• Journal of Powder Materials
• /
• v.26 no.5
• /
• pp.383-388
• /
• 2019

To improve the mechanical properties of aluminum, graphene has been used as a reinforcing material, yielding graphene-reinforced aluminum matrix composites (GRAMCs). Dispersion of graphene materials is an important factor that affects the properties of GRAMCs, which are mainly manufactured by mechanical mixing methods such as ball milling. However, the use of only mechanical mixing process is limited to achieve homogeneous dispersion of graphene. To overcome this problem, in this study, we have prepared composite materials by coating aluminum particles with graphene by a self-assembly reaction using poly vinylalcohol and ethylene diamine as coupling agents. The scanning electron microscopy and Fourier-transform infrared spectroscopy results confirm the coating of graphene on the Al surface. Bulk density of the sintered composites by spark plasma sintering achieved a relative density of over 99% up to 0.5 wt.% graphene oxide content.

• 한국신재생에너지학회:학술대회논문집
• /
• 2009.06a
• /
• pp.406-409
• /
• 2009

In this work, the magnetite ($Fe_3O_4$)/multi-walled carbon nanotubes (MWNTs) composites for lithium secondary battery were prepared. Nano-$Fe_3O_4$ was deposited by chemical coprecipitation of $Fe^{2+}$ and $Fe^{3+}$ in the presence of MWNTs in alkaline solutions. Transmission electron spectroscopy (TEM) and X-ray diffraction (XRD) analyses indicated that nano-$Fe_3O_4$ particles had a good crystallinity of cubic specimens and many tiny particles attached on the surfaces of the MWNTs. The electrochemical properties of $Fe_3O_4$/MWNTs composites as anodes in lithium-secondary batteries were evaluated by cyclic voltammetry and galvanostatic charge/discharge techniques. The as-prepared $Fe_3O_4$/MWNTs composites showed an initial lithium storage capacity of 1120 mAh/g and a reversible capacity of 394 mAh/g after 100 cycles, demonstrating better performance than that of the commercial graphite anode materials.

• Composites Research
• /
• v.25 no.6
• /
• pp.178-185
• /
• 2012

One of a unique technique in manipulating a multifunctional composite is demonstrated in this study. An electric field is applied to a liquid suspension in order to align the inclusions along with the direction electric field. This is called FAiMTa(Field Aided Micro Tailoring). It makes orthotropic polymer composites by arranging the micro and/or nano size particle inclusions in chain-line formation. Several kinds of particles such as $Al_2O_3$, graphite, CNT(Carbon Nano Tube), W(Tungsten) are tested to verify the effectiveness of the FAiMTa. The particles redistributed in an epoxy suspension and their coupons show that mechanical and thermal properties of orthotropic and random composites containing those particles depend on the trend of particles' alignment. The micro-images of the functional composite from FAiMTa have been captures and their physical properties demonstrate their wide-range and state-of-the-art application for advanced multifunctional composites.

• Composites Research
• /
• v.23 no.3
• /
• pp.7-12
• /
• 2010

In order to increase the electrical conductivity and the mechanical properties of carbon fabric composites, multi-walled carbon nanotubes (MWCNTs) and carbon nanofibers (CNFs) were deposited on carbon fabrics by anodic and cathodic electrophoretic deposition (EPD) processes. In the cathodic EPD, carbon nano-particles and nano-sized Cu particles were simultaneously deposited on the carbon fabric, which gave a synergetic effect on the enhancement of properties as well as the degree of deposition. The hybridization of carbon nano-particles and micron-sized carbon fiber significantly improved the through-the-thickness electrical conductivity. In addition, both MWCNTs and CNFs were deposited onto the carbon fabric for multi-scale hybrid composites. Multi-scale deposition improved the through-the-thickness electrical conductivity, compared to the deposition of either MWCNTs or CNFs.

• Korean Journal of Materials Research
• /
• v.13 no.4
• /
• pp.213-218
• /
• 2003

Fibrous monolithic control of$ Al_2$$O_3$ -$ZrO_2$composite was investigated by multi-pass extrusion process. To obtain sound $Al_2$$O_3$-X $O_2$sintered bodies, burning out and sintering process were carefully carried out. The sintered bodies showed continuous, fibrous monolithic microstructure without any swelling. Many microcracks were observed at the $Al_2$$O_3$-$ZrO_2$interfaces due to the mismatching of thermal expansion coefficient between $Al_2$$O_3$ and $ZrO_2$phase. Most of m- $ZrO_2$grains included twin defects such as (001), (010) and (011) type to accommodate the phase transformation induced stress.

