共查询到20条相似文献,搜索用时 31 毫秒
1.
Cheila G. Mothé Michelle G. Mothé Alan T. Riga Kenneth S. Alexander 《Journal of Thermal Analysis and Calorimetry》2011,106(3):637-642
Thermal properties of some shedded snake skins in comparison with human skins are represented by thermogravimetry (TG), derivative
thermogravimetry (DTG), and differential thermal analysis (DTA) to predict process condition as dermal pathway for administration
of drugs or it be used as model membranes for permeation studies. Thermal behavior by TG/DTG and DTA curves for four kinds
of shedded snake skins as Boelens Python (BP), Eastern Indigo Snake (EIS), Emerald Tree Boa (ETB), and Cascavel (CBR) were
similar in relation to their decomposition temperatures at 100 °C and 230–400 °C of its constituents, however, their properties
were different in the residue content (inorganic or carbonaceous substances). Similar thermal properties were also exhibited
by human skins’ samples, however, they presented different residue and constituents’ content. 相似文献
2.
Adriana Fuliaş Titus Vlase Gabriela Vlase Nicolae Doca 《Journal of Thermal Analysis and Calorimetry》2010,99(3):987-992
The thermoanalytical curves (TA), i.e. TG, DTG and DTA for pure cephalexin and its mixtures with talc, magnesium stearate,
starch and microcrystalline cellulose, respectively, were drawn up in air and nitrogen at a heating rate of 10 °C min−1. The thermal degradation was discussed on the basis of EGA data obtained for a heating rate of 20 °C min−1. Until 250 °C, the TA curves are similar for all mixtures, up this some peculiarities depending on the additive appears.
These certify that between the pure cephalosporin and the excipients do not exists any interaction until 250 °C. A kinetic
analysis was performed using the TG/DTG data in air for the first step of cephalexin decomposition at four heating rates:
5, 7, 10 and 12 °C min−1. The data processing strategy was based on a differential method (Friedman), an integral method (Flynn–Wall–Ozawa) and a
nonparametric kinetic method (NPK). This last one allowed an intrinsic separation of the temperature, respective conversion
dependence on the reaction rate and less speculative discussions on the kinetic model. All there methods had furnished very
near values of the activation energy, this being an argument for a single thermooxidative degradation at the beginning (192–200 °C). 相似文献
3.
Alexandra Ioiţescu Gabriela Vlase T. Vlase G. Ilia N. Doca 《Journal of Thermal Analysis and Calorimetry》2009,96(3):937-942
The synthesis of four types of hydroxyapatite synthesized from calcium chloride and four different organic phosphites is presented.
The method of synthesis chosen is the sol–gel route, which has a number of advantages compared to other methods, like the
intimate contact between reactants and the milder synthesis conditions. The samples were thermally treated, the TG/DTG/DTA
curves being obtained at four heating rates, namely: 7, 10, 12 and 15 °C min−1. The samples were characterized before and after the thermal treatment using FT-IR analysis. The FT-IR spectra certified
that the formed compounds represent hydroxyapatite. Based on the information from the TG curves and IR spectra interpretation,
a reaction mechanism was proposed. 相似文献
4.
P. J. Sánchez-Soto A. Ruiz-Conde R. Bono M. Raigón E. Garzón 《Journal of Thermal Analysis and Calorimetry》2007,90(1):133-141
The thermal evolution of a slate rock sample (Berja, Almería, Spain) has been studied. The phase minerals identified in this
sample were mica (illite), chlorite (clinochlore) and quartz as major components, with minor microcline, iron oxide and a
mixed-layer or interstratified phase (montmorillonite-chlorite). This slate is highly silico-aluminous (48.33 mass% silica,
22.04 mass% alumina), and ca. 20 mass% of other elements, mainly Fe2O3 (8.35 mass%), alkaline-earths and alkaline oxides.
Two main endothermic DTA effects, centered at 640 and 730°C, were observed. The more important contribution of total mass
loss (7.15 mass%) was found between 500–900°C, with two DTG peaks detected at 630 and 725°C. All these effects were associated
to the dehydroxylation of structural OH groups of 2:1 layered silicates mixed in the slate. The dehydroxylation of the layered
silicates evidenced by dilatometry, produced a rapid increase of expansion between 600–800°C. The thermal evolution of the
slate upper 800°C indicated the first sintering effects associated to shrinkage, which is also favoured by its low particle
size (average 23 μm) and the presence of a liquid or vitreous phase as increasing the heating temperature. The application
of thermal diffractometry to the slate sample allowed to study the formation of dehydroxylated crystalline phases from the
layered silicates after heating. At 1000°C, β-quartz, dehydroxylated illite, iron oxide, relicts of microcline and the vitreous
phase were present in the sample. All these results are interesting to know the thermal behaviour of a complex mineral mixture
as identified in the slate. 相似文献
5.
