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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 19 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS1971

Studies of reaction geometry in oxidation and reduction of the alkaline silver electrode

Two methods of surface area estimations of sintered silver electrodes have given roughness factors of 58 and 81. One method is based on constant current oxidation, the other is based on potentiostatic oxidation. Examination of both wire and sintered silver electrodes via scanning electron microscopy at various stages of oxidation have shown that important structural features are mounds of oxide. In potentiostatic oxidations these appear to form on sites instantaneously nucleated while in constant current oxidations progressive nucleation is indicated.

Butler, E. A.↗
NASA NTRS1972

Non-gassing nickel-cadmium battery electrodes and cells

The concept of a negative limited nongassing nickel-cadmium battery was demonstrated by constructing and testing practical size experimental cells of approximately 25 Ah capacity. These batteries operated in a gas-free manner and had measured energy densities of 10-11 Wh/lb. Thirty cells were constructed for extensive testing. Some small cells were tested for over 200 cycles at 100% depth. For example, a small cell with an electrodeposited cadmium active mass on a silver screen still had 55% of its theoretical capacity (initial efficiency was 85%). There was no evidence of deterioration of gassing properties with cycling of the nickel electrodes. The charge temperature was observed to be the most critical variable governing nickel electrode gassing. This variable was shown to be age dependent. Four types of cadmium electrodes were tested: an electrodeposited cadmium active mass on a cadmium or silver substrate, a porous sintered silver substrate based electrode, and a Teflon bonded pressed cadmium electrode. The electrodeposited cadmium mass on a silver screen was found to be the best all-around electrode from a performance point of view and from the point of view of manufacturing them in a size required for a 25 Ah size battery.

Luksha, E.↗
NASA NTRS1978

Fabrication and testing of silver-hydrogen cells

Silver electrodes containing various additives were fabricated and tested in single electrode cells in order to improve the electrochemical utilization of sintered silver cathodes in Ag-H2 aerospace batteries. A standard stack arrangement was used which featured a NASA-developed organic-inorganic separator. All cells were cycled in a regime designed to remove 75% of the cells nominal capacity based on 3.3 gms/AHr Ag utilization. In cases where performance degradation was observed, the main feature mode appeared to be corrosion of either the expanded silver current collector or the connection between the silver electrode and the electrode tab. Promising silver electrodes from single electrode studies were used in the construction of 35 AHr Ag-H2 cells. Two such cells were constructed and installed in heavy walled pressure vessels for testing. Based on the data obtained from all cells tested during the program, four lightweight 35 AHr cells were fabricated. During acceptance testing these cells yielded an average gravimetric energy density of 30 WHr/1b.

Debicarri, D. J.↗
NASA NTRS1971

NiCd battery electrodes, C-150

A research program to develop and evaluate electrodes for a nongassing negative limited nickel-cadmium cell is described. The concept of the negative limited cell and its implications on electrode structure are discussed. The key element is the development of a cadmium electrode with high hydrogen overvoltage. For this, Teflon-bonded Cd electrodes and silver-sinter based Gc electrodes were manufactured and in preliminary experiments their physical and electrochemical characteristics were evaluated. Hydrogen evolution on cadmium was found to occur approximately 100 mV more cathodic than on silver. Both electrode structures exhibit a fairly sharp potential rise at the end of the charging cycle and the advent of gas evolution occurs at potentials between -1.2 and -1.3 V versus a Hg/HgO reference electrode. These results are compared with conventional Ni-sinter based Cd electrodes.

Holleck, G.↗
NASA NTRS1975

Design and fabrication of silver-hydrogen cells

The design and fabrication of silver-hydrogen secondary cells capable of delivering higher energy densities than comparable nickel-cadmium and nickel-hydrogen cells and relatively high cycle life is presented. An experimental task utilizing single electrode pairs for the optimization of the individual electrode components, the preparation of a design for lightweight 20Ahr cells, and the fabrication of four 20Ahr cells in heavy wall test housing containing electrode stacks of the lightweight design are described. The design approach is based on the use of a single cylindrical self-contained cell with a stacked disc sequence of electrodes. The electrode stack design is based on the use of NASA- Astropower Separator Material, PPF fuel cell anodes, an intercell electrolyte reservoir concept and sintered silver electrodes. Results of performance tests are given.

