Journal of Powder Materials

Volume 16(5); October 2009

Enhancement of the Light Harvesting of Dye-sensitized Solar Cell by Inserting Scattering Layer: Jung-Gyu Nam, Bum-Sung Kim, Jai-Sung Lee; J Korean Powder Metall Inst. 2009;16(5):305-309.; DOI: https://doi.org/10.4150/KPMI.2009.16.5.305

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Abstract PDF: The effect of light scattering layers (400 nm, TiO_2 particle) of 4 mum thickness on the dye-sensitized solar cell has been investigated with a 12 mum thickness of photo-anode (20 nm, TiO_2 particle). Two different structures of scattering layers (separated and back) were applied to investigate the light transmitting behaviors and solar cell properties. The light transmittance and cell efficiency significantly improved with inserting scattering layers. The back scattering layer structure had more effective transmitting behavior, but separated scattering layer (center: 2 mum, back: 2 mum) structure (9.83% of efficiency) showing higher efficiency (0.6%), short circuit current density (0.26 mA/cm2) and fill factor (0.02). The inserting separating two scattering layers improved the light harvesting, and relatively thin back scattering layer (2 mum of thickness) minimized interruption of ion diffusion in liquid electrolyte.

Synthesis of TiC/Co Composite Powder by the Carbothermal Reduction Process: Gil-Geun Lee, Gook-Hyun Ha; J Korean Powder Metall Inst. 2009;16(5):310-315.; DOI: https://doi.org/10.4150/KPMI.2009.16.5.310

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Abstract PDF: Ultra-fine TiC/Co composite powder was synthesized by the carbothermal reduction process without wet chemical processing. The starting powder was prepared by milling of titanium dioxide and cobalt oxalate powders followed by subsequent calcination to have a target composition of TiC-15 wt.%Co. The prepared oxide powder was mixed again with carbon black, and this mixture was then heat-treated under flowing argon atmosphere. The changes in the phase, mass and particle size of the mixture during heat treatment were investigated using XRD, TG-DTA and SEM. The synthesized oxide powder after heat treatment at 700°C has a mixed phase of TiO_2 and CoTiO_3 phases. This composite oxide powder was carbothermally reduced to TiC/Co composite powder by the solid carbon. The synthesized TiC/Co composite powder at 1300°C for 9 hours has particle size of under about 0.4 mum.

Production of Fe Amorphous Powders by Gas-atomization Process and Subsequent Spark Plasma Sintering of Fe Amorphous-ductile Cu Composite Powders Produced by Ball-milling Process (I) - I. Gas Atomization and Production of Composite Powders -: Ho-Jin Ryu, Jae-Hyun Lim, Ji-Soon Kim, Jin-Chun Kim, H.J. Kim; J Korean Powder Metall Inst. 2009;16(5):316-325.; DOI: https://doi.org/10.4150/KPMI.2009.16.5.316

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Abstract PDF: Fe based (Fe_68.2C_5.9Si_3.5B_6.7P_9.6Cr_2.1Mo_2.0Al_2.0) amorphous powder, which is a composition of iron blast cast slag, were produced by a gas atomization process, and sequently mixed with ductile Cu powder by a mechanical ball milling process. The experiment results show that the as-prepared Fe amorphous powders less than 90 mum in size has a fully amorphous phase and its weight fraction was about 73.7%. The as-atomized amorphous Fe powders had a complete spherical shape with very clean surface. Differential scanning calorimetric results of the as-atomized Fe powders less than 90 mum showed that the glass transition, T_g, onset crystallization, T_x, and super-cooled liquid range DeltaT=T_x-T_g were 512, 548 and 36°C, respectively. Fe amorphous powders were mixed and deformed well with 10 wt.% Cu by using AGO-2 high energy ball mill under 500 rpm.

Production of Fe Amorphous Powders by Gas-Atomization Process and Subsequent Spark Plasma Sintering of Fe amorphous-ductile Cu Composite Powder Produced by Ball-milling Process (II) - II. SPS Behaviors of Composite Powders and their Characteristics -: Jin-Chun Kim, Ji-Soon Kim, H.J. Kim, Jeong-Gon Kim; J Korean Powder Metall Inst. 2009;16(5):326-335.; DOI: https://doi.org/10.4150/KPMI.2009.16.5.326

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Abstract PDF: Fe based (Fe_68.2C_5.9Si_3.5B_6.7P_9.6Cr_2.1Mo_2.0Al_2.0) amorphous powder, which is a composition of iron blast cast slag, were produced by a gas atomization process, and sequently mixed with ductile Cu powder by a mechanical ball milling process. The Fe-based amorphous powders and the Fe-Cu composite powders were compacted by a spark plasma sintering (SPS) process. Densification of the Fe amorphous-Cu composited powders by spark plasma sintering of was occurred through a plastic deformation of the each amorphous powder and Cu phase. The SPS samples milled by AGO-2 under 500 rpm had the best homogeneity of Cu phase and showed the smallest Cu pool size. Micro-Vickers hardness of the as-SPSed specimens was changed with the milling processes.

