Microstructure, resistivity, and shear strength of electrically conductive adhesives made of silver-coated copper powder

Electrically conductive adhesives were made using silver-coated copper powders (filler) and epoxy. Resistivity, microstructure and shear strength of prepared adhesives were studied using two-point resistance measurements, Scanning Electron Microscope (SEM) and universal tensile tests, respectively. Effect of filler concentration (70-85 wt%), silver concentration (10-50 wt%), particles morphology (flake or spherical) and addition of graphite (2-15 wt%) were investigated on prepared adhesives properties. Results showed that by increasing the filler percentage from 70 to 85 wt%, the electrical resistivity decreases from 6.2 x 10(-3) to 3 x 10(-3) Omega.cm. Furthermore, the electrical resistivity of adhesives is proportional to the silver content of the filler particles. Regarding the morphological effect of filler particles, it was found that by replacing 40 wt% of the flake with spherical particles in the adhesive with a filler content of 75 wt%, the electrical resistivity of the adhesive reduces from 5.6 x 10(-3) to 4.5 x 10(-3) Omega.cm, while the electrical resistivity of the adhesive containing 50 wt% of the spherical particles reached to 1.1 x 10(-2) Omega.cm. Graphite addition to adhesive formula in concentrations less than 6 wt%, slightly lowered the resistivity of the adhesives. Increasing the graphite addition from 6 to 15 wt% enhanced the electrical resistivity from 2.8 x 10(-3) to 1.7 x 10(-2) Omega.cm. The shear strength of the adhesives is inversely proportional to the filler percentage in the adhesives

Effects of Native Vacancies on Nb-Doped MgH 2 Using Density Functional Theory Calculations

In the present work, we considered the effect of Nb and charged vacancies on the properties of magnesium hydride. We performed spin-polarized ab initio calculations substituting an Mg atom by an Nb impurity. Then, some charged vacancies were included in the MgH 2 + Nb system (V H , V Mg , or V Mg-H ). In each case, three possible charge states were considered (+1, 0, or -1). We computed cohesion and formation energies, band gap, and magnetic moment. We also calculated the transition level energy value and the density of states. Nb states are located in the gap, and a magnetic moment is induced. In the case of the system with charged vacancies, we found that V H + and V H 0 are the more probable vacancies formed, and the states near the Fermi level (E F ) are filled, thus getting an important reduction in the band gap.Fil: Gaztañaga, Francisco. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto de Física del Sur. Universidad Nacional del Sur. Departamento de Física. Instituto de Física del Sur; Argentina. Universidad Nacional del Sur. Departamento de Ingeniería Eléctrica y de Computadoras; ArgentinaFil: Luna, Carla Romina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto de Física del Sur. Universidad Nacional del Sur. Departamento de Física. Instituto de Física del Sur; Argentina. Universidad Nacional del Sur. Departamento de Ingeniería Eléctrica y de Computadoras; ArgentinaFil: Orazi, Valeria. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto de Física del Sur. Universidad Nacional del Sur. Departamento de Física. Instituto de Física del Sur; Argentina. Universidad Nacional del Sur. Departamento de Ingeniería Eléctrica y de Computadoras; ArgentinaFil: Gonzalez, Estela Andrea. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto de Física del Sur. Universidad Nacional del Sur. Departamento de Física. Instituto de Física del Sur; Argentina. Universidad Nacional del Sur. Departamento de Ingeniería Eléctrica y de Computadoras; ArgentinaFil: Faccio, Ricardo. Universidad de la República; UruguayFil: Jasen, Paula Verónica. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto de Física del Sur. Universidad Nacional del Sur. Departamento de Física. Instituto de Física del Sur; Argentina. Universidad Nacional del Sur. Departamento de Ingeniería Eléctrica y de Computadoras; Argentin