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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 775 records · Page 43
All sourcesNASA NTRSDOE OSTI
DOE OSTI2015

Utilizing maleic acid as a novel fuel for synthesis of PbFe{sub 12}O{sub 19} nanoceramics via sol–gel auto-combustion route

PbFe{sub 12}O{sub 19} nanostructures were prepared in an aqueous solution by the sol–gel auto-combustion method using Pb(NO{sub 3}){sub 2} and Fe(NO{sub 3}){sub 3} as starting materials and various carboxylic acids, including oxalic acid, malonic acid, succinic acid and maleic acid as fuel and reducing and capping agents. The as-synthesized products were characterized by X- ray diffraction, scanning electron microscopy, and X-ray energy dispersive spectroscopy. The effect of carboxylic acid type, Pb{sup +} {sup 2} to carboxylic acid molar ratio, and calcination temperature was investigated on the morphology of the products and several experiments were carried out to obtain the optimal reaction conditions. It was found that the phase and the morphology of the products are influenced by the investigated parameters. Furthermore, vibrating sample magnetometer (VSM) was used to study the magnetic properties of PbFe{sub 12}O{sub 19} samples. - Graphical abstract: Display Omitted - Highlights: • PbFe{sub 12}O{sub 19} nanoceramics were synthesized from Fe(NO{sub 3}){sub 3} and Pb(NO{sub 3}){sub 2} via the sol–gel auto combustion method. • The maleic acid can be instead of common capping agent and fuel in auto-combustion sol–gel. • The synthesized PbFe{sub 12}O{sub 19} is a hard magnetic material. • The specific saturation magnetization and coercivity are 27 emu/g and 1900 Oe, respectively.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2023

Additive manufacturing as a processing route for steel-aluminum bimetallic structures

Here we present results on the fabrication of steel-aluminum bi-metallic structures using directed energy deposition additive manufacturing. The challenges associated with the fabrication of a sharp transition from steel to aluminum are uncovered using ex-situ characterization techniques and thermo-mechanical modeling of the deposition process. It was found that the fabrication of a sharp steel-aluminum transition is challenging with extensive cracking observed at the interface. The cracking was attributed to the combined effect of residual stress development due to thermal expansion coefficient mismatch and the presence of ordered intermetallics with low ductility at the interface. Using a coupled thermodynamic and thermo-mechanical modeling approach, potential pathways to enable the fabrication of steel-aluminum bi-metallic structures using additive manufacturing are proposed. The results presented here can lay the foundation for future work on the fabrication of bi-metallic steel-aluminum structures using directed energy deposition.

36 MATERIALS SCIENCE↗
DOE OSTI2013

A facile mixed-solvothermal route to γ-Bi{sub 2}MoO{sub 6} nanoflakes and their visible-light-responsive photocatalytic activity

Graphical abstract: γ-Bi2MoO6 nanoflakes were successfully synthesized by a mixed-solvothermal process. The visible-light-responsive photocatalytic activities of the obtained γ-Bi2MoO6 nanoflakes were evaluated by photodegradation of Rhodamie B under visible light. The high degradation efficiency of RhB was attributed to the good crystallization and flake-like morphology of γ-Bi2MoO6 nanostructures, which is in accord with the photocurrent result. - Highlights: • γ-Bi{sub 2}MoO{sub 6} nanoflakes were obtained by a mixed-solvothermal process with SDBS as surfactant. • The photocurrent test was taken to characterize the photocatalytic activity. • The nanopowders exhibit high efficient photocatalytic activity under visibile-light irradiation. - Abstract: γ-Bi{sub 2}MoO{sub 6} nanoflakes were successfully synthesized by a mixed-solvothermal process with SDBS involved in the reaction. The as-prepared γ-Bi{sub 2}MoO{sub 6} was characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), and UV–vis absorption spectroscopy. The effect of different ratio of solvents on the resulting products was investigated. The visible-light-responsive photocatalytic activities of the obtained γ-Bi{sub 2}MoO{sub 6} nanoflakes were evaluated by photodegradation of Rhodamie B under visible light (λ > 400 nm). The high degradation efficiency of RhB was attributed to the good crystallization and flake-like morphology of γ-Bi{sub 2}MoO{sub 6} nanostructures, which is in accord with the photocurrent result.

