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At least 91 records · Page 5
All sourcesNASA NTRSDOE OSTI
DOE OSTI2023

Indirect additive manufacturing process

A method for indirect additive manufacturing of an object, the method comprising: (i) separately feeding a powder from which said object is to be manufactured and either a difunctional curable monomer according to Formula (I) or an adhesive polymer binder into an additive manufacturing device; (ii) dispensing selectively positioned droplets of said difunctional curable monomer or adhesive polymer binder, from a printhead of said additive manufacturing device, into a bed of said powder to bind particles of said powder with said difunctional curable monomer or adhesive polymer binder to produce a curable preform having a shape of the object to be manufactured; and, in the case of the difunctional curable monomer, (iii) curing said curable preform to form a crosslinked object.

Saito, Tomonori↗
DOE OSTI2023

Reducing warpage in a hybrid large-scale additive manufacturing and compression molding process

In recent years, a hybrid manufacturing process, developed by combining extrusion-based large-scale additive manufacturing (AM) and compression molding (CM) techniques, has shown promising outcomes for producing structurally functional parts. The process can be used with both short fiber-reinforced composites and neat polymers and hence, even multi-material parts can be manufactured easily. This process offers the advantages of structural enhancement by having a desired fiber orientation using a large-scale AM process, as well as rapid manufacturing capability using a CM process. In the large-scale AM process, the alignment of fibers in the deposition direction enables significant improvement in the mechanical properties of the manufactured parts. However, the anisotropy resulting from the directional arrangement of fibers also introduces challenges related to warpage in the produced parts. This study aims to identify the causes of warpage and propose strategies to mitigate it. The research involves the use of preforms manufactured through the large-scale AM, which are then combined with the neat resin for CM manufacturing. A finite element-based numerical simulation model is developed, employing a sequentially coupled thermomechanical approach. Through a parametric study using the simulation models, optimization of printing direction and preform geometry is performed to minimize warpage. This contributes to the advancement and wider adoption of AM/CM hybrid manufacturing to produce structurally functional parts.

Jo, Eonyeon↗
DOE OSTI2023

Method for fabrication of sleeveless photonic crystal canes with an arbitrary shape

The fabrication of sleeveless canes utilizes a preform with an array of glass canes in the preform. At least one tube-sleeve encircles the array of glass canes and is secured to the array of glass canes. The array of glass canes is moved into a furnace wherein the array of glass canes is heated. The furnace is maintained at a furnace temperature within the range of 2000° C. to 1700° C. and the array of glass canes is drawn from the furnace. The drawing of the array of glass canes both scales down the glass canes and elongates the glass canes. Maintaining the furnace at a furnace temperature within the range of 2000° C. to 1700° C. assures that the array of glass canes and the glass canes maintain their original shape.

