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At least 1,657 records · Page 92

All sources NASA NTRS DOE OSTI

NASA NTRS2001

A New Direction for NASA Materials Science Research Using the International Space Station

NASA recently created a fifth Strategic Enterprise, the Office of Biological and Physical Research (OBPR), to bring together physics, chemistry, biology, and engineering to foster interdisciplinary research. The Materials Science Program is one of five Microgravity Research disciplines within this new enterprise's Division of Physical Sciences Research. The Materials Science Program will participate within this new enterprise structure in order to facilitate effective use of ISS facilities, target scientific and technology questions and transfer scientific and technology results for Earth benefits. The Materials Science research will use a low gravity environment for flight and ground-based research in crystallization, fundamental processing, properties characterization, and biomaterials in order to obtain fundamental understanding of various phenomena effects and relationships to the structures, processing, and properties of materials. Completion of the International Space Station's (ISS) first major assembly, during the past year, provides new opportunities for on-orbit research and scientific utilization. Accommodations will support a variety of Materials Science payload hardware both in the US and international partner modules with emphasis on early use of Express Rack and Glovebox facilities. This paper addresses the current scope of the flight investigator program. These investigators will use the various capabilities of the ISS to achieve their research objectives. The type of research and classification of materials being studied will be addressed. This includes the recent emphasis being placed on nanomaterials and biomaterials type research. Materials Science Program will pursue a new, interdisciplinary approach, which contributes, to Human Space Flight Exploration research. The Materials Science Research Facility (MSRF) and other related American and International experiment modules will serve as the foundation for this research. Discussion will be included to explain the changing concept for materials science research processing capabilities aboard the ISS along with the various ground facilities necessary to support the program. Finally, the paper will address the initial utilization schedule and strategy for the various materials science payloads including their corresponding hardware.

Schlagheck, Ronald↗

DOE OSTI2024

Predictive Self-Healing Seals for Gas Transmission

03 NATURAL GAS↗

NASA NTRS1993

Microspheres for laser velocimetry in high temperature wind tunnel

The introduction of non-intrusive measurement techniques in wind tunnel experimentation has been a turning point in error free data acquisition. Laser velocimetry has been progressively implemented and utilized in various wind tunnels; e.g. subsonic, transonic, and supersonic. The success of the laser velocimeter technique is based on an accurate measurement of scattered light by seeding particles introduced into the flow stream in the wind tunnel. Therefore, application of appropriate seeding particles will affect, to a large extent the acquired data. The seeding material used depends on the type of experiment being run. Among the seeding material for subsonic tunnel are kerosene, Kaolin, and polystyrene. Polystyrene is known to be the best because of being solid particles, having high index of refraction, capable of being made both spherical and monodisperse. However for high temperature wind tunnel testing seeding material must have an additional characteristic that is high melting point. Typically metal oxide powders such as Al2O3 with melting point 3660 F are used. The metal oxides are, however polydispersed, have a high density, and a tendency to form large agglomerate that does not closely follow the flow velocity. The addition of flame phase silica to metal oxide helps to break up the agglomerates, yet still results in a narrow band of polydispersed seeding. The less desirable utility of metal oxide in high temperature wind tunnels necessitates the search for a better alternative particle seeding which this paper addresses. The Laser Velocimetry (LV) characteristic of polystyrene makes it a prime candidate as a base material in achieving the high temperature particle seeding inexpensively. While polystyrene monodisperse seeding particle reported has been successful in a subsonic wind tunnel, it lacks the high melting point and thus is not practically usable in a high temperature wind tunnel. It is well known that rise in melting point of polystyrene can be achieved by a cross-linking technique. Since polystyrene already possesses all the desired characteristics for LV, to circumvent the low melting point, a cross-linking technique was investigated.

