Sample records for nanocrystalline ni3c synthesized

  1. Syntheses of nanocrystalline BaTiO3 and their optical properties

    NASA Astrophysics Data System (ADS)

    Yu, J.; Chu, J.; Zhang, M.

    Stoichiometric and titanium-excess nanocrystalline barium titanates were synthesized using a hydrothermal process at various hydrothermal temperatures and with further heat treatment at 500 °C and 900 °C. Owing to the different process conditions, the excess titanium exists in different states and configurations within the nanocrystalline BaTiO3 matrix; this was demonstrated by X-ray diffraction, Raman scattering, and photoluminescence. In these nanocrystalline BaTiO3, the 590, 571, 543 and 694 nm light emission bands were observed; mechanisms leading to such emissions were also discussed.

  2. Microstructural Investigation, Raman and Magnetic Studies on Chemically Synthesized Nanocrystalline Ni-Doped Gadolinium Oxide (Gd1.90Ni0.10O3- δ )

    NASA Astrophysics Data System (ADS)

    Sarkar, B. J.; Mandal, J.; Dalal, M.; Bandyopadhyay, A.; Satpati, B.; Chakrabarti, P. K.

    2018-03-01

    Nanocrystalline Ni-doped gadolinium oxide (Gd1.90Ni0.10O3- δ , GNO) is synthesized by co-precipitation method. The as-prepared sample is annealed in vacuum at 700°C for 6 h. Analyses of the x-ray diffractogram by Rietveld refinement method, transmission electron microscopy and Raman spectroscopy of GNO recorded at room temperature confirmed the pure crystallographic phase and complete substitution of Ni-ions in Gd2O3 lattice. Magnetization ( M) as a function of temperature ( T) and magnetic field ( H) is measured by a superconducting quantum interference device magnetometer, which suggests the presence of ferromagnetic/antiferromagnetic phases together with a paramagnetic phase. From the M-T curve it can be shown that the ferromagnetic phase dominates over para-/antiferromagnetic phases in the temperature range of 300-100 K, but from 100 K to 50 K, the antiferromagnetic phase dominates over ferro-/paramagnetic phases. Hysteresis loops recorded at different temperatures indicate the presence of weak ferro-/antiferromagnetism, which dominates in the low field region (˜ 4000 Oe), above which magnetization increases linearly. The sharp increase of magnetization in M-T curve observed in the temperature range of 50-5 K confirms the presence of dominating ferromagnetic plus paramagnetic phase over antiferromagnetic part. For the first time a combined formula generated from three-dimensional (3D) spin wave model and Johnston formula is proposed to analyze the coexistence of different magnetic phases in different temperature ranges. Interestingly, the combined formula successfully explains the co-existence of different magnetic phases along with their contribution at different temperatures. The onset of ferromagnetism in Gd1.90Ni0.10O3- δ is explained by oxygen vacancy mediated F-centre exchange (FCE) coupling mechanism.

  3. Nanocrystalline NiNd0.01Fe1.99O4 as a gas sensor

    NASA Astrophysics Data System (ADS)

    Shinde, Tukaram J.; Gadkari, Ashok B.; Jadhav, Sarjerao R.; Kumar, Surender; Dalawai, Sanjeev P.; Vasambekar, Pramod N.

    2015-06-01

    Nanocrystalline NiNd0.01Fe1.99O4 has been synthesized by oxalate co-precipitation method and was characterized by X-ray diffraction technique. X-ray diffraction analysis confirms the formation of single phase cubic spinel structure. Crystallite size of the ferrite lies in the nano-particle range. The gas sensing properties of nanocrystalline ferrite were studied for gases like Cl2, LPG and C2H5OH. It was observed that NiNd0.01Fe1.99O4 is more sensitive towards chlorine followed by LPG at an operating temperature 277 °C compared to ethanol.

  4. Enhancement of photocatalytic activity of combustion-synthesized CeO2/C3N4 nanoparticles

    NASA Astrophysics Data System (ADS)

    Li, Dong-Feng; Yang, Ke; Wang, Xiao-qin; Ma, Ya-Li; Huang, Gui-Fang; Huang, Wei-Qing

    2015-09-01

    Nanocrystalline CeO2/C3N4 was synthesized via a one-step solution combustion method using urea as fuel for the first time. The effects of the molar ratio of urea to cerium chloride on the photocatalytic activity of the synthesized samples were investigated. The synthesized nanocrystalline CeO2/C3N4 shows small size and large surface exposure area. Photocatalytic degradation of methylene blue demonstrates that the synthesized nanocrystalline CeO2/C3N4 possesses enhanced photocatalytic activity. It is proposed that the enhanced photocatalytic activity might be related to the favorable morphology and structure, and the effective charge separation between C3N4 and CeO2 in the photocatalytic process.

  5. Room Temperature Antiferromagnetic Ordering of Nanocrystalline Tb1.90Ni0.10O3

    NASA Astrophysics Data System (ADS)

    Mandal, J.; Dalal, M.; Sarkar, B. J.; Chakrabarti, P. K.

    2017-02-01

    Nanocrystalline Ni-doped terbium oxide (Tb1.90Ni0.10O3) has been synthesized by the co-precipitation method followed by annealing at 700°C for 6 h in vacuum. The crystallographic phase and the substitution of Ni2+ ions in the lattice of Tb2O3 are confirmed by Rietveld analysis of the x-ray diffraction pattern using the software MAUD. High-resolution transmission electron microscopy is also carried out to study the morphology of the sample. Magnetic measurements are carried out at different temperatures from 5 K to 300 K using a superconducting quantum interference device (SQUID) magnetometer. The dependence of the magnetization of Tb1.90Ni0.10O3 as a function of temperature ( M- T) and magnetic field ( M- H) suggests the presence of both paramagnetic and antiferromagnetic phase at room temperature, but antiferromagnetic phase dominates below ˜120 K. The lack of saturation in the M- H curve and good fitting of the M- T curve by the Johnston formula also indicate the presence of both paramagnetic and antiferromagnetic phase at room temperature. Interestingly, an antiferromagnetic to ferromagnetic phase transition is observed below ˜40 K. The result also shows a high value of magnetization at 5 K.

  6. Nanocrystalline NiNd{sub 0.01}Fe{sub 1.99}O{sub 4} as a gas sensor

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Shinde, Tukaram J., E-mail: pshindetj@yahoo.co.in; Gadkari, Ashok B.; Jadhav, Sarjerao R.

    2015-06-24

    Nanocrystalline NiNd{sub 0.01}Fe{sub 1.99}O{sub 4} has been synthesized by oxalate co-precipitation method and was characterized by X-ray diffraction technique. X-ray diffraction analysis confirms the formation of single phase cubic spinel structure. Crystallite size of the ferrite lies in the nano-particle range. The gas sensing properties of nanocrystalline ferrite were studied for gases like Cl{sub 2}, LPG and C{sub 2}H{sub 5}OH. It was observed that NiNd{sub 0.01}Fe{sub 1.99}O{sub 4} is more sensitive towards chlorine followed by LPG at an operating temperature 277 °C compared to ethanol.

  7. Synthesis of porous nanocrystalline NiO with hexagonal sheet-like morphology by homogeneous precipitation method

    NASA Astrophysics Data System (ADS)

    Sharma, Ravi Kant; Ghose, Ranjana

    2015-04-01

    Porous nanocrystalline NiO has been synthesized by a simple homogeneous precipitation method in short time at low calcination temperature without using any surfactant, chelating or gelating agents. The porous nanocrystalline NiO with a hexagonal sheet-like morphology were obtained by calcination of Ni(OH)2 nanoflakes at 500 °C. The calcination temperature strongly influences the morphology, crystallite size, specific surface area, pore volume and optical band gap of the samples. The samples were characterized using powder X-ray diffraction, thermal gravimetric analysis, FT-IR spectroscopy, UV-Visible diffuse reflectance spectroscopy, surface area measurements, field emission scanning electron microscopy coupled with energy dispersive X-ray analysis and transmission electron microscopy. The chemical activity of the samples was tested by catalytic reduction of 4-nitrophenol with NaBH4.

  8. Microstructures and mechanical properties of nanocrystalline NiTi intermetallics formed by mechanosynthesis

    NASA Astrophysics Data System (ADS)

    Arunkumar, S.; Kumaravel, P.; Velmurugan, C.; Senthilkumar, V.

    2018-01-01

    The formulation of nanocrystalline NiTi shape memory alloys has potential effects in mechanical stimulation and medical implantology. The present work elucidates the effect of milling time on the product's structural characteristics, chemical composition, and microhardness for NiTi synthesized by mechanical alloying for different milling durations. Increasing the milling duration led to the formation of a nanocrystalline NiTi intermetallic at a higher level. The formation of nanocrystalline materials was directed through cold fusion, fracturing, and the development of a steady state, which were influenced by the accumulation of strain energy. In the morphological study, uninterrupted cold diffusion and fracturing were visualized using transmission electron microscopy. Particle size analysis revealed that the mean particle size was reduced to 93 μm after 20 h of milling. The mechanical strength was enhanced by the formation of a nanocrystalline intermetallic phase at longer milling time, which was confirmed by the results of Vickers hardness analyses.

  9. Room temperature ferromagnetism of nanocrystalline Nd1.90Ni0.10O3

    NASA Astrophysics Data System (ADS)

    Sarkar, B. J.; Mandal, J.; Dalal, M.; Bandyopadhyay, A.; Chakrabarti, P. K.

    2018-05-01

    Nanocrystalline sample of Ni2+ doped neodymium oxide (Nd1.90Ni0.10O3-δ, NNO) is synthesized by co-precipitation method. Analysis of X-ray diffraction (XRD) pattern by Rietveld refinement method confirms the desired phase of NNO and complete substitution of Ni2+ ions in the Nd2O3 lattice. Analyses of transmission electron microscopy (TEM) and Raman spectroscopy of NNO recorded at room temperature (RT) also substantiate this fact. Besides, no traces of impurities are found in the analyses of XRD, TEM and Raman data. Room temperature hysteresis loop of NNO suggests the presence of weak ferromagnetism (FM) in low field region ( 600 mT), but in high field region paramagnetism of the host is more prominent. Magnetization vs. temperature ( M- T) curve in the entire temperature range (300-5 K) is analyzed successfully by a combined equation generated from three-dimensional (3D) spin wave model and Curie-Weiss law, which suggests the presence of mixed paramagnetic phase together with ferromagnetic phase in the doped sample. The onset of magnetic ordering is analyzed by oxygen vacancy mediated F-center exchange (FCE) coupling mechanism.

  10. Trace elements study of high purity nanocrystalline silicon carbide (3C-SiC) using k0-INAA method

    NASA Astrophysics Data System (ADS)

    Huseynov, Elchin; Jazbec, Anze

    2017-07-01

    Silicon carbide (3C-SiC) nanoparticles have been irradiated by neutron flux (2×1013 n·cm-2·s-1) at TRIGA Mark II type research reactor. After neutron irradiation, the radioisotopes of trace elements in the nanocrystalline 3C-SiC were studied as time functions. The identification of isotopes which significantly increased the activity of the samples as a result of neutron radiation was carried out. Nanocrystalline 3C-SiC are synthesized by standard laser technique and the purity of samples was determined by the k0-based Instrumental Neutron Activation Analysis (k0-INAA) method. Trace elements concentration in the 3C-SiC nanoparticles were determined by the radionuclides of appropriate elements. The trace element isotopes concentration have been calculated in percentage according to k0-INAA method.

  11. Electrical impedance spectroscopy of neutron-irradiated nanocrystalline silicon carbide (3C-SiC)

    NASA Astrophysics Data System (ADS)

    Huseynov, Elchin M.

    2018-01-01

    It the present work, impedance spectra of nanocrystalline 3C-SiC particles have been comparatively analyzed before and after neutron irradiation. Resonance states and shifts were observed at the impedance spectra of nanocrystalline 3C-SiC particles after neutron irradiation. Relaxation time has been calculated from interdependence of real and imaginary parts of impedance of nanocrystalline 3C-SiC particles. Calculated relaxation times have been investigated as a function of neutron irradiation period. Neutron transmutation (31P isotopes production) effects on the impedance spectra and relaxation times have been studied. Moreover, influence of agglomeration and amorphous transformation to the impedance spectra and relaxation times of nanocrystalline 3C-SiC particles have been investigated.

  12. Evaluation of structural, morphological and magnetic properties of CuZnNi (CuxZn0.5-xNi0.5Fe2O4) nanocrystalline ferrites for core, switching and MLCI's applications

    NASA Astrophysics Data System (ADS)

    Akhtar, Majid Niaz; Khan, Muhammad Azhar; Ahmad, Mukhtar; Nazir, M. S.; Imran, M.; Ali, A.; Sattar, A.; Murtaza, G.

    2017-01-01

    The influence of Cu substitution on the structural and morphological characteristics of Ni-Zn nanocrystalline ferrites have been discussed in this work. The detailed and systematic magnetic characterizations were also done for Cu substituted Ni-Zn nanoferrites. The nanocrystalline ferrites of Cu substituted CuxZn0.5-xNi0.5Fe2O4 ferrites (x=0, 0.1, 0.2, 0.3, 0.4 and 0.5) were synthesized using sol gel self-combustion hybrid method. X-ray diffraction (XRD), Field emission scanning electron microscopy (FESEM), Transmission electron microscope (TEM) and Vibrating sample magnetometer (VSM) were used to investigate the properties of Cu substituted nanocrystalline ferrites. Single phase structure of Cu substituted in Ni-Zn nanocrystalline ferrites were investigated for all the samples. Crystallite size, lattice constant and volume of the cell were found to increase by increasing Cu contents in spinel structure. The better morphology with well-organized nanocrystals of Cu-Zn-Ni ferrites at x=0 and 0.5 were observed from both FESEM and TEM analysis. The average grain size was 35-46 nm for all prepared nanocrystalline samples. Magnetic properties such as coercivity, saturation, remanence, magnetic squareness, magneto crystalline anisotropy constant (K) and Bohr magneton were measured from the recorded M-H loops. The magnetic saturation and remanence were increased by the incorporation of Cu contents. However, coercivity follow the Stoner-Wolforth model except for x=0.3 which may be due to the site occupancy and replacement of Cu contents from octahedral site. The squareness ratio confirmed the super paramgnetic behaviour of the Cu substituted in Ni-Zn nanocrystalline ferrites. Furthermore, Cu substituted Ni-Zn nanocrystalline ferrites may be suitable for many industrial and domestic applications such as components of transformers, core, switching, and MLCI's due to variety of the soft magnetic characteristics.

  13. Synthesis and properties of nickel-doped nanocrystalline barium hexaferrite ceramic materials

    NASA Astrophysics Data System (ADS)

    Waqar, Moaz; Rafiq, Muhammad Asif; Mirza, Talha Ahmed; Khalid, Fazal Ahmad; Khaliq, Abdul; Anwar, Muhammad Sabieh; Saleem, Murtaza

    2018-04-01

    M-type barium hexaferrite ceramics have emerged as important materials both for technological and commercial applications. However, limited work has been reported regarding the investigation of nanocrystalline Ni-doped barium hexaferrites. In this study, nanocrystalline barium hexaferrite ceramics with the composition BaFe12- x Ni x O19 (where x = 0, 0.3 and 0.5) were synthesized by sol-gel method and characterized using X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy, vibrating sample magnetometer and precision impedance analyzer. All the synthesized samples had single magnetoplumbite phase having space group P63/mmc showing the successful substitution of Ni in BaFe12O19 without the formation of any impurity phase. Average grain size of undoped samples was around 120 nm which increased slightly with the addition of Ni. Saturation magnetization ( M s) and remnant magnetization ( M r) increased with the addition of Ni, however, coercivity ( H c) decreased with the increase in Ni from x = 0 to x = 0.5. Real and imaginary parts of permittivity decreased with the increasing frequency and increased with Ni content. Dielectric loss and conductivity showed slight variation with the increase in Ni concentration.

  14. Investigating the Thermal and Phase Stability of Nanocrystalline Ni-W Produced by Electrodeposition, Sputtering, and Mechanical Alloying

    NASA Astrophysics Data System (ADS)

    Marvel, Christopher Jonathan

    The development of nanocrystalline materials has been increasingly pursued over the last few decades. They have been shown to exhibit superior properties compared to their coarse-grain counterparts, and thus present a tremendous opportunity to revolutionize the performance of nanoscale devices or bulk structural materials. However, nanocrystalline materials are highly prone to grain growth, and if the nanocrystalline grains coarsen, the beneficial properties are lost. There is a strong effort to determine the most effective thermal stability mechanisms to avoid grain growth, but the physical nature of nanocrystalline grain growth is still unclear due to a lack of detailed understanding of nanocrystalline microstructures. Furthermore, the influence of contamination has scarcely been explored with advanced transmission electron microscopy techniques, nor has there been a direct comparison of alloys fabricated with different bulk processes. Therefore, this research has applied aberration-corrected scanning transmission electron microscopy to characterize nanocrystalline Ni-W on the atomic scale and elucidate the physical grain growth behavior. Three primary objectives were pursued: (1) explore the thermal stability mechanisms of nanocrystalline Ni-W, (2) evaluate the phase stability of Ni-W and link any findings to grain growth behavior, and (3) compare the influences of bulk fabrication processing, including electrodeposition, DC magnetron sputtering, and mechanical alloying, on the thermal stability and phase stability of Ni-W. Several thermal stability mechanisms were identified throughout the course of this research. First and foremost, W-segregation was scarcely observed to grain boundaries, and it is unclear if W-segregation improves thermal stability contrary to most reports in the 2 literature. Long-range Ni4W chemical ordering was observed in alloys with more than 20 at.% W, and it is likely Ni4W domains reduce grain boundary mobility. In addition, lattice

  15. Electrode characteristics of nanocrystalline (Zr, Ti)(V, Cr, Ni) 2.41 compound

    NASA Astrophysics Data System (ADS)

    Majchrzycki, W.; Jurczyk, M.

    The electrochemical properties of nanocrystalline Zr 0.35Ti 0.65V 0.85Cr 0.26Ni 1.30 alloy, which has the hexagonal C14 type structure, have been investigated. This material has been prepared using mechanical alloying (MA) followed by annealing. The amorphous phase forms directly from the starting mixture of the elements, without other phase formation. Heating the MA samples at 1070 K for 0.5 h resulted in the creation of ordered alloy. This alloy was used as negative electrode for Ni-MH x battery. The electrochemical results show very little difference between the nanocrystalline and polycrystalline powders, as compared with the substantial difference between these and the amorphous powder. In the annealed nanocrystalline Zr 0.35Ti 0.65V 0.85Cr 0.26Ni 1.30 powders discharging capacities up to 150 mA h g -1 (at 160 mA g -1 discharging current) have been measured. The properties of nanocrystalline electrode were attributed to the structural characteristics of the compound caused by mechanical alloying.

  16. Nanocrystalline CuNi alloys: improvement of mechanical properties and thermal stability

    NASA Astrophysics Data System (ADS)

    Nogues, Josep; Varea, A.; Pellicer, E.; Sivaraman, K. M.; Pane, S.; Nelson, B. J.; Surinach, S.; Baro, M. D.; Sort, J.

    2014-03-01

    Nanocrystalline metallic films are known to benefit from novel and enhanced physical and chemical properties. In spite of these outstanding properties, nanocrystalline metals typically show relatively poor thermal stability which leads to deterioration of the properties due to grain coarsening. We have studied nanocrystalline Cu1-xNix (0.56 < x < 1) thin films (3 μm-thick) electrodeposited galvanostatically onto Cu/Ti/Si (100) substrates. CuNi thin films exhibit large values of hardness (6.15 < H < 7.21 GPa), which can be tailored by varying the composition. However, pure Ni films (x = 1) suffer deterioration of their mechanical and magnetic properties after annealing during 3 h at relatively low temperatures (TANN > 475 K) due to significant grain growth. Interestingly, alloying Ni with Cu clearly improves the thermal stability of the material because grain coarsening is delayed due to segregation of a Cu-rich phase at grain boundaries, thus preserving both the mechanical and magnetic properties up to higher TANN.

  17. Nanocrystalline LaOx/NiO composite as high performance electrodes for supercapacitors.

    PubMed

    Du, Guo; Zeng, Zifan; Xiao, Bangqing; Wang, Dengzhi; Yuan, Yuan; Zhu, Xiaohong; Zhu, Jiliang

    2017-12-21

    Nanocrystalline LaO x /NiO composite electrodes were synthesized via two types of facile cathodic electrodeposition methods onto nickel foam followed by thermal annealing without any binders. Scanning electron microscopy and transmission electron microscopy investigation revealed that LaO x nanocrystalline particles with an average diameter of 50 nm are uniformly distributed in the NiO layer or alternately deposited with the NiO layer onto the substrate. It is speculated that LaO x particles can participate in the faradaic reaction directly and offer more redox sites. Besides this, the unique Ni/La layered structure facilitates the diffusion of ions and retards the electrode polarization, thus leading to a better rate capability and cycling stability of NiO. As a result, the obtained electrodes display very competitive electrochemical performance (a specific capacitance of 1238 F g -1 at a current density of 0.5 A g -1 , excellent rate capability of 86% of the original capacitance at 10 A g -1 and excellent cycling stability of 93% capacitance after 10 000 cycles). In addition, asymmetric coin devices were assembled using LaO x /NiO as the positive electrode and active carbon as the negative electrode. The assembled asymmetric devices demonstrate a high energy density of 13.12 W h kg -1 at a power density of 90.72 W kg -1 .

  18. Elucidation of reaction mechanism involved in the formation of LaNiO3 from XRD and TG analysis

    NASA Astrophysics Data System (ADS)

    Dharmadhikari, Dipti V.; Athawale, Anjali A.

    2013-06-01

    The present work is focused on the synthesis and elucidation of reaction mechanism involved in the formation of LaNiO3 with the help of X-ray diffraction (XRD) and thermogravimetric (TG) analysis. LaNiO3 was synthesized by hydrothermal method by heating at 160°C under autogenous pressure for 6h. Pure phase product was obtained after calcining the hydrothermally activated product for 6h at 700°C. The various phases of the product obtained after hydrothermal treatment and calcination followed by the formation of pure phase nanocrystalline lanthanum nickel oxide could be determined from XRD analysis of the samples. The reaction mechanism and phase formation temperature has been interpreted by thermogravimetric analysis of the hydrothermally synthesized product and XRD analysis.

  19. Electrode characteristics of nanocrystalline AB{sub 5} compounds prepared by mechanical alloying

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Chen, Z.; Chen, Z.; Zhou, D.

    1998-10-01

    Nanocrystalline LaNi{sub 5} and LaNi{sub 4.5}Si{sub 0.5} synthesized by mechanical alloying were used as negative materials for Ni-MH batteries. It was found that the electrodes prepared with the nanocrystalline powders had similar discharge capacities, better activation behaviors, and longer cycle lifetimes, compared with the negative electrode prepared with polycrystalline coarse-grained LaNi{sub 5} alloy. The properties of the electrodes prepared with these nanocrystalline materials were attributed to the structural characteristics of the compounds caused by mechanical alloying.

  20. Ni-doped (CeO2- δ )-YSZ mesoarchitectured with nanocrystalline framework: the effect of thermal treatment on structure, surface chemistry and catalytic properties in the partial oxidation of methane (CPOM)

    NASA Astrophysics Data System (ADS)

    Somacescu, Simona; Florea, Mihaela; Osiceanu, Petre; Calderon-Moreno, Jose Maria; Ghica, Corneliu; Serra, Jose Manuel

    2015-11-01

    Ni-doped (CeO2- δ )-YSZ (5 mol% Ni oxide, 10 mol% ceria) mesoarchitectures (MA) with nanocrystalline framework have been synthesized by an original, facile and cheap approach based on Triton X100 nonionic surfactant as template and water as solvent at a strong basic pH value. Following the hydrothermal treatment under autogenous pressure ( 18 bars), Ni, Ce, Y, and Zr were well ordered as MA with nanocrystalline framework, assuring thermal stability. A comprehensive investigation of structure, texture, morphology, and surface chemistry was performed by means of a variety of complementary techniques (X-Ray Diffraction, XRD; Raman Spectroscopy, RS; Brunauer—Emmett—Teller, BET; Temperature—Programmed Reduction, TPR; Transmission Electron Microscopy, TEM and DF-STEM; X-ray Photoelectron Spectroscopy, XPS; Catalytic activity and selectivity). N2 sorption measurements highlighted that the mesoporous structure is formed at 600 °C and remains stable at 800 °C. At 900 °C, the MA collapses, favoring the formation of macropores. The XRD and Raman Spectroscopy of all samples showed the presence of a pure, single phase with fluorite-type structure. At 900 °C, an increased tetragonal distortion of the cubic lattice was observed. The surface chemistry probed by XPS exhibits a mixture of oxidation states (Ce3+ + Ce4+) with high percentage of Ce3+ valence state 35 % and (Ni3+ and Ni2+) oxidation states induced by the thermal treatment. These nanoparticles assembled into MA show high stability and selectivity over time in catalytic partial oxidation of methane (CPOM). These promising performances suggest an interesting prospect for introduction as anode within IT-SOFC assemblies.

  1. Weakly-agglomerated nanocrystalline (ZrO 2) 0.9(Yb 2O 3) 0.1 powders hydrothermally synthesized at low temperature

    NASA Astrophysics Data System (ADS)

    Dell'Agli, Gianfranco; Mascolo, Giuseppe; Mascolo, Maria Cristina; Pagliuca, Concetta

    2006-09-01

    Nanocrystalline ytterbia (10 mol%)-doped cubic zirconia powders were synthesized by hydrothermal treatment of either an amorphous co-precipitate of hydrated ytterbia-zirconia or of zirconia xerogel in mixture with crystalline Yb 2O 3. The treatments were performed at 110 °C in the presence of diluted (0.2 M) or concentrated (2.0 M) solution of (K 2CO 3 + KOH) mineralizer and for different reaction times. The reaction times for the full crystallization of cubic-YbSZ-based products were determined for both the employed precursors and for each mineralizer solution. The various fully crystallized products were characterized in their degree of agglomeration and sintered at 1500 °C for 2 h. The best performance on sintering was achieved with the less agglomerated powder synthesized from the mechanical mixture and in the presence of the diluted solution of the mineralizer. The resulting density was the highest achieved with materials having the same composition.

  2. Effect of Fe3O4 addition on dielectric properties of LaFeO3 nano-crystalline materials synthesized by sol-gel method

    NASA Astrophysics Data System (ADS)

    Laysandra, H.; Triyono, D.

    2017-04-01

    Dielectric properties of nano-crystalline material LaFeO3.xFe3O4 with x = 0, 0.1, 0.2, 0.3, and 0.4 at.% have been studied by impedance spectroscopy method. LaFeO3 was synthesized by sol-gel method resulting nano-particle. Then, it was mixed with Fe3O4 powder. The mixture powder was pressed to form pellet and then sintered at 1300°C for 1 h to form nano-crystalline of LaFeO3.xFe3O4. X-ray diffraction characterization at room temperature for all samples show two phases i.e. perovskite LaFeO3 (orthorhombic) as a main phase and Fe3O4 (cubic) as second phase. It is found that the crystallite size of main phase increases with addition of Fe3O4 until 0.3 at.%. The electrical properties as a function of temperature (300-500 K) and frequency (100 Hz - 1 MHz) are presented in Nyquist and Bode plots. It is observed that from equivalent circuit and their parameters, dielectrical properties are contributed by grain and grain boundary. The dielectric constant, ε‧ were calculated by parallel plate method and their values reach up to 107 exhibiting typical colossal dielectric constant (CDC) material like behavior.

  3. Effects of grain size on the properties of bulk nanocrystalline Co-Ni alloys

    NASA Astrophysics Data System (ADS)

    Qiao, Gui-Ying; Xiao, Fu-Ren

    2017-08-01

    Bulk nanocrystalline Co78Ni22 alloys with grain size ranging from 5 nm to 35 nm were prepared by high-speed jet electrodeposition (HSJED) and annealing. Microhardness and magnetic properties of these alloys were investigated by microhardness tester and vibrating sample magnetometer. Effects of grain size on these characteristics were also discussed. Results show that the microhardness of nanocrystalline Co78Ni22 alloys increases following a d -1/2-power law with decreasing grain size d. This phenomenon fits the Hall-Petch law when the grain size ranges from 5 nm to 35 nm. However, coercivity H c increases following a 1/d-power law with increasing grain size when the grain size ranges from 5 nm to 15.9 nm. Coercivity H c decreases again for grain sizes above 16.6 nm according to the d 6-power law.

  4. Biocompatible nanocrystalline natural bonelike carbonated hydroxyapatite synthesized by mechanical alloying in a record minimum time.

    PubMed

    Lala, S; Brahmachari, S; Das, P K; Das, D; Kar, T; Pradhan, S K

    2014-09-01

    Single phase nanocrystalline biocompatible A-type carbonated hydroxyapatite (A-cHAp) powder has been synthesized by mechanical alloying the stoichiometric mixture of CaCO3 and CaHPO4.2H2O powders in open air at room temperature within 2h of milling. The A-type carbonation in HAp is confirmed by FTIR analysis. Structural and microstructure parameters of as-milled powders are obtained from both Rietveld's powder structure refinement analysis and transmission electron microscopy. Size and lattice strain of nanocrystalline HAp particles are found to be anisotropic in nature. Mechanical alloying causes amorphization of a part of crystalline A-cHAp which is analogous to native bone mineral. Some primary bond lengths of as-milled samples are critically measured. MTT [3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide] assay test reveals high percentage of cell viability and hence confirms the biocompatibility of the sample. The overall results indicate that the processed A-cHAp has a chemical composition very close to that of biological apatite. Copyright © 2014 Elsevier B.V. All rights reserved.

  5. Production of Nanocrystalline Ni-20Cr Coatings for High-Temperature Applications

    NASA Astrophysics Data System (ADS)

    Kumar, Manoj; Singh, Harpreet; Singh, Narinder

    2014-04-01

    Presynthesized nanocrystalline Ni-20Cr powder was deposited on SA 516 and T91 boiler steels by a high-velocity oxy-fuel spraying process. Ni-20Cr powder was synthesized by the ball milling approach. The high-temperature oxidation behavior of bare and coated samples was then studied under cyclic isothermal conditions at 900 °C for 50 cycles. The kinetics of oxidation was established using weight change measurements for the bare and coated boiler steels. Uncoated and coated samples of T91 steel were exposed to the superheated zone of a power plant boiler at 750 °C under cyclic conditions for 15 cycles. Each cycle consisted of 100 h of heating followed by 1 h of cooling. Attempts were made to study the kinetics of erosion-corrosion using weight change and thickness loss data for the samples. Different characterization techniques were used to study the oxidized and eroded-corroded samples, including x-ray diffraction, scanning electron microscopy/energy-dispersive spectroscopy, and x-ray mapping analyses. The Ni-20Cr alloy powder coating was found to offer excellent oxidation resistance to the base steels and was successful in reducing the weight gain of SA 516 steel by 98.5 % and that of T91 steel by 65 %. The coating was observed to reduce the erosion-corrosion rate of T91 steel by 86 % in terms of thickness loss. This indicates that the investigated nanostructured coating can be a better choice over conventional coating for erosion-corrosion control of boiler tubes.

  6. Structural analysis of nanocrystalline ZnTe alloys synthesized by melt quenching technique

    NASA Astrophysics Data System (ADS)

    Singh, Harinder; Singh, Tejbir; Thakur, Anup; Sharma, Jeewan

    2018-05-01

    Nanocrystalline ZnxTe100-x (x=0, 5, 20, 30, 40, 50) alloys have been synthesized using melt quenching technique. Energy-dispersive X-Ray spectroscopy (EDS) has been used to verify the elemental composition of samples. Various absorption modes are recorded from Fourier transform infrared spectroscopy (FTIR) confirming the formation of ZnTe. The structural study has been performed using X-Ray Diffraction (XRD) method. All synthesized samples have been found to be nanocrystalline in nature with average crystallite size in the range from 49.3 nm to 77.1 nm. Results have shown that Zn0Te100 exhibits hexagonal phase that transforms into a cubic ZnTe phase as the amount of zinc is increased. Pure ZnTe phase has been obtained for x = 50. The texture coefficient (Tc) has been calculated to find the prominent orientations of different planes.

  7. Surface Properties of a Nanocrystalline Fe-Ni-Nb-B Alloy After Neutron Irradiation

    NASA Astrophysics Data System (ADS)

    Pavùk, Milan; Sitek, Jozef; Sedlačková, Katarína

    2014-09-01

    The effect of neutron radiation on the surface properties of the nanocrystalline (Fe0.25Ni0.75)81Nb7B12 alloy was studied. Firstly, amorphous (Fe0.25Ni0.75)81Nb7B12 ribbon was brought by controlled annealing to the nanocrystalline state. After annealing, the samples of the nanocrystalline ribbon were irradiated in a nuclear reactor with neutron fluences of 1×1016cm-2 and 1 × 1017cm-2 . By utilizing the magnetic force microscopy (MFM), topography and a magnetic domain structure were recorded at the surface of the ribbon-shaped samples before and after irradiation with neutrons. The results indicate that in terms of surface the nanocrystalline (Fe0.25Ni0.75)81Nb7B12 alloy is radiation-resistant up to a neutron fluence of 1 × 1017cm-2 . The changes in topography observed for both irradiated samples are discussed

  8. Amorphization of nanocrystalline 3C-SiC irradiated with Si+ ions

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Jiang, Weilin; Wang, Haiyan; Kim, Ickchan

    2010-11-23

    Irradiation induced amorphization in nanocrystalline and single crystal 3C-SiC has been studied using 1 MeV Si+ ions under the identical irradiation conditions at room temperature and 400 K. The disordering behavior has been characterized using in-situ ion channeling and ex-situ x-ray diffraction methods. The results show that, compared to single crystal 3C-SiC, full amorphization of small 3C-SiC grains (~3.8 nm in size) occurs at a slightly lower dose at room temperature. For grains with sizes of 3.0 - 3.8 nm, the amorphization dose is lower at room temperature than 400 K. A significantly lower dose for amorphization of smaller grainsmore » (2.0 nm in size) is observed at 400 K. The behavior has been interpreted based on the competition between the interface and interior amorphization.« less

  9. Amorphization of nanocrystalline 3C-SiC irradiated with Si+ ions

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Jiang, Weilin; Wang, H.; Zhang, Yanwen

    2010-01-01

    Irradiation induced amorphization in nanocrystalline and single crystal 3C-SiC has been studied using 1 MeV Si+ ions under identical irradiation conditions at room temperature and 400 K. The disordering behavior has been characterized using in-situ ion channeling and ex-situ x-ray diffraction methods. The results show that, compared to single crystal 3C-SiC, full amorphization of small 3C-SiC grains (~3.8 nm in size) at room temperature occurs at a slightly lower dose. Grain size decreases with increasing dose until a fully amorphized state is attained. The amorphization dose increases at 400 K relative to room temperature. However, at 400 K, the dosemore » for amorphization for 2.0 nm grains is about a factor of 4 and 8 smaller than for 3.0 nm grains and bulk single crystal 3C-SiC, respectively. The behavior is attributed to the dominance of defect-stimulated interfacial amorphization.« less

  10. Magneto-structural studies of sol-gel synthesized nanocrystalline manganese substituted nickel ferrites

    NASA Astrophysics Data System (ADS)

    Pandav, R. S.; Patil, R. P.; Chavan, S. S.; Mulla, I. S.; Hankare, P. P.

    2016-11-01

    Nanocrystalline NiFe2-xMnxO4 (2≥x≥0) ferrites were prepared by sol-gel method. X-ray diffraction patterns reveal that synthesized compounds are in single phase cubic spinel lattice for all the composition. The surface morphology of all the samples were studied by scanning electron microscopy. The particle size measured from transmission electron microscopy and X-ray diffraction patterns confirms the nanosized dimension of the as-prepared powder. The elemental analysis was carried out by energy dispersive X-ray analysis technique. Magnetic properties such as saturation magnetization, coercivity and remanence are studied as a function of increasing Mn concentration at room temperature. The saturation magnetization shows a decreasing trend with increase in Mn content. The substitution of manganese in the nickel ferrite affects the structural and magnetic properties of cubic spinels.

  11. Stability of nanocrystalline Ni-based alloys: coupling Monte Carlo and molecular dynamics simulations

    NASA Astrophysics Data System (ADS)

    Waseda, O.; Goldenstein, H.; Silva, G. F. B. Lenz e.; Neiva, A.; Chantrenne, P.; Morthomas, J.; Perez, M.; Becquart, C. S.; Veiga, R. G. A.

    2017-10-01

    The thermal stability of nanocrystalline Ni due to small additions of Mo or W (up to 1 at%) was investigated in computer simulations by means of a combined Monte Carlo (MC)/molecular dynamics (MD) two-steps approach. In the first step, energy-biased on-lattice MC revealed segregation of the alloying elements to grain boundaries. However, the condition for the thermodynamic stability of these nanocrystalline Ni alloys (zero grain boundary energy) was not fulfilled. Subsequently, MD simulations were carried out for up to 0.5 μs at 1000 K. At this temperature, grain growth was hindered for minimum global concentrations of 0.5 at% W and 0.7 at% Mo, thus preserving most of the nanocrystalline structure. This is in clear contrast to a pure Ni model system, for which the transformation into a monocrystal was observed in MD simulations within 0.2 μs at the same temperature. These results suggest that grain boundary segregation of low-soluble alloying elements in low-alloyed systems can produce high-temperature metastable nanocrystalline materials. MD simulations carried out at 1200 K for 1 at% Mo/W showed significant grain boundary migration accompanied by some degree of solute diffusion, thus providing additional evidence that solute drag mostly contributed to the nanostructure stability observed at lower temperature.

  12. Characterization of honeycomb-like "β-Ni(OH) 2" thin films synthesized by chemical bath deposition method and their supercapacitor application

    NASA Astrophysics Data System (ADS)

    Patil, U. M.; Gurav, K. V.; Fulari, V. J.; Lokhande, C. D.; Joo, Oh Shim

    Nanostructured nickel hydroxide thin films are synthesized via a simple chemical bath deposition (CBD) method using nickel nitrate Ni(NO 3) 2 as the starting material. The deposition process is based on the thermal decomposition of ammonia-complexed nickel ions at 333 K. The structural, surface morphological, optical, electrical and electrochemical properties of the films are examined. The nanocrystalline "β" phase of Ni(OH) 2 is confirmed by the X-ray diffraction analysis. Scanning electron microscopy reveals a macroporous and interconnected honeycomb-like morphology. Optical absorption studies show that "β-Ni(OH) 2" has a wide optical band-gap of 3.95 eV. The negative temperature coefficient of the electrical resistance of "β-Ni(OH) 2", is attributed to the semiconducting nature of the material. The electrochemical properties of "β-Ni(OH) 2" in KOH electrolyte are examined by cyclic voltammetric (CV) measurements. The scan-rate dependent voltammograms demonstrate pseudocapacitive behaviour when "β-Ni(OH) 2" is employed as a working electrode in a three-electrode electrochemical cell containing 2 M KOH electrolyte with a platinum counter electrode and a saturated calomel reference electrodes. A specific capacitance of ∼398 × 10 3 F kg -1 is obtained.

  13. Hydrogen Storage Characteristics of Nanocrystalline and Amorphous Nd-Mg-Ni-Based NdMg12-Type Alloys Synthesized via Mechanical Milling

    NASA Astrophysics Data System (ADS)

    Zhang, Yanghuan; Shang, Hongwei; Hou, Zhonghui; Yuan, Zeming; Yang, Tai; Qi, Yan

    2016-12-01

    In this study, Mg was partially substituted by Ni with the intent of improving the hydrogen storage kinetics performance of NdMg12-type alloy. Mechanical milling technology was adopted to fabricate the nanocrystalline and amorphous NdMg11Ni + x wt pct Ni ( x = 100, 200) alloys. The effects of Ni content and milling duration on the microstructures and hydrogen storage kinetics of as-milled alloys have been systematically investigated. The structures were characterized by XRD and HRTEM. The electrochemical hydrogen storage properties were tested by an automatic galvanostatic system. Moreover, the gaseous hydrogen storage properties were investigated by Sievert apparatus and a differential scanning calorimeter connected with a H2 detector. Hydrogen desorption activation energy of alloy hydrides was estimated by using Arrhenius and Kissinger methods. The results reveal that the increase of Ni content dramatically ameliorates the gaseous and electrochemical hydrogen storage kinetics performance of the as-milled alloys. Furthermore, high rate discharge ability (HRD) reach the maximum value with the variation of milling time. The maximum HRDs of the NdMg11Ni + x wt pct Ni ( x = 100, 200) alloys are 80.24 and 85.17 pct. The improved gaseous hydrogen storage kinetics of alloys via increasing Ni content and milling time can be attributed to a decrease in the hydrogen desorption activation energy.

  14. Synthesis, characterization, and photocatalytic properties of nanocrystalline NZO thin films

    NASA Astrophysics Data System (ADS)

    Aryanto, D.; Hastuti, E.; Husniya, N.; Sudiro, T.; Nuryadin, B. W.

    2018-03-01

    Nanocrystalline Ni-doped ZnO (NZO) thin films were synthesized on glass substrate using sol-gel spin coating methods. The effect of annealing on the structural and optical properties of nanocrystalline thin film was studied using X-ray diffractometer (XRD), field emission scanning electron microscopy (FESEM), UV-VIS spectrophotometry, and photoluminescence (PL). The results showed that the annealing temperature strongly influenced the physical properties of nanocrystalline NZO thin films. The photocatalytic properties of nanocrystalline NZO thin films were evaluated using an aqueous solution of Rhodamine-B. The photocatalytic activity of nanocrystalline NZO thin films increased with the increase of annealing temperature. The results indicated that the structure, morphology, and band gap energy of nanocrystalline NZO thin films played an important role in photocatalytic activity.

  15. Nanocrystalline composites of transition metal molybdate (Ni1-xCoxMoO4; x = 0, 0.3, 0.5, 0.7, 1) synthesized by a co-precipitation method as humidity sensors and their photoluminescence properties

    NASA Astrophysics Data System (ADS)

    Jeseentharani, V.; Dayalan, A.; Nagaraja, K. S.

    2018-04-01

    In this study, nanocrystalline transition metal nickel-cobalt molybdate (Ni1-xCoxMoO4, NiCM; x = 0, 0.3, 0.5, 0.7, 1) composites were prepared using a simple co-precipitation method. The composites were characterized by thermogravimetric/differential thermal analysis, Fourier transform-infrared spectroscopy, X-ray diffraction, scanning electron microscopy, and transmission electron microscopy. The NiCM composites were studied to determine their possible use as humidity sensors, and photoluminescence (PL) measurements were obtained. The sensing study was performed in environments with different relative humidity levels (5-98%). The maximum sensitivity of 18624 ± 168 was observed with the Ni0.7Co0.3MoO4 composite where the humidity could be calculated according to the relationship: Sf = R5%/R98%, where R5% and R98% are the dc resistances at 5 and 98% RH, respectively. The photoluminescence measurements acquired at room temperature for the NiCMs included green and red emission peaks when excited at a wavelength (λex) of 520 nm.

  16. High surface area nanocrystalline hausmannite synthesized by a solvent-free route

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Herrera-Miranda, Daniel; Ponrouch, Alexandre; Pons, Josefina

    Highlights: ► High surface area Mn{sub 3}O{sub 4} nanoparticles obtained by a solvent-free low temperature route. ► 3,6,9-Trioxadecanoic acid allows to obtain nanocrystalline hausmannite. ► Tape casted electrodes show up to 300 mAh g{sup −1} capacity after more than 40 cycles at a C/3 rate. ► Upper cut off voltage strongly influences capacity retention upon cycling at high C rates. -- Abstract: Nanocrystalline high surface area Mn{sub 3}O{sub 4} powder was obtained at low temperature by a solvent-free route. The precursor was a mixture of manganese (II) acetate, 3,6,9-trioxadecanoic acid (TODA) and ammonium acetate that were intimately mixed by groundingmore » in an agate mortar. Nanocrystalline Mn{sub 3}O{sub 4} was obtained by thermal treatment at 120 °C. Powder X-ray diffraction, selected area electron diffraction, high resolution transmission electron microscopy, and Fourier transformed infrared characterization confirmed the formation of the hausmannite phase. The as-prepared mesoporous material has high specific surface area (120 m{sup 2} g{sup −1}). The performances of tape casted Mn{sub 3}O{sub 4} nanopowder electrodes were investigated as anode material for lithium ion batteries. High capacity values were achieved at diverse C rates. Capacity fading was found to be dependent on the upper cut off voltage, the presence of a plateau at 2.25 V vs. Li{sup +}/Li being detrimental for long term cyclability.« less

  17. Structural, optical and photo-catalytic activity of nanocrystalline NiO thin films

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Al-Ghamdi, Attieh A.; Abdel-wahab, M. Sh., E-mail: mshabaan90@yahoo.com; Materials Science and Nanotechnology Department, Faculty of Postgraduate Studies for Advanced Sciences, Beni-Suef University, Beni-Suef

    2016-03-15

    Highlights: • Synthesis of nanocrystalline NiO thin films with different thicknesses using DC magnetron sputtering technique. • Effect of film thickness and particle size on photo-catalytic degradation of methyl green dye under UV light was studied. • The deposited NiO thin films are efficient, stable and possess high photo-catalytic activity upon reuse. - Abstract: Physical deposition of nanocrystalline nickel oxide (NiO) thin films with different thickness 30, 50 and 80 nm have been done on glass substrate by DC magnetron sputtering technique and varying the deposition time from 600, 900 to 1200 s. The results of surface morphology and opticalmore » characterization of these films obtained using different characterization techniques such as X-ray diffraction (XRD), field emission scanning electron microscope (FESEM), photoluminescence (PL) and UV–vis spectrophotometry provide important information like formation of distinct nanostructures in different films and its effect on their optical band gap which has decreased from 3.74 to 3.37 eV as the film thickness increases. Most importantly these films have shown very high stability and a specialty to be recycled without much loss of their photo-catalytic activity, when tested as photo-catalysts for the degradation of methyl green dye (MG) from the wastewater under the exposure of 18 W energy of UV lamp.« less

  18. Electrocatalytic performances of g-C3N4-LaNiO3 composite as bi-functional catalysts for lithium-oxygen batteries

    PubMed Central

    Wu, Yixin; Wang, Taohuan; Zhang, Yidie; Xin, Sen; He, Xiaojun; Zhang, Dawei; Shui, Jianglan

    2016-01-01

    A low cost and non-precious metal composite material g-C3N4-LaNiO3 (CNL) was synthesized as a bifunctional electrocatalyst for the air electrode of lithium-oxygen (Li-O2) batteries. The composition strategy changed the electron structure of LaNiO3 and g-C3N4, ensures high Ni3+/Ni2+ ratio and more absorbed hydroxyl on the surface of CNL that can promote the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER). The composite catalyst presents higher activities than the individual components g-C3N4 and LaNiO3 for both ORR and OER. In non-aqueous Li-O2 batteries, CNL shows higher capacity, lower overpotentials and better cycling stability than XC-72 carbon and LaNiO3 catalysts. Our results suggest that CNL composite is a promising cathode catalyst for Li-O2 batteries. PMID:27074882

  19. Study of magnetic and electrical properties of nanocrystalline Mn doped NiO.

    PubMed

    Raja, S Philip; Venkateswaran, C

    2011-03-01

    Diluted Magnetic Semiconductors (DMS) are intensively explored in recent years for its applications in spintronics, which is expected to revolutionize the present day information technology. Nanocrystalline Mn doped NiO samples were prepared using chemical co-precipitation method with an aim to realize room temperature ferromagnetism. Phase formation of the samples was studied using X-ray diffraction-Rietveld analysis. Scanning electron microscopy and Energy dispersive X-ray analysis results reveal the nanocrystalline nature of the samples, agglomeration of the particles, considerable particle size distribution and the near stoichiometry. Thermomagnetic curves confirm the single-phase formation of the samples up to 1% doping of Mn. Vibrating Sample Magnetometer measurements indicate the absence of ferromagnetism at room temperature. This may be due to the low concentration of Mn2+ ions having weak indirect coupling with Ni2+ ions. The lack of free carriers is also expected to be the reason for the absence of ferromagnetism, which is in agreement with the results of resistivity measurements using impedance spectroscopy. Arrhenius plot shows the presence of two thermally activated regions and the activation energy for the nanocrystalline Mn doped sample was found to be greater than that of undoped NiO. This is attributed to the doping effect of Mn. However, the dielectric constant of the samples was found to be of the same order of magnitude very much comparable with that of undoped NiO.

  20. Sucrose-aided combustion synthesis of nanosized LiMn 1.99- yLi yM 0.01O 4 (M = Al 3+, Ni 2+, Cr 3+, Co 3+, y = 0.01 and 0.06) spinels . Characterization and electrochemical behavior at 25 and at 55 °C in rechargeable lithium cells

    NASA Astrophysics Data System (ADS)

    Amarilla, J. M.; Petrov, K.; Picó, F.; Avdeev, G.; Rojo, J. M.; Rojas, R. M.

    Doubly doped LiMn 1.99- yLi yM 0.01O 4 (M = Al 3+, Ni 2+, Cr 3+, Co 3+; y = 0.01 and 0.06) spinels have been synthesized by the sucrose-aided combustion method. Combined TG/DTA and XRD studies have shown that stoichiometric single-phase spinels are formed after annealing of the samples at 700 °C for 1 h. The samples obtained are nanocrystalline materials having a narrow size-distribution and a coherent domain size between 40 and 60 nm, depending on the amount of fuel (sucrose) used in the synthesis. The influence of the Li-excess, the type of M n+-dopant cation and the amount of fuel used in the synthesis on the electrochemical behavior of the spinels in a Li-cell at room and at elevated temperature (55 °C) has been studied. At 25 °C all the spinels synthesized have a good capacity retention after 100 cycles, QRt-100 > 92%. At 55 °C the increase of the Li-excess improves the cycling performances. Rate capability studies show that the spinels retain >90% of their capacity even at 5 C rate. The synergic effect of the Li-excess and the particle size on the electrochemical properties of the spinels as cathode material has been settled. The LiMn 1.93Li 0.06M 0.01O 4, (M = Al 3+, Ni 2+) spinels, with cyclabilities >99.9% by cycle at both 25 and 55 °C, and high rate capabilities, are the ones that show the best electrochemical properties.

  1. Biomimetic three-dimensional nanocrystalline hydroxyapatite and magnetically synthesized single-walled carbon nanotube chitosan nanocomposite for bone regeneration

    PubMed Central

    Im, Owen; Li, Jian; Wang, Mian; Zhang, Lijie Grace; Keidar, Michael

    2012-01-01

    Background Many shortcomings exist in the traditional methods of treating bone defects, such as donor tissue shortages for autografts and disease transmission for allografts. The objective of this study was to design a novel three-dimensional nanostructured bone substitute based on magnetically synthesized single-walled carbon nanotubes (SWCNT), biomimetic hydrothermally treated nanocrystalline hydroxyapatite, and a biocompatible hydrogel (chitosan). Both nanocrystalline hydroxyapatite and SWCNT have a biomimetic nanostructure, excellent osteoconductivity, and high potential to improve the load-bearing capacity of hydrogels. Methods Specifically, three-dimensional porous chitosan scaffolds with different concentrations of nanocrystalline hydroxyapatite and SWCNT were created to support the growth of human osteoblasts (bone-forming cells) using a lyophilization procedure. Two types of SWCNT were synthesized in an arc discharge with a magnetic field (B-SWCNT) and without a magnetic field (N-SWCNT) for improving bone regeneration. Results Nanocomposites containing magnetically synthesized B-SWCNT had superior cytocompatibility properties when compared with nonmagnetically synthesized N-SWCNT. B-SWCNT have much smaller diameters and are twice as long as their nonmagnetically prepared counterparts, indicating that the dimensions of carbon nanotubes can have a substantial effect on osteoblast attachment. Conclusion This study demonstrated that a chitosan nanocomposite with both B-SWCNT and 20% nanocrystalline hydroxyapatite could achieve a higher osteoblast density when compared with the other experimental groups, thus making this nanocomposite promising for further exploration for bone regeneration. PMID:22619545

  2. Structure and properties of electrodeposited nanocrystalline Ni and Ni-Fe alloy continuous foils

    NASA Astrophysics Data System (ADS)

    Giallonardo, Jason Derek

    This research work presents the first comprehensive study on nanocrystalline materials produced in bulk quantities using a novel continuous electrodeposition process. A series of nanocrystalline Ni and Ni-Fe alloy continuous foils were produced and an intensive investigation into their structure and various properties was carried out. High-resolution transmission electron microscopy (HR-TEM) revealed the presence of local strain at high and low angle, and twin boundaries. The cause for these local strains was explained based on the interpretation of non-equilibrium grain boundary structures that result when conditions of compatibility are not satisfied. HR-TEM also revealed the presence of twin faults of the growth type, or "growth faults", which increased in density with the addition of Fe. This observation was found to be consistent with a corresponding increase in the growth fault probabilities determined quantitatively using X-ray diffraction (XRD) pattern analysis. Hardness and Young's modulus were measured by nanoindentation. Hardness followed the regular Hall-Petch behaviour down to a grain size of 20 nm after which an inverse trend was observed. Young's modulus was slightly reduced at grain sizes less than 20 nm and found to be affected by texture. Microstrain based on XRD line broadening was measured for these materials and found to increase primarily with a decrease in grain size or an increase in intercrystal defect density (i.e., grain boundaries and triple junctions). This microstrain is associated with the local strains observed at grain boundaries in the HR-TEM image analysis. A contribution to microstrain from the presence of growth faults in the nanocrystalline Ni-Fe alloys was also noted. The macrostresses for these materials were determined from strain measurements using a two-dimensional XRD technique. At grain sizes less than 20 nm, there was a sharp increase in compressive macrostresses which was also owed to the corresponding increase in

  3. Effect of milling atmosphere on structural and magnetic properties of Ni-Zn ferrite nanocrystalline

    NASA Astrophysics Data System (ADS)

    Hajalilou, Abdollah; Hashim, Mansor; Ebrahimi-Kahrizsangi, Reza; Masoudi Mohamad, Taghi

    2015-04-01

    Powder mixtures of Zn, NiO, and Fe2O3 are mechanically alloyed by high energy ball milling to produce Ni-Zn ferrite with a nominal composition of Ni0.36Zn0.64Fe2O4. The effects of milling atmospheres (argon, air, and oxygen), milling time (from 0 to 30 h) and heat treatment are studied. The products are characterized using x-ray diffractometry, field emission scanning electron microscopy equipped with energy-dispersive x-ray spectroscopy, and transmitted electron microscopy. The results indicate that the desired ferrite is not produced during the milling in the samples milled under either air or oxygen atmospheres. In those samples milled under argon, however, Zn/NiO/Fe2O3 reacts with a solid-state diffusion mode to produce Ni-Zn ferrite nanocrystalline in a size of 8 nm after 30-h-milling. The average crystallite sizes decrease to 9 nm and 10 nm in 30-h-milling samples under air and oxygen atmospheres, respectively. Annealing the 30-h-milling samples at 600 °C for 2 h leads to the formation of a single phase of Ni-Zn ferrite, an increase of crystallite size, and a reduction of internal lattice strain. Finally, the effects of the milling atmosphere and heating temperature on the magnetic properties of the 30-h-milling samples are investigated. Project supported by the University Putra Malaysia Graduate Research Fellowship Section.

  4. Defect structure in electrodeposited nanocrystalline Ni layers with different Mo concentrations

    NASA Astrophysics Data System (ADS)

    Kapoor, Garima; Péter, László; Fekete, Éva; Gubicza, Jenő

    2018-05-01

    The effect of molybdenum (Mo) alloying on the lattice defect structure in electrodeposited nanocrystalline nickel (Ni) films was studied. The electrodeposited layers were prepared on copper substrate at room temperature, with a constant current density and pH value. The chemical composition of these layers was determined by EDS. In addition, X-ray diffraction line profile analysis was carried out to study the microstructural parameters such as the crystallite size, the dislocation density and the stacking fault probability. It was found that the higher Mo content yielded more than one order of magnitude larger dislocation density while the crystallite size was only slightly smaller. In addition, the twin boundary formation activity during deposition increased with increasing Mo concentration. The results obtained on electrodeposited layers were compared with previous research carried out on bulk nanocrystalline Ni-Mo materials with similar compositions but processed by severe plastic deformation.

  5. Stress-induced solid-state amorphization of nanocrystalline Ni and NiZr investigated by atomistic simulations

    NASA Astrophysics Data System (ADS)

    Meraj, Md.; Deng, Chuang; Pal, Snehanshu

    2018-01-01

    In this study, the feasibility of stress induced solid-state amorphization (SSA) of nanocrystalline (NC) Ni and NiZr alloys having ˜10 nm grain size has been investigated under constant tensile load (uniaxial and triaxial) via molecular dynamics simulations. In order to track the structural evaluation in both NC Ni and NiZr alloys during the SSA process, various types of analysis have been used, including simulated X-ray diffraction, centro-symmetry parameter, Voronoi cluster, common neighbor analysis, and radial distribution function. It is found that SSA in both NC Ni and NiZr alloys can only be achieved under triaxial loading conditions, and the hydrostatic tensile stress required for SSA is significantly lower when at. % Zr is increased in the NC NiZr alloy. Specifically, SSA in NC Ni and Ni-5 at. % Zr alloy was observed only when the temperature and hydrostatic tensile stress reached 800 K and 6 GPa, while SSA could occur in NC Ni-10 at. % Zr alloy under just 2 GPa of hydrostatic tensile stress at 300 K.

  6. Ferromagnetic resonance in bulk nanocrystalline Ni

    NASA Astrophysics Data System (ADS)

    Prakash Madduri, P. V.; Mathew, S. P.; Kaul, S. N.

    2018-03-01

    A detailed lineshape analysis of the ferromagnetic resonance (FMR) spectra taken on pulse electrodeposited nanocrystalline (nc-) Ni sheets (with the average crystallite size, d, varying from 10 nm to 40 nm) at temperatures ranging from 113 K to 325 K yield accurate values for saturation magnetization, Ms (T), Landé splitting factor, g, anisotropy field, Hk (T) , resonance field, Hres , and FMR linewidth, ΔHpp (T) . Thermally-excited spin-wave (SW) excitations completely account for Ms (T) and the SW description of Ms (T) gives the values for the saturation magnetization and spin-wave stiffness at absolute zero of temperature, i.e., Ms (0) and D0 , for nc-Ni samples of different d that are in excellent agreement with the corresponding values deduced previously from an elaborate SW analysis of the bulk magnetization data. While Ms (0) varies with d as Ms (0) d - 3 / 2,D0 follows the power law D0 ∼d 4 / 3 . The angular variations of Hres in the 'in-plane' as well as 'out-of-plane' sample configurations, demonstrate that the main contribution to Hk (T) comes from the cubic magnetocrystalline anisotropy. The exchange-conductivity mechanism describes the observed thermal decline of ΔHpp reasonably well but fails to explain the very large magnitude of ΔHpp at any given temperature. By comparison, the Landau-Lifshitz-Gilbert (LLG) damping gives a much greater contribution to ΔHpp but the LLG contribution is relatively insensitive to temperature.

  7. Effect of rapid thermal annealing on nanocrystalline TiO2 thin films synthesized by swift heavy ion irradiation

    NASA Astrophysics Data System (ADS)

    Thakurdesai, Madhavi; Kanjilal, D.; Bhattacharyya, Varsha

    2012-08-01

    Irradiation by swift heavy ions (SHI) is unique tool to synthesize nanocrystalline thin films. We have reported transformation of 100 nm thick amorphous films into nanocrystalline film due to irradiation by 100 MeV Ag ion beam. Oblate shaped nanoparticles having anatase phase of TiO2 were formed on the surface of the irradiated films. In the present investigation, these films are annealed at 350 °C for 2 min in oxygen atmosphere by Rapid Thermal Annealing (RTA) method. During RTA processing, the temperature rises abruptly and this thermal instability is expected to alter surface morphology, structural and optical properties of nanocrystalline TiO2 thin films. Thus in the present work, effect of RTA on SHI induced nanocrystalline thin films of TiO2 is studied. The effect of RTA processing on the shape and size of TiO2 nanoparticles is studied by Atomic Force Microscopy (AFM) and Scanning Electron Microscopy (SEM). Glancing Angle X-ray Diffraction (GAXRD) studies are carried to investigate structural changes induced by RTA processing. Optical characterization is carried out by UV-vis spectroscopy and photoluminescence (PL) spectroscopy. The changes observed in structural and optical properties of nanocrystalline TiO2 thin films after RTA processing are attributed to the annihilation of SHI induced defects.

  8. Investigation of electronic and local structural changes during lithium uptake and release of nano-crystalline NiFe2O4 by X-ray absorption spectroscopy

    NASA Astrophysics Data System (ADS)

    Zhou, Dong; Permien, Stefan; Rana, Jatinkumar; Krengel, Markus; Sun, Fu; Schumacher, Gerhard; Bensch, Wolfgang; Banhart, John

    2017-02-01

    Nano-crystalline NiFe2O4 particles were synthesized and used as active electrode material for a lithium ion battery that showed a high discharge capacity of 1534 mAh g-1 and charge capacity of 1170 mAh g-1 during the 1st cycle. X-ray absorption spectroscopy including XANES and EXAFS were used to investigate electronic and local structural changes of NiFe2O4 during the 1st lithiation and de-lithiation process. As lithium is inserted into the structure, tetrahedral site Fe3+ ions are reduced to Fe2+ and moved from tetrahedral sites to empty octahedral sites, while Ni2+ ions are unaffected. As a consequence, the matrix spinel structure collapses and transforms to an intermediate rock-salt monoxide phase. Meanwhile, the inserted Li is partially consumed by the formation of SEI and other side reactions during the conversion reaction. With further lithiation, the monoxide phase is reduced to highly disordered metallic Fe/Ni nanoparticles with a number of nearest neighbors of 6.0(8) and 8.1(4) for Fe and Ni, respectively. During subsequent de-lithiation, the metal particles are individually re-oxidized to Fe2O3 and NiO phases instead to the original NiFe2O4 spinel phase.

  9. Structural and magnetic properties of Ni0.8M0.2Fe2O4 (M = Cu, Co) nano-crystalline ferrites

    NASA Astrophysics Data System (ADS)

    Vijaya Babu, K.; Satyanarayana, G.; Sailaja, B.; Santosh Kumar, G. V.; Jalaiah, K.; Ravi, M.

    2018-06-01

    Nano-crystalline nickel ferrites are interesting materials due to their large physical and magnetic properties. In the present work, two kinds of spinel ferrites Ni0.8M0.2Fe2O4 (M = Cu, Co) are synthesized by using sol-gel auto-combustion method and the results are compared with NiFe2O4. The structural properties of synthesized ferrites are determined by using X-ray powder diffraction; scanning electron microscope and Fourier transform infrared spectroscopy. The cation distribution obtained from X-ray diffraction show that cobalt/copper occupies only tetrahedral site in spinel lattice. The lattice constant increases with the substitution of cobalt/copper. The structural parameters like bond lengths, tetrahedral and octahedral edges have been varied with the substitution. The microstructural study is carried out by using SEM technique and the average grain size is increased with nickel ferrite. The initial permeability (μi) is improving with the substitution. The observed g-value from ESR is approximately equal to standard value.

  10. Synthesis of carbon nanofibers by CVD as a catalyst support material using atomically ordered Ni3C nanoparticles

    NASA Astrophysics Data System (ADS)

    Li, Meifeng; Li, Na; Shao, Wei; Zhou, Chungen

    2016-12-01

    Atomically ordered nickel carbide (Ni3C) nanoparticles in polygonal shapes were prepared through the reduction of nickelocene. A novel type of carbon nanofiber (CNF) with twisted conformation was synthesized successfully by catalytic chemical vapor deposition (CCVD) using the obtained Ni3C nanoparticles at a relatively low temperature of 350 °C, which is below the lower limit temperature of 400 °C for the growth of CNFs using metal catalysts. The growth mechanism of the twisted CNFs from Ni3C was freshly derived based on the detailed characterizations. Compared with the growth of CNFs from Ni, graphene layers nucleate at monoatomic step edges and grow in a layer-by-layer manner, while the rotation of the polygonal Ni3C nanoparticles fabricates the twisted conformation during the CNF growth. The electrochemical activity and performance of the twisted CNFs loaded with Pt as electrode catalysts for a polymer electrolyte membrane fuel cell (PEMFC) were measured to be better than those of straight CNFs grown from Ni nanoparticles at 500 °C, since the specific surface conformation helps to make the loaded Pt more homogeneous.

