Study on Mechanism of Electrodeposition of Y(Ⅲ) in Molten LiF-YF_3-Y_2O_3 by Cyclic Voltammetry

１ＩｎｔｒｏｄｕｃｔｉｏｎＴｈｅｓｔｕｄｙｏｎｔｈｅｅｌｅｃｔｒｏｃｈｅｍｉｃａｌｂｅｈａｖｉｏｒｏｆｒａｒｅｅａｒｔｈｅｌｅｍｅｎｔｓｉｎｍｏｌｔｅｎｃｈｌｏｒｉｄｅｏｒｆｌｕｏｒｉｄｅｉｓｏｆｇｒｅａｔｉｍｐｏｒｔａｎｃｅｔｏｔｈｅｐｒｅｐａｒ...     

Cathodic Process of Ti(Ⅳ) in Molten LiF-NaF

ＣａｔｈｏｄｉｃＰｒｏｃｅｓｓｏｆＴｉ（Ⅳ）ｉｎＭｏｌｔｅｎＬｉＦ－ＮａＦＳｈｉＱｉｎｇｒｏｎｇａｎｄＤｕａｎＳｈｕｚｈｅｎ石青荣，段淑贞（ＵｎｉｖｅｒｓｉｔｙｏｆＳｃｉｅｎｃｅａｎｄＴｅｃｈｎｏｌｏｇｙＢｅｉｊｉｎｇ，Ｂｅｉｊｉｎｇ１０００８３，Ｃ...     

High-temperature Reference Electrodes Used in Molten Fluorides

The thermodynamic and dynamic behaviour of Ni~(2+)|Ni couple in FLINAK melt is investigated by us-ing EMF measurement and micropolarization method.The couple shows the Nernstian reversibility and alarge exchange current density(6 mA·cm~(-2)).A single crystal LaF_3 which is a fluoride ion conductor usedas a membrane of the Ni~(2+)|Ni couple reference electrode is reliable in FLINAK melts at 973 K.The poten-tial of LaF_3 membrane reference electrode is constant within±2 mV.The boron nitride used as a saltbridge was not good in FLINAK melts.The platinum electrode is studied by using micropolarization.Theequilibrium potential of Pt electrode is dependent on the absorption and the electrochemical reaction.Thepotential is stable for a constant composition at constant temperature.     

电子束横焊3mm纯铌板的熔池形态研究

高能加速器纯铌超导腔内导体,要求加工后的外表面光滑平整,以保证其特殊性能的要求。在电子束平焊全熔透情况下,超导腔焊缝正面在反冲压力作用下易发生未焊满及塌陷等缺陷。本文采用合适的电子束横焊工艺参数,得到了符合工艺要求的正面余高焊缝。并且建立了3mm厚的高纯铌板横焊过程的二维模型,针对不同的焊接参数分别设计了不同尺寸和形状的熔池,结合VOF算法,模拟焊接熔池里液态金属自由表面存在状态,得到了不同焊接参数下熔池的演变过程。实验结果显示,焊接熔宽随焊接线能量的升高而增大,数值模拟与实验结果较吻合。     

LiF-NaF-KF-K_2TiF_6熔盐中Ti(IV)的电化学还原及电结晶过程

采用循环伏安法和计时电流法研究了700℃时LiF-NaF-KF-K2TiF6熔盐中Ti(IV)在铂电极上阴极电化学还原机理以及电结晶过程。结果表明:Ti(IV)的电化学还原机理为三步骤电荷传递反应:Ti(IV)+e→Ti(III);Ti(III)+2e→Ti(I);Ti(I)+e→Ti(0),且阴极过程可逆;电结晶过程为瞬时形核。     