Drachenberg, Derrek Reginald↗
DOE OSTI2020

Synthesis and Characterization of Pd-based Nanomaterials

Bimetallic nanoparticles (BNPs) consist of two different types of metals or alloys that are bonded together. Unique properties such as optical, electronic, thermal, and catalytic effects differ for each type of BNP. Important BNPs range from Au-Pd, Ag- Pt, Au-Pt, and Ag-Ni. Pd bimetallic nanoparticles are of interest due to their many applications such as catalysis and sensing. Bimetallic catalysts have increase reaction rates and have improved catalyst stability through the geometry and ligand distribution. Pd nanoparticles are considered to be a strong catalyst due to their high activity at low temperatures and high tolerance to moisture. The catalytic properties of bimetallic nanoparticles depend on the structural properties such as size and shape. Core-shell, hollow structure, and multi-shell alloy are three possible structures nanoparticles can form as bimetallic catalysts. BNPs can be synthesized through different methods to control the size, shape, and structure. To obtain different morphologies, a variety of methods can be performed. Different methods can range from the usage of the glancing angle deposition (GLAD) to the galvanic replacement reaction, but the methods all depend on the properties of the metals. The galvanic displacement reaction was the method used to obtain Pd-based nanoparticles. This reaction is best know for obtaining hollow shaped NPs. To determine what redox process was preformed, the activity series of metals was used. From the activity series of metals, silver (Ag) was selected to preform Pd-based nanoparticles. Objectives: Synthesize Ag nanoparticles and Ag-Pd nanoparticles to understand the morphology. Characterize the synthesized nanoparticles using scanning electron microscopy (SEM), phase analysis light scattering (PALS), dynamic light scattering (DLS), energy dispersive X-ray spectroscopy (EDS), and UV-Vis spectroscopy. Results: In the UV-Vis spectrum, the Ag-Pd bimetallic NP's plasmon band decreased as the volume of palladium increased. The surface charge increases as the concentration of palladium increases. The Pd{sup 2+} ions interact with the sodium citrate surface, and decrease the negative charge. Conclusion: Ag-Pd nanoparticles were successfully created and stabilized with sodium citrate. The addition of Pd decreased the prominent plasmon band of the Ag nanoparticles. The SEM analysis showed that Ag nanoparticles had a well-defined structure, while the Ag-Pd nanoparticles showed hollow and rough structure. The EDX analysis confirmed the presence of silver and palladium. This material can be used in many industrial and research fields such as organic synthesis, fuel cells, and environmental sensing and remediation.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2024

Accelerating the Scalability of PrintCast structures using High Pressure Die Casting

PrintCast composites are fabricated by infiltrating a metal mesh or preform (e.g., an additively-manufactured 316L lattices) with molten metal of a lower melting temperature (e.g., A380 aluminum). The resulting PrintCast composite has been shown in the literature to produce diverse and unique mechanical properties that are controllable at the local or global level by adjusting volume-fraction and/or topology of the preforms geometry and overall volume fraction. Although promising mechanical and thermal properties have been achieved at the laboratory scale level, the scalability from laboratory to full scale components has been limited using conventional casting infiltration. This work highlights how using high pressure die casting can significantly advance the development and eventual deployment of PrintCast approaches at large scales. We have successfully produced 9-inch by 6-inch by 1-inch thick PrintCast 316L stainless steel/A380 aluminum “bricks” via high pressure die casting. Initial findings show excellent infiltration and production capability. The resulting approach demonstrates the scalability and manufacturability of hybrid cost effective metal-metal matrix composites at larger length scales with high quality infiltration results.

Splitter, Derek↗
DOE OSTI2024

Additive manufacturing process for producing aluminum-boron carbide metal matrix composites

A method for additive manufacturing of a composite object containing a bonded network of boron carbide particles and aluminum occupying spaces between boron carbide particles, the method comprising: (i) producing a porous preform constructed of boron carbide by an additive manufacturing process in which particles of boron carbide are bonded together; and (ii) infiltrating molten aluminum, at a temperature of 1000-1400° C., into pores of said porous preform to produce said composite object constructed of boron carbide particles within an aluminum matrix, wherein the boron carbide is present in the composite object in an amount of 30-70 wt. %. The resulting composite material is also herein described.

Cramer, Corson L.↗
DOE OSTI2022

Fully Distributed Multi-Material Magnetic Sensing Structures for Multiparameter DAS Applications

