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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 1,801 records · Page 100
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Development of Ionic Liquid-Additized, GF-5/6 Compatible Low-Viscosity Oils for Automotive Engine and Rear Axle Lubrication for 4% Improved Fuel Economy

This joint project among ORNL, GM, and DRO successfully developed ionic liquid-additized low viscosity lubricants, SAE 0W-12 and 70W-80, for both IC engine and rear axle lubrication, respectively, and demonstrated combined vehicle fuel economy improvement (FEI). Phosphonium-alkylphosphate ILs have been found to be the most effective among the candidates in protecting surface damage from both sliding wear and rolling contact fatigue, and optimal IL concentrations have been determined. The IL’s impact on three-way catalyst seems to be significantly less adverse than the conventional ZDDP. Oil formulations were optimized for both energy efficiency and wear protection. Tribological bench testing of the IL-additized low-viscosity oils showed at least 40% lower boundary friction, more than 60% lower elastohydrodynamic friction, and greater than 50% less wear compared with commercial baselines. IL-additized lubricants have demonstrated FEI by 9.9% in engine dynamometer tests under extreme conditions and 6.9% increased power output in gear rig tests. Prototype IL-additized engine oil and rear axle fluid exhibited combined FEI of 1.39% and 3.24% benchmarked against the state-of-the-art baselines in vehicle testing of fresh oils under the Federal Test Procedure (FTP) city cycle and Highway Fuel Economy Driving Schedule (HWFET), respectively. Used oil analysis suggested that the IL-additized low-viscosity oils produced less wear than the commercial baselines. The gained fundamental understanding and demonstrated FEI in this work pave the way for future development and implementation of the ionic liquid technology.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2014

Compressor bleed cooling fluid feed system

A compressor bleed cooling fluid feed system for a turbine engine for directing cooling fluids from a compressor to a turbine airfoil cooling system to supply cooling fluids to one or more airfoils of a rotor assembly is disclosed. The compressor bleed cooling fluid feed system may enable cooling fluids to be exhausted from a compressor exhaust plenum through a downstream compressor bleed collection chamber and into the turbine airfoil cooling system. As such, the suction created in the compressor exhaust plenum mitigates boundary layer growth along the inner surface while providing flow of cooling fluids to the turbine airfoils.

33 ADVANCED PROPULSION SYSTEMS↗
DOE OSTI2018

A New Method of Creating High-Temperature Speckle Patterns and Its Application in the Determination of the High-Temperature Mechanical Properties of Metals

Speckle techniques, such as DIC (Digital Image Correlation) and DSP (Digital Speckle Photography), are frequently used to determine the high-temperature mechanical properties of materials. Speckle techniques require the creation of a random speckle pattern on the surface of the specimen. The most commonly used approach to creating a high-contrast speckle pattern is to spray a layer of black paint particles on a white background. However, in a high-temperature environment, the paint particles tend to peel off or burn off. In this paper, we present an approach that uses a novel laser-engraving technology, where the created speckles will sustain temperatures as high as the melting temperature of the specimen. The size, density, depth and distribution of the speckles can be controlled to suit a particular situation. Since the pattern is part of the specimen, it will never disappear, until the melting temperature of the metal is reached. As an application, we used the technique to determine the elastic modulus of Ti up to 600{sup °}C and tungsten up to 1000{sup °}C.

42 ENGINEERING↗
DOE OSTI2015

Locomotion of bacteria in liquid flow and the boundary layer effect on bacterial attachment

