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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 721 records · Page 40
All sourcesNASA NTRSDOE OSTI
DOE OSTI2023

Dislocation-Assisted Quasi-Two-Dimensional Semiconducting Nanochannels Embedded in Perovskite Thin Films

Defect engineering in perovskite thin films has attracted extensive attention recently due to the films’ atomic-scale modification, allowing for remarkable flexibility to design novel nanostructures for next generation nanodevices. However, the defect-assisted three-dimensional nanostructures in thin film matrices usually has large misfit strain and thus causes unstable thin film structures. In contrast, defect-assisted one- or two-dimensional nanostructures embedded in thin films can sustain large misfit strains without relaxation, which make them suitable for defect engineering in perovskite thin films. Here, we reported the fabrication and characterization of edge-type misfit dislocation-assisted two-dimensional BiMnO x nanochannels embedded in SrTiO 3 /La 0.7 Sr 0.3 MnO 3 /TbScO 3 perovskite thin films. The nanochannels are epitaxially grown from the surrounding films without noticeable misfit strain. Diode-like current rectification was spatially observed at nanochannels due to the formation of Schottky junctions between BiMnO x nanochannels and conducting La 0.7 Sr 0.3 MnO 3 thin films. Such atomically scaled heterostructures constitute more flexible ultimate functional units for nanoscale electronic devices.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2024

Compressibility Studies of Copper Selenides Obtained by Cation Exchange Reaction Revealing the New CsCl Phase

In this study, we conducted a high-pressure investigation of Cu 2-x Se nanostructures with pyramid- and plate-like morphologies, created through cation exchange from zinc-blende CdSe nanocrystals and wurtzite CdSe nanoplatelets respectively. Using a diamond anvil cell setup at the APS synchrotron, we observed the phase transitions in the Cu 2-x Se nanostructures up to 40 GPa, identifying a novel CsCl-type lattice with Pm-3m symmetry above 4 GPa. This CsCl-type structure, previously unreported in copper selenides, was partially retained after decompression. Our results indicate that the initial crystalline structure of CdSe does not affect the stability of Cu 2-x Se nanostructures formed via cation exchange. Both morphologies of Cu 2-x Se sintered under compression, potentially contributing to the stabilization of the high-pressure phase through interfacial defects. These findings are significant for discovering new phases with potential applications in future technologies.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2025

Revealing Progressive Degradation of Cobalt Oxide Nanoparticles During Thermochemical Redox Cycling via Operando STEM-EELS

Metal oxides are promising materials for long-duration thermochemical energy storage. Efforts to characterize their reaction kinetics, conversion rate, and morphological evolution during thermochemical cycling have largely focused on bulk and microscale measurements. However, the design of nanostructured metal oxides could improve the reaction reversibility and kinetics, warranting the development of platforms to investigate how these materials behave at the nanoscale. Here, we demonstrate the use of correlative, time-resolved electron energy loss spectroscopy and imaging in an environmental transmission electron microscope for studying the thermochemical cyclability of cobalt oxide nanoparticles with high spatial and temporal resolution. The spectroscopic data reveal a striking decrease in reaction kinetics after the first cycle, resulting from sintering-driven nanostructural densification. Comparison between cycling in humid and dry air shows that atmospheric conditions can modulate reaction transition temperatures but have limited effects on sintering over multiple cycles, suggesting long-term durability will instead rely on synthetic and/or nanostructural modifications.

25 ENERGY STORAGE↗
DOE OSTI2020

Nano-Ceramic Cathodes via Co-sputtering of Gd–Ce Alloy and Lanthanum Strontium Cobaltite for Low-Temperature Thin-Film Solid Oxide Fuel Cells

We report the electrochemical performance and structural characteristics of porous nanostructured ceramic cathodes for thin-film solid oxide fuel cells (TF-SOFCs) based on yttria-stabilized zirconia (YSZ) electrolytes. The nanostructured cathode is obtained through magnetron co-sputtering of gadolinium–cerium (Gd–Ce) alloy and lanthanum strontium cobaltite perovskite targets. The resultant nanostructure and composition of the ceramic cathode are controlled by adjusting the co-sputtering conditions. The peak power densities in our fabricated TF-SOFCs are the highest reported values for YSZ-based electrolyte SOFCs, showing 0.14, 0.48, 1.21, 2.56, and 3.01 W/cm2 at 450, 500, 550, 600, and 650 °C, respectively, operating under air and pure hydrogen fuel. The results show that the porosity and composition of the cathode greatly affect the resulting peak power densities. This work illustrates the capability of sputtering to produce stable, scalable, nano-ceramic cathodes with superb peak power densities when integrated in TF-SOFCs.

