5Cu/(10NiO-NiFe2O4)金属陶瓷惰性阳极钠钾混合电解质电解腐蚀研究

采用传统粉末冶金技术制备了铝电解用5Cu/(NiFe2O4-10NiO)金属陶瓷惰性阳极,对其在钠钾冰晶石混合冰晶石中进行电解腐蚀。研究结果表明,从微观来看,阳极存在腐蚀现象。电解过程的槽电压波动剧烈。Fe、Ni和Cu组元的平衡浓度分别为150×10-6、42×10-6及40×10-6,腐蚀速率比常规电解条件下的低。     

低温电解质熔体中NiFe_2O_4基惰性阳极电解腐蚀初探

通过电解前后阳极的外观形貌、微观形貌及槽电压,研究不同槽型对电解腐蚀的影响,并以优化后的电解槽研究5Cu/(NiFe2O4-10NiO)金属陶瓷惰性阳极在Na3AlF6-K3AlF6-AlF3-Al2O3电解质中的电解腐蚀。结果表明:电解后阳极存在一定程度的腐蚀,且少量电解质已渗透到阳极中。     

NiFe_2O_4基惰性阳极的润湿性及气泡析出行为

利用座滴法和双室透明电解槽对NiFe2O4基惰性阳极的润湿性和气泡析出行为进行研究。结果表明,电解质对NiFe2O4基惰性阳极的润湿性要优于碳素阳极。在低电流密度情况下电解,阳极气泡的析出是一个动态过程,它先在阳极表面形核,以球形方式长大,小气泡在长大过程逐渐汇聚偏移,然后逸出。惰性阳极上析出的气泡尺寸比碳素阳极小,在阳极上的逗留时间也更短。大电流密度情况下,气泡的生成速度加快,尺寸降低,很难准确测量气泡的直径。     

Studies on the corrosion and the behavior of inert anodes in aluminum electrolysis

The corrosion rates of inert anodes based on tin oxide and nickel ferrite cermet materials were studied as a function of some operating parameters. To reach a better understanding of the corrosion mechanism, the behavior of the anodes was observed under some specific conditions, such as in pure cryolite, at high current densities, at different potentials, and at varying cathode surface areas. It was confirmed that low alumina concentrations led to catastrophic corrosion of the anodes and that high current densities and high as well as low NaF/AlF₃ molar ratios were also detrimental. The corrosion rate of tin oxide based anodes showed a minimum (so-called “normal corrosion”) at anodic potentials of 2.2 to 2.4 V with respect to aluminum. The normal corrosion is due to chemical dissolution of the anode material and reduction of the corrosion products into the cathode metal. The corrosion rate increased with increasing cathode surface area. At potentials higher than ～2.5 V, the anodes showed catastrophic corrosion. Catastrophic corrosion can be ascribed to decomposition of the anode material by depletion of alumina at the anode surface provoked by low bulk concentration of alumina and/or high current density.     

微波加热配碳还原分解铁酸锌的工艺及机理研究

研究了利用微波配碳还原焙烧分解铁酸锌的工艺及机理。利用碳气化控制、化学控制及扩散控制模型研究了样品中铁酸锌分解的动力学行为,并考察了微波功率、反应温度、配碳比和粒度对铁酸锌分解率的影响。结果表明,样品的微波加热碳热还原试验的控制步骤为碳气化控制,活化能为39.21kJ/mol,在微波加热温度850℃、C/ZnFe2O4质量比为1∶4、粒径74～89μm、微波功率1.8kW、加热时间60min的条件下,铁酸锌的分解率达到90%。     

烧结温度对NiFe2O4/TiN复合陶瓷惰性阳极材料性能的影响

采用两步烧结法制备了掺杂质量分数为7%TiN的NiFe₂O₄/TiN复合陶瓷惰性阳极材料,重点研究了烧结温度对NiFe₂O₄/TiN复合陶瓷惰性阳极材料的微观结构及性能的影响.研究结果表明:随着烧结温度的升高,惰性阳极材料的晶粒间隙变小,气孔逐渐减少,晶粒间结合度提高,体积密度呈先升高后降低趋势,在1325℃时达到最大值5.20g/cm³,但材料内部存在微裂纹;烧结温度为1300℃时,材料表现出较好的综合性能,抗弯强度达到最大值66.77MPa,一次热震强度剩余率为95.54%,表现出良好的耐高温冰晶石熔盐腐蚀能力;烧结温度超过1300℃时,材料内部缺陷尺寸增加,电解质成分更容易渗入到阳极材料中,耐腐蚀性能下降.     

