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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 181 records · Page 10
All sourcesNASA NTRSDOE OSTI
DOE OSTI2021

Impact of illumination and encapsulant resistivity on polarization-type potential-induced degradation on n-PERT cells

Power loss caused by polarization-type potential-induced degradation (PID-p) in a variety of high-performance photovoltaic cell types has been observed to be recoverable via subsequent illumination and in some cases preventable via simultaneous illumination. In this report, we describe the results of a study in which the front faces of n-PERT cells encapsulated in polymers with a broad range of electrical resistivity were exposed to varying and controlled irradiance during PID testing. For a low resistivity ethylene-vinyl acetate copolymer encapsulant, no reduction in the rate or extent of power loss was observed for irradiance as high as 1,000 W/m 2 , whereas for high and intermediate resistivity polyolefin encapsulants, 100 and 300 W/m 2 , respectively, prevented power loss. We introduce a simple model based on charge accumulation that facilitates interpretation of these results whereby degradation via charge accumulation under voltage stress and recovery due to light exposure are opposing and interdependent phenomena that describe the susceptibility of a module to power loss.

14 SOLAR ENERGY↗
DOE OSTI2023

A one-pot synthesis of high-density biofuels through bifunctional mesoporous zeolite-encapsulated Pd catalysts

Developing a powerful bifunctional catalyst for tandem reactions is essential to the future carbon neutrality by reducing the energy consumption in chemical industries. Herein, mesoporous zeolite-encapsulated palladium (Pd) nanoparticles (Pd@meso-ZSM-5) synthesized via emulsification-demulsification followed by a dry-gel transformation method were demonstrated to have a remarkable catalytic performance for a one-pot multiple tandem reaction of cyclic ketones (cyclopentanone, cyclohexanone) to bicyclic alkanes (bicyclopentane, bicyclohexane). Compared with supported catalysts (Pd/meso-ZSM-5) and microporous zeolite-encapsulated catalysts (Pd@ZSM-5) with a primary product of monocyclic alkane (cyclopentane, cyclohexane), Pd@meso-ZSM-5 shows much higher catalytic efficiency for the bicyclic alkanes synthesis, which was previously unattainable in the conventional two-step synthesis route. Controlled experiments and detailed characterizations show that mesoporosity provides sufficient space for the generation and diffusion of large molecular intermediates, and the intimate acid-Pd interface promotes the conversion of intermediates. As a result, this work proposes a design strategy for a mesoporous zeolite-encapsulated metal catalyst, which efficiently provides cooperative acid-hydrogenation catalysis.

09 BIOMASS FUELS↗
DOE OSTI2017

Defect-mediated, thermally-activated encapsulation of metals at the surface of graphite

Here, we show that 3 metals – Dy, Ru, and Cu – can form multilayer intercalated (encapsulated) islands at the graphite (0001) surface if 2 specific conditions are met: Defects are introduced on the graphite terraces to act as entry portals, and the metal deposition temperature is well above ambient. Focusing on Dy as a prototype, we show that surface encapsulation is much different than bulk intercalation, because the encapsulated metal takes the form of bulk-like rafts of multilayer Dy, rather than the dilute, single-layer structure known for the bulk compound. Carbon-covered metallic rafts even form for relatively unreactive metals (Ru and Cu) which have no known bulk intercalation compound.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Encapsulation of hygroscopic liquids via polymer precipitation in non-aqueous emulsions

Here, encapsulation of ionic liquids (ILs) and phase change materials (PCMs) can overcome limitations associated with bulk materials, e.g., slow mass transfer rates, high viscosities, or susceptibility to external environment. Single step soft-templated encapsulation methods commonly use interfacial polymerization for shell formation, with a multifunctional monomer in the continuous phase and another in the discontinuous phase, and thus do not give pristine core material. We posit that polymer precipitation onto emulsion droplets in non-aqueous emulsions could produce a robust shell without contamination of the core, ideal for the encapsulation of water-sensitive or water-miscible materials. Solutions of commodity polymers were added to the continuous phase of non-aqueous Pickering emulsions stabilized by alkylated graphene oxide (GO) nanosheets such that the change in solubility of the polymer led to formation of robust shells and the production of capsules that could be isolated. We demonstrate that a polymer precipitation approach can produce capsules with pristine core of the IL 1-ethyl-3-methylimidazolium hexafluorophosphate [Emim][PF 6 ] or the salt hydrate PCM magnesium nitrate hexahydrate (MNH) and shell of nanosheets and polystyrene, poly(methyl methacrylate), or polyethylene. The capsules are approximately 80 wt% [Emim][PF 6 ] or >90 wt% MNH, and the core can undergo multiple cycles of solidification and melting without leakage or destruction. This novel, single-step methodology provides a distinct advantage to access capsules with pristine core composition and is amenable to different core and shell, paving the way for tailoring capsule composition for desired applications.

