• Bulletin of the Korean Chemical Society
• /
• 제35권1호
• /
• pp.111-116
• /
• 2014

The kinetics and mechanism of oxidation of sulfanilic acid by N-chloro-p-toluene sulfonamide (chloramine-T) have been studied in acid medium. The species of chloramine-T were analysed on the basis of experimental observations and predominantly reactive species was taken into account for proposition of most plausible reaction mechanism. The derived rate law (1) conforms to such a mechanism. $$-\frac{d[CAT]}{dt}=\frac{kK_1[RNHCl][SA]}{K_1+[H^+]}$$ (1) All kinetic parameters were evaluated. Activation parameters such as energy and entropy of activation were calculated to be $(61.67{\pm}0.47)kJmol^{-1}$ and $(-62.71{\pm}2.48)kJmol^{-1}$ respectively employing Eyring equation.

• 한국수소및신에너지학회논문집
• /
• 제22권2호
• /
• pp.168-177
• /
• 2011

A set of kinetics study on the reduction with $CH_4$, oxidation with steam and oxidation with air was performed for $Fe_2O_3/ZrO_2$. $Fe_2O_3/ZrO_2$ was prepared by aerial oxidation method. The reactivity experiments were performed in a thermogravimetric analyzer (TGA) with different reacting gas concentrations and temperatures. The obtained activation energy of reduction by methane, oxidation by water and oxidation by air are 219 kJ/mol, 238 and 20 respectively.

• Carbon letters
• /
• 제6권1호
• /
• pp.1-5
• /
• 2005

Isotropic pitch based carbon fibers were exposed to isothermal oxidation in carbon dioxide gas to study the activation kinetics under the temperature of 800~$1100^{\circ}C$. The kinetic equation $f=1-{\exp}(-at^b)$ was introduced and the constant b was obtained in the range of 0.92~1.25. It was shown that the activated carbon fiber shows the highly specific surface area (SSA) when the constant b comes close to 1. The activation kinetics were evaluated by the reaction-controlling regime (RCR) according to changes of the apparent activation energy with changes of the conversion. It was observed that the activation energies increase from 47.6 to 51.2 kcal/mole with the conversion increasing from 0.2 to 0.8. It was found that the pores of the activated carbon fiber under the chemical reaction were developed well through the fiber.

• 한국세라믹학회지
• /
• 제43권11호
• /
• pp.724-727
• /
• 2006

It has long been known that the oxidation kinetics of Zr-based alloys undergoes a crossover from parabolic to cubic in the pretransition period (before breakaway of the oxide scale). This kinetic crossover, however, is not fully understood yet. We have earlier proposed a model for the Zr-oxidation kinetics, in a closed form for the first time, by taking into account a compressive strain energy gradient as a diffusional driving force in addition to a chemical potential gradient of component oxygen across the ZrO$_2$ scale upon Zr [J. Nucl. Mater., 299 (2001) 235]. In this paper, we experimentally reconfirm the validity of the proposed model by using the thermogravimetric data on mass gain of Zr in a plate and wire form, respectively, in air atmosphere at different temperatures in the range of 500$^{\circ}$ to 800$^{\circ}C$, and subsequently report on the numerical values for oxygen chemical diffusivity and strain energy gradient across the oxide scale.

• 한국세라믹학회지
• /
• 제41권9호
• /
• pp.657-662
• /
• 2004

마그카본계 내화물의 산화저항성을 증대시키기 위하여 섭씨 100$0^{\circ}C$에서 120$0^{\circ}C$에서 산화기구를 조사하고, TiC를 첨가하여 산화저항성 증가에 대한 효과를 관찰하였다. 산소공급을 위해 공기를 분당 0.2리터의 속도로 흘려주었으며 열천칭으로 무게변화가 없어질 때까지 매 30초 간격마다 무게감소를 측정하였다 본 실험에서 사용된 마그카본계 시편의 산화거동과 관련한 유효확산 계수는 1.39${\times}$$10^{-4}$ $m^2$/sec이다. 이러한 실험조건에서 총체적인 산화공정은 산화된 기공층을 통하여 내부로 향하는 산소의 확산에 의해 지배되는 반응으로 해석할 수 있다. TiC를 첨가한 시편은 마그카본계 내화물의 산화 저항성을 증대시켰다.

