Single particle crushing of nonmetallic inorganic brittle materials

Abstract

Crushing of nonmetallic inorganic brittle materials such as silicate glass, quartz and other rock minerals has been drawing attention, because of the growing technological importance of ultrafine powder for producing highly qualified functional ceramics. The crushing phenomenon of a solid material is essentially dependent on the structure-sensitive defects such as microcracks. It is also accompanied essentially by nonlinear, irreversible and irrecoverable process. Furthermore, this is the initiation of microcracks, growth and propagation of fracture cracks, which are strongly influenced by loading and environmental conditions as well as shape and size of a specimen of brittle materials. In addition, this process is dynamically conducted in high speed transitional state. An attempt is made in this paper to review the current information of the crushing of a single particle of nonmetallic inorganic brittle materials. Thus, this paper is primarily concerned with some mechanical properties relevant to the crushing of the brittle materials, status of fractured products and size dependence, loading rate and environmental conditions relevant to the crushing phenomena of materials. The experimental results are summarized from the phenomenological point of view. The mineralogical observations of fractured surface of a crushed single particle clearly indicate that the fracture of materials having a cleavage structure is the transcrystalline type. The fracture strength and the specific fracture energy of most of nonmetallic inorganic materials increase with the decrease of their size in the range of about 10 μm to 120 mm. Under about 10 μm, the fracture strength decreases with decreasing particle size. The loading-rate effect on fracture strength and other mechanical properties can be recognized over a wide range of loading rate. A singularity of crushing behaviour of a single particle can be observed under impact loading of duration comparable to the natural (intrinsic) period of a specimen. Especially, at this impact loading, the crushing efficiency appears to be at its maximum. It may also be noted that environmental water in the crushing of a single particle is one of the important factors affecting the fracture behaviour of a single particle.