scholarly journals Kinetic Analysis of the Transformation from 14M Martensite to L21 Austenite in Ni-Fe-Ga Melt Spun Ribbons

Metals ◽  
2021 ◽  
Vol 11 (6) ◽  
pp. 849
Author(s):  
Alejandro F. Manchón-Gordón ◽  
Raúl López-Martín ◽  
Jhon J. Ipus ◽  
Javier S. Blázquez ◽  
Peter Svec ◽  
...  
Keyword(s):  
Melt Spinning ◽  
Room Temperature ◽  
Solidification Process ◽  
Austenite Phase ◽  
Isothermal Kinetics ◽  
Martensitic Transition ◽  
Characteristic Parameters ◽  
First Order ◽  
Kinetics Of ◽  
Good Agreement

In this study, the non-isothermal kinetics of the martensitic transition from 14M modulated martensite to austenite phase in Ni55Fe19Ga26 ribbons obtained by melt-spinning has been analyzed. The proximity of the martensitic transition to room temperature makes it very sensitive to pressure and subtle differences for different pieces of the ribbon (ascribed to stresses stored in the ribbon during its rapid solidification process). Despite the dispersion in the characteristic parameters of the transition, a general behavior is observed with a decreasing activation energy as the heating rate increases due to the nucleation driven character of the transition. It has been shown that a first-order autocatalysis can describe the temperature evolution of the austenite fraction using only two experimental temperatures. Predicted curves are in good agreement with experimental data.

Vulcanization of Elastomers. 23. The Chemical Kinetics of Vulcanization Reactions and The Physical Properties of The Vulcanizates. I

1960 ◽  
Vol 33 (2) ◽  
pp. 335-341
Author(s):  
Walter Scheele ◽  
Karl-Heinz Hillmer
Keyword(s):  
Activation Energy ◽  
Physical Properties ◽  
Chemical Kinetics ◽  
Kcal Mole ◽  
First Order ◽  
Equilibrium Swelling ◽  
Kinetics Of ◽  
Kinetics Of Vulcanization ◽  
Limiting Value ◽  
Good Agreement

Abstract As a complement to earlier investigations, and in order to examine more closely the connection between the chemical kinetics and the changes with vulcanization time of the physical properties in the case of vulcanization reactions, we used thiuram vulcanizations as an example, and concerned ourselves with the dependence of stress values (moduli) at different degrees of elongation and different vulcanization temperatures. We found: 1. Stress values attain a limiting value, dependent on the degree of elongation, but independent of the vulcanization temperature at constant elongation. 2. The rise in stress values with the vulcanization time is characterized by an initial delay, which, however, is practically nonexistent at higher temperatures. 3. The kinetics of the increase in stress values with vulcanization time are both qualitatively and quantitatively in accord with the dependence of the reciprocal equilibrium swelling on the vulcanization time; both processes, after a retardation, go according to the first order law and at the same rate. 4. From the temperature dependence of the rate constants of reciprocal equilibrium swelling, as well as of the increase in stress, an activation energy of 22 kcal/mole can be calculated, in good agreement with the activation energy of dithiocarbamate formation in thiuram vulcanizations.

The kinetics and the mechanism of oxidative decarboxylation of benzilic acid by acidic permanganate (stopped-flow technique) — An autocatalytic study

2004 ◽  
Vol 82 (9) ◽  
pp. 1372-1380 ◽  
Author(s):  
Sairabanu A Farokhi ◽  
Sharanappa T Nandibewoor
Keyword(s):  
Activation Parameters ◽  
Oxidative Decarboxylation ◽  
Two Stage ◽  
First Order ◽  
First Order Kinetics ◽  
Stage Process ◽  
Benzilic Acid ◽  
Reaction Constants ◽  
Kinetics Of ◽  
Good Agreement

The kinetics of the oxidation of benzilic acid by potassium permanganate in an acidic medium were studied spectrophotometrically. The reaction followed a two-stage process, wherein both stages of the reaction followed first-order kinetics with respect to permanganate ion and benzilic acid. The rate of the reaction increased with an increase in acid concentration. Autocatalysis was observed by one of the products, i.e., manganese(II). A composite mechanism involving autocatalysis has been proposed. The activation parameters of the reaction were calculated and discussed and the reaction constants involved in the mechanisms were calculated. There is a good agreement between the observed and calculated rate constants under different experimental conditions.Key words: oxidation, autocatalysis, benzilic acid, two-stage kinetics.