This dissertation demonstrates the first of its kind distributed magnetic field sensor based on a fiber optic distributed acoustic sensing (DAS) scheme. Ferromagnetic nickel and Metglas® were dispersed internally within a fiber optic preform and then drawn on an in-house fiber optic draw tower to lengths in the kilometers. Due to the close proximity of the ferromagnetic metals and fiber optic core, the magnetostrictive strain response of the ferromagnetic materials when exposed to a magnetic field would perturbate within the fiber cladding and transfer that strain, internally, to the fiber optic core. Strain resulting from the magnetostrictive effect allows the DAS based sensor to accurately translate strain into readable magnetic field data. Due to the high sensitivity seen in this sensor design, multiparameter sources, acoustic and magnetic fields, were tested and validated and a three dimensional magnetic-field vector sensor was proposed. Numerical analysis of the novel sensor design was first implemented using COMSOL Multiphysics, where inputs such as magnetostrictive element shape, size, distance, and number were first investigated. Upon optimizing system constraints, the sensor design was further modified such that single mode operation was consistent across multiple fiber draws while retaining high strain transfer from the ferromagnetic elements to the fiber optic core. Ferromagnetic material selection was evaluated as a function of the saturation magnetostriction constants and a total of 4 modules were used to fully characterize the complex physics involved in this sensor design. All fabrication and testing were performed in-house using a full scale 3-story fiber draw tower and custom environmental testing stations to imitate naturally occurring events such as magnetic or acoustic point sources. A unique stacking method was used to embed ferromagnetic nickel and Metglas® into a fiber optic preform which when combined with a custom fiber draw process resulted in consistent multi-material fibers drawn to lengths of 1-km. In-house testing facilities included different types of electromagnetic generators, in addition to a soil test bed, and an outdoor test bed which allowed 100 meters of fiber to be tested simultaneously. All tested sensors demonstrated high strain transfer capabilities on the order of 0.01-10 μϵ depending on the materials used, ferromagnetic rod number, and core to metal spacing. Due to the sensitivity of the system the difference between AC and DC was distinct, and directional magnetostriction was studied. Transverse and longitudinal magnetic wave propagation was controlled through a solenoid and rectangular Helmholtz coil, both built in-house. A three-dimensional magnetic field vector sensor was proposed due to the success of the magnetic field sensor, and a design was proposed and initially tested to validate direction as a function of field strength and distance. To summarize, this dissertation explores the first fully distributed magnetic field sensor using DAS based techniques and one of the first multi-material fiber draw processes which can produce consistent single mode fiber up to 1-km. Due to extensive FEA modeling, multiple iterations of the magnetic sensor were fully characterized and an equation describing the relationship between sensor design and strain transfer has been created and validated experimentally. Multi-parameter tests including acoustic and magnetic fields were implemented and an algorithm was developed to separate the mixed signals. Finally, a test was performed to demonstrate the feasibility of sensing magnetic fields directionally. Cumulative results demonstrate a high-quality sensor alternative to current designs which may surpass other magnetic sensors due to innate multi-parameter capabilities, in addition to the inexpensive production cost and extremely long operating lengths.

02 PETROLEUM↗
DOE OSTI2021

Evaluation of Low-Pressure-Sintered Multi-Layer Substrates for Medium-Voltage SiC Power Modules: Preprint

Direct-bonded aluminum (DBA) multi-layer substrates have been fabricated using low-pressure silver sintering. These multi-layer substrates can be used to reduce the peak electric field strength inside power modules. This benefit is particularly important for medium-voltage silicon carbide (SiC) MOSFETs due to their higher operating voltages. The voiding content and defect density of the bond used to create the multi-layer substrate stackup is critical to the thermal performance and reliability of the power module. This work two low-pressure-assisted sintering techniques; one using nano-silver preform and the other using nano-silver paste to bond 23 mm by 49 mm DBA substrates. Scanning acoustic microscopy (C-SAM) is used to evaluate the bond quality after sintering. To evaluate the reliability of the sintered multi-layer substrates, passive thermal cycling from –40 °C to 200 °C was performed. Cross-sections were cut at pre-determined intervals and imaged with Scanning Electron Microscopy (SEM). After 1,000 thermal cycles, minor cracking was observed, but no failures have occurred.

28 EE - Advanced Manufacturing Office (EE-5A)↗
DOE OSTI2021

Preventing Electrolyte Decomposition on a Ca Metal Electrode Interface Using an Artificial Solid‐Electrolyte Interphase

