• Journal of the Korean Crystal Growth and Crystal Technology
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• v.8 no.3
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• pp.508-512
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• 1998

The NTC thermistors were sintered by using microwave hybrid heating method at $1100^{\circ}C$~$1300^{\circ}C$ and those electrical properties were investigated. The obtained $B_{25^{\circ}C/85^{\circ}C}$ values from temperature dependence of electrical resisitivity were around 3100~3200 K which were almost the same values as conventionally sintered ones. Compared with conventional sintering process, this process could complete whole sintering process within 20 minutes. This the processing time and energy consumption could be reduced through this rapid heating by using microwave hybrid heating.t there were showed only two peaks, glycolide melting peak and lower molecular weight melting peak without lauryl alcohol. Conversion increased slowly with the reaction time up to 50 minutes, and then gave a sudden increase above that. The reaction time to disappear in glycolide melting peak during polymerization was shortened with the increase of lauryl alcohol content. Zero-shear viscosity of polyglycolic acid decreased with the increase of free acid content in glycolide.ssional energy and bending hysteresis increased. \circled3 Surface characteristics such as friction coefficient and thickness variation of highly shrinkage fabrics became relatively roughened state. \circled4 Since stiffened and roughened characteristics of highly shrinkage fabrics, drapabilities of them were significantly lowered. Additionally thermal insulation property of high shrinkage fabric was higher than that of low shrinkage fabric due to bulky and thickened feature. From the results, it is considered that the silk fabrics with high filling shrinkage have the good bulkiness and heat keeping properties and thus they have the suitable characteristics for high quality men's and women's formal garments.

• Journal of the Korean Ceramic Society
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• v.34 no.3
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• pp.233-240
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• 1997

The Ru-based thick film resistor(TFR) for sintering at 90$0^{\circ}C$ was synthesized to prepare the LCR net-work. These compositions of pyrochlore could be prepared by decreasing the amount of PbO and increasing alumina and silica contents of glass frit. In this study, the sheet resistances of the TFTs. which sint-ered at 90$0^{\circ}C$ after printing on alumina substrate, the sheet resistances of the TFRs on inductor and capa-citor substrate and the interphase between TFR and substrate were observed. And the changes of the sheet resistance were obtained with the contents of RuO2. In case of the TFR sintered at 90$0^{\circ}C$, the sheet resis-tances on alumina substrates were in the range of 103~106$\Omega$/$\square$, but the sheet resistances of TFR on in-ductor and capacitor substrate were not obtained.

• Journal of the Korean Society of Propulsion Engineers
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• v.8 no.4
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• pp.16-25
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• 2004

Theoretical analysis for predicting the heat transport limitation of a copper powder sintered wick heat pipe was performed. The heat pipe diameter was 8mm and water was used for working fluid. The particle diameter was classified by 5 different meshes, and each capillary pressures and heat transport limitations. thermal resistances were analyzed according to the operating temperatures, wick thicknesses and inclination angles, based on the effective capillary radius($r_c$), porosity($\varepsilon$), Permeability (K). The wick capillary limitation was increased according as the particle diameter and the wick thickness and the operating temperature were increased. As the porosity and the capillary radius were larger. then the heat transport limitation was higher. The thermal resistance was greatly increased according as the wick thickness was increased.

• Membrane Journal
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• v.15 no.4
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• pp.349-354
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• 2005

YSZ (yttria-stabilized zirconia) determined with an electrolyte that analyzed thermal stability along sintering condition and an electric characteristic. As sintering temperature increases by SEM, grain grows and it showed that pore decreases relatively. and confirmed effect by grain size. It evaluated that particle internal resistance and electric performance by resistance in an electrolyte and electricity conductivity measurement through ac impedance measurement in temperature of $800\~1000^{\circ}C$ in 2-probe method In order to recognize an electric characteristic. In dry process and wet process, density was each 6.13, 6.25 $g/cm^3$ and the relative density was each 98, 99$\%$ when sintering condition is $1400^{\circ}C$.

