• Journal of the Korean Institute of Gas
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• v.27 no.3
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• pp.19-26
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• 2023

Hydrogen, a clean energy source free of COx emissions, is poised to replace fossil fuels, with its usage on the rise. Despite its high energy content per unit mass, hydrogen faces limitations in storage and transportation due to its low storage density and challenges in long-term storage. In contrast, ammonia offers a high storage capacity per unit volume and is relatively easy to liquefy, making it an attractive option for storing and transporting large volumes of hydrogen. While NH₃ decomposition is an endothermic reaction, achieving excellent low-temperature catalytic activity is essential for process efficiency and cost-effectiveness. The study examined the effects of different zeolite types (5A, NaY, ZSM5) on NH₃ decomposition activity, considering differences in pore structure, cations, and Si/Al-ratio. Notably, the 5A zeolite facilitated the high dispersion of Ni across the surface, inside pores, and within the structure. Its low Si/Al ratio contributed to abundant acidity, enhancing ammonia adsorption. Additionally, the presence of Na and Ca cations in the support created medium basic sites that improved N₂ desorption rates. As a result, among the prepared catalysts, the 15 wt%Ni/5A catalyst exhibited the highest NH₃ conversion and a high H₂ formation rate of 23.5 mmol/g_cat·min (30,000 mL/g_cat·h, 600 ℃). This performance was attributed to the strong metal-support interaction and the enhancement of N₂ desorption rates through the presence of medium basic sites.

• Journal of the Korean Applied Science and Technology
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• v.30 no.4
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• pp.575-585
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• 2013

This research was performed to evaluate the recycling feasibility as a construction material of dredged harbor soil mixed with clay and glass frit. Concentration of heavy metals of the dredged soil from D harbor was severly high, showing Zn of 526.0~13,150.1 mg/kg. The dredged soil was maily composed of 48.30 wt% $SiO_2$, 16.60 wt% $Al_2O_3$, 10.10 wt% CaO, 7.75 wt% $Fe_2O_3$. The clay and the glass frit contained 70.82 wt% $SiO_2$ and $Al_2O_3$ 18.78 wt%, and 71.75 wt% $SiO_2$, 13.99 wt% CaO, 8.51 wt% $Na_2O$, respectively. After adding 10~40 wt% to the clay and sintering them at $1,000^{\circ}C$ or $1,100^{\circ}C$, the compressive strength of the sintered specimens showed $132.6{\sim}178.5kgf/cm^2$ or $581.2{\sim}793.7kgf/cm^2$, respectively. In case of SC46 with the addition 40 wt% of the dredged soil to the clay, the compressive strength ($793.7kgf/cm^2$) of specimen sintered at $1,100^{\circ}C$ was over 5 times higher than that at $1,000^{\circ}C$. The specimen mixed with 40 wt% of dredged soil, 60 wt% of clay and 1 wt% of glass frit satisfied the 1st grade standard for clay brick by KS L 4201. The results of all specimens by Korean Standard Leaching Test also satisfied the standard criteria.

• Korean Journal of Environmental Agriculture
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• v.19 no.5
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• pp.401-418
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• 2000

