• Journal of Korea Foundry Society
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• v.19 no.6
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• pp.493-500
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• 1999

Squeeze casting was used for fabricating a light metal base composite having high strength and wearresistance. Reactive sintering was used to prepare the preform of Squeeze casting. To utilize Fe-Al intermetallic compounds and SiC particle as a reinforcement, there needs to prepare Fe-Al mixed powder at 50, 60, 70at.%Al, and add SiC powder to the above mixture at 4, 7, 16, 24wt.%. The prepared mixture with SiC was reactive sintered in a tube furnace at $660^{\circ}C$ to get a porous hybrid preform of intermetallic compound and SiC. The preform prepared above was placed in a metal mold, preheated at $660^{\circ}C$ AC4C matrix was injected into the mold with the temperature of the melt at $610^{\circ}C$ After these processes, 66MPa was applied to the mold for 5 minute to finish the whole procedure. The maximum reaction temperature was increased with the increased Al amount, but decreased with the increased SiC amount. The density of the preform was decreased with SiC amount increase in the compacts due to swelling of the preform. An optical microscope was applied to observe the micro structure and the dispersion of the reinforcements. To analyze phases, We utilized XRD, EDS. Hardness test were chosen to get the information of mechanical properties. There were no significant changes in micro structure between the composite and preform. However, it was shown that uniform dispersion of the reinforcers and complete infiltration of the melt into the preform were achieved through the procedure of the squeeze casting. It was observed that the hardness of the composite is decreased with increased SiC amount, resulting from the volumetric expansion of the preform.

• Journal of the Korean institute of surface engineering
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• v.18 no.3
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• pp.125-133
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• 1985

About 1 mm thick nickel electrodeposits were obtained from nickel sulphamate baths at 40 to 60$^{\circ}C$ over the range of current densities form 5 to 25 A/$dm^2$. Deposits from above about 1.2V of cathode overpotential had randomly distributed fine grains due to a higher nucleation rate and hence had a high hardness. A deposit obtained at 0.63 V had the [110] orientation with a field oriented fine structure which yield a relatively high hardness. Deposite obtained at the intermediate overpotentials showed the [100] orientation with coarse field oriented structure whose column width tended to decrease with increasing cathode overpotential, which, in turn, gave rise to an increase in hardness. Residual stresses of the deposits measured by X-ray technique were mostly tensile but did not exceed 80 MPa, and were occasionally very small compressive. The cathode current efficiency was above 90% in all the electrolysis conditions, whereas the anode current efficiency varied from 50 to 90% with current density, bath temperature and nickel chloride concentration, among which the chloride was the most influential.

• Journal of the Korean institute of surface engineering
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• v.55 no.6
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• pp.460-468
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• 2022

Due to its high electrical conductivity, low contact resistance, good weldability and high corrosion resi-stance, gold is widely used in electronic components such as connectors and printed circuit boards (PCB). Gold ion salts currently used in gold plating are largely cyan-based salts and non-cyanic salts. The cya-nide bath can be used for both high and low hardness, but the non-cyanide bath can be used for low hardness plating. Potassium gold cyanide (KAu(CN)₂) as a cyanide type and sodium gold sulfite (Na₃[Au(SO)₃]₂) salt as a non-cyanide type are most widely used. Although the cyan bath has excellent performance in plating, potassium gold cyanide (KAu(CN)₂) used in the cyan bath is classified as a poison and a toxic substance and has strong toxicity, which tends to damage the positive photoresist film and make it difficult to form a straight side-wall. There is a need to supplement this. Therefore, it is intended to supplement this with an eco-friendly process using sodium sulfite sodium salt that does not contain cyan. Therefore, the main goal is to form a gold plating layer with a controllable hardness using a non-cyanide gold plating solution. In this study, the composition of a non-cyanide gold plating solution that maintains hardness even after annealing is generated through gold-palladium alloying by adding thallium, a crystal regulator among electrolysis factors affecting the structure and hardness, and changes in plating layer structure and crystallinity before and after annealing the correlation with the hardness.

• Transactions of the Korean hydrogen and new energy society
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• v.8 no.3
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• pp.121-129
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• 1997

$ZrV_{0.1}Mn_{0.7}Ni_{1.2}$ alloy ingot (bulk alloy) made by the arc melting was found to be consisting of mostly of $ZrV_{0.2}Mn_{0.98}Ni_{1.04}$ matrix alloy and $ZrV_{0.01}Mn_{0.13}Ni_{1.2}$ 2nd phase alloy. The former alloy had the form of the C15 type Laves alloy structure and the latter one had the intermetallic compound structure of $Zr_9Ni_{11}$. In order to investigate the effect of these two phases on the electrochemical charge-discharge characteristics of bulk $ZrV_[0.1}Mn_0.7}Ni_{1.2}$ alloy, the matrix and the 2nd phase alloys were fabricated separately by arc melting method and their electrochemical characteristics were studied and compared with the bulk alloy. It was found that the discharge capacity was the lowest of 160 mAh/g in the 2nd phase alloy. The matrix alloy exhibited 200 mAh/g. Both were lower than that of the bulk alloy of 250 mAh/g. The matrix and the bulk alloys showed a similar properties in the activation stage, the high rate dischargeability and the self discharge characteristics. Also a signigicant capacity decrease was observed after activation in both alloys. Whereas the 2nd phase alloy showed the very different characteristics. This alloy was found to be difficult to activate. However the capacity was remained constant after the activation. Also the self discharge rate was seen to be better than those of the matrix and the bulk alloys.

