Abart Rainer, Petrishcheva Elena, Habler Gerlinde, Sutter Christoph, Fischer Franz Dieter, Predan Jozef, Kegl Marko, Rammerstorfer Franz G
Department of Lithospheric Research, University of Vienna, Josef-Holaubek-Platz 2, 1090 Vienna, Austria.
Institute of Mechanics, Montanuniversität Leoben, Franz-Josef-Strasse 18/II, 8700 Leoben, Styria Austria.
Phys Chem Miner. 2022;49(5):14. doi: 10.1007/s00269-022-01183-9. Epub 2022 May 3.
A system of edge cracks was applied to polished (010) surfaces of K-rich gem-quality alkali feldspar by diffusion-mediated cation exchange between oriented feldspar plates and a Na-rich NaCl-KCl salt melt. The cation exchange produced a Na-rich layer at and beneath the specimen surface, and the associated strongly anisotropic lattice contraction lead to a tensile stress state at the specimen surface, which induced fracturing. Cation exchange along the newly formed crack flanks produced Na-enriched diffusion halos around the cracks, and the associated lattice contraction and tensile stress state caused continuous crack growth. The cracks nucleated with non-uniform spacing on the sample surface and quickly attained nearly uniform spacing below the surface by systematic turning along their early propagation paths. In places, conspicuous wavy cracks oscillating several times before attaining their final position between the neighboring cracks were produced. It is shown that the evolution of irregularly spaced towards regularly spaced cracks including the systematic turning and wavyness along the early propagation paths maximizes the rate of free energy dissipation in every evolutionary stage of the system. Maximization of the dissipation rate is suggested as a criterion for selection of the most probable evolution path for a system undergoing chemically induced diffusion mediated fracturing in an anisotropic homogeneous brittle material.
The online version contains supplementary material available at 10.1007/s00269-022-01183-9.
通过定向长石片与富钠的氯化钠 - 氯化钾盐熔体之间的扩散介导阳离子交换，在富钾宝石级碱性长石的抛光（010）表面上施加了一个边缘裂纹系统。阳离子交换在试样表面及其下方产生了一个富钠层，相关的强烈各向异性晶格收缩导致试样表面处于拉伸应力状态，从而引发断裂。沿着新形成的裂纹侧面进行的阳离子交换在裂纹周围产生了富钠扩散晕，相关的晶格收缩和拉伸应力状态导致裂纹持续扩展。裂纹在样品表面以不均匀的间距成核，并通过沿着其早期扩展路径的系统转向在表面以下迅速达到近乎均匀的间距。在某些地方，会产生明显的波浪状裂纹，这些裂纹在到达相邻裂纹之间的最终位置之前会振荡几次。结果表明，从不规则间距的裂纹向规则间距的裂纹演变，包括沿着早期扩展路径的系统转向和波浪状，在系统的每个演化阶段都使自由能耗散率最大化。耗散率最大化被建议作为选择在各向异性均匀脆性材料中经历化学诱导扩散介导断裂的系统最可能演化路径的一个标准。
在线版本包含可在10.1007/s00269-022-01183-9获取的补充材料。
