Hydrogen Permeability of Borosilicate Glasses

Borosilicate glass-forming compositions R₂O – B₂O₃ – SiO₂ – R_aO_b (R — Li, Na, K; R_a — Zn, PbO) are investigated. A correlation-regression analysis of the criteria (the silicate modulus, the oxygen number, the structure cohesion factor, the relative molar volumes of the components) affecting the hydrogen permeability of glasses is carried out. The tendency for permeability variations depending on the component composition and the above specified criteria is identified.     

Effect of Radiation on Glasses in Borosilicate and Boron-Lead-Silicate Systems

The effect of an electron flux and gamma radiation on glasses produced in a synthetic glass batch is considered. The origin of the radiation color centers arising in glasses and the disintegration of these centers in thermal and photodecolorization is investigated.     

Radiation Resistance of Porous Glasses

The sintering and evaporation of porous glasses under exposure to CO₂ laser radiation are investigated. It is demonstrated that the resistance of porous glasses to middle-IR laser radiation depends on the conditions of their preparation. The threshold radiation power densities necessary for sintering porous glasses of different compositions are obtained. The optical breakdown in porous glasses is studied. The resistance to near-IR laser radiation is determined for porous glasses prepared under different conditions.     

Gamma Radiation Effects on the Strength of a Borosilicate Glass

The effects of ⁶⁰Co gamma radiation on the strength-related mechanical properties of a borosilicate glass were examined. Although the glass darkened considerably, only a very slight densification was observed after irradiation to levels of 10⁸ rads. The strength distributions were not appreciably changed by the irradiation, nor was the calculated slow crack growth parameter, or N value. Neither did radiation affect the elastic modulus or the fracture toughness of the glass. Gamma radiation does not affect the strength below 10⁸ rads.     

Thermochemistry of Sodium Borosilicate Glasses

Glasses synthesized in the system Na²0-B ²0₃−SiO₂ were studied by high-temperature (974 K) solution calorimetry. The sign of the heats of mixing along four joins in the ternary reflects the presence or absence of glass-glass immiscibility. Calculations of binary phase diagrams using thermochemical data and a configurational entropy model give good agreement with experimental determinations, but complexities arise due to the simplicity of the entropy model used.     

Birefringence and Microstructure of Anisotropic Borosilicate Glasses

Optically anisotropic glasses were obtained by the uniaxial stretching of phase-separated borosilicate glasses in the transformation temperature range. The sign inversion of the birefringence, induced by subsequent heat treatments, was correlated with microstructure. The positive birefringence is attributed to form birefringence and the negative birefringence to "distribution birefringence" caused by the anisotropic distribution of the separated phase.     

添加剂对铅硅酸盐低熔点玻璃热性能的影响

采用常规玻璃熔融退火工艺制备了两组铅硅酸盐玻璃试样,玻璃组成为(物质的量含量,下同):(55-x)PbO-(10+x)B2O3-30SiO2-5ZnO(x=0,5,10,15)和(55-x)PbO-10B2O3-30SiO2-5ZnO-xSB2O3(x=5,10,15),以及与两组参照的传统铅硅酸盐玻璃55PbO-5Al2O3-10B2O3-30SiO2.利用热膨胀仪观察氧化物添加剂对玻璃转变温度范围△T(T1-Tg)的影响.实验结果表明,随着氧化硼加入量的不断提高,玻璃的转变温度(Tg)与软化温度(Tf)随之提高,而△T先减小后增大,即出现所谓的硼反常现象.当添加的氧化锑量在5%～10%(物质的量含量,下同)范围时,与参照样品相比,玻璃的软化温度(Tf)基本保持不变而转变温度(Tg)则提高10℃以上.当添加的氧化锑量达到15%时,玻璃的转变温度(Tg)与软化温度(Tf)均显著下降,但△T基本保持不变.     

