• 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 Mechanical Science and Technology
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• v.14 no.11
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• pp.1244-1249
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• 2000

Burr and shape distortion are two main problems in micro-grooving. In this study, a simplified model is proposed based on large thrust force due to the tool edge radius. Experiments are conducted with a single crystal diamond tool on a 3-axis snaper-like machine varying the depth of cuts, and groove angles on brass, aluminum and OFHC. Experiments have shown that the thrust force becomes a dominant variable in burr generation compared to the principal force when the depth of cut is less than 2${\mu}m$. And fewer burrs develop on more brittle materials. Shape distortion is significant only when the groove angle is small and the depth of cut is larger than 30 ${\mu}m$.

• Proceedings of the KIEE Conference
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• 2002.11a
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• pp.167-169
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• 2002

Selective, highly stable determination of serotonin was achieved in cyclic voltammetric measurement carried out at electrochemically treated conductive boron-doped diamond electrode. Boron-doped diamond electrodes were prepared on single crystal Si wafers by microwave plasma chemical vapor deposition and $B_2O_3$ was dissolved in acetone/methanol(9:1) mixture solution so that the B/C weight ratio ca. $10^4ppm$. Serotonin is a kind of indoleamines, which secreted from adrenal marrow cells. The serious problem to detection of serotonin is the interference phenomena of electroactive constituent, including AA. In this study, electrochemical treatment of HDD was carried out to discriminate between serotonin and AA responses. Experimental results showed that the peak potential of AA oxidation shift to the positive direction and the oxidation peak of serotonin was unchanged.

• Journal of Powder Materials
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• v.20 no.5
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• pp.355-358
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• 2013

Micro trench structures are applied in gratings, security films, wave guides, and micro fluidics. These micro trench structures have commonly been fabricated by micro electro mechanical system (MEMS) process. However, if the micro trench structures are machined using a diamond tool on large area plate, the resulting process is the most effective manufacturing method for products with high quality surfaces and outstanding optical characteristics. A nonferrous metal has been used as a workpiece; recently, and hybrid materials, including polymer materials, have been applied to mold for display fields. Thus, the machining characteristics of polymer materials should be analyzed. In this study, machining characteristics were compared between nonferrous metals and polymer materials using single crystal diamond (SCD) tools; the use of such materials is increasing in machining applications. The experiment was conducted using a square type diamond tool and a shaper machine tool with cutting depths of 2, 4, 6 and 10 ${\mu}m$ and a cutting speed of 200 mm/s. The machined surfaces, chip, and cutting force were compared through the experiment.

• Journal of the Korean Ceramic Society
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• v.29 no.12
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• pp.926-934
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• 1992

Uniform diamond films in a few $\textrm{mm}^2$ size and locally isolated diamond single crystals in size of 60 $\mu\textrm{m}$ were synthesized on Si-wafer and Al2O3 substrate by the method of acetylene flame. The effects of substrate temperature and flow ratio of oxygen to acetylene on the morphology of deposited diamond were investigated. According to the observations of growth behavior of diamond on Si substrate with respect to substrate surface pretreatment and flow ratio, it was shown that well faceted diamonds could grow uniformly when flow ratio was above 0.9 and substrates were densely scratched. With increasing substrates temperature, the crystal morphology changes from octahedron bounded by only {111} plane below 850$^{\circ}C$ to cubo-octahedron with almost equal development of {111} and {100} plane in the temperature range of 850∼950$^{\circ}C$. Between 950∼1050$^{\circ}C$, the {111} faces become rough and concave. Above 1050$^{\circ}C$, new crystallites begin to grow on concave {111} surface and overall morphology looks like cubo-octahedron with degenerated {111} faces. These changes of morphology can be understood in terms of the different growth mode of each crystallographic plane with respect to the substrate temperature and supersaturation. And the observed phenomena on {111} planes can be related to the face instability and twin generation.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.06a
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• pp.1223-1227
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• 2005

Fine microgroove is the key component to fabricate micro-grating, micro-grating lens and so on. Conventional groove fabrication methods such as etching and lithography have some problems in efficiency and surface integrity. This study deals with the creation of ultra-precision micro grooves using non-rotational diamond tool and CNC machining center. The shaping type machining method proposed in the study allows to produce V-shaped grooves of $40\mu{m}$ in depth with enough dimensional accuracy and surface. For the analysis of machining characteristics in micro V-grooving, three components of cutting forces and AE signal are measured and processed. Experimental results showed that large amplitude of cutting forces and AE appeared at the beginning of every cutting path, and cutting forces had a linear relation with the cross-sectional area of uncut chip thickness. From the results of this study, proposed micro V-grooving technique could be successfully applied to forming the precise optical parts like prism patterns on light guide panel of TFT-LCD.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.17 no.6
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• pp.272-276
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• 2007

The various colored cubic zirconia single crystals for jewelry were grown by skull melting method of excellent productivity. The cubic zirconia is similar to the character of diamond, which has high refractive index, large dispersion and high hardness. It is possible that the development of new colored cubic zirconia by doping 3d-transition elements or 4f-rare earth elements. The colored cubic zirconia is representative of synthetic gemstone which was grown up by mixing one or over two materials among $Pr_6O_{11},\;TiO_2,\;MnO_2\;and\;Er_2O_3$ as coloring agent. Subsequent heat treatment improves the quality of color and uniformity. This study is aimed the color reappearance of cubic zirconia such as natural peridot, smoky-quartz and red-tourmaline.

• Korean Journal of Crystallography
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• v.6 no.1
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• pp.14-26
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• 1995

The growth mechanism of diamond thin films, deposited by Hot Filament CVD, was investigated through observation of changes in their surface morphology as a function of the substance temperature and deposition time. Amorphous carbon or DLC thin films were deposited at low substrate temperature. Diamond films consisting of square-shaped particles, whose surfaces are (100) planes, were deposited at an intermedate temperature. At high substrate temperatures, diamond films consisting of the particles showing both (100) and (111) plane were deposited. The (100) proferred orientation of the diamond films are believed to be due to a relatively high supersaturation during deposition, and the growth condition for the diamond films having (100) preferred orientation can be applied to the single crystal growth since no twins are generated on the (100) plane. The grain size of the diamond films did not change with increasing temperature and its increasing rate with increasing deposition time was the same irrespective of the substrate temperature. However, the nucleation density increased with substrate temperature and its increasing rate with deposition time was much higher for the films deposited at higher substrate temperature.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.15 no.3
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• pp.114-119
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• 2005

This study has been carried out with the eight HPHT processed NOUV diamonds - two yellow, two yellowish green, two green and two orangy yellow color stones. The gemological properties of these diamonds included a highly saturated body color, graphitized fractures around the girdles, tension cracks around crystalline inclusions, long-wave UV with medium yellowish green to a very strong yellowish green luminescence, and short-wave UV with faint yellowish green to a strong yellowish green luminescence. Distinctive features of spectroscopic properties include absorption peaks at 415 nm and 503 nm a strong absorption band at $460{\sim}480nm$ and a H2 center at 986nm. Infrared spectra showed an absorption peak at $1344cm^{-1}$ (C center), which is the characteristics related to single substitutional nitrogen.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2009.06a
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• pp.1033-1034
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• 2009