硅衬底的SrTiO3淀积膜的湿敏特性与机理研究

对无定形多孔SrTiO₃膜电导率随相对湿度的变化进行了理论模型分析.该模型也适用于其他多孔半导体陶瓷材料.实验样品用氩离子束镀膜技术在SiO₂/Si衬底上淀积SrTiO₃膜并制成平面型电阻结构.结果表明，在室温下，当相对湿度从12%变化至53%时，电流缓慢下降；而当相对湿度从53%变化至92%时，电流又显著上升，即在高湿度条件下具有良好的湿敏特性.电流及其在高湿条件下的上升率随测试频率而增大.吸附响应时间明显长于脱附时间. 关键词：     

Effect of humidity on the a.c. impedance of CH3NH3SnCl3 hybrid films

Impedance spectroscopy measurements show that complex conductivity of thermally ablated CH₃NH₃SnCl₃ films is strongly enhanced when humidity increases. Coplanar two-electrode test devices are modeled through an equivalent circuit comprising one resistance and two constant phase elements. It is shown that the influence of ambient humidity is mainly resistive. The dynamic responses of the devices to humidification/dehumidification cycles point out that the a.c. current varies by more than three orders of magnitude when humidity is varied between dry air and 80% relative humidity. The rise times are few hundred seconds while fall times are as short as few tens of seconds. This observation suggests that impedance variations are determined by mechanisms involving loosely bound water molecules physisorbed at the surface of the hybrid film. The results obtained are discussed in terms of protonic conduction.     

Proton conductivity of phosphoric acid derivative of fullerene

The proton conductive property of methano [60] fullerene diphosphoric acid has been investigated under various humidity conditions at the temperature range between 15 and 45 °C. It shows proton conductivity as high as 10⁻² S cm⁻¹ at 25 °C under relative humidity of 95%. Thermal analyses including TG–DTA and thermal desorption mass spectroscopy (TDS) confirm that the compound is thermally stable up to 200 °C. Proton conduction of the compound depends very much on humidity or water content. The logarithmic conductivity at 25 °C is increased linearly with increasing relative humidity. The activation energy (E_a) estimated from the slope of log(σT) vs. 1/T is decreased from 1.08 to 0.52 eV, as the relative humidity is increased from 40% to 75%. The humidity dependence of conductivity is discussed in the light of the observed hydration isotherm.     

聚合物纳米孔隙增透膜制备工艺的研究

论述了聚合物纳米孔隙增透膜的制备工艺流程,分析了聚合物材料分子量、实验环境温度和湿度、溶剂挥发性等条件对纳米孔隙增透膜的影响。研究表明,聚合物材料分子量的增大、温度的降低、湿度的升高以及采用挥发性弱的溶剂都将导致增透膜孔隙尺寸的增大,孔隙越大其对光的散射损耗就会增大,所以增透膜的透过率就越低。通过大量的试验分析得出一组较理想的工艺参量:使用低分子量的聚合物材料(小于15 kg/mol),环境温度大于25℃、环境相对湿度小于30%,在采用低沸点的溶剂如四氢呋喃等措施下可有效降低增透膜散射损耗。     

Chaoticity analysis of the current through pure, hydrogenated and hydrophobically modified PEG-Si thin films under varying relative humidity

Polyethylene Glycol has an irregular current characteristic under constant voltage and slowly varying relative humidity. The current through a thin film of Gamma-isocyanatopropyltriethoxysilane added Polyethylene glycol (PEG-Si), its hydrogenated and hydrophobically modified forms, as a function of increasing relative humidity at equal time steps is analyzed for chaoticity. We suggest that the irregular behavior of current through PEG-Si thin films as a function of increasing relative humidity could best be analyzed for chaoticity using both time series analysis and detrended uctuation analysis; the relative humidity is kept as a slowly varying parameter. The presence of more then one regime is suggested by the calculation of the maximal Lyapunov exponents. Furthermore, the maximal Lyapunov exponent in each of the regimes was positive, thus confirming the presence of low dimensional chaos. DFA also confirms the presence of at least two different regimes, in agreement with the behavior of the maximal Lyapunov exponent in the time series analysis. We also suggest that the irregular behavior of the current through PEG-Si can be reduced by hydrogenating and hydrophobically modifying PEG-Si and the improvement in stability can be confirmed by our study.      

