Preparation and Properties of Nitrogen-Containing Na2O-B2O3 Glasses

Up to 3.3 wt% nitrogen can be incorporated into Na₂O-B₂O₃ glass melts. The melting procedure is described, and structure models are given. In contrast to N-containing silicate glasses, the borate glasses were transparent; however, micrographs of their fracture surfaces showed some crystallinity. Properties were determined as a function of the N and Na₂O contents of the glasses. Compared with N-containing silicate glasses, the properties of borate glasses are much less changed by the nitrogen introduced.     

Formation and Properties of GeSe2–Ga2Se3–PbI2 Novel Chalcohalide Glasses

The glass-forming region of the GeSe₂–Ga₂Se₃–PbI₂ system was determined and homogeneous glasses were prepared. The maximum dissolvable PbI₂ can be up to 50 mol%. The structures of glasses were characterized by Raman spectroscopy. The thermal, optical, and some basic physical properties of the glasses were investigated. The results show that GeSe₂–Ga₂Se₃–PbI₂ glasses have a wide region of transmission window (0.7–16 μm) and high refractive index (∼2.5) with the addition of PbI₂. The glasses have good glass-forming ability and high glass transition temperatures. Consequently, these novel glasses may be promising candidate materials for infrared optics and nonlinear optical field.     

Preparation and Properties of Oxynitride Glasses Made from Potassium Metaphosphate

Potassium phosphate oxynitride (KPON) glasses were made by heating crystalline KPO₃ at 702^° to 775^°C in dry ammonia. The softening temperature, thermal expansion coefficient, refractive index, and dissolution rate in water were measured as a function of nitrogen content and compared with the properties of oxynitride glasses made from LiPO₃ and NaPO₃.     

Electrical Resistivity of Titanium-Containing Glasses

Titanium-containing glasses were prepared by fusion of a base glass (BaO·B₂O₃SiO₂) and TiO₂ and/or Ti₂O₃ in Ar. Their resistivities did not vary with melting time and temperature. Interaction of Ti⁴⁺ and Ti³⁺ in the glasses was deduced by spectroscopy, but the valence states in the batch compositions were preserved in the glasses, according to the chemical analysis. Glasses containing either Ti⁴⁺ or Ti³⁺ had very high resistivities, whereas the glass prepared by melting a mixture of a Ti⁴⁺-containing and a Ti³⁺-containing glass had much lower resistivity. All results confirmed the possibility of controlling the resistivity by batch composition for these glasses.     

Effects of Doping Trivalent Ions in Bismuth Borate Glasses

Bismuth borate glasses from the system: 40Bi₂O₃–59B₂O₃–1Tv₂O₃ (where Tv=Al, Y, Nd, Sm, and Eu) and three glasses of composition: 40Bi₂O₃–60B₂O₃, 37.5Bi₂O₃–62.5B₂O₃ and 38Bi₂O₃–60B₂O₃–2Al₂O₃ were prepared by melt quenching and characterized by density, UV-visible absorption spectroscopy and differential thermal analysis (DTA) studies. Bismuth borate glasses exhibit a very strong optical absorption band just below their absorption edge. Glasses were devitrified by heat treatment at temperatures above their glass transition temperatures and the crystalline phases produced in them were characterized by Fourier transform infrared (FTIR) absorption spectroscopy and X-ray diffraction (XRD). Bi₃B₅O₁₂ was found to be the most abundant phase in all devitrified samples. DTA studies on glasses and FTIR and XRD analysis on crystallized samples revealed that very small amounts of trivalent ion doping causes significant changes in the devitrification properties of bismuth borate glasses; rare-earth ions promote the formation of metastable BiBO₃–I and BiBO₃–II phases during glass crystallization.     

Properties of Nitrogen-Containing Yttria—Alumina—Silica Melts and Glasses

The viscosity and solubility of nitrogen in Y₂O₃–Al₂O₃–SiO₂ melts have been systematically examined. The effects of nitrogen content on viscosity for Y-Al-Si-O-N melts and on Vickers hardness of oxynitride glasses also have been examined. Although the viscosity of Y₂O₃–Al₂O₃–SiO₂ melts was decreased, the solubility of nitrogen into the melts was increased with increased Y₂O₃ content. These results indicated that the yttrium ion behaved as a network modifier. Therefore, the structural units for viscous flow became small, and the amount of nonbridging oxygen increased in the melts when the Y₂O₃ content increased. The viscosity of Y-Al-Si-O-N melts and Vickers hardness of oxynitride glasses remarkably increased with increased nitrogen content. These results suggested that the substitution of nitrogen for oxygen in the melts may have led to a high average coordination of nonmetal atoms and that the increased cross-linking produced a more rigid glass network.     

