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At least 307 records · Page 17
All sourcesNASA NTRSDOE OSTI
DOE OSTI2014

Effects of TiO{sub 2} addition and electron irradiation on superconducting and mechanical properties of Bi{sub 2}Sr{sub 2}CaCu{sub 2}O{sub 8} (Bi-2212) superconductor

Titanium Oxide (TiO{sub 2}) compounds having very high melting point with lower heat capacity, is an excellent candidate for reinforcement of brittle materials such as superconductor ceramics. In addition to high melting point, the TiO{sub 2} is also capable of establishing flux pinning centers in bismuth-based superconductors such as the Bi-2212. To further enhance the flux pinning properties, irradiation is one of the techniques that can be used to re-create the required point defects. In this study, the effects of TiO{sub 2} addition and electron irradiation on Bi-2212 superconductor were studied. TiO{sub 2} added Bi-2212 superconductor samples with 5%, 10% and 15% weight percentage addition respectively, were prepared using the conventional solid-state reaction method. The samples were irradiated with electron beam with radiation dose of 100 KGray. Characterization was performed by X-ray Diffraction (XRD) and Scanning Electron Microscopy (SEM). The transition temperature (T{sub c}) and the critical current density (J{sub c}) of the samples were also measured. The XRD patterns for all the samples show well-defined peaks all of which could be indexed on the basis of a Bi-2212 phase structure. In addition, the XRD patterns indicate that electron irradiation did not change the structure of Bi-2212 superconducting phase. Results of SEM micrographs show disorientation in the texture of the microstructure for samples that are subjected to electron irradiation. The grains are seen to align randomly with higher degree of orientation. With regard to TiO{sub 2} additions, only small TiO{sub 2} addition sustained the superconducting properties upon irradiation. Addition of more than 5% weight percentage of TiO{sub 2} degrades the superconducting properties of the irradiated samples. Formation of weak-links may result in higher grain boundaries orientation within the superconducting grains and thus deteriorates the inter-grains connectivity and resulted in lower T{sub c} and degradation of J{sub c}. The strength of the superconductor reduced significantly when subjected to electron irradiation.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2020

High Temperature Additive Architectures for 65% Efficiency (Final Report)

GE Power (GEP) proposed a development program that targets advanced high temperature additive components that contribute towards the DOE’s goal for advanced gas turbines that are capable of 65%, or greater, efficiency in combined cycle application. GEP proposed to leverage state-of-the-art additive manufacturing to develop novel and innovative component airfoil and end wall architectures that provide cooling flow savings while maintaining the component durability expected in today’s gas turbines. The objective of this program was to develop advanced component designs and architectures enabled by additive manufacturing, and the materials systems and additive manufacturing technology required for these designs. This Phase I program leveraged existing design and analysis knowledge and techniques for additive materials and methods and utilized extensive analytical evaluations to develop and refine designs for advanced turbine hot gas path (HGP) components. The design will be the basis for development and testing in a potential Phase II program. The goal of this Phase I program was to establish a feasible conceptual design for advanced additive turbine hot section components along with a technology maturation plan involving testing to address risk areas and needed validation. It was approached through two primary elements: 1) conceptual design and analysis of wall architectures, advanced airfoil cooling concepts, and advanced system-level concepts, and 2) investigation of additive modalities and associated materials systems. The Phase I program has concluded with the down-select of a primary design concept for a potential Phase II program.

36 MATERIALS SCIENCE↗
DOE OSTI2020

On the Robustness of Network Community Structure Under Addition of Edges

Communities represent important functional modules in networked systems. A key goal in preserving such communities is understanding their robustness under perturbations. Previous research has studied the impact of node removals and edge removals on the community structure. However, the impact of edge additions on the robustness of the community structure is relatively unknown. Edge additions or false positive edges may simulate measurement errors or external exceptional events that threaten the functionality of networked systems. Here, we study the impact of edge additions on the community structure using Lancichinetti-Fortunato-Radicchi (LFR) benchmark networks. We show that, for a fixed network size, the impact of edge additions is greater on networks with initially weak community structure than on networks with strongly clustered structures. In addition, we find that the perception of the impact is also dependent on the community detection algorithm used to uncover communities. In particular, we found that modularity-based methods such as Leiden and Louvain are less affected than information-theoretic and message passing-based methods such as Infomap and Label Propagation. Our results demonstrate that edge addition can (a) significantly impact the community structure of networks based on their initial conditions, and (b) the perception of the impact is dependent on the community detection algorithm used. We describe limitations, open challenges, and how this methodology can inform the design of resilient networked systems under edge additions.

