• 한국세라믹학회지
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• 제28권2호
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• pp.146-152
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• 1991

Ultra fine and homogeneous (Ni0.4Zn0.6)Fe2O4 ferrite powders were prepared by direct-wet, Hydrothermal and coprecipitation methods. In case that specific surface areas of Ni-Zn ferrite powders were over 220㎡/g, 100㎡/g, 30㎡/g individually direct-wet, hydrothermal and coprecipitation methods. The Ni-Zn ferrite magnetic fluids of which Solvents were benzene or kerosene was prepared by making cation surfactant adsorbed on the surface of the (Ni0.4Zn0.6)Fe2O4. The results that measured dispersion and viscosity by making cation surfactant adsorbed were as follows. 1. The adsorption amount of Oleric acid be proportioned the specific surface area of powders. 2. The maximum amount of Oleric acid was 36wt% of dried powders which has 220㎡/g of specific surface area. 3. The stability of fluid by direct-wet synthesis emthod in benzene or kerosene solvent excellent.

• 한국지열·수열에너지학회논문집
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• 제6권1호
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• pp.17-22
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• 2010

A sliding accident on the road have a high percentage by road freezing, especially, it is often appeared at bridges and tunnel of freezing areas. Thus, the stability of road operations is enhanced by preventing a partial freezing phenomenon. According to the geothermal snow melting system analysis, a pattern of thermal conductivity is found out about pavement materials of concrete and asphalt when it is buried. For the feasibility study on geothermal snow melting system, analysis of the ground melting point when operating system, life evaluation of pavements and safety evaluation of pipes are performed.

• 청정기술
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• 제28권2호
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• pp.154-162
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• 2022

알루미늄 (Al) 금속을 전구체 및 구조체로 이용, 수열 반응을 통하여 Al@Al₂O₃와 Al@Ni-Al LDH (LDH = layered double hydroxide) 코어-쉘 복합 구조체를 합성하였다. 제조된 구조체의 형상, 조성, 결정 구조는 수용액에 존재하는 이온들에 의하여 크게 영향을 받았으며, 이를 활용하여 다양한 특성의 촉매 구조체 유도가 가능하였다. Al@Ni-Al LDH 코어-쉘 구조체의 환원을 통하여 Ni 나노 입자가 고정화된 Ni/Al@Al₂O₃ 촉매를 제조하였고, CO₂ 메탄화 반응에 적용하여 촉매의 특성을 평가하였다. Ni/Al@Al₂O₃ 촉매는 전통적 incipient wetness impregnation 방법에 의하여 제조된 Ni/Al₂O₃ 촉매에 비교하여 Ni 입자의 분산도와 균일성이 매우 높았으며 약 2 배 이상의 CO₂ 전환율로 높은 촉매적 활성과 더불어 구조의 안정성을 보여 주었다. 이러한 Ni/Al@Al₂O₃ 구조체 촉매의 우수한 특성은 Al 금속을 기반으로 한 새로운 개념의 촉매 구조체 설계와 합성 방법의 타당성을 보여준다.

• Carbon letters
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• 제26권
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• pp.25-30
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• 2018

The dielectric medium used in electrophoretic displays (EPDs) is required to be an environmentally friendly solvent with high density, low viscosity, and a large electric constant. Hydrofluoroether, a highly fluorinated solvent with eco-friendly characteristics, is regarded as a viable alternative medium for EPDs, owing to the similarity of its physical properties to those of the conventional EPD medium. Surface modification of particles is required, however, in order for it to disperse in the charged solvent. Also, positive/negative charges should be present on the particle surface to enable electrophoretic behavior. In this study, carbon black particles wrapped with positively charged nitrogen (N-CBs) were fabricated by a simple hydrothermal process using a poly(diallyldimethylammonium chloride) solution as a black coloring agent for the EPD. The dispersion behavior of N-CBs was investigated in various solvents.

• Corrosion Science and Technology
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• 제9권6호
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• pp.265-269
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• 2010

This paper describes the exfoliation and surface modification of muscovite mica for UV coating formulation. For the exfoliation of the mica, hydrothermal process was used in the presence of lithium nitrate ($LiNO_3$). After the cation exchange with $Li^+$ ions, the surface of the mica was modified with several amphiphilic substances to increase compatibility and storage stability in UV coating formulation. Such a hydrophobic surface modification affected colloidal stability as well as dispersibility of the exfoliated mica in UV coating solution. Anticorrosive property of mica/UV coated steel plates was tested by salt spray test (SST) and compared with sodium montmorillonite ($Na^+$-MMT)/UV coated steel plates.

• Journal of Electrochemical Science and Technology
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• 제4권1호
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• pp.19-26
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• 2013

Graphene/Ni-Al layered double hydroxide (LDH) hybrid materials were synthesized by a hydrothermal reaction. Hexagonal Ni-Al LDH particles nucleated and grew on graphene sheets, thus preventing restacking of the graphene sheets and aggregation of the Ni-Al LDH nanoparticles upon drying. Electrode made from the graphene/Ni-Al LDH hybrid materials showed a substantial improvement in electrochemical capacitance relative to those made with pure Ni-Al LDH nanoparticles. In addition, the graphene/Ni-Al LDH hybrid composite materials showed remarkable stability after 4000 cycles with over 100% capacitance retention. These materials are thus very promising for use in electrochemical capacitor electrodes.