Klein, M. G.↗
NASA NTRS1972

NiCd battery electrodes, C-150

Electrodes for a nongassing negative limited nickel-cadmium cell are discussed. The key element is the development of cadmium electrodes with high hydrogen overvoltage. For this, the following electrode structures were manufactured and their physical and electrochemical characteristics were evaluated: (1) silver-sinter-based Cd electrodes, (2) Teflon-bonded Cd electrodes, (3) electrodeposited Cd sponge, and (4) Cd-sinter structures.

Holleck, G.↗
NASA NTRS1979

Solar cell with improved N-region contact and method of forming the same

An improved solar cell, and method of forming the same are disclosed. It is characterized by a semiconductor silicon wafer of P-type material having diffused therein a shallow N-type region. A sintered silver contact is affixed to the surface of the N-type region at the outer surface. The improved solar cell is formulated from silver powder blended with silver metaphosphate for establishing a zone of increased carrier concentration. An aluminum or silver-aluminum alloy contact is affixed to the P-type wafer at the outer surface opposite the N-type region.

Bube, K. R.↗
NASA NTRS2019

Characterization of Low-Temperature, Co-Fired Ceramic-Manufactured Electrostatic Thruster-Closeout Report

The goal of the project was to evaluate prototypes of an experimental thruster developed by the University of Arkansas (UA), Fayetteville, AR. The design under evaluation is a radio frequency (RF) electrostatic thruster that was fabricated using the low-temperature, co-fired ceramic (LTCC) materials and fabrication process. This materials system is analogous to printed circuit board (PCB) technology with the most significant difference being that the laminate is replaced by a ceramic material and the copper layer is replaced by printed sinterable silver paste. LTCC designs are baked after fabrication and assembled to realize an entirely monolithic structure with internal conductors, vias, and cavities. In this process, the LTCC electrostatic thruster (LTCC-ET) that is the subject of the present work becomes a monolithic ceramic thruster capable of withstanding temperatures in excess of 500 ºC. The UA and NASA Marshall Space Flight Center (MSFC) jointly performed prototype testing on the LTCC-ET under a NASA Cooperative Agreement Notice (CAN) award. The LTCC-ET was tested at MSFC in May 2018 over a 1-week period. There were two goals for the test program: (1) Testing to determine the operating parameters required to create plasma ignition in the test articles. This was explored by setting a propellant flowrate and increasing RF power until plasma ignition was observed. Testing was conducted with both argon and krypton. (2) Investigate the thrust and specific impulse (Isp) performance of the thruster as a function of propellant flowrate and grid voltage. This goal was not met during the project as technical challenges in maintaining stable plasma ignition arose due to stress and heating of the RF power feed. In summary, a prototype thruster design (consisting of three packaged units) was fabricated by UA and tested for the first time under vacuum conditions at MSFC to experimentally determine basic performance metrics and functionality. It was found that the design was not sufficiently optimized or robust enough in its initial iteration to support a significant test campaign or characterization program. It was concluded that the propellant outlet channels must be reduced in size with the flowpaths adjusted to increase propellant residence time in the thruster, and that the RF connector must be replaced with a version capable of handling higher power throughput and heating. However, even in its unoptimized form, a plasma could be produced in the LTCCET, demonstrating the efficacy of the design approach. The design is especially compelling due to its low cost to manufacture and, more importantly, its scalability of size and power throughput. Low cost and scalability are also important in that additional functionalities, such as thrust vectoring and plume charge neutralization, can be integrated into future designs with minimal additional cost. This project has matured the LTCC-ET development Technology Readiness Level (TRL) from 1 to 2. The low-cost RF plasma source portion of the LTCC device was matured from TRL 2 to 4 through the demonstration of RF plasma ignition under vacuum conditions.

Huang, P.-H. A.↗
NASA NTRS1972

NiCd battery electrodes

The objective of this research program was to develop and evaluate electrodes for a negative limited nickel-cadmium cell and to prove its feasibility. The program consisted of three phases: (1) the development of cadmium electrodes with high hydrogen overvoltage characteristics, (2) the testing of positive and negative plates, and (3) the fabrication and testing of complete negative limited NiCd cells. The following electrode structures were manufactured and their physical and electrochemical characteristics were evaluated: (1) silver sinter-based Cd electrodes, (2) Teflon-bonded Cd electrodes, (3) electrodeposited Cd sponge, and (4) Cd-sinter structures. All cadmium electrode structures showed a sharp increase in potential at the end of charge, with the advent of hydrogen evolution occurring at approximately -1.3 V versus Hg/HgO. The hydrogen advent potentials on pure cadmium structures were 50 to 70 mV more cathodic than those of their silver-containing counterparts.

