• 한국분말야금학회:학술대회논문집
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• 한국분말야금학회 2006년도 Extended Abstracts of 2006 POWDER METALLURGY World Congress Part2
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• pp.1196-1197
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• 2006

FePt binary-alloy nanopowder has been successfully synthesized by chemical vapor condensation process with two metal organic precursors, i.e., iron pentacarbonyl and platinum acetylacetonate. Average particle size of the powder was less than 50 nm with very narrow size distribution, revealing high dispersion capability. Characteristics of the powder could be controlled by changing process parameters such as reaction temperature, chamber pressure, as well as gas flow rate. Magnetic properties of the synthesized FePt nanopowder were investigated and analyzed in terms of the powder characteristics.

• 한국방사선학회논문지
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• 제16권5호
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• pp.527-536
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• 2022

본 연구는 우주방사선 차폐물질 설계를 위한 선행연구 차원에서 우주방사선에 대한 물질별 방사선 차폐특성을 분석하였다. 특히 EMP 및 방사선 차폐에 효과가 있다고 알려진 경량 연자성 복합소재에 대한 우주방사선 차폐물질 활용 가능성을 확인하고자 하였다. 이를 위해 Monte Carlo N-Particle(MCNP) 모델링 기법과 열중성자 차폐실험을 수행하였으며, MCNP의 우주방사선 모델인 Skymap.dat를 활용하였다. 연구결과 폴리에틸렌, 붕소폴리에틸렌, 탄소나노튜브 등 탄소와 수소를 함유한 물질의 경우 증발 중성자 에너지 영역 대 이하의 중성자 감소에 효과적인 것으로 나타났으며 SS316, 경량 연자성 물질 등 철을 함유한 물질은 캐스케이드 중성자 차폐성능이 뛰어난 것을 확인할 수 있었다. 특히 경량 연자성 물질의 경우 붕소를 함유하고 있어 저속중성자 영역의 중성자 감소에도 효과적인 것으로 나타났으며, 향후 탄소 및 수소 등 탄성산란 물질을 보강한다면 우주방사선 중성자 전 영역에서 유의미한 차폐효과를 보여줄 것으로 기대된다.

• Journal of Magnetics
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• 제19권3호
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• pp.210-214
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• 2014

The effects of manganese substitution on the crystallographic and magnetic properties of Li-Zn-Cu ferrite, $Li_{0.5}Zn_{0.2}Cu_{0.4}Mn_xFe_{2.1-x}O_4$ ($0.0{\leq}x{\leq}0.8$), were investigated. Ferrites were synthesized via a conventional ceramic method. We confirmed the formation of crystallized particles using X-ray diffraction, field emission scanning electron microscopy and $M{\ddot{o}}ssbauer$ spectroscopy. All of the samples showed a single phase with a spinel structure, and the lattice constants linearly decreased as the substituted manganese content increased, and the particle size of the samples also somewhat decreased as the doped manganese content increased. All the $M{\ddot{o}}ssbauer$ spectra can be fitted with two Zeeman sextets, which are the typical spinel ferrite spectra of $Fe^{3+}$ with A- and B-sites, and one doublet. The cation distribution was determined from the variation of the $M{\ddot{o}}ssbauer$ parameters and of the absorption area ratio. The magnetic behavior of the samples showed that an increase in manganese content led to a decrease in the saturation magnetization, whereas the coercivity was nearly constant throughout. The maximum saturation magnetization was 73.35 emu/g at x = 0.0 in $Li_{0.5}Zn_{0.2}Cu_{0.4}Mn_xFe_{2.1-x}O_4$.