内蒙古发现大型富钛矿床

采用循环伏安法和计时电流法研究了700℃时LiF-NaF-KF-K2TiF6熔盐中Ti（Ⅳ）在铂电极上阴极电化学还原机理以及电结晶过程。结果表明：Ti（Ⅳ）的电化学还原机理为三步骤电荷传递反应：Ti（Ⅳ）＋e→Ti（Ⅲ）；Ti（Ⅲ）＋2e→Ti（Ⅰ）；Ti（Ⅰ）＋e→Ti（0），且阴极过程可逆：电结晶过程为瞬时形核。     

CaCl2熔盐中自烧结电解制备粉体Cr3C2及其机制

以氧化铬和石墨粉为原料,采用聚乙烯醇粘接,压制成阴极片,以光谱石墨棒为阳极,在800℃氯化钙熔盐中,恒电压3.2V下,阴极片自烧结电解制备碳化铬.采用XRD、SEM和EDX对样品进行表征.结果表明:粘接的阴极片满足熔盐电解的强度要求,通过熔盐电解过程的自烧结阴极片有效地粘接在一起,并制备出具有良好烧结性能、组分单一的Cr3C2粉体.该法制备Cr3C2的电流效率不低于37.3％.采用恒电位电解法和循环伏安法对电解机制的研究表明,熔盐电解制备Cr3C2的反应机制为:Cr2O3+e→Cr+O2-,Cr+C→Cr3C2两步完成.     

CaCl2熔盐中自烧结电解制备碳化钒及其机制

以氧化钒和石墨粉为原料,采用聚乙烯醇粘接制备阴极片。以光谱石墨棒为阳极,阴极片在800℃氯化钙熔盐中自烧结,恒电压3.2 V下,通过熔盐电解法制备碳化钒。结果表明:粘接的阴极片强度满足熔盐电解的要求,通过熔盐电解,不仅完成阴极片自烧结的过程,并制备出组分单一的碳化钒粉体。通过不同电解阶段产物的物相及循环伏安曲线对反应机制进行研究的结果表明:碳化钒的形成过程为3步反应:V5++(C)→V3++(C)→V2++(C)→V(Cx)。     

Electrochemical Preparation of Mg-Li-A1-Er Alloys by Co-reduction in Molten Chloride

The electrochemical behavior of Mg,Li,Al and Er were investigated by electrochemical techniques in LiClKCl-MgCl2-AlCl3-ErCl3 melts at 823 K.The cyclic voltammetry and chronopotentiometry indicated that the co-reduction of Mg,Li,Al and Er occurs at current densities more negative than-0.89 A.cm-2.Er(III) under-potential deposited on pre-reduced Al electrode formed Al-RE alloys.X-ray diffraction(XRD) results indicated that Mg17Al12,Al2Er,Al2Er3 and Al4Li9 phases were prepared by galvanostatic electrolysis.ICP analyses of samples showed that lithium and aluminum contents of Mg-Li-Al-Er alloys could be controlled by concentration of AlCl3 and cathodic current density.     

Electrochemical boriding of titanium for improved mechanical properties

In this study, we introduce a rapid boriding technique that can produce very thick titanium diboride (TiB₂) layers on titanium substrates. We also discuss the effects of process duration on boride layer thickness, chemistry and, morphology. In our experiments, the boriding of commercial purity titanium (CP-Ti) substrates was carried out in an electrochemical cell in which we used a mixture of sodium tetraborate and sodium carbonate as the base ingredients of molten electrolyte at 950 °C and at current density of 300 mA/cm². The titanium test pieces were attached to the cathode holder of the electrochemical cell while a graphite crucible served as the anode. Both TiB and TiB₂ phases were detected by X-ray diffraction method even after 5 min of treatment. Scanning electron microscopy (SEM) images verified that the production of 4.5 µm thick TiB₂ layers was feasible after boriding for an hour. The boride layers consisted of a homogeneous TiB₂ phase on the top and TiB whiskers toward the substrate. The micro-indentation studies indicated that the layer on top has hardness values as high as 40 GPa. The main advantages of this technique are its ability to produce very thick and hard TiB₂ quickly and to create no gaseous emissions or solid wastes during or after the treatment.     

