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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 307 records · Page 17
All sourcesNASA NTRSDOE OSTI
DOE OSTI2019

High-performance room-temperature sodium–sulfur battery enabled by electrocatalytic sodium polysulfides full conversion

Room-temperature sodium–sulfur (RT-Na–S) batteries are highly desirable for grid-scale stationary energy storage due to their low cost; however, short cycling stability caused by the incomplete conversion of sodium polysulfides is a major issue for their application. Herein, we introduce an effective sulfiphilic host, gold nanodots decorated on hierarchical N-doped carbon microspheres (CN/Au/S), to achieve completely reversible conversion reactions in the S cathode by electrocatalyzing the low-kinetics conversion of Na 2 S 4 into NaS 2 (discharge process) or S (charge process). Besides, gold nanodots and N-doped carbon can increase the conductivity of the S cathode and provide strong polar–polar adsorption of sodium polysulfides to alleviate the shuttling effects. When serving as the cathode, the CN/Au/S composite can realize enhanced sulfur utilization, excellent cycling stability, and outstanding rate capability. This work deepens our understanding of the catalytic effect of gold atoms on sulfur molecules, opening a new avenue for cathode design and development of advanced RT-Na–S batteries.

25 ENERGY STORAGE↗
DOE OSTI2021

Gamma radiation-induced defects in KCl, MgCl 2 , and ZnCl 2 salts at room temperature

Room temperature post-irradiation measurements of diffuse reflectance and electron paramagnetic resonance spectroscopies were made to characterize the long-lived radiation-induced species formed from the gamma irradiation of solid KCl, MgCl 2 , and ZnCl 2 salts up to 100 kGy. The method used showed results consistent with those reported for electron and gamma irradiation of KCl in single crystals. Thermal bleaching of irradiated KCl demonstrated accelerated disaggregation of defect clusters above 400 K, due to decomposition of Cl 3 - . The defects formed in irradiated MgCl 2 comprised a mixture of Cl 3 - , F-centers, and Mg + associated as M-centers. Further, Mg metal cluster formation was also observed at 100 kGy, in addition to accelerated destruction of F-centers above 20 kGy. Irradiated ZnCl 2 afforded the formation of Cl 2 - due to its high ionization potential and crystalline structure, which decreases recombination. The presence of aggregates in all cases indicates the high diffusion of radicals and the predominance of secondary processes at 295 K. Additionally, thermal bleaching studies showed that chloride aggregates’ stability increases with the ionization potential of the cation present. The characterization of long-lived radiolytic transients of pure salts provides important information for the understanding of complex salt mixtures under the action of gamma radiation.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Polymer-based microfluidic device for on-chip counter-diffusive crystallization and in situ X-ray crystallography at room temperature

Proteins are long chains of amino acid residues that perform a myriad of functions in living organisms, including enzymatic reactions, signalling, and maintaining structural integrity. Protein function is determined directly by the protein structure. X-ray crystallography is the primary technique for determining the 3D structure of proteins, and facilitates understanding the effects of protein structure on function. The first step towards structure determination is crystallizing the protein of interest. We have developed a centrifugally-actuated microfluidic device that incorporates the fluid handling and metering necessary for protein crystallization. Liquid handling takes advantage of surface forces to control fluid flow and enable metering, without the need for any fluidic or pump connections. Our approach requires only the simple steps of pipetting the crystallization reagents into the device followed by either spinning or shaking to set up counter-diffusive protein crystallization trials. The use of thin, UV-curable polymers with a high level of X-ray transparency allows for in situ X-ray crystallography, eliminating the manual handling of fragile protein crystals and streamlining the process of protein structure analysis. We demonstrate the utility of our device using hen egg white lysozyme as a model system, followed by the crystallization and in situ, room temperature structural analysis of the hub domain of calcium–calmodulin dependent kinase II (CaMKIIβ).

