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1.
Nilgün Yener Müşerref Önal Gökçe Üstünışık Y. Sarıkaya 《Journal of Thermal Analysis and Calorimetry》2007,88(3):813-817
An industrial raw material taken from Beypazarı (Ankara, Turkey) region was heated at different temperatures in the 100–1100°C
interval for 2 h. The volumetric percentage of particles having diameter below 2 μm in an aqueous suspension of the material
held 24 h were determined as 85% by the particle size distribution analysis. The mineralogical composition of the material
was obtained as mass% of 81% sepiolite, 15% dolomite, and 4% interparticle water by using the X-ray diffraction (XRD) and
thermal analysis (TG, DTA) data. The temperature ranges were determined for the dehydrations of the interparticle water and
the zeolitic water as 25–340°C, for the dehydration of the bound water as 340–580°C, and for the dehydroxylation of the hydroxyls
as 800–833°C in the sepiolite. The zig-zag changes in the specific surface area (S/m2 g−1) and specific micro-and mesopore volume (V/cm3 g−1) with the temperature increases were discussed according to the dehydrations and dehydroxylation of the sepiolite. 相似文献
2.
Poly(dimethylsiloxane) (PDMS) composites were prepared by simple blending process using palygorskite (PG) or modified palygorskite (MP). This study has been designed to determine the influences of PG or MP on the thermal stability and the mechanical properties of PDMS composites. The thermal stability of PG and MP were also studied by thermogravimetric analysis (TGA). The results showed that MP had the similar thermal stability to PG, and PG or MP not only increased the thermal stability but also improved the mechanical properties of PDMS composites. Meanwhile, compared with PG/PDMS composites, MP/PDMS composites had better thermal stability and mechanical properties owing to the better dispersion of MP into the matrix, the stronger chemical interfacial interaction between MP and the matrix. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
3.
N. Lahav D. Ovadyahu A. Gutkin E. Mastov T. Menjeritzki A. Adin L. Rubinstein D. Tropp S. Yariv 《Journal of Thermal Analysis and Calorimetry》1994,42(1):67-84
A device was constructed in which a clay suspension is hermetically heated at 220°C for a few minutes. This thermal treatment
is accompanied by a pressure increase in the cell. Once the valve is opened, there is a fast release of the pressure inside
the cell and a sudden evolution of the interparticle water. This shock leads to a quasi explosion of the clay particle. This
technique was named thermal vapour pressure shock explosion (TSE). The effect of TSE treatment on the properties of palygorskite
suspensions was investigated. Palygorskite suspensions in water are rather unstable and particles smaller than 3 μm in size
are not found before a TSE treatment. Stabilization of the suspension can be obtained by TSE treatments and/or by using a
dispersing agent such as pyrophosphate, or both. As a result of TSE treatments smaller particles are obtained, the dispersiveness
of the particles is improved and electrophoretic mobility is increased. Electron microscopy scans showed that the aggregates
of needles which form the palygorskite fibres, disintegrate to separated thin needles as a result of the TSE treatment.
Dedicated to Professor Lisa Heller-Kallai on the occasion of her 65th birthday 相似文献
4.
Characterization,correlation and kinetics of dolomite samples as outlined by thermal methods 总被引:1,自引:0,他引:1
In this study, the decomposition behavior of four dolomite samples of different origin was studied by X-ray diffractometer
and simultaneous TG-DTA experiments. Three different decomposition regions were determined known as dehydration of inter-particle
water, formation of MgO and calcite and decomposition of calcite. Kinetic analysis of these decomposition regions was analyzed
and the related activation energies are determined. It was observed that the activation energies were in the range of 48–137
kJ mol−1. 相似文献
5.
J. L. Pérez-Rodríguez F. Franco V. Ramírez-Valle L. A. Pérez-Maqueda 《Journal of Thermal Analysis and Calorimetry》2005,82(3):769-774
Summary The differences on the thermal behaviour (DTG-DTA) of antigorite sample measured before and after sonication have been studied.
Sonication treatment produces negligible changes in the structure of the material but substantial textural modifications.
These modifications produce changes in the thermal behaviour of antigorite sample. Thus, it has been observed a decrease in
the dehydroxylation temperature as measured by DTG and DTA effects. For sonication treatments longer than 20 h, two new effects
of dehydroxylation are observed, the intensity of these two new effects increases with the sonication time showing a modification
in the release of structural OH. It has been also observed that the formation of forsterite takes place simultaneously with
the dehydroxylation of the antigorite. The high temperature exothermic effect is due to the recrystallization of forsterite
and not to the formation of forsterite as traditionally assumed. Modifications in the thermal dehydroxylation of antigorite
observed in this study are related to the pronounced decrease in particle size obtained by sonication. 相似文献
6.
