• 한국세라믹학회지
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• 제44권4호
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• pp.230-234
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• 2007

Cordierite ceramics were fabricated via a reaction sintering process using ceramics-filled polysiloxane as a precursor for cordierite ceramics. In this study, the effects of the additive composition, additive content, and sintering temperature on the sintered density and compressive strength of cordierite ceramics have been investigated The sintered densities of reaction-sintered cordierite ceramics containing $TiO_2$ as an additive were insensitive to the additive composition, additive content, and sintering temperature and ranged from $1.92g/cm^3\;to\;2.06g/cm^3$. In contrast, the cordierite ceramics containing $Y_2O_3$ showed a maximal density of $2.21g/cm^3$ at 5 wt% addition and at a sintering temperature of $1400^{\circ}C$. The compressive strength of cordierite ceramics showed the same tendency with the density. Typical compressive strength of cordierite ceramics containing 5 wt% $Y_2O_3$ as a sintering additive and sintered at $1400^{\circ}C\;was\;{\sim}480MPa$.

• 한국세라믹학회지
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• 제17권2호
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• pp.80-88
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• 1980

The sintering phenomena and piezoelectric properties of PZT ceramics of composition $Pb(Zr_{0.54} Ti_{0.46})O_3$ were investigated when a small quantity of $La_2O_3$ , $LaMnO_3$, $LaCrO_3$ were added. The unwanted chemical composition change in PZT during sinterin porces du to PbO evaporation poses a severe problem in PZt manufacturinig. It is observed tat an addition of small amount of $LaMnO_3$ to PZT markedly decreases the evaporation of PbO during sintering . The green compact of (1-x) PZT.xLaMnO3(x=0.02~0.10) could be sintered of under O2 atmosphere alone with no significant loss of PbO. The planar coupling factor kp of the sintered $0.98Pb(Zr_{0.54} Ti_{0.46})O_{3.0.02}LaMnO}3$ is similar to that of commercial PZT 6A. Microstructure investigation shows that part of sintering process of $Pb(Zr, Ti)O_3$.$LaMnO_3$ system progresses via liquid phase sintering. It is believed that the evaporation of PbO in PZT sintering is restricted by the addition of $LaMnO_3$ due to the above phenomena. Furthermore the solid solution of $LaMnO_3$ in PZT causes diffuses phase transition.

• 한국분말재료학회지
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• 제17권1호
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• pp.13-22
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• 2010

The unique features of spark plasma sintering process are the possibilities of a very fast heating rate and a short holding time to obtain fully dense materials. $\beta$-SiC powder with 0, 2, 6, 10 wt% of $\alpha$-SiC particles (seeds) and 4 wt% of Al-B-C (sintering aids) were spark plasma sintered at $1700-1850^{\circ}C$ for 10 min. The heating rate, applied pressure and sintering atmosphere were kept at $100^{\circ}C/min$, 40 MPa and a flowing Ar gas (500 CC/min). Microstructural development of SiC as function of seed content and temperature during spark plasma sintering was investigated quantitatively and statistically using image analysis. Quantitative image analyses on the sintered SiC ceramics were conducted on the grain size, aspect ratio and grain size distribution of SiC. The microstructure of SiC sintered up to $1700^{\circ}C$ consisted of equiaxed grains. In contrast, the growth of large elongated SiC grains in small matrix grains was shown in sintered bodies at $1750^{\circ}C$ and the plate-like grains interlocking microstructure had been developed by increasing sintering temperature. The introduction of $\alpha$-SiC seeds into $\beta$-SiC accelerated the grain growth of elongated grains during sintering, resulting in the plate-like grains interlocking microstructure. In the $\alpha$-SiC seeds added in $\beta$-SiC, the rate of grain growth decreased with $\alpha$-SiC seed content, however, bulk density and aspect ratio of grains in sintered body increased.

• 한국결정성장학회지
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• 제15권2호
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• pp.68-74
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• 2005

지정 폐기물인 electrical arc furnace(EAF) 더스트에는 액상을 형성하는 fluk 성분이 많이 포함되어있어, 점토와 혼합하면 시편의 소결온도를 낮춰주고 기계적 강도를 향상시키는 장점이 있다. 그러나 더스트-점토 계 벽돌 제조시 더스트 첨가량을 증가시키면 소결과정에서 과도한 액상이 생성되어 제품 불량률이 높아진다. 점토-더스트 계 시편의 소결공정 중에 발생하는 액상을 제어하기 위하여 $Al_2O_3$를 첨가하고 물리적 특성 변화를 분석하였다. $Al_2O_3$가 첨가된 더스트-점토계 소결체는 기공크기가 감소되면서 미세구조가 균일해졌다. 이에 따라 기계적 강도가 증가되었고 동시에 최대강도가 나타나는 온도가 높아졌다. 또한 겉보기 밀도가 증가되었고 흡수율은 감소하였다. 첨가된 $Al_2O_3$는 mullite($3Al_2O_3{\cdot}2SiO_2$)를 생성함으로서, 액상형성에 참여할 $SiO_2$을 소모시키고 동시에 액상의 점도를 높여, 소결체의 내화도를 증진시키고 따라서 소결과정에서 시편 불량률을 낮출 것으로 분석되었다.

