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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 199 records · Page 11
All sourcesNASA NTRSDOE OSTI
DOE OSTI2017

Photocatalytic metal–organic frameworks for organic transformations

Metal–organic frameworks (MOFs) have attracted increasing attention for applications in heterogeneous photocatalysis. Here, modifications of metal nodes and organic linkers, as well as encapsulation of active species in the pores of MOFs enable the generation of photoactive materials for catalyzing organic transformations. MOF composites integrating noble metal nanoparticles or traditional photoactive semiconductors can combine the advantages of both materials, and also improve the photocatalytic performance via synergistic effects. In this Highlight, we discuss recent examples of photoactive MOFs and their use as photocatalysts for organic reactions.

42 ENGINEERING↗
DOE OSTI2017

Induction time of a polymorphic transformation

When a solution is supersaturated with respect to multiple polymorphs, the polymorph with the lowest nucleation barrier will form first. If this is a metastable polymorph, it will persist until the induction of nuclei of a lower free-energy phase, marking the onset of a polymorphic transformation. Induction of a more stable polymorph can occur under two conditions: a.) during steady-state nucleation, or b.) after complete crystal growth of the metastable phase. Using the theory of competing stochastic processes, we derive the rare probability of forming a higher-barrier, more-stable polymorph during steady-state nucleation, and use this to explain variations in crystallization products between repeat experiments, which may underlie the phenomenon of "Disappearing Polymorphs". We also derive the induction time of a stable phase from a solution equilibrated with a metastable phase, and show that once the stable phase nucleates, bulk metastable crystals will spontaneously ripen onto nanoscale nuclei or seeds of a more stable phase, thermodynamically driving dissolution-reprecipitation processes. Existing strategies to prolong or shorten the lifetimes of transient metastable phases are reviewed and interpreted within the context of polymorphic induction. Finally, the analyses in this work are conducted from classical nucleation and crystal growth theories, suggesting that paradigms shifts to 'non-classical' nucleation theories may not be necessary to rationalize multistage crystallization.

36 MATERIALS SCIENCE↗
DOE OSTI2016

Real-Time Examination of Atomistic Mechanisms during Shock-Induced Structural Transformation in Silicon

Experimental determination of atomistic mechanisms linking crystal structures during a compression driven solid-solid phase transformation is a long standing and challenging scientific objective. Also, when using new capabilities at the Dynamic Compression Sector at the Advanced Photon Source, the structure of shocked Si at 19 GPa was identified as simple hexagonal and the lattice orientations between ambient cubic diamond and simple hexagonal structures were related. Furthermore, this approach is general and provides a powerful new method for examining atomistic mechanisms during stress-induced structural changes.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Transformational challenge reactor design characteristics

The Transformational Challenge Reactor (TCR) program was conceived with the goal to reduce costs and time frames associated with advanced reactor deployment by leveraging developments in advanced manufacturing, advanced materials, data science, and rapid prototyping and testing. The final deliverable of the TCR program was to be an operational test of a novel reactor design. The TCR core design incorporates a dense tri-structural-isotropic/SiC fuel form and volumetrically efficient yttrium hydride moderator, both of which were manufactured and characterized under the TCR program. The TCR is a 3 MW{sub th} He-cooled experimental nuclear reactor designed to reach a total integrated burnup of less than 24 effective full-power hours to keep the radioactive source term to a very low level. TCR design process revealed a positive moderator coefficient; however, the negative doppler coefficients for the fuel and thermal expansion of fuel, moderator, and core support plate yield an overall negative reactivity coefficient. Calculated fuel element temperatures and stresses are well within safety margins. The maximum hypothetical accident (i.e., de-pressurized loss of forced cooling) yields only a modest increase in reactor temperatures that are all within safety margins. This paper summarizes the high-level TCR design characteristics, which were derived from neutronics, thermohydraulics, thermomechanics, and safety analyses.

