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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 379 records · Page 21
All sourcesNASA NTRSDOE OSTI
NASA NTRS1984

A High-speed Characterization Technique for Solar Silicon

High-speed crystal growth techniques demand high-speed characterization techniques to allow a timely feed-back of information to the crystal growers. The unique properties of the Si electrolyte-contact (SEC) provide for an extremely fast and simple measurement of the light-induced photo-current for any piece of Si without lengthy preparation of the specimen. Electropolishing at high anodic current densities allows for insitu generation of fresh surfaces whereas preferential etching of defects in various modes is possible at low current densities. In n-type Si a simple estimation of the minority-carrier diffusion length is possible in many cases. Laser-scanning enables local probing of the photocurrent and provides data about the homogeneity of a sample. The experimental realization of the method is described in detail and examples are given and discussed.

Lehmann, V.↗
DOE OSTI2022

A Double Sided LGAD-Based Detector Providing Timing, Position, and Track Angle Information

We describe a detector concept which combines small pixels enabled by 3D sensor-electronics integration with gain produced by a Low Gain Avalanche Diode (LGAD) layer. The detector is double-sided, with electrons collected by the cathode, which provides timing information, and an anode with small pixels to provide position and angle information. The cathode can be coarse grained, providing timing with fewer fast amplifiers to limit power consumption. The anode layer benefits from the gain of the LGAD, with larger signals that also limit the power needed. Position can be reconstructed by measuring the pattern of total charge deposited on the anode. Angle and depth of charge deposit can be measured by the shapes of the anode pulses. We describe a possible assembly technology based on 3D integration.

3D Integration↗
DOE OSTI2021

Investigating Ternary Li–Mg–Si Zintl Phase Formation and Evolution for Si Anodes in Li-Ion Batteries with Mg(TFSI) 2 Electrolyte Additive

Improved electrochemical performance of Si was recently reported by adding multivalent cation salts (such as Mg 2+ , Al 3+ , Ca 2+, etc.) in the electrolyte. This is achieved via the formation in an in situ manner of relatively more stable Li-M-Si ternary phases with less chemical reactivity. These phases stabilize Si anions and thus reduce side reactions with electrolytes at the surface and eventually benefit the overall electrochemistry. To understand the mechanism of ternary Zintl phase formation and its dynamics upon lithiation/delithiation, high-resolution solid-state 7 Li and 29 Si nuclear magnetic resonance (NMR) are utilized to directly probe the local Li and Si environments on Si electrodes harvested from coin and pouch cells at various states of (de)lithiation. The NMR spectra along with the electrochemical characterization reveal that lithiation of Si starts from the surface Si-O layer further confirmed by 7 Li– 29 Si cross-polarization NMR. Lithiation progresses with heterogeneous silicon clustering with Si -4 anions at high states of lithiation. At a fully lithiated state, the formation of overlithiated Si species is detected. At a low-voltage region (below 100 mV), direct evidence for Mg-ion insertion is found, postulated by two possible mechanisms: ion exchange with fully or overlithiated binary domains (Li 3.75+x Si) and/or a coinsertion with slightly underlithiated domains (similar to Li 3.55 Si). Upon delithiation, Li extraction starts from overlithiated Si domains. No evidence is found for electrochemical Mg removal. Evidence for a lithium-deficient Li y Mg 0.1 Si phase is found as a result of Li removal during charging. This investigation sheds light on the possible mechanisms of a new Si anode chemistry, which could enable the development of stable Si-based anodes for lithium-ion batteries.

25 ENERGY STORAGE↗
DOE OSTI2022

Mitigating Interfacial Mismatch between Lithium Metal and Garnet-Type Solid Electrolyte by Depositing Metal Nitride Lithiophilic Interlayer

