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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 OSTI2019

Exsolution and electrochemistry in perovskite solid oxide fuel cell anodes: Role of stoichiometry in Sr(Ti,Fe,Ni)O 3

The exsolution of metal cations from oxides under reducing fuel conditions ends in the formation of surface metallic nanoparticles, which can reduce Solid Oxide Fuel Cell anode polarization resistance. However, the loss of the B-site cations shifts the stoichiometry of the perovskite oxide. Depending on the amount exsolved and the initial stoichiometry, the exsolution can presumably shift the oxide away from its single-phase perovskite region. Herein, the direct comparison of initially stoichiometric composition Sr(Ti 0.3 Fe 0.63 Ni 0.07 )O 3-δ (STFN0) with initially A-site deficient Sr 0.95 (Ti 0.3 Fe 0.63 Ni 0.07 )O 3-δ (STFN5) is conducted and reported. X-ray diffraction along with scanning and transmission electron microscopy analysis of the oxides, which are both reduced at 850 °C in H 2 /H 2 O/Ar, demonstrates a similar size and density of exsolved Fe–Ni alloy nanoparticles, albeit with slightly different alloy compositions. Whereas the oxide phase in reduced STFN5 shows a well-ordered perovskite structure, the greater B-site deficiency in reduced STFN0 results in a highly disordered and strained structure. The electrochemical performance of STFN0 anodes is inferior to that of STFN5 anodes, and even worse than SrTi 0.3 Fe 0.7 O 3-δ (Ni-free) anodes. It appears that an initial Sr deficiency is important to avoid a too-high B-site deficiency after exsolution, which distorts the perovskite structure and impairs electrochemical processes.

25 ENERGY STORAGE↗
DOE OSTI2012

Gallium composition dependence of crystallographic and thermoelectric properties in polycrystalline type-I Ba{sub 8}Ga{sub x}Si{sub 46-x} (nominal x=14-18) clathrates prepared by combining arc melting and spark plasma sintering methods

The gallium composition dependence of crystallographic and thermoelectric properties in polycrystalline n-type Ba{sub 8}Ga{sub x}Si{sub 46-x} (nominal x=14-18) compounds with the type-I clathrate structure is presented. Samples were prepared by combining arc melting and spark plasma sintering methods. Powder x-ray diffraction, Rietveld analysis, scanning electron microscopy, and energy-dispersive x-ray spectroscopy show that the solubility limit of gallium in the type-I clathrate phase is close to x=15, which is slightly higher than that for a single crystal. The carrier concentration at room temperature decreases from 2 Multiplication-Sign 10{sup 21} cm{sup -3} to 4 Multiplication-Sign 10{sup 20} cm{sup -3} as the Ga content x increases. The Seebeck coefficient, the electrical conductivity, and the thermal conductivity vary systematically with the carrier concentration when the Ga content x varies. The effective mass (2.0m{sub 0}), the carrier mobility (10 cm{sup 2} V{sup -1} s{sup -1}), and the lattice thermal conductivity (1.1 W m{sup -1} K{sup -1}) are determined for the Ga content x=14.51. The dimensionless thermoelectric figure of merit ZT is about 0.55 at 900 K for the Ga content x=14.51. The calculation of ZT using the experimentally determined material parameters predicts ZT=0.8 (900 K) at the optimum carrier concentration of about 2 Multiplication-Sign 10{sup 20} cm{sup -3}. - Graphical abstract: The gallium composition dependence of crystallographic and thermoelectric properties is presented on polycrystalline n-type Ba{sub 8}Ga{sub x}Si{sub 46-x} with the type-I clathrate structure prepared by combining arc melting and spark plasma sintering methods. The thermoelectric figure of merit ZT reaches 0.55 at 900 K due to the increase in the Ga content (close to x=15), and a calculation predicts further improvement of ZT at the optimized carrier concentration. Highlights: Black-Right-Pointing-Pointer Crystallographic properties of Ba{sub 8}Ga{sub x}Si{sub 46-x} clathrates are characterized. Black-Right-Pointing-Pointer Arc melting and spark plasma sintering process enables increase of Ga content. Black-Right-Pointing-Pointer We elucidate the Ga composition dependence of thermoelectric properties. Black-Right-Pointing-Pointer Thermoelectric figure of merit ZT is improved due to the increased Ga content. Black-Right-Pointing-Pointer Calculation predicts a potential ZT=0.8 at 900 K at optimized carrier concentration.

