• Bulletin of the Korean Chemical Society
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• 제31권11호
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• pp.3233-3237
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• 2010

A $Li[Ni_{0.3}Co_{0.4}Mn_{0.3}]O_2$ cathode was modified by coating with Li-La-Ti-O, and the effect of the coating thickness on their electrochemical properties was studied. The thickness of the coating on the surface of $Li[Ni_{0.3}Co_{0.4}Mn_{0.3}]O_2$ was increased by increasing the wt % of the coating material. The rate capability of the Li-La-Ti-O-coated electrode was superior to that of the pristine sample. 1- and 2-wt %-coated samples showed considerable improvement in capacity retention at high C rates. However, the rate capability of a 5-wt %-coated sample decreased. All the coated samples showed a high discharge capacity and slightly improved cyclic performance under a high cut-off voltage (4.8 V) condition. Results of a storage test confirmed that the Li-La-Ti-O coating layer was effective in suppressing the dissolution of the transition metals as it offered protection from the attack of the acidic electrolyte. In particular, the 2- and 5-wt %-coated samples showed a better protection effect than the 1-wt %-coated sample.

• 한국전기전자재료학회논문지
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• 제37권2호
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• pp.215-222
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• 2024

Ni-rich cathode materials have been developed as the most promising candidates for next-generation cathode materials for lithium-ion batteries because of their high capacity and energy density. In particular, the electrochemical performance of lithium-ion batteries could be enhanced by increasing the contents of nickel ion. However, there are still limitations, such as low structural stability, cation mixing, low capacity retention and poor rate capability. Herein, we have successfully developed the nanorod-type Ni-rich cathode materials by using co-precipitation method. Particularly, the nanorod-type primary particles of LiNi_0.7Co_0.15Mn_0.15O₂ could facilitate the electron transfer because of their longitudinal morphology. Moreover, there were holes at the center of secondary particles, resulting in high permeability of the electrolyte. Lithium-ion batteries using the prepared nanorod-type LiNi_0.7Co_0.15Mn_0.15O₂ achieved highly improved electrochemical performance with a superior rate capability during battery cycling.

• 대한화학회지
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• 제51권2호
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• pp.154-159
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• 2007

유리 및 고정화된 Bacillus brevis에 의한 큐놀린의 분해를 조사하였다. 코코넛 껍질 탄소에 고정화된 Bacillus brevis에 의한 큐놀린 분해 속도는 폼조각에 고정화되었거나 유리된 미생물에 의한 속도보다 빠르다. 시료에 존재하는 큐놀린 100 ppm을 완전히 제거하기 위해서는 코코넛 껍질 탄소에 고정화된 Bacillus brevis로 만든 생촉매를 물속에서 20시간 유지시키면 되었다. 이 생촉매는 꽤 긴 보존기간과 적절한 재생력을 가지고 있었다.

• Journal of Electrochemical Science and Technology
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• 제13권2호
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• pp.254-260
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• 2022

Trimethylammonium tetrafluoroborate (TriMA BF₄), consisting of the smallest trialkylammonium ion, was investigated for use in electrochemical double-layer capacitors. Despite the presence of a proton in TriMA⁺, cycle life tests in acetonitrile (AN) and -butyrolactone (GBL) showed a good capacity retention with a 1.8 V cut-off voltage. The rate of electrolysis of TriMA BF₄ in GBL was lower than that in AN because of the lower conductivity in GBL. As a consequence, the cells based on GBL achieved a higher capacitance and longer life than those with AN. TriMA BF₄ had a higher conductivity and lower viscosity than the quaternary salt tetraethylammonium tetrafluoroborate in GBL, as well as higher ionic mobility, these factors resulted in a higher rate capability.

