• Tribology and Lubricants
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• v.17 no.3
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• pp.191-197
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• 2001

Nano adhesion and friction characteristics between SPM(scanning electron microscope) tips and flat plates of different materials were experimentally studied. Tests were performed to measure adhesion and friction in AFM(atomic force microscope) and LFM(lateral force microscope) modes in different conditions of relative humidity. Three different Si$_3$N$_4$ tips (rdaii : 15nm, 22nm and 50 nm) and three different flat plates of Si-wafer(100), W-DLC(tungsten-incorporated diamond-like carbon) and DLC were used. Results generally showed that adhesion and friction increased with the tip radius, and W-DLC and DLC surfaces were superior to Si-wafer. But the adhesion force of Si-wafer showed non linearity with the tip radius while W-DLC and DLC surfaces showed good correlation to the “JKR model”. It was found that high adhesion force between Si-wafer and a large radius of tip was caused by a capillary action due to the condensed water.

• Journal of the Korean Society for Precision Engineering
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• v.7 no.3
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• pp.37-47
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• 1990

In accordance with the high precision of mechanical elements, it has been required to high precision in surface roughness measurement and, therefore, stylus tip radius is manufa- ctured less than 2 .mu. m through ion sputter machining. In this experiment, by suing ion sputter machined stylus pf fine tip, radius and lapping machined stylus, surface roughness of standard specimens, silicon wafer were measured and then Rmax, Ra, RMS value were investi- gatedaccording to the variation of tip radius of stylus. As a result, measuring error due to the variation of stylus tip radius in surface roughness measurement was decreased by using ion sputter machined stylus and also the measuring accuracy was improved. And the measuring variation of Ra, RMS calculated from correlation coefficient lager than 0.9 on the wave of short period and amplitude using ion sputter machined stylus of fine tip radius.

• Journal of Power System Engineering
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• v.12 no.3
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• pp.66-71
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• 2008

Diamond-like-carbon (DLC) coatings could be good candidates as solid lubricants for cutting tools in dry machining of aluminum alloy. In this work, DLC thin films were produced as a friction reduction coating for WC-Co insert tip using the plasma immersion ion beam deposition (PIIED) technique. DLC coatings were also coated on $Al_2O_3$ specimens and high temperature wear tested up to $400^{\circ}C$ in dry air to observe the survivability of the DLC coating in simulated severe cutting conditions using a pin-on-disc tribotester with Hertzian contact stress of 1.3GPa. It showed reduced friction coefficients of minimum 0.02 up to $400^{\circ}C$. And cutting performance of DLC coated WC-Co insert tips to Al 6061 alloy were conducted in a high speed machining center. The main problems of built-up edge formation in aluminum machining are drastically reduced with improved surface roughness. The improvements were mainly related to the low friction coefficient of DLC to Al alloy and the anti-adhesion of Al alloy to WE due to the inertness of DLC.

• Journal of Mechanical Science and Technology
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• v.18 no.10
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• pp.1772-1781
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• 2004

The mechanical as well as tribological characteristics of coating films as thin as a few nm become more crucial as applications in micro-systems grow. Especially, the amorphous carbon film has a potential to be used as a protective layer for micro-systems. In this work, quantitative evaluation of nano-indentation, scratching, and wear tests were performed on the 7nm thick amorphous carbon film using an Atomic Force Microscope (AFM). It was shown that AFM-based nano-indentation using a diamond coated tip can be feasibly utilized for mechanical characterization of ultra-thin films. Also, it was found that the critical load where the failure of the carbon film occurred was about 18${\mu}$N by the ramp load scratch test. Finally, the wear experimental results showed that the quantitative wear rate of the carbon film ranged 10$\^$-9/～10$\^$-8/ ㎣ /N cycle. These experimental methods can be effectively utilized for a better understanding the mechanical and tribological characteristics at the nano-scale.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.17 no.6
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• pp.1-6
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• 2018

Recently nano meter size pattern (sub-micro scale) can be machined mechanically using a diamond tool. Many studies have found a 'size effect' which referred to a specific cutting energy increase with the decrease in the uncut chip thickness at micro scale machining. A new analysis method was suggested in order to observe 'size effect' in nano scale machining and to verify the cause of the 'size effect' in this study. The diamond tool was indented to a vertical depth of 1,000nm depth in order to simplify the stress state and the normal force was measured continuously. The tip rounding was measured quantitatively by AFM. Based on the measurements and theoretical analysis, it was verified that the main cause of the 'size effect' in nano scale machining is geometrically necessary dislocations, one of the intrinsic material characteristics. st before tool failure.

