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Novel anatase titanium dioxide (TiO2) microspheres with exposed {001} facets were successfully synthesized via a facile and controllable hydrothermal approach using sodium fluoroborate as the reagent. The products were characterized by X-ray powder diffraction (XRD), scanning electron microscopy (SEM), and X-ray photoelectron spectroscopy (XPS). XRD results showed that the TiO2 microspheres were anatase phase and had good crystallinity. SEM images showed that the as prepared TiO2 samples displayed surface of microspheres with exposed {001} facets and a mean diameter of 3.2 µm. Experimental results revealed that the as-prepared TiO2 micro- spheres might be assembled by nanosheets. The formation process of the TiO2 microspheres was preliminarily investigated. [ABSTRACT FROM AUTHOR]

The effects of 400 keV helium ion irradiation dose and temperature on the microstructure of the Ti3SiC2 ceramic were systematically investigated by grazing incidence x-ray diffraction, scanning electron microscopy, and transmission electron microscopy. The helium irradiation experiments were performed at both room temperature (RT) and 500 °C with a fluence up to 2.0 ×1017 He+/cm2 that resulted in a maximum damage of 9.6 displacements per atom. Our results demonstrate that He irradiations produce a large number of nanometer defects in Ti3SiC2 lattice and then cause the dissociation of Ti3SiC2 to TiC nano-grains with the increasing He fluence. Irradiation induced cell volume swelling of Ti3SiC2 at RT is slightly higher than that at 500 °C, suggesting that Ti3SiC2 is more suitable for use in a high temperature environment. The temperature dependence of cell parameter evolution and the aggregation of He bubbles in Ti3SiC2 are different from those in Ti3AlC2. The formation of defects and He bubbles at the projected depth would induce the degradation of mechanical performance. [ABSTRACT FROM AUTHOR]

We develop an isotropic empirical potential for molecular hydrogen (H2) and deuterium (D2) by fitting to solidstate data, which is appropriate for classical molecular dynamics (CMD) approach. Based on the prior isotropic intermolecular potential used in self-consistent phonon approximation, a zero-point energy term and an embedded energy term are introduced to describe the H2–H2 and D2–D2 interactions in CMD simulations. The structure, cohesive energy and elastic properties of solid H2 (D2) are used as the fitting database. The present method is tested by calculating the melting point of solid H2, and the pressure and bulk elastic modulus as a function of volume. The developed potentials well reproduce many properties of solid H2 and D2. [ABSTRACT FROM AUTHOR]

The microstructures of titanium (Ti), an attractive tritium (T) storage material, will affect the evolution process of the retained helium (He). Understanding the diffusion behavior of He at the atomic scale is crucial for the mechanism of material degradation. The novel diffusion behavior of He has been reported by molecular dynamics (MD) simulation for the bulk hcp-Ti system and the system with grain boundary (GB). It is observed that the diffusion of He in the bulk hcp-Ti is significantly anisotropic (the diffusion coefficient of the [0001] direction is higher than that of the basal plane), as represented by the different migration energies. Different from convention, the GB accelerates the diffusion of He in one direction but not in the other. It is observed that a twin boundary (TB) can serve as an effective trapped region for He. The TB accelerates diffusion of He in the direction perpendicular to the twinning direction (TD), while it decelerates the diffusion in the TD. This finding is attributable to the change of diffusion path caused by the distortion of the local favorable site for He and the change of its number in the TB region. [ABSTRACT FROM AUTHOR]