Study of moisture sorption behavior of urea inclusion compounds with aliphatic guests and with linear polymers

Urea is known to form stable inclusion compounds (IC) with a wide variety of guests, which include aliphatic organic substances as well as linear polymers. Urea in its native form is also known to undergo deliquescence when exposed to an atmosphere of higher water activity. The purpose of the present study was to determine and compare the moisture sorption profiles of the uncomplexed urea as well as ICs of urea with different guests. Urea ICs with two types of guest moieties were prepared, that is, either monosubstituted unbranched alkane derivatives possessing an anchor length of 16 carbons or linear polymer poly (ethylene glycol) of different molecular weights. The formation of ICs was confirmed through thermal analysis and powder X‐ray diffraction/single crystal diffraction. The ICs were exposed to environment of varying water activity in dynamic water sorption analyzer, and the rate and extent of moisture uptake were determined. Critical relative humidity of urea and representative ICs was determined by two techniques. Urea ICs were found to demonstrate greater resistant to deliquescence as exhibited by increase in critical relative humidity in comparison with uncomplexed urea. Thermodynamic considerations involved in the process of deliquescence are discussed. Copyright © 2013 John Wiley & Sons, Ltd.     

Fabrication of solid-state fuel cell based on DNA film

We have fabricated a fuel cell based on the DNA film (DNAFC) and examined its properties under various humidity conditions at room temperature. The open-circuit voltage of a DNAFC is generated by supplying H₂ gas to the anode. The open-circuit voltage strongly depends on the humidity conditions, and in a DNA film, the optimum condition in which the open-circuit voltage attains a value as high as 0.55 V is achieved under the relative humidity condition of 55%. Furthermore, the cell voltage of the DNAFC decreases with an increase in current density, as observed in fuel cells such as proton exchange membrane fuel cell, solid oxide fuel cell, and several others. These results indicate that DNA film can be used as the fuel cell electrolyte under approximately 55% humidity condition.     

MIS structure with polyamide insulator under the conditions of water vapor sorption

A silicon MIS structure with sulfonate-containing aromatic polyamide as a gate insulator is prepared with the aim of using it as a capacitive-type humidity detector. A detector made of this material offers a high sensitivity at an elevated relative humidity and a high speed of response. Measurements of the capacitance of the structure at different frequencies basically make it possible to determine the water distribution in the polymer matrix. The high-frequency (1 MHz) capacitance versus relative humidity dependence (i.e., the calibration curve of the detector) is typical of the isotherms of water vapor sorption by similar polymers.     

Effect of External Electric Field on the Proton Conductivity of Nafion Films

The current-voltage characteristics of Nafion films were studied depending on the ambient humidity, electrode voltage, and temperature. It was shown that the film can contain free (polarization current) and bound water; the latter can be completely removed under vacuum conditions. The current decreased with time at constant electrode voltage because of water removal from the film in the absence of electrochemical processes. A theoretical model in the form of the Nernst–Planck equation was considered; it describes the proton transport through the film in an electric field. The inverse problem of restoring the diffusion coefficient from the experimental proton conductivity was solved.     

Graphene oxide thin film coated quartz crystal microbalance for humidity detection

In this paper, we demonstrated that chemically derived graphene oxide (GO) thin film as a humidity sensitive coating deposited on quartz crystal microbalances (QCMs) for humidity detection. By exposing GO thin film coated QCMs to various relative humidity (RH) environments at room temperature, the humidity sensing characteristics of the QCMs such as sensitivity and linearity, response and recovery, humidity hysteresis were investigated. The experiment results show that GO thin film coated QCMs exhibit an excellent humidity sensing performance. Moreover, the possible humidity sensing mechanism of GO thin film coated QCMs was also investigated by monitoring the crystal's motional resistance change. It is suggested that the frequency response of the QCMs is dependent on water molecules adsorbed/desorbed masses on GO thin film in the low RH range, and on both water molecules adsorbed/desorbed masses on GO thin film and variations in interlayer expansion stress of GO thin film derived from swelling effect in the high RH range.     

Slow-rise and fast-drop current feature of ultraviolet response spectra for ZnO-nanowire film modulated by water molecules

This study describes the fabrication of ZnO-nanowire films by electro-chemical anodization of Zn foil.The ZnO films are characterized by field emission scanning electron microscopy,X-ray diffraction patterns,and transmission electron microscopy,respectively.The ultraviolet(UV) photo-response properties of the surface-contacted ZnO film are studied through the current evolution processes under different relative humidities.Unlike the usually observed current spectra of the ZnO films,the drop time is shorter than the rise time.The photo-conductivity gain G and the response time τ are both increased with the increase of the applied bias.The photo-conductivity gain G is lowered with the increase of the environmental humidity,while the response time τ is increased.These results can be explained by considering three different surface processes:1) the electron-hole(e-p) pair generation by the UV light illumination,2) the following surface O2-species desorption,and 3) the photo-catalytic hydrolysis of water molecules adsorbed on the ZnO surface.The slow-rise and fast-drop current feature is suggested to originate from the sponge-like structure of the ZnO nanowires.     

