• The Transactions of the Korean Institute of Electrical Engineers C
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• v.48 no.2
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• pp.76-79
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• 1999

Low-hydrogenated DLC films were coated on the Mo-tip FEAs by 'layer-by-layer' process based on the plasma-enhanced CVD method. The hydrogen content in the DLC film deposited by the 'layer-by-layer' process was appeared to be remarkably lowered through SIMS analysis. Also, the low-hydrogenated DLC-coated Mo-tip FEA showed good potentiality for FED applications in terms of turn-on voltage, emission current, emission stability and light emitting uniformity.

• Korean Journal of Materials Research
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• v.14 no.4
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• pp.300-306
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• 2004

A laser welding has been made between sintered tip of Fe-Co-W and low carbon steel shank for the diamond saw blade. The welding characteristics and formation of defect has been investigated carefully for the weld fusion zone in different welding condition. Full penetration has been observed for the whole range of heat input investigated in the present work. Bead width and under-fill have been increased with the increase of heat input. With increasing of heat input small cavities were decreased while large cavities were increased. The ratio of total cavity area to the entire weld bead area was not changed significantly with change of heat input. Most of cavities were found near the tip, and supposed to be formed from the pore in the tip.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.11 no.7
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• pp.508-516
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• 1998

Mo-tip field emitter arrays(FEAs) were fabricated by conventional Spindt process and their life time characteristics and failure mode were evaluated. The fabricated Mo-tip FEA could generate at least $0.35\{mu} A/tip$ emission current for about 320 persistently under a constant gate bias of 140 V and was finally destroyed through self-healing mode. Thin diamond-like carbon films were coated on the M-tip by plasma-enhanced CVD and the dependence of emission properties upon the DLC thickness was investigated. By DLC coating, the turn-on voltage and emission current were appeared to be improved whereas the current fluctuation was increased in the DLC thickness range of $0~1,000\{AA}$.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2003.10a
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• pp.339-346
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• 2003

Molecular dynamic simulations of nano indentation on single-crystal silicon (100) surface were performed using diamond indentor. Silicon substrate and diamond indentor were modeled diamond structure with Tersoff potential model. Phase transformation of silicon, incipient plastic deformation, change of incident temperature distribution are investigated through the change of potential energy distribution, displacement-load diagram, the change of kinetic energy distribution and displacements of silicon atoms. Phase transformation is highly localized and consists of a high-density region surrounding the tip. Axial load linearly increased according to the indenting depth. Number of atoms with high kinetic energy increased at the interface between substrate and indentor tip.

• Journal of Welding and Joining
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• v.21 no.3
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• pp.58-67
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• 2003

In this study, the formation mechanism of discontinuities in the laser fusion zone of diamond saw blade was investigated. $CO_2$ laser weldings were conducted along the butt between Fe base sintered tip and carbon steel shank with sets of variable welding parameters. The effect of heat input on irregular humps, outer cavity, inner cavity and bond strengh was evaluated. The optimum heat input to have a proper humps was in the range of 10.4~$17.6kJm_{-1}$. With increasing heat input, both outer and inner cavities were reduced. The outer cavity was caused by insufficient refill of keyhole, while inner cavity was caused by trapping of bubble in molten metal. The bubble came from sintered tip and intensive vaporization at bottom tip of the keyhole. A gas formation and low melting point element vaporization were not occurred during welding. We could not find any relationship between bond strength and amount of discontinuities. Because the fracture were occurred in not only sintered tip but also carbon steel shank due to hardness distributions.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2002.05a
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• pp.926-931
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• 2002

Although ceramic plates with many micro-hales are used as MCP (Micro-channel plate) for electron amplification, catalytic converters, filters, electrical insulators and thermal conductors in integrated circuits, the drilling of micro-hales in the ceramics is difficult because of their low thermal conductivity, high hardness and brittleness. Therefore, in this work, the machining of ceramic green body fellowed by sintering of green body was employed fur fabricating ceramic plates with many micro-holes. The micro-drilling of alumina green body was performed with diamond abrasive WC drills, and the cutting force w.r.t. drilling times was measured for the determination of toot life. From the investigation of the wear of micro-drill tip w.r.t. drilling times, the wear mechanism of tip during micro-drilling of ceramic green body was suggested.

