Thermal stresses of large-dimension lithium hydride ceramics during the sintering process and strength analysis based on process-based failure assessment diagram

Lithium hydride (LiH) is an important hydrogen storage, heat storage and neutron shielding material. When used in neutron shielding structure, its size and strength have certain requirements, which would be met by LiH ceramics. However, it fails easily during sintering due to severe thermal stress and high brittleness. In this study, the influences of the dimension, furnace temperature cooling rate, and convection condition on the mechanical behavior were systematically examined. The results indicated that larger dimensions and faster furnace temperature cooling rates resulted in higher maximum stresses. Furthermore, convection was beneficial for reducing the thermal stress. Accordingly, a process-based failure assessment diagram method was proposed to evaluate the safety of LiH ceramics, and a bilinear precise temperature control approach was proposed. Based on this method, the tube thickness was increased by 25 % and the cooling time was reduced by 32 % compared to those using linear temperature control in an example. The conclusion and method could be applied to optimize the temperature control for more practical large-dimension sintering.