• 한국지하수토양환경학회지:지하수토양환경
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• 제17권2호
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• pp.7-14
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• 2012

Batch tests were carried out to evaluate the thermal treatment of low volatile organic compounds in low-permeability soil. The chemical oxidation by sodium persulfate catalyzed by heat and Fe (II) was evaluated. Enhanced persulfate oxidation of n-decane (C-10), n-dodecane (C-12), n-tetradecane (C-14), n-hexadecane (C-16), and phenanthrene was observed with thermal catalyst, indicating increased sulfate radical production. Slight enhancement of the pollutants oxidation was observed when initial sodium persulfate concentration increased from 5 to 50 g/L. However, the removal efficiency greatly decreased as soil/water ratio increased. It indicates that mass transfer of the pollutants as well as the contact between the pollutants and sulfate radical were inhibited in the presence of solids. In addition, more pollutants can be adsorbed on soil particles and soil oxidant demand increased when soil/water ratio becomes higher. The oxidation of the pollutants was significantly improved when catalyzed by Fe(II). The sodium persulfate consumption increased at the same time because the residual Fe(II) acts as the sulfate radical scavenger.

• Journal of Electrical Engineering and Technology
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• 제8권5호
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• pp.1157-1162
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• 2013

We proposed AlGaN/GaN high-electron-mobility transistors (HEMTs) using thermal oxidation for NiOx passivation. Auger electron spectroscopy, secondary ion mass spectroscopy, and pulsed I-V were used to study oxidation features. The oxidation process diffused Ni and O into the AlGaN barrier and formed NiOx on the surface. The breakdown voltage of the proposed device was 1520 V while that of the conventional device was 300 V. The gate leakage current of the proposed device was 3.5 ${\mu}A/mm$ and that of the conventional device was 1116.7 ${\mu}A/mm$. The conventional device exhibited similar current in the gate-and-drain-pulsed I-V and its drain-pulsed counterpart. The gate-and-drain-pulsed current of the proposed device was about 56 % of the drain-pulsed current. This indicated that the oxidation process may form deep states having a low emission current, which then suppresses the leakage current. Our results suggest that the proposed process is suitable for achieving high breakdown voltages in the GaN-based devices.

• 통합자연과학논문집
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• 제3권3호
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• pp.153-156
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• 2010

Oxidation behaviors of porous silicon were investigated by the measurement of area of $SiO_2$ vibrational peaks in FT-IR spectra during thermal oxidation of porous silicon at corresponding temperatures. Visible photoluminescent porous silicon samples were obtained from an electrochemical etch of n-type silicon of resistivity between 1-10 ${\Omega}/cm$. The etching solution was prepared by adding an equal volume of pure ethanol to an aqueous solution of HF. The porous silicon was illuminated with a 300 W tungsten lamp for the duration of etch. Etching was carried out as a two-electrode galvanostatic procedure at applied current density of 200 $mA/cm^2$ for 5 min. The porosity of samples prepared was about 80%. After formation of porous silicon, the samples were thermally oxidized at $100^{\circ}C$, $200^{\circ}C$, $300^{\circ}C$, and $400^{\circ}C$, respectively. The growth rate of $SiO_2$ layer of porous silicon was investigated by using FT-IR spectroscopy. The effect of oxidation of porous silicon was presented.

• 한국재료학회지
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• 제23권1호
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• pp.1-6
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• 2013

A simple thermal oxidation of Cu thin films deposited on planar substrates established a growth of vertically aligned copper oxide (CuO) nanorods. DC sputter-deposited Cu thin films with various thicknesses were oxidized in environments of various oxygen partial pressures to control the kinetics of oxidation. This is a method to synthesize vertically aligned CuO nanorods in a relatively shorter time and at a lower cost than those of other methods such as the popular hydrothermal synthesis. Also, this is a method that does not require a catalyst to synthesize CuO nanorods. The grown CuO nanorods had diameters of ~100 nm and lengths of $1{\sim}25{\mu}m$. We examined the morphology of the synthesized CuO nanorods as a function of the thickness of the Cu films, the gas environment, the oxidation time, the oxidation temperature, the oxygen gas flow rate, etc. The parameters all influence the kinetics of the oxidation, and consequently, the volume expansion in the films. Patterned growth was also carried out to confirm the hypothesis of the CuO nanorod protrusion and growth mechanism. It was found that the compressive stress built up in the Cu film while oxygen molecules incorporated into the film drove CuO nanorods out of the film.