36 MATERIALS SCIENCE↗
DOE OSTI2013

Effect of reductant and PVP on morphology and magnetic property of ultrafine Ni powders prepared via hydrothermal route

Graphical abstract: The ultrafine Ni powders with the shapes including sphere, pearl-string, leaf, fish-bone, hexagonal sheet and silknet were prepared through one-step hydrothermal reduction using different reductants. Their saturation magnetization, remanent magnetization and coercivity sequentially increase, and the coercivity of hexagonal sheet-like Ni powders increases by 25% compared with the Ni bulk counterpart. - Highlights: • The ultrafine Ni powders with various shapes of sphere, fish-bone, hexagonal sheet, etc. • Facile and one-step hydrothermal reduction using three reductants and PVP additive was developed. • Magnetic properties of the ultrafine Ni powders with different shapes were measured. • Compared with bulk Ni material, coercivity of hexagonal sheet Ni increases by 25%. • The formation mechanism of the shapes was suggested. - Abstract: The ultrafine nickel particles with different shapes including sphere, pearl-string, leaf, fish-bone, hexagonal sheet and silknet were prepared through one-step hydrothermal reduction using hydrazine hydrate, sodium hypophosphite and ethylene glycol as reductants, polyvinylpyrrolidone as structure-directing agent. It has been verified with the characterization of X-ray powder diffraction and transmission/scanning electronic microscopy that as-prepared products belong to face-centered cubic structure of nickel microcrystals with high purity and fine dispersity. The magnetic hysteresis loops measured at room temperature reveal that the values of saturation magnetization, remanent magnetization and coercivity rise sequentially from silknet, sphere to hexagonal sheet. In comparison with nickel bulk counterpart, the coercivity of the hexagonal sheet nickel powders increases by 25%.

36 MATERIALS SCIENCE↗
DOE OSTI2014

CdSe@ZnS nanocomposites prepared by a mechanochemical route: No release of Cd{sup 2+} ions and negligible in vitro cytotoxicity

Graphical abstract: - Highlights: • CdSe@ZnS nanocomposites were produced by milling. • Negligible cadmium leakage was observed. • No toxicity against living cells was documented. • The material is suitable for biological imaging. - Abstract: CdSe@ZnS nanocomposites have been prepared by a two-step solid state mechanochemical synthesis. CdSe prepared from Cd and Se elements in the first step was mixed with zinc acetate and sodium sulphide in the second step of milling to prepare a CdSe@ZnS nanocomposite. In the third step, the obtained nanocomposite was coated with L-cysteine to prepare a biocompatible system. The crystallite size of the new type of nanocomposite was 20–35 nm for cubic CdSe and 3–8 nm for hexagonal ZnS as calculated from XRD, TEM and SEM data. The synthesised samples show good crystallinity and have been tested for dissolution and cytotoxicity. The dissolution of cadmium from CdSe@ZnS was less than 0.05 μg mL{sup −1}, whereas a value of 0.8 μg mL{sup −1} was measured for CdSe alone. The binding of ZnS with CdSe in the nanocomposite practically eliminated the release of cadmium into solution. As a consequence, a very low cytotoxic activity has been evidenced for CdSe@ZnS. The nanocomposites coated with L-cysteine have a great potential as fluorescent labels in biomedical engineering.

36 MATERIALS SCIENCE↗
DOE OSTI2014

Synthesis of luminescent nanocrystals and solid solutions in the YNbO{sub 4}–EuNbO{sub 4} system via hydrothermal route

