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DOE OSTI2021

High-performance ammonia oxidation catalysts for anion-exchange membrane direct ammonia fuel cells

Low-temperature direct ammonia fuel cells (DAFCs) use carbon-neutral ammonia as a fuel, which has attracted increasing attention recently due to ammonia's low source-to-tank energy cost, easy transport and storage, and wide availability. However, current DAFC technologies are greatly limited by the kinetically sluggish ammonia oxidation reaction (AOR) at the anode. Herein, we report an AOR catalyst, in which ternary PtIrZn nanoparticles with an average size of 2.3 ± 0.2 nm were highly dispersed on a binary composite support comprising cerium oxide (CeO 2 ) and zeolitic imidazolate framework-8 (ZIF-8)-derived carbon (PtIrZn/CeO 2 -ZIF-8) through a sonochemical-assisted synthesis method. Additionally, the PtIrZn alloy, with the aid of abundant OH ad provided by CeO 2 and uniform particle dispersibility contributed by porous ZIF-8 carbon (surface area: ~600 m 2 g -1 ), has shown highly efficient catalytic activity for the AOR in alkaline media, superior to that of commercial PtIr/C. The rotating disk electrode (RDE) results indicate a lower onset potential (0.35 vs. 0.43 V), relative to the reversible hydrogen electrode at room temperature, and a decreased activation energy (~36.7 vs. 50.8 kJ mol -1 ) relative to the PtIr/C catalyst. Notably, the PtIrZn/CeO 2 -ZIF-8 catalyst was assembled with a high-performance hydroxide anion-exchange membrane to fabricate an alkaline DAFC, reaching a peak power density of 91 mW cm -2 . Unlike in aqueous electrolytes, supports play a critical role in improving uniform ionomer distribution and mass transport in the anode. PtIrZn nanoparticles on silicon dioxide (SiO 2 ) integrated with carboxyl-functionalized carbon nanotubes (CNT–COOH) were further studied as the anode in a DAFC. A significantly enhanced peak power density of 314 mW cm -2 was achieved. Density functional theory calculations elucidated that Zn atoms in the PtIr alloy can reduce the theoretical limiting potential of *NH 2 dehydrogenation to *NH by ~0.1 V, which can be attributed to a Zn-modulated upshift of the Pt–Ir d-band that facilitates the N–H bond breakage.

25 ENERGY STORAGE↗

NASA NTRS2011

Energy Storage Project

NASA's Exploration Technology Development Program funded the Energy Storage Project to develop battery and fuel cell technology to meet the expected energy storage needs of the Constellation Program for human exploration. Technology needs were determined by architecture studies and risk assessments conducted by the Constellation Program, focused on a mission for a long-duration lunar outpost. Critical energy storage needs were identified as batteries for EVA suits, surface mobility systems, and a lander ascent stage; fuel cells for the lander and mobility systems; and a regenerative fuel cell for surface power. To address these needs, the Energy Storage Project developed advanced lithium-ion battery technology, targeting cell-level safety and very high specific energy and energy density. Key accomplishments include the development of silicon composite anodes, lithiated-mixed-metal-oxide cathodes, low-flammability electrolytes, and cell-incorporated safety devices that promise to substantially improve battery performance while providing a high level of safety. The project also developed "non-flow-through" proton-exchange-membrane fuel cell stacks. The primary advantage of this technology set is the reduction of ancillary parts in the balance-of-plant--fewer pumps, separators and related components should result in fewer failure modes and hence a higher probability of achieving very reliable operation, and reduced parasitic power losses enable smaller reactant tanks and therefore systems with lower mass and volume. Key accomplishments include the fabrication and testing of several robust, small-scale nonflow-through fuel cell stacks that have demonstrated proof-of-concept. This report summarizes the project s goals, objectives, technical accomplishments, and risk assessments. A bibliography spanning the life of the project is also included.

Mercer, Carolyn R.↗

NASA NTRS2012

The Transition-Edge-Sensor Array for the Micro-X Sounding Rocket

The Micro-X sounding rocket program will fly a 128-element array of transition-edge-sensor microcalorimeters to enable high-resolution X-ray imaging spectroscopy of the Puppis-A supernova remnant. To match the angular resolution of the optics while maximizing the field-of-view and retaining a high energy resolution (< 4 eV at 1 keV), we have designed the pixels using 600 x 600 sq. micron Au/Bi absorbers, which overhang 140 x 140 sq. micron Mo/Au sensors. The data-rate capabilities of the rocket telemetry system require the pulse decay to be approximately 2 ms to allow a significant portion of the data to be telemetered during flight. Here we report experimental results from the flight array, including measurements of energy resolution, uniformity, and absorber thermalization. In addition, we present studies of test devices that have a variety of absorber contact geometries, as well as a variety of membrane-perforation schemes designed to slow the pulse decay time to match the telemetry requirements. Finally, we describe the reduction in pixel-to-pixel crosstalk afforded by an angle-evaporated Cu backside heatsinking layer, which provides Cu coverage on the four sidewalls of the silicon wells beneath each pixel.

