• Title/Summary/Keyword: Diamond crystal

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A Study on the Precision Machining Characteristics in Heavy Cutting of Al-alloy (Al합금의 중절삭시 정밀가공 특성에 관한 연구)

  • 권용기;김동현
    • Proceedings of the Korean Society of Machine Tool Engineers Conference
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    • 2002.10a
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    • pp.203-208
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    • 2002
  • This paper deals with turning experiments of aluminium alloy using a single crystal diamond with round cutting edge. A face cutting was conducted using a special precision machine to study the characteristic phenomena in heavy cutting of aluminium alloy. In many cases, one of the most important matter on the surface integrity is about a damaged layer remaining just under the surface after machining. A machined surface roughness can be improved at a small geometrical surface roughness under special cutting conditions, even if a steady vibration exists between a tool and a workpiece.

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Microstructure of ZnO Thin Film on Nano-Scale Diamond Powder Using ALD (나노급 다이아몬드 파우더에 ALD로 제조된 ZnO 박막 연구)

  • Park, S.J.;Song, S.O.
    • Journal of the Korean Vacuum Society
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    • v.17 no.6
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    • pp.538-543
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    • 2008
  • Recently a nano-scale diamond is possible to manufacture forms of powder(below 100 nm) by new processing of explosion or deposition method. Using a sintering of nano-scale diamond is possible to manufacture of grinding tools. We have need of a processing development of coated uniformly inorganic to prevent an abnormal grain growth of nano-crystal and bonding obstacle caused by sintering process. This paper, in order to improve the sintering property of nano-scale diamond, we coated ZnO thin films(thickness: $20{\sim}30\;nm$) in a vacuum by ALD(atomic layer deposition) Economically, in order to deposit ZnO all over the surface of nano-scale diamond powder, we used a new modified fluidized bed processing replaced mechanical vibration effect or fluidized bed reactor which utilized diamond floating owing to pressure of pulse(or purge) processing after inserted diamond powders in quartz tube(L: 20 mm) then closed quartz tube by porosity glass filter. We deposited ZnO thin films by ALD in closed both sides of quartz tube by porosity glass filter by ALD(precursor: DEZn($C_4H_{10}Zn$), reaction gas: $H_2O$) at $10^{\circ}C$(in canister). Processing procedure and injection time of reaction materials set up DEZn pulse-0.1 sec, DEZn purge-20 sec, $H_2O$ pulse-0.1 sec, $H_2O$ purge-40 sec and we put in operation repetitive 100 cycles(1 cycle is 4 steps) We confirmed microstructure of diamond powder and diamond powder doped ZnO thin film by TEM(transmission electron microscope) Through TEM analysis, we confirmed that diamond powder diameter was some $70{\sim}120\;nm$ and shape was tetragonal, hexagonal, etc before ALD. We confirmed that diameter of diamond powders doped ZnO thin film was some $70{\sim}120\;nm$ and uniform ZnO(thickness: $20{\sim}30\;nm$) thin film was successfully deposited on diamond powder surface according to brightness difference between diamond powder and ZnO.

Crystal Dependence in Micro Scratching of Carbon Steel - Groove Formation of Cementite and Ferrite Phases -

  • Taniyama, H.;Eda, H.;Sato, J.;Shimizu, J.;Zhou, L.
    • Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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    • 2002.10b
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    • pp.197-198
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    • 2002
  • In order to produce micromachined parts with a great dimensional accuracy, it is important to clarify the influence of heterogeneity and/or discontinuity of workpiece materials on the micromachining process, because almost all structural materials are composed of heterogeneous and/or homogeneous crystal grains at the micro scale. Experiments where JIS S25C steel had been scratched with a diamond triangular pyramid indenter were conducted under a field emission scanning electron microscope (FE-SEM). The difference of plastic deformation at a groove scratched between a pearlite zone and a proeutectoid ferrite zone was investigated through comparison with the groove scratched of a pearlite zone and a proeutectoid ferrite zone.

