In view of the potential applications of 5‐(benzothiazole‐2‐yl)‐4‐hydroxyisophthalaldehyde (BHI) in the rapid identification of cyanide, the mechanism of excited‐state intramolecular proton transfer (ESIPT) of BHI has been studied in this work. By exploring the geometric parameters of hydrogen bonding in aprotic solvents with different polarities, infrared (IR) vibrational spectroscopy can confirm that hydrogen bonding is enhanced in the first excited state (S1). It is worth mentioning that the enhancement of hydrogen bonding in the S1 state by polar solvents is particularly important. In light‐induced excitation, by comparing the energy gaps of the leading molecular orbitals and the charge recombination around the proton acceptor and donor in aprotic solvents of different polarities, it is further predicted that polar solvents can promote the ESIPT process of BHI. In order to clarify the detailed ESIPT mechanism, we constructed the potential energy curves, searched for the transition state (TS) form, and determined the ESIPT mechanism for BHI fluorophore. Herein, we not only elucidated the excited‐state behavior of BHI, but also proposed a mechanism for regulating ESIPT by solvent polarity.
An improved rheological model is obtained to perfect the formula of agglomeration, deagglomeration and stacking mode of particles based on a previous model with the experimental data and statistical mechanics. It is believed that the time evolution of the microstructure determines the rheological behaviour of semisolid metal (SSM), and the effective solid volume fraction connect them perfectly. The new model can describe the time-dependent and time- independent rheological behaviour under a uniform theory. Then, the study on AlSi4Mg2 alloy shows that the predicted apparent viscosity agrees well with the experimental results. The correlation between the apparent viscosity and its microstructure is also identified. This verifies the reliability of the present model.
The time-dependent behaviour of AlSi4Mg2 alloy has been investigated with the ICF model. It shows that the apparent viscosity increases with decreasing the shearing time and increasing the resting time, especially at the initial stage. The above variations depend on its microstructure affected by solid volume fraction and shear rate, respectively. It is found that the agglomerating time is about 100 times as long as the deagglomerating time, which agrees with the experiment data.
The rheological characteristics of AlSi4Mg2 alloy at steady state are studied theoretically based on the ICF model. It is shown that the solid volume fraction and shear rate have obvious effect on the rheological behaviour. Specifically, the apparent viscosity increases when the solid volume fraction increases and the shear rate decreases, the corresponding microstructure parameter n has the similar trend. It shows that there is a closely relationship between the steady state viscosity and its microstructure. The AlSi4Mg2 alloy has the pseudoplastic behaviour. The agreement of theoretical prediction and the experimental results indicates the ICF model is reliable to predict the rheological behaviour of AlSi4Mg2.
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