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2.
The phase equilibria in the solid state in the system FeVO 4?CCu 3V 2O 8 and FeVO 4?CCuO have been determined. Based on the obtained DTA and XRD analysis results and some additional research, a phase diagram in the whole subsolidus area of the system CuO?CV 2O 5?CFe 2O 3 has been worked out. Eighteen subsidiary subsystems can be distinguished in this ternary system. Basic properties of the obtained phases with howardevansite- and lyonsite-type structure have been investigated by DTA, IR, and SEM methods. 相似文献
3.
The effect of mechanical activation on the structure and thermal reactions of glasses has been studied on the example of Na–Al–Fe
phosphate glasses. These glasses are used in nuclear technology for immobilization of radioactive waste. The glasses were
activated by grinding in a planetary mill. Mechanical activation causes a decrease of the T
g temperature as well as of the glass crystallization temperature. The type of crystalline phases formed and the quantitative
proportions between them are changing. Analysis of inter-atomic interactions in the structure of glass was applied to explain
the observed regularities governing the crystallization of the activated glasses. 相似文献
4.
The kinetics of decomposition of hydrogen peroxide in the liquid phase of the ternary system LiOH-H 2O 2-H 2O was studied in the presence the solid phase of Li 2O 2·H 2O and without it. The main kinetic parameters of the processes studied were determined. 相似文献
5.
Glasses in the system Li 2O–SnO–B 2O 3 system were prepared by a melt-quenching method. Thermal and viscous properties and local structure of these glasses were investigated. The SnO–B 2O 3 glasses exhibited relatively low glass-transition temperatures ( Tg) around 350 °C and excellent thermal stability against crystallization. Viscosity measurements in the vicinity of Tg indicated that the glasses were considerably fragile compared to alkali borate glasses. Fraction of four-coordinated boron was maximized at the composition with 50 mol% SnO and that of nonbridging oxygen, which is not purely ionic in alkali borate systems but partially covalent, augmented with an increase in the SnO content. Correlation between glass properties and structure was discussed in the SnO–B 2O 3 binary system. 相似文献
6.
The crystallization kinetics of Cs 2O–Fe 2O 3–P 2O 5 glasses containing 12.5–27 mol% Cs 2O were studied by using differential scanning calorimetry under nonisothermal conditions. Strong dependence of activation energy with temperature was observed, indicating the complex nature of the crystallization process. The various crystallization products were identified by X-ray diffraction technique. CsFeP 2O 7 was found to be the major crystalline phase in all cases. The overall activation energy obtained by classical model-free kinetic method was compared with that of isoconversional method; and from the results, the dependence of activation energy on extent of reaction and average temperature was delineated. 相似文献
7.
Multicomponent glasses from the SiO 2–P 2O 5–K 2O–MgO–CaO–CuO system acting as slow release fertilizers were synthesized by the melt-quenching technique. The influence of CuO and P 2O 5 addition on the structure of glasses was evaluated by FTIR, Raman, 31P, and 29Si MAS NMR spectroscopies. The studies showed that the Cu 2+ ions displacing Ca 2+ ions and Mg 2+ ions in the structure of glass prefer to associate with the phosphorus Q 1 species, forming the Q 0 species with chemically stable POCu bonds. This is accompanied by the reduction of the degree of polymerization of the phospho-oxygen sub-network, with a simultaneous increased degree of polymerization of the silico-oxygen sub-network of the silicate–phosphate glasses. 相似文献
8.
The effect of the SrO addition on the microstructure and structure of the glazes from the SiO2–Al2O3–CaO–MgO–K2O system was investigated in this study. The results were obtained by testing the ability of the frits crystallization, the stability of the crystallizing phases during the single-step fast-firing cycle depending on their chemical composition and the effect of addition of strontium oxide. Differential scanning calorimetry (DSC) curves showed that all glazes crystallized, and diopside and anorthite were mainly identified as dominant phases in the obtained glazes, while the size and amount of each depended on the amount of SrO introduced. The thermal characteristic of the frits was carried out using DSC, and crystalline phases were determined by X-ray diffractometry. The glaze microstructure was investigated by scanning electron microscopy and transmission electron microscopy. Additional information on the microstructure of frits was derived from spectroscopic studies in the mid-infrared range. 相似文献
9.
