Optical Measurement of Particle Size and Velocity
Dual-beam laser-Doppler anemometers simultaneously determine velocity and size distribution of particles in flowing fluid.
Smith, J. L.↗
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Results for “Particle Size”
Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.
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Effects of Particle Size Distribution with Efficient Packing on Powder Flowability and Selective Laser Melting Process
The powder bed-based additive manufacturing (AM) process contains uncertainties in the powder spreading process and powder bed quality, leading to problems in repeatability and quality of the additively manufactured parts. This work focuses on identifying the uncertainty induced by particle size distribution (PSD) on powder flowability and the laser melting process, using Ti6Al4V as a model material. The flowability test results show that the effect of PSDs on flowability is not linear, rather the PSDs near dense packing ratios cause significant reductions in flowability (indicated by the increase in the avalanche angle and break energy of the powders measured by a revolution powder analyzer). The effects of PSDs on the selective laser melting (SLM) process are identified by using in-situ high-speed X-ray imaging to observe the melt pool dynamics during the melting process. The results show that the powder beds made of powders with dense packing ratios exhibit larger build height during laser melting. The effects of PSD with efficient packing on powder flowability and selective laser melting process revealed in this work are important for understanding process uncertainties induced by feedstock powders and for designing mitigation approaches.
36 MATERIALS SCIENCE↗
A comparison of two methods of measuring particle size of Al2O3 produced by a small rocket motor
Tank collection and spectrophotometric tests in determining aluminum oxide particle size produced by small rocket engine
Dobbins, R. A.↗
Stirring and peristaltic pumping alter flow electrode particle size and morphology
Flowable carbon-based electrodes are widely studied in electrochemical systems for energy storage and water treatment. Most laboratory- and pilot-scale studies employ active mixing for slurry preparation and handling and use peristaltic pumps for slurry circulation. Magnetic stirring is the most prevalent mixing method at the laboratory scale, and the combination of magnetic mixing and peristaltic pumping is favored for convenience and compatibility with particulate suspensions. However, these methods can strongly affect particle size and morphology (and therefore cell performance). In this study, we evaluate how mixing and pumping influence particle degradation in two commonly used carbon materials: spherical carbon black (CB) beads and powdered activated carbon (AC). We performed 24 h stirring-only experiments using magnetic, orbital, and overhead stirring. Separately, we conducted 32 h circulation experiments using a commercial peristaltic pump. Particle morphology and size were analyzed using optical microscopy and laser diffraction. The initially spherical CB beads (~580 μm, 1.5 wt%) exhibit rapid and extensive breakdown under both peristaltic pumping and magnetic stirring. By comparison, AC particles (initially ~31 μm) tested at 1.5 and 15 wt% showed measurable size reductions of up to ~25 % under either stirring or pumping. In conclusion, these findings highlight the need to account for and quantify morphological changes caused by both stirring and pumping in the design and associated evaluation of flowable electrode systems.
Chemistry↗
Analytical inversions in remote sensing of particle size distributions. I - Multispectral extinctions in the anomalous diffraction approximation. II Angular and spectral scattering in diffraction approximations
Consideration is given to analytical inversions in the remote sensing of particle size distributions, noting multispectral extinctions in anomalous diffraction approximation and angular and spectral scattering in diffraction approximation. A closed-form analytical inverse solution is derived in order to reconstruct the size distribution of atmospheric aerosols. The anomalous diffraction approximation to Mie's solution is used to describe the particles. Experimental data yield the geometrical area of aerosol polydispersion. Size distribution is thus found from a set of multispectral extinction measurements. In terms of the angular and spectral scattering of light in a narrow forward cone, it is shown that an analytical inverse solution may also be found for the Fraunhofer approximation to the Kirchhoff diffraction, and for an improved expression of this approximation due to Penndorf (1962) and Shifrin-Punina (1968).
