• 한국결정성장학회:학술대회논문집
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• 한국결정성장학회 2000년도 Proceedings of 2000 International Nano Crystals/Ceramics Forum and International Symposium on Intermaterials
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• pp.65-86
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• 2000

Rare earth-doped ceria powders with a composition of Ce0.8R0.2O1.9(R=Yb, Y, Gd, Sm, Nd and La) were prepared by heating the oxalate coprecipitate. The green compacts began to shrink at 600$^{\circ}$-700$^{\circ}C$. The relative density after the sintering at 1200$^{\circ}$ and 1400$^{\circ}C$ became higher for the higher green density. The samples were densified above 98% relative density by the sintering ant 1600$^{\circ}C$ for 4 h and the grain sizes (4.7-7.6$\mu\textrm{m}$) showed a tendency to become larger with increasing ionic radius of doped-rare earth element. In the intial stag of sintering at 700$^{\circ}$-800$^{\circ}C$, the dominant mass transport process changed from lattice diffusion to grain boundary diffusion to grain boundary diffusion with heating time. The porosity during the intermediated and final stage of the sintering at 1200$^{\circ}$ and 1400$^{\circ}C$ decreased by the mass transport through lattice diffusion with grain growth.

• 대한치과기공학회지
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• 제40권1호
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• pp.17-25
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• 2018

Purpose: When casting of ceramics, proper amount of deflocculant was added for disperse the particles in slip. In this study, examined the optimum amount of APMA(ammonium polymethaacrylate) water as deflocculant for casting the zirconia. Methods: The 100 g of zirconia powder were ball milled with 300 g zirconia ball, 90 g of distilled water, and APMA water in polyethylene pot for 24 hours. The amount of APMA water were added as deflocculant from 0.5 to 0.9 g at an intervals of 0.1 g. The viscosity of slip with no deflocculant showed 1362c.p. and the minimum viscosity with 580c.p. obtained when the slip contained 0.7% of deflocculant. Bar type specimens were casted with plaster mold and biscuit fired at $1100^{\circ}C$ for 1 hours. Biscuit fired specimens were finished with $60mm(L){\times}14mm(W){\times}10mm(H) bar$. Finished specimens were 2nd fired at $1500^{\circ}C$ for 1 hour. Results: Regardless the addition of deflocculant, all 2nd fired specimens showed 0% of apparent porosity and water absorption. The specimens with no deflocculant showed 24% of drying shrinkage and 27.4% firing shrinkage. On the other hand, The specimens with deflocculant showed 17.4% of drying shrinkage and 17.6% firing shrinkage regardless the amount of deflocculant. The maximum bulk density with $6.09g/cm^3$ obtained when the specimens casted with 0.7~0.9% of deflocculant contained slips. Bend strength of specimen with no deflocculant showed 680 MPa and the maximum bend strength with 814 MPa obtained when the specimen casted with 0.7% of diflocculant contained slip. Conclusion : It was found that the particle shape of the powder according to the dispersing agent is added, the particle size, sintering temperature and affect the particle size distribution, sintering time, sintering atmosphere, such a great influence on the sintering.

• 한국자기학회:학술대회 개요집
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• 한국자기학회 2008년도 Asian Magnetics Conference
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• pp.126.1-126.1
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• 2008

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 1996년도 춘계학술대회 논문집
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• pp.292-294
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• 1996

Dielectric properties were investigated at Mn doped 0.17($Ba_{0.53}$, $Pb_{0.47}$)0-$0.16Nd_2O_3$-$0.67TiO_2$ system in microwave frequency. It was observed that dielectric constant of 90.1, quality factor of 1320 (at 3.8GHz) and temperature coefficient of resonance frequency 2.3 ppm/$^{\circ}C$ for 0.5wt% Mn doped 0.17($Ba_{0.53}$, $Pb_{0.47}$)0-$0.16Nd_2O_3$-$0.67TiO_2$ system in sintering condition $1290^{\circ}C$/2hr. The quality factor increase due to the compensation effect of Mn ions yp to 0.5wt% and the decrease due to the interface relaxation effect. The temperature coefficient of resonance frequency increases to negative direction with increasing the amounts of Mn.

• Transactions on Electrical and Electronic Materials
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• 제3권3호
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• pp.21-24
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• 2002

Two kinds of $Nd_{1+X}Ba_{2-X}Cu_3O_{7-{\delta}}$, the sintering samples and zone melting samples, were heat-treated under pure Ar at 950$^{circ}C$. The substitution of Nd ion for Ba ion in the $Nd_{1+X}Ba_{2-X}Cu_3O_{7-{\delta}}$ before and after the heat treatment was investigated by XRD. In order to confirm the effects of the heat treatment, the Tc and Jc of samples with/without the heat treatment under Ar were comparatively studied. $Nd_{1+X}Ba_{2-X}Cu_3O_{7-{\delta}}$ samples were oxygenated under pure oxygen at $300^{circ}C$. From the XRD pattern it was found that the sample with x<0.4 was transferred from tetragonal phase to orthorhombic phase after the oxygenation, while the sample with x>0.4 did not show the phase transition even after a long time oxygenation. Therefore, the low oxygen partial pressure (Ar+1 % O$_2$) was used for the ambient atmosphere of the zone-melting samples, which could reduce the melting temperature and depress the substitution of Nd for Ba. After the improvement in the zone-melting process, the Jc value was increased to 2 x $10^4$A/$cm^2$ (0 T, 78 K). The particle orientation and the structure of zone-melted NdBaCuO were studied by the XRD and SEM analysis.

