• 청정기술
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• 제29권2호
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• pp.87-94
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• 2023

폐리튬계 이차전지로부터 유가금속을 회수하는 것은 한정된 지구자원의 활용 측면에서 매우 중요하다. 최근 자동차의 전지로 많이 사용하고 있는 LiFePO₄ 전지 양극재 성분에는 리튬이 약 5.2% 함유되어 있으며, 사용 후 전지에서 리튬 재활용을 통하여 다시 전지의 원료로써 사용할 수 있다. 본 연구에서는 폐LiFePO₄ 양극재 분말에 함유된 리튬을 선택적으로 침출하기 위하여 일반적으로 많이 사용하고 있는 무기산의 일종인 저농도 황산을 이용하였다. 그리고 각 성분의 침출율 및 분리효율을 비교·분석을 위하여 침출 시 광액농도를 변수로 2 스텝 침출 공정을 적용하여 최적의 침출조건을 도출하고자 하였다. 광액농도를 변수로 침출 시 철 및 인 성분이 거의 침출되지 않는 200 g/L의 광액농도 조건에서는 타 조건과 분리 효율이 약 200배 이상 높은 것으로 확인되었다. 이에 리튬의 선택적 침출 및 회수에 있어서 침출조건을 최적화하였다.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 춘계학술대회논문집E
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• pp.282-287
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• 2001

The CSCM Upwind method and Material Transport Analysis (MTA) have been used to predict the thermal response and ablation rate for non-charring material to be used as thermal protection material (TPM) in KSR-III test rocket nozzle. The thermal boundary conditions such as cold wall heat-transfer rate and recovery enthalpy for MTA code are obtained from the upwind Navier-Stokes solution procedure. The heat transfer rate and temperature variations at rocket nozzle wall were studied with shape change of the nozzle surface as time goes by. The surface recession was severely occurred at nozzle throat and this affected nozzle performance such as thrust coefficient substantially.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2005년도 추계 학술발표회 제17권2호
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• pp.487-490
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• 2005

In this study, for the establishment of the performance evaluation methods and the quality control standards of durability recovery method, the data of indoor durability test and the data of the long term exposure test under the coast are accumulated and analyzed. As a result of the indoor test, durability of repair material was more superior to that of plain concrete, but as a result of investigating and evaluating exposure test at 30 month of exposure age under the coastal environment, the difference in electric potential and the reinforcement corrosion at place replaced with repair material are found.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 1996년도 춘계학술대회 논문집
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• pp.123-128
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• 1996

As electrode materials like as Cu-Pb, Cu-Bi, WC-Ag, W-Ag for vacuum circuit breaker have high chopping current or bad insulation-recovery characteristics, it can affect induction machinery like as transformer and motor. To produce low surge electrode material, it have been suggested Co-Ag-Te electrode which were infiltrated with Ag-Te intermetallic compound into sintered Co matrix in vacuum. In this paper, we would like to represent that production method and microstructure of Co-Ag-Te electrode material in each condition. The microstructure and characteristics of Ag-Te intermetallic compound and Co-(Ag-Te) electrode were investigated by using optical microscope, SEM, XRD, EPMA.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 1995년도 춘계학술대회 논문집
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• pp.31-34
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• 1995

The NO$_2$ gas-deteotion characteristics were investigated using the functional organic Langmuir-Blodgett(LB) files of Dilithium phthalocyanines(Li$_2$Pc). The optimum conditions for a film deposition were obtained through a study of $\pi$-A isotherms, and the deposited film status was confirmed by the ellipsometry measurements. A propel number of layers for the gas-detection was proved to be 9 layers from a measurement of a measurement of change in the electrical conductivities when the films were exposed to the 200 ppm of the NO$_2$ gases. A response time, recovery time, and reproducibility were also studied. A proper temperature which was able to activate gas interaction between NO$_2$ gases and Li$_2$Pc LB films was around 150$^{\circ}C$ judging from the electrical conductivities in a temperature range of 20 to 200$^{\circ}C$. It was found that at 150\ulcorner there are increments of electrical conductivities by 65 tines, 30 seconds of response time and 60 seconds of recovery tine when the filmswere exposed to the gasses.

