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1.
In this paper, the thermal behaviours of two organophosphorous compounds, N,N-dimethyl-N′,N′-diphenylphosphorodihydrazidic (NDD) and diphenyl amidophosphate (DPA), were studied by thermogravimetery (TG), differential
thermal analysis (DTA) and differential scanning calorimetery (DSC) techniques under non-isothermal conditions. The results
showed that NDD melts about 185 °C before it decomposes. NDD decomposition occurs in two continuous steps, in the 190–410 °C
temperature range. First thermal degradation stage for NDD results a broad exothermic peak in the DTA curve that is continued
with a small exothermic peak at the end of decomposition process. On the other hand, applying TG-DTA techniques indicates
that DPA melts about 150 °C before it decomposes. This compound decomposes in the temperature range of 230 to 330 °C in two
steps. These steps are endothermic and exothermic, respectively. Activation energy and pre-exponential factor for the first
step of decomposition of each compound were found by means of Kissinger method and were verified by Ozawa–Flynn–Wall method.
Activation energy obtained by Kissinger method for the first stage of NDD and DPA decompositions are 138 and 170 KJ mol−1, respectively. Finally, the thermodynamic parameters (ΔG
#, ΔH
# and ΔS
#) for first step decomposition of investigated organophosphorous were determined. 相似文献
2.
Simultaneous
thermogravimetry (TG) and differential thermal analysis (DTA) techniques were
used for the characterization the thermal degradation of loratadine, ethyl-4-(8-chloro-5,6-dihydro-11H-benzo[5,6]cyclohepta[1,2-b]pyridin-11-ylidine)-1-piperidinecarboxylate.
TG analysis revealed that the thermal decomposition occurs in one step in
the 200–400°C range in nitrogen atmosphere. DTA and DSC curves showed
that loratadine melts before the decomposition and the decomposition products
are volatile in nitrogen. In air the decomposition follows very similar profile
up to 300°C, but two exothermic events are observed in the 170–680°C
temperature range.
Flynn–Wall–Ozawa method was used
for the solid-state kinetic analysis of loratadine thermal decomposition.
The calculated activation energy (E
a)
was 91±1 kJ mol–1 for α between
0.02 and 0.2, where the mass loss is mainly due to the decomposition than
to the evaporation of the decomposition products. 相似文献
3.
Budrugeac P. Trandafir Viorica Albu Madalina Georgiana 《Journal of Thermal Analysis and Calorimetry》2003,72(2):581-585
The methods of the thermal analysis (TG, DTG and DTA) were used in order to investigate the effect of the hydration degree
on the thermal behaviour of some collageneous matrices. It was pointed out that the degradation of hydrated collagen in the
temperature range 20-400°C occurs through two successive processes accompanied by mass losses. The first process, consisting
in the collagen dehydration, is endothermic and takes place in the temperature range ≈25 - ≈125°C. The second process is exothermic
and consists in the decomposition and/or thermo-oxidation of dry collagen. The thermal parameters of both processes depend
on the hydration degree of collagen. The observed dependencies show that the hydrothermal and thermo-oxidative stability of
collagen are strongly correlated with its water content.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
4.
It is shown that the use of differential thermal analysis (DTA) to follow the pyrolysis of cellulose in air products two and sometimes three exothermic peaks. The first peak is associated with the combustion of volatile material, released in the degradation process, the second is caused by the glowing combustion of the carbonaceous residue, and the final exotherm is probably due to the combustion of product gases.The thermogravimetric analysis (TG) data in air show a preliminary loss of water followed by a mass loss of about 85% due to the production of the combustible volatiles. This second step appears identical to the degradation process in nitrogen, but in air the degradation products ignite to produce the first exothermic peak on the DTA. The glowing combustion DTA peak is associated with a further mass loss of about 15% on the TG plot. The use of a thermomechanical analyser shows that a small shrinkage of 3% occurs between 45 and 110°C, with the major collapse taking place between 300 and 370°C. There is, however, an expansion of 10% between 370 and 405°C, believed to be due to a crosslinking reaction. 相似文献
5.
