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At least 1,459 records · Page 81
All sourcesNASA NTRSDOE OSTI
DOE OSTI2016

Particle Resuspension Simulation Capability to Substantiate DOE-HDBK-3010 Data

The data provided in the U.S. Department of Energy (DOE) Handbook, DOE-HDBK-3010 provides data such as airborne release fractions and respirable fractions which are widely used in safety analysis and facility design. These fractions are often used as conservative bounds, despite the fact that the original data may have been obtained at a different scale or in a different configuration than the end application. The use of computational techniques to augment these data can be used to extend laboratory-scale data applicability to facility-scale decisions. Our prior report described an approach using Sandia National Laboratories (SNL) computer codes to simulate particle releases from various accident scenarios. The relevant physics controlling the particle resuspension phenomena can be highly problem-dependent. They can include surface tension for particles or surfaces with liquid present, van der Waals forces for small particles, electrostatic forces for charged particles, and mechanical interactions with surface features larger than the particles sizes. The complexity of this phenomenon and recent developments have been described in a recent review by Henry and Minier. (authors)

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2014

Ice Nucleation of Bare and Sulfuric Acid-coated Mineral Dust Particles and Implication for Cloud Properties

Ice nucleation properties of different dust species coated with soluble material are not well understood. We determined the ice nucleation ability of bare and sulfuric acid coated mineral dust particles as a function of temperature (-25 to -35 deg C) and relative humidity with respect to water (RHw). Five different mineral dust species: Arizona test dust (ATD), illite, montmorillonite, quartz and kaolinite were dry dispersed and size-selected at 150 nm and exposed to sulfuric acid vapors in the coating apparatus. The condensed sulfuric acid soluble mass fraction per particle was estimated from the cloud condensation nuclei activated fraction measurements. The fraction of dust particles nucleating ice at various temperatures and RHw was determined using a compact ice chamber. In water-subsaturated conditions, compared to bare dust particles, we found that only coated ATD particles showed suppression of ice nucleation ability while other four dust species did not showed the effect of coating on the fraction of particles nucleating ice. The results suggest that interactions between the dust surface and sulfuric acid vapor are important, such that interactions may or may not modify the surface via chemical reactions with sulfuric acid. At water-supersaturated conditions we did not observed the effect of coating, i.e. the bare and coated dust particles had similar ice nucleation behavior.

Kulkarni, Gourihar R.↗
DOE OSTI2013

Chemical Characterization of Individual Particles and Residuals of Cloud Droplets and Ice Crystals Collected On Board Research Aircraft in the ISDAC 2008 Study

Although it has been shown that size of atmospheric particles has a direct correlation with their ability to act as cloud droplet and ice nuclei, the influence of composition of freshly emitted and aged particles in nucleation processes is poorly understood. In this work we combine data from field measurements of ice nucleation with chemical imaging of the sampled particles to link aerosol composition with ice nucleation ability. Field measurements and sampling were conducted during the Indirect and Semidirect Aerosols Campaign (ISDAC) over Barrow, Alaska, in the springtime of 2008. In-situ ice nucleation measurements were conducted using a Continuous Flow Diffusion Chamber (CFDC). Measured number concentrations of ice nuclei (IN) varied from frequent values of 0.01 per liter to more than 10 per liter. Residuals of airborne droplets and ice crystals were collected through a counterflow virtual impactor (CVI). The compositions of individual atmospheric particles and the residuals were studied using Computer Controlled Scanning Electron Microscopy with Energy Dispersive X-ray analysis (CCSEM/EDX) and Scanning Transmission X-ray Microscopy coupled with Near Edge X-ray Absorption Fine Structure spectroscopy (STXM/NEXAFS). Chemical analysis of cloud particle residuals collected during an episode of high ice nucleation suggests that both size and composition may influence aerosol's ability to act as IN. The STXM/NEXAFS chemical composition maps of individual residuals have characteristic structures of either inorganic or black carbon cores coated by organic materials. In a separate flight, particle samples from a biomass burning plume were collected. Although it has previously been suggested that episodes of biomass burning contribute to increased numbers of highly effective ice nuclei, in this episode we observed that only a small fraction were effective ice nuclei. Most of the particles from the biomass plume episode were smaller in size and were composed of homogeneous organic material without identifiable cores.