1. Production of the artificial zeolite from coal ash Coal fly ash is mainly composed of several oxides including $SiO_2$ and $Al_2O_3$ derived from inorganic compounds remained after burning. As minor components, $Fe_2O_3$ and oxides of Mg, Ca, P, Ti (trace) are also contained in the ash. These components are presented as glass form resulting from fusion in the process of the combustion of coal. In other word, coal ash may refer to a kind of aluminosilicate glass that is known to easily change to zeolite-like materials by hydrothermal reaction. Lots of hot seawater is disposing near thermal power plants after cooling turbine generator periodically. Using seawater in the hydrothermal reaction caused to produce low price artificial zeolite by reduction of sodium hydroxide consumption, heating energy and water cost. As coal ash were reacted hydrothermally, peaks of quartz and mullite in the ash were weakened and disappeared, and new Na-Pl peaks were appeared strengthily. Si-O-Si bonding of the bituminous coal ash was changed to Si-O-Al (and $Fe^{3+}$) bonding by the reaction. Therefore the produced Na-Pl type zeolite had high CEC of 276.7 $cmol^+{\cdot}kg^{-1}$ and well developed molecular sieve structure with low concentration of heavy metals. 2. Utilization of the artificial zeolite in agro-environment The artificial zeolite(1g) could remove 123.5 mg of zinc, 164.7 mg copper, 184.4 mg cadmium and 350.6 mg lead in the synthetic wastewater. The removability is higher 2.8 times in zinc, 3.3 times in copper, 4.7 times in cadmium and 4.8 times in lead than natural zeolite and charcoal powder. When the heavy metals were treated at the ratio of 150 $kg{\cdot}ha^{-1}$ to the rice plant, various growth inhibition were observed; brownish discoloration and death of leaf sheath, growth inhibition in culm length, number of panicles and grains, grain ripening and rice yield. But these growth inhibition was greatly alleviated by the application of artificial zeolite, therefore, rice yield increased $1.1{\sim}3.2$ times according to the metal kind. In addition, the concentration of heavy metals in the brown rice also lowered by $27{\sim}75%$. Artificial Granular Zeolites (AGZ) was developed for the purification of wastewater. Canon exchange capacity was 126.8 $cmol^+{\cdot}kg^{-1}$. AGZ had Na-Pl peaks mainly with some minor $C_3S$ peaks in X-ray diffractogram. In addition, AGZs had various pore structure that may be adhere the suspended solid and offer microbiological niche to decompose organic pollutants. AGZ could remove ammonium, orthophosphate and heavy metals simultaneously. Mixing ratio of artificial zeolite in AGZs was related positively with removal efficiency of $NH_4\;^+$ and negatively with that of $PO_4\;^{3-}$. Root growth of rice seedling was inhibited severely in the mine wastewater because of strong acidity and high concentration of heavy metals. As AGZ(1 kg) stayed in the wastewater(100L) for 4days, water quality turned into safely for agricultural usage and rice seedlings grew normally.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.51 no.8
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• pp.340-346
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• 2002

Capacitor material utilized in the downsizing passive devices and integration of passive devices requires the physical and electrical properties at given area such as capacitor thickness reduction, relative dielectric constant increase, low leakage current and thermal stability. common capacitor materials, $Al_2O_3$, $SiO_2$, $Si_3N_4$, $SiO_2$/$Si_3N_4$, TaN and et al., used until recently have reached their physical limits in their application to integration of passive devices. $Ta_2O_{5}$ is known to be a good alternative to the existing materials for the capacitor application because of its high dielectric constant (25~35), low leakage current and high breakdown strength. Despite the numerous investigations of $Ta_2O_{5}$ material, there have little been established the clear understanding of the annealing effect on capacitance characteristic and conduction mechanism. This study presents the dielectric properties $Ta_2O_{5}$ MIM capacitor structure Processed by $O_2$ RTA oxidation. X-ray diffraction patterns showed the existence of amorphous phase in $600^{\circ}C$ annealing under the $O_2$ RTA and the formation of preferentially oriented-$Ta_2O_{5}$ in 650, $700^{\circ}C$ annealing and the AES depth profile showed $O_2$ RTA oxidation effect gives rise to the $O_2$ deficientd into the new layer. The leakage current density respectively, at 3~1l$\times$$10_{-2}$(kV/cm) were $10_{-3}$~$10_{-6}$(A/$\textrm{cm}^2$). In addition, behavior is stable irrespective of applied electric field. the frequency vs capacitance characteristic enhanced stability more then $Ta_2O_{5}$ thin films obtained by $O_2$ reactive sputtering. The capacitance vs voltage measurement that, Vfb(flat-band voltage) was increase dependance on the $O_2$ RTA oxidation temperature.

• Journal of the Korean institute of surface engineering
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• v.35 no.3
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• pp.127-132
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• 2002

High speed performance of ferroelectric Pb(Zr,Ti)$O_3$ (PZT) based capacitors is reported. La substitution up to 10% was performed to systematically lower the coercive and saturation voltages of epitaxial ferroelectric capacitors grown on Si using a ($Ti_{0.9}$ /$Al_{0.1}$ )N/Pt conducting barrier composite. Ferroelectric capacitors substituted with 10% La show significantly lower coercive voltage compared to capacitors with 0% and 3% La. This is attributed to a systematic decrease in the tetragonality (i.e., c/a ratio) of the ferroelectric phase. Furthermore, the samples doped with 10% La showed dramatically better retention and pulse width dependent polarization compared to the capacitors with 0% and 3% La. These capacitors show promise as storage elements in low power high density memory architectures.

