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Comparison of ASR Mitigation Methodologies
Mohammad S. Islam 한국콘크리트학회 2014 International Journal of Concrete Structures and M Vol.8 No.4
This study evaluates the dosages of Class F fly ash, lithium nitrate and their combinations to suppress the excessive expansion caused by alkali?silica reactivity (ASR). In order to serve the proposed objective, the mortar bar specimens were prepared from (1) four dosages of Class F fly ash, such as 15, 20, 25 and 30 % as a partial replacement of Portland cement, (2) up to six dosages of lithium nitrate, such as lithium-to-alkali molar ratios of 0.59, 0.74, 0.89, 1.04, 1.19 and 1.33, and (3) the combination of lithium salt (lithium-to-alkali molar ratio of 0.74) and two dosages of Class F fly ash (15 and 20 % as a partial replacement of Portland cement). Percent contribution to ASR-induced expansion due to the fly ash or lithium content, test duration and their interaction was also evaluated. The results showed that the ASR-induced expansion decreased with an increase in the admixtures in the mortar bar. However, the specimens made with the both Class F fly ash and lithium salt produced more effective mitigation approach when compared to those prepared with fly ash or lithium salt alone. The ASR-induced expansions of fly ash or lithium bearing mortar bars by the proposed models generated a good correlation with those obtained by the experimental procedures.
Kim, Dong Wook,Lee, Dong Hun,Ahn, Su Mi,Kim, Do Youb,Suk, Jungdon,Choi, Dong Hoon,Kang, Yongku Elsevier 2017 Journal of Power Sources Vol.347 No.-
<P><B>Abstract</B></P> <P>In spite of several desirable properties such as high stability against superoxide anion and low vapor pressure, <I>N</I>-methyl-2-pyrrolidone (NMP) electrolyte is reported not suitable for use in lithium-oxygen (Li-O<SUB>2</SUB>) batteries because of severe degradation upon cycling and low oxygen efficiency. In this work, we find that NMP electrolyte is reactive with O<SUB>2</SUB> gas in the presence of lithium metal and such O<SUB>2</SUB>-consuming reaction (<I>i.e.,</I> autoxidation) is a possible cause for the poor performance in Li-O<SUB>2</SUB> batteries with NMP electrolyte. The autoxidation of NMP is verified by direct measurement of the depletion of O<SUB>2</SUB> gas in the hermetically sealed symmetric Li/Li cells via in-situ gas pressure analysis. In-situ differential electrochemical mass spectroscopy (DEMS) experiment reveals that the autoxidation resulted in significant O<SUB>2</SUB> consumption upon discharge, very low O<SUB>2</SUB> efficiency upon charge, and eventually fast capacity fading. Lithium nitrate (LiNO<SUB>3</SUB>), which provides a protective layer on the surface of lithium metal, is employed to suppress the autoxidation, leading to significantly enhanced oxygen efficiency and cycle life.</P> <P><B>Highlights</B></P> <P> <UL> <LI> NMP electrolyte is reactive with O<SUB>2</SUB> gas in the presence of lithium metal. </LI> <LI> Autoxidation is verified by in-situ gas pressure analysis and DEMS. </LI> <LI> Autoxidation results in low O<SUB>2</SUB> efficiency and fast capacity fading. </LI> <LI> LiNO<SUB>3</SUB> is employed to suppress the autoxidation. </LI> <LI> LiNO<SUB>3</SUB> is efficient in enhancing oxygen efficiency and cycle life. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>
플라이애시와 질산리튬을 사용한 시멘트 경화체의 ASTM C 1260 적용성 검토
김성권,윤경구,홍승호,강문식 한국도로학회 2012 한국도로학회논문집 Vol.14 No.3
The purpose of this study was to review application of ASTM C 1260 for cement matrix with flyash and lithium nitrate using reactive aggregate. The experimental program included the accelerated mortar bar test (AMBT: ASTM C 1260) for the slate which was evaluated as reactive aggregate by ASTM C 1260 at the previous study. The cement, which was substituted by 10, 20, 30% flyash containing less than 10%CaO, could control ASR expansion. From the experiment applying lithium nitrate to control ASR, the mortar bar containing lithium nitrate showed more than 0.1% expansion at 14 days. This is probably due to dissolution of lithium nitrate in NaOH solution during test periods. Thus,it is necessary to adopt another test method to verify the control effect of lithium nitrate against alkali-silica reaction. 본 논문에서는 ASTM C 1260을 이용하여 국내산 골재를 대상으로 알칼리-실리카 반응 판정 결과 반응성으로 판정된 골재를 대상으로 알칼리-실리카 반응 억제효과를 고찰하기 위하여 플라이애시와 질산리튬을 사용한 시멘트 경화체의 ASTM C 1260 적용성을 평가하였다. 알칼리-실리카 반응에 의한 팽창현상이 발생하는 지역에서 CaO 함량이 낮은 플라이애시를 시멘트 중량의 10, 20, 30%를 대체하는 경우 ASTM C 1260으로 알칼리-실리카 반응 억제효과를 확인할 수 있었다. 그러나 질산리튬을 사용할 경우는 ASTM C 1260은 시편을 1N NaOH 수용액에 수침하여 80℃의 온도로 길이변화를 유도하므로 시편내에 혼입된 질산리튬 성분이 외부로 용출될 수 있기 때문에 알칼리-실리카 반응 억제효과를 도출하지 못하였다. 따라서 질산리듐의 ASR 억제효과를 확인하기 위해서는 다른 시험방법을 고려해야 한다.