Processes during the electrorefining and electrowinning of lead

The anodic and cathodic processes in the fluorosilicate electrolytes during galvanostatic deposition under (DC) and polarity reversal current (PRC) regimes were investigated. It was established that, during the process of lead electrorefining from concentrated electrolyte without applying PRC, at c.d. i = 300 A/m² (3 A/dm²), after 60–80 h of the 95 h operation cycle, a limiting anodic polarization barrier value (Δ?_Acr = 200 mV) is attained. In this case bismuth and antimony start to dissolve actively from the anodes and are deposited onto the cathode, while under PRC conditions Δ?_Acr is not reached even after 95 h. The cathodic deposits are rounded crystal grains and display pronounced epitaxial growth. Spectral analysis shows that Sb is the main impurity of cathodic lead instead of Bi.During the electrowinning of the lead, without using H₃PO₄ as an inhibitor of β-PbO₂ parasitic deposition onto the inert graphite anodes, it was established that a critical value of the anodic potential ?_Acr = 1430–1500 mV/SCE) exists, under which β-PbO₂ is not deposited. If H₃PO₄ is present, β-PbO₂ is not deposited onto the graphite anodes at any values of the anodic potential.     

铁酸锌纳米薄膜的液相水热合成

以不锈钢和玻璃作为基底,氟铁酸铵和硼酸为前驱体,用液相沉积法得到水合氧化铁薄膜,然后在0.2mol/L的Zn2+溶液中进行水热转化,最终形成铁酸锌薄膜。通过XRD、SEM和TEM对薄膜的物相和表面形貌进行表征,用XPS对薄膜表面元素价态进行确定,结果表明:在水热温度为175~250℃、pH=5~11、水热时间12h可以成功合成铁酸锌薄膜,铁酸锌粒径约20nm。紫外-可见光吸收谱(UV-Vis)表明其光响应范围为λ<473nm,电化学测试表明其光生电位低于不锈钢的自腐蚀电位。     

Al_2O_3-CaO-CaF_2渣系性能的研究

对Al_2O_3-CaO-CaF_2渣系的初晶温度、电导率以及物相组成进行了研究。研究结果表明:向CaO-Al_2O_3二元系中分别添加10%、15%以及20%的CaF_2时,Al_2O_3-CaO-CaF_2系的渣样电导率随着CaF_2含量的增加而增大,初晶温度不断降低;随着渣系的温度升高,该渣样的电导率也不断增大,当添加20%CaF_2时,Al_2O_3-CaO-CaF_2渣的初晶温度为1 468℃。A_2O_3-CaO-CaF_2渣系中主要物相组成为CaAl_2O_4、Ca_2Al_3O_6F、Ca_2AlF_7以及AlF_3。CaF_2添加量为10%时,熔渣中有大量的CaAl_2O_4物质,随着CaF_2添加量的增加,CaAl_2O_4物质越来越少,而Ca_2Al_3O_6F和Ca_2AlF_7物质越来越多。     

Character of the corrosion destruction of inert anodes during electrolysis of cryolite alumina melt and the reasons for it

The behavior of inert anodes during the electrolysis of the cryolite alumina melt in a laboratory electrolyzer is investigated at 960°C. On the basis of the electrolysis tests of more than 150 anodes with various structures and compositions, the character of their corrosion and possible reasons for it are revealed. It is shown that the physical and physical-chemical processes of the interaction of the molten electrolyte and oxygen evolved from the anode material are the basis of the phenomena of the corrosion destruction of anodes. The requirements for increasing the corrosion stability of the structure of inert anodes are formulated.     

