Ashutosh Goel

Influence of NiO on the crystallization kinetics of near stoichiometric cordierite glasses nucleated with TiO2

This work presents the effect of NiO on the thermal behavior and the crystallization kinetics of glasses lying near the stoichiometric cordierite composition nucleated with TiO2. Three glasses with NiO content varying between 1 and 5 mol% have been synthesized in Pt crucibles. Activation energies for structural relaxation and viscous flow have been calculated using the data obtained from differential thermal analysis (DTA). Kinetic fragility of the glasses along with other thermal parameters has been calculated. Non-isothermal crystallization kinetic studies have been employed to study the mechanism of crystallization in all three glasses. The crystallization sequence in the glasses has been followed by x-ray diffraction analysis of the heat treated glass samples in the temperature range of 800–1200 °C. μ-cordierite has been observed to be the first crystalline phase in all the glass samples after heat treatment at 850 °C, while NiO plays an important role in determining the crystallization sequence at higher temperatures, leading to the formation of α-cordierite.

Influence of ZnO on the crystallization kinetics and properties of diopside-Ca-Tschermak based glasses and glass-ceramics

We report on the influence of ZnO on the structural, thermal, and crystallization behavior of the diopside-Ca-Tschermak based glasses, and on the processing, microstructure, and the properties of the sintered glass ceramics. Four glasses with nominal compositions of CaMg0.8Al0.4Si1.8O6, CaMg0.75Zn0.05Al0.4Si1.8O6, CaMg0.70Zn0.10Al0.4Si1.8O6, and CaMg0.60Zn0.20Al0.4Si1.8O6 were obtained by melting at 1580u2009°C for 1 h. Structural and thermal behavior of the glasses was investigated by Fourier-transform infrared spectroscopy, density measurements, dilatometry, and differential thermal analysis. Nonisothermal crystallization kinetics has been employed to study the crystallization mechanism in the glasses. Sintering, crystallization, microstructure, and properties of the glass ceramics were investigated under nonisothermal heating conditions in the temperature range of 850–1000u2009°C.

Sintering and crystallization behavior of CaMgSi2O6–NaFeSi2O6 based glass-ceramics

We report on the synthesis, sintering, and crystallization behaviors of a glass with a composition corresponding to 90u2002molu2009%u2002CaMgSi2O6−10u2002molu2009%u2002NaFeSi2O6. The investigated glass composition crystallized superficially immediately after casting of the melt and needs a high cooling rate (rapid quenching) in order to produce an amorphous glass. Differential thermal analysis and hot-stage microscopy were employed to investigate the glass forming ability, sintering behavior, relative nucleation rate, and crystallization behavior of the glass composition. The crystalline phase assemblage in the glass-ceramics was studied under nonisothermal heating conditions in the temperature range of 850–950u2009°C in both air and N2 atmosphere. X-ray diffraction studies adjoined with the Rietveld–reference intensity ratio method were employed to quantify the amount of crystalline phases, while electron microscopy was used to shed some light on the microstructure of the resultant glass-ceramics. Well sintered glass-ceramics with ...

Crystallisation kinetics of diopside-Ca-Tschermak based glasses nucleated with Cr2O3 and Fe2O3

We report on the crystallisation behaviour and non-isothermal crystallisation kinetic studies of two diopside (CaMgSi2O6)-Ca-Tschermak (CaAl2SiO6) based glasses nucleated with Fe2O3 and Cr2O3. The two glasses with compositions corresponding to CaMg0.75Al0.5Si1.75O6 and Ca0.9Mg0.65Li0.1Al0.5La0.1Si1.75O6 were prepared by the melt-quenching technique. Structural investigations on the glasses have been made by density measurements, molar volume and infrared spectroscopy (FTIR). Non-isothermal crystallisation kinetic studies have been employed to study the mechanism of crystallisation in all the four glasses. Bulk crystallisation was obtained and augite crystallised out being the primary crystalline phase in both the glasses. Crystallisation sequence in the glasses has been followed by X-ray diffraction (XRD) analysis, scanning electron microscopy (SEM) and FTIR.