Mechanical Properties of Porous Ceramics

Abstract

It is widely known that increasing interest in porous ceramics is due to their special properties, which comprise high volumetric porosity (up to 90%) with open or closed pores, and a broad range of pore sizes (micropores: d < 2 nm; mesopores: 50 nm > d > 2 nm and macropores: d > 50 nm). These properties have many uses comprehending macroscaled devices, mesoscaled materials and microscaled pieces. During their usage, these materials are usually submitted to thermal and/or mechanical loading stresses. Therefore, it is a premise to understand how these porous structures behave under thermomechanical stresses to design materials that show adequate properties for the required application. In this context, the aim of this chapter is to review the mechanical properties of macroporous ceramics.

Mechanical characterization of sol-gel alumina-based ceramics with intragranular reinforcement of multiwalled carbon nanotubes

“…The decisive factor producing the low values for hardness is the lack of densification, which describes the presence of significant porosities that reduces the volume exposed to mechanical stresses. Some models correlate the porosity and the values of several mechanical properties of the porous, brittle solid ceramics [36][37][38]. Typically, Young's modulus, bending strength, or the hardness of alumina exhibit a drastic decrease with an increase in porosity [39,40].…”

Closed porosity ceramics and glasses

“…Gibson and Ashby (GA) developed their theories by emphasizing on the solid matrix (strut/truss to lattice concept), instead another common one called minimum solid area (MSA) model proposed by Rice, focuses on the space holder that is pore, the details for such models are discussed extensively. 11,[161][162][163] It is important to note that none of those models can properly be applied to all range of porosity levels. However, broadly speaking hardness and elastic modulus data fits more accurately than fracture toughness and strength which may vary considerably from the models.…”

“…For the mechanical behavior of porous materials, different models have been proposed; however, ambiguity still remains especially for the closed‐cell solid structures. Gibson and Ashby (GA) developed their theories by emphasizing on the solid matrix (strut/truss to lattice concept), instead another common one called minimum solid area (MSA) model proposed by Rice, focuses on the space holder that is pore, the details for such models are discussed extensively . It is important to note that none of those models can properly be applied to all range of porosity levels.…”

Macroporous high-temperature insulators physical properties by in situ CA6 formation: Does the calcium source matter?

“…Another key property for a macroporous insulator is its pore size distribution, which affects both mechanical strength and thermal conductivity at high temperatures [18][19][20]. Regarding the latter, some computational studies pointed out that pore sizes ranging from 3 µm to 0.5 µm are the ideal to interact and spread the thermal radiation at high temperatures (1000ºC -2000ºC) [20].…”