25 ENERGY STORAGE↗
DOE OSTI2023

Sub-100 mA/cm 2 CO 2 -to-CO Reduction Current Densities in Hierarchical Porous Gold Electrocatalysts Made by Direct Ink Writing and Dealloying

While most research efforts on CO 2 -to-CO reduction electrocatalysts focus on boosting their selectivity, the reduction rate, directly proportional to the reduction current density, is another critical parameter to be considered in practical applications. This is because mass transport associated with the diffusion of reactant/product species becomes a major concern at a high reduction rate. Nanostructured Au is a promising CO 2 -to-CO reduction electrocatalyst for its very high selectivity. However, the CO 2 -to-CO reduction current density commonly achieved in conventional nanostructured Au electrocatalysts is relatively low (in the range of 1–10 mA/cm 2 ) for practical applications. In this work, we combine direct ink writing-based additive manufacturing and dealloying to design a robust hierarchical porous Au electrocatalyst to improve the mass transport and achieve high CO 2 -to-CO reduction current densities on the order of 64.9 mA/cm 2 with CO partial current density of 33.8 mA/cm 2 at 0.55 V overpotential using an H-cell configuration. Although the current density achieved in our robust hierarchical porous Au electrocatalyst is one order of magnitude higher than the one achieved in conventional nanostructured electrocatalysts, we found that the selectivity of our system is relatively low, namely 52%, which suggests that mass transport remains a critical issue despite the hierarchical porous architecture. We further show that the bulk dimension of our electrocatalyst is a critical parameter governing the interplay between selectivity and reduction rate. In conclusion, the insights gained in this work shed new light on the design of electrocatalysts toward scale-up CO 2 reduction and beyond.

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

Facile Interfacial Reduction Suppresses Redox Chemical Expansion and Promotes the Polaronic to Ionic Transition in Mixed Conducting (Pr,Ce)O 2−δ Nanoparticles

Mixed ionic/electronic conductors (MIECs) are essential components of solid-state electrochemical devices, such as solid oxide fuel/electrolysis cells. For efficient performance, MIECs are typically nanostructured, to enhance the reaction kinetics. However, the effect of nanostructuring on MIEC chemo-mechanical coupling and transport properties, which also impact cell durability and efficiency, has not yet been well understood. Here, in this work, Pr 0.2 Ce 0.8 O 2−δ (PCO20) nanopowders were prepared by coprecipitation, then sintered in a modified dilatometer at three different temperatures (600, 725, and 850 °C) for microstructure evolution, resulting in three samples with different average particle sizes (23, 30, and 53 nm). The chemical strain and electronic/ionic conductivity were then measured simultaneously on stable nanostructures in four isotherms from 550 to 400 °C with steps in pO 2 (1 to 10 –4 atm O 2 ). A microcrystalline bar was prepared and measured for comparison. Particle size reduction led to a monotonically decreasing isothermal redox chemical strain, confirmed by in situ high-temperature, controlled-atmosphere XRD measurements. The corresponding conductivity measurements provided defect chemical insight into the particle size-dependent chemical expansion behavior. The significant weakening of the pO 2 dependence and decreased activation energy for electrical conduction with decreasing particle size indicated a decrease in the reduction enthalpy of PCO, shifting the transition from (Pr) polaronic to ionic behavior to higher pO 2 . STEM-EELS measurements confirmed the majority of Pr was reduced to 3+ in the nanoparticles, while Ce remained 4+. These results demonstrate suppression of deleterious chemical expansion and tailoring of the dominant charge carrier simply through controlling the particle size, providing insights for MIEC microstructural design.

ceria↗
DOE OSTI2020

Assembly of Disordered Cocontinuous Morphologies by Multiblock Copolymers with Random Block Sequence and Length Dispersity