Environmental Molecular Sciences Laboratory↗
DOE OSTI2019

X-ray Phase Contrast Imaging of the Impact of a Single HMX Particle in a Polymeric Matrix

A thorough understanding of the mechanisms by which high explosives (HEs) are shock initiated, especially at the particle scale, is still in demand. One approach to explain shock initiation phenomenon is hot spot theory, which suggests that distributed energy in energetic material is localized due to shock or impact to generate the high temperatures for ignition. Here, we focus on the impact response of a HE polycrystalline particle, specifically HMX, in a polymer matrix. This represents a simplified analog of a traditional polymer-bonded explosive (PBX) formulation. A light gas gun, together with high-speed x-ray phase contrast imaging (PCI), was used to study the impact response of a single particle of production-grade HMX in a Sylgard-184® matrix. The high-speed x-ray PCI allows for real-time visualization of HE particle behavior. The experiments revealed that, at impact velocities of ~ 200 m s -1 , the energetic particle was cracked and crushed. When the impact velocity was increased to 445 m s -1 , a significant volume expansion of the particle was observed. This volume expansion is considered to be the result of chemical reaction within the HE particle.

42 ENGINEERING↗
DOE OSTI2020

X-ray Phase Contrast Imaging of the Impact of Multiple HMX Particles in a Polymeric Matrix

The initiation of high explosives (HEs) under shock loading lacks a comprehensive understanding: particularly at the particle scale. One common explanation is the hot spot theory, which suggests that energy in the material resulting from the impact event is localized in a small area causing an increase in temperature that can lead to ignition. This study focuses on the response of HMX particles (a common HE) within a polymer matrix (Sylgard-184 (R)), a simplified example of a polymer-bound explosive (PBX). These PBXs consist of multiple HMX particles in a single polymer-bound sample. A light gas gun was used to load the samples at impact velocities above 400 m/s. The impact events were visualized using X-ray phase-contrast imaging (PCI) allowing real-time observation of the impact event. The experiment used two different types of samples (multi-particle and two crystals) and found evidence of cracking and debonding in both sample types. Additionally, it was found that the multiple particle samples showed similar evidence of damage at lower velocities than that of single particle samples. This is an expected result as the multiple particles add additional interfaces for stress concentration and frictional heating.

42 ENGINEERING↗
DOE OSTI2022

$T\overline{T}$ deformations and the width of fundamental particles

We provide a simple geometric meaning for deformations of so-called $T\overline{T}$ type in relativistic and non-relativistic systems. Deformations by the cross products of energy and momentum currents in integrable quantum field theories are known to modify the thermodynamic Bethe ansatz equations by a “CDD factor”. In turn, CDD factors may be interpreted as additional, fixed shifts incurred in scattering processes: a finite width added to the fundamental particles (or, if negative, to the free space between them). We suggest that this physical effect is a universal way of understanding $T\overline{T}$ deformations, both in classical and quantum systems. We first show this in non-relativistic systems, with particle conservation and translation invariance, using the deformation formed out of the densities and currents of particles and momentum. This holds at the level of the equations of motion, and for any interaction potential, integrable or not. We then argue, and show by similar techniques in free relativistic particle systems, that $T\overline{T}$ deformations of relativistic systems produce the equivalent phenomenon, accounting for length contractions. We also show that, in both the relativistic and non-relativistic cases, the width of particles is equivalent to a state-dependent change of metric, where the distance function discounts the particles’ widths, or counts the additional free space. This generalises and explains the known field-dependent coordinate change describing $T\overline{T}$ deformations. The results connect such deformations with generalised hydrodynamics, where the relations between scattering shifts, widths of particles and state-dependent changes of metric have been established.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2021

Ionic conductivity optimization of composite polymer electrolytes through filler particle chemical modification

