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At least 1,459 records · Page 81

All sources NASA NTRS DOE OSTI

NASA NTRS2017

Development of NASA's Sample Cartridge Assembly: Summary of GEDS Design, Development Testing, and Thermal Analyses

Outline: Background of ISS (International Space Station) Material Science Research Rack; NASA SCA (Sample Cartridge Assembly) Design; GEDS (Gravitational Effects in Distortion in Sintering) Experiment Ampoule Design; Development Testing Summary; Thermal Modeling and Analysis. Summary: GEDS design development challenging (GEDS Ampoule design developed through MUGS (Microgravity) testing; Short duration transient sample processing; Unable to measure sample temperatures); MUGS Development testing used to gather data (Actual LGF (Low Gradient Furnace)-like furnace response; Provided sample for sintering evaluation); Transient thermal model integral to successful GEDS experiment (Development testing provided furnace response; PI (Performance Indicator) evaluation of sintering anchored model evaluation of processing durations; Thermal transient model used to determine flight SCA sample processing profiles).

O'Connor, Brian↗

NASA NTRS2015

Selective Laser Melting Inconel 718 Restart Study

Selective Laser Melting (SLM) machines can occasionally shut down (such as in the event of a power failure), which requires the SLM build to be restarted. It has been observed that machine restarts can produce visible "restart lines" in the part, and, in at least one instance, a test specimen containing a restart line exhibited poor mechanical properties. The goal of this study is to evaluate the effect of different machine restart factors on the mechanical properties of the produced SLM material. Test specimens were produced by varying time to restart, the number of re-sinters, and whether or not the build required re-levelling. These are build variables that are typically controlled by the machine operator. Test results indicate that re-leveling and using three re-sinters produces acceptable material. Statistical analysis indicates that re-leveling and re-sintering have strong effects on the resulting material properties. Additionally, the visibility of a restart line loosely correlates with material properties such that obvious restart lines tended to indicate worse material properties.

Tilson, William G.↗

NASA NTRS2018

Physical and Biological Properties of Cobalt- and Copper-Doped Calcium Phosphates as Bone Substitute Materials

Arthritis, osteoporosis, and other bone diseases and defects are common medical issues worldwide. By utilizing ceramic biomaterials as bone substitutes to treat these diseases, bone regeneration can be promoted and toxicity from the substitute material can be limited. Calcium phosphate (CaP) ceramics have become popular as bone substitutes due to their biocompatibility and similarity in composition to natural bone. The purpose of this research was to investigate the physical properties and biological responses of CaP-based bone substitutes, doped with metal ions. Some metal ions are present in natural bone in small amounts, and recent studies show they affect the biological responses of CaPs significantly. Dopants such as magnesium (Mg), strontium (Sr), silicon (Si) and iron (Fe) alter the phase composition, mechanical properties, osteogenesis and angiogenesis properties of CaPs, depending on their concentration and method of addition. In the present study, the effects of cobalt (Co) and copper (Cu) on the physical and biological properties of two main CaP materials, brushite cement (BrC) and tricalcium phosphate (TCP), have been investigated. Different concentrations of dopants in forms of oxide and/or chloride were selected and their effect on phase composition, sintering behavior, density, setting time, compressive strength and in vitro interaction with osteosarcoma and osteoblast cells were studied. Different techniques of sample preparation, challenges during cement preparation and compact sample pressing, sintering, and methods of dopant addition are discussed. The presence of Cu in tricalcium phosphate was found to increase thermal stability of the material and decrease the impact of sintering temperature on porosity. In addition, Cu caused a reduction in expression of inflammatory gene markers by human osteoblast cells and an increased expression at early time points due of osteoinductive markers.The addition of Cu and Co to brushite cement caused an increase in thermal stability of the material, and the addition of Cu caused significant increase in setting time. Small dopant amounts of Co caused decrease in setting time, but higher amounts caused an increase. In addition, Cu dopant in small amounts resulted in an increase of compressive strength. Both Cu and Co led to a decrease in expression of inflammatory gene markers by osteoblast and osteosarcoma cells respectively, and Cu also caused an increase in osteoinductive marker expression. Thus, these results indicate that Cu and Co have a positive impact on the physical, mechanical and biological properties of calcium phosphate biomaterials.

