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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 793 records · Page 44
All sourcesNASA NTRSDOE OSTI
DOE OSTI2018

Room-Temperature Phototransistor with Negative Photoresponsivity of 10 8 A W -1 Using Fullerene-Sensitized Aligned Carbon Nanotubes

Detection of low intensity light down to a few photons requires photodetectors with high gain. In this paper, a new photodetector is reported based on C 60 -sensitized aligned carbon nanotube (CNT) transistors with an extremely high responsivity of 10 8 A W -1 (gain > 10 8 ) in the ultraviolet and visible range, and 720 A W -1 (gain = 940) in the infrared range. In contrast to most sensitized phototransistors that operate on the photogating effect, the new photodetector operates on the modulation of the electrons scattering in the CNTs, leading to negative photoconductivity. Comparison with similar photodetectors using random CNT networks shows the benefit of using aligned CNTs. Finally, at room temperature, the aligned CNT photodetectors are demonstrated to detect a few tens of photons per CNT.

47 OTHER INSTRUMENTATION↗
DOE OSTI2017

Quantification of Sheet Resistance in Boron-Diffused Silicon Using Micro-Photoluminescence Spectroscopy at Room Temperature

A micro-photoluminescence-based technique is presented, to quantify and map sheet resistances of boron-diffused layers in silicon solar cell precursors with micron-scale spatial resolution at room temperature. The technique utilizes bandgap narrowing effects in the heavily-doped layers, yielding a broader photoluminescence spectrum at the long-wavelength side compared to the spectrum emitted from lightly doped silicon. By choosing an appropriate spectral range as a metric to assess the doping density, the impacts of photon reabsorption on the analysis can be avoided; thus, an accurate characterization of the sheet resistance can be made. This metric is demonstrated to be better representative of the sheet resistance than the surface doping density or the total dopant concentration of the diffused layer. The technique is applied to quantify sheet resistances of 12-um-wide diffused fingers in interdigitated back-contact solar cell precursors and large diffused areas. The results are confirmed by both 4-point probe and time-of-flight secondary-ion mass spectrometry measurements. Lastly, the practical limitations associated with extending the proposed technique into an imaging mode are presented and explained.

14 SOLAR ENERGY↗
DOE OSTI2011

Minimally Invasive Catheter Procedures to Assist Complicated Pacemaker Lead Extraction and Implantation in the Operating Room

We report on percutaneous catheter procedures in the operating room (OR) to assist complicated manual extraction or insertion of pacemaker (PM) and implantable cardioverter defibrillator leads. We retrospectively reviewed complicated PM revisions and implantations performed between 2004 and 2009 that required percutaneous catheter procedures performed in the OR. The type of interventional procedure, catheter and retrieval system used, venous access, success rates, and procedural complications were analyzed. In 41 (12 female and 29 male [mean age 62 {+-} 17 years]) of 3021 (1.4%) patients, standard manual retrieval of old leads or insertion of new leads was not achievable and thus required percutaneous catheter intervention for retrieval of misplaced leads and/or recanalisation of occluded central veins. Thirteen of 18 (72.2%) catheter-guided retrieval procedures for misplaced (right atrium [RA] or ventricle [RV; n = 3], superior vena cava [n = 2], brachiocephalic vein [n = 5], and subclavian vein [n = 3]) lead fragments in 16 patients were successful. Percutaneous catheter retrieval failed in five patients because there were extremely fixed or adhered lead fragments. Percutaneous transluminal angiography (PTA) of central veins for occlusion or high-grade stenosis was performed in 25 patients. In 22 of 25 patients (88%), recanalization of central veins was successful, thus enabling subsequent lead replacement. Major periprocedural complications were not observed. In the case of complicated manual PM lead implantation or revision, percutaneous catheter-guided extraction of misplaced lead fragments or recanalisation of central veins can be performed safely in the OR, thus enabling subsequent implantation or revision of PM systems in the majority of patients.

