• Carbon letters
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• v.14 no.2
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• pp.105-109
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• 2013

Effects of the amount of nickel powder (Ni) in Ni-carbon fiber (CF) hybrid filler systems on the conductivity(or resistivity) and thermal coefficient of resistance (TCR) of filled high density polyethylene were studied. Increases of the resistivity and TCR with increasing Ni concentration at a given hybrid filler content were observed. Using the fiber contact model, we showed that the main role of Ni in the hybrid filler system is to decrease the interfiber contact resistance when Ni concentration is less than the threshold point. The formation of structural defects leading to reduced reinforcing effect resulted in both a reduction of strength and an increase of the coefficient of thermal expansion in the composite film; these changes are responsible for the increases of both resistivity and TCR with increasing Ni concentration in the hybrid filler system.

• The Journal of the Convergence on Culture Technology
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• v.8 no.5
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• pp.749-754
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• 2022

High adhesion and water resistance of the skin surface are required for wearable and skin-attachable electronic patches in various medical applications. In this study, we report a stretchable electronic patch that mimics the drainable structure pattern of the hexagonal channels of frog's pads and the sucker of an octopus based on carbon-based conductive polymer composite materials. The hexagonal channel structure that mimics the pads of frogs drains water and improves adhesion through crack arresting effect, and the suction structure that mimics an octopus sucker shows high adhesion on wet surfaces. In addition, the high-adhesive electronic patch has excellent adhesion to various surfaces such as silicone wafer (max. 4.06 N/cm²) and skin replica surface (max. 1.84 N/cm²) in dry and wet conditions. The high skin-adhesive electronic patch made of a polymer composite material based on a polymer matrix and carbon particles can reliably detect electrocardiogram (ECG) in dry and humid environments. The proposed electronic patch presents potential applications for wearable and skin-attachable electronic devices for detecting various biosignals.

• Proceedings of the Korean Vacuum Society Conference
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• 2016.02a
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• pp.354.2-354.2
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• 2016

Mycosporine-like amino acids (MAAs) are small secondary metabolites produced by organisms that live in environments with high volumes of sunlight, is an important group of novel bioactive compounds having immense biotechnological poten-tials due to their UV screening properties and Polypyrrole (PPy) is a type of organic polymer formed by polymerization of pyrrole. A novel composite nanofilm (~60 nm) of mycosporine-like amino acid (MAA) and polypyrrole is synthesized by interfacial polymerization technique. This composite nanofilm is conductive and has strong photoresponse. A photoelectric UV sensor is fabricated by depositing the composite film onto a silicon chip. This UV sensor shows good sensitivity, selectivity and stability for UV detection.

• Polymer(Korea)
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• v.36 no.5
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• pp.599-605
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• 2012

The physicochemical properties such as surface hardness, solvent mechanical wear resistance, and resistance to scratch properties of poly(3,4-ethylenedioxythiophene) (PEDOT) thin film prepared by vapor phase polymerization (VPP) was effectively improved by post-treatment of various metal alkoxide sol solutions. Metal oxide layer derived from sol-gel process of metal alkoxide was generated on the PEDOT thin film layer by VPP, resulting in improving mechanical properties of the conductive thin films without any deterioration of their original surface resistance. Several kinds of silicone and titanium alkoxide derivatives with various functional groups were used as metal alkoxide sol sources. Among them, PEDOT-metal oxide composite thin film derived tetraethyl orthosilicate showed the best performance in the terms of surface resistance, transmittance, and various physicochemical properties. The effect of metal alkoxide content in washing solution, oxidant content and drying temperature have been investigated in order to optimize the various properties of PEDOT-metal oxide composite thin film.

• Applied Chemistry for Engineering
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• v.33 no.2
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• pp.210-215
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• 2022

Two types of lignin materials with a different surface ionic character were used and polypyrrole layer was introduced on the lignin surface to obtain polypyrrole@lignin and polypyrrole@lignosulfonate composites using a simple chemical oxidation polymerization, reported in a previous article. Polypyrrole was effectively prepared regardless of the lignin type and the resulting composites were investigated using scanning electron microscope (SEM), cyclic voltammetry (CV), and impedance analysis. SEM and CV results showed that the obtained composites retained stable electrochemical properties after introduction of polypyrrole on the lignin surface. Impedance analyses showed that the surface properties of composites were dependent on lignin characteristics. In addition, the composites were embedded in agarose, an gelifying agent, to obtain conductive gels. It was found that the conductive gels possessed an electrical conductivity and also retained stable electrochemical properties, which indicated that the conductive gels might be useful for some applications.