Paula Santos Nunes Marília Santos Bezerra L. P. Costa Juliana Cordeiro Cardoso R. L. C. AlbuquerqueJr. M. O. Rodrigues Gabriela Borin Barin Francilene Amaral da Silva A. A. S. Araújo 《Journal of Thermal Analysis and Calorimetry》2010,99(3):1011-1014
The purpose of this study was to evaluate the physical–chemical properties of collagen (CL) and usnic acid/collagen-based
(UAC) films, using differential thermal analysis (DTA), thermogravimetry (TG/DTG), infrared spectroscopy (FTIR), and scanning
electron microscopy (SEM). Both films were prepared by casting process using polyethylene glycol 1500 (PEG 1500) as plasticizer.
In the spectrum of UAC, similar bands of the usnic acid are observed, indicating that the polymerization (film formation)
did not affect the stability of the drug. Distinctly, DTA curve of UAC did not show an endothermic peak at 201 °C, indicative
that the drug was incorporated into the polymeric system. These results were corroborated by the scanning electron microscopy
(SEM). The TG/DTG curves of UAC presented a different thermal decomposition profile compared to the individual compounds and
CL. These findings suggest the occurrence of molecular dispersion or solubilization of the drug in the collagen film. 相似文献
6.
R. M. Queiroz Luiza H. O. Pires Ruth C. P. de Souza J. R. Zamian A. G. de Souza G. N. da Rocha Filho C. E. F. da Costa 《Journal of Thermal Analysis and Calorimetry》2009,97(1):163-166
Hydrotalcite was synthesised by co-precipitation method, calcined and characterized by XRD, BET, IR and TG/DTA/DTG analyses
and tested as solid base catalyst in the transesterification of soybean oil with methanol, achieving a methyl ester content
of 99.5%. The thermal decomposition of hydrotalcite calcined occurred in four mass loss steps at 28, 105, 203 and 400 °C.
The hydrotalcite was recovered and through a simple evaluation by TG/DTA/DTG techniques it was found that at 500 °C is the
temperature, where the organic matter should be eliminated from the catalyst. This study shows the importance of thermal analysis
in the evaluation of the recovery temperature of hydrotalcite. 相似文献
7.
Hélio Salvio Neto Jivaldo do Rosário Matos 《Journal of Thermal Analysis and Calorimetry》2011,103(1):393-399
In this work, TG/DTG and DSC techniques were used to the determination of thermal behavior of prednicarbate alone and associated
with glyceryl stearate excipient (1:1 physical mixture). TG/DTG curves obtained for the binary mixture showed a reduction
of approximately 37 °C to the thermal stability of drug (
T\textdm/\textdt = 0 \textDTG\textMax T_{{{\text{d}}m/{\text{d}}t = 0\,{\text{DTG}}}}^{\text{Max}} ). The disappearance of stretching band at 1280 cm−1 (νas C–O, carbonate group) and the presence of streching band with less intensity at 1750 cm−1 (νs C–O, ester group) in IR spectrum obtained to the binary mixture submitted at 220 °C, when compared with IR spectrum of drug
submitted to the same temperature, confirmed the chemical interaction between these substances due to heating. Kinetics parameters
of decomposition reaction of prednicarbate were obtained using isothermal (Arrhenius equation) and non-isothermal (Ozawa)
methods. The reduction of approximately 45% of activation energy value (E
a) to the first step of thermal decomposition reaction of drug in the 1:1 (mass/mass) physical mixture was observed by both
kinetics methods. 相似文献
8.
Corina Duda-Seiman T. Vlase Gabriela Vlase Rodica Cinca Mariana Anghel N. Doca 《Journal of Thermal Analysis and Calorimetry》2011,105(3):851-858
Verapamil is a phenyl-alchil-amine type pharmaceutical largely used as a specific calcium antagonist. Knowledge of drug-excipient
compatibility represents an important phase in development of different dosage forms. Hyphenated techniques are versatile
for obtaining such necessary information’s. The TG/DTG/DTA curves were obtained in air at different heating rates and in nitrogen.
