共查询到20条相似文献,搜索用时 109 毫秒
1.
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
2.
N. G. Tyurnina O. L. Belousova A. I. Domanskii L. A. Doronina V. L. Ugolkov 《Glass Physics and Chemistry》2010,36(3):294-303
The glass formation region in the SrO-B2O3-SiO2 system has been refined. The order of formation of crystalline phases in the system has been investigated at SrO contents
of 50–75 mol %. It has been demonstrated that, at low temperatures, the 2SrO · SiO2 and 3SrO · B2O3 phases crystallize first irrespective of the composition. The congruent melting temperature of the 3SrO · B2O3 · SiO2 compound is determined to be 1180 ± 10°C. The triangulation previously performed for the SrO-B2O3-SiO2 system in the concentration range 50–75 mol % SrO has been confirmed. 相似文献
3.
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
4.
S. S. Ordan’yan D. D. Nesmelov S. V. Vikhman 《Refractories and Industrial Ceramics》2009,50(5):391-393
Experiments and calculations have been applied to the structure of the triple eutectic system SiC–W2B5–LaB6(T
eu = 1900 ± 40°C), composition in mol.%: 10 LaB6, 44 SiC, 46 W2B5, error ±2–3%, which opens up prospects for making ceramic materials for various purposes. 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.
R. G. Kuryaeva 《Glass Physics and Chemistry》2011,37(3):243-251
The refractive index of potassium aluminosilicate glass of the KAlSi3O8 composition in the pressure range up to 6.0 GPa has been measured using a polarizing interference microscope and an apparatus
with diamond anvils. The changes in the relative density, which characterize the compressibility of the K2O · Al2O3 · 6SiO2 glass, have been estimated in the pressure range under investigation from the measured refractive indices within the framework
of the theory of photoelasticity. The results have been compared with the data previously obtained for the Na2O · Al2O3 · 6SiO2 glass. Although the molar contents of Al2O3 and M
2O (where M = K or Na) are identical in these glasses, the KAlSi3O8 glass exhibits a higher compressibility, which agrees with the lower degree of depolymerization of this glass as compared
to that observed in the NaAlSi3O8 glass. The pressure derivative of the bulk modulus K′
t
, which is calculated from the Birch-Murnaghan equation for the KAlSi3O8 glass (K′
t
= 7–9), is higher than that for the NaAlSi3O8 glass (K′
t
= 5.5–6.0). An increase in the pressure derivative of the bulk modulus K′
t
upon replacement of the Na+ cations by the K+ cations is explained by the inhibition of compression of the large K+ cations, which are located in cavities and have a considerably larger orbital radius than the Na+ cations. This manifests
itself in the fact that the curves describing the dependences of the change in the relative density (d − d0)/d (compressibility) on the pressure P for the KAlSi3O8 and NaAlSi3O8 glasses converge at pressures above 4.0 GPa. 相似文献
7.
A. Katsaounis 《Journal of Applied Electrochemistry》2008,38(8):1097-1110
The origin of the effect of non-faradaic electrochemical modification of catalytic activity (NEMCA) or Electrochemical Promotion
was investigated via temperature-programmed-desorption (TPD) of oxygen, from polycrystalline Pd films deposited on 8 mol%Y2O3–stabilized–ZrO2 (YSZ), an O2− conductor, under high-vacuum conditions and temperatures between 50 and 250 °C. Oxygen was adsorbed both via the gas phase
and electrochemically, as O2−, via electrical current application between the Pd catalyst film and a Au counter electrode. Gaseous oxygen adsorption gives
two adsorbed atomic oxygen species desorbing at about 300 °C (state β1) and 340–500 °C (state β2). The creation of the low temperature peak is favored at high exposure times (exposure >1 kL) and low adsorption temperatures
(Tads < 200 °C). The decrease of the open circuit potential (or catalyst work function) during the adsorption at high exposure times,
indicates the formation of subsurface oxygen species which desorbs at higher temperatures (above 450 °C). The desorption peak
of this subsurface oxygen is not clear due to the wide peaks of the TPD spectra. The TPD spectra after electrochemical O2− pumping to the Pd catalyst film show two peaks (at 350 and 430 °C) corresponding to spillover Oads and
according to the reaction:
The formation of the spillover oxygen species is an intermediate stage before the formation of the atomic adsorbed oxygen, Oads. Mixed gaseous and electrochemical adsorption was carried out in order to simulate the Electrochemical Promotion conditions.
The initial surface coverage with oxygen from the gas phase plays a very important role on the high or low effect of polarization.