• Journal of environmental and Sanitary engineering
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• v.14 no.2
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• pp.40-45
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• 1999

This study deals with an investigation on low cost adsorbents locally available n dyeing wastewater treatment of color removal. Peat, bentonite, slag and fly ash were utilized for this study. Considering that low cost adsorbents contained in $SiO_2$, $Fe_2O_3$ and $Al_2O_3$ compositions, and coagulants were mainly used aluminate and ferrate in color removal. Color of dyeing wastewater was high removed in peat, berntonite and slag except for fly ash with passed time. It could be known that color removal of peat and slag were increased to pH 4, but was hardly changed with advancing to alkaline. Color intended to be high removed with increasing of agitation speed but to be almost slow after 150rpm. As a result on the experiment of Freundlich adsorption isotherms, adsorption intensity(l/n) appeared to be peat>fly ash>slag>bentonite and adsorption capacity(k) came out peat>bentonite>slag>fly ash. Therefore, if low cost adsorbents substituted for existing adsorbents, peat, bentonite and slag could look forward to an expected economical effect.

• Advances in environmental research
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• v.8 no.1
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• pp.55-69
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• 2019

The generation of ferrous slag, an industrial by-product from the iron ore industry, results in serious environmental problems. The chemical compositions indicate 30-34% SiO₂, 30-34% CaO, 18-22% Al₂O₃ and 0.5-0.6% Fe₂O₃. The specific gravity, moisture content and pH are in the range of 1.3-1.65, 9.1-10% and 8.5-9.0 respectively. The major part of the slag is composed of sand-size particles. The problems of disposal of slag could be minimized by considering its use in various environmental engineering applications providing additional value to the by-product. This paper mainly focuses on the potential utilization and valorisation of ferrous slag in both water and wastewater treatments. It is effective for the treatment of water and wastewater containing nutrients, heavy metals and polluted river/stormwater.

• 한국생물공학회:학술대회논문집
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• 2000.11a
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• pp.342-345
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• 2000

Effect of volcanic ash on cell growth of Aspergillus sp. and production of exopolymers by Agrobacterium sp. and Aureobasidium pullualns was investigated. The volcanic ash contained various mineral salts such as $SiO_2$, $Al_2O_3$, CaO, $K_2O$. Maximal cell growth of Aspergillus sp. was obtained when 0.3% volcanic ash was added to medium. Cell growth of Aspergillus sp. increased with higher concentration of volcanic ash in medium. Amount of cell growth with 0.3 % volcanic ash was 6.7 times higher than that without volcanic ash. Volcanic ash also stimulated production of exopolymer as well as cell growth. Production of curdlan with 0.1% volcanic ash was 12.40 g/l whereas that without volcanic ash was 9.15 g/l. Production of pullulan with volcanic ash was also higher than that without volcanic ash.

• Steel and Composite Structures
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• v.22 no.4
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• pp.745-752
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• 2016

An investigation has been done to study the evolution of the microstructure, mechanical and electrical properties of AlMgSi alloy destined for the transport of electric energy, in function of the deformation caused by the cold drawing process. We identified that drawing of aluminum wire causes development of a fibrous texture of type <111> and <100>. We notice also that the electrical resistivity and mechanical resistance increases with the increasing of the deformation level. Characterization methods used in this work is: The Electron Back Scattered Diffraction EBSD, X-Ray diffraction, Vickers microhardness, Tensile test, Measuring electrical resistivity, the Scanning Electron Microscope (SEM) and Energy Diffraction Spectrum (EDS).

• Nuclear Engineering and Technology
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• v.46 no.2
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• pp.125-146
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• 2014

This review aims to provide a synthesis of the knowledge generated and the lessons learned in roughly 15 years of UMo dispersion fuel R&D in Europe through a series of irradiation experiments. A lot of irradiations were also performed outside of Europe, particularly in the USA, Russia, Canada, Korea and Argentina. In addition, a large number of out-of-pile investigations were done throughout the world, providing support to the understanding of the phenomena governing the UMo behaviour in pile. However, the focus of this article will be on the irradiations and Post-Irradiation Examination (PIE) results obtained in European experiments. The introduction of the article provides a historic overview of the evolution and progress in the high density UMo dispersion fuel development. The ensuing sections then provide further details on the various phases of the development, from the UMo dispersion in a pure Al matrix through the addition of Si to the matrix to address the interaction layer formation and finally to the more advanced solutions to the excessive swelling encountered in various experiments. This review was based only on published results or results that are currently in the process of being published.