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At least 793 records · Page 44
All sourcesNASA NTRSDOE OSTI
DOE OSTI2012

Deposition of nanostructured photocatalytic zinc ferrite films using solution precursor plasma spraying

Highlights: Black-Right-Pointing-Pointer Highly economic solution precursor route capable of producing films/coating even for mass scale production. Black-Right-Pointing-Pointer Pure spinel phase ZnFe{sub 2}O{sub 4} porous, immobilized films deposited in single step. Black-Right-Pointing-Pointer Parameter optimization yields access to nanostructuring in SPPS method. Black-Right-Pointing-Pointer The ecofriendly immobilized ferrite films were active under solar radiation. Black-Right-Pointing-Pointer Such magnetic system display advantage w.r.t. recyclability after photocatalyst extraction. -- Abstract: Deposition of pure spinel phase, photocatalytic zinc ferrite films on SS-304 substrates by solution precursor plasma spraying (SPPS) has been demonstrated for the first time. Deposition parameters such as precursor solution pH, concentration, film thickness, plasma power and gun-substrate distance were found to control physico-chemical properties of the film, with respect to their crystallinity, phase purity, and morphology. Alkaline precursor conditions (7 < pH {<=} 10) were found to favor oxide film formation. The nanostructured films produced under optimized conditions, with 500 mM solution at pH {approx} 8.0, yielded pure cubic phase ZnFe{sub 2}O{sub 4} film. Very high/low precursor concentrations yielded mixed phase, less adherent, and highly inhomogeneous thin films. Desired spinel phase was achieved in as-deposited condition under appropriately controlled spray conditions and exhibited a band gap of {approx}1.9 eV. The highly porous nature of the films favored its photocatalytic performance as indicated by methylene blue de-coloration under solar radiation. These immobilized films display good potential for visible light photocatalytic applications.

36 MATERIALS SCIENCE↗
DOE OSTI2012

The use of novel biodegradable, optically active and nanostructured poly(amide-ester-imide) as a polymer matrix for preparation of modified ZnO based bionanocomposites

Highlights: Black-Right-Pointing-Pointer A novel biodegradable and nanostructured PAEI based on two amino acids, was synthesized. Black-Right-Pointing-Pointer ZnO nanoparticles were modified via two different silane coupling agents. Black-Right-Pointing-Pointer PAEI/modified ZnO BNCs were synthesized through ultrasound irradiation. Black-Right-Pointing-Pointer ZnO particles were dispersed homogeneously in PAEI matrix on nanoscale. Black-Right-Pointing-Pointer The effect of ZnO nanoparticles on the properties of synthesized polymer was examined. -- Abstract: A novel biodegradable and nanostructured poly(amide-ester-imide) (PAEI) based on two different amino acids, was synthesized via direct polycondensation of biodegradable N,N Prime -bis[2-(methyl-3-(4-hydroxyphenyl)propanoate)]isophthaldiamide and N,N Prime -(pyromellitoyl)-bis-L-phenylalanine diacid. The resulting polymer was characterized by FT-IR, {sup 1}H NMR, specific rotation, elemental analysis, thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), X-ray diffraction (XRD) and field emission scanning electron microscopy (FE-SEM) analysis. The synthesized polymer showed good thermal stability with nano and sphere structure. Then PAEI/ZnO bionanocomposites (BNCs) were fabricated via interaction of pure PAEI and ZnO nanoparticles. The surface of ZnO was modified with two different silane coupling agents. PAEI/ZnO BNCs were studied and characterized by FT-IR, XRD, UV/vis, FE-SEM and TEM. The TEM and FE-SEM results indicated that the nanoparticles were dispersed homogeneously in PAEI matrix on nanoscale. Furthermore the effect of ZnO nanoparticle on the thermal stability of the polymer was investigated with TGA and DSC technique.

