【作者】 李运刚；

【导师】 翟玉春；

【作者基本信息】 东北大学 ， 冶金物理化学， 2005， 博士

【摘要】 金属钨具有极高的熔点、强度和硬度以及良好的化学稳定性，但由于其生产成本高、脆性高、难于进行常规的机械加工使它的应用受到了极大限制。显然，为了降低金属钨的生产费用，扩大金属钨的应用范围，研究生产金属钨的新方法、研究金属钨与其他常用金属材料形成的梯度材料的制备技术是非常必要的。本文就ZnO—WO₃—Na₂WO₄（简写为ZNWNAO）体系中用电化学方法制备致密金属钨以及Fe—W梯度材料的基础进行了详细的研究。 采用差热分析法、热重法、X—射线衍射分析法、平行四电极法、旋转柱体法和拉筒法首次分别对ZNWNAO体系的初晶温度、热失重、熔盐的结构、电导率、粘度特性和表面张力进行了研究。结果表明：在研究的组成范围内，体系初晶温度小于750℃；体系熔融状态失重很少，对体系的组成基本不产生影响；体系固态下主要物相为Na₂W₂O₇、Na_2.4Zn_0.8W₂O₈和Na₂WO₄，各相的多少与原始组成中的Na₂WO₄、WO₃、ZnO含量多少有关；体系的电导率与温度的关系遵从熔盐电导率与温度关系的一般规律；体系各组元对电导率的影响规律受X_ZnO与X_WO3比值的控制，并且，在Na₂WO₄含量一定的条件下，X_ZnO与X_WO3比值为1时体系的电导率最大；体系的粘度与温度的关系遵循熔盐粘度与温度关系的一般规律；在ZnO和WO₃摩尔比小于1的范围内，用Na₂WO₄逐步替代WO₃使粘度减小，在大于1的范围内，粘度增大；体系氧化锌含量增多，粘度增大；体系的表面张力与温度具有良好的线性关系，在800～900℃范围内，随着温度的升高体系的表面张力降低；氧化锌含量一定时，三氧化钨含量的增加使体系表面张力减小；三氧化钨含量一定时，增加氧化锌含量使体系表面张力增大。 采用循环伏安法、计时电位法和计时电流法对ZNWNAO体系的电化学反应机理、电结晶过程进行了详细研究。认为：钨的电化学反应为一步得6个电子的准可逆反应；Zn²⁺的放电比WO₄^2-更困难，所对应的阴极还原电位比WO₄^2-负约130mV；在920℃下测定的含钨离子的扩散系数为4.77×10^-8cm²．s^-1。；钨的电结晶过程为半球形三维晶核的连续形核过程。 研究了熔盐的组成、电流密度、电流波形、电沉积时间、温度等因素对沉积物的物理形态影响；研究了电流密度、电沉积温度等因素对电沉积钨电流效率的影响。认为在ZNWNAO熔盐体系中电沉积得到致密钨的最佳工艺条件是：熔盐组成为更多还原

【Abstract】 Tungsten has very high melting point, strength, hardness and well-known chemical stability. Because of its high production costs, brittleness and bad machining property, the applied range of tungsten is confined extremely. In order to decrease the production costs of tungsten and widen the application area of tungsten, it is necessary that new methods of production tungsten and preparation technology of Fe-W gradient material should be researched. In the present work, the preparation technology of dense tungsten and Fe-W gradient material are studied by electrochemical method in ZnO-WO₃-Na₂WO₄ system.Differential thermal analysis, TGA, XRD, four parallel electrode method, rotating cylinder method as well as slide method have been appli（?）d to investigate respectively primary crystallization temperature, weight loss at high temperature, structure, conductivity, viscosity and surface tension in ZnO-WO₃-Na₂WO₄ system. It was found that primary crystallization temperature of the system is less than 750℃ in measuring range. Weight loss of the system at molten state is very small. The main phases in melts are Na₂W₂O₇, Na_2.4Zn_0.8W₂O₈ and Na₂WO₄. The relation between conductivity and temperature follows general rule of conductivity in molten salt. The conductivity of the system in melts is influenced by ratio of X_ZnO to X_WO3 and when concentration of Na₂WO₄ is invariable, the conductivity is maximal at the ratio being 1. In the range of the ratio of X_ZnO to X_WO3 being less than 1, substituting Na₂WO₄ for WO₃ decreases the viscosity of the system and being greater than 1, increases the viscosity. The surface tension of the system is reduced with temperature rise.Cyclic voltammetry, chronopotentiometry as well as chronoamperometry have applied to investigate the electrochemical mechanism of tungsten deposition in ZnO-WO₃-Na₂WO₄ system. It was found that the electrode process is a 6-electron transferred quasi-reversible process. The diffusion coefficient of tungsten ion was measured as 4.77 ×10^-7 cm².s^-1 at 920℃. The electrodeposition of tungsten is a process of three-dimensional progressive nucleation.The influence of composition, current density, current waveform, electrodepositing time and temperature on coating and current efficiency were researched. The optimal更多还原