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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 811 records · Page 45
All sourcesNASA NTRSDOE OSTI
DOE OSTI2018

Temperature sensor based on a polymer diffraction grating with silver nanoparticles

The method is suggested for producing an optical temperature noncontact sensor on a polymer polymethylmethacrylate (PMMA) substrate with a diffraction optical element formed by implanting low-energy high-dose silver ions through a surface mask. Ion implantation is performed at an energy of 30 keV, a radiation dose of 5.0 × 10{sup 16} ion cm{sup −}2 and an ion beam current density of 2 μA cm{sup −}2 through a surface metal mask having the form of grid with square periodical holes (cells) of size 25 μm. In the course of implantation, silver nanoparticles are produced in periodical unmasked domains of irradiated PMMA. Operation of the temperature sensor on diffraction microstructures made of polymer with silver nanoparticles is demonstrated in the range from 20 °C to 95 °C by testing it with a probe radiation of a He – Ne laser. (paper)

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2018

Structural Transformation of “Silica+Zn” Nanocomposite after Annealing in Oxidizing Atmosphere

It has been found that “hot” high-fluence Zn{sup +} implantation leads to the formation of the extended layer with zinc-based nanoclusters of size up to 10 nm in SiO{sub 2} film. The precipitate’s crystalline nature is confirmed by HRTEM studies. Post-implantation annealing at 700°C for 60 min leads to Zn atoms redistribution in implanted region, formation of the larger crystallites (up to 25 nm) and the small Zn nanoparticles surrounded by the oxide shells (core (Zn)/shell(ZnO) structure) as well as the voids formation at the interface “Zn nanocluster/SiO{sub 2} matrix”. The number of the core (Zn)/shell (ZnO) structures and the voids increases after annealing at 700°C for 120 min.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2018

Viability of Different Types of Cells Cultivated on the Surface of Medical Electret

The effect of the electric field of a medical electret on the basis of tantalum pentoxide (Ta{sub 2}O{sub 5}) on the viability of human fibroblasts, multipotent mesenchymal stromal bone marrow cells, osteocytes, and chondrocytes cultivated on the surface of tantalum orthopedic implants with an electret coating was studied in vitro. Using the methods of photocolorimetic analysis and scanning electron microscopy, difference in the metabolic activity and cell morphology, in the character of the cell attachment to the implants and distribution by their surface, associated with the value and character of the electric charge distribution on the surface of these implants and the type of cellular test systems, were detected. Unclear mechanisms of the effect of the electric field of medical electrets on the functional activity of different types of the organism cell and tissues dictate the need for further experimental developments and fundamental studies in this field.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2018

In Situ Modification and Analysis of the Composition and Crystal Structure of a Silicon Target by Ion-Beam Methods

The method of Rutherford backscattering (RBS) with channeling is widely used in compositional analysis and structural determination. An experimental process line for in situ ion implantation and RBS spectrometry is presented, and its technical parameters are given. The parameters of a probing beam needed to reach a several-percent error in the study of distribution profiles of impurities and defects are detailed. The resolution of this method was estimated using the spectrum of alpha particles produced in the decay of {sup 239}Pu and based on the RBS spectrum from a silicon monocrystal. The implantation of Xe{sup +} ions with an energy of 100 keV into a silicon monocrystal and the RBS analysis of targets in the channeling mode were performed without breach of vacuum conditions. The distribution profiles of implanted atoms and defects in irradiated monocrystals were examined.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2019

The Impact of Radiotherapy on Reoperation Rates in Patients Undergoing Mastectomy and Breast Reconstruction