In general mixed adsorption leads to much higher oxygen coverages compare with that observed either under gaseous or electrochemical
adsorption. The binding strength of the atomic adsorbed oxygen (state β2) was investigated as a function of applied potential. It was found that the binding energy decreases linearly with increasing
catalyst potential and work function. Similar behavior has been observed for oxygen adsorption on Pt, Ag and Au deposited
on YSZ in previous studies. 相似文献
8.
La0.6Sr0.4Co0.2Fe0.8O3−δ
oxides were synthesized by citrate method and hydrothermal method. The oxides prepared by citrate method are perovskite type
structure, while the oxides by hydrothermal method have a small amount of secondary phase in the powder. Pyrex glass seal
and Ag melting seal provided reliable gas-tight sealing of disk type dense membrane in the range of operation temperature,
but commercial ceramic binder could not be removed from the support tube without damage to the tube or membrane. Though the
degree of gas tightness increases in the order of glass>Ag>ceramic binder, in the case of glass seal, the undesired spreading
of glass leads to an interfacial reaction between it and the membrane and reduction of effective permeation area. The oxygen
flux of La0.6Sr0.4Co0.2Fe0.8O3−δ
membrane increases with increasing temperature and decreasing thickness, and the oxygen permeation flux through 1.0 mm membrane
exposed to flowing air (P
h
=0.21 atm) and helium (P1=0.037 atm) is ca. 0.33 ml/cm2·min at 950 °C. X-ray diffraction analysis for the membrane after permeation test over 160 h revealed that La2O3 and unknown compound were formed on the surface of membrane. The segregation compounds of surface elements formed on both
surfaces of membrane irrespective of spreading of glass sealing material.
This paper was presented at the 6
th
Korea-China Workshop on Clean Energy Technology held at Busan, Korea, July 4–7, 2006. 相似文献
9.
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
10.
Synthetic spinels of the system MgO-Cr2O3-Al2O3-Fe2O3 are considered and the desirability of organizing their production for the refractory industry is demonstrated.
Translated from Novye Ogneupory, No. 6, pp. 32–35, June 2008. 相似文献
11.
Xiaojuan Liang Haiquan Xu Jing Chen Juncai Sun Yuxiang Yang Xiangnong Liu 《Glass Physics and Chemistry》2011,37(3):330-342
Experiments on preparation of mica/Fe3O4 pearlescent pigment were performed to discuss influences of several crucial parameters on final products. The samples were
characterized by XRD, HRSEM, FTIR and color measurement, the content of Fe3O4 on the mica surface was also analyzed by XPS. It was found that the smoothness, compactness and colour deepness of the coating
were influenced by different pH values and temperatures. The optimum preparation parameters of mica/Fe3O4 pearlescent pigment were obtained: the value of pH ≥ 9.2; the concentration of sodium hydroxide was 0.5 mol/l; the concentration
ratio of Fe3+ to Fe2+ was 1.6 : 1; the velocity of magnetic stirring was 138 ≤ v ≤ 151 r/min; reaction temperature was 70–80°C; calcination temperature was 350°C and calcination time was 3 h. 相似文献
12.
In this study, 10B2O3/polyimide (PI) hybrid materials were synthesized with the aim to improve their thermal stability and neutron shielding properties.
3,3′-Diaminodiphenyl sulfone (DADPS) reacted with 3,3′,4,4′-benzophenonetetracarboxylic dianhydride (BTDA) in N-methyl-2-pyrrolidone (NMP) and mixed with amine functionalized 10B2O3 to prepare a series of poly (amic acid), meanwhile, corresponding PIs were obtained via the thermal imidization procedures.
The morphologies and structures of the prepared hybrid materials were characterized by scanning electron microscopy (SEM)
and Fourier transform infrared spectroscopy (FT-IR). The thermooxidative and flame retardancy properties of the PI films were
examined by thermogravimetric analysis (TGA) and limiting oxygen ındex (LOI). The experimental results showed that as the
amount of functionalized 10B2O3 was increased, flame retardant properties of the hybrid films were increased. Hybrid materials were also irradiated with
thermal neutrons. The neutron shielding properties increasing depends on the amount and the distribution of the 10B isotope. 相似文献
13.
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
14.
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
15.
