Comparison Of Mercury Distribution Between The Types Of Spent Fluorescent Lamp

Rhee, S.W.,Park, H.-S.,Choi, H.H. PAS 2015 ARCHIVES OF METALLURGY Vol.60 No.2

<B>Abstract</B><P>Spent fluorescent lamps(SFLs) such as linear type lamp, compact type lamp and U-type lamp are used to estimate mercury distribution in the components of lamps. Determination of mercury concentration in the components of spent fluorescent lamp is performed by the DMA method. Mercury concentration in the components of spent fluorescent lamp can be varied with the manufactures of lamp. Mercury portion in phosphor powder and glass from any types of spent fluorescent lamp is estimated to be higher than 99% by the analysis of mercury distribution. Through mercury distribution in the components for SFLs, the mercury concentration in phosphor powder is much higher than that in other components regardless of the type of lamp. Hence, it is desirable that phosphor powder of spent fluorescent lamps should be controlled separately and safely.</P>

Properties Of MgB2/Ga Composites Prepared By Mechanical Alloying

Yoon, K.,Ahn, J.-H. PAS 2015 ARCHIVES OF METALLURGY Vol.60 No.2

<B>Abstract</B><P>In this study, we examined the effect of Ga-doping and mechanical alloying in MgB2 on microstructural and phase evolution. A comparison was made between <I>in-situ</I> and <I>ex-situ</I> processed Mg-B-Ga samples. Densification was markedly improved by <I>ex-situ</I> sintering of ball-milled MgB2+Ga. The Ga-doping and ball-milling prior to sintering resulted in the formation of impurity phases such as MgO, Ga5Mg2 and Ga2O3. Lattice parameter of MgB2 increased with increasing ball-milling duration as well as by Ga-doping.</P>

Morphology Change Of Si Deposit In Molten Salt Electrorefining

Ryu, H.Y.,Kwon, S.C.,Han, M.H.,An, Y.S.,Lee, J.S.,Lee, J.H. PAS 2015 ARCHIVES OF METALLURGY Vol.60 No.2

<B>Abstract</B><P>The effects of processing parameters on the morphology change in a Si deposit recovered by means of molten salt electrorefining are evaluated using electrochemical techniques such as cyclic voltammetry and chronopotentiometry at 800°C. It was found that concentration of K2SiF6 and current density were important parameters in determining deposit size. Higher concentrations of K2SiF6 were effective in coarsening the silicon deposit and decreasing the cell potential. Silicon nanofiber was recovered at 5 wt% of K2SiF6 whereas dense particles were prepared at 30 and 50 wt% of K2SiF6. The morphology of the Si deposit was determined by the concentration of Si in the electrolyte which is related to the formation of crystal and growth of Si. The formation mechanism of the Si deposit was interpreted by using high resolution TEM as well as electrochemical properties.</P>

Surface Treatment And Modification Of Graphene Using Organosilane And Its Thermal Stability

Kim, D.-S.,Dhand, V.,Rhee, K.-Y.,Park, S.-J. PAS 2015 ARCHIVES OF METALLURGY Vol.60 No.2

<B>Abstract</B><P>In this study, graphene was functionalized via acid oxidation in the presence of a mixture of concentrated sulfuric acid and nitric acid. The oxidized graphene was silanized using the coupling agent, 3-aminopropyltriethoxsilane, resulting in functionalized graphene. The oxidized graphene and functionalized graphene were characterized by X-Ray diffraction, Fourier transform infrared spectroscopy, High-resolution micro Raman spectroscopy, thermogravimetric analysis, and atomic force microscopy to confirm the presence of functional moieties on the graphene surface. Thermal studies also demonstrate that the functionalized material is thermally stable up to higher temperatures.</P>

Extraction Of Cobalt From Spent CMB Catalyst Using Supercritical CO2

Joo, S.-H.,Shin, S.M. PAS 2015 ARCHIVES OF METALLURGY Vol.60 No.2

<B>Abstract</B><P>The metal extraction from spent CMB catalyst using supercritical CO2(scCO2) was investigated with single organic system, binary organic system and ternary organic system to extract metal ions. Leaching solution of spent CMB catalyst containing 389 mg L<SUP>−1</SUP> Co<SUP>2+</SUP>, 187 mg L<SUP>−1</SUP> Mn<SUP>2+</SUP>, 133 mg L<SUP>−1</SUP> Na<SUP>+</SUP>, 14.97 mg L<SUP>−1</SUP> Ca<SUP>2+</SUP> and 13.2 mg L<SUP>−1</SUP> Mg<SUP>2+</SUP>. The method consists of scCO2/ligands complexation process and metal extraction process at 60°C and 200bar. The result showed the Co and Mn was selectively extracted from Mg, Ca and Na in the ternary system of mixture of Cyanex272, DEA and Alamine304-I.</P>

Novel Extraction Process Of Rare Earth Elements From NdFeB Powders Via Alkaline Treatment

