Search NASA⌕ Search

SEARCH · Search NASA

Results for “Structured packing”

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.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 613 records · Page 34
All sourcesNASA NTRSDOE OSTI
NASA NTRS2004

Self Assembled Structures by Directional Solidification of Eutectics

Interest in ordered porous structures has grown because of there unique properties such as photonic bandgaps, high backing packing density and high surface to volume ratio. Inspired by nature, biometric strategies using self assembled organic molecules dominate the development of hierarchical inorganic structures. Directional solidification of eutectics (DSE) also exhibit self assembly characteristics to form hierarchical metallic and inorganic structures. Crystallization of diphasic materials by DSE can produce two dimensional ordered structures consisting of rods or lamella. By selective removal of phases, DSE is capable to fabricate ordered pore arrays or ordered pin arrays. Criteria and limitations to fabricate hierarchical structures will be presented. Porous structures in silicon base alloys and ceramic systems will be reported.

Dynys, Frederick W.↗
DOE OSTI2018

Recent Progress in Biomass–Derived Electrode Materials for High Volumetric Performance Supercapacitors

Here, tremendous efforts have been spent on the development of electrical energy storage (EES) systems with high volumetric performance in the past few years due to the evergrowing demand of miniaturized, portable electronic devices, and electric vehicles. Among all the EES devices, supercapacitors with electrode materials derived from biosources have attracted special attention due to their eco-friendliness, natural abundance, their intrinsic porous structures as well as their renewable and sustainable features. However, the relatively low packing densities make their specific volumetric capacitance intrinsically low, which has largely limited their further application in the supercapacitors. To address these issues, various promising approaches ranging from structural manufacture to compositional design are applied and significant breakthroughs are witnessed in recent years. In this progress report, key factors influencing the volumetric performance of biomass-derived electrode materials are systematically discussed with a particular focus spanning from fundamental to operational aspects. This work provides insights into the development of high-volumetric-performance biomass-derived supercapacitors by comprehensively summarizing recent advances in the rational structural design and fabrication. Perspectives regarding the future challenges and promising research directions on the design of next-generation EES devices are also provided.

36 MATERIALS SCIENCE↗
DOE OSTI2016

Remote Dismantling and Packaging of the RPV and Thermal Shield at the Obrigheim NPP - 16073

