Oxynitride Glasses

Oxynitride glasses are grain boundary phases within silicon nitride ceramics. The desire to understand their nature led to various investigations on oxynitride glass formation, structure, properties, and crystallization. This paper provides a review of oxynitride glasses and outlines the effect of glass chemistry, including nitrogen contents and cation ratios, on properties such as glass transition temperature, Young's modulus, and viscosity and relates this to structural features within the glass. A short outline of crystallization of oxynitride glasses to form glass–ceramics is presented.     

Arsenate Glasses

Stability regions were determined for a new family of glasses. Arsenic pentoxide (As₂O₅) forms binary glasses with alkali metal oxides (except Li₂O) and the known glass-formers B₂O₃, P₂O₅, GeO₂, and TeO₂. It also forms ternary glasses with Li₂O and a variety of alkaline earth, transition metal, and post-transition metal oxides when gallium oxide (and in some instances indium oxide) is present as a third component.     

Tellurite Glasses

The boundaries of regions of glass-forming compositions were determined in binary tellurite systems with alkali, alkaline-earth, and heavy-metal oxides, and in the ternary systems TeO₂-WO₃-Ta₂O₅, TeO₂-WO₃-BaO, TeO₂-WO₃-Bi₂O₃, and TeO₂-WO₃-Tl₂O. On the basis of a structural interpretation of liquid immiscibility in binary oxide systems and of X-ray diffraction investigation of the structure of tellurite glasses, a crystallochemical interpretation of glass formation is proposed, as well as a method for calculating the modifier-poor boundaries of the regions of glass-forming compositions in binary systems. An investigation of the crystallizability, density, optical constants, spectral transmission characteristics, and chemical durability of the tellurite glasses as functions of their chemical compositions has led to the development of a new flint-type optical glass, with n _d= 2.1608 and v = 17.4, possessing a high chemical durability and resistance to devitrification.     

含铅玻璃及其无铅化的研究

介绍了铅对人体的危害,综述了一些为限制铅的使用及排放而制定的相关法规,详细介绍了铅玻璃在现阶段中的一些主要用途和目前人们对这些玻璃的无铅化方面的工作。指出电子产品无铅化的迫切性。     

New Arsenate Glasses

A variety of new ternary arsenate glasses formed from mixtures of ionic alkali-metal meta-arsenates (MAsO₃) with somewhat covalent higher valence metal oxides (MO_x) have been prepared. From rate-of-hydrolysis comparisons, it has been found that bonding in these glasses is enhanced by de-protonization. The latter is enhanced through processing using alkali-metal flourides and increases the number of direct oxygen links between the higher valence metals. Stabilization also tends to increase with the covalent bonding or chain-forming character of the latter metals as well as with the electrostatic binding between alkali-metal ions and the chain linkage oxygens.     

Lead Galliate Glasses

Glasses have been formed in the binary system PbO–Ga₂O₃ within the compositional range extending from 60 to 80 mol% PbO. These glasses exhibit infrared cutoff values near 7.75 μm. The glasses are orange-red as a result of a cutoff in visible transmission near 500 nm. The glass transformation temperature decreases with increasing PbO concentration, whereas the thermal-expansion coefficient and density increase with increasing PbO content. Glasses containing 70 to 75 mol% PbO are good glass formers, with little tendency to crystallize, and exhibit good weathering behavior on exposure to normal atmosphere.     

Rare-Earth Aluminogermanate Glasses

The present study is a comparison of the properties of rare-earth aluminogermanate and rare-earth aluminosilicate glasses. Several properties have been measured, including density, transformation temperature, softening point, thermal expansion, Vickers hardness, magnetic susceptibility, Verdet constant, and IR transmission. The property data are discussed in relationship to the structure of these glasses and the field strength of the rare-earth ions. The Vickers hardness numbers of the glasses are discussed using a unique theory of hardness which involves the relationship between hardness and atom/ion packing in material structures.     

Bismuth Phosphate Glasses

Homogeneous glasses are formed in the Bi₂O₃-P₂O₅ system up to 35 mol% (63.8 wt%) Bi₂O₃. In property vs composition plots, the thermal expansion coefficient and tan δ exhibit minima, and hardness and activation energy for conduction show maxima at about 20 mol% Bi₂O₃. The deformation temperature of the glasses also increases abruptly at this composition. This anomalous behavior is interpreted in terms of a change in the function of Bi³⁺ ions from network formers to network modifiers.     

Zinc Tellurite Glasses

Glass formation was observed in the system ZnO-TeO₂ in mixtures containing 20 to 40 mole % ZnO. Softening occurred at 350°C and the glasses crystallized at 400°C. High dielectric constants (ca. 20) and high electrical resistivities (ca. 10¹¹ ohm-cm⁻¹) were measured. The zinc tellurite glasses have a higher density and refractive index and are considerably softer than silicate glasses. The optical transmission range was between 0.38 and 6.6μ with two absorption bands in the infrared. Spectra of Cu²⁺ and Nd³⁺ doped samples are also given.     

