• 한국표면공학회:학술대회논문집
• /
• 한국표면공학회 2013년도 춘계학술대회 논문집
• /
• pp.170-170
• /
• 2013

We present a novel etching technique for 2-dimentional (2-D) hexagonal boron nitride (h-BN) by using capacitively coupled plasma (CCP) of oxygen combined with a post-treatment by de-ionized (DI) water. Oxygen CCP etching process for h-BN has been systematically studied. It is found that a passivation layer was generated to obstruct further etching while it can be easily and radically removed by DI water. An essential cleaning effect also has been observed in the etching process, organic residues are successfully removed and the surface roughness has much decreased. Considering h-BN is the most important 2-D dielectric material and its potential application for graphene to silicon-based electronic devices, such an etching method can be widely used to control the 2-D h-BN thickness and improve the surface quality.

• 한국분말재료학회지
• /
• 제9권5호
• /
• pp.365-369
• /
• 2002

Silica hydrogel was synthesized by the reaction of liquid sodium silicate with sulfuric acid. The condensation polymerization of the synthesized hydrogel was carried out via an aging process under the acidic or alkaline conditions. Nano porous silica with the pore size below 3 nm and surface area of $715m^2/g$, was obtained by the above processes in acidic ranges(pH : 3~5). The pore size and surface area of the silica varied with pH, and in alkaline ranges(pH : 8~10), those were 21 nm and $300m^2/g$ respectively. The characteristics of the silica varied with the thermal treatment which caused the change of surface area, pore volume and pore diameter.

• 동력기계공학회지
• /
• 제14권4호
• /
• pp.50-55
• /
• 2010

In order to investigate tribological effects of nano copper particles impregnated(CuN) on surface polytetrafluoroethylene(PTFE) on sealing wear and an experimental study was carried out to determine the wear behavior of copper nano-particles impregnation two kind thickness in super critical $CO_2$ liquid. Experimental results showed that the friction coefficients of CuN PTFE at the low sliding speed(0.44m/s) and the oil temperature ($60^{\circ}C$) were higher than that of virgin PTFE. And a thin nano copper particles impreganated thickness was formed on the surface in the PTFE and the specimen with this treatment has much better friction properties than the original one. Fortunately, at the high load(80 N) and the oil temperature, the friction coefficient of CuN PTFE was lower than that of virgin PTFE. This evidenced the load carrying capacity of CuN PTFE was much better than that of virgin PTFE under the high load condition(80 N) specially. Therefore, it can be concluded that the friction coefficient variation of CuN PTFE is very small but its wear rate decreases greatly with increase in sliding speed.

• 한국표면공학회지
• /
• 제55권1호
• /
• pp.24-31
• /
• 2022

This study investigated the effect of pre-treatment on the PEO film formation of AZ91 Mg alloy. The pre-treatment was conducted for 10 min at room temperature in 0.5 M oxalic acid (C₂H₂O₄) solution containing various ammonium fluoride (NH₄F) concentrations. The pre-treated AZ91 Mg specimens were anodized at 100 mA/cm² of 300 Hz AC for 2 min in 0.1 M NaOH + 0.4 M Na₂SiO₃ solution. When AZ91 Mg alloy was pretreated in 0.5 M oxalic acid with NH₄F concentration less than 0.3 M, continuous dissolution of the AZ91 Mg alloy occurred together with the formation of black smuts and arc initiation time for PEO film formation was very late. It was noticed that corrosion rate of the AZ91 Mg alloy became faster if small amount of NH₄F concentration, 0.1 M, is added. The fast corrosion is attributable to fast formation of porous fluoride together with porous oxides in the reaction products. On the other hand, when AZ91 Mg alloy was pretreated in 0.5 M oxalic acid with sufficient NH₄F more than 0.3 M, a thin and dense protective film was formed on the AZ91 Mg alloy surface which resulted in faster initiation of arcs and formation of PEO film.

• 한국결정성장학회지
• /
• 제29권6호
• /
• pp.239-244
• /
• 2019

수소 분위기 열처리 및 수소 플라즈마 처리의 두 가지 수소화 표면개질을통해 나노다이아몬드 seed 입자의 분산 향상 및 평탄한 초미세 나노결정질 다이아몬드 박막증착을 위한 핵형성 밀도 향상을 확보하였다. 수소화 처리 이후 나노다이아몬드 입자 표면의 탄소-산소 및 산소-수소 결합기가 탄소-수소 결합기로 전환되는 화학적 표면개질이 진행되었고 Zeta 전위가 증가하였다. 분산도 향상에 따라 나노다이아몬드 응집체 크기가 현저하게 감소하였고 핵형성 밀도는 크게 증가하였다. 600℃, 수소분위기에서 열처리 이후 나노다이아몬드 평균 입자 크기가 3.5 ㎛에서 34.5 nm로 크게 감소하였고, seeding 된 Si 기판 표면에서 ~3.9 × 10¹¹ nuclei/㎠의 매우 높은 핵형성 밀도를 확보하였다.

