Search NASA⌕ Search

SEARCH · Search NASA

Results for “Particle Size Distribution”

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 1,315 records · Page 73
All sourcesNASA NTRSDOE OSTI
DOE OSTI2015

Preparation of meta-stable phases of barium titanate by Sol-hydrothermal method

Two low-cost chemical methods of sol–gel and the hydrothermal process have been strategically combined to fabricate barium titanate (BaTiO{sub 3}) nanopowders. This method was tested for various synthesis temperatures (100 °C to 250 °C) employing barium dichloride (BaCl{sub 2}) and titanium tetrachloride (TiCl{sub 4}) as precursors and sodium hydroxide (NaOH) as mineralizer for synthesis of BaTiO{sub 3} nanopowders. The as-prepared BaTiO{sub 3} powders were investigated for structural characteristics using x-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The overall analysis indicates that the hydrothermal conditions create a gentle environment to promote the formation of crystalline phase directly from amorphous phase at the very low processing temperatures investigated. XRD analysis showed phase transitions from cubic - tetragonal - orthorhombic - rhombohedral with increasing synthesis temperature and calculated grain sizes were 34 – 38 nm (using the Scherrer formula). SEM and TEM analysis verified that the BaTiO{sub 3} nanopowders synthesized by this method were spherical in shape and about 114 - 170 nm in size. The particle distribution in both SEM and TEM shows that as the reaction temperature increases from 100 °C to 250 °C, the particles agglomerate. Selective area electron diffraction (SAED) shows that the particles are crystalline in nature. The study shows that choosing suitable precursor and optimizing pressure and temperature; different meta-stable (ferroelectric) phases of undoped BaTiO{sub 3} nanopowders can be stabilized by the sol-hydrothermal method.

36 MATERIALS SCIENCE↗
DOE OSTI2015

Temporally and Spatially Resolved x-ray Fluorescence Measurements of in-situ Drug Concentration in Metered-Dose Inhaler Sprays

Drug concentration measurements in MDI sprays are typically performed using particle filtration or laser scattering. These techniques are ineffective in proximity to the nozzle, making it difficult to determine how factors such as nozzle design will affect the precipitation of co-solvent droplets in solution-based MDIs, and the final particle distribution. In optical measurements, scattering from the constituents is difficult to separate. We present a novel technique to directly measure drug distribution. A focused x-ray beam was used to stimulate x-ray fluorescence from the bromine in a solution containing 85% HFA, 15% ethanol co-solvent, and 1 / IPBr. Instantaneous concentration measurements were obtained with 1 ms temporal resolution and 5 spatial resolution, providing information in a region that is inaccessible to many other diagnostics. The drug remains homogeneously mixed over time, but was found to be higher at the centerline than at the periphery. This may have implications for oropharyngeal deposition in vivo. Measurements in the dynamic, turbulent region of MDIs allow us to understand the physical links between formulation, inspiration, and geometry on final particle size and distribution. This will ultimately lead to a better understanding of how MDI design can be improved to enhance respirable fraction.

fluorescence↗
DOE OSTI2016

HISCALE: Best Estimate Aerosol Size Distribution by airborne measurements

The data were collected during the Holistic Interactions of Shallow Clouds, Aerosols, and Land-Ecosystems (HI-SCALE, http://www.arm.gov/campaigns/aaf2016hiscale) field campaign as part of ARM Aerial Facility (AAF) deployment. The ARM Aerial Facility Gulfstream-1 was deployed at Bartlesville, OK, for two intensive observation periods from April 23 through May 22 and from August 27 through September 25, 2016. The G-1 aircraft performed 38 (17+21) research flights over the ARM Southern Great Plains (SGP) Atmospheric Observatory to measure atmospheric turbulence, cloud water content and drop size distributions, aerosol precursor gases, aerosol chemical composition and size distributions. The current data set presents Best Estimate Aerosol Size Distribution: a merged aerosol size distribution composed of the data from 4 sensors: two aerosol spectrometers (FIMS and PCASP) and two cloud probes (CAS and FCDP). Aerosol chemical composition, measured by the Aerodyne High Resolution Time-of-Flight Aerosol Mass Spectrometer (HR-ToF-AMS), was used to estimate aerosol refractive index (RI) required for correction of the equivalent optical size into geometric size