Cummings, Haley V.↗

NASA NTRS2020

Implementation Concept of Operation for a Multi-Purpose Cassegrain Solar Concentrator, Micro-Spectrometers, and Electrostatic Neutralizers to Enable In Situ Construction Activities plus Lunar, Planetary, and Deep Space Science Exploration on the Moon

The ability to utilize regolith would support human missions to the Moon and Mars by both stabilizing the surface as well as the use of indigenous resources. Precision landing requirements include surface stabilization to prevent damage or contamination due to regolith projectiles as a result of plume interaction with regolith. The use of indigenous resources rather than hauling materials from Earth appears to be economically a palatable option by converting indigenous resources to usable products. However, such activities have new technical challenges to overcome the issues related to lunar environmental conditions, a wide range of temperature fluctuation, extremely high vacuum, and electrostatically charged fine regolith dusts. For both the regolith sintering and extraction of resources onsite, a Cassegrain solar concentrator was studied for not only sintering lunar regolith into a hardened stabilized surface, but also other multiple applications. This report illustrates a Cassegrain solar concentrator that has multi-functional capabilities for space missions. Proper design and implementation of high-performance lightweight composite materials for the primary mirror of the Cassegrain concentrator can offer multiple capabilities to be performed on the Moon. The multiple applications studied with Cassegrain concentrators are (1) Solar sintering for landing pad and habitats, (2) Harvest of volatiles: H2O, O2, H2, and He-3, (3) Space antenna for telemetry and telecommunication, and (4) Space telescope with 20-meter aperture that exceeds the space telescopes to date in terms of the State-of-Art (SOA) in resolution and aperture diameter. In this study, a key emphasis was placed on the NASA Langley-developed boron nitride nanotube (BNNT) nanocomposite technology which is ideal for the segmented primary mirror structure of the Cassegrain system because it promises a very low coefficient of thermal expansion (CTE) and negligible Poisson ratio. Also, BNNT nanocomposites offer several noticeable benefits, such as light weight, radiation shielding capability, and mechanical strength for structural applications. Additionally, the NASA Langley-developed bullet-like micro-spectrometer and electrostatic power generator were reviewed for mineral mapping applications and electrostatic power generation and dust mitigation from electrostatically charged regolith.

landing pad↗

NASA NTRSDate not supplied

Process Recipes for Additively Printed Copper Ink Flexible Circuits using Direct Write Methods

In this paper, the process-recipes and process-performance relationships for additive-printing of copper circuits using direct-write methods have been studied. The process has been implemented on the direct write platform. Interest in the use of additive printing methods for the manufacture of micro-circuits has grown immensely in recent times. Direct write methods have been shown to have the ability to create circuits in a limited manner. However, the process recipes and the effect of process parameters on the manufactured properties are not well understood. Copper ink is a good and cost-effective alternative to silver ink but its use has lagged owing to an increased propensity for oxidation. In this paper, photonic curing has been used to sinter copper ink to make the traces conductive. The method flashes high energy light that sinter metal particles instantaneously and the temperature of the substrate remains low. The effect of the different photonic sintering profiles on the mechanical and electrical properties of the printed traces has been studied in this paper.The print process parameters also play an important role in the line width and height that has been studied to print with the desired line profile for the end application. An LC filter circuit is been printed with SMD components been attached using an electrically conductive adhesive (ECA). The manufactured flexible LC filter is been tested for its frequency sweep to compare with the commercially available LC filer with the help of the Bode plot.

Process control↗

DOE OSTI2015

Composite materials formed with anchored nanostructures

A method of forming nano-structure composite materials that have a binder material and a nanostructure fiber material is described. A precursor material may be formed using a mixture of at least one metal powder and anchored nanostructure materials. The metal powder mixture may be (a) Ni powder and (b) NiAl powder. The anchored nanostructure materials may comprise (i) NiAl powder as a support material and (ii) carbon nanotubes attached to nanoparticles adjacent to a surface of the support material. The process of forming nano-structure composite materials typically involves sintering the mixture under vacuum in a die. When Ni and NiAl are used in the metal powder mixture Ni.sub.3Al may form as the binder material after sintering. The mixture is sintered until it consolidates to form the nano-structure composite material.