36 MATERIALS SCIENCE↗
DOE OSTI2016

Heteropoly acid encapsulated into zeolite imidazolate framework (ZIF-67) cage as an efficient heterogeneous catalyst for Friedel–Crafts acylation

A new strategy has been developed for the encapsulation of the phosphotungstic heteropoly acid (H{sub 3}PW{sub 12}O{sub 40} denoted as PTA) into zeolite imidazolate framework (ZIF-67) cage and the PTA@ZIF-67(ec) catalysts with different PTA content were prepared. The structure of the catalysts was characterized by XRD, BET, SEM, FT-IR, ICP-AES and TG. The catalytic activity and recovery properties of the catalysts for the Friedel-Crafts acylation of anisole with benzoyl chloride were evaluated. The results showed that 14.6–31.7 wt% PTA were encapsulated in the ZIF-67 cage. The PTA@ZIF-67(ec) catalysts had good catalytic activity for Friedel-Crafts acylation. The conversion of anisole can reach ~100% and the selectivity of the production can reach ~94% over 26.5 wt% PTA@ZIF-67(ec) catalyst under the reaction condition of 120 °C and 6 h. After reaction, the catalyst can be easily separated from the reaction mixture by the centrifugation. The recovered catalyst can be reused five times and the selectivity can be kept over 90%. - Graphical abstract: The PTA@ZIF-67 catalysts with different PTA content were prepared by encapsulating the PTA into ZIF-67 cage and the as-synthesized catalysts exhibited good catalytic activity for the Friedel–Craft acylation of anisole with benzoyl chloride.

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

Impulse-driven release of gas-encapsulated drops

Gas-encapsulated drops, much like antibubbles, are drops enclosed in a bubble within a liquid. They show potential as payload carriers in fluid transport and mixing techniques where sound waves can be leveraged to induce the collapse of the gas core and the subsequent release of the drop. Here, the interaction of millimetre-sized gas-encapsulated drops with impulsive laser-induced shock waves is investigated to gain fundamental insights into the release process. Experimental synchrotron X-ray phase contrast imaging, which allows the drop dynamics to be visualised inside the encapsulating bubble, is complemented by numerical simulations to study the intricate physics at play. Three drop dynamical release regimes are discovered, namely the drop impact , partial deposition and jet impact regimes. The regime type is mainly dependent on the shape of the bubble interface impacting the drop and the associated Weber and Reynolds numbers. The drop dynamics of the drop impact and partial deposition regimes show similarities with the canonical configuration of drops impacting flat liquid surfaces, whereas the jet impact regime resembles binary drop collisions, which allows existing scaling laws to be applied to describe the underlying processes. The release of the drop is investigated numerically. The time evolution of the drop dissemination within the surrounding liquid discloses enhanced mixing for dynamics involving high Weber and Reynolds numbers such as the drop impact and jet impact regimes.

42 ENGINEERING↗
DOE OSTI2021

Tuning the Conductivity of Hexa-Zirconium(IV) Metal–Organic Frameworks by Encapsulating Heterofullerenes

Electrical conductivity in metal–organic frameworks (MOFs) has a great potential for energy storage applications and electrocatalysis. Zirconium-based MOFs such as NU-901 and NU-1000 have a low electrical conductivity due to the redox innocence of Zr–oxo bonds. Recently, it has been shown that the electrical conductivity of NU-901 can be increased by 11 orders of magnitude by physically encapsulating fullerene (C 60 ) in its diamond pore. This effect is due to the host–guest interaction between the electron-rich 1,3,6,8-tetrakis(p-benzoate)pyrene (TBAPy 4– ) organic linkers of NU-901 (host) and the electron-poor fullerene (guest). Herein, we used density functional theory to study heterofullerene (C 59 X; X = B, Al, Ga, In, Si, Ge, and Sn) encapsulation in NU-901. Furthermore, our study suggests that encapsulated heterofullerenes enhance the electrical conductivity of the NU-901 MOF even further than C 60 .