• Transactions on Electrical and Electronic Materials
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• v.16 no.6
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• pp.351-354
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• 2015

In this study, alumina plates 9~25 μm in size were used as thermal fillers, and epoxy resin was used as a polymer matrix. Oriented alumina plate/epoxy composites were prepared using a rolling method. The effect of ordering alumina plates increased with alumina plate size. The thermal conductivity and flexural strength of the composites were investigated. The horizontal thermal conductivity of the oriented composite was significantly higher than the vertical thermal conductivity. The horizontal thermal conductivity of the 75 wt% alumina content was 8.78 W/mk, although the vertical thermal conductivity was 1.04 W/mk. Ordering of the alumina plate using a rolling method significantly improved the thermal conductivity in the horizontal direction. The flexural strengths of the ordered alumina/epoxy composites prepared at different curing temperatures were measured.

• Composites Research
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• v.32 no.3
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• pp.127-133
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• 2019

Although carbon nanotubes(CNTs) have outstanding theoretical mechanical and electrical properties, CNT fibers(CNTFs) have not yet reached that level. Particularly, tensile strength is only about 10% or less, so studies for making up for it are being actively conducted. As a way for improving mechanical strength, methods such as synthesizing long CNT, orientation, chemical cross-linking, hydrogen bonding and polymer infiltration are being studied. In this review paper, we report preparation methods for highly conductive and strong CNTF/Carbon composites through coating and infiltration followed by carbonization of carbon precursor polymers such as polyacrylonitrile (PAN) and polydopamine (PDA) on CNTFs.

• Korean Journal of Metals and Materials
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• v.46 no.12
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• pp.817-822
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• 2008

Metal matrix composite (MMC) materials having low electrical contact resistance based on 316L stainless steel (STS) matrix alloy with $ZrB_2$ particles were fabricated for PEMFC (Polymer Electrolyte Membrane Fuel Cell) separator by powder metallurgy (PM). The effects of the boride particle addition into the matrix alloy on microstructure, surface morphology, and interfacial contact resistance (ICR) between the samples and gas diffusion layer (GDL) were investigated. Both conventional and PM 316L STS samples showed high ICR due to the existence of non-conductive passive film on the alloy surface. The addition of the boride particles, however, remarkably reduced ICR of the samples. SEM observation revealed that the boride particles were protruded out of the matrix surface and particle density existing on the surface increased with increasing the boride content, causing increase of the total contact area between the conductive particles and GDL. ICR of the samples also decreased with increasing the boride content resulted from the increased contact area.

• Journal of Adhesion and Interface
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• v.11 no.4
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• pp.174-180
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• 2010

The effect of carbon nanotube surface treatment on the interface and thermal conductivity of carbon nanotube-based poly(methylmethacrylate) (PMMA) composites was investigated. Coagulation and atomic-transfer radical polymerization (ATRP) was applied to modify the surface of multi-wall carbon nano-tube. The composite of ATRP method used carbon nanotube showed the higher transparency and thermal conductivities than that of the coagulation method used. In comparison to the thermal conductivity of pure PMMA, 0.21 W/mK, the ATRP carbon nanotube used PMMA/MWNT composite showed a thermal conductivity of 0.38 W/mK. The interface between carbon nanotube and PMMA was observed by scanning electron microscope and uniform dispersion of carbon nanotube was observed without any void in the PMMA matrix. It may be beneficial to transport the phonon without any scattering and it may result in a higher thermal conductivity.

• Elastomers and Composites
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• v.55 no.1
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• pp.59-66
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• 2020

Herein, we investigated the thermal conductivity and thermal stability of natural rubber composite systems containing hybrid fillers of boron nitride (BN) and aluminum nitride (AlN). In the hybrid system, the bimodal distribution of polygonal AlN and planar BN particles provided excellent filler-packing efficiency and desired energy path for phonon transfer, resulting in high thermal conductivity of 1.29 W/mK, which could not be achieved by single filler composites. Further, polyethylene glycol (PEG) was compounded with a commonly used naphthenic oil, which substantially increased thermal conductivity to 3.51 W/mK with an excellent thermal stability due to facilitated energy transfer across the filler-filler interface. The resulting PEG-incorporated hybrid composite showed a high thermal degradation temperature (T₂) of 290℃, a low coefficient of thermal expansion of 26.4 ppm/℃, and a low thermal distortion parameter of 7.53 m/K, which is well over the naphthenic oil compound. Finally, using the Fourier's law of conduction, we suggested a modeling methodology to evaluate the cooling performance in thermal management system.