62 RADIOLOGY AND NUCLEAR MEDICINE↗
DOE OSTI2019

Non-conservative Management of Placenta Accreta Spectrum in the Hybrid Operating Room: A Retrospective Cohort Study

Introduction: Hysterectomy is the standard of care in placenta accreta spectrum (PAS). To reduce the risks of obstetric hemorrhage during surgery, endovascular interventions have been proposed. Our aim is to evaluate the feasibility and safety of the overall non-conservative management of PAS in the hybrid operating room (OR) to replace the classic two-step procedure (catheterization in the interventional radiology suite and transfer to conventional OR). Materials and Methods: This is a retrospective study of series of patients with histopathologic confirmation of PAS treated in the hybrid OR at the same university hospital. We used for comparison our historical cohort managed with the standard two-step procedure. Results: We included 110 patients, 80 in the conventional OR and 30 in the hybrid OR. There were no cases of major complications attributable to the endovascular procedures. In the two-step procedure, there were 10 (12.5%) intra-arterial catheter displacements that required repositioning in the conventional OR under mobile C-arm fluoroscopy and no cases in the hybrid OR (p = 0.04). The mean operative time was 380 + 42 min in the conventional OR and 296 + 66 min in the hybrid OR (p = .00001). There were no differences in the gestational age at delivery, postoperative length of stay, or large-volume blood transfusion. There were no maternal deaths. Conclusions: The overall non-conservative management of PAS in the hybrid OR has shown to be feasible and safe in our series, offering potential advantages to replace the classic two-step procedure. More studies are needed to evaluate whether this strategy is cost-effective and whether it may improve maternal and perinatal outcomes.

62 RADIOLOGY AND NUCLEAR MEDICINE↗
DOE OSTI2011

Formation of an SEI on a LiMn(2)O(4) Cathode during Room Temperature Charge-Discharge Cycling Studied by Soft X-Ray Absorption Spectroscopy at the Fluorine K-edge

The solid electrolyte interface (SEI) formation on the surface of LiMn{sub 2}O{sub 4} electrodes during room temperature charge-discharge cycling was studied using soft X-ray absorption spectroscopy at the Fluorine (F) K-edge. LiMn{sub 2}O{sub 4} electrodes without any binder were prepared by electrostatic spray deposition to eliminate the signal originating from the PVDF binder in the F K-edge X-ray absorption spectra. The F K-edge absorption spectra show that the SEI layer forms at a very early stage of cycling. SEI growth takes place during discharge. In addition, LiF formation is accelerated if the discharge step follows a charge step. The F K-edge absorption spectra suggest that the major component of the SEI is LiF.

25 ENERGY STORAGE↗
DOE OSTI2018

Paths to Room-Temperature Superconductivity

Superconducting state at room temperature is a perfectly realistic phenomenon, and there are various paths aimed at reaching this goal. Some of them are described briefly in this presentation. One can expect that the first breakthrough will occur with the use of the high-pressure methods. An external pressure is the thermodynamic parameter, and its change allows one to create new structures, including that of sulfur hydride displaying the record value of the critical temperature.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2018

Enhanced Room-Temperature Ferromagnetism Observed in SiO{sub 2}-Coated CuO Nanostructures

In this paper, the magnetic properties of pure CuO and SiO{sub 2}-coated CuO nanocrystals were reported. Strongly enhanced room-temperature ferromagnetism was observed in SiO{sub 2}-coated CuO nanocrystals, whose saturation magnetization is two orders of magnitude enhanced compared to that of the uncoated CuO nanocrystals. The mechanism of this enhancement was investigated. It points out the main origin of ferromagnetism in these CuO nanocrystals is the uncompensated surface state, so that the coating of SiO{sub 2} can effectively protect the surface state to improve the ferromagnetism in these CuO nanocrystals.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2018

Structural Confinement Assisted a Robust Superparamagnetic State in MgNi{sub 2}O{sub 3} and MgNi{sub 1.5}Co{sub 0.5}O{sub 3} Nanoparticles at Room Temperature

In this study, ideal spherical-shaped cubic metal oxide nanoparticles of < 30 nm in size were prepared by a citric acid sol-gel combustion method. The detailed structural analysis and microscopic techniques clearly support the existing grade of structural confinement effect in MgNi{sub 2}O{sub 3} and MgNi{sub 1.5}Co{sub 0.5}O{sub 3}. Temperature-dependent magnetisation studies at various applied fields revealed a moderate change of T{sub B} near room temperature by distinct particle size. Magnetic crystalline anisotropy and energy barrier density theoretical model results suggested the importance of innermost magnetic particle stability-aided spin orientation with a fascinating magnetic moment in superparamagnetic region exerted by Ni and Co remarkably postured as a significant part of these nanoparticles.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2019

