Glass matrix composites with lead zirconate titanate particles processed by microwave heating

The possibility of toughening glass and ceramics by addition of a piezoelectric particulate secondary phase is the focus of current research. It is hypothesised that stress concentrations at the tip of an advancing crack can re-orient piezoelectric domains within the reinforcement in the direction of the stress field around the crack, thus dissipating energy which contribute to fracture toughness increment of the composite. Previous work has focussed on producing glass/piezoelectric inclusion composites by conventional sintering. This process is accompanied by extended porosity formation, as well as Pb depletion in the PZT phase. In several cases, the long processing times required to fully sinter the glass matrix lead to glass-PZT reactions and to loosing the stoichiometry of the PZT inclusions. In this study, the novel production of new glass matrix composites reinforced with piezoelectric inclusions by using microwave heating was investigated. Specifically, lead-zirconate-titanate (PZT) particles in lead silicate and borosilicate glass matrices were considered. Mixtures of glass and PZT powders were prepared and used to fabricate powder compacts by uniaxial cold-pressing. In order to achieve densification, the compacts were subsequently heated in a single mode applicator, connected to a generator operating at the 2.45 GHz ISM frequency.

Mechanical performance and fracture behaviour of glass-matrix composites reinforced with molybdenum particles

A borosilicate glass-matrix composite has been fabricated by addition of molybdenum particles in various volume fractions. In order to systematically investigate the effect of metallic particulate reinforcement on the overall composite mechanical behaviour, a FEM based numerical model was prepared. The study focused on the global elastic and fracture response of the composites. By studying crack propagation patterns, toughening mechanisms such as crack deflection and load transfer were detected, thus enabling to assess the influence of second phase volume fraction on composite fracture toughness. Microscopy observations of fracture surfaces were performed to support the numerical results. © 2005 Elsevier Ltd. All rights reserved