• Journal of the Korean Vacuum Society
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• v.22 no.3
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• pp.119-125
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• 2013

In this study, we studied the properties of ZnO(Al) and ZnO(AlGa) thin film according to film thickness deposited on SLG by In-line magnetron sputtering system. XRD, FESEM, 4-point probe, Hall measurement system and UV/Vis-NIR spectrophotometer were employed to analyze the properties of ZnO(Al) and ZnO(AlGa) thin film. The all films exhibited (002) preferential orientation with clear peak shape and high intensity. The carrier concentration and Hall mobility of ZnO(Al) and ZnO(AlGa) thin film were improved with increasing thickness. The resistivity of both films decreased when the film thickness was raised from 500 nm to 1,450 nm. And then relatively the resistivity of ZnO(AlGa) film was lower than that of ZnO(Al) film. The transmittance of the films decreased with increasing film thickness but all films exhibited optical transmittances of over 83.3% in the visible region.

• Transactions of the Korean hydrogen and new energy society
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• v.25 no.6
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• pp.570-576
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• 2014

LFG (Land-Fill Gas) includes components of $CH_4$, $CO_2$, $O_2$, $N_2$, and water. The preparation of synthesis gas from LFG as a DME (Dimethyl Ether) feedstock was studied by methane reforming of $CO_2$, $O_2$ and steam over NiO-MgO-$CeO_2$/$Al_2O_3$ catalyst. Our experiments were performed to investigate the effects of methane conversion and syngas ratio on the amount of LFG components over NiO-MgO-$CeO_2$/$Al_2O_3$ catalyst. Results were obtained through the activity reaction experiments at the temperature of $900^{\circ}C$ and GHSV of 4,000. The results were as following; it has generally shown that methane conversion rate increased with the increase of oxygen and carbon dioxide amounts. Highly methane conversion of 92~93% and syngas ratio of approximately 1.0 were obtained in the feed of gas composition flow-rate of 243ml/min of $CH_4$, 241ml/min of $CO_2$, 195ml/min of $O_2$, 48ml/min of $N_2$, and 360ml/min of water, respectively, under reactor pressure of 15 bar for 50 hrs of reaction time. Also, it was shown that catalyst deactivation by coke formation was reduced by excessively adding oxygen and steam as an oxidizer of the methane reforming.

• Applied Chemistry for Engineering
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• v.28 no.1
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• pp.87-94
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• 2017

In this study, a catalyst based on $Pt/Al_2O_3$ supported on Mg was prepared by a wet impregnation method to investigate the $CH_4-SCR$ reaction characteristics of various alumina supports. Alumina supported on $Pt/Al_2O_3$ catalyst was converted to an $Al_2O_3$ composite, and when Mg was added, oxygen species of the active metal Pt were controlled due to electrophobic characteristics. Oxygen-controlled Pt used as a reducing agent inhibited the oxidation of $CH_4$ to $CO_2$. The addition of Mg also promoted the adsorption of NO species and the conversion of NO to $NO_2$ due to the NOx storage property on the catalyst surface.

• 한국정보디스플레이학회:학술대회논문집
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• 2009.10a
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• pp.272-275
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• 2009

A new green phosphor, ($Mg_{1-x-yZnx)$)$Al_2O_4:Mn^{2+}{_y}$ (0 x 0.6, 0.001 y 0.01), was synthesized by a flux-assisted solid reaction and its vacuum ultraviolet (VUV) excitation and emission characteristics were examined in this study. The chromaticity and peak intensity of the $(Mg_{0.79}Zn_{0.2})Al_2O_4:Mn^{2+}{_{0.01}}$ (x = 0.177, y = 0.745) phosphor were found to be more desirable than that of $Zn_2SiO_4:Mn^{2+}$ (x = 0.216, y = 0.72) phosphor as a green primary color.

• Journal of the Korean Chemical Society
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• v.37 no.10
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• pp.867-873
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• 1993

Influences of crystallization time and $H_2O/Al_2O_3$ ratio of the reaction mixtures on the synthesis of AlPO$_4$-5 molecular sieve have been studied by X-ray powder diffraction, nitrogen adsorption, scanning electron microscope (SEM), and solid state $^{27}$Al magic angle spinning nuclear magnetic resonance (MAS NMR) techniques. The degree of crystallinity of AlPO$_4$-5 follows a sigmoid pattem as crystallization time increases. The induction period is shorter than 1 h when the crystallization process is carried out at 150$^{\circ}$C. The conversion of reactants to product, AlPO$_4$-5, can be clearly observed, and all of the determined physical properties change abruptly after about 2 h. It is found that increase in $H_2O/Al_2O_3$ ratio of the reaction mixtures not only changes the crystal morphology from aggregates to hexagonal single crystals, but also results in the formation of longer AlPO$_4$-5 crystals.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.29 no.3
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• pp.115-122
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• 2019

Electric arc furnace dust (EAFD), which is a dust waste generated in the steel manufacturing process, contains heavy metals. Recently, researches of recycling a large amount of valuable metals such as zinc and iron in EAFD are being actively carried out. In this study, EAFD is used as a substitute for cobalt in blue ceramic pigments without any pretreatment. Then, the synthesized blue ceramic pigment using EAFD was micronized and formulated as a ceramic ink for inkjet printer. The particle size distribution, crystal structure and color characteristics during the micronization process were investigated for the development of ceramic ink. $Co_{0.75}Zn(EAFD)_{0.25}Al_2O_4$ ceramic pigments showed excellent blue coloric properties and monomodal distribution through micronization process. The average particle size of $Co_{0.75}Zn(EAFD)_{0.25}Al_2O_4$ ceramic pigments after 3 hours of milling was $0.271{\mu}m$, which is smaller than $0.303{\mu}m$, which is the average particle size of $CoAl_2O_4$ ceramic pigments without EAFD after 5 hours of milling. Especially, it was confirmed that $Co_{0.75}Zn(EAFD)_{0.25}Al_2O_4$ ceramic pigments showed a color difference (${\Delta}E{^*}_{ab}$) value of 5.67, which smaller than ${\Delta}E{^*}_{ab}$ value of $CoAl_2O_4$ during micronization. These results show that EAFD can be used as a raw material for a blue ceramic pigment by replacing expensive cobalt without any pretreatment.

