Effect of the interaction between basicity and reductive character of melting atmosphere – both extreme – on the oxidation and coordination states assumed by transition metals when doped to silicate glasses

The influence of an extremely reductive melting atmosphere on the oxidation and coordination states adopted by transition metals in an ultrabasic host was evaluated. An invert glass (46SiO(2)center dot 11Na(2)O center dot 21CaO center dot 22BaO, basicity = 0.71) was synthesized in container-less conditions, on a jet of Ar 5%H-2. Performed measurements included optical absorption,…

Effect of thermal treatments below devitrification temperature on the magnetic and magnetocaloric properties in mechanically alloyed Fe70Zr30 powders

In this work, the relaxation of the amorphous structure of mechanically alloyed Fe70Zr30 powders has been analyzed through interrupted heating ramps below the devitrification temperature. As a result of such thermal treatment, Curie temperature and temperature at maximum magnetic entropy change curves shift to higher temperatures as the temperature of heating treatment increases. This effect…

A practical analysis for decelerated growth processes to get physically meaningful kinetic parameters from classical nucleation and growth theory despite of overgrowth

We have analyzed the overgrowth problem arising in decelerated growth processes of spherical crystals in the frame of classical nucleation and growth theory developed by Kolmogorov, Johnson and Mehl, and Avrami (KJMA). To do that, simulations of decelerated growth transformations with a constant nucleation rate have been performed, changing the linear growth rate of spherically…

Oxidation and coordination states assumed by transition metal dopants in an invert ultrabasic silicate glass

An ultrabasic invert silicate glass (46SiO2.11Na2O.21CaO.22BaO, optical basicity index equal to 0.71) was synthesized (O2 atmosphere) and used as host for various transition metal dopants. Optical absorption, emission and electron paramagnetic spectroscopies were used to characterize oxidation and coordination states. Some of the dopants displayed only their maximal oxidation state (Ti4+, V5+, Cr6+, Mo6+ and…

Hg/Sn amalgam degradation of ancient glass mirrors

Tin amalgam, which is obtained by pouring mercury onto a sheet of tin, has been used in the production of reflective coatings for mirrors. The corrosion processes of the amalgam layer were investigated in several mirrors from historical buildings located in southern Spain using SEM/EDS, XPS, and GID. Mercury and Sn4+ are present as spheres…

Crystallization behavior of (GeS2)(0.1)(Sb2S3)(0.9) glass

The crystal growth kinetics of antimony trisulfide in (GeS2)(0.1)(Sb2S3)(0.9) glass has been studied by microscopy and DSC. The linear crystal growth kinetics has been confirmed in the temperature range 492 <= T <= 515 K (E-G = 405 +/- 7 kJ mol(-1)). The applicability of standard growth models has been assessed. From the crystal growth…