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1.
The preparation of rutile type solid solutions in (TiO2)x -(RuO2)1−x system in the 0≤x ≤0.7 concentration range is described. The single phase solid solutions are formed by controlled nanocrystallization of amorphous
gels prepared by the sol-gel method. The kinetics of this crystallization process has been analyzed. It was found that the
crystallization does not correspond to the Johnson-Mehl-Avrami model and it can be described by the two-parameter Šesták-Berggren
kinetic model.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
2.
This study reports experimental investigations by DTA/TG analysis of (1−x)SnO2−xCuO compositions, up to 1773 K and at two oxygen partial pressures (i.e. air and argon). In air, DTA/TG results showed thermal
effects due exclusively to CuO presence in the initial mixture. No binary compounds were formed. The reduction process of
CuO to Cu2O over 1273 K as well as the formation over 1373 K of the liquid phase, have been evidenced. In argon atmosphere, CuO to Cu2O reduction reaction is shifted toward 1205 K, while the liquid phase appears in the studied mixtures over 1473 K. The formation
of an eutectic composition between SnO2−Cu2O, melting at 1491 K, coordinates:0.932Cu2O+0.068SnO2, has been experimentally established in argon.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
3.
A. Książczak T. Książczak T. Zielenkiewicz 《Journal of Thermal Analysis and Calorimetry》2004,77(1):233-242
DSC method was used to study thermal stability of nitrocompounds. It was assumed the model to estimate stability of solid
phase in which perfect solid phase is totally stable and amorphous-liquid domains connected with impurities decompose according
to the kinetic model determined for the liquid phase above the melting point. The influence of sample purity on relative stability,
which is k
l/k
s — ratio of decomposition rate constants in liquid and solid phase, at temperature 20 K below the melting point was predicted.
The increase of liquid domains in solid phase causes decrease of k
l/k
s ratio (relative stability) at chosen temperature.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
4.
The binary and ternary systems M'O(M'CO3)-Nb2O5 and M'O(M'CO3)-MO-Nb2O5, where M'=Ca,Sr and Ba and M=Cu, Ni, Cd, Zn and Pb, were investigated by means of thermal analysis in the temperature range 20–1500°C. The boundaries
of stability of the solid solutions Sr2−xMexNb2O7,Sr2−xMxNb2O7, Sr4−xMxNb2O9 and Sr6−xMxNb2O11 were determined by means of X-ray diffraction, and IR and Raman spectroscopy. The possibility of prognostication of the phase
fields of stable solid solutions by calculation from the diagrams of the ‘comparative electronegativity of atoms vs. tolerance
factor’ was demonstrated. The kinetic parameters of the interactions in theSrCO3+MO+Nb2O5 powder mixtures were established.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
5.
The thermal stability of the solid solutions of Fe2Mo1–xTixO4 for x=0.0 to 1.0 in air, had been investigated in the temperature range 303–1173 K using differential thermal analysis and thermogravimetry
(DTA and TG). The products obtained by heating the sample in air, at different temperatures, have been characterized by X-ray
diffraction and IR-studies. The results show that all the ferrite samples undergo surface oxidation during initial heating.
On heating to 823 K, the samples undergo oxidation of the octahedral site cations only and forma cation deficient spinel phase.
On further heating in air, the ferrites undergo complete oxidation.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
6.
The oxidation of Ni100–xPx(7.3 at%<x<25.0 at%) powders in air in the temperature range 350–450°C was determined by kinetics and X-ray diffraction. The isothermal
kinetics was modeled using theGinstling–Brounstein equations. The oxidation process was found to be thermally activated with
activation energy 127.8 kJ mol–1 for x=7.3 at% to 157.7 kJ mol–1 for x=25.0 at%. It was found that the rate constants for x=7.3 at% were approximately 100 times lower than those for x=25.0 at%.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
7.
