熔盐电解法制备Cu-Zr中间合金工艺及机理研究

发布时间：2018-01-25 17:51

本文关键词： 熔盐电解铜锆母合金制备熔盐电化学　出处：《江西理工大学》2017年硕士论文　论文类型：学位论文

【摘要】：Cu-Zr系合金在航空航天,核工业,电子芯片,运输等领域得到广泛运用。目前制备的铜锆合金分布不均匀,操作繁琐,不能连续化生产。本文以LiF-BaF_2-CaF_2-ZrO_2为熔盐体系,制备铜锆合金,研究了不同温度和阴极电流密度下对槽电压和电流效率的影响,制备出Cu-Zr二元母合金。在1233K下以LiF-BaF_2-CaF_2-ZrO_2-MgO为熔盐体系,纯铜棒为自耗阴极,制备出铜锆镁三元合金。熔盐电化学研究锆在阴极上沉积机理:对电极和参比电极分别为石墨和铂丝的条件下利用循环伏安法、计时电位法、计时电流法研究熔盐体系中Zr~(4+)在钨丝工作电极上的电化学还原机理,对电极和参比电极分别为钨棒和铂丝的条件下研究Zr~(4+)在钨丝工作电极上的电化学还原机理。将制备的铜锆合金做XRD和SEM检测分析,得到合金的成分及形貌。结论如下:1.电解质体系LiF-BaF_2-CaF_2在温度1373-1473K下,电解过程中具有较好的热稳定性和流动性,加入二氧化锆和氧化镁后保持较好的导电性质,在高温下熔盐密度较合金密度小,制备出的合金沉于石墨坩埚底部被熔盐覆盖不易与空气接触导致烧损。2.液态铜为阴极制备铜锆合金过程中:1373-1473K温度下进行电解具有可行性。槽电压随着电解温度的升高而下降,槽电压与阴极电流密度成正比。在温度为1420K下,电流密度在1.0~1.5A/cm2范围内,电流密度小于1.29A/cm2时,电流效率随着电流密度的增加从62%增加至66.5%,在电流密度大于1.29A/cm2时,电流效率随着电流密度的增大从66.5%减小至63%,在电流密度为1.29A/cm2时电流效率有一个最大值,此时电流效率最高,为66.5%。3.在温度为1233K条件下以铜棒为自耗阴极,在电解质LiF-BaF_2-CaF_2中加入氧化镁和二氧化锆可以制备出铜锆镁三元合金。4.三电极体系的熔盐电化学研究:石墨作为对电极,在20%LiF-22%CaF_2-58%BaF_2电解质体系中加入质量分数为(0.5~0.9%)的ZrO_2,锆离子在钨电极上还原为金属锆的过程为两步还原,即Zr~(4+)+2e→Zr2+,Zr2++2e→Zr,反应过程为准可逆反应。在不同扫描速率下,锆离子的还原峰电流和扫描速率平方根呈良好的线性关系,说明Zr~(4+)的还原过程受扩散步骤的控制。计时电位扫描出两个平台,且析出电位分别为-0.87V和-1.07V,验证了锆离子在体系中还原为两步还原。经计算得锆离子在钨电极上的还原过程为两步,且分别得两个电子的反应过程。运用计时电流法,通过Cottrell方程计算出离子扩散系数为6.7×10-6cm2/s。在钨电极上析出金属锆的成核机理为瞬时成核。5.三电极体系的对电极为钨棒,在20%LiF-22%CaF_2-58%BaF_2-ZrO_2熔盐体系中,锆的电化学还原过程分为两步,还原过程每一步得两个电子。
[Abstract]:Cu-Zr alloys are widely used in aerospace, nuclear industry, electronic chip, transportation and so on. In this paper, copper-zirconium alloy was prepared with LiF-BaF_2-CaF_2-ZrO_2 as molten salt system. The effects of different temperature and cathode current density on the cell voltage and current efficiency are studied. Cu-Zr binary master alloy was prepared. LiF-BaF_2-CaF_2-ZrO_2-MgO was used as molten salt system and pure copper rod as self-consuming cathode at 1233K. Copper zirconium magnesium ternary alloy was prepared. Electrochemical study on deposition mechanism of zirconium on cathode: cyclic voltammetry and chronopotentiometry were used under the conditions that the electrode and reference electrode were graphite and platinum wire respectively. The electrochemical reduction mechanism of Zr~(4 on tungsten wire working electrode in molten salt system was studied by chronoamperometric method. The electrochemical reduction mechanism of Zr~(4 on tungsten wire working electrode was studied under the condition that the electrode and reference electrode were tungsten rod and platinum wire respectively. The prepared copper-zirconium alloy was detected by XRD and SEM. The composition and morphology of the alloy were obtained. The conclusions are as follows: 1. The electrolyte system LiF-BaF_2-CaF_2 is at 1373-1473K. The electrolysis process has good thermal stability and fluidity, adding zirconia and magnesium oxide to maintain a better conductivity, the density of molten salt at high temperature is lower than the alloy density. The prepared alloy is deposited at the bottom of the graphite crucible and covered with molten salt. 2. During the process of preparing Cu-Zr alloy with liquid copper as cathode, it is difficult to contact with air and cause burning loss. Electrolysis at 1373-1473K is feasible. The cell voltage decreases with the increase of electrolysis temperature. The cell voltage is directly proportional to the cathode current density. At 1420K, the current density is in the range of 1.0 ~ 1.5A / cm ~ 2, and the current density is less than 1.29A / cm ~ 2. The current efficiency increases from 62% to 66.5 with the increase of current density. When the current density is greater than 1.29 A / cm ~ 2, the current efficiency decreases from 66.5% to 63% with the increase of current density. When the current density is 1.29 A / cm ~ 2, the current efficiency is the highest, which is 66.5. 3. The copper rod is used as the self-dissipating cathode at 1233K. Copper zirconium magnesium ternary alloy. 4. electrochemical study of molten salt in the three-electrode system: graphite as opposite electrode is prepared by adding magnesium oxide and zirconia into electrolyte LiF-BaF_2-CaF_2. In the LiF-22F2-58F2 electrolyte system of LiF-22F2, add ZrO_2 with a mass fraction of 0. 5%. The reduction process of zirconium ion to zirconium metal on tungsten electrode is two-step reduction, that is, Zr~(4) 2e. 鈫抁r2 ,Zr2 2e. 鈫扷nder different scanning rates, the reduction peak current of zirconium ion and the square root of scanning rate show a good linear relationship. The results show that the reduction process of Zr~(4 is controlled by diffusion step. Two platforms are scanned by chronopotentiometry, and the precipitation potentials are -0.87V and -1.07V, respectively. It was verified that the reduction of zirconium ion in the system was two steps. The reduction process of zirconium ion on tungsten electrode was two steps and two electrons were obtained respectively. The chronoamperometric method was used. The ion diffusion coefficient calculated by Cottrell equation is 6.7 脳 10 ~ (-6) cm ~ 2 / s. The nucleation mechanism of zirconium precipitates on tungsten electrode is instantaneous nucleation. The opposite electrode of three-electrode system is tungsten. Yes. In the LiF-22F2-58F2-ZrO2 molten salt system, the electrochemical reduction process of zirconium is divided into two steps, and two electrons are obtained in each step of the reduction process.
【学位授予单位】：江西理工大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TF811

【参考文献】