Sintered samples of nickel ferrite nickel oxide ceramic, usually used as the ceramic phase of cermet inert anode in aluminum electrolysis, were prepared and characterized. The solubilities of NiFe 2O 4 NiO ceramics we...Sintered samples of nickel ferrite nickel oxide ceramic, usually used as the ceramic phase of cermet inert anode in aluminum electrolysis, were prepared and characterized. The solubilities of NiFe 2O 4 NiO ceramics were measured using an equilibration technique in the Na 3AlF 6 10%AlF 3 5%CaF 2 5 %Al 2O 3 melts at 960 ℃. Electrical resistivity was also measured for NiFe 2O 4 NiO ceramic samples prepared using the usual ceramic technique as function of temperature and content of NiO with an improved pyroconductivity test device, consisting of a specially constructed closed furnace and a Potentiostat/Galvanostat, based on the conventional direct current four probe technique. Results show that, under the experimental conditions, the solubility of Fe from NiFe 2O 4 is 0.06% and Ni from NiFe 2O 4 is 0.008%. The solubility of Fe and Ni from NiFe 2O 4 NiO ceramic is inversely related to each other. The solubility of Ni increases but overall solubility of NiFe 2O 4 NiO ceramics decreases with increasing NiO content. The studied ceramic samples have a semiconductor behavior where electrical resistivity ρ decreases with increasing temperature and the resistivity ρ increases with increasing porosity. The resistivity ρ of NiFe 2O 4 NiO ceramic shows a minimum with increasing the content of NiO at various temperatures.展开更多
The electrical conductivity of cermet 83(90NiFe2O4-10NiO)-17Ni at different temperatures was measured in air, the operating performance of inert anode was evaluated in a laboratory electrolysis cell with various elect...The electrical conductivity of cermet 83(90NiFe2O4-10NiO)-17Ni at different temperatures was measured in air, the operating performance of inert anode was evaluated in a laboratory electrolysis cell with various electrolyte compositions. The results indicate that the electrical resistivity of cermet studied has negative temperature coefficient, which is the characteristic of semi-conducting material. The proper addition of AlF3 in the bath can improve the corrosion resistance of cermet inert anode, but excess adding amount will cause the catastrophic corrosion. Post-examination of anodes shows that metal Ni leaches preferentially on the anode surface. Chemical dissolution, electrolyte penetration as well as electrochemical dissolution serve as major corrosion mechanisms.展开更多
The solid state interdiffusion between NiFe204 and NiO in nitrogen atmosphere was studied by means of diffusion couple technique. NiFe204/NiO diffusion couple with plane interfaces was made by clamping method and sint...The solid state interdiffusion between NiFe204 and NiO in nitrogen atmosphere was studied by means of diffusion couple technique. NiFe204/NiO diffusion couple with plane interfaces was made by clamping method and sintering at 1 300℃ for 10 h. Scanning electronic microscopy （SEM） and energy-dispersive X-ray spectrometry （EDS） were used to analyze the microstructure and phase composition of the diffusion couples. The results indicate that a porous layer of uniform thickness forms along the NiFe2O4/NiO bonding interface and exhibits a deep penetration in the NiFe2O4 due to the Kirkendall effect. Furthermore, SEM observations reveal that the needle-like nickel ferrite precipitates form in NiO near the interface and the formation mechanism of them are inferred to be diffusion type solid-state phase changes.展开更多
文摘Sintered samples of nickel ferrite nickel oxide ceramic, usually used as the ceramic phase of cermet inert anode in aluminum electrolysis, were prepared and characterized. The solubilities of NiFe 2O 4 NiO ceramics were measured using an equilibration technique in the Na 3AlF 6 10%AlF 3 5%CaF 2 5 %Al 2O 3 melts at 960 ℃. Electrical resistivity was also measured for NiFe 2O 4 NiO ceramic samples prepared using the usual ceramic technique as function of temperature and content of NiO with an improved pyroconductivity test device, consisting of a specially constructed closed furnace and a Potentiostat/Galvanostat, based on the conventional direct current four probe technique. Results show that, under the experimental conditions, the solubility of Fe from NiFe 2O 4 is 0.06% and Ni from NiFe 2O 4 is 0.008%. The solubility of Fe and Ni from NiFe 2O 4 NiO ceramic is inversely related to each other. The solubility of Ni increases but overall solubility of NiFe 2O 4 NiO ceramics decreases with increasing NiO content. The studied ceramic samples have a semiconductor behavior where electrical resistivity ρ decreases with increasing temperature and the resistivity ρ increases with increasing porosity. The resistivity ρ of NiFe 2O 4 NiO ceramic shows a minimum with increasing the content of NiO at various temperatures.
基金Project(2005CB623703) supported by the National Basic Research Program of China Project(50474051) supported by the National Natural Science Foundation of China Project(03JJY3080) supported by the Natural Science Foundation of Hunan Province, China
文摘The electrical conductivity of cermet 83(90NiFe2O4-10NiO)-17Ni at different temperatures was measured in air, the operating performance of inert anode was evaluated in a laboratory electrolysis cell with various electrolyte compositions. The results indicate that the electrical resistivity of cermet studied has negative temperature coefficient, which is the characteristic of semi-conducting material. The proper addition of AlF3 in the bath can improve the corrosion resistance of cermet inert anode, but excess adding amount will cause the catastrophic corrosion. Post-examination of anodes shows that metal Ni leaches preferentially on the anode surface. Chemical dissolution, electrolyte penetration as well as electrochemical dissolution serve as major corrosion mechanisms.
文摘制备了添加不同含量的Cu和Ni金属粉末作为导电组元的NiFe2O4基金属陶瓷材料,研究了材料的物相组成、显微组织以及金属相含量对材料致密度和电导率的影响。研究结果表明,所制备的金属陶瓷材料由NiFe2O4和Cu Ni合金相组成,其中细小且形状不规则的(Cu Ni)相均匀地镶嵌在NiFe2O4陶瓷基体上;试样的致密度在金属含量为0～20%范围内存在极大值;Cu Ni NiFe2O4金属陶瓷遵循半导体导电机理,其电导率随着温度的升高和金属含量的增大而增大。
基金Project(50721003) supported by the National Natural Science Fund for Innovation Group of ChinaProject(2008AA030501) supported by the National High Technology Research and Development Program of China
文摘The solid state interdiffusion between NiFe204 and NiO in nitrogen atmosphere was studied by means of diffusion couple technique. NiFe204/NiO diffusion couple with plane interfaces was made by clamping method and sintering at 1 300℃ for 10 h. Scanning electronic microscopy （SEM） and energy-dispersive X-ray spectrometry （EDS） were used to analyze the microstructure and phase composition of the diffusion couples. The results indicate that a porous layer of uniform thickness forms along the NiFe2O4/NiO bonding interface and exhibits a deep penetration in the NiFe2O4 due to the Kirkendall effect. Furthermore, SEM observations reveal that the needle-like nickel ferrite precipitates form in NiO near the interface and the formation mechanism of them are inferred to be diffusion type solid-state phase changes.