36 MATERIALS SCIENCE↗

DOE OSTI2016

Lutetium oxide-based transparent ceramic scintillators

In one embodiment, a transparent ceramic of sintered nanoparticles includes gadolinium lutetium oxide doped with europium having a chemical composition (Lu.sub.1-xGd.sub.x).sub.2-YEu.sub.YO.sub.3, where X is any value within a range from about 0.05 to about 0.45 and Y is any value within a range from about 0.01 to about 0.2, and where the transparent ceramic exhibits a transparency characterized by a scatter coefficient of less than about 10%/cm. In another embodiment, a transparent ceramic scintillator of sintered nanoparticles, includes a body of sintered nanoparticles including gadolinium lutetium oxide doped with a rare earth activator (RE) having a chemical composition (Lu.sub.1-xGd.sub.x).sub.2-YRE.sub.YO.sub.3, where RE is selected from the group consisting of: Sm, Eu, Tb, and Dy, where the transparent ceramic exhibits a transparency characterized by a scatter coefficient of less than about 10%/cm.

36 MATERIALS SCIENCE↗

DOE OSTI2016

Electrically-conductive proppant and methods for making and using same

Electrically-conductive sintered, substantially round and spherical particles and methods for producing such electrically-conductive sintered, substantially round and spherical particles from an alumina-containing raw material. Methods for using such electrically-conductive sintered, substantially round and spherical particles in hydraulic fracturing operations.

36 MATERIALS SCIENCE↗

DOE OSTI2017

ALD coating of nuclear fuel actinides materials

The invention provides a method of forming a nuclear fuel pellet of a uranium containing fuel alternative to UO.sub.2, with the steps of obtaining a fuel form in a powdered state; coating the fuel form in a powdered state with at least one layer of a material; and sintering the powdered fuel form into a fuel pellet. Also provided is a sintered nuclear fuel pellet of a uranium containing fuel alternative to UO.sub.2, wherein the pellet is made from particles of fuel, wherein the particles of fuel are particles of a uranium containing moiety, and wherein the fuel particles are coated with at least one layer between about 1 nm to about 4 nm thick of a material using atomic layer deposition, and wherein the at least one layer of the material substantially surrounds each interfacial grain barrier after the powdered fuel form has been sintered.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗

DOE OSTI2019

Spatter reduction laser scanning strategy in selective laser melting

An additive manufacturing system wherein a gentle sintering run on heat-fusible particles is followed closely by a selective laser melting run. The laser sintering run slightly sinters the particles and causes the particles to adhere to each other, but not necessarily deform and lose their original shape. The particles become connected via bridges between each other, which holds them in place. During the laser melting run, the powder melts in place, with minimum particle ejection or mobility, since the particles form a network of connected particles.

Khairallah, Saad↗

DOE OSTI2019

Investigation of Powder Processing, Heat Treating, and Texturing to Improve Gas Atomized alnico Magnets for use in Electric Drive Motors

Alnico permanent magnet materials have been proposed as a rare earth free permanent magnet alternative during an ongoing search to replace rare earth permanent magnets that are used for interior permanent magnet motors, a common motor found in electric vehicles. A powder processing approach was used to study two alnico alloys (Full-Co and lower cost Co-Lean, both with enhanced coercivity) to anticipate high volume manufacturing needed to supply millions of permanent magnets to interior permanent magnet motors. In this study the two alloys were gas atomized, compression molded, and solid-state sintered to fabricate near-final shape alnico magnets. The Full-Co displayed abnormal grain growth (resulting in >1 mm size grains) during sintering while the Co-Lean did not (~20 μm – 400 μm sized grains depending on the sintering hold times). Solid state grain alignment was used to promote a <001> textured (easy axis) microstructure to enhance magnetic properties, yet both alloys did not show predicted grain alignment behavior. Comparisons of the powder processing, microstructures, and magnetic properties of the two alloys will be discussed, as well as an evaluation as to why non-theoretical processing behavior of the Full-Co and Co-Lean alnico permanent magnets is occurring. Preliminary interior permanent magnet motor designs for alnico magnets are discussed, as this is the overarching objective for powder-based alnico permanent magnets.

Rinko, Emily↗

DOE OSTI2019

System and method for nuclear reactor fuel having freeze-cast matrix impregnated with nucleotide-rich material

A multiphase composite, formed by freeze-casting, lyophilization, and sintering, has sintered particles forming a scaffold having at least one region of aligned porosity; and a second phase formed in pores of the scaffold. In a particular embodiment, the second phase is a nuclear fuel, in another, the first phase is a nuclear fuel, and in others, both phases are nuclear fuels. In some embodiments, the first phase is a ceramic, and in other embodiments a metal such as stainless steel. In other embodiments, the second phase is a metal, and in other embodiments a ceramic. In some embodiments the second phase is positioned in a subset of pores of the scaffold, at least some additional pores being filled with a third phase. In embodiments, the second phase is also sintered.

