• 한국정밀공학회지
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• 제25권9호
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• pp.32-37
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• 2008

Freestanding hydride vapor phase epitaxy grown GaN(Gallium Nitride) substrates subjected to various polishing methods were characterized for their surface and subsurface conditions, Although CMP(Chemical Mechanical Polishing) is one of the best approaches for reducing scratches and subsurface damages, the removal rate of Ga-polar surface in CMP is insignificant($0.1{\sim}0.3{\mu}m$/hr) as compared with that of N-polar surface, Therefore, conventional MP(Mechanical Polishing) is commonly used in the GaN substrate fabrication process, MP of (0001) surface of GaN has been demonstrated using diamond slurries with different abrasive sizes, Diamond abrasives of size ranging from 30nm to 100nm were dispersed in ethylene glycol solutions and mineral oil solutions, respectively. Significant change in the surface roughness ($R_a$ 0.15nm) and scratch-free surface were obtained by diamond slurry of 30nm in mean abrasive size dispersed in mineral oil solutions. However, MP process introduced subsurface damages confirmed by TEM (Transmission Electronic Microscope) and PL(Photo-Luminescence) analysis.

• 기술사
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• 제30권6호
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• pp.144-152
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• 1997

Development of diamond wheel with fine grains and multi-pore structures were newely attempted to be studied in this paper. Wheels, that are employed for the smooth and mirrow finishing of die materials such as tungsten carbide alloy using tool and die materials, must have both performances to remove tool marks efficiently and to contact elastically with curved surfaces. Diamond abrasive grains were bonded firmly by a melamine to prevent the decrease of machining efficiency due to grain sinking within the bond materials. Also, highly foamed structures were developed to increase the flexibility of the wheel, and to induce active self-sharpening by increasing contact pressure between the wheel and work sufaces. In this paper, melamine-bonded diamond wheels are trial manufactured, then the forming method of wheels are explained.

• Advances in nano research
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• 제12권6호
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• pp.583-592
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• 2022

In this paper, a pulsed picosecond laser dressing method for bronze-bonded diamond wheel is studied systematically and comprehensively. The picosecond laser pulse ablation experiment is carried out, and the ablation thresholds of bronze-bonded and diamond abrasive particle are measured respectively. The results indicate that the single-pulse ablation thresholds of bronze-bonded are 0.89J/cm², 0.24J/cm² during strong/weak ablation stages. And the multi-pulse ablation thresholds of diamond abrasive particle are 1.69J/cm², 0.49J/cm² during strong/weak ablation stages. Obviously, diamond grains have less thermal damage during the process of gentle ablation. The diamond grains of the grinding wheel surface are graphitized during laser dressing. The bronze-bonded is relatively smooth and organizational stability, and the diamond grits have suitable prominent height, which are beneficial to maintain the good grinding performance of dressed bronze-bonded diamond grinding wheels.

• Tribology and Lubricants
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• 제35권6호
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• pp.330-336
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• 2019

Conditioning is a process involving pad surface scraping by a moving metallic disk that is electrodeposited with diamond abrasives. It is an indispensable process in chemical-mechanical planarization, which regulates the pad roughness by removing the surface residues. Additionally, conditioning maintains the material removal rates and increases the pad lifetime. As the conditioning continues, the pad profile becomes unevenly to be deformed, which causes poor polishing quality. Simulation calculates the density at which the diamond abrasives on the conditioner scratch the unit area on the pad. It can predict the profile deformation through the control of conditioner dwell time. Previously, this effect of the diamond shape on conditioning has been investigated with regard to microscopic areas, such as surface roughness, rather than global pad-profile deformation. In this study, the effect of diamond shape on the pad profile is evaluated by comparing the simulated and experimental conditioning using two conditioners: a) random-shaped abrasive conditioner (RSC) and b) uniform-shaped abrasive conditioner (USC). Consequently, it is confirmed that the USC is incapable of controlling the pad profile, which is consistent with the simulation results.