• Korean Journal of Optics and Photonics
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• v.18 no.4
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• pp.264-269
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• 2007

Today's research has been focused on changing the light source from filament to LED for luminarie illumination to overcome the shortcoming of a filament. The purpose of this research is to make an appropriate high power LED package structure for luminarie. We simulated radiation patterns of the various structures by the ray tracing simulator (Light Tools), and also analyzed the radiation patterns using an LED test system (OL770). As we increased an inner reflector angle, the radiation pattern split into two peaks and the angle between two peaks became larger. In addition, when we increased an outer reflector angle, the angle between side peaks gradually decreased, while it increased again when the angle reach $50^{\circ}$. These results could be understood from the ray tracing of the light reflected from two reflectors. We made the high power LED package for luminarie on the condition of the optimized structure which was made by ray tracing simulation results, and we measured the radiation patterns by using an LED test system, and these results were well matched to the simulation results.

• Korean Journal of Materials Research
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• v.10 no.2
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• pp.160-165
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• 2000

We have investigated the electrical and diffusion barrier properties of MgO produced on the surface of Cu (Mg) alloy. Also the diffusion barrier property of the interfacial MgO between Cu alloy and $SiO_2$ has been examined. The results show that the $150\;{\AA}$-MgO layer on the surface remains stable up to $700^{\circ}C$, preventing the interdiffusion of C Cu and Si in Si/MgO/Cu(Mg) structure. It also has the breakdown voltage of 4.5V and leakage current density of $10^{-7}A/\textrm{cm}^2/$. In addition, the combined structure of $Si_3N4(100{\AA})/MgO(100{\AA})$ increases the breakdown voltage up to lOV and reduces the leakage current density to $8{\tiems}10^{-7}A/\textrm{cm}^2$. Furthermore, the interfacial MgO formed by the chemical reac­t tion of Mg and $SiO_2$ reduces the diffusion of copper into $SiO_2$ substrate. Consequently, Cu(Mg) alloy can be applied as a g gate electrode in TFT /LCDs, reducing the process steps.

• Korean Journal of Materials Research
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• v.5 no.6
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• pp.673-681
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• 1995

Surface morphology and preferred orientation of 20${\mu}{\textrm}{m}$ gold electrodeposit formed from aqueous solution of the sodium gold sulfite were studied in terms of current density, plating temperature and Au concentration. As the current density changed from 13.0mA/$\textrm{cm}^2$ to 4.6mA/$\textrm{cm}^2$, the solution temperature from 3$0^{\circ}C$ to 6$0^{\circ}C$, pH from 12.0 to 9.0, agitation speed from 0 rpm to 3200rpm and Au concentration from 10g/1 to 14 g/1, local Au concentration near the cathodic surface increased. With increasing the Au concentration, the surface morphology chanced from porous structure to fine-grained structure. Furthermore, it was observed that the preferred orentation of the Au layer changed from (111) to (220) upon the same variation In the Au concentration. The surface morphology and the preferred orientation of the Au layer were found to be closely related to each other.

• Journal of the Korean Society of Safety
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• v.32 no.1
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• pp.9-14
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• 2017

Diffusion bonding is a technique that has the ability to join materials with minimum change in joint micro-structure and deformation of the component. The quality of the joints produced was examined by metallurgical characterization and the joint micro-structure developed across the diffusion bonding was related to changes in mechanical properties as a function of the bonding time. An increase in bonding time also resulted in an increase in the micro-hardness of the joint interface from 55 VHN to 180 VHN, The increase in hardness was attributed to the formation of intermetallic compounds which increased in concentration as bonding time increased.

• Journal of the Korean Society for Heat Treatment
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• v.6 no.2
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• pp.49-58
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• 1993

Isothermal transformation behavior during patenting and variations of microstructure and tensile strength of patented wires were investigated in Si-added high carbon steel. The TTT curves of the steels were made for two different austenitizing temperature. As the salt bath temperature was increased, the observed microstructures were bainite at $450^{\circ}C$, the mixture of bainite and pearlite at $500^{\circ}C$, and to pearlite at $600^{\circ}C$, The tensile strength of patented wire exhibited the highest value when the structure was pearlite. while the bainitic structure showed the lowest.

• Journal of Powder Materials
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• v.20 no.1
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• pp.48-52
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• 2013

A study of oxidation kinetic of Fe-36Ni alloy has been investigated using thermogravimetric apparatus (TGA) in an attempt to define the basic mechanism over a range of temperature of 400 to $1000^{\circ}C$ and finally to fabricate its powder. The oxidation rate was increased with increasing temperature and oxidation behavior of the alloy followed a parabolic rate law at elevated temperature. Temperature dependence of the reaction rate was determined with Arrhenius-type equation and activation energy was calculated to be 106.49 kJ/mol. Based on the kinetic data and micro-structure examination, oxidation mechanism was revealed that iron ions and electrons might migrate outward along grain boundaries and oxygen anion diffused inward through a spinel structure, $(Ni,Fe)_3O_4$.