共查询到20条相似文献,搜索用时 437 毫秒
1.
R. O. Macêdo T. G. do Nascimento J. W. E. Veras 《Journal of Thermal Analysis and Calorimetry》2001,64(2):757-763
The compatibilities and stabilities of some binary mixtures and generic hydrochlorothiazide formulations were studied by using
TG, DSC and a DSC-photovisual system. The kinetic parameters were determined via the Arrhenius equations. Tablet B presented
higher compatibility and thermal stability than those of tablets A and C. The photovisual system demonstrated that the decomposition
of tablet A occurs before the melting point, due to the Maillard reaction between the hydrochlorothiazide and lactose present
in the formulation. The behaviour and rate constants of binary mixtures suggest that lactose can be substituted for microcrystalline
cellulose, MC(101), in tablet A. The DSC and TG data revealed different characteristics of compatibility and stability in
generic formulations from different manufacturers.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
2.
Antonilêni F. D. Medeiros Ana Flávia O. Santos F. S. de Souza I. D. B. Júnior J. Valdilânio J. V. V. Procópio D. P. de Santana R. O. Macêdo 《Journal of Thermal Analysis and Calorimetry》2007,89(3):775-781
Compatibility studies between active drugs and excipients are substantial in the pharmaceutical technology. The objective
of the present work was to develop pre-formulated mixtures of metronidazole (MT) obtained by spray drying (SPDR) and their
thermoanalytical characterization. Dynamic and isothermal TG, conventional DSC and DSC coupled to a photovisual system were
used. DSC experiments with both techniques confirmed the homogeneity of the conventional and pre-formulated mixtures. The
TG data made possible the comparison the thermal stability of the different mixtures. Similar thermal stabilities were found
of the conventional and pre-formulated mixtures, with slower particles sizes of MT. 相似文献
3.
F. Santos de Souza A. P. Gomes Barreto R. O. Macêdo 《Journal of Thermal Analysis and Calorimetry》2001,64(2):739-743
The present work proposes evaluation of the gelatinization processes of starch by means of DSC coupled with a photovisual
system. The use of DSC, TG and DTA for a fast and efficient evaluation of the starch is suggested. The DSC curves of starch
gels with water contents of 20, 30, 40 and 50% (mass/v) exhibited different phase transitions, corresponding to the gelatinization
processes at the different water contents for the different lots. The DSC-photovisual system confirmed calorimetric behaviour
differences between the starch lots studied.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
4.
M. A. M. Al-Gurashi A. A. B. El-Ahmadi S. M. A. Katib K. M. Abd El-Salaam 《Journal of Thermal Analysis and Calorimetry》1994,41(4):859-870
Thermal decomposition of cobalt and nickel nicotinate was studied by TG, DTG and DSC. The mechanism of decomposition has been
established from TG and DSC data. The kinetic parameters namelyE, A together with ΔH were calculated from DSC curves using mechanistic and non-mechanistic integral equations.
Zusammenfassung Mittels TG, DTG und DSC wurde die thermische Zersetzung von Cobaltund Nickelnikotinat untersucht. Der Zersetzungsmechanismus wurde anhand der TG-und DSC-Daten entwickelt. Die kinetischen ParameterE, A wurden zusammen mit ΔH anhand der DSC-Kurven mit Hilfe von mechanistischen und nichtmechanistischen Integrationsgleichungen berechnet.相似文献
5.
C. D. Bertol A. P. Cruz H. K. Stulzer F. S. Murakami M. A. S. Silva 《Journal of Thermal Analysis and Calorimetry》2010,102(1):187-192
Primaquine (PQ) is the drug of choice for the radical cure of Plasmodium vivax malaria, and currently being administered in solid dosage form. In this study, the compatibility studies were carried out
using differential scanning calorimetry (DSC), thermogravimetry (TG), and fourier transformed infrared (FT-IR). Non-isothermal
and isothermal methods were employed to investigate kinetic parameters under nitrogen and air atmospheres using TG. The DSC
investigations obtained by physical mixtures showed slight alterations in the melting temperatures of PQ with some excipients.
The FT-IR confirmed the possible interactions obtained by DSC for the physical mixtures with PQ and lactose, magnesium stearate
and mannitol. The results showed that the thermal decomposition followed a zero order kinetic in both atmospheres in non-isothermal
method. The activation energy in both methods using nitrogen atmosphere was similar, and in air atmosphere the activation
energy decreased. 相似文献
6.
NaNTO·H2O was prepared by mixing 3‐nitro‐1,2,4‐triazol‐5‐one (NTO) aqueous solution and sodium hydroxide aqueous solution. Its thermal decomposition and kinetics were studied under non‐isothermal conditions by DSC and TG/DTG methods. The kinetic parameters were obtained from analysis of the DSC and TG/DTG curves by the Kissinger method, the Ozawa method, the differential method and the integral method. The most probable mechanism function for the thermal decomposition of the first stage was suggested by comparing the kinetic parameters. The critical temperature of thermal explosion (Tb) was 240.93 °C. The theoretical investigation on the structure unit of the title compound was carried out by DFT‐B3LYP/CEP‐31G methods; atomic net charges and the population analysis were discussed. 相似文献
7.
