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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 181 records · Page 10
All sourcesNASA NTRSDOE OSTI
DOE OSTI2019

Characterization and Integrated Fabrication of Al Components with Thick TiC{sub p}/Al Composite Coatings via Self-Propagating Reaction

A novel and quick process combining self-propagating reaction with vacuum-expendable pattern casting is presented to accomplish integrated preparation of millimeter-thick TiC{sub p}/Al composite coatings on the Al substrate. Titanium and graphite powders were mixed with the polytetrafluoroethylene (PTFE) additive and pasted on the expendable polystyrene (EPS) followed by compaction. Al components with in situ TiC{sub p}/Al composite coating were simultaneously synthesized at a relatively low temperature of molten Al, which was poured into the assembly of EPS and powder compact inside the silica sands. Differential scanning calorimetry, x-ray diffraction, scanning electron microscopy with energy-dispersive spectroscopy and transmission electron microscopy were used to systematically investigate the thermodynamic characteristics of the reaction, the phase constituents, microstructure and tribological properties of the coatings. The infiltration model describing the densification of the reaction coatings was also developed for the critical wetting condition. The wear characteristics were assessed using a pin-on-disk tribometer with various loads. Results showed that uniform TiC particles stimulated by the PTFE-activated self-propagating reaction afforded superior mechanical properties and wear resistance.

36 MATERIALS SCIENCE↗
DOE OSTI2013

Nanocrystalline Cs{sub x}WO{sub 3} particles: Effects of N{sub 2} annealing on microstructure and near-infrared shielding characteristics

In order to further improve the near-infrared shielding properties of cesium tungsten bronze (Cs{sub x}WO{sub 3}) for solar filter applications, Cs{sub x}WO{sub 3} particles were prepared by solvothermal reaction method and the effects of nitrogen annealing on the microstructure and near-infrared shielding properties of Cs{sub x}WO{sub 3} were investigated. The obtained Cs{sub x}WO{sub 3} samples were characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy and spectrophotometer. The results indicate that nanosheet-like Cs{sub x}WO{sub 3} particles with hexagonal structure began to transform into nanorods after annealed at temperature higher than 600 °C. The near-infrared shielding properties of Cs{sub x}WO{sub 3} particles could be further improved by N{sub 2} annealing at 500–700 °C. Particularly, the 500 °C-annealed Cs{sub x}WO{sub 3} samples in the N{sub 2} atmosphere showed best near-infrared shielding properties. It was suggested that the excellent near-infrared shielding ability of the 500 °C-annealed Cs{sub x}WO{sub 3} samples is correlated with its minimum O/W atomic ratio and most oxygen vacancies. Highlights: • N{sub 2} annealing could further improve the near-infrared (NIR) shielding of Cs{sub x}WO{sub 3}. • Effects of N{sub 2} annealing on microstructure and NIR shielding of Cs{sub x}WO{sub 3} were studied. • The 500 °C-N{sub 2}-annealed Cs{sub x}WO{sub 3} exhibited minimum O/W ratio and most oxygen vacancies. • The 500 °C-N{sub 2}-annealed Cs{sub x}WO{sub 3} particles exhibited best NIR shielding properties.

36 MATERIALS SCIENCE↗
DOE OSTI2015

Low temperature one-step synthesis of rutile TiO{sub 2}/BiOCl composites with enhanced photocatalytic activity

