Post-Combustion CO2 Capture with Encapsulated Ionic Liquids,
Review of findings from the NETL sponsored project on encapsulated Ionic Liquids for CO2 Capture
20 FOSSIL-FUELED POWER PLANTS↗
SEARCH · Engineering Papers
Results for “ENCAPSULATION”
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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Transparent Conductive Encapsulants for Photoelectrochemical Applications
Utilizing sunlight to directly perform photoelectrochemical reactions is a promising route to renewable, net carbon-neutral fuels. However, a common problem with solar fuel production is semiconductor degradation in aqueous environments. An ideal protection layer should (1) prevent solution from reaching the semiconductor, (2) maintain charge transfer to and from solution, and (3) be transparent to light above the semiconductor band gap. While there have been substantial advances toward layers that meet these requirements, they are not easily adapted to new surfaces or new reactions, which can make protection difficult for newly developed photoabsorbers and (photo)electrochemical reaction pairings. In this work, we demonstrate the use of transparent conductive encapsulants (TCEs) to meet these requirements while also allowing for photoelectrode- and reaction-agnostic adaptability. TCEs are composed of an ethyl-vinyl acetate matrix with embedded conductive metal-coated microspheres that can be laminated to semiconductors. First, the electrochemical behavior of TCE-coated electrodes for the reduction of methyl viologen is characterized, demonstrating through-TCE electrical conduction. Then, photoelectrochemical measurements on TCE-protected semiconductors demonstrate the flexibility of this protection scheme. Finally, long-term photoelectrochemical measurements probe the efficacy of TCEs as protection layers. These findings demonstrate the potential of TCEs as adaptable protection layers in various photoelectrochemical applications.
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Multi angle laser light scattering evaluation of field exposed thermoplastic photovoltaic encapsulant materials
Abstract As creep of polymeric materials is potentially a safety concern for photovoltaic modules, the potential for module creep has become a significant topic of discussion in the development of IEC 61730 and IEC 61215. To investigate the possibility of creep, modules were constructed, using several thermoplastic encapsulant materials, into thin‐film mock modules and deployed in Mesa, Arizona. The materials examined included poly(ethylene)‐co‐vinyl acetate (EVA, including formulations both cross‐linked and with no curing agent), polyethylene/polyoctene copolymer (PO), poly(dimethylsiloxane) (PDMS), polyvinyl butyral (PVB), and thermoplastic polyurethane (TPU). The absence of creep in this experiment is attributable to several factors of which the most notable one was the unexpected cross‐linking of an EVA formulation without a cross‐linking agent. It was also found that some materials experienced both chain scission and cross‐linking reactions, sometimes with a significant dependence on location within a module. The TPU and EVA samples were found to degrade with cross‐linking reactions dominating over chain scission. In contrast, the PO materials degraded with chain scission dominating over cross‐linking reactions. Although we found no significant indications that viscous creep is likely to occur in fielded modules capable of passing the qualification tests, we note that one should consider how a polymer degrades, chain scission or cross‐linking, in assessing the suitability of a thermoplastic polymer in terrestrial photovoltaic applications.
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Mechanisms of adhesion degradation at the photovoltiac module's cell metallization-encapsulant interface
Adhesion measurements and chemical characterization of the encapsulant/silver metallization interface of a photovoltaic (PV) module through temperature, humidity, and voltage bias exposures were conducted. Results demonstrate two independent degradation mechanisms: (a) with voltage bias, the ionic conduction of Na + ions through the encapsulant results in the formation of sodium silicate at the silver metallization surface, thereby weakening that interface and (b) with moisture ingress, dissociation of the silane bonding to silver in the silver oxide similarly weakens this interface resulting in significantly lower debond energies.
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Environmentally Friendly Novel Maleated Poly(vinyl alcohol) Grafted 1, 4-Butanediol Modified with Biopolymer for Encapsulation of Capsaicin
Nowadays, hydrogels are widely used in many fields, for instance as biosensors, in tissue engineering and in agriculture due to their high swelling behavior in water and their softness. The objective of this work was to study the preparation and physical properties of maleated poly (vinyl alcohol) (PVAM)-graft-butanediol (BDO) (PVAM-graft-BDO) using K{sub 2}S{sub 2}O{sub 8} as an initiator. The highest grafting efficiency of 92% was found at 7:3 PVAM-graft-BDO. The swelling behavior of the PVAM-graft-BDO increased with an increasing BDO content. The highest swelling ratio of the PVAM-graft-BDO of 250% was found at 7:3 PVAM:BDO. Moreover, the maximum tensile strength of the PVAM-graft-BDO was observed at 9:1 PVAM:BDO. The elongation at break of the PVAM-graft-BDO was improved by the addition of natural rubber-graft-cassava starch (NS). The PVAM-graft-BDO was used as a polymer matrix for the encapsulation of capsaicin. The results showed that the rate of capsaicin release from the polymer matrix in a water medium was controlled by the BDO portion and the NS content. After use, it was easily degraded in natural soil.