Mohammad Reza Sovizi Seyed Ghorban Hosseini 《Journal of Thermal Analysis and Calorimetry》2013,111(3):2143-2148
Understanding the response of drugs and their formulations to thermal stresses is an integral part of the development of stable medicinal products. In the present study, the thermal degradation of two drug samples (cetirizine and simvastatin) was determined by differential scanning calorimetery (DSC) and simultaneous thermogravimetery/differential thermal analysis (TG/DTA) techniques. The results of TG analysis revealed that the main thermal degradation for the cetirizine occurs during two temperature ranges of 165–227 and 247–402 °C. The TG/DTA analysis of simvastatin indicates that this drug melts (at about 143 °C) before it decomposes. The main thermal degradation for the simvastatin occurs during two endothermic behaviors in the temperature ranges of 238–308 and 308–414 °C. The influence of the heating rate (5, 10, 15, and 20 °C min?1) on the DSC behavior of both the drug samples was verified. The results showed that as the heating rate was increased, decomposition temperatures of the compounds were increased. Also, the kinetic parameters such as activation energy and frequency factor for the compounds were obtained from the DSC data by non-isothermal methods proposed by ASTM E696 and Ozawa. Based on the values of activation energy obtained by ASTM E696 method, the values of activation energy for cetirizine and simvastatin were 120.8 and 170.9 kJ mol?1, respectively. Finally, the values of ΔS #, ΔH #, and ΔG # of their decomposition reaction were calculated. 相似文献
6.
Zou Hantao Yi Changhai Wang Luoxin Liu Hongtao Xu Weilin 《Journal of Thermal Analysis and Calorimetry》2009,97(3):929-935
Thermogravimetric (TG), differential thermal analysis (DTA) and thermal degradation kinetics, FTIR and X-ray diffraction (XRD)
analysis of synthesized glycine–montmorillonite (Gly–MMT) and montmorillonite bound dipeptide (Gly–Gly–MMT) along with pure
Na–MMT samples have been performed. TG analysis at the temperature range 25–250 °C showed a mass loss for pure Na–MMT, Gly–MMT
and Gly–Gly–MMT of about 8.0%, 4.0% and 2.0%, respectively. DTA curves show the endothermic reaction at 136, 211 and 678 °C
in pure Na–MMT whereas Gly–MMT shows the exothermic reaction at 322 and 404 °C and that of Gly–Gly–MMT at 371 °C. The activation
energies of the first order thermal degradation reaction were found to be 1.64 and 9.78 kJ mol−1 for Gly–MMT and Gly–Gly–MMT, respectively. FTIR analyses indicate that the intercalated compounds decomposed at the temperature
more than 250 °C in Gly–MMT and at 250 °C in Gly–Gly–MMT. 相似文献
7.
G. Madhurambal M. Mariappan S. Hariharan P. Ramasamy S. C. Mojumdar 《Journal of Thermal Analysis and Calorimetry》2013,112(2):1031-1037
Mixed crystals of various proportions of zinc magnesium ammonium sulfate were grown by slow evaporation of aqueous solution at room temperature. The bright and transparent crystals obtained were characterized through thermal (TG–DTA) and FTIR spectral analyses. A fitting decomposition pattern for the compound was formulated on the TG curve which shows two stage mass losses between 133 and 478.75 °C. DTA curve shows exothermic peaks in this temperature range supporting the formulated decomposition pattern. The FTIR spectra show the vibration frequencies due to the formation of zinc magnesium ammonium sulfate mixed crystals. Detailed structural analysis of the compound is under progress. 相似文献
8.
G. Madhurambal M. Mariappan S. Hariharan P. Ramasamy S. C. Mojumdar 《Journal of Thermal Analysis and Calorimetry》2013,112(2):1127-1132
Mixed crystals of 0.1 and 0.25 zinc magnesium ammonium sulphate were grown by slow evaporation of aqueous solution at room temperature. The bright and transparent crystals obtained were characterized by thermal (TG–DTA), FTIR and XRD analyses. A fitting decomposition pattern for the compound was formulated on the TG curve which shows two stage mass losses between 133 and 478.75 °C. In this temperature range, DTA curve shows exothermic peaks supporting the formulated decomposition pattern. The FTIR spectra show the vibration frequencies due to the formation of zinc magnesium ammonium sulphate mixed crystals. Detailed structural analysis of the compound is under progress. 相似文献
9.
