• 한국전기전자재료학회:학술대회논문집
• /
• 한국전기전자재료학회 1999년도 추계학술대회 논문집
• /
• pp.117-120
• /
• 1999

The relationship between the DC degradation characteristics of the ZnO varistor and the ambient sintering-process is investigated in this study. ZnO varistors made of Matsuoka's composition were fabricated by standard ceramic techniques. The ambient sintering-process is performed at the extraordinary electrical-furnace which is equipped with the vacuum system. The Gas of sintering process was oxygen, nitrogen, argon, air respectively. The microstructure of ZnO varistors be made use of SEM equipment. The condition of DC degradation tests were conducted at $115\pm2^{\circ}C$ for periods up to 13 h. Current-voltage analysis is used to determine nonlinear coefficients($\alpha$). Resistance-frequency and capacitance-frequency analysis are accomplished to the understanding of electrical properties as DC degradation test. From above analysis, it is found that the ZnO varistor sintered in oxygen atmosphere showed superior properties at the DC degradation test.

• 한국전기전자재료학회:학술대회논문집
• /
• 한국전기전자재료학회 2006년도 추계학술대회 논문집 Vol.19
• /
• pp.196-197
• /
• 2006

In this study, low temperature sintering multilayer piezoelectric transformer for DC-DC converter were manufactured using (PbCaSr)Ti(MnSb)$O_3$ ceramics and thin their electrical properties were investigated according to the vanation of frequency and load resistance. The voltage step-up ratio of multilayer piezoelectric transformer showed the maximum value m the vicinity of 1.3MHz and increased according to the increase of load resistance. When the output impedance coincided with the load resistance, the piezoelectric transformer showed the temperature rise of about $21^{\circ}C$ under the output power of 6W.

• 한국세라믹학회지
• /
• 제31권11호
• /
• pp.1378-1386
• /
• 1994

The characteristic of calcined BaTiO3 powder and sintered PTC ceramics was investigated varing with calcination temperature and time of BaTiO(C2O4)2.4H2O synthesized from BaCl2.2H2O, TiCl4, oxalic acid and ethanol by oxalic acid method. When the particle size was less than 0.1 ${\mu}{\textrm}{m}$ by controlling calcination temperature and time, the resistance at room temperature was measured very high (above M{{{{ OMEGA }}). However, when the calcined particle sizes ranged from 0.2 to 0.3 ${\mu}{\textrm}{m}$, the resistance was 100 {{{{ OMEGA }} (After sintering, the grain size was 10~30 ${\mu}{\textrm}{m}$ homogeneously with the addition of dopant in sintering, the resistivity, resistance, $\alpha$ value and jumped to were 110{{{{ OMEGA }}.cm, 24$^{\circ}C$/% and 106{{{{ OMEGA }}, respectively.

• 한국전기전자재료학회논문지
• /
• 제20권4호
• /
• pp.332-336
• /
• 2007

In this study, multilayer piezoelectric transformer was manufactured using the PMN-PNN-PZT ceramic and then the electrical characteristics were investigated according to the variations of frequency and load resistance. The voltage step-up ratio of multilayer piezoelectric transformer showed the maximum value at the vicinity of 75 kHz and increased according to the increase of load resistance. When the output impedance coincided with the load resistance, the multilayer piezoelectric transformer showed the temperature rise of less than $20^{\circ}C$ at the output power of 20 W. As the results, the multilayer piezoelectric transformer manufactured at low co-firing temperature of $940^{\circ}C$ using PMN-PNN-PZT ceramics could be stably driven as the step-down transformers.

• 한국세라믹학회지
• /
• 제36권1호
• /
• pp.89-96
• /
• 1999

석고몰드의 단점을 극복할 수 있는 다공질 알루미나 몰드의 제조저건을 확립하였다. 다공질 알루미나 몰드의 제조를 위해 활성탄의 질량비에 따라 조성비를 달리하여 첨가한 후, ESA와 유동특성 등을 조하삼으로써 안정된 이상 슬러리를 제조하였으며, 이를 석고몰드에 캐스팅하여 얻은 원통형 알루미나 몰드를 사용하여 활성탄의 양과 소결온도에 따른 수축율 변화와 마모에 대한 저항성을 측정하였다. 다공질 알루미나 몰드의 소결에서는 비수축 소결구인 표면확산에 의해 입자간 넥 강도의 증진을 통한 몰드의 강도 증진을 도모하는 것이 바람직하며, 이를 위해 1,00$0^{\circ}C$이하에서 유지시간의 변화에 따른 열역학적 방법, 1,00$0^{\circ}C$이상의 온도에서 알루미나의 수축을 억제하면서 빠른 승온속도를 열처리온도에 따른 동역학적 방법과 이 두가지 방법을 혼합하는 방법 등으로 구분하여 다동질 알루미나 몰드의 소결조건을 분석하였다. 위 방법들에 대한 다공질 알루미나 몰드의 캐스팅 특성을 분석한 결과, 복합 소결법이 최적임을 알수 있었다. 제조된 다공질 알루미나 몰드의 비교적 높은 강도를 보였으며, 석고몰드레 비해 빠른 건조시간, 산, 염기에 대한 내식성 및 캐스팅 특성이 우수하였다.