36 MATERIALS SCIENCE↗
Graphitic encapsulation of MgO and Fe{sub 3}C nanoparticles in the reaction of iron pentacarbonyl with magnesium
A simple method to produce highly ordered carbon nanostructures by combustion synthesis is presented. Graphite-encapsulated magnesium oxide, iron carbide nanoparticles and carbon nanobelts were synthesized by the one-step reduction of iron pentacarbonyl with magnesium. High-resolution transmission electron microscopy analysis of the products revealed nanocrystalline MgO and Fe{sub 3}C particles surrounded by a well-crystallized, tight graphite film. The possible formation mechanism is presented and discussed. - Highlights: • We present a simple method to produce highly ordered carbon nanostructures by combustion synthesis. • The cubic MgO particles are completely coated by tight graphitic shells. • The mechanism of formation a distant carbon film on MgO surface has been discussed. • The presented method can be applied to synthesis of other core-shell structures.
36 MATERIALS SCIENCE↗
Durability of ionomer encapsulants in photovoltaic modules
Ethylene vinyl acetate (EVA) has for decades been the preferred material for photovoltaic (PV) module encapsulation. However, while it is relatively inexpensive and initially adheres well to module components, EVA discolors with age and - as interfacial adhesion degrades - becomes susceptible to delamination, ultimately resulting in reduced module efficiency and shortened service lifetimes. As potential replacements for EVA, ionomer thermoplastic materials cure faster, are more resistant to discoloration and potential induced degradation, and do not evolve corrosive acetic acid, making them compatible with new device materials such as perovskites. Since there is limited information on ionomer durability for PV module applications, a series of field and accelerated laboratory aging studies were conducted to assess ionomer interface stability in the presence of terrestrial environmental stressors. It is shown that adhesion to the glass and cell interfaces of PV modules is inferior to EVA, both before and after aging, rendering ionomers particularly susceptible to delamination after short timeframes. Potential solutions to improve ionomer adhesion are discussed.
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Adsorption, Ordering, and Local Environments of Surfactant-Encapsulated Polyoxometalate Ions Probed at the Air–Water Interface
The continued development and application of surfactant-encapsulated polyoxometalates (SEPs) relies on understanding the ordering and organization of species at their interface and how these are impacted by the various local environments to which they are exposed. In this paper, we report on the equilibrium properties of two common SEPs adsorbed to the air–water interface and probed with surface-specific vibrational sum-frequency generation (SFG) spectroscopy. These results reveal clear shifts in vibrational band positions, the magnitude of which scales with the charge of the SEP core, which is indicative of a static field effect on the surfactant coating and the associated local chemical environment. This static field also induces ordering in surrounding water molecules that is mediated by charge screening via the surface-bound surfactants. From these SFG measurements, we are able to show that Mo 132 -based SEPs are more polar than Mo 72 V 30 SEPs. Disorder in the surfactant chain packing at the highly curved SEP surfaces is attributed to large conic volumes that can be sampled without interactions with neighboring chains. Measurements of adsorption isotherms yield free energies of adsorption to the air–water interface of -46.8 ± 0.4 and -44.8 ± 1.2 kJ/mol for the Mo 132 and Mo 72 V 30 SEPs, respectively, indicating a strong propensity for the fluid surface. Finally, the influence of intermolecular interactions on the surface adsorption energies is discussed.
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
Activation and Assembly of Plasmonic-Magnetic Nanosurfactants for Encapsulation and Triggered Release
Multifunctional surfactants hold great potentials in catalysis, separation, and biomedicine. Highly active plasmonic-magnetic nanosurfactants are developed through a novel acid activation treatment of Au–Fe 3 O 4 dumbbell nanocrystals. The activation step significantly boosts nanosurfactant surface energy and enables the strong adsorption at interfaces, which reduces the interfacial energy one order of magnitude. Mediated through the adsorption at the emulsion interfaces, the nanosurfactants are further constructed into free-standing hierarchical structures, including capsules, inverse capsules, and two-dimensional sheets. The nanosurfactant orientation and assembly structures follow the same packing parameter principles of surfactant molecules. Furthermore, nanosurfactants demonstrate the capability to disperse and encapsulate homogeneous nanoparticles and small molecules without adding any molecular surfactants. The assembled structures are responsive to external magnetic field, and triggered release is achieved using an infrared laser by taking advantage of the enhanced surface plasmon resonance of nanosurfactant assemblies. Finally, solvent and pH changes are also utilized to achieve the cargo release.