The addition of filler particles to polymer electrolytes is known to increment their ionic conductivity (IC). A detailed understanding of how the interactions between the constituent materials are responsible for the enhancement remains to be developed. A significant contribution is ascribed to an increment of the polymer amorphous fraction, induced by the fillers, resulting in the formation of higher ionic conductivity channels in the polymer matrix. However, the dependence of IC on the particle weight load and its composition on the polymer morphology is not fully understood. This work investigates Li-ion transport in composite polymer electrolytes (CPE) comprising Bi-doped LLZO particles embedded in PEO:LiTFSI matrixes. We find that the IC optimizes for very low particle weight loads (5-10%) and that both its magnitude and the load are required, strongly dependent on the garnet particle composition. Based on structural characterization results and electrochemical impedance spectroscopy, a mechanism is proposed to explain these findings. It is suggested that the Li-molar content in the garnet particle controls its interactions with the polymer matrix, resulting at the optimum loads reported, in the formation of high ionic conductivity channels. We propose that filler particle chemical manipulation of the polymer morphology is a promising avenue for the further development of composite polymer electrolytes.

bismuth↗
DOE OSTI2015

Improving aluminum particle reactivity by annealing and quenching treatments: Synchrotron X-ray diffraction analysis of strain

In bulk material processing, annealing and quenching metals such as aluminum (Al) can improve mechanical properties. On a single particle level, affecting mechanical properties may also affect Al particle reactivity. Our study examines the effect of annealing and quenching on the strain of Al particles and the corresponding reactivity of aluminum and copper oxide (CuO) composites. Micron-sized Al particles were annealed and quenched according to treatments designed to affect Al mechanical properties. Furthermore, synchrotron X-ray diffraction (XRD) analysis of the particles reveals that thermal treatment increased the dilatational strain of the aluminum-core, alumina-shell particles. Flame propagation experiments also show thermal treatments effect reactivity when combined with CuO. An effective annealing and quenching treatment for increasing aluminum reactivity was identified. Our results show that altering the mechanical properties of Al particles affects their reactivity.

36 MATERIALS SCIENCE↗
DOE OSTI2015

Entanglement and the process of measuring the position of a quantum particle

We explore the entanglement-related features exhibited by the dynamics of a composite quantum system consisting of a particle and an apparatus (here referred to as the “pointer”) that measures the position of the particle. We consider measurements of finite duration, and also the limit case of instantaneous measurements. We investigate the time evolution of the quantum entanglement between the particle and the pointer, with special emphasis on the final entanglement associated with the limit case of an impulsive interaction. We consider entanglement indicators based on the expectation values of an appropriate family of observables, and also an entanglement measure computed on particular exact analytical solutions of the particle–pointer Schrödinger equation. The general behavior exhibited by the entanglement indicators is consistent with that shown by the entanglement measure evaluated on particular analytical solutions of the Schrödinger equation. In the limit of instantaneous measurements the system’s entanglement dynamics corresponds to that of an ideal quantum measurement process. On the contrary, we show that the entanglement evolution corresponding to measurements of finite duration departs in important ways from the behavior associated with ideal measurements. In particular, highly localized initial states of the particle lead to highly entangled final states of the particle–pointer system. This indicates that the above mentioned initial states, in spite of having an arbitrarily small position uncertainty, are not left unchanged by a finite-duration position measurement process. - Highlights: • We explore entanglement features of a quantum position measurement. • We consider instantaneous and finite-duration measurements. • We evaluate the entanglement of exact time-dependent particle–pointer states.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2015

Evaluation of the surface roughness effect on suspended particle deposition near unpaved roads

The downwind transport and deposition of suspended dust raised by a vehicle driving on unpaved roads was studied for four differently vegetated surfaces in the USA states of Kansas and Washington, and one barren surface in Nevada. A 10 m high tower adjacent to the source (z10 m downwind) and an array of multi-channel optical particle counters at three positions downwind of the source measured the flux of particles and the particle size distribution in the advecting dust plumes in the horizontal and vertical directions. Aerodynamic parameters such as friction velocity (u*) and surface roughness length (z0) were calculated from wind speed measurements made on the tower. Particle number concentration, PM10 mass exhibited an exponential decay along the direction of transport. Coarse particles accounted for z95% of the PM10 mass, at least to a downwind distance of 200 m from the source. PM10 removed by deposition was found to increase with increasing particle size and increasing surface roughness under similar moderate wind speed conditions. The surface of dense, long grass (1.2 m high and complete surface cover) had the greatest reduction of PM10 among the five surfaces tested due to deposition induced by turbulence effects created by the rougher surface and by enhanced particle impaction/ interception effects to the grass blades.

