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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 145 records · Page 8
All sourcesNASA NTRSDOE OSTI
NASA NTRS1985

Computer-aided selection of materials for cryogenic turbopump bearings

The life requirement for the angular contact ball bearings in the Space Shuttle Main Engine (SSME) high-pressure-oxygen turbopump (HPOTP) is 7.5 hours. In actual operation, significantly shorter service life has been experienced. The objective of this current program is to identify bearing materials and/or materials processing techniques offering significant potential for extending HPOTP bearing performance life. A thermomechanical analysis of the HPOTP shaft/bearing system was performed with the SHABERTH (SHaft-BEaring-THermal) computer program. Bearing fatigue life, ball-race contact stress, heat generation rate, bulk ring temperatures, and circumferential stress in the inner rings were quantified as functions of radial load, thrust load, and ball-race contact friction. The analysis results were used to formulate criteria that are being used for the selection of special materials for future turbopump bearings.

Maurer, R. E.↗
NASA NTRS1988

Bearing optimization for SSME HPOTP application

The space shuttle main engine (SSME) high-pressure oxygen turbopumps (HPOTP) have not experienced the service life required of them. To improve the life of the existing turbopump bearings, modifications to the bearings that could be retrofitted into the present bearing cavity are being investigated. Several bearing parameters were optimized using the computer program SHABERTH, which performs a thermomechanical simulation of a load support system. The computer analysis showed that improved bearing performance is feasible if low friction coefficients can be attained. Bearing geometries were optimized considering heat generation, equilibrium temperatures, and relative life. Two sets of curvatures were selected from the optimization: an inner-raceway curvature of 0.54, an outer-raceway curvature of 0.52, and an inner-raceway curvature of 0.55, an outer-raceway curvature of 0.53. A contact angle of 16 deg was also selected. Thermal gradients through the bearings were found to be lower with liquid lubrication than with solid film lubrication. As the coolant flowrate through the bearing increased, the ball temperature decreased but at a continuously decreasing rate. The optimum flowrate was approximately 4 kg/s. The analytical modeling used to determine these feasible modifications to improve bearing performance is described.

Armstrong, Elizabeth S.↗
DOE OSTI2022

Membrane absorption process for CO2 capture

Processes and systems for the capture of CO 2 from a CO 2 -containing gas stream are provided. The CO 2 -containing gas stream is passed to a membrane contactor absorber wherein the CO 2 -containing gas contacts or passes a first side of a membrane element while a CO 2 selective solvent with a viscosity between 0.2 and 7 cP contacts, passes or flows on second side of the membrane, opposed to the first side. The CO 2 permeates through the hollow fiber membrane pores and is chemically absorbed into the solvent.

Li, Shiguang↗
DOE OSTI2021

Chiral-induced spin selectivity enables a room-temperature spin light-emitting diode

In traditional optoelectronic approaches, control over spin, charge, and light requires the use of both electrical and magnetic fields. In a spin-polarized light-emitting diode (spin-LED), charges are injected, and circularly polarized light is emitted from spin-polarized carrier pairs. Typically, the injection of carriers occurs with the application of an electric field, whereas spin polarization can be achieved using an applied magnetic field or polarized ferromagnetic contacts. We used chiral-induced spin selectivity (CISS) to produce spin-polarized carriers and demonstrate a spin-LED that operates at room temperature without magnetic fields or ferromagnetic contacts. The CISS layer consists of oriented, self-assembled small chiral molecules within a layered organic-inorganic metal-halide hybrid semiconductor framework. The spin-LED achieves ±2.6% circularly polarized electroluminescence at room temperature.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2021

Pushing the efficiency limit of low-cost, industrially relevant Si solar cells to > 22.5% by advancing cell structures and technology innovations (Final Report)