The rutile TiO{sub 2}/BiOCl composites were successfully fabricated by a facile one-step hydrolysis method at low temperature (50 °C). The X-ray diffraction, scanning electron microscopy, transmission electron microscopy, UV–vis diffuse reflectance spectra, Fourier transform infrared spectroscopy, Brunauer–Emmett–Teller, and X-ray photoelectron spectroscopy measurements were employed to characterize the phase structures, morphologies, optical properties, surface areas, and electronic state of the samples. The rutile TiO{sub 2}/BiOCl composites exhibited higher photocatalytic activity than pure BiOCl and rutile TiO{sub 2} for the degradation of phenol under artificial solar light irradiation. In addition, the photocatalytic mechanism has also been investigated and discussed. The enhanced photocatalytic performance of rutile TiO{sub 2}/BiOCl composites is closely related to the heterojunctions between BiOCl and rutile TiO{sub 2}, which can not only broaden the light adsorption range of BiOCl but also improve the electron–hole separation efficiency under artificial solar light irradiation. - Highlights: • Rutile TiO{sub 2}/BiOCl was prepared by a low temperature one-step hydrolysis method. • The synthetic method is quite convenient and energy-saving. • The composites exhibit enhanced photocatalytic activity on phenol degradation. • The high photocatalytic activity relates to the heterojunctions of BiOCl and TiO{sub 2}.

36 MATERIALS SCIENCE↗
DOE OSTI2017

Microstructural characteristics of σ phase and P phase in Ru-containing single crystal superalloys

Microstructural instability caused by topologically close-packed (TCP) phase precipitation restricts the useful compositional range of advanced Ni-base single crystal superalloys in industrial applications. Limited systematic investigations of TCP formers (Cr and Mo) additions on microstructural evolution of both the σ phase and the P phase in Ru-containing single crystal superalloys have been reported. In this study, the microstructural characteristics of σ phase and P phase were investigated in three Ru-containing superalloys with different levels of Cr and Mo additions at 950 °C and 1100 °C by using phase extraction, X-ray diffraction, scanning electron microscope and high resolution transmission electron microscopy. The experimental results indicated that the high level additions of Cr and Mo promoted the formation of σ phase and P phase, respectively. The amount of σ phase was much higher than that of P phase after long term exposure at 950 °C and 1100 °C. The sheet-like σ phase existed in the alloy with higher Cr addition after thermal exposure at 950 °C and 1100 °C for 1000 h, while the needle-like P phase precipitated in high Mo content alloy after thermal exposure at 1100 °C for 1000 h and the intergrowth of σ phase and P phase was observed after thermal exposure at 950 °C for 500 h. Both the σ phase and P phase were enriched in Re, W, Cr and Mo, but the σ phase contained more Re and Cr while the P phase contained more Mo and Ni, and Ru was found in both phases. The nucleation of σ phase was much easier than P phase due to the more ledge steps in the interfacial structure between σ phase and matrix, as well as the higher partitioning ratios of Re, Cr and Mo. This study is helpful to understand the microstructural evolution of σ phase and P phase, and to optimize the alloy design in Ru-containing superalloys. - Highlights: •Microstructures of σ phase and P phase were characterized in detail. •Cr and Mo influenced the precipitation of σ phase and P phase, respectively. •Partitioning ratios and interfacial relationship decided precipitation behaviors.

36 MATERIALS SCIENCE↗
DOE OSTI2013

Silver chromate and silver dichromate nanostructures: Sonochemical synthesis, characterization, and photocatalytic properties

Graphical abstract: In this work, Ag{sub 2}CrO{sub 4} and Ag{sub 2}Cr{sub 2}O{sub 7} nanostructures have been sonochemically prepared using silver salicylate. The effect of preparation parameters on the morphology of the products was investigated by SEM images. Highlights: ► Herein, Ag{sub 2}CrO{sub 4} and Ag{sub 2}Cr{sub 2}O{sub 7} nanostructures have been sonochemically prepared. ► The effect of preparation parameters on the morphology of the products was investigated. ► The photocatalytic activity of the as-prepared Ag{sub 2}CrO{sub 4} nanoparticles was tested. ► XPS spectra indicated the high purity of Ag{sub 2}Cr{sub 2}O{sub 7} nanostructures obtained. - Abstract: In this work, Ag{sub 2}CrO{sub 4} and Ag{sub 2}Cr{sub 2}O{sub 7} nanostructures have been produced via a sonochemical method using silver salicylate as precursor. Besides silver salicylate, Na{sub 2}CrO{sub 4} and (NH{sub 4}){sub 2}Cr{sub 2}O{sub 7} as starting reagents were applied. To investigate the effect of preparation parameters on the morphology and particle size of Ag{sub 2}CrO{sub 4} and Ag{sub 2}Cr{sub 2}O{sub 7}, sonication time, type of surfactant and its concentration were changed. The as-produced nanostructures were characterized by techniques like powder X-ray diffraction, scanning electron microscopy, and X-ray photoelectron spectroscopy. The scanning electron micrographs showed that particle-like and rod-like nanostructures of Ag{sub 2}CrO{sub 4} and Ag{sub 2}Cr{sub 2}O{sub 7} were produced using different surfactants. To investigate the catalytic properties of Ag{sub 2}CrO{sub 4} nanoparticles, photooxidation of methyl orange (MO) was performed. According to the obtained results, it was found that the methyl orange degradation was about 87.3% after 280 min irradiation of visible light.

