TiO2直接电解还原过程的研究

采用SEM、EDS、XRD等方法对TiO2直接电化学还原产物进行分析,指出TiO2电极的还原是从外向内由高价到低价再到金属逐步进行的.对还原过程中电流、还原气相产物的分析结果表明:还原过程电流效率低,并且电流效率随电解时间延续而降低,阳极产物CO、CO2与阴极中间产物Ca发生副反应以及副反应产物炭黑造成电流短路是电流效率低的主要原因.提高电流效率的途径有两条:一是增大阴、阳极间距,减小副反应的发生;二是使电解池表面熔盐不断导出,或采取某一隔离措施,使副反应产生的炭黑在阴、阳极之间不造成电流短路.     

电化学还原TiO2制备金属钛及反应过程的研究

采用熔盐电解法,在900℃熔盐CaCl2中以烧结TiO2为阴极,石墨棒为阳极制备出了金属钛.研究了不同温度下烧结阴极的形貌及其对电解反应的影响.结果表明：600℃下烧结4 h的阴极具有良好电化学反应性能;电解过程中脱氧速度不均匀;TiO2电极的还原是由外向内,由高价向低价再到金属分步进行的;电解还原过程电流效率低约为15%.阴极的孔隙大小和颗粒尺寸会影响电极的反应速度.     

N80碳钢CO2／HAc腐蚀电化学过程

采用动电位扫描、恒电位极化和电化学交流阻抗测试技术,研究了乙酸(HAc)对N80碳钢在50℃、饱和CO2的1%NaCl溶液中的电化学腐蚀行为的影响,并讨论了阴极、阳极的反应机理.研究表明:HAc能够直接在电极表面还原,使阴极极限电流增加.HAc未改变阳极反应机理,但能够加速中间产物的形成/溶解过程,从而加速阳极溶解过程.在饱和CO2溶液体系,乙酸盐易与碳酸生成HAc,而参与电化学反应.因此,无论是HAc还是乙酸盐均能够加速N80碳钢电极的CO2腐蚀.     

锌合金牺牲阳极海水干湿交替条件下的电化学性能研究

对Zn-Al-Cd合金牺牲阳极在海水全浸和海水干湿交替条件下的电化学性能进行了对比研究,并对阳极表面腐蚀产物的形貌和阳极表面溶解状况进行了分析。随着干湿交替次数的增加,锌合金阳极的工作电位逐渐正移,发出电流的能力逐渐减弱,阳极活性逐渐降低,电流效率明显下降。在干湿交替条件下,锌合金阳极表面腐蚀产物更为致密,表面溶解状况不如全浸时的均匀。表面腐蚀产物层致密和局部腐蚀是造成干湿交替条件下锌合金牺牲阳极活性和电流效率降低的主要原因。     

碳热还原法合成TiB2的反应传质机理

在XRD、SEM、能谱分析、TEM、TG-DSC等实验分析的基础上,对以TiO2、B2O3、C为原料,通过碳热还原法合成TiB2粉末的反应传质机理进行了研究,阐明碳热还原法合成TiB2的反应传质机理,建立碳热还原法合成TiB2的反应传质模型。研究表明:在碳热还原TiO2的过程中,由低温到高温,最稳定的还原产物分别是Ti4O7和Ti3O5,尤其当温度超过1300℃以后,Ti3O5为最稳定的还原产物。在碳热还原TiO2与B2O3合成TiB2的反应过程中,DDSC曲线上有几个明显的吸热峰,这分别对应于TiO2→Ti4O7→Ti3O5→TiB2的反应阶段。碳与氧化物颗粒之间是通过CO/CO2气体偶实现质量传递的。在反应体系中,B2O2(g)气相、Ti3O5(s)固相分别是形成TiB2的前驱体。     

铜电解短路的阴极电流变化与结瘤形貌

铜电解精炼生产过程中,结瘤引起的阴阳极间短路会造成明显的电流效率损失和产品质量下降,检测阴极电流的变化趋势可以快速且准确地判断短路是否发生.本文通过在实验室构建铜电解系统对单个结瘤短路前后的现象进行研究,探究结瘤生长全过程的阴极电流变化规律,观察分析结瘤形貌的变化特点,并进一步利用COMSOL Multiphysics...     