• 한국산업융합학회 논문집
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• 제23권4_2호
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• pp.675-682
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• 2020

Multi-wire sawing is the prominent technology employed to cut hard material ingots into wafers. This paper aimed to research the effect of diamond toughness index on the cutting performance of electroplated diamond wire. Three different toughness index of diamond abrasives were used to manufacture electroplated diamond wires. The cutting performance of electroplated diamond wire is verified through experiments, in which sapphire ingot are cut using single wire sawing machine. A single wire saw for constant load slicing is developed for the cutting performance evaluation of electroplated diamond wire. Choosing the cutting depth, total cutting depth, cutting force and wear of electroplated diamond wires as evaluation parameters, the performance of electroplated diamond wire is evaluated. The results of this study showed that there was a significant direct relationship between the toughness index of diamond abrasives and the cutting performance. Results demonstrated that diamond abrasive with a high toughness index showed higher cutting performance. However, all diamond abrasives showed similar cutting performance under low load conditions. The results of this paper are useful for the development of cutting large diameter ingots and cutting high hardness ingots at high speed.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2012년도 추계학술대회 논문집
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• pp.147-148
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• 2012

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2008년도 춘계학술대회 논문집
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• pp.361-362
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• 2008

• 한국분말재료학회지
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• 제16권6호
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• pp.416-423
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• 2009

Diamond/SiC composites are appropriate candidate materials for heat conduction as well as high temperature abrasive materials because they do not form liquid phase at high temperature. Diamond/SiC composite consists of diamond particles embedded in a SiC binding matrix. SiC is a hard material with strong covalent bonds having similar structure and thermal expansion with diamond. Interfacial reaction plays an important role in diamond/SiC composites. Diamond/SiC composites were fabricated by high temperature and high pressure (HPHT) sintering with different diamond content, single diamond particle size and bi-modal diamond particle size, and also the effects of composition of diamond and silicon on microstructure, mechanical properties and thermal properties of diamond/SiC composite were investigated. The critical factors influencing the dynamics of reaction between diamond and silicon, such as graphitization process and phase composition, were characterized. Key factor to enhance mechanical and thermal properties of diamond/SiC composites is to keep strong interfacial bonding at diamond/SiC composites and homogeneous dispersion of diamond particles in SiC matrix.

• 한국표면공학회지
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• 제28권4호
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• pp.225-235
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• 1995

To investigate the effects of pretreatment and substrate bias on the characteristics of the diamond thin films, the thin films were deposited on the p-type Si(100) wafer by MPECVD using mixtures of $H_2$, $CH_4$, and $O_2$ gases. Deposition was carried out at the substrate temperature of $900^{\circ}C$ and at the pressure of 40torr. The effect of the pretreatment on the film formation was the examined by using SiC and diamond powders as abrasive powders. Furthermore, the substrate bias effect on the formation of the diamond film was also examined. The highest nucleation density was observed for the pretreatment with 40~60$\mu\textrm{m}$ size of diamond powders and a negative bias potential(-50V). Many defects and(111) twins in the diamond films were observed.

• 한국기계가공학회지
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• 제21권5호
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• pp.77-83
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• 2022

A high-hardness tool material is required to reduce extreme abrasive wear when drilling carbon fiber reinforced plastic (CFRP). Single-crystal diamond is the hardest material in the world, but it is very expensive to be used as a cutting tool. Polycrystalline diamond (PCD) is a diamond grit fused at a high temperature and pressure, and diamond-like carbon (DLC) is an amorphous carbon with high hardness. This study compares DLC coatings and PCD inserts to conventional TiAlN-coated tungsten carbide drills. In fiberglass and carbon fiber reinforced polymer drilling, the tool wear of DLC-coated carbide was approximately half that of TiAlN-coated tools, and slight tool wear occurred in the case of PCD insert end drills.