• 한국표면공학회지
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• 제33권2호
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• pp.115-125
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• 2000

TiN films were deposited onto Stellite 6B alloy (Co base) by the reactive magnetron sputter ion plating. As the bias increases, TiN film changes from columnar structure to dense structure with great hardness and smooth surface due to densification and resputtering by ion bombardment. The content of oxygen and carbon impurities in the TiN film decreases greatly when the substrate bias is applied. The preferred orientation of the TiN films changes from (200) to (111) with decreasing $N_2$/Ar ratio, and from (200) to (111) and then (220) with increasing the substrate bias. The change of the preferred orientation is discussed in terms of surface energy and strain energy which are related to the impurity contents and the ion bombardment damage. The hardness of the TiN film increases with increasing compressive stress generated in the film by virtue of ion bombardment. It becomes as high as up to 3500kgf/mm$^2$ when an appropriate substrate bias is applied.

• 대한기계학회논문집A
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• 제25권10호
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• pp.1590-1596
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• 2001

The shot peening process is most often used to improve fatigue properties of metal parts. The single most critical parameter of the shot peening process is the shot ball itself. Without the correct quality media, all other shut peening parameters are extraneous and the desired fatigue improvement and consistency of improvement will not be achieved. Shot peening involves modifications of the surface and subsurface condition of a material that can be described by the change of the residual stresses, the hardness, and the surface roughness. This Paper Presents the shot peening to optimize the shot ball parameters. The effect of shot peening parameter on the surface roughness, surface hardness and residual stress are investigated.

• 반도체디스플레이기술학회지
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• 제12권1호
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• pp.61-65
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• 2013

We investigated the wearable dynamics of diamond spherical abrasive during the substrate surface polishing under the pad compression via classical molecular dynamics modeling. We performed three-dimensional molecular dynamics simulations using the Morse potential functions for the copper substrate and the Tersoff potential function for the diamond abrasive. The pad hardness had a big impact on the wearable dynamics of the abrasive. The moving speed of the abrasive decreased with increasing hardness of the pad. As the hardness decreased, the abrasive was indented into the pad and then the sliding motion of the abrasive was increased. So the pad hardness was greatly influenced on the slide-to-roll ratio as well as the wearable rate.

• 한국진공학회지
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• 제18권2호
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• pp.97-101
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• 2009

현대의 반도체 산업에서 공정 중 가장 큰 비중을 차지하며, 가장 많은 자본과 인력을 소비하는 것이 바로 세정 공정이다. 세정공정은 소자의 작동에 영향을 미치고 기능을 저하시킬 수 있는 이물질 입자들을 제거하는 것이다. 특히 소자를 식각하기 위한 Photoresist(PR) 과정이 끝날 때마다 항상 세정 과정이 포함되어야 했다. 또한, Photoresist(PR) 공정 중 생성된 HDI-PR(high dose implanted photoresist)은 세정 과정에서 제거가 힘들기 때문에 현대의 고밀도 집적회로 세정 공정에서는 건식 세정과 습식 세정을 혼용하여 여러 단계의 세정 공정을 거치게 된다. 이 논문에서는 기존 플라즈마 방식으로 대표되는 건식 세정과 약액으로 대표되는 습식 세정을 동시에 사용하는 방식을 사용하여 약액활성화 방법(Plasma Liquid-Vapor Activation; PLVA)을 제안하여 실험을 실시하였고 HDI-PR을 활성화된 용액에 담근 후 Nano-Indenter를 이용하여 표면강도와 탄성계수를 측정했다. Nano-indenter는 특정한 기하학적 형태를 가지는 Tip을 표면에 압입한 후 압입하중과 압입깊이를 측정함으로서 시료의 표면강도와 탄성계수를 측정하였다. 그 결과 plasma로 활성화된 PR stripper 용액으로 strip한 후의 시료의 표면 강도가 크게 줄어든 것을 확인하였다. 이는 이후 물리적 표면 세정 공정을 후 공정으로 사용한다면 보다 효율적인 HDI-PR을 제거할 수 있을 것으로 사료된다.

