기계적합금화에 의한 Fe2O3-Mg계 연자성 콤포지트의 합성 및 평가
Synthesis and characterization of soft magnetic composite in Fe2O3-Mg system by mechanical alloying
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초록
본 연구에서는 Fe2O3-Mg계 혼합분말을 사용하여 연자성 복합재료를 제조하기 위하여 기계적 합금화법(MA)을적용하였다. 초미세 조직을 가진 연자성 α-Fe/MgO 복합재료를 얻기 위하여 X선 회절, 열분석 및 자기특성 측정을 통하여최적 볼밀조건 및 열처리 조건을 조사하였다. Fe2O3와 순금속 Mg의 혼합분말을 30분 동안 MA 처리한 결과. α-Fe 기지에MgO가 분산된 α-Fe/MgO 복합분말을 얻을 수 있었다. MA 분말시료의 자화값은 볼밀처리 시간에 따라 증가하여 MA 5시간 시료에서 69.5 emu/g의 최대값이 관찰되었다. 또한 MA 처리에 의하여 α-Fe의 결정립 미세화와 함께 보자력이 증가하는자기경화 현상이 관찰되었다. MA 분말시료의 벌크화를 위하여 소결온도 800~1000 o C, 압력 60 MPa에서 SPS 소결을 실시하였다. X선 회절 결과로부터, 5시간 MA 처리한 분말을 800 o C에서 SPS 소결시킨 α-Fe/MgO 연자성 복합재료의 경우 α-Fe 상 평균 결정립 크기가 110 nm임을 알 수 있었다.
Abstract
We have applied mechanical alloying (MA) to produce soft magnetic composite material using a mixture of elemental Fe2O3-Mg powders. An optimal milling and heat treatment conditions to obtain soft magnetic α-Fe/MgO composite with fine microstructure were investigated by X-ray diffraction, differential scanning calorimetry (DSC) and vibrating sample magnetometer (VSM) measurement. It is found that α-Fe/MgO composite powders in which MgO is dispersed in α-Fe matrix are obtained by MA of Fe2O3 with Mg for 30 min. The saturation magnetization of ball-milled powders increases with increasing milling time and reaches to a maximum value of 69.5 emu/g after 5 h MA. The magnetic hardening due to the reduction of the α-Fe grain size by MA was also observed. Densification of the MA powders was performed in a spark plasma sintering (SPS) machine at 800~1000 o C under 60 MPa. X-ray diffraction result shows that the average grain size of α-Fe in α-Fe/MgO nanocomposite sintered at 800 o C is in the range of 110 nm.
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