No Signature of Room Temperature Ferromagnetism in Fe-Doped ITO Thin Films

Iron (Fe)-doped indium tin oxide thin films (In{sub 0.95 − x}Fe{sub x}Sn{sub 0.05}){sub 2}O{sub 3} at x = 0.00, 0.05, 0.10, and 0.15 were deposited onto glass substrates using an electron beam evaporation technique. The coated thin films were characterized by X-ray diffractometer (XRD), UV-VIS-NIR spectrophotometer, photoluminescence spectrophotometer, scanning electron microscope, and vibrating sample magnetometer to study their structural, optical, morphological, and magnetic properties, respectively. The crystallite size of the films increased from 18 to 30 nm with Fe concentration (x). The morphology showed the formation of nanorods. The bandgap of the films decreased from 3.94 to 3.81 eV. The X-ray photoelectron spectroscopy (XPS) studies confirm the presence of Fe ions in two different oxidation states (Fe{sup 2+}, Fe{sup 3+}). The magnetic studies revealed the paramagnetic behavior of the films at room temperature and at low temperature (5 K). The effective magnetic moment (μ{sub eff}) of Fe-doped indium tin oxide thin films was calculated using Langevin theory of paramagnetism extending to Curie’s law. The effective magnetic moment (μ{sub eff}) was increased on increasing the dopant concentration.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2019

Development of Room-Temperature Ferromagnetism in Nanocomposite CdO Codoped with Al and Gd: Treatment in Hydrogen Atmosphere

Cadmium oxide codoped with Al and Gd ion powders was synthesised by thermal codecomposition of a mixture of complexes of cadmium acetate dihydrate, gadolinium acetate hydrate, and aluminum nitrate nonahydrate. The mass ratio of Al/Cd was fixed while the mass ratio of Gd/Cd varied systematically. The purpose of the present study is to synthesise and study the transparent conducting oxide (TCO) CdO powder having room-temperature ferromagnetic (RT-FM) properties. To realize that purpose, the synthesised Al/Gd-codoped CdO powder was annealed under hydrogen gas with certain conditions. The X-ray diffraction (XRD) method confirmed the formation of a single nanocrystalline structure; thus, both Al/Gd ions were incorporated into CdO lattice forming solid solutions. Magnetic measurements revealed that some of the doped CdO powders gained paramagnetic (PM) properties where the susceptibility increases with increasing dopant Gd content; the measured effective magnetic moment of dopant Gd{sup 3+} was around 8 μ{sub B}. Furthermore, the magnetic energy of the created RT-FM of the codoped CdO samples by hydrogenation was found to be dependent on the Gd% doping level. For hydrogenated CdO powder doped with 3% Gd, the coercivity (H{sub c}) was 195.9 Oe, the remanence (M{sub r}) was 0.77 memu/g, the saturation magnetisation (M{sub s}) was 5.05 memu/g, and the energy product (U{sub m}) was 150.6 merg/g. Thus, the possibility of production of TCO CdO with RT-FM, where magnetic characteristics can be tailored by doping and post treatment under H{sub 2} gas, was proven. Thus, a new potential candidate to be used as a dilute magnetic semiconductor (DMS) was successfully synthesised.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2019

Magnetocaloric Effect in La{sub 0.67}Ba{sub 0.33}Mn{sub 0.95}Ni{sub 0.05}O{sub 3} Manganite Near Room Temperature

