• Tribology and Lubricants
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• v.5 no.2
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• pp.94-100
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• 1989

Friction and Wear behavior of continuous graphite fiber composites was studied for different fiber orientations against the sliding direction. The effect of fiber orientation on friction and wear of the composite and on the deformation of the counterface was investigated experimentally. Pin on disk type testing machine was built and employed to generate the friction and wear data. A graphite fiber composite plate was produced by the bleeder ply molding in an autoclave and machined into rectangular pin specimens with specific fiber orientations, i.e., normal, transverse, and longitudinal directions. Three different wear conditions were employed for two different periods of time, 24 and 48 hours. The wear track of the worn specimens and the metal counterface was examined with a scanning electron microscope (SEM) to observe the damaged fibers on the surface and wear film generation on the counterface. Wear mechanism of the composite during sliding wear is proposed based on the experimental results.

• Journal of Powder Materials
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• v.4 no.2
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• pp.106-112
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• 1997

$Cu-Al_20_3 $ composite powders were prepared by hydrogen reduction of $Cu^{2+}$ from ammoniacal copper sulfate solution on alumina core using autoclave. The copper reduction rate and the properties of copper layer were investigated using Scanning Electron Microscope(SEM), X-ray diffractometer, size and chemical analyzers. The reduction rate of $Cu^{2+}$ showed the maximum value when the molar ratio of [$NH_3$]/[$Cu^{2+}$] was 2. In order to prevent the agglomeration of Cu powder and ethane reduction rate, $Fe^{2+}$ and anthraquinone which act as catalysis were added in the solution. Catalysis was effectively chanced with the addition of two elemerts at a time. Optimum conditions obtained in this study were hydrogen reduction temperature of 205$^{\cire}C$, stirring speed of 500 rpm and hydrogen partial pressure of 300 psi. Obtained $Cu-Al_20_3 $ composite Powders were found to have the uniform and continuous copper coating layer of nodule shape with 3~5 $\mu$m thickness.

• Journal of the Korean Applied Science and Technology
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• v.23 no.4
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• pp.362-367
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• 2006

This paper describes the experiments for investigating the effects of thermal stability of several commercial carpet mate materials. The melting point and thermal decomposition temperature was measured by means of a differential scanning calorimeter(DSC) in air condition. The DSC data and burning test results of nylon bulked continuous filament(N-BCF) yarn 100%, nylon(NY), polypropylene(PP), and a new material named polytrimethyleneterephthalate(PTT) were analysed to obtain the effect on their thermal stability. Conclusively, we observed that PTT and PP were approximately $380^{\circ}C$ and $240^{\circ}C$ to start the thermal decomposition, respectively. In other words, PTT is thermally the most stable material for carpet manufacturing.

• The Journal of the Acoustical Society of Korea
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• v.24 no.1E
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• pp.1-6
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• 2005

The inner hair cell stereocilia of the guinea pig cochlea was examined under a scanning electron microscope (SEM) after loud tone exposure onto the ear drum of the animal. Before and after guinea pigs were exposed to intensive and continuous tone such as 106 dB SPL in intensity, the functioning of the cochlea was monitored by N1-N2 audiograms. The structural damage of the stereocilia of inner hair cells (IHCs) and outer hair cells (OHCs) was examined using the SEM in x 1500 magnification. The comparison between the functional change of the cochlea and the structural damage of the IHC stereocilia is done by means of photographic observation. It can be shown that the functional change might be related to the structural damage of the IHC stereocilia after intensive acoustic trauma.

• Proceedings of the KWS Conference
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• 2002.10a
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• pp.456-462
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• 2002

In the present work, a low cost and fine pitch bumping process by electroless Ni/immersion Au UBM (under bump metallurgy) and stencil printing for the solder bump on the Al pad is discussed. The Chip used this experimental had an array of pad 14x14 and zincate catalyst treatment is applied as the pretreatment of Al bond pad, it was shown that the second zincating process produced a dense continuous zincating layer compared to first zincating. Ni UBM was analyzed using Scanning electron microscopy, Energy dispersive x-ray, Atomic force microscopy, and X-ray diffractometer. The electroless Ni-P had amorphous structures in as-plated condition. and crystallized at 321 C to Ni and Ni$_3$P. Solder bumps are formed on without bridge or missing bump by stencil print solder bump process.

