钨的电化学还原机理及结晶过程研究

利用循环伏安法和计时电位法研究了NaCl-KCl-NaF-Na_2WO_4熔盐体系电沉积物的电化学还原机理,并利用计时电流法对钨的结晶过程进行研究。结果表明,NaCl-KCl-NaF-Na_2WO_4熔盐体系电沉积钨的电极过程为由电荷迁移速度和扩散速度混合控制的准可逆过程,钨的还原机理为0.5W_2O_7~(2-)+6e→W+3.5O~(2-)。钨的电结晶过程符合半球形三维晶核的瞬间成核过程。     

钛离子在低碳钢电极上电结晶形核过程的研究

应用循环伏安法及计时电流法研究了低价钛离子在低碳电极上电结晶形核过程的规律。研究表明，在ＬｉＣｌ－ＫＣｌ低共晶体系中，当温度为７２３～７８３Ｋ、低价钛离子浓度为１．０４ｗｔ％～８．２８ｗｔ％时，钛在低碳钢电极上以纯钛形式析出时存在电结晶形核过程，在电结晶形核过程中初始晶核产生的数量起主导作用，晶核长大的过程中伴随着新核的产生，晶核长大过程符合半球形三维成核长大模型，受扩散控制。在同一浓度下，钛的晶     

KCl-NaCl-NaF-SiO_2熔盐体系中硅离子的还原机理研究

在KCl-NaCl-NaF-SiO2熔盐体系中,以铂丝为参比电极、研究电极,高纯石墨坩埚为辅助电极,采用循环伏安法和计时电位法对硅离子的还原机理进行了研究,结果表明此电化学反应为扩散控制的不可逆电极过程;求得硅离子在熔盐中的扩散系数D=1.33×10-3cm2/s(CSi4+=1.21×10-4mol/cm3,T=1 073 K)。     

H_2SO_4-NH_4F-SbF_3体系中锑的电化学成核机理

采用循环伏安法、恒电位阶跃法和SEM技术研究了H2SO4-NH4F-SbF3体系中锑的电结晶机理。结果表明,锑电化学成核机理与电位有关,其电结晶按照包含成核阶段的螺旋位错生长机理进行。     

Cr^3＋电镀溶液中Cr电结晶机理

用计时电流法研究了Ｃｒ＾３＋镀液中Ｃｒ在玻璃碳电极上的电结晶机理，并根据理论导出瞬时成核和连续成核的理论模型，实验结果和理论模型的分析表明，Ｃｒ在玻璃碳电极上的沉积按瞬时成核和三维生长机理进行，其法向生长速度常数Ｋ′和混合速度常数Ｋ＾２Ｎ０随过电位的增大而明显增大。     

熔盐电沉积硅的基础研究

在FLINAK-Na2SiF6熔盐体系中,以Pt为参比电极、硅钢片为工作电极、石墨为辅助电极,在750℃下,用循环伏安法和计时电位法对Si4+的电化学反应机理和扩散系数进行了研究。结果表明:该熔盐体系进行电沉积硅是可行的,该体系中硅离子的还原为扩散控制的可逆电极过程,且产物不可溶;整个还原过程为Si4++4e→Si0;该熔盐体系中阴极电位不应负于-2V,否则会有Na沉积出来,从而影响沉积层质量;Si4+的扩散系数为:D=5 42×10-11m2/s(C=2 58×103mol/m3)。     

完善生产微碳铬铁"堆底法"工艺探讨

通过“热兑法”生产实践,对“堆底法”生产微碳铬铁的增碳机理有了新的认识,“热兑法”是在炉外加硅铬合金,其脱硅反应没有电极参与,增碳少,可炼出含C≤0.03％的微碳铬铁,品级率〉90％,而“堆底法”在炉内加硅铬合金,脱硅反应有电极参与,增碳严重,因此提出“堆底法”的改善措施,效果较好。     

冰晶石基熔融电解质中SiO_2的电化学还原

以钨丝为工作电极研究了冰晶石基熔融盐中SiO_2的电化学还原。根据循环伏安法和计时电位法的测定结果,硅的沉积机理为包含前置均相化学反应的4电子可逆传递过程。     

加压氢还原沉析钴和镍的动力学

<正> 一、电结晶过程动力学 H_2沉析Co或Ni金属粉末的过程是电结晶过程。在非均质体系中(硫酸铵介质),此过程实际上包括金属的还原,晶核生成和晶核长大等三个步骤。     