36 MATERIALS SCIENCE↗
DOE OSTI2013

The “quiet Goldschmidt”—a mechanochemical, thermoanalytical, and spectroscopic study of selected steps of the aluminothermic reaction

The Goldschmidt reaction (2Al+α-Fe{sub 2}O{sub 3}) was investigated both under mechanical and thermal activation by employing a combination of analytical methods such as ESR and Mössbauer spectroscopy, magnetic susceptibility, X-ray powder diffraction, and thermal analysis (TA). Both the mechanical treatment and the TA runs under air caused the reaction conditions of “quiet redox reactions” due to a retarding effect and enabled a reaction study in a “slow motion mode”. This allowed to establish distinct partial steps of the integral reaction process depending on the intensity of the mechanical impact, the educt composition, the gas phase composition, and, finally, the thermal excitation in the TA runs. Particular attention was payed to the role of the gas phase and to the reaction of aluminum with differently activated oxygen species. The phlegmatizing effect was traced back to the formation of Al{sub 2}O{sub 3} coverages of the Al particles. - Highlights: • The usually extremely violent Goldschmidt reaction was studied in a “slow motion mode”. • Both the mechanochemical and the thermal treatment caused a phlegmatizing effect on the reaction. • Early reaction stages were sensitively indicated by ESR and magnetic measurements. • Intermediates and final products were characterized by XRD and Mössbauer data. • Differently activated oxygen species react with aluminum to form an oxide coverage retarding the vigorous reaction.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2013

Investigation of the photoactivity of pristine and mixed phase N-doped titania under visible and solar irradiation

Nitrogen doped titania nano-particles were synthesized by sol–gel method with an aim to investigate the impact of doping in titanium matrix and the titania phases on their photocatalytic activity under visible and solar irradiation. The structural, optical and chemical characterization of the prepared materials were done using X-ray diffraction analysis, scanning electron microscopy, UV–visible diffuse reflectance spectroscopy, photoluminescence spectroscopy, and Fourier transform infrared spectroscopy. The samples were calcined at different temperatures (200 °C–600 °C) to obtain different phases. All the samples showed red-shift in the visible region attributable to the doping of nitrogen in the titania matrix. The samples calcined at low temperatures showed high photocatalytic activity compared to the high temperature samples. The enhancement in the visible light activity may be attributed to the large amount of nitrogen present in the surface region of the catalyst and reduced carrier recombination. Among the high temperature samples the high activity may be due to the presence of mixed phase as well. - Highlights: • Pristine and mixed phases of N doped titania synthesized at different temperatures. • High visible light photoactivity exhibited by pristine rutile phase and mixed phase. • Role of surface N in rutile and matrix embedded N in other samples corroborated.

36 MATERIALS SCIENCE↗
DOE OSTI2020

In-situ observation of nano-oxide and defect evolution in 14YWT alloys

Nanostructured ferritic alloys (NFAs) are considered as candidates for structural components in advanced nuclear reactors due to their excellent radiation resistance as a result of a high density of nano-oxides (NOs) in the microstructure. Therefore, gaining an understanding on the stability of NOs under irradiation is crucial. In this study, we have investigated the evolution of defects and NOs in 14YWT NFAs under in-situ Kr ion irradiation at room temperature (RT) and 450°C up to 10 dpa. It has been found that irradiations at 450°C do not create any changes in the NOs, similar to the bulk irradiations. On the other hand, elemental mapping indicates that NOs dissolve mostly after 10 dpa irradiations at RT. Thus, while defects are both annihilated and pinned by NOs at low doses (before the dissolution of NOs), glissile loops start to escape to the foil surface at high doses (after the dissolution of NOs), justifying the significantly low fraction of (111) loops compared to the literature values. Furthermore, high resolution transmission electron microscopy analysis has shown that the NOs are mostly coherent Y 2 Ti 2 O 7 particles with pyrochlore crystal structure after both RT and 450°C irradiations, similar to those observed before irradiation.

