) peaks and a green band centered at about 510?nm are observed in the fluorescence spectrum of MWNTs/Cu-doped ZnO composite powder annealed at 450?°C. Furthermore, MWNTs and Cu doping significantly improve the UV absorption ability of ZnO.     

Carbon nanotubes and nanostructures grown from diamond-like carbon and polyethylene

We report a simple way to synthesize carbon nanotubes and nanostructures from the solid phase. Vacuum annealing of diamond-like carbon (DLC) films or polyethylene mixed with catalyst in argon atmosphere leads to the formation of nanotubes and nanostructures. High-resolution transmission electron microscopy studies reveal highly graphitized multi-walled nanotubes (MWNTs) or amorphous fibre-like structures, depending on the catalyst amount. This synthesis process may give a new approach to understanding the phase transition of different carbon allotropes into nanotubes or nanostructures. Received: 3 July 2001 / Accepted: 3 July 2001 / Published online: 2 October 2001     

浓硝酸处理前后多壁碳纳米管的荧光特性研究

对浓硝酸处理前后多壁碳纳米管的荧光特性进行了研究,结果发现多壁碳纳米管在浓硝酸处理前后都能产生荧光;与浓硝酸处理前相比,浓硝酸处理后的多壁碳纳米管的荧光有所增强,且荧光谱峰向短波长方向发生蓝移。碳纳米管产生的荧光与碳纳米管在其缺陷处捕获激发光的能量以及最低空轨道和最高占有轨道之间的能隙有关。多壁碳纳米管在浓硝酸处理前后都有缺陷,因而都能在其缺陷处捕获激发光能量而产生荧光;浓硝酸处理引起多壁碳纳米管的缺陷增多、捕获激发光能量增加因而荧光也随之增强。碳纳米管的最低空轨道和最高占有轨道之间的能隙随其长度减小而增大,浓硝酸处理引起多壁碳纳米管被削短导致其最低空轨道和最高占有轨道之间的能隙增大,因而引起多壁碳纳米管的荧光谱峰向短波方向蓝移。