CdO—Sb2O3—WO3热敏半导瓷工艺参数与性能关系的探讨

CdO-Sb2O3-WO3热敏半导瓷，是一种在一定温区内具有线性阻温特性的热敏陶瓷元件，并由两种主晶相，锑酸镉及钨酸镉组成。这种材料的特性是：阻温特性在一个相当宽的温区内呈线性变化，工作温度区较宽，具有广泛的,如制作测温诗、控温仪、热导计等。本文对该材料的制造工艺参数：氧分压、保温时间、掺杂元素与其阻温特性进行探讨，获得一些初步结论。     

碳纤维机敏水泥基复合材料温阻特性

研究了碳纤维水泥基复合材料的温阻特性，探讨了碳纤维特性(掺量、长径比)、水泥基体特性和热循环次数对温阻特性的影响．结果表明：在升温初期，碳纤维水泥基复合材料电阻随温度升高而降低。呈现负温度系数(negative temperature coefficient，NTC)效应；升高到一定温度后。呈现正温度系数(positive temperature coefficient，PTC)效应．该材料独特的温阻特性为其在智能结构中实现温控和火灾预警提供了材料基础．     

烧结工艺对液相合成（SrPb）TiO3基陶瓷热敏特性影响的研究

本文在液相合成（ＳｒＰｂ）ＴｉＯ３粉的基础上，研究了升温速率、保温时间、烧结温度及降温方式对（ＳｒＰｂ）ＴｉＯ３基陶瓷的Ｖ型ＰＴＣ热敏特性的影响。实验表明：升温速率对其热敏特性影响不大，保温时间和烧结温度的作用是一致的，具有一最佳范围。而降浊方式对材料的热敏特性影响较大。综合各因素的影响，本配方中，样品的烧结制度定为：以２００℃／ｈ的速率升温，在１２５０℃保温１ｈ，炉冷至９５０℃，保温０．５ｈ，再     

民用飞机蓄电池选型浅析

介绍了当前民用飞机蓄电池的主要功能和类型,对比分析了镍镉蓄电池和锂离子蓄电池在功率密度、充放电特性、维护性、使用寿命、安全性、经济性以及适航性方面的差异,结果表明锂离子蓄电池在功率密度和充/放电特性方面明显占优势,而镍镉蓄电池电池由于其目前应用时间长,在维护性、寿命、安全性、经济性和适航性等方面具有优势。     

镉超标稻谷饲料化的可行性分析

近年来,我国土地重金属污染日益严峻,镉污染尤为严重。在众多农作物中,水稻对镉有较强的生理耐受和富集能力,大多数被污染土壤区域收获的稻谷镉含量超标,不适合人类直接食用。这部分稻谷来源广、数量大,如何消耗这些"镉米"是近期迫切需要解决的问题。"镉米"所含有的营养成分与普通稻谷并无明显差异。在饲料原料紧缺的情况下,将"镉米"饲料化,通过动物的首过代谢减少其对人的毒害作用是一不错的消耗"镉米"的途径。文章就我国"镉米"生产现状、镉直接暴露对机体的危害、镉米饲料化可行性、能量饲料原料的替代需求及镉在机体内的吸收沉积规律和阻控等进行了梳理分析。     

贵州某环境污染区人群镉暴露水平分析

目的了解贵州某镉污染区农作物污染状况及人群镉暴露水平。方法通过随机抽样方法获得调查人群(1 349人),采用三日询问法获得人群膳食消费量,原子吸收法测定膳食镉含量,电感耦合等离子质谱检测尿镉用于内暴露评估。结果采集粮食样品957份。完成186人的膳食调查和1 349人尿样筛查。污染区玉米、土豆及青菜的镉含量超过食物中镉限量值,青菜镉含量(均值0.2 mg/kg)高于其他食物,青菜镉的贡献达50.8%。污染区90%以上人群膳食镉暴露超标,90%以上人群尿镉超过2μg/g·Cr, 70%以上人群尿镉超过5μg/g·Cr, 10%左右人群尿镉超过15μg/g·Cr。结论膳食中镉主要来源为青菜,防止通过农作物—人食物链的人体镉暴露,建议定期开展健康筛查。     

镉系量子点的细胞毒性——镉离子之辩

量子点是一种具有卓越荧光性能的新型纳米材料,在生物医学领域具有广泛的应用前景,故其生物安全性引起了人们的广泛关注.本文阐述了镉系量子点的细胞毒性机制的相关研究进展,重点关注镉离子的释放在镉系量子点的细胞毒性发挥的作用,以及相关的研究方法.     