Zhu, Dongzi↗
DOE OSTI2018

Viewing internal bubbling and microexplosions in combusting metal particles via x-ray phase contrast imaging

The combustion performance of metal particles for explosives, propellants, pyrotechnics, and bio-agent defeat can be optimized by controlling the chemistry, size, and coatings of the particles. Many pure and composite metal fuels used in these applications have been observed to microexplode during combustion. This causes particles to fragment, revealing fresh surfaces, which may enhance burn rates and efficiencies. Despite these potential benefits, few have attempted to control the bubbling and the microexplosion of metal powders as they combust in molten states. Here, we choose Al:Zr composite powders as a representative system to study bubbling and microexplosions and to identify active mechanisms. Using synchrotron x-rays and phase contrast imaging, we observe molten metal particles of various sizes as they burn in air at temperatures ranging from 2700 to 3500 K. We characterize bubble nucleation and growth in the interior of the particles during the combustion process, and we identify heterogeneous nucleation, slow growth and coalescence of bubbles, as well as rapid bubble growth leading to microexplosions. Bubble growth rates and Laplace pressures are calculated, and we find that during slow expansion growth rates are similar to classical predictions of bubble growth in superheated liquids. For rapid expansions we find that a critical growth rate of ~0.5m s –1 , independent of the initial particle size, is necessary to enable microexplosions. We calculate the rate of gas generation that is needed to enable this growth and we conclude that nitrogen is the gas most likely driving rapid bubble growth and fragmentation. Furthermore these results provide the first in situ observations of the mechanisms that control bubbling and microexplosions during the combustion of metal particles.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Toxicological assessment of mesoporous silica particles in the nematode Caenorhabditis elegans

Highlights: • C. elegans is a suitable in vivo model to evaluate the toxicity of MSPs. • MSPs are well-ingested and located along the gastrointestinal tract of C. elegans. • Evaluation of lifespan and healthspan demonstrate the safety of micro-sized MSPs. • Nano-sized particles have a negative impact on C. elegans lifespan and healthspan. • Functionalization of nanoparticles’ surface reduces their toxicity in C. elegans. Here we report the toxicological evaluation of mesoporous silica particles (MSPs) in the nematode C. elegans. Specifically, we have investigated the effect of bare micro- (M0) and nano-sized (N0) MSPs, and their corresponding functionalized particles with a starch derivative (Glu-N) (M1 and N1, respectively) on C. elegans ageing parameters. The toxicity of MSPs, their impact on C. elegans lifespan, movement capacity, progeny and ability to survive upon exposure to acute oxidative stress were assessed. This study demonstrated that both size particles assayed (M0 and N0), labeled with rhodamine and monitored through fluorescence microscopy, are ingested by the nematode. Moreover, toxicity assays indicated that bare nano-sized particles (N0) have a negative impact on the C. elegans lifespan, reducing mobility and progeny production. By contrast, micro-sized particles (M0) proved innocuous for the nematodes. Furthermore, functionalization of nanoparticles with starch derivative reduced their toxicity in C. elegans. Thus, oral intake of N1 comparatively increased the mean lifespan and activity rates as well as resistance to oxidative stress. The overall findings presented here demonstrate the influence of MSP size and surface on their potential toxicity in vivo and indicate the silica-based mesoporous particles to be a potential support for encapsulation in oral delivery applications. Furthermore, the good correlation obtained between healthy aging variables and viability (mean lifespan) validates the use of C. elegans as a multicellular organism for nanotoxicology studies of MSPs.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2013