Chung, K.W.,Kim, C.-J.,Yoon, H.-S. PAS 2015 ARCHIVES OF METALLURGY Vol.60 No.2

<B>Abstract</B><P>The alkaline treatment of NdFeB powders in NaOH solution at various equivalent amounts of NaOH at 100°C was performed. The resultant powders were then leached in 0.5M H2SO4 solution at 25°C for 2 minutes. At 5 equivalents of NaOH, neodymium in NdFeB powders was partially transformed to neodymium hydroxide. The transformation of neodymium to neodymium hydroxide actually occurred at 10 equivalents of NaOH and was facilitated by increasing the equivalent of NaOH from 10 to 30. In addition, iron was partially transformed to magnetite during the alkaline treatment, which was also promoted at a higher equivalent of NaOH. The leaching yield of neodymium from alkaline-treated powders was increased with an increasing equivalent of NaOH up to 10; however, it slightly decreased with the equivalent NaOH of over 10. The leaching yield of iron was inversely proportional to that of rare earth elements. NdFeB powders treated at 10 equivalents of NaOH showed a maximum leaching yield of neodymium and dysprosium of 91.6% and 94.6%, respectively, and the lowest leaching yield of iron of 24.2%, resulting in the highest selective leaching efficiency of 69.4%.</P>

Alumina Coating To Realize Desired Pore Characteristics Of Sintered Diatomite Membrane

Ha, J.-H.,Park, Y.-H.,Song, I.-H. PAS 2015 ARCHIVES OF METALLURGY Vol.60 No.2

<B>Abstract</B><P>Porous ceramic membranes prepared from natural materials such as diatomite, have lately attracted great interest in industrial applications due to their cost-effectiveness. In this study, we attempted to prepare an alumina coating to be deposited over a sintered diatomite-kaolin composite support layer in order to reduce the largest pore size to below 0.4 <I>μ</I>m; such a coating could be potentially used in water treatment applications for bacterial removal.</P>

Improved Light Conversion Efficiency Of Dye-Sensitized Solar Cell By Dispersing Submicron-Sized Granules Into The Nano-Sized TiO2 Layer

Song, S.A.,Lim, M.J.,Jung, K.Y.,So, W.-W.,Moon, S.-J. PAS 2015 ARCHIVES OF METALLURGY Vol.60 No.2

<B>Abstract</B><P>In this work, TiO2 nanoparticles and submicron-sized granules were synthesized by a hydrothermal method and spray pyrolysis, respectively. Submicron-sized granules were dispersed into the nano-sized TiO2 layer to improve the light conversion efficiency. Granules showed better light scattering, but lower in terms of the dye-loading quantity and recombination resistance compared with nanoparticles. Consequently, the nano-sized TiO2 layer had higher cell efficiency than the granulized TiO2 layer. When dispersed granules into the nanoparticle layer, the light scattering was enhanced without the loss of dye-loading quantities. The dispersion of granulized TiO2 led to increase the cell efficiency up to 6.51%, which was about 5.2 % higher than that of the electrode consisting of only TiO2 nanoparticles. Finally, the optimal hydrothermal temperature and dispersing quantity of granules were found to be 200°C and 20 wt%, respectively.</P>

Oxide Formation In Metal Injection Molding Of 316L Stainless Steel

Jang, Jin Man,Lee, Wonsik,Ko, Se-Hyun,Han, Chulwoong,Choi, Hanshin PAS 2015 ARCHIVES OF METALLURGY Vol.60 No.2

<B>Abstract</B><P>The effects of sintering condition and powder size on the microstructure of MIMed parts were investigated using water-atomized 316L stainless steel powder. The 316L stainless steel feedstock was injected into micro mold with micro features of various shapes and dimensions. The green parts were debound and pre-sintered at 800°C in hydrogen atmosphere and then sintered at 1300°C and 1350°C in argon atmosphere of 5torr and 760torr, respectively. The oxide particles were formed and distributed homogeneously inside the sample except for the outermost region regardless of sintering condition and powder size. The width of layer without oxide particles are increased with decrease of sintering atmosphere pressure and powder size. The fine oxides act as the obstacle on grain growth and the high sintering temperature causes severe grain growth in micro features due to larger amount of heat gain than that in macro ones.</P>

Effect Of Ti Powder Addition On The Fabrication Of TiO2 Nanopowders

Raihanuzzaman, R.M.,Park, H.Y.,Ghomashchi, R.,Kwon, T.H.,Son, H.-T.,Hong, S.J. PAS 2015 ARCHIVES OF METALLURGY Vol.60 No.2

<B>Abstract</B><P>Sintered samples of Ti added TiO2 nanopowders were fabricated by combined application of magnetic pulsed compaction (MPC) and sintering. The effect of Ti nano powder on density, shrinkage and hardness of the samples were investigated as part of the study. The optimum processing conditions were found to be around 0.5 GPa MPC pressure and 1450°C sintering temperature, illustrating maximum density, hardness and minimum shrinkage. High pressure compaction using MPC was found to enhance density with increasing MPC pressure up to 0.9 GPa, and significantly reduce the total shrinkage (about 16% in this case) in the sintered bulks compared to other general processes (about 18%). While sintered samples blended with micro Ti showed presence of microstructural cracks, the samples with 1-2% nano Ti had less or no cracks on them. Overall, the inclusion of nano Ti indicated improvement in mechanical properties of TiO2 nanopowders sintered preforms as opposed to micro Ti-added TiO2.</P>