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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
DOE OSTI2020

Towards the scale-up production of cellulose nanocomposites using melt processing: A critical review on structure-processing-property relationships

Cellulose nanomaterials (CNMs) naturally exist in plant biomass. The success of extraction of CNMs opened up a new era of using plant biomass for innovative industrial applications. Because CNMs are abundant, renewable, biodegradable, transparent, light weight and low in cost, they are ideal materials for large volume applications such as packaging, automotive, building and infrastructure. In many potential application areas, CNM-enable products appear in a composite form, mostly polymer composites. Additionally, the industrial-scale manufacturing of CNM/thermoplastic composites remains as a set of unsolved problems for academia and industry. A prime challenge in applications is the nanoscale dispersion of CNMs in thermoplastic matrices during melt processing. Both bench-scale and pilot-scale studies have been conducted to solve the dispersion issue of CNMs. In this article, research related to the dispersion of CNMs in thermoplastic matrices during melt processing were critically reviewed. All research papers were classified into three groups: chemically-aided dispersion, physically-aided dispersion and mechanically-aided dispersion. Numerous factors affect the CNM dispersion and the mechanical performance of its nanocomposites. There are material-related factors, including CNM types and forms, polymer matrices, surface modification, coupling agents, etc. Furthermore, extrusion processing parameters also play a significant role, covering screw rotation speed, extrusion barrel temperature settings and screw design. In addition, the material-related factors interact with the processing-related factors. Understanding all factors and their interactions are important for moving CNM nanocomposites research a step further towards industrial-relevant production, which is the final ambitious goal of this manuscript.

42 ENGINEERING↗
DOE OSTI2014

Biopolymer foams - Relationship between material characteristics and foaming behavior of cellulose based foams

Biopolymers are becoming increasingly important to both industry and consumers. With regard to waste management, CO{sub 2} balance and the conservation of petrochemical resources, increasing efforts are being made to replace standard plastics with bio-based polymers. Nowadays biopolymers can be built for example of cellulose, lactic acid, starch, lignin or bio mass. The paper will present material properties of selected cellulose based polymers (cellulose propionate [CP], cellulose acetate butyrate [CAB]) and corresponding processing conditions for particle foams as well as characterization of produced parts. Special focus is given to the raw material properties by analyzing thermal behavior (differential scanning calorimetry), melt strength (Rheotens test) and molecular weight distribution (gel-permeation chromatography). These results will be correlated with the foaming behavior in a continuous extrusion process with physical blowing agents and underwater pelletizer. Process set-up regarding particle foam technology, including extrusion foaming and pre-foaming, will be shown. The characteristics of the resulting foam beads will be analyzed regarding part density, cell morphology and geometry. The molded parts will be tested on thermal conductivity as well as compression behavior (E-modulus, compression strength)

36 MATERIALS SCIENCE↗
DOE OSTI2025

Oxide Dispersion Strengthened Ferritic Steel Wire Feedstock Development for Larger Format Additive Manufacturing (CRADA Final Report)

This CRADA project funded through DOE’s INFUSE program sought to demonstrate the viability of fabricating large, complex parts from oxide dispersion strengthened (ODS) steel with advanced manufacturing. Exhibiting excellent radiation tolerance and high mechanical performance at elevated temperatures, ODS steel is a promising structural material candidate for near-plasma components in fusion energy systems. Its use, however, has been limited by a lack of manufacturability. This project sought to produce ODS steel wire through a solid-state shear assisted extrusion process and then demonstrate that the wire can undergo controlled local melting while being welded with the final part sufficiently retaining the beneficial properties of ODS steel. This would allow the use of wire-arc additive manufacturing (WAAM) to manufacture large-scale ODS parts, even though ODS is currently only available as a powder. WAAM is a promising technique for producing components like the replaceable ARC vacuum vessel in CFS’ fusion reactor design. Meanwhile, this project will also expand PNNL’s capability in producing custom wire feedstock with friction extrusion, enabling downstream large-scale manufacturing with WAAM and solid-state based additive manufacturing. The project achieved its goals of developing tooling and fixturing to produce ODS wire at smaller diameters than previous projects. Several small lengths of wire of 1.5 mm and 2.5 mm diameter in the range of 2.5-30 mm long were produced at tool temperatures that are known to cause ODS particle coarsening (~1200 °C). Fixtures and tooling for longer (>1 m) wires were developed but further process development is needed reduce tool temperature during extrusions and to increase wire length needed for WAAM testing and development.