  11. Synthesis of carbon nanofibers by CVD as a catalyst support material using atomically ordered Ni3C nanoparticles.

    PubMed

    Li, Meifeng; Li, Na; Shao, Wei; Zhou, Chungen

    2016-11-22

    Atomically ordered nickel carbide (Ni 3 C) nanoparticles in polygonal shapes were prepared through the reduction of nickelocene. A novel type of carbon nanofiber (CNF) with twisted conformation was synthesized successfully by catalytic chemical vapor deposition (CCVD) using the obtained Ni 3 C nanoparticles at a relatively low temperature of 350 °C, which is below the lower limit temperature of 400 °C for the growth of CNFs using metal catalysts. The growth mechanism of the twisted CNFs from Ni 3 C was freshly derived based on the detailed characterizations. Compared with the growth of CNFs from Ni, graphene layers nucleate at monoatomic step edges and grow in a layer-by-layer manner, while the rotation of the polygonal Ni 3 C nanoparticles fabricates the twisted conformation during the CNF growth. The electrochemical activity and performance of the twisted CNFs loaded with Pt as electrode catalysts for a polymer electrolyte membrane fuel cell (PEMFC) were measured to be better than those of straight CNFs grown from Ni nanoparticles at 500 °C, since the specific surface conformation helps to make the loaded Pt more homogeneous.

  12. Enhanced Hydrogen Storage Kinetics of Nanocrystalline and Amorphous Mg₂Ni-type Alloy by Melt Spinning.

    PubMed

    Zhang, Yang-Huan; Li, Bao-Wei; Ren, Hui-Ping; Li, Xia; Qi, Yan; Zhao, Dong-Liang

    2011-01-18

    Mg₂Ni-type Mg₂Ni 1-x Co x (x = 0, 0.1, 0.2, 0.3, 0.4) alloys were fabricated by melt spinning technique. The structures of the as-spun alloys were characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM). The hydrogen absorption and desorption kinetics of the alloys were measured by an automatically controlled Sieverts apparatus. The electrochemical hydrogen storage kinetics of the as-spun alloys was tested by an automatic galvanostatic system. The results show that the as-spun (x = 0.1) alloy exhibits a typical nanocrystalline structure, while the as-spun (x = 0.4) alloy displays a nanocrystalline and amorphous structure, confirming that the substitution of Co for Ni notably intensifies the glass forming ability of the Mg₂Ni-type alloy. The melt spinning treatment notably improves the hydriding and dehydriding kinetics as well as the high rate discharge ability (HRD) of the alloys. With an increase in the spinning rate from 0 (as-cast is defined as spinning rate of 0 m/s) to 30 m/s, the hydrogen absorption saturation ratio () of the (x = 0.4) alloy increases from 77.1 to 93.5%, the hydrogen desorption ratio () from 54.5 to 70.2%, the hydrogen diffusion coefficient (D) from 0.75 × 10 - 11 to 3.88 × 10 - 11 cm²/s and the limiting current density I L from 150.9 to 887.4 mA/g.

  13. Effect of Dy3+ substitution on structural and magnetic properties of nanocrystalline Ni-Cu-Zn ferrites

    NASA Astrophysics Data System (ADS)

    Kabbur, S. M.; Ghodake, U. R.; Nadargi, D. Y.; Kambale, Rahul C.; Suryavanshi, S. S.

    2018-04-01

    Nanocrystalline Ni0.25Cu0.30Zn0.45DyxFe2-xO4 (x = 0.0, 0.025, 0.05, 0.075, 0.1 and 0.125 mol.) ferrimagnetic oxides have been synthesized by sol-gel autocombustion route. X-ray diffraction study reveals the formation of spinel cubic structure with an expansion of the unit cell by Dy addition. Bertaut method was employed to propose the site occupancy i.e. cation distribution for elements at A-tetrahedral and B-octahedral sites of spinel lattice. The intrinsic vibrational absorption bands i.e. υ1 (712-719 cm-1) and υ2 (496-506 cm-1) are observed for tetrahedral and octahedral sites respectively. The microstructural aspect confirms the formation of an average grain size (∼7-99 nm) with presence of expected elements. Magnetization studies reveal that the magnetic moments are no longer linear but exhibit canting effect due to spin frustration. The frequency dispersion spectrum of initial permeability has been explained based on grain size, saturation magnetization and anisotropy constant. Thermal hysteresis curve (initial permeability versus temperature) indicates magnetic disordering to paramagnetic state at Néel temperature (TN). High values of TN show that the present ferrite samples are cation-ordered with d-electrons contributing towards the magnetic interaction at the sublattice.

  14. High temperature wear performance of HVOF-sprayed Cr3C2-WC-NiCoCrMo and Cr3C2-NiCr hardmetal coatings

    NASA Astrophysics Data System (ADS)

    Zhou, Wuxi; Zhou, Kesong; Li, Yuxi; Deng, Chunming; Zeng, Keli

    2017-09-01

    A novel Cr3C2-WC-NiCoCrMo and commercial Cr3C2-NiCr thermal spray-grade powders with particle size of -45 + 15 μm were prepared by an agglomeration and sintering process. Cr3C2-WC-NiCoCrMo and Cr3C2-NiCr coatings were deposited by high velocity oxygen fuel (HVOF) spraying. The fundamental properties of both coatings were evaluated and friction wear test against Al2O3 counterbodies of both coatings at high temperatures (450 °C, 550 °C, 650 °C) were carried out ball-on-disk high temperature tribometer. All specimens were characterized by optical microscopy, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy with energy dispersive spectroscopy (SEM/EDS) and 3D non-contact surface mapping profiler. The results have shown that the Cr3C2-WC-NiCoCrMo coating exhibited lower porosity, higher micro-hardness compared to the Cr3C2-NiCr coating. The Cr3C2-WC-NiCoCrMo coating also exhibited better wear resistance and higher friction coefficient compared to the Cr3C2-NiCr coating when sliding against the Al2O3 counterpart. Wear rates of both coatings increased with raising temperature. Both coatings experienced abrasive wear; hard phase particles (WC and Cr3C2) with different sizes, distributed in the matrix phase, will effectively improve the resistance against wear at high temperatures.

  15. Electrical relaxation, optical and magnetic studies of nanocrystalline lithium ferrite synthesized by different chemical routes

    NASA Astrophysics Data System (ADS)

    Cheruku, Rajesh; Govindaraj, G.; Vijayan, Lakshmi

    2017-12-01

    The nanocrystalline lithium ferrite was synthesized by wet chemical methods such as solution combustion technique, sol-gel, and hydrothermal for a comparative study. Different characterization techniques like x-ray powder diffraction and thermal analysis were employed to confirm the structure and phase. Temperature-dependent Raman analysis was employed to classify the phonon modes associated with precise atomic motions existing in the synthesized materials. Morphology of sample surface was explored by scanning electron microscopy, and elemental analysis was done by energy dispersive spectroscopy analysis. The nanocrystalline nature of the materials was confirmed through transmission electron microscopy. Magnetic properties of these samples were explored through a vibrating sample magnetometer. Ac electrical impedance spectroscopy data were investigated using two Cole-Cole functions, and activation energies were calculated for all materials. Among them, solution combustion prepared lithium ferrite shows the highest conductivity and lowest activation energy.

  16. Structural and Mechanical Properties of the ZrC/Ni-Nanodiamond Coating Synthesized by the PVD and Electroplating Processes for the Cutting Knifes

    NASA Astrophysics Data System (ADS)

    Chayeuski, V.; Zhylinski, V.; Cernashejus, O.; Visniakov, N.; Mikalauskas, G.

    2018-04-01

    In this work, combined gradient ZrC/Ni-nanodiamond ultradispersed diamonds (UDD) coatings were synthesized on the surface of knife blades made of hard alloy WC-2 wt.% Co by electroplating and cathode arc evaporation PVD techniques to increase the durability period of a wood-cutting milling tool. The microstructure, phase and elemental composition, microhardness, and adhesion strength of the coatings were investigated. Ni-UDD layer is not mixed with the ZrC coating and hard alloy substrate. Cobalt is present in Ni-UDD layer after deposition of ZrC. The ZrC/Ni-nanodiamond coating consists of separate phases of zirconium carbide (ZrC), α-Ni, and Ni-UDD. The maximum value of microhardness of the Ni-nanodiamond coating is 5.9 GPa. The microhardness value of the ZrC/Ni-nanodiamond coatings is 25 ± 6 GPa, which corresponds to the microhardness of the hard alloy substrate and ZrC coating. The obtained high values of the critical loads on the scratch track of the ZrC/Ni-nanodiamond coating in 24 N prove a sufficiently high value of the adhesion strength of the bottom Ni-UDD layer with WC-Co substrate. Pilot testing of ZrC/Ni-nanodiamond-coated cutting tools proved their increasing durability period to be 1.5-1.6 times higher than that of bare tools, when milling laminated chipboard.

  17. Synthesis, structure stability and magnetic properties of nanocrystalline Ag-Ni alloy

    NASA Astrophysics Data System (ADS)

    Santhi, Kalavathy; Thirumal, E.; Karthick, S. N.; Kim, Hee-Je; Nidhin, Marimuthu; Narayanan, V.; Stephen, A.

    2012-05-01

    Silver-nickel alloy nanoparticles with an average size of 30-40 nm were synthesized by chemically reducing the mixture of silver and nickel salts using sodium borohydride. The structure and the magnetic properties of the alloy samples with different compositions were investigated. The phase stability of the material was analysed after annealing the sample in vacuum at various temperatures. The material exhibits single fcc phase which is stable up to 400 °C and Ni precipitation sets in when the sample is annealed to 500 °C. The thermal analysis using DSC was carried out to confirm the same. The alloy compositions are found to be in close correlation with the metal salt ratios in the precursors. The synthesized samples exhibit weak paramagnetic to ferromagnetic behaviour. The magnetic measurements reveal that by adjusting the precursor ratio, the Ni content in the material can be altered and hence its magnetic properties tailored to suit specific requirements. The formation of Ag-Ni alloy is confirmed by the observed Curie temperature from the magneto thermogram. Annealing the sample helps to produce significant enhancement in the magnetization of the material.

  18. Wear-triggered self-healing behavior on the surface of nanocrystalline nickel aluminum bronze/Ti3SiC2 composites

    NASA Astrophysics Data System (ADS)

    Zhai, Wenzheng; Lu, Wenlong; Zhang, Po; Wang, Jian; Liu, Xiaojun; Zhou, Liping

    2018-04-01

    Self-healing can protect materials from diverse damages, but is intrinsically difficult in metals. This paper demonstrates a potential method through a simultaneous decomposition and oxidation of Ti3SiC2 to achieve healing of stress cracking on the surface of nickel aluminum bronze (NAB)/Ti3SiC2 nanocrystalline composites during fretting wear. At the finest nanocrystalline materials, a crack recovery would be attained at 76.5%. The repetitive fretting wear leads to a modest amount of 'flowability' of Ti3SiC2 toward the crack, facilitating crack recovery. Along with the wear-triggered self-healing, the NAB/Ti3SiC2 shows an improved tribological performance with the stable decreased friction torque due to the formation of lubrication TiO2 oxide.

  19. Evidence that abnormal grain growth precedes fatigue crack initiation in nanocrystalline Ni-Fe

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Furnish, Timothy A.; Bufford, Daniel C.; Ren, Fang

    Prior studies on the high-cycle fatigue behavior of nanocrystalline metals have shown that fatigue fracture is associated with abnormal grain growth (AGG). However, those previous studies have been unable to determine if AGG precedes fatigue crack initiation, or vice-versa. The present study shows that AGG indeed occurs prior to crack formation in nanocrystalline Ni-Fe by using a recently developed synchrotron X-ray diffraction modality that has been adapted for in-situ analysis. The technique allows fatigue tests to be interrupted at the initial signs of the AGG process, and subsequent microscopy reveals the precursor damage state preceding crack initiation.

  20. Evidence that abnormal grain growth precedes fatigue crack initiation in nanocrystalline Ni-Fe

    DOE PAGES

    Furnish, Timothy A.; Bufford, Daniel C.; Ren, Fang; ...

    2018-09-06

    Prior studies on the high-cycle fatigue behavior of nanocrystalline metals have shown that fatigue fracture is associated with abnormal grain growth (AGG). However, those previous studies have been unable to determine if AGG precedes fatigue crack initiation, or vice-versa. The present study shows that AGG indeed occurs prior to crack formation in nanocrystalline Ni-Fe by using a recently developed synchrotron X-ray diffraction modality that has been adapted for in-situ analysis. The technique allows fatigue tests to be interrupted at the initial signs of the AGG process, and subsequent microscopy reveals the precursor damage state preceding crack initiation.

  1. Facile Synthesis of A 3D Flower-Like Mesoporous Ni@C Composite Material for High-Energy Aqueous Asymmetric Supercapacitors.

    PubMed

    Liu, Song; An, Cuihua; Zang, Lei; Chang, Xiaoya; Guo, Huinan; Jiao, Lifang; Wang, Yijing

    2018-04-16

    A 3D flower-like mesoporous Ni@C composite material has been synthesized by using a facile and economical one-pot hydrothermal method. This unique 3D flower-like Ni@C composite, which exhibited a high surface area (522.4 m 2  g -1 ), consisted of highly dispersed Ni nanoparticles on mesoporous carbon flakes. The effect of calcination temperature on the electrochemical performance of the Ni@C composite was systematically investigated. The optimized material (Ni@C 700) displayed high specific capacity (1306 F g -1 at 2 A g -1 ) and excellent cycling performance (96.7 % retention after 5000 cycles). Furthermore, an asymmetric supercapacitor (ASC) that contained Ni@C 700 as cathode and mesoporous carbon (MC) as anode demonstrated high energy density (60.4 W h kg -1 at a power density of 750 W kg -1 ). © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  2. Influence of La3+ Substitution on Structure, Morphology and Magnetic Properties of Nanocrystalline Ni-Zn Ferrite

    PubMed Central

    Dasan, Y. K.; Guan, B. H.; Zahari, M. H.; Chuan, L. K.

    2017-01-01

    Lanthanum substituted Ni-Zn ferrite nanoparticles (Ni0.5Zn0.5LaxFe1-xO4; 0.00 ≤x≤ 1.00) synthesized by sol-gel method were presented. X-ray diffraction patterns reveal the typical single phase spinel cubic ferrite structure, with the traces of secondary phase for lanthanum substituted nanocrystals. In addition, the structural analysis also demonstrates that the average crystallite size varied in the range of 21–25 nm. FTIR spectra present the two prominent absorption bands in the range of 400 to 600 cm-1 which are the fingerprint region of all ferrites. Surface morphology of both substituted and unsubstituted Ni-Zn ferrite nanoparticle samples was studied using FESEM technique and it indicates a significant increase in the size of spherical shaped particles with La3+ substitution. Magnetic properties of all samples were analyzed using vibrating sample magnetometer (VSM). The results revealed that saturation magnetization (Ms) and coercivity (Hc) of La3+ substituted samples has decreased as compared to the Ni-Zn ferrite samples. Hence, the observed results affirm that the lanthanum ion substitution has greatly influenced the structural, morphology and magnetic properties of Ni-Zn ferrite nanoparticles. PMID:28081257

  3. Influence of La3+ Substitution on Structure, Morphology and Magnetic Properties of Nanocrystalline Ni-Zn Ferrite.

    PubMed

    Dasan, Y K; Guan, B H; Zahari, M H; Chuan, L K

    2017-01-01

    Lanthanum substituted Ni-Zn ferrite nanoparticles (Ni0.5Zn0.5LaxFe1-xO4; 0.00 ≤x≤ 1.00) synthesized by sol-gel method were presented. X-ray diffraction patterns reveal the typical single phase spinel cubic ferrite structure, with the traces of secondary phase for lanthanum substituted nanocrystals. In addition, the structural analysis also demonstrates that the average crystallite size varied in the range of 21-25 nm. FTIR spectra present the two prominent absorption bands in the range of 400 to 600 cm-1 which are the fingerprint region of all ferrites. Surface morphology of both substituted and unsubstituted Ni-Zn ferrite nanoparticle samples was studied using FESEM technique and it indicates a significant increase in the size of spherical shaped particles with La3+ substitution. Magnetic properties of all samples were analyzed using vibrating sample magnetometer (VSM). The results revealed that saturation magnetization (Ms) and coercivity (Hc) of La3+ substituted samples has decreased as compared to the Ni-Zn ferrite samples. Hence, the observed results affirm that the lanthanum ion substitution has greatly influenced the structural, morphology and magnetic properties of Ni-Zn ferrite nanoparticles.

  4. Host-Sensitized and Tunable Luminescence of GdNbO4:Ln3+ (Ln3+ = Eu3+/Tb3+/Tm3+) Nanocrystalline Phosphors with Abundant Color.

    PubMed

    Liu, Xiaoming; Chen, Chen; Li, Shuailong; Dai, Yuhua; Guo, Huiqin; Tang, Xinghua; Xie, Yu; Yan, Liushui

    2016-10-17

    Up to now, GdNbO 4 has always been regarded as an essentially inert material in the visible region with excitation of UV light and electron beams. Nevertheless, here we demonstrate a new recreating blue emission of GdNbO 4 nanocrystalline phosphors with a quantum efficiency of 41.6% and host sensitized luminescence in GdNbO 4 :Ln 3+ (Ln 3+ = Eu 3+ /Tb 3+ /Tm 3+ ) nanocrystalline phosphors with abundant color in response to UV light and electron beams. The GdNbO 4 and GdNbO 4 :Ln 3+ (Ln 3+ = Eu 3+ /Tb 3+ /Tm 3+ ) nanocrystalline phosphors were synthesized by a Pechini-type sol-gel process. With excitation of UV light and low-voltage electron beams, the obtained GdNbO 4 nanocrystalline phosphor presents a strong blue luminescence from 280 to 650 nm centered around 440 nm, and the GdNbO 4 :Ln 3+ nanocrystalline phosphors show both host emission and respective emission lines derived from the characterize f-f transitions of the doping Eu 3+ , Tb 3+ , and Tm 3+ ions. The luminescence color of GdNbO 4 :Ln 3+ nanocrystalline phosphors can be tuned from blue to green, red, blue-green, orange, pinkish, white, etc. by varying the doping species, concentration, and relative ratio of the codoping rare earth ions in GdNbO 4 host lattice. A single-phase white-light-emission has been realized in Eu 3+ /Tb 3+ /Tm 3+ triply doped GdNbO 4 nanocrystalline phosphors. The luminescence properties and mechanisms of GdNbO 4 and GdNbO 4 :Ln 3+ (Ln 3+ = Eu 3+ /Tb 3+ /Tm 3+ ) are updated.

  5. Effect of Temperature on Nucleation of Nanocrystalline Indium Tin Oxide Synthesized by Electron-Beam Evaporation

    NASA Astrophysics Data System (ADS)

    Shen, Yan; Zhao, Yujun; Shen, Jianxing; Xu, Xiangang

    2017-07-01

    Indium tin oxide (ITO) has been widely applied as a transparent conductive layer and optical window in light-emitting diodes, solar cells, and touch screens. In this paper, crystalline nano-sized ITO dendrites are obtained using an electron-beam evaporation technique. The surface morphology of the obtained ITO was studied for substrate temperatures of 25°C, 130°C, 180°C, and 300°C. Nano-sized crystalline dendrites were synthesized only at a substrate temperature of 300°C. The dendrites had a cubic structure, confirmed by the results of x-ray diffraction and transmission electron microscopy. The growth mechanism of the nano-crystalline dendrites could be explained by a vapor-liquid-solid (VLS) growth model. The catalysts of the VLS process were indium and tin droplets, confirmed by varying the substrate temperature, which further influenced the nucleation of the ITO dendrites.

  6. A model for the CO-inhibited form of [NiFe] hydrogenase: synthesis of (CO)3Fe(μ-StBu)3Ni{SC6H3-2,6-(mesityl)2} and reversible CO addition at the Ni site

    PubMed Central

    Ohki, Yasuhiro; Yasumura, Kazunari; Ando, Masaru; Shimokata, Satoko; Tatsumi, Kazuyuki

    2010-01-01

    A [NiFe] hydrogenase model compound having a distorted trigonal-pyramidal nickel center, (CO)3Fe(μ-StBu)3Ni(SDmp), 1 (Dmp = C6H3-2,6-(mesityl)2), was synthesized from the reaction of the tetranuclear Fe-Ni-Ni-Fe complex [(CO)3Fe(μ-StBu)3Ni]2(μ-Br)2, 2 with NaSDmp at -40 °C. The nickel site of complex 1 was found to add CO or CNtBu at -40 °C to give (CO)3Fe(StBu)(μ-StBu)2Ni(CO)(SDmp), 3, or (CO)3Fe(StBu)(μ-StBu)2Ni(CNtBu)(SDmp), 4, respectively. One of the CO bands of 3, appearing at 2055 cm-1 in the infrared spectrum, was assigned as the Ni-CO band, and this frequency is comparable to those observed for the CO-inhibited forms of [NiFe] hydrogenase. Like the CO-inhibited forms of [NiFe] hydrogenase, the coordination of CO at the nickel site of 1 is reversible, while the CNtBu adduct 4 is more robust. PMID:20147622

  7. Cytotoxicity Evaluation and Magnetic Characteristics of Mechano-thermally Synthesized CuNi Nanoparticles for Hyperthermia

    NASA Astrophysics Data System (ADS)

    Amrollahi, P.; Ataie, A.; Nozari, A.; Seyedjafari, E.; Shafiee, A.

    2015-03-01

    CuNi alloys are very well known, both in academia and industry, based on their wide range of applications. In the present investigation, the previously synthesized Cu0.5Ni0.5 nanoparticles (NPs) by mechano-thermal method were studied more extensively. Phase composition and morphology of the samples were studied by employing x-ray diffraction (XRD), field-emission scanning electron microscopy (FESEM), and transmission electron microscopy (TEM) techniques. The Curie temperature ( T c) was determined by differential scanning calorimetry (DSC). In vitro cytotoxicity was studied through methyl-thiazolyl-tetrazolium (MTT) assay. XRD and FESEM results indicated the formation of single-phase Cu0.5Ni0.5. TEM micrographs showed that the mean particle size of powders is 20 nm. DSC results revealed that T c of mechano-thermally synthesized Cu0.5Ni0.5 is 44 °C. The MTT assay results confirmed the viability and proliferation of human bone marrow stem cells in contact with Cu0.5Ni0.5 NPs. In summary, the fabricated particles were demonstrated to have potential in low concentrations for cancer treatment applications.

  8. Effect of Co2+ and Y3+ ions insertion on the microstructure development and magnetic properties of Ni0.5Zn0.5Fe2O4 powders synthesized using Co-precipitation method

    NASA Astrophysics Data System (ADS)

    Rashad, M. M.; Rayan, D. A.; Turky, A. O.; Hessien, M. M.

    2015-01-01

    Nanocrystalline Ni0.5Zn0.5-xCoxFe2-zYzO4 powders (x=0-0.3 and z from 0 to 0.3) have been synthesized via a facile co-precipitation technique. X-ray diffraction (XRD), scanning electron microscopy (SEM) and vibrating sample magnetometer (VSM) are utilized in order to study the effect of variation of cobalt and yttrium substitutions and its impact on crystalline size, lattice parameter, X-ray density, microstructure and magnetic properties of the formed powders. X-ray diffraction data indicated that, after doping, all samples consisted of the main spinel phase for the formed precursors precipitated at pH 10 annealed at 1000 oC for 2 h. The lattice parameter and the unit cell were decreased linearly with increasing Co content whereas they were increased with increasing the Y incorporation. Additionally, the porosity was increased with increasing Co concentration while it was decreased with increasing the Y insertion. The mean ionic radii and hopping and bond lengths was decreased with the value of Co2+ and they were increased with the value of Y3+ ion as well as both of Y3+ and Co2+ ions. The microstructures of the produced powders were found to be cubic like structure. The addition of Y3+ ion suppressed the grain size whereas addition of Co2+ ion enhanced the grain growth availably. An examination of the magnetic properties revealed an increase in saturation magnetization with increasing Co and Y concentrations incorporation up to x=0.3. Meanwhile, the formed powders exhibited superparamagnetic characteristics. A high saturation magnetization (77.0 emu/g) was achieved for Ni0.5Zn0.2Co0.3Fe2O4 sample annealed at 1000 oC for 2 h.

  9. Development of Nanocrystalline Zeolite Materials for the Decontamination of Chemical Warfare Agents

    DTIC Science & Technology

    2008-11-17

    phosphite (CH3O)2P(O)H or DMP. There is -40-20020406080100 In te ns ity ppm a) b) c) d) * ** ** ** * * 33 37 1225 9 Figure 6. 31P MAS NMR spectra...The main objective of this research is to use novel nanocrystalline zeolite materials synthesized in our laboratories for the decontamination of...nanocrystalline zeolite materials. In these studies, we have focused our attention on the decontamination of 2-CEES and DMMP, two simulants for mustard gas

  10. Grain growth of nanocrystalline 3C-SiC under Au ion irradiation at elevated temperatures

    NASA Astrophysics Data System (ADS)

    Zhang, Limin; Jiang, Weilin; Dissanayake, Amila; Varga, Tamas; Zhang, Jiandong; Zhu, Zihua; Hu, Dehong; Wang, Haiyan; Henager, Charles H., Jr.; Wang, Tieshan

    2016-01-01

    Nanocrystalline silicon carbide (SiC) represents an excellent model system for a fundamental study of interfacial (grain boundary) processes under nuclear radiation, which are critical to the understanding of the response of nanostructured materials to high-dose irradiation. This study reports on a comparison of irradiation effects in cubic phase SiC (3C-SiC) grains of a few nanometres in size and single-crystal 3C-SiC films under identical Au ion irradiation to a range of doses at 700 K. In contrast to the latter, in which the lattice disorder is accumulated to a saturation level without full amorphization, the average grain size of the former increases with dose following a power-law trend. In addition to coalescence, the grain grows through atomic jumps and mass transport, where irradiation-induced vacancies at grain boundaries assist the processes. It is found that a higher irradiation temperature leads to slower grain growth and a faster approach to a saturation size of SiC nanograins. This unusual behaviour could be associated with irradiation-induced grain nucleation and growth in amorphous SiC matrix in which the 3C-SiC grains are embedded. The results could potentially have a positive impact on structural components of advanced nuclear energy systems.

  11. One-step facile synthesis of Ni2P/C as cathode material for Ni/Zn aqueous secondary battery

    NASA Astrophysics Data System (ADS)

    Li, JiLan; Chen, ChangGuo

    2018-01-01

    Nickel phosphides/carbon(Ni2P/C) composites have been successfully synthesized via a simple one-pot hydrothermal method using glucose as carbon source for the first time. By contrast, the pure Ni2P was prepared under the same conditions without glucose. The results show that glucose not only provide the carbon source, but also prevent the aggregation of Ni2P particles. The as-obtained Ni2P/C composites and pure Ni2P were used as cathode material for alkaline Ni/Zn battery. Owing to unique Ni2P/C composites and loose, Ultra thin flower-like shape the synthesized Ni2P/C material delivers high capacity of 176 mAh g-1 at 1 A g-1 and 82 mAh g-1 at 5 A g-1 current density in Ni2P/C-Zn battery. Moreover, it shows a good cycling life that capacity fading only about 6.2% after 1500 cycles. All of these indicate that the prepared Ni2P/C composites may be a new promising cathode material for Ni-Zn rechargeable battery.

  12. A polyethylene glycol-assisted route to synthesize Pb(Ni 1/3Nb 2/3)O 3-PbTiO 3with improved electric properties

    NASA Astrophysics Data System (ADS)

    Ye, Yin; Yu, Shuhui; Huang, Haitao; Zhou, Limin

    2007-07-01

    Polyethylene glycol (PEG)-assisted solid state reaction route is employed to prepare the relaxor-type ferroelectric powders and ceramics of (1-x)Pb(Ni 1/3Nb 2/3)O 3-xPbTiO 3 (PNN-PT) with the morphotropic phase boundary (MPB) composition at x=0.36 (0.64PNN-0.36PT). PEG additive with the molecular weight of 200 is introduced into PNN-PT oxide precursors in order to obtain the perovskite phase. The XRD and TG/DSC results demonstrate that the interactions between PbO and PEG favor the transformation from the lead-rich pyrochlore to the lead-deficient pyrochlore, thus facilitating the formation of the perovskite. Consequently, nearly pure perovskite 0.64PNN-0.36PT powders are synthesized at a relatively low temperature of 850 °C. A significant improvement of electric properties of the ceramics sintered at 1200 °C is achieved by PEG modification. The dielectric constant at room temperature and the maximum dielectric constant at T c reach 4987 and 24307, respectively, at a frequency of 1 kHz. The piezoelectric constant d 33 is 460 pC/N.

  13. Structural, dielectric and impedance spectroscopic studies of Ni0.5Zn0.5-xLixFe2O4 nanocrystalline ferrites

    NASA Astrophysics Data System (ADS)

    Venkatesh, Davuluri; Ramesh, K. V.

    2017-09-01

    Nanocrystalline lithium substituted Ni-Zn ferrites with composition Ni0.5Zn0.5-xLixFe2O4 (x = 0.00-0.25 in steps of 0.05) were synthesized by the citrate gel auto-combustion method and were sintered at 1000∘C for 4 h in air atmosphere. The structural, dielectric, impedance spectroscopic and magnetic properties were studied by using X-ray diffraction, impedance analyzer and vibrating sample magnetometer respectively. The X-ray diffraction patterns confirm that all samples exhibit a single phase cubic spinel structure. Suitable cation distribution for all compositions has been proposed by using the X-ray diffraction line intensity calculations and the theoretical lattice parameter for each composition was observed in close agreement with the experimental ones and thereby supporting the proposed distribution. An increase in the saturation magnetization was observed up to x = 0.10 level of Li+ substitution and thereafter magnetization reduced for higher concentrations to the highest level of Li+ substitution. The dielectric constant and the DC resistivity of Ni-Zn-Li ferrites were noticed to decrease with increase in the Li+ ion concentration. The impedance spectroscopic studies by using the Cole-Cole plots were studied in order to obtain the relaxation time, grain resistance and grain capacitance. AC conductivity initially remained almost independent of frequency for lower frequencies and thereafter for higher frequencies the AC conductivity increased with increase of Lithium concentration.

  14. Effect of Mo on Microstructures and Wear Properties of In Situ Synthesized Ti(C,N)/Ni-Based Composite Coatings by Laser Cladding.

    PubMed

    Wu, Fan; Chen, Tao; Wang, Haojun; Liu, Defu

    2017-09-06

    Using Ni60 alloy, C, TiN and Mo mixed powders as the precursor materials, in situ synthesized Ti(C,N) particles reinforcing Ni-based composite coatings are produced on Ti6Al4V alloys by laser cladding. Phase constituents, microstructures and wear properties of the composite coatings with 0 wt % Mo, 4 wt % Mo and 8 wt % Mo additions are studied comparatively. Results indicate that Ti(C,N) is formed by the in situ metallurgical reaction, the (Ti,Mo)(C,N) rim phase surrounding the Ti(C,N) ceramic particle is synthesized with the addition of Mo, and the increase of Mo content is beneficial to improve the wear properties of the cladding coatings. Because of the effect of Mo, the grains are remarkably refined and a unique core-rim structure that is uniformly dispersed in the matrix appears; meanwhile, the composite coatings with Mo addition exhibit high hardness and excellent wear resistance due to the comprehensive action of dispersion strengthening, fine grain strengthening and solid solution strengthening.

  15. Effect of Mo on Microstructures and Wear Properties of In Situ Synthesized Ti(C,N)/Ni-Based Composite Coatings by Laser Cladding

    PubMed Central

    Chen, Tao; Wang, Haojun

    2017-01-01

    Using Ni60 alloy, C, TiN and Mo mixed powders as the precursor materials, in situ synthesized Ti(C,N) particles reinforcing Ni-based composite coatings are produced on Ti6Al4V alloys by laser cladding. Phase constituents, microstructures and wear properties of the composite coatings with 0 wt % Mo, 4 wt % Mo and 8 wt % Mo additions are studied comparatively. Results indicate that Ti(C,N) is formed by the in situ metallurgical reaction, the (Ti,Mo)(C,N) rim phase surrounding the Ti(C,N) ceramic particle is synthesized with the addition of Mo, and the increase of Mo content is beneficial to improve the wear properties of the cladding coatings. Because of the effect of Mo, the grains are remarkably refined and a unique core-rim structure that is uniformly dispersed in the matrix appears; meanwhile, the composite coatings with Mo addition exhibit high hardness and excellent wear resistance due to the comprehensive action of dispersion strengthening, fine grain strengthening and solid solution strengthening. PMID:28878190

  16. Mechanically Driven Grain Boundary Relaxation: A Mechanism for Cyclic Hardening in Nanocrystalline Ni

    DTIC Science & Technology

    2012-01-01

    enforce a minimum separation distance (25% of the simulation cell length) between grain nucleation sites, giving more equiaxed grains and a tighter...de d by [ M as sa ch us et ts I ns tit ut e of T ec hn ol og y] a t 1 5: 36 1 2 Fe br ua ry 2 01 2 electrodeposited nanocrystalline Ni with

  17. Synthesis of Mesoporous Nanocrystalline Zirconia by Surfactant-Assisted Hydrothermal Approach.

    PubMed

    Nath, Soumav; Biswas, Ashik; Kour, Prachi P; Sarma, Loka S; Sur, Ujjal Kumar; Ankamwar, Balaprasad G

    2018-08-01

    In this paper, we have reported the chemical synthesis of thermally stable mesoporous nanocrystalline zirconia with high surface area using a surfactant-assisted hydrothermal approach. We have employed different type of surfactants such as CTAB, SDS and Triton X-100 in our synthesis. The synthesized nanocrystalline zirconia multistructures exhibit various morphologies such as rod, mortar-pestle with different particle sizes. We have characterized the zirconia multistructures by X-ray diffraction study, Field emission scanning electron microscopy, Attenuated total refection infrared spectroscopy, UV-Vis spectroscopy and photoluminescence spectroscopy. The thermal stability of as synthesized zirconia multistructures was studied by thermo gravimetric analysis, which shows the high thermal stability of nanocrystalline zirconia around 900 °C temperature.

  18. Cyclic and isothermal oxidation behavior at 1100 and 1200 C of Ni-20Cr, Ni-20Cr-3Mn, Ni-20Cr-3Si, and Ni-40Cr alloys

    NASA Technical Reports Server (NTRS)

    Lowell, C. E.

    1973-01-01

    Alloys of Ni-20Cr, Ni-20Cr-3Mn, Ni-20Cr-3Si, and Ni-40Cr were cyclically oxidized at 1100 and 1200 C for up to 100 hours. Oxidation behavior was judged by sample thickness and weight change, metallography, diffraction, and microprobe analysis. The least attacked were Ni-40Cr and Ni-20Cr-3Si. The alloy Ni-20Cr-3Mn was much less attacked than Ni-20Cr, but more than the other alloys. The formation of Cr2O3 accounted for the increased resistance of Ni-Cr and Ni-20Cr-3Si, and the formation of MnCr2O4 accounts for the improvement in Ni-20Cr-3mn over Ni-20Cr.

  19. Electrochemically synthesized nanocrystalline spinel thin film for high performance supercapacitor

    NASA Astrophysics Data System (ADS)

    Gupta, Vinay; Gupta, Shubhra; Miura, Norio

    Spinels are not known for their supercapacitive nature. Here, we have explored electrochemically synthesized nanostructured NiCo 2O 4 spinel thin-film electrode for electrochemical supercapacitors. The nanostructured NiCo 2O 4 spinel thin film exhibited a high specific capacitance value of 580 F g -1 and an energy density of 32 Wh kg -1 at the power density of 4 kW kg -1, accompanying with good cyclic stability.

  20. [Raman studies of nanocrystalline BaTiO3 ceramics].

    PubMed

    Xiao, Chang-jiang; Jin, Chang-qing; Wang, Xiao-hui

    2008-12-01

    High pressure can significantly increase the densification. Further, during the high pressure assisted sintering, the nucleation rate is increased due to reduced energy barrier and the growth rate is suppressed due to the decreased diffusivity. Thus high pressure enables the specimen to be fabricated with relatively lower temperature and shorter sintering period that assures to obtain dense nanocrystalline ceramics. Dense nanocrystalline BaTiO3 ceramics with uniform grain sizes of 60 and 30 nm, respectively, were obtained by pressure assisted sintering. The crystal structure and phase transitions were investigated by Raman scattering at temperatures ranging from -190 to 200 degrees C. The Raman results indicated that the evolution of Raman spectrum with grain size is characterized by an intensity decrease, a broadening of the line width, a frequency shift, and the disappearance of the Raman mode. With increasing temperature, similar to 3 mm BaTiO3 normal ceramics, the successive phase transitions from rhombohedral to orthorhombic, orthorhombic to tetragonal, and tetragonal to cubic were also observed in nanocrystalline BaTiO3 ceramics. In addition, when particle size is reduced to the nanoscale, one will find some unusual physical properties in nanocrystalline ceramics, compared with those of coarse-grained BaTiO3 ceramics. The different coexistences of multiphase were found at different temperature. Especially, the ferroelectric tetragonal and orthorhombic phase can coexist at room temperature in nanocrystalline BaTiO3 ceramics. The phenomenon can be explained by the internal stress. The coexistences of different ferroelectric phases at room temperature indicate that the critical grain size for the disappearance of ferroelectricity in nanocrystalline BaTiO3 ceramics fabricated by pressure assisted sintering is below 30 nm.

  1. Effects of Ni content on nanocrystalline Fe-Co-Ni ternary alloys synthesized by a chemical reduction method

    NASA Astrophysics Data System (ADS)

    Chokprasombat, Komkrich; Pinitsoontorn, Supree; Maensiri, Santi

    2016-05-01

    Magnetic properties of Fe-Co-Ni ternary alloys could be altered by changing of the particle size, elemental compositions, and crystalline structures. In this work, Fe50Co50-xNix nanoparticles (x=10, 20, 40, and 50) were prepared by the novel chemical reduction process. Hydrazine monohydrate was used as a reducing agent under the concentrated basic condition with the presence of poly(vinylpyrrolidone). We found that the nanoparticles were composed of Fe, Co and Ni with compositions according to the molar ratio of the metal sources. Interestingly, the particles were well-crystalline at the as-prepared state without post-annealing at high temperature. Increasing Ni content resulted in phase transformation from body centered cubic (bcc) to face centered cubic (fcc). For the fcc phase, the average particle size decreased when increased the Ni content; the Fe50Ni50 nanoparticles had the smallest average size with the narrowest size distribution. In additions, the particles exhibited ferromagnetic properties at room temperature with the coercivities higher than 300 Oe, and the saturation magnetiation decreased with increasing Ni content. These results suggest that the structural and magnetic properties of Fe-Co-Ni alloys could be adjusted by varying the Ni content.

  2. THERMALLY STABLE NANOCRYSTALLINE TIO2 PHOTOCATALYSTS SYNTHESIZED VIA SOL-GEL METHODS MODIFIED WITH IONIC LIQUID AND SURFACTANT MOLECULES

    EPA Science Inventory

    Recently, sol-gel methods employing ionic liquids (ILs) have shown significant implications for the synthesis of well-defined nanostructured inorganic materials. Herein, we synthesized nanocrystalline TiO2 particles via an alkoxide sol-gel method employing a water-immi...

  3. Optical and structural properties of Mo-doped NiTiO3 materials synthesized via modified Pechini methods

    NASA Astrophysics Data System (ADS)

    Pham, Thanh-Truc; Kang, Sung Gu; Shin, Eun Woo

    2017-07-01

    In this study, molybdenum (Mo)-doped nickel titanate (NiTiO3) materials were successfully synthesized as a function of Mo content through a modified Pechini method followed by a solvothermal treatment process. Various characterization methods were employed to investigate the optical and structural properties of the materials. XRD patterns clearly showed that the NiTiO3 structure maintained a single phase with no observed crystalline structure transformations, even after the addition of 10 wt.% Mo. In the Raman spectra and XRD patterns, peak positions shifted with a change in Mo content, confirming that the NiTiO3 lattice was doped with Mo. On the other hand, Mo doping of NiTiO3 materials changed their optical properties. DRS-UV demonstrated that the addition of Mo increased photon absorption within the UV region. Relaxation processes were inhibited by Mo doping, which was evident in the PL spectra. Structural properties of the prepared materials were studied via FE-SEM and HR-TEM. The measured surface area increased proportionally with Mo content due to a reduction in grain size of the materials.

  4. Sonochemical synthesis of porous NiTiO3 nanorods for photocatalytic degradation of ceftiofur sodium.

    PubMed

    Pugazhenthiran, N; Kaviyarasan, K; Sivasankar, T; Emeline, A; Bahnemann, D; Mangalaraja, R V; Anandan, S

    2017-03-01

    Porous NiTiO 3 nanorods were synthesized through the sonochemical route followed by calcination at various temperature conditions. Surface morphology of the samples was tuned by varying the heat treatment temperature from 100 to 600°C. The synthesized NiTiO 3 nanorods were characterized by transmission electron microscopy, X-ray photoelectron spectroscopy, X-ray diffraction, diffused reflectance spectroscopy, photoluminescence spectroscopy and Brunauer-Emmett-Teller (BET) analyses. The characterization studies revealed that the NiTiO 3 nanomaterial was tuned to porous and perfectly rod shaped structure during the heat treatment at 600°C. The porous NiTiO 3 nanorods showed visible optical response and thus can be utilized in the photocatalytic degradation of ceftiofur sodium (CFS) under direct sunlight. The photoluminescence intensity of the porous NiTiO 3 nanorods formed while heating at 600°C was lower than that of the as-synthesized NiTiO 3 sample owing to the photogenerated electrons delocalization along the one dimensional nanorods and this delocalization resulted in the reduction of the electron-hole recombination rate. The photocatalytic degradation of ceftiofur sodium (CFS) was carried out using NiTiO 3 nanorods under the direct sunlight irradiation and their intermediate products were analysed through HPLC to deduce the possible degradation mechanism. The porous NiTiO 3 nanorods exhibited an excellent photocatalytic activity towards the CFS degradation and further, the photocatalytic activity was increased by the addition of peroxomonosulfate owing to the simultaneous generation of both OH and SO 4 - . Copyright © 2016 Elsevier B.V. All rights reserved.

  5. Synthesis, crystal structure and spectroscopy properties of Na 3AZr(PO 4) 3 ( A=Mg, Ni) and Li 2.6Na 0.4NiZr(PO 4) 3 phosphates

    NASA Astrophysics Data System (ADS)

    Chakir, M.; El Jazouli, A.; de Waal, D.

    2006-06-01

    Na 3AZr(PO 4) 3 ( A=Mg, Ni) phosphates were prepared at 750 °C by coprecipitation route. Their crystal structures have been refined at room temperature from X-ray powder diffraction data using Rietveld method. Li 2.6Na 0.4NiZr(PO 4) 3 was synthesized through ion exchange from the sodium analog. These materials belong to the Nasicon-type structure. Raman spectra of Na 3AZr(PO 4) 3 ( A=Mg, Ni) phosphates present broad peaks in favor of the statistical distribution in the sites around PO 4 tetrahedra. Diffuse reflectance spectra indicate the presence of octahedrally coordinated Ni 2+ ions.

  6. Studies on the sensing behaviour of nanocrystalline CuGa(2)O(4) towards hydrogen, liquefied petroleum gas and ammonia.

    PubMed

    Biswas, Soumya Kanti; Sarkar, Arpita; Pathak, Amita; Pramanik, Panchanan

    2010-06-15

    In the present article, the gas sensing behaviour of nanocrystalline CuGa(2)O(4) towards H(2), liquefied petroleum gas (LPG) and NH(3) has been reported for the first time. Nanocrystalline powders of CuGa(2)O(4) having average particle sizes in the range of 30-60nm have been prepared through thermal decomposition of an aqueous precursor solution comprising copper nitrate, gallium nitrate and triethanol amine (TEA), followed by calcination at 750 degrees C for 2h. The synthesized nanocrystalline CuGa(2)O(4) powders have been characterised through X-ray diffraction (XRD), transmission electron microscopy (TEM), field-emission scanning electron microscopy (FESEM) study, energy dispersive X-ray (EDX) analysis and BET (Brunauer-Emmett-Teller) surface area measurement. The synthesized CuGa(2)O(4) having spinel structure with specific surface area of 40m(2)/g exhibits maximum sensitivity towards H(2), LPG, and NH(3) at 350 degrees C.

  7. Phase fields of nickel silicides obtained by mechanical alloying in the nanocrystalline state

    NASA Astrophysics Data System (ADS)

    Datta, M. K.; Pabi, S. K.; Murty, B. S.

    2000-06-01

    Solid state reactions induced by mechanical alloying (MA) of elemental blends of Ni and Si have been studied over the entire composition range of the Ni-Si system. A monotonous increase of the lattice parameter of the Ni rich solid solution, Ni(Si), is observed with refinement of crystallite size. Nanocrystalline phase/phase mixtures of Ni(Si), Ni(Si)+Ni31Si12, Ni31Si12+Ni2Si, Ni2Si+NiSi and NiSi+Si, have been obtained during MA, over the composition ranges of 0-10, 10-28, 28-33, 33-50, and >50 at. % Si, respectively. The results clearly suggest that only congruent melting phases, Ni31Si12, Ni2Si, and NiSi form, while the formation of noncongruent melting phases, Ni3Si, Ni3Si2, and NiSi2, is bypassed in the nanocrystalline state. The phase formation during MA has been discussed based on thermodynamic arguments. The predicted phase fields obtained from effective free energy calculations are quite consistent with those obtained during MA.

  8. Optical and electrical properties of mechanochemically synthesized nanocrystalline delafossite CuAlO2.

    PubMed

    Prakash, T; Prasad, K Padma; Ramasamy, S; Murty, B S

    2008-08-01

    Nanocrystalline p-type semiconductor copper aluminum oxide (CuAlO2) has been synthesized by mechanical alloying using freshly prepared Cu2O and alpha-AlO2O3 nanocrystals in toluene medium. A study on structural property performed with different alloying and post annealing durations, by X-ray diffraction (XRD) reveals the formation of single phase with average crystallite size approximately 45 nm. Optical absorbance onset at 364.5 nm confirms its wide band gap nature (E(g) = 3.4 eV) and the fluorescence emission behaviour (390 nm) confirms its direct band type transition. The activation energy for electrical conduction has been calculated by Arrhenius plots using impedance measurement. Both grain and grain boundary conductivity takes place with almost equal activation energies of approximately 0.45 eV. The paper discusses synthesis, structural, optical and electrical properties of delafossite CuAlO2 in detail.

  9. Thermolysis synthesis of pure phase NiO from novel sonochemical synthesized Ni(II) nano metal-organic supramolecular architecture.

    PubMed

    Hanifehpour, Younes; Morsali, Ali; Mirtamizdoust, Babak; Joo, Sang Woo; Soltani, Behzad

    2017-07-01

    Nano-structures of a new supramolecular coordination compound of divalent nickel with the pyrazol (pzH) containing the terminal azide anions, [Ni(pzH) 2 (N 3 ) 2 ] (1), with discrete molecular architecture (DMA) in solid state was synthesized via sonochemical method. The new nanostructure was characterized by scanning electron microscopy, X-ray powder diffraction, IR, and elemental analysis. Compound 1 was structurally characterized by single crystal X-ray diffraction and the single-crystal X-ray data shows that the coordination number of Ni (II) ions is six, (NiN 6 ), with four N-donor atoms from neutral "pzH" ligands and two N-donors from two terminal azide anions. The supramolecular features in these complexes are guided and controlled by weak directional intermolecular interactions. The structure of the title complex was optimized by density functional theory calculations. Calculated structural parameters and IR spectra for the title complex are consistent with the crystal structure. The NiO nanoparticles were obtained by thermolysis of 1 at 180°C with oleic acid as a surfactant. Copyright © 2017 Elsevier B.V. All rights reserved.

  10. Structural, morphological and magnetic properties of pure and Ni-doped ZnO nanoparticles synthesized by sol-gel method

    NASA Astrophysics Data System (ADS)

    Undre, Pallavi G.; Birajdar, Shankar D.; Kathare, R. V.; Jadhav, K. M.

    2018-05-01

    In this work pure and Ni-doped ZnO nanoparticles have been prepared by sol-gel method. Influence of nickel doping on structural, morphological and magnetic properties of prepared nanoparticles was investigated by X-ray diffraction technique (XRD), Scanning electron microscopy (SEM) and Pulse field magnetic hysteresis loop. X-ray diffraction pattern shows the formation of a single phase with hexagonal wurtzite structure of both pure and Ni-doped ZnO nanoparticles. The lattice parameters `an' and `c' of Ni-doped ZnO is slightly less than that of pure ZnO nanoparticles. The crystalline size of prepared nanoparticles is found to be in 29 and 31 nm range. SEM technique used to examine the surface morphology of samples, SEM image confirms the nanocrystalline nature of present samples. From the pulse field hysteresis loop technique pure and Ni-doped ZnO nanoparticles show diamagnetic and ferromagnetic behavior at room temperature respectively.

  11. Preliminary Microstructural and Microscratch Results of Ni-Cr-Fe and Cr3C2-NiCr Coatings on Magnesium Substrate

    NASA Astrophysics Data System (ADS)

    Istrate, B.; Munteanu, C.; Lupescu, S.; Benchea, M.; Vizureanu, P.

    2017-06-01

    Thermal coatings have a large scale application in aerospace and automotive field, as barriers improving wear mechanical characteristics and corrosion resistance. In present research, there have been used two types of coatings, Ni-Cr-Fe, respectively Cr3C2-NiCr which were deposited on magnesium based alloys (pure magnesium and Mg-30Y master alloy). There have been investigated the microstructural aspects through scanning electronic microscopy and XRD analysis and also a series of mechanical characteristics through microscratch and indentation determinations. The results revealed the formation of some adherent layers resistant to the penetration of the metallic indenter, the coatings did not suffer major damages. Microstructural analysis highlighted the formation of Cr3C2, Cr7C3, Cr3Ni2, Cr7Ni3, FeNi3, Cr-Ni phases. Also, the apparent coefficient of friction for Ni-Cr-Fe coatings presents superior values than Cr3C2-NiCr coatings.

  12. Formation of g-C3N4@Ni(OH)2 Honeycomb Nanostructure and Asymmetric Supercapacitor with High Energy and Power Density.

    PubMed

    Dong, Bitao; Li, Mingyan; Chen, Sheng; Ding, Dawei; Wei, Wei; Gao, Guoxin; Ding, Shujiang

    2017-05-31

    Nickel hydroxide (Ni(OH) 2 ) has been regarded as a potential next-generation electrode material for supercapacitor owing to its attractive high theoretical capacitance. However, practical application of Ni(OH) 2 is hindered by its lower cycling life. To overcome the inherent defects, herein we demonstrate a unique interconnected honeycomb structure of g-C 3 N 4 and Ni(OH) 2 synthesized by an environmentally friendly one-step method. In this work, g-C 3 N 4 has excellent chemical stability and supports a perpendicular charge-transporting direction in charge-discharge process, facilitating electron transportation along that direction. The as-prepared composite exhibits higher specific capacities (1768.7 F g -1 at 7 A g -1 and 2667 F g -1 at 3 mV s -1 , respectively) compared to Ni(OH) 2 aggregations (968.9 F g -1 at 7 A g -1 ) and g-C 3 N 4 (416.5 F g -1 at 7 A g -1 ), as well as better cycling performance (∼84% retentions after 4000 cycles). As asymmetric supercapacitor, g-C 3 N 4 @Ni(OH) 2 //graphene exhibits high capacitance (51 F g -1 ) and long cycle life (72% retentions after 8000 cycles). Moreover, high energy density of 43.1 Wh kg -1 and power density of 9126 W kg -1 has been achieved. This attractive performance reveals that g-C 3 N 4 @Ni(OH) 2 with honeycomb architecture could find potential application as an electrode material for high-performance supercapacitors.

  13. Improved ferroelectric and photoluminescence properties in Pr3+ substituted Na0.5Bi0.5TiO3 synthesized using hydrothermal route

    NASA Astrophysics Data System (ADS)

    Goutham, Cilaveni; Kandula, Kumara Raja; Raavi, Sai Santhosh Kumar; Asthana, Saket

    2018-04-01

    Nanocrystalline Pr3+ substituted NBT was synthesized using hydrothermal technique. Pr3+ modifies the ferroelectric NBT optically active and enhances the electrical properties with small structural changes. Aiming to the development of the bottom up optoelectronic devices this optimized nanoscale Na0.5Bi0.5-xPrxTiO3(x = 0.005) compound is synthesized hydrothermally. X-ray diffraction pattern shows that the system is stabilized in the Rhombohedral (space groupR3c) phase indicating the local strain inhomogeneity. PE loop shows that there is a decrement in the Ec value compared with compounds synthesized using conventional methods. The strong red emission assigned to prominent transition of the Pr3+ ions at 610nm was observed along with weak blue-green emission, indicating the potential use of the system. Energy transfer from host system to Pr3+ ions is responsible for red emission while blue green emission is due to quenching of 3P0 induced by intervalence charge transfer state.

  14. The formation and structure of mechano-synthesized nanocrystalline Sr{sub 3}Fe{sub 2}O{sub 6.4}: XRD Rietveld, Mössabuer and XPS analyses

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Al-Rawas, A.D., E-mail: arawas@squ.edu.om; Widatallah, H.M.; Al-Harthi, S.H.

    2015-05-15

    Highlights: • The formation of mechano-synthesized nanocrystalline Sr{sub 3}Fe{sub 2}O{sub 7−δ} is investigated. • Pre-milling the reactants substantially lowers the formation temperature. • The core and surface structures were studied. • XRD and {sup 57}Fe Mössbauer spectroscopic analyses indicate the δ-value to be 0.60. • XPS shows a complex surface structure for the mechanosynthesized Sr{sub 3}Fe{sub 2}O{sub 7−δ} nanoparticles. - Abstract: The influence of ball milling and subsequent sintering of a 3:1 molar mixture of SrCO{sub 3} and α-Fe{sub 2}O{sub 3} on the formation of Sr{sub 3}Fe{sub 2}O{sub 7−δ} double perovskite is investigated with different analytical techniques. Milling the mixturemore » for 110 h leads to the formation of SrCO{sub 3}-α-Fe{sub 2}O{sub 3} nanocomposites and the structural deformation of α-Fe{sub 2}O{sub 3} via the incorporation of Sr{sup 2+} ions. Subsequent sintering of the pre-milled reactants’ mixture has led to the partial formation of an SrFeO{sub 3} perovskite-related phase in the temperature range 400–600 °C. This was followed by the progressive development of an Sr{sub 3}Fe{sub 2}O{sub 7−δ} phase that continued to increase with increasing sintering temperature until a single-phased nanocrystalline Sr{sub 3}Fe{sub 2}O{sub 7−δ} phase was attained at 950 °C (12 h). This temperature is ∼350 °C lower than the temperature at which the material is prepared conventionally using the ceramic method. The evolution of different structural phases during the reaction process is discussed. Rietveld refinement of the X-ray diffraction data shows a value of 0.60 for the oxygen deficiency δ, in consistency with the Fe{sup 3+}/Fe{sup 4+} ratio derived from the {sup 57}Fe Mössbauer data recorded at both 300 K and 78 K. The Mössbauer data suggests that the Sr{sub 3}Fe{sub 2}O{sub 6.4} nanoparticles are superparamagnetic with blocking temperatures below 78 K. The surfaces of the Sr{sub 3}Fe{sub 2}O{sub 6

  15. Inhibition of growth and biofilm formation of clinical bacterial isolates by NiO nanoparticles synthesized from Eucalyptus globulus plants.

    PubMed

    Saleem, Samia; Ahmed, Bilal; Khan, Mohammad Saghir; Al-Shaeri, Majed; Musarrat, Javed

    2017-10-01

    Nanotechnology based therapeutics has emerged as a promising approach for augmenting the activity of existing antimicrobials due to the unique physical and chemical properties of nanoparticles (NPs). Nickel oxide nanoparticles (NiO-NPs) have been suggested as prospective antibacterial and antitumor agent. In this study, NiO-NPs have been synthesized by a green approach using Eucalyptus globulus leaf extract and assessed for their bactericidal activity. The morphology and purity of synthesized NiO-NPs determined through various spectroscopic techniques like UV-Visible, FT-IR, XRD, EDX and electron microscopy differed considerably. The synthesized NiO-NPs were pleomorphic varying in size between 10 and 20 nm. The XRD analysis revealed the average size of NiO-NPs as 19 nm. The UV-Vis spectroscopic data showed a strong SPR of NiO-NPs with a characteristic spectral peak at 396 nm. The FTIR data revealed various functional moieties like C=C, C-N, C-H and O-H which elucidate the role of leaf biomolecules in capping and dispersal of NiO-NPs. The bioactivity assay revealed the antibacterial and anti-biofilm activity of NiO-NPs against ESβL (+) E. coli, P. aeruginosa, methicillin sensitive and resistant S. aureus. Growth inhibition assay demonstrated time and NiO-NPs concentration dependent decrease in the viability of treated cells. NiO-NPs induced biofilm inhibition was revealed by a sharp increase in characteristic red fluorescence of PI, while SEM images of NiO-NPs treated cells were irregular shrink and distorted with obvious depressions/indentations. The results suggested significant antibacterial and antibiofilm activity of NiO-NPs which may play an important role in the management of infectious diseases affecting human health. Copyright © 2017 Elsevier Ltd. All rights reserved.

  16. Crystallite size strain analysis of nanocrystalline La0.7Sr0.3MnO3 perovskite by Williamson-Hall plot method

    NASA Astrophysics Data System (ADS)

    Kumar, Dinesh; Verma, Narendra Kumar; Singh, Chandra Bhal; Singh, Akhilesh Kumar

    2018-04-01

    The nanocrystalline Sr-doped LaMnO3 (La0.7Sr0.3MnO3 = LSMO) perovskite manganites having different crystallite size were synthesized using the nitrate-glycine auto-combustion method. The phase purity of the manganites was checked by X-ray diffraction (XRD) measurement. The XRD patterns of the sample reveal that La0.7S0.3MnO3 crystallizes into rhombohedral crystal structure with space group R-3c. The size-dependence of structural lattice parameters have been investigated with the help of Rietveld refinement. The structural parameters increase as a function of crystallite size. The crystallite-size and internal strain as a function of crystallite-size have been calculated using Williamson-Hall plot.

  17. g-C3N4/NiAl-LDH 2D/2D Hybrid Heterojunction for High-Performance Photocatalytic Reduction of CO2 into Renewable Fuels.

    PubMed

    Tonda, Surendar; Kumar, Santosh; Bhardwaj, Monika; Yadav, Poonam; Ogale, Satishchandra

    2018-01-24

    2D/2D interface heterostructures of g-C 3 N 4 and NiAl-LDH are synthesized utilizing strong electrostatic interactions between positively charged 2D NiAl-LDH sheets and negatively charged 2D g-C 3 N 4 nanosheets. This new 2D/2D interface heterojunction showed remarkable performance for photocatalytic CO 2 reduction to produce renewable fuels such as CO and H 2 under visible-light irradiation, far superior to that of either single phase g-C 3 N 4 or NiAl-LDH nanosheets. The enhancement of photocatalytic activity could be attributed mainly to the excellent interfacial contact at the heterojunction of g-C 3 N 4 /NiAl-LDH, which subsequently results in suppressed recombination, and improved transfer and separation of photogenerated charge carriers. In addition, the optimal g-C 3 N 4 /NiAl-LDH nanocomposite possessed high photostability after successive experimental runs with no obvious change in the production of CO from CO 2 reduction. Our findings regarding the design, fabrication and photophysical properties of 2D/2D heterostructure systems may find use in other photocatalytic applications including H 2 production and water purification.

  18. Novel synthesis of Ni-ferrite (NiFe{sub 2}O{sub 4}) electrode material for supercapacitor applications

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Venkatachalam, V.; Jayavel, R., E-mail: rjvel@annauniv.edu

    Novel nanocrystalline NiFe{sub 2}O{sub 4} has been synthesized through combustion route using citric acid as a fuel. Phase of the synthesized material was analyzed using powder X-ray diffraction. The XRD study revealed the formation of spinel phase cubic NiFe{sub 2}O{sub 4} with high crystallinity. The average crystallite size of NiFe{sub 2}O{sub 4} nanomaterial was calculated from scherrer equation. The electrochemical properties were realized by cyclic voltammetry, chronopotentiometry and electrochemical impedance spectroscopy. The electrode material shows a maximum specific capacitance of 454 F/g with pseudocapacitive behavior. High capacitance retention of electrode material over 1000 continuous charging-discharging cycles suggests its excellent electrochemicalmore » stability. The results revealed that the nickel ferrite electrode is a potential candidate for energy storage applications in supercapacitor.« less

  19. Structural, Magnetic and Microwave Properties of Nanocrystalline Ni-Co-Gd Ferrites

    NASA Astrophysics Data System (ADS)

    Nikzad, Alireza; Parvizi, Roghaieh; Rezaei, Ghasem; Vaseghi, Behrooz; Khordad, Reza

    2018-02-01

    A series of Co- and Gd-substituted NiFe2O4 ferrite nanoparticles with the formula Ni1- x Co x Fe2- y Gd y O4 (where x = 0.0-1.0 and y = 0.0-0.1) have been successfully synthesized using a hydrothermal method. X-ray diffraction and field emission scanning electron microscopy results indicated that a highly crystallized spherical ferrite nanoparticle structure was obtained along with an increase in the lattice parameters. Compositional analysis of the prepared nanoferrite powders has been carried out using energy-dispersive x-ray (EDX) spectra. The EDX analysis reveals the presence of Ni, Co, Gd and Fe elements in the specimens. Magnetization and the coercive field improved dramatically with an increase in the amount of cobalt and gadolinium added, attributed to the redistribution of cations in the spinel nanoferrite structure. Saturation magnetization and coercivity values up to 99 emu/g and 918 Oe, respectively, were measured using a vibration sample magnetometer at room temperature. Comparative microwave absorption experiments demonstrated that the reflection loss (RL) properties enhanced with increasing substitution of cations in the Ni-ferrite spinel structure for an absorber thickness of 1.8 mm. A maximum RL of - 26.7 dB was obtained for substituted Ni-Co-Gd nanoferrite with x = 1.0 and y = 0.1 at a frequency of 9.4 GHz with a bandwidth of 3.6 GHz (RL ≤ - 10 dB). Experimental results revealed that the synthesized nanoparticles possessed great potential in microwave absorption applications.

  20. Grain size effects on stability of nonlinear vibration with nanocrystalline NiTi shape memory alloy

    NASA Astrophysics Data System (ADS)

    Xia, Minglu; Sun, Qingping

    2017-10-01

    Grain size effects on stability of thermomechanical responses for a nonlinear torsional vibration system with nanocrystalline superelastic NiTi bar are investigated in the frequency and amplitude domains. NiTi bars with average grain size from 10 nm to 100 nm are fabricated through cold-rolling and subsequent annealing. Thermomechanical responses of the NiTi bar as a softening nonlinear damping spring in the torsional vibration system are obtained by synchronised acquisition of rotational angle and temperature under external sinusoidal excitation. It is shown that nonlinearity and damping capacity of the NiTi bar decrease as average grain size of the material is reduced below 100 nm. Therefore jump phenomena of thermomechanical responses become less significant or even vanish and the vibration system becomes more stable. The work in this paper provides a solid experimental base for manipulating the undesired jump phenomena of thermomechanical responses and stabilising the mechanical vibration system through grain refinement of NiTi SMA.

  1. Bimetallic NiFe2O4 synthesized via confined carburization in NiFe-MOFs for efficient oxygen evolution reaction

    NASA Astrophysics Data System (ADS)

    Fang, Zhiqiang; Hao, Zhaomin; Dong, Qingsong; Cui, Yong

    2018-04-01

    Transition metal oxides that derived from metal-organic framework (MOF) precursor have intensively received attention because of their numerous electrochemical applications. Bimetallic Ni-Fe oxides have been rarely reported on the basis of MOF-related strategy. Herein, a bimetallic NiFe2O4 was successfully synthesized via confined carburization in NiFe-MOF precursors and characterized by XRD, XPS, SEM, and TEM. After conducting an investigation of oxygen evolution reaction (OER), the as-synthesized NiFe2O4 material exhibited good catalytic efficiency and high stability and durability in alkaline media. The as-synthesized NiFe2O4 material would promote the development of MOFs in non-noble-metal OER catalyst.

  2. Cyclic compression response of micropillars extracted from textured nanocrystalline NiTi thin-walled tubes

    DOE PAGES

    Ghassemi-Armaki, Hassan; Leff, Asher C.; Taheri, Mitra L.; ...