We report the structural, magnetic, and magnetocaloric properties of La{sub 0.67}Ba{sub 0.33}Mn{sub 0.95}Ni{sub 0.05}O{sub 3} (LBMNO) manganite, synthesized by sol-gel method. X-ray diffraction (XRD) analysis using Rietveld refinement showed that this sample crystallizes in the rhombohedral structure with R 3-bar c space group. Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM) analysis were used to confirm the structure formation of the LBMNO material. The temperature dependent magnetization data revealed a transition from ferromagnetic (FM) to paramagnetic (PM) phase at T{sub C}= 308 K. Using Arrott plots, it was found that the transition is of a second order. From the measured magnetization data as a function of magnetic applied field, the magnetic entropy change (−ΔS{sub M}) and the relative cooling power RCP have been determined. In the vicinity of T{sub C} (−ΔS{sub M}) reached a maximum value of 2.15 J kg{sup − 1} K{sup − 1} and a large RCP value of about 299 J kg{sup − 1} under 5 T{sup − 1}. This magnetocaloric effect has been analyzed by considering the Landau theory of magnetic phase transition. Consequently, our sample can be considered a promising material in room-temperature magnetic refrigeration.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2019

Hydrogen-Induced Room-Temperature Ferromagnetism in Carbon-Incorporated CdO

Carbon-incorporated CdO (CdO–C) nanocrystallites were synthesised by sol–gel technique including sucrose (C{sub 12}H{sub 22}O{sub 11}) as a source of carbon ions. This investigation aimed to disclose the necessary synthesis conditions to create room-temperature ferromagnetic (RT-FM) properties in host CdO–C system. Therefore, structural, optical and magnetic properties of CdO–C samples were systematically investigated. The X-ray diffraction (XRD) method was used to study the structural properties, and the diffuse reflection spectroscopy (DRS) method was used to study the optical properties. It was established that post-annealing of synthesised samples in H{sub 2} atmosphere could create RT-FM. The experimental results were discussed in the framework of previous studies of other transparent conducting oxides (TCOs). The magnetic properties of CdO–C system were studied here for the first time. It was found that CdO–C nanopowder of tailored FM properties could be used as a candidate for TCO applications.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2019

Oxygen Vacancy-Induced Room Temperature Ferromagnetism in Rutile TiO{sub 2}

As oxygen vacancies play an important role in ferromagnetism of rutile TiO{sub 2}, a method of γ-ray irradiates rutile TiO{sub 2} single crystals was subtly proposed to study the effect of oxygen vacancies on magnetic properties. Remarkably, room temperature ferromagnetism was observed in γ-ray irradiated rutile TiO{sub 2} single crystals, and the saturation magnetization is the strongest when dose is 4 × 10{sup 4} Gy which assigned to ESR results. Since the displacement threshold energy of Ti atom is much bigger than that of O atom, the defects produced by γ-irradiation are mainly oxygen vacancies. After irradiation, XPS, PL spectra indicate the presence of oxygen vacancies(V{sub O}), Ti{sup 3+}, and V{sub O}-Ti{sup 3+} composite defects.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2018

Processing Parameter Control of Lifetime-Limiting Failure Mechanisms in Al-Si Cast Alloys at Room and Elevated Temperatures

Aluminum-silicon cast alloys widely used throughout the transportation sector, A356, 319, and A390, have been studied with respect to chemical compositions and processing parameters that control the resultant mechanical behavior. First, the development of strengthening mechanisms is discussed in terms of the role that alloying elements, solidification behavior, and thermal treatments play. Based on this understanding, an extensive matrix of material conditions was developed and characterized in order to provide practical guidelines for alloy development. In order to provide an understanding of lifetime-limiting failure mechanisms, fatigue crack growth and hot compressive dwell behaviors were further investigated. Fatigue crack growth tests were conducted for all alloys at R = 0.1 and room temperature, and creep–fatigue of 319 was studied at R = − 1.5 and 250 °C. The role of processing parameters in controlling the mechanical properties is identified and discussed, and recommendations for optimized design are made.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Room-Temperature Charpy Impact Property of 3D-Printed 15-5 Stainless Steel

In this study, the room-temperature Charpy impact property of 3D-printed 15-5 stainless steel was investigated by a combined experimental and finite element modeling approach. The experimentally measured impact energy is 10.85 ± 1.20 J/cm{sup 2}, which is comparable to the conventionally wrought and non-heat treated 15-5 stainless steel. In parallel to the impact test experiment, a finite element model using the Johnson–Cook material model with damage parameters was developed to simulate the impact test. The simulated impact energy is 10.46 J/cm{sup 2}, which is in good agreement with the experimental data. The fracture surface from the experimentally tested specimen suggests that the 3D-printed specimens undergo predominately brittle fracture.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Friction Stir Welding of Low-Carbon AISI 1006 Steel: Room and High-Temperature Mechanical Properties