Thermogravimetric analysis (TGA) and differential scanning calorimetric (DSC) studies were carried out on gamma radiation synthesized polydiallyldimethylammonium chloride (PDADMAC). The polymer was found to undergo thermal degradation in two stages. The first stage showed a weight loss of 33% and the second stage showed a weight loss of 67%. The DSC thermogram shows two endothermic peaks corresponding to the two stages in the TG thermogram and the experimental enthalpy change associated with the first and second stages were 650 J g−1 and 129.5 J g−1, respectively. The nth-order kinetic parameters (order of the reaction, activation energy and the pre-exponential factor) were determined from a single dynamic DSC or thermogravimetric (TG) thermogram by the method of least square. Theoretical TG/differential thermogravimetric (DTG) and DSC thermograms derived from the calculated kinetic parameters were in good agreement with the experimental ones at the heating rate employed. However, the kinetic parameters determined using TG and DSC were different. This leads to the conclusion that the degradation mechanism could be complicated and may consists of a number of parallel or consecutive reactions. The glass transition temperature (Tg) of the polymer was found to be around 150 °C depending on the test method employed. 相似文献
8.
Introduction3 Nitro 1,2 ,4 triazol 5 one (NTO)metalcomplexeshavemanyspecialstructuresandsomepotentialusesinammunition .1 4 Wepreviouslypreparedanddeterminedthecrystalstructureofitsmagnesiumcomplex ,5andinthispaper ,wediscusseditsthermalbehaviorbyDSCandTG/DTGtechniquesandstudieditsnon isothermalkineticsbythemeansoftheKissingermethod ,theOzawamethod ,thedifferentialmethodandtheintegralmethod .ExperimentalSample[Mg(H2 O) 6 ](NTO) 2 ·2H2 Owaspreparedasfollows :AcalculatedamountofMg(OH… 相似文献
9.
Shipra Baluja Nirmal Pandya Nayan Vekariya 《Russian Journal of Physical Chemistry A, Focus on Chemistry》2008,82(9):1601-1604
Thermal analyses of some Schiff bases, derivative of α-napthylamine, were performed by the DSC, TG and DTA techniques. The
thermograms were used to determine various kinetic parameters, such as the order of degradation (n), energy of activation (E), frequency factor (A), and entropy change (ΔS), by the Freeman-Carroll method.
The text was submitted by the authors in English. 相似文献
10.
B. Tiţa Eleonora Marian D. Tiţa Gabriela Vlase N. Doca T. Vlase 《Journal of Thermal Analysis and Calorimetry》2008,94(2):447-452
Thermal analysis is one of the most widely used methods for studying the solid state of pharmaceutical substances.
TG/DTG and DSC curves provide important information regarding the physical properties of the pharmaceutical compounds (stability,
compatibility, polymorphism, kinetic analysis, phase transitions etc.).
The purpose of a kinetic investigation is to calculate the kinetic parameters and the kinetic model for the studied process.
The results are further used to predict the system’s behaviour in various circumstances.
A kinetic study regarding the diazepam, nitrazepam and oxazepam thermal decomposition was performed, under non-isothermal
and isothermal conditions and in a nitrogen atmosphere, for the temperature steps: 483, 498, 523, 538 and 553 K. The TG/DTG
data were processed by three methods: isothermal model-fitting, Friedman’s isothermal-isoconversional and Nomen-Sempere non-parametric
kinetics.
In the model-fitting methods the kinetic triplets (f(α), A and E
a) that defines a single reaction step resulted in being at variance with the multi-step nature of diazepines decomposition.
The model-free approach represented by isothermal and non-isothermal isoconversional methods, gave dependences of the activation
energies on the extent of conversion.
It is very difficult to obtain an accord with the similar data which resulted under non-isothermal conditions from a previous
work.
The careful treatment of the kinetic parameters obtained in different thermal conditions was confirmed to be necessary, as
well as a different strategy of experimental data processing. 相似文献
11.
The kinetics and thermodynamics of the thermal dehydration of crystalline powders of MgC2O4 · 2 H2O were studied by means of thermal analyses both at constant temperatures and at linearly increasing temperatures. The dehydration of the dihydrate is regulated by one of the Avrami-Erofeyev laws. The kinetic parameters from TG at constant temperatures are in good agreement with those from TG at the lowest rate of rising temperatures. The dynamic dehydration kinetics was also examined, using DSC recorded simultaneously with TG at linearly increasing temperatures. The validity of the estimated mechanism and kinetic parameters is briefly discussed. 相似文献
12.