Objective: The aim of this study was to determine the impact of postmastectomy radiotherapy (PMRT) on reoperation rates in women with breast cancer undergoing mastectomy and breast reconstruction. Methods: Between June 2001 and December 2015, 832 breast cancer patients treated with mastectomy and breast reconstruction with (n = 159) or without (n = 673) PMRT were analyzed retrospectively. Reoperations following breast reconstruction were categorized into the following three types: anticipated, unanticipated, and others. Multivariable logistic regression models were used to evaluate the impact of PMRT on overall and unanticipated reoperations according to different breast reconstruction types after adjusting for relevant covariates. Results: With a median follow-up of 58.5 months, a total of 1298 operations were performed in 832 breast cancer patients. The rates of overall and unanticipated reoperations were 46.2% and 7.7%, respectively. Multivariable analysis showed that PMRT was not associated with overall reoperations in either implant-based reconstruction patients (odds ratio [OR] 1.00, 95% confidence interval [CI] 0.43–2.37, p = 0.995) or autologous reconstruction patients (OR 0.85, 95% CI 0.52–1.40, p = 0.533); however, the impact of PMRT on unanticipated reoperations differed by reconstruction type. In patients who received implant-based reconstructions, PMRT was associated with a 3.05-fold (95% CI 1.20–7.75, p = 0.019) higher odds of unanticipated reoperations, while there was no difference in patients who underwent autologous reconstruction (OR 1.17, 95% CI 0.51–2.66, p = 0.713). Delayed reconstruction or delayed–immediate reconstructions were associated with an increased risk of both overall and unanticipated reoperations in both reconstruction cohorts. Conclusions: PMRT appears to be associated with an increased risk of unanticipated reoperations among patients receiving implant-based reconstruction, but not among those receiving autologous reconstruction. The risk of reoperation should be taken into consideration when selecting the appropriate breast reconstruction type when PMRT is planned.

62 RADIOLOGY AND NUCLEAR MEDICINE↗
DOE OSTI2021

Helium Bubbles and Blistering in a Nanolayered Metal/Hydride Composite

Helium is insoluble in most metals and precipitates out to form nanoscale bubbles when the concentration is greater than 1 at.%, which can alter the material properties. Introducing controlled defects such as multilayer interfaces may offer some level of helium bubble management. This study investigates the effects of multilayered composites on helium behavior in ion-implanted, multilayered ErD 2 /Mo thin film composites. Following in-situ and ex-situ helium implantation, scanning and transmission electron microscopy showed the development of spherical helium bubbles within the matrix, but primarily at the layer interfaces. Bubble linkage and surface blistering is observed after high fluence ex-situ helium implantation. These results show the ability of metallic multilayers to alter helium bubble distributions even in the presence of a hydride layer, increasing the lifetime of materials in helium environments.

36 MATERIALS SCIENCE↗
DOE OSTI2025

Stereochemical Control of Water Transport Properties in Thiol‐yne Polymers

Barrier polymers underpin almost every commercial sector, yet the needs of several emerging areas remain unmet by commercially‐available materials, including temporary orthopedic implants, transient health monitors, neural implants, and other long‐term implants. The ability to tune polymer composition independently of polymer structure positions thiol‐yne click chemistry as a promising platform to serve these emerging technologies. Here, this work describes the differences in the hierarchical structure of stoichiometrically identical materials which differ only in the proportion of the cis versus trans backbone alkene stereochemistry. Varying the isomer content in this way directs different temperature and rate dependent crystallization behavior, which affords control over micron‐scale structure. This investigation focuses on how these stereochemical features affect the water vapor permeation process by several methods and develops an understanding of how this unique structural regularity improves barrier performance relative to a commercially available water barrier polymer, poly(ethylene terephthalate).

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2018

3D‐Printed Carbon Electrodes for Neurotransmitter Detection

Abstract Implantable neural microsensors have significantly advanced neuroscience research, but the geometry of most probes is limited by the fabrication methods. Therefore, new methods are needed for batch‐manufacturing with high reproducibility. Herein, a novel method is developed using two‐photon nanolithography followed by pyrolysis for fabrication of free‐standing microelectrodes with a carbon electroactive surface. 3D‐printed spherical and conical electrodes were characterized with slow scan cyclic voltammetry (CV). With fast‐scan CV, the electrodes showed low dopamine LODs of 11±1 n m (sphere) and 10±2 n m (cone), high sensitivity to multiple neurochemicals, and high reproducibility. Spherical microelectrodes were used to detect dopamine in a brain slice and in vivo, demonstrating they are robust enough for tissue implantation. This work is the first demonstration of 3D‐printing of free‐standing carbon electrodes; and the method is promising for batch fabrication of customized, implantable neural sensors.