Highlights: • Nanocrystals: YNbO{sub 4}:Eu{sup 3+} were directly formed under hydrothermal conditions at 240 °C. • The nanocrystals (10–20 nm) were luminescent and had ellipsoidal morphology. • The complete solid solutions in the YNbO{sub 4}–EuNbO{sub 4} system were also directly formed. • The PL intensity and R/O intensity ratio changed depending on heating temperature. - Abstract: Luminescent nanocrystals having distinctive ellipsoidal morphology and the complete solid solution of monoclinic phase in the YNbO{sub 4}–EuNbO{sub 4} system were hydrothermally formed under weakly basic conditions at 180–240 °C for 5 h. The excitation spectra of the Y{sub 1−x}Eu{sub x}NbO{sub 4} nanocrystals, which consisted of the charge transfer (CT) band around 240–270 nm due to [NbO{sub 4}]{sup 3−}–Eu{sup 3+} interaction and several sharp bands corresponding to the f–f transitions of Eu{sup 3+}, e.g. the most intense absorption band at 395 nm ({sup 7}F{sub 0}→{sup 5}L{sub 6}), showed that the compounds could be excited by both ultraviolet and visible light. A dominant red emission at 610 nm and a weak orange emission at 590 nm assigned to {sup 5}D{sub 0}→{sup 7}F{sub 2} and {sup 5}D{sub 0}→{sup 7}F{sub 1} transitions of Eu{sup 3+}, respectively were observed in the as-prepared nanocrystals containing europium under excitation at 395 nm. The heat treatment at temperatures more than 1000 °C in air was effective for the improvement in the photoluminescence intensity of the as-prepared solid solutions. By the enhancement in the crystallinity and crystallite growth of the monoclinic phase through heat treatment at 1300 °C in air, the luminescence intensity of the as-prepared solid solution, Y{sub 0.75}Eu{sub 0.25}NbO{sub 4} (x = 0.25), which showed the most significant photoluminescence, became more than 5 times as strong as that before the heat treatment.

36 MATERIALS SCIENCE↗
DOE OSTI2014

A facile route to synthesize CdZnSe core–shell-like alloyed quantum dots via cation exchange reaction in aqueous system

Highlights: • Water-soluble CdZnSe alloyed QDs synthesized by cation exchange reaction. • The as-prepared CdZnSe QDs have fairly good luminescence properties. • The surface defects of obtained QDs were removed due to the alloyed structure. - Abstract: Water-soluble CdZnSe alloyed nanocrystals have been successfully prepared via “green” cation exchange reaction in aqueous system. The X-ray diffraction (XRD) patterns indicate that the as-prepared nanocrystals had high crystallinity and small particle size of 4–5 nm. The absorption spectra of CdZnSe show red shift of 100 nm from 375 to 475 nm. Moreover, the band-gap photoluminescent (PL) emission has a red shift of 50 nm from 430 to 480 nm with the increase of the reaction time. On the basis of the PL properties and transmission electron microscopy (TEM) images, one kind of core–shell-like structure model was proposed, which resulted from the different cation exchange reaction rates. This structure could greatly improve the luminescence properties by the removal of surface defect of quantum dots. This work would support potential applications in optoelectronic devices, and biomedical tags fields.

36 MATERIALS SCIENCE↗
DOE OSTI2014

Structure and electrochemistry of NaFePO{sub 4} and Na{sub 2}FePO{sub 4}F cathode materials prepared via mechanochemical route

Highlights: • Na{sub 2}FePO{sub 4}F is prepared by mechanochemically assisted solid state synthesis. • The crystal and local structure are studied by XRPD, FTIR, Mössbauer, and NMR. • Na{sup +}/Li{sup +} ion exchange is completed with the formation of NaLiFePO{sub 4}F. • The average D{sub Li} (10{sup −15} cm{sup 2} s{sup −1}) is determined from GITT measurements. - Abstract: Nanostructured NaFePO{sub 4} (space group Pmnb) and Na{sub 2}FePO{sub 4}F (space group Pbcn) were prepared by a quick and facile mechanochemically assisted solid state synthesis. Low-crystalline Na{sub 2}FePO{sub 4}F was formed as a result of direct mechanochemical reaction of NaFePO{sub 4} with NaF. It crystallizes upon subsequent heating to 600 °C and decomposes at higher temperatures. Crystal and local structure were analyzed by XRD using Rietveld refinement, FTIR, Mössbauer, and NMR spectroscopy. Electrochemical properties were studied by galvanostatic cycling in lithium cells and GITT. Although NaFePO{sub 4} showed some electrochemical activity, neither electrochemical nor chemical Na{sup +}/Li{sup +} exchange was observed by XRD. On contrary, electrochemical and chemical Na{sup +}/Li{sup +} ion exchange occurred in the case of Na{sub 2}FePO{sub 4}F and accomplished with the NaLiFePO{sub 4}F formation. Li{sup +} diffusion coefficient in NaLiFePO{sub 4}F at different delithiated/lithiated states was determined from GITT. Carbon-coated Na{sub 2}FePO{sub 4}F shows discharge capacity of 116 mA h g{sup −1} at 0.1 C rate within the 2.0–4.2 V voltage range and a good cyclability.