97 MATHEMATICS AND COMPUTING↗
DOE OSTI2023

ETF Grout Expansion: Evaluation of MgO Additions and Struvite Precipitation Protocol for Potential Expansion

The ETF ammonia tolerant grout waste form was developed by the Vitreous State Laboratory (VSL) to stabilize ammonium and thereby prevent emission of ammonia vapor during solidification of an ammonium-rich, concentrated sulfate aqueous waste stream generated at the Hanford Effluent Treatment Facility (ETF). VSL did not observe expansion in samples prepared during the waste form development work. However, Savannah River National Laboratory (SRNL) personnel did encounter expansion, in some cases up to 20+ volume percent expansion in ETF grout samples while preforming work scope to evaluate compositional ranges for ETF brine and of the precipitation and solidification reagent. The work requests can be found in Washington River Protection Services (WRPS) Statement of Work (SOW), Requisitions #: 339922 Revisions 0 and 1, March 11, 2021, and November 2021. Additional evaluation was requested by WRPS SOW Requisitions #: 356730, Revision 1, February 1, 2022, to determine whether differences in the slags or differences in sample preparation protocols used by VSL and SRNL were the cause of the expansion observed in the SRNL samples. G. Chen, WRPS, arranged a materials exchange between VSL and SRNL and coordinated the VSL protocol for grouting and curing 1L of Base Case ETF simulant. Materials were exchanged between VSL and SRNL and both laboratories performed the VSL struvite precipitation-solidification protocol and cured samples for at least 28 days. VSL and SRNL encountered expansion, at varying degrees, in all samples prepared under the material exchange and grouting protocol. Additional material exchange testing between VSL and SRNL and alternative materials evaluation to further investigate the causes of grout expansion and differentiate the effects of various dry materials, grouting procedures, and curing containers was requested by WRPS SOW Requisitions #: 356730, Revision 2, January 10, 2023. Pacific Northwest National Laboratory (PNNL) assembled and distributed materials to both laboratories for testing. Observations from this study indicated variations in MgO additions, water-to-dry mix (dm) ratios and curing containers did not correlate to ETF ammonia grout expansion. In comparison to previous work, SRNL observed the addition rate of NaOH to be a potential factor for the final pH in the struvite precipitation step. In the current testing NaOH was added in bulk (5-10 mL at one time) during the precipitation step. The resulting pH was 7.57-9.15 which is slightly higher than pH observed at a slower addition rate. Additional testing is needed to identify the presence and/or struvite stability in high-pH struvite precipitant ETF ammonia grout samples. Therefore, based on current data, it is unknown if NaOH addition rate is the fundamental cause of grout expansion.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
NASA NTRS1995

Effect of Nb2O5 and V2O5 addition on the superconducting properties of YBa2Cu3O(y) thin films

