共查询到20条相似文献,搜索用时 31 毫秒
1.
H. Shigematsu Y. Akishige T. Matsui T. Tojo H. Kawaji T. Atake 《Journal of Thermal Analysis and Calorimetry》2005,81(3):555-558
Summary The phase diagram of the mixed crystal (K1-xRbx)2SeO4 was determined by means of thermal analysis and neutron scattering experiments. The hexagonal to orthorhombic phase transition line exists for any x. The normal-incommensurate phase transition temperature decreases continuously with increasing Rb content. However, the incommensurate-commensurate phase transition was not observed except for K2SeO4. According to the clear softening of the Σ2- Σ 3 phonon branches and the finite frequency at 0 K for x>0.34, an existence of the hypothetical phase transition was confirmed. 相似文献
2.
Y. Akishige H. Shigematsu T. Tojo H. Kawaji T. Atake 《Journal of Thermal Analysis and Calorimetry》2005,81(3):537-540
Summary Specific heats on the single crystals of Sr2Nb2O7, Sr2Ta2O7 and (Sr1-xBax)2Nb2O7 were measured in a wide temperature range of 2-600 K. Heat anomalies of a λ-type were observed at the incommensurate phase transition of TINC (=495 K) on Sr2Nb2O7 and at the super-lattice phase transition of TSL (=443 K) on Sr2Ta2O7; the transition enthalpies and the transition entropies were estimated. Furthermore, a small heat anomaly was observed at the low temperature ferroelectric phase transition of TLOW (=95 K) on Sr2Nb2O7. The transition temperature TLOW decreases with increasing Ba content x and it vanishes for samples of x>2%. 相似文献
3.
Summary We have fabricated glasses in the Bi-2223 HTc superconductor system with Bi2Sr2Ca2Cu3-xErxO10+ δ nominal composition, where x=0.5 and 1.0, by the glass-ceramic technique. Using an analysis developed for non-isothermal crystallization studies, information on some aspects of crystallization temperature and thermal properties has been obtained. The crystallization studies were made using DTA with several uniform rates. The calculations of crystallization activation energies, Ea, and the Avrami parameters, n, were made based on the non-isothermal kinetic theory of Kissinger and the Ozawa’s equations. The DTA data of the samples showed that the first crystallization temperature, Tx1, increases and the second crystallization temperature, Tx2, decreases by increasing the Er concentration. This suggests that the Er substitution had significant effect on the glassification of the BSCCO material due to change on the surface nucleation and increased ionic activities at high temperature region. The activation energy for crystallization, Ea, of the samples was also showed an increase at high Er concentration case. However, the Avrami parameter, n, decreased from 2.5 to 1.7 for x=0.5 and 1.0 samples, respectively. This suggests that the growth mechanism is diffusion-controlled and three-dimensional parabolic growth takes place near the first crystallization temperature. The oxidization rates and the activation barrier for oxygen out-diffusion process, E, was calculated using the TG data. It was found that the total mass gain in the x=0.5 sample is comparably smaller than that of the x=1.0 sample. This shows that the oxygen absorption of the x=1.0 sample is faster than the x=0.5 sample, leading to increase in the oxidization rate in the x=1.0 material. 相似文献
4.
A. V. Knyazev N. G. Chernorukov N. Yu. Kuznetsov 《Russian Journal of Inorganic Chemistry》2011,56(12):1875-1878
Compounds of composition Li
x
Na1 − x
VWO6 (0 ≤ x ≤ 1), which are synthetic analogues of brannerite-type minerals, were produced for the first time by solid-state synthesis
at high temperatures. The structure of the compounds and their unlimited miscibility in the solid phase in the LiVWO6-NaVWO6 binary system were determined by X-ray diffraction. The phase equilibrium diagram was studied by differential thermal analysis
together with thermodynamic modeling. It was found that the system under investigation is described by the regular solid solutions
model. 相似文献
5.
Phase relations in
the solid state in the FeVO4–Co3V2O8
system, in the whole range of components concentration have been studied.
It was found that the composition of the phase of the howardevansite type
structure, formed in the investigated system, corresponds with the Co2.616Fe4.256V6O24 formula. The phase of the lyonsite type structure
has a homogeneity range with the Co3+1.5xFe4–xV6O24 formula (0.476 formula (0.476<x<1.667).
