An intensive exploration of the microstructural transformation undergone of phlogopite single-crystal film under electron beam (EB) irradiation at 0–1000 kGy: The influence of lattice stability on H-atom mobility. (1st May 2023)

• Record Type: Journal Article
• Authors: Wang, Honglong; Yang, Chenguang; Wang, Xiaoguang; Li, Jiayan; Su, Xiaoya; Fang, Ke; Li, Jintang; Jiang, Linxu
• Is Part Of: Ceramics international. Volume 49(2023)Part A
• Page Start: 14445
• Page End: 14458
• Publication Date: 2023-05-01
• Subjects: Phlogopite -- Layered-silicate -- Electron-beam irradiation -- Lattice stability -- H-atom migration -- Dehydroxylation; Ceramics -- Periodicals; Céramique industrielle -- Périodiques; Ceramics; Periodicals; Electronic journals; 666
• DOI: 10.1016/j.ceramint.2023.01.033
• Languages: English
• ISSNs: 0272-8842

Abstract

Abstract: An in-depth understanding of the microstructural transformation that the matrix of clay undergoes prior to the complete dissolution of metal package container is crucial for predicting the effectiveness of the matrix of clay purposed as backfill material in the high-level radioactive waste (HLRW) disposal. Although irradiation can strongly influence microstructure its effect remains unclear. Herein, pure phlogopite single-crystal was chosen as a model material and irradiated in air by an electron beam (EB) at 0–1000 kGy. Variation in chemical/crystalline structure and microstructural transformation mechanism were explored by FT-ATR IR, XRD, TGA, CA and XPS. Key results reveal that irradiation caused extensive octahedral OH cleavage and lattice damage, marginal Si–OH formation and surface wettability elevation. With absorbed dose increases to 1000 kGy the majority of samples exhibited lattice plane expansion while the 200 kGy-irradiated sample exhibited shrinkage. 100 and 200 kGy-irradiated samples exhibited a variation level of ±2.5% (±0.3 Å) and a gap of 0.4 Å in (001) lattice plane. Concurrently, the amount of H2 O and valance of metal element decreased while surface hydrophilicity increased slightly. 200 kGy-irradiated sample exhibited a CA of 7°, lower the pristine sample near 15°. Overall, phlogopite lattice appears to be unstable to EB irradiation at 0–1000 kGy. Transformation mechanism involves framework cleavage, H-atom migration, hydrogen-bond formation/destruction and reduction of electron. H-atom migration and hydrogen-bond variation played key roles. Normal silicate crystal appears to be unstable to medium-intensity β -ray irradiation. To enhance lattice stability, the number of OH and hydrogen bond should be reduced. This conclusion guides the design of radiation-resistant silicate material for use as backfill or curing material in HLRW disposal. For example, for curing material (e.g., glass), the concentration of OH in matrix base needs to be reduced. This cognization emphasises the role of OH in novel microstructural transformation.