Search NASA⌕ Search

Engineering topics

Spadaccini, Christopher

Publications and source records attributed to Spadaccini, Christopher.

At least 19 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2024

System and method for computed axial lithography (CAL) for 3D additive manufacturing

In one aspect the present disclosure relates to a system for forming a three dimensional (3D) object from a volume of photo-responsive material contained within a material container. A plurality of optical projection subsystems are adapted to be arranged at least partially circumferentially around a material container containing the volume of photo-responsive material, and are controlled by a controller. The optical projection subsystems direct optical projections at a plurality of angles θ through the volume of photo-responsive material. The optical projections are further directed about a z axis extending through the volume of photo-responsive material. The plurality of optical subsystems are further controlled by the controller to provide each of the optical projections with a calculated three-dimensional intensity distribution acting over a fixed temporal exposure period, which is sufficient to at least one of cure or remove selected portions of the volume of photo-responsive material, and leave other portions unmodified, to form a desired 3D part.

Kelly, Brett↗
DOE OSTI2024

Additive manufacturing of hierarchical three- dimensional micro-architected aerogels

Disclosed here is a method for making a three-dimensional micro-architected aerogel, comprising: (a) curing a reaction mixture comprising a co-sol-gel material (e.g., graphene oxide (GO)) and at least one catalyst to obtain a crosslinked co-sol-gel (e.g., GO hydrogel); (b) providing a photoresin comprising a solvent, a photoinitiator, a crosslinkable polymer precursor, and a dispersion of the crosslinked co-sol-gel (e.g., GO hydrogel); (c) curing the photoresin using projection microstereolithography layer-by-layer to produce a wet gel having a pre-designed three-dimensional structure; (d) drying the wet gel to produce a dry gel; and (e) pyrolyzing the dry gel to produce a three-dimensional micro-architected aerogel (e.g., graphene aerogel). Also disclosed is a photoresin for projection microstereolithography, comprising a solvent, a photoinitiator, a crosslinkable polymer precursor, and a dispersion of a crosslinked co-sol-gel.

Worsley, Marcus A.↗
DOE OSTI2024

Base-catalyzed sol-gel inks for direct ink writing of high resolution hierarchically porous carbon aerogels

According to one aspect of an inventive concept, an ink includes a base catalyst, a sol gel precursor composition, and a block copolymer. According to another aspect of an inventive concept, an aerogel includes a three-dimensional printed structure having printed ligaments geometrically arranged, where an average diameter of the printed ligaments is in a range of greater than 0 microns and less than 50 microns. In addition, an average distance between a center of a first of the printed ligaments and a center of a second of the printed ligaments is at least equal to the average diameter of the printed ligaments, where the first and the second of the printed ligaments are adjacent. Each printed ligament includes of a plurality of random pores, where an average diameter of the random pores is less than 50 nanometers.

Zhu, Cheng↗
DOE OSTI2023

Neutron generation using pyroelectric crystals

A method for producing a neutrons includes producing a voltage of negative polarity of at least −100 keV on a surface of a deuterated or tritiated target in response to a temperature change of a pyroelectric crystal of less than about 40° C., the pyroelectric crystal having the deuterated or tritiated target coupled thereto, pulsing a deuterium ion source to produce a deuterium ion beam, accelerating the deuterium ion beam to the deuterated or tritiated target, and directing the ion beam onto the deuterated or tritiated target to make neutrons using at least one element of the following: a voltage of the pyroelectric crystal and a high gradient insulator (HGI) surrounding the pyroelectric crystal. The accelerating of the deuterium ion beam is achieved by using an ion accelerating mechanism comprising a pyroelectric stack accelerator having a first thermal altering mechanism for changing a temperature of the pyroelectric stack accelerator.

Tang, Vincent↗
DOE OSTI2023

Laser pulse shaping for additive manufacturing

The present disclosure relates to an apparatus for additively manufacturing a product in a layer-by-layer sequence, wherein the product is formed using powder particles deposited on an interface layer of a substrate. A laser generates first and second beam components. The second beam component has a higher power level and a shorter duration than the first beam component. A mask creates a 2D optical pattern in which only select portions of the second beam components can irradiate the powder particles. The first beam component heats the powder particles close to a melting point, where the particles experience surface tension forces relative to the interface layer. While the particles are heated, the second beam component further heats the particles and also melts the interface layer before the surface tension forces can act on and distort the particles, enabling the particles and the interface layer are able to bond together.