A Reliable Reference Electrode in Molten Carbonate and Its Applications

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LiF─NaF─K2TiF6熔盐中Ti(Ⅳ)的电化学还原

用循环伏安法和卷积技术研究了LiF-NaF低共熔体中,以K2TiF6形式加入的Ti(Ⅳ)在铂电极上阴极还原机理,计算了各还原步骤所传递的电子数。结果表明,Ti(Ⅳ)的电化学还原机理为耦联均相歧化反应的三步骤电荷传递反应。     

Investigation on Preparation of Tb2Fe17 by Direct Electrochemical Reduction of Tb4O7-Fe2O3 Pellet in Molten Calcium Chloride

在CaCl2熔盐中直接电化学还原固态Tb4O7与Fe2O3(Tb∶Fe=2∶17)的混合 粉末, 一步制得了金属间化合物Tb2Fe17. 结合混合氧化物烧结片在850 ℃的CaCl2 熔盐中3.1 V电解不同时间段产物的成分分析探讨了还原机理：Fe2O3优先还原 成金属Fe, 随后Tb4O7粉末在Fe上还原逐渐生成Tb2Fe17. 采用不锈钢筛网电极 循环伏安法证明了Tb4O7在Fe上的欠电位还原.     

氟化物熔盐中快速电脱氧制备金属钒及其机理

以偏钒酸铵为原料,采用"煤气还原+原位烧结"工艺制备高活性V_2O_3阴极片,在氟化物体系熔盐中实现了快速电脱氧制备金属钒,并通过测定循环伏安曲线结合恒电位电解实验,研究了电解过程的反应机理。结果表明:V_2O_3在氟化物熔盐中可实现快速电脱氧,电解4 h后所得金属钒的氧含量降至0.218%(质量分数,下同);V_2O_3阴极电脱氧产生的O~(2-)在脱氧反应区可原位生成铝氧氟络合离子并进一步产生金属铝,从而引发阴极的铝热还原反应,导致V_2O_3熔盐电脱氧过程同时存在直接电还原反应和铝热还原反应,其中后者起着关键的加速作用;在熔盐中添加适量Al_2O_3可强化V_2O_3电脱氧过程,在其他条件不变的情况下电脱氧时间可缩短至3 h。     

Pt掺杂W-Ru-Se纳米簇合物电催化氧还原性能

以低温合成法制备了Pt掺杂的W-Ru-Se纳米簇合物,并应用旋转圆盘电极线性电位扫描法测试其对氧还原反应的电催化性能,采用XRD、EDS、XPS表征结构及表面组成。结果表明,掺杂Pt后W-Ru-Se对氧还原反应活性明显提高,尤其以掺杂5%Pt(质量分数, 下同)的W-Ru-Se活性提高最为显著,在0.5 mol?L-1 H2SO4中Pt-W-Ru-Se (5%Pt)的氧还原起始电位为0.25 V,峰电流密度为310 mA?mg-1,是W-Ru-Se峰电流密度的2.2倍,活性接近于Pt/C。电解液中存在甲醇时,Pt-W-Ru-Se (5%Pt)的活性和抗甲醇性优于Pt/C     

Electrochemical decomposition of SiO2 pellets to form silicon in molten salts

Direct electrochemical reduction of porous SiO₂ pellets in molten CaCl₂ salt and CaCl₂-NaCl salt mixture was investigated by applying 2.8 V potential. The study focused on the effects of temperature, particle size of SiO₂ powder starting material and the behavior of cathode contacting materials during electrochemical reduction process. The starting materials and the electrolysis products were characterized by X-ray diffraction analysis and scanning electron microscopy mainly. The studies showed that smaller particle sizes and higher temperatures had slightly positive effects in increasing the reduction rate within the ranges covered in this study. The results were interpreted from variations of current and accumulative electrical charge that passed through the cell as a function of duration of electrochemical reduction under different conditions. Microstructures and compositions of the reduced pellets were used to infer that electrochemical reduction of SiO₂ in molten salts may become a method to produce silicon that could be used in solar energy utilization. Furthermore, X-ray diffraction analysis results indicated that the silicon produced at the cathode reacts with contacting materials; nickel, and iron in stainless steel to form Ni-Si and Fe-Si compounds due to very reactive nature of silicon especially at high temperatures.     

