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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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At least 127 records · Page 7
All sourcesNASA NTRSDOE OSTI
NASA NTRS2002

Particle Size Effects on Flow Properties of PS304 Plasma Spray Feedstock Powder Blend

The effects of BaF2-CaF2 particle size and size distribution on PS304 feedstock powder flowability have been investigated. Angular BaF2-CaF2 eutectic powders were produced by comminution and classified by screening to obtain 38 to 45 microns 45 to 106 microns, 63 to 106 microns, 45 to 53 microns, 63 to 75 microns, and 90 to 106 microns particle size distributions. The fluorides were added incrementally from 0 to 10 wt% to the other powder constituents of the PS304 feedstock: nichrome, chromia, and silver powders. The flow rate of the powder blends decreased linearly with increasing concentration of the fluorides. Flow was degraded with decreasing BaF2-CaF2 particle size and with increasing BaF2-CaF2 particle size distribution. A semiempirical relationship is offered to describe the PS304 powder blend flow behavior. The Hausner Ratio confirmed the funnel flow test results, but was slightly less sensitive to differences in BaF2-CaF2 particle size and size distribution. These findings may have applicability to other powders that do not flow easily, such as ceramic powders.

Stanford, Malcolm K.↗
NASA NTRS2005

Improved Small-Particle Powders for Plasma Spraying

Improved small-particle powders and powder-processing conditions have been developed for use in plasma spray deposition of thermal-barrier and environmental barrier coatings. Heretofore, plasma-sprayed coatings have typically ranged in thickness from 125 to 1,800 micrometers. As explained below, the improved powders make it possible to ensure complete coverage of substrates at unprecedently small thicknesses of the order of 25 micrometers. Plasma spraying involves feeding a powder into a hot, high-velocity plasma jet. The individual powder particles melt in the plasma jet as they are propelled towards a substrate, upon which they splat to build up a coating. In some cases, multiple coating layers are required. The size range of the powder particles necessarily dictates the minimum thickness of a coating layer needed to obtain uniform or complete coverage. Heretofore, powder particle sizes have typically ranged from 40 to 70 micrometers; as a result, the minimum thickness of a coating layer for complete coverage has been about 75 micrometers. In some applications, thinner coatings or thinner coating layers are desirable. In principle, one can reduce the minimum complete-coverage thickness of a layer by using smaller powder particles. However, until now, when powder particle sizes have been reduced, the powders have exhibited a tendency to cake, clogging powder feeder mechanisms and feed lines. Hence, the main problem is one of synthesizing smaller-particle powders having desirable flow properties. The problem is solved by use of a process that begins with a spray-drying subprocess to produce spherical powder particles having diameters of less than 30 micrometers. (Spherical-particle powders have the best flow properties.) The powder is then passed several times through a commercial sifter with a mesh to separate particles having diameters less than 15 micrometers. The resulting fine, flowable powder is passed through a commercial fluidized bed powder feeder into a plasma spray jet.

Nguyen, QuynhGiao, N.↗
NASA NTRS2014

On Characterizing Particle Shape

It is well known that particle shape affects flow characteristics of granular materials, as well as a variety of other solids processing issues such as compaction, rheology, filtration and other two-phase flow problems. The impact of shape crosses many diverse and commercially important applications, including pharmaceuticals, civil engineering, metallurgy, health, and food processing. Two applications studied here include the dry solids flow of lunar simulants (e.g. JSC-1, NU-LHT-2M, OB-1), and the flow properties of wet concrete, including final compressive strength. A multi-dimensional generalized, engineering method to quantitatively characterize particle shapes has been developed, applicable to both single particle orientation and multi-particle assemblies. The two-dimension, three dimension inversion problem is also treated, and the application of these methods to DEM model particles will be discussed. In the case of lunar simulants, flow properties of six lunar simulants have been measured, and the impact of particle shape on flowability - as characterized by the shape method developed here -- is discussed, especially in the context of three simulants of similar size range. In the context of concrete processing, concrete construction is a major contributor to greenhouse gas production, of which the major contributor is cement binding loading. Any optimization in concrete rheology and packing that can reduce cement loading and improve strength loading can also reduce currently required construction safety factors. The characterization approach here is also demonstrated for the impact of rock aggregate shape on concrete slump rheology and dry compressive strength.

