• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2012.05a
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• pp.324-325
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• 2012

다이아몬드 마이크로 블레이드의 절삭 효율을 향상시키고 소결 공정 중 윤활제의 유동성과 젖음성이 다이아몬드 마이크로 블레이드의 물성에 미치는 영향을 연구하기 위해 Cu/Sn 금속 결합재에 표면을 부식시킨 $WS_2$와 부식을 시키지 않은 $WS_2$ 윤활제를 각각 동일한 체적 분율로 첨가하였다. 윤활제의 표면 개질에 따른 마이크로 블레이드 결합재의 내마모성과 굽힘 강도 시험을 행하였고, 실착 절삭 시험을 위한 마이크로 블레이드 시편을 제작하여 수명 및 효율을 평가하였다. Cu/Sn 금속 결합재 파면에서의 $WS_2$ 입자 방향 분석을 통해 표면 개질 과정을 거친 $WS_2$가 압축소결 공정 중 압축 방향에 수직하게 위치하려는 경향이 크게 나타났으며, 이는 소결체의 강도와 경도를 향상시켰다. 마이크로 블레이드의 절삭 효율 및 수명을 평가하기 위한 실착 절삭 시험 결과, 윤활제 표면 부식처리는 처리하지 않은 경우에 비하여 절삭성능은 비슷하게 관찰되었으나 결합재와의 계면 결함을 줄이므로써 블레이드의 수명을 연장시킬 수 있었다.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.16 no.12
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• pp.1212-1217
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• 2004

This study investigated the improvement effect of a small portion of surfactant on the supercooling and the phase change temperature of TMA 30 wt% clathrate compound when surfactant is added to the clathrate compound. The experiments are carried out under various conditions; the concentration of additive ranges between 0.08～0.12 wt% and the temperature of heat source ranges between -8 and -6$^{\circ}C$. The experimental results show that the phase change temperature with the surfactant of 0.1 wt% is lower by 1$^{\circ}C$ than TMA 30 wt% and the supercooling is reduced by 1$0^{\circ}C$.

• Journal of Adhesion and Interface
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• v.10 no.2
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• pp.90-97
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• 2009

Dispersion and self-sensing evaluation for single-carbon fiber reinforced in three different acid-treated CNT-epoxy nanocomposites were investigated by electro-micromechanical techniques and wettability tests. Self-sensing based on contact resistivity exhibited more noise for single carbon fiber/acid-treated CNT-epoxy composites than it did for untreated CNT. However, the apparent modulus was higher the acid treated case than the untreated case which is attributed to better stress transfer. The interfacial shear strength (IFSS) between carbon fibers and the CNT-epoxy was lower than that between carbon fiber and neat epoxy due to the increased viscosity associated with the addition of the CNT. The CNT-epoxy nanocomposite exhibited more hydrophobicity than did neat epoxy. Change in the thermodynamic work of adhesion was consistent with changes in the IFSS but disproportional to that of the apparent modulus. The optimum condition of acid treatment on the need can be obtained instead of the maximum condition.

• Applied Chemistry for Engineering
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• v.24 no.4
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• pp.363-369
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• 2013

In this work, the effects of ozone treatments on mechanical interfacial properties of carbon fibers-reinforced nylon-6 matrix composites were investigated. The surface properties of ozone treated carbon fibers were studied by Fourier transform infrared spectroscopy (FT-IR) and X-ray photoelectron spectroscopy (XPS). Mechanical interfacial properties of the composites were investigated using critical stress intensity factor ($K_{IC}$). The cross-section morphologies of ozone-treated carbon fiber/nylon-6 composites were observed by scanning electron microscope (SEM). As a result, $K_{IC}$ of the ozone-treated carbon fibers-reinforced composites showed higher values than those of as-received carbon fibers-reinforced composites due the enhanced $O_{1s}/C_{1s}$ ratio of the carbon fiber by the ozone treatments. This result concludes that the mechanical interfacial properties of nylon-6 matrix composites can be controlled by suitable ozone treatments on the carbon fibers.

• Clean Technology
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• v.10 no.2
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• pp.61-72
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• 2004

In this study, aqueous/semi-aqueous cleaning agents which consist of organic solvent, surfactant, cosurfactant, and water were developed by changing formulation parameters such as organic solvent type and contents, surfactant type and contents, and cosurfactant/surfactant(A/S) ratio, etc.. And physical properties and flux removal of the formulated cleaning agents have been evaluated. Also, the performance of oil-water separation from the rinse water contaminated during the cleaning process was evaluated for its recycling. The formulated cleaning agents in this work expected to have good penetration because of their low viscosity and low surface tension values of 30.2~32.5 dyne/cm. The flux removal with the terpene type cleaning agent was higher than that with hydrocarbon type cleaning agent and two commercial products (CPA(commercial product A), CPB(commercial product B)). And the performance of oil-water separation by gravity settling from the rinse water contaminated with formulated cleaning agent and soils was shown to be very good. The cleaning agents developed in this work were applied to surface mounting technology(SMT) cleaning process for manufacturing electronic parts at L electronic company. As a result, the newly developed cleaning agents showed two times better cleaning speed for removal of solder cream than the conventional ond containing ethanol and IPA(isopropyl alcohol). In addition, malodor and VOC problems generated by the previous organic cleaning agents have been solved in the manufacturing field through introduction of the non-volatile and environmental-friendly cleaning agents to the field.