The IR spectra of pure compound and its char at 400 °C (by U-ATR technique) and the IR identification of Evolved Gasses allowed
some discussions on the thermally induced events. In the solid dosage forms verapamil was mixed with talc, magnesium stearate,
starch, and cellulose, and the corresponding thermoanalytical curves were compared with that one of pure I. No physical or
chemical interactions were observed till 250 °C. A kinetic analysis was performed for TG step of verapamil between 250 and
350 °C. The data at four heating rates (7, 10, 12, 15 °C min−1) were processed on a strategy using at last three different kinetic methods. For these, the NPK method seems to be less speculative,
allowing an objective determination of the kinetic parameters. 相似文献
9.
M. R. Sovizi 《Journal of Thermal Analysis and Calorimetry》2010,102(1):285-289
Data on the thermal stability of drugs was required to obtain information for handling, storage, shelf life and usage. In
this study, the thermal stability of two nonsteroidal anti-inflammatory drugs (NSAIDs) was determined by differential scanning
calorimetry (DSC) and simultaneous thermogravimetery/differential thermal analysis (TG/DTA) techniques. The results of TG
analysis revealed that the main thermal degradation for the naproxen and celecoxib occurs in the temperature ranges of 196–300
and 245–359 °C, respectively. The TG/DTA analysis of compounds indicates that naproxen melts (at about 158.1 °C) before it
decomposes. However, the thermal decomposition of the celecoxib started about 185 °C after its melting. The influence of the
heating rate (5, 10, 15, and 20 °C min−1) on the DSC behavior of the both 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 various methods, the following order for the thermal stability was noticed: naproxen
> celecoxib. Finally, the values of ΔS
#, ΔH
#, and ΔG
# of their decomposition reaction were calculated. 相似文献
10.
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
11.
M. Kuliffayová L’. Krajči I. Janotka V. Šmatko 《Journal of Thermal Analysis and Calorimetry》2012,108(2):425-432
The kaolin sand containing 36 wt% of kaolinite was thermally transformed at 650 °C/L h to the burnt kaolin sand (BKS) with
relevant content of metakaolinite. Thermal behaviour of composites with substitution of Portland cement (PC) by the BKS containing
0, 5, 10 and 15 wt% of metakaolinite and water-to-solid ratio of 0.5 kept for 90 days in 20 ± 1 °C water was studied by thermal
analysis. TG/DTA/DTG studies concerned calciumsilicate hydrate and calciumaluminate hydrate formation, portlandite dehydroxylation
and calcite decarbonation. The influence of curing time and metakaolinite content were estimated. The reduction in portlandite
content was observed in PC–BKS composites opposite to that found in the reference PC system. Compressive strength uptakes
were observed in PC–BKS composites relative to that of reference PC system. BKS is characterized as effective pozzolanic material
giving cement composites of high performance. The above findings were confirmed by X-ray diffraction analysis (XRD) and scanning
electron microscopy (SEM) results. 相似文献
12.
K. E. Ozbas 《Journal of Thermal Analysis and Calorimetry》2008,93(2):641-649
In this study, the relationship between particle size and pyrolysis characteristics of Elbistan lignite was examined by using
the thermogravimetric (TG/DTG) and differential thermal analysis (DTA) techniques. Lignite samples were separated into different
size fractions. Experiments were conducted at non-isothermal conditions with a heating rate of 10°C min−1 under nitrogen atmosphere up to 900°C. Pyrolysis regions, maximum pyrolysis rates and characteristic peak temperatures were
determined from TG/DTG curves. Thermogravimetric data were analyzed by a reaction rate model assuming first-order kinetics.
Apparent activation energy (E) and Arrhenius constant (A
r) of pyrolysis reaction of each particle size fraction were evaluated by applying Arrhenius kinetic model. The apparent activation
energies in the essential pyrolysis region were calculated as 27.36 and 28.81 kJ mol−1 for the largest (−2360+2000 μm) and finest (−38 μm) particle sizes, respectively. 相似文献
13.
The Pb(IO3)2 crystals have been grown in sodium meta silicate gel using the single diffusion method at room temperature. The grown crystals
were characterized by thermo analytical techniques (TG, DTA, and DTG), X-ray powder diffraction (XRD), and FTIR spectroscopy.
The crystal system is confirmed to be orthorhombic having lattice parameters a = 6.09 Å, b = 16.68 Å, and c = 5.58 Å by powder
X-ray diffraction analysis. FTIR study reveals that lead iodate crystal is anhydrous. TG, DTA, and DTG analysis shows a remarkable
thermal stability. 相似文献
14.
