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1.
R. P. Yavetskiy E. A. Vovk S. V. Parkhomenko V. F. Tkachenko I. G. Polyakova A. L. Prosvirnin 《Glass Physics and Chemistry》2009,35(4):389-396
The physicochemical features of the phase formation upon crystallization of monolithic glasses of the strontium diborate stoichiometric
composition are investigated. It is demonstrated that the first phase crystallizing on the surface of the SrO · 2B2O3 glass is the strontium borate Sr4B14O25, which plays the role of a precursor for the subsequent crystallization of the SrB4O7 borate. The temperature corresponding to the maximum crystal nucleation rate on the surface and the time of complete “operation”
of nuclei are determined using differential thermal analysis. The optical glass-ceramics prepared by the two-stage crystallization
are surface-crystallized glasses in which the filling density of the surface is approximately equal to 30% and the content
of the main phase SrB4O7 is as high as ∼ 70%. No second harmonic generation of neodymium laser radiation in the glass-ceramics is observed because
of both the absence of the preferred orientation of SrB4O7 nonlinear optical crystals and the small crystal sizes (considerably smaller than the coherence length of the SrB4O7 crystal) in the direction perpendicular to the glass surface. 相似文献
2.
V. V. Golubkov V. L. Stolyarova Z. G. Tyurnina N. G. Tyurnina 《Glass Physics and Chemistry》2010,36(5):554-560
The structure of single-phase glasses in the BaO-B2O3-SiO2 system has been studied by the large- and small-angle X-ray scattering techniques. The glasses containing 40 mol % BaO upon equimolar replacement of B2O3 by SiO2 have been investigated. It has been demonstrated that the incorporation of barium ions into structural groupings fixes their position and provides ordering in the distribution of barium ions at interatomic distances up to at least 5 Å. The glasses under investigation are homogeneous, and their inhomogeneity is determined by thermal density fluctuations and fluctuations of the concentration of a part of barium ions distributed in a statistically random manner in the volume of the glass. The observed ordering in the distribution of barium ions is not reduced to the formation of local clusters with an increased concentration of barium ions but is most likely a characteristic feature of the bulk glass structure. The glass structure is consistent with the model of ideal associated solutions. 相似文献
3.
The effect of the relative volume of the conducting phase on the electroconductivity of phase-separated glasses in the ternary system Na2O–B2O3–SiO2, whose compositions are on the same glass transition isotherm at 550°C, is investigated. It is demonstrated that the electroconductivity of phase-separated sodium borosilicate glasses does not depend on the relative volume of the conducting phase (within the limits from 0.3 to 0.9) under the condition that its composition invariable. 相似文献
4.
The quaternary glasses of mixed divalent oxides including ZnO, MgO, CdO within a phosphate network former were prepared. Vanadium pentoxide was introduced as a dopant in the range from 0.5 to 3%. Optical and infrared absorption studies for all glass samples were carried out. The optical spectra reveal the presence of both V3+ and V4+ ions in the studied host mixed divalent oxides phosphate glass. Fourier transform infrared absorption spectral analysis indicates the appearance of distinct vibrational bands due to the presence of characteristic phosphate groups depending on the glass composition and the ratio of V2O5 content. The optical band gap and Urbach energy were calculated and discussed in relation to the effect of V2O5 content. Finally, the glasses were optically and structurally examined affter gamma irradiation with a dose of 80 KGy. 相似文献
5.
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
6.
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
7.
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
8.
Single crystals of potassium zinc phosphate, namely, K2(Zn3P4O14), are grown by crystallization of a glass of the related compound. The crystal structure of the compound is determined using single-crystal X-ray diffraction. 相似文献
9.
The features of the volumetric nucleation of crystals in glass obtained by melting furnace slags with the additive of SiO2, chromium sesquioxide Cr2O3, are studied by the methods of differential thermal and Xray phase analysis and optical microscopy. Upon the introduction of Cr2O3 as the catalytic additive, two phases are sequentially formed in the glass: magnesiochromite (MgO · Cr2O3) and diopside (CaO · MgO · 2SiO2). The characteristics of homogeneous and heterogeneous crystallization are determined: the stationary nucleation rate, nonstationary nucleation time, crystal growth rate, and their temperature dependences are obtained. Practical recommendations on the use of the obtained glass are given. 相似文献
10.