For one-dimensional model of porous electrode (PE), an equation for the ideal ratio between the local conductivities of liquid
phase κL(x) and solid phase κs(x), which provides uniform distributions of potential and current inside the PE, is obtained. It is shown that the principal
possibilities of levering action of both phases are similar; however, the shapes of their ideal conductivity profiles are
mirror-opposite. To gain a beneficial effect at the expense of conductivity of liquid phase, κL(x) should increase monotonically from the rear current lead to the frontal side of PE provided that the conductivities of phases
are equal in the middle of PE. The effect of distortions of ideal κL(x) profile is analyzed. It is found that, with regard to the natural upper limit of solution conductivity, the best conditions
for the levering action of ideal κL(x) profile should be expected in the porous matrices with low conductivity. It is shown that the formation of even few zones
with opposite-shaped κL(x) profile inside PE (the solution conductivity decreases towards the frontal side of PE) leads to more nonuniform potential
distribution and a decrease in the PE operation efficiency (especially at high total current density). 相似文献
8.
Two mixtures of the binary system K-behenate/glycerol, x
KC22 = 0.30 and 0.50 (x = mole fraction), have been investigated as a function of temperature using small- and wide-angle X-ray diffraction (XRD)
and differential scanning calorimetry (DSC). The binary phase diagram based on texture observations using polarizing optical
microscopy was confirmed. XRD and DSC measurements provided concordant results with respect to the range of the phase regions
in the phase diagram. Only differences between the DSC curves for rising and falling temperatures were detected. The recorded
XRD and DSC data of the liquid crystals and gel phases observed are also in agreement with previously reported investigations
on K-soap/glycerol. The C ⇆ G and G ⇆ Lα phase transitions correlate with a sharp shift in the d value of the first small-angle reflection. The G phase is characterized by a split of the first small-angle reflections.
Also, the position and shape of the wide-angle reflections change and the peak intensity is reduced.
Received: 5 July 1999 Accepted in revised form: 27 July 1999 相似文献
9.
The electrochemical behaviour of new doped Li-M-Mn-O (M = Al, Fe, Ni) spinel oxides in liquid electrolyte lithium cells was
studied. The insertion electrode materials were obtained by heating stoichiometric amounts of thoroughly mixed LiOH and M
x
Mn1−
x
CO3 (M = Fe, Ni; x = 0.08−0.15) or Al
x
Mn1−
x
(CO3) (OH)
y
, in the case of Al, at 380 °C in air for 20 h. The transition metal-doped samples, particularly those containing Ni or obtained
at low temperatures, where the resulting spinel was cation-deficient and highly disordered, exhibited the best cycling performance
in the potential window 3.3−2.3 V. Cell capacity was retained by 80% after 200 cycles. Capacity fading was observed on increasing
the firing temperature, together with improved crystallinity and the disappearance of cation vacancies. This impaired electrochemical
behaviour is ascribed to a Jahn-Teller effect, which induces an X-ray-detectable cubic-tetragonal phase transition upon lithium
insertion. The phase transition was undetectable in the low-temperature samples. The influence of the Jahn-Teller distortion
is thus seemingly lessened by a highly disordered structure.
Received: 25 November 1997 / Accepted: 28 January 1998 相似文献
10.
A multicomponent system of complex refractory oxides of the composition Zn2 − x
(Zr
a
Sn
b
)1 − x
Fe2x
O4 (a + b = 1; a: b = 1: 5, 1: 4, 1: 3, 1: 2, 1: 1, 2: 1, 3: 1, 4: 1; x = 0−1.0; Δx = 0.05) was studied by X-ray diffraction. The samples were prepared from oxides of appropriate metals by low-temperature
plasma synthesis (hydrogen-oxygen flame). Two phases with wide homogeneity ranges were identified: α phase crystallized in
the crystal system of inverse cubic spinel and β phase with the structure of tetragonal spinel. The phase boundaries were
found. Structural data are presented for about 100 solid solutions. 相似文献
11.
The sorption kinetics for the removal aldehydes from aqueous solutions with Amberlite XAD-16 and MPP particles impregnated
with Primene JM-T was investigated. A model, accounting for the simultaneous mass transfer and chemical reaction, is developed
to describe the process. It is based on the analogy to the diffusion and reaction in a stagnant liquid sphere, but corrected
for the porosity and particle properties influencing the diffusion. The developed model describes the kinetic behavior of
the process in the low concentration region rather well. However, in the high concentration region, larger discrepancies are
observed. Initially, the influence of the flow rate was investigated to eliminate the effect of the external mass transfer.