The effect of Nb2O5 and V2O5 addition on the superconducting properties and microstructure of YBa2Cu3O(y) has been studied in thin films. Polycrystalline targets for laser ablation were prepared by mixing high purity V2O5 or Nb2O5 powders with a well characterized YBa2Cu3O(y) powder in the range 0 to 4 wt percent by solid state reaction method. Thin films (approximately 1500 A thickness) of the above targets were grown on (100) SrTiO3 (STO) and (100) LaAlO3 (LAO) substrates at 700 C temperature by pulsed laser deposition (PLD) technique. In the case of Nb2O5 addition we have noticed an increase in J(sub c) up to 0.5 wt percent and higher additive concentration (greater than 0.5 wt percent) have degraded the superconducting properties. However, in the case of V2O3 addition, there is an improvement in current density and microstructural properties up to 1 wt percent and the superconducting properties degrade for concentrations greater than 1 wt percent. The best J(sub c) for 0.5 wt percent of Nb2O5 added YBCO thin film is 1.6 x 10(exp 6) A/sq cm and for that of V2O5 added sample is 3.4 x 10(exp 6) A/sq cm at 77 K as compared to the pure YBa2Cu3O(y) (YBCO) film J(sub c) (1.2 x 10(exp 6) A/sq cm) observed on STO substrates. The reason for improvement in J(sub c) and microstructural properties in the case of V2O5 addition could be due to the low melting of V2O5 (690 C) which can act as a very good surfactant during deposition. Over all, we have realized that Nb2O5 addition or V2O5 addition to YBCO have shown significant improvement over the undoped YBa2Cu3O(7-x) films grown under identical conditions.

Srinivas, S.↗
NASA NTRS2014

Cleaning Process Development for Metallic Additively Manufactured Parts

Additive Manufacturing of metallic components for aerospace applications offers many advantages over traditional manufacturing techniques. As a new technology, many aspects of its widespread utilization remain open to investigation. Among these are the cleaning processes that can be used for post finishing of parts and measurements to verify effectiveness of the cleaning processes. Many cleaning and drying processes and measurement methods that have been used for parts manufactured using conventional techniques are candidates that may be considered for cleaning and verification of additively manufactured parts. Among these are vapor degreasing, ultrasonic immersion and spray cleaning, followed by hot air drying, vacuum baking and solvent displacement drying. Differences in porosity, density, and surface finish of additively manufactured versus conventionally manufactured parts may introduce new considerations in the selection of cleaning and drying processes or the method used to verify their effectiveness. This presentation will review the relative strengths and weaknesses of different candidate cleaning and drying processes as they may apply to additively manufactured metal parts for aerospace applications. An ultrasonic cleaning technique for exploring the cleanability of parts will be presented along with an example using additively manufactured Inconel 718 test specimens to illustrate its use. The data analysis shows that this ultrasonic cleaning approach results in a well-behaved ultrasonic cleaning/extraction behavior. That is, it does not show signs of accelerated cavitation erosion of the base material, which was later confirmed by neutron imaging. In addition, the analysis indicated that complete cleaning would be achieved by ultrasonic immersion cleaning at approximately 5 minutes, which was verified by subsequent cleaning of additional parts.

Tramel, Terri L.↗
NASA NTRS2019

Fracture Control for Additively Manufactured Spacecraft Structures

This paper describes how the intent of current NASA fracture control requirements may be applied to “fracture critical” additively manufactured spacecraft hardware. Fracture control is a multi-discipline design and certification methodology that is applied in order to mitigate catastrophic failure of structures resulting from growth of an undetected crack-like defect. The methodology is defined in existing NASA standards and is required on all human-rated space structures. As legacy spacecraft structures have been built using primarily metallic and composite materials manufactured using well established methods, guidance for application of fracture control to parts composed of these material types has been established and is documented in several NASA requirements. Additive manufactured structures offer advantages in design flexibility and manufacturing efficiency and as a result are expected to continue to be used more and more in the future. Recently, relevant guidance has been published by NASA to define materials and processes requirements for certain additive manufactured hardware, but procedures for fracture control are not addressed yet in any requirements or guidance document. While use of additive manufactured parts in non-critical scenarios may be of relatively low concern in current structural certification processes, there is a need for new fracture control guidance in order to use and certify additively manufacture hardware that is “fracture critical” where failure of the part may result in loss of life or loss of vehicle. Assurance of damage tolerance, i.e., that as-built flaws in a given part either do not exist or will not grow to become catastrophic, is of particular interest to the fracture control community. This poses a challenge due to the fact that damage tolerance behavior is not well understood in additive manufactured parts compared to legacy material types and manufacturing techniques. The discussion contained herein is necessary at this time as new guidance in this area should be founded collaboratively by the technical community at large. Different hardware types (e.g., pressure vessel, structural member) are described to highlight specific challenges and solutions for each. The discussion concludes with considering specific disciplines within fracture control (non-destructive evaluation, materials & processes, fracture mechanics, and structural certification) in a proposed extension of existing fracture control requirements to additive manufactured parts.

