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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 793 records · Page 44
All sourcesNASA NTRSDOE OSTI
DOE OSTI2014

Phase Transfer-Catalyzed Fast CO2 Absorption by MgO-Based Absorbents with High Cycling Capacity

CO2 capture from pre-combustion syngas in the temperature range of 250-400°C is highly desirable from an energy efficiency perspective. Thermodynamically, MgO is a promising material for CO2 capture, but the gas-solid reaction to produce MgCO3 is kinetically slow due to high lattice energy. We report here fast CO2 absorption over a solid MgO-molten nitrate/nitrite aggregate through phase transfer catalysis, in which the molten phase serves as both a catalyst and reaction medium. Reaction with CO2 at the gas-solid-liquid triple phase boundary results in formation of MgCO3 with significant reaction rate and a high conversion of MgO. This methodology is also applicable to other alkaline earth oxides, inspiring the design of absorbents which require activation of the bulk material.

carbonate↗
DOE OSTI2023

Extremely Thin Perfect Absorber by Generalized Multipole Bianisotropic Effect

Symmetry breaking plays a crucial role in understanding the fundamental physics underlying numerous physical phenomena, including the electromagnetic response in resonators, giving rise to intriguing effects such as directional light scattering, supercavity lasing, and topologically protected states. Here, this work demonstrates that adding a small fraction of lossy metal (as low as 1 × 10 −6 in volume) to a lossless dielectric resonator breaks inversion symmetry (IS), thereby lifting its degeneracy, leading to a strong bianisotropic response. In the case of the metasurface composed of such resonators, this effect leads to unidirectional perfect absorption while maintaining nearly perfect reflection from the opposite direction. It has developed more general Onsager‐Casimir relations for the polarizabilities of particle arrays, taking into account the contributions of quadrupoles, which shows that bianisotropy is not solely due to dipoles, but also involves high‐order multipoles. The experimental validation demonstrates an extremely thin terahertz‐perfect absorber with a wavelength‐to‐thickness ratio of up to 25,000, where the material thickness is only 2% of the theoretical minimum thickness dictated by the fundamental limit. The findings can pave a new route to design devices for applications involving optical‐to‐heat conversion processes.

36 MATERIALS SCIENCE↗
DOE OSTI2023

First of Their Kind: Solar Cells with a Dry-Processed Perovskite Absorber Layer via Powder Aerosol Deposition and Hot-Pressing

Preparing halide perovskite films by solvent-free, powder-based processing approaches currently attracts more and more attention. However, working solar cells employing dry, powder-based halide perovskite thin films, have not been demonstrated so far. Herein, perovskite solar cells are presented where the absorber layer is prepared by transferring readily synthesized perovskite powders into a compact thin film using a fully dry-powder-processing concept. Compact thin films are deposited via an optimized powder aerosol deposition (PAD) process. Pressing at 120 °C further improves the morphology and the optoelectronic film properties. Integrating the perovskite films in a solar cell configuration results in fully working devices, with champion power conversion efficiencies of >6%. While the (optoelectronic) properties of the PAD-processed films are found to be comparable with their solution-processed counterparts, investigations of the solar cell stack suggest deterioration of the electron-transport layer properties due to the PAD process, and the presence of hydrates at the perovskite surface to be important factors that contribute to the limited solar cell efficiency. Herein, perspectives to overcome the identified limitations are outlined, emphasizing the high potential and realizability of efficient perovskite solar cells based on dry-powder-processing approaches in the future.

14 SOLAR ENERGY↗
DOE OSTI2015

Efficacy of a Radiation Absorbing Shield in Reducing Dose to the Interventionalist During Peripheral Endovascular Procedures: A Single Centre Pilot Study

PurposeThis prospective pilot study was undertaken to evaluate the feasibility and effectiveness of using a radiation absorbing shield to reduce operator dose from scatter during lower limb endovascular procedures.Materials and MethodsA commercially available bismuth shield system (RADPAD) was used. Sixty consecutive patients undergoing lower limb angioplasty were included. Thirty procedures were performed without the RADPAD (control group) and thirty with the RADPAD (study group). Two separate methods were used to measure dose to a single operator. Thermoluminescent dosimeter (TLD) badges were used to measure hand, eye, and unshielded body dose. A direct dosimeter with digital readout was also used to measure eye and unshielded body dose. To allow for variation between control and study groups, dose per unit time was calculated.ResultsTLD results demonstrated a significant reduction in median body dose per unit time for the study group compared with controls (p = 0.001), corresponding to a mean dose reduction rate of 65 %. Median eye and hand dose per unit time were also reduced in the study group compared with control group, however, this was not statistically significant (p = 0.081 for eye, p = 0.628 for hand). Direct dosimeter readings also showed statistically significant reduction in median unshielded body dose rate for the study group compared with controls (p = 0.037). Eye dose rate was reduced for the study group but this was not statistically significant (p = 0.142).ConclusionInitial results are encouraging. Use of the shield resulted in a statistically significant reduction in unshielded dose to the operator’s body. Measured dose to the eye and hand of operator were also reduced but did not reach statistical significance in this pilot study.

