Surface Photovoltage Studies of Moisture Sensitive Characteristic of Copper Tetrasulfonato-Phthalocyanine

The surface photovoltaic characteristic of copper tetrasulfonato- phthalocyanine (CuTsPc) in water vapor was studied by surface photovoltage spectroscopy (SPS). It was found that the adsorption of water vapor caused some marvelous changes of the photovoltaic response, that is, the SPS signal diminished rapidly and even reversed; the bands were widened and displayed a bathochromic shift. The dependence of surface photovoltage on the vapor pressure indicates that the reversed signal reaches to a maximum when the vapor pressure is 4.7×102 Pa. The time response velocity, reversibility, selectivity and reproducibili-ty were examined as well. All results obtained show that CuTsPc is of great significance in the manufacture of moisture sensitive devices. In addition, the mechanism of moisture sensitivity is discussed.     

Synthesis, Structure and Properties of Novel Quaternized Carboxymethyl Chitosan with Drug Loading Capacity

A modified approach to prepare novel amphipathic octadecyl-quaternized carboxymethyl chitosan (QACMC) was reported, in which carboxymethyl chitosan (CMC), prepared from chitosan, was made to react with glycidyl octadecyl dimethylammonium chloride; thus, the octadecyl quaternary ammonium group was introduced into CMC. The structure and thermal properties of these derivatives were characterized by Fourier transform infrared spectroscopy (FTIR), proton nuclear magnetic resonance spectroscopy (¹H-NMR), X-ray diffraction (XRD), and differential scanning calorimetry (DSC). The crystalline properties of QACMC were perfect, and it had a high degree of crystallinity. All the chitosan derivatives had good thermal stability when the temperature was lower than 200 °C. The moisture-absorption and retention abilities of QACMC were lower than that of hyaluronic acid (HA) and CMC. The carboxymethyl and quaternary ammonium groups did not show a synergistic effect, and the effects of both the molar mass and the hydrophobic side chains of long alkyl moieties were important. Minocycline hydrochloride was successfully incorporated into QACMC polymeric micelles with a remarkably high efficiency (10.9%, mass fraction). QACMC promises to be a high-potential delivery vector for lipophilic drugs.     

Dielectric spectroscopy of low-losses sugar lyophiles: III: The influence of moisture on the dielectric response of freeze-dried lactose

This paper presents the results of a dielectric spectroscopy study of freeze-dried lactose with a range of moisture contents. Dielectric properties were measured over a wide range of frequency (10⁻¹ to 10⁶ Hz) and temperature (−120 °C to 120 °C). Four relaxation processes were analysed with respect to moisture content and corresponding relaxation mechanisms were suggested. Two processes (γ and β) were observed in the sub-T_g range of temperature and another two processes were observed near to and above the glass transition temperature, T_g. The relatively high-frequency γ-process was ascribed to the mobility of pendant hydroxymethyl groups and exhibited only a weak dependence on moisture content. The most moisture sensitive process was the second sub-T_g (Johari-Goldstein) β-process, whereby the relaxation time changed by 2 orders of magnitude as the moisture was increased by 7%. Also the third process (α-relaxation, near T_g) was sensitive to moisture content and was in good agreement with DSC data measured for freeze-dried lactose. The fourth process was a proton percolation process at the micro-crystals formed at the surface of amorphous particles during heating at the temperatures higher than T_g and shows the moisture dependence.     

Pd-Cu-Clx/Al2O3催化剂对CO氧化的稳定性

CO催化氧化广泛应用于空气净化、机动车尾气治理和CO气体传感器中.在CO氧化催化剂设计与制备过程中,催化剂与使用环境密切相关.例如工业和机动车尾气净化需要在高温(200–600°C)下进行,而对于半密闭空间(隧道或者地下停车场)空气净化需要在室温和高相对湿度下进行.频繁冷启动导致半密闭空间CO浓度累积而超过排放控制标准,因此制备室温、高相对湿度下CO氧化催化剂是面临的重要问题之一.负载型Wacker催化剂对于CO低温催化氧化的研究一直受到广泛关注.环境中少量水的存在会促进负载型Wacker催化剂对CO的低温氧化性能,但随着水沉积量的增加,活性位点将被覆盖,并且Pd和Cu活性组分之间的紧密结构被破坏,从而导致催化剂的失活,即催化剂的稳定性变差.因此,为了提高催化剂在高相对湿度下的稳定性,利用二乙氧基二甲基硅烷对Al2O3载体进行硅烷化处理,以增加载体的疏水性,考察载体疏水改性对CO低温氧化过程中催化剂稳定性的影响.催化剂的稳定性测试结果表明,在0°C,100%相对湿度条件下,未改性催化剂在约20 h内CO转化率由81%下降到50%;载体硅烷化后制备的催化剂在反应进行150 h后,CO转化率仍保持在78%,即反应活性未见降低.由此表明催化剂载体经有机硅烷改性后,可显著增强催化剂在低温、高相对湿度下的稳定性.N2吸附/脱附和水吸附实验结果表明,载体硅烷化改性并未对催化剂的比表面积产生影响,但显著降低了催化剂上水沉积速度和沉积量,未改性催化剂的初始吸水速度是改性后催化剂的4倍,但改性后催化剂的饱和吸水率仅占未改性催化剂的1/3.X射线衍射结果表明,载体预处理后活性物种Cu2(OH)3Cl晶粒尺寸有所增加.氢气程序升温还原、X射线光电子能谱结果表明,载体硅烷化预处理改善了催化剂中Cu和Pd物种的化学分布及接触状态,增加了与Pd物种紧密接触的Cu物种的量,从而促进了Cu物种的还原.与此同时,载体硅烷化显著降低了催化剂表面Cl离子的浓度,从而影响到对CO吸附.为了进一步研究水与催化剂稳定性之间的关系,采用原位红外漫反射(In situ DRIFT)对催化剂进行表征.负载型Wacker催化剂对CO氧化反应机理为:Pd是CO氧化反应的活性中心,通过Pd和Cu物种之间的氧化还原循环来实现CO氧化,且Pd+比Pd2+具有更高的CO氧化性能.反应气氛中水的存在,有利于CO在Pd+上氧化、以及金属态Pd被Cu2+物种再氧化的过程,同时水也显著促进了催化剂表面碳酸盐的生成以及抑制了活性物种Pd+生成.与表面碳酸盐累积相比,水对于活性物种Pd+生成的抑制作用是导致催化剂活性降低的主要原因.     

