Ionene–surfactant complexes: temperature and humidity sensitive materials

Solid stoichiometric complexes of [3,12]-ionene and dodecyl sulfate form upon reaction of the bromide of the ionene and the silver salt of dodecyl sulfate in methanol. IR, DSC, and TG investigations indicated that the solid complexes are stable between 30 and 120 °C. TG and DSC also showed that the complexes easily take up water at ambient conditions. These samples are optically isotropic. When exposed to an increased humidity they exhibit optical anisotropy, i.e., birefringence, which is caused by the formation of a hexagonal mesogenic phase. Mesogenicity is necessarily accompanied by a further uptake of water (4–5 H₂O molecules per ionic unit), which is dependent on the relative humidity. The phase behavior as a function of temperature and controlled relative humidity was studied using birefringence measurements and polarizing microscopy.     

Effect of the protonation level of poly(o-phenylenediamine) (PoPD) on the ac impedance of humidity-sensitive PoPD/poly(vinyl alcohol) composite film

A composite film consisting of poly(o-phenylenediamine) (PoPD) and poly(vinyl alcohol) (PVA) has been prepared, and the effect of the protonation level of PoPD on the response of the composite to humidity been investigated by ac impedance measurements. The electrochemical system of the PoPD/PVA composite in a humid atmosphere is represented by an electrochemical equivalent circuit containing film (R_film, C_film), Warburg (W) and interfacial (R_ct, C_dl) impedance. R_film was increased with decreasing protonation level of the PoPD in relative humidity regions higher than 40%, but it was almost independent of the protonation level in humidity regions lower than this percentage.     

Co-precipitation synthesis,humidity sensing and photoluminescence properties of nanocrystalline Co2+ substituted zinc(II)molybdate (Zn1–xCoxMoO4; x = 0, 0.3, 0.5, 0.7, 1)

Zinc-cobalt molybdate composites (Zn_1–xCo_xMoO₄; x = 0, 0.3, 0.5, 0.7, 1) were synthesised by a simple co-precipitation method and characterised by thermogravimetric/differential thermal analysis (TG/DTA), Fourier transform-infrared (FT-IR), Fourier transform Raman (FT-Raman) spectroscopy, X-ray diffraction spectroscopy (XRD), scanning electron microscopy (SEM/EDAX) and transmission electron microscopy (TEM). The surface area was calculated by BET analysis in the adsorption/desorption isotherm. The humidity sensing properties of zinc-cobalt molybdates were tested by dc electrical measurements at different relative humidity environments (RH = 5–98%). The electrical resistance of the composites linearly decreases and the maximum sensitivity of 3672 ± 110 was observed for the Zn_0.3Co_0.7MoO₄ (ZnCM-4) composite towards humidity, which is calculated by the relation S_f = R_5%/R_98%, where the response time is 200 s and the recovery time is 100 s. Photoluminescence (PL) measurement at the room temperature of ZnM-1 composite exhibited a blue emission peak at 475 nm (λ_em) when excited at a wavelength (λ_ex) of 430 nm. During Co²⁺ substitution in Zn²⁺ matrix, a green and red emission peak was observed when excited at a wavelength (λ_ex) of 520 nm.     

One-step measurements of powder resistivity as a function of relative humidity and its effect on charging

A new one-step technique to measure the effect of ambient humidity on powder resistivity has been previously presented. In this article, we provide more experimental data obtained with five different powders. One-step measurements and traditional multi-step measurements were performed. Also, additional measurements were performed using standard resistivity cell. Results were compared and it could be concluded that the new technique provided meaningful results although significant hysteresis was observed during humidification and drying cycles. Finally, charging of the powder was also measured and it was noticed that it decreases with decreasing resistivity and increasing humidity.     

Vapor deposition of ultrathin hydrophilic polymer coatings enabling candle soot composite for highly sensitive humidity sensors

Candle soot (CS) is a desirable carbon nanomaterial for sensors owing to its highly porous nanostructure and large specific surface area. CS is advantageous in its low-cost and facile preparation compared to graphene and carbon nanotubes, but its pristine nanostructure is susceptible to collapse, hampering its application in electronic devices. This article reports conformal coating of nanoscale crosslinked hydrophilic polymer on CS film using initiated chemical vapor deposition, which well preserved the CS nanostructure and obtained nanoporous CS@polymer composites. Tuning coating thickness enabled composites with different morphologies and specific surface areas. Surprisingly, the humidity sensor made from composite with the lowest filling degree, thus largest specific surface area, showed relatively low sensitivity, which is likely due to its discontinuous structure, thus insufficient conductive channels. Composite sensor with optimum filling degree shows excellent sensing response of more than 10³ with the linearity of R² = 0.9400 within a broad relative humidity range from 11% to 96%. The composite sensor also exhibits outstanding sensing performance compared to literature with low hysteresis (3.00%), a satisfactory response time (28.69 s), and a fast recovery time (0.19 s). The composite sensor is fairly stable and durable even after 24 h soaking in water. Furthermore, embedding a humidity sensor into a face mask realizes real-time monitoring of human breath and cough, suggesting promising applications in respiratory monitoring.     