• Elastomers and Composites
• /
• v.54 no.4
• /
• pp.313-320
• /
• 2019

A typical wear pattern was reported to resemble the fatigue crack growth behavior considering its mechanism, especially for amorphous rubbers such as styrene-butadiene rubber (SBR). In this study, the wear and crack growth rates were correlated using two separate experiments for carbon black and silica-reinforced selected rubber compounds. The wear rate was determined using a blade-type abrasion tester, where the frictional energy input during wearing was measured. The crack propagation rate was determined under different tearing energy inputs using a home-made fatigue tester, with a pure-shear test specimen containing pre-cracks. The rates of abrasion and crack propagation were plotted on a log-log scale as a function of frictional and tearing energies, respectively. Reasonable agreement was observed, indicating that the major mechanism of the abrasion pattern involved repeated crack propagation.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2010.06a
• /
• pp.99-99
• /
• 2010

Polymer nanocomposite has been attracting much attention as a new insulation material, since homogeneous dispersion of nm-sized inorganic fillers can improve various properties significantly. In this paper, various kinds of epoxy based nanocomposites were made and AC breakdown strength of Nano-TiO2 and micro-silica filler mixture of epoxy based composites were studied by sphere to sphere electrode. Moreover, nano- and micro-filler combinations were adopted as an approach toward practical application of nanocomposite insulation materials. Nano-TiO2 particle size is about 10nm and composites ratio was resin (100) : hardener (82) : accelerator (1.5). AC breakdown test was performed at room temperature (25 [$^{\circ}C$], 80 [$^{\circ}C$] and 100 [$^{\circ}C$] in the vicinity of Tg (90[$^{\circ}C$]). And thermal conductivity were measured by ASTM-D5470.

• Macromolecular Research
• /
• v.17 no.8
• /
• pp.609-615
• /
• 2009

Two types of nano composite were obtained by in situ chemical method in polyaniline (PANI)/dodecyl-benzenesulfonic acid (DBSA) system depending on the use of either ammonium persulfate (APS) or ferric chloride ($FeCl_3$) as the oxidant. In order to study the difference of the two composites in the surface characteristics, thermal stability, and electric properties, the composite films were studied by transmission electron microscopy (TEM), X-ray diffraction (XRD), thermogravimetric analysis (TGA), and temperature dependent DC electrical conductivity. The results revealed a large difference in the surface morphology, thermal stability, and the microstructure properties between the two composites, and these differences were considered responsible for the molecular order and conductivity.

• Carbon letters
• /
• v.14 no.4
• /
• pp.247-250
• /
• 2013

In this study, we present a facile method of fabricating graphene oxide (GO) films on the surface of polyimide (PI) via layer-by-layer (LBL) assembly of charged GO. The positively charged amino-phenyl functionalized GO (APGO) is alternatively complexed with the negatively charged GO through an electrostatic LBL assembly process. Furthermore, we investigated the water vapor transmission rate and oxygen transmission rate of the prepared (reduced GO $[rGO]/rAPGO)_{10}$ deposited PI film (rGO/rAPGO/PI) and pure PI film. The water vapor transmission rate of the GO and APGO-coated PI composite film was increased due to the intrinsically hydrophilic property of the charged composite films. However, the oxygen transmission rate was decreased from 220 to 78 $cm^3/m^2{\cdot}day{\cdot}atm$, due to the barrier effect of the graphene films on the PI surface. Since the proposed method allows for large-scale production of graphene films, it is considered to have potential for utilization in various applications.

• Journal of the Microelectronics and Packaging Society
• /
• v.25 no.4
• /
• pp.95-99
• /
• 2018

High thermal conductivity films with electrically insulating properties have a great potential for the effective heat transfer as substrate and thermal interface materials in high density and high power electronic packages. There have been lots of studies to achieve high thermal conductivity composites using high thermal conductivity fillers such alumina, aluminum nitride, boron nitride, CNT and graphene, recently. Among them, hexagonal-boron nitride (h-BN) nano-sheet is a promising candidate for high thermal conductivity with electrically insulating filler material. This work presents an enhanced heat transfer properties of ceramic/polymer composite films using h-BN nano-sheets and PVA polymer resins. The h-BN nano-sheets were prepared by a mechanical exfoliation of h-BN flakes using organic media and subsequent ultrasonic treatment. High thermal conductivities over $2.8W/m{\cdot}K$ for transverse and $10W/m{\cdot}K$ for in-plane direction of the cast films were achieved for casted h-BN/PVA composite films. Further improvement of thermal conductivity up to $13.5W/m{\cdot}K$ at in-plane mode was achieved by applying uniaxial compression at the temperature above glass transition of PVA to enhance the alignment of the h-BN nano-sheets.