共查询到20条相似文献,搜索用时 46 毫秒
1.
I. A. Zvereva A. M. Sankovich A. B. Missyul’ V. L. Ugolkov 《Glass Physics and Chemistry》2010,36(2):209-216
The processes of phase formation in the Nd2O3-TiO2-Na2CO3 system have been investigated in the temperature range 500–1100°C. The mechanism of the high-temperature solid-phase reaction
of formation of the complex oxide Na2Nd2Ti3O10 has been studied. It has been established that the Na2Nd2Ti3O10 compound is formed from the intermediate product Na0.5Nd0.5TiO3 with a perovskite structure in the temperature range 830–890°C and from the NaNdTiO4 oxide with a perovskite-like layered structure in the temperature range 960–1100°C. 相似文献
2.
The 0D-1D Lithium titanate (Li4Ti5O12) heterogeneous nanostructures were synthesized through the solvothermal reaction using lithium hydroxide monohydrate (Li(OH)·H2O) and protonated trititanate (H2Ti3O7) nanowires as the templates in an ethanol/water mixed solvent with subsequent heat treatment. A scanning electron microscope
(SEM) and a high resolution transmission electron microscope (HRTEM) were used to reveal that the Li4Ti5O12 powders had 0D-1D heterogeneous nanostructures with nanoparticles (0D) on the surface of wires (1D). The composition of the
mixed solvents and the volume ratio of ethanol modulated the primary particle size of the Li4Ti5O12 nanoparticles. The Li4Ti5O12 heterogeneous nanostructures exhibited good capacity retention of 125 mAh/g after 500 cycles at 1C and a superior high-rate
performance of 114 mAh/g at 20C. 相似文献
3.
L. F. Grigor’eva S. A. Petrov O. Yu. Sinel’shchikova I. A. Drozdova V. V. Gusarov 《Glass Physics and Chemistry》2007,33(1):72-79
The mechanism of formation of barium titanate Ba2Ti9O20 in the BaO-TiO2 and BaO-SrO-TiO2 systems is investigated using initial mixtures prepared by three methods, namely, mechanical grinding of the initial reactants, coprecipitation from aqueous solutions of salts, and the sol-gel technique. It is established that, irrespective of the preparation procedure, the formation of Ba2Ti9O20 proceeds through the formation of the intermediate phases BaTi4O9 and BaTi5O11. The nature of the intermediate phases is determined by the homogeneity and dispersion of the initial mixture, as well as by the stability of the intermediate phase. The most optimum conditions for the synthesis of Ba2Ti9O20 are provided by the formation of BaTi5O11 as an intermediate phase upon heat treatment of the coprecipitation products in the nanocrystalline state. The metastability and structural defects in the BaTi5O11 intermediate phase encourage a decrease in the temperature of the final heat treatment by 100–150°C in the course of the preparation of Ba2Ti9O20 single-phase ceramics. 相似文献
4.
Amorphous La2O-TiO2 powders were synthesized by the polymerized complex (PC) method. The activation energies for crystallization and grain growth
of La2Ti2O7 from these precursors were determined from results of XRD and DTA and compared with those for La2Ti2O7 precursors by the conventional solid-state reaction (SSR). Activation energy of grain growth of La2Ti2O7 in PC-sample was determined to be 7.1 kJ/mol while that of SSR sample was 14.8 kJ/mol. The energy required for the phase
transformation from amorphous PC sample to layered perovskite was 432 kJ/mol, while the SSR sample did not show this transition
below 900‡C. It was clearly demonstrated that the La2Ti2O7 crystals were formed at a lower temperature and they grew in size faster in the sample prepared by the PC method relative
to the sample prepared by the SSR method. Mixing of elements in molecular level in PC preparation appeared responsible for
these differences. 相似文献
5.
Combined UV-visible and FTIR spectral studies of undoped and Nd2O3 –doped sodium silicophosphate glasses were carried out to characterize the optical and structural properties of such glasses. The base undoped silicophosphate glass exhibits strong UV absorption which is due to the presence of unavoidable trace iron impurities (mainly Fe3+ ions) present contaminated within the raw materials used for the preparation of such glasses. Nd2O3 –doped glasses show characteristic absorption bands extending in the entire visible region which are attributed to the contribution of Nd3+ ions with distinct peaks which are almost constant with the increase of dopant. This comes from the combined compact glass structure containing two glass forming units and the shielding of the rare-earth ions. Infrared absorption spectra of the studied glasses reveal characteristic IR bands due to the combination of both silicate and phosphate groups. The introduction of Nd2O3 within the dopant level (2 %) produces no variations in the IR vibrational bands due to the presence of the two structural silicate and phosphate groups giving compactness of the network structure. The deconvoluted spectra reveal the presence of phosphate groups in a slightly high ratio due to the high content of P2O5 in the composition. 相似文献
6.