Fymat, A. L.↗
Variations in GARS powder microstructure as a function of powder chemistry and particle size
The properties of metal produced through powder metallurgy depends on the feedstock used. Powders produced via gas atomization reaction synthesis (GARS) are used to produce oxide dispersion strengthened alloys. The desired powder size range can vary for each consolidation technique. However, powder microstructure also can vary with powder particle size, which in turn can impact the microstructure and properties of the consolidated parts. In this study, GARS powders are characterized via inductively coupled plasma mass spectroscopy, inert gas fusion, and high-resolution x-ray diffraction to determine variations in elemental and phase compositions. Transmission electron microscopy was used to understand microstructure variations as a function of chemistry and size. Across the three batches tested intermetallic content was 0.73–1.35 wt% in the 0-20 μm powder batch and increased to 2.46–3.80 wt% in the coarse 45-106 μm batch. Across all batches, volume percent of surface oxidation decreased with powder diameter, with volume percents within the range of 0.75–1.2 % across 10 μm powder particles, and below 0.4 % across coarse powder particles approximately 100 μm in diameter. These observations were supported by inert gas fusion measurements. However, the oxide layer was thicker in coarse powder particles due to a slower cooling rate. Increasing oxygen content in atomization gas to 2000 ppm and adding yttrium increased both the surface oxidation content and yttrium intermetallic content. Lastly, intermetallic phases within the powder coarsened with powder size. Intermetallic morphology changed from fine spherical intermetallic and columnar dendritic growth to a cellular structure with finer spherical intermetallic, to coarse irregular intermetallic and intermetallic along grain boundaries as a result of slower cooling rate and solidification rate in coarse powder particles. Furthermore, the addition of zirconium does not appear to significantly change intermetallic morphology, but the composition changed from a Y-Fe rich intermetallic to a Y-Zr-Fe intermetallic.
42 ENGINEERING↗
Laboratory Simulation of Impacts upon Aluminum Foils of the Stardust Spacecraft: Calibration of Dust Particle Size from Comet Wild 2
Metallic aluminium alloy foils exposed on the forward, comet-facing surface of the aerogel tray on the Stardust spacecraft are likely to have been impacted by the same cometary particle population as the dedicated impact sensors and the aerogel collector. The ability of soft aluminium alloy to record hypervelocity impacts as bowl-shaped craters offers an opportunistic substrate for recognition of impacts by particles of a wide potential size range. In contrast to impact surveys conducted on samples from low Earth orbit, the simple encounter geometry for Stardust and Wild 2, with a known and constant spacecraft-particle relative velocity and effective surface-perpendicular impact trajectories, permits closely comparable simulation in laboratory experiments. For a detailed calibration programme we have selected a suite of spherical glass projectiles of uniform density and hardness characteristics, with well-documented particle size range from 10 microns to nearly 100 microns. Light gas gun buckshot firings of these particles at approximately 6km s)exp -1) onto samples of the same foil as employed on Stardust have yielded large numbers of craters. Scanning electron microscopy of both projectiles and impact features has allowed construction of a calibration plot, showing a linear relationship between impacting particle size and impact crater diameter. The close match between our experimental conditions and the Stardust mission encounter parameters should provide another opportunity to measure particle size distributions and fluxes close to the nucleus of Wild 2, independent of the active impact detector instruments aboard the Stardust spacecraft.
Kearsley, A. T.↗
Preparation of large-particle-size monodisperse latexes in space - Polymerization kinetics and process development
Monodisperse polystyrene latexes are prepared by seeded emulsion polymerization; however, sizes larger than 2 microns are difficult to prepare because of the creaming and settling of the particles and their sensitivity to mechanical shear. Preparation in space would obviate the creaming and settling, and allow agitation just sufficient for good heat transfer and mixing. Three polymerizations yielding 3-5 micron size particles were carried out successfully on the third flight of the 'Columbia' launched Mar. 22, 1982; however, four polymerizations yielding sizes up to 10 microns on the fourth flight launched June 27, 1982 were incomplete owing to apparatus malfunction. The results of these polymerizations and the prospects of developing a preparative space process are reviewed.
Vanderhoff, J. W.↗
Particle size distributions in Arctic polar stratospheric clouds, growth and freezing of sulfuric acid droplets, and implications for cloud formation
The paper uses particle size and volume measurements obtained with the forward scattering spectrometer probe model 300 during January and February 1989 in the Airborne Arctic Stratospheric Experiment to investigate processes important in the formation and growth of polar stratospheric cloud (PSC) particles. It is suggested on the basis of comparisons of the observations with expected sulfuric acid droplet deliquescence that in the Arctic a major fraction of the sulfuric acid droplets remain liquid until temperatures at least as low as 193 K. It is proposed that homogeneous freezing of the sulfuric acid droplets might occur near 190 K and might play a role in the formation of PSCs.