The melting temperature and the volume of the unit cell of the lyonsite type
structure phase increases together with the rise of cobalt quantity contained
in it. Basing on the results of the DTA and XRD measurements a phase diagram
of the FeVO4–Co3V2O8
system up to the solidus line was constructed. 相似文献
6.
Bulk samples of Se85-xTe15Bix glassy alloys are obtained by melt quenching technique. Differential scanning calorimetry has been applied to determine the
thermal properties of Se-rich Se85-xTe15Bix glassy alloys at different heating rates. The glass transition temperature (T
g) is found to shift to a higher temperature with increasing heating rate and with Bi addition. Activation energy and fragility
of the system is also calculated. Specific heat is evaluated and a jump in heat capacity is observed at T
g. Theoretical parameters viz; density, molar volume, number of atoms per unit volume, lone pair electrons and cohesive energy
of the system are also reported. 相似文献
7.
M. G. Zuev 《Russian Journal of Inorganic Chemistry》2007,52(3):424-426
The phase composition has been studied and an equilibrium phase diagram has been designed for the Al2O3-Li2O-R2O5 (R = Ta or Nb) systems in the subsolidus region up to 1000°C and 85 mol % Li2O. New phases with the composition Li1+x Al1?x O2?x , where x = 0–0.67, have been found. 相似文献
8.
S. A. Gromilov S. V. Korenev I. V. Korolkov K. V. Yusenko I. A. Baidina 《Journal of Structural Chemistry》2004,45(3):482-489
Synthesis of five binary complex salts with an [Ir(NH3)5Cl]2+ complex cation is described. The counterions are [ReCl6]2–, [IrCl6]2–, [ReBr6]2–, and Cl–. A polycrystal X-ray diffraction study has been performed for [Ir(NH3)5Cl]2[ReCl6]Cl2, and its crystal structure has been determined. A series of Ir
x
Re1–x
phases (0.5 x > 1) were obtained by reductive thermolysis. For the Ir-Re system, the history of the V/Z(x) dependence has been refined.Original Russian Text Copyright © 2004 by S. A. Gromilov, S. V. Korenev, I. V. Korolkov, K. V. Yusenko, and I. A. BaidinaTranslated from Zhurnal Strukturnoi Khimii, Vol. 45, No. 3, pp. 508–515, May–June 2004. 相似文献
9.
Anna Blonska-Tabero 《Journal of Thermal Analysis and Calorimetry》2008,93(3):707-710
A new phase Cd4Fe7+xV9+xO37+4x, where −0.5<x<1.5, has been obtained in the solid-state in the FeVO4−Cd4V2O9 system. The temperature of incongruent melting and the unit cell volume of this phase decrease with decreasing the content
of cadmium. The IR spectrum and SEM image of the new phase are presented. 相似文献
10.
R. L. Frost W. Martens M. O. Adebajo 《Journal of Thermal Analysis and Calorimetry》2005,81(2):351-355
Summary High resolution TG coupled to a gas evolution mass spectrometer has been used to study the thermal properties of a chromium based series of Ni/Cu hydrotalcites of formulae NixCu6-xCr2(OH)16(CO3)×4H2O where x varied from 6 to 0. The effect of increased Cu composition results in the increase of the endotherms and mass loss steps to higher temperatures. Evolved gas mass spectrometry shows that water is lost in a number of steps and that the interlayer carbonate anion is lost simultaneously with hydroxyl units. Differential scanning calorimetry was used to determine the heat flow steps for the thermal decomposition of the synthetic hydrotalcites. Hydrotalcites in which M2+ consist of Cu, Ni or Co form important precursors for mixed metal-oxide catalysts. The application of these mixed metal oxides is in the wet catalytic oxidation of low concentrations of retractable organics in water. Therefore, the thermal behaviour of synthetic hydrotalcites, NixCu6-xCr2(OH)16CO3×nH2O was studied by thermal analysis techniques in order to determine the correct temperatures for the synthesis of the mixed metal oxides. 相似文献
11.