The overall objective of this program is to achieve ~23% bifacial n-type cell efficiencies by developing and implementing optimized homogeneous or selective boron (B) emitter on front and tunnel oxide passivated contact (TOPCon) on rear side, in combination with advanced fine-line screen-printing metallization with floating busbars. During this research project, first we developed a technology roadmap to drive the 21% n-PERT cell efficiency from 21% to 23% by transforming the cell design to n-TOPCon and establishing the requirements for each layer, including B emitter, rear n-TOPCon, n-base Si and screen-printed contacts. Next, consistent with our roadmap, we developed advanced homogeneous implanted B emitter (150-180 Ω/⌫) passivated with ALD Al 2 O 3 layer capped with PECVD SiN x /SiO x double-layer antireflection coating This gave a very low recombination current density of 10-15 fA/cm 2 prior to metallization. In addition, we demonstrated metallized recombination current density of ~31 fA/cm 2 for this advanced homogeneous B emitter with industrial screen-printed, fire-through contacts with 40 μm wide grid lines, floating busbars and implementation of an advanced Ag-Al paste which resulted in local or reduced area metal-Si contact under the grid lines with virtually no emitter surface etching. This paste reduced the full area metallized J oe,metal from >1100 fA/cm 2 to ~700 fA/cm 2 . We also developed novel processes for the formation of p + /p ++ selective B emitter by a) single B diffusion with selective etch back and b) two-steps diffusion with implanted B in field region and APCVD B diffusion under the metal grid. We achieved very low un-metallized recombination current density (J 0 ) of ~18 fA/cm 2 for the selective p ++ p + emitters (30/150 Ω/⌫) and metallized J 0 of ~28 fA/cm 2 with ~3% screen-printed metal contact to p ++ regions. Next, we developed the technology for n-TOPCon by growing phosphorus-doped LPCVD and PECVD poly-Si on top of ~ 15Å chemically grown (NAO) tunnel oxide. After an optimized anneal at 875 °C for 30 min, passivated n-TOPCon have unmetallized J 0 of ~ 5 fA/cm 2 which went down further to ~ 1 fA/cm 2 after a 700 Å SiN x capping layer and simulated contact firing cycle at 770 °C. After screen-printed fire-through metallization on this n-TOPCon with ~13% metal coverage, metallized J 0 value increased to only ~5 fA/cm 2 which is among the lowest reported value to the best of our knowledge for screen-printed metallization. Finally, we integrated all the above technology innovations and enhancements and demonstrated low-cost manufacturable screen-printed n-TOPCon bifacial Si solar cell with ~23% efficiencies. Based on the experimental and theoretical understanding developed in this project, we have developed a new technology roadmap that shows that implementation of busbarless contacts, 10-20 ms bulk lifetime Si, and selective B emitter or selective TOPCon on the front can drive ~23% efficient cells achieved in this research to ~25% at low-cost.

14 SOLAR ENERGY↗
DOE OSTI2025

Characterization of Performance Degradation Mechanisms in Low-Cost High Throughput DI-O3 Layer for Passivated Contact Silicon Solar Cells

Characterization and mitigating performance limiting defects in Silicon (Si) PV is one of key areas to be addressed to improve PV hardware costs and energy yield in order to lower the levelized cost of energy (LCOE) of installed PV cost to $0.02/kWh. As Si PV cells efficiencies have surpassed 22% and approaching 23%, the recombination at the metal contacts have become the focus point to be addressed. Passivated contact technologies—having a heterojunction with a band-gap larger than silicon between the metal and silicon—have emerged as a great potential for future highand ultrahigh-efficiency solar cells, as it concurrently reduces recombination and increases carrier selectivity, by incorporating thin films within the contact structure. Passivated contact Si solar cell technologies use a wide variety of tunnel layers—playing a crucial role to passivate metal contacts and tunnel charge carriers—including stoichiometric silicon oxide (SiO 2 ) grown by thermal oxidation and Low-Pressure Chemical Vapor Deposition (LPCVD) technique and silicon oxide (SiO x ) by hot nitric acid. However, thorough investigations on understanding the failure and performance degradation mechanisms associated with tunnel layers are still limited to date. Unlocking those degradation characteristics in crucial tunnel layers could improve the reliability and energy yield of passivated contact Si solar cells. Besides, the technique of growing aforementioned tunneling layers are low throughput, and requires high temperature processes and/or a vacuum environment. In this project, we investigated the performance degradation mechanisms of a low-cost high-throughput ozonated oxide (DI-O 3 ) tunnel layer for the passivated contact Si solar cells.

14 SOLAR ENERGY↗
DOE OSTI2021

Robust passivation of CdSeTe based solar cells using reactively sputtered magnesium zinc oxide

Magnesium zinc oxide (MZO, Mg x Zn 1-x O) is a leading emitter for CdTe-based solar cells due to its transparency and the ability to tune its conduction band offset with the absorber. Devices employing alloyed cadmium selenide telluride (CST, CdSe y Te 1-y ) absorbers achieved high efficiency (>19%) using MZO deposited by reactive sputtering over a broad composition range (3.68–3.92 eV, x: 0.20–0.35). Minimal differences in implied and measured open circuit voltage indicate that the contacts are well passivated and highly selective across the spectrum of MZO employed. Device performance insensitivity to MZO composition, which is not observed in CdTe devices, is attributed to the formation of an oxygenated interface layer. Se volatility creates a group VI deficiency at the interface that drives O migration from the MZO into the absorber. This introduces conductivity in the emitter not present in its as-deposited state, contributing to the exceptional performance observed. It is shown that the quality of device passivation depends on the oxidation state of the as-deposited MZO such that intelligent control and management of the reactive sputtering process is required.