Solid-state lithium batteries are generally considered as the next-generation battery technology that benefits from inherent nonflammable solid electrolytes and safe harnessing of high-capacity lithium metal. Among various solid-electrolyte candidates, cubic garnet-type Li 7 La 3 Zr 2 O 12 ceramics hold superiority due to their high ionic conductivity (10 –3 to 10 –4 S cm -1 ) and good chemical stability against lithium metal. However, practical deployment of solid-state batteries based on such garnet-type materials has been constrained by poor interfacing between lithium and garnet that displays high impedance and uneven current distribution. Herein, we propose a facile and effective strategy to significantly reduce this interfacial mismatch by modifying the surface of such garnet-type solid electrolyte with a thin layer of silicon nitride (Si 3 N 4 ). This interfacial layer ensures an intimate contact with lithium due to its lithiophilic nature and formation of an intermediate lithium–metal alloy. The interfacial resistance experiences an exponential drop from 1197 to 84.5 Ω cm 2 . Lithium symmetrical cells with Si 3 N 4 -modified garnet exhibited low overpotential and long-term stable plating/stripping cycles at room temperature compared to bare garnet. Furthermore, a hybrid solid-state battery with Si 3 N 4 -modified garnet sandwiched between lithium metal anode and LiFePO 4 cathode was demonstrated to operate with high cycling efficiency, excellent rate capability, and good electrochemical stability. This work represents a significant advancement toward use of garnet solid electrolytes in lithium metal batteries for the next-generation energy storage devices.

25 ENERGY STORAGE↗
NASA NTRS2023

Galvanic Protected Anode Materials for Molten Regolith Electrolysis

This effort aimed to explore the use of refractory alloys as long-lifetime electrode materials for use in a molten regolith electrolysis (MRE) reactor, a technology that can produce oxygen (O2) from regolith. To find a material capable of withstanding the high temperatures and corrosive nature of molten regolith, first-principles thermodynamic calculations were performed on platinum group metals in the presence of iron (Fe) and silicon (Si) to determine favorable compositions for resisting unwanted secondary phases that could form on the surface of the material. As a result of these first-principles calculations, the kinetic properties of elements such as aluminum (Al), Fe, and Si can be more easily derived, which would provide insight into the longevity of such a material when used in an MRE reactor. The effort funded by this CIF project mapped the entire phase diagram of platinum group metals, which is beneficial not only to MRE where high temperatures and molten material are present, but also aerospace applications like turbine materials, terrestrial metal processing techniques, and energy storage applications. This project narrowed a broad spectrum of refractory metals down to a small list of alloys that would be able to survive not only the high temperatures of an MRE reactor, but also the thermodynamic forces that would cause inferior alloys to form secondary phases, which would ultimately consume the electrodes of the reactor. This research needs to be followed up with experimental demonstrations of these alloys in an MRE environment.

Kevin Grossman↗
DOE OSTI2020

Structurally controlled deposition of silicon onto nanowires

Provided herein are nanostructures for lithium ion battery electrodes and methods of fabrication. In some embodiments, a nanostructure template coated with a silicon coating is provided. The silicon coating may include a non-conformal, more porous layer and a conformal, denser layer on the non-conformal, more porous layer. In some embodiments, two different deposition processes, e.g., a PECVD layer to deposit the non-conformal layer and a thermal CVD process to deposit the conformal layer, are used. Anodes including the nanostructures have longer cycle lifetimes than anodes made using either a PECVD or thermal CVD method alone.

25 ENERGY STORAGE↗
DOE OSTI2022

Structurally controlled deposition of silicon onto nanowires

Provided herein are nanostructures for lithium ion battery electrodes and methods of fabrication. In some embodiments, a nanostructure template coated with a silicon coating is provided. The silicon coating may include a non-conformal, more porous layer and a conformal, denser layer on the non-conformal, more porous layer. In some embodiments, two different deposition processes, e.g., a PECVD layer to deposit the non-conformal layer and a thermal CVD process to deposit the conformal layer, are used. Anodes including the nanostructures have longer cycle lifetimes than anodes made using either a PECVD or thermal CVD method alone.

Wang, Weijie↗
DOE OSTI2023

Structurally controlled deposition of silicon onto nanowires

Provided herein are nanostructures for lithium ion battery electrodes and methods of fabrication. In some embodiments, a nanostructure template coated with a silicon coating is provided. The silicon coating may include a non-conformal, more porous layer and a conformal, denser layer on the non-conformal, more porous layer. In some embodiments, two different deposition processes, e.g., a PECVD layer to deposit the non-conformal layer and a thermal CVD process to deposit the conformal layer, are used. Anodes including the nanostructures have longer cycle lifetimes than anodes made using either a PECVD or thermal CVD method alone.

