• 한국세라믹학회:학술대회논문집
• /
• 한국세라믹학회 2003년도 추계총회 및 연구발표회 초록집
• /
• pp.197.1-197
• /
• 2003

• 한국세라믹학회지
• /
• 제17권3호
• /
• pp.133-140
• /
• 1980

Nonohmic properties of ZnO ceramics with various small amounts of additives were studied in relation to sintering temperature and additive content. The kinds of additives used were basic additives ($Bi_2O_3$, $BaCO_3$, $MnCO_3$, $Cr_2O_3$) and $KNO_3$ Especially this study has focused on the effects of $KNO_3$ in ZnO ceramics with basic additives. SEM studies indicated that microstructures of ZnO, $KNO_3$ and basic additives showed homogenuous grain size in comparison to ZnO and basic additives compounds. The nonohmic exponent ($\alpha$) in ZnO, $KNO_3$ and basic additives component were measured as high as 40.

• The Korean Journal of Ceramics
• /
• 제6권3호
• /
• pp.193-200
• /
• 2000

Si$_3$N$_4$powder with 2 wt% $Al_2$O$_3$and 6 wt% $Y_2$O$_3$additives was sintered by the gas pressure sintering (GPS) technique. The unlubricated wear behavior depending on sintering conditions such as sintering temperature, pressure, and sintering time was investigated. When the sintering temperature and time increased, the larger elongated grains were formed and the microstructural heterogeneity increased. When sintering pressure increased, grain growth, however, was impeded. Also, the wear properties depended on microstructure and friction coefficient were related to grain size. Based on the experimental results, the wear properties were associated with initial friction coefficients as well as mechanical properties including fracture toughness and flexural strength.

• 한국전기전자재료학회:학술대회논문집
• /
• 한국전기전자재료학회 2004년도 추계학술대회 논문집 Vol.17
• /
• pp.435-438
• /
• 2004

The effects sintering additives such as $xwt%(0.242Bi_2O_3-0.782V_2O_5)$ on the microwave dielectric and sintering properties of $MgCo_2(VO_4)_2$ ceramics were investigated. Highly dense samples were obtained for $MgCo_2(VO_4)_2$ at the sintering temperature of $950^{\circ}C$ with $0.242Bi_2O_3-0.758V_2O_5$ additions of $0.5{\sim}5wt%$. The microwave dielectric properties of $MgCo_2(VO_4)_2$ with $0.5wt%(0.242Bi_2O_3-0.758V_2O_5)$ sintered at $950^{\circ}C$ were as follows : $Q{\times}f_0\;=\;45,375GHz,\;\epsilon_r\;=\;9.7\;and\;\tau_f\;=\;-23.2ppm/^{\circ}C$.

• 한국결정성장학회지
• /
• 제32권2호
• /
• pp.51-54
• /
• 2022

연료전지에 사용되는 귀금속 전류집전체의 물성은 소재 기공도에 크게 영향을 받는다. 따라서 소재 기공도를 제어 위한 다양한 노력들이 진행되어왔다. 이중 많이 사용되는 전략으로 재료 열처리 시 기공형성제를 첨가하는 것이다. 기존의 기공형성제는 3차원 구조체였다. 본 연구에서는 차별화 전략으로 Ag 전류집전체의 기공도를 높이기 위해 2차원 구조 나노시트를 소결방지제로 첨가하였다. 실제로 나노시트 첨가에 의해 소결밀도가 감소되는 것을 보여주었다. 2차원 소재로는 초나노 두께(~ 1 nm)를 갖는 RuO₂ 나노시트가 이용되었다.

• 소성∙가공
• /
• 제27권1호
• /
• pp.48-53
• /
• 2018

Aluminum nitride (AlN) is used by the semiconductor industry that has requirements for high thermal conductivity. The theoretical thermal conductivity of single crystal AlN is 320W/mK. Whereas, the values measured for polycrystalline AlN ceramics range from 20 W/mK to 280 W/mK. The variability is strongly dependent upon the purity of the starting materials and non-uniform dispersibility of the sintering additive. The conventional AlN sintering additive used yttria ($Y_2O_3$), but the dispersibility of the powder in the mixing process was important. In this study, we investigated the mechanical and thermal conductivity of yttrium nitrate ($Y(NO_3)_3{\cdot}6H_2O$), as a sintering additive in order to improve the dispersibility of $Y_2O_3$. The sintering additives content was in the range of 2 to 4.5wt.%. The density of AlN gradually increased with increasing contents of sintering additive and the flexural strength gradually increased as well. The flexural strength of the sintered body containing 4 wt% of $Y_2O_3$ and $Y(NO_3)_3{\cdot}6H_2O$ was 334.1 MPa and 378.2 MPa, respectively. The thermal conductivities were 189.7W/mK and 209.4W/mK, respectively. In the case of hardness, there was only a slight difference and the average value was about 10 GPa. Therefore, densification, density and strength values were found to be proportional to its content. It was confirmed that AlN using $Y(NO_3)_3{\cdot}6H_2O$ displayed relatively higher thermal conductivity and mechanical properties than the $Y_2O_3$.

