稀土电解槽的研究现状及发展趋势

综述了国内外稀土电解槽的类型和特点,国内在稀土电解槽的电场、磁场、流场、熔盐性质、工艺条件、电阻常数以及电解槽的热平衡和电极材料等方面的研究现状。提出了槽电压与结构参数之间的关系以及结构参数的优化设计方法,根据槽容量进行优化设计可显著降低槽电压,达到节能降耗的目的。     

双功能型嵌入镍纳米颗粒的碳棱柱状微米棒电极用于电化学甲醇氧化助力的节能产氢

With the rapid development of human society, clean energy forms are imperative to sustain the normal operations of various mechanical and electrical facilities under a cozy environment. Hydrogen is considered among the most promising clean energy sources for the future. Recently, electrochemical water splitting has been considered as one of the most efficient approaches to harvest hydrogen energy, which generates only non-pollutant water on combustion. However, the sluggish anodic oxygen evolution reaction significantly restricts the efficiency of water splitting and requires a relatively high cell voltage to drive the electrolysis. Therefore, seeking a thermodynamically favorable anodic reaction to replace the sluggish oxygen evolution reaction by utilizing highly active bifunctional electrocatalysts for the anodic reaction and hydrogen evolution are crucial for achieving energy-efficient hydrogen production for industrial applications. Nevertheless, it is known that the oxygen evolution reaction can be replaced with other useful and thermodynamically favorable reactions to reduce the electrolysis voltage for realizing energy-efficient hydrogen production. Therefore, in this study, we present a bifunctional nickel nanoparticle-embedded carbon (Ni@C) prism-like microrod electrocatalyst synthesized via a two-step method involving the synthesis of a precursor metal-organic framework-74 and subsequent carbonization treatment for methanol oxidation and hydrogen evolution. The interfacial structure consisting of a nickel and carbon skeleton was realized via in situ carbonization. However, the dispersed nickel nanoparticles do not easily aggregate owing to the partition by the surrounding carbon as it would sufficiently expose the active Ni sites to the electrolytes, ensuring fast charge transfer between the catalyst and electrolytes by accelerating the electrochemical kinetics. In the anodic methanol oxidation, the products were detected as carbon dioxide and formate with faradaic efficiencies of 36.2% and 62.5%, respectively, at an applied potential of 1.55 V. Meanwhile, the Ni@C microrod catalyst demonstrated high activity and durability (2.7% current decay after 12 h of continuous operation) toward methanol oxidation, which demonstrates that methanol oxidation precedes oxidation under voltage forces. Notably, the bifunctional catalyst not only exhibits excellent performance toward methanol oxidation but also yields a low overpotential of 155 mV to drive 10 mA∙cm⁻² toward hydrogen evolution in 1.0 mol∙L⁻¹ KOH aqueous solution with 0.5 mol∙L⁻¹ methanol at room temperature, which guarantees the hydrogen production efficiency. More importantly, the constructed two-electrode electrolyzer produced a current density of 10 mA∙cm⁻² at a low cell voltage of 1.6 V, which decreased by 240 mV after replacing the oxygen evolution reaction with methanol oxidation.     

镁电解槽中制备镁稀土合金的电解工艺及机制研究

在模拟镁电解槽中,采用电解法制备出稀土含量<10%的镁稀土合金;研究了熔盐中RECl3和CaCl2的含量、电解温度和阴极电流密度对合金中RE含量和电流效率的影响。并采用循环伏安实验和还原实验研究电解制备镁稀土合金的机制。研究结果表明,电解制备镁稀土合金最佳的工艺条件为:熔盐中RECl3和CaCl2的含量分别为3%和10%(质量分数),电解温度为948 K,阴极电流密度约为8 A.cm-2。其电解过程机制为:阴极上只电解出金属镁,而后金属镁把稀土元素还原出来,形成镁稀土合金。     

基于波动模态耦合的铝电解槽磁流体稳定性傅立叶级数法分析

铝电解槽内磁流体稳定性对铝电解生产有重要影响。本文结合铝电解槽实体仿真的电磁场计算结果,应用傅立叶级数法对槽内磁流体波动稳定性进行数值计算,并对波动的模态耦合问题进行了重点分析。在此基础上,本文以某320kA铝电解槽为研究载体分析了槽长宽比设计对磁流体稳定性的影响,结果表明:波动的不稳定分量集中分布在频谱图中重力波模态密集的低频区域;不考虑母线对体系的影响,增大槽的长宽比,有利于提高磁流体的稳定性。     

阳极结构调整对稀土电解槽的影响

以目前使用的6 k A稀土电解槽为研究对象,采用实验验证与数值模拟计算相结合的方式对采用不同阳极结构的稀土电解槽进行了全面分析讨论。使用斜角切割阳极片可以在维持电解槽槽电压、氧化物利用率、产品合格率等技术指标不变的情况下,克服传统正交切割阳极片在使用过程中随着阳极片反应消耗造成电流效率降低及缩短石墨坩埚使用寿命的现象。其可作为稀土电解槽工艺改造的一个发展方向。     

