Microstructural design of materials for aerostatic bearings

The aim of this work is to investigate the development of a high strength porous cementitious composite manufactured via cold-pressed compaction for use as the restrictor in aerostatic bearings for high precision applications since they provide a number of advantages over conventional orifice restrictors. The selection of suitable materials and microstructural design of composites phases is essential to the development of material for optimum stiffness, strength, porosity and permeability. A variety of high purity (99.98% SiO2) silica particle types was mixed with ordinary Portland cement to produce the composite mixtures. A full factorial design (2241) was carried out to study the effects of silica properties (size and geometry) and uniaxial pressures (10 MPa and 30 MPa) on mechanical properties and microstructure of the ceramic composites. The cementitious composite manufactured using small silica particles, non-spherical shape and low level of compaction pressure exhibited the most appropriate properties for the stated application of porous bearings.