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1.
V. Balek J. L. Pérez-Rodríguez L. A. Pérez-Maqueda J. Šubrt J. Poyato 《Journal of Thermal Analysis and Calorimetry》2007,88(3):819-823
Thermal behaviour of natural vermiculite (Santa Olalla, Huelva, Spain) was investigated by TG, DTA, emanation thermal analysis
(ETA) and high temperature XRD on heating in the temperature range from 30 to 1100°C before and after vibratory mill grinding.
Microstructure changes of natural and ground vermiculite samples were characterized by using ETA under in situ conditions
of heating. By comparing the ETA and XRD results it was demonstrated that a decrease of radon release rate measured by ETA
characterized the decrease in the interlayer spacing of the vermiculite samples that followed the dehydration.
Dedicated to the memory of Professor Dr. Ferenc Paulik who passed away on October 12, 2005. 相似文献
2.
Balek V. Mitsuhashi T. Šubrt J. Bakardjieva S. Málek Z. 《Journal of Thermal Analysis and Calorimetry》2003,72(1):119-127
Emanation thermal analysis (ETA) was used for characterization of thermal behaviour of SiCf/SiC composites on heating in argon and air, respectively. Effect of gas environment (argon, air) and helium ions implantation
on the microstructure development of the SiCf/SiC composite prepared by chemical vapour infiltration (CVI) from Nicalon CG fibres was investigated under in situ conditions
of heating. The annealing of near surface structure irregularities was observed in the range 280-700°C and evaluated by means
of the mathematical model, assuming that the structure irregularities served as diffusion paths for radon. The ETA reflected
the formation of amorphous silica and its subsequent crystallization to crystoballite. Morphology of the SiCf/SiC samples before and after the heat treatments was characterized by means of SEM.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
3.
V. A.?Cardoso L. M.?Nunes J. C. O.?Santos I. M. G.?Santos M. M.?Conceio J. R.?Santos Jr. A. G.?Souza 《Journal of Thermal Analysis and Calorimetry》2005,79(2):361-365
Summary Sugar cane bagasse lignin (SCBL) was extracted with formic acid (FA) from a sugar and alcohol factory residue, and used for blends preparation with polyvinylpyrrolidone (PVP). Casting from DMSO and FA solutions were used as preparation procedure. PVP and PVP/SCBL blends were also irradiated with ultraviolet light (Hg lamp). Blend formation and irradiation effects were examined through thermogravimetric analysis (TG) and infrared spectroscopy (FTIR). Results suggest a greater interaction between PVP and SCBL chains in PVP/SCBL 95/5 cast from DMSO and in the 95/5 and 90/10 blends cast from FA. Pure PVP shows a thermal stability decrease due to irradiation and this effect is minimized in the PVP/SCBL blends. The initial stage of the thermal decomposition of PVP is anticipated by the SCBL incorporation. 相似文献
4.
Balek V. Šubrt J. Mitsuhashi T. Beckman I. N. Györyová K. 《Journal of Thermal Analysis and Calorimetry》2002,67(1):15-35
The paper reviews the actual state of the development and use of emanation thermal analysis (ETA). Examples of its recent applications are presented. The advantages of ETA in the microstructure characterization of materials under in situ conditions of their heat treatment are outlined.This revised version was published online in November 2005 with corrections to the Cover Date. 相似文献
5.
V. Balek N. Todorova C. Trapalis V. Štengl E. Večerníková J. Šubrt Z. Malek G. Kordas 《Journal of Thermal Analysis and Calorimetry》2005,80(2):503-509
Summary Titania-based photocatalytic materials were prepared by sol-gel method using Fe3+ and polyethyleneglycol (PEG600) as additives. Thermogravimetry (TG), differential thermal analysis (DTA) and evolved gas analysis (EGA) with MS detection were used to elucidate processes that take place during heating of Fe3+ containing titania gels. The microstructure development of the Fe2O3/TiO2 gel samples with and without PEG600 admixtures was characterized by emanation thermal analysis (ETA) under in situ heating in air. A mathematical model was used for the evaluation of ETA results. Surface area and porosity measurements of the samples dried at 120°C and the samples preheated for 1 h to 300 and 500°C were compared. From the XRD measurements it was confirmed that the crystallization of anatase took place after thermal heating up to 600°C. 相似文献
6.
