• Proceedings of the KIEE Conference
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• 1999.07d
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• pp.1501-1503
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• 1999

The $(Sr_{0.85}Ca_{0.15})TiO_3$(SCT) thin films are deposited on Pt-coated electrode$(Pt/TiO_2/SiO_2/Si)$ using RF sputtering method. Ag, Cu, Al, Pt films for the formation of top eletrode were doposited on SCT thin films by thermal evaporator and sputtering. The effects of top electodes have be studied on SCT samples with a variety of top electrode materials.

• Journal of Korea Foundry Society
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• v.18 no.3
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• pp.271-274
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• 1998

Effects of Si and Ni addition on the microstructure and mechanical properties of the Cu-12wt.%Al-5wt.%Fe-1wt.%Mn alloy have been investigated experimentally. Microstructure of the as-cast specimen is found to be refined markedly by additions of Ni and Si. By the addition of Ni, volume fraction of the ${\kappa}$ phase is increased, but volume fraction of the ${\gamma}$ phase is decreased. Hardness is increased with the addition of Ni, due to increasing of ${\kappa}$ phase which is harder than ${\gamma}$ phase. However, Charpy impact value is not significally decreased possibly due to the formation of isolate ${\kappa}$ phase.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2007.11a
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• pp.281-281
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• 2007

Low Temperature Co-fired Ceramic (LTCC) technology has been used in electronic device for various functions. LTCC technology is to fire dielectric ceramic and a conductive electrode such as Ag or Cu thick film below the temperature of $900^{\circ}C$ simultaneously. The glass-ceramic has been widely used for LTCC materials due to its low sintering temperature, high mechanical properties and low dielectric constants. To obtain the high strength, addition of filler, the microstructure should have various crystals and low pores in a composite. In this study, two glass frits were mixed with different alumina size(0.5, 2, 3.7um) and sintered at the range of $850{\sim}950^{\circ}C$. The microstructure, crystal phases, thermal and mechanical properties of the composites were investigated using FE-SEM, XRD, TG-DTA, Dilatomer. When the particle size of $Al_2O_3$ filler increased, the starting temperatures for the densification of the sintered bodies, onset point of crystallization, peak crystallization temperature in the glass-ceramic composites decreased gradually. After sintered at $900^{\circ}C$, the glass frits were crystallized as $CaAl_2Si_2O_8\;and\;CaMgSi_2O_6$. The purpose of our study is to understand the relationship between the $Al_2O_3$ particle size and thermal properties in composites.

• Journal of Electrochemical Science and Technology
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• v.2 no.3
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• pp.168-173
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• 2011

The availability, low toxicity, and high degree of technological development make silicon the most likely material to be used in solar cells, the cost of solar cells depends entirely on cost of high purity silicon production. The present work was conducted to electrodeposite of silicon from $K_2SiF_6$, an inexpensive raw material prepared from fluorosilicic acid ($H_2SiF_6$) produced in Iraqi Fertilizer plants, and using inexpensive graphite material as cathode electrode. The preparation of potassium fluorosilicate was performed at ($60^{\circ}C$) in a three necks flask provided with a stirrer, while the electro deposition was performed at $750^{\circ}C$ in a three-electrodes configuration with melt containing in graphite pot. High purity potassium fluorosilicate (99.25%) was obtained at temperature ($60^{\circ}C$), molar ratio-KCl/$H_2SiF_6$(1.4) and agitation (600 rpm). Spongy compact deposits were obtained for silicon with purity not less than (99.97%) at cathode potential (-0.8 V vs. Pt), $K_2SiF_6$ concentration (14% mole percent) with grain size (130 ${\mu}m$) and level of impurities (Cu, Fe and Ni) less than (0.02%).

