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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 289 records · Page 16
All sourcesNASA NTRSDOE OSTI
DOE OSTI2016

High-Performance Polymer Solar Cells Based on a Wide-Bandgap Polymer Containing Pyrrolo[3,4- f ]benzotriazole-5,7-dione with a Power Conversion Efficiency of 8.63%

A novel donor–acceptor type conjugated polymer based on a building block of 4,8-di(thien-2-yl)-6-octyl-2-octyl-5H-pyrrolo[3,4-f]benzotriazole-5,7(6H)-dione (TZBI) as the acceptor unit and 4,8-bis(5-(2-ethylhexyl)thiophen-2-yl)­benzo­[1,2-b:4,5-b']dithiophene as the donor unit, named as PTZBIBDT, is developed and used as an electron-donating material in bulk-heterojunction polymer solar cells. The resulting copolymer exhibits a wide bandgap of 1.81 eV along with relatively deep highest occupied molecular orbital energy level of -5.34 eV. Based on the optimized processing conditions, including thermal annealing, and the use of a water/alcohol cathode interlayer, the single-junction polymer solar cell based on PTZBIBDT:PC71BM ([6,6]-phenyl-C71-butyric acid methyl ester) blend film affords a power conversion efficiency of 8.63% with an open-circuit voltage of 0.87 V, a short circuit current of 13.50 mA cm -2 , and a fill factor of 73.95%, which is among the highest values reported for wide-bandgap polymers-based single-junction organic solar cells. The morphology studies on the PTZBIBDT:PC71BM blend film indicate that a fibrillar network can be formed and the extent of phase separation can be mani­pulated by thermal annealing. These results indicate that the TZBI unit is a very promising building block for the synthesis of wide-bandgap polymers for high-performance single-junction and tandem (or multijunction) organic solar cells.

Lan, Liuyuan↗
DOE OSTI2016

Electrochemical behaviour of naked sub-nanometre sized copper clusters and effect of CO 2

The study of the electrochemical behavior (in the presence of N 2 or CO 2 ) of size-controlled naked Cu 5 and Cu 20 nanoclusters, prepared using a combination of gas-phase cluster ion sources, mass spectrometry, and soft-landing techniques, evidences some relevant results regarding the redox behavior of these sub-nanometre sized copper particles and the effect of CO 2 on them. Cu 20 nanoclusters show anodic redox processes occurring at much lower potential with respect to Cu 5 nanoclusters, which behave relatively similar to much larger Cu particles. However, Cu 5 nanoclusters coordinate effectively CO 2 (hydrogen carbonate) in solution, different from Cu 20 nanoclusters and larger Cu particles. This effect, rather than the redox behavior, is apparently connected to the ability of Cu 5 nanoclusters to reduce CO 2 under cathodic conditions at low overpotential. In conclusion, although preliminary, these results provide rather exciting indications on the possibility of realizing low overpotential electrocatalytic conversion of CO 2 .

36 MATERIALS SCIENCE↗
DOE OSTI2015

High electron mobility ZnO film for high-performance inverted polymer solar cells

High-quality ZnO films (ZnO-MS) are prepared via magnetron sputtering deposition with a high mobility of about 2 cm{sup 2}/(V·s) and are used as electron transport layer for inverted polymer solar cells (PSCs) with polymer poly[4,8-bis(5-(2-ethylhexyl)thiophen-2-yl)benzo[1,2-b:4,5-b′] dithiophene-co-3-fluorothieno[3,4-b]thiophene-2-carboxylate]:[6,6]-phenyl C71-butyric acid methyl ester as the active layer. A significant improvement of J{sub SC}, about 20% enhancement in contrast to the devices built on sol-gel derived ZnO film (ZnO-Sol), is found in the ZnO-MS based device. High performance ZnO-MS based PSCs exhibit power conversion efficiency (PCE) up to 8.55%, which is much better than the device based on ZnO-Sol (PCE = 7.78%). Further research on cathode materials is promising to achieve higher performance.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2015

Preliminary experimental investigation of a complex dual-band high power microwave source