碳氢烧蚀层的厚度对聚乙烯醇薄膜阻气性能的影响

 以ICF实验塑料靶丸保气的需求为背景,研究了水蒸气在低压等离子体聚合碳氢（CH）膜、聚乙烯醇（PVA）膜、聚苯乙烯（PS）膜中的扩散渗透行为。根据实验数据,算出在40℃ 90%相对湿度下,水蒸气在三种样品膜中的渗透系数分别为1.906×10^-13,5.950×10^-15,.432×10 ^-14mol·m/(m²·s·Pa),并借助多层复合膜模型的近似算法,算出在40 ℃ 90%相对湿度的外界环境下,类似多层塑料微球结构的三层复合膜中,PVA阻气层所处环境的相对湿度为53.06%,推导出PVA所处环境的相对湿度与外层CH层厚度的关系式。研究表明：CH烧蚀层越厚,PVA所处环境的相对湿度越小,保气性能越好。     

预取向半晶态高分子片晶结构形成微观机理及其应力-应变响应特性的分子动力学模拟

通过分子动力学模拟方法对不同预取向聚乙烯醇熔体(polyvinyl alcohol,PVA)形成的半晶态高分子熔体形成核结晶及拉伸过程中的应力-应变响应特性进行了系统地研究.模拟结果显示预取向度高的PVA熔体对应更快的成核动力学.通过追踪全trans伸直链长度(dtt)、成核原子维诺体积(V)和中心对称参数(S)等序参量在不同取向度熔体下的等温成核与结晶演化过程,给出了PVA熔体成核路径及形成半晶态的分子构象;通过对形成的半晶态高分子结构进一步分析,发现随着熔体取向度的增加,晶体和无定型对应的取向度也会增加,但是当应变剪切大于5时,其对应的结晶度、晶体和无定型取向度不再发生变化;通过对无定型区链结构的定义与分析,可知取向度越高的熔体对应越高的Tie链数目,随着熔体取向度的增加,Loop链的数目也会减小;通过恒速拉伸应力测试可知,所形成半晶态高分子结构力学响应会随着取向度及Tie链数增加而增加,当取向及Tie链数目相同时,应力-应变曲线形状大小也基本保持一致.     

新型复合固体除湿材料的吸附和解吸性能研究

为实现固体除湿系统吸附材料的低温再生及提高吸附材料的除湿效率,制备了新型复合固体除湿材料。新型复合固体除湿材料是以陶瓷纤维为基质,运用MgCl2浸渍改性硅胶及CaCl2二次强化方法而形成的复合物,复合固体除湿材料中MgCl2和CaCl2浓度均为25%。通过恒温恒湿空调室实验研究温度、风速、湿度对MgCl2/CaCl2改性复合材料除湿性能及再生特性。实验表明:在温度20℃、湿度70%条件下,复合固体除湿材料除湿量可达161 mg/g,是未改性除湿材料的3.2倍,是单一改性除湿材料的1.3倍;当系统平衡时,其除湿速率分别是未改性除湿材料的6.1倍,是单一改性除湿材料的2.6倍。除湿材料的平衡吸附量和吸附速率均与相对湿度成正比,与温度成反比;且风速在0.5 m/s条件时具有最大的除湿量。同时,在约70℃较低的脱附温度,8 min可脱附≥90%的总吸附水量,每1 g吸附剂可脱附水量高达145 mg;脱附再生6次后,除湿量依然较高为138 mg/g,且基本不再变化。     

Structure and properties of thin-film metal-poly(p-xylylene) hybrid nanocomposites

Thin-film hybrid metal-poly(p-xylylene) composites synthesized by vacuum co-condensation were examined. It was demonstrated that the structure of the composites consists of a matrix comprised of polymer globules and inorganic filler nanoparticles. The shape, structure, and size of the polymer globules depend on the film thickness and the nature of the filler nanoparticles. Studying the conductivity of these materials demonstrated that it is determined by hopping conduction via surface states of the matrix. At high frequencies of the voltage applied (above 500 Hz), the electric conduction characteristics depend appreciably on the processes of recharging of the surface states of the matrix and of the nanoparticle-matrix interfaces. Tests of lithium battery anodes prepared from nanocomposites showed that these materials are promising for manufacturing chemical current sources.     

