• 한국세라믹학회지
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• 제39권7호
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• pp.693-698
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• 2002

반응소결 탄화규소의 잔류 실리콘 양을 최소화하기 위해 3성분계 탄화규소 분말을 혼합하여 최밀 충전 반음소결 탄화규소를 제조하였다. 기지상의 충전밀도 증가로 인해 반응소결 중 실리콘의 불완전 침윤이 발생하였으며, 이로 인한 잔류 기공은 조대 탄화규소 입자의 표면을 따라 존재함을 확인하였다. 불완전 침윤은 승온 중 분해되지 않고 남은 산화물이 실리콘의 용융 온도 이상에서 분해되어 생긴 고립기공에 의한 것으로 확인되었다. 기지상의 표면에 존재하리라 여겨지는 산화물을 제거하기 위해 침윤전 열처리 및 부식처리를 통해 완전침윤을 달성하였다.

• 한국전기전자재료학회논문지
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• 제20권10호
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• pp.873-877
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• 2007

In order to apply a complex multilayer chip LC filter, this study has estimated the interfacial reaction and coupling properties of dielectric materials $Pb(Fe_{1/2}Nb_{1/2})O_3$ and Ni-Zn-Cu ferrite materials through low-temperature co-sintering (LTCS). PFN powders were fabricated using double calcinated at $700^{\circ}C$ and then $850^{\circ}C$. While the perovskite phase rate was found to be 91 %, after heat treatment at $900^{\circ}C$ for 6h, the perovskite phase rate and density exhibited a value of 100 % and 7.46$g/cm^3$, respectively. The PFN/Ni-Zn-Cu ferrite, PFN/CUO (or $Pb_2Fe_2O_5$) and ferrite/CuO (or $Pb_2Fe_2O_5$) were mechanically coupled through interfacial reactions after the specimen was co-sintered at $900^{\circ}C$ for 6 h. No intermediate layer exists for the mutual coupling reaction. This result indicates the possibility of low-temperature co-sintering without any interfacial reaction layer for a multilayer chip LC filter.

• 한국재료학회지
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• 제19권2호
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• pp.55-60
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• 2009

In this study, Ti powder was fabricated from Ti scrap by a hydrogenation-dehydrogenation (HDH) method. The Ti powders were compacted by Spark plasma sintering (SPS) and the microstructure and mechanical properties of the powders were investigated. A hydrogenation reaction of Ti scrap occurred at temperatures near $450^{\circ}C$ with a sudden increase in the reaction temperature and a decrease in the pressure of the hydrogen gas as measured in a furnace during the hydrogenation process. In addition, a dehydrogenation process was carried out at $750^{\circ}C$ for 2hrs in a vacuum of $10^{-4}torr$. The Ti powder sizes obtained by hydrogenation-dehydrogenation and mechanical milling processes were in the range of $1{\sim}90{\mu}m$ and $1{\sim}100{\mu}m$, respectively. To fabricate Ti compacts, Ti powders were sintered under an applied uniaxial punch pressure of 40 MPa at in a range of $900{\sim}1200^{\circ}C$ for 5 min. The relative density of a SPSed compact was 99.6% at $1100^{\circ}C$, and the tensile strength decreased with an increase in the sintering temperature. However, the hardness increased as the sintering temperature increased.

• 한국세라믹학회지
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• 제36권11호
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• pp.1261-1265
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• 1999

Effect of SiC particle size of the densification of Al2O3-SiC composite during pressureless sintering was investigated. Two types of SiC powders having average particle size of 0.15${\mu}{\textrm}{m}$ and 3${\mu}{\textrm}{m}$ were used. Densification rate of the specimen containing 0.15${\mu}{\textrm}{m}$ SiC particles was slower than that of the specimen containg 3${\mu}{\textrm}{m}$ SiC particles. Although the relative density of the specimen containing 0.15${\mu}{\textrm}{m}$ SiC particles was below 90% of theoretical density after sintering at 155$0^{\circ}C$ the complete closure of open pores occurred. Therefore full densification could be obtained by subsequent HIP. On the other hand in the specimen containing 3${\mu}{\textrm}{m}$ SiC particles the complete closed pore was observed at 95% of theoretical density. Such a fast pore closure in the specimen containing 0.15${\mu}{\textrm}{m}$ SiC particles is likely to occur as a result of dense reaction layer formation on the specimen surface which is attributed to the high reactivity of small size particles with sintering atmosphere.

