查看更多>>摘要：? 2022 Elsevier B.V.The effect of equal-channel angular pressing on structural phase transformations and mechanical properties of the as-cast hypoeutectic Al–4Ca–1.3Fe–0.8Mn–0.1Zr–0.1Sc alloy has been studied. ECAP was carried out under isothermal conditions at a temperature of 200 °C, with a channel intersection angle of 110o, using the BC route and the number of passes N = 6. After ECAP, a substructure with an increased dislocation density has developed in the alloy. ECAP led, firstly, to the evolution of the dendritic structure (dendrites elongate and merge with each other), and secondly, to the refinement of the Al4Ca, Al4Ca(Fe) and Al3?x(Fe, Mn) eutectic phase particles to nano- and submicron scale, their mixing and partial segregation of calcium. The tensile tests of the ECAP processed alloy showed that its strength increased, while its ductility decreased. The yield point increased from 122 to 257 MPa, the ultimate tensile strength increased from 174 to 281–314 MPa, and the relative elongation decreased from 6 to 1–3%. After ECAP, the strength is higher, and the relative elongation is lower for longitudinal specimens compared to transverse specimens.
查看更多>>摘要：? 2022 Elsevier B.V.The energetic and electronic properties of intrinsic point defects in germanium sulfide (GeS) were studied using first-principles methods. Point defects including single-site (e.g., vacancies, interstitials, and anitisites) and double-site defects (e.g., Schottky defects, Frenkel pairs) were considered. It was found that the lowest formation energy for neutral defects is associated with the Schottky dimer (SD), independent of chemical potentials of the species, and not with vacancies, as previously reported for similar materials like GeSe, SnS and SnSe. Furthermore, SD were studied in these similar materials and found to be energetically more stable than neutral vacancies for GeSe and similarly stable to Sn vacancy defects in SnS and SnSe. Charged states of the defects were considered and found to be energetically preferred over neutral defects. On allowing the defects to charge, Ge2- vacancy (VGe?2) defects were found to be the most stable defects in both Ge-rich and Ge-poor environments; consistent with the experimentally reported nonstoichiometric nature of GeS. Negative formation energies were obtained for Ge vacancies, in both environmental conditions, and thus they are expected to form spontaneously. The electronic structure was affected by the incorporation of point defects. For Ge vacancies, the Fermi level shifted below the valence band maxima (VBM), indicating p-type conductivity in agreement with experimental observations. S vacancies introduced occupied defect states and hybridized with VBM, and the fundamental bandgap was retained, indicating no preferential conductivity. The possibility of doping GeS to obtain n-type conductivity was explored.
查看更多>>摘要：? 2022 Elsevier B.V.CdS decorated anatase TiO2 without capping ligands between them was constructed by the reaction of amorphous TiO2 sphere modified by thioglycolic acid with Cd2+ during the heating process (95 °C) directly. We have confirmed that the crystallization of amorphous TiO2 and the formation of CdS particles are driven by the decomposition of thioglycolic acid. Moreover, the dissociation of thioglycolic acid also avoids the influence of ligand on the charge transfer between TiO2 and CdS which is beneficial to improving the photocatalytic activity. Benefiting from this fabrication strategy, the photocatalytic activity of the obtained photocatalysts presents the enhanced activity in the wastewater treatment under visible light irradiation compared to conventionally prepared photocatalysts with the ligand.
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