Microwave sintering reactor design for lithium hydride ceramics: From dielectric properties to electromagnetic thermal behavior

Lithium hydride (LiH) is widely utilized in aerospace, nuclear energy, and hydrogen storage applications due to its excellent thermal neutron moderation characteristics and hydrogen storage capabilities. The traditional hightemperature sintering process of LiH often leads to non-uniform temperature gradients and thermal stress distributions, resulting in excessive grain growth and the formation of cracks within and on the surface of LiH components. To address these issues, this study explores the sintering process of LiH components using microwave heating, which is characterized by uniform heating. Initially, dielectric testing was conducted to investigate the electromagnetic-thermal coupling mechanisms of LiH at various temperatures. Subsequently, a finite element numerical model was employed to examine the effects of parameters such as cavity shape, cavity size, waveguide position, and microwave power on the thermal field uniformity during the microwave heating of thick-walled LiH components. The results indicate a process parameter that maintains the internal temperature difference of thick-walled LiH within 1 degrees C (0.463-0.74 degrees C). Finally, experiments comparing samples obtained under conventional heating and microwave heating conditions demonstrated that microwave sintering significantly enhances interfacial migration within the LiH samples, resulting in a dense metallurgical bond within the components. Therefore, employing a microwave-assisted approach for the fabrication of thick-walled LiH products is entirely feasible and shows promise in reducing component defects and regulating internal microstructures.