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Perovskite chalcogenides are gaining substantial interest as an emerging class of semiconductors for optoelectronic applications. High-quality samples are of vital importance to examine their inherent physical properties. We report the successful crystal growth of the model system, BaZrS 3 and its Ruddlesden–Popper phase Ba 3 Zr 2 S 7 by a flux method. X-ray diffraction analyses showed the space group of Pnma with lattice constants of a = 7.056(3) Å, b = 9.962(4) Å, and c = 6.996(3) Å for BaZrS 3 and P 4 2 / mnm with a = 7.071(2) Å, b = 7.071(2) Å, and c = 25.418(5) Å for Ba 3 Zr 2 S 7 . Rocking curves with full width at half maximum of 0.011° for BaZrS 3 and 0.027° for Ba 3 Zr 2 S 7 were observed. Pole figure analysis, scanning transmission electron microscopy images, and electron diffraction patterns also establish the high quality of the grown crystals. The octahedral tilting in the corner-sharing octahedral network is analyzed by extracting the torsion angles. 

The emerging applications of hydrogels in devices and machines require hydrogels to maintain robustness under cyclic mechanical loads. Whereas hydrogels have been made tough to resist fracture under a single cycle of mechanical load, these toughened gels still suffer from fatigue fracture under multiple cycles of loads. The reported fatigue threshold for synthetic hydrogels is on the order of 1 to 100 J/m 2 . We propose that designing anti-fatigue-fracture hydrogels requires making the fatigue crack encounter and fracture objects with energies per unit area much higher than that for fracturing a single layer of polymer chains. We demonstrate that the controlled introduction of crystallinity in hydrogels can substantially enhance their anti-fatigue-fracture properties. The fatigue threshold of polyvinyl alcohol (PVA) with a crystallinity of 18.9 weight % in the swollen state can exceed 1000 J/m 2 . 

ABSTRACT A virtual X-Ray Laboratory for Materials Science and Engineering has been developed and used as a flexible and powerful tool to help undergraduate and graduate students become familiar with the design and operation of the X-ray equipment in visual and interactive ways in order to learn fundamental principles underlying X-ray analytical methods. The virtual equipment and lab assignments have been used for: (i) authentic online experimentation, (ii) homework and control assignments with traditional and blended courses, (iii) preparing students for hands-on work in physical X-ray labs, (iv) lecture demonstrations, and (v) performance-based assessment of students’ ability to apply gained theoretical knowledge for operating actual equipment and solving practical problems. Students have also used the virtual diffractometer linked and synchronized with an actual powder diffractometer for blended experimentation. Using the associated learning and content management system (LCMS) and authoring tools, instructors kept track of students’ performance and designed new virtual experiments and more personalized learning assignments for students. The lab has also been integrated with the MITx course available on the massive open online course edX platform for Massachusetts Institute of Technology for undergraduate students.