36 MATERIALS SCIENCE↗
DOE OSTI2013

Morphology-controlled synthesis of Ag{sub 3}PO{sub 4} nano/microcrystals and their antibacterial properties

Graphical abstract: The Ag{sub 3}PO{sub 4} with rhombic dodecahedral, spherical and small size particles were controllable fabricated just by changing the types of the solvent. The materials possess good antibacterial properties toward different kinds of bacteria. - Highlights: • The Ag{sub 3}PO{sub 4} with three morphologies were controllable fabricated. • The Ag{sub 3}PO{sub 4} as-prepared possess obvious antibacterial properties in the dark. • The antibacterial ability of Ag{sub 3}PO{sub 4} could be greatly improved under the visible light irradiation. - Abstract: We reported the controllable fabrication of Ag{sub 3}PO{sub 4} nano/microcrystals through a simple solution-based precipitation reaction. The samples were characterized by X-ray powder diffraction, scanning electron microscopy, transmission electron microscopy and infrared spectroscopy. The results indicated that the Ag{sub 3}PO{sub 4} crystals with three different morphology, including the rhombic dodecahedron of 500 nm, the sphere of 100 nm and the particles with small-size of 20 nm, could be obtained in the solvents of water, ethylene glycol (EG) and dimethyl sulfoxide (DMSO). The antibacterial assay showed that all samples possess obvious antibacterial properties. In addition, the Ag{sub 3}PO{sub 4} with small size of 20 nm showed better activity due to their high specific surface areas. Notably, we have found that the antibacterial ability of Ag{sub 3}PO{sub 4} could be greatly improved under the visible light irradiation, which are superior to that in the dark and commercial streptomycin.

36 MATERIALS SCIENCE↗
DOE OSTI2015

Mesoporous hollow Zn{sub 2}SiO{sub 4}:Mn{sup 2+} nanospheres: The study of photoluminescence and adsorption properties

Graphical abstract: Mesoporous hollow structure of Zn{sub 2}SiO{sub 4}:Mn{sup 2+} phosphors. - Highlights: • Mesoporous hollow Zn{sub 2}SiO{sub 4}:Mn{sup 2+} nanospheres are prepared via the layer-by-layer technique. • The Zn{sub 2}SiO{sub 4}:Mn{sup 2+} nanospheres exhibit better adsorption capabilities of Pb{sup 2+}, Fe{sup 3+} than Cd{sup 2+}. • The Zn{sub 2}SiO{sub 4}:Mn{sup 2+} nanospheres exhibit strong green emission around 524 nm. • With the increase of doped Mn{sup 2+} concentration, the emission peak shows a red-shift. - Abstract: Mesoporous hollow Zn{sub 2}SiO{sub 4}:Mn{sup 2+} nanospheres were prepared via the layer-by-layer technique using CTAB as surfactant. The structures/microstructures and morphologies of the as-synthesized phosphors were characterized by X-ray diffraction, scanning electron microscope, transmission electron microscope and N{sub 2} adsorption–desorption porosimetry. The adsorption capacity to remove toxic metal ions in water was tested and the results showed that the Zn{sub 2}SiO{sub 4}:Mn{sup 2+} nanospheres exhibited better adsorption capabilities of Pb{sup 2+}, Fe{sup 3+} than Cd{sup 2+}. Moreover, the as-obtained hollow Zn{sub 2}SiO{sub 4}:Mn{sup 2+} phosphors exhibited strong green emission around 524 nm at room temperature. When the atomic ratio of Zn to Mn was 97:3, the emission intensity of Zn{sub 2}SiO{sub 4}:Mn{sup 2+} phosphor was about 1.2 times that of commercial phosphors. Furthermore, with the increase of doped Mn{sup 2+} concentration, the emission peak showed a red-shift.