Yang, Cheng↗
DOE OSTI2018

3D‐Printed Carbon Electrodes for Neurotransmitter Detection

Abstract Implantable neural microsensors have significantly advanced neuroscience research, but the geometry of most probes is limited by the fabrication methods. Therefore, new methods are needed for batch‐manufacturing with high reproducibility. Herein, a novel method is developed using two‐photon nanolithography followed by pyrolysis for fabrication of free‐standing microelectrodes with a carbon electroactive surface. 3D‐printed spherical and conical electrodes were characterized with slow scan cyclic voltammetry (CV). With fast‐scan CV, the electrodes showed low dopamine LODs of 11±1 n m (sphere) and 10±2 n m (cone), high sensitivity to multiple neurochemicals, and high reproducibility. Spherical microelectrodes were used to detect dopamine in a brain slice and in vivo, demonstrating they are robust enough for tissue implantation. This work is the first demonstration of 3D‐printing of free‐standing carbon electrodes; and the method is promising for batch fabrication of customized, implantable neural sensors.

Yang, Cheng↗
DOE OSTI2017

Assessing the oxidation states and structural stability of the Ce analogue of brannerite

The Ce-containing analogue of brannerite (ie, UTi2O6) was previously considered to be stoichiometric (ie, CeTi2O6); however, it has recently been determined that the material is O deficient. This oxygen-deficient material has been suggested to be charged balanced by the presence of a minor concentration of Ce3+ or by the A-site being cation deficient with the Ce oxidation state being 4+. A variety of Ti-containing oxides (including brannerite) have been investigated as potential nuclear wasteforms, and it is necessary to understand the electronic structure of a proposed nuclear wasteform material as well as how the structure responds to radiation from incorporated waste elements. The radiation resistance of a material can be simulated by ion implantation. The objective of this study was to confirm the Ce oxidation state in the cation- and oxygen-deficient material (ie, Ce0.94Ti2O6 - δ) and to determine how radiation damage affects this material. X-ray photoelectron spectroscopy (XPS) and X-ray absorption near-edge spectroscopy were used to study Ce0.94Ti2O6 - δ before and after being implanted with 2 MeV Au- ions. Analysis of the Ce 3d XPS spectra from the as-synthesized samples by using a previously developed fitting method has unequivocally shown that Ce adopts both 4+ (major) and 3+ (minor) oxidation states, which was confirmed by examination of magnetic susceptibility data. Analysis of XPS and X-ray absorption near-edge spectroscopy spectra from ion-implanted materials showed that both Ce and Ti were reduced because of radiation damage and that the local coordination environments of the cations are greatly affected by radiation damage.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2019

Role of cardiac {sup 123}I-mIBG imaging in predicting arrhythmic events in stable chronic heart failure patients with an ICD

Background: Despite therapeutic improvement, the prognosis of chronic heart failure (CHF) remains unfavorable partly due to arrhythmia and sudden cardiac death (SCD). This prospective study evaluated myocardial {sup 123}I-meta-iodobenzylguanidine ({sup 123}I-mIBG) scintigraphy as a predictor of arrhythmic events (AE) in CHF patients. Methods: 170 CHF patients referred for implantable cardioverter-defibrillator (ICD) implantation for both primary and secondary prevention were enrolled. All patients underwent planar and SPECT imaging. Early and late heart-to-mediastinum (H/M) ratio, {sup 123}I-mIBG washout (WO), early and late summed SPECT scores were calculated The primary endpoint was an AE: sustained ventricular tachycardia, resuscitated cardiac arrest, appropriate ICD therapy or SCD. The secondary endpoint was appropriate ICD therapy. Results: During a median follow-up of 23.3 months, 69 patients experienced an AE. Early summed score (ESS) was the only independent predictor of AE [HR 1.023 (1.003-1.043)]. Focussing on only patients with an ICD for primary prevention, ESS was the only independent predictor of AE [HR 1.028 (1.007-1.050)]. {sup 123}I-mIBG-derived parameters failed to be independent predictors of appropriate ICD therapy. However there was a “bell-shaped” relation between {sup 123}I-mIBG scintigraphy-derived parameters and AE and appropriate ICD therapy, i.e., those with intermediate {sup 123}I-mIBG abnormalities tended to be at higher risk of events. Conclusion: Although SPECT {sup 123}I-mIBG scintigraphy was associated with AE in CHF patients with ICD implantation for primary and secondary prevention, no association was found between {sup 123}I-mIBG scintigraphy-derived parameters and appropriate ICD therapy.

