Preparation of UN, α/β‐U ₂ N ₃, and Their Converted UN Pellets

Carbothermic reduction and nitridization (CTR‐N) approach is a promising and convenient method for commercial production of UN. In this work, low carbon content (<400 ppm) α‐U 2 N 3 , β‐U 2 N 3 , and UN powders were synthesized from U 3 O 8 by CTR‐N approach. The U 2 N 3 decomposed to UN at high temperatures. By adding α‐U 2 N 3 or β‐U 2 N 3 to UN powder as the raw material for spark plasma sintering (SPS) without long‐time ball‐milling, the obtained UN pellet density was significantly improved compared to that from UN powder alone. The α‐U 2 N 3 and β‐U 2 N 3 powders facilitated densification at the same level. The optimal U 2 N 3 /UN ratio was found to be 0.1. High U 2 N 3 /UN ratios (>0.5) decreased the pellet density. High‐density (>95% theoretical density) UN pellets were prepared from 0.1U 2 N 3 /UN powder by SPS at temperatures above 1650°C and pressure of 55 MPa in vacuum.