• Journal of Energy Engineering
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• v.13 no.1
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• pp.82-91
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• 2004

In order to utilize inorganic components in coal and wastewater sludge as an environmentally stable material, slag-forming is considered as one of the suitable methods better than producing as an ash. Coal slag that was produced by gasification as well as the slag made from wastewater sludge by incineration or melting process have been analyzed with the viewpoint of recyclability. Slags produced by water quenching exhibited a cracked shape that has a size of few millimeters with sharp edges. Slags contain the unburned carbon content below 0.15％ and expose mostly amorphous structural characteristics. Analysis results in the extraction of heavy metal compounds demonstrate that both slags from coal and wastewater sludge could be utilized as a safe recycle material even with a Japanese environmental regulation that is ten times more stringent than the current Korean standard. Slags from coal and wastewater sludge show significant differences in contents of each heavy metal compound. Since the future trend of environmental regulation shifts to the control of total content for each heavy metal compound, proper mixing of slags that contain different heavy metal contents might be an option for manufacturing recycle materials.

• Journal of Korea Foundry Society
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• v.8 no.3
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• pp.322-328
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• 1988

3.9%C-2.0%Si-Fe 조성의 압분체(壓粉體)를 $1350^{\circ}$, Ar가스 분위기에서 50분간 용해한 용탕에 시판(市販) misch metal과 misch metal hydride인 MmH와 $MmH_2$를 각각 여러비율로 첨가(添加)한후 서냉(徐冷)및 급냉(急冷)한 시편의 흑연형상(黑鉛形狀)의 변화로부터 misch metal hydride의 구상화능(球狀化能)과 흑연구상화(黑鉛球狀化) 기구(機構) 로서의 기포설(氣泡說)의 타당성을 고찰한 결과 다음과 같은 결론을 얻었다. 1) Misch metal은 0.5% 이상, 그리고 misch metal hydride는 0.25% 이상 첨가한 때 구상흑연(球狀黑鉛)과 CV 흑연(黑鉛)이 나타났으며, misch metal hydride를 첨가한 때가 misch metal에 비하여 흑연립수(黑鉛粒數)가 더 많았다. 이와같이 misch metal hydride의 첨가량이 misch metal에 비하여 적었음에도 흑연립수(黑鉛粒數)가 더 많은 것을 보면 Mm으로부터 방출되는 다수(多數)의 수소기포(水素氣泡)가 구상흑연(球狀黑鉛)의 정출장소로 되는 것으로 해석되기 때문에 기포설(氣泡說)이 타당하다고 생각된다. 2) Misch metal 과 misch metal hydride의 첨가량(添加量)이 1.0%로 증가되면 두경우 모두 흑연립수(黑鉛粒數)가 감소하였다. 이는 용탕중에 개재된 수소기포(水素氣泡)의 실수율차이에 의한 잔류 수소기포수의 증가율둔화와 첨가량(添加量)의 증가에 따른 잔류 misch metal량의 상대적(相對的) 증가로 인한 다량의 잔류 misch metal이 응고과정에서 수소를 재흡수 용해하여 흑연입수를 결정하는 용탕중의 유효수소기포수(有效水素氣泡數)를 감소시켰기 때문으로 생각된다.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.3
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• pp.356-363
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• 2017

Blast furnace slag(BFS) is a by-product generated during the manufacture of pig ion, and is divided into water-cooled slag(WS) and air-cooled slag(AS) by the coking method of BFS. In this study, concrete specimens with ternary binders were produced at the various replacement levels of cement by AS. Various mechanical properties of concrete, such as compressive and split tensile strengths, absorption and water permeable pore, were measured. In addition, the chloride ions penetration resistance and carbonation resistance were tested to evaluate the durability of concrete incorporating AS. The experimental data indicated that the use of AS up to a maximum of 10% replacement level enhanced the concrete performance. However, a higher replacement of AS exhibited poor mechanical properties and concrete durability.