A. S. de Araujo V. J. Fernandes Jr. G. J. T. Fernandes 《Journal of Thermal Analysis and Calorimetry》1997,49(1):567-572
The acid properties of the Ca/NaY zeolite were investigated by means ofn-butylamine desorption and thermal decomposition, using both thermogravimetry (TG) and differential scanning calorimetry (DSC). The total acidity of the zeolite was calculated from the TG data, while DSC was used with the Borchardt-Daniels kinetic model to determine the relative acid strength of the catalyst, given in J per acid site. The enthalpies of these processes are proportional to the acid site strength in each specific temperature range.This work was supported by Conselho National de Desenvolvimento Científico e Tecnológico (CNPq). The authors are very grateful to M. L. C. Rodrigues and C. I. Braga, from D. P. Instrumentos Científicos. 相似文献
13.
DSC measurements in open pans are often disturbed by mass losses such as sublimation during melting or release of water during
chemical reactions. By simultaneous DSC and TG measurements the DSC signal can be corrected. For this purpose, a temperature
dependent calibration function has to be determined by which the SDTA signal from the TGA/SDTA851e measuring cell can be converted into a heat flow curve (DSC).
By this procedure, accurate heat of melting can be determined despite ongoing sublimation in open pans. This method is illustrated
with reference of the melting of anthracene.
Additionally, condensation reactions were investigated and analyzed by DSC/TG even under ambient pressure, knowing the heat
of evaporation. Using phenol formaldehyde resins the influence of the presence or the release of volatile reaction products
on the reaction rate and kinetic parameters were studied.
In general, the method can be used to correct DSC curves for thermal effects related to mass change.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
14.
Kinetics of the oxidation of magnetite (Fe3O4) to hematite (a-Fe2O3) are studied in air using simultaneous TG/DSC. The mechanism is complex and the differences between the kinetic conclusions
and Arrhenius parameters based on either TG or DSC are discussed. As in our previous work on CaCO3 [1], the determination of a satisfactory baseline for the DSC results adds considerable uncertainty to those kinetic results.
Consequently the calculations based on the TG data are considered superior. Solid state reactivity varies from one source
of material to another and the results are compared for two different commercial samples of magnetite, both presumably prepared
by wet chemical methods. These materials are much more reactive than the material studied previously [2], which had been coarsened
and refined at high temperatures. In that earlier study, the metastable spinel, g-Fe2O3, was formed as an intermediate in the oxidation to the final stable form, a-Fe2O3. The exothermic reaction of the gamma to alpha form of the product during the oxidation process destroys the direct comparison
between the TG and DSC results, since the former only detects the change in mass of the sample and not the crystallographic
transformation. The TG results, however, represent the true oxidation process without superposition of the structural aspects.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
15.
A. Hazra K. Alexander D. Dollimore A. Riga 《Journal of Thermal Analysis and Calorimetry》2004,75(1):317-330
The present study was aimed at determining the kinetics of evaporation and establishing vapor pressure curves for both single and multi-component systems by thermogravimetry (TG) and differential scanning calorimetry (DSC). Essential oils (e.g. lavender oil, orange oil, clove oil and eucalyptus oil, etc.) are typically multi-component systems consisting of various volatile pure components (e.g. linalyl acetate, limonene, cinnamaldehyde, etc.) which resemble single component systems. In this study linalyl acetate was taken as the calibration compound for TG. The vapor pressure curves for the pure substances were plotted using TG and vapor pressure plots for clove oil and eucalyptus oil were constructed using DSC. The thermodynamic and kinetic parameters of the pure compounds were compared to that of the multi-component systems to quantitatively and qualitatively measure the influence of different compounds on each other. The k-value from the vapor pressure data for linalyl acetate was calculated as 112006 Pa kg0.5mol0.5s-1 m-2 K-0.5. The vapor pressure values were used to determine the Antoine constants using the SPSS 10.0 software.This revised version was published online in November 2005 with corrections to the Cover Date. 相似文献
16.
N. Petranović D. Minić T. J. Sabo D. Doković 《Journal of Thermal Analysis and Calorimetry》2000,59(3):807-814
Thermal properties of facial and meridional uns-cis-[Co(eddp)gly]0.5H2O complexes were investigated by means of DSC and TG techniques. It wasshown that the processes of thermal decomposition of
these complexes are multi-stepdegradation processes, which can also be well separated into individual steps, depending onthe
molecular symmetry. Thus, the process of thermal degradation of the meridional isomerof the above complex consists of 4 well-separated
steps in the temperature interval from 100to 500°C. The corresponding kinetic and thermodynamic parameters of this process
weredetermined, and a possible mechanism is discussed.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
17.