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2017

ACE-ENA: Best Estimate Aerosol Size Distribution by airborne measurements

These data were collected during the Aerosol and Cloud Experiments in the Eastern North Atlantic field campaign as part of ARM Aerial Facility deployment (ACE-ENA, https://www.arm.gov/research/campaigns/aaf2017ace-ena). The ARM Aerial Facility Gulfstream-1 was deployed at Lajes Air Base (IATA: TER, ICAO: LPLA), on Terceira Island in the Azores, Portugal, for the two Intensive Observation Periods from June 20 through July 22, 2017 (IOP#1) and from January 11 through February 22, 2018 (IOP#2). The G-1 aircraft performed 20+19 research flights over the ARM Eastern North Atlantic (ENA) site and Atlantic Ocean to measure atmospheric turbulence, cloud water content and drop size distributions, aerosol precursor gases, aerosol chemical composition and size distributions. The current data set presents Best Estimate Aerosol Size Distribution: a merged aerosol size distribution composed of the data from 4 sensors: two aerosol spectrometers (FIMS and PCASP) and two cloud probes (CAS and FCDP). Aerosol chemical composition, measured by the Aerodyne High Resolution Time-of-Flight Aerosol Mass Spectrometer (HR-ToF-AMS), was used to estimate aerosol refractive index (RI) required for correction of the equivalent optical size into geometric size.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2013

Synthesis and characterization of thermally stable large-pore mesoporous nanocrystallineanatase

Thermally stable mesoporous nanocrystalline TiO{sub 2} with a pure anatase structure was obtained by sol–gel synthesis (in combination with hydrothermal treatment) using titanium tetrabutoxide and dibenzo-18-crown-6 as a structure-directing agent in presence of surfactant and/or La{sup 3+} ions additives. Nanocrystalline TiO{sub 2} demonstrates various textures with a well-defined spherical morphology (micro- and nanospheres), a crystallite size of no greater than 10 nm (XRD), and a narrow pore size distribution. Spherical particles of micrometer scale in the presence of La{sup 3+} ions do not form. TiO{sub 2} calcined (at 500 °C) after hydrothermal treatment (at 175 °C) has a significantly more developed porous structure as compared with TiO{sub 2} which was not treated hydrothermally. For example, specific surface area amounts 137 m{sup 2} g{sup −1} and 69 m{sup 2} g{sup −1}, pore volume 0.98 cm{sup 3} g{sup −1} and 0.21 cm{sup 3} g{sup −1}, pore diameter 17.5 nm and 12.5 nm respectively for samples hydrothermally treated and not treated. - Graphical abstract: Large-pore mesoporous nanocristalline anatase. Highlights: ► Large-pore mesoporous nanocrystalline TiO{sub 2} was obtained by sol–gel synthesis. ► Crown ether was used as template in presence of surfactant and/or La{sup 3+} ions. ► Anatase (crystalline size<11 nm) is the only crystalline phase present in TiO{sub 2}. ► TiO{sub 2} shows well-defined homogeneous spherical morphology (micro- and nano-spheres)

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2025

New Particle Formation Event Dataset at the Southern Great Plains (SGP) Observatory from 2018 to 2023

This data set contains observations of new particle formation (NPF) events collected at the U.S. Department of Energy’s Atmospheric Radiation Measurement (ARM) Southern Great Plains (SGP) observatory from 2018 to 2023. Measurements include particle number size distributions, radiance measurements, and associated meteorological variables from onsite instrumentation relevant for identifying and characterizing NPF events. Events were identified using standardized criteria and documented to support investigations of aerosol nucleation, growth dynamics, and their interactions with local atmospheric conditions. The data set provides a multi-year record that enables evaluation of seasonal and interannual variability in NPF occurrence and intensity at a mid-continental site. These data are intended to support studies of aerosol-cloud-climate interactions and model evaluation within both ARM and the broader atmospheric science community. More information can be found within the README_NPF_SGP_2018_2023.docx file.

event↗
DOE OSTI2021

Microscopic ejecta measurements from hypervelocity impacts on aluminum and powdered regolith targets

Meteoroids and space debris pose a two-fold threat to spacecraft due to the risk of both mechanical damage from the impact and electrical damage from the impact-generated plasma, which produces electromagnetic emissions. Analysis of impact products, however, has the potential to provide useful information about planetary rings and small solar system bodies, such as asteroids and comets. Understanding the plasma dynamics and radiation mechanism is essential to addressing the impact threat and extracting science data from impacts. Charge attachment to condensed-phase debris may lead to a dusty plasma under certain conditions, so interpreting hypervelocity impacts requires knowledge of both the nature of the plasma and of the ejecta. We address the latter with measurements of the microscopic ejecta distribution produced by light gas gun impacts on solid aluminum and powdered regolith simulant targets. We examine both the size and shape of the ejecta using thin-film witness plates and find that the size distributions of microscopic ejecta follow power laws. Observations from the powdered regolith simulant match well with disruption experiments of solid basalt, while measurements from the aluminum impacts diverge from extrapolations based on studies of macroscopic debris. Analysis of the ejecta shape shows a transition from smooth to irregularly shaped ejecta at the material grain size, and the shape of debris may provide insight on the phase of the ejected material. Finally, based on our results, we predict a significant number of secondary impacts on plasma sensors due to ejecta, even at considerable distance from the target, supporting the hypothesis that charged dust affects plasma measurements in the ejecta curtain.