Proton: The Particle

The purpose of this article is to review briefly the nature of protons: creation at the Big Bang, abundance, physical characteristics, internal components, and life span. Several particle discoveries by proton as the experimental tool are considered. Protons play important roles in science, medicine, and industry. This article was prompted by my experience in the curative treatment of cancer patients by protons and my interest in the nature of protons as particles. The latter has been stimulated by many discussions with particle physicists and reading related books and journals. Protons in our universe number ≈10{sup 80}. Protons were created at 10{sup −6} –1 second after the Big Bang at ≈1.37 × 10{sup 10} years beforethe present. Proton life span has been experimentally determined to be ≥10{sup 34} years; that is, the age of the universe is 10{sup −24}th of the minimum life span of a proton. The abundance of the elements is hydrogen, ≈74%; helium, ≈24%; and heavier atoms, ≈2%. Accordingly, protons are the dominant baryonic subatomic particle in the universe because ≈87% are protons. They are in each atom in our universe and thus involved in virtually every activity of matter in the visible universe, including life on our planet. Protons were discovered in 1919. In 1968, they were determined to be composed of even smaller particles, principally quarks and gluons. Protons have been the experimental tool in the discoveries of quarks (charm, bottom, and top), bosons (W{sup +}, W{sup −}, Z{sup 0}, and Higgs), antiprotons, and antineutrons. Industrial applications of protons are numerous and important. Additionally, protons are well appreciated in medicine for their role in radiation oncology and in magnetic resonance imaging. Protons are the dominant baryonic subatomic particle in the visible universe, comprising ≈87% of the particle mass. They are present in each atom of our universe and thus a participant in every activity involving matter.

62 RADIOLOGY AND NUCLEAR MEDICINE↗
DOE OSTI2017

Investigation of pre-existing particles in Al 5083 alloys

Pre-existing particles formed in Al 5083 alloys (H131 and H116) have been investigated using scanning transmission electron microscopy(STEM), energy-dispersive X-ray spectroscopy(EDS), atom probe tomography (APT), and small angle neutron scattering (SANS). Three types of pre-existing particles, Al 6 Mn, Mg 2 Si, and α-Al(Mn,Fe)Si, were observed in Al 5083 alloys, and their relative fraction was obtained from EDS results. The average size, number density, and interfacial area of pre-existing particle were calculated using STEM and SANS results. In addition, an extra layer rich in Mg and Si was found on a pre-existing Mg 2 Si particle, and an Al 6 Mn layer was identified on an α-Al(Mn,Fe)Si particle. Thermodynamic calculations were also applied to investigate the possible pre-existing particles formed in the alloys, which can be used to explain the extra layers formed on Mg 2 Si and α-Al(Mn,Fe)Si particles.

36 MATERIALS SCIENCE↗
DOE OSTI2025

Synthesis of UO 2 nanoparticles via coulometric titration: influence of electrolytes and ligands on synthesized particle properties

Here, this study investigates the controlled synthesis of uranium oxide nanoparticles (UO 2 NPs) via coulometric titration under ambient conditions, focusing on the impact of electrolyte anions, salt concentrations, and strongly complexing ligands on particle formation and properties. Using dilute solutions of mineral acids (HNO 3 , HCl, and HClO 4 ), we demonstrate that the choice of electrolyte anion affects particle size, polydispersity, and surface charge. Particle characterization using dynamic light scattering and transmission electron microscopy shows that particles synthesized in perchlorate are largest and show a high degree of polydispersity. In comparison, particles synthesized in chloride are smaller and more uniform in size. Synthesis in nitrate yields a wide variety of particle sizes, with the major fraction (>65 %) having a smaller size than that obtained in the other two electrolytes. The presence of more strongly coordinating ligands such as sulfate and acetate modulate hydrolysis and condensation reactions, with sulfate suppressing nanoparticle formation across a wide concentration range ([SO 4 2- ] > 5 mM) and acetate enabling stable colloidal suspensions at [HOAc] ≤ 0.1 M. Synthesis in concentrated electrolytes (2 M NaNO 3 , NaCl, or NaClO 4 ) accelerates reaction kinetics but introduces challenges, as particles showed increased polydispersity and aggregation, and were more prone to oxidation. Electrolyte effects on actinide oxide nanoparticle formation are discussed and a short comparison to established nanoparticle syntheses is drawn. This work underscores the importance of tailoring synthesis parameters to achieve desired nanoparticle properties, providing valuable insights for optimizing UO 2 NP production for various applications.