The formation of biofilm greatly affects the performance of biological reactors, which highly depends on bacterial swimming and attachment that usually takes place in liquid flow. Therefore, bacterial swimming and attachment on flat and circular surfaces with the consideration of flow was studied experimentally. Besides, a mathematical model comprehensively combining bacterial swimming and motion with flow is proposed for the simulation of bacterial locomotion and attachment in flow. Both experimental and theoretical results revealed that attached bacteria density increases with decreasing boundary layer thickness on both flat and circular surfaces, the consequence of which is inherently related to the competition between bacterial swimming and the non-slip motion with flow evaluated by the Péclet number. In the boundary layer, where the Péclet number is relatively higher, bacterial locomotion mainly depends on bacterial swimming. Thinner boundary layer promotes bacterial swimming towards the surface, leading to higher attachment density. To enhance the performance of biofilm reactors, it is effective to reduce the boundary layer thickness on desired surfaces. - Highlights: • Study of bacterial locomotion in flow as an early stage in biofilm formation. • Mathematical model combining bacterial swimming and the motion with flow. • Boundary layer plays a key role in bacterial attachment under flow condition. • The competition between bacterial swimming and the motion with flow is evaluated.

42 ENGINEERING↗
DOE OSTI2021

Surface Acoustic Wave Sensors for Refrigerant Leak Detection: Compact, Inexpensive, Selective and Sensitive Sensors

Pacific Northwest National Laboratory (PNNL), in collaboration with Parker and Hannifin, is developing a compact, inexpensive, and highly sensitive and selective surface acoustic wave sensor coated with fluorophillic sorbent for detecting fluorocarbon leaks from HVAC systems. Having a highly effective sorbent sensitive to fluorocarbon refrigerant vapors provides a means to develop a sensing device for leak detection. Surface acoustic wave (SAW) sensors with a gas sensing film deposited between the delay lines or on the interdigital transducer have been used to detect gas and vapor molecules in harsh environments with high sensitivity. As part of this project, PNNL screened several sorbent materials that are shown to be selective towards fluorocarbon refrigerant (R32) molecule. The identified sorbent materials were synthesized, characterized, and tested towards R32 using various spectroscopic technique. Next, the sorbent material was coated on a SAW sensor as a thin film using vapor deposition and drop coating methods. The coated thin film was further characterized and tested towards the detection of pure R32 and R32 in ambient air at room temperature to demonstrate the SAW response towards R32 in presence of other competing gases and vapors in air.

42 ENGINEERING↗
DOE OSTI2025

Surface and bulk two-level-system losses in lithium niobate acoustic resonators

Lithium niobate (LN) is a promising material for building acoustic resonators used in quantum applications, but its performance is limited by poorly understood material defects called two-level systems (TLSs). Here, in this work, we fabricate high-performance acoustic resonators from LN with quality factors up to 6 ×10 7 and use them to separate bulk and surface contributions to TLS loss. By comparing these bulk acoustic wave (BAW) resonators with previous surface-acoustic-wave and phononic-crystal studies, we show that devices with high surface-participation ratios are limited by surface TLSs, while our BAW devices reveal an intrinsic bulk TLS limit. Through systematic surface treatments and microscopy, we demonstrate that BAW resonator performance remains unchanged despite surface modifications, confirming operation in a bulk-limited regime. Here, our work establishes quantitative bounds on both surface and bulk TLS losses in LN within the context of the material growth and fabrication approaches we have pursued, and it provides guidance for future device engineering and materials development.