36 MATERIALS SCIENCE↗
DOE OSTI2015

A simple route for making surfactant free lead sulfide (PbS) quantum dots

Highlights: • Surfactant free PbS NCs were successfully synthesised using CoSP technique. • The technique eliminates the requirements of washing to remove the ligands. • Grinding using mortar and pestle creates well separated PbS QDs. • Surfactant free PbS NCs are stable and do not show any degradation with time. - Abstract: An efficient, cost effective and less time consuming method suitable for mass production of surfactant free quantum dots (QDs) of lead sulfide (PbS) is reported. PbS nanocrystals (NCs) are first synthesised by continuous spray pyrolysis (CoSP) technique and de-agglomeration into PbS quantum dots (QDs) is achieved by vigorous mechanical grinding using mortar and pestle. Lead acetate and thiourea were used as the precursor materials for preparation of surfactant free PbS NCs. The broadening in XRD peaks of ground NCs as compared to as synthesized PbS NCs clearly indicated the reduction in particle size to be QDs of PbS. The TEM images also showed that ground PbS NCs were nearly spherical in shape having an average diameter in the range of 4–6 nm. The shift in optical gap from 0.41 eV to 1.47 eV supported the QD formation.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2016

A soft chemical route to the synthesis of BiFeO{sub 3} nanoparticles with enhanced magnetization

Highlights: • Pure BiFeO{sub 3} nanoparticles have been synthesized at relatively low temperature. • Decomposition behavior of BiFeO{sub 3} precursor gel is investigated. • Particle size dependent magnetic properties have been confirmed. • Greatly improved magnetization is observed for BiFeO{sub 3} nanostructure. - Abstract: Utilization of BiFeO{sub 3} (BFO) into modern device applications is restricted by its very low magnetic moments and high leakage current. Enhancement in magnetization is a real challenge for multiferroic BFO in the context of device miniaturization and high density information storage system. In this study a significant improvement in magnetization has been recorded for BFO nanoparticles, exploiting the beneficial effect of size confinement. BFO nanoparticles with different size in the range of 21–68 nm are synthesized via modified Pechini sol–gel approach followed by leaching with acetic acid. X-ray diffraction result confirms pure and well crystallized BFO annealed at temperature lower than 600 °C, compared to more than 800 °C for the traditional solid-state sintering process. A strong size-dependent magnetization which increases with decreasing particle size is confirmed with a value of 1.4 emu/g for 40 nm particles in contrast to 7.5 emu/g for 21 nm particles.

36 MATERIALS SCIENCE↗
DOE OSTI2016

Photocatalytic activity of Li-doped TiO{sub 2} nanoparticles: Synthesis via ionic liquid-assisted hydrothermal route

Highlights: • TiO{sub 2}: Li nanoparticles were synthesized via an ionic liquid-assisted hydrothermal method. • The doping of Li to anatase TiO{sub 2} affects the properties of the resultant product. • TiO{sub 2}: Li nanoparticles were used as a photocatalyst for the degradation of dye. • TiO{sub 2}: Li nanoparticles were used as sensor, and antibacterial agent. • TiO{sub 2}: Li were used as reducing agent for the reduction of Cr{sup 6+} to Cr{sup 3+}. - Abstract: We have proposed a simple one pot synthesis of lithium-doped TiO{sub 2} nanoparticles (TiO{sub 2}:Li) via an ionic liquid-assisted hydrothermal method and their potential use as a photocatalyst for the degradation of organic dye, as well as the reduction of toxic Cr{sup 6+} to non toxic Cr{sup 3+}. The structure of TiO{sub 2}:Li nanoparticles was examined by XRD, FTIR, XPS, Raman, UV–vis, Photoluminescence spectroscopy and morphology by SEM and TEM. The incorporation of Li into anatase-phase TiO{sub 2} affected the optical properties of the resultant TiO{sub 2} nanoparticles. The photocatalytic activity of the TiO{sub 2}:Li nanoparticles was determined by degradation of trypan blue. Degradation studies showed improved photocatalytic activity of TiO{sub 2}:Li nanoparticles compared to TiO{sub 2} nanoparticles and bulk TiO{sub 2}. TiO{sub 2}:Li nanoparticles also functioned as a detoxification agent which was confirmed by the reduction of Cr{sup 6+} to Cr{sup 3+}.