    2017-06-22

    Compression-compression cyclic deformation of nanocrystalline NiTi tubes intended for medical stents and with an outer diameter of 1 mm and wall thickness of 70 μm was studied using micropillars produced by FIB with the loading axis orthogonal to the tube axis. These micropillars were cycled in a displacement-controlled mode using a nanoindenter equipped with a flat punch to strain levels of 4, 6 and 8% in each cycle and specimens were subjected to several hundred cycles. Furthermore, the cyclic response of two NiTi tubes, one with Af of 17 °C and the other with an Af of -5 °C ismore » compared. The texture of the tube with the Af of -5 °C was measured at the microscopic level using transmission electron microscopy and at the macroscopic level by X-ray diffraction and good agreement was noted. Characteristics such as i) a reduction in the forward transformation stress, ii) increase in maximum stress for a given displacement amplitude, and iii) a reduction in the hysteresis loop area, all with increasing number of cycles, observed typically during cyclic deformation of conventional macroscopic specimens, were captured in the micropillar cyclic tests. Our observations lead to the conclusion that micropillar compression testing in a cyclic mode can enable characterizing the orientation-dependent response in such small dimension components that see complex loading in service, and additionally provide an opportunity for calibrating constitutive equations in micromechanical models.« less

  3. Nanocrystalline ferroelectric BaTiO3/Pt/fused silica for implants synthetized by pulsed laser deposition method

    NASA Astrophysics Data System (ADS)

    Jelínek, Miroslav; Drahokoupil, Jan; Jurek, Karel; Kocourek, Tomáš; Vaněk, Přemysl

    2017-09-01

    The thin-films of BaTiO3 (BTO)/Pt were prepared to test their potential as coatings for titanium-alloy implants. The nanocrystalline BTO/Pt bi-layers were successfully synthesized using fused silica as substrates. The bi-layers were prepared using KrF excimer laser ablation at substrate temperatures (Ts) ranging from 650 °C to 750 °C. The microstructure and composition of the deposits were investigated by scanning electron microscope, x-ray diffraction and wavelength dispersive x-ray spectroscopy methods. The electrical characterization of the Pt/BTO/Pt capacitors indicated ferroelectric-type response in BTO films containing (40-140) nm-sized grains. The technology, microstructure, and functional response of the layers are presented in detail.

  4. Structural and physical properties of antibacterial Ag-doped nano-hydroxyapatite synthesized at 100°C

    PubMed Central

    2011-01-01

    Synthesis of nanosized particle of Ag-doped hydroxyapatite with antibacterial properties is in the great interest in the development of new biomedical applications. In this article, we propose a method for synthesized the Ag-doped nanocrystalline hydroxyapatite. A silver-doped nanocrystalline hydroxyapatite was synthesized at 100°C in deionized water. Other phase or impurities were not observed. Silver-doped hydroxyapatite nanoparticles (Ag:HAp) were performed by setting the atomic ratio of Ag/[Ag + Ca] at 20% and [Ca + Ag]/P as 1.67. The X-ray diffraction studies demonstrate that powders made by co-precipitation at 100°C exhibit the apatite characteristics with good crystal structure and no new phase or impurity is found. The scanning electron microscopy (SEM) observations suggest that these materials present a little different morphology, which reveals a homogeneous aspect of the synthesized particles for all samples. The presence of calcium (Ca), phosphor (P), oxygen (O), and silver (Ag) in the Ag:HAp is confirmed by energy dispersive X-ray (EDAX) analysis. FT-IR and FT-Raman spectroscopies revealed that the presence of the various vibrational modes corresponds to phosphates and hydroxyl groups. The strain of Staphylococcus aureus was used to evaluate the antibacterial activity of the Ca10-xAgx(PO4)6(OH)2 (x = 0 and 0.2). In vitro bacterial adhesion study indicated a significant difference between HAp (x = 0) and Ag:HAp (x = 0.2). The Ag:Hap nanopowder showed higher inhibition. PMID:22136671

  5. Structural and physical properties of antibacterial Ag-doped nano-hydroxyapatite synthesized at 100°C

    NASA Astrophysics Data System (ADS)

    Ciobanu, Carmen Steluta; Massuyeau, Florian; Constantin, Liliana Violeta; Predoi, Daniela

    2011-12-01

    Synthesis of nanosized particle of Ag-doped hydroxyapatite with antibacterial properties is in the great interest in the development of new biomedical applications. In this article, we propose a method for synthesized the Ag-doped nanocrystalline hydroxyapatite. A silver-doped nanocrystalline hydroxyapatite was synthesized at 100°C in deionized water. Other phase or impurities were not observed. Silver-doped hydroxyapatite nanoparticles (Ag:HAp) were performed by setting the atomic ratio of Ag/[Ag + Ca] at 20% and [Ca + Ag]/P as 1.67. The X-ray diffraction studies demonstrate that powders made by co-precipitation at 100°C exhibit the apatite characteristics with good crystal structure and no new phase or impurity is found. The scanning electron microscopy (SEM) observations suggest that these materials present a little different morphology, which reveals a homogeneous aspect of the synthesized particles for all samples. The presence of calcium (Ca), phosphor (P), oxygen (O), and silver (Ag) in the Ag:HAp is confirmed by energy dispersive X-ray (EDAX) analysis. FT-IR and FT-Raman spectroscopies revealed that the presence of the various vibrational modes corresponds to phosphates and hydroxyl groups. The strain of Staphylococcus aureus was used to evaluate the antibacterial activity of the Ca10- x Ag x (PO4)6(OH)2 ( x = 0 and 0.2). In vitro bacterial adhesion study indicated a significant difference between HAp ( x = 0) and Ag:HAp ( x = 0.2). The Ag:Hap nanopowder showed higher inhibition.

  6. Influence of Annealing on Microstructure and Mechanical Properties of a Nanocrystalline CrCoNi Medium-Entropy Alloy

    PubMed Central

    Schuh, Benjamin; Völker, Bernhard; Todt, Juraj; Kormout, Karoline S.; Schell, Norbert; Hohenwarter, Anton

    2018-01-01

    An equiatomic CrCoNi medium-entropy alloy was subjected to high-pressure torsion. This process led to a refinement of the microstructure to a grain size of about 50 nm, combined with a strong increase in the materials hardness. Subsequently, the thermodynamic stability of the medium entropy alloy was evaluated by isothermal and isochronal heat treatments. Annealed samples were investigated by scanning and transmission electron microscopy as well as X-ray diffraction, and were subjected to tensile tests to establish microstructure-property relationships. Furthermore, a comparison of mechanical properties with a grade 316L stainless steel was performed in order to evaluate if the CrCoNi alloy is competitive with commercially available structural materials in the nanocrystalline state. A minority phase embedded in the face-centered cubic matrix of the CrCoNi alloy could be observed in multiple annealed states, as well as the as-received and high-pressure torsion processed material. For 200 h of annealing at 500 °C, it was determined that the minority phase has a hexagonal-closed-packed crystal structure. A possible explanation for the formation of the phase is a preferential segregation of Co to stacking faults. PMID:29695142

  7. (001) 3C SiC/Ni contact interface: In situ XPS observation of annealing induced Ni2Si formation and the resulting barrier height changes

    NASA Astrophysics Data System (ADS)

    Tengeler, Sven; Kaiser, Bernhard; Chaussende, Didier; Jaegermann, Wolfram

    2017-04-01

    The electronic states of the (001) 3C SiC/Ni interface prior and post annealing are investigated via an in situ XPS interface experiment, allowing direct observation of the induced band bending and the transformation from Schottky to ohmic behaviour for the first time. A single domain (001) 3C SiC sample was prepared via wet chemical etching. Nickel was deposited on the sample in multiple in situ deposition steps via RF sputtering, allowing observation of the 3C SiC/Ni interface formation. Over the course of the experiments, an upward band bending of 0.35 eV was observed, along with defect induced Fermi level pinning. This indicates a Schottky type contact behaviour with a barrier height of 0.41 eV. The subsequent annealing at 850 °C for 5 min resulted in the formation of a Ni2Si layer and a reversal of the band bending to 0.06 eV downward. Thus explaining the ohmic contact behaviour frequently reported for annealed n-type 3C SiC/Ni contacts.

  8. Characterization of PrNiO3-δ as oxygen electrode for SOFCs

    NASA Astrophysics Data System (ADS)

    Vibhu, Vaibhav; Flura, Aurélien; Nicollet, Clément; Fourcade, Sébastien; Penin, Nicolas; Bassat, Jean-Marc; Grenier, Jean-Claude; Rougier, Aline; Pouchard, Michel

    2018-07-01

    The praseodymium nickelate PrNiO3-δ was recently identified as one of the decomposition products of Pr2NiO4+δ oxygen electrode, raising the question of the role of this perovskite compound on the Pr2NiO4+δ performance and ageing behaviour. Herein, the electrochemical properties of PrNiO3-δ as cathode for Solid Oxide Fuel Cells (SOFCs) is reported. PrNiO3-δ, synthesized from the citrate-nitrate route, cristallizes in an orthorhombic structure (S.G.: Pnma). Under air, a transition to high temperature rhombohedral structure (S.G.: R-3c) occurs at around 600 °C, while its oxygen vacancy amount increases from δ ≈ 0.05 at room temperature up to 0.10 at high temperature. Thermal gravimetry analysis (TGA) measurements coupled with X-ray diffraction (XRD) characterizations show that above 1000 °C, in air, PrNiO3-δ starts to decompose into Pr2NiO4+δ and NiO through an intermediate transformation into Pr4Ni3O10+δ. The value of the polarization resistance (Rp) of co-sintered GDC-PrNiO3-δ electrode, at 950 °C in air for 2 h, is 0.91 Ω cm2 at 600 °C under air. It remains much higher than that of co-sintered GDC-Pr2NiO4+δ electrode (Rp = 0.15 Ω cm2), which means that the perovskite does not play any significant role in the electrochemical performance during long term operation of the Pr2NiO4+δ electrode.

  9. Glucose- and Cellulose-Derived Ni/C-SO3H Catalysts for Liquid Phase Phenol Hydrodeoxygenation

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Kasakov, Stanislav; Zhao, Chen; Barath, Eszter

    2015-01-19

    Sulfonated carbons were explored as functionalized supports for Ni nanoparticles to hydrodeoxygenate (HDO) phenol. Both hexadecane and water were used as solvents. The dual-functional Ni catalysts supported on sulfonated carbon (Ni/C-SO3H) showed high rates for phenol hydrodeoxygenation in liquid hexadecane, but not in water. Glucose and cellulose were precursors to the carbon supports. Changes in the carbons resulting from sulfonation of the carbons resulted in variations of carbon sheet structures, morphologies and the surface concentrations of acid sites. While the C-SO3H supports were active for cyclohexanol dehydration in hexadecane and water, Ni/C-SO3H only catalyzed the reduction of phenol to cyclohexanolmore » in water. The state of 3 – 5 nm grafted Ni particles was analyzed by in situ X-ray absorption spectroscopy. The results show that the metallic Ni was rapidly formed in situ without detectable leaching to the aqueous phase, suggesting that just the acid functions on Ni/C-SO3H are inhibited in presence of water. Using in situ IR spectroscopy, it was shown that even in hexadecane, phenol HDO is limited by the dehydration step. Thus, phenol HDO catalysis was further improved by physically admixing C-SO3H with the Ni/C-SO3H catalyst to balance the two catalytic functions. The minimum addition of 7 wt.% C-SO3H to the most active of the Ni/C-SO3H catalysts enabled nearly quantitative conversion of phenol and the highest selectivity (90%) towards cyclohexane in 6 h, at temperatures as low as 473 K, suggesting that the proximity to Ni limits the acid properties of the support.« less

  10. Glucose- and cellulose-derived Ni/C-SO3H catalysts for liquid phase phenol hydrodeoxygenation.

    PubMed

    Kasakov, Stanislav; Zhao, Chen; Baráth, Eszter; Chase, Zizwe A; Fulton, John L; Camaioni, Donald M; Vjunov, Aleksei; Shi, Hui; Lercher, Johannes A

    2015-01-19

    Sulfonated carbons were explored as functionalized supports for Ni nanoparticles to hydrodeoxygenate (HDO) phenol. Both hexadecane and water were used as solvents. The dual-functional Ni catalysts supported on sulfonated carbon (Ni/C-SO3H) showed high rates for phenol hydrodeoxygenation in liquid hexadecane, but not in water. Glucose and cellulose were precursors to the carbon supports. Changes in the carbons resulting from sulfonation of the carbons resulted in variations of carbon sheet structures, morphologies and the surface concentrations of acid sites. While the C-SO3H supports were active for cyclohexanol dehydration in hexadecane and water, Ni/C-SO3H only catalysed the reduction of phenol to cyclohexanol in water. The state of 3-5 nm grafted Ni particles was analysed by in situ X-ray absorption spectroscopy. The results show that the metallic Ni was rapidly formed in situ without detectable leaching to the aqueous phase, suggesting that just the acid functions on Ni/C-SO3H are inhibited in the presence of water. Using in situ IR spectroscopy, it was shown that even in hexadecane, phenol HDO is limited by the dehydration step. Thus, phenol HDO catalysis was further improved by physically admixing C-SO3H with the Ni/C-SO3H catalyst to balance the two catalytic functions. The minimum addition of 7 wt % C-SO3H to the most active of the Ni/C-SO3H catalysts enabled nearly quantitative conversion of phenol and the highest selectivity (90%) towards cyclohexane in 6 h, at temperatures as low as 473 K, suggesting that the proximity to Ni limits the acid properties of the support. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  11. Simple solution-combustion synthesis of Ni-NiO@C nanocomposites with highly electrocatalytic activity for methanol oxidation

    NASA Astrophysics Data System (ADS)

    Yu, Jie; Ni, Yonghong; Zhai, Muheng

    2018-01-01

    Transition metal and its oxide composite nanomaterials are attracting increasing research interest due to their superior properties and extensive applications in many fields. In this paper, Ni-NiO@C nanocomposites were successfully synthesized in one step via a simple solution-combustion route, employing NiCl2 as the Ni source, oxygen in the atmosphere as the oxygen source, and ethanol as the solvent. The final product was characterized by powder X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), energy dispersive X-ray spectrometry (EDS), (high resolution) transmission electron microscopy (TEM/HRTEM), and Raman spectra. N2 gas sorption-desorption experiments uncovered that the BET surface area of Ni-NiO@C nanocomposites reached 161.9 m2 g-1, far higher than 34.2 m2 g-1 of Ni-NiO. The electrochemical measurement showed that the as-produced Ni-NiO@C nanocomposites presented better catalytic activity for the electro-oxidation of methanol than Ni-NiO and NiO, which provides a new catalyst selection for the electro-oxidation of methanol.

  12. First-principles study on the stability and magnetoelectric properties of multiferroic materials XTiO3 (X = Mn, Fe, Co, Ni)

    NASA Astrophysics Data System (ADS)

    Chen, Xing-Yuan; Lai, Guo-Xia; Gu, Di; Zhu, Wei-Ling; Lai, Tian-Shu; Zhao, Yu-Jun

    2018-04-01

    The XTiO3 (X = Mn, Fe, Co and Ni) materials with R3c structure could be grown under critical conditions based on first-principles calculations and thermodynamic stability analysis. FeTiO3 and MnTiO3 could be synthesized relatively easily under metal-rich and O-poor conditions, while NiTiO3 could be stable under Ni-rich, O-rich and Ti-poor conditions. The predicted R3c CoTiO3 under thermodynamic equilibrium conditions is suggested to be synthesized under Co-rich, O-rich and Ti-poor conditions, but the calculated phonon dispersion indicates R3c CoTiO3 becomes unstable under the dynamical conditions. The ferroelectric behavior in the XTiO3 (X = Mn, Fe, Co and Ni) system could be dominated by the Ti ion with d0 state and the strong hybridization between Ti and O, while the magnetic property is mainly caused by the contribution of 3d transition metal.

  13. High-Temperature Erosive Behavior of Plasma Sprayed Cr3C2-NiCr/Cenosphere Coating

    NASA Astrophysics Data System (ADS)

    Mathapati, Mahantayya; Doddamani, Mrityunjay; Ramesh, M. R.

    2018-02-01

    This research examines the deposition of Cr3C2-NiCr/cenosphere and Cr3C2-NiCr coatings on MDN 321 steel through the process of plasma spray. In this process, the solid particle erosion test is established at 200, 400, 600 °C with 30° and 90° impact angles. Alumina erodent is adopted to investigate the erosive behavior of the coating at higher temperatures. The properties of the Cr3C2-NiCr/cenosphere coating are established based on the microhardness, the adhesive strength, the fracture toughness, and the ductility. To quantify volume loss as a result of erosion, an optical profilometer is used. At higher temperature, decrease in the erosion volume loss of Cr3C2-NiCr/cenosphere and Cr3C2-NiCr coatings is observed. The erosion-resistive property of Cr3C2-NiCr/cenosphere coating is higher than that of MDN 321 steel by 76%. This property is influenced by high-temperature stability of mullite, alumina, and protective oxide layer that is formed at elevated temperatures. The morphology of eroded coating discloses a brittle mode of material removal.

  14. Impacts of neodymium on structural, spectral and dielectric properties of LiNi0.5Fe2O4 nanocrystalline ferrites fabricated via micro-emulsion technique

    NASA Astrophysics Data System (ADS)

    Gilani, Zaheer Abbas; Warsi, Muhammad Farooq; Khan, Muhammad Azhar; Shakir, Imran; Shahid, Muhammad; Anjum, Muhammad Naeem

    2015-09-01

    Soft ferrites are technologically advanced smart materials and their properties can be tailored by controlling the chemical composition and judicial choice of the metal elements. In this article we discussed the effect of rare earth neodymium (Nd3+) on various properties of LiNi0.5NdxFe2-xO4 spinel ferrites. These ferrites have been synthesized by facile micro-emulsion route and characterized by X-ray diffraction (XRD), fourier transform infrared spectroscopy (FTIR), a.c. electrical conductivity and thermal analysis. The influence of Nd3+ doping on structural and electrical parameters has been investigated. XRD analysis revealed the formation of single cubic spinel structure for x≤0.07. Few traces of secondary phase (NdFeO3) were found for x≥0.105. The secondary phase induced owing to the solubility limit of Nd3+ cations in these ferrites. The lattice parameter (a) and crystallite size (D) both exhibit non-linear relation. The values of "a" and "D" were found in the range 8.322-8.329 Å and 25-32 nm respectively. These variations were attributed to the larger ionic radius of Nd3+ cations as compared to the host cations and lattice strain produced in these ferrites. The dielectric parameters were studied in the range 1 MHz to 3 GHz and these parameters were damped by Nd3+ incorporation and also by increasing the frequency. The reduced dielectric parameters observed in wide frequency range proposed that these nanocrystalline ferrites are potential candidates for fabricating the devices which are required to operate at GHz frequencies.

  15. Monoclinic β-Li2TiO3 nanocrystalline particles employing novel urea assisted solid state route: Synthesis, characterization and sintering behavior

    NASA Astrophysics Data System (ADS)

    Tripathi, Biranchi M.; Mohanty, Trupti; Prakash, Deep; Tyagi, A. K.; Sinha, P. K.

    2017-07-01

    Pure phase monoclinic nano-crystalline Li2TiO3 powder was synthesized by a novel urea assisted solid state synthesis method using readily available and economical precursors. A single phase and well crystalline Li2TiO3 powder has been obtained at slightly lower temperature (600-700 °C) and shorter duration (2 h) as compared to the conventional solid state method. The proposed method has significant advantages in comparison to other viable methods mainly in terms of phase purity, powder properties and sinterability. Analysis of chemical composition using inductively coupled plasma atomic emission spectroscopy (ICP-AES) shows no loss of lithium from Li2TiO3 in the proposed method. The emergence of monoclinic Li2TiO3 phase was confirmed by X-ray diffraction (XRD) pattern of as-synthesized powder. The crystallite size of Li2TiO3 powder was calculated to be in the range of 15-80 nm, which varied as a function of urea composition and temperature. The morphology of as-prepared Li2TiO3 powders was examined by scanning electron microscope (SEM). The effect of urea composition on phase and morphology was investigated so as to delineate the role of urea. Upon sintering at < 1000 °C temperature, the Li2TiO3 powder compact attained about 98% of the theoretical density with fine grained (grain size: 2-3 μm) microstructure. It indicates excellent sinter-ability of Li2TiO3 powder synthesized by the proposed method. The fine grained structure is desirable for better tritium breeding performance of Li2TiO3. Electrochemical impedance spectroscopy at variable temperature showed good electrical properties of Li2TiO3. The proposed method is simple, anticipated to be cost effective and convenient to realise for large scale production of phase pure nanocrystalline and having significantly enhanced sinter-ability Li2TiO3 powder.

  16. On processing of Ni-Cr3C2 based functionally graded clads through microwave heating

    NASA Astrophysics Data System (ADS)

    Kaushal, Sarbjeet; Gupta, Dheeraj; Bhowmick, Hiralal

    2018-06-01

    In the current study, functionally graded clads (FGC) of Ni-Cr3C2 based composite powders with varying percentage of Cr3C2 (0%–30% by weight) were developed on austenitic stainless steel (SS-304) substrate through microwave hybrid heating method. A domestic microwave oven working at 2.45 GHz and variable power level of 180–900 W was used to conduct the experimental trials. The exposure time was varied with compositional gradient and was optimized. Scanning electron microscopic (SEM) image of the FGC shows the uniform distribution of Cr3C2 particles inside the Ni matrix. Presence of Ni3C, Ni3Si, Ni3Cr2, and Cr3C2 phases was observed in the different layers of FGC. The top FGC layer exhibits the maximum value of microhardness of order 576 ± 25 HV which was 2.5 times more than that of the substrate.

  17. Influence of boric acid (H3BO3) concentration on the physical properties of electrochemical deposited nickel (Ni) nanowires

    NASA Astrophysics Data System (ADS)

    Kananathan, J.; Sofiah, A. G. N.; Samykano, M.; Ulakanathan, S.; Lah, N. A. C.; Harun, W. S. W.; Sudhakar, K.; Kadirgama, K.; Ngui, W. K.; Siregar, J. P.

    2017-10-01

    Authors have investigated the influence of the stabilizer (Boric Acid) concentration during the template-assisted electrochemical deposition of Nickel (Ni) nanowires in Anodic Alumina Oxide (AAO) templates. The synthesis was performed using Ni Sulfate Hexahydrate (NiSO4.6H2O) as metal salts and Boric Acid (H3BO3) as a stabilizer. The mixture of both solutions creates electrolyte and utilized for the electrochemical deposition of Ni nanowires. During the experiment, the boric acid concentration varied between 5 g/L, 37.5 g/L and 60 g/L with a deposition temperature of 80 °C (constant). After the electrochemical deposition process, AAO templates were cleaned with distilled water before dissolution in Sodium Hydroxide (NaOH) solution to obtain the freestanding Ni nanowires. Physical properties of the synthesized Ni nanowires were analyzed using Field Emission Scanning Electron Microscopy (FESEM), Energy Dispersive Spectroscopy (EDX) and X-ray Diffraction (XRD). The physical properties of obtained Ni nanowires has eloborated by taking into account the effect of boric acid concentration on the surface morphology, growth length, elemental composition and crystal orientation crystal of the synthesized nickel nanowires. The finding exposes that the boric acid concentration does not influence all aspects in the physicals properties of the synthesized Ni nanowires. The boric acid concentration did not affect the surface texture and crystal orientation. However, shorter Ni nanowires obtained as the concentration of boric acid increased.

  18. The effect of solution pH on the electrochemical performance of nanocrystalline metal ferrites MFe2O4 (M=Cu, Zn, and Ni) thin films

    NASA Astrophysics Data System (ADS)

    Elsayed, E. M.; Rashad, M. M.; Khalil, H. F. Y.; Ibrahim, I. A.; Hussein, M. R.; El-Sabbah, M. M. B.

    2016-04-01

    Nanocrystalline metal ferrite MFe2O4 (M=Cu, Zn, and Ni) thin films have been synthesized via electrodeposition-anodization process. Electrodeposited (M)Fe2 alloys were obtained from aqueous sulfate bath. The formed alloys were electrochemically oxidized (anodized) in aqueous (1 M KOH) solution, at room temperature, to the corresponding hydroxides. The parameters controlling the current efficiency of the electrodeposition of (M)Fe2 alloys such as the bath composition and the current density were studied and optimized. The anodized (M)Fe2 alloy films were annealed in air at 400 °C for 2 h. The results revealed the formation of three ferrite thin films were formed. The crystallite sizes of the produced films were in the range between 45 and 60 nm. The microstructure of the formed film was ferrite type dependent. The corrosion behavior of ferrite thin films in different pH solutions was investigated using open circuit potential (OCP) and potentiodynamic polarization measurements. The open circuit potential indicates that the initial potential E im of ZnFe2O4 thin films remained constant for a short time, then sharply increased in the less negative direction in acidic and alkaline medium compared with Ni and Cu ferrite films. The values of the corrosion current density I corr were higher for the ZnFe2O4 films at pH values of 1 and 12 compared with that of NiFe2O4 and CuFe2O4 which were higher only at pH value 1. The corrosion rate was very low for the three ferrite films when immersion in the neutral medium. The surface morphology recommended that Ni and Cu ferrite films were safely used in neutral and alkaline medium, whereas Zn ferrite film was only used in neutral atmospheres.

  19. Grain boundary character distribution in nanocrystalline metals produced by different processing routes

    DOE PAGES

    Bober, David B.; Kumar, Mukal; Rupert, Timothy J.; ...

    2015-12-28

    Nanocrystalline materials are defined by their fine grain size, but details of the grain boundary character distribution should also be important. Grain boundary character distributions are reported for ball-milled, sputter-deposited, and electrodeposited Ni and Ni-based alloys, all with average grain sizes of ~20 nm, to study the influence of processing route. The two deposited materials had nearly identical grain boundary character distributions, both marked by a Σ3 length percentage of 23 to 25 pct. In contrast, the ball-milled material had only 3 pct Σ3-type grain boundaries and a large fraction of low-angle boundaries (16 pct), with the remainder being predominantlymore » random high angle (73 pct). Furthermore, these grain boundary character measurements are connected to the physical events that control their respective processing routes. Consequences for material properties are also discussed with a focus on nanocrystalline corrosion. As a whole, the results presented here show that grain boundary character distribution, which has often been overlooked in nanocrystalline metals, can vary significantly and influence material properties in profound ways.« less

  20. In-situ formation of Ni4Ti3 precipitate and its effect on pseudoelasticity in selective laser melting additive manufactured NiTi-based composites

    NASA Astrophysics Data System (ADS)

    Gu, Dongdong; Ma, Chenglong

    2018-05-01

    Selective laser melting (SLM) additive manufacturing technology was applied to synthesize NiTi-based composites via using ball-milled Ti, Ni, and TiC mixed powder. By transmission electron microscope (TEM) characterization, it indicated that the B2 (NiTi) matrix was obtained during SLM processing. In spite of more Ti content (the Ti/Ni ratio >1), a mass of Ni-rich intermetallic compounds containing Ni4Ti3 with nanostructure features and eutectic Ni3Ti around in-situ Ti6C3.75 dendrites were precipitated. Influence of the applied laser volume energy density (VED) on the morphology and content of Ni4Ti3 precipitate was investigated. Besides, nanoindentation test of the matrix was performed in order to assess pseudoelastic recovery behavior of SLM processed NiTi-based composites. At a relatively high VED of 533 J/mm3, the maximum pseudoelastic recovery was obtained due to the lowest content of Ni4Ti3 precipitates. Furthermore, the precipitation mechanism of in-situ Ni4Ti3 was present based on the redistribution of titanium element and thermodynamics analysis, and then the relationship of Ni4Ti3 precipitate, VED and pseudoelastic recovery behavior was also revealed.

  1. Thermoelectric transport properties of Ca3Co4- x Ni x O9+ δ oxide materials

    NASA Astrophysics Data System (ADS)

    Park, K.; Cha, J. S.; Nam, S. W.; Choi, S.-M.; Seo, W.-S.; Lee, S.; Lim, Y. S.

    2016-01-01

    Nano-sized Ca3Co4- x Ni x O9+ δ (0 ≤ x ≤ 0.3) thermoelectric powders are synthesized by using the solution combustion method, with aspartic acid as a combustion fuel. The synthesized Ca3Co4- x Ni x O9+ δ nano-sized powders exhibit a spherical-like shape and a smooth surface. Higher Ni content results in a smaller grain size and a higher porosity, resulting in a decrease in the electrical conductivity. However, the Seebeck coefficient of Ni-added Ca3Co4O9 is much higher than that of Ca3Co4O9. The highest power factor (1.4 × 10-4 Wm-1K-2), which is more than nine times larger than that of Ca3Co4O9, is attained for Ca3Co0.38Ni0.2O9+ δ at 800 °C. The addition of a small amount of Ni is highly effective in improving the thermoelectric properties of Ca3Co4O9. We believe that Ca3Co4- x Ni x O9+ δ is a potential p-type thermoelectric material for renewable energy conversion.

  2. Facile synthesis and microwave absorbability of C@Ni–NiO core–shell hybrid solid sphere and multi-shelled NiO hollow sphere

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Wu, Hongjing, E-mail: wuhongjing@mail.nwpu.edu.cn; Wu, Guanglei, E-mail: wuguanglei@mail.xjtu.edu.cn; Wu, Qiaofeng

    2014-11-15

    We reported the preparation of C@Ni–NiO core–shell hybrid solid spheres or multi-shelled NiO hollow spheres by combining a facile hydrothermal route with a calcination process in H{sub 2} or air atmosphere, respectively. The synthesized C@Ni–NiO core–shell solid spheres with diameters of approximately 2–6 μm were in fact built from dense NiO nanoparticles coated by random two-dimensional metal Ni nanosheets without any visible pores. The multi-shelled NiO hollow spheres were built from particle-like ligaments and there are a lot of pores with size of several nanometers on the surface. Combined Raman spectra with X-ray photoelectron spectra (XPS), it suggested that themore » defects in the samples play a limited role in the dielectric loss. Compared with the other samples, the permeability of the samples calcined in H{sub 2} and air was increased slightly and the natural resonance frequency shifted to higher frequency (7, 11 and 14 GHz, respectively), leading to an enhancement of microwave absorption property. For the sample calcined in H{sub 2}, an optimal reflection loss less than − 10 was obtained at 7 GHz with a matching thickness of 5.0 mm. Our study demonstrated the potential application of C@Ni–NiO core–shell hybrid solid sphere or multi-shelled NiO hollow sphere as a more efficient electromagnetic (EM) wave absorber. - Highlights: • C@Ni–NiO core–shell hybrid solid sphere was synthesized by a facile method. • Multi-shelled NiO hollow sphere was synthesized by a facile method. • It suggested that the defects in the samples play a limited role in dielectric loss. • The permeability of the samples calcined in H{sub 2} and air was increased. • Microwave absorbability of C@Ni–NiO core–shell hybrid solid sphere was investigated.« less

  3. Rapid Polyol-Assisted Microwave Synthesis of Nanocrystalline LiFePO4/C Cathode for Lithium-Ion Batteries.

    PubMed

    Paul, Baboo Joseph; Gim, Jihyeon; Baek, Sora; Kang, Jungwon; Song, Jinju; Kim, Sungjin; Kim, Jaekook

    2015-08-01

    Nanocrystalline LiFePO4/C has been synthesized under a very short period of time (90 sec) using a polyol-assisted microwave heating synthesis technique. The X-ray diffraction (XRD) data indicates that the rapidly synthesized materials correspond to phase pure olivine. Post-annealing of the as-prepared sample at 600 °C in argon atmosphere yields highly crystalline LiFePO4/C. The morphology of the samples studied using scanning electron microscopy (SEM) reveals the presence of secondary particles formed from aggregation of primary particles in the range of 30-50 nm. Transmission electron microscopy (TEM) images reveal a thin carbon layer coating on the surface of the primary particle. The charge/discharge studies indicate that the as-prepared and annealed LiFePO4/C samples delivered initial discharge capacities of 126 and 160 mA h g-1, respectively, with good capacity retentions at 0.05 mA cm-2 current densities. The post-annealing process indeed improves the crystallinity of the LiFePO4 nanocrystals, which enhances the electrode performance of LiFePO4/C.

  4. Production of hydrogen using nanocrystalline protein-templated catalysts on m13 phage.

    PubMed

    Neltner, Brian; Peddie, Brian; Xu, Alex; Doenlen, William; Durand, Keith; Yun, Dong Soo; Speakman, Scott; Peterson, Andrew; Belcher, Angela

    2010-06-22

    For decades, ethanol has been in use as a fuel for the storage of solar energy in an energy-dense, liquid form. Over the past decade, the ability to reform ethanol into hydrogen gas suitable for a fuel cell has drawn interest as a way to increase the efficiency of both vehicles and stand-alone power generators. Here we report the use of extremely small nanocrystalline materials to enhance the performance of 1% Rh/10% Ni@CeO(2) catalysts in the oxidative steam reforming of ethanol with a ratio of 1.7:1:10:11 (air/EtOH/water/argon) into hydrogen gas, achieving 100% conversion of ethanol at only 300 degrees C with 60% H(2) in the product stream and less than 0.5% CO. Additionally, nanocrystalline 10% Ni@CeO(2) was shown to achieve 100% conversion of ethanol at 400 degrees C with 73% H(2), 2% CO, and 2% CH(4) in the product stream. Finally, we demonstrate the use of biological templating on M13 to improve the resistance of this catalyst to deactivation over 52 h tests at high flow rates (120 000 h(-1) GHSV) at 450 degrees C. This study suggests that the use of highly nanocrystalline, biotemplated catalysts to improve activity and stability is a promising route to significant gains over traditional catalyst manufacture methods.

  5. Significant enhancement in photocatalytic performance of Ni doped BiFeO3 nanoparticles

    NASA Astrophysics Data System (ADS)

    Nadeem, M.; Khan, Wasi; Khan, Shakeel; Shoeb, Mohd; Husain, Shahid; Mobin, Mohammad

    2018-06-01

    In the present work, we have investigated the effect of Ni doping on the microstructure and photocatalytic properties of BiFeO3 samples. All the compositions of BiFe1‑xNixO3 (0 ≤ x ≤ 0.07) have been synthesized via cost effective ethylene glycol based sol-gel method. The Rietveld refinement of the XRD data revealed rhombohedral crystal structure with R3c space group. The FTIR spectroscopy confirms the formation of BiFeO3 compound. UV–visible DRS result affirmed that the band gap of the samples can be tuned towards visible range by the Ni substitution. The photoluminescence spectra indicate lower intensity with the Ni content, signify reduction in recombination rate of the electron-hole pairs. The photocatalytic response of the nanoparticles was examined for the degradation of methylene blue (MB) dye under visible light irradiation and the highest photocatalytic response was observed for 7% Ni doped sample. Therefore, the observed results suggest potential application of the synthesized nanoparticles for wastewater treatment purpose.

  6. Microstructure and Sliding Wear Performance of Cr7C3-(Ni,Cr)3(Al,Cr) Coating Deposited from Cr7C3 In Situ Formed Atomized Powder

    NASA Astrophysics Data System (ADS)

    Zhu, Hong-Bin; Shen, Jie; Gao, Feng; Yu, Yueguang; Li, Changhai

    2017-01-01

    This work is aimed at developing a new type of Cr7C3-(Ni,Cr)3(Al,Cr) coating for parts used in heavy-duty diesel engines. The feedstock, in which the stripe-shaped Cr7C3 was in situ formed, was firstly prepared by vacuum melting and gas atomization and then subjected by high-velocity oxy-fuel spraying to form the coatings. The carbon content, microstructure and phase constitution of the powders, as well as the sprayed coatings, were analyzed by chemical analysis, SEM and XRD. The hardness and sliding wear performance of the sprayed coatings were also tested and compared to a commercial Cr3C2-NiCr coating used on piston rings. The results showed that the content of carbon in feedstock was almost the same as designed, and that the volume content of in situ formed Cr7C3 was increased with carbon and chromium added. The major phases of the powders and sprayed coatings are Cr7C3 and Cr-alloyed Ni3Al. Only a small amount of carbon lost during the spraying process. As Cr7C3 content increased in the coatings, the microhardness at room temperature was firstly increased to about 1000Hv0.3. The microhardness of the coatings stayed almost constant, while the testing temperature was raised up to 700 °C for 0.5 h, which illustrates the potential application of the investigated coatings under high temperature conditions. The coatings containing 70 and 77 vol.% Cr7C3 showed the most promising wear resistance, lower friction coefficient and better tribological compatibility to gray cast iron counterpart than other tested Cr7C3-(Ni,Cr)3(Al,Cr) coatings and the reference Cr3C2-NiCr coating.

  7. Preparation and characterization of polyol assisted ultrafine Cu-Ni-Mg-Ca mixed ferrite via co-precipitation method

    NASA Astrophysics Data System (ADS)

    Boobalan, T.; Pavithradevi, S.; Suriyanarayanan, N.; Manivel Raja, M.; Ranjith Kumar, E.

    2017-04-01

    Nanocrystalline spinel ferrite of composition Cu0.2Ni0.2Mg0.2Ca0.4Fe2O4 is synthesized by wet hydroxyl co-precipitation method in ethylene glycol as chelating agent and sodium hydroxide as precipitator at pH 8. Ethylene glycol is utilized as the medium which serves as the dissolvable and in addition a complexing specialist. The synthesized particles are annealed at various temperatures. Thermogravimetric investigation affirms that at 280 °C ethylene glycol is dissipated totally and stable phase arrangement happens over 680 °C. FTIR spectra of as synthesized and annealed at 1050 °C recorded between 400 cm-1 and 4000 cm-1. Structural characterizations of all the samples are carried out by X-ray diffraction (XRD) technique. Transmission electron microscopy (TEM) and scanning electron microscopy (SEM) affirm that the particles are spherical and cubic shape with the crystallite size of 12 nm to 32 nm. Magnetic measurements are performed utilizing vibrating sample magnetometer at room temperature.

  8. Hydrogen Gas Sensing Characteristics of Nanostructured NiO Thin Films Synthesized by SILAR Method

    NASA Astrophysics Data System (ADS)

    Karaduman, Irmak; Çorlu, Tugba; Yıldırım, M. Ali; Ateş, Aytunç; Acar, Selim

    2017-07-01

    Nanostructured NiO thin films have been synthesized by a facile, low-cost successive ionic layer adsorption and reaction (SILAR) method, and the effects of the film thickness on their hydrogen gas sensing properties investigated. The samples were characterized by scanning electron microscopy (SEM), x-ray diffraction (XRD) analysis, and energy-dispersive x-ray analysis. The XRD results revealed that the crystallinity improved with increasing thickness, exhibiting polycrystalline structure. SEM studies showed that all the films covered the glass substrate well. According to optical absorption measurements, the optical bandgap decreased with increasing film thickness. The gas sensing properties of the nanostructured NiO thin films were studied as a function of operating temperature and gas concentration. The samples showed good sensing performance of H2 gas with high response. The maximum response was 75% at operating temperature of 200°C for hydrogen gas concentration of 40 ppm. These results demonstrate that nanostructured NiO thin films synthesized by the SILAR method have potential for application in hydrogen detection.

  9. Synthesis, structure, and properties of nickel complexes with nitrilotris(methylenephosphonic acid) [Ni(H{sub 2}O)3N(CH2PO{sub 3}H){sub 3}] and Na{sub 4}[Ni(H{sub 2}O)N(CH{sub 2}PO{sub 3}){sub 3}] ∙ 11H{sub 2}O

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Somov, N. V., E-mail: somov@phys.unn.ru; Chausov, F. F., E-mail: chaus@yandex.ru; Zakirova, R. M.

    2016-03-15

    Nitrilotris(methylenephosphonato)triaquanickel and tetrasodium nitrilotris(methylenephosphonato) aquanickelate undecahydrate were synthesized and characterized. The crystal of [Ni(H{sub 2}O){sub 3}N(CH{sub 2}PO{sub 3}H){sub 3}] is composed of linear coordination polymers and belongs to sp. gr. P2{sub 1}/c, Z = 4, a = 9.17120(10) Å, b = 16.05700(10) Å, c = 9.70890(10) Å, β = 115.830(2)°. The Ni atom is in an octahedral coordination formed by two oxygen atoms of one phosphonate ligand, one oxygen atom of another ligand molecule, and three water molecules in a meridional configuration. The crystal of Na{sub 4}[Ni(H{sub 2}O)N(CH{sub 2}PO{sub 3}){sub 3}] ∙ 11H{sub 2}O has an island dimeric chelate structuremore » and belongs to sp. gr. C2/c, Z = 8, a = 18.7152(2) Å, b = 12.05510(10) Å, c = 21.1266(2) Å, β = 104.4960(10)°. The Ni atom has a slightly distorted octahedral coordination involving one nitrogen atom and closes three five-membered N–C–P–O–Ni rings sharing the Ni–N bond.« less

  10. Structural characterization of nanocrystalline cadmium sulphide powder prepared by solvent evaporation technique

    NASA Astrophysics Data System (ADS)

    Pandya, Samir; Tandel, Digisha; Chodavadiya, Nisarg

    2018-05-01

    CdS is one of the most important compounds in the II-VI group of semiconductor. There are numerous applications of CdS in the form of nanoparticles and nanocrystalline. Semiconductors nanoparticles (also known as quantum dots), belong to state of matter in the transition region between molecules and solids, have attracted a great deal of attention because of their unique electrical and optical properties, compared to bulk materials. In the field of optoelectronic, nanocrystalline form utilizes mostly in the field of catalysis and fluid technology. Considering these observations, presented work had been carried out, i.e. based on the nanocrystalline material preparation. In the present work CdS nano-crystalline powder was synthesized by a simple and cost effective chemical technique to grow cadmium sulphide (CdS) nanoparticles at 200 °C with different concentrations of cadmium. The synthesis parameters were optimized. The synthesized powder was structurally characterized by X-ray diffraction and particle size analyzer. In the XRD analysis, Micro-structural parameters such as lattice strain, dislocation density and crystallite size were analysed. The broadened diffraction peaks indicated nanocrystalline particles of the film material. In addition to that the size of the prepared particles was analyzed by particle size analyzer. The results show the average size of CdS particles ranging from 80 to 100 nm. The overall conclusion of the work can be very useful in the synthesis of nanocrystalline CdS powder.

  11. Hot Corrosion Behavior of Bare, Cr3C2-(NiCr) and Cr3C2-(NiCr) + 0.2wt.%Zr Coated SuperNi 718 at 900 °C

    NASA Astrophysics Data System (ADS)

    Mudgal, Deepa; Singh, Surendra; Prakash, Satya

    2015-01-01

    Corrosion in incinerators, power plants, and chemical industries are frequently encountered due to the presence of salts containing sodium, sulphur, and chlorine. To obviate this problem, bare and coated alloys were tested under environments simulating the conditions present inside incinerators and power plants. 0.2 wt.% zirconium powder was incorporated in the Cr3C2-(NiCr) coating powder. The original powder and Zr containing powder was sprayed on Superni 718 alloy by D-gun technique. The bare and coated alloys were tested under Na2SO4 + K2SO4 + NaCl + KCl and Na2SO4 + NaCl environment. The corrosion rate of specimens was monitored using weight change measurements. Characterization of the corrosion products has been done using FE-SEM/EDS and XRD techniques. Bare and coated alloys showed very good corrosion resistance under given molten salt environments. Addition of 0.2wt.%Zr in Cr3C2-25%(NiCr) coating further greatly reduced the oxidation rate as well as improved the adherence of oxide scale to the coating surface during the time of corrosion.

  12. The luminescence properties of nanocrystalline phosphors Mg2SiO4:Eu3+

    NASA Astrophysics Data System (ADS)

    Kolomytsev, A. Y.; Mamonova, D. V.; Manshina, A. A.; Kolesnikov, I. E.

    2017-11-01

    Nanocrystalline Eu3+-doped Mg2SiO4 powders were prepared with combined Pechini-solid phase synthesis. The structural properties were investigated with XRD, SEM and Raman spectroscopy. XRD pattern indicated that Mg2SiO4:Eu3+ were obtained with formation of other phase: MgO. Raman spectrum revealed good homogeneity and crystallinity of synthesized nanopowders. The luminescence properties were studied with measurement of excitation and emission spectra and decay curves. The effect of Eu3+ concentration on 5D0 level lifetime was studied. Most probably, the observed shortening of 5D0 level lifetime with Eu3+ concentration is caused by increase of nonradiative process probability.

  13. Exciton-polariton state in nanocrystalline SiC films

    NASA Astrophysics Data System (ADS)

    Semenov, A. V.; Lopin, A. V.

    2016-05-01

    We studied the features of optical absorption in the films of nanocrystalline SiC (nc-SiC) obtained on the sapphire substrates by the method of direct ion deposition. The optical absorption spectra of the films with a thickness less than ~500 nm contain a maximum which position and intensity depend on the structure and thickness of the nc-SiC films. The most intense peak at 2.36 eV is observed in the nc-SiC film with predominant 3C-SiC polytype structure and a thickness of 392 nm. Proposed is a resonance absorption model based on excitation of exciton polaritons in a microcavity. In the latter, under the conditions of resonance, there occurs strong interaction between photon modes of light with λph=521 nm and exciton of the 3С polytype with an excitation energy of 2.36 eV that results in the formation of polariton. A mismatch of the frequencies of photon modes of the cavity and exciton explains the dependence of the maximum of the optical absorption on the film thickness.

  14. Effect of magnetic field annealing on the magneto-elastic properties of nanocrystalline NiFe2O4

    NASA Astrophysics Data System (ADS)

    Sowmya, N. Shara; Srinivas, A.; Saravanan, P.; Reddy, K. Venu Gopal; Reddy, Monaji Vinitha; Das, Dibakar; Kamat, S. V.

    2017-08-01

    The effect of magnetic-field annealing on the strain sensitivity (q) and saturation magnetostriction (λs) of NiFe2O4 nanoparticles synthesized by citrate-gel method was investigated. The use of field-annealing resulted in improved magnetoelastic properties at the expense of coercivity. A maximum λs of -40 ppm at 2 kOe, associated with q value of -3.3 ppm/Oe at 5 Oe was achieved in the field-annealed NiFe2O4.

  15. Magnetic Anisotropy and Chemical Order of Artificially Synthesized L10-Ordered FeNi Films on Au-Cu-Ni Buffer Layers

    NASA Astrophysics Data System (ADS)

    Kojima, Takayuki; Mizuguchi, Masaki; Koganezawa, Tomoyuki; Osaka, Keiichi; Kotsugi, Masato; Takanashi, Koki

    2012-01-01

    L10-FeNi films were grown by alternate monatomic layer deposition on Au-Cu-Ni buffer layers at several substrate temperatures (Ts), and the relation between the uniaxial magnetic anisotropy energy (Ku) and the long-range chemical order parameter (S) was investigated. A large Ku of (7.0 ±0.2) ×106 erg/cm3 and S of 0.48 ±0.05 were obtained. The value of Ku was larger than those reported previously for artificially synthesized FeNi films. It was first found that both Ku and S increased with Ts, and Ku was roughly proportional to S.

  16. Fabrication of aligned porous LaNi0.6Fe0.4O3 perovskite by water based freeze casting

    NASA Astrophysics Data System (ADS)

    Soltani, Niloofar; Martínez-Bautista, Rubén; Bahrami, Amin; Huerta Arcos, Lázaro; Cassir, Michel; Chávez Carvayar, José

    2018-05-01

    A novel porous cathode of LaNi0.6Fe0.4O3 perovskite with aligned porosities was engineered for solid oxide fuel cells. LaNi0.6Fe0.4O3 was produced through metal nitrate and acid citric combustion method and calcined at different temperatures. The synthesized LNF at 600 °C shows specific surface area (SBET) of 24.4 m2 g-1 and an average pore size of 12.2 nm. The chemical composition and structure of LaNi0.6Fe0.4O3 synthesized at temperature 600-1400 °C, were analyzed by XRD, XPS and HRTEM. SEM observations of freeze cast nano-sized LNF showed the vertically aligned hexagonal walls. These walls contain a great value of fine pores which accelerate the gas transportation.

  17. Detailed Study of BSA Adsorption on Micro- and Nanocrystalline Diamond/β-SiC Composite Gradient Films by Time-Resolved Fluorescence Microscopy.

    PubMed

    Handschuh-Wang, Stephan; Wang, Tao; Druzhinin, Sergey I; Wesner, Daniel; Jiang, Xin; Schönherr, Holger

    2017-01-24

    The adsorption of bovine serum albumin (BSA) on micro- and nanocrystalline diamond/β-SiC composite films synthesized using the hot filament chemical vapor deposition (HFCVD) technique has been investigated by confocal fluorescence lifetime imaging microscopy. BSA labeled with fluorescein isothiocyanate (FITC) was employed as a probe. The BSA FITC conjugate was found to preferentially adsorb on both O-/OH-terminated microcrystalline and nanocrystalline diamond compared to the OH-terminated β-SiC, resulting in an increasing amount of BSA adsorbed to the gradient surfaces with an increasing diamond/β-SiC ratio. The different strength of adsorption (>30 times for diamond with a grain size of 570 nm) coincides with different surface energy parameters and differing conformational changes upon adsorption. Fluorescence data of the adsorbed BSA FITC on the gradient film with different diamond coverage show a four-exponential decay with decay times of 3.71, 2.54, 0.66, and 0.13 ns for a grain size of 570 nm. The different decay times are attributed to the fluorescence of thiourea fluorescein residuals of linked FITC distributed in BSA with different dye-dye and dye-surface distances. The longest decay time was found to correlate linearly with the diamond grain size. The fluorescence of BSA FITC undergoes external dynamic fluorescence quenching on the diamond surface by H- and/or sp 2 -defects and/or by amorphous carbon or graphite phases. An acceleration of the internal fluorescence concentration quenching in BSA FITC because of structural changes of albumin due to adsorption, is concluded to be a secondary contributor. These results suggest that the micro- and nanocrystalline diamond/β-SiC composite gradient films can be utilized to spatially control protein adsorption and diamond crystallite size, which facilitates systematic studies at these interesting (bio)interfaces.

  18. Structural and Electrochemical Study of Hierarchical LiNi(1/3)Co(1/3)Mn(1/3)O2 Cathode Material for Lithium-Ion Batteries.

    PubMed

    Li, Li; Wang, Lecai; Zhang, Xiaoxiao; Xie, Man; Wu, Feng; Chen, Renjie

    2015-10-07

    In this study, a facile nanoetching-template route is developed to synthesize porous nanomicrohierarchical LiNi1/3Co1/3Mn1/3O2 microspheres with diameters below 1.5 μm, using porous CoMnO3 binary oxide microspheres as the template. The unique morphology of CoMnO3 template originates from the contraction effect during the oxidative decomposition of Ca0.2Mn0.4Co0.4CO3 precursors and is further improved by selectively removing calcium carbonate with a nanoetching process after calcination. The as-synthesized LiNi1/3Co1/3Mn1/3O2 microsphere, composed of numerous primary particles and pores with size of dozens of nanometers, illustrates a well-assembled porous nanomicrohierarchical structure. When used as the cathode material for lithium-ion batteries, the as-synthesized microspheres exhibit remarkably enhanced electrochemical performances with higher capacity, excellent cycling stability, and better rate capability, compared with the bulk counterpart. Specifically, hierarchical LiNi1/3Co1/3Mn1/3O2 achieves a high discharge capacity of 159.6 mA h g(-1) at 0.2 C with 98.7% capacity retention after 75 cycles and 133.2 mA h g(-1) at 1 C with 90% capacity retention after 100 cycles. A high discharge capacity of 135.5 mA h g(-1) even at a high current of 750 mA g(-1) (5 C) is also achieved. The nanoetching-template method can provide a general approach to improve cycling stability and rate capability of high capacity cathode materials for lithium-ion batteries.

  19. Thermal conductivity in nanocrystalline-SiC/C superlattices

    DOE PAGES

    Habermehl, S.; Serrano, J. R.

    2015-11-17

    We reported the formation of thin film superlattices consisting of alternating layers of nitrogen-doped SiC (SiC:N) and C. Periodically terminating the SiC:N surface with a graphitic C boundary layer and controlling the SiC:N/C thickness ratio yield nanocrystalline SiC grains ranging in size from 365 to 23 nm. Frequency domain thermo-reflectance is employed to determine the thermal conductivity, which is found to vary from 35.5 W m -1 K -1 for monolithic undoped α-SiC films to 1.6 W m -1 K -1 for a SiC:N/C superlattice with a 47 nm period and a SiC:N/C thickness ratio of 11. A series conductancemore » model is employed to explain the dependence of the thermal conductivity on the superlatticestructure. Our results indicate that the thermal conductivity is more dependent on the SiC:N/C thickness ratio than the SiC:N grain size, indicative of strong boundary layerphonon scattering.« less

  20. Growth of boron doped hydrogenated nanocrystalline cubic silicon carbide (3C-SiC) films by Hot Wire-CVD

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Pawbake, Amit; Tata Institute of Fundamental Research, Colaba, Mumbai 400 005; Mayabadi, Azam

    Highlights: • Boron doped nc-3C-SiC films prepared by HW-CVD using SiH{sub 4}/CH{sub 4}/B{sub 2}H{sub 6}. • 3C-Si-C films have preferred orientation in (1 1 1) direction. • Introduction of boron into SiC matrix retard the crystallanity in the film structure. • Film large number of SiC nanocrystallites embedded in the a-Si matrix. • Band gap values, E{sub Tauc} and E{sub 04} (E{sub 04} > E{sub Tauc}) decreases with increase in B{sub 2}H{sub 6} flow rate. - Abstract: Boron doped nanocrystalline cubic silicon carbide (3C-SiC) films have been prepared by HW-CVD using silane (SiH{sub 4})/methane (CH{sub 4})/diborane (B{sub 2}H{sub 6}) gasmore » mixture. The influence of boron doping on structural, optical, morphological and electrical properties have been investigated. The formation of 3C-SiC films have been confirmed by low angle XRD, Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), Fourier transform infra-red (FTIR) spectroscopy and high resolution-transmission electron microscopy (HR-TEM) analysis whereas effective boron doping in nc-3C-SiC have been confirmed by conductivity, charge carrier activation energy, and Hall measurements. Raman spectroscopy and HR-TEM analysis revealed that introduction of boron into the SiC matrix retards the crystallanity in the film structure. The field emission scanning electron microscopy (FE-SEM) and non contact atomic force microscopy (NC-AFM) results signify that 3C-SiC film contain well resolved, large number of silicon carbide (SiC) nanocrystallites embedded in the a-Si matrix having rms surface roughness ∼1.64 nm. Hydrogen content in doped films are found smaller than that of un-doped films. Optical band gap values, E{sub Tauc} and E{sub 04} decreases with increase in B{sub 2}H{sub 6} flow rate.« less

  1. Transport, Thermal, and Magnetic Properties of YbNi3X9 (X = Al, Ga): A Newly Synthesized Yb-Based Kondo Lattice System

    NASA Astrophysics Data System (ADS)

    Yamashita, Tetsuro; Miyazaki, Ryoichi; Aoki, Yuji; Ohara, Shigeo

    2012-03-01

    We have succeeded in synthesizing a new Yb-based Kondo lattice system, YbNi3X9 (X = Al, Ga). Our study reveals that YbNi3Al9 shows typical features of a heavy-fermion antiferromagnet with a Néel temperature of TN = 3.4 K. All of the properties reflect a competition between the Kondo effect and the crystalline electric field (CEF) effect. The moderate heavy-fermion state leads to an enhanced Sommerfeld coefficient of 100 mJ/(mol\\cdotK2), even if ordered antiferromagnetically. On the other hand, the isostructural gallide YbNi3Ga9 is an intermediate-valence system with a Kondo temperature of TK = 570 K. A large hybridization scale can overcome the CEF splitting energy, and a moderately heavy Fermi-liquid ground state with high local moment degeneracy should form at low temperatures. Note that the quality of single-crystalline YbNi3X9 is extremely high compared with those of other Yb-based Kondo lattice compounds. We conclude that YbNi3X9 is a suitable system for investigating the electronic structure of Yb-based Kondo lattice systems from a heavy-fermion system with an antiferromagnetically ordered ground state to an intermediate-valence system.

  2. Stress-dependent grain size evolution of nanocrystalline Ni-W and its impact on friction behavior

    DOE PAGES

    Argibay, N.; Furnish, T. A.; Boyce, B. L.; ...

    2016-06-07

    The friction behavior of ultra-nanocrystalline Ni-W coatings was investigated. A critical stress threshold was identified below which friction remained low, and above which a time-dependent evolution toward higher friction behavior occurred. Founded on established plasticity models we propose a correlation between surface grain size and applied stress that can be used to predict the critical stress separating the two friction regimes. Lastly, this interpretation of plasticity models suggests that macro-scale low and high friction regimes are respectively associated with the nano-scale mechanisms of grain boundary and dislocation-mediated plasticity.

  3. Synthesis of nanocrystalline Ni/Ce-YSZ powder via a polymerization route

    NASA Astrophysics Data System (ADS)

    Abolghasemi, Z.; Tamizifar, M.; Arzani, K.; Nemati, A.; Khanfekr, A.; Bolandi, M.

    2013-08-01

    Pechini process was used for preparation of three kinds of nanocrystalline powders of yttria-stabilized zirconia (YSZ): doped with 1.5 mol% nickel oxide, doped with 15 mol% ceria, and doped with 1.5 mol% nickel oxide plus 15 mol% ceria. Zirconium chloride, yttrium nitrate, cerium nitrate, nickel nitrate, citric acid and ethylene glycol were polymerized at 80 °C to produce a gel. XRD, SEM and TEM analyses were used to investigate the crystalline phases and microstructures of obtained compounds. The results of XRD revealed the formation of nanocrystalline powder at 900 °C. Morphology of the powder calcined at 900 °C, examined with a scanning electron microscope, showed that the presence of nickel and cerium inhibited the grain growth in the system. The average crystallite size of the material doped with nickel oxide (9.33 nm) was bigger than the one doped with cerium oxide (9.29 nm), while the YSZ doping with the two oxides simultaneously promoted the grain growth with crystallite size of 11.37 nm. Yttria-stabilized zirconia powder with a mean crystallite size of 9.997 nm was prepared successfully by this method.

  4. Isolation and Structural Characterization of Two Very Large, and Largely Empty, Endohedral Fullerenes: Tm@C3v-C94 and Ca@C3v-C94

    PubMed Central

    Che, Yuliang; Yang, Hua; Wang, Zhimin; Jin, Hongxiao; Lu, Chunxin; Zuo, Tianming; Beavers, Christine M.

    2009-01-01

    The structures of two newly synthesized endohedral fullerenes - Tm@C3v-C94 and Ca@C3v-C94 - have been determined by single crystal X-ray diffraction on samples co-crystallized with NiII(octaethylporphyrin). Both compounds exhibit the same cage geometry and conform to the isolated pentagon rule (IPR). The metal ions within these rather large cages are localized near one end and along the C3 axis. While the calcium ion is situated over a C-C bond at a 6:6 ring junction, the thulium ion is positioned above a six-membered ring of the fullerene. PMID:19507844

  5. Optical and dielectric properties of NiFe2O4 nanoparticles under different synthesized temperature

    NASA Astrophysics Data System (ADS)

    Parishani, Marziye; Nadafan, Marzieh; Dehghani, Zahra; Malekfar, Rasoul; Khorrami, G. H. H.

    In this research, NiFe2O4 nanoparticles was prepared via the simple sol-gel route, using different sintering temperature. This nanoparticle was characterized via X-ray diffraction (XRD) pattern, scanning electron microscopy (SEM), and FTIR spectra. The XRD patterns show by increasing the synthesized temperature, the intensity, and broadening of peaks are decreased so the results are more crystallization and raising the size of nanoparticles. The size distribution in the histogram of the NiFe2O4 nanoparticles is 42, 96, and 315 nm at 750 °C, 850 °C, and 950 °C, respectively. The FTIR spectra were evaluated using Kramers-Kronig method. Results approved the existing of certain relations between sintering temperatures and grain size of nanoparticles. By raising the temperature from 750 °C to 950 °C, the grain size was increased from 70 nm to 300 nm and the optical constants of nanoparticles were strongly related to synthesizing temperature as well. Since by increasing temperature, both real/imaginary parts of the refractive index and dielectric function were decreased. Consequently, the transversal (TO) and longitudinal (LO) phonon frequencies are detected. The TO and LO frequencies have shifted to red frequencies by increasing reaction temperature.

  6. Ultrasonic-assisted solution combustion synthesis of porous Na3V2(PO4)3/C: formation mechanism and sodium storage performance

    NASA Astrophysics Data System (ADS)

    Chen, Qiuyun; Liu, Qing; Chu, Xiangcheng; Zhang, Yiling; Yan, Youwei; Xue, Lihong; Zhang, Wuxing

    2017-04-01

    Solution combustion synthesis (SCS) is an effective and rapid method for synthesizing nanocrystalline materials. However, the control over size, morphology, and microstructure are rather limited in SCS. Here, we develop a novel ultrasonic-assisted solution combustion route to synthesize the porous and nano-sized Na3V2(PO4)3/C composites, and reveal the effects of ultrasound on the structural evolution of NVP/C. Due to the cavitation effects generated from ultrasonic irradiation, the ultrasonic-assisted SCS can produce honeycomb precursor, which can be further transformed into porous Na3V2(PO4)3/C with reticular and hollow structures after thermal treatment. When used as cathode material for Na-ion batteries, the porous Na3V2(PO4)3/C delivers an initial discharge capacity of 118 mAh g-1 at 0.1 C and an initial coulombic efficiency of 85%. It can retain 93.8% of the initial capacity after 120 cycles at 0.2 C. The results demonstrate that ultrasonic-assisted SCS can be a new strategy to design crystalline nanomaterials with tunable microstructures.

  7. Structural and magnetic properties of FexNi100-x alloys synthesized using Al as a reducing metal

    NASA Astrophysics Data System (ADS)

    Srakaew, N.; Jantaratana, P.; Nipakul, P.; Sirisathitkul, C.

    2017-08-01

    Iron-nickel (Fe-Ni) alloys comprising nine different compositions were rapidly synthesized from the redox reaction using aluminum foils as the reducing metal. Compared with conventional chemical syntheses, this simple approach is relatively safe and allows control over the alloy morphology and magnetic behavior as a function of the alloy composition with minimal oxidation. For alloys having low (10%-30%) Fe content the single face-centered cubic (FCC) FeNi3 phase was formed with nanorods aligned in the (1 1 1) crystalline direction on the cluster surface. This highly anisotropic morphology gradually disappeared as the Fe content was raised to 40%-70% with the alloy structure possessing a mixture of FCC FeNi3 and body-centered cubic (BCC) Fe7Ni3. The FCC phase was entirely replaced by the BCC structure upon further increase the Fe content to 80%-90%. The substitution of Ni by Fe in the crystals and the dominance of the BCC phase over the FCC structure gave rise to enhanced magnetization. By contrast, the coercive field decreased as a function of increasing Fe because of the reduction in shape anisotropy and the rise of saturation magnetization.

  8. The influence of void and porosity on deformation behaviour of nanocrystalline Ni under tensile followed by compressive loading

    NASA Astrophysics Data System (ADS)

    Meraj, Md.; Nayak, Shradha; Krishanjeet, Kumar; Pal, Snehanshu

    2018-03-01

    In this paper, we present a lucid understanding about the deformation behaviour of nanocrystalline (NC) Ni with and without defects subjected to tensile followed by compressive loading using molecular dynamic (MD) simulations. The embedded atom method (EAM) potential have been incorporated in the simulation for three kinds of samples-i.e. for NC Ni (without any defect), porous NC Ni and NC Ni containing a centrally located void. All the three samples, which have been prepared by implementing the Voronoi method and using Atom Eye software, consist of 16 uniform grains. The total number of atoms present in NC Ni, porous NC Ni and NC Ni containing a void are 107021, 105968 and 107012 respectively. The stress-strain response of NC Ni under tensile followed by compressive loading are simulated at a high strain rate of 107 s-1 and at a constant temperature of 300K. The stress-strain curves for the NC Ni with and without defects have been plotted for three different types of loading: (a) tensile loading (b) compressive loading (c) forward tensile loading followed by reverse compressive loading. Prominent change in yield strength of the NC Ni is observed due to the introduction of defects. For tensile followed by compressive loading (during forward loading), the yield point for NC Ni with void is lesser than the yield point of NC Ni and porous NC Ni. The saw tooth shape or serration portion of the stress-strain curve is mainly due to three characteristic phenomena, dislocation generation and its movement, dislocation pile-up at the junctions, and dislocation annihilation. Both twins and stacking faults are observed due to plastic deformation as the deformation mechanism progresses. The dislocation density, number of clusters and number of vacancy of the NC sample with and without defects are plotted against the strain developed in the sample. It is seen that introduction of defects brings about change in mechanical properties of the NC Ni. The crystalline nature of NC Ni

  9. Ordered mesoporous MFe(2)O(4) (M = Co, Cu, Mg, Ni, Zn) thin films with nanocrystalline walls, uniform 16 nm diameter pores and high thermal stability: template-directed synthesis and characterization of redox active trevorite.

    PubMed

    Haetge, Jan; Suchomski, Christian; Brezesinski, Torsten

    2010-12-20

    In this paper, we report on ordered mesoporous NiFe(2)O(4) thin films synthesized via co-assembly of hydrated ferric nitrate and nickel chloride with an amphiphilic diblock copolymer, referred to as KLE. We establish that the NiFe(2)O(4) samples are highly crystalline after calcination at 600 °C, and that the conversion of the amorphous inorganic framework comes at little cost to the ordering of the high quality cubic network of pores averaging 16 nm in diameter. We further show that the synthesis method employed in this work can be readily extended to other ferrites, such as CoFe(2)O(4), CuFe(2)O(4), MgFe(2)O(4), and ZnFe(2)O(4), which could pave the way for innovative device design. While this article focuses on the self-assembly and characterization of these materials using various state-of-the-art techniques, including electron microscopy, grazing incidence small-angle X-ray scattering (GISAXS), time-of-flight secondary ion mass spectrometry (TOF-SIMS), X-ray photoelectron spectroscopy (XPS), as well as UV-vis and Raman spectroscopy, we also examine the electrochemical properties and show the benefits of combining a continuous mesoporosity with nanocrystalline films. KLE-templated NiFe(2)O(4) electrodes exhibit reasonable levels of lithium ion storage at short charging times which stem from facile pseudocapacitance.

