• Bulletin of the Korean Chemical Society
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• v.2 no.4
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• pp.138-141
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• 1981

The rate of the bromine-exchange reaction between gallium bromide and i-butyl bromide in 1,2,4-trichlorobenzene or nitrobenzene was measured at 19, 25 and $40^{\circ}C$, using i-butyl bromide labelled with Br-82. The results indicated that the exchange reaction was second order with respect to gallium bromide and first order with respect to i-butyl bromide. The third-order rate constant determined at $19{\circ}C$ was $3.28{\times}10^{-2}l^2{\cdot}mole^{-2}{\cdot}sec^{-1}$ in 1,2,4-trichlorobenzene and $9.25{\times}10^{-3}l^2{\cdot}mole^{-2}{\cdot}sec^{-1}$ in nitrobenzene. The activation energy, the enthalpy of activation and the entropy of activation for the exchange reaction were also determined.

• Bulletin of the Korean Chemical Society
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• v.2 no.3
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• pp.86-89
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• 1981

The rate of the bromine-exchange reaction between gallium bromide and n-propyl bromide in 1,2,4-trichlorobenzene and in nitrobenzene was measured at 19, 25 and $40^{\circ}C$, using n-propyl bromide labelled with Br-82. The results indicated that the exchange reaction was second order with respect to gallium bromide and first order with respect to n-propyl bromide. The third-order rate constant determined at $19^{\circ}C$ is $2.9{\times} 10^{-2}l^2{\cdot}mole^{-2}{\cdot}sec^{-1}$ in 1,2,4-trichlorobenzene and $4.5{\times}10^{-3}l^2{\cdot}mole^{-2}{\cdot}sec^{-1}$. in nitrobenzene. The activation energy, the enthalpy of activation and the entropy of activation for the exchange reaction were also determined. Reaction mechanism for the bromine exchange of n-propyl bromide seemed to be similar to those observed in earlier studies with other alkyl bromides.

• Journal of the Korean institute of surface engineering
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• v.44 no.4
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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.

• Elastomers and Composites
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• v.12 no.1
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• pp.27-32
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• 1977

The kinetics of azo-coupling reaction of N-acetyl-H-acid (1-acetamino-8-hydroxynaphthalene-3, 6-disulfonic acid) with several heterocyclic diasonium compounds such as diazotiged 3-aminopyridine, 3-aminoquinoline, 8-aminoauinoline and aniline was studied. It was found that reactions proceeded at remarkably different rate. Reaction rate was in increasing order; 3-aminopyridine, 3-aminoquinoline, 8-aminoauinoline and aniline. And the activation energies were 9.62, 10.10, 10.39, 10.70 Kcal/mole, respectively. Especially, the rate constant of 3-aminopyridine was 100 times larger than that of benzene diasonium compound even in strong acidity. Hammett plot was also made of the rate constants obtained against the heterocyclic substituent constants reported in the literature. A good linear relationship was obtained and the reaction constant of N-acetyl H-acid was calculated to be 3.14.

• Archives of Pharmacal Research
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• v.2 no.1
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• pp.35-47
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• 1979

In order to increase the dissolution rate of furosemide(4-choro-N-furfury1-5-sulfamoy1 anthranilic acid_, various ratio coprecipitates with water-soluble polymers, such as polyvinylpyrrolidone and polythylene glycol, of different molecular weight, were prepared and quantitatively studied by comparing their dissolution characteristics of furosemide at powder state and at nondisintegrating disk state containing constant surface area at various temperatures and rotating velocities. The dissolution characteristics of furosemide from pure furosemide disks and 1:2(w/w) furosemide-PVP coprecipitate disks were in accordance with Noyes-Nernst equation and the rate constant of dissolution was proportional to the square root of rotating velocity of the disks. The intrinsic rate of dissoluton at 150 rpm, 37.deg.C was $2.21{\times}10^{-7}$ for the PVP 10, 000 COPRECIPITATE, $1.64{\times}10^{-7}$ for the PVP 40, 000 coprecipitate, and$ 1.44 {\times} 10^{-7}$for the PVP 360, 000 corprecipitate, while the rate was $1.27{\times}10^{-8}M/cm^{2} min$ for pure furosemide, repectively. The activation energy of dissolution was about 17, 000 for furosemide and about 7, 300 cal/mole for the 1:2 furosemide PVP 40, 000 coprecipitate, respectively.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.11 no.4
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• pp.54-61
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• 2002