B. Egrdoğan Alver M. Sakici E. Yörükoğullari Y. Yilmaz M. Güven 《Journal of Thermal Analysis and Calorimetry》2008,94(3):835-840
The water adsorption properties of sepiolite having dolomite supplied from Eskisehir region and their exchanged forms (K+, Na+, Mg2+ and Ca2+) were investigated. The sepiolite samples were characterized using XRD, TG-DTA, DSC and nitrogen adsorption methods. The
temperature ranges were determined for the dehydrations of hydroscopic and zeolitic water as 30–200°C, for the dehydration
of the bound water as 250–750°C and for the dehydroxylation of hydroxyls as 810–850°C in the sample. It was observed that
the value of percent mass loss for natural and modified samples varied in the range from 36.70 to 39.05%. Two mass loss steps
for all samples were observed using a differential scanning calorimetry (DSC) in the range of 30–550°C. Adsorption isotherms
for water on natural and modified forms were obtained at pressures up to 2.39 kPa. Uptake of water increased as K-SEP.<Na-SEP.<Mg-SEP.<Ca-SEP.
for sepiolite samples at 293 K. 相似文献
7.
Kristóf J. Frost R. L. Kloprogge J. T. Horváth E. Makó É. 《Journal of Thermal Analysis and Calorimetry》2002,69(1):77-83
The thermal behaviour of mechanochemically treated kaolinite has been investigated under dynamic and controlled rate thermal analysis (CRTA) conditions. Ten hours of grinding of kaolinite results in the loss of the d(001) spacing and the replacement of some 60% of the kaolinite hydroxyls with water. Kaolinite normally dehydroxylates in a single mass loss stage between 400 and 600°C. CRTA technology enables the dehydroxylation of the ground mineral to be observed in four overlapping stages at 385, 404, 420 and 433°C under quasi-isobaric condition in a self-generated atmosphere. It is proposed that mechanochemical treatment of the kaolinite causes the localization of the protons when the long range ordering is lost.This revised version was published online in November 2005 with corrections to the Cover Date. 相似文献
8.
V. Balek E. R. Vance V. Zeleňák Z. Málek J. Šubrt 《Journal of Thermal Analysis and Calorimetry》2007,88(1):93-98
Emanation thermal
analysis (ETA) was used to characterize the thermal reactivity of amorphous
brannerite mineral of general formula U1–xTi2+xO6
(locality El Cabril, near Cordoba, Spain). It was demonstrated that on sample
heating up to 880°C microstructure changes taking place in the sample
were accompanied by the formation of new radon diffusion paths, followed by
their closing up during the final transformation of amorphous to crystalline
brannerite in the range 900–1020 °C. Relative changes in structure
irregularities that served as radon diffusion paths during heating and subsequent
cooling of the sample to temperatures of 300, 550, 750, 880, 1020 and 1130°C,
respectively, were determined from the ETA results. Mass losses in temperature
ranges of 230–315, 570–760 and 840–1040°C were observed
by thermogravimetry. Mass spectrometry indicated the release of CO2 mainly
due to the decomposition of minor carbon amount in the brannerite mineral
sample. 相似文献
9.
Ramesh Chandra Nigam 《Fresenius' Journal of Analytical Chemistry》1968,234(5):352-354
Conclusion The method proposed is convenient and less time consuming in comparison with the gravimetric pyrophosphate method. If reasonable precautions were observed the magnesium values determined by this method were quite accurate. 相似文献
10.
K. Michalik Zofia Drzazga Anna Michnik M. Kaszuba 《Journal of Thermal Analysis and Calorimetry》2006,84(1):119-123
A differential
scanning calorimetry study of the thermal behavior of nevirapine and azidothymidine
in water solution was carried out. For nevirapine scan rate dependent and
irreversible endothermic peak were found. Thermal degradation of nevirapine
as well as NVP – AZT mixture is relatively well described by the model
involving only one irreversible step determined by a first-order rate constant.
The estimated kinetic constants and activation energies indicate that the
degradation process proceeds slower for nevirapine in presence of AZT ligands
than without them. 相似文献
11.
Pérez-Maqueda L. A. Balek V. Poyato J. Pérez-Rodríquez J. L. Šubrt J. Bountsewa I. M. Beckman I. N. Málek Z. 《Journal of Thermal Analysis and Calorimetry》2003,71(3):715-726
Emanation thermal analysis (ETA), thermogravimetry, DTA and XRD were used in thermal characterization of natural vermiculite
(Santa Olalla, Huelva, Spain) and of Na+- and - exchanged vermiculite samples during heating in air in the range 25-1100°C. A good agreement between the results of
these methods was found. Changes in the radon release rate measured by ETA, which reflected the decrease and collapse of the
interlayer space after the release of water as well as the formation of new crystalline phases were evaluated using a mathematical
model. The model used for the evaluation was found suitable for the quantitative characterization of microstructure changes
during in situ conditions of heating of vermiculite samples.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
12.
