• 한국재료학회지
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• 제9권6호
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• pp.609-614
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• 1999

The effect of the amount of $SiO_2$dopant on the behavior of $AlO_2$$O_3$-composite formation by melt oxdation of Al-alloy was examined in this paper. The $SiO_2$powder was spread on the top surface of the Al-1Mg-3-Si-5Zn-1Cu alloy in th alumina crucible. The selected amount of each powder was 0.03, 0.10, 0.16g/$\textrm{cm}^2$. The oxidation behavior was determined by observing the weight gain after the heat treatment for 10 hours at 1373K. The macroscopic structure of formed oxide layer was examined by an optical microscope. The top surface and the cross-section of the grown oxide layer were investigated by SEM and analysed by EDX. The $SiO_2$ powder was determined to enhance oxidation by thermit reaction with Al which reduced the growth incubation period of the oxidation layer. As the amount of the $SiO_2$dopant increased, the growth rate decreased due to the precipitated Si which blocked the Al-alloy channel in the composite materials. However, more uniform layer was obtained due to the occurrance of the enhanced oxidation reaction in the whole alloy surface compared to the case of addition of less amount of dopant.

• 한국안광학회지
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• 제15권4호
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• pp.313-317
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• 2010

목적: 이 연구 목적은 가공한 마그네슘 합금 AZ31 안경테를 plasma electrolytic oxidation(PEO) 표면 처리 후 표면특성에 대하여 조사하는 것이다. 방법: Plasma electrolytic oxidation(PEO) 표면 처리는 DC 전압을 변화시키며 처리하였고, 피막의 상 분석은 X-ray 회절기로 측정하였고, 형태학적 미세구조는 주사전자현미경로 관찰하였다. 그리고 피막층에 존재하는 원소의 농도를 에너지 분산 X-선 스펙트럼으로 조사하였다. 결과: PEO 처리시 전압이 증가함에 따라 XRD 측정 결과 MgO 피크가 증가하였으며, SEM 사진에서는 표면의 산화피막이 조밀하게 생기는 것을 확인 할 수 있었다. 그리고 EDS에서 성분의 변화도 일치함을 보여주었다. 결론: PEO 산화피막층은 전압이 증가 할수록 MgO 화합물의 형성이 점점 증가하기 때문에 산화막의 결정화가 진행되며, 65V에 60초 처리 시 표면상태, 접촉각, 내식성 시험에서 가장 좋은 결과를 보여 주었다.

• 한국표면공학회지
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• 제32권4호
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• pp.531-537
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• 1999

A copper based leadframe was oxidized in brown-oxide forming solution, then the growth characteristics of brown oxide and the effect of brown-oxide formation on the adhesion strength of leadframe to epoxy molding compound (EMC) were studied by using sandwiched double cantilever beam (SDCB) specimens. The brown oxide is composed of fine acicular CuO, and its thickness increased up to ~150 nm within 2 minutes and saturated. Bare leadframe showed alomost no adhesion to EMC, while once the brown-oxide layer formed on the Surface of leadframe, the adhesion strength increased up to ~80 J/$\m^2$ within 2 minutes. Correlation between oxide thickness, $\delta$ and the adhesion strength in terms of interfacial fracture toughness, $G_{c}$ was linear. Considering the above results, we might conclude that the main adhesion mechanism of brown-oxide treated leadframe to EMC is mechanical interlocking, in which fine acicular CuO plays a major role.e.

• 한국재료학회지
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• 제28권4호
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• pp.201-207
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• 2018

Infrared(IR) heating has many advantages, such as energy efficiency, reduced heating time, cleanliness, equipment compactness, high drying rate and easy automation. These features of IR heating provide widely industrial applications, such as surface heat treatment in semiconductor fabrication, thermoforming of polymers, drying and disinfection of food products, heating to metal forging, and drying of wet materials. In this study, the characteristics of a protected gold mirror were examined by spectrophotometer and the lifetime of the coating layers were evaluated by a cross-cutting method and salt spray test. The effects of manufacturing conditions on the protected gold mirror were seen and remedies for these effects were noted in order to improve the properties of the protected gold mirror in the drying process. The reflectance and lifetime of the protected gold mirror was influenced by manufacturing conditions, such as surface roughness and forming conditions of the anti-oxide layer, the adhesion layer, the reflecting layer and the protection layer. The results of this study showed that the protected gold mirror manufactured using a buffing method for pre-treatment resulted in the most effective reflectance. In addition, $Al_2O_3$ coating on an Al substrate as an anti-oxide layer was more effective than the anodizing process in the test of reflectance. Furthermore, the protected gold mirror manufactured by layers forming of various materials resulted in the most effective reflectance and lifetime when coated with $Al_2O_3$ as the anti-oxide layer, coated Cr as the adhesion layer, and coated $MgF_2$ as the protection layer.