The Effect of Excess Samarium Oxide on the Preparation of Sm-Fe Alloy Powder by Reduction-diffusion Method: Hun Kwak, Jung-Goo Lee, Chul-Jin Choi; J Korean Powder Metall Inst. 2009;16(5):336-341.; DOI: https://doi.org/10.4150/KPMI.2009.16.5.336

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To produce alloy powders with only Sm_2Fe_17 single phase by reduction-diffusion (R-D) method, the effect of excess samarium oxide on the preparation of Sm-Fe alloy powder during R-D heat treatment was studied. The quantity of samarium oxide was varied from 5% to 50% whereas iron and calcium were taken 0% and 200% in excess of chemical equivalent, respectively. The pellet type mixture of samarium, iron powders and calcium granulars was subjected to heat treatment at 1100°C for 5 hours. The R-D treated pellet was moved into deionized water and agitated to separate Sm-Fe alloy powders. After washing them in deionized water several times, the powders were washed with acetic acid to remove the undesired reaction products such as CaO. By these washing and acid cleaning treatment, only 0.03 wt% calcium remained in Sm-Fe alloy powders. It was also confirmed that the content of unreacted alpha-Fe in Sm_2Fe_17 matrix gradually decreased as the percentage of samarium oxide is increased. However, there was no significant change above 40% excess samarium oxide.

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The Influence of Mechanical Milling on the Structure and Magnetic Properties of Sm-Fe-N Powder Produced by the Reduction-Diffusion Process
Jung-Goo Lee, Seok-Won Kang, Ping-Zhan Si, Chul-Jin Choi
Journal of Magnetics.2011; 16(2): 104. CrossRef

Surface Roughness and Sintering Characteristics of Fe-8 wt%Ni Component Fabricated by PIM: Berm-Ha Cha, Jai-Sung Lee; J Korean Powder Metall Inst. 2009;16(5):342-350.; DOI: https://doi.org/10.4150/KPMI.2009.16.5.342

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Development of nanoparticulate materials technology is essential to processing of highly functional nanoparticulate materials and components with small and complex shape. In this paper, the effect of particle size on surface roughness and shrinkage of sintered Fe-8 wt%Ni nanopowder components fabricated by PIM were investigated. The Fe-8 wt%Ni nanopowder was prepared by hydrogen reduction of ball-milled Fe_2O_3-NiO powder. Feedstock of nanopowder prepared with the wet-milled powder was injection molded into double gear shaped part at 120°C. After sintering, the sintered part showed near full densified microstructure having apparently no porosity (98%T.D.). Surface roughness of sintered bulk using nanopowder was less than 815 nm and it was about seven times lower than 7 mum that is typically obtainable from a sintered part produced from PIM.

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Opportunity and Challenges of Iron Powders for Metal Injection Molding
Abhijeet Premkumar Moon, Srinivas Dwarapudi, Kameswara Srikar Sista, Deepak Kumar, Gourav Ranjan Sinha
ISIJ International.2021; 61(7): 2015. CrossRef
Densification and microstructural development during sintering of powder injection molded Fe micro–nanopowder
Joon-Phil Choi, Hyun-Gon Lyu, Won-Sik Lee, Jai-Sung Lee
Powder Technology.2014; 253: 596. CrossRef
Consolidation of Hierarchy-Structured Nanopowder Agglomerates and Its Application to Net-Shaping Nanopowder Materials
Jai-Sung Lee, Joon-Phil Choi, Geon-Yong Lee
Materials.2013; 6(9): 4046. CrossRef
Consolidation of Iron Nanopowder by Nanopowder-Agglomerate Sintering at Elevated Temperature
Jai-Sung Lee, Joon-Chul Yun, Joon-Phil Choi, Geon-Yong Lee
Journal of Korean Powder Metallurgy Institute.2013; 20(1): 1. CrossRef
Manufacturing of Micro Gas Bearing by Fe-Ni Nanopowder and Metal Mold Using LIGA
Soo-Jung Son, Young-Sang Cho, Dae-Jung Kim, Jong-Hyun Kim, Suk-Sang Chang, Chul-Jin Choi
Journal of Korean Powder Metallurgy Institute.2012; 19(2): 140. CrossRef

