Ternary rare earth germanium systems with Cu and Ag—A review and a contribution to their assessment

Constitutional data of the R-(Ag, Cu)-Ge systems, with R=rare earth, are summarized and discussed. Crystal structures of the phases formed in the binary boundary systems and in the ternary systems are assessed, and the phase equilibria observed in the reported ternary systems are reviewed with special attention to the isothermal sections (generally at 400 or 600 °C) of the phase diagrams. Some regularities observed in the trends of the constitutional properties of the ternary R-(Ag, Cu)-Ge alloys are briefly described.     

Electrochemical and mechanical behaviour of Sn‐2.5Ag‐0.5Cu and Sn‐48Bi‐2Zn solders

In this paper, two tin‐based alloys (Sn‐2.5Ag‐0.5Cu and Sn‐48Bi‐2Zn) are proposed as new lead‐free solders. Alloys have been developed by melting pure elements. Samples have been evaluated in terms of microstructure, corrosion resistance and mechanical features. Corrosion tests have been performed in 3% NaCl solution by polarization curves and electrochemical impedance spectroscopy (EIS). SEM observations and EDS analysis were carried out on samples before and after corrosion tests. Static monotonic tensile tests have been performed on three specimens for each alloy. SEM and EDS analysis revealed the presence of Sn‐Ag and Sn‐Cu intermetallic compounds within the Sn‐Ag‐Cu alloy. As a result of corrosion test, the Sn‐Ag‐Cu alloy showed a better corrosion resistance with respect to Sn‐Bi‐Zn. Both alloys evidenced good mechanical properties higher than the traditional Sn‐Pb system. Sn‐Ag‐Cu seems to be a suitable soldering material.     

About the Al–Cu–Si isothermal section at 500 °C and the stability of the ɛ-Cu15Si4 phase

The 500 °C isothermal section of the Al–Cu–Si system has been determined in the whole composition range, with special attention to the Cu-rich corner. A number of Cu–Si binary alloys equilibrated at 500–780 °C have also been investigated.A ternary point compound at 1.5 at% Al and 21 at% Si has been identified. It has the same crystal structure of the binary phase previously reported as ?-Cu₁₅Si₄. This phase however is not stable in the binary system, at least between 500 and 780 °C, and it is stabilised by small amounts of impurities. The γ₁-(Al,Cu) phase dissolves about 11.5 at% Si and ternary solubility extends in the direction of a constant valence electron concentration. The binary κ-(Cu,Si) phase is stable in a ternary solubility range close to the (Cu) terminal solid solution.     

Transformations and seasonal adjustment

Abstract.  We address the problem of seasonal adjustment of a nonlinear transformation of the original time series, measured on a ratio scale, which aims at enforcing two essential features: additivity and orthogonality of the components. The posterior mean and variance of the seasonally adjusted series admit an analytic finite representation only for particular values of the transformation parameter, e.g. for a fractional Box–Cox transformation parameter. Even if available, the analytical derivation can be tedious and difficult. As an alternative we propose to compute the two conditional moments of the seasonally adjusted series by means of numerical and Monte Carlo integration. The former is both fast and reliable in univariate applications. The latter uses the algorithm known as the 'simulation smoother' and it is most useful in multivariate applications. We present two case studies dealing with robust seasonal adjustment under the square root and the fourth root transformation. Our overall conclusion is that robust seasonal adjustment under transformations is feasible from the computational standpoint and that the possibility of transforming the scale ought to be considered as a further option for improving the quality of seasonal adjustment.     

Cobalt-based nanoparticles as catalysts for low temperature hydrogen production by ethanol steam reforming

Results obtained in the synthesis, characterization and application as catalyst of cobalt nanoparticles are reported. Cobalt nanoparticles were prepared via reduction method in aqueous solution. Structural characterization was carried out using X-ray diffraction (XRD), morphological studies were performed with a scanning electron microscope equipped with a field emission gun (FE-SEM). A DC-superconducting quantum interference device “SQUID” magnetometer was used to measure the room temperature (RT) magnetic hysteresis cycle in the −5 ÷ 5 Tesla (T) μ₀H magnetic field range as well as magnetization as a function of temperature. This material is constituted by very small primary particles (∼2.8 nm radius) which appear amorphous to XRD and have a superparamagnetic behaviour. However, annealing at 773 K and also utilization in the catalytic reactor at the same temperature result in XRD detectable cubic Co nanocrystals. These unsupported cobalt nanoparticles were found catalytically active in the ethanol steam reforming reaction, producing hydrogen with 90% yield at 773 K. These nanoparticles show a better catalytic behaviour compared to those of more conventional Co and Ni based catalysts, due to very low CO and methane production, and with moderate formation of carbonaceous materials.