Mixed alkaline-earth effects on several mechanical and thermophysical properties of aluminate glasses and melts

Owing to heterogeneous nucleation at the melt-crucible interface, it is difficult to access the dynamic and physical properties of supercooled liquids of poor glass formers when using a conventional melting technique. To avoid the interface nucleation, we apply a containerless aerodynamic levitation laser-melting technique to measure the viscosity, density, and surface tension of a poor glass-forming system, ie, the mixed alkaline-earth aluminate melts. The temperature and composition (Ca/Sr) dependence of thermal-physical properties are investigated on both thermodynamically stable and metastable supercooled melts. In addition, the levitation laser-melting technique is used to quench the melts to glasses, and then the mixed alkaline-earth effects are investigated on Vickers micro-hardness and glass transition temperatures. By comparing the chosen silicate and aluminate series, we have identified weaker mixed alkaline-earth effects in aluminate series than those in silicate series, and this difference could be attributed to the different structural roles of alkaline-earth elements in two glass series.     

Nitrogen Dissolution in Sodium Alkaline-Earth Metaphosphate Melts

Phosphorus oxynitride glasses were prepared by remelting (5O – X )Na₂O · X BaO · 50P₂O₅, X = 0, 10, 20, 25, and 30, and 30Na₂O · 20MO · 50P₂O₅, M = Mg, Ca, Sr, and Ba', glasses in anhydrous ammonia. The nitrogen content depends upon the temperature and time of remelting in ammonia and the concentration and size of the alkaline-earth ion. Nitriding the starting glass decreased the dissolution rate in deionized water and thermal expansion coefficient and increased the dilatometric softening temperature and refractive index. The dissolution rate of the base glass in deionized water depended upon the concentration and size of the alkaline-earth ion, but for nitrided glasses, it was essentially independent of the alkaline-earth cation. The thermal expansion coefficient for all the oxynitride glasses decreased with increasing alkaline-earth concentration and cation field strength.     

Flame Spectrophotometric Analysis of Glasses: II, Calcium, Magnesium, and Barium, Including the Alkalis

The amount of calcium, magnesium, and barium, as well as of the alkali elements, in many glass compositions can be rapidly estimated with a flame spectrophotometer. Since the flame emission of the alkaline-earth elements is altered by such glass constituents as aluminum, iron, titanium, phosphorus, and zirconium, these elements should be removed, before flame analysis, by precipitation with ammonium hydroxide. With the elimination of the hydrous oxides and with corrections for the background interferences in the flame emission of the alkaline earths by the elements remaining, satisfactory flame analyses can be obtained. The mean difference between chemical and flame results for a series of 27 glasses of widely varying composition is approximately 0.15% for each element determined.     

Properties of Aluminoborate Glasses of Group II Metal Oxides: I, Glass Formation and Thermal Expansion

The glass formation of the aluminoborates of Group II metal oxides depends on the atomic weight of the oxide and on the electronic configuration of the metal ion. The participation of zinc, cadmium, and magnesium ions as network formers in the glass is shown from measurements of thermal expansion. The linear thermal expansion of the alkaline-earth aluminoborates varies from 4.7 × 10⁻⁶ to 16 × 10⁻⁶ per °C.     

Properties of diopside- and phlogopite-based melts and glasses

A study into the glass-forming properties displayed by diopside- and phlogopite-based melts is summed up. It is demonstrated that the alkaline-earth oxide ratio can be used as a criterion in assessing the suitability of a mixture for the production of glassy and glass ceramic materials. It is shown that machinable materials can be fabricated from phlogopite—fluoride mixes.     

Effect of Impurities on Sic Whisker Morphology

Thermal decomposition of polymeric organosilicon, as precursor to Sic whiskers, in the presence of impurities such as alkali and alkaline-earth metals and aluminum resulted in glass beads or droplets on the β-Sic whiskers. Semiquantitative analysis of typical whiskers and whiskers with glass beads were performed using a transmission electron microscope equipped with an energy-dispersive X-ray spectrometer and a scanning transmission electron microscope equipped with an electron energy loss spectrometer. The major impurities identified were correlated with the processing method employed     

Engineering the crystallization behavior of CsPbBr3 quantum dots in borosilicate glass through modulating the glass network modifiers for wide-color-gamut displays

The in-situ growth of CsPbBr₃ perovskite quantum dots (QDs) inside glass has been regarded as an alternative approach to improve their stability. Alkaline-earth metal oxides has multiple effects on the structure of the glass network. Herein, four types of alkaline-earth metal oxides are introduced into borosilicate glasses to modulate glass network structure, which has quite different effects on the crystallization behavior of CsPbBr₃ QDs. The reason can be ascribed to the different impacts of alkaline-earth metal on phase separation, nucleation, and growth procedure. Moreover, CsPbBr₃ QDs embedded in glass (CsPbBr₃ QD@glass) exhibit superior thermostability and photostability compared with CsPbBr₃ QDs powder. Finally, a white light-emitting diode achieving 124% of National Television System Committee (NTSC) gamut is fabricated using the CsPbBr₃ QD@glass, K₂SiF₆:Mn⁴⁺ phosphor film, and blue chip-on-board. This work provides a reference for modulating the glass network modifiers to regulate the crystallization behavior of perovskite QDs.     

