Quantitative Infrared Thermography (IRT) and Holographic Interferometry (HI): Nondestructive Testing (NDT) for Defects Detection in the Silicate Ceramics Industry

Abstract

Ceramics are inorganic materials fabricated by a high-temperature chemical reaction. Most ceramics are oxides, but the term is also used for silicides, nitrides and oxynitrides, hybrids and other inorganic materials. It is convenient to consider ceramics that are essentially silicates, called traditional ceramics, separately from all of the others. In the ceramic industry testing systems are seldom employed for detecting on-line the presence of defects in ceramic tiles. Defects in the ceramic body are usually originated during the pressing stage due to the incorrect use of process parameters or to the improper selection of raw materials. These defects are generally characterized by the inclusion of heterogeneous materials or agglomerates, which decreases the structural strength jeopardizing the final quality of the produced piece. Disagreeable repercussions on the sale market, especially on higher-quality ceramics such as porcelain, are characterized by the lack of specific nondestructive testing (NDT) techniques that “certify”, pre-emptive, the quality of the produced piece. The integration of IRT and HI for the NDT of a green ceramic tile with both fabricated and real defects (cracks caused by the natural shrinkage process), allowed us to produce a clear “defects map”.