• 한국생산제조학회지
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• 제18권3호
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• pp.328-335
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• 2009

In order to 1ransport the steel roll coil effectively and safely to the destination, the stability of the steel roll coil which induced the minimum movements during the 1ransportation was s1rongly required. The basic 1ransportation equipment for the steel roll coil such as the wedge is made of 100% imported wood known as the apitong. However, the material characteristic such as the rigidity has caused permanent damages to the steel roll coil and the damaged steel roll coils were not easily restorable. Thus it was unsuitable for other purposes. The introduction of new materials to manufacturing wedges which would have a good recovery performance and thus enable the wedge prevention or reduction to the steel roll coil or any other products during the 1ransportation is needed. Due to the fact that recovering damage of the coil is almost impossible, we have to find the new type of wedge that can substitute the apitong wedge. Therefore, we are going to develop a wedge that does not damage rolled steel coil and has better recovery and softness than existing apitong wedge.

• 한국전기전자재료학회논문지
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• 제24권5호
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• pp.410-415
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• 2011

In this paper, we investigated the fault current limiting and the load voltage sag suppressing characteristics of the flux-lock type SFCL, designed with the additive polarity winding, according to the variations of turn number's ratio and the comparative analysis between the resistive type and the flux-lock type SFCLs were performed as well. From the analysis for the short-circuit tests, the flux-lock type SFCL designed with the larger turn number's ratio was shown to perform more effective fault current limiting and load voltage sag suppressing operations compared to the flux-lock type SFCL designed with the lower turn number's ratio through the fast quench occurrence of the high-$T_C$ superconducting (HTSC) element comprising the flux-lock type SFCL. In addition, the recovery time of the flux-lock type SFCL after the fault removed could be confirmed to be shorter in case of the flux-lock type SFCL designed with the lower turn number ratio.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2003년도 The 8th Asian Symposium on Precision Forging ASPF
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• pp.73-79
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• 2003

Recently many kinds of gears have been produced by forging in order to enhance the mechanical properties of the gears and the productivity of the process. Developments in forging technology are the reason for the increased usage. However, a critical problem of the forged gears is the dimensional change or distortion caused by elastic recovery after forging, and relief of the residual stresses during subsequent heat treatments. Distortion is of great concern to the manufacturers of precision parts, because it influences directly the dimensional accuracy and the grade of carburized bevel gears. In the present paper, distortion due to cold forging and heat treatment of bevel gears is investigated. Distortions of forged gears, machined gears and die are measured and compared. Numerical analysis is used to simulate the complete cold forging process and heat treatment process for the machined gears and shows good agreement with the experimental measurements.

• 한국전기전자재료학회논문지
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• 제14권7호
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• pp.551-556
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• 2001

In this work, the recovery of etching damage in the etched PZT thin film with $O_2$ annealing has been studied. The PZT thin films were etched as a function of Cl$_2$/Ar and additive CF$_4$ into Cl$_2$(80%) /Ar(20%). the etch rates of PZT thin films were 1600$\AA$/min at Cl$_2$(80%)/Ar(20%) and 1970 $\AA$/min at 30% additive Cf$_4$ into Cl$_2$(80%)/Ar(20%). In order to recover the characteristics of etched PZT thin films, the etched PZT thin films were annealed in $O_2$ atmosphere at various temperatures. From the hysteresis curves, ferroelectrical properties are improved by $O_2$ annealing process. The improvement of ferroelectric behavior is consistent with the increase of the (100) and (200) PZT phase revealed by x-ray diffraction (XRD). From x-ray photoelectron spectroscopy (XPS) analysis, intensities of Pb-O, Zr-O and Ti-O peak increase and the chemical residue peak is reduced by $O_2$ annealing. From the atomic force microscopy (AFM) images. it shows that the surface morphology of re-annealed PZT thin films after etching is improved.

• 한국전기전자재료학회논문지
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• 제19권1호
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• pp.7-12
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• 2006

Local minority carrier lifetime control by means of particle irradiation is an useful technology for Production of modern silicon Power devices. Crystal damage due to ion irradiation can be easily localized by choosing appropriate irradiation energy and minority tarrier lifetime can be reduced locally only in the damaged layer. In this work, proton irradiation technology was used for improving the switching characteristics of a un diode. The irradiation was carried out with various energy and dose condition. The device was characterized by current-voltage, capacitance-voltage, and reverse recovery time measurements. Forward voltage drop was increased to 1.1 V at forward current of 5 A, which was $120\%$ of its original device. Reverse leakage current was 64 nA at reverse voltage of 100 V, and reverse breakdown voltage was 670 V which was the same voltage as original device without irradiation. The reverse recovery time of device was reduced to about $20\%$ compared to that of original device without irradiation.