• Korean Journal of Dental Materials
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• v.43 no.4
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• pp.317-322
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• 2016

The effect of ice-quenching after degassing on the hardness change during simulated porcelain firing in a metal-ceramic Pd-Au-Ag alloy was investigated by means of hardness test, field emission scanning electron microscopic observations, and X-ray diffraction analysis. The hardness decreased by ice-quenching after degassing, which was induced by the homogenization of the ice-quenched specimen. The decreased hardness by ice-quenching after degassing was recovered from the 1st opaque stage which was the first stage of the remaining firing process for bonding porcelain. The microstructural change showed that the increase in hardness during the remaining firing process was caused by precipitation. The ice-quenching after degassing did not affect the hardness change during the subsequent porcelain firing process.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2016.11a
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• pp.178-178
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• 2016

최근 Zn-Mg 합금 박막은 고내식성의 합금상 형성, 치밀한 부식생성물의 부식억제 등으로 인해 순수한 Zn 박막 및 기타 Zn 계 합금 박막 대비 우수한 내식성을 나타난다고 보고되고 있다. 그러나 여러 문헌에서 보고된 Zn-Mg 박막 각기 다른 결정구조, 미세조직을 나타내며, 이는 Zn-Mg 박막이 낮은 융점을 나타내기 때문에 박막 합성 공정 중에 발생하는 열량에 따라 Zn-Mg 박막의 결정구조, 미세조직 등이 변화한 것으로 판단된다. 본 연구에서는 Zn-Mg 박막의 결정구조에 따른 내식특성을 평가하기 위하여 비대칭 마그네트론 스퍼터링 공정 중 합성온도를 제어하며 Zn-Mg 박막을 합성하였으며 그에 따른 박막의 결정구조, 내식성에 관해 연구하였다. Zn-Mg 박막은 10wt.% Mg 합금 타겟을 사용하였으며, 합성 온도는 상온에서 최고 $150^{\circ}C$로 제어하였다. Zn-Mg 박막의 결정구조, 미세조직은 X선 회절 분석기 (XRD)와 전계방출형 주사전자현미경 (FE-SEM)을 사용하여 분석하였으며, 동전위 분극시험을 통해 결정구조에 따른 Zn-Mg 박막의 내식성을 분석하였다. 상온에서 합성한 Zn-Mg 박막은 비정질의 결정구조가 형성되었으며, 상온이상 $50^{\circ}C$이하에서는 결정질의 Zn 상과 비정질상이 공존하는 Zn-Mg 박막이 합성되었다. 또한 $100^{\circ}C$이상에서는 Zn, $Mg_2Zn_{11}$, $MgZn_2$ 상이 공존하는 결정질의 Zn-Mg 박막이 합성되었다. 상온에서 합성된 Zn-Mg 박막의 경우 급냉이 이루어지는 스퍼터링 공정의 특성상 비정질의 결정구조가 형성되었으나, Zn는 융점이 낮아 상온부근에서도 재결정이 이루어지기 때문에 $50^{\circ}C$ 이하의 낮은 온도에서 합성하여도 결정질의 Zn 상이 형성되었다. $Mg_2Zn_{11}$, $MgZn_2$ 과 같은 Zn와 Mg의 합금상의 경우 형성과정에서 일정 수준의 열이 요구되기 때문에 낮은 온도에서는 형성이 억제되고 일정 이상의 온도에서 형성되었다. FE-SEM 분석 결과를 통하여 $50^{\circ}C$ 이하의 낮은 온도에서 합성한 Zn-Mg 박막은 치밀한 미세구조를 나타내었으며, $100^{\circ}C$이상에서 합성한 Zn-Mg 박막의 미세구조는 밀도가 비교적 낮은 구조임을 확인하였다. 3.5% NaCl 수용액에서의 동전위 분극시험 결과 낮은 온도에서 합성한 Zn-Mg 박막이 고온에서 합성한 Zn-Mg 박막 대비 치밀한 구조가 형성되었기 때문에 우수한 내식성을 나타내었다.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.10 no.3
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• pp.239-244
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• 2000

