• 한국재료학회지
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• 제1권1호
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• pp.9-17
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• 1991

화학증착법에 의해 $Si_3N_4-TiC$ 복합재료 위에 코팅된 TiC 박막은 TiN 박막에 비하여 우수한 미세구조와 열충격저항, 계면결합을 가지고 있는 것으로 나타났다. 화학증착법에 의한 TiN 박막은 TiC 박막에 비해 강철과의 마찰계수가 작고 화학적으로 안정하였다. 실험결과는 코팅된 절삭공구가 우수한 내 마모성을 갖고 있는 것으로 나타났다. 또한, 다중 코팅된 절삭공구는 단일 코팅된 공구보다 우수한 내 마모성을 보였다

• 한국재료학회지
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• 제16권1호
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• pp.50-57
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• 2006

Phase mixtures of Titanium boride, nitride, and carbide powder were produced by the reduction of a mixture of titanium and boron oxides with carbon via a gas-solid phase reaction. Boron oxides produce a vapour phase or decompose to a metal sub-oxide gaseous species when reduced at elevated temperature. The mechanism of BO sub-oxide gas formation from $B_2O_3$ and its subsequent reduction to titanium diboride for the production of uniform size hexagonal platelets is explained. These gaseous phases are critical for the formation of boride, nitride and carbide ceramics. For the production of ceramic phase composite microstructures, the nitrogen partial pressure was the most critical factor. Some calculated equilibrium phase fields has been verified experimentally. The theoretical approach therefore identifies conditions for the formation of phase mixtures. The thermodynamic and kinetic factors that govern the phase constituents are also discussed.

• 한국재료학회지
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• 제10권5호
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• pp.328-334
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• 2000

산화티탄의 광촉매 반응을 이용하여 휘발성 유기화합물(VOC)를 분해제거 하기 위하여 산화티탄을 glass bead에 sol-gel법으로 코팅하였다. 코팅막의 물성은 XRD, BET, SEM을 통해 분헉하였으며, 산화티탄이 galss bead를 채운 실험실규모의 광촉매 반응기를 이용 VOC중 벤젠 및 TCE 가스의 광촉매반응에 의한 분해효율에 대해 연구 컴토하였다. 반응기내의 잔류시간에 따른 가스농도 차이를 gas chromatography로 비교 분석하여 그 분해효율을 계산하였다. 이와 같은 정적인 상태의 실험결과, 400ppmv의 농도의 TCE인 경우 80%의 분해효율을 얻었으며, 50ppmv에서 300ppmv 농도의 벤젠인 경우 65%의 분해효율을 얻었다.

• 한국세라믹학회지
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• 제30권9호
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• pp.731-739
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• 1993

R-curve measurements were performed on Al2O3(matrix)-ZrO2-SiC whisker composite and Al2O3-ZrO2, Al2O3-SiC whisker composites in the favor of comparing the effect of ZrO2 and SiC whisker, as a second phase, to Al2O3 matrix. Al2O3-SiC whisker and Al2O3-ZrO2-SiC whisker were fabricated by hot pressing at 1$700^{\circ}C$, 15MPa and Al2O3-ZrO2 by pressureless sintering at 1$600^{\circ}C$. A controlled flaw/strength technique was utilized to determine fracture resistance as a function of crack extension and R-curve behaviour was determined from the relationship which is KR=K0(Δa)m. R-curveresults were KR=6.173$\times$Δa0.031 for Al2O3-ZrO2, KR=18.796$\times$Δa0.172 for Al2O3-SiC whisker and KR=11.96$\times$Δa0.110 for Al2O3-ZrO2-SiC whisker composite. From the analysis of R-curve and expeirmental data above three composites, it is found that R-curve behaviour of Al2O3-ZrO2-SiC whisker composite was dominated initially by the strengthening effect of ZrO2 and after, some extended crack were influenced by the effect of SiC whisker. Analysis of SEM and X-ray data revealed that whisker bridging in the crack wake and whisker pull-out mechanisms were the main mechanism for the R-curve behaviour.

• 한국세라믹학회지
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• 제22권5호
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• pp.9-16
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• 1985

Agglomeration of Y-PSZ and its related properties were studied. The ultrafine $ZrO_2$ powder containg 3 mol% $Y_2O_3$ was prepared by 1) coprecipitation method b) hot petroleum drying method c) sol-gel method and the characteristics of calcined powders and the microstructures of sintered body were observed. Powder prepared by the coprecipitation method was about 125$\AA$ in crystallite size and 0.1~1.0${\mu}{\textrm}{m}$ of intra-agglomerate pore size when calcined at $600^{\circ}C$ for 1 hour. because of small crystallite size and weak agglo merate strength resultant densification of sintered body was high. But above the temperature of 130$0^{\circ}C$ efflorescent phenomena due to anions attached to powder surface was observed. Powder prepared by hot petroleum drying method was 65$\AA$ in crystallite size and 1~10${\mu}{\textrm}{m}$ of intraagglome-rate pore size and it was observed that the agglemerates were formed during the calcining process. In this case despite of small crystallite size the rate of sintering was slow and the existing lenticular interagglomerate pore was not eliminated to the final stage of sintering. Powder prepared by sol-gel method showed solid agglomertes due to rapi dhydrolysis reaction. In this powder which involves strong solid agglomerates overall sintering rate was determined by the sintering between the agglomerates and therefore sinterability of powders made by sol-gel method was very poor.

