Equiaxed

Particle shape also affects the sintering of a powder compact. Jagged or irregular shaped particles, which have a high surface area to volume ratio, have a higher driving force for densification and sinter faster than equiaxed particles. High aspect ratio platey particles, whiskers, and fibers, which pack poorly, sinter poorly. 

The stmcture of reinforcements can be either equiaxed or acicular. The nature of their placement within a composite, the composite architecture, is critical to the resultant composite properties. Possible architectures are summarized in Figure 1. 

Equiaxed particles, which ate well dispersed in the ceramic matrix, tend to produce isotropic composite behavior. The particles, either ceramic or metaUic, may be single crystal or polycrystalline in nature. 

Equiaxed crystals growing from solution in mould centre... 

Why is it undesirable to have a columnar grain structure in castings Why is a fine equiaxed grain structure the most desirable option What factors determine the extent to which the grain structure is columnar or equiaxed ... 

The cells in foams are polyhedral, like grains in a metal (Fig. 25.8). The cell walls, where the solid is concentrated, can be open (like a sponge) or closed (like a flotation foam), and they can be equiaxed (like the polymer foam in the figure) or elongated... 

Figure 2.13. Schematic of stractures obtained by CVD (a) columnar grains with domed tops, (b) faceted columnar grains, (c) equiaxed fine grains.

Other authors (2) prefer a different grain structural classification. Specifically, these classifications are (1) columnar, (2) equiaxed, (3) dendritic, (4) nodular, and (5) fibrous. This classification is more in terms of overall structure than in terms of macroscopic and physical properties. 

Equiaxed. These grains grow to relatively larger sizes than in case 1. 

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