The optical absorption spectra of undoped soda lime silicate glass together with two glasses doped with either (1 % nano Fe2O3 ) or with both (1 % Nano Fe2O3 + 5 % cement dust) have been measured from 200 to 2400 nm before and after gamma irradiation with a dose of 8 Mrad. The undoped glass reveals strong UV absorption with two distinct peaks which are attributed trace ferric iron ions present as impurity. Upon gamma irradiation , this base glass exhibits three peaks at 240,310 and 340 nm and the resolution of an induced broad visible band centered at 530 nm. The two doped glasses show an additional small visible band at about 440 nm and followed by a very broad band centered at 1050 nm. Upon gamma irradiation, the two doped samples reveal the decrease of the intensities of the spectrum. The two additional bands are related to ferric (Fe+3) ions to the band at (440 nm) while and the broad band at 1050 nm is due to ferrous iron (Fe+2) ions. The decrease of the intensities of the UV-visible spectrum upon irradiation can be related to of capturing freed electrons during irradiation . Infrared spectra of the glasses reveal repetitive characteristic absorption bands of silicate groups including bending modes of Si–O–Si or O–Si–O, symmetric stretching , antisymmetric stretching and some other peaks due to carbonate , molecular water , SiOH vibrations . Upon gamma irradiation, the IR spectra reveal a small change in the base spectrum while the IR spectra of the two doped glasses remain unchanged. The change of the IR spectrum of the base glass is related to suggested changes in the bond angles or bond lengths of the mid band structural units. The doped glasses show resistance to gamma irradiation because the nano Fe2O3 can capture released electrons and positive holes. 相似文献
11.
S. A. Nemov A. V. Marchenko P. P. Seregin E. A. Tomil’tsev 《Glass Physics and Chemistry》2007,33(6):658-660
Triply and doubly charged states of europium are revealed by 151Eu Mössbauer spectroscopy in the structure of glasses of the composition (mol %) 19.5Al2O3, 31.5SiO2, 26.5MnO, and 22.5Eu2O3. The isomer shifts in the Mössbauer spectra of Eu3+ and Eu2+ ions in the structure of glasses differ from the isomer shifts in the spectra of the Eu2O3 and EuO compounds. This difference is explained by the fact that the electron density at 151Eu nuclei is affected by the manganese and aluminum atoms, which are not bound directly to the europium atoms. The broadening of the spectra of the Eu2+ ions in glasses is caused by the nonuniform isomer shift. 相似文献
12.
V. V. Golubkov N. G. Tyurnina Z. G. Tyurnina V. L. Stolyarova 《Glass Physics and Chemistry》2009,35(5):455-462
The structure of single-phase glasses in the SrO-B2O3-SiO2 system has been studied by the small-and large-angle X-ray scattering technique. The glasses containing 35, 40, and 45 mol
% SrO upon equimolar replacement of B2O3 by SiO2 have been investigated. It has been demonstrated that the glasses do not contain chemical inhomogeneity regions. The inhomogeneity
of the glasses is determined only by thermal density fluctuations. The isothermal compressibility varies insignificantly upon
replacement of B2O3 by SiO2 and decreases with an increase in the SrO content. The glass structure is consistent with the model of ideal associated solutions. 相似文献
13.
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
14.
Cerium oxide is one of the most important rare earth elements that is introduced into glass compositions due to its great effects on the optical properties. CeO2 was introduced in Hench’s patented SiO2-Na2O-CaO-P2O5 glasses with different concentrations in order to study its effect on the optical behavior of this glass including optical band gap, transmittance, reflectance and refractive index and to give a complete view for the optical properties on cerium oxide-doped silicate glasses. 相似文献
15.
The Sb2O3 doping lead-free glass in Bi2O3-B2O3-BaO ternary system were prepared in the composition of several different subsystem, and the glass powder was produced through
the process of water quenching. Glass transition temperatures (T
g
), glass soften temperatures(T
s
), the volume resistivity (ρ) in the temperature range of 80–200°C, and linear thermal coefficients of expansion in the temperatures
range of 25–300°C (α25–300) were measured for subsystems along with the different ratio of Bi2O3, B2O3 and BaO. For these subsystems, T
g
ranged from 458 to 481°C, and T
s
ranged from 490 to 512°C, both decreasing with the increasing of Bi2O3/B2O3 ratio, and increasing with the increasing of BaO/B2O3 ratio. The measured α25–300 ranged from 65.3 to 76.3 × 10−7 K−1, with values increasing with increasing Bi2O3/B2O3 and BaO/B2O3 ratio. The volume resistivity remains at a high standards, which may caused by it’s non-alkali composition, and it fluctuated
from 1013 to 1011 Ω cm with the temperature varied from 80–200°C. The structure of Bi2O3-B2O3-BaO ternary leadfree glass system was mearsured by FT-IR. The IR studies indicate that these glasses are made up of [BiO6], [BO3], and [BO4] basic structural units, and it appears that Ba2+ acts as a glass-modifier in this ternary system, but the Bi3+ has entered the glass network when it is in relative high content so as to change the α25–300, T
s
and T
g
. 相似文献
16.
