• 한국건설순환자원학회논문집
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• 제7권4호
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• pp.121-127
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• 2012

본 연구에서는 플라이애시를 치환한 시멘트 모르터의 양생온도에 따른 강도증진을 검토하기 위하여 등가재령방법에 의한 강도증진해석을 실시하였다. 플라이애시를 30% 치환한 시멘트모르터의 겉보기활성화에너지를 ASTM C 1074 방법에 의하여 산정한 결과 34.75KJ/mol로 산정되었고, 이를 토대로 Plowman 모델과 Gompertz 모델을 이용하여 해석한 결과 해석치가 측정치를 양호하게 추정함을 알 수 있었고 특히 Gompertz 모델식이 보다 양호한 추정 정밀도를 갖는 것으로 확인되었다.

• 한국안전학회지
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• 제5권2호
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• pp.17-23
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• 1990

This study was performed by experiments with ASTM's apparatus for determination of autoignition temperature to obtain autoignition characteristics of 1-Heptene, 2-Heptene and 3-Heptene, respectively. As results, minimum autoignition temperatures (MAIT) of 1-Heptene, 2-Heptene and 3-Heptene were 246$^{\circ}C$, 248$^{\circ}C$ and 254$^{\circ}C$, respectively and each dropping volume of these temperatures was 0.25$m\ell$, 0.20$m\ell$ and 0.20$m\ell$. Instantaneous ignition temperatures measured at each dropping volume of Heptene were 371$^{\circ}C$, 357$^{\circ}C$ and 342$^{\circ}C$, respectively. Relation ignition delay time with ignition temperature at minimum autoignition temperature agreed well with Semenov's equation, and the values of apparent activation energy from this equation were 47Kca1/mo1 for 1-Heptene, 35Kca1/mo1 for 2-Heptene and 29Kca1/mo1 for 3-Heptene. It was found that the values of apparent activation energy decreased as the position of double bond changed from end to center in C-C chain.

• Carbon letters
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• 제6권1호
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• pp.1-5
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• 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.

• 한국표면공학회지
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• 제44권4호
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• pp.131-136
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• 2011

A kinetic study has been made for the growth of nanocrystalline diamond (NCD) particles to a continuous thin film on silicon substrate in a microwave plasma chemical vapor deposition reactor. Parameters of deposition have been microwave power of 1.2 kW, the chamber pressure of 110 Torr, and the Ar/$CH_4$ ratio of 200/2 sccm. The deposition has been carried out at temperatures in the range of $400\sim700^{\circ}C$ for the times of 0.5~16 h. It has been revealed that a continuous diamond film evolves from the growth and coalescence of diamond crystallites (or particles), which have been heterogeneously nucleated at the previously scratched sites. The diamond particles grow following an $h^2$ = k't relationship, where h is the height of particles, k' is the particle growth rate constant, and t is the deposition time. The k' values at the different deposition temperatures satisfy an Arrhenius equation with the apparent activation energy of 4.37 kcal/mol or 0.19 eV/ atom. The rate limiting step should be the diffusion of carbon species over the Si substrate surface. The growth of diamond film thickness (H) shows an H = kt relationship with deposition time, t. The film growth rate constant, k, values at the different deposition temperatures show another Arrhenius-type expression with the apparent activation energy of 3.89 kcal/mol or 0.17 eV/atom. In this case, the rate limiting step might be the incorporation reaction of carbon species from the plasma on the film surface.

• Korean Chemical Engineering Research
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• 제43권2호
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• pp.294-298
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• 2005

연소기체로부터 이산화탄소를 흡수하는 유동층 공정에 사용되는 흡수제의 흡수 및 재생 반응특성을 측정 및 고찰하였다. 유동층 공정을 위해서 제조된 흡수제 Sorb NH의 흡수 및 재생 반응속도는 순수한 $Na_2CO_3$보다 더 빨랐다. 흡수 반응에서 Sorb NH의 겉보기 활성화에너지는 -10,100 cal/g mol, 순수한 $Na_2CO_3$의 겉보기 활성화에너지는 -12,200cal/g mol이었다. 재생반응에서 Sorb NH의 겉보기 활성화에너지는 약 12,050 cal/g mol, 순수한 $Na_2CO_3$의 활성화에너지는 약 11,320 cal/g mol이었다.