• 한국재료학회지
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• 제28권7호
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• pp.371-375
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• 2018

The manganese-, nickel-, and aluminum-doped cobalt ferrite powders, $Mn_{0.2}Co_{0.8}Fe_2O_4$, $Ni_{0.2}Co_{0.8}Fe_2O_4$, and $Al_{0.2}CoFe_{1.8}O_4$, are fabricated by the sol-gel method, and the crystallographic and magnetic properties of the powders are studied in comparison with those of $CoFe_2O_4$. All the ferrite powders are nano-sized and have a single spinel structure with the lattice constant increasing in $Mn_{0.2}Co_{0.8}Fe_2O_4$ but decreasing in $Ni_{0.2}Co_{0.8}Fe_2O_4$ and $Al_{0.2}CoFe_{1.8}O_4$. All the $M{\ddot{o}}ssbauer$ spectra are fitted as a superposition of two Zeeman sextets due to the tetrahedral and octahedral sites of the $Fe^{3+}$ ions. The values of the magnetic hyperfine fields of $Ni_{0.2}Co_{0.8}Fe_2O_4$ are somewhat increased in the A and B sites, while those of $Mn_{0.2}Co_{0.8}Fe_2O_4$ and $Al_{0.2}CoFe_{1.8}O_4$ are decreased. The variation of $M{\ddot{o}}ssbauer$ parameters is explained using the cation distribution equation, superexchange interaction and particle size. The hysteresis curves of the ferrite powders reveal a typical soft ferrite pattern. The variation in the values of saturation magnetization and coercivity are explained in terms of the site distributions, particle sizes and the spin magnetic moments of the doped ions.

• 마이크로전자및패키징학회지
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• 제22권3호
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• pp.45-50
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• 2015

Glycine-nitrate와 citric acid를 이용하여 단상의 Ni-Zn ferrite, Ba-ferrite 나노입자와 두 나노복합체 ferrite의 전구체를 제조하고 이를 열처리하여 XRD 및 FT-IR로 각각의 상 분석을, SEM으로 분말의 형상과 크기를, VSM으로 자기적 특성과 합성된 나노복합체 ferrite에서의 exchange-coupling 상호작용을 확인하였다. XRD 분석 결과, 자전 연소법으로 얻은 전구체로 단상의 Ni-Zn ferrite와 Ba-ferrite 나노 입자 및 $BaFe_{12}O_{19}/Ni_{0.5}Zn_{0.5}Fe_2O_4$ 나노복합체 페라이트가 합성되었으며, 나노복합체에는 $BaFe_{12}O_{19}$와 $Ni_{0.5}Zn_{0.5}Fe_2O_4$가 잘 분포되어 있어 경자성과 연자성이 공존하고 있음을 확인하였고, 나노복합체 페라이트의 히스테리시스 곡선의 형상을 통해 경자성과 연자성 사이에 exchange-copuling이 잘 이루어졌음을 확인할 수 있었다. VSM으로 측정한 나노복합체의 경우. GNP로 제조한 precursor를 $900^{\circ}C$에서 하소한 $BaFe_{12}O_{19}/Ni_{0.5}Zn_{0.5}Fe_2O_4$ 나노복합체는 포화자화 81.69 emu/g, 잔류자화 38 emu/g, 보자력 2598.48G를 나타내었다. $Ni_{0.5}Zn_{0.5}Fe_2O_4/BaFe_{12}O_{19}$ 복합체에서 $BaFe_{12}O_{19}$의 무게비가 증가 할수록 보자력은 증가하였고, 포화자화값과 잔류자화 값은 감소하였다.

• Advances in nano research
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• 제3권3호
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• pp.169-176
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• 2015

Iron nanoparticles were made by using the modified coprecipitation technique. Usually the characteristics of synthesised particles depend upon the process parameters such as the ratio of the iron ions, the pH of the solution, the molar concentration of base used, type of reactants and temperature. A modified coprecipitation method was adopted in this study. A magnetic stirrer was used for mixing and the morphology and nature of particles were observed after synthesis. Nanoparticles were characterised through XRD. Obtained nanoparticles showed the formation of magnetite and maghemite under citric acid and oxalic acid as stabilisers respectively. The size of nanoparticle was greatly affected by the use of different types of stabilisers. Results show that citric acid greatly reduced the obtained particle size. Particle size as small as 13 nm was obtained in this study. The effects of different kinds of nucleating agents were also observed and two different types of nucleating agents were used i.e. potassium hydroxide (KOH) and copper chloride ($CuCl_2$). Results show that the use of nucleating agent in general pushes the growth phase of nanoparticles towards the end of coprecipitation reaction. The particles obtained after addition of nucleating agent were greater in size than particles obtained by not utilising any nucleating agent. These particles have found widespread use in medical sciences, energy conservation and electronic sensing technology.