• 한국결정성장학회지
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• 제26권1호
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• pp.28-34
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• 2016

원적외선 방사세라믹은 인체의 피부 안쪽으로 깊숙이 적외선을 침투시켜 온열 및 치료환경을 주는 매력적인 재료로써, 열적 치료 장치, 온열 매트, 히터 등과 같은 분야에 많은 응용이 되고 있다. 본 연구에서는 소결 온도와 시간을 변화시킴으로써 높은 방사율을 가지는 원적외선 방사세라믹의 소결 조건을 최적화하고자 하였다. 원적외선 방사체의 상 분석은 XRD로, 그 파단면의 미세구조는 SEM을 이용하여 분석하였다. 원적외선 방사율의 측정은 FT-IR으로 행하여, 결과를 종합적으로 해석하여 소결체의 최적 공정 조건을 확립하였다.

• 한국연소학회:학술대회논문집
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• 한국연소학회 2007년도 제34회 KOSCO SYMPOSIUM 논문집
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• pp.176-183
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• 2007

An experimental study was performed to investigate the effects of mixing quality, inlet pressure, nozzle diameter on CO emission and radiation characteristics in porous ceramic fiber radiant burners. Observations of combustion characteristics occurring inside the burner system which was insulated fiber mat, were investigated by measuring temperature, CO emission and radiation characteristics. Combustion was achieved at the firing rate of $88{\sim}99$ kcal/hr, inlet pressure of $100{\sim}250$mm$H_2O$. CO emissions were found to be strongly dependent on the operating conditions. There was a tendency that CO concentration increased as the firing rate increases. The reason for rise of CO concentration is that it becomes the relatively rich condition. The fiber burner exhibit significant both spectral intensity peaks in the bands at 2.5${\mu}m$ and 4.0${\mu}m$ relatively, There is a small difference in the variable mixing tube. However spectral intensity increased with the firing rate.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2006년도 하계학술대회 논문집 Vol.7
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• pp.323-324
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• 2006

저온동시 소결용 세라믹스, LTCC를 사용한 RF/MW용 고유전율 세라믹을 개발하기 위하여 300이상의 고유전율과 낮은 손실 계수를 가지는 것으로 알려진 $Ag(Nb_{1/4}Ta_{3/4})O_3$ 고용체와 $CaTiO_3$, $TiO_2$를 각각 혼합하여 공진주파수의 온도 계수가 0에 가까운 안정된 유전체 특성을 얻고자 하였다. 유전율의 온도 안정성을 도모하기 위해 음의 온도 계수를 갖는 $CaTiO_3$, $TiO_2$와 양의 온도계수를 갖는 $CaTiO_3$ 및 $TiO_2$를 일정 분율로 혼합한 복합체 구조의 시편을 제작하였다. LTCC 소자로의 적용을 위해 3wt.%의 CuO를 첨가하여 소결 온도를 낮추었으며, 소결 시편의 상 분석, 미세구조 및 전기적 특성을 조사하였다.

• The Korean Journal of Ceramics
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• 제4권4호
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• pp.394-398
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• 1998

$Pb_{1-x}Sr_x(Mg-{1}2}W_{1}2})O_3$$ ceramics for application in the microwave frequency range were investigated by dielectric constant and X-ray diffraction measurements. The dielectric constant curves showed two concentration dependent characteristics in the $$Pb(Mg-{1}2}W_{1}2})O_3$-rich$ region. As the Sr constant further increases to x=0.3 the dielectric curve levels off. In the concentration range between x=0.4 and x=1 in which dielectric constant dependence on temperature is negligible, it decreases and Qf value increases in the microwave frequency with increasing Sr. The temperature coefficient (${\tau}_{\varepsilon} $) of the dielectric constant changes from the negative to positive value between x=0.9 and x=1. The dielectric constant, Qf and $\tau\varepsilon$ are correlated with tolerance factor(t). From the X-ray diffraction results for $0.1{\le}x{\le}1$ the cell parameter is found to decrease as x increases and B-site ordering is observed in all the composition ranges.

• The Korean Journal of Ceramics
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• 제7권2호
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• pp.63-69
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• 2001

We investigated strength degradations from cyclic contact fatigue in self-toughened glass-ceramics. Hertzian indentation was used to induce cyclic contact load. Dynamic fatigue was also performed with changing stress rates from 0.01 to 10000 MPa/sec. After that, strength data and fracture origins were analysed. As the number of contact cycles increased or stressing rate decreased, severe strength degradation occurred by as much as 50% because of radial cracks developed from microcrack coalescence.