The Obrigheim Nuclear Power Plant (KWO) is located in the Federal State of Baden- Wuerttemberg in Germany and was operated by the EnKK-KWO. The Nuclear Power Plant - a light water pressurized water reactor with 357 MW of electrical power - was operated from 1968 to 2005. In June 2009 the Energiewerke Nord GmbH (EWN) was charged with the dismantling planning and dismantling of the reactor. According to the German nuclear and radiation protection law, several licenses will be required for the realisation of this task. This also applies to the disposal of the waste produced by dismantling, which must finally be stored in the German final repository for low and medium-radioactive waste (underground repository 'Konrad'). In spring 2010 EWN completed all application documents for the dismantling of the reactor pressure vessel (RPV) and the RPV internals and EnKK-KWO delivered them to the responsible Environmental Ministry of Baden-Wuerttemberg. Since then it has been worked intensively on the design, construction and manufacturing of the facilities for dismantling. With a separate notification of amendment, it was applied for the license to install and commission the facilities for the dismantling of the RPV and the RPV internals at the Environmental Ministry of Baden-Wuerttemberg in October 2010. This notification of amendment was confirmed in summer 2012. In September 2011 the work process and test plan and the technical information about the campaign for the removal of the radioactive waste resulting from the RPV with internals, peripheral components and secondary waste with the aim of final disposal in the Federal Repository 'Konrad' was submitted to the Federal Office for Radiation Protection. The evaluation and assessment of the work process and test plan was concluded in August 2013, when it was audited by TUV Nord EnSys without any further measures and indications. On September 10 the work process and test plan was released by the Federal Office for radiation protection. The dismantling of the RPV internals upper core and lower core structure started in September 2013 in the wet cutting area in room 01.106/306 and were finished in October 2014. In the presentation 'Dismantling of the Obrigheim NPP Reactor and Waste Management' held on the WM Symposia in Phoenix, 2014, an overview about the remote cutting and packaging of the upper and lower core structure was given. In today's presentation the subsequent dismantling activities will be outlined and evaluated. The presentation will start with the short description of the basic frame conditions for the nuclear licensing procedure, important procedural principles, and necessary plant-specific conditions. After the remote cutting and packing of the reactor internals of the upper and lower core structure was completed, the wet cutting area 'reactor room 01.106/306' was cleaned and the reactor room rebuilt into a cutting area for peripheral components. After the peripheral components were dismantled, all preconditions were set to lift the RPV from its mounting position and to arrange it in the upper reactor room 01.306. After these activities were completed, the lifting of the RPV was prepared and the cutting area 'Dismantling of the RPV insulation in the reactor room 01.106/306' was set up. To carry out this task, a strand jack unit with connection block was installed on the bridge of the reactor building crane. The opening created by the dismantling of the pool plate was closed with a flap door. The manipulators used for the wet cutting of the RPV internals were also used for the remote dismantling of the RPV insulation and mounted in the cutting area. The remote facilities were handled from a control centre and/or control stand. The air-technical housing which has already been used for the remote dismantling of the RPV internals was designed for the dismantling of the RPV insulation and was extended for this dismantling scope with appropriate ventilation systems. A special feature is the fixation of the RPV insulation at the RPV corpus. The RPV insulation consists of insulation wool, wire mesh and metal-sheet insulation. This 'Sandwich Construction' is detached with a steel corset at the RPV corpus and partly tightened. The insulation of the RPV bottom dome is tightened at the supporting frame. Due to the activation of the material in the core area and the resulting high ambient dose rate the RPV insulation can only be dismantled remotely. Additionally, as asbestos fibers are expected to be found in the insulation the dismantling has to be performed according to the Technical Rules for hazardous substances. The demolition, restoration or maintenance works have to be performed remotely according to the Technical Rules for hazardous substances when the RPV is located in the cutting area. But in case of dismantling of a power reactor no such experience can be found. Beginning with the explanation of the technical, radiological and substantial boundary conditions this presentation will not only impart knowledge about the dismantling of the RPV insulation but also about the remote controlled packaging of the metal sheet insulation and the manual conditioning of the RPV insulation. Subsequently, reports on the remotely controlled cutting and packaging of the RDB are given. Here is particularly interesting that cutting methods have been used and how the activity determination of the segments was carried out. On the basis of the evaluation of the realisation the subsequent dismantling activities will be lined out. In parallel to the dismantling tasks, the waste package documentation for the final repository was issued, checked and confirmed for the containers loaded with parts of the RDB internals. The most important stages are exemplified in this presentation. (authors)

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2018

Evaluation of Alternative Designs for a High Temperature Particle-to-SCO2 Heat Exchanger

This paper presents an evaluation of alternative particle heat-exchanger designs, including moving packed-bed and fluidized-bed designs, for high-temperature heating of a solar-driven supercritical CO2 (sCO2) Brayton power cycle. The design requirements for high pressure (= 20 MPa) and high temperature (= 700 degrees C) operation associated with sCO2 posed several challenges requiring high-strength materials for piping and/or diffusion bonding for plates. Designs from several vendors for a 100 kW-thermal particle-to-sCO2 heat exchanger were evaluated as part of this project. Cost, heat-transfer coefficient, structural reliability, manufacturability, parasitics and heat losses, scalability, compatibility, erosion and corrosion, transient operation, and inspection ease were considered in the evaluation. An analytical hierarchy process was used to weight and compare the criteria for the different design options. The fluidized-bed design fared the best on heat transfer coefficient, structural reliability, scalability and inspection ease, while the moving packed-bed designs fared the best on cost, parasitics and heat losses, manufacturability, compatibility, erosion and corrosion, and transient operation. A 100 kWt shell-and-plate design was ultimately selected for construction and integration with Sandia's falling particle receiver system.

