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In this work, we use the finite element method to investigate the free volume evolution, as well as the martensite transformation effect and its connection with the pretreatment strain, in a shape memory alloy-metallic glass composite. Our simulation results show that the martensite phase transformation can enhance the blocking effect while relieving the free volume localization. The synergistic effect among the martensite transformation effect, blocking effect, and shear band interaction in the composite is responsible for the tensile plasticity and work-hardening capability. In addition, we design a Sierpinski carpet-like fractal microstructure so that the composite exhibits improved tensile performance as a result of the enhanced synergistic effect. However, the tensile performance of the composite deteriorates with increasing pretreatment strain since the martensite transformation effect is weakened. [ABSTRACT FROM AUTHOR]

In the present research, we use a first principles calculation to investigate the electronic structure and optical properties of Mo-, Pt- and Rh-doped rutile TiO2. The results indicate that the band gap of the Mo-, Pt-, and Rh-doped systems decreases to 1.758, 0.906, and 0.971 eV, respectively, compared with the 1.968 eV band gap of intrinsic TiO2, which is due to the hybridization of the doped atom d and O p orbital electrons, resulting in the formation of an impurity level and enhanced conductivity. The charge-difference density maps show that the covalence is enhanced in the region around Ti atoms for Mo- and Pt-doped systems, whereas Rh doping has little effect on the covalence. Based on these results, the bond population is 0.42, 0.28, and 0.27 for Mo–O, Pt–O, and Rh–O bonds, respectively. In the absorption spectrum, the peaks of the doped systems decrease significantly and redshift. Compared with the Mo-doped system, the Rh- and Pt-doped systems have lower static dielectric constant and dielectric loss in the low-energy region, which is promising for fascinating applications in microelectronic components. [ABSTRACT FROM AUTHOR]

Based on first-principles simulations with the generalized gradient approximation (GGA) of the Perdew-Burke-Ernzerhof (PBE) functional, we studied the electronic structures and optical properties of hexagonal silicon nitride (β-Si3N4) doped with IV A elements, C, Ge, Sn and Pb. It was found that the Ge-doped system is characterized by a more stable structure with a lower formation energy of 2.584 eV compared with those of the C-, Sn- and Pb-doped systems of 3.877 eV, 5.249 eV and 7.672 eV, respectively. The band gap (EG) of the Pb-doped system was the lowest at 1.6 eV, displaying semiconducting characteristics. Additionally, there was a transition from a direct band gap to an indirect band gap in the C-doped system. Charge difference density analysis showed that the covalent property of the C-N bonds was enhanced by expansion of the electron-free region and the larger Mulliken population values of 0.71 and 0.86. Furthermore, lower absorption and reflectivity peaks at 11.30 eV were observed for the C-doped system, demonstrating its broader potential for application in photoelectric and microelectronic devices. [ABSTRACT FROM AUTHOR]