36 MATERIALS SCIENCE↗
DOE OSTI2024

From phase decomposition to evaporation: A multi-modal evaluation of thermally degraded model lightweight high-entropy alloy

Lightweight high-entropy alloys (LHEAs) have the potential to replace conventional lightweight materials due to their superior mechanical properties and thermal stability. However, the thermal degradation pattern of LHEAs from phase decomposition to evaporation is not clear. We develop a new Al-based dual phase (FCC + HCP) LHEA—AlTi 0.45 CuZn, and further investigate its thermal degradation behavior for potential high-temperature structural applications. Using multimodal advanced characterization techniques such as differential scanning calorimetry/thermogravimetric analysis, scanning/transmission electron microscopy, and synchrotron X-ray diffraction/pair distribution function (XRD/PDF), a sequence of thermal degradation events beyond the thermal phase stability limit—between 250 and 360 °C—is observed. These include phase decomposition at ~360 °C, Zn evaporation at ~750 °C, and LHEA melting at 880 °C which results in ~25% cumulative weight loss. The formation of Al-Ti phase off the AlTi 0.45 CuZn matrix is due to the largest negative mixing enthalpy for Al-Ti than other binary pairs. Similarly, Zn evaporation from AlTi 0.45 CuZn LHEA is due to its faster evaporation rate than other constituent elements. The high-resolution synchrotron XRD and PDF results support the aforementioned observations; in addition, they reveal local atomic arrangements, local strain, and sluggish grain growth in the LHEA. Among other LHEAs of close density range (5.55 ≤ ρ ≤ 5.85 g/cc), the investigated LHEA exhibits outstanding nano-indentation hardness values due to the coupled grain size effect and HCP phase strengthening of the FCC matrix. As the search for LHEAs for lightweight applications grows, this study shows the potential use of AlTi 0.45 CuZn LHEA for structural applications even at elevated temperatures.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2016

Effective Schottky barrier lowering of Ni silicide/p-Si(100) using an ytterbium confinement structure for high performance n-type MOSFETs

A simple but effective rare earth metal (RE) confinement structure is demonstrated to suppress surface accumulation of Yb generally encountered in the RE metal incorporated Ni silicide system. The confinement structure is realized by inserting a Ti diffusion barrier layer between Yb and Ni layers. Yb atoms can be constrained in a specified reaction region during silicidation as evidenced by Auger electron spectroscopy and cross-section transmission electron microscopy analysis. The RE metal confinement structure provides a complementary metal-oxide-semiconductor compatible approach for further Schottky barrier height engineering and is a promising method for future technology nodes.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Accelerating exploitation of Co-Al-based superalloys from theoretical study

The discovery of γ'-Co 3 (Al,W) opens up a pathway to exploit novel Co-Al-based alloys as candidates of the next generation of superalloys. Inspired by the unexpected finding of γ'-Co 3 (Al,W), we present a comprehensive investigation concerning the effect of alloying elements on phase stabilities and mechanical properties of Co 3 Al. Up to 22 transition metal elements, e.g. Sc, Ti, V, Cr, Mn, Fe, Ni, Y, Zr, Nb, Mo, Tc, Ru, Rh, Pd, Hf, Ta, W, Re, Os, Ir, and Pt, are considered. Results show that W, Ti, Re, V, and Ta favor to occupy the Al-sublattice. Pd, Pt, Rh, Ni, Ir, Fe, and Ru favor to occupy the Co-sublattice. The others can occupy both the Co- and Al-sublattices. W, Ta, V, Ti, Nb, Re, Mo, Pt, and Cr are shown to stabilize Co3Al. It verifies that elastic properties are roughly in inverse proportional to the volume change induced by alloying elements within each group of 3d, 4d, or 5d. Based on the analysis of electronic configurations, the influence mechanism of alloying elements is traceable from the chemical bonding and the geometry of charge density. We report the present calculations are in favorable accord with available experimental data in the literature.

