Thermal conductivities of neptunium and americium mononitrides

Nishi, Tsuyoshi; Takano, Masahide ; Ito, Akinori; Akabori, Mitsuo; Arai, Yasuo; Minato, Kazuo 

Neptunium nitride (NpN) and americium nitride (AmN) were prepared by carbothermic reduction of the respective dioxides. The thermal diffusivities of NpN and AmN were measured by using a laser flash method. The heat capacities of NpN and AmN were determined with the drop calorimetry. The thermal diffusivity of NpN tends to remain unchanged with increasing temperature in the temperature range from 473 to 1473 K, and that of AmN tends to slightly decrease with increasing temperature in the same temperature range. The heat capacity of NpN obtained was close to those of UN and PuN, while that of AmN was slightly smaller than those of UN, NpN and PuN. The thermal conductivities of NpN and AmN were determined from the measured thermal diffusivities, heat capacities and bulk densities. It was found that the thermal conductivities of NpN and AmN slightly increased with temperature in the temperature range investigated.