Lee-Seung Kang

Recycling process for recovery of gallium from GaN an e-waste of LED industry through ball milling, annealing and leaching

Waste dust generated during manufacturing of LED contains significant amounts of gallium and indium, needs suitable treatment and can be an important resource for recovery. The LED industry waste dust contains primarily gallium as GaN. Leaching followed by purification technology is the green and clean technology. To develop treatment and recycling technology of these GaN bearing e-waste, leaching is the primary stage. In our current investigation possible process for treatment and quantitative leaching of gallium and indium from the GaN bearing e-waste or waste of LED industry dust has been developed. To recycle the waste and quantitative leaching of gallium, two different process flow sheets have been proposed. In one, process first the GaN of the waste the LED industry dust was leached at the optimum condition. Subsequently, the leach residue was mixed with Na2CO3, ball milled followed by annealing, again leached to recover gallium. In the second process, the waste LED industry dust was mixed with Na2CO3, after ball milling and annealing, followed acidic leaching. Without pretreatment, the gallium leaching was only 4.91 w/w % using 4M HCl, 100°C and pulp density of 20g/L. After mechano-chemical processing, both these processes achieved 73.68 w/w % of gallium leaching at their optimum condition. The developed process can treat and recycle any e-waste containing GaN through ball milling, annealing and leaching.

Preparation of the Nano Cobalt Powder by Wet Chemical Reduction Method

Spherical nanosized cobalt powder with an average size of 150-400 nm was successfully prepared at room temperature from cobalt sulfate heptahydrate (). Wet chemical reduction method was adopted to synthesize nano cobalt powder and hypophosphorous acid () was used as reduction agent. Both the HCP and the FCC Co phase were developed while concentration ranged from 0.7 M to 1.1 M. Secondary phase such as and were also observed. Peaks for the crystalline Co phase having HCP and FCC structure crystallized as increasing the concentration of , indicating that the amount of reduction agent was enough to reduce . Consequently, a homogeneous Co phase could be developed without second phase when the ratio exceeded 7.

Microstructure and Electrical Properties of Amorphous Films Grown on Cu/Ti/ /Si Substrates using RF Magnetron Sputtering

Amorphous Bi5Nb3O15 (BNO) films were grown at room temperature (RT) on a Cu/Ti/SiO2 /Si substrate using radio frequency magnetron sputtering. All the films were well formed on the Cu electrode with a sharp interface between the film and the electrode. The dielectric constant of the amorphous BNO film grown under 25 W was 46, with a low dissipation factor of 2.7% at 100 kHz. This film exhibited a low leakage current density of 5.5 × 10-8 A/cm2 at 4.5 V and a large breakdown voltage of 7.2 V. However, the electrical properties deteriorated as the sputtering power and the growth temperature increased due to the increased surface roughness; this was because a film with a rough surface generally has a larger surface area, and there can be electric field intensification at surface asperity, which degrade the electrical properties of the film. In addition, the electrical properties were not influenced by the oxygen partial pressure (OPP) because the variation of OPP during the growth of the films did not affect their surface roughness. The amorphous BNO film grown on the Cu/Ti/SiO2/Si substrate at RT under 25 W may be a good candidate material for an embedded capacitor.

Materials flow analysis of neodymium, status of rare earth metal in the Republic of Korea

Materials flow analysis of neodymium, status of rare earth elements (REEs) in the Republic of Korea has been investigated. Information from various resources like the Korean Ministry of Environment, Korea international trade association, United Nations Commodity Trade Statistics Database and from individual industry were collected and analyzed for materials flow analysis of neodymium. Demand of neodymium in the Republic of Korea for the year 2010 was 409.5 tons out of which the majority of neodymium, i.e., 68.41% was consumed by domestic electronics industry followed by medical appliances manufacturing (13.36%). The Republic Korea is one of the biggest consumer and leading exporter of these industrial products, absolutely depends on import of neodymium, as the country is lacking natural resources. The Republic of Korea has imported 325.9 tons of neodymium permanent magnet and 79.5 tons of neodymium containing equipment parts mainly for electronics, medical appliances, and heavy/light vehicles manufacturing industry. Out of which 95.4 tons of neodymium permanent magnet get exported as an intermediate product and 140.6 tons of neodymium in the form of consumable products get exported. Worldwide the neodymium is at the high end of supply chain critical metal because of increasing demand, scarcity and irreplaceable for technological application. To bring back the neodymium to supply stream the recycling of end of life neodymium-bearing waste can be a feasible option. Out of total domestic consumption, only 21.9 tons of neodymium have been collected and subsequently recycled. From material flow analysis, the requirement for an efficient recycling system and element-wise material flow management for these REEs in the Republic of Korea were realized and recommended.

