Fluoride glasses for multifunctional multifiber systems

Technological processes are developed for fabricating fluoride glass products with the use of different molding methods, such as free molding, controlled molding, mechanically activated injection molding, and forced molding at low temperatures and high pressures. A multimodule facility is designed for fabricating fluorozirconate, fluorohafnate, and fluoroaluminate glass products in the form of disks, plates, cylinders, blocks, tubes, rods, and optical fibers. Fluoride glass products are intended for the use in multifunctional multifiber systems for transmitting molecular, thermal, and other types of information.     

Fluoride and tellurite glasses for thin-film IR viewers

We have studied optical characteristics of Er³⁺-, Ho³⁺-, and Yb³⁺-doped ZBLAN and TWL glasses. Their luminescence was excited at wavelengths of 975, 378, and 449 nm. The 975-nm radiation excited the Yb³⁺ (² F _7/2 → ² F _5/2), and the excitation energy was then transferred to the Er³⁺ and Ho³⁺. The short-wavelength excitation led to cross-relaxation processes: (⁴ F _7/2, ² F _7/2) → (⁴ I _11/2, ² F _5/2) for the Er³⁺-Yb³⁺ pair (378 nm) and (⁵ F ₃, ² F _7/2) → (⁵ I ₅, ² F _5/2) for the Ho³⁺-Yb³⁺ (449 nm). At the three excitation wavelengths, we observed green luminescence in the range 525–550 nm. Using the glasses studied here, we prepared thin colorless lacquer films potentially attractive for hidden information recording and hidden labeling of various objects and materials.     

Fluoride bridging modes in fluorozirconate glasses by x-ray and computer simulation studies

A second characteristic ZrZr distance due to edge-sharing (ZrF_n) polyhedra which is observed in crystalline α-ZrF₄ (high temperature form) and is also suggested by recent X-ray studies of BaF₂ZrF₄ glasses, has been observed in ion dynamics computer simulation studies. Experimental X-ray and computer simulation results both imply that about one out of each four bridges between Zr pairs involve two fluoride ions, and that this proportion is almost independent of composition in the binary system.     

Optical Fluoride Nanoceramics

Inorganic Materials - This paper examines methods for the fabrication of optical fluoride nanoceramics and the compaction behavior of precursor powders. We discuss the basic drawbacks to the...     

Infrared glasses

Driven by applications in hot fields such as optical communications, lasers, sensors, etc. infrared glasses have to be considered as key components in the development of devices for telecom signal amplification, fibre-laser emission as well as for passive functions related to IR remote spectroscopy or thermal imaging. Stable vitreous materials with low-phonon energies are found in the family of fluorides and chalcogenides glasses; they offer the advantage of excellent transparency in the mid-IR and weak nonradiative relaxation when doped with rare earth elements. Despite the number of candidates only a very limited number of glass compositions can be shaped into good optical waveguides such as channel or fibre. When possible, this led to remarkable amplification in the 1.3 μm region and lasing emission in the blue or mid-IR. Non-linear optical properties of chalcogen-based glasses are also of special interest for fast all optical switching and photo-induced effects.     

Conducting glasses

Ion-conducting tellurite glasses are built from trigonal bipyramidal TeO₄ units. Neutron diffraction as well as Raman and IR spectroscopic studies have shown that there is a continuous transition from TeO₄ → TeO₃₊₁ → TeO₃ as the alkali oxide content is progressively increased, non-bridging oxygens being created in the process. Electrical conduction in both single and mixed alkali tellurite glasses is satisfactorily explained by the interchange transport mechanism, based on the site-memory effect exhibited by the glass network.     

Nitrate glasses

A large number of new nitrate glasses have been prepared. Their formation depends upon a balance in anion to cation ratio as influenced by anionic cluster size and cation field strengths. Vitreous combinations of M⁺, M²⁺, M³⁺ and/or M⁴⁺ nitrates, save for M⁺-M⁺ combinations, have been obtained.     

Metallic glasses

Metallic glasses are a new class of materials produced by rapidly quenching the melts at rates often exceeding a million deg/sec. These have been found to display an optimum combination of properties such as high strength, good bend ductility, improved corrosion resistance and excellent soft magnetic properties. Thus, metallic glasses are emerging as economically viable competitors to conventional engineering materials. A clear understanding of the atomic structure of metallic glasses and its change during annealing are of prime importance. Although techniques such as field-ion microscopy (fim) x-ray diffraction and small angle x-ray scattering have been employed for this purpose, high resolution electron microscopic (hrem) investigations conducted during the last few years aided greatly in deriving information on the atomic scale. Availability of high-voltage high-resolution electron microscopes has been mainly responsible for this happy situation. Studies on several metallic glasses have revealed thathrem images contain well-defined pattern of fringes over local regions, even though the diffraction pattern is that of a typical amorphous structure. The details of structure in the early stages of crystallization derived throughhrem, fim and analytical microscopic techniques are presented and discussed.     

