Electrorefining Vanadium

Application of molten-salt electrorefining techniques to the production of high-purity vanadium and also to the refining of lower-purity vanadium products to ductile-grade metal.     

Developments in Alkaline Tin Electrorefining

Although alkaline stannate baths for electrorefining of tin have been used for some time, there is still room for improvement The effects of alkali concentration, current density and temperature on the cathodic current efficiency have been studied, and a bath temperature of 75°C is recommended. To avoid unstable conditions in the bath, a special treatment to the anode and application of an auxiliary cathode are necessary. Many of the metallic impurities present in the crude tin anode go into the slimes in the form of hydroxides, but lead impurities can only be tolerated if concentrations are less than one percent.     

Fused Salt Electrorefining of Beryllium

The US Bureau of Mines has achieved laudable progress in its striving to attain high-purity beryllium. The following is a discussion of the Bureau’s work on the fused salt electrorefining of beryllium.     

Fatigue Behavior of Solid-State Additive Manufactured Inconel 625

A transformative hybrid solid-state additive manufacturing process provides a new path to fabricate or repair components with wrought-like performance. In this work, the fatigue behavior of Inconel 625 (IN625) manufactured via a high-shear deposition process is quantified for the first time. In this unique process, feedstock is deposited via a hollow non-consumable rotating cylindrical tool, thereby generating heat and plastically deforming the feedstock through controlled pressure as consecutive layers are metallurgically bonded upon a substrate. To quantify the fatigue behavior of the as-deposited IN625, stress-life experiments were conducted, where improved fatigue resistance was observed compared with the feedstock. Post-mortem analysis of the as-deposited IN625 revealed a similar fatigue nucleation and growth mechanism to the feedstock for a majority of the specimens tested in this study. Last, a microstructure-sensitive fatigue life model was utilized to elucidate structure–property fatigue mechanism relations of the as-deposited and feedstock IN625 materials.     

Photoelectrochemical Behavior of Copper in Some Activating Solutions

Concurrent measurements of dark current and photocurrent under potentiodynamic conditions in Na₂SO₄, NaClO₄, and NaNO₃ solutions evidence a change in the conductance type of the oxide film during the metal's transition from passive state to dissolution.     

Impacting Behavior of Large Oxidized Copper Particles in Cold Spraying

In a previous study, it has been experimentally demonstrated that surface oxide films of metallic particles have significant influence on the properties of cold-sprayed coatings. To clearly reveal the underlying mechanism, this study focused further on the effect of particle oxidation on the deposition behavior of oxidized Cu powder. Results show that the presence of the oxide films on the particles’ surface can inhibit the plastic deformation of the particles. In addition, results concerning the morphologies and oxygen content of the rebounded particles show that the particles have experienced large plastic deformation that results in the break-up of the oxide films during the impacting process. Correspondingly, the hardness of the coating deposited with the oxidized powder is a little lower than that with the annealed powder because of the inferior plastic deformation and strain-hardening effect.     

铜质接地网材料电化学腐蚀行为

取安徽省八座500kV变电站土壤按水土比1∶1配制试验介质,对铜质接地网材料进行电化学测试和极化曲线测试,结果表明,铜质接地网材料在试验介质中的腐蚀均属于活化控制,没有明显的氧扩散控制;电化学阻抗谱测试结果表明,铜质接地网材料在试验介质中浸泡4h,反应只受电极溶解控制。     

海水中紫铜缓蚀剂的缓蚀性能及表面分析

采用失重法、极化曲线、扫描电镜和XPS能谱分析等方法,对苯并三氮唑(BTA)及其复合缓蚀剂对海水中紫铜的缓蚀性能进行了试验。结果表明,BTA与柠檬酸钠之间存在很好的协同效应,当BTA浓度为2mg/L,柠檬酸钠浓度为20mg/L时,缓蚀率达到96.0%,腐蚀速率为10μm/a。极化曲线试验结果表明,BTA与柠檬酸钠复合缓蚀剂为混合型缓蚀剂。扫描电镜和XPS能谱分析表明,体系中添加了BTA和柠檬酸钠复合缓蚀剂后紫铜表面光亮,基本没有腐蚀;且在试片表面形成了Cu_2O、Cu(Ⅰ)-BTA和Cu(Ⅰ)-络合物的非水溶性保护膜,从而有效地抑制了紫铜在海水中的溶解腐蚀。     

表面纳米化纯钛沉积铜的摩擦行为研究

采用微弧氧化法在纯钛表面制备TiO_2孔径在400 nm左右的介孔层,同时用电化学脉冲沉积法将铜沉积在介孔层上,对改性层进行滑动摩擦实验,利用扫描电镜、激光显微镜对改性层的表面形貌、磨损后深度进行了表征。结果表明,TiO_2纳米介孔层会对沉积铜的粒径的大小、形状产生影响;试样的磨损机制主要表现为犁沟磨损、粘着磨损及和磨粒磨损;二氧化钛介孔层及铜粒径的存在提高了纯钛的抗磨减磨性能。     