36 MATERIALS SCIENCE↗
DOE OSTI2015

The process of EDC-NHS cross-linking of reconstituted collagen fibres increases collagen fibrillar order and alignment

We describe the production of collagen fibre bundles through a multi-strand, semi-continuous extrusion process. Cross-linking using an EDC (1-ethyl-3-(3-dimethylaminopropyl)carbodiimide), NHS (N-hydroxysuccinimide) combination was considered. Atomic Force Microscopy and Raman spectroscopy focused on how cross-linking affected the collagen fibrillar structure. In the cross-linked fibres, a clear fibrillar structure comparable to native collagen was observed which was not observed in the non-cross-linked fibre. The amide III doublet in the Raman spectra provided additional evidence of alignment in the cross-linked fibres. Raman spectroscopy also indicated no residual polyethylene glycol (from the fibre forming buffer) or water in any of the fibres.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Analytical Study and Experimental Verification of Shear-Thinning Ink Flow in Direct Ink Writing Process

Abstract Direct ink writing (DIW) process is a facile additive manufacturing technology to fabricate three-dimensional (3D) objects with various materials. Its versatility has attracted considerable interest in academia and industry in recent years. As such, upsurging endeavors are invested in advancing the ink flow behaviors in order to optimize the process resolution and the printing quality. However, so far, the physical phenomena during the DIW process are not revealed in detail, leaving a research gap between the physical experiments and its underlying theories. Here, we present a comprehensive analytical study of non-Newtonian ink flow behavior during the DIW process. Different syringe-nozzle geometries are modeled for the comparative case studies. By using the computational fluid dynamics (CFD) simulation method, we reveal the shear-thinning property during the ink extrusion process. Besides, we study the viscosity, shear stress, and velocity fields, and analyze the advantages and drawbacks of each syringe-nozzle model. On the basis of these investigations and analyses, we propose an improved syringe-nozzle geometry for stable extrusion and high printing quality. A set of DIW printing experiments and rheological characterizations are carried out to verify the simulation studies. The results developed in this work offer an in-depth understanding of the ink flow behavior in the DIW process, providing valuable guidelines for optimizing the physical DIW configuration toward high-resolution printing and, consequently, improving the performance of DIW-printed objects.

Engineering↗
DOE OSTI2010

Entrapment and Structure of an Extrahelical Guanine Attempting to Enter the Active Site of a Bacterial DNA Glycosylase, MutM

MutM, a bacterial DNA glycosylase, protects genome integrity by catalyzing glycosidic bond cleavage of 8-oxoguanine (oxoG) lesions, thereby initiating base excision DNA repair. The process of searching for and locating oxoG lesions is especially challenging, because of the close structural resemblance of oxoG to its million-fold more abundant progenitor, G. Extrusion of the target nucleobase from the DNA double helix to an extrahelical position is an essential step in lesion recognition and catalysis by MutM. Although the interactions between the extruded oxoG and the active site of MutM have been well characterized, little is known in structural detail regarding the interrogation of extruded normal DNA bases by MutM. Here we report the capture and structural elucidation of a complex in which MutM is attempting to present an undamaged G to its active site. The structure of this MutM-extrahelical G complex provides insights into the mechanism MutM employs to discriminate against extrahelical normal DNA bases and into the base extrusion process in general.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2022

Quasi-static and dynamic response of a Cu/Nb composite following equal channel angular extrusion

The article presents a study of the plastic properties of a Cu–18%Nb composite following equal channel angular extrusion under both low- and high-strain rate loadings. The microstructures are characterized by optical and scanning electron microscopy as well as electron backscatter diffraction. Comparisons are also made with a Cu–50%Nb laminate made by accumulative roll bonding. Textures obtained within the respective phases in the extruded composite closely mimic those previously reported for the pure components alone (Cu, Nb). Grain sizes of the major phase (Cu) exhibit broad distributions, due largely to partial recrystallization during the extrusion process. Further re-crystallization is obtained within localized deformation bands produced at high strain rates (3 × 10 3 s –1 ). While the degree of anisotropy and the strain rate sensitivity of the composite response are similar to those of pure Cu after extrusion, the strength levels of the composite are somewhat greater, falling broadly between those obtained in the pure components after extrusion to comparable plastic strains. Furthermore, the implications for selection of composite composition and processing for achieving higher strengths are briefly discussed.

