Uribe-Zorita María de, Álvarez-Lloret Pedro, Ramajo Beatriz, Reynes Javier F, Marcos Celia
Department of Geology, Faculty of Geology, University of Oviedo, C. Jesús Arias de Velasco s/n, 33005 Oviedo, Spain.
Scientific-Technical Services, University of Oviedo, 33005 Oviedo, Spain.
Materials (Basel). 2025 Jun 28;18(13):3077. doi: 10.3390/ma18133077.
This work investigated the structural response and phase transformation dynamics of silica-bearing cherts subjected to high-temperature processing (up to 1400 °C) and prolonged mechanochemical activation. Through a combination of X-ray diffraction (XRD) with Rietveld refinement, differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and transmission electron microscopy (HRTEM), we trace the crystallographic pathways of quartz, moganite, tridymite, and cristobalite under controlled thermal and mechanical stress regimes. The experimental results demonstrated that phase behavior is highly dependent on intrinsic properties such as initial phase composition, impurity presence, and crystallinity. Heating at 1400 °C induced irreversible conversion of quartz, moganite, and tridymite into cristobalite. Samples enriched in cristobalite and tridymite exhibited notable increases in crystallinity, whereas quartz-dominant samples showed either stability or a decline in structural order. Rietveld analyses underscored the critical influence of microstrain and crystallite size on thermal resilience and phase persistence. Thermal profiles revealed by DSC and TGA expose overlapping processes including polymorphic transitions, minor phase dehydration, and redox-driven changes, likely associated with trace components. Mechanochemical processing resulted in partial amorphization and the emergence of phases such as opal and feldspar minerals (microcline, albite, anorthite), interpreted as the product of lattice collapse and subsequent reprecipitation. Heat treatment of chert leads to a progressive rearrangement and recrystallization of its silica phases: quartz collapses around 1000 °C before recovering, tridymite emerges as an intermediate phase, and cristobalite shows the greatest crystallite size growth and least deformation at 1400 °C. These phase changes serve as markers of high-temperature exposure, guiding the identification of heat-altered lithic artefacts, reconstructing geological and diagenetic histories, and allowing engineers to adjust the thermal expansion of ceramic materials. Mechanochemical results provide new insights into the physicochemical evolution of metastable silica systems and offer valuable implications for the design and thermal conditioning of silica-based functional materials used in high-temperature ceramics, glasses, and refractory applications. From a geoarchaeological standpoint, the mechanochemically treated material could simulate natural weathering of prehistoric chert tools, providing insights into diagenetic pathways and lithic degradation processes.
本研究调查了含硅燧石在高温处理（高达1400°C）和长时间机械化学活化下的结构响应和相变动力学。通过结合X射线衍射（XRD）与Rietveld精修、差示扫描量热法（DSC）、热重分析（TGA）以及透射电子显微镜（高分辨透射电子显微镜，HRTEM），我们追踪了在可控热应力和机械应力条件下石英、莫来石、鳞石英和方石英的晶体学路径。实验结果表明，相行为高度依赖于诸如初始相组成、杂质存在和结晶度等固有特性。在1400°C加热导致石英、莫来石和鳞石英不可逆地转变为方石英。富含方石英和鳞石英的样品结晶度显著增加，而以石英为主的样品则表现出结构稳定性或结构有序性下降。Rietveld分析强调了微观应变和微晶尺寸对热弹性和相持久性的关键影响。DSC和TGA揭示的热曲线显示了包括多晶型转变、次要相脱水以及可能与痕量成分相关的氧化还原驱动变化等重叠过程。机械化学处理导致部分非晶化，并出现了诸如蛋白石和长石矿物（微斜长石、钠长石、钙长石）等相，这被解释为晶格坍塌和随后再沉淀的产物。燧石的热处理导致其硅相逐渐重排和再结晶：石英在1000°C左右坍塌后恢复，鳞石英作为中间相出现，方石英在1400°C时显示出最大的微晶尺寸增长和最小的变形。这些相变作为高温暴露的标志，有助于识别受热改变的石器文物、重建地质和成岩历史，并使工程师能够调整陶瓷材料的热膨胀。机械化学研究结果为亚稳硅系统的物理化学演化提供了新的见解，并对用于高温陶瓷、玻璃和耐火材料应用的硅基功能材料的设计和热调节具有重要意义。从地质考古学的角度来看，经过机械化学处理的材料可以模拟史前燧石工具的自然风化，为成岩路径和石器降解过程提供见解。
