Search

The formation of the microdroplets on fibres for the MDT test offers an opportunity to carry out surface tension measurements based on the angle of contact between the resin and the fibre. Liquid microdroplets of epoxy were deposited on glass fibres, and their diameter, length and cone angle were measured. The equilibrium shape of the droplet can be derived from the principle of conservation of work and energy. If the surface tension of the polymer droplet and the specific surface energy of the polymer coated fibre are similar, then the interfacial tension is given simply by: [sub γint] = (1- m)[sub γ], where m is the gradient of a linear plot of functions of the measured parameters and [sub γ] is the liquid surface tension. The measurement of contact angles on a droplet/fibre system have been reported previously; however, our method proposes a different geometry and consequently a simpler solution to the problem, with an additional advantage of verification on the droplet equilibrium and accuracy of measurements. [ABSTRACT FROM AUTHOR]

A survey of published literature reveals a difference in the density of amorphous and crystalline solids (organic and inorganic) on the order of 10%–15%, whereas for metallic alloys, it is found to be typically less than 5%. Standard geometric models of atomic packing can account for the polymeric and inorganic glasses without requiring changes in interatomic separations (bond lengths). By contrast, the relatively small difference in density between crystalline and glassy metals (and metallic alloys) implies variations in interatomic separations due to merging orbitals giving rise to reduced atomic volumes. To test this hypothesis, quantum density functional theory computations were carried out on ordered and irregular clusters of aluminum. The results point to decreasing interatomic distances with decreasing coordination, from which one can deduce that the geometrical method of random hard sphere packing significantly underestimates the densities of amorphous metallic alloys. [ABSTRACT FROM AUTHOR]

Zr41.25Ti13.75Ni10Cu12.5Be22.5 (at.%) bulk metallic glass (BMG) is annealed at 676 K for various times. The influence of the microstructural evolution on the mechanical properties is studied by tensile test and micro hardness test at room temperature. The structural relaxation due to the short time annealing does not affect the deformation behavior of the BMG. The nanocrystallization inducing embrittlement is due to the presence of nano-scale particles promoting the crack forming and propagating during the tensile deformation. The existence of nano-scale particles also enhances the viscosity of the amorphous phase within the shear band and even obstructs the formation of the shear band at the indenter tip, which results in a strengthening phenomenon in the annealed BMG under the indentation load. [ABSTRACT FROM AUTHOR]