This research was aimed
to investigate the role of clay on the combustion and kinetic behavior of
crude oils in limestone matrix. For this purpose, simultaneous TG (thermogravimetry)
and DTA (differential thermal analysis) experiments were performed at three
different heating rates as 10–15 and 20°C min–1,
respectively. A uniform trend of decreasing activation energies was observed
with the addition of clay. It was concluded that clays surface area affects
the values of Arrhenius constant, while it is the catalytic properties of
clay, which lower the activation energies of all the reactions, involved in
the combustion process. 相似文献
7.
Balek V. Zeleňák V. Mitsuhashi T. Bakardjieva S. Šubrt J. Haneda H. 《Journal of Thermal Analysis and Calorimetry》2002,67(1):83-89
Results of emanation thermal analysis (ETA) characterizing microstructure changes of SiC based materials during heat treatment in argon are demonstrated. This method made it possible to reveal fine changes of the texture of SiC nano-sized powders, SiC micro-sized powders and SiC whiskers under in situconditions of the heating. ETA curves can serve as fingerprints of the respective samples.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.
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
10.
The decomposition behaviour of dolomite samples has been carried out by simultaneous DTA-TG experiments. Dolomite samples
could be classified broadly into two categories as regular and iron-bearing dolomites based on DTA decomposition temperatures.
The mass% FeO of all the dolomite samples was identified by DTA and the results are confirmed by atomic absorption spectrophotometer
experiments.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
11.
DTA/TG
and X-ray investigations were carried out on different building composites
in order to examine their relative hydration processes. The presence of lime,
hemihydrate gypsum, ferosilicate, and some other wastes as leaner and hydrophobic
additive in different proportions into composites provokes hydration reactions,
leading to calcium silicate hydrate (CSH), ettringite and an intermediate
phase formation with varying chemical composition of calcium, aluminum, silicon
and sulfur.
DTA curves indicate several transformations taking
place between composites components, related to hydration of some phases.
The content of ettringite component corresponds to the properties and it is
used as an indicator for the possibility of industrial application. It is
found out that gypsum based cementitious binders could be used as building
material in the industry. The same time it is confirmed that the selected
wastes could be considered as secondary raw materials. 相似文献
12.
V. Balek L. A. Pérez-Maqueda J. Poyato Z. Černý V. Ramírez-Valle I. M. Buntseva J. L. Pérez-Rodríguez 《Journal of Thermal Analysis and Calorimetry》2007,88(1):87-91
The effect of grinding
on thermal behavior of pyrophyllite and talc as commonly used ceramic clay
minerals was investigated by DTA, TG, emanation thermal analysis (ETA), B.E.T.
surface area (s.a.) measurements, X-ray diffraction (XRD) and scanning electron
microscopy (SEM).
A vibratory mill was used in this study, grinding
time was 5 min. It was found that the grinding caused an increase in surface
area and a grain size reduction of the samples. From TG and DTA results it
followed that grinding caused a decrease of the temperature at which the structure
bound OH groups released. The formation of high temperature phases was enhanced
with the ground samples. For the ground talc sample the crystallization of
non-crystalline phase into orthorhombic enstatite was observed in the range
of 800°C. For ground pyrophyllite a certain agglomeration of grains was
observed in the range above 950°C. Moreover, for both clays the ETA characterized
a closing up of subsurface irregularities caused by grinding as a decrease
of the emanation rate in the range 250–400°C. The comparison of
thermal analysis results with the results of other methods made it possible
to better understand the effect of grinding on the ceramic clays. 相似文献
13.