62 RADIOLOGY AND NUCLEAR MEDICINE↗
DOE OSTI2022

Devices for Thermal Conductivity Measurements of Electroplated Bi for X-ray TES Absorbers

Electroplated bismuth (Bi) is commonly used in transition-edge sensors (TESs) for X-rays because of its high stopping power and low heat capacity (Collan in Phys Rev B 1:2888, 1970, Yan in Appl Phys Lett 111:192602, 2017). Electroplated Bi is usually grown on top of another metal that acts as seed layer, typically gold (Au), making it challenging to extrapolate its thermoelectric properties. In this work, we present four-wire resistance measurement structures that allow us to measure resistance as a function of temperature of electroplated Bi independently of Au. The results show that the thermal conductivity of the Bi at 3 K is high enough to ensure the correct thermalization of X-ray photons when used as an absorber for TESs.

Bismuth↗
DOE OSTI2019

A Novel Rigid PU Foam Based on Modified Used Palm Oil as Sound Absorbing Material

Novel bio-polyol was successfully synthesized from used palm oil (UPO) and was further tested for preparing rigid polyurethane (PU) foams. In this work, the modified used palm oil (MUPO) was synthesized in a single step process, by epoxidation together with ring opening reactions. The reagent ratios and reaction time for MUPO synthesis were also studied. The chemical structure of MUPO was confirmed by {sup 1}H-NMR spectroscopy and FTIR. The hydroxyl value of MUPO increased with reaction time and depended also on reagent ratio. The GPC trace of MUPO showed a bimodal distribution and the molecular weight slightly decreased with OH value. New rigid PU foams were prepared from MUPO. The foam cell size and compressive strength at 10% strain increased with OH value. All the rigid PU foams had excellent sound absorption coefficients. The lowest OH value (OHV = 100 mg KOH/g) provided sound absorption from 2200 Hz. In addition, the flammability of PU foams was improved by adding 30% wt of triphosphate (TPP) as flame retardant. The investigations showed that a bio-polyol based on UPO was suitable for preparing rigid PU foams that could serve as alternative sound absorbing materials. Graphical Abstract: .

36 MATERIALS SCIENCE↗
DOE OSTI2018

Development of Broadband Microwave Absorber and Measurement of Its Magnetic and Microwave Properties

Toroid shape Co-doped barium hexaferrites of composition (BaFe{sub 11}CoO{sub 19}) are prepared by standard sintering technology as a sample. In this work, XRD is used to identify the structure of synthesized sample. Vibrating sample magnetometer is used to obtain magnetic hysteresis loop of sample. Scanning electron microscope is used for surface morphology of sample. The complex permeability and permittivity are measured with commercial automation measurement set up in the 2–18 GHz frequency range. As a result of measurement, the calculation of reflection loss of the synthesized samples has been carried out. Investigation of microwave absorption properties revealed that the maximum reflection loss of Co-doped barium hexaferrite sample is around −20 dB and almost flat in the measurement frequency band. From these results, it was concluded that Co-doped barium hexaferrites of composition had a good potential as microwave absorber in the broadband frequency range.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2019

Magnetic, Microwave Absorbing Performance of Al{sub 8}Mn{sub 5} Alloy with La Dopant

The Al{sub 8}Mn{sub 5 − x}La{sub x} (x = 0, 0.2, 0.6, 1.0) powders were triumphantly manufactured by vacuum melting and planetary mill equipment. The influences of La content on phase constitution, morphology, saturation magnetization, and electromagnetic parameters were investigated by related equipment. The consequences demonstrate that Al{sub 8}Mn{sub 4}La phase, average size of particulate increases and the saturation magnetization (Ms) decreases as La content increased. The minimum reflectivity of Al{sub 8}Mn{sub 4.4}La{sub 0.6} powder reaches about −43.5 dB in the range of 10.8 to 11.7 GHz, and the effective bandwidth (RL < − 10 dB) can obtain about 1.70 GHz with the best matching thickness of 1.8 mm. These manifest Al{sub 8}Mn{sub 5-x}La{sub x} (x = 0, 0.2, 0.6, 1.0) powders possess the capacity to be excellent microwave absorbing materials.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2019

Magnetic Resonated Bilayer Square-Ring–Enabled Dual-Peak Metamaterial Absorber in P-Band