基于光纤锥级联结构的湿度传感器

提出了一种基于普通单模光纤粗锥级联结构的马赫-曾德尔干涉湿度传感器.将两根单模光纤对芯熔融成一个粗锥,并依次级联,形成光纤锥-单模光纤-光纤锥-单模光纤-光纤锥结构.外界环境湿度、温度的改变使传感器的纤芯基模和包层模的光程差发生改变,引起传感器干涉光谱发生变化.通过监测干涉谱波长和能量的变化实现对外界物理量的测量.实验结果表明,当空气中湿度在35~95%RH范围内变化时,传感器的湿度灵敏度为-0.065dB/%RH,线性度为0.997;当温度在30~80℃范围内变化时传感器的温度灵敏度为69.4pm/℃,线性度为0.998.该传感器可以避免温湿度的交叉影响,实现单参量的同时在线区分测量.     

Enhanced-performance relative humidity sensor based on MOF-801 photonic crystals

We proposed an enhanced-performance relative humidity (%RH) nano-sensor based on MOF-801/TiO₂ one-dimensional photonic crystals (1DPC). The maximum reflectance-peak wavelength of it shifted obviously in the range of 20%-90% under varying %RH levels, due to the highly moisture-sensitive MOF-801 film in the 1DPC structure. It was demonstrated that the linear spectrum sensitivity of the MOF-801/TiO₂ %RH 1DPC sensor is exceeding 119 pm/%RH from 20%RH to 90% RH, and the sensitivity of reflection power variations exhibits 1.34 dB/%RH with the resolvable relative humidity variation less than 0.1%RH at 15°C. Meanwhile, the sensor shows a fast optical response time less than 100 ms with exceptional repeatability and reliability, which promises successful measurements of human respiration. Moreover, the sensor performance on the structure of 1DPC is investigated, representing a tradeoff between the sensing sensitivity and response time.     

湿度对水泥生料近红外光谱检测的影响及补偿方法

近红外光谱检测已被应用于水泥生料成分的快速检测,但现场环境中的湿度等因素会对光谱产生干扰,从而降低检测精度。为了提高检测精度,在实验分析湿度对水泥生料近红外光谱检测影响的基础上研究了补偿方法。在水泥厂选取了24份水泥生料样本,其中18份作为校正集,6份作为验证集;水泥生料中的有效成分为SiO2,Al2O3,Fe2O3和CaCO3,各成分含量的标准值由X射线荧光光谱分析测出。首先,将校正集的18份样本每份重复装样测5次光谱,用得到的90个光谱建立模型Ⅰ;再每份样品制作5个湿度梯度样本,其获得过程为,先将样本放置在电加热平台上,用玻璃棒将样本摊平,180℃下加热30 min,再将样本放置在散热片上进行降温,待样品恢复室温后取出进行第一次光谱扫描,得到1个光谱,将测量后的样本放入搅拌器,使用装有去离子水的喷雾器对其喷雾两次,然后搅拌30 s混合均匀,测量混合后的样本得到下一个光谱,重复该过程,得到具有湿度梯度的5个光谱。所有样本均采用烘干法进行湿度测量,样本湿度变化区间在0.6%~2%以内。对每个湿度梯度的样本测量1次,用得到的这90个光谱建立模型Ⅱ。然后,将验证集的6份样本每份制作5个湿度梯度,获取方式与校正集相同,对每个湿度梯度的样本测量1次,得到30个光谱。所有光谱均采用多元散射校正预处理,拟合波段选择4000~5000 cm^-1,建模方法采用偏最小二乘法。比较同一份样本的5个湿度梯度,可以看到在5200 cm^-1处光谱差异最大,在其他位置也有肉眼可见的明显差异,因此,湿度变化对全波段光谱有明显的影响。最后,将这30个光谱输入模型Ⅰ与模型Ⅱ进行验证,并对比模型Ⅰ与模型Ⅱ的预测均方根误差RMSEP。模型Ⅱ中SiO2,Al2O3,Fe2O3和CaCO3的预测均方根误差RMSEP比模型Ⅰ分别减小了25%,31.3%,33.3%和25%。实验结果表明,水泥生料样本湿度对近红外光谱模型的预测结果具有一定的影响,采用具有湿度梯度的样本进行建模可有效降低湿度对预测结果的影响。     

Development and validation of a novel rheological test device and measurement system for determining the influence of humidity on viscosity

Although a strong impact of humidity on polymers and the formation of their molecular network is known, the complex interactions between humidity, temperature, diffusion, reaction kinetics, rheological behaviour and mechanical properties are not fully understood yet. Most current approaches solely analyse the relationships between environmental conditions in a solidified or crosslinked state and the mechanical properties. In contrast, this work focusses on measuring changes in rheological properties depending on relative humidity in the liquid state. A custom designed novel measuring geometry is introduced and validated. It enables for the first time to rheometrically investigate the influence of relative humidity on reactive systems during their cross-linking process. Our results significantly depict the influence of humidity on the cross-linking process and the gel time. The potential of the introduced measuring geometry for improving reactive systems, adapting these precisely to environmental boundary conditions or assuring product performance is hereby demonstrated. This is especially important for industrial manufacturing processes running at different production sites around the world in different climatic zones or repair processes being performed outdoor, e.g. for wind energy plants.     

铜在空气中生成碱式碳酸铜的热力学分析

从热力学角度研究了酸度、湿度、水的存在状态不同时,单质铜在空气中生成碱式碳酸铜的电动势及其自由能变。通过计算发现:在酸性条件下,p H的大小对于反应的自发性没有影响;大气中二氧化碳溶解达到饱和时,空气湿度增加,反应的自发性略微增加;相同条件下,水由气态变为液态时,反应的自发性增幅较大。