The hydrogel of the mixed oxide Al2O3-30% Y0.1Zr0.9O2 was prepared by precipitation of ammonia from a water-alcohol mixture (1 : 5). The Al2O3-30% Y0.1Zr0.9O2 compound thus synthesized was characterized using differential scanning calorimetry, transmission electron microscopy, and
the BET adsorption method. The obtained sample consisted of spherical particles with an average size of 16–20 nm and a specific
surface area of 167 m2/g. The Al2O3-30% Y0.1Zr0.9O2 powder was pressed at 300 MPa and then calcinated at 1600°C for 2 h in air. The topographic and structural features of the
prepared ceramics were determined using atomic force microscopy and X-ray electron probe microanalysis. The porosity, the
Vickers microhardness, and the tensile strength were determined by mercury porometry. 相似文献
16.
V. N. Sigaev E. A. Alieva S. V. Lotarev N. M. Lepekhin Yu. S. Priseko A. V. Rasstanaev 《Glass Physics and Chemistry》2009,35(1):13-20
A method is proposed for local crystallization of glasses under laser irradiation. This method makes it possible to nucleate and grow microcrystals with a size distribution similar to a monodisperse distribution for several fractions of a second in any glass region chosen in advance. It is demonstrated using glasses in the La2O3-B2O3-GeO2 system as an example that the crystallization of the stillwellite-like phase LaBGeO5 with the composition close to the composition of the initial glass is observed in the glass under irradiation with the copper vapor laser operating in the high-speed pulse modulation mode. Strips (up to ~300 μm) produced at a specified depth from the glass surface contain extended regions consisting of uniformly distributed crystals, which have almost identical sizes, exhibit a pronounced faceting, and are identified using X-ray diffraction. The size and the number of crystals can be changed over a wide range by varying laser treatment conditions. This opens up the way to the design of new glass-ceramic materials in which the location of the crystalline phase in the glass bulk is controlled by a developer. 相似文献
17.
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
18.
SrAl2O4: (Eu2+, Dy3+) phosphor was prepared by solid state reaction. B2O5 as a flux was added in SrAl2O4:(Eu
2+, Dy3+) in order to accelerate a solid state reaction. In this paper, the effects of B2O3 on the crystal structure and the phosphorescent properties of the material have been evaluated. The synthesized phosphor
exhibited a broad band emission spectrum peaking at 520 nm, and the spectrum peak showed little effect by the B2O3 contents. The maximum afterglow intensity of the SrAl2O4: (Eu2+, Dy3+) phosphor was obtained at the B2O3 content of 5%. Adding the B2O3 caused uniform distortion to the crystal structure of the phosphor and resulted in reducing the lengths of a and c axes and
Β angle of the SrAl2O4 crystal. The uniform distortion was accompanied with crystal defects which can trap the holes generated by the excitation
of Eu2+ ions. The afterglow characteristic of the SrAl2O4: (Eu2+, Dy3+) phosphor was thus enhanced. 相似文献
19.
A. M. Starik B. I. Lukhovitskii N. S. Titova 《Combustion, Explosion, and Shock Waves》2008,44(3):249-261
The possibility of intensification of ignition of a methane-oxygen mixture in a supersonic flow behind the front of an oblique
shock wave by means of excitation of O2 molecules to the states a
1Δg and b
1Σg+ in an electric discharge is discussed. Through numerical simulations, activation of O2 molecules by an electric discharge is demonstrated to speed up chain reactions in the CH4-O2 mixture and to reduce the induction-zone length. Even a small amount of energy input to O2 molecules in the discharge (≈3·0−2 J/cm3) can reduce the ignition-delay length by a factor of hundreds and initiate combustion at distances of ≈1 m from the discharge
zone at comparatively low temperatures of the gas behind the front (≈1000 K) and moderate pressures (≈105 Pa). Excitation of O2 molecules by an electric discharge is much more efficient than simple heating of the mixture.
__________
Translated from Fizika Goreniya i Vzryva, Vol. 44, No. 3, pp. 3–16, May–June, 2008. 相似文献
20.
Straight In2O3 nanowires (NWs) with diameters of 50 nm and lengths ≥2 μm have been grown on Si(001) via the wet oxidation of In at 850°C
using Au as a catalyst. These exhibited clear peaks in the X-ray diffraction corresponding to the body centred cubic crystal
structure of In2O3 while the photoluminescence (PL) spectrum at 300 K consisted of two broad peaks, centred around 400 and 550 nm. The post-growth
nitridation of In2O3 NWs was systematically investigated by varying the nitridation temperature between 500 and 900°C, flow of NH3 and nitridation times between 1 and 6 h. The NWs are eliminated above 600°C while long nitridation times at 500 and 600°C
did not result into the efficient conversion of In2O3 to InN. We find that the nitridation of In2O3 is effective by using NH3 and H2 or a two-step temperature nitridation process using just NH3 and slower ramp rates. We discuss the nitridation mechanism and its effect on the PL. 相似文献