  10. Oxidation behaviour of Fe-Ni alloy nanoparticles synthesized by thermal plasma route

    NASA Astrophysics Data System (ADS)

    Ghodke, Neha; Kamble, Shalaka; Raut, Suyog; Puranik, Shridhar; Bhoraskar, S. V.; Rayaprol, Sudhindra; Mathe, V. L.

    2018-04-01

    Here we report synthesis of Fe-Ni nanoparticles using thermal plasma route. In thermal plasma, gas phase nucleation and growth at sufficiently higher temperature is observed. The synthesized Fe-Ni nanoparticles are examined by X-ray Diffraction, Raman Spectroscopy, Vibrating Sample Magnetometer and Thermo gravimetric Analysis. Formation of 16-21 nm sized Fe-Ni nanoparticles having surface oxidation show maximum value of magnetization of ˜107 emu/g. The sample synthesized at relatively low power (4kW) show presence of carbonaceous species whereas the high power (6 kW) synthesis does not depicts carbonaceous species. The presence of carbonaceous species protects oxidation of the nanoparticles significantly as evidenced from TGA data.

  11. Preparation and electrochemical properties of NiO-Co3O4 composite as electrode materials for supercapacitors

    NASA Astrophysics Data System (ADS)

    Wang, X. W.; Zheng, D. L.; Yang, P. Z.; Wang, X. E.; Zhu, Q. Q.; Ma, P. F.; Sun, L. Y.

    2017-01-01

    The precursor of NiO-Co3O4 composites was synthesized via a simple hydrothermal process. After that, the precursor was calcined at 300 °C for 3 h to obtain the composite powders. The powders calcined at 300 °C showed amorphous, and the powders calcined at 400 °C and 500 °C for comparison showed the composite phase of NiO and Co3O4. The composite products showed a microstructure of micro-spheres. For the samples calcined at 300 °C for 3 h, the specific capacitance reached 801 F g-1 at a current density of 1 A g-1.

  12. Structural Evolution during Milling, Annealing, and Rapid Consolidation of Nanocrystalline Fe–10Cr–3Al Powder

    PubMed Central

    Kumar, Rajiv; Bakshi, S. R.; Joardar, Joydip; Parida, S.; Raja, V. S.; Singh Raman, R. K.

    2017-01-01

    Structural changes during the deformation-induced synthesis of nanocrystalline Fe–10Cr–3Al alloy powder via high-energy ball milling followed by annealing and rapid consolidation by spark plasma sintering were investigated. Reduction in crystallite size was observed during the synthesis, which was associated with the lattice expansion and rise in dislocation density, reflecting the generation of the excess grain boundary interfacial energy and the excess free volume. Subsequent annealing led to the exponential growth of the crystallites with a concomitant drop in the dislocation density. The rapid consolidation of the as-synthesized nanocrystalline alloy powder by the spark plasma sintering, on the other hand, showed only a limited grain growth due to the reduction of processing time for the consolidation by about 95% when compared to annealing at the same temperature. PMID:28772633

  13. Nanostructured Mg 2Ni materials prepared by cold rolling and used as negative electrode for Ni-MH batteries

    NASA Astrophysics Data System (ADS)

    Pedneault, Sylvain; Huot, Jacques; Roué, Lionel

    In the present work, cold rolling has been investigated as a new means of producing Mg-based metal hydrides for nickel-metal hydride (Ni-MH) batteries. Structure and electrochemical evolution of 2Mg-Ni cold-rolled samples were investigated as a function of the number of rolling passes as well as heat treatment. It was found that nanocrystalline Mg 2Ni alloy can be obtained by an appropriate three step process involving rolling, heat treatment and rolling again. It was shown that the number of primary and secondary rolling passes must be carefully optimized in order to favour the complete formation of Mg 2Ni alloy having a nanocrystalline structure (∼10 nm in crystallite size) without excessive sample oxidation. Actually, the best result was obtained by first rolling 90 times, followed by a heat treatment at 400 °C for 4 h and roll again 20 times. The resulting material displayed an initial discharge capacity of 205 mAh g -1, which is quite similar to that obtained with ball-milled Mg 2Ni alloy.

  14. Phase, microstructure and hydrogen storage properties of Mg-Ni materials synthesized from metal nanoparticles.

    PubMed

    Shao, Huaiyu; Chen, Chunguang; Liu, Tong; Li, Xingguo

    2014-04-04

    After Mg and Ni nanoparticles were fabricated by hydrogen plasma metal reaction, Mg-rich MgxNi₁₀₀₋x(75 < x < 90) materials were synthesized from these metal nanoparticles to study the synergistic effects for hydrogen storage in these samples to show both good kinetics and high capacity. These MgxNi₁₀₀₋x materials may absorb hydrogen with a capacity of around 3.3-5.1 wt% in 1 min at 573 K. The Mg₉₀Ni₁₀ sample shows a hydrogen capacity of 6.1 wt%. The significant kinetic enhancement is thought to be due to the unique nanostructure from the special synthesis route, the catalytic effect of the Mg₂Ni nano phase, and the synergistic effects between the Mg₂Ni and Mg phases in the materials. An interesting phenomenon which has never been reported before was observed during pressure composition isotherm (PCT) measurements. One steep step in the absorption process and two obviously separated steps in the desorption process during PCT measurements of Mg₈₀Ni₂₀ and Mg₉₀Ni₁₀ samples were observed and a possible reason from the kinetic performance of the Mg₂Ni and Mg phases in absorption and desorption processes was explained. These MgxNi₁₀₀₋x materials synthesized from Mg and Ni nanoparticles show high capacity and good kinetics, which makes these materials very promising candidates for thermal storage or energy storage and utilization for renewable power.

  15. Structural, optical and magnetic behaviour of nanocrystalline Volborthite

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Arvind, Hemant K., E-mail: hemantarvind@gmail.com; Kumar, Sudhish, E-mail: skmlsu@gmail.com; Kalal, Sangeeta

    2016-05-06

    Nanocrystalline sample of Volborthite (Copper Pyrovanadate: Cu{sub 3}V{sub 2} (OH){sub 2}O{sub 7}.2H{sub 2}O) has been synthesized using wet chemical route and characterized by XRD, SEM, FTIR, UV-Vis-NIR spectroscopic and magnetization measurements. Room temperature X-ray diffraction analysis confirms the single phase monoclinic structure and nanocrystalline nature of Volborthite. The UV-Visible optical absorption spectrum displays two broad absorption peaks in the range of 200-350 nm and 400-1000 nm. The direct band gap is found to be E{sub g}= ∼2.74 eV. Bulk Volborthite was reported to be a natural frustrated antiferromagnet, however our nanocrystalline Volborthite display week ferromagnetic hysteresis loop with very small coercivity andmore » retentivity at room temperature.« less

  16. Thermally Induced Interdiffusion and Precipitation in a Ni/Ni 3 Al System

    DOE PAGES

    Sun, C.; Martinez, E.; Aguiar, J. A.; ...

    2015-05-20

    Ordered Ni 3Al intermetallic precipitates constitute the main hardening sources of Ni-based superalloys. Here, we report the interdiffusion and precipitation behavior in a Ni/Ni3Al model system. The deposition of Ni3Al on a pure Ni layer at 500°C generated L12-structured γ' (Ni3Al) precipitates, preferentially at the interface. After annealing at 800°C for 1 h, interdiffusion between Ni and Ni3Al layers occurred, and the γ' precipitates that grew near the parent Ni/Ni 3Al interface are ~2.8 times larger in size than those formed in the matrix. In conclusion, Monte Carlo simulations indicate that vacancies preferentially diffuse along the Ni/Ni 3Al interface, increasingmore » the probability of precipitation.« less

  17. Fabrication of Co@SiO2@C/Ni submicrorattles as highly efficient catalysts for 4-nitrophenol reduction.

    PubMed

    Guo, Xiaohui; Zhang, Min; Zheng, Jing; Xu, Jingli; Hayat, Tasawar; Alharbi, Njud S; Xi, Baojuan; Xiong, Shenglin

    2017-09-12

    In this paper, an extended Stöber method has been developed to fabricate a Ni 2+ -polydopamine (PDA) complex coated on Co 3 [Co(CN) 6 ] 2 @SiO 2 composites. After one-step carbonization involving the heat treatment of a Prussian blue analogue (PBA) of Co 3 [Co(CN) 6 ] 2 cores and the PDA-Ni 2+ shell under a nitrogen atmosphere, homogeneous Co@SiO 2 @C/Ni submicrorattles were synthesized. Notably, the silica interlayer played a vital role in the formation of such Co@SiO 2 @C/Ni submicrorattle structures. Without the protection of SiO 2 , Co-Ni@C composites were obtained instead and aggregated seriously due to sintering at high temperature. While with the silica layer as the spacer, the obtained Co@SiO 2 @C/Ni composites were not only well dispersed in the solution, but could also be adjusted in terms of the size and density of Ni nanoparticles (NPs) on the surface. Moreover, the size of core Co and surficial Ni NPs can be facilely modulated via changing the calcination temperature, which can effectively control the catalytic performance of the as-prepared nanocomposites. The as-prepared Co@SiO 2 @C/Ni submicrorattles were employed as the reaction catalyst for the reduction of 4-nitrophenol (4-NP), and exhibit both superior catalytic activity and cycling stability to Co@SiO 2 and Co-Ni@C composites.

  18. Effect of CeO2 on Cyclic Hot-Corrosion Behavior of Detonation-Gun Sprayed Cr3C2-NiCr Coatings on Ni-Based Superalloy

    NASA Astrophysics Data System (ADS)

    Saladi, Sekar; Menghani, Jyoti; Prakash, Satya

    2015-03-01

    The hot-corrosion behavior of detonation-gun sprayed Cr3C2-NiCr coatings with and without 0.4 wt.% CeO2 additive on Ni-based superalloy inconel-718 is comparatively discussed in the present study. Hot-corrosion studies were carried out at 900 °C for 100 cycles in Na2SO4-60%V2O5 molten salt environment under cyclic heating and cooling conditions on bare and coated superalloys. The thermo-gravimetric technique was used to establish kinetics of hot-corrosion. XRD, FESEM/EDAX, and EDX mapping techniques were used to analyze the corrosion products of bare and coated samples. The results indicate that Cr3C2-NiCr-CeO2-coated superalloy showed better hot-corrosion resistance as compared to bare and Cr3C2-NiCr-coated superalloys. The addition of CeO2 has improved micro-hardness, porosity, and surface roughness values of Cr3C2-NiCr-CeO2 coating. The overall weight gain and parabolic rate constant of Cr3C2-NiCr-CeO2-coated superalloy were found to be lowest in the present study signifying that the addition of CeO2 in Cr3C2-NiCr powder has contributed to the development of adherent and dense oxide scale on the coating at elevated temperature.

  19. Nanocrystalline CuInS2 And CuInSe2 via Low-Temperature Pyrolysis Of Single-Source Molecular Precursors

    NASA Technical Reports Server (NTRS)

    Castro, Stephanie L.; Bailey, Sheila G.; Raffaelle, Ryne P.; Banger, Kulbinder K.; Hepp, Aloysius F.

    2002-01-01

    Single-source precursors are molecules which contain all the necessary elements for synthesis of a desired material. Thermal decomposition of the precursor results in the formation of the material with the correct stoichiometry, as a nanocrystalline powder or a thin film. Nanocrystalline materials hold potential as components of next-generation Photovoltaic (PV) devices. Presented here are the syntheses of CuInS2 and CuInSe2 nanocrystals from the precursors (PPh3)2CuIn(SEt)4 and (PPh3)2CuIn(SePh)4, respectively. The size of the nanocrystals varies with the reaction temperature; a minimum of 200 C is required for the formation of the smallest CuInS2 crystals (approximately 1.6 nm diameter); at 300 C, crystals are approximately 7 nm.

  20. Enhanced H2S Sensing Performance of a p-type Semiconducting PdO-NiO Nanoscale Heteromixture

    NASA Astrophysics Data System (ADS)

    Balamurugan, C.; Jeong, Y. J.; Lee, D. W.

    2017-10-01

    Semiconducting nanocrystalline nickel oxide (NiO) and PdO-doped NiO heteromixture (2, 5 and 10 wt%) have been synthesized via a metal-citrate complex method. The obtained materials were further characterized using TG/DTA, FT-IR, UV-vis, XRD, XPS, BET/BJH, SEM and TEM analyses to determine their structural and morphological properties. The results indicated that the spherical, uniform PdO nanoparticles were densely deposited on the NiO surface mainly in diameters of 10-15 nm. Moreover, the existence of various defect states was also analyzed with the help of photoluminescence (PL) spectroscopy. The gas response characteristics of synthesized materials were evaluated in the presence and absence of toxic gases such as hydrogen sulfide (H2S), carbon monoxide (CO), liquid petroleum gas (LPG), and ethanol (C2H5OH). The experimental results revealed that the sensitivity and selectivity of the NiO-based sensor material are dependent on the weight% of PdO loading in the NiO nanopowder. Among the investigated compound, the 5 wt% PdO-doped NiO sensor material showed excellent sensitivity and selectivity to 100 ppm H2S with a fast response/recovery characteristics of 6 s and 10 s, respectively. Furthermore, the 5 wt% PdO-doped NiO based sensor showed a linear relationship between the different concentrations of H2S gas and a significantly higher response to H2S even at the low concentration of 20 ppm (43%) at 60 °C. The dominant H2S gas sensing mechanisms in the NiO and 5 wt% PdO-doped NiO nanomaterials are systematically discussed based on the obtained characterization results.

  1. Thermal formation effect of g-C3N4 structure on the visible light driven photocatalysis of g-C3N4/NiTiO3 Z-scheme composite photocatalysts

    NASA Astrophysics Data System (ADS)

    Pham, Thanh-Truc; Shin, Eun Woo

    2018-07-01

    The development of efficient visible-light driven photocatalysts has attracted considerable attention in environmental protection and remediation. In this study, the facile thermal polymerization of dicyandiamide (DCDA) to graphitic carbon nitride (g-C3N4) in the presence of nickel titanium trioxide (NiTiO3) was investigated for fabricating g-C3N4 and NiTiO3 composite (CNT) photocatalysts to understand the influence of the presence of NiTiO3 on the thermal formation of g-C3N4 layers from DCDA and to find an optimal processing temperature for fabricating CNT photocatalysts. To examine the effect of NiTiO3 on the fabrication of CNT photocatalysts, a gas phase environment (flowing air or nitrogen) and different processing temperatures were employed as preparation variables to control the properties of the CNT photocatalysts. In addition, the CNT photocatalysts were applied for the visible light driven photocatalytic degradation of methylene blue to evaluate their photocatalytic performances. The CNT photocatalyst prepared at T = 500 °C showed the highest photocatalytic activity, which was caused by the optimal morphology of g-C3N4 in the composite photocatalysts. The NiTiO3 inorganic phase in the composite photocatalysts acted as a catalyst to accelerate the thermal polymerization to form the g-C3N4 structure and as a promoter to increase the photocatalytic activity during photodegradation.

  2. Expansion of antimonato polyoxovanadates with transition metal complexes: (Co(N3C5H15)2)2[{Co(N3C5H15)2}V15Sb6O42(H2O)]·5H2O and (Ni(N3C5H15)2)2[{Ni(N3C5H15)2}V15Sb6O42(H2O)]·8H2O.

    PubMed

    Antonova, Elena; Näther, Christian; Kögerler, Paul; Bensch, Wolfgang

    2012-02-20

    Two new polyoxovanadates (Co(N(3)C(5)H(15))(2))(2)[{Co(N(3)C(5)H(15))(2)}V(15)Sb(6)O(42)(H(2)O)]·5H(2)O (1) and (Ni(N(3)C(5)H(15))(2))(2)[{Ni(N(3)C(5)H(15))(2)}V(15)Sb(6)O(42)(H(2)O)]·8H(2)O (2) (N(3)C(5)H(15) = N-(2-aminoethyl)-1,3-propanediamine) were synthesized under solvothermal conditions and structurally characterized. In both structures the [V(15)Sb(6)O(42)(H(2)O)](6-) shell displays the main structural motif, which is strongly related to the {V(18)O(42)} archetype cluster. Both compounds crystallize in the triclinic space group P1 with a = 14.3438(4), b = 16.6471(6), c = 18.9186(6) Å, α = 87.291(3)°, β = 83.340(3)°, γ = 78.890(3)°, and V = 4401.4(2) Å(3) (1) and a = 14.5697(13), b = 15.8523(16), c = 20.2411(18) Å, α = 86.702(11)°, β = 84.957(11)°, γ = 76.941(11)°, and V = 4533.0(7) Å(3) (2). In the structure of 1 the [V(15)Sb(6)O(42)(H(2)O)](6-) cluster anion is bound to a [Co(N(3)C(5)H(15))(2)](2+) complex via a terminal oxygen atom. In the Co(2+)-centered complex, one of the amine ligands coordinates in tridentate mode and the second one in bidentate mode to form a strongly distorted CoN(5)O octahedron. Similarly, in compound 2 an analogous NiN(5)O complex is joined to the [V(15)Sb(6)O(42)(H(2)O)](6-) anion via the same attachment mode. A remarkable difference between the two compounds is the orientation of the noncoordinated propylamine group leading to intermolecular Sb···O contacts in 1 and to Sb···N interactions in 2. In the solid-state lattices of 1 and 2, two additional [M(N(3)C(5)H(15))(2)](2+) complexes act as countercations and are located between the [{M(N(3)C(5)H(15))(2)}V(15)Sb(6)O(42)(H(2)O)](4-) anions. Between the anions and cations strong N-H···O hydrogen bonds are observed. In both compounds the clusters are stacked along the b axis in an ABAB fashion with cations and water molecules occupying the space between the clusters. Magnetic characterization demonstrates that the Ni(2+) and Co(2+) cations do not

  3. Nanocrystalline SiC film thermistors for cryogenic applications

    NASA Astrophysics Data System (ADS)

    Mitin, V. F.; Kholevchuk, V. V.; Semenov, A. V.; Kozlovskii, A. A.; Boltovets, N. S.; Krivutsa, V. A.; Slepova, A. S.; Novitskii, S. V.

    2018-02-01

    We developed a heat-sensitive material based on nanocrystalline SiC films obtained by direct deposition of carbon and silicon ions onto sapphire substrates. These SiC films can be used for resistance thermometers operating in the 2 K-300 K temperature range. Having high heat sensitivity, they are relatively low sensitive to the magnetic field. The designs of the sensors are presented together with a discussion of their thermometric characteristics and sensitivity to magnetic fields.

  4. Phase evolution, mechanical and corrosion behavior of Fe(100-x) Ni(x) alloys synthesized by powder metallurgy

    NASA Astrophysics Data System (ADS)

    Singh, Neera; Parkash, Om; Kumar, Devendra

    2018-03-01

    In the present investigation, Fe(100-x) Ni(x) alloys (x = 10, 20, 30, 40 and 50 wt%) were synthesized through the evolution of γ-taenite and α-kamacite phases by powder metallurgy route using commercially available Fe and Ni powders. Mechanically mixed powders of Fe and Ni were compacted at room temperature and sintered at three different temperatures 1000, 1200 and 1250 °C for 1 h. Both Ni concentration and sintering temperature have shown a strong impact on the phase formation, tribological and electrochemical behavior. Micro structural study has shown the formation of taenite (γ-Fe,Ni) and kamacite (α-Fe,Ni) phases in the sintered specimens. An increase in Ni fraction resulted in formation of more taenite which reduces hardness and wear resistance of specimens. Increasing the sintering temperature decreased the defect concentration with enhanced taenite formation, aiding to higher densification. Taenite formed completely in Fe50Ni50 after sintering at 1250 °C. Tribological test revealed the maximum wear resistance for Fe70Ni30 specimen due to the presence of both kamacite and taenite in significant proportions. The formation of taenite as well as the decrease in defect concentration improves the corrosion resistance of the specimens significantly in 1M HCl solution. A maximum corrosion protection efficiency of around ∼87% was achieved in acidic medium for Fe50Ni50, sintered at 1250 °C.

  5. Role of nanocrystallinity on the chemical ordering of Co xPt 100-x nanocrystals synthesized by wet chemistry

    DOE PAGES

    Cordeiro, Marco; Kameche, Farid; Ngo, Anh -Tu; ...

    2015-03-17

    Co xPt 100–x nanoalloys have been synthesized by two different chemical processes either at high or at low temperature. Their physical properties and the order/disorder phase transition induced by annealing have been investigated depending on the route of synthesis. It is demonstrated that the chemical synthesis at high temperature allows stabilization of the fcc structure of the native nanoalloys while the soft chemical approach yields mainly poly or non crystalline structure. As a result the approach of the order/disorder phase transition is strongly modified as observed by high-resolution transmission electron microscopy (HR-TEM) studies performed during in situ annealing of themore » different nanoalloys. The control of the nanocrystallinity leads to significant decrease in the chemical ordering temperature as the ordered structure is observed at temperatures as low as 420 °C. Furthermore, this in turn preserves the individual nanocrystals and prevents their coalescence usually observed during the annealing necessary for the transition to an ordered phase.« less

  6. Syntheses, spectroscopic characterization, thermal study, molecular modeling, and biological evaluation of novel Schiff's base benzil bis(5-amino-1,3,4-thiadiazole-2-thiol) with Ni(II), and Cu(II) metal complexes

    NASA Astrophysics Data System (ADS)

    Chandra, Sulekh; Gautam, Seema; Rajor, Hament Kumar; Bhatia, Rohit

    2015-02-01

    Novel Schiff's base ligand, benzil bis(5-amino-1,3,4-thiadiazole-2-thiol) was synthesized by the condensation of benzil and 5-amino-1,3,4-thiadiazole-2-thiol in 1:2 ratio. The structure of ligand was determined on the basis of elemental analyses, IR, 1H NMR, mass, and molecular modeling studies. Synthesized ligand behaved as tetradentate and coordinated to metal ion through sulfur atoms of thiol ring and nitrogen atoms of imine group. Ni(II), and Cu(II) complexes were synthesized with this nitrogen-sulfur donor (N2S2) ligand. Metal complexes were characterized by elemental analyses, molar conductance, magnetic susceptibility measurements, IR, electronic spectra, EPR, thermal, and molecular modeling studies. All the complexes showed molar conductance corresponding to non-electrolytic nature, expect [Ni(L)](NO3)2 complex, which was 1:2 electrolyte in nature. [Cu(L)(SO4)] complex may possessed square pyramidal geometry, [Ni(L)](NO3)2 complex tetrahedral and rest of the complexes six coordinated octahedral/tetragonal geometry. Newly synthesized ligand and its metal complexes were examined against the opportunistic pathogens. Results suggested that metal complexes were more biological sensitive than free ligand.

  7. Preparation and properties of TiC-Ni cermets using Ni-plated TiC

    NASA Astrophysics Data System (ADS)

    Shin, Soon-Gi

    2002-04-01

    TiC powders were coated with Ni by a chemical plating technique and the pressed compacts sintered at 1623K. The density of the sintered bodies was 98-99%. Compared with mechanically-mixed powder, Ni-plated TiC powders gave a more uniform microstructure in which TiC particles were well dispersed in the Ni matrix. The cermets exhibited ductile fracture for TiC-70 vol.% Ni and brittle fracture for TiC-30 vol.% Ni. The flexural strength was improved by the homogeneous dispersion of TiC. The thermal expansion coefficient increased with a decrease in Ni content, following a nearly linear law of mixtures on the basis of volume fractions of pure TiC and Ni.

  8. Nanosized LiM YMn 2- YO 4 (M = Cr, Co and Ni) spinels synthesized by a sucrose-aided combustion method . Structural characterization and electrochemical properties

    NASA Astrophysics Data System (ADS)

    Amarilla, J. M.; Rojas, R. M.; Pico, F.; Pascual, L.; Petrov, K.; Kovacheva, D.; Lazarraga, M. G.; Lejona, I.; Rojo, J. M.

    Spinels of composition LiM YMn 2- YO 4, M = Cr 3+, Co 3+, or Ni 2+, Y = 0.1 and 1 for the Cr and Co dopants, Y = 0.05 and 0.5 for the Ni sample, have been synthesized by a sucrose-aided combustion method. The samples as prepared require of an additional thermal treatment at 700 °C, 1 h to get stoichiometric single-phase spinels. The samples consist of aggregated particles of small size (45-50 nm) as deduced from transmission electron microscopy and X-ray powder diffraction. The electrochemical behaviour of the six spinels as cathodes in lithium cells has been analysed at 5 and 4 V under high current, 1 C rate. At 5 V the discharge capacity of LiNi 0.5Mn 1.5O 4 is higher than the one shown by LiCrMnO 4 and LiCoMnO 4, and it shows an elevated cyclability, i.e. capacity retention of 85.3% after 100 cycles. At 4 V the discharge capacity is similar for LiNi 0.05Mn 1.95O 4, LiCr 0.1Mn 1.9O 4 and LiCo 0.1Mn 1.9O 4, and all the three spinels show similar and very high cyclability, i.e. capacity retention >90% after 100 cycles. The spinels preserve their starting capacity up to currents as high as 2 C rate. The nanometric size of the samples explains the high rate capability of the synthesized spinels.

  9. Li1.2Mn0.6Ni0.1Co0.1O2 microspheres constructed by hierarchically arranged nanoparticles as lithium battery cathode with enhanced electrochemical performance

    NASA Astrophysics Data System (ADS)

    Remith, P.; Kalaiselvi, N.

    2014-11-01

    Novel lithium-rich layered Li1.2Mn0.6Ni0.1Co0.1O2 microspheres containing hierarchically arranged and interconnected nanostructures have been synthesized by a combination of template-free co-precipitation and solid-state methods. The in situ formed γ-MnO2 spherical template upon co-precipitation gets sacrificed during the course of solid-state fusion of cobalt, nickel and lithium precursors to produce the title compound in the form of microspheres constructed by nanoparticles as building blocks. Porous and hollow microspheres of Li1.2Mn0.6Ni0.1Co0.1O2 are formed out of the spontaneous aggregation of nanoparticles, obtained from the custom-designed synthesis protocol. The growth mechanism of Li1.2Mn0.6Ni0.1Co0.1O2 spheres could be understood in terms of the Kirkendall effect and Ostwald ripening. The nanocrystalline Li1.2Mn0.6Ni0.1Co0.1O2 compound is obtained as a solid solution consisting of rhombohedral R3&cmb.macr;m and monoclinic C2/m group symmetries, as evidenced by XRD, Raman spectra and HRTEM equipped with FFT and STEM. The currently synthesized Li1.2Mn0.6Ni0.1Co0.1O2 cathode exhibits an appreciable discharge capacity of 242 mA h g-1 at a current density of 50 mA g-1, due to the synergistic effect of the capacity obtained from the rhombohedral and monoclinic phases.Novel lithium-rich layered Li1.2Mn0.6Ni0.1Co0.1O2 microspheres containing hierarchically arranged and interconnected nanostructures have been synthesized by a combination of template-free co-precipitation and solid-state methods. The in situ formed γ-MnO2 spherical template upon co-precipitation gets sacrificed during the course of solid-state fusion of cobalt, nickel and lithium precursors to produce the title compound in the form of microspheres constructed by nanoparticles as building blocks. Porous and hollow microspheres of Li1.2Mn0.6Ni0.1Co0.1O2 are formed out of the spontaneous aggregation of nanoparticles, obtained from the custom-designed synthesis protocol. The growth mechanism of Li1

  10. Synthesis, characterization and magnetic properties of nanocrystalline FexNi80-xCo20 ternary alloys

    NASA Astrophysics Data System (ADS)

    Dalavi, Shankar B.; Theerthagiri, J.; Raja, M. Manivel; Panda, R. N.

    2013-10-01

    Fe-Ni-Co alloys of various compositions (FexNi80-xCo20,x=20-50) were synthesized by using a sodium borohydride reduction route. The phase purity and crystallite size was ascertained by using powder X-ray diffraction (XRD). The alloys crystallize in the face centered cubic (fcc) structure with lattice parameters, a=3.546-3.558 Å. The XRD line broadening indicates the fine particle nature of the materials. The estimated crystallite sizes were found to be 27.5, 27, 24, and 22.8 nm for x=20, 30, 40, and 50; alloys respectively. Scanning electron micrograph studies indicates particle sizes to be in the range of 83-60 nm for Fe-Ni-Co alloys. The values of saturation magnetization for FexNi80-xCo20 are found to be in the range of 54.3-41.2 emu/g and are significantly lower than the bulk values (175-180 emu/g). The coercivity decreases from 170 to 122 Oe with decrease in Fe content. The observed magnetic behavior has been explained on the basis of size, surface effects, spin canting and the presence of superparamagnetic fractions in the ultrafine materials.

  11. Ni@Fe2O3 heterodimers: controlled synthesis and magnetically recyclable catalytic application for dehalogenation reactions

    NASA Astrophysics Data System (ADS)

    Nakhjavan, Bahar; Tahir, Muhammad Nawaz; Natalio, Filipe; Panthöfer, Martin; Gao, Haitao; Dietzsch, Michael; Andre, Rute; Gasi, Teuta; Ksenofontov, Vadim; Branscheid, Robert; Kolb, Ute; Tremel, Wolfgang

    2012-07-01

    Ni@Fe2O3 heterodimer nanoparticles (NPs) were synthesized by thermal decomposition of organometallic reactants. After functionalization, these Ni@Fe2O3 heterodimers became water soluble. The pristine heterodimeric NPs were characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD), Mössbauer spectroscopy and magnetic susceptibility measurements. A special advantage of the heterodimers lies in the fact that nanodomains of different composition can be used as catalysts for the removal of environmentally hazardous halogenated pollutants.Ni@Fe2O3 heterodimer nanoparticles (NPs) were synthesized by thermal decomposition of organometallic reactants. After functionalization, these Ni@Fe2O3 heterodimers became water soluble. The pristine heterodimeric NPs were characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD), Mössbauer spectroscopy and magnetic susceptibility measurements. A special advantage of the heterodimers lies in the fact that nanodomains of different composition can be used as catalysts for the removal of environmentally hazardous halogenated pollutants. Electronic supplementary information (ESI) available. See DOI: 10.1039/c2nr12121b

  12. Low-energy charge transfer excitations in NiO

    NASA Astrophysics Data System (ADS)

    Sokolov, V. I.; Pustovarov, V. A.; Churmanov, V. N.; Ivanov, V. Yu; Yermakov, A. Ye; Uimin, M. A.; Gruzdev, N. B.; Sokolov, P. S.; Baranov, A. N.; Moskvin, A. S.

    2012-08-01

    Comparative analysis of photoluminescence (PL) and photoluminescence excitation (PLE) spectra of NiO poly- and nanocrystals in the spectral range 2-5.5 eV reveals two PLE bands peaked near 3.7 and 4.6 eV with a dramatic rise in the low-temperature PLE spectral weight of the 3.7 eV PLE band in the nanocrystalline NiO as compared with its polycrystalline counterpart. In frames of a cluster model approach we assign the 3.7 eV PLE band to the low-energy bulk-forbidden p-d (t1g(π)-eg) charge transfer (CT) transition which becomes the allowed one in the nanocrystalline state while the 4.6 eV PLE band is related to a bulk allowed d-d (eg-eg) CT transition scarcely susceptible to the nanocrystallization. The PLE spectroscopy of the nanocrystalline materials appears to be a novel informative technique for inspection of different CT transitions.

  13. Grain boundary and triple junction diffusion in nanocrystalline copper

    NASA Astrophysics Data System (ADS)

    Wegner, M.; Leuthold, J.; Peterlechner, M.; Song, X.; Divinski, S. V.; Wilde, G.

    2014-09-01

    Grain boundary and triple junction diffusion in nanocrystalline Cu samples with grain sizes, , of ˜35 and ˜44 nm produced by spark plasma sintering were investigated by the radiotracer method using the 63Ni isotope. The measured diffusivities, Deff, are comparable with those determined previously for Ni grain boundary diffusion in well-annealed, high purity, coarse grained, polycrystalline copper, substantiating the absence of a grain size effect on the kinetic properties of grain boundaries in a nanocrystalline material at grain sizes d ≥ 35 nm. Simultaneously, the analysis predicts that if triple junction diffusion of Ni in Cu is enhanced with respect to the corresponding grain boundary diffusion rate, it is still less than 500ṡDgb within the temperature interval from 420 K to 470 K.

  14. Stability of an Electrodeposited Nanocrystalline Ni-Based Alloy Coating in Oil and Gas Wells with the Coexistence of H2S and CO2

    PubMed Central

    Sui, Yiyong; Sun, Chong; Sun, Jianbo; Pu, Baolin; Ren, Wei; Zhao, Weimin

    2017-01-01

    The stability of an electrodeposited nanocrystalline Ni-based alloy coating in a H2S/CO2 environment was investigated by electrochemical measurements, weight loss method, and surface characterization. The results showed that both the cathodic and anodic processes of the Ni-based alloy coating were simultaneously suppressed, displaying a dramatic decrease of the corrosion current density. The corrosion of the Ni-based alloy coating was controlled by H2S corrosion and showed general corrosion morphology under the test temperatures. The corrosion products, mainly consisting of Ni3S2, NiS, or Ni3S4, had excellent stability in acid solution. The corrosion rate decreased with the rise of temperature, while the adhesive force of the corrosion scale increased. With the rise of temperature, the deposited morphology and composition of corrosion products changed, the NiS content in the corrosion scale increased, and the stability and adhesive strength of the corrosion scale improved. The corrosion scale of the Ni-based alloy coating was stable, compact, had strong adhesion, and caused low weight loss, so the corrosion rates calculated by the weight loss method cannot reveal the actual oxidation rate of the coating. As the corrosion time was prolonged, the Ni-based coating was thinned while the corrosion scale thickened. The corrosion scale was closely combined with the coating, but cannot fully prevent the corrosive reactants from reaching the substrate. PMID:28772995

  15. A Nanocrystalline Fe2O3 Film Anode Prepared by Pulsed Laser Deposition for Lithium-Ion Batteries

    NASA Astrophysics Data System (ADS)

    Teng, Xiaoling; Qin, Youzhi; Wang, Xia; Li, Hongsen; Shang, Xiantao; Fan, Shuting; Li, Qiang; Xu, Jie; Cao, Derang; Li, Shandong

    2018-02-01

    Nanocrystalline Fe2O3 thin films are deposited directly on the conduct substrates by pulsed laser deposition as anode materials for lithium-ion batteries. We demonstrate the well-designed Fe2O3 film electrodes are capable of excellent high-rate performance (510 mAh g- 1 at high current density of 15,000 mA g- 1) and superior cycling stability (905 mAh g- 1 at 100 mA g- 1 after 200 cycles), which are among the best reported state-of-the-art Fe2O3 anode materials. The outstanding lithium storage performances of the as-synthesized nanocrystalline Fe2O3 film are attributed to the advanced nanostructured architecture, which not only provides fast kinetics by the shortened lithium-ion diffusion lengths but also prolongs cycling life by preventing nanosized Fe2O3 particle agglomeration. The electrochemical performance results suggest that this novel Fe2O3 thin film is a promising anode material for all-solid-state thin film batteries.

  16. Conductivity and Dielectric Relaxation Properties of Annealed Cr-Substituted Ni-Ferrite Nanoparticles

    NASA Astrophysics Data System (ADS)

    El-Ghazzawy, E. H.

    2017-10-01

    Nanocrystalline NiCr x Fe2- x O4 spinel samples with x = 0.1 and 0.2 have been synthesized by coprecipitation method and annealed at 620°C and 1175°C for 4 h. Their electrical properties were investigated as functions of frequency in the range of 100 Hz to 100 kHz and temperature in the range of 308 K to 358 K. The dielectric constant ( ɛ^' } ) and dielectric loss factor ( {tan} δ ) appeared to decrease with increasing frequency, while the alternating-current (AC) conductivity ( σ^' } ) increased. These dielectric parameters increased with increasing temperature. On the other hand, impedance spectroscopy gave Cole-Cole plots with only one semicircular arc for all the samples, indicating that the grain-boundary contribution was dominant in the conduction mechanism.

  17. Diodes of nanocrystalline SiC on n-/n+-type epitaxial crystalline 6H-SiC

    NASA Astrophysics Data System (ADS)

    Zheng, Junding; Wei, Wensheng; Zhang, Chunxi; He, Mingchang; Li, Chang

    2018-03-01

    The diodes of nanocrystalline SiC on epitaxial crystalline (n-/n+)6H-SiC wafers were investigated, where the (n+)6H-SiC layer was treated as cathode. For the first unit, a heavily boron doped SiC film as anode was directly deposited by plasma enhanced chemical vapor deposition method on the wafer. As to the second one, an intrinsic SiC film was fabricated to insert between the wafer and the SiC anode. The third one included the SiC anode, an intrinsic SiC layer and a lightly phosphorus doped SiC film besides the wafer. Nanocrystallization in the yielded films was illustrated by means of X-ray diffraction, transmission electronic microscope and Raman spectrum respectively. Current vs. voltage traces of the obtained devices were checked to show as rectifying behaviors of semiconductor diodes, the conduction mechanisms were studied. Reverse recovery current waveforms were detected to analyze the recovery performance. The nanocrystalline SiC films in base region of the fabricated diodes are demonstrated as local regions for lifetime control of minority carriers to improve the reverse recovery properties.

  18. Microstructure and wear properties of laser clad Ti2Ni3Si/Ni3Ti multiphase intermetallic coatings

    NASA Astrophysics Data System (ADS)

    Wang, H. M.; Tang, H. B.; Cai, L. X.; Cao, F.; Zhang, L. Y.; Yu, R. L.

    2005-05-01

    Wear resistant Ti2Ni3Si/Ni3Ti multiphase intermetallic coatings with a microstructure consisting of Ti2Ni3Si primary dendrites and interdendritic Ti2Ni3Si/Ni3Ti eutectic were fabricated on a substrate of 0.2% C plain carbon steel by a laser cladding process with Ti-Ni-Si alloy powders. The Ti2Ni3Si/Ni3Ti coatings have excellent wear resistance and a low coefficient of friction under metallic dry sliding wear test conditions with hardened 0.45% C carbon steel as the silide-mating counterpart. The excellent tribological properties of the coating are attributed to the high hardness, strong covalent-dominant atomic bonds of the ternary metal silicide Ti2Ni3Si and to the high yield strength and strong yield anomaly of the intermetallic compound Ni3Ti.

  19. Nanocrystalline nickel ferrite particles synthesized by non-hydrolytic sol-gel method and their composite with biodegradable polymer.

    PubMed

    Yin, H; Casey, P S; Chow, G M

    2012-11-01

    Targeted drug delivery has been one of the most important biomedical applications for magnetic particles. Such applications require magnetic particles to have functionalized surfaces/surface coatings that facilitate their incorporation into a polymer matrix to produce a polymer composite. In this paper, nanocrystalline nickel ferrite particles with an oleic acid surface coating were synthesized using a non-hydrolytic sol-gel method and incorporated into a biodegradable polymer matrix, poly(D,L-lactide) PLA prepared using a double emulsion method. As-synthesized nickel ferrite particles had a multi-crystalline structure with chemically adsorbed oleic acid on their surface. After forming the PLA composite, nickel ferrite particles were encapsulated in PLA microspheres. At low nickel ferrite concentrations, composites showed very similar surface charges to that of PLA. The composites were magnetically responsive and increasing the nickel ferrite concentration was found to increase magnetization of the composite.

  20. High magnetization Fe-Co and Fe-Ni submicron and nanosize particles by thermal decomposition and hydrogen reduction

    NASA Astrophysics Data System (ADS)

    Cui, B. Z.; Marinescu, M.; Liu, J. F.

    2014-05-01

    This paper reports morphology, structure, and magnetic properties of air-stable soft magnetic FexCo100-x (x = 65, 50, and 34) and Fe50Ni50 (at. %) submicron and nanosize particles fabricated by template-free thermal decomposition of nitrates of Fe, Co, and Ni and subsequent hydrogen reduction. The particle compositions were tuned by modification of the precursor solution concentrations. The as-synthesized Fe-Co and Fe50Ni50 particles have body centered cubic and face centered cubic poly-nanocrystalline structures, respectively. The Fe-Co and Fe50Ni50 particles have particle sizes in the range of 28-200 nm and 70-480 nm, and average grain sizes of 16-29 nm and 20-24 nm, respectively. The particle and grain sizes were controlled by tuning particle composition, and the temperature and time of hydrogen reduction. Saturation magnetization Ms as high as 207-224 emu/g and intrinsic coercivity Hci of 59-228 Oe were obtained in the Fe-Co particles reduced at 550 °C for 90 min. Of special note, the Ms of 224 emu/g (˜2.3 T) obtained in the Fe65Co35 particles is among the highest values for Fe-Co particles reported so far. Ms of 135-137 emu/g and Hci of 59-111 Oe were obtained in the Fe50Ni50 particles reduced at 500 or 550 °C for 20 min.

  1. The chemical and catalytic properties of nanocrystalline metal oxides prepared through modified sol-gel synthesis

    NASA Astrophysics Data System (ADS)

    Carnes, Corrie Leigh

    The goal of this research was to synthesize, characterize and study the chemical properties of nanocrystalline metal oxides. Nanocrystalline (NC) ZnO, CuO, NiO, Al2O3, and the binary Al2O 3/MgO and ZnO/CuO were prepared through modified sol gel methods. These NC metal oxides were studied in comparison to the commercial (CM) metal oxides. The samples were characterized by XRD, TGA, FTIR, BET, and TEM. The NC samples were all accompanied by a significant increase in surface area and decrease in crystallite size. Several chemical reactions were studied to compare the NC samples to the CM samples. One of the reactions involved a high temperature reaction between carbon tetrachloride and the oxide to form carbon dioxide and the corresponding metal chloride. A similar high temperature reaction was conducted between the metal oxide and hydrogen sulfide to form water and the corresponding metal sulfide. A room temperature gas phase adsorption was studied where SO2 was adsorbed onto the oxide. A liquid phase adsorption conducted at room temperature was the destructive adsorption of paraoxon (a toxic insecticide). In all reactions the NC samples exhibited greater activity, destroying or adsorbing a larger amount of the toxins compared to the CM samples. To better study surface area effects catalytic reactions were also studied. The catalysis of methanol was studied over the nanocrystalline ZnO, CuO, NiO, and ZnO/CuO samples in comparison to their commercial counterparts. In most cases the NC samples proved to be more active catalysts, having higher percent conversions and turnover numbers. A second catalytic reaction was also studied, this reaction was investigated to look at the support effects. The catalysis of cyclopropane to propane was studied over Pt and Co catalysts. These catalysts were supported onto NC and CM alumina by impregnation. By observing differences in the catalytic behavior, support effects have become apparent.

  2. Temperature dependence of Ni3S2 nanostructures with high electrochemical performance

    NASA Astrophysics Data System (ADS)

    Wang, Y. L.; Wei, X. Q.; Li, M. B.; Hou, P. Y.; Xu, X. J.

    2018-04-01

    Different Ni3S2 nanostructures have been successfully synthesized at different temperatures by a facile and efficient solvothermal method. The Ni3S2 nanostructures with three-dimensional (3D) nanosheets array and silkworm eggs-like morphologies were obtained by adjusting the reaction temperature. A large number of 3D nanosheets are interconnected to form an open network structure with porous of Ni3S2 at 180 °C, and electrochemical tests showed that the special structure exhibited the outstanding specific capacitance (1357 F g -1 at 1 A g-1) and excellent cycling stability (maintained 91% after 3000 cycles). In comparison, the performance of Ni3S2 silkworm eggs-like structure is not very perfect. This may be due to the fact that the 3D nanosheets with porous structure can improve the electrochemical performance by shortening effectively the diffusion path of electrolyte ions and increasing the active sites during charging and discharging. Among them, the reaction temperature is the main factor to control the formation of the 3D nanosheets array. These results indicated the Ni3S2 nanosheets promising applications as high-performance supercapacitor electrode materials.

  3. Characteristics of ZrC/Ni-UDD coatings for a tungsten carbide cutting tool

    NASA Astrophysics Data System (ADS)

    Chayeuski, V. V.; Zhylinski, V. V.; Rudak, P. V.; Rusalsky, D. P.; Višniakov, N.; Černašėjus, O.

    2018-07-01

    This work deals with the features of the structure of combined ZrC/Ni-ultradisperse diamonds (UDD) coating synthesized by electroplating and cathode arc evaporation physical vapor deposition (CAE-PVD) techniques on the tungsten carbide WC - 2 wt% Co on cutting inserts to improve tool life. The microstructure, phase composition, and micro-scratch test analysis of the ZrC/Ni-UDD coating were studied. The ZrC/Ni-UDD coating consists of separate phases of zirconium carbide ZrC, α-Ni, and Ni-UDD phase. The surface morphology of the coating shows a pattern with pits, pores, and particles. Separated nanodiamond particles are present in the pores of the combined coating. Therefore, the structure of the bottom layer of Ni-UDD affects the morphology of the surface of the ZrC/Ni-UDD coating. The obtained value of the critical loads on the scratch track of the coating in 26 N proves a sufficiently high value of the adhesion strength of the intermediate Ni-UDD-layer with hard alloy of WC-Co substrate. Due to their unique structure ZrC/Ni-UDD-coatings can be used to increase the durability period of a wood-cutting milling tool for cutting chipboard by CNC machines.

  4. Three-dimensional hierarchical NiCo2O4 nanowire@Ni3S2 nanosheet core/shell arrays for flexible asymmetric supercapacitors

    NASA Astrophysics Data System (ADS)

    Liu, Bo; Kong, Dezhi; Huang, Zhi Xiang; Mo, Runwei; Wang, Ye; Han, Zhaojun; Cheng, Chuanwei; Yang, Hui Ying

    2016-05-01

    Three-dimensional (3D) hierarchical NiCo2O4@Ni3S2 core/shell arrays on Ni foam were synthesized by a facile, stepwise synthesis approach. The 3D heterogeneous NiCo2O4 nanostructure forms an interconnected web-like scaffold and serves as the core for the Ni3S2 shell. The as-prepared NiCo2O4@Ni3S2 nanowire array (NWA) electrodes exhibited excellent electrochemical performance, such as high specific areal capacitance and excellent cycling stability. The specific areal capacitance of 3.0 F cm-2 at a current density of 5 mA cm-2 is among the highest values and the only 6.7% capacitance decay after 10 000 cycles demonstrates the excellent cycling stability. A flexible asymmetric supercapacitor (ASC) was fabricated with activated carbon (AC) as the anode and the obtained NiCo2O4@Ni3S2 NWAs as the cathode. The ASC device exhibited a high energy density of 1.89 mW h cm-3 at 5.81 W cm-3 and a high power density of 56.33 W cm-3 at 0.94 mW h cm-3. As a result, the hybrid nanoarchitecture opens a new way to design high performance electrodes for electrochemical energy storage applications.Three-dimensional (3D) hierarchical NiCo2O4@Ni3S2 core/shell arrays on Ni foam were synthesized by a facile, stepwise synthesis approach. The 3D heterogeneous NiCo2O4 nanostructure forms an interconnected web-like scaffold and serves as the core for the Ni3S2 shell. The as-prepared NiCo2O4@Ni3S2 nanowire array (NWA) electrodes exhibited excellent electrochemical performance, such as high specific areal capacitance and excellent cycling stability. The specific areal capacitance of 3.0 F cm-2 at a current density of 5 mA cm-2 is among the highest values and the only 6.7% capacitance decay after 10 000 cycles demonstrates the excellent cycling stability. A flexible asymmetric supercapacitor (ASC) was fabricated with activated carbon (AC) as the anode and the obtained NiCo2O4@Ni3S2 NWAs as the cathode. The ASC device exhibited a high energy density of 1.89 mW h cm-3 at 5.81 W cm-3 and a high power

  5. Structural, Optical, and Photocatalytic Properties of Quasi-One-Dimensional Nanocrystalline ZnO, ZnOC:nC Composites, and C-doped ZnO

    NASA Astrophysics Data System (ADS)

    Shalaeva, E. V.; Gyrdasova, O. I.; Krasilnikov, V. N.; Melkozerova, M. A.; Baklanova, I. V.; Buldakova, L. Yu.

    Various thermolysis rotes of zinc glicolate complexes are considered for the synthesis of quasi-one-dimensional nanostructured aggregates ZnO and Zn-O-C used as photocatalysts. Structural features of quasi-one-dimensional aggregates Zn-O-C and ZnO are investigated in detail. Transmission electron microscopy, Raman spectroscopy, and electron paramagnetic resonance spectroscopy methods demonstrate that the aggregates Zn-O-C have either composite structure (ZnO crystallites in amorphous carbon matrix) or a C-doped ZnO single-phase structure depending on heat treatment conditions, and that all the aggregates exhibit as a rule a tubular morphology, a nanocrystalline structure with a high specific surface area, and a high concentration of singly charged oxygen vacancies. The mechanism of the nanocrystalline structure formation is discussed and the effect of thermolysis condition on the formation of the textured structure of aggregates is investigated. The results of examination of the photocatalytic and optical absorption properties of the synthesized aggregates are presented. The photocatalytic activity for the hydroquinone oxidation reaction under ultraviolet and visible light increases in the series: the reference ZnO powder, quasi-one-dimensional ZnO, quasi-one-dimensional aggregates C-doped ZnO, and this tendency correlates with the reduction of the optical gap width. As a result of our studies, we have arrived at an important conclusion that thermal treatment of ZnO:nC composites allows a C-doped ZnO with high catalytic activity. This increasing photoactivity of C-doped ZnO aggregates is attributed to the optimal specific surface area and electron-energy spectrum restructuring to be produced owing to the presence of singly charged oxygen vacancies and carbon dissolved in the ZnO lattice.

  6. Shock-induced microstructural response of mono- and nanocrystalline SiC ceramics

    NASA Astrophysics Data System (ADS)

    Branicio, Paulo S.; Zhang, Jingyun; Rino, José P.; Nakano, Aiichiro; Kalia, Rajiv K.; Vashishta, Priya

    2018-04-01

    The dynamic behavior of mono- and nanocrystalline SiC ceramics under plane shock loading is revealed using molecular-dynamics simulations. The generation of shock-induced elastic compression, plastic deformation, and structural phase transformation is characterized at different crystallographic directions as well as on a 5-nm grain size nanostructure at 10 K and 300 K. Shock profiles are calculated in a wide range of particle velocities 0.1-6.0 km/s. The predicted Hugoniot agree well with experimental data. Results indicate the generation of elastic waves for particle velocities below 0.8-1.9 km/s, depending on the crystallographic direction. In the intermediate range of particle velocities between 2 and 5 km/s, the shock wave splits into an elastic precursor and a zinc blende-to-rock salt structural transformation wave, which is triggered by shock pressure over the ˜90 GPa threshold value. A plastic wave, with a strong deformation twinning component, is generated ahead of the transformation wave for shocks in the velocity range between 1.5 and 3 km/s. For particle velocities greater than 5-6 km/s, a single overdriven transformation wave is generated. Surprisingly, shocks on the nanocrystalline sample reveal the absence of wave splitting, and elastic, plastic, and transformation wave components are seamlessly connected as the shock strength is continuously increased. The calculated strengths 15.2, 31.4, and 30.9 GPa for ⟨001⟩, ⟨111⟩, and ⟨110⟩ directions and 12.3 GPa for the nanocrystalline sample at the Hugoniot elastic limit are in excellent agreement with experimental data.

  7. Raman and dielectric studies of GdMnO3 bulk ceramics synthesized from nano powders

    NASA Astrophysics Data System (ADS)

    Samantaray, S.; Mishra, D. K.; Roul, B. K.

    2017-05-01

    Nanocrystalline GdMnO3 (GMO) powders has been synthesized by a simple chemical route i. e. pyrophoric reaction technique and then sintered in the form of bulk pellet at 850°C for 24 hours by adopting slow step sintering schedule. It is observed that by reducing the particles size, chemical route enhances the mixing process as well as decreasing the sintering temperature to get single phase material system in compared to the polycrystalline sample prepared directly from the micron sized commercial powder. Raman spectroscopic studies confirm that the sample is in single phase without any detectable impurity. Frequency dependent dielectric properties i.e., dielectric constant (K) and dielectric loss (tanδ) of GMO ceramics sintered at 850°C for 24 hours were studied at room temperature. The sample showed high K value (˜2736) in the frequency of 100 Hz at room temperature.

  8. Thermal Stability of Nanocrystalline Alloys by Solute Additions and A Thermodynamic Modeling

    NASA Astrophysics Data System (ADS)

    Saber, Mostafa

    Nanocrystalline alloys show superior properties due to their exceptional microstructure. Thermal stability of these materials is a critical aspect. It is well known that grain boundaries in nanocrystalline microstructures cause a significant increase in the total free energy of the system. A driving force provided to reduce this excess free energy can cause grain growth. The presence of a solute addition within a nanocrystalline alloy can lead to the thermal stability. Kinetic and thermodynamic stabilization are the two basic mechanisms with which stability of a nanoscale grain size can be achieved at high temperatures. The basis of this thesis is to study the effect of solute addition on thermal stability of nanocrystalline alloys. The objective is to determine the effect of Zr addition on the thermal stability of mechanically alloyed nanocrysatillne Fe-Cr and Fe-Ni alloys. In Fe-Cr-Zr alloy system, nanoscale grain size stabilization was maintained up to 900 °C by adding 2 at% Zr. Kinetic pinning by intermetallic particles in the nanoscale range was identified as a primary mechanism of thermal stabilization. In addition to the grain size strengthening, intermetallic particles also contribute to strengthening mechanisms. The analysis of microhardness, XRD data, and measured grain sizes from TEM micrographs suggested that both thermodynamic and kinetic mechanisms are possible mechanisms. It was found that alpha → gamma phase transformation in Fe-Cr-Zr system does not influence the grain size stabilization. In the Fe-Ni-Zr alloy system, it was shown that the grain growth in Fe-8Ni-1Zr alloy is much less than that of pure Fe and Fe-8Ni alloy at elevated temperatures. The microstructure of the ternary Fe-8Ni-1Zr alloy remains in the nanoscale range up to 700 °C. Using an in-situ TEM study, it was determined that drastic grain growth occurs when the alpha → gamma phase transformation occurs. Accordingly, there can be a synergistic relationship between grain growth

  9. Syntheses, spectroscopic characterization, thermal study, molecular modeling, and biological evaluation of novel Schiff's base benzil bis(5-amino-1,3,4-thiadiazole-2-thiol) with Ni(II), and Cu(II) metal complexes.

    PubMed

    Chandra, Sulekh; Gautam, Seema; Rajor, Hament Kumar; Bhatia, Rohit

    2015-02-25

    Novel Schiff's base ligand, benzil bis(5-amino-1,3,4-thiadiazole-2-thiol) was synthesized by the condensation of benzil and 5-amino-1,3,4-thiadiazole-2-thiol in 1:2 ratio. The structure of ligand was determined on the basis of elemental analyses, IR, (1)H NMR, mass, and molecular modeling studies. Synthesized ligand behaved as tetradentate and coordinated to metal ion through sulfur atoms of thiol ring and nitrogen atoms of imine group. Ni(II), and Cu(II) complexes were synthesized with this nitrogen-sulfur donor (N2S2) ligand. Metal complexes were characterized by elemental analyses, molar conductance, magnetic susceptibility measurements, IR, electronic spectra, EPR, thermal, and molecular modeling studies. All the complexes showed molar conductance corresponding to non-electrolytic nature, expect [Ni(L)](NO3)2 complex, which was 1:2 electrolyte in nature. [Cu(L)(SO4)] complex may possessed square pyramidal geometry, [Ni(L)](NO3)2 complex tetrahedral and rest of the complexes six coordinated octahedral/tetragonal geometry. Newly synthesized ligand and its metal complexes were examined against the opportunistic pathogens. Results suggested that metal complexes were more biological sensitive than free ligand. Copyright © 2014 Elsevier B.V. All rights reserved.

  10. Role of the nanocrystallinity on the chemical ordering of Co(x)Pt(100-x) nanocrystals synthesized by wet chemistry.

    PubMed

    Kameche, Farid; Ngo, Anh-Tu; Salzemann, Caroline; Cordeiro, Marco; Sutter, Eli; Petit, Christophe

    2015-11-14

    Co(x)Pt(100-x) nanoalloys have been synthesized by two different chemical processes either at high or at low temperature. Their physical properties and the order/disorder phase transition induced by annealing have been investigated depending on the route of synthesis. It is demonstrated that the chemical synthesis at high temperature allows stabilization of the fcc structure of the native nanoalloys while the soft chemical approach yields mainly poly or non crystalline structure. As a result the approach of the order/disorder phase transition is strongly modified as observed by high-resolution transmission electron microscopy (HR-TEM) studies performed during in situ annealing of the different nanoalloys. The control of the nanocrystallinity leads to significant decrease in the chemical ordering temperature as the ordered structure is observed at temperatures as low as 420 °C. This in turn preserves the individual nanocrystals and prevents their coalescence usually observed during the annealing necessary for the transition to an ordered phase.

  11. Controlling Directional Liquid Motion on Micro- and Nanocrystalline Diamond/β-SiC Composite Gradient Films.

    PubMed

    Wang, Tao; Handschuh-Wang, Stephan; Huang, Lei; Zhang, Lei; Jiang, Xin; Kong, Tiantian; Zhang, Wenjun; Lee, Chun-Sing; Zhou, Xuechang; Tang, Yongbing

    2018-01-30

    In this Article, we report the synthesis of micro- and nanocrystalline diamond/β-SiC composite gradient films, using a hot filament chemical vapor deposition (HFCVD) technique and its application as a robust and chemically inert means to actuate water and hazardous liquids. As revealed by scanning electron microscopy, the composition of the surface changed gradually from pure nanocrystalline diamond (hydrophobic) to a nanocrystalline β-SiC surface (hydrophilic). Transmission electron microscopy and Raman spectroscopy were employed to determine the presence of diamond, graphite, and β-SiC phases. The as-prepared gradient films were evaluated for their ability to actuate water. Indeed, water was transported via the gradient from the hydrophobic (hydrogen-terminated diamond) to the hydrophilic side (hydroxyl-terminated β-SiC) of the gradient surface. The driving distance and velocity of water is pivotally influenced by the surface roughness. The nanogradient surface showed significant promise as the lower roughness combined with the longer gradient yields in transport distances of up to 3.7 mm, with a maximum droplet velocity of nearly 250 mm/s measured by a high-speed camera. As diamond and β-SiC are chemically inert, the gradient surfaces can be used to drive hazardous liquids and reactive mixtures, which was signified by the actuation of hydrochloric acid and sodium hydroxide solution. We envision that the diamond/β-SiC gradient surface has high potential as an actuator for water transport in microfluidic devices, DNA sensors, and implants, which induce guided cell growth.

  12. Microemulsion based approach for nanospheres assembly into anisotropic nanostructures of NiMnO3 and their magnetic properties

    NASA Astrophysics Data System (ADS)

    Jha, Menaka; Kumar, Sandeep; Garg, Neha; Ramanujachary, Kandalam V.; Lofland, Samuel E.; Ganguli, Ashok K.

    2018-02-01

    The present study focuses on synthesis of anisotropic nanostructures of nickel manganese oxide (NiMnO3) obtained by thermal decomposition of nanocrystalline nickel manganese oxalate precursor, Ni0.5Mn0.5(C2O4)·2H2O which crystallized as nanorods. The synthesis of the oxalate precursor has been carried out via microemulsion-mediated process with cationic and non-ionic surfactants. The microemulsion led to reverse micelles, and the film flexibility of the micelle in presence of non-ionic surfactant (Tergitol) was reduced by increasing the chain length of the co-surfactant (1-butanol, 1-hexanol and 1-octanol) which led to the increase in reaction rate and hence increase in the aspect ratio of the nickel manganese oxalate by up to four times. However, in the presence of cationic surfactant, highly uniform nickel manganese oxalate nanorods were obtained. Further, the decomposition of the oxalate precursor was optimized to maintain the anisotropy of the rods of ternary metal oxide (NiMnO3). An electron microscopy study showed that the rods were made up of an assembly of ultrafine nanospheres. The NiMnO3 nanostructures were all ferrimagnetic with Curie temperature ranging between 437 and 467 K showing increasing saturation magnetization with increase in aspect ratio of the nanorods.

  13. Size dependent exchange bias in single-phase Zn0.3Ni0.7Fe2O4 ferrite nanoparticles

    NASA Astrophysics Data System (ADS)

    Mohan, Rajendra; Ghosh, Mritunjoy Prasad; Mukherjee, Samrat

    2018-07-01

    We report the microstructural and magnetic characterization of single phase nanocrystalline partially inverted Zn0.3Ni0.7Fe2O4 mixed spinel ferrite. The samples were annealed at 200 °C, 400 °C, 600 °C, 800 °C and 1000 °C. X-ray diffraction results indicate phase purity of all the samples and application of Debye- Scherrer yielded a crystallite size variation from 5 nm to 33 nm for the different samples. Magnetic measurements have revealed the freezing of interfacial spins which were the cause of the large horizontal M-H loop shift causing large exchange bias with high anisotropy. The magnetic measurements show a hysteresis loop with high effective anisotropy constant due to highly magnetically disordered surface spin at 5 K.

  14. Synthesis and characterization of nanocrystalline graphite from coconut shell with heating process

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Wachid, Frischa M., E-mail: frischamw@yahoo.com, E-mail: adhiyudhaperkasa@yahoo.com, E-mail: afandisar@yahoo.com, E-mail: nurulrosyidah92@gmail.com, E-mail: darminto@physics.its.ac.id; Perkasa, Adhi Y., E-mail: frischamw@yahoo.com, E-mail: adhiyudhaperkasa@yahoo.com, E-mail: afandisar@yahoo.com, E-mail: nurulrosyidah92@gmail.com, E-mail: darminto@physics.its.ac.id; Prasetya, Fandi A., E-mail: frischamw@yahoo.com, E-mail: adhiyudhaperkasa@yahoo.com, E-mail: afandisar@yahoo.com, E-mail: nurulrosyidah92@gmail.com, E-mail: darminto@physics.its.ac.id

    Graphite were synthesized and characterized by heating process of coconut shell with varying temperature (400, 800 and 1000°C) and holding time (3 and 5 hours). After heating process, the samples were characterized by X-ray diffraction (XRD) and analyzed by X'pert HighScore Plus Software, Scanning Electron Microcope-Energy Dispersive X-Ray (SEM-EDX) and Transmission Electron Microscope-Energy Dispersive X-Ray (TEM-EDX). Graphite and londsdaelite phase were analyzed by XRD. According to EDX analysis, the sample was heated in 1000°C got the highest content of carbon. The amorphous carbon and nanocrystalline graphite were observed by SEM-EDX and TEM-EDX.

  15. Synthetic Ni3S2/Ni hybrid architectures as potential contrast agents in MRI

    NASA Astrophysics Data System (ADS)

    Ma, J.; Chen, K.

    2016-04-01

    Traditional magnetic resonance imaging (MRI) contrast agents mainly include superparamagnetic (SPM) iron oxide nanoparticle as T 2 contrast agent for liver and paramagnetic Gd (III)-chelate as T 1 contrast agent for all organs. In this work, weak ferromagnetic kale-like and SPM cabbage-like Ni3S2@Ni hybrid architectures were synthesized and evaluated as potential T 1 MRI contrast agents. Their relatively small r 2/r 1 ratios of 2.59 and 2.38, and high r 1 values of 11.27 and 4.89 mmol-1 L s-1 (for the kale-like and cabbage-like Ni3S2@Ni, respectively) will shed some light on the development of new-type MRI contrast agents.

  16. Characterization of Nanocrystalline Nickel-Cobalt Alloys Synthesized by Direct and Pulse Electrodeposition

    NASA Astrophysics Data System (ADS)

    Salehi, M.; Saidi, A.; Ahmadian, M.; Raeissi, K.

    2014-01-01

    Nanocrystalline Ni-Co alloys are electrodeposited by direct (DC) and pulse current (PC) in an electrolyte solution which consisted of nickel sulfate, cobalt sulfate and boric acid. Electrodeposition parameters including current density, electrolyte pH and pulse times in a single electrolyte bath were changed. XRD pattern showed that the structure of the alloys depends on Co content and the synthesis parameter and changed from single phase structure (fcc) to dual phase structure (fcc + hcp). The Co content in the deposited alloys declined from 70 at.% to 50 at.% by increasing in direct current from 70 mA/cm2 to 115 mA/cm2 and also decreased from 75 at.% to 33 at.% with decrease in pH values from 4 to 2. By applying PC the Co content changed from 76 at.% to 41 at.%. Magnetic properties measurements showed the saturation magnetization (Ms) increased with increasing the Co content. There was no significant effect on coercivity values (Hc) with change in Co content and about 40 Oe was obtained for all samples. The grain size of deposited alloys obtained between 24-58 nm and 15-21 nm by applying DC and PC, respectively.

  17. Unraveling the Semiconducting/Metallic Discrepancy in Ni 3(HITP) 2

    DOE PAGES

    Foster, Michael E.; Sohlberg, Karl; Allendorf, Mark D.; ...

