• Journal of the Mineralogical Society of Korea
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• v.22 no.3
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• pp.261-277
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• 2009

This study is aimed to emphasize the significance of ore selection in lime manufacturing through the evaluation of applied-mineralogical impact factors of crude ores controlling calcination characteristics for some domestic limestones used currently for lime manufacturing. To do this work, systematic characterization and determination were carried out for the limestone ores and their calcination products in a fixed calcining condition (target temperature: $1000^{\circ}C$, retention time: 30 minutes, 2, 4, 10, 16 hours), and the results were correlated and discussed. Selected high-Ca limestones in this study are as much as > 98 wt%, but they are somewhat diverse in crystallinity, texture, and impurity composition. Synthesized quicklimes are varied depending on such a difference in ore characters. The Pungchon limestone has relatively very low calcination rate, and the limestones from the Gabsan formation and the Jeongseon formation exhibit good quality in calcination rate and decrepitation. Among these samples, the limestone ore from the Jeongseon formation is evaluated to be the best for crude ore in manufacturing of highly-reactive quicklime. In addition, it is characteristic that the Gabsan limestone comparative rich in Fe-bearing mineral such as pyrite and goethite is more conspicuous in sintering effect.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.11 no.6
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• pp.239-245
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• 2001

$Al/Al_2O_3$composites were prepared from the reaction of mullite preforms and amorphous silica in aluminum melt at $1100^{\circ}C$ for 5 hrs. The chemical reaction between mullite preform and aluminum melt has formed the interconnected microstructure. The metal content of $Al/Al_2O_3$composite was controlled with the variable of the apparent porosity according to the sintering temperature of mullite preforms; $1600^{\circ}C$,$ 1625^{\circ}C$, $1650^{\circ}C$ and $1700^{\circ}C$, the mechanical properties of $Al/Al_2O_3$composite were investigated upon the content of Al. The mullite preform sintered above $1600^{\circ}C$ showed the chemical reaction with the penetrated Al melt, but the mullite sintered at $1600^{\circ}C$ didnt react with aluminum melt owing to the non-wetting of Al melt/mullite preform. The influences of penetration direction on the mechanical properties of composites were considered with the two different models of the perpendicular pattern and the parallel pattern to the direction of Al melt penetration. With the increase of Al metal penetration content, the fracture strength of $Al/Al_2O_3$composite decreased and the fracture toughness of composite increased. The microstructure of $Al/Al_2O_3$composite was determined by the direction of metal penetration, but the fracture strength and fracture toughness of composite didnt show the dependence on metal penetration direction.

• Journal of Korean Society of Environmental Engineers
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• v.35 no.2
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• pp.144-150
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• 2013

Hybrid ceramic membrane (HCM) processes that combined ozonation with a ceramic membrane (CM) or a reactive ceramic membrane (RM), an iron oxide nanoparticles (IONs) incorporated-CM were investigated for membrane fouling control. Alumina disc type microfiltration and ultrafiltration membranes doped with IONs by sintering method were tested under varying mass fraction of IONs. Scanning electron microscope (SEM) images showed that IONs were well-doped on the CM surface and doped IONs were approximately 50 nm in size. Change in the pure water permeability of RM was negligible compared to that of CM. These results indicate that IONs incorporation onto CM had little effect on CM performance in terms of the flux. Natural organic matter (NOM) fouling and fouling recovery patterns during HCM processes confirmed that the RM-ozonation process enhanced the destruction of NOM and reduced the extent of fouling more than the CM-ozonation process by hydroxyl radical formation in the presence of IONs on RM. In addition, analyses of NOM in the feed water and the permeate showed that the efficiency of membrane fouling control results from the NOM degradation during HCM processes; leading to removal and transformation of relatively high contents of aromatic, high molecular weight and hydrophobic NOM fractions.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.352.1-352.1
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• 2014