McElroy, Mark↗
NASA NTRS2019

Fracture Control for Additive Manufactured Spacecraft Structures

This paper describes how the intent of current NASA fracture control requirements may be applied to “fracture critical” additively manufactured spacecraft hardware. Fracture control is a multi-discipline design and certification methodology that is applied in order to mitigate catastrophic failure of structures resulting from growth of an undetected crack-like defect. The methodology is defined in existing NASA standards and is required on all human-rated space structures. As legacy spacecraft structures have been built using primarily metallic and composite materials manufactured using well established methods, guidance for application of fracture control to parts composed of these material types has been established and is documented in several NASA requirements. Additive manufactured structures offer advantages in design flexibility and manufacturing efficiency and as a result are expected to continue to be used more and more in the future. Recently, relevant guidance has been published by NASA to define materials and processes requirements for certain additive manufactured hardware, but procedures for fracture control are not addressed yet in any requirements or guidance document. While use of additive manufactured parts in non-critical scenarios may be of relatively low concern in current structural certification processes, there is a need for new fracture control guidance in order to use and certify additively manufacture hardware that is “fracture critical” where failure of the part may result in loss of life or loss of vehicle. Assurance of damage tolerance, i.e., that as-built flaws in a given part either do not exist or will not grow to become catastrophic, is of particular interest to the fracture control community. This poses a challenge due to the fact that damage tolerance behavior is not well understood in additive manufactured parts compared to legacy material types and manufacturing techniques. The discussion contained herein is necessary at this time as new guidance in this area should be founded collaboratively by the technical community at large. Different hardware types (e.g., pressure vessel, structural member) are described to highlight specific challenges and solutions for each. The discussion concludes with considering specific disciplines within fracture control (non-destructive evaluation, materials & processes, fracture mechanics, and structural certification) in a proposed extension of existing fracture control requirements to additive manufactured parts.