36 MATERIALS SCIENCE↗
DOE OSTI2013

A Case Study on Maximizing Aqua Feed Pellet Properties Using Response Surface Methodology and Genetic Algorithm

Aims: The present case study is on maximizing the aqua feed properties using response surface methodology and genetic algorithm. Study Design: Effect of extrusion process variables like screw speed, L/D ratio, barrel temperature, and feed moisture content were analyzed to maximize the aqua feed properties like water stability, true density, and expansion ratio. Place and Duration of Study: This study was carried out in the Department of Agricultural and Food Engineering, Indian Institute of Technology, Kharagpur, India. Methodology: A variable length single screw extruder was used in the study. The process variables selected were screw speed (rpm), length-to-diameter (L/D) ratio, barrel temperature (degrees C), and feed moisture content (%). The pelletized aqua feed was analyzed for physical properties like water stability (WS), true density (TD), and expansion ratio (ER). Extrusion experimental data was collected by based on central composite design. The experimental data was further analyzed using response surface methodology (RSM) and genetic algorithm (GA) for maximizing feed properties. Results: Regression equations developed for the experimental data has adequately described the effect of process variables on the physical properties with coefficient of determination values (R2) of > 0.95. RSM analysis indicated WS, ER, and TD were maximized at L/D ratio of 12-13, screw speed of 60-80 rpm, feed moisture content of 30-40%, and barrel temperature of = 80 degrees C for ER and TD and > 90 degrees C for WS. Based on GA analysis, a maxium WS of 98.10% was predicted at a screw speed of 96.71 rpm, L/D radio of 13.67, barrel temperature of 96.26 degrees C, and feed moisture content of 33.55%. Maximum ER and TD of 0.99 and 1346.9 kg/m3 was also predicted at screw speed of 60.37 and 90.24 rpm, L/D ratio of 12.18 and 13.52, barrel temperature of 68.50 and 64.88 degrees C, and medium feed moisture content of 33.61 and 38.36%. Conclusion: The present data analysis indicated that WS is mainly governed by barrel temperature and feed moisture content, which might have resulted in formation of starch-protein complexes due to denaturation of protein and gelatinization of starch. Screw speed coupled with temperature and feed moisture content controlled the ER and TD values. Higher screw speeds might have reduced the viscosity of the feed dough resulting in higher TD and lower ER values. Based on RSM and GA analysis screw speed, barrel temperature and feed moisture content were the interacting process variables influencing maximum WS followed by ER and TD.

09 BIOMASS FUELS↗
NASA NTRS1987

Slip casting and extruding shapes of rhemium with metal oxide additives. Part 2: Development of grain stabilized rhenium parts for resistojets

The adaptation of the powdered particle process used for pure metal oxides to the coprocessing of rhenium oxides suitable to produce pure miniature resistojet hardware has been successful. Both slip casting and extrusion processes were used. The metal oxide ZrO2 was stabilized into the cubic phase with Y2O3, for use as a potentially grain stabilizing additive to rhenium. Straight meter long tubing in two sizes are reported. Tubing suitable for resistojet ohmic heater use of fully fired dimensions of nominally 3.8 mm o.d. x 2.2 mm i.d.. and 1.26 mm o.d. x .45 mm i.d. with 0, 0.5, 1.0 and 5.0% zirconia additives were produced for further study. Photomicrographs of these are discussed. The addition of the metal oxide zirconia to rhenium resulted in more dense and less porous parts. The additions of phase stabilized zirconia most likely act as a sintering aid. Tubes of varying diameter were slip cast which were representative of miniature pressure cases.