Fang-Mo Chang Chen-Chia Huang Shin-Ming Shen Sun-I Chen 《Journal of Thermal Analysis and Calorimetry》1995,44(2):405-417
The effects of various burning rate catalysts on thermal decomposition of cured glycidyl azide polymer (GAP)-ammonium perchlorate (AP) propellants have been studied by means of thermal analysis and a modified vacuum stability test (MVST). Four types of iron-containing catalysts examined in this paper are catocene, ferrocenecarboxaldehyde (FCA), ferrocene, and ferric oxide. Results of differential thermal analysis (DTA) and thermogravimetric analysis (TG) revealed that the catalysts play an important role in the decomposition of both AP and GAP. The peak decomposition temperature (T m) of DTA curves and onset decomposition temperature (T o) of TG patterns considerably shifted to a lower temperature as the concentration of catalysts increased in the propellants. The endothermic temperature of AP, however, is unaffected by the presence of burning rate catalysts in all cases. The activation energy of decomposition of the propellants in range of 80 to 120°C is determined, based on the MVST results. 相似文献
10.
This work focuses on the thermal and mineralogical transformations of
red wall tile pastes. The pastes contain different amounts of calcareous and
are prepared with Brazilian raw materials. Thermal transformations are evaluated
by TG, DTG and DTA, dilatometric analysis, and X-ray diffraction. Four endothermic
transformations were identified and interpreted as the release of physically
adsorbed water, dehydration of hydroxides, dehydroxylation of kaolinite, and
decomposition of carbonate. An exothermic transformation within the 925–950°C
range is associated to crystallization of new phases such as calcium aluminosilicates
and mullite. TG measurements indicate that the total mass loss of the pastes
is dependent on the amount of calcareous addition. Dilatometric analysis indicates
the onset of sintering at around 900°C, leading to shrinkage of the pellets.
The thermal analysis results agree well with the X-ray diffraction. 相似文献
11.
The TG and DTA of a new series of Mn(II) and Cu(II) complexes with a number of newly prepared bisazo-dianil ligands were studied
in the temperature range (20-700°C). The TG and DTG curves display to main steps, the first one within the temperature range
(25-330°C) correspond to the elimination of water or and ethanol from the complexes. The second step within the range (350-625°C)
is due to the decomposition of the complexes yielding the metal oxides as the final product. The rate constants of the dehydration
and decomposition reactions were determined, from which some kinetic parameters were evaluated. The DTA curves show that the
dehydration of the metal complexes is an endothermic reaction. In all cases the anhydrous metal complexes undergo exothermic
decomposition reactions to give the metal oxide. The thermodynamic parameters (ΔE, ΔH, ΔS, ΔG) for the occurring processes
are calculated. The electrical conductivities of the solid complexes were measured and the activation energy of the complex
and its free ligand are also calculated.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
12.
G. Madhurambal M. Mariappan S. C. Mojumdar 《Journal of Thermal Analysis and Calorimetry》2010,100(3):853-856
A mixed crystal of urea–thiourea was grown by slow evaporation of aqueous solution at room temperature. The bright and transparent crystals obtained were characterized by thermogravimetric–differential thermal analysis (TG–DTA), UV and FTIR spectroscopic analyses. A fitting decomposition pattern for the title compound was formulated on the TG curve which shows a two stage weight loss between 200 and 750 °C. In this temperature range DTA curve shows exothermic peaks supporting the formulated decomposition pattern. The UV and FTIR spectra show the characteristic absorption, vibration frequencies due to urea–thiourea mixed crystals. Detailed structural analysis of the compound is under progress. 相似文献
13.
A. M. Abdel-Rehim 《Journal of Thermal Analysis and Calorimetry》2001,64(3):1283-1296
Scheelite (calcium tungstate)is the product of one of the processing methods of wolframite by its roasting with calcium oxide
or limestone or its fusion with calcium chloride, followed by acid processing of calcium tungstate with the formation of tungstic
acid. Scheelite occurs in contact metamorphic deposits, hydrothermal veins and pegmatites.
The present work illustrates a thermal analysis study of synthesis of scheelite by sintering of wolframite with calcite and
sintering of tungsten oxide with calcite or calcium oxide using a derivatograph. The reaction products were identified microscopically
and by using a Siemens Crystalloflex diffractometer.
The DTA curve of sintering of wolframite with calcite shows the beginning of the reaction at 560°C with the formation of scheelite.
The intensive formation of scheelite is represented by the medium and wide endothermic peak at 740°C. This is followed directly
by a large and sharp endothermic peak at 860°C, representing the dissociation of unreacted calcite.
The DTA curve of tungsten trioxide shows three thermal effects. The sharp exothermic peak at 320°C represents the oxidation
of tungsten oxide content of lower valency. The endothermic peaks at 750 and 1090°C are related to polymorphic changes of
tungsten trioxide. The beginning of its sublimation is observed at temperature higher than 800°C.
