Fabrication and Mechanical Properties of Lightweight Ceramics Produced by Sintering of Hollow Spheres

Lightweight ceramics with densities in the range 8 to 24% of theoretical were fabricated by sintering hollow glass spheres. The densification behavior, which was complex, involved uniform shrinkage of the spheres, local densification, deformation of the spheres, and coarsening of the cells. A major flaw population was found to be relatively large areas which were devoid of spheres. There was a distinct difference in the mechanical behavior and fracture path for the low‐ and high‐density materials. The behavior of the high‐density materials appeared to agree well with existing micromechanical models in terms of Young's modulus, fracture toughness, and density. The fracture toughness of these cellular materials per unit weight is similar to that of bulk glass but is not translated into strength because of the relatively large flaw sizes in the final microstructure.