Fabrication of Mg Ferrite/permalloy Magnetic Nano-composites

Abstract

Dense {Mg(Fe1-xMnx)2O4/53Fe-47Ni permalloy (0≤x≤0.4)} magnetic nano-composites consisting of spinel and alloy phases have been fabricated from N2-atomized metal particles and fine-powder mixtures of MgO/α-Fe2O3/MnO using a combination of pulsed electric current pressure sintering (PECPS) and hot isostatic pressing (HIP). Fe-Ni permalloy particles were coated with the mixed metal oxide powders homogeneously by passing these mixtures through a narrow gap (1 mm) under high shear compression in Ar. Mixed powder compacts of permalloy with the fine metal oxides were densified into the green bodies having relative densities of 83-85 % under isostatic high pressure of 1 GPa at room temperature. Then green powder compacts were pre-sintered at 823 K for 3 min under a uniaxial pressure of 100 MPa in Ar using a PECPS. The pre-sintered bodies composed of spinel ferrite and permalloy revealed the relative densities of 94-96 %; the mixed metal oxides changed into magnesium spinel ferrites Mg(Fe1-xMnx)2O4 during a short heating time. Then hot isostatic pressing (HIP: (1123 K/6 h/200 MPa-Ar)) was adopted to sinter the pre-sintered bodies into a near full density without an encapsulation, however, a sintering atmosphere control was performed using a ferrite muffle in order to maintain the both phase. Sintered nano-composites with the relative density more than 99.5 % have a saturation magnetization density ≥1 T and moderate permeability values of 30-35 at 10 MHz, which values have been expected from a material design.