36 MATERIALS SCIENCE↗
DOE OSTI2012

Effect of Gd dopant concentration on the defect engineering in ceria nanostructures

Graphical abstract: Display Omitted Highlights: ► Investigates the ionic conductivity of defect engineered Gd doped nano scale ceria. ► Reveals that there exists an optimum concentration of dopant to engineer ceria with large O{sub 2} vacancies. ► For the first time the Nanosponge morphology observed in the Gd doped nanoceria. ► It is observed that 5% of Gd in ceria is optimum to induce appropriate amount of defects. ► Thereby an enhanced ionic conductivity is achieved in 5% Gd doped ceria. -- Abstract: In this study, the fabrication and characterization of pure and gadolinium (Gd) doped ceria nanostructures (Ce{sub 1−x}Gd{sub x}O{sub 2−δ} where x = 0.05, 0.1 and 0.2) are investigated. The origin of defect formation has been systematically investigated by XRD and UV-Visible Raman. All the fabricated ceria are found to be “Nanosponge” morphology which is observed by using FESEM technique. The charge transfer of O{sup 2−} ions and Ce{sup 3+}/Ce{sup 4+} in the ceria host due to these defect structures are studied by UV–DRS. Impedance analysis is showed an enhanced ionic conductivity for 5% Gd doped ceria compared to other concentration of Gd, revealing that the dopant concentration is a critical parameter in engineering a large number of vacancy defects in ceria nanostructures.

36 MATERIALS SCIENCE↗
DOE OSTI2013

Dielectric investigations in nanostructured tetragonal BaTiO{sub 3} ceramics

Highlights: ► Nanostructured BaTiO{sub 3} ceramics processed by an innovative protocol. ► Dielectric relaxations related to strains and vacancies. ► Dielectric and ferroelectric properties enhanced by strain. - Abstract: In this paper, structural and dielectric properties of BaTiO{sub 3} ceramics obtained under extreme conditions were investigated. The temperature dependent dielectric investigations revealed that the phase transition temperatures of the BaTiO{sub 3} ceramics were raised as a function of residual strains associated to the nanostructuration, while structural characterizations showed a tetragonal arrangement at room temperature. From the frequency dependence analyses of the imaginary parts of dielectric permittivity, impedance and modulus function, three relaxation processes were identified. Two of them exhibit activation energies of 0.45 and 0.63 eV, and were attributed to single and double-ionization of oxygen vacancies. The whole set of results also indicated that the electrons resulting from the ionization of oxygen vacancies are trapped and do not contribute to the electrical conductivity, while the physical properties of the analyzed samples were enhanced by retaining a strained microstructure.

36 MATERIALS SCIENCE↗
DOE OSTI2013

Three-dimensional graphene/LiFePO{sub 4} nanostructures as cathode materials for flexible lithium-ion batteries

Graphical abstract: Graphene/LiFePO{sub 4} composites as a high-performance cathode material for flexible lithium-ion batteries have been prepared by using a co-precipitation method to synthesize graphene/LiFePO4 powders as precursors and then followed by a solvent evaporation process. - Highlights: • Flexible LiFePO{sub 4}/graphene films were prepared first time by a solvent evaporation process. • The flexible electrode exhibited a high discharge capacity without conductive additives. • Graphene network offers the electrode adequate strength to withstand repeated flexing. - Abstract: Three-dimensional graphene/LiFePO{sub 4} nanostructures for flexible lithium-ion batteries were successfully prepared by solvent evaporation method. Structural characteristics of flexible electrodes were investigated by X-ray diffraction (XRD), atomic force microscopy (AFM) and scanning electron microscopy (SEM). Electrochemical performance of graphene/LiFePO{sub 4} was examined by a variety of electrochemical testing techniques. The graphene/LiFePO{sub 4} nanostructures showed high electrochemical properties and significant flexibility. The composites with low graphene content exhibited a high capacity of 163.7 mAh g{sup −1} at 0.1 C and 114 mAh g{sup −1} at 5 C without further incorporation of conductive agents.