Wang, Weijie↗
NASA NTRS2001

Further Investigations of the Passive Optical Sample Assembly (POSA) - I Flight Experiment

The Passive Optical Sample Assembly-I (POSA-I), part of the Mir Environmental Effects Payload (MEEP), was designed to study the combined effects of contamination, atomic oxygen, ultraviolet radiation, vacuum, then-nal cycling, and other constituents of the space environment on spacecraft materials. The MEEP program is a Phase I International Space Station Risk Mitigation Experiment. Candidate materials for the International Space Station (ISS) were exposed in a specially designed "suitcase" carrier, with identical specimens facing either Mir or space. The payload was attached by EVA to the exterior of the Mir docking module during the STS-76 mission (f'ig. 1). It was removed during the STS-86 mission after an 18-month exposure. During the mission, it received approximately 7 x 1019 atoMS/CM2 atomic oxygen, as calculated by polymer mass loss, and 413 ESH of solar ultraviolet radiation on the Mir-facing side. The side facing away from Mir received significant contaminant deposition, so atomic oxygen fluence has not been reliably determined. The side facing away from Mir received 571 ESH of solar UV. Contamination was observed on both the Mir-facing and space-facing sides of the POSA-I experiment , with a greater amount of deposition on the space facing side than the Mir side. The contamination has been determined to be outgassed silicone photofixed by ultraviolet radiation and converted to silicate by atomic oxygen interaction. Electron spectroscopy for chemical analysis (ESCA) with depth profiling indicated the presence of 26 - 31 nm silicate on the Mir-facing side and 500 - 1000 nm silicate on the space-facing side. The depth profiling also showed that the contaminant layer was uniform, with a small amount of carbon present on the surface and trace amounts of nitrogen, phosphorus, sulfur, and tin. The surface carbon layer is likely due to post-flight exposure in the laboratory and is similar to carbonaceous deposits on control samples. EDAX and FTIR analysis concurred with ESCA for the presence of silicon, oxygen, and carbon. Nearly 400 samples were exposed on POSA-I, which included materials such as thermal control coatings polymeric films, optical materials, and multi-layer insulation blankets. A previous paper discussed the effects of the space environment exposure and contaminant deposition on candidate materials for ISS, including Z93P inorganic thermal control coating, various anodizes, and multi-layer insulation blankets. This paper details the investigation of environmental effects on the remainder of POSA-I samples, particularly the innovative conductive thermal control coatings developed by AZ Technology of Huntsville, AL and HT Research Institute of Chicago, IL. The silicone/silicate contamination had a significant impact on the solar absorptance of white inorganic thermal control coatings on the space-facing side of POSA-I. The effect of contamination on electrical conductivity is discussed. Samples of conductive anodized aluminum developed by Boundary Technologies of Buffalo Grove, IL were also exposed on POSA-I. The effects of the space environment and contaminant deposition on the optical and electrical properties of the conductive anodized aluminum are discussed.

Finckenor, Miria M.↗
NASA NTRS2014

Effects of Low Earth Orbit on Docking Seal Materials

Spacecraft docking seals are typically made of silicone elastomers. When such seals are exposed to low Earth orbit (LEO) conditions, they can suffer damage from ultraviolet (UV) radiation and atomic oxygen (AO, or monoatomic oxygen, the predominant oxygen species in LEO). An experiment flew on the International Space Station (ISS) to measure the effects of LEO on seal materials S0383-70 and ELA-SA-401 and various mating counterface materials which included anodized aluminum. Samples flown in different orientations received different amounts of UV and AO. The hypotheses were that most of the damage would be from UV, and 10 days or more of exposure in LEO would badly damage the seals. Eighteen seals were exposed for 543 days in ram (windward), zenith (away from Earth), or wake (leeward) orientations, and 15 control samples (not flown) provided undamaged baseline leakage. To determine post-flight leak rates, each of the 33 seals were placed in an O-ring groove of a leak test fixture and pressure tested over time. Resistance temperature detectors (RTDs), pressure transducers, and LabVIEW (National Instruments) programs were used to measure and analyze the temperature and pressure and calculate leakage. Average leakage of control samples was 2.6 x 10(exp -7) lbs/day. LEO exposure did not considerably damage ELA-SA-401. The S0383-70 flight samples leaked at least 10 times more than ELA-SA-401 in all cases except one, demonstrating that ELA-SA-401 may be a more suitable sealing material in LEO. AO caused greater damage than UV; samples in ram orientation (receiving an AO fluence of 4.3 x 10(exp 21) atoms/(sq cm) and in wake (2.9x 10(exp 20) atoms/(sq cm)) leaked more than those in zenith orientation (1.58 x 10(exp 20) atoms/(sq cm)), whereas variations in UV exposure did not seem to affect the samples. Exposure to LEO did less damage to the seals than hypothesized, and the data did not support the conjecture that UV causes more damage than AO.