Ennis, Bryan J.↗
NASA NTRS2017

Self-Healing Technologies for Wiring and Surfaces in Aerospace and Deep Space Exploration Applications

Self-healing technologies have been identified as critical technology gaps for future exploration. NASA and KSC have been working in this area for multiple years with established intellectual property; however, there are many challenges that remain in this area of research. How do we mimic what the body does so naturally when we as NASA have unique requirements? We have been investigating several mechanisms for self-healing: microencapsulation with a healant core to fill in voids in the case of mechanical puncture and flowable (or sealable)systems that have inherent chemical properties that allow the materials to flow back together when cut or damaged. The microcapsules containing healant have to be durable and robust, must be able to take high temperatures to meet NASA unique requirements, provide good capillary flow of the healant, and be small in diameters to fill in damage voids in thin films or surfaces. Sealable systems have to flow in a range of temperatures and yet be lightweight and chemically resistant. The systems currently being developed are based on polyimide and polyurethane matrices and have been studied for use in high performance wiring systems, inflatable systems, and habitation structures. Self-healing or self-sealing capability would significantly reduce maintenance requirements and increase the safety and reliability performance of critical systems. Advances in these self-healing technologies and some of the unique challenges needed to be overcome in order to incorporate a self-healing mechanism into wiring or thin films systems will be addressed.

Self-healing technologies↗
NASA NTRSDate not supplied

Grain Shape Characterization as an Enabling Capability for Lunar Surface Technologies

Lunar regolith has unique physical and geotechnical properties compared with familiar granular materials on Earth, and most lunar simulants as well. Specifically, the cohesion, angle of repose, and compressibility are much higher, and flowability is much lower for lunar regolith than otherwise similar terrestrial-derived materials[1,2]. There is confusion in the literature about the relative importance of vacuum, gravity, and inherent grain characteristics in driving these differences. Here we emphasize the importance of characterizing grain types and shapes for designing and test-ing lunar surface technologies, including for rover mobility, material handling, soil sampling, and heat transfer analyses. We demonstrate laboratory capabilities and preliminary studies, and outline further work to better characterize and simulate lunar grains to reduce risks for surface activities

K. M. Cannon↗
NASA NTRSDate not supplied

Exploration of Particle Size Engineering and Microencapsulation Technologies for Multifunctional Applications

There is a critical need for high performance materials for functional and space-based applications, including tires for exploratory rovers and external structures for landing vehicles. Novel ternary borides, such as iron aluminum boride (Fe2AlB2) and molybdenum aluminum boride (MoAlB), have emerged as potential materials for such application owing to their hardness, mechanical behavior and oxidation resistance. In this poster presentation, we will present different methods of fabricating these particles and engineering them for additive manufacturing and other related manufacturing practices. As an integral component of this study, we will demonstrate technologies to (a) synthesize these particles and (b) microencapsulate these particles with bioplastics like polylactic acid (PLA). The resulting particles will be evaluated for their processability as coatings on hydroxyapatite and Inconel particles using microstructural and flowability studies. It is expected that these particles can be used for 3D printing.

ceramics↗
NASA NTRSDate not supplied

3d Particle Geometry Characterization of Apollo Regolith Samples Via Laser Diffraction and Dynamic Image Analysis

Establishing a fundamental understanding of regolith mechanics hinges on the characterization of the foundational physical parameters that dictate granular particle interactions both on micro- and macro-scales. Specifically, particle size distribution, particle geometry and grain density govern the geotechnical properties, including compressibility, shear strength, hydraulic conductivity (i.e., permeability), void ratio (i.e., porosity), and thermal conductivity of the lunar regolith. The absence of terrestrial geologic processes on the lunar surface, a lack of water, clay minerals, and organic material in lunar soils, and the narrow compositional range in terms of mineral diversity of the regolith produces a unique problem when attempting to project terrestrial soil mechanics concepts to the lunar surface. Additionally, the occurrence of agglutinates, exclusive to the lunar surface, further disassociates the physical behavior (e.g., particle crushability, flowability, etc.) of regolith from that observed in terrestrial soils.

