Preparation and Characterization of Master Alloys Fe48Cr15Mo14C15B6Y2 Metallic Glasses

The purpose of this work is the characterization of a master alloy of metal glass based on iron Fe48Cr15Mo14C15B6Y2. Two types of alloys studied B1 which has been prepared by the use of pure element and the other B2 which has been prepared by the use of raw materials. The thermal and structural properties of the samples are measured by a combination of high temperature differential scanning calorimeter (HTDSC), X-ray diffraction and scanning electron microscopy (SEM). Chemical compositions are checked by energy dispersive spectroscopy analysis.Fil: Bendjemil, Badis. University of Badji -Mokhtar; Argelia. Faculty of Sciences and Technology; ArgeliaFil: Seghairi, Nassima. Faculty of Sciences and Technology; ArgeliaFil: Lavorato, Gabriel Carlos. Dipa rtimento di Chimica Universita' di Torino; Italia. Comisión Nacional de Energía Atómica. Gerencia del Área Investigaciones y Aplicaciones no Nucleares; ArgentinaFil: Castellero, Alberto. Dipa rtimento di Chimica Universita' di Torino; ItaliaFil: Bougdira, Jamal. Université de Nancy, Faculté des Sciences et. Techniques; FranciaFil: Vinai, Franco. Instituto Nazionale di Ricerca Metrologica; ItaliaFil: Baricco, Marcello. Dipa rtimento di Chimica Universita' di Torino; Itali

Nanoporous Microtubes via Oxidation and Reduction of Cu–Ni Commercial Wires

Metallic porous microtubes were obtained from commercial wires (200–250 µm diameter) of Cu-65Ni-2Fe, Cu-44Ni-1Mn and Cu-23Ni, alloys (wt. %) by surface oxidation at 1173 K in air, removal of the unoxidized core by chemical etching, and reduction in annealing in the hydrogen atmosphere. Transversal sections of the partially oxidized wires show a porous layered structure, with an external shell of CuO (about 10 μm thick) and an inner layer of NiO (70–80 μm thick). In partially oxidized Cu-44Ni-1Mn and Cu-23Ni, Cu2O is dispersed in NiO because the maximum solubility of Cu in NiO is exceeded, whereas in Cu-65Ni-2Fe, a Cu2O shell is present between CuO and NiO layers. Chemical etching removed the unoxidized metallic core and Cu2O with formation of porous oxide microtubes. Porosity increases with Cu content because of the larger amount of Cu2O in the partially oxidized wire. After reduction, the transversal sections of the metallic porous microtubes show a series of f.c.c.-(Cu,Ni) solid solutions with different compositions, due to the segregation of CuO and NiO during oxidation caused by the different diffusion coefficients of Ni and Cu in the respective oxides. Pore formation occurs at each step of the process because of the Kirkendall effect, selective phase removal and volume contraction