The kinetics of solid‐state reactions toward consensus, Part 3. Searching for consistent kinetic results: SCTA vs. conventional thermal analysis

Ortega, Abraham Barrero

doi:10.1002/kin.10026

Cited by 13 publications

(4 citation statements)

References 43 publications

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“…1). [67][68][69] By plotting f(a) versus time-of-reaction, a linear relation shall be obtained, with the corresponding slope giving the reaction rate of the process.…”

Section: Determination Of Kinetic Parametersmentioning

confidence: 99%

Probing Pseudopolymorphic Transitions in Pharmaceutical Solids using Raman Spectroscopy: Hydration and Dehydration of Theophylline

Amado

Nolasco

Ribeiro‐Claro

2007

Journal of Pharmaceutical Sciences

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Theophylline is known to undergo vapor phase induced hydrate-anhydrate pseudopolymorphic transformations, which can affect its bioavailability. In this work, the kinetics of the pseudopolymorphic transitions of theophylline crystals in different storage conditions is studied using a vibrational spectroscopic technique. While the hydration is a single-step process with a half-life time of ca. 5 h, the dehydration occurs through a two-step mechanism. In addition, the phase stability of hydrate-anhydrate systems in different relative humidity (RH) conditions was probed. The critical RH for anhydrous teophylline was found to be at ca. 79%, while the critical RH for dehydration is ca. 30%. ß

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“…1). [67][68][69] By plotting f(a) versus time-of-reaction, a linear relation shall be obtained, with the corresponding slope giving the reaction rate of the process.…”

Section: Determination Of Kinetic Parametersmentioning

confidence: 99%

Probing Pseudopolymorphic Transitions in Pharmaceutical Solids using Raman Spectroscopy: Hydration and Dehydration of Theophylline

Amado

Nolasco

Ribeiro‐Claro

2007

Journal of Pharmaceutical Sciences

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“…Because the partial pressure of the gases is proportional to the rate, the reaction proceeds at a constant overall rate previously selected by the user, under a constant partial pressure of evolved gas. Previous works have demonstrated the efficiency of CRTA to control the influence of experimental factors [18][19][20]. This method has been previously used to control the texture and the structure for many materials [21][22][23] through kinetic control of the thermal reaction of their precursors, and it has been reported that CRTA has higher sensitivity and resolution than the conventional methods.…”

Section: Introductionmentioning

confidence: 98%

Carbothermal synthesis of vanadium nitride: Kinetics and mechanism

Ortega

Roldán

Real

2006

Int J of Chemical Kinetics

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Constant rate thermal analysis (CRTA) has been used for the first time to study the kinetics of the carbothermal reduction of V 2 O 5 in nitrogen to obtain vanadium nitride. It is noteworthy to point out that CRTA method allows both a good control of pressure in the sample surroundings and the use of reaction rates low enough to keep temperatures gradients at a negligible level to avoid any heat or mass transfer phenomena. This method allows one to control the texture and the structure of many materials through kinetic control of the thermal treatment of the precursors. The precise control of the external parameters of the reaction shows that CRTA is an attractive method for kinetic studies and leads to more reliable kinetic data. It has been shown that the carbothermal synthesis of vanadium nitride is best described by a three-dimensional diffusion kinetic model (the Jander equation) with an activation energy which falls in the range of 520-540 kJ/mol. C

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“…The experimental technique of controlled rate thermal analysis (CRTA), which has higher sensitivity and resolution than the conventional thermoanalytical methods, was employed. The CRTA technique has been specially developed to reduce pressure and temperature gradients throughout the sample and to carry out more meaningful experiments 23,24 …”

Section: Introductionmentioning

confidence: 99%

The Multistep Nature of the Kaolinite Dehydroxylation: Kinetics and Mechanism

Ortega

Macı́as

Gotor

2009

Journal of the American Ceramic Society

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The thermal dehydroxylation of kaolinite has been reexamined using small sample weights, a homogeneous particle size distribution and high-vacuum conditions in order to reduce the influences of heat and mass-transfer phenomena. The controlled rate thermal analysis (CRTA) technique, which was specially developed to minimize the pressure and temperature gradients through the sample, was employed to carry out meaningful kinetic experiments. Two advanced isoconversional methods, the Vyazovkin and the Galwey methods, were used complementarily to determine the dependence of the activation energy on the degree of conversion. For this purpose, the Vyazovkin method has been adapted to CRTA experiments. It was demonstrated that there are at least two different stages, revealing the multistep nature of this reaction. The activation energy for the first step, which is assigned to nucleation and the growth of nuclei, decreases from 100 to 75 kJ/mol. The second stage corresponds to a diffusion process and the activation energy rises to 120 kJ/mol because of the metakaolinite formation, which closes the interlamellar channels and leaves isolated patches of kaolinite from which the water escapes with difficulty.

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The kinetics of solid‐state reactions toward consensus, Part 3. Searching for consistent kinetic results: SCTA vs. conventional thermal analysis

Cited by 13 publications

References 43 publications

Probing Pseudopolymorphic Transitions in Pharmaceutical Solids using Raman Spectroscopy: Hydration and Dehydration of Theophylline

Probing Pseudopolymorphic Transitions in Pharmaceutical Solids using Raman Spectroscopy: Hydration and Dehydration of Theophylline

Carbothermal synthesis of vanadium nitride: Kinetics and mechanism

The Multistep Nature of the Kaolinite Dehydroxylation: Kinetics and Mechanism

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