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2022

Room temperature doping of Ln 3+ in perovskite nanoparticles: a halide exchange mediated cation exchange approach

This study presents a halide exchange mediated cation exchange strategy for a room temperature doping of trivalent lanthanide cations (Ln 3+ ) in cesium lead halide (CsPbX 3 ) nanoparticles (NPs). Post-synthetic addition of LnCl 3 [Ln = Nd, Sm, Eu, Tb, Dy, and Yb] to a solution of CsPbBr 3 NPs generates the corresponding lanthanide doped NPs which display host sensitized Ln 3+ emission. Structural and spectroscopic characterizations indicate a successful halide exchange and substitutional displacement of Pb 2+ by Ln 3+ . The effect of halide identity in controlling the Ln 3+ sensitization was also evaluated. Here, a photophysical framework is presented that can be used to predict the Ln 3+ sensitization in perovskite NPs semiempirically, thereby removing the constraints of trial and error in designing a perovskite NP-Ln 3+ host–guest combination.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2024

Room temperature chemical transformation of SnSe to Ag 2 Se nanocrystals via cation exchange

Atomic-scale control of the chemical composition of semiconductor nanocrystals through a cation exchange reaction affords greater tunability in the design of multifunctional semiconductor composite nanocrystals. Here, we report a facile route to SnSe–Ag 2 Se composite nanocrystals using cation exchange at room temperature. Starting from freshly synthesized SnSe nanorods, we leverage the strong distortion of the Sn 2+ octahedral coordination in SnSe and the hard–soft acid–base (HSAB) principle, to promote the exchange of an Sn 2+ ion with two Ag + ions in methanol leading to Ag 2 Se/SnSe nanocomposites. The morphology and chemistry of the nanocrystals evolve from nanorods with SnSe@Ag 2 Se (core@shell) structures for SnSe-rich composites to nanorods with a random distribution of Sn 2+ and Ag + ions for nearly equimolar composites, and finally to irregular fragmented nanocrystals for Ag 2 Se-rich composites. A mechanistic understanding of the observed morphology evolution is discussed using the change in the cation coordination from octahedral (Sn 2+ ) to tetrahedral (Ag + ) geometry and the accompanying expansion of the hcp Se 2– sublattice. Interestingly, the synthesized composite nanocrystals exhibit an optical band gap value tunable within a wide energy range by increasing the Ag 2 Se/SnSe ratio. This work provides a useful and facile strategy to modify the optical behavior of semiconductor nanomaterials, which can be leveraged for the design of better optical and/or photovoltaic devices.

36 MATERIALS SCIENCE↗
DOE OSTI2025

Room temperature crystal field splitting of curium resolved by circularly polarized luminescence spectroscopy

Coordination of Cm(III) with a chiral decadentate ligand N,N,N',N'-tetrakis[(6-carboxypyridin-2-yl)methyl]-1,2-diaminocyclohexane (tpadac) generated complexes with strong luminescence allowing for the unprecedented measurement of well-resolved Cm(III) circularly polarized luminescence spectra. Quantitative resolution of the electronic structure of the [Cm(tpadac)][K] complexes was achieved at room temperature, highlighting the strength of the combination of luminescence and circularly polarized luminescence spectroscopies to unravel the fundamental electronic structure of Cm(III). These results are a clear demonstration that these spectroscopies are powerful yet simple tools for the fundamental understanding of electronic structure, which opens the door to future investigations of other Cm(III) complexes in geometries relevant to nuclear applications, and even other 5f-elements.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2026

350 ps Ultrafast room-temperature scintillation realized on CsPbBr 3 -based single crystals via Br 2 over-doping