21 SPECIFIC NUCLEAR REACTORS AND ASSOCIATED PLANTS↗
DOE OSTI2017

Transport and Transformation of Selenium and Other Constituents of Flue‐Gas Desulfurization Wastewater in Water‐Saturated Soil Materials

Constructed wetland treatment systems are used to remove selenium (Se) from flue‐gas desulfurization (FGD) wastewater (WW). However, direct confirmation of the mechanism responsible for FGD WW Se retention in soil is lacking. A laboratory‐based soil column study was performed to develop an evidence‐based mechanism of Se retention and to study the behavior and the retention capacity of FGD WW constituents in water‐saturated soil. A deoxygenated 1:1 mixture of FGD WW and raw water was delivered to the columns bottom‐up at a flux of 1.68 cm d −1 for 100 d. Some of the columns were flushed with the raw water at the same rate for an additional 100 d. Column effluent was analyzed for constituents of concern. Results showed a complete retention of FGD WW Se in the soil materials. Boron and fluorine were partially retained; however, sulfur, sodium, and chlorine retention was poor, agreeing with field observations. The FGD WW Se was retained in soil near the inlet end of the columns, indicating its limited mobility under reduced conditions. Sequential extraction procedure revealed that retained Se was mainly sequestered as stable/residual forms. Bulk‐ and micro‐X‐ray absorption near‐edge structure spectroscopy confirmed that Se was mainly retained as reduced/stable species [Se(IV), organic Se, and Se(0)]. This study provides direct evidence for FGD WW Se retention in water‐saturated soil via the transformation of oxidized Se into reduced/stable forms. Core Ideas The mechanism of FGD wastewater Se retention in water‐saturated soil was studied. Sequential fractionation of Se, micro‐XRF, and micro‐ and bulk‐XANES were used. Behavior of FGD wastewater constituents in saturated soil was comparable to field‐scale observations. FGD wastewater Se exhibited strong retention in reduced soil. Reduced/stable species of Se governed the retention mechanism.

Galkaduwa, Madhubhashini B.↗
DOE OSTI2013

Transforming Markets for Energy-Efficient Buildings in China: Final Report on Activity Conducted by the Institute for Market Transformation (IMT) Under Cooperative Agreement DE-FC01-00EE10672 with the U.S. Department of Energy (DOE)

This report summarizes activity conducted by the Institute for Market Transformation and a team of American and Chinese partners in development of a new building energy-efficiency code for the transitional climate zone in the People's Republic of China.

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗
DOE OSTI2021

Candidate Core Designs for the Transformational Challenge Reactor

Early cycle activities under the Transformational Challenge Reactor (TCR) program focused on analyzing and maturing four reactor core design concepts: two fast-spectrum systems and two thermal-spectrum systems. A rapid, iterative approach has been implemented through which designs can be modified and analyzed and subcomponents can be manufactured in parallel over time frames of weeks rather than months or years. To meet key program initiatives (e.g., timeline, material use), several constraints—including fissile material availability (less than 250 kg of HALEU), component availabilities, materials compatibility, and additive manufacturing capabilities—were factored into the design effort, yielding small (less than one cubic meter in volume) cores with near-term viability. The fast-spectrum designs did not meet the fissile material constraint, so the thermal-spectrum systems became the primary design focus. Since significant progress has been made on advanced moderator materials (YH x ) under the TCR program, gas-cooled thermal-spectrum systems using less than 250 kg of HALEU that occupy less than 1 m 3 are now feasible. The designs for two of these systems have been evolved and matured. In both thermal-spectrum design concepts, bidirectional coolant flow is used. Coolant flows down through YH x moderator elements and is reversed in a bottom manifold and core support structure, and then flows up though or around the fuel elements. The main difference between the two thermal-spectrum design concepts is the fuel elements—one uses traditional UO 2 ceramic fuel, and the other uses UN-bearing TRISO fuel particles embedded inside a SiC matrix. Finally, core neutronics and thermal performance for these systems are assessed and summarized herein.