Among the wide variety of nanostructures accessible by self-assembly of block copolymers, cocontinuous morphologies are of great interest for separations, catalysis, sensing, and energy storage due to their ability to integrate distinct properties of the constituent polymers. Furthermore, we investigate the tendency to form disordered cocontinuous phases of multiblock copolymers (MBCs) with random block sequence and length dispersity prepared by step-growth polymerization of pre-made telechelic polymers, specifically using thiol-Michael addition between diacrylate functionalized polystyrene (PS) and poly (D,L - lactide) (PLA) chains and a small molecule dithiol. In the phase diagram so established, disordered cocontinuous nanostructures occupy a wide window (≈ 25 % vol) at a modest segregation strength of χN = 15, close to the critical value for microphase separation. At a higher segregation strength of χN = 30, only a moderately wide (≈ 10 vol %) cocontinuous window is found, with MBCs instead tending to form ordered nanostructures. Although the breadth of the cocontinuous widow is less than that found in prior work on analogous randomly end-linked copolymer networks (RECNs), the MBC architecture offers offsetting advantages in terms of solution and melt processability.

36 MATERIALS SCIENCE↗
DOE OSTI2024

Insights into the Surface Electronic Structure and Catalytic Activity of InO x /Au(111) Inverse Catalysts for CO 2 Hydrogenation to Methanol

In this article, the direct conversion of carbon dioxide (CO 2 ) into methanol (CH 3 OH) via low-temperature hydrogenation is crucial for recycling anthropogenic CO 2 emissions and producing fuels or high value chemicals. Nevertheless, it continues to be a great challenge due to the trade-off between selectivity and catalytic activity. For CO 2 hydrogenation, In 2 O 3 catalysts are known for their high CH 3 OH selectivity. Subsequent studies explored depositing metals on In 2 O 3 to enhance CO 2 conversion. Despite extensive research on metal (M) supported In 2 O 3 catalysts, the role of In-M alloys and M/In 2 O 3 interfaces in CO 2 activation and CH 3 OH selectivity remains unclear. In this work, we have examined the behavior of In/Au(111) alloys and InO x /Au(111) inverse systems during CO 2 hydrogenation using synchrotron-based ambient-pressure X-ray photoelectron spectroscopy (AP-XPS) and catalytic tests in a batch reactor. Indium forms alloys with Au(111) after deposition. The In-Au(111) alloys display high reactivity towards CO 2 and can dissociate the molecule at room temperature to generate InO x nanostructures. At very low coverages of In (≤ 0.05 ML), the InO x nanostructures are not stable under CO 2 hydrogenation conditions and the active In-Au(111) alloys produces mainly CO and little methanol. An increase in indium coverage to 0.3 ML led to stable InOx nanostructures under CO 2 hydrogenation conditions. These InO x /Au(111) catalysts displayed a high selectivity (~ 80 %) towards CH 3 OH production and an activity for CO 2 conversion that was at least 10 times larger than that of plain In 2 O 3 or Cu(111) and Cu/ZnO(000$\overline{1)}$ benchmark catalysts. The results of AP-XPS show that InO x /Au(111) produces methanol via methoxy intermediates. Inverse oxide/metal catalysts containing InOx open up a possibility for improving CO 2 → CH 3 OH conversion in processes associated with the control of environmental pollution and the production of high value chemicals.

36 MATERIALS SCIENCE↗
DOE OSTI2025

Crystalline Peptoid Nanofibers with a Single-Unit Cell Cross Section

Ultranarrow crystalline one-dimensional nanostructures formed from soft materials facilitate precise structural control in nanomaterial design, which is essential for biomedicine and nanotechnology applications. Systematic control of their hierarchical structure is challenging due to the complexities of simultaneously manipulating multiple noncovalent interactions at such small scales. We employed a polypeptoid crystal motif as a supramolecular synthon to engineer ultranarrow crystalline nanofibers constrained to a single lattice axis by incorporating a single ionizable side chain into the hydrophobic core of a nanosheet-forming peptoid. Cryogenic transmission electron microscopy of the nanofibers revealed detailed molecular arrangements of a unit-cell cross-section and the presence of distinct pH-dependent lattice isoforms that resulted in morphological transformations. Molecular dynamics simulations demonstrated that the ionizable side chain plays a critical role in changing the local conformation of the unit cell, which further impacts the dimensionality of hierarchical structures. Moreover, these fibers were readily functionalized with biological ligands to afford one-dimensional (1D) protein arrays. This approach for the high-precision bottom-up assembly of ultranarrow 1D nanostructures offers significant potential for developing novel biomimetic nanostructures.