Abstract Calcium ion batteries are gaining attention as alternatives to lithium‐ion technology because they offer comparable properties at reduced cost and improved safety. However, progress has been limited because of the inability to efficiently and reversibly plate and strip Ca metal anodes in organic electrolytes. Moreover, the inorganic components of the solid‐electrolyte interphase (SEI) that form via decomposition of the electrolyte often do not allow for the diffusion of Ca ions. In this work, an approach combining density functional theory and ab initio molecular dynamics (AIMD) simulations is utilized to show that the use of a preformed artificial SEI layer of amorphous can potentially prevent electrolyte decomposition. First, Ca is shown to be able to intercalate into an amorphous layer (up to Ca 1.5 Al 2 O 3 ) and diffuse through on a reasonable time scale. Through calculation of the density of states, the system is found to remain insulating up to the equilibrium stoichiometry. Finally, AIMD simulations with a realistic organic electrolyte environment are used to show that this calcinated layer completely prevents the decomposition of solvent molecules. This approach can provide a route to efficient rechargeable Ca ion batteries, paving the way for cheap large‐scale energy storage.

Young, Joshua↗
DOE OSTI2025

B‐Staging and Crosslinking of Polycarbosilane at Room Temperature: Cure Mechanism and Properties

The viscosity of polycarbosilane (PCS) polymers is not advantageous for free forming. Various fillers and heat are used to obtain a formable paste. Due to the low yield stress, structures and preforms tend to slump or resin will flow out, especially during the curing of the polymer. B-staging of PCS allows for a more stable structure from room temperature until the full cure of the allyl groups occurs with heat. Additionally, hydrosilation is an effective means of crosslinking at room temperature and controlling viscosity. A network structure was formed in SMP-10 using silane and a vinyl-based crosslinker to bridge each polymer chain. Pt addition catalysts were added to enhance the increase in viscosity to make a lightly crosslinked gel to aid in thickening and forming and to improve the ceramic yield at 1000°C. In conclusion, this enables several options for controlling rheology and improving the properties of preceramic polymers to avoid slumping during curing.

inorganic polymers↗
DOE OSTI2024

Ability of x‐ray computed tomography to resolve critical flaw size in laser‐based, paste stereolithography ceramic printing of alumina

Abstract Complex alumina parts were printed using vat photopolymerization (VPP), which is a stereolithography‐based additive manufacturing (AM) technique used to shape ceramic preforms, or green parts. The critical flaw size was determined using classical fracture mechanics techniques. The strength and fracture toughness were measured and compared to flaws detected in x‐ray computed tomography (XCT or CT) distributions as well as the fracture surfaces. The strength was lower compared traditionally made alumina, and that is due to layering effects, slurry defects, and printing defects. The critical flaw size from fracture mechanics was 206 µm. XCT has high enough resolution to detect the critical flaw size and much smaller features, where the average flaw size observed in CT scans was around 80–100 µm. The fracture surfaces indicate that flaws causing failure are larger than that of the critical flaw size (∼300 µm), but fracture surfaces do not show definitive features compared to traditionally made ceramics. Since XCT can observe flaws smaller than the critical flaw size, this method can be used as a screening technique.

36 MATERIALS SCIENCE↗
DOE OSTI2025

Volcano‐like Activity Trends in Au@Pd Catalysts: The Role of Pd Loading and Nanoparticle Size

The addition of palladium (Pd) to preformed gold nanoparticles (Au NPs) enables the formation of core‐shell structures with enhanced catalytic performance in oxidation reactions. However, predicting the precise palladium content required to achieve maximum catalytic activity remains difficult based on current understanding. Herein, Pd was systematically introduced onto titania‐supported Au NPs (2, 6, and 10 nm) to evaluate their performance in benzyl alcohol oxidation. A volcano‐like trend in catalytic activity was observed, where activity increased with Pd addition, peaked, and then declined. The Pd loading required for maximum activity depended on Au NP size: ≈40 at% Pd/Au for 2.6 nm, ≈20 at% Pd/Au for 6.4 nm, and ≈12.5 at% Pd/Au for 10.6 nm. For Au NPs > 6 nm, peak activity aligned with monolayer Pd coverage, while for smaller NPs (2–3 nm), optimal Pd content was below monolayer predictions. X‐ray absorption spectroscopy revealed a core‐shell structure at low Pd content, but higher Pd loadings led to Pd diffusion into the Au core. This structural transformation likely caused activity decline, indicating that AuPd alloying negatively impacts catalysis. These results highlight that core‐shell Au@Pd catalysts outperform AuPd alloys and provide crucial insights for designing highly active bimetallic catalysts.