• Journal of Korea Foundry Society
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• v.11 no.6
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• pp.475-481
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• 1991

In this study the fabrication technology and mechanical properties of AC8A/$Al_2O_3$ Composites by squeeze casting process were investigated to develope for application as the piston materials that require good friction, wear resistance, and thermal stability. AC8A/$Al_2O_3$ composistes without a porosity and the break of preform were fabricated at the melt temperature of $740^{\circ}C$, the preform temperature of $500^{\circ}C$, and mold temperature of $400^{\circ}C$ under the applied pressure of $1200kg/cm^2$ as the results of the observation of microstructures. As the results of this study, the tensile strength of AC8A/$Al_2O_3$ composites was not increased linearly with $Al_2O_3$ volume fraction and so it seemed not to agree with the rule of mixture, which had been used often in metal matrix composite. Also the tensile strength after thermal fatigue test was little different from that before the test. Consequently it was thought that AC8A/$Al_2O_3$ composites fabricated under our experimental conditions had a good thermal stability and subsequently a good interface bonding. Wear rate(i.e., volume loss per unit sliding distance) of AC8A/$Al_2O_3$ composites was decreased with $Al_2O_3$ volume fraction and the sliding speed at both room temperature and $250^{\circ}C$ and so there was a good correlation between wear rate and hardness. Also the wear rate of AC/8A20% $Al_2O_3$ composities was obtained the value of $1.65cm^3/cm$ at sliding speed of 1.14m/sec as compared with about $3.0\;{\times}10^{-8}cm^3/cm$ hyereutectie Al-Si alloy(Al-16%Si-2%Cu-1%Fe-1%Ni), which applied presently for piston materials. The wear behavior of $Al_2O_3$ composites was observed to a type of abrasive wear by the SEM view of wear surface.

• Journal of Environmental Science International
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• v.8 no.4
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• pp.491-496
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• 1999

Removal of Cu(II), Cr(III) and Pb(II) ions from aqueous solutions using the adsorption process on the loesses has been investigated. Variations of contact time, pH, adsorption isotherms and selectivity of coexisting ions were experimental parameters. pH of KJ and YIK samples diluted to 1% solution, was rearly the same with each value of pH 5.58 and 5.49, and both samples showed weak acidic properties. From chemical analysis, both samples contain remarkably different amounts of ${SiO}_{2}$, ${Al}_{2}O_{3}$ and ${Fe}_{2}O_{3}$. From XRD measurement, quartz was mainly observed in both samples. Kaolinite was also observed, also in both samples, but Feldspar was only observed in KJ sample. Adsorption of metal ions on the loesses were reached at equilibrium by shaking for about 30min. The adsorption of Cr(III) ion was higher than that of Cu(II) oand Pb(II) ions. The order of amount adsorbed among the investigated ions was Cr(III)>Pb(II)>Cu(II). In acidic solution, the adsorptivity of loesses was increased as pH increased. The adsorption of Cr(III) ion on the loesses were fitted to the Freundlich isotherms. Freundlich constants(1/n) of KJ and YIK loesses were 0.54 and 0.55, respectively.

• Journal of Magnetics
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• v.8 no.1
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• pp.32-35
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• 2003

Magnetic funnel Junctions (MTJs) were fabricated on thermally oxidized Si (100) wafers using DC magnetron sputtering. The film Structures were Ta(50 ${\AA}$)/CU(100 ${\AA}$)$Ni_{80}Fe_{20}(20 $ ${\AA}$)/Cu(50 ${\AA}$)/$Mn_{75}Ir_{25}(100 $ ${\AA}$)/$Co_{70}Fe_{30}(25$ ${\AA}$)/Al-O(15 ${\AA}$)/$Co_{70}Fe_{30}(25 $ ${\AA}$)/$Ni_{80}Fe_{20}(t)/Ta(50 $ ${\AA}$), with t=0 ${\AA}$, 100 and 1000 ${\AA}$, respectively. X-ray diffraction has shown improvement of (111) texture of IrMn$_3$ and Cu by annealing. The exchange-biased energy is almost inversely proportional to temperature. The difference between the coercivity H$_c$ and the exchange biased field H$_E$ for t = 0 $_3$ sample is smaller than that for t = 1000 ${\AA}$. For the pinned layer, the decreasing rate of the coercivity with the temperature is higher compared to that of the exchange field, but variation of H$_c$ is similar to that of the exchange field for free layer.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2017.05a
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• pp.153-153
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• 2017