• 전기화학회지
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• 제11권2호
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• pp.125-129
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• 2008

리튬이온폴리머전지는 휴대용 전자기기와 전기자동차 등의 차세대 동력원으로 주목을 받고 있다. 본 연구에서는 폴리에틸렌 분리막에 소량의 부기 화합물과 고분자를 코팅하여 제조된 표면 개질 분리막을 리튬이온폴리머전지에 적용함으로써 전지 특성을 향상시키고자 하였다. 불화 알루미늄과 아크릴로니트릴-메틸 메타크릴레이트 공중합체를 폴리에틸렌 지지체에 코팅하여 얻어진 표면 개질 분리막을 이용하여 제조된 리튬이온폴리머전지는 충 방전 싸이클 과정 중에 균일한 전도성 고체 전해질 계면이 전극 표면에 형성되어 낮은 계면 저항값을 보였으며, 이에 따라 불화 알루미늄을 포함하고 있지 않는 리튬이온폴리머전지와 비교하여 싸이클 특성과 고율 방전 특성이 크게 향상되었다. 표면 개질된 분리막을 이용하여 제조된 리튬이온폴리머전지를 0.5 C rate로 충 방전한 결과, 초기 방전용량 150 mAh/g을 나타내었으며, 300싸이클에서 133 mAh/g의 방전 용량을 유지하여 우수한 용량 보존특성을 나타내었다.

• 한국산림과학회지
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• 제103권4호
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• pp.703-708
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• 2014

본 연구는 몽골 반건조 지역 현지에서 토양 개량이 묘목의 활착 및 생장에 미치는 효과를 알아보기 위해 수행되었다. 이를 위하여 알칼리성 사질 토양인 연구대상지에 2년생 백양나무(Populus sibirica)와 비술나무(Ulmus pumila) 묘목을 심고 질소(시비량에 따라 2수준), 황, 인공보습제, 황토가공소재 등을 처리하였다. 4개월 뒤, 두 수종의 묘목 활착률은 질소 시비량의 증가에 따라 감소하였다. 일반적으로 질소의 시비는 양분을 공급하여 묘목의 활착률 및 생장을 높이는 것으로 알려져 있다. 그러나 본 연구 결과에서 나타난 활착률 감소는 과다시비로 인한 토양 삼투압의 증가에 의한 것으로 보인다. 두 수종 모두 황토가공물질 처리구에서 근원경 생장에 유의한 증가가 나타났다. 그리고 백양나무의 경우 인공보습제 처리구에서도 근원경 생장이 유의하게 증가하였는데, 이는 백양나무가 건조에 내성이 있음에도 불구하고 수분 요구도가 높은 포플러속에 속하기 때문인 것으로 보인다. 반면 황 처리는 두 수종의 활착률과 근원경 생장 모두에서 효과가 없는 경향이 나타났는데, 이는 건조지 토양의 낮은 황산화율 때문으로 추정된다. 향후 건조/반건조 지역에서 토양 개량의 장기적인 효과를 알아보기 위하여 묘목 생장 및 토양 특성에 대한 지속적인 모니터링이 요구되며, 연구 수종에 적합한 시비량 산정을 위한 추가 연구가 필요한 것으로 판단된다.

• 한국조경학회지
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• 제26권2호
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• pp.54-61
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• 1998

The subsurface environment of the root zone area can set the stae for "do or die" of the turfgrass plant. The good condition of the greens is verified by their physical properties. Therefore, this study was carried to evaluate on the existing green of Hwasan C.C. by undisturbed soil Core Anaysis. We completed the ISTRC SYSTEM BenchMarking of the undisturbed core samples taken from Green #1, Green #5, Green #9-"Best" area, and Green #9-"Stressed" area for the Hwasan C.C.. It was also our understanding that the greens were in "good" to "very good" conditioni. THe exception might be Green #9-"Stress" area, which was the stressed area. The stressed area was confined to a ridge across Green #9. The organic content test results comfirmed the development of organic layering in depth 0-2.5cm. For the amount of compaction in the upper root zones and te development of the green's respective organic layers, the infiltration rates were high in Green #1, Green #5, and Green #9 "Stressed" area. The depicted aerificaton hole might be the probable cause of the relatively high infiltraton rate. Green #9-"Best" area had a tested infiltration rate of 18.75cm/hr. Either this area had not been aerified, or the undisturbed sample did not contain a aerification cavity. The water retention capacity of the undisturbed samples was good. When the greens were first constructed, the original root zone mix had been relatively low water retention properties. And the bulk density and the porosity of the undisturbed samples were good. In the result, all the greens were similar except for the infiltration. Thus, we supposed that Green #9-"Stressed" area might be ainly influenced by the amount of irrigation water and the configuration of the green's surface. There had been a reduction in the amount of irrigation water as the water retention capacity in the greens was promoted. Especially, it had gradually become more of a problem as the green had matured in Green #9-"Stressed" area. Because Green #9-"Stressed" area was a ridge area. The reduction in the amount of irrigation water might be the probable cause of the stress in Green #9-"Stressed" area. Our final observation related to the soil texture and the particle size distribution of the sand. Though and sand contant of all the tested greens were good, the gravel content of them exceeded ISTRC Guidelines. In particle size distribution of the sand, the very coarse and the coarse content of all the tested greens exceeded, but the rest was insufficient. The stability is a function of the material retained on the 0.25mm mesh screen. But, the content of all the tested greens was very insufficient. Though all the greens was serviceable, the coarse root zone sands, such as the sand in the tested greens, tended to be "unstable". Thus, we recommend using a topdressing/aerification sand which should be more in line with ISTRC/USGA Guidelines.;unstable". Thus, we recommend using a topdressing/aerification sand which should be more in line with ISTRC/USGA Guidelines.ines.

