• Journal of the Korean Ceramic Society
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• v.40 no.5
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• pp.481-487
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• 2003

A technique for determination of proportions of char, coal ana coke is needed in order to monitor pulverized coal injection performance in operating blast furnace. Quantitative X-ray powder diffraction analysis can be applied to the problem providing that structural information on carbonaceous materials, coal, char, coke and their mixture are known. Chars were prepared from a coal at different temperatures (1000∼1400$^{\circ}C$) and were characterised by X-Ray powder Diffraction (XRD). The XRD result gave crystallite size (height Lc and diameter, La), aromaticity, number of (002) plane in carbon, and d-spacing. As a result, with increasing heat treat temperature of char, Lc$_{(002)}$, La$_{(10)}$ and number of (002) plane in carbon were increased, and d-spacing and FWHM(Full With Half Maximum) were decreased. Result of prediction of amount of char from the mixtures (char, coke and ore) based on the Lc$_{(002)}$ information of two mixtures (coke and char) showed very close values expected.

• Polymer(Korea)
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• v.24 no.6
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• pp.845-853
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• 2000

The optimum cure cycle and carbonization condition were selected by the DSC and TGA analysis and green bodies were prepared by the method of hot press molding and then carbonized up to 140$0^{\circ}C$. Additives such as graphite powder, carbon black, milled carbon fiber and carbon fiber mat, which were considered to be effective in improving the interlaminar shear strength, were also added to check their effects on the density and porosity of products. Then, their relations with mechanical properties such as ILSS and flexural strength were investigated. The composites added 9 vol% of graphite powder showed the greatest values of ILSS and flexural strength. Otherwise, in case of adding carbon black, the composites showed the slight improvement of ILSS at its contents of 3 vol% but the flexural strength was decreased. When milled carbon fiber and carbon fiber mat were added, the lack of resin and the heat shrinkage during the carbonization caused the delamination, resulting in decreasing the density, ILSS and flexural strength.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.02a
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• pp.279-279
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• 2010

한국형 헬륨 냉각 고체형 증식(Helium Cooled Solid Breeder : HCSB) 시험 블랑켓(Test Blanket Module : TBM)은 삼중수소 증식을 위해서 $Li_2TiO_3$ 및 $Li_4SiO_4$ 페블을 고려하고 있으며, 중성자 반사 재료로는 SiC가 코팅된 흑연 페블을 사용할 예정이다. $Li_2TiO_3$ 및 $Li_4SiO_4$ 페블을 제조하기 위해서는 먼저 각각의 분말 제조가 선행되어야 한다. $Li_2TiO_3$ 분말을 합성하기 위해서는 먼저 Lithium 금속염과 Isopropoxide를 용매 및 폴리머 캐리어로서의 두 가지 기능을 하는 에틸렌글리콜에 첨가한 후 가열하여 완전히 용해시킨 후 혼합 용액을 건조시켜 겔형의 전구체를 제조한다. 이를 하소한 후 결정화시켜 Titanate 분말을 얻는데 이때의 건조, 하소 및 결정화 온도의 조건에 따른 분말의 크기 및 특성이 각각 다르다. 즉 하소 온도가 $600^{\circ}C$ 미만이면 열분해된 폴리머로부터 잔유 탄소가 남게 되고, $700^{\circ}C$를 초과하면 결정화가 시작된다. 이렇게 얻어진 Titanate분말은 지르코니아 볼을 이용하여 약 24 시간 동안 볼 밀링 과정을 통해 입도분포가 좁은 미세한 Titanate 분말로 만들었다. $Li_2TiO_3$ 페블은 위의 과정에서 얻어진 미세분말에 바인더를 이용하여 페블화 시킨 후 $1200^{\circ}C$의 전기로에서 최종 소결한 것이다. 중성자 반사 재료인 흑연페블은 강도가 약하기 때문에 표면에 SiC를 수 ${\mu}m$ 코팅해서 사용할 예정이다. 선행실험으로 건식법을 이용하여 SiC 코팅을 실시했으며, 그 결과를 소개할 것이다.

