SEARCH · Search NASA
Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.
Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.
Radiographic, penetrant, ultrasonic shear wave and ultrasonic delta inspection methods for critical defect determination
Investigation of surface Rayleigh wave response with simulated defects
Ion bombardment effects on single crystal defect production studied with X ray methods
Ion-implanted GaAs junction diodes anneal behavior and defect nature
Defect F centers formation in MgO, discussing optical absorption bands, oscillator strengths, luminescence band, impurity centers, etc
Study of defect structures with field ion microscope
Determining feasibility of using laser beam holography for detection and characterization of bond defects in composite material structures
Unbiased estimate and tests for readiness index for systems with unknown defects not causing system failure
Impurity effects of annealing of radiation defects in p-type silicon, considering annealing temperature
Production and annealing of defects in lithium diffused bulk silicon after irradiation with 30 MeV electrons and fission neutrons at 300 K
Defects and annealing in electron irradiated lithium diffused silicon solar cells
Quenched and aged Pt, investigating secondary defects for vacancies clustering modes by transmission electron and field-ion microscopy
The effort reported here represents data of lithium properties in bulk-silicon samples before and after irradiation for analytical information required to characterize the interactions of lithium with radiation-induced defects in silicon. A model of the damage and recovery mechanisms in irradiated-lithium-containing solar cells is developed based on making measurements of the Hall coefficient and resistivity of samples irradiated by 1-MeV electrons. Experiments on bulk samples included Hall coefficient and resistivity measurements taken as a function of: (1) bombardment temperature, (2) resistivity, (3) fluence, (4) oxygen concentration, and (5) annealing time at temperatures from 300 to 373 K.
Demonstration that dye penetrant indications on the heat-affected zone of 2014-T6 aluminum GMA weldments are frequently caused by superficial surface conditions and are less than 0.007 in. deep. The following methods are suggested for minimization of these surface defects: stabilization of the arc, application of dc ?GTA' welding procedures, reduction of the caustic etch time, and use of fine grain materials.
Use of space-charge-limited current (SCLC) to observe defect annealing in neutron-irradiated silicon. From the observation of the trap-filled-limit voltage a deep-trap concentration in the irradiated unannealed crystals is found to be at least 1.4 x 10 to the 12th power per cu cm. Shallow traps are also observed. This deep-trap concentration decreases with anneal temperature up to 200 C, above which SCLC can no longer be observed. There is evidence that at least some of this decrease is due to the conversion of the deep traps to shallow traps.
The influence of substrate imperfections on the nucleation and growth of fcc metals on alkali halides is discussed. Films deposited on well characterized substrated under well defined vacuum evaporation conditions are investigated. The experimental results of this work are correlated with similar work by other investigators. Models which have been proposed by various authors to explain experimental results are critically examined and areas of difficulty are pointed out. The influence of defects on nucleation rate and the orientation of the film is emphasized. Specific examples of impurity effects, irradiation effects and the influence of amorphous layers are discussed in detail. Evidence is shown that the formation of multiply twinned particles is a result of coalescence and growth. The only consistent model for the orienting influence of impurities is shown to be a chemical reaction effect. It is demonstrated that an alkali metal impurity is very likely responsible for the orienting influence of both water vapor exposure and irradiation. A negative result is found for the reported possibility of an orienting influence being transmitted through an amorphous layer.
In order to improve reliability and the useful lifetime of solar cell arrays for space use, a program was undertaken to develop radiation-hardened lithium-doped silicon solar cells. These cells were shown to be significantly more resistant to degradation by ionized particles than the presently used n-p nonlithium-doped silicon solar cells. The results of various analyses performed to develop a more complete understanding of the physics of the interaction among lithium, silicon, oxygen, and radiation-induced defects are presented. A discussion is given of those portions of the previous model of radiation damage annealing which were found to be in error and those portions which were upheld by these extensive investigations.
The main objective of the survey reported was a quantitative comparison of different visual functions at identical retinal points of individual patients. The possibility to develop objective forms of visual-field testing was also explored, taking into account reports by Frydrychowicz and Harms (1940) and Harms (1951). These investigators had insisted that pupillary responses to light are depressed in areas of homonymous scotomata. The shapes of homonymous visual field defects are discussed together with questions regarding the association and dissociation of symptoms.