Fabrication and volume loading studies for Mo30W matrix surrogate cermets

Abstract

Ceramic-metallic composite (cermet) fuel forms are promising options for use in nuclear thermal propulsion (NTP) due to their high melting point, inherent hydrogen compatibility, retained strength at high temperatures, and high thermal conductivity. Spark plasma sintering was used to fabricate cermet materials, resulting in improved microstructural characteristics. An alloy of molybdenum with 30 wt% tungsten was used as the matrix material. Spherical yttria stabilized zirconia (YSZ) and both spherical and angular hafnium nitride (HfN) were used as surrogate fuel particles for the cermets. Utilizing a new lab-scale particle coating method, high density composites with excellent particle-matrix interfaces were fabricated. The effects of volume loading on the microstructure of the matrix were also examined, testing particle loadings up to 90 vol%. Initial stage sintering models were applied to understand the effects of the added particles on the sintering of the Mo30W matrix. Recommendations for fabrication of uranium bearing cermets using Mo30W are also included.