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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 757 records · Page 42
All sourcesNASA NTRSDOE OSTI
DOE OSTI2022

Silicon nanocluster anion-argon cation recombination via hybrid continuum-molecular dynamics calculations

Prediction of the charge distribution on particles in an aerosol is critical not only in electrical mobility based characterization methods, but also in understanding the role that charging plays in particle growth in gas phase synthesis reactors. The latter is particularly important in non-thermal plasma synthesis reactors, wherein nanoclusters form and grow from vapor phase precursors in a high electron and high ion density environment. In plasmas, because free electrons are much less massive and much more mobile than positive gas ions, nanocluster charge distributions are biased negative. Furthermore, neutral or even positively charged nanoclusters may exist, depending on the rate of nanocluster-gas ion recombination, and nanocluster-nanocluster collisions may greatly contribute to nanocluster growth if not Coulombically suppressed.

42 ENGINEERING↗
DOE OSTI2019

Highly efficient removal of both cationic and anionic dyes from wastewater with a water-stable and eco-friendly Fe-MOF via host-guest encapsulation

Here, a water-stable cationic Fe based metal organic framework, CPM-97-Fe, was successfully synthesized in a large scale by a modified method (CPM: Crystalline Porous Materials). The adsorption behaviors, including removal efficiency, adsorption kinetics and isotherms of nine hazardous dyes in wastewater were investigated with different pH and organic solvents. The pseudo-second-order adsorption rate constant follows the order of Reactive Brilliant Red X-3B (X-3B, 0.0205 g mg -1 min -1 ) > Acid orange 7 (AO7, 0.0112 g mg -1 min -1 ) > Congo Red (CR, 0.0080 g mg -1 min -1 ) > Methylene Blue (MB, 0.0061 g mg -1 min -1 ) > Rhodamine B (RhB, 0.0049 g mg -1 min -1 ) > Croscein Scarlet 3B (CS3B, 0.0041 g mg -1 min -1 ) > Methyl Blue (MB, 0.0017 g mg -1 min -1 ) = New Coccine (NC, 0.0017 g mg -1 min -1 ) > Acid Black 1 (AB1, 0.0014 g mg -1 min -1 ). It is found that the adsorption quasi-equilibrium can reach quickly within 30 min, but the dyes with proper structure (i.e. proper distance between two sulfonic groups, less azo benzene hindrance effect, more reactive Cl groups, and more benzene rings), smaller molecular size, more negative charges, lower molecular mass favor the faster adsorption. The adsorption capacity obeys another sequence of CR (831 mg g -1 ) > X-3B (648 mg g -1 ) > AO7 (502 mg g -1 ) > MLB (380 mg g -1 ) > CS3B (356 mg g -1 ) > AB1 (325 mg g -1 ) > RhB (306 mg g -1 ) > MB (304 mg g -1 ) > NC (157 mg g -1 ). It is disclosed that CPM-97-Fe can adsorb more dyes with larger molecular mass, less negative charges, and a proper structure. Especially for Congo red, the adsorption capacity on CPM-97-Fe is 831 mgg -1 , 8.1 times that on activated carbon (103 mgg -1 ). Even the adsorption capacities of very bulky Rhodamine B and Methyl Blue reach as high as 306 and 304 mgg -1 , respectively, ranking the highest level among MOF materials. Moreover, the special structure of CPM-97-Fe with big open windows and high specific surface area of 1397.0 m 2 g -1 contributes to the fast adsorption and high capacity towards all investigated dyes via the host-guest encapsulation mechanism including electrostatic interaction, ion exchange, π-π stacking interaction, as well as pore filling.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Systematic DFT study of the impact of anionic variations on the physical properties of Cd1-xMnxX (XS, Se, Te; x = 6.25%)

Highlights: • The structural and electronic properties are investigated with most accurate mBJ potential. • The FM state stability is illustrated for Cd{sub 0.9375}Mn{sub 0.0625}S/Se/Te DMSs. • The FM semiconducting nature depicts potential applications in magneto-optic applications. • The absorption shifts within the visible range with S to Te variation that is verified by E{sub g}. • Thermoelectric properties indicate dominant hole-carriers and suitability at high temperatures. - Abstract: The structural and electronic properties are theoretically investigated for Cd{sub 1-x}Mn{sub x}X (XS, Se, Te; x = 6.25%) diluted magnetic semiconductors, which are further employed for extracting the magnetic, optical and thermoelectric properties using modified-Becke-Johnson (mBJ) potential. Ferromagnetic state stability is confirmed through the computed enthalpy of formation and the cohesive energies. The electronic properties elucidate Cd{sub 1-x}Mn{sub x}X (XS, Se, Te; x = 6.25%) as ferromagnetic semiconductors because both spin channels have Fermi energy level (E{sub F}) within the band gap, depicting potential applications in spintronic devices. The calculated optical response indicates shifts in the absorption within the visible energy that is consistent with the computed direct band gap values (1.9 eV–3.1 eV). Thermoelectric properties observed within 200 K–800 K show positive Seebeck coefficient indicating holes as majority charge carriers. Although Mn-doping suppresses the power factor, however, it improves with temperature, showing a potential for optimizing the thermoelectric performance.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