Eckart, M. E.↗

DOE OSTI2021

Modulating Interactions between Molten Polystyrene and Porous Solids Using Atomic Layer Deposition

Understanding and modulating the interactions between molten polymers and porous solids is important for numerous processes and phenomena including catalytic conversion of polymers and fabrication of nanocomposites and nanostructured materials. Although changing the surface composition of pores would enable modulation of interactions between polymer and nanoporous solids, it is challenging to achieve such a control without inducing significant changes to the size and structure of nanopores. In this work, we demonstrate that the interactions between molten polystyrene (PS) and disordered packings of SiO 2 nanoparticles (NPs) can be modulated by changing the surface composition of the NPs using atomic layer deposition (ALD). A disordered packing of silica NPs is modified with varying surface coverages of TiO 2 , WO 3 and CaCO 3 , with coverages estimated by the mass gain and the refractive index change of NP packings. Based on the time required to fully infiltrate these ALD-modified NP packings via capillarity, the contact angles for PS on different surfaces prepared via ALD are determined. The contact angle gradually changes from that of pure SiO 2 to that of the fully covered surfaces. The contact angles for PS on SiO 2 , TiO 2 , WO 3 and CaCO 3 are found to be 20°, 62°, 70° and 10°, respectively. Interestingly, the contact angles and interfacial energies between PS and the ALD-modified surfaces do not correlate strongly with the water contact angle of these surfaces; thus, caution must be exercised in predicting how a polymer would wet or interact with porous solids solely based on their hydrophilicity. Furthermore, the method presented in this work can be extended to study the interactions between a wide range of polymers and surfaces in porous media, which will have important implications for designing new catalytic materials for polymer upcycling reactions as well as novel NP-polymer composite films and membranes with enhanced mechanical and transport properties.

36 MATERIALS SCIENCE↗

NASA NTRS2012

Quality Control Method for a Micro-Nano-Channel Microfabricated Device

A variety of silicon-fabricated devices is used in medical applications such as drug and cell delivery, and DNA and protein separation and analysis. When a fluidic device inlet is connected to a compressed gas reservoir, and the outlet is at a lower pressure, a gas flow occurs through the membrane toward the outside. The method relies on the measurement of the gas pressure over the elapsed time inside the upstream and downstream environments. By knowing the volume of the upstream reservoir, the gas flow rate through the membrane over the pressure drop can be calculated. This quality control method consists of measuring the gas flow through a device and comparing the results with a standard curve, which can be obtained by testing standard devices. Standard devices can be selected through a variety of techniques, both destructive and nondestructive, such as SEM, AFM, and standard particle filtration.

Grattoni, Alessandro↗

DOE OSTI2022

Large-format battery anodes comprising silicon particles

Large-scale anodes containing high weight percentages of silicon suitable for use in lithium-ion energy storage devices and batteries, and methods of manufacturing the same, are described. The anode material described herein can include a film cast on a current collector substrate, with the film including a plurality of active material particles and a conductive polymer membrane coated over the active material particles. In some embodiments, the conductive polymer membrane comprises polyacrylonitrile (PAN). The method of manufacturing the anode material can include preparation of a slurry including the active material particles and the conductive polymer material, casting the slurry on a current collector substrate, and subjecting the composite material to drying and heat treatments.

25 ENERGY STORAGE↗

DOE OSTI2024

Large-format battery anodes comprising silicon particles

Evans, Tyler↗

DOE OSTI2021

Dielectric metasurfaces made from vertically oriented nanoresonators

Dielectric metasurfaces control optical wavefronts via nanoscale resonators laid out across a surface. However, most metasurfaces are, by design, planar. In this work, we demonstrate the ability to fabricate dielectric metasurfaces with vertically oriented dielectric resonators using membrane projection lithography. We first numerically characterize the resonant modes of an array of vertically oriented germanium ellipses with no substrate and identify a narrowband region where the resonators satisfy the first Kerker condition. We then fabricate seven metasurfaces by depositing germanium ellipses onto walls of a 3D micrometer-sized silicon nitride photonic scaffold and characterize their transmission. We find that signatures of the multipolar modes seen in the unsupported array persist in the supported array, but the overall behavior is more complicated due to the scaffold. Further, we show that for a conceptual metasurface containing two coupled, vertically oriented ellipses, the ellipses can generate a sharp resonance with a quality factor of 240.

