• Journal of the Korean Ceramic Society
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• v.48 no.5
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• pp.348-353
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• 2011

By gel-casting, the silicon-polymer green bodies were prepared for silicon nitride ceramics, sintered by microwave gas phase reaction. Considering the viscosity and the idle time of slurries, we decided the operational conditions of related processes, and the optimum concentrations of raw materials powders, organic monomers, cross-linker, dispersant, initiator, and catalyst. So we could get the machinable green bodies, having about 50 MPa of bending strength without cracks by selecting drying conditions carefully.

• The Transactions of the Korean Institute of Electrical Engineers
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• v.43 no.5
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• pp.789-794
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• 1994

In this study, the structural and microwave dilelectric properties of 0.15BaO-0.15SmS12TOSI3T-0.7TiOS12T ceramics with sintering and annealing conditions were investigated. In the specimen sintered at 1350 [$^{\circ}C$], dielectric constant and quality factor were good values of 80.19,2006 (fS10T=4.6851[GHz]). To improve the $\tau$S1fT of specimen which was manufactured by the optimumsintering condition (1350[$^{\circ}C$],2[Hr.]), annealed from 2[hr.] to 16[hr.] at the annealing temperature of 1200 [$^{\circ}C$]. Increasing the annealing time, dielectric constant was almost constant and quality factor was increased. In the specimen of 4[hr.] annealed, the temperature coefficient of resonant frequency was minimum value, and increased with increasing the annealing time.

• Proceedings of the Korean Society Of Semiconductor Equipment Technology
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• 2003.05a
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• pp.29-33
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• 2003

최근 이동 정보통신 분야의 발전에 따라 단말기 및 관련 부품들을 소형 경량화 하는 것이 매우 중요한 기술요소로 부각되고 있다. 이를 위해서는 기판의 배선밀도를 높이는 것과 개별 부품 또는 모듈의 크기와 무게를 줄이는 것이 절실히 필요하며, 이러한 요구에 부응하기 위해 기존의 다층 PCB 기술이나 MCM 기술에 비해 우수한 배선밀도와 양호한 전기적 특성을 갖는 저온 동시소성 세라믹(Low Temperature Co-fired Ceramic) 기술이 개발, 적용되고 있다. 본 논문에서는 이러한 LTCC 기판의 소결에 있어 기존의 소결 공정인 전기로 소결 공정과 microwave를 이용한 소결 공정을 이용하여 소결 하였을 때, LTCC 기판의 수축율과 무게감소, 그에 따른 밀도변화, SEM 을 이용한 표면형상 분석을 통해 급속가열을 통한 공정시간의 단축, 낮은 에너지 소비로 인한 제조단가의 절감, 균일한 가열로 인한 소결온도의 저하 등의 장점을 갖는 microwave sintering 을 적용할 수 있는 가능성을 제시하였다.

• 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.41 no.8
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• pp.599-604
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• 2004

The LTCCs (Low-Temperature Co-fired Ceramics) are very important for electronic industry to build smaller RF modules and to fulfill the necessity for miniaturization of devices in wireless communication industry. The dielectric materials with sintering temperature $T_{sint}$＜90$0^{\circ}C$ are required. In this study, BaO-N $d_2$ $O_3$-Ti $O_2$ (BNT ： 20∼40 wt％) for ceramic materials and L $a_2$ $O_3$- $B_2$ $O_3$-Ti $O_2$ (LBT ： 80∼60 wt％) for crystallizable glasses were used. The glass/ceramic composites were investigated for sintering behavior, phase evaluation, densities, interface reaction and microwave dielectric properties. It was found that the addition LBT glass frist significantly lowered the sintering temperature to below 90$0^{\circ}C$ and the densification with increasing addition LBT glass frist developed rapidly which was meant to be namely 90％ of relative density. The sintered bodies ekhibited applicable dielectric properties, namely 15 for $\varepsilon$$_{r}$,, 10000 GHz for Q＊ $f_{0}$. The results suggest that the composites have good potential as a new candidate for LTCC materials.

