烧结氧分压对25(20Ni-Cu)/(10NiO-NiFe_(2)O_(4))金属陶瓷微观结构及其力学与电学性能的影响

Effect of sintering oxygen partial pressure on microstructure and its mechanical and electrical properties of 25(20Ni-Cu)/(10NiO-NiFe_(2)O_(4))cermets

为提高金属陶瓷的相对密度,优化物相组成,采用可控氧分压烧结制备名义成分为25(20Ni-Cu)/(10NiO-NiFe_(2)O_(4))的金属陶瓷,并基于Fe-Ni-O三元相平衡热力学,探究烧结氧分压对材料微观组织、力学与电学性能的影响,揭示不同烧结氧分压下,金属陶瓷的失氧反应与组织演变机制。研究结果表明,烧结氧分压影响了尖晶石相的分解和金属相的氧化过程,进而决定金属陶瓷的平衡相组成;当氧分压为2.1~12.1 Pa时,NiFe_(2)O_(4)相有一定程度的分解,且金属相含量高于标准含量,经1250℃烧结后,金属陶瓷的平衡相组成为CuNiFe-NiO-NiαFe_(3−α)O_(4)。金属陶瓷的力学性能和电导率均随氧分压的升高而降低,当氧分压为2.1 Pa时,样品相对密度最高,达99.7%,抗弯强度达176.86 MPa,室温电导率为14 S·cm^(-1)。

In order to improve the relative density and optimize the phase composition of cermets,the cermets with a nominal composition of 25(20Ni-Cu)/(10NiO-NiFe_(2)O_(4))were prepared by controlled oxygen partial pressure sintering.Based on the thermodynamics of ternary phase equilibrium of Fe-Ni-O,the influence of the sintering oxygen partial pressure on the microstructure,mechanical and electrical properties of the materials was explored,and the effect of different oxygen partial pressures on the sintered cermets was revealed.Under different sintering oxygen partial pressures,the oxygen loss reaction and organization evolution mechanism of cermets were revealed.The results show that the sintering oxygen partial pressure affects the decomposition of the spinel phase and the oxidation process of the metal phase,which in turn determines the equilibrium phase composition of the cermet.NiFe_(2)O_(4)phase is partially decomposed,and the metal phase is higher than the standard content when the oxygen partial pressure is in the range of 2.1−12.1 Pa,and the equilibrium phase composition of the cermet after sintering at 1250℃is CuNiFe-NiO-NiαFe_(3−α)O_(4).The mechanical properties and electrical conductivity of the cermets decrease with the increase of oxygen partial pressure,and the samples has the highest relative density of 99.7%,flexural strength of 176.86 MPa,and room temperature conductivity of 14 S·cm−1 when the oxygen partial pressure is 2.1 Pa.