• 한국초전도ㆍ저온공학회논문지
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• 제5권1호
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• pp.40-43
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• 2003

The phase transformation, variation of secondary phase, and critical current density $(J_c) for (Bi,Pb)_2Sr_2Ca_2Cu_3O_10 (2223)$ tapes have been studied through the thermal slide heat treatment (TSHT) process. This process consists of a multiple variations of oxygen partial pressures and temperatures at the initial heat treatment During the initial heat treatment some secondary phase such as $(Ca,Sr)_2CuO_3(2/1 AEC), (Ca,Sr)_{14}Cu_{24}O_{41} (14/24 AEC), and (Bi,Pb)_2Sr_2CuO_y$(2201, amorphous phase) farm in Bi-2223 tapes, especially at the 2223 grain boundaries. These secondary phases are detrimental to the phase transformation and final properties. In order to control the secondary phase in Bi-2223 tapes the amount and size of secondary phases among the TSHT process were observed. The results indicate that the amount and particle size of AEC particles were smaller when the TSHT process was used than when the normal process at the initial heat treatment was used which results in the improved $J_c$ properties after the final process.

• 한국재료학회지
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• 제12권9호
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• pp.712-717
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• 2002

New wet chemical method so called precipitation-evaporation method was suggested for preparing spinel structure lithium manganese oxide ($LiMn_2$$O_4$) for Li ion secondary battery. Using precipitation-evaporation method, $LiMn_2$$O_4$ cathode materials suitable for Li ion secondary batteries can be synthesized. Single spinel phase $LiMn_2$$O_4$ powder was synthesized at lower temperature compared to that of prepared by solid-state method. $LiMn_2$$O_4$ powder prepared by precipitation-evaporation method showed uniform, small size and well defined crystallinity particles. Li ion secondary battery using $LiMn_2$$O_4$ as cathode materials prepared by precipitation-evaporation method and calcined at $800^{\circ}C$ showed discharge capacity of 106.03mAh/g and discharge capacity of 95.60mAh/g at 10th cycle. Although Li ion secondary battery showed somewhat smaller initial capacity but good cyclic ability. It is suggested that electro-chemical properties can be improved by controlling particle characteristics by particle morphology modification during calcination and optimizing Li ion secondary battery assembly conditions.

• 열처리공학회지
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• 제34권4호
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• pp.179-184
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• 2021

Two types of secondary hardening martensitic steels, 10Co-14Ni and 6Co-5Ni, were produced by vacuum induction melting to investigate the effect of ausforming process on mechanical properties. According to the results of present study, the alloy samples ausformed at low temperature indicated a rather low hardness level in overall aging time despite the refinement of martensite lath width. As the result can closely be related with the presence of primary carbides precipitated within the initial austenite matrix, we confirmed that, in ultrahigh strength secondary hardening martensitic alloy steels, the ausforming process can rather limit the degree of secondary hardening during the subsequent aging treatment.

• Progress in Superconductivity
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• 제4권1호
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• pp.90-93
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• 2002

The sintering process of BSCCO 2223 tapes is a complex process that is very sensitive to parameters, such as temperature, oxygen partial pressure, heating and cooling rate and holding time. During the first heat treatment, 2212 phase of precursor powder is partially transformed into 2223 phase and some residual secondary phases, such as $(Bi,Pb)_2$$Sr_2$CuO／sub y／(2201), $(Ca,Sr)_2$CuO／sub y／(2/1AEC), (Ca,Sr)／sub 14／Cu／sub 24／O／sub 41／(14／24 AEC) etc. The secondary phases are difficult to be removed from the BSCCO 2223 matrix on the heat treatment. These secondary phases degrade the critical current density. In order to minimize the amount and size of alkaline earth cuprate(AEC) particles step heat treatment is applied during the first heat treatment under the varying atmosphere. Experimental results showed that by adapting the step heat treatment process, the amount and particle size of the secondary phases in the final tapes are decreased. Consequently, the BSCCO 2223grain texture and Jc properties are improved.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2001년도 The 6th International Symposium of East Asian Resources Recycling Technology
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• pp.3-8
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• 2001

The mineral industry of the United States is going through a challenging time. The US as an industrial nation faces with increasing demand in raw materials to fuel various industrial sectors but, at the same time, meeting environmental constraints associated with excavating and extracting these raw materials. In addition, gradual depletion of material resources. and the necessity of handling more complex forms of resources of primary origin have led to a decline in her resource productivity, once a strategic advantage of the U.S. As a result. the United States currently relies heavily upon foreign importation of various materials such as precious and strategic metals. However, since the US is the major consumer of most of these materials, the recovery of these values from scrap would help renew her position as a resource-producing nation, and ultimately help spur its domestic economy. Furthermore. recycling would also help maintain a clean environment and reduce energy consumption. In this paper. the author attempts to discuss opportunities and challenges lied ahead of the US mineral in relation to recovering their much-needed resources from secondary sources. The need and demand in various metals in the US will be reviewed and discussed. The implication of resource recovery from secondary sources will also be discussed. Extraction methods treating secondary sources are inherently different from those for primary sources. There is a need for new technologies which are metallurgically efficient and environmentally benign in treating secondary sources. Ways to meet such a need will be examined and key factors to be considered in approaching these challenges will be discussed.

