• Journal of the Korean Society for Heat Treatment
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• v.5 no.4
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• pp.233-239
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• 1992

A study of the precipitation process of Al-Li binary alloy at low ageing temperature has been carried by electrical resistivity measurement. Two types of G.P.zones were formed during ageing at low temperature. G.P. (1) zone and G.P. (2) zone have been formed primarily at ageing temperature below $60^{\circ}C$ and at ageing temperature range of $80^{\circ}C$ to $100^{\circ}C$, respectively. Therefore the precipitation process of Al-Li binary alloy was as follows; G.P.(1) zone ${\rightarrow}$ G.P.(2) zone ${\rightarrow}{\delta}^{\prime}{\rightarrow}{\delta}$ G.P. (1) zone might be affected by excess vacancies, but G.P. (2) zone might be affected by secondary defects. clusters and Li-vacancy pairs. The activation energy for formation of G.P. (2) zone is 0.87eV. It is lower than that of Al-Cu alloy.

• 한국전기화학회:학술대회논문집
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• 2000.04a
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• pp.38-38
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• 2000

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2007.06a
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• pp.256-256
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• 2007

As a candidate for lead-free piezoelectric materials, dense ($(Na_{0.47}K_{0.47}Li_{0.06})NbO_3$ (LNKN6) ceramics were developed by conventional sintering process. Sintering temperature was lowered by adding $Li_2O$ as a sintering aid. Abnormal grain growth in the LNKN6 ceramics was observed with varying $Li_2O$ content. The electrical properties of LNKN6 ceramics were investigated as a function of $Li_2O$ concentration. When the sample sintered at $1000^{\circ}C$ for 4h with the addition of 1 mol% $Li_2O$, electromechanical coupling factor ($k_p$) and piezoelectric coefficient ($d_{33}$) of LNKN6 ceramics were found to reach the highest values of 0.40 and 184 pC/N, respectively.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.10 no.3
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• pp.239-244
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• 2000

Synthesis and high temperature phase stability of $_{1+x}$ Co$_{y}$ Mn$_{2-y}$ $O_4$(0$\leq$x$\leq$0.2,y=0,1/9,1/6) spinel, both the excess lithium and cobalt added, have been studied. The spinel was prepared by oxalate precipitation method as the wet chemical process. Oxalate derived spinel was synthesized by heating of precipitates at temperature lower than $600^{\circ}C$. As a result of the TG-DTA and XRD analysis of prepared and quenched powders, it was found that reversible phase transitions started at temperatures $T_1$, $T_2$및 $T_{2'}$. The transitions involved weight (oxygen) loss and gain during heating and cooling. The effects of Li excess and Co doping on the spinel lattice constant, phase stability and transition temperatures of the prepared powders are investigated. This study would provide important data for determining the spinel preparation process such as synthesis temperature and cooling speed.

• Journal of the Korean Electrochemical Society
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• v.11 no.4
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• pp.297-303
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• 2008

$LiNiO_2$ cathode powders with fine size have been synthesized by spray pyrolysis from the spray solution with citric acid and ethylene glycol. The as-prepared powders with spherical shape, porous structure and micron size turned into $LiNiO_2$ powders with micron size and regular morphology after post-treatment at $800^{\circ}C$. The initial discharge capacities of the $LiNiO_2$ powders changed from 199 to 171mAh/g when the concentrations of the citric acid and ethylene glycol added to the spray solutions were changed from 0 to 1 M. The maximum initial discharge capacity of the $LiNiO_2$ powders obtained from the spray solution with citric acid and ethylene glycol was 198 mAh/g when the lithium component added to the spray solution was 6 mol% excess of the stoichiometric amount. The discharge capacities of the fine-sized $LiNiO_2$ powders dropped from 198 to 163 mAh/g by the 30 th cycle at a current density of 0.1 C.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.14 no.4
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• pp.341-349
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• 2002

Heat and mass transfer characteristics of a surfactant-added LiBr-$H_2O$ solution flowing over a single horizontal tube were examined experimentally. The parameters considered were surfactant (2-ethyl-1-hexanol) concentration, solution temperature at the top of the tube and absorber pressure. Even with an amount of the surfactant below the solubility limit, heat and mass transfer performances were enhanced tremendously. The Nusselt and Sherwood numbers increased by about 70% and 340%, respectively, when 10 ppm of the surfactant was added. However, an excess amount of the surfactant in the solution did not bring a further enhancement. The absorption performance deteriorated when the non-condensable gases were extracted from the system (by a vacuum pump) since the vaporized surfactant was also extracted during the process. Therefore, it is desirable to add a sufficient amount of the surfactant (more than 10 ppm) to maintain high performance of absorption.

