• Journal of Advanced Marine Engineering and Technology
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• v.32 no.6
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• pp.862-868
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• 2008

Many studies have been conducted to increase heat transfer in fluid. One of the various heat transfer enhancement techniques is suspending fine metallic or nonmetallic solid powder in traditional fluid. Nanofluid is defined as a new kind of heat transfer fluid containing a very small quantity of nanometer particles that are uniformly and stably suspended in a liquid. This study investigates the effect of nanofluid containing diamond, CuNi and CuAg nanometer particles, and proposes the heat transport mechanism of nanofluid. The test result shows that the thermal conductivity of nanofluid is much higher than that of traditional fluid, and the increasing rate of the conductivity is dependent on the conductivity of the solid metal.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 1998.03a
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• pp.19-24
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• 1998

This paper aims to clarify the effects of grinding conditions on the ground surface and bending strength in surface grinding of various ferrites with diamond wheel. The main conclusions obtained were as follows. The surface roughness becomes better at lower wheel speed in the case of v/V=1$\times$10-3, and the condition of v/V=1$\times$10-4shows the best performance for the finish grinding. When the relative contact temperature becomes lower at a constant value of v/V, the ground surface exhibits lower roughness. The ground surface shows that the fracture process during grinding becomes more brittle at the higher value of v/V. The damage depth which affect the bending strength is below 10$\mu$m in the grinding condition of S=10㎣/mm.s with the diamond tool after dressing & truing, however, the depth increases with increasing removal rate(S). When the strength degradation due to grinding is larger, the removal depth for the recovery of strength requires a larger size.

• Proceedings of the Korean Vacuum Society Conference
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• 2004.02a
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• pp.105-106
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• 2004

• Proceedings of the KSME Conference
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• 2001.06c
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• pp.83-87
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• 2001

A 110 mm diameter aspheric metal secondary mirror for a test model of an earth observation satellite camera was fabricated by ultra-precision single point diamond turning (SPDT). Aluminum alloy for mirror substrates is known to be easily machinable, but not polishable due to its ductility. A harder material, Ni, is usually electrolessly coated on an Al substrate to increase the surface hardness for optical polishing. Aspheric metal secondary mirror without a conventional polishing process, the surface roughness of Ra=10nm, and the form error of $Ra={\lambda}/12({\lambda}=632nm)$ has been required. The purpose of this research is to find the optimum machining conditions for reflector cutting of electroless-Ni coated Al alloy and apply the SPDT technique to the manufacturing of ultra precision optical components of metal aspheric reflector.

• Proceedings of the Materials Research Society of Korea Conference
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• 2003.11a
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• pp.39-39
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• 2003

Molecular dynamics (MD) simulation was performed to study the stress induced grain boundary migration caused by the interaction of dislocations with a gain boundary. The simulation was carried out in a Ni block (295020 atoms) with a ∑ = 5 (210) grain boundary and an embedded atom potential for Ni was used for the MD calculation. Stress was provided by indenting a diamond indenter and the interaction between Ni surface and diamond indenter was assumed to have a fully repulsive force to emulate a faction free surface. Results showed that the indentation nucleated perfect dislocations and the dislocations produced stacking faults in the form of a parallelepiped tube. The parallelepiped tube consisted of two pairs of parallel dislocations with Shockley partials and was produced successively during the penetration of the indenter. The dislocations propagated along the parallelepiped slip planes and fully merged onto the ∑ = 5 (210) grain boundary without emitting a dislocation on the other grain. The interaction of the dislocations with the grain boundary induced the migration of the grain boundary plane in the direction normal to the boundary plane and the migration continued as long as the dislocations merged onto the grain boundary plane. The detailed mechanism of the conservative motion of atoms at the gram boundary was associated with the geometric feature of the ∑ = 5 (210) grain boundary.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2009.06a
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• pp.56-56
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• 2009

반도체 device가 점점 고집적화, 다층화 되면서 막질의 평탄화를 위한 CMP (chemical mechanical planarization) 공정은 반도체 제작 공정에서 필수 요건이 되었다. 특히 pad conditioning은 CMP 공정 중, 막질의 제거율과 균일도를 유지시키기 위한 중요한 공정이다. 하지만, conditioner를 장시간 사용할 경우 slurry residue와 같은 잔류 오염물질들이 conditioner의 표면의 오염을 유발할 수 있고 이로 인해 conditioner의 수명이 단축되거나 웨이퍼 표면에 결함을 유발할 수도 있다. 본 연구에서는 이를 방지하기 위해 vapor SAM을 이용하여 Ni conditioner 표면에 소수성 박막을 증착하여 오염여부를 평가해 보았다. 먼저, Ni wafer를 이용하여 증착 온도와 압력에 따라 소수성 박막을 증착하여 표면특성을 평가해 보았다. 증착전과 후에 Ni wafer 표면의 접촉각은 contact angle analyzer (Phoenix 400, SEO, Korea)를 이용하여 측정하였다. 박막 표면 형상과 거칠기는 AFM (XE-100, PSIA, Korea)를 이용하여 평가되었고 묘면 성분 분석을 위해 FT-IR (Nicolet 6700, Thermo Scientific, USA)이 사용되었다. SEM (S-4800, Hitach, Japan)은 박막 증착 전과 후의 conditioner를 이용하여 실제 conditioning후 conditioner 표면의 particle 오염정도를 관찰하기 위해 사용되었다. 또한, conditioner 표면에 실제 오염되어있는 particle 개수를 평가하기 위해 particle size analyzer (Accusizer 780A, Particle Sizing Systems Co., USA)을 사용하였다. 본 실험을 통해 최적 증착 조건을 확립하였으며 실제 conditioner 표면에 소수성 박막을 증착 후 $100^{\circ}$ 이상의 높은 contact angle을 확인할 수 있었다. 또한, 소수성 박막이 증착된 conditioner의 경우 실제 conditioning후 표면 particle 오염이 현저히 감소되었음을 확인할 수 있었다.