Dye, James E.↗
Fundamental studies relating particle size effects to infrared spectra Final report, 1 Jun. 1967 - 31 May 1968
Infrared spectra of powdered rocks - effects of particle size, surface roughness, and spectrometer angle of view on emission spectra variations
Source record↗
Studies on remote sensing method of particle size and water density distribution in mists and clouds using laser radar techniques
A method of remote measurement of the particle size and density distribution of water droplets was developed. In this method, the size of droplets is measured from the Mie scattering parameter which is defined as the total-to-backscattering ratio of the laser beam. The water density distribution is obtained by a combination of the Mie scattering parameter and the extinction coefficient of the laser beam. This method was examined experimentally for the mist generated by an ultrasonic mist generator and applied to clouds containing rain and snow. Compared with the conventional sampling method, the present method has advantages of remote measurement capability and improvement in accuracy.
Shimizu, H.↗
Simple algorithms for remote determination of mineral abundances and particle sizes from reflectance spectra
Algorithms were developed, based on Hapke's (1981) equations, for remote determinations of mineral abundances and particle sizes from reflectance spectra. In this method, spectra are modeled as a function of end-member abundances and illumination/viewing geometry. The method was tested on a laboratory data set. It is emphasized that, although there exist more sophisticated models, the present algorithms are particularly suited for remotely sensed data, where little opportunity exists to independently measure reflectance versus article size and phase function.
Johnson, Paul E.↗
Impact of secondary particle size and two-layer architectures on the high-rate performance of thick electrodes in lithium-ion battery pouch cells
Increasing lithium-ion battery gravimetric energy density to > 300 Wh/kg, while simultaneously meeting a cost target of $80/kWh, is of paramount importance to increasing the driving range and affordability of electric vehicles. One way to address this goal is to reduce inactive components by increasing electrode areal capacities, but conventional thick electrode designs typically perform poorly at high discharge rates due to Li + mass transport limitations. Here we compare the rate capability and cycle life of NMC 532/graphite pouch cells made with five different thick cathode and anode designs paired together in 25 combinations. We find that using different particle sizes to structure both the cathode and anode architectures in two-layer configurations results in a 2X capacity improvement over the worst-performing combination at high discharge rates (97 vs. 46 mAh/g at 2C). These different cathode/anode designs also translate to different cycle life performance, with many cells cycled at C/2 achieving ~80% capacity retention after 1000 cycles, and cells cycled at 2C showing different degrees of capacity fade. Altogether, these results demonstrate that simple, scalable changes in electrode design can significantly improve the performance of thick electrodes for high energy density batteries.
25 ENERGY STORAGE↗
Micron-sized particles detected near Neptune by the Voyager 2 plasma wave instrument
Observations and an analysis are presented of the micron-sized-particle impacts observed by the plasma-wave instrument aboard the Voyager 2. After a detailed description of signals produced by the dust impacts, the impact noise is interpreted in terms of the number density and mass of the particles. The likely sources of the particles are discussed.
Gurnett, D. A.↗
Particle Size Measurements From the First Fundamentals of Ice Crystal Icing Physics Test in the NASA Propulsion Systems Laboratory
This paper presents particle measurements by the Artium Technologies, Inc. Phase Doppler Interferometer and High Speed Imaging instruments from the first Fundamental Ice Crystal Icing Physics test conducted in the NASA Propulsion Systems Laboratory. The work focuses on humidity sweeps at a larger and a smaller median volumetric diameter. The particle size distribution, number density, and water content measured by the Phase Doppler Interferometer and High Speed Imaging instruments from the sweeps are presented and compared. The current capability for these two instruments to measure and discriminate ICI conditions is examined.
Aircraft icing↗
Particle Size Measurements from the first Fundamentals of Ice Crystal Icing Physics Test in the NASA Propulsion Systems Laboratory
This presentation shows particle measurements by the Artium Technologies, Inc. Phase Doppler Interferometer and High Speed Imaging instruments from the first Fundamental Ice Crystal Icing Physics test conducted in the NASA Propulsion Systems Laboratory. The work focuses on humidity sweeps at a larger and a smaller median volumetric diameter. The particle size distribution, number density, and water content measured by the Phase Doppler Interferometer and High Speed Imaging instruments from the sweeps are presented and compared. The current capability for these two instruments to measure and discriminate ICI conditions is examined.
