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Ductile Ti45Cu40Ni7.5Zr5Sn2.5 and Cu47.5Zr47.5Al5 bulk metallic glasses (BMGs) present different work hardening abilities under compression. Microstructural investigations reveal that nanoscale chemical heterogeneities occur throughout the samples. The morphology of the chemically heterogeneous domains in the as-cast Ti45Cu40Ni7.5Zr5Sn2.5 BMG is irregular and significantly interconnected. In contrast, the as-cast Cu47.5Zr47.5Al5 BMG exhibits a spherical morphology of the chemically heterogeneous regions. Furthermore, the distribution of the nanoscale chemical heterogeneity is macroscopically inhomogeneous throughout the material. These findings suggest that the different work hardening abilities of the Ti45Cu40Ni7.5Zr5Sn2.5 and Cu47.5Zr47.5Al5 BMGs possibly originate from the different morphologies and distributions of the chemically heterogeneous regions. [ABSTRACT FROM AUTHOR]

A Zr74.9Ti10.5Ni14.6 nanostructure-dendrite composite was prepared by copper mold casting. X-ray diffraction, and scanning and transmission electron microscopies, reveal a microstructure comprising ultrafine-scale dendrites with hexagonal structure and a two-phase interdendritic matrix, consisting of nanocrystalline hexagonal and tetragonal phases. Room temperature compression tests show evident yielding and 6% plastic strain together with work hardening up to 1622 MPa. These results indicate that composite materials based on hexagonal phases might be an alternative to composites containing body-centered cubic phase reinforcements. [ABSTRACT FROM AUTHOR]

Microstructural investigation of an as-cast Cu47.5Zr47.5Al5 bulk metallic glass (BMG) reveals two amorphous phases formed by liquid phase separation. The morphology of the phase separated amorphous regions is spherical with 10–20 nm in size. These areas are homogeneously distributed throughout the sample. Moreover, a macroscopic heterogeneity also occurs along with the nano-scale liquid phase separation. The macroscopic heterogeneity can be distinguished from the different degree of the chemical fluctuations in the sample, and the existence of nano-scale crystals of less than 5 nm in size. Presumably, both the macroscopic heterogeneity and the nano-scale phase separation enhance branching of the shear bands during deformation in the Cu47.5Zr47.5Al5 BMG. [ABSTRACT FROM AUTHOR]

The dendrites in the Ti66.1Cu8Ni4.8Sn7.2Nb13.9 nanostructure–dendrite composite deformed up to 25% reveal an interaction of primary and secondary shear bands. A detailed analysis of the lattice images of the interaction regions in the dendrites using high resolution transmission electron microscopy indicates local amorphization and lattice distortion/disordering near to the apex of the primary shear bands in the dendrite. Furthermore, moiré fringes are formed at the edge of the interaction regions between the primary and secondary shear bands suggesting gradual structural changes in the dendrites. [ABSTRACT FROM AUTHOR]

During deformation of Ti66.1Cu8Ni4.8Sn7.2Nb13.9 nanostructure-dendrite composite, primary and secondary shear bands form under perpendicular orientation. Detailed investigation of the microstructure of deformed specimens reveals deformed body-centered-cubic (bcc) β-Ti dendrites forming a stepped morphology at the interfaces between the bcc β-Ti dendrites and the nanostructured matrix, consisting of hexagonal close packed (hcp) α-Ti and body-centered-tetragonal (bct) Ti2Cu phases. In the nanostructured matrix, the primary shear bands pass through coherent grain boundaries between the hcp α-Ti and the bct Ti2Cu phases. In contrast, the secondary shear bands in the nanostructured matrix are arrested by sandwiched nanoscale grains of the hcp α-Ti and bct Ti2Cu phases. [ABSTRACT FROM AUTHOR]

We have used polyvinylcarbazole, PVK, in combination with poly(p-phenylene vinylene), PPV and a green-emitting, soluble derivative, poly(4,4′-diphenylene diphenylvinylene) or briefly PDPV, to fabricate triple-layer light-emitting diodes PPV/PVK/PDPV/metal, with indium tin oxide as the anode. We report luminances in excess of 1300 cd/m2 with Al cathodes, turn-on voltages of ∼8 V in structures 300 nm thick, and internal efficiencies in the range 0.4%–0.8% for Al and Ca cathodes; at least ten times higher than for single-layer PDPV devices. Quantum efficiencies for Ca or Al electrodes are only a factor 1.5 different. The improvements over single-layer PDPV devices are considered to be due to better hole injection by PPV and to the formation of a hole barrier at the PPV/PVK interface, which forces a better balance of the electron and hole currents. © 1996 American Institute of Physics. [ABSTRACT FROM AUTHOR]