In Situ Evolution of Pores in Lithium Hydride at Elevated Temperatures Characterized by X-ray Computed Tomography

The evolution of defects such as pores at elevated temperatures is crucial for revealing the thermal stability of lithium hydride ceramic. The in situ evolution of pores in sintered lithium hydride ceramic from 25 degrees C to 500 degrees C, such as the statistics of pores and the 3D structure of pores, was investigated by X-ray computed tomography. Based on the statistics of pores, the porosity significantly increased from 25 degrees C to 200 degrees C and decreased after 200 degrees C, due to the significant change in the number and total volume of the round-shaped pores and the branched crack-like pores with an increasing temperature. According to the 3D structure of pores, the positions of pores did not change, and the sizes of pores went up in the range of 25-200 degrees C and went down after 200 degrees C. Some small round-shaped pores with an Equivalent Diameter of less than 9 mu m appeared at 200 degrees C and disappeared at elevated temperatures. Some adjacent pores of all types connected at 200 degrees C, and some branched crack-like pores gradually disconnected with an increasing temperature. The expansion of pores at 200 degrees C caused by the release of residual hydrogen and the contraction of pores after 200 degrees C because of the migration and diffusion of some hydrogen in pores might be the reason for the evolution of pores with an increasing temperature.