• Journal of the Korean Ceramic Society
• /
• v.44 no.4 s.299
• /
• pp.198-201
• /
• 2007

Multi-walled carbon nanotube (M-CNT)/Nafion nanocomposites were prepared by solution casting to elucidate the effect of M-CNT addition, from 0 to 7 wt%, on the viscoelastic behavior of the composites. The M-CNT bundles induced by the Nafion polymer were determined to be uniformly distributed for the 1 wt% M-CNT/Nafion nanocomposites. The 1 wt% M-CNT/Nafion composite exhibited the highest blocking stress of 2.3 kPa due to its high elastic modulus of 0.485 GPa. From a dynamic mechanical analysis, the 1 wt% M-CNT had the highest storage and loss moduli compared with the other samples in all frequency and temperature ranges. From the storage modulus data, the M-CNT loaded composites had similar $T_g$ values near $120^{\circ}C$. The glass transition temperatures of the M-CNT loaded composites were $120^{\circ}C$ (1 wt%), $117^{\circ}C$ (3 wt%), $117^{\circ}C$ (5 wt%), and $135^{\circ}C$ (7 wt%), suggesting that the effect of the M-CNTs on the Nafion film begins at 1 wt%. Thus, it has been concluded that the 1 wt% M-CNT disported composite is attractive for actuator applications.

• Korean Chemical Engineering Research
• /
• v.47 no.2
• /
• pp.203-207
• /
• 2009

In the NCAs(non-conductive adhesive) for adhesion of Micro Electro Mechanical System(MEMS), there are some problems such as delamination and cracking, because of the differences of CTE(coefficients of thermal expansion) between NCAs and substrates. Addition of inorganic particle or flexibilizer have been performed to solve those problems. In this study, to improve the flexibility of epoxy adhesive, epoxy/siloxane composites were prepared by adding 1, 3, or 5 phr of amino modified siloxane(AMS). Glass transition temperatures(Tg), moduli and CTE of those composites were measured to confirm effects of siloxane on thermal/mechanical properties of siloxane/epoxy-composites. Tg of AMS/epoxy-composites decreased from $134^{\circ}C$ to $122^{\circ}C$ with increasing AMS contents and moduli decreased from 2,425 MPa to 2,143 MPa with increasing AMS contents. But CTE of AMS/epoxy-composites increased from $67ppm/^{\circ}C$ to $71ppm/^{\circ}C$ with increasing AMS contents. In short, the addition of siloxane is effective for enhancing the flexibility of epoxy but leads to the decrease of Tg.

• Transactions of the Korean Society of Machine Tool Engineers
• /
• v.10 no.6
• /
• pp.78-84
• /
• 2001

In the present study, SiCSi-$Si_3 N_4$-SiC ceramic composites that contained up to 30 wt% of dispersed SiC particles were fabricat-ed cia hot-pressing with an oxynitride glass. The microstructure, the mechanical properties and the cutting performance of resulting ceramic composites were investigated. By fixing the composition as $Si_3 N_4$-20wf%SiC, the effect of sintering time on the microstructure, the mechanical properties and the cutting performance were also investigated. The longer sir-tering time is, the bigger the grain size of SiC is. The fracture toughness(-$K_k$) of the $Si_3 N_4$-SiC ceramic composites increased with the increase of gain size, while the flexural strengthh($\sigma$) decreased. For machining SCM440, the insert with 20wt%r SiC sintered for 8 hours showed the longest tool life while the insert with 20wt% SiC sintered for 12 hours showed the longest tool life for machining gray cast iron.

• Journal of the Korean Ceramic Society
• /
• v.39 no.2
• /
• pp.145-152
• /
• 2002

Four commercial alumina powders having different particle size of $0.5{\mu}m,\;2.8{\mu}m,\;12{\mu}m,\;and\;45{\mu}m$ were presintered at 1120$^{\circ}C$ for 2h and then lanthanum aluminosilicate glass was infiltrated at 1100$^{\circ}C$ for 2h in the interval of 0.1h to investigate the penetration kinetic of the glass into the alumina preforms. The infiltration distance is parabolic with respect to time as described by the Washburn equation and the penetration rate constant, K, increases with raising the alumina particle size. The strength of glass-alumina composites increases as the alumina particle size reaches to 2.8${\mu}m$ due to the increase in packing, however, decreases with further increasing the alumina particle size. The fracture toughness of the composites rises with increasing the alumina particle size due to the crack bowing and the interaction between crack and alumina particles.

• Proceedings of the Materials Research Society of Korea Conference
• /
• 2003.11a
• /
• pp.138-138
• /
• 2003

Low temperature co-fired ceramic (LTCC) technology offers significant benefits over the other established packaging technologies for high density, high microwave frequency, and fast signal application. Most conventional electroceraramics do not meet the basic requirements in respect of sinterability for LTCC technology. Attention is, therefore, focused on the role of glasses because of the capability they supply with lower sintering temperatures. In this study, commercial ceramic (MBRT-90) in the system BaO-N $d_2$ $O_3$-Ti $O_2$ (BNT: 40 ~ 80 wt%) and L $a_2$ $O_3$- $B_2$ $O_3$-Ti $O_2$ glass (LBT;60 ~ 20 wt%) were prepared. These glass/ceramic composites were evaluated for sintering behavior, phase evaluation, densities, interface reaction, crystallinity, microstructure and microwave dielectric properties. It was found that the addition LBT glass frits significantly lowered the sintering temperature to below 90$0^{\circ}C$ and as temperature increased (750~90$0^{\circ}C$) densification developed dynamically which was meant to be as over 95% of relative density. It is supposed that in the microstructure, the grain size was increased accompanying with the formation of different phases such as LaB $O_3$ and Ti $O_2$ under the condition of increasing sintering temperature. The sintered bodies represented applicable dielectric properties, namely 20 ~ 40 for $\varepsilon_{{\gamma}}$, ~ 10000 GHz for Q* $f_{0}$ and 10~80 ppm/$^{\circ}C$ for $\tau$$_{f}$. The results suggest that the composite is one of feasible candidates for the microwave use in LTCC technology.y.e use in LTCC technology.y.