36 MATERIALS SCIENCE↗
DOE OSTI2014

Structural and electrical properties of nanostructured Ni{sub 0.25}Co{sub 0.75}MnP{sub 2}O{sub 7}

Graphical abstract: - Highlights: • Nanostructured pyrophosphate Ni{sub 0.25}Co{sub 0.75}MnP{sub 2}O{sub 7} were synthesized and characterized by XRD and SEM. • The ac-conductivity at different values of temperature for Ni{sub 0.25}Co{sub 0.75}MnP{sub 2}O{sub 7} nanomaterials shows frequency independence in the lower frequency range. • Obvious improvements of the electrical conductivity and the electrochemical properties are achieved comparatively Mn{sub 2}P{sub 2}O{sub 7}. • The electrochemical behaviors of Ni{sub 0.25}Co{sub 0.75}MnP{sub 2}O{sub 7} were studied using cyclic voltammetry. - Abstract: The nanostructured pyrophosphate Ni{sub 0.25}Co{sub 0.75}MnP{sub 2}O{sub 7} was prepared. The synthesis technique was based on the hydrothermal method at 150 °C using poly-ethylene-glycol (PEG-10000) as surfactant with further calcination at 500 °C. A structural analysis of Ni{sub 0.25}Co{sub 0.75}MnP{sub 2}O{sub 7} compound was carried out by applying X-ray diffraction (XRD) and using the Rietveld method. Morphological characterizations were performed using a scanning electron microscope (SEM) and transmission electron microscopy (TEM). A comparative study of the electrical conductivity of Mn{sub 2}P{sub 2}O{sub 7} and Ni{sub 0.25}Co{sub 0.75}MnP{sub 2}O{sub 7} nanomaterials was carried out by impedance spectroscopy in the temperature range 500–680 °C. The activation energies for MnP{sub 2}O{sub 7} and Ni{sub 0.25}Co{sub 0.75}MnP{sub 2}O{sub 7} were 2.00 and 0.88 eV, respectively. Ni{sub 0.25}Co{sub 0.75}MnP{sub 2}O{sub 7} nanomaterial presents a good electric conductivity compared to Mn{sub 2}P{sub 2}O{sub 7}, due to the substitution effect. The improvement of the electronic and ionic conductivity makes the Ni{sub 0.25}Co{sub 0.75}MnP{sub 2}O{sub 7} nanomaterial possible electrode materials for rechargeable batteries. The electrochemical behaviors of Ni{sub 0.25}Co{sub 0.75}MnP{sub 2}O{sub 7} were studied using cyclic voltammetry.

36 MATERIALS SCIENCE↗
DOE OSTI2014

Enhancement of the photocatalytic property of TiO{sub 2} columnar nanostructured films by changing deposition angle

Highlights: • Isolated and inclined columnar TiO{sub 2} nanostructures were obtained by sputtering Ti, and subsequently annealing. • The film performed photocatalytic decolorization effectively under UV irradiation. • The photocatalytic efficiency increased with deposition angle, which results in a more porous micro structure of the films. - Abstract: Isolated and inclined columnar nanostructured TiO{sub 2} films were obtained by sputtering titanium with glancing angle deposition method and subsequently annealing in air. Compared with flat film, TiO{sub 2} film fabricated with this method has higher porosity; compared with TiO{sub 2} powder, it overcomes the obstacles of immobilization and recycling. The TiO{sub 2} photocatalysis was evaluated by the degradation of methyl orange under UV light. It was indicated that the photocatalytic performance increased with deposition angle, which changed the porosity of the films. The relationship between deposition angle (the angle between the target and substrate surface) and the TiO{sub 2} columnar inclination angle (the angle between TiO{sub 2} columnar and substrate normal) was discussed.

