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1.
The Na 2O–CaO–SiO 2 ternary glass–ceramic with the composition of 49 mass% Na 2O, 20 mass% CaO, and 31 mass% SiO 2 was prepared by the conventional method. The ternary glass–ceramic was characterized using X-ray diffraction (XRD), differential thermal analysis (DTA), thermogravimetric analysis, Fourier transform infrared spectroscopy, and scanning electron microscopy techniques. The Na 2CaSiO 4 phase, having the cubic crystal system, with the crystallite size of 25.14 nm and lattice parameter of 0.7506 nm was determined from the XRD pattern. The activation energy of the glass–ceramic calculated from the DTA curves was found to be 162.02 kJ mol ?1. The Avrami exponent was found to be ~2 indicating a one-dimensional growth process. The mass loss percent from ambient temperature to 1,173 K is less than 1 %. The density was calculated to be 2,723 kg m ?3. The fine-grained microstructure with the particle sizes less than 1 μm was confirmed by the scanning electron microscope micrograph. 相似文献
4.
High-pressure vapor–liquid equilibria for the binary carbon dioxide–2-methyl-1-butanol and carbon dioxide–2-methyl-2-butanol systems were measured at 313.2 K. The phase equilibrium apparatus used in this work is of the circulation type in which the coexisting phases are recirculated, on-line sampled, and analyzed. The critical pressure and corresponding mole fraction of carbon dioxide for the binary carbon dioxide–2-methyl-1-butanol system at 313.2 K were found to be 8.36 MPa and 0.980, respectively. The critical point of the binary carbon dioxide–2-methyl-2-butanol was also found 8.15 MPa and 0.970 mole fraction of carbon dioxide. In addition, the phase equilibria of the ternary carbon dioxide–2-methyl-1-butanol–water and carbon dioxide–2-methyl-2-butanol–water systems were measured at 313.2 K and several pressures. These ternary systems showed the liquid–liquid–vapor phase behavior over the range of pressure up to their critical point. The binary equilibrium data were all reasonably well correlated with the Redlich–Kwong (RK), Soave–Redlich–Kwong (SRK), Peng–Robinson (PR), and Patel–Teja (PT) equations of state with eight different mixing rules the van der Waals, Panagiotopoulos–Reid (P&R), and six Huron–Vidal type mixing rules with UNIQUAC parameters. 相似文献
5.
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
6.
Crystallization of BaO–SrO–TiO 2– SiO2–Al 2O 3-based glass ceramics, prepared by sol–gel process, was evaluated in terms of the effect of sintering temperature on phase evolution and electrical properties. The characterization of the samples was performed by X-ray diffraction (XRD) analysis, scanning electron microscopy (SEM) studies and impedance spectroscopy analysis. The XRD results demonstrate that fresnoite phase starts to crystallize at 700 °C and perovskite phase appears at 900 °C. The glass ceramic samples sintered at high temperatures contained three crystalline phases, including perovskite, feldspar and fresnoite. In addition, SEM observation showed that the average grain size increased and the porosity decreased with increasing sintering temperature. Furthermore, the measurement of impedance spectroscopy suggests that there is a minimum value of the activation energy associated with the sintering temperature of the glass ceramics. The possible explanation of the sintering temperature dependence was discussed. 相似文献
7.
Journal of Sol-Gel Science and Technology - ZnO–B2O3–SiO2:Mn2+ (ZBSM) optical-storage glass–ceramics doped with ZnF2 were successfully prepared via sol–gel method. The... 相似文献
8.
This work deals with the prediction and experimental measurements of the (solid + liquid) equilibrium (SLE) in acid medium for industrial purposes. Specific systems including KCl–ethanol–water–HCl and K 2SO 4–water–H 2SO 4 were analyzed. At first, a critical discussion of SLE calculations was given, based on the well-known UNIQUAC extended and LIQUAC models. Two new proposals were derived, considering the explicit necessity of a new reference state for SLE calculations for the studied (solvents + acid) mixtures. The solubility of KCl in water–ethanol–HCl mixed solvents was measured in the temperature range of 300.15 to 315.15 K using an analytical gravimetric method. These results combined with some other experimental data reported in the open literature let us to propose a set of parameters for the new models. They included the interaction parameters between ethanol and the H + ion. The prediction capability of the new models, for calculations in acid medium, was illustrated. Experimentally, it was observed that the (K 2SO 4 + water + H 2SO 4) system presented the unusual behavior of increasing K 2SO 4 solubility with an increase in the sulfuric acid concentration. This was accurately predicted by the newly proposed models. 相似文献
9.