Deposition and Characterization of Li2O–SiO2–P2O5 Thin Films

Amorphous lithium electrolyte thin films, xLi₂O·ySiO₂·zP₂O₅, were deposited by rf magnetron sputtering of pure and mixed-phase lithium silicate, lithium phosphate, SiO₂, Li₂O, and Li₂CO₃ targets, and their compositions were determined using proton-induced y -ray emission spectroscopy, energy-dispersive X-ray analysis, Rutherford backscattering spectrometry, and atomic-emission spectroscopy. The deposition conditions were chosen to assure thermalization of the sputtered flux, which proved to be necessary in order to obtain a homogeneous distribution of Si and P in the films. Optical absorption and ac impedance measurements showed that glass-in-glass phase separation occurred in a large SiO₂-rich domain of the composition diagram. In contrast to bulk glasses, all of the Li₂O–SiO₂ films were phase-separated, including those with lithia contents larger than lithium disilicate. High-performance liquid chromatography measurements revealed that, analogous to bulk glasses, the addition of SiO₂ to Li₂O-P₂O₅ compositions reduced the number of phosphate anion dimers, trimers, and higher anion polymers in the films through the formation of -Si-O-P-bonds. However, in contrast to bulk glasses, the distribution of phosphate anion polymers followed closely the Flory distribution, with the fraction of anion polymers decreasing monotonically with increasing chain length.     

Solid-state NMR Evidence of 4-, 5, and 6-Fold Aluminum Sites in Roller-Quenched SiO2-A12O3 Glasses

The structures of roller-quenched SiO₂-Al₂O₃ glasses containing 10 to 50 wt% Al₂O₃ were investigated by TEM and high-resolution ²⁷Al and ²⁹Si magic angle sample spinning nuclear magnetic resonance (MASS-NMR) spectroscopy. The chemical shifts observed in the NMR spectra of these phase-separated (on the TEM scale) glasses provide evidence, for the existence of all three (4-, 5-, and 6-jold) Al-coordination units in these glasses and for the presence of A1 in both the Si-rich and Si-poor phases.     

Oxyfluoronitride Glasses with High Elastic Modulus and Low Glass Transition Temperatures

The preparation and properties of novel calcium aluminosilicate glasses containing both nitrogen and fluorine are reported. Nitrogen increases Young's modulus and microhardness of oxide glasses by ∼25%. However, one of the major disadvantages of the use of oxynitride glasses for high-stiffness applications is the fact that nitrogen also increases glass viscosity. Melting temperatures of the order of ∼1700°C are required to achieve sufficiently low viscosities for glass forming and drawing processes. Fluorine substitution for oxygen in Ca–Si–Al–O–N glasses yields significant decreases in glass transition temperature and glass melting temperature as well as increasing nitrogen solubility to levels much higher than that previously reported for glasses made by melting CaO, SiO₂, Si₃N₄, and Al₂O₃ powder mixtures. The important effect that N results in increased elastic modulus is not diminished by the addition of fluorine. Thus, it is possible to produce novel oxyfluoronitride glasses with a high elastic modulus but melting and working can be carried out at more conventional glass processing temperatures.     

Properties and Structure of Lanthanum Borate Glasses

Glass formation limits were determined for the lanthanum borate glasses. Stable immiscibility prevents the formation of clear glasses over the range 0 to 20 mol% La₂O₃, but excellent quality glasses could be formed between 20 and 28 mol% La₂O₃. Data are reported for the density, refractive index, thermal expansion coefficient, glass transformation and dilatometric softening temperatures, transformation range viscosity, helium permeability, and chemical durability of these glasses. A limited Raman and infrared spectroscopy study suggests that lanthanum plays a similar structural role in these glasses and in the related crystals.     