铜电解液净化过程中黑铜粉的形成机理

对电解法制备黑铜粉的机理进行研究,考察了铜离子浓度、砷离子浓度对黑铜粉形成的影响。采用扫描电镜观察阴极产物的微观形貌,利用循环伏安曲线、恒电位阶跃暂态曲线研究玻碳电极表面黑铜粉的形核过程。研究表明,在低浓度铜溶液中,随着砷浓度的增大,沉积层逐渐从疏松块状结构变为疏松粉末状结构;铜在玻碳电极上的电结晶遵循液相传质控制的三维生长机理,随着As"浓度增加,形核速率增大;在低浓度铜溶液中(3 g/L),As~(3+)的加入大大促进了晶核的形成,使晶粒过于细化,从而形成了黑铜粉。     

CaO-SiO2-Na2O-CaF2-Al2O3-MgO渣系的结晶温度

通过差热分析仪测定了CaO-SiO2—Na2O-CaF2—Al2O3—MgO系连铸结晶器保护渣的结晶温度。在本实验渣系条件下，连铸保护渣的结晶温度随着渣中CaO／SiO2值、Na2CO3含量、CaF2含量和MgO含量的增加而升高，随着渣中Al2O3含量的增加而降低。化学成分通过改变粘度，来影响晶核形成速度和晶体成长速度，从而决定了连铸保护渣的结晶性能。结晶温度随着保护渣粘度的降低而升高。     

Crystallization Behavior in Fluoride-Free Mold Fluxes Containing TiO2/ZrO2

  The time temperature transformation (TTT) diagrams of fluoride free mold fluxes containing TiO2/ZrO2 were constructed through the confocal scanning laser microscope (CSLM) technique. It was found that the crystallization temperature of F free mold fluxes containing TiO2 or ZrO2 increases, while incubation time decreases with increasing basicity. The crystallization tendency increases with the zirconia addition in slag melt, as it may be thought that the addition solubility is limited in molten slag and the solid particles act as heterogeneous nucleation sites. Three types of crystal morphologies were observed, corresponding to different crystallization mechanisms. CaSiO3 and Ca3Si2O7 precipitate in the slag with low basicity, and Ca2SiO4 was formed with increasing basicity. The addition of TiO2 promotes the precipitation of CaTiO3. The logarithm of crystal growth rate increased with increasing isothermal temperature, suggesting that the crystal/melt interface reaction is the controlling step in the present experiment.     

非晶La2O3薄膜的阻变存储性能研究

采用脉冲激光技术在Pt/Ti/SiO2/Si衬底上沉积了非晶La2O3薄膜,制作并分析了Pt/La2O3/Pt堆栈层的直流电压与脉冲电压诱导的电阻转变特性。Pt/La2O3/Pt器件单元表现出了稳定的双极性电阻转变,其高低阻态比大于两个数量级。经过大于1.8×106s的读电压,高低阻态的电阻值没有明显的变化,表现出了良好的数据保持能力。通过研究高低阻态的电流电压关系、电阻值与器件面积的关系,揭示了导电细丝的形成和破灭机制是导致Pt/La2O3/Pt器件发生电阻转变现象的主要原因。     

The crystallization kinetics of sodalites grown by the hydrothermal transformation of kaolinite studied by 29Si MAS NMR

The hydrothermal transformation of kaolinite to basic sodalite Na8[AlSiO4]6 (OH.H2O)2 and hydroxoborate sodalite Na8[AlSiO4]6 [B(OH)4]2 has been investigated at different temperatures (353 and 473 K). In the early stage of the reactions, the crystallization kinetics was studied by X-ray powder diffraction, thermogravimetry, IR spectroscopy and 29Si MAS NMR spectroscopy. Besides the crystallization of the sodalites, no further intermediate phases were formed. MAS NMR of the 29Si nucleus has been found to be a versatile tool to follow the progress of reactions from the signal ratio of the initial material and the crystallization product because the differences in chemical shifts result in well-separated signals. From these measurements, the growth rates of the sodalites could be determined quantitatively even for the very early stages of crystallization. It was found that sodium carbonate impurities in the NaOH solution used for the synthesis has an important influence on the reaction kinetics.     

