• Journal of the Korean Society of Industry Convergence
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• v.27 no.2_2
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• pp.371-375
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• 2024

Epoxy resins are widely used in various fields due to their high adhesion, mechanical strength, and solvent resistance. However, as the volume decreases during the hardening process and the cooling process after hardening, stress is generated and when an external force is applied, the brittle material exhibits destruction behavior. To complement this, research has been conducted using inorganic nanofillers such as halloysite nanotube(HNT). HNT has a nanotube structure with the chemical formula of Al₂Si₂O₅(OH)₄·nH₂O and is a natural sediment of aluminosilicate. It has been used as additive to improve the mechanical properties of epoxy composites with exchange of amine group as a terminal functional group. In order to simplify complicated procedures of common wet method, a dry coating machine was designed and used for amine group exchange in previous research. In this study, they were applied as filler in epoxy composites, and mechanical properties such as tensile strength and flexural strength of composites were examined.

• Korean Chemical Engineering Research
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• v.47 no.2
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• pp.203-207
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• 2009

In the NCAs(non-conductive adhesive) for adhesion of Micro Electro Mechanical System(MEMS), there are some problems such as delamination and cracking, because of the differences of CTE(coefficients of thermal expansion) between NCAs and substrates. Addition of inorganic particle or flexibilizer have been performed to solve those problems. In this study, to improve the flexibility of epoxy adhesive, epoxy/siloxane composites were prepared by adding 1, 3, or 5 phr of amino modified siloxane(AMS). Glass transition temperatures(Tg), moduli and CTE of those composites were measured to confirm effects of siloxane on thermal/mechanical properties of siloxane/epoxy-composites. Tg of AMS/epoxy-composites decreased from $134^{\circ}C$ to $122^{\circ}C$ with increasing AMS contents and moduli decreased from 2,425 MPa to 2,143 MPa with increasing AMS contents. But CTE of AMS/epoxy-composites increased from $67ppm/^{\circ}C$ to $71ppm/^{\circ}C$ with increasing AMS contents. In short, the addition of siloxane is effective for enhancing the flexibility of epoxy but leads to the decrease of Tg.

• Composites Research
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• v.34 no.6
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• pp.434-439
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• 2021

Graphene and polyaniline with thermoelectric properties are one of the potential substitutes for inorganic materials for flexible thermoelectric applications. In this study, we studied the photo-induced thermoelectric effect of graphene-polyaniline composites. The graphene-polyaniline composites were synthesized by introducing an amine functional group to graphene oxide for covalently connecting graphene and polyaniline, reducing the graphene oxide, and then polymerizing the graphene oxide with aniline. Graphene-polyaniline composites were prepared by changing the aniline contents in order to expect an optimal photothermoelectric effect, and their structural properties were confirmed through FT-IR and Raman analysis. The photocurrent and photovoltage characteristics were analyzed by irradiating light asymmetrically without an external bias and the current and voltage with various aniline contents. While the photocurrent trends to the electrical conductivity of the graphene-polyaniline composites, the photovoltage was related to the temperature change of the graphene-polyaniline composite, which was converted into thermal energy by light.

• Proceedings of the Korean Radioactive Waste Society Conference
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• 2004.06a
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• pp.97-104
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• 2004

Double-layered polysulfone composite films, containing cerium activated yttrium silicate (CAYS) as a flour, were prepared from double casting of two polymeric solutions, and their morphology and physical strength were superior to those of single-layered composites. The prepared polymeric films consist of a dense bottom layer and a CAYS-holding top layer. The former is made of coagulating the polysulfone and methylene chloride binary solution and works as a supporter to improve the composite's physical strength, while the latter holding the inorganic fluor plays a role as an active site to detect the radioactive contamination. The prepared films revealed two distinguished, but tightly attached, double layers, their attachment being identified by morphology of the interface between two layers. As prepared by water immersion coagulation, the films have highly developed macropores, compared with a dense structure in the film prepared by evaporation. In the radionuclide detection test of the CAYS-impregnated composites, the films have reliable detection capacity at a radionuclide spotting test. The double-layered composites with the dense support layer show a better stability in holding the radionuclides spotted on the surface as well as an improvement in physical strength, compared with the single-layer composites having shortcomings such as being too porous or being brittle.

• Corrosion Science and Technology
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• v.17 no.2
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• pp.74-80
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• 2018

The electronic industries require environmentally-friendly and highly functional materials to enhance the quality of human life. Home appliances require insect repellent steels that work to protect household microwave ovens from incurring damage by insects such as fire ants and cockroaches in tropical regions. Thus, POSCO has developed new types of functional steels, coated with an array of organic-inorganic hybrid composites on the steel surface, to cover panels in microwave ovens and refrigerators. The composite solution uses a fine dispersion of hybrid solution with polymeric resin, inorganic and a pyrethroid additive in aqueous media. The hybrid composite solution coats the steel surface, by using a roll coater and is cured using an induction curing furnace on both the continuous galvanizing line and the electro-galvanizing line. The new steels were evaluated for quality performances, salt spray test for corrosion resistance and biological performance for both insect repellent and antimicrobial activity. The new steels with organic-inorganic composite coating exhibit extraordinarily biological functionalities, for both insect repellent and antimicrobial activities for short and long term tests. The composite-coating solution and experimental results are discussed and suggest that the molecular level dispersion of insecticide on the coating layer is key to biological functional performances.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2003.10a
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• pp.25-28
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• 2003