36 MATERIALS SCIENCE↗
DOE OSTI2025

Probing New Hadronic Forces with Heavy Exotic Atoms

We explore the potential of precision spectroscopy of heavy exotic atoms where electrons are substituted by negative hadrons to detect new force carriers with hadronic couplings. The selected transitions are unaffected by nuclear contact terms, thus enabling highly accurate calculations using bound-state QED, provided that the nuclear polarization is under control. Alternatively, we demonstrate that the dipole polarizability, a fundamental property of nuclei, can be extracted from the spectroscopy of exotic atoms in a novel way by combining two transitions while maintaining high sensitivity to new physics. Based on existing data, we extracted world-leading bounds on mediator masses ranging from 0.1 to 10 MeV for two benchmark models and show that forthcoming experiments could enhance the sensitivity to new physics by 2 orders of magnitude.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2020

Contoured PPM-EMAT Design for Ultrasonic Communication On Metallic Pipe Channels

Ultrasonic guided waves can be used as the carriers of information in ultrasonic communication for pipe or plate channels. Permanent Periodic Magnet (PPM) Electromagnetic Acoustic Transducer (EMAT) can potentially provide unique capabilities for a communication system as a non-contact transmitter and receiver, which can selectively generate different modes of shear-horizontal (SH) waves. The SH wave shows the potentials in achieving high bitrate without error in ultrasonic communication. However, when a steel pipe is used as the communication channel, especially one with a radius comparable to the size of the transducer, no guided wave signal can be excited or detected by existing PPM-EMAT's with flat coupling surface. In this paper, a 3D printed magnet holder is designed which can shape the magnet array. Also, the transmitter/receiver coils are made of flexible printed circuit which can fit over the curvature of the pipe channels. The contoured PPM-EMAT transmitter and receiver can conform to the surface of the steel pipe channel in order to generate and detect torsional waves. Experimental tests of signal transmission with PPM-EMAT on a 160cm-long stainless steel pipe determine the optimal frequency for communication to be 916KHz. Information transmission experimental results confirm the validity of contoured PPM-EMAT for communication with a bitrate of 5kbps.

Huang, Xin↗
NASA NTRS1976

Review of world experience and properties of materials for encapsulation of terrestrial photovoltaic arrays

Published and unpublished information relating to encapsulation systems and materials properties was collected by searching the literature and appropriate data bases (over 1,300 documents were selected and reviewed) and by personal contacts including site and company visits. A data tabulation summarizing world experience with terrestrial photovoltaic arrays (50 installations) is presented in the report. Based on criteria of properties, processability, availability, and cost, candidate materials were identified which have potential for use in encapsulation systems for arrays with a lifetime of over 20 years high reliability, an efficiency greater than 10 percent, a total price less than $500/kW, and a production capacity of 500,000 kW/yr. The recommended materials (all commercially available) include, depending upon the device design, various borosilicate and soda-lime glasses and numerous polymerics suitable for specific encapsulation system functions.

Carmichael, D. C.↗
NASA NTRS1989

Materials thermal and thermoradiative properties/characterization technology

Reliable properties data on well characterized materials are necessary for design of experiments and interpretation of experimental results. The activities of CINDAS to provide data bases and predict properties are discussed. An understanding of emissivity behavior is important in order to select appropriate methods for non-contact temperature determination. Related technical issues are identified and recommendations are offered.

Dewitt, D. P.↗
NASA NTRS2023

Development of an Ultra High-Pressure Metals Promoted Combustion in Oxygen Test Apparatus

Materials flammability data is needed at pressures higher than ever tested before (greater than 10,000 psi). WSTF has designed and is currently building a metals flammability apparatus that can test metals up to 30,000 psi. Solid progress was achieved on the chamber in terms of system build up and fulfilling requirements to perform a NASA Test Readiness Review. Understanding metals flammability data at extreme pressure opens the doors for higher pressure and higher performance oxygen systems. Proposed systems include more reliable/higher performance propulsion systems and more reliable/lighter Environmental Control Life Support Systems (ECLSS). The test system needed for this testing required significant research and development to select a pressurization method and eliminate contact with potentially flammable materials back to the chamber. No additional promoted combustion data was collected in FY21. This International Research & Development (IRAD) proposal was critical to getting the system very close to operational status. This capability is critical to collect forward leaning material flammability data for future spacecraft and ground systems. Forward work has been identified and funding is being sought outside of the Center Innovation Fund (CIF) process for late FY23/FY24.

