Sintering of heterogeneous ceramic compacts

Sintering of heterogeneous ceramic compacts

“…The instantaneous density during sintering was then calculated from the recorded shrinkage and from the final density. The relative density of the zirconia matrix in the zirconia-alumina composite can be calculated [10] as where 0m is the instantaneous relative density of the matrix, 0t is the instantaneous relative density of the composite and F is the solid volume fraction of alumina.…”

“…1). Abnormal grain growth,-which is encountered in A1203-A1203 studies [10], is not a problem for the two-phase system.…”

“…Experimental works which study the effect of inhomogeneity on sintering are relatively few, particularly with respect to any estimation of the stresses arising from the presence of the heterogeneities [6][7][8][9][10]. Local variations in density, usually formed during powder preparation or during compacting procedures, give rise to differential sintering rates within a compact.…”

Densification of Particulate Ceramic Composites: The Role of Heterogeneities

“…Under the assumption that the densification rate of the inclusionfree, identical matrix, E , is known, the instantaneous matrix densification rate, E of a partfculate composite containing a volume fraction, f, of the di~~~rsed phase can be shown to be [4] € com (3) This equation is based on the critical assumption that the densifying compact is quantitatively represented by the behavior of an inert spherical particle surrounded by a densifying, uniform mantle of matrix material. It further is based on a continuum model in which, necessarily, particle size or transport mechanism considerations must be absent.…”

“…The potential for improved performance is, however, offset by the increased difficulties that the processing of such composites present. In particular, it has been commonly observed that free sintering of particulate composites is significantly hampered, even at modest volume fractions of the dispersed inclusions [1][2][3]. One way to report the retardation effects is to regard densification as driven by an externally applied, effective mechanical stress, (referred to as the sintering stress, ~).…”