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A quantitative multi-phase-field model for non-isothermal and polycrystalline solidification was developed and applied to dilute multicomponent alloys with hexagonal close-packed structures. The effects of Lewis coefficient and undercooling on dendrite growth were investigated systematically. Results show that large Lewis coefficients facilitate the release of the latent heat, which can accelerate the dendrite growth while suppress the dendrite tip radius. The greater the initial undercooling, the stronger the driving force for dendrite growth, the faster the growth rate of dendrites, the higher the solid fraction, and the more serious the solute microsegregation. The simulated dendrite growth dynamics are consistent with predictions from the phenomenological theory but significantly deviate from the classical JMAK theory which neglects the soft collision effect and mutual blocking among dendrites. Finally, taking the Mg-6Gd-2Zn (wt.%) alloy as an example, the simulated dendrite morphology shows good agreement with experimental results. [ABSTRACT FROM AUTHOR]

Three ester-containing gemini surfactants (CmDEGs) were used to construct UV-responsive micellar systems with sodium trans-ortho-methoxycinnamate (trans-NaOMCA) as photo-sensitive additive. The effect of tail-chain length and spacer chain length on the UV-responsive ability was preliminarily explored. Longer tail chain and shorter spacer chain are favorable factors for enhancing UV-responsive ability. The addition of trans-NaOMCA into N,N′-bis(2-(dodecanoyloxy)ethyl)-N,N,N′,N′-tetramethyl-1,3-propane diammonium dibromide (C12DEG3) aqueous solution leads to a peak in zero-shear viscosity (η0) versus composition curve, and its further addition induces aqueous two-phase separation. For the C12DEG3/trans-NaOMCA/H2O mixed micellar systems, the UV responsiveness of significant decrease in η0 ascribes to microstructural transitions arising from the changes in counterion binding modes due to the trans-cis photoisomerization of NaOMCA. In comparison with the gemini surfactant 12-3-12, C12DEG3 has ester groups introduced in its tail chains. The introduction of ester groups leads to a significant effect on enhancing the photo-responsive ability in viscosity decrease of the constructed UV-responsive micellar systems. Furthermore, the effect of the addition of an amino acid–based surfactant sodium lauroylglutamate (SLGlu) into the C12DEG3/trans-NaOMCA/H2O mixed system on the UV-responsive behaviors was explored. In addition to UV-induced significant decrease in η0 and phase transition from aqueous two-phase systems (ATPS) to isotropic single-phase systems, the addition of SLGlu can also cause UV-induced increase in η0 and lead to richer UV-induced phase transition behaviors. The reason leading to these differences due to the presence of SLGlu was discussed based on 1H NMR spectra, molecular dynamics (MD) simulation, and molecular electrostatic potential (MEP) analysis. [ABSTRACT FROM AUTHOR]