    2018-01-10

    Here, Ni 3(2,3,6,7,10,11-hexaiminotriphenylene) 2 is a π-stacked layered metal–organic framework material with extended π-conjugation that is analogous to graphene. Published experimental results indicate that the material is semiconducting, but all theoretical studies to date predict the bulk material to be metallic. Given that previous experimental work was carried out on specimens containing complex nanocrystalline microstructures and the tendency for internal interfaces to introduce transport barriers, we apply DFT to investigate the influence of internal interface defects on the electronic structure of Ni 3(HITP) 2. The results show that interface defects can introduce a transport barrier by breaking the π-conjugation and/ormore » decreasing the dispersion of the electronic bands near the Fermi level. We demonstrate that the presence of defects can open a small gap, in the range of 15–200 meV, which is consistent with the experimentally inferred hopping barrier.« less

  18. Influence of Sn on the magnetic ordering of Ni-Sn alloy synthesized using chemical reduction method

    NASA Astrophysics Data System (ADS)

    Dhanapal, K.; Narayanan, V.; Stephen, A.

    2016-05-01

    The Ni-Sn alloy was synthesized using borohydride assisted chemical reduction method. The composition of the synthesized alloy was determined using atomic absorption spectroscopy which revealed that the observed composition of Sn is high when compared to the initial composition. The ultrafine particles are clearly observed from field emission scanning electron microscope for all the sample. The X-ray diffraction measurement confirmed that the as-synthesized samples are of amorphous like nature while the samples annealed at 773 K showed crystalline nature. The Fourier transform infrared spectroscopy confirmed metallic bond stretching in the alloy samples. The crystallization and phase transition temperature was observed from differential scanning calorimetry. The shift in the crystallization temperature of Ni with increasing percentage of Sn was observed. The vibrating sample magnetometer was employed to understand the magnetic behavior of the Ni-Sn alloy. As-synthesized alloy samples showed paramagnetic nature while the annealed ones exhibit the soft ferromagnetic, antiferromagnetic and paramagnetic nature. The saturation magnetization value and magnetic ordering in the Ni-Sn alloys depend on the percentage of Sn present in the alloy.

  19. A practical grinding-assisted dry synthesis of nanocrystalline NiMoO{sub 4} polymorphs for oxidative dehydrogenation of propane

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Chen Miao, E-mail: chenmiao@sinochem.com; Zhejiang Chemical Industry Research Institute, Hangzhou 310023; Wu Jialing

    2011-12-15

    A practical two-stage reactive grinding-assisted pathway waste-free and cost-effective for the synthesis of NiMoO{sub 4} has been successfully developed. It was demonstrated that proper design in synthetic strategy for grinding plays a crucial role in determining the ultimate polymorph of NiMoO{sub 4}. Specifically, direct grinding (DG) of MoO{sub 3} and NiO rendered {alpha}-NiMoO{sub 4} after annealing, whereas sequential grinding (SG) of the two independently pre-ground oxides followed by annealing generated {beta}-NiMoO{sub 4} solid solution. Characterizations in terms of Raman and X-ray diffraction suggest the creation of {beta}-NiMoO{sub 4} precursor in the latter alternative is the key aspect for the formationmore » of {beta}-NiMoO{sub 4}. The DG-derived {alpha}-NiMoO{sub 4} tested by oxidative dehydrogenation of propane exhibited superior activity in contrast to its analog synthesized via conventional coprecipitation. It is suggested that the favorable chemical composition facilely obtained via grinding in contrast to that by coprecipitation was essential for achieving a more selective production of propylene. - Graphical Abstract: Grinding-assisted synthesis of NiMoO{sub 4} offers higher and more reproducible activities in contrast to coprecipitation for oxidative dehydrogenation of propane, and both {alpha}- and {beta}-NiMoO{sub 4} can be synthesized. Highlights: Black-Right-Pointing-Pointer NiMoO{sub 4} was prepared through grinding-assisted pathway. Black-Right-Pointing-Pointer Direct/sequential grinding rendered {alpha}-, {beta}-NiMoO{sub 4}, respectively. Black-Right-Pointing-Pointer Grinding-derived {alpha}-NiMoO{sub 4} showed high and reproducible activity for oxidative dehydrogenation of propane.« less

  20. Electron transport in nanocrystalline SiC films obtained by direct ion deposition

    NASA Astrophysics Data System (ADS)

    Kozlovskyi, A.; Semenov, A.; Skorik, S.

    2016-12-01

    Electrical conductivity of nanocrystalline SiC films obtained by direct ion deposition was investigated within the temperature interval from 2 to 770 K. It were investigated the samples of films with 3С-SiC polytype structure and the heteropolytype films formed by layers of different polytypes SiC (3C-SiC/21R-SiC, 21R-SiC/27R-SiC, 3C-SiC/15R-SiC). The films had n-type conductivity that ensured a small excess of silicon ions. The thermally activated character of electron transport in the 3С-SiC polytype films was established. In the heteropolytype films the temperature dependence of the electrical resistance was described by the relation R(T) = R0 × exp[-kT/E0]. It was shown that the charge transport mechanism in the heteropolytype samples is electron tunneling through potential barriers formed by the conduction band offset in the contact region of the heterojunction. Tunnel charge transport occurs due to the presence of discrete energy states in the forbidden band caused the dimensional quantization.

  1. Solvothermal synthesis of nanocrystalline TiO 2 in toluene with surfactant

    NASA Astrophysics Data System (ADS)

    Kim, Chung-Sik; Moon, Byung Kee; Park, Jong-Ho; Choi, Byung-Chun; Seo, Hyo-Jin

    2003-10-01

    Synthesis of narrow-dispersed nanocrystalline TiO 2 was investigated by surfactant-aided solvothermal synthetic method in toluene solutions. Titanium isopropoxide (TIP) was used as precursor, which was decomposed at high temperature in the surfactant-dissolved solution. After the solution was thermally treated at 250°C for 20 h in an autoclave, low-dispersed TiO 2 nanocrystalline particles with average size of <6 nm were synthesized. When sufficient amount of TIP or surfactant was added in the solution, long dumbbell-shaped nanorods were formed, which may be due to the oriented growth of particles along [0 0 1] axis. Characterization of products was investigated by X-ray diffraction and transmission electron microscopy.

  2. Material properties of perovskites in the quasi-ternary system LaFeO3-LaCoO3-LaNiO3

    NASA Astrophysics Data System (ADS)

    Tietz, F.; Arul Raj, I.; Ma, Q.; Baumann, S.; Mahmoud, A.; Hermann, R. P.

    2016-05-01

    An overview is presented on the variation of electrical conductivity, oxygen permeation, and thermal expansion coefficient as a function of the composition of perovskites in the quasi-ternary system LaFeO3-LaCoO3-LaNiO3. Powders of thirteen nominal perovskite compositions were synthesized under identical conditions by the Pechini method. The powder X-ray diffraction data of two series, namely La(Ni0.5Fe0.5)1-xCoxO3 and LaNi0.5-xFexCo0.5O3, are presented after the powders had been sintered at 1100 °C for 6 h in air. The measurements revealed a rhombohedral structure for all compositions except LaNi0.5Fe0.5O3 for which 60% rhombohedral and 40% orthorhombic phase was found. The maximum DC electrical conductivity value of the perovskites at 800 °C was 1229 S cm-1 for the composition LaCoO3 and the minimum was 91 S cm-1 for the composition LaCo0.5Fe0.5O3. The oxygen permeation of samples with promising conductivities at 800 °C was one order of magnitude lower than that of La0.6Sr0.4Co0.8Fe0.2O3 (LSCF). The highest value of 0.017 ml cm-2 min-1 at 950 °C was obtained with LaNi0.5Co0.5O3. The coefficients of thermal expansion varied in the range of 13.2×10-6 K-1 and 21.9×10-6 K-1 for LaNi0.5Fe0.5O3 and LaCoO3, respectively. 57Fe Mössbauer spectroscopy was used as probe for the oxidation states, local environment and magnetic properties of iron ions as a function of chemical composition. The substitution had a great influence on the chemical properties of the materials.

  3. Production of nanocrystalline metal powders via combustion reaction synthesis

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Frye, John G.; Weil, Kenneth Scott; Lavender, Curt A.

    Nanocrystalline metal powders comprising tungsten, molybdenum, rhenium and/or niobium can be synthesized using a combustion reaction. Methods for synthesizing the nanocrystalline metal powders are characterized by forming a combustion synthesis solution by dissolving in water an oxidizer, a fuel, and a base-soluble, ammonium precursor of tungsten, molybdenum, rhenium, or niobium in amounts that yield a stoichiometric burn when combusted. The combustion synthesis solution is then heated to a temperature sufficient to substantially remove water and to initiate a self-sustaining combustion reaction. The resulting powder can be subsequently reduced to metal form by heating in a reducing gas environment.

  4. Improvement of the magnetic moment of NiZn ferrites induced by substitution of Nd3+ ions for Fe3+ ions

    NASA Astrophysics Data System (ADS)

    Wu, Xuehang; Chen, Wen; Wu, Wenwei; Wu, Juan; Wang, Qing

    2018-05-01

    Four types of Ni-Zn based ferrites materials having the general formula Ni0.5Zn0.5NdxFe2-xO4 (0.0 ≤ x ≤ 0.12) have been successfully synthesized by calcining oxalates in air and the influence of Nd content on the structure and magnetic properties of Ni0.5Zn0.5NdxFe2-xO4 is studied. X-ray diffraction examination confirms that a high-crystallized Ni0.5Zn0.5NdxFe2-xO4 with cubic spinel structure is obtained when the precursor is calcined at 1000 °C in air for 2 h. The substitutions of Nd3+ ions for partial Fe3+ ions do not change the spinel crystalline structure of MFe2O4. The incorporation of Nd3+ ions in place of Fe3+ ions in Ni-Zn ferrites increases the average crystallite size. Specific saturation magnetization decreases with increase in Nd content. This is because Nd3+ ions with smaller magnetic moment preferentially fill the octahedral sites. In addition, antiferromagnetic FeNdO3 increases with increase in Nd content. In this study, Ni0.5Zn0.5Nd0.08Fe1.92O4, calcined at 1000 °C, exhibits the highest magnetic moment (4.2954 μB) and the lowest coercivity (28.82 Oe).

  5. 3D Reticular Li1.2Ni0.2Mn0.6O2 Cathode Material for Lithium-Ion Batteries.

    PubMed

    Li, Li; Wang, Lecai; Zhang, Xiaoxiao; Xue, Qing; Wei, Lei; Wu, Feng; Chen, Renjie

    2017-01-18

    In this study, a hard-templating route was developed to synthesize a 3D reticular Li 1.2 Ni 0.2 Mn 0.6 O 2 cathode material using ordered mesoporous silica as the hard template. The synthesized 3D reticular Li 1.2 Ni 0.2 Mn 0.6 O 2 microparticles consisted of two interlaced 3D nanonetworks and a mesopore channel system. When used as the cathode material in a lithium-ion battery, the as-synthesized 3D reticular Li 1.2 Ni 0.2 Mn 0.6 O 2 exhibited remarkably enhanced electrochemical performance, namely, superior rate capability and better cycling stability than those of its bulk counterpart. Specifically, a high discharge capacity of 195.6 mA h g -1 at 1 C with 95.6% capacity retention after 50 cycles was achieved with the 3D reticular Li 1.2 Ni 0.2 Mn 0.6 O 2 . A high discharge capacity of 135.7 mA h g -1 even at a high current of 1000 mA g -1 was also obtained. This excellent electrochemical performance of the 3D reticular Li 1.2 Ni 0.2 Mn 0.6 O 2 is attributed to its designed structure, which provided nanoscale lithium pathways, large specific surface area, good thermal and mechanical stability, and easy access to the material center.

  6. Oxidant effect of La(NO3)3·6H2O solution on the crystalline characteristics of nanocrystalline ZrO2 films grown by atomic layer deposition

    NASA Astrophysics Data System (ADS)

    Oh, Nam Khen; Kim, Jin-Tae; Kang, Goru; An, Jong-Ki; Nam, Minwoo; Kim, So Yeon; Park, In-Sung; Yun, Ju-Young

    2017-02-01

    Nanocrystalline ZrO2 films were synthesized by atomic layer deposition method using CpZr[N(CH3)2]3 (Cp = C5H5) as the metal precursor and La(NO3)3·6H2O solution as the oxygen source. La element in the deposited ZrO2 films could not be detected as its content was below the resolution limit of the X-ray photoelectron spectroscopy. The alternative introduction of La(NO3)3·6H2O solution to conventionally used H2O as the oxidant effectively altered the crystalline structure, grain size, and surface roughness of the grown ZrO2 films. Specifically, the crystalline structure of the ZrO2 film changed from a mixture of tetragonal and monoclinic phases to monoclinic phase. The average grain size also increased, and the resulting film surface became rougher. The average grain sizes of the ZrO2 films prepared from La(NO3)3·6H2O solution at concentrations of 10, 20, 30, and 40% were 280, 256, 208, and 200 nm, respectively, whereas that prepared using H2O oxidant was 142 nm. However, the concentration of La(NO3)3·6H2O solution minimally influenced the crystalline characteristics of the nanocrystalline ZrO2 films i.e., the crystalline structure, grain size, and surface roughness except for crystallite size.

  7. Mechanical properties, microstructure and thermal stability of a nanocrystalline CoCrFeMnNi high-entropy alloy after severe plastic deformation

    DOE PAGES

    Schuh, B.; Mendez-Martin, F.; Völker, B.; ...

    2015-06-24

    An equiatomic CoCrFeMnNi high-entropy alloy (HEA), produced by arc melting and drop casting, was subjected to severe plastic deformation (SPD) using high-pressure torsion. This process induced substantial grain refinement in the coarse-grained casting leading to a grain size of approximately 50 nm. As a result, strength increased significantly to 1950 MPa, and hardness to similar to 520 MV. Analyses using transmission electron microscopy (TEM) and 3-dimensional atom probe tomography (3D-APT) showed that, after SPD, the alloy remained a true single-phase solid solution down to the atomic scale. Subsequent investigations characterized the evolution of mechanical properties and microstructure of this nanocrystallinemore » HEA upon annealing. Isochronal (for 1 h) and isothermal heat treatments were performed followed by microhardness and tensile tests. The isochronal anneals led to a marked hardness increase with a maximum hardness of similar to 630 HV at about 450 degrees C before softening set in at higher temperatures. The isothermal anneals, performed at this peak hardness temperature, revealed an additional hardness rise to a maximum of about 910 MV after 100 h. To clarify this unexpected annealing response, comprehensive microstructural analyses were performed using TEM and 3D-APT. New nano-scale phases were observed to form in the originally single-phase HEA. After times as short as 5 min at 450 degrees C, a NiMn phase and Cr-rich phase formed. With increasing annealing time, their volume fractions increased and a third phase, FeCo, also formed. It appears that the surfeit of grain boundaries in the nanocrystalline HEA offer many fast diffusion pathways and nucleation sites to facilitate this phase decomposition. The hardness increase, especially for the longer annealing times, can be attributed to these nano-scaled phases embedded in the HEA matrix. The present results give new valuable insights into the phase stability of single-phase high-entropy alloys as

  8. MgCoAl and NiCoAl LDHs synthesized by the hydrothermal urea hydrolysis method: Structural characterization and thermal decomposition

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Chagas, L.H., E-mail: lhchagas-prometro@inmetro.gov.br; Instituto Nacional de Metrologia Qualidade e Tecnologia, Divisão de Metrologia de Materiais, 25250-020 Duque de Caxias, RJ; De Carvalho, G.S.G.

    Highlights: • We synthesized MgCoAl and NiCoAl LDHs by the urea hydrolysis method. • Aluminum rich and crystalline materials have been formed. • The calcination of the LDHs generated mixed oxides with high surface areas. - Abstract: Layered double hydroxides (LDHs) with Mg/Co/Al and Ni/Co/Al were synthesized for the first time by the urea hydrolysis method. The experimental conditions promoted aluminum rich and crystalline materials. The formation of LDHs was investigated by powder X-ray diffraction (XRD), chemical analysis, solid state nuclear magnetic resonance with magic angle spinning ({sup 27}Al-MAS-NMR), simultaneous thermogravimetric/differential thermal analysis (TGA/DTA), FTIR spectroscopy, scanning electron microscopy (SEM),more » and N{sub 2} adsorption–desorption experiments. A single phase corresponding to LDH could be obtained in all the investigated compositions. Thermal calcination of these LDHs at 500 °C resulted in the formation of solid solutions in which Al{sup 3+} was dissolved. All the calcined materials have rock-salt like structures and high surface areas.« less

  9. Structural, optical, and magnetic properties of Cu- and Ni-codoped CdO dilute magnetic nanocrystalline semiconductor: effect of hydrogen post-treatment

    NASA Astrophysics Data System (ADS)

    Dakhel, A. A.; Bououdina, M.

    2015-06-01

    Cadmium oxide codoped with Cu and Ni ions powders was synthesised by thermal co-decomposition of a mixture of cadmium, copper, and nickel acetylacetonates. The mass ratio of Cu/Cd was fixed, while the Ni/Cd mass ratio was varied systematically. The purpose of the present study is to prepare powders having room-temperature ferromagnetic (RT-FM) properties. X-ray fluorescence (XRF) and X-ray diffraction (XRD) confirm the purity and the formation of single nanocrystalline structure of the as-prepared powders. The energy bandgap of the as-prepared powders was found to vary slightly and then increases by 3.96-38.02 % after post-H2-treatment. Magnetic measurements reveal that all as-prepared doped CdO powders gained partial (RT-FM) properties. Furthermore, the created RT-FM is dependent on the Ni% doping level. After annealing under H2 gas, a strong enhancement of RT-FM was observed, especially for 1.2 % Ni-doping-level powder where the whole powder became ferromagnetic with coercivity, remanence, and saturation magnetisation of 249.2 Oe, 4.52 memu/g, and 14.57 memu/g, respectively, representing an increase by ~241.3, 1062, and 1700 %, respectively, in comparison with the as-prepared sample. Thus, it was proved, for the first time, the possibility of producing of codoped CdO with RT-FM, where the magnetic characteristics can be tailored by doping and post-treatment under H2 atmosphere, thus a new potential candidate for dilute magnetic semiconductor (DMS).

  10. Blending Cr 2O 3 into a NiO-Ni electrocatalyst for sustained water splitting

    DOE PAGES

    Gong, Ming; Zhou, Wu; Kenney, Michael James; ...

    2015-08-24

    The rising H 2 economy demands active and durable electrocatalysts based on low-cost, earth-abundant materials for water electrolysis/photolysis. Here we report nanoscale Ni metal cores over-coated by a Cr 2O 3-blended NiO layer synthesized on metallic foam substrates. The Ni@NiO/Cr 2O 3 triphase material exhibits superior activity and stability similar to Pt for the hydrogen-evolution reaction in basic solutions. The chemically stable Cr 2O 3 is crucial for preventing oxidation of the Ni core, maintaining abundant NiO/Ni interfaces as catalytically active sites in the heterostructure and thus imparting high stability to the hydrogen-evolution catalyst. The highly active and stable electrocatalystmore » enables an alkaline electrolyzer operating at 20 mA cm –2 at a voltage lower than 1.5 V, lasting longer than 3 weeks without decay. Thus, the non-precious metal catalysts afford a high efficiency of about 15 % for light-driven water splitting using GaAs solar cells.« less

  11. Multifunctionality of nanocrystalline lanthanum ferrite

    NASA Astrophysics Data System (ADS)

    Rai, Atma; Thakur, Awalendra K.

    2016-05-01

    Nanocrystalline lanthanum ferrite has been synthesized by adopting modified Pechini route. No evidence of impurity or secondary phase has been detected up to the detection of error limit of X-ray diffractometer (XRD). Rietveld refinement of X-ray diffraction pattern reveals orthorhombic crystal system with space group Pnma (62).Crystallite size and lattice strain was found to be ˜42.8nm and 0.306% respectively. Optical band gap was found to be 2.109 eV, by UV-Visible diffused reflectance spectrum (DRS). Brunauer-Emmet-Teller (BET) surface area was found to be ˜3.45 m2/g. Magnetization-hysteresis (M-H) loop was recorded at room temperature (300K) reveals weak ferromagnetism in Nanocrystalline lanthanum ferrite. The weak ferromagnetism in lanthanum ferrite is due to the uncompensated antiferromagnetic spin ordering. Ferroelectric loop hysteresis observed at room temperature at 100Hz depicts the presence of ferroelectric ordering in LaFeO3.Simultanious presence of magnetic and ferroelectric ordering at room temperature makes it suitable candidate of Multiferroic family.

  12. Multifunctionality of nanocrystalline lanthanum ferrite

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Rai, Atma, E-mail: atma@iitp.ac.in; Thakur, Awalendra K.; Centre for Energy and Environment, Indian Institute of Technology Patna 800013 India

    2016-05-06

    Nanocrystalline lanthanum ferrite has been synthesized by adopting modified Pechini route. No evidence of impurity or secondary phase has been detected up to the detection of error limit of X-ray diffractometer (XRD). Rietveld refinement of X-ray diffraction pattern reveals orthorhombic crystal system with space group Pnma (62).Crystallite size and lattice strain was found to be ∼42.8nm and 0.306% respectively. Optical band gap was found to be 2.109 eV, by UV-Visible diffused reflectance spectrum (DRS). Brunauer-Emmet-Teller (BET) surface area was found to be ∼3.45 m{sup 2}/g. Magnetization-hysteresis (M-H) loop was recorded at room temperature (300K) reveals weak ferromagnetism in Nanocrystalline lanthanummore » ferrite. The weak ferromagnetism in lanthanum ferrite is due to the uncompensated antiferromagnetic spin ordering. Ferroelectric loop hysteresis observed at room temperature at 100Hz depicts the presence of ferroelectric ordering in LaFeO{sub 3}.Simultanious presence of magnetic and ferroelectric ordering at room temperature makes it suitable candidate of Multiferroic family.« less

  13. Tuning the magnetocaloric properties of La0.7Ca0.3MnO3 manganites through Ni-doping

    NASA Astrophysics Data System (ADS)

    Gómez, A.; Chavarriaga, E.; Supelano, I.; Parra, C. A.; Morán, O.

    2018-04-01

    The effect of Ni2+ doping on the magnetic and magnetocaloric properties of La0.7Ca0.3MnO3 manganites synthesized via the auto-combustion method is reported. The aim of studying Ni2+-substituted La0.7Ca0.3Mn1 - xNixO3 (x = 0 , 0.02 , 0.07, and 0.1) manganites was to explore the possibility of increasing the operating temperature range for the magnetocaloric effect through tuning of the magnetic transition temperature. X-ray diffraction analysis confirmed the phase purity of the synthesized samples. The substitution of Mn3+ ions by Ni2+ ions in the La0.7Ca0.3MnO3 lattice was also corroborated through this technique. The dependence of the magnetization on the temperature reveals that all the compositions exhibit a well-defined ferromagnetic to paramagnetic transition near the Curie temperature. A systematic decrease in the values of the Curie temperature is clearly observed upon Ni2+ doping. Probably the replacement of Mn3+ by Ni2+ ions in the La0.7Ca0.3MnO3 lattice weakens the Mn3+-O-Mn4+ double exchange interaction, which leads to a decrease in the transition temperature and the magnetic moment in the samples. By using Arrott plots, it was found that the phase transition from ferromagnetic to paramagnetic is second order. The maximum magnetic entropy changes observed for the x = 0 , 0.02 , 0.07, and 0.1 composites was 0.85, 0.77, 0.63, and 0.59 J/kg K, respectively, under a magnetic field of 1.5 T. In general, it was verified that the magnetic entropy change achieved for La0.7Ca0.3Mn1 - xNixO3 manganites synthesized via the auto-combustion method is higher than those reported for other manganites with comparable Ni2+-doping levels synthesized via standard solid state reaction. The addition of Ni2+ increases the value of the relative cooling power as compared to that of the parent compound. The highest value of this parameter (∼60 J/kg) is found for a Ni-doping level of 2% around 230 K in a field of 1.5 T.

  14. The 1200 C cyclic oxidation behavior of two nickel-aluminum alloys (Ni3AL and NiAl) with additions of chromium, silicon, and titanium

    NASA Technical Reports Server (NTRS)

    Lowell, C. E.; Santoro, G. J.

    1972-01-01

    The alloys Ni3Al and NiAl with and without 1 and 3 atomic percent chromium, silicon, and titanium replacing the aluminum were cyclically oxidized at 1200 C for times to 200 hours, and the results were compared with those obtained with the alloy B-1900 subjected to the same oxidation process. The evaluation was based on metal recession, specific weight change, metallography, electron microprobe analysis, and X-ray diffraction. The oxidation resistance of Ni3Al was improved by Si, unaffected by Ti, and degraded by Cr. The oxidation resistance of NiAl was slightly improved by Ti, unaffected by Si, and degraded by Cr. The oxidation resistance of Ni3Al with 1 atomic percent Si was nearly equal to that of NiAl. Alloy B-1900 exhibited oxidation resistance comparable to that of Ni3Al + Cr compositions.

  15. Gas response properties of citrate gel synthesized nanocrystalline MgFe{sub 2}O{sub 4}: Effect of sintering temperature

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Patil, J.Y.; Mulla, I.S.; Suryavanshi, S.S., E-mail: sssuryavanshi@rediffmail.com

    2013-02-15

    Graphical abstract: Display Omitted Highlights: ► Synthesis of nanocrystalline MgFe{sub 2}O{sub 4} by economical citrate gel combustion method. ► Structural, morphological, and gas response properties of MgFe{sub 2}O{sub 4}. ► Enhancement in selectivity of MgFe{sub 2}O{sub 4} towards LPG with sintering temperature. ► Use of MgFe{sub 2}O{sub 4} to detect different gases at different operating temperatures. -- Abstract: Spinel type MgFe{sub 2}O{sub 4} material was synthesized by citrate gel combustion method. The effect of sintering temperature on structural, morphological, and gas response properties was studied. The powder X-ray diffraction pattern and transmission electron microscope study confirms nanocrystalline spinel structure ofmore » the synthesized powder. The material was tested for response properties to various reducing gases like liquid petroleum gas (LPG), acetone, ethanol, and ammonia. The results demonstrated n-type semiconducting behavior of MgFe{sub 2}O{sub 4} material. It was revealed that MgFe{sub 2}O{sub 4} sintered at 973 K was most sensitive to LPG at 648 K and to acetone at 498 K. However MgFe{sub 2}O{sub 4} sintered at 1173 K exhibited higher response and selectivity to LPG with marginal increase in the operating temperature. Furthermore, the sensor exhibited a fast response and a good recovery. It was observed that the particles size, porosity, and surface activity of the sensor material is affected by the sintering temperature.« less

  16. High rate performance of LiNi{sub 1/3}Co{sub 1/3}Mn{sub 1/3}O{sub 2} cathode material synthesized by a carbon gel–combustion process for lithium ion batteries

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Chen, Jian, E-mail: chemcj@126.com; Zhao, Na; Li, Guo-Dong, E-mail: lgd@jlu.edu.cn

    2016-01-15

    Graphical abstract: The cycling stability of the LiNi{sub 1/3}Co{sub 1/3}Mn{sub 1/3}O{sub 2} electrode was investigated at different discharge rates from 5 C to 50 C. - Highlights: • The LiNi{sub 1/3}Co{sub 1/3}Mn{sub 1/3}O{sub 2} was prepared via a carbon gel–combustion process. • The sample showed high purity and nanosized particles. • The LiNi{sub 1/3}Co{sub 1/3}Mn{sub 1/3}O{sub 2} electrode shows excellent rate capability and cyclic performance. - Abstract: The LiNi{sub 1/3}Co{sub 1/3}Mn{sub 1/3}O{sub 2} electrode material was prepared via a carbon gel–combustion process using resorcinol–formaldehyde gel as fuel and nitrate as an oxidizer. The carbon gel process ensures the molecular-level homogeneitymore » of the chemical product. The gas derived from carbon gel separates the raw material particles and restrains the growth of the grains to some extent, and well-crystallized nanosized powders are obtained with calcination at 700 °C for 6 h. As the cathode material for lithium-ion batteries, the discharge capacity of LiNi{sub 1/3}Co{sub 1/3}Mn{sub 1/3}O{sub 2} was as high as 175.6 mA h g{sup −1} in the first cycle at 0.5 C, and it could remain 163.0 mA h g{sup −1} within the voltage range of 2.5–4.4 V after 50 cycles. The electrode also showed outstanding rate capacities at high discharge rates such as 30 C and 50 C, suggesting the applications of the material in high power lithium-ion batteries.« less

  17. Ni Foam-Ni3 S2 @Ni(OH)2 -Graphene Sandwich Structure Electrode Materials: Facile Synthesis and High Supercapacitor Performance.

    PubMed

    Wang, Xiaobing; Hu, Jiangjiang; Su, Yichang; Hao, Jin; Liu, Fanggang; Han, Shuang; An, Jian; Lian, Jianshe

    2017-03-23

    A novel Ni foam-Ni 3 S 2 @Ni(OH) 2 -graphene sandwich-structured electrode (NF-NN-G) with high areal mass loading (8.33 mg cm -2 ) has been developed by sulfidation and hydrolysis reactions. The conductivity of Ni 3 S 2 and Ni(OH) 2 were both improved. The upper layer of Ni(OH) 2 , covered with a thin graphene film, is formed in situ from the surface of the lower layer of Ni 3 S 2 , whereas the Ni 3 S 2 grown on Ni foam substrate mainly acts as a rough support bridging the Ni(OH) 2 and Ni foam. The graphene stabilized the Ni(OH) 2 and the electrochemical properties were effectively enhanced. The as-synthesized NF-NN-G-5mg electrode shows a high specific capacitance (2258 F g -1 at 1 A g -1 or 18.81 F cm -2 at 8.33 mA cm -2 ) and an outstanding rate property (1010 F g -1 at 20 Ag -1 or 8.413 F cm -2 at 166.6 mA cm -2 ). This result is around double the capacitance achieved in previous research on Ni 3 S 2 @Ni(OH) 2 /3DGN composites (3DGN=three-dimensional graphene network). In addition, the as-fabricated NF-NN-G-5mg composite electrode has an excellent cycle life with no capacitance loss after 3000 cycles, indicating a potential application as an efficient electrode. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  18. Structural and magnetic properties of nanocrystalline NiFe2O4 thin film prepared by spray pyrolysis technique

    NASA Astrophysics Data System (ADS)

    Chavan, Apparao R.; Chilwar, R. R.; Shisode, M. V.; Hivrekar, Mahesh M.; Mande, V. K.; Jadhav, K. M.

    2018-05-01

    The nanocrystalline NiFe2O4 thin film has been prepared using a spray pyrolysis technique on glass substrate. The prepared thin film was characterized by using X-ray diffraction (XRD), Fourier transform Infrared spectroscopy (FTIR), and Field Emission-Scanning Electron Microscopy (FE-SEM) characterization techniques for the structural and microstructural analysis. The magnetic property was measured using vibrating sample magnetometer (VSM) at room temperature. X-ray diffraction studies show the formation of single phase spinel structure of the thin film. The octahedral and tetrahedral vibration in the sample was studied by Fourier transform infrared (FT-IR) spectra. Magnetic hysteresis loop was recorded for thin film at room temperature. At 15 kOe, saturation magnetization (Ms) was found to increase while coercivity (Hc) decreases with thickness of the NiFe2O4 thin film.

  19. Model for temperature-dependent magnetization of nanocrystalline materials

    NASA Astrophysics Data System (ADS)

    Bian, Q.; Niewczas, M.

    2015-01-01

    A magnetization model of nanocrystalline materials incorporating intragrain anisotropies, intergrain interactions, and texture effects has been extended to include the thermal fluctuations. The method relies on the stochastic Landau-Lifshitz-Gilbert theory of magnetization dynamics and permits to study the magnetic properties of nanocrystalline materials at arbitrary temperature below the Currie temperature. The model has been used to determine the intergrain exchange constant and grain boundary anisotropy constant of nanocrystalline Ni at 100 K and 298 K. It is found that the thermal fluctuations suppress the strength of the intergrain exchange coupling and also reduce the grain boundary anisotropy. In comparison with its value at 2 K, the interparticle exchange constant decreases by 16% and 42% and the grain boundary anisotropy constant decreases by 28% and 40% at 100 K and 298 K, respectively. An application of the model to study the grain size-dependent magnetization indicates that when the thermal activation energy is comparable to the free energy of grains, the decrease in the grain size leads to the decrease in the magnetic permeability and saturation magnetization. The mechanism by which the grain size influences the magnetic properties of nc-Ni is discussed.

  20. Phase Structures and Magnetic Properties of Graphite Nanosheets and Ni-Graphite Nanocomposite Synthesized by Electrical Explosion of Wire in Liquid

    NASA Astrophysics Data System (ADS)

    Nguyen, Minh-Thuyet; Kim, Jin-Hyung; Lee, Jung-Goo; Kim, Jin-Chun

    2018-03-01

    The present work studied on phases and magnetic properties of graphite nanosheets and Ni-graphite nanocomposite synthesized using the electrical explosion of wire (EEW) in ethanol. X-ray diffraction and field emission scanning electron microscope were used to investigate the phases and the morphology of the nanopowders obtained. It was found that graphite nanosheets were absolutely fabricated by EEW with a thickness of 29 nm and 3 μm diameter. The as-synthesized Ni-graphite composite powders had a Ni-coating on the surfaces of graphite sheets. The hysteresis loop of the as-exploded, the hydrogen-treated composite nanopowders and the sintered samples were examined with a vibrating sample magnetometer at room temperature. The Ni-graphite composite exposed the magnetic behaviors which are attributed to Ni component. The magnetic properties of composite had the improvement from 10.2 emu/g for the as-exploded powders to 15.8 emu/g for heat-treated powders and 49.16 emu/g for sintered samples.

  1. Hydrogenation thermodynamics of melt-spun magnesium rich Mg-Ni nanocrystalline alloys with the addition of multiwalled carbon nanotubes and TiF3

    NASA Astrophysics Data System (ADS)

    Hou, Xiaojiang; Hu, Rui; Zhang, Tiebang; Kou, Hongchao; Li, Jinshan

    2016-02-01

    Based on the complexity of hydrogen absorption/desorption process and from the perspective of overall control, the as-cast Mg-10wt%Ni (Mg10Ni) alloy has been successively optimized by melt-spinning and surface catalyzed to realize the internal refinement as well as surface modification. The isothermal hydrogenation behavior of modified Mg-rich alloys has been investigated in this work. The results indicate that melt-spun Mg10Ni catalyzed by multiwalled carbon nanotubes (MWCNTs) coupling with TiF3 possesses superior activation properties and can absorb 6.23 wt% at 250 °C under 2.5 MPa. It is worth mentioning that the hydrogenation capacities of Mg10Ni-MWCNTs-TiF3 are 5.93 wt% and 5.99 wt% within the initial 1 min and 5 min, respectively. Meanwhile, the catalytic effect of MWCNTs and TiF3 has been discussed. The improved activation performance as well as the thermodynamics properties of Mg10Ni catalyzed by MWCNTs and TiF3 is attributed to the synergistic effect on dissociation of H2 molecules, diffusion of H-atoms and heterogeneous nucleation of hydrides.

  2. Synthesis, spectroscopic, magnetic and thermal properties of bimetallic salts, [Ni(L)][MCl4] [where M=Co(II), Zn(II), Hg(II) and L=3,7-bis(2-aminoethyl)-1,3,5,7-tetraazabicyclo(3.3.1)nonane]. X-ray structure of [Ni(L)][CoCl4].

    PubMed

    Nami, Shahab A A; Husain, Ahmad; Siddiqi, K S; Westcott, Barry L; Kopp-Vaughn, Kristin

    2010-01-01

    New bimetallic complex salts corresponding to the formulation [Ni(L)][MCl(4)] have been synthesized by the facile reaction between [Ni(L)](ClO(4))(2) and [MCl(2)(PPh(3))(2)] in high yields [where M=Co(II), Zn(II), Hg(II) and L=3,7-bis(2-aminoethyl)-1,3,5,7-tetraazabicyclo(3.3.1)nonane]. The complexes were characterized by IR, electronic spectra, TGA/DSC, magnetic moment and conductivity measurements. The X-ray crystal structure for [Ni(L)][CoCl(4)] clearly establishes the cationic-anionic interaction. It crystallizes in the space group P1 with unit cell dimensions a=7.1740(15)A, b=8.1583(16)A and c=8.3102(16)A. A square-planar geometry is evident for the [Ni(L)](2+) cation while the anion is found to be tetrahedral. A two-step thermolytic pattern is observed in the pyrolysis of the bimetallic complex salts. Copyright 2009 Elsevier B.V. All rights reserved.

  3. Cs0.9Ni3.1Se3: A Ni-Based Quasi-One-Dimensional Conductor with Spin-Glass Behavior.

    PubMed

    Sun, Fan; Guo, Zhongnan; Liu, Ning; Wu, Dan; Lin, Jiawei; Cheng, Erjian; Ying, Tianping; Li, Shiyan; Yuan, Wenxia

    2018-04-02

    In this work, we report the discovery of a new Ni-based quasi-one-dimensional selenide: Cs 0.9 Ni 3.1 Se 3 . This compound adopts the TlFe 3 Te 3 -type structure with space group P6 3 / m, which consists of infinite [Ni 3 Se 3 ] chains with face-sharing Ni 6 octahedra along the c direction. The lattice parameters are calculated as a = 9.26301(4) Å and c = 4.34272(2) Å, with the Ni-Ni distance in the ab plane as 2.582(3) Å, suggesting the formation of a Ni-Ni metallic bond in this compound. Interestingly, it has been found that Cs 0.9 Ni 3.1 Se 3 is nonstoichiometric, which is different from the other TlFe 3 Te 3 -type phases reported so far. Structure refinement shows that the extra Ni atom in the structure may occupy the 2c site, together with Cs atoms. Cs 0.9 Ni 3.1 Se 3 shows metallic behavior with monotonously decreased resistivity with temperatures from 300 to 0.5 K. Measurements on the magnetic susceptibility display a spin-glass state below 7 K. The specific heat curve gives a Sommerfeld coefficient of 14.6 mJ·K -2 ·mol -1 and a Debye temperature of 143.6 K. The discovery of this new compound enriches the diversity of low-dimensional materials in a transition-metal-based family and also sheds light on the structure-property relationship of this system.

  4. Synthesis and Characterization of Polyol-Assisted Nano Cu0.2Ni0.2Sn0.2Ba0.4 Fe2O4 by a Wet Hydroxyl Route

    NASA Astrophysics Data System (ADS)

    Pavithradevi, S.; Suriyanarayanan, N.; Boobalan, T.; Velumani, S.; Chandramohan, M.; Manivel Raja, M.

    2017-08-01

    Nanocrystalline spinel ferrite of composition Cu0.2Ni0.2Sn0.2Ba0.4 Fe2O4 has been synthesized by a wet hydroxyl chemical route in ethylene glycol as chelating agent and sodium hydroxide as precipitator at pH 8. Ethylene glycol has been used as the medium which serves as the solvent as well as a complexing agent. The synthesized particles are annealed at temperatures of 350°C, 700°C, and 1050°C. Thermogravimetric (TG) analysis confirms that at 240°C, ethylene glycol has evaporated completely, and a stable phase is formed above 670°C. Fourier transform infrared (FT-IR) spectroscopy of mixed Cu0.2Ni0.2Sn0.2Ba0.4 ferrite nanoparticles like as synthesized and annealed at 1050°C are recorded between 400 cm-1 and 4000 cm-1. FT-IR appraises the structural formation of Cu0.2Ni0.2Sn0.2Ba0.4 Fe2O4 between the as-synthesized sample and the sample annealed at 1050°C. Structural characterizations of all the samples are carried out by x-ray diffraction (XRD) technique. XRD reveals that the particle size increases with the increase in annealing temperatures. Transmission electron microscopy (TEM) and scanning electron microscopy (SEM) confirms that the particles are flaky and spherical with the crystallite size in the range of 11-27 nm. The decrement of dielectric properties, like dielectric constant and dielectric loss, with the increment of frequency as seen in all the samples is an usual dielectric behavior of spinel ferrites. The lack of net magnetization is noticed immediately when the applied magnetic field is removed which prompts superparamagnetic behavior, as seen in all the samples.

  5. Synthesis and electrochemical properties of Li2/3Ni1/3Mn2/3O2 as a novel 5 V class positive electrode material for lithium-ion batteries

    NASA Astrophysics Data System (ADS)

    Chiba, Kazuki; Shikano, Masahiro; Sakaebe, Hikari

    2016-02-01

    A lithium nickel manganese oxide, O3-Li2/3Ni1/3Mn2/3O2, is synthesized from the precursor, P3-Na2/3Ni1/3Mn2/3O2, by a Na+/Li+ ion exchange reaction using molten salt. Post-heating at 300, 400, 500, 600, and 700 °C is carried out for 5 h in air. The products are characterized by powder XRD, inductively coupled plasma-atomic emission spectroscopy (ICP-AES), SEM, 6Li-magic-angle-spinning-NMR, and electrochemical measurements. The charge/discharge profiles of O3-Li2/3Ni1/3Mn2/3O2, thermally treated at 500 °C, show a high-potential plateau region at 4.8 V. Furthermore, sloping voltage profiles are observed at an average voltage of 3.21 V. An initial discharge capacity of 257 mA h g-1 is obtained between 2.0 and 4.8 V with a current density of 15 mA g-1 at 25 °C. This capacity corresponds to 0.90 electron transfers per formula unit. This study shows that Post-heating of O3-Li2/3Ni1/3Mn2/3O2 is effective to improve its electrochemical properties.

  6. Quantitative analysis of Ni2+/Ni3+ in Li[NixMnyCoz]O2 cathode materials: Non-linear least-squares fitting of XPS spectra

    NASA Astrophysics Data System (ADS)

    Fu, Zewei; Hu, Juntao; Hu, Wenlong; Yang, Shiyu; Luo, Yunfeng

    2018-05-01

    Quantitative analysis of Ni2+/Ni3+ using X-ray photoelectron spectroscopy (XPS) is important for evaluating the crystal structure and electrochemical performance of Lithium-nickel-cobalt-manganese oxide (Li[NixMnyCoz]O2, NMC). However, quantitative analysis based on Gaussian/Lorentzian (G/L) peak fitting suffers from the challenges of reproducibility and effectiveness. In this study, the Ni2+ and Ni3+ standard samples and a series of NMC samples with different Ni doping levels were synthesized. The Ni2+/Ni3+ ratios in NMC were quantitatively analyzed by non-linear least-squares fitting (NLLSF). Two Ni 2p overall spectra of synthesized Li [Ni0.33Mn0.33Co0.33]O2(NMC111) and bulk LiNiO2 were used as the Ni2+ and Ni3+ reference standards. Compared to G/L peak fitting, the fitting parameters required no adjustment, meaning that the spectral fitting process was free from operator dependence and the reproducibility was improved. Comparison of residual standard deviation (STD) showed that the fitting quality of NLLSF was superior to that of G/L peaks fitting. Overall, these findings confirmed the reproducibility and effectiveness of the NLLSF method in XPS quantitative analysis of Ni2+/Ni3+ ratio in Li[NixMnyCoz]O2 cathode materials.

  7. Synergetic interface between NiO/Ni3S2 nanosheets and carbon nanofiber as binder-free anode for highly reversible lithium storage

    NASA Astrophysics Data System (ADS)

    Jiang, Jialin; Ma, Chao; Yang, Yinbo; Ding, Jingjing; Ji, Hongmei; Shi, Shaojun; Yang, Gang

    2018-05-01

    A novel heterostructure of NiO/Ni3S2 nanoflake is synthesized and composited with carbon nanofibers (CNF) membrane. NiO/Ni3S2 nanoflakes are homogeneously dispersed in CNF network, herein, NiO/Ni3S2 like leaf and CNF like branch. Carbon nanofibers network efficiently prevents the pulverization and buffers the volume changes of NiO/Ni3S2, meanwhile, NiO/Ni3S2 nanoflakes through the conductive channels of carbon nanofibers own improved Li+ diffusion ability and structural stability. The capacity of NiO/Ni3S2/CNF reaches to 519.2 mA g-1 after 200 cycles at the current density of 0.5 A g-1 while NiO/Ni3S2 fades to 71 mAh g-1 after 40 cycles. Owing to the synergetic structure, the resultant binder-free electrode NiO/Ni3S2/carbon nanofibers shows an excellent reversible lithium storage capability.

  8. Material properties of perovskites in the quasi-ternary system LaFeO 3–LaCoO 3–LaNiO 3

    DOE PAGES

    Tietz, F.; Arul Raj, I.; Ma, Q.; ...

    2016-02-02

    We present an overview on the variation of electrical conductivity, oxygen permeation, oxygen surface exchange and thermal expansion coefficient as a function of the composition of perovskites in the quasi-ternary system LaFeO 3–LaCoO 3–LaNiO 3. Powders of thirteen nominal perovskite compositions were synthesized under identical conditions by the Pechini method. The powder X-ray diffraction data of two series, namely La(Ni 0.5Fe 0.5) 1-xCo xO 3 and LaNi 0.5- xFe xCo 0.5O 3, are presented after the powders had been sintered at 1100 C for 6 h in air. The measurements revealed a rhombohedral structure for all compositions except LaNi 0.5Femore » 0.5O 3 for which 60% rhombohedral and 40% orthorhombic phase was found. Moreover, the maximum DC electrical conductivity value of the perovskites at 800 C was 1229 S cm-1 for the composition LaCoO 3 and the minimum was 91 S cm-1 for the composition LaCo 0.5Fe 0.5O 3. The oxygen permeation of samples with promising conductivities at 800 C was one order of magnitude lower than that of La 0.6Sr 0.4Co 0.8Fe 0.2O 3 (LSCF). The highest value of 0.017 ml cm -2 min-1 at 950 C was obtained with LaNi 0.5Co 0.5O 3. The coefficients of thermal expansion varied in the range of 13.2 x 10 -6 K -1 and 21.9 x 10 -6 K -1 for LaNi 0.5Fe 0.5O 3 and LaCoO 3, respectively. 57Fe M ssbauer spectroscopy was used as probe for the oxidation states, local environment and magnetic properties of iron ions as a function of chemical composition. Ultimately, the substitution had a great influence on the chemical properties of the materials.« less

  9. Preparation method of Ni@Pt/C nanocatalyst affects the performance of direct borohydride-hydrogen peroxide fuel cell: Improved power density and increased catalytic oxidation of borohydride.

    PubMed

    Hosseini, Mir Ghasem; Mahmoodi, Raana

    2017-08-15

    The Ni@Pt/C electrocatalysts were synthesized using two different methods: with sodium dodecyl sulfate (SDS) and without SDS. The metal loading in synthesized nanocatalysts was 20wt% and the molar ratio of Ni: Pt was 1:1. The structural characterizations of Ni@Pt/C electrocatalysts were investigated by field emission scanning electron microscopy (FE-SEM), energy-dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), transmission electron microscopy (TEM) and high-resolution transmission electron microscopy (HR-TEM). The electrocatalytic activity of Ni@Pt/C electrocatalysts toward BH 4 - oxidation in alkaline medium was studied by means of cyclic voltammetry (CV), chronopotentiometry (CP), chronoamperometry (CA) and electrochemical impedance spectroscopy (EIS). The results showed that Ni@Pt/C electrocatalyst synthesized without SDS has superior catalytic activity toward borohydride oxidation (22016.92Ag Pt -1 ) in comparison with a catalyst prepared in the presence of SDS (17766.15Ag Pt -1 ) in NaBH 4 0.1M at 25°C. The Membrane Electrode Assembly (MEA) used in fuel cell set-up was fabricated with catalyst-coated membrane (CCM) technique. The effect of Ni@Pt/C catalysts prepared with two methods as anode catalyst on the performance of direct borohydride-hydrogen peroxide fuel cell was studied. The maximum power density was obtained using Ni@Pt/C catalyst synthesized without SDS at 60°C, 1M NaBH 4 and 2M H 2 O 2 (133.38mWcm -2 ). Copyright © 2017 Elsevier Inc. All rights reserved.

  10. Structural, morphological and optical properties of LiCo0.5Ni0.45Ag0.05O2 thin films

    NASA Astrophysics Data System (ADS)

    Haider, Adawiya J.; AL-Rsool, Rusul Abed; AL-Tabbakh, Ahmed A.; Al-Gebori, Abdul Nasser M.; Mohamed, Aliaa

    2018-05-01

    Pulsed Laser Deposition (PLD) method has been successfully used for the synthesized of nano-crystalline cathode m aterial LiCo0.5Ni0.45Ag0.05O2 (LCNAO) thin film. LCNAO Ferromagnetic using pulsed Nd-YAG laser with wavelength (λ = 532 nm) and duration (10 ns) and energy fluence (1.4 J/cm2) with different substrate temperature (100, 200, 300) ˚C and O2 pressure at 10 mbar. The structural, morphological and optical properties of the films were determined by X-ray Diffraction (XRD), Scan Electron Microscopy (SEM), Atomic Force microscope (AFM) and UV-VIS spectroscopy respectively. It is observed that partial layer to spinel transformation takes place during post annealing and the average particle size of the LiCo0.5Ni0.45Ag0.05O2 is found to be (1-12) nm from SEM measurement. Finally the optical properties of the thin films have been studied at different Substrate temperature. It found the energy gap decreases from 4.2 to 3.8 eV when the substrate's temperature increasing from 100° C into 300 °C of the LCNAO films. These mean that the optical quality of LCNAO films is improved due to the increase in crystalline size and reduction of defect sites.

  11. Transition from Irradiation-Induced Amorphization to Crystallization in Nanocrystalline Silicon Carbide

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Jiang, Weilin; Jiao, Liang; Wang, Haiyan

    2011-12-01

    Response to irradiation of nanocrystalline 3C-SiC is studied using 2 MeV Au+ ions near the critical temperature for amorphization and is compared to the behavior of its monocrystalline counterpart under the identical irradiation conditions. The irradiated samples have been characterized using in-situ ion channeling, ex-situ x-ray diffraction, and helium ion microscopy. Compared to monocrystalline 3C-SiC, a faster amorphization process in the nanocrystalline material (average grain size = 3.3 nm) is observed at 500 K. However, the nanograin grows with increasing ion fluence at 550 K and the grain size tends to saturate at high fluences. The striking contrast demonstrates amore » sharp transition from irradiation-induced interface-driven amorphization at 500 K to crystallization at 550 K. The results could show potential impacts of nanocrystalline SiC on nuclear fuel cladding and structural components of next-generation nuclear energy systems.« less

  12. Growth of C60 thin films on Al2O3/NiAl(100) at early stages

    NASA Astrophysics Data System (ADS)

    Hsu, S.-C.; Liao, C.-H.; Hung, T.-C.; Wu, Y.-C.; Lai, Y.-L.; Hsu, Y.-J.; Luo, M.-F.

    2018-03-01

    The growth of thin films of C60 on Al2O3/NiAl(100) at the earliest stage was studied with scanning tunneling microscopy and synchrotron-based photoelectron spectroscopy under ultrahigh-vacuum conditions. C60 molecules, deposited from the vapor onto an ordered thin film of Al2O3/NiAl(100) at 300 K, nucleated into nanoscale rectangular islands, with their longer sides parallel to direction either [010] or [001] of NiAl. The particular island shape resulted because C60 diffused rapidly, and adsorbed and nucleated preferentially on the protrusion stripes of the crystalline Al2O3 surface. The monolayer C60 film exhibited linear protrusions of height 1-3 Å, due to either the structure of the underlying Al2O3 or the lattice mismatch at the boundaries of the coalescing C60 islands; such protrusions governed also the growth of the second layer. The second layer of the C60 film grew only for a C60 coverage >0.60 ML, implying a layer-by-layer growth mode, and also ripened in rectangular shapes. The thin film of C60 was thermally stable up to 400 K; above 500 K, the C60 islands dissociated and most C60 desorbed.

  13. EXAFS spectrum peculiarities of Y 1- xYb xNi 2B 2C

    NASA Astrophysics Data System (ADS)

    Cortes, R.; Fomicheva, L. N.; Menushenkov, A. P.; Meyer-Klaucke, W.; Konarev, P. V.; Tsvyashchenko, A. V.

    2001-09-01

    The results on the temperature dependent EXAFS studies of the local structure peculiarities of Y 1- xYb xNi 2B 2C series synthesized at a high pressure of 8 GPa are presented. The interrelation between the local structure of Y 1- xYb xNi 2B 2C and its superconducting and magnetic properties was observed supporting the model where the contributions from all type of the nearest atoms to the electron-phonon coupling are important and cannot be neglected.

  14. Z-Scheme NiTiO 3 /g-C 3 N 4 Heterojunctions with Enhanced Photoelectrochemical and Photocatalytic Performances under Visible LED Light Irradiation

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Huang, Zhenyu; Zeng, Xiaoqiao; Li, Kai

    Direct Z-scheme NiTiO3/g-C3N4 heterojunctions were successfully assembled by using simple calcination method and the photoelectrochemical and photocatalytic performance were investigated by light emitting diode (LED). The photoanode composed by the heterojunction with about 50 wt% NiTiO3 content exhibits the best photoelectrochemical activity with photoconversion efficiency up to 0.066%, which is 4.4 and 3.13 times larger than NiTiO3 or g-C3N4. The remarkably enhanced photoelectrochemical and photocatalytic activity of the heterojunction can be due to the efficiently photogenerated electron-hole separation by a Z-scheme mechanism.

  15. Microstructure and wear behaviors of laser clad NiCr/Cr3C2-WS2 high temperature self-lubricating wear-resistant composite coating

    NASA Astrophysics Data System (ADS)

    Yang, Mao-Sheng; Liu, Xiu-Bo; Fan, Ji-Wei; He, Xiang-Ming; Shi, Shi-Hong; Fu, Ge-Yan; Wang, Ming-Di; Chen, Shu-Fa

    2012-02-01

    The high temperature self-lubricating wear-resistant NiCr/Cr3C2-30%WS2 coating and wear-resistant NiCr/Cr3C2 coating were fabricated on 0Cr18Ni9 austenitic stainless steel by laser cladding. Phase constitutions and microstructures were investigated, and the tribological properties were evaluated using a ball-on-disc wear tester under dry sliding condition at room-temperature (17 °C), 300 °C and 600 °C, respectively. Results indicated that the laser clad NiCr/Cr3C2 coating consisted of Cr7C3 primary phase and γ-(Fe,Ni)/Cr7C3 eutectic colony, while the coating added with WS2 was mainly composed of Cr7C3 and (Cr,W)C carbides, with the lubricating WS2 and CrS sulfides as the minor phases. The wear tests showed that the friction coefficients of two coatings both decrease with the increasing temperature, while the both wear rates increase. The friction coefficient of laser clad NiCr/Cr3C2-30%WS2 is lower than the coating without WS2 whatever at room-temperature, 300 °C, 600 °C, but its wear rate is only lower at 300 °C. It is considered that the laser clad NiCr/Cr3C2-30%WS2 composite coating has good combination of anti-wear and friction-reducing capabilities at room-temperature up to 300 °C.

  16. Syntheses, crystal structures and magnetic properties of complexes based on [Ni(L-L)3]2+ complex cations with dimethylderivatives of 2,2‧-bipyridine and TCNQ

    NASA Astrophysics Data System (ADS)

    Černák, Juraj; Hegedüs, Michal; Váhovská, Lucia; Kuchár, Juraj; Šoltésová, Daniela; Čižmár, Erik; Feher, Alexander; Falvello, L. R.

    2018-03-01

    From the aqueous-methanolic systems Ni(NO3)2 - LiTCNQ - 5,5‧-dmbpy and Ni(NO3)2 - LiTCNQ - 4,4‧-dmbpy three novel complexes [Ni(5,5‧-dmbpy)3](TCNQ)2 (1), [Ni(4,4‧-dmbpy)3](TCNQ)2 (2) and [Ni(4,4‧-dmbpy)3]2(TCNQ-TCNQ)(TCNQ)2•0.60H2O (3), were isolated in single crystal form. The new compounds were identified using chemical analyses and IR spectroscopy. Single crystal studies of all samples corroborated their compositions and have shown that their ionic structures contain the complex cations [Ni(5,5‧-dmbpy)]2+ (1) or [Ni(4,4‧-dmbpy)]2+ (2 and 3). The anionic parts of the respective crystal structures 1-3 are formed by TCNQṡ- anion-radicals and in 3 also by a σ-dimerized dianion (TCNQ-TCNQ)2- with a C-C distance of 1.663(5) Å. The supramolecular structures are governed by weak hydrogen bonding interactions. The variable-temperature (2-300 K) magnetic studies of 1 and 3 confirmed the presence of magnetically active Ni(II) atoms with S = 1 and TCNQṡ- anion-radicals with S = 1/2 while the (TCNQ-TCNQ)2- dianion is magnetically silent. The magnetic behavior was described by a complex magnetic model assuming strong antiferromagnetic interactions between some TCNQṡ- anion-radicals.

  17. Microstructure and thermal conductivity of surfactant-free NiO nanostructures

    NASA Astrophysics Data System (ADS)

    Sahoo, Pranati; Misra, Dinesh K.; Salvador, Jim; Makongo, Julien P. A.; Chaubey, Girija S.; Takas, Nathan J.; Wiley, John B.; Poudeu, Pierre F. P.

    2012-06-01

    High purity, nanometer sized surfactant-free nickel oxide (NiO) particles were produced in gram scale using a solution combustion method and characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), gas pycnometry and gas adsorption analysis (BET). The average particle size of the as-synthesized NiO increases significantly with the preheating temperature of the furnace, while the specific surface area decreases. A BET specific surface area of ∼100 m2/g was obtained for NiO nanoparticles with size as small as 3 nm synthesized at 300 °C. The thermal conductivity (κ) of pressed pellets of the synthesized NiO nanoparticles obtained using spark plasma sintering (SPS) and uniaxial hot pressing is drastically decreased (∼60%) compared to that of NiO single crystal. This strong reduction in κ with particle size suggests the suitability of the synthesized surfactant-free NiO nanoparticles for use as nanoinclusions when designing high performance materials for waste heat recovery.

  18. Room Temperature Magnetic Behavior In Nanocrystalline Ni-Doped Zro2 By Microwave-Assisted Polyol Synthesis

    NASA Astrophysics Data System (ADS)

    Parimita Rath, Pragyan; Parhi, Pankaj Kumar; Ranjan Panda, Sirish; Priyadarshini, Barsharani; Ranjan Sahoo, Tapas

    2017-08-01

    This article, deals with a microwave-assisted polyol method to demonstrate a low temperature route < 250°C, to prepare a high temperature cubic zirconia phase. Powder XRD pattern shows broad diffraction peaks suggesting nanometric size of the particles. Magnetic behavior of 1-5 at% Ni doped samples show a threshold for substitutional induced room temperature ferromagnetism up to 3 at% of Ni. TGA data reveals that Ni-doped ZrO2 polyol precursors decompose exothermically below 300°C. IR data confirms the reduction of Zr(OH)4 precipitates to ZrO2, in agreement with the conclusions drawn from the TGA analysis.

  19. Removal of cadmium(II) ions from aqueous solution using Ni (15 wt.%)-doped α-Fe2O3 nanocrystals: equilibrium, thermodynamic, and kinetic studies.

    PubMed

    OuldM'hamed, Mohamed; Khezami, L; Alshammari, Abdulrahman G; Ould-Mame, S M; Ghiloufi, I; Lemine, O M

    2015-01-01

    The present publication investigates the performance of nanocrystalline Ni (15 wt.%)-doped α-Fe2O3 as an effective nanomaterial for the removal of Cd(II) ions from aqueous solutions. The nanocrystalline Ni-doped α-Fe2O3 powders were prepared by mechanical alloying, and characterized by X-ray diffraction and a vibrating sample magnetometer. Batch-mode experiments were realized to determine the adsorption equilibrium, kinetics, and thermodynamic parameters of toxic heavy metal ions by Ni (15 wt.%)-doped α-Fe2O3. The adsorption isotherms data were found to be in good agreement with the Langmuir model. The adsorption capacity of Cd(II) ion reached a maximum value of about 90.91 mg g(-1) at 328 K and pH 7. The adsorption process kinetics was found to comply with pseudo-second-order rate law. Thermodynamic parameters related to the adsorption reaction, free energy change, enthalpy change and entropy change, were evaluated. The found values of free energy and enthalpy revealed a spontaneous endothermic adsorption-process. Moreover, the positive entropy suggests an increase of randomness during the process of heavy metal removal at the adsorbent-solution interface.

  20. Reactivity of the Ni-->B dative sigma-bond in the nickel boratrane compounds [kappa4-B(mimBut)3]NiX (X=Cl, OAc, NCS, N3): synthesis of a series of B-functionalized tris(2-mercapto-1-tert-butylimidazolyl)borato complexes, [YTmBut)]NiZ.

    PubMed

    Pang, Keliang; Tanski, Joseph M; Parkin, Gerard

    2008-02-28

    The nickel boratrane complexes [kappa4-B(mimBut))3]Ni(kappa1-OAc), [kappa4-B(mimBut)3]NiNCS and [kappa4-B(mimBut)3]NiN3 are obtained via metathesis of the chloride ligand of [kappa4-B(mimBut)3]NiCl with TlOAc, KSCN and NaN3, respectively; the Ni-->B bond in these complexes is a site of reactivity, thereby providing a means of synthesizing nickel complexes that feature B-functionalized tris(mercaptoimidazolyl)borate derivatives, [YTmBut]NiZ.

  1. The Bulk Nanocrystalline zn Produced by Mechanical Attrition

    NASA Astrophysics Data System (ADS)

    Zhu, X. K.; Zhao, K. Y.; Li, C. J.; Tao, J. M.; Chan, T. L.; Koch, C. C.

    The purpose of experiment was to produce bulk nanocrystalline Zn by mechanical attrition. The bulk nanocrystalline Zn produced by mechanical attrition was studied. The microstructural evolution during cryomilling and subsequent room temperature milling was characterized using scanning electron microscopy (SEM) and X-ray diffraction (XRD). In this paper, Nanocrystalline Zn was produced by insitu consolidation of Zn elemental powder using mechanical attrition at liquid nitrogen and room temperature. For the samples studied, the longest elongation of 65% and highest stress of 200 MPa is obtained in nanocrystalline Zn during tensile testing at the condition of strain rate (10-3 sec-1) and 20°C which is equal to 0.43 Tm (Tm is the melting temperature of pure Zn).

  2. Photocatalytic removal of Congo red dye using MCM-48/Ni2O3 composite synthesized based on silica gel extracted from rice husk ash; fabrication and application.

    PubMed

    Shaban, Mohamed; Abukhadra, Mostafa R; Hamd, Ahmed; Amin, Ragab R; Abdel Khalek, Ahmed

    2017-12-15

    MCM-48 mesoporous silica was successfully synthesized from silica gel extracted from rice husk ash and loaded by nickel oxide (Ni 2 O 3 ). The resulted composite was characterized using X-ray diffraction, scanning electron microscope, and UV-vis spectrophotometer. The role of MCM-48 as catalyst support in enhancing the photocatalytic properties of nickel oxide was evaluated through the photocatalytic degradation of Congo red dye under visible light source. MCM-48 as catalyst support for Ni 2 O 3 shows considerable enhancement in the adsorption capacity by 17% and 29% higher than the adsorption capacity of MCM-48 and Ni 2 O 3 , respectively. Additionally, the photocatalytic degradation percentage increased by about 64% relative to the degradation percentage using Ni 2 O 3 as a single component. The adsorption mechanism of MCM-48/Ni 2 O 3 is chemisorption process of multilayer form. The using of MCM-48 as catalyst support for Ni 2 O 3 enhanced the adsorption capacity and the photocatalytic degradation through increasing the surface area and prevents the nickel oxide particles from agglomeration. This was done through fixing nickel oxide particles throughout the porous structure which providing more exposed active adsorption sites and active photocatalyst sites for the incident photons. Based on the obtained results, supporting of nickel oxide particles onto MCM-48 are promising active centers for the degradation of Congo red dye molecules. Copyright © 2017 Elsevier Ltd. All rights reserved.

  3. Molten salt synthesis of nanocrystalline phase of high dielectric constant material CaCu3Ti4O12.

    PubMed

    Prakash, B Shri; Varma, K B R

    2008-11-01

    Nanocrystalline powders of giant dielectric constant material, CaCu3Ti4O12 (CCTO), have been prepared successfully by the molten salt synthesis (MSS) using KCl at 750 degrees C/10 h, which is significantly lower than the calcination temperature (approximately 1000 degrees C) that is employed to obtain phase pure CCTO in the conventional solid-state reaction route. The water washed molten salt synthesized powder, characterized by X-ray powder diffraction (XRD), Scanning electron microscopy (SEM), and Transmission electron microscopy (TEM) confirmed to be a phase pure CCTO associated with approximately 150 nm sized crystallites of nearly spherical shape. The decrease in the formation temperature/duration of CCTO in MSS method was attributed to an increase in the diffusion rate or a decrease in the diffusion length of reacting ions in the molten salt medium. As a consequence of liquid phase sintering, pellets of as-synthesized KCl containing CCTO powder exhibited higher sinterability and grain size than that of KCl free CCTO samples prepared by both MSS method and conventional solid-state reaction route. The grain size and the dielectric constant of KCl containing CCTO ceramics increased with increasing sintering temperature (900 degrees C-1050 degrees C). Indeed the dielectric constants of these ceramics were higher than that of KCl free CCTO samples prepared by both MSS method and those obtained via the solid-state reaction route and sintered at the same temperature. Internal barrier layer capacitance (IBLC) model was invoked to correlate the observed dielectric constant with the grain size in these samples.