Viscosity and Microstructure of Phase-Separated Borosilicate Glasses

The viscosity of a sodium borosilicate glass (SiO₂ 70, B₂O₃ 23, and Na₂O 7 wt%) was measured as a function of heat-treatment temperature and time for phase separation. The viscosity was shown to approach an equilibrium value unique to the heat-treatment temperature. The magnitude of the equilibrium viscosity increased as the heat-treatment temperature decreased. These results, plus electron microscopy of microstructure development, established that the viscosity of phase-separated borosilicate glasses is primarily controlled by the composition of the continuous, high-viscosity phase and that the effect, if any, of the microstructure size is small. In contrast to previous reports, the heat-treatment time required to attain the equilibrium composition was extremely long.     

硼硅酸盐玻璃结构与其熔体性质研究

对硼硅酸盐玻璃结构及其熔体性质展开研究,通过红外光谱分析了Al2O3对硼硅酸盐玻璃结构的影响,测试了玻璃熔体的高温粘度和抗折强度.研究结果表明:当玻璃中Al2O3/SiO2物质的量比在1.2％～6.5％,(R2O-Al2O3)/B2O3的物质的量比在0.04 ～0.41范围内时,Al3+全部以[AlO4]形式存在,是玻璃网络形成体,B3+大部分以[BO3]的形式存在,是玻璃网络外体,少部分以[BO4]形式存在,是玻璃网络形成体.增加玻璃熔体中Al2O3的含量,玻璃中游离氧含量和[BO4]含量减少,[BO3]含量增加,玻璃的高温粘度增大,熔制温度升高,抗折强度降低.     

Development of Porous Antireflective Films on Borosilicate Glasses

Experiments were conducted to characterize the development of gradient-index antireflective (GIAR) films formed on a phase-separated alkali borosilicate glass. Solution chemistry, secondary-ion mass spectrometry, Auger electron spectroscopy, weight-loss, scanning electron microscopy, and specific surface area analyses were used to evaluate a proposed model for film formation. The results suggest that the film-forming process is more complicated than proposed. For near-optimum heat trcatments, the film-formation acid treatment was virtually nonselective; only for much longer than optimum annealing times was selectivity evident. The graded-index films may result from precipitation of dissolved glass. The analyses were complicated by major compositional variations existing in the as-received glass.     

含钐稀土硼硅酸盐玻璃形成能力

通过玻璃形成区实验探索了含钐稀土硼硅酸盐玻璃的形成区范围,研究了Sm2O3含量对稀土玻璃形成区的影响和相应的玻璃形成区图,以及Al2O3含量对含钐稀土硼硅酸盐玻璃形成区的影响. 结果表明,当Sm2O3含量从10%增加到30%时,玻璃形成区有所增大,但当Sm2O3含量大于30%时玻璃形成区减小,当Al2O3含量为20%~25%时有较大的稀土玻璃形成区. 同时利用热分析结果所得到的玻璃析晶倾向参数b值,讨论了含钐稀土硼硅酸盐玻璃的形成能力,其中当Sm2O3含量为20%, Al2O3含量为25%时,b=0.8~0.85,这时玻璃形成能力较大.     

The Redox Potential of Borosilicate Glasses

The effect of different factors on the redox potential of potassium-borosilicate glasses is considered. It is demonstrated that this potential is formed under the effect of a number of opposite factors, where one of the factors often predominates. Thus, the raw materials have the deciding role in the formation of the redox potential of high-alkaline glasses. In predicting this potential, it is necessary to take into account the type and the coordination state of acid oxides.     

Gamma Radiation Shielding and Mechanical Studies on Highly Dense Lithium Iron Borosilicate Glasses Modified by Zinc Oxide

Silicon - Five glass samples of a new zinc-iron lithiumborosilicate (LBSFZ) with the chemical formula 64.8B2O3–8.5SiO2–1.5Fe2O3 – (25.2 − x)Li2O - x ZnO...     