McElroy, Mark↗
NASA NTRSDate not supplied

Metallic Powder Core Tubular Wire (PCTW) Development for Additive Manufacturing

NASA Langley Research Center (LaRC) in Hampton, VA, and the Center for Welding, Joining, and Coating Research (CWJCR) in the Department of Metallurgical and Materials Engineering at the Colorado School of Mines (CSM) in Golden, CO, have collaborated for nearly fifteen years to develop metallic powder core tubular wire (PCTW) feedstock for additive manufacturing (AM) using electron beam deposition. The motivation for this development was to offset dealloying observed during deposition of titanium and aluminum alloy solid wire feedstock in the LaRC electron beam freeform fabrication (EBF3) system and to explore novel alloy compositions by tailoring the powder fill. EBF3 is a fusion-based AM process that is performed under vacuum and is consequently prone to vaporization loss of low vapor pressure alloying elements. Research spanning four graduate student research projects succeeded in developing the basic methodology to fabricate PCTW, the mass balance equations used to define the powder fill, microstructure control through particulate inoculation, and the feasibility of producing metal matrix composite materials. Metallic PCTW is comprised of a thin foil sheath wrapped around a powder blend. Fabrication of PCTW at CSM was accomplished using a tubular wire mill system to first bend a flat strip into a u-shaped cross section, deposit a powder fill, create a lap joint to seal the wire, and draw to final diameter. Powder management systems were developed to ensure uniform mixing of powder constituents and identify feed rates for optimum fill ratios. Processing parameters were successfully developed for titanium and aluminum alloy sheaths to account for material work hardening during drawing. Mass balance equations were developed to account for compositional contributions of the sheath and powder fill. PCTW composition can be adjusted through selection of the sheath or powder materials. PCTWs were successfully developed to offset Al loss in deposits of Ti-6-4 and Mg loss in Al 6061, resulting in deposits that were within the composition limits for each material. Ti-6-4 deposits were fabricated using PCTW comprised of commercially pure (CP) titanium sheath and a fill of pre-alloyed Ti-6-4 powder with additions of elemental Al and V powders. Additions of both elements were required to account for the CP Ti from the sheath, and Al was further enhanced to offset documented losses in EBF3 deposits. For Al 6061 deposits, composition was modulated through the choice of sheath material. The PCTW was made using an Al 5052 sheath to supplement Mg content and a fill composition of pre-alloyed 6061 powder with additions of Si and Cu.The slower solidification rate of the EBF3 process compared with laser powder bed fusion processes can lead to coarse-grained microstructures and mechanical property anisotropy. EBF3deposits of Ti-6-4 exhibited large epitaxially grown β grains, which result in degraded mechanical properties in the deposition direction. Microstructure refinement was achieved through a combination of electron beam modulation and the use of a PCTW designed for Ti-6-4 deposits and modified by the addition of powder made from Fe and B. Resulting deposits exhibited reductions in β grain size, α phase colony intercept length and lath width, and an increased volume fraction of β phase. The mechanism of microstructure refinement was related to precipitation of boride particles. Hardness testing confirmed that mechanical property anisotropy was reduced and an overall increase in hardness was achieved.Metal matrix composite (MMC) materials offer strength and stiffness benefits over unreinforced materials. Two methods were investigated using PCTW technology for producing Al 6061 basedMMC materials; the direct addition of SiC reinforcing particles and the in-situ generation of reinforcements through reaction synthesis of precursor powders. Al 6061 based MMCs reinforced with SiC exhibited particle clustering and formation of aluminum carbides during deposition. The application of a Ni coating to the SiC particles prior to incorporation into the powder fill eliminated aluminum carbide formation and aided particle distribution during deposition. Modulation of beam focus and power further reduced aluminum carbide formation and aided particle distribution. In reaction synthesis, precursor additions undergo an exothermic reaction during deposition to form new ceramic products, generally of finer scale than the initial precursor components. The product phases provide reinforcement in the MMC and act as nucleation sites during solidification, resulting in grain refinement, improved mechanical properties, and reduced susceptibility to solidification cracking. Higher tensile strength and stiffness were demonstrated in Al 6061 based MMCs with 2 vol% reinforcement. These combined research efforts demonstrate the potential of PCTW technology for customizing of alloy composition and achieving microstructure control. A manufacturing process for titanium- and aluminum-based PCTWs was developed based on iterative design, theoretical calculations, and empirical data. PCTW technology successfully mitigated Al loss from Ti-6-4 and Mg loss in Al 6061, resulted in grain refinement in Ti-6-4, and demonstrated fabrication of Al based MMCs

Marcia S Domack↗
NASA NTRSDate not supplied

NASA Efforts to Explore Additively Manufactured Thermal Protection Systems

Development of the thermal protection system (TPS) needed to protect external and internal surfaces during launch, ascent, cruise, and reentry, is a very specialized field with expertise developed over seven decades and has enabled successful robotic as well as human exploration. Well known examples are: 1) the ablative heatshield that protected Apollo Astronauts during reentry in 1960’s, 2) reusable TPS used on the Space Shuttle Orbiter, which is now sought after by commercial space industry, and 3) hot structures, such as Carbon-Carbon and other high temperature materials needed to operate control surfaces and sharp leading edges during hypervelocity flight. TPS function demands fail-safe design to ensure mission success. One TPS does not fit all, and each application requires a unique material along with manufacturing and integration approach. TPS mass is a key metric. A robust but inefficient TPS reduces payload mass. Mission- and domain-unique TPS development and flight certification efforts have been expensive with long lead times. As a result, there are limited TPS choices with high cost. For future commercial efforts to be successful, the ability to rapidly develop TPS, based on specific needs and at a lower cost, without compromising either mass efficiency or functionality is necessary. NASA is looking into this. Additive manufacturing (AM) techniques have shown their utility in making complex parts and, through automation, the potential to reduce cost and schedule in some applications. The promise of additive manufacturing to TPS, while exciting, is unexplored. In the past several years, NASA has made exploratory investments in internal development as well as in small business and universities through SBIR and STTR programs. In addition, NASA is bringing together the TPS as well as Additive Manufacturing communities to explore approaches to prioritize focus areas for broad benefits. The very first “Additively Manufactured Thermal Protection System Workshop,” to be held at NASA Johnson Space Center in Houston at the end of March of this year, is the culmination of a year-long effort to engage the research, development, and user communities involved in both TPS as well as additive manufacturing. The workshop participants include representatives from large and small commercial space industry, DoD, Federally Funded Research and Development Centers, University Researchers and NASA personnel. The proposed talk will highlight future TPS needs of both emerging commercial and Government interests, NASA’s development efforts in additively manufactured TPS, and the findings and recommendations from the first AM TPS Workshop.