Preparation and Characterization of Muscovite Mica/UV Coating Materials for Steel
( In Woo Cheong ),( Hyeon Seok Kim ),( Dong Seop Hwang ),( Hye Jin Yoo ),( Jin Tae Kim ),( Jae Ryung Lee ) 한국부식방식학회(구 한국부식학회) 2010 Corrosion Science and Technology Vol.9 No.6
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 (LiNO3). 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.
Choi, Haeyoung,Bae, YeoJi,Lee, Sang-Min,Ha, Yoon-Cheol,Shin, Heon-Cheol,Kim, Byung Gon The Korean Electrochemical Society 2022 Journal of electrochemical science and technology Vol.13 No.1
ANODE-free Li-metal batteries (AFLMBs) operating with Li of cathode material have attracted enormous attention due to their exceptional energy density originating from anode-free structure in the confined cell volume. However, uncontrolled dendritic growth of lithium on a copper current collector can limit its practical application as it causes fatal issues for stable cycling such as dead Li formation, unstable solid electrolyte interphase, electrolyte exhaustion, and internal short-circuit. To overcome this limitation, here, we report a novel dual-salt electrolyte comprising of 0.2 M LiPF<sub>6</sub> + 3.8 M lithium bis(fluorosulfonyl)imide in a carbonate/ester co-solvent with 5 wt% fluoroethylene carbonate, 2 wt% vinylene carbonate, and 0.2 wt% LiNO<sub>3</sub> additives. Because the dual-salt electrolyte facilitates uniform/dense Li deposition on the current collector and can form robust/ionic conductive LiF-based SEI layer on the deposited Li, a Li/Li symmetrical cell exhibits improved cycling performance and low polarization for over 200 h operation. Furthermore, the anode-free LiFePO<sub>4</sub>/Cu cells in the carbonate electrolyte shows significantly enhanced cycling stability compared to the counterparts consisting of different salt ratios. This study shows an importance of electrolyte design guiding uniform Li deposition and forming stable SEI layer for AFLMBs.
하성민,임정우,이고은,오승교,이규태 한국공업화학회 2016 한국공업화학회 연구논문 초록집 Vol.2016 No.1
휴대용 전자 기기의 발달 및 전기 자동차의 상용화로 날로 증대되는 고용량 이차 전지에 대한 요구를 만족시키기 위해 높은 이론 용량의 리튬 공기 전지가 많은 주목을 받고 있다. 리튬 공기 전지는 리튬 금속 전극과 공기극으로 구성되어 있어 이로부터 야기되는 많은 문제점을 가지고 있는데 이들 중 가장 큰 문제는 높은 과전압으로 인한 낮은 에너지 효율이다. 이 문제를 위해 도입된 액상 촉매는 과전압을 줄여서 리튬 공기 전지의 성능을 크게 개선하였지만 cycle이 진행됨에 따라 효과가 감쇄하여 과전압이 다시 증가하는 한계가 나타났다. 본 연구에서는 이러한 액상 촉매의 효과가 열화 되는 현상을 이해하기 위하여 그의 원인과 메커니즘을 분석하였다. 또한 이를 바탕으로 LiNO<sub>3</sub>를 사용하여 액상 촉매의 성능 열화를 억제하였다.
질산 리튬의 혼합에 따른 접촉점화 추진제의 액적낙하 실험 평가
박성현(Seonghyeon Park),이경환(Kyounghwan Lee),강홍재(Hongjae Kang),이종광(Jongkwang Lee) 한국추진공학회 2021 한국추진공학회 학술대회논문집 Vol.2021 No.5
과산화수소는 저독성 물질로서 기존의 독성 추진제를 대체할만한 접촉점화 산화제로서 주목받고 있다. 과산화수소 기반의 추진제는 기존 추진제 조합에 비해 낮은 점화성능을 보완하기 위해 연료나 산화제에 점화반응을 돕는 첨가물을 첨가한다. 이 연구에서는 90% 과산화수소를 산화제로서 사용하였으며, 이온성 물질인 BMIM SCN을 연료로서 사용하였다. 용해성이 우수한 과산화수소에 질산 리튬을 0~20 wt.% 혼합하여 액적낙하 실험을 수행하고, 점화지연시간 단축 가능성을 확인하였다. 질산 리튬을 20 wt.% 혼합한 추진제는 질산 리튬을 혼합한 추진제에 비해 점화지연시간이 확연히 감소하는 경향을 보였다. Hydrogen peroxide having low toxicity have attracted attention as non-toxic hypergolic oxidizer replacing a novel toxic propellant. Since hypergolic propellant pairs based on hydrogen peroxide have low ignition performance, they have introduced additives which help ignition reaction. In this study, 90% hydrogen peroxide was used as oxidizer and BMIM SCN was used as hypergolic fuel. Difference of ignition delay for hypergolic pairs introducing 0~20 wt.% LiNO3 was measured in the drop test. Propellants with 20 wt.% LiNO3 can significantly reduce ignition delay than non-added propellants.