Jinbin Zhang

Thermodynamic calculations were performed in the Co-Nb-V ternary system on the isothermal sections at 1000 °C and 1200 °C, and several vertical sections at different compositional ranges were constructed using the CALPHAD methodology, drawing upon published experimental measurements. An internally consistent set of thermodynamic parameters describing the Gibbs free energies of the individual phases in the Co-Nb-V ternary system was established, yielding strong agreement between the calculated phase equilibria and reported experimental data. Furthermore, isothermal sections at other temperatures, along with the liquidus surface of the Co-Nb-V system, were subsequently calculated.

Fe additives may play an important role in the preparation of aluminum-based hydrolysis hydrogen powder, with high hydrogen yield, low cost, and good oxidation resistance. Therefore, it is necessary to ascertain the effect of Fe on the hydrogen production performance of Al-Bi-Sn composite powders. According to the calculated vertical cross-section of the Al-10Bi-7Sn-(0~6)Fe (wt.%) quasi-binary system, Al-10Bi-7Sn-xFe (x = 0, 0.5, 1.5, 3) wt.% composite powders for hydrogen production were prepared by the gas-atomization method. The results showed that the Al-10Bi-7Sn-1.5Fe (wt.%) powder exhibited an extremely fast hydrogen generation rate at 50 °C, which reached 1105 mL·g⁻¹ in 27 min in distilled water, 1086 mL·g⁻¹ in 15 min in 0.1 mol·L⁻¹ NaCl solution, and 1086 mL·g⁻¹ in 15 min in 0.1 mol·L⁻¹ CaCl₂ solution. In addition, the antioxidant properties of these powders were also investigated. The results showed that the hydrogen production performance of the Al-10Bi-7Sn-1.5Fe (wt.%) powder could retain 91% of its hydrogen production activity, even though the powder was exposed to 25 °C and 60 RH% for 72 h. The addition of Fe not only promoted the hydrogen generation rate of the Al-Bi-Sn composite powders, but also improved their oxidation resistance. The Al-10Bi-7Sn-1.5Fe (wt.%) composite powder shows great potential for mobile hydrogen source scenarios with rapid hydrogen production.

In this work, two isothermal sections of the Co-Ta-Si ternary system at 900 °C and 1100 °C are constructed in the whole composition range via phase equilibrium determination with the help of electron probe microanalysis (EPMA) and X-ray diffraction (XRD) techniques. Firstly, several reported ternary phases G (Co₁₆Ta₆Si₇), G″ (Co₄TaSi₃), E (CoTaSi), L (Co₃Ta₂Si) and V (Co₄Ta₄Si₇) are all re-confirmed again. The G″ phase is found to be a kind of high-temperature compound, which is unstable at less than 1100 °C. Additionally, the L phase with a large composition range (Co_32–62Ta_26–36Si_10–30) crystallizes with a hexagonal crystal structure (space group: P6₃/mmc, C14), which is the same as that of the binary high-temperature λ₁-Co₂Ta phase. It can be reasonably speculated that the ternary L phase results from the stabilization toward low-temperature of the binary λ₁-Co₂Ta through adding Si. Secondly, the binary CoTa₂ and SiTa₂ phases are found to form a continuous solid solution phase (Co, Si)Ta₂ with a body-centered tetragonal structure. Thirdly, the elemental Si shows a large solid solubility for Co-Ta binary compounds while the Ta and Co are hardly dissolved in Co-Si and Ta-Si binary phases, respectively.

The tunability of semi-conductivity in SrTiO₃ single crystal substrates has been realized by a simple encapsulated annealing method under argon atmosphere. This high temperature annealing-induced property changes are characterized by the transmission spectra, scanning electron microscopy (SEM) and synchrotron-based X-ray absorption (XAS). We find the optical property is strongly influenced by the annealing time (with significant decrease of transmittance). A sub gap absorption at ~427 nm is detected which is attributed to the introduction of oxygen vacancy. Interestingly, in the SEM images, annealing-induced regularly rectangle nano-patterns are directly observed which is contributed to the conducting filaments. The XAS of O K-edge spectra shows the changes of electronic structure by annealing. Very importantly, resistance switching response is displayed in the annealed SrTiO₃ single crystal. This suggests a possible simplified route to tune the conductivity of SrTiO₃ and further develop novel resistance switching materials.

In this study, the isothermal sections of the Co-Re-Ta ternary system at 1100, 1200, and 1300 °C have been experimentally investigated by means of electron probe microanalysis and X-ray diffraction. The results indicated the following: (1) The solid solubilities of the λ₃, (εCo, Re), χ-Re₇Ta₃, and bcc-(Ta) phases were large and changed very little from 1100 to 1300 °C; (2) more interestingly, the λ₂ phase, with a very limited solubility of Re, was surrounded by the λ₃ phase; (3) the solubility of Re for the μ-Co₆Ta₇ phase increased slowly from 1100 to 1300 °C. These experimental results will be useful for Co-based high-temperature alloys, especially as a supplement for thermodynamic databases.

Two isothermal sections of the Ni-V-Ta ternary system at 1200 °C and 1000 °C have been experimentally established using X-ray diffraction, electron probe microanalysis, energy dispersive spectroscopy, and differential scanning calorimeter with equilibrated key alloys. The equilibrium composition of each phase is measured by electron probe microanalysis and energy dispersive spectroscopy. The results indicate that: (1) nine three-phase and eight three-phase regions were confirmed in the isothermal section at 1200 °C and 1000 °C, respectively; (2) the C14 phase with a large solubility of about 51.2 at. % Ni was observed at 1200 °C, while it forms a single-phase region at 1000 °C; (3) a small liquid region was confirmed at 1200 °C, but disappeared at 1000 °C.