• 비파괴검사학회지
• /
• 제34권5호
• /
• pp.377-383
• /
• 2014

위치 감응형 전극 네트워크(addressable conducting network, ACN)는 탄소섬유 복합재료와 전극 사이의 접촉저항을 통해 구조물의 손상 감지가 가능하다. 손상 감지를 위한 위치 감응형 전극 네트워크의 신뢰성을 향상시키기 위해서는 전극과 복합재료 사이의 접촉저항이 최소화되어야 한다. 본 연구에서는 은 나노 전극을 탄소섬유 복합재료 위에 인쇄전자기술을 이용하여 제작하였다. 은 전극이 형성된 복합재료는 은 나노 잉크의 소결온도와 복합재료의 표면거칠기에 따라 제작되었으며, 이에 따른 접촉저항을 측정하였다. 또한, 전자주사현미경(scanning electron microscope, SEM)을 통해 전극과 복합재료 사이의 계면을 관찰하였다. 본 연구를 통해, 은 나노 잉크의 소결온도가 $120^{\circ}C$, 복합재료의 표면거칠기가 0.230a일 때, $0.3664{\Omega}$의 최소 접촉저항을 나타냈다.

• 한국분말재료학회지
• /
• 제22권3호
• /
• pp.203-207
• /
• 2015

This study investigated the microstructure and wear resistance property of HPHT(high pressure high temperature) sintered PDC(polycrystalline diamond compact) in accordance with initial molding pressure. After quantifying an identical amount of diamond powder, the powder was inserted in top of WC-Co sintered material, and molded under four different pressure conditions (50, 100, 150, $200kgf/cm^2$). The obtained diamond compact underwent sintering in high pressure, high temperature conditions. In the case of the $50kgf/cm^2$ initial molding pressure condition, cracks were formed on the surface of PDC. On the other hand, PDCs obtained from $100{\sim}200kgf/cm^2$ initial molding pressure conditions showed a meticulous structure. As molding pressure increased, low Co composition within PDC was detected. A wear resistance test was performed on the PDC, and the $200kgf/cm^2$ condition PDC showed the highest wear resistance property.

• 한국세라믹학회지
• /
• 제51권5호
• /
• pp.498-504
• /
• 2014

Particulate nitride composites have been fabricated by sintering the compacted powder of AlN and 5 - 64.3 mol% $Al_2O_3$, with a small addition of $Y_2O_3$ ($Y_2O_3$/AlN, 1 wt%), in 1-atm nitrogen gas at $1650-1900^{\circ}C$. The composites were characterized in terms of sintering behavior, phase relations, microstructure and thermal shock resistance. AlN, 27R AlN pseudopolytype, and alminium oxynitride (AlON, $5AlN{\cdot}9Al_2O_3$) were found to existin the sintered material. Regardless of batch composition, the AlN-$Al_2O_3$ powder compacts exhibited similar sintering behavior; however, the degree of shrinkage commonly increased with increasing $Al_2O_3$ content, consequently giving high sintered bulk density. By increasing the $Al_2O_3$ addition up to ${\geq}50 mol%$, the matrix phase in the sintered material was converted from AlN or 27R to AlON. Above $1850^{\circ}C$, a liquid phase was formed by the reaction of $Al_2O_3$ with AlN, aided by $Y_2O_3$ and mainly existed at the grain boundaries of AlON. Thermal shock resistance was superior in the sintered composite consisting of AlON with dispersed AlN or AlN matrix phase.

• 한국분말재료학회지
• /
• 제21권6호
• /
• pp.460-466
• /
• 2014

Al-Si-SiC composite powders with intra-granular SiC particles were prepared by a gas atomization process. The composite powders were mixed with Al-Zn-Mg alloy powders as a function of weight percent. Those mixture powders were compacted with the pressure of 700 MPa and then sintered at the temperature of $565-585^{\circ}C$. T6 heat treatment was conducted to increase their mechanical properties by solid-solution precipitates. Each relative density according to the optimized sintering temperature of those powders were determined as 96% at $580^{\circ}C$ for Al-Zn-Mg powders (composition A), 97.9% at $575^{\circ}C$ for Al-Zn-Mg powders with 5 wt.% of Al-Si-SiC powders (composition B), and 98.2% at $570^{\circ}C$ for Al-Zn-Mg powders with 10 wt.% of Al-Si-SiC powders (composition C), respectively. Each hardness, tensile strength, and wear resistance test of those sintered samples was conducted. As the content of Al-Si-SiC powders increased, both hardness and tensile strength were decreased. However, wear resistance was increased by the increase of Al-Si-SiC powders. From these results, it was confirmed that Al-Si-SiC/Al-Zn-Mg composite could be highly densified by the sintering process, and thus the composite could have high wear resistance and tensile strength when the content of Al-Si-SiC composite powders were optimized.

• 한국분말재료학회지
• /
• 제12권2호
• /
• pp.131-135
• /
• 2005

7xxx series Al alloy has the most attractive properties including its excellent high specific strength, stress corrosion cracking and corrosion-resistance. However, in case of the Al-Zn system, the liquid phase has a transient aspect because of the high solid solubility of Zn in Al. Therefore, transient liquid phase sintering behavior was observed during the sintering process. And the amount of liquid and its duration were influenced by the process variables including heating rate and final sintering temperature. At high heating rates($100^{\circ}C/min$), the liquid fraction increased during sintering because diffusion was minimized and therefore local saturation could easily occur. The sintered density increased with increasing heating rate.