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Takashi Wakasugi Fumitaka Tsukihashi Nobuo Sano 《Journal of the American Ceramic Society》1991,74(7):1650-1653
The BN solubilities for B2 O3 , B2 O3 ─SiO2 , and B2 O3 ─CaO systems have been measured mainly at 1823 K using a graphite crucible. The capability of the systems for nitrogen dissolution is compared with that of silicate systems in terms of nitride capacity. The dependence of nitrogen solubility in molten CaO containing 15 mol% of B2 O3 on oxygen and nitrogen partial pressures is also investigated. It has been found that there are two mechanisms for nitrogen dissolution, namely as chemically bonded nitrogen and as physically dissolved nitrogen gas. 相似文献
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A partial molar volume technique was used to estimate the coordination number of oxygen ions around a boron ion in PbO·2B2 O3 and BaO·2B2 O3 melts. The boron coordination number appeared to be lower in the melt than in the crystal of PbO·2B2 O3 , whereas it was nearly the same in the melt and crystal of BaO·2B2 O3 . 相似文献
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E. F. RIEBLING 《Journal of the American Ceramic Society》1973,56(6):303-309
Binary Sb2 O3 -GeO2 glasses containing 45 mol% Sb2 O3 and ternary Sb2 O3 -B2 O3 -GeO2 glasses containing 50 mol% GeO2 were prepared. Their densities (volumes), refractive indices, and infrared spectra were determined, and their colors and high-temperature viscosities were estimated visually. Small amounts of Sb2 O3 (∼10 mol%) appear to perturb neither the Ge-O-Ge network nor those B-O-Ge networks with small B/Ge ratios (∼0.2). The B-O-Ge networks with larger B/Ge ratios (∼1.0) depolymerize in the presence of even less Sb2 O3 . Amounts of Sb2 O3 >10 mol% appear to depolymerize the Ge-O-Ge and Ge-O-B networks progressively, possibly with the formation of chains. A structurally sensitive ir isofrequency contour technique developed for ternary glass systems was applied successfully to these Sb2 O3 -B2 O3 -GeO2 glasses. These contours can thus readily detect significant network depolymerization in the absence of the usual network modifiers. 相似文献
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《Journal of the American Ceramic Society》1975,58(9-10):460-460
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Yaping Zhang Yunxia Yang Yuwen Ou Wei Hua Jiahua Zheng Guorong Chen 《Journal of the American Ceramic Society》2009,92(8):1881-1883
Glasses with compositions 50Bi2 O3 – x Sb2 O3 –10B2 O3 –(40– x ) SiO2 ( x =0, 1, 3, 5, 8, 10) have been prepared by conventional melt quench technique. Substitution of Sb2 O3 for SiO2 exerted an obvious effect on properties of glasses, especially, increased glass transition temperature ( T g ) and crystalline temperature ( T c ) greatly. Results of infrared transmission spectra attributed the effect to the formation of new bridging bonds of Sb–O–B and Sb–O–Si in glass network. 相似文献
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Ultrasonic shear and longitudinal measurements were made in Bz03 from 650° to 1000° C. From these data both the shear and volume relaxation time spectra were determined. The spectra had the same temperature dependence, although the volume spectrum was always broader than the shear spectrum. The shear relaxation process can be represented by a single relaxation time above 800° C in the region where the shear viscosity is Arrhenius. Both processes exhibit an increasingly broad distribution of relaxation times in the non-Arrhenius region. The temperature dependence of the shear spectrum was analyzed in terms of a distribution of activation energies. A surprising conclusion of this study is that activation energies at low temperatures are smaller than the activation energy in the Arrhenius region. 相似文献
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Phase relationships in the system Li2O, B2O3-B2O3 were studied by the quenching method using twenty compositions. The crystalline phases encountered were (a) Li2O, B2O3, which melts congruently at 849°± 2°C., (b) Li2O.-2B2O3, which melts congruently at 917°± 2°C., (c) a new compound, 2Li2O-5B2O3, which melts incongruently at 856°± 2°C. and dissociates below 696°± 4°C., (d) Li2O.3B2O3, which melts incongruently at 834°± 4°C. and dissociates below 595°± 20°C., and (e) probably Li2O.4B2O3, which melts incongruently at 635°± 10°C. Reactions were sluggish at temperatures near 600°C., resulting in metastable relations. Hence phase equilibrium data relating to the lower stability limit of Li2O.3B2O3 and to the upper stability limit of Li2O.4B2O3 are considered to be tentative. Properties of the glasses and crystalline phases were studied. The refractive index of the glasses increased with the addition of Li2O up to 22%, but further additions up to 40% had no substantial effect. Glasses containing less than 30% Li2O were water soluble. Limited data on the density and thermal expansion of the glasses are presented. Li2OB2O3 was euhedral, lath-shaped, length-fast, biaxial negative (2V = 27°), with nα= 1.540, nβ= 1.612, nγ= 1.616. Li2O.2B2O3 was uniaxial negative, with ne= 1.560, nw= 1.605. Li2O.3B2O3 was biaxial negative (2V = 75° to 80°), with nα= 1.576, nβ= 1.602, nγ= 1.605. X-ray powder diffraction data for the five crystalline compounds are presented. Thermal expansion data for Li2O-B2O3 and Li2O.2B2O3 and limited data on the fluorescent properties of the compounds are given. X-ray diffraction data are also presented for Li2O.B2O3.4H2O and Li2O.-5B2O3. 10H2O. Li2O B2O3 was obtained by heating the first hydrate at 450° to 680° C. X-ray diffraction showed Li2O.4B2O3 and Li2O-3B2O3 to be the crystalline products obtained during heating the decahydrate at 500°C. and 600°C., respectively. 相似文献