Carbon nanotubes(CNTs), since their first discovery, have been considered as new promising materials in various fields of applications including field emission displays, memory devices, electrodes, NEMS constituents, hydrogen storages and reinforcements in composites due to their extra-ordinary properties. The carbon nanotube reinforced nanocomposites have attracted attention owing to their outstanding mechanical and electrical properties and are expected to overcome the limit of conventional materials. Various application areas are possible for carbon nanotube reinforced nanocomposites through the functionalization of carbon nanotubes. Carbon nanotube reinforced polymer matrix nanocomposites have been fabricated by liquid phase process including surface functionalization and dispersion of CNTs within organic solvent. In case of carbon nanotube reinforced polymer matrix nanocomposites, the mechanical strength and electrical conducting can be improved by more than an order of magnitude. The carbon nanotube reinforced polymer matrix nanocomposites can be applied to high strength polymers, conductive polymers, optical limiters and EMI materials. In spite of successful development of carbon nanotube reinforced polymer matrix nanocomposites, the researches on carbon nanotube reinforced inorganic matrix nanocomposites show limitations due to a difficulty in homogeneous distribution of carbon nanotubes within inorganic matrix. Therefore, the enhancement of carbon nanotube reinforced inorganic nanocomposites is under investigation to maximize the excellent properties of carbon nanotubes. To overcome the current limitations, novel processes, including intensive milling process, sol-gel process, in-situ process and spark plasma sintering of nanocomposite powders are being investigated. In this presentation, current research status on carbon nanotube reinforced nanocomposites with various matrices are reviewed.

• Journal of the Korea Furniture Society
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• v.19 no.5
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• pp.358-364
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• 2008

Wood-inorganic material composite (WIC) was prepared by impregnating wood with copper sulfate ($CuSO_4\;5H_2O$) solution and by immersed wood in sodium carbonate($Na_2CO_3$) solution in order to introduce insoluble copper compounds {copper carbonate hydroxide, $CuCO_3\;Cu(OH)_2$} into the wood to give fungicidal effects in treated-wood. The weight percent gains (WPGs) of treated wood reached maximum value by impregnation of 20% copper sulfate solution and immersion in about 15% sodium carbonate solution for 24 hrs. Inorganic substances were present mainly in the lumina and cross-field pitting of tracheides. These substances were proved to be the insoluble copper carbonate hydroxide against water by the energy dispersive X-ray analyzer in conjunction with a scanning electron microscope (SEM-EDXA). The treated specimens showed high preservative effectiveness because the weight losses were hardly occurred by the fungi degradation test.

• Journal of Powder Materials
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• v.22 no.6
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• pp.403-407
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• 2015

Poly-methylmetacrylate (PMMA) is mainly applied in the plastic manufacturing industry, but PMMA is weak and gradually got discolor. The strength of PMMA can be improved through organic-inorganic hybrid nano composites with inorganic nano particles such as, $SiO_2$ or ZrO. However, inorganic nano particles are mostly agglomerated spontaneously. In this study, the zeta potential is controlled using different types of organic solvent with different concentrations, dispersibillity of $SiO_2$ nano particles on the PMMA particle are analyzed. When 3 M acetic acid is used, absolute value of the zeta potential is higher, $SiO_2$ nano particle is well attached, and dispersed on the PMMA particle surface. Results indicate that the absolute value of the zeta potential affects the stability of $SiO_2$ dispersion.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2006.06a
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• pp.232-233
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• 2006

In recent years the interest in organic/inorganic hybrid materials has increased at a fast rate. Nano organic-inorganic hybrid composites have shown advantages for preparing hard coating layers. Especially, nano hybrid composite has low environmental pollution. It has high transparency, hardness, toughness, thermal dissociation temperature, hydrophobicity by using nano sized inorganic material. There are many ways in which these materials may be synthesized, a typical one being the use of silica and silanes using the sol-gel process. The structure of sol-gel silica evolves as a result of these successive hydrolysis and condensation reactions and the subsequent drying and curing. The sol-gel reactions are catalyzed by acids and produce silica sol solutions. The silica sol grows until they reach a size where a gel transition occurs and a solid-like gel is formed. Colloidal silica(CS)/silane sol solutions were synthesized in variation with parameters such as different acidity and reaction time. In order to understand their physical and chemical properties, sol-gel coating films were fabricated on glass. From all sol-gel solutions, seasoning effect of sol-gel coating layer on glass was observed.

• Composites Research
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• v.19 no.6
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• pp.32-37
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• 2006

This paper summarizes the processing inorganic continuous fibers from Korean minerals. Continuous filament fibers have been produced from two rocks, basalt and quartz diorite porphyry(QDP), by melting method. The essence of the method is that the vitrified materials was placed into the bushing, platinum/rhodium alloy crucible with a nozzle, and heated electrically to a temperature which allowed fiber spinning. Vitrified basalt without additive was suitable for producing continuous filament fiber. However doping quartz diorite porphyry with boric oxide yielded a material which could be pulled continuously.