• Journal of Powder Materials
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• v.11 no.2
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• pp.118-123
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• 2004

A formation of aluminum hydroxide by hydrolysis reaction in the water has been studied by using nano aluminum powder fabricated by pulsed wire evaporation(PWE) method. The hydroxide type and morphology depending on temperature and pH were examined by structural analysis. The Boehmite($Al_2O_3$.$H_2O$ or AIO(OH)) was predominantly formed in high temperature region over 4$0^{\circ}C$, while the Bayerite($Al_2O_3$.$H_2O$ or $Al(OH)_3$) below $30^{\circ}C$ of hydrolysis temperature. The Boehmite formation was preferred to the Bayerite in acidic solution in the same hydrolysis temperature. The slowly formed Bayerite phase showed facet crystalline structure, while the fast formed Boehmite was fine fiber with a large aspect ratio of several nm in diameter and several hundred nm in length, and with much larger specific surface area(SSA) than that of Bayerite. The highest SSA was about $420m^2$/g.

• Journal of the Korean Geosynthetics Society
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• v.6 no.1
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• pp.39-43
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• 2007

Geocomposites of needle punched and spunbonded nonwovens having the reinforcement and drainage functions were manufactured by use of thermal bonding method. The physical properties (e.g. tensile, tear and bursting strength, permittivity) of these multi-layered nonwovens were dependent on the processing parameters of temperatures, pressures, bonding periods etc. - in manufacturing by use of thermal bonding method. Therefore, it is very meaningful to optimize the processing parameters and physical properties of the geocomposites by thermal bonding method. In this study, an algorithm has been developed to optimize the process of the geocomposites using an artificial neural network (ANN). Geocomposites were employed to examine the effects of manufacturing methods on the analysis results and the neural network simulations have been applied to predict the changes of the nonwovens performances by varying the processing parameters.

• Journal of the Optical Society of Korea
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• v.11 no.3
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• pp.138-141
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• 2007

We suggest that supercontinuum can be used for absorption spectroscopy to observe the exciton levels of a semiconductor nano-structure. Exciton absorption spectrum of a GaAs/AlGaAs quantum well was observed using supercontinuum generated by a microstructrured fiber pumped by a femtosecond (fs) pulsed laser. Significantly narrower peaks were observed in the absorption spectrum from 11 K up to room temperature than photoluminescence (PL) spectrum peaks. Because supercontinuum is coherent light and can readily provide high enough intensity, this method can provide a coherent ultra-broad band light source to identify exciton levels in semiconductors, and be applicable to coherent nonlinear spectroscopy such as electromagnetically induced transparency (EIT), lasing without inversion (LWI) and coherent photon control in semiconductor quantum structures.

• Korean Journal of Materials Research
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• v.25 no.10
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• pp.531-536
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• 2015

GNPs have several excellent mechanical properties including high strength, a good young's modulus, thermal conductivity, corrosion resistance, electronic shielding, etc. In this study, CF/GNP/Epoxy composites were manufactured using GNP weight ratios of 0.15 wt%, 0.3 wt%, 0.5 wt%, 0.7 wt% and 1 wt%. The composites were manufactured with a mechanical method (3-roll-mill). Tensile, impact and wear tests were performed according to ASTM standards D3039, D256 and D3181, respectively. The results show that the CF/GNP0.3wt%/Epoxy composites have good mechanical properties, e.g., tensile strength and impact and wear resistance. In this study, both carbon fabric and GNPs were used as reinforcements in the composites. The mechanical properties increased and weight loss decreased as the GNP content in the resin films was increased.

• Carbon letters
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• v.18
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• pp.30-36
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• 2016

Well-dispersed Ag₃VO₄ nanoparticles @polyacrylonitrile (PAN) nanofibers were synthesized by an easily controlled, template-free method as a photo-catalyst for the degradation of methylene blue. Their structural, optical, and photocatalytic properties have been studied by X-ray diffraction, transmission electron microscopy, field-emission scanning electron microscopy equipped with rapid energy dispersive analysis of X-ray, photoluminescence, and ultraviolet-visible spectroscopy. The characterization procedures revealed that the obtained material is PAN nanofibers decorated by Ag₃VO₄ nanoparticles. Photocatalytic degradation of methylene blue investigated in an aqueous solution under irradiation showed 99% degradation of the dye within 75 min. Finally, the antibacterial performance of Ag₃VO₄ nanoparticles @PAN composite nanofibers was experimentally verified by the destruction of Escherichia coli. These results suggest that the developed inexpensive and functional nanomaterials can serve as a non-precious catalyst for environmental applications.