36 MATERIALS SCIENCE↗
DOE OSTI2014

Temperature and acidity effects on WO{sub 3} nanostructures and gas-sensing properties of WO{sub 3} nanoplates

Graphical abstract: Generally, large acid quantity and high temperature are beneficial to the formation of anhydrous WO3, but the acidity effect on the crystal phase is weaker than that of temperature. Large acid quantity is found helpful to the oriented growth of tungsten oxides, forming a nanoplate-like product. - Highlights: • Large acid quantity is propitious to the oriented growth of a WO{sub 3} nanoplate. • Effect of acid quantity on crystal phases of products is weaker than that of temperature. • One step hydrothermal synthesis of WO{sub 3} is facile and can be easily scaled up. • A WO{sub 3} nanoplate shows a fast response and distinct sensing selectivity to acetone gas. - Abstract: WO{sub 3} nanostructures were successfully synthesized by a facile hydrothermal method using Na{sub 2}WO{sub 4}·2H{sub 2}O and HNO{sub 3} as raw materials. They are characterized by X-ray diffraction (XRD), scanning electron microscope (SEM) and transmission electron microscope (TEM). The specific surface area was obtained from N{sub 2} adsorption–desorption isotherm. The effects of the amount of HNO{sub 3}, hydrothermal temperature and reaction time on the crystal phases and morphologies of the WO{sub 3} nanostructures were investigated in detail, and the reaction mechanism was discussed. Large amount of acid is found for the first time to be helpful to the oriented growth of tungsten oxides, forming nanoplate-like products, while hydrothermal temperature has more influence on the crystal phase of the product. Gas-sensing properties of the series of as-prepared WO{sub 3} nanoplates were tested by means of acetone, ethanol, formaldehyde and ammonia. One of the WO{sub 3} nanoplates with high specific surface area and high crystallinity displays high sensitivity, fast response and distinct sensing selectivity to acetone gas.

36 MATERIALS SCIENCE↗
DOE OSTI2014

Hydrogen production via reforming of biogas over nanostructured Ni/Y catalyst: Effect of ultrasound irradiation and Ni-content on catalyst properties and performance

Highlights: • Synthesis of nanostructured Ni/Y catalyst by sonochemical and impregnation methods. • Enhancement of size distribution and active phase dispersion by employing sonochemical method. • Evaluation of biogas reforming over Ni/Y catalyst with different Ni-loadings. • Preparation of highly active and stable catalyst with low Ni content for biogas reforming. • Getting H{sub 2}/CO very close to equilibrium ratio by employing sonochemical method. - Abstract: The effect of ultrasound irradiation and various Ni-loadings on dispersion of active phase over zeolite Y were evaluated in biogas reforming for hydrogen production. X-ray diffraction, field emission scanning electron microscopy, energy dispersive X-ray, Brunauer–Emmett–Teller, Fourier transform infrared analysis and TEM analysis were employed to observe the characteristics of nanostructured catalysts. The characterizations implied that utilization of ultrasound irradiation enhanced catalyst physicochemical properties including high dispersion of Ni on support, smallest particles size and high catalyst surface area. The reforming reactions were carried out at GHSV = 24 l/g.h, P = 1 atm, CH{sub 4}/CO{sub 2} = 1 and temperature range of 550–850 °C. Activity test displayed that ultrasound irradiated Ni(5 wt.%)/Y had the best performance and the activity remained stable during 600 min. Furthermore, the proposed reaction mechanism showed that there are three major reaction channels in biogas reforming.

36 MATERIALS SCIENCE↗
DOE OSTI2014

Vanadium oxides nanostructures: Hydrothermal synthesis and electrochemical properties