• 한국세라믹학회지
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• 제38권8호
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• pp.710-715
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• 2001

반응소결공정(RSP : Reaction Sintering Process)을 이용하여 YF댸₃와 Fe₂O₃의 성분에 소결첨가재 Bi₂O₃를 첨가하여 YIG를 합성하였다. Bi₂O₃첨가량과 소결온도에 따른 YIG 소결체의 미세구조 및 자기적 특성변화에 대해 주사전자현미경, X-선 회절분석기 및 시료 진동형 자력계를 이용하여 조사하였다. 소량의 소결첨가재 Bi₂O₃첨가시 YIG 소결체의 격자상수는 12.387에서 12.420 Å으로 증가하였다. 이는 상대적으로 이온반경이 큰 Bi 이온이 12면체 Y 이온 자리로 치환되었기 때문인 것으로 여겨진다. Bi₂O₃를 1.0 wt% 첨가하였을 때 비교적 균질한 미세구조를 보였으며, 1350℃에서 소결한 YIG의 밀도가 이론밀도의 98% 이상의 치밀화를 보였다. Bi₂O₃가 0.0 wt%에서 1.5 wt%로 첨가량이 증가함에 따라 상온에서의 포화자화값(M/sub s/)은 조금씩 증가하는 경향을 보였으나 큰 변화는 없었다. 반응소결공정을 이용 YIG 소결시 소결첨가제 Bi₂O₃가 1.0 wt%이고, 소결온도 1350℃에서 비교적 우수한 소결특성과 자기특성을 가지는 YIG 소결체를 얻을 수 있었다.

• 한국재료학회지
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• 제4권4호
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• pp.393-400
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• 1994

1$\mu \textrm{m}$이하의 텅스텐 분말에 구리를 균일하게 코팅하는 공정을 새로이 개발했다. 구리가 코팅된 $\mu \textrm{m}$이하의 텅스텐 분말을 이용하여 액상소결하였으며, 구리가 균일하게 분포된 W-Cu합금을 얻을 수있었다. 본 연구에서 개발된 방법에 의해 구리의 함유량을 10wt.%이하로 낮추면서도 균일한 W-Cu합금을 얻을 수 있었으며, 특히 코발트를 같은 방식에 의해 첨가하면 구리액상이 형성된 후 급격히 치밀화하여 96% 이상의 상대밀도를 갖는 W-Cu 합금을 제작하는데 성공하였다. 코발트 첨가에 의한 급격한 치밀화의 증가는 텅스텐과 구리액상 사이의 접착성 향상에 기인하는 것으로 밝혀졌다.

• 한국분말재료학회지
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• 제12권6호
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• pp.387-392
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• 2005

The p-type semiconductor $Bi_2Te_3-Sb_2Te_3$ thermoelectric materials were fabricated by melting, milling and sintering process and their thermoelectric properties were characterized. The compound materials were ball-milled with milling time and the powders were sintered by spark plasma sintering process. The ball milled powders had equiaxial shape and approedmately $1\~3{\mu}m$ in size. The figure of meritz of sintered thermoelectric materials decreased with milling time because of lowered electrical resistivity. The thermoelectric properties of $Bi_2Te_3-Sb_2Te_3$ materials have been discussed in terms of electrical property with ball mill process.

• 한국세라믹학회지
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• 제28권11호
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• pp.935-941
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• 1991

Effects of calcination process and ZrO2 addition on the electrical properties of [(Ba0.82Sr0.08Ca0.1)O]m(Ti1-$\chi$Zr$\chi$)O2 ceramics have been investigated. With the variation of A/B-site ratio m of the dielectric formulations, sintering behavior and the resistivity after sintering in a reducing atmosphere have been affected by the calcination process. When the dielectric formulations of m=1.01 were sintered in a reducing atmosphere, the room-temperature resitivity of 109 {{{{ OMEGA }}.cm was obtained for samples processed with two-step calcination, which was much lower than 1012 {{{{ OMEGA }}.cm of samples calcined once. It was confirmed that high resistivity of Ca-doped BaTiO3 ceramics, after sintering in a reducing atmosphere, is maintained by acceptor-like behavior of CaTi" which is formed by Ca substitution to Ti-site. It was also found out that the critical amount of B-site Ca substitution for reduction inhibition of BaTiO3 is around 0.005 mol. With the increasing amount of ZrO2 addition to dielectric formulations, Curie peak was depressed and Curie temperature was lowered due to the enhanced diffuse phase transition.tion.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2005년도 추계학술대회 논문집 Vol.18
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• pp.220-223
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• 2005

We studied the effect of composition, processing, and sintering temperature on the microwave properties of $Mg_{3-x}Co_x(VO_4)_2$ system which is applicable to LTCC. When $Mg_{3-x}Co_x(VO_4)_2$ was fabricated by solid-state reaction process and sintered at the temperature range of $800\sim910^{\circ}C$, it was found that the optimum composition of x was 2 at which microwave properties of 910$^{\circ}C$-sintered one were as follows: $Q\times f_0\sim55,200GHz$ and $\varepsilon_r\sim10$. When $(MgCo_2)(VO_4)_2$ was fabricated by sol-gel process and sintered at 800$^{\circ}C$, $Q\timesf_0$was 34,400GHz which is much high compared to those fabricated by solid-state reaction process at the same sintering temperature.

• 한국재료학회지
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• 제23권11호
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• pp.620-624
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• 2013

Nanocrystalline materials have recently received significant attention in the area of advanced materials engineering due to their improved physical and mechanical properties. A solid-solution nanocrystalline powder, (Ti,Mo)C, was prepared via high-energy milling of Ti-Mo alloys with graphite. Using XRD data, the synthesis process was investigated in terms of the phase evolution. Rapid sintering of nanostuctured (Ti,Mo)C hard materials was performed using a pulsed current activated sintering process (PCAS). This process allows quick densification to near theoretical density and inhibits grain growth. A dense, nanostructured (Ti,Mo)C hard material with a relative density of up to 96 % was produced by simultaneous application of 80 MPa and a pulsed current for 2 min. The average grain size of the (Ti,Mo)C was lower than 150 nm. The hardness and fracture toughness of the dense (Ti,Mo)C produced by PCAS were also evaluated. The fracture toughness of the (Ti,Mo)C was higher than that of TiC.