The application of the coating supports the mechanical characteristics of the implant, and various materials and coatings are currently being used in the implant in a way to accelerate adhesion. Especially, plasma electrolytic oxidation (PEO) coating has been proposed continually with good surface treatment of titanium alloys. Also, the PEO process can incorporate Ca and P ions on the titanium surface through variables varied factor. PEO process for bioactive surface has carried out in electrolytes containing Ca and P ions. Natural bone is composed of mineral elements such as Mg, Si, Zn, Sr, and Mn, etc. Especially, Mg and Si of these elements play role in bone formation and growth after clinical implantation of bio-implants. In this study, corrosion charateristics of PEO-treated Ti-6Al-4V alloy in solution containing Si and Mg ions has been investigated using several experimental techniques. The PEO-treated surfaces were identified by X-ray diffraction, using a diffractometer (XRD, Philips X' pert PRO, Netherlands) with Cu $K{\alpha}$ radiation. The morphology was observed by field-emission scanning electron microscopy (FE-SEM, Hitachi 4800, Japan) and energy-dispersive X-ray spectroscopy (EDX, Oxford ISIS 310, England). The potentiodynamic polarization and AC impedance tests for electrochemical degradations were carried out in 0.9% NaCl solution at similar body temperature using a potentiostat with a scan rate of 1.67mV/s and potential range from -1500mV to + 2000mV.

• Journal of Conservation Science
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• v.30 no.4
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• pp.457-466
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• 2014

Rigorous analysis was performed to identify the structure and materials of the murals to study techniques used on mural tombs of ancient Daegaya era(6th century). The murals were painted by applying mortar on the walls and the ceiling after building a stone chamber and creating ground layers on mortar layers. Mud was applied on most of the mortar layers on four sides of the walls except the ceiling. Sand was not used in mortar but was made of materials with pure calcium substances. In addition, shells in irregular sizes with incomplete calcination were mixed; and the mortar's white powder was inferred as lime obtained by calcination of oyster shells. Kaolinite($Al_2Si_2O_5(OH)_4$) was used in the ground layer, Cinnabar(HgS) was used for red pigment, Malachite($Cu_2CO_3(OH)_2$) for green and Lead white($PbCO_3{\cdot}Pb(OH)_2$) for white. Mud plaster was applied on the mortar and was composed thinly and densely using clayey of particle size smaller than that of medium sand. It was assumed that the finishing was for repair after long time had passed since the mortar layer came off. Using lime made with oyster shells as mortar is unprecedented in ancient Korean mural tombs and its durability was very poor, suggesting that Gaya's mortar production technique was relatively behind compared to that of Koguryo's in the same era.

• Economic and Environmental Geology
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• v.28 no.3
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• pp.251-257
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• 1995

Three PEA (Pulverised Fuel Ash) samples, which were fresh, 17 and some 40 years weathered, were collected from two major British power plants. Batch leaching tests with these samples using distilled water and simulated industrial leachate showed higher amounts of element liberation from fresh ash, including Ca, Na, K, S (as $SO^{2-}_4$, $Cr_{total}$, Cu, Li Ni, Mo and CI and this seems to indicate their surface association and easier dissolution when contact with water. On the contrary Mg, Al, Ba, Si, V, As and Se do not show such readily leachable concentrations and these elements might be more associated with glass fraction in PFA particle rather than surface. Although element concentrations in the weathered ash are much lower than those in the initial leachate from the fresh ash, elements are still detected as resonable concentrations, with rather constant levels and this seems to demonstrate the element release from unstable glass phase of PFA particle. Fe, Ca, $Cr_{total}$, Cu, Ni, Zn and Hg were removed from the synthetic leachate by PFA and this is also confirmed by gain in solid PFA. The order of element retention is Meaford weathered ash > Drax weathered ash > Drax fresh ash in decreasing order and this conforms with the degree of weathering. Namely, the more wethered, the more wethered, the more effective in metal retention from the synthetic leachate.