DeMuth, James A.↗
DOE OSTI2022

System and method for computed axial lithography (CAL) for 3D additive manufacturing

In one aspect the present disclosure relates to a system for forming a three dimensional (3D) object from a volume of photo-responsive material contained within a material container. A plurality of optical projection subsystems are adapted to be arranged circumferentially around a material container containing the volume of photo-responsive material, and are controlled by a controller. The optical projection subsystems direct optical projections at a plurality of angles θ through the volume of photo-responsive material. The optical projections are further directed about a z axis extending through the volume of photo-responsive material. The plurality of optical subsystems are further controlled by the controller to provide each of the optical projections with a calculated three-dimensional intensity distribution acting over a fixed temporal exposure period, which is sufficient to at least one of cure or remove selected portions of the volume of photo-responsive material, and leave other portions unmodified, to form a desired 3D part.

Kelly, Brett↗
DOE OSTI2022

Anisotropic Thermally Conductive Composites Enabled by Acoustophoresis and Stereolithography

Opportunities to improve thermal management in electronic devices are currently hindered by processing constraints that limit thermal conductivity in polymer-matrix composites. Active patterning of filler particles is a promising route to improve conductivity while retaining processability by improving particle contact density and directing heat along optimized pathways. Here, we employ acoustic patterning to align and compact filler particles into stripes during stereolithographic 3D printing. This approach produces polymer-based composite materials with highly efficient embedded heat transport pathways which reach 95 vol% particle utilization (relative to the parallel conduction upper limit). These composites exhibit anisotropic thermal conductivity up to 300% higher than unpatterned composites, with in-plane anisotropy ratios of up to 350%. Combining this high conductivity with 3D printing enables materials with engineered heat networks that optimize transport from hot spots to heatsinks while maintaining low viscosity for fast particle patterning and for infiltration around electronic components. Finally, numerical simulations of acoustic assembly of particles with varied geometry, when compared to experimentally characterized particle packing, illuminate pathways for further improving conductivity by optimizing particle geometry for alignment and stacking of particles with maximum contact surface area.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Systems and methods for electrical energy storage

The present disclosure relates to an electrical energy storage apparatus which forms an interpenetrating, three dimensional structure. The structure may have a first non-planar channel filled with an anode material to form an anode, and a second non-planar channel adjacent the first non-planar channel filled with a cathode material to form a cathode. A third non-planar channel may be formed adjacent the first and second non-planar channels and filled with an electrolyte. The first, second and third channels are formed so as to be interpenetrating and form a spatially dense, three dimensional structure. A first current collector is in communication with the first non-planar channel and forms a first electrode, while a second current collector is in communication with the second non-planar channel and forms a second electrode. A separator layers separates the current collectors.

Duoss, Eric B.↗
DOE OSTI2021

Direct ink writing of boron carbide monoliths

Direct ink writing – an extrusion-based additive manufacturing process – followed by pressureless sintering was investigated to produce boron carbide monoliths. The effects of ceramic powder loading and Pluronic binder concentration on the rheology of boron carbide pastes were studied and linked to both processing behaviour and final outcome in terms of sintered density and hardness. The effects of printing parameters, in particular orifice diameter and printing speed, were also investigated. Reducing the size of the extrusion nozzle from 584 μm to 406 μm led to significantly better shape retention, lower surface roughness, as well as higher density and hardness. A 203 μm printing orifice was also trialled but was unsuccessful due to faster drying kinetics that occurred with smaller ceramic struts resulting in rapid warping and nozzle clogging. Carbon-black – 8 wt% relative to B 4 C – acted as an effective sintering aid to increase both density and hardness. After optimisation of feedstock and printing parameters, few-layer samples (3–5 layers) had a density as high as ~ 97 % TD and a hardness of ~ 30 GPa. On the other hand, 18-layer specimens had a sintered density of ~ 87 % TD, despite a fully dense microstructure, due to the formation of a 3D array of inter-strut pores. Nevertheless, several issues that arose during manufacturing and post-processing were detrimental to the density and structural integrity of printed specimens; these issues were identified, discussed, and suggestions for future work are provided in this report.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Three-dimensional deterministic graphene architectures formed using three-dimensional templates

