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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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Preliminary results on the evolution of the IR spectrum of hydrogenated carbon grains as a function of heat treatment are presented. The transformation of C-H and C-C bonding configurations is considered and the correlation with other properties of grains, such as their microstructure, is analyzed.
The kinetics of unidirectional capillary infiltration of silicon melt into microporous carbon preforms have been investigated as a function of the pore morphology and melt temperature. The infiltrated specimens showed alternating bands of dark and bright regions, which corresponded to the unreacted free carbon and free silicon regions, respectively. The decrease in the infiltration front velocity for increasing infiltration distances, is in qualitative agreement with the closed-form solution of capillarity driven fluid flow through constant cross section cylindrical pores. However, drastic changes in the thermal response and infiltration front morphologies were observed for minute differences in the preforms microstructure. This suggests the need for a dynamic percolation model that would account for the exothermic nature of the silicon-carbon chemical reaction and the associated pore closing phenomenon.
We present results for low temperature and pressure experiments of ice formation. These experiments were performed for comparison to Kuiper Belt Objects.
The high molecular weight organic products of Fischer-Tropsch/Haber-Bosch syntheses on the surfaces of Fe-silicate catalysts have been studied by GCMS. Additional information is contained in the original extended abstract.
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Density functional theory (DFT) calculations of cyanate (OCN(-)) charge-transfer complexes were performed to model the "XCN" feature observed in interstellar icy grain mantles. OCN(-) charge-transfer complexes were formed from precursor combinations of HNCO or HOCN with either NH3 or H2O. Three different solvation strategies for realistically modeling the ice matrix environment were explored, including (1) continuum solvation, (2) pure DFT cluster calculations, and (3) an ONIOM DFT/PM3 cluster calculation. The model complexes were evaluated by their ability to reproduce seven spectroscopic measurements associated with XCN: the band origin of the OCN(-) asymmetric stretching mode, shifts in that frequency due to isotopic substitutions of C, N, O, and H, plus two weak features. The continuum solvent field method produced results consistent with some of the experimental data but failed to account for other behavior due to its limited capacity to describe molecular interactions with solvent. DFT cluster calculations successfully reproduced the available spectroscopic measurements very well. In particular, the deuterium shift showed excellent agreement in complexes where OCN(-) was fully solvated. Detailed studies of representative complexes including from two to twelve water molecules allowed the exploration of various possible solvation structures and provided insights into solvation trends. Moreover, complexes arising from cyanic or isocyanic acid in pure water suggested an alternative mechanism for the formation of OCN(-) charge-transfer complexes without the need for a strong base such as NH3 to be present. An extended ONIOM (B3LYP/PM3) cluster calculation was also performed to assess the impact of a more realistic environment on HNCO dissociation in pure water.
A body of semiconductor material having a first surface and a second surface spaced from the first surface includes a first layer along the first surface, a second layer along the second surface, a third layer between and contiguous to the first and second layers. The third layer is of a conductivity type opposite that of the first and second layers so as to form first and second P-N junctions respectively therebetween. The thickness of the third layer is at least twice the minority carrier diffusion length of the semiconductor material, so that carriers generated within the third layer have a high probability of being collected by one of the P-N junctions. The body includes means for electrically connecting the first and second P-N junctions and means for transferring the carriers collected at the first P-N junction to a portion of the first surface.
Modern climate models of Mars tend to predict a colder, icier early climate than previously imagined. While alteration of mafic terrain under warm, wet conditions is relatively well understood, a significant knowledge gap exists in how weathering might occur under redominantly glaciated environments on Mars. In such conditions, it is unclear whether all or any of the variety of aqueous alteration phases expressed in contemporaneous early martian surfaces could be formed, or how erosion of mafic bedrock and transport of sediment would comparatively change. Please see attachment.
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