The DTA curves of sintering of tungsten trioxide with calcite or calcium oxide indicate that the intensive formation of scheelite
takes place by endothermic reactions at 660 and 545°C respectively. The medium and small endothermic peaks at 520 and 730°Con
the DTA curve of tungsten trioxide with calcium oxide represent the dehydration of calcium oxide and the loss of carbon dioxide
due to some carbonatization of calcium oxide with carbon dioxide from air, respectively.
The produced scheelite is colorless in thin sections, has distinct cleavage (101), crystallizes in the tetragonal system in
the form of tabular crystals and is optically positive.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
14.
This study focuses on the thermal and mineralogical transformations of clay ceramic pastes. The pastes contain different amounts of sugarcane bagasse ash waste. Thermal and mineralogical changes occurring during firing were characterized by differential thermal analysis, thermogravimetry analysis (TG), X-ray diffraction (XRD), and scanning electron microscopy. On heating three endothermic events within the 73.5–75.7, 276.9–283.5, and 567.1–573.5 °C temperature ranges were identified. The endothermic valleys could be mainly interpreted as the release of physically adsorbed water, dehydration of hydroxides, and dehydroxylation of kaolinite, respectively. Two exothermic events within the 618.9–690.1 and 948 °C temperature ranges were identified. The exothermic peaks are associated with the decomposition of organic compounds and crystallization of mullite from metakaolinite, respectively. TG results indicate that the clay ceramic pastes had a total mass loss in the 13.1–13.6 % range, and are dependent on the sugarcane bagasse ash waste amount added. It was found that the replacement of natural clay with sugarcane bagasse ash waste, in the range up to 20 wt%, influenced the thermal behavior and technological properties of the clay ceramic pastes. In addition, the thermal analysis results agree well with the XRD. 相似文献
15.
Differential thermal analysis (DTA) of low-rank coals of high lignite to subbituminous rank from coal mines of Pakistan is
reported. The studies carried out in dynamic oxygen atmosphere indicate that the exothermic reactions occur between 300 and
650°C and that the samples undergo stepwise oxidation of the organic matter rather than a continuous process as indicated
by the pattern of shoulders from 250 to 350°C accompanying the main peak around 450°C. The effect of heating rate, particle
size and volatile content was also studied in relation to oxidation. The results show that the increase in heating rate from
10 to 80 deg min−1 results in a marked shift in all the events in the DTA curve towards higher temperatures. As for the effect of particle size,
the DTA records of 100–75, 150–100, 250–150 μm and greater than 250 μm fractions show that the magnitude and position of shoulder
peaks are more sensitive to changes in particle sizes compared to the main peak. The curves recorded to study the effect of
changing volatile content of samples between 30–40% indicate a complex pattern of shoulders accompanying the main peak. In
general, the number of shoulder peaks increases with increasing volatile content of samples but their positions do not follow
any trend. The DTA curves recorded in nitrogen contain ill-de-fined oxothermic effects over the 300–750°C temperature range.
These curves consist of an endothermic peak around 150°C, two exothermic shoulders in the temperature region 300–400°C and
a large broad exothermic whip between 500 and 700°C. The heating rates have similar effects as in oxygen while the particle
size do not influence the results.
It has been concluded that the organic matter in the coals studied here is extremely heterogeneous with different burning
characteristics; as a result it is very difficult to quantify energy changes associated with poorly resolved exothermic events
along the DTA curve. The effects also dominate in N2 atmosphere thus making identification of mineral matter difficult. The overall pattern of DTA events in oxygen can be correlated
with the heating rate, particle size and volatile content of samples. 相似文献
16.
Marta Worzakowska 《Journal of Thermal Analysis and Calorimetry》2008,93(3):799-803
The preliminary studies of the thermal behaviour of polyester obtained in polycondensation process of cyclohex-4-ene-1,2-dicarboxylic
anhydride and ethylene glycol and its new epoxidized form have been performed. The thermal characterization of initial polyester
and its completely oxidized form was done by using differential scanning calorimetry (DSC) and thermogravimetric analysis
(TG). The non-isothermal DSC was applied to determine the influence of time and the temperature on the chemical modification
of initial polyester using 38-40% solution of peracetic acid. On the basis of DSC profiles it has been found that the endothermic
transition, due to the degradation process of initial polyester was characteristic feature under controlled heating program.
