• Advances in materials Research
• /
• v.9 no.3
• /
• pp.171-187
• /
• 2020

The microstructural evolution of different compositions of Mg-Sn alloys (30%Sn-70%Mg, 40%Sn-60%Mg and 50%Sn-50%Mg) is studied at first to understand the changes observed with change in tin content and deformation conditions. The Mg₂Sn phase increases with increase in tin content and a significant substructure development is found in 50%Sn-50%Mg alloy. The above observation led to further deformation studies on Mg₂Sn based thermoelectric materials with higher tin percentage. The microstructure in terms of Electron backscatter diffraction (EBSD)measurements is studied in detail followed by the determination of thermoelectric properties i.e., Seebeck coefficient and electrical conductivity for both as cast and extruded Mg_(2+x)Sn-Ag alloys. The electrical conductivity of the extruded Mg_(2+x)Sn-.3wt%Ag {x =1} alloy was found to be more than its as cast counterpart while the Seebeck coefficient values remained almost the same.

• Proceedings of the Materials Research Society of Korea Conference
• /
• 2010.05a
• /
• pp.47.1-47.1
• /
• 2010

Mg합금은 모든 구조용 재료 중에서 비강도가 크며 가공성이 가장 우수하여 재료의 실제 적용시에 2차 가공비 측면에서 다른 경량재료에 비해 유리하다. 그래서 경량화를 필요로 하는 최근 산업체의 요구를 충족시킬 수 있는 재료이다. 그러나 마그네슘 합금의 적용이 매우 제한되는 이유는 결정구조가 hcp로서 냉간가공이 어렵고, 강화기구가 석출경화 및 고용강화로 제한되기 때문에 기계적 성질, 즉 강도와 연성이 모두 낮다. 특히 고온에서 기계적 성질이 급격히 저하되기 때문에 구조용 재료로써는 사용이 어렵다. 따라서, 본 연구에서는 고온에서 안정한 MgZn상과 항복강도를 향상시키는 Mg4Ag상의 석출을 보이는 Mg-Zn-Mn-Ag합금의 시효거동 및 미세조직 변화에 대해 검토하고자 하였다. 본 합금의 석출거동, 미세조직 및 경도 변화에 미치는 시효처리의 영향에 관한 연구를 수행하기 위해 Pandat Program을 이용해 열역학적 계산을 통한 상태도 해석 및 석출상을 예측 하였다. 계산된 결과는 DSC실험을 통해 비교 분석함으로써 신뢰성을 확보하였고 미세조직 및 석출상 분석을 위해 OM, SEM 그리고 XRD로 관찰하였다. 또한, 시효처리에 따른 기계적 특성을 분석하기 위해 상온 및 고온 인장시험을 하였고, 인장시험 후 파단면 분석을 통하여 재료의 파괴거동을 분석하였다.

• Journal of Applied Biological Chemistry
• /
• v.64 no.3
• /
• pp.253-261
• /
• 2021

In this study, the ginseng sprout has produced through smart farm was classified according to its size and divided into above-ground (AG) and below-ground (BG) parts to compare ginsenoside contents and antioxidant activity. In the case of the AG part, the total phenolic contents were the highest at 5.16 mg/g in medium (M) size and the lowest at 2.23 mg/g in largest (L) size. The BG part also showed the highest content in the M size, but there was no significant difference. Also, the total flavonoid contents were also high in the M size in both the AG (5.16 mg/g) and BG (1.28 mg/g) parts. The major ginsenosides in the AG part were Re (20.33-24.15 mg/g) > Rd (11.36-27.42 mg/g) > Rg1 (4.48-5.54 mg/g) and the main ginsenosides in the BG part were Rb1 (5.09-8.61 mg/g) > Re (4.48-5.54 mg/g) > Rc (3.11-4.11 mg/g) in orders. In the case of M size, Re and Rd were approximately 4- and 19-folds higher at 24.15 mg/g and at 27.42 mg/g in the AG part and 5.20 mg/g and 1.43 mg in the BG part, respectively. In addition, F3 and Rh1 were detected in the AG part, but not in the BG part. 2,2-diphenyl-1-picrylhydrazyl (74.95%), 2,4,6-azino-bis (3-ethylbenzothiazoline-6-sulphnoic acid) diammonium salt (94.47%), and hydroxyl (70.39%) radical scavenging activities and FRAP (2.169) assay were the highest in M size than other sizes.