• Composites Research
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• v.26 no.4
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• pp.254-258
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• 2013

Polypropylene films reinforced with multi-walled carbon nanotubes and exfoliated graphite nanoplatelets were fabricated by extrusion, and the effects of filler type and take-up speed on the mechanical properties and microstructure of composite films were investigated. Differential scanning calorimetry revealed that the addition of carbon nanomaterials resulted in increased degree of crystallinity. However, increasing the take-up speed reduced the degree of crystallinity, which indicates that tension-induced orientations of polymer chains and carbon nanomaterials and the loss of degree of crystallinity due to rapid cooling at high take-up speeds act as competing mechanisms. These observations were in good agreement with tensile properties, which are governed by the degree of crystallinity, where the C-grade exfoliated graphite nanoplatelet with a surface area of $750m^2/g$ showed the greatest reinforcing effect among all types of carbon nanomaterials used. Scanning electron microscopy was employed to observe the carbon nanomaterial dispersion and orientation, respectively.

• Korean Journal of Materials Research
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• v.2 no.6
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• pp.428-435
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• 1992

AISI 4600 Iron powder was mixed with 0~1.0% phosphor as F$e_2$P powder and/or 0~0.8% carbon as graphite powder in rotating mixer. Mixed powder was pressed 800MPa in double-punch mould. Compacts were sintered at 115$0^{\circ}C$for 30 min. in vacuum or mixed hydrogen and nitrogen gas. Sintered compacts were ground and polished, and etched by 2% nital etchant. The microstructure was observed by image analyzer and optical microscope. Density and microhardness were tested by ASTM B3l2 and Microvickers hardness tester. The results obtained were as follows : (1) As the amount of F$e_2$P powder increased, sintered microstructure showed more densified effect and the grain size was larger. (2) The shape of pore was rounded and the number of pore was decreased by F$e_2$P addition. But mean pore size was larger with F$e_2$P content. (3) Simultaneous alloying addition of F$e_2$P and graphite brought about larger grain growth than respective addition. (4) Sintering atmosphere did not affect the microstructure. (5) Hardness of sintered compact increased with phosphrous and carbon content.

• Korean Chemical Engineering Research
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• v.60 no.3
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• pp.377-385
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• 2022

Surface morphology and adsorption characteristics of charcoals prepared from Korean traditional kiln were analyzed, and their moisture adsorption capacities were examined with respect to humidity and temperature change. Moisture adsorption capacities of red-clay powder, activated carbon fiber fabric (ACF fabric) and activated carbon fiber paper(ACF paper) were also examined to compare with those of charcoals. Moisture adsorption capacity of charcoal was low less than 45% humidity due to its hydrophobic property, but it slowly and linearly increased as increasing the humidity. Moisture adsorption capacity of red-clay powder was similar to charcoal at low level humidity, it increased exponentially as increasing the humidity showing Type V adsorption isotherm. Therefore, the weather forecast annal prepared by employee of weather centre in Joseon Dynasty is experimentally approved. ACF fabric and ACF paper show excellent moisture adsorption capacities, which can be used to humidity measuring sensor. Adsorption isotherm of charcoal slice was peculear showing the mixed Type I and Type IV due to low-pressure hysteresis that was occurred from embedment of nitrogen in crevice of charcoal. The specific surface area of charcoal increased by grinding charcoal slice to powder, resulted in increasing the desorption amount of adsorbent at low relative pressure.