• Macromolecular Research
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• v.16 no.4
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• pp.345-352
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• 2008

Poly(lactic-co-glycolic acid) (PLGA) tubes (5 mm in diameter) were fabricated using an electro spinning method and used as a scaffold for artificial blood vessels through the hybridization of smooth muscle cells (SMCs) and endothelial cells (ECs) differentiated from canine bone marrow under previously reported conditions. The potential clinical applications of these artificial blood vessels were investigated using a canine model. From the results, the tubular-type PLGA scaffolds for artificial blood vessels showed good mechanical strength, and the dual-layered blood vessels showed acceptable hybridization behavior with ECs and SMCs. The artificial blood vessels were implanted and substituted for an artery in an adult dog over a 3-week period. The hybridized blood vessels showed neointimal formation with good patency. However, the control vessel (unhybridized vessel) was occluded during the early stages of implantation. These results suggest a shortcut for the development of small diameter, tubular-type, nanofiber blood vessels using a biodegradable material (PLGA).

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.18 no.4
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• pp.109-116
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• 2019

The mechanical deformation of a battery separator causes internal short-circuiting of the cathode - anode, which directly affects the explosion/ignition of batteries. To increase the mechanical properties of the separator fabricated by electro-spinning, use of a thermal pressing method is inevitable. Therefore, this research aims to maximize the mechanical strength of a porous separator by finding the proper thermal press temperatures given to Electro-spun Polyacrylonitrile (PAN) nanofibers. The different thermal press temperatures $25^{\circ}C$, $50^{\circ}C$, $75^{\circ}C$, and $100^{\circ}C$ were applied to the electro-spun fiber at 30 MPa pressure for one hour. The higher the temperature, the higher the resultant tensile strength; however, a higher temperature also lowered the strain and porosity. Thus, the membrane thermal pressed at $50^{\circ}C$ showed the best mechanical properties and the second highest porosity. Using the data, $50^{\circ}C$ was judged as the best thermal pressing temperature in terms of performance.

• Transactions of the Korean hydrogen and new energy society
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• v.32 no.1
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• pp.86-91
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• 2021

In order to save the energy in vehicles using renewable energy, it is necessary to reduce the weight of parts with polymer matrix composites. Carbon nanotube (CNT) is the nano-scale reinforcement used to increase the interlaminar strength of fiber reinforced composites or enhance the fracture toughness of polymer. However, since the degree of improvement in mechanical properties varies according to the various experimental conditions such as shape of reinforcement, types of matrix and dispersion of reinforcement, research to find the optimal conditions is essentially needed. In this study, CNT/epoxy composites with different CNT concentration were fabricated under the same conditions, and the optimal CNT content (2 wt%) was found through Mode 1 fracture toughness test. Furthermore, through optical microscopy, it was confirmed that the fracture toughness was rather decreased due to the CNT aggregation when the CNT content exceeded 2 wt%.

• Advances in nano research
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• v.14 no.3
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• pp.261-271
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• 2023

The present study follows three main goals. First, an analytical solution with high accuracy is developed to assess the effects of embedding pre-strained shape memory alloy (SMA) wires on the critical buckling temperatures of rectangular sandwich plates made of soft core and graphite fiber/epoxy (GF/EP) face sheets based on piecewise low-order shear deformation theory (PLSDT) using Brinson's model. As the second goal, this study compares the effects of SMAs on the thermal buckling of sandwich plates with those of carbon nanotubes (CNTs). The glass transition temperature is considered as a limiting factor. For each material, the effective ranges of operating temperature and thickness ratio are determined for real situations. The results indicate that depending on the geometric parameters and thermal conditions, one of the SMAs and CNTs may outperform the other. The third purpose is to study the thermal buckling of sandwich plates with advanced hybrid SMA/CNT/GF/EP composite face sheets. It is shown that in some circumstances, the co-incorporation of SMAs and CNTs leads to an astonishing enhancement in the critical buckling temperatures of sandwich plates.

• Membrane Journal
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• v.22 no.6
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• pp.404-414
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• 2012

In order to investigate $SO_2$ removal, PEI hollow fiber membranes were produced by a dry-wet phase inversion method. The membrane support layer on surface was coated with PEBAX1657$^{(R)}$ and PEG blending materials. Modules were prepared for the single gas permeation characteristics of composite membrane according to temperature and pressure. As a result, $SO_2$ permeance and $SO_2/N_2$ selectivity were 220~1220 GPU and 100~506 through operating condition, respectively. Moreover, $SO_2/CO_2/N_2$ mixture gas was used to compare the performance of separation properties according to temperature, pressure and retentate flow rate difference. $SO_2$ removal efficiency was increased with pressure and temperature.