• 대한전기학회:학술대회논문집
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• 대한전기학회 1998년도 추계학술대회 논문집 학회본부 C
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• pp.847-849
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• 1998

The effect of $Al_{2}O_{3}$ additives on the microstructure, mechanical and electrical properties of ${\beta}$-SiC+39vol.%$ZrB_2$ electroconductive ceramic composites by pressureless sintering were investigated. The ${\beta}$-SiC+39vol.%$ZrB_2$ ceramic composites were pressureless sintered by adding 4, 8, 12wt.% $Al_{2}O_{3}$ powder as a liquid forming additives at $1950^{\circ}C$ for 1h. Phase analysis of composites by XRD revealed mostly of $\alpha$-SiC(6H), $ZrB_2$ and weakly $\alpha$-SiC(4H), $\beta$-SiC(15R) phase. The relative density of composites was lowered by gaseous products of the result of reaction between $\beta$-SiC and $Al_{2}O_{3}$ therefore, porosity was increased with increased $Al_{2}O_{3}$ contents. The fracture toughness of composites was decreased with increased $Al_{2}O_{3}$ contents, and showed the maximum value of $1.4197MPa{\cdot}m^{1/2}$ for composite added with 4wt.% $Al_{2}O_{3}$ additives. The electrical resistivity of ${\beta}$-SiC+39vol.%$ZrB_2$ electroconductive ceramic composite was increased with increased $Al_{2}O_{3}$ contents, and showed positive temperature coefficient resistance (PTCR) in the temperature from $25^{\circ}C$ to $700^{\circ}C$.

• 한국재료학회지
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• 제21권4호
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• pp.220-224
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• 2011

Zircon has excellent thermal, chemical, and mechanical properties, but it is hard to make a dense sintered product because of dissociation during the sintering process. This study analyzes how the addition of $SiO_2$ and $Al_2O_3$ affects the mechanical properties of sintered zircon, particularly in regards to reducing the thermal dissociation and improving the mechanical properties of $ZrSiO_4$. Zircon specimens containing different amounts of $SiO_2$ and $Al_2O_3$ were prepared and sintered to observe how the mechanical properties of $ZrSiO_4$ changed according to the differing amount of $SiO_2$ and $Al_2O_3$. The $ZrSiO_4$ that was used for the starting material was ground by ball mill to an average particle size of 3 ${\mu}m$. The $SiO_2$ and $Al_2O_3$ that was used for additives were ground to an average particle size of 3 ${\mu}m$ and 0.5 ${\mu}m$, respectively. Adding $SiO_2$ resulted in transformation in the liquid phase at high temperatures, which had little effect on suppressing the thermal dissociation but enhanced the mechanical properties of $ZrSiO_4$. When $Al_2O_3$ was added, the mechanical properties of $ZrSiO_4$ decreased due to the formation of pores and abnormal grains in the microstructure of the sintered zircon.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2008년도 제39회 하계학술대회
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• pp.1228-1229
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• 2008

The composites were fabricated 61[vol.%] ${\beta}$-SiC and 39[vol.%] $TiB_2$ powders with the liquid forming additives of 12[wt%] $Al_2O_3+Y_2O_3$ as a sintering aid by pressure or pressureless annealing at 1,650[$^{\circ}C$] for 4 hours. Reactions between SiC and transition metal $TiB_2$ were not observed in the microstructure and the phase analysis of the SiC-$TiB_2$ electroconductive ceramic composites. Phase analysis of SiC-$TiB_2$ composites by XRD revealed mostly of ${\alpha}$-SiC(6H), $TiB_2$, and In Situ $YAG(Al_5Y_3O_{12})$. The relative density, the flexural strength and the Young's modulus showed the highest value of 88.32[%], 136.43[MPa] and 52.82[GPa] for pressure annealed SiC-$TiB_2$ composites at room temperature. The electrical resistivity showed the lowest value of 0.0162[${\Omega}{\cdot}cm$] for pressure annealed SiC-$TiB_2$ composite at 25[$^{\circ}C$]. The electrical resistivity of the pressure annealed SiC-$TiB_2$ composite was positive temperature coefficient resistance (PTCR) but the electrical resistivity of the pressureless annealed SiC-$TiB_2$ composites was negative temperature coefficient resistance(NTCR) in the temperature ranges from 25[$^{\circ}C$] to 700[$^{\circ}C$].