thermal scaling↗
A model predicting the evolution of ice particle size spectra and radiative properties of cirrus clouds. Part 2: Dependence of absorption and extinction on ice crystal morphology
This study builds upon the microphysical modeling described in Part 1 by deriving formulations for the extinction and absorption coefficients in terms of the size distribution parameters predicted from the micro-physical model. The optical depth and single scatter albedo of a cirrus cloud can then be determined, which, along with the asymmetry parameter, are the input parameters needed by cloud radiation models. Through the use of anomalous diffraction theory, analytical expressions were developed describing the absorption and extinction coefficients and the single scatter albedo as functions of size distribution parameters, ice crystal shapes (or habits), wavelength, and refractive index. The extinction coefficient was formulated in terms of the projected area of the size distribution, while the absorption coefficient was formulated in terms of both the projected area and mass of the size distribution. These properties were formulated as explicit functions of ice crystal geometry and were not based on an 'effective radius.' Based on simulations of the second cirrus case study described in Part 1, absorption coefficients predicted in the near infrared for hexagonal columns and rosettes were up to 47% and 71% lower, respectively, than absorption coefficients predicted by using equivalent area spheres. This resulted in single scatter albedos in the near-infrared that were considerably greater than those predicted by the equivalent area sphere method. Reflectances in this region should therefore be underestimated using the equivalent area sphere approach. Cloud optical depth was found to depend on ice crystal habit. When the simulated cirrus cloud contained only bullet rosettes, the optical depth was 142% greater than when the cloud contained only hexagonal columns. This increase produced a doubling in cloud albedo. In the near-infrared (IR), the single scatter albedo also exhibited a significant dependence on ice crystal habit. More research is needed on the geometrical properties of ice crystals before the influence of ice crystal shape on cirrus radiative properties can be adequately understood. This study provides a way of coupling the radiative properties of absorption, extinction, and single scatter albedo to the microphysical properties of cirrus clouds. The dependence of extinction and absorption on ice crystal shape was not just due to geometrical differences between crystal types, but was also due to the effect these differences had on the evolution of ice particle size spectra. The ice particle growth model in Part 1 and the radiative properties treated here are based on analytical formulations, and thus represent a computationally efficient means of modeling the microphysical and radiative properties of cirrus clouds.
Mitchell, David L.↗
Turbulent Concentration of mm-Size Particles in the Protoplanetary Nebula: Scale-Dependent Cascades
The initial accretion of primitive bodies (here, asteroids in particular) from freely-floating nebula particles remains problematic. Traditional growth-by-sticking models encounter a formidable "meter-size barrier" (or even a mm-to-cm-size barrier) in turbulent nebulae, making the preconditions for so-called "streaming instabilities" difficult to achieve even for so-called "lucky" particles. Even if growth by sticking could somehow breach the meter size barrier, turbulent nebulae present further obstacles through the 1-10km size range. On the other hand, nonturbulent nebulae form large asteroids too quickly to explain long spreads in formation times, or the dearth of melted asteroids. Theoretical understanding of nebula turbulence is itself in flux; recent models of MRI (magnetically-driven) turbulence favor low-or- no-turbulence environments, but purely hydrodynamic turbulence is making a comeback, with two recently discovered mechanisms generating robust turbulence which do not rely on magnetic fields at all. An important clue regarding planetesimal formation is an apparent 100km diameter peak in the pre-depletion, pre-erosion mass distribution of asteroids; scenarios leading directly from independent nebula particulates to large objects of this size, which avoid the problematic m-km size range, could be called "leapfrog" scenarios. The leapfrog scenario we have studied in detail involves formation of dense clumps of aerodynamically selected, typically mm-size particles in turbulence, which can under certain conditions shrink inexorably on 100-1000 orbit timescales and form 10-100km diameter sandpile planetesimals. There is evidence that at least the ordinary chondrite parent bodies were initially composed entirely of a homogeneous mix of such particles. Thus, while they are arcane, turbulent concentration models acting directly on chondrule size particles are worthy of deeper study. The typical sizes of planetesimals and the rate of their formation can be estimated using a statistical model with properties inferred from large numerical simulations of turbulence. Nebula turbulence is described by its Reynolds number Re = (L/eta)(exp 4/3), where L = H alpha(exp 1/2) is the largest eddy scale, H is the nebula gas vertical scale height, alpha the turbulent viscosity parameter, and eta is the Kolmogorov or smallest scale in turbulence (typically about 1km), with eddy turnover time t(sub eta). In the nebula, Re is far larger than any numerical simulation can handle, so some physical arguments are needed to extend the results of numerical simulations to nebula conditions. In this paper, we report new physics to be incorporated into our statistical models.
mm-size particles↗