• Journal of the Korean Ceramic Society
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• v.41 no.6
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• pp.444-449
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• 2004

The microwave dielectric properties of low temperature sintered BaO-Nd$_2$O$_3$-TiO$_2$ (here after BNT) with a Pb-based glass-ceramics were studied in order to investigate their applicability to Low Temperature Co-fired Ceramics (LTCC) for fabrication of multilayered Radio Frequency (RF) passive components module. The BNT ceramics, with 5∼30 wt% of PbO-TiO$_2$-A1$_2$O$_3$-SiO$_2$ based glass-ceramics, were sintered at 105$0^{\circ}C$, which is lower than 130$0^{\circ}C$, sintering temperature of pure BNT ceramics. With increasing the amount of the glass-ceramics, sintering rate of the ceramics become activated due to the softening of glass, resulting in low-temperature densification. BaO-Nd$_2$O$_3$-TiO$_2$ microwave ceramics with 20 wt% glass-ceramics exhibit sintered relative densities over 95% and dielectric constant of 72, quality factor of 1500, and temperature coefficient of frequency of +22 ppm/$^{\circ}C$. This enhanced dielectric properties are attributed to mainly the presence of crystalline phases PbTiO$_3$ within the Pb-based glass.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.34 no.5
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• pp.342-347
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• 2021

Phase evolution, sintering behavior, microstructure, and microwave dielectric properties of (1-x) mol Ba₃V₄O₁₃ - (x) mol BaV₂O₆ system were investigated. The sintered specimens of all compositions consisted of Ba₃V₄O₁₃ and BaV₂O₆, and no secondary phase was observed. As x increased, the linear shrinkage decreased to the composition of x=0.5, and then increased again, implying that Ba₃V₄O₁₃ and BaV₂O₆ phases interfered mutually with each other during sintering. All compositions showed a dense microstructure with a large grain growth. Cracks were observed in some compositions because of the relatively high sintering temperature of 620~640℃. As x increased, the dielectric constant increased, while the quality factor was maintained from about 50,000 GHz to about 70,000 GHz up to the composition of x=0.9, and then decreased to 20,987~27,180 GHz at the composition of x=1.0. As x increased, the temperature coefficient of the resonance frequency showed a (+) value from a (-) value. The dielectric constant, the quality factor, and the temperature coefficient of resonant frequency of x=0.7 composition sintered at 640℃ for 4 hours were 10.61, 71,126 GHz, and -4.9 ppm/℃, respectively. This composition showed a good chemical compatibility with Al powder, indicating that the Ba₃V₄O₁₃-BaV₂O₆ ceramics are a candidate material for ULTCC (Ultra-Low Temperature Co-fired Ceramics) applications.

• The Proceeding of the Korean Institute of Electromagnetic Engineering and Science
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• v.12 no.3
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• pp.25-34
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• 2001

There are many kinds of dielectric materials in microwave dielectric filters for mobile telecomunication. But It is need to new dielectric materials for IMT200O, Bluetooth, wireless LAN to miniaturize the dielectric filters. These kinds of materials should have high dielectric constants, high Q, and low firing sintering temperature(<900˚C ). Multilayer monolithic dielectric filters are manufactured by BiNb04, dielectric ceramics cofired at 875˚C .

• Proceedings of the Korea Concrete Institute Conference
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• 2006.05b
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• pp.609-612
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• 2006

The quality of the concrete compression strength can be determined after the passage of 28 days, but if any defect is found the quality of concrete after that length of time, there can be serious problems in dismantling and repair. Thus, in response to the use of concrete using non sintering cement (NSC), the present study purposed to propose a method of managing the strength of high strength concrete using NSC in comparison with high strength concrete using ordinary Portland cement (OPC) through early strength estimation using microwave, which enables the quick estimation of the strength of high strength concrete using NSC.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.60 no.12
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• pp.2270-2275
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• 2011

The sintering behavior and microwave properties of ferrite ($Ba_3Co_{2-2x}Zn_{2x}Fe_{24}O_{41}$ ceramics) were investigated for microwave applications. Also PIFA type antenna with ferrite was simulated. All samples were prepared by the solid state reaction method and sintered at $1350^{\circ}C$. All ceramics had relatively density above of 92% compare with theoretical density of $Ba_3Co_2Fe_{24}O_{41}$ ceramics. From the XRD pattens, the Z-type phase was existed as main phase in $Ba_3Co_{2-2x}Zn_{2x}Fe_{24}O_{41}$ ceramics. The permittivity and permeability of $Ba_3Co_{2-2x}Zn_{2x}Fe_{24}O_{41}$ ceramics were increased with Zn additions and decreased rapidly over frequency of 200~600 MHz. Several PIFA type antennas with ferrite and FR4 were simulated. All antenna structure had return loss of less than -10 dB at each resonant frequency. Simulated antenna using both ferrite and FR4 showed size reduction of 25% without a significant decrement of efficiency.