Gennaro, Sylvain D. (ORCID:0000000222090831)↗

NASA NTRS1999

Fracture Probability of MEMS Optical Devices for Space Flight Applications

A bending fracture test specimen design is presented for thin elements used in optical devices for space flight applications. The specimen design is insensitive to load position, avoids end effect complications, and can be used to measure strength of membranes less than 2 microns thick. The theoretical equations predicting stress at failure are presented, and a detailed finite element model is developed to validate the equations for this application. An experimental procedure using a focused ion beam machine is outlined, and results from preliminary tests of 1.9 microns thick single crystal silicon are presented. These tests are placed in the context of a methodology for the design and evaluation of mission critical devices comprised of large arrays of cells.

Fettig, Rainer K.↗

DOE OSTI2021

Characterization of suspended membrane waveguides towards a photonic atom trap integrated platform

We demonstrate an optical waveguide device, capable of supporting the high, in-vacuum, optical power necessary for trapping a single atom or a cold atom ensemble with evanescent fields. Our photonic integrated platform, with suspended membrane waveguides, successfully manages optical powers of 6 mW (500 μ m span) to nearly 30 mW (125 μ m span) over an un-tethered waveguide span. This platform is compatible with laser cooling and magneto-optical traps (MOTs) in the vicinity of the suspended waveguide, called the membrane MOT and the needle MOT, a key ingredient for efficient trap loading. We evaluate two novel designs that explore critical thermal management features that enable this large power handling. This work represents a significant step toward an integrated platform for coupling neutral atom quantum systems to photonic and electronic integrated circuits on silicon.

36 MATERIALS SCIENCE↗

NASA NTRS1998

Fire Resistant, Moisture Barrier Membrane

A waterproof and breathable, fire-resistant laminate is provided for use in tents, garments, shoes, and covers, especially in industrial, military and emergency situations. The laminate permits water vapor evaporation while simultaneously preventing liquid water penetration. Further, the laminate is fire-resistant and significantly reduces the danger of toxic compound production when exposed to flame or other high heat source. The laminate may be applied to a variety of substrates and is comprised of a silicone rubber and plurality of fire-resistant, inherently thermally-stable polyimide particles.

St.Clair, Terry L.↗

NASA NTRS2000

Fire Resistant, Moisture Barrier Membrane

St.Clair, Terry L.↗

DOE OSTI2020

Gating of Hydrophobic Nanopores with Large Anions

In this report, understanding ion transport in nanoporous materials is critical to a wide variety of energy and environmental technologies, ranging from ion-selective membranes, drug delivery, and biosensing, to ion batteries and supercapacitors. While nanoscale transport is often described by continuum models that rely on a point charge description for ions and a homogeneous dielectric medium for the solvent, here, we show that transport of aqueous solutions at a hydrophobic interface can be highly dependent on the size and hydration strength of the solvated ions. Specifically, measurements of ion current through single silicon nitride nanopores that contain a hydrophobic-hydrophilic junction show that transport properties are dependent not only on applied voltage but also the type of anion. We find that in Cl - -contained solutions the nanopores only conducted ionic current above a negative voltage threshold. On the other hand, introduction of large polarizable anions, such as Br - and I - , facilitated the pore wetting, making the pore conductive at all examined voltages. Molecular dynamics simulations revealed that the large anions, Br - and I - , have a weaker solvation shell compared to that of Cl - , and consequently were prone to migrate from the aqueous solution to the hydrophobic surface, leading to the anion accumulation responsible for pore wetting. The results are essential for designing nanoporous systems that are selective to ions of the same charge, for realization of ion-induced wetting in hydrophobic pores, as well as for fundamental understanding on the role of ion hydration shell on the properties of solid/liquid interfaces.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

DOE OSTI2020

Measurements of enhanced performance in an indirect drive inertial confinement fusion experiment when reducing the contact area of the capsule support

Experimental results from indirectly driven inertial confinement fusion experiments testing the performance gained from using an alternate capsule tent support are reported. The polar tent describes an alternate geometry for the thin membrane used to support the Deuterium–Tritium (DT) filled capsule. In this work, the contact area is reduced by 23 times by locating the tent support close to the poles of the capsule. The polar tent experiments are repeats of previous 3 shock 1.63 MJ, 400 TW high foot experiments and use a 165 μm thick silicon doped carbon hydrogen plastic (CH) shell. Using the polar tent support, we report a DT neutron yield of 1.07 ×1016, 76% higher than the expected Y DT ∝V 7.7 scaling. This is, at the time of writing, the highest neutron yield to date from a CH shell implosion. Furthermore, we find that the inferred pressure when using the polar tent is significantly above the model based on analytic scaling even when accounting for tent effects. Analysis of x-ray and neutron images shows the reduction of lobes produced by nominal tent features. The reduction of these features in the polar tent experiments leads to decreased low mode (P2 and P4) asymmetry compared to the nominal tent results.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗

DOE OSTI2020

Devices and methods for electrochemical liquid phase epitaxy

Electrochemical liquid phase epitaxy (ec-LPE) processes and devices are provided that can form precipitated epitaxial crystalline films or layers on a substrate. The precipitated films may comprise a semiconductor, such as germanium, silicon, or carbon. Dissolution into, saturation within, and precipitation of the semiconductor from a liquid metal electrode (e.g., Hg pool) near an interface region with a substrate yields a polycrystalline semiconductor material deposited as an epitaxial film. Reactor cells for use in an electrochemical liquid phase epitaxy (ec-LPE) device are also provided that include porous membranes to facilitate formation of the precipitated epitaxial crystalline films.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗

NASA NTRS2002

A Piezoelectric Unimorph Deformable Mirror Concept by Wafer Transfer for Ultra Large Space Telescopes

Future concepts of ultra large space telescopes include segmented silicon mirrors and inflatable polymer mirrors. Primary mirrors for these systems cannot meet optical surface figure requirements and are likely to generate over several microns of wavefront errors. In order to correct for these large wavefront errors, high stroke optical quality deformable mirrors are required. JPL has recently developed a new technology for transferring an entire wafer-level mirror membrane from one substrate to another. A thin membrane, 100 mm in diameter, has been successfully transferred without using adhesives or polymers. The measured peak-to-valley surface error of a transferred and patterned membrane (1 mm x 1 mm x 0.016 mm) is only 9 nm. The mirror element actuation principle is based on a piezoelectric unimorph. A voltage applied to the piezoelectric layer induces stress in the longitudinal direction causing the film to deform and pull on the mirror connected to it. The advantage of this approach is that the small longitudinal strains obtainable from a piezoelectric material at modest voltages are thus translated into large vertical displacements. Modeling is performed for a unimorph membrane consisting of clamped rectangular membrane with a PZT layer with variable dimensions. The membrane transfer technology is combined with the piezoelectric bimorph actuator concept to constitute a compact deformable mirror device with a large stroke actuation of a continuous mirror membrane, resulting in a compact A0 systems for use in ultra large space telescopes.

continuous mirror↗

DOE OSTI2024

Effect of Engineered Cracks in Catalyst Layers on PEMFC Catalyst Layer Durability

Proton exchange membrane fuel cells (PEMFCs) are expected to play a pivotal role in decarbonizing the transportation sector, and particularly heavy-duty vehicles (HDVs). However, improvements in durability are needed for PEMFCs to compete with state-of-the-art power sources for HDVs. Here, we examine how catalyst layer (CL) cracks that are engineered affect the CL durability by using patterned silicon templates to control the CL crack density at the micrometer scale. Electrochemical analyses show that the initial PEMFC performance is relatively unaffected by crack density, but the performance after durability testing was strongly affected. Specifically, CLs with high crack density showed higher performance relative to CLs without cracks after application of a carbon corrosion accelerated stress test. Electrochemical analyses coupled with X-ray computed tomography and scanning transmission electron microscopy with energy dispersive X-ray spectroscopy showed that the cracks provide shorter oxygen diffusion pathways to reaction sites, leading to decreased oxygen transport resistance. Additionally, we observed that the catalyst durability is unaffected by cracks. Our results provide a mechanistic explanation of the role of cracks in CL durability.

30 DIRECT ENERGY CONVERSION↗

NASA NTRS1989

Structure/permeability relationships of silicon-containing polyimides

The permeability to H2, O2, N2, CO2 and CH4 of three silicone-polyimide random copolymers and two polyimides containing silicon atoms in their backbone chains, was determined at 35.0 C and at pressures up to about 120 psig (approximately 8.2 atm). The copolymers contained different amounts of BPADA-m-PDA and amine-terminated poly (dimethyl siloxane) and also had different numbers of siloxane linkages in their silicone component. The polyimides containing silicon atoms (silicon-modified polyimides) were SiDA-4,4'-ODA and SiDA-p-PDA. The gas permeability and selectivity of the copolymers are more similar to those of their silicone component than of the polyimide component. By contrast, the permeability and selectivity of the silicon-modified polyimides are more similar to those of their parent polyimides, PMDA-4,4'-ODA and SiDA-p-PDA. The substitution of SiDA for the PMDA moiety in a polyimide appears to result in a significant increase in gas permeability, without a correspondingly large decrease in selectivity. The potential usefulness of the above polymers and copolymers as gas separation membranes is discussed.

Stern, S. A.↗