预焙铝电解槽电流效率与阳极电流分布的数学模型

在复杂的综合数学模型的基础上, 利用正交多元回归法研究了预焙电解槽中电流效率与阳极电流分布的关系, 得到一个代数方程式, 同时, 用这个代数方程式分析了阳极电流分布与电流效率的关系.分析结果表明: 阳极电流分布与电流效率都随时间和空间而改变; 阳极电流分布的改变引起电流效率的改变; 在Kuhn Tucker 理论的基础上, 还讨论了系列电流不变时的最佳电流效率, 由于电解槽中磁场、流场分布不均匀等原因, 并非严格均匀的阳极电流分布才能得到最高的电流效率.     

DSP控制CO_2焊引弧研究

CO2焊是一种生产效率高、成本低的高效焊接方法。传统的CO2焊采用接触式短路引弧,引弧时间长、成功率不高、稳定性差。分析了影响和提高引弧成功率的因素,并以DSP控制焊机为平台,设计了一种通过限制引弧过程焊接电流来进行引弧的方法。该引弧方法中,焊接过程中的电流为被控制对象,在电压为空载及以上,短路刚发生即电流不为零时就对电流进行控制,使整个引弧过程中电流值不大于给定峰值,从而达到限制引弧电流的目的。试验证明,该方法引弧时间短、一次性引弧成功率高、稳定性好,为后续CO2焊接稳定可靠的进行提供了有利条件。     

Study on DSP controlled CO2 arc ignition

CO2焊是一种生产效率高、成本低的高效焊接方法.传统的CO2焊采用接触式短路引弧,引弧时间长、成功率不高、稳定性差.分析了影响和提高引弧成功率的因素,并以DSP控制焊机为平台,设计了一种通过限制引弧过程焊接电流来进行引孤的方法.该引孤方法中,焊接过程中的电流为被控制对象,在电压为空载及以上,短路刚发生即电流不为零时就对电流进行控制,使整个引弧过程中电流值不大于给定峰值,从而达到限制引弧电流的目的.试验证明,该方法引孤时间短、一次性引孤成功率高、稳定性好,为后续CO2焊接稳定可靠的进行提供了有利条件.     

脉冲参数对LiCl-NaCl-KCl-TiCl_x熔盐体系沉积钛的影响

以TA3钛板为阳极,纯镍板为阴极,在550℃的LiCl-NaCl-KCl-TiCl_x体系中,研究钛离子阴极电化学行为;同时研究脉冲电解参数对阴极沉积过程的影响。结果表明:阴极上Ti~(3+)的电化学行为是经放电变成Ti~(2+)再进一步被还原成Ti的过程;与恒电流电解相比,脉冲电解更易得到致密沉积产物,且产物结晶度更高、氧氮含量更低;脉冲电解参数对阴极产物沉积形貌有重要影响,电解周期(t_c)为10min时,通断比(n)过大或过小均不利于阴极产物长大,且阴极电流效率低。最佳脉冲电解条件为阴极电流密度0.3A/cm~2、通电周期20min、通断比(n)1,此时获得的阴极产物结晶度高,颗粒尺寸大且产物致密,电流效率达87.4%。     

制钛过程中阴极钙钛矿的形成与阳极溢出气体间的关系

采用FFC剑桥工艺在熔融CaCl₂中电解二氧化钛时,钙钛矿是阴极上不可避免形成的相。本文研究了在制备钛的过程中,阴极钙钛矿的形成与阳极释放气体的关系。结果表明,阴极上相的形成主要有三个阶段,包括钙钛矿的形成、钙钛矿的脱氧及钛的低价氧化物脱氧为TiO、和TiO到Ti的脱氧。尽管分解电压低于CaCl₂,但阴极形成的钙钛矿与从阳极释放的气体密切相关。由于短时间内钙钛矿的形成造成过电压,因而阳极释放出氯气,氯气的量取决于TiO₂和电解过程中产生的不同低价钛的量。当钛的低价氧化物介于Ti₃O₅和TiO₂之间时,在第一脱氧阶段TiO₂和氯的质量比为9：2到46：2。在氯气释放的过程中阳极没有明显的消耗。钙钛矿的形成和Ti₂O的脱氧是在熔融CaCl₂中电解制备钛的主要限制性环节。从TiO₂到Ti的总电流效率是24.07％。目前第一阶段的电流效率在22.37％~44.74％之间,第二阶段在30.18％~37.72％之间。     