In one embodiment, a composition of matter includes: a plurality of ligaments each independently comprising one or more layers of graphene; where the plurality of ligaments are arranged according to a deterministic three-dimensional (3D) pattern. In another embodiment, a method of forming a deterministic three-dimensional (3D) architecture of graphene includes: forming or providing a substrate structurally characterized by a predefined 3D pattern; forming one or more layers of metal on surfaces of the substrate; and forming one or more layers of graphene on surfaces of the metal.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Tunable Mechanical Metamaterial with Constrained Negative Stiffness for Improved Quasi-Static and Dynamic Energy Dissipation

Here we present the computational design, fabrication, and experimental validation of a mechanical metamaterial in which the damping of the material is significantly increased without decreasing the stiffness by embedding a small volume fraction of negative stiffness (NS) inclusions within it. Unlike other systems that dissipate energy primarily through large-amplitude deformation of nonlinear structures, this metamaterial dissipates energy by amplifying linear strains in the viscoelastic host material. By macroscopically tuning the pre-strain of the metamaterial via mechanical loading, the embedded NS inclusions operate about a constrained buckling instability. When further macroscopic vibrational excitation is applied, the inclusions amplify the strains of the surrounding viscoelastic medium. This results in enhanced dissipation of mechanical energy when compared to voided or neat comparison media. Microstereolithography, an emerging high-resolution additive manufacturing (AM) technology, is employed to fabricate the deeply subwavelength inclusions which ensures broadband damping behavior. The mechanically induced broadband energy dissipation and manufacturing approach further differentiate the metamaterial from other approaches that exploit resonances, large deformations, or non-mechanical instabilities. The computational design, fabrication, and experimental evaluation reported is the first dynamic demonstration of such a mechanically tunable NS metamaterial, potentially enabling components with integrated structural and damping capabilities.

42 ENGINEERING↗
DOE OSTI2018

Three-dimensional electronic scaffold for cardiac applications

Disclosed here is a three-dimensional electronic scaffold, comprising a porous scaffold and a plurality of micro-strain gauges distributed spatially inside the porous scaffold, wherein the micro-strain gauges are adapted to detect contraction force. Also disclosed is a method comprising detecting and mapping intra-tissue cardiac contraction force of one or more cardiac cells or tissues disposed in a three-dimensional electronic scaffold, wherein the three-dimensional electronic scaffold comprises a porous scaffold and a plurality of micro-strain gauges distributed spatially inside the porous scaffold and in contact with the cardiac cells or tissues, and wherein the micro-strain gauges are adapted to detect contraction force of the cardiac cells or tissues.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2018

Cross-phase separation of nanowires and nanoparticles

In one embodiment, a process includes creating a mixture of an aqueous component, nanowires and nanoparticles, and a hydrophobic solvent and allowing migration of the nanowires to the hydrophobic solvent, where the nanoparticles remain in the aqueous component. Moreover, the nanowires and nanoparticles are in the aqueous component before the migration.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2018

Three-dimensionally patterned energy absorptive material and method of fabrication

A three-dimensionally patterned energy absorptive material and fabrication method having multiple layers of patterned filaments extrusion-formed from a curable pre-cursor material and stacked and cured in a three-dimensionally patterned architecture so that the energy absorptive material produced thereby has an engineered bulk property associated with the three-dimensionally patterned architecture.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Methods and compositions for rapid thermal cycling

The rapid thermal cycling of a material is targeted. A microfluidic heat exchanger with an internal porous medium is coupled to tanks containing cold fluid and hot fluid. Fluid flows alternately from the cold tank and the hot tank into the porous medium, cooling and heating samples contained in the microfluidic heat exchanger's sample wells. A valve may be coupled to the tanks and a pump, and switching the position of the valve may switch the source and direction of fluid flowing through the porous medium. A controller may control the switching of valve positions based on the temperature of the samples and determined temperature thresholds. A sample tray for containing samples to be thermally cycled may be used in conjunction with the thermal cycling system. A surface or internal electrical heater may aid in heating the samples, or may replace the necessity for the hot tank.

36 MATERIALS SCIENCE↗
DOE OSTI2016

System and method for 3D printing of aerogels

A method of forming an aerogel. The method may involve providing a graphene oxide powder and mixing the graphene oxide powder with a solution to form an ink. A 3D printing technique may be used to write the ink into a catalytic solution that is contained in a fluid containment member to form a wet part. The wet part may then be cured in a sealed container for a predetermined period of time at a predetermined temperature. The cured wet part may then be dried to form a finished aerogel part.

36 MATERIALS SCIENCE↗