• Journal of the Korean Society for Heat Treatment
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• v.30 no.6
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• pp.264-270
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• 2017

In this study, while the abrasive plates for diamond have been prepared through mechanical alloying and sintering of elemental powders, a fabrication route of plasma thermal coatings has been adopted for the first time. When diamond knife is sharped or polished, a metal plate has been applied, which is made of mechanical alloying and sintering. In this study, in order to develop a cost - effective manufacturing process, plasma coatings of FeCrNi and Ti on cast iron plate were applied together with Al intermediate layer coatings. The plasma coatings were successfully performed, and the optimum coating layer conditions were discussed in terms of micro-structural observations at the interfaces.

• Journal of the Korean Ceramic Society
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• v.52 no.4
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• pp.279-283
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• 2015

Ni (100 nm thick) was deposited onto synthesized diamonds to fabricate etched diamonds. Next, those diamonds were annealed at varying temperatures ($400{\sim}1200^{\circ}C$) for 30 minutes and then immersed in 30 wt% $HNO_3$ to remove the Ni layers. The etched properties of the diamonds were examined with FE-SEM, micro-Raman, and VSM. The FE-SEM results showed that the Ni agglomerated at a low annealing temperature (${\sim}400^{\circ}C$), and self-aligned hemisphere dots formed at an annealing temperature of $800^{\circ}C$. Those dots became smaller with a bimodal distribution as the annealing temperature increased. After stripping the Ni layers, etch pits and trigons formed with annealing temperatures above $400^{\circ}C$ on the surface of the diamonds. However, surface graphite layers existed above $1000^{\circ}C$. The B-H loop results showed that the coercivity of the samples increased to 320 Oe (from 37 Oe) when the annealing temperature increased to $600^{\circ}C$ and then, decreased to 150 Oe with elevated annealing temperatures. This result indicates that the coercivity was affected by magnetic domain pinning at temperatures below $600^{\circ}C$ and single domain behavior at elevated temperatures above $800^{\circ}C$ consistent with the microstructure results. Thus, the results of this study show that the surface of diamonds can be etched.

• Proceedings of the KWS Conference
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• 2009.11a
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• pp.66-66
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• 2009

Various alloy system, such as Cu-Sn-Ti, Cu-Ag-Ti, and Ni-B-Cr-based alloy are used for the brazing of diamond grits. However, the problem of the adhesion strength between the diamond grits and the brazed alloy is presented. The adhesion strength between the diamond grits and the melting filler alloy is predicted by the contact angle, thereby, instead of diamond grit, the study on the wettability between the graphite and the brazing alloy has been indirectly executed. In this study, Cu-13Sn-12Ti filler alloy was manufactured, and the contact angles, the shear strengths and the interfacial area between the graphites(diamond grits) and braze matrix were investigated. The contact angle was decreased on increasing holding time and temperature. The results of shear strength of the graphite joints brazed filler alloys were observed that the joints applied Cu-13Sn-12Ti alloy at brazing temperature 940 $^{\circ}C$ was very sound condition indicating the shear tensile value of 23.8 MPa because of existing the widest carbide(TiC) reaction layers. The micrograph of wettability of the diamond grit brazed filler alloys were observed that the brazement applied Cu-13Sn-12Ti alloy at brazing temperature $990^{\circ}C$ was very sound condition because of existing a few TiC grains in the vicinity of the TiC layers.

• Journal of Welding and Joining
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• v.28 no.3
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• pp.49-58
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• 2010

Various alloy system, such as Cu-Sn-Ti, Cu-Ag-Ti, and Ni-B-Cr-based alloy are used for the brazing of diamond grits. However, the problem of the adhesion strength between the diamond grits and the brazed alloy is presented. The adhesion strength between the diamond grits and the melting filler alloy is predicted by the contact angle, thereby, instead of diamond grit, the study on the wettability between the graphite and the brazing alloy has been indirectly executed. In this study, Cu-13Sn-12Ti filler alloy was manufactured, and the contact angles, the shear strengths and the interfacial area between the graphites (diamond grits) and braze matrix were investigated. The contact angle was decreased on increasing holding time and temperature. The results of shear strength of the graphite joints brazed filler alloys were observed that the joints applied Cu-13Sn-12Ti alloy at brazing temperature $940^{\circ}C$ was very sound condition indicating the shear tensile value of 23.8 MPa because of existing the widest carbide(TiC) reaction layers. The micrograph of wettability of the diamond grit brazed filler alloys were observed that the brazement applied Cu-13Sn-12Ti alloy at brazing temperature $990^{\circ}C$ was very sound condition because of existing a few TiC grains in the vicinity of the TiC layers.