• Geomechanics and Engineering
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• 제17권5호
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• pp.475-483
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• 2019

Vegetation cover plays a vital role in stabilizing the soil structure, thereby contributing to surface erosion control. Surface vegetation acts as a shelterbelt that controls the flow velocity and reduces the kinetic energy of the water near the soil surface, whereas vegetation roots reinforce the soil via the formation of root-particle interactions that reduce particle detachment. In this study, two vegetation-testing trials were conducted. The first trial was held on cool-season turfgrasses seeded in a biopolymer-treated site soil in an open greenhouse. At the end of the test, the most suitable grass type was suggested for the second vegetation test, which was conducted in an environmental control chamber. In the second test, biopolymers, namely, starch and xanthan gum hydrogels (pure starch, pure xanthan gum, and xanthan gum-starch mixtures), were tested as soil conditioners for improving the water-holding capacity and vegetation growth in sandy soils. The results support the possibility that biopolymer treatments may enhance the survival rate of vegetation under severe drought environments, which could be applicable for soil stabilization in arid and semiarid regions.

• 한국지반공학회논문집
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• 제27권10호
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• pp.5-12
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• 2011

본 연구에서는 해안지역의 지반개량과 통시에 오염된 간극수를 정화하기 위한 방법으로 반응컬럼을 이용한 연직배수 공법의 반응컬럼 길이의 결정을 위하여 제강슬래그의 반응성을 평가하였다. 제강슬래그의 카드륨에 대한 반응성을 초기 농도와 pH의 변화에 따라 실험을 수행하였다. 반응시간에 따른 카드륨의 제거량을 유사이차 반응식을 이용해서 평형흡착량($q_e$)과 유사이차 반응상수($k_2$)를 통해 정량적으로 평가하였다. 필요 반응시간은 유사이차 반응모델에서 계산된 평형흡착량($q_e$)와과 유사이차 반응상수($k_2$)의 곱의 역수로 제안하였다. 필요 반응시간을 이용하여 반응컬럼의 길이를 결정할 수 있을 것으로 판단된다.

• 한국환경복원기술학회지
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• 제19권1호
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• pp.1-11
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• 2016

Currently, urban green space is disappearing due to urbanization, industrialization and various environmental problems including the disruption of the ecology in urban areas. To solve such problems and increase urban green area, roof greening has been suggested as an alternative. Through observing the responses of three plant species (Mukdenia rossii, Dianthus chinensis, and Pachysandra terminalis) plantrd on the soil mixed with Geohumus, this study investigated the effect of Gehumus on soil water content and plant survival. Soil water content of the rooftop soils has been increased when mixed with Geohumus. The responses were proportional to the amount of Geohumus in the mixture. Geohumus exerted a stronger influence on raising soil moisture content for soil A which had lower water-holding capacity. The stress responses of the plants varied in relation to the amount of Geohumus and soil moisture content. The stress response was lowest for Dianthus chinensis and increased in the order of Mukdenia rossii and Pachysandra terminalis. With the highest plant stress, Pachysandra terminalis showed the lowest survival rate among the three species. Without irrigation, the plants survived only for six weeks on green roofs. The survival rate differed depending on the amount of Geohumus mixed. The results of the experiment showed, with some exceptions, that Geohumus helped to improve soil water content, reduce plant stress, and extend plant survival period.