• The Transactions of the Korean Institute of Electrical Engineers B
• /
• v.49 no.4
• /
• pp.240-245
• /
• 2000

The self-field losses in a long multifilamentary Bi-2223/AgMgNi tape with varying transport current, voltage tap configurations, frequency and tape arrangements were investigated. Experimental results show that the measured losses are strongly dependent on voltage gap configurations but independent on tape arrangements. All voltage taps except the center tap are found to agree well with those predicted by Norris for an elliptical conductor. The self-field losses are purely hysteretic in nature in the range of applied frequencies for the transport currents below the critical current.

• Bulletin of the Korean Chemical Society
• /
• v.33 no.12
• /
• pp.4023-4027
• /
• 2012

Cytotoxicity assessment of silver nanoparticles (AgNPs) was performed using MTT-based microfluidic image cytometry (${\mu}FIC$). The $LC_{50}$ value of HeLa cells exposed to AgNPs in the microfluidic device was estimated as 46.7 mg/L, which is similar to that estimated by MTT-based IC for cells cultured in a 96 well plate (49.9 mg/L). These results confirm that the ${\mu}FIC$ approach can produce cytotoxicity data that is reasonably well-matched with that of the conventional 96 well plate system with much higher efficiency. This ${\mu}FIC$ method provides many benefits including ease of use and low cost, and is a more rapid in vitro cell based assay for AgNPs. This may aid in speeding up data acquisition in the field of nanosafety and make a significant contribution to the quantitative understanding of nanoproperty-toxicity relationships.

• Journal of Yeungnam Medical Science
• /
• v.3 no.1
• /
• pp.209-213
• /
• 1986

To study the therapeutic effect of ribavirin, a broad spectrum antiviral agent, for chronic hepatitis B in pediatric patients, 24 patients who were diagnosed as chronic hepatitis B (elevated SGOT and SGPT and positive HBsAg and HBeAg for more than 6 months) at the pediatric department of Yeungnam University Hospital from Mar. 1, 1985 to Sep. 30, 1986 were randomly divided into two groups. Ribavirin was administered to 11 patients in dose of 15mg/kg/day and 13 patients were control group and both groups were followed for 12 months. Serum HBsAg and HBeAg were measured with RIA(Ausria-1I and Abbott-HBe, respectively) and compared in PIN ratio (counts per minute of patient's sample/counts per minute of normal serum). There were no statistically significant reductions in PIN ratios of HBsAg and HBeAg in both groups between prior to the therapy and 12 months follow-up period. It seems that ribavirin does not have the therapeutic effect on chronic hepatis B in children. Also, there were no noticeable side effects from ribavirin therapy.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.16 no.7
• /
• pp.627-633
• /
• 2003

The effects of alloying-element additions to Ag sheath on thermal conductivity and mechanical properties of Bi-2223 superconductor tapes have been evaluated. In order to evaluate the effects of sheath alloys and their configuration on the properties of tape, various combinations of Ag and Ag alloys were selected as the inner and outer sheath. Thermal conductivity of the tapes was evaluated by using thermal integral method at 10 ∼120 K. It was observed that the addition of Mg, Sb, and Au to Ag sheath significantly decreased the thermal conductivity at low temperature probably due to the alloying effect. Specifically, the thermal conductivity of AgMg, AgSb, and AgAu at 40 K were 411.4, 142.3, and 109.7 W/(m·K), respectly, which is about 2∼9 times lower than that of Ag (1004.6 W/(m·K)). In addition, the thermal conductivity of alloy-sheathed tape was significantly dependent on their thermal conductivities of constituent sheath materials. The mechanical properties of alloy-sheathed tapes were also evaluated. Yield strength and tensile strength were improved but workability decreased for alloy-sheathed tapes.

