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1.
A. Braileanu M. Zaharescu D. CriŞan D. FĂtu E. Segal C. Danciulescu 《Journal of Thermal Analysis and Calorimetry》1996,47(2):569-575
Former studies concerning the formation of the compounds in the pseudobinary systems of Bi2O3-MO type (M =Ca, Sr, Ca+Sr) have shown that the reaction which occurs with the highest rate is that between Bi2O3 and CaO. In the present work CaCO3 was used as CaO source. We carried out an investigation of the thermal decomposition of CaCO3 in the presence of Bi2O3 in comparison with the decomposition of pure CaCO3.The presence of Bi2O3 exerts a complex influence on the CaCO3 decomposition acting on the nucleation as well as on the diffusion of CO2. The decomposition of the samples with low Bi2O3 content follows the mechanism of a contracting sphere. A change from surface nucleation to bulk nucleation is recorded for higher amounts of Bi2O3. 相似文献
2.
Fe2O(SO4)2 is a secondary product of the decomposition of FeSO4⋅H2O. Part I of this study presents results on the synthesis of Fe2O(SO4)2 in gaseous environment containing either low or high concentration of oxygen. In this paper the existence of differences
between the structures of Fe2O(SO4)2 and Fe2(SO4)3 is proved on the basis of a detailed thermal study of Fe2O(SO4)2 upon dynamic heating (differential thermal analysis) and upon isothermal heating (thermal-analytic balance) in various gaseous
environments as well as by presenting kinetic data on the processes of decomposition of both compounds.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
3.
Tetracyanonickelate compounds as sorptive materials and the substitution of their H2O content by D2O
Anna Sopková Katarína Györyová Michal Šingliar 《Journal of inclusion phenomena and macrocyclic chemistry》1986,4(4):369-377
The compounds NiNi(CN)4·3,5H2O and Ni(NH3)2Ni(CN)4·H2O have been studied to examine the possibility of substituting their H2O or NH3 content by D2O. Contact with D2O was performed after heating the compounds to several temperatures. Depending on the degree of decomposition of the original compounds different ranges of substitution were possible. In such manner the compounds NiNi(CN)4·3,5D2O, NiNi(CN)4·5D2O, Ni(NH3)2Ni(CN)4·D2O, and Ni(D2O)2Ni(CN)4·D2O were prepared and thermally they were less stable than the original ones. The substitution by D2O is in agreement with the sorptive properties of the original tetracyanonickelate against different organic compounds using GC, since these could substitute the guest component and sometimes also the ligands during their decomposition. 相似文献
4.
V. Parvanova 《Journal of Thermal Analysis and Calorimetry》2006,86(3):761-765
Potassium
peroxotitanate was synthesized by the peroxo method. During the thermal decomposition
K2Ti2O5
can be obtained. The isothermal conditions for decomposition of K2[Ti2(O2)2(OH)6]·3H2O
were determined on the base of DTA, TG and DSC results. DTA and TG curves
were recorded in the temperature range 20 and 900°C at a heating rate
of 10°C min–1. The obtained intermediate
compounds were characterized by means of quantitative analysis and IR spectroscopy.
The mechanism of thermal decomposition of K2[Ti2(O2)2(OH)6]·3H2O to K2Ti2O5
was studied. The optimal conditions for obtaining K2Ti2O5
were determined (770°C for 10 h). 相似文献
5.
Yuying Yang Zhongai Hu Xiuli Shang Renjiang Lv Chao Kong Hongxiao Zhao 《Frontiers of Chemistry in China》2006,1(1):59-62
In this study, a novel method was used to prepare well-separated and spherical tricobalt tetraoxide (Co3O4) nanosized particles. The overall process involves three steps: preparation of insoluble carboxyl-containing grafted starch
copolymer (ISC), formation of precursor (ISC-Co), decomposition of ISC-Co, and phase transition of Co3O4 nanoparticles. The Infrared spectra used for ISC and ISC-Co are discussed. The decomposition of the precursor was studied
by thermogravimetric-differential thermal analysis, the crystalline phase was characterized by x-ray diffraction, and the
size distribution and shape of particles were observed by transmission electron microscopy.
Translated from Journal of Northwest Normal University (Natural Science Edition), 2005, 5(5) (in Chinese) 相似文献
6.
