• 한국자기학회지
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• 제19권3호
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• pp.106-112
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• 2009

상온에서 준강자성을 띠는 $Ni_{1-x}Mg_xFe_2O_4$ ferrite 내에 존재하는 금속양이온 Ni을 Mg로 대치시킬 때 나타나는 결정학적 구조의 변화와 자기적 성질 변화, 그리고 양이온의 분포를 X-선 회절무늬와 $M{\ddot{o}}ssbauer$ spectrum을 측정하고 분석하여 연구하였다. $NiFe_2O_4$ ferrite의 $M{\ddot{o}}ssbauer$ spectrum 공명흡수면적비(oct/tet)는 1.007로서 거의 완전한 inverse spinel 구조를 형성하나 Mg의 함량인 x가 증가함에 따라 Mg 이온이 tetrahedral site를 점유하게 되어 면적비(oct/tet)가 점차 증가하여 $MgFe_2O_4$의 경우 1.449로서 불완전한 inverse spinel 구조를 형성한다. 시료들의 isomer shift 값으로부터 $Ni_{1-x}Mg_xFe_2O_4$ ferrite계 내에 존재하는 Fe는 $Fe^{3+}$ 상태임을 알 수 있다. 비자성 이온인 Mg의 함량이 증가함에 따라 최인접 금속 양이온에 의해 발생되는 A-B exchange interaction이 발생할 확률이 작아져서 magnetic hyperfine field가 감소하며 Yafet-Kittel 자기구조를 나타낸다.

• 한국표면공학회지
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• 제50권3호
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• pp.212-218
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• 2017

$Mg_xNi_yZn_{1-x-y}Fe_2O_4$ ferrite powders were prepared by self-propagating high temperature synthesis followed by classifying with an ultrasonic wet-magnetic separation unit to get high pure nano-sized particles. The $Mg_xNi_yZn_{1-x-y}Fe_2O_4$ ferrites were well formed by using several powders like iron, nickel oxide, zinc oxide and magnesium oxide at 0.1 MPa of oxygen pressure. The ultrasonic wet-magnetic separation of pre-mechanical milled ferrite powders resulted in producing the powders with average size of 800 nm. The addition of a surfactant during the wet-magnetic separation process improved productivity more than twice. The coercive force, maximum magnetization and residual magnetization of the $Mg_xNi_yZn_{1-x-y}Fe_2O_4$ nano-powders with 800 nm size were 3651 A/m, $53.92Am^2/kg$ and $4.0Am^2/kg$, respectively.

• 한국표면공학회:학술대회논문집
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• 한국표면공학회 2016년도 추계학술대회 논문집
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• pp.201.2-201.2
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• 2016

$Mg_xNi_yZn_{1-x-y}Fe_2O_4$ ferrite powders were prepared by self-propagating high temperature synthesis followed by classified by ultrasonic wet-magnetic separation method to get nano-sized particles with high purity. The $Mg_xNi_yZn_{1-x-y}Fe_2O_4$ ferrites were well formed by using several powders like iron, nickel oxide, zinc oxide and magnesium oxide at 0.1 MPa of oxygen pressure. The ultrasonic wet-magnetic separation of pre-mechanical milled ferrite powders produced the powders with average size of $3.7-0.8{\mu}m$. The addition of a surfactant during the separation process improved productivity more than twice. The coercive force, maximum magnetization and residual magnetization of the $Mg_xNi_yZn_{1-x-y}Fe_2O_4$ nano-powders with 810 nm size were 45.89 Oe, 53.92 emu/gOe, 0.4 emu/Oe, respectively.

• 한국정보통신학회:학술대회논문집
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• 한국해양정보통신학회 2000년도 춘계종합학술대회
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• pp.109-114
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• 2000

본 연구에서는 전파흡수체용 ferrite-Rubber Composite에서 Ferrite의 열처리 온도와 Composite의 전파흡수특성과의 상관관계에 관하여 알아보았다. 이때 Ferrite는 스피넬 구조의 형성과 결정입의 비교적 큰 성장을 위하여 1100, 1200, 1300 $^{\circ}C$에서 각각 2시간 열처리 처리하였다. 열처리 온도를 달리하여 제조한 Ferrite-Rubber Composite는 A가 Mn인 경우에는 열처리 온도가 높을수록 반사감쇠량이 작아지는 경향을 보였다. 그러나 A가 Cu와 Mg인 경우 열처리 은도가 높을수록 페라이트의 반사감쇠량이 커지는 경향을 보였다. 이로부터 전파흡수체용 Ferrite는 화학조성에 따라서 적정 열처리 온도가 존재함을 알 수 있었다.

• 한국항해학회지
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• 제22권4호
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• pp.69-75
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• 1998

The super wideband electromagnetic wave absorber in RF-A-PF type has been proposed, which can be used for an anechoic chamber, wall material to prevent TV ghost, etc, In this paper, $Ni_x-Mg_{0.1}-Zn_(1-x-0.1){\cdot}Fe_2O_4$ Ferrite Powder has been fabricated. Using this, then, [$Ni_x-Mg_{0.1}-Zn_(1-x-0.1){\cdot}Fe_2O_4$-Rubber composite for RF-layer in the RF-A-PF type absorber has been fabricated and its characteristics has been analyzed. As a result, it has been shown that the $Ni_x-Mg_{0.1}-Zn_(1-x-0.1){\cdot}Fe_2O_4$-Rubber composit with the quantity $_x$ of $Ni_x$ between 0.5 and 0.6 is suitable for the RF-layer in the case of which the grain size is sub-micrometer order.