X-ray absorption spectroscopy↗
DOE OSTI2021

Absolute quantitation of propranolol from 200-μm regions of mouse brain and liver thin tissues using laser ablation-dropletProbe-mass spectrometry

Rationale: The ability to quantify drugs and metabolites in tissue with sub-mm resolution is a challenging but much needed capability in pharmaceutical research. To fill this void, a novel surface sampling approach combining laser ablation with the commercial dropletProbe automated liquid surface sampling system (LA-dropletProbe) was developed and presented here.Methods: Parylene C-coated 200 × 200 μm tissue regions of mouse brain and kidney thin tissue sections were analyzed for propranolol by laser ablation of tissue directly into a preformed liquid junction. Propranolol was detected by high performance liquid chromatography with positive ion mode electrospray ionization tandem mass spectrometry. Quantitation was achieved via application of a stable isotope-labeled internal standard and an external calibration curve.Results: Absolute concentration of propranolol determined from 200 × 200 µm tissue regions were compared to propranolol concentrations obtained from 2.3-mm-diameter tissue punches of adjacent, non-coated sections using standard bulk tissue extraction protocols followed by regular HPLC-MS/MS analysis. Average concentration of propranolol in both organs determined by the two employed methods agreed within ±12%. Furthermore, the relative abundance of phase II hydroxypropranolol glucuronide metabolites were recorded and found to be consistent with previous results.Conclusions: This work illustrates that depositing a thin parylene C layer onto thin tissue prior to analysis, which seals the surface and prevents direct liquid extraction of the drug from the tissue, coupled to the novel LA-dropletProbe surface sampling system is a viable approach for sub-mm resolution quantitative drug distribution analysis.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2020

The practice and economics of hybrid poplar biomass production for biofuels and bioproducts in the Pacific Northwest

Hybrid poplar demonstration-scale farms were managed in Oregon, Washington, Idaho, and California to establish management practices, yields, harvesting methods, and the economics of biomass production. Yield during the 2-year establishment cycle averaged 3.5 dry Mg ha –1 year –1 increasing to 11.6 Mg ha –1 year –1 in the ensuing 3-year coppice cycle. Populus deltoides (Bartram ex Marsh.) × P. maximowiczii (Henry) varieties preformed best in Oregon during the coppice cycle with the best variety producing 18.1 Mg ha –1 year –1 , while P. ×generosa (Henry) varieties maximized yields in Washington at 22.1 Mg ha –1 year –1 . P. ×canadensis (Moench) varieties excelled in Idaho and California with upper yields of 13.6 Mg ha –1 year –1 and 12.9 Mg ha –1 year –1 , respectively. Stands were cut with a single-pass harvester 2 years after planting and a second time after 3 years of coppice growth; material capacity, limited by poor ground conditions, varied between 21.7 to 31.3 green Mg h –1 . Chemical composition averaged 1.87% inorganics, 7.74% extractives, 26.90% lignin, 38.07% glucan, 13.66% xylan, 1.61% galactan, 1.14% arabinan, and 2.76% mannan. Production costs (USD) projected over a 20-year rotation of six coppice cycles were $71.81 Mg –1 in Washington, $89.91 Mg –1 in Oregon, $98.76 Mg–1 in Idaho, and 179.07 Mg–1 in California. Here, land rental, establishment, crop care, harvest, transportation, and land restoration, respectively, accounted for 23%, 5%, 19%, 30%, 17%, and 6% of total feedstock cost. Farms were successfully restored to conditions existing before poplar conversion. In the absence of fertilization, increases in soil pH and decreases in nitrate-nitrogen, zinc, iron, and organic matter were consistently noted but could not be associated with poplar production alone.