• 한국표면공학회:학술대회논문집
• /
• 한국표면공학회 2016년도 추계학술대회 논문집
• /
• pp.189-189
• /
• 2016

In this study, the Al-rich AlTiSiN thin films that consisted of TiN/AlSiN nano-multilayers were deposited on the steel substrate by magnetron sputtering, and their high-temperature oxidation behavior was investigated, which has not yet been adequately studied to date. Since the oxidation behavior of the films depends sensitively on the deposition method and deposition parameters which affect their crystallinity, composition, stoichiometry, thickness, surface roughness, grain size and orientation, the oxidation studies under various conditions are imperative. AlTiSiN nano-multilayer thin films were deposited on a tool steel substrate, and their oxidation behavior of was investigated between 600 and $1000^{\circ}C$ in air. Since the amount of Al which had a high affinity for oxygen was the largest in the film, an ${\alpha}-Al_2O_3-rich$ scale formed, which provided good oxidation resistance. The outer surface scale consisted of ${\alpha}-Al_2O_3$ incoporated with a small amount of Ti, Si, and Fe. Below this outer surface scale, a thin ($Al_2O_3$, $TiO_2$, $SiO_2$)-intermixed scale formed by the inwardly diffusing oxygen. The film oxidized slower than the $TiO_2-forming$ kinetics and TiN films, but faster than ${\alpha}-Al_2O_3-forming$ kinetics. During oxidation, oxygen from the atmosphere diffused inwardly toward the reaction front, whereas nitrogen and the substrate element of iron diffused outwardly to a certain extent.

• Food Science and Biotechnology
• /
• 제18권2호
• /
• pp.526-532
• /
• 2009

Quenching mechanisms and kinetics of $\alpha$-, $\beta$-, $\gamma$-, and $\delta$-tocopherol in photosensitized oxidation of lard were studied. Lard at 0.03, 0.07, 0.11, and 0.3 M in methylene chloride containing $4.4{\times}10^{-6}\;M$ chlorophyll and 0, 0.1, 0.3, and 0.6 mM $\alpha$-, $\beta$-, $\gamma$-, and $\delta$-tocopherol were stored under light for 4 hr, respectively. Oxidation was determined by headspace oxygen and peroxide value. Tocopherols prevented the photosensitized oxidation of lard (p<0.05). Steady state kinetic study showed that $\alpha$-, $\beta$-, $\gamma$-, and $\delta$-tocopherol prevented the photosensitized oxidation of lard by quenching singlet oxygen. Singlet oxygen quenching rates of $\alpha$-, $\beta$-, $\gamma$-, and $\delta$-tocopherol by headspace oxygen depletion were 1.86, 2.39, 2.47, and $2.11{\times}10^7/M/sec$, respectively. The quenching rates of $\alpha$-, $\beta$-, $\gamma$-, and $\delta$-tocopherol by peroxide value were 1.42, 1.11, 0.97, and $0.42{\times}10^7/M/sec$, respectively. The quenching rates of tocopherols were slightly different depending on the measurements of oxidation.

• Nuclear Engineering and Technology
• /
• 제26권1호
• /
• pp.90-99
• /
• 1994

손상 핵연료에서 발생하는 주요한 현상중의 하나는 수중기의 분해로 갭에 존재하는 산소에 의해 $UO_2$ 가 $UO_{2+}$x/로 산화되고, 이로 인해 결정립내에서의 핵분열기체 확산계수가 증가하여 결과적으로 핵분열 기체의 방출이 증대하는 현상이다. 본 논문은 일반적인 원자로 운전 조건하에서 원자로 및 손상 핵연료의 운전조건을 고려하여 소결체의 산화거동을 모사하고 이를 바탕으로 소결체 산화가 핵분열기체의 방출 중대에 미치는 영향을 분석하였다. 소결체 산화거동은 갭에는 150기압의 포화된 순수한 수증기만이 존재한다는 가정하에 분석하였고, 산화에 의한 핵분열기체의 방출 증대 효과를 정량적으로 분석하기 위해 방출중대 인자를 도입하였다. 실험 치와 비교한 결과 방출증대 인자는 소결체 산화에 의한 핵분열기체의 방출증대 효과를 잘 예측하였다.

• 한국표면공학회지
• /
• 제44권1호
• /
• pp.13-20
• /
• 2011

This study investigated the high temperature oxidation behavior of Fe-22%Cr-5.8%Al alloy and the oxidation kinetics of the alloy were discussed. Bulk samples were prepared by VAM (vacuum arc melting) and hot forging. High temperature oxidation testes were isothermally conducted up to 100 hours in 79%$N_2$+21%$O_2$ environment at three different temperatures ($900^{\circ}C$, $1000^{\circ}C$, $1100^{\circ}C$). The weight gain was measured after oxidation according to oxidation time (2, 4, 6, 8, 10, 15, 20, 25, 30, 60, 80, 100 hours). The weight gain significantly increased with increasing oxidation temperature. As the temperature increased, the oxidized samples showed sequential formation of $Al_2O_3$, Cr-rich oxide, Fe-rich oxide. The activation energy of high temperature oxidation was obtained as 306.63 KJ/mol. $Al_2O_3$ were developed on the surface in the early stage of oxidation, representing protective role of oxidation. However, Fe-based and Cr-based oxides leaded to breakaway of oxide layer, thus resulted in the significant increase of additional oxidation.

• 한국재료학회지
• /
• 제23권1호
• /
• pp.1-6
• /
• 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.