R. Kovtun↗
DOE OSTI2020

Determining Design Criteria for Feeding Biomass into a Fluidized Bed Using a Feed Screw

Many pathways have been discovered for the thermochemical conversion of biomass to products. These pathways often show very promising results on the benchtop scale and could be economical with the appropriate scale up. However, many of the fundamental challenges of scaling up thermochemical reactions are not well understood. One primary problem area that rarely receives much upfront attention is feeding large quantities of biomass into thermochemical reactors. As biomass transitions from ambient to reactor conditions, it undergoes chemical and physical changes that affect its flowability. Often these changes lead to agglomeration of feed particles within the transfer screw, leading to large clumps of feed entering and disrupting the fluidized bed, or more critically leading to a plug in the feed screw causing costly downtime and maintenance to remove. This transitional phase must be better understood for scale up of conversion technologies to be successful. The Feedstock-Conversion Interface Consortium (FCIC) is a collaboration of eight National Laboratories. FCIC is currently conducting research on screw feeding of biomass into thermochemical fluidized bed reactors. Heat transfer models have been constructed for the screw/reactor interface. Mechanical forces on biomass within screw feeder are being determined, as well as how those forces change by varying feed screw design. Feedstock physical and chemical properties are then being measured along these temperature and mechanical force gradients. This work will better inform feed screw design for scale up, increasing the success rate of future biorefineries. Discussion will include research approach, testing, and preliminary results.

09 BIOMASS FUELS↗
DOE OSTI2021

Biomass Feedstock National User Facility--Improving Bale Deconstruction and Material Flow

The project aims to reduce feedstock variability using a quality-by-design approach beginning when the biomass is introduced to the process and will continue through the size reduction process, which will yield the results of fine generation reduction, contaminant removal, control of the physical and chemical critical material attributes in the process, and management of the flowability.

09 BIOMASS FUELS↗
DOE OSTI2021

High-temperature NMR MAS probe with optimized temperature gradient across sample rotor

A rotor housing assembly for NMR spectroscopy. An elongate rotor has a distal drive end, a proximal end and an internal sample space positioned along its length between the drive and proximal ends. The rotor is driveable about a rotation axis by a drive gas flow. A rotor housing has an interior space in which the rotor is at least partially received. At least one first heated gas flow inlet is positioned opposite the internal sample space, through which a first heated gas flow is controllably flowable into the interior space to heat it and the rotor. At least a pair of spaced apart second heated gas flow outlets are axially spaced from the first heated gas flow inlet to controllably convey a second heated gas flow to heat distal and proximal areas of the sample space to minimize a temperature gradient extending axially within the sample space.

Mehta, Hardeep S.↗
DOE OSTI2022

Biochar as a Building Material: Sequestering Carbon and Strengthening Concrete

It is possible to offset the carbon footprint of concrete by 60 kg (132 lbs) per cubic yard of ready-mix by deeply sequestering carbon with an engineered biochar additive. Our multidisciplinary team specializing in char production and cementitious materials has demonstrated that for every ton of cement, adding 100 kg of engineered biochar will not only lock in carbon, but also strengthen concrete in all key dimensions via enhancements to hydration and integration into the hardened matrix. As a non-chemical, inert additive the cement sequestration (CemSeq) char product can fully complement other powerful tools to reduce cement emissions and unlock the possibility for carbon negative concrete by 2050. The key findings of our initial research have shown that to achieve this the following are required: tailored milling of the char, using fast pyrolysis to produce the char, and modulating the cement flowability.

biochar↗
DOE OSTI2022

High energy density redox flow device

Redox flow devices are described including a positive electrode current collector, a negative electrode current collector, and an ion-permeable membrane separating said positive and negative current collectors, positioned and arranged to define a positive electroactive zone and a negative electroactive zone; wherein at least one of said positive and negative electroactive zone comprises a flowable semi-solid composition comprising ion storage compound particles capable of taking up or releasing said ions during operation of the cell, and wherein the ion storage compound particles have a polydisperse size distribution in which the finest particles present in at least 5 vol % of the total volume, is at least a factor of 5 smaller than the largest particles present in at least 5 vol % of the total volume.