acoustic wave phenomena↗
DOE OSTI2016

SU-F-T-462: Lessons Learned From a Machine Incident Reporting System

Purpose: Linear accelerators must operate with minimal downtime. Machine incident logs are a crucial tool to meet this requirement. They providing a history of service and demonstrate whether a fix is working. This study investigates the information content of a large department linear accelerator incident log. Methods: Our department uses an electronic reporting system to provide immediate information to both key department staff and the field service department. This study examines reports for five linac logs during 2015. The report attributes for analysis include frequency, level of documentation, who solved the problem, and type of fix used. Results: Of the reports, 36% were documented as resolved. In another 25% the resolution allowed treatment to proceed although the reported problem recurred within days. In 5% only intermediate troubleshooting was documented. The remainder lacked documentation. In 60% of the reports, radiation therapists resolved the problem, often by clearing the appropriate faults or reinitializing a software or hardware service. 22% were resolved by physics and 10% by field service engineers. The remaining 8% were resolved by IT, Facilities, or resolved spontaneously. Typical fixes, in order of scope, included clearing the fault and moving on, closing and re-opening the patient session or software, cycling power to a sub-unit, recalibrating a device (e.g., optical surface imaging), and calling in Field Service (usually resolving the problem through maintenance or component replacement). Conclusion: The reports with undocumented resolution represent a missed opportunity for learning. Frequency of who resolves a problem scales with the proximity of the person’s role (therapist, physicist, or service engineer), which is inversely related to the permanence of the resolution. Review of lessons learned from machine incident logs can form the basis for guidance to radiation therapists and medical physicists to minimize equipment downtime and ensure safe operation.

61 RADIATION PROTECTION AND DOSIMETRY↗
DOE OSTI2020

Enhancement of Photoemission on p-Type GaAs Using Surface Acoustic Waves

We demonstrate that photoemission properties of p-type GaAs can be altered by surface acoustic waves (SAWs) generated on the GaAs surface due to dynamical piezoelectric fields of SAWs. Multiphysics simulations indicate that charge-carrier recombination is greatly reduced, and electron effective lifetime in p-doped GaAs may increase by a factor of 10× to 20×. It implies a significant increase, by a factor of 2× to 3×, of quantum efficiency (QE) for GaAs photoemission applications, like GaAs photocathodes. Conditions of different SAW wavelengths, swept SAW intensities, and varied incident photon energies were investigated. Essential steps in SAW device fabrication on a GaAs substrate are demonstrated, including deposition of an additional layer of ZnO for piezoelectric effect enhancement, measurements of current–voltage (I–V) characteristics of the SAW device, and ability to survive high-temperature annealing. Results obtained and reported in this study provide the potential and basis for future studies on building SAW-enhanced photocathodes, as well as other GaAs photoelectric applications.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2020

First-principles study of the topological surface states of α-Sn(111)

α-Sn is on the boundary of a couple of distinct topological phases. It will transform into a topological insulator under a suitable strain. However, a clear picture of its topological surface states (TSSs) is still lacking. Furthermore we perform first-principles calculations on the electronic structure of α-Sn(111) surface to identify its TSSs and reveal their properties. The results show that the presence of valence band reorganizes the TSSs in the inverted sp gap into two Dirac cones. The lower one is in the valence band continuum; the upper one resides in the gap between the valence and conduction bands. We also demonstrate the transformation of the surface states by switching on or off of strain and/or spin-orbit coupling. Without spin-orbit coupling, only the TSSs associated with the lower Dirac cone survive, and they are spin unpolarized. The results are useful for understanding and engineering the topological properties of α-Sn.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2017

CFD Simulation of Bubble Growing Under a Downward Facing Surface

The heat removing of downward facing surface is an important issue in many areas, including nuclear safety, solar storage system and electronic cooling devices. Therefore, the characteristic and heat removal capability of downward facing boiling were investigated by many experiments in recent years. Among these studies, the thickness of bubble is considered as an important parameter. The increasing of bubble thickness will increase the thermal resistance of cooling process and reduce the cooling ability. In order to focus on the dynamics of bubble thickness, Das et al. injected air into sodium dodecyl sulphate (SDS) solution through a nozzle under the horizontal downward facing surface. The bubble will be formed by the air injection and kept under the horizontal plate. The diameter of nozzle, horizontal plate and SDS solution tank are 2 mm, 20 mm and 30 mm, respectively. The growing processing and the stable thickness of the bubble were recorded in the experiment. Basing on the conditions of Das's experiment, the appropriate computational fluid dynamics (CFD) simulation was conducted. The growing process and the stable thickness of bubble under difference contact angle are predicted by CFD in this study.