镉青铜生产的防护措施

镉青铜是一种具有高层电性、导热性．且有良好的耐磨性的金属材料，它的抗腐蚀性能也很好，因此常用于制作常温或高温下工作的高层电、耐磨的零件，是国防军工部门需用的重要有色金属材料之一。但在搞青铜生产过程中，由于搞的沸点低（767℃），在1250℃熔炼温度下形成红黄色的     

红壤在江河突发镉污染事件应急处置中的作用研究

利用红壤可吸附镉和分散于水后可混凝沉淀镉的沉淀化合物的特性除镉:把红壤制成的稀泥浆加入含镉的水中使之成为浊水,加入碱剂使成弱碱性,生成的镉的沉淀化合物细粒附着于泥形成的絮状物上,待泥沉降后,镉与水得以分离。研究了不同含泥量、p H值、镉的初始浓度、放置时间、温度等对除镉效果的影响,确定了适宜的条件。当水中镉含量不大于2.5mg/L、含泥量达到0.8×103 mg/L时,单级除镉率可达85%以上。此法可移植、应用于河水突发镉污染事件的应急处置。     

某冶炼厂周边居民膳食镉暴露风险的初步评估

目的分析测定某冶炼厂周边居民土壤、主要食物与饮用水中镉的水平,并对居民通过膳食途径暴露镉的健康风险进行初步评估。方法收集冶炼厂周边污染组及对照组的主要食物90份、饮用水27份和土壤47份,用石墨原子吸收光谱法测定样品中镉的含量;结合居民膳食调查数据,与暂定的每月可耐受摄入量(provisional tolerable monthly intake,PTMI)及安全限值(margins of safety,MOS)比较,初步评估该冶炼厂周边居民对主要食物的镉暴露风险。结果冶炼厂周边污染区的土壤、大米、叶菜类、根茎类蔬菜和饮用水镉含量的中位水平分别为0.464 mg/kg、0.348 mg/kg、1.148 mg/kg、1.742 mg/kg和0.006 mg/L,对照区(冶炼厂10 km外)的分别为0.155 mg/kg、0.104 mg/kg、0.580 mg/kg、0.817 mg/kg和0.009 mg/L;结合膳食调查与居民尿镉的测定,污染区和对照区居民的镉暴露分别为每月556.123μg/kg和204.588μg/kg,MOS值分别为0.044和0.169;污染区各类食物中,蔬菜对膳食镉暴露的贡献最高(88.9%和85.4%)。结论冶炼厂对周边地区的食物造成比较严重的镉污染,并且可能危害到当地居民的身体健康。     

SrTiO_3基BLC二次烧成过程中显微结构的观察与分析

利用高温金相显微镜、SEM/EDAX和反光显微镜对以SrTiO_3为基的边界层陶瓷电容器(BLC)的烧结过程和绝缘化以后的晶粒和晶界结构进行了观察和分析。研究结果表明,掺有CuO和GeO_2的SrTiO_3的烧结过程为有液相参加的反应液相烧结,半导化以后的陶瓷的绝缘可以通过气相扩散和液相扩散的方式进行。气相扩散绝缘化过程是以离子扩散为主的沿晶界的扩散,金属离子和氧气同时向晶界扩散,氧的扩散使晶界区域发生氧化而绝缘,金属离子的扩散有利于晶界阻挡层的形成。液相扩散绝缘化过程与R.Wernicke提出的选择熔化理论相符,但晶界不一定要富钛。     

Removal of cadmium and nickel from wastewater using bagasse fly ash--a sugar industry waste

The bagasse fly ash, an industrial solid waste of sugar industry, was used for the removal of cadmium and nickel from wastewater. As much as 90% removal of cadmium and nickel is possible in about 60 and 80 min, respectively, under the batch test conditions. Effect of various operating variables, viz., solution pH, adsorbent dose, adsorbate concentration, temperature, particle size, etc., on the removal of cadmium and nickel has been studied. Maximum adsorption of cadmium and nickel occurred at a concentration of 14 and 12 mg x l(-1) and at a pH value of 6.0 and 6.5, respectively. A dose of 10 g x l(-1) of adsorbent was sufficient for the optimum removal of both the metal ions. The material exhibits good adsorption capacity and the adsorption data follow the Langmuir model better then the Freundlich model. The adsorption of both the metal ions increased with increasing temperature indicating endothermic nature of the adsorption process. Isotherms have been used to determine thermodynamic parameters of the process, viz., free energy change, enthalpy change and entropy change.     