14 SOLAR ENERGY↗
DOE OSTI2019

Evaluation of Alternative Designs for a High Temperature Particle-to-sCO 2 Heat Exchanger

This paper presents an evaluation of alternative particle heat-exchanger designs, including moving packed-bed and fluidized-bed designs, for high-temperature heating of a solar-driven supercritical CO 2 (sCO 2 ) Brayton power cycle. The design requirements for high pressure (=20 MPa) and high temperature (=700 °C) operation associated with sCO 2 posed several challenges requiring high-strength materials for piping and/or diffusion bonding for plates. Designs from several vendors for a 100 kW-thermal particle-to-sCO 2 heat exchanger were evaluated as part of this project. Cost, heat-transfer coefficient, structural reliability, manufacturability, parasitics and heat losses, scalability, compatibility, erosion and corrosion, transient operation, and inspection ease were considered in the evaluation. An analytic hierarchy process was used to weight and compare the criteria for the different design options. The fluidized-bed design fared the best on heat transfer coefficient, structural reliability, scalability, and inspection ease, while the moving packed-bed designs fared the best on cost, parasitics and heat losses, manufacturability, compatibility, erosion and corrosion, and transient operation. A 100 kWt shell-and-plate design was ultimately selected for construction and integration with Sandia's falling particle receiver system.

14 SOLAR ENERGY↗
DOE OSTI2016

Effect of solvent/polymer infiltration and irradiation on microstructure and tensile properties of carbon nanotube yarns

Recently carbon nanotube (CNT) yarns have been gaining importance as an approach to harvest the excellent properties of the CNTs. However, the properties of CNT yarns at this stage are well below the expected value. Investigation of the structure of CNT yarns and possible approaches to enhance the strength and modulus are reported. Scanning electron microscopy and focused ion beam imaging reveal the inherently porous structure and poor orientation, emphasizing the need to enhance packing of CNT bundles in the yarns for increased strength and modulus. Densification of CNT yarn by toluene or polystyrene increases the strength by 140 or 172 % and modulus by 79 or 218 %, respectively, as compared to that of the pristine yarn. E-beam irradiation was investigated as a means to introduce crosslinking and enhanced internanotubes bonding to increase strength and modulus. However, the irradiation resulted in generation of defects and damages to the yarn contributing to reduction in strength and modulus. Raman spectroscopy studies on the irradiated samples reveal the change in bonding characteristics resulting in poor mechanical properties. As a result, denser packing of nanotubes and increased interaction without any damage is the key to improve the properties of CNT yarns.

36 MATERIALS SCIENCE↗
DOE OSTI2020

First-principles study on the mechanical and thermodynamic properties of MoNbTaTiW

Refractory high-entropy alloys (RHEAs) are emerging as new materials for high temperature structural applications because of their stable mechanical and thermal properties at temperatures higher than 2273 K. In this study, the mechanical properties of MoNbTaTiW REDEA are examined by applying calculations based on first-principles density functional theory (DFT) and using a large unit cell with 100 randomized atoms. The phase calculation of MoNbTaTiW with CALPHAD method shows the existence of a stable body-centered cubic structure at a high temperature and a hexagonal closely packed phase at a low temperature. The predicted phase, shear modulus, Young’s modulus, Poisson’s ratio, and hardness values are consistent with available experimental results. The linear thermal expansion coefficient, vibrational entropy, and vibrational heat capacity of MoNbTaTiW RHEA are investigated in accordance with Debye-Grüneisen theory. These results may provide a basis for future research related to the application of RHEAs.