Effect of Interfaces on the Crystallization Behavior of PDMS

The reversible thermal behavior of a non-entangled semicrystalline polymer, poly(dimethylsiloxane), PDMS, was investigated in the presence of sub-micron particles. Filled polymer systems of this type are characterized by a large surface-to-volume ratio but lack the external confinement that is typical for a thin film geometry. Differential-scanning calorimetry (DSC) measurements indicate that the presence of the nanometric solid additives enhances the crystallization rate as compared to native PDMS melts. Different types of additives and surface interactions resulted in a similar effect, suggesting that the origin of the enhanced crystallinity is non-specific. The effect is attributed to entropic interactions in the boundary layer.     

Effect of relative humidity on the electrical transport properties of poly(thionaphtheneindole)

Poly(thionaphtheneindole) (pTNI) conducting polymer has previously been observed to undergo a large variation in the electrical conductivity as a function of relative humidity. In this paper the electrical characteristics of this material as a function of the adsorbed water are studied. Isothermal current-time and current-voltage plots can be understood in terms of an ionic charge transfer inside the polymer, controlled by a diffusion limited electrodic process. The charge transfer at the electrodes is probably due to proton reduction at the cathode and water oxidation at the anode.     

The effect of absorbed water on hydronium NASICON and Hyceram

The bulk resistance of bonded hydronium NASICON, (Hyceram^TM), was studied at 45°C in relative humidities ranging from 40% to 100% in both H₂O/N₂ and D₂O/N₂ atmospheres. The bulk resistance was found to increase exponentially with decreasing relative humidity. In addition, the isotope effect remained close to 2.2 over the range of relative humidities tested; therefore proton hopping (Grotthus mechanism) was shown to be the dominant conduction mechanism from saturation down to 40% relative humidity. Saturated and desiccated samples of hydronium NASICON powder were prepared for X-ray diffraction (XRD) and thermogravimetric analysis (TGA). The XRD patterns revealed that the change in the lattice plane spacings arising from the absorption of water was negligible. TGA showed that the x=1.5 form of hydronium NASICON contained at least 1.5 moles of absorbed water per mole of NASICON when saturated. In addition, the absorbed water was shown to be weakly held by the lattice since its evolution from the saturated sample was rapid. These XRD and TGA results suggested that the molecules of absorbed water occupy lattice sites which might afford considerable freedom of rotational and translational motion.     

Effect of PVA functionalization on hydrophilicity of Y-junction single wall carbon nanotubes

Hydrophilic surface of carbon nanotubes (CNTs) are of great interest for various applications including chemical and biological sensing. Surface functionalization of single wall carbon nanotubes (SWNTs) mats with a biocompatible polymer polyvinyl alcohol (PVA) was studied. PVA modification induced a drastic change in water wettability of the SWNT surface transforming it from hydrophobic to highly hydrophilic. These PVA modified SWNTs mats have also demonstrated increasing impedance variation in relative humidity compared to the pristine nanotubes. An appreciable change in conductivity of Y-junction SWNT mats as a function of relative humidity indicates its potential application as humidity sensor. This higher sensitivity for humidity variation shown in Y-junction SWNT mats could be attributed to the greater portion of semiconducting nanotubes in these mats revealed by Raman analysis. A possible conductance changing mechanism of surface modified SWNTs mats is discussed.     

光纤SPR湿敏传感器及其共振光谱特性研究

提出并研制了基于光纤SPR传感探针的新型湿敏传感器。首先研究了光纤SPR传感探针对环境湿度变化的敏感特性,在此基础上提出在光纤SPR传感探针表面增覆不同厚度且具有水分子吸附功能的PVA薄膜来实现环境相对湿度的监测。研究结果表明,增覆双层PVA薄膜的光纤SPR传感探针在高湿区具有较好监测效果,其共振强度对应的相对湿度测量灵敏度达到1.59%/%RH,较光纤SPR探针呈现显著提高。而增覆单层PVA薄膜的光纤SPR传感探针在高湿区共振波长对应的相对湿度监测灵敏度达到2.411nm/%RH。此外所提出的新型光纤SPR湿敏探针在PVA薄膜失效后经过特殊工艺处理仍可重复镀膜使用。