• 자원리싸이클링
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• 제22권3호
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• pp.28-35
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• 2013

태양광 산업에서 폐기물로 발생하는 Si/SiC 혼합슬러지를 재활용하는 것은 환경과 경제적인 측면에서 중요하다. 이러한 재활용을 위해서 Si/SiC 혼합물의 소결특성을 분석하는 것이 필요하다. 본 연구에서는 SiC함량에 따른 소결특성을 살펴보기 위해서 공기분급기를 이용하여 Si/SiC 혼합물에서 SiC 함량을 변화시켰다. SiC 함량이 변화된 Si/SiC 혼합물에 카본블랙, 점토 및 수산화알루미늄을 첨가하여 소결하였다. Si/SiC 혼합물의 특성분석 및 첨가제 변화에 따른 Si/SiC 혼합물 소결체의 특성변화를 SEM, XRD, 입도분석 및 겉보기 밀도변화를 측정하여 분석하였다. SEM 및 입도분석결과, SiC 95% 시료의 경우에는 원시료 및 SiC 75% 시료와 비교하여 1 ${\mu}m$ 크기 이하의 미립입자가 크게 감소하여 공기분급을 통한 미세입자 제거가 SiC 함량 제어에 효과가 있음을 확인할 수 있었다. 수산화알루미늄을 첨가함에 따라서 ${\beta}$-Cristobalite 가 감소하고 mullite 생성량이 증가하였으며, 카본블랙의 첨가가 소결특성 향상에 영향을 주는 것을 확인하였다.

• The Korean Journal of Ceramics
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• 제2권3호
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• pp.152-156
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• 1996

Fine (~0.09 $\mu$m) $\beta$-SiC Powders with 3.3wt% of large (~0.44$\mu$m) $\alpha$-SiC of $\beta$-SiC particles (seeds) added were hotpressed at 175$0^{\circ}C$ using $Y_2O_3$, $Al_2O_3$ and CaO as sintering aids and then annealed at 185$0^{\circ}C$ for 4 h to enhance grain growth. The resultant microstructure and polytypes were analyzed by high resolution electron microscopy (HREM).Growth of $\beta$-SiC with high density of microtwins and formation of ${\alpha}/{\beta}$ composite grains consisting of $\alpha$-SiC domain sandwiched between $\beta$-SiC domains were found in both specimens. When large $\alpha$-SiC (mostly 6H) seeds were added, the $\beta$-SiC transformend preferentially to the 6H polytype. In contrast, when large $\beta$-SiC (3C) seeds were added, the fine $\beta$-SiC transformed preferentially to the 4H polytype. Such results suggested that the polytype formation in SiC was influenced by crystalline form of seeds added as well as the chemistry of sintering aids. The ${\alpha}/{\beta}$ interface played and important role in the formation of elongated grains as evidenced by presence of ${\alpha}/{\beta}$ composite grains with high aspect ratio.

• 한국세라믹학회지
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• 제37권2호
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• pp.152-157
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• 2000

Si3N4/SiC nanocomposite ceramics containing 5 wt%dispersed SiC particles were prepared by gas-pressure-sintering at 200$0^{\circ}C$ under nitrogen atmosphere. SiC particles with average sizes of 0.2 and 0.5${\mu}{\textrm}{m}$ were used, and the effect of the SiC particle size on the microstructure was investigated. The addition of SiC particles effectively suppressed the growth of the Si3N4 matrix grains. The effect of grain growth inhibition was higher in the nanocomposites dispersed with fine SiC. SiC particles were dispersed uniformly inside Si3N4 matrix grains and on grain boundaries. When the fine SiC particles were added, large fraction of the SiC particles was trapped inside the grains. On the other hand, when the large SiC particles were added, most of the SiC particles were located on grain boundaries. Typically, the fraction of SiC particles located at grain boundaries was higher in the specimen prepared from $\beta$-Si3N4 than in the specimen prepared from $\alpha$-Si3N4.

• 한국재료학회지
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• 제23권4호
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• pp.250-254
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• 2013

In order to increase the toughness of ZTA(zirconia toughened alumina) ceramics, the present study focused on rearrangement and densification of particles according to the particle size of the parent material. When rough alumina was used for production of ZTA, densification behavior was observed in the specimen sintered at a temperature over $1550^{\circ}C$. However, it was found that the densification behavior was occurred in the specimen sintered at $1450^{\circ}C$ when fine alumina powder was used. High relative density exceeding 98% was obtained when fine alumina powder was mixed with 15 wt% of 3Y-TZP and sintered at $1600^{\circ}C$. Also, a hardness of 1820.2 Hv was obtained when a specimen containing 10 wt% of 3Y-TZP was sintered at $1600^{\circ}C$. In the case of 3Y-TZP containing rough alumina powder that had been sintered the hardness value was around 1720.3 Hv. It was predicted that an improved toughening effect in ZTA could be achieved by using finer alumina powder as the parent material.