• 열처리공학회지
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• 제16권5호
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• pp.253-259
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• 2003

In this study, to find out the reason of deterioration in surface roughness of steel and cast iron after Tufftride, it has been investigated on the relation between the surface roughness and various factors such as the evolution of compound layer, surface morphology, and surface hardness, and change of pore ratio in the compound layer during Tufftride at $580^{\circ}C$. It is found that the surface roughness was increased with the evolution of compound layer during Tufftride of steel and cast iron. The change of surface roughness after Tufftride was reduced with decreasing tho content of carbon and cementite ($Fe_3C$) in the materials. in the cast irons, the various shaped graphites that was exposed to the surface should induce the discontinuous growth of the compound layer, and this resulted in the incoherent interfaces between matrix and compound layer and the deterioration of surface roughness. In the steels, the existence of cementites in the matrix resulted in the incoherent interfaces between matrix and compound layer. It is considered that during Tufftride the surface roughness must be mainly influenced by the formation of the incoherent interface between compound layer and matrix that is affected by some factors such as the microstructure, the composition, and the hardness of the matrix.

• Journal of Periodontal and Implant Science
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• 제32권2호
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• pp.315-324
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• 2002

The purpose of this in vitro study was to evaluate the efficiency of Er:YAG laser on calculus removal and the morphologic changes and hardness of the irradiated surface at different power settings. This experiment used human teeth which were extracted due to periodontal disease and had a band of calculus. Forty root slabs ($5{\times}5mm$) were made and divided into control group and irradiated groups. Experimental groups were as follows; Control group (root planing), Group1 (irradiated with laser at 30mJ), Group2 (irradiated with laser at 60mJ), Group3 (irradiated with laser at 100mJ). Twelve root slab embedded in resin block were used in each group. Er:YAG laser was applied under water irrigation with the tip held perpendicular to the root surface in contact mode. The treatment time was measured until the calculus was removed completely under naked eyes. The efficiency of calculus removal was evaluated by the time for removal. Morphological changes of laser irradiated site were observed under SEM and the surface hardness was measured using a VH tester. The results were as follows; 1. The efficiency of laser scaling was increased with increasing the energy level of irradiation(p<0.05). 2. The morphological changes such as carbonization, crater and scale-like defects in the irradiated root surface were frequently observed with increasing the energy level. 3. The surface hardness tended to increase at 60mJ and 100mJ irradiated groups than that of control group. From the results evaluting on the efficiency, morphological change and surface hardness, lower energy level was suggested for the clinical application of the Er:YAG laser in scaling.

• The Journal of Advanced Prosthodontics
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• 제16권2호
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• pp.115-125
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• 2024

PURPOSE. The purpose of this in vitro study was to investigate the fracture resistance, surface hardness, and color stain of 3D printed, CAD-CAM milled, and conventional interim materials. MATERIALS AND METHODS. A total of 80 specimens were fabricated from auto polymerizing polymethyl methacrylate (PMMA), bis-acryl composite resin, CAD-CAM polymethyl methacrylate resin (milled), and 3D printed composite resin (printed) (n = 20). Forty of them were crown-shaped, on which fracture strength test was performed (n = 10). The others were disc-shaped specimens (10 mm × 2 mm) and divided into two groups for surface hardness and color stainability tests before and after thermal cycling in coffee solution (n = 10). Color parameters were measured with a spectrophotometer before and after each storage period, and color differences (CIEDE2000 [DE00]) were calculated. The distribution of variables was measured with the Kolmogorov Smirnov test, and one-way analysis of variance (ANOVA), Tukey HSD, Kruskal-Wallis, Mann-Whitney U tests were used in the analysis of quantitative independent data. Paired sample t-test was used in the analysis of dependent quantitative data (P < .05). RESULTS. The highest crown fracture resistance values were determined for the 3D printed composite resin (P < .05), and the lowest were observed in the bis-acryl composite resin (P < .05). Before and after thermal cycling, increase in mean hardness values were observed only in 3D printed composite resin (P < .05) and the highest ΔE₀₀ value were observed in PMMA resin for all materials (P < .05). CONCLUSION. 3D printing and CAD-CAM milled interim materials showed better fracture strength. After the coffee thermal cycle, the highest surface hardness value was again found in 3D printing and CAD-CAM milled interim samples and the color change of the bis-acryl resin-based samples and the additive production technique was higher than the PMMA resin and CAD-CAM milled resin samples.