Leakage↗
DOE OSTI2024

Fluoro‐Ethylene‐Carbonate Plays a Double‐Edged Role on the Stability of Si Anode‐Based Rechargeable Batteries During Cycling and Calendar Aging

Abstract The energy storage density of Li‐ion batteries can be improved by replacing graphite anodes with high‐capacity Si‐based materials, though instabilities have limited their implementation. Performance degradation mechanisms that occur in Si anodes can be divided into cycling stability (capacity retention after repeated battery cycles) and calendar aging (shelf life). While cycling instabilities and improvement strategies have been researched intensively, there is little known about the underlying mechanisms that cause calendar aging. In this work, multiple electron microscope techniques are used to explore the mechanism that governs calendar aging from the sub‐nanometer‐to‐electrode scale. Plasma focused ion beam tomography is used to create 3D reconstructions of calendar aged electrodes and revealed the growth of a LiF‐rich layer at the interface between the copper current collector and the silicon material, which can lead to delamination and increased interfacial impendence. The LiF layer appeared to derive from the fluoro‐ethylene‐carbonate electrolyte additive, which is commonly used to improve cycling stability in Si‐based systems. The results reveal that additives necessary to improve cycling stability can cause performance degradation over the long‐term during calendar aging. The results show that high performing, stable systems require careful design to simultaneously mitigate both cycling and calendar aging instabilities.

25 ENERGY STORAGE↗
DOE OSTI2021

Minimizing Cr-Evaporation from Balance Of Plant Components By Utilizing Cost-Effective Alumina-Forming Austenitic Steels

A solid oxide fuel cell (SOFC) is a clean and efficient energy conversion device. The development of intermediate-temperature SOFCs has made it preferable to use metallic interconnects (MICs) to greatly reduce the cost and significantly increase the efficiency compared to ceramic interconnect materials. However, gaseous chromium species will evaporate from the chromium-containing layer formed on the surface of commonly used MICs and balance of plant (BoP) components. Volatile chromium species have been shown to form solid deposits which poison the cathodes of SOFCs, causing drastic cell performance degradation and thereby limiting commercialization. In order to alleviate the Cr poisoning and achieve long-term high performance of SOFC stacks, various Al 2 O 3 -forming austenitic (AFA) stainless steels applied at different temperatures are evaluated in this project. Based on our Phase I results (500 h operation), it is shown that on the AFAs, an alumina-based protective layer forms under high temperature that is invulnerable to water vapor effects and suppresses the diffusion of chromium and manganese which can prevent the generation of spinels on the alloy surface. Therefore, 310S, OC4 and OC5 at 800 °C and 625, OC11 and OC11LZ at 900 °C are selected to be tested in the Phase II long-term operation. From the results, we find that besides the lower Cr evaporation rates and better oxidation resistance of AFAs than benchmark alloys after short-term (500 h) operation, AFAs also possess the sturdy and compact alumina layer after a long-term operation (5000 h). A protective oxide layer is of great importance for the long-term high-temperature operation of structural materials. The high-temperature oxidation behavior of AFAs and commercial 310S and 625 alloys in Air + 10% H 2 O at 800 °C and 900 °C is systematically investigated. Severe breakaway oxidation and minor spallation are observed for the 310S and 625 after the long-term operation, while the AFAs show high oxidation resistance. It is found that the formation of a continuous alumina layer could greatly prevent the volatilization of chromium vapors. In addition, the corresponding evolving models are discussed. Chromium evaporation from BoP components in high-temperature environment could severely deteriorate the electrochemical performance of SOFC. Several methods were applied to evaluate the Cr evaporation rates of BoP after 500 h exposure at 800 °C to 900 °C in air with 10% H 2 O. An optimal method was designed to exclude the effect of silicon (Si) deposits from quartz tube and sodium (Na) deposits from the sodium carbonate on the oxidation process and the chemical interaction between Cr gaseous species and alumina tube which could provide further quantitative correlation of the evaporated Cr species quantities and degradation rates of SOFC. Based on the great performance of AFAs after long-term operation, AFAs are assembled with Anode-supported cells (ASC) to investigate the the Cr deposition of anode-supported cell under a constant current density of 0.5 A cm -2 at 800 °C with AFA alloys compared with commercial alloys. In addition, the anodic and cathodic processes are deconvoluted by distribution of relaxation times (DRT) method which are comprehensively discussed. It is found out that the voltage exhibited a slight decrease of 5.09 % and 1.54 % in the presence of OC11 and OC11LZA alloy, respectively. However, a considerable decrease of 22.14 % and 12.06 % was determined in the presence of 310S and 625 alloy, respectively. AFAs possessing the low-cost, low Cr evaporation rates and the high oxidation resistance will make it of great potential to replace the existing BoP components.