• Journal of the Korean Electrochemical Society
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• v.22 no.3
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• pp.87-103
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• 2019

Nonaqueous organic electrolyte solution in commercially available lithium-ion batteries, due to its flammability, corrosiveness, high volatility, and thermal instability, is demanding to be substituted by safer solid electrolyte with higher cycle stability, which will be utilized effectively in large-scale power sources such as electric vehicles and energy storage system. Of various types of solid electrolytes, composite solid electrolytes with polymer matrix and active inorganic fillers are now most promising in achieving higher ionic conductivity and excellent interface contact. In this review, some kinds and brief history of solid electrolyte are at first introduced and consequent explanations of polymer solid electrolytes and inorganic solid electrolytes (including active and inactive fillers) are comprehensively carried out. Composite solid electrolytes including these polymer and inorganic materials are also described with their electrochemical properties in terms of filler shapes, such as particle (0D), fiber (1D), plane (2D), and solid body (3D). In particular, in all-solid-state lithium batteries using lithium metal anode, the interface characteristics are discussed in terms of cathode-electrolyte interface, anode-electrolyte interface, and interparticle interface. Finally, current requisites and future perspectives for the composite solid electrolytes are suggested by help of some decent reviews recently reported.

• Composites Research
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• v.30 no.5
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• pp.323-330
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• 2017

In this study, multiscale analysis in which the information obtained from molecular dynamics simulation is applied to the continuum mechanics level is conducted to investigate the effects of clustering of silicon carbide nanoparticles reinforced into polypropylene matrix on mechanical behavior of nanocomposites. The elastic behavior of polymer nanocomposites is observed for various states of nanoparticulate agglomeration according to the model reflecting the degradation of interphase properties. In addition, factors which mainly affect the mechanical behavior of the nanocomposites are identified, and new index 'clustering density' is defined. The correlation between the clustering density and the elastic modulus of nanocomposites is understood. As the clustering density increases, the interfacial effect decreased and finally the improvement of mechanical properties is suppressed. By considering the random distribution of the nanoparticles, the range of elastic modulus of nanocomposites for same value of clustering density can be investigated. The correlation can be expressed in the form of exponential function, and the mechanical behavior of the polymer nanocomposites can be effectively predicted by using the nanoparticulate clustering density.

• Journal of Adhesion and Interface
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• v.16 no.3
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• pp.101-107
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• 2015

Epoxy resin toughening agents such as core/shell nanoparticles, CTBN epoxy, polyester polyols, and polyurethane have been widely used in order to compensate for the brittleness and improve the impact resistance of the epoxy resin. In this work, a few tougheners mentioned above were individually added into adhesive compositions to observe the effects of physical and mechanical properties. Both flexural strength and flexural modulus were measured with UTM while impact strength was analyzed with Izod impact tester. The obtained results showed that the addition of toughening agents afforded positive performance in terms of flexibility and impact resistance of the cured epoxy resin. Furthermore, DMA experiments suggested that the trends of storage modulus data of each epoxy resin composition coincided with the trends of flexural modulus data. FE-SEM images showed that toughening agents formed circled-shape particles when it was cured in epoxy resin composition at high temperature by phase separation. The existence of particles in the cured samples explains why epoxy resin with toughener has higher impact resistance.

• Restorative Dentistry and Endodontics
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• v.33 no.1
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• pp.45-53
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• 2008

The purpose of this study was to determine the effects on the elastic moduli of the adhesive and the hybrid layer from thermocycling. Twenty one human molars were used to create flat dentin surfaces. Each specimen was bonded with a light-cured composite using one of three commercial adhesives (OptiBond FL [OP], Clearfil SE Bond [CL], and Xeno III [XE]). These were sectioned into two halves and subsequently cut to yield 2-mm thickness specimens; one specimen for immediate bonding test without thermocycling and the other subjected to 10,000 times of thermocycling. Nanoindentation test was performed to measure the modulus of elasticity of the adhesive and the hybrid layer, respectively, using an atomic force microscope. After thermocycling, XE showed a significant decrease of the modulus in the adhesive layer (p < 0.05). Adhesives containing hydrophilic monomers are prone to hydrolytic degradation. It may result in the reduced modulus of elasticity, which leads to the mechanically weakened bonding interface.

• Composites Research
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• v.27 no.4
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• pp.168-173
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• 2014

The optimum condition of glass fiber/epoxy composites was investigated according to mixing ratio of two epoxy matrices. Novolac type epoxy and isocyanate modified epoxy were used as composites matrix. Based on chemical composition of mixing matrix, optimum mixing ratio of epoxy resins was obtained through various experiments. In order to investigate thermal stability and interface of epoxy resin, glass transition temperature was observed by DSC instrument, and static contact angle was measured by reflecting microscope. Change of IR peak and $T_g$ was conformed according to different epoxy mixing ratio. After fabrication of glass fiber/epoxy composites, tensile, compression, and flexural properties were tested by UTM by room and high temperature. The composites exhibited best mechanical properties when epoxy mixing ratio was 1:1.