紫铜在清远乡村大气环境中的腐蚀行为

通过金相显微镜、扫描电镜、X射线衍射仪(XRD)、能量色散谱(EDS)和电化学阻抗谱(EIS),研究了紫铜在清远乡村大气环境中暴露不同时间后的腐蚀行为。结果表明:紫铜在清远乡村大气环境暴露后,有局部腐蚀发生。随着时间的延长,腐蚀产物增多,并逐渐覆盖了铜表面形成较为致密的膜层,导致腐蚀速率下降。在暴露的前6个月,紫铜的腐蚀产物主要是Cu_2O,随着时间的延长,大气中其他污染物对铜腐蚀的影响增加,12个月后腐蚀产物中出现了CuOHCl和CuS。     

厌氧微生物对紫铜腐蚀行为的影响

采用开路电位、电化学极化曲线、电化学阻抗谱(EIS)研究了紫铜在海洋厌氧菌影响下的腐蚀行为。结果表明,扫描电子显微镜SEM形貌分析结果表明在紫铜上附着的SRB海洋微生物呈微弯杆状,材料表面形成较致密的半透明的生物细菌膜。电化学测试结果表明,紫铜在SRB细菌培养基海水中的腐蚀过程主要受活化极化控制,SRB微生物的存在导致紫铜的开路电位和活化极化率变小,从而加速了紫铜的腐蚀进程。     

添加金属铜对MH-Ni电池的内压及其他性能的影响

研究了添加铜对MH-Ni电池循环初期的内压、容量及自放电等性能的影响。研究结果表明,添加铜可以降低MH-Ni电池的充电内压,降低电池的容量,加大电池的自放电。     

新型铜合金细化添加剂对铸造铅黄铜变质处理效果的影响

新型细化添加剂对铸造铅黄铜变质处理的效果表明,细化效果良好,铸造铅黄铜组织由粗大的板条状变为细小的针状或等轴状,组织均匀性提高,同时可显著提高铅黄铜的力学性能.细化效果衰退较慢,静置保温180min后,材料仍具有较好细化效果和力学性能.新型铜合金细化添加剂对铸件壁厚不敏感,壁厚3mm～12mm,均可获得较好的细化效果和性能;采用新型铜合金细化添加剂变质处理可大幅度提高铅黄铜的流动性,变质处理后,铅黄铜的流动性比未变质处理的平均提高了29.78%.     

铜电解添加剂的作用机理及生产实践

随着现代工业的发展,对阴极铜质量的要求更加严格,但阴极铜质量的优劣,取决于它们的组织结构和杂质含量,若要获得优质阴极铜,必须严格控制好各项技术条件.添加剂就是一项主要的控制因素,实践证明,加入适量添加剂,是获得结构致密、表面光滑、杂质含量少的优质阴极铜的有效措施.     

连续挤压铜母线的高温流变应力行为研究

在Gleeble1500热模拟机上对连续挤压铜母线在应变速率为0.01～1.0 s-1、变形温度300～700℃条件下进行高温等温热压缩试验,并探讨了其高温流变应力行为.结果表明:当温度大于或等于500℃时,铜母线高温流变应力曲线显示出较为明显的稳态流变曲线特征,且为典型的单峰动态软化曲线;在温度小于500℃时,稳态流变曲线特征不明显,材料较难以进入稳态流变.变形温度越高或应变速率越低,动态软化曲线特征越明显.用Zener-Hollomon参数的双曲正弦函数形式能较好地描述铜母线高温变形时的流变应力行为,其热变形激活能Q经计算为205.445 kJ/mol,Z方程为:Z=εexp(205.445/RT).     

Comparison of the Oxidation Behavior of Nanocrystalline and Coarse-Grain Copper

The Oxidation of an electro-deposited nanocrystalline Cu (nc Cu) and a conventional coarse-grain Cu (cg Cu) was investigated at 30–800 ° C under 1 atm of oxygen. Both Cu samples formed external scales of copper oxide (Cu₂O+CuO). At the lower temperature (30–300 °C) the very slow oxidation rates of both the nc and cg Cu might be attributed to the formation of a protective Cu₂O surface layer. However at the higher temperature (300–700 °C), oxidation rates of the nc Cu were obviously faster than those of the cg Cu, which was attributed to faster diffusion of various species along grain boundaries both in the metal and in the scale. In particular, the scale grew faster on the nc Cu by means of not only rapid external oxidation as a result of outward diffusion of Cu-ions but also a significant contribution from inward diffusion of oxygen along the grain boundaries in the scales. Compared with the cg Cu, dissolved O₂ in the nc Cu may have a certain effect on the faster oxidation of the nc Cu. Above 700°C, the difference seemed to disappear as a result of the ineffectiveness of grain-boundary diffusion.     

热压缩过程中20-TiC铜合金动态再结晶行为分析

对某复合材料厂生产的20-TiC铜合金的动态再结晶行为进行了研究和分析,并且对实测的应力-应变曲线进行了拟合。结果表明:拟合的应力-应变曲线平滑无波浪,比较适宜研究材料的动态再结晶行为。根据拟合的应力-应变曲线可知,在一定的变形温度下,应变速率越大,应力最大值越大,在一定的应变速率下,变形温度越高,应力最大值越小。通过应力-应变曲线可以得到材料动态再结晶的临界应变值。