Processing eutectics in space

Experimental work is reported which was directed toward obtaining interface shape control while a numerical thermal analysis program was being made operational. An experimental system was developed in which the solid-liquid interface in a directionally solidified aluminum-nickel eutectic could be made either concave to the melt or convex to the melt. This experimental system provides control over the solid-liquid interface shape and can be used to study the effect of such control on the microstructure. The SINDA thermal analysis program, obtained from Marshall Space Flight Center, was used to evaluate experimental directional solidification systems for the aluminum-nickel and the aluminum-copper eutectics. This program was applied to a three-dimensional ingot, and was used to calculate the thermal profiles in axisymmetric heat flow. The results show that solid-liquid interface shape control can be attained with physically realizable thermal configurations and the magnitudes of the required thermal inputs were indicated

Processing eutectics in space

The investigations of directional solidification have indicated the necessity of establishing a secure foundation in earth-based laboratory processing in order to properly assess low-gravity processing. Emphasis was placed on evaluating the regularity of microstructure of the rod-like eutectic Al-Al3Ni obtained under different conditions of growth involving the parameters of thermal gradient, solidification rate, and interfacial curvature. In the case of Al-Al3Ni, where the Al3Ni phase appears as facets rods, solidification rate was determined to be a controlling parameter. Zone melting of thin eutectic films showed that for films of the order of 10 to 20 micrometers thick, the extra surface energy appears to act to stabilize a regular microstructure. The results suggest that the role of low-gravity as provided in space-laboratory processing of materials is to be sought in the possibility of generating a higher thermal gradient in the solidifying ingot for a given power input-output arrangement than can be obtained under normal one-g processes

Processing eutectics in space

Studies which have been done in an earth-based laboratory environment have generally not yielded specimens with the degree of perfection required of the eutectic microstructure to provide test data to evaluate their nonstructural applications. It has been recognized that the low-g environment of an orbiting space laboratory provides a unique environment to re-examine the process of solidification with the goal of producing better microstructures. The objective of this program is to evaluate the feasibility of using the space environment for producing eutectics with microstructures which can be of value on earth. In carrying out this objective, evaluative investigations were carried out on the technology of solidification in a 1-g environment to provide sound baseline data for planning space laboratory experiments

Experimental investigation of thermal annealing of nuclear-reactor-induced coloration in fused silica

Spectral transmission characteristics of fused silica over range of temperature prior to nuclear irradiation and during thermal annealing of reactor-induced coloratio

Notes on the Biology of \u3ci\u3eSaperda Imitans\u3c/i\u3e Infesting Wind-Damaged Black Cherry in Allegheny Hardwood Stands

This paper reports observations made on the life history and biology of Saperda imitans Felt & Joutel in black cherry, Prunus serotina Ehrh. S. imitans was the principle longhorned beetle (Coleoptera: Cerambycidae) reared from bolts collected from 68 wind-thrown black cherry at the Kane Experimental Forest in northwestern Pennsylvania. It was also the only species that overwintered in the sapwood/outer heartwood, and thus impacted the commercial value of these trees. Gaurotes cyanipennis (Say) was the only other cerambycid reared from caged bolts taken from wind-thrown black cherry. The cerambycids Stenocorus vittiger (Randall), Arthophylax attenuatus (Haldman), G. cyanipennis, Neoclytus acuminatus acuminatus (F.), Clytus ruricola (Olivier), Cyrtophorus verrucosus (Olivier), and Astylopsis macula (Say) were captured in ethanol-baited Lindgren® funnel traps placed in wind-thrown stands, but were not reared from cherry logs. S. imitans was not caught in these traps and apparently it is not attracted to ethanol baits. Neither S. imitans nor G. cyanipennis were reared from completely uprooted trees (dead) or trees with a major portion of the root system still embedded in soil (live). Preferred hosts were black cherry with moist phloem and epicormic branches with \u3c25% live foliage (dying). The density of S. imitans galleries was similar for dying trees in each of three diameter classes; 20-30 cm, \u3e30-40 cm, \u3e40cm. Samples taken from the upper half of the first 5 m of black cherry boles had a higher density of galleries than did those from the lower half. The beetle was recovered in low numbers from branches \u3c10 cm in basal diameter. S. imitans is univoltine and in 2007 peak emergence of adults occurred from late May to early June. Results identified the condition of wind-damaged black cherry most susceptible to an infestation of S. imitans. This information can be used to establish salvage priorities following a weather event such as this

Optical absorption in transparent materials following high-temperature reactor irradiation

Reactor irradiation effects on optical absorption levels in fused silic

Application of diffusion barriers to the refractory fibers of tungsten, columbium, carbon and aluminum oxide

A radio frequency powered ion-plating system was used to plate protective layers of refractory oxides and carbide onto high strength fiber substrates. Subsequent overplating of these combinations with nickel and titanium was made to determine the effectiveness of such barrier layers in preventing diffusion of the overcoat metal into the fibers with consequent loss of fiber strength. Four substrates, five coatings, and two metal matrix materials were employed for a total of forty material combinations. The substrates were tungsten, niobium, NASA-Hough carbon, and Tyco sapphire. The diffusion-barrier coatings were aluminum oxide, yttrium oxide, titanium carbide, tungsten carbide with 14% cobalt addition, and zirconium carbide. The metal matrix materials were IN 600 nickel and Ti 6/4 titanium. Adhesion of the coatings to all substrates was good except for the NASA-Hough carbon, where flaking off of the oxide coatings in particular was observed