• Journal of the Korean Crystal Growth and Crystal Technology
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• v.27 no.1
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• pp.42-46
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• 2017

$SrAl_2O_4$ : $Eu^{2+}$,$Dy^{3+}$ phosphorescent phosphors were synthesized by skull melting method. The molar ratio of oxides in the phosphors synthesized by the skull melting technique was $SrCO_3$ : $Al(OH)_3$ : $Eu_2O_3$ : $Dy_2O_3$= 1 : 2 : 0.015 : 0.02. Crystal structure and surface morphology were investigated by scanning electron microscopy (SEM) and X-ray diffraction (XRD) analysis. Optical properties of the synthesized $SrAl_2O_4$ : $Eu^{2+}$,$Dy^{3+}$ were measured by photoluminescence (PL) spectrometer for in-depth study on the excitation, emission and afterglow properties. From the PL measurements, it was found that excitation occurred in the wavelength range from 300 to 420 nm with peak position at 360 nm. The emission spectrum showed a broad curve in the wavelength from 450 to 600 nm with peak position at 530 nm. $SrAl_2O_4$ : $Eu^{2+}$,$Dy^{3+}$ phosphors exhibited afterglow properties with emission that lasted for a long period.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.22 no.2
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• pp.73-77
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• 2012

Co-(0.8 wt%) and Ce-(0.4 wt%) doped cubic zirconia ($ZrO_2$ : $Y_2O_3$ = 80 : 20, 70 : 30, 60 : 40, 50 : 50 wt%) single crystals grown by a skull melting method were heat-treated in $N_2$ at $1000^{\circ}C$ for 5 hrs. The orange, yellowish brown and brown colored as-grown single crystals were changed into either brownish red, yellow and green color after the heat treatment. Before and after the heat treatment, the YSZ (yttria-stabilized zirconia) single crystals were cut for wafer form (${\phi}6.5mm{\times}t2mm$). The optical and structural properties were examined by UV-VIS spectrophotometer and X-ray diffraction. Absorption by $Ce^{3+}(^2F_{5/2,7/2}(4f){\rightarrow}^2T_g(5d^1))$, $Co^{2+}(^4A_2(^4F){\rightarrow}^4T_1(^4F)$ or $^4T_1(^4P))$ and $Co^{3+}$, change of ionization energy and lattice parameter were confirmed.

• Journal of environmental and Sanitary engineering
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• v.14 no.3
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• pp.123-129
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• 1999

The utilization methods of algae biomass have been studied constantly in whole world. These are $\circled1$the wastewater treatment if waste stabilization pond and oxidation ditch etc. and $\circled2$the biosorption of heavy metals and recovery of strategic' precious metals and $\circled3$the single-celled protein production and the production of chemicals like coloring agent and $\circled4$the production of electric energy through methane gasification. The culture system also has been developed constantly in relation with such utilization method developments. In the result of experimental operation under continuous and cyclic irradiation of light, using high rate algae biomass culture pond(HRABCP), which had been made so as to be an association system with the various items which had been managed to have high efficiency for algae culture, the algae production of the 12 hours-irradiance pond was 41.48 Chlorophyll-a ${\mu}g/L$ only in spite of having the more chance of $CO_2$ synthesis to algae cell than the 24 hours-irradiance pond. This means that the energy supply required for dark-reaction of photosynthesis is very important like this. The difference of algae production between continuous and cyclc irradiation explains that the dark-reaction of photosynthesis acts on algae production as the biggest primary factor. The continuous irradiance on HRABCP made the good algae-production($1403.97{\;}{\mu}g$ Chlorophyll-a/mg) and the good oxygen-production(5.8 mg $O_2/L$) and the good solid-liquid seperation. especially, DO concentration through the oxygen-production was enough to fishes' survival.

• Resources Recycling
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• v.21 no.4
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• pp.76-85
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• 2012

Fluorescent lamps generally involve mercury within their lamp bulbs. Thus if the lamps are disposed as they are, it might cause environmental pollution. On the other hand, as the life of the lamps depends on the degradation of the discharge performance, the fluorescent substance composing the fluorescent substance coating can be recycled by reusing them as the recycled fluorescent substance. Also, the glass material composing the glass bulbs can be reused. The range of search was limited in the open patents of USA (US), European Union (EU), Japan (JP), Korea (KR) and SCI journals from 1977 to 2011. Patents and journals were collected using key-words searching and filtered by filtering criteria. The trends of the patents and journals was analyzed by the years, countries, companies, and technologies. Recovery method of metals from spent fluorescent lamps is mainly the focus on the recovery of precious metals using acid treatment and, detoxification technology is related with controlling process of mercury using a filter system.