V Parvanova 《Journal of Thermal Analysis and Calorimetry》2006,86(2):443-447
Bi-peroxotitanate
was synthesized by a peroxo method and after thermal decomposition Bi2Ti2O7
was obtained. DTA, TG and DSC curves of Bi2[Ti2(O2)4(OH)6]5H2O were recorded and used to determine
isothermal conditions suitable for obtaining the intermediate samples corresponding
to the phases observed during the thermal decomposition. The samples were
identified by quantitative analysis, IR spectroscopy and X-ray analysis. The
experimental results were used to propose a mechanism of thermal decomposition
of the investigated compound to a nanosized Bi2Ti2O7.
The optimum conditions were also determined for obtaining Bi2Ti2O7,
which is applicable for piezosensors. 相似文献
7.
Zhenmian Shao Sébastien Saitzek Pascal Roussel Olivier Mentré Felicia Prihor Gheorghiu Rachel Desfeux 《Journal of solid state chemistry》2010,183(7):1652-1662
A series of compounds with the general formula (La1−xNdx)2Ti2O7 (0.0≤x≤1.0) has been prepared by the sol-gel method. The decomposition of the gel was characterized by thermo-gravimetric analysis coupled to mass spectrometry, indicating the reaction is achieved above 850 °C. The lattice parameters versus x show an expected decrease in the a and b parameters while c and the β angle remain almost unchanged with respect to the monoclinic symmetry conserved for the full solid solution. Dielectric, piezoelectric and ferroelectric properties were measured on the entire series. 相似文献
8.
The solubility isotherm of the system Dy2O3-SeO2-H2O at 100°C was studied and drawn. The selenites present in the system were identified and isolated. A thorough TG, DTG and DTA analysis was made. By modelling the conditions of TG, DTG and DTA analysis, the phases of the thermal decomposition were isolated and identified. The chemistry of the reaction was described. 相似文献
9.
W. Xinmin Q. Chuansong Q. Songsheng T. Zhicheng 《Journal of Thermal Analysis and Calorimetry》2007,90(2):569-573
Rare-earth perchlorate complex coordinated with glycine [Nd2(Gly)6(H2O)4](ClO4)6·5H2O was synthesized and its structure was characterized by using thermogravimetric analysis (TG), differential thermal analysis
(DTA), chemical analysis and elementary analysis. Its purity was 99.90%. Heat capacity measurement was carried out with a
high-precision fully-automatic adiabatic calorimeter over the temperature range from 78 to 369 K. A solid-solid phase transformation
peak was observed at 256.97 K, with the enthalpy and entropy of the phase transformation process are 4.438 kJ mol−1 and 17.270 J K−1 mol−1, respectively. There is a big dehydrated peak appears at 330 K, its decomposition temperature, decomposition enthalpy and
entropy are 320.606 K, 41.364 kJ mol−1 and 129.018 J K−1 mol−1, respectively. The polynomial equations of heat capacity of this compound in different temperature ranges have been fitted.
The standard enthalpy of formation was determined to be −8023.002 kJ mol−1 with isoperibol reaction calorimeter at 298.15 K. 相似文献
10.
The thermal decomposition of Co(NO3)2·6H2O (1) as well as that one of NO[Co(NO3)3] (Co(NO3)2·N2O4) (2) was followed by thermogravimetric (TG) measurements, X-ray recording and Raman and IR spectra. The stepwise decomposition reactions of 1 and 2 leading to anhydrous cobalt(II)nitrate (3) were established. In N2 atmosphere, cobalt oxides are finally formed whereas in H2/N2 (10% H2) cobalt metal is produced. Rapid heating of cobalt(II)nitrate hexahydrate causes melting (formation of a hydrate melt) and therefore side reactions in the hydrate melt by incoupled reactions and evolution/evaporation of different species as, e.g., HNO3, NO2, etc. In case of larger amounts in dense packing in the sample container, the formation of oxo(hydoxo)nitrates is possible at higher temperature. For 2, its thermal decomposition to 3 was followed and its decomposition mechanism is proposed. 相似文献
11.