Ultrafast scintillators are essential for next-generation radiation detection, positron emission tomography, and high-speed medical imaging. All-inorganic CsPbBr 3 perovskites are attractive candidates because of their high stopping power, and excellent optical quality, yet their long carrier lifetimes result in slow scintillation responses on the order of hundreds of nanoseconds. Here, we demonstrate that controlled over-doping with Br 2 produces CsPbBr 3.03 single crystals with sub-nanosecond scintillation at room temperature while preserving crystal quality. Single crystals grown by the Bridgman method exhibit high transparency and maintain the orthorhombic perovskite structure. Br 2 over-doping induces a slight lattice expansion (about 0.42% increase in unit-cell volume) while maintaining the orthorhombic perovskite phase and high optical transparency. Optical absorption reveals a slight redshift of the absorption edge after Br 2 introduction, indicating a modified defect landscape. Time-resolved photoluminescence and radioluminescence measurements show that Br 2 doping creates dense and efficient recombination centers that reduce the scintillation decay time from more than 100 ns in undoped crystals to 350 ps under 5.486 MeV α-particle excitation, and the scintillation decay time decreases by two orders of magnitude. The doped crystals also achieve a spatial resolution of 12 lp mm −1 in X-ray imaging. These results reveal a defect-engineering route for achieving ultrafast scintillation in halide perovskites and highlight the potential of Br 2 -modified CsPbBr 3 for fast timing applications.

Li, Zongxiao [Chinese Academy of Sciences (CAS), N↗
DOE OSTI2024

Determination of electron-hole pair creation energy in Cd 0.9 Zn 0.1 Te 0.98 Se 0.02 quaternary semiconductor for room-temperature gamma-ray detection

We report the first-time measurement of the electron-hole pair (ehp) creation energy (W ehp ) in novel Cd 0.9 Zn 0.1 Te 0.98 Se 0.02 (CZTS) quaternary semiconductor. CZTS in single crystalline form is poised to be the future of large-volume room-temperature gamma-ray detectors due to its excellent compositional homogeneity with highly reduced defects, high-Z (atomic number) constituents, wide bandgap (1.6 eV), and superior charge transport properties. Despite a great deal of study of the material and device properties since its inception, the W ehp in CZTS has not been measured experimentally. Accurate determination of W ehp is essential for calibration of the spectrometer and other theoretical calculations. In this study we have used an absolute calibration approach, which is based on an iterative approach that yields the Wehp as the best-fit parameter. Using a 241 Am alpha emitting radioisotope and a planar CZTS detector, the Wehp in CZTS was calculated to be 4.47 eV. The obtained value has been validated by accurately predicting the peak energy for gamma rays emitted by a 137 Cs source and read by a CZTS detector with different dimensions. The dependences of the calculated W ehp value on the detector dimensions, type of interaction, and effect of charge trapping are also discussed.

42 ENGINEERING↗
DOE OSTI2020

Prediction of room-temperature multiferroicity in strained MoCr 2 S 6 monolayer

The contrasting d-orbital occupation required for ferroelectricity vs ferromagnetism makes it difficult for their coexistence in two-dimensional materials, especially at high temperature. To resolve this intrinsic contradiction, we propose a layered MoCr 2 S 6 multiferroics by alloying magnetic Cr element into the ferroelectric 1T phase of the MoS 2 matrix. First-principles calculations disclose that a spontaneous symmetry breaking, depending on the Mo atom displacement, leads to a robust ferroelectricity, which coexists with a ferromagnetic order originated from two neighboring Cr atoms. The effect can be further enhanced by tensile strain to bring about a room-temperature multiferroicity. Our results shed new light on the fundamental understanding of multiferroics and display promising applications in spintronics and multistate data storage.

2D materials↗
DOE OSTI2020

Room temperature multiferroicity and magnetodielectric coupling in 0–3 composite thin films

