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Yang, Fei

Publications and source records attributed to Yang, Fei.

14 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2024

A thermal evaporation–trapping strategy to synthesize flexible and robust oxygen electrocatalysts for rechargeable zinc–air batteries

Great efforts have been devoted to the development of bifunctional electrocatalysts to accelerate the sluggish kinetics of cathodic oxygen reduction/evolution reactions (ORR/OER) in zinc–air batteries (ZABs). Here we report a thermal evaporation–trapping synergistic strategy to fabricate a bifunctional electrocatalyst of flexible N-doped carbon fiber cloth loaded with both CoFe-oxide nanoparticles and single-atom Co/Fe–Nx sites, in which the thermal evaporation process functions in both downsizing CoFe-oxide nanoparticles and trapping the evaporated Co/Fe species to generate Co/Fe–Nx sites. The obtained flexible electrocatalyst, directly serving as an oxygen electrode, displays a small potential gap of 0.542 V for the OER/ORR, large peak power densities (liquid-state ZAB: 237.4 mW cm2 ; solid-state ZAB: 141.1 mW cm2 ), and excellent charge–discharge cycling stability without decay after working more than 770 hours. Furthermore, in situ Raman spectroscopy characterization and theoretical calculations reveal that CoFe2O4 species is responsible for the OER while atomic Fe/Co sites play a key role in the ORR

Zhang, Hong-Bo↗
DOE OSTI2023

Observing ion diffusion and reciprocating hopping motion in water

When an ionic crystal dissolves in solvent, the positive and negative ions associated with solvent molecules release from the crystal. However, the existing form, interaction, and dynamics of ions in real solution are poorly understood because of the substantial experimental challenge. We observed the diffusion and aggregation of polyoxometalate (POM) ions in water by using liquid phase transmission electron microscopy. Real-time observation reveals an unexpected local reciprocating hopping motion of the ions in water, which may be caused by the short-range polymerized bridge of water molecules. We find that ion oligomers, existing as highly active clusters, undergo frequent splitting, aggregation, and rearrangement in dilute solution. The formation and dissociation of ion oligomers indicate a weak counterion-mediated interaction. Furthermore, POM ions with tetrahedral geometry show directional interaction compared with spherical ions, which presents structure-dependent dynamics.

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

Fe–N–C Boosts the Stability of Supported Platinum Nanoparticles for Fuel Cells

The poor durability of Pt-based nanoparticles dispersed on carbon black is the challenge for the application of long-life polymer electrolyte fuel cells. Recent work suggests that Fe- and N-codoped carbon (Fe-N-C) might be a better support than conventional high-surface-area carbon. In this work, we find that the electrochemical surface area retention of Pt/Fe-N-C is much better than that of commercial Pt/C during potential cycling in both acidic and basic media. In situ inductively coupled plasma mass spectrometry studies indicate that the Pt dissolution rate of Pt/Fe-N-C is 3 times smaller than that of Pt/C during cycling. Density functional theory calculations further illustrate that the Fe-N-C substrate can provide strong and stable support to the Pt nanoparticles and alleviate the oxide formation by adjusting the electronic structure. The strong metal-substrate interaction, together with a lower metal dissolution rate and highly stable support, may be the reason for the significantly enhanced stability of Pt/Fe-N-C. In conclusion, this finding highlights the importance of carbon support selection to achieve a more durable Pt-based electrocatalyst for fuel cells.

25 ENERGY STORAGE↗
DOE OSTI2021

Recent Advances in Electrocatalysts for Proton Exchange Membrane Fuel Cells and Alkaline Membrane Fuel Cells

The rapid progress of proton exchange membrane fuel cells (PEMFCs) and alkaline exchange membrane fuel cells (AMFCs) has boosted the hydrogen economy concept via diverse energy applications in the past decades. For a holistic understanding of the development status of PEMFCs and AMFCs, recent advancements in electrocatalyst design and catalyst layer optimization, along with cell performance in terms of activity and durability in PEMFCs and AMFCs, are summarized in this report. The activity, stability, and fuel cell performance of different types of electrocatalysts for both oxygen reduction reaction and hydrogen oxidation reaction are discussed and compared. Research directions on the further development of active, stable, and low-cost electrocatalysts to meet the ultimate commercialization of PEMFCs and AMFCs are also discussed.

36 MATERIALS SCIENCE↗
DOE OSTI2020

The physiochemical alteration of flax fibers structuring components after different scouring and bleaching treatments

Scouring and bleaching are essential steps in flax yarn production; however, in many cases, these treatments have relatively low selectivity on non-cellulosic polysaccharides (NCPs) and lignin. Herein, the specific chemical properties of flax fibers through a variety of scouring and/or bleaching procedures are reviewed to understand their correlations with the mechanical and morphological characteristics. The hydrolysis behaviors of hemicellulose and lignin are different from those of cellulose during chlorine-alkali-oxygen (Cl-AO), enzyme-alkali-oxygen (EAO), and alkali-oxygen (AO) treatments, while the structural hemicellulose polysaccharides fractions were not affected by acid pretreatment followed by alkali scouring (AA) treatment. It was found that the unbleached AA treatment improved scouring efficiency to the greatest extent by decreasing 73.3 % of hemicellulose content and 59.8 % of lignin content compared to the untreated flax fibers and obtained the highest tensile strength (6.58 cN/dtex) and elongation (3.73 %). Delignification was more crucial on fiber tenacity and fineness than hemicellulose removal (R 2 = 0.71, 0.79 vs R 2 = 0.46, 0.61). Within the hemicellulose fractions, a corresponding beneficial relationship between the xylan (XYL) composition and flax fiber properties is presented. The correlation of GM and GGM contents in hemicellulose with flax fiber length was significant with R 2 value 0.97 and 0.99, respectively. This work provides insight into the hydrolysis behavior of hemicellulose and a basis for developing scouring and/or bleaching models that can predict fiber properties.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2019