V. Balek M. Beneŝ J. Ŝubrt J. L. Pérez-Rodriguez P. E. Sánchez-Jiménez L. A. Pérez-Maqueda J. Pascual-Cosp 《Journal of Thermal Analysis and Calorimetry》2008,92(1):191-197
Emanation thermal analysis (ETA), thermogravimetry and high temperature XRD were used to characterize the thermal behavior
during dehydration of natural Na montmorillonite (Upton Wyoming, USA) and homoionic montmorillonite (MMT) samples saturated
with different cations, i.e. Li+, Cs+, NH4+, Mg2+ and Al3+. ETA results characterized radon mobility and microstructure changes that accompanied the mass loss of the samples due to
dehydration on heating in air. A collapse of interlayer space between the silicate sheets after water release from the MMT
samples was characterized by a decrease of the radon release rate, ΔE. Decreases in c-axis basal spacing (d
001) values determined from XRD patterns for the different montmorillonite samples follow the sequence:
The decrease of the radon release rate (ΔE) determined by ETA that characterized microstructure changes due to collapse of interlayer space corresponded well to differences
in the c-axis basal spacing (Δd
001) values determined from the XRD patterns before and after samples dehydration. 相似文献
14.
Emanation Thermal Analysis (ETA), based on the measurement of the release of radon from previously labelled samples, has been
used for 'in-situ’ characterisation of the morphology changes of intercalated montmorillonitic clay. The thermal behaviour
of hydroxyaluminium intercalated montmorillonite was monitored in course of the preparation of alumina pillared montmorillonite,
making possible to determine optimal temperature for the isothermal treatment of the intermediate product. Moreover, the thermal
stability of alumina pillared montmorillonite porous structure was determined from the ETA data. A good agreement of ETA data
and surface area, XRD patterns. DTA, and TG resulted was found.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
15.
T. Sato M. Hubáček V. Balek J. Šubrt O. Kriz T. Mitsuhashi 《Journal of Thermal Analysis and Calorimetry》2000,60(2):661-665
Processes taking place during formation of B-C-N ceramics by thermal treatment of organic precursors were investigated using
emanation thermal analysis (ETA), differential thermal analysis (DTA) and thermogravimetry (TG). An additional information
about thermal behavior of precursors used for preparation of BC4N, BN and CNx ceramic systems by heating in argon up to 1100°C
was obtained. The ETA enabled us to characterize microstructure changes in the samples at in situ conditions of thermal treatment.
A good agreement of ETA, TG and DTA results was found.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
16.
The melting behaviour in the pseudo-binary system (UO2 + NpO2) has been studied experimentally for the first time in this work with the help of laser heating under controlled atmosphere. It has been observed that the solidus and liquidus lines of this system follow an ideal solution behaviour (negligible mixing enthalpy) between the well-established solid/liquid transition temperatures of pure UO2 (3130 K) and that recently assessed for NpO2 (T = 3070 K). Pre- and post-melting material characterizations performed with the help of X-ray diffraction and Raman spectroscopy are also consistent with ideal mixing of the two end members. Such behaviour follows the similar structure and bonding properties of tetravalent uranium and neptunium and the similar melting points of the two oxides. The interest of this investigation is twofold. From a technological viewpoint, it indicates that the incorporation of NpO2 in UO2 fuel or transmutation targets is a viable option to recycle neptunium without inducing any relevant change in the chemical or thermal stability of the uranium dioxide matrix, even up to the melting point. From a more fundamental perspective, it confirms that actinide dioxides, and particularly UO2, tend to mix in a way closer to ideal, the closer are the atomic numbers, 5-f electron shell filling, atomic radii and oxygen potentials of the metals forming the pure dioxides. 相似文献
17.