In order to promote the power conversion efficiency of a magnetically insulated transmission line oscillator (MILO) and obtain microwaves in dual bands, an axially extracted C-band virtual cathode oscillator (VCO) with multiple resonant cavities is introduced to partially utilize the load current of an S-band MILO. The formed novel dual-band high power microwave source called MILO and VCO is investigated with simulation and experimentally. A dual-band radiation antenna is designed to effectively radiate microwaves generated by the MILO and the VCO, respectively, while avoiding them being influenced by the microwave reflection and diffraction. The preliminary experimental results measured by the dual-band diagnostic system show that both the MILO and the VCO operate normally under repeated shots. A microwave of 2.1 GHz, 1.70 GW is generated from the MILO and a 0.37 GW microwave at frequencies of 4.1 GHz and 3.8 GHz is generated from the VCO under the condition of about 440 kV and 35 kA. Compared with a single MILO (10.6%), a MILO and VCO achieves higher total power and efficiency (13.4%) in both S and C bands, indicating that the load current of the MILO partially couples into the beam-wave interaction in the VCO and then contributes to the output microwaves. However, more works are needed regarding the spectrum purification of the VCO and promotion of the output power of both the MILO and the VCO.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2022

Surface Regulating of a Double–Perovskite Electrode for Protonic Ceramic Fuel Cells to Enhance Oxygen Reduction Activity and Contaminants Poisoning Tolerance

Protonic ceramic fuel cells (PCFCs) are one of the most efficient energy conversion devices. However, the performance of current PCFCs is greatly limited by the sluggish oxygen reduction reaction (ORR) kinetics and the fast degradation of cathode due to contaminants poisoning (such as Cr species and steam). In this work, we report a surface regulating of a double perovskite PrBa 0.5 Sr 0.5 Co 1.5 Fe 0.5 O 5+δ (PBSCF) cathode by a Pr 0.9 Fe 0.7 Co 0.3 O 3 (PFC) catalyst coating to enhance the ORR activity and stability. When tested in direct contact with Cr in the air with 3% H 2 O at 650 °C, the polarization resistance (Rp) of the PFC-PBSCF electrode increases from $\approx$0.39 to 0.45 Ω cm 2 after 100 h operation; in contrast, the R p of a PBSCF electrode increases from 0.63 to 0.82 Ω cm 2 . Further, a PCFC with the PFC-PBSCF cathode demonstrates an excellent peak power density ($\approx$1.08 W cm -2 at 650 °C) and significantly enhanced durability (degradation rate of 0.03 % h -1 ), much better than those of the cells with a PBSCF cathode ($\approx$0.75 W cm -2 and degradation rate of 0.12 % h -1 ). Raman spectroscopy and density functional theory calculations indicate that the PFC catalyst coating diminishes the formation of Cr species, such as (Ba 1-x Sr x )CrO 4 , on the cathode surface.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2026

Advanced PEM Electrolyzer Membrane for Hydrogen Crossover Mitigation

An unintended reaction in the electrochemical conversion of water to hydrogen in proton exchange membrane (PEM) electrolyzers is the crossover of hydrogen from the anode to the oxygen-containing cathode through the membrane, creating hydrogen losses and safety concerns. Efforts to date have focused on embedding platinum catalysts in perfluorosulfonic (PFSA) membranes to convert H 2 to protons. The objective of this project is to design and develop hydrocarbon (HC) proton exchange membranes (PEMs) that can help overcome the risk of high H 2 crossover in current PEM electrolyzer (ELX) stacks by designing and optimizing the gas recombination catalyst (GRC) within the membrane and membrane electrode assembly (MEA) structure.

08 HYDROGEN↗
DOE OSTI2018

Long-Life Lithium-Sulfur Batteries with a Bifunctional Cathode Substrate Configured with Boron Carbide Nanowires