A new compound of (Rb,K)2Cu3(P2O7)2 is obtained by high-temperature reactions from a mixture of RbNO3, KNO3, Cu(NO3)2, and (NH4)4P2O7. The crystal structure was solved by direct methods and refined to R 1 = 0.056 for 5022 independent reflections. The compound belongs to a rhombic crystal system, P212121, Z = 8, a = 9.9410(7) Å, b = 13.4754(6) Å, c = 18.6353 (3) Å, and R = 0.056. The basis of the structure is a complex copper-phosphate skeleton of the composition of [Cu3(P2O7)2]2–, which can be regarded as consisting of two types of heteropolyhedral layers parallel to the (001) plane. The layers are alternated with each other, forming a frame, in the cavities of which the positions of alkali cations are located, statistically populated with K+ and Rb+ ions. Based on the refined populations of the positions of alkali cations, an exact chemical formula of the compound can be written as Rb1.28K0.72Cu3(P2O7)2. The compound is the most complex among those known to this day of the composition of A2 IB3 II(P2O7)2 (A = Li, Na, K, Rb, or Cs; B = Ni, Cu, or Zn). 相似文献
7.
I. A. Zvereva V. F. Popova E. A. Tugova N. S. Pylkina V. V. Gusarov 《Glass Physics and Chemistry》2005,31(6):808-811
The phase equilibria are investigated and the phase diagram is constructed for the Gd2O3-SrAl2O4 pseudobinary join of the Gd2O3-SrO-Al2O3 ternary oxide system. One ternary compound, namely, Gd2SrAl2O7, is revealed in the Gd2O3-SrAl2O4 join. It is found that this compound undergoes congruent melting. 相似文献
8.
An optical material, namely, the potassium aluminosilicophosphate glass activated with trivalent titanium ions, is synthesized and studied. The optimum concentration range (0.2–10.0 wt % Ti2O3) that provides the best physical, luminescent, and kinetic properties of glasses is determined. This makes it possible to use the sensitizing properties of Ti3+ ions to the greatest extent.Original Russian Text Copyright © 2004 by Fizika i Khimiya Stekla, Batyaev, Leonov. 相似文献
9.
One of the most promising anode materials for Li-ion batteries, Li4Ti5O12, has attracted attention because it is a zero-strain Li insertion host having a stable insertion potential. In this study,
we suggest two different synthetic processes to prepare Li4Ti5O12 using anatase TiO2 nanoprecursors. TiO2 powders, which have extraordinarily large surface areas of more than 250 m2 g-1, were initially prepared through the urea-forced hydrolysis/precipitation route below 100°C. For the synthesis of Li4Ti5O12, LiOH and Li2CO3 were added to TiO2 solutions prepared in water and ethanol media, respectively. The powders were subsequently dried and calcined at various
temperatures. The phase and morphological transitions from TiO2 to Li4Ti5O12 were characterized using X-ray powder diffraction and transmission electron microscopy. The electrochemical performance of
nanosized Li4Ti5O12 was evaluated in detail by cyclic voltammetry and galvanostatic cycling. Furthermore, the high-rate performance and long-term
cycle stability of Li4Ti5O12 anodes for use in Li-ion batteries were discussed. 相似文献
10.
Reem AL-Wafi 《SILICON》2017,9(5):657-661
We have fabricated an Al/n-Si/Bi4Ti3O12/Au photodiode by the sol-gel method. The photoelectrical response of the diode was measured under dark and various light intensity conditions. The photocurrent of the diode increases with increase in light intensity. The light sensitivity value of the photosensor was measured and observed to increase from 5.06 × 10?8 (under dark) to 2.34 × 10?4 A (under 100 mW/cm2). Furthermore, other parameters for instance, ideality factor and barrier height of the photosensors were calculated. The ideality factor and barrier height of the Al/n-Si/Bi4Ti3O12/Au photosensor were found to be 3.01 and 0.86 eV respectively. Also capacitance-voltage (C-V) characteristics were measured. The C-V graph indicates changeable behavior with the varying frequency. The value of capacitance and the interface state density Dit value decrease with increase in frequency. Thus, the obtained results indicate that the Al/n-Si/Bi4Ti3O12/Au photosensor can be used as a photosensor in optoelectronic applications. 相似文献
11.
S. V. Stolyar N. G. Tyurnina Z. G. Tyurnina L. A. Doronina 《Glass Physics and Chemistry》2008,34(4):509-511
The temperature dependences of the viscosity are investigated for three series of glass melts in the SrO-B2O3-SiO2 system with a constant strontium oxide content equal to 35, 40, or 45 mol % in the viscosity range from 1010 to 1013 P. 相似文献
12.