Barr, Francis A.↗
DOE OSTI2019

Simulation Assisted Design for an Additively Manufactured Autoclave Tool Accounting for an Anisotropic Expansion

Carbon fiber reinforced polymer composites have been used in Big Area Additive Manufacturing (BAAM) to decrease the distortion during the printing process and increase functional stiffness. These materials are also important for additively manufactured autoclave tooling which expands when exposed to the high temperatures of the operational cycle, causing the dimensions of the mold to differ from the targeted design. Since the reinforcing fibers generally align during the extrusion process, the thermal expansion of the composite along the deposition direction is restrained by fibers, whereas the thermal expansion perpendicular to the bead is largely unconstrained. This leads to an anisotropic expansion of the material that is dependent upon the local deposition path, which may be tortuous and complex. To obtain an accurate final part geometry during the autoclave process, a computational prediction of the thermal expansion of a tool is required to account for the complex extrusion deposition directions. A multi-step approach is presented that accounts for (1) anisotropic thermal expansion of the extruded bead, (2) the complex deposition directions, and (3) internal geometry determined by slicing software. The thermal expansion coefficient in the deposition direction and perpendicular to the deposition direction were measured at multiple locations in the test specimen. A revised model geometry was generated to achieve the target dimensions when accounting for thermal expansion.

Hassen, Ahmed↗
NASA NTRS1980

Development of a solvent processed insensitive propellant

Two types of low vulnerability propellants are studied which are distinguished by whether the binder is a rubber, such as polyurethane or CTBN, or a plasticizable polymer such as ethyl cellulose or cellulose acetate. The former propellants are made by a partial cure extrusion process while the latter are made by the conventional solvent process. Emphasis is given to a cellulose binder (plasticizer) RDX composition. The type of binder used, the particle size of the RDX and the presence of small quantities of nitrocellulose in the solvent processed compositions have important influences on the mechanical and combustion characteristics of the propellant. The low temperature combustion is of particular concern because of potential breakup of the grains that can lead to instability.

Trask, R.↗
DOE OSTI2015

Pre-conceptual Development and characterization of an extruded graphite composite fuel for the TREAT Reactor

In an effort to explore fuel systems that are more robust under accident scenarios, the DOE-NE has identified the need to resume transient testing. The Transient Reactor Test (TREAT) facility has been identified as the preferred option for the resumption of transient testing of nuclear fuel in the United States. In parallel, NNSA’s Global Threat Reduction Initiative (GTRI) Convert program is exploring the needs to replace the existing highly enriched uranium (HEU) core with low enriched uranium (LEU) core. In order to construct a new LEU core, materials and fabrication processes similar to those used in the initial core fabrication must be identified, developed and characterized. In this research, graphite matrix fuel blocks were extruded and materials properties of were measured. Initially the extrusion process followed the historic route; however, the project was expanded to explore methods to increase the graphite content of the fuel blocks and explore modern resins. Materials properties relevant to fuel performance including density, heat capacity and thermal diffusivity were measured. The relationship between process defects and materials properties will be discussed.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2018

Low shear process for producing polymer composite fibers

A method for producing a polymer composite fiber comprised of a polymer matrix with filaments incorporated therein whose lengthwise dimensions are substantially oriented with the axial dimension of the composite fiber, the method comprising subjecting a melt comprised of a polymer matrix and filaments to an extrusion process in which the melt is extruded into a fibrous form in the absence of screw extruders and in the substantial absence of shear forces that result in breakage of the filaments, followed by cooling and solidification of the extruded melt to provide the polymer composite fiber. Integration of these polymer composite fibers with additive manufacturing technologies, particularly rapid prototyping methods, such as FFF and 3D printing, are also described. The resulting polymer composite fibers and articles made thereof are also described.

36 MATERIALS SCIENCE↗
DOE OSTI2015

Spectroscopic investigation of the constituent components effect on the biodegradable package characteristics

The effect of the nature and the content of the plasticizers (water, glycerol) on the corn starch based biodegradable packages properties (crystalline-amorphous) and also on their degradation process after absorption of distilled water were investigated by {sup 1}H NMR relaxation and {sup 13}C CP/MAS NMR spectroscopies. For this goal, a set of 14 samples with various starch/glycerol/water (mass %) ratios were prepared and investigated after extrusion process in order to establish their crystalline or amorphous character. The composition having starch/glycerol/water 68/17/15 mass % ratio was found to have a dominant amorphous character and very similar features with a commercial specimen (USA) used for the package. It was also found that this best package is extremely degraded after just one day under water absorption. The most resistant package was that with a large content of starch (78/19.5/2.5)