36 MATERIALS SCIENCE↗
DOE OSTI2012

Synthesis, characterization and magnetic performance of Co-incorporated ordered mesoporous carbons

Highlights: Black-Right-Pointing-Pointer A facile one-pot aqueous self-assembly strategy for the synthesis Co-incorporated ordered mesoporous carbons (Co-OMCs). Black-Right-Pointing-Pointer Co-OMCs exhibit typical ferromagnetic characteristics. Black-Right-Pointing-Pointer Saturation magnetization strength can be easily adjusted by changing the content of cobalt. Black-Right-Pointing-Pointer Carbonization temperatures have significant effects on the structure and magnetic properties of Co-OMCs. -- Abstract: Co-incorporated ordered mesoporous carbon (Co-OMC) with magnetic frameworks has been synthesized via a one-pot self-assembly strategy. The effects of cobalt loading on carbon matrix, adsorption properties and magnetic properties of the resultant mesostructured cobalt/carbon composites were investigated by nitrogen sorption, X-ray diffraction (XRD), transmission electron microscopy (TEM), thermogravimetric analysis (TG) and magnetometer measurements. The results show that the mesoporous composites with a high cobalt content (such as 18.0 wt%) possess an ordered and uniform mesoporous structure (5.3 nm), high surface areas (up to 687 m{sup 2}/g) and high pore volumes (up to 0.54 cm{sup 3}/g). Cobalt nanoparticles of size 4-9 nm are confined inside the mesopores or walls of the mesoporous carbon. These materials exhibit typical ferromagnetic characteristics. The saturation magnetization strength can be easily adjusted by changing the content of cobalt. The carbonization temperatures have significant effects on the structure and magnetic properties of Co-OMC also.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2012

Microstructural, electrical and optical properties of indium tin oxide (ITO) nanoparticles synthesized by co-precipitation method

Highlights: Black-Right-Pointing-Pointer The grain size of the ITO is decreased from 28.7 to 9.0 nm by increasing Sn dopant. Black-Right-Pointing-Pointer The strain values increased with the incorporation of Sn in In{sub 2}O{sub 3} host lattice. Black-Right-Pointing-Pointer The lower resistivity of 4.9 {Omega} cm is obtained for 10 at.% Sn doped ITO. Black-Right-Pointing-Pointer The band gap varies from 3.62 to 3.89 eV with dopant concentration of Sn. -- Abstract: In the present study, the synthesis of Tin doped indium oxide (ITO) nanopowder at different compositions (In/Sn = 0, 5, 10, 15 at %) was carried out by co-precipitation method. The decomposition of precipitated indium tin acetylacetonate precursor to form In{sub 2}O{sub 3}-SnO{sub 2} (Sn{sub 1-x}In{sub x}O{sub 2}) at 400 Degree-Sign C was confirmed by the thermal and FTIR studies. The changes in strain and grain size of the synthesized particle with respect to dopant concentration were determined from the X-ray diffraction (XRD) analysis. Transmission electron microscopy (TEM) images support to confirm the grain size. The optical properties on ITO nanoparticles were analyzed with UV-visible spectroscopy, and band gap was found to vary from 3.62 to 3.89 eV with Sn dopant concentration. This variation was ascribed to the quantum confinement effect.

36 MATERIALS SCIENCE↗
DOE OSTI2012

Preparation, phase structure and microwave dielectric properties of CoLi{sub 2/3}Ti{sub 4/3}O{sub 4} ceramic