Ghorieshi, Anthony↗

DOE OSTI2022

ELASTOMERIC MICROVASCULAR SELF-HEALING MATERIALS

Damaged elastomeric diaphragms within pneumatic controllers used in the oil and gas industry lead to an unintended release of methane. Self-healing microvascular materials capable of healing various types of damage have been fabricated. These microvascular materials are designed to replace currently available commercial diaphragms found in pneumatic controllers and provide a solution to reduce unintended methane leaks. Poly(dimethylsiloxane) (PDMS) was used as the main matrix material, with additional testing conducted on polyurethane and flexibilised epoxy materials. Microvascular networks were implemented into the elastomeric membranes to act as ves- sels to deliver healing agents to the damaged areas. The complex, interdigitated channel networks were created using a 3D printed custom compounded filament composed of polylactic acid (PLA) and tin(II) oxalate. Two-part liquid casting polymers were poured around the channels into a mould to create samples with the scaffolding of the microvascular channels intact. Hollow microvascular networks were created by placing the samples within a vacuum oven at 250◦C which causes the thermal depolymerisation of PLA into its gaseous monomers. The manufactured materials were placed in test stands and pressurized using nitrogen gas to determine their healing and mechanical behaviour. Self-healing behaviour was demonstrated using PDMS matrix materials and healing chemistries within a pressure test cell. This test cell was designed to detect any damage to a sample by record- ing an outlet pressure. Damages including puncture holes, diagonal cuts and star-shaped central iv cuts were applied to the samples and a reduction in the outlet pressure was recorded for all sam- ples. A variation in channel spacing and diameter was studied to determine the optimal design of the microvascular network for self-healing performance. The mechanical performance of elastomeric membrane materials within a diaphragmatic pressurised stand was observed. Deformations and strains around the channels and channel inter- sections at the midplane of the materials were recorded using digital image correlation. Normal stresses were calculated using Hooke’s law and the material properties of the PDMS matrix. A reduction in leak rate, implying the success of self-healing, was recorded within manu- factured diaphragm samples tested within a commercial valve. PDMS is the favourable material when compared to polyurethane and flexibilised epoxy for creating

03 NATURAL GAS↗

DOE OSTI2015

Comparison of Integral Parameter Estimated Uncertainties in Fast Neutron Systems with COMMARA-2.1 and COMMARA-2.0 Covariance Data

This paper shows the main differences between the COMMARA-2.0 and COMMARA-2.1 evaluated covariance data in the uncertainty estimation of integral parameters of interest for a large number of typical innovative fast neutron systems. The study provides some guidelines to the nuclear data evaluators on which materials and which reaction types need to be evaluated most accurately to achieve reliable results in computational analyses of similar systems. The assessment of the quality and reliability of the covariance data is outside the scope of the study.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗

DOE OSTI2018

Tensile performance of sustainable Strain-Hardening Cementitious Composites with hybrid PVA and recycled PET fibers

Highlights: • SHCCs with hybrid PVA/PET fibers are theoretically and experimentally studied. • A semi-empirical way to predict strain capacity of hybrid-fiber SHCCs is proposed. • The impacts of PET fiber surface treatment and curing time are explored. • SHCCs achieve satisfactory performance even 50% PVA fibers are replaced by PET fibers. • Using PET fibers in SHCCs effectively reduces material cost and environmental impact. - Abstract: Strain-Hardening Cementitious Composite (SHCC) is a type of advanced construction material that can enhance the resiliency and durability of structures. However, the high cost of the constituents limits the wide application of SHCCs. To reduce the material cost and improve the sustainability, this study explores the potential of replacing commonly-used polyvinyl alcohol (PVA) fibers by recycled polyethylene terephthalate (PET) fibers. The potential of fiber hybridization was first evaluated using micromechanical modeling, and the ultimate tensile strain of hybrid-fiber SHCCs was estimated using a semi-empirical method. Then the tensile performance of SHCCs after standard curing and accelerated aging was experimentally evaluated, and the crack pattern development with increasing tensile strain was recorded. Satisfactory mechanical performance can be achieved even when 50% of PVA fibers are replaced by recycled PET fibers with surface treatment. In addition, using recycled PET fibers in SHCCs can significantly reduce the material cost and environmental impact.