62 RADIOLOGY AND NUCLEAR MEDICINE↗
DOE OSTI2023

Grain boundary softening from stress assisted helium cavity coalescence in ultrafine-grained tungsten

The formation of helium cavities in coarse-grained materials produces hardening proportional to the number density and size of the cavities and due to the interaction of dislocations with intragranular helium defects. In nanostructured metals containing a high density of interfacial sinks, preferential cavity formation in the grain boundaries instead produces softening that is often attributed to enhanced interfacial plasticity. Here, employing two grades of ultrafine-grained tungsten, we explore this effect using targeted implantation studies to map cavity evolution as a function of the irradiation conditions and quantify its impact on the mechanical response through nanoindentation. Softening is reported at implantation temperatures above the threshold for preferential grain boundary cavity formation but at a sufficiently low fluence prior to the growth of intragranular cavities. Collective changes in the mean cavity size, density, and morphology beneath a residual impression on an implanted surface indicate that cavity coalescence accompanied the reduction in hardness. Complementary atomistic simulations demonstrate that, in tungsten grain structures exhibiting softening, grain boundary bubble coalescence is driven by stress concentrations that further act to localize strain in the grain boundaries through cooperative deformation processes involving local atomic shuffling and sliding, dislocation emission, and even the nucleation of unstable twinning events.

36 MATERIALS SCIENCE↗
DOE OSTI2017

Effects of alloying elements on the elastic properties of bcc Ti-X alloys from first-principles calculations

Titanium alloys are great implant materials due to their mechanical properties and biocompatibility. However, a large difference in Young’s modulus between bone (~10–40 GPa) and common implant mate-rials (ie. Ti-6Al-4V alloy ~ 110 GPa) leads to stress shielding and possible implant failure. Here, the present work predicts the single crystal elastic stiffness coefficients (c ij ’s) for five binary systems with the body centered cubic lattice of Ti-X (X = Mo, Nb, Ta, Zr, Sn) using first-principles calculations based on Density Functional Theory. In addition, the polycrystalline aggregate properties of bulk modulus, shear modulus, Young’s modulus, and Poisson ratio are calculated. It is shown that the lower Young’s modulus of these Ti-alloys stems from the unstable bcc Ti with a negative value of (c 11 –c 12 ). The data gathered from these efforts are compared with available experimental and other first-principles results in the literature, which set a foundation to design biocompatible Ti alloys for desired elastic properties.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Revealing the synergistic effects of sequential and simultaneous dual beam irradiations in tungsten via in-situ TEM

Elucidating the synergistic effects of different energetic beams on the radiation response of nuclear materials is critical for developing an improved methodology for their evaluation when exposed to extreme environments. This article describes in-situ sequential (He implantation followed by Kr irradiation and vice-versa) and simultaneous (heavy ion Kr irradiation and He implantation) dual beam irradiations performed on tungsten at 1223 K. Dislocation loop density, average area, and total loop damage as a function of irradiation history and dose/fluence are quantified. The loop Burgers vectors and cavity damage (cavity density, size and total change in volume) are also determined at the final maximum dose for each condition. The loop damage evolution was different in all cases, with the smallest loop damage observed in the simultaneous experiment. Annihilation of Kr generated dislocation loops during He implantation in the Kr + He experiment was an unanticipated observation that may be explained by the dynamic evolution of dislocation loop sink strengths and time-dependent defect fluxes. Dislocation loop raft formation, denuded zones near extended defects, and cavity damage are compared across the different conditions. The phenomena observed and discussed in this work will stimulate further experimental and computational modeling activities leading to improved fundamental understanding of the irradiation response of nuclear materials under reactor-similar environments.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Helium-bubble-enhanced disordering of intermetallic phase under irradiation