36 MATERIALS SCIENCE↗
DOE OSTI2016

Studies on synthesis of reduced graphene oxide (RGO) via green route and its electrical property

Highlights: • RGO-1 and RGO-2 were synthesized by green method using different phytoextracts. • M. indica L., S. tuberosum L. phytoextracts act as reducing and stabilizing agents. • Conjugated structure of graphene is established following partial reduction of GO. • Electrical conductivities of RGO-1 and RGO-2 are higher than GO. - Abstract: An environmentally friendly method has been applied for the preparation of reduced graphene oxide (RGO). This method was developed by using polyphenols that contained a phytoextract of Mangifera indica L. along with Solanum tuberosum L. as reducing agents since they are non-toxic and naturally available. The phytoextracts used in the production of RGO was set between 60 and 70 °C. Graphene oxide (GO) was prepared by modified Hummer’s method as reported in earlier findings. Structural and morphological studies demonstrate that the part of the oxygen functionalities in GO can be removed by following green reduction. Characterizations of the resulting product have been done by X-ray diffraction, FTIR, UV–vis and Raman spectroscopy. FESEM, TEM, EDX spectrum, TGA, DLS and Zeta potential measurements of the samples have also been carried out to study the morphological, thermal and surface charge characteristics. Electrical conductivity was also measured to check the extent of reduction of GO to RGO.

36 MATERIALS SCIENCE↗
DOE OSTI2017

Structural and magnetic properties of nanocrystalline Bi{sub 1-x}La{sub x}FeO{sub 3} (0.0 ≤ x ≤ 0.4) synthesized by a mechanochemical route

Highlights: • A mechanochemical reaction produces Bi{sub 1-x}La{sub x}FeO{sub 3} and NaCl in ambient conditions. • Heating at 600 °C and ulterior washing yields ferrite phase for all the compositions. • The synthesized powders consist of agglomerates of Bi{sub 1-x}La{sub x}FeO{sub 3} nanoparticles. • La-content influences the crystal structure and Néel temperature of the materials. • The presence of two canting levels of antiparallel spins causes a complex magnetism. - Abstract: Bi{sub 1-x}La{sub x}FeO{sub 3} (0.0 ≤ x ≤ 0.4) powders were prepared by means of a solid acid-base reaction induced by mechanochemical energy. Bi, La and Fe chlorides were high-energy ball-milled with NaOH, yielding a mixture of Bi{sub 1-x}La{sub x}FeO{sub 3} and NaCl. After heating and washing, nanoparticles of Bi{sub 1-x}La{sub x}FeO{sub 3} were obtained as a main product, with low contents of secondary phases. Structural characterization was performed by X-ray diffraction (Rietveld refinement) and Raman spectroscopy. The hyperfine magnetic behavior was analyzed by means of Mössbauer spectroscopy and the microstructure of the particles was evaluated by transmission electron microscopy. Differential scanning calorimetry was employed to investigate the thermal behavior of the samples and magnetic measurements at room temperature were also carried out. Crystal structure transitions as a function of composition were identified. Moreover, an intricate magnetic behavior was observed, which was explained on the basis of the concomitant contribution of two different canting levels of the antiparallel spins.

36 MATERIALS SCIENCE↗
DOE OSTI2018

A facile in-situ etching route to hollow C@SnO2 nanocomposites and their gas-sensing properties

Highlights: • Hollow C@SnO{sub 2} nanostructure has been designed via a facile in-situ etching technique.. • The C@SnO{sub 2} products possess a high surface are and a hollow carbon core. • The growth of SnO{sub 2} nanosheets and the removal of silica template can be synchronously performed. • The C@SnO{sub 2} products manifest highly sensitive and selective to n-butanol as gas-sensing sensor. - Abstract: A novel hollow carbon@SnO{sub 2} nanocomposite has been developed via a high cost-effective and facile in-situ etching technique. The as-prepared C@SnO{sub 2} product has a high surface area of about 115 m{sup 2} g{sup −1} and a hollow carbon core, where a lot of SnO{sub 2} nanosheets grow onto the carbon shell. Particularly, the silica core as the sacrificial template can be fully removed by hydrofluoric acid (HF) byproduct during the reaction process. Moreover, the deposition of SnO{sub 2} sheets and the removal of the silica template can be synchronously performed by a simple one-step process. When applied as the gas-sensing material, the C@SnO{sub 2} product manifests highly sensitive and selective to n-butanol. The large surface area, hollow nanostructure and the perfect combination of SnO{sub 2} nanosheets and carbon layer contribute to the enhanced gas-sensing performances. The method described in our work can also be employed to design other hollow metal oxides@carbon hybrids for energy storage and catalysis.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2018