42 ENGINEERING↗
DOE OSTI2021

Solid particulate mass and number from ducted fuel injection in an optically accessible diesel engine in skip-fired operation

Ducted fuel injection (DFI) is a new combustion strategy that has been shown to significantly attenuate soot formation in diesel engines. While previous studies have used optical diagnostics and optical filter smoke number methods to show that DFI reduces in-cylinder soot formation and engine-out soot emissions, respectively, this is the first study to measure solid particle number (PN) emissions in addition to particle mass (PM). Furthermore, this study quantitatively evaluates the use of transient particle instruments for measuring particles from skip-fired operation in an optical single cylinder research engine (SCRE). Engine-out PN was measured using an engine exhaust particle sizer following a catalytic stripper, and PM was measured using a photoacoustic analyzer. The study improves on earlier preliminary emissions studies by clearly showing that DFI reduces overall PM by 76%–79% and PN for particles larger than 23 nm by 77% relative to conventional diesel combustion at a 1200-rpm, 13.3-bar gross indicated mean effective pressure operating condition. The degree of engine-out PM reduction with DFI was similar across both particulate measurement instruments used in the work. Through the use of bimodal distribution fitting, DFI was also shown to reduce the geometric mean diameter of accumulation mode particles by 26%, similar to the effects of increased injection pressure in conventional diesel combustion systems. This work clearly shows the significant solid particulate matter reductions enabled by DFI while also demonstrating that engine-out PN can be accurately measured from an optical SCRE operating in a skip-fired mode. Based on these results, it is believed that DFI has the potential to enable fuel savings when implemented in multi-cylinder engines, both by lowering the required frequency of active diesel particulate filter regeneration, and by reducing the backpressure imposed by exhaust filtration systems.

33 ADVANCED PROPULSION SYSTEMS↗
NASA NTRS2011

Evaluation of an Electrostatic Dust Removal System with Potential Application in Next-Step Fusion Devices

The ability to manage inventories of carbon, tritium, and high-Z elements in fusion plasmas depends on means for effective dust removal. A dust conveyor, based on a moving electrostatic potential well, was tested with particles of tungsten, carbon, glass and sand. A digital microscope imaged a representative portion of the conveyor, and dust particle size and volume distributions were derived before and after operation. About 10 cu mm volume of carbon and tungsten particles were moved in under 5 seconds. The highest driving amplitude tested of 3 kV was the most effective. The optimal driving frequency was 210 Hz (maximum tested) for tungsten particles, decreasing to below 60 Hz for the larger sand particles. Measurements of particle size and volume distributions after 10 and 100 cycles show the breaking apart of agglomerated carbon, and the change in particle distribution over short timescales 1 s).

Friesen, F. Q. L.↗
DOE OSTI2024

Segmentation of RDX and TNT in X‐Ray Computed Tomography Reconstructions of Melt‐Cast Explosives

ABSTRACT Three‐dimensional mesoscale characterization of heterogeneous melt‐cast high explosives is challenging because of the difficulty differentiating binder from explosive crystals: two functionally different materials which are typically similar in density by design. Here, we report an algorithm which can differentiate hexahydro‐1,3,5‐trinitro‐1,3,5‐triazine (RDX) from 2,4,6‐trinitrotoluene (TNT) in x‐ray computed tomography (CT) volumes with tens of microns resolution. This method allows us to quantify RDX/TNT content, porosity, and RDX domain size. We calibrated the segmentation algorithm using simulated x‐ray CT volumes containing object models of RDX crystals within a TNT matrix. We then segmented and analyzed CT data for Composition B (Comp B), a 60/40 RDX/TNT mixture, and Cyclotol, a 75/25 RDX/TNT mixture. We examined melt‐cast samples fabricated with 100% theoretical maximum density (TMD) and 85% TMD. For the 100% TMD Comp B and Cyclotol samples, the RDX content values calculated by segmentation were 3% and 9% lower, respectively, than the values measured by high‐performance liquid chromatography on material from the same synthesis lots. This result is consistent with the expected underreporting of RDX content resulting from x‐ray CT resolution limits on RDX particles with diameters smaller than 25 µm. The 85% TMD samples were less accurately segmented with our algorithm due to the confounding presence of voids.