• 한국세라믹학회지
• /
• 제22권1호
• /
• pp.60-66
• /
• 1985

Hard shaped bodies are made by sintering a cold-pressed compact of a boron carbide compound which contains a densification aid. Titanium diboride and carbon were used as a densification aid in a range of 1% to 10% by weight. The effects of sintering temperature and additives on linear shrinkage porosity hardness bend strength and microstructure were examined. The initial partical size dependence on the sintered density was also discussed.

• 한국세라믹학회지
• /
• 제39권1호
• /
• pp.45-50
• /
• 2002

평균입경 25$\mu m$의 Si조대분말에 소결조제의 조성과 양을 변화시켜 질화반응 질화규소 (RBSN)세라믹스를 제조할 때 나타나는 치밀화 거동, 미세구조의 발달 및 기계적 특성에 대하여 고찰하였다. 6wt% $Y_2O_3$ + 1wt% $Al_2O_3$(6YlA)의 소결조제를 첨가한 경우에는 치밀화를 이루지 못하였으나, 6wt% $Y_2O_3+3\;wt%\;Al_2O_3+2\;wt%\;SiO_2(6Y3A2S)$와 9wt% $Y_2O_3$+1.5wt% $A1_2O_3$+ 3w% $SiO_2$(9Yl.5A3S)의 소결조제를 첨가하여 이론밀도에 가까운 치밀화를 이루었다. $1900^{\circ}C$에서 소결한 6Y3A2S시편의 경우, 960MPa의 높은 파괴강도값과 $6.5MPa.m^{1/2}$의 파괴인성값을 얻었다.

• 대한전기학회논문지:전기물성ㆍ응용부문C
• /
• 제55권11호
• /
• pp.505-513
• /
• 2006

The present study investigated the influence of the content of $Al_2O_3+Y_2O_3$ sintering additives on the microstructure, mechanical and electrical properties of the pressureless-sintered $SiC-ZrB_2$ electroconductive ceramic composites. Phase analysis of composites by XRD revealed mostly of ${\alpha}-SiC(4H),\;ZrB_2,\;{\beta}-SiC(15R)$ and In Situ $YAG(Al_5Y_3O_{12})$. The relative density and the flexural strength showed the highest value of 86.8[%] and 203[Mpa] for $SiC-ZrB_2$ composite with an addition of 8[wt%] $Al_2O_3+Y_2O_3$ as a sintering aid at room temperature respectively. Owing to crack deflection and crack bridging of fracture toughness mechanism, the fracture toughness showed 3.7 and $3.6[MPa{\cdot}m^{1/2}]\;for\;SiC-ZrB_2$ composites with an addition of 8 and 12[wt%] $Al_2O_3+Y_2O_3$ as a sintering aid at room temperature respectively. Abnormal grain growth takes place during phase transformation from ${\beta}-SiC\;into\;{\alpha}-SiC$ was correlated with In Situ YAG phase by reaction between $Al_2O_3\;and\;Y_2O_3$ additives during sintering. The electrical resistivity showed the lowest value of $6.5{\times}10^{-3}[({\Omega}{\cdot}cm]$ for the $SiC-ZrB_2$ composite with an addition of 8[wt%] $Al_2O_3+Y_2O_3$ as a sintering aid at room temperature. The electrical resistivity of the $SiC-ZrB_2$ composites was all positive temperature coefficient(PTCR) in the temperature ranges from $25[^{\circ}C]\;to\;700[^{\circ}C]$. The resistance temperature coefficient showed the highest value of $3.53{\times}10^{-3}/[^{\circ}C]\;for\;SiC-ZrB_2$ composite with an addition of 8[wt%] $Al_2O_3+Y_2O_3$ as a sintering aid in the temperature ranges from $25[^{\circ}C]\;to\;700[^{\circ}C]$. In this paper, it is convinced that ${\beta}-SiC$ based electroconductive ceramic composites for heaters or ignitors can be manufactured by pressureless sintering.

• 한국결정성장학회지
• /
• 제25권1호
• /
• pp.6-12
• /
• 2015

율속제어소결은 소결 공정 중 실시간으로 측정되는 시편의 팽창/수축거동을 이용해 일정한 수축거동을 하도록 로의 파워를 조정하는 소결방법으로, 온도를 조절하기 위해 로의 파워를 제어하는 일반적인 소결에 비해 시편의 소결 과정을 세밀히 제어할 수 있으며, 특히 소결공정의 최적화를 이룰 수 있는 장점이 있다. 본 연구에서는 탄화붕소의 소결에 율속 제어소결을 적용해 각 공정변수의 조절에 따른 소결온도 및 입자성장의 변화를 조사하여 그 상관관계를 규명하고 이를 기존의 이론에 맞추어 해석함으로써 율속제어소결을 어떻게 소결공정 최적화에 이용할 수 있는지 그 가능성을 알아보았으며 이를 통해 향후 미지 소재의 소결공정에 율속제어공정을 어떻게 적용할 수 있는지 고찰해 보았다.