Dense composites of zircon-mullite, characterization, influence of the composition on the mechanical and fracture properties

Refractory materials based on zircon (ZrSiO4) are made for high temperature applications (1400-1500oC). Their use has shown that they are highly resistant to chemical attack and to corrosion or degradation by smelted metals and glass. Meanwhile mullite (3Al2O3.2SiO2) has become an important material in traditional ceramics as well as in fine or advanced ceramics. Although polyphase ceramics have always been produced, compound materials, also known as composites, are now being developed industrially and technologically since they expand the design capacity of the properties and behaviors of materials. This work studies the influence of the amounts of each one of the phases on the mechanical properties of a compound ceramic material of zircon-mullite obtained by direct sintering, from pieces consolidated by plaster mold casting of concentrated aqueous suspensions. Materials with a matrix of zircon with mullite dispersed up to 45% w/p were obtained. The following properties were measured: Mechanical resistance (σf), elasticity module (E), fracture tenacity fracture (KIC), and the energy at the start of the crack (γNBT) observing a distinctly fragile behavior and well defined tendencies in the crystalline composition of the composites. The increase in the proportion of the second phase improves almost all the values of these mechanical properties. The results are also explained by the microstructures obtained by MEB (au)