In order to investigate the effect of magnetic metal on the absorption performance of metamaterial absorber (MMA), a dual-peak MMA based on magnetic metal nickel is designed and demonstrated in the P-band (300–1000 MHz). Two-layer square-ring-metal resonator arrays and two-layer dielectric substrates are arranged alternately with each other to constitute the proposed dual-peak MMA backed with a reflective metal plate. The influences of copper or nickel metallic layers on the absorption coefficients are comparatively analyzed. For the nickel MMA, the dual-peak absorption coefficients of 99.82% and 99.09% are achieved at 394 MHz and 605 MHz, respectively. Moreover, the thickness of dual-peak MMA could be reduced to 9 mm by employing magnetic metal nickel. The physical mechanism of dual-peak absorption is illustrated by surface current distributions, magnetic field distributions and power loss density distributions. The relationship between the changes of geometric dimensions and the shift of peak absorption frequencies is ultimately discussed. These results could provide instructive guidance for realizing a thin dual-peak MMA in the P-band.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2019

Absorbing boundary condition (ABC) and perfectly matched layer (PML) in numerical beam propagation: a comparison

The absorbing boundary condition (ABC) and the perfectly matched layer (PML) are employed to suppress the numerical reflections in wave propagation methods. The PML has earlier been shown to fail at the grazing angle propagation of beam. The ABC is preferred over the PML where refractive index is not an analytic function. We have explored the performance of the ABC in reflection-less absorption of non-paraxial propagation of beams and have compared it against the PML. We have considered an example of the propagation of Gaussian beams through a homogeneous medium terminated with ABC or PML. We have used the collocation method for propagation. We have found that both the boundary conditions are comparable in performance. The ABC performed relatively better than the PML for beams at smaller angles. However, the performance of the PML is better than that of the ABC at larger tilt angles.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2019

Yb-doped fiber laser mode-locked with Au nanocages/SiO{sub 2} saturable absorber

Au nanocages/SiO{sub 2} (Au-NCs/SiO{sub 2}) are prepared through a seed-mediated growth method, and the performance is investigated in an all-fiber passively mode-locked ytterbium-doped fiber laser, for the first time. Its saturating intensity and modulation depth are measured to be about 0.461 MW/cm{sup 2} and 5.3%, respectively. With the Au-NCs/SiO{sub 2} saturable absorbers (SA) film, the pulse with the pulse duration of 1.116 ns and repetition rate of 32.02 MHz was generated at 1063.14 nm, under the pump power of 342 mW. And the corresponding average output power of 4.82 mW was obtained. These results indicate that Au-NCs/SiO{sub 2} has excellent saturable absorption properties with the potential for important applications in the field of ultra-short pulse lasers.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Narrow and wide band tunable absorbers based on gold squares dispersed in liquid crystal

In this paper, the absorption behavior of gold squares with different sizes has been investigated. Our study includes gold squares in two, three and four different sizes dispersed in liquid crystal to propose an absorber with post fabrication tunability. In this case, more than 95% narrow band as well as wide band absorptions have been obtained when two and three sizes of gold squares have been used. Moreover, wide band absorption spectrum with the full width at half maximum of about 0.31 µm has been obtained when there are four different sizes of gold squares in our structure. Also, graphene has been utilized to boost the narrow band absorption from about 80 to 95%.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2019

Passively Q-switched erbium-doped fiber laser using quantum dots CdSe embedded in polymer film as saturable absorber

We demonstrate a passively Q-switched erbium doped fiber laser (EDFL) based on quantum dots (QD) CdSe as a saturable absorber (SA). The synthesized CdSe powder was embedded into a poly(methyl methacrylate) (PMMA) using emulsion polymerization process. The film is sandwiched between two fiber connector via an adapter to form a fiber-compatible SA device. By integrating the SA device into the EDFL ring cavity, the stable Q-switched operation is achieved at 1559.35 nm as the pump power is varied within 30–118 mW. The laser has a pump threshold of 20.4 mW. The pulse repetition rate shows an increasing trend from 33.2 to 68.45 kHz, whereas the pulse width exhibits a decreasing trend from 10.04 to 4.30 μs as the pump power is increased from 30 to 118 mW. The highest pulse energy of 11.83 nJ is obtained at a pump power of 118 mW. These results indicate that QD CdSe is a promising SA for Q-switching laser operation.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2022

Effect of inoculation with prion dilutions within the dynamic range of ELISA absorbance on prion incubation period