• Journal of the Korea Institute of Military Science and Technology
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• v.2 no.1
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• pp.183-193
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• 1999

Semiconducting (Sr0.85Ca0.15)TiO3 ceramics were prepared by conventional powder synthesis techniques, and then alkaline metallic cations were diffused into the ceramic bodies. The threshold voltage of the ceramics increases with increasing diffusion time and the amount of diffused materials. The ceramics had boundary potential heights of 0.01 ~ 2.89 eV, while their boundary resistance ranged from 2.2 $M{\Omega}$ to 120.4 $M{\Omega}$. Such electrical characteristics of the boundaries were correlated with the boundary structure of the ceramics obtained by transmission electron microscopy.

• ETRI Journal
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• v.13 no.2
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• pp.42-53
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• 1991

고유전율 적충세라믹 커패시터 소재인 $BaTiO_3$ 자기물은 일반적으로 큐리오도인 약 $120^{\circ}C$부근에서 유전율이 최고 약 10,000정도로 증가한 다음 급격히 감소하므로 적절한 이동체를 첨가하여 큐리온도를 상온으로 이동시켜 상온에서 최대 유전율을 이용하여야 한다. 그리고$BaTiO_3$ 자기물은 $1300^{\circ}C$이상의 고온소결시 고가인 Pd전극이 요구된다. 그러나 자기물의 소결온도를 저온화화면 저가의 Ag합금으로 전극재료를 대체할 수 있다. 본 연구에서는 이동제로서 $CaSnO_3$ 를 이용하여 큐리온도를 상온으로 이동시켰다. 또한 소결온도를 저온화하기 위하여 $BaTiO_3$ 세라믹에 여러가지 산화물을 첨가하여 소결현상을 살펴보았다. 실험결과 첨가제를 넣지 않은 경우 소결온도는 $1350^{\circ}C$의 고온이 필요한 반면, $CuO,B_2O_3$는 $1050^{\circ}C$의 낮은 온도에서도 치밀화와 입도성장이 잘 일어났다. 특히 $B_2$$O_3$ 를 첨가한 경우는 $1250^{\circ}C$이상에서 소결할 때 절연저항이 낮아 유전손실이 큰 문제점을 보였지만, 최대 유전율이 11,000 정도로 높고, 양호한 유전율의 온도변화 특성을 나타내어 우수한 고유전율 소재의 첨가제로 응용될 가능성을 보였다

• Journal of the Korean Ceramic Society
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• v.39 no.11
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• pp.1074-1082
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• 2002

Nanocomposite PMN-PT-BT/Ag/MgO was prepared by sintering at $950{\circ}C$ with addition of $AgNO_3$ and MgO sol to the PMN-PT-BT powder sinterable at $1200{\circ}C$. The low-temperature-sinterable PMN-PT-BT/Ag powder prepared by the modified mixed oxide method was calcined at $600{\circ}C$ for 1h and surface modified with the MgO sol of 0-10 wt% and then subjected to consolidation at $850-950{\circ}C$ for 4h under a flowing oxygen. The nanocomposite PMN-PT-BT/Ag/MgO(0.5wt%) sintered at $950{\circ}C$ showed the microstructure with grains of $1-3{\mu}m$, the second phase of MgO of $0.1-0.3{\mu}m$ by SEM and Ag of << $1{\mu}m$ qualitatively by SIMS. It showed the sintered relative density of 99%, the room temperature dielectric constant of 17200, the dielectric loss of 2.1% and the specific resistivity of $5.46{\times}10^{12}{\Omega}{\cdot}cm$. But the PMN-PT-BT/Ag/MgO(0 wt%) nanocomposite sintered at $950{\circ}C$ showed a little better properties : the sintered relative density of 99.5%, the room temperature dielectric constant of 19500, the dielectric loss of 2.1% and the specific resistivity of $7.30{\times}10^{12}{\Omega}{\cdot}cm$.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.11a
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• pp.179-179
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• 2008

