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At least 1,135 records · Page 63
All sourcesNASA NTRSDOE OSTI
DOE OSTI2019

Engineering Accessible Adsorption Sites in MOFs for CO 2 Capture (Final Report)

The overall goal of this project was to synthesize metal-organic frameworks (MOFs) with improved CO 2 adsorption and selectivity properties for potential application in removing this greenhouse gas from flue gas streams during fossil fuel processing. MOFs are an important class of 2-dimensional (2D) and 3D supramolecular coordination polymer networks that are comprised of organic linkers (ligands) and metal ion-units or clusters. They generally possess very high surface area, porosity, variable thermal stability and tunable chemistry, which make them potentially candidates CO 2 adsorption. The three specific objectives of this project were as follows: 1) To synthesize MOFs with metal ions adsorption sites in more accessible locations within the structures (towards the center of the organic linkers) in order to enhance their CO 2 adsorption characteristics; 2) To investigate the CO 2 adsorption properties of new MOFs containing pyrazine- and other nitrogen containing ligands as possible improved alternatives to known amine-functionalized MOFs; and 3) To investigate the nature of the adsorption sites and mechanism(s) by conducting computational studies on CO 2 adsorption within the MOF structures and compare the results with experimental observations. The main outcomes of this research are as follows. Nitrogen-containing ligands that possesses a diaza-12-crown-4-ether moiety at the center of two phenylcarboxylic acid groups was utilized to synthesize 3D MOFs in which the added transition metal ions (i.e.CO 2 + and Mn2+) were coordinated within the crown moieties. Therefore, the structures had the metal ions in more accessible locations. The new 3D structures, being non-porous however, showed negligible adsorption capacity for CO 2 . The ligand 2,3,5,6,-pyrazinetetracarboxylic acid (PZTC) was successfully used to synthesize four new MOFs, each with one of the following metal ion; Ca2+(1D), Zn2+(2D), Mn2+ (3D) and Gd3+(3D), and with the dimensionality (D) indicated. The Ca-, Zn- and Mn- PZTC-based MOFs had no obvious accessible pores and showed no adsorption capacity for CO 2 . Gd-PZTC structure however, showed promising capacities of 1.0 mmol/g and 0.6 mmol/g at 273K and 298 K respectively. Another nitrogen-containing ligand explored was 2,2’-dinitro- trans-4,4’- stilbenedicarboxylic acid (DNSDC) and in combination with a co-ligand, 2,2’-bipyridine (2,2’-BPY). The combination of DNSDC with CO 2 + and Mn2+ yielded four new thermally stable MOFs that showed significant CO 2 absorption capacities. The experimental CO 2 adsorption capacities varied among the structures, ranging between 1.8 mmol/g at 256 K and 0.8 mmol/g at 298K. The DNSDC-based structures maintained significant stability and capacities over many adsorption cycles at 298K. With 2,2’-diamino- trans-4,4’-stillbene dicarboxylic acid (DASDC) as ligand instead of DNSDC, new 3D MOF structures were also synthesized. The structures however were less stable, and decomposed on activation (exposure to vacuum and or solvents) and therefore showed negligible CO 2 adsorption capacities. The dinitro-stilbene based MOFs showed promising CO 2 adsorption capacities, thermal stabilities and recyclability, and therefore showed potential for application in CO 2 removal from flue gas. The research accomplishments presented herein supports the Department of Energy’s (DOE) Office of Fossil Energy and the National Energy Technology Laboratory (NETL) mission in the area of research that advances the science of coal technologies, specifically carbon capture and storage. The research outcomes can guide rational design/synthesis strategies towards producing advanced materials for CO 2 capture. However, further research is needed in order to develop the materials to meet or exceed capacities and stabilities that are reported for their counterparts.