This study examines the effect of various infectious prion titers within the dynamic range as measured by ELISA on incubation period. We inoculated ovinized transgenic mice with seven decreasing dilutions of a fast-incubating scrapie strain. The highest inoculum group was a 20% w/v brain homogenate from a sheep with scrapie. The subsequent six inoculum dilutions ranged from the highest ELISA optical density reading of 4.000 to a dilution where scrapie prions were not detectable by ELISA. Multiple comparison analysis demonstrated variation in the incubation periods between some inoculum groups. Incubation periods were similar between inoculum groups unless their optical density differed by more than ≈2 units of absorbance. These data will inform the interpretation of future studies that compare incubation periods in experimentally inoculated animals for TSE research.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2019

Broadband coherent perfect absorber with PT-symmetric 2D-materials

We suggest graphene and a two-dimensional (2D) Weyl semimetal (WSM) as 2D materials for the realization of a broadband coherent perfect absorber (CPA) respecting overall PT-symmetry. We also demonstrate the conditions for mutually equal amplitudes and phases of the left and right incoming waves to realize a CPA. 2D materials in our system play the role to enhance the absorption rate of a CPA once the appropriate parameters are inserted in the system. We show that a 2D WSM is more effective than graphene in obtaining the optimal conditions. We display the behavior of each parameter governing the optical system and show that optimal conditions of these parameters give rise to enhancement and possible experimental realization of a broadband CPA-laser.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2022

“Self-trapping” in solar cell hybrid inorganic-organic perovskite absorbers

In the simplest picture, a “self-trapped” polaron forms when an excess electron or hole deforms a crystal lattice, creating a potential well with bound states. Properties of self-trapped polarons in methylammonium lead iodide perovskite (MAPbI 3 ), which is widely used as solar cell absorber, are of great interest, and are a subject of ongoing investigations and debates concerning the existence of large polarons with the co-presence of metastable self-trapping. Herein, we employ a self-interaction-free density functional theory method to investigate the stability of small polarons in tetragonal MAPbI 3 phase. The electron small polaron is found to be unstable, while the hole small polaron is found to be metastable at realistic operation temperatures of solar cells. Further, the hole polaron is found to have a hole band close to the conduction band, which in conjunction with its metastability suggests that small polarons will have an appreciable effect on charge-carrier recombinations in MAPbI 3 . Further, in this study, we posit that the existence of the metastable polarons in addition to the large polarons may explain the experimentally observed non-monotonic temperature dependence of bimolecular charge-carrier recombination rate in tetragonal MAPbI 3 phase.

14 SOLAR ENERGY↗
DOE OSTI2020

Optimum power analysis of a self-reactive wave energy point absorber with mechanically-driven power take-offs

This paper studies a self-reactive ocean wave energy converter (WEC) where energy is absorbed through the relative motion between a floating buoy on the ocean surface and a submerged body. Two types of direct-drive power take off (PTO) systems are examined. One adopts a ball screw system in inverse driving mode with mechanical motion rectifier (MMR) that converts the oscillating bi-directional input heave motion into unidirectional rotation to drive an electromagnetic generator, and another one uses a ball screw system to directly drive the generator (called non-MMR). Dynamic models for both types of PTOs are established and integrated with the overall WEC system model in both the time and frequency domains. Numerical simulation is used to investigate the dynamic performance of both PTOs. The influences of the PTO inerter, which is from the rotational inertia of the flywheel and generator, and the WEC drag damping coefficient are discussed and explored. The analytical closed-form solution for the optimum condition of the non-MMR system is derived based on the criterion of maximum power absorption, and numerical simulation yields the optimum condition for the MMR system. Overall, the results under regular and irregular waves show that the PTO inerter in the MMR system can improve the power absorption for small wave periods and maintain the same performance for large wave periods. The PTO inerter in the non-MMR system shifts the peak frequency. The WEC drag damping negatively influences the power absorption in both PTO systems, especially at large wave periods.

16 TIDAL AND WAVE POWER↗
DOE OSTI2019

10% Efficiency Cu(In,Ga)Se2 Solar Cell with Strongly (220)/(204) Oriented Cu-Poor Absorber Layers Sputtered Using Single Quaternary Target

Cu-poor CIGS thin films were fabricated by RF magnetron sputtering from a single quaternary target with the composition of Cu0.7In0.7Ga0.3Se2, in an effort to improve the cell efficiency of CIGS solar cells. The Cu-poor thin films with the ([Cu]/[In]+[Ga]) composition ratios of 0.70-0.77 were obtained showing that the composition of the target can be transferred to the film. It was also observed that the strongly (220)/(204) preferred orientation appeared at the substrate temperatures higher than 600 degrees C, which is known to be essential for achieving high-quality CIGS solar cells. This result indicates that the Cu-Se compounds present in trace amounts of CIGS films hinder the (112) orientation and promotes the growth of the (220) orientation. As a result, the CIGS absorber layer with the Cu-poor composition and the (220)/(204) preferred orientation exhibited a drastically improved cell efficiency of 10.02%.

14 SOLAR ENERGY↗