• 한국분말재료학회지
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• 제21권4호
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• pp.286-293
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• 2014

The electrochemical properties of cells assembled with the $LiNiO_2$ (LNO) recycled from cathode materials of waste lithium secondary batteries ($Li[Ni,Co,Mn]O_2$), were evaluated in this study. The leaching, neutralization and solvent extraction process were applied to produce high-purity $NiSO_4$ solution from waste lithium secondary batteries. High-purity NiO powder was then fabricated by the heat-treatment and mixing of the $NiSO_4$ solution and $H_2C_2O_4$. Finally, $LiNiO_2$ as a cathode material for lithium ion secondary batteries was synthesized by heat treatment and mixing of the NiO and $Li_2CO_3$ powders. We assembled the cells using the $LiNiO_2$ powders and evaluated the electrochemical properties. Subsequently, we evaluated the recycling possibility of the cathode materials for waste lithium secondary battery using the processes applied in this work.

• 한국정보디스플레이학회:학술대회논문집
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• 한국정보디스플레이학회 2008년도 International Meeting on Information Display
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• pp.953-956
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• 2008

Using the theoretical model of Auger electron emission, effects of MgO properties which include band gap energy, escape probability, gas ion, and doping elements on the yield of secondary electron emission were examined. The results indicated that the band gap of MgO must be decreased and escape probability must be enhanced in order to increase the yield of secondary electrons from Xe ions and that may proved to be a critical for achieving high luminance efficacy in ac-PDPs.

• 전기화학회지
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• 제10권1호
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• pp.31-35
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• 2007

이 리뷰를 통하여, 휴대폰용 리튬이차전지의 최근 기술동향을 설명하였다. 휴대폰용 이차전지로는 니카드, 니켈-금속수소, 리튬이온 혹은 리튬이온폴리머의 세 가지 형태의 전지가 있으며, 리튬 이차전지가 에너지밀도 측면에서 가장 성능이 우수하다. 즉, 동일한 용량을 갖는 이차전지 가운데 가장 작고 가벼운 것은 리튬이차전지이다. 이러한 리튬이차전지의 시장은 매년 약 15%의 높은 성장을 기록하고 있다. 연구개발은 $LiFePO_4$를 포함하는 새로운 양극, $Li_4Ti_5O_{10}$, Si, 주석 등의 새로운 음극소재, 새로운 전해질과 안정성 확보에 관한 것을 중심으로 진행되고 있다.

• 대한금속재료학회지
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• 제46권7호
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• pp.437-442
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• 2008

The synthesis and hydration of Calcium Sulfo Aluminate[$3CaO{\cdot}3Al_2O_3{\cdot}CaSO_4(C_4A_3{\overline{S}})$, CSA cement utilizing secondary steelmaking refining slags is studied for recycling the discarded steel plant wastes to meet the environmental requrations imposed on the steel industry. Raw materials of secondary refining slag, lime sludge, gypsum and bauxite were prepared to be sintered at $1,250^{\circ}C$. The sintered samples were hydrated for 1, 3 and 7 days to evaluate the mineralogical and physico-mechanical properties. The hydration products evaluated with the aid of SEM and XRD analyses confirmed the formation and the continuing growth of ettringite phase with the further hydration times, which plays a role in developing the early strength and the expansion properties of cements. The physico-mechanical properties of hydrated CSA products employing the recycled steelmaking refining slags determined in terms of compressive strength and linear expansion of hydrated products are found to be superior to those of the Ordinary Portland Cement(OPC) or the other commercial CSA cements.

• 한국세라믹학회지
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• 제40권4호
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• pp.365-370
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• 2003

The phase development process of $Ba_2$ $Ti_{9}$ $O_{20}$ ceramics is not clearly known and frequently accompanies second phases which deteriorate dielectric properties. In synthesizing $Ba_2$ $Ti_{9}$ $O_{20}$ ceramics, in order to trace the reaction sequence during conventional solid-state reaction in BaO-Ti $O_2$ system, different barium sources of BaC0$_3$ and BaTi0$_3$ precursor were used as starting materials. From the analysis of XRD patterns, different secondary phases could be identified depending on the barium source used, which might mean that the equilibrium phases in BaO-Ti $O_2$ system are very difficult to be synthesized. Because the BaTi0$_3$ precursor provides short diffusion paths of ions, the system revealed less secondary phases during solid state reaction. In synthesizing BaO-xSm$_2$0$_3$-4.5Ti0$_2$ system using different barium sources, different secondary phases were developed also. Microstructure and dielectric properties were examined and discussed in terms of secondary phase development.