K. Przybylski T. Brylewski M. Bućko 《Journal of Thermal Analysis and Calorimetry》1995,45(5):1099-1108
Calcination conditions of the precursor powders, i.e. temperature, type of atmosphere and duration, were determined with a view to obtain superconducting powders with the most advantageous physico-chemical properties. Investigated were powders in the Y?Ba?Cu?O system prepared by the sol-gel method. Thermogravimetric examinations of the powders have revealed that the decomposition kinetics of BaCO3 determines the formation rate of the superconducting YBa2Cu3O7?x (‘123’) phase. It follows from the decomposition kinetics of BaCO3 that the process is the most intensive in argon, whereas in static air and oxygen it is the slowest. The phase composition analysis (XRD) and low-temperature magnetic susceptibility measurements of the calcinated powders, confirm the above mentioned changes in the decomposition kinetics. The reaction of barium carbonate can be completed if the calcination process is conducted at the temperature of 850°C for 25 h, yielding easily sinterable powders for obtaining single-phase superconducting bulk samples with advantageous functional parameters. 相似文献
12.
Single crystals of KNbO3 (KN), KTaO3 (KT), and KTa1−xNbxO3 (x=0.44, KTN) have been prepared by hydrothermal synthesis in highly concentrated KOH mineralizer solutions. The traditional problems of inhomogeneity, non-stoichiometry, crystal striations and crystal cracking resulting from phase transitions associated with this family compounds are minimized by the hydrothermal crystal growth technique. Crystals of good optical quality with only minor amounts of metal ion reduction can be grown this way. Reactions were also designed to provide homogeneous distribution of tantalum and niobium metal centers throughout the KTN crystal lattice to maximize its electro-optic properties. Synthesis was performed at relatively low (500-660 °C) temperatures in comparison to the flux and Czochralski techniques. This work represents the largest crystals of this family of compounds grown by hydrothermal methods to date. 相似文献
13.
Preparations were characterized by specific surface area, thermogravimetry, and X-ray diffractometry. Thermal effects observed were (a) sulfur loss, (b) sintering, (c) crystallization and transformation of the crystalline phase(s). Thermoanalytical curves indicate that decomposition of the sulfate occurs in two distinct steps. Decrease of surface area due to (b) and (c) is concomitant to decomposition of sulfate. Sulfate was found to hinder sintering, crystallization and phase transformations of ZrO2 and TiO2. In low-titania and -zirconia sulfated TiO2-ZrO2 the minor component enhances the effect of sulfate. In equimolar TiO2-ZrO2 sulfate decomposition is accompanied by rapid formation of crystalline TiZrO4.This work was supported by the MOL Rt., Hungary, which is gratefully acknowledged. 相似文献
14.
The decomposition pattern of tetraalkyl-tetrathiomolybdates with general formula (R4N)2MoS4 (with R increasing from methyl to heptyl) was determined by means of differential thermal analysis (DTA), thermogravimetric analysis (TGA) and mass spectroscopy (MS) techniques. The complexity of thermal decomposition reactions increases with the size of the R4N group. Prior to decomposition at least one phase transition seems to occur in all complexes. The onset of thermal reactions was also a function of the tetra-alkylammonium precursor. All compounds decompose without forming sulfur rich MoS2+x intermediates. For R = methyl to pentyl precursors the MoS2 produced was nearly stoichiometric, however for R = hexyl and heptyl the S content was significantly reduced with a Mo:S ratio of about 1.5. The carbon and hydrogen residual contents in the product increased with the number of C atoms in R4N; for N contamination no clear trend was obvious. SEM images show that the formation of macro-pores was also a function of the alkyl group in R4N. The MoS2 materials obtained show a sponge-like morphology. Results of DSC experiments in combination with in situ X-ray diffraction also revealed the complex thermal behavior of (R4N)2MoS4 materials; reversible and irreversible phase transitions and glass-like transformations were identified in the low temperature range (35-140 °C), before the onset of decomposition. 相似文献
15.
[Fe(N2H4)2(CH3COO)2] was synthesised and characterized for the first time by chemical analysis, magnetic measurements, electronic and IR spectral studies. Its thermal reactivity was ascertained by thermogravimetric (TG) and derivative thermogravimetric (DTG) techniques and it has been concluded that unlike some other metal carboxylate hydrazinates, it does not show any autocatalytic behaviour. The decomposition was also subjected to kinetic analysis using the equations of Coats-Redfern and Horowitz-Metzger by the method of weighted least-squares. 相似文献
16.
Thermodynamical data of rare earth complexes with amino acid are important for engineering chemistry and fundamental chemistry.