• 한국응용과학기술학회지
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• 제30권2호
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• pp.233-243
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• 2013

무지개 빛을 내는 무기진주광택안료는, 내광성, 내용제성 및 내열성 등이 물리적 화학적 안정성이 우수하여 다양한 분야에서 응용되고 있다. 본 연구는 수열합성방법을 사용하여 마이카 티타니아에 파란색 코팅 안료인 염화코발트를 기본으로 화장품 안료로 사용되는 진주광택안료를 합성하였다. 코발트에 의한 안료의 색상을 보완하고자 코발트와 금속 염의 비를 달리하여 안료를 코팅하고, 이를 통해 금속염의 종류에 따라 다양한 색차값을 구현하는 진주광택 안료를 합성하였다. 코발트와 첨가된 금속 염 전구체의 조성비와, 금속 염의 종류에 따라 코팅 특성과 색상을 조절할 수 있었고, 안료의 다양한 색상변화 특성을 색차계를 통해 확인 하였다. 합성된 안료는 SPM, SEM, XRD, EDS 기기를 통해 특성을 분석하였다.

• 공업화학
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• 제29권6호
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• pp.740-745
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• 2018

본 연구에서는 비정질 칼슘 포스페이트(ACP) 나노 입자의 합성과 특성 분석을 진행하였다. 염화칼슘(calcium chloride ($CaCl_2$))과 아데노신 인산나트륨(disodium adenosine triphosphate ($Na_2ATP$)) 그리고 피트산 나트륨(sodium phytate) 첨가제를 열수 반응을 통해 상대적으로 단분산된 100 nm 크기 이하의 ACP 나노 입자를 성공적으로 합성하였고 나노 입자의 화학적 조성과 구조를 재료 분석을 통해 확인하였다. 피트산 나트륨 첨가제의 사용을 통해 얻은 ACP 나노 입자는 비정질성을 유지하고 결정성 하이드록시아파타이트(HAP)로의 전환을 방지하는 안정성이 향상되었음을 발견하였다. 본 연구를 통해 발견된 향상된 안정성을 가지는 ACP 나노 입자는 재생 의학 분야에서의 생체 적합 물질로의 응용에 중요한 잠재적 용도가 있을 것이라 사료된다.

• 자원환경지질
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• 제25권1호
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• pp.41-50
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• 1992

Mineral assemblages, mineral chemistries and stable isotope compositions of altered rocks of the Ogmae, Seongsan, Haenam and Gusi mines near the Haenam volcanic field in the southwestern part of the Korea peninsula were studied. Characteristic hydrothermal alteration zones in these deposits occurring in the Cretaceous volcanics and volcanogenic sediments, acidic tuff, and rhyolite, were outlined. Genetic environment with particular reference to the spatial and temporal relationships for these deposits were considered. The alteration zones defined by a mineral assemblage in the Ogmae and Seongsan deposits can be classified as alunite, pyrophyllite, kaolinite or dickite, quartz, illite or illite/smectite. Alunite was not developed in the Gusi and Haenam deposits. Boundaries between the adjacent zones are always gradational except for vein-type alunite. Alteration zones are superimposed upon each other in some localities. These deposits formed $71.8{\pm}2.8{\sim}76.6{\pm}2.9$ Ma ago, which is the almost same age of later volcanic rocks $79.4{\pm}1.7{\sim}82.8{\pm}1.2$ Ma, the Haenam Group, corresponding to Campanian. It indicates that hydrothermal alteration of these deposits appeared to be related to felsic volcanism in the area. Consideration of the stability between kaolinite, alunite, pyrite and pyrophyllite, and the geothermometry based on the mineral chemistry of illite and chlorite suggests that the maximum formation temperature for alunite and pyrophyllite can be estimated at about $250^{\circ}C$ and $240{\sim}290^{\circ}C$, respectively. It also suggests that these deposits were formed by acidic sulfate solution with high aqueous silica and potassium activity in a shallow depth environment. Compositional variation of alunite also suggests that the physico-chemical conditions fluctulated considerably during alteration processes, indicating shallow depth environment. The Haenam deposit was formed at a relatively greater depth than the others. The sulfur isotope composition of alunite and pyrite indicates that sulfur probably had a magmatic source, and the oxygen isotope composition for kaolinite indicates that the magmatic hydrothermal solution was diluted by circulating meteoric water.

• 한국광물학회지
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• 제18권3호
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• pp.227-236
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• 2005

밀양점토광상의 알루미늄이 풍부한 다이아스포아 단괴에서 열수변질 기원 전기석은 집합체나 미립으로 산출한다 대부분의 전기석 결정은 미세한 대구조가 특징적인데, 이는 열수변질 작용동안 개방계의 유체혼합과 같은 변동이 심한 환경에서 형성되었음을 지시한다. 본 전기석의 화학적 진동누대 구조의 양상은 결정축의 방향과는 무관하게 흡사한 특징을 보인다. Mg는 결정성장 초기, Fe는 후기 단계동안에 부화되었으며, Fe/Mg의 비는 규칙적으로 진동함을 보여 준다. 화학분석, 후방산란영상(BSE), X-선 화학분석도에 따르면 전기석내 진동누대구조는 Fe와 Mg 함량변화에 주로 제어되었으며 봉소함량의 기여도는 미미하다. 전기석이 다이아스포아와 딕카이트로 변질되는 것으로 볼 때 전기석은 B, Fe, Mg의 활동도가 감소하면서 이들 고알루미나 광물에 비하여 불안정해 진다. 그러므로 열수계내 알루미늄 활동도가 전기석의 안정성을 제어하는 것으로 볼 수 있다.