低温燃烧合成稀土氧化物掺杂钨基粉末的研究

Adding fine and uniformly dispersed rare earth oxide particles into tungsten matrix is an important route of improving its properties. This project puts forward the idea of preparing the tungsten-base powder doped with rare earth oxides using low temperature combustion synthesis method. Firstly, homogeneous precursor composed of fine particles is synthesized by low temperature combustion synthesis process, and then tungsten-base powder doped with rare earth oxide is obtained by reducing the combustion synthesized precursor. The main focus of the project is to solve the difficulties of the refinement and uniform distribution of rare earth oxide particles. The thermodynamics and kinetics of the combustion synthesis process are investigated in order to reveal the nucleation and growth mechanisms of the precursor particles. The influences of the compositions of raw materials, ignition condition, combustion atmosphere and other factors on the phase constituents, homogeneity, particle size and structure of the obtained precursor are investigated. The thermodynamics of the reduction reaction of the combustion synthesized precursor, and the growth mechanisms and kinetics of reduction particles are investigated to controll the particle size, structure and uniform dispersion of rare earth oxide particles. This project is expected to broaden the application of low temperature cumbustion synthesis method, enrich the theory and practice of combustion synthesis field, and provide approch and guidence to fabricate high performace powder matellurgy materials doped with oxides and other oxide dispersion strengthened materials.

在金属钨基体中引入细小且均匀分布的稀土氧化物（La2O3，Y2O3等）粒子是提高金属钨性能的一种重要方法。本项目提出将低温燃烧合成用于制备稀土氧化物掺杂钨基粉末的研究思路，首先利用低温燃烧合成制备出粒度细小、混合均匀的前驱体，再将前驱体进行还原反应制备稀土氧化物掺杂钨基粉末，重点解决稀土氧化物粒子细化和均匀掺杂的难题。研究燃烧合成体系的热力学和动力学，揭示前驱体粒子的形核和生长机制，确立原料配比、点燃条件和燃烧环境等对前驱体物相、均匀性、粒度和结构的影响规律；研究前驱体各组分还原反应过程中的热力学、各种粒子生长机制和生长动力学，实现稀土氧化物粒子粒度、结构和掺杂分布均匀性的可控。该研究拓展了低温燃烧合成的应用，丰富了燃烧合成领域的理论与实践，并可为发展新型氧化物掺杂、弥散强化等高性能粉末冶金材料提供思路和借鉴。

金属钨（W）具有一系列优异特性，在现代国防、原子能工业、电真空、电光源等工程应用领域占有重要地位。金属W通常采用粉末冶金方法制备，在获得高致密度的前提下，细化晶粒和弥散强化是提高材料性能的有效手段。本项目使用溶液燃烧合成了氧化镧（La2O3）掺杂纳米钨粉，并使用该粉末制备了超细晶W合金，研究成果主要包括以下几个方面：（1）研究了La2O3源（硝酸镧）对溶液燃烧合成钨氧化物的相态、形貌以及还原过程的影响，成功制备了不同La2O3掺杂量的纳米W粉。（2）研究了溶液燃烧合成La2O3掺杂量的纳米W粉的致密化行为，成功制备了超细晶钨合金，并研究了其显微组织和物理性能。（3）研究了溶液燃烧合成纳米W粉的致密化和晶粒生长动力学，以及La2O3颗粒的演化过程及对晶粒生长抑制机理。