Developing high-energy-density lithium–sulfur (Li–S) batteries relies on the design of electrode substrates that can host a high sulfur loading and still attain high electrochemical utilization. Herein, a new bifunctional cathode substrate configured with boron-carbide nanowires in situ grown on carbon nanofibers (B 4 C@CNF) is established through a facile catalyst-assisted process. The B 4 C nanowires acting as chemical-anchoring centers provide strong polysulfide adsorptivity, as validated by experimental data and first-principle calculations. Meanwhile, the catalytic effect of B 4 C also accelerates the redox kinetics of polysulfide conversion, contributing to enhanced rate capability. As a result, a remarkable capacity retention of 80% after 500 cycles as well as stable cyclability at 4C rate is accomplished with the cells employing B 4 C@CNF as a cathode substrate for sulfur. Moreover, the B 4 C@CNF substrate enables the cathode to achieve both high sulfur content (70 wt%) and sulfur loading (10.3 mg cm -2 ), delivering a superb areal capacity of 9 mAh cm -2 . In addition, Li–S pouch cells fabricated with the B 4 C@CNF substrate are able to host a high sulfur mass of 200 mg per cathode and deliver a high discharge capacity of 125 mAh after 50 cycles.

25 ENERGY STORAGE↗
DOE OSTI2024

A red-light-powered silicon nanowire biophotochemical diode for simultaneous CO 2 reduction and glycerol valorization

A bias-free photochemical diode, in which a p-type photocathode is connected to an n-type photoanode to harness light for driving photoelectrochemical reduction and oxidation pairs, serves as a platform for realizing light-driven fuel generation from CO 2 . However, the conventional design, in which cathodic CO 2 reduction is coupled with the anodic oxygen evolution reaction (OER), requires substantial energy input. Here we present a photochemical diode device that harnesses red light (740 nm) to simultaneously drive biophotocathodic CO 2 -to-multicarbon conversion and photoanodic glycerol oxidation as an alternative to the OER to overcome the above thermodynamic limitation. The device consists of an efficient CO 2 -fixing microorganism, Sporomusa ovata, interfaced with a silicon nanowire photocathode and a Pt–Au-loaded silicon nanowire photoanode. This photochemical diode operates bias-free under low-intensity (20 mW cm –2 ) red light irradiation with ~80% Faradaic efficiency for both the cathodic and anodic products. Finally, this work provides an alternative photosynthetic route to mitigate excessive CO 2 emissions and efficiently generate value-added chemicals from CO 2 and glycerol.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2024

Local ionic transport enables selective PGM-free bipolar membrane electrode assembly

Bipolar membranes in electrochemical CO 2 conversion cells enable different reaction environments in the CO 2 -reduction and O 2 -evolution compartments. Under ideal conditions, water-splitting in the bipolar membrane allows for platinum-group-metal-free anode materials and high CO 2 utilizations. In practice, however, even minor unwanted ion crossover limits stability to short time periods. Here we report the vital role of managing ionic species to improve CO 2 conversion efficiency while preventing acidification of the anodic compartment. Through transport modelling, we identify that an anion-exchange ionomer in the catalyst layer improves local bicarbonate availability and increasing the proton transference number in the bipolar membranes increases CO 2 regeneration and limits K + concentration in the cathode region. Through experiments, we show that a uniform local distribution of bicarbonate ions increases the accessibility of reverted CO 2 to the catalyst surface, improving Faradaic efficiency and limiting current densities by twofold. Using these insights, we demonstrate a fully platinum-group-metal-free bipolar membrane electrode assembly CO 2 conversion system exhibiting <1% CO 2 /cation crossover rates and 80-90% CO 2 -to-CO utilization efficiency over 150 h operation at 100 mA cm -2 without anolyte replenishment.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2017

Magnesium ion mobility in post-spinels accessible at ambient pressure

We propose that Ti-containing post-spinels may offer a practically-accessible route to fast multivalent ion diffusion in close-packed oxide lattices, with the caveat that substantial thermodynamic driving forces for conversion reactions exist. First-principles modeling of a new mixed V/Ti post-spinel phase reveals a possible route to ambient-pressure oxide cathodes exhibiting fast Mg diffusion.

36 MATERIALS SCIENCE↗
NASA NTRS1982

The phototron: A light to RF energy conversion device

The phototron, a photoelectric device that converts light to radio frequency energy, is described. It is a vacuum tube, free electron, device that is mechanically similar to a reflex klystron with the hot filament cathode replaced by a large area photocathode. The device can operate either with an external voltage source used to accelerate the photoelectrons or with zero bias voltage; in which case the photokinetic energy of the electrons sustains the R.F. oscillations in the tuned R.F. circuit. One basic design of the phototron was tested. Frequencies as high as about 1 GHz and an overall efficiency of about 1% in the biased mode were obtained. In the unbiased mode, the frequencies of operation and efficiences are considerably lower. Success with test model suggests that considerable improvements are possible through design refinements. One such design refinement is the reduction of the length of the electron flight path.

