Tailoring the Properties of Ceramic-Based Composites Using Co-Extrusion Processing
Co-extrusion processing is a powder-based forming method that uses the simultaneous ram extrusion of two or more materials to form multi-phase systems with functionally designed architectures. A functionally designed material has functional properties that are specifically tailored for an application by changing the macrostructure (100’s of microns) with little or no change in overall composition. Thus, co-extrusion can be used to improve the functional properties of composite materials, with or without a concurrent boost of its intrinsic properties. An example of a functionally designed material with a coaxially co-extruded architecture, known in the ceramic field as a “fibrous monolith”, has elongated cells of a major (70-90 vol.%) phase surrounded by cell boundaries of a minor (10-30 vol.%) phase. A variety of strong-phase/weaker-phase combinations have been demonstrated, including Si3N4/BN, SiC/graphite, SiC/BN. Several wear resistant-phase/ductilephase combinations have also been studied, including Diamond(Co)/WC(Co) for use in the petroleum drilling industry. The presentation will cover co-extrusion processing as a technology, applications that are being considered or are in production for most of the latter materials combinations, and a discussion of the functional properties that can be achieved using co-extrusion as a means to create functionally designed materials.
G. Hilmas and J. Watts, "Tailoring the Properties of Ceramic-Based Composites Using Co-Extrusion Processing", Advances in Science and Technology, Vol. 45, pp. 1385-1393, 2006