09 BIOMASS FUELS↗
DOE OSTI2025

Part distortion monitoring in additive manufacturing using machining

In additive manufacturing, accumulation of residual stresses can result in severe part distortion from the desired preform shape. Current methods for in-situ part distortion monitoring in additive manufacturing typically require expensive sensors, or capital equipment, and require time-consuming post-processing to understand the shape deviation. This paper presents an in-situ method, in the context of hybrid manufacturing, for part distortion detection using machining of additively manufactured parts. As a surrogate, three test artifacts were used to represent different distorted geometries. The tool axis positions from the machine tool controller and the cutting power were monitored during a facing operation. Cutting power data was used to detect the tool entry and exit in the workpiece using a novel approach with power standard deviation metric. The workpiece geometry and distorted configuration was subsequently predicted for positional and rotational deviations to within 2 mm accuracy using synchronized tool position data with cutting power. The proposed method can be used in a hybrid (additive and subtractive) machine tool to periodically check part distortion in the additive build. The method is applicable for any additive process and is low-cost and computationally inexpensive.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Two distinct rotations of bithiazole DNA intercalation revealed by direct comparison of crystal structures of Co(III)•bleomycin A 2 and B 2 bound to duplex 5'-TAGTT sites

Bleomycins constitute a family of anticancer natural products that bind DNA through intercalation of a C-terminal tail/bithiazole moiety and hydrogen-bonding interactions between the remainder of the drug and the minor groove. The clinical utility of the bleomycins is believed to result from single- and double-strand DNA cleavage mediated by the HOO-Fe(III) form of the drug. The bleomycins also serve as a model system to understand the nature of complex drug-DNA interactions that may guide future DNA-targeted drug discovery. In this study, the impact of the C-terminal tail on bleomycin-DNA interactions was investigated. Toward this goal, we determined two crystal structures of HOO-Co(III)•BLMA 2 “green” (a stable structural analogue of the active HOO-Fe(III) drug) bound to duplex DNA containing 5'-TAGTT, one in which the entire drug is bound (fully bound) and a second with only the C-terminal tail/bithiazole bound (partially bound). The structures reported here were captured by soaking HOO-Co(III)•BLMA 2 into preformed host–guest crystals including a preferred DNA-binding site. While the overall structure of DNA-bound BLMA 2 was found to be similar to those reported earlier at the same DNA site for BLMB 2 , the intercalated bithiazole of BLMB 2 is “flipped” 180° relative to DNA-bound BLMA 2 . Further, this finding highlights an unidentified role for the C-terminal tail in directing the intercalation of the bithiazole. In addition, these analyses identified specific bond rotations within the C-terminal domain of the drug that may be relevant for its reorganization and ability to carry out a double-strand DNA cleavage event.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2021

Formation, structure, and thermal stability evolution of ternesite based on a single-stage sintering process

Highlights: • The synthesis of high-purity ternesite based on a single-stage sintering process was firstly studied. • The formation mechanism and crystallization behaviour of ternesite during sintering were investigated. • The structure perfection and symmetry of ternesite crystals were increased with its growth. • The growth and structural development of ternesite crystals during sintering resulted in a higher thermal stability of itself. Ternesite was prepared via a single-stage solid-state reaction from stoichiometric quantities of the CaCO{sub 3}, SiO{sub 2} and CaSO{sub 4}·2H{sub 2}O precursors. In this paper, the formation, structure, and thermal stability evolution of ternesite during sintering were investigated ex situ after quenching. The optimal sintering temperature for the formation of high-purity ternesite was approximately 1200 °C for 12 h, of which the purity level can reach as high as 96.3%. The results from scanning electron microscopy analysis suggest that the formation of ternesite benefited from the preformation of the intermediate silicate phase. Increasing the sintering temperature from 1100 °C to approximately 1250 °C was favourable for the growth of ternesite crystals, and a prolonged duration can also promote this behaviour. The structural perfection and symmetry of ternesite crystals increased with its growth, which was demonstrated by a multimethod approach. By means of thermal analysis, the growth and structural development of ternesite crystals during sintering eventually resulted in a higher thermal stability.

36 MATERIALS SCIENCE↗