20 FOSSIL-FUELED POWER PLANTS↗
DOE OSTI2019

Engineering Accessible Adsorption Sites in MOFs for CO 2 Capture

The overall goal of this project was to synthesize metal-organic frameworks (MOFs) with improved CO 2 adsorption and selectivity properties for potential application in removing this greenhouse gas from flue gas streams during fossil fuel processing. MOFs are an important class of 2-dimensional (2D) and 3D supramolecular coordination polymer networks that are comprised of organic linkers (ligands) and metal ion-units or clusters. They generally possess very high surface area, porosity, variable thermal stability and tunable chemistry, which make them potential candidates for CO 2 adsorption. The three specific objectives of this project were as follows: 1) To synthesize MOFs with metal ion adsorption sites in more accessible locations within the structures (towards the center of the organic linkers) in order to enhance their CO 2 adsorption characteristics; 2) To investigate the CO 2 adsorption properties of new MOFs containing pyrazine- and other nitrogen containing ligands as possible improved alternatives to known amine-functionalized MOFs; and 3) To investigate the nature of the adsorption sites and mechanism(s) by conducting computational studies on CO 2 adsorption within the MOF structures and compare the results with experimental observations. The main outcomes of this research are as follows: Nitrogen-containing ligands that possess a diaza-12-crown-4-ether moiety at the center of two phenylcarboxylic acid groups were utilized to synthesize 3D MOFs in which the added transition metal ions (i.e. Co 2+ and Mn 2+ ) were coordinated within the crown moieties. Therefore, the structures had the metal ions in more accessible locations. The new 3D structures, being non-porous however, showed negligible adsorption capacity for CO 2 . The ligand 2,3,5,6,-pyrazinetetracarboxylic acid (PZTC) was successfully used to synthesize four new MOFs, each with one of the following metal ions; Ca 2+ (1D), Zn 2+ (2D), Mn 2+ (3D) and Gd 3+ (3D), and with the dimensionality (D) indicated. The Ca-, Zn- and Mn- PZTC-based MOFs had no obvious accessible pores and showed no adsorption capacity for CO 2 . Gd-PZTC structure however, showed promising capacities of 1.0 mmol/g and 0.6 mmol/g at 273K and 298 K respectively. Another nitrogen-containing ligand explored was 2,2’-dinitro- trans-4,4’- stilbenedicarboxylic acid (DNSDC) and in combination with a co-ligand, 2,2’-bipyridine (2,2’-BPY). The combination of DNSDC with Co 2+ and Mn 2+ yielded four new thermally stable MOFs that showed significant CO 2 absorption capacities. The experimental CO 2 adsorption capacities varied among the structures, ranging between 1.8 mmol/g at 256 K and 0.8 mmol/g at 298K. The DNSDC-based structures maintained significant stability and capacities over many adsorption cycles at 298K. With 2,2’-diamino- trans-4,4’-stillbene dicarboxylic acid (DASDC) as ligand instead of DNSDC, new 3D MOF structures were also synthesized. The structures, however, were less stable, and decomposed on activation (exposure to vacuum and or solvents) and therefore showed negligible CO 2 adsorption capacities. The dinitro-stilbene based MOFs showed promising CO 2 adsorption capacities, thermal stabilities and recyclability, and therefore showed potential for application in CO 2 removal from flue gas. The research accomplishments presented herein support the Department of Energy’s (DOE) Office of Fossil Energy and the National Energy Technology Laboratory (NETL) mission in the area of research that advances the science of coal technologies, specifically carbon capture and storage. The research outcomes can guide rational design/synthesis strategies towards producing advanced materials for CO 2 capture. However, further research is needed in order to develop the materials to meet or exceed capacities and stabilities that are reported for their counterparts.

20 FOSSIL-FUELED POWER PLANTS↗
NASA NTRS1980

Application of the multigrid method to grid generation

The multigrid method (MGM), used to numerically solve the pair of nonlinear elliptic equations commonly used to generate two dimensional boundary-fitted coordinate systems is discussed. Two different geometries are considered: one involving a coordinate system fitted about a circle and the other selected for an impinging jet flow problem. Two different relaxation schemes are tried: one is successive point overrelaxation and the other is a four-color scheme vectorizeable to take advantage of a parallel processor computer for greater computational speed. Results using MGM are compared with those using SOR (doing successive overrelaxations with the corresponding relaxation scheme on the fine grid only). It is found that MGM becomes significantly more effective than SOR as more accuracy is demanded and as more corrective grids, or more grid points, are used. For the accuracy required, it is found that MGM is two to three times faster than SOR in computing time. With the four-color relaxation scheme as applied to the impinging jet problem, the advantage of MGM over SOR is not as great. This may be due to the effect of a poor initial guess on MGM for this problem.

