• Carbon letters
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• 제15권1호
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• pp.1-14
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• 2014

Carbon nanofibers (CNFs) with diameters in the submicron and nanometer range exhibit high specific surface area, hierarchically porous structure, flexibility, and super strength which allow them to be used in the electrode materials of energy storage devices, and as hybrid-type filler in carbon fiber reinforced plastics and bone tissue scaffold. Unlike catalytic synthesis and other methods, electrospinning of various polymeric precursors followed by stabilization and carbonization has become a straightforward and convenient way to fabricate continuous CNFs. This paper is a comprehensive and brief review on the latest advances made in the development of electrospun CNFs with major focus on the promising applications accomplished by appropriately regulating the microstructural, mechanical, and electrical properties of as-spun CNFs. Additionally, the article describes the various strategies to make a variety of carbon CNFs for energy conversion and storage, catalysis, sensor, adsorption/separation, and biomedical applications. It is envisioned that electrospun CNFs will be the key materials of green science and technology through close collaborations with carbon fibers and carbon nanotubes.

• Journal of the Optical Society of Korea
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• 제10권1호
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• pp.1-10
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• 2006

Optical transparency and high diffraction efficiency are two essential factors for high performance of the photopolymer. Optical transparency mainly depends on the miscibility between polymer binder and photopolymerized polymer, while diffraction efficiency depends on the refractive index modulation between polymer binder and photopolymerized polymer. For most of organic materials, the large refractive index difference between two polymers accompanies large structural difference that leads to the poor miscibility and thus poor optical quality via light scattering. Therefore, it is difficult to design a high-performance photopolymer satisfying both requirements. In this work, first, we prepared a new phase-stable photopolymer (PMMA) with large refractive index modulation and investigated the optical properties. Our photopolymer is based on modified poly (methyl methacrylate) as a polymer binder, acryl amide as a photopolymerizable monomer, triethanolamine as initiator, and yellow eosin as a photosensitizer at 532 nm. Diffraction efficiency over 85% and optical transmittance over 90% were obtained for the photopolymer. Second, Organic-inorganic nanocomposite films were prepared by dispersing an aromatic methacrylic monomer and a photo- initiator in organic-inorganic hybrid sol-gel matrices. The film properties could be controlled by optimizing the content of an organically modified silica precursor (TSPEG) in the sol-gel matrices. The photopolymer film modified with the organic chain (TSPEG) showed high diffraction efficiency (> 90%) under an optimized condition. High diffraction efficiency could be ascribed to the fast diffusion and efficient polymerization of monomers under interference light to generate refractive index modulation. The TSPEG modified photopolymer film could be successfully used for holographic memory.

• 대한치과기공학회지
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• 제29권1호
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• pp.121-131
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• 2007

A preparation process's conditions of aqueous sol which contains anatase-type nano titania particles with photocatalyic properties was established by using Yoldas process, so called, DCS(Destabilization of Colloidal Solution) process in this study. And crystal size change and phase transformation of titania particles in aqueous titania sol depending on reaction conditions was investigated by a light scattering method and XRD analysis of frozen dried powders, respectively. This sol with photo catalytic nano titania particles was used to the following hydrophilic hybrid coating film's fabrication and its properties was evaluated. Subsequently, for coating film using the above mentioned aqueous titania sol, non-aqueous titania sol was prepared without any chemical additives and its time stability according to aging time was investigate. By using the above mentioned aqueous titania sol and non-aqueous sol, a complex oxide coating sol for metal and ceramic substrate and a organic-inorganic hybrid coating sol for polymer substrate was prepared and it's hydrophilicity depending on UV irradiation conditions was evaluated. As a conclusions, the following results were obtained. (1)Aqueous titania sol The average particle size of titania in formed aqueous titania sol was distributed between 20$\sim$90nm range depending on reaction conditions. And the crystal phase of titania powders obtained by frozen drying method was changed from amorphous state to anatase and subsequently transformed to rutile crystal phase and it is attributed to concentration gradient in aqueous sol. (2)Non-aqueous titania sol Non-aqueous titania sol was prepared using methanol as a solvent and a little distilled water for hydrolysis and nitric acid as a catalyst were used. The obtained non-aqueous titania sol was stable at room temperature for 20 days. Additionally, non-aqueous titania sol with addition of chealating reagent such as acethylaceton and ethylene glycol prolonged the stability of sol by six months. (3)Complex sol and hybrid sol with super hydrophilicity The above mentioned aqueous titania sol as a main photocataylic component and non-aqueous titania sol as a binder for coating process was used to prepare a complex sol used for metal, ceramic and wood material substrate and also to prepare the organic-inorganic hybrid sol for polymer substrate such as polycarbonate and polyethylene, in which process APMS(3-Aminopropyltrimethoxysilane), GPTS(3-Glycidoxypropyl-trimethoxysilane) as a hydrophilic silane compound and HEMA(2-Hydroxyethyl methacrylate) as a forming network in hybrid coating film were used. The hybrid coating film such as prepared through this process showed a superhydrophilicity below 1$10^{\circ}$ depending on processing conditions and a pencil's hardness over 6 H.