  4. Potential applications of cold sprayed Cu50Ti20Ni30 metallic glassy alloy powders for antibacterial protective coating in medical and food sectors.

    PubMed

    El-Eskandrany, M Sherif; Al-Azmi, Ahmed

    2016-03-01

    Mechanical alloying was utilized for synthesizing of metallic glassy Cu50Ti20Ni30 alloy powders, using a low energy ball milling technique. The metallic glassy powders obtained after 100 h of ball milling had an average particle size of 1.7 mm in diameter and possessed excellent thermal stability, indexed by a relatively high glass transition temperature (358.3 °C) with a wide supercooled liquid region (61 °C). This amorphous phase crystallized into Ti2Cu and CuTiNi2 ordered phases through two overlapped crystallization temperatures at 419.3 °C and 447.5 °C, respectively. The total enthalpy change of crystallization was -4.8 kJ/mol. The glassy powders were employed as feedstock materials to double-face coating the surface of SUS 304 substrate, using cold spraying process under helium gas pressure at 400 °C. This coating material had an extraordinary high nanohardness value of 3.1 GPa. Moreover, it showed a high resistance to wear with a low value of the coefficient of friction ranging from 0.45 to 0.45. Biofilms were grown on 20-mm(2) SUS304 sheets coated coupons inoculated with 1.5 × 10(8) CFU ml(-1)E. coli. Significant biofilm inhibition (p The inhibition of biofilm formation by nanocrystalline powders of Cu-based provides a practical approach to achieve the inhibition of biofilms formation. Copyright © 2015 Elsevier Ltd. All rights reserved.

  5. Fine Structure Study of the Plasma Coatings B4C-Ni-P

    NASA Astrophysics Data System (ADS)

    Kornienko, E. E.; Bezrukova, V. A.; Kuz'min, V. I.; Lozhkin, V. S.; Tutunkova, M. K.

    2017-12-01

    The article considers structure of coatings formed of the B4C-Ni-P powder. The coatings were deposited using air-plasma spraying with the unit for annular injection of powder. The pipes from steel 20 (0.2 % C) were used as a substrate. The structure and phase composition of the coatings were studied by optical microscopy, scanning electron microscopy, transmission electron microscopy and X-ray diffractometry. It is shown that high-density composite coatings consisting of boron carbide particles distributed in the nickel boride metal matrix are formed using air-plasma spraying. The areas with round inclusions characterized by the increased amount of nickel, phosphorus and boron are located around the boron carbide particles. Boron oxides and nickel oxides are also present in the coatings. Thin interlayers with amorphous-crystalline structure are formed around the boron carbide particles. The thickness of these interlayers does not exceed 1 μm. The metal matrix material represents areas with nanocrystalline structure and columnar crystals.

  6. Ga2O3 and GaN nanocrystalline film: reverse micelle assisted solvothermal synthesis and characterization.

    PubMed

    Sinha, Godhuli; Ganguli, Dibyendu; Chaudhuri, Subhadra

    2008-03-01

    Gallium oxide (beta-Ga2O3) nanoparticles were successfully deposited on quartz glass substrates using sodium bis(2-ethylhexyl) sulfosuccinate (AOT)/n-hexane/ethylene glycol monomethyl ether (EGME) reverse micelle-mediated solvothermal process with different omega values. The mean diameter of Ga2O3 particles was approximately 2-3 nm and found to be approximately independent of omega values of the reverse micelles. However, when the Ga2O3 nanocrystalline films were nitrided at 900 degrees C under flowing NH3 atmosphere for 1 h, the mean diameter of the resulted gallium nitride (wurtzite-GaN) nanoparticles varied from 3-9 nm. Both nanocrystalline films of Ga2O3 and GaN were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), Fourier transform infrared (FTIR) spectroscopy, UV-vis spectroscopy and photoluminescence in order to study their chemical and physical properties explicitly.

  7. A Readily Accessible Chiral NNN Pincer Ligand with a Pyrrole Backbone and Its Ni(II) Chemistry: Syntheses, Structural Chemistry, and Bond Activations.

    PubMed

    Wenz, Jan; Kochan, Alexander; Wadepohl, Hubert; Gade, Lutz H

    2017-03-20

    A new class of chiral C 2 -symmetric N-donor pincer ligands, 2,5-bis(2-oxazolinyldimethylmethyl)pyrroles (PdmBox)H, was synthesized starting from the readily available ethyl 2,2-dimethyl-3-oxobutanoate (1). The synthesis of the ligand backbone was achieved by oxidative enole coupling with CuC1 2 followed by Paal-Knorr-type pyrrole synthesis. The corresponding protioligands ( R PdmBox)H (R = iPr: 5a; Ph: 5b) were obtained by condensation with amino alcohols and subsequent zinc-catalyzed cyclization. Reaction of the lithiated ligands with [NiCl 2 (dme)] yielded the corresponding square-planar nickel(II) complexes [( R PdmBox)NiCl] (6a/b). Salt metathesis of 6a with the corresponding alkali or cesium salts in acetone led to the formation of air- and moisture-stable [( iPr PdmBox)NiX] (X = F (7), X = Br (8), X = I (9), X = N 3 (10), X = OAc (11). Furthermore, the conversion of [( iPr PdmBox)NiF] (7) with hydride transfer reagents such as PhSiH 3 led to the stable hydrido species [( iPr PdmBox)NiH] (27), the stoichiometric transformations of which were studied. Treatment of 6a with organometallic reagents such as ZnEt 2 , PhLi, PhC≡CLi, NsLi, or ( 4F Bn) 2 Mg(THF) 2 gave the corresponding alkyl, alkynyl, or aryl complexes. The availability of the new nonisomerizable PdmBox pincer ligands allowed the comparative study of their ligation to square-planar complexes as helically twisted spectator ligands as opposed to the enforced planar rigidity of their iso-PmBox analogues and the way this influences the reactivity of the Ni complexes.

  8. Preparation and characterization of Ni-P/Ni3.1B composite alloy coatings

    NASA Astrophysics Data System (ADS)

    Wang, Yurong; He, Jiawei; Wang, Wenchang; Shi, Jianhua; Mitsuzaki, Naotoshi; Chen, Zhidong

    2014-02-01

    The preparation of Ni-P/Ni3.1B composite alloy coating on the surface of copper was achieved by co-deposition of Ni3.1B nanoparticles with Ni-P coating during electroless plating. Ni-P-B alloy coating was obtained by heat-treating the as-plated Ni-P/Ni3.1B composite coating. The effect of the concentration of sodium alginate, borax, thiourea, Ni3.1B, temperature, and pH value on the deposition rate and B content were investigated and determined to be: 30 g L-1, 10 g L-1, 2 mg L-1, 20 mg L-1, 70 °C and 9.0 , respectively. Sodium alginate and thiourea were played as surfactant for coating Ni3.1B nanoparticles and stabilizer for the plating bath, respectively. Ni-P/Ni3.1B composite coating had good performance such as corrosion resistance and solderability.

  9. Magnetism and charge density wave in GdNiC2 and NdNiC2

    NASA Astrophysics Data System (ADS)

    Klimczuk, Tom; Kolincio, Kamil; Wianiarski, Michal; Strychalska-Nowak, Judyta; Górnicka, Karolina

    The RNiC2 compounds form in an orthorhombic Amm2 crystal structure with Ni and the rare-earth (R) metal chains along the crystallographic a-axis. This system is of particular interest because both a CDW and a long range magnetic ordering phases have been observed together. We report the specific heat, magnetic, magnetotransport and galvanomagnetic properties of GdNiC2 and NdNiC2 antiferromagnets. Complex B-T phase diagrams were built based on the specific heat data. Large negative magnetoresistance due to Zeeman splitting of the electronic bands and partial destruction of a charge density wave ground state is observed above TN. The magnetoresistance and Hall measurements show that at low temperatures a magnetic field induced transformation from antiferromagnetic order to a metamagnetic phase results in the partial suppression of the CDW. This project is financially supported by National Science Centre (Poland), Grant Number: UMO-2015/19/B/ST3/03127.

  10. Ni doped Fe3O4 magnetic nanoparticles.

    PubMed

    Larumbe, S; Gómez-Polo, C; Pérez-Landazábal, J I; García-Prieto, A; Alonso, J; Fdez-Gubieda, M L; Cordero, D; Gómez, J

    2012-03-01

    In this work, the effect of nickel doping on the structural and magnetic properties of Fe3O4 nanoparticles is analysed. Ni(x)Fe(3-x)O4 nanoparticles (x = 0, 0.04, 0.06 and 0.11) were obtained by chemical co-precipitation method, starting from a mixture of FeCl2 x 4H2O and Ni(AcO)2 x 4H2O salts. The analysis of the structure and composition of the synthesized nanoparticles confirms their nanometer size (main sizes around 10 nm) and the inclusion of the Ni atoms in the characteristic spinel structure of the magnetite Fe3O4 phase. In order to characterize in detail the structure of the samples, X-ray absorption (XANES) measurements were performed on the Ni and Fe K-edges. The results indicate the oxidation of the Ni atoms to the 2+ state and the location of the Ni2+ cations in the Fe2+ octahedral sites. With respect to the magnetic properties, the samples display the characteristic superparamagnetic behaviour, with anhysteretic magnetic response at room temperature. The estimated magnetic moment confirms the partial substitution of the Fe2+ cations by Ni2+ atoms in the octahedral sites of the spinel structure.

  11. Magnetic properties of Sn-substituted Ni-Zn ferrites synthesized from nano-sized powders of NiO, ZnO, Fe2O3, and SnO2

    NASA Astrophysics Data System (ADS)

    Ali, MA; Uddin, MM; Khan, MNI; Chowdhury, FUZ; Hoque, SM; Liba, SI

    2017-06-01

    A series of Ni0.6-x/2Zn0.4-x/2Sn x Fe2O4 (x = 0.0, 0.05, 0.1, 0.15, 0.2, and 0.3) (NZSFO) ferrite composities have been synthesized from nano powders using a standard solid state reaction technique. The spinel cubic structure of the investigated samples has been confirmed by x-ray diffraction (XRD). The magnetic properties such as saturation magnetization ({M}{{s}}), remanent magnetization ({M}{{r}}), coercive field ({H}{{c}}), and Bohr magneton (μ) are calculated from the hysteresis loops. The value of {M}{{s}} is found to decrease with increasing Sn content in the samples. This change is successfully explained by the variation of A-B interaction strength due to Sn substitution in different sites. The compositional stability and quality of the prepared ferrite composites have also been endorsed by the fairly constant initial permeability ({μ }^{\\prime }) over a wide range of frequency. The decreasing trend of {μ }^{\\prime } with increasing Sn content has been observed. Curie temperature {T}{{C}} has been found to increase with the increase in Sn content. A wide spread frequency utility zone indicates that the NZSFO can be considered as a good candidate for use in broadband pulse transformers and wide band read-write heads for video recording. The composition of x = 0.05 shows unusual results and the possible reason is also mentioned with the established formalism.

  12. Nanocrystalline SiC and Ti 3SiC 2 Alloys for Reactor Materials: Diffusion of Fission Product Surrogates

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Henager, Charles H.; Jiang, Weilin

    2014-11-01

    MAX phases, such as titanium silicon carbide (Ti 3SiC 2), have a unique combination of both metallic and ceramic properties, which make them attractive for potential nuclear applications. Ti 3SiC 2 has been suggested in the literature as a possible fuel cladding material. Prior to the application, it is necessary to investigate diffusivities of fission products in the ternary compound at elevated temperatures. This study attempts to obtain relevant data and make an initial assessment for Ti 3SiC 2. Ion implantation was used to introduce fission product surrogates (Ag and Cs) and a noble metal (Au) in Ti 3SiC 2,more » SiC, and a dual-phase nanocomposite of Ti 3SiC 2/SiC synthesized at PNNL. Thermal annealing and in-situ Rutherford backscattering spectrometry (RBS) were employed to study the diffusivity of the various implanted species in the materials. In-situ RBS study of Ti 3SiC 2 implanted with Au ions at various temperatures was also performed. The experimental results indicate that the implanted Ag in SiC is immobile up to the highest temperature (1273 K) applied in this study; in contrast, significant out-diffusion of both Ag and Au in MAX phase Ti 3SiC 2 occurs during ion implantation at 873 K. Cs in Ti 3SiC 2 is found to diffuse during post-irradiation annealing at 973 K, and noticeable Cs release from the sample is observed. This study may suggest caution in using Ti 3SiC 2 as a fuel cladding material for advanced nuclear reactors operating at very high temperatures. Further studies of the related materials are recommended.« less

  13. Tribological Performance of Ni3Al Matrix Self-Lubricating Composites Containing Multilayer Graphene and Ti3SiC2 at Elevated Temperatures

    NASA Astrophysics Data System (ADS)

    Yan, Zhao; Shi, Xiaoliang; Huang, Yuchun; Deng, Xiaobin; Yang, Kang; Liu, Xiyao

    2017-09-01

    The application of Ni3Al-based alloy (NA) in the field of aerospace was limited by its poor tribological properties. For improving the tribological performance of NA, multilayer graphene (MLG) and Ti3SiC2 were added in Ni3Al matrix composites. Tribological behavior of Ni3Al matrix composites containing 1.5 wt.% MLG and 10 wt.% Ti3SiC2 (NMT) against Si3N4 ball at 12 N-0.2 m/s from 25 to 750 °C was investigated. The results showed that NMT exhibited the excellent tribological behavior [lower friction coefficients (0.26-0.57) and less wear resistance (3.1-6.5 × 10-6 mm3 N-1 m-1)] due to synergetic effect of MLG and Ti3SiC2 over a wide temperature range from 25 to 750 °C. At 25-350 °C, part of MLG enriched on worn surface could play a role in reducing friction and improving wear resistance. At 350-550 °C, although MLG gradually lost the lubricating properties, the partial decomposition of Ti3SiC2 could continually improve the tribological properties of NMT. At 550-750 °C, Ti3SiC2 on worn surface was oxidized to form lubricating film, while Ti3SiC2 in the subsurface played an important role in supporting the film, resulting in the excellent high-temperature tribological performance. The research had good guiding significance for the preparation of wide temperature range self-lubricating material and the study of synergetic effect of complex solid lubricants.

  14. Characterization of synthetic nanocrystalline mackinawite: crystal structure, particle size, and specific surface area

    PubMed Central

    Jeong, Hoon Y.; Lee, Jun H.; Hayes, Kim F.

    2010-01-01

    Iron sulfide was synthesized by reacting aqueous solutions of sodium sulfide and ferrous chloride for 3 days. By X-ray powder diffraction (XRPD), the resultant phase was determined to be primarily nanocrystalline mackinawite (space group: P4/nmm) with unit cell parameters a = b = 3.67 Å and c = 5.20 Å. Iron K-edge XAS analysis also indicated the dominance of mackinawite. Lattice expansion of synthetic mackinawite was observed along the c-axis relative to well-crystalline mackinawite. Compared with relatively short-aged phase, the mackinawite prepared here was composed of larger crystallites with less elongated lattice spacings. The direct observation of lattice fringes by HR-TEM verified the applicability of Bragg diffraction in determining the lattice parameters of nanocrystalline mackinawite from XRPD patterns. Estimated particle size and external specific surface area (SSAext) of nanocrystalline mackinawite varied significantly with the methods used. The use of Scherrer equation for measuring crystallite size based on XRPD patterns is limited by uncertainty of the Scherrer constant (K) due to the presence of polydisperse particles. The presence of polycrystalline particles may also lead to inaccurate particle size estimation by Scherrer equation, given that crystallite and particle sizes are not equivalent. The TEM observation yielded the smallest SSAext of 103 m2/g. This measurement was not representative of dispersed particles due to particle aggregation from drying during sample preparation. In contrast, EGME method and PCS measurement yielded higher SSAext (276–345 m2/g by EGME and 424 ± 130 m2/g by PCS). These were in reasonable agreement with those previously measured by the methods insensitive to particle aggregation. PMID:21085620

  15. Effect of cobalt doping on structural and optical properties of nanocrystalline La0.8Pb0.2CrO3 orthochromite

    NASA Astrophysics Data System (ADS)

    Zarrin, Naima; Shahidhusain

    2018-04-01

    We have synthesized nanocrystalline La0.8Pb0.2Cr1-xCoxO3 (0≤x≤0.3) through sol-gel process and studied their structural and optical properties. X-ray diffraction patterns reveal that the samples conform in the orthorhombic crystal symmetry with Pnma space group. Structural parameters are refined by Rietveld Refinement using Fullprof software. Lattice parameters and unit cell volume of doped samples are found to decrease with increase in Co doping. The optical energy band gapdecreases whereas Urbach energy increases with the increase in Co content.

  16. The effect of temperature on the structure and magnetic properties of Co0.5Ni0.5Fe2O4 spinel nanoferrite

    NASA Astrophysics Data System (ADS)

    Abdallah, Hafiz M. I.; Moyo, Thomas; Ngema, Nokwanda

    2015-11-01

    Nanocrystalline Co0.5Ni05Fe2O4 ferrite with average crystallite size of 7.6 nm and lattice constant of 0.8372 nm was synthesized via a glycol-thermal process. The structure parameters and morphology of the as-synthesized sample and annealed samples were characterized by XRD, EDX, FTIR, HRSEM and HRTEM. The hyperfine interactions, iron distribution on the tetrahedral and octahedral sites for the as-synthesized sample and samples annealed at 500 °C were deduced by Mössbauer spectroscopy measurements at 300 K. The magnetization measurements for the as-synthesized and annealed samples (300-900 °C) were obtained by a vibrating sample magnetometer on a cryogen free measurement system at different isothermal temperatures (4-300 K) in external applied magnetic fields of ±5 T. The temperature dependence of the magnetic properties such as coercive field, saturation magnetization, remanent magnetization and squareness of hysteresis loops were investigated. The sample transformed from single-domain to multi-domain configuration at particle size of about 31 nm. At 300 K, the sample annealed at 700 °C exhibits a maximum coercivity. The as-prepared sample shows a substantial increase in coercivity from 0.182 kOe at 300 K to 6.018 kOe at 4 K.

  17. High-Temperature Exposure Studies of HVOF-Sprayed Cr3C2-25(NiCr)/(WC-Co) Coating

    NASA Astrophysics Data System (ADS)

    Singh, Harpreet; Kaur, Manpreet; Prakash, Satya

    2016-08-01

    In this research, development of Cr3C2-25(NiCr) + 25%(WC-Co) composite coating was done and investigated. Cr3C2-25(NiCr) + 25%(WC-Co) composite powder [designated as HP2 powder] was prepared by mechanical mixing of [75Cr3C2-25(NiCr)] and [88WC-12Co] powders in the ratio of 75:25 by weight. The blended powders were used as feedstock to deposit composite coating on ASTM SA213-T22 substrate using High Velocity Oxy-Fuel (HVOF) spray process. High-temperature oxidation/corrosion behavior of the bare and coated boiler steels was investigated at 700 °C for 50 cycles in air, as well as, in Na2SO4-82%Fe2(SO4)3 molten salt environment in the laboratory. Erosion-corrosion behavior was investigated in the actual boiler environment at 700 ± 10 °C under cyclic conditions for 1500 h. The weight-change technique was used to establish the kinetics of oxidation/corrosion/erosion-corrosion. X-ray diffraction, field emission-scanning electron microscopy/energy-dispersive spectroscopy (FE-SEM/EDS), and EDS elemental mapping techniques were used to analyze the exposed samples. The uncoated boiler steel suffered from a catastrophic degradation in the form of intense spalling of the scale in all the environments. The oxidation/corrosion/erosion-corrosion resistance of the HVOF-sprayed HP2 coating was found to be better in comparison with standalone Cr3C2-25(NiCr) coating. A simultaneous formation of protective phases might have contributed the best properties to the coating.

  18. Ni.sub.3 Al-based intermetallic alloys having improved strength above 850.degree. C.

    DOEpatents

    Liu, Chain T.

    2000-01-01

    Intermetallic alloys composed essentially of: 15.5% to 17.0% Al, 3.5% to 5.5% Mo, 4% to 8% Cr, 0.04% to 0.2% Zr, 0.04% to 1.5% B, balance Ni, are characterized by melting points above 1200.degree. C. and superior strengths at temperatures above 1000.degree. C.

  19. Thermally Stable Nanocrystalline Steel

    NASA Astrophysics Data System (ADS)

    Hulme-Smith, Christopher Neil; Ooi, Shgh Woei; Bhadeshia, Harshad K. D. H.

    2017-10-01

    Two novel nanocrystalline steels were designed to withstand elevated temperatures without catastrophic microstructural changes. In the most successful alloy, a large quantity of nickel was added to stabilize austenite and allow a reduction in the carbon content. A 50 kg cast of the novel alloy was produced and used to verify the formation of nanocrystalline bainite. Synchrotron X-ray diffractometry using in situ heating showed that austenite was able to survive more than 1 hour at 773 K (500 °C) and subsequent cooling to ambient temperature. This is the first reported nanocrystalline steel with high-temperature capability.

  20. Pt/Ni(OH)2–NiOOH/Pd multi-walled hollow nanorod arrays as superior electrocatalysts for formic acid electrooxidation† †Electronic supplementary information (ESI) available. See DOI: 10.1039/c5sc02544c Click here for additional data file.

    PubMed Central

    Xu, Han; Ding, Liang-Xin; Feng, Jin-Xian

    2015-01-01

    The catalytic activity and durability are crucial for the development of high-performance electrocatalysts. To design electrocatalysts with excellent electroactivity and durability, the structure and composition are two important guiding principles. In this work, novel Pt/Ni(OH)2–NiOOH/Pd multi-walled hollow nanorod arrays (MHNRAs) are successfully synthesized. The unique MHNRAs provide fast transport and short diffusion paths for electroactive species and high utilization rate of catalysts. Because of the special surface and synergistic effects, the Pt/Ni(OH)2–NiOOH/Pd MHNRA electrocatalysts exhibit high catalytic activity, high durability and superior CO poisoning tolerance for the electrooxidation of formic acid in comparison with Pt@Pd MHNRAs, commercial Pt/C, Pd/C and PtRu/C catalysts. PMID:28757980

  1. Stability of an Electrodeposited Nanocrystalline Ni-Based Alloy Coating in Oil and Gas Wells with the Coexistence of H₂S and CO₂.

    PubMed

    Sui, Yiyong; Sun, Chong; Sun, Jianbo; Pu, Baolin; Ren, Wei; Zhao, Weimin

    2017-06-09

    The stability of an electrodeposited nanocrystalline Ni-based alloy coating in a H₂S/CO₂ environment was investigated by electrochemical measurements, weight loss method, and surface characterization. The results showed that both the cathodic and anodic processes of the Ni-based alloy coating were simultaneously suppressed, displaying a dramatic decrease of the corrosion current density. The corrosion of the Ni-based alloy coating was controlled by H₂S corrosion and showed general corrosion morphology under the test temperatures. The corrosion products, mainly consisting of Ni₃S₂, NiS, or Ni₃S₄, had excellent stability in acid solution. The corrosion rate decreased with the rise of temperature, while the adhesive force of the corrosion scale increased. With the rise of temperature, the deposited morphology and composition of corrosion products changed, the NiS content in the corrosion scale increased, and the stability and adhesive strength of the corrosion scale improved. The corrosion scale of the Ni-based alloy coating was stable, compact, had strong adhesion, and caused low weight loss, so the corrosion rates calculated by the weight loss method cannot reveal the actual oxidation rate of the coating. As the corrosion time was prolonged, the Ni-based coating was thinned while the corrosion scale thickened. The corrosion scale was closely combined with the coating, but cannot fully prevent the corrosive reactants from reaching the substrate.

  2. Luminescence, magnetic and vibrational properties of novel heterometallic niccolites [(CH3)2NH2][CrIIIMII(HCOO)6] (MII=Zn, Ni, Cu) and [(CH3)2NH2][AlIIIZnII(HCOO)6]:Cr3+

    NASA Astrophysics Data System (ADS)

    Mączka, Mirosław; Pietraszko, Adam; Pikul, Adam; Hermanowicz, Krzysztof

    2016-01-01

    We report synthesis of three novel heterometallic MOFs, [(CH3)2NH2][CrIIIMII(HCOO)6] with M=Zn (DMCrZn), Ni (DMCrNi) and Cu (DMCrCu), crystallizing in the niccolite type structure. We also successfully synthesized [(CH3)2NH2][AlCu(HCOO)6] (DMAlCu) and [(CH3)2NH2][AlZn(HCOO)6] doped with 5.8 mol% of Cr3+ (DMAlZn: Cr). X-ray diffraction shows that DMCrZn, DMCrNi and DMAlZn: Cr3+ crystallize in the trigonal structure (space group P 3 bar1c) while DMCrCu and DMAlCu crystallize in the monoclinic structure (space group C2/c). Magnetic investigation of the chromium-based niccolites reveals no magnetic order in DMCrZn and ferromagnetic order in DMCrNi and DMCrCu below 23 and 11 K, respectively. Optical studies show that DMCrZn and DMAlZn: Cr samples exhibit efficient emission typical for chromium ions located at sites of strong crystal field with the Dq/B values 2.62 and 2.67, respectively. We also discuss role of geometrical parameters in stability of the perovskite and niccolite structures.

  3. CP/MAS ¹³C NMR study of pulp hornification using nanocrystalline cellulose as a model system.

    PubMed

    Idström, Alexander; Brelid, Harald; Nydén, Magnus; Nordstierna, Lars

    2013-01-30

    The hornification process of paper pulp was investigated using solid-state (13)C NMR spectroscopy. Nanocrystalline cellulose was used to serve as a model system of the crystalline parts of the fibrils in pulp fibers. Characterization of the nanocrystalline cellulose dimensions was carried out using scanning electron microscopy. The samples were treated by drying and wetting cycles prior to NMR analysis where the hornification phenomenon was recorded by spectral changes of the cellulose C-4 carbon signals. An increase of the crystalline signal and a decrease of the signals corresponding to the accessible amorphous domains were found for both paper pulp and nanocrystalline cellulose. These spectral changes grew stronger with repeating drying and wetting cycles. The results show that cellulose co-crystallization contribute to hornification. Another conclusion is that the surfaces of higher hydrophobicity in cellulose fibrils have an increased preference for aggregation. Copyright © 2012 Elsevier Ltd. All rights reserved.

  4. Impact of High-Temperature, High-Pressure Synthesis Conditions on the Formation of the Grain Structure and Strength Properties of Intermetallic Ni3Al

    NASA Astrophysics Data System (ADS)

    Ovcharenko, V. E.; Ivanov, K. V.; Boyangin, E. N.; Krylova, T. A.; Pshenichnikov, A. P.

    2018-01-01

    The impact of the preliminary load on 3Ni+Al powder mixture and the impact of the duration of the delay in application of compacting pressure to synthesis product under the conditions of continuous heating of the mixture up to its self-ignition on the grain size and strength properties of the synthesized Ni3Al intermetallide material have been studied. The grain structure of the intermetallide synthesized under pressure was studied by means of metallography, transmission electron microscopy and EBSD analysis, with the dependence of ultimate tensile strength on the grain size in the synthesized intermetallide having been investigated at room temperature and at temperatures up to 1000°C. It is shown that an increase in the pressure preliminarily applied to the initial mixture compact results in reduced grain size of the final intermetallide, whereas an increase in pre-compaction time makes the grain size increased. A decrease in the grain size increases the ultimate tensile strength of the intermetallide. The maximum value of the ultimate tensile strength in the observed anomalous temperature dependence of this strength exhibits a shift by 200°C toward higher temperatures, and the ultimate strength of the synthesized intermetallide at 1000°C increases roughly two-fold.

  5. Synthesis of nanocrystalline ZnO thin films by electron beam evaporation

    NASA Astrophysics Data System (ADS)

    Kondkar, V.; Rukade, D.; Bhattacharyya, V.

    2018-05-01

    Nanocrystalline ZnO thin films have potential for applications in variety of optoelectronic devices. In the present study, nanocrystalline thin films of ZnO are grown on fused silica substrate using electron beam (e-beam) evaporation technique. Phase identification is carried out using Glancing angle X-ray diffraction (GAXRD) and Raman spectroscopy. Ultraviolet-Visible (UV-Vis) spectroscopic analysis is carried out to calculate energy band gap of the ZnO film. Surface morphology of the film is investigated using atomic force microscopy (AFM) and field emission scanning electron microscopy (FESEM). Highly quality nanocrystalline thin films of hexagonal wurtzite ZnO are synthesized using e-beam evaporation technique.

  6. Effect of carbide additions on grain growth in TiC-Ni cermets

    NASA Astrophysics Data System (ADS)

    Shin, Soon-Gi; Lee, Jun-Hee

    2006-02-01

    The growth of carbide particles in TiC-XC-2 vol.% Ni and TiC-XC-30 vol.% Ni alloys, where X=Zr, Cr, W, Ta and Mo, was fitted to an equation of the form d3-do 3=Kt. The grain growth behavior during liquid phase sintering at 1673K decreased markedly with the addition of Mo2C or WC, changed little for TaC, and increased with the addition of ZrC or Cr3C2. The grain contiguity decreased with increasing Ni content in the TiC-Mo2C-Ni alloy and was greater in the alloys with smaller growth rate constant. Consequently, the effect of carbide addition on the grain growth of 2 vol.% Ni alloys was found to be similar to that of 30 vol.% Ni alloys. The grain growth mechanism could be explained by the effect of contiguous carbide grain boundaries in restricting the overall grain growth, as well as the area of the solid/liquid interfaces in the alloy by the usual solution/reprecipitation model.

  7. Nanocrystalline ordered vanadium carbide: Superlattice and nanostructure

    NASA Astrophysics Data System (ADS)

    Kurlov, A. S.; Gusev, A. I.; Gerasimov, E. Yu.; Bobrikov, I. A.; Balagurov, A. M.; Rempel, A. A.

    2016-02-01

    The crystal structure, micro- and nanostructure of coarse- and nanocrystalline powders of ordered vanadium carbide V8C7 have been examined by X-ray and neutron diffraction and electron microscopy methods. The synthesized coarse-crystalline powder of ordered vanadium carbide has flower-like morphology. It was established that the real ordered phase has the composition V8C7-δ (δ ≅ 0.03) deviating from perfect stoichiometric composition V8C7. The vanadium atoms forming the octahedral environment □V6 of vacant sites in V8C7-δ are displaced towards the vacancy □. The presence of carbon onion-like structures was found in the vanadium carbide powders with a small content of free (uncombined) carbon. The nanopowders of V8C7-δ carbide with average particle size of 20-30 nm produced by high-energy milling of coarse-crystalline powder retain the crystal structure of the initial powder, but differ in the lattice deformation distortion anisotropy.

  8. Conversion of CH4/CO2 to syngas over Ni-Co/Al2O3-ZrO2 nanocatalyst synthesized via plasma assisted co-impregnation method: Surface properties and catalytic performance

    NASA Astrophysics Data System (ADS)

    Rahemi, Nader; Haghighi, Mohammad; Akbar Babaluo, Ali; Fallah Jafari, Mahdi; Khorram, Sirous

    2013-09-01

    Ni/Al2O3 catalyst promoted by Co and ZrO2 was prepared by co-impregnation method and treated with glow discharge plasma. The catalytic activity of the synthesized nanocatalysts has been tested toward conversion of CH4/CO2 to syngas. The physicochemical characterizations like XRD, EDX, FESEM, TEM, BET, FTIR, and XPS show that plasma treatment results in smaller particle size, more surface concentration, and uniform morphology. The dispersion of nickel in plasma-treated nanocatalyst was also significantly improved, which was helpful for controlling the ensemble size of active phase atoms on the support surface. Improved physicochemical properties caused 20%-30% enhancement in activity of plasma-treated nanocatalyst that means to achieve the same H2 or CO yield, the plasma-treated nanocatalyst needed about 100 °C lower reaction temperature. The H2/CO ratio got closer to 1 at higher temperatures and finally at 850 °C H2/CO = 1 is attained for plasma-treated nanocatalyst. Plasma-treated nanocatalyst due to smaller Ni particles and strong interaction between active phase and support has lower tendency to keep carbon species on its structure and hence excellent stability can be observed for this catalyst.

  9. PtNi Alloy Cocatalyst Modification of Eosin Y-Sensitized g-C3N4/GO Hybrid for Efficient Visible-Light Photocatalytic Hydrogen Evolution

    NASA Astrophysics Data System (ADS)

    Wang, Peng; Zong, Lanlan; Guan, Zhongjie; Li, Qiuye; Yang, Jianjun

    2018-02-01

    An economic and effective Pt-based alloy cocatalyst has attracted considerable attention due to their excellent catalytic activity and reducing Pt usage. In this study, PtNi alloy cocatalyst was successfully decorated on the g-C3N4/GO hybrid photocatalyst via a facile chemical reduction method. The Eosin Y-sensitized g-C3N4/PtNi/GO-0.5% composite photocatalyst yields about 1.54 and 1178 times higher hydrogen evolution rate than the Eosin Y-sensitized g-C3N4/Pt/GO-0.5% and g-C3N4/Ni/GO-0.5% samples, respectively. Mechanism of enhanced performance for the g-C3N4/PtNi/GO composite was also investigated by different characterization, such as photoluminescence, transient photocurrent response, and TEM. These results indicated that enhanced charge separation efficiency and more reactive sites are responsible for the improved hydrogen evolution performance due to the positive synergetic effect between Pt and Ni. This study suggests that PtNi alloy can be used as an economic and effective cocatalyst for hydrogen evolution reaction. [Figure not available: see fulltext.

  10. Low-Temperature Synthesis of Superconducting Nanocrystalline MgB 2

    DOE PAGES

    Lu, Jun; Xiao, Zhili; Lin, Qiyin; ...

    2010-01-01

    Magnesium diboride (MgB 2 ) is considered a promising material for practical application in superconducting devices, with a transition temperature near 40 K. In the present paper, nanocrystalline MgB 2 with an average particle size of approximately 70 nm is synthesized by reacting LiBH 4 with MgH 2 at temperatures as low as 450 ° C. This synthesis approach successfully bypasses the usage of either elemental boron or toxic diborane gas. The superconductivity of the nanostructures is confirmed by magnetization measurements, showing a superconducting critical temperature of 38.7 K.

  11. Mechanical properties of nanocrystalline cobalt

    NASA Astrophysics Data System (ADS)

    Karimpoor, Amir A.; Erb, Uwe

    2006-05-01

    Due to their excellent wear and corrosion properties, nanocrystalline cobalt and several cobalt alloys made by electrodeposition are currently being developed as environmentally benign replacement coatings for hard chromium electrodeposits. The focus of this study is on the mechanical properties of nanocrystalline cobalt, which are currently not well understood. A comparison is presented for hardness, tensile properties, Charpy impact properties and fracture surface analysis of both nanocrystalline (grain size: 12 nm) and conventional polycrystalline (grain size: 4.8 m) cobalt. It is shown that the hardness and tensile strength of nanocrystalline cobalt is 2-3 times higher than for polycrystalline cobalt. However, in contrast to other nanocrystalline materials tested previously, nanocrystalline cobalt retains considerable ductility with elongation to fracture values up to 7%.

  12. Shear-Coupled Grain Growth and Texture Development in a Nanocrystalline Ni-Fe Alloy during Cold Rolling

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Li, Li; Ungár, Tamás; Toth, Laszlo S.

    The evolution of texture, grain size, grain shape, dislocation and twin density has been determined by synchrotron X-ray diffraction and line profile analysis in a nanocrystalline Ni- Fe alloy after cold rolling along different directions related to the initial fiber and the long axis of grains. The texture evolution has been simulated by the Taylor-type relaxed constraints viscoplastic polycrystal model. The simulations were based on the activity of partial dislocations in correlation with the experimental results of dislocation density determination. The concept of stress-induced shear-coupling is supported and strengthened by both the texture simulations and the experimentally determined evolution ofmore » the microstructure parameters. Grain-growth and texture evolution are shown to proceed by the shear-coupling mechanism supported by dislocation activity as long as the grain size is not smaller than about 20 nm.« less

  13. Ammonia-evaporation-induced construction of three-dimensional NiO/g-C3N4 composite with enhanced adsorption and visible light-driven photocatalytic performance

    NASA Astrophysics Data System (ADS)

    Tzvetkov, George; Tsvetkov, Martin; Spassov, Tony

    2018-07-01

    Novel visible light-driven heterostructured NiO/g-C3N4 photocatalyst has been designed and successfully prepared via ammonia-evaporation-induced method. The synthetic strategy consists of grafting the surface of g-C3N4 with Ni(NH3)62+ complex followed by its hydrolysis at lower pH to form nano-wrinkled thin film of α-Ni(OH)2. The final NiO/g-C3N4 hybrid was obtained after calcination of the Ni(OH)2/g-C3N4 precursor at 350 °C. Scanning electron microscopy, transmission electron microscopy, X-ray diffraction, FTIR, N2 adsorption/desorption, UV-vis diffuse reflectance and photoluminescence spectroscopy were used to characterize the resulting material. Our results revealed the formation of meso-/macroporous three-dimensional hierarchical honeycomb-like structure with high BET surface area (141 m2 g-1). The photocatalytic performance of the composite under visible light (λ > 400 nm) irradiation was evaluated through degradation of Malachite Green (MG) from aqueous medium at room temperature (25 °C). For the sake of comparison, the physico-chemical and photocatalytic properties of the pristine g-C3N4 and nanostructured NiO were also examined. Results indicated that NiO/g-C3N4 is much more active than pristine g-C3N4 and NiO in the photodegradation of MG. The enhanced photocatalytic performance of the composite was mainly attributed to the combination of high adsorption capacity which facilitates the direct redox reactions of dye and the efficient inhibition of photo-generated electron-hole pair recombination. Superoxide radicals (•O2-) and photo-generated holes (h+) were found to be the main active species in the process.

  14. Synthesis and Magnetic Properties of Fe-Co-Ni/C Nanocomposites

    NASA Astrophysics Data System (ADS)

    Muratov, D. G.; Kozhitov, L. V.; Karpenkov, D. Yu.; Yakushko, E. V.; Korovin, E. Yu.; Vasil'ev, A. V.; Popkova, A. V.; Kazaryan, T. M.; Shadrinov, A. V.

    2018-03-01

    Nanoparticles of the Fe-Co-Ni ternary alloy, encapsulated in the carbon matrix of nanocomposites, have been synthesized, The structure, phase composition, and magnetic properties of the obtained materials have been determined with the help of diffractometry and magnetometry. It has been established that nanoparticles of the ternary alloy are formed due to solution of cobalt in the Fe-Ni alloy. The composition of the nanoparticles of the alloy depends on the mass percent ratio of the metas in the precursor. With growth of the iron content, nanoparticles of the ternary alloy with various composition are formed with FCC and BCC crystal lattice structure. As the synthesis temperature and relative iron content are increased, the magnetization of the Fe-Co-Ni/C nanocomposites increases from 26 to 157 A·m2/kg. The coercive force is determined by the synthesis temperature, the size of the nanoparticles, and the composition of the alloy, and its value varies from 330 to 43 Oe.

  15. Change of magnetic properties of nanocrystalline alloys under influence of external factors

    NASA Astrophysics Data System (ADS)

    Sitek, Jozef; Holková, Dominika; Dekan, Julius; Novák, Patrik

    2016-10-01

    Nanocrystalline (Fe3Ni1)81Nb7B12 alloys were irradiated using different types of radiation and subsequently studied by Mössbauer spectroscopy. External magnetic field of 0.5 T, electron-beam irradiation up to 4 MGy, neutron irradiation up to 1017 neutrons/cm2 and irradiation with Cu ions were applied on the samples. All types of external factors had an influence on the magnetic microstructure manifested as a change in the direction of the net magnetic moment, intensity of the internal magnetic field and volumetric fraction of the constituent phases. The direction of the net magnetic moment was the most sensitive parameter. Changes of the microscopic magnetic parameters were compared after different external influence and results of nanocrystalline samples were compared with their amorphous precursors.

  16. Crystallographic and magnetic properties of nanocrystalline perovskite structure SmFeO3 orthoferrite

    NASA Astrophysics Data System (ADS)

    Kumar, Ashwini; Shen, Jingdong; Zhao, Huihui; Zhengjian, Qi; Li, Qi

    2018-05-01

    In this article, we present the structural and magnetic studies of pristine SmFeO3 nanocrystalline ceramic samples as sintered at temperature 850 °C and 1000 °C. X-ray powder diffraction data confirm the existence of single-phase nature with orthorhombic (Pbnm) structure of the samples. The SEM image reveals spherical particles with a size range of 60-130 nm for SFO-850 and SFO-1000 samples. X-ray absorption spectroscopy studies on Fe L3,2 and O K-edges of SmFeO3 sample revealed the homo-valence state of Fe in these materials. From magnetization studies it has been observed the materials exhibit ferromagnetic and antiferromagnetic (canted spin structure) sub-lattices, which results strong magnetic anisotropy in the system.

  17. Ultrafast surface modification of Ni3S2 nanosheet arrays with Ni-Mn bimetallic hydroxides for high-performance supercapacitors.

    PubMed

    Zou, Xu; Sun, Qing; Zhang, Yuxin; Li, Guo-Dong; Liu, Yipu; Wu, Yuanyuan; Yang, Lan; Zou, Xiaoxin

    2018-03-14

    Amorphous Ni-Mn bimetallic hydroxide film on the three-dimensional nickle foam (NF)-supported conductive Ni 3 S 2 nanosheets (denoted as Ni-Mn-OH@Ni 3 S 2 /NF) is successfully synthesized by an ultrafast process (5 s). The fascinating structural characteristic endows Ni-Mn-OH@Ni 3 S 2 /NF electrodes better electrochemical performance. The specific capacitance of 2233.3 F g -1 at a current density of 15 A g -1 can achieve high current density charge and discharge at 20/30 A g -1 that the corresponding capacitance is 1529.16 and 1350 F g -1 , respectively. As well as good cycling performance after 1000 cycles can maintain 72% at 15 A g -1 . The excellent performance can be attributed to unique surface modification nanostructures and the synergistic effect of the bimetallic hydroxide film. The impressive results provide new opportunity to produce advanced electrode materials by simple and green route and this material is expected to apply in high energy density storage systems.

  18. Metal-insulator transition in Nd(1-x)Eu(x)NiO(3) compounds.

    PubMed

    Escote, M T; Barbeta, V B; Jardim, R F; Campo, J

    2006-07-05

    Polycrystalline Nd(1-x)Eu(x)NiO(3) (0≤x≤0.5) compounds were synthesized in order to investigate the character of the metal-insulator (MI) phase transition in this series. Samples were prepared through the sol-gel route and subjected to heat treatments at ∼1000 °C under oxygen pressures as high as 80 bar. X-ray diffraction (XRD) and neutron powder diffraction (NPD), electrical resistivity ρ(T), and magnetization M(T) measurements were performed on these compounds. The NPD and XRD results indicated that the samples crystallize in an orthorhombic distorted perovskite structure, space group Pbnm. The analysis of the structural parameters revealed a sudden and small expansion of ∼0.2% of the unit cell volume when electronic localization occurs. This expansion was attributed to a small increase of ∼0.003 Å of the average Ni-O distance and a simultaneous decrease of ∼-0.5° of the Ni-O-Ni superexchange angle. The ρ(T) measurements revealed a MI transition occurring at temperatures ranging from T(MI)∼193 to 336 K for samples with x = 0 and 0.50, respectively. These measurements also show a large thermal hysteresis in NdNiO(3) during heating and cooling processes, suggesting a first-order character of the phase transition at T(MI). The width of this thermal hysteresis was found to decrease appreciably for the sample Nd(0.7)Eu(0.3)NiO(3). The results indicate that cation disorder associated with increasing substitution of Nd by Eu is responsible for changing the first-order character of the transition in NdNiO(3).

  19. Electrodeposition of Nanocrystalline Ni–Fe Alloy Coatings Based on 1-Butyl-3-Methylimidazolium-Hydrogen Sulfate Ionic Liquid.

    PubMed

    He, Xinkuai; Zhang, Chuang; Zhu, Qingyun; Lu, Haozi; Cai, Youxing; Wu, Luye

    2017-02-01

    The electrodeposition of nanocrystalline Ni–Fe alloy coatings and associated nucleation/growth processes are investigated on the glassy carbon (GC) electrode in 1-butyl-3-methylimidazolium-hydrogen sulfate ([BMIM]HSO4) ionic liquid (IL). Cyclic voltammetric data suggest that the co-electrodeposition of Ni–Fe alloys is quasi-reversible. Moreover, chronoamperometry results indicate that the electrodeposition proceeds via a simultaneous nucleation and three-dimensional growth mechanism. In addition, the effects of electrodeposition potential and electrolyte temperature on the coating thickness and Fe content are also studied. The microstructure and composition of the Ni–Fe alloy coatings on Cu substrate are investigated using scanning electron microscopy (SEM), X-ray diffraction (XRD) and energy-dispersive spectroscopy (EDS). SEM observations show that these electrodeposits present a dense and compact structure, EDS analysis indicates that the coatings are composed of Ni and Fe, XRD pattern shows the coatings are crystalline with a face-centred cubic (fcc) structure. Tafel plots reveal that the Ni–Fe alloy prepared from [BMIM]HSO4 IL presents better corrosion resistance than that of pure Ni.

  20. Luminescence and related properties of nanocrystalline porous silicon

    NASA Astrophysics Data System (ADS)

    Koshida, N.

    This document is part of subvolume C3 'Optical Properties' of volume 34 'Semiconductor quantum structures' of Landolt-Börnstein, Group III, Condensed Matter, on the optical properties of quantum structures based on group IV semiconductors. It discusses luminescence and related properties of nanocrystalline porous silicon. Topics include an overview of nanostructured silicon, its fabrication technology, and properties of nanocrystalline porous silicon such as confinement effects, photoluminescence, electroluminesce, carrier charging effects, ballistic transport and emission, and thermally induced acoustic emission.

  1. Mechanically induced self-propagating reaction and consequent consolidation for the production of fully dense nanocrystalline Ti{sub 55}C{sub 45} bulk material

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Sherif El-Eskandarany, M., E-mail: msherif@kisr.edu.kw; Al-Hazza, Abdulsalam

    2014-11-15

    We employed a high-energy ball mill for the synthesis of nanograined Ti{sub 55}C{sub 45} powders starting from elemental Ti and C powders. The mechanically induced self-propagating reaction that occurred between the reactant materials was monitored via a gas atmosphere gas-temperature-monitoring system. A single phase of NaCl-type TiC was obtained after 5 h of ball milling. To decrease the powder and grain sizes, the material was subjected to further ball milling time. The powders obtained after 200 h of milling possessed spherical-like morphology with average particle and grain sizes of 45 μm and 4.2 nm, respectively. The end-products obtained after 200more » h of ball milling time, were then consolidated into full dense compacts, using hot pressing and spark plasma sintering at 1500 and 34.5 MPa, with heating rates of 20 °C/min and 500 °C/min, respectively. Whereas hot pressing of the powders led to severe grain growth (∼ 436 nm in diameter), the as-spark plasma sintered powders maintained their nanograined characteristics (∼ 28 nm in diameter). The as-synthesized and as-consolidated powders were characterized, using X-ray diffraction, high-resolution electron microscopy, and scanning electron microscopy. The mechanical properties of the consolidated samples obtained via the hot pressing and spark plasma sintering techniques were characterized, using Vickers microhardness and non-destructive testing techniques. The Vickers hardness, Young's modulus, shear modulus and fracture toughness of as-spark plasma sintered samples were 32 GPa, 358 GPa, 151 GPa and 6.4 MPa·m{sup 1/2}, respectively. The effects of the consolidation approach on the grain size and mechanical properties were investigated and are discussed. - Highlights: • Room-temperature synthesizing of NaCl-type TiC • Dependence on the grain size on the ball milling time • Fabrication of equiaxed nanocrystalline grains with a diameter of 4.2 nm • Fabrication of nanocrystalline bulk TiC

  2. Evaluation and comparision of dc resistivity of NiZr x Co x Fe2-2x O4, Ni0.5Sn0.5Co x Mn x Fe2-2x O4, Mg1-x Ca x Ni y Fe2-y O4 and Mg1-x Ni x Co y Fe2-y O4 nanocrytalline materials

    NASA Astrophysics Data System (ADS)

    Ali, Rajjab; Gilani, Zaheer Abbas; Shahzad Shifa, Muhammad; Asghar, H. M. Noor Ul Huda Khan; Azhar Khan, Muhammad; Naeem Anjum, Muhammad; Nauman Usmani, Muhammad; Farooq Warsi, Muhammad; Khawaja, Imtiaz U.

    2017-11-01

    Four series nanocrystalline ferrites with nominal composition, NiZr x Co x Fe2-2x O4 (x  =  0.0, 0.2, 0.4, 0.6, 0.8) Ni0.5Sn0.5Co x Mn x Fe2-2x O4 (x  =  0.0, 0.2, 0.4, 0.6, 0.8), Mg1-x Ca x Ni y Fe2-y O4 (x  =  0.0, 0.2, 0.4, 0.6, 0.8; y  =  0, 04, 0.8, 1.2, 1.6) and Mg1-x Ni x Co y Fe2-y O4 (x,y  =  0.0, 0.2, 0.4, 0.6, 0.8) have been fabricated using the microemulsion synthesis route. The synthesized materials are investigated for dc electrical resistivity measurements. The variation of dc electrical resistivity of these materials has been explainedon the basis of hopping mechanism of both holes and electrons.

  3. Hydrothermal synthesis of mesoporous rod-like nanocrystalline vanadium oxide hydrate V{sub 3}O{sub 7}·H{sub 2}O from hydroquinone and V{sub 2}O{sub 5}

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Mjejri, I.; Etteyeb, N.; Sediri, F., E-mail: faouzi.sediri@ipeit.rnu.tn

    2013-09-01

    Graphical abstract: - Highlights: • Rod-like nanocrystalline V{sub 3}O{sub 7}·H{sub 2}O has heen synthesized hydrothermally. • Molar ratio is key factor for structure and morphology. • Electrochemical properties were also studied. • CV has revealed reversible redox behavior with charge–discharge cycling. - Abstract: Rod-like nanocrystalline V{sub 3}O{sub 7}·H{sub 2}O has been synthesized hydrothermally via a simple and elegant route. Techniques X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, thermal analysis (TG-DTA), X-ray photoelectron spectroscopy (XPS), UV–vis spectroscopy and nitrogen adsorption/desorption isotherms have been used to characterize the structure, morphology and composition of the materials.more » The as-prepared V{sub 3}O{sub 7}·H{sub 2}O nanorods are up to several of micrometers in length, about 130 nm in width and about 70 nm in thickness in average, respectively. Cyclic voltammetric characterization of thin films of V{sub 3}O{sub 7}·H{sub 2}O nanorods has revealed reversible redox behavior with charge–discharge cycling corresponding to the reversible lithium intercalation/deintercalation.« less

  4. Facile synthesis of nickel-based metal organic framework [Ni3(HCOO)6] by microwave method and application for supercapacitor

    NASA Astrophysics Data System (ADS)

    Luo, Jujie; Yang, Xing; Wang, Shumin; Bi, Yuhong; Nautiyal, Amit; Zhang, Xinyu

    The metal organic framework (MOF) [Ni3(HCOO)6] was synthesized via the simple and fast microwave method, and the effect of irradiation power on crystallinity of synthesized Ni-based MOF was studied. The samples were characterized by using Fourier Transform Infrared Spectroscopy (FTIR), X-ray diffraction (XRD), and scanning electron microscopy (SEM). The synthesized Ni-based MOF was electrochemically characterized by using galvanostatic charge-discharge (GCD), cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS) techniques. The synthesized MOF showed the highest specific capacitance of 1196.2F/g at 1A/g with excellent cyclability (86.04% capacitance retention after 2,000 cycles), thereby demonstrating its potential application in supercapacitors.

  5. Optimization and Analysis of Thermoelectric Properties of Unfilled Co(1-x-y)Ni(x)Fe(y)Sb3 Synthesized via a Rapid Hydrothermal Procedure.

    PubMed

    Gharleghi, Ahmad; Chu, Yu-Hsien; Lin, Fei-Hung; Yang, Zong-Ren; Pai, Yi-Hsuan; Liu, Chia-Jyi

    2016-03-02

    A series of nanostructured co-doped Co(1-x-y)Ni(x)Fe(y)Sb3 were fabricated using a rapid hydrothermal method at 170 °C for a duration of 12 h, followed by evacuated-and-encapsulated heating at 580 °C for a short period of 5 h. The resulting samples were characterized using powder X-ray diffraction, field emission scanning electron microscopy, bulk density, electronic and thermal transport measurements. The power factor of Co(1-x-y)Ni(x)Fe(y)Sb3 is significantly enhanced in the high-temperature region due to significant enhancement of the electrical conductivity and absolute value of thermopower. The latter arises from the onset of bipolar effect being shifted to higher temperatures as compared with the non-doped CoSb3. The room temperature thermal conductivity falls in the range between 1.22 and 1.67 W m(-1) K(-1) for Co(1-x-y)Ni(x)Fe(y)Sb3. The thermal conductivity of both the (x,y) = (0.14,10) and (0.14,12) samples is measured up to 600 K and found to decrease with increasing temperature. The thermal conductivity of the (0.14,10) sample goes down to ∼1.02 W m(-1) K(-1). As a result, zT = 0.68 is attained at 600 K. The lattice thermal conductivity is analyzed to gain insight into the contribution of various scattering processes that suppress the heat transfer through the phonons in Co(1-x-y)Ni(x)Fe(y)Sb3. The effect of the simultaneous presence of Co, Ni, and Fe elements on the electronic structure and transport properties of Co(1-x-y)Ni(x)Fe(y)Sb3 is described using the quantum mechanical tunneling theory of electron transmission among the potential barriers.

  6. Dielectric and magnetic studies of Cr+3 doped nickel ferrite by combustion method

    NASA Astrophysics Data System (ADS)

    Parveez, Asiya; Shekhawat, M. S.; Sindhu, S.; Srikanth, C.; Nayeem, Firdous; Mohd. Shariff, S.; Sinha, R. R.; Chaudhuri, Arka; Khader, S. Abdul

    2018-05-01

    Cr+3 doped nickel ferrite nanoparticles having the basic composition NiCrxFe2-xO4 (x=0, 0.1, 0.15, 0.2, 1) were prepared using auto combustion method. Structural, dielectric, a.c conductivity and magnetic properties of these samples, which are sintered at 800°C were studied. The structures of the synthesized samples were probed by X-ray diffraction (XRD) studies. The peaks observed in the XRD spectrum indicated single phase spinel cubic structure for the synthesized samples. Surface morphology of the samples has been investigated using Field Emission Scanning Electron Microscope (FESEM). The dielectric constant (ɛ') and dielectric loss factor (ɛ″) of nanocrystalline nickel ferrites were investigated as a function of frequency and Cr+3 concentration at room temperature over the frequency range 100 Hz to 1 MHz using Hioki make LCR Hi-Tester 3250. The dependence of ɛ' and ɛ″ with the frequency of the alternating applied electric field is in accordance with the Maxwell-Wagner type interfacial polarization, which is in agreement with the Koop's theory. The electrical conductivity (σac) deduced from the measured dielectric data has been thoroughly analyzed and found that the conduction mechanism in NiCrxFe2-xO4 nanoferrites are in conformity with the electron hopping model. The magnetic properties of Cr+3 doped nano-nickel ferrite were analyzed using a Vibrating Sample Magnetometer (VSM). It is observed that the values of saturation magnetization decreases along with the increase in chromium content.

  7. Microstructure, Mechanical Properties, and Two-Body Abrasive Wear Behavior of Cold-Sprayed 20 vol.% Cubic BN-NiCrAl Nanocomposite Coating

    NASA Astrophysics Data System (ADS)

    Luo, Xiao-Tao; Yang, Er-Juan; Shang, Fu-Lin; Yang, Guan-Jun; Li, Chen-Xin; Li, Chang-Jiu

    2014-10-01

    20 vol.% cubic boron nitride (cBN) dispersoid reinforced NiCrAl matrix nanocomposite coating was prepared by cold spray using mechanically alloyed nanostructured composite powders. The as-sprayed nanocomposite coating was annealed at a temperature of 750 °C to enhance the inter-particle bonding. Microstructure of spray powders and coatings was characterized. Vickers microhardness of the coatings was measured. Two-body abrasive wear behavior of the coatings was examined on a pin-on-disk test. It was found that, in mechanically alloyed composite powders, nano-sized and submicro-sized cBN particles are uniformly distributed in nanocrystalline NiCrAl matrix. Dense coating was deposited by cold spray at a gas temperature of 650 °C with the same phases and grain size as those of the starting powder. Vickers hardness test yielded a hardness of 1063 HV for the as-sprayed 20 vol.% cBN-NiCrAl coating. After annealed at 750 °C for 5 h, unbonded inter-particle boundaries were partially healed and evident grain growth of nanocrystalline NiCrAl was avoided. Wear resistance of the as-sprayed 20 vol.% cBN-NiCrAl nanocomposite coating was comparable to the HVOF-sprayed WC-12Co coating. Annealing of the nanocomposite coating resulted in the improvement of wear resistance by a factor of ~33% owing to the enhanced inter-particle bonding. Main material removal mechanisms during the abrasive wear are also discussed.

  8. The crystal structures of Ni{sub 3+x}Sn{sub 4}Zn and Ni{sub 6+x}Sn{sub 8}Zn and their structural relations to Ni{sub 3+x}Sn{sub 4}, NiSn and Ni{sub 5−δ}ZnSn{sub 4}

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Schmetterer, Clemens, E-mail: clemens.schmetterer@univie.ac.at; Effenberger, Herta Silvia; Rajamohan, Divakar

    2016-06-15

    The crystal structures of two new compounds were determined from single-crystal X-ray diffraction measurements: Ni{sub 3+x}Sn{sub 4}Zn, (x~1.35, a=7.110(2) Å, b=4.123(1) Å, c=10.346(3) Å, β=90.23(2)°, space group I2/m, Z=2. R1=0.025, wR2=0.059 for 748 unique reflections, 35 variable parameters) and Ni{sub 6+x}Sn{sub 8}Zn, x~1.35 (a=12.379(3) Å, b=4.095(1) Å, c=12.155(3) Å, β=116.25(3)°, space group C2/m, Z=2. R1=0.026, wR2=0.052 for 1346 unique reflections, 60 variable parameters). In addition, a structural refinement was performed for Ni{sub 3+x}Sn{sub 4}, x~0.13 (a=12.264(3) Å, b=4.066(1) Å, c=5.223(2) Å, β=104.85(3)°, space group C2/m, Z=2. R1=0.019, wR2=0.046 for 617 unique reflections, 29 variable parameters). The three compounds show pronouncedmore » similarities among each other as well as to the crystal structures of surrounding binary Ni–Sn and ternary Ni–Sn–Zn compounds. In particular, the two new compounds form a homologous series with Ni{sub 3+x}Sn{sub 4}, x~0.13. They contain “Ni{sub 4}Sn{sub 4}” and “Ni{sub 2}Sn{sub 4}” building blocks which by different interconnection build up the distinct structures. Topological relations with NiSn and Ni{sub 5−δ}Sn{sub 4}Zn, δ~0.25 are evident. - Graphical abstract: Projection of the structure of Ni{sub 6+x}ZnSn{sub 8}, x~1.35 and constituent building blocks. Display Omitted - Highlights: • The crystal structures of Ni{sub 6+x}Sn{sub 8}Zn and Ni{sub 3+x}Sn{sub 4}Zn were determined using single crystal XRD. • Topological relations to Ni–Sn and Ni–Sn–Zn compounds were established and discussed. • Common structural units were identified and their interconnection patterns described.« less

  9. Synthesis and characterization of carbon coated LiCo1/3Ni1/3Mn1/3O2 and bio-mass derived graphene like porous carbon electrodes for aqueous Li-ion hybrid supercapacitor

    NASA Astrophysics Data System (ADS)

    Ramkumar, B.; Yuvaraj, S.; Surendran, S.; Pandi, K.; Ramasamy, Hari Vignesh; Lee, Y. S.; Kalai Selvan, R.

    2018-01-01

    For the fabrication of aqueous Li-ion hybrid supercapacitor, carbon coated LiCo1/3Ni1/3Mn1/3O2 (or LiCo1/3Ni1/3Mn1/3O2@C composite) is synthesized by polymeric precursor method with subsequent thermal decomposition procedures for carbon coating. Graphene like porous carbon is obtained by chemical activation from the biomass of Agave Americana. The XRD analysis reveals that LiCo1/3Ni1/3Mn1/3O2 is having a hexagonal layered structure and activated carbon exists in both amorphous and graphitic nature. The TEM image infers that LiCo1/3Ni1/3Mn1/3O2 particles having the non-uniform shape with sub-micron size and the LiCo1/3Ni1/3Mn1/3O2 particles are embedded into amorphous carbon cloud in the composite. The activated carbon shows the specific surface area of 1219 m2 g-1. Finally, the fabricated aqueous LiCo1/3Ni1/3Mn1/3O2@C‖AC hybrid supercapacitor delivers the specific capacitance of 56 F g-1 with good capacity retention even after 5000 cycles.

  10. Microwave assisted combustion synthesis of nanocrystalline CoFe2O4 for LPG sensing

    NASA Astrophysics Data System (ADS)

    Chaudhari, Prashant; Acharya, S. A.; Darunkar, S. S.; Gaikwad, V. M.

    2015-08-01

    A microwave-assisted citrate precursor method has been utilized for synthesis of nanocrystalline powders of CoFe2O4. The process takes only a few minutes to obtain as-synthesized CoFe2O4. Structural properties of the synthesized material were investigated by X-ray diffraction; scanning electron microscopy, Thermogravimetric analysis (TGA) and Fourier transform infrared spectroscopy. The gas sensing properties of thick film of CoFe2O4 prepared by screen printing towards Liquid Petroleum Gas (LPG) revealed that CoFe2O4 thick films are sensitive and shows maximum sensitivity at 350°C for 2500 ppm of LPG.

  11. Solid-state graphene formation via a nickel carbide intermediate phase [Nickel carbide (Ni 3C) as an intermediate phase for graphene formation

    DOE PAGES

    Xiong, W; Zhou, Yunshen; Hou, Wenjia; ...