36 MATERIALS SCIENCE↗
DOE OSTI2015

Ternary and coupled binary zinc tin oxide nanopowders: Synthesis, characterization, and potential application in photocatalytic processes

Highlights: • Mechanochemically synthesized nanocrystalline zinc tin oxide (ZTO) powders. • Photocatalytic degradation of alprazolam in the presence of ZTO water suspensions. • Coupled binary ZTO exhibits enhanced photocatalytic activity compared to ternary ZTO. - Abstract: In this paper, ternary and coupled binary zinc tin oxide nanocrystalline powders were prepared via simple solid-state mechanochemical method. X-ray diffraction, scanning electron microscopy, Raman and reflectance spectroscopy were used to study the structure and optical properties of the obtained powder samples. The thermal behavior of zinc tin oxide system was examined through simultaneous thermogravimetric-differential scanning calorimetric analysis. The efficiencies of ternary (Zn{sub 2}SnO{sub 4} and ZnSnO{sub 3}) and coupled binary (ZnO/SnO{sub 2}) zinc tin oxide water suspensions in the photocatalytic degradation of alprazolam, short-acting anxiolytic of the benzodiazepine class of psychoactive drugs, under UV irradiation were determined and compared with the efficiency of pure ZnO and SnO{sub 2}.

36 MATERIALS SCIENCE↗
DOE OSTI2016

Near white light emitting ZnAl{sub 2}O{sub 4}:Dy{sup 3+} nanocrystals: Sol–gel synthesis and luminescence studies

Highlights: • ZnAl{sub 2}O{sub 4}:Dy{sup 3+} spinel synthesized using sol–gel method. • Characterized by XRD, SEM and PL spectroscopy. • Investigations of emission, excitation and lifetime properties. • Evaluation of defect centers and trap parameters of the system. • Evaluation of CIE indices of near white light emitting phosphor. - Abstract: ZnAl{sub 2}O{sub 4}:Dy{sup 3+} nanoparticles were synthesized using citrate sol–gel method and characterized systematically using X-ray diffraction, scanning electron microscopy and photoluminescence spectroscopy. Emission spectrum of pure ZnAl{sub 2}O{sub 4} shows intense violet blue emission under ultra violet irradiation. Based on electron paramagnetic resonance (EPR) results; it was attributed to presence of singly ionized oxygen vacancy centres in ZnAl{sub 2}O{sub 4}. On doping Dy{sup 3+} in ZnAl{sub 2}O{sub 4}, complete host–dopant energy transfer does not take place. Local structural investigation and lifetime measurements reveal that dysprosium ion is distributed between both Zn{sup 2+} and Al{sup 3+} sites. Near white light from ZnAl{sub 2}O{sub 4}:Dy{sup 3+} is attributed to combined host and dopant luminescence. The trap parameters such as activation energy (E) and frequency factor (s) for TSL glow peak 165 °C were determined using different heating rate method. Thermally stimulated emission showed the presence of oxygen related defect centre.

