A Study on Synthesis and Magnetic Properties of Soft Magnetic Materials Sintered at Low Temperature

The initial NiCuZn synthetic ferrite were acquired from thermally decomposing the metal nitrates Fe($NO_3$)$_3$ㆍ$9H_2$O, Zn($NO_3$)$_2$ㆍ$6H_2$O, Ni($NO_3$3)$_2$ㆍ $6H_2$O and Cu(NO$_3$)$_2$ㆍ $3H_2$O at 1$50^{\circ}C$ for 24 hours and was calcined at $500^{\circ}C$. Each of those was pulverized for 3 and 9 hours in a steel ball mill and was sintered between $700^{\circ}C$ and $1,000^{\circ}C$ for 1 hour, and then their microstructures and magnetic properties were examined. We could make the initial specimens chemically bonded in liquid at the temperature as low as $150 ^{\circ}C$, by using the melting points less than $ 200^{\circ}C$ of the metal nitrates instead of the mechanical ball milling, then narrowed a distance between the particles into a molecular level, and thus lowed sintering temperature by at least $200 ^{\circ}C$ to $300^{\circ}C$ Their initial permeability was 50 to 490 and their saturation magnetic induction density and coercive force 2,400G and 0.3 Oe to 1.2 Oe each, which were similar to those of NiCuZn ferrite synthesized in the conventional process.

저온 소결용 연자성 물질의 합성 및 자기적 특성 연구

Fe($NO_3$)$_3$ㆍ$9H_2$O, Zn($NO_3$)$_2$ㆍ$6H_2$O, Ni($NO_3$3)$_2$ㆍ $6H_2$O, Cu($NO_3$)$_2$ㆍ $3H_2$O와 같은 질산 금속염들을 $150^{\circ}C$로 24시간 동안 열분해하여 최초 NiCuZn ferrite 분체를 얻었으며, 이 분체 시료를 $500^{\circ}C$로 가소한 후 각각 볼밀 분쇄를 행하고 $700∼1000^{\circ}C$까지 각각 1시간씩 소결을 행하여 이에 대한 자기적 특성을 조사하였다. 일반 세라믹스 공정 보다 질산금속염들의 $ 200^{\circ}C$이하의 저 융점인 것을 이용하여 이들 출발 시료를 $150^{\circ}C$의 저온에서 액상의 화학결합이 가능하게 입자간의 거리를 분자적 거리로 좁힐 수 있었으며, 이로 인해 소결반응 점을 최소한 200∼ $300^{\circ}C$ 이상 낮출 수 있었다. 또한 이들의 초투자율은 50∼490, 포화자속밀도 및 보자력은 각각 2,400G와 0.3∼1.2 Oe정도로 보통의 ferrite 소결체의 특성과 유사하게 나타났다.