Inconel 690 alloy has widely been used in power plant and high temperature facilities because it has high thermal resistance and toughness. But we have little design data about the creep behaviors of the alloy. Therefore, in this study, an apparatus has been designed and built for conducting creep tests under constant load conditions. A series of creep tests on Inconel 690 alloy have been performed to get the basic design data and life prediction of inconel products and we have gotten the following results. First, the stress exponents decrease as the test temperatures increase. Secondly, the creep activation energy gradually decreases as the stresses become bigger. thirdly, the constant of Larson-Miller Parameters on this alloy is estimated about 10. And last the fractographs at the creep rupture show both the ductile and the brittle fracture according to the creep conditions.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2003.10a
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• pp.248-253
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• 2003

Titanium alloy has widely been used as glasses rim material because it has high specific strength and also is light, harmless to men. But, we have little design data about the creep behaviors of the alloy. Therefore, in this study, an apparatus has been designed and built for conducting creep tests under constant load conditions. A series of creep tests on them have been performed to get the basic design data and life prediction of titanium products and we have gotten the following results. First, the stress exponents decrease as the test temperatures increase. Secondly, the creep activation energy gradually decreases as the stresses become bigger. Thirdly, the constant of Larson-Miller parameters on this alloy is estimated about 13. And last, the fractographs at the creep rupture show both the ductile and the brittle fracture according to the creep conditions.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2004.10a
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• pp.22-27
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• 2004

Super-duralumin has widely been used as the part materials of aerospace and automobile industry because it has high specific strength and also is light. But, we have little design data about the creep behaviors of the alloy. Therefore, in this study, every creep test under four constant stress conditions have been conducted for four temperature conditions. A series of creep tests had been performed to get the basic design data and life prediction of super-duralurnin products and we have gotten the following results. First, the stress exponents showed the descending trend as the test temperatures increase. Secondly, the creep activation energy gradually decreased as the stresses become bigger. Thirdly, the constant of Larson-Miller parameters on this alloy was estimated about 6. And last, the fractographs at the creep rupture showed both the brittle fracture due to the transgranular rupture.

• Transactions of the Korean Society of Automotive Engineers
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• v.14 no.2
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• pp.16-22
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• 2006

Stainless steel has widely been used in various industrial fields because it has high corrosion resistance. But, we have little design data about the creep life prediction of SUS316L stainless steel. Therefore, in this study, a series of creep tests and study on them under 16 constant stress and temperature combined conditions have been performed to get the creep design data and life prediction of SUS316L stainless steels and we have gotten the following results. First, the stress exponents decrease as the test temperatures increase. Secondly, the creep activation energy gradually decreases as the stresses become bigger. Thirdly, the constant of Larson-Miller parameters on this alloy is estimated about 10. And last, the creep rupture fractographs show the intergranular ductile fracture with many dimples.

• Journal of Mechanical Science and Technology
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• v.20 no.8
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• pp.1209-1216
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• 2006

An AZ31 magnesium alloy was tested at constant temperatures ranging from 423 to 473 K (0.46 to 0.51 Tm) under constant stresses. All of the creep curves exhibited two types depending on stress levels. At low stress (${\sigma}/ G < 4 {\times}10^{-3}$), the creep curve was typical of class A (Alloy type) behavior. However, at high stresses (${\sigma}/ G > 4 {\times}10^{-3}$), the creep curve was typical of class M (Metal type) behavior. At low stress level, the stress exponent for the steady-state creep rate was of 3.5 and the true activation energy for creep was 101 kJ/mole which is close to that for solute diffusion. It indicates that the dominant deformation mechanism was glide-controlled dislocation creep. At low stress level where n=3.5, the present results are in good agreement with the prediction of Fridel model.