Lee, Yen Jea↗
DOE OSTI2021

Water mediated growth of oriented single crystalline SrCO3 nanorod arrays on strontium compounds

Abstract Morphology-controlled strontianite nanostructures have attracted interest in various fields, such as electrocatalyst and photocatalysts. Basic additives in aqueous strontium solutions is commonly used in controlling strontianite nanostructures. Here, we show that trace water also serves an important role in forming and structuring vertically oriented strontianite nanorod arrays on strontium compounds. Using in situ Raman spectroscopy, we monitored the structural evolution from hydrated strontium to strontianite nanorods, demonstrating the epitaxial growth by vapor–liquid–solid mechanism. Water molecules cause not only the exsolution of Sr liquid droplets on the surface but also the uptake of airborne CO 2 followed by its ionization to CO 3 2− . The existence of intermediate SrHO + –OCO 2 2− phase indicates the interaction of CO 3 2− with SrOH + in Sr(OH) x (H 2 O) y cluster to orient strontianite crystals. X-ray diffraction simulation and transmission electron microscopy identify the preferred-orientation plane of the 1D nanostructures as the (002) plane, i.e., the growth along the c-axis. The anisotropic growth habit is found to be affected by the kinetics of carbonation. This study paves the way for designing and developing 1D architecture of alkaline earth metal carbonates by a simple method without external additives at room temperature.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Rheological dynamics and structural characteristics of supramolecular assemblies of β-cyclodextrin and sulfonic surfactants

Cyclodextrins are highly functional compounds with a hydrophobic cavity capable of forming supramolecular inclusion complexes with various classes of molecules including surfactants. The resultant rich nanostructures and their dynamics are an interesting research problem in the area of soft condensed matter and related applications. In this paper, we report novel dynamical supramolecular assemblies based on the complexation of β-cyclodextrin with 3 different sulfonic surfactants, which are sodium hexadecylsulfate, sodium dodecylbenzenesulfonate, and myristyl sulfobetaine. It was observed that a β-cyclodextrin : surfactant/2 : 1 molar ratio was ideal for inducing axial growth and imparting large viscosities in the suspensions. Such complexation processes were accompanied by intriguing nanostructural phase behaviors and rheological properties that were very sensitive to the molecular architecture of sulfonic surfactants. The presence of an amino group in the head group of the surfactant allowed for large viscosities that reached 2.4 × 10 4 Pa s which exhibited gel-like behavior. In contrast, smaller viscosity values with a lower consistency index were observed when a bulky aromatic ring was present instead. DIC microscopy was used to visually probe the microstructure of the systems with respect to sulfonate molecular architecture. Additionally, surface tension measurements, and FTIR and NMR spectroscopies were used to gain insights into the nature of interactions that lead to the complexation and nanostructural characteristics. Finally, mechanics correlating the supramolecular morphologies to the rheological properties were proposed.

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

Sequence-dependent self-assembly of supramolecular nanofibers in periodic dynamic block copolymers

Block copolymers (BCPs) can spontaneously self-assemble into various nanostructured morphologies which enable their diverse applications in selective membranes, polymer electrolytes, and optoelectronics. To expand the range of nanostructures accessible to block copolymers, we designed dynamic block copolymers (DBCPs) that combine the phase separation of traditional block copolymers with the supramolecular self-assembly of periodic dynamic polymers. We demonstrate that DBCPs synthesized with a periodic block sequence self-assemble into high aspect ratio supramolecular nanofibers with well-ordered PEG and PDMS domains, in contrast to those synthesized with a random sequence which do not form nanofibers but have disordered morphologies. The periodicity of the block sequence ensures regular placement of dynamic bonds along the polymer chain, which enables stacking of the hydrogen bonding units into ordered 1D supramolecular nanofibers and delays the onset of terminal flow by up to 60 °C compared to the random block sequence. The hierarchically assembled supramolecular nanofibers display complex mechanical and thermal phase behavior arising from the interplay between phase separation of the dissimilar polymer backbones and supramolecular interactions between dynamic bonds. Despite identical bulk composition, the periodic DBCPs demonstrate ionic conductivity values over two orders of magnitude higher than their random counterparts due to the formation of well-ordered, interconnected, high aspect ratio ion-transporting PEG domains. In conclusion, these results highlight the potential for DBCPs as an emerging material platform to achieve advanced, self-assembled nanostructured morphologies.