Ohring, S.↗
NASA NTRS1979

Development of an improved toughness hyperpure silica reflective heat shield

High purity three dimensionally woven silica-silica materials were evaluated for use as a tough reflective heat shield for planetary entry probes. A special weave design was selected to minimize light piping effects through the heat shield thickness. Various weave spacings were evaluated for densification efficiency with an 0.7 micron particle size high purity silica. Spectral hemispherical reflectance was measured from 0.2 to 2.5 microns at room temperature. Reflectance increases due to densification and purity of material were measured. Reflectance of 3D hyperpure silica was higher than 3D astroquartz silica for all wavelengths. Mechanical properties were measured in beam flexure and beam shear tests. Results indicated strengths lower than reported for slip cast fused silica. Low strengths were attributed to low densities achieved through vacuum impregnation.

Rusert, E. L.↗
NASA NTRS1981

Porous tooling process for manufacture of graphite/polyimide composites

A porous tooling system was selected for the processing of Graphite/PMR-15 Polyimide laminates in thickness up to 3.2 mm. (0.125 inch). This tool system must have a reasonable strength, permeability dimensional stability, and thermal conductivity to accomplish curing at 600 F and 200 psi and 200 psi autoclave temperature and pressure. A permeability measuring apparatus was constructed and permeability vs. casting water level determined to produce tools at three different permeability levels. On these tools, laminates of 5, 11, and 22 plies (.027, .060, and 0.121 inch) were produced and evaluated by ultrasonic, mechanical, and thermal tests to determine the effect of the tool permeability on the cured laminates. All tools produced acceptable laminates at 5 and 11 plies but only the highest permeability produced acceptable clear ultrasonic C-Scans. Recommendations are made for future investigations of design geometry, and strengthening techniques for porous ceramic tooling.

Smiser, L. W.↗
NASA NTRS1987

Strain energy release rates of composite interlaminar end-notch and mixed-mode fracture: A sublaminate/ply level analysis and a computer code

A computer code is presented for the sublaminate/ply level analysis of composite structures. This code is useful for obtaining stresses in regions affected by delaminations, transverse cracks, and discontinuities related to inherent fabrication anomalies, geometric configurations, and loading conditions. Particular attention is focussed on those layers or groups of layers (sublaminates) which are immediately affected by the inherent flaws. These layers are analyzed as homogeneous bodies in equilibrium and in isolation from the rest of the laminate. The theoretical model used to analyze the individual layers allows the relevant stresses and displacements near discontinuities to be represented in the form of pure exponential-decay-type functions which are selected to eliminate the exponential-precision-related difficulties in sublaminate/ply level analysis. Thus, sublaminate analysis can be conducted without any restriction on the maximum number of layers, delaminations, transverse cracks, or other types of discontinuities. In conjunction with the strain energy release rate (SERR) concept and composite micromechanics, this computational procedure is used to model select cases of end-notch and mixed-mode fracture specimens. The computed stresses are in good agreement with those from a three-dimensional finite element analysis. Also, SERRs compare well with limited available experimental data.

Valisetty, R. R.↗
NASA NTRS1993

A new clustering algorithm applicable to multispectral and polarimetric SAR images

We describe an application of a scale-space clustering algorithm to the classification of a multispectral and polarimetric SAR image of an agricultural site. After the initial polarimetric and radiometric calibration and noise cancellation, we extracted a 12-dimensional feature vector for each pixel from the scattering matrix. The clustering algorithm was able to partition a set of unlabeled feature vectors from 13 selected sites, each site corresponding to a distinct crop, into 13 clusters without any supervision. The cluster parameters were then used to classify the whole image. The classification map is much less noisy and more accurate than those obtained by hierarchical rules. Starting with every point as a cluster, the algorithm works by melting the system to produce a tree of clusters in the scale space. It can cluster data in any multidimensional space and is insensitive to variability in cluster densities, sizes and ellipsoidal shapes. This algorithm, more powerful than existing ones, may be useful for remote sensing for land use.