    2015-11-10

    Direct formation of graphene with controlled number of graphitic layers on dielectric surfaces is highly desired for practical applications. Despite significant progress achieved in understanding the formation of graphene on metallic surfaces through chemical vapor deposition (CVD) of hydrocarbons, very limited research is available elucidating the graphene formation process via rapid thermal processing (RTP) of solid-state amorphous carbon, through which graphene is formed directly on dielectric surfaces accompanied by autonomous nickel evaporation. It is suggested that a metastable hexagonal nickel carbide (Ni 3C) intermediate phase plays a critical role in transforming amorphous carbon to 2D crystalline graphene and contributing tomore » the autonomous Ni evaporation. Temperature resolved carbon and nickel evolution in the RTP process is investigated using Auger electron spectroscopic (AES) depth profiling and glancing-angle X-ray diffraction (GAXRD). Formation, migration and decomposition of the hexagonal Ni 3C are confirmed to be responsible for the formation of graphene and the evaporation of Ni at 1100 °C. The Ni 3C-assisted graphene formation mechanism expands the understanding of Ni-catalyzed graphene formation, and provides insightful guidance for controlled growth of graphene through the solid-state transformation process.« less

  12. Hierachical Ni@Fe2O3 superparticles through epitaxial growth of γ-Fe2O3 nanorods on in situ formed Ni nanoplates

    NASA Astrophysics Data System (ADS)

    Tahir, Muhammad Nawaz; Herzberger, Jana; Natalio, Filipe; Köhler, Oskar; Branscheid, Robert; Mugnaioli, Enrico; Ksenofontov, Vadim; Panthöfer, Martin; Kolb, Ute; Frey, Holger; Tremel, Wolfgang

    2016-05-01

    One endeavour of nanochemistry is the bottom-up synthesis of functional mesoscale structures from basic building blocks. We report a one-pot wet chemical synthesis of Ni@γ-Fe2O3 superparticles containing Ni cores densely covered with highly oriented γ-Fe2O3 (maghemite) nanorods (NRs) by controlled reduction/decomposition of nickel acetate (Ni(ac)2) and Fe(CO)5. Automated diffraction tomography (ADT) of the Ni-Fe2O3 interface in combination with Mössbauer spectroscopy showed that selective and oriented growth of the γ-Fe2O3 nanorods on the Ni core is facilitated through the formation of a Fe0.05Ni0.95 alloy and the appearance of superstructure features that may reduce strain at the Ni-Fe2O3 interface. The common orientation of the maghemite nanorods on the Ni core of the superparticles leads to a greatly enhanced magnetization. After functionalization with a catechol-functional polyethylene glycol (C-PEG) ligand the Ni@γ-Fe2O3 superparticles were dispersible in water.One endeavour of nanochemistry is the bottom-up synthesis of functional mesoscale structures from basic building blocks. We report a one-pot wet chemical synthesis of Ni@γ-Fe2O3 superparticles containing Ni cores densely covered with highly oriented γ-Fe2O3 (maghemite) nanorods (NRs) by controlled reduction/decomposition of nickel acetate (Ni(ac)2) and Fe(CO)5. Automated diffraction tomography (ADT) of the Ni-Fe2O3 interface in combination with Mössbauer spectroscopy showed that selective and oriented growth of the γ-Fe2O3 nanorods on the Ni core is facilitated through the formation of a Fe0.05Ni0.95 alloy and the appearance of superstructure features that may reduce strain at the Ni-Fe2O3 interface. The common orientation of the maghemite nanorods on the Ni core of the superparticles leads to a greatly enhanced magnetization. After functionalization with a catechol-functional polyethylene glycol (C-PEG) ligand the Ni@γ-Fe2O3 superparticles were dispersible in water. Electronic supplementary

  13. Unexpected Reactivity of [(η(5) -1,2,4-tBu3 C5 H2 )Ni(η(3) -P3 )] towards Main Group Nucleophiles and by Reduction.

    PubMed

    Mädl, Eric; Balázs, Gábor; Peresypkina, Eugenia V; Scheer, Manfred

    2016-06-27

    The reduction of [Cp'''Ni(η(3) -P3 )] (1; Cp'''=η(5) -1,2,4-tBu3 C5 H2 ) with potassium produces the complex anion [(Cp'''Ni)2 (μ,η(2:2) -P8 )](2-) (2), which contains a realgar-like P8 unit. The anionic triple-decker sandwich complex [(Cp'''Ni)2 (μ,η(3:3) -P3 )](-) (3) with a cyclo-P3 middle deck is obtained when 1 is treated with NaNH2 as a nucleophile. Na[3] can subsequently be oxidized with AgOTf to the neutral triple-decker complex [(Cp'''Ni)2 (μ,η(3:3) -P3 )] (4). In contrast, 1 reacts with LiPPh2 to give the anionic compound [(Cp'''Ni)2 (μ,η(2:2) -P6 PPh2 )](-) (5), a complex containing a bicyclic P7 fragment capped by two Cp'''Ni units. Protonation of Li[5] with HBF4 leads to the neutral complex [(Cp'''Ni)2 (μ,η(2:2) -(HP6 PPh2 )] (6). Adding LiNMe2 to 1 results in [Cp'''Ni(η(2) -P3 NMe2 )](-) (7) becoming accessible, a complex which forms as a result of nucleophilic attack at the cyclo-P3 ring of 1. The complexes K2 [2], Na[3], 4, 6, and Li[7] were fully characterized and their structures determined by single-crystal X-ray diffraction. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  14. Improvement of the functional properties of nanostructured Ti-Ni shape memory alloys by means of thermomechanical processing

    NASA Astrophysics Data System (ADS)

    Kreitcberg, Alena

    Severe plastic deformation (SPD) is commonly used for nanostructure formation in Ti-Ni shape memory alloys (SMAs), but it increases the risk of damage during processing and, consequently, negatively affects functional fatigue resistance of these materials. The principal objective of this project is, therefore, to study the interrelations between the processing conditions, damageability during processing, microstructure and the functional properties of Ti-Ni SMAs with the aim of improving long-term functional performances of these materials by optimizing their processing conditions. First, microstructure and fatigue properties of Ti-Ni SMAs were studied after thermomechanical treatment (TMT) with different combinations of severe cold and warm rolling (CR and WR), as well as intermediate and post-deformation annealing (IA and PDA) technological steps. It was shown that either when WR and IA were introduced into the TMT schedule, or CR intensity was decreased, the fatigue life was improved as a consequence of less processing-induced damage and higher density of the favorable B2-austenite texture. This improvement was reached, however, at a price of a lower multi-cycle functional stability of these materials, the latter being a direct consequence of the microstructure coarsening after higher-temperature lower-intensity processing. At the end of this study, however, it was not possible to distinguish between contributions to the functional performances of Ti-Ni SMAs from different processing-related features: a) grain/subgrain size; b) texture; and c) level of rolling-induced defects. To be capable of separating contributions to the functional properties of Ti-Ni alloys from grain/subgrain size and from texture, the theoretical crystallographic resource of recovery strain after different TMTs and, therefore, different textures, were calculated and compared with the experiment. The comparative analysis showed that the structural factors (grain/subgrain size) strongly

  15. Crystallography of in-situ transformations of the M 7C3 carbide in the cast Fe-Cr-Ni alloy

    NASA Astrophysics Data System (ADS)

    Kraposhin, V. S.; Kondrat'ev, S. Yu.; Talis, A. L.; Anastasiadi, G. P.

    2017-03-01

    In the process of holding of the cast heat-resistant Fe-Cr-Ni (0.45C-25Cr-35Ni) alloy at 1150°C, the eutectic chromium carbide present in its structure undergoes a gradual transition M 7C3 → M 23C6. The gradual formation of domains of the M 23C6 carbide inside the particles of the M 7C3 carbide makes it possible to assume that the observed phase transition is the well-known carbide transformation of the in situ type. The mechanism of the in situ transformation of the crystal structure of the carbide from M 7C3 into M 23C6 with a change in the number of nearest metal neighbors of carbon atoms is explained within the previously developed combinatory model of polymorphic transitions in the metals.

  16. Two 3D structured Co-Ni bimetallic oxides as cathode catalysts for high-performance alkaline direct methanol fuel cells

    NASA Astrophysics Data System (ADS)

    Liu, Yan; Shu, Chengyong; Fang, Yuan; Chen, Yuanzhen; Liu, Yongning

    2017-09-01

    Two NiCo2O4 bimetallic oxides were synthesized via a facile hydrothermal method. SEM and TEM observations show that these materials have three-dimensional (3D) dandelion-like (DL) and flower-like (FL) morphologies. Their large specific surface areas (90.68 and 19.8 m2·g-1) and porous structures provide many active sites and effective transport pathways for the oxygen reduction reaction (ORR). Electrochemical measurements with a rotating ring-disc electrode (RRDE) indicate that the electron transfer numbers of the NiCo2O4-DL and NiCo2O4-FL catalysts for ORR in an alkaline solution are 3.97 and 3.91, respectively. Fuel cells were assembled with the bimetallic oxides, PtRu/C and a polymer fiber membrane (PFM) as cathode catalysts, anode catalyst and electrolyte film, respectively. For NiCo2O4-DL, the peak power density reaches up to 73.5 mW·cm-2 at 26 °C, which is the highest room-temperature value reported to date. The high catalytic activity of NiCo2O4 is mainly attributed to the presence of many Co3+ cations that directly donate electrons to O2 to reduce it via a more efficient and effective route. Furthermore, the catalytic performance of NiCo2O4-DL is superior to that of NiCo2O4-FL because it has a higher specific surface area and is less crystalline.

  17. Manipulating the Temperature of Sulfurization to Synthesize α-NiS Nanosphere Film for Long-Term Preservation of Non-enzymatic Glucose Sensors

    NASA Astrophysics Data System (ADS)

    Lin, Hsien-Sheng; Shi, Jen-Bin; Peng, Cheng-Ming; Zheng, Bo-Chi; Cheng, Fu-Chou; Lee, Ming-Way; Lee, Hsuan-Wei; Wu, Po-Feng; Liu, Yi-Jui

    2018-04-01

    In this study, alpha nickel sulfide (α-NiS) nanosphere films have been successfully synthesized by electroplating the nickel nanosheet film on the indium tin oxide (ITO) glass substrate and sulfuring nickel-coated ITO glass substrate. First, we electrodeposited the nickel nanosheet films on the ITO glass substrates which were cut into a 0.5 × 1 cm2 size. Second, the nanosheet nickel films were annealed in vacuum-sealed glass ampoules with sulfur sheets at different annealing temperatures (300, 400, and 500 °C) for 4 h in vacuum-sealed glass ampoules. The α-NiS films were investigated by using X-ray diffraction (XRD), variable vacuum scanning electron microscopy (VVSEM), field emission scanning electron microscopy/energy dispersive spectrometer (FE-SEM/EDS), cyclic voltammogram (CV), electrochemical impedance spectroscopy (EIS), ultraviolet/visible/near-infrared (UV/Visible/NIR) spectra, and photoluminescence (PL) spectra. Many nanospheres were observed on the surface of the α-NiS films at the annealing temperature 400 °C for 4 h. We also used the high-resolution transmission electron microscopy (HR-TEM) for the analysis of the α-NiS nanospheres. We demonstrated that our α-NiS nanosphere film had a linear current response to different glucose concentrations. Additionally, our α-NiS nanosphere films were preserved at room temperature for five and a half years and were still useful for detecting glucose at low concentration.

  18. A Threonine Stabilizes the NiC and NiR Catalytic Intermediates of [NiFe]-hydrogenase*

    PubMed Central

    Abou-Hamdan, Abbas; Ceccaldi, Pierre; Lebrette, Hugo; Gutiérrez-Sanz, Oscar; Richaud, Pierre; Cournac, Laurent; Guigliarelli, Bruno; De Lacey, Antonio L.; Léger, Christophe; Volbeda, Anne; Burlat, Bénédicte; Dementin, Sébastien

    2015-01-01

    The heterodimeric [NiFe] hydrogenase from Desulfovibrio fructosovorans catalyzes the reversible oxidation of H2 into protons and electrons. The catalytic intermediates have been attributed to forms of the active site (NiSI, NiR, and NiC) detected using spectroscopic methods under potentiometric but non-catalytic conditions. Here, we produced variants by replacing the conserved Thr-18 residue in the small subunit with Ser, Val, Gln, Gly, or Asp, and we analyzed the effects of these mutations on the kinetic (H2 oxidation, H2 production, and H/D exchange), spectroscopic (IR, EPR), and structural properties of the enzyme. The mutations disrupt the H-bond network in the crystals and have a strong effect on H2 oxidation and H2 production turnover rates. However, the absence of correlation between activity and rate of H/D exchange in the series of variants suggests that the alcoholic group of Thr-18 is not necessarily a proton relay. Instead, the correlation between H2 oxidation and production activity and the detection of the NiC species in reduced samples confirms that NiC is a catalytic intermediate and suggests that Thr-18 is important to stabilize the local protein structure of the active site ensuring fast NiSI-NiC-NiR interconversions during H2 oxidation/production. PMID:25666617

  19. A threonine stabilizes the NiC and NiR catalytic intermediates of [NiFe]-hydrogenase.

    PubMed

    Abou-Hamdan, Abbas; Ceccaldi, Pierre; Lebrette, Hugo; Gutiérrez-Sanz, Oscar; Richaud, Pierre; Cournac, Laurent; Guigliarelli, Bruno; De Lacey, Antonio L; Léger, Christophe; Volbeda, Anne; Burlat, Bénédicte; Dementin, Sébastien

    2015-03-27

    The heterodimeric [NiFe] hydrogenase from Desulfovibrio fructosovorans catalyzes the reversible oxidation of H2 into protons and electrons. The catalytic intermediates have been attributed to forms of the active site (NiSI, NiR, and NiC) detected using spectroscopic methods under potentiometric but non-catalytic conditions. Here, we produced variants by replacing the conserved Thr-18 residue in the small subunit with Ser, Val, Gln, Gly, or Asp, and we analyzed the effects of these mutations on the kinetic (H2 oxidation, H2 production, and H/D exchange), spectroscopic (IR, EPR), and structural properties of the enzyme. The mutations disrupt the H-bond network in the crystals and have a strong effect on H2 oxidation and H2 production turnover rates. However, the absence of correlation between activity and rate of H/D exchange in the series of variants suggests that the alcoholic group of Thr-18 is not necessarily a proton relay. Instead, the correlation between H2 oxidation and production activity and the detection of the NiC species in reduced samples confirms that NiC is a catalytic intermediate and suggests that Thr-18 is important to stabilize the local protein structure of the active site ensuring fast NiSI-NiC-NiR interconversions during H2 oxidation/production. © 2015 by The American Society for Biochemistry and Molecular Biology, Inc.

  20. Microstructural and optical properties of Mn doped NiO nanostructures synthesized via sol-gel method

    NASA Astrophysics Data System (ADS)

    Shah, Shamim H.; Khan, Wasi; Naseem, Swaleha; Husain, Shahid; Nadeem, M.

    2018-04-01

    Undoped and Mn(0, 5%, 10% and 15%) doped NiO nanostructures were synthesized by sol-gel method. Structure, morphology and optical properties were investigated through XRD, FTIR, SEM/EDS and UV-visible absorption spectroscopy techniques. XRD data analysis reveals the single phase nature with cubic crystal symmetry of the samples and the average crystallite size decreases with the doping of Mn ions upto 10%. FTIR spectra further confirmed the purity and composition of the synthesized samples. The non-spherical shape of the nanostructures was observed from SEM micrographs and gain size of the nanostructures reduces with Mn doping in NiO, whereas agglomeration increases in doped sample. Optical band gap was estimated using Tauc'srelation and found to increase on incorporation of Mn upto 10% in host lattice and then decreases for further doping.

  1. Iron-rich (Fe1-x-yNixCoy)88Zr7B4Cu1 nanocrystalline magnetic materials for high temperature applications with minimal magnetostriction

    NASA Astrophysics Data System (ADS)

    Martone, Anthony; Dong, Bowen; Lan, Song; Willard, Matthew A.

    2018-05-01

    As inductor technology advances, greater efficiency and smaller components demand new core materials. With recent developments of nanocrystalline magnetic materials, soft magnetic properties of these cores can be greatly improved. FeCo-based nanocrystalline magnetic alloys have resulted in good soft magnetic properties and high Curie temperatures; however, magnetoelastic anisotropies persist as a main source of losses. This investigation focuses on the design of a new Fe-based (Fe,Ni,Co)88Zr7B4Cu1 alloy with reduced magnetostriction and potential for operation at elevated temperatures. The alloys have been processed by arc melting, melt spinning, and annealing in a protective atmosphere to produce nanocrystalline ribbons. These ribbons have been analyzed for structure, hysteresis, and magnetostriction using X-Ray diffraction, vibrating sample magnetometry (VSM), and a home-built magnetostriction system, respectively. In addition, Curie temperatures of the amorphous phase were analyzed to determine the best performing, high-temperature material. Our best result was found for a Fe77Ni8.25Co2.75Zr7B4Cu1 alloy with a 12 nm average crystallite size (determined from Scherrer broadening) and a 2.873 Å lattice parameter determined from the Nelson-Riley function. This nanocrystalline alloy possesses a coercivity of 10 A/m, magnetostrictive coefficient of 4.8 ppm, and amorphous phase Curie temperature of 218°C.

  2. Nanocrystalline sp{sup 2} and sp{sup 3} carbons: CVD synthesis and applications

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Terranova, M. L.; Rossi, M.; Tamburri, E., E-mail: emanuela.tamburri@uniroma2.it

    The design and production of innovative materials based on nanocrystalline sp{sup 2}- and sp{sup 3}-coordinated carbons is presently a focus of the scientific community. We present a review of the nanostructures obtained in our labs using a series of synthetic routes, which make use of chemical vapor deposition (CVD) techniques for the selective production of non-planar graphitic nanostructures, nanocrystalline diamonds, and hybrid two-phase nanostructures.

  3. [Effect of temperature on the structure of CaO-MgO-Al2O3-SiO2 nanocrystalline glass-ceramics studied by Raman spectroscopy].

    PubMed

    Li, Bao-Wei; Ouyang, Shun-Li; Zhang, Xue-Feng; Jia, Xiao-Lin; Deng, Lei-Bo; Liu, Fang

    2014-07-01

    In the present paper, nanocrystalline glass-ceramic of CaO-MgO-Al2O3-SiO2 system was produced by melting method. The CaO-MgO-Al2O3-SiO2 nanocrystalline glass-ceramic was measured by Raman spectroscopy in the temperature range from -190 to 310 degrees C in order to study the effect of temperature on the structure of this system nanocrystalline glass-ceramics. The results showed that different non-bridge oxygen bond silicon-oxygen tetrahedron structural unit changes are not consistent with rising temperature. Further analyses indicated that: the SiO4 tetrahedron with 2 non-bridged oxygen (Q2), the SiO4 tetrahedron with 3 non-bridged oxygen (Q(1)), which are situated at the edge of the 3-D SiO4 tetrahedrons network, and the SiO4 tetrahedron with 4 non-bridged oxygen (Q(0)), which is situated outside the 3-D network all suffered a significant influence by the temperature change, which has been expressed as: shifts towards the high wave-number, increased bond force constants, and shortened bond lengths. This paper studied the influence of temperature on CMAS system nanocrystalline glass-ceramics using variable temperature Raman technology. It provides experiment basis to the research on external environment influence on CMAS system nanocrystalline glass-ceramics materials in terms of structure and performance. In addition, the research provides experimental basis for controlling the expansion coefficient of nanocrystalline glass-ceramic of CaO-MgO-Al2O3-SiO2 system.

  4. Composite Ni/NiO-Cr2O3 Catalyst for Alkaline Hydrogen Evolution Reaction

    PubMed Central

    Bates, Michael K.; Jia, Qingying; Ramaswamy, Nagappan; Allen, Robert J.; Mukerjee, Sanjeev

    2015-01-01

    We report a Ni–Cr/C electrocatalyst with unprecedented mass-activity for the hydrogen evolution reaction (HER) in alkaline electrolyte. The HER kinetics of numerous binary and ternary Ni-alloys and composite Ni/metal-oxide/C samples were evaluated in aqueous 0.1 M KOH electrolyte. The highest HER mass-activity was observed for Ni–Cr materials which exhibit metallic Ni as well as NiOx and Cr2O3 phases as determined by X-ray diffraction (XRD) and X-ray absorption spectroscopy (XAS) analysis. The onset of the HER is significantly improved compared to numerous binary and ternary Ni-alloys, including Ni–Mo materials. It is likely that at adjacent Ni/NiOx sites, the oxide acts as a sink for OHads, while the metallic Ni acts as a sink for the Hads intermediate of the HER, thus minimizing the high activation energy of hydrogen evolution via water reduction. This is confirmed by in situ XAS studies that show that the synergistic HER enhancement is due to NiOx content and that the Cr2O3 appears to stabilize the composite NiOx component under HER conditions (where NiOx would typically be reduced to metallic Ni0). Furthermore, in contrast to Pt, the Ni(Ox)/Cr2O3 catalyst appears resistant to poisoning by the anion exchange ionomer (AEI), a serious consideration when applied to an anionic polymer electrolyte interface. Furthermore, we report a detailed model of the double layer interface which helps explain the observed ensemble effect in the presence of AEI. PMID:26191118

  5. Thermal treatment to enhance saturation magnetization of superparamagnetic Ni nanoparticles while maintaining low coercive force

    NASA Astrophysics Data System (ADS)

    Ishizaki, Toshitaka; Yatsugi, Kenichi; Akedo, Kunio

    2018-05-01

    Superparamagnetic nanoparticles capped by insulators have the potential to decrease eddy current and hysteresis losses. However, the saturation magnetization ( M s) decreases significantly with decreasing the particle size. In this study, superparamagnetic Ni nanoparticles having the mean size of 11.6 ± 1.8 nm were synthesized from the reduction of Ni(II) acetylacetonate in oleylamine with the addition of trioctylphosphine, indicating the coercive force ( H c) less than 1 Oe. Thermal treatments of the Ni nanoparticles were investigated as a method to enhance the M s. The results indicated that the M s was enhanced by an increase of the Ni mass ratio with increasing thermal treatment temperature. However, the decomposition behavior of the capping layers indicated that their alkyl chains actively decomposed at temperatures above 523 K to form Ni3P via reaction between Ni and P, resulting in particle growth with a significant increase in the H c. Therefore, the optimal temperature was determined to be 473 K, which increased the Ni ratio without formation of Ni3P while maintaining particle sizes with superparamagnetic properties. Further, the M s could be improved by 22% (relative to the as-synthesized Ni nanoparticles) after thermal treatment at 473 K while maintaining the H c to be less than 1 Oe.

  6. Experimental investigation of in-situ transformations of the M 7C3 carbide in the cast Fe-Cr-Ni alloy

    NASA Astrophysics Data System (ADS)

    Kraposhin, V. S.; Kondrat'ev, S. Yu.; Talis, A. L.; Anastasiadi, G. P.

    2017-03-01

    The microstructure and the phase composition of a heat-resistant Fe-Cr-Ni alloy (0. 45C-25Cr-35Ni) has been investigated in the cast state and after annealing at 1150°C for 2-100 h. After a 2-h high-temperature annealing, the fragmentation of the crystal structure of the eutectic M 7C3 carbides into domains of 500 nm in size with a partial transition into M 23C6 carbides is observed. After a 100-h holding, the complete transition of the hexagonal M 7C3 carbides into M 23C6 with a face-centered cubic structure occurs. The carbide transition M 7C3 → M 23 can be considered to be an in situ transformation.

  7. Hollow core-shell structured Ni-Sn@C nanoparticles: a novel electrocatalyst for the hydrogen evolution reaction.

    PubMed

    Lang, Leiming; Shi, Yi; Wang, Jiong; Wang, Feng-Bin; Xia, Xing-Hua

    2015-05-06

    Pt-free electrocatalysts with high activity and low cost are highly pursued for hydrogen production by electrochemically splitting water. Ni-based alloy catalysts are potential candidates for the hydrogen evolution reaction (HER) and have been studied extensively. Here, we synthesized novel hollow core-shell structure Ni-Sn@C nanoparticles (NPs) by sol-gel, chemical vapor deposition, and etching processes. The prepared electrocatalysts with porous hollow carbon layers have a high conductivity and large active area, which exhibit good electrocatalytic activity toward HER. The Tafel slope of ∼35 millivolts per decade measured in acidic solution for Ni-Sn@C NPs is the smallest one to date for the Ni-Sn alloy catalysts, and exceeds those of the most non-noble metal catalysts, indicating a possible Volmer-Heyrovsky reaction mechanism. The synthetic method can be extended to prepare other hollow core-shell structure electrocatalysts for low-temperature fuel cells.

  8. Development of a flat-field spectrometer with a wideband Ni/C multilayer grating in the 1–3.5 keV range

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Imazono, Takashi

    2016-07-27

    To develop a flat-field spectrometer with coverage of the 1–3.5 keV range, a wideband Ni/C multilayer grating was invented. The multilayer consists of two kinds of layer structures. One is a conventional periodic multilayer of thickness D{sub 1} = 5.6 nm, Ni thickness ratio to the multilayer period γ{sub 1} = 0.5 and the number of layers N{sub 1} = 79. Both the first and last layers are Ni. The other is a C/Ni bilayer of D{sub 2} = 8.4 nm, γ{sub 2} = 0.53 and N{sub 2} = 2. The first layer is C and then Ni. The aperiodicmore » multilayer from the topmost C/Ni bilayer was coated on a laminar-type grating having an effective grating constant of 1/2400 mm, groove depth of 2.8 nm, and duty ratio (land width/groove period) of 0.5. In a preliminary experiment, the diffraction efficiency was in excess of 0.8% in the energy range of 2.1-3.3 keV and the maximum of 5.4% at 3.1 keV at a constant angle of incidence of 88.54°, which is considerably higher than that of an Au-coated grating before deposition of the multilayer.« less

  9. Effect of Ni doping on structural and optical properties of Zn{sub 1−x}Ni{sub x}O nanopowder synthesized via low cost sono-chemical method

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Singh, Budhendra, E-mail: bksingh@ua.pt; Kaushal, Ajay, E-mail: ajay.kaushal@ua.pt; Bdikin, Igor

    2015-10-15

    Highlights: • Pure and Ni doped ZnO nanopowders were synthesized by low cost sonochemical method. • The optical properties of Zn{sub 1−x}Ni{sub x}O nanopowders can be tuned by varying Ni content. • The results reveal the solubility limit of Ni into ZnO matrix as below 8%. - Abstract: Zn{sub 1−x}Ni{sub x}O nanopowders with different Ni contents of x = 0.0, 0.04 and 0.08 were synthesized via cost effective sonochemical reaction method. X-ray diffraction (XRD) pattern reveals pure wurtzite phase of prepared nanostructures with no additional impurity peaks. The morphology and dimensions of nanoparticles were investigated using scanning electron microscope (SEM).more » A sharp and strong peak for first order optical mode for wurtzite zinc oxide (ZnO) structure was observed at ∼438 cm{sup −1} in Raman spectra. The calculated optical band gap (E{sub g}) from UV–vis transmission data was found to decrease with increase in Ni content. The observed red shift in E{sub g} with increasing Ni content in ZnO nanopowders were in agreement with band gap behaviours found in their photoluminescence (PL) spectra. The synthesised ZnO nanopowders with controlled band gap on Ni doping reveals their potential for use in various electronic and optical device applications. The results were discussed in detail.« less

  10. Formation of Fe3O4@SiO2@C/Ni hybrids with enhanced catalytic activity and histidine-rich protein separation.

    PubMed

    Zhang, Yanwei; Zhang, Min; Yang, Jinbo; Ding, Lei; Zheng, Jing; Xu, Jingli; Xiong, Shenglin

    2016-09-21

    In this paper, we have developed an extended Stöber method to construct a Ni(2+)-polydopamine (PDA) complex thin coating on Fe3O4@SiO2 spheres, which can be carbonized to produce hybrid composites with metallic nickel nanoparticles embedded in a PDA-derived thin graphitic carbon layer (named Fe3O4@SiO2@C/Ni). Interestingly, by introducing a thin SiO2 spacer layer between PDA-Ni(2+) and Fe3O4, the reverse electron transfer from PDA to Fe3O4 is probably able to be suppressed in the calcination process, which leads to the in situ reduction of only Ni(2+) by PDA instead of Fe3O4 and Ni(2+). Consequently, the size and density of nickel nanoparticles on the surface of SiO2@Fe3O4 can be finely adjusted. Moreover, it is found that the ability of tuning nickel nanoparticles is mainly dependent on the thickness of the spacer layer. When the thickness of the SiO2 spacer is beyond the electron penetration depth, the size and density of nickel nanoparticles can be exactly tuned. The as-prepared Fe3O4@SiO2@C/Ni was employed as the catalyst to investigate the catalytic performance in the reduction of 4-nitrophenol (4-NP); furthermore, nickel nanoparticles decorated on Fe3O4@SiO2@C spheres display a strong affinity to His-tagged proteins (BHb and BSA) via a specific metal affinity force between polyhistidine groups and nickel nanoparticles.

  11. Evaluation of the magnetocaloric response of nano-sized La0.7Ca0.3Mn1-xNixO3 manganites synthesized by auto-combustion method

    NASA Astrophysics Data System (ADS)

    Gómez, Adrián; Chavarriaga, Edgar; Supelano, Iván; Parra, Carlos Arturo; Morán, Oswaldo

    2018-05-01

    A systematic study of the dependence of the magnetization on the magnetic field around the ferromagnetic-paramagnetic phase transition temperature is carried out on La0.7Ca0.3Mn1-xNixO3 (x=0, 0.02, 0.07, and 1) samples synthesized by auto-combustion method. The successful substitution of Mn3+ ions by Ni2+ ions in the La0.7Ca0.3MnO3 lattice is corroborated by X-ray diffraction technique. Banerjees criteria, Arrott plots, and the scaling hypothesis are used to analyze the experimental data. It is verified that the Ni-doping increases the operating temperature range for magnetocaloric effect through tuning of the magnetic transition temperature. Probably, the replacement of Mn3+ by Ni2+ ions in the La0.7Ca0.3MnO3 lattice weakens the Mn3+-O-Mn4+ double exchange interaction, which leads to a decrease in the transition temperature and magnetic moment in the samples. The Arrott plots suggest that the phase transition from ferromagnetic to paramagnetic in the nano-sized manganite is of second order. The analysis of the magnetization results show that the maximum magnetic entropy changes observed for x=0, 0.02, 0.07, and 0.1 compositions are 0.85, 0.77, 0.63, and 0.59 J/kg K, under a magnetic field of 1.5 T. These values indicate that the magnetic entropy change achieved for La0.7Ca0.3Mn1-xNixO3 manganites synthesized by auto-combustion method is higher than those reported for other manganites with comparable Ni-doping levels but synthesized by standard solid state reaction. It is also observed that the addition of Ni2+ increases the value of the relative cooling power as compared to that of the parent compound. The highest value of this parameter (˜60 J/kg) is found for a Ni-doping level of 2 % around 230 K in a field of 1.5 T.

  12. Structural transitions and multiferroic properties of high Ni-doped BiFeO3

    NASA Astrophysics Data System (ADS)

    Betancourt-Cantera, L. G.; Bolarín-Miró, A. M.; Cortés-Escobedo, C. A.; Hernández-Cruz, L. E.; Sánchez-De Jesús, F.

    2018-06-01

    Nickel doped bismuth ferrite powders, BiFe1-x NixO3 (0 ≤ x ≤ 0.5), were synthesized by high-energy ball milling followed by an annealing at 700 °C. A detailed study about the substitution of Fe3+ by Ni2+ on the crystal structure and multiferroic properties is presented. The X-ray diffraction patterns reveal the formation of rhombohedral structure with small amounts of Bi2Fe4O9 as a secondary phase for x < 0.1. Also it is inferred the stabilization of a Bi25FeO40, sillenite phase, as the amount of Ni2+ substitution increases, reaching up 95.23% of sillenite for x = 0.5. The magnetic behavior indicates the frustration of the G-antiferromagnetic order typical of the un-doped BiFeO3, caused by the presence of small amounts of Ni2+ (x < 0.1) on the structure. The DC conductivity exhibited a little increment with increasing Ni content (up to x = 0.1). Although the conductivity increases, for nickel concentrations of 0.2-0.5, the bismuth ferrites doped with nickel retain their property of being an electrical insulating material. Behavior modifications of electrical conductivity, permittivity and dielectric loss versus frequency are related with crystal structure transformations, when nickel concentration is increased.

  13. NiCo2S4 nanosheet-decorated 3D, porous Ni film@Ni wire electrode materials for all solid-state asymmetric supercapacitor applications.

    PubMed

    Saravanakumar, Balasubramaniam; Jayaseelan, Santhana Sivabalan; Seo, Min-Kang; Kim, Hak-Yong; Kim, Byoung-Suhk

    2017-12-07

    Wire type supercapacitors with high energy and power densities have generated considerable interest in wearable applications. Herein, we report a novel NiCo 2 S 4 -decorated 3D, porous Ni film@Ni wire electrode for high performance supercapacitor application. In this work, a facile method is introduced to fabricate a 3D, porous Ni film deposited on a Ni wire as a flexible electrode, followed by decoration with NiCo 2 S 4 as an electroactive material. The fabricated NiCo 2 S 4 -decorated 3D, porous Ni film@Ni wire electrode displays a superior performance with an areal and volumetric capacitance of 1.228 F cm -2 and 199.74 F cm -3 , respectively, at a current density of 0.2 mA cm -1 with a maximum volumetric energy and power density (E V : 6.935 mW h cm -3 ; P V : 1.019 W cm -3 ). Finally, the solid state asymmetric wire type supercapacitor is fabricated using the fabricated NiCo 2 S 4 -decorated 3D, porous Ni film@Ni wire as a positive electrode and N-doped reduced graphene oxide (N-rGO) as a negative electrode and this exhibits good areal and volumetric capacitances of C A : 0.12 F cm -2 and C V : 19.57 F cm -2 with a higher rate capability (92%). This asymmetric wire type supercapacitor demonstrates a low leakage current and self-discharge with a maximum volumetric energy (E V : 5.33 mW h cm -3 ) and power (P V : 855.69 mW cm -3 ) density.

  14. Reaction between NiO and Al2O3 in NiO/γ-Al2O3 catalysts probed by positronium atom

    NASA Astrophysics Data System (ADS)

    Li, C. Y.; Zhang, H. J.; Chen, Z. Q.

    2013-02-01

    NiO/γ-Al2O3 catalysts with NiO content of 9 wt% and 24 wt% were prepared by solid state reaction method. They are annealed in air at temperatures from 100 °C to 1000 °C. Positron lifetime spectra were measured to study the microstructure variation during annealing process. Four positron lifetime components were resolved with two long lifetime τ3 and τ4, which can be attributed to the ortho-positronium lifetime in microvoids and large pores, respectively. It was found that the longest lifetime τ4 is rather sensitive to the chemical environment of the large pores. The NiO active centers in the catalysts cause decrease of both τ4 and its intensity I4, which is due to the spin-conversion of positronium induced by NiO. However, after heating the catalysts above 600 °C, abnormal increase of the lifetime τ4 is observed. This is due to the formation of NiAl2O4 spinel from the reaction of NiO and γ-Al2O3. The generated NiAl2O4 weakens the spin-conversion effect of positronium, thus leads to the increase of o-Ps lifetime τ4. Formation of NiAl2O4 is further confirmed by both X-ray diffraction and X-ray photoelectron spectroscopy measurements.

  15. Synthesis of new 2-amino-4H-pyran-3,5-dicarboxylate derivatives using nanocrystalline MIIZr4(PO4)6 ceramics as reusable and robust catalysts under microwave irradiation

    NASA Astrophysics Data System (ADS)

    Safaei-Ghomi, Javad; Javidan, Abdollah; Ziarati, Abolfazl; Shahbazi-Alavi, Hossein

    2015-08-01

    In the present paper, we report the successful synthesis of nanocrystalline MIIZr4(PO4)6 ceramics (M: Mn, Ni, Fe, Co). These nano-structures were characterized by X-ray diffraction, scanning electron microscopy, and vibrating sample magnetometer (VSM). Size of nano-structures was in the range of 20-150 nm. Nano-MIIZr4(PO4)6 as an efficient and green catalyst has been used for the preparation of 2-amino-4H-pyran-3,5-dicarboxylate derivatives by the three-component condensation reaction of ethyl cyanoacetate, ethyl acetoacetate, and various aromatic aldehydes under microwave irradiation. Extraordinarily, the best results were obtained using MnZr4(PO4)6 nanocrystallines as an efficient catalyst. This method provides several advantages including easy work-up, excellent yields, short reaction times, using of microwave as green method, recoverability of the catalyst, and little catalyst loading.

  16. Nickel sulfide/graphitic carbon nitride/strontium titanate (NiS/g-C3N4/SrTiO3) composites with significantly enhanced photocatalytic hydrogen production activity.

    PubMed

    Luo, Xiu-Li; He, Gang-Ling; Fang, Yue-Ping; Xu, Yue-Hua

    2018-05-15

    NiS/g-C 3 N 4 /SrTiO 3 (NS/CN/STO) composites were prepared using a facile hydrothermal method. The synergistic effect of g-C 3 N 4 /SrTiO 3 (CN/STO) heterojunction and NiS cocatalyst enhanced the photocatalytic hydrogen evolution activity of NS/CN/STO. A hydrogen production rate of 1722.7 μmol h -1  g -1 was obtained when the 2%NiS/20%g-C 3 N 4 /SrTiO 3 (2NS/20CN/STO) was used for the photocatalytic hydrogen evolution in the presence of methanol used as a sacrificial agent under UV-vis light irradiation; the photocatalytic hydrogen production rate of 2NS/20CN/STO is 32.8, 8.9 and 4.2 times the value of that obtained with pure g-C 3 N 4 , SrTiO 3 and 20%g-C 3 N 4 /SrTiO 3 (20CN/STO), respectively. Moreover, in photoelectrochemical investigations when compared with 20CN/STO, SrTiO 3 and g-C 3 N 4 , 2NS/20CN/STO exhibited significant photocurrent enhancement. The heterojunction and cocatalyst in NS/CN/STO improved the charge separation efficiency and the lifetime of the charge carriers, leading to the enhanced generation of electrons for photocatalytic hydrogen production. Copyright © 2018 Elsevier Inc. All rights reserved.

  17. STM-electroluminescence from clustered C3N4 nanodomains synthesized via green chemistry process.

    PubMed

    Andrade, E P; Costa, B B A; Chaves, C R; de Paula, A M; Cury, L A; Malachias, A; Safar, G A M

    2018-01-01

    A Scanning Tunneling Microscopy/Spectroscopy (STM/STS) and synchrotron X-ray diffraction study on clustered C 3 N 4 nanoparticles (nanoflakes) is conducted on green-chemistry synthesized samples obtained from chitosan through high power sonication. Morphological aspects and the electronic characteristics are investigated. The observed bandgap of the nanoflakes reveals the presence of different phases in the material. Combining STM morphology, STS spectra and X-ray diffraction (XRD) results one finds that the most abundant phase is graphitic C 3 N 4 . A high density of defects is inferred from the XRD measurements. Additionally, STM-electroluminescence (STMEL) is detected in C 3 N 4 nanoflakes deposited on a gold substrate. The tunneling current creates photons that are three times more energetic than the tunneling electrons of the STM sample. We ponder about the two most probable models to explain the observed photon emission energy: either a nonlinear optical phenomenon or a localized state emission. Copyright © 2017 Elsevier B.V. All rights reserved.

  18. Manipulating the Temperature of Sulfurization to Synthesize α-NiS Nanosphere Film for Long-Term Preservation of Non-enzymatic Glucose Sensors.

    PubMed

    Lin, Hsien-Sheng; Shi, Jen-Bin; Peng, Cheng-Ming; Zheng, Bo-Chi; Cheng, Fu-Chou; Lee, Ming-Way; Lee, Hsuan-Wei; Wu, Po-Feng; Liu, Yi-Jui

    2018-04-19

    In this study, alpha nickel sulfide (α-NiS) nanosphere films have been successfully synthesized by electroplating the nickel nanosheet film on the indium tin oxide (ITO) glass substrate and sulfuring nickel-coated ITO glass substrate. First, we electrodeposited the nickel nanosheet films on the ITO glass substrates which were cut into a 0.5 × 1 cm 2 size. Second, the nanosheet nickel films were annealed in vacuum-sealed glass ampoules with sulfur sheets at different annealing temperatures (300, 400, and 500 °C) for 4 h in vacuum-sealed glass ampoules. The α-NiS films were investigated by using X-ray diffraction (XRD), variable vacuum scanning electron microscopy (VVSEM), field emission scanning electron microscopy/energy dispersive spectrometer (FE-SEM/EDS), cyclic voltammogram (CV), electrochemical impedance spectroscopy (EIS), ultraviolet/visible/near-infrared (UV/Visible/NIR) spectra, and photoluminescence (PL) spectra. Many nanospheres were observed on the surface of the α-NiS films at the annealing temperature 400 °C for 4 h. We also used the high-resolution transmission electron microscopy (HR-TEM) for the analysis of the α-NiS nanospheres. We demonstrated that our α-NiS nanosphere film had a linear current response to different glucose concentrations. Additionally, our α-NiS nanosphere films were preserved at room temperature for five and a half years and were still useful for detecting glucose at low concentration.

  19. Method to synthesize bulk iron nitride

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Monson, Todd; Lavernia, Enrique J.; Zheng, Baolong

    Bulk iron nitride can be synthesized from iron nitride powder by spark plasma sintering. The iron nitride can be spark plasma sintered at a temperature of less than 600°C. and a pressure of less than 600 MPa, with 400 MPa or less most often being sufficient. High pressure SPS can consolidate dense iron nitrides at a lower temperature to avoid decomposition. The higher pressure and lower temperature of spark discharge sintering avoids decomposition and limits grain growth, enabling enhanced magnetic properties. The method can further comprise synthesis of nanocrystalline iron nitride powders using two-step reactive milling prior to high-pressure sparkmore » discharge sintering.« less

  20. Electrical and structural properties of ZnO synthesized via infiltration of lithographically defined polymer templates

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Chang-Yong Nam; Stein, Aaron; Kisslinger, Kim

    We investigate the electrical and structural properties of infiltration-synthesized ZnO. In-plane ZnO nanowire arrays with prescribed positional registrations are generated by infiltrating diethlyzinc and water vapor into lithographically defined SU-8 polymer templates and removing organic matrix by oxygen plasma ashing. Transmission electron microscopy reveals that homogeneously amorphous as-infiltrated polymer templates transform into highly nanocrystalline ZnO upon removal of organic matrix. Field-effect transistor device measurements show that the synthesized ZnO after thermal annealing displays a typical n-type behavior, ~1019 cm -3 carrier density, and ~0.1 cm 2 V -1 s -1 electron mobility, reflecting highly nanocrystalline internal structure. The results demonstratemore » the potential application of infiltration synthesis in fabricating metal oxide electronic devices.« less

  1. Electrical and structural properties of ZnO synthesized via infiltration of lithographically defined polymer templates

    DOE PAGES

    Chang-Yong Nam; Stein, Aaron; Kisslinger, Kim; ...

    2015-11-17

    We investigate the electrical and structural properties of infiltration-synthesized ZnO. In-plane ZnO nanowire arrays with prescribed positional registrations are generated by infiltrating diethlyzinc and water vapor into lithographically defined SU-8 polymer templates and removing organic matrix by oxygen plasma ashing. Transmission electron microscopy reveals that homogeneously amorphous as-infiltrated polymer templates transform into highly nanocrystalline ZnO upon removal of organic matrix. Field-effect transistor device measurements show that the synthesized ZnO after thermal annealing displays a typical n-type behavior, ~1019 cm -3 carrier density, and ~0.1 cm 2 V -1 s -1 electron mobility, reflecting highly nanocrystalline internal structure. The results demonstratemore » the potential application of infiltration synthesis in fabricating metal oxide electronic devices.« less

  2. Solution combustion synthesis of the nanocrystalline NCM oxide for lithium-ion battery uses

    NASA Astrophysics Data System (ADS)

    Habibi, Amirhosein; Jalaly, Maisam; Rahmanifard, Roohollah; Ghorbanzadeh, Milad

    2018-02-01

    In this study, the NCM cathode with a chemical composition of {{{LiNi}}}1/3}{{{Co}}}1/3}{{{Mn}}}1/3}{{{O}}}2 were synthesized through a solution combustion method. In this method, metal nitrates and urea were used as precursors and fuel, respectively. The powder obtained from combustion were transferred into a alumina crucible and insert to the muffle furnace and calcined at 750 °C for 15 h. The crystallite size of the sample was calculated with sherer equation to be about 41 nm. The prepared cathode were characterized using x-ray diffraction (XRD), scanning electron microscopy (SEM), thermogravimetry analysis (TGA), differential scanning calorimetry (DSC) and battery charge-discharge test. The initial charge and discharge capacities of {{{LiNi}}}1/3}{{{Co}}}1/3}{{{Mn}}}1/3}{{{O}}}2 electrode containing 94% active material at a rate of 0.05 C in voltage window of 2.5-4.3 V at room temperature was obtained 168.03 and 150.01 mAh g-1, respectively.

  3. The fabrication of foam-like 3D mesoporous NiO-Ni as anode for high performance Li-ion batteries

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Huang, Peng, E-mail: huangp07@lzu.edu.cn; Department of Physics, Lanzhou University, Lanzhou 730000; Zhang, Xin

    2015-03-15

    Graphical abstract: Foam-like 3 dimensional (3D) mesoporous NiO on 3D micro-porous Ni was fabricated. - Highlights: • We prepare NiO-Ni foam composite via hydrothermal etching and subsequent annealing. • The NiO exhibits novel foam-like 3D mesoporous architecture. • The NiO-Ni anode shows good cycle stability. - Abstract: Foam-like three dimensional mesoporous NiO on Ni foam was fabricated via facile hydrothermal etching and subsequent annealing treatment. The porous NiO consists of a large number of nanosheets with mean thickness about 50 nm, among which a large number of mesoscopic pores with size ranges from 100 nm to 1 μm distribute. Themore » electrochemical performance of the as-prepared NiO-Ni as anode for lithium ion battery was studied by conventional charge/discharge test, which shows excellent cycle stability and rate capability. It exhibits initial discharge and charge capacities of 979 and 707 mA h g{sup −1} at a charge/discharge rate of 0.7 C, which maintain of 747 and 738 mA h g{sup −1} after 100 cycles. Even after 60 cycles at various rates from 0.06 to 14 C, the 10th discharge and charge capacities of the NiO-Ni electrode can revert to 699 and 683 mA h g{sup −1} when lowering the charge/discharge rate to 0.06 C.« less

  4. Influence of surface and finite size effects on the structural and magnetic properties of nanocrystalline lanthanum strontium perovskite manganites

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Žvátora, Pavel; Veverka, Miroslav; Veverka, Pavel

    2013-08-15

    Syntheses of nanocrystalline perovskite phases of the general formula La{sub 1−x}Sr{sub x}MnO{sub 3+δ} were carried out employing sol–gel technique followed by thermal treatment at 700–900 °C under oxygen flow. The prepared samples exhibit a rhombohedral structure with space group R3{sup ¯}c in the whole investigated range of composition 0.20≤x≤0.45. The studies were aimed at the chemical composition including oxygen stoichiometry and extrinsic properties, i.e. size of the particles, both influencing the resulting structural and magnetic properties. The oxygen stoichiometry was determined by chemical analysis revealing oxygen excess in most of the studied phases. The excess was particularly high for themore » samples with the smallest crystallites (12–28 nm) while comparative bulk materials showed moderate non-stoichiometry. These differences are tentatively attributed to the surface effects in view of the volume fraction occupied by the upper layer whose atomic composition does not comply with the ideal bulk stoichiometry. - Graphical abstract: Evolution of the particle size with annealing temperature in the nanocrystalline La{sub 0.70}Sr{sub 0.30}MnO{sub 3+δ} phase. Display Omitted - Highlights: • The magnetic behaviour of nanocrystalline La{sub 1−x}Sr{sub x}MnO{sub 3+δ} phases was analyzed on the basis of their crystal structure, chemical composition and size of the particles. • Their Curie temperature and magnetization are markedly affected by finite size and surface effects. • The oxygen excess observed in the La{sub 1−x}Sr{sub x}MnO{sub 3+δ} nanoparticles might be generated by the surface layer with deviated oxygen stoichiometry.« less

  5. Synthesis and characterization of TiC nanopowders via sol-gel and subsequent carbothermal reduction process

    NASA Astrophysics Data System (ADS)

    Chen, Xu; Fan, Jinglian; Lu, Qiong

    2018-06-01

    TiC nanocrystalline powders were synthesized by in-situ carbothermic reduction of Ti-O-C precursor under vacuum atmosphere. And the Ti-O-C precursor was formed by sol-gel method from titanium butyrate (TBOT) and sucrose. To obtain stable sol, TBOT was directly added into mixed solution which contains water, sucrose, acetic acid (AcOH) and acetylacetone (ACAC). This procedure is more convenient and economical because it avoids the use of alcohol which is used as solvent in most reports of alkoxide hydrolysis sol-gel method. TG-DSC, XRD, FTIR and SEM/TEM were employed to analyze and characterize the product during the entire process. The phase composition and crystalline structure parameters of powders with different C/Ti molar ratio were investigated by Rietveld refinement method, and elemental quantitative analysis of the samples were performed. Furthermore, the optimal parameters of carbothermal reduction were obtained and the grain growth mechanism was demonstrated. The results show that TiC nanocrystalline powders (C/Ti molar ratio is 3.5 in the precursor) were synthesized at 1300 °C for 2 h, which have near standard lattice parameter, well crystallinity and fine average grain size ( 37.4 nm).

  6. High Temperature Behavior of Cr3C2-NiCr Coatings in the Actual Coal-Fired Boiler Environment

    NASA Astrophysics Data System (ADS)

    Bhatia, Rakesh; Sidhu, Hazoor Singh; Sidhu, Buta Singh

    2015-03-01

    Erosion-corrosion is a serious problem observed in steam-powered electricity generation plants, and industrial waste incinerators. In the present study, four compositions of Cr3C2-(Ni-20Cr) alloy coating powder were deposited by high-velocity oxy-fuel spray technique on T-91 boiler tube steel. The cyclic studies were performed in a coal-fired boiler at 1123 K ± 10 K (850 °C ± 10 °C). X-ray diffraction, scanning electron microscopy/energy dispersive X-ray analysis and elemental mapping analysis techniques were used to analyze the corrosion products. All the coatings deposited on T-91 boiler tube steel imparted hot corrosion resistance. The 65 pctCr3C2 -35 pct (Ni-20Cr)-coated T-91 steel sample performed better than all other coated samples in the given environment.

  7. Synthesis and properties of the compound: LiNi 3/5Cu 2/5VO 4

    NASA Astrophysics Data System (ADS)

    Ram, Moti

    2009-12-01

    The LiNi 3/5Cu 2/5VO 4 is synthesized by solution-based chemical method and its formation has been checked by X-ray diffraction (XRD) study. XRD study shows a tetragonal unit cell structure with lattice parameters of a = 11.6475 (18) Å, c = 2.4855 (18) Å and c/ a = 0.2134 Å. Electrical properties are verified using complex impedance spectroscopy (CIS) technique. Complex impedance analysis reveals following points: (i) the bulk contribution to electrical properties up to 200 °C, (ii) the bulk and grain boundary contribution at T ≥ 225 °C, (iii) the presence of temperature dependent electrical relaxation phenomena in the material. D.c. conductivity study indicates that electrical conduction in the material is a thermally activated process.

  8. Synthesis, structural studies and antimicrobial activity of N'-((2Z, 3E)-3-(hydroxyimino)butan-2-ylidene)-2-phenylacetohydrazide and its Co(II), Ni(II) complexes

    NASA Astrophysics Data System (ADS)

    Karadeniz, Şeyma; Ataol, Cigdem Yuksektepe; Şahin, Onur; İdil, Önder; Bati, Hümeyra

    2018-06-01

    A new aroylhydrazoneoxime, N'-((2Z, 3E)-3-(hydroxyimino)butan-2-ylidene)-2-phenylacetohydrazide ligand (LH2) and its Ni(II) and Co(II) complexes, have been synthesized and characterized by elemental and thermal analyses, IR and UV-vis spectroscopy, magnetic moment and X-ray diffraction. The antimicrobial activities of these compounds were tested by using minimal inhibitory concentration method (MIC). The ligand-containing aroylhydrazone and oxime groups and its Ni complex crystallize in the triclinic system and P 1 - space group, while its Co complex crystallizes in the monoclinic system and the C 2/c space group. X-ray results show that the ligand in the keto form is transformed into enolic form when it forms coordination. From elemental analysis data, the stoichiometry of Co(II) complex was found to be 1:2 (metal/ligand), but 1:1 for Ni(II). IR spectra indicate that the ligand acts as monoanionic NNO- tridentate and coordination takes place form through the oxime nitrogen, imine nitrogen, and enolate oxygen atoms.

  9. Electron microscopy characterization of Ni-Cr-B-Si-C laser deposited coatings.

    PubMed

    Hemmati, I; Rao, J C; Ocelík, V; De Hosson, J Th M

    2013-02-01

    During laser deposition of Ni-Cr-B-Si-C alloys with high amounts of Cr and B, various microstructures and phases can be generated from the same chemical composition that results in heterogeneous properties in the clad layer. In this study, the microstructure and phase constitution of a high-alloy Ni-Cr-B-Si-C coating deposited by laser cladding were analyzed by a combination of several microscopy characterization techniques including scanning electron microscopy in secondary and backscatter imaging modes, energy dispersive spectroscopy (EDS), electron backscatter diffraction (EBSD), and transmission electron microscopy (TEM). The combination of EDS and EBSD allowed unequivocal identification of micron-sized precipitates as polycrystalline orthorhombic CrB, single crystal tetragonal Cr5B3, and single crystal hexagonal Cr7C3. In addition, TEM characterization showed various equilibrium and metastable Ni-B, Ni-Si, and Ni-Si-B eutectic products in the alloy matrix. The findings of this study can be used to explain the phase formation reactions and to tune the microstructure of Ni-Cr-B-Si-C coatings to obtain the desired properties.

  10. Ultrafine Nanocrystalline CeO2@C-Containing NaAlH4 with Fast Kinetics and Good Reversibility for Hydrogen Storage.

    PubMed

    Zhang, Xin; Liu, Yongfeng; Wang, Ke; Li, You; Gao, Mingxia; Pan, Hongge

    2015-12-21

    A nanocrystalline CeO2@C-containing NaAlH4 composite is successfully synthesized in situ by hydrogenating a NaH-Al mixture doped with CeO2@C. Compared with NaAlH4 , the as-prepared CeO2@C-containing NaAlH4 composite, with a minor amount of excess Al, exhibits significantly improved hydrogen storage properties. The dehydrogenation onset temperature of the hydrogenated [NaH-Al-7 wt % CeO2@C]-0.04Al sample is 77 °C lower than that of the pristine sample because of a reduced kinetic barrier. More importantly, the dehydrogenated sample absorbs ∼4.7 wt % hydrogen within 35 min at 100°C and 10 MPa of hydrogen. Compositional and structural analyses reveal that CeO2 is converted to CeH2 during ball milling and that the newly formed CeH2 works with the excess of Al to synergistically improve the hydrogen storage properties of NaAlH4. Our findings will aid in the rational design of novel catalyst-doped complex hydride systems with low operating temperatures, fast kinetics, and long-term cyclability. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  11. Induced spin-polarization of EuS at room temperature in Ni/EuS multilayers

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Poulopoulos, P., E-mail: poulop@upatras.gr; Materials Science Department, University of Patras, 26504 Patras; Goschew, A.

    2014-03-17

    Ni/EuS multilayers with excellent multilayer sequencing are deposited via e-beam evaporation on the native oxide of Si(100) wafers at 4 × 10{sup −9} millibars. The samples have very small surface and interface roughness and show sharp interfaces. Ni layers are nanocrystalline 4–8 nm thick and EuS layers are 2–4 nm thick and are either amorphous or nanocrystalline. Unlike for Co/EuS multilayers, all Eu ions are in divalent (ferromagnetic) state. We show a direct antiferromagnetic coupling between EuS and Ni layers. At room temperature, the EuS layers are spin-polarized due to the proximity of Ni. Therefore, Ni/EuS is a candidate for room-temperature spintronics applications.

  12. Synthesis of nanocrystalline NiO/ZnO heterostructured composite powders by sol-gel auto combustion method and their characterizations

    NASA Astrophysics Data System (ADS)

    Tangcharoen, Thanit; Klysubun, Wantana; Kongmark, Chanapa

    2018-03-01

    Nanocrystalline NiO/ZnO heterostructured composite powders were prepared by the sol-gel auto combustion method, based on nickel and zinc nitrate precursors and using diethanolamine (DEA) as novel fuel. The composition of different NiO and ZnO ratios, ranging from 100/0, 95/5, 90/10, 80/20, 60/40, 50/50, 40/60, 20/80, 10/90, 5/95 to 0/100, were studied. The structural, chemical bonding, morphological, optical, and fluorescence properties including the local atomic structure of each calcined sample were systematically investigated by means of X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy (SEM), UV-visible diffuse reflectance spectroscopy (UV-DRS), photoluminescence (PL) spectroscopy, and synchrotron X-ray absorption spectroscopy (XAS), respectively. For the ZnO concentration below 20%, both XRD and Raman spectroscopy results revealed only the NiO phase. This conformed to the observation of Zn K-edge and Ni K-edge X-ray absorption near edge structure (XANES). The Zn ions found in the samples of low ZnO concentration exhibited six-fold coordination with oxygen atoms rather than the four-fold coordination found in the wurtzite (WZ) structure of ZnO. In contrast, the Ni ions which are found in the samples of low NiO concentration (≤10%) are coordinated both tetrahedrally and octahedrally by four or six oxygen atoms, respectively, rather than the six-fold coordination which is usually observed for Ni ions in the rock salt (RS) form of NiO. All analytical results obtained from experimental XANES spectra were verified by the theoretical calculation of absorption spectra using the FEFF9.7 code. The UV-DRS results showed that there was an increase in the reflectance efficiency for both infrared and visible light conditions as the content of ZnO increases; meanwhile, the values for the energy gap (Eg) of all composite samples were higher than that of pure NiO and ZnO. In addition, the PL spectra revealed major blue emission bands observed at 490

  13. Optimizing Heat Treatment Process of Fe-13Cr-3Mo-3Ni Martensitic Stainless of Steel

    NASA Astrophysics Data System (ADS)

    Anwar, M. S.; Prifiharni, S.; Mabruri, E.

    2017-05-01

    The Fe-13Cr-3Mo-3Ni stainless steels are modified into martensitic stainless steels for steam turbine blades application. The working temperature of steam turbine was around 600 - 700 °C. The improvement properties of turbine blade material is necessary to maintain steam turbine work. The previous research revealed that it has corrosion resistance of Fe-13Cr-3Mo-3Ni which is better than 13Cr stainless steels in the chloride environment. In this work, the effect of heat treatment on microstructure and hardness of Fe-13Cr-3Mo-3Ni stainless steels has been studied. The steel was prepared by induction melting followed by hot forging. The steels were austenitized at 1000, 1050, and 1100 °C for 1 hour and were tempered at 600, 650, and 700 °C for 1 hour. The steels were then subjected to metallographic observation and hardness test of Rockwell C. The optimal heat treatment of Fe-13Cr-3Mo-3Ni was carried out austenitized in 1050 °C and tempered in 600 - 700 °C.

  14. SmNiO3/NdNiO3 thin film multilayers

    NASA Astrophysics Data System (ADS)

    Girardot, C.; Pignard, S.; Weiss, F.; Kreisel, J.

    2011-06-01

    Rare earth nickelates RENiO3 (RE =rare earth), which attract interest due to their sharp metal-insulator phase transition, are instable in bulk form due to the necessity of an important oxygen pressure to stabilize Ni in its 3+ state of oxidation. Here, we report the stabilization of RE nickelates in [(SmNiO3)t/(NdNiO3)t]n thin film multilayers, t being the thickness of layers alternated n times. Both bilayers and multilayers have been deposited by metal-organic chemical vapor deposition. The multilayer structure and the presence of the metastable phases SmNiO3 and NdNiO3 are evidenced from by x-ray and Raman scattering. Electric measurements of a bilayer structure further support the structural quality of the embedded RE nickelate layers.

  15. Electrodeposition and Characterization of Ni-Al2O3 Nanocomposite Coatings on Steel

    NASA Astrophysics Data System (ADS)

    Akhtar, Khalida; Khan, Zia Ullah; Gul, Muhammad; Zubair, Naila; Shah, Syed Sajjad Ali

    2018-05-01

    Monodispersed alumina particles were synthesized by the homogeneous precipitation under reflux boiling. The particles were employed as reinforcement additives in the electrodeposited Ni-Al2O3 composite coatings on steel. The deposited pure Ni and Ni-Al2O3 composite coatings were analyzed by SEM, XRD, and microhardness tester. The wear resistance and friction coefficient of the coated samples were determined by using a ball-on-disk tribometer. Furthermore, XRD analysis showed that coating temperature and the presence of particles in the deposited coatings had a noticeable effect on the preferred orientation of the crystalline faces of the nickel grains. Significant differences were noted in the texture coefficient of the pure Ni and Ni-Al2O3 composite coatings produced at different temperatures. These differences were attributed to the changes in the microstructure of the matrix caused by the embedded Al2O3 particles. Results revealed that wear resistance and the friction coefficient were turned out to be higher and smaller, respectively, for the composite coatings as compared to pure Ni coating at a given sliding distance. It was noted that the corrosion resistance of these specimens increased in the following order: bare substrate < pure Ni coating < Ni-Al2O3 nanocomposite coatings.

  16. Ni3S2 nanowires grown on nickel foam as an efficient bifunctional electrocatalyst for water splitting with greatly practical prospects.

    PubMed

    Zhang, Dawei; Li, Jingwei; Luo, Jiaxian; Xu, Peiman; Wei, Licheng; Zhou, Dan; Xu, Weiming; Yuan, Dingsheng

    2018-06-15

    It is essential to synthesize low-cost, earth-abundant bifunctional electrocatalysts for both the hydrogen evolution reaction (HER) and oxygen evolution reactions (OER) for water electrolysis. Herein, we present a one-step sulfurization method to fabricate Ni 3 S 2 nanowires directly grown on Ni foam (Ni 3 S 2 NWs/Ni) as such an electrocatalyst. This synthetic strategy has several advantages including facile preparation, low cost and can even be expanded to large-scale preparation for practical applications. The as-synthesized Ni 3 S 2 NWs/Ni exhibits a low overpotential of 81 and 317 mV to render a current density of 10 mA cm -2 for the HER and OER, respectively, in 1.0 mol l -1 KOH solution. The Ni 3 S 2 NWs/Ni was integrated to be the cathode and the anode in the alkaline electrolyzer for overall water splitting with a current density of 10 mA cm -2 afforded at a cell voltage of 1.63 V. More importantly, this electrolyzer maintained its electrocatalytic activity even after continual water splitting for 30 h. Owing to its simple synthesis process, the earth-abundant electrocatalyst and high performance, this versatile Ni 3 S 2 NWs/Ni electrode will become a promising electrocatalyst for water splitting.

  17. Ni3S2 nanowires grown on nickel foam as an efficient bifunctional electrocatalyst for water splitting with greatly practical prospects

    NASA Astrophysics Data System (ADS)

    Zhang, Dawei; Li, Jingwei; Luo, Jiaxian; Xu, Peiman; Wei, Licheng; Zhou, Dan; Xu, Weiming; Yuan, Dingsheng

    2018-06-01

    It is essential to synthesize low-cost, earth-abundant bifunctional electrocatalysts for both the hydrogen evolution reaction (HER) and oxygen evolution reactions (OER) for water electrolysis. Herein, we present a one-step sulfurization method to fabricate Ni3S2 nanowires directly grown on Ni foam (Ni3S2 NWs/Ni) as such an electrocatalyst. This synthetic strategy has several advantages including facile preparation, low cost and can even be expanded to large-scale preparation for practical applications. The as-synthesized Ni3S2 NWs/Ni exhibits a low overpotential of 81 and 317 mV to render a current density of 10 mA cm‑2 for the HER and OER, respectively, in 1.0 mol l‑1 KOH solution. The Ni3S2 NWs/Ni was integrated to be the cathode and the anode in the alkaline electrolyzer for overall water splitting with a current density of 10 mA cm‑2 afforded at a cell voltage of 1.63 V. More importantly, this electrolyzer maintained its electrocatalytic activity even after continual water splitting for 30 h. Owing to its simple synthesis process, the earth-abundant electrocatalyst and high performance, this versatile Ni3S2 NWs/Ni electrode will become a promising electrocatalyst for water splitting.

  18. Multiferroic properties of nanocrystalline BaTiO 3

    NASA Astrophysics Data System (ADS)

    Mangalam, R. V. K.; Ray, Nirat; Waghmare, Umesh V.; Sundaresan, A.; Rao, C. N. R.

    2009-01-01

    Some of the Multiferroics [H. Schmid, Ferroelectrics 162 (1994) 317] form a rare class of materials that exhibit magneto-electric coupling arising from the coexistence of ferromagnetism and ferroelectricity, with potential for many technological applications [J.F. Scott, Nat. Mater. 6 (2007) 256; N.A. Spaldin, M. Fiebig, Science 309 (2005) 391]. Over the last decade, an active research on multiferroics has resulted in the identification of a few routes that lead to multiferroicity in bulk materials [C. Ederer, N.A. Spaldin, Nat. Mater. 3 (2004) 849; D.V. Efremov, J. van den Brink, D.I. Khomskii, Nat. Mater. 3 (2004) 853; N. Hur, S. Park, P.A. Sharma, J.S. Ahn, S. Guha, S.W. Cheong, Nature 429 (2004) 392]. While ferroelectricity in a classic ferroelectric such as BaTiO 3 is expected to diminish with the reducing particle size, [C.H. Ahn, K.M. Rabe, J.M. Triscone, Science 303 (2004) 488; J. Junquera, P. Ghosez, Nature 422 (2003) 506] ferromagnetism cannot occur in its bulk form [N.A. Hill, J. Phys. Chem. B 104 (2000) 6694]. Here, we use a combination of experiment and first-principles simulations to demonstrate that multiferroic nature emerges in intermediate size nanocrystalline BaTiO 3, ferromagnetism arising from the oxygen vacancies at the surface and ferroelectricity from the core. A strong coupling between a surface polar phonon and spin is shown to result in a magnetocapacitance effect observed at room temperature, which can open up possibilities of new electro-magneto-mechanical devices at the nano-scale.

  19. Polarity-driven oxygen vacancy formation in ultrathin LaNiO 3 films on SrTiO 3

    DOE PAGES

    Tung, I-Cheng; Luo, Guangfu; Lee, June Hyuk; ...