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

In Vitro Encapsulation of Functionally Active Abiotic Photosensitizers Inside a Bacterial Microcompartment Shell

Bacterial microcompartments (BMCs) are self-assembling, selectively permeable protein shells that encapsulate enzymes to enhance catalytic efficiency of segments of metabolic pathways through means of confinement. The modular nature of BMC shells' structure and assembly enables programming of shell permeability and underscores their promise in biotechnology engineering efforts for applications in industry, medicine, and clean energy. Realizing this potential requires methods for encapsulation of abiotic molecules, which have been developed here for the first time. We report in vitro cargo loading of BMC shells with ruthenium photosensitizers (RuPS) by two approaches-one involving site-specific covalent labeling and the other driven by diffusion, requiring no specific interactions between cargo molecules and shell proteins. The highly stable shells retain encapsulated cargo over 1 week without egress and preserve RuPS photophysical activity. Finally, this study is an important foundation for further work that will converge biological BMC architecture with synthetic chemistry to facilitate biohybrid photocatalysis.

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

Tunable Encapsulation Structure of Block Copolymer Coated Single-Walled Carbon Nanotubes in Aqueous Solution

The nano-sized and shape-tunable molecular building blocks can provide great opportunities for the fabrication of precisely controlled nanostructures. In this work, we have fabricated a molecular building block of single-walled carbon nanotubes (SWNTs) coated by PPO-PEO-PPO block copolymers whose encapsulation structure can be controlled via temperature or addition of small molecules. The structure and optical properties of SWNT-block copolymers have been investigated by small angle neutron scattering (SANS), ultraviolet-visible (UV-vis) spectroscopy, atomic force microscopy (AFM), and molecular dynamics (MD) simulation. The structure of the hydrated block copolymer layer surrounding SWNT can be controlled reversibly by varying temperature as well as by irreversibly adding 5-methylsalicylic acid (5MS). Increasing hydrophobicity of the polymers with temperature and strong tendency of 5MS to interact with both block copolymers and orbitals of the SWNTs are likely to be responsible for the significant structural change of the block copolymer encapsulation layer, from loose corona shell to tightly encapsulating compact shell. These result shows an efficient and simple way to fabricate and manipulate carbon-based nano building blocks in aqueous systems with tunable structure.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2022

Quantifying the Influence of Defects on Selectivity of Electrodes Encapsulated by Nanoscopic Silicon Oxide Overlayers

Encapsulation of electrocatalysts and photocatalysts with semipermeable nanoscopic oxide overlayers that exhibit selective transport properties is an attractive approach to achieve high redox selectivity. However, defects within the overlayers-such as pinholes, cracks, or particle inclusions-may facilitate local high rates of parasitic reactions by creating pathways for facile transport of undesired reactants to exposed active sites. Scanning electrochemical microscopy (SECM) is an attractive method to determine the influence of defects on macroscopic performance metrics thanks to its ability to measure the relative rates of competing electrochemical reactions with high spatial resolution over the electrode. Here, we report the use of SECM to determine the influence of overlayer defects on the selectivity of silicon oxide (SiOx) encapsulated platinum thin-film electrocatalysts operated under conditions where two competing reactions-the hydrogen evolution and Fe(III) reduction reactions-can occur. After an SECM methodology is described to determine spatially resolved selectivity, representative selectivity maps are correlated with the location of defects that are characterized by optical, electron, and atomic force microscopies. This analysis reveals that certain types of defects in the oxide overlayer are responsible for ∼60-90% of the partial current density toward the undesired Fe(III) reduction reaction. By correcting for defect contributions to Fe(III) reduction rates, true Fe(III) permeability values for the SiOxoverlayers were determined to be over an order of magnitude lower than permeabilities determined from analyses that ignore the presence of defects. Lastly, different types of defects were studied revealing that defect morphology can have varying influence on both redox selectivity and calculated permeability. This work highlights the need for spatially resolved measurements to evaluate the performance of oxide-encapsulated catalysts and understand their performance limits.

