No abstract

Research into the recycling of electronics waste materials, such as cathode ray tubes (CRTs) and in particular their component glasses, is required by both French and European legislation. One possible solution to the problem of CRT glass waste is to convert it into foam glass, a material with very promising properties. Foam glasses can be prepared from CRT glasses containing heavy elements (lead, barium) through reaction with a reducing agent such as TiN or SiC. The present experimental study sought to determine the mechanism of foam glass formation and the structural differences between bulk and foam glasses. Additionally, the specific characteristics of bulk and foam glasses such as density, porosity, thermal and mechanical properties were determined, as well as their structural characteristics, using X-ray diffraction, differential scanning calorimetry, photoelectron spectroscopy and scanning electron microscopy with energy dispersive spectroscopy. The results indicate that reutilisation of CRT glass in the form of foam glass is a very promising recycling option.

The substitution of germanium in the α-quartz structure is a method investigated to improve the piezoelectric properties and the thermal stability of α-quartz. Growth of α-quartz type Si(1-x)Ge(x)O(2) single crystals was performed using a temperature gradient hydrothermal method under different experimental conditions (pressure, temperature, nature of the solvent, and the nutrient). To avoid the difference of dissolution kinetics between pure SiO(2) and pure GeO(2), single phases Si(1-x)Ge(x)O(2) solid solutions were prepared and used as nutrients. The influence of the nature (cristobalite-type, glass) and the composition of this nutrient were also studied. Single crystals were grown in aqueous NaOH (0.2-1 M) solutions and in pure water. A wide range of pressures (95-280 MPa) and temperatures (315-505 °C) was investigated. Structures of single crystals with x = 0.07, 0.1, and 0.13 were refined, and it was shown that the structural distortion (i.e., θ and δ) increases with the atomic fraction of Ge in an almost linear way. Thus, the piezoelectric properties of Si(1-x)Ge(x)O(2) solid solution should increase with x, and this material could be a good candidate for technological applications requiring a high piezoelectric coupling factor or high thermal stability.