• 제목/요약/키워드: Oxidation time dependence

검색결과 27건 처리시간 0.025초

빛이 홍화씨기름 산화 및 토코페롤 분해의 온도의존성에 미치는 영향 (Effects of Light on Temperature Dependence of Safflower Oil Oxidation and Tocopherol Degradation)

  • 왕선영;최은옥
    • 한국식품과학회지
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    • 제44권3호
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    • pp.287-292
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    • 2012
  • 홍화씨기름의 과산화물값과 공액이중산값은 빛의 존재와 상관없이 산화시간과 산화온도가 증가함에 따라 증가했으나, 동일한 온도에서는 빛의 존재 하에서 높은 과산화물값과 공액이중산값을 보여 빛은 홍화씨기름의 산화를 촉진시켰다. 빛은 홍화씨기름 산화 및 토코페롤 분해 속도의 온도의존성을 감소시켰으며, 따라서 산화온도는 광산화에서보다는 자동산화에서 더욱 중요한 인자로 작용했다.

플라즈마 산화시간과 열처리 조건에 따른 터널링 자기저항비의 온도의존특성에 관한 연구 (A Study on Temperature Dependence of Tunneling Magnetoresistance on Plasma Oxidation Time and Annealing Temperature)

  • 김성훈;이성래
    • 한국자기학회지
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    • 제14권3호
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    • pp.99-104
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    • 2004
  • 자기 터널 접합(Magnetic Tunnel Junction, MTJ)의 플라즈마 산화시간과 열처리 온도에 따른 자기저항(Tunneling Magnetoresistance, TMR) 온도의존특성을 연구하였다. 플라즈마 산화시간을 30$_{s}$ 70$_{s}$ 까지 10$_{s}$ 간격으로 변화시켜 측정한 결과, 산화시간 50초에서 상온에서 25.3%의 가장 높은 TMR 비를 얻었다. 스핀 분극도 $P_{0}$ 스핀파 지수(spin wave parameter) $\alpha$를 구한 결과, 산화시간 50$_{s}$ 에서 40.3%의 가장 높은 스핀 분극도와 가장 낮은 온도 의존 특성인 (10$\pm$4.742)${\times}$$10^{-6}$ $K^{-1.5}$스핀파 지수(spin wave parameter) $\alpha$값을 얻었다. 그리고 온도별 열처리 결과 175$^{\circ}C$에서 TMR비가 25.3%에서 27.5%까지 증가하였으며 스핀파 지수는 (10$\pm$0.719)${\times}$$10^{-6}$ K $^{-1.5}$ 까지 감소하여 온도의존도가 감소하였다.

Tunnel i unction-Mangnetorsistance in Co-Al-O$_{x}$-NiFe with oxidation conditions of Al thickness

  • Jeon, Dong-Min;Park, Jin-Woo;Suh, Su-Jeong
    • 한국표면공학회지
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    • 제34권5호
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    • pp.494-498
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    • 2001
  • Ferromagnets(FM)-Al-$O_{x}$ -Ferromagnets (FM) tunneling junctions were evaluated by changing the fabricating conditions of an Al-X$/_{x}$ layer. The junction composed of a thicker Al-$O_{x}$ shows the low resistance and the stable MR ratio about 16% in a wide range of oxidation time. For the junctions with the thinner Al-$O_{x}$ , they showed a fast increase of the barrier width as an increase of an oxidation time and exhibited a strong bias dependence. As oxidation time increased, the coercivity ($H_{c}$ ) of bottom Co layer increased gradually due to the local oxidation of Co bottom layer at a interface. However, the small formation of Co oxide did not largely influence on the deterioration of MR ratio.