• Nuclear Engineering and Technology
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• v.53 no.5
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• pp.1534-1539
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• 2021

This study reports on the dissolution behavior of SrO in LiCl at varying SrO concentrations from low concentrations to excess. The amount of SrO dissolved in the molten salt and the species present upon cooling were determined. The thermal behavior of LiCl containing various concentrations of SrO was investigated. The experimental results were compared with results from the simulated results using the HSC Chemistry software package. Although the reaction of SrO with LiCl in the standard state at 650 ℃ has a slightly positive Gibbs free energy, SrO was found to be highly soluble in LiCl. Experimentally determined SrO concentrations were found to be considerably higher than those present in used nuclear fuel (<2 g/kg). As Sr-90 is one of the most important heat-generating nuclides in used nuclear fuel, this finding will be impactful in the development of fast, simple, and proliferation-resistant heat reduction processes for used nuclear fuel without the need for separating nuclear materials. Heat reduction is important as it decreases both the volume necessary for final disposal and the worker handling risk.

• Nuclear Engineering and Technology
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• v.54 no.2
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• pp.653-660
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• 2022

The interaction between UN and CdCl₂ in the LiCl-KCl molten eutectic was studied at 1023 K. The chlorination was monitored by sampling and recording the redox potential of the medium. At 1023 K the chlorination of UN with cadmium chloride in the molten LiCl-KCl eutectic proceeds completely and results in the formation of uranium chlorides. The melts of the LiCl-KCl-UCl₃ or LiCl-KCl-UCl₄ compositions can be obtained by the end of experiment depending on the presence of metallic cadmium in the reaction zone. The higher the concentration of the chlorinating agent, the faster the reaction rate. At [CdCl₂]/[UN] = 1.65 (10% excess) the reaction proceeds to completion in about 7.5 h. At [CdCl₂]/[UN] = 7 the complete chlorination takes 2.5-3 h.

• Proceedings of the Materials Research Society of Korea Conference
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• 2010.05a
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• pp.37.2-37.2
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• 2010

Recently $Li_{1.2}Ni_{0.2}Mn_{0.6}O_2$ has been consistently examined and investigated by scientists because of its high lithium storage capacity, which exceeds beyond the conventional theoretical capacity based on conventional chemical concepts. Consequently, $Li_{1.2}Ni_{0.2}Mn_{0.6}O_2$ is considered as one of the most promising cathode candidates for next generation in Li rechargeable batteries. Yet the mechanism and the origin of the overcapacity have not been clarified. Previously, many authors have demonstrated simultaneous oxygen evolution during the first delithiation. However, it may only explain the high capacity of the first charge process, and not of the subsequent cycles. In this work, we report a clarified interpretation of the structural evolution of $Li_{1.2}Ni_{0.2}Mn_{0.6}O_2$, which is the key element in understanding its anomalously high capacity. We identify how the structural evolution of $Li_{1.2}Ni_{0.2}Mn_{0.6}O_2$ occurs upon the electrochemical cycling through careful study of electrochemical profiles, ex-situ X-ray diffraction (XRD), HR-TEM, Raman spectroscopy, and first principles calculation. Moreover, we successfully separated the structural change at subsequent cycles (mainly cation rearrangement) from the first charge process (mainly oxygen evolution with Li extraction) by intentionally synthesizing sample with large particle size. Consequently, the intermediate states of structural evolution could be well resolved. All observations made through various tools lead to the result that spinel-like cation arrangement and lithium environment are created and embedded in layered framework during repeated electrochemical cycling.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.10 no.5
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• pp.362-366
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• 2000

$Li_{0.44}MnO_2$cathode material has high reversibility during lithium insertion processes and is not easily damaged through over-charging or over-discharging. $Mn_2O_3$is often present as an impurity phase, and reduce the electrochemical capacity of electrode because this phase is electrochemically inert. Adding of excess NaOH reduced the $Mn_2O_3$to the content under undetectable by X-ray diffraction. Because the capacity can be increased in the cathode materials with larger unit cell, some of the manganese was replaced with titanium having larger ion size, and powders with the formula $Li_{0.44}T_{iy}Mn_{1-y}O_2$(where y = 0.11, 0.22, 0.33, 0.44, and 0.55) was synthesized and characterized. A maximum reversible capacity of 150 mAh/g was obtained for $Li/P(EO)_8$LiTFSI/$Li_{0.44}Ti_{0.22}Mn_{0.78}O_2$cells in electrochemical potential spectroscopy (ECPS) experiments. Cells with the titanium-doped manganese oxides exhibited a fade rate of 0.12 % or less per cycle.