Piotr Szynkaruk Marek Wesolowski Malgorzata Samson-Rosa 《Journal of Thermal Analysis and Calorimetry》2010,102(2):505-512
Thermal decomposition of magnesium salts of organic acids used in medicine (Mg acetate, Mg valproate, Mg lactate, Mg citrate,
Mg hydrogen aspartate, Zn hydrogen aspartate) was analyzed by thermoanalytical, calorimetrical, and computational methods.
Thermoanalytical studies were performed with aid of a derivatograph. 50-, 100-, and 200-mg samples were heated in a static
air atmosphere at a heating rate of 3, 5, 10, and 15 °C min−1 up to the final temperature of 700–900 °C. By differential thermal analysis (DTA), thermogravimetry (TG), and derivative
thermogravimetry (DTG) methods, it has been established that thermal decomposition of the salts under study occurs via two
stages. The first stage (dehydratation) was distinctly marked on the thermoanalytical curves. Calorimetrical studies were
carried out by using of a heat-flux Mettler Toledo differential scanning calorimetry (DSC) system. Ten milligram samples of
compounds under study were heated in the temperature range from 20 to 400 °C at a heating rate of 10 and 20 °C min−1 under an air stream. The studies showed that the values of transitions heats and enthalpies of dehydration for investigated
salts varied with the increasing of heating rate. For chemometric evaluation of thermoanalytical results, the principal component
analysis (PCA) was applied. This method revealed that points on PC1 versus PC2 diagrams corresponding to the compounds of
similar chemical constitution are localized in the similar ranges of the first two PC’s values. This proves that thermal decomposition
reflects similarity in the structure of magnesium salts of organic acids. 相似文献
15.
F. Sahnoune N. Saheb B. Khamel Z. Takkouk 《Journal of Thermal Analysis and Calorimetry》2012,107(3):1067-1072
Thermal analysis techniques remain important tools amongst the large variety of methods used for analysis of the dehydroxylation
of kaolinite. In the present study, the kinetics of dehydroxylation of Algerian kaolinite, wet ball milled for 5 h followed
by attrition milling for 1 h, was investigated using differential thermal analysis (DTA) and thermogravimetry (TG). Experiments
were carried out between room temperature and 1350 °C at heating rates of 5, 10 and 20 °C min−1. The temperature of dehydroxylation was found to be around 509 °C. The activation energy and frequency parameter evaluated
through isothermal DTA treatment were 174.69 kJ mol−1 and 2.68 × 109 s−1, respectively. The activation energies evaluated through non-isothermal DTA and TG treatments were 177.32 and 177.75 kJ mol−1, respectively. Growth morphology parameters n and m were found to be almost equal to 1.5. 相似文献
16.
Mothé Filho H. F. Gonçalves M. L. A. Mothé C. G. 《Journal of Thermal Analysis and Calorimetry》2002,67(2):381-389
Thermal degradation of granite and marble industry reject (GMIR), a red clay (RC)and their composites were studied by non-isothermal
thermogravimetry (TG/DTG) in nitrogen atmosphere, differential thermal analysis (DTA) and derivative thermogravimetry(DTG)
in air atmosphere. Measurements were made in the temperature range of 25–1000,25–1200 and 25–1400°C. The kinetic parameters
were determined by Flynn–Wall and Kissinger's methods. The results indicate the absent dominance of one mechanism of reaction,
and the composites show smaller values of kinetic parameters than GMIR or RC.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
17.
The thermal decompositions of dehydrated or anhydrous bivalent transition metal (Mn, Fe, Co, Ni, Cu, Zn, Cd) and alkali rare
metal (Mg, Ca, Sr, Ba) methanesulfonates were studied by TG/DTG, IR and XRD techniques in dynamic Air at 250–850 °C. The initial
decomposition temperatures were calculated from TG curves for each compound, which show the onsets of mass loss of methanesulfonates
were above 400 °C. For transition metal methanesulfonates, the pyrolysis products at 850 °C were metal oxides. For alkali
rare metal methanesulfonates, the pyrolysis products at 850 °C of Sr and Ba methanesulfonates were sulphates, while those
of Mg and Ca methanesulfonate were mixtures of sulphate and oxide. 相似文献
18.