36 MATERIALS SCIENCE↗
DOE OSTI2017

Composite electrolytes ceramic Li{sub 7}La{sub 3}Zr{sub 2}O{sub 12}/glassy Li{sub 2}O-Y{sub 2}O{sub 3}-SiO{sub 2}

Highlights: • We synthesized Li{sub 7}La{sub 3}Zr{sub 2}O{sub 12}-x wt% 40.2Li{sub 2}O·5.7Y{sub 2}O{sub 3}·54.1SiO{sub 2} (x = 1–10) composites. • Density of the composite samples is higher than one of the sintered Li{sub 7}La{sub 3}Zr{sub 2}O{sub 12}. • The composition with x = 5 has high total conductivity, 2.5 × 10{sup −5} S cm{sup −1} at 25 °C. - Abstract: We have investigated the effect of lithium yttrium-silicate glass 40.2Li{sub 2}O·5.7Y{sub 2}O{sub 3}·54.1SiO{sub 2} on the density and total conductivity of tetragonal Li{sub 7}La{sub 3}Zr{sub 2}O{sub 12}. An optimal sintering temperature (1200 °C) was selected on the basis of a composite with 1 wt% of the glass having the highest density and total conductivity after annealing at this temperature. A series of composites Li{sub 7}La{sub 3}Zr{sub 2}O{sub 12}-x wt% 40.2Li{sub 2}O·5.7Y{sub 2}O{sub 3}·54.1SiO{sub 2} (x = 1–10) was prepared. The samples were characterized by X-ray diffraction, scanning electron microscopy and differential scanning calorimetry. The data revealed that the sintering additive interacted with Li{sub 7}La{sub 3}Zr{sub 2}O{sub 12}, causing the glass to crystallize during annealing. The conductivity of the composites was studied using complex impedance spectroscopy over a temperature range of 20–250 °C. The composite with x = 5 exhibited the highest total conductivity at room temperature: 2.5 × 10{sup −5} S cm{sup −1}.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Ti3+-TiO2/Ce3+-CeO2 Nanosheet heterojunctions as efficient visible-light-driven photocatalysts

Highlights: • A novel Ti{sup 3+}-TiO{sub 2}/Ce{sup 3+}-CeO{sub 2} nanosheet heterojunction is fabricated. • It owns the bandgap of 2.6 eV and extends the photoresponse to visible light region. • It exhibits excellent visible-light-driven photocatalytic performance. • It is due to synergy of Ti{sup 3+}, Ce{sup 3+} co-doping and nanosheet heterojunction. - Abstract: Novel Ti{sup 3+}-TiO{sub 2}/Ce{sup 3+}-CeO{sub 2} nanosheet heterojunctions are successfully prepared via a facile hydrothermal approach combined with a wet-chemical deposition precipitation and an in situ solid-state chemical reduction strategy. The structures of the as-prepared samples are characterized in detail by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, atomic force microscopy, X-ray photoelectron spectroscopy and UV–vis diffuse reflectance spectroscopy. The results show that Ti{sup 3+} and Ce{sup 3+} are both doped into the lattice of TiO{sub 2} and CeO{sub 2}, respectively, which narrow the band gap to 2.7 eV and extend the photoresponse to visible light region. The photocatalytic degradation rate of methyl orange and methylene blue are as high as 93.3% and 97.1% under visible-light illumination, respectively. The high degradation rate is attributed to the efficient doping of Ti{sup 3+} and Ce{sup 3+}, formation of surface oxygen vacancy and heterojunction, which favors the absorption of visible light and separation of photogenerated charge carriers.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2016

Electrochemical synthesis of p-Cu{sub 2}O/n-ZnO nanorods hetero-junction for photovoltaic application