Cadmium halide glasses. II. - Chloride glasses

New chloride glasses based on CdCl₂ have been discovered in the binary composition (Cd_0.5Ba_0.5)Cl₂ and in the two ternary systems CdCl₂-BaCl₂-KCl and CdCl₂-BaCl₂-NaCl within the limits in mole percent: 30–60 CdCl₂, 15–50 BaCl₂, 0–35 KCl or NaCl. Other chlorides such as LiCl, CsCl₂, ZnCl₂, PbCl₂, SrCl₂, AgCl may be included in the glass composition. Only thin samples may be obtained by quenching the melt. Although less hygroscopic than ZnCl₂ glasses, they undergo a surface attack by atmospheric water. For a representative glass Cd_0.5Ba_0.3K_0.2Cl_1.8, glassy transition occurs at 167° C, crystallization at 221 and melting at 363° C. Their optical transmission range lies continuously from the U.V.-visible spectrum to 16 μ in I.R. region. They appear thus as attractive new materials for infrared technology at 10.6 μ and for low-loss optical fibres. The structural discussion is based on the assumption of the 6-coordination of cadmium.     

上转换氟化物光纤激光器

氟化物玻璃是一种性能优异的激光基质材料。本文介绍了稀土离子上转换发光的机理和光纤顺的基本结构，综述了近几年来对掺Ｔｍ＾３＋、Ｐｒ＾３＋、Ｅｒ＾３＋、Ｈｏ＾３＋和Ｎｄ＾３＋的上转换氟化物光纤激光器的研究和应用概况。     

A Prolonged-Release Fluoride Tablet

Abstract

A prolonged-release tablet of sodium fluoride was prepared by dispersing the sodium fluoride in a waxy matrix. The prolonged release in 6 human subjects was demonstrated by urinary data.     

A Prolonged-Release Fluoride Tablet

A prolonged-release tablet of sodium fluoride was prepared by dispersing the sodium fluoride in a waxy matrix. The prolonged release in 6 human subjects was demonstrated by urinary data.     

Micro-machining of optical glasses — A review of diamond-cutting glasses

In order to diamond-turn optical glasses to a nanometric surface finish, it is critical to determine the transition point from brittle mode to ductile mode. This paper presents various experimental techniques to study this transition and discusses the mechanism of the surface generation. It has been recognized that tool wear is a serious issue in diamond turning of glasses. Thus, research in future should be concentrated on this field to enable the technology to be applied in commercial production.     

Ionic sulphate glasses

Sulphate glasses are typical ionic glasses in the sense they are constituted of discrete anions. In this review various physical properties of K₂SO₄, Na₂SO₄ and ZnSO₄ glasses have been reported. A model of random close packing of ions has been suggested and used to interpret several properties including the origin of mixed alkali effect.     

Novel organic-inorganic glasses

The preparation and properties of novel organic-inorganic glasses with phenyl groups covalently bonded to phosphorus in an inorganic glass are presented. Phenyl phosphonic acid (PPA) can be incorporated into tin and zinc fluorophosphate glasses (MO/MF₂/PO_2.5PPA) at levels up to 72 mol%. The T _g's of these glasses range from below room temperature to near 200°C depending on glass composition. For low melt glasses, these glasses have low moisture absorption and may solubilize dyes, organic photoconductors, NLO molecules, and pharmaceuticals. Several applications have been considered.     

Fibre reinforced glasses

A new method of preparing fibre reinforced glasses is put forward, which is based on further developments of the known slurry method and the sol-gel technique. This method combines the advantages of the two procedures. The prepregs are hot-pressed and the influence of preparation parameters on the bending strength are investigated. The pressure, temperature, time of pressing, granulation of the glass powder, the type of sol-gel solution and the gas atmosphere during the hot-pressing were all studied.     

Towards ultrastrong glasses

The development of new glassy materials is key for addressing major global challenges in energy, medicine, and advanced communications systems. For example, thin, flexible, and large-area glass substrates will play an enabling role in the development of flexible displays, roll-to-roll processing of solar cells, next-generation touch-screen devices, and encapsulation of organic semiconductors. The main drawback of glass and its limitation for these applications is its brittle fracture behavior, especially in the presence of surface flaws, which can significantly reduce the practical strength of a glass product. Hence, the design of new ultrastrong glassy materials and strengthening techniques is of crucial importance. The main issues regarding glass strength are discussed, with an emphasis on the underlying microscopic mechanisms that are responsible for mechanical properties. The relationship among elastic properties and fracture behavior is also addressed, focusing on both oxide and metallic glasses. From a theoretical perspective, atomistic modeling of mechanical properties of glassy materials is considered. The topological origin of these properties is also discussed, including its relation to structural and chemical heterogeneities. Finally, comments are given on several toughening strategies for increasing the damage resistance of glass products.