Thermal analysis of soybean oil based polyols 总被引:3,自引:1,他引:2
B. Lin L. Yang H. Dai Q. Hou L. Zhang 《Journal of Thermal Analysis and Calorimetry》2009,95(3):977-983
Soybean oil based polyols (5-OH polyol, 10-OH polyol and 15-OH polyol) were synthetised from epoxidized soybean oil. The melting
peak of polyols and the relationship between melting peak and the number-average functionality of hydroxyl in polyols were
investigated by differential scanning calorimetry (DSC). The thermal decomposition of polyols and some of their thermal properties
by thermogravimetry (TG) and derivative thermogravimetry (DTG) were also studied. The thermal stability of polyols in a nitrogen
atmosphere was very close hence they had a same baseplate of triglyceride for polyols. The extrapolated onset temperature
of polyols in their thermal mass loss, first step had a decreasing order: 5-OH polyol>10-OH polyol>15-OH polyol due to the
difficulty in forming multiple elements ring of them had the same order.
The thermal behavior of polyols under non-isothermal conditions using Friedman’s differential isoconversional method with
different heating rates indicated that the 5-OH polyol had the lowest activation energy in thermal decomposition amongst these
polyols according to the same fractional mass loss because of the weakest intramolecular oligomerization. The 15-OH polyol
was prior to reach the mass loss region because the six-member ring is more stable than the three-member ring from 10-OH polyol
and more easily formed. 相似文献
18.
The theoretical background for the use of radon diffusion as a probe of microstructure changes in solids is given. The high sensitivity of the emanation thermal analysis (ETA) in the study of solid state processes especially interactions taking place on surfaces and in the near surface layers is described. The increasing sensitivity of the method towards bulk processes with rising temperature is theoretically shown. The background considerations to be used in the mathematical modeling of temperature dependences of the radon release from solids on heating (i.e. simulated ETA curves) are presented. Various models for radon diffusion and various functions describing the annealing of structure irregularities, which served as diffusion paths for radon, were used in the modeling. It was shown, that ETA is able to characterize microstructure changes in the surface layers of the thickness from several nanometers to several micrometers.This revised version was published online in November 2005 with corrections to the Cover Date. 相似文献
19.
D. S. Gouveia R. Rosenhaim M. A. M. A. de Maurera S. J. G. Lima C. A. Paskocimas E. Longo A. G. Souza I. M. G. Santos 《Journal of Thermal Analysis and Calorimetry》2004,75(2):453-460
With the aim of obtaining materials with applications in pigments, CoxZn7-xSb2O12 spinels were synthesized using the Pechini method. This method consists in the formation of a polymeric net, where the metallic
cations are homogeneously distributed. In this work, two types of alcohol (ethyl glycol and ethylene glycol) were used for
the synthesis of a zinc antimoniate spinel, CoxZn7-xSb2O12 (x=0-7). The materials were characterized by termogravimetry (TG) and differential thermal analysis (DTA). TG results indicated
a decrease in total mass loss when cobalt was added to the solution substituting zinc, for samples prepared using the two
different alcohols. Decomposition temperatures, obtained by TG and DTA, presented a decreasing behavior as cobalt was added
to the material. In relation to the alcohols, all results indicated a better polymerization of the resin when ethylene glycol
was used, being the most indicated one for cation immobilization. X-ray diffraction did not show differences between the two
alcohols - both presented the spinel phase (Co, Zn)2.33Sb0.67O4. Samples with higher quantity of cobalt also presented ilmenite phase (Co, Zn)Sb2O6.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
20.
Földesová M. Lukáč P. Dillinger P. Balek V. Svetík S. 《Journal of Thermal Analysis and Calorimetry》1999,58(3):671-675
Zeolites chemically modified with 1, 4 or 6 M aqueous solutions of NaOH were studied by DTA, TG and ETA (emanation thermal analysis) in the temperature range 201–200°C. The structural changes in the modified zeolites at room temperature and in the modified zeolites annealed at 1000°C were studied by XRD analysis. Thermal analysis demonstrated dehydration, dehydroxylation, structural changes and a glass transition. A gradual loss in crystallinity of the chemically modified zeolites was also observed. XRD analysis revealed structural changes caused by chemical treatment and also by annealing.This revised version was published online in November 2005 with corrections to the Cover Date. 相似文献