36 MATERIALS SCIENCE↗

DOE OSTI2017

Development of Type A Transport Packagings - 17073a

ORNL ships a wide variety of radioisotopes. Many of these are associated with the DOE Isotope Program and Office of Nuclear Materials Integration (ONMI) and can be shipped as DOT Type A quantities of material. The DOT Specification 6M Type B packaging previously used for many shipments at ORNL is no longer authorized. Most materials could be shipped in Type B packagings, but many of them can meet the requirements for shipping as Type A. As a result, ORNL is working with a packaging manufacturer to develop, test, and certify several Type A packagings. These include a 38 L (10 gal) Type A packaging primarily to be used for transport of Cf-252 sources, a 208 L (55 gal) Type A packaging primarily to be used for transport of americium/curium/lanthanide oxide materials recovered from high-burnup targets, and a Type A packaging for transport of irradiated actinium targets. These are being developed with consideration for both gamma and neutron shielding for contents reading up to 5000 R/h. (authors)

07 ISOTOPE AND RADIATION SOURCES↗

DOE OSTI2016

A Spinel-integrated P2-type Layered Composite: High-rate Cathode for Sodium-ion Batteries

Sodium-ion batteries (SIB) are being intensively investigated, owing to the natural abundance and low cost of Na resources. However, the SIBs still suffer from poor rate capability due to the large ionic radius of Na+ ion and the significant kinetic barrier to Na+-ion transport. Here, we present an Fd-3m spinel-integrated P2-type layered composite (P2 + Fd-3m) material as a high-rate cathode for SIBs. The P2 + Fd-3m composite material Na0.50Ni1/6Co1/6Mn2/3O2 shows significantly enhanced discharge capacity, energy density, and rate capability as compared to the pure P2-type counterpart. The composite delivers a high capacity of 85 mA h g-1 when discharging at a very high current density of 1500 mA g-1 (10C rate) between 2.0 and 4.5 V, validating it as a promising cathode candidate for high-power SIBs. The superior performance is ascribed to the improved kinetics in the presence of the integrated-spinel phase, which facilitates fast electron transport to coordinate with the timely Na+-ion insertion/extraction. The findings of this work also shed light on the importance of developing lattice doping, surface coating, and electrolyte additives to further improve the structural and interfacial stability of P2-type cathode materials and fully realize their practical applications in sodium-ion batteries.

Zheng, Jianming↗

DOE OSTI2024

Bipolar Organic Cathodes for Stable and Sustainable Na‐Ion and Rechargeable Al Batteries

Bipolar organic materials have emerged as promising cathode materials for rechargeable batteries because of their high voltage and high capacity. However, they suffer from poor cyclic stability and slow reaction kinetics. In this work, we designed and synthesized two bipolar organic cathode materials, containing carbonyl (n‐type) and amine (p‐type) functional groups, as well as extended conjugation structures, for Na‐ion batteries (NIBs) and rechargeable aluminum batteries (RABs). As universal electrode materials, bipolar organic materials exhibited exceptional electrochemical performance in terms of high capacity, high voltage, long cycle life, and fast rate capability. Further, the extended conjugation structures in backbones of the bipolar organic materials facilitate the π–π stacking with graphene, playing a critical role in the high performance. Furthermore, the formation of a stable and robust NaF‐rich cathode electrolyte interphase was shown to stabilize the bipolar organic cathode in NIBs. Electrochemical kinetic measurements reveal that both functional groups undergo reversible redox reactions. Specifically, the electron transfer rate constant of the p‐type amine group is one order of magnitude higher than that of the n‐type carbonyl group. These results highlight the efficacy of developing bipolar organic materials for achieving high‐performance organic cathode in NIBs and RABs.

25 ENERGY STORAGE↗

DOE OSTI2015

Cr-Doped TiSe 2 - A Layered Dichalcogenide Spin Glass

Abstract not provided

Luo, Huixia↗

DOE OSTI2015

σ–π-Band Inversion in a Novel Two-Dimensional Material

In this paper, we present a theoretical study of a new type of two-dimensional material exhibiting a pentagonal arrangement of C and Si atoms. Pentagonal SiC 2 is investigated with density functional theory-based calculations to show that the buckled nanostructure is dynamically stable, and exhibits an indirect energy band gap and an enhanced electronic dispersion with respect to the all-carbon counterpart. Computed Born effective charges exhibit a significant anisotropy for C and Si atoms that deviates substantially from their static effective charges. We establish an accurate tunability of the vertical location of the p-p-σ and p-p-π bands and show that under compressive biaxial strain the density of states decreases, and conversely for tensile biaxial strain. Finally, this coupling between the tunability of strain-mediated density of states and semiconducting properties in a monolayered structure may allow for the development of applications in semiconducting stretchable electronics.