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

Exposure to traffic-generated air pollutants mediates alterations in brain microvascular integrity in wildtype mice on a high-fat diet

Highlights: • Exposure to vehicle emissions alters BBB permeability in high-fat-fed C57BL/6 mice. • Vehicle emission exposures exacerbate oxLDL levels in animals on a high-fat diet. • Alterations in neurovascular integrity are associated with increased oxLDL receptors. • Exposures result in reduced TJ protein expression associated with MMP-2/9 activity. Air pollution-exposure is associated with detrimental outcomes in the central nervous system (CNS) such as cerebrovascular disorders, including stroke, and neurodegenerative diseases. While the mechanisms of these CNS-related outcomes involved have not been fully elucidated, exposure to traffic-generated air pollutants has been associated with altered blood brain barrier (BBB) integrity and permeability. The current study investigated whether inhalation exposure to mixed vehicle emissions (MVE) alters cerebral microvascular integrity in healthy 3 mo old C57BL/6 mice, as well as whether exposure-mediated effects were exacerbated by a high-fat (HF) vs. low-fat (LF) diet. Mice on each diet were randomly assigned to be exposed to either filtered air (FA) or MVE [100 PM/m{sup 3} vehicle emissions mixture: 30 µg PM/m{sup 3} gasoline engine + 70 µg PM/m{sup 3} diesel engine emissions; median size ~ 60 nm; particle mass size distribution median of ~ 1 µm (range: < 0.5–20 µm)] for 6 h/d, 7d/wk, for 30d. Using sodium fluorescein as a tracer, we observed a significant increase in BBB permeability in both HF + MVE exposed and HF + FA animals, compared to LF + FA controls. Exposure to HF + MVE also led to a significant increase plasma ox-LDL and ox-LDL scavenger receptors (LOX-1 and CD-36) expression in the cerebral vasculature. Histological analysis revealed decreased expression of TJ protein, claudin-5, associated with increased matrix metalloproteinase (MMP)−9 activity and oxidative stress in the cerebral vasculature of HF + MVE mice, compared to LF + MVE. Such findings indicate that inhalation exposure to traffic-generated pollutants, coupled with a HF diet, results in altered BBB integrity and increased ox-LDL signaling in the cerebral vasculature in a wildtype animal model.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2018

A semi-empirical NO x model for LES in pulverized coal air-staged combustion

Numerical simulation of pulverized coal combustion with the large eddy simulation (LES) method can provides important instructions on the design optimization of boilers. Because of its huge computational cost, a simple but reliable NO x prediction model is required in LES. Through the air-staged combustion experiments of six kinds of coals which conducted in an electric heated down-fired furnace (DFF), the relationship between NO x reduction and CO+H 2 generation in the fuel-rich zone was identified. Based on this observation, a semi-empirical modeling strategy was proposed: instead of CHi which is difficult to calculate, the concentration of CO+H 2 is used to quantify NO homogeneous reduction. An integrated NO x prediction model was proposed and implemented into LES simulation. Here, the results proved the new model can accurately predict different NO x evolution characteristics under various conditions. Furthermore, the comparison indicated the LES method performs better on NO x prediction than the RANS method, especially in the area where the turbulent fluctuation is relatively stronger.

97 MATHEMATICS AND COMPUTING↗
DOE OSTI2015

Sol–gel method as a way of carbonyl iron powder surface modification for interaction improvement

This article presents a method for modification of carbonyl iron particles’ surface (CIP), (d{sub 50}=4–9 µm) by silica coatings obtained using the sol–gel method. Reaction parameters were determined to obtain dry magnetic powder with homogeneous silica coatings without further processing and without any by-product in the solid or liquid phase. This approach is new among the commonly used methods of silica coating of iron particles. No attempt has been made to cover a carbonyl iron surface by silica in a waste-free method, up to date. In the current work two different silica core/shell structures were made by the sol–gel process, based on different silica precursors: tetraethoxy-silane (TEOS) and tetramethoxy-silane (TMOS). The dependence between the synthesis procedure and thickness of silica shell covering carbonyl iron particles has been described. Surface morphology of the modified magnetic particles and the coating thickness were characterized with the use of scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Determination of the physicochemical structure of the obtained materials was performed by the energy-dispersive X-ray spectroscope (EDS), and the infrared technique (IR). The surface composition was analyzed using X-ray photoelectron spectroscopy (XPS). Additionally, distribution of particle size was measured using light microscopy. The new, efficient process of covering micro-size CIP with a nanometric silica layer was shown. Results of a performed analysis confirm the effectiveness of the presented method. - Highlights: • Proper covering CIP by sol–gel silica layer avoids agglomeration. • A new solid waste-free method of CIP coating is proposed. • Examination of the properties of modified CIP in depends on washing process. • Coatings on CIP particles doesn’t change the magnetic properties of particles.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2014

