Microstructural characterization and mechanical behavior of glassceramics crystallized by microwave energy

Abstract

The aim of this study will be to verify the viability of an alternative process of crystallization using microwave energy and to establish a crystallization protocol for three commercial glass-ceramics; to evaluate the effect of this crystallization on microstructure, density, hardness, fracture toughness and biaxial flexural strength of these glass-ceramics; and to analyze their optical properties (translucency). The null hypothesis is that the crystallization by microwave energy will not affect the microstructural characteristics and consequently the mechanical properties of these ceramic materials. 180 discs will be made from blocks of three different glass-ceramics: lithium disilicate (IPS e.max CAD, Ivoclar Vivadent) and lithium silicates reinforced by zirconia (I - Suprinity, Vita Zahnfabrik; II -Celtra, Dentsply); according to ISO 6872 (dimensions: 12 x 1.2 mm). SiCpapers with granulation #400, 600, 1200 and 2500 will be used for specimens polishing. Half specimens of each group will be crystallized in the conventional furnace, according to the manufacturer's recommendations, and the other half specimens will be crystallized by microwave energy using a protocol that will be defined by a previous pilot study. The microstructural characterization will be made from the measurement of density, translucency, scanning electron microscopy(SEM) and X-ray diffraction (XRD). The mechanical behavior will be measured by the biaxial flexural test, Vickers hardness and fracture toughness. Fracture analysis will also be performed on the fractured specimens to determine the origin of the fracture and the relationship between the crack and the microstructure of the studied materials. (AU)