Abstract Magnesium potassium phosphate cement (MKPC) is gaining increasing popularity for specialized applications, e.g., structural rehabilitation, waste encapsulation, and 3D printing. However, the mechanical properties of struvite-K, the binding phase of MKPC, have rarely been examined. This study utilized synchrotron-based high-pressure X-ray diffraction to determine the intrinsic mechanical properties of struvite-K at the unit-cell scale, for the first time. The deformation of the unit cell, axial incompressibility, and bulk modulus was studied under hydrostatic pressures up to ~10 GPa. The unit cell shifts from orthorhombic to monoclinic lattice below 1 GPa; phase transition and amorphization occur at ~5 and ~10 GPa, respectively. The axial incompressibility shifts from anisotropy to isotropy, and the bulk modulus increases from 27 to 37 GPa upon phase transition. The experimental results are of great importance in calibration of atomistic modelling and provide implications on the problem with nanoindentation for studying mechanical properties of struvite-K or MKPC.

中文翻译：

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鸟粪石-K 的机械性能：高压 X 射线衍射研究

摘要 磷酸镁钾水泥 (MKPC) 在专业应用中越来越受欢迎，例如结构修复、废物封装和 3D 打印。然而，MKPC 的结合相鸟粪石-K 的机械性能很少被研究。该研究首次利用基于同步加速器的高压 X 射线衍射在晶胞尺度上确定鸟粪石-K 的内在机械性能。在高达 ~10 GPa 的静水压力下研究了晶胞的变形、轴向不可压缩性和体积模量。晶胞在1GPa以下从斜方晶格转变为单斜晶格；相变和非晶化分别发生在~5 和~10 GPa。轴向不可压缩性从各向异性转变为各向同性，相变时体积模量从 27 GPa 增加到 37 GPa。实验结果对原子模型的校准非常重要，并为研究鸟粪石-K 或 MKPC 的机械性能的纳米压痕问题提供了启示。