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1.
Carmen Paraschiv B. Jurca Adelina Ianculescu Oana Carp 《Journal of Thermal Analysis and Calorimetry》2008,94(2):411-416
Two bismuth ferrite potential precursors systems, namely Fe(NO3)3·9H2O-Bi(NO3)3·9H2O-glycine/urea with different metal nitrate/organic compound molar ratios have been investigated in order to evaluate their
suitability as BiFeO3 precursors. The presence into the precursor of both reducing (glycine and urea) and oxidizing (NO3−) components, modifies dramatically their thermal behaviour comparative with the raw materials, both from the decomposition
stoichiometries and temperature occurrence intervals points of view. Also, the thermal behaviour is dependent on the fuel
nature but practically independent with the fuel content. The fuel nature influences also some characteristics of the resulted
oxides (phase composition, morphologies). In the case of the oxides prepared using urea as fuel, a faster evolution toward
a single phase composition with the temperature rise is evidenced, the formation of the BiFeO3 perovskite phase being completed in the temperature range of 500–550°C. 相似文献
2.
V. Ya. Yablokov I. L. Smel’tsova I. A. Zelyaev S. V. Mitrofanova 《Russian Journal of General Chemistry》2009,79(8):1704-1706
Rates of thermal decomposition of glycine, alanine, and serine are described by the equation of first order reaction in the
temperature range 200–300°C. Apparent rate constants and apparent activation energies of decomposition of α-amino acids were
evaluated. It was found that the main gaseos reaction product is carbon dioxide. 相似文献
3.
A. Zalga Z. Moravec J. Pinkas A. Kareiva 《Journal of Thermal Analysis and Calorimetry》2011,105(1):3-11
The preparation and characterization of the M′–M′′–O nitrate–tartrate (M′ = Ca, Ba, Gd and M′ = W, Mo) precursor gels synthesized
by simple, inexpensive, and environmentally benign aqueous sol–gel method is reported. The obtained gels were studied by thermal
(TG/DSC) analysis. TG/DSC measurements revealed the possible decomposition pathway of synthesized M′–M′′–O nitrate–tartrate
gels. For the synthesis of different metal tungstates and molybdates, the precursor gels were calcined at different temperatures
(650, 800, and 900 °C). According to the X-ray diffraction (XRD) analysis data, the crystalline compounds CaMo1-x
W
x
O4 doped with Ce3+ ions, BaMo1-x
W
x
O4 doped with Eu3+ ions and Gd2Mo3O12 were obtained from nitrate–tartrate gels annealed at 650–900 °C temperatures. The XRD data confirmed that the fully crystalline
single-phase powellite, scheelite, or Gd2(MoO4)3 structures were formed already at 650 °C. Therefore, the suggested sol–gel method based on the complexation of metal ions
with tartaric acid is suitable for the preparation of mixed tungstates–molybdates at relatively low temperature in comparison
with solid-state synthesis. 相似文献
4.
E. Arico F. Tabuti F. C. Fonseca D. Z. de Florio A. S. Ferlauto 《Journal of Thermal Analysis and Calorimetry》2009,97(1):157-161
The thermal behavior of the yttria-stabilized zirconia (YSZ) and nickel oxide (YSZ–NiO) composite mixtures with the addition
of graphite, multiwall carbon nanotubes and functionalized multiwall carbon nanotubes was studied. The YSZ–NiO composite is
the precursor of the YSZ–Ni anode of solid oxide fuel cells. The anode exhibits a porous structure, which is usually obtained
by the addition of carbon containing pore formers. Thermal analysis and X-ray diffraction evidenced that the properties of
carbonaceous materials (C) and atmosphere have a strong influence on the thermal evolution of the reactions taking place upon
heating the anode precursor. The dependence of both the carbon content and the chemical nature of the ceramic matrix on the
thermal behavior of the composite were investigated. The discussed results evidenced important features for optimized processing
of the anode. 相似文献
5.
Oxidative degradation and pyrolysis of polyvinyl chloride in the temperature range 200–500°C in binary mixtures containing
sodium, potassium, and calcium nitrates and nitrites and calcium hydroxide were studied. A scheme of oxidative degradation
of polyvinyl chloride and of binding of chlorine and carbon present in the polymer in the reactions of the degradation products
with the mixture components was suggested. 相似文献
6.