The processes of thermal dehydration and decomposition of Mn(NO3)2 ·.6H2O and its deuterated analogue were studied by DTA, TG and DSC. Comparisons were made between the data obtained for the two compounds. The following phase transitions were observed: melting of the compound; dehydration to monohydrate; dehydration of the monohydrate, accompanied by its partial decomposition to MnO2; and decomposition of the anhydrous nitrate to MnO2.The DSC data were used to determine the enthalpies of the phase transitions, and those corresponding to the partial dehydration were compared with the calculated ones. The formal kinetic parameters (E
* andA) for the three stages (without the melting stage) were calculated from the TG curves, and the corresponding kinetic equations are reported.
Zusammenfassung Mittels DTA, TG und DSC wurde der Verlauf der thermischen Dehydratation und Zersetzung von deuteriertem und undeuteriertem Mn(NO3)2·6H2O untersucht und die erhaltenen Ergebnisse beider Verbindungen miteinander verglichen. Folgende Phasenumwandlungen konnten beobachtet werden: Schmelzen der Verbindung; Dehydratation bis zum Monohydrat; Dehydratation des Monohydrates unter teilweiser Zersetzung zu MnO2; Zersetzung von wasserfreiem Nitrat zu MnO2. DSC-Daten wurden zur Bestimmung der Enthalpien für die Phasenumwandlungen benutzt, die so ermittelten Ergebnisse für die partielle Dehydratation wurden mit den berechneten verglichen. Anhand der TG-Kurven wurden die formellen kinetischen Parameter (E * undA) der drei Schritte (ohne Schmelzvorgang) berechnet und die entsprechenden kinetischen Gleichungen beschrieben.相似文献
18.
A mixed metal carboxylate, cadmium(II)bis(oxalato)cobaltate(II)pentahydrate, has been synthesized and characterized by elemental
analysis, IR spectral, reflectance and X-ray powder diffraction studies. Thermal decomposition studies (TG, DTG and DTA) in
air showed that the compound decomposed to CdCoO3 at 370°C through the formation of an anhydrous compound at ~194°C. Finally,
CdCoO2 is generated at 1000°C. DSC study in nitrogen up to 550°C showed the formation of a mixture of CdO and Co3O4 as end products. The kinetic parameters have been evaluated for the dehydration and decomposition steps using four non-mechanistic
equations, i.e., Freeman and Carroll, Coats and Redfern, Flynn and Wall, MacCallum and Tanner equations. Using seven mechanistic
equations, the rate controlling processes of the dehydration and decomposition mechanism are also inferred. The kinetic parameters,
DH and DS obtained from DSC are discussed. IR and X-ray powder diffraction studies identified some of the decomposition products. A
tentative mechanism for the decomposition in air is proposed.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
19.
Mustafa Versan Kök 《Journal of Thermal Analysis and Calorimetry》2014,115(2):1533-1539
In this study, thermal characteristics and kinetics of three different origin class-G cements (Mix, Bolu, and Nuh) were studied using thermogravimetry (TG/DTG) and differential scanning calorimeter (DSC). In DSC curves at different heating rates a number of peaks were observed consistently in different temperature intervals. TG/DTG is used to identify the detected phases and the corresponding mass loss. In the dehydration kinetic study of the different origin class-G cement samples, three different methods (Arrhenius, Kissinger, and Augis & Bennett) is used to determine the dehydration kinetic parameters of the cement samples and the results are discussed. 相似文献
20.
Daqing Wang Baoxue Zhou Yuanjang Jia Feng Shi Yiping Fan 《Journal of Thermal Analysis and Calorimetry》1995,45(1-2):221-226
The complex Mn(Nica)2Cl2 (Nica=nicotinamide) was prepared, and its decomposition was studied by means of TG and DSC. The IR spectra of the products
of thermal decomposition were examined at every stage. Kinetic analysis of the first stage of thermal decomposition was performed
via the TG-DTG curves, and the kinetic parameters were obtained from analysis of the TG-DTG curves with integral and differential
methods. The most probable kinetic function was suggested from a comparison of the kinetic parameters. Mathematical expressions
were derived for the kinetic compensation effect.
Zusammenfassung Der Komplex Mn(Nica)2Cl2 (Nica steht für Nikotinamid) wurde hergestellt und seine Zersetzung mittels TG und DSC untersucht. Die thermisch zersetzten Substanzen jedes Schrittes wurden mittels IR-Spektren untersucht. Anhand der TG-DTG-Kurven erstellte man eine kinetische Analyse des ersten Schrittes der thermischen Zersetzung, die kinetischen Parameter wurden aus den TG-DTG-Kurven unter Einsatz von Integrations- und Differentialmethoden ermittelt. Durch Vergleich der kinetischen Parameter wurde die wahrscheinlichste kinetische Funktion vorgeschlagen. Mathematische Ausdrücke für den kinetischen Kompensationseffekt wurden erhalten.相似文献