Wong, Yiu-Fai↗
NASA NTRS1990

Airframe structural optimization for maximum fatigue life

A methodology is outlined for optimization of airframe structures under dynamic constraints to maximize service life of specified fatigue-critical components. For practical airframe structures, this methodology describes the development of sensitivity analysis and computational procedures for constraints on the steady-state dynamic response displacements and stresses. Strain energy consideration is used for selection of structural members for modification. Development of a design model and its relation to an analysis model, as well as ways to reduce the dimensionality of the problem via approximation concepts, are described. This methodology is demonstrated using an elastic stick model for the MH-53J helicopter to show service life improvements of the hinge fold region.

D. P. Schrage↗
NASA NTRS1993

RAPID: The imaging energetic particle spectrometer on Cluster

The RAPID spectrometer for the Cluster mission, an advanced particle detector for the analysis of suprathermal plasma distributions in the energy range from 20 to 400 keV and from 2 keV/nuc to 1500 keV for electrons and ions, respectively, is presented. Novel detector concepts in combination with pinhole acceptance permit the measurement of angular distributions over a range of 180 deg in polar angle for either species. The detection principle for the ionic component is based on a two dimensional analysis of a particle's velocity and energy. Electrons are identified by the well known energy range relationship. The detection techniques are described and selected areas in geospace are used to highlight the scientific objectives of this investigation.

Wilken, B.↗
NASA NTRS1993

Cirrus microphysics observations made during FIRE 2: Small particles, high concentrations, and probe comparisons

Aircraft observations of cirrus cloud microphysics were made near Coffeyville, Kansas during Nov. and Dec. 1991. Cloud microphysics measurements were made using both a PMS 2DC probe and an ice particle replicator, both were mounted on the UND Citation aircraft. Intercomparison is made of the size, area, and ice mass spectra determined from these probes. The PMS 2DC undercounts particles for D less than 70 microns and the replicator oversizes particles for D greater than 150 microns, at least when column rosettes are encountered. High concentrations of particles with D less than 50 microns are noted in selected portions of the 22 Nov. 91 replicator data set. Relations between the maximum dimension of a crystal and its shadow area (known as area dimensional relationships) are computed from the PMS data. Area and mass dimensional relationships are used to give a simple analytical expression for computing the wavelength dependent absorption coefficient averaged over a size bin. Calculations based upon the replicator data show that crystals with D less than 50 microns contribute significantly to the solar extinction and infrared absorption coefficients during some time intervals.

Arnott, W. P.↗
NASA NTRS1997

Modern Airfoil Ice Accretions

This report presents results from the first icing tests performed in the Modem Airfoils program. Two airfoils have been subjected to icing tests in the NASA Lewis Icing Research Tunnel (IRT). Both airfoils were two dimensional airfoils; one was representative of a commercial transport airfoil while the other was representative of a business jet airfoil. The icing test conditions were selected from the FAR Appendix C envelopes. Effects on aerodynamic performance are presented including the effects of varying amounts of glaze ice as well as the effects of approximately the same amounts of glaze, mixed, and rime ice. Actual ice shapes obtained in these tests are also presented for these cases. In addition, comparisons are shown between ice shapes from the tests and ice shapes predicted by the computer code, LEWICE for similar conditions. Significant results from the tests are that relatively small amounts of ice can have nearly as much effect on airfoil lift coefficient as much greater amounts of ice and that glaze ice usually has a more detrimental effect than either rime or mixed ice. LEWICE predictions of ice shapes, in general, compared reasonably well with ice shapes obtained in the IRT, although differences in details of the ice shapes were observed.

Addy, Harold E., Jr.↗
NASA NTRS2003

An Integrated Magnetic Circuit Model and Finite Element Model Approach to Magnetic Bearing Design

A code for designing magnetic bearings is described. The code generates curves from magnetic circuit equations relating important bearing performance parameters. Bearing parameters selected from the curves by a designer to meet the requirements of a particular application are input directly by the code into a three-dimensional finite element analysis preprocessor. This means that a three-dimensional computer model of the bearing being developed is immediately available for viewing. The finite element model solution can be used to show areas of magnetic saturation and make more accurate predictions of the bearing load capacity, current stiffness, position stiffness, and inductance than the magnetic circuit equations did at the start of the design process. In summary, the code combines one-dimensional and three-dimensional modeling methods for designing magnetic bearings.