THE KINETICS OF THE DECOMPOSITION REACTIONS OF THE LOWER PARAFFINS: I. n-BUTANE

1938 ◽  
Vol 16b (5) ◽  
pp. 176-193 ◽  
Author(s):  
E. W. R. Steacie ◽  
I. E. Puddington
Keyword(s):  
Reaction Rate ◽  
High Pressures ◽  
The Other ◽  
First Order ◽  
Decomposition Reactions ◽  
Temperature And Pressure ◽  
Products Of Reaction ◽  
Kinetics Of ◽  
Good Agreement ◽  
Mechanism Of The Reaction

The kinetics of the thermal decomposition of n-butane has been investigated at pressures from 5 to 60 cm. and temperatures from 513 to 572 °C. The initial first order rate constants at high pressures are given by[Formula: see text]The results are in good agreement with the work of Frey and Hepp, but differ greatly from that of Paul and Marek. The reaction rate falls off strongly with diminishing pressure; this is rather surprising for a molecule as complex as butane. The first order constants in a given run fall rapidly as the reaction progresses. The last two facts suggest that chain processes may be involved.A large number of analyses of the products of reaction have been made at various pressures, temperatures, and stages of the reaction, the method being that of low-temperature fractional distillation. The products are virtually independent of temperature and pressure over the range investigated. The initial products, obtained by extrapolation to zero decomposition, are:—H2, 2.9; CH4, 33.9; C3H6, 33.9; C2H4, 15.2; C2H6, 14.1%. The mechanism of the reaction is discussed, and the results are compared with those of the other paraffin decompositions.

Pyrolysis of Sugarcane Bagasse: A Consecutive Reactions Kinetic Model from TGA Experiments

2010 ◽  
Vol 660-661 ◽  
pp. 593-598 ◽  
Author(s):  
Kássia Graciele dos Santos ◽  
Taisa S. Lira ◽  
Valéria V. Murata ◽  
Marco Gianesella ◽  
Marcos A.S. Barrozo
Keyword(s):  
Kinetic Model ◽  
Sugarcane Bagasse ◽  
Room Temperature ◽  
Linear Method ◽  
Pyrolysis Kinetics ◽  
Heating Rates ◽  
Exponential Factor ◽  
Consecutive Reactions ◽  
Kinetics Of ◽  
Good Agreement

The pyrolysis kinetics of sugarcane bagasse in nitrogen flow was studied by thermogravimetric analysis from room temperature to 1173 K at different heating rates (1.5, 3, 5, 10, 15, 20, 30 and 50 K/min). As there are three distinct devolatilization peaks in the DTG curve, each peak was associated to thermal decomposition of an individual biomass subcomponent (hemicellulose, cellulose and lignin). The kinetic model adopted was a consecutive reactions model. The kinetic parameters of the pyrolysis process, such as activation energy and pre-exponential factor, were calculated by least squares non-linear method and Scilab are used as the simulation tool. The simulated results showed a good agreement with the experimental data and the parameters found are similar to reported by the literature.

Hydrogen-Induced Phase Separation of Palladium-Rhodium Alloys Using an Environmental Cell TEM

1997 ◽  
Vol 3 (S2) ◽  
pp. 591-592
Author(s):  
D.F. Teter ◽  
R.D. Field ◽  
D.J. Thoma
Keyword(s):  
Phase Separation ◽  
Hydrogen Absorption ◽  
Melt Spinning ◽  
Room Temperature ◽  
Annealing Treatment ◽  
Miscibility Gap ◽  
Environmental Cell ◽  
Cold Rolled ◽  
Kinetics Of

The palladium-rhodium system has been extensively studied for its hydrogen absorption characteristics. However, the phase diagram of the palladium-rhodium system has not been conclusively determined below 800 K. Shield and Williams have experimentally determined the incoherent miscibility gap in Pd-Rh alloys using electrical resistivity studies, however the coherent miscibility gap and spinodal have not been determined. Recently work by Noh and Flanagan has suggested that hydrogen enhances metal atom mobility and may increase the kinetics of phase separation in Pd-Rh alloys. Field and Thoma found that hydrogen causes a Pd-10%Rh alloy to decompose during an in situhydrogen charging experiment in an environmental cell TEM. According to the calculations by Gonis et al. of the miscibility gap for the palladium-rhodium system, the Pd-10%Rh alloy may be within the chemical spinodal at room temperature.In this work, two palladium-rhodium compositions were investigated. The first was a Pd-10 at.% Rh alloy produced by melt-spinning, and the second was a Pd-30at.%Rh alloy which had been arc-melted and cold rolled followed by an annealing treatment to homogenize the material. TEM specimens were prepared by punching 3 mm disks from the material.