• KSBB Journal
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• v.23 no.6
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• pp.463-469
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• 2008

During the last decade, monacolin-K biosynthesized by fermentation of red yeast rice (Monascus strains) was proved to have an efficient cholesterol lowering capability, leading to rapid increase in the market demand for the functional red yeast rice. In this study, the production medium composition and components were optimized on a shake flask scale for monacolin-K production by Monascus pilosus (KCCM 60160). The effect of three different soybean flours on the monacolin-K production were studied in order to replace the nitrogen sources of basic production medium (yeast extract, malt extract and beef extract). Among the several experiments, the production medium with dietary soybean flour to replace a half of yeast extract was very good for monacolin-K production. Plackett-Burman experimental design was used to determine the key factors which are critical to produce the biological products in the fermentation. According to the result of Plackett-Burman experimental design, a second order response surface design was applied using yeast extract, beef extract and $(NH_4)_2SO_4$ as factors. Applying this model, the optimum concentration of the three variables was obtained. The maximum monacolin-K production (369.6 mg/L) predicted by model agrees well with the experimental value (418 mg/L) obtained from the experimental verification at the optimal medium. The yield of monacolin-K was increased by 67% as compared to that obtained with basic production medium in shake flasks.

• Clean Technology
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• v.28 no.1
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• pp.46-53
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• 2022

The agglomeration characteristics of coal and silica sand were investigated under various conditions using mixed samples consisting of coal, silica sand, and potassium hydroxide, which is an agglomeration accelerator. The samples were prepared by either physically mixing or using aqueous solutions. The experiments using the physically mixed powder samples were performed with a two hour reaction time. The results showed that the number of aggregates generated increased as the reaction temperature and the total potassium content increased. The experiments using aqueous solutions were performed at 880 ℃, which is the operating temperature of a fluidized bed boiler, and at 980 ℃, which assumes a local hot spot. The amount of agglomeration generated as the reaction time increased and the total potassium content increased was identified. In the experiment performed at 880 ℃, the amount of aggregate generated clearly increased with the reaction time, and in the experiment performed at 980 ℃, assuming a local hot spot, a large amount of aggregate was generated in a relatively short time. The aggregates became harder as the potassium content increased. When the total potassium content was less than 1.37 wt.%, the aggregates were weak at both temperatures and collapsed even with a slight impact. Additionally, the surface characteristics of the silica sand and ash aggregates were observed by SEM-EDS analysis. The analysis revealed a large amount of potassium at the bonding sites. This result indicates that there is a high possibility of aggregation in the form of a eutectic compound when the alkali component is increased.

• Journal of the Korean Recycled Construction Resources Institute
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• v.12 no.1
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• pp.82-93
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• 2024

Since the cement industry generates more than 60 % of CO₂ during the clinker production process, supplementary cementitious materials are used worldwide to reduce CO₂ efficiently. Mainly used supplementary cementitious materials such as blast furnace slag and fly ash, which are used in various industries including the cement industry, concrete admixtures, and ground solidification materials. However, since their availability is expected to decrease in the future according to the carbon neutrality strategy of each industry, new supplementary cementitious materials should be used to achieve the cement industry's goal for increasing the additive content of Portland cement. Limestone is a material that already has a large amount in the cement industry and has the advantage of high grinding efficiency, so overseas developed countries established Portland limestone cement standards and succeeded in commercialization. This study was an experimental study conducted to evaluate the possibility of utilizing domestic PLC, the effect of fineness and replacement ratio on the physical properties of cement was investigated, and the environmental impact of cement was evaluated by analyzing CO₂ emissions.

• Korean Journal of Materials Research
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• v.6 no.5
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• pp.515-523
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• 1996

세라믹 전구체로서 PCS와 PMS 두 종류의 실린콘 고분자를 합성하여 7, 15, 33 wt.%의 Mo분말, Mo(CO)6 금속화합물과 혼합한 뒤 130$0^{\circ}C$이상 가열하면 탄화물과 규화물의 다양한 세라믹복합재로 전이되었다. 특히 PMS용액에 7, 15 wt.% Mo분말을 분산하여 초음파 처리하면 열분해 수율이 60%까지 개선되고 전도성 소재인 SiC/MoSi2 복합조성의 세라믹스가 합성되었다. 그러나 풍부한 유기 반응기를 가진 PCS와 카보닐기가 탄소공급원으로 작용하는 Mo(CO)6를 반응물로 사용하였을 때는 SiC와 Mo2C와 같은 탄화물과 미향의 MoSi2 그리고 미확인상을 포함한 세라믹 복합상들이 얻어졌다.