International Journal of Applied Glass Science最新文献

We report, for the first time, an early evidence of structure-terahertz (THz) property relationship for two tie-lines within the sodium borosilicate glass system. The NaBSi series was chosen to study the effect of the substitution of silicon dioxide for boron oxide, whereas the BNaSi series studies the substitution of silicon dioxide for sodium oxide. Nuclear magnetic resonance, infrared absorption, and Raman spectroscopies were used to determine structural changes across both series. THz time-domain spectroscopy was used to record the refractive index over the measured bandwidth. Individual measurements at .502 THz were used as a frequency of focus for comparisons. The foundation for the proposed structure-THz property relationship is based on higher measurable THz refractive index changes correlated to a depolymerized glass network, R > .5, a network consisting of SiO₄ tetrahedra and charge-deficient [BØ₄]⁻ tetrahedra-forming borosilicate danburite and reedmergnerite rings with mixed Si–O–B bridges, and the formation of nonbridging oxygen (nbO) atoms on silicate tetrahedra. A polymerized glass network, R < .5, consists of homonuclear boroxol and silica rings within sodium borate and silicate subnetworks. Calculated and experimental fractions of tetrahedral borate and silicate tetrahedra with one nbO, optical basicity, density, and network connectivity data support the structure-THz property relationship.

The electronic structure, interatomic bonding, and optical properties of mixed alkaline-earth metal oxides MO (M = Mg, Ca) on amorphous silica glasses were calculated by combined ab initio molecular dynamics and the orthogonalized linear combination of atomic orbitals approaches. With the addition of alkaline-earth metal oxides, the original structural network model is destroyed, nonbridging oxygen is generated, and the covalent bonding is reduced, which reduces the total bond order density for silicate glass. The complex dielectric function plot shows that there are three distinct peaks in the imaginary part of the original silica glasses, and the last two peaks level off with the modification of alkaline earth oxides.

This work aimed to explore the effect of high pressures at room temperature on the vibrational modes and the thermal properties and stability of barium disilicate glass (BaO-2SiO₂) (BS2). The BS2 was prepared through the conventional melting route at atmospheric pressure. After being submitted to different pressure values (2.5 GPa, 4.0 GPa, and 7.7 GPa) and room temperature, the samples were characterized ex situ by Raman spectroscopy and differential thermal analysis. With this, it is possible to see that the pressure modifies the Raman vibrational modes of the glass, in the region associated with the Si-O-Si symmetrical bending modes. The Si-O symmetrical stretching vibrational modes (Qⁿ) remain unchanged, however there are changes on values of glass transition and decrease crystallization temperature, as well as the parameters of thermal stability of the glass.

The structural chemistry of the near-surface region of soda–lime–silica (SLS) glass is described in terms of silicate network connectivity using X-ray photoelectron spectroscopy (XPS). A thorough investigation of O1s and Si2p spectral lines by sequential XPS measurements, accompanied by Ar⁺ sputtering, revealed the variation of concentration of bridging oxygen, non-bridging oxygen (NBO), and hydrous species (SiOH/H₂O) as a function of depth from the glass surface. The O_total/Si atomic ratio was calculated to vary in the range of 2.90–3.74 throughout the depth of sputtering for a total duration of 110 min, while considering each of the aforementioned oxygen speciations in the curve-fitted spectra of O1s orbital. The glass surface up to a depth of 1–3 nm had the highest O_total/Si ratio of 3.74, which was representative for a mechanically weak structure with Q⁰ and Q¹ species, marked by the respective linkages of four and three NBOs per silica tetrahedral unit. This dictates the vital contribution of the hydrous species associated with silanol groups to the near-surface structure of SLS glass.

The role of the melting conditions and furnaces used to the obtained final colors has always been a question raised when investigating formulations and recipes of historical glasses. The focus of the present work is the reproduction of three recipes of red enamel glass of the manuscript by Neri, L'arte vetraria (1612) following the translation and comments by Kunckel's in Ars Vitraria Experimentalis (1679). The reproductions include the production of each individual compound of the selected recipes following instructions, and the final glass production in electric and wood-fire furnaces to assess the effect of different melting conditions. A multianalytical approach was used to fully characterize the produced samples allowing the study of the enamel chemical composition, color, crystals formations, and thermal properties. The results indicate that no significant color differences may be attributed to the melting conditions. However, it revealed that the samples produced in the electric furnace at 1200°C present a high crystallinity degree and the formation of white crystals at room temperature in a short period of time. The formation of crystals on glass is critical, and historically, to avoid it, these recipes must have been made at temperatures between 1050 and 1100°C.

Using an emittance technique with a fast CO₂ laser heating of glass samples, the high-temperature absorption spectra in the near-infrared region of ultrapure and colored (Co-, Cu-, Mn-, and Ni-doped) glasses are measured. The effects of higher glass temperatures on these absorption spectra are explained in the framework of the ligand field theory. Thus, the temperature-dependent absorption bands of the previous transition metal ions are assigned to electronic transitions among the ligand field energy levels of these ions. In particular, spectral shifts, spectral broadening, and changes in absorption strength are ascribed to changes in the structural symmetry of the ionic sites in the glass matrix and to changes of the ligand field strength at increasing temperatures.

Besides, the temperature-dependent Rosseland mean absorptions of the sulfate fined soda lime silicate glass melts, colored with the previous transition metal ions, are derived from the absorption spectra. Combining all the data, semiempirical correlations are derived, which predict the Rosseland thermal radiation properties as a function of glass temperature and of glass redox chemistry. The latter property involves the temperature-dependent concentration of the specific valency of the coloring ions, determined independently, e.g. by a Gibbs minimization redox calculation tool.

Vickers hardnesses of RO–Al₂O₃–SiO₂ glasses were measured over a broad range of compositions, ranging from ternary endpoints to mixed ratios of RO (CaO with MgO, SrO, or BaO), with the systematic variation of Al₂O₃ and SiO₂ levels. The hardnesses of CAS and MAS glasses are similar, ranging from 6.7 to 7.2 GPa, with the replacement of CaO with MgO producing a marginal increase in hardness. The substitution of SrO or BaO for CaO generally produced in a decrease in hardness down to 4.5 GPa with BaO. The sensitivity to alumina and silica levels, however, was much greater ranging from a minimum of 4.5 GPa to a maximum of ∼8.2 GPa. The correlation of the Vickers hardness with melting temperature was observed in the CAS system but generally not in the RO-blended glasses. Overall, a combined cation field strength of modifier cations determined the hardness above the critical RO blending ratio.