Thermomagnetic detection of recrystallization in FeCoNbBCu nanocrystalline alloys

The recrystallization process in FeCoNbBCu nanocrystallinealloys is evidenced from thermomagnetic results as a significant decrease in magnetization at the second crystallization stage. The lowering in the volume fraction of α-FeCo crystals indicates that some of these crystals contribute to the boride phases formed. Electron microscopy images reveal that the final microstructure consists of large crystals (∼500 nm) of a fcc (FeCo)23B6(FeCo)23B6 phase and small crystals (∼20 nm) of bcc α-FeCo and of some boride phases as such (FeCo)2B

Gestión de la investigación en la Universidad Nacional de Cuyo (1949-2010)

La Universidad Nacional de Cuyo, desde su origen, consideró a la investigación como una de sus funciones básicas. En tal sentido este libro surge como una propuesta para sistematizar, preservar y difundir información institucional, relacionada a la gestión del área específica. La Secretaría de Ciencia, Técnica y Posgrado de esta Casa de Estudios, a fines de 2009, invitó a participar de la iniciativa a quienes fueron responsables de esta tarea y a investigadores interesados en la historia de la institución, los que aportaron información y el valor de su experiencia. En el desarrollo de la obra se puede verificar claramente la evolución de estructuras y la definición de políticas científicas desarrolladas en la UNCuyo, ligadas a momentos históricos, políticas nacionales, locales e institucionales. Del relato de cada autor se observa que: planificación, mecanismos y estrategias de promoción de la investigación manifiestan una continuidad de esfuerzos cuyo objeto es incentivar la producción del conocimiento y su transferencia a las aulas y al medio. De la compiladora de la obra: Patricia Pons, Licenciada en Ciencias De la Educación de la Pontificia Universidad Católica Argentina Santa María de los Buenos Aires; se encuentra en la etapa de finalización de sus estudios de Maestría en Gestión de la Ciencia, la Técnica y la Innovación de la Universidad Nacional de General Sarmiento; Directora General de Ciencia y Técnica de la Secretaría de Ciencia Técnica y Posgrado de la Universidad Nacional de Cuyo

Effects of anharmonic strain on phase stability of epitaxial films and superlattices: applications to noble metals

Epitaxial strain energies of epitaxial films and bulk superlattices are studied via first-principles total energy calculations using the local-density approximation. Anharmonic effects due to large lattice mismatch, beyond the reach of the harmonic elasticity theory, are found to be very important in Cu/Au (lattice mismatch 12%), Cu/Ag (12%) and Ni/Au (15%). We find that is the elastically soft direction for biaxial expansion of Cu and Ni, but it is for large biaxial compression of Cu, Ag, and Au. The stability of superlattices is discussed in terms of the coherency strain and interfacial energies. We find that in phase-separating systems such as Cu-Ag the superlattice formation energies decrease with superlattice period, and the interfacial energy is positive. Superlattices are formed easiest on (001) and hardest on (111) substrates. For ordering systems, such as Cu-Au and Ag-Au, the formation energy of superlattices increases with period, and interfacial energies are negative. These superlattices are formed easiest on (001) or (110) and hardest on (111) substrates. For Ni-Au we find a hybrid behavior: superlattices along and like in phase-separating systems, while for they behave like in ordering systems. Finally, recent experimental results on epitaxial stabilization of disordered Ni-Au and Cu-Ag alloys, immiscible in the bulk form, are explained in terms of destabilization of the phase separated state due to lattice mismatch between the substrate and constituents.Comment: RevTeX galley format, 16 pages, includes 9 EPS figures, to appear in Physical Review

Coupling Binary and Ternary Information in Assessing the Fcc/Hcp Relative Phase Stability and Martensitic Transformation in Fe-Mn-Co and Fe-Mn-Si Alloys

This paper presents a study of the composition dependence of the fcc/hcp martensitic transformation temperatures and relative phase stability of these structures in Fe-Mn-Co and Fe-Mn-Si alloys. The approach combines new experimental determinations of Ms and As in the binary systems Fe-Mn and Fe-Co, and in both ternary systems with a critical analysis of the previously published experimental data, and thermodynamic calculations. It is shown how this combination of binary and ternary information with various methods of analysis can be used to establish the T0-temperatures in the Fe-Mn-Co system and to refine the thermodynamic description of the metastable hcp structure of the Fe-Co system. The present methods also help to detect possible inconsistencies in the previously reported Ms and As data for Fe-Mn-Si alloys, which is used as a basis for discussing the most recent calculation of Ms temperatures in this system