Hybrid effects in the fracture toughness of polyvinyl butyral-based nanocomposites

Hybrid polyvinyl butyral (PVB) nanocomposite films comprising surface-treated carbon nanotubes (CNT-COOH) and nanoclays (NC) were tested for their “trouser-leg” fracture toughness in comparison to the values of the respective CNT and NC parent composites and to that of the pristine PVB film. Relative to the fracture toughness of the pristine PVB, the parent composites PVB/CNT-COOH-0.2% and PVB/NC-2% and the PVB/CNT-COOH-0.2%/NC-2% hybrid exhibited 105, 118, and 181% improvements, respectively. These were both impressive fracture toughness improvements and a significant hybrid effect – the latter being only slightly lower than the nominal maximum effect of 223% based on the combined improvements of the parent composites. Part of the samples was tested qualitatively by ball impact test of ballistic glass samples with relevant films. Among these samples, the hybrid film presented the best result. A significant linear correlation between fracture surface energy and roughness values was taken to reflect a fracture resistance mechanism of crack front slowdown by its interactions with nanoparticles

Crystal Nucleation And Growth Kinetics Of Naf In Photo-Thermo-Refractive Glass

Photo-thermo-refractive (PTR) glass is an optically transparent photosensitive oxide glass. Upon heating, the UV-exposed regions of this glass undergo copious crystallization of NaF nano-crystals giving rise to a permanent, localized refractive index change. But the unexposed parts of the glass also undergo some crystallization which causes unwanted light scattering. Holographic optical elements produced from PTR glass have been used in special laser systems. In this article we report, for the first time since the invention of PTR glass about half a century ago, the steady-state nucleation rates, nucleation time-lags and crystal growth rates for UV-unexposed PTR glass estimated in a wide temperature range, from Tg ~ 470 C up to 750 C. A self-consistent description of these data is presented in the framework of classical nucleation theory using the interfacial free energy of the critical nuclei and the effective diffusion coefficient as adjustable parameters. The diffusivity calculated from crystallization kinetics and that estimated from viscous flow via the Stokes-Einstein-Eyring equation show a decoupling phenomenon. © 2013 Elsevier B.V

Crystal nucleation and growth kinetics of NaF in photo-thermo-refractive glas

International audiencePhoto-thermo-refractive (PTR) glass is an optically transparent photosensitive oxide glass. Upon heating, the UV-exposed regions of this glass undergo copious crystallization of NaF nano-crystals giving rise to a permanent, localized refractive index change. But the unexposed parts of the glass also undergo some crystallization which causes unwanted light scattering. Holographic optical elements produced from PTR glass have been used in special laser systems. In this article we report, for the first time since the invention of PTR glass about half a century ago, the steady-state nucleation rates, nucleation time-lags and crystal growth rates for UV-unexposed PTR glass estimated in a wide temperature range, from Tg ~ 470 °C up to 750 °C. A self-consistent description of these data is presented in the framework of classical nucleation theory using the interfacial free energy of the critical nuclei and the effective diffusion coefficient as adjustable parameters. The diffusivity calculated from crystallization kinetics and that estimated from viscous flow via the Stokes-Einstein-Eyring equation show a decoupling phenomenon

Influence of niobium and titanium introduction on optical and physical properties of silicate glasses

The effects on optical and mechanical properties of introducing large amounts of TiO2 and Nb2O5 in a silicate matrix have been studied. Raman spectroscopy has been carried out in order to tentatively establish correlations between structural and physical properties. The high linear refractive index and the increase of the hardness for increasing d0 ions concentration have been related to the formation of a denser glass network dominated by corner linked NbO6 and TiO6 octahedra