• Proceedings of the Korea Concrete Institute Conference
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• 2003.11a
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• pp.98-101
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• 2003

The Alkali-Aggregate Reaction (AAR) may cause a serious failure in the concrete structures. Several researchers in some nations have performed the continuous studies to prevent failure of a concrete structures by the AAR distress as well as the studies to manifest the mechanism. The ASTM Standards to prevent failure by potential AAR aggregates were established in 1950. The KS F2545 and KS F 2546 were established to test the susceptibility of aggregate to potential AAR in 1982. But the researches on the AAR have not been performed affluently in Korea because the distress due to AAR has seldom been reported officially. In this study, the Chemical Method and Scanning Electron Microscopy (SEM) were used to verifying the cause of the pattern crack on the surface and internal crack in the plain concrete pavement. It can be concluded that the distress of a specific site in plain concrete pavement was mainly due to AAR, and the chemical method and SEM may be the effective tools for verifying the cause of AAR distresses.

• 한국정보디스플레이학회:학술대회논문집
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• 2003.07a
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• pp.401-406
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• 2003

New planar discharge structured AC-PDP has been developed by using TFCS (Thick Film Ceramic Sheet) technology. By applying TFCS to AC-PDP, a sustaining electrode and scanning electrodes are embedded in the TFCS. It is shown that panel performances such as electrical and optical characteristics are superior to commercialized coplanar AC-PDP as well as cost reduction. Moreover the experimental result shows panel performances can be improved drastically by continuous development.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.32 no.9
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• pp.796-803
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• 2008

Ultrasonic testing uses the directivity of the ultrasonic wave, which propagates in on direction. The directivity is expressed as the relationship between the propagate direction and its sound pressure. The directivity of an ultrasonic wave is related to the choice of probe arrangement, testing sensitivity and scanning pitch and correct measurement of defect size and location. This paper describes on the directivity measurement of ultrasonic wave using the visualization method. The directivity of shear wave emitted from the angle beam transducer were constant during propagation. The difference of directivity was existed between 2 MHz and 4 MHz angle beam transducers. When these experimental results were compared with the theory which was based on the continuous wave, it showed good agreement with theoretical directivity on the principal lobe.

• Laser Solutions
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• v.6 no.2
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• pp.19-26
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• 2003

6061 aluminum alloy sheets were I-square butt welded using a continuous wave Nd:YAC laser. Heat inputs were varied from 54.6 to 80 J/mm for butt welding using different sets of the laser power and the weld speed. I-square butt welds were also made with and without Ar shielding gas. The effect of Ar shielding gas and heat input on the mechanical properties and formability was investigated using Vickers hardness, transverse-weld tensile and bulge test. Porosity on the weld beads and sections and hot crack on the fracture surfaces of transverse-weld tensile test specimens were investigated using optical and scanning electron microscopy The experimental results showed that mechanical properties and formability of 6061 aluminum alloy laser welds were degraded compared to those of base metal. Mechanical properties and formability of 6061 aluminum alloy laser welds were not substantially changed when Ar shielding gas was supplied or heat inputs were varied.

• Bulletin of the Korean Chemical Society
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• v.35 no.8
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• pp.2251-2256
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• 2014

We have successfully decorated reduced graphene oxide (RGO) with silver nanoparticles (AgNPs) by microwaving silver alkylcarbamate for 13 seconds using 1-amino-4-methylpiperazine. Uniform AgNPs (20-40 nm) were effectively prepared, and 1-amino-4-methylpiperazine acted as a reaction medium, reducing agent, and stabilizer. Particle size and morphology were correlated with the silver alkylcarbamate concentration and microwave time. The graphene/AgNPs composites were characterized by Raman, X-ray diffraction, and scanning electron microscopy to confirm that the AgNPs were uniformly decorated onto the graphene. Measurements of the transparent conductive property at room temperature indicated that these graphene/AgNPs nanosheets with 55.45% transmittance were electrically continuous with a sheet resistance of approximately $43{\Omega}/{\Box}$.