Development of high performance visible light responsive solar cell materials has attracted wide interest due to their potential applications in the energy industries. In this work, ZnO nanorods films were successfully prepared on the ITO coated glass substrates via simple three electrode electrochemical deposition route. The Cu{sub 2}O nanoparticles were then electrodeposited on the surface of ZnO nanorods to form p-Cu{sub 2}O/n-ZnO core-shell hetero-structure. The synthesized ZnO, Cu{sub 2}O films and p-Cu{sub 2}O/n-ZnO hetero-structure were characterized by low angle x-ray diffraction, scanning electron microscopy, and UV-Visible spectrophotometer. Due to the hierarchical morphologies and core-shell structure, p-Cu{sub 2}O/n-ZnO hetero-structure shows a prominent visible-light-driven photocatalytic performance under the low intensity light irradiation. The obtained results suggest that it is possible to synthesize ZnO nanorods, Cu{sub 2}O films and p-Cu{sub 2}O/n-ZnO core-shell hetero-structure by a simple, cost effective and environment friendly electrodeposition process which can be useful for water splitting and solar cell device fabrication.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2016

Urchin-like artificial gallium oxide nanowires grown by a novel MOCVD/CVD-based route for random laser application

A novel procedure based on a two-step method was developed to obtain β-Ga{sub 2}O{sub 3} nanowires by the chemical vapor deposition (CVD) method. The first step consists in the gallium micro-spheres growth inside a metal-organic chemical vapor deposition environment, using an organometallic precursor. Nanoscale spheres covering the microspheres were obtained. The second step involves the CVD oxidization of the gallium micro-spheres, which allow the formation of β-Ga{sub 2}O{sub 3} nanowires on the micro-sphere surface, with the final result being a nanostructure mimicking nature's sea urchin morphology. The grown nanomaterial is characterized by several techniques, including X-ray diffraction, scanning electron microscopy, energy-dispersive X-ray, transmission electron microscopy, and photoluminescence. A discussion about the growth mechanism and the optical properties of the β-Ga{sub 2}O{sub 3} material is presented considering its unknown true bandgap value (extending from 4.4 to 5.68 eV). As an application, the scattering properties of the nanomaterial are exploited to demonstrate random laser emission (around 570 nm) when it is permeated with a laser dye liquid solution.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2015

Cathodic cage plasma deposition of TiN and TiO{sub 2} thin films on silicon substrates

Cathodic cage plasma deposition (CCPD) was used for growing titanium nitride (TiN) and titanium dioxide (TiO{sub 2}) thin films on silicon substrates. The main advantages of the CCPD technique are the uniformity, tridimensionality, and high rate of the film deposition that occurs at higher pressures, lower temperatures, and lower treatment times than those used in conventional nitriding treatments. In this work, the influence of the temperature and gas atmosphere upon the characteristics of the deposited films was investigated. The TiN and TiO{sub 2} thin films were characterized by x-ray diffraction, scanning electron microscopy, and Raman spectroscopy to analyze their chemical, structural, and morphological characteristics, and the combination of these results indicates that the low-cost CCPD technique can be used to produce even and highly crystalline TiN and TiO{sub 2} films.

36 MATERIALS SCIENCE↗
DOE OSTI2014

High quality single atomic layer deposition of hexagonal boron nitride on single crystalline Rh(111) four-inch wafers

The setup of an apparatus for chemical vapor deposition (CVD) of hexagonal boron nitride (h-BN) and its characterization on four-inch wafers in ultra high vacuum (UHV) environment is reported. It provides well-controlled preparation conditions, such as oxygen and argon plasma assisted cleaning and high temperature annealing. In situ characterization of a wafer is accomplished with target current spectroscopy. A piezo motor driven x-y stage allows measurements with a step size of 1 nm on the complete wafer. To benchmark the system performance, we investigated the growth of single layer h-BN on epitaxial Rh(111) thin films. A thorough analysis of the wafer was performed after cutting in atmosphere by low energy electron diffraction, scanning tunneling microscopy, and ultraviolet and X-ray photoelectron spectroscopies. The apparatus is located in a clean room environment and delivers high quality single layers of h-BN and thus grants access to large area UHV processed surfaces, which had been hitherto restricted to expensive, small area single crystal substrates. The facility is versatile enough for customization to other UHV-CVD processes, e.g., graphene on four-inch wafers.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Study of the physical properties of CuS thin films grown by SILAR method