Ethiraj Venkatapathy↗
DOE OSTI2020

Study of Additive Manufacturing Application to Geothermal Technologies

Geothermal reservoir characterization, field construction, and reservoir operations are very technology intensive activities that contribute significantly to the cost of delivering electricity produced from geothermal resources. Many geothermal technologies, such as downhole tools and drilling equipment, have unusual material, design, and manufacturing considerations dictated by the harsh geothermal environment and extreme aspect ratios required for deployment in a borehole. An additional challenge that faces geothermal applications is the low tool production volume needed to support the industry. Whereas tens of thousands of Oil & Gas wells are drilled and completed in the U.S. annually, there are typically only tens of geothermal wells that are drilled and completed. If a tool typically used in Oil & Gas applications cannot be directly used for geothermal, then the cost associated with making the tool suitable for geothermal is often prohibitive. There is therefore a much smaller inventory of technologies available to geothermal as compared to Oil & Gas and the level of efficiency and sophistication associated with field practice suffers accordingly. A number of advanced manufacturing methods, such as additive manufacturing, have received increased R&D as well as commercial attention in recent years because of their ability to rapidly prototype complex parts. Additive manufacturing in particular provides an opportunity to increase the technology available to the geothermal industry by either reducing fabrication costs associated with complex components or enabling economic production of low volume parts where specialized tooling is often required. Additional potential benefits of additive manufacturing include increased design freedom to make higher performing parts that cannot be made conventionally, the ability to integrate components into assemblies without joining operations, and the ability to economically fabricate variations on design in cases, such as casting molds, where there are large up-front costs associated with tooling. We have recently completed a study that investigated technology needs, representative use cases, manufacturability, and a techno-economic framework for comparing conventional to additive manufacturing methods for geothermal applications. This paper will provide an overview of this recent effort, describe the different elements of the assessment, and summarize the key takeaways related to both the feasibility of using additive manufacturing for geothermal technology applications as well as the potential benefits and impacts.

Polsky, Yarom↗
DOE OSTI2016

Effect of Alloying Additions on Wrought FeCrAl Alloys for Accident-Tolerant Fuel Cladding

Nuclear-grade wrought Fe-Cr-Al alloys are under development as one of the candidate materials for accident-tolerant fuel (ATF) cladding for light water reactors (LWRs) because of their superior oxidation and corrosion resistance in high-temperature steam environment compared to Zr-based alloys that are currently in service. Numerous efforts have been made for the development of the FeCrAl alloys with the ATF concept. The current researches focused on optimizing the balance between the improved environmental compatibility and sufficient mechanical properties in both normal service condition and under accident scenario, as well as fabricability of seamless tube product for fuel cladding applications. Alloying addition is one of the key factors to control the various properties. The effect of Cr and Al additions on the properties in model Fe-Cr-Al-Y alloys were systematically examined by the authors, and the candidate base alloy composition with 13 wt.% Cr and 5 wt.% Al was proposed for further development. The modified FeCrAl alloys with Mo and Nb additions were also investigated in order to achieve improved strength. It was revealed that the microstructure control together with the thermal stability to retain desired microstructure were also the dominant factors for successful development of ATF FeCrAl alloys, especially when the fabricability of seamless tube production was also considered. This paper summarizes further investigation of alloying effects with a wide composition range of Cr and Al additions in the model alloys, as well as the effect of minor alloying additions of Mo, Nb, and Zr, through evaluation of the tensile properties. The combined effect of microstructure control is also discussed. Effect of alloying additions on tensile properties of wrought FeCrAl alloys was investigated. Minor alloying additions such as Al, Mo, Nb, and Zr were found to improve room-temperature tensile strength of the wrought FeCrAl alloys significantly. It was also found that stabilized deformed microstructure consisting of subgrains was also effective to improve the properties compared to the recrystallized grain structure. Optimization to balance the properties and the seamless FeCrAl tube fabricability is currently in progress. (authors)