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
NASA NTRSDate not supplied

Fabrication of Extruded Polyphenylsulfone – Boron Nitride Composite Tapes

Polyphenylsulfone (PPSU) is a high-temperature, chemically resistant thermoplastic with high impact resistance that is often used in interior aircraft cabin components, medical devices, and membranes. The aforementioned properties have led to interest investigating PPSU’s compatibility with hexagonal boron nitride (hBN) platelets as a thermally conductive, electrical composite insulator for high power-density electric machines. Preliminary trials extruding PPSU-hBN composite tapes showed promising dielectric properties and higher thermal conductivity as a function of hBN concentration compared to their neat analog. On the other hand, only few studies have reported on the extrusion process and resulting thermo-mechanical properties for PPSU and its composites made with chopped fiber reinforcement or fillers, none of which containing boron nitride filler. Prospects may exist for this type of material to be incorporated into extrusion-based additive manufacturing techniques to print other composites bearing unique properties useful for aerospace. Loading levels with up to approximately 23 wt% were achieved using micro-size BN platelets without observing any significant affects to PPSU’s glass-transition temperature. This work includes a description of the rheological properties of PPSU, the extrusion parameters for mixing and compounding the PPSU-hBN composite tapes, and the thermal and thermo-mechanical properties of PPSU-hBN composites.

polyphenylsulfone↗
NASA NTRSDate not supplied

Fabrication of Extruded Polyphenylsulfone – Boron Nitride Composite Tapes

Polyphenylsulfone (PPSU) is a high-temperature, chemically resistant thermoplastic with high impact resistance that is often used in interior aircraft cabin components, medical devices, and membranes. The aforementioned properties have led to interest investigating PPSU’s compatibility with hexagonal boron nitride (hBN) platelets as a thermally conductive, electrical composite insulator for high power-density electric machines. Preliminary trials extruding PPSU-hBN composite tapes showed promising dielectric properties and higher thermal conductivity as a function of hBN concentration compared to their neat analog. On the other hand, only few studies have reported on the extrusion process and resulting thermo-mechanical properties for PPSU and its composites made with chopped fiber reinforcement or fillers, none of which contained boron nitride filler. Prospects may exist for this type of material to be incorporated into extrusion-based additive manufacturing techniques to print other composites bearing unique properties useful for aerospace. Loading levels with up to approximately 23 wt% were achieved using micro-size BN platelets without observing any significant affects to PPSU’s glass-transition temperature. This work includes a description of the rheological properties of PPSU, the extrusion parameters for mixing and compounding the PPSU-hBN composite tapes, and the thermal and thermo-mechanical properties of PPSU-hBN composites.

Tiffany Williams↗
DOE OSTI2019

System and process for formation of extrusion products

Devices and processes for performing shear-assisted extrusion include a rotatable extrusion die with a scroll face configured to draw plasticized material from an outer edge of a billet generally perpendicularly toward an extrusion orifice while the extrusion die assembly simultaneously applies a rotational shear and axial extrusion force to the billet.

Lavender, Curtis A.↗
DOE OSTI2016

Development of thermoelectric fibers for miniature thermoelectric devices

Miniature thermoelectric (TE) devices may be used in a variety of applications such as power sources of small sensors, temperature regulation of precision electronics, etc. Reducing the size of TE elements may also enable design of novel devices with unique form factor and higher device efficiency. Current industrial practice of fabricating TE devices usually involves mechanical removal processes that not only lead to material loss but also limit the geometry of the TE elements. In this project, we explored a powder-processing method for the fabrication of TE fibers with large length-to-area ratio, which could be potentially used for miniature TE devices. Powders were milled from Bi2Te3-based bulk materials and then mixed with a thermoplastic resin dissolved in an organic solvent. Through an extrusion process, flexible, continuous fibers with sub-millimeter diameters were formed. The polymer phase was then removed by sintering. Sintered fibers exhibited similar Seebeck coefficients to the bulk materials. Moreover, their electrical resistivity was much higher, which might be related to the residual porosity and grain boundary contamination. Prototype miniature uni-couples fabricated from these fibers showed a linear I-V behavior and could generate millivolt voltages and output power in the nano-watt range. Further development of these TE fibers requires improvement in their electrical conductivities, which needs a better understanding of the causes that lead to the low conductivity in the sintered fibers.

36 MATERIALS SCIENCE↗