Design and Fabrication of High Activity Retention Al-Based Composite Powders for Mild Hydrogen Generation

Al–Bi–Sn–Cu composite powders for hydrogen generation were designed from the calculated phase diagram and prepared by the gas atomization process. The morphologies and structures of the composite powders were investigated using X-ray diffraction (XRD) and a scanning electron microscope (SEM) equipped with energy-dispersive X-ray (EDX) spectroscopy, and the results indicate that the Cu additive enhanced the phase separation between the Al-rich phase and the (Bi, Sn)-rich phase. The hydrogen generation performances were investigated by reacting the materials with distilled water. The Al–Bi–Sn–Cu powders reveal a stable hydrogen generation rate, and the Al–10Bi–7Sn–3Cu (wt%) powder exhibits the best hydrogen generation performance in 50 °C distilled water which reaches 856 mL/g in 800 min. In addition, the antioxidation properties of the powders were also studied. The Al–10Bi–7Sn–3Cu (wt%) powder has a good resistance to oxidation and moisture, which shows great potential for being the hydrogen source for fuel cell applications.

Effect of Long-Time Annealing at 1000 °C on Phase Constituent and Microhardness of the 20Co-Cr-Fe-Ni Alloys

The phase constituent and microhardness of the arc-melted 20Co-Cr-Fe-Ni alloys, in both as-cast state and after annealing at 1000 °C for 30 days, were experimentally investigated by scanning electron microscopy (SEM) and X-ray diffraction (XRD). Experiment results indicated that a uniform, stable, single Face-Center Cubic (FCC) phase can be obtained in as-cast 20 Co-Cr-Fe-Ni alloys with less than 30 at.% Cr. Annealing at 1000 °C has no effect on their phase composition and microhardness. When the Cr content is above 40 at.%, the σ phase forms and its volume fraction increases with the Cr content, which leads to an increase in microhardness. Annealing at 1000 °C for 30 days can slightly decrease the volume fraction of the σ phase and slightly decrease the alloy microhardness. Except for the Fe-rich alloys, the alloy microhardness increases with the Cr content when the Co and Ni or the Co and Fe contents were fixed. Moreover, comparing with the thermodynamically calculated phase diagram based on the TCFE database, it has been proved that the calculation can predict the phase stability of the FCC phase and the 1000 °C isothermal section. However, it fails to predict the stability of the σ phase near the liquidus. The present results will help to design and process treatment of the Co-Cr-Fe-Ni based high entropy alloys.

Experimental investigation and thermodynamic calculations of the Bi-Ni-Pb phase diagram

The article presents an experimental study of a phase diagram of a ternary Bi-Ni-Pb system using differential thermal analysis (DTA), scanning electron microscopy (SEM) with energy dispersive spectrometry (EDS), and X-ray powder diffraction (XRD) analysis. The investigated ternary alloys were selected from three vertical sections (x(Bi)=0.75, x(Ni)=0.1 and x(Pb)=0.9) and two isothermal sections at 100 and at 300?C. The obtained experimental results were compared with the thermodynamically extrapolated phase diagram of the Bi-Ni-Pb ternary system based on the thermodynamic parameters for the constitutive binary systems available in literature. Reasonably close agreement between the experimental data and the calculated phase diagram was obtained.

Effect of Electromagnetic Stirring on the Microstructure and Properties of Fe-Cr-Co Steel

High chromium steel has been synthesized by an induction furnace adopting electromagnetic stirring (EMS). Varying amounts of cobalt was added to obtain 3, 6, and 12% Co in the steel. The melt was allowed to solidify with or without EMS in a rotary magnetic field. The effects of the varying cobalt content and the stirring have been characterized by the microstructural evolution and the consequent improvement in mechanical properties. The application of a rotary EMS during solidification has shown a significant effect on the grain refining, the reduction of element segregation, the promotion of eutectic volume fraction, and the consequent improvement of mechanical properties, including hardness and high-temperature strength. The formation mechanism of the eutectic structure and the precipitation of M7C3 and M23C6 carbides was discussed according to the calculated phase diagram. The increment of cobalt content improved the eutectic volume fraction. Cobalt addition also enhanced the hardness and the yield tensile strength, provided that the ingot structure was homogenized by the EMS.

