Research On Preparation And Properties Of 17Ni/?10NiO-NiFe₂O₄? Cermet Doped With Cr₂O₃

Based on the fact that the NiFe₂O₄ based cermet as an inert anode for aluminum electrolysis industry is expected to completely solve the problem of environmental pollution caused by using the carbon anode,and the discharge can reach the emission-free and low-energy requirement of the electrolytic process,it has become the focus of the research in the field of materials and the international aluminum industry.Funded by the international science and technology cooperation?2010DFA52130?,the 17Ni/?10NiO-NiFe₂O₄?cermet with good performance and widely focused is chosen as the representative of NiFe₂O₄ based cermet,and the cermet samples are prepared by doping different content of Cr₂O₃.By using XRD,SEM,EDS and other means of detection and analysis,to explore in detail the impact of the different content of Cr₂O₃ doping on the phase composition,microstructure,densification,mechanical properties,high temperature oxidation resistance and high temperature static corrosion resistance of cermets.The research results are as follows:1.The qualified 10NiO-NiFe₂O₄ ceramic matrix is prepared by sintering process of preserving 6 hours at 1200?;the 17Ni/?10NiO-NiFe₂O₄?cermet samples with different content of Cr₂O₃ are successfully prepared by powder metallurgy.The pressing pressure is 300 Mpa,and the vacuum sintering process is preserving 3 hours at 1250?.2.The different content of Cr₂O₃ doping on 17Ni/?10NiO-NiFe₂O₄?cermet is consisted of Ni,NiO and NiFe₂O₄.Cr₂O₃ dopant was dissolved in the NiFe₂O₄ phase of the ceramic matrix,which led to the distortion of the NiFe₂O₄ lattice and promoted the sintering densification.With the increase of Cr₂O₃ doping amount,the densification degree of cermets is gradually increased,and the relative density of the sample with Cr₂O₃ doping content of 2% and 4% is as high as 97.53% and 99.19% respectively,than the undoped samples increased 3.32% and 4.98% respectively.3.The mechanical properties of cermets can be greatly improved by Cr₂O₃ doping,and the effect is more striking with the increase of Cr₂O₃ doping amount.When the Cr₂O₃ doping amount is 4%,the mechanical properties of samples is best.The hardness,fracture toughness and flexural strength of samples are achieved 797.02 N·mm-2?5.09 MPa·m1/2?192.3650 Mpa respectively.Followed by 2% Cr₂O₃ doped samples,the hardness,fracture toughness and flexural strength are achieved 787.86 N·mm-2?4.70 MPa·m1/2?162.2317 Mpa.4.Doping Cr₂O₃ is helpful to improve the high temperature oxidation resistance of cermets.With the increase of Cr₂O₃ doping amount,the high temperature oxidation resistance is better.When the Cr₂O₃ doping amount is 2% and 4%,per unit area of the oxidation rate are 6.0753mg×cm-2?4.3131mg×cm-2 respectively after oxidation of 30 hours,than the undoped samples reduced 37.64% and 55.73% respectively.5.By adding a proper amount of Cr₂O₃,the corrosion resistance of cermets can be greatly improved.When the content of Cr₂O₃ is 2%,the sample is more easily to form a dense layer in the molten salt corrosion.The corrosion resistance of the samples doped with 2% Cr₂O₃ is the best,and the corrosion rate is 1.7736×10-3g×cm-2×h-1,which is 30.14% of the undoped samples,and the corrosion depth is 2.7882cm×y-1,than the undoped samples reduced 69.45%.