36 MATERIALS SCIENCE↗
DOE OSTI2022

Combined Effects of Uniform Applied Pressure and Electrolyte Additives in Lithium-Metal Batteries

The development of lithium-metal batteries with good performance and long lifetimes requires fundamental insight into the mechanisms underlying performance improvements from individual design strategies and the interactions between multiple improvement approaches. Here, in this work, we investigated the individual and combined effects of applied pressure and a LiAsF 6 electrolyte additive on the performance of anode-free lithium-metal batteries; we employed various pressure application methods, which vary both in magnitude and uniformity. Both approaches individually improve cycling performance of anode-free lithium-metal batteries. Pressure increases the cycling efficiency at both the anode and cathode by promoting improved morphologies, while the LiAsF 6 additive additionally improves performance at the anode by enhancing the solid electrolyte interphase (SEI) properties. The combination of uniform applied pressure and a LiAsF 6 electrolyte additive produces lithium-metal batteries with cycling performance higher than can be achieved with either approach alone. This additional performance improvement is able to be realized due to the complementary rather than competitive nature of the mechanisms underlying applied pressure (lithium morphology) and electrolyte additives (SEI properties). Our results highlight the importance of moving beyond the investigation of isolated design strategies and demonstrate that superior cycling can be achieved by combining multiple approaches.

25 ENERGY STORAGE↗
DOE OSTI2018

Influence of Cobalt and Molybdenum Additives on the Structure and Shape Memory Parameters of Reaction-Sintered Porous Nickel Titanium Alloys

We have studied the structure and properties of porous nickel titanium (TiNi) alloys obtained upon reaction sintering of Ti and Ni powders with Co and Mo additives. It is established that Co and Mo doping additives retain the compaction of Ni powder achieved at the initial stage of sintering. The maximum deformation of porous samples loaded in the austenite state was observed upon adding Co, while the addition of Mo resulted in minimum deformation. The addition of Co leads to single-stage martensitic transformation in TiNi phase, while the addition of Mo leads to the two-stage transformation that is more homogeneous over the volume. Both Co and Mo additives lead to increase in the maximum accumulated strain due to the formation of favorably oriented stress-induced martensite and reoriented quench-induced martensite.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
NASA NTRSDate not supplied

Large Scale and Multi-Alloy Rocket Engine Component Development using Various Metal Additive Manufacturing Techniques

The NASA Marshall Space Flight Center (MSFC) has been involved with various forms of metallic additive manufacturing (AM) for use in liquid rocket engine component design, development, and testing since 2010. These AM techniques have been demonstrated to significantly reduce hardware cost, shorten fabrication schedules, increase reliability by reducing the number of joints, and improve hardware performance by allowing fabrication of designs not feasible by conventional means. The focus at the NASA MSFC for these metal additive manufacturing techniques include laser powder-bed fusion (L-PBF), blown powder directed energy deposition (DED), arc-based deposition, and Laser Wire Direct Closeout (LWDC). A variety of components have been evaluated and tested including thrust chamber injectors, injector components such as faceplates, regeneratively-cooled combustion chambers, regeneratively-cooled nozzles, gas generator and preburner hardware, and augmented spark igniters. To support these component applications in harsh environments, NASA has advanced a variety of “standard” additive manufacturing alloys such as those in the superalloy-family and also evolved new alloys including GRCop-84, GRCop-42, NASA HR-1, and JBK-75. The purpose of this presentation is to discuss the various component programs at the NASA MSFC using AM to develop, fabricate, and test combustion devices hardware and the evolution of the new additive alloys. One of these projects that will be highlighted is Rapid Analysis and Manufacturing Propulsion Technology (RAMPT), which includes new process development for large scale AM components, multi-metallic AM components, including unique component designs using additive manufacturing. Additional information will be provided on the development of other components, hot-fire testing, post-processing of AM techniques including surface enhancements (polishing) techniques, material and process characterization, future development programs, and dissemination of data to industry partners.