promoted combustion↗
DOE OSTI2023

Switchable system for high-salinity brine desalination and fractional precipitation

A saline feed stream flows into a liquid-liquid extraction system; and a volatile organic solvent flows through a main compressor. The compressed volatile organic solvent then flows through a solvent regenerator, which can be a heat exchanger or a combination of a vaporization device and a condenser, to cool the volatile organic solvent. The cooled volatile organic solvent in liquid phase then flows into the liquid-liquid extraction system, where the saline feed stream contacts the volatile organic solvent to selectively extract water from the saline feed stream into the volatile organic solvent, producing a concentrated brine and an organic-rich mixture of water and the volatile organic solvent. The organic-rich mixture flows from the liquid-liquid extraction system into the solvent regenerator, where the organic-rich mixture is heated to produce an organic-rich vapor and desalinated water; and the organic-rich vapor is recycled as volatile organic solvent back into the liquid-liquid extraction system.

Wilson, Aaron D.↗
DOE OSTI2021

Discovery and characterization of bromodomain 2–specific inhibitors of BRDT

Bromodomain testis (BRDT), a member of the bromodomain and extraterminal (BET) subfamily that includes the cancer targets BRD2, BRD3, and BRD4, is a validated contraceptive target. All BET subfamily members have two tandem bromodomains (BD1 and BD2). Knockout mice lacking BRDT-BD1 or both bromodomains are infertile. Treatment of mice with JQ1, a BET BD1/BD2 nonselective inhibitor with the highest affinity for BRD4, disrupts spermatogenesis and reduces sperm number and motility. To assess the contribution of each BRDT bromodomain, we screened our collection of DNA-encoded chemical libraries for BRDT-BD1 and BRDT-BD2 binders. High-enrichment hits were identified and resynthesized off-DNA and examined for their ability to compete with JQ1 in BRDT and BRD4 bromodomain AlphaScreen assays. These studies identified CDD-1102 as a selective BRDT-BD2 inhibitor with low nanomolar potency and >1,000-fold selectivity over BRDT-BD1. Structure–activity relationship studies of CDD-1102 produced a series of additional BRDT-BD2/BRD4-BD2 selective inhibitors, including CDD-1302, a truncated analog of CDD-1102 with similar activity, and CDD-1349, an analog with sixfold selectivity for BRDT-BD2 versus BRD4-BD2. BROMOscan bromodomain profiling confirmed the great affinity and selectivity of CDD-1102 and CDD-1302 on all BET BD2 versus BD1 with the highest affinity for BRDT-BD2. Cocrystals of BRDT-BD2 with CDD-1102 and CDD-1302 were determined at 2.27 and 1.90 Å resolution, respectively, and revealed BRDT-BD2 specific contacts that explain the high affinity and selectivity of these compounds. These BD2-specific compounds and their binding to BRDT-BD2 are unique compared with recent reports and enable further evaluation of their nonhormonal contraceptive potential in vitro and in vivo.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2024

Investigation of Point-Contact Strategies for CFD Simulations of Pebble-Bed Reactor Cores

This study numerically investigated the effects of various contact strategies on the thermal hydraulic behavior within a structured bed of 100 explicitly modeled pebbles. Four contact strategies and two thermal hydraulic conditions were considered. The strategies to avoid contact singularities include decreasing the pebble diameter, increasing the pebble diameter, bridging the pebble surfaces near the contact region, and capping the pebble surfaces near the contact region. One strategy, Strategy 3a, which involves bridging with a cylinder equal to 10% of the pebble diameter, was selected as the baseline strategy because it addressed the contact singularity while minimizing the geometric changes that affect the bed porosity. The two thermal hydraulic conditions were full-power operation (Case 1) and pressurized loss of forced cooling or PLOFC (Case 2). Simulations of the conjugate heat transfer within the structured bed were performed using the Reynolds-averaged Navier–Stokes approach with the realizable k-ϵ turbulence model and two-layer all y + wall treatment. The thermal-fluid quantities of interest were compared between the contact strategies for each case. In Case 1, the hydraulic behavior was sensitive to the contact strategy, with large differences in the pressure drop (30%) and volume-average velocity (4%). The thermal behavior was not sensitive, with less than a 0.5% difference across the strategies. To better understand the separate effects of each heat transfer mode, Case 2 was divided into the following subcases: conduction (Case 2a); conduction/radiation (Case 2b); and conduction/radiation/convection (Case 2c). Case 2a represents an early phase of the PLOFC transient. Case 2b represents an intermediate phase of the PLOFC transient, with the pebble temperatures sufficiently high for the radiative heat transfer to be non-negligible. Case 2c represents a late phase of the PLOFC transient after the establishment of the natural circulation of the heat transfer fluid. For Case 2, large differences in the contact strategy were observed only in Case 2a with only conduction. The difference in the maximum pebble temperature was 23% in Case 2a, 2% in Case 2b, and 0.3% in Case 2c.