The two characteristic transitions for the new epoxidized polyester, the exothermic peak corresponded to the thermal crosslinking
of epoxidized polyester (322.8–336.4°C) and the endothermic decomposition peak of the cured material (363.8–388.9°C) were
observed. The peak maximum temperatures (Tmax) and the heat of cross-linking reaction (ΔHc) for epoxypolyester prepared at 20–60°C under 1–4 h were evaluated. The Tmax1 were almost independent from epoxidation conditions,
while, the values of ΔHc were dependent from conditions of synthesis. The ΔHc values of this process decreased when time of oxidation increased. The highest values of ΔHc at 40°C were obtained. Additionally, TG experiments confirmed two separated degradation steps of the new epoxidized polyester
indicating the ester (370–380°C) and ether (450–460°C) bond breakdown. 相似文献
17.
Qiang Xu Cong Jin Greg Griffin Yong Jiang 《Journal of Thermal Analysis and Calorimetry》2014,115(2):1651-1660
Microscale thermal analysis, bench scale cone calorimetric and real scale burning tests were conducted to evaluated fire safety performance of expanded polystyrene (EPS) foam. Simultaneous thermal analysis was used to study the thermal degradation of the foam in nitrogen, air, and oxygen environments at four heating rates. An endothermic effect is observed only in nitrogen environment, while two exothermic effects are observed in oxygen and air environments. In the nitrogen environment, the onset temperature of the endothermic effect and the endothermic peak temperature are much higher than that of the exothermic processes observed in air and oxygen environments. The Flynn–Wall–Ozawa method is utilized to analyze the degradation kinetics of the non-isothermal thermogravimetry. The activation energies calculated for an air environment, in a conversion range α = 20–70 %, are lower than those for an oxygen environment. The temperature range for this conversion range is 275–371 °C. The enthalpies of the first exothermic effect exceed that of the oxygen environment by 10–45 %. Bench scale cone calorimetric tests were carried out at incident heat flux of 25, 35, and 50 kW m?2 with two sets of cone equipment. Heat release rate, ignition time, effective heat of combustion, and critical heat flux required for ignition is obtained. In real scale burning tests, the EPS boards were ignited in sandwich structures. Fire spread speeds were derived from temperature measurement inside sandwich structure. 相似文献
18.
F. Chong Tho L. Natova D. Ruschev 《Journal of Thermal Analysis and Calorimetry》1991,37(11-12):2723-2727
Eugenol and isoeugenol were investigated by means of thermal analysis. It was observed that eugenol and isoeugenol have one characteristic endothermic effect at 260° and 290°C, respectively, and two exothermic effects in the temperature intervals 270°–590°C. The DTA curves of the benzoyl esters of eugenol and isoeugenol begin with endothermic effects at 70° and 95°C, respectively, which coincide with the melting points of these compounds. 相似文献
19.
G. Madhurambal M. Mariappan B. Ravindran S. C. Mojumdar 《Journal of Thermal Analysis and Calorimetry》2011,104(3):885-891
Mixed crystals of various proportions of urea thiourea were grown by slow evaporation of aqueous solution at room temperature.
The bright and transparent crystals obtained were characterized using thermogravimetry–differential thermal analysis (TG–DTA)
and FTIR spectroscopic analyses. A fitting decomposition pattern for the title compound was formulated on the TG curve which
shows a two-stage mass loss between 175 and 750 °C. In this temperature range, DTA curves show exothermic peaks supporting
the formulated decomposition pattern. The FTIR spectra show the characteristic absorption, vibration frequencies due to urea
thiourea. Detailed structural analysis of the compound is under progress. 相似文献
20.
By thermoanalytical methods TG, DTG, DTA there have been investigated the processes occurring during the formation of ceramic
materials on the basis of Al2O3, ZrO2, Si3N4, SiC,and inorganic binder. IR spectroscopy has been an additional research method. It's been determined that with the use
of H3PO4 as the binder for ceramic materials, the mechanisms of thermal decomposition are connected with the following processes:
1. removal of weakly tied and crystallized water in the temperature range of120–230°C, the removal being characterized by
the endothermic effect, 2. interaction of the initial powder components of the ceramic materials with orthophosphoric acid
conditioned by a strong exothermic effect on the DTA curve in the range of 230–530°C, 3. overlapping of endo- and exo-effects,
testifying to a complex mechanism of thermal transformations, 4.oxidizing of the non-reacted silicon at the temperature of
720(760)°C, an increase of mass is observed on the TG curve as a result of the formation of SiO2 – crystoballite.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献