• 마이크로전자및패키징학회지
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• 제30권4호
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• pp.79-85
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• 2023

(1-4x)Bi_1.5Zn_1.0Nb_1.5O₇-3xBi₂Zn_2/3Nb_4/3O₇-2xLiZnNbO₄(x=0.03-0.21) 조성의 새로운 저온 동시 소성 세라믹(LTCC) 유전체는 Bi_1.5Zn_1.0Nb_1.5O₇-xLi₂CO₃(x=0.03-0.21) 혼합물을 850℃~920℃에서 4 시간 반응성 액상소결(reactive liquid phase sintering)을 하여 제조하였다. 소결이 진행되는 동안 Li₂CO₃는 Bi_1.5Zn_1.0Nb_1.5O₇과 반응하여 Bi₂Zn_2/3Nb_4/3O₇과 LiZnNbO₄를 생성하였고 얻어진 소결체의 상대 소결밀도는 이론 밀도의 96% 이상이었다. 초기 Li₂CO₃ 함량(x)을 조절하여 최종 소결체내에 존재하는 Bi_1.5Zn_1.0Nb_1.5O₇, Bi₂Zn_2/3Nb_4/3O₇ 및 LiZnNbO₄ 상의 상대적인 함량을 제어함으로써 높은 유전율(ε_r), 낮은 유전손실(tan δ) 및 NP0 특성(TCε ≤ ±30 ppm/℃)의 유전율 온도계수(TCε)를 갖는 유전체를 개발할 수 있었다. Li₂CO₃의 첨가가 x=0.03 mol에서 x=0.15 mol로 증가함에 따라 얻어진 복합체 내의 Bi₂Zn_2/3Nb_4/3O₇와 LiZnNbO₄의 부피 분율은 증가하였고, Bi_1.5Zn_1.0Nb_1.5O₇의 부피 분율은 감소하였다. 그 결과 복합체의 유전율(ε_r)은 148.38에서 126.99로 유전손실(tan δ)은 5.29×10^-4에서 3.31×10^-4로 그리고 유전율 온도계수(TCε)는 -340.35 ppm/℃에서 299.67 ppm/℃로 변화되었다. NP0 특성을 갖는 유전체는 Li₂CO₃의 함량이 x=0.09일 때 얻을 수 있었고, 이 때의 유전율(ε_r)은 143.06, 유전손실(tan δ)값은 4.31×10^-4, 그리고 유전율 온도계수(TCε)값은 -9.98 ppm/℃ 이었다. Ag전극과의 화학적 호환성 실험은 개발된 복합 재료는 Ag 전극과 동시 소성 과정에서 전극과 반응이 없음을 보여주었다.

• 한국결정성장학회지
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• 제7권3호
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• pp.473-480
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• 1997

소결조제로 $Al^2O^3$와$Y^2O^3$를 첨가한 $\beta$-SiC 분말에 seed로서 1 wt% 및 wt%$\beta$-SiC 휘스커를 첨가한 시편과 첨가하지 않은 시편을 $1850^{\circ}C$ 에서 5-10 시간 동안 열처리를 행하였다. Seed로서 1-3 wt% $\beta$-SiC 휘스커의 첨가는 액상소결 탄화규소의 미세구조와 기계적특성에 의미 있는 영향을 미치지 않았다. 이는 $\beta$-SiC 휘스커가 액상이 존재하는 고온가압소결 조건에서 불안정하기 떼문이라고 생각된다. $\beta$-SiC 휘스커를 1 wt% 첨가하여 $1950^{\circ}C$에서 5시간 동안 열처리한 시편의 강도 및 파괴인성은 각각 465 MPa 및 5.8 MPa $m^{1/2}$이었고, 동일조건에서 제조된 $\beta$-SiC 휘스커를 펌가하지 않은 시편의 강도 및 피괴인성은 각각 451 MPa 및 5.5 MPa $m^{1/2}$이었다.

• 한국분말재료학회지
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• 제16권5호
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• pp.316-325
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• 2009

Fe based (Fe$_{68.2}$C$_{5.9}$Si$_{3.5}$B$_{6.7}$P$_{9.6}$Cr$_{2.1}$Mo$_{2.0}$Al$_{2.0}$) amorphous powder, which is a composition of iron blast cast slag, were produced by a gas atomization process, and sequently mixed with ductile Cu powder by a mechanical ball milling process. The experiment results show that the as-prepared Fe amorphous powders less than 90 $\mu$m in size has a fully amorphous phase and its weight fraction was about 73.7%. The as-atomized amorphous Fe powders had a complete spherical shape with very clean surface. Differential scanning calorimetric results of the as-atomized Fe powders less than 90 $\mu$m showed that the glass transition, T$_g$, onset crystallization, T$_x$, and super-cooled liquid range $\Delta$T=T$_x$-T$_g$ were 512, 548 and 36$^{\circ}C$, respectively. Fe amorphous powders were mixed and deformed well with 10 wt.% Cu by using AGO-2 high energy ball mill under 500 rpm.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1999년도 추계학술대회 논문집 학회본부 C
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• pp.894-896
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• 1999