Graphical abstract: For chemical compatibility tests with silver electrode, mixtures of ceramic powders with 20 wt% Ag powders were cofired and analyzed to detect interactions between the low-fired samples and electrodes. XRD patterns and backscattered electron image of CoLi{sub 2/3}Ti{sub 4/3}O{sub 4} ceramics added with 1.5 wt% BCB cofired with Ag at 900 Degree-Sign C for 2 h are presented in . Backscattered electron image analysis reveals no interaction to form new phases after firing. This observation is also confirmed by the evidence of no difference between the XRD patterns before and after firing. It is obvious that the reaction of low-fired CoLi{sub 2/3}Ti{sub 4/3}O{sub 4} ceramics with Ag electrodes did not occur. Highlights: Black-Right-Pointing-Pointer A new microwave dielectric ceramic with good properties was reported. Black-Right-Pointing-Pointer The addition of BaCu(B{sub 2}O{sub 5}) can lower the sintering temperature from 1050 Degree-Sign C to 900 Degree-Sign C. Black-Right-Pointing-Pointer The addition of BaCu(B{sub 2}O{sub 5}) does not induce degradation of properties. Black-Right-Pointing-Pointer BCB added CoLi{sub 2/3}Ti{sub 4/3}O{sub 4} ceramics can co-fire with Ag electrode. -- Abstract: A new low loss microwave dielectric ceramic with composition of CoLi{sub 2/3}Ti{sub 4/3}O{sub 4} was prepared by a conventional solid-state reaction method. The compound has a cubic spinel structure [Fd-3m (227)] similar to MgFe{sub 2}O{sub 4} with lattice parameters of a = 8.3939 Angstrom-Sign , V = 591.42 Angstrom-Sign {sup 3}, Z = 8 and {rho} = 4.30 g/cm{sup 3}. This ceramic has a low sintering temperature ({approx}1050 Degree-Sign C) and good microwave dielectric properties with relative permittivity of 21.4, Q Multiplication-Sign f value of 35,000 GHz and {tau}{sub f} value of -22 ppm/ Degree-Sign C. Furthermore, the addition of BaCu(B{sub 2}O{sub 5}) (BCB) can effectively lower the sintering temperature from 1050 Degree-Sign C to 900 Degree-Sign C and does not induce much degradation of the microwave dielectric properties. Compatibility with Ag electrode indicates that the BCB added CoLi{sub 2/3}Ti{sub 4/3}O{sub 4} ceramics are good candidates for LTCC applications.

36 MATERIALS SCIENCE↗
DOE OSTI2012

Fabrication of flower-like Ni{sub 3}(NO{sub 3}){sub 2}(OH){sub 4} and their electrochemical properties evaluation

Graphical abstract: Ni{sub 3}(NO{sub 3}){sub 2}(OH){sub 4} nano-flakes materials, which have a flower-like structure, were successfully synthesized by a facile solvothermal method without adding any surfactant. The as-prepared Ni{sub 3}(NO{sub 3}){sub 2}(OH){sub 4} possesses a maximum specific capacitance of 2212.5 F g{sup −1} at the current density of 5 mA, suggesting its potential application in electrode material for secondary batteries and electrochemical capacitors. Highlights: ► Flower-like Ni{sub 3}(NO{sub 3}){sub 2}(OH){sub 4} materials were fabricated in a simple method. ► High specific capacitance of 2212.5 F g{sup −1} has been achieved. ► For the first time the effects of concentration and temperature on its specific capacitance has been studied. -- Abstract: Flower-like Ni{sub 3}(NO{sub 3}){sub 2}(OH){sub 4} was successfully synthesized by a facile solvothermal method. The microstructure and surface morphology of prepared Ni{sub 3}(NO{sub 3}){sub 2}(OH){sub 4} were physically characterized by X-ray diffraction (XRD) analysis, scanning electron microscopy (SEM) and transmission electron microscope (TEM). The electrochemical properties studies were carried out using cyclic voltammetry (CV), chronopotentiometry technology and AC impedance spectroscopy, respectively. The results indicate that the flower-like structure has a profound impact on electrode performance at high discharge capacitance. A maximum specific capacitance of 2212.5 F g{sup −1} at the current density of 5 mA could be achieved, suggesting its potential application in electrode material for secondary batteries and electrochemical capacitors. Furthermore, the effects of Ni(NO{sub 3}){sub 2}·6H{sub 2}O concentration and temperature on the microstructure and specific capacitance of prepared Ni{sub 3}(NO{sub 3}){sub 2}(OH){sub 4} have also been systematically studied. The results show that flower-like structure can be formed when the concentration is appropriate, while the temperature has just little effect on its electrochemical properties.

36 MATERIALS SCIENCE↗
DOE OSTI2012

Polymer/organosilica nanocomposites based on polyimide with benzimidazole linkages and reactive organoclay containing isoleucine amino acid: Synthesis, characterization and morphology properties