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EFFECTS OF REACTION TIME AND pH ON FENTON'S BATCH PROCESS FOR THE TREATMENT OF LEACHATE

  • Choi, Heung-Jin;Kim, Il-Kyu
    • 한국물환경학회지
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    • 제18권2호
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    • pp.169-187
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    • 2002
  • The effects of important parameters such as reaction time and pH on the Fenton's process were evaluated using a batch reactor. It was proven that organic materials and heavy metals in leachate could be successfully removed by Fenton's reagent. Favorable operation conditions were investigated. It was observed that the reaction between ferrous iron and hydrogen peroxide with the production of hydroxyl radical was almost complete in 10 minutes. That is, the oxidation of organic materials by Fenton's reagent was so fast that it was complete in 30 minutes with batch experiments. With the formation of carbonic acid, pH of the batch reactor decreased to favorable acidic conditions without acid addition. The oxidation of organic materials in the leachate showed a pH dependence and was most efficient in the pH range of 2-3.

절연막층의 플라즈마 산화시간에 따른 CoFe/AlO/CoFe/NiFe 구조의 터널자기저항 효과 연구 (Effect of Plasma Oxidation lime on TMR Devices of CoFe/AlO/CoFe/NiFe Structure)

  • 이영민;송오성
    • 한국전기전자재료학회논문지
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    • 제15권4호
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    • pp.373-379
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    • 2002
  • We investigated the evolution of magnetoresistance and magnetic property of tunneling magnetoresistive(TMR) device with microstructure and plasma oxidation time. TMR devices have potential applications for non volatile MRAM and high density HDD reading head. We prepared the tunnel magnetoresistance(TMR) devices of Ta($50{\AA}$)/NiFe($50{\AA}$)/IrMn($150{\AA}$)/CoFe($50{\AA}$)/Al($13{\AA}$)-O/CoFe($40{\AA}$)/FiFe($400{\AA}$)/Ta(($50{\AA}$) structure which have $100{\times}100\mu\textrm{m}^2$ junction area on $2.5{\times}2.5\textrm{cm}^2$ Si/$SiO_2$(($1000{\AA}$) substrates by an inductively coupled plasma(ICP) magnetron sputter. We fabricated the insulating layer using an ICP plasma oxidation method by with various oxidation time from 30 sec to 360 sec, and measured resistances and magnetoresistance(MR) ratios of TMR devices. We found that the oxidized sample for oxidation time of 80 sec showed the highest MR radio of 30.31 %, while the calculated value regarding inhomogeneous current effect indicated 25.18 %. We used transmission electron microscope(TEM) to investigate microstructural evolution of insulating layer. Comparing the cross-sectional TEM images at oxidation time of 150 sec and 360 sec, we found that the thickness and thickness variation of 360 sec-oxidized insulating layer became 30% and 40% larger than those of 150 sec-oxidized layer, repectively. Therefore, our results imply that increase of thickness variation with oxidation time may be one of the major treasons of the MR decrease.

Reaction-Bonded Al2O3 Ceramics Using Oxidation of Al Alloy Powder

  • Lee, Hyun-Kwuon
    • 한국재료학회지
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    • 제24권5호
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    • pp.236-242
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    • 2014
  • Fabrication of reaction-bonded $Al_2O_3$ (RBAO) ceramics using Al-Zn-Mg alloy powder was studied in order to improve traditional RBAO ceramic processing using Al powder. The influence on reaction-bonding and microstructure, as well as on physical and mechanical properties, of the particulate characteristics of the $Al_2O_3$-Al alloy powder mixtures after milling, was revealed. Variation of the particulate characteristics of this $Al_2O_3$-Al alloy powder mixture with milling time was reported previously. To start, the $Al_2O_3$-Al alloy powder mixture was milled, reaction-bonded, post-sintered, and characterized. During reaction-bonding of the $Al_2O_3$-Al alloy powder mixture compacts, oxidation of the Al alloy took place in two stages, that is, there was solid- and liquid-state oxidation of the Al alloy. The solid-state oxidation exhibited strong dependence on the density of surface defects on the Al-alloy particles formed during milling. Higher milling efficiency resulted in less participation of the Al alloy in reaction-bonding. This was because of its consumption by chemical reactions during milling, and subsequent powder handling, and could be rather harmful in the case of over-milling. In contrast to very little dependence of oxidation of the Al alloy on its particle size after milling, the relative density, microstructure, and flexural strength were strongly dependent on particle size after milling (i.e., on milling efficiency). The relative density and 4-point flexural strength of the RBAO ceramics in this study were ~98% and ~365 MPa, respectively, after post-sintering at $1,600^{\circ}C$.