Highlights: • Vanadium oxides nanostructures were synthesized hydrothermally. • Reversible redox behavior with doping/dedoping process. • Doping/dedoping is easier for Li{sup +} to Na{sup +}. • Energy-related applications such as cathodes in lithium batteries. - Abstract: A facile and template-free one-pot strategy is applied to synthesize nanostructured vanadium oxide particles via a hydrothermal methodology. X-ray diffraction (XRD), scanning electron microscope (SEM), Fourier transforms infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS) have been used to characterize the structure and morphology of the samples. The products are gradually changed from sheet-shaped VO{sub 2}(B) to rod-like V{sub 3}O{sub 7}·H{sub 2}O with decreasing cyclohexanediol as both protective and reducing agent. The specific surface area of the VO{sub 2}(B) nanosheets and V{sub 3}O{sub 7}·H{sub 2}O nanorods was found to be 22 and 16 m{sup 2} g{sup −1}, respectively. Thin films of VO{sub 2}(B) and V{sub 3}O{sub 7}·H{sub 2}O deposited on ITO substrates were electrochemically characterized by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The voltammograms show reversible redox behavior with doping/dedoping process corresponding to reversible cation intercalation/de-intercalation into the crystal lattice of the nanorods/nanosheets. This process is easier for the small Li{sup +} cation than larger ones Na{sup +}.

36 MATERIALS SCIENCE↗
DOE OSTI2014

Ferrous sulfate based low temperature synthesis and magnetic properties of nickel ferrite nanostructures

Highlights: • Novel low temperature synthesis of nickel ferrite nanoparticles. • Comparison with two conventional synthesis techniques including hydrothermal method. • XRD results confirm the formation of crystalline nickel ferrites at 110 °C. • Superparamagnetic particles with applications in drug delivery and hyperthermia. • Magnetic properties superior to conventional methods found in new process. - Abstract: We report a simple, low temperature and surfactant free co-precipitation method for the preparation of nickel ferrite nanostructures using ferrous sulfate as the iron precursor. The products obtained from this method were compared for their physical properties with nickel ferrites produced through conventional co-precipitation and hydrothermal methods which used ferric nitrate as the iron precursor. X-ray diffraction analysis confirmed the synthesis of single phase inverse spinel nanocrystalline nickel ferrites at temperature as low as 110 °C in the low temperature method. Electron microscopy analysis on the samples revealed the formation of nearly spherical nanostructures in the size range of 20–30 nm which are comparable to other conventional methods. Vibrating sample magnetometer measurements showed the formation of superparamagnetic particles with high magnetic saturation 41.3 emu/g which corresponds well with conventional synthesis methods. The spontaneous synthesis of the nickel ferrite nanoparticles by the low temperature synthesis method was attributed to the presence of 0.808 kJ mol{sup −1} of excess Gibbs free energy due to ferrous sulfate precursor.

36 MATERIALS SCIENCE↗
DOE OSTI2016

One pot synthesis of CdS/TiO{sub 2} hetero-nanostructures for enhanced H{sub 2} production from water and removal of pollutants from aqueous streams

Highlights: • Novel one pot synthesis of CdS/TiO{sub 2} hetero nanostructures by combustion synthesis. • Excellent visible light photocatalytic activity for H{sub 2} production from water. • Enhanced activity for the removal of Cr(VI) from aqueous streams. - Abstract: To achieve more effective coupling of cadmium sulfide (CdS) to the TiO{sub 2}, single step synthesis of CdS/TiO{sub 2} composites is advantageous. In the present study a novel one pot synthesis of several CdS/TiO{sub 2} hetero-nanostructures was explored through combustion technique. As the process involves the simultaneous nucleation of CdS and TiO{sub 2} it leads to the proper connectivity between the constituent materials. All the catalysts were characterized by using several techniques and the excellent visible light activity of the composites has been asserted by the H{sub 2} production from water containing sacrificial reagents, removal of methylene blue and Cr(VI) from aqueous streams. Therefore the present synthetic strategy which is devoid of using molecular linker at interface is more suitable for solar applications, which require faster rates of electron transfer at the hetero junctions.

