Failure Causing Defects in Ceramics: What NDE Should Find

Abstract

The various types of defects causing failure in a variety of ceramic materials are illustrated. Examples are drawn from such ceramics as piezoelectric, infrared transmitting, and potential turbine materials. Both machining and processing defects are shown as sources of failure. The former are selected to illustrate the effects of machining parameters. Processing defects illustrated include pores, foreign particles and large grains, or clusters of these. Changes in the size of defects with specimen size are also noted. Keywords ABSTRACTThe various types of defects causing failure in a variety of ceramic materials are illustrated. Examples are drawn from such ceramics as piezoelectric, infrared transmitting, and potential turbine materials. Both machining and processing defects are shown as sources of failure. The former are selected to illustrate the effects of machining parameters. Processing defects illustrated include pores, foreign particles and large grains, or clusters of these. Changes in the size of defects with specimen size are also noted.

Properties of Single‐Component Metal–Organic Framework Crystal‐Glass Composites

“…Minor compositional inhomogeneities, such as larger crystallites or clusters present on the surface of pellets may have contributed to the formation of surface defects, by providing preferential locations for flaws upon pressure-heat-treatment when preparing the MOF-CGCs. [26] The glass (a g ZIF-62) 1.0 pellet however, was comparatively free of surface defects (Figure 4f), highlighting the high quality of pellet produced from melt-quenched samples of ZIF-62(Zn) glass. Despite the presence of surface defects, single-component MOF-CGC samples showed no evidence of individual ZIF-62(Zn) crystallites on the surface, suggesting good interfacial compatibility between the crystalline and glass-phases.…”

Ultrasonic characterization of structural ceramics

“…If this is indeed the case, it must concluded that the higher measured values are related to the pore size and distribution evident in the specimens with the larger grain size. For specimens with equivalent bulk density this would have to be accounted for by the value assigned to the porosity correction factor b in equation (2).…”

Hierarchical Surface Texturing of Hydroxyapatite Ceramics: Influence on the Adhesive Bonding Strength of Polymeric Polycaprolactone

“…For ceramic implants, the surface, in addition, strongly affects the mechanical strength and wear resistance. Based on their inherent brittle nature, the strength of ceramics is highly sensitive to the existence of surface flaws (cracks, pores, scratches) and even in their absence failure may occur initiated from the microscopic roughness of large grains [ 11 , 12 ]. For that reason, commercial full-ceramic ZrO 2 or Al 2 O 3 artificial hip and knee implants are typically polished (R a < 10 nm) to avoid surface defects and to achieve a high strength and a low-friction surface [ 13 , 14 ].…”