Transformation Range Viscosity Research Articles

Formation and properties of soda lime germanate glasses

The glass formation region has been determined for the soda lime germanate system. This system includes regions of both homogeneous and phase separated glass formation. The density, molar volume, refractive index, molar refractivity, thermal expansion coefficient, glass transformation temperature, and transformation range viscosity have been determined. The homogeneous glasses display behavior typical of the germanate anomaly, with little effect of the replacement of soda by lime. The phase separated glasses exhibit behavior which can be explained by considering the effect of morphology on glass properties.

Properties of alkali–alkaline earth metaphosphate glasses

Several properties of alkali–alkaline earth metaphosphate glasses have been measured. These properties include density, transformation range viscosity and dc electrical conductivity, with emphasis on the conductivity measurements. Glasses studied include series in which Li 2O or Na 2O is replaced by MgO, CaO or BaO, mixed alkali glasses containing a constant concentration of BaO and a series in which ZnO replaces BaO. The conductivity decreases by orders of magnitude as an alkaline earth oxide replaces either Na 2O or Li 2O. Replacement of one alkaline earth by another while maintaining the identity of the alkali ion has a much smaller effect on the conductivity of these glasses. The mixed alkali effect is evident in the conductivities of the Li–Na and Na–K glasses.

Effects of water content on aluminosilicate glasses and the relation to strong/fragile liquid theory

The effect of variations in water content on the transformation range properties of 25Na 2O25Al 2O 350SiO 2, 10Na 2O10CaO20Al 2o 360SiO 2, 20CaO20Al 2O 360SiO 2, and 20Y 2O 320Al 2O 360SiO 2 glasses are presented. Samples of these glasses were prepared with a range of water of hydroxyl contents by melting under various partial pressures of water. With an increase in water content of each glass, a decrease in both the glass transformation temperature, T g, and the transformation range viscosity are observed. The magnitude of these effects of water depends strongly on composition and is correlated with the activation energy for viscous flow. The data from this study are combined with the known effects of water on the properties of phosphate, borate, heavy metal fluoride, and other silicate glasses to show that the flow properties of ‘strong’ liquids are affected much more dramatically than those of ‘fragile’ liquids. These data are used to determine a quantitative empirical relationship between the magnitude of the effect of water on flow properties and the fragility of the glass-forming liquid.

ChemInform Abstract: Effect of Water Concentration on the Properties of Commercial Soda‐Lime‐Silica Glasses.

The effect of water concentration on the properties of three commercial soda-lime-silica glasses has been measured. Water (H2O) concentration varied from 50 to 550 ppm-wt. Properties measured include glass transformation temperature, transformation range viscosity, thermal expansion coefficient, electrical conductivity, and refractive index. The viscosity, Tg, and electrical conductivity decreased with increasing water content, while the thermal expansion coefficient and refractive index were unaffected by changes in water concentration.

Effect of Water Concentration on the Properties of Commercial Soda‐Lime‐Silica Glasses

The effect of water concentration on the properties of three commercial soda‐lime‐silica glasses has been measured. Water (H2O) concentration varied from 50 to 550 ppm‐wt. Properties measured include glass transformation temperature, transformation range viscosity, thermal expansion coefficient, electrical conductivity, and refractive index. The viscosity, Tg, and electrical conductivity decreased with increasing water content, while the thermal expansion coefficient and refractive index were unaffected by changes in water concentration.

Calcium fluoroaluminate glasses

Binary calcium aluminate glasses containing 59–70 mol % CaO have been formed, as have a series of glasses in which CaF2 replaces CaO. The transformation range viscosity and glass transformation temperature of the binary glasses decreases as the CaO concentration increases, whereas the thermal expansion coefficient, refractive index, and infrared cutoff wavelength increase. The substitution of CaF2 for CaO results in a decrease in the refractive index, viscosity, and glass transformation temperature, an increase in the thermal expansion coefficient and electrical conductivity, and no detectable change in the infrared cutoff wavelength. Magic angle spinning nuclear magnetic resonance indicates that the aluminum ions in these glasses are in tetrahedral coordination. These results will be discussed in terms of the structures of these glasses.

