S. Valdez

In silico studies of the magnetic octahedral B6 − cluster—nitric oxide and [B6 −–NO]−–O2 interactions

All-electron calculations based on density functional theory (DFT) for B6−, [B6–NO]−, and [B6–NO–O2]− were done in gas and aqueous phases, in order to validate their feasibility as nanovehicle for drug delivery. The quantum descriptors reveal that the octahedral B6− cluster shows semiconductor and magnetic behavior, low chemical reactivity, and zero polarity. On the other hand, bonding of the NO molecule with the B6− cluster produces a complex where the physic-chemical properties do not suffer drastic alterations, except that the polarity increases and a reduction of the work function takes place. These results suggest that the new [B6–NO]− cluster can be applied for some biological function. Furthermore, the interaction between [B6–NO]− and O2 generates a geometric transition from octahedron to pentagonal bipyramid, where the NO molecule remains bonded and the O2 molecule is activated in such superoxide cluster.

Microhardness, Microstructure and Electrochemical Efficiency of an Al--(Zn/xMg) Alloy After Thermal Treatment

The influence of Mg on the microhardness,microstructure and electrochemical efficiency of Al(Zn/xMg) alloys have been investigated.Al(Zn/xMg) alloys were prepared by metal mould casting method to diminish the process cost and to generate an alloy with homogenous microstructure and less casting porosity.Vickers hardness,X-ray diffraction,scanning electron microscopy and transmission electron microscopy were performed to determine the Mg influence on the AlZn alloy.Electrochemical efficiency was used to relate the influence of Mg with the thermal treatment on the corrosion behavior of the Al(Zn/xMg) alloy.The results reveals the presence of Al 32(MgZn) 49 phase for two events;the first is when the Mg content is above 5.49% in as-cast condition,and the second after the thermal treatment is carried out at 450℃ for 5 h.The results also show that the microhardness and electrochemical efficiency have been influenced by the presence of Al 32(MgZn) 49 phase.The addition of Mg modifies the microstructure,increases the content of Al 32(MgZn) 49 phase and improves the electrochemical efficiency.

Un recorrido por las propiedades microestructurales de la aleación Al-Fe-Cr

Al-Fe-Cr alloy was rapidly solidified by means of melt spinning technique. Alloy structure has been studied by SEM, TEM and X-Ray diffraction. The ribbons were annealing at 500 ��C during 48 hours, in order to study the influence of thermal treatment onto the Al-Fe-Cr microstructure. The melt-spun Al- Fe-Cr microstructure underwent a considerable refinement as compared with same composition alloy produced by conventional methods of melting and casting. In melt�]spun ribbons the grain size decreases as the cooling increases. An ordered B2 type structure was obtained in all ternary rapidly solidified and annealed alloys at all cooling rates schedules.