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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.

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At least 559 records · Page 31
All sourcesNASA NTRSDOE OSTI
NASA NTRS2022

Probing Dark Current Random Telegraph Signal in a Small Pitch Vertically Pinned Photodiode CMOS Image Sensor after Proton Irradiation

Dark Current degradation and Dark Current Ran- dom Telegraph Signal after proton irradiation are studied in new scale silicon microvolumes by using a commercial CMOS Image Sensor. Results show that previously reported empirical models describing the Displacement Damage induced degradations are still valid despite the 10 to 100 times smaller depletion volume used. In addition, no evidence of significant Total Ionizing Dose effects is observed. Finally the reduction of the fraction of Random Telegraph Signal (RTS) pixels detected and of the fraction of multi-level RTS pixels is directly linked to the reduction in pixel volume.

CMOS Image Sensor (CIS)↗
DOE OSTI2018

Micro-crack Pinning and Interfacial Fracture in Mixed Metal Oxide Reinforced Epoxy Nanocomposite

The effects of mixed metal oxides (Ce{sub x}Zr{sub 1−x}O{sub 2}) nanoparticle dispersion on the mechanical properties and fracture mechanisms of epoxy polymer matrix and its composite with glass fiber system are reported in this paper. Ce{sub x}Zr{sub 1−x}O{sub 2} nanoparticles are synthesized using sol–gel method, and its crystallinity is optimized. Epoxy nanocomposites are synthesized by a dispersion technique, and the compressive properties are optimized. The glass transition temperature has been improved. Epoxy with 5 wt.% of Ce{sub 0.75}Zr{sub 0.25}O{sub 2} shows optimal results with an increase of 17.4% in compressive modulus, and an increase of 23.4% in compressive strength with respect to those of neat epoxy. This improvement attributes to higher strength of shearing of polymer during the fracture of the nanoparticle interface. Micro-crack kinks at the interfaces can further delay fracture under compression. E-glass fabric-reinforced 5 wt.% Ce{sub 0.75}Zr{sub 0.25}O{sub 2}–epoxy nanocomposite also shows improvement in the mechanical properties via nanoscale interface with fibers. This type of ceramic nanocomposites has useful applications in thermal/electrical insulations besides improving the compressive/buckling properties.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2022

Experimental measurements of fluid flow in an 84-pin hexagonal rod bundle with spacer grid for a gas-cooled fast modular reactor

A 50 MW e helium-cooled fast modular reactor (FMR) is under development, and as part of the Department of Energy Integrated Research Project (IRP), Texas A&M University is conducting the thermal-hydraulic characterization of its baseline core configuration. Here, we experimentally investigated the axial and cross flow fields characteristics in the hexagonal fuel rod bundle composed of 84 rods, a central rod, and spacer grids at a Reynolds number of 12,000. A fully transparent experimental facility resembling of one unit of the fuel assembly was constructed. Time-resolved particle image velocimetry (TR-PIV) measurements were performed to characterize hydraulic behavior downstream the spacer grid. Velocity measurements were conducted in the axial and radial direction of the rod bundle. From the PIV velocity vector fields, the full-field flow statistics were computed for the mean velocity, vorticity, and Reynolds stresses. An analysis of the energy decay downstream of the spacer grid was conducted with calculations of secondary-flow intensities, turbulent kinetic energy, power spectrum, and spatial-temporal velocity cross correlations. The vorticity field was obtained and pairs of counter-rotating vortexes were identified using a 3D reconstruction of several measurement planes. The data from this experimental campaign will be used to validate numerical models based on Computational Fluid Dynamics and other codes.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2020

Analytic model of the remobilization of pinned glide dislocations: Including dislocation drag from phonon wind

Here, we discuss the effect of a non-constant dislocation drag coefficient on the very high strain rate regime within an analytic model describing mobile-immobile dislocation intersections applicable to fcc polycrystals. Based on previous work on dislocation drag, we estimate its temperature and pressure dependence and its effects on stress–strain rate relations. In the high temperature regime, we show that drag can remain the dominating effect even down to intermediate strain rates. We also discuss the consequences of having a limiting dislocation velocity, a feature which is typically predicted by analytic models of dislocation drag, but which is somewhat under debate because a number of MD simulations predict supersonic dislocations.

42 ENGINEERING↗
DOE OSTI2019

HT9 swelling in high burnup fast reactor fuel pin components

The irradiation-induced void swelling of HT9 stainless steel has been observed many times, but there are little data available to quantify the amount of swelling expected as a function of neutron exposure and temperature. This is further complicated by potential heat-to-heat chemical variations or heat treatment conditions during fabrication. Herein, this paper summarizes the results of most of the relevant previously completed studies, then focuses on the swelling behavior of HT9 mixed-oxide fuel cladding and wrapper wire irradiated to high neutron exposures. Note that the hexagonal duct used for the ACO-3 experiment (in the Fast Flux Test Facility, or FFTF) was also made from HT9 and has been studied previously by other researchers. The cladding enables a wider range of operating temperatures. Immersion density and transmission electron microscopy were used to identify a peak in the amount of swelling located axially, just below core centerline, for both the cladding and the wire. The peak roughly coincided with a peak seen in the cladding diameter profile. The wrapper wire showed enhanced swelling compared to the cladding, likely due to over-tempering during wire fabrication heat treatment. The grains showed decreased martensitic structure were larger in size. These data do not provide for the means to fully characterize the swelling of HT9, but do provide further insight into the factors controlling it. The onset of breakaway swelling was not indicated in this data.

36 MATERIALS SCIENCE↗