• 대한금속재료학회지
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• 제46권2호
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• pp.105-110
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• 2008

Process of the hydroxyapatite (HA) formation on bioactive titanium metal prepared by NaOH treatment in a modified-simulated body fluid (mSBF) containing bovine serum albumin (BSA) was investigated by high resolution transmission electron microscope attached with energy dispersive X-ray spectrometer (EDX). The amorphous titanate, which was formed on titanium surface by NaOH treatment, combined with the calcium ions in the liquid to form an amorphous calcium titanite. With increasing of soaking time in the liquid, an amorphous calcium titanite combined with the phosphate ions to form an amorphous calcium phosphate with low Ca/P atomic ratio, and it grows as aggregates of plate (or needle)-like substance on titanium surface. The crystalline apatite layers, which are needle-shaped with the c axis parallel to the long axis, are formed in an amorphous calcium phosphate with further increase in soaking time. The formation of needle-shaped apatite layers can be explained by electrostatic effects and difference of concentration between calcium, phosphate, and albumin ions.

• 대한금속재료학회지
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• 제47권2호
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• pp.114-120
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• 2009

The viscosities of $CaO-SiO_2-Al_2O_3-MgO$ flux were measured under the condition of $CaO/SiO_2=1.0-1.3$ and 5-20 wt%MgO. Submerged arc welding flux with $5wt%Al_2O_3$ content had the lowest critical temperature and widest solid-liquid coexisting region at about 5 wt%MgO. It indicateds that both critical temperature and viscosity depend on the kind of primary phase of molten flux. Viscous behavior of the molten flux at 1773 K was analyzed in the view of silicate structure changed by FT-IR spectroscopy. Based on the critical temperature and the behavior of viscosity at a fixed temperature, it could be proposed that the contents of MgO and $Al_2O_3$ in SAW flux show a pronounced effect on preventing contamination in maintaining the liquid phase flux after welding process.

• 자원리싸이클링
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• 제29권2호
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• pp.62-68
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• 2020

2000년대에 접어들면서 선택적 촉매 환원(SCR) 촉매에 대한 광범위한 수요가 점차 증가하고 있다. SCR 촉매는 환경보호를 위해 질소산화물(NOx)의 배출 방지에 사용 된다. 일반적으로 SCR 촉매의 주성분은 TiO₂(70~80 %), WO₃(7~10 %), V₂O₅(~1 %) 등으로 구성되어있다. SCR 폐촉매는 대개 매립되어 폐기 되는데, 분해도가 극히 낮아 매립지에 영구적으로 남아있게 된다는 문제점을 가지고 있다. 따라서 환경을 보호하고 페촉매에 함유되어 있는 유가금속의 회수를 위하여 새로운 첨단기술의 개발이 필요하다. 이러한 SCR 폐촉매의 처리를 위해 침출 및 액-액 추출과 같은 습식제련법이 설계되고 개발되었다. 첫 번째 단계에서 SCR 폐촉매로부터 바나듐과 텅스텐을 선택적으로 침출한 후, 액-액 추출 공정에 의해 처리되었다. 바나듐과 텅스텐의 선택적 추출을 위해 D2EHPA, PC 88A, TBP, Cyanex 272, Aliquat 336과 같은 다양한 상용 용매추출제를 이용한 실험을 수행하였다. 바나듐과 텅스텐의 추출 및 분리를 위해 세정(scrubbing) 및 탈거(stripping) 연구가 수행되고 최적화 되었다. 3상의 생성을 억제하기 위해 iso-decanol 시약을 사용하여 최적화 하였다.

• Journal of Applied Biological Chemistry
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• 제63권2호
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• pp.125-129
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• 2020

Environmental pollution caused by various heavy metals is a serious global problem. To solve this problem, microbial bioremediation of contaminated metals has developed rapidly as an effective strategy when physical and chemical techniques are not suitable. In this study, cadmium (Cd)-tolerant soil bacteria were isolated via artificial induction in laboratory conditions instead of screening bacteria naturally adapted to metal-contaminated soils. Wild-type (WT) bacteria grown in uncontaminated soils were artificially and sequentially adapted to gradually increasing Cd concentrations of up to 15 mM. The resultant cells, named Soil-CdR15, survived at a Cd concentration of 10 mM, whereas WT cells failed to survive with 4 mM Cd on solid media for 2 d. In liquid media containing Cd, the SoilCdR15 cells grew with 15 mM Cd for 7 d, whereas the WT cells could not grow with 5 mM Cd. Both Soil-CdR15 and WT cells removed approximately 35% of Cd at the same capacity from liquid media containing either 0.5 or 1.0 mM Cd over 2 d. In addition to Cd, the Soil-CdR15 cells showed increased resistance to nickel, zinc, and arsenic compared to WT cells. The Soil-CdR cells were identified as Burkholderia sp. by partial sequencing of 16S rRNA. The data presented in this study demonstrate that isolation of heavy metal-tolerant microorganisms via artificial induction in laboratory conditions is possible and may be useful for the application of the microorganisms for the bioremediation of heavy metals.