Provenza, Andrew J.↗
NASA NTRS2004

Polymeric blends for sensor and actuation dual functionality

The invention described herein supplies a new class of electroactive polymeric blend materials which offer both sensing and actuation dual functionality. The blend comprises two components, one component having a sensing capability and the other component having an actuating capability. These components should be co-processable and coexisting in a phase separated blend system. Specifically, the materials are blends of a sensing component selected from the group consisting of ferroelectric, piezoelectric, pyroelectric and photoelectric polymers and an actuating component that responds to an electric field in terms of dimensional change. Said actuating component includes, but is not limited to, electrostrictive graft elastomers, dielectric electroactive elastomers, liquid crystal electroactive elastomers and field responsive polymeric gels. The sensor functionality and actuation functionality are designed by tailoring the relative fraction of the two components. The temperature dependence of the piezoelectric response and the mechanical toughness of the dual functional blends are also tailored by the composition adjustment.

St. Clair, Terry L.↗
NASA NTRS2009

Progressive Band Selection

Progressive band selection (PBS) reduces spectral redundancy without significant loss of information, thereby reducing hyperspectral image data volume and processing time. Used onboard a spacecraft, it can also reduce image downlink time. PBS prioritizes an image's spectral bands according to priority scores that measure their significance to a specific application. Then it uses one of three methods to select an appropriate number of the most useful bands. Key challenges for PBS include selecting an appropriate criterion to generate band priority scores, and determining how many bands should be retained in the reduced image. The image's Virtual Dimensionality (VD), once computed, is a reasonable estimate of the latter. We describe the major design details of PBS and test PBS in a land classification experiment.

Fisher, Kevin↗
NASA NTRS2010

Workload: Measurement and Management

Poster: The workload research project has as its task to survey the available literature on: (1) workload measurement techniques; and (2) the effects of workload on operator performance. The first set of findings provides practitioners with a collection of simple-to-use workload measurement techniques along with characterizations of the kinds of tasks each technique has been shown reliably address. This allows design practitioners to select and use the most appropriate techniques for the task(s) at hand. The second set of findings provides practitioners with the guidance they need to design for appropriate kinds and amounts of workload across all tasks for which the operator is responsible. This guidance helps practitioners design systems and procedures that ensure appropriate levels of engagement across all tasks, and avoid designs and procedures that result in operator boredom, complacency, loss of awareness, undue levels of stress, or skill atrophy that can result from workload that distracts operators from the tasks they perform and monitor, workload levels that are too low, too high, or too consistent or predictable. Only those articles that were peer reviewed, long standing and generally accepted in the field, and applicable to a relevant range of conditions in a select domain of interest, in analogous "extreme" environments to those in space were included. In addition, all articles were reviewed and evaluated on uni-dimensional and multi-dimensional considerations. Casner & Gore also examined the notion of thresholds and the conditions that may benefit mostly from the various methodological approaches. Other considerations included whether the tools would be suitable for guiding a requirement-related and design-related question. An initial review of over 225 articles was conducted and entered into an EndNote database. The reference list included a range of conditions in the domain of interest (subjective/objective measures), the seminal works in workload, as well as summary works

