Large Phase Separation Research Articles

Large supercooled liquid region and phase separation in the Zr–Ti–Ni–Cu–Be bulk metallic glasses

Results of calorimetric, differential thermal analysis, and structural measurements are presented for a series of bulk metallic glass forming compositions in the Zr–Ti–Cu–Ni–Be alloy system. The calorimetric data for five alloys, prepared along the tie line between phase separating and nonphase separating compositions, show that the transition from phase separating to nonphase separating behavior is smooth. The bulk glasses near the center of the tie line exhibit large supercooled liquid regions: ΔT≈135 K, the largest known for a bulk metallic glass.

Piezoelectric Franz–Keldysh effect in strained GaInN/GaN heterostructures

Pseudomorphic Ga1−xInxN/GaN single heterostructures in the composition range 0<x<0.2 have been investigated by photoreflectance and photoluminescence spectroscopy. Strong Franz–Keldysh oscillations near the band gap of the ternary film are observed and attributed to a large constant piezoelectric field of up to 0.63 MV/cm. This allows an accurate determination of the electric field. A significant redshift between the optical band gap from photoreflectance and the luminescence maximum is observed. Luminescence is proposed to originate in the indirect transitions between the electric field tilted band edges in GaInN. The presence of this field is expected to dominate the bandstructure and the recombination and transport processes in strained nitride structures. We find no evidence for large inhomogeneities or phase separation in this material.

Polyethylene blends with a phenoxy

Abstract Melt blends of a phenoxy with two types of high-density polyethyl-enes (PE) having different melt viscosities were prepared over a full range of compositions using a Brabender Plasticorder. Morphological, thermal, and mechanical properties of the blends were studied. SEM (scanning electron microscopy) micrographs showed a two-phase morphology of the blends. T m (crystalline melting temperature) of PE decreased by 3°–6°C, whereas Tg (glass transition temperature) of phenoxy increased up to 11°C. The decrease and increase of T m and T g were most pronounced when the viscosities of the components were similar. Mechanical properties of the blends generally showed negative deviation from the additivity rule, due to the large phase separation and poor interfacial adhesion.

Melt blends of polyethylene with a phenoxy

Melt blends of high density polyethylene (PE) with a phenoxy have been prepared over a full composition range using a Brabender Plasticorder. Scanning electron microscopy (SEM) micrographs showed a clear phase separation, viz. particle-in-matrix or co-continuous morphology depending on the composition. T m (crystalline melting temperature) of PE decreased by 3–6 °C, whereas T g (glass transition temperature) of phenoxy increased up to ca 11 °C in the blends. Mechanical properties of the blends showed a negative deviation from linear additivity due to large phase separation (~ several μm) and poor interfacial adhesion.