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Novel Alignment Layers for Ion Beam Method and the Orientations of Liquid Crystal

  • Ahn, Han-Jin;Kim, Kyung-Chan;Kim, Jong-Bok;Baik, Hong-Koo;Park, Chang-Joon;Hwang, Jeoung-Yeon;Seo, Dae-Shik
    • 한국정보디스플레이학회:학술대회논문집
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    • 2004.08a
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    • pp.1155-1158
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    • 2004
  • Various inorganic alignment layers of nematic liquid crystal (NLC) molecules were investigated. Ar ion beam (IB) irradiation was utilized for alignment method and homogenous and homeotropic orientations with tilt angle were obtained on the suitable inorganic thin films. Proper doping materials were added to diamond-like carbon (DLC) films. In the case of homogeneous alignment, nitrogen doping affected the increase of pretilt angle, while the fluorine bonding in the DLC films was induced the tilted homeotropic alignment cause its extreme hydrophobic property. These results showed that ion beam irradiation method could be applied to the various alignment mode of NLC such as IPS, TN and MVA.

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Kinematic Modeling and Analysis of Silicon Wafer Grinding Process (실리콘 웨이퍼 연삭 가공의 기구학적 모델링과 해석)

  • 김상철;이상직;정해도
    • Proceedings of the Korean Society of Precision Engineering Conference
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    • 2002.05a
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    • pp.42-45
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    • 2002
  • General wheel mark in mono-crystalline silicon wafer finding is able to be expected because it depends on radius ratio and angular velocity ratio of wafer and wheel. The pattern is predominantly determined by the contour of abrasive grits resulting from a relative motion. Although such a wheel mark is made uniform pattern if the process parameters are fixed, sub-surface defect is expected to be distributed non-uniformly because of characteristic of mono-crystalline silicon wafer that has diamond cubic crystal. Consequently it is considered that this phenomenon affects the following process. This paper focused on kinematic analysis of wafer grinding process and simulation program was developed to verify the effect of process variables on wheel mark. And finally, we were able to predict sub-surface defect distribution that considered characteristic of mono-crystalline silicon wafer

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Multidirectional Liquid Crystal Orientation by Using Ion Beam Irradiation

  • Ahn, Han-Jin;Kim, Kyung-Chan;Kim, Jong-Bok;Hwang, Byung-Har;Baik, Hong-Koo
    • 한국정보디스플레이학회:학술대회논문집
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    • 2005.07a
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    • pp.543-546
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    • 2005
  • We have investigated the alignment ability of multi-domains by using ion beam irradiation on diamond-like carbon (DLC) thin film layers. The DLC thin films were deposited by plasma enhanced chemical vapor deposition (PECVD) system and the low energy ion beam is irradiated from Kaufman type ion gun. The direction of liquid crystal alignment is varied by the direction of Ar ion beam irradiation.

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Effect of Crystal Orientation on Material Removal Characteristics in Sapphire Chemical Mechanical Polishing (사파이어 화학기계적 연마에서 결정 방향이 재료제거 특성에 미치는 영향)

  • Lee, Sangjin;Lee, Sangjik;Kim, Hyoungjae;Park, Chuljin;Sohn, Keunyong
    • Tribology and Lubricants
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    • v.33 no.3
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    • pp.106-111
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    • 2017
  • Sapphire is an anisotropic material with excellent physical and chemical properties and is used as a substrate material in various fields such as LED (light emitting diode), power semiconductor, superconductor, sensor, and optical devices. Sapphire is processed into the final substrate through multi-wire saw, double-side lapping, heat treatment, diamond mechanical polishing, and chemical mechanical polishing. Among these, chemical mechanical polishing is the key process that determines the final surface quality of the substrate. Recent studies have reported that the material removal characteristics during chemical mechanical polishing changes according to the crystal orientations, however, detailed analysis of this phenomenon has not reported. In this work, we carried out chemical mechanical polishing of C(0001), R($1{\bar{1}}02$), and A($11{\bar{2}}0$) substrates with different sapphire crystal planes, and analyzed the effect of crystal orientation on the material removal characteristics and their correlations. We measured the material removal rate and frictional force to determine the material removal phenomenon, and performed nano-indentation to evaluate the material characteristics before and after the reaction. Our findings show that the material removal rate and frictional force depend on the crystal orientation, and the chemical reaction between the sapphire substrate and the slurry accelerates the material removal rate during chemical mechanical polishing.