Direct on-line studies of a C2HCl3/He/O2 microwave discharge plasma made possible the evolution and detection of many unfamiliar ionic species. Numerous ionic chlorocarbons,
chlorohydrocarbons, oxygenated chlorohydrocarbons, oxygenated hydrocarbon radicals, and simple hydrocarbon species were identified
mass spectrometrically as by-products: C
m
Cl
n
(m = 1–4, 6, 8; n = 1–8), C
m
H
n
Cl
x
(m = 1–4, 6, 7, 10; n, x = 1–6), C
m
H
n
Cl
x
O
y
(m = 1–5, 12; n = 1–7; x = 1, 2, 4, 6; y = 1–3),
C
n
H2n−1O (n = 2, 3), C
m
H
n
(m = 2, 4, 6, 8; n = 2, 4), and so on. The studies clearly showed the presence of various unfamiliar positive ionic O-containing species such
as C2ClO2, CCl3CO, C2H2Cl4O2, and C4H2Cl6O3. It is apparent that positive-ion reactions play a significant role in producing many ionic species in the chemistry of C2HCl3 plasmas. 相似文献
12.
Tatiana Nedoseykina Pavel Plyusnin Yuri Shubin Sergey Korenev 《Journal of Thermal Analysis and Calorimetry》2010,102(2):703-708
Thermolysis of double complex salt [Pd(NH3)4][AuCl4]2 has been studied in helium atmosphere from ambient to 350 °C. The XAFS of Pd K and Au L3 edges and thermogravimetry measurements have been carried out to characterize the intermediates and the final product. In
the temperature range 115–160 °C the complex is decomposed to form Pd(NH3)2Cl2 and AuCl4−x
N
x
species with x ranging from 2 to 3. Subsequent heating of the intermediate up to 300 °C leads to the total loss of NH3. The Au–Cl and Au–Au bonds form the local environment of Au at the stage of decomposition while only four chlorine atoms
are around Pd. At the temperature of 330 °C the Au and Pd nanoparticles as well as residues of palladium chloride are detected.
The final product consists of separated Au and Pd nanoparticles. 相似文献
13.
The influence of the synthesis conditions (rotation speed used for spin-coating deposition of the film, film drying temperature, and the ratio of the PbI2 and CH3NH3I reactants in solutions) on the microstructure, phase composition, and spectral-luminescent properties of films of organic-inorganic perovskite CH3NH3PbI3–xCl x (x = 0, 0.02) was elucidated. 相似文献
14.
Quentin Cacciuttolo Julien Vulliet Virginie Lair Michel Cassir Armelle Ringuedé 《Journal of Solid State Electrochemistry》2018,22(12):3663-3671
This paper is dedicated to the impact of pressure on the electrochemical behaviour of LSCF (La1-xSrxCoyFe1-yO3-δ) anode in high-temperature electrolysers. This study was carried out with symmetrical cells associating LSCF electrodes to a 3YSZ (yttrium-stabilised zirconia) electrolyte. Impedance spectroscopy measurements were performed using a three-electrode configuration, at temperature as high as 700 to 800 °C, in a pressure range from 1 to 30 bar. A clear improvement in terms of electrode resistance decrease is highlighted, mainly due to faster oxygen adsorption/desorption kinetics and a better supply of gas to electrochemical reaction sites. Other assumptions were considered and analysed, such as the impact of pressure on LSCF electrical conductivity and on the mechanical contacts. Thus, three contributions were determined as limiting steps at low pressure, up to 5 bar, whilst for higher pressure, the optimised conditions in operation are reached. This study completes a previous one related to a modelling approach. 相似文献
15.
L. F. Brum Malta Marta Eloisa Medeiros 《Journal of Thermal Analysis and Calorimetry》2005,81(1):149-152
Summary This work reports the room-temperature stabilization of the Bi4V2-xFexIIO11-1.5x γ ‘ phase, a promising ionic conductive material that finds application in solid oxide fuel cell and oxygen sensor devices. The Fe(II) cation proved to be a better stabilizer than Fe(III), which was previously used, since a lower substitution degree of V5+ is needed for the former. Powder X-ray diffraction, Fourier-transform infrared spectroscopy and differential scanning calorimetry were used in these experiments. 相似文献
16.