ChemInform Abstract: PROPERTIES OF LEAD FLUOROSILICATE GLASSES

AbstractEs werden Blei ‐ Fluorosilicat‐Gläser mit bis zu 25 mol‐% PbF2 dargestellt; Gläser mit 30 mol‐% PbF2 kristallisieren während des Abkühlens.

ChemInform Abstract: VISCOSITY AND THERMAL EXPANSION OF MIXED‐ALKALI SODIUM‐POTASSIUM BORATE GLASSES

AbstractSowohl die Viskosität als auch die thermischen Expansionskoeffizienten ′von Na‐ K‐Boratgläsem sind eine Funktion des Na2O/K2O‐Verhältnisses.

Effect of R3+ Ions on the Structure and Properties of Lanthanum Borate Glasses

Glass formation in the systems (mole percent) 25La2O3· xR2O3· (75 ‐ X)B2O3 (R = Al, Ga) and (25 ‐ x)La2O3· xLn2O3· 75B2O3 (Ln = Gd, Er, Y) was investigated. Up to 25 mol% Al2O3 or Ga2O3 can be substituted for B2O3, but more than ∼ 5 mol% Ln2O3 substituted for La2O3 caused macro phase separation. X‐ray diffraction and infrared analysis of these glasses and their devitrified products indicate that the basic structural units are similar to (B3O6)∞ chains found in binary 25La2O3* 75B2O3 glass. However, the BO4 units in the (B3O6)∞ chains are replaced by AlO4 or GaO4, units when Al2O3 or GaZO3 is substituted for B2O3. In these systems, Al2O3, Ga2O3, and B2O3 act as glass formers, whereas Ln2O3 and La2O3 act as network modifiers. The substitution of either R2O3 or Ln2O3 in the lanthanum borate system changes the separation distance between adjacent (B3O6)∞ chains. The effect of this structural change on the molar volume, transformation temperature, thermal expansion coefficient, and transformation‐range viscosity is discussed.

ChemInform Abstract: PREPARATION AND PROPERTIES OF SILVER BORATE GLASSES

AbstractEs werden Silberboratglä‐ ser mit 0‐ 30 mol‐°/o AgzO gebildet, deren Farbe von farblos bei den Ag‐freien Gläsern bis rötlich‐braun für die Gläser mit 30 mol% AgzO reicht (Absorptionsbanden bei z 407, z 3lO und z 250 nm).

Properties of Lead Fluorosilicate Glasses

Lead fluorosilicate glasses containing up to 25 mol% PbF2 were prepared. The dc electrical conductivity, thermal expansion, and transformation‐range viscosity of these glasses indicate that they are anionic conductors and that fluorine significantly decreases the continuity of the vitreous network.

Preparation and Properties of Silver Borate Glasses

Silver borate Basses containing 0 to 30 mol% Ag2O were formed. Properties measured include density, thermal expansion coefficient, glass transformation and dilatometric softening temperatures, transformation‐range viscosity, dc electrical conductivity, and helium permeability and diffusivity. Optical spectroscopy revealed that the color of these glasses results from absorption bands at ∼407, ∼310, and ∼250 nm. Each band increased in intensity as the silver oxide content of the glass was increased. The properties of these glasses were consistent with the structural model currently used to describe the structure of alkali borate glasses. No evidence for the existence of phase separation was found for the conditions of the present study.