42 ENGINEERING↗
DOE OSTI2025

Preliminary Modeling of Triply Periodic Minimal Surface (TPMS) Structures with RELAP5-3D

This poster goes over preliminary work performed on modeling triply periodic minimal surfaces (TPMS) with RELAP5-3D. The poster starts off with the need for advanced nuclear fuel designs for future reactors, and how TPMS are being researched for this purpose. There is then a focus on what a TPMS is and then moves onto the motivation for why this geometry is being modeled and looked into. The methodology is then shown for how data from different experiments will be used for pre-test predictions and eventual creation of empirical coefficients and multipliers to be used in models. Then there is a show of how data would be compared between the experimental tests, CFD, and RELAP5-3D values. The results from the simulations and comparisons are then presented to show how the CFD and RELAP5-3D compare to each other currently, with no experimental data to compare to for one test model. Results from the second test model are also presented to show that there is stability in the solving of that model.

42 - ENGINEERING↗
DOE OSTI2021

Selective Biosorption of Valuable Rare Earth Elements Among Co-Occurring Lanthanides

To meet the increasing demand for rare earth elements (REEs) essential for low carbon-intensity energy technologies, new methods are needed for selective REE extraction from unconventional resources. Only a few REEs have significant economic value, but isolation of target rare earths from co-occurring lanthanides is challenging due to their similar chemical behavior. We present a novel approach to enhance separation of specific REEs from lanthanide mixtures. Escherichia coli cells engineered with lanthanide binding tags (LBTs) were immobilized in nonadsorbing, permeable polyethylene glycol diacrylate beads and packed into continuous flow, fixed-bed columns. Breakthrough of 15 rare earths in the +3 oxidation state resulted in notable differences in adsorption selectivity, with greatest separation between europium (Eu) and lanthanum (La) due to competitive displacement. REE adsorption onto fixed-bed columns was predicted by coupling a surface complexation model to a calibrated one-dimensional dual porosity transport model that accounts for interbead advective and intrabead diffusive transport. A tradeoff between high-abundance, low-affinity native carboxyl sites and low-abundance, high-affinity engineered LBT sites dictates process recovery efficiency and selectivity. Key chemical and operational parameters are identified to maximize selective extraction of high-value lanthanides, achieving a threefold enhancement of Eu recovery relative to La in a mixed REE solution.

