Abstract
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 °C to 500 °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 °C to 200 °C and decreased after 200 °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 °C and went down after 200 °C. Some small round-shaped pores with an Equivalent Diameter of less than 9 μm appeared at 200 °C and disappeared at elevated temperatures. Some adjacent pores of all types connected at 200 °C, and some branched crack-like pores gradually disconnected with an increasing temperature. The expansion of pores at 200 °C caused by the release of residual hydrogen and the contraction of pores after 200 °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.
Highlights
Accepted: 2 September 2021Lithium hydride (LiH), one of the most important ceramic materials in nuclear engineering, is an ideal material for neutron shielding and moderating due to the combination of a high absorption cross-section, high hydrogen density and high melting point (~683 ◦ C) [1,2,3,4,5]
The current paper studied the temperature effect on the pores of sintered LiH ceramic by X-ray computed tomography (XCT)
The temperature effect on the pores of sintered LiH ceramic was investigated by XCT
Summary
Accepted: 2 September 2021Lithium hydride (LiH), one of the most important ceramic materials in nuclear engineering, is an ideal material for neutron shielding and moderating due to the combination of a high absorption cross-section, high hydrogen density and high melting point (~683 ◦ C) [1,2,3,4,5]. As a special ceramic which has an easy deliquescence and combustion in air at room temperature [6,7], LiH ceramic might have complex properties at a high temperature. The mechanical property of LiH under high temperatures was measured, indicating that the tensile strength of sintered LiH increased slightly before 300 ◦ C and decreased after 300 ◦ C [7,8]. The evolution of its microstructures, such as grains, intrinsic defects and micro-cracks, might lead to its tensile strength change with the temperature. Was not sufficient to explain the change of tensile properties with the temperature. It is critical to measure the amount, size, and location of defects such as pores and inclusions of LiH, especially at different temperatures, which may help us understand the thermal damage mechanism
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