Understanding and controlling phase transformations in metals and alloys under irradiation is vital to the design of irradiation-tolerant materials. The L1 2 -ordered intermetallic phase in nickel-based superalloys provides superior high-temperature mechanical properties and corrosion resistance. Here, we studied the order-disorder transformation kinetics of an L1 2 -structured gamma-prime phase in nickel-based superalloy Rene N4 under krypton ion irradiation and the effect of pre-implanted helium gas bubbles on the kinetics of phase transformation. Furthermore, the presence of pre-implanted helium gas bubbles significantly enhances the order-disorder transformation of L1 2 -structured gamma-prime phase under irradiation at 300 °C. The evolution of pre-implanted helium gas bubbles under irradiation implies that helium gas bubbles could effectively trap irradiation-induced vacancies and impede the reordering process of anti-site defects in gamma-prime phase.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Blister resistant targets for nuclear reaction experiments with α-particle beams

Solid targets for nuclear measurements that use α-particle beams commonly experience a form of degradation known as blistering. The effect can prevent the use of solid targets for high intensity α-particle experiments, often necessitating complex gas target systems. To combat this problem, three different blister resistant target backings were designed for use in direct reaction measurements with high intensity α-particle beams. The blister resistant target designs utilize gas diffusive properties of fused silica, sintered metal, and porous evaporated metal. Each target was implanted with 22 Ne ions and bombarded with α-particle beam to test blister resistance. Targets were characterized and monitored using the 22 Ne(p, γ) 23 Na reaction to determine the degradation of implanted material, and compare them to typical implanted noble gas targets. We find that all targets studied exhibit resistance to blistering, with the porous evaporated metal targets displaying the least amount of target material degradation.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2020

Optimization of target lifetime for production of 14 MeV neutrons

Two methods are examined for extending the life of tritium targets for production of 14 MeV neutrons by the 3 H( 2 H,n) 4 He nuclear reaction. With thick film targets the neutron production rate decreases with time due to isotope exchange of tritium in the film with implanted deuterium. Here, the target life is maximized by operating the target at elevated temperature where the implanted deuterium mixes by thermal diffusion throughout the entire thickness of the film. The number of neutrons obtained from a target is then proportional to the initial tritium content of the film. A novel thin-film target design was also developed and tested. With these thin-film targets, the incident deuterium is implanted through the tritide into the underlying substrate material. A thin permeation barrier layer between the tritide film and substrate, reduces the rate of tritium loss from the tritide film. Good thin-film target performance was achieved using W and Fe for the barrier and substrate materials respectively. Thin-film targets were fabricated and tested and shown to produce similar number of neutrons as thick-film targets while using only a small fraction of the amount of tritium.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2022

Effects of helium cavity size and morphology on the strength of pure titanium

In this study, high-purity α-titanium was implanted with helium to observe cavity morphology – size, number density, and form (i.e., bubbles vs. voids) – effects on materials strength. Increasing implantation temperatures lead to an Arrhenius-type (i.e., exponential) increase in cavity size, a transition from spherical bubbles to faceted voids, and a marked increase in strength (~20–50%). Implanted samples deformed uniformly in contrast to nano-compression of unimplanted or alloyed titanium, but pillars with the largest faceted voids developed a type of bulging localized deformation. Affected voids were repeatedly sheared, becoming rough and shrunken. Dislocation-cavity interactions and the role of helium content within cavities are considered.

36 MATERIALS SCIENCE↗