• 한국세라믹학회지
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• 제18권2호
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• pp.83-90
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• 1981

In this study, the effect of additions on magnetic properties in the system of [$Ni_{0.32}Zn_{0.68}$] 1-x Mx $Fe_2O_4$ have been investigated. The additions, Co or Mg or Cu, was added in turn in place of M, and its composition was varied from 0.1 mo1% to 0.5 mo1%. The materials were blended by hot petroleum drying method, and sintered with the rate of 30$0^{\circ}C$/h in the air. The sintering temperatures were varied from 110$0^{\circ}C$ to 130$0^{\circ}C$, with the intervals of 5$0^{\circ}C$, and matured for 3hrs. The results are: 1) The permeability decreased when the addition, MgO or CoO, was added, and it increased when CuO was added. 2) Resistivity had the lowest Value when CuO was added.

• 한국재료학회지
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• 제10권3호
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• pp.223-226
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• 2000

산소 결핍 페라이트 (oxygen deficient ferrites, ODF) $MeFe_2O_{4-\delta}$는 약 $300^{\circ}C$의 낮은 온도에서 $CO_2$를 C와 $O_2$로 분해한다. 본 연구에서는 $(Ni_x,\;Zn_{1-x}Fe_2_4$ 초미세 페라이트 분말을 수열합성법으로 제조하여 $CO_2$ 분해특성을 살펴보았다. 제조된 페라이트는 XRD 분석 결과, 페라이트의 전형적인 스피넬 구조를 보여주고 있으며, ICP-AES, EDS 정량분석에 의하여 초기 혼합 조성비와 거의 동일한 조성비로 합성되었음을 알 수 있었다. 제조된 (Ni, Zn)-ferrites 분말의 BET 비표면적은 약 $110\textrm{mg}^2$/g$ 이상의 큰 값으로 나타났으며, 입자크기는 약 5~10nm로 매우 작았다. 산소결핍 페라이트 $(Ni_x,\;Zn_{1-x})Fe_2O_{4-{$\delta}}$의 $CO_2$ 분해 효율은 조성에 따라 큰 차이를 보이지 않았으며 3원계 (Ni, Zn)-ferrite가 Ni-ferrite보다 더 높았다.

• 한국재료학회지
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• 제13권6호
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• pp.365-368
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• 2003

Small amounts of additives such as mol % 0.13 NiO and mol % 0.01 $CaCO_3$were added to Cu-Zn-Mg ferrites. Basic composition of the Cu-Zn-Mg ferrites was $Cu_{Cu}$X/$Fe_{0.054}$ /$Zn_{0.486}$$Mg_{0.407}$ $Fe_{1.946}$ $O_4$(group A) and $Cu_{0.263}$$Fe_{0.027}$ $Zn_{0.503}$ $Mg_{0.262}$ $Fe_{1.973}$ $O_4$(group B). Specimens were sintered at different temperatures (1010, 1030, $1050^{\circ}C$) for 2 hours in air followed by an air cooling. Then, effects of various composition and sintering temperatures on the microstructure and the magnetic properties such as inductions, coercive forces, and initial permeabilities of the Cu-Zn-Mg ferrites were investigated. The average grain size increased with the increase of sintering temperature. The magnetic properties obtained from the aforementioned Cu-Zn-Mg ferrite specimens were 1,724 gauss for the maximum induction, 1.0 oersted for the coercive force, and 802 for the initial permeability. These magnetic properties indicated that the specimens could be utilized as the core of IFT (intermediate frequency transformer) and antenna in the amplitude modulation.

• Journal of Magnetics
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• 제16권2호
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• pp.164-168
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• 2011

Magnetic nanoparticles can potentially be used in drug delivery systems and for hyperthermia therapy. The applicability of $Fe_3O_4$, $CoFe_2O_4$, $MgFe_2O_4$, and $NiFe_2O_4$ nanoparticles for the same was studied by evaluating their magnetization, thermal efficiency, and biocompatibility. $Fe_3O_4$ and $CoFe_2O_4$ nanoparticles exhibited large magnetization. $Fe_3O_4$ and $NiFe_2O_4$ nanoparticles exhibited large induction heating. $MgFe_2O_4$ nanoparticles exhibited low magnetization compared to the other nanoparticles. $NiFe_2O_4$ nanoparticles were found to be cytotoxic, whereas the other nanoparticles were not cytotoxic. This study indicates that $Fe_3O_4$ nanoparticles could be the most suitable ones for hyperthermia therapy.

• 열처리공학회지
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• 제9권1호
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• pp.34-44
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• 1996

Austenite stainless steel was produced by arc welding with current 650A, voltage 50V and welding speed 10cm/min. It was post-welded and then heat treated at $1,050^{\circ}C$ for 120min. And then it was immersed in water or in air. The microstructural changes, ferrite contents, mechanical properties, and stress corrosion cracking(SCC) were investigated. The SCC was studied in 42wt% boiling $MgCl_2$($140^{\circ}C$) under the constant stress using SCC elongation curve. The results showed that; 1. The as-welded spedimen seemed to increase ${\delta}$-ferrite content largely, and revealed continuous network of lathy and vermicular type. The post-welded heat treatment changed the morphologies of ferrite from continuous type to island type. 2. The as-welded, air and water quenched specimens had the ${\delta}$-ferrite content 9.7%, 3.2% and 2.1% respectively. We also showed that ${\delta}$-ferrite was Cr-rich and Ni-poor by EPMA. 3. The time of failure on the SCC was measured and it was used for corrosion elongation curve. The condition of SCC was investigated under $35kgf/mm^2$ load and the results were as follows; 4. The intergranullar cracking by stress corrosion was most distinct in weld metal while the transgranular cracking occurred in the air cooled specimen.