Holleck, G.↗
NASA NTRSDate not supplied

Print-Consistency and Process-Interaction for Inkjet-Printed Copper on Flexible Substrate

Printed electronics is a fastest growing and emerging technology that have shown much potential in several industries including automotive, wearables, healthcare, and aerospace. Its applications can be found not only in flexible but also in large area electronics. The technology provides an effective and convenient method to additively deposit conductive and insulating materials on any type of substrate. Comparing with traditional manufacturing processes, which involves chemical etching, this technology also comes to be relatively environmental friendly. Despite its status, it is not without its challenges. Starting from the material being compatible in the printer equipment to the point of achieving fine resolutions, and with excellent properties are some of the challenges that printed electronics face. Among the myriad of printing technologies such as Aerosol Jet, micro-dispensing, gravure printing, screen printing, Inkjet printing, Inkjet has gained much attention due to its low-cost, low material consumption, and roll-to-roll capability for mass manufacturing. The technology has been widely used in home and office, but recently gained interest in printed electronics in a research and development setting. Conductive materials used in Inkjet printing generally comprises of metal Nanoparticles that need to be thermally sintered for it to be conductive. The preferred metal of choice has been mostly silver due to its excellent electrical properties and ease in sintering. However, silver comes to be expensive than its counterpart copper. Since copper is prone to oxidation, much focus has been given towards photonic sintering that involves sudden burst of pulsed light at certain energy to sinter the copper Nanoparticles. With this technique, only the printed material gets sintered in a matter of seconds without having a great impact on its substrate, due to which it is also preferred in low temperature applications. With all the knowledge, there is still a large gap in the process side with copper where it is important to look how the print process affects the resolution of the print along with the effect of post-print processes on electrical and mechanical properties. In this paper, a copper Inkjet ink is utilized for understanding the effect of Inkjet print parameters on the ejected droplet and its resolution. Post-print process is also quantified using a photonic sintering equipment for excellent electrical and mechanical properties. To demonstrate the complete process, commercial-off-the-shelf components will also be mounted on the additively printed pads via Inkjet. Statistically, control charting technique will be utilized to understand the capability of the Inkjet process.

printed electronics↗
NASA NTRS1992

Tribological and mechanical comparison of sintered and hipped PM212: High temperature self-lubricating composites

Selected tribological, mechanical and thermophysical properties of two versions of PM212 (sintered and hot isostatically pressed, HIPped) are compared. PM212, a high temperature self-lubricating composite, contains 70 wt percent metal bonded chromium carbide, 15 wt percent CaF2/BaF2 eutectic and 15 wt percent silver. PM212 in the sintered form is about 80 percent dense and has previously been shown to have good tribological properties from room temperature to 850 C. Tribological results of a fully densified, HIPped version of PM212 are given. They are compared to sintered PM212. In addition, selected mechanical and thermophysical properties of both types of PM212 are discussed and related to the tribological similarities and differences between the two PM212 composites. In general, both composites display similar friction and wear properties. However, the fully dense PM212 HIPped composite exhibits slight lower friction and wear than sintered PM212. This may be attributed to its generally higher strength properties. The sintered version displays stable wear properties over a wide load range indicating its promise for use in a variety of applications. Based upon their properties, both the sintered and HIPped PM212 have potential as bearing and seal materials for advanced high temperature applications.

Dellacorte, Christopher↗
NASA NTRS1992

Tribological and mechanical comparison of sintered and HIPped PM212 - High temperature self-lubricating composites

Selected tribological, mechanical and thermophysical properties of two versions of PM212 (sintered and hot isostatically pressed, HIPped) are compared. PM212, a high temperature self-lubricating composite, contains 70 wt percent metal bonded chromium carbide, 15 wt percent CaF2/BaF2 eutectic and 15 wt percent silver. PM212 in the sintered form is about 80 percent dense and has previously been shown to have good tribological properties from room temperature to 850 C. Tribological results of a fully densified, HIPped version of PM212 are given. They are compared to sintered PM212. In addition, selected mechanical and thermophysical properties of both types of PM212 are discussed and related to the tribological similarities and differences between the two PM212 composites. In general, both composites display similar friction and wear properties. However, the fully dense PM212 HIPped composite exhibits slight lower friction and wear than sintered PM212. This may be attributed to its generally higher strength properties. The sintered version displays stable wear properties over a wide load range indicating its promise for use in a variety of applications. Based upon their properties, both the sintered and HIPped PM212 have potential as bearing and seal materials for advanced high temperature applications.

Dellacorte, Christopher↗