• Elastomers and Composites
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• v.46 no.2
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• pp.125-131
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• 2011

The effects of chopped kenaf fiber concentration on mechanical property of polypropylene (PP) composite are investigated. The addition of kenaf increased the tensile strength, flexural modulus, impact strength, specific gravity, and HDT, while decreased the elongation%, flexural strength, and melt flow index. The increase of mechanical properties is due to increased surface area contacting between fiber and polymer matrix and fiber-fiber interaction. Volatile extractives in the kenaf seemed to decrease the interfacial adhesion between kenaf surface and PP.

• Journal of Sasang Constitutional Medicine
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• v.14 no.1
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• pp.100-111
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• 2002

1. The Purpose of study An experimental study has done to examine the effect of defense on gastric mucosal damage of Jowesungcheong-tang. 2. The Material and Method of study Mice had intragastric injected with JST extract before indome thacin treatment which induces hemorrh age erosion artificially. General morphology, infiltrative cell in mucosa, the distribution of UEA-I, COX-1, MAC-1. ICAM, and Apoptotic cell were objected (Ahhreviation) JST :Jowesungcheong-tang, UEA-I : ulex europaeus agglutinin-I, COX-1: cyclooxyhenase-1, ICAM : intercellular adhesion molecule-1, GPE : Gastropathy elicitated mice 3. The results and Conclusions of study 1) The degree of hemorrhage erosion in GPE-group had increased conspicuously in gastric gland proper. JST -group were the same as normal 2) The noticeable increase of granular lecocytes and lymphocytes in GEP-group were seen, but in JST group, the configuration is decreased 3) The decrease of UEA-I positive reacted cells, COX-1, surface epithelial cells and the increase of MAC-l positive cells, ICAM-l positive cells had shown in GPE-group, but in JST-group UEA-I positive cells, COX-1 surface epithelial cells were in creased and MAC-1 positive cells, ICAM-l positive cells were decreased than GPE-group. 4) A number of apoptotic cells were distributed in hemorrhage erosion. The remarkable decrease of apoptotic cells were shown in JST-group.

• Tribology and Lubricants
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• v.36 no.2
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• pp.55-63
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• 2020

Recently, graphene has attracted considerable attention owing to its unique electrical, optical, thermal, and mechanical properties. The broad spectrum of applications from optics, sensors, and electronics to biodevice have been proposed based on these properties. In particular, graphene has been proposed as a protective coating layer and solid lubricant for microdevices and nanodevices because of its high mechanical strength, chemical inertness, and low friction characteristics. During the past decade, extensive efforts have been made to explore the tribological characteristics of graphene under various conditions and to expand its applicability. In addition to the experimental approaches, the molecular simulations performed provide fundamental insights into the friction and wear characteristics of graphene resulting from molecular interactions. This work is a review of the studies conducted over the past decade on the tribological characteristics of graphene using molecular simulation. These studies demonstrate the principal mechanisms of the superlubricity of graphene and help clarify the influences of surface conditions on tribological behavior. In particular, the investigation of the effects of the number of layers, strength of adhesion to the substrate, surface roughness, and commensurability provides deeper insights into the tribological characteristics of graphene. These fundamental understandings can help elucidate the feasibility of graphene as a protective coating layer and solid lubricant for microdevices and nanodevices.

• Bulletin of the Korean Chemical Society
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• v.34 no.3
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• pp.801-809
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• 2013

We investigate sensitivity and limit of detection (LOD) of trace copper (Cu) metal using pristine carbon nanotube (CNT) and acidified CNT (ACNT) electrodes. Squarewave based anodic stripping voltammetry (SWASV) is used to determine the stripped Cu concentration. Prior to performing the SWASV measurements, its optimal conditions are determined and with that, effects of potential scan rate and $Cu^{2+}$ concentration on stripping current are evaluated. The measurements indicate that (1) ACNT electrode shows better results than CNT electrode and (2) stripping is controlled by surface reaction. In the given $Cu^{2+}$ concentration range of 25-150 ppb, peak stripping current has linearity with $Cu^{2+}$ concentration. Quantitatively, sensitivity and LOD of Cu in ACNT electrode are 9.36 ${\mu}A\;{\mu}M^{-1}$ and 3 ppb, while their values are 3.99 ${\mu}A\;{\mu}M^{-1}$ and 3 ppb with CNT electrode. We evaluate the effect of three different water solutions (deionized water, tap water and river water) on stripping current and the confirm types of water don't affect the sensitivity of Cu. It turns out by optical inspection and cyclic voltammetry that superiority of ACNT electrode to CNT electrode is attributed to exfoliation of CNT bundles and improved interfacial adhesion occurring during oxidation of CNTs.