• Clean Technology
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• v.21 no.3
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• pp.184-190
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• 2015

Most of LNT catalysts use noble metals such as Pt for low temperature NO_x oxidation but there is an economic weakness. For the purpose of overcoming this, this study is to develop DeNO_x catalyst for LNT excluding PGM (platinum group metal) such as Pt, Pd, Rh, etc. To do so, Al/Co/Ni catalyst selected as a preliminary test is used to study fundamental property and NO_x’s conversion according to calcined temperature. Ultimately, that is, Al/Co/Ni mixed metal oxide which does not use PGM is selected and physicochemical characterization is performed by way of XRD, EDS, SEM, BET and ramp test and NO_x conversion is also analyzed. This study shows that all samples consist of mixed oxides of spinel structure of Co₂AlO₄ and NiAl₂O₄ and have enough pore volume and size for redox. But as a result of NH₃-TPD test, it is desired that calcined temperature needs to be maintained at 700 ℃ or lower. Also only samples which are processed under 500 ℃ satisfied NO and NO_x conversion simultaneously through ramp test. Based on this study’s results, optimum calcined temperature for Al/Co/Ni=1.0/2.5/0.3 mixed metal oxide catalyst is 500 ℃.

• Journal of the Korean Ceramic Society
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• v.25 no.2
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• pp.117-124
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• 1988

The properties of the powders of the system Al2O3-ZrO2-Y2O3 prepared by precipitation method were investigated. Al2(SO4)3$.$18H2O3, ZrOCl2$.$8H2O and YCl3$.$6H2O were used as starting materials. Amorphous aluminum hydrate prepared by precipitation method was completely transformed to alpha Al2O3 as a result of calcining at 1100$^{\circ}C$ for 1 hr and gamma, delta and theta phases appeared as transition phases. In ZrO2-Y2O3 system prepared by co-precipitation method, the crystallization temperature of ZrO2 was increase with Y2O3 contents. The coupled crystallization occured in coprecipitated Al2O3-ZrO2-Y2O3 system, therefore the formation temperature of alpha Al2O3 and ZrO2-Y2O3 system. In this ternary system, the powder morphology showed a particular shape which was composed of large Al2O3 grains having small spherical ZrO2 particles within large Al2O3 grain and relatively large ZrO2 particles along the grian boundaries.

• Bulletin of the Korean Chemical Society
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• v.35 no.5
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• pp.1516-1522
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• 2014

A series of 20 wt % $(NH_4)_2SO_4$ and 3 wt % $Al_2O_3$ surface treatments were applied to $Li[Li_{0.2}Mn_{0.54}Co_{0.13}Ni_{0.13}]O_2$ substrates. The $Li[Li_{0.2}Mn_{0.54}Co_{0.13}Ni_{0.13}]O_2$ substrates were synthesized using a co-precipitation method. Sample (a) was left pristine and variations of the 20 wt % $(NH_4)_2SO_4$ and 3 wt % $Al_2O_3$ were applied to samples (b), (c) and (d). XRD was used to verify the space group of the samples as R$\bar{3}$m. Additional morphology and particle size data were obtained using SEM imagery. The $Al_2O_3$ coating layers of sample (b) and (d) were confirmed by TEM images and EDS mapping of the SEM images. 2032-type coin cells were fabricated in a glove box in order to investigate their electrochemical properties. The cells were charged and discharged at room temperature ($25^{\circ}C$) between 2.0V and 4.8V during the first cycle. The cells were then charged and discharged between 2.0V and 4.6V in subsequent cycles. Sample (d) exhibited lower irreversible capacity loss (ICL) in the first charge-discharge cycle as compared to sample (c). Sample (d) also had a higher discharge capacity of ~250 mAh/g during the first and second charge-discharge cycles when compared with sample (c). The rate capability of the $Al_2O_3$-coated sample (b) and (d) was lower when compared with sample (a) and (c). Sample (d), coated with $Al_2O_3$ after the surface treatment with $(NH_4)_2SO_4$, showed an improvement in cycle performance as well as an enhancement of discharge capacity. The thermal stability of sample (d) was higher than that of the sample (c) as the result of DSC.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.21 no.5
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• pp.218-224
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• 2011

LAS ($Li_2O-Al_2O_3-SiO_2$) ceramics were sintered by a solid-state reaction. $CaCO_3$ and $ZrO_2$ were added to the ${\beta}$-spodumene ($Li_2O-Al_2O_3-4SiO_2$) composition of the LAS system for enhancement of sintering behavior and mechanical strength, respectively. We have investigated the sintering characteristics, microstructures, mechanical properties and thermal expansion characteristics according to the change of the amount of additive and sintering temperature of the ${\beta}$-spodumene. At 0.1 mol% $CaCO_3$, the densification of ${\beta}$-spodumene was significantly improved. At 0.04 mol% $ZrO_2$, the strength of ${\beta}$-spodumene was also improved. For all the selected all compositions, the thermal expansion coefficient was measured by a dilatometer, which revealed 1.2 to $1.7{\times}10^6/^{\circ}C$.