36 MATERIALS SCIENCE↗

DOE OSTI2015

A method for the direct measurement of electronic site populations in a molecular aggregate using two-dimensional electronic-vibrational spectroscopy

Two dimensional electronic spectroscopy has proved to be a valuable experimental technique to reveal electronic excitation dynamics in photosynthetic pigment-protein complexes, nanoscale semiconductors, organic photovoltaic materials, and many other types of systems. It does not, however, provide direct information concerning the spatial structure and dynamics of excitons. 2D infrared spectroscopy has become a widely used tool for studying structural dynamics but is incapable of directly providing information concerning electronic excited states. 2D electronic-vibrational (2DEV) spectroscopy provides a link between these domains, directly connecting the electronic excitation with the vibrational structure of the system under study. In this work, we derive response functions for the 2DEV spectrum of a molecular dimer and propose a method by which 2DEV spectra could be used to directly measure the electronic site populations as a function of time following the initial electronic excitation. We present results from the response function simulations which show that our proposed approach is substantially valid. This method provides, to our knowledge, the first direct experimental method for measuring the electronic excited state dynamics in the spatial domain, on the molecular scale.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

DOE OSTI2016

Evolution of thermoelectric performance for (Bi,Sb){sub 2}Te{sub 3} alloys from cutting waste powders to bulks with high figure of merit

Bi{sub 2}Te{sub 3} based cutting waste powders from cutting wafers were firstly selected as raw materials to prepare p-type Bi{sub 2}Te{sub 3} based thermoelectric (TE) materials. Through washing, reducing, composition correction, smelting and resistance pressing sintering (RPS) process, p-type (Bi,Sb){sub 2}Te{sub 3} alloy bulks with different nominal stoichiometries were successfully obtained. The evolution of microstructure and TE performance for (Bi,Sb){sub 2}Te{sub 3} alloys were investigated in detail. All evidences confirmed that most of contaminants from line cutting process such as cutting fluid and oxides of Bi, Sb or Te could be removed by washing, reducing and smelting process used in this work. The carrier content and corresponding TE properties could be adjusted effectively by appropriate composition correction treatment. At lastly, a bulk with a nominal stoichiometry of Bi{sub 0.44}Sb{sub 1.56}Te{sub 3} was obtained and its' dimensionless figure of merit (ZT) was about 1.16 at 90 °C. The ZT values of Bi{sub 0.36}Sb{sub 1.64}Te{sub 3} and Bi{sub 0.4}Sb{sub 1.6}Te{sub 3} alloy bulks could also reach 0.98 and 1.08, respectively. Different from the conventional recycling technology such as hydrometallurgy extraction methods, the separation and extraction of beneficial elements such as Bi, Sb and Te did not need to be performed and the Bi{sub 2}Te{sub 3} based bulks with high TE properties could be directly obtained from the cutting waste powders. In addition, the recycling technology introduced here was green and more suitable for practical industrial application. It can improve material utilization and lower raw material costs of manufacturers. - Graphical abstract: Three kinds of typical morphologies for the fractographs: typical lamellar structure, agglomerated submicron-sized granules and dispersed cubic particles from the initial cutting waste powders. - Highlights: • Bi{sub 2}Te{sub 3} based wastes were directly selected as raw materials for TE alloys. • Contaminants from cutting fluid and oxides could be effectively removed. • Bulk Bi{sub 0.44}Sb{sub 1.56}Te{sub 3} with ZT of 1.16 was obtained from Bi{sub 2}Te{sub 3} based wastes. • Different from hydrometallurgy, the recycling method introduced here was green. • Directly recycling Bi{sub 2}Te{sub 3} wastes can lower raw material costs of manufacturers.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

DOE OSTI2014

Phase stability and defect physics of a ternary ZnSnN(2) semiconductor: first principles insights.

First-principles calculations show that ZnSnN2 has a very small formation enthalpy, and the donor defects such as SnZn antisites and ON impurities have high concentration, making the material degenerately n-type, which explains the observed high electron concentration. ZnSnN2 can be regarded as a new material that combines a metal-like conductivity with an optical bandgap around 2 eV.