Characteristics of an electrochemical reduction of Ta2O5 for the preparation of metallic tantalum in a LiCl–Li2O molten salt

The electrochemical reduction of Ta₂O₅ in a LiCl–Li₂O molten salt system has been carried out in an electrolytic cell with an integrated cathode assembly. During the electrochemical run, Ta₂O₅ reacts chemically with Li₂O to form LiTaO₃. The chronopotentiometry method was used to prepare the metallic tantalum from Ta₂O₅. The electrolysis of Li₂O and the reduction of Ta₂O₅ and/or LiTaO₃ take place simultaneously at the cathode part of an electrolysis cell. The recycle of Li₂O by an O²⁻ diffusion occurs in the cell. The results suggest that the metallic tantalum is prepared successfully by an electrochemical reduction in the LiCl–Li₂O molten salt.     

CaCl2熔盐中直接电化学还原制备铽-镝-铁合金机制

提出了一种梯度氮化法制备出低阻、高稳定性的a-Ta(N)/TaN双层Cu扩散阻挡层.该方法有效地避免了异质元素的引入和高N含量导致的高电阻率.用四点探针(FPP)、X射线衍射(XRD)、高分辨透射电子显微镜(HRTEM)进行薄膜电性能和结构的表征.分析结果表明,梯度氮化工艺能调控金属Ta膜的相结构和金属Ta中的N原子浓度,从而获得低阻a-Ta(N)/TaN双层Cu扩散阻挡层结构.600℃高温老化退火的实验结果进一步证明此结构具有高的热稳定性.     

CaCl2熔盐中直接电化学还原制备铽-镝-铁合金机制

CaCl2熔盐为电解质,石墨棒作辅助电极、铂片作参比电极,以定组成Tb2O3、Dy2O3、Fe2O3(1:1:2)均匀混合氧化物粉体制成工作电极,利用循环伏安法和计时电流法对电化学还原制备铽-镝-铁合金的过程进行研究,并以石墨棒为阳极,混合氧化物烧结片为阴极,采用恒电位电解法对电化学测试结果进行检验并利用XRD分析电解产物的组成。结果表明,CaCl2熔盐中电化学还原可以制备出铽-镝-铁合金;混合氧化物电化学还原制备铽镝铁合金是不可逆过程,合金生成按照Fe、DyFe5、TbFe3、DyFe2和TbFe2的先后顺序5步完成;电化学还原过程是在Fe|Fe2O3|CaCl2、Tb-Dy-Fe|Tb2O3-Dy2O3|CaCl2两个三相界线上先后进行。     

TiO2电化学还原法提取金属钛的阴极制备工艺

研究TiO2电化学还原法提取金属钛的阴极制备参数——烧结温度和烧结时间。采用SEM、EDS等方法研究烧结温度、烧结时间对TiO2阴极微观结构、孔隙率的影响及不同烧结条件下TiO2阴极电解产物结构和氧含量的变化。结果表明：烧结条件主要影响电极的粒度大小、孔隙尺寸和孔隙分布：在较高温度下烧结较长时间获得的电极片粒度较粗,而孔隙率的变化比较复杂。电极的颗粒尺寸、孔隙率直接影响脱氧率：粒度较小的电极在试验条件下可被充分还原;电极中的开孔和闭孔都有利于电化学还原过程的进行。在1000~1100 °C下烧结4 h获得的TiO2阴极脱氧效果较好。