Wegst, Ulrike G. K.↗

DOE OSTI2019

Spatter reduction laser scanning strategy in selective laser melting

36 MATERIALS SCIENCE↗

DOE OSTI2021

Lanthanum Strontium Cobaltite-Alumina Fiber Composite Contact Material for Solid Oxide Fuel Cells

Short alumina fibers were added to LSCo contact material to enhance the contact strength and improve thermal cycle stability. Alumina fiber from 2.5 v% to 20 v% were mixed with LSCo and sintered at elevated temperatures. Sintering study showed retardation in densification of LSCo matrix with increasing alumina content. Sintered bulk strength exhibited similar behavior where strength greatly reduced at high alumina v%. Coefficient of thermal expansion showed consistent results with prediction from rule of mixture. Contact strength using anode supported YSZ bilayer coupons improved greatly with the presence of small amount (2.5-5 v%) alumina fibers and no substantial reduction after 10 deep thermal cycles. Candidate LSCo-Al2O3 contact materials was validated in a generic stack test fixture for 1000h at 800oC followed by 10 thermal cycles. Results of impedance analysis showed substantial improvement in thermal cycle stability as compared to LSCo parent materials.

SOFC cathode, strength, LSCo, alumina↗

DOE OSTI2021

Electrically conductive proppant

Electrically conductive sintered, substantially round and spherical particles and methods for producing such electrically conductive sintered, substantially round and spherical particles from an alumina-containing raw material. Methods for using such electrically conductive sintered, substantially round and spherical particles in hydraulic fracturing operations.

Cannan, Chad↗

DOE OSTI2021

Grain boundary enhanced UN and U3Si2 pellets with improved oxidation resistance

A method of forming a water resistant boundary on a fissile material for use in a water cooled nuclear reactor is described. The method comprises mixing a powdered fissile material selected from the group consisting of UN and U 3 Si 2 with an additive selected from oxidation resistant materials having a melting or softening point lower than the sintering temperature of the fissile material, pressing the mixed fissile and additive materials into a pellet, sintering the pellet to a temperature greater than the melting point of the additive. Alternatively, if the melting point of the oxidation resistant particles is greater than the sintering temperature of UN or U 3 Si 2 , then the oxidation resistant particles can have a particle size distribution less than that of the UN or U 3 Si 2 .

Lahoda, Edward J.↗

DOE OSTI2023

Grain boundary enhanced UN and U 3 Si 2 pellets with improved oxidation resistance

A method of forming a water resistant boundary on a fissile material for use in a water cooled nuclear reactor is described. The method comprises mixing a powdered fissile material selected from the group consisting of UN and U3Si2 with an additive selected from oxidation resistant materials having a melting or softening point lower than the sintering temperature of the fissile material, pressing the mixed fissile and additive materials into a pellet, sintering the pellet to a temperature greater than the melting point of the additive. Alternatively, if the melting point of the oxidation resistant particles is greater than the sintering temperature of UN or U3Si2, then the oxidation resistant particles can have a particle size distribution less than that of the UN or U3Si2.

Lahoda, Edward J.↗

DOE OSTI2024

3D printed carbon fiber reinforced carbon as an energy efficient alternative to graphite for EFAS tooling

As Electric Field Assisted Sintering (EFAS) gains more industrial acceptance and use, it becomes more important to develop more efficient means to implement this technology. To this aim, 3D printed continuous carbon fiber reinforced carbon (CCC) was manufactured and fabricated into tooling for EFAS systems as an alternative to traditional graphite tooling. The impact of fiber orientation on the thermal and electrical properties of the CCC was characterized. Sample material was sintered in Tokai G535 graphite tooling, under common processing conditions and compared with CCC tooling. There was nearly 50 % energy savings compared to graphite while maintaining equivalent sample density and microstructure plus keeping ram temperatures 39 % cooler. This is due to spatial control of generated heat and thermal diffusivity within the molds, by means of fiber orientation anisotropy. Finite element modeling of the tooling design supported the experimental results as well as displays the effect of optimization of this 3D printed CCC material.

36 MATERIALS SCIENCE↗