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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 1,207 records · Page 67
All sourcesNASA NTRSDOE OSTI
DOE OSTI2025

Microstructurally informed synchrotron x-ray analysis revealing helium defect transitions in ultrafine grained tungsten

The formation of insoluble gaseous defects in materials due to nuclear transmutation or ion implantation involves the diffusion of impurity atoms to form atomic defect clusters that coalesce into bubbles or cavities and ultimately degrade the material properties. Transmission electron microscopy (TEM) is limited in its ability to resolve sub-nanometer gas clusters whereas X-ray diffraction (XRD) provides information pertaining to local atomic changes. Here, in this study, helium (He) implanted ultrafine grained tungsten is explored through a multimodal defect characterization campaign combining TEM-informed Small Angle X-ray Scattering (SAXS) analysis, XRD lattice parameter measurements, and nanoscale He cluster quantification from a region of reciprocal space accessible via Wide Angle X-ray Scattering (WAXS). Moderate elevated temperature implantations are shown to produce high concentrations of sub-nanoscale He clusters and small, homogeneously distributed cavities, which collectively are linked to lattice expansion and further substantiated through complementary atomistic simulations. Increased implantation temperatures encourage the diffusion of these defects to the grain boundaries (GBs), leading to lattice relaxation and the growth of large GB cavities manifesting as bimodal size distributions in the SAXS analysis. Overall, our results demonstrate the utility of multimodal synchrotron X-ray analysis in bridging the gap between microscale He cavity quantification and atomic-scale defect analysis.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Reversible solid oxide cells: Early performance and microstructural evolution during electrolysis and switched mode operation

Incorporating more renewables into our energy mix will require a diversity of technological solutions. Reversible solid oxide cell systems (RSOCs) operating reversibly between fuel cell and electrolysis modes with high round-trip efficiencies offer one such solution. However, questions remain about the stability of the oxygen and fuel electrodes under reversible operation. Here, in this study, single cells with the configuration Ni-YSZ|YSZ|GDC10|NNO-NDC50|NNO are operated by reversible cycling under potentiostatic conditions. Test conditions are chosen to be representative of average stack conditions that are likely to be encountered during operation of a stack constructed of such cells. The results of reversible cycling over 500 h (21 cycles) are compared with operating the cells under potentiostatic conditions in the electrolysis-only mode (i.e., without cycling). Voltage-current density (DC), AC complex impedance spectroscopy, distribution of relaxation times (DRT) analysis, and scanning electron microscopy (SEM) indicate excellent reversibility and stability of the neodymium nickelate-based oxygen electrodes in both electrolysis and reversible cycling modes. Degradation behavior is attributed to the loss and coarsening of connected Ni particles in the fuel electrode, particularly in the active layer. However, reversible operation mitigates this degradation compared to operation in the electrolysis-only (SOEC-only) mode.

25 ENERGY STORAGE↗
DOE OSTI2023

The effect of ink ball milling time on interparticle interactions and ink microstructure and their influence on crack formation in rod-coated catalyst layers

This work investigates the influence of ballmilling (sometimes also referred to as jar roller milling) time on cathode catalyst layer (CL) inks and electrode properties using formulations and coating methods relevant for industrial manufacturing. Four CL inks with the same composition were milled for 24, 48, 72, or 96 h. Rheological investigation of these inks showed a reduction of elastic moduli and steady-shear viscosity with continuous ink milling, which is correlated to a decrease in particle-particle interactions as well as formation of smaller agglomerates. Optical microscopy (OM) analysis of the fabricated electrodes revealed a trend in surface crack formation; formulations milled for 24 h contained the lowest average surface crack area percentages of 0.370% at heavy-duty loadings of ~0.300 mg Pt cm -2 , compared to 2.418% for the ink milled for 96 h. Further characterization of the CL through transmission electron microscopy (TEM) imaging showed a decrease in the mean agglomerate and pore size with milling time. Furthermore, these smaller electrode features were consistent with reduced fracture resistance and, hence, development of larger stresses during drying. Our results highlight the need to consider ink processing as an important component in defect-free CL manufacturing.

30 DIRECT ENERGY CONVERSION↗