2018 | AFC ACCOMPLISHMENTS 48 performed. SPS parameters such as temperature and hold times were tested to select the optimum conditions that resulted in high density pellets. These dense UB2 and UB4 pellets were then examined for purity and mechanical integrity via Scanning Electron Microscopy (SEM) and X-Ray Diffraction (XRD).The pellets were then shipped back to Los Alamos National Laboratory (LANL) and were prepared for thermal diffusivity and thermal expansion measurements via Laser Flash Analysis (LFA) and dilatometry.These measured values were used along with specific heat values from the literature to calculate their thermal conductivity as a function of temperature up to 1500˚C. Accomplishments: The full set of tested SPS temperatures under a 5 minute hold and resulting densities, measured via immersion density, are shown in Figure 1 along with the densities reported byWhite (2015) from conventional sintering of UB2 under a 4 hour hold.To achieve densities above 90%TD for UB2 samples with conventional sintering, a 350˚C increase is necessary compared to the temperatures required for SPS. Both UB2 and UB4 samples show a decrease in achieved density when tested a few weeks apart under the same conditions.This is true for samples that were sintered via SPS and conventionally, and it shows that these materials are very susceptible to oxygen impurities. Since UB2 and UB4 powders can pick up impurities even when kept in glovebox atmospheres with very low levels of O2 it is recommended that they are prepared in small quantities to be used immediately. The XRD patterns from the sintered pellets with the highest densities, namely those sintered at 1750˚C are shown in Figure 2 for (a) UB2 and (b) UB4, respectively, together with refer- ence data for each material.The pattern from the white clay that was used as a holder for both these scans is also included in Figure 2. Despite some interference from the clay pattern, both the UB2 and UB4 samples are shown to be phase pure as no secondary phases were detected. In Figure 3, the typical Figure 3: SEM backscatter image showing the typical microstructure of an (a) UB2 and (b) UB4 sample sintered by SPS at 1750˚C.