Recovery of Copper Powder from MoO₃ Leaching Solution: Hyun-Seon Hong, Hang-Chul Jung, Geun-Hong Kim, Man-Sik Kong; J Korean Powder Metall Inst. 2009;16(5):351-357.; DOI: https://doi.org/10.4150/KPMI.2009.16.5.351

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A two-step recovery method was developed to produce copper powders from copper chloride waste solution as byproducts of MoO_3 leaching process. The first step consisted of replacing noble copper ions with external Fe3+ ions which were formed by dissolving iron scraps in the copper chloride waste solution. The replaced copper ions were subsequently precipitated as copper powders. The second step was cementation of entire solution mixture to separate (pure) copper powders from aqueous solution of iron chloride. Cementation process variables of temperature, time, and added amount of iron scraps were optimized by using design of experiment method and individual effects on yield and efficiency of copper powder recovery were investigated. Copper powders thus obtained from cementation process were further characterized using various analytical tools such as XRD, SEM-EDS and laser diffraction and scattering methods.Cementation process necessitated further purification of recovered copper powders and centrifugal separation method was employed, which successfully yielded copper powders of more than 99% purity and average 1sim2mum in size.

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Recovery of Tin as Tin oxide nanoparticles from waste printed circuit boards for photocatalytic dye degradation
Dina Magdy Abdo, Sabah Mohamed Abdelbasir, Shakinaz Taha El-Sheltawy, Ibrahim Ahmed Ibrahim
Korean Journal of Chemical Engineering.2021; 38(9): 1934. CrossRef
Recovery of Copper Powder form MoO3Leaching Solution Using Cementation Reaction System
Geon-Hong Kim, Hyun-Seon Hong, Hang-Chul Jung
Journal of Korean Powder Metallurgy Institute.2012; 19(6): 405. CrossRef

Mechanical Properties of Bulk Amorphous Ti₅₀Cu₂₀Ni₂₀Al₁₀ Fabricated by High-energy Ball Milling and Spark-plasma Sintering: H.V. Nguyen, J.C. Kim, J.S. Kim, Y.J. Kwon, Y.S. Kwon; J Korean Powder Metall Inst. 2009;16(5):358-362.; DOI: https://doi.org/10.4150/KPMI.2009.16.5.358

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Abstract PDF: Ti_50Cu_20Ni_20Al_10 quaternary amorphous alloy was prepared by high-energy ball milling process. A complete amorphization was confirmed for the composition of Ti_50Cu_20Ni_20Al_10 after milling for 30hrs. Differential scanning calorimetry showed a large super-cooled liquid region (DeltaT_x = T_x T_g, T_g and T_x: glass transition and crystallization onset temperatures, respectively) of 80 K. Prepared amorphous powders of Ti_50Cu_20Ni_20Al_10 were consolidated by spark-plasma sintering. Densification behavior and microstructure changes were investigated. Samples sintered at higher temperature of 713 K had a nearly full density. With increasing the sintering temperature, the compressive strength increased to fracture strength of 756 MPa in the case of sintering at 733 K, which showed a 'transparticle' fracture. The samples sintered at above 693 K showed the elongation maximum above 2%.

Formation and Thermal Properties of Amorphous Ti₄₀Cu₄₀Ni₁₀Al₁₀ Alloy by Mechanical Alloying: Hyun-Goo Kim; J Korean Powder Metall Inst. 2009;16(5):363-369.; DOI: https://doi.org/10.4150/KPMI.2009.16.5.363

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Abstract PDF: The amorphization process and the thermal properties of amorphous Ti_40Cu_40Ni_10Al_10 powder during milling by mechanical alloying were examined by X-ray diffractometry (XRD), differential scanning calorimetry (DSC), and transmission electron microscopy (TEM). The chemical composition of the samples was examined by an energy dispersive X-ray spectrometry (EDX) facility attached to the scanning electron microscope (SEM). The as-milled powders showed a broad peak (2theta = 42.4°) with crystalline size of about 5.0 nm in the XRD patterns. The entire milling process could be divided into three different stages: agglomeration (0 < t_m ≤ 3 h), disintegration (3 h < t_m ≤ 20 h), and homogenization (20 h < t_m ≤ 40 h) (t_m: milling time). In the DSC experiment, the peak temperature T_p and crystallization temperature T_x were 466.9°C and 444.3°C, respectively, and the values of T_p, and T_x increased with a heating rate (HR). The activation energies of crystallization for the as-milled powder was 291.5 kJ/mol for T_p.

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