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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 91 records · Page 5
All sourcesNASA NTRSDOE OSTI
DOE OSTI2023

Kinetic Growth of Multicomponent Microcompartment Shells

An important goal of systems and synthetic biology is to produce high value chemical species in large quantities. Microcompartments, which are protein nanoshells encapsulating catalytic enzyme cargo, could potentially function as tunable nanobioreactors inside and outside cells to generate these high value species. Modifying the morphology of microcompartments through genetic engineering of shell proteins is one viable strategy to tune cofactor and metabolite access to encapsulated enzymes. However, this is a difficult task without understanding how changing interactions between the many different types of shell proteins and enzymes affect microcompartment assembly and shape. Here, we use multiscale molecular dynamics and experimental data to describe assembly pathways available to microcompartments composed of multiple types of shell proteins with varied interactions. As the average interaction between the enzyme cargo and the multiple types of shell proteins is weakened, the shell assembly pathway transitions from (i) nucleating on the enzyme cargo to (ii) nucleating in the bulk and then binding the cargo as it grows to (iii) an empty shell. Atomistic simulations and experiments using the 1,2-propanediol utilization microcompartment system demonstrate that shell protein interactions are highly varied and consistent with our multicomponent, coarse-grained model. Furthermore, our results suggest that intrinsic bending angles control the size of these microcompartments. Altogether, our simulations and experiments provide guidance to control microcomparmtent size and assembly by modulating the interactions between shell proteins.

defects↗
DOE OSTI2022

Unblocking a rigid purine MOF for kinetic separation of xylenes

The separation of xylene isomers still remains an industrially challenging task. Here, we synthesized and studied porous purine-based metal–organic frameworks (MOFs) for their potential in xylene separations. In particular, Zn(purine)I showed excellent para-xylene/ortho-xylene separation capability with a diffusion selectivity of 6 and high equilibrium adsorption selectivity as indicated by coadsorption experiments. This high selectivity is attributed to the shape and size of the channel aperture within the rigid framework of Zn(purine)I.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2021

Solvation sheath reorganization enables divalent metal batteries with fast interfacial charge transfer kinetics

Efficient, rechargeable Mg and Ca batteries Divalent rechargeable metal batteries such as those based on magnesium and calcium are of interest because of the abundance of these elements and their lower tendency to form dendrites, but practical demonstrations are lacking. Hou et al . used methoxyethyl amine chelants in which the ligands attach to the metal atom in more than one place, modulating the solvation structure of the metal ions to enable a facile charge-transfer reaction (see the Perspective by Zuo and Yin). In full battery cells, these components lead to high efficiency and energy density. Theoretical calculations were used to understand the solvation structures. —MSL

Science & Technology - Other Topics↗
NASA NTRS1993

Kinetics of the Reaction C2H + O2 from 193 to 350 K Using Laser Flash Kinetic Infrared Absorption Spectroscopy

Rate coefficients for the reaction C2H + O2 are measured from 193 to 350 K by using transient absorption spectroscopy with an infrared color center laser. Ethynyl radicals are produced by pulsed laser photolysis of C2H2 in a temperature variable flow cell and a tunable color center laser probes the transient removal Of C2H ((bar-X(sup 2))Sigma(+))(0,0,0)) in absorption. The rate coefficient has a slight negative temperature dependence over the range 193-350 K which can be expressed as k(O2) = (1.5 +/- 0.3) x 10(exp -11) exp((230 +/- 36)/T) Cu cm/(Molecule.s). The lack of a pressure dependence under our experimental conditions strongly suggests that the HCCOO* complex is short lived with respect to encountering a collision and rapidly dissociates to products without competition from collisional stabilization to HCCOO or collisionally induced dissociation to reactants.

Opansky, Brian J.↗
DOE OSTI2023

Fast Surface Oxygen Release Kinetics Accelerate Nanoparticle Exsolution in Perovskite Oxides

Exsolution is a recent advancement for fabricating oxide-supported metal nanoparticle catalysts via phase precipitation out of a host oxide. A fundamental understanding and control of the exsolution kinetics are needed to engineer exsolved nanoparticles to obtain higher catalytic activity toward clean energy and fuel conversion. Since oxygen release via oxygen vacancy formation in the host oxide is behind oxide reduction and metal exsolution, we hypothesize that the kinetics of metal exsolution should depend on the kinetics of oxygen release, in addition to the kinetics of metal cation diffusion. In this report we probe the surface exsolution kinetics both experimentally and theoretically using thin-film perovskite SrTi 0.65 Fe 0.35 O 3 (STF) as a model system. We quantitatively demonstrated that in this system the surface oxygen release governs the metal nanoparticle exsolution kinetics. As a result, by increasing the oxygen release rate in STF, either by reducing the sample thickness or by increasing the surface reactivity, one can effectively accelerate the Fe 0 exsolution kinetics. Fast oxygen release kinetics in STF not only shortened the prereduction time prior to the exsolution onset, but also increased the total quantity of exsolved Fe 0 over time, which agrees well with the predictions from our analytical kinetic modeling. The consistency between the results obtained from in situ experiments and analytical modeling provides a predictive capability for tailoring exsolution, and highlights the importance of engineering host oxide surface oxygen release kinetics in designing exsolved nanocatalysts.

36 MATERIALS SCIENCE↗