Actinide hydrolysis↗
DOE OSTI2020

A filtering strategy for the numerical convergence of radiation transport through purely absorbing particle clouds

Radiation transport through particle clouds plays a major role in many engineering applications. Here in this paper, we study this problem by means of solving the radiative transport equation (RTE) on a Eulerian continuous domain. The particle clouds are generated through direct numerical simulation of Navier-Stokes equations coupled with Lagrangian particle transport at different Stokes numbers. We confirm the earlier observation noted in the literature that the solution to the RTE on Eulerian mesh diverges when the Eulerian mesh size is of the order of the particle diameter. This observation is often called the homogenization error stemming from relegation of number density onto the Eulerian domain. In order to circumvent this divergence problem, we propose a filtering strategy that spreads the information of the particles to the neighboring cells in a way that the representation of the particles remains the same even when the mesh size is smaller than that of the particle size. We show through our simulations that our filtering strategy solves the issue of homogenization error for the cases where the Beer-Bouger law is valid.

42 ENGINEERING↗
DOE OSTI2018

The effects of Cr particles addition on the aging behavior and mechanical properties of SiCp/7075Al composites

Highlights: • The novel investigated the effects of Cr particles on the aging behavior and mechanical properties of SiC{sub p}/7075Al composites. • The addition of Cr particles didn't change precipitation sequence, but significantly degraded precipitation kinetics of composites. • Cr particles had a significant effect on the tensile properties of the peak-aged composite because of Mg aggregation. - Abstract: The effects of Cr particles addition on the aging behavior and mechanical properties of SiC{sub p}/7075Al composites were systematically investigated. The results show that the precipitation sequence of (5 vol% Cr + 50 vol% SiC)/7075Al composites (C-7075Al) is still: GP zone → η′ → η (MgZn{sub 2}), but Cr particles degrade the precipitation kinetics of the C-7075Al composite in comparison to (5 vol% SiC{sub p} + 50 vol% SiC{sub p})/7075Al (B-7075Al) because of reduced dislocation density present in the matrix and higher thermal activation energy of the η′ phase. Besides, the addition of Cr particles has a significant effect on the mechanical properties of the C-7075Al composite during the aging process. In contrast to the as-cast state, the ultimate tensile strength of the C-7075Al composite obtains an increase of 120 MPa at the peak-aged period, significantly lower than those of 7075Al alloy (207 MPa) and the B-7075Al composite (151 MPa), which is attributable to the severe aggregation of elemental Mg at the interface between Cr particles and the Al matrix.

36 MATERIALS SCIENCE↗
DOE OSTI2014

One-step hydrothermal synthesis, characterization and magnetic properties of orthorhombic PrCrO{sub 3} cubic particles

Highlights: • Orthorhombic PrCrO{sub 3} cubic particles were prepared by a simple and facile one-step hydrothermal method. • The possible formation mechanism of PrCrO{sub 3} cubic particles was proposed. • The as-synthesized PrCrO{sub 3} exhibited behaviors of magnetic transition and negative magnetization. - Abstract: Orthorhombic PrCrO{sub 3} cubic particles were synthesized by a simple and facile one-step hydrothermal method of processing temperature 280 °C for 7 days. The products prepared in this paper have been characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR) and field-emission scanning electron microscopy (FESEM). The magnetic properties of the final sample are also studied. The XRD pattern shows the pure orthorhombic phase for PrCrO{sub 3} particles, the XPS and FTIR results further demonstrate the purity and composition of the product. FESEM images show cubic morphology for the PrCrO{sub 3} particles. The possible growth mechanism for PrCrO{sub 3} cubic particles is proposed. Through the investigation of magnetic properties, it can be seen that the orthorhombic PrCrO{sub 3} cubic particles exhibit behaviors of magnetic transition and negative magnetization. The Néel temperature is about 232 K and the magnetic hysteresis loop under 4 K shows that the coercivity (H{sub C}) and remanence (M{sub r}) is about 1728 Oe and 4.88 emu/g, respectively.

36 MATERIALS SCIENCE↗