Pulsed laser deposited ZnO films and their humidity sensing behavior

The present paper describes an opto-electronic humidity sensor based on thin film of zinc oxide prepared by pulsed laser deposition method. Being optical in nature it gives electromagnetic disturbance-free monitoring. The sensing element is a right-angled isosceles prism with its base coated with ZnO thin film. Films have been characterized by XRD, SEM, and optical transmission. Film grown with substrate at room temperature is amorphous whereas that grown at elevated temperature is single crystalline with grain size 38.52 nm. Film deposited at room temperature is sensitive to humidity over a wide range i.e. 5–90RH% while that deposited at elevated temperature is found to be insensitive to humidity. The sensor shows better sensitivity for higher range of humidity. The response and recovery time of the sensor element have also been evaluated. This sensor configuration can be used for on-line applications and in-situ monitoring.     

Effects of humidity and temperature on the fatigue behaviour of an extruded AZ61 magnesium alloy

Load‐controlled fatigue tests were performed at 20 and 50 °C using two relative humidity levels of 55 and 80% to characterize the influence of humidity and temperature on the fatigue behaviour of an extruded AZ61 magnesium alloy. Fatigue tests were also conducted at 150 °C. No significant variation in fatigue properties was noticed with respect to temperature over the range from 20 to 50 °C for both the humidity levels. Fatigue limits in the range 140–150 MPa were observed for relative humidity of 55%. Fatigue strength decreased significantly with increase in temperature to 150 °C. Further, a significant reduction in fatigue strength with a fatigue limit of ～110 MPa was observed with increase in relative humidity to 80% at 20 and 50 °C. The crack initiation and propagation remained transgranular under all test conditions. The fatigue fracture at low stress amplitudes and high relative humidity of 80% results from the formation of corrosion pits at the surface and their growth to a critical size for fatigue‐crack initiation and propagation. The observed reduction in fatigue strength at high humidity is ascribed to the effects associated with fatigue–environment interaction.     

Electrical sensing properties of silica aerogel thin films to humidity

Mesoporous silica aerogel thin films have been fabricated by dip coating of sol-gel derived silica colloid on gold electrode-patterned alumina substrates followed by supercritical drying. They were evaluated as the sensor elements at relative humidity 20-90% and temperature 15-35 °C under an electrical field of frequency 1-100 kHz. Film thickness and pore structure were two main parameters that determined the sensor performance. The film with a greater thickness showed a stronger dielectric characteristic when moisture abounded, and presented a smaller hysteresis loop and a higher recovery rate, due to the large size of pore throats. As the film thickness decreased, at low humidity the surface conductivity enhanced and the response rate increased. The silica aerogel based humidity sensor can be modeled as an equivalent electrical circuit composed of a resistor and a capacitor in parallel, and is driven by ionic conduction with charged proton carriers.     

Method for linearizing output signal of broadband electrolytic relative humidity sensor

This paper describes sensors for measuring the humidity and temperature of vapor/air media and a technique for improving them by linearizing their output signals. The latter made it possible to raise sensor sensitivity and measurement accuracy over the relative humidity range from 10 to 98%.Translated from Izmeritel'naya Tekhnika, No. 6, pp. 66–68, June, 1993.     

便携式温湿度舒适性测试仪研究

为了解列车运行时客室内温湿度的动态变化以及该变化对乘客舒适性的影响,研究设计一种便携式温湿度舒适性实时测试系统。通过在高速列车实测温湿度数据和乘客调查问卷的统计分析基础上,给出适用于我国高速列车的温湿度舒适性评价指标。系统以STM32系列处理器和数字式温湿度传感器SHT21为核心,采用模块化设计,由电源模板、温湿度测量模块、存储模块和LCD显示模块组成。实验表明该系统可满足高速列车客室内温湿度动态变化及乘客温湿度舒适性的测试要求。     

Structural,optical and excellent humidity sensing behaviour of ZnSnO<Subscript>3</Subscript> nanoparticles: effect of annealing