El-Shobaky G. A. Radwan N. R. E. Radwan F. M. 《Journal of Thermal Analysis and Calorimetry》2002,68(1):275-287
The results obtained showed that the addition of small amounts of LiNO3 to the reacting mixed solids, consisting of equimolar proportion of Fe2O3 and basic MgCO3 much enhanced the thermal decomposition of magnesium carbonate. The addition of 12 mol% LiNO3 (6 mol% Li2O) decreased the decomposition temperature of MgCO3 from 525.5 to362°C. MgO underwent solid–solid interaction with Fe2O3 at temperatures starting from800°C yielding MgFe2O4. The amount of ferrite produced increased by increasing the precalcination temperature of the mixed solids. However, the
completion of this reaction required prolonged heating at elevated temperature above 1100°C. Doping with Li2O much enhanced the solid–solid interaction between the mixed oxides leading to the formation of MgFe2O4 phase at temperatures starting from 700°C. The addition of 6 mol% Li2O to the mixed solids followed by precalcination at 1050°C for 4 h resulted in complete conversion of the reacting oxides
into magnesium ferrite. The heat treatment of pure and doped solids at 900–1050°C effected the disappearance of most of IR
transmission bands of the free oxides with subsequent appearance of new bands characteristic for MgFe2O4 structure. The promotion effect of Li2O towards the ferrite formation was attributed to an effective increase in the mobility
of the various reacting cations. The activation energy of formation (ΔE) of magnesium ferrite was determined for pure and variously doped solids and the values obtained were 203, 126, 95 and 61
kJ mol−1 for pure mixed solids and those treated with 1.5, 3.0 and 6.0 mol% Li2O, respectively.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
7.
R. Lach M. M. Bućko K. Haberko M. Szumera R. Gajerski 《Journal of Thermal Analysis and Calorimetry》2013,112(2):727-730
Co-precipitation of alumina/YAG precursor from aluminum and yttrium nitrates solution with ammonium carbonate results in dawsonite (NH4Al(OH)2CO3). Its crystallographic parameters differ from the compound precipitated without the yttrium additive. It indicates that yttrium ions become incorporated into the dawsonite structure. The DSC/TG and X-ray measurements show decomposition of dawsonite at elevated temperature resulting in γ-Al2O3 which transforms to δ and θ modifications at still higher temperatures. The full transformation to α-Al2O3 and YAG occurs at temperatures higher than 1,230 °C. 相似文献
8.
M. R. Barati 《Journal of Sol-Gel Science and Technology》2009,52(2):171-178
Nanocrystalline Mg–Cu–Zn ferrite powders were successfully synthesized through nitrate–citrate gel auto-combustion method.
Characterization of the nitrate–citrate gel, as-burnt powder and calcined powders at different calcination conditions were
investigated by using XRD, DTA/TG, IR spectra, EDX, VSM, SEM and TEM techniques. IR spectra and DTA/TGA studies revealed that
the combustion process is an oxidation–reduction reaction in which the NO3
− ion is oxidant and the carboxyl group is reductant. The results of XRD show that the decomposition of the gel indicated a
gradual transition from an amorphous material to a crystalline phase. In addition, increasing the calcination temperature
resulted in increasing the crystallite size of Mg–Cu–Zn ferrite powders. VSM measurement also indicated that the maximum saturation
magnetization (64.1 emu/g) appears for sample calcined at 800 °C while there is not much further increase in M
s at higher calcination temperature. The value of coercivity field (H
c) presents a maximum value of 182.7 Oe at calcination temperature 700 °C. TEM micrograph of the sample calcined at 800 °C
showed spherical nanocrystalline ferrite powders with mean size of 36 nm. The toroidal sample sintered at 900 °C for 4 h presents
the initial permeability (μ
i) of 405 at 1 MHz and electrical resistivity (ρ) of 1.02 × 108 Ω cm. 相似文献
9.
I. Oja
Açik J. Madarász M. Krunks K. Tõnsuaadu D. Janke G. Pokol L. Niinistö 《Journal of Thermal Analysis and Calorimetry》2007,88(2):557-563
Thermal decomposition of precursor xerogels for TiO2,
obtained by gelling of acetylacetonate-modified titanium(IV) tetraisopropoxide
(prepared at Ti-alkoxide:acetylacetone molar ratios of 1:1 (Ti-1) and 1:2
(Ti-2)) in boiling 2-methoxyethanol, was monitored by simultaneous TG/DTA/EGA-MS
and EGA-FTIR measurements. Thermal degradation processes of Ti-1 and Ti-2
in the temperature range of 30–700°C consist of six mass loss steps,
the total mass loss being 46.3% and 54.4%, respectively. EGA by FTIR and MS
revealed release of H2O below 120°C; followed by
evolution of acetone and acetic acid between approximately 100 and 320°C,
and that of CO2 up to 560°C. Acetylacetone is evolved
to a significant extent from sample Ti-2 at 120–200°C. 相似文献
10.
S. F. Santos M. C. de Andrade J. A. Sampaio A. B. da Luz T. Ogasawara 《Journal of Thermal Analysis and Calorimetry》2007,87(3):743-746
TiO2–CeO2 oxides
for application as ceramic pigments were synthesized by the Pechini method.