Phase transition and luminescence properties of GdTiNbO6:Eu3+ formed by hydrothermal route

Highlights: • Phase transition and luminescence of hydrothermal GdTiNbO{sub 6}:Eu{sup 3+} were investigated. • RE{sup 3+} radius 0.1061 nm was the boundary between the aeschynite and euxenite. • GdTiNbO{sub 6}:0.30Eu{sup 3+} was preferred for UV-B excitation, 0.50Eu{sup 3+} for Vis-light excitation. • The decay lifetime of 615 nm emission (ex = 405 nm) was 570∼571 μs. - Abstract: The dependences of phase transition and luminescence properties upon both Eu{sup 3+} concentration and heating temperature in air were investigated for GdTiNbO{sub 6}:Eu{sup 3+} fine crystals formed hydrothermally at 240 °C as aeschynite-type Eu{sub x}Gd{sub 1-x}TiNbO{sub 6} solid solution. The as-prepared aeschynite solid solution in the concentration range x ≥ 0.70 did not show the phase transformation from an aeschynite- to an euxenite-type structure caused by heating at 1300 °C for 1 h in air. The present study suggested that the phase boundary between the aeschynite- and euxenite-type RETiNbO{sub 6} in the EuTiNbO{sub 6}-GdTiNbO{sub 6} system, where RE was a rare earth, lay in the average RE{sup 3+} ionic radius 0.1061 nm. The intense emissions attributed to the {sup 5}D{sub 0}→{sup 7}F{sub 1} and {sup 5}D{sub 0}→{sup 7}F{sub 2} transitions of Eu{sup 3+} for the as-prepared samples were more improved by heating at 1100–1300°C in air. The material doped with 30 mol% Eu{sup 3+} was preferred for UV-B excitation, in contrast, the material with 50 mol% Eu{sup 3+} was preferred for visible light excitation.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2018

A rapid molecular precursor solid-state route to crystalline Fe 2 GeS 4 nanoparticles

Iron germanium sulfide (Fe 2 GeS 4 ) recently emerged as a potential thin film solar photovoltaic absorber. The introduction of the third element—germanium (Ge)—viewed as a solution for overcoming multiple barriers of a photovoltaic pyrite, confers stability to Fe 2 GeS 4 at elevated temperatures, typically required for accomplishing grain growth in Gen 2 thin film PV. A facile synthesis of Fe 2 GeS 4 nanoparticles from molecular precursors, comprising mechanical mixing of starting materials followed by a two-hour annealing in a sulfur-rich atmosphere is presented herein. Further processing of the resulting Fe 2 GeS 4 nanopowders at elevated temperatures demonstrates high thermal stability of Fe 2 GeS 4 (up to 500 °C), in comparison with pyrite, which shows onset of pyrrhotite upon heating above 160 °C. Based on the secondary crystalline phases formed, here we propose a mechanism of decomposition of Fe 2 GeS 4 at high temperatures. Films fabricated with Fe 2 GeS 4 were further annealed and revealed that Fe 2 GeS 4 withstands high temperatures in thin film.

36 MATERIALS SCIENCE↗
DOE OSTI2024

A general flame aerosol route to high-entropy nanoceramics

High-entropy ceramics are an emerging class of materials with fascinating characteristics. However, elemental immiscibility and crystal complexity limit the development of a general synthesis strategy, and common methods yield bulk materials. Here, we introduce a transformative non-equilibrium flame aerosol technique for synthesizing high-entropy nanoceramics. This scalable, one-step process enables the production of high-entropy oxide nanoceramics with an unprecedented diversity of crystal structures, including fluorite-phase materials that integrate up to 22 distinct cation elements. The method’s capacity for entropic stabilization and grain refinement significantly improves the thermal stability of these nanostructures. In a representative application, a Pt-(MgCoNiCuZn)O high-entropy single-atom catalyst showed superior activity and long-term stability, maintaining constant CO 2 conversion over 670 h and dramatically outperforming conventional catalysts. Finally, the general approach opens a vast composition and structure space for the creation of high-entropy oxide nanomaterials for application across diverse fields, including catalysis, energy storage, sensing, and thermal management.

36 MATERIALS SCIENCE↗