36 MATERIALS SCIENCE↗
DOE OSTI2026

Structured for success: conjugated polymer binders with tailored composition and architecture for lithium-ion batteries

Conjugated polymer binders are replacing conventional binders in lithium-ion batteries. Herein, we examine how molecular engineering and hierarchical nanostructuring govern binder functionality and electrochemical performance. Lithium-ion batteries (LIBs) are the leading energy storage technology, yet enhancing their energy density and cycle life remains critical. Significant progress has been made in high-capacity anodes and high-voltage cathodes, but their performance is hindered by electrode degradation, where it is related to the behaviors of binders at the surface and interface. Conventional non-conductive binders like poly(vinylidene difluoride) (PVDF), combined with conductive additives, often fail to maintain electrical pathways under repeated volume changes. Alternatively, conjugated polymer binders have emerged as a superior alternative, simultaneously offering intrinsic conductivity, mechanical flexibility, and strong adhesion through π-conjugated backbones and functional groups. Their tunable molecular structure enables efficient electron/ion transport while mitigating electrode cracking. Additionally, the development of hierarchically ordered nanostructures in conjugated polymer binder can further enhance their electrochemical performance. This review examines the design principles of conjugated polymer binders, focusing on molecular engineering and nanostructural control to optimize their performance in high-loading electrodes, such as silicon-based anodes. By addressing key challenges in binder functionality, these advanced materials pave the way for next-generation high-energy-density LIBs.

Jin, Xiuyu↗
DOE OSTI2025

Harnessing emergent multiple scattering resonances in a photonic glass structure for photoelectrochemical energy conversion

Light trapping nanostructures are often necessary to improve carrier collection yields in semiconductor photoelectrodes with intrinsically poor electron transport. Photonic crystal templates can generate tailorable light trapping via periodic and precise nanostructure, though this is not a scalable strategy for photoelectrochemical (PEC) applications. It is therefore critical to identify alternative mechanisms for light trapping that tolerate disorder. Light trapping in disordered media is generated by the diffusive transport caused by multiple scattering. In some cases, multiple scattering can generate resonances that resemble those observed in photonic crystals. While resonant multiple scattering is a disorder tolerant light trapping mechanism, it is unclear if the effect is sufficiently adaptable, or even useful, for PEC applications. Here, we describe a photonic omission glass, a nanostructure that can controllably induce resonances in multiple scattering transport. We characterized the emergence of these resonances after coating a disordered SiO 2 colloidal structure with a layer of TiO 2 , which functions both as dielectric contrast and as a light absorbing semiconductor. We show in finite element simulations and spectroscopic characterization that the resonant multiple scattering effect improves light trapping near the interface between the structure and the bulk electrolyte. This effect, coupled with the increased electrochemically active surface area, results in a hierarchically structured TiO 2 photoanode with orders of magnitude higher photocurrents compared to an equivalent planar photoanode for PEC reactions such as alkaline water oxidation. We show that controlling this resonant multiple scattering effect can be advantageous for improving PEC energy conversion in disordered photoelectrodes.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2020

Morphology and chemical behavior of model CsO x /Cu 2 O/Cu(111) nanocatalysts for methanol synthesis: Reaction with CO 2 and H 2

Cs is a promoter of Cu-based catalysts for the synthesis of alcohols from CO 2 hydrogenation. Scanning tunneling microscopy and ambient-pressure x-ray photoelectron spectroscopy were used to study the morphology and chemical properties of surfaces generated by the deposition of cesium on Cu 2 O/Cu(111) and Cu(111) substrates. CsO x nanostructures were formed after Cs metal was deposited on Cu 2 O/Cu(111) at 300 K. The formed CsO x protrude over the surface of copper oxide by 2–4 Å, with the dimension at the base of the nanostructures being in the range of 1–3 nm. Heating to elevated temperature induced significant changes in the size and dispersion of the CsO x nanostructures, and there was a clear reconstruction of the copper oxide substrate, which then exhibited long range order with a hexagonally packed structure. The as-deposited and annealed surfaces of CsO x /Cu 2 O/Cu(111) were more reactive toward CO 2 than plain Cu 2 O/Cu(111) or clean Cu(111). Yet, none of them were stable in the presence of H 2 , which fully reduced the copper oxide at 400–450 K. In CsO x /Cu(111), the CsO x nanoclusters were dispersed all over the metallic copper in no particular order. The CsO x species had an average width of 2 nm and ~1 Å height. The CsO x /Cu(111) systems exhibited the highest activity for the binding and dissociation of CO 2 , indicating that the CsO x -copper interface plays a key role in alcohol synthesis.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2020

