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1.
Kitheri Joseph R. Venkata Krishnan K.V. Govindan Kutty P.R. Vasudeva Rao 《Thermochimica Acta》2011,512(1-2):67-70
The crystallization kinetics of Cs2O–Fe2O3–P2O5 glasses containing 12.5–27 mol% Cs2O 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. CsFeP2O7 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
2.
《Comptes Rendus Chimie》2002,5(11):751-757
Glasses in the system Li2O–SnO–B2O3 system were prepared by a melt-quenching method. Thermal and viscous properties and local structure of these glasses were investigated. The SnO–B2O3 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–B2O3 binary system. 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 article presents a simple method that can be used to get the concentration of various species in mixed-modifier borate glasses. By using the fraction of four coordinated boron in xCaO (30 − x)Na2O70B2O3 (0 ≤ x ≤ 27.5 mol%) and xCaO(40 − x)Na2O60B2O3 glasses (10 ≤ x ≤ 40 mol%), the concentration of BO4− and asymmetric BO3 units related to each modifier oxide could be determined. CaO has a greater tendency to form asymmetric BO3 units in the first glass series, while Na2O has the ability to form BO4 units to a greater extent. In xCaO(40 − x)Na2O60B2O3 glasses, BO4− and asymmetric BO3 units are formed at the same rate from Na2O and CaO. The fraction of four coordinated boron, can be predicted by treating the studied glasses as if they are mixtures of Na2O–B2O3 and CaO–B2O3 matrices. The change in N4 is due to change in the relative concentration of these matrices. 相似文献
5.
Diamond composites were prepared by sintering diamond grains with low melting Na2O–B2O3–SiO2 vitrified bonds in air. The influence of ZnO on the wettability and flowing ability of Na2O–B2O3–SiO2 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
6.
Mária Chromčíková Marek Liška Magdaléna Lissová Petr Mošner Ladislav Koudelka 《Journal of Thermal Analysis and Calorimetry》2013,114(3):947-954
The structural relaxation of three compositional series of PbO–WO3–P2O5 glasses with composition (0.5 ? x/2)PbO·xWO3·(0.5 ? x/2)P2O5, x = 0, 0.1, 0.2, 0.3, 0.4, and 0.5; 0.5PbO·xWO3·(0.5 ? x)P2O5, x = 0, 0.1, 0.2, and 0.3; and (0.5 ? x)PbO·xWO3·0.5P2O5, x = 0, 0.1, 0.2, 0.3, 0.4, and 0.5 was studied by thermomechanical analysis. The structural relaxation was studied in the transformation region using the Tool–Narayanaswamy–Moynihan’s and Tool–Narayanaswamy–Mazurin’s models. The relaxation function of Kohlrausch Williams and Watts was used. The parameters of both models were calculated by nonlinear regression analysis of thermodilatometric curves measured by thermomechanical analyzer under the constant load. Both models very well describe the experimental data. It was found that the modulus is increasing with increasing amount of WO3 in all glasses. On the contrary, the width of the spectrum of relaxation times is decreasing with increasing amount of WO3 in all studied glasses. Both models possess the values of metastable melt thermal expansion coefficient equal to their experimental value. 相似文献
7.
Aparna V. Deshpande Jayraj R. Rane Laxman V. Jathar 《Journal of Sol-Gel Science and Technology》2009,49(3):268-276
Glass samples are prepared with different amount of glycerol as drying control chemical additive (DCCA) via acid catalysed
sol–gel method. These samples are given solvent treatment namely rinse and dip with methanol while drying of the sample. In
rinse treatment solid sample is rinsed with small amount of methanol while in dip treatment sample is dipped for 5 h in methanol.
Comparative studies of these treated samples containing varied DCCA concentration are carried out by measuring optical transmission,
mechanical strength and bulk density. Various instrumental techniques used for analysis are FTIR, DTA-TGA, XRD, SEM and TEM.
The untreated samples take long time to dry up and to come out of the cuvette and show very less transmission in UV region
which is much enhanced by solvent treatment. On the basis of this study, the solvent treated glass samples with DCCA amount
8 ml in the composition used are found to have the maximum UV transmission, good mechanical strength and may be useful as
silica gel host matrices for solid state dye lasers and other applications. The UV transmission reported in the present studies
is 90% in 337 nm region, which is the wavelength of N2 laser pumping. 相似文献
8.
