Динамическая восприимчивость нанокомпозита пористое стекло/Ga-In-Sn в области сверхпроводимости

Interest to studies of gallium alloys increased recently in relation to their prospective applications for self-healing superconducting connections and wires. Special attention is focused on superconductive properties of nanostructured alloys. In the present work we studied the ac susceptibility of a porous glass/Ga-In-Sn nanocomposite within the temperature range from 1.9 to 8 K at bias fields up to 5 T. Two superconducting phase transitions were revealed with temperatures of 5.6 and 3.1 K. Phase diagrams were created. Positive curvature of the parts of critical lines was demonstrated and treated within the framework of a proximity effect model. Vortex activation barriers were found from shifts of the maxima of the imaginary parts of susceptibility with changing the ac frequency. A bend was shown on the field dependence of the activation barriers.

Hardness Development of Mechanically-Bonded Hybrid Nanostructured Alloys through High-Pressure Torsion

Processing through the application of high-pressure torsion (HPT) provides significant grain refinement in bulk metals at room temperature. These ultrafine-grained (UFG) materials after HPT generally demonstrate exceptional mechanical properties. Recent reports demonstrated the bulk-state reactions for mechanical bonding of dissimilar lightweight metal disks to synthesize hybrid alloy systems by utilizing conventional HPT processing. Accordingly, the present report provides a comprehensive summary of the recent work on processing of several UFG hybrid alloy systems including Al-Mg and Al-Cu by HPT under 6.0 GPa at room temperature and a special emphasis was placed on understanding the evolution of hardness. This study demonstrates a significant opportunity for the application of HPT for a possible contribution to current enhancements in diffusion bonding, welding and mechanical joining technologies as well as to an introduction of hybrid engineering nanomaterials.

Thermal Characterization of Fe50Co50 and Fe65Co35 Nanostructured Alloys

Las aleaciones magnéticas nanoestructuradas a base de FeCo se destacan entre las aleaciones magnéticas convencionales a base de Fe por presentar óptimas propiedades magnéticas blandas, requeridas en una variedad de aplicaciones tecnológicas, industriales y biomédicas. En este trabajo se presentan los resultados obtenidos de la caracterización térmica por calorimetría diferencial de barrido y termogravimetría magnética de polvos puros de Fe y Co, y de polvos magnéticos nanoestructurados a base de Fe50Co50 y Fe65Co35 preparados por el método de Aleado Mecánico de elevada energía. Por medio de estas técnicas y bajo la influencia de diferentes atmósferas inertes como Helio (He), Nitrógeno (N2) y Argón (Ar), se evidenciaron los eventos térmicos que tienen lugar desde temperatura ambiente hasta 900 °C para muestras molidas a diferentes tiempos (0, 10, 15, 20 y 25 horas), eventos tales como las temperaturas de transición magnética y de orden – desorden características de este tipo de muestras y del proceso de molienda. Palabras clave: Caracterización Térmica, Análisis Termogravimétrico, Termogravimetría Magnética, Aleaciones Nanoestructuradas, Aleado Mecánico, Transiciones de Fase.