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

Next generation of extreme-resolution electron beam lithography

In top down nanofabrication research facilities around the world, the direct-write high-resolution patterning tool of choice is overwhelmingly electron beam lithography. Remarkably small features can be written in a variety of polymeric resists [V. R. Manfrinato et al., Nano Lett. 14, 4406 (2014); V. R. Manfrinato, A. Stein, L. Zhang, Y. Nam, K. G. Yager, E. A. Stach, and C. T. Black, Nano Lett. 17, 4562 (2017)]. However, this technology, which in this article the authors will refer to as conventional electron beam lithography (CEBL), is reaching its practical resolution and precision limits [V. R. Manfrinato et al., Nano Lett. 14, 4406 (2014)]. Hydrogen depassivation lithography (HDL) [J. N. Randall, J. W. Lyding, S. Schmucker, J. R. Von Ehr, J. Ballard, R. Saini, and Y. Ding, J. Vac. Sci. Technol. B 27, 2764 (2009); J. N. Randall, J. B. Ballard, J. W. Lyding, S. Schmucker, J. R. Von Ehr, R. Saini, H. Xu, and Y. Ding, Microelectron. Eng. 87, 955 (2010)] is a different version of electron beam lithography that is not limited in resolution and precision in the way that CEBL is. It uses a cold field emitter, a scanning tunneling microscope (STM) tip, to deliver a small spot of electrons on a Si (100) 2 × 1 H-passivated surface to expose a self-developing resist that is a monolayer of H adsorbed to the Si surface. Subnanometer features [S. Chen, H. Xu, K. E. J. Goh, L. Liu, and J. N. Randall, Nanotechnology 23, 275301 (2012)], and even the removal of single H atoms can be routinely accomplished [M. A. Walsh and M. C. Hersam, Annu. Rev. Phys. Chem. 60, 193 (2009)]. It is known that the H desorption process at low biases is a multielectron process [E. Foley, A. Kam, J. Lyding, and P. Avouris, Phys. Rev. Lett. 80, 1336 (1998)], but the tunneling distribution of the electrons from the STM tip to the Si surface lattice is not known. The authors have developed a simple model that demonstrates that the combination of two highly nonlinear processes creates a much higher contrast exposure mechanism than CEBL. Currently, HDL has been used almost exclusively on the Si (100) surface and has a limited number of pattern transfer techniques including Si and Ge patterned epitaxy, selective atomic layer deposition of TiO2 followed by reactive ion etching [J. B. Ballard, T. W. Sisson, J. H. G. Owen, W. R. Owen, E. Fuchs, J. Alexander, J. N. Randall, and J. R. Von Ehr, J. Vac. Sci. Technol. B 31, 06FC01 (2013)], and selective deposition of dopant atoms for quantum devices and materials [Workshop on 2D Quantum MetaMaterials held at NIST, Gaithersburg, MD, April 25–26, 2018, edited by J. Owen and W. P. Kirk]. While the throughput of HDL is very low, going parallel in a big way appears promising [J. N. Randall, J. H. G. Owen, J. Lake, R. Saini, E. Fuchs, M. Mahdavi, S. O. R. Moheimani, and B. C. Schaefer, J. Vac. Sci. Technol. B 36, 6 (2018)]. However, the most exciting aspect of HDL is its atomic-scale resolution and precision, which is key to nanoscale research. The authors see HDL emerging as the ultimate high-resolution patterning tool in top down nanofabrication research facilities.

42 ENGINEERING↗
DOE OSTI2019

Compact feature-aware Hermite-style high-order surface reconstruction

High-order surface reconstruction is now a commonly used technique for mesh generation and adaptation, geometric and physical modeling, and high-order numerical methods for solving partial differential equations (PDEs). However, surface reconstruction from a relatively coarse mesh remained a challenging problem, especially for surfaces with sharp features. Here in this paper, we introduce a new method to address this challenge by improving the previous state of the art, including continuous moving frames (CMF) and weighted averaging of local fittings (WALF) (Eng Comput 28 (2012)), in two aspects. First, we significantly improve the robustness of reconstruction from coarse meshes using a Hermite-style least squares approximation to incorporate normals of the surface and tangents of the feature curves. Second, we ensure both G 0 continuity and high-order accuracy of the reconstruction near sharp features by generating parametric surface elements with an iterative feature-aware parameterization. We present the theoretical framework of our method and compare it against point-based methods in terms of accuracy and stability. We demonstrate the use of the proposed technique in generating high-order meshes for finite element methods, and show that it enables nearly identical solutions as using the meshes generated from exact geometry, while allowing additional flexibility.

42 ENGINEERING↗
DOE OSTI2021

Integrated TBC/EBC for SiC Fiber Reinforced SiC Matrix Composites for Next Generation Gas Turbines (Final Report)