The phase composition and structure of fusion-cast refractories composed of 57.0 – 84.2% Cr2O3, 4.3 – 36.1% MgO, 2.0 – 9.7% Al2O3, and 2.4 – 6.9% SiO2 have been studied by petrographic and x-ray spectral microprobe analysis methods. Refractories high in MgO with modulus M = (Cr2O3 +Al2O3)/MgO = 1.64 – 3.1 are shown to consist of spinel phase Mg(Cr, Al)2O4 and silicate glass. Refractory materials (80.8 – 84.2% Cr2O3, 4.3 – 4.7% MgO, 2.0 – 9.7% Al2O3, and 2.7 – 6.9% SiO2 with M = 18.7 – 20.2) are three-phase systems composed of spinel, escolaite, and glass phase. These materials, owing to their high corrosion resistance, have promising potentiality for practical applications.__________Translated from Novye Ogneupory, No. 12, pp. 69 – 74, December, 2004. 相似文献
17.
Swiatkowska-Warkocka Z Kawaguchi K Wang H Katou Y Koshizaki N 《Nanoscale research letters》2011,6(1):226
Spherical iron oxide nanocomposite particles composed of magnetite and wustite have been successfully synthesized using a
novel method of pulsed laser irradiation in ethyl acetate. Both the size and the composition of nanocomposite particles are
controlled by laser irradiation condition. Through tuning the laser fluence, the Fe3O4/FeO phase ratio can be precisely controlled, and the magnetic properties of final products can also be regulated. This work
presents a successful example of the fabrication of ferro (ferri) (FM)/antiferromagnetic (AFM) systems with high chemical
stability. The results show this novel simple method as widely extendable to various FM/AFM nanocomposite systems. 相似文献
18.
Yu. P. Udalov D. V. Grishchenko V. V. Kulakov I. V. Poznyak A. Yu. Pechenkov 《Glass Physics and Chemistry》2008,34(5):623-633
The morphology of the quenched and slowly crystallized samples in the ZrO2-Al2O3 system is investigated in the composition range 25–70 wt % ZrO2. It is revealed that, irrespective of the cooling rate, the samples contain large baddeleyite (or corundum) crystals, eutectic mixtures, and characteristic regions of intergrown elongated baddeleyite and corundum grains with micron sizes. These regions have the same phase composition at any initial ratio between zirconium and aluminum oxides and at any cooling rates of the melt. A hypothesis is put forward that these regions are products of the decomposition of ZrO2 · 2Al2O3 associates. 相似文献
19.
Yu. K. Startsev A. A. Pronkin I. A. Sokolov I. V. Murin 《Glass Physics and Chemistry》2011,37(3):263-282
The glasses, in which oxygen was partially replaced with sulfur, have been synthesized in the Na2O-P2O5-Na2S system. The chemical and chromatographic analyses of the glasses synthesized have been performed. The temperature-concentration
dependences of electrical conductivity of the glasses have been studied over a wide temperature range; the glass transition
temperatures and the nature of charge carriers have been determined. The IR spectra and Raman spectra have been recorded at
room temperature; the density and microhardness of the glasses and ultrasound velocity have been measured. A comparison of
the electrical conductivities of the investigated glasses with those of the earlier studied glasses in the Na2O-P2O5 system has shown their fair coincidence. The introduction of sodium sulfide into the Na2O-P2O5 system is accompanied by an approximately threefold increase in electrical conductivity, although the concentrations of charge
carriers (sodium ions) in the glasses amount to ∼17 and ∼26 mmol/cm3, respectively. The rise in electrical conductivity has been assumed to be caused by the increase in the degree of dissociation
of polar structural chemical units including sulfide ions and by the higher mobility of sodium ions in the oxygen-free matrix. 相似文献
20.
V. A. Sokolov T. Ya. Malysheva M. D. Gasparyan 《Refractories and Industrial Ceramics》2008,49(2):146-148
Details are given of the synthesis and testing of flux-cast refractory materials in the alumina-rich region of the Al2O3-MgO-B2O3 system; XRD and petrography indicate that the main structure-forming phases are corundum and magnesian spinel. In subordinate
amounts there are the boroaluminate 9Al2O3·2B2O3 and the previously unknown compound 4Al2O3·MgO·2B2O3, whose composition has been established by microprobe analysis. Corrosion tests showed that three-component systems containing
magnesium and boron oxides at levels of 5–10% do not increase the corrosion resistance of refractories in molten sodium-calcium-silicate
glass and electrovacuum borosilicate glass.
__________
Translated from Novye Ogneupory, No. 3, pp. 161–163, March, 2008. 相似文献