The $\beta$-SiC+$ZrB_2$ ceramic composites were pressureless-sintered and annealed by adding 4, 8, 12wt% $Al_{2}O_{3}+Y_{2}O_{3}$(6 : 4wt%) powder as a liquid forming additives at $1800^{\circ}C$ for 4h. The relative density is over 79.3% of the theoretical density and phase analysis of the composites by XRD revealed of $\alpha$-SiC(6H, 4H), $ZrB_2$, $Al_{5}Y_{2}O_{12}$ and $\beta$-SiC(15R). Flexural strength showed the highest of 301.33MPa for composites added with 8wt% $Al_{2}O_{3}+Y_{2}O_{3}$ additives at room temperature. Owing to crack deflection and crack bridging of fracture toughness mechanism, the fracture toughness showed the highest of $3.6979MPa{\cdot}m^{1/2}$ for composites added with 8wt% $Al_{2}O_{3}+Y_{2}O_{3}$ additives at room temperature. The electrical resistivity was measured by the Pauw method from $25^{\circ}C$ to $700^{\circ}C$. The electrical resistivity of the composites showed the PTCR(Positive Temperature Coefficient Resistivity).

• 한국재료학회지
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• 제25권5호
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• pp.215-220
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• 2015

The effect of Al content on the processing of reaction-bonded $Al_2O_3$ (RBAO) ceramics using 40v/o ~ 80v/o Al-Zn-Mg alloy powder was studied in order to improve traditional RBAO ceramic processes that use ~ 40v/o pure Al powder. The influence of high Al content in starting $Al_2O_3$-Al alloy powder mixtures on its particulate characteristics, reaction-bonding, microstructure, physical and mechanical properties was revealed. Starting $Al_2O_3$-Al alloy powder mixtures with 40v/o ~ 80v/o Al alloy powder were milled, reaction-bonded, post-sintered, and characterized. With an increasing Al alloy content, the milling efficiency of Al alloy powder was lowered, resulting in a larger particle size after milling. However, in spite of the larger particle size of Al alloy powder, the oxidation, i.e., reaction-bonding, of the Al alloy was successfully completed via solid and liquid state oxidation, in which the activation energy of the oxidation was nearly the same regardless of Al alloy content. After reaction-bonding and post-sintering at $1600^{\circ}C$, RBAO ceramics from 80v/o Al alloy content showed a relative density of ~97% and a flexural strength of 251 MPa compared to ~ 96% and 353 MPa for RBAO ceramics from 40v/o Al alloy content, respectively. The lower flexural strength at 80v/o Al alloy content was due to the weak spinel phase that formed from Zn, Mg alloying elements in Al.

• 대한전기학회논문지:전기물성ㆍ응용부문C
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• 제50권5호
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• pp.221-225
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• 2001

The effect of $Al_2O_3+Y_2O_3$ additives on fracture toughness of ${\beta}-SiC-TiB_2$ composites by hot-pressed sintering was investigated. The ${\beta}-SiC-TiB_2$ ceramic composites were hot-press sintered and pressureless-annealed by adding 16, 20, 24 wt% ${\beta}-SiC-TiB_2$(6:4 wt%) powder as a liquid forming additives at low temperature(1800 $^{\circ}C$) for 4 h. Phase analysis of composites by XRD revealed mostly of ${\alpha}$-SiC(6H), $TiB_2$, and YAG($Al_5Y_3O_{12}$). The relative density was over 95-88 % of the theoretical density, and the porosity increased with increasing $Al_2O_3+Y_2O_3$ contents because of the increasing tendency of pore formation. The fracture toughness showed the highest value of 5.88 MPa${\cdot}m^{1/2}$ for composites added with 20 wt% $Al_2O_3+Y_2O_3$ additives at room temperature. The electrical resistivity showed the lowest value of $5.22{\times}10^{-4}\;{\Omega}\;{\cdot}\;cm$ for composite added with 20 wt% $Al_2O_3+Y_2O_3$ additives at room temperature, and was all positive temperature coefficeint resistance(PTCR) against temperature up to 900 $^{\circ}C$.

• 한국표면공학회지
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• 제50권6호
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• pp.510-515
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• 2017

In this study, a transient liquid phase sintering (TLPS) process of Ag pastes mixed with a fusible metal alloy of Bi58Sn42 with the melting temperature of $138^{\circ}C$, was examined. After screen printing of the Ag pastes with and without Bi58Sn42 powders on polyimide (PI) substrates, the electrodes were heat-treated at different temperatures in the range between 150 and $300^{\circ}C$ for 60 min in air. Comparing the electrical conductivity of the Ag pastes with and without Bi58Sn42 alloy powder after the heat treatment, it was manifested that the low melting temperature alloy definitely played a major role in an increased conductivity when it is added into the Ag pastes by providing more electrical conduction paths between Ag particles. This can be explained by the fact that capillary force of the melts of Bi58Sn42 can contribute to the rearrangement of the Ag particles during the heat-treatment inducing better connectivity between the Ag particles.