• 한국주조공학회지
• /
• 제23권5호
• /
• pp.244-250
• /
• 2003

The aim of this study is fabricating of composite filler metal (CFM) by a combination of selective laser sintering (SLS) of stainless steel powders (RapidSteel $2.0^{TM}$ and liquid phase infiltration of Ag-28 wt.%Cu alloy. Porous stainless steel body with inter-connected pore channels was fabricated by SLS, binder decomposing and densification processes. By the direct contact infiltration, the narrow inter-particle channels of the porous body were completely filled with the Ag-28 wt.%Cu alloy infiltrant. During infiltration, the dissolved elements of Fe, Ni and Cr from the porous body were solved into copper solid solution phases, which consist of eutectic structure of composite metal matrix. The S10C/CFM/S10C joints, which have narrow clearance gaps between them up to 10 micrometers, were joined successfully by self-feeding of filler metal from the matrix of CFM. The CFM kept its original thickness and microstructure after brazing. The tensile strength of brazed specimen was higher than 30 kgf/$mm^2$ and showed a typical ductile fracture mode in the CFM.

• Journal of Welding and Joining
• /
• 제20권3호
• /
• pp.54-59
• /
• 2002

Overlays is a treatment of the surface and near-surface regions of a material to allow the surface to perform functions that are distinct from those frictions demanded far the bulk of the material. Welding, thermal spray, quenching, carburizing and nitration have been used as the surface treatment. Especially, weld overlay is a relatively thick layer of filler metal applied to a carbon or low-alloy steel base metal for the purpose of providing a wear resistant surface. In this study, weld overlay was performed by MAG welding on the base metal(SS400) with filler metal which contain composite powders($Cr_3C_2+Mn+Mo+NbC$) and solid wire(JIS-YGW11). Characteristics of hardness and wear resistance on overlays were analyzed by EDS, EPMA, XRD and microstructures. Carbide formations were $M(Cr, Fe)_7C_3$ and NbC phases. And carbide volume fraction, hardness and specific wear resistance of overlays were increased with increasing powder feed rate and decreasing wire fred rate. Hardness and wear resistance were almost proportioned to carbide volume fraction of overlay.

• 한국전기전자재료학회:학술대회논문집
• /
• 한국전기전자재료학회 1999년도 춘계학술대회 논문집
• /
• pp.548-551
• /
• 1999

The cure characteristics of metal particle filled DGEBA/MDA/SN/ zeolite epoxy resin composite system for EMI shielding were investigated by dynamic DSC run method and FT-lR spectroscopy. As the heating rate increased, the peak temperature on dynamic DSC curve increased because of the rapid cure reaction. From the straight line of the Kissinger plot, the curing reaction activation energy and pre-exponential factor could be obtained. As the post-curing time at 15$0^{\circ}C$ increased, the glass increased the glass transition temperature or the thermal stability increased. When the post curing time is too long, the system filled with metallic Al particle can be thermally oxidized by the catalytic reaction of metal filler and the thermal stability of the composite for the EMI shielding application may be decreased.

• Korean Chemical Engineering Research
• /
• 제58권1호
• /
• pp.64-68
• /
• 2020

본 연구에서는, 열 전도성 충진제로 충진 된 에폭시복합체를 사용하여 금속 구리판에 이를 코팅한 기판이 제조되었다. 에폭시 복합체의 열전도도를 향상시키기 위해서는 에폭시 매트릭스에 있는 전도성 필러의 최적 분산을 통한 전도성 네트워크를 형성하게 하고, 인접한 필러 입자들 사이에서 열 저항 접합의 수를 감소시키는 것이 중요한 요소이다. 이는 에폭시는 열전도도가 0.2~0.3 W 밖에 안되기 때문에 높은 열전도도를 유지하기 위해선 열전도성 필러가 서로 연결되어 입자간에 갭이 적어야 열저항을 감소시킬수 있기 때문이다. 본 연구의 목적은 에폭시 수지에 Al₂O₃와 Boron Nitride (BN) 충진제를 균일하게 분산시켜 고방열 에폭시 복합체를 개발하는 데 있다. 그 결과, Al₂O₃와 Boron nitride Filler가 에폭시 수지 매트릭스에 서로 연결되어 에폭시 수지와 알루미나/Boron nitride 하이브리드 필러 간에 계면 공극 없이 분산되어 열전도도 특성 향상을 확인 할 수 있었고, 표면 처리한 s-BN 필러가 에폭시 수지의 매트릭스의 계면접착력을 향상시켰으며, 계면 공극을 최소화함에 따라 높은 열전도도 특성을 확보 할 수 있었다.

• Journal of Mechanical Science and Technology
• /
• 제16권9호
• /
• pp.1078-1083
• /
• 2002

Ceramics are significantly used in many industrial applications due to their excellent mechanical and thermal properties such as high temperature strength, low density, high hardness, low thermal expansion, and good corrosion resistive properties, while their disadvantages are brittleness, poor formability and high manufacturing cost. To combine advantages of ceramics with those of metals, they are often used together as one composite component, which necessiates reliable joining methods between metal and ceramic. Direct brazing using an active filler metal has been found to be a reliable and simple technique, producing strong and reliable joints. In this study, the fracture characteristics of Si$_3$N$_4$ ceramic joined to ANSI 304L stainless steel with a Ti-Ag-Cu filler and a Cu (0.25-0.3 mm) interlayer are investigated as a function of strain rate and temperature. In order to evaluate a local strain a couple of strain gages are pasted at the ceramic and metal sides near joint interface. As a result the 4-point bending strength and the deflection of interlayer increased at room temperature with increasing strain rate. However bending strength decreased with temperature while deflection of interlayer was almost same. The fracture shapes were classified into three groups ; cracks grow into the metal-brazing filler line, the ceramic-brazing filler line or the ceramic inside.

