Dynamic shock wave driven simultaneous crystallographic and molecular switching between α-Fe2O3 and Fe3O4 nanoparticles - a new finding.

Switchable nanostructured materials with a low-cost and fast processing have diverse practical applications in the modern electronic industries, but such materials are highly scarce. Hence, there is a great demand for identifying the externally stimulated solid-state switchable phase transition materials for several industrial applications. In this paper, we present the experimentally observed solid-state molecular level switchable phase transitions of nanocrystalline iron oxide materials: {α-Fe2O3 (R-3c) to Fe3O4 (Fd-3m) and Fe3O4 (Fd-3m) to α-Fe2O3 (R-3c)} under dynamic shock wave loaded conditions, and the results were evaluated by diffraction, and vibrational and optical spectroscopic techniques. To date, this is most probably the first report which demonstrates the simultaneous molecular and crystallographic switchable-phase-transitions enforced by dynamic shock waves such that the title material is proposed for sensors and molecular switching applications.

Thermal decomposition of propargyl alcohol: single pulse shock tube experimental and ab initio theoretical study.

Thermal decomposition of propargyl alcohol (C3H3OH), a molecule of interest in interstellar chemistry and combustion, was investigated using a single pulse shock tube in the temperature ranging from 953 to 1262 K. The products identified include acetylene, propyne, vinylacetylene, propynal, propenal, and benzene. The experimentally observed overall rate constant for thermal decomposition of propargyl alcohol was found to be k = 10((10.17 ± 0.36)) exp(-(39.70 ± 1.83)/RT) s(-1). Ab initio theoretical calculations were carried out to understand the potential energy surfaces involved in the primary and secondary steps of propargyl alcohol thermal decomposition. Transition state theory was used to predict the rate constants, which were then used and refined in a kinetic simulation of the product profile. The first step in the decomposition is C-O bond dissociation, leading to the formation of two important radicals in combustion, OH and propargyl. This has been used to study the reverse OH + propargyl radical reaction, about which there appears to be no prior work. Depending on the site of attack, this reaction leads to propargyl alcohol or propenal, one of the major products at temperatures below 1200 K. A detailed mechanism has been derived to explain all the observed products.