Electrochemical Behavior of Silicon in the (NaCl-KCl-NaF-SiO<Subscript>2</Subscript>) Molten Salt

The electrochemical behavior of silicon was investigated in a molten salts system including saturation silicon dioxide. Silicon was electrodeposited and MoSi₂ was formed on the employed molybdenum working electrode by the diffusivities of silicon and the substrate metals. Transient electrochemical techniques such as cyclic voltammetry and chronoamperometry were used to study the reaction mechanism at the molybdenum electrode. Cyclic voltammograms showed the possibility of electrodeposition of Si at −0.64 V versus Pt reference electrode in a NaCl-KCl-NaF-SiO₂ system at 1073 K (800 °C). The electrodeposition of Si is single-step charge-transfer process and the cathode process is irreversible. Chronoamperometry studies indicated that electrocrystallization of Si is controlled by progressive nucleation with a three-dimensional growth mechanism.     

The Effect of P2O5 on the Crystallization Behaviors of Ti-Bearing Blast Furnace Slags Using Single Hot Thermocouple Technique

The present paper investigates how the P₂O₅ addition influences the crystallization behaviors of Ti-bearing blast furnace (Ti-BF) slags with different basicity using Single Hot Thermocouple Technique. It was found that the basicity showed a significant effect on the crystallization behaviors of the Ti-BF slags, and the trend of formation of the rod-shape crystal decreased while the trend of formation of dendrite crystal increased with increasing basicity. The addition of P₂O₅ was found to promote the formation of rod-shape crystal. The basicity and crystallization temperature that the rod-shape crystal could be formed increased, while the incubation time of formation of the rod-shape crystal decreased with increasing P₂O₅ content. Scanning electron microscope equipped with energy-dispersive X-ray spectroscope and X-ray diffraction were employed to observe the morphology and determine the crystalline phase of the Ti-enriched crystals. The results indicated that the rod-shape crystal was rutile. The kinetics of the formation of rutile was studied, and the mechanism of crystallization and growth was further discussed. The results indicated that the crystallization of rutile was one-dimensional interface-controlled growth, and the nucleation rate varied with the holding time.     

Co68.5Fe4Si10B17.5非晶合金晶化动力学行为研究

采用示差热分析(DSC)研究了旋铸急冷法在大气环境中制备出的Co68.5Fe4Si10B17.5非晶合金的非等温晶化的动力学行为。研究发现:在连续加热条件下,随升温速率的加快,合金的特征温度Tg,Tx,Tp均向高温区移动。当分别采用晶化开始温度和峰值温度时,所得非晶合金的激活能并不是稳定值。用Doyle-Ozawa方法计算出的激活能值比Kissinger法计算出的激活能值要大。非晶态Co68.5Fe4Si10B17.5合金的晶化百分比与退火温度和退火时间的关系曲线均呈S型。随加热速度的增加,非晶合金的晶化百分比与温度的关系曲线向高温处移动。     

升温速率对钛渣赤泥粉煤灰微晶玻璃析晶的影响

以钛渣代替二氧化钛为晶核剂制备赤泥粉煤灰微晶玻璃,对其微观形貌进行表征,并考察钛渣添加量对微晶玻璃的析晶动力学参数和微观形貌的影响。结果表明,随着钛渣添加量的增多,析晶活化能呈逐渐减小的趋势,晶化指数呈逐渐增大趋势。当钛渣的添加量为6.6%时,活化能降低为581.45kJ/mol,晶化指数为0.8,出现了分布均匀的晶核,晶粒明显长大,析晶效果较好。     

振动激发金属液原位形核的物理模拟

为了提高铸坯的等轴晶率、细化凝固组织,以30%氯化铵水溶液和铁素体不锈钢为研究对象,分别进行了物理模拟和浇注实验.结果发现:当一种带有冷却结构和高频振动的晶核发射器棒体插入氯化铵溶液时,在棒体表面将迅速形成大量的细小晶粒.这些晶粒在振动作用下被连续不断地弹射至溶液中,成为凝固过程中等轴晶的形核核心;晶核发射器的冷却强度越大、振动频率越高,则形成的晶粒数量越多且粒径越小;铁素体不锈钢液经振动激发形核处理后,凝固组织中的等轴晶率超过了80%.