Nandini Chatterjee Sudhapada Basu S. K. Palit Mrinal M. Maiti 《Journal of Polymer Science.Polymer Physics》1995,33(12):1705-1712
Thermal degradation of polyacrylonitrile (PAN) has been studied by combined differential thermal analysis, thermogravimetry, and XRD analysis. On the basis of the experimental observations, it has been suggested that the intramolecular polymerization of nitrile groups to a conjugated polyimine structure is initially limited to only the amorphous zone of PAN, which involves little evolution of off-gases. Polymerization of nitrile group in the crystalline zone starts with the melting of crystallites with the evolution of off-gases from the amorphous-crystalline zone interface. ©1995 John Wiley & Sons, Inc. 相似文献
13.
The reaction between SiO2 and MgO at temperatures up to 1500°C was studied using thermal analysis, with X-ray diffraction being used to identify reaction products. The reaction is slow and results in the formation of Mg2SiO4 and MgSiO3, with minor amounts of SiO2·nH2O and residual amounts of unreacted SiO2 and MgO. Complete reaction of the starting materials to form Mg2SiO4 can only be achieved by maintaining the mixture at 1500°C for extended periods of time (>1 h). 相似文献
14.
The influence of sodium chloride on the course of thermal decomposition of calcite, magnesite and dolomite was studied partly under dynamic, and partly under quasi-isothermal heating conditions. Four different types of sample holders were applied in the experiment, i.e., the partial pressure of carbon dioxide was also different in the four cases. It was found that the presence of sodium chloride reduced the decomposition temperature in every case. The extent of this reduction amounted to about 10°C in the case of calcite, 40–80°C in the case of magnesite, and 10–40°C and 10–20°C for the first and second decomposition stages, respectively, of dolomite. 相似文献
15.
Balek V. Zeleňák V. Mitsuhashi T. Beckman I. N. Haneda H. Bezdička P. 《Journal of Thermal Analysis and Calorimetry》2002,67(1):63-72
Emanation thermal analysis (ETA) was used in the characterization of microstructure changes during heating ofprecursors for the titania based materials: hydrous titania, TiO2nH2O (n=0.58) and hydrous titania containing 10% ruthenia,(TiO2)0.9(RuO2)0.1nH2O (n=1.5). The precursors were heated at the constant rate 6 K min–1 in argon flow in the range 20–1000°C. ETA results were compared with the theoretical curves simulating the temperature dependences of radon release rate, E(T). Two mathematical models were used in the simulation. The models considered either subsequent or simultaneous solid state processes (i.e. dehydration, crystallization orphase transition, resp.) during thermal treatment of titania based materials. A good agreement was found between experimental and the simulated ETA curves. The results of ETA were confirmed by XRD patterns of intermediate products of thermal treatment of the precursors.This revised version was published online in November 2005 with corrections to the Cover Date. 相似文献
16.
N. Voyer A. Soisnard Sara J. Palmer W. N. Martens R. L. Frost 《Journal of Thermal Analysis and Calorimetry》2009,96(2):481-485
Zn-Al hydrotalcites and Cu-Al hydrotalcites were synthesised by coprecipitation method and analysed by X-ray diffraction (XRD)
and thermal analysis coupled with mass spectroscopy. These methods provide a measure of the thermal stability of the hydrotalcite.
The XRD patterns demonstrate similar patterns to that of the reference patterns but present impurities attributed to Zn(OH)2 and Cu(OH)2. The analysis shows that the d003 peak for the Zn-Al hydrotalcite gives a spacing in the interlayer of 7.59 ? and the estimation
of the particle size by using the Debye-Scherrer equation and the width of the d003 peak is 590 ?. In the case of the Cu-Al
hydrotalcite, the d003 spacing is 7.57 ? and the size of the diffracting particles was determined to be 225 ?.
The thermal decomposition steps can be broken down into 4 sections for both of these hydrotalcites. The first step decomposition
below 100°C is caused by the dehydration of some water absorbed. The second stage shows two major steps attributed to the
dehydroxylation of the hydrotalcite. In the next stage, the gas CO2 is liberated over a temperature range of 150°C. The last reactions occur over 400°C and involved CO2 evolution in the decomposition of the compounds produced during the dehydroxylation of the hydrotalcite. 相似文献
17.