《Arabian Journal of Chemistry》2020,13(1):966-973
Phosphate glasses have several technological interests due to their specific physical properties such as high thermal expansion coefficient, high refractive indice and low melting temperature, that make them suitable for use as conductors, ionic conductors, semiconductors and biomedical materials. The phosphate glasses, in particular the pyrophosphate forms, are not widely studied. In this work we have elaborated the Na2Pb1−xCuxP2O7 glasses, with a large range of composition (0 ≤ x ≤ 1), by conventional melting method. Thermal parameters of the glasses were determined using the differential scanning calorimetry. The structure of the glasses was investigated by IR spectroscopy. The local environment of paramagnetic ions Cu2+ was analyzed by EPR and magnetic measurements. It was showed that the network structure of the glasses was drastically influenced by the copper content. 相似文献
9.
《Ceramurgia International》1979,5(1):18-22
Surface tension, density, and volatility of sodium disilicate, modified by additions of 1%, 5%, 10%, mole La2O3, have been evaluated at temperatures varying from 900 to 1500°C, under highly reducing conditions. These results and related data (such as activation energy of evaporation reaction; thermal expansivity; temperature coefficient of surface tension; nonideal behaviour; surface adsorption) have made possible interpretation of the role played by lanthanum in modifying the properties of the base glass. 相似文献
10.
Xuexin Wang Shu Cai Guohua Xu Xinyu Ye Mengguo Ren Kai Huang 《Journal of Sol-Gel Science and Technology》2013,67(3):629-638
To improve the initial corrosion resistance and then make the degradation rate of magnesium alloys to meet the biomedical application, crack-free CaO–P2O5–SrO–Na2O bioglass-ceramic coatings were synthesized on AZ31 magnesium alloy substrates using a sol–gel dip-coating technique followed by a heat-treatment in the temperature range of 400–500 °C. The effects of heat-treatment on the phase constituents, surface characteristics and corrosion resistances of the coatings were investigated. It was shown that the crystallization of Ca2P2O7 occurred after the glass was treated at 400 °C. As the temperature increased from 400 °C to 450 °C, besides main phase Ca2P2O7, β-Ca(PO3)2 and Ca4P6O19 were identified as minor crystal phases in the glass–ceramic. No new phase was detected with the temperature increasing to 500 °C except for the further crystallization. Meanwhile, the water contact angles of the coatings decreased with the increase of heat-treatment temperature due to the great crystallization. The corrosion resistances of the coated magnesium alloys were studied by electrochemical corrosion techniques in the simulated body fluid. The results revealed that the coating heat-treated at 400 °C exhibited superior corrosion resistance because of less crystallization, suggesting that the calcium phosphate bioglass–ceramic coating can provide effective protection for magnesium alloy substrate to control its initial degradation in vivo and maintain the desired mechanical properties. 相似文献
11.
L. Srinivasa Rao M. Srinivasa Reddy D. Krishna Rao N. Veeraiah 《Solid State Sciences》2009,11(2):578-587
Li2O–MoO3–B2O3 glasses mixed with different concentrations of CuO (ranging from 0 to 1.2 mol%) were prepared. The samples were characterized by X-ray diffraction, scanning electron microscopy and differential scanning calorimetry. Optical absorption, luminescence, ESR, IR and dielectric properties (viz., dielectric constant ?′, loss tan δ and a.c. conductivity σac, over a wide range of frequency and temperature) of these glass materials have been investigated. The results of differential scanning calorimetric studies suggest that the glass forming ability is higher for the glasses containing CuO beyond 0.6 mol%. The analysis of results of the dielectric properties has revealed that the glasses possess high insulating strength when the concentration of CuO is >0.6 mol%. The variation of a.c. conductivity with the concentration of CuO passes through a maximum at 0.6 mol%. In the high-temperature region, the a.c. conduction seems to be connected with the mixed conduction viz., electronic conduction and ionic conduction. The optical absorption spectra of these glasses exhibited bands due to Cu+ ions in the UV region in addition to the conventional band due to Cu2+ ions in the visible region. The ESR spectral studies have indicated that there is a gradual adoption of Cu2+ ions from ionic environment to covalent environment as the concentration of CuO increases beyond 0.6 mol% in the glass matrix. The luminescence spectra excited at 271 nm have exhibited an intense yellow emission band centered at about 550 nm and a relatively broad blue emission band at about 450 nm; these bands have been attributed to the 3D1 → 1S0 transition of isolated Cu+ ions and 3D1 → 1S0 transition of (Cu+)2 pairs, respectively. The quantitative analysis of the results of all these studies has indicated that as the concentration of CuO is increased beyond 0.6 mol% in the glass matrix, a part of Cu2+ ions have been reduced to Cu+ ions that have influenced the physical properties of these glasses to a substantial extent. 相似文献
12.