Factors Influencing the Direct Electrochemical Reduction of Nb_2O_5 Pellets to Nb Metal in Molten Chloride Salts

Powder compacted and sintered Nb_2O_5 pellets were cathodically polarised against graphite anode in calcium chloride melt at 1173 K to study the influence of various factors on the electrochemical reduction of the oxide.The parameters were;duration and temperature of electrolysis,open porosity of pellets,nature of anode,mode of electrolysis and configuration of the oxide cathode.The experiments were also conducted in KC1,KC1-25 mol%CaCl_2 and NaCl melts to understand the effect of melt composition on the electroreduction.Different Ca-Nb-O and Nb-O intermediates were found in the pellets electrolysed for different durations of time in CaCl_2 melt which eventually reduced to Nb.The current efficiency of the process decreased with increasing duration of electrolysis.Decrease in electrolysis temperature from 1173 to 1073 K led to the decrease in the rate of reduction of the oxide pellets.Pellets with high open porosity reduced faster.Carbon contamination of the melt was relatively less when pyrolytic graphite was used as anode.Of all the melts studied,the reduction was found to be better in calcium chloride melt,that too when alumina crucible was used as container of the melt.     

双膜三室电沉积金属锰联产EMD的离子传输过程

针对传统单槽电解金属锰或二氧化锰存在能耗高、资源利用率低、环境污染严重等问题,提出双膜三室电解法实现阴极电沉积锰同时阳极联产电解二氧化锰,中隔室电化学再生硫酸。通过分析各隔室离子浓度变化,探究双膜三室电解法技术可行性,并对比三种离子交换膜对电沉积效果的影响。结果表明:双膜三室电解法电沉积金属锰同时联产电解二氧化锰可以实现,并且阴极电流效率可达80%以上,阳极电流效率可达60%以上,中隔室酸回收率高于65%;与Ionsep-HC、LANRAN-AM相比,TRJM-10W均相膜槽压最低,电解12 h后,阴极电流效率为86.25%,阳极电流效率为70.6%,中隔室酸回收率可达73.08%,但阴极液pH增幅最大,中间液Mn^2+浓度最高。     

TiO2电极中O2-的形成及迁移过程研究

采用融盐电解法,在900℃熔盐CaCl2中以烧结TiO2为阴极,石墨棒为阳极制备金属钛。研究O2-在TiO2电极中的形成及其迁移过程。结果表明:实验高温促使TiO2结构中氧空位的形成及O2-产生;O2-通过氧空位从阴极内部迁移到表面,钛酸钙是电解过程的必然中间产物,阴极表面生成的致密金属层钛阻碍O2-从阴极内部往表面的迁移。     

氧化物与氟化物的加入对氯化物熔盐体系电解制备Mg-La合金的影响

以石墨坩埚为阳极,钨棒为阴极,在750℃的MgCl2-LaCl3-KCl熔盐体系中,采用恒电位电解制备Mg—La合金。研究氧化物和氟化物的加入对电解的影响,通过XRD对部分Mg-La合金产物和电解渣进行表征。随着MgO或La203在熔盐电解质中加入量的增加,电流效率和所得合金产物的质量都减小,表明MgO和La203参与电解质中的反应。在加入的氧化物质量相同的情况下,MgO与La2O3相比对电流效率和合金产物质量的影响更明显。XRD研究结果表明：MgO或La2O3加入到熔盐电解质中后,有LaOCl生成,LaOCl电解渣的生成是氧化物对电解消极影响的主要原因。在本实验的的熔盐体系中,CaF2的加入对消除MgO的负面影响没有积极意义,这可能和镧化合物在熔盐电解质中的复杂反应有关。     

Preparation of Ti by direct electrochemical reduction of solid TiO2 and its reaction mechanism

An electrochemical method for the direct reduction of solid TiO2 was introduced, in which the oxygen is ionized, dissolved in the molten salt and discharged at the anode, leaving pure titanium at the cathode. Titanium was prepared from TiO2 via molten salt electrolysis, and experimental process was studied in detail. The reductive products of TiO2 were analyzed through XRD, SEM, XPS and so on. The results indicate that titanium with high purity is obtained by the electrochemical reduction. Through thermogravimetric analysis of molten CaCl2, it is shown that the dehydration of CaCl2 has to be strictly controlled to eliminate hydrolysis. The cyclic voltammetry studies on the TiO2 cathode electrochemical system show that the reduction of TiO2 is conducted step by step, from exterior to interior and from high-valence to low-valence. The conclusions were also confirmed by study on thermodynamics analysis. The current efficiency can be improved by loading different voltages in different stages.     

