铝电解惰性阳极制备及其应用研究

【作者】 王宇栋；

【导师】 戴永年；

【作者基本信息】 昆明理工大学 ， 有色金属冶金， 2012， 博士

【摘要】 因为惰性阳极拥有许多诱人的优点,例如：彻底杜绝了铝电解工业的温室气体排放,减低了生产成本等。但是因为此项技术难度很大,至今仍没有惰性阳极能用于铝电解生产的报导。本文作者及其同事在总结前人对惰性阳极研究正反两方面经验的基础上,通过一系列高温电解质浸泡及高温氧化或电解试验,优选出(WC-M)涂层复材、(Al2O3-M)金属陶瓷和(NiFe2O4-M)金属陶瓷三种材料作为研究对象,并用上述三种材料制作的惰性阳极完成铝电解小试。结果表明：在上述三种材料制作的惰性阳极中,以(NiFe2O4-M)阳极的抗腐蚀性最优。但在批量和深入电解应用中,却暴露出许多问题,如由于NiFe2O4氧化物相与Cu-Ni合金相的物理性能差异大、互相润湿性差,导致(NiFe2O4-M)阳极在压制脱模时极易破断,压成型成功率还不足30%；因(NiFe2O4-M)阳极的烧结属互不相溶两相机械混合物的烧结,常规烧结工艺易导致烧结体出现横向裂纹、变形、流淌等缺陷,造成烧结成品率低；现有的电解质会造成惰性阳极腐蚀过快或导电性能下降过快。为了克服上述问题,作者及其同事发明了以下三种创新技术：(1)在NiFe2O4粉末与金属粉末混合并压成形前,预先使用高能球磨法使NiFe2O4研磨到纳米/准纳米级别,然后再与金属粉末混合进行普通球磨。此项技术显著改善了NiFe2O4陶瓷粉末与金属粉末M之间的润湿性和相溶性,使压成型成功率提高到95%以上,同时改善了阳极的烧结性能和应用效果；(2)(NiFe2O4-M)惰性阳极的主要成分-陶瓷相NiFe2O4与金属相Cu-Ni是两种物理性能差异很大的物质,烧结温度相差也大。采用作者设计的“同步烧结”工艺后(即制造一种工艺环境,使NiFe2O4尖晶石的烧结与配入金属粉Cu、Ni的烧结在同一温度、同一保温时间内完成),消除了烧结裂纹和变形流淌等缺陷,显著提高了烧结产品质量,将烧结成功率从25%提高到90%以上；(3)深入开展了(NiFe2O4-M)惰性阳极与电解质的“互适应”研究,优良的互适应性意味着(NiFe2O4-M)惰性阳极可以长时间保持良好导电性和抗腐蚀性。研究结果表明：(NiFe2O4-M)阳极在当前的常规电解质中有较好的导电性,但抗腐蚀性欠佳；在某些低温电解质中的抗腐蚀性较好,但低温电解质会导致阴极铝下层形成导电不良的阴极结壳而使系统导电性变坏,不能有效地进行铝电解；本课题组所发明的NAIE型理想电解质具备常规和低温电解质的优点,与(NiFe2O4-M)阳极配合使用具有良好的互适应性、有持久的导电性(100小时电解中阳极的电阻约为0.5Ω)和满意的抗腐蚀性(100小时的电解后测量不出腐蚀量),可推荐进入中试使用。在有关部门的经费合作和支持下,采用NAIE理想电解质配合(NiFe2O4-M)惰性阳极作铝电解已进入中试阶段。中试电解槽装备了自动加料槽控机,电解电流为4kA及自热式加热,预计1-2年后可完成。更多还原

【Abstract】 The conductive materials resisting against high temperature corrosion and oxidation are mainly used to make inert anodes for aluminium electrolysis in this thesis. Therefore, the fabrication and application of inert anode for aluminium electrolysis are main contents of the thesis.Because the inert anodes have several obvious advantages in aspects of eliminating green-house gas release and saving production cost, many researchers have been of primary concern to inert anodes. But the inert anodes have not been used in aluminium electrolysis up to now because of existing many difficulties.In this work, firstly, author and his colleagues made choice of a coating composite of (WC-M)/316L,(Al2O3-M) and (NiFe2O4-M) from many materials by soaking tests in electrolytes melting, high temperature oxide tests or electrolysis. Then three types of inert anodes made up of the above three materials and completed tests of aluminium electrolysis. Results shown up that (NiFe2O4-M) anode had better corrosive resistance than other two candidates. But when (NiFe2O4-M) cermet inert anodes were tried further with a batch of anodes, the results proved out that when (NiFe2O4-M) was used as inert anodes, many problems were protruded out again, for examples, anode green bodies were often broken down at pattern drawing in press compacting, success rate was less than30%; In addition, cracks or bending of sintered anodes appeared often in the sintering; otherwise present electrolytes were not suitable with (NiFe2O4-M) anode.In order to overcome the above problems, author and his colleagues presented following technical inventions:1. Before mixing with metallic powder, calcined NiFe2O4was ball-milled by high energy grinding to nano or quasi-nano sizes which were late ball-milled together with metallic powder in common ball-mill, which is beneficial to improve wetting characteristics of NiFe2O4towards metallic powders. After the process was introduced, success rate of press-compacting anode green bodies increased to above95%, but was only than30%without high energy ball-mill;2. The (NiFe2O4-M) anodes are mechanical mixture of NiFe2O4ceramic phase and Cu-Ni metallic phase. Generally, the sintered temperatures of the above two phases are different. The synchro-sintering means that the above two phase were sintered at same temperature and in same duration by means of adjusting the ratio of Cu to Ni in metallic phase in order that the above two phases have very near sintering temperature. After synchro-sintering process was introduced, the bending or cracks of sintered anodes were disappeared satisfactorily;3. The mutual appropriation of (NiFe2O4-M) anode with different electrolytes was researched thoroughly by completing many electrolysis tests in different electrolytes. Good mutual appropriation means that (NiFe2O4-M) anodes can keep on better conductivity and lest corrosion for long electrolysis. The tests results pointed out that (NiFe2O4-M) anodes were not appropriated with present electrolytes used commonly and low melting point electrolytes because in the former, the anodes were corroded more rapidly, and in the later, the conductivity did not keep on for long because of producing curdling cathode crust without better conductivity. On the bases of the above results, writer and his colleagues invented a new Na3AlF6Ideal Electrolyte (NAIE) which is composed of Na3AlF6、Al2O3and the others. When electrolyzing in NAIE electrolyte, the (NiFe2O4-M) anode kept on better conductivity and resistance against corrosion for long. Subsequently repeated electrolysis tests were done, the results shown up that for100hs electrolysis tests, the (NiFe2O4-M) anodes were only corroded with trace and were able to keep on ideal electric conductivity in NAIE electrolyte.Presently (NiFe2O4-M) anodes and aluminium electrolysis in NAIE electrolyte have been developed already into pilot test stage with4kA current cell.更多还原