Ratiram Gomaji Chaudhary Harjeet D. Juneja Mangesh Pandharinath Gharpure 《Journal of Thermal Analysis and Calorimetry》2013,112(2):637-647
Seven novel divalent transitional metal chelate polymers compounds (commonly known as chelate compounds or metal coordination complexes or polymer complexes) have been characterized by thermogravimetry (TG), differential thermal gravimetry (DTG) and differential thermal analysis (DTA) methods. Thermal decomposition behaviour of Mn(II), Co(II), Ni(II), Cu(II), Zn(II), Cd(II) and Hg(II) polymers with terphthaoyl-bis(p-methoxyphenylcarbamide) has been investigated by thermogravimetric analysis (TGA) at heating rate 10 °C min?1 under nitrogen atmosphere. TG/DTA of chelate compounds were shown to be a stable compound against thermal decomposition which was measured on the basis of final decomposing temperature, but it is observed in some curves that decomposition takes place at low temperature due to the lattice water, which is always placed at outer coordination sphere of the central metal ion. The presence of both lattice and coordinated water were noteworthy investigated in Co(II), Ni(II) and Cu(II) chelate polymer compounds, whereas lattice water found in Zn(II), Cd(II) and Hg(II). However, Mn(II) showed only coordinated water. Thermal stabilities for release of lattice water, coordinated water and organic moiety that occur in sequential decomposition of chelate compounds are explained on the basis of ionic size effect and electronegativity. The processes of thermal degradation taking place in seven chelate polymers were studied comparatively by TG/DTG/DTA curves which indicating the difference in the thermal decomposition. Coats–Redfern integral method is used to determine the kinetic parameters for the successive steps in the decomposition sequence of TG curves. Scanning electron microscope images of some chelate polymers were shown in previous publication revealed that particle sizes of chelate polymers were found to be of nanomaterial level therefore, resulting chelate compounds might be called as nanomaterial. 相似文献
19.
M. A. Zayed F. A. Nour El-Dien M. F. Hawash M. A. Fahmey 《Journal of Thermal Analysis and Calorimetry》2010,102(1):305-312
Gliclazide (GL, C15H21N3O3S) drug is used as non-insulin-dependant diabetes mellitus. The drug was investigated using thermal analysis (TA) measurements
(TG/DTG) and electron impact mass spectral (EI–MS) fragmentation at 70 eV techniques. The mass spectra of GL at different
values of ion source temperatures (400, 416, 425, and 440 K) are recorded and investigated. Semiempirical MO calculation,
using PM3 procedure, has been carried out on neutral molecule and positively charged species. These calculations included
bond length, bond order, bond strain, partial charge distribution, ionization energy, and heats of formation (ΔH
f). PM3 procedure provides a basis for fine distinction among sites of initial bond cleavage, which is crucial to the rationalization
of subsequent fragmentation of the molecule. The primary fragmentation pathway in both TA and MS (at different values of ion
source temperature) is initiated by S–N bond rupture. TA and DTG show one main weight loss at 250.38 °C and four peaks at
271.6, 360.99, 427.93 and 479.17 °C in DTA, which may be attributed to various fragments. Also, the rate constant (K′) of thermal degradation has been tested isothermally at 210 and 600 °C. The calculated rate values are 9.6 × 10−3 and 0.33 × 10−3 s−1, respectively, and discussed. In MS, the effect of ion source temperature on mass spectral fragmentation processes is discussed
on the basis of energy considerations using quasi equilibrium theory. 相似文献
20.
Co3xNi3−3x(PO4)2·8H2O (x = 1, 0.8, 0.6, 0.4, 0.2, and 0) were synthesized via simple wet chemical reaction and energy saving route method. The final decomposition products of hydrates are corresponding anhydrous tri(cobalt nickel) diphosphates. The metal and water contents of the synthesized hydrates were confirmed by AAS and TG/DTG/DTA techniques, respectively. The observed metal and water contents agree well with the formula of the title compounds. The crystal structures and lattice parameters as well as crystallite sizes of the studied compounds were determined using XRD data. The results from XRD and TG/DTG/DTA techniques confirmed that Co3xNi3−3x(PO4)2·8H2O at all ratios were the single phase. The FTIR spectra of studied compounds were recorded and assigned. The thermal behaviours of single and binary tri(cobalt nickel) diphosphate octahydrates were studied for the first time. The morphologies of the studied compounds were investigated by using the SEM technique. The micrographs of all studied compounds exhibited the thin plated morphology. The surface area and the pore size data of anhydrous forms were measured by N2 adsorption at −190 °C according to the BET method. The anhydrous forms of binary metal phosphate at x = 0.8, Co2.4Ni0.6(PO4)2, exhibits the highest surface area and expects to improve the catalytic activity. 相似文献