However, they have rarely been reported. In this work, a series of crystalline complexes of rare earth perchlorate coordinated
with glutamic acid have been synthesized in water medium, and their thermodynamical data, including the heat capacity in low
temperature range and the standard enthalpy of formation, were determined. These complexes were identified to be [RE2(Glu)2(H2O)8](ClO4)4·H2O (RE = Nd, Eu, Dy) by using thermogravimetric analysis (TG), differential thermal analysis (DTA), and chemical and elementary
analyses. Their purity has been determined. No melting points were observed for all the three complexes. The heat capacity
of the complexes was measured by an adiabatic calorimeter from 79 to 370 K. Abnormal heat capacity values were detected for
two of the complexes and the decomposition range of one complex was found. The temperature, enthalpy change and entropy change
of the decomposition processes of the three complexes were calculated. The polynomial equations of heat capacity in the experimental
temperature range have been obtained by least squares fitting. The standard enthalpy of formation was determined by an isoperibol
reaction calorimeter at 298.15 K.
Supported by the Research Fund of Beijing Institute of Petro-Chemical Technology (N06-06) 相似文献
17.
The synthesis and thermal decomposition of Na2(SO4)2·2H2O in both air and nitrogen are described. The synthesis was performed by two different procedures, but in both cases the same product was obtained, corresponding to the general formula given above. The crystals obtained were investigated by methods of X-ray powder diffraction, and chemical and thermal analysis. The differences in thermal decomposition in air and nitrogen are discussed. 相似文献
18.
Treatment of H2S and NH3 using the non-thermal plasma (NTP) methods was investigated. Two NTP systems were used in this study, one consisting of a multi-cell plate-to-wire reactor (PTW), and the other consisting of an ozonization chamber and the multi-cell PTW reactor. Each cell of the PTW reactor had a sheet of copper foil embedded in dielectric layers as its high voltage electrode and a wired rack as its gounded electrode. Use of the wired rack type electrode allowed large flow throughput, and promoted intense local electric fields. The experiments showed that under constant energy input, the decomposition efficiency of H2S or NH3 decreased with increasing initial concentration of the gas, and increased with increasing injected ozone and relative humidity. Injection of NH3 into H2S stream did not improve the H2S decomposition efficiency but was necessary for removal of sulfite-containing compounds in the discharge air. 相似文献
19.
Sagrario M. Montemayor L. A. García-Cerda J. R. Torres-Lubián O. S. Rodríguez-Fernández 《Journal of Sol-Gel Science and Technology》2007,42(2):181-186
In this work the synthesis of CoFe2O4-SiO2 and NiFe2O4-SiO2 nanocomposites was studied via the sol–gel method, using the polymerized complex route. The polymerized precursors obtained
by the reaction of citric acid, ethylene glycol, tetraethylorthosilicate, ferric nitrate, and cobalt nitrate or nickel chloride
were characterized by nuclear magnetic resonance (NMR) and infrared (IR) spectroscopy. NMR and IR spectra of the precursors,
without and with metallic ions, show the formation of polymeric chains with ester and ether groups and complexes of metal-polymeric
precursor. The nanocomposites were obtained by the thermal decomposition of the organic fraction and characterized by X-ray
diffraction (XRD) and vibrating sample magnetometry (VSM). XRD patterns show the formation of CoFe2O4 and NiFe2O4 in an amorphous silica matrix above 400 °C in both cases. When the calcination temperature was 800 °C the particle size of
the crystalline phases, calculated using the Scherrer equation, reached ∼35 nm for the two oxides. VSM plots show the ferrimagnetic
behavior that is expected for this type of magnetic material; the magnetization at 12.5 KOe of the CoFe2O4-SiO2 and NiFe2O4-SiO2 compounds was 29.5 and 17.4 emu/g, respectively, for samples treated at 800 °C. 相似文献
20.
Thermal decomposition of Bi(SCN)3, Cd(SCN)2, Pb(SCN)2 and Cu(SCN)2 has been studied. The thermal analysis curves and the diffraction patterns of the solid intermediate and final products of the pyrolysis are presented. The gaseous products of the decomposition (SO2 and CO2) were detected and quantitatively determined. Thermal, X-ray and chemical analyses have been used to establish the nature of the reactions occurring at each stage in the decomposition.This revised version was published online in November 2005 with corrections to the Cover Date. 相似文献