• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2012.05a
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• pp.293-294
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• 2012

탄소섬유 복합재의 기계적 강도를 높이기 위하여 탄소섬유상에 ZnO 나노구조체를 도금하는 연구를 수행하였다. 전기도금을 이용하여 정전위법으로 탄소섬유상에 ZnO 나노구조체를 도금시킨 후 에폭시 YD-128과 경화제 KBH1089를 이용하여 탄소섬유 복합재를 제작하였다. 제작된 탄소섬유 복합재는 실험규격 ASTM D2344를 준수하였으며 ILSS(Interaminar Shear Strength)시험으로 강도를 측정하였다. 본 연구결과 탄소섬유에 인가되는 coulomb양을 조절함으로서 ZnO 나노구조체 형상을 제어할 수 있었으며, 일반탄소섬유 복합재와 ZnO 나노구조체가 도금된 탄소섬유 복합재의 강도를 비교하였을 때 ZnO 나노구조체가 도금 된 탄소섬유 복합재에서 더 높은 강도 값을 얻을 수 있었다.

• Applied Science and Convergence Technology
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• v.27 no.4
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• pp.61-64
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• 2018

The basic principle and concept for hydrogen production via water-splitting process are introduced. In particular, recent research activities and their progress in the photoelectrochemical water-splitting process are investigated. The material perspectives of semiconducting photocatalysts are considered from metal oxides, including titanium oxides, to carbon compounds and perovskites. Various structural configurations, from conventional photoanodes with metal cathodes to tandem and nanostructures, are also studied. The pros and cons of each are described in terms of light absorption, charge separation/photoexcited electron-hole pair recombinations and further solar-to-hydrogen efficiency. In this research, we attempt to provide a broad view of up-to-date research and development as well as, possibly, future directions in the photoelectrochemical water-splitting field.

• Journal of the Korean Ceramic Society
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• v.53 no.4
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• pp.393-399
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• 2016

We have successfully fabricated 3D (3-dimensional) nanostructures of $TiO_2$ coated with a $g-C_3N_4$ layer via hydrothermal and sintering methods to enhance photoelectrochemical (PEC) performance. Due to the coupling of $TiO_2$ and $g-C_3N_4$, the nanostructures exhibited good performance as the higher conduction band of $g-C_3N_4$, which can be combined with $TiO_2$. To fabricate 3D nanostructures of $g-C_3N_4/TiO_2$, $TiO_2$ was first grown as a double layer structure on FTO (Fluorine-doped tin oxide) substrate at $150^{\circ}C$ for 3 h. After this, the $g-C_3N_4$ layer was coated on the $TiO_2$ film at $520^{\circ}C$ for 4 h. As-prepared samples were varied according to loading of melamine powder, with values of loading of 0.25 g, 0.5 g, 0.75 g, and 1 g. From SEM and TEM analysis, it was possible to clearly observe the 3D sample morphologies. From the PEC measurement, 0.5 g of $g-C_3N_4/TiO_2$ film was found to exhibit the highest current density of $0.12mA/cm^2$, along with a long-term stability of 5 h. Compared to the pristine $TiO_2$, and to the 0.25 g, 0.75 g, and 1 g $g-C_3N_4/TiO_2$ films, the 0.5 g of $g-C_3N_4/TiO_2$ sample was coated with a thin $g-C_3N_4$ layer that caused separation of the electrons and the holes; this led to a decreasing recombination. This unique structure can be used in photoelectrochemical applications.

• Korean Chemical Engineering Research
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• v.55 no.1
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• pp.115-120
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• 2017

In recent, it is worldwide issued that nanoscale science and technology as a solution have supported to increase the sensing performance in carbon nanotube based biosensor system. Containing material chemistry in various nanostructures has formed their high potentials for stabilizing and activating biocatalyst as a bioreceptor for medical, food contaminants, and environmental detections using electrode modification technologies. Especially, the large surface area provides the attachment of biocatalysts increasing the biocatalyst loading. Therefore, nano-scale engineering of the biocatalysts have been suggested to be the next stage advancement of biosensors. Here, we would like to study the electrical mechanism depending on the exposure methods (soaking or dropping) to the sample solution to the assembled carbon nanotubes (CNTs) on the gold electrodes of biosensor for a simple and highly sensitive detection. We performed various experiments using polar and non-polar solutions as sampling tests and identified electrical response of assembled CNTs in those solutions.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.29 no.12
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• pp.803-808
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• 2016

In this work, one dimension $In_2O_3$ nanostructures as detecting materials for indoor toxic gases were synthesized by an electrospinning process. The morphology of electrospun $In_2O_3$ nanofibers was controlled by electrolyte composition, applied voltage and working distance between a nozzle and a substrate. The synthesized $In_2O_3$ nanofibers-based paste with/without carbon black additives was prepared for the integration on a sensor device. The integration of $In_2O_3$ sensing materials was conducted by a hand-printing of the paste into the interdigit Au electrodes patterned on Si wafer. Gas sensing properties on CO and HCHO gases were characterized at $300^{\circ}C$. The evaluated sensing properties such as sensitivity, response time and recovery time were improved in $In_2O_3$ nanofiber pastes with carbon black, compared to the paste without carbon black.