Radiation-Induced Surface Conductivity in an Alkaline-Earth Boroaluminosilicate Glass Measured with Elevated-Temperature Scanning Probe Microscopy

A 50 mW 325 nm He:Cd laser was used to irradiate the fracture surface of a commercial alkaline-earth boroaluminosilicate display glass (Corning Code 1737) held at temperatures above 800 K. After this treatment, the surface of the glass was found to be conductive for several hours in a temperature range between room temperature and 850 K. The conductivity shows an activation energy of 0.18 eV. Scanning tunneling spectroscopy measurements indicate that the glass surface is semiconducting with a bandgap of ∼4.4 eV. It is possible to form topographical images of the surface of the glass using the electron tunneling current; the observed topography corresponds to that acquired using atomic force imaging from the same area.     

Interrelation of Diffusion and Thermodynamic Characteristics in Silicate Glass and Glass-Forming Melts

A correlation was established between the character of the concentration dependence of the self-diffusion coefficients and the deviation from ideality for mixed alkali silicate glass and melts and a melt containing alkaline and alkaline-earth cations.     

Alkaline and alkaline-earth silicate glasses and glass-ceramics from municipal and industrial wastes

Municipal (bottom ash and glass cullet coming from the municipal solid waste incineration and a community glass recycling program, respectively) and industrial (steel fly ash) wastes are particularly suitable to be subjected to a vitrification/devitrification process, leading to the production of alkaline and alkaline-earth silicate differently colored glasses with good chemical properties, capable to be transformed into surface nucleated basaltic glass-ceramics. These materials were investigated by means of differential thermal analysis, durability and release tests, X-ray diffraction and scanning electron microscopy.     

Reactions of Glasses with Aqueous Solutions

The kinetics of the reactions of various glasses with water and aqueous solutions with pH from 1 to 13 was studied. Simple binary alkali oxide-silica glasses were examined as well as some ternary glasses derived from the binary compositions by substituting alkaline-earth oxides for silica. All components of the glass were determined in the extract; the glasses varied from those very easily decomposed by water to those having durability comparable to that of commercial glasses. The equilibrium conditions of the system glass-water are distinguished from the approach to that equilibrium normally observed in such experiments. The rates of removal of various glass constituents under varied experimental conditions are reported and potential mechanisms for these reactions are discussed.     

Optical,Spectral, and Radiation-Shielding Properties of High-Lead Phosphate Glasses

The spectral, optical, physicochemical, radiative, and radiation-shielding properties of glasses in the PbO-P₂O₅-R _m O _n system (where R _m O _n stands for Group I–V element oxides) are investigated as a function of their composition. The composition of a colorless radiation-resistant high-lead glass suitable for production on a semicommercial scale is determined. The properties and optical quality parameters of the glass are studied. The new phosphate glass is a lead metaphosphate containing aluminum, alkali, and alkaline-earth oxides. This glass is resistant to radiation at doses up to 10⁷ R and has an optical transmission edge at 360 nm. The coefficient of absorption of gamma radiation for the new glass is larger than those of dense silicate flints. According to the optical parameters, the new glass lies between dense flints and dense barium flints in the Abbe diagram and compensates for the absence of the latter flints in catalogues of radiation-resistant glasses.     

Viscosity, Density, and Electrical Resistivity of Molten Alkaline-Earth Borate Glasses with 3 Mole % of Potassium Oxide

Viscosity, density, and electrical resistivity were determined on three series of molten alkaline-earth borate glasses, each containing 3 mole % of potassium oxide. A previous investigation of these properties of the binary alkaline-earth borates was limited by the formation of two immiscible liquids at low alkaline-earth oxide concentrations. To overcome this difficulty 3 mole % of K₂O was added to each composition. The properties of this new series of glasses were compared with the previous work. The densities at room and elevated temperatures were in the order BaO > SrO > CaO on a mole per cent basis. The reverse order was noted for the viscosity data. The electrical resistivity decreased with increasing concentration of alkaline-earth oxide at 1000°C. and at 1100°C. but increased at 800°C. and at 900°C.     