• Journal of Electrochemical Science and Technology
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• v.15 no.2
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• pp.261-267
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• 2024

An unconventional fabrication technique of nanoelectrode was developed using atomic force microscopy (AFM) and hydrogel. Until now, the precise control of electroactive area down to a few nm² has always been an obstacle, which limits the wide application of nanoelectrodes. Here, the nanometer-sized contact between the boron-doped diamond (BDD) as conductive AFM tip and the agarose hydrogel as solid electrolyte was well governed by the feedback amplitude of oscillation in the non-contact mode of AFM. Consequently, this low-cost and feasible approach gives rise to new possibilities for the fabrication of nanoelectrodes. The electroactive area controlled by the set point of AFM was investigated by cyclic voltammetry (CV) of the ferrocenmethanol (FcMeOH) combined with quasi-solid agarose hydrogel as an electrolyte. Single copper (Cu) nanoparticle was deposited at the apex of the AFM tip using this platform whose electrocatalytic activity for nitrate reduction was then investigated by CV and Field Emission-Scanning Electron Microscopy (FE-SEM), respectively.

• Proceedings of the KWS Conference
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• 2002.10a
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• pp.639-643
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• 2002

The main purpose of this study was to investigate the formation mechanisms of imperfections such as irregular humps, outer cavity and inner cavity in the laser fusion zone of diamond saw blade. Laser beam welding was conducted to join two parts of blade; mild steel shank and Fe-Co-Ni sintered tip. The variables were beam power and travel speed. The microstructure and elements distributions of specimens were analyzed with SEM, AES, EPMA and so on. It was found that these imperfections were responded to heat input. Irregular humps were reduced in 10.4∼17.6kJ/m heat input range. However there were no clear evidences, which could explain the relations between humps formation and heat input. The number of outer cavity and inner cavity decreased as heat input was increased. Considering both possible defects formations mechanisms, it could be thought that outer cavity was caused by insufficient refill of keyhole, which was from rapid solidification of molten metal and fast molten metal flow to the rear keyhole wall at low heat input. More inner cavities were found near the interface of the fusion zone and sintered segment and in the bottom of the fusion zone. Inner cavity was mainly formed in the upper fusion zone at high heat input whereas was in the bottom at low heat input. Inner cavity was from trapping of coarsened preexist pores in the sintered tip and metal vapor due to rapid solidification of molten metal before the bubbles escaped.

• International Journal of Precision Engineering and Manufacturing
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• v.8 no.2
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• pp.54-58
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• 2007

This paper describes an atomic force microscope (AFM)-based instrument for measuring the nanoscale cutting edge profiles of diamond cutting tools. The instrument consists of a combined AFM unit and an optical sensor to align the AFM tip with the top of the diamond cutting tool edge over a submicron range. In the optical sensor, a aser beam is emitted from a laser diode along the Y-axis and focused to a small beam spot with a diameter of approximately $10{\mu}m$ at the beam waist, which is then received by a photodiode. The top of the tool edge is first brought into the center of the beam waist by adjusting it in the X-Z-plane while monitoring the variation in the photodiode output. The cutting tool is then withdrawn and its top edge position at the beam center is recorded. The AFM tip can also be positioned at the beam center in a similar manner to align it with the top of the cutting edge. To reduce electronic noise interference on the photodiode output and thereby enhance the alignment accuracy, a technique is applied that can modulate the photodiode output to an AC signal by driving the laser diode with a sinusoidal current. Alignment experiments and edge profile measurements of a diamond cutting tool were carried out to verify the performance of the proposed system.

• International Journal of Korean Welding Society
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• v.2 no.1
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• pp.21-24
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• 2002

The main purpose of this study was to investigate the formation mechanisms of imperfections such as irregular humps, outer cavity and inner cavity in the laser fusion zone of diamond saw blade. Laser beam welding was conducted to join two parts of blade; mild steel shank and Fe-Co-Ni sintered tip. The variables were beam power and travel speed. The microstructure and elements distributions of specimens were analyzed with SEM, AES, EPMA and so on. It was found that these imperfections were responded to heat input. Irregular humps were reduced in 10.4∼l7.6kJ/m heat input range. However there were no clear evidences, which could explain the relations between humps formation and heat input. The number of outer cavity and inner cavity decreased as heat input was increased. Considering both possible defects formations mechanisms, it could be thought that outer cavity was caused by insufficient refill of keyhole, which was from rapid solidification of molten metal and fast molten metal flow to the rear keyhole wall at low heat input. More inner cavities were found near the interface of the fusion zone and sintered segment and in the bottom of the fusion zone. Inner cavity was mainly formed in the upper fusion zone at high heat input whereas was in the bottom at low heat input. Inner cavity was from trapping of coarsened preexist pores in the sintered tip and metal vapor due to rapid solidification of molten metal before the bubbles escaped.