• 열처리공학회지
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• 제19권2호
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• pp.83-89
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• 2006

The surface phase changes, the hardness variations, the nitrogen contents and the corrosion resistances of 17-4 PH stainless steel have been investigated after nitrogen permeation(solution nitriding) at a temperature ranges from $1050^{\circ}C$ to $1150^{\circ}C$ The phases appeared at the nitrogen-permeated surface layer were shown to martensite plus austenite and austenite, depending on the variation of nitrogen and chromium contents. And the surface hardness was also depended on the phases appeared at the surface layer from 370 Hv to 220 Hv. The precipitates exhibited at the nitrogen-permeated surface layer were niobium nitride, niobium chromium nitride and carbo-nitride in the austenite and martensite matrices. The surface nitrogen contents were followed by the Cr contents of the surface layers, representing 0.55% at the temperatures of $1050^{\circ}C$ and $1150^{\circ}C$ respectively, and 0.96% at $1100^{\circ}C$ at the distances of $60{\mu}m$ from the outmost surface. From the comparison of the corrosion resistances between nitrogen-permeated and solution-annealed steels, nitrogen permeation remarkably improved the corrosion resistance in the solution of 1 N $H_2SO_4$ due to the increase of nitrogen content in the surface austenite phase.

• 한국재료학회지
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• 제19권9호
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• pp.457-461
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• 2009

Recently, metal molding has become essential not only for automobile parts, but also mass production, and has greatly influenced production costs as well as the quality of products. Its surface has been treated by carburizing, nitriding and induction hardening, but these existing treatments cause considerable deformation and increase the expense of postprocessing after treatment; furthermore, these treatments cannot be easily applied to parts that requiring the hardening of only a certain section. This is because the treatment cannot heat the material homogeneously, nor can it heat all of it. Laser surface treatment was developed to overcome these disadvantages, and, when the laser beam is irradiated on the surface and laser speed is appropriate, the laser focal position is rapidly heated and the thermal energy of surface penetrates the material after irradiation, finally imbuing it with a new mechanical characteristic by the process of self-quenching. This research estimates the material characteristic after efficient and functional surface treatment using HPDL, which is more efficient than the existing CW Nd:YAG laser heat source. To estimate this, microstructural changes and hardness characteristics of three parts (the surface treatment part, heat affect zone, and parental material) are observed with the change of laser beam speed and surface temperature. Moreover, the depth of the hardened area is observed with the change of the laser beam speed and temperature.

• 대한설비공학회:학술대회논문집
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• 대한설비공학회 2009년도 하계학술발표대회 논문집
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• pp.916-921
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• 2009

In this study, lubrication characteristics of sliding members were compared with the change of the hardness of friction surfaces and the application of nano-oil. The materials of the specimens were gray cast iron (AISI 35, AISI 60) and nickel chromium molybdenum steel (AISI 4320). The Friction coefficients and the temperature variations of on the frictional surfaces were measured by disk-on-disk tribotester under the condition of fixed rotating speed. The friction surfaces were observed by scanning electron microscope (SEM). In the results, the friction coefficients of the disk surface were increased as hardness difference was increased. The friction coefficient lubricated in nano-oil was less than mineral oil. This is because a spherical nano particle plays a tiny ball bearing between the frictional surfaces, improved the lubrication characteristics.