Copper ⇌ Alkali Ion Exchange of Alkali Aluminosillcate Glasses in Copper-Containing Molten Salt: I, Monovalent Copper Salt, CuCl

Cu⁺⇌ R⁺ (R = Li, Na, and K) ion exchange experiments were conducted for 20R₂O·10Al₂O₃·70SiO₂ glasses in molten CuCl at 550°C in air and nitrogen atmospheres. The depth profiles of the copper incorporated into glasses were determined with an electron microprobe X-ray analyzer. The total amount of diffusing copper, M _t, strongly depended on the type of alkali ion in the glass and the ion-exchange atmosphere; i.e., M _t increased with increasing cationic size in the order Li < Na < K and M _t was greater in air than in nitrogen. The Cu ⇌ R⁺ ion exchange kinetics are discussed in detail.     

Bioactivity of Na2O-CaO-SiO2 Glasses

Bioactivities of Na₂O-CaO-SiO₂ glasses were evaluated by examining the formation of bonelike apatite, which is responsible for their bonding to living bone, on their surfaces in a simulated body fluid, using thin-film X-ray diffraction and Fourier-transform infrared reflection spectroscopy. It was found that glasses in a wide compositional region in the P₂O₅-free Na₂O-CaO-SiO₂ system can show bioactivity, as those in the P₂O₅-containing system. The rate of apatite formation on the surfaces of glasses varied largely with the composition of the glasses. Under a constant SiO₂ content of 50 mol%, a glass containing equimole of Na₂O and CaO showed the highest rate of the apatite formation. Variation in the rate of apatite formation with the glass composition corresponded well with the rate of increase in the degree of the supersaturation of the simulated body fluid with respect to the apatite due to dissolution of sodium and calcium ions from the glasses. Little difference was observed in the rates of ion dissolution and of apatite formation between P₂O₅-containing Bioglass 45S5-type and a corresponding P₂O₅-free Na₂O-CaO-SiO₂ glass. It is believed that P₂O_s-free Na₂O-CaO-SiO₂ glasses also show bioactivity as high as that of Bioglass.     

Synthesis and Characterization of a SiAION Glass

Homogeneous SiAION glasses containing up to 1 wt% nitrogen were synthesized via a pressureless method with a controlled quench rate and structurally investigated using ²⁷Al and ²⁹Si magic-angle spinning nuclear magnetic resonance (MAS NMR), Raman, and infrared (IR) spectroscopies. Minor changes occur with the incorporation of nitrogen into the aluminosilicate glass structure as evidenced by modifications to spectra of a nitrogen-free aluminosilicate glass. The ²⁷Al MAS NMR spectrum of the SiAION glass shows the existence of aluminum in 4-,5-, and 6-coordination to oxygen. The ²⁹Si MAS NMR spectra show a distribution of silicon sites in 4-coordination to oxygen. Raman and IR spectra of the SiAION glass show additional features due to incorporation of nitrogen in the structure compared with spectra of nitrogen-free aluminosilicate glasses.     

Preparation by a Sol-Gel Process of Borosilicate Glasses Containing Microcrystals of Tellurium and Zinc Telluride

Borosilicate glasses, 5B₂O₃· 95SiO₂ (mol%), containing TeO₂ and ZnO nominally equivalent to 10 wt% Te and ZnTe were prepared by a solgel method from Si(OC₂H₅)₄, B(OCH₃)₃, H₆TeO₆, and Zn(NO₃)₂. A study by electron spectroscopy for chemical analysis (ESCA) showed that glasses heated at high temperature (450°C) in air contained both Te⁶⁺ and Te⁴⁺ ions on the surface layer, but that mainly Te⁴⁺ ions occurred inside the bulk glass. When solgel-derived borosilicate glasses containing the TeO₂ compound were reduced at elevated temperature in a hydrogen atmosphere, Te crystallites ranging in size from 4 to 15 nm were produced at a lower temperature, between 200° and 250°C. The absorption edge moved from the infrared to the visible wavelength region as the particle size decreased to about 4 nm. For glasses containing both TeO₂ and ZnO, ZnTe crystallites formed at high temperature—over 300°C—and existed along with the Te phase.     

Auger Spectroscopic Analysis of Bioglass Corrosion Films

Auger spectroscopy and ion beam milling were used to determine surface compositional profiles on a series of bioglass implant materials after exposure to simulated body conditions. Four glasses were examined, a soda-lime-silica glass and 3 compositions produced by adding 3, 6, and 12 wt% P₂O₅ to the ternary glass. An SiO₂-rich layer is formed on the surface of all glasses investigated. As P₂O₅ is added to the bulk composition, a second film rich in Ca and P forms at the SiO₂-rich film-water interface. The rate of formation of the Ca-P film increases as the P₂O₅ content of the bulk glass increases. When glasses are corroded under identical conditions, the thickness of the Ca-P layer increases as the P₂O₅ content of the bulk composition is increased.     