L. Valenzano Y. Noël R. Orlando C. M. Zicovich-Wilson M. Ferrero R. Dovesi 《Theoretical chemistry accounts》2007,117(5-6):991-1000
The equilibrium geometry, the Raman and IR vibrational spectra at the Γ point, TO–LO splitting, IR intensities, Born and dielectric
tensors of magnesite MgCO3, dolomite MgCa(CO3)2 and calcite CaCO3 have been calculated with the periodic ab initio program CRYSTAL, by using an all-electron gaussian type basis set and the
B3LYP hamiltonian. LO (longitudinal-optical) modes are computed by correcting the dynamical matrix through Born charges and
high frequency dielectric tensors obtained from well localized Wannier functions and a saw-tooth computational scheme. The
mean absolute difference between calculated and experimental frequencies (IR TO and LO and RAMAN) is as small as 6.9 cm−1 for magnesite, 7.7 cm−1 for dolomite and 8.5 cm−1 for calcite. Calculated IR intensities are in semiquantitative agreement with experiment. The modes of the three compounds
are compared through graphical animation available on the CRYSTAL web-site. 相似文献
18.
The influence of water vapour on the course of the thermal decompositions of pure calcite, magnesite and dolomite, and of these materials mixed with 2% sodium chloride, was studied partly under dynamic, and partly under quasi-isothermal heating conditions. The sample holders used were of four different types, i.e. the carbon dioxide in direct contact with the solid phase of the sample was at different partial pressures. The investigations were carried out in the presence of dried air as well as in air of 60% and 100% humidity content. It is stated that the presence of water vapour increases the decomposition temperature of the first stage of dolomite decomposition (by about 20–50°C) but reduces it in the second stage (by about 5–10°C), as it does in the decomposition of calcite and magnesite. It was also found that the presence of sodium chloride and water vapour together reduces the temperature of both decomposition stages of dolomite. 相似文献
19.
J. H. Sharp F. W. Wilburn R. M. McIntosh 《Journal of Thermal Analysis and Calorimetry》1991,37(9):2021-2029
TG, DTG and DTA curves of magnesite are dependent on procedural variables, especially sample mass, heating rate and partial pressure of carbon dioxide, in a similar manner to those of calcite [1], although the magnitude of the effect is less for magnesite. The first stage of the decomposition of dolomite varies with increasing partial pressure of carbon dioxide in an anomalous manner and hence the effects of these procedural variables (except heating rate) are not similar to those observed for magnesite and calcite. The second stage of the decomposition of dolomite is, however, strongly dependent on these procedural variables and behaves in a manner that would be predicted for a sample of calcite diluted with magnesia. A 11 molar mixture of magnesite and calcite also behaves as would be predicted from the behaviour of the single carbonates but differently from that of dolomite.
We wish to thank Pilkington Brothers plc for granting leave of absence to RMM. 相似文献
Zusammenfassung TG-, DTG- und DTA-Kurven von Magnesit sind Ähnlich wie bei Kalzit [1] abhÄngig von den Versuchsparametern, besonders von Probenmasse, Aufheizgeschwindigkeit und Partialdruck von Kohlendioxid, obwohl das Ausma\ dieses Einflusses bei Magnesit geringer ist. Der erste Schritt der Zersetzung von Dolomit Ändert sich in einer ungewöhnlichen Weise durch Erhöhung des Partialdruckes von Kohlendioxid und deshalb unterscheidet sich der Einflu\ dieser Versuchsparameter (mit Ausnahme der Probenmasse) von dem, der bei Magnesit und Kalzit beobachtet wurde. Der zweite Schritt bei der Zersetzung von Dolomit ist stark von diesen Versuchsparametern abhÄngig und verlÄuft so, wie man es für eine mit Magnesia verdünnte Kalzitprobe voraussagen würde. Eine Gemisch aus Magnesit und Kalzit im VerhÄltnis 11 verhÄlt sich ebenso, wie man es auf Grund des Verhaltens der einfachen Karbonate voraussagen würde, unterscheidet sich jedoch von dem des Dolomits.
We wish to thank Pilkington Brothers plc for granting leave of absence to RMM. 相似文献
20.
A. Saravanakumaar A. Senthilkumar S. S. Saravanakumar M. R. Sanjay Anish Khan 《International Journal of Polymer Analysis and Characterization》2018,23(6):529-536
This study aims to examine the effect of sodium hydroxide (NaOH) treatment on the physico-chemical properties, structure, thermal, tensile and surface topography of Carica papaya fibers (CPFs). The surface of raw CPFs was modified by soaking with 5% NaOH solution for 15, 30, 45, 60, 75 and 90?min. The results of thermo-gravimetric analysis revealed that the optimum treatment time for alkali treatment was 60?min. It was found that the alkali treatment improved the properties of the CPFs. The results of TGA, FT-IR, XRD and AFM suggest that the treated CPF is a suitable alternative as reinforcement in polymer composites. 相似文献