36 MATERIALS SCIENCE↗
DOE OSTI2016

Synthesis of belt-like BiOBr hierarchical nanostructure with high photocatalytic performance

Highlights: • BiOBr hierarchical nanobelts (NBs) were solvothermally prepared. • NBs show higher specific surface area and photoabsorption than BiOBr nanosheets. • NBs exhibit higher photoactivity than the nanosheets. - Abstract: One-dimensional (1D) bismuth oxyhalide (BiOX) hierarchical nanostructures are always difficult to prepare. Herein, we report, for the first time, a simple synthesis of BiOBr nanobelts (NBs) via a facile solvothermal route, using bismuth subsalicylate as the template and bismuth source. The BiOBr nanobelts are composed of irregular single crystal nanoparticles with highly exposed (0 1 0) facets. Compared with the BiOBr nanosheets (NSs) with dominant exposed (0 0 1) facets, they exhibit higher photocatalytic activity toward degradation of Rhodamine B and Methylene Blue under visible light irradiation. The higher photocatalytic performance of BiOBr NBs arises from their larger specific surface area and higher photoabsorption capability. This study provides a simple route for synthesis of belt-like Bi-based hierarchical nanostructures.

36 MATERIALS SCIENCE↗
DOE OSTI2016

Scalable and template-free synthesis of nanostructured Na{sub 1.08}V{sub 6}O{sub 15} as high-performance cathode material for lithium-ion batteries

Highlights: • Nanostructured Na{sub 1.08}V{sub 6}O{sub 15} was synthesized through additive-free sol-gel process. • Prepared Na{sub 1.08}V{sub 6}O{sub 15} demonstrated high capacity and sufficient cycling stability. • The reaction temperature was optimized to allow scalable Na{sub 1.08}V{sub 6}O{sub 15} fabrication. - Abstract: Developing high-capacity cathode material with feasibility and scalability is still challenging for lithium-ion batteries (LIBs). In this study, a high-capacity ternary sodium vanadate compound, nanostructured NaV{sub 6}O{sub 15}, was template-free synthesized through sol-gel process with high producing efficiency. The as-prepared sample was systematically post-treated at different temperature and the post-annealing temperature was found to determine the cycling stability and capacity of NaV{sub 6}O{sub 15}. The well-crystallized one exhibited good electrochemical performance with a high specific capacity of 302 mAh g{sup −1} when cycled at current density of 0.03 mA g{sup −1}. Its relatively long-term cycling stability was characterized by the cell performance under the current density of 1 A g{sup −1}, delivering a reversible capacity of 118 mAh g{sup −1} after 300 cycles with 79% capacity retention and nearly 100% coulombic efficiency: all demonstrating its significant promise of proposed strategy for large-scale synthesis of NaV{sub 6}O{sub 15} as cathode with high-capacity and high energy density for LIBs.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Facile synthesis of high surface area nanostructured ceria-zirconia-yttria-lanthana solid solutions with the assistance of lauric acid and dodecylamine

Highlights: • High surface area nanostructured ceria-zirconia-yttria-lanthana solid solutions are synthesized by a facile method. • Hydrophobic surfaces are obtained with the addition of lauric acid and dodecylamine in the synthesis. • The introduced lauric acid and dodecylamine are chemically adsorbed onto the surface of materials through a coordination effect. • Excellent thermal stability are obtained in lauric acid and dodecylamine assisted materials. - Abstract: Co-precipitation combined with the assistance of lauric acid and dodecylamine was used to synthesize high surface area nanostructured ceria-zirconia-yttria-lanthana solid solutions (CZ-L and CZ-D). The promotion effects of lauric acid and dodecylamine were studied systematically by N{sub 2} adsorption-desorption, scanning electron microscopy (SEM), transmission electron microscopy (TEM), FT-IR and Raman analysis. After being thermal aged at 1100 °C for 4 h in air, CZ-L and CZ-D present high surface areas of 26 m{sup 2}/g and 16 m{sup 2}/g, respectively. The results indicate that the added lauric acid and dodecylamine are chemically adsorbed onto the surface of materials through coordination effect. The obtained hydrophobic surface could greatly decrease the amount of superficial adsorbed water on the material and significantly reduce the surface tension. The addition of lauric acid and dodecylamine could also effectively support the network structures of the material and resist the collapse of pores upon drying and calcination.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2018

Synthesis and physical properties of NaxTO2 (T = Mn, Co) nanostructures for cathode materials in Na-ion batteries