• Journal of Electrochemical Science and Technology
• /
• v.14 no.1
• /
• pp.59-65
• /
• 2023

Sodium hydroxide solutions are often employed as sterilization agents in the pharmaceutical industry. Here, the chloride content is considered as a critical impurity. In this study, an electrochemical method was developed to remove chloride ions (Cl^-) through the oxidative deposition of AgCl on a Ag anode. The Cl^- content in the commercially available 50% w/w NaOH solution employed was approximately 100 mg Cl^-/kg NaOH. As the OH^- content is approximately 18,000 times higher than the Cl^- content, the formation of AgCl may be expected to be thermodynamically less favorable than the formation of Ag₂O. However, activation energies for AgCl and Ag₂O formation have been reported to be approximately 3.8 and 31.2 kJ/mol, respectively, and indicate that AgCl formation is favored. AgCl can be selectively produced by controlling the anode potential. Here, the Cl^- concentration was reduced to less than 50 mg Cl^-/kg NaOH when an anode potential of 0.18 or 0.19 V vs. Hg/HgO (reference electrode) was applied for one hour at 50℃. XRD analysis and visual monitoring of the Ag anode confirmed the oxidative deposition of AgCl on the anode surface as well as the electrochemical desalination of the concentrated NaOH solution.

• Resources Recycling
• /
• v.10 no.5
• /
• pp.29-35
• /
• 2001

This study was carried out to recover gold, silver and valuable metals from the printed circuit boards (PCBs) of waste computers. PCBs samples were crushed under 1 mm by a shredder and separated into 30% conducting and loft nonconducting materials by an electrostatic separator. The conducting materials contained valuable metals which were then used as feed materials for magnetic separation. 42% of magnetic materials from the conducting materials was removed by magnetic separation as nonvaluable materials and the others, 58% of non magnetic materials, was used as leaching samples containing 0.227 mg/g Au and 0.697 mg/g Ag. Using the materials of leaching from magnetic separation, more than 95% of copper, iron, zinc, nickel and aluminium was dissolved in 2.0M sulfuric acid solution, added with 0.2M hydrogen peroxide at $85^{\circ}C$. Au and Ag were not extracted in this solution. On the other hand, more than 95% of gold and 100% of silver were leached by the selective leaching with a mixed solvent (0.2M($NH_4$)$_2$$S_2$$O_3$,0.02M $CuSO_4$,0.4M $NH_4$OH). Finally, the residues were reacted with a NaCl solution to leach Pb whereas sulfuric acid was used to leach Sn. Recoveries reached 95% and 98% in solution, respectively.

• Journal of Korean Society of Environmental Engineers
• /
• v.34 no.11
• /
• pp.715-719
• /
• 2012

We investigated the effects of electrochemical characteristics and generation of chlorine by the different amount of Ru coating which was prepared for $RuO_2$/Ti electrode coated with 1.5 mg, 2.5 mg, 5.5 mg, 8.5 mg Ru per unit area ($cm^2$). As a Result of the cycle voltammetry experiments, chlorine overvoltage of Ru-coated electrodes showed to be the nearly sustained value of approximately 1.15V (vs. Ag/AgCl). By contrary, According to the results of the AC impedance spectroscopy and potentiodynamic polarization tests, the amount of Ru per unit area ($cm^2$) included 2.5 mg, 3.5 mg as $RuO_2$/Ti offered the highest levels of durability which was electrode resistance and corrosion rate appeared to be $0.4582{\Omega}$, $0.5267{\Omega}$ and 0.082 mm/yr, 0.058 mm/yr, respectively. It was also observed that generation of chlorine coated with 3.5 mg per unit area ($cm^2$) was the highest value of 15.2 mg/L.