Indium Tin Oxide (ITO) films are the most extensively studied and commonly used as ones of TCO films. The ITO films having a high electric conductivity and high transparency are easily fabricated on glass substrate at a substrate temperature over $250^{\circ}C$. However, glass substrates are somewhat heavy and brittle, whereas plastic substrates are lightweight, unbreakable, and so on. For these reasons, it has been recently suggested to use plastic substrates for flexible display application instead of glass. Many reaearchers have tried to produce high quality thin films at rood temperatures by using several methods. Therefore, amorphous ITO films excluding thermal process exhibit a decrease in electrical conductivity and optical transparency with time and a very poor chemical stability. However the amorphous Indium Gallium Zinc Oxide (IGZO) offers several advantages. For typical instance, unlike either crystalline or amorphous ITO, same and higher than a-IGZO resistivity is found when no reactive oxygen is added to the sputter chamber, this greatly simplifies the deposition. We reported on the characteristics of a-IGZO thin films were fabricated by RF-magnetron sputtering method on the PEN substrate at room temperature using 3inch sputtering targets different rate of Zn. The homogeneous and stable targets were prepared by calcine and sintering process. Furthermore, two types of IGZO TFT design, a- IGZO source/drain material in TFT and the other a- ITO source/drain material, have been fabricated for comparison with each other. The experimental results reveal that the a- IGZO source/drain electrode in IGZO TFT is shown to be superior TFT performances, compared with a- ITO source/drain electrode in IGZO TFT.

• Journal of Korea Foundry Society
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• v.23 no.1
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• pp.30-39
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• 2003

Porous hybrid preforms were fabricated by reactive sintering using the compacts consisting of SiC particles, Fe and Al powders. Squeeze casting processing was employed to produce the composite in which the matrix phase is Al-Si7Mg. The microstructural change and wear resistance of the composites were investigated in terms of an amount of SiC particles. The wear loss was increased with increasing the contact pressure in the alloy containing SiC particles coated with Cu. The most drastic change was found to the specimen tested at 2.5 MPa of contact pressure. Concerning the alloys containing SiC particles coated with Ni-P, a drastic increase in the wear loss exhibited at 2 MPa of contact pressure in those alloys containing 4 and 8 wt. % of SiC particles coated with Ni-P. In the alloy containing 16 wt. % a proportional increase in wear loss was observed to the change of contact pressure. With respecting to the sliding velocity, the wear loss of the alloy containing SiC particles coated with Cu increased at the initial stage of wear process and then decreased. Similar result was found in the alloys containing SiC particles coated with Ni-P. On the basis of the present results obtained, it was found that wear resistance of the alloys tested was improved to show in the order of the alloy reinforced by coated SiC particles > by uncoated SiC particles > by intermetallic compound without SiC particles.

• Journal of Powder Materials
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• v.28 no.1
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• pp.51-58
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• 2021

The conversion of carbon preforms to dense SiC by liquid infiltration is a prospectively low-cost and reliable method of forming SiC-Si composites with complex shapes and high densities. Si powder was coated on top of a 2.0wt.% Y2O3-added carbon preform, and reaction bonded silicon carbide (RBSC) was prepared by infiltrating molten Si at 1,450℃ for 1-8 h. Reactive sintering of the Y2O3-free carbon preform caused Si to be pushed to one side, thereby forming cracking defects. However, when prepared from the Y2O3-added carbon preform, a SiC-Si composite in which Si is homogeneously distributed in the SiC matrix without cracking can be produced. Using the Si + C → SiC reaction at 1,450℃, 3C and 6H SiC phases, crystalline Si, and Y2O3 were generated based on XRD analysis, without the appearance of graphite. The RBSC prepared from the Y2O3-added carbon preform was densified by increasing the density and decreasing the porosity as the holding time increased at 1,450℃. Dense RBSC, which was reaction sintered at 1,450℃ for 4 h from the 2.0wt.% Y2O3-added carbon preform, had an apparent porosity of 0.11% and a relative density of 96.8%.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2010.06a
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• pp.307-307
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• 2010