36 MATERIALS SCIENCE↗
DOE OSTI2024

Air‐Ice‐Ocean Coupling During a Strong Mid‐Winter Cyclone: Observing Coupled Dynamic Interactions Across Scales

Abstract Arctic cyclones are key drivers of sea ice and ocean variability. During the 2019–2020 Multidisciplinary drifting Observatory for the Study of Arctic Climate (MOSAiC) expedition, joint observations of the coupled air‐ice‐ocean system were collected at multiple spatial scales. Here, we present observations of a strong mid‐winter cyclone that impacted the MOSAiC site as it drifted in the central Arctic pack ice. The sea ice dynamical response showed spatial structure at the scale of the evolving and translating cyclonic wind field. Internal ice stress and ocean stress play significant roles, resulting in timing offsets between the atmospheric forcing and the ice response and post‐cyclone inertial ringing in the ice and ocean. Ice motion in response to the wind field then forces the upper ocean currents through frictional drag. The strongest impacts to the sea ice and ocean from the passing cyclone occur as a result of the surface impacts of a strong atmospheric low‐level jet (LLJ) behind the trailing cold front and changing wind directions between the warm‐sector LLJ and post cold‐frontal LLJ. Impacts of the cyclone are prolonged through the coupled ice‐ocean inertial response. Local impacts of the approximately 120 km wide LLJ occur over a 12 hr period or less and at scales of a kilometer to a few tens of kilometers, meaning that these impacts occur at combined smaller spatial scales and faster time scales than most satellite observations and coupled Earth system models can resolve.

Meteorology & Atmospheric Sciences↗
DOE OSTI2021

Predicting orientation-dependent plastic susceptibility from static structure in amorphous solids via deep learning

It has been a long-standing materials science challenge to establish structure-property relations in amorphous solids. Here we introduce a rotationally non-invariant local structure representation that enables different predictions for different loading orientations, which is found essential for high-fidelity prediction of the propensity for stress-driven shear transformations. This novel structure representation, when combined with convolutional neural network (CNN), a powerful deep learning algorithm, leads to unprecedented accuracy for identifying atoms with high propensity for shear transformations (i.e., plastic susceptibility), solely from the static structure in both two- and three-dimensional model glasses. The data-driven models trained on samples at one composition and a given processing history are found transferrable to glass samples with different processing histories or at different compositions in the same alloy system. Our analysis of the new structure representation also provides valuable insight into key atomic packing features that influence the local mechanical response and its anisotropy in glasses.

36 MATERIALS SCIENCE↗
DOE OSTI2020

High-pressure annealing driven nanocrystal formation in Zr 50 Cu 40 Al 10 metallic glass and strength increase

Pressure-induced structural changes in metallic glasses have been of great interest as they are expected to open new ways to synthesize novel materials with unexpected properties. Here, we investigated the effect of simultaneous high-pressure and high-temperature treatment on the structure and properties of a Zr 50 Cu 40 Al 10 metallic glass by in situ X-ray structure measurement and property analysis of the final material. We found the unusual formation of Cu-rich nanocrystals at high pressure and temperature, accompanied by significant strength and hardness enhancement. Based on reverse Monte Carlo modeling and molecular dynamics simulations, the structure of the metallic glass changed to a densely packed, chemically uniform configuration with high short-range and medium-range ordering at high pressure and temperature. These results show that high-pressure annealing processes provide a new way to improve and control properties without changing their composition.

36 MATERIALS SCIENCE↗
DOE OSTI2016

Twinning in fcc lattice creates low-coordinated catalytically active sites in porous gold

We describe a new mechanism for creation of catalytically active sites in porous gold. Samples of porous gold prepared by de-alloying Al{sub 2}Au exhibit a clear correlation between the catalytic reactivity towards CO oxidation and structural defects in the fcc lattice of Au. We have found that on the stepped (211) surfaces quite common twin boundary defects in the bulk structure of porous gold can form long close-packed rows of atoms with the coordination number CN = 6. DFT calculations confirm that on these low-coordinated Au sites dioxygen chemisorbs and CO oxidation can proceed via the Langmuir–Hinshelwood mechanism with the activation energy of 37 kJ/mol or via the CO–OO intermediate with the energy barrier of 19 kJ/mol. The existence of the twins in porous gold is stabilized by the surface energy.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2018