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Gerard E. Lenain Herbert A. McKinstry Dinesh K. Agrawal 《Journal of the American Ceramic Society》1985,68(9):224-C
The X-ray diffraction pattern for potassium-zirconium phosphate is significantly improved when the material is prepared by the sol-gel route rather than the powder method. Peaks at high, low, and intermediate angles are presented and compared for the two methods. It is assumed that the more nearly homogeneous mixing of the elements in the sol-gel process is responsible for the significant improvement in crystallinity. 相似文献
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Enthalpy relaxation processes in a B,O3 glass were investigated calorimetrically in the temperature region from well below to near the glass-transition temperature Tg . The low-temperature ( Ta Tg - 100 K) or sub-sub- Tg anneals stabilize the glass structure. On heating, the annealed sample shows an excess endothermic peak above the annealing temperature Ta , and gradually recovers the original enthalpy without heating through Tg . The enthalpy relaxation evolves in a continuous manner with annealing time as seen in the recovery process. As Ta approaches Tg , a gradual transformation of the sub-sub- Tg behavior to that characteristic of the sub- Tg anneal occurs. The relaxation spectrum exhibits a broad distribution of relaxation times with activation energies of ∼ 105 J/mol. The so-called β distribution commonly used in the analysis of the sub- Tg relaxation processes is seen to be too narrow to describe the sub-sub- Tg behavior. Possible mechanisms for the sub-sub- Tg relaxation phenomena are proposed. 相似文献
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Time-index of refraction isotherms were measured for B2 O3 glass starting from both a high and a low temperature in the transformation region. The equilibrium index values at each temperature, obtained from both types of approach curve, were identical. As in the case of the density values, the equilibrium refractive index curve as a function of temperature for this glass is not a straight line. The two-relaxation-times (crossover) model was applied to B2 O3 glass and fitted the data as well as it did in previous experiments with borosilicate crown and GeO2 glasses. The reverse crossover which was predicted by the model was experimentally confirmed with the B2 O3 glass. The spectrum of relaxation times narrowed with decreasing temperature, indicating approach to another region of single relaxation associated with the low-temperature Arrhenius region. The relaxation times for the low-temperature crossover agreed well with those from the high-temperature curves, indicating complete linearity in the experiments. The spectrum of relaxation times was slightly asymmetrical at constant pressure and very asymmetrical at constant volume. 相似文献
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Raman spectra were measured on B2 O3 -SiO2 glasses heat-treated at different temperatures and for different periods of time. It was found that the intensity ratio of the 810- and 475-cm−1 bands depended on the thermal history and composition of glass. The intensity vs heat-treatment temperature curve exhibited a maximum in the glass-transition temperature range. High-temperature Raman spectra were measured on 0.5B2 O3 -0.5SiO2 glass, both with increasing and decreasing temperature, between room temperature and 600°C. Above 300°C with increasing temperature, the intensity of the 810-cm−1 band decreased, whereas the intensity of the 475-cm−1 band increased. The changes reversed with decreasing temperature. The reversible change of the intensity of the two bands was interpreted as a reversible formation and decomposition of boroxy rings with temperature. The reaction becomes very sluggish below the glass transition so that the intensity ratio stayed constant below 300°C. 相似文献
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G. Bhattacharya S. Zhang M. E. Smith D. D. Jayaseelan W. E. Lee 《Journal of the American Ceramic Society》2006,89(10):3034-3042
B2 O3 mineralizes spinel formation from stoichiometric (1:1 mole ratio) calcined magnesia and alumina. After 3 h at 1100°C, X-ray diffraction (XRD) shows the mineralization effect of B2 O3 is limited to 1.5 wt% additions with higher B2 O3 contents leading to Mg3 B2 O6 formation and reduced spinel content. Boron nuclear magnetic resonance, electron probe microanalysis (EPMA), scanning electron microscopy, transmission electron microscopy (TEM) and XRD reveal formation of a boron-containing liquid. Energy dispersive spectroscopy in the TEM and EPMA of the glassy phases formed from solidification of the liquid reveal that initially it is Mg borate, later becoming a magnesia-modified boroaluminate, composition suggesting dissolution–precipitation as opposed to templated growth as the mechanism of this liquid phase mediated mineralization. 相似文献