Rare-Earth Aluminosilicate Glasses

Rare-earth aluminosilicate glasses of the general formula 20R₂O₃· 20Al₂O₃· 60SiO₂ have been formed for 10 of the 14 possible rare-earth oxides. Two series of "mixed-rare-earth" glasses were also formed (Nd/Er and Nd/Y). These glasses exhibit exceptionally high glass transformation temperatures, moderate thermal expansion coefficients, and refractive indices of approximately 1.65. The glass transformation temperature and thermal expansion coefficients vary linearly with the field strength of the rare-earth ion. No evidence of a "mixed-rare-earth effect" was observed. MAS-NMR indicates that the aluminum ions are tetrahedrally coordinated in at least some of these glasses.     

Antimony Oxide Glasses

Glass compositions containing antimony oxide as a glassformer were developed. The stabilizing oxides used in these compositions were A1₂O₃, Na₂O, and K₂O. Glasses formed from these oxides, containing antimony oxide in amounts up to 78% by weight, transmitted infrared radiation in wave lengths up to 6.2 μ. The compositional range and some properties of these glasses are given.     

Heavy-Metal Oxide Glasses

Heavy-metal oxide glasses might arbitrarily be defined as those containing over 50 cation percent of bismuth and lead which participate in the glass structure as network formers. Glass systems based on these heavy-metal oxides in silicates, borates, phosphates, germanates, and ferrites are surveyed. Gallate systems are emphasized since they have a unique ability to form stable glasses while maintaining key properties, such as the best infrared transmission and the highest nonlinear optical susceptibilities and diamagnetic Verdet constants for oxide glasses.     

Radiation Dosimeter Glasses

Ionizing radiations produce visible colors in glasses containing certain multiple valence ions. The coloration, which is dependent on the radiation dose, is generally unstable. Combinations of certain ions can produce glasses with sufficient color stability to be used as dosimeters. Combinations of Mn-Fe, Mn-V, and Mn-V-Fe were studied. The response of glasses containing Mn-V-Fe was independent of the intensity of radiation and they may be used in the range between 10⁵ to 2 × 10⁷ roentgens.     

Scandium-Containing Oxynitride Glasses

Oxynitride glasses were made by atom-for-atom substitution of Sc³⁺ for Mg²⁺ in the Mg-Si-O-N and Mg-Si-Al-O-N systems. Good-quality glasses containing up to 7 mol% Sc₂O₃ were obtained. For a constant cation ratio, an increased N/O ratio gives glasses with increased elastic modulus, Vickers microhardness, density, and glass transition temperature.     

Constitution of Mixed-Alkali Phosphate Glasses: Constitution of Lithium-Rubidium Phosphate Glasses

In a previous study of the constitution of lithium-sodium-potassium phosphate glasses slight but definite cationic effects were observed. The constitution of lithium-rubidium phosphate glasses with , the number average chain length, varying from 1.25 to 9.00 was determined by paper chromatographic methods to follow the effect of substituting the rather large rubidium ion (1.47 A) for the small lithium ion (0.68 A). Systematic changes were observed; these changes, however, were numerically small. With the increase in the rubidium substitution for lithium the pyrophosphate content of the glass decreased and the tripolyphosphate content increased. Glasses with values as low as 1.5 (Li/Rb = 1/1) could be made by quenching the platinum crucible containing the melt in water. The = 1.25 glass, however, devitrified when thus made. It could be prepared only by the new copper-block-cooled strip furnace technique.     

Porous Silicon Oxycarbide Glasses

High-surface-area silicon oxycarbide gels and glasses were synthesized from mixtures of methyldimethoxysilane (MDMS) and tetraethoxysilane (TEOS) through acidic hydrolysis and condensation. A surface area of ∼275 m²/g and an average pore size of ∼30 Å was obtained for a 50% MDMS-50% TEOS glass at 800°C under a flowing argon atmosphere. The average pore size was increased by aging the precursor gels in ammonium hydroxide. The increased average pore size and the higher strength of the mesoporous gel network enhanced the surface-area stability of the glasses; in this case, surface areas >200 m²/g were retained at 1200°C under an argon atmosphere. ²⁹Si MAS NMR spectra revealed that an oxycarbide structure was established in the mesoporous glasses obtained after pyrolysis of the aged gels. The role of carbon was demonstrated by comparing the surface-area stability of the oxycarbide glasses with that of pure silica and that of oxycarbide glasses where all the carbon groups were removed through low-temperature plasma-oxidation treatments. In the absence of carbon, the thermal stability of the surface area decreased dramatically.     

无氟乳浊玻璃

氟化物是常用的玻璃乳浊剂,但污染环境。阐述了无氟乳浊玻璃如磷酸盐乳浊玻璃、氧化物乳浊玻璃、分相乳浊玻璃的成分和制备工艺,并指出存在的问题和发展方向。     

光学玻璃进展

总结了1982年《光学玻璃》出版以来光学玻璃品种和制造技术方面的进展,包括光学玻璃质量和检测标准的提高,特高、特低折射率新品种玻璃牌号,无铅无砷环保玻璃,光学玻璃连续熔炼和直接压型,非球面透镜精密模压和精密型料等。     

Elastic Properties of Glasses

A theoretical study of the possible mechanisms involved in the elastic deformation of a silicate glass indicates that if the only work done when such a glass is deformed is in the stretching or compressing of the Si-O-Si links, Poisson's ratio should be 0.25. Values less than this can be explained when the energy of deformation of the SiO₄ tetrahedra is considered and values greater than 0.25 if one takes into account the work done in deforming large modifying ions which fill the interstices in which they are located.