• 한국정보디스플레이학회:학술대회논문집
• /
• 2005.07b
• /
• pp.1466-1469
• /
• 2005

We report effects of electrical aging on the emission stability of carbon nanotube (CNT) paste for low cost and high low-cost and large area field emission devices or displays. Photosensitive carbon nanotube paste was formulated by using of spin on glass (SOG) as an inorganic binder and investigated emission properties and stability depending on electrical aging condition.

• Journal of the Korean Society of Fisheries and Ocean Technology
• /
• v.35 no.4
• /
• pp.421-427
• /
• 1999

The critical fracture energy and failure mechanisms of GF/PP composites are investigated in the temperatures range of the ambient temperature to $-50^{\circ}C$ The critical fracture energy increase as fiber volume fraction ratio increased The critical fracture energy shows a maximum at ambient temperature and it tends to decrease as temperature goes up. Major failure mechanisms can be classfied such as fiber matrix debonding, fiber pull-out and/or delamination and matrix deformation.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2009.06a
• /
• pp.176-176
• /
• 2009

Influences of dose and particle size of $Al_2O_3$ filler and sintering time on the dielectric properties of $Al_2O_3$ filler/CaO-$Al_2O_3-SiO_2$ (CAS) glass composites were investigated with a view to applying the composites to the substrate material in low temperature co-firing ceramic (LTCC) technology. The increased addition of $Al_2O_3$ filler with the particle size of 1 ${\mu}m$ monotonically decreased the density of the sintered specimen at a given temperature, while sintering of the 10 wt% $Al_2O_3$ added specimen at $925^{\circ}C$ for 2 h demonstrated 96.0 % of the relative density, dielectric constant of 6.34, and quality factor of 2,760 GHz. As for the influence of the particle size of the $Al_2O_3$ filler, there existed an optimum particle size (30 ${\mu}m$) to ensure successful densification (96.5 %) of the 10 wt% $Al_2O_3$/CAS composites at $925^{\circ}C$ for 2 h, at which condition the specimen demonstrated dielectric constant of 5.45 and quality factor of 3,740 GHz. When the influence of the sintering time of the 10 wt% $Al_2O_3$) (30 ${\mu}m$) added specimen was investigated at the sintering temperature of $925^{\circ}C$, an overly long sintering time degraded dielectric properties due to the over-sintering and the significant growth of the second phase such as anorthite, while the sintering for 4 h demonstrated 96.58 % of the relative density, dielectric constant of 5.4, and quality factor of 4,050 GHz. These results demonstrate the feasibility of the investigated material as the substrate material in LTCC technology.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.22 no.5
• /
• pp.397-404
• /
• 2009

Effects of ceramic filler types and dose on the low temperature sintering and dielectric properties of ceramic/$CaO-Al_2O_3-SiO_2$ (CAS) glass composites were investigated. All of the specimens were sintered at $850{\sim}900^{\circ}C$ for 2 h, which conditions are required by the low-temperature co-firing ceramic (LTCC) technology. Ceramic fillers of $CaCO_3$, $Al_2O_3$, $CaCO_3-Al_2O_3$ mixture, and $CaCO_3-Al_2O_3$ compound ($CaAl_2O_4$), respectively, were used. The addition of $Al_2O_3$ yielded the crystalline phase of alumina, which was associated with the inhibition of sintering, while, $CaCO_3$ resulted in no apparent crystalline phase but the swelling was significant. The additions of $CaCO_3-Al_2O_3$ mixture and $CaAl_2O_4$, respectively, yielded the crystalline phases of alumina and anorthite, and the sintering properties of both composites increased with the increase of filler addition and the sintering temperature. In addition, the $CaAl_2O_4$/CAS glass composite, sintered at $900^{\circ}C$, demonstrated good microwave dielectric properties. In overall, all the investigated fillers of 10 wt% addition, except $CaCO_3$, yielded reasonable sintering (relative density, over 93 %) and low dielectric constant (less than 5.5), demonstrating the feasibility of the investigated composites for the application of the LTCC substrate materials.

• Korean Journal of Materials Research
• /
• v.8 no.7
• /
• pp.628-633
• /
• 1998

단사정 HBO2 분막을 무기접착제로 이용하여 선택적 레이저 소결 기술을 적용시켜 알루미나-글래스 복합재료를 제조하였다. 만들어진 green SLS 시험편을 여러 온도에서 열처리하여 글래스-세라믹 복합재료를 얻었다. 글래스의 양이 많을수록 복합재료는 높은 밀도와 높은 굽힘강도를 보여주었다. 열처리 온도 $900^{\circ}C$에서 복합재료는 최대 밀도와 최대 강도를 나타낸다. 이것은 글래스의 낮은 점도로 인한 좋은 유동성 때문에 글래스의 재분배가 이루어졌기에 가능하다고 생각되어진다. 그리고 기공이 많은 열처리한 SLS 시험편에 콜로이드 실리카를 주입시켜 치밀화시켰다.