On-line sorption-based systems for determination of cadmium with atomic spectrometry detectors

Determination of cadmium is often required in various environmental, biological and food samples as it is recognized worldwide as a toxic metal. However, these analysis with atomic spectrometry detectors are often difficult due to relatively low content of cadmium and complex matrices. Several preconcentration/separation procedures to determine cadmium have been devised, among them the methods based on sorbent extraction are the most popular. They can be easily implemented and controlled in flow injection (FI) or sequential injection (SI) systems to perform appropriate sample pretreatment. This work reviews the papers, published from 1990, concerning procedures based on sorption principles for on-line determination of cadmium. They were compared using experimental enhancement factor (EF) and concentration efficiency (CE) values.     

Cadmium(II) and zinc(II) adsorption by the aquatic moss Fontinalis antipyretica: effect of temperature, pH and water hardness

The biosorption of cadmium(II) and zinc(II) ions onto dried Fontinalis antipyretica, a widely spread aquatic moss, was studied under different values of temperature, initial pH and water hardness. The equilibrium was well described by Langmuir adsorption isotherms. Maximum biosorption capacity of cadmium was independent on temperature and averaged 28.0 mg g(-1) moss, whereas for zinc, capacity increased with temperature, from 11.5 mg g(-1) moss at 5 degrees C to 14.7 mg g(-1) moss at 30 degrees C. Optimum adsorption pH value was determined as 5.0 for both metal ions. Cadmium uptake was unaffected by the presence of calcium ions, but zinc sorption was improved when water hardness increased from 101.1 to 116.3 mg CaCO(3)l(-1). Inversely, as hardness increases, the competition with calcium ions strongly reduces the affinity of the biosorbent for zinc.     

陶瓷地理标志产品微量元素迁移量检测研究

利用电感耦合等离子体质谱仪对20种陶瓷地理标志产品中的砷、镉、铬、镍、铅、锑、锌、铜、锰等9种微量元素迁移量情况进行检测。结果显示,镉、铬、锑在20种地理标志产品陶瓷中均未检出;铅、锌、铜、锰迁移量在有釉瓷（陶）器的多数种类中检出,其中锌迁移量突出;砷、镍迁移量在无釉陶器中检出。     

Accumulation of cadmium in livers and kidneys in Greenlanders

In the Arctic, the traditional diet exposes its people to a very high intake of cadmium because it is highly concentrated in the liver and kidneys of commonly eaten marine mammals. In one study in Greenland, the cadmium intake was estimated to 182 microg/day/person in the fall and 346 in the spring. To determine whether the cadmium is accumulated in humans, we analyzed autopsy samples of liver and kidneys from 95 ethnic Greenlanders (aged 19-89) who died from a wide range of causes. The cadmium concentration in liver (overall mean 1.97 microg/g wet wt) appeared to be unrelated to any particular age group, whereas the concentrations in the kidneys peaked in Greenlanders between 40 and 50 years of age (peak concentration 22.3 microg/g wet wt). Despite the high cadmium levels in the typical Greenlander diet, we found that the cadmium concentrations in livers and kidneys were comparable to those reported from Denmark, Sweden, Australia and Great Britain. Furthermore, even though the mean cadmium intake from the diet was estimated to be 13-25 times higher in Greenlanders than in Danes, we found similar cadmium levels in the kidneys of both. Seal livers and kidneys are the main source of cadmium in the diet of Greenlanders, but these tissues are not eaten in Denmark. Thus, our results suggest that the accumulation of cadmium from Greenlander's marine diet is very low.     