Introduction to special issue: Colloidal quantum dots

The quantum confinement effect has driven the development and exploration of colloidal semiconductor nanocrystals over approximately the past three decades. These semiconductor nanostructures are typically synthesized as stable colloidal dispersions in solution-phase chemical batch reactions at relatively low temperatures. Researchers have developed a wide range of reaction conditions to produce a variety of shapes, compositions, and structures with well-controlled sizes and low polydispersities. The shape can be controlled to produce confinement in one, two, or all three spatial dimensions, the latter defining a “quantum dot.” Combining two or more semiconductors within the various nanostructures produces additional optical and electronic degrees of freedom. These mixed compositional nanostructures have properties not accessible in bulk semiconductor systems. Further, researchers have fabricated novel nanoheterostructures, such as “dot-in-rods,” quantum wells, core/shell structures, giant-core/shell tetrapods where the core is one material and the arm is another, Janus structures that consist of spherical structures with well-defined internal heterostructures, nano-dumbbells, hollow-core structures, and many other novel and interesting structures. The structural variations are seemingly only limited by the creativity of the various researchers engaged in these endeavors.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Effects of surface vacancy-adatom pair formation on PFC tungsten surface morphological response

Abstract We report a simulation study of the effect of He-irradiation-induced surface vacancy-adatom pair formation on the surface morphological evolution of plasma-facing component (PFC) tungsten and examine a number of factors that impact such evolution. Our analysis is based on self-consistent dynamical simulations according to an atomistically-informed, continuum-scale surface evolution model that has been developed following a hierarchical multiscale modeling strategy and can access the spatiotemporal scales of relevance to fuzz formation. The model accounts for the flux of surface adatoms generated as a result of the surface vacancy-adatom pair formation effect upon He implantation, which contributes to the anisotropic growth of surface nanostructural features due to the different rates of adatom diffusion along and across step edges of islands on the tungsten surface. We have carried out atomic-scale computations of optimal diffusion pathways along and across island step edges on the W(110) surface and calculated Ehrlich–Schwoebel (ES) barriers in adatom diffusion along and across such step edges. This aspect of surface adatom diffusion contributes to anisotropic surface atomic fluxes, terrace and step diffusive currents, and has been incorporated into our PFC surface evolution model, which predicts the formation of preferentially aligned nanoridge stripe patterns on the PFC surface. We establish that these anisotropic diffusive currents accelerate nanotendril growth on the PFC surface and the onset of surface nanostructure pattern formation. We also explore systematically the dependence of the PFC surface morphological response on the surface temperature and He ion incident flux, characterize in detail the resulting surface topographies and growth kinetics, and compare the predicted surface morphologies with experimental observations. Our simulation predictions for the emerging surface nanostructure patterns under certain plasma exposure conditions are consistent with experimental findings in the literature.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Active Temporal Control of Radiative Heat Transfer with Graphene Nanodisks

The ability to dynamically control the radiative transfer of heat at the nanoscale holds the key to the development of a diverse number of technologies, ranging from nanoscale thermal-management systems to improved thermophotovoltaic devices. Recently, graphene has emerged as an ideal material to achieve this goal, since it can be electrically doped to support surface plasmons, collective oscillations of the conduction electrons. These resonances produce large and spectrally narrow optical cross sections, which dictate the emission and absorption properties of the graphene nanostructure and, thus, the heat that it radiatively exchanges with other objects and the environment. For attainable levels of doping, the plasmons supported by graphene nanostructures naturally lie in the midinfrared part of the spectrum, which is the most relevant wavelength range for radiative heat transfer under realistic temperatures. Furthermore, these resonances are actively tunable, thus providing full dynamic control over the heat transfer. Motivated by this great potential, we present a comprehensive analysis of the temporal evolution of the radiative heat transfer between arrangements of graphene nanodisks, showing that it is possible to exploit the tunability of these structures to obtain actively controlled heat transfer scenarios not possible with conventional passive nanostructures. We report the results of this work provide a framework for achieving fully dynamical control over nanoscale radiative heat transfer and thus provide fundamental insights into this process.

36 MATERIALS SCIENCE↗