• Economic and Environmental Geology
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• v.28 no.6
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• pp.571-577
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• 1995

Several acid-sulfate clay deposits associated with silicic magmas occur in the Haenam area of the southwestern part of Korea. Geology of the studied area consists of tuffs, granitic rocks, quartz porphyry, rhyolite, andesite and sedimentary rocks. The granitic rocks and quartz porphyry intruded tuffs and sedimentary rocks. The rhyolite and tuffs around the mines have undergone hydrothermally weak or strong alteration. Gold contents with major and trace elements have been determined for a total of sixty-seven specimens of fresh igneous rocks, wall rocks and minerals such as dickite and alunite by graphite furnace atomic absorption spectrometer and inductively coupled plasma. Gold is enriched in the alunite vein and the silicified zone, but is depleted in dickites and hydrothermally altered rocks with dickite of the Seongsan deposit. Gold is especially concentrated near the faults or conjunction area of two faults. High content of gold is shown in the mineral assemblages of alunitequartz- pyrite in the alunite vein and silicic zone of the Seongsan deposit compared with that of minerals and rocks from another deposits distributed in the studied area. Gold content in tuffs and dickites with pyrite is generally low. Gold content in silicified tuff tends to show positive correlations with content of As, Hg and Sb. Variation trends of Cd, Hg and Sb are similar to those of gold content. From the result of gold content variations, gold may be transported and concentrated by mineralizing solutions ascending along the cracks like fault. Therefore, it is important to survey alunite vein and silicified zone at the conjunction of faults, and to analyze pathfinder elements such as As, Hg and Sb for geological and geochemical exploration of gold in the studied deposits.

• Journal of the Korea Concrete Institute
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• v.25 no.4
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• pp.457-465
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• 2013

This study discussed the influence of mixtures and curing conditions on the development of strength and microstructure of RPC using ternary pozzolanic materials. Through pilot experiment, various RPC was manufactured by adding single or mixed ternary pozzolanic materials such as silica fume, blast furnace slag and fly ash by mass of cement, up to 0~65%, and cured by using 4 types of method which are water and air-dried curing at $20^{\circ}C$, steam and hot-water curing at $90^{\circ}C$. The results show that the use of ternary pozzolanic materials and a suitable curing method are an effective method for improving development of strength and microstructure of RPC. The unit volume of cement was greatly reduced in RPC with ternary pozzolanic materials and unlike hydration reaction in cement, the pozzolanic reaction noticeably contributes to a reduction in hydration heat and dry shrinkage. A considerable improvement was found in the flexural strength of RPC using ternary pozzolanic materials, and then the utilization of a structural member subjected to bending was expected. The X-ray diffractometer (XRD) analysis and Scanning Electronic Microscope (SEM) revealed that the microstructure of RPC was denser by using the ternary pozzolanic materials than the original RPC containing silica fume only.

• Journal of the Korea Institute of Building Construction
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• v.12 no.1
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• pp.54-63
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• 2012

The purpose of this study is to examine the potential for reducing the environmental load and $CO_2$ gas when cement is produced by using cement substitutes. These substitutes consisted of blast furnace slag, red mud and silica fume, which were industrial by-products. The most optimum mix was derived when alkali accelerator was added to low carbon inorganic composite mixed with industrial by-product at room temperature. It is determined that hardened properties and the results of compressive strength tests changed based on CaO content, Si/Al, the mixing ratio and the amount of alkali accelerator, curing conditions and W/B. The results of test analysis suggest that the optimum mix of low carbon inorganic composite is CaO content 30%, Si/Al 4, the mixed ratio of alkali accelerator $(NaOH:Na_2SiO_3)$ 50g:50g, the amount of alkali accelerator 100g and W/B 31%. In addition, if contraction is complemented, low carbon inorganic composite with superior performance could be developed.

• Journal of the Korea Concrete Institute
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• v.24 no.6
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• pp.659-666
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• 2012

To secure the thermal crack resistance of mass concrete, researches and the field applications of low heat portland cement (LPC), ternary blended cement (TBC) which is produced by blending ordinary portland cement with blast furnace slag and fly ash, and early strength low heat blended cement (EBC) increased in recent years. Although the model for adiabatic temperature rise is necessary for estimating the risk of thermal cracking of concrete structures, sufficient data have not been accumulated for these mixtures. In addition, the differences in adiabatic test results have been reported for the volume of test specimens. Therefore, the present study evaluated the characteristics of adiabatic temperature rise based on the type of binder and the volume of the adiabatic test specimen. Test results indicated that the maximum temperature rise ($Q_{\infty}$) and the reaction factor (r) of TBC were the lowest. Test results also showed that $Q_{\infty}$ and r changed with respect to the volume of test specimen. $Q_{\infty}$ and r obtained from 6l equipment were lower than those of 50l equipment. Therefore, corrections with respect to this phenomenon was confirmed and the corrections factors are presented.