In this ambitious project, a significant challenge preventing widespread use of ceramic matrix composites in hot section components of gas power generating turbines was addressed. Hot section components made from SiC fiber reinforced SiC matrix composites (SiC/SiC composites), have the potential to achieve a combined cycle energy efficiency of above 65%. To achieve this efficiency, the temperature of the combustion gases on the turbine component surface is expected to reach as high as ~1700ºC (3100ºF). However, SiC/SiC composites suffer from volatilization at high temperature under high velocity steam environment – typical in a turbine hot chamber. This integrated collaborative project, between two research groups at Clemson University and a team of engineers and scientists at GE Gas Power, focused on design, fabrication and evaluation of a new graded environmental barrier coating. Using the excellent compositional tailorability of polymer derived ceramics (PDCs), we developed an integrated EBC/BC that smoothly transitions from bottom SiC/SiC bond interface to hermetic sesquioxide (Y 2 O 3 ) top surface. This smooth compositional transition avoided the sharp CTE mismatch at interfaces to greatly reduce the thermal stress. The developed EBC is compatible with and bonds well with the bond coat that GE uses. The top hermetic oxide surface ensures low oxygen transportation and volatilization rates under the high velocity steam environment. The graded microstructure with increasing sesquioxide concentration also decreases the amount of Si and C elements near the top hermetic sesquioxide layer. Coatings made using a process suitable for manufacturing – atmospheric plasma spraying was demonstrated. The microstructure of coatings made using this process were fully characterized. Finally, the performance of these coatings was investigated under the most demanding conditions for this application. Specifically, high temperature, high velocity steam exposure; thermal shock test; and thermal cycling tests. The graded coatings performed exceptionally well in all these tests. Specific suggestions for future development in this area have also been identified. In addition to the excellent technical progress, this project helped initiate a robust collaboration between the research groups at Clemson and GE Gas Power. It also provided a high-quality learning and mentoring opportunity for the three post-doctoral research associates and two UG students at Clemson University who worked on this project. All proposed tasks, sub-tasks were completed, and all milestones achieved.

03 NATURAL GAS↗
DOE OSTI2018

Flake Formation in Phase Layers of a Cutting Ceramic

Flake formation (cracking) is observed in inserts of untreated cutting ceramic and also during diffusional strengthening of the inserts’ surface layer by nitrogen on heating in a muffle furnace to 450–500°C, with the creation of γ-phase (a protective layer), the removal of carbon from the atomic cells, and the formation of titanium nitride. Heat-treatment conditions for inserts of cutting ceramic are established such that the flake content at their surface is reduced. Treatment to prevent flake formation is proposed: heating in a sealed muffle furnace with a nitrogen atmosphere to 250–280°C at a pressure of 0.25 MPa. In this process, the titanium carbide at the surface of the inserts is converted to titanium nitride as a result of carbon diffusion, with the formation of a protective γ-phase layer. By removing carbon from the surface layer of the inserts and ensuring the diffusion of nitrogen into the cutting ceramic, with the formation of titanium nitride in the γphase, the durability and performance of the inserts are improved, along with their mechanical properties.

36 MATERIALS SCIENCE↗
DOE OSTI2015

The impact of immobile zones on the transport and retention of nanoparticles in porous media

Nanoparticle transport and retention within porous media is treated by conceptualizing the porous media as a series of independent collectors (e.g., Colloid Filtration Theory). This conceptualization assumes that flow phenomena near grain–grain contacts, such as immobile zones (areas of low flow), exert a negligible influence on nanoparticle transport and assumes that retention and release of particles depends only on surface chemistry. This study investigated the impact of immobile zones on nanoparticle transport and retention by employing synchrotron X–ray computed microtomography (SXCMT) to examine pore–scale silver nanoparticle distributions during transport through three sand columns: uniform iron oxide, uniform quartz, and well–graded quartz. Extended tailing was observed during the elution phase of all experiments suggesting that hydraulic retention in immobile zones, not detachment from grains, was the source of tailing. A numerical simulation of fluid flow through an SXCMT data set predicted the presence of immobile zones near grain–grain contacts. SXCMT–determined silver nanoparticle concentrations observed that significantly lower nanoparticle concentrations existed near grain–grain contacts throughout the duration of all experiments. In addition, the SXCMT–determined pore–scale concentration gradients were found to be independent of surface chemistry and grain size distribution, suggesting that immobile zones limit the diffusive transport of nanoparticles toward the collectors. Furthermore, these results suggest that the well–known overprediction of nanoparticle retention by traditional CFT may be due to ignoring the influences of grain–grain contacts and immobile zones. As such, accurate prediction of nanoparticle transport requires consideration of immobile zones and their influence on both hydraulic and surface retention.

42 ENGINEERING↗

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