• 한국진공학회:학술대회논문집
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• 한국진공학회 1999년도 제17회 학술발표회 논문개요집
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• pp.122-122
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• 1999

Graphite with its advantages of high thermal conductivity, low thermal expansion coefficient, and low elasticity, has been widely used as a structural material for high temperature. However, graphite can easily react with oxygen at even low temperature as 40$0^{\circ}C$, resulting in CO2 formation. In order to apply the graphite to high temperature structural material, therefore, it is necessary to improve its oxidation resistive property. Silicon Carbide (SiC) is a semiconductor material for high-temperature, radiation-resistant, and high power/high frequency electronic devices due to its excellent properties. Conventional chemical vapor deposited SiC films has also been widely used as a coating materials for structural applications because of its outstanding properties such as high thermal conductivity, high microhardness, good chemical resistant for oxidation. Therefore, SiC with similar thermal expansion coefficient as graphite is recently considered to be a g행 candidate material for protective coating operating at high temperature, corrosive, and high-wear environments. Due to large lattice mismatch (~50%), however, it was very difficult to grow thick SiC layer on graphite surface. In theis study, we have deposited thick SiC thin films on graphite substrates at temperature range of 700-85$0^{\circ}C$ using single molecular precursors by both thermal MOCVD and PEMOCVD methods for oxidation protection wear and tribological coating . Two organosilicon compounds such as diethylmethylsilane (EDMS), (Et)2SiH(CH3), and hexamethyldisilane (HMDS),(CH3)Si-Si(CH3)3, were utilized as single source precursors, and hydrogen and Ar were used as a bubbler and carrier gas. Polycrystalline cubic SiC protective layers in [110] direction were successfully grown on graphite substrates at temperature as low as 80$0^{\circ}C$ from HMDS by PEMOCVD. In the case of thermal MOCVD, on the other hand, only amorphous SiC layers were obtained with either HMDS or DMS at 85$0^{\circ}C$. We compared the difference of crystal quality and physical properties of the PEMOCVD was highly effective process in improving the characteristics of the a SiC protective layers grown by thermal MOCVD and PEMOCVD method and confirmed that PEMOCVD was highly effective process in improving the characteristics of the SiC layer properties compared to those grown by thermal MOCVD. The as-grown samples were characterized in situ with OES and RGA and ex situ with XRD, XPS, and SEM. The mechanical and oxidation-resistant properties have been checked. The optimum SiC film was obtained at 85$0^{\circ}C$ and RF power of 200W. The maximum deposition rate and microhardness are 2$mu extrm{m}$/h and 4,336kg/mm2 Hv, respectively. The hardness was strongly influenced with the stoichiometry of SiC protective layers.

• 대한치과보철학회지
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• 제53권3호
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• pp.198-206
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• 2015

목적: 다양한 크기의 마이크로그루브가 형성된 티타늄 표면에 열산화 처리를 한 복합 표면의 표면특성을 규명하고, 인간치주인대세포 배양 시 표면에 따른 다양한 세포행동들간 차이와 상관관계를 분석하고자 하였다. 재료 및 방법: Grade II 티타늄 디스크를 시편으로 제작하였다. 포토리소그라피를 이용하여 티타늄 시편의 마이크로그루브 크기를 폭/깊이 $0/0{{\mu}m}$, $15/3.5{{\mu}m}$, $30/10{{\mu}m}$, $60/10{{\mu}m}$로 각각 형성하였다. 평활한 티타늄 표면인 대조군(ST)을 제외한 모든 실험군(ST/TO, Gr15-TO, Gr30-TO, Gr60-TO)에 $700^{\circ}C$에서 3시간동안 열산화 처리하고, 주사현미경 사진을 사용하여 표면특성을 평가하였다. 인간치주인대세포를 배양한 후 BrdU (Bromdeoxyuridine) 실험, 알칼리성 인산가수분해효소 활성 실험, 세포외 칼슘 침착 실험을 통해 세포접착, 세포분화 및 골광화를 평가하였다. 통계분석으로는 일요인분산분석과 피어슨상관관계분석(SPSS version 17.0)을 사용하였다. 결과: 열산화를 동반한 마이크로그루브가 형성된 실험군(Gr15-TO, Gr30-TO, Gr60-TO)들은 평활한 대조군(ST)과 단순 열산화 처리 실험군(ST-TO)에 비하여 BrdU 실험, 알칼리성 인산가수분해효소 활성 실험, 세포 외 칼슘 침착 실험 모두에서 유의하게 증가된 활성도를 나타내었다. 특히, Gr60-TO군은 대조군 및 Gr15-TO, Gr30-TO, Gr60-TO 군 등에 비해 가장 증진된 세포접착 및 골아세포분화/골광화를 나타냈다. 결론: 본 연구의 한계 내에서, 열산화 처리 및 마이크로그루브 복합 티타늄 표면은 골아세포분화에 효과적 방법임이 확인되었다. 본 연구에서 규명 된 적정한 마이크로그루브 크기와 열산화 처리 조건은 마이크로그루브-열산화 복합 표면 티타늄 임플란트 개발의 기초 확립에 기여할 수 있을 것이다.