• The Korean Journal of Ceramics
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• 제6권4호
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• pp.359-363
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• 2000

Reduced nicotinamide adenine dinucleotide (NADH) was encapsulated in transparent porous sol-gel silicate gels using by different organoalkoxysilane precursor. Characteristics optical absorption and fluorescence of NADH in the gels were examined with depending on NADH concentration and compared. Optical absorption in the aminopropyltrimethoxysilane (APTMS) gel is highest and remains constant during aging the gel. Thus, it is found that NADH in the APTMS gel is most stable and activated. On the other hand, methyltriethoxysilane (MTES) gel presents the lowest optical absorption diminishing with aging the gel. Measurable increase of fluorescence with raising the NADH concentration is observed except for the APTMS gel due to its solubility in the buffer during fluorescence measurement.

• The Korean Journal of Ceramics
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• 제6권2호
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• pp.143-149
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• 2000

Monolithic refractory technology has been developed for RH vessels, with the purpose of reducing the total refractory cost. The technology includes the use of an improved monolithic refractory and microwave drying. The improved monolithic refractory was an alumina-spinel composition, of the type used in steel ladles, to which fine alumina was added to increase the density and corrosion resistance. The microwave drying method, previously developed and used to dry the monolithic lining in steel ladles, was modified for use in drying the dense, 500mm thick lining in RH vessels. This work has resulted in significant cost savings.

• 오토저널
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• 제7권2호
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• pp.1-9
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• 1985

화인세락믹스가 앞으로 산업의 비약적 발전을 뒷받침할 새로운 재료로 세상의 주목을 끌기 시작 한 지 이미 수년이 경과하였다. 처음에는 기대만이 부풀어 단시일내에 공업재료의 주역자리를 차지할 것같은 일종의 열병상태가 되기도 하였다. 그러나, 최근에 와서 드디어 기대와 현실을 구별하여야 할 많은 문제점이 있음을 인식함과 아울러 이를 실현하기 위해서 지금 무엇을 어떻게 하여야 할 것인가를 진지하게 토론하게 되었다. 자동차분야를 살펴 보아도 car-electronics를 뒷 받침하고 있는 기능성 세라믹스는 이미 확고한 자리를 차지하고 있는데 비하여 구조용 세라믹 스는 지금 막 첫발을 내딛기 시작하였다. 자동차의 장래를 생각할 때 새로운 재료에 기대하는 바가 크며, 특히 화인세라믹스는 그 기대에 부응할 수 있는 충분한 소질을 갖고 있음은 의심할 여지가 없다. 그러나 자동차의 경우, 상품으로서의 매력, 신뢰성, 가격 등의 면에서 엄격한 제 약이 있으며 실용화에는 아직도 많은 미해결의 문제가 산적해 있다. "화인세라믹스 발전의 견 인차적 역할을 자동차가 한다"는 열띤 기대도 있고, 또 이 기대를 단순한 꿈으로 끝내지 않기 위해서는 이제부터 무엇을 어떻게 하여야 할 것인가를 구체적으로 생각하는 데 다소나마 도움이 될까 하여, 자동차에서의 세라믹스 이용의 현황을 간추려 보았다. 또 여기에 서는 소위 화인세 라믹스에 한정시키지 않고 좀 더 넓은 관점에서, 세라믹스를 생각해 보기로 한다.각해 보기로 한다.

• 한국재료학회지
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• 제11권12호
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• pp.1086-1090
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• 2001

Composition effects on microstructure and metallizing properties of the alumina sintered body were evaluated to develop the metallized alumina tubes having superior properties for electronic devices. SEM observation revealed that resultant micrographs and fractographs were varied with composition chance of additives and $SiO_2$-rich specimens showed better microstructural characteristics with uniform distribution of fine and round particles than other CaO-rich or MgO-rich ones. The resultant interfacial microstructure of the $SiO_2$-rich metallized alumina tubes also showed good metallizing properties with no defects between layers and uniform thickness of metallizing layer.

• 마이크로전자및패키징학회지
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• 제18권3호
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• pp.9-17
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• 2011

Nano-composite solders have been studied to improve the properties of Pb-free solder joints. The nanoparticles in the composite solders were carbon nanotubes(CNTs), metals (Ag, Ni, Cr, etc.), ceramics (SiC, $ZrO_2$, $TiB_2$, etc.). To fabricate the nano-composite solders, mechanical mixing methods and in-situ fabrication method has been used for well-dispersed nano phase. The characteristic properties of the nano-composite solders were high creep resistance, low undercooling, low IMC growth rate and fine microstructures. More researches on the nano-composite solders are required to improve the processibility and the reliability of the nano-composite solder joints.

• 한국세라믹학회지
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• 제40권4호
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• pp.371-374
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• 2003

Various types of equation for mixing rule on permittivity of mixture have been proposed, but none of these is not perfect because of the inconsistency between the actual geometrical configuration and the basic model for calculation. Serial model and parallel model are lower and upper extremes of mixing manner, the apparent permittivity of any other type of mixture stay between these two extreme states. For the random mixture of the stumpy fine particles, customarily the logarithmic mixing rule has been applied. But, the logarithmic mixing rule does not give the proper value of permittivity in low or high mixing rate of constituent. The author proposed the new mixing rule that gives better consistency with measured value in whole mixing range compared to the logarithmic rule. In this paper, a desirable refinement on the equation proposed in the previous paper is made to adapt to thr configuration image of actual compound and then the equation has been expanded to the complex permittivity to apply the mixing rule on the dissipative materials cases.