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Fabrication of Full-Density Mg-Ferrite/FeNi Permalloy Nanocomposites with a High-Saturation Magnetization Density of 1 T



Dense nanocomposites consisting of spinel Mn-doped Mg-ferrite and permalloy, (Mg[Fe1 − xMnx]2O4(0 ≤ x ≤ 0.4)/53Fe–47Ni), have been fabricated from powder mixtures of MgO/α-Fe2O3/MnO and N2-atomized metal particles utilizing high-pressure cold isostatic press (CIP), pulsed electric current pressure sintering (PECPS), and capsule-free hot isostatic pressing (HIP). Metal particles were coated with the mixed oxide powders homogeneously under high shear compression in Ar. The coated powders were densified into relative densities of 83–85% by high pressure CIPing (1 GPa). They were then presintered at 823 K for 3 min under uniaxial pressure of 100 MPa in Ar using a PECPS. The pre-sintered bodies had relative densities of 93–95% composed of spinel ferrite and permalloy; the mixed metal oxides were changed into magnesium ferrites by heating briefly at low temperature. Then, HIP (1123 K/6 h/196 MPa-Ar) was adopted to densify the pre-sintered bodies into a nearly full density; furthermore, a sintering atmosphere control was performed using ferrite muffles to maintain both phases. Sintered materials consisting of granular metal particles (φ 8.5 μm) isolated and surrounded by a thin ferrite discontinuous layer (0.2–1.3 μm) with a relative density ≥99.5% revealed both a saturation magnetization density ≥1 T and moderate permeability values of 30–35 at 1 MHz.