25 ENERGY STORAGE↗
DOE OSTI2015

Encapsulated silicene: A robust large-gap topological insulator

The quantum spin Hall (QSH) effect predicted in silicene has raised exciting prospects of new device applications compatible with current microelectronic technology. Efforts to explore this novel phenomenon, however, have been impeded by fundamental challenges imposed by silicene’s small topologically nontrivial band gap and fragile electronic properties susceptible to environmental degradation effects. Here we propose a strategy to circumvent these challenges by encapsulating silicene between transition-metal dichalcogenides (TMDCs) layers. First-principles calculations show that such encapsulated silicene exhibit a two-orders-of-magnitude enhancement in its nontrivial band gap, which is driven by the strong spin–orbit coupling effect in TMDCs via the proximity effect. Moreover, the cladding TMDCs layers also shield silicene from environmental gases that are detrimental to the QSH state in free-standing silicene. In conclusion, the encapsulated silicene represents a novel two-dimensional topological insulator with a robust nontrivial band gap suitable for room-temperature applications, which has significant implications for innovative QSH device design and fabrication.

36 MATERIALS SCIENCE↗
DOE OSTI2016

Encapsulation of Perovskite Nanocrystals into Macroscale Polymer Matrices: Enhanced Stability and Polarization

Lead halide perovskites hold promise for photonic devices, due to their superior optoelectronic properties. However, their use is limited by poor stability and toxicity. We demonstrate enhanced water and light stability of high-surface-area colloidal perovskite nanocrystals by encapsulation of colloidal CsPbBr 3 quantum dots into matched hydrophobic macroscale polymeric matrices. This is achieved by mixing the quantum dots with presynthesized high-molecular-weight polymers. In this work, we monitor the photoluminescence quantum yield of the perovskite-polymer nanocomposite films under water-soaking for the first time, finding no change even after >4 months of continuous immersion in water. Furthermore, photostability is greatly enhanced in the macroscale polymer-encapsulated nanocrystal perovskites, which sustain >10 10 absorption events per quantum dot prior to photodegradation, a significant threshold for potential device use. Control of the quantum dot shape in these thin-film polymer composite enables color tunability via strong quantum-confinement in nanoplates and significant room temperature polarized emission from perovskite nanowires. Not only does the high-molecular-weight polymer protect the perovskites from the environment but also no escaped lead was detected in water that was in contact with the encapsulated perovskites for months. In conclusion, our ligand-passivated perovskite-macroscale polymer composites provide a robust platform for diverse photonic applications.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Encapsulating Semiconductor Quantum Dots in Supramolecular Cages Enables Ultrafast Guest–Host Electron and Vibrational Energy Transfer

In the field of supramolecular chemistry, host- guest systems have been extensively explored to encapsulate a wide range of substrates, owing to emerging functionalities in nano-confined space that cannot be achieved in dilute solutions. However, host-guest chemistry is still limited to encapsulation of small guests. Herein, we construct a water-soluble metallo-supramolecular hexagonal prism with a large hydrophobic cavity by anchoring multiple polyethylene glycol chains onto the building blocks. Then, assembled prisms are able to encapsulate quantum dots (QDs) with diameters of less than 5.0 nm. Furthermore, we find that the supramolecular cage around each QD strongly modifies the photophysics of the QD by universally increasing the rates of QD relaxation processes via ultrafast electron and vibrational energy transfer. In conclusion, taken together, these efforts expand the scope of substrates in host-guest systems and provide a new approach to tune the optical properties of QDs.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2014

Protein Encapsulation via Polypeptide Complex Coacervation

Proteins have gained increasing success as therapeutic agents; however, challenges exist in effective and efficient delivery. In this work, we present a simple and versatile method for encapsulating proteins via complex coacervation with oppositely charged polypeptides, poly(L-lysine) (PLys) and poly(D/L-glutamic acid) (PGlu). A model protein system, bovine serum albumin (BSA), was incorporated efficiently into coacervate droplets via electrostatic interaction up to a maximum loading of one BSA per PLys/PGlu pair and could be released under conditions of decreasing pH. Additionally, encapsulation within complex coacervates did not alter the secondary structure of the protein. Lastly the complex coacervate system was shown to be biocompatible and interact well with cells in vitro. A simple, modular system for encapsulation such as the one presented here may be useful in a range of drug delivery applications.

