چكيده به لاتين
5Ni/10Nio-90NiFe2O4 cermets are considered as inert anodes for electrolyzing process of molten alumina-cryolite. Reseaches continue on improving these materials’ properties. In this study influence of BaO and MgO additives on physical and mechanical properties and microstructur of these cermets was investigated. Primarily, 10NiO-90NiFe2O4 powder synthesized using admixtion of nickel and iron sulphates and calsination at 1000C in air atmosphere. After mixing the compound with Ni metal powder, magnesium and barium carbonates that including 0, 1, 3 and 5 %wt MgO and BaO respectively, they pressed bu CIP method and then sintered at 1300 C in vaccum. One sample had both of BaO and MgO additives with molar ratio of 1:1 and one other did not include any additives. After sintering the samples, properties such as density and porosity, phase analysis, microstructure analysis were conducted by Archimedes method, X-ray diffraction, scanning electron microscope respectively. Mechanical tests including 3-point bending and microhardness of samples also performed.Resultes showed that the density of samples without any additive was approximately 91%, which increased to 95% by adding 5%wt BaO. XRD patterns of samples demonstrated partialy dissolution of BaO in NiFe2O4 spinel and formation of BaFe2O4 and BaFe12O19 phases that due to lower melting points, they affected the sintering process more significantly and so relative densities and bending strengths was increased to 96% and 91.5 MPa respectively. According to low hardness of formed phases rather than NiFe2O4, hardness of mentioned samples (with BaO) decreased when the additive value reached 5%wt. In samples included MgO additive, part of this additive solved in NiFe2O4 spinel and remained MgO formed MgFe2O4 that due to refractoriness of the system this additive couldn’t improved the sintering process. Therefore, in comparison of undoped samples, relative density and bending strength of samples doped with MgO reduced to 83% And 44.2 MPa Respectively. Generaly, compared results among BaO and MgO doped samples showed that MgO performance in hardness tests were reasonable than BaO doped samples, however inverse results obtained for density and 3-point bending tests.
