Cu-Ni-NiFe₂O₄金属陶瓷的制备与性能研究

【作者】 张刚；

【导师】 黎文献； 李劼；

【作者基本信息】 中南大学 ， 材料学， 2004， 硕士

【摘要】 本文以开发铝电解惰性阳极为目标，针对氧化物陶瓷良好的耐腐蚀性能和金属合金优异的导电性能和机械性能，用粉末冶金的方法制备出以NiFe₂O₄陶瓷相为基体，添加以Cu、Ni或Cu-Ni合金作为导电组元的金属陶瓷惰性电极材料。用等温饱和法研究了多种尖晶石型氧化物在熔盐中的腐蚀性能；用DTA-TG分析和XRD等方法研究了不同煅烧气氛对NiFe₂O₄陶瓷合成条件的影响；在此基础上分析了金属陶瓷在烧结过程中氧化物陶瓷的离解和金属相被氧化的问题；探讨了原料的球磨处理时间、烧结温度、烧结时间和金属组元的添加方式、成份与含量等工艺条件对NiFe₂O₄基金属陶瓷的致密度和导电率等性能的影响；研究了NiFe₂O₄基金属陶瓷的导电机理。获得的主要结果如下： 1)对比研究了NiFe₂O₄、ZnFe₂O₄、ZnAl₂O₄等多种尖晶石型氧化物在Na₃AlF₆-Al₂O₃熔盐体系中的腐蚀行为，发现NiFe₂O₄陶瓷饱和溶解度最小，因此本文以其为金属陶瓷的首选基体材料； 2)NiFe₂O₄陶瓷合适的合成条件为：在空气气氛中，以Fe₂O₃和NiO为原料，采用固相烧结在1150℃下煅烧6小时即可得到NiFe₂O₄陶瓷粉体； 3)烧结气氛对金属陶瓷的烧结影响很大。在弱氧化烧结气氛下，即将氧分压保持在金属相（Cu、Ni、Cu-Ni）的氧化反应平衡氧分压和陶瓷相（NiFe₂O₄）的离解反应平衡氧分压之间，可以解决烧结过程中金属相被氧化和陶瓷相离解的问题； 4)提高烧结温度有利于提高金属陶瓷惰性阳极材料的致密度和导电率，但烧结温度过高会造成金属相的溢出和试样变形。 5)金属Ni是一种良好的烧结助剂，它不仅与NiFe₂O₄的烧结性能良好，而且能有效改善Cu与NiFe₂O₄的润湿性，提高烧结温度； 6)NiFe₂O₄基金属陶瓷在高温下呈现半导体电导的性质；在金属含量小于30％时，其高温导电性能主要是由陶瓷相导电性能和金属相含量及其分布状况决定； 7)金属相的添加方式、种类和含量对金属陶瓷的性能影响较大。金属相以Cu、Ni粉末形式加入，可得到金属相组织细小、分散均匀、致密度高、导电性能良好的金属陶瓷试样，其性能远高于相同条件下以Cu-Ni合金为金属相的金属陶瓷；金属相含量越高，材料的导电性能越好；Ni一NIFeZO4金属陶瓷较Cu一NIFeZO;和Cu一Ni一NIFeZO;金属陶瓷在相同温度下更易实现材料的致密化;上述三种金属陶瓷的高温导电性能都比纯NIFeZO4陶瓷的普遍高出l一2个数量级，其中以Cu一Ni一NireZO4金属陶瓷的导电性能最佳。更多还原

【Abstract】 The project of cermets, used as the inert anodes for aluminum electrolysis, has been carrying out combined with low corrosion of oxides and perfect conductivity of alloy. NiFe2O4-based cermets were prepared by doping the NiFe2O4 ceramic matrix with the mixed powders of Cu and Ni as the electrical conducting metallic elements. The corrosive behaviors of several ferrites in melts are investigated with isothermal-saturation method. The effects of calcining atmosphere on synthesized condition of NiFe2O4 are studied with DTA-TG and XRD. On the basis, sintering atmosphere are analyzed the oxidization of metal phase and decomposition of ceramic phase during the sintering process. The effects of technics parameters, such as the ball milling time, the adding styles of metallic elements, the sintering time, the sintering temperature and the contents of metallic phase on the relative density and electrical conductivity of the cermets were studied. The electrical conductive mechanism of NiFe2O4-based cermets was investigated.The mainly conclusions and findings can be summarized as follows:1) The NiFe2O4 ceramic is selected to be the based materials of cermets duo to its lowest saturated solution in Na3AlF6-Al2O3 melts among several ferrites;2) The synthetical condition of NiFe2O4 is found to be suitable as Fe2O3 and NiO calcined at 1150℃ for 6 hours;3) The sintering atmosphere has an effect on the molding performance apparently. Sintering atmosphere are efficaciously controlled at various temperature to avoid the oxidization of metal phase and decomposition of ceramic phase during the sintering process;4) Raising sintering temperature can increase the relative density and conductivity of cermets, however, excessively high sintering temperature may make low-melting-point metals melt and flowed out of the sample or deformation;5) Nickel is a favorable sintering aid. It can improve the wettability between Cu and NiFe2O4 due to a good sintering performance between NiFe2O4 andNi.6) NiFe2O4-based cermets obey the semi-conductive mechanism. When the content of metal is less than 30%, the pyroconductivity of cermets are mainly determined by the conductivity of ceramic phase and the dispersion and content of metallic phase.7) The adding styles, compounds and content of metallic elements have notable influence on the properties of the NiFe2O4-based cermets. The high density and electric conductivity are obtained when the metallic elements were added in the form of the Cu and Ni powders owing to metallic phase dispersed finely and uniformly, Ni-NiFe2O4 cermets were easier to obtain the compacted structure than Cu-NiFe2O4 and Cu-Ni-NiFe2O4 sintered at the same temperature and preconditioned without metal effusion from cermets and distribution homogeneousness of metal phase in cermets when the contents of addictive metal was added from 0 to 20%. The conductivity of the above cermets, which the best conductive behavior of cermet is Cu-Ni-NiFe2O4, is at least 2-3 magnitude higher than that of nickel ferrite;更多还原