As a result of human underground mining activities, phyllite has been extensively reused to make raw ceramic materials and concrete aggregates. Building materials are a significant source of indoor radon, and radon gas emitted from phyllite poses radiation risks to humans. High temperatures can alter the structural properties of rocks, impacting radon exhalation. Thus, this study examined phyllite's radon exhalation rate after heat treatment ranging from 25 °C to 1000 °C. The effects of changes in pore structure and mineral composition on phyllite's radon exhalation were analyzed in detail using nuclear magnetic resonance (NMR), polarizing optical microscopy (POM), three-dimensional microscopy (3DM), and scanning electron microscopy (SEM). Results indicate that the radon exhalation rate initially increases and then decreases with rising temperature. This rate correlates positively with both total porosity and micropore porosity. Processes such as free water evaporation, pyrite oxidation, quartz phase transformation, and chlorite dehydroxylation within phyllite contribute to pore development and the movement of free radon within pore spaces. The highest total porosity and radon exhalation rate occur at 700 °C, measuring 8.6 % and 6.14 Bq/m2·h, respectively—4.30 times and 1.18 times higher than at 25 °C. Additionally, mineral decomposition and melting reduce pore connectivity and effective porosity, hindering radon migration. These findings offer guidance for assessing radon radiation risks and indoor radon potential in phyllite-based building materials.

中文翻译：

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热效应下千枚岩的氡呼出率研究


由于人类的地下采矿活动，千枚石已被广泛重新用于制造陶瓷原料和混凝土骨料。建筑材料是室内氡的重要来源，千枚岩排放的氡气对人类构成辐射风险。高温会改变岩石的结构特性，影响氡的呼出。因此，本研究检查了 25 °C 至 1000 °C 热处理后千枚岩的氡呼出速率。 采用核磁共振 （NMR） 、偏振光学显微镜 （POM） 、三维显微镜 （3DM） 和扫描电子显微镜 （SEM） 详细分析孔结构和矿物组成变化对千枚岩氡呼出量的影响。结果表明，氡呼出速率随温度升高而先增加后降低。该速率与总孔隙率和微孔隙率呈正相关。千枚岩内的游离水蒸发、黄铁矿氧化、石英相变和亚氯酸盐脱羟基化等过程有助于孔隙的形成和游离氡在孔隙空间内的移动。总孔隙率和氡呼出速率在 700 °C 时最高，分别为 8.6 % 和 6.14 Bq/m2·h，分别是 25 °C 时的 4.30 倍和 1.18 倍。 此外，矿物分解和熔化会降低孔隙连通性和有效孔隙率，从而阻碍氡的迁移。这些发现为评估千枚岩基建筑材料的氡辐射风险和室内氡潜力提供了指导。