New mechanism of thin film growth by charged clusters

  • Hwang, Nong-Moon;Kim, Doh-Yeon
    • Journal of the Korean Crystal Growth and Crystal Technology
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    • v.9 no.3
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    • pp.289-294
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    • 1999
  • The charged clusters or particles, which contain hundreds to thousands of atoms or even more, are suggested to from in the gas phase in the thin film processes such as CVD, thermal evaporation, laser ablation, and flame deposition. All of these processes are also phase synthesis of the nanoparticels. Ion-induced or photo-induced nucleation is the main mechanism for the formation of these nanoclusters or nanoparticles in the gas phase. Charge clusters can make a dense film because of its self-organizing characteristics while neutral ones make a porous skeletal structure because of its Brownian coagulation. The charged cluster model can successfully explain the unusual phenomenon of simultaneous deposition and etching taking place in diamond and silicon CVD processes. It also provides a new interpretation on the selective deposition on a conducting material in the CVD process. The epitaxial sticking of the charged clusters on the growing surface is getting difficult as the cluster size increases, resulting in the nanostructure such as cauliflower or granular structures.

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Generation of Tilt in the nematic liquid crystal using a-C:H Thin Films Deposited Using PECVD Method (PECVD 장치를 사용하여 증착된 a-C:H 박막을 이용한 네마틱 액정의 틸트 발생)

  • Park, Chang-Joon;Hwang, Jeoung-Yeon;Seo, Dae-Shik;Ahn, Han-Jin;Kim, Kyeong-Chan;Baik, Hong-Koo
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • 2003.11a
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    • pp.469-472
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    • 2003
  • The nematic liquid crystal (NLC) aligning capabilities using a-C:H thin film deposited at the three kinds of rf bias condition were investigated. A high pretilt angle of about $11^{\circ}$ by the ion beam alignment method was observed on the a-C:H thin film (polymer-like carbon) deposited at 1W rf bias condition, and the low pretilt angle of the NLC was observed on the a-C:H thin film(diamond-like carbon) deposited at rf 30W and 60W bias condition. Consequently, the high NLC pretilt angle and the good aligning capabilities of LC alignment by the IB alignment method on the a-C:H thin film deposited at 1W rf bisa condition can be achieved.

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Study on the growth of 4H-SiC single crystal with high purity SiC fine powder (고순도 SiC 미분말을 적용한 4H-SiC 단결정 성장에 관한 연구)

  • Shin, Dong-Geun;Kim, Byung-Sook;Son, Hae-Rok;Kim, Moo-Seong
    • Journal of the Korean Crystal Growth and Crystal Technology
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    • v.29 no.6
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    • pp.383-388
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    • 2019
  • High purity SiC fine powder with metal impurity contents of less than 1 ppm was synthesized by improved carbothermal reduction process, and the synthesized powder was used for SiC single crystal growth in RF heating PVT device at temperature above 2,100℃. In-situ x-ray image analyzer was used to observe the sublimation of the powder and single crystal growth behavior during the growth process. SiC powder was used as a source of single crystal growth, exhausted from the outside of the graphite crucible at the growth temperature and left graphite residues. During the growth, the flow of raw materials was concentrated in the middle and influenced the growth behavior of SiC single crystals. This is due to the difference in temperature distribution inside the crucible due to the fine powder. After the single crystal growth was completed, the single crystal ingot was cut into a 1 mm thick single crystal substrate and finely polished using a diamond abrasive slurry. A dark yellow 4H-SiC was observed overall of single crystal substrate, and the polycrystals generated in the outer part may be caused by the incorporation of impurities such as the bubble layer mixed in the process of attaching the seed crystal to the seed holder.