Black, Katie A.↗
DOE OSTI2017

Self-assembled nanotextures impart broadband transparency to glass windows and solar cell encapsulants

Most optoelectronic components and consumer display devices require glass or plastic covers for protection against the environment. Optical reflections from these encapsulation layers can degrade the device performance or lessen the user experience. In this paper, we use a highly scalable self-assembly based approach to texture glass surfaces at the nanoscale, reducing reflections by such an extent so as to make the glass essentially invisible. Our nanotextures provide broadband antireflection spanning visible and infrared wavelengths (450–2500 nm) that is effective even at large angles of incidence. This technology can be used to improve the performance of photovoltaic devices by eliminating reflection losses, which can be as much as 8% for glass encapsulated cells. In contrast, solar cells encapsulated with nanotextured glass generate the same photocurrent as when operated without a cover. Finally, ultra-transparent windows having surface nanotextures on both sides can withstand three times more optical fluence than commercial broadband antireflection coatings, making them useful for pulsed laser applications.

14 SOLAR ENERGY↗
DOE OSTI2023

Encapsulation Residual Stress and Ferrite Loss in Inductive Coil Assemblies

As inductive wireless charging reaches higher power levels, thermal management and mechanical durability become more critical. To address these concerns, past works have demonstrated the benefit of encapsulating coil assemblies in thermally conductive materials. However, due to the sensitivity of the MnZn ferrites commonly used in coil assemblies to mechanical stress, care must be taken to avoid creating large stresses in the ferrite that cause higher hysteresis loss. The stress formation in the encapsulant curing process is overviewed and modeled and an experiment is performed to demonstrate the effect in a small-scale coil assembly. Finally, the effect is shown in the reduced coil-coil efficiency of a first generation high power inductive power transfer prototype using a stiff epoxy compared to better performance in a second prototype using a softer thermally-conductive silicone encapsulant.

Foote, Andrew↗
DOE OSTI2019

Field-Aged Glass/Backsheet and Glass/Glass PV Modules: Encapsulant Degradation Comparison

Ethylene vinyl acetate (EVA) is the predominant encapsulant in crystalline-silicon photovoltaic (PV) modules; however, its degradation is a subject of major concern, which causes significant power loss under field conditions. This article presents a comparison of EVA degradation in field-aged PV modules with glass/backsheet (G/B) and glass/glass (G/G) architectures. Modulelevel characterization included UV fluorescence imaging and I-V measurements. Material analytical techniques, including colorimetry, differential scanning calorimetry, thermogravimetric analysis, Fourier transform infrared spectroscopy, and Raman spectroscopy, were performed to correlate the module performance parameters with EVA material properties. An intense EVA discoloration in G/G modules was observed, which was corroborated by higher module Isc and Pmax degradation rates compared with its counterpart G/B modules. Higher power degradation was accompanied by a significant increase in EVA crosslinking, vinyl acetate content, yellowness index, and presence of functional groups containing unsaturated moieties that are linked to degradation products of photothermal reaction, and a higher decrease in the degree of crystallinity. The absence of a polymeric backsheet in hermetically sealed G/G modules, which restricts photobleaching and enhances the entrapment of volatile acetic acid and other degradation by-products, plays a major role in causing higher EVA degradation in G/G modules. This article concludes that EVA might have been a good choice of an encapsulant for the G/B modules over the decades, but it may prove to be an inappropriate choice for the G/G modules because of potential degassing, corrosion, and/or discoloration issues. Ionomers or polyester-based encapsulants like polyolefins could be best suited for G/G modules as it appears to be a current trend in the industry.

14 SOLAR ENERGY↗
DOE OSTI2016

Measurements of the work function of single-walled carbon nanotubes encapsulated by AgI, AgCl, and CuBr using Kelvin probe technique with different kinds of probes

We report the results on the measurements of the work function of single-walled carbon nanotubes encapsulated by Agl (AgI@SWCNT), AgCl (AgCl@SWCNT), and CuBr (CuBr@SWCNT) by the local Kelvin probe technique. We found the values of the work function of tubes encapsulated with AgI and AgCl (Φ(AgI@SWCNT) = 5.08 ± 0.02, Φ(AgCl@SWCNT) = 5.10 ± 0.02 eV) to exceed substantially that of pristine carbon nanotubes, and the value of the work function of carbon nanotubes encapsulated with CuBr is Φ(CuBr@SWCNT) = 4.89 ± 0.03 (eV). The measurements are carried out using different kinds of microscope probes including multi-walled carbon nanotube tips.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