The influence of the particle morphology was investigated for both physical and reactive sorption. Physical sorption experiments
were used to determine the factor τ that takes the particle properties influencing the diffusion into account. It was shown that the diffusion is faster in XAD-16
than in MPP impregnated systems. Reaction rate constant k
x
was determined by fitting the model to the experimental data. Sorption of benzaldehyde appears to be significantly slower
(k
x
∼10−4 l/mol s) than the sorption of pentanal (k
x
∼10−3 l/mol s) due to the slower chemical reaction. The influence of the particle size was investigated for the sorption of pentanal
with XAD-16. It was observed that the particle size does influence the diffusion term, but does not have an effect on the
reaction rate. On the other hand, the extractant loading influences the reaction rate slightly in the low concentration region,
whereas the initial concentration of the solute has more pronounced effect. 相似文献
12.
Hashimoto T. Yoshinaga M. Ueda Y. Komazaki K. Asaoka K. Wang S. 《Journal of Thermal Analysis and Calorimetry》2002,69(3):909-917
The phase transitions of Ba2-xSrxIn2O5 were investigated with various thermal analyses and high-temperature X-ray diffraction. It was clarified that crystal structure
of Ba2-xSrxIn2O5 with x=0.0~0.4 varies from brownmillerite through distorted perovskite to another distorted perovskite with increase of temperature.
The phase transition from brownmillerite to distorted perovskite was revealed to be first order, whereas transition from distorted
perovskite to another one was second order. The specimen with x≥0.5 showed only one first order phase transition from brownmillerite to distorted perovskite. The phase diagram of Ba2-xSrxIn2O5 was established and existence of tricritical point at ~1100°C with x=0.4~0.5 was suggested.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
13.
DSC was used for heat capacity measurements of pure RuO2 in the temperature range from 300 to 1170 K of solid solutions corresponding to the compositions of (Ti1−x Rux )O2 (x ≤0.15 and x ≥0.85) and in the temperature range from 300 to 1550 K of pure TiO2. The analysis of experimental data obtained within ±2%
of accuracy has shown that the characteristic temperatures representing the harmonic lattice vibrations do not strongly depend
on the chemical composition x . It was demonstrated that non-harmonic heat capacity is strongly correlated to x. The existence of additional excess heat
capacity was observed with the mixed oxide solid solution samples of low Ru content and explained by the defect formation
model.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
14.
Y. Arita T. Ogawa B. Tsuchiya T. Matsui 《Journal of Thermal Analysis and Calorimetry》2008,92(2):403-406
Heat capacities, electrical conductivities and phase transition temperature of hafnium hydrides, HfHx (0.99≤x≤1.83), were studied using a direct heating pulse calorimeter and a differential scanning calorimeter from room temperature
to above 500 K. The heat capacity of HfH1.83 was larger than that of pure hafnium and showed no anomaly of heat capacity. In contrast, there were λ-type peaks for the
heat capacity and DSC curves for HfHx (1.1≤x≤1.6) near 385 and 356 K. The anomalies of heat capacity and electrical conductivity of HfHx (1.1≤x≤1.6) were considered the result of phase transition and order-disorder phase transition for hydrogen in the hafnium hydride
lattice for HfHx (1.1≤x≤1.3). 相似文献
15.
DTA and XRD studies of the Fe2V4O13–Cr2V4 O13 system have shown that continuous solid solutions of a Fe2–xCrxV4O13 type, bearing a Fe2 V4 O13 structure, are formed in the system. With the increasing degree of the Cr3+ ion incorporation into the Fe2 V4 O13 structure, a contraction of the solid solution crystal lattice develops. Solid solutions of a Fe2–x Crx V4 O13 type melt incongruently, their melting temperature increasing from 953 to 1003 K with increase in the degree of the Cr3+ ion incorporation. The solid product of melting Fe2–x Crx V4 O13 solid solutions for 0.2<x >1.2 is the Fe1–x Crx VO4 solution phase, and for x ≤0.2 and x ≥1.4 – the Fe1–x Crx VO4 phase as well as FeVO4 or CrVO4 , respectively.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
16.