Chen, Shiyou↗

DOE OSTI2021

Formation Pathway of Wurtzite-like Cu 2 ZnSnSe 4 Nanocrystals

Cu 2 ZnSnSe 4 is a direct band gap semiconductor composed of Earth-abundant elements, making it an attractive material for thin film photovoltaic technologies. Cu 2 ZnSnSe 4 crystallizes in the kesterite structure type as a bulk material, but it can also crystallize in a metastable wurtzite-like crystal structure when synthesized on the nanoscale. The wurtzite-like polymorph introduces unique and useful properties to Cu 2 ZnSnSe 4 materials, including widely tunable band gaps and superior composi-tional flexibility as compared to kesterite Cu 2 ZnSnSe 4 . Here, we investigate the formation pathway of colloidally prepared wurtzite-like Cu 2 ZnSnSe 4 nanocrystals. We show that this quaternary material forms through a chain of reactions, starting with binary Cu 3 Se 2 nanocrystals that, due to both kinetic and thermodynamic reasons, preferentially react with tin to yield hexagonal copper tin selenide intermediates. Furthermore, these ternary intermediates then react with zinc to form the resulting wurtzite-like Cu 2 ZnSnSe 4 nanocrystals. Based on this formation pathway, we suggest synthetic methods that may prevent the for-mation of unwanted impurity phases that are known to hamper the efficiency of Cu 2 ZnSnSe 4 -based optoelectronic devices.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

DOE OSTI2025

A simplified approach for creep damage and remaining life calculation for materials surveillance in advanced reactors

High temperature reactor materials will experience a combination of mechanical degradation caused by creep and fatigue and environmental degradation caused by neutron irradiation and, in some cases, exposure to corrosive coolants. A materials surveillance program is one option for ensuring the safe, reliable operation of key reactor components under these conditions. Such a program would monitor the degradation in key material properties over time, using this data to predict how changes in the material properties affect components performance. This could then be used to make plant operational decisions and support eventual plant license extensions. Past work de-scribes such a material surveillance program based on passively actuated mechanical test articles that impose creep-fatigue type loading on test materials driven only by changes in temperature, for example those experienced by components under standard operating cycles. This report focuses on two aspects of the proposed material surveillance program: how to design the test articles to mimic the mechanical response of the corresponding component and how to use ex-situ test data to deter-mine the amount of damaged experienced by the test article (and hence the corresponding compo-nent) in service. Specifically, this report derives and validated simplified methods for both tasks, replacing earlier, more complicated approaches based on simulating the test article response and finding the best specimen design or current damage via complex numerical optimization. The sim-plified methods for each task developed here can be implemented in spreadsheet software and are simple enough for practical use in future operating plants. This report derives the methods (one for sizing and two options for damage inference), verifies the simplified approaches versus more so-phisticated methods, and compares the results of applying the simplified methods to previous re-sults using the complex numerical optimization approach. The report also provides a worked sam-pled problem applying the simplified techniques to a realistic high temperature reactor component.

22 GENERAL STUDIES OF NUCLEAR REACTORS↗

NASA NTRS1972

Hydrogen environment embrittlement

Hydrogen embrittlement is classified into three types: internal reversible hydrogen embrittlement, hydrogen reaction embrittlement, and hydrogen environment embrittlement. Characteristics of and materials embrittled by these types of hydrogen embrittlement are discussed. Hydrogen environment embrittlement is reviewed in detail. Factors involved in standardizing test methods for detecting the occurrence of and evaluating the severity of hydrogen environment embrittlement are considered. The effect of test technique, hydrogen pressure, purity, strain rate, stress concentration factor, and test temperature are discussed. Additional research is required to determine whether hydrogen environment embrittlement and internal reversible hydrogen embrittlement are similar or distinct types of embrittlement.

Gray, H. R.↗

NASA NTRS1972

Hydrogen environment embrittlement.

Hydrogen embrittlement is classified into three types: internal reversible hydrogen embrittlement, hydrogen reaction embrittlement, and hydrogen environment embrittlement. Characteristics of and materials embrittled by these types of hydrogen embrittlement are discussed. Hydrogen environment embrittlement is reviewed in detail. Factors involved in standardizing test methods for detecting the occurrence of and evaluating the severity of hydrogen environment embrittlement are considered. The effects of test technique, hydrogen pressure, purity, strain rate, stress concentration factor, and test temperature are discussed.

Gray, H. R.↗