21 SPECIFIC NUCLEAR REACTORS AND ASSOCIATED PLANTS↗
NASA NTRS1972

An actuator extension transformation for a motion simulator and an inverse transformation applying Newton-Raphson's method

A set of equations which transform position and angular orientation of the centroid of the payload platform of a six-degree-of-freedom motion simulator into extensions of the simulator's actuators has been derived and is based on a geometrical representation of the system. An iterative scheme, Newton-Raphson's method, has been successfully used in a real time environment in the calculation of the position and angular orientation of the centroid of the payload platform when the magnitude of the actuator extensions is known. Sufficient accuracy is obtained by using only one Newton-Raphson iteration per integration step of the real time environment.

Dieudonne, J. E.↗
NASA NTRS1976

Development and evaluation of a Hadamard transform imaging spectrometer and a Hadamard transform thermal imager

A spectrometric imager and a thermal imager, which achieve multiplexing by the use of binary optical encoding masks, were developed. The masks are based on orthogonal, pseudorandom digital codes derived from Hadamard matrices. Spatial and/or spectral data is obtained in the form of a Hadamard transform of the spatial and/or spectral scene; computer algorithms are then used to decode the data and reconstruct images of the original scene. The hardware, algorithms and processing/display facility are described. A number of spatial and spatial/spectral images are presented. The achievement of a signal-to-noise improvement due to the signal multiplexing was also demonstrated. An analysis of the results indicates both the situations for which the multiplex advantage may be gained, and the limitations of the technique. A number of potential applications of the spectrometric imager are discussed.

Harwit, M.↗
NASA NTRS2008

A Synthetic Quadrature Phase Detector/Demodulator for Fourier Transform Transform Spectrometers

A method is developed to demodulate (velocity correct) Fourier transform spectrometer (FTS) data that is taken with an analog to digital converter that digitizes equally spaced in time. This method makes it possible to use simple low cost, high resolution audio digitizers to record high quality data without the need for an event timer or quadrature laser hardware, and makes it possible to use a metrology laser of any wavelength. The reduced parts count and simplicity implementation makes it an attractive alternative in space based applications when compared to previous methods such as the Brault algorithm.

Campbell, Joel↗
DOE OSTI2018

Fourier Transform-Ion Cyclotron Resonance Mass Spectrometry as a Platform for Characterizing Multimeric Membrane Protein Complexes

Membrane protein characterization is consistently hampered by challenges with expression, purification, and solubilization. Among several biophysical techniques employed for their characterization, native-mass spectrometry (MS) has emerged as a powerful tool for the analysis of membrane proteins and complexes. Here, two MS platforms, the FT-ICR and Q-ToF, have been explored to analyze the homotetrameric water channel protein, AquaporinZ (AqpZ), under non-denaturing conditions. This 97 kDa membrane protein complex can be readily liberated from the octylglucoside (OG) detergent micelle under a range of instrument conditions on both MS platforms. Increasing the applied collision energy of the FT-ICR collision cell yielded varying degrees of tetramer (97 kDa) liberation from the OG micelles, as well as dissociation into the trimeric (72 kDa) and monomeric (24 kDa) substituents. Tandem-MS on the Q-ToF yielded higher intensity tetramer signal and, depending on the m/z region selected, the observed monomer signal varied in intensity. Precursor ion selection of an m/z range above the expected protein signal distribution, followed by mild collisional activation, is able to efficiently liberate AqpZ with a high S/N ratio. The tetrameric charge state distribution obtained on both instruments demonstrated superpositioning of multiple proteoforms due to varying degrees of N-terminal formylation. .

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2018

Nucleation and phase transformation pathways in electrolyte solutions investigated by in situ microscopy techniques

Identification of crystal nucleation and growth pathways is of fundamental importance for synthesis of functional materials, which requires control over size, orientation, polymorph, and hierarchical structure, often in the presence of additives used to tune the energy landscape defining these pathways. Furthermore we summarize the recent progress in application of in situ TEM and AFM techniques to monitor or even tune the pathway of crystal nucleation and growth.

36 MATERIALS SCIENCE↗