Abstract:
Glass-ceramics (GCs) are one such category of materials which offer the possibility of combining the special properties of conventional sintered ceramics with distinctive characteristics of glasses. GCs are ceramic materials formed either through the controlled nucleation and crystallization of glass or sintering and crystallization of powdered glass. It is however, possible to develop modern GC materials with features unknown, thus far, in either ceramics or glasses or in other materials such as metals or organic polymers.
The glass-ceramic compositions under investigation have been designed along diopside (CaMgSi2O6) — jadeite (NaAlSi2O6) join with varying diopside/jadeite molar ratio. The partial substitution of B203 for Si02 has been made in all compositions in accordance with substitution scheme 0.3 Si4}H 0.4 B3+ so as to decrease the melting point of the glass compositions and improve the sintering and flow properties of the resultant glass-ceramics, thus, enhancing their potential for technological applications. All the glasses were prepared by melt-quenching technique in the temperature range of 1500-1550°C in two form i.e. bulk and frit. The bulk glasses were used for density, dilatometry and mechanical characterization (Elastic modulus, Poisson's ratio and Indentation hardness). The glass frit was milled to fine powder with mean particle size varying between 10 — 20 gm. Sintering and crystallization behavior of glasses were studied by using differential scanning calorimetry (DSC). DSC was performed on all the glasses in the temperature range of 25 — 1200°C at different heating rates 5 to 30 K/min. Johnson-Mehl-Avrami equations were used to investigate the crystallization kinetics on these glasses from DSC data.
Glass powder compacts were prepared from glass powder and sintered at different temperatures varying between 800 - 900°C for 1 h, respectively. The heating rate will be 5 K/min. The crystalline phase evolution in the sintered glass-ceramics were studied by XRD analysis (after crushing of glass-ceramics to powder form, particle size < 45 μm) while the microstructure observations was done on polished samples under SEM. Young's modulus, CTE, elastic modulus and Poisson's ratio of glasses calculated. Experimental result was analyzed and discussed which provide future directions in order to produce technologically useful materials.
