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Shelf life aging of DC-302 silicone molding compound

Description: DC-302 silicone molding compound (Dow Corning Corporation) was packaged 10 different ways, stored at three different temperatures, and tested for spiral flow periodically for 8 months. The material was very stable at 5/sup 0/C and fairly stable at 24/sup 0/C. It was sensitive to heat, however, and was unstable at 55/sup 0/C. Samples that were stored for 12 months at 5/sup 0/C showed no significant change in physical properties.
Date: August 1, 1978
Creator: McFarland, J. W.
Partner: UNT Libraries Government Documents Department

Solution hardening and strain hardening at elevated temperatures

Description: Solutes can significantly increase the rate of strain hardening; as a consequence, the saturation stress, at which strain hardening tends to cease for a given temperature and strain rate, is increased more than the yield stress: this is the major effect of solutes on strength at elevated temperatures, especially in the regime where dynamic strain-aging occurs. It is shown that local solute mobility can affect both the rate of dynamic recovery and the dislocation/dislocation interaction strength. The latter effect leads to multiplicative solution strengthening. It is explained by a new model based on repeated dislocation unlocking, in a high-temperature limit, which also rationalizes the stress dependence of static and dynamic strain-aging, and may help explain the plateau of the yield stress at elevated temperatures. 15 figures.
Date: October 1, 1982
Creator: Kocks, U.F.
Partner: UNT Libraries Government Documents Department

Polymerization of Pu(IV) in aqueous nitric acid solutions

Description: The polymerization of Pu(IV) in aqueous nitric acid solutions has been studied spectrophotometrically both to establish the influence of large UO{sub 2}(NO{sub 3}){sub 2} concentrations on the polymerization rates and, more generally, to review the influence of the major parameters on the polymer reaction. Typically, experiments have been performed at 50{sup 0}C and with 0.05 M Pu in nitric acid solutions that vary in acidity from 0.07 to 0.4 M. An induction period usually precedes the polymer growth stage during which time nucleation of primary hydrolysis products occurs. Uranyl nitrate retards the polymerization reaction by approximately 35% in spite of the counteracting influence of the nitrate ions associated with this solute. The rate of polymer formation, expressed as d(percent polymer)/dt, has been shown to depend on the total plutonium concentration in reactions where the Pu(IV) concentration remained constant; and it is therefore suggested that the polymer reaction rate is not first order with respect to the concentration of plutonium as was previously thought. It has been shown further that accurate acid determinations on stock reagents are essential in order to obtain reliable polymerization experiments. Satisfactory procedures for these analyses did not exist, so appropriate modifications to the iodate precipitation methods were developed. The most ideal plutonium reagent material has been shown to be crystalline Pu(IV) nitrate because it can be added directly to acid solutions without the occurrence of unintentional hydrolysis reactions.
Date: October 1, 1980
Creator: Toth, L.M.; Friedman, H.A. & Osborne, M.M.
Partner: UNT Libraries Government Documents Department

Damage nucleation in Si during ion irradiation

Description: Damage nucleation in single crystals of silicon during ion irradiation is investigated. Experimental results and mechanisms for damage nucleation during both room and liquid nitrogen temperature irradiation with different mass ions are discussed. It is shown that the accumulation of damage during room temperature irradiation depends on the rate of implantation. These dose rate effects are found to decrease in magnitude as the mass of the ions is increased. The significance of dose rate effects and their mass dependence on nucleation mechanisms is discussed.
Date: January 1, 1984
Creator: Holland, O.W.; Fathy, D. & Narayan, J.
Partner: UNT Libraries Government Documents Department

Potential for supplying solar thermal energy to industrial unit operations

Description: Previous studies have identified major industries deemed most appropriate for the near-term adoption of solar thermal technology to provide process heat; these studies have been based on surveys that followed standard industrial classifications. This paper presents an alternate, perhaps simpler analysis of this potential, considered in terms of the end-use of energy delivered to industrial unit operations. For example, materials, such as animal feed, can be air dried at much lower temperatures than are currently used. This situation is likely to continue while economic supplies of natural gas are readily available. However, restriction of these supplies could lead to the use of low-temperature processes, which are more easily integrated with solar thermal technology. The adoption of solar technology is also favored by other changes, such as the relative rates of increase of the costs of electricity and natural gas, and by energy conservation measures. Thus, the use of low-pressure steam to provide process heat could be replaced economically with high-temperature hot water systems, which are more compatible with solar technology. On the other hand, for certain operations such as high-temperature catalytic and distillation processes employed in petroleum refining, there is no ready alternative to presently employed fluid fuels.
Date: April 1, 1980
Creator: May, E.K.
Partner: UNT Libraries Government Documents Department

Tensile properties of bare-rolled ingot-sheet beryllium from room temperature to 800$sup 0$C

Description: Tensile properties of bare-rolled ingot-sheet beryllium from room temperature to 800 deg C are reported. While strength values show a steady decrease above room temperature, tensile elongations exhibit peaks at approximately 300 and 700 deg C. The strainhardening exponent varies with temperature and amount of strain, and ranges between approximately 0.10 and 0.26. Metallographic examinations reveal cleavage fracture at the lower temperatures, accompanied by severe grain deformation above room temperature. This is followed by a temperature range in which ductile rupture occurs, and finally, at the higher temperatures, grainboundary failure. The low BeO content of this material and the post-rolling heat treatment given to the sheet are factors which improve the high-temperature ductility as compared to other grades of beryllium. (auth)
Date: December 13, 1973
Creator: Miley, D.V. & Brugger, R.P.
Partner: UNT Libraries Government Documents Department

Conversion of para to orthohydrogen in a gamma-ray and neutron radiation field

Description: The radiation-induced conversion of para to orthohydrogen was investigated at pressures between 150 and 2200 psig (1 to 15 x 10/sup 6/ N/meter/ sup 2/) at three temperatures: 77 deg K (LN/sub 2/), 200 deg K (dry ice), and 300 deg K (ambient). Two radiation dose levels were studied: gamma rays only at 8 x 10/sup 6/ rads and a combination of 5 x 10/sup 14/ n/cm/sup 2/ E> 1 MeV, plus gamma rays at 8 x 10/sup 5/ rads. The conversion at LN/sub 2/ temperature was nearly zero in all cases. (auth)
Date: November 1, 1973
Creator: Conant, J.W.; Edeskuty, F.J.; Huston, J.E. & Thome, F.V.
Partner: UNT Libraries Government Documents Department

Comparison of elementary geothermal-brine power-production processes

Description: From applied technology geothermal committee meeting; Idaho Falls, Idaho, USA (7 Aug 1973). A comparison of three simple geothermal power- production systems shows that the flashed steam and the compound systems are favored for use with high-temperature brines. The binary system becomes economically competitive only when used on low-temperature brines (enthalpies less than 350 Btu/lb). Geothermal power appears to be economically attractive even when low-temperature brines are used. (auth)
Date: August 1, 1973
Creator: Green, M.A. & Laird, A.D.K.
Partner: UNT Libraries Government Documents Department