Maximum Annealing Temperature Research Articles

THERMAL SHRINKAGES OF HOT-PRESSED POLYETHYLENE SINGLE-GRYSTAL MATS DURING ANNEALING

According to the hot compression ratio (CR), the polyethylene (PE) single-crystal mats are known to have the fine structures1); the intra-lamellar slip or chain tilting type for the lower stage of CR, and the fiber texture type for the higher stage of CR. In this study, we observed with a micrometer the changes in the external dimensions, length l, width w and thickness d, of hot-pressed PE mats upon annealing in free-length at temperatures between 100°C and 130°C. A coefficient of shrinkage is defined by Sx=Δx/x, where x denotes l, w or d.Results were interpreted in terms of the structural changes during the annealing, which has been discussed in a previous paper2):(1) Sl for the mats compressed with low CR shows a maximum annealing temperature at Ta=120°C, this has been ascribed to the rotation of lamellar fragments vertically to the direction of deformation axis. While for the mats compressed with high CR, Sl increased monotonically with increasing Ta up to 130°C.(2) The value of Sd reaches a maximum at Ta=110°C and 120°C for the low CR and the high CR mats, respectively. Above these temperatures Sd decreases as a result of the lamellar thickening and the growth of crystallite size.(3) With increasing Ta, the values of Sw are influenced by the increase in the degree of (100) planar orientation, hence the value becomes negative.(4) The bulk contruction Sv=Sl+Sd+Sw has a maximum value at Ta=110-120°C, whereas Sv for the low CR mats is larger than that of the high CR ones. The decrease in Sv above 120°C is brought on by the fact that the expanded unit cell dimensions decrease to their original sizes during the annealing at elevated temperatures.

Fast Neutron Effects on GaAsP Schottky Barrier Diodes and Hall Effect Devices

GaAsP Schottky barrier diodes and Hall effect devices were exposed to fast neutron radiation at room temperature at fluences ranging from 1013 neutrons cm-2 (E > 10 keV) to 8.9 × 1016 neutrons cm-2 (E > 10 keV). The carrier removal rate for the n-type material with a nominal doping of 5 × 1015 cm-3 and irradiated at a fluence of 9.7 × 1014 neutrons cm-2 (E > 10 keV) was determined from the capacitance-voltage characteristics of the diodes and was found to range between 5 and 6 cm-1. The change in conductivity of the GaAsP with neutron radiation measured on the Hall effect devices agrees very well with the diode measurements, while the change in effective carrier concentration appears to be slightly greater in the diodes than in the Hall devices. The Hall effect device measurements showed that the GaAsP material tends to become intrinsic after irradiation at high neutron fluence levels. The decrease in minority carrier lifetime after neutron irradiation was observed from the transient photocurrent response of the neutron-irradiated diodes generated by an ionizing X-ray pulse. Isochronal annealing of the neutron-irradiated diodes showed approximately a 40 percent recovery in carrier concentration over a wide temperature range starting at 225°C and continuing up to the maximum annealing temperature of 580°C.