Structure and Physical Properties of Borosilicate as Potential Bioactive Glasses

Borosilicate bioactive glasses containing titanium dioxide were prepared and investigated. The corrosion behavior of samples was examined for all samples upon immersion in phosphate solution. The erosion of the outer surface and ion exchange processes of the glass with the surrounding solution were studied by measuring the weight loss. Results were compared with samples that do not contain titanium dioxide. The final result of the reaction is the precipitation of hydroxyapatite. Characterization of the glasses was carried out by FTIR (Fourier transform infrared) absorption spectra before and after immersion in phosphate solution. The different crystalline phases and crystallographic parameters were explored using X-ray diffraction (XRD) analyzes and all indicate the precipitation of hydroxyapatite. A scanning electron microscope (SEM) is used to observe the morphological changes of the surfaces upon immersion. The atomic ratio of the final result product was obtained by the energy dispersive x-ray analysis (EDX) unit attached to the SEM. Changes in pH of the leaching solution were measured and evaluated. All measurements confirm that the studied glass has a high degree of biological activity which makes it very suitable for the field of biomaterials and other various medical applications.     

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.     

The Effect of Bivalent Cations on the Physicochemical Properties and Structure of Borosilicate Glasses

The effect of modifier oxides (MgO, CaO, SrO, BaO, and ZnO) introduced instead of SiO₂ into borosilicate glass on glass properties is investigated. It is established that the physicochemical properties (TCLE, softening temperature, mircohardness, density, water resistance) of glasses are determined mainly by structure and phase composition and, to a lesser extent, depend on the type of modifier oxide.     

Electron Micrographs of Some Borosilicate Glasses and Their Internal Structure

Many electron micrographs were obtained for borosilicate glass which had been subjected to chemical attack after heat-treatment at various temperatures and durations in order to study changes in internal structure, the so-called "phase separation." Both replica and direct-transmission methods were applied to Vycor-type glass. The two kinds of picture showed good agreement with each other. The conclusions obtained are as follows: (1) So-called quenched-state glass contains a glassy microphase of alkali borate, with dimensions less than 100 a.u., which corresponds to the so-called low-melting component; (2) the longer the heat-treatment time under constant temperature the larger the size of this glassy microphase becomes; (3) another kind of glassy microphase (SiO₂-rich) which corresponds to the so-called high-melting component is also enlarged with increasing heat-treatment time; (4) the size of both glassy microphases shows different values with different heat-treatment temperatures. Based on the experimental results described, a discussion of the relation between the internal structure and some physical properties of the glass is presented.     

Characterization and Luminescence Properties of Mn-Doped Zinc Borosilicate Glasses and Glass-Ceramics

Silicon - Zinc borosilicate glasses and their corresponding glass-ceramics in the system 55ZnO-25SiO2-20B2O3 (mol%) with different concentrations of MnO were prepared. The effect of MnO addition...     

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.     

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.     

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.     

Electrical Properties of Yttrium-Aluminum-Silicon Oxynitride Glasses

The ac electrical properties of several Y-Al-Si oxynitride glasses were measured as a function of temperature at 20° to 625°C in the frequency range 50 to 10⁵ Hz. The low-field dc conductivity was also determined. Dispersions in the dielectric constant associated with the peaks in the tan δ curves were observed in all cases. The peaks in tan δ shifted to higher frequencies with increasing temperature. Below ∼400°C, the ac conductivity was proportional to ωⁿ with 0.5< n 0, and the density of defect states were estimated using a model consisting of carrier hopping over a potential barrier. At all temperatures the dc conductivity could be described by an Arrhenius equation.     

Electrical Properties of Nonconventional Bi-Ba-Cu-O Glasses

Electrical properties of Bi-Ba-Cu-O glasses have been systematically investigated, and possible conduction mechanisms are discussed. Conductivity behavior is described by a small-polaron hopping mechanism. log σ_o, the slope of the log σ- W straight line, and the magnitude of the polaron bandwidth reveal that adiabatic hopping is dominant in the glasses. The Seebeck coefficient, S , of the Bi₁₆BaCu₃O_y glass is positive, indicating that the glass is a p -type hole conductor. The positive deviation of the observed S value from the theoretical S value is explained by assuming that the only oxygens bonded to both Cu²⁺ and Cu⁺ ions mediate indirect Cu⁺-O-Cu²⁺ hopping.     

The Effect of Iron Oxides on the Properties and Structure of Glazed Glasses

The effect of iron oxides with a molar content of 2.5 to 35.0% (above 100%) on the properties of aluminoborosilicate glasses is investigated. The specifics of phase separation in iron-bearing glasses and their heat-treatment products and the kinetics of liquation processes are demonstrated. The valence-coordination state of iron ions and the effect of thermal treatment on this state are identified. The dependence of the physicochemical properties of glasses on their chemical composition and structure is considered. The possibility of making colored glaze coating with preset properties and textures is substantiated.     

Phase Separation in Borosilicate Glasses

Dielectric measurements and direct-transmission electron microscopy were used to analyze the phase separation and alteration in sodium borosilicate glasses. Metal impregnation of the glasses after leaching was particularly useful in observing the topology of separated phases whose characteristic dimensions are about 100 A. The results indicate that borosilicate glasses such as Vycor and Pyrex are fully phase separated when rapidly cooled from the melt and that subsequent heat treatment serves only to alter the structural characteristics of the separated phases. The topological characteristics of the initially segregated phases suggest that phase separation may occur by spinodal decomposition.     

Effect of Incorporation of Nitrogen on the Structure and Dielectric Properties of Modified Oxide Sol-Precipitated Borosilicate Glasses and Glass-Ceramics

Glasses and glass-ceramics have received considerable attention as substrate materials in electronic packaging because of their low (<5) dielectric constant at 1 MHz. It is also known that low molecular weight species lower the contribution to electronic polarization which is primarily responsible for changes in the dielectric constant at these frequencies. In this study, borosilicate gels have been synthesized using a modified oxide sol-precipitation process utilizing oxide precursors. Nitridation of these gels has been initiated by combining air and ammonia heat treatments at different temperatures. The effects of incorporation of nitrogen on the structure of these gels have been studied using scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR). Similarly, the effects of nitrogen on the densification behavior of these gels have also been analyzed. At the same time, the dielectric constants of these glasses have been measured using impedance techniques. FTIR results indicate that the incorporation of nitrogen helps to decrease the borosiloxy (B-O-Si) bonds, causing a corresponding increase in B-N and Si-N bonds. Introduction of nitrogen into the gel network was seen to retard the densification kinetics and delay the crystallization onset for most of the nitrided glasses, while causing a gradual lowering of the dielectric constant.     

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.     

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.     

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.     

Ion Exchange in Sodium Borosilicate Glasses

The kinetics of K⁺-Na⁺ exchange in sodium borosilicate glasses containing 20 mol% Na₂O were studied as a function of glass composition and exchange time and temperature. The distribution of K in the glass after exchange in molten KNO₃ was determined using an electron microprobe. In those specimens which were not chemically attacked by the molten salt, the K profiles were consistent with Fickean behavior. The calculated interdiffusion coefficients varied with local composition in each specimen. This composition dependence and its variation with temperature could be fitted approximately to a mixed-alkali model using the Nernst-Planck relation for diffusive fluxes. However, some deviation from this behavior, presumably as a result of the generation of microscopic stresses around an exchange site, was observed. The dependence of the apparent activation energy, , on the B/Si ratio was analogous to that of the activation energy for ionic conduction in these glasses: decreased with increasing fraction of nonbridging oxygen. This result disagrees with the presumed behavior in sodium aluminosilicate glasses.