Physicochemical Degradation of Titania-Stabilized Soluble Phosphate Glasses for Medical Applications

Four different formulations of phosphate glasses in the system P₂O₅–CaO–Na₂O–TiO₂ were developed. Their physicochemical, morphologic, and structural evolution was analyzed during in vitro degradation in SBF (simulated body fluid) at 37°C up to 16 weeks. The results showed that the addition of TiO₂ into the glass system enhanced both the elastic modulus and the chemical durability of the glasses. Indeed, the elastic modulus increased from 66.6 to 75.95 GPa and the weight loss percentage diminished from 1.6% to 0.3% with the addition of 8 mol% TiO₂. A uniform and superficial degradation mechanism could be observed throughout the dissolution time by means of environmental scanning electron microscopy (ESEM), inductively coupled plasma mass spectroscopy (ICP-MS), and Raman spectroscopy. The degradation process undergone by these glasses allows them to maintain their mechanical properties during the degradation process. Therefore, these materials offer an interesting choice for slowly resorbable materials in biomedical applications.     

Oxidation States of Chromium Dissolved in Glass Determined by X-ray Photoelectron Spectroscopy

The oxidation states of chromium dissolved in binary sodium silicate glasses were analyzed by X-ray photoelectron spectroscopy (XPS). The measured "equilibrium" Cr⁶⁺ fractions in glasses with varying Na₂O contents are shown to be in good agreement with results obtained by other techniques reported in the literature. XPS was then used to analyze the interface of a sodium silicate glass/chromium alloy (Inconel 718) seal. It is shown that Cr²⁺ and Cr³⁺ were the major chromium species dissolved in the glass interfacial region.     

Alkali-Resistant Magnesium Aluminosilicate Oxynitride Glasses

Glasses containing up to 3.3 wt% nitrogen were prepared in the system MgO─Al₂O₃─SiO₂─AIN─Si₃N₄. GlasGlass transition temperature, density, and elastic properties increased with increasing nitrogen content. Resistance against aqueous alkaline solutions was determined by weight loss measurements, solution and surface analysis. The good durability of both oxide and oxynitride glasses is caused by a protective surface layer. The introduction of nitrogen decreases the alkaline attack. The data suggest that nitrogen is incorporated as Si─N boxhs.     

Nature of Alumina in Phosphate Glass: II, Structure of Sodium Alurninophosphate Glass

We have used ²⁷Al and ³¹P magic angle spinning nuclear magnetic resonance (MAS NMR) spectroscopy and X-ray photoelectron spectroscopy (XPS) to describe quantitatively the relationships between the composition, structure, and properties of glasses in the Na₂O.Al₂O₃.P₂O₅ (NAP) system. In general, the glass properties (evaluated in part I) are most sensitive to changes in Al coordination. ²⁷ Al MAS NMR spectra reveal that octahedrally coordinated Al is most abundant in glasses with O/P ratios less than 3.5, the pyrophosphate structural limit. Tetrahedrally coordinated Al is most abundant in glasses with O/P greater than 3.5. Decreasing Al(OP)₆/Al(OP)₄ ratio generally correlates with decreasing glass transition temperature and refractive index. The compositional dependence of glass structure and properties can be qualitatively understood using a crystal chemical model based on oxygen charge balancing by the different Al and P moieties.     

Study of Crystallization Kinetics in Glasses along the Diopside–Ca-Tschermak Join

We report on the thermal stability and crystallization kinetics of the glasses in the diopside (CaMgSi₂O₆)–Ca-Tschermak (CaAl₂SiO₆) system. Four glasses with compositions corresponding to different diopside/Ca-Tschermak ratio were studied. Structural investigations on the glasses have been made by employing Infrared spectroscopy (FTIR). Activation energies for structural relaxation and viscous flow have been calculated using the data obtained from differential thermal analysis. The existence of glass-in-glass phase separation was observed in all the glasses. Kinetic fragility of the glasses along with other thermal parameters have also been calculated. Nonisothermal crystallization kinetic studies have been employed to study the mechanism of crystallization in all the four glasses. The Avrami parameter for the glass powders is ∼2, indicating the existence of intermediate mechanism of crystallization. Crystallization sequence in the glasses has been followed by X-ray diffraction analysis, scanning electron microscopy, and FTIR.