Acoustic Shock Wave-Induced Amorphous to Crystalline Phase Transitions of Li2SO4─Raman Spectroscopic and Thermal Calorimetric Approach.

In this context, we have reexamined the acoustical shock wave-induced amorphous-glassy-crystalline-amorphous phase transitions in the Li2SO4 sample under 0, 1, 2, and 3 shocked conditions by implementing the detailed Raman spectroscopic approach. The recorded Raman spectroscopic data clearly reveal that the transition from the amorphous-glassy-crystalline state occurs because of a significant reduction of the translational disorder of lithium cations, particularly [Li (2)] ions wherein a slight reduction of the librational disorder of SO4 anions takes place, whereas the crystalline to amorphous transition occurs only at the third shocked condition because of the librational disorder of SO4 anions. The double degenerate υ2 and υ4 Raman modes provide a clear indication of the occurrence of the librational disorder of SO4 anions at the third shocked condition. Followed by the internal Raman modes, a detailed discussion is provided on the external Raman modes of the Li ions and SO4 ions with respect to the observed phase transitions, wherein it is found that the regions of lattice modes are significantly altered at each and every point of phase transition. Furthermore, the thermal and magnetic measurements have been performed for the above-mentioned state of Li2SO4 samples, whereby the obtained results of the magnetic loops and the thermal property resemble the observed structural transitions with respect to the number of shock pulses such that the inter-relationship of the structure-electrical-magnetic-thermal properties of Li2SO4 could be explored.

Acoustic Shock Wave-Induced Solid-State Fusion of Nanoparticles: A Case Study of the Conversion of One-Dimensional Rod Shape into Three-Dimensional Honeycomb Nanostructures of CdO for High-Performance Energy Storage Materials.

Herein, we describe the solid-state fusion of rod-shaped to honeycomb-shaped cadmium oxide particles (CdO NPs) caused by the process of repeated exposure to acoustic shock waves. Significant changes have been observed in structurally and morphologically dependent properties. For instance, at the 200-shocked condition, the high-pressure CdO-B2 phase is present as a secondary phase wherein all of the rod-shaped particles have been transformed into honeycomb-shaped CdO particles which possess comparatively higher specific-capacitance than CdO nanorods (NRs). The computed specific capacitance values for the 0, 100, and 200 shocked samples at a scan rate of 100 m V s-1 are computed to be 433, 415, and 583 F g-1, respectively. The second-stage decomposition temperature points of the CdO NPs have significantly increased in accordance with the morphological changes from rod to honeycomb patterns such that the values are 343, 526, and 534 °C, respectively, for 0, 100, and 200 shocked conditions. Note that such honeycomb nanostructured CdO particles by shock-wave processing have never been observed, to date. Due to the superior energy storage abilities as well as the spectacular high thermal stability of the honeycomb CdO nanostructures compared to CdO NRs, shocked CdO with honeycomb nanostructures can be considered as energy storage materials.