Freeman, J. W.↗
DOE OSTI2025

CO 2 Electrolysis Using Metal-Supported Solid Oxide Cells with Infiltrated Pr 0.5 Sr 0.4 Mn 0.2 Fe 0.8 O 3-$δ$ Catalyst

Electrochemical conversion of CO 2 to CO is demonstrated with symmetric-structured metal supported solid oxide cells (MS-SOC). Perovskite Pr 0.5 Sr 0.4 Mn 0.2 Fe 0.8 O 3-δ (PSMF) and Pr 6 O 11 catalysts were infiltrated into the MS-SOC cathode and anode, using 3 cycles with firing at 850 °C and 8 cycles with firing at 800 °C, respectively. Upon reduction during operation, the perovskite PSMF was transformed to Ruddlesden–Popper structure with a highly efficient electrocatalytic activity. The impact of operating temperature (600–800 °C) and overpotential (0–1.8 V) on the CO 2 conversion was investigated. The highest CO 2 conversion of 57.2% was achieved at 750 °C and 1.8 V. During extended operation for 150 h at 750 °C and 1.2 V, a cell demonstrated relatively stable performance, with initial current density of 535 mA cm -2 and CO 2 conversion of 23%. Degradation mechanisms were studied by posttest characterization.

25 ENERGY STORAGE↗
DOE OSTI2015

Carbon dioxide capture using resin-wafer electrodeionization

The present invention provides a resin-wafer electrodeionization (RW-EDI) apparatus including cathode and anode electrodes separated by a plurality of porous solid ion exchange resin wafers, which when in use are filled with an aqueous fluid. The apparatus includes one or more wafers comprising a basic ion exchange medium, and preferably includes one or more wafers comprising an acidic ion exchange medium. The wafers are separated from one another by ion exchange membranes. The fluid within the acidic and/or basic ion exchange wafers preferably includes, or is in contact with, a carbonic anhydrase (CA) enzyme to facilitate conversion of bicarbonate ion to carbon dioxide within the acidic medium. A pH suitable for exchange of CO.sub.2 is electrochemically maintained within the basic and acidic ion exchange wafers by applying an electric potential across the cathode and anode.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2015

An X-band high-impedance relativistic klystron amplifier with an annular explosive cathode

The feasibility of employing an annular beam instead of a solid one in the X-band high-impedance relativistic klystron amplifier (RKA) is investigated in theory and simulation. Small-signal theory analysis indicates that the optimum bunching distance, fundamental current modulation depth, beam-coupling coefficient, and beam-loaded quality factor of annular beams are all larger than the corresponding parameters of solid beams at the same beam voltage and current. An annular beam RKA and a solid beam RKA with almost the same geometric parameters are compared in particle-in-cell simulation. Output microwave power of 100 MW, gain of 50 dB, and power conversion efficiency of 42% are obtained in an annular beam RKA. The annular beam needs a 15% lower uniform guiding magnetic field than the solid beam. Our investigations demonstrate that we are able to use a simple annular explosive cathode immersed in a lower uniform magnetic field instead of a solid thermionic cathode in a complicated partially shielding magnetic field for designing high-impedance RKA, which avoids high temperature requirement, complicated electron-optical system, large area convergence, high current density, and emission uniformity for the solid beam. An equivalent method for the annular beam and the solid beam on bunching features is proposed and agrees with the simulation. The annular beam has the primary advantages over the solid beam that it can employ the immersing uniform magnetic field avoiding the complicated shielding magnetic field system and needs a lower optimum guiding field due to the smaller space charge effect.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2015

Negative space charge effects in photon-enhanced thermionic emission solar converters