Additive Manufacturing↗
DOE OSTI2018

Effect of Ag Addition on the Surface Topography and the Vibrational Dynamics of MgB{sub 2}

We fabricated MgB{sub 2} samples with Ag additions using in situ solid-state reaction via a single-step sintering to study the effect of Ag on the structural, vibration, and superconducting properties of MgB{sub 2} samples. Ag addition to MgB{sub 2} resulted in a significant improvement in J{sub c} although no appreciable effect was observed in the lattice parameters and the superconducting transition temperature T{sub c}. Dramatic increase in the grain size was observed with Ag addition and topographic measurements with atomic force microscopy revealed the formation of Ag–Mg nanoparticles 5–20 nm in size at 2 and 4 wt% Ag additions. The fact that these samples showed high J{sub c} values suggests that the nanoparticles formed as a result of Ag addition are responsible for enhanced flux pinning. Raman spectroscopy measurements showed that Ag additions also increased disorder in the system and thereby affected the line width of the Raman active E{sub 2g} mode.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2024

Competition Between Growth and Removal in Zirconia Nanocrystal-Derived Tribofilms: The Role of Co-additives

Antiwear additives permit energy-efficient lubrication of gearboxes, bearings, and other tribological interfaces. We study zirconia (ZrO 2 ) nanocrystal additives, which readily form protective tribofilms in tribological contacts. Our prior work demonstrated cooperative antiwear performance between ZrO 2 and the S- and P-based co-additives in fully formulated hydrocarbon gear oils. Here, we extend that work by examining the growth kinetics of the ZrO 2 tribofilms, including the influence of the co-additives. In the boundary lubrication regime for mixed rolling-sliding contacts, the initial phase of ZrO 2 tribofilm growth is soon overtaken by removal processes, phenomena whose importance has gone unnoticed in prior work. Tribofilm removal affects the steady-state thickness and morphology of the tribofilm as well as its growth kinetics. The S- and P-based co-additives are incorporated into the ZrO 2 tribofilm, and alter the competition between the growth and removal processes, increasing initial net growth rates per contact cycle and contributing to a more polished final interface. This work highlights the significance of removal processes in determining tribofilm antiwear performance, and suggests several routes for improving tribofilm growth kinetics using co-additives.

Coadditives↗
DOE OSTI2019

Thermal Analysis of Rare Earth Additions to HY100

This paper discusses the results of a series of experiments on rare earth additions to HY100. Previous work has found little or no refinement to occur with rare earth additions to this alloy. Thermal analysis has been used to provide a better understanding of this and assist in the development of a suitable grain refiner. Heats of HY100 were melted in an induction furnace and tapped into a small hand ladle. Thermal analysis cups were poured from the ladle, and the resulting cooling data recorded. Heats with no additions and 0.3 wt.% rare earth silicide were poured. Commercial software analyzed the cooling curves to determine the liquidus and solidus temperatures. A manual analysis was employed for identifying the peritectic and other reactions. Examination of the cooling curves detected the liquidus, solidus and even peritectic reactions. It was observed that the solidification changed with the rare earth silicide or engineered grain refiner additions. Additional phase reactions appeared before the solidus were not present in the baseline heat. Phase identification was done with thermodynamic calculations. The solidus, peritectic and liquidus were found. Rare earth inclusions were observed in the microstructure of the treated steel. Interestingly, macrostructure examination indicated no reduction in overall grain size. Thermodynamic predictions also indicated that the inclusions formed late during solidification. It was postulated that the additions caused a change in solidification but those occurred late enough during freezing that the resulting microstructure was not affected.

36 MATERIALS SCIENCE↗