CuS thin films were obtained using the SILAR method on an amorphous glass substrate. All experiments were performed at room temperature. CuS thin films were deposited at 30, 40, 50 and 60 cycles, respectively. Structural, morphological and optical properties of the structures that increase the thickness of nanostructured CuS thin films were investigated. X-ray diffraction, scanning electron microscopy, atomic force microscopy, RAMAN and optical absorption measurements were carried out in order to examine the physical properties of CuS thin films. As a result of the analysis, we can say that the thickness increase positively affects the crystal structure of CuS thin films. In addition, the energy bandgap range of CuS thin films ranged from 2.22 to 1.78 eV. Analysis results of CuS thin films using SILAR method show that thickness is an important factor for thin film studies.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2012

Dielectric properties and electrical conductivity of the hybrid organic-inorganic polyvanadates (H{sub 3}N(CH{sub 2}){sub 4}NH{sub 3})[V{sub 6}O{sub 14}]

Plate-like crystals of the polyvanadate (H{sub 3}N(CH{sub 2}){sub 4}NH{sub 3})[V{sub 6}O{sub 14}] have been synthesized via an hydrothermal treatment. X-ray powder diffraction, scanning electron microscope, Fourier transform infrared spectroscopy, electron spin resonance and complex impedance spectroscopy were used to analyze the hybrid material. The frequency dependence of AC conductivity at different temperatures indicates that the CBH model is the probable mechanism for the AC conduction behavior. The conductivity was measured by complex impedance spectroscopy which is equal to 31.10{sup -3} {Omega}{sup -1} m{sup -1} at 443 K. The Arrhenius diagram is not linear, it presents a rupture situated at 357 K and the activation energies' average values are 0.22 eV and 0.14 eV, deduced from the Arrhenius relation. - Graphical abstract: At high temperature {epsilon} Double-Prime increases more rapidly which is due to the increasing conduction loss which rises with the increment in the DC conductivity. Highlights: Black-Right-Pointing-Pointer Rectangular plate-like crystals (H{sub 3}N(CH{sub 2}){sub 4}NH{sub 3})[V{sub 6}O{sub 14}] were synthesized. Black-Right-Pointing-Pointer frequency and temperature dependence of AC conductivity indicate CBH model. Black-Right-Pointing-Pointer The temperature dependence of DC conductivity exhibits two conduction mechanisms.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2015

Magnetic and structural properties of nanostructured Fe–20Al–2Cr powder mixtures

Nanostructured Fe–20Al–2Cr (wt.%) powders have been prepared using high energy planetary ball-mill. Changes in structural, morphological and magnetic properties of the powders during mechanical alloying (MA) and during subsequent annealing have been examined by X-ray diffraction, scanning electron microscopy (SEM) and vibrating sample magnetometer (VSM). The observed structural and microstructural changes have been related to several processes occurring during MA. After MA, the material becomes significantly disordered and refines to nanoscale grain sizes (~ 14 nm). The obtained bcc α-Fe(Al,Cr) solid solution shows a ferromagnetic behavior. Upon subsequent annealing at 400 °C, α-Fe{sub 2}O{sub 3} and spinel oxides are formed at the surface of particles, while structural defects disappeared as Fe(Al,Cr) solid solution becomes more ordered and grain growth occurs. The saturation magnetization (Ms) shows lower values after annealing, attributed to the formation of metal oxides with low magnetic moment. - Graphical abstract: Display Omitted - Highlights: • Nanostructured Fe–Al–Cr powders were prepared by MA. • Careful analysis of the XRD patterns by using the Rietveld refinement • The lattice distortion is evidenced by the increase of both the lattice parameter and the static Debye Waller parameter. • Annealing at 400 °C stabilizes the microstructure at the nanometer range and leads to the formation of Fe{sub 3}O{sub 4} and Fe{sub 2}O{sub 3} oxides. • Both the milled and annealed samples are ferromagnetic.

36 MATERIALS SCIENCE↗