Effects of Composition and Environment on the Fracture of Fluoride Glasses

Indentation-crack-length procedures were used to determine the critical fracture toughness (K_IC) and the sensitivity to environmentally enhanced crack growth in heavy-metal fluoride glasses of varying chemical composition. The data show that while K_IC was more or less invariant with composition, some glasses were more susceptible to subcritical crack growth than others. The results are interpreted in terms of existing crack-growth models. A technique for predicting K_IC from fundamental atomic bonding and crystal-structure data for these glasses is discussed.     

Structure and Electrical Properties of Iron Borosilicate Glasses

Glassesofnominal composition 25SiO₂- 30Na₂O-2Al₂O₃-x Fe₂O₃-(43- x)B₂O₃ (x = 1 to 6 mol%) were prepared by the ordinary melt quenching technique. The influence of Fe₂O₃ substitution at the expense of B₂O₃ on structure and electrical conductivity of sodium borosilicate glasses was investigated. The conductivity was found to increase with increasing Fe₂O₃ content. A double channel conduction mechanism was introduced to explain the electrical conductivity measurements. Moreover, the activation energy decreases considerably in the temperature range from 473 to 773 °K. The activation energies of conduction in various temperature regions were calculated. The conduction was best described by sodium ion migration and hopping between the two valence states of iron. FTIR absorption spectra in the spectral range 1600-400 cm^?1 were measured and a deconvolution analysis technique (DAT) using Gaussian peaks was introduced to analyze the studied glasses. Different characteristic bands were observed and attributed to different types of borate besides silicate vibrational groups.     

Radiation Effects on the Physical Properties of Low-Expansion-Coefficient Glasses and Ceramics

The effects of irradiation on the coefficient of thermal expansion (CTE), the density, and the elastic moduli of low-CTE materials such as amorphous SiO₂, ultra-low-expansion glass, β-SiC, Astrositall, and Zerodur were surveyed. It was found that the properties of all of these materials were affected by radiation exposures up to 2 × 10⁹ rd; SiO₂ and SiC were the most radiation-resistant of the materials studied.     

Effect of Composition on the Mechanical Properties of Aluminosilicate and Borosilicate Glasses

Elastic moduli and fracture toughness were determined for several glasses in the systems soda-alumina-silica, calcia-alumina-silica, and soda-boric oxide-silica. Results for the aluminosilicates are analyzed in terms of Al³⁺:Na⁺ ratios. The mechanical properties do not show maxima or minima at the Al³⁺:Na⁺ ratio of 1, in contrast to conductivity, helium permeability, and refractive index. The moduli and toughness increase with Al³⁺:Na⁺ ratio, which is consistent with increased coherency of the glass network. Glasses which contain B₂O₃ instead of Al₂O₃ have slightly higher moduli but are considerably tougher. The moduli of calcium aluminosilicate glasses are ∼25% greater than sodium aluminosilicates, whereas the fracture toughnesses are similar.     

Fracture- and Indentation-Induced Structural Changes of Sodium Borosilicate Glasses

It is known that indentation using a diamond indenter induces permanent densification to result in plastic or inelastic deformation of glass. However, it is still unclear whether a high tensile stress causes such a structural change or not. In this study, fracture- and indentation-induced structural changes of glasses with the compositions of 20 Na₂O − 40x B₂O₃ – (80−40x) SiO₂ (in mol%, x = 0, 0.5, 1, 1.5) are investigated. Two-point bending tests of the glass fibers are performed to apply a high tensile stress to the glasses, and Vickers indentation tests of the glasses are also carried out for comparison. The structural change of the glass is evaluated by using Raman spectroscopy. It is elucidated that a tensile side of the fractured fiber for every composition shows a permanent structural change, which is characterized by a lower wave number shift of Raman peak assigned to the Si-O-Si bending vibration mode. It is also found that the behaviors of Raman peaks of the fractured fiber are opposite to those of the indented glass under a high compressive stress.