Friction stir welding (FSW) is an ecologically benign solid-state joining process. In this work, FSW of low-carbon AISI 1006 steel was carried out to study the microstructure and mechanical properties of the resulting joints at both room temperature (RT) and 200 °C. In the parameter space investigated here, a rotational tool speed and translation feed combination of 1200 rpm and 60 mm/min produced a defect-free weld with balanced mechanical properties and a superior Vickers microhardness profile compared to all other conditions and to base metal (BM). At faster translation feeds (100 and 150 mm/min), wormhole defects were observed in the weld microstructure and were attributed to higher strain rate experienced by the weld zone. Under tensile loading, welded material exhibited yield strength that was up to 86 and 91% of the BM at RT and 200 °C, respectively. On the other hand, tensile strength of welded material was nearly similar to that of the base metal at both RT and 200 °C. However, at both temperatures the tensile ductility of the welded joints was observed to be significantly lower than the BM. Annealing of the 1200 rpm and 60 mm/min FSW specimen resulted in tensile strength of 102% compared to base material and 47% increase in the strain at failure compared to the as-welded specimen. The Charpy impact values revealed up to 62 and 53% increase in the specific impact energy for the 1200 rpm and 60 mm/min welded joints as compared with the BM.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Effect of the As-Forged and Heat-Treated Microstructure on the Room Temperature Anisotropic Ductile Fracture of Inconel 718

The purpose of the present work was to investigate the effect of primary carbides and the δ-phase on the anisotropic ductile fracture of Inconel 718 in the forging process. Inconel 718 alloys were prepared by VIM + VAR processes with various carbon contents (0.009 and 0.027 wt.%). Then, the alloys were forged and annealed at temperatures of 980 and 1030 °C. The room temperature mechanical anisotropy of the alloys was evaluated at the longitudinal direction (LD) and transverse direction (TD). Tensile and impact tests were used to characterize the mechanical properties of the specimens. The microstructural characterization and the fractography of the alloys were carried out by FE-SEM. The obtained results showed that the fracture strain and the impact energy in the TD were 30-50% lower than the LD. The fracture was accelerated by the δ-phase, leading to the reduction of impact energy in the longitudinal and the lateral directions up to 50%. The low-carbon alloy indicated similar characteristics in both the LD and the TD. Aligned carbides changed the fracture path from a zigzag path in the LD to a fibrous path in the TD, while the δ-phase created a flat fracture path. The shear lip area ratio in the tensile fracture cross section was decreased by reducing ductility.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Planar Anisotropy, Tension–Compression Asymmetry, and Deep Drawing Behavior of Commercially Pure Titanium at Room Temperature

The planar anisotropy (PA) and tension–compression asymmetry (TCA) of the CP-Ti were investigated via uniaxial tension and compression tests at room temperature. The formability and the earing behavior of the CP-Ti sheet were studied via deep drawing experiment. The deep drawing simulations using the uniaxial tensile and the compressive curves as the hardening rules were compared with each other and with the experimental results. The CP-Ti sheet showed PA and TCA in yielding and strain hardening. The PA was characterized by the plastic strain ratio r{sub 0}, r{sub 45}, and r{sub 90} of 1.47, 2.06, and 2.05. The TCA showed PA, which showed tension–compression yield strength ratios of 1.12, 1.08, and 1.04 in 0°, 45°, and 90° in the rolling direction, and tensile and compressive hardening exponent ratios of 0.86, 0.8, and 0.62. The orientation distribution functions (ODFs) analysis demonstrated that the tensile and the compressive deformation textures were different and showed PA. The simulative results, including the simulated forming force and the earing profiles using the uniaxial tensile and compressive curves as the hardening rules, were not in agreement with each other. The results were not in good agreement with the experimental results, implying that the TCA had an important effect on the formability of the sheet. The TCA tended to reduce the thickness of the deep drawing parts, increase the earing ratio, and affect the drawing force.

36 MATERIALS SCIENCE↗