01 COAL, LIGNITE, AND PEAT↗
DOE OSTI2021

Minimizing Cr-Evaporation from Balance of Plant Components by Utilizing Cost-Effective Alumina-Forming Austenitic Steels

A solid oxide fuel cell (SOFC) is a clean and efficient energy conversion device. The development of intermediate-temperature SOFCs has made it preferable to use metallic interconnects (MICs) to greatly reduce the cost and significantly increase the efficiency compared to ceramic interconnect materials. However, gaseous chromium species will evaporate from the chromium-containing layer formed on the surface of commonly used MICs and balance of plant (BoP) components. Volatile chromium species have been shown to form solid deposits which poison the cathodes of SOFCs, causing drastic cell performance degradation and thereby limiting commercialization. In order to alleviate the Cr poisoning and achieve long-term high performance of SOFC stacks, various Al2O3-forming austenitic (AFA) stainless steels applied at different temperatures are evaluated in this project. Based on our Phase I results (500 h operation), it is shown that on the AFAs, an alumina-based protective layer forms under high temperature that is invulnerable to water vapor effects and suppresses the diffusion of chromium and manganese which can prevent the generation of spinels on the alloy surface. Therefore, 310S, OC4 and OC5 at 800 °C and 625, OC11 and OC11LZ at 900 °C are selected to be tested in the Phase II long-term operation. From the results, we find that besides the lower Cr evaporation rates and better oxidation resistance of AFAs than benchmark alloys after short-term (500 h) operation, AFAs also possess the sturdy and compact alumina layer after a long-term operation (5000 h). A protective oxide layer is of great importance for the long-term high-temperature operation of structural materials. The high-temperature oxidation behavior of AFAs and commercial 310S and 625 alloys in Air + 10% H 2 O at 800 °C and 900 °C is systematically investigated. Severe breakaway oxidation and minor spallation are observed for the 310S and 625 after the long-term operation, while the AFAs show high oxidation resistance. It is found that the formation of a continuous alumina layer could greatly prevent the volatilization of chromium vapors. In addition, the corresponding evolving models are discussed. Chromium evaporation from BoP components in high-temperature environment could severely deteriorate the electrochemical performance of SOFC. Several methods were applied to evaluate the Cr evaporation rates of BoP after 500 h exposure at 800 °C to 900 °C in air with 10% H 2 O. An optimal method was designed to exclude the effect of silicon (Si) deposits from quartz tube and sodium (Na) deposits from the sodium carbonate on the oxidation process and the chemical interaction between Cr gaseous species and alumina tube which could provide further quantitative correlation of the evaporated Cr species quantities and degradation rates of SOFC. Based on the great performance of AFAs after long-term operation, AFAs are assembled with Anode-supported cells (ASC) to investigate the the Cr deposition of anode-supported cell under a constant current density of 0.5 A cm -2 at 800 °C with AFA alloys compared with commercial alloys. In addition, the anodic and cathodic processes are deconvoluted by distribution of relaxation times (DRT) method which are comprehensively discussed. It is found out that the voltage exhibited a slight decrease of 5.09 % and 1.54 % in the presence of OC11 and OC11LZA alloy, respectively. However, a considerable decrease of 22.14 % and 12.06 % was determined in the presence of 310S and 625 alloy, respectively. AFAs possessing the low-cost, low Cr evaporation rates and the high oxidation resistance will make it of great potential to replace the existing BoP components.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Understanding the Origin of the Nonpassivating Behavior of Si-Based Anodes during the Initial Cycles