Highlights: ► A reactive organoclay was formed using L-isoleucine amino acid as a swelling agent. ► Polyimide was synthesized from benzimidazole diamine and pyromellitic dianhydride. ► Imide and benzimidazole groups assured the thermal stability of the nanocomposites. ► Nanocomposite films were prepared by an in situ polymerization reaction. ► The TEM micrographs of nanocomposites revealed well-exfoliated structures. -- Abstract: Polyimide–silica nanocomposites are attractive hybrid architectures that possess excellent mechanical, thermal and chemical properties. But, the dispersion of inorganic domains in the polymer matrix and the compatibility between the organic and inorganic phases are critical factors in these hybrid systems. In this investigation, a reactive organoclay was prepared via ion exchange reaction between protonated form of difunctional L-isoleucine amino acid as a swelling agent and Cloisite Na{sup +} montmorillonite. Amine functional groups of this swelling agent formed an ionic bond with the negatively charged silicates, whereas the remaining acid functional groups were available for further interaction with polymer chains. Then organo-soluble polyimide (PI) have been successfully synthesized from the reaction of 2-(3,5-diaminophenyl)-benzimidazole and pyromellitic dianhydride in N,N-dimethylacetamide. Finally, PI/organoclay nanocomposite films enclosing 1%, 3%, 5%, 7% and 10% of synthesized organoclay were successfully prepared by an in situ polymerization reaction through thermal imidization. The synthesized hybrid materials were subsequently characterized by Fourier transform infrared spectroscopy, X-ray diffraction, electron microscopy, and thermogravimetric analysis techniques. The PI/organoclay nanocomposite films have good optical transparencies and the mechanical properties were substantially improved by the incorporation of the reactive organoclay.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2013

CuO cauliflowers for supercapacitor application: Novel potentiodynamic deposition

Graphical abstract: Schematic experimental setup used for the potentiodynamic mode of electrodeposition for the synthesis of CuO cauliflower onto stainless steel substrate. Highlights: ► Synthesis of CuO using potentiodynamic mode of electrodeposition. ► Uniformly spread cauliflower-like nanostructure. ► CuO cauliflowers provide high specific capacitance with good stability. ► CuO cauliflowers show high power and energy density values. -- Abstract: In present investigation, synthesis and characterization of novel cauliflower-like copper oxide (CuO) and its electrochemical properties have been performed. The utilized CuO cauliflowers were prepared by potentiodyanamic mode from an aqueous alkaline bath. X-ray diffraction pattern confirm the formation of monoclinic CuO cauliflowers. Scanning electron micrograph analysis reveals that CuO cauliflowers are uniformly spread all over the substrate surface with the surface area of 49 m{sup 2} g{sup −1} with bimodal pore size distribution. Electrochemical analysis shows that CuO cauliflower exhibits high specific capacitance of 179 Fg{sup −1} in 1 M Na{sub 2}SO{sub 4} electrolyte with 81% capacity retention after 2000 cycles. The Ragone plot discovers better power and energy densities of cauliflowers-like CuO sample. Present investigation illustrates that the potentiodynamic approach for the direct growth of cauliflower-like CuO is simple and cost-effective and can be applied for synthesis of other metal oxides, polymers etc.

36 MATERIALS SCIENCE↗
DOE OSTI2013

First-principles study on doping and temperature dependence of thermoelectric property of Bi{sub 2}S{sub 3} thermoelectric material

Graphical abstract: The direction-induced ZT is found. At ZZ direction and n = 1.47 × 10{sup 19} cm{sup −3}, the ZT can reach maximal value, 0.36, which is three times as much as maximal laboratorial value. This result matches well the analysis of electron effective mass. Highlights: ► Electrical transportations of Bi{sub 2}S{sub 3} depend on the concentration and temperature. ► The direction-induced ZT is found. ► At ZZ direction and n = 1.47 × 10{sup 19} cm{sup −3}, the ZT can reach maximal value, 0.36. ► The maximal ZT value is three times as much as maximal laboratorial value. ► By doping and temperature tuning, Bi{sub 2}S{sub 3} is a promising thermoelectric material. - Abstract: The electronic structure and thermoelectric property of Bi{sub 2}S{sub 3} are investigated. The electron and hole effective mass of Bi{sub 2}S{sub 3} is analyzed in detail, from which we find that the thermoelectric transportation varies in different directions in Bi{sub 2}S{sub 3} crystal. Along ac plane the higher figure of merit (ZT) could be achieved. For n-type doped Bi{sub 2}S{sub 3}, the optimal doping concentration is found in the range of (1.0–5.0) × 10{sup 19} cm{sup −3}, in which the maximal ZT reaches 0.21 at 900 K, but along ZZ direction, the maximal ZT reaches 0.36. These findings provide a new understanding of thermoelectricity-dependent structure factors and improving ZT ways. The donor concentration N increases as T increases at one bar of pressure under a suitable chemical potential μ, but above this chemical potential μ, the donor concentration N keeps a constant.