阳极导电材料对铁钨锡合金粉电解铁的影响

研究阳极导电材料碳素钢、316L不锈钢、铅钙合金、石墨、钛涂钌板、钛板和铜板在硫酸盐和氯盐体系中对铁钨锡合金粉电解铁的影响。结果表明:电解24 h,上述阳极导电材料在氯盐中的阴极电流效率为90%、90%、66%、66%、54%、49%、33%,在硫酸盐中的阴极电流效率为90%、87%、82%、81%、73%、68%、54%。槽电压均逐渐升高,在氯盐体系中,石墨、铅钙合金、钛涂钌板和钛板作阳极导电材料时,电解液pH逐渐降低;碳素钢、316L不锈钢和铜板作阳极导电材料时,电解液pH逐渐升高。在硫酸盐体系中,铜板和碳素钢作阳极导电材料时,电解液pH基本不变;316L不锈钢作阳极导电材料时,pH逐渐升高;铅钙合金、石墨和钛板作阳极导电材料时,pH先升高后降低。基于槽电压、阴极电流效率,选择适宜的电解体系为硫酸盐体系,该体系中适宜的阳极导电材料为铅钙合金。     

Research on Electrochemical Behavior of Ti-Ir-Ru Anode Coating in Electrolytic Antifouling of Flowing Brine

By electrochemical techniques, the electrochemical behavior of Ti-Ir-Ru anode coating was studied in electrolytic antifouling of flowing brine. The effect of the brine’s flow rate and the anode/cathode interval on electrolysis was also considered. The results indicated that the brine’s flow rate had remarkable effect on the characteristic of the Ti-Ir-Ru anode. The electrolytic voltage and the evolved active chlorine concentration of Ti-Ir-Ru anode increased with increasing flow rate. Its energy consumption displayed the same variable rule as the electrolytic voltage. But the current density reduced with increasing flow rate. Increasing flow rate favored attenuation of the thickness of mass-transfer control layer and expediting the oxygen’s mass transfer, which accelerated the cathode polarization and the oxygen absorption reaction. The maximal current efficiency for Ti-Ir-Ru anode was obtained at the anode/cathode interval of 5 cm with the current density of 60 mA/cm². At this point, Ti-Ir-Ru anode also had relatively low electrolytic voltage. The above operating procedure was ideal for electrolyzing flowing brine using Ti-Ir-Ru anode coating.     

Electrowinning rare-earth and uranium metals from their oxides

A discussion of the technique developed by the Federal Bureau of Mines: the electrolysis of a fluoride melt containing the oxide of the metal in question, depositing the molten metal at the cathode, and evolving carbon monoxide at the anode.     

Preparation and characterization of tungsten nanopowders from WC scrap in molten salts

Tungsten carbide (WC) scrap was used as a consumable anode to prepare tungsten powder in NaCl–KCl melt at 1023 K for the first time. The electrolysis process was investigated. Results showed that the tungsten component in WC anode was dissolved as W^2 + into the NaCl–KCl melt. The cathode reaction was controlled by the diffusion of tungsten ions. The effect of electrolysis parameters, including the anode–cathode distance, cathode current density and different electrolysis ways (galvanostatic and potentiostatic electrolysis), on the purity and grain size of the cathode deposits was studied. It showed that a large anode–cathode distance was beneficial to the formation of pure tungsten powder at the cathode. With increasing the cathode current density, the tungsten grain size first decreased and then increased. When the cathode current density was 0.125 A cm^− 2, tungsten powder with a diameter of smaller than 100 nm was obtained. Deposits prepared through galvanostatic and potentiostatic electrolysis was compared in the end.