Conformations of peptoids in nanosheets result from the interplay of backbone energetics and intermolecular interactions

Significance Commonly observed secondary structures of proteins, such as α -helices and β -sheets, are built from a trans- amide backbone with residues sampling a single region of the Ramachandran plot. Here we report a secondary structure displayed by biomimetic peptoid polymers in which the backbone exhibits the cis conformation and alternating residues display rotational states of opposed (pseudo)chirality. This structure is linear and untwisted and enables strands to pack densely into extended bilayer nanosheets.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Vibrational relaxation dynamics in layered perovskite quantum wells

Significance Halide perovskites, especially layered perovskites, offer a number of advantages to creating bright and efficient light-emitting devices and other optoelectronic applications. The organic–inorganic hybrid layered perovskite features complex lattice dynamics due to the ionic character of the crystal and the softness arising from noncovalent bonds between molecular moieties and the inorganic network. Especially, the packing geometry of the organic barriers leads to a structural deformation of inorganic octahedral, which strongly affects the properties that are crucial for device applications. In this work, we use high-resolution resonant impulsive stimulated Raman spectroscopy of a variety of ligand substitutions in layered perovskites. We find the composition of organic ligands can substantially change the dephasing rate of optical phonons and their temperature dependence, due to varying degrees of anharmonicity in the lattice and dynamic structural disorder.

36 MATERIALS SCIENCE↗
DOE OSTI2025

A twist grain boundary phase in aqueous solutions of the nucleic acid tetramer GTAC

At high concentration, long Watson/Crick (WC) double-helixed DNA forms columnar crystal or liquid crystal phases of linear, parallel duplex chains packed on periodic lattices. This can also be a structural motif of short NA oligomers such as the 5’-GTAC-3’ studied here, which makes four-base WC duplexes having hydrophobic blunt ends. End-to-end aggregation then assembles these duplexes into columns and columnar phases are stabilized, in spite of breaks in the double helix every four bases. But the new degrees of freedom introduced by such breaks also enable opportunities for a more diverse palette of self-assembly modes, producing striking self-assemblies of DNA that would not be achievable with contiguous polymers. These include recently reported three-dimensional (3D) periodic low-density nanoscale networks of GCCG, and the twist grain boundary (TGB) phase presented here. In the TGB, columns of GTAC pairs assemble into monolayer sheets in which the duplex columns are mutually parallel. However, unlike in the columnar crystals, these sheets stack in helical fashion into lamellar arrays in which the column axis of each layer is rotated through a 60° angle with respect to the columns in neighboring layers. This assembly of DNA is unique in that it the fills a 3D volume wherein the major grooves of columns in each layer mutually enter and interlock with the major grooves of columns in neighboring layers. This locking is optimized by small adjustments in structure enabled by the breaks in the duplex backbones.

DNA↗
DOE OSTI2024

Relationship between molecular structure and corrugations in self-assembled polypeptoid nanosheets revealed by cryogenic electron microscopy

Designing conformationally dynamic molecules that self-assemble into predictable nanostructures remains an important unmet challenge. This paper describes how atomic-scale cryogenic transmission electron microscopy (cryo-TEM) can be used to explore the relationship between molecular structure and self-assembly of block copolymers. We examined sheetlike micelles formed in water using a series of diblock copolypeptoids with the same hydrophilic block and three distinct crystalline hydrophobic blocks. Our cryo-TEM images revealed all the structures share nansoscale features, but differ in their intermolecular packing geometries. Different molecular arrangements, parallel and antiparallel V-shaped crystal motifs, were revealed by two-dimensional atomic-scale through-plane images. However, images from tilted samples revealed an unexpected feature when the hydrophobic polypeptoid block comprised phenyl rings with substituted bromine atoms at the para position. The nanosheets contained atomic-scale corrugations that were absent in the other systems which comprised unsubstituted aliphatic and aromatic side chains. We hypothesize that these corrugations are due to the dipolar characteristics of the brominated phenyl group and interactions between this group and water molecules. Published by the American Physical Society 2024