• 열처리공학회지
• /
• 제35권3호
• /
• pp.139-149
• /
• 2022

In the automobile and shipbuilding industries, various materials and components require superior surface strength, excellent wear resistance and good resistance to repeated loads. To improve the surface properties of the materials, various surface heat treatment methods are used, which include carburizing, nitriding, and so on. Among them, carburizing treatment is widely used for structural steels containing carbon. The effective carburizing thickness required for materials depends on the service environment and the size of the components. In general, however, there is a limit in evaluation of the surface properties with a standardized mechanical test method because the thickness or cross-sectional area of the carburized layer is limited. In this regard, the nanoindentation technique has lots of advantages, which can measure the mechanical properties of the material surface at the nano and micro scale. It is possible to understand the relationship between the microstructural change in the hardened layer by carburizing treatment and the mechanical properties. To be spread to practical applications at the industrial level, in this paper, the principle of the nanoindentation method is described with a representative application for analyzing the mechanical properties of the carburized material.

• 열처리공학회지
• /
• 제34권2호
• /
• pp.75-80
• /
• 2021

The crystal grains of polycrystalline diamond vary depending on deposition conditions and growth thickness. The diamond thin film deposited by the CVD method has a very rough growth surface. On average, the surface roughness of a diamond thin film deposited by CVD is in the range of 1-100 um. However, the high surface roughness of diamond is unsuitable for application in industrial applications, so the surface roughness must be lowered. As the surface roughness decreases, the scattering of incident light is reduced, the heat conduction is improved, the mechanical surface friction coefficient can be lowered, and the transmittance can also be improved. In addition, diamond-coated cutting tools have the advantage of enabling ultra-precise machining. In this study, the surface roughness of diamond was improved by thermal diffusion reaction between diamond carbon atoms and ferrous metals at high temperature for diamond thin films deposited by MPCVD.

• 전기화학회지
• /
• 제13권4호
• /
• pp.246-250
• /
• 2010

In this study, nano-crystallized $Al_2O_3$ was coated on the surface of $LiFePO_4$ powders via a novel dry coating method. The influence of coated $LiFePO_4$ upon electrochemical behavior was discussed. Surface morphology characterization was achieved by transmission electron microscopy (TEM), clearly showing nano-crystallized $Al_2O_3$ on $LiFePO_4$ surfaces. Furthermore, it revealed that the $Al_2O_3$-coated $LiFePO_4$ cathode exhibited a distinct surface morphology. It was also found that the $Al_2O_3$ coating reduces capacity fading especially at high charge/discharge rates. Results from the cyclic voltammogram measurements (2.5-4.2 V) showed a significant decrease in both interfacial resistance and cathode polarization. This behavior implies that $Al_2O_3$ can prevent structural change of $LiFePO_4$ or reaction with the electrolyte on cycling. In addition, the $Al_2O_3$ coated $LiFePO_4$ compound showed highly improved area-specific impedance (ASI), an important measure of battery performance. From the correlation between these characteristics of bare and coated $LiFePO_4$, the role of $Al_2O_3$ coating played on the electrochemical performance of $LiFePO_4$ was probed.

• 한국표면공학회지
• /
• 제41권4호
• /
• pp.163-168
• /
• 2008

The dental orthodontic bracket requires good mechanical properties, such as elastic strength and frictional resistance, combined with a high resistance to corrosion. The objective of this study was to investigate the effects of TiN and ZrN coating on corrosion resistance of orthodontic brackets using various electrochemical methods. Brackets manufactured by Ormco Co. were used, respectively, for experiment. Ion plating was carried out for coatings of bracket using Ti and Zr coating materials with nitrogen gas. Ion plated surface of each specimen was observed with field emission scanning electron microscopy(FE-SEM), energy dispersive Xray spectroscopy(EDS) and electrochemical tester. The corrosion potential of the TiN and ZrN coated bracket was comparatively high. The current density of TiN and ZrN coated bracket was smaller than that of non-coated bracket in 0.9% NaCl solution. Pit nucleated at angle of bracket slot.

• 마이크로전자및패키징학회지
• /
• 제25권4호
• /
• pp.47-52
• /
• 2018

본 연구에서는 디스플레이에 적용되는 기능성 고분자 필름의 나노구조에 의한 기계적 물성 저하 문제를 해결하기 위해 열처리 방법과 멀티스케일 계층구조를 통한 PMMA(Poly(methyl-methacrylate)) 필름의 내구성 향상에 대해 연구하였다. PMMA 필름의 기계적 특성을 향상시키기 위한 열처리 공정은 고온/고압의 자유제적 제어공정과 고온 공정 후 급속히 냉각시키는 공정으로 구성되어 있으며, 열 나노임프린트를 이용하여 스크래치로부터 나노구조를 보호하기 위한 멀티스케일 계층구조를 형성하였다. 연필경도 시험에 의해 발생한 미세구조의 손상에 대한 평가를 위해 표면 형상 변화와 기능성 변화를 평가하였으며, 이를 통하여 열처리와 멀티스케일 계층구조가 스크래치에 의한 정접촉각 감소와 투과율 손실 저감에 효과적임을 확인하였다.