In the present work the polymeric network of the pigment precursor was studied
using thermal analysis. Results obtained using TG and DTA showed the occurrence
of three main mass loss stages and profiles associated to the decomposition
of the organic matter and crystallization. The kinetics of the degradation
was evaluated by means of TG applying different heating rates. The activation
energies (E
a) and
reaction order (n) for each stage were
determined using Horowitz–Metzger, Coats–Redfern, Kissinger and
Broido methods. Values of E
a
varying between 257–267 kJ mol–1 and n=0–1 were found. According to the kinetic
analysis the decomposition reactions were diffusion controlled. 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.
Camila S. Xavier R. A. Candeia M. I. B. Bernardi S. J. G. Lima E. Longo C. A. Paskocimas L. E. B. Soledade A. G. Souza Iêda M. G. Santos 《Journal of Thermal Analysis and Calorimetry》2007,87(3):709-713
Magnesium and zinc ferrites
have been prepared by the polymeric precursor method. The organic material
decomposition was studied by thermogravimetry (TG) and differential thermal
analysis (DTA). The variation of crystalline phases and particle morphology
with calcination temperature were investigated using X-ray diffraction (XRD)
and scanning electronic microscopy (SEM), respectively. The colors of the
ferrites were evaluated using colorimetry. Magnesium ferrite crystallizes
above 800°C, presenting a yellow- orange color with a reflectance peak
at the 600–650 nm range, while zinc ferrite crystallizes at 600°C,
with a reflectance peak between 650–700 nm, corresponding to the red-brick
color. 相似文献
13.
Guiying Wang Wenxiang Zhang Honglei Lian Qingsheng Liu Dazhen Jiang Tonghao Wu 《Reaction Kinetics and Catalysis Letters》2002,75(2):343-351
Catalytic decomposition of ethanol in the presence of steam over Pd supported on a porous carbonaceous material was studied. XPS and TEM were used for the catalyst characterization. Experiments were performed under atmospheric pressure, temperature of 320-360°C and H2O/C2H5OH molar ratio 8.1. It was found that the catalyst exhibited a high activity and long-term stability for the ethanol decomposition into a gas mixture containing carbon oxides, methane and hydrogen. 相似文献
14.
A. I. Bulavchenko A. T. Arymbaeva M. G. Demidova E. A. Maksimovskii 《Colloid Journal》2011,73(6):748-752
A procedure is elaborated for preparing powders of ammonium and potassium nitrates with microsized particles and stable sols
with particle sizes of 7–16 nm based on isothermal mass crystallization from Tergitol NP-4-stabilized water-in-oil microemulsions
in decane. The crystallization process is studied by turbidimetry and photon-correlation spectroscopy. The isolated powders
are characterized by scanning electron microscopy, while sols and microemulsions are studied by photon-correlation spectroscopy.
Evaporation of water from microemulsion droplets upon stirring water-in-oil micellar solutions at 25–45°C is shown to be the
reason for the salt crystallization. It is ascertained that the time of the onset of crystallization and the morphology of
resulting particles depend on temperature, content of an aqueous pseudophase, and the nature of a salt. A desolubilization-emulsion
hypothesis is proposed for explaining the formation of nanoparticle powders and organosols. 相似文献
15.
Thermal decomposition of M(mal/fum)·xH2O (M=Mn, Co, Ni) has been studied in static air atmosphere from ambient to 500°C employing TG-DTG-DTA, XRD and IR spectroscopic
techniques. After dehydration the anhydrous maleate salts decompose to metal oxalate in the temperature range of 320–360°C,
which at higher temperature undergo an abrupt oxidative pyrolysis to oxides. The anhydrous fumarate salts have been found
to decompose directly to oxide phase. A comparison of thermal analysis reveals that fumarates are thermally more stable than
maleates. 相似文献
16.
Y. S. Malghe S. R. Dharwadkar K. Krishnan K. D. Singh Mudher 《Journal of Thermal Analysis and Calorimetry》2009,96(1):49-52
The phase transitions in the LaCrO3 were studied using bulk dilatometry and high temperature X-ray diffractometry from room temperature to 1050 and 1200°C, respectively.
LaCrO3 was prepared at 500°C from oxalate precursor employing microwave heating technique. Bulk shrinkage measurements on LaCrO3 pellets were carried out using dilatometer designed and fabricated in our own laboratory. Dilatometric curves of LaCrO3 showed two peaks in ΔL/L vs. temperature curves in the range 200–400 and 800–1000°C, respectively. These phase transitions have been confirmed using
high temperature X-ray diffractometry. The role of simple technique like bulk dilatometry in detecting and monitoring the
polymorphic transformations in solids is discussed for lanthanum chromates. 相似文献
17.