36 MATERIALS SCIENCE↗
DOE OSTI2018

Forensic Analysis of Faulted NSTX-U Inner Poloidal Field Coil

The failure of the NSTX-U PF1A upper coil suspended plasma operations during the project's first operational campaign after commissioning. Initial nondestructive testing and examination of the failed coil was followed by extensive nondestructive radiography. Destructive testing facilitated visual borescope/videoscope inspection through the cooling path, vacuum testing, and electrical testing of every conductor segment. One conductor cooling path visually evidenced a void through the sidewall of the cooling path in a layer-to-layer region. The identified void in the conductor cooling path was not proximal to a braze or joggle. Electrical testing indicated that the voided conductor segment was a member of a group of 14 conductor segments that evidenced low-resistance connectivity. Four braze joints and two lead segments were subjected to 400-lbf/in 2 hydrostatic pressure testing followed by helium leak testing and evidenced that there were no detectable leaks in the tested cooling path segments. The faulted region was proximal to the center of the coil pack and evidenced historical electrical pitting and molten conductor debris. Samples of the epoxy resin insulation system were extracted and analyzed with dynamic mechanical analysis and differential scanning calorimetry techniques. Epoxy resin insulation samples were subjected to immersion testing per ASTM D570. Metallurgical samples were extracted from the coil pack conductors and subjected to hardness testing and grain structure analysis. The base material testing results indicated no abnormalities. In conclusion, the coil incipient failure was determined to most likely have resulted from conductive material located between conductor and insulation layers.

25 ENERGY STORAGE↗
DOE OSTI2016

Influence of Fe underlayers on stress evolution of Ti in Ti/Fe multilayers

A series of 40–2 nm bilayer spacing Ti/Fe multilayers were sputter-deposited. As the length scale of individual Ti layers equaled to 2 nm, Ti phase transforms from a hexagonal close packed (hcp)-to-body centered cubic (bcc) crystal structures for equal layer thicknesses in Ti/Fe multilayers. Further equal reductions in bilayer spacing to less than 1 nm resulted in an additional transformation from a crystalline to amorphous structure. Atom probe tomography reveals significant intermixing between layers which contributes to the observed phase transformations. Real-time, intrinsic growth stress measurements were also performed to relate the adatom mobility to these phase transformations. For the hcp Ti/bcc Fe multilayers of equivalent volume fractions, the multilayers undergo an overall tensile stress state to a compressive stress state with decreasing bilayer thickness for the multilayers. When the above phase transformations occurred, a modest reduction in the overall compressive stress of the multilayer was noted. Depending on the Fe thickness, the Ti growth was observed to be a tensile to compressive growth change to a purely compressive growth for thinner bilayer spacing. Fe retained a tensile growth stress regardless of the bilayer spacing studied.

36 MATERIALS SCIENCE↗
NASA NTRS1987

Solar array flight experiment/dynamic augmentation experiment

This report presents the objectives, design, testing, and data analyses of the Solar Array Flight Experiment/Dynamic Augmentation Experiment (SAFE/DAE) that was tested aboard Shuttle in September 1984. The SAFE was a lightweight, flat-fold array that employed a thin polyimide film (Kapton) as a substrate for the solar cells. Extension/retraction, dynamics, electrical and thermal tests, were performed. Of particular interest is the dynamic behavior of such a large lightweight structure in space. Three techniques for measuring and analyzing this behavior were employed. The methodology for performing these tests, gathering data, and data analyses are presented. The report shows that the SAFE solar array technology is ready for application and that new methods are available to assess the dynamics of large structures in space.

Young, Leighton E.↗