In this contribution, we combined electrochemical cycling and X-ray photoelectron spectroscopy (XPS) to understand the nonpassivating behavior of the solid electrolyte interphase (SEI) on Si anodes during the first cycles. Based on galvanostatic measurements, we show that the irreversible capacity loss is reduced after the first cycle, and it stays almost constant from the second cycle onwards. XPS was used to determine the root causes of the Coulombic inefficiency, showing that the rate of decomposition of the organic solvents strongly decreased after the first cycle, whereas the rate of salt decomposition is almost unchanged between cycles. We determine that the inhibition of the decomposition reaction of the organic solvent is responsible for the lower Coulombic loss during the second electrochemical cycle in comparison to the first, whereas the nonpassivating behavior toward the salt decomposition is one of the main causes of capacity loss upon cycling. Here, we further revisit the role of cracking in contributing to capacity loss. Whereas high volumetric expansion remains an issue plaguing the performance of Si anodes, our chronoamperometry studies reveal that the SEI formed on Si anodes does not passivate even when the electrode is fully expanded, and no additional surface is exposed. Overall, our work establishes the need to address the chemical and electrochemical instability of the SEI on the Si anode in addition to the more notorious issue of cracking.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2023

Lead leaching and electrowinning in acetic acid for solar module recycling

It is imperative to recover lead (Pb) contained in end-of-life solar modules. In this paper, a two-step leaching and electrowinning process using acetic acid is investigated for Pb recovery. Acetic acid with hydrogen peroxide can dissolve Pb quickly and, under some conditions, in a matter of minutes. Pb electrowinning has been successfully demonstrated from aqueous solutions of 0.009 M lead(II) acetate with 0–10% v/v acetic acid. Pb-containing deposits are found on both the copper cathode and graphite anode. X-ray diffraction, energy-dispersive X-ray spectroscopy, and Fourier transform infrared spectroscopy confirm the presence of metallic Pb and Pb(II) oxide (PbO) co-deposits on the cathode. Further, there is also the formation of lead subacetate on the cathode under certain conditions. On the anode, the deposit consists of lead(IV) oxide and superoxide (PbO 2 and Pb 1–x O 2 ). A Pb recovery rate of 99% is achieved in 0.009 M lead(II) acetate solutions with 10% v/v acetic acid by applying a reduction potential of either –0.8 V or –1.0 V versus the silver/silver chloride reference electrode for 24h. Pb leaching with acetic acid is also demonstrated from milled silicon solar modules.

14 SOLAR ENERGY↗
NASA NTRS2014

Method of Forming Textured Silicon Substrate by Maskless Cryogenic Etching

Disclosed herein is a textured substrate comprising a base comprising silicon, the base having a plurality of needle like structures depending away from the base, wherein at least one of the needle like structures has a depth of greater than or equal to about 50 micrometers determined perpendicular to the base, and wherein at least one of the needle like structures has a width of less than or equal to about 50 micrometers determined parallel to the base. An anode and a lithium ion battery comprising the textured substrate, and a method of producing the textured substrate are also disclosed.

Yee, Karl Y.↗
NASA NTRS1996

Simultaneous Use Of Zr And Mg Anodes In XPS

Improved x-ray source for x-ray photoelectron spectroscopy (XPS) contains both zirconium anode with beryllium window and magnesium anode with aluminum window. Previously unresolvable peaks of electron-energy spectrum become resolvable. Developed specifically for use in analyzing distributions of chemical constituents in surface layers of specimens of 2219 aluminum alloy and in determining the depths of surface oxide layers and relative proportions of aluminum and oxide in layers. Also used to study chemical constituents of surface layers in other material systems - for example, thin oxide films on silicon-based semiconductor devices, oxide films on alloys, and surface layers affecting adhesion of paints or bonding materials.

Allgeyer, D. F.↗
NASA NTRS1995

Thermal Switch for Satellite Temperature Control

An active radiator tile (ART) thermal valve has been fabricated using silicon micromachining. Intended for orbital satellite heat control applications, the operational principal of the ART is to control heat flow between two thermally isolated surfaces by bring the surfaces into intimate mechanical contact using electrostatic actuation. Prototype devices have been tested in a vacuum and demonstrate thermal actuation voltages as low as 40 volts, very good thermal insulation in the OFF state, and a large increase in radiative heat flow in the ON state. Thin, anodized aluminum was developed as a coating for high infrared emissivity and high solar reflectance.

Ziad, H.↗