Glass formation and vibrational spectra of glasses in the RSO4-Na2B4O7-K2SO4 (R = Mg, Ca, Sr, Ba) systems

The regions of glass formation in the RSO₄-Na₂B₄O₇-K₂SO₄ (R = Mg, Ca, Sr, Ba) systems are determined. These regions are completely concentrated in the borate-rich region of the concentration triangle and occupy approximately 20% of the triangle area. The IR and Raman spectra of the glasses under investigation are recorded. It is revealed that the vibrational spectra of the glasses depend on the type of alkaline-earth metal cation. It is assumed that the structure of the glasses is determined by the glass-forming borate motifs with embedded sulfate anion tetrahedra.     

31P and 29Si Magic-Angle Sample-Spinning NMR Investigation of the Structural Environment of Phosphorus in Alkaline-Earth Silicate Glasses

²⁹Si and ³¹P magic-angle sample-spinning NMR spectroscopy indicates that phosphorus added as P₂O₅ to alkaline-earth metasilicate glasses is present as monomeric (PO₄)^3– structural units and that incorporation of this phosphorus increases the average polymerization of the silicate portion of the glass. These results are consistent with published interpretations of Raman spectra of similar composition.     

High-Temperature Energy Relations in Borates: Alkaline-Earth and Lead Borate Compounds and Their Glasses

The high-temperature energy relations in some alkaline-earth and lead borate glasses and compounds of the same compositions are reported. The data obtained with a continuous high-temperature calorimeter and by solution calorimetry in 2 N nitric acid were combined to give heat content versus temperature curves from 25° to 1100°C. The heats of fusion, entropies of fusion, entropy changes vs. temperature, and the free-energy changes from crystal to glass at 25°C are given. Previously unavailable X-ray diffraction data for strontium diborate and calcium diborate are reported.     

Catalytic Etherification of Glycerol to Diglycerol Over Heterogeneous Calcium-Based Mixed-Oxide Catalyst: Reusability and Stability

The activities of different heterogeneous alkaline-earth metal oxide catalysts and mixed-metal oxide catalysts were investigated. Glycerol etherification was carried out at 250°C in a three-necked glass reactor vessel at atmospheric pressure. In a typical experiment, 50 g of anhydrous glycerol was loaded into the reactor. Then, 2 wt.% of catalyst was added to the reactor. The reactor was then heated to the appropriate reaction temperature in nitrogen atmosphere under continuous stirring. The heterogeneous CaO catalyst showed the highest catalytic conversion (72%) compared with other alkaline-earth metal oxides, with a diglycerol yield of 19%. The highest glycerol conversion of 96% and diglycerol yield of 52% were observed for the mixed-metal oxide catalyst (Ca_1.6Al_0.4La_0.6O₃). Reusability and stability of this catalyst were tested. The ICP-AES analysis was performed to confirm the leaching of the metal species in the liquid phase of the reaction mixture.     

碱土金属氧化物对高铝瓷烧结性能的影响

研究了碱土金属氧化物对高铝瓷烧结性质的影响，发现碱土金属氧化物增加高铝瓷韧性的同时并不降低其机械强度。加入不同的碱土金属氧化物其晶粒长宽比不同，一般来讲高长宽比的坯体有较高的韧性和机械强度及韦伯模数。     

Compressibility of Binary Alkaline-Earth Borate Glasses at High Pressures

Compression data to 10,000 atm. were obtained for a series of barium, strontium, and calcium borate glasses at 21°C. The compressibility was found to be in the order Ba > Sr > Ca at corresponding molar concentrations and was not appreciably affected by pressure in the experimental pressure range. Comparison of data on alkali and alkaline-earth borate glasses shows that the compressibility at corresponding molar concentrations is smaller in the alkaline-earth glasses. Numerical comparisons at appropriate compositions show that a large part of the decreased compressibility produced by the alkaline-earth oxides arises from electrovalent sources.     

Internal Friction of Simple Alkali Silicate Glasses Containing Alkaline-Earth Oxides: I, Experimental Results

The internal friction of simple alkali silicate glasses to which systematic alkaline-earth oxide additions were made was investigated. These additions produced two significant results: (1) The two peaks previously reported in alkali silicate glasses were shifted to higher temperatures and decreased in height and (2) a third peak was found in some glasses which became more pronounced with increasing alkaline-earth oxide content. Internal friction measurements of alkali-free silicate and phosphate glasses also are described. In these glasses, peaks were present which closely resembled those found in glasses containing alkali.