scholarly journals Reaction Kinetics of Carbon Dioxide in Aqueous Diethanolamine Solutions Using the Stopped-Flow Technique

2012 ◽  
Vol 19 (1) ◽  
pp. 55-66 ◽  
Author(s):  
Marta Siemieniec ◽  
Hanna Kierzkowska-Pawlak ◽  
Andrzej Chacuk
Keyword(s):  
Carbon Dioxide ◽  
Reaction Kinetics ◽  
Rate Constants ◽  
Reaction Rate ◽  
Reaction Rate Constant ◽  
Stopped Flow ◽  
First Order ◽  
Pseudo First Order ◽  
Kinetics Of ◽  
Good Agreement

Reaction Kinetics of Carbon Dioxide in Aqueous Diethanolamine Solutions Using the Stopped-Flow Technique The pseudo-first-order rate constants (kOV) for the reactions between CO2 and diethanolamine have been studied using the stopped-flow technique in an aqueous solution at 293, 298, 303 and 313 K. The amine concentrations ranged from 167 to 500 mol·m-3. The overall reaction rate constant was found to increase with amine concentration and temperature. Both the zwitterion and termolecular mechanisms were applied to correlate the experimentally obtained rate constants. The values of SSE quality index showed a good agreement between the experimental data and the corresponding fit by the use of both mechanisms.

Fluorescent Whitening Agents

1976 ◽  
Vol 46 (7) ◽  
pp. 539-544 ◽  
Author(s):  
L. A. Holt ◽  
I. H. Leaver ◽  
B. Milligan
Keyword(s):  
Vinyl Acetate ◽  
Polymer Films ◽  
Room Temperature ◽  
Polar Solvents ◽  
Fluorescence Studies ◽  
First Order ◽  
Absorption And Fluorescence Spectroscopy ◽  
Fluorescent Whitening Agents ◽  
Kinetics Of ◽  
Photo Decomposition

Ultraviolet absorption and fluorescence spectroscopy have been used to determine the nature and extent of photo-decomposition of fluorescent whitening agents in polymer films and in surface-whitened wool. Irradiation of the coumarin (I) in polymer films at 365 nm gives rise to a mixture of photodimers which rapidly revert to I on irradiation at wavelengths less than 320 nm. Irradiation of the stilbene (II) at 365 nm also gives a photodimer which absorbs strongly around 350 nm, but this reverts only slowly to II on irradiation. Fluorescence studies indicate that there is an increase in the degree of aggregation of I in polymer films with increasing whitener concentration, and that the kinetics of whitener photodecomposition change from first-order at low whitener concentration (0.0025%) to second-order at the higher concentration (2.5%) used in surface-whitening. The coumarin (I) is more stable to light in poly(vinyl acetate) film cast from formic acid than in films cast from less polar solvents, probably because of differences in the degree of whitener aggregation. The photostability of I in poly(vinyl acetate) film is also improved if the film is heated for short periods or stored at room temperature for longer periods.

Effect of human neuronal tau on denaturation and reactivation of rabbit muscle D-glyceraldehyde-3-phosphate dehydrogenase

2000 ◽  
Vol 351 (1) ◽  
pp. 233-240 ◽  
Author(s):  
Yong-Hui CHEN ◽  
Rong-Qiao HE ◽  
Ying LIU ◽  
Yang LIU ◽  
Zhi-Gang XUE
Keyword(s):  
Protein Kinase ◽  
Room Temperature ◽  
Guanidine Hydrochloride ◽  
Marked Change ◽  
The Other ◽  
Rabbit Muscle ◽  
Native Conformation ◽  
First Order ◽  
Kinetics Of