Identification of Plasma Current Center by Neural Network Inference in EAST

For the efficient and safe operation of experimental advanced superconducting tokamak (EAST), it is necessary to accurately identify and control the plasma current and its central position. In this article, neural network is used to identify the position of the plasma current center. The model trained by the basic back-propagation neural network can well match the relationship between the electromagnetic diagnostic signals and plasma current center positions. Both noisy simulation data and experimental data are applied to train and test the neural network inference model. Adding 0.1% noise to the training data is proven to improve the noise immunity of the inference model. Basic neural networks trained with both noisy simulation data and actual experimental data show good results with sufficient inputs; however, in both cases, the performance degrades significantly when only the poloidal field coil currents are given as inputs. For this kind of time-series problem, the dynamic neural network containing delay and feedback architecture is introduced, and an improved model requiring much fewer inputs is trained and tested for current center inference. Furthermore, some parameters of this model are compared and analyzed in this article. With suitable neural network architecture, the mapping between the controlled variables (poloidal field coil currents) and response variables (plasma current center) can be well-established.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2019

Bacillus thuringiensisCry1Da_7 and Cry1B.868 Protein Interactions with Novel Receptors Allow Control of Resistant Fall Armyworms,Spodoptera frugiperda(J.E. Smith)

Two new modified Bacillus thuringiensis (Bt) proteins, Cry1Da_7 and Cry1B.868, with activity against fall armyworms (FAW), Spodoptera frugiperda (J.E. Smith), were evaluated for their potential to bind new insect receptors compared to proteins currently deployed as plant-incorporated protectants (PIPs) in row crops. Results from resistant insect bioassays, disabled insecticidal protein (DIP) bioassays, and cell-based assays using insect cells expressing individual receptors demonstrate that receptor utilizations of the newly modified Cry1Da_7 and Cry1B.868 proteins are distinct from each other and from those of commercially available Bt proteins such as Cry1F, Cry1A.105, Cry2Ab, and Vip3A. Accordingly, these two proteins target different insect proteins in FAW midgut cells and when pyramided together should provide durability in the field against this economically important pest.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2019

Three-dimensional characterization of hardened paste of hydrated tricalcium silicate by serial block-face scanning electron microscopy

With the application of a three-dimensional (3D) characterization technique, serial block-face scanning electron microscopy (SBFSEM), the 3D microstructure of a hydrated cement monomineral, tricalcium silicate (C 3 S), was measured with nanoscale resolution. The 3D morphologies of anhydrous particles, hydrated products, and capillary pores were visualized. Closed and open pores were discovered inside an anhydrous particle. The size and distribution of both the anhydrous C 3 S particles and their capillary pores were analyzed quantitatively and the porosity was determined to be 9%. The distribution of pores was found to be in a good agreement with the inner and outer product model of Hu et. al., with an inner shell distance of 860 nm. Here, considering the spatial resolution of the instrument and the volume of sample measured, most pores in this experiment could be characterized as capillary pores.

3D microstructure↗
DOE OSTI2019

Three-dimensional structure investigation of Waterborne Paint by Electron Microscopic Imaging

In this paper, the three-dimensional (3D) spatial structure of a TiO 2 coated waterborne paint film has been successfully investigated by serial block-face scanning electron microscopy (SBFSEM). The investigation clearly shows the spatial distribution of the TiO2 particles in the paint film and illustrates the degree of dispersion of the particles in the composite material. More than 58% of the volume of the TiO 2 particles are between 1.0 × 10 6 nm 3 to 1.0 × 10 7 nm 3 and the minimum distance between different particles can be detected is 124 nm. Different types of voids can be found in the 3D image of the cured water-borne paint film: voids that exist in the paint itself, voids produced by particle shedding, water evaporating and particles stacking. Among these voids, the ones produced by particle shedding is a cutting artefact. The research provides a different approach to clearly present the 3D spatial structure of paints and can clearly illustrate different kinds of voids inside the water-borne paint. While the resulting 3D structure of the paint, especially the different voids are important for further systematic research on the relationships between the spatial microstructure and the physical and chemical properties of the water-borne paint.

36 MATERIALS SCIENCE↗
DOE OSTI2019

DC current controller for continuously variable series reactor

A direct current controller includes a rectifier configured to convert alternating current input into a direct current output. A converter electrically coupled to the rectifier generates a converted direct current voltage that regulates a converted direct current from the direct current output of the rectifier and synthesizes an ac component of an alternating current grid to counteract an induced back-emf. A direct current controller central controller coupled to the converter regulates the converted direct current.

Wang, Fei (Fred)↗
DOE OSTI2018

3D microstructure reconstruction of casting aluminum alloy based on serial block-face scanning electron microscopy

In this work, the inner microstructure of aluminum-silicon casting alloy was experimentally investigated to reveal the spatial morphology and phase distribution. Its industrial use is as a light-weight structural material. As a powerful three-dimensional (3D) imaging tool at the nano-scale, the serial block-face scanning electron microscopy (SBFSEM) was employed to investigate the specimens. After being 3D reconstructed, the images were visualized to identify preference for several specific intermetallics by quantitative analysis. It was found that these phases have certain relationships in spatial distribution and differences in spatial shapes. In conclusion, the spatial distribution of cracks was studied to understand their propagation and growth.

3D microstructure reconstruction↗