Results of studying the spectral and luminescent properties of Eu 3+ ions upon homogeneous excitation of POCl 3–SnCl 4– -UO 2+
2–Eu 3+ and D 2O– 235UO 2+
2–Eu 3+ solutions by -particles are presented. It was found that the radioluminescence intensity of Eu 3+ ions in both solvents increases proportionally to the energy input by -particles. The yield of radioluminescence photons from europium ions in the POCl 3–SnCl 4–UO 2+
2–Eu 3+ solutions is more than nine times as high as that in D 2O–UO 2+
2–Eu 3+. The radiation-chemical yields of excited 5
D
0 states of Eu 3+ ions are 0.74 ± 0.07 and 0.18 ± 0.02 ions/100 eV in POCl 3–SnCl 4–UO 2+
2–Eu 3+ and D 2O–UO 2+
2–Eu 3+ solutions, respectively. 相似文献
10.
The glasses within composition as: (80 − x)V 2O 5/20Bi 2O 3/ xBaTiO 3 with x = 2.5, 5, 7.5 and 10 mol% have been prepared. The glass transition ( Tg) increases with increasing BaTiO 3 content. Synthesized glasses ceramic containing BaTi 4O 9, Ba 3TiV 4O 15 nanoparticles of the order of 25–35 nm and 30–46 nm, respectively were estimated using XRD. The dielectric properties over wide ranges of frequencies and temperatures were investigated as a function of BaTiO 3 content by impedance spectroscopy measurements. The hopping frequency, ωh, dielectric constant, ε′, activation energies for the DC conduction, Eσ, the relaxation process, Ec, and stretched exponential parameter β of the glasses samples have been estimated. The, ω h, β, decrease from 51.63 to 0.31 × 10 6 (s −1), 0.84 to 0.79 with increasing BaTiO 3 respectively. Otherwise, the Eσ, increase from 0.279 to 0.306 eV with increasing BaTiO 3. The value of dielectric constant equal 9.5·10 3 for the 2.5BaTiO 3/77.5V 2O 5/20Bi 2O 3 glasses-ceramic at 330 K for 1 KHz which is ten times larger than that of same glasses composition. Finally the relaxation properties of the investigated glasses are presented in the electric modulus formalism, where the relaxation time and the respective activation energy were determined. 相似文献
11.
In the present work, silica and titania reinforced polybenzoxazine (PBZ– SiO2–TiO 2) hybrid nanomaterial possessing high surface free energy have been developed using dimethylol-functional benzoxazine monomer (4HBA-BZ), tetraethoxysilane (TEOS), 3-(isocyanatopropyl)triethoxysilane (ICPTS), titaniumisopropoxide (TIPO) through an in situ sol–gel process. Data obtained from the contact angle measurement indicate that the hybrid materials are hydrophilic in nature and possess a high surface free energy. For example, hybrid PBZ obtained from 1:1:0.6:0.4 (m:m:w:w) ratio of 4HBA-BZ:ICPTS:TEOS:TIPO (PBST 4) exhibit a high surface free energy of 38.2 mJm ?2 which is higher than that of neat polybenzoxazine (29.5 mJm ?2). Further data resulted from thermal studies indicate that the hybrid PBZ possess higher values of T g, thermal stability and char yield than those of neat PBZ. 相似文献
12.
A novel coating process, TiO 2 sol enhanced Ni–P electroless composite coatings on carbon steel, is presented in this paper. Transparent TiO 2 sol was added into the electroless plating Ni–P solution at a controlled rate, leading to in situ synthesis of a triple-layered Ni–P–TiO 2 composite coating, i.e. the inner, transition and outer layers. The inner layer has a thickness of ~3 μm, mainly composed of Ni and P elements. The transition layer of the coating has a relatively high content of TiO 2 with a thickness of ~500 nm and a columnar-structure. The thickness of the outer layer was ~7 μm, with almost evenly distributed Ni, P and TiO 2. The hardness and Young’s modulus of the composite coating were greatly improved to ~10 and ~200 GPa, respectively, compared to ~6 and ~110 GPa of the traditional Ni–P coating. 相似文献
13.
In order to evidence the structural changes induced by CuO and V 2O 5 in the phosphate glass network and their modifier or former role, x(CuO·V 2O 5)(100 − x)[P 2O 5·CaO] glass system was prepared and investigated using Raman spectroscopy (0 ≤ x ≤ 40 mol%).Raman spectra of the studied glasses present the specific bands of the phosphate glasses at low concentration of transition metal (TM) ions, but at higher concentration ( x > 7 mol%) a strong depolymerization of the phosphate network appears; non-bridging oxygen atoms are involved in VOP and CuOP bonds and new short units are formed. For a high concentration of V 2O 5 ( x > 10 mol%) the Raman bands of V 2O 5 prevail in the spectra; this fact suggests that vanadium oxide imposes its structural units in the network acting thus as a network glass former.2D correlation analysis was also applied for the concentration-dependent Raman spectra in order to verify the assignments of the vibration modes and to find correlations in the changes induced by TM ions content. 2D correlation maps indicate a good correlation between the bands at ∼705 cm −1 assigned to POP stretching vibration and at ∼1175 cm −1 assigned to PO 2 groups which suggest the depolymerization of the phosphate network. The correlation between the 1270 cm −1 and 930 cm −1 bands also suggests that V 2O 5 oxide is responsible for PO bonds breaking and POV formation. 相似文献
14.