• 한국재료학회지
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• 제11권11호
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• pp.986-990
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• 2001

An optimum route to fabricate the $A1_2O_3/Fe-Ni$ alloy nanocomposites with sound microstructure and enhanced mechanical properties as well as magnetism was investigated. To prepare homogeneous nanocomposite powders of Fe-Ni alloy and $Al_2O_3$, the solution-chemistry routes using $Al_2O_3 \; Ni(NO_3)_2{\cdot}6H_2O$ and $Fe(NO_3)_3{\cdot}9H_2O$ powders were applied. Microstructural observation of the powder mixture revealed that the Fe-Ni alloy particles of about 20 nm in size were homogeneously surrounded $A1_2O_3$, forming nanocomposite powder. The hot-pressed composite showed improved fracture toughness and magnetic response. These results suggest that the synergy materials with an improved mechanical properties and excellent functionality can be fabricated by controlled powder preparation and consolidation processing.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2004년도 추계학술대회 논문집
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• pp.92-96
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• 2004

In this paper, polishing method using bonded magnetic abrasive particle has been applied to the micro mold polishing. Through process control using the Run-to-Run control, it tried to form the surface roughness In order to grasp the influence of the surface roughness which is reached by selection of control factor and the factor, a design of experiment was been processed. The study is processed with a purpose of to embody and to maintain the surface roughness of nano scale by the basis of an influence between a control factor and the factors which has been selected in this way. As a result, the result of the process control converged at a target value of surface roughness Ra 10nm and Rmax 50nm

• 한국재료학회:학술대회논문집
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• 한국재료학회 2011년도 춘계학술발표대회
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• pp.9.2-9.2
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• 2011

Ultrathin polyelectrolyte (PE) multilayer films prepared by the versatile layer-by layer (LbL) assembly method have been utilized for the preparation of light-emitting diodes, electrochromic, membrane, and drug delivery system, as well as for selective area patterning and particle surface modification because the various materials with specific properties can be inserted into the film with nano-level thickness irrespective of the size or the shape of substrate. Since the introduction of the LbL technique in 1991 by Decher and Hong, various hydrophilic materials can be inserted within LbL films through complementary interactions (i.e., electrostatic, hydrogen-bonding or covalent interaction). In this study, it is demonstrated that LbL SA multilayer films based on nucleophilic substitution reaction can allow the preparation of the highly efficient magnetic and/or optical films and nonvolatile memory devices.

• Journal of Biosystems Engineering
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• 제42권4호
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• pp.323-329
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• 2017

Purpose: Biocompatible capsules have recently been highlighted as a novel platform for delivering various components, such as drug, food, and agriculture pesticides, to overcome the current limitations of living systems, such as those in agriculture, biology, the environment, and foods. However, few active targeting systems using biocompatible capsules and physical forces simultaneously have been developed in the agricultural engineering field. Methods: Here, we developed an active targeting delivery platform that uses biocompatible alginate capsules and controls movements by magnetic forces for agricultural and biological engineering applications. We designed and fabricated large-scale biocompatible capsules, using custom-made nozzles ejecting alginate solutions for encapsulation. Results: To develop the active target delivery platforms, we incorporated iron oxide nanoparticles in the large-scale alginate capsules. The sizes of alginate capsules were controlled by regulating the working conditions, such as concentrations of alginate solutions and iron oxide nanoparticles. Conclusions: We confirmed that the iron oxide particle-incorporated large-scale alginate capsules moved actively in response to magnetic fields, which will be a good strategy for active targeted delivery platforms for agriculture and biological engineering applications, such as for the controlled delivery of agriculture pesticides and biocontrol agents.