• 마이크로전자및패키징학회지
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• 제8권2호
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• pp.9-13
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• 2001

$(Ba_{0.5}Pb_{0.5})Nd_2Ti_5O_{14}$(마이크로파 유전체 세라믹스에 borosilicate계 유리를 첨가하여 저온소결 특성과 마이크로파 특성을 조사하였다. Borosilicate계 유리가 2~3 wt% 첨가된 경우 $950^{\circ}C$의 소결 온도에서 소결성이 향상됨과 동시에 품질계수도 놀아지는 것을 확인할 수 있었다. BPNT에 3 wt%의 유리를 첨가함으로써 $950^{\circ}C$에서 유전율은 90에서 75 정도로 약간의 감소를 보였으나 마이크로파 품질계수 (Q$\times$f)는 4500 정도로 잘 유지되었고 공진주파수의 온도계수도 +10 $ppm/^{\circ}C$로서 잘 유지되는 결과를 나타내었다.

• 한국세라믹학회지
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• 제50권6호
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• pp.364-371
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• 2013

The sintering behavior of monolithic SiC is examined using the binary sintering additive of $Al_2O_3$-rare earth oxide ($RE_2O_3$, where RE = Sc, Nd, Dy, Ho, or Yb). Through hot pressing at 20 MPa and $1750^{\circ}C$ for 1 h in an Ar atmosphere for 52 nm fine ${\beta}$-SiC powder added with 5 wt% sintering additive, a SiC density of > 97% is achieved, which indicates the effectiveness of $Al_2O_3-RE_2O_3$ system as a sintering of additive for SiC. Based on this result, 7 wt% of $Al_2O_3-Sc_2O_3$ is tested as an additive system for the fabrication of a continuous SiC fiber-reinforced SiC-matrix composite ($SiC_f$/SiC). Electrophoretic deposition combined with the application of ultrasonic pulses is used to efficiently infiltrate the matrix phase into the voids of $Tyranno^{TM}$-SA3 fabric. After hot pressing, a composite density of > 97% is obtained, along with a maximum flexural strength of 443 MPa.

• Korean Chemical Engineering Research
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• 제53권2호
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• pp.145-149
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• 2015

LiCl 용융염에서 희토류 금속을 포함한 $Nd_2O_3-La_2O_3-NiO$ 복합산화물의 전해환원을 통한 $La_{0.5}Nd_{0.5}Ni_5$ 합금제조에 대한 연구를 수행하였다. $Nd_2O_3-La_2O_3-NiO$ 복합산화물은 $1100^{\circ}C$에서 소결시에 $NiNd_2O_4$ (스피넬)과 $LaNiO_3$ (페로브스카이트) 구조가 생성되었다. 스피넬 및 페로브스카이트 구조는 복합산화물의 전해환원 반응속도를 증가시켰다. LiCl 용융염에서 전해환원 반응 동안 $Nd_2O_3-La_2O_3-NiO$ 복합산화물은 Ni, $NiLa_2O_4$ 등의 다양한 중간생성물을 거쳐 $La_{0.5}Nd_{0.5}Ni_5$ 합금으로 환원됨을 확인할 수 있었다. XRD 분석결과를 통해 최종 생성물인 $La_{0.5}Nd_{0.5}Ni_5$의 생성 메카니즘을 제시하였다.

• 한국세라믹학회지
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• 제27권2호
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• pp.169-178
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• 1990

The sintering characteristics of ZrO2 were analyzed in terms of pore microstructure and kinetics of pore elimination. The pore structue of the ZrO2 sample prepared from colloid suspension was characterized by three distinct types of pores ; intradomain, interdomain, and intergglomerate pores. Sintering data at 1600$^{\circ}C$ showed that pores larger than a certain critical size(∼3$\mu\textrm{m}$) were difficult to remove, and this was analyzed in terms of the interagglomerate pore formed from the suspension under the condition of low kinetic stability, that is, the stability ratio smaller than its critical value. A theoretical equation for densification rate was derived and was applied to the densification rate of the ZrO2 polycrystalline body containging both the matrix(the 1st-generation) pores and the interagglomerate (the 2nd-generation) pores under the condition of slow grain growth.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2001년도 기술교육위원회 창립총회 및 학술대회 의료기기전시회
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• pp.72-75
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• 2001

In this paper, the $Sr_{1-x}Ca_{x}TiO_{3}(0{\leq}x{\leq}0.2)$ 2)-based grain boundary layer ceramics were fabricated to measured dielectric properties and voltage-current properties. The sintering temperature and time were $1420\sim1520^{\circ}C$, 4hours, in $N_{2}$ gas, respectively. The structural and the dielectric properties were investigated by SEM, X-ray, HP4194A and K6517. The 2nd phase formed by thermal diffusion from the surface lead to a very high apparent dielectric constant, $\varepsilon_r$ > 50000. X-ray diffraction patterns exhibited cubic structure for all specimens. Increasing content of Ca, the peak intensity were decreased.ﱇﶖ⨀ਆᘍ܀㘱㔮㠹㬅K䍄乍