22 GENERAL STUDIES OF NUCLEAR REACTORS↗
DOE OSTI2021

Cryo nanomanipulator probe with integrated gas injection

A probe assembly for use with a charged particle instrument includes an elongate body having a proximal end for positioning outside of a charged particle instrument enclosed environment, a distal end for positioning within the enclosed environment and a longitudinal axis. A port interface is located on the body between the proximal and distal ends, and is coupleable to a nanomanipulator system of the charged particle instrument. A probe needle is positioned at a distal end of the body and is selectively positionable from outside the enclosed environment to contact a specimen within the enclosed environment. At least one gas injection needle is adjustably positioned near the probe needle. The gas injection needle is connectable to a source of pressurized gas to selectively inject gas in the area of the probe needle within the enclosed environment.

Perea, Daniel E.↗
NASA NTRS2023

Investigating Abrasion Effects of Lunar Simulant Grain Sizes on Candidate Spacesuit Fabric

Lunar dust is identified as one of the most significant challenges during the Apollo exploration missions due to its extremely abrasive and electrostatic characteristics. As NASA and the space industry prepare for the upcoming Artemis missions, researching and testing with lunar simulant is quintessential to understanding the effects of lunar dust on the systems and equipment that will be deployed on the lunar surface. Testing will also provide paths that lead to developing technologies and cleaning tools that could be used for dust mitigation. Additionally, it is expected that any hardware that will be exposed to the dusty environment should undergo rigorous testing to ensure it will maintain long-term performance and operate on the lunar surface. For this study, exterior spacesuit fabric was observed. Abrasion is one of the main concerns of lunar dust exposure for spacesuit fabric. Three different abrasion methods were chosen: a rotary tumbler, the Martindale method, and Accelerotor. These abrasion methods were tested on coated and uncoated spacesuit material, Orthofabric, to understand the abrasion rates of sieved lunar simulant and investigate if the addition of ceramic coating mitigated dust abrasion. To summarize, the testing results provided that larger grains are more abrasive than smaller grains, and the selected ceramic coatings did not minimize abrasion during the controlled abrasion tests. It is important to note that the selected ceramic coatings were not designed or intended to provide protection from the abrasive lunar environment. It is recommended to select additional ceramic coatings with an elevated TRL of 5 or greater for testing with Orthofabric and lunar simulant. As an additional note, contact angle measurements were not accounted for in coating selection and should be a factor when selecting adhesion resistant coatings for lunar dust.

grain size↗
DOE OSTI2025

Self‐Assembled Monolayer Templating for Engineered Nanopinholes in Passivated Contact Solar Cells

We present a novel self-assembled monolayer (SAM)-based technique to make nanopinhole-enabled passivated contacts on silicon solar cells by tuning the SAM coverage area and etch selectivity. We deposit trimethyl-silyl Si(CH 3 ) 3 groups using hexamethyldisilazane (HMDS) as the precursor over passivating dielectric layers and their stacks (SiO 2 , SiN x , SiO 2 /SiN x ) and interrupt the HMDS attachment chemistry shortly before a full monolayer is formed on its surface. Subsequent etching in dilute HF produces pinholes through the dielectric layers due to the higher etch resistance of the SAM to HF etching. The pinhole areal density (10 4 –10 8 /cm 2 ) and size (10–1000 nm) can be tuned both by duration of HMDS attachment and HF etch time. Pinholes were characterized by atomic force microscopy, tetramethylammonium hydroxide (TMAH) selective etch, and Ag decoration by electroless plating. Polysilicon (poly-Si) passivated contacts enabled by pinholes were formed by subsequent deposition of doped amorphous silicon (a-Si:H) followed by thermal crystallization and dopant drive-in. At optimal areal pinhole density ≈10 7 /cm 2 , contacts exhibit both passivation and carrier transport via pinholes as evidenced by electron beam induced current, transmission line measurements, and carrier lifetime measurements. Solar cells based with these pinhole contacts show V oc = 723 mV and FF = 80.3%. The remaining SAM layer does not affect device performance.

14 SOLAR ENERGY↗