• Macromolecular Research
• /
• 제17권12호
• /
• pp.1032-1038
• /
• 2009

A polypyrrole (PPy)/alumina composite filler prepared via in-situ polymerization of pyrrole on alumina particles was incorporated into $Nafion^{(R)}$ to improve the performance of ionic polymer-metal composite (IPMC) actuators. The IPMCs with the pristine PPy without alumina support did not show bending displacements superior to that of the bare Nafion-based IPMC, except at a high PPy content of 4 wt%. This result was attributed to the low redox efficiency of the PPy alone in the IPMC and may have also been related to the modulus of the IPMC. However, at the optimized filler contents, the cyclic displacement of the IPMCs bearing the PPy/alumina filler was 2.2 times larger than that of the bare Nafion-based IPMC under an applied AC potential of 3 Vat 1 Hz. Even under a low AC potential of 1.5 V at 1 Hz, the displacement of the PPy/alumina-based IPMCs was a viable level of performance for actuator applications and was 2.7 times higher than that of the conventional Nafion-based IPMC. The generated blocking force was also improved with the PPy/aiumina composite filler. The greatly enhanced performance and the low-voltage-operational characteristic of the IPMCs bearing the PPy/alumina filler were attributed to the synergic effects of the neighboring alumina moiety near the PPy moiety involving electrochemical redox reactions.

• 한국정밀공학회지
• /
• 제23권8호
• /
• pp.100-107
• /
• 2006

The objective of this research is to investigate the electromagnetic interference(EMI) shielding characteristics of fiber reinforced composites. We fabricated glass and carbon fiber reinforced composites filled with metal powder and nano carbon black. The measurements of shielding effectiveness(SE) were carried out frequency range 300MHz - 1GHz for commercial purposes such as electric or telecommunication devices. The return loss and loss due to absorption were also measured as a function of frequency in the micro wave(300MHz-1GHz) region. It is observed that the SE of the composites is the frequency dependent, increase with the increases in filler loading. The Mg metal powder filled composite showed higher SE compared to that of carbon black. The Mg metal powder/epoxy composite was shown to exhibit up to 40dB of SE. The results indicates that the composite having higher filler loading can be used for the purpose of EMI shielding as well as for some microwave applications.

• 폴리머
• /
• 제26권5호
• /
• pp.644-652
• /
• 2002

전자파 차폐용 개스킷으로 적용할 수 있는 금속계 입자와 상온경화형 실리콘 수지의 페이스트계에 대한 정량적인 해석을 수행하였다. 금속입자 충전 복합재료의 전기 전도성 및 유변학적 거동은 입자의 형상, 크기, 분산상태에 많은 영향을 받는다. 고충전계에서 입자들은 매우 복잡한 응집상태를 형성하며 전단속도와 같은 외부요인에 의해 응집구조가 변하고 이에 따라 전기 전도도가 달라지게 된다. 본 연구에서는 금속입자의 평균직경 및 분산성에 따른 영향을 점도측정 및 전기 전도도 측정 방법을 통해 해석하였으며 이를 통해 금속입자의 선정기준을 제시하였다. 금속입자의 종류에 따라 점도분포, 전단응력의 영향, 전기 전도성의 변화 등이 차이를 보였다. 상대적으로 직경이 큰 입자에서 전단응력에 의한 영향이 두드러지게 나타났으며 동일 함량에서 분산성의 제어를 통해 점도 및 전기 전도도의 개선이 가능함을 보였다.

• 열처리공학회지
• /
• 제27권4호
• /
• pp.169-174
• /
• 2014

The effect of varying amounts of graphite and $TiB_2$ on the electrical conductivity of composite bipolar plates was systematically studied. In this study, Titanium diboride ($TiB_2$) which has a high electrical conductivity, was selected as a filler and a additive material instead of conventional graphite. For proper distribution of the filler and matrix materials, ball milling using alumina balls was conducted for 1h, and then the hot press method was applied for the preparation of composite samples. The results showed a rapid increase in the electrical conductivity of composite bipolar plates at the critical filler content. However, $TiB_2$ and graphite composite bipolar plates showed similar increases in the electrical conductivity even though $TiB_2$ has a higher electrical conductivity than graphite. In addition, it was also found that a small addition of $TiB_2$ to graphite filler could be very effective for increasing the electrical conductivity and flexural strength of the composite bipolar plate.

• 한국전기전자재료학회논문지
• /
• 제34권5호
• /
• pp.314-320
• /
• 2021

Controlling ambient humid condition through high performance humidity sensors has become important for various fields, including industrial process, food storage, and the preservation of historic remains. Although aerosol deposited humidity sensors using ceramic BaTiO₃ (BT) material have been widely studied because of their longtime stability, there remain critical disadvantages, such as low sensitivity, low linearity, and slow response/recovery time in case of the sensors fabricated at room temperature. To achieve superior humidity sensing properties even at room temperature condition, BT-Cu composite films utilizing aerosol deposition (AD) process have been proposed based on the percolation theory. The BT-Cu composite films showed gradually improved sensing properties until the Cu concentration reached 15 wt% in the composite film. However, the excessive Cu (above 30 wt%) containing BT-Cu composite films showed a rapid decrease of the sensing properties. The results of observed surface morphology of the AD fabricated composite films, to figure out the metal filler effect, showed correlation between surface topography as well as size and the amount of open pores according to the metal filler content. Overall, it is very important not only dielectric constant of the humidity sensing films but also microstructures, because they affect either the variation range of capacitance by ambient humidity or adsorption/desorption of ambient humidity onto/from the humidity sensing films.