To evaluate the thermal stability of materials, various criteria have been used. Not only the simple parameters, as characteristic temperatures, but also the combined criteria E/ RT p , k f ( T) and criterion based on the length of induction period of crystallization have been taken into account. Four gels with the composition Li 2O–2SiO 2– nTiO 2 ( n = 0.00, 0.03, 0.062, and 0.1) were prepared and the validity of the criteria was tested by applying them to these gels. The results indicate that thermal stability of the studied gels decrease with amount of TiO 2. 相似文献
10.
The rheology of mixtures of hydrated aluminum oxide and hydrated titanium dioxide sols was investigated. It was shown that flow curves depend on the mixture composition, the age of initial sols, the contact time of components, and the temperature. At low deformation rates, particles are aligned with the flow; this effect is partially reversible. At high shear rates, a discontinuity appears in the system; the effect depends on the age of initial sols. 相似文献
11.
Using ion-selective electrode(s) (ISE) the activity coefficients of NaCl in the system NaCl–NH 4Cl–H 2O at 10, 25, and 40°C were measured by a computer-controlled automatic titration system. The ionic strength fractions of NH 4Cl were 0.2, 0.4, 0.6, and 0.8, respectively. It was found that the influence of the NH 4+ cation on the Na glass ISE was small enough to be neglected up to 3.0 mol-kg -1. The Pitzer equation was adopted to calculate the activity coefficients of NaCl in this system and compared with the experimental data. Comparison of results indicates that the Pitzer parameters correlated from solubility data are suitable for calculating the activity coefficients for this system within the saturated solutions. 相似文献
12.
The mixture { yNaCl + (1 – y)CaCl 2}(aq) has been studied with the hygrometric method at the temperature 25°C. The water activities were measured at total molalities from 0.25 mol-kg –1 to near saturation for different ionic-strength fractions y of NaCl with y = 0.33, 0.50, and 0.67. The obtained data allow the calculation of osmotic coefficients. The experimental results are compared with the predictions of the Zdanovskii–Stokes–Robinson (ZSR), Kusik and Meissner (KM), Robinson and Stokes (RS), Lietzke and Stoughton (LS II), Reilly–Wood–Robinson (RWR), and Pitzer models. From the measured osmotic coefficients, the Pitzer ionic mixing parameters Na Ca and Na Ca Cl are determined and are used to predict the solute activity coefficients in the mixtures. The excess Gibbs energy is also determined. These results are compared with those given in the literature. 相似文献
13.
A phase equilibria diagram of the partial system NdPO 4–K 3PO 4–KPO 3 has been developed as part of the research aimed at determining the phase equilibrium relationships in the oxide system Nd 2O 3–K 2O–P 2O 5. The investigations were conducted using thermoanalytical techniques, X-ray powder diffraction analysis and reflected-light microscopy. Three isopleths existing between: K 3Nd(PO 4) 2–K 4P 2O 7, NdPO 4–K 5P 3O 10 and NdPO 4–K 4P 2O 7 have been identified in the partial NdPO 4–K 3PO 4–KPO 3 system. Previously unknown potassium-neodymium phosphate “K 4Nd 2P 4O 15” has been discovered in the latter isopleth section. This phosphate exists in the solid phase up to a temperature of 890 °C at which it decomposes into the parent phosphates NdPO 4 and K 4P 2O 7. Four invariant points: two quasi-ternary eutectics, E 1 (1057 °C) and E 2 (580 °C) and two quasi-ternary peritectics, P 1 (1078 °C) and P 2 (610 °C), occur in the NdPO 4–K 3PO 4–KPO 3 region. 相似文献
14.
A zinc oxide pigment with an admixture of bismut oxide has been prepared as new yellow pigment for colouring of plastics and
paints. The effect of the Bi 2 O 3 in the starting mixture on the colour hue of the pigment has been evaluated. The calcination conditions of the pigment synthesis
have been established. The synthesis of these pigments was followed by thermal analysis using a derivatograph apparatus in
our laboratory. The optimum conditions for the synthesis of pigments and the properties of the products have been estimated.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
15.
The kinetics of alkaline hydrolysis of 2-chloroquinoxaline (QCl) with hydroxide ion was investigated spectrophotometrically
at different percentages of aqueous–organic solvent mixtures with acetonitrile (10–60% v/v) and with dimethylesulphoxide (10–80%)
over the temperature range from 25 to 45 °C. The reaction was performed under pseudo first order conditions with respect to
2-chloroquinoxaline (QCl). An increase in the percentage of organic solvent (v/v) has different effects on the reaction rate
constants, presumably due to hydrogen bond donor and acceptor differences of the media and other solvatochromic parameters.