• Korean Chemical Engineering Research
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• v.46 no.2
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• pp.397-401
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• 2008

The nanoparticle-agglomerates are synthesized by laser ablation, which have the morphology of dendrite structure. The filtration performance of a conventional micron-fibrous metal filter was improved by adhering nanoparticle-agglomerates onto the filter surface. The Sintered-Nanoparticle-Agglomerates-adhered Filter (SNAF) adhered with nanostructured material was made by heat treatment after deposition of nanoparticle-agglomerates sintered in aerosol phase onto the micron-fibrous metal filter. As the sintering temperature increases, the pressure drop of the filter increases a little but the filtration efficiency increases remarkably. This is due to increase of surface area of nanoparticle-agglomerates adhered onto the micron-fibrous metal filter.

• Journal of the Korean Ceramic Society
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• v.55 no.2
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• pp.178-184
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• 2018

In the present study, $TiB_2-Co$ composite coatings were thermally sprayed onto the surface of a 304 stainless steel substrate using an atmospheric plasma spray (APS). The phase analysis of the powders and plasma-sprayed coatings was performed using X-ray diffractometry analysis. The microstructures of the coatings were studied by a scanning electron microscope (SEM). The average particle size and flowability of the feedstocks were also measured. Both $TiB_2-32Co$ and $TiB_2-45Co$ (wt.%) coatings possessed typical dense lamellar structures and high-quality adhesion to the substrate. The oxidation behaviors of the coatings were studied at $900^{\circ}C$ in an atmospheric environment. In addition, the cross-sectional images of the oxidized coatings were analyzed by SEM. A thin and well-adhered layer was formed on the surface of both $TiB_2-Co$ coatings, confirming satisfactory high-temperature oxidation resistance. The kinetic curves corresponding to the isothermal oxidation of the coatings illustrated a short transient stage from rapid to slow oxidation during the early portion of the oxidation experiment.

• Current Industrial and Technological Trends in Aerospace
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• v.8 no.1
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• pp.96-103
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• 2010

The propulsion systems such as upper stages of launch vehicles, orbiters, spacecrafts have to operate in the zero gravity environment. Because the flight condition where the vehicle undergoes is different from the normal gravity state, many studies have been being in progress. Fluid behavior in the zero gravity condition is differently shown in the normal gravity state because the importance of the intermolecular force, such as adhesion, cohesion, and surface tension is enlarged. In this paper, we investigate the characteristic of fluid behavior and describe effects and problems on the liquid propulsion system due to these fluid behavior. We also check which studies are in progress in order to solve these problems.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2004.10a
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• pp.100-103
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• 2004

In this work, the effects of oxy-fluorination on surface characteristics of carbon fibers were investigated in mechanical interfacial properties of carbon fibers-reinforced composites. The surface properties of the carbon fibers were determined by X-ray photoelectron spectroscopy (XPS), FT-IR. and contact angle measurements. And their mechanical interfacial properties of the composites were studied in interlaminar shear strength (ILSS) and critical stress intensity factor $(K_{IC})$. As experimental results, the $F_{1S}/C_{1S}$ ratio of carbon fiber surfaces was increased by oxy-fluorination, due to the development of the oxygen containing functional groups. The mechanical interfacial properties of the composites, including ILSS and $K_{IC}$, had been improved in the oxy-fluorination on fibers. These results could be explained that the oxy-fluorination was resulted in the increase of the adhesion between fibers and matrix in a composite system.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2005.11a
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• pp.23-26
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• 2005

In this work, effects of oxygen plasma on surfc1ce characteristics of carbon fibers were investigated in impact strength of carbon fibers-reinforced composites. The surface properties of the carbon fibers were determined by acid/base values, FT-IR, and X-ray photoelectron spectroscopy (XPS). Also, the mechanical properties of the composites were studied by impact strength measurements. As experimental results, the $O_{IS}/C_{IS}$ ratio of the carbon fiber surfaces treated by oxygen plasma was increased compared to that of untreated ones, possibly due to development of oxygen-containing functional groups. The mechanical properties of the composites, including impact strength had been improved by the oxygen plasma on fibers. These results could be explained that the oxygen plasma resulted in the increase of the adhesion of between fibers and matrix in a composite system.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1997.10a
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• pp.1067-1071
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• 1997

A new type of gripper for micrometer-size objects is developed using piezoelectric multi-layer benders. It is composed of three chopsticks, two of which are designed to grip micro-objects. The third one is reserved for helping the two when objects are released from the chopsticks. It is well known that a micro object is much easier to grasp than to release it after holding it. The electrostatic force between the chopsticks and an object is believed to be the main cause of adhesion in a dry environment. The surface tension becomes very important when liquids are present or in a liquid. The third auxiliary chopsticks is introduced to solve there surface effects. All the three chopsticks are made of tungsten wires with sharpened ends by etching. When grasping microparts, the two chopsticks are utilized, and, when releasing them anywhere the parts are located, the third one reduces the electrostatic force between the objects and the chopstick may be to help the other two chopsticks to hold an objects in a desired orientation. We constructed the three chopstick gripoer for micro objects and test their function by holding and releasing an object of a diameter of 100 micrometers. We make use of open loop voltage control. The bender displacement resolution is sub-micrometer. The gripping forces, about tens of mN are obtained. The experiment shows that the third auxiliary chopstick functions effectively.