Magnetoelectric (ME) composite thin films are promising candidates for novel applications in future nanoelectronics, spintronics, memory and other multifunctional devices as they exhibit much higher ME coupling and transition temperatures (Tc) than well-known single phase multiferroics discovered to date. Among the three types of multiferroic composite nanostructures, (2-2) layered and (1-3) vertically aligned composite nanostructures exhibit comparatively smaller ME coupling due to different shortcomings which restrict their use in many applications. Here we study the morphological, piezoresponse force microscopic (PFM), ferroelectric, magnetic, and magnetodielectric properties of 0-3 (magnetic nanoparticles (0) homogeneously distributed in ferroelectric matrices (3)) multiferroic composite thin films. The Pb(Fe 0.5 Nb 0.5 )O 3 (PFN) - Ni 0.65 Zn 0.35 Fe 2 O 4 (NZFO) particulate composite films were synthesized by pulsed laser deposition (PLD). These particulate composite thin films are completely c-axis oriented with very low surface roughness. We observed magnetic and ferroelectric T c above room temperature (RT) for all composite thin films. The PFN-NZFO 0-3 composites exhibit large polarization, high saturated magnetization with low coercive field, low dielectric loss along with magnetodielectric coupling at RT. These nanocomposites might be utilized in next generation nano/microelectronics and spintronic devices.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Room temperature depinning of the charge-density waves in quasi-two-dimensional 1T-TaS 2 devices

Here we report on the depinning of nearly commensurate charge-density waves in 1T-TaS 2 thin films at room temperature. A combination of the differential current–voltage measurements with the low-frequency noise spectroscopy provides unambiguous means for detecting the depinning threshold field in quasi-2D materials. The depinning process in 1T-TaS 2 is not accompanied by an observable abrupt increase in electric current—in striking contrast to depinning in the conventional charge-density-wave materials with quasi-1D crystal structure. We explained it by the fact that the current density from the charge-density waves in the 1T-TaS 2 devices is orders of magnitude smaller than the current density of the free carriers available in the discommensuration network surrounding the commensurate charge-density wave islands. The depinning fields in 1T-TaS 2 thin-film devices are several orders of magnitude larger than those in quasi-1D van der Waals materials. Obtained results are important for the proposed applications of the charge-density wave devices in electronics.

2D materials↗
DOE OSTI2021

Radio frequency mixing modules for superconducting qubit room temperature control systems

As the number of qubits in nascent quantum processing units increases, the connectorized RF (radio frequency) analog circuits used in first generation experiments become exceedingly complex. The physical size, cost, and electrical failure rate all become limiting factors in the extensibility of control systems. We have developed a series of compact RF mixing boards to address this challenge by integrating I/Q quadrature mixing, intermediate frequency/LO (local oscillator)/RF power level adjustments, and direct current bias fine tuning on a 40 × 80 mm 2 four-layer printed circuit board with electromagnetic interference shielding. The RF mixing module is designed to work with RF and LO frequencies between 2.5 and 8.5 GHz. The typical image rejection and adjacent channel isolation are measured to be ~27 dBc and ~50 dB. By scanning the drive phase in a loopback test, the module short-term amplitude and phase linearity are typically measured to be 5 ×10 -4 (V pp /V mean ) and 1 ×10 -3 radian (pk-pk). The operation of the RF mixing board was validated by integrating it into the room temperature control system of a superconducting quantum processor and executing randomized benchmarking characterization of single and two qubit gates. We measured a single-qubit process infidelity of 9.3(3) × 10 -4 and a two-qubit process infidelity of 2.7(1) × 10 -2 .

47 OTHER INSTRUMENTATION↗
DOE OSTI2021

X-ray diffraction and equation of state of the C–S–H room-temperature superconductor

X-ray diffraction indicates that the structure of the recently discovered carbonaceous sulfur hydride (C–S–H) room-temperature superconductor is derived from previously established van der Waals compounds found in the H 2 S–H 2 and CH 4 –H 2 systems. Crystals of the superconducting phase were produced by a photochemical synthesis technique, leading to the superconducting critical temperature T c of 288 K at 267 GPa. X-ray diffraction patterns measured from 124 to 178 GPa, within the pressure range of the superconducting phase, are consistent with an orthorhombic structure derived from the Al 2 Cu-type determined for (H 2 S) 2 H 2 and (CH 4 ) 2 H 2 that differs from those predicted and observed for the S–H system at these pressures. The formation and stability of the C–S–H compound can be understood in terms of the close similarity in effective volumes of the H 2 S and CH 4 components, and denser carbon-bearing S–H phases may form at higher pressures. Furthermore, the results are crucial for understanding the very high superconducting T c found in the C–S–H system at megabar pressures.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