K. De Buysser I. Van Driessche J. Schaubroeck S. Hoste 《Journal of Sol-Gel Science and Technology》2008,46(2):133-136
A novel sol–gel synthetic route using water-soluble precursor salts is presented as a synthetic path for a high-purity negative
thermal expansion material, ZrW2O8. This synthetic route involves a sol–gel method with the use of EDTA as complexing agent. The aqueous solution is transformed
into a ceramic material after a two-step heat treatment: gelation at 60 °C and reactive sintering at 1,180 °C. The decomposition
of the gel is monitored with infrared spectroscopy and TGA. The high-temperature heat treatment results in ZrW2O8 with its characteristic negative thermal expansion behaviour α[75–130 °C]: −9.8 ± 1.6 μm/m °C and α[175–300 °C]: −1.2 ± 0.2 μm/m °C. 相似文献
18.
Three solid wastes generated from the vegetable tanning of bovine skin in the Leather Industry (shavings, trimmings and buffing dust) were mixed together in the same proportions in which they were produced and the mixture was then used as a pyrolysis precursor for this research study. The optimal pyrolysis conditions for obtaining energy from the generated fractions (char, tar and gas fraction), and the preparation of activated carbons from the carbonaceous material (char), were established. The final conditions were chosen from two different points of view, the thermogravimetric results (TG/DTG) obtained at different heating rates (2–20 °C/min) and an optimization of the pyrolysis parameters by means of experiments carried out in a conventional furnace. The pyrolysis conditions finally selected were: heating rate (5 °C/min), final temperature (750 °C), and time at final temperature (60 min) and inert gas flow (N2 150 ml/min). The carbonaceous material (char) obtained exhibits good properties as a solid fuel due to its high calorific value and relatively low ash content. It also shows suitable characteristics as a precursor for the preparation of activated carbons. The condensable fraction has a predominantly phenolic nature and contains significant amounts of nitrogen compounds (nitriles, diketopiperazines, etc.), alkanes, alkenes, acids and esters, derived from the decomposition of tannins and collagen, with possible industrial applications in the preparation of chemical products. The gaseous phase is rich in carbon monoxide and carbon dioxide, and also contains a certain amount of methane and hydrogen. The syngas content increases with the pyrolysis temperature. A kinetic study of the pyrolysis was carried out using a model of independent reactions. The variation in the heating rate produced a slight shift to higher temperatures of the decomposition peaks, although this did not significantly affect either the kinetic parameters of the degradation processes or the percentage weight losses. 相似文献
19.
Thermal
decomposition of cadmium succinate dihydrate, CdC4H4O4·2H2O, was studied in dynamic helium and air atmospheres by means of simultaneous
TG, DTA and MS analysis. It was found that dehydration of CdC4H4O4·2H2O takes place in the temperature range 80–165°C and
at low heating rates formation of monohydrate was stated.
The
anhydrous cadmium succinate decomposes at about 350°C to metallic cadmium.
The gaseous products of cadmium succinate decomposition are CO2
and H2O. Formation of small amounts of 3-phenylpropanal
and 1,7-octadiene during decomposition in helium was revealed. In helium cadmium
evaporates at the temperature of decomposition and the residue consists of
small amount of elementary carbon formed in result of pyrolysis of succinate
groups. In air cadmium oxidizes and the final solid product of decomposition
is CdO. 相似文献
20.
Yong-yong Wu Fang-li Jing Shi-zhong Luo Wei Chu Hong-zhi Ni 《Journal of Sol-Gel Science and Technology》2011,58(1):142-147
Metal (Cu, Zn, Al) nitrates and chlorides were used for preparing CuZnAl xerogels by a sol–gel route with propylene oxide
as gelation initiator. The CuZnAl mixed-metal oxides were further obtained by thermal treatment the xerogels at 500 °C for
5 h in air. Thermal decomposition behavior of the CuZnAl xerogels, the microstructures and the reducibility of the calcined
xerogels were investigated by thermogravimetry (TG), scanning electron microscope (SEM), powder X-ray diffraction (XRD), N2 adsorption/desorption (BET, BJH) and temperature-programmed reduction (TPR) techniques. The catalytic activity in dehydrocyclization
of ethylenediamine (ED) with 1, 2-propyleneglycol (PG) to 2-methylpyrazine (2-MP) was carried out at 380 °C. The results displayed
that the CuZnAl mixed-metal oxides prepared using nitrates as the metal precursors had a higher metallic Cu dispersion and
a superior low-temperature reducibility than those prepared by chlorides, which results in a higher catalytic activity for
the synthesis of 2-methylpyrazine. Especially when the molar ratio of Cu/Zn/Al = 2:1:2, the catalyst using nitrates as the
metal precursors improved the selectivity of 2-MP to 87.5%. 相似文献