36 MATERIALS SCIENCE↗
DOE OSTI2013

A novel solvethermal method for the preparation of magnetic monodisperse Fe{sub 3}O{sub 4} nanoparticles II: High-surface-activity ferrihydrite used as precursor

Graphical abstract: The magnetic monodisperse Fe{sub 3}O{sub 4} nanoparticles (NPs) were prepared by novel solvethemal method at moderate temperature using high surface active ferrihydrit and iron powder as precursors in orgnic solvent. - Highlights: • Facile synthesis of organic ligands-coated monodisperse Fe{sub 3}O{sub 4} nanoparticles at low temperature. • Low-cost high surface active ferrihydrit and reductive iron powder were used as precursors. • N{sub 2}-free reaction environment. • Organic ligands act as reductive. - Abstract: Magnetic monodisperse Fe{sub 3}O{sub 4} nanoparticles (NPs) were prepared from ferrihydrite and iron powder by a novel solvethermal method at moderate temperatures in aqueous and organic solvent media. The effects of temperature and solvent medium on the phase and particle size of Fe{sub 3}O{sub 4} NPs were investigated. The products were characterized by X-ray powder diffraction, infrared spectroscopy, differential scanning calorimetry–thermogravimetric analysis, transmission electron microscopy, and vibrating sample magnetometry. At 120 °C in the organic medium, uniform organic-ligand-coated superparamagnetic Fe{sub 3}O{sub 4} NPs were produced; the particle size increased with the temperature, and the calculated mean particle size was 8.9 nm. At 180 °C in the aqueous medium, pure-phase Fe{sub 3}O{sub 4} was obtained. Thus, the organic solvent did not only serve as a solvent but also participated in the reaction. Fe{sub 3}O{sub 4} production in the aqueous and organic solvent media had different mechanisms.

36 MATERIALS SCIENCE↗
DOE OSTI2015

Novel organic–inorganic amorphous photoactive hybrid films with rare earth (Eu{sup 3+}, Tb{sup 3+}) covalently embedded into silicon–oxygen network via sol–gel process

Highlights: • The hybrids are prepared through the hydrolysis and condensation process. • The hybrids are amorphous and heat stabilized. • The hybrids containing Eu{sup 3+} and Tb{sup 3+} show the typical red and green emissions. - Abstract: Novel organic–inorganic hybrid amorphous thin films were synthesized by linking lanthanide (Tb{sup 3+}, Eu{sup 3+}) complexes through 3,4-bis(3-(triethoxysilyl)propylcarbamoyloxy)benzoic acid using sol–gel method. These inorganic–organic hybrids were characterized in detail by Fourier transform infrared spectroscopy, wide angle X-ray diffraction, themogravimetric analysis, scanning electron microscope, and fluorescence spectra. The above research results indicate that the hybrids possess high thermal-stability, amorphous structure features and especially favorable luminescent performances, such as long luminescent decay lifetime, high quantum yield etc.

36 MATERIALS SCIENCE↗
DOE OSTI2013

Interactions in 1-ethyl-3-methyl imidazolium tetracyanoborate ion pair: Spectroscopic and density functional study

Density Functional Theory is used to investigate a weakly coordinating room-temperature ionic liquid, 1-ethyl-3-methyl imidazolium tetracyanoborate ([Emim]{sup +}[TCB]{sup -}). Four locally stable conformers of the ion pair were located. Atoms-in-molecules (AIM) and electron density analysis indicated the existence of several hydrogen bonds. Further investigation through the Natural Bond Orbital (NBO) and Natural Energy Decomposition Analysis (NEDA) calculations provided insight into the origin of interactions in the [Emim]{sup +}[TCB]{sup -} ion pair. Strength of molecular interactions in the ionic liquid was correlated with frequency shifts of the characteristic vibrations of the ion pair. Harmonic vibrations of the ion pair were also compared with the experimental Raman and Infrared spectra. Vibrational frequencies were assigned by visualizing displacements of atoms around their equilibrium positions and through Potential Energy Distribution (PED) analysis.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