In thermionic energy converters, electrons in the gap between electrodes form a negative space charge and inhibit the emission of additional electrons, causing a significant reduction in conversion efficiency. However, in Photon Enhanced Thermionic Emission (PETE) solar energy converters, electrons that are reflected by the electric field in the gap return to the cathode with energy above the conduction band minimum. These electrons first occupy the conduction band from which they can be reemitted. This form of electron recycling makes PETE converters less susceptible to negative space charge loss. While the negative space charge effect was studied extensively in thermionic converters, modeling its effect in PETE converters does not account for important issues such as this form of electron recycling, nor the cathode thermal energy balance. Here, we investigate the space charge effect in PETE solar converters accounting for electron recycling, with full coupling of the cathode and gap models, and addressing conservation of both electric and thermal energy. The analysis shows that the negative space charge loss is lower than previously reported, allowing somewhat larger gaps compared to previous predictions. For a converter with a specific gap, there is an optimal solar flux concentration. The optimal solar flux concentration, the cathode temperature, and the efficiency all increase with smaller gaps. For example, for a gap of 3 μm the maximum efficiency is 38% and the optimal flux concentration is 628, while for a gap of 5 μm the maximum efficiency is 31% and optimal flux concentration is 163.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
NASA NTRS2011

NASA Tech Briefs, February 2011

Topics covered include: Multi-Segment Radius Measurement Using an Absolute Distance Meter Through a Null Assembly; Fiber-Optic Magnetic-Field-Strength Measurement System for Lightning Detection; Photocatalytic Active Radiation Measurements and Use; Computer Generated Hologram System for Wavefront Measurement System Calibration; Non-Contact Thermal Properties Measurement with Low-Power Laser and IR Camera System; SpaceCube 2.0: An Advanced Hybrid Onboard Data Processor; CMOS Imager Has Better Cross-Talk and Full-Well Performance; High-Performance Wireless Telemetry; Telemetry-Based Ranging; JWST Wavefront Control Toolbox; Java Image I/O for VICAR, PDS, and ISIS; X-Band Acquisition Aid Software; Antimicrobial-Coated Granules for Disinfecting Water; Range 7 Scanner Integration with PaR Robot Scanning System; Methods of Antimicrobial Coating of Diverse Materials; High-Operating-Temperature Barrier Infrared Detector with Tailorable Cutoff Wavelength; A Model of Reduced Kinetics for Alkane Oxidation Using Constituents and Species for N-Heptane; Thermally Conductive Tape Based on Carbon Nanotube Arrays; Two Catalysts for Selective Oxidation of Contaminant Gases; Nanoscale Metal Oxide Semiconductors for Gas Sensing; Lightweight, Ultra-High-Temperature, CMC-Lined Carbon/Carbon Structures; Sample Acquisition and Handling System from a Remote Platform; Improved Rare-Earth Emitter Hollow Cathode; High-Temperature Smart Structures for Engine Noise Reduction and Performance Enhancement; Cryogenic Scan Mechanism for Fourier Transform Spectrometer; Piezoelectric Rotary Tube Motor; Thermoelectric Energy Conversion Technology for High-Altitude Airships; Combustor Computations for CO2-Neutral Aviation; Use of Dynamic Distortion to Predict and Alleviate Loss of Control; Cycle Time Reduction in Trapped Mercury Ion Atomic Frequency Standards; and A (201)Hg+ Comagnetometer for (199)Hg+ Trapped Ion Space Atomic Clocks.

Source record↗
DOE OSTI2015

Study on a discal TEM-TE{sub 11} mode converter loaded high-efficiency magnetically insulated transmission line oscillator

An integrative high power microwave device is proposed, which consists of a high-efficiency L-band Magnetically Insulated Transmission Line Oscillator (MILO) and a discal TEM–TE{sub 11} mode converter. The MILO with a shrunken load composed of a step-like cathode and a ladder-like beam collector can generate a 1.58 GHz, 5.7 GW microwave with the efficiency of 20.8% at the diode voltage of 560 kV in simulation. The discal converter utilizes a pair of sectorial two-double radial waveguides and a pair of sectorial cross section waveguides to adjust the phase-difference and realizes the mode conversion in a length of less than half wavelength at 1.58 GHz. In the preliminary experiment, the proposed device generates over 2 GW, 1.575 GHz microwave with the pulse duration of over 50 ns in a 420 kV diode voltage; the corresponding efficiency is 14.9%; the radiation pattern is the ideal TE{sub 11} mode.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