배전용 CN/CV 케이블의 절연재료 및 가교방식별 열화특성연구 (An Experimental investigation on the dependation characteristics of CN/CV cables : dependence on the materials and curing process)

  • 김화종;최영훈;안용규;김관성;구자윤
    • 대한전기학회:학술대회논문집
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    • 대한전기학회 1992년도 하계학술대회 논문집 B
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    • pp.969-972
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    • 1992
  • It is shown that the ac breakdown strength, treeing phenomena, oxidation level, and crystallinity of unaged and aged distribution CV cables vary with XLPE insulations (characterizing anti-oxidation) and curing process. The maximum size of bow-tie tree in insulation influenced on the decrease of ac breakdown strength and the increase of oxidation level and crystallinity of XLPE according to aging time lead to increase the size and density of bow-tie trees.

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망간징크 페라이트 단결정의 산화-환원반응에 따른 미세구조의 변화 (Microstructural Evoluation from the Oxidation-Reduction of Mn-Zn Ferrite Single Crystal)

  • 윤상영;김문규
    • 한국세라믹학회지
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    • 제27권5호
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    • pp.652-660
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    • 1990
  • Oxidation of Mn-Zn ferrite was made in air at various temperatures ranging from 400$^{\circ}C$ to 1150$^{\circ}C$. Subsequent reduction fo these oxidized samples was also made in air at 1300-1350$^{\circ}C$ where the spinel phase of Mn-Zn ferrite is stable. Morphological observation revealed that the shape of precipitated hematite was plate or lath type on the close-packed habit plane of {111} ferrite which has a definite orientation relationship. The growth of precipitates showed the behavior fo parabolic dependence of the oxidating time. An apparent activation energy for the growth was found to be 125${\pm}$3Kcal/mol. The fact that pores are observed along the precipitates illustrates the oxidation to occur dominantly by the counterdiffusion of cations and ction vacancies. For the reductio reaction pores are found to form at the site once occupied by the precipitates and at the surface. This observation illustrates that the oxygen volitalization from interior region to the surface is the dominant process for the reduction reaction.

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ECR 산소 플라즈마를 이용한 저온 열산화 (Low Temperature Thermal Oxidation using ECR Oxygen Plasma)

  • 이정열;강석원;이진우;한철희;김충기
    • 전자공학회논문지A
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    • 제32A권3호
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    • pp.68-77
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    • 1995
  • Characteristics of electron cyclotron resonance (ECR) plasma thermal oxide grown at low-temperature have been investigated. The effects of several process parameters such as substrate temperature, microwave power, gas flow rate, and process pressure on the growth rate of the oxide have been also investigated. It was found that the plasma density, reactive ion species, is strongly related to the growth rate of ECR plasma oxied. It was also found that the plasma density increases with microwave power while it decreases with decreasing O2 flow rate. The oxidation time dependence of the oxide thichness showed parabolic characteristics. Considering ECR plasma thermal oxidation at low-temperature, the linear as well as parabolic rate constants calculated from fitting data by using the Deal-Grove model was very large in comparison with conventional thermal oxidation. The ECR plasma oxide grown on (100) crystalline-Si wafer exhibited good electrical characteristics which are comparable to those of thermal oxide: fixed oxide charge(N$_{ff}$)= 7${\times}10^{10}cm^{-2}$, interface state density(N$_{it}$)=4${\times}10^[10}cm^{-2}eV^{-1}$, and breakdown field > 8MV/cm.

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