• Title, Summary, Keyword: Thermal oxidation

Search Result 973, Processing Time 0.054 seconds

Characterization on the Thermal Oxidation of Raw Natural Rubber Thin Film using Image and FT-IR Analysis

  • Kim, Ik-Sik;Cho, Hwanjeong;Sohn, Kyung-Suk;Choi, Hwa-Soon;Kim, Sung-Uk;Kim, Sinkon
    • Elastomers and Composites
    • /
    • v.55 no.1
    • /
    • pp.51-58
    • /
    • 2020
  • In this study, the thermal oxidation of raw natural rubber (NR) was investigated under controlled conditions by optical image and fourier transform infrared (FT-IR) analysis. The thermal oxidation was performed on a transparent thin film of raw NR coated on a KBr window in a dark chamber at 80℃ under low humidity conditions to completely exclude moisture and restrict light oxidation. Images of the thin film of raw NR were obtained before and after thermal oxidation. FT-IR absorption spectra were measured in the transmission mode at different thermal exposure times. The thermal oxidation of NR was examined by the changes in the absorption peaks at 3449, 1736, 1447, 1377, 1242, 1072, and 833 cm-1, which corresponded to a hydroxyl group (-OH), a carbonyl group (-C=O) from an aldehyde and a ketone, a methylene group (-CH2-), a methyl group (-CH3), a carbon-oxygen single bond (-C-O) from an epoxide, a carbon-oxygen bond (-C-O) from an ether, an alcohol, a peroxide, or a cyclic peroxide, and a cis-methine group (cis-CCH3=CH-), respectively. In the initial stage of thermal oxidation, two different types of free radicals were produced quickly and randomly by the homolytic cleavage of a double bond and allylic hydrogen abstraction. Aldehydes and ketones were formed from chain scissions of the double bonds and alcohols were produced from allylic hydrogen abstraction at the methylene or methyl groups. Two reactions seemed to proceed competitively with each other. At a later stage, oxidative crosslinks seemed to dominate through the combination of free radicals such as an allyl radical (CH=CHCH2·), alkoxy radical (RO·), and peroxy radical (ROO·) and the reaction of a hydroperoxide (-ROOH) with a double bond. The image obtained after thermal oxidation showed hardening without cracks. Based on these observations, a plausible two-step mechanism was suggested for chain hardening caused by the thermal oxidation.

Characteristics and Formation of Thermal Oxidative Film Silicon Carbide for MOS Devices (MOS 소자용 Silicon Carbide의 열산화막 생성 및 특징)

  • O, Gyeong-Yeong;Lee, Gye-Hong;Lee, Gye-Hong;Jang, Seong-Ju
    • Korean Journal of Materials Research
    • /
    • v.12 no.5
    • /
    • pp.327-333
    • /
    • 2002
  • In order to obtain the oxidation layer for SiC MOS, the oxide layers by thermal oxidation process with dry and wet method were deposited and characterized. Deposition temperature for oxidation layer was $1100^{\circ}C$~130$0^{\circ}C$ by $O_2$ and Ar atmosphere. The oxide thickness, surface morphology, and interface characteristic of deposited oxide layers were measurement by ellipsometer, SEM, TEM, AFM, and SIMS. Thickness of oxidation layer was confirmed 50nm and 90nm to with deposition temperature at $1150^{\circ}C$ and $1200{\circ}C$ for dry 4 hours and wet 1 hour, respectively. For the high purity oxidation layer, the necessity of sacrificial oxidation which is etched for the removal of the defeats on the wafer after quickly thermal oxidation was confirmed.

The Combustion Characteristics of Cyclonic Recuperative Thermal Oxidation System for Volatile Organic Compounds (VOC를 대상으로한 Cyclonic recuperative thermal oxidation system의 연소특성 연구)

  • 현주수;이시훈;임영준
    • Proceedings of the Korea Society for Energy Engineering kosee Conference
    • /
    • /
    • pp.573-578
    • /
    • 2003
  • 본 논문은 산업체에서 발생하는 휘발성 유기물질을 연소하는 직접연소기술에 선회연소 개념을 접목하여 개발된 Cyclonic recuperative thermal oxidation system의 연소성능 실험 결과이다. 기존의 recuperative system의 열효율이 75%로 regenerative thermal oxidation보다 낮아 운전비가 많이 소요되는 단점을 극복하기 위해 기존의 연소실에 cyclone 연소시스템을 적용하여 고효율화 시키고자 하는 것이 핵심이다.(중략)