Qiangbin Yang Yi He Changjun Zou Jizhuang Wang Hongjie Li Dayong Qing 《Journal of Solid State Electrochemistry》2018,22(10):2969-2976
Molybdenum disulfide (MoS2) or tungsten disulfide (WS2), as a promising catalyst, is widely investigated for hydrogen evolution reaction (HER). In this work, a composite electrocatalysts MoxW1-xS2 is successfully decorated on carbon fiber paper (CFP) through a facile hydrothermal method. The three-dimensional porous CFP can enable the diffusion and penetration of electrolyte. Comparing with MoS2 and WS2 catalyst, the composite electrocatalyst MoxW1-xS2 nanosheets can expose the large number of electrochemically active sites. Hence, the as-prepared MoxW1-xS2/CFP (3:1) exhibit the outstanding HER catalytic activity with the small Tafel slope of 68 mV dec?1 and the low overpotential of ??178.4?±?0.5 mV at a current density of 10 mA cm?2. Chronoamperometric current test for 18 h confirm the long-term stability of the composite electrocatalyst. 相似文献
17.
The solubility and the physicochemical properties (densities, viscosities, refractive indices, conductivities and pH) in the
liquid-solid metastable system (NaCl-KCl-CaCl2-H2O) at 308.15 K have been investigated using the isothermal evaporation method, and the dry-salt phase diagram, water-phase
diagram, and the diagram of physicochemical properties vs. composition in the system were plotted. One three-salt cosaturated point, three metastable solubility isotherm curves, and
three crystallization regions corresponding to sodium chloride, potassium chloride and calcium chloride tetrahydrate were
formed, and neither solid solution nor double salts were found. On the basis of the extended Harvie-Weare (HW) model and its
temperature-dependent equation, the values of the Pitzer parameters β(0), β(1), C
ϕ for NaCl, KCl and CaCl2, the mixing ion-interaction parameters θNa,K, θNa,Ca, θK,Ca, ΨNa,K,Cl, ΨNa,Ca,Cl, ΨK,Ca,Cl, and the Debye-Hückel parameter A
ϕ and the chemical potentials of the minerals in the quaternary system at 308.15 K were fitted, and the predictive solubility
based on the temperature-dependent equation and the chemical potentials of the minerals agrees well with the experimental
data. 相似文献
18.
19.
N. B. Babanly Z. E. Salimov M. M. Akhmedov M. B. Babanly 《Russian Journal of Electrochemistry》2012,48(1):68-73
The EMF method with a solid Cu+-conducting electrolyte of Cu4RbCl3I2 was sued to study the Cu-Tl-Te system in the temperature range of 300–420 K. A diagram of solid-phase equilibriums of this
system is constructed, partial molar functions of copper in alloys, standard thermodynamic functions of formation and standard
entropies of CuTlTe2, CuTl4Te3, Cu2TlTe2, Cu3TlTe2, Cu9TlTe5 triple compounds and Cu
x
Tl5 − x
Te3 solid solutions (0 < x < 1) are calculated. The obtained results confirmed the assumption as to the possibility of using this modification for the
EMF technique for thermodynamic studies of copper-containing triple systems, even if they contain a less noble component than
copper. 相似文献
20.
G. Nenartaviciene K. Tõnsuaadu D. Jasaitis A. Beganskiene A. Kareiva 《Journal of Thermal Analysis and Calorimetry》2007,90(1):173-178
In this study the formation of chromium substituted YBa2Cu4O8 (Y-124) superconductors has been investigated by TG/DTA measurements. The YBa2(Cu1−xCrx)4O8 ceramics with nominal compositions of x=0.01, 0.03, 0.05, 0.10 and 0.20 have been prepared by an aqueous sol-gel method using aqueous mixtures of the corresponding
metal acetates and nitrates. Homogeneous precursor gels were obtained by complexing metal ions with tartaric acid. To assist
the interpretation of the results obtained the synthesis products were additionally characterized by X-ray powder diffraction
(XRD) and resistivity measurements. It was determined that doping the YBa2Cu4O8 phase with chromium has a strong effect on the phase purity and superconducting properties of the synthesis products. 相似文献