• 한국식품과학회지
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• 제29권5호
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• pp.860-868
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• 1997

여러 종류(8종)의 유지로 부터 추출한 불검화물과, 강력한 자동산화억제력이 있다고 알려진 53종의 식물체(농산물 및 생약) 메탄을 추출물을 유지에 첨가한후 $180^{\circ}C$에서 14 혹은 16시간 연속 가열하는 동안 유지의 지방산조성을 측정하여 이들 추출물들이 유지의 고열 가열 산화에 미치는 영향을 연구하였다. 추출된 유지의 불검화물들은 모두 $180^{\circ}C$의 고온 가열산화 조건에서 항산화력을 나타내지 못하였다. 그러나 53종의 농산물 및 생약중에서는 일부 종들은 강력한 가열산화 억제력을 나타내었다. 특히, 대황, 백굴체, 정향 등의 메탄올 추출물은 강력한 가열산화 억제력을 나타내었다. 또한 이들 대황, 백굴체 및 정향의 메탄올 추출물들이, 면실유를 $180^{\circ}C$에서 1일 7시간씩 8일간 가열 처리하는 과정에서 면실유의 linoleic acid 파괴 및 중합체 생성에 미치는 영향을 연구하였다. 이 결과 정향 및 백굴체추출물은 $180^{\circ}C$에서 장기간의 가열조건에서도 linoleic acid 파괴 억제 및 중합체 생성을 억제하는 효과가 크게 나타낸 반면, 대황의 경우에는 장기 가열산화 조건에서 지방산의 파괴에 대한 억제력은 미미하였으나, 중합체 생성억제력은 비교적 양호하였다.

• 대한치과보철학회지
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• 제41권6호
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• pp.699-713
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• 2003

Statement of problem. Titanium is the most important material for biomedical and dental implants because of their high corrosion resistance and good biocompatibility. These beneficial properties are due to a protective passive oxide film that spontaneously forms on the surface. Purpose. The purpose of this study was to evaluate the responses of osteoblast-like cells on different surface treatments on Ti discs. Material and Methods. Group 1 represented the machined surface with no treatment. Group 2 surfaces were sandblasted with $50{\mu}m\;Al_2O_3$ under $5kgf/cm^2$ of pressure. Groups 3 and 4 were sandblasted under the same conditions. The samples were treated on a titanium oxide surface with reactive sputter depositioning and thermal oxidation at $600^{\circ}C$ (Group 3) and $800^{\circ}C$ (Group 4) for one hour in an oxygen environment. The chemical composition and microtopography were analyzed by XRD, XPS, SEM and optical interferometer. The stability of $TiO_2$ layer was studied by petentiodynamic curve. To evaluate cell response, osteoblast extracted from femoral bone marrow of young adult rat were cultured for cell attachment, proliferation and morphology on each titanium discs. Results and Conclusion. The results were as follows : 1. Surface roughness values were, from the lowest to the highest, machined group, $800^{\circ}C$ thermal oxidation group, $600^{\circ}C$ thermal oxidation group and blasted group. The Ra value of blasted group was significantly higher than that of $800^{\circ}C$ thermal oxidation group (P=0.003), which was not different from that of $600^{\circ}C$ thermal oxidation group (P<0.05). 2. The degree of cell attachment was highest in the $600^{\circ}C$ thermal oxidation group after four and eight hours (P<0.05), but after 24 hours, there was no difference among the groups (P>0.05). 3. The level of cell proliferation showed no difference among the groups after one day, three days, and seven days (P>0.05). 4. The morphology and arrangement of the cells varied with surface roughness of the discs.

• Corrosion Science and Technology
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• 제2권3호
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• pp.155-160
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• 2003

Plasma spraying technique was used to fabricate functionally graded coating (FGC) of NiCrAIY/YSZ 8wt%$Y_2O_3-ZrO_2$ on a Co-base superalloy (HAYNES 188) substrate. Six layers were coated on the substrate for building up compositionally graded architecture. Conventional thermal barrier coating (TBC) of NiCrAIY/SZ with sharp interface was also fabricated. As-coated FGC and TBC samples were exposed at the temperature of $1100^{\circ}C$ for 10, 50, 100 hours in air. Microstructural change of thermally exposed samples was examined. Pores and microcracks were formed in YSZ layer due to evolution of thermal internal stress at high temperature. The amount of pores and microcracks in YSZ layer were increased with increasing exposure time at high temperature. High temperature oxidation of coatings occurred mainly at the NiCrAIY/YSZ interface. In comparison with the case of TBC. the increased area of the NiCrAIY/YSZ interface in FGC is likely to attribute to forming the higher amount of oxides.

• 한국에너지공학회:학술대회논문집
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• 한국에너지공학회 2000년도 추계 학술발표회 논문집
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• pp.211-214
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• 2000

휘발성 유기물질은 ground level ozone의 전구체로써 미래 대기오염의 주원인이 될것으로 판단되는 물질이며 구미각국에서는 1990년 초반부터 그리고 국내에서는 최근에 와서 규제가 확정된 물질이다. 대표적인 휘발성 유기물질의 종류와 배출원을 Table 1과 Table 2에 나타내었다.(중략)