• Journal of the Korea Concrete Institute
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• v.24 no.6
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• pp.715-726
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• 2012

Since strength and diffusion coefficient of concrete, representative concrete properties that in change with age, the time effect must be considered in the analysis of chloride penetration. In this study, an evaluation of correlation between accelerated diffusion coefficient, apparent diffusion coefficient, and compressive strength in high performance concrete with various mineral admixtures such as ground granulated blast furnace slag, fly ash, and silica fume was performed. For this work, thirty mix proportions were prepared. Accelerated diffusion coefficients at the age of 28, 91, 180, and 270 days were evaluated. For apparent diffusion coefficient, submerging test for 6 months was performed. For evaluation of compressive strength with ages, the compressive strength test was carried out at an age of 7, 28, 91, 180 days. The results of accelerated diffusion coefficient, apparent diffusion coefficient, and strength were compared, and the correlation was analyzed considering time dependency. From this study, linear relationship between accelerated diffusion and apparent diffusion coefficient were obtained regardless of concrete age. The linear relations were also observed in strength-accelerated diffusion coefficient and strength-apparent diffusion coefficient regardless of concrete age.

• Korean Chemical Engineering Research
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• v.50 no.5
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• pp.860-865
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• 2012

Although biomass syngas is very low calorific gas, it is utilized by means of dual fuel combustion technology in the fields of industrial furnace and boiler as a substitute oil technology. The basic structure of duel fuel combustion burner is designed so that low caloric gas fuel is supplied around an oil burner in the middle. In the present study, three types of mixing burners were manufactured to conduct performance experiment. Low caloric gas was evenly distributed around the oil burner and the method of changing the angle of gas nozzle was applied. CO generation decreased according to the increase of the amount of air for combustion. In addition, the shapes and colors of flame changed according to the proportions of gas and oil used. Remained flame after combustion was from the lack of atomization at the exit of oil burner. Although it was difficult to maintain the optimum air ratio due to different required air ratio for oil and syngas, stable combustion was able to maintained within excess oxygen concentration of 4.7~8.2%. From this study, it was shown that the oil atomization at the exit of fuel oil nozzle was promoted by the increased rate of syngas combustion and the CO concentration in flue gas lower than only fuel oil combustion.

• 한국신재생에너지학회:학술대회논문집
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• 2010.06a
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• pp.252.2-252.2
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• 2010

Biomass is considered to be a major potential fuel and renewable resource for the future. In fact, there is high potential to produce the large amount of energy from biomass around the world. In this study, to obtain basic data for practical application of wood pellet and wood pellet boiler system as heating system in agriculture, agricultural biomass resources were surveyed, pellet was made of agricultural by-product such as stem of rape, oat and rice, ricehusk and sawdust and wood pellet boiler system with capacity of 116 kW was manufactured and installed in greenhouse of $38.5m{\times}32m$. High heating value, bulk density and ash content of pellet made of agricultural by-product and efficiency and heating performance of this system was estimated. Rice straw was the largest agricultural biomass in 2005 and the total amount of rice straw converted into energy of $131.71{\times}10^{11}$ kJ. And in 2005, total amount of forest' by-product converted into energy of $29,277.05{\times}10^{11}$ kJ. High heating values of pellets made of agricultural by-products of stem and seed of rape, stem of oat, rice straw and rice husk were 16,034, 16,026, 16,089, 15,650, 15,044 kJ/kg respectively. High heating values of pellets made of agricultural by-products were 83.6% compared to that of wood pellet. Average bulk density of pellets made of agricultural by-products of stem and seed of rape, stem of oat, rice straw and rice husk was 1,400 $kg/m^3$. Ash contents of the pellets were 6.6, 7.0, 6.2, 5.5, 33% respectively. Ash content of rice husk pellet was the largest compared to other kind of pellets. To increase efficiency of agricultural pellet boiler, the boiler adopted secondary heat exchanger. The agricultural pellet boiler designed and manufactured in this study had high efficiency of 84.2% compared to the conventional agricultural pellet boiler, when water flow rate, exhaust gas temperature and average combustion furnace temperature were 39L/min, $180^{\circ}C$, $680^{\circ}C$ respectively. And pellet supplying and pausing time were 13, 43 seconds respectively. In March of 2010, prices of wood pellet, agricultural tax free diesel, diesel, kerosene were 350 won/kg, 811 won/L, 1,422 won/L, 976 Won/L respectively. Also in terms of energy, prices per same heating value were 77.8, 90.1, 158, 108.4 Won/Mcal. Energy saving rate of wood pellet was 16, 50, 39% compared to agricultural tax free diesel, diesel and kerosene respectively.