C. Bhongale A. Ghule R. Murugan H. Chang 《Journal of Thermal Analysis and Calorimetry》2001,65(3):891-905
In this work, dehydration of sodium diphosphate decahydrate Na4P2O7⋅10H2O and phase transformations of Na4P2O7 in open air have been studied in detail by thermo-Raman spectroscopy. The spectra were measured continuously in a temperature
range from room temperature up to 600°C for the bands of P2O7
4- and H2O. The spectral variation showed one step of dehydration and four-phase transformations. The thermo-Raman intensity(TRI) and
differential thermo-Raman intensity (DTRI) curves calculated from the characteristic bands of H2O also showed one step of dehydration with the loss of all hydrated water in the temperature interval from 45 to 69°C. Thermogravimetric
measurements supported this result. The thermo-Raman investigation indicated the transformation of Na4P2O7 from low temperature phase to high temperature phase proceed through pre-transitional region from 75 to 410°C before the
major orientational disorder at 418°C and minor structural modifications at 511,540 and 560°C. The results from differential
scanning calorimetry and differential thermal analysis on Na4P2O7 showed endotherms at 407,517, 523, 548, 557°C and 426, 528, 534, 555, 565°C, respectively.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
13.
Qingyu Pang Yong Zhang Jia Zhu Xiaozhen Song Xiangrong Wang Qian Zhang 《Journal of Sol-Gel Science and Technology》2014,72(3):581-586
Crystallization of BaO–SrO–TiO2–SiO2–Al2O3-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
14.
R. V. Panin N. R. Khasanova A. M. Abakumov W. Schnelle J. Hadermann E. V. Antipov 《Russian Chemical Bulletin》2006,55(10):1717-1722
Sodium ruthenium(III,IV) oxide Na1−x
Ru2O4 was synthesized by the solid state reaction of Na2CO3 and RuO2 in inert atmosphere and characterized by X-ray powder diffraction, electron diffraction, and high-resolution transmission
electron microscopy. The compound crystallizes in the CaFe2O4-type structure (space group Pnma, Z = 4, a = 9.2641(7) Å, b = 2.8249(3) Å, c = 11.1496(7) Å). Double rutile-like chains of the RuO6 octahedra form a three-dimensional framework, whose tunnels contain sodium cations. The structure contains two crystallographically
independent sites of ruthenium atoms randomly occupied by the RuIII and RuIV cations. The superstructure with the doubled b parameter found for one of the samples under study using electron diffraction is caused, probably, by ordering of the Ru
cations in the rutile-like chains. The Na1− x
Ru2O4 compound exhibits temperature-independent paramagnetism with χ0 = 1.9·10−4 cm3 (mole of Ru−1).
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 1655–1660, October, 2006. 相似文献
15.
Wen Yao Zhang Li Xiao Ping Yang Lei Sang Shi Hua 《Russian Journal of Physical Chemistry A, Focus on Chemistry》2019,93(6):1032-1037
Russian Journal of Physical Chemistry A - The solubility data for ternary systems Na2SO4–Na2B4O7–H2O and Li2B4O7–Na2B4O7–H2O at 273 K were obtained experimentally by the... 相似文献
16.
Maria Ochsenkühn-Petropulu Irene Vottea Rachel Argyropulu Leonidas Mendrinos Klaus-Michael Ochsenkühn 《Mikrochimica acta》1999,130(4):289-294
Coatings of the high-temperature superconductor YBa2Cu3O7–x (x = 0.1–0.2) (YBCO), were deposited on commercial Ni,Ti and stainless steel substrates, by an electrophoretic deposition technique. Sintering and annealing procedures were followed in order to get strongly adherent superconducting films. The suitability of the used substrates was tested by measuring the stoichiometry and the superconducting properties of the deposited coatings by X-ray diffraction analysis (XRD), Raman spectroscopy and magnetization measurements with a superconducting quantum interference device (SQUID). 相似文献
17.
The partial substitution of CaF2 for CaO in the Na2O–CaO–SiO2–P2O5 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 CaF2 for CaO in glass composition, the volume density, apparent porosity, bending strength and microhardness of the glass–ceramics have been significantly improved. Furthermore, CaF2 promotes glass crystallization which does not inhibit the glass–ceramic bioactivity. 相似文献
18.