Comparison of structural and electrical properties of Co{sup 2+}doped Mn-Zn soft nano ferrites prepared via coprecipitation and hydrothermal methods

Graphical abstract: - Highlights: • Coprecipitation and hydrothermal synthesis of Co{sup 2+} doped Mn-Zn ferrites. • Dielectric measurements at 3 MHz and 1 GHz frequencies. • Enhanced DC electrical resistivity for samples prepared from hydrothermal technique. • Impedance studies for the prepared samples showing major contribution due to grains. - Abstract: A series of Co doped Mn-Zn ferrites compounds with the formula Mn{sub 0.5}Zn{sub 0.5−x}Co{sub x}Fe{sub 2}O{sub 4} (x = 0, 0.15, 0.25, 0.35 and 0.50) were successfully synthesized by polyethylene glycol-assisted coprecipitation and hydrothermal methods. The structural characterization of the samples was done using X-ray diffraction (XRD), scanning electron microscopy (SEM), atomic force microscopy (AFM) and Fourier transform infrared spectroscopy (FTIR). All the samples found to have cubic spinel structure. The average crystallite size of all nanoparticles were estimated using Scherrer's formula and found to lie between 10 and 25 ± 3 nm with small size distribution of particles prepared by hydrothermal method. The FTIR spectrum showed two absorption bands of tetrahedral and octahedral metal-oxygen sites. DC electrical resistivity varied from 4.12 × 10{sup 7} to 8.32 × 10{sup 10} ohm cm with cobalt doping. The dielectric measurements were performed from 20 Hz to 3 MHz and from 1 MHz to 1 GHz frequency ranges. The value of dielectric constant (ε′) varies from 15.54 to 106.25 (1 MHz) and 6.73–16.48 (1 GHz) for all the samples at room temperature. Impedance spectroscopy was carried out from 20 Hz to 3 MHz, at room temperature to study the grains and grain boundaries effect.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Nanopore networks in colloidal silica assemblies characterized by XCT for confined fluid flow modeling

Fluid flow through nanopore structures has exhibited different behavior than that described by Darcy's law, derived from pore networks of micrometer scale. Here, pressure assemblies of colloidal silica spheres of specified diameters from 94 to 620 nanometers were prepared as model nano-porous media. The smaller silica spheres tended to form random packing, but some substantial ordering was found in the packing of the larger silica spheres. X-ray computed tomography (XCT), with a voxel resolution of 16 nm, was used to characterize the nanopore networks. The porosity of the Nano-XCT pore network (34%) was less than the total porosity of the assemblies as determined by X-ray attenuation (52%), possibly due to the limits of voxel resolution during segmentation. Fluid flow in the nanopore networks was simulated using the single-phase Lattice Boltzmann Method, and the simulated permeability was compared with the empirical and experimental values. Based on our characterization, although a well-ordered packing of silica spheres was not achieved, it was found that the nanopore networks in the colloidal silica assemblies had pore size distributions corresponding to the particle sizes. The simulated permeability was less than the experimental measurement for water flow, but the complex packing of silica spheres and surface chemistry issues need to be considered in future research.

02 PETROLEUM↗
DOE OSTI2016

Small Angle X-ray Scattering for Nanoparticle Research

X-ray scattering is a structural characterization tool that has impacted diverse fields of study. It is unique in its ability to examine materials in real time and under realistic sample environments, enabling researchers to understand morphology at nanometer and ångström length scales using complementary small and wide angle X-ray scattering (SAXS, WAXS), respectively. Herein, we focus on the use of SAXS to examine nanoscale particulate systems. We provide a theoretical foundation for X-ray scattering, considering both form factor and structure factor, as well as the use of correlation functions, which may be used to determine a particle’s size, size distribution, shape, and organization into hierarchal structures. The theory is expanded upon with contemporary use cases. Both transmission and reflection (grazing incidence) geometries are addressed, as well the combination of SAXS with other X-ray and non-X ray characterization tools. Furthermore, we conclude with an examination of several key areas of research where X-rays scattering has played a pivotal role, including in situ nanoparticle synthesis, nanoparticle assembly, and in operando studies of catalysts and energy storage materials. Throughout this review we highlight the unique capabilities of X-ray scattering for structural characterization of materials in their native environment.

36 MATERIALS SCIENCE↗