• 한국신재생에너지학회:학술대회논문집
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• 2010.06a
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• pp.75.2-75.2
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• 2010

We studied the fabrication of polycrystalline silicon (pc-Si) films as seed layers for application of pc-Si thin film solar cells, in which amorphous silicon (a-Si) films in a structure of glass/Al/$Al_2O_3$/a-Si are crystallized by the aluminum-induced layer exchange (ALILE) process. The properties of pc-Si films formed by the ALILE process are strongly determined by the oxide layer as well as the various process parameters like annealing temperature, time, etc. In this study, the effects of the oxide film thickness on the crystallization of a-Si in the ALILE process, where the thickness of $Al_2O_3$ layer was varied from 4 to 50 nm. For preparation of the experimental film structure, aluminum (~300 nm thickness) and a-Si (~300 nm thickness) layers were deposited using DC sputtering and PECVD method, respectively, and $Al_2O_3$ layer with the various thicknesses by RF sputtering. The crystallization of a-Si was then carried out by the thermal annealing process using a furnace with the in-situ microscope. The characteristics of the produced pc-Si films were analyzed by optical microscope (OM), scanning electron microscope (SEM), Raman spectrometer, and X-ray diffractometer (XRD). As results, the crystallinity was exponentially decayed with the increase of $Al_2O_3$ thickness and the grain size showed the similar tendency. The maximum pc-Si grain size fabricated by ALILE process was about $45{\mu}m$ at the $Al_2O_3$ layer thickness of 4 nm. The preferential crystal orientation was <111> and more dominant with the thinner $Al_2O_3$ layer. In summary, we obtained a pc-Si film not only with ${\sim}45{\mu}m$ grain size but also with the crystallinity of about 75% at 4 nm $Al_2O_3$ layer thickness by ALILE process with the structure of a glass/Al/$Al_2O_3$/a-Si.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2009.11a
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• pp.5-5
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• 2009

Thin-film-transistors (TFTs) that can be prepared at low temperatures have attracted much attention because of the great potential for transparent and flexible electronics. One of the mainstreams in this field is the use of organic semiconductors such as pentacene. But device performance of the organic TFTs is still limited due to low field-effect mobility and rapid degradation after exposing to air. Alternative approach is the use of amorphous oxide semiconductors as a channel. Amorphous oxide semiconductors (AOSs) based TFTs showed the fast technological development, because AOS films can be fabricated at room temperature and exhibit the possibility in application like flexible display, electronic paper, and larges solar cells. Among the various AOSs, a-IGZO has lots of advantages because it has high channel mobility, uniform surface roughness and good transparency. [1] The high mobility is attributed to the overlap of spherical s-orbital of the heavy post-transition metal cations. This study demonstrated the effect of the variation in channel thickness from 30nm to 200nm on the TFT device performance. When the thickness was increased, turn-on voltage and subthreshold swing was decreased. The a-IGZO channels and source/drain metals were deposited with shadow mask. The a-IGZO channel layer was deposited on $SiO_2$/p-Si substrates by RF magnetron sputtering, where RF power is 150W. And working pressure is 3m Torr, at $O_2/Ar$ (2/28 sccm) atmosphere. The electrodes were formed with electron-beam evaporated Ti (30 nm) and Au (70 nm) bilayer. Finally, Al (150nm) as a gate metal was thermal-evaporated. TFT devices were heat-treated in a furnace at 250 $^{\circ}C$ and nitrogen atmosphere for 1hour. The electrical properties of the TFTs were measured using a probe-station. The TFT with channel thickness of 150nm exhibits a good subthreshold swing (SS) of 0.72 V/decade and on-off ratio of $1{\times}10^8$. The field effect mobility and threshold voltage were evaluated as 7.2 and 8 V, respectively.

• Clean Technology
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• v.26 no.3
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• pp.221-227
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• 2020

When the waste solid fuel (SRF, Bio-SRF) is burnt in a boiler, a problem occurs in the combustion process involving the alkali components (Na, K) contained in large amounts in the fuel. The alkaline component has a low melting point, which usually forms low melting point salt in the temperature of the furnace, with the resulting low melting point salts attaching to the heat pipe to form a clinker. Various additives are used to suppress clinker generation, and the additive based on the kaolinite has alkali-aluminum-silica to inhibit the clinker. In this study, the reactivity of the additives based on the kaolinite was compared. The additives utilized were R-kaolinite, B-kaolinite, and A-kaolinite. Also silica and MgO were sourced as the comparison group. The experimental group was employed as a laboratory-scale batch horizontal reactor. The additive and alkaline salts were reacted at a weight ratio of 1 : 1, and the reaction temperature was performed at 900 ℃ for 10 hours. The first measurement of HCl occurring during the experiment was performed 30 minutes after the detection tube was used, and the process was repeated every hour after the experiment. After the reaction, solid residues were photographed for characterization analysis by means of an optical microscope. The reaction characteristics of the kaolinite were confirmed based on the analysis results.