• Restorative Dentistry and Endodontics
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• v.39 no.4
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• pp.276-281
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• 2014

Objectives: The purpose of this study was to compare the cutting efficiency of a newly developed microprojection tip and a diamond-coated tip under two different engine powers. Materials and Methods: The apical 3 mm of each root was resected, and root-end preparation was performed with upward and downward pressure using one of the ultrasonic tips, KIS-1D (Obtura Spartan) or JT-5B (B&L Biotech Ltd.). The ultrasonic engine was set to power-1 or -4. Forty teeth were randomly divided into four groups: K1 (KIS-1D / Power-1), J1 (JT-5B / Power-1), K4 (KIS-1D / Power-4), and J4 (JT-5B / Power-4). The total time required for root-end preparation was recorded. All teeth were resected and the apical parts were evaluated for the number and length of cracks using a confocal scanning micrscope. The size of the root-end cavity and the width of the remaining dentin were recorded. The data were statistically analyzed using two-way analysis of variance and a Mann-Whitney test. Results: There was no significant difference in the time required between the instrument groups, but the power-4 groups showed reduced preparation time for both instrument groups (p < 0.05). The K4 and J4 groups with a power-4 showed a significantly higher crack formation and a longer crack irrespective of the instruments. There was no significant difference in the remaining dentin thickness or any of the parameters after preparation. Conclusions: Ultrasonic tips with microprojections would be an option to substitute for the conventional ultrasonic tips with a diamond coating with the same clinical efficiency.

• Laser Solutions
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• v.7 no.3
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• pp.25-36
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• 2004

This study was performed to clarification of the formation of weld discontinuities in the dissimilar laser fusion zone. Welding parameters were beam power of 1300, 1430, 1560, and 1700 W and travel speed of 1, 1.3, and 1.7 m/min. Most cavities in the fusion zone were observed near the tip. Cavities in the fusion zone observed to be formed and grown from pores in the tip. More cavities were formed as the beam position moves to the tip side. Small cavities were decreased but large cavities were increased when the energy input increased. W content in the fusion zone was increased with heat input and as the beam position close to the tip. In the fusion zone, W content in the dendrite boundary was increased with heat input. Considering the propagation path and fracture morphology, cracks were solidification cracking, and were initiated and propagated along the dendrite boundaries. The formation of cracks might be related with the W rich ${\mu}$ phase which was formed in the grain boundaries and dendrite boundaries.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.11 no.6
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• pp.465-471
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• 1998

Diamond-like carbon (DLC) films have been prepared by means of the plasma enhanced chemical vapor deposition (PECVD) method using vertical-capacitor electrodes. The deposition rata in our experiment is relatively small compared with that in the conventional PECVD methods, which implies that the accumulation of the neutral $CH_n$ radicals on the substrates due to the gravitational movement may not contribute to the deposition of DLC films. The hardness and the transparency were measured as a function of the ratio of the partial pressure of $CH_4-H_2$ mixtures or the hydrogen contents of specimens. The coefficients of friction between DLC films and a $Si_3N_4$ tip measured by using a lateral force microscope are in the range of 0.024 to 0.033 which depend on the hydrogen contents in DLC, and the surface roughness depends mainly on the deposition rate. The optical gaps increase with increasing the hydrogen contents. DCL films deposited on Pt-coated Si wafers show the stable emission characteristics, and the turn-on fields are in the range of 11 to 20 $V/\mu$m.

• Korean Journal of Crystallography
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• v.12 no.2
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• pp.102-112
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• 2001

The mechanical properties of silicon crystals are important from the viewpoint of wafer and device fabrication processes. It is now widely recognized that silicon undergoes a series of phase transformations when subjected to high pressures, using conventional high pressure devices, such as diamond anvils or indenters. Diamond tip scratching on a silicon surface in the various conditions introduces various kinds of mechanical damage and stressed states. Micro Raman spectroscopy was used to observe the phase transition of single crystal silicon. As results, different morphologies were observed as functions of scratching speed and loading condition and various phases were observed as functions of scratching speed and loading condition.

• Proceedings of the KIEE Conference
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• 1997.11a
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• pp.273-275
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• 1997

We fabricated the conventional silicon tips coated with a diamond-like carbon (DLC) film. The DLC films are prepared by the filtered cathodic vacuum arc (FCVA) technique. With increasing nitrogen content in DLC film, the work function($\phi$) and the turn-on voltage decrease and the emission current increases. This phenomenon is due to the fact that the Fermi-level moves to the conduction band by increasing nitrogen doping concentration. We have tested on the stability of the DLC film coated silicon tip during 2 hours at 500V.