High temperature compressive mechanical behavior of joined biomorphic silicon carbide ceramics

Abstract

Silicon carbide-based, environmentally conscious, biomorphic ceramics were fabricated by the reactive infiltration of molten silicon into porous, carbonaceous preforms derived from pyrolysis of African Bubinga wood. The bulk microstructure and high temperature mechanical properties of these ceramics were studied. These biomorphic ceramics mimic the fibrous microstructure of the wood resulting in high strength and anisotropy. The compressive strength parallel to fiber direction, which is the growth direction of the tree, was 750 MPa at 1100 °C and 300 MPa at 1350 °C. The compressive strength perpendicular to fiber direction was 215 MPa at 1100 °C and 120 MPa at 1350 °C. These materials were joined using the ARCJoinT approach. The microstructure of the joints was studied by scanning electron microscopy and the high temperature strength was measured in compression, with the joint oriented 45° to the compression axis. The joined specimens had strengths from 615 MPa at 1100 °C to 250 MPa at 1350 °C when the fibers were parallel to the compression axis (forming 45° with the joint plane), which are about 20% lower than the strength of the bulk material in the same orientation. The strengths ranged from 373 MPa at 1100 °C to 175 MPa at 1350 °C when the fibers were forming 45° with the compression axis (perpendicular to the joint plane), which are lower than the average strength of the bulk material compressed axially and in the perpendicular direction.