  • PDF

Synthesis and Characterization of Alumina Composite Membrane by Al Evaporation and Thermal Oxidation (알루미늄의 진공증발과 열산화에 의한 알루미나 복합분리막의 제조 및 특성분석)

  • 이동호;최두진;현상훈
    • Journal of the Korean Ceramic Society
    • /
    • v.32 no.3
    • /
    • pp.349-358
    • /
    • 1995
  • The ceramic composite membrane was synthesized by thermal oxidation after evaporation of Al on the support prepared by slip casting process. Oxidation was performed at $700^{\circ}C$ and 80$0^{\circ}C$ under dry oxygen atmosphere. It was considered as optimum oxidation condition that the membrane showed a knudsen behaviro. A further oxidation resulted in an increase of gas permeability because top layer became densified. Then, a multi-layered composite membrane was synthesized through a sol-gel method, evaporation and thermal oxidation of Al coating processes. While the membrane was thermally stable up to 80$0^{\circ}C$, gas permeability was rapidly decreased even at a slight amount of deposition of Al.

  • PDF

The Oxidation Effect of Semiconductor Carbon Nanotube (반도체 탄소나노튜브의 산화열처리 효과)

  • Kim, Jwa-Yeon;Park, Kyung-Soon
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
    • /
    • /
    • pp.126-127
    • /
    • 2005
  • Semiconductor carbon nanotube was grown on oxided silicon wafer with Atmosphere Pressure Chemical Vapor Deposition (APCVD) ethmod and investigated the electrical property after thermal oxidation at 300$^{\circ}C$ in air. The electrical property was measured at room temperature in air after thermal oxidation at 300$^{\circ}C$ for various times in air. Semiconductor carbon nanotube was steadily changed to metallic carbon nanotube as increasing of thermal oxidation times at 300$^{\circ}C$ in air.

  • PDF

Effects of Thermal Oxidation on Corrosion Resistance of Stainless Steels for Muffler Materials (머플러용 스테인리스강의 내식성에 미치는 열적 산화의 영향)

  • Kim, Dongwoo;Kim, Heesan
    • Korean Journal of Metals and Materials
    • /
    • v.46 no.10
    • /
    • pp.652-661
    • /
    • 2008
  • Reduction of NOx in emission gas, improvement of engine efficiency, and extension of warranty period has made demands for developing materials more corrosively resistant to the inner-muffler environments or predicting the lifetime of materials used in muffler more precisely. The corrosion inside muffler has been explained with condensate corrosion mainly though thermal oxidation experiences prior to condensate corrosion. Hence, the aim of this study is to describe how the thermal oxidation affects the corrosion of stainless steel exposed to the inner-muffler environments. Auger electron spectroscopy and electrochemical tests were employed to analyze oxide scale and to evaluate corrosion resistance, respectively. Thermal oxidation has different role of condensate corrosion depending on the temperature: inhibiting condensate corrosion below $380^{\circ}C$ and enhancing condensate corrosion above $380^{\circ}C$. The low temperature oxidation causes to form compact oxide layer functioning a barrier for penetrating condensate into a matrix. Although though thermal oxidation caused chromium-depleted layer between oxide layer and matrix, the enhancement of the condensate corrosion in high temperature oxidation resulted from corrosion-induced crevice formed by oxide scale rather than corrosion in chromium-depleted layer. It was proved by aids of anodic polarization tests and measurements of pitting corrosion potentials. By the study, the role of high temperature oxidation layer affecting the condensate corrosion of stainless steels used as muffler materials was well understood.