The chemi-resistive humidity sensing behaviour of as prepared and annealed fcc-ZnSnO₃ nanoparticles synthesized using wet chemical synthesis method is reported here. The effect of annealing on the evolution of varied nano-morphology of ZnSnO₃ is in accordance to Ostwald’s ripening law. The optical energy bandgap energy change from 4.64 to 3.84 eV for annealed samples confirms the role of annealing over improved sensing performance. At room temperature, an excellent humidity sensitivity of 4155% and response/recovery time of 19/22 s. is observed for 500 °C annealed ZnSnO₃ sample within 08–97% relative humidity range. The experimental data observed over the entire range of RH values well fitted with the Freundlich adsorption isotherm model, and revealing two distinct water adsorption regimes. This indicates that with an increase in annealing temperature the samples show improved adsorption capacity and strength. The excellent humidity sensitivity observed in the annealed nanostructures is attributed to Grotthuss mechanism considering the availability and distribution of available adsorption sites. This present result proposes utilization of low cost synthesis technique of ZnSnO₃ holds the promising capabilities as a potential candidate for the fabrication of next generation humidity sensors.     

环境试验设备温湿度校准系统的研制

介绍基于MSC1200的温湿度自动校准系统。以JJF 1101-2003《环境试验设备温度、湿度校准规范》为设计依据,硬件以美国TI公司的MSC1200作为测量、信号处理以及通信核心部件,组成一套多通道高精度温湿度采集仪。按照校准规范的要求设计专用的校准软件,通过RS232接口与温湿度采集仪通信,将测量数据进行显示、绘图、存储,计算并自动生成满足要求的原始记录及校准报告,从而实现校准过程程序化、规范化、自动化,满足计量部门对环境试验设备温湿度校准的需要。     

Nanofibre fabrication in a temperature and humidity controlled environment for improved fibre consistency

Fabricating nanofibres with reproducible characteristics is an important demand in the membrane industry in order to establish commercial viability. In this study, the effect of controlled atmospheric conditions on electrospun cellulose acetate (CA) nanofibres was evaluated for temperatures ranging 17.5–32.5 °C and relative humidity ranging 20–70%. CA solution (0.2 g/mL) in a solvent mixture of acetone/dimethylformamide/ethanol (2:2:1) was electrospun into nonwoven fibre mesh with the fibre diameter ranging from 150 nm to 1 μm. The resulting nanofibres were analysed by differential scanning calorimetry, showing a correlation of reducing melt enthalpy with increasing atmospheric temperature. The opposite was seen with increasing atmospheric humidity, which conferred increasing melt enthalpy. Analysis of scanning electron microscopy images provided a correlation of reducing average fibre diameter with increasing atmospheric temperature and increasing fibre diameter with increasing atmospheric humidity. These results correlate with the melt enthalpy results, suggesting that finer CA nanofibres infer a lower melt enthalpy. Together these studies provide strong evidence that the controlled atmospheric conditions affect the fibre diameter of the resulting electrospun nanofibres. A salient observation in this study was that increased humidity reduced the effect of fibre beading yielding a more consistent and therefore better quality of fibre. This has apparent implications for the reproducibility of nanofibre production and offers a new method of controlling fibre morphology. This study has highlighted the requirement to control atmospheric conditions during the electrospinning process to fabricate reproducible fibre mats.     

控制空调系统微生物污染的温湿度条件分析

查阅整理大量的国内外文献资料,对我国空调系统内主要的微生物及其温湿度生理学进行统计与分析,得出控制空调系统微生物污染的有效温湿度范围,研究工作可为我国空调洁净技术中温湿度控制的应用提供理论依据.     

