氧化锆基金属陶瓷惰性电极在熔渣体系中应用的基础研究

In recent years, a new concept of metallurgical technology by controlling oxygen flow in the given direction with application of voltage was used for direct reduction of metal from ore and the refining process of liquid metal. It is critical to develop the inert electrode used in molten slag and metal at high temperature for the industrialization of this technology. In this project, zirconia based cermet with addition of refractory metal (molybdenum) to obtain high conductivity was chosen because of its high stability in molten slag and steel at high temperature. Firsty,The basic model of electrical conductivity of cermet is established based on the characterization of microstructure and the formation of conducting net structure. Based on this, the cermet electrode with stable structure and good propertie will be prepared for the next investigation of performance. Secondly, the performance of cermet under application conditions is investigated, including high temperature electical properties and corrosion resistance in melting slag. The temperature dependence resistivity model is established by consideration of the contribution of different carriers at high temperature and the corrosion resistance will be investigated in different slag systems. Based on these,the prediction model of resistivity of electrode at molten slag is given by consideration of interaction between electrode and molten slag and the electrode reaction.Finally, the database containing cermets preparation, structure, properties and performance will be constructed, which will lay the foundation for materials design and application in melt slags as well as in the induction heating industry to replace the graphite and refractory metal.

近年来，国内外冶金工作者提出的利用外电场引导氧离子定向迁移的"可控氧流冶金"概念被用于直接从矿物熔体中短路还原提取金属以及对金属溶液的精炼过程，而高温熔体中用的惰性电极材料开发成为其能否实现工业化的关键之一。本项目基于熔渣短路还原及钢液外加电场脱氧的应用条件，首先通过对氧化锆基金属陶瓷材料的初步设计、制备、结构表征和导电机理的基础性研究，获得结构稳定、性能良好的金属陶瓷电极；在此基础上，进一步研究材料的服役性能，包括高温导电特性和机理、抗熔渣侵蚀性能以及在熔渣侵蚀条件下的导电机理和材料性能衰减特征等；通过在高温熔渣中进行电导率原位测定，建立两个重要的使用性能：抗渣侵蚀性和高温导电性的动态关系；最后得到金属陶瓷组成、制备、结构、性能及服役性能之间关系的基本数据库，为应用于高温熔渣体系中的电极设计提供理论依据，同时也可以为该材料在惰性电极、感应加热等应用领域代替石墨及难熔金属产品奠定基础。

本项目基于熔渣短路还原及钢液外加电场脱氧的应用条件，首先通过对氧化锆基金属陶瓷材料的初步设计、制备、结构表征和导电机理的基础性研究，获得结构稳定、性能良好的金属陶瓷电极，并建立了电导率预测模型；在此基础上，进一步研究材料的服役性能，得到Mo-ZrO2金属陶瓷的高温导电特性和机理，当金属含量大于逾渗阈值时，金属陶瓷以电子电导为主，当金属含量小时，主要表现为离子电导，并测得在Mo含量为5vol%时，其不同温度段的电导活化能。对于金属陶瓷在熔渣中应用的另一个重要问题，即材料的抗侵蚀性能，我们通过选择不同类型的熔渣进行试验，得到金属陶瓷在不同类型熔渣中的侵蚀机理主要分为化学反应型和扩散渗透型。但不管哪种类型的侵蚀都能在2小时左右形成稳定的侵蚀层，起到隔断熔渣和金属陶瓷材料之间的相互扩散和反应，从而起到保护材料作用。在后期的工艺模拟和动态的电导率测试结果都表明，Mo-ZrO2金属陶瓷能够在熔渣中稳定工作。项目根据计划完成了ZrO2基金属陶瓷的制备，结构表征，电性能以及在不同渣系中抗侵蚀性能研究，并进行了工艺模拟及动态性能测试，完成了计划书的全部研究内容。建立了制备、结构和性能之间的关系及材料在不同渣系中的侵蚀机理、侵蚀速率。研究结果表明30-40 vol% Mo含量的Mo-ZrO2金属陶瓷兼具良好的导电性能和抗侵蚀性能，能够在不同的渣系中作为电极应用，为“可控氧流冶金”概念的进一步工业化奠定了基础。