• 한국표면공학회:학술대회논문집
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• 한국표면공학회 2017년도 춘계학술대회 논문집
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• pp.150.2-150.2
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• 2017

This research was conducted to investigate in detail the effect of $PO_4{^{3-}}$, $CO_3{^{2-}}$ and $F^-$ anions on the electrochemical properties of the thin air-formed oxide film-covered AZ31 Mg alloy. In this work, native air-formed oxide films on AZ31 Mg alloy samples were prepared by knife-abrading method and the changes in the electrochemical properties of the air-formed oxide film were investigated in electrolytes containing 0.01 M, 0.05 M and 0.1 M of $PO_4{^{3-}}$, $CO_3{^{2-}}$ and $F^-$ anions. It was observed that the trend of open circuit potential (OCP) transients changed only in the solution containing $PO_4{^{3-}}$ ions. The Nyquist plots obtained from electrochemical impedance spectroscopy (EIS) showed that the resistance of the new surface films formed in fluoride ion containing bath increased with the increase in concentration of fluoride ions but the resistance of surface films formed in carbonate ion containing bath decreased with the increase in concentration of carbonate ions. The potentiodynamic polarization curves illustrated that under anodic polarization, there was growth of porous passive layer only in fluoride ion containing solution while the surface layer formed in phosphate and carbonate ion containing solutions lost its passivity at high anodic potential of $2.5V_{Ag/AgCl}$.

• 센서학회지
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• 제29권6호
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• pp.420-426
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• 2020

A metal oxide semiconductor gas sensor is operated by measuring the changes in resistance that occur on the surface of nanostructures for gas detection. ZnO, which is an n-type metal oxide semiconductor, is widely used as a gas sensor material owing to its high sensitivity. Various ZnO nanostructures in gas sensors have been studied with the aim of improving surface reactions. In the present study, the sol-gel and vapor phase growth techniques were used to fabricate nanostructures to improve the sensitivity, response, and recovery rate for gas sensing. The sol-gel method was used to synthesize SnO₂ nanoparticles, which were used as the seed layer. The nanoparticles size was controlled by regulating the process parameters of the solution, such as the pH of the solution, the type and amount of solvent. As a result, the SnO₂ seed layer suppressed the aggregation of the nanostructures, thereby interrupting gas diffusion. The ZnO nanostructures with a sol-gel processed SnO₂ seed layer had larger specific surface area and high sensitivity. The gas response and recovery rate were 1-7 min faster than the gas sensor without the sol-gel process. The gas response increased 4-24 times compared to that of the gas sensor without the sol-gel method.

• 센서학회지
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• 제28권4호
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• pp.236-239
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• 2019

In this work, we performed an optical simulation study on the performance of a PMDPP3T:PCBM based on an organic photovoltaic (PV) device. The virtual PV device was developed in Lumerical, finite-difference time-domain (FDTD) solutions. Different layers of the PV cell have been defined through the incorporation of complex refractive index value of those layers' constituent materials. During the simulation study, the effect of the variation active layer thickness on an ideal short circuit current density ($J_{sc,ideal}$) of the PV cell has been, first, observed. Thereafter, we have investigated the impact of surface roughness of a transparent conducting oxide (TCO) electrode on $J_{sc,ideal}$ of the PV cells. From this simulation, it has been observed that the $J_{sc,ideal}$ value of the PV cell is strongly dependent on the thickness of its active layer and the photon absorption of the PV cell has gradually decreased with the increment of the TCO's surface roughness. As a result, the capability of the PV device has been reduced with the increment of the surface roughness of the TCO.

• 한국표면공학회지
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• 제28권1호
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• pp.23-33
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• 1995

AISI 304 stainless steel has high resistance to corrosion due to the presence of a self-healing chromium oxide film on the surface, which also accounts for the difficulty in plating. Surface cleaning of this alloy is of fundamental importance in gold plating since its effectiveness puts an upper limit on the quality of the final coating. The cleaning of AISI 304 stainless steel was investigated with elimination of artificial passive oxide film and degreasing of remaining buffing wax as stearic acid. The familiar cleaning methods i.e. ultrasonic cleaning, electro-cleaning and activation treatment were fabricated in this study. Activation treatment showed best cleaning efficiency for elimination of passive oxide film among these methods, which was also confirmed by AES (Auger electron spectrometer) analysis. However, the best condition of cleaning was obtained by combining these methods. Electrocleaning time, for degreasing the stearic acid layer, was decreased with increasing amount of added KCN.

• 한국표면공학회지
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• 제31권2호
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• pp.101-108
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• 1998

The effect of oxidation-reduction heating conditions on coating adherence of hot-dip galvanized steel containing silicon has beeninvestigated. The presence of a stbke sillicon oxide formed on the steel surface has been shown to be very detrimenal to proper wetting by liquid zinc. When the steel has more than the critical sillicon content neeled to from a stable external oxide, the use of oxidation-reduction method has been found successful in obtaining a good quality, coated product with excellence adhreence. This can be explained by the formation of an iron oxide. The iron oxrtion of the scale is reduced, leaving the stable oxides dispersed in a fresh metallic iron surface layer. This reduced iron surface is easily wetted by the liquid zinc and excellent adherence is obtained.

• 열처리공학회지
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• 제14권2호
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• pp.81-88
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• 2001

The effects of post-oxidation and sulfnitriding treatments on the phase transformation in the nitrided case of tool steels have been studied. Dense and compact $Fe_3O_4$ layer was formed at the outer surface of nitride compound layer by post-oxidation treatment and multi layer of iron sulfide(FeS) was formed in the compound layer by sulfnitriding treatment. The surface hardness decreased because of formation of the soft oxide or sulfide at the nitride surface. Diffusion layer of nitride case was not affected by post-oxidation treatment or sulfnitriding treatment of nitrided alloy tool steels.