V. I. Strakhov I. V. Ivanova A. I. Arsirii K. Velkova V. P. Migal' S. I. Gershkovich 《Refractories and Industrial Ceramics》2005,46(5):322-324
Data on interactions in the ZrO2 - Fe2O3 system stabilized by oxides in a high-temperature form at 1750°C are obtained. Of all zirconia-based compositions, only magnesium-zirconium
cubic solid solution enters into an active reaction with Fe2O3 to yield MgFe2O4. The solid solutions formed by ZrO2 with oxides of yttrium, neodymium, and calcium resist degradation by attack from Fe2O3; part of iron oxide undergoes dissolution in cubic ZrO2.
__________
Translated from Novye Ogneupory, No. 9, pp. 40 – 43, September, 2005. 相似文献
13.
The properties of CaCu3.1Ti4O12.1 [CC3.1TO] ceramics with the addition of Al2O3 nanoparticles, prepared via a solid-state reaction technique, were investigated. The nanoparticle additive was found to inhibit
grain growth with the average grain size decreasing from approximately 7.5 μm for CC3.1TO to approximately 2.0 μm for the
unmodified samples, while the Knoop hardness value was found to improve with a maximum value of 9.8 GPa for the 1 vol.% Al2O3 sample. A very high dielectric constant > 60,000 with a low loss tangent (approximately 0.09) was observed for the 0.5 vol.%
Al2O3 sample at 1 kHz and at room temperature. These data suggest that nanocomposites have a great potential for dielectric applications. 相似文献
14.
Structure and crystalline behavior of the ternary system ZnO-B2O3-P2O5 glasses were investigated by means of X-ray diffraction (XRD) and infrared Raman spectra. The research showed that number
of the planar [BO3] units increases with the increase of B2O3 content. When the B2O3 content is above ≥10 mol %, the relative content of planar [BO3] units increases rapidly and causes weakening of the glass structure and decrease in the chemical stability. In the crystallized
glasses the predominant crystal phase Zn2P2O7 decreases with the increase of B2O3 content, while the crystal phase BPO4 increases with it, which cause the declining of chemical stability and the decrease of thermal coefficients of expansion. 相似文献
15.
Layered ceramics based on bismuth–calcium cobaltite with varied cobalt oxide contents is synthesized by the solid-phase method, the ceramics phase composition is determined, and the microstructure, thermal expansion, electroconductivity, and thermal electromotive force are investigated. The formation of just one compound, ternary oxide composed of Bi2Ca2Co1.7O y , is established within the quasi-binary Bi2Ca2O5–CoO z system. The effect of the cobalt oxide content on the Bi2Ca2Co x O y ceramics’ microstructure and physicochemical properties is analyzed. The single-phased ceramic sample Bi2Ca2Co1.7O y demonstrated the highest power factor value among all the investigated samples—26.0 μW/(m K2) at a temperature of 300 K. This sample showed the lowest value of the thermal linear expansion coefficient of 9.72 × 10–6 K–1. 相似文献
16.
I. A. Zvereva O. I. Silyukov A. V. Markelov A. B. Missyul’ M. V. Chislov I. A. Rodionov D. -Sh. Li 《Glass Physics and Chemistry》2008,34(6):749-755
The processes of phase formation in the Na2CO3-TiO2 and Na2CO3-TiO2-Nd2O3 systems are investigated in the temperature range 600–900°C. The high-temperature solid-phase reactions underlying the process of formation of complex oxide NaNdTiO4 are studied. It is established that the synthesis of the NaNdTiO4 compound occurs through the reaction of the intermediate product Na8Ti5O14 with neodymium oxide in the temperature range 720–780°C. The optimum method is proposed for synthesizing NaNdTiO4, which makes it possible to reduce the temperature of the synthesis, to avoid the formation of impurities, and to obtain the product in a finely dispersed state. 相似文献
17.
S. A. Petrov O. Yu. Sinel'shchikova L. F. Grigor'eva I. B. Patrina N. O. Ovchinnikov V. V. Gusarov 《Glass Physics and Chemistry》2005,31(6):803-807
The ramsdellite-type phases crystallizing in the Li2O-Fe2O3-TiO2 system in the course of synthesis in gaseous media at different oxygen partial pressures are studied. Solid solutions based on the ramsdellite structure with the composition Li2Ti3?xFe x O7 ? δ (0 ≤ x ≤ 0.7) are prepared in an oxidizing medium (PO2 = 1 atm) for the first time. Analysis of the results obtained by electron paramagnetic resonance and Mossbauer spectroscopy revealed that, in these solid solutions, all iron ions are in the oxidation state Fe+3. 相似文献
18.
