Fabrice Célarié

Thermal stress analysis and supercontinuum generation in germanate-tellurite composite fibers

The build-up of thermal stress inside germanate-tellurite composite preforms prepared by a modified built-in casting technique was quantitatively evaluated with a theoretical model. This analysis has shown that for particular combinations of tellurite glass-made core and germanate-tellurite glass-made cladding, accumulations of thermal stress in extension and in compression occur over two different temperature ranges during the cooling of the preforms toward ambient temperature. When the glass properties are appropriate, these two regimes of stress accumulation can counterbalance each other in order to achieve a moderate structural stress inside the composite preforms. The composite fibers drawn from these preforms were then pumped with a mode-locked fiber laser centered at 1.91 µm to assess their potential for supercontinuum generation in the infrared.

Evidence and modeling of mechanoluminescence in a transparent glass particulate composite

Mechanoluminescence (ML) of a transparent alkali-phosphate glass composite with SrAl2O4:Eu, Dy particles is reported. Uniaxial compression experiments show the linear dependence of the mechanoluminescence intensity with the mechanical power. A theoretical model, based on the physics of delayed processes (in analogy of viscoelasticity), is proposed. This model accurately predicts the ML intensity changes induced by a complex mechanical loading and provides a convincing description of the mechanoluminescence response.

Interaction between Deformation and Crack Initiation under Vickers Indentation in Na2O-TiO2-SiO2 Glasses

An observed minimum in the critical crack initiation load at Poissons ratio (ν) of 0.21-0.22 in Na2O-TiO2-SiO2 glasses was investigated. Vickers indentation was used to examine hardness and average cracking length, fracture toughness was measured through the single-edge pre-cracked beam method (SEPB), and volumes of densification and shear flow around indents were measured using atomic force microscopy (AFM). Relations between the critical crack initiation load and hardness, average crack length, fracture toughness, and the volume fractions of densification and shear flow were studied. No correlations were observed between hardness, average crack length, or fracture toughness with the critical crack initiation load. A link between the minimum in crack initiation load and a change in deformation mechanisms (densification vs. shear flow) was observed.

The Influence of Cu Content on the Mechanical Properties of Copper-Borate Glasses

We report on the mechanical properties of xCuO-(50-x)PbO-50B2O3 (x from 0 to 30 mol%) copper-lead-borate glasses. Their mechanical properties were investigated by the mechanical resonance technique and by the indentation measurement. The replacement of lead by copper improves the packing efficiency, and enhances the elastic moduli, hardness and the fracture toughness of glasses.