N. V. Kosova E. T. Devyatkina V. V. Kaichev D. G. Kellerman 《Russian Journal of Electrochemistry》2008,44(5):543-549
The cathode materials of the composition LiNi1 − 2x
Co
x
Mn
x
O2 (x = 0.1, 0.2. 0.33) synthesized from the Ni, Co, Mn mixed hydroxides and LiOH by using mechanical activation method are studied.
It is shown that all synthesized compounds have layered structure described by the space group R-3m. With the decreasing of the nickel content the cell volume and the degree of structure disordering decrease. According to
XPS data, the electronic main state of d-ions at the prepared samples’ surfaces corresponds to Ni2+, Co3+, and Mn4+. An increase in the nickel content leads to the increase of the Ni2p
3/2 and Co2p
3/2 binding energy, which points to the change in the Me-O bond covalence. According to magnetic susceptibility measurements
data, the nickel ions in LiNi0.6Co0.2Mn0.2O2 exist in the two oxidation states: Ni2+ and Ni3+. It is shown that this sample has the highest specific discharge capacity (∼170 mAh/g). The positions of redox peaks in the
differential capacitance curves depend on the sample composition: with the increasing of nickel content they are shifted toward
lower voltages.
Based on the paper presented in the IX International Conference “Basic Problems of Energy Conversion in Lithium Electrochemical
Systems” (Ufa, 2006). 相似文献
19.
Reenamoni Saikia Chaliha K. Annapurna Anal Tarafder V.S. Tiwari P.K. Gupta Basudeb Karmakar 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2010,75(1):243-250
Precursor glass of composition 25K2O–25Nb2O5–50SiO2 (mol%) doped with Er2O3 (0.5 wt% in excess) was isothermally crystallized at 800 °C for 0–100 h to obtain transparent KNbO3 nanostructured glass–ceramics. XRD, FESEM, TEM, FTIRRS, dielectric constant, refractive index, absorption and fluorescence measurements were carried out to analyze the morphology, dielectric, structure and optical properties of the glass–ceramics. The crystallite size of KNbO3 estimated from XRD and TEM is found to vary in the range 7–23 nm. A steep rise in the dielectric constant of glass–ceramics with heat-treatment time reveals the formation of ferroelectric nanocrystalline KNbO3 phase. The measured visible photoluminescence spectra have exhibited green emission transitions of 2H11/2, 4S3/2 → 4I15/2 upon excitation at 377 nm (4I15/2 → 4G11/2) absorption band of Er3+ ions. The near infrared (NIR) emission transition 4I13/2 → 4I15/2 is detected around 1550 nm on excitation at 980 nm (4I15/2 → 4I11/2) of absorption bands of Er3+ ions. It is observed that photoluminescent intensity at 526 nm (2H11/2 → 4I15/2), 550 nm (4S3/2 → 4I15/2) and 1550 nm (4I13/2 → 4I15/2) initially decrease and then gradually increase with increase in heat-treatment time. The measured lifetime (τf) of the 4I13/2 → 4I15/2 transition also possesses a similar trend. The measured absorption and fluorescence spectra reveal that the Er3+ ions gradually enter into the KNbO3 nanocrystals. 相似文献
20.
Ling Pei Ni Hu Gang Deng Yiwan Chen Yeguang Bie Meiya Li Xiaolian Liu 《Journal of Sol-Gel Science and Technology》2012,64(3):711-717
The effects of Tb substitution on the structural and electrical properties of ferroelectric Bi4Ti3O12 (BTO) thin films grown on Pt/TiO2/SiO2/Si substrates by a sol–gel process have been reported. X-ray diffraction indicated A-site Tb substitutions did not change the polycrystalline bi-layered Aurivillius structure of the BTO, but a lattice distortion was observed. The leakage current behavior at room temperature of the films was studied and it was found that the leakage current density decreased from 10?2 to 10?4 A/cm2 with the increase of x under 150 kV/cm. The remnant polarization (2P r ) and dielectric constant (ε r) increase firstly and then decreases with the increase of the Tb content. We observed a substantial increase in the remnant polarization (2P r ) with Tb substitution and obtained a maximum value of~60 μC/cm2 at an applied electric field of 500 kV/cm for x = 0.4. Moreover, this BTT-0.4 capacitor did not show fatigue behaviors after 1.0 × 1010 switching cycles, suggesting an anti-fatigue character. 相似文献