E. Marin A. Lanzutti L. Guzman L. Fedrizzi 《Journal of Coatings Technology and Research》2012,9(3):347-355
In this study, innovative TiO2/Al2O3 mono/multilayers were applied by atomic layer depositions (ALD) on ASTM-AZ-31 magnesium/aluminum alloy to enhance its well-known
scarce corrosion resistance. Four different configurations of ALD layers were tested: single TiO2 layer, single Al2O3 layer, Al2O3/TiO2 bilayer and Al2O3/TiO2/Al2O3/TiO2 multilayer deposited using Al[(CH3)]3 (trimethylaluminum, TMA), and TiCl4 and H2O precursors. All depositions were performed at 120°C to obtain an amorphous-like structure of both oxide layers. The four
coatings were then investigated using different techniques, such as scanning electron microscope (SEM), stylus profilometer,
glow discharge optical emission spectrometry (GDOES) and polarization curves in 0.05-M NaCl solution. The thickness of all
the coatings was around 100 nm. The layers compositions were successfully investigated by the GDOES technique, although obtained
data seem to be affected by substrate roughness and differences in sputtering rates between ceramic oxides and metallic magnesium
alloy. Corrosion resistance showed to be strongly enhanced by the nanometric coatings, giving lower corrosion current densities
in 0.05-M NaCl media with respect to the uncoated substrate (from 10−4 to 10−6 A/cm2 for the single layers and from 10−4 to 10−8 A/cm2 for the bi- and multilayers). All polarization curves on coated samples also showed a passive region, wider for the bi-layer
(from −0.58 to −0.43 V with respect to Ag/AgCl) and multilayer (from −0.53 to −0.38 V with respect to Ag/AgCl) structures. 相似文献
19.
I. A. Sokolov I. V. Murin V. D. Khripun N. A. Valova Yu. K. Startsev A. A. Pronkin 《Glass Physics and Chemistry》2008,34(3):227-239
The concentration dependence of the electrical conductivity of glasses in the Tl2O-B2O3 system is studied. The nature of charge carriers in this system is experimentally investigated for the first time. It is demonstrated using the Hittorf, Tubandt, and Hebb-Liang-Wagner techniques and the Faraday law that neither Tl+ ions nor electrons are involved in the electricity transport. The verification of the Faraday law does not reveal the presence of thallium in the amalgam of the cathode or a change in the sample weight after electrolysis, to within the experimental error. This allows one to make the inference that protons can be charge carriers in glasses of the Tl2O-B2O3 system. It is shown using extended X-ray absorption fine structure (EXAFS) spectroscopy that Tl3+ ions and thallium Tl0 reduced to the metallic state are absent in the structure of the glasses under investigation. This means that thallium in glasses of the Tl2O-B2O3 system occurs only in the form of Tl+ ions. The analysis of the IR spectroscopic data leads to only a qualitative conclusion that the water content in the glasses insignificantly increases with an increase in the thallium oxide content. An increase in the electrical conductivity of glasses in the Tl2O-B2O3 system with an increase in the thallium oxide content is explained by the increase in the number of protons formed upon dissociation of H+[BO4/2]? structural-chemical units, because their concentration increases with increasing Tl2O content. In the structure of boron oxide, impurity hydrogen enters predominantly into the composition of H+[O2/2BO?] structural-chemical units, for which the dissociation energy is higher than that for the H+[BO4/2]? structural-chemical units. The increase in the concentration of H+[BO4/2]? structural-chemical units is accompanied by the increase in the number of dissociated protons, which are charge carriers in glasses of the Tl2O-B2O3 system. 相似文献
20.
The crystallization of strontium borate glasses containing 16.7–43.0 mol % SrO is investigated. New crystalline compounds of the hypothetical compositions 2SrO · 3B2O3 (metastable) and SrO · 5B2O3 (stable below 750°C), as well as the metastable diborate modification β-SrO · 2B2O3, are revealed, and their X-ray powder diffraction data are obtained. It is demonstrated that, with a deficit of strontium oxide, the 4SrO · 7B2O3 compound forms solid solutions. Strontium triborate SrO · 3B2O3, which was previously prepared only through the dehydration of crystal hydrates, is produced using crystallization of glasses. The thermal stability of this compound is studied. The influence of the dispersity on the stability of different crystalline phases is discussed. Variants of the phase diagram for the SrO · B2O3-B2O3 system in the case of monolithic and dispersed samples are proposed from analyzing the experimental results and the data available in the literature. 相似文献