Structure-Property Relations in Lanthanide Borate Glasses

Glass formation in the system Ln2O3-B2O3 (Ln = Nd, Sm) was studied. Glasses could be formed in the range from 0 to -28 mol% rare-earth oxide (Ln2O3), but liquid immiscibility in these systems limits the range of homogeneous glasses to 0 to 1.5 and 25 to 28 mol% Ln2O3. The infrared spectra indicate that the rare-earth-rich glasses are structurally similar to rare-earth metaborates (LnB3O6) which contain (B3O6)- chains. The variation in density, transformation temperature, thermal expansion coefficient, and transformation-range viscosity of these glasses with the size of the rare-earth ion is discussed. Glasses near the metaborate composition have a transformation temperature of =700°C, which is high for binary borate glasses. Glasses could not be formed in the systems EU2O3-, Gd2O3-, HO2O3-, and Er2O3-B2O3, even by quenching at =1300°C/s. The sudden lack of glass formation in the system Ln2O3-B2O3 with Ln3+ ions smaller than Sm3+ is explained on the basis of the size effect of the Ln3+ ion on the stability of (B3O6)- chains in these metaborates.

Transformation Range Behavior of Lithium Galliosilicate Glasses

The transformation range viscosity and thermal expansion behavior of lithium galliosilicate glasses were studied. The glass transformation and dilatometric softening temperatures exhibit maxima at gallium to lithium ratios of somewhat greater than one. Similar behavior was observed for the transformation range viscosity. The effect of phase separation on the dilatometric softening temperature is discussed in detail. These results are compared with those obtained for lithium alumino‐silicate glasses in other studies. The results are discussed in terms of the structural role of aluminum and gallium in the glass network.

ChemInform Abstract: TRANSFORMATION RANGE VISCOSITY OF FLUOROZIRCONATE GLASSES

AbstractDie Viskosität im Glasbildungsbereich wird für Fluorozirkonat‐Mehrkomponentengläser im System 0.56 ZrF4 ‐ (O.34‐x) BaFQ‐ 0.06 LaF3 ‐ 0.04 AIF, ‐ x RF mit R: Li, Na, K, Cs gemessen.

ChemInform Abstract: PROPERTIES AND MORPHOLOGY OF BARIUM GERMANATE GLASSES

AbstractDie Dichte, das Wärmeausdehnungsverhalten und die Viskosität im Glasbildungbereich werden für Bariumgermanat‐Gläser mit 0‐9 mol‐′l/o BaO gemessen.

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.

Transformation Range Viscosity of Fluorozirconate Glasses

Transformation range viscosity was measured for multicomponent fluorozirconate glasses in the system 0.56ZrF4·(0.34‐x)BaF2·0.06LaF3·0.04AlF3·xRF, where R =Li, Na, K, or Cs. The results indicate that the viscosity of these glasses can be described by an Arrhenius equation over the viscosity range from 107 to 1012 Pa·s with an activation energy of the order of 650 to 850 kJ. In general, the effects of alkali fluoride additions on the viscosity of fluorozirconate glasses are comparable to those in silicate systems.

Properties and Morphology of Barium Germanate Glasses

The density, thermal expansion behavior, and transformation‐range viscosity of barium germanate glasses containing 0 to 9 mol% BaO were measured. The addition of BaO to Ge02 resulted in phase separation at all BaO concentrations. The results of the property measurements indicate that glasses containing up to 3 mol% BaO consist of a matrix of essentially pure GeO2 with barium‐rich droplets. Glasses containing 6 mol% BaO or more consist of two interconnected vitreous phases. The morphology of glasses containing between approximately 3.5 and 5.5 mol% BaO can be altered from the droplet/matrix form to that of two continuous phases by the appropriate heat treatment.

Influence of water on the viscosity and thermal expansion of sodium trisilicate glasses

The transformation range viscosity, activation energy for viscous flow and the dilatometric critical temperature of sodium trisilicate glasses are all decreased by addition of water, whereas the thermal expansion coefficient in the elastic region is not altered to a significant extent. Although these effects are similar to those observed in vitreous silica, they are considerably reduced in magnitude. Since sodium trisilicate glasses are already highly depolymerized by the presence of Na 2O, the additional depolymerization due to small additions of water does not seem adequate to explain these results. It is suggested that water behaves similarly to the alkali oxides and that the results of this study may be due to an extreme case of the mixed-alkali effect.