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Body-centered cubic ion correlation experiment

Description: The results of an interlaboratory correlation experiment involving eight laboratory sites studying the ion irradiation of molybdenum are presented. The program was comprised of three parts. The first part compared the radiation damage produced in a reference specimen of molybdenum by ions of different masses and different energies. The second part of the program compared measurements on a common micrograph supplied to all participants in the program. The results from all the sites agreed very well. The value of standard deviation in the measurement of void volume fraction corresponded to 10 percent of the average measured value and the spread between highest and lowest reported value was 35 percent. The third part of the program compared the microstructural characteristics of a transmission electron microscope (TEM) specimen that was passed from site to site (''round robin''). The results of this part of the experiment showed greater variations from the different participants than the results from the common micrograph. One of the principal sources of discrepancy was the measurement of the foil thickness which was necessary for computation of void number density. The standard deviation in the measurements of void volume fraction (swelling) corresponded to 20 percent of the measured average value. The spread between the highest and lowest value was 70 percent. This latter value gives an idea of the conceivable differences in results due to experimental techniques between two experiments.
Date: April 1, 1977
Creator: Brimhall, J.L. (comp.)
Partner: UNT Libraries Government Documents Department

Radiation damage studies in CTR materials using dual-beam irradiation

Description: A dual beam, ion irradiation facility for studying radiation damage problems applicable to fusion first walls has been described. Experiments on molybdenum have shown that co-implanted helium can alter the internal void microstructure during heavy ion irradiation but does not appreciably change the total swelling. Heavy ion irradiation of a Nb-1 Zr alloy have shown that irradiation can induce precipitate formation and that existing precipitates can influence the damage microstructure.
Date: January 1, 1980
Creator: Brimhall, J.L.
Partner: UNT Libraries Government Documents Department

Effect of helium on void swelling in vanadium

Description: Little difference in void microstructural swelling of vanadium is observed when helium is injected simultaneously with a 46- or 5-MeV nickel beam as compared to no helium injection, at least at high dose rates. At lower dose rates, a strong helium effect is seen when the helium is injected prior to heavy ion bombardment. The effect of the helium is shown to be a strong function of the overall displacement damage rate. (DLC)
Date: January 1, 1975
Creator: Brimhall, J.L. & Simonen, E.P.
Partner: UNT Libraries Government Documents Department

Mechanical strength and stability of lithium aluminate

Description: Pacific Northwest Laboratory (PNL) investigated the strength and resistance to thermal shock of lithium aluminate annular pellets. The room temperature, axial compressive fracture strength of pellets made at Westinghouse Advanced Energy Systems (WAES) varied from 80 to 133 ksi. The strength at 430{degrees}C (806{degrees}F) was to 30 to 40% lower. The strength at 900{degrees}C (1652{degrees}F) showed a wide variation with one measurement near 90 ksi. These strength values are consistent with other data and predictions made in the literature when the grain size and porosity of the microstructure are taken into account. In diametral compression tests, the fracture strengths were much lower due to the existence of tensile stresses in some pellet regions from this type of loading. However, the fracture stresses were still generally higher than those reported in the literature; this fracture resistance probably reflects the better quality of the pellets tested in this study. Measurements on pellets made at PNL indicated lower strengths compared to the WAES material. This strength difference could be accounted for by different processing technologies: material made at PNL was cold-pressed and sintered with high porosity whereas the WAES material was isostatically hot-pressed with high density. Thermal shocking of the material by ramping to 900{degrees}C in two minutes did not have an observable effect on the microstructure or the strength of any of the pellets.
Date: June 1, 1992
Creator: Brimhall, J.L.
Partner: UNT Libraries Government Documents Department