The data were discussed in terms of the Kamelt-Taft parameter and E
T(30). A nonlinear relation between the logarithm of the rate constant and reciprocal of the dielectric constant suggests the
presence of selective solvation by the polar water molecules. Activation parameters Δ H
#, Δ S
# and Δ G
# were determined and discussed. 相似文献
17.
Electrolytic reduction of the uranium oxide in LiCl–Li 2O molten salt for the treatment of spent nuclear fuel requires the separation of the residual salt from the reduced metal product, which contains about 20 wt% salt. In order to separate the residual salt and reuse it in the electrolytic reduction, a vacuum distillation process was developed. Lab-scale distillation equipment was designed and installed in an argon atmosphere glove box. The equipment consisted of an evaporator in which the reduced metal product was contained and exposed to a high temperature and reduced pressure; a receiver; and a vertically oriented condenser that operated at a temperature below the melting point of lithium chloride. We performed experiments with LiCl–Li 2O salt to evaluate the evaporation rate of LiCl salt and varied the operating temperature to discern its effect on the behavior of salt evaporation. Complete removal of the LiCl salt from the evaporator was accomplished by reducing the internal pressure to <100 mTorr and heating to 900 °C. We achieved evaporation efficiency as high as 100 %. 相似文献
18.
The partial system ErPO 4–NaPO 3–Er(PO 3) 3 of the Er 2O 3–Na 2O–P 2O 5 oxide system has been investigated by thermoanalytical methods and X-ray powder diffraction. On the basis of the obtained results the phase diagram of the partial system is proposed. The system is bounded by three subsystems: (i) ErPO 4–Er(PO 3) 3, (ii) Er(PO 3) 3–NaPO 3 and (iii) ErPO 4–NaPO 3. Their phase diagrams are proposed. In the Er(PO 3) 3–NaPO 3 subsystem an intermediate compound NaEr(PO 3) 4 occurs; it melts incongruently at 655 °C. It was found that ErPO 4 and NaEr(PO 3) 4 form a section which is a real system only in the subsolidus region (below 646 °C). Two ternary invariant points (one ternary peritectic and one ternary eutectic) occur in the investigated partial system ErPO 4–NaPO 3–Er(PO 3) 3. 相似文献
19.
Diamond composites were prepared by sintering diamond grains with low melting Na 2O–B 2O 3–SiO 2 vitrified bonds in air. The influence of ZnO on the wettability and flowing ability of Na 2O–B 2O 3–SiO 2 vitrified bonds was characterized by wetting angle, the interfacial bonding states between diamond grains and the vitrified bonds were observed by scanning electron microscope (SEM), and the micro-scale bonding mechanism in the interfaces was investigated by means of energy-dispersive spectrometer (EDS), Fourier transform infrared (FTIR) spectrometer and X-ray photoelectron spectroscopy (XPS). The experimental results showed that ZnO facilitated the dissociation of boron/silicon–oxygen polyhedra and the formation of larger amount of non-bridging oxygen in the glass network, which resulted in the increase of the vitrified bonds' wettability and the formation of –CO, –O–H and –C–H bonds on the surface of diamond grains. B and Si diffused from the vitrified bonds to the interface, and C–C, C–O, CO and C–B bond formed on the surface of sintered diamond grains during sintering process, by which the interfacial bonding between diamond grains and the vitrified bonds was strengthened. 相似文献
20.
The standard ( p∘=0.1 MPa) molar enthalpy of formation of crystalline 2-hydroxypyridine N-oxide was measured, at T=298.15 K, by static bomb calorimetry and the standard molar enthalpy of sublimation, at T=298.15 K, was obtained using Calvet microcalorimetry. These values were used to derive the standard molar enthalpy of formation of 2-hydroxypyridine N-oxide in gaseous phase, and to evaluate the dissociation enthalpy of the N–O bond. Additionally, high-level density functional theory calculations using the B3LYP hybrid exchange-correlation energy functional have been performed for the three isomers of hydroxypyridine N-oxide in order to confirm the experimental trend for the dissociation enthalpy of the (N–O) bond. 相似文献
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