Indentation tests and rolling simulations of a compliant wheel on soil at different consistencies

The investigation presented addresses the response of a compliant wheel in interaction with deformable soil dependent on the water content, and accordingly on soil consistency. Two fine soils are considered. The basic soil properties and the soil shear strength are obtained from routine tests. A non-pneumatic Tweel in full size is tested in a loading device against a rigid base and against soil placed in a container in order to assess its stiffness and the compressional behavior of the soil, respectively. The measured pressure sinkage curves are then utilized in conjunction with a standard explicit FEM code to calibrate a hyperelastic model for the Tweel and an elasto-plastic constitutive model for the soil. Soil-tire interface strength is obtained from shear tests on a flat tire section embedded in soil. The numerical model is then applied to investigate how the water content affects the global response of the tire-soil system under different scenarios of free rolling, braking and driving. The methodology followed, complemented by appropriate soil testing, can be used as guide for the implementation of more elaborate models.     

Organic lighting devices are plausibly more vulnerable to oxygen than moisture

Long lifetime and high efficiency are strongly desired for electronic devices. Encapsulation is especially required for organic light-emitting diodes (OLEDs) because they are extremely sensitive to the ambient moisture and oxygen. However, few studies had investigated their individual effects. We found in this study that even with a trace amount, oxygen showed drastically marked effects on both the short- and long-term properties of OLEDs, either typical or tandem. It is unprecedented to see that moisture did not compromise the device performance at least within the 20 ppm level. In contrary, the moisture helped alleviate the attack of oxygen via reducing its kinetic energy and collision probability striking on the aluminum surface. The findings suggest a more stringent oxygen control in fabrication and encapsulation to achieve an upmost device performance.     

水分红外测量原理及方法

介绍了几种水分测量方法的测量原理和优缺点。对离线式测量和在线式测量进行了对比。讨论了红外辐射吸收式水分测量法,叙述了双波长和三波长红外水分仪,并对二者进行了比较,同时展望了水分测量的未来。     

The role of electrochemical migration and moisture adsorption on the reliability of metallized ceramic substrates

Data presented here have resulted from an extensive investigation into fundamental mechanisms involved in electrochemical migration and dendrite growth on metallized ceramic substrates. Significant new results are presented, and pertinent data from previous studies are outlined to provide a comprehensive, coherent analysis of the complex process of electrochemical migration. A number of critical issues are addressed including formation of an absorbed moisture layer and the effect of humidity on the thickness and conductivity of this layer. Migration has been quantified by examining dendrite morphology and dendrite growth rates. Morphology and growth rates are nearly identical for immersion tests in both bulk and thin layer electrolytes, but is quite different in absorbed layers of moisture. Immersion tests are still useful in determining the effects of solution variables that would be difficult or impossible to quantify in adsorbed moisture layers. In addition the maximum velocity theory for predicting dendrite growth rates can be used for predicting general trends, but requires further refinement for more precise predictions. Clearly the most important parameters affecting reliability are the adsorption of moisture combined with surface contamination.     

The moisture absorption characteristics of crosslinked vinyl terminated polyethers compared with epoxies

Processable and practically useful thermosetting resins are almost invariably highly polar. For this and other reasons they can absorb considerable moisture, which affects their physical, electrical and mechanical properties. Crosslinked vinyl terminated oligomeric polyethers (VTPs) of very low polarity are described and their moisture absorption characteristics are compared with those of a standard amine cured Epikote 828® epoxy resin cured with metaphenylene diamine (MPD). The equilibrium moisture absorption of the vinyl terminated polymers is about one-tenth of that of the epoxy system, but their diffusivity is higher. The dependence of the equilibrium uptake on temperature, relative humidity, specimen thickness and oligomer proportions is discussed. The effect of moisture saturation on the d.c. volume resistivity is considered. Moisture prevents the resin from obeying Ohm's law.