温湿度检定箱的湿度均匀度与波动度的测试方法

在温湿度检定箱的湿度均匀度与波动度测试中,针对现有湿度传感器准确度难以满足要求的情况,提出将同种型号规格的湿度传感器在同一台湿度标准装置上进行校准、并加修正值使用的测量方法,减小了测量不确定度,满足湿度均匀度和波动度的测量要求。精密露点仪测量结果验证了该方法的有效性。     

Simultaneous measurement of humidity and temperature by combining a reflective intensity-based optical fiber sensor and a fiber Bragg grating

A novel sensor capable of simultaneously measuring temperature and humidity has been fabricated and demonstrated using optical fiber waveguides. The sensor head is composed of a fiber Bragg grating and a low-finesse Fabry-Perot interferometric cavity. The Fabry-Perot cavity was fabricated using the electrostatic self-assembled monolayer process for the molecular-level deposition of materials of different thicknesses that form a humidity-sensitive coating on the end of the fiber, while the in-line Bragg grating fiber element is used to monitor temperature. Experimental results for a humidity range from 11% to 97% RH and for a temperature range from 10/spl deg/C to 85/spl deg/C are shown.     

The effect of temperature and humidity on electrospinning

Electrospinning is a process that generates nanofibres. Temperature and humidity affect this process. In this article the influence of humidity and temperature on the formation and the properties of nanofibres are studied using cellulose acetate (CA) and poly(vinylpyrrolidone) (PVP) as target materials. The experiments indicate that two major parameters are dependent of temperature and have their influence on the average fibre diameter. A first parameter is the solvent evaporation rate that increases with increasing temperature. The second parameter is the viscosity of the polymer solution that decreases with increasing temperature. The trend in variation of the average nanofibre diameter as a function of humidity is different for CA and PVP, which can be explained by variations in chemical and molecular interaction and its influence on the solvent evaporation rate. As the humidity increases, the average fibre diameter of the CA nanofibres increases, whilst for PVP the average diameter decreases. The average diameter of nanofibres made by electrospinning change significantly through variation of temperature and humidity.     

室内空间温度、湿度的检测方法

依据GB/T18204.13-2000和GB/T18204.14-2000的规定,结合有温度、湿度要求的室内空间或各类实验室的实际内部环境情况,使用温场测量记录仪,重点布放在其有效工作区域内,对室内环境温湿度的均匀度、波动度、偏差的测量及试验数据的论证,确定该检测方法具有实用性和可行性。     

Development of a mathematical model for the effect of temperature and relative humidity on the water vapour permeability of plastic films

The water vapour permeability constants of three flexible films (LDPE, PET and a laminate of both films) were determined at 20, 30 and 40 °C and from 55 to 90% relative humidities. The relationship between permeability and temperature followed the Arrhenius model for the three films. The relative humidity also influenced the permeability of the films. A mathematical model describing permeance (P/X - the permeability of laminates or films) as a function of external relative humidity and temperature was developed. The model can be used to predict the permeance of the three films at different temperatures and relative humidities.     

Modeling of temperature and humidity ratio in an automobile passenger compartment for automobile air conditioning systems

This study investigates thermal dynamic modeling of a passenger compartment in an air conditioned automobile equipped with HVAC (heating, ventilation, and air conditioning). In particular, dynamics of temperature and humidity ratio, both critical to passenger comfort, in the passenger compartment are examined. By analyzing enthalpy change during an automobile air conditioning circulation cycle on a psychrometric chart, heat exchange between outside environment and the passenger compartment can be modeled as functions of operation settings of the HVAC. With enthalpy content decomposed into sensible heat and latent heat, changes in heat content can be attributed to the changes in the corresponding temperature and humidity ratio, respectively. Consequently, impacts resulting from the mismatch between two heat characteristics on temperature and humidity ratio can be formulated accordingly: room sensible heat factor (RSHF) of the passenger compartment and apparatus sensible heat factor (ASHF) of the HVAC. A Matlab/Simulink simulation is implemented to verify the proposed model under several control policies that either maintain constant enthalpy or maintain constant temperature in the passenger compartment. With these two temperature and humidity ratio models derived, further research on designing control policies to achieve better passenger comfort for general automobile air conditioning systems can be derived and tested.     