최근 유한연료의 고갈로 인해 세계 유가가 불안정 됨으로서 대체 에너지에 대한 연구가 많이 진행 되고 있다. 특히 압전 소자를 이용한 에너지 하베스팅은 압전 역효과를 이용한 것으로서 주변에서 무의미하게 버려지는 진동이나 바람, 열 에너지를 실 생활에 사용할 수 있는 전기 에너지로 변환할 수 있는 유망한 기술 중 하나이다. 이러한 에너지 하베스팅 기술은 일본과 같은 선진국에서 이미 지하철 및 일반 다리와 같이 진동이 극히 많은 곳에서 응용되고 있다. 이러한 에너지 하베스팅 기술을 응용 하려면 전압출력 계수($g_{33}$)가 높아야 한다. 이것은 압전 d 상수와 유전상수에 영향을 많이 받는 것으로 알려져 있다. 현재가지 응용되는 압전 하베스팅 조성은 Pb(Zr,Ti)$O_3$ (PZT)를 기초로한 세라믹이 응용되고 있다. Pb(Zr,Ti)$O_3$ (PZT) 세라믹은 Morpohotropic phase boundary(MPB)에서 전기기계 결합계수 (kp) 와 기계적 품질계수 (Qm) 이 각각 0.5와 500으로 우수한 특성을 나타낸다. 또한 큐리온도 (Tc) 도 $400^{\circ}C$로 온도 안정성 또한 높다. 하지만 $1000^{\circ}C$ 이상에서 소결하는 PbO는 소결 중 급격한 휘발로 환경적 오염 뿐 아니라 특성의 저하를 야기시킨다. 그래서 몇몇 나라에서는 그 사용을 제한하고 점차적으로 사용을 줄여 나가고 있는 동시에 PbO가 첨가되어 있지 않은 Lead-Free 세라믹의 연구가 많이 진행되고 있다. Lead-Free 세라믹 중 alkaline niobate를 기초로 한 페로브스카이트 구조의 ($Na_{0.5}K_{0.5})NbO_3$ (NKN) 은 PbO를 기초로 한 세라믹을 대체할 유망한 후보자 중 하나이다. 하지만 NKN세라믹의 K 성분의 조해성 및 고온에서의 휘발로 인해 일반 적인 소결 방법으로는 고밀도의 세라믹을 얻기 매우 어렵다. 그래서 Hot pressing, Hot forging, RTGG(Reactive Template Grain Growth), SPS(Spark plasma Sintering)와 같은 특별한 소결 법을 이용하거나 $K_8CuNb_4O_{23}$(KCN) 이나 $K_{5.4}Cu_{1.3}Ta_{10}O_{29}$(KCT) 등을 첨가하여 그 소결성을 향상 시키는 방법도 있다. 또한 압전 d상수를 향상 시키기 위해 $Nb_2O_5$나, $La_2CO_3$, $CeO_2$, $Li_2CO_3$ 등을 치환함으로써 압전 d상수를 향상 시켜 전압출력 계수를 높이는 연구 또한 많은 보고가 되어 있다. 특히 $Li_2CO_3$의 첨가는 일반 적인 소결 방법으로도 밀도의 조밀함을 향상 시켜 그에 따른 높은 유전율과 전기기계 결합계수, 압전 d상수를 가져 많은 연구가 되어지고 있다. 그래서 본 연구에서는 일반적인 ($K_{0.5}N_{0.5})_{1-x}Li_x(Nb_{0.96}Sb_{0.04})O_3$ + 0.2mol%$La_2O_3$ + 1.2mol%$K_8CuNb_4O_{23}$ 세라믹에 x(=Li) 치환에 따른 유전 및 압전특성을 조사하였다.

• Economic and Environmental Geology
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• v.54 no.2
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• pp.285-297
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• 2021

Globally, nuclear-decommissioning facilities have been increased in number, and thereby hundreds of thousands of wastes, such as concrete, soil, and metal, have been generated. For this reason, there have been numerous efforts and researches on the development of technology for volume reduction and recycling of solid radioactive wastes, and this study reviewed and examined thoroughly such previous studies. The waste concrete powder is rehydrated by other processes such as grinding and sintering, and the processes rendered aluminate (C3A), C4AF, C3S, and ��-C2S, which are the significant compounds controlling the hydration reaction of concrete and the compressive strength of the solidified matrix. The review of the previous studies confirmed that waste concretes could be used as recycling cement, but there remain problems with the decreasing strength of solidified matrix due to mingling with aggregates. There have been further efforts to improve the performance of recycling concrete via mixing with reactive agents using industrial by-products, such as blast furnace slag and fly ash. As a result, the compressive strength of the solidified matrix was proved to be enhanced. On the contrary, there have been few kinds of researches on manufacturing recycled concretes using soil wastes. Illite and zeolite in soil waste show the high adsorption capacity on radioactive nuclides, and they can be recycled as solidification agents. If the soil wastes are recycled as much as possible, the volume of wastes generated from the decommissioning of nuclear power plants (NPPs) is not only significantly reduced, but collateral benefits also are received because radioactive wastes are safely disposed of by solidification agents made from such soil wastes. Thus, it is required to study the production of non-sintered cement using clay minerals in soil wastes. This paper reviewed related domestic and foreign researches to consider the sustainable recycling of concrete waste from NPPs as recycling cement and utilizing clay minerals in soil waste to produce unsintered cement.