• Korean Chemical Engineering Research
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• v.61 no.4
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• pp.505-516
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• 2023

Plastic's ease of processing drives its growing production, resulting in a surge of plastic waste. Addressing this issue, catalytic upcycling emerges as a promising remedy. Various metals (Ru, Pt, etc.) and supports (TiO₂, CeO₂, etc.) have been employed for the chemical recycling of polyolefin plastics. Strategies to enhance liquid fuel selectivity and minimize methane include manipulating particle size, introducing heterogeneous metals, and tuning support characteristics. Simultaneously, endeavors to optimize catalysts by reducing precious metal usage were pursued. This study explores enhancing economic viability in hydrogenolysis and hydrocracking reactions, underscoring the potential of catalystdriven upcycling to tackle plastic waste.

• Resources Recycling
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• v.10 no.5
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• pp.29-35
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• 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 Technologic Dentistry
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• v.9 no.1
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• pp.39-49
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• 1987

This study done to evaluate some surface treatment methods in metal coping which can increase the bond strength between porcelain and metal. Therefore this experiment was performed according to the Mc Lean's Theory of bond strength between porcelain and strength between porcelain and metal. In the experiment the author measured respective thermal expansion coefficents in three types of metal(Tallasium, Vera Bond and Rexillium) and Vita Porcelain to get the differences in the coefficents between porcelain and metals. And using insteron testing machine, the author also performed Planar interface shear bond tests on the 45 specimens(15 specimens in oxide surface, rough surface and fine surface treatment methods respectively) to measure bond strength between metal and porcelain. The results Were as follows, 1. The differences in thermal expansion coefficients between three types of metal and Vita procelain: Talladium - $1.2\;10^{-6/0}\;C$, Vera Bond - $1.6\;10^{-6/0}\;C$, Rexillium - $1.9\;10^{-6/0}\;C$. 2. The bond strength in oxide surface on the Shear bond test was the lowest among the treatment methods. 3. There was no significant differences in treatment methods of rough surface of fine surface. 4. In the oxide surface treatment method, there were significant differences(P<0.05)between Vera bond and Rexillium, and between Talladium and Rexillium. 5. In the fine surface treatment, there was a significant difference(P<0.05)between Talladium and Rexillium.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.12 no.2
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• pp.73-79
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• 2002

The polyol process which applies to cobalt, nickel. copper and precious metals is a interesting and unexpected example of such a method for preparing uniform metal powders. The reaction proceeds via dissolution, and the polyol acts simultaneously as a solvent, a reducing agent, and to some extent a protective agent. Submicrometer uniform cobalt particles can be obtained by seeding the reactive medium ($AgNO_3$) to achieve a complete substitution of homogeneous by heterogeneous nucleation. By varying the number of nuclei it is possible to control to some extent the average particle size in the submicrometer (0.5$\mu$m) range.

• International Journal of Automotive Technology
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• v.8 no.6
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• pp.667-674
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• 2007

Various types of NOx storage catalysts for NGV's were designed, manufactured, and tested in this work on a model gas test bench. As in most of other studies on NOx storage catalyst, alkaline earth metal barium(Ba) was used as the NOx adsorbing substance. The barium-based experimental catalysts were designed to contain different amounts of Ba and precious metals at various ratios. Reaction tests were performed to investigate the NOx storage capacity and the NOx conversion efficiency of the experimental catalysts. From the results, it was found that when Ba loading of a catalyst was increased, the quantity of NOx stored in the catalyst increased in the high temperature range over 350. With more Ba deposition, the NOx conversion efficiency as well as its peak value increased in the high temperature range, but decreased in the low temperature range. The best of de-NOx catalyst tested in this study was catalyst B, which was loaded with 42.8 g/L of Ba in addition to Pt, Pd and Rh in the ratio of 7:7:1. In the low temperature range under $450^{\circ}C$, the NOx conversion efficiencies of the catalysts were lower when $CH_4$, instead of either $C_3H_6$ or $C_3H_8$, was used as the reductant.

• Proceedings of the IEEK Conference
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• 2001.10a
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• pp.472-477
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• 2001

Spent catalysts containing platinum were generated in petroleum refinery and other chemical industries. The reclamation of precious metals from such wastes has long been attempted in view of their rare, expensive and indispensable nature. In this study, the recovery of platinum from petroleum catalysts was attempted by a method consisting mainly of dissolving alumina substrate with sulfuric acid thereby concentrating insoluble platinum. Also, platinum dissolved partially in sulfuric acid was recovered by a cementation method using aluminum metal as a reductive agent. The effect of temperature, time, concentration of sulfuric acid. and pulp density on the dissolution of substrate was investigated. When the substrate of platinum catalyst was ${\gamma}$-AI$_2$O$_3$ about 95% alumina was dissolved in 6.0M sulfuric acid at 10$0^{\circ}C$ for 2 hours. When the substrate was the mixture of ${\gamma}$-A1$_2$O$_3$and $\alpha$-A1$_2$O$_3$about 92% was dissolved after 4 hours. As a result, more than 99% of platinum could be recovered by this method and aluminum sulfate was obtained as byproduct.