• 한국수소및신에너지학회논문집
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• 제33권4호
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• pp.343-352
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• 2022

Co/Al₂O₃ nanopowder was used as a catalyst to investigate the effect of catalyst support, reduction temperature, sodium borohydride (NaBH₄) concentration, sodium hydroxide (NaOH) concentration, and reaction temperature on the characteristics of NaBH₄ hydrolysis. The Co/Al₂O₃ nanopowder showed a high catalytic activity among various catalysts. Catalyst reduction at 250℃ exhibited a relatively good activity. The activity decreased with an increase in the NaBH₄ concentration. Conversely, the activity increased and then decreased with an increase in the NaOH concentration. Additionally, the activity increased with an increase in the reaction temperature. The value of apparent activation energy was 40.81 kJ/mol, which was lower than the other Co-based catalysts. Thus, Co/Al₂O₃ nanopowder catalyst can be widely used for NaBH₄ hydrolysis owing to its superior catalytic activity.

• 한국세라믹학회지
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• 제32권3호
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• pp.341-348
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• 1995

An analysis of the use of temperature profiles in the determination of the kinetic parameters of combustion synthesis of Ti5Si3 were investigated. From profile analysis, an apparent activation energy of 12KJ/mol was calculated. The Maximum heating rate achieved during 10wt% Ti5Si3 reaction by the product dilution method was approximately $1.5\times$104 K/s. Coupling this value with the measured wave velocity of 7.02 cm/s yields a maximum thermal gradient of 2.14$\times$103 K/cm. The value of tr (=t*) was calculated to be 1.2$\times$10-1 s and the value of td (=tx) was calculated to be 32.89 s. Using the definition of t* and the measured wave velocity, the effective thermal diffusivity, $\alpha$, was calculated to be 0.59$\times$10 $\textrm{cm}^2$/s. From these analysis, the power function, G, was also calculated.

• 한국응용과학기술학회지
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• 제28권1호
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• pp.22-28
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• 2011

Esterification reaction between succinic acid[SA] and 1,4-butanediol [BD] was kinetically investigated in the presence of organometallic catalysts (ESCAT-100Ag18, MBTO) at $150{\sim}180^{\circ}C$. The reaction followed from the measurement of the quantity of water which was distilled from the reaction vessel. The esterification reaction was carried out under the first order kinetics with respect to the concentration of reactants and catalyst, respectively. The overall reaction order was 2nd. From the examination of relationship between apparent reaction rate constants and reciprocal absolute temperature, the activation energy has been calculated as 146.70 kJ/mol(ESCAT-100Ag18) and 87.57 kJ/mol(MBTO), respectively.

• 한국응용과학기술학회지
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• 제26권4호
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• pp.415-421
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• 2009

Esterification reaction between succinic acid[SA] and 1,4-butanediol [BD} was kinetically investigated in the presence of organic metal catalysts (alkyl-silver oxide(ASO),CAT 100E) at $150{\sim}190^{\circ}C$. The reaction rates measured by the amount of distilled water from the reaction vessel. The esterification reaction was carried out under the first order kinetics with respect to the concentration of reactants and catalyst, respectively. The overall reaction order was 2nd. From the examination of relationship between apparent reaction rate constants and reciprocal absolute temperature, the activation energy has been calculate as 146.70 kJ/mol with ASO catalyst and 43.04 kJ/mol with CAT 100E catalyst.

• 한국결정성장학회지
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• 제9권1호
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• pp.64-69
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• 1999

PANrP 탄소섬유의 고온연신에서의 변형 거동을 검토하기 위해서, 일정 하중하에서 내부저항 가열법에 의해 $1200^{\circ}C$부터 $2200^{\circ}C$까지 열처리 온도를 변화시키며 섬유의 strain 변화를 측정하였다. 부하된 응력이 증가함에 따라서 strain 변화가 크게 발생하며 또한 열처리 온도 약 $1700^{\circ}C$를 경계로 해서 그 온도 이상과 이하 사이에는 큰 차이를 보였다. 각 응력에 있어서의 strain 속도 변화로부터 얻어진 활성화 에너지는 70 MPa 및 322 MPa에 대하여 각각 67.46 및 52.27 kJ/mol로써, 큰 응력의 경우가 작은 응력을 부하하는 것 보다 섬유구조 발달에 있어서 더욱 효과적이라는 것을 알았다.