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Millimeter-Scale Exfoliation of hBN with Tunable Flake Thickness for Scalable Encapsulation
As a two-dimensional (2D) dielectric material, hexagonal boron nitride (hBN) is in high demand for applications in photonics, nonlinear optics, and nanoelectronics. Unfortunately, the high-throughput preparation of macroscopic-scale, high-quality hBN flakes with controlled thickness is an ongoing challenge, limiting device fabrication and technological integration. In this report we present a metal thin-film exfoliation method to prepare hBN flakes with millimeter-scale dimension, near-unity yields, and tunable flake thickness distribution from 1-7 layers, a substantial improvement over scotch tape exfoliation. The single crystallinity and high quality of the exfoliated hBN are demonstrated with optical microscopy, atomic force microscopy, Raman spectroscopy, and second harmonic generation. We further explore a possible mechanism for the effectiveness and selectivity based on thin-film residual stress measurements, density functional theory calculations, and transmission electron microscopy imaging of the deposited metal films. We find that the magnitude of the residual tensile stress induced by thin film deposition plays a key role in determining exfoliated flake thickness in a manner which closely resembles 3D semiconductor spalling. Lastly, we demonstrate that our exfoliated, large-area hBN flakes can be readily incorporated as encapsulating layers for other 2D monolayers. Altogether, this method brings us one step closer to the high throughput, mass production of hBN-based 2D photonic, optoelectronic, and quantum devices.
2D materials↗
Ultra-sensitive Hall sensors based on graphene encapsulated in hexagonal boron nitride
The encapsulation of graphene in hexagonal boron nitride provides graphene on substrate with excellent material quality. Here, we present the fabrication and characterization of Hall sensor elements based on graphene boron nitride heterostructures, where we gain from high mobility and low charge carrier density at room temperature. We show a detailed device characterization including Hall effect measurements under vacuum and ambient conditions. We achieve a current- and voltage-related sensitivity of up to 5700 V/AT and 3 V/VT, respectively, outpacing state-of-the-art silicon and III/V Hall sensor devices. Finally, we extract a magnetic resolution limited by low frequency electric noise of less than 50 nT/√(Hz) making our graphene sensors highly interesting for industrial applications.
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
Silver clusters encapsulated in C{sub 60}: A density functional study
We explore the possibility of formation of endohedral complexes of Ag{sub n} atoms (n=1-9) inside C{sub 60} molecule using density functional theory and molecular dynamics. The obtained results reveal that Ag{sub n} (n=8) atoms can form stable complexes with the C{sub 60} molecule. Encapsulation of large number of Ag{sub n} atoms (n>8) make C{sub 60} cage instable, showing distortion of cage. Binding energy/atom increases with the number of Ag atoms up to n=4, after that it increases. Ionization potential decreases till n=4 and then increases, electron affinity increases till n=4 and then shows oscillatory nature as a function of Ag atoms inside the cage. Homo –Lumo gap shows no systematic pattern. Our results agreed well with the data available.
36 MATERIALS SCIENCE↗
Assessing the Causes of Encapsulant Delamination in PV Modules
Delamination of the encapsulant is one of the most prevalent PV module field failures. This paper will present examples of various types of delaminations that have been observed in the field. It will then discuss the development of accelerated stress tests designed to duplicate those field failures and thus provide tools for avoiding them in the future.
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Monolithic Encapsulation of Perovskite Solar Cells with Transparent Conductive Composites for Long-Term Stability
This final technical report summarizes the findings of the University of Hawaiʻi and the National Renewable Energy Laboratory on the encapsulation of perovskite solar cells using novel polymers to enable extended operational lifetimes.
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Encapsulant Thermal Accelerated Aging (90 Celsius, no UV) Experimental Data
Chemical and thermal characterization (FTIR-ATR, Soxhlet extraction, DSC) of polymeric encapsulants (EVA, POE, EPE) aged under thermal accelerated aging, without the presence of a UV source
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FTIR analysis of unaged encapsulants
Fourier transform infrared spectroscopy (FITR) analysis (in ATR mode) of unaged encapsulants (EVA, POE, EPE) from a commercial source.
characterization↗
Encapsulant UV Accelerated Aging Experimental Data
Chemical and thermal characterization (FTIR-ATR, Soxhlet extraction, DSC) of polymeric encapsulants (EVA, POE, EPE) aged under accelerated aging conditions containing an UV source.
accelerated aging↗
Adhesion Degradation of the Metallization-Encapsulant Interface
Adhesion of the silver metallization/ encapsulant interface was measured through temperature, humidity and voltage bias stress. Results indicate that adhesion at this interface is severely compromised by even short exposures to humidity and quickly plateaus with further, prolonged, exposure. The magnitude of degradation is also identical to that measured through a three-month outdoor, on-sun, exposure. While the addition of a voltage bias also appears capable of further degrading adhesion below this plateau level, in the absence of humidity, adhesion may be similarly degraded.
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