Penetration of Polycrystalline Alumina by Glass at High Temperatures

Abstract

An analysis of interfacial energies in a solid-liquid system showed that complete penetration of a liquid along grain boundaries in a microstructure forming during liquid-phase sintering is not necessarily associated with complete wetting or spreading at the solid-liquid interface. Investigations were made on the penetration of Ca0-A1,03-Si02 glasses into dense polycrystalline aluminas. Initial penetration was along threegrain junctions or grain boundaries by a solution/reaction between the liquid and defect-containing alumina along interfaces. Degree of penetration was variable, and it was dependent on internal strain and MgO addition. Extended heat treatments reduced liquid penetration.

Origins and Applications of London Dispersion Forces and Hamaker Constants in Ceramics

“…194,199 -203 Moreover, for Al 2 O 3 (both pure and containing various amounts of CaO, SiO 2 , or other impurities) extensive penetration of dense polycrystals by silicate liquids occurs, leading eventually to widespread disruption, i.e., deflocculation of the grains, which may mean the dihedral angle is low or the liquid is virtually wetting. 185,204 Al 2 O 3 powders initially mixed into glasses give similar results, in which particles remain widely separated, but do concentrate somewhat while settling because of gravity. 205 However, for Al 2 O 3 and MgO, which can be extensively penetrated by silicate liquids, 206 a discernable fraction of boundaries is not wetted or obviously penetrated.…”

“…170,184 Complementary approaches to probe the particle interactions and the roles of interfacial composition begin with considering the solid phase (either powder or dense polycrystal, initially) being immersed in a massive amount of liquid at high temperature, as demonstrated by Shaw and others. [185][186][187][188] Such systems largely evolve in the absence of the capillary forces induced by liquidvapor interfaces, under conditions where dispersion forces, and also surface energies, can be dominant. Consider when a small amount of refractory particles is immersed at high temperature in a liquid matrix: A dilute suspension is realized.…”

Microstructure-based modelling and experimental investigation of crack propagation in glass–alumina functionally graded materials

“…Nevertheless, as predicted by the microscale simulations, the cracks induced on the FGM cross-section preferentially evolve starting from pores and moving towards pores. Moreover, the experimentally observed crack paths are likely to develop along the alumina grain boundaries, where the glass is usually located, 36 as predicted by the numerical model. The good qualitative agreement between simulations and experimental observations confirms the reliability of the approach.…”

Potassium-based composition for a bioactive glass

“…In both cases, there was not a sharp interface between the glass coating and the alumina substrate, since the glass gradually penetrated into the alumina bulk (graded area in Fig. 3) [19].…”