Mechanical strength and stability of lithium aluminate

Description: Pacific Northwest Laboratory (PNL) investigated the strength and resistance to thermal shock of lithium aluminate annular pellets. The room temperature, axial compressive fracture strength of pellets made at Westinghouse Advanced Energy Systems (WAES) varied from 80 to 133 ksi. The strength at 430{degrees}C (806{degrees}F) was to 30 to 40% lower. The strength at 900{degrees}C (1652{degrees}F) showed a wide variation with one measurement near 90 ksi. These strength values are consistent with other data and predictions made in the literature when the grain size and porosity of the microstructure are taken into account. In diametral compression tests, the fracture strengths were much lower due to the existence of tensile stresses in some pellet regions from this type of loading. However, the fracture stresses were still generally higher than those reported in the literature; this fracture resistance probably reflects the better quality of the pellets tested in this study. Measurements on pellets made at PNL indicated lower strengths compared to the WAES material. This strength difference could be accounted for by different processing technologies: material made at PNL was cold-pressed and sintered with high porosity whereas the WAES material was isostatically hot-pressed with high density. Thermal shocking of the material by ramping to 900{degrees}C in two minutes did not have an observable effect on the microstructure or the strength of any of the pellets.
Date: June 1, 1992
Creator: Brimhall, J. L.
Partner: UNT Libraries Government Documents Department

Computing the time dependence of void size distributions during irradiation and annealing

Description: The response of particle size distributions to annealing is described analytically by the Wagner--Lifshitz--Slyosov theory of coarsening. Although the theory has been used to predict void annealing kinetics in irradiated materials, the limits of the model prevent a complete interpretation of the rate controlling mechanisms. These limits are overcome with a numerical solution to the problem for the combined influences of volume diffusion, surface kinetics, and irradiation-induced point defects. A computer program has been written which calculates and updates with time the necessary kinetic and material parameters. The time dependence of the radius distribution function is determined from a finite difference solution to the continuity equation. The program provides wide latitude in simulating and analyzing the dependence of swelling and void growth kinetics on point defect kinetics, point defect sink efficiencies, and variations in irradiation and annealing history. The consequences of including the size distribution in the kinetic analysis are calculated for voids in molybdenum and compared with theoretical predictions of void growth from Brailsford and Bullough and of coarsening from Wagner--Lifshitz--Slyosov theory. (auth)
Date: January 1, 1976
Creator: Simonen, E. P. & Brimhall, J. L.
Partner: UNT Libraries Government Documents Department

Summary report of BCC ion correlation experiment. [800 to 1000/sup 0/C; voids; swelling; Ni/sup 2//sup+/, Mo/sup+/, Cu/sup 4//sup+/, and H/sup+/ ions]

Description: An interlaboratory program was established to compare the radiation damage produced in Mo at 800 to 1000/sup 0/C by different ions of different energies. The program included comparisons of microstructures produced by different ions, of measurements on a round robin TEM specimen, and of measurements on a common micrograph. Results are discussed. Ions used included Ni/sup 2 +/, Mo/sup +/, Cu/sup 4 +/, and H/sup +/.
Date: August 17, 1976
Creator: Brimhall, J L
Partner: UNT Libraries Government Documents Department

Radiation-induced segregation in candidate fusion-reactor alloys

Description: The effect of radiation on surface segregation of minor and impurity elements has been studied in four candidate fusion reactor alloys. Radiation induced surface segregation of phosphorus was found in both 316 type stainless steel and in Nimonic PE-16. Segregation and depletion of the other alloying elements in 316 stainless steel agreed with that reported by other investigators. Segregation of nitrogen in ferritic HT-9 was enhanced by radiation but no phosphorus segregation was detected. No significant radiation enhanced or induced segregation was observed in a Ti-6Al-4V alloy. The results indicate that radiaton enhanced grain boundary segregation could contribute to the embrittlement of 316 SS and PE-16.
Date: July 1, 1981
Creator: Brimhall, J.L.; Baer, D.R. & Jones, R.H.
Partner: UNT Libraries Government Documents Department

Effect of pulsed irradiation on void swelling in nickel

Description: This study has compared the void microstructure in nickel induced by a pulsed ion bombardment to that induced by a steady-state irradiation. Pulse cycles of 10 seconds on and 10 seconds off produced no measurable difference in the void growth and swelling in the temperature range 775 to 975/sup 0/K compared to continuous irradiation at the same instantaneous dose rate. Void annealing during the pulse annealing period was minimal due to the large void sizes which were obtained in these irradiations. Hence no measurable effect of pulsing on void growth was observed.
Date: July 1, 1981
Creator: Brimhall, J.L.; Charlot, L.A. & Simonen, E.P.
Partner: UNT Libraries Government Documents Department

Develop techniques for ion implantation of PLZT (lead-lanthanum-zirconate-titanate) for adaptive optics