• 한국수소및신에너지학회논문집
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• 제19권2호
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• pp.118-123
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• 2008

For the hydrogen recirculation system of the PEMFC (polymer electrolyte membrane fuel cell), the ejector is useful to improve the efficiency of the fuel cell system. However, conventional ejector does not keep its entrainment ratio good when the various power duties is required by the fuel cell system. In this study, the variable multi-ejector acceptable in the whole duty range required from the fuel cell hybrid mini-bus is developed. Consequently, the performance of the developed ejector is verified by the experiments based on the real operating conditions.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2013년도 추계학술대회 논문집
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• pp.95-96
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• 2013

In this paper, an operation algorithm for the fuel cell-battery hybrid power system is proposed. As the output current slope of the fuel cell is normally limited to protect the fuel cells' defection, efficient power distribution algorithm between the fuel cell and battery is very important for the successful hybrid control operation. For the experimentation, a 1kW dc-dc converter with 500W fuel cell stack and 1kWh Li-polymer battery is implemented.

• 한국섬유공학회:학술대회논문집
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• 한국섬유공학회 2002년도 봄 학술발표회 논문집
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• pp.459-461
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• 2002

A new class of materials based on organic and inorganic species combined at a molecule level has obtained more attention recently[1]. HPA(heteropolyacid) shows unmatched applied perspective in terms of synthesis chemistry, analysis chemistry, biology, medicine and materials science[2]. As a potential photochemical material, the hybrid system of HPA and polymer has been investigated. However, the design and synthesis of heteropolyacid-based hybrids, which are at the forefront of the materials chemistry research, is still in its infancy. (omitted)

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2005년도 춘계학술대회
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• pp.357-360
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• 2005

Hyundai Motor Company developed the second generation of fuel cell hybrid electric vehicle based on Tucson SUV in 2004. This vehicle has cold start capability below -10C and its driving performances including maximum speed and accelerating time are almost similar to conventional Tucson SUV's performances without any sacrifice in terms of cabin space. Especially. the cold start capability was realized by utilizing only internal power sources such as fuel cell power and high voltage lithium ion polymer battery. In this paper, we will briefly introduce specifications of Tucson FCEV and its driving performances based on field test and simulations.

• 신재생에너지
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• 제1권1호
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• pp.32-36
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• 2005

We studied the optoelectronic properties of hybrid solar cells formed by mixing cadmium sulfide [CdS] nanorods with a conjugated polymer, poly-2-methoxy, 5-[2'-ethy[hexyloxy]-1,4-p-phenylenevinylene[MEH-PPV]. CdS nanorods were grown vertically on Ti substrates by electrochemical deposition through a porous alumina template. Absorption spectrum of the composite layer was the same as the superposition of the absorption spectrum of each individual layer. The photoluminescence signal from MEH-PPV film was reduced as a result of the mixing. The energy conversion efficiency of MEH-PPV improved from $0.0012\%$ to about $0.60\%$ when combined with the vertically aligned CdS nanorods.

• Macromolecular Research
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• 제13권2호
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• pp.96-101
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• 2005

Thin-film humidity sensors were prepared using inorganic/organic hybrid polyelectrolytes, which were prepared from the sol-gel reaction of copolymers of [2-(methacryloyloxy)ethyl]dimethylpropylammonium bromide (MEPAB), n-butyl methacrylate (BMA), and 3-(trimethoxysilyl)propyl methacrylate (TSPM) with tetraethyl ortho-silicate (TEOS). The humidity-sensitive polyelectrolytes were composed of the copolymers having the following mole ratios of MEPAB, BMA, and TSPM: 60/30/10, 55/30/15, and 50/30/20. We found that the impedance varied with the content of MEPAB or TEOS; it ranged from $10^{7} to 10^{3}\Omega$ between 20 and $95\%$ relative humidity, which is the range required for a humidity sensor operating at ambient humidity. In addition we investigated a number of characteristics of these humidity sensors, such as their hysteresis, response time, temperature dependence, frequency dependence, water durability, and long-term stability.

• Composites Research
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• 제26권5호
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• pp.273-278
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• 2013

PLA/PP polymer blends in various ratios (PLA:PP = 9:1, 4:1, 3:1, and 1:1), and their composites (PLA:PP = 1:1) with sisal fiber (10, 15 and 20 wt%) were fabricated using MAPP as compatibilizer. The aim of the work was to reduce the cost of biodegradable composites as well as to improve the impact strength of PLA using PP, a relatively cheaper thermoplastic. The developed composites were characterized for their morphological and mechanical properties. The tensile strength and modulus of the blends were decreased with increasing PP content whereas the strain at break and impact strength are increased. The tensile strength, modulus and water absorption were increased for hybrid composites with increasing fiber content.