High resistance and low porosity ceramic
Introduction
Technical ceramics deals with the use of ceramic materials in technological applications. The word ceramics derives from the Greek word keramos, whose Sanskrit root means "to burn". In its strict sense it refers to clay in all its forms. However, the modern use of this term includes all non-metallic inorganic materials that are formed by the action of heat (see sintering).
Until the years 1950-65, the most important materials were traditional clays, used in pottery, bricks, tiles and the like, along with cement and glass. The traditional art of ceramics is described in pottery. You can also search for the history of rakú, a unique ancient oriental technique.
Historically, ceramic products have been hard, porous and brittle. The study of ceramics consists of a wide range of methods to mitigate these problems and accentuate the potential of the material, as well as offer non-traditional uses. This has also been sought by incorporating them into composite materials such as cermets, which combine metallic and ceramic materials.
Mechanical properties of ceramics
Ceramic materials are generally brittle or glassy. They almost always fracture under tensile stress and have little elasticity, given that they tend to be porous materials. Pores and other microscopic imperfections act as notches or stress concentrators, reducing resistance to the aforementioned stresses.
The elastic modulus reaches quite high values of the order of 311 GPa in the case of titanium carbide (TiC). The value of the elastic modulus depends on the temperature, decreasing non-linearly as it increases.
These materials show plastic deformations. However, due to the rigidity of the structure of the crystalline components there are few slip systems for moving dislocations and deformation occurs very slowly. With non-crystalline (glassy) materials, viscous fluidity is the main cause of plastic deformation, and it is also very slow. Even so, it is omitted in many applications of ceramic materials.
They have high compressive strength compared to metals even at high temperatures up to 1500 °C (2732 °F). Under compression loads the incipient cracks tend to close, while under tensile or shear loads the cracks tend to separate, leading to fracture.
The fracture toughness values in ceramic materials are very low, barely exceeding the value of 1 MPa.m, values that can be considerably increased by methods such as fiber reinforcement or phase transformation in zirconia.