Description: Research was conducted at Pacific Northwest Laboratory to develop high photosensitivity adaptive optical elements utilizing ion implanted lanthanum-doped lead-zirconate-titanate (PLZT). One centimeter square samples were prepared by implanting ferroelectric and anti-ferroelectric PLZT with a variety of species or combinations of species. These included Ne, O, Ni, Ne/Cr, Ne/Al, Ne/Ni, Ne/O, and Ni/O, at a variety of energies and fluences. An indium-tin oxide (ITO) electrode coating was designed to give a balance of high conductivity and optical transmission at near uv to near ir wavelengths. Samples were characterized for photosensitivity; implanted layer thickness, index of refraction, and density; electrode (ITO) conductivity; and in some cases, residual stress curvature. Thin film anti-ferroelectric PLZT was deposited in a preliminary experiment. The structure was amorphous with x-ray diffraction showing the beginnings of a structure at substrate temperatures of approximately 550/sup 0/C. This report summarizes the research and provides a sampling of the data taken during the report period.
Date: July 1, 1987
Creator: Batishko, C.R.; Brimhall, J.L.; Pawlewicz, W.T.; Stahl, K.A. & Toburen, L.H.
Partner: UNT Libraries Government Documents Department

Dual-beam, charged-particle irradiation facility for simulation of nuclear environment

Description: Heavy-ion bombardment provides a method for simulating neutron damage to metals and other materials. Simultaneous implantation of He/sup +/ ions allows the study of effects of neutronically generated helium in these samples. A 2-MeV Van de Graaff and a 2-MeV tandem accelerator at Battelle, Pacific Northwest Laboratories (PNL) have been combined to provide dual-beam irradiation with heavy ions, Ni/sup + +/ or Ta/sup + +/, and with He/sup +/ ions. This irradiation facility allows independent control of beam currents and energies for both heavy-ion and helium-ion beams, as well as sample temperatures to 1200/sup 0/C. It will be used both for investigation of materials for advanced reactor applications and for basic studies of radiation damage mechanisms. Preliminary results on molybdenum irradiated to two dose levels at 1000/sup 0/C, with and without simultaneous helium implantation, show the effect of helium on void nucleation. When helium is continuously implanted, the number of voids increases with dose. Without helium, existing voids grow in size but the number is unchanged. At higher heavy-ion dose rates, this effect of helium is less pronounced.
Date: February 1, 1978
Creator: Kissinger, H. E.; Brimhall, J. L.; Simonen, E. P. & Charlot, L. A.
Partner: UNT Libraries Government Documents Department

Temperature and strain-rate effects on deformation mechanisms in irradiated stainless steel

Description: Analysis of the deformation microstructures in ion-irradiated stainless steel shows twinning to be the predominant deformation mode at room temperature. Dislocation channelling also occurs under slow strain rate conditions. Stresses required for twinning were calculated by the model of Venables and are compatible with observed yield stresses in neutron-irradiated material if loops are the principal twin source. Computation of the expected radiation hardening from the defect structure, based on a simple model, is consistent with yield strengths measured on neutron-irradiated steels. Lower yield stresses and greater thermal energy at 288 C lessen the probability of twinning and dislocation channeling becomes the primary deformation mode at the higher temperature. However, preliminary early results show that some twinning does occur in the irradiated stainless steel even at the higher temperature when higher strain rates are used.
Date: November 1, 1994
Creator: Brimhall, J. L.; Cole, J. I.; Vetrano, J. S. & Bruemmer, S. M.
Partner: UNT Libraries Government Documents Department

Metastable phase formation in Be-Nb intermetallic compounds

Description: Amorphous structures or metastable crystalline phases are produced in sputter-deposited Beryllium-Niobium (Be-Nb) alloys (5-15 at. % Nb) depending on the substrate temperature. The metastable phases transform to the stable Be{sub 12}Nb, Be{sub 17}Nb{sub 2}Nb phases on annealing at temperatures >800{degree}C. No Be{sub 5}Nb phase was found and the Be{sub 17}Nb{sub 2} phase is stable to low temperature. The Be{sub 12}Nb phase appeared to have a stoichiometric range of about 5.5 to 7.7 at. % Nb. The formation of the metastable phases is consistent with current models and theories. 17 refs., 1 fig., 2 tabs.
Date: November 1, 1990
Creator: Brimhall, J.L.; Charlot, L.A. & Bruemmer, S.M.
Partner: UNT Libraries Government Documents Department