Gore, Brian Francis↗
DOE OSTI2016

Advantages gained by Optimized ZIRLO and AXIOM PWR cladding materials

In support of industry's demands for higher performance cladding alloy materials, the Optimized ZIRLO alloy was developed as an evolutionary improvement of the ZIRLO alloy to obtain a significant improvement in corrosion performance and hydrogen pickup while maintaining the overall robust performance of ZIRLO alloy. Currently with operating experience in over 40 plants and burnup reaching over 70 GWd/MTU, a majority of the Westinghouse-fueled US PWR fleet, covering almost all Westinghouse fuel designs, has adopted full regions of Optimized ZIRLO cladding. Across all of these applications, Optimized ZIRLO cladding has demonstrated greatly improved corrosion performance and structural stability. These demonstrated improvements offer increased operational margin and flexibility, in support of industry trends toward increased core operating fuel duties and evolving regulatory requirements such as accident scenarios. Underpinning these benefits are the extensive post irradiation exam (PIE) data obtained from both pool-side and hot-cell exams for Optimized ZIRLO cladding. Building on the successes of Optimized ZIRLO cladding, and in recognition of increasingly challenging fuel management practices, and revised LOCA regulatory rules restricting cladding hydrogen content, AXIOM cladding is being rolled out for full lead test assembly irradiation. The AXIOM alloy, Westinghouse's next generation robust alloy targeting very high fuel duties, is designed to provide improved corrosion resistance, lower hydrogen pick-up, and lower creep and growth compared to current Westinghouse products. AXIOM cladding has been irradiated in a variety of reactors worldwide, including both commercial and test reactors. Extensive PIE data is available for various burnup levels, with leading rods approaching 75 GWd/MTU. The AXIOM composition was selected to ensure enhanced operating performance on multiple fronts, including the optimum combination of corrosion resistance and wear resistance, reduced hydrogen pick-up, improved dimensional stability, and robustness in aggressive coolant chemistry conditions. The present paper provides high burnup performance data, capturing the advantages gained by introducing Optimized ZIRLO and AXIOM alloy as PWR cladding materials. (authors)

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2022

Conceptual design of inverted core lead bismuth eutectic fast reactor for marine applications

The development of an inverted core fast reactor aims to generate 60 MWth for about 30 Effective Full Power Years without refueling. The reactor design is a transportable reactor using UO{sub 2} fuel and lead-bismuth-eutectic cooled designed for marine applications and is intended to improve the reactor performances compared to the normal core design: better condition for passive cooling system capability by lower core pressure drop, taking advantage of potential power uprate from the lower maximum fuel temperature. Systematic design processes are presented in this work: fuel pin geometry selection, fuel assembly (FA) design, and core design. A relationship between pressure drops, coolant velocity, maximum fuel temperature, coolant channel diameter, and fuel volume fraction was introduced in a single graph used as a tool to select fuel pin geometry. Fuel fabrication capability also took place in consideration of FA design which led to 7 holes per FA, and two-dimensional temperature distribution studies were also carried out. Core design processes including radial zoning, axial zoning, and core optimization were conducted using Monte Carlo code MCS, which is UNIST CORE laboratory in-house code. The current core design uses 3 fuel enrichment levels and 3 FA types to control the local power distribution and power shift during its lifetime. (authors)

21 SPECIFIC NUCLEAR REACTORS AND ASSOCIATED PLANTS↗
DOE OSTI2021

A multi-dimensional parametric study of variability in multi-phase flow dynamics during geologic CO 2 sequestration accelerated with machine learning

Successful geologic CO 2 storage projects depend on numerical simulations to predict reservoir performance during site selection, injection verification, and post-injection monitoring phases of the project. These numerical simulations solve non-linear sets of coupled partial differential equations, while accounting for multi-phase fluid dynamics on the basis of constitutive equations that are embedded into the solution scheme. As a consequence, individual simulations often require tens to hundreds of hours to complete on high-performance computing clusters. Moreover, laboratory experiments reveal that parametric functions for capillary pressure and relative permeability exhibit substantial variability, even within the same rock type. This combination of computational expense and wide-ranging parametric variability means that there remains substantial uncertainty in the behavior of multi-phase CO 2 -water systems, particularly in the context of feedbacks between relative permeability and capillary pressure. To bridge this knowledge gap, here we develop a novel workflow that utilizes physics-based numerical simulation to train an artificial neural network (ANN) emulator for interrogating the multivariate parameter space that governs both capillary pressure and relative permeability. With this approach, the ANN is trained to emulate both fluid pressure distribution and CO 2 saturation, which are then interrogated quantitatively to generate parametric response surface mappings with high-fidelity resolution. Results from this study initially show that capillary entry pressure is the dominant control on both CO 2 plume geometry and fluid pressure propagation when considering the combined effects of capillary pressure and relative permeability, particularly when phase interference is low and residual CO 2 saturation is high. Moreover, the ANN emulator provides tremendous computational speed-up by computing 2691 individual simulations in several minutes; whereas, the same simulation ensemble would have required ~3 years of simulation time using only physics-based simulation methods (25,000 times speed up).

58 GEOSCIENCES↗