癸酸-棕榈酸/SiO_2相变储湿复合材料的制备与表征

以SiO2为载体,癸酸-棕榈酸为相变材料,采用溶胶-凝胶法制备了癸酸-棕榈酸/SiO2相变储湿复合材料,利用等温吸放湿法、步冷曲线法、FTIR、SEM、激光粒度分析仪(LPSA)、BET、TGA和DSC等对其进行性能测试和表征。结果表明:癸酸-棕榈酸/SiO2相变储湿复合材料的载体材料SiO2具有"笼"结构,其大量微孔形成三维空间网格结构既可以通过癸酸-棕榈酸与SiO2的物理嵌合方式包裹与束缚相变材料,又可以通过SiO2的亲水性能吸附水分子,具有良好的热湿性能。癸酸-棕榈酸/SiO2相变储湿复合材料表面光滑圆润无明显凹陷,颗粒粒径较小且均匀性较好(粒径为82.14nm、孔体积为0.010 7mL/g、孔比表面积为25.16m2/g、孔平均直径为26.63nm),属于纳米级有机相变芯材/无机基体复合材料;相变温度为19.88~23.13℃、相变潜热为38.55~42.56J/g,癸酸-棕榈酸的质量分数约为31.59%,满足人体舒适度的温度范围,适合在建筑领域中广泛应用。     

温湿效应下嵌入式共固化复合材料阻尼性能

将温湿环境实验与阻尼性能测试技术相结合,搭建了温湿环境中嵌入式共固化复合材料阻尼性能的实验测试平台,提出使用最小二乘技术求解相对阻尼系数的新方法,分别探讨了温度和湿热耦合参数对嵌入式共固化碳纤维/双马来酰亚胺复合材料阻尼系数的影响曲线。结果表明:嵌入式共固化复合材料的相对阻尼系数随温度的升高先增加再减小后增大;湿热耦合作用下相对阻尼系数随湿度和温度的提高而增大。为该新型复合材料阻尼结构的设计和全天候应用奠定了基础。      

Lanthanum doped barium stannate for humidity sensor

A few samples in the system Ba_1−xLa_xSnO₃ (x = 0.00, 0.01, 0.05 and 0.10) have been synthesized by the solid state ceramic route. Powder X-ray diffraction (XRD) pattern of the samples was recorded to confirm the formation of a single phase solid solution. The inferences drawn from the analysis of the X-ray diffraction pattern are that, the lattice parameter and bulk density decrease with increasing concentration of lanthanum. The resistance and capacitance of all the samples in the frequency range 20 Hz–1 MHz and relative humidity (RH) range 10–95% have been measured at 31 °C. It is observed that the frequency has more influence on the capacitance as compared to resistance. Among all the samples, the sample Ba_0.99La_0.01SnO₃ (bearing sample code BSL1) exhibits superior response to the change in humidity. The resistance of sample BSL1 changes almost three orders of magnitude where as capacitance changes only one order of magnitude within the RH range 10–95%. The variation of conductivity with RH for samples BSL0 and BSL1 is linear. The response and recovery time of these samples during adsorption and desorption of water vapor are less than 1 min. It is observed that at a particular relative humidity, temperature and frequency (i.e. for RH 10%, temperature 31 °C and frequency 1 kHz) conductivity of barium stannate increases sharply (almost four orders of magnitude) as dopant (La) concentration increases from 0 to 10 mol% which is explained in terms of charge compensation mechanism.     

相变储湿纤维/石膏复合材料的制备及综合性能

以抹灰石膏作为基体材料,将相变储湿纤维掺入抹灰石膏中,制备相变储湿纤维/石膏复合材料,对其基本性能、储湿调湿性能、相变调温性能和耐久性能进行测试与分析。利用FTIR和SEM研究相变储湿纤维/石膏复合材料的结构组成和微观形貌。结果表明：当相变储湿纤维掺量为40.0wt%时,相变储湿纤维/石膏复合材料具有最佳性能和良好耐久性能,其标准扩散度用水量为0.70、初凝时间为40 min、终凝时间为55 min、体积密度为1 005.56 kg·m^-3、拉伸连接强度为0.10 MPa、抗压强度为2.55 MPa;在相对湿度40%~65%时的平衡含湿量为0.0395~0.0935 g·g^-1;从35℃至20℃的降温时间为100 s,相变平台明显;经过循环试验,相变储湿纤维/石膏复合材料的吸放湿性能下降小于10%,相变调温性能下降小于5%。