$BaTiO_3$를 기본조성으로 하는 PTC 써미스터는 Curie 온도이상에서 저항이 급격히 상승하는 산화물 반도체 세라믹이다. 이러한 성질을 이용하여 degaussing 소자, 정온 발열체, 온도센서, 전류 제한소자 등 상업적으로 여러 분야에서 연구되고 있다. 또한 원가절감 등을 위하여 Ni 내부전극을 사용하여 환원 분위기에서 소결하는 칩 타입에 대한 연구가 진행되고 있다. 본 연구에서는 Sm 함량(0.1at%~1.0at%)을 달리한 $BaTiO_3$(Si, Mn, Ca) 계를 선택하여 3%$H_2/N_2$ 분위기에서 1200~$1260^{\circ}C$, 2h 소결한 후 공기 중에서 재산화 처리하고 재산화 시간에 따른 PTC 특성 변화에 대하여 고찰하였다. 재산화 온도와 시간은 각각 $800^{\circ}C$와 0.5h~10h으로 하였다. Sm 함량을 달리하여 환원 분위기에서 소결한 시편의 미세구조와 PTC 특성과의 상관관계를 관찰한 결과, 소결온도가 낮을수록 PTC 특성은 좋아졌으며, 상온 비저항은 Sm 함량이 높아질수록 낮아졌다. 또한 Sm 함량이 높아질수록 jumping ratio$(R_{max}/R_{25^{\circ}C})$는 낮아졌다. 재산화 시간에 따른 PTC 특성은 다소 떨어졌지만 소결온도에 따라 달리 나타났다. Jumping ratio$(R_{max}/R_{25^{\circ}C})$는 Sm을 0.7 at% 첨가한 계에서 재산화를 1시간 처리한 시편에서 가장 우수하였다.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.11a
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• pp.209-209
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• 2008

$BaTiO_3$는 대표적인 강유전체 재료로서 적층형 세라믹 콘덴서 (MLCC), PTC thermistor, resonator 등 다양한 분야에서 사용되고 있다. $BaTiO_3$ 기본조성으로 하는 PTC 써미스터는 온도가 올라감에 따라 저황이 높아지는 특성을 가지고 있으며, 이러한 PTCR 특성은 작동되는 큐리온도에 따라 그 적용이 달라진다. PTCR 소자는 소결온도, 소결분위기, 불순물, 첨가제 등의 제조공정상의 인자들과 기공률, 결정립 크기 등이 복합적으로 작용해 PTCR 특성에 영향을 미치기 때문에 제조하기에 무척 까다로운 소자로 알려져 있다. 하지만 우수한 특성을 지닌 PTCR 소자를 제조하기 위하여 새로운 조성개발이 이루어지고 있으며, 전기적 특성 개선, 재현성 확보, 제조원가 절감 등의 측면에서 새로운 공정개발이 이루어지고 있다. 본 연구에서는 Sm을 첨가한 $BaTiO_3$계 재료의 PTCR 특성에 미치는 Ti/Ba ratio 등의 변화에 따른 영향을 조사하고 공기 중과 환원분위기 중에서 소결된 시편의 차이점과 재산화 처리에 따른 PTC 특성에 미치는 영향을 R-T 측정으로 고찰하였다. 본 조성은 환원 분위기에서 소결할 경우 그 미세구조는 Ti/Ba ratio비가 높을 때 grain size가 커져 상온 비저항을 낮출 수 있었다. Sm 첨가로 상온 비저항값은 낮출 수 있었으나 공기 중에서 재산화 처리하더라도 jumping ratio$(R_{max}/R_{25^{\circ}C})$는 Ti/Ba ratio와 거의 무관한 것으로 분석되었다.

• Journal of the Korean Ceramic Society
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• v.37 no.11
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• pp.1065-1070
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• 2000

TiO$_2$의 첨가가 Mn-Zn ferrites의 전자기적 물성에 미치는 효과에 대해 연구하였다. TiO$_2$의 첨가량이 증가함에 따라 밀도와 전기비저항이 증가된 반면 초기투자율은 감소하였다. TiO$_2$의 첨가에 따라 Fe$^{2+}$ ion의 증가에 기인하여 전력손실의 최소 값을 나타내는 온도가 저온으로 이동하였다. TiO$_2$를 0.12wt% 첨가한 시편의 경우, 100 kHz, 200 mT, 8$0^{\circ}C$ 측정 조건에서는 소결온도가 증가함에 따라 전력손실이 감소하였으며 125$0^{\circ}C$ 소결한 시편이 340 mW/㎤으로 가장 낮은 값을 보였다. 500 kHz, 50 mT, 8$0^{\circ}C$의 측정 조건에서는 소결 온도가 감소함에 따라 전력손실이 감소하였으며 115$0^{\circ}C$ 소결한 시편이 105 mW/㎤으로 가장 낮은 전력손실 값이 관찰되었다.