Iron redox effect on the structure and viscosity of a sodium silicate glass and melt.

The viscosity of silicate melts is one of the most important physical properties for understanding high-temperature phenomena in magmatic systems and material processing. The effects of composition and temperature on viscosity have long been elucidated. Although iron ions are the main components of magmatic systems, their influence on viscosity remains unclear because the behavior of iron is complicated; iron ions have two redox states, Fe3+ and Fe2+.

Photoluminescence Study of Undoped and Eu-Doped Alkali-Niobate Aluminosilicate Glasses and Glass-Ceramics.

In this study, the photoluminescence (PL) behavior of two aluminosilicate glass series containing alkali-niobates ranging from 0.4 to 20 mol% was investigated. The glasses exhibit an intense visible emission centered at ~18,400 cm for the peralkaline series and at higher energies (~19,300 cm) for the metaluminous glasses.

Glass science behind lithium silicate glass-ceramics.

Objectives: Lithium silicate-based glass ceramics have evolved as a paramount restorative material in restorative and prosthetic dentistry, exhibiting outstanding esthetic and mechanical performance. Along with subtractive machining techniques, this material class has conquered the market and satisfied the patients' needs for a long-lasting, excellent, and metal-free alternative for single tooth replacements and even smaller bridgework. Despite the popularity, not much is known about the material chemistry, microstructure and terminal behaviour.

Toughening by revitrification of LiSiO crystals in Obsidian® dental glass-ceramic.

As a predominantly lithium-metasilicate-containing glass-ceramic, Obsidian® (Glidewell Laboratories, USA) has a peculiar composition and microstructure among other dental lithium silicates, warranting an evaluation of the crystallization process to establish relationships between microstructural evolution and mechanical properties. Blocks of the pre-crystallized material were processed into slices measuring 12 × 12 × 1.5 mm and subjected to the mandatory crystallization firing by interruption the heating ramp at temperatures between 700 °C and 820 °C (dwell time between 0 min and 10 min).

Thermal Evolutions to Glass-Ceramics Bearing Calcium Tungstate Crystals in Borate Glasses Doped with Photoluminescent Eu Ions.

Thermal evolutions of calcium-tungstate-borate glasses were investigated for the development of luminescent glass-ceramics by using Eu dopant in a borate glass matrix with calcium tungstate, which was expected to have a combined character of glass and ceramics. This study revealed that single-phase precipitation of CaWO crystals in borate glass matrix was possible by heat-treatment at a temperature higher than glass transition temperature for (100-) (33CaO-67BO)-CaWO ( = 8-15 mol%). Additionally, the crystallization of CaWO was found by Raman spectroscopy due to the formation of W=O double bondings of WO tetrahedra in the pristine glass despite starting with the higher calcium content of CaWO.

Low-temperature degradation increases the cyclic fatigue resistance of 3Y-TZP in bending.

Objective: Due to past failures of orthopedic 3Y-TZP femoral implants linked to accelerated tetragonal-to-monoclinic phase transformation (t → m), the susceptibility to 'low-temperature degradation' or 'ageing' of 3Y-TZP has been advertised as detrimental to its long-term structural stability. However, no systematic mechanistic experiments on the fatigue resistance of aged 3Y-TZP under cyclic loading can support such statement. In this study, we aim to clarify this issue.

Chairside CAD/CAM materials. Part 1: Measurement of elastic constants and microstructural characterization.

Objective: A deeper understanding of the mechanical behavior of dental restorative materials requires an insight into the materials elastic constants and microstructure. Here we aim to use complementary methodologies to thoroughly characterize chairside CAD/CAM materials and discuss the benefits and limitations of different analytical strategies.

Methods: Eight commercial CAM/CAM materials, ranging from polycrystalline zirconia (e.

Dioxygen oxidation Cu(II) → Cu(III) in the copper complex of cyclo(Lys-dHis-βAla-His): a case study by EXAFS and XANES approach.

A former spectroscopic study of Cu(II) coordination by the 13-membered ring cyclic tetrapeptide c(Lys-dHis-βAla-His) (DK13), revealed the presence, at alkaline pH, of a stable peptide/Cu(III) complex formed in solution by atmospheric dioxygen oxidation. To understand the nature of this coordination compound and to investigate the role of the His residues in the Cu(III) species formation, Cu K-edge XANES, and EXAFS spectra have been collected for DK13 and two other 13-membered cyclo-peptides: the diastereoisomer c(Lys-His-βAla-His) (LK13), and c(Gly-βAla-Gly-Lys) (GK13), devoid of His residues. Comparison of pre-edge peak features with those of Cu model compounds, allowed us to get information on copper oxidation state in two of the three peptides, DK13 and GK13: DK13 contains only Cu(III) ions in the experimental conditions, while GK13 binds only with Cu(II).