SiC whisker strengthened UO2–Mo composite pellets with superior thermal-mechanical properties

UO 2 –Mo composites are expected to be candidate materials for use as enhanced thermal fuel in the next generation of high-level safety reactors. Nevertheless, the UO 2 matrix tends to create micro-cracks caused by thermal stress generated during the sintering process. A novel type of UO 2 –Mo-SiC w composite is fabricated by spark plasma sintering (SPS) to enhance the thermal-mechanical properties of UO 2 . In the composite, SiC w is dispersed uniformly in the UO 2 matrix to form microspheres , and Mo is distributed in a three-dimensional network to form heat-conduction channels. Micro-cracks in the UO 2 matrix are significantly suppressed in the UO 2 –Mo composite, since only a small amount of SiC w is incorporated into the UO 2 . Indentation testing indicates a great capability of the SiC w to sharply enhance the crack propagation resistance of the UO 2 matrix. The estimated indentation fracture toughness reaches 0.91 MPa m 1/2 with the incorporation of 0.5 vol% SiC w , representing a 68.5% improvement over the value of 0.54 MPa m 1/2 obtained for the UO 2 –Mo composite. The thermal conductivity of the UO 2 –4Mo composite at 1000 °C was enhanced by approximately 54.3%, 60.1% and 67.2% for a SiC w content of 0.5, 2, and 4 vol%, respectively, compared with pure UO 2 . These results provide new insight for further improving the safety and lifespan of UO 2 fuel in reactors.