Human neuronal tau-40 (htau-40) has been used to study denaturation and renaturation of rabbit muscle D-glyceraldehyde-3-phosphate dehydrogenase (GAPDH, EC 1.2.1.12). Inactivation of GAPDH incubated with tau was more distinguishably detected than that of control GAPDH during thermal and guanidine hydrochloride (GdnHCl) denaturation. However, tau did not influence the activity of GAPDH at room temperature or in solution without GdnHCl. A marked change in both the emission intensity and emission maximum of the intrinsic fluorescence at 335nm of GAPDH with tau was observed when GdnHCl concentration was 0.8M, but that of the control without tau occurred in 1.2M GdnHCl. The first-order rate of the decrease in the fluorescence intensity of the enzyme with tau was approximately twice as great as that of GAPDH without tau. Kinetics of inactivation of GAPDH with tau in 0.2M GdnHCl was a monophasic procedure, instead of the biphasic procedure followed by the control, as described before [He, Zhao, Yan and Li (1993) Biochim. Biophys. Acta 1163, 315–320]. Similar results were obtained when the enzyme was thermally denatured at 45°C. It revealed that tau bound to the denatured GAPDH but not the native molecule. On the other hand, tau suppressed refolding and reactivation of GAPDH when this enzyme was reactivated by dilution of GdnHCl solution. Furthermore, tau improved the aggregation of the non-native GAPDH in solutions. It suggested that tau acted in an anti-chaperone-like manner towards GAPDH in vitro. However, tau lost that function when it was aggregated or phosphorylated by neuronal cdc2-like protein kinase. It showed that tau's anti-chaperone-like function depended on its native conformation.

Effect of Fe on the Martensitic Transition, Magnetic and Magnetocaloric Properties in Ni-Mn-In Melt-spun Ribbons

2016 ◽  
Vol 66 (4) ◽  
pp. 403 ◽  
Author(s):  
D.M. Raj kumar ◽  
N.V. Rama Rao ◽  
S. Esakki Muthu ◽  
S. Arumugam ◽  
M. Manivel Raja ◽  
...  
Keyword(s):  
Room Temperature ◽  
Magnetic Entropy Change ◽  
Thermal Hysteresis ◽  
Entropy Change ◽  
Austenite Phase ◽  
High Magnetic Fields ◽  
Martensitic Transition ◽  
Magnetic Entropy ◽  
Fe Content ◽  
Magnetocaloric Properties

The effect of Fe on the martensitic transitions, magnetic and inverse magnetocaloric effect in Ni47Mn40-xFexIn13 ribbons (x = 1, 2, 3 and 5) has been investigated. All the ribbon compositions under study have shown the presence of austenite phase at room temperature. The variation of martensitic transition with the increase in Fe-content is non-monotonic. The thermal hysteresis of the martensitic transition increased with the increase in Fe-content. The martensitic transitions shifted to lower temperatures in the presence of high magnetic fields. A maximum magnetic entropy change (∆SM) of 50 Jkg-1K-1 has been achieved in the Ni47Mn38Fe2In13 (x = 1) ribbon at 282 K for an applied field of 5 T.

NMR Study of the Crystallization Kinetics of Cis-Poly(Isoprene)s

1973 ◽  
Vol 46 (1) ◽  
pp. 22-29 ◽  
Author(s):  
R. C. Hirst ◽  
H. Y. Chen
Keyword(s):  
Room Temperature ◽  
Curve Shape ◽  
X Ray Diffraction ◽  
Rigid Lattice ◽  
X Ray ◽  
Nmr Study ◽  
Accurate Comparison ◽  
Dilatometric Studies ◽  
Kinetics Of ◽  
Good Agreement

Abstract The satisfactory agreement between our NMR results and X-ray diffraction results for the crystallinity in stark rubber at room temperature lead us to conclude that the NMR rigid lattice fraction, PRL, may be taken as equal to the fractional crystallinity obtained by other methods. Similarly, the good agreement between the time dependence of PRL at low temperature and the theoretical curve shape strongly suggest that the NMR crystallinity method works well down to at least −25° C for natural rubber and synthetic cis-poly (isoprene). It would be desirable to compare carefully the NMR crystallinity found for rubber crystallized at −25° C with X-ray diffraction results, but we have been unable to find any such X-ray diffraction studies at −25° C. Maximum values of ΔV/V≅0.025 from dilatometric studies appear to imply somewhat smaller crystallinities than those found by NMR, but an accurate comparison is not possible without having X-ray diffraction densities at −25° C. While the present experiments were carried out on unfilled, unstretched, unvulcanized samples, the NMR crystallinity method is equally applicable to samples which are filled, stretched, and vulcanized. Naturally any additive or impurity containing hydrogen is a possible source of interference, but there should be no difficulty in correcting for such interferences.

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