Cadmium bioaccumulation factors for terrestrial species: application of the mechanistic bioaccumulation model OMEGA to explain field data

In environmental risk assessment of metals it is often assumed that the biota-to-soil accumulation factor (BSAF) is generic and constant. However, previous studies have shown that cadmium bioaccumulation factors of earthworms and small mammals are inversely related to total soil concentrations. Here, we provide an overview of cadmium accumulation in terrestrial species belonging to different trophic levels, including plants, snails and moles. Internal metal concentrations of these species are less than linearly related to total soil levels, which is in accordance with previously observed trends. The mechanistic bioaccumulation model OMEGA (Optimal Modeling for Ecotoxicological Applications) is used to provide a quantitative explanation of these trends in cadmium accumulation. Our results indicate that the model accurately predicts cadmium accumulation in earthworms, voles and shrews when accounting for geochemical availability of metals and saturable uptake kinetics.     

Lead and cadmium levels of commonly administered pediatric syrups in Nigeria: A public health concern?

Fifty different pediatric syrups were randomly sampled from patent medicine stores and pharmaceutical shops within Awka, in Anambra State between November 2007 and May 2008. Syrups were ashed before digestion using conc. aqua regia, HCl:HNO₃ (3:1) and lead and cadmium were assayed with AAS 205A. Results revealed that 60 and 98% of the sample size had lead and cadmium respectively. The lead levels ranged from 0.01 in chloroquine to 1.08 mg/l in magcid suspension. The highest level of cadmium was seen in magcid suspension with concentration of 2.45 mg/l while lowest concentration of 0.01 in emzolyn and colipan. About 41.2% of the locally made syrup had none detectable levels of lead while all the syrup had detectable levels of cadmium.Lead levels ranged from 0.01 mg/l in cadiphen manufactured in Dholka, India to 0.09 in maxiquine made in England. About 68.8% of the imported syrups of the imported syrups had non detectable levels of lead. Chloramphenicol and zentel albendazole syrups had 0.60 and 0.88 mg/l of cadmium respectively. Bellis cough syrup showed the lowest level (0.01 mg/l) of cadmium. Only erythromycin suspension representing 6.3% had non detectable level of cadmium of the imported syrups. Due to the Cd and Pb levels found, we suggest that the behaviour scenario (here, self administration without medical assistance) should be properly taken under control. Along with this, contamination sources or vulnerable practices during syrups preparation should be also assessed in a tiered approach, towards the minimization of noxious presence in syrups and the promotion of quality of Nigerian-made products.     

Phytoprotective influence of bacteria on growth and cadmium accumulation in the aquatic plant Lemna minor

Certain plants are known to accumulate heavy metals, and can be used in remediation of polluted soil or water. Plant-associated bacteria, especially those that are metal tolerant, may enhance the total amount of metal accumulated by the plant, but this process is still unclear. In this study, we investigated metal enhancement vs. exclusion by plants, and the phytoprotective role plant-associated bacteria might provide to plants exposed to heavy metal. We isolated cadmium-tolerant bacteria from the roots of the aquatic plant Lemna minor grown in heavy metal-polluted waters, and tested these isolates for tolerance to cadmium. The efficiency of plants to accumulate heavy metal from their surrounding environment was then tested by comparing L. minor plants grown with added metal tolerant bacteria to plants grown axenically to determine, whether bacteria associated with these plants increase metal accumulation in the plant.Unexpectedly, cadmium tolerance was not seen in all bacterial isolates that had been exposed to cadmium. Axenic plants accumulated slightly more cadmium than plants inoculated with bacterial isolates. Certain isolates promoted root growth, but overall, addition of bacterial strains did not enhance plant cadmium uptake, and in some cases, inhibited cadmium accumulation by plants. This suggests that bacteria serve a phytoprotective role in their relationship with Lemna minor, preventing toxic cadmium from entering plants.     

Case-control study of toenail cadmium and prostate cancer risk in Italy

A role of cadmium exposure in prostate cancer etiology has been suggested by epidemiologic and laboratory studies, but conclusive evidence on this topic is still lacking. We investigated the relation between cadmium exposure, estimated by determining toenails cadmium levels, and prostate cancer risk in forty patients newly diagnosed with prostate cancer and fifty-eight hospital controls recruited in two provinces from southern and northern Italy. We found an excess cancer risk in subjects in the third and fourth (highest) quartiles of toenail cadmium concentration (odds ratio 1.3 and 4.7, respectively) compared with subjects in the bottom quartile. Results were basically unchanged when limiting the analysis to each province or entering toenail cadmium concentrations as continuous values in the regression model (P=0.004). Despite the limited statistical stability of the point estimates, these findings appear to support the hypothesis that cadmium exposure increases prostate cancer risk.