Uranium dioxide (UO₂) composites with uranium diboride (UB₂) and uranium tetraboride (UB₄) have been proposed as advanced fuel candidates due to their high thermal conductivity, high melting point, high fissile density and their ability to incorporate a built-in burnable poison by tailoring the targeted ¹⁰B/¹¹B ratio. As such, it is important to assess the fabrication, and thermal and micromechanical properties of such composites. In this work, UO₂-UB₂ and UO₂-UB₄ samples with boride phase fractions of 5, 15 and 30 wt% were fabricated to high densities (above 95% theoretical density) via spark plasma sintering (SPS). This enabled sintering at relatively low temperatures and short timescales. SPS also aided in maintaining the target phase fractions of the samples as reactions between the constituent phases were suppressed due to the short timescales and reducing environment during sintering. Thermal diffusivity measurements from 299 to 1273 K were conducted through laser flash analysis (LFA). The diffusivity increased as a function of boride weight fraction, and UB₂ additions increased the thermal diffusivity of the composites more than UB₄ additions. Assessment of the LFA results indicated that in-situ reactions between the UO₂ and boride phases that suppress the thermal diffusivity occur above 800 K for all samples. Oxidation of the boride phase was proposed as the underlying reaction. This was supported by thermodynamic assessments from the literature, as well as microstructural, crystallographic, and nanoindentation characterization performed on these samples.

具有高导热率，高熔点，高裂变密度和掺入二硼化铀的能力的二氧化铀（UO ₂）与二硼化铀（UB ₂）和四硼化铀（UB ₄）的复合材料已被建议用作高级燃料。通过调整目标¹⁰ B / ¹¹ B比例来减少可燃毒物的摄入。因此，重要的是评估这种复合材料的制造，热和微机械性能。在这项工作中，UO ₂ -UB ₂和UO ₂ -UB ₄通过火花等离子体烧结（SPS）将硼化物相分数为5、15和30 wt％的样品制备为高密度（理论密度为95％以上）。这使得能够在相对较低的温度和较短的时间范围内进行烧结。SPS还有助于维持样品的目标相分数，因为在烧结过程中由于较短的时间尺度和减少的环境，成分相之间的反应受到抑制。通过激光闪光分析（LFA）进行了299至1273 K的热扩散率测量。扩散率随硼化物重量分数的增加而增加，UB _2的添加量比UB _4的添加量增加复合材料的热扩散率。对LFA结果的评估表明，UO ₂之间的原位反应对于所有样品，抑制热扩散率的硼化物相出现在800 K以上。提出了硼化物相的氧化作为基础反应。文献中的热力学评估，以及对这些样品进行的微结构，晶体学和纳米压痕表征，都证明了这一点。