Influence of some Natural Antioxidants Effect on Thermal Oxidation in Palm Oil (몇가지 천연 산화방지물의 첨가가 가열 팜유에 미치는 영향)

  • Chang, Young-Sang;Yi, Young-Soo;Kang, Woo-Suk;Shin, Zae-Ik
    • Journal of the Korean Applied Science and Technology
    • /
    • v.6 no.1
    • /
    • pp.9-14
    • /
    • 1989
  • Effectiveness of some natural antioxidants were investigated by measuring the physico-chemical charcteristics and fatty acid composition during thermal oxidation in palm oil. Tocopherol showed most enhanced thermal oxidation stabilities compared to the other natural antioxidants. AR spice was no good AOM stability and changes of acid value but the other parameters were obtained desirable results. The changes of linoleic aicd content was slightly decreased during thermal oxidation. Addition of rosemary and glycyrriza extract increased the stabilities of oil less than tocopherol and AR spice. Order of antioxdative effects was tocopherol, AR spice and others. There was no significiant difference in stability of rosemary and glycyrriza extract.

Failure Mechanisms for Zirconia Based Thermal Barrier Coatings

  • Lee, Eui Y.;Kim, Jong H.
    • The Korean Journal of Ceramics
    • /
    • v.4 no.4
    • /
    • pp.340-344
    • /
    • 1998
  • Failure mechanisms were investigated for the two layer thermal barrier coatings consisting of NiCrAlY bond coat and $ZrO_2$-8wt.% $Y_2O_3$ ceramic coating during cyclic oxidation. $Al_2O_3$ developed at the ceramic coating/bond coat interface first, followed by the Cr/Ni rich oxides such as $NiCr_2O_4$ and $Ni(Al, Cr)_2O_4$ during cyclic oxidation. It was observed that the spalling of ceramic coatings took place primarily within the NiCrAlY bond coat oxidation products or at the interface between the bond coat oxidation products and zirconia based ceramic coating or the bond coat. It was also observed that the fracture within these oxidation products occurred with the formation of $Ni(Cr, Al)_2O_4$ spinel or Cr/Ni rich oxides. It was therefore concluded that the formation of these oxides was a life-limiting event for the thermal barrier coatings.

  • PDF

Large-Scale Synthesis of Cu2O Nanowires by Thermal Oxidation Method (열 산화법을 이용한 Cu2O 나노선의 대면적 합성)

  • Lee, Geun-Hyoung
    • Korean Journal of Materials Research
    • /
    • v.24 no.7
    • /
    • pp.388-392
    • /
    • 2014
  • $Cu_2O$ nanowires were synthesized at large scale on copper plate by thermal oxidation in air. The effect of oxidation time and temperature on the morphology of the nanowires was examined. The oxidation time had no effect on the diameter of the nanowires, while it had a great effect on the density and the length of the nanowires. The density and the length of the nanowires increased, and then decreased, with increasing oxidation time. The oxidation temperature had a tremendous effect on the size-distribution as well as the density of the nanowires. When the oxidation temperature was $700^{\circ}C$, uniform size-distribution and high density of the nanowires was achieved. At lower and higher temperatures, the density of the nanowires was lower, and they displayed a broader size-distribution. It is suggested that the $Cu_2O$ nanowires were grown via a vapor-solid mechanism because no catalyst particles were observed at the tips of the nanowires.

Thermal Emissivity of Nuclear Graphite as a Function of Its Oxidation Degree (1) -Effects of Density, Porosity, and Microstructure-

  • Seo, Seung-Kuk;Roh, Jae-Seung;Kim, Eung-Seon;Chi, Se-Hwan;Kim, Suk-Hwan;Lee, Sang-Woo
    • Carbon letters
    • /
    • v.10 no.3
    • /
    • pp.225-229
    • /
    • 2009
  • Thermal emissivity of commercial nuclear graphites (IG-110, PCEA, IG-430 and NBG-18) following changes in oxidation degrees were examined. Specimens were oxidized to 0%, 5%, and 10% in air flow of 5l/min at $600^{\circ}C$ using a furnace, and the thermal emissivities were measured using an infrared spectrum analyzer. The measuring temperatures for the thermal emissivity were $100^{\circ}C$, $200^{\circ}C$, $300^{\circ}C$, $400^{\circ}C$ $500^{\circ}C$. Also density and porosity of the specimens were observed to compare with thermal emissivity. Results showed that emissivity increased with oxidation, and the 10% oxidized NBG-18 showed the highest emissivity (0.890) which value is larger for 24% than the value of as-received specimen. Investigation of factors affecting the emissivity revealed that increases in the surface roughness and porosity due to oxidation were responsible for the increase in emissivity after oxidation.