基于最大-最小蚂蚁系统优化ELM的电解槽故障诊断

针对铝电解槽故障特征种类繁多,难以快速准确的实现故障类型诊断,设计了一种基于最大-最小蚂蚁系统(MMAS)优化的极限学习机(ELM)故障诊断方法。介绍了电解槽常见的故障类型及其对槽电压的影响,对采集到的故障情况下的槽电压信号进行降噪处理,根据对降噪后故障信号的局域均值分解(LMD)结果得到故障特征。采用ELM算法辨识故障类型,针对ELM算法存在的参数问题,采用MMAS对ELM隐含层参数寻优。结果表明,MMAS优化的ELM既保证了较快的训练速度,同时获得了更高的故障测试正确率。     

铝电解磷生铁的快速测定

磷生铁系由生铁和磷铁重新熔炼而成 ,在铝电解生产中主要用于电解槽阴极棒的浇铸和阳极炭块的组装。据文献 [1 ]提高铝电解用磷生铁质量 ,可减少磷生铁热膨胀系数 ,使磷生铁与碳素体的接触压降降低 ,同时减少本身的电阻率 ,能有效提高电解生产效益。而磷生铁中磷的含量对其性能起决定性影响 ,因此对磷的测定就显得非常重要。目前铝行业中对磷生铁含磷量的测定没有一种理想的方法 ,从磷生铁中磷的含量范围 ( 0 .8%～ 3.0 % )和操作简单快速能满足生产需要考虑 ,选用磷钒钼酸光度法。试样用稀硫 -硝混酸溶解 ,过硫酸铵氧化磷及碳化物 ,在适宜…     

电化学合成1, 4-双[2-(3, 4, 5-三甲氧基苯基)乙烯基]苯

1,4-双[2-(3,4,5-三甲氧基苯基]苯[简称HPV]采用有机电化学的方法合成,对合成的原理和方法进行研究和探讨,得到此化合物的三种异构体的淡黄色混合物,即含29.4%全顺式,44.7%顺-反式和25.9%全顺式。所得混合物熔点范围为103-155℃,总得率为92%。     

通过温和的镍腐蚀制备珊瑚状FeNi(OH)x/Ni作为一种一体化高效水分解电极

高效稳定并可同时催化析氧反应(OER)和析氢反应(HER)的非贵金属催化剂对于实现廉价水分解电解槽的商业化十分重要.虽然众多研究表明FeNi(OH)x是一种极具潜力的催化剂,但是在基础研究与更有实用前景的电极之间仍有许多空白亟待填补.比如,基础研究多基于薄膜电极,其催化剂内部导电性的影响通常可以忽略.而基于实用化的电极则需要负载较厚的催化剂膜以获得更多的活性位,与此同时,其催化剂内部导电性的不利影响将会增大.此外,物质传递方面也会出现类似的情况.因此,一些在基础研究中显示出高本征活性的催化剂,在更加接近实际应用的体系下难以表现出预期的高活性.对于这一问题,目前鲜有相关的研究报道.基于上述分析,本文报道了一种经济且环保的方法,以制备珊瑚状的FeNi(OH)x/Ni催化剂.在碱性条件下,该催化剂具有同时催化OER和HER,从而实现全水分解的能力.在催化剂的制备过程中,具有高本征活性的FeNi(OH)x纳米片借助Fe(NO3)3对Ni温和的腐蚀过程,被原位负载到珊瑚状镍骨架上.这些纳米片与电沉积制备的珊瑚镍骨架以及3D泡沫镍基底一起构成了一体化的析气电极.这样的电极结构有助于暴露活性位、电解质快速传递和气体产物的迅速释放.此外,与珊瑚状金属镍骨架的复合也有利于减轻较厚的催化剂薄膜所带来的导电性降低的负面影响.在1.0mol L-1 KOH溶液中,以FeNi(OH)x/Ni同时作为阳极和阴极而构建的对称电解槽表现出了优异的催化活性,只需要施加1.52 V的槽压即获得10 mA cm-2的催化电流密度.其活性甚至优于当前最佳的由贵金属催化剂RuO2和Pt/C构建的非对称电解槽所表现出来的活性(10 mA cm-2的槽压为1.55 V).本文提供了一种简便易行且十分可靠的制备更加实用、具有潜力且可负担的水分解装置的策略.     

Cell Volume Effect on the Ferroelectric Stability of Perovskite Oxides PbTiO3 and BaTiO3 from First Principle Calculation

Electronic structure of ferroelectric PbTiO3 and BaTiO3 is calculated by the full potential linearized augmented plane wave method. The total energy as a function of the displacement of Ti-cation is obtained for PbTiO3 and BaTiO3 at different cell volumes. At experimental cell volume, Ti-displacement lowers the total energy and the ferroelectricity is stable. When the cell volume is reduced to 90%, total energy is increased with Ti-displacement and ferroelectricity will disappear. The cell volume effect is also confirmed by comparison of the density of states of Ti and O at different cell volumes.