• 한국세라믹학회지
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• 제32권11호
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• pp.1255-1261
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• 1995

Mullite-spinel-zirconia composites were prepared by reaction sintering of calcined alumina and magnesia, and zircon powders. The influence of calcining temperature on densification processes and on mechaical properties of subsequently sintered compacts was investigated. The mullite was formed by the reaction of $\alpha$-Al2O3 and amorphous SiO2 at firing temperatures over 141$0^{\circ}C$. The mullitization proceeded more rapidly in the specimen calcined at 110$0^{\circ}C$ than at either 120$0^{\circ}C$ or 130$0^{\circ}C$. Microstructures before and after the mullitization (or mullite dissociation) showed different morphologies, and their effects on mechanical properties were significant. The flexural strength and fracture toughness of the specimen calcined at 130$0^{\circ}C$ and subsequently fired at 145$0^{\circ}C$ were 316 MPa and 4.2Mpa.m1/2, respectively.

• 한국세라믹학회지
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• 제45권11호
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• pp.675-680
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• 2008

The effect of pore former content on both porosity and pore structure was investigated for porous sintered reaction-bonded silicon nitrides (SRBSNs). A spherical PMMA with $d_{50}=8{\mu}m$ was employed as a pore-former. Its amount ranged from 0 to 30 part. Porous SRBSNs were fabricated by post-sintering at various temperatures where the porosity was controlled at $12{\sim}52%$. The strong tendency of increasing porosity with PMMA content and decreasing porosity with sintering temperature was observed. Measured pore-channel diameter increased $(0.3{\rightarrow}1.1{\mu}m)$ with both PMMA content and sintering temperature.

• 한국세라믹학회지
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• 제31권9호
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• pp.957-968
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• 1994

Manufacturing process of porous glass by the filler method was studied. Commercial soda-lime-silicate glass powder was mixed with inorganic salt as the filler such as KCl, K2SO4, Na2SO4. Sintering shrinkages of mixed powders with the variation of sintering temperature were compared, and the effects of the fillers to shrinkages of mixed powder were increased in the order of Na2SO4${\mu}{\textrm}{m}$ of pore diameter were manufactured when the filler sizes 100~200 ${\mu}{\textrm}{m}$. The open pore volume of porous glass is determined by the quantity of filler and porous glasses having open pore volume between 30 and 70 vol% are available. Available sintering temperature range for preparation of porous glass is from the softening temperature of the glass powder to eutectic melting temperature of DTA curve of mixed powder.

• 한국세라믹학회지
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• 제33권6호
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• pp.686-692
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• 1996

• 한국세라믹학회지
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• 제48권5호
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• pp.368-372
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• 2011

Aluminum nitride (AlN) has excellent thermal conductivity, whereas it has some disadvantage such as low sinterability. In this study, the effects of sintering additive content and sintering condition on thermal conductivity of pressureless sintered AlN ceramics were examined on the variables of 1~3 wt% sintering additive ($Y_2O_3$) content at $1900^{\circ}C$ in $N_2$ atmosphere with holding time of 2~10 h. All AlN specimens showed higher thermal conductivity as the $Y_2O_3$ content and holding time increase. The formation of secondary phases (yttrium aluminates) by reaction of $Y_2O_3$ and $Al_2O_3$ from AlN surface promoted the thermal conductivity of AlN specimens, because the secondary phases could reduce the oxygen contents in AlN lattice. Also, thermal conductivity was increased by long sintering time because of the uniform distribution and the elimination of the secondary phases at the grain boundary by the evaporation effect during long holding time. A carbothermal reduction reaction was also affected on the thermal conductivity. The thermal conductivity of AlN specimens sintered at $1900^{\circ}C$ for 10 h showed 130~200W/mK according to the content of sintering additive.

• 한국분말야금학회:학술대회논문집
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• 한국분말야금학회 2006년도 Extended Abstracts of 2006 POWDER METALLURGY World Congress Part 1
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• pp.457-458
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• 2006