The structures of binary xCaO · (100 ? x)SiO 2 glasses with x = 10, 20 and 30 mol-% and ternary (20 ? x)CaO · xP 2O 5 · 80SiO 2 glasses with x = 3, 10, 15, 17 and 20 mol-% have been studied by means of classical molecular dynamics simulations using both the melt-quenched and the sol–gel protocols. The structural picture derived correlates the bioactive behaviour to the combined effects of the connectivity of the extended silicate network and to the tendency to form (or not to form) non-homogeneous domains. In this context, a mathematical relationship that relates the Ca/P ratio in the Ca phosphate micro-segregation zones to the P 2O 5 content in ternary glasses has been developed and this has been used to fine-tuning the optimum amount of P in a glass for its highest in vitro bioactivity. The composition with optimal Ca/P ratio, 80Si–14.8Ca–5.2P, has been synthesized and the results of bioactivity tests have confirmed the prediction. 相似文献
15.
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
16.
The partial substitution of CaF 2 for CaO in the Na 2O–CaO–SiO 2–P 2O 5 system was conducted by the sol–gel method and a comparison of the glass–ceramic properties was reported. Based on thermogravimetric and differential thermal analysis, the gels were sintered with a suitable heat treatment procedure. The glass–ceramic properties were characterized by X-ray diffraction, fourier-transform infrared spectroscopy, scanning electron microscopy, energy dispersive spectrometer and so on, and the bioactivity of the glass–ceramic was evaluated by in vitro assays in simulated body fluid. Results indicate that with the partial substitution of CaF 2 for CaO in glass composition, the volume density, apparent porosity, bending strength and microhardness of the glass–ceramics have been significantly improved. Furthermore, CaF 2 promotes glass crystallization which does not inhibit the glass–ceramic bioactivity. 相似文献
17.
Thermal stability of PbO was studied. Reactivity of oxides in the systems PbO–M 2O 3 ( M = In, Fe) was investigated up to 650 °C. Using the DTA and XRD methods, parts of investigated ternary oxide systems, labelled by compounds: V 2O 5, Pb 8V 2O 13 and M 2O 3 ( M = In, Fe), have been divided into partial ternary systems. IR spectra of compounds Pb 2MV 3O 11 ( M = In, Fe) have been compared. 相似文献
18.
By means of the conventional quenching route, the glass series 33Na 2O– xSrO– xTiO 2–(50 ? 2 x)B 2O 3–17P 2O 5 ( x = 0–12.5 mol%) were prepared. The amorphous state of samples was verified by X-ray diffraction (XRD). Density, molar volume, micro-hardness, glass transition temperature ( T g), and crystallization temperature ( T c) parameters are determined for each glass. The results show that they depend strongly on the chemical compositions. The structure approach of the glasses is determined by Infrared spectroscopy (IR). This investigation highlights that the glassy-matrix contains various phosphate and borate structural units. The crystallization of the high-TiO 2 glasses by heat-treatments favors the formation of titanate phosphate Na 4TiO(PO 4) 2 or Sr 0.5Ti 2(PO 4) 3 along with Sr 3(PO 4) 2 inside the glass-matrix. 相似文献
19.
The ternary system La 2O 3–K 2O–P 2O 5 has been examined by thermal, X-ray, IR and microscopic methods. The existence of three double potassium-lanthanum phosphates,
K 3La(PO 4) 2, KLa(PO 3) 4 and K 2La(PO 3) 5 has been confirmed, and the phase diagram of the ternary system La 2O 3–K 2O–P 2O 5 over the composition range LaPO 4–K 3PO 4–P 2O 5 has been determined.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
20.
This paper reports on the preparation of SO 4 2?/Fe 2O 3–TiO 2–Nd 2O 3 (SFTN) by combustion method. The effect of Nd content on catalytic activity was investigated. The prepared materials doped and undoped by Nd were compared by means of TG-DTG, XRD, FT-IR, NH 3-TPD and TEM techniques. Results indicated that the introduction of Nd improved the catalytic activities of the catalysts. Catalytic activity of SFTN was the highest with 98.3 % menthol conversion when Nd content was at 2 wt%. The introduction of Nd stabilized the coordination bond between the sulfate irons and the metallic oxides, helping in the formation of solid acid sites, enhancing the dispersion of catalyst particles, and inhibiting the growth of catalyst particles under heating. 相似文献
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