Chiang, Yet-Ming↗
DOE OSTI2023

Biomass Feedstock Flow Modeling at Exascale

Variable biomass feedstock handling in hoppers and screw conveyors can cause upstream failures and disrupt downstream conversion operations. Understanding how particle size, shape, and moisture content affect feedstock flowability is important for efficient biorefinery operation. We present the use of our open-source discrete element method (DEM) solver for predicting flows in large scale hoppers and assess its performance on state-of-the-art high performance computing platforms that use heterogenous computing architectures.

bioenergy↗
DOE OSTI2023

Metal-ceramic composite powders

A process for manufacturing metal-ceramic composite material powder comprising ball milling metal powder and ceramic nanoparticles to yield a metal-ceramic composite powder comprising ceramic nanoparticles embedded in a metal matrix powder particles; wherein the ball milling is performed using a ceramic milling media and a milling vessel having a ceramic interior surface. Metal matrix nanocomposite powders comprising ceramic nanoparticles imbedded in metal matrix powder particles; wherein the metal matrix powder particles have a spherical shape; wherein there is uniform distribution the ceramic nanoparticles; wherein the nanocomposite powders have good flowability.

Chen, Lianyi↗
DOE OSTI2024

Advanced Instrumentation for Metal Additive Manufacturing

Laser powder bed fusion (LPBF) is the most widely used process for metal additive manufacturing (AM), particularly where complex geometries provide performance advantages unattainable with traditional manufacturing techniques. However, LPBF is highly sensitive to innate variability in both the powder spreading and fusion steps, often leading to defects such as pores that are difficult to detect yet significantly impair component mechanical properties and fatigue life. This thesis presents a range of novel instruments enabling both precise assessment of powder layer characteristics and in-situ thermal metrology of metal AM to advance the quality control of LPBF. First, leveraging a custom X-ray microscope and a radiation-transport model developed through this work, transmission X-ray imaging is used to study spreading of thin metal powder layers. Effective layer depth is directly mapped at a process-relevant size scale, surpassing optical techniques that can only estimate local deposition from layer surface topography. Layer packing density and quality are shown to be influenced by powder flowability and particle size relative to nominal powder layer thickness. Layer quality is additionally connected to the geometry of the spreading implement and its velocity. This technique and its presented findings enable pairing feedstocks with spreading strategies that create layers with consistent packing density and uniformity. Second, a twofold approach is employed to optically interrogate the laser fusion step of LPBF for observing signatures of defect formation. Aperture division multiplexing is conceptualized, providing for simultaneous laser delivery and high-fidelity infrared (IR) process monitoring through a common optic. In-situ microscopy at 50 μm spatial resolution and at mid-wave IR wavelengths is proven readily achievable with the first purpose-built optic of this type. Next, a bespoke imaging spectrometer, along with a temperature-emissivity separation technique, is used to retrieve accurate process temperatures over a 1000 K range. Data from these instruments are correlated to porosity as fine as 4.3 μm in two LPBF test artifacts, as verified using computed tomography (CT), establishing the viability of robust optically-based component qualification.

Penny, Ryan↗
DOE OSTI2024

High energy density redox flow device

Redox flow devices are described including a positive electrode current collector, a negative electrode current collector, and an ion-permeable membrane separating said positive and negative current collectors, positioned and arranged to define a positive electroactive zone and a negative electroactive zone; wherein at least one of said positive and negative electroactive zone comprises a flowable semi-solid composition comprising ion storage compound particles capable of taking up or releasing said ions during operation of the cell, and wherein the ion storage compound particles have a polydisperse size distribution in which the finest particles present in at least 5 vol % of the total volume, is at least a factor of 5 smaller than the largest particles present in at least 5 vol % of the total volume.

Chiang, Yet-Ming↗
DOE OSTI2022

Wedge-Shaped Hopper Design for Milled Woody Biomass Flow

The bioenergy industry has been challenged by unstable flow and transport of milled biomass in material handling operations. Handling issues such as hopper clogging and auger jamming are attributed to knowledge gaps between existing handling units designed for bulk solids and their suitability for milled biomass with high compressibility. This work investigates various flow behaviors of granular woody biomass in wedge-shaped hoppers. Herein, hopper flow physical experiments and numerical simulations are conducted to study the influence of the critical material attributes and critical processing parameters on the flow pattern, arching, and throughput. The results show that (1) the preferred flow pattern, mass flow, can be achieved by controlling the material’s internal friction angle, hopper inclination, and hopper wall friction; (2) hopper arching, governed by the competing gravity-driven force against flow resistance from material internal friction and material–wall friction, can be controlled by the hopper wall friction angle and the inclination angle; and (3) flow throughput can be accurately estimated from our empirical equation with inputs of hopper outlet geometry and particle-scale to bulk-scale material attributes. This study elucidates woody biomass flow physics and provides guidance for industrial equipment design.

09 BIOMASS FUELS↗