Thermodynamic Calculation of the Rare Earth Permanent Magnets: Fe-RE (RE=Ho, Er, Tm, Sm) Binary Systems

The experimental data of phase equilibria and thermodynamic properties of the Fe-RE (RE=Ho, Er, Tm, Sm) binary systems were reviewed. The previous thermodynamic calculation of the Fe-RE (RE=Ho, Er, Tm, Sm) binary systems were discussed based on the comparison of the calculated phase diagram and thermodynamic properties with the experimental data. The compared results show that more experimental information of phase diagram and thermodynamic properties in the Fe-RE (RE=Ho, Er, Tm, Sm) binary systems should be determined and then thermodynamic re-calculation of these binary systems would be performed to develop compatible and available thermodynamic database of the RE-Fe-B ternary systems. It is indispensable to study the relations between alloy compositions, microstructure and magnetic properties of novel Nd-Fe-B-based permanent magnets.

Experimental and thermodynamic description of ternary Bi-Cu-Ga system

Phase diagram of the Bi-Cu-Ga ternary system has been investigated experimentally with 27 alloys and analytically by using a Calphad method. Thirteen annealed alloys at 200?C were investigated by using scanning electron microscopy (SEM) with energy dispersive spectrometry (EDS), and X-ray powder diffraction (XRD) methods. Temperatures of phase transformation were determined with 14 alloys which are lying along three vertical sections Bi-Cu0.5Ga0.5, Cu-Bi0.5Ga0.5 and Ga-Bi0.5Cu0.5 by using differential thermal analysis (DTA). Based on the experimental result and by using Calphad method, ternary phase diagrams were constructed with a new description of liquidus phase. Calculated phase diagram and experimentally obtained results are in good agreement. Liquidus projection and invariant reaction were calculated by using new thermodynamic parameters for liquidus phase.

Experimental Study and Thermodynamic Calculation of BaO-Lu2O3 Binary System

Only one intermediate compound Ba3Lu4O9was identified at 1373, 1573 and 1773K in the BaO-Lu2O3system in present work.Based on the available experimental phase diagram and relevant thermodynamic data, BaO-Lu2O3 binary system was optimized and calculated by using CALPHAD method. The Gibbs free energy of high temperature solution was described by an ionic two-sublattice model as (Ba2+,Lu3+)P(O2-)Q. The calculated phase diagram, Gibbs energy of intermediate phase Ba3Lu4O9and Gibbs energy of mixingagreewell with experimental resultswithin error limits. The study will offer theoretical basis for further research of the phosphor matrix system of BaO-Lu2O3-SiO2, but also provide new idea for the phase diagram and thermodynamic research on related metallurgical slags, refractories, high-temperature superconductivity material systems.

Ab-initio study of structural, elastic, electronic and thermodynamic properties of BaxSr1−xS ternary alloys

The structural, elastic, electronic and thermodynamic properties of BaxSr1−xS ternary alloys have been investigated using the full-potential (linearized) augmented plane wave method. The ground state properties, such as lattice constant, bulk modulus and elastic constants, are in good agreement with numerous experimental and theoretical data. The dependence of the lattice parameters, bulk modulus and band gap on the composition x was analyzed. Deviation of the lattice constant from Vegard’s law and the bulk modulus from linear concentration dependence (LCD) was observed. The microscopic origins of the gap bowing were explained by using the approach of Zunger et al. The thermodynamic stability of BaxSr1−xS alloy was investigated by calculating the excess enthalpy of mixing, ΔHm and the calculated phase diagram showed a broad miscibility gap with a critical temperature.