• Proceedings of the Korean Society For Composite Materials Conference
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• 2001.05a
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• pp.268-271
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• 2001

When compared to other composite materials such as FRP and MMC, hybrid composite material is more attractive one due to the high specific strength and the resistance to fatigue. However, the fracture mechanism of hybrid composite material is extremely complicated because of the bonding structure of metals and FRP. Recently, nondestructive technique has been used to evaluate the fracture mechanism of these composite materials. In this study, AE technique has been used to clarify the fracture mechanism and the degree of damage for Al 7075/CFRP hybrid composite material. It was found that AE event, energy and amplitude among AE parameters were effective to evaluate fracture process of Al 7075/CFRP composite material. In addition, the relationship between the AE signal and the characteristics of failure surface using optical microscope was discussed.

• Applied Microscopy
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• v.43 no.1
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• pp.9-13
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• 2013

The helium ion microscope (HIM) has recently emerged as a novel tool for imaging and analysis. Based on a bright ion source and small probe, the HIM offers advantages over the conventional field emission scanning electron microscope. The key features of the HIM include (1) high resolution (ca. 0.25 nm), (2) great surface sensitivity, (3) great contrast, (4) large depth-of-field, (5) efficient charge control, (6) reduced specimen damage, and (7) nanomachining capability. Due to the charge neutralization by flood electron beam, there is no need for conductive metal coating for the observation of insulating biological specimens by HIM. There is growing evidence that the HIM has substantial potential for high-resolution imaging of uncoated insulating biological specimens at the nanoscale.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2004.10a
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• pp.552-555
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• 2004

The reliability issue of the probe tip/recording media interface is one of the most crucial concerns in the Atomic Force Microscope (AFM)-based recording technology. In this work, the tribological characteristics of the probe/media interface were investigated by performing wear tests using an AFM. The ranges of applied normal load and sliding velocity for the wear test were 10 to 50nN and 2 to 20$\mu$m/s respectively. The damage of the probe tip was quantitatively as well as qualitatively characterized by Field Emission Scanning Probe Microscope (FESEM) analysis and calculated based on Archard s wear equation. It was shown that the wear coefficient of the probe tip was in the order of 10$^{-4}$ ~ 10$^{-3}$ , and significant contamination at the end of the probe tip was observed. Thus in order to implement the AFM-based recording technology, tribological optimization of the probe/media interface must be achieved.

• Journal of Powder Materials
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• v.18 no.1
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• pp.49-55
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• 2011

Ni nanowires were fabricated using anodic aluminum oxide (AAO) membrane as a template by electrochemical deposition. The nanowires were formed within the walls of AAO template with 200 nm in pore diameter. After researching proper voltage and temperature for electrochemical deposition, the length of Ni nanowires was controlled by deposition time and the supply of electrolyte. The morphology and microstructure of Ni nanowires were investigated by field emission scanning electron microscope (FE-SE), X-ray diffraction (XRD) and transmission electron microscope (TEM).

• Proceedings of the KIEE Conference
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• 2008.05a
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• pp.185-186
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• 2008

Use of the carbon nanotube is superior to general powder state materials of dispersion property. Because its ratio of diameter and length(aspect ratio) is very large, it has been known as a type of ideal nano-reinforcement composite. It used solution mixing method for specimen fabrication. To research dispersion property, we used FE-SEM(Field Emission Scanning Electron Microscope) and AFM(Atomic Force Microscope). As a result, this tendency confirms new conductivity network in which the carbon nanotube between carbon black constitute molecules shows a bond by similar constructive property.

• Korea-Australia Rheology Journal
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• v.16 no.4
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• pp.201-212
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• 2004

Properties of polymer based nanocomposites depend on dispersion state of embedded fillers. In order to examine the effect of dispersion state on rheological properties, a new bi-mode FENE dumbbell model was proposed. The FENE dumbbell model includes two separate ensemble sets of dumbbells with different fric­tion coefficients, which simulate behavior of well dispersed and aggregated carbon nanotubes (CNTs). A new parameter indicating dispersion state of the CNT was proposed to account for degree of dispersion quantitatively as well as qualitatively. Rheological material functions in elongational, steady shear, and oscillatory shear flows were obtained numerically. The CNT/epoxy nanocomposites with different dis­persion state were prepared depending on whether a solvent is used for the dispersion of CNTs or not. Dis­persion state of the CNT in the epoxy nanocomposites was morphologically characterized by the field emission scanning electronic microscope and the transmission electron microscope images. It was found that the numerical prediction was in a good agreement with experimental results especially for steady state shear flow.

• Journal of the Korean Society for Heat Treatment
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• v.23 no.6
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• pp.344-349
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• 2010

Silicon carbide nanowires were grown by heat treatment of the films at $1200^{\circ}C$ after amorphous SiC thin films were deposited on graphite substrate by radio frequency magnetron sputtering at $600^{\circ}C$. It was confirmed that SiC nanowires with the diameter of 20-60 nm and length of about 50nm were grown from Field Emission Scanning Election Microscope (FE-SEM) and Transmission Election Microscope (TEM) observation. The diameter of nanowires was increased as heat treatment time is increased. The nanowires were identified to ${\beta}$-SiC single crystalline from X-Ray Diffraction(XRD) analysis. It was observed from this study that deposition temperature of samples was critical to the crystallization of nanowires. On the other hand, the effect of deposition time was insignificant.

• Proceedings of the Materials Research Society of Korea Conference
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• 2010.05a
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• pp.48.1-48.1
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• 2010

Cu has been used for metallic interconnects in ULSI applications because of its lower resistivity according to the scaling down of semiconductor devices. The resistivity of Cu lines will affect the RC delay and will limit signal propagation in integrated circuits. In this study, we investigated the characteristics of electroplated Cu films according to the variation of concentration of organic additives. The plating electrolyte composed of $CuSO_4{\cdot}5H_2O$, $H_2SO_4$ and HCl, was fixed. The sheet resistance was measured with a four-point probe and the material properties were investigated with XRD (X-ray Diffraction), AFM (Atomic Force Microscope), FE-SEM (Field Emission Scanning Electron Microscope) and XPS (X-ray Photoelectron Spectroscopy). From these experimental results, we found that the organic additives play an important role in formation of Cu film with lower resistivity by EPD.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2014.11a
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• pp.186-186
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• 2014

In this study, corrosion behaviors of Ti-xNb alloys for biomaterials. The Ti-xNb binary alloys contained from 10 wt. % to 50 wt. % contents were manufactured by vacuum arc-melting furnace. Microstructures of the alloys were examined by optical microscope (OM) and field emission scanning electron microscope (FE-SEM). In order to identify the phase constitutents of the Ti-xNb alloys, X-ray diffractometer (XRD) with a Cu K radiation was used. The corrosion behaviors were investigated using potentiostat (Model2273,EG & GCo, USA) in NaCl solution at $(36.6{\pm}1.0)^{\circ}C$.

• Journal of Welding and Joining
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• v.32 no.2
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• pp.9-13
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• 2014

Friction stir welding (FSW) was successfully performed about 900MPa grade Twinning Induced Plastisity (TWIP) steel. A PCBN tool with convex-type shoulder was applied. Optimal process conditions were deduced. Microstructure and mechanical properties such as hardness, tensile strength and impact absorbed energy were observed and evaluated, respectively. An optical microscope (OM) and a field emission scanning electron microscope (FE-SEM) was selected for observing the grain structure.