• 에너지공학
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• 제11권2호
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• pp.99-105
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• 2002

A finite volume numerical approach is developed and used to simulate convection-dominated melting and solidification problems. The present approach is based on the enthalpy-porosity method that is traditionally used to track the motion of the liquid-solid front and to obtain the temperature and velocity profiles in the liquid-phase. The enthalpy-porosity model treats the solid-phase as the porosity in all computational cells that are located on the solid-liquid interfacial boundary. Concerning the computational cells that are fully located in the solid side of the interfacial boundary, the zero value of the porosity severely suppresses the velocity vector to practically a non-existent value that could be set equal to zero. A comparative analysis with the previous numerical approaches is performed to demonstrate the improved features of the presented model. Results of a melting and solidification experiments are also used to assess and evaluate the performance of the model.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2015년도 제46회 하계학술대회
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• pp.1235-1236
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• 2015

This paper reports hyperelastically stretchable strain gauges based on liquid metal (eutectic gallium-indium;EGaIn) and a platinum-catalyzed silicone elastomer ($Ecoflex^{TM}$). A custom liquidmetal patterning setup was operated to fabricate liquidmetal straingauge on flexible substrate. The printed strain gauges were tested under cyclic uniaxial stretching, twisting, even bending of human finger. By engineering the orientation of solid wires placed over two terminals of t he printed liquid metal resistor, we stably achieved the stretchability of ~800 % which is the highest value reported so far, to the best of our knowledge.

• 분석과학
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• 제11권6호
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• pp.499-504
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• 1998

An analytical method for the simultaneous measurement of trace Cu, Sn, and Bi in sea water has been investigated by Inductively Coupled Plasma-Mass Spectrometry. Amberlite IRC-718 resin was used as a solid phase in solid-liquid extraction technique for the removal of matrix interferences such as Na, S, P, and other polyatomic ion species. Recoveries of 99.8% for Cu, 99.6% for Sn, and 97.9% for Bi were obtained for the standard spiked sample. The developed method was applied to analysis of trace metals in sea water.

• 한국막학회:학술대회논문집
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• 한국막학회 1993년도 춘계 총회 및 학술발표회
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• pp.25-27
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• 1993

Multiphase equilibrium-based processes for separation and purification generally utilize dispersed systems in which one phase is dispersed in the other as bubbles or drops or thin films. Using microporous membranes, novel techniques have been developed such that multiphase processes can now be carried out in a nondispersive fashion for gas-liquid (Sirkar, 1992) and liquid-liquid (Prasad and Sirkar, 1992) contacting processes. Among such processes, only nondispersive solvent extraction of pollutants using microporous membranes will be of concern here. These processes employ immobilized immiscible phase interfaces at the pore mouths in a microporous membrane. Through such interfaces, solutes are extracted into the solvent as two immiscible phases flow on two sides of a microporous membrane. Many advantages of such a technique over conventional dispersion-based extractors have been summarized (Prasad and Sirkar, 1992).

• 접착 및 계면
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• 제24권2호
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• pp.41-53
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• 2023

형태가변형 전자 소자는 늘림, 굽힘 등 기계적으로 변형된 상태에서도 초기 소자 특성이 유지되는 소자를 말한다. 형태가변형 전자 소자에 적용되는 여러 전도성 소재 중 갈륨 기반 액체 금속은 상온에서 액체 상태로 존재하며 우수한 형태가변성과 전기 전도성, 낮은 인체유해성으로 인해 최근 다양한 형태가변형 전자 소자에 적용되고 있다. 본 고에서는 최근 보고된 여러 연구들을 중심으로 갈륨 기반 액체 금속을 소개하고 이를 활용한 다양한 형태가변형 전자 소자 및 제조 공정에 대해 논하고자 한다.

• Nuclear Engineering and Technology
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• 제56권3호
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• pp.1081-1090
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• 2024

The liquid Lead-bismuth eutectic is used as the coolant for Gen-IV reactor concepts. However, due to its strong corrosive and high operating temperature, it is difficult to accurately measure the flow rate in long-term operating conditions. Venturi flowmeter is a simple structured flowmeter, which plays a very important role in the flow measurement of high-temperature liquid metals, especially since the existing flowmeters are difficult to be competent. It has the advantages of easy maintenance and stable operation. Therefore, it is necessary to study the operating conditions of the venturi flowmeter under high-temperature conditions. This work performs a series of simulations of the fluid-solid interaction between the flow liquid metal and venturi flowmeter with COMSOL software, including the dimensional sensitivity analysis of the venturi flowmeter to explore the most suitable structure and parameters for liquid heavy metal, the sensitivity analysis of the geometric parameters of the venturi tube on the varying conditions. It shows that when the contraction angle of the venturi flowmeter is 33°, the diffusion angle is 13°, the diameter of the throat is 8 mm, and the temperature of the lead-bismuth eutectic is 733.15 K, it is most suitable for the measurement in the lead-bismuth circuit.