Leszek Rycerz Ewa Ingier-Stocka Slobodan Gadzuric Marcelle Gaune-Escard 《Journal of Thermal Analysis and Calorimetry》2010,101(2):455-461
Differential Scanning Calorimetry was used to study phase equilibrium in EuBr2–RbBr binary system. It was established that this system includes two eutectics and three stoichiometric compounds. First
of them, Rb2EuBr4, decomposes peritectically at 778 K. Second one, RbEuBr3, undergoes the solid–solid phase transition at 732 K and melts incongruently at 852 K. Third compound, RbEu2Br5, melts congruently at 888 K. The composition and temperature values of eutectics were determined as x(EuBr2) = 0.316; T
eut = 776 K and x(EuBr2) = 0.797; T
eut = 859 K. Mixing enthalpy was measured by direct calorimetry on the whole composition range. The minimum of the mixing enthalpy
occurs around the composition x(EuBr2) ≈ 0.4. The electrical conductivity of liquid mixtures was also investigated over the whole composition range and measured
down to temperatures below solidification. The specific conductance (liquid phase) plotted against the mole fraction of EuBr2 shows a broad minimum at x(EuBr2) ~ 0.6. The activation energy for conductivity changes with temperature. Results obtained are discussed in terms of possible
complex formation. 相似文献
17.
F. Skuban D. M. Petrović S. R. Lukić M. M. Garić I. O. Gúth 《Journal of Thermal Analysis and Calorimetry》2000,59(3):877-883
The paper describes results of a study of glasses of the type Cux (AsSe1.4 I0.2 )100–x for x =0, l, 5, 10, 15, 20 and 25 at% Cu, by the methods of thermomechanical analysis. Values of the thermal coefficients of linear
expansion in solid and visco-plastic phase were determined and the dependence of this parameter on copper concentration was
established. The experimental method used enabled the determination of characteristics glass transition temperature and the
temperature of the beginning of deformation, and it was found that these parameters increase with increase in the copper content.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
18.
X-ray phase analysis (XRD), differential thermal analysis (DTA) and IR spectroscopy have shown that continuous substitution
solid solutionsin are formed in the FeVMoO7–CrVMoO7 system. With increasing the degree of Cr3+ ion incorporation into the FeVMoO7 structure, a crystal lattice contraction of the Fe1–xCrxVMoO7 solid solution arise. Elevation of temperature of its incongruent melting and gradual shifting of the corresponding IR absorption
bands towards higher wavenumbers have been noticed, as well. The solid product of incongruent melting for x≤0.5 is the Fe4–yCryV2 Mo3 O20 solid solutions phase, whereas for x>0.5 Fe2–zCrz(MoO4)3 and Fe2–u Cru O3 solid solutions.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
19.
I. V. Baklanova V. N. Krasil’nikov L. A. Perelyaeva O. I. Gyrdasova 《Theoretical and Experimental Chemistry》2011,47(4):215-218
lid solutions Ti1−x
M
x
O2−x/2 in the anatase and rutile forms were obtained from the precursors Ti1−x
M
x
(OCH2CH2O)2−x/2 at T = 450–900 °C. The temperature and concentration dependence of the phase transformation of anatase to rutile in Ti1−x
M
x
O2−x/2 was investigated by Raman spectroscopy. It was shown that the anatase phase is stabilized most effectively by the Eu3+ dopant. 相似文献
20.
D. A. Medvedev T. A. Zhuravleva A. A. Murashkina V. S. Sergeeva B. D. Antonov 《Russian Journal of Physical Chemistry A, Focus on Chemistry》2010,84(9):1623-1627
The phase composition, linear thermal expansion coefficient, electroconductivity (in the temperature interval 600–900°C and
partial pressures of oxygen 10−5–0.21 atm) of solid-oxide materials based on gadolinium-barium cobaltite doped with 3d-elements BaGdCo2 − x
Me
x
O5 + δ, Me = Cu, Fe; x = 0.0, 0.2, …, 2.0 were investigated. The homogeneity regions of samples were established by means of X-ray phase analysis.
It was shown that the linear thermal expansion coefficient of cobaltite decreases with an increase in the copper or iron concentration.
It was established that the electroconductivity of BaGdCo2 − x
Me
x
O5 + δ decreases with an increase in x. We concluded that upon a decrease in p(O2), the electroconductivity of samples first decreases and then reaches a horizontal plateau. 相似文献