Optimization of Wet Reduction Processing for Nanosized Cobalt Powder

Abstract Nano-sized cobalt powder was fabricated by wet chemical reduction method at room temperature. Theeffects of various experimental variables on the overall properties of fabricated nano-sized cobalt powders have beeninvestigated in detail, and amount of NaOH and reducing agent and dropping speed of reducing agent have been prop-erly selected as experimental variables in the present research. Minitab program which could find optimized conditionswas adopted as a statistic analysis. 3D Scatter-Plot and DOE (Design of Experiments) conditions for synthesis of nano-sized cobalt powder were well developed using Box-Behnken DOE method. Based on the results of the DOE process,reproducibility test were performed for nano-sized cobalt powder. Spherical nano-sized cobalt powders with an averagesize of 70-100 nm were successfully developed and crystalline peaks for the HCP and FCC structure were observedwithout second phase such as Co(OH) 2 .Keywords: Nano-sized cobalt powder, Wet chemical reduction, Design of experiments, Reproducibility

Research and Development Status of Low-Cost Fe-based Cathode Materials for Lithium Secondary Batteries

이차전지(Secondary battery)는 사용 후 다시 충전 하여 재사용이 가능하고 전기에너지를 고효율로 저 장, 사용함으로써 에너지 효율성을 극대화하고 온실 가스 배출량을 감소시킬 수 있어 다양한 산업군의 동 력원으로 사용되고 있다. 이차전지에는 납축전지 (Lead-acid), 니켈카드뮴전지(Ni-Cd), 니켈수소전지(NiMH), 리튬이차전지(Lithium secondary battery)가 있 는데, 이중 리튬이차전지는 액상 전해액을 사용하는 리튬이온전지(Lithium ion battery), 젤(Gel)상의 고분 자 전해액을 사용하는 리튬폴리머전지(Lithium polymer battery)로 분류된다. 이차전지 중 리튬이차 전지는 고출력이면서 부피/중량당 에너지밀도가 가장 우수한 경쟁력을 바탕으로 새로운 응용분야로 사업 영역이 확대되고 있는 추세이다[1]. 현재 리튬이차전지의 최대 수요처는 소형 에너지 저장시스템을 사용하는 노트북 PC, 휴대전화 및 휴 대용 전자기기로 2010년 94억

Synthesis and analysis CdSe Quantum dot with a Microfluidic Reactor Using a Combinatorial Synthesis System

에서 2020년 220억

Materials Flow Analysis of Metallic Cobalt and Its Powder in Korea

까지 성장할 것으로 예측되고, 중대형 에너지 저장 시스템으로의 응용도 급속도로 확대되어, 전기자동 차 및 하이브리드 자동차의 전지시장 규모는 2020 년까지 302억

Synthesis and Electrochemical Performance of Li 2 MnSiO 4 for Lithium Ion Battery Prepared by Amorphous Silica Precusor

, 에너지저장분야는 257억

Microstructure and Electrical Properties of Amorphous

까지 성장 할 것으로 예측된다[2]. 이렇게 첨단산업의 발전과 새로운 수요처의 등장으로 이들의 동력원으로 사용 될 리튬이차전지의 기술적 발전이 절실히 요구되고 있다. 리튬이차전지의 핵심소재는 양극, 음극, 전해질, 분 리막으로 구분되고, 현재 상용화된 리튬이차전지의 양극소재로는 리튬코발트산화물(LiCoO2)이, 음극소재 로는 카본계(Graphite)가 사용되고 있다. 이 중 양극 소재는 가장 많은 재료비 비중을 차지하고 있을 뿐 만 아니라 전지의 성능을 좌우하는 중요한 핵심소재 이다. LiCoO2는 전체 양극소재 시장의 70% 이상을 차지하고 있으나, 함유된 코발트의 높은 가격으로 리 튬이차전지의 단가를 높이고 있다. 따라서 코발트를 대체할 만한 매장량이 풍부하고 가격이 저렴한 철 (Fe)을 양극소재로 개발할 필요가 있다. 양극소재의 전이금속으로 저가의 철을 사용하는 것으로는 LiFePO4 가 대표적이고, 이 소재는 양극소재 수요량 이 큰 중대형 에너지 저장시스템에서 필히 사용될 전 망이다. 최근에는 Li2FeSiO4, LiFeSO4F, LiFeBO3 등의 연구결과들이 보고되고 있으며 저가 양극소재