Highlights: • Synthesis of stable Na{sub x}TO{sub 2} (T = Mn, Co) nanostructures using a sol–gel method. • Absence of any long-range magnetic ordering in both compounds till 5 K. • Activated type conduction at high temperatures and VRH at low temperatures in Na{sub x}CoO{sub 2}. • Disorder assisted VRH conduction takes place in Na{sub x}MnO{sub 2} near room temperature. • Cyclic voltammetry confirm reversibility of Na ion in a coin cell using Na{sub x}TO{sub 2} cathode. - Abstract: We prepared Na{sub x}TO{sub 2} (T = Mn, Co) nanostructures to use as cathode material in Na-ion batteries. The Rietveld refinement of X-ray diffraction data confirms the hexagonal symmetry. Scanning and transmission electron microscopy measurements show hexagonal and rod-shape morphology for T = Co and Mn, respectively. The magnetic measurements indicate the presence of variable oxidation states of Mn/Co ions, but no long range ordering till 5 K. We find that the Na{sub 0.6}MnO{sub 2} is highly insulating whereas Na{sub 0.7}CoO{sub 2} is semiconducting in nature. The conduction in Na{sub 0.7}CoO{sub 2} takes place through both variable range hopping (VRH) as well as activation mechanisms in different temperature ranges. However, for Na{sub 0.6}MnO{sub 2} the VRH prevails at elevated temperatures. Furthermore, the coin cells have been fabricated and tested the electrochemical behavior using cyclic voltammetry, which confirms the reversibility of Na-ions during intercalation/de-intercalation.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2020

Unlocking multiphysics design guidelines on Si/C composite nanostructures for high-energy-density and robust lithium-ion battery anode

In general, current material fabrication guidance for novel designs of Si/C composite particle materials focuses on electrochemical behavior and redox reactions at the nano/micro level. However, such guidance cannot provide detailed information for predicting mechanical deformations of the composite particles, especially when the mechanical field coupled with electrochemical and thermal fields. Here, we establish an electro-chemo-mechanical model and implement it to quantitatively analyze the multiphysics behavior of five representative Si/C composite nanostructures. Modeling and computation discover that yolk-shell and dual-shell structures are more robust in terms of particle fractures. When considering electrochemical performance, the yolk-shell structure is the best among the compared five Si/C composites. Finally, we map design guidance to further illustrate quantitative structure-property relationships. This study provides novel insights on Si/C composite nanostructure anode material design and additional powerful design tools for next-generation high-energy-density lithium-ion batteries.

25 ENERGY STORAGE↗
DOE OSTI2020

High-efficiency solar thermophotovoltaic system using a nanostructure-based selective emitter

Herein, we present the design, fabrication, optimization, and experimental results of a high-efficiency planar solar thermophotovoltaic (STPV) system utilizing a micro-textured absorber and a nanostructure multilayer metal-dielectric coated selective emitter fabricated on a tungsten (W) substrate. Light absorptance of more than 90% was achieved at visible and near-infrared wavelengths using the microtextured absorbing surface. The nanostructure selective emitter consists of two thin-film optical coatings of silicon nitride (Si3N4) and a layer of W in between to increase the surface emissivity in spectral regimes matching the quantum efficiency of the thermophotovoltaic (TPV) cells. Gallium antimonide (GaSb)-based TPV cells are used in our STPV design. The experiment was conducted at different operating temperatures using a high-power continuous wave laser diode stack as a simulated source of concentrated incident radiation. Our experimental setup measured a maximum electrical output power density of 1.71 W/cm 2 at 1676 K STPV temperature, and the overall power conversion efficiency of 8.4% after normalizing the output power density to the emitter area. This is the highest STPV system efficiency reported so far for any experimental STPV device. The incident optical laser power on the absorber side was 131 W. This is equivalent to a solar concentration factor of ~2100, which is within the practical limit and readily achievable with Fresnel lens setup.

14 SOLAR ENERGY↗