Synthesis and high temperature phase stability of $_{1+x}$ Co$_{y}$ Mn$_{2-y}$ $O_4$(0$\leq$x$\leq$0.2,y=0,1/9,1/6) spinel, both the excess lithium and cobalt added, have been studied. The spinel was prepared by oxalate precipitation method as the wet chemical process. Oxalate derived spinel was synthesized by heating of precipitates at temperature lower than $600^{\circ}C$. As a result of the TG-DTA and XRD analysis of prepared and quenched powders, it was found that reversible phase transitions started at temperatures $T_1$, $T_2$및 $T_{2'}$. The transitions involved weight (oxygen) loss and gain during heating and cooling. The effects of Li excess and Co doping on the spinel lattice constant, phase stability and transition temperatures of the prepared powders are investigated. This study would provide important data for determining the spinel preparation process such as synthesis temperature and cooling speed.

• Journal of the Mineralogical Society of Korea
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• v.19 no.3 s.49
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• pp.153-162
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• 2006

Fluid inclusions in amethyst from the Samcheonpo amethyst deposit of the Waryongsan area, Kyongnam generally grouped into four different types: Type I (liquid-rich and $10{\sim}23wt%$ NaCl, $Th=289{\sim}359^{\circ}C$), Type II (vapor-rich and $2{\sim}10wt%$ NaCl, $Th=304{\sim}365^{\circ}C;$), Type III (halite-bearing, $31{\sim}54wt%$ NaCl, $Th=259{\sim}510^{\circ}C;$), and Type IV ($CO_{2}-bearing\;9{\sim}13wt%\;NaCl,\;126{\sim}277^{\circ}$). Type I, II, and III inclusions are confined in the lower part of the amethyst and Type IV in the upper, which indicates significant hydrothermal activity during the earliest stage of the amethyst growth or the solidus condition of granitic rocks. The earliest fluid exsolved from the crystallizing granitic magma formed Type IIIa which is spatially associated with silicate melt inclusions. The homogenization behavior of Type IIIa inclusions by dissolution of the halite crystal after the bubble disappearance indicates that Type IIIa inclusions were trapped at some relatively elevated pressure. Exsolution of Type IIIb, I, II forming fluids with gradual decrease in their salinity was followed. The last fluid was $CO_{2}-bearing$ fluid (Type IV), which is assumed to be derived by decarbonization reactions with the surrounding sedimentary rocks. It suggests that the fine-grained granitic rocks containing the Samcheonpo amethyst crystallized at the sub-solvus condition saturated with water and exsolved abundant water.

• Journal of the Korean Magnetics Society
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• v.11 no.5
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• pp.232-238
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• 2001

Experimentally it is well known that the magnetic properties significantly deteriorate when nanocomposite bonded magnet are made from nanocomposite ribbon. A decrease in maximum energy product of F $e_3$B+N $d_2$F $e_{14}$B nanocomposite from 14 MGOe in nanocomposite ribbon to 6.5 MGOe in powder compact was fecund to be general. Thus, the present study is focused on finding out the root of exchange decoupling of N $d_4$F $e_{73.5}$ $Co_3$H $f_{0.5}$G $a_{0.5}$ $B_{18.5}$ nanocomposite powder compacts. The exchange decoupling behavior of the powder compact of F $e_3$B+N $d_2$F $e_{14}$B composition was studied by measuring DC demagnetization and isothermal remanent demagnetization curves, which are essential for plotting produced $\delta$M curve. From the $\delta$M plot the deterioration in the magnetic properties resulted from the fact that the magnetostatic interaction became dominant rather thanthe exchange interaction in powder compact. It is concluded that the demagnetization behavior governed by the dominant magnetostatic interaction reduced the remanence magnetization, which caused the reduction of maximum energy Product of the powder compact. We also found that the elimination of residual stress which is unavoidably accumulated during grinding process enhanced the magnetic properties considerably.bly.bly.