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991.
Electrochemical stripping of gold from Au-Ni-Cu electronic connector scrap in an aqueous solution of thiourea 总被引:2,自引:0,他引:2
The electrochemical behaviour of a gold-plated connector from electronic scrap in aqueous thiourea solution has been investigated. An attempt was made to recover gold from scrap in a nontoxic thiourea medium by an electrochemical method rather than the traditional cyanide process. Linear sweep voltammetry indicated that thiourea extraction of gold is more efficient in acidic solution than in neutral and alkaline. Hydrochloric acid is preferable to control the pH of the solutions; the optimum concentration of thiourea is 2.5% (0.33 m). Analysis of voltammetric data yielded a critical potential (0.40 V vs SCE), which is the upper limit for significant extraction of gold from scrap. Higher potentials should be avoided in practice to prevent decomposition of thiourea and its passivation of the scrap. Electrolysis at constant potential indicated that gold was extracted selectively in the range 0.20–0.30 V vs SCE. Electrolysis at potentials either less than 0.15 V vs SCE or greater than 0.40 V vs SCE is not recommended, because of slow dissolution in the former and severe passivation in the latter. 相似文献
992.
The effects of ultrasonic oscillations and die materials on die pressure, productivity of extrusion, melt viscosity of metallocene‐catalyzed linear low density polyethylene (mLLDPE), as well as their mechanism were studied in a special ultrasonic oscillations extrusion system developed in our lab. Die materials used in our experiment included steel, brass, and polytetrafluoroethylene (PTFE). The experimental results showed that ultrasonic oscillations as well as die materials have great influence on the rheological and processing behavior of mLLDPE. Ultrasonic oscillations can greatly increase the productivity of mLLDPE melt extruded through different dies, and can decrease the die pressure and the melt viscosity of mLLDPE. Compared with steel or brass die, mLLDPE melt extruded through PTFE die is more sensitive to ultrasonic oscillations. A possible mechanism for the improved processability of mLLDPE is proposed in this article. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 1873–1878, 2003 相似文献
993.
Efficacy of tertiary butylhydroquinone on the storage and heat stability of liquid canola shortening 总被引:1,自引:0,他引:1
Z. J. Hawrysh P. J. Shand C. Lin B. Tokarska R. T. Hardin 《Journal of the American Oil Chemists' Society》1990,67(9):585-590
The sensory (odor and flavor) and physicochemical characteristics of tertiary butylhydroquinone (TBHQ) treated and butylated
hydroxyanisole/toluene (BHA/BHT) treated liquid canola shortenings, subjected to accelerated storage (Schaal oven test at
65°C) and deep fat heating (at 185°C), were determined. Data for the Schaal oven test indicate that TBHQ was effective in
retarding oxidative rancidity in liquid canola shortenings. However, addition of the commonly used mixture of BHA/BHT to canola
shortenings resulted in only a slight decrease in oxidation during schaal oven storage. The results obtained from deep fat
heating of canola liquid shortening show that neither TBHQ nor BHA/BHT was effective in enhancing oxidative and thermal stability
of this product. 相似文献
994.
The effects of donor and acceptor doping on the piezoelectric properties of 18Pb(Mg1/3 Nb2/3 )O3 ·39PbZrO3 ·43PbTiO3 ternary solid solution have been investigated. The dopants influence in a pronounced way both the crystal structure and microstructure of the materials. The materials are transformed from the rhombohedral to the tetragonal structure, and the grain size is reduced when Nb 5+ cations are added. The crystal structures are transformed from the rhombohedral to the cubic structure, and grain growth is enhanced, when Mg 2+ cations are included. The values of K P and K are maximized for 1-mol%-Nb5+ -doped samples (K P = 0.69, K = 1152); the Q m factor and E c are optimized for 4-mol%-Mg2+ -doped samples ( Q m = 1534, E c = 0.56). 相似文献
995.
高性能玻璃纤维增强材料 总被引:1,自引:1,他引:1
林树益 《玻璃钢/复合材料》1996,(1):8-12
本文简要评述了国内外高性能玻纤增强材料如高强度、高模量、高硅氧、抗辐照、抗碱、空心玻璃纤维等的研究进展与现状;同时评述了高新玻纤制品的现状及其应用,如连续原丝毡、针织缝编毡、3D织物、复铜板薄毡、膨体纱系列产品、增强热塑性塑料玻纤基材等。 相似文献
996.
从提高学生职业能力理念出发,以高素质技能型人才培养为目标,教学改革和课程体系设计为先导,整合信息安全课程体系并进行优化,构建人才培养新方案,对教学内容进行有效探索,以期提高信息安全专业人才培养质量. 相似文献
997.
林奕水 《网络安全技术与应用》2014,(12):50-51
IPv6作为下一代物联网IP层技术,进一步扩大了地址空间,并在国家政策的号召以及国家电网公司的积极响应下在电力、石油等方面获得了广泛的应用,为智能电网与下一代互联网的深度融合探索道路、提供经验。但是其应用中仍然存在较多重大的问题,其中最为突出的就是其安全性和真实性。当前的网络体系结构,大多数情况下并不检查源地址,这就导致源地址伪造事件很容易发生。本文主要分析了物联网对IPv6的需求,总结了多种IPv6源地址验证方案,并重点对SAVS框架下的IPv6源地址验证方案进行分析和探讨。 相似文献
998.
999.
用共沉淀法制备Fe3O4磁流体,总结出用十二烷基磺酸钠与聚乙二醇作为表面活性剂制备水基磁流体的合适条件:(1)反应温度为室温或不高于35℃;(2)表面活性剂十二烷基磺酸钠的最佳用量为0.0030~0.0040 g/80 mL;(3)第一次包裹的最佳pH为9~10;(4)聚乙二醇作为第二次包裹的表面活剂时,体系最佳温度为40℃左右;(5)表面活性剂聚乙二醇的最佳用量为0.0050~0.0060 g/80 mL。通过实验制得了能稳定存在180 d的水基磁流体。并用透射电镜、红外光谱、分光光度计、古埃磁天平等进行了初步表征。 相似文献
1000.
The moisture absorption behavior of diglycidyl ether of bisphenol A/ethylene diamine resins incorporating a carboxy‐terminated butadiene–acrylonitrile rubber was investigated and associated with their morphology of phase separation. Although the diffusion coefficient of moisture was increased with the rubber content, its activation energy and free volume for moisture diffusion were barely changed until phase inversion occurred. After phase inversion, the free volume was significantly increased, and the activation energy decreased. In addition, the moisture absorption also reduced the β‐transition temperature of the resins and slightly increased the glass‐transition temperature before phase inversion. However, the reverse was found after phase inversion. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 3718–3724, 2002 相似文献