Investigation of the processes of obtaining plastic treatment and electrochemical behaviour of lead alloys in their capacity as anodes during the electroextraction of zinc I. Behaviour of Pb---Ag, Pb---Ca and PB---Ag---Ca alloys

The influence of the mode of obtaining and plastic treatment of binary Pb---Ag and Pb---Ca, and ternary Pb---Ag---Ca alloys (used as anodes in Zn electro-extraction from sulphate electrolytes) on their electrochemical behaviour and corrosion resistance is studied.It has been established that the rolled Pb---Ag alloys possess a higher corrosion resistance and lower anodic polarization compared to the cast lead-silver ones due to the structural fineness and homogeneity of the plastic deformed anodes. The plastic deformation of the ternary alloys with calcium content of 0.06% causes Pb₃Ca precipitation in the solid solution. The hot-rolled alloys form an solid solution of Pb₃Ca with fine-grained structure, deformed through the rolling direction. The cold-rolled alloys possess clearly expressed oriented structures also through the rolling direction.Cast and plastically deformed Pb---Ca anodes possess better electrochemical and corrosion characteristics than pure Pb but a considerably higher anodic polarization and lower corrosion resistance than Pb---Ag alloys. Both Pb---Ca systems, with a calcium content of 0.08 and 0.11 % are very appropriate for the preparation of ternary Pb---Ag---Ca alloys. These alloys (Pb---Ag 0.5 %-Ca 0.11 %) possess better electrochemical and corrosion characteristics than binary Pb---Ca ones. Only ternary rolled alloys have equal corrosion and electrochemical properties to those of the alloy Pb---Ag (0.75%–1.0%) used in practice.     

nNaF·AlF3-Al2O3-Sc2O3系电解质初晶温度数学模型的研究

通过对冰晶石—氧化铝—氧化钪系电解质进行五因子一次回归正交实验,求出了其初晶温度受Al2O3、AlF3、CaF2、MgF2、Sc2O3等5个因素影响的函数关系。研究表明,上述5个因素对电解质初晶温度的影响程度,由高到低依次为:Sc2O3、MgF2、Al2O3、AlF3、CaF2。每1%Sc2O3平均降低初晶温度8 219℃。因此Sc2O3的加入可以显著的降低电解温度,起到节能降耗的作用。     

电解铝工艺中钠冰晶石电解体系的影响因素

基于钠冰晶石电解质体系,比较了Na3AlF6-AlF3-CaF2(3%)-Al2O3体系和Na3AlF6-AlF3-CaF2(3%)-LiF(1%)-Al2O3体系液相线温度和电导率。结果表明:得出LiF在体系中虽有利于降低液相线温度和改善体系的导电性,但不是主要影响因素,Al2O3的溶解度和AlF3的剩余量才是影响体系的主要因素;而且AlF3的剩余量与Al2O3的溶解度成反比,合理选用AlF3的配比是体系的关键。     

Investigation of the processes of obtaining plastic treatment and electrochemical behaviour of lead alloys in their capacity as anodes during the electroextraction of zinc I. Behaviour of PbAg, PbCa and PBAgCa alloys

The influence of the mode of obtaining and plastic treatment of binary PbAg and PbCa, and ternary PbAgCa alloys (used as anodes in Zn electro-extraction from sulphate electrolytes) on their electrochemical behaviour and corrosion resistance is studied.It has been established that the rolled PbAg alloys possess a higher corrosion resistance and lower anodic polarization compared to the cast lead-silver ones due to the structural fineness and homogeneity of the plastic deformed anodes. The plastic deformation of the ternary alloys with calcium content of 0.06% causes Pb₃Ca precipitation in the solid solution. The hot-rolled alloys form an solid solution of Pb₃Ca with fine-grained structure, deformed through the rolling direction. The cold-rolled alloys possess clearly expressed oriented structures also through the rolling direction.Cast and plastically deformed PbCa anodes possess better electrochemical and corrosion characteristics than pure Pb but a considerably higher anodic polarization and lower corrosion resistance than PbAg alloys. Both PbCa systems, with a calcium content of 0.08 and 0.11 % are very appropriate for the preparation of ternary PbAgCa alloys. These alloys (PbAg 0.5 %-Ca 0.11 %) possess better electrochemical and corrosion characteristics than binary PbCa ones. Only ternary rolled alloys have equal corrosion and electrochemical properties to those of the alloy PbAg (0.75%–1.0%) used in practice.     