• Composites Research
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• v.37 no.3
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• pp.155-161
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• 2024

Boron nitride nanotubes and carbon nanotubes are the most representative one-dimensional nanostructures, and have received great attention as reinforcement for multifunctional composites for their excellent physical properties. The two nanotubes have similar excellent mechanical stiffness, strength, and heat conduction properties. Therefore, the reinforcing effect of these two nanotubes is greatly influenced by the properties of their interface with the polymer matrix. In this paper, recent comparative studies on the reinforcing effect of boron nitride nanotubes and carbon nanotubes through experimental pull-out test and in-silico simulation are summarized. In addition, the conflicting aspect of the two different nanotubes with structural defects in their side wall is discussed on the viscoelastic damping performance of nanocomposites.

• Proceedings of the Materials Research Society of Korea Conference
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• 2011.10a
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• pp.16.2-16.2
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• 2011

Graphene has attracted significant attention due to its unique characteristics and promising nanoelectronic device applications. For practical device applications, it is essential to synthesize high-quality and large-area graphene films. Graphene has been synthesized by eloborated mechanical exfoliation of highly oriented pyrolytic graphite, chemical reduction of exfoliated grahene oxide, thermal decomposition of silicon carbide, and chemical vapor deposition (CVD) on metal substrates such as Ni, Cu, Ru etc. The CVD has advantages over some of other methods in terms of mass production on large-areas substrates and it can be easily separated from the metal substrate and transferred to other desired substrates. Especially, plasma-enhanced CVD (PECVD) can be very efficient to synthesize high-quality graphene. Little information is available on the synthesis of graphene by PECVD even though PECVD has been demonstrated to be successful in synthesizing various carbon nanostructures such as carbon nanotubes and nanosheets. In this study, we synthesized graphene on $Ni/SiO_2/Si$ and Cu plate substrates with CH4 diluted in $Ar/H_2$ (10%) by using an inductively-coupled PECVD (ICPCVD). High-quality graphene was synthesized at as low as $700^{\circ}C$ with 600 W of plasma power while graphene layer was not formed without plasma. The growth rate of graphene was so fast that graphene films fully covered on substrate surface just for few seconds $CH_4$ gas supply. The transferred graphene films on glass substrates has a transmittance at 550 nm is higher 94%, indicating 1~3 monolayers of graphene were formed. FETs based on the grapheme films transferred to $Si/SiO_2$ substrates revealed a p-type. We will further discuss the synthesis of graphene and doped graphene by ICPVCD and their characteristics.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.37 no.6
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• pp.615-620
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• 2013

There is considerable interest in developing energy sources capable of larger power densities. In our previous works, we proved that by coupling an exothermic chemical reaction with 1D nanostructures, a self-propagating reactive wave can be driven along its length with a concomitant electrical pulse of high specific power, which we identified as a thermopower wave. Herein, we discuss details about many different aspects of a thermopower wave. Different alignment degree in vertically aligned CNT films is evaluated in the reactive wave speed and correlated with its thermal reaction that affects the change in the magnitude of energy generation. The effects of the temperature-dependent properties of chemical fuels and CNTs are evaluated. Furthermore, we explore the convection and radiation portions in this thermal wave as well as the synchronization between the thermal reaction transfer and the oscillation of the electrical signal.

• Proceedings of the KIEE Conference
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• 2007.11a
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• pp.90-91
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• 2007

Nano-sized conical-type tungsten(W) field-emitters based on carbon nanotubes(CNTs) are fabricated with the configuration of CNTs/catalyst/buffer/W-tip by adopting various buffer layers, such as TiN, Al, Al/TiN, and Al/hi/TiN. This study focuses on elucidating how the buffer layers affect the structural properties of CNTs and the electron-emission characteristics of CNT-emitters. Field-emission scanning electron microscopy(FESEM) and high-resolution transmission electron microscopy(HRTEM) are used to monitor the nanostructures and surface morphologies of all the catalysts and CNTs grown. The crystalline structure of CNTs is also characterized by Raman spectroscopy. Furthermore, the measurement of field-emission characteristics for all the field-emitters fabricated shows that the emitter using the Al/Ni/TiN stacked buffer reveals the most excellent performances, such as maximum emission current of $202{\mu}A$, threshold field of 2.08V/${\mu}m$, and long-term (up to 24h) stability of emission current.

• Journal of the Korean Ceramic Society
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• v.46 no.3
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• pp.225-228
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• 2009

The processing and characterization of ceramic nanocomposites, which produce bulk nanostructures with attractive mechanical properties, have been emphasized and introduced at Prof. Mukherjee's Lab at UC Davis. The following subjects will be introduced in detail in Part II, III, and IV. In Part II, the paper will describe a three-phase alumina-based nanoceramic composite demonstrating superplasticity at a surprisingly lower temperature and higher strain rate. The next part will show that an alumina-carbon nanotube-niobium nanocomposite produced fracture toughness values that are three times higher than that of pure nanocrystalline alumina. It was possible to take advantage of both fiber-toughening and ductile-metal toughening in this investigation. In the fourth section, discussed will be a silicon-nitride/silicon-carbide nanocomposite, produced by pyrolysis of liquid polymer precursors, demonstrating one of the lowest creep rates reported so far in ceramics at the comparable temperature of $1400^{\circ}C$. This was first achieved by avoiding the oxynitride glass phase at the intergrain boundaries. One important factor in the processing of these nanocomposites was the use of the electrical field assisted sintering method. This allowed the sintering to be completed at significantly lower temperatures and during much shorter times. These improvements in mechanical properties will be discussed in the context of the results from the microstructural investigations.