钾冰晶石—氧化钪体系中铝热还原反应过程的研究

在钾冰晶石—氧化钪熔盐中,采用铝热还原和直接电解制备铝钪合金。在引入Al3Sc相生成自由能并考虑活度后,热力学计算表明,铝热还原氧化钪反应在本试验条件下可以发生。750℃在K3AlF6-2%Sc2O3(CR=1.22)熔盐中,电解制备的合金中钪含量可达0.97%,而铝热还原反应所获合金中钪含量小于0.18%,且随反应时间的延长和熔盐中氧化钪浓度的增加,合金钪含量的增幅趋缓。电解合金中钪分布均匀,而铝热还原合金中钪主要存在于边缘区域。     

Anodic behaviour of the Pb–Co3O4 composite coating in copper electrowinning

The electrochemical and corrosion properties of Pb–Co₃O₄ (about 3% Co) composite anode for copper electrowinning without additives as well as in the presence of two combinations of organic additives in the electrolyte have been investigated and compared with those of Pb–Sb 5.85% anode. The formation of PbO₂ layer on the surface of these electrodes was traced by cyclic voltametric measurements using rotating disc electrode (RDE) method. The Pb–Co₃O₄ composite anode shows a depolarizing effect on the process of oxygen evolution as compared to Pb–Sb anode. The corrosion rate of Pb–Co₃O₄ anode during prolonged polarization is approximately 6.7 times lower than that of Pb–Sb anode. The influence of the tested organic additives on the anodic behaviour of both anodes is negligible.     

不同烧结条件下V_2O_5对NiFe_2O_4基惰性阳极结构和性能的影响

采用两步冷压—烧结法制备了V_2O_5掺杂NiFe_2O_4尖晶石阳极材料,研究在不同烧结条件下,V_2O_5添加剂对NiFe_2O_4尖晶石结构和性能的影响。结果表明,向NiFe_2O_4陶瓷基体中引入V_2O_5后形成了低共熔点物质Ni_2FeVO_6,形成液相烧结,能够促进晶粒生长。试样的气孔率和抗弯强度均随着V_2O_5添加量的增加而不断下降。添加0.5%V_2O_5后,低温条件下烧制所得样品的平均气孔率和抗弯强度与相同条件下制备的无添加剂样品的平均气孔率相近。高温条件下延长烧结时间能够降低样品的平均气孔率,但陶瓷基体内会因为部分晶粒的异常生长导致惰性阳极力学性能的弱化。     

掺杂La2O3对金属陶瓷惰性阳极性能的影响

采用Fe-Ni合金为基体,增强相用AlO,掺杂少量的LaO制备一种金属陶瓷惰性阳极试样,分析了烧结温度对试样2323结构的影响,研究了掺杂LaO对试样的体积密度、气孔率、导电率、高温氧化性能,腐蚀速率的影响。23     

铝电解惰性阳极材料研究现状

论述了铝电解工业中使用惰性阳极的意义,提出惰性阳极应符合的标准并对惰性阳极的优缺点进行了分析.综述了国内外近年来对于合金阳极、氧化锡阳极、金属陶瓷阳极及氧化铈涂层阳极等惰性阳极材料的研究成果,总结了目前惰性阳极材料研究亟待解决的主要问题.     

Y2O3对NiCr-Cr3C2金属陶瓷涂层热腐蚀性能影响行为研究

本文利用超音速火焰喷涂技术(HVOF),在20G钢表面制备了掺杂1wt.%、3wt.%、5wt.%三种不同含量Y2O3的NiCr-Cr3C2金属陶瓷复合涂层,并探究了其在650℃,Na2SO4/K2SO4熔盐环境中的热腐蚀性能。利用扫描电镜(SEM)、显微硬度计、拉伸试验机等对涂层的微观结构和力学性能进行了表征,利用X射线衍射仪(XRD)、拉曼光谱、X射线能谱仪(EDS)对复合涂层热腐蚀产物形貌、物相进行分析。结果表明掺杂1wt.%Y2O3的NiCr-Cr3C2复合涂层结构致密、孔隙率低、结合强度高,显微硬度达到801HV。热腐蚀过程中掺杂Y2O3的NiCr-Cr3C2复合涂层表面均生成耐蚀性良好且致密的Cr2O3膜。随着Y2O3掺杂量的增加,涂层的耐热腐蚀性能先升高后下降,当Y2O3掺杂量为1wt.%时,复合涂层表现出最佳的耐热腐蚀性能。