    2017-10-18

    Oxide heterostructures offer a pathway to control emergent phases in complex oxides, but their creation often leads to boundaries that have a polar discontinuity. In order to fabricate atomic-scale arrangements of dissimilar materials, we need a clear understanding of the pathways by which materials resolve polarity issues. By examining the real-time lattice structure in-situ during growth for the case of polar LaNiO 3 synthesized on non-polar SrTiO 3 (001), we demonstrate how films in ultra-thin limit form as LaNiO 2.5 and then evolve into LaNiO 3 as the thickness increases. Theory explains how the polar energetics drives the formation ofmore » oxygen vacancies and the stability of these phases with thickness and structure.« less

  20. Nickel antimony oxide (NiSb2O6): A fascinating nanostructured material for gas sensing application

    NASA Astrophysics Data System (ADS)

    Singh, Archana; Singh, Ajendra; Singh, Satyendra; Tandon, Poonam

    2016-02-01

    Fabrication of nanocrystalline NiSb2O6 thin films via sol-gel spin coating method towards the development of liquefied petroleum gas (LPG) sensor operable at room temperature (25 °C) is being reported. Nanostructural, surface morphological and optical properties of trirutile-type NiSb2O6 have been investigated in order to explore the parameters of interest. The crystallite size has been found to be 19 nm. A detailed sensing performance (sensitivity, sensor response, response and recovery times, reproducibility and long term stability) of NiSb2O6 nanostructures grown on alumina substrate has been investigated.

  1. Electrical and structural properties of ZnO synthesized via infiltration of lithographically defined polymer templates

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Nam, Chang-Yong, E-mail: cynam@bnl.gov; Stein, Aaron; Kisslinger, Kim

    We investigate the electrical and structural properties of infiltration-synthesized ZnO. In-plane ZnO nanowire arrays with prescribed positional registrations are generated by infiltrating diethlyzinc and water vapor into lithographically defined SU-8 polymer templates and removing organic matrix by oxygen plasma ashing. Transmission electron microscopy reveals that homogeneously amorphous as-infiltrated polymer templates transform into highly nanocrystalline ZnO upon removal of organic matrix. Field-effect transistor device measurements show that the synthesized ZnO after thermal annealing displays a typical n-type behavior, ∼10{sup 19 }cm{sup −3} carrier density, and ∼0.1 cm{sup 2} V{sup −1} s{sup −1} electron mobility, reflecting highly nanocrystalline internal structure. The results demonstrate themore » potential application of infiltration synthesis in fabricating metal oxide electronic devices.« less

  2. Dendrite-Free Nanocrystalline Zinc Electrodeposition from an Ionic Liquid Containing Nickel Triflate for Rechargeable Zn-Based Batteries.

    PubMed

    Liu, Zhen; Cui, Tong; Pulletikurthi, Giridhar; Lahiri, Abhishek; Carstens, Timo; Olschewski, Mark; Endres, Frank

    2016-02-18

    Metallic zinc is a promising anode material for rechargeable Zn-based batteries. However, the dendritic growth of zinc has prevented practical applications. Herein it is demonstrated that dendrite-free zinc deposits with a nanocrystalline structure can be obtained by using nickel triflate as an additive in a zinc triflate containing ionic liquid. The formation of a thin layer of Zn-Ni alloy (η- and γ-phases) on the surface and in the initial stages of deposition along with the formation of an interfacial layer on the electrode strongly affect the nucleation and growth of zinc. A well-defined and uniform nanocrystalline zinc deposit with particle sizes of about 25 nm was obtained in the presence of Ni(II) . Further, it is shown that the nanocrystalline Zn exhibits a high cycling stability even after 50 deposition/stripping cycles. This strategy of introducing an inorganic metal salt in ionic liquid electrolytes can be considered as an efficient way to obtain dendrite-free zinc. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  3. Effect of Reaction Period on Stoichiometry, Phase Purity, and Morphology of Hydrothermally Synthesized Cu2NiSnS4 Nanopowder

    NASA Astrophysics Data System (ADS)

    Babu, G. Sahaya Dennish; Shajan, X. Sahaya; Alwin, S.; Ramasubbu, V.; Balerao, Gopal M.

    2018-01-01

    The effect of reaction period on the phase purity, morphology, and stoichiometry of Cu2NiSnS4 (CNTS) nanopowder prepared by hydrothermal method has been investigated. Polyvinylpyrrolidone (PVP) and thioglycolic acid were used as capping agent and sulfur source, respectively. The presence of cubic stannite crystal structure and its phase purity were confirmed by powder x-ray diffraction analysis and Raman spectroscopy. Furthermore, the morphological, crystallographic, and optical features of the prepared CNTS nanopowder were characterized by field-emission scanning electron microscopy, transmission electron microscopy, and ultraviolet-visible (UV-Vis) spectrophotometry. The elemental ratios of Cu/(Ni + Sn) and Ni/Sn showed that the stoichiometry of CNTS was maintained for the compounds synthesized at 230°C with reaction period of 24 h. The occurrence of Cu+, Ni2+, Sn4+, and S2- was evaluated by x-ray photoelectron spectroscopy. The prepared material was used as counter electrode in a dye-sensitized solar cell (DSSC) as an alternative to platinum (Pt), resulting in conversion efficiency of 0.92%. These results indicate that CNTS is a prospective material to replace conventional Pt-based counter electrodes in DSSCs.

  4. Enhancement of the physical properties of novel (1- x) NiFe2O4 + ( x) Al2O3 nanocomposite

    NASA Astrophysics Data System (ADS)

    Mansour, S. F.; Ahmed, M. A.; El-Dek, S. I.; Abdo, M. A.; Kora, H. H.

    2017-07-01

    NiFe2O4, Al2O3 and their nanocomposites; (1- x) NiFe2O4 + ( x) Al2O3, 0.0 ≤ x ≤ 1; were synthesized using the citrate-nitrate technique. The crystal structure was examined by X-ray diffraction, the microstructure was observed by transmission electron microscopy. The Curie temperature T C grows until reaching more than 1100 K with increasing alumina content ( x), while the saturation magnetization ( M s) decreased. The large improvement of room temperature resistivity which achieved two orders of magnitude from x = 0 to x = 70% was interpreted from the fact that the NiFe2O4 grains become electrically isolated and the conduction path is broken by the insulating Al2O3 nanoparticulates in the composite. The electrical properties of the nanocomposite could thus be tuned easily by adjusting the Al2O3 ratio to realize the targeted value of losses and resistivity at any temperature and frequency.

  5. Syntheses, structure and magnetic properties of two vanadate garnets Ca{sub 5}M{sub 4}V{sub 6}O{sub 24} (M=Co, Ni)

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Wang, Nannan; College of Materials Science and Engineering, Fuzhou University, Fuzhou, Fujian 350108; He, Zhangzhen, E-mail: hcz1988@hotmail.com

    2015-08-15

    Two vanadate compounds Ca{sub 5}M{sub 4}V{sub 6}O{sub 24} (M=Co, Ni) have been synthesized by a high-temperature solid-state reaction. The compounds are found to crystallize in the cubic system with a space group Ia-3d, which exhibit a typical garnet structural framework. Magnetic measurements show that Ca{sub 5}M{sub 4}V{sub 6}O{sub 24} (M=Co, Ni) exhibit similar magnetic behaviors, in which Ca{sub 5}Co{sub 4}V{sub 6}O{sub 24} possesses an antiferromagnetic ordering at T{sub N}=~6 K while Ca{sub 5}Ni{sub 4}V{sub 6}O{sub 24} shows an antiferromagnetic ordering at T{sub N}=~7 K. - Graphical abstract: Garnet vanadate compounds Ca{sub 5}M{sub 4}V{sub 6}O{sub 24} (M=Co, Ni) have been synthesizedmore » by a high-temperature solid-state reaction. Structural features and magnetic behaviors are also investigated. - Highlights: • New type of garnet vanadates Ca{sub 5}M{sub 4}V{sub 6}O{sub 24} (M=Co, Ni) are synthesized by a high-temperature solid-state reaction. • Structural features are confirmed by single crystal samples. • Magnetic behaviors are firstly investigated in the systems.« less

  6. From two-dimensional graphene oxide to three-dimensional honeycomb-like Ni3S2@graphene oxide composite: insight into structure and electrocatalytic properties

    NASA Astrophysics Data System (ADS)

    Wei, Xinting; Li, Yueqiang; Xu, Wenli; Zhang, Kaixuan; Yin, Jie; Shi, Shaozhen; Wei, Jiazhen; Di, Fangfang; Guo, Junxue; Wang, Can; Chu, Chaofan; Sui, Ning; Chen, Baoli; Zhang, Yingtian; Hao, Hongguo; Zhang, Xianxi; Zhao, Jinsheng; Zhou, Huawei; Wang, Shuhao

    2017-12-01

    Three-dimensional (3D) graphene composites have drawn increasing attention in energy storage/conversion applications due to their unique structures and properties. Herein, we synthesized 3D honeycomb-like Ni3S2@graphene oxide composite (3D honeycomb-like Ni3S2@GO) by a one-pot hydrothermal method. We found that positive charges of Ni2+ and negative charges of NO3- in Ni(NO3)2 induced a transformation of graphene oxide with smooth surface into graphene oxide with wrinkled surface (w-GO). The w-GO in the mixing solution of Ni(NO3)2/thioacetamide/H2O evolved into 3D honeycomb-like Ni3S2@GO in solvothermal process. The GO effectively inhibited the aggregation of Ni3S2 nanoparticles. Photoelectrochemical cells based on 3D Ni3S2@GO synthesized at 60 mM l-1 Ni(NO3)2 exhibited the best energy conversion efficiency. 3D Ni3S2@GO had smaller charge transfer resistance and larger exchange current density than pure Ni3S2 for iodine reduction reaction. The cyclic stability of 3D honeycomb-like Ni3S2@GO was good in the iodine electrolyte. Results are of great interest for fundamental research and practical applications of 3D GO and its composites in solar water-splitting, artificial photoelectrochemical cells, electrocatalysts and Li-S or Na-S batteries.

  7. Microwave absorption properties of Ni/(C, silicides) nanocapsules

    PubMed Central

    2012-01-01

    The microwave absorption properties of Ni/(C, silicides) nanocapsules prepared by an arc discharge method have been studied. The composition and the microstructure of the Ni/(C, silicides) nanocapsules were determined by means of X-ray diffraction, X-ray photoelectric spectroscopy, and transmission electron microscope observations. Silicides, in the forms of SiOx and SiC, mainly exist in the shells of the nanocapsules and result in a large amount of defects at the ‘core/shell’ interfaces as well as in the shells. The complex permittivity and microwave absorption properties of the Ni/(C, silicides) nanocapsules are improved by the doped silicides. Compared with those of Ni/C nanocapsules, the positions of maximum absorption peaks of the Ni/(C, silicides) nanocapsules exhibit large red shifts. An electric dipole model is proposed to explain this red shift phenomenon. PMID:22548846

  8. Synthesis of NiMn-LDH Nanosheet@Ni3S2 Nanorod Hybrid Structures for Supercapacitor Electrode Materials with Ultrahigh Specific Capacitance.

    PubMed

    Yu, Shuai; Zhang, Yingxi; Lou, Gaobo; Wu, Yatao; Zhu, Xinqiang; Chen, Hao; Shen, Zhehong; Fu, Shenyuan; Bao, Binfu; Wu, Limin

    2018-03-27

    One of the key challenges for pseudocapacitive electrode materials with highly effective capacitance output and future practical applications is how to rationally construct hierarchical and ordered hybrid nanoarchitecture through the simple process. Herein, we design and synthesize a novel NiMn-layered double hydroxide nanosheet@Ni 3 S 2 nanorod hybrid array supported on porous nickel foam via a one-pot hydrothermal method. Benefited from the ultrathin and rough nature, the well-defined porous structure of the hybrid array, as well as the synergetic effect between NiMn-layered double hydroxide nanosheets and Ni 3 S 2 nanorods, the as-fabricated hybrid array-based electrode exhibits an ultrahigh specific capacitance of 2703 F g -1 at 3 A g -1 . Moreover, the asymmetric supercapacitor with this hybrid array as a positive electrode and wood-derived activated carbon as a negative electrode demonstrates high energy density (57 Wh Kg -1 at 738 W Kg -1 ) and very good electrochemical cycling stability.

  9. Neutron diffraction studies of the Na-ion battery electrode materials NaCoCr{sub 2}(PO{sub 4}){sub 3}, NaNiCr{sub 2}(PO{sub 4}){sub 3}, and Na{sub 2}Ni{sub 2}Cr(PO{sub 4}){sub 3}

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Yahia, H. Ben; Essehli, R., E-mail: ressehli@qf.org.qa; Avdeev, M.

    The new compounds NaCoCr{sub 2}(PO{sub 4}){sub 3}, NaNiCr{sub 2}(PO{sub 4}){sub 3}, and Na{sub 2}Ni{sub 2}Cr(PO{sub 4}){sub 3} were synthesized by sol-gel method and their crystal structures were determined by using neutron powder diffraction data. These compounds were characterized by galvanometric cycling and cyclic voltammetry. NaCoCr{sub 2}(PO{sub 4}){sub 3}, NaNiCr{sub 2}(PO{sub 4}){sub 3}, and Na{sub 2}Ni{sub 2}Cr(PO{sub 4}){sub 3} crystallize with a stuffed α-CrPO{sub 4}-type structure. The structure consists of a 3D-framework made of octahedra and tetrahedra that are sharing corners and/or edges generating channels along [100] and [010], in which the sodium atoms are located. Of significance, in the structuresmore » of NaNiCr{sub 2}(PO{sub 4}){sub 3}, and Na{sub 2}Ni{sub 2}Cr(PO{sub 4}){sub 3} a statistical disorder Ni{sup 2+}/Cr{sup 3+} was observed on both the 8g and 4a atomic positions, whereas in NaCoCr{sub 2}(PO{sub 4}){sub 3} the statistical disorder Co{sup 2+}/Cr{sup 3+} was only observed on the 8g atomic position. When tested as negative electrode materials, NaCoCr{sub 2}(PO{sub 4}){sub 3}, NaNiCr{sub 2}(PO{sub 4}){sub 3}, and Na{sub 2}Ni{sub 2}Cr(PO{sub 4}){sub 3} delivered specific capacities of 352, 385, and 368 mA h g{sup −1}, respectively, which attests to the electrochemical activity of sodium in these compounds. - Highlights: • NaCoCr{sub 2}(PO{sub 4}){sub 3}, NaNiCr{sub 2}(PO{sub 4}){sub 3}, and Na{sub 2}Ni{sub 2}Cr(PO{sub 4}){sub 3} were synthesized by sol-gel method. • The crystal structures were determined by using neutron powder diffraction data. • The three compounds crystallize with a stuffed α-CrPO{sub 4}-type structure. • The three compounds were tested as anodes in sodium-ion batteries. • Relatively high specific capacities were obtained for these compounds.« less

  10. Thermal Stabilization and Mechanical Properties of Nanocrystalline Iron-Nickel-Zirconium Alloys

    NASA Astrophysics Data System (ADS)

    Kotan, Hasan

    Ultrafine grained and nanostructured materials are promising for structural applications because of the high strength compared to coarse grained counterparts. However, their widespread application is limited by an inherently high driving force for thermally induced grain growth, even at low temperatures. Accordingly, the understanding of and control over grain growth in nanoscale materials is of great technological and scientific importance as many physical properties (i.e. mechanical properties) are functions of the average grain size and the grain size distribution within the microstructure. Here, we investigate the microstructural evolution and grain growth in Fe-Ni alloys with Zr addition and differentiate the stabilization mechanisms acting on grain boundaries. Fe-Ni alloys are chosen for stability investigations since they are important for understanding the behavior of many steels and other ferrous alloys. Zirconium is proven to be an effective grain size stabilizer in pure Fe and Fe-base systems. In this study, nanocrystalline alloys were prepared by high energy ball milling. In situ and ex situ experiments were utilized to directly follow grain growth and microstructural evolution as a function of temperature and composition. The information obtained from these experiments enables the real time observation of microstructural evolution and phase transformation and provides a unique view of dynamic reactions as they occur. The knowledge of the thermal stability will exploit the potential high temperature applications and the consolidation conditions (i.e. temperature and pressure) to obtain high dense materials for advanced mechanical tests. Our investigations reveal that the grain growth of Fe-Ni alloys is not affected by Ni content but strongly inhibited by the addition of 1 at% Zr up to about 700 °C. The microstructural stability is lost due to the bcc-to-fcc transformation (occurring at 700°C) by the sudden appearance of abnormally grown fcc grains

  11. "Bulk" Nanocrystalline Metals: Review of the Current State of the Art and Future Opportunities for Copper and Copper Alloys

    NASA Astrophysics Data System (ADS)

    Tschopp, M. A.; Murdoch, H. A.; Kecskes, L. J.; Darling, K. A.

    2014-06-01

    It is a new beginning for innovative fundamental and applied science in nanocrystalline materials. Many of the processing and consolidation challenges that have haunted nanocrystalline materials are now more fully understood, opening the doors for bulk nanocrystalline materials and parts to be produced. While challenges remain, recent advances in experimental, computational, and theoretical capability have allowed for bulk specimens that have heretofore been pursued only on a limited basis. This article discusses the methodology for synthesis and consolidation of bulk nanocrystalline materials using mechanical alloying, the alloy development and synthesis process for stabilizing these materials at elevated temperatures, and the physical and mechanical properties of nanocrystalline materials with a focus throughout on nanocrystalline copper and a nanocrystalline Cu-Ta system, consolidated via equal channel angular extrusion, with properties rivaling that of nanocrystalline pure Ta. Moreover, modeling and simulation approaches as well as experimental results for grain growth, grain boundary processes, and deformation mechanisms in nanocrystalline copper are briefly reviewed and discussed. Integrating experiments and computational materials science for synthesizing bulk nanocrystalline materials can bring about the next generation of ultrahigh strength materials for defense and energy applications.

  12. Excitation of luminescence of the nanoporous bioactive nanocrystalline carbonate-substituted hydroxyapatite for early tooth disease detection

    NASA Astrophysics Data System (ADS)

    Goloshchapov, D. L.; Minakov, D. A.; Domashevskaya, E. P.; Seredin, P. V.

    This paper deals with the luminescence characteristics of an analogue of the mineral component of dental enamel of the nanocrystalline B-type carbonate-substituted hydroxyapatite (CHAP) with 3D defects (i.e. nanopores of ∼2-5 nm) on the nanocrystalline surface. The laser-induced luminescence (LIL) of the synthesized CHAP samples was in the range of ∼515 nm (∼2.4 eV) and is due to CO3 groups replacing the PO4 group. It was found that the intensity of the luminescence of the CHAP is caused by structurally incorporated CO3 groups in the HAP structure. Furthermore, the intensity of the luminescence also decreases as the number of the above intracentre defects (CO3) in the apatite structure declines. These results are potentially promising for developing the foundations for precise methods for the early detection of caries in human solid dental tissue.

  13. Structural and optical properties of NiFe2O4 synthesized via green technology

    NASA Astrophysics Data System (ADS)

    Patel, S.; Saleem, M.; Varshney, Dinesh

    2018-05-01

    The nanoparticles of NiFe2O4 were successfully synthesized via green technology using banana peel extract as the catalyst as well as the medium for reaction technique is reported. Analysis of X-ray diffraction spectrum revealed the cubic structure for the prepared spinel ferrite samples crystallized into cubic spinel structure with the space group Fd3m. The Retvield refinement was carried out which obeyed the results obtained from the XRD spectrum analysis of the sample. Raman spectrum provided confirmation for the spinel structure formation and five active Raman modes were observed. Since the optical band-gap value shows inverse response to the crystallite size, The UV-Vis spectrum study confirmed dual but reduced band-gap value.

  14. Structural characterization, electrical conductivity and open circuit voltage studies of the nanocrystalline La10Si6O27 electrolyte material for SOFCs

    NASA Astrophysics Data System (ADS)

    Jena, Paramananda; Jayasubramaniyan, S.; Patro, P. K.; Lenka, R. K.; Sinha, Amit; Muralidharan, P.; Srinadhu, E. S.; Satyanarayana, N.

    2018-02-01

    Nanocrystalline La10Si6O27 apatite-type sample was synthesized by the co-precipitation method. Thermal behavior, phase, structure, morphology and elemental composition of La, O and Si of the synthesized La10Si6O27 sample were investigated through TG/DTA, XRD, FTIR, Raman spectroscopy and SEM-EDX measurements respectively. Formation of phase purity of the nanocrystalline La10Si6O27 sample was confirmed by analysing the measured X-ray powder diffraction (XRD) pattern using Rietveld refinement and the calculated average crystallite size of the La10Si6O27 sample was found to be 33 nm. The electrical conductivity of the sintered La10Si6O27 pellet was investigated as a function of temperature ranging from 200 to 800 °C under air and it was found to be 1.92 × 10-3 S cm-1 at 800 °C. The chemical stability of La10Si6O27 powder under oxidizing and reducing atmospheres was confirmed from the analysis of the measured XRD pattern and Raman spectral results. Open circuit potential of a button cell, made up of the La10Si6O27 sample, was tested up to 800 °C with both oxygen and hydrogen at opposite sides of the cell and was found to 1 V. Hence, the results demonstrate that La10Si6O27 could be a promising solid electrolyte material for the solid oxide fuel cell (SOFC) applications.

  15. Superplastic Deformation Mechanisms of Superfine/Nanocrystalline Duplex PM-TiAl-Based Alloy.

    PubMed

    Gong, Xuebo; Duan, Zhenxin; Pei, Wen; Chen, Hua

    2017-09-19

    In this paper, the equiaxed superfine/nanocrystalline duplex PM-TiAl-based alloy with (γ + α₂) microstructure, Ti-45Al-5Nb (at %), has been synthesized by high-energy ball milling and vacuum hot pressing sintering. Superplastic deformation behavior has been investigated at 1000 °C and 1050 °C with strain rates from 5 × 10 -5 s -1 to 1 × 10 -3 s -1 . The effects of deformation on the microstructure and mechanical behaviors of high Nb containing TiAl alloy have been characterized and analyzed. The results showed that, the ultimate tensile strength of the alloy was 58.7 MPa at 1000 °C and 10.5 MPa at 1050 °C with a strain rate of 5 × 10 -5 s -1 , while the elongation was 121% and 233%, respectively. The alloy exhibited superplastic elongation at 1000 and 1050 °C with an exponent (m) of 0.48 and 0.45. The main softening mechanism was dynamic recrystallization of γ grains; the dislocation slip and γ/γ interface twinning were responsible for superplastic deformation. The orientation relationship of γ/γ interface twinning obeyed the classical one: (001) γ //(110) γ .

  16. Ti, Ni and TiNi nanoparticles physically synthesized by Ar+ beam milling.

    PubMed

    Torres Castro, A; López Cuéllar, E; José Yacamán, M; Ortiz Méndez, U

    2008-12-01

    When the size of a particle decreases around 100 nm or less, there is a change in properties from those shown in the bulk material. In this work approximately 3 nm nanoparticles of Ni, Ti and TiNi bimetallic are produced using physical vapor deposition (PVD). Nanoparticles are characterized by High Resolution Transmission Electron Microscopy (HRTEM), High Angle Annular Dark Field (HAADF), Electron Diffraction (ED). The results show that all nanoparticles maintain the same crystal structure of bulk material but a change in their lattice parameter is produced.

  17. Physical properties and surface/interface analysis of nanocrystalline WO3 films grown under variable oxygen gas flow rates

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Vemuri, R. S.; Carbjal-Franco, G.; Ferrer, D. A.

    2012-10-15

    Nanocrystalline WO3 films were grown by reactive magnetron sputter-deposition in a wide range of oxygen gas flow rates while keeping the deposition temperature fixed at 400 oC. The physical characteristics of WO3 films were evaluated using grazing incidence X-ray diffraction (GIXRD), X-ray reflectivity (XRR) and transmission electron microscopy (TEM) measurements. Physical characterization indicates that the thickness, grain size, and density of WO3 films are sensitive to the oxygen gas flow rate during deposition. XRD data indicates the formation of tetragonal WO3 films. The grain size increases from 21 to 25 nm with increasing oxygen gas flow rate to 65%, atmore » which point the grain size exhibits a decreasing trend to attain the lowest value of 15 nm at 100% oxygen. TEM analysis provides a model consisting of isotropic WO3 film (nanocrystalline)-SiO2 interface (amorphous)-Si(100) substrate. XRR simulations, which are based on this model, provide excellent agreement to the experimental data indicating that the normalized thickness of WO3 films decreases with the increasing oxygen gas flow rate. The density of WO3 films increases with increasing oxygen gas flow rate.« less

  18. Effect of MoO3 on the synthesis of boron nitride nanotubes over Fe and Ni catalysts.

    PubMed

    Nithya, Jeghan Shrine Maria; Pandurangan, Arumugam

    2012-05-01

    Synthesis of boron nitride nanotubes at reduced temperature is important for industrial manufactures. In this study boron nitride nanotubes were synthesized by thermal evaporation method using B/Fe2O3/MoO3 and B/Ni2O3/MoO3 mixtures separately with ammonia as the nitrogen source. The growth of boron nitride nanotubes occurred at 1100 degrees C, which was relatively lower than other metal oxides assisted growth processes requiring higher than 1200 degrees C. MoO3 promoted formation of B2O2 and aided boron nitride nanotubes growth at a reduced temperature. The boron nitride nanotubes with bamboo shaped, nested cone structured and straight tubes like forms were evident from the high resolution transmission electron microscopy. Metallic Fe and Ni, formed during the process, were the catalysts for the growth of boron nitride nanotubes. Their formation was established by X-ray diffraction. FT Raman showed a peak due to B-N vibration of BNNTs close to 1370 cm(-1). Hence MoO3 assisted growth of boron nitride nanotubes is advantageous, as it significantly reduced the synthesis temperature.

  19. Synthesis of three-dimensional mesoporous Cu-Al layered double hydroxide/g-C3N4 nanocomposites on Ni-foam for enhanced supercapacitors with excellent long-term cycling stability.

    PubMed

    Adhikari, Surya Prasad; Awasthi, Ganesh Prasad; Kim, Kyung-Suk; Park, Chan Hee; Kim, Cheol Sang

    2018-03-26

    In this study, a novel composite of Cu-Al layered double hydroxide (LDH) nanosheets and g-C3N4-covered Ni-foam was fabricated via a simple and facile two-step process. First, g-C3N4 sheets were deposited on Ni-foam by via electrodeposition method on a three-electrode system (Ni-foam@g-C3N4) and then, Cu-Al LDH nanosheets were grown on the Ni-foam via in situ redox reaction using a hydrothermal process (Ni-foam@Cu-Al LDH/g-C3N4). The FE-SEM image confirmed that the Cu-Al LDH nanosheets arose vertically and were anchored on the surface of electrodeposited g-C3N4 sheets, thus generating unique 3D porous interconnected networks. The electrochemical capacitive performances of the as-prepared samples were evaluated by cyclic volatammetry (CV), galvanostatic charge/discharge tests, and electrochemical impedance spectra (EIS) Nyquist plots. The specific capacitances of the Ni-foam@Cu-Al LDH/g-C3N4 nanocomposite measured from the CV curve (770.98 F g-1 at 50 mV s-1) and the galvanostatic charge/discharge curve (831.871 at 0.4 A g-1) were significantly higher than the others. Moreover, the Ni-foam@Cu-Al LDH/g-C3N4 nanocomposite revealed a remarkable high-current capacitive behavior and the capacitance retention could be maintained at 92.71% even after 5000 cycles of CV. Thus, the obtained results demonstrated that the as-prepared nanocomposite has great potential to be used as a novel supercapacitor electrode.

  20. Chemical synthesis of L10 Fe-Pt-Ni alloy nanoparticles

    NASA Astrophysics Data System (ADS)

    Deepchand, Vimal; Abel, Frank M.; Tzitzios, Vasileios; Hadjipanayis, George C.

    2018-05-01

    This work focuses on the study of the magnetic and structural properties of chemically synthesized FePt1-xNix nanoparticles, with Ni content x in the range 0.2-0.4. We report the effect of Ni substitution on the L10 structure, on both the as-synthesized and annealed nanoparticles. A decrease in nanoparticle size as well as in chemical order is observed with an increase in Ni content, for both the as-made and annealed nanoparticles. The results also show that the post annealing procedure at 700oC significantly enhanced the L10 ordering of the nanoparticles. Substitution of nickel leads to a decrease in coercivity from 14.9 kOe in FePt to 0.8 kOe for FePt0.6Ni0.4 alloy, while the magnetization at 3 T is increased from 48 emu/g to 88 emu/g.

  1. Structural, optical and morphological characterization of Cu-doped α-Fe2O3 nanoparticles synthesized through co-precipitation technique

    NASA Astrophysics Data System (ADS)

    Lassoued, Abdelmajid; Lassoued, Mohamed Saber; Dkhil, Brahim; Gadri, Abdellatif; Ammar, Salah

    2017-11-01

    Pure and copper (Cu concentration varying from 2 to 8%) doped hematite (α-Fe2O3) nanocrystals were synthesized through co-precipitation method using simple equipment. X-ray Diffraction (XRD), Transmission Electron Microscopy (TEM), Scanning Electron Microscopy (SEM), Fourier Transform Infra-Red (FT-IR), Raman spectroscopy, Differential Thermal Analysis (DTA), Thermo Gravimetric Analysis (TGA) and Ultraviolet-Visible (UV-Vis) techniques were used to characterize the synthesized samples. XRD measurements confirm that all the prepared nanocrystals consist only in nanocrystalline hematite phase. These results along with TEM and SEM show that the size of the nanoparticles decreases with Cu-doping down to 21 nm. FT-IR confirm the phase purity of the nanoparticles synthesized. The Raman spectroscopy was used not only to prove that we synthesized pure and Cu-doped hematite but also to identify their phonon modes. The TGA showed three mass losses, whereas DTA resulted in three endothermic peaks. The UV-Vis absorption measurements confirm that the decrease of particle size is accompanied by a decrease in the band gap value from 2.12 eV for pure α-Fe2O3 down to 1.91 eV for 8% Cu-doped α-Fe2O3. 8% Cu-doped hematite had the smallest size, the best crystallinity and the lowest band gap.

  2. Magnetic properties of intermetallic compounds La(Ni,Co,Cu)3

    NASA Astrophysics Data System (ADS)

    Tazuke, Y.; Tanikawa, H.; Okano, A.; Miyaji, T.

    2006-09-01

    LaNi3 exhibited a metallic antiferromagnetic property with T N = 30 K. La(Ni1-x Cox )3 with x = 0.01, 0.03 and 0.05 exhibited ferromagnetic properties, T C increasing linearly with increasing x . La(Ni1-2z Coz Cuz )3 with z = 0.015 exhibited a ferromagnetic property with a small T C. A La(Ni1-y Cuy )3 sample with y = 0.01 exhibited a Pauli-paramagnetic property; those with y = 0.02, 0.03 and 0.04 exhibited gradual metamagnetic behavior and that with y = 0.05 exhibited a ferromagnetic property. The gradual metamagnetic M -H variations are numerically simulated by using Landau-type free energies. The results suggest that the gradual metamagnetic behavior occurs from an antiferromagnetic state to a ferromagnetic one.

  3. Nano-Crystalline Thermally Evaporated Bi2Se3 Thin Films Synthesized from Mechanically Milled Powder

    NASA Astrophysics Data System (ADS)

    Amara, A.; Abdennouri, N.; Drici, A.; Abdelkader, D.; Bououdina, M.; Chaffar Akkari, F.; Khemiri, N.; Kanzari, M.; Bernède, J. C.

    2017-08-01

    Bi2Se3 powder has been successfully synthesized via mechanical ball milling of bismuth and selenium as starting materials. X-ray diffraction characterization revealed the formation of the rhombohedral and orthorhombic phases of Bi2Se3 material belonging to systems with space groups R\\bar{3}m and Pbnm, respectively. The advantageous last finding is confirmed by the Rietveld refinement of the x-ray diffraction data. Furthermore, the analysis of the x-ray data of thermally deposited thin films revealed that both orthorhombic and rhombohedral phases are coexisting in the layer. The morphology of the ball milled powder was studied by scanning electron microscopy. The phase formation of the material is confirmed by Raman spectroscopy. M-H (Magnetization versus Magnetic field) curve indicates that Bi2Se3 powder has a ferromagnetic behavior. Additionally, absorbance and transmittance measurements were carried out on the obtained thermally evaporated thin films and yielded a band gap of 1.33 eV supporting the potential application of the heterogeneous rhombohedral/orthorhombic Bi2Se3 material in photovoltaics.

  4. Enhanced stability of Zr-doped Ba(CeTb)O(3-δ)-Ni cermet membrane for hydrogen separation.

    PubMed

    Wei, Yanying; Xue, Jian; Fang, Wei; Chen, Yan; Wang, Haihui; Caro, Jürgen

    2015-07-25

    A mixed protonic and electronic conductor material BaCe(0.85)Tb(0.05)Zr(0.1)O(3-δ) (BCTZ) is prepared and a Ni-BCTZ cermet membrane is synthesized for hydrogen separation. Stable hydrogen permeation fluxes can be obtained for over 100 h through the Ni-BCTZ membrane in both dry and humid conditions, which exhibits an excellent stability compared with Ni-BaCe(0.95)Tb(0.05)O(3-δ) membrane due to the Zr doping.

  5. Exploring the Room-Temperature Ferromagnetism and Temperature-Dependent Dielectric Properties of Sr/Ni-Doped LaFeO3 Nanoparticles Synthesized by Reverse Micelle Method

    NASA Astrophysics Data System (ADS)

    Naseem, Swaleha; Khan, Shakeel; Husain, Shahid; Khan, Wasi

    2018-03-01

    This paper reports the thermal, microstructural, dielectric and magnetic properties of La0.75Sr0.25Fe0.65Ni0.35O3 nanoparticles (NPs) synthesized via reverse micelle technique. The thermogravimetric analysis of as-prepared NPs confirmed a good thermal stability of the sample. Powder x-ray diffraction data analyzed with a Rietveld refinement technique revealed single-phase and orthorhombic distorted perovskite crystal structure of the NPs having Pbnm space group. The transmission electron microscopy images show the crystalline nature and formation of nanostructures with a fairly uniform distribution of particles throughout the sample. Temperature-dependent dielectric properties of the NPs in accordance with the Kramers-Kronig transformation (KKT) model, universal dielectric response model and jump relaxation model have been discussed. Electrode or interface polarization is likely the cause of the observed dielectric behavior. Due to grain boundaries and Schottky barriers of the metallic electrodes of semiconductors, the depletion region is observed, which gives rise to Maxwell-Wagner relaxation and hence high dielectric constants. Magnetic studies revealed the ferromagnetic nature of the prepared NPs upon Sr and Ni doping in LaFeO3 perovskite at room temperature. Therefore, these NPs could be a potential candidate as electrode material in solid oxide fuel cells.

  6. Ce doped NiO nanoparticles as selective NO2 gas sensor

    NASA Astrophysics Data System (ADS)

    Gawali, Swati R.; Patil, Vithoba L.; Deonikar, Virendrakumar G.; Patil, Santosh S.; Patil, Deepak R.; Patil, Pramod S.; Pant, Jayashree

    2018-03-01

    Metal oxide gas sensors are promising portable gas detection devices because of their advantages such as low cost, easy production and compact size. The performance of such sensors is strongly dependent on material properties such as morphology, structure and doping. In the present study, we report the effect of cerium (Ce) doping on nickel oxide (NiO) nano-structured thin film sensors towards various gases. Bare NiO and Ce doped NiO nanoparticles (Ce:NiO) were synthesized by sol-gel method. To understand the effect of Ce doping in nickel oxide, various molar percentages of Ce with respect to nickel were incorporated. The structure, phase, morphology and band-gap energy of as-synthesized nanoparticles were studied by XRD, SEM, EDAX and UV-vis spectroscopy. Thin film gas sensors of all the samples were prepared and subjected to various gases such as LPG, NH3, CH3COCH3 and NO2. A systematic and comparative study reveals an enhanced gas sensing performance of Ce:NiO sensors towards NO2 gas. The maximum sensitivity for NO2 gas is around 0.719% per ppm at moderate operating temperature of 150 °C for 0.5% Ce:NiO thin film gas sensor. The enhanced gas sensing performance for Ce:NiO is attributed to the distortion of crystal lattice caused by doping of Ce into NiO.

  7. An innovative architectural design to enhance the electrochemical performance of La2NiO4+δ cathodes for solid oxide fuel cell applications

    NASA Astrophysics Data System (ADS)

    Sharma, Rakesh K.; Burriel, Mónica; Dessemond, Laurent; Martin, Vincent; Bassat, Jean-Marc; Djurado, Elisabeth

    2016-06-01

    An architectural design of the cathode microstructure based on combining electrostatic spray deposition (ESD) and screen-printing (SP) techniques has demonstrated to be an innovative strategy to enhance the electrochemical properties of La2NiO4+δ (LNO) as oxygen electrode on Ce0.9Gd0.1O2-δ (CGO) electrolyte for solid oxide fuel cells. For this purpose, the influence of the ESD process parameters on the microstructure has been systematically investigated. Electrochemical performances of four selected cathode microstructures are investigated: (i) 3-D coral nanocrystalline (average particle size ∼ 100 nm) LNO film grown by ESD; (ii) 3-D coral nanocrystalline film (average particle size ∼ 150 nm) grown by ESD with a continuous nanometric dense interface; (iii) porous screen-printed LNO film (average particle size ∼ 400 nm); and (iv) 3-D coral nanocrystalline film (average particle size ∼ 150 nm) with a continuous nanometric dense interface prepared by ESD topped by a LNO current collector prepared by SP. A significant reduction in the polarization resistance (Rpol) is obtained (0.08 Ω cm2 at 700 °C) for 3-D coral topped by the SP layer. Moreover LNO is found to be stable and compatible with CGO up to 800 °C for only 10 days duration in air, making it potentially suitable for SOFCs cathode application.

  8. Dielectric property of NiTiO{sub 3} doped substituted ortho-chloropolyaniline composites

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Lakshmi, Mohana; Faisal, Muhammad; Roy, Aashish S.

    2013-11-15

    Ortho-chloropolyaniline (OCP)-NiTiO{sub 3} composites have been synthesized via in-situ polymerization of ortho-chloroaniline with various weight percentages of NiTiO{sub 3.} Fourier Transform Infrared spectroscopic studies of Ortho-chloropolyaniline and its composites indicated the formation of composites as a result of Vander Waal's interaction between OCP and NiTiO{sub 3} particles. Surface morphology of OCP and OCP-NiTiO{sub 3} composites were studied using Scanning Electron Microscope (SEM). The SEM micrographs indicated a modified morphology after the composite formation. Dielectric properties and electric modulus of OCP and OCP-NiTiO{sub 3} composites have been investigated in the frequency range of 50 Hz – 5 MHz. It has beenmore » noticed that electrical resistance decreases with increase in weight percentage of NiTiO{sub 3} particles in polymer matrix as well as with applied frequency. The display of semicircular arcs in Cole-Cole plots indicates the formation of series resistor and capacitor in network causing a decrease in the relaxation time and as a result conductivity enhances in these composites. The facile and cost effective synthesis process and excellent dielectric and conductivity response of these materials makes them promising materials for practical applications.« less

  9. Dielectric property of NiTiO{sub 3} doped substituted ortho-chloropolyaniline composites

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Lakshmi, Mohana; Faisal, Muhammad; Roy, Aashish S.

    Ortho-chloropolyaniline (OCP)-NiTiO{sub 3} composites have been synthesized via in-situ polymerization of ortho-chloroaniline with various weight percentages of NiTiO{sub 3.} Fourier Transform Infrared spectroscopic studies of Ortho-chloropolyaniline and its composites indicated the formation of composites as a result of Vander Waal's interaction between OCP and NiTiO{sub 3} particles. Surface morphology of OCP and OCP-NiTiO{sub 3} composites were studied using Scanning Electron Microscope (SEM). The SEM micrographs indicated a modified morphology after the composite formation. Dielectric properties and electric modulus of OCP and OCP-NiTiO{sub 3} composites have been investigated in the frequency range of 50 Hz – 5 MHz. It has beenmore » noticed that electrical resistance decreases with increase in weight percentage of NiTiO{sub 3} particles in polymer matrix as well as with applied frequency. The display of semicircular arcs in Cole-Cole plots indicates the formation of series resistor and capacitor in network causing a decrease in the relaxation time and as a result conductivity enhances in these composites. The facile and cost effective synthesis process and excellent dielectric and conductivity response of these materials makes them promising materials for practical applications.« less

  10. Formation Mechanism of Spherical TiC in Ni-Ti-C System during Combustion Synthesis.

    PubMed

    Zhu, Guoliang; Wang, Wei; Wang, Rui; Zhao, Chuanbao; Pan, Weitao; Huang, Haijun; Du, Dafan; Wang, Donghong; Shu, Da; Dong, Anping; Sun, Baode; Jiang, Sheng; Pu, Yilong

    2017-08-29

    The formation mechanism of TiC particles in a Ni-Ti-C system were revealed by using differential thermal analysis (DTA), XRD, and SEM to identify the reaction products in different temperature ranges. The results indicated that the synthesis mechanism of TiC in Ni-Ti-C system was complex; several reactions were involved in the combustion synthesis of TiC-Ni composite. The Ni-Ti intermediate phases play important roles during the formation of TiC. Moreover, the influence of heating rate on the size range of TiC was also discussed.

  11. Formation Mechanism of Spherical TiC in Ni-Ti-C System during Combustion Synthesis

    PubMed Central

    Zhu, Guoliang; Wang, Wei; Wang, Rui; Zhao, Chuanbao; Pan, Weitao; Huang, Haijun; Du, Dafan; Wang, Donghong; Shu, Da; Dong, Anping; Sun, Baode; Jiang, Sheng; Pu, Yilong

    2017-01-01

    The formation mechanism of TiC particles in a Ni-Ti-C system were revealed by using differential thermal analysis (DTA), XRD, and SEM to identify the reaction products in different temperature ranges. The results indicated that the synthesis mechanism of TiC in Ni-Ti-C system was complex; several reactions were involved in the combustion synthesis of TiC-Ni composite. The Ni-Ti intermediate phases play important roles during the formation of TiC. Moreover, the influence of heating rate on the size range of TiC was also discussed. PMID:28850088

  12. Atomistic modeling of La 3+ doping segregation effect on nanocrystalline yttria-stabilized zirconia

    DOE PAGES

    Zhang, Shenli; Sha, Haoyan; Castro, Ricardo H. R.; ...

    2018-01-01

    The effect of La 3+ doping on the structure and ionic conductivity change in nanocrystalline yttria-stabilized zirconia (YSZ) was studied using a combination of Monte Carlo and molecular dynamics simulations.

  13. 3-D dumbbell-like LiNi1/3Mn1/3Co1/3O2 cathode materials assembled with nano-building blocks for lithium-ion batteries

    NASA Astrophysics Data System (ADS)

    Ryu, Won-Hee; Lim, Sung-Jin; Kim, Won-Keun; Kwon, HyukSang

    2014-07-01

    Dumbbell-like microsphere carbonate precursors including multi-transition metal components (Ni1/3Mn1/3Co1/3CO3) assembled with nano-building blocks were synthesized by urea-assisted solvo/hydrothermal method, and layered cathode materials (LiNi1/3Mn1/3Co1/3O2) were subsequently prepared using the similarly shaped carbonate precursors for Li-ion batteries. For the synthesis of hierarchical microsphere structures, the partial addition of viscous organic solvent (e.g. ethylene glycol) in aqueous solution played a crucial role, not only in suppressing the sudden particle growth but also in regulating the directional crystallization of carbonate particles on the surface. The dumbbell-like LiNi1/3Mn1/3Co1/3O2 assembled with nanocubes prepared via the urea-assisted solvo/hydrothermal method exhibited better electrochemical characteristics, such as initial discharge capacity, cyclic performance, and rate-capability as a cathode material of Li-ion batteries, compared with the LiNi1/3Mn1/3Co1/3O2 materials prepared via the conventional co-precipitation method.

  14. Synthesis of ferrite and nickel ferrite nanoparticles using radio-frequency thermal plasma torch

    NASA Astrophysics Data System (ADS)

    Son, S.; Taheri, M.; Carpenter, E.; Harris, V. G.; McHenry, M. E.

    2002-05-01

    Nanocrystalline (NC) ferrite powders have been synthesized using a 50 kW-3 MHz rf thermal plasma torch for high-frequency soft magnet applications. A mixed powder of Ni and Fe (Ni:Fe=1:2), a NiFe permalloy powder with additional Fe powder (Ni:Fe=1:2), and a NiFe permalloy powder (Ni:Fe=1:1) were used as precursors for synthesis. Airflow into the reactor chamber was the source of oxygen for oxide formation. XRD patterns clearly show that the precursor powders were transformed into NC ferrite particles with an average particle size of 20-30 nm. SEM and TEM studies indicated that NC ferrite particles had well-defined polygonal growth forms with some exhibiting (111) faceting and many with truncated octahedral and truncated cubic shapes. The Ni content in the ferrite particles was observed to increase in going from mixed Ni and Fe to mixed permalloy and iron and finally to only permalloy starting precursor. The plasma-torch synthesized ferrite materials using exclusively the NiFe permalloy precursor had 40%-48% Ni content in the Ni-ferrite particle, differing from the NiFe2O4 ideal stoichiometry. EXAFS was used to probe the cation coordination in low Ni magnetite species. The coercivity and Neel temperature of the high Ni content ferrite sample were 58 Oe and ˜590 °C, respectively.

  15. Effect of powder reactivity on fabrication and properties of NiAl/Al2O3 composite coated on cast iron using spark plasma sintering

    NASA Astrophysics Data System (ADS)

    Beyhaghi, Maryam; Kiani-Rashid, Ali-Reza; Kashefi, Mehrdad; Khaki, Jalil Vahdati; Jonsson, Stefan

    2015-07-01

    Powder mixtures of Ni, NiO and Al are ball milled for 1 and 10 h. X-ray diffractometry and differential thermal analysis show that while ball milling for 1 h produced mechanically activated powder; 10 h ball milling produced NiAl and Al2O3 phases. Dense NiAl/Al2O3 composite coatings are formed on gray cast iron substrate by spark plasma sintering (SPS) technique. The effect of powder reactivity on microstructure, hardness and scratch hardness of NiAl/Al2O3 coatings after SPS is discussed. Results show that in the coating sample made of mechanically activated powder in situ synthesis of NiAl/Al2O3 composite coating is fulfilled and a thicker well-formed diffusion bond layer at the interface between coating and substrate is observed. The diffusion of elements across the bond layers and phase evolution in the bond layers were investigated. No pores or cracks were observed at the interface between coating layer and substrate in any of samples. Higher Vickers hardness and scratch hardness values in coating made of 10 h ball milled powder than in coating fabricated from 1 h ball milled powder are attributed to better dispersion of Al2O3 reinforcement particles in NiAl matrix and nano-crystalline structure of NiAl matrix. Scratched surface of coatings did not reveal any cracking or spallation at coating-substrate interface indicating their good adherence at test conditions.

  16. Magnetic, Optical and Magneto-optical Properties of Ni2MnGe Alloy Films

    NASA Astrophysics Data System (ADS)

    Kim, R. J.; Kudryavtsev, Y. V.; Kim, K. W.

    2005-03-01

    The influence of atomic ordering on the magnetic, the optical and the magneto-optical (MO) properties of Ni2MnGe Heusler alloy (HA) films was investigated. The bulk Ni2MnGe HA was prepared by arc melting, and the films were deposited by flash evaporation onto glass substrates at several substrate temperatures from 150 to 730 K. The bulk Ni2MnGe HA exhibits the cubic L21 structure with a = b = c = 0.5761 nm, and the annealed (at 573 K) bulk alloy is in the tetragonal structure with a = b = 0.5720 nm and c = 0.5865 nm. While the films deposited at 720 K show a well-ordered L21 structure, the deposition at 150 K < T < 710 K results in the formation of a nanocrystalline or an amorphous microstructure. It was found the structural disorder in Ni2MnGe films induces lack of the ferromagnetic order and noticeable changes in the optical and MO response.

  17. Extended phase diagram of R NiC2 family: Linear scaling of the Peierls temperature

    NASA Astrophysics Data System (ADS)

    Roman, Marta; Strychalska-Nowak, Judyta; Klimczuk, Tomasz; Kolincio, Kamil K.

    2018-01-01

    Physical properties for the late-lanthanide-based R NiC2 (R =Dy , Ho, Er, and Tm) ternary compounds are reported. All the compounds show antiferromagnetic ground state with the Néel temperature ranging from 3.4 K for HoNiC2 to 8.5 K for ErNiC2. The results of the transport and galvanomagnetic properties confirm a charge density wave state at and above room temperature with transition temperatures TCDW=284 , 335, 366, and 394 K for DyNiC2, HoNiC2, ErNiC2, and TmNiC2, respectively. The Peierls temperature TCDW scales linearly with the unit cell volume. A similar linear dependence has been observed for the temperature of the lock-in transition T1 as well. Beyond the intersection point of the trend lines, the lock-in transition is no longer observed. In this Rapid Communication we demonstrate an extended phase diagram for the R NiC2 family.

  18. Using DR52c/Ni2+ mimotope tetramers to detect Ni2+ reactive CD4+ T cells in patients with joint replacement failure.

    PubMed

    Zhang, Yan; Wang, Yang; Anderson, Kirsten; Novikov, Andrey; Liu, Zikou; Pacheco, Karin; Dai, Shaodong

    2017-09-15

    T cell mediated hypersensitivity to nickel (Ni 2+ ) is one of the most common causes of allergic contact dermatitis. Ni 2+ sensitization may also contribute to the failure of Ni 2+ containing joint implants, and revision to non-Ni 2+ containing hardware can be costly and debilitating. Previously, we identified Ni 2+ mimotope peptides, which are reactive to a CD4 + T cell clone, ANi2.3 (Vα1, Vβ17), isolated from a Ni 2+ hypersensitive patient with contact dermatitis. This T cell is restricted to the major histocompatibility complex class II (MHCII) molecule, Human Leukocyte Antigen (HLA)-DR52c (DRA, DRB3*0301). However, it is not known if Ni 2+ induced T cell responses in sensitized joint replacement failure patients are similar to subjects with Ni 2+ induced contact dermatitis. Here, we generated DR52c/Ni 2+ mimotope tetramers, and used them to test if the same Ni 2+ T cell activation mechanism could be generalized to Ni 2+ sensitized patients with associated joint implant failure. We confirmed the specificity of these tetramers by staining of ANi2.3T cell transfectomas. The DR52c/Ni 2+ mimotope tetramer detected Ni 2+ reactive CD4 + T cells in the peripheral blood mononuclear cells (PBMC) of patients identified as Ni 2+ sensitized by patch testing and a positive Ni 2+ LPT. When HLA-typed by a DR52 specific antibody, three out of four patients were DR52 positive. In one patient, Ni 2+ stimulation induced the expansion of Vβ17 positive CD4 + T cells from 0.8% to 13.3%. We found that the percentage of DR52 positivity and Vβ17 usage in Ni 2+ sensitized joint failure patients are similar to Ni sensitized skin allergy patients. Ni 2+ independent mimotope tetramers may be a useful tool to identify the Ni 2+ reactive CD4 + T cells. Copyright © 2017 Elsevier Inc. All rights reserved.

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

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Kong, Ling-Bin, E-mail: konglb@lut.cn; School of Materials Science and Engineering, Lanzhou University of Technology, Lanzhou 730050; Deng, Li

    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 andmore » 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

  20. Interpenetration of a 3D Icosahedral M@Ni12 (M=Al, Ga) Framework with Porphyrin-Reminiscent Boron Layers in MNi9 B8.

    PubMed

    Zheng, Qiang; Wagner, Frank R; Ormeci, Alim; Prots, Yurii; Burkhardt, Ulrich; Schmidt, Marcus; Schnelle, Walter; Grin, Yuri; Leithe-Jasper, Andreas

    2015-11-09

    Two ternary borides MNi9 B8 (M=Al, Ga) were synthesized by thermal treatment of mixtures of the elements. Single-crystal X-ray diffraction data reveal AlNi9 B8 and GaNi9 B8 crystallizing in a new type of structure within the space group Cmcm and the lattice parameters a=7.0896(3) Å, b=8.1181(3) Å, c=10.6497(4) Å and a=7.0897(5) Å, b=8.1579(4) Å, c=10.6648(7) Å, respectively. The boron atoms build up two-dimensional layers, which consist of puckered [B16 ] rings with two tailing B atoms, whereas the M atoms reside in distorted vertices-condensed [Ni12 ] icosahedra, which form a three-dimensional framework interpenetrated by boron porphyrin-reminiscent layers. An unusual local arrangement resembling a giant metallo-porphyrin entity is formed by the [B16 ] rings, which, due to their large annular size of approximately 8 Å, chelate four of the twelve icosahedral Ni atoms. An analysis of the chemical bonding by means of the electron localizability approach reveals strong covalent B-B interactions and weak Ni-Ni interactions. Multi-center dative B-Ni interaction occurs between the Al-Ni framework and the boron layers. In agreement with the chemical bonding analysis and band structure calculations, AlNi9 B8 is a Pauli-paramagnetic metal. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  1. Nanocrystalline hydroxyapatite doped with selenium oxyanions: a new material for potential biomedical applications.

    PubMed

    Kolmas, Joanna; Oledzka, Ewa; Sobczak, Marcin; Nałęcz-Jawecki, Grzegorz

    2014-06-01

    Selenium-substituted hydroxyapatites containing selenate SeO4(2-) or selenite SeO3(2-) ions were synthesized using a wet precipitation method. The selenium content was determined by atomic absorbance spectrometry. The raw, unsintered powders were also characterized using powder X-ray diffraction, middle-range FT-IR spectroscopy and transmission electron microscopy with energy-dispersive X-ray spectroscopic microanalysis. The synthesized apatites were found to be pure and nanocrystalline with a crystal size similar to that in bone mineral. The incorporation of selenium oxyanions into the crystal lattice was confirmed. The toxicity of hydroxyapatites containing selenite or selenate ions was evaluated with a protozoan assay and bacterial luminescence test. Copyright © 2014 Elsevier B.V. All rights reserved.

  2. Influence of annealing temperature on the microstructure and magnetic properties of Ni/NiO core-shell nanowires

    NASA Astrophysics Data System (ADS)

    Xiang, Wenfeng; Liu, Yuan; Yao, Jiangfeng; Sun, Rui

    2018-03-01

    Ni/NiO core-shell nanowires (NWs) were synthesized by thermal annealing of Ni NWs and variations in the microstructure, surface morphology, and magnetic properties of the NWs as a function of annealing temperature were investigated. The results showed that the grain size and crystal quality of NiO increased with an increasing annealing temperature. Specially, the effect of annealing temperature was much greater than annealing time for the formation of Ni/NiO NWs during the oxidization process. The total weight gain of the Ni/NiO NWs continuously increased when the annealing temperature was lower than 400 °C and the annealing time was more than 2 h; however, the weight gain of the Ni/NiO NWs was almost constant after annealing for 40 min when the annealing temperature was higher than 500 °C. The thorns on the surface of the Ni/NiO NWs gradually passivated and magnetic properties declined when the annealing temperature was increased from 300 °C to 400 °C. Smooth Ni/NiO NWs with no magnetic properties were prepared when the annealing temperature was over 500 °C. The detail study regarding the formation and evolution of Ni/NiO NWs is of considerable value and may provide useful information regarding the choice of post-treatment parameters for different applications of Ni/NiO NWs.

  3. Physical property and electronic structure characterization of bulk superconducting Bi3Ni

    NASA Astrophysics Data System (ADS)

    Kumar, Jagdish; Kumar, Anuj; Vajpayee, Arpita; Gahtori, Bhasker; Sharma, Devina; Ahluwalia, P. K.; Auluck, S.; Awana, V. P. S.

    2011-07-01

    We report the experimental and theoretical study of the magnetic nature of the Bi3Ni system. The structure is found to be orthorhombic (Pnma) with lattice parameters a = 8.879 Å, b = 4.0998 Å and c = 4.099 Å. The title compound is synthesized via a solid state reaction route by quartz vacuum encapsulation of 5 N purity stoichiometric ingredients of Ni and Bi. The superconducting transition temperature is found to be 4.1 K as confirmed from magnetization and specific heat measurements. The lower critical field (Hc1) and irreversibility field (Hirr) are around 150 and 3000 Oe respectively at 2 K. Upper critical field (Hc2), as determined from in-field (up to 4 T) ac susceptibility, is found to be around 2 T at 2 K. The normal state specific heat is fitted using the Sommerfeld-Debye equation C(T) = γT + βT3 + δT5 and the parameters obtained are γ = 11.08 mJ mol - 1 K - 2, β = 3.73 mJ mol - 1 K - 4 and δ = 0.0140 mJ mol - 1 K - 6. The calculated electronic density of states (DOS) at the Fermi level N(EF) and Debye temperature ΘD are 4.697 states/eV/f.u. and 127.7 K respectively. We also estimated the value of the electron-phonon coupling constant (λ) to be 1.23, which when substituted in the MacMillan equation gives Tc = 4.5 K. Density functional theory (DFT) based calculations for experimentally determined lattice parameters show that Ni in this compound is non-magnetic and ferromagnetic interactions seem to play no role. The Stoner condition IN(EF) = 0.136 per Ni atom also indicates that the system cannot have any ferromagnetism. The fixed spin moment (FSM) calculations, by fixing total magnetic moment on the unit cell, also suggested that this system does not exhibit any signatures of ferromagnetism.

  4. Engineered Mott ground state in a LaTiO3+δ/LaNiO3 heterostructure

    NASA Astrophysics Data System (ADS)

    Cao, Yanwei; Liu, Xiaoran; Kareev, M.; Choudhury, D.; Middey, S.; Meyers, D.; Kim, J.-W.; Ryan, P. J.; Freeland, J. W.; Chakhalian, J.

    2016-01-01

    In pursuit of creating cuprate-like electronic and orbital structures, artificial heterostructures based on LaNiO3 have inspired a wealth of exciting experimental and theoretical results. However, to date there is a very limited experimental understanding of the electronic and orbital states emerging from interfacial charge transfer and their connections to the modified band structure at the interface. Towards this goal, we have synthesized a prototypical superlattice composed of a correlated metal LaNiO3 and a doped Mott insulator LaTiO3+δ, and investigated its electronic structure by resonant X-ray absorption spectroscopy combined with X-ray photoemission spectroscopy, electrical transport and theory calculations. The heterostructure exhibits interfacial charge transfer from Ti to Ni sites, giving rise to an insulating ground state with orbital polarization and eg orbital band splitting. Our findings demonstrate how the control over charge at the interface can be effectively used to create exotic electronic, orbital and spin states.

  5. Engineered Mott ground state in a LaTiO3+δ/LaNiO3 heterostructure

    PubMed Central

    Cao, Yanwei; Liu, Xiaoran; Kareev, M.; Choudhury, D.; Middey, S.; Meyers, D.; Kim, J.-W.; Ryan, P. J.; Freeland, J.W.; Chakhalian, J.

    2016-01-01

    In pursuit of creating cuprate-like electronic and orbital structures, artificial heterostructures based on LaNiO3 have inspired a wealth of exciting experimental and theoretical results. However, to date there is a very limited experimental understanding of the electronic and orbital states emerging from interfacial charge transfer and their connections to the modified band structure at the interface. Towards this goal, we have synthesized a prototypical superlattice composed of a correlated metal LaNiO3 and a doped Mott insulator LaTiO3+δ, and investigated its electronic structure by resonant X-ray absorption spectroscopy combined with X-ray photoemission spectroscopy, electrical transport and theory calculations. The heterostructure exhibits interfacial charge transfer from Ti to Ni sites, giving rise to an insulating ground state with orbital polarization and eg orbital band splitting. Our findings demonstrate how the control over charge at the interface can be effectively used to create exotic electronic, orbital and spin states. PMID:26791402

  6. Engineered Mott ground state in a LaTiO 3+δ/LaNiO 3 heterostructure

    DOE PAGES

    Cao, Yanwei; Liu, Xiaoran; Kareev, M.; ...

    2016-01-21

    In pursuit of creating cuprate-like electronic and orbital structures, artificial heterostructures based on LaNiO 3 have inspired a wealth of exciting experimental and theoretical results. However, to date there is a very limited experimental understanding of the electronic and orbital states emerging from interfacial charge transfer and their connections to the modified band structure at the interface. Towards this goal, we have synthesized a prototypical superlattice composed of a correlated metal LaNiO 3 and a doped Mott insulator LaTiO 3+δ, and investigated its electronic structure by resonant X-ray absorption spectroscopy combined with X-ray photoemission spectroscopy, electrical transport and theory calculations.more » The heterostructure exhibits interfacial charge transfer from Ti to Ni sites, giving rise to an insulating ground state with orbital polarization and e g orbital band splitting. Here, our findings demonstrate how the control over charge at the interface can be effectively used to create exotic electronic, orbital and spin states.« less

  7. Oxygen potentials in Ni + NiO and Ni + Cr2O3 + NiCr2O4 systems

    NASA Astrophysics Data System (ADS)

    Kale, G. M.; Fray, D. J.

    1994-06-01

    The chemical potential of O for the coexistence of Ni + NiO and Ni + Cr2O3 + NiCr2O4 equilibria has been measured employing solid-state galvanic cells, (+) Pt, Cu + Cu2O // (Y2O3)ZrO2 // Ni + NiO, Pt (-) and (+) Pt, Ni + NiO // (Y2O3)ZrO2 // Ni + Cr2O3 + NiCr2O4, Pt (-) in the temperature range of 800 to 1300 K and 1100 to 1460 K, respectively. The electromotive force (emf) of both the cells was reversible, reproducible on thermal cycling, and varied linearly with temperature. For the coexistence of the two-phase mixture of Ni + NiO, δΜO 2(Ni + NiO) = -470,768 + 171.77T (±20) J mol-1 (800 ≤ T ≤ 1300 K) and for the coexistence of Ni + Cr2O3 + NiCr2O4, δΜO 2(Ni + Cr2O3 + NiCr2O4) = -523,190 + 191.07T (±100) J mol-1 (1100≤ T≤ 1460 K) The “third-law” analysis of the present results for Ni + NiO gives the value of ‡H{298/o} = -239.8 (±0.05) kJ mol-1, which is independent of temperature, for the formation of one mole of NiO from its elements. This is in excellent agreement with the calorimetric enthalpy of formation of NiO reported in the literature.

  8. Phase Equilibria of the Fe-Ni-Sn Ternary System at 270°C

    NASA Astrophysics Data System (ADS)

    Huang, Tzu-Ting; Lin, Shih-Wei; Chen, Chih-Ming; Chen, Pei Yu; Yen, Yee-Wen

    2016-12-01

    The Fe-42 wt.% Ni alloy, also known as a 42 invar alloy (Alloy 42), is used as a lead-frame material because its thermal expansion coefficient is much closer to Si substrate than Cu or Ni substrates. In order to enhance the wettability between the substrate and solder, the Sn layer was commonly electroplated onto the Alloy 42 surface. A clear understanding of the phase equilibria of the Fe-Ni-Sn ternary system is necessary to ensure solder-joint reliability between Sn and Fe-Ni alloys. To determine the isothermal section of the Fe-Ni-Sn ternary system at 270°C, 26 Fe-Ni-Sn alloys with different compositions were prepared. The experimental results confirmed the presence of the Fe3Ni and FeNi phases at 270°C. Meanwhile, it observed that the isothermal section of the Fe-Ni-Sn ternary system was composed of 11 single-phase regions, 19 two-phase regions and nine tie-triangles. Moreover, no ternary compounds were found in the Fe-Ni-Sn system at 270°C.

  9. Size-dependent capacitance of NiO nanoparticles synthesized with cathodic contact glow discharge electrolysis

    NASA Astrophysics Data System (ADS)

    Allagui, Anis; Alami, Abdul Hai; Baranova, Elena A.; Wüthrich, Rolf

    2014-09-01

    NiO nanoparticles of 70, 91 and 107 nm average diameter are synthesized by cathodic contact glow discharge electrolysis at 30, 36 and 42 VDC respectively, in 2 M H2SO4 + 0.5 M ethanol + 2.5 mg ml-1 of PVP, and are investigated for electrochemical energy storage. From the cyclic voltammetry and galvanostatic charge-discharge measurements in 1 M KOH, it was found that a maximum specific capacitance of 218 F g-1 is achieved with the 70 nm NiO nanoparticles at 2.7 A g-1. Larger nanoparticles of 91 and 107 nm diameter exhibit specific capacitances of 106 and 63 F g-1, respectively, suggesting a size-dependent capacitive performance enhanced with decreasing particles size.

  10. Unique and hierarchically structured novel Co3O4/NiO nanosponges with superior photocatalytic activity against organic contaminants

    NASA Astrophysics Data System (ADS)

    Raja, Vahini; Puvaneswaran, Senthil Kumar; Swaminathan, Karuthapandian

    2017-12-01

    In the present study, novel Co3O4/NiO nanosponges designed for the photocatalytic degradation of organic contaminants were synthesized by a simple precipitation technique. The formation of sponge-like nanostructures was clearly evident through the TEM analysis. The photocatalytic efficiency was tested against rhodamine B (RhB) and congo red (CR) dye solutions. Co3O4/NiO nanosponges showed excellent and enhanced photocatalytic efficacy compared to those of Co3O4, NiO nanoparticles, and standards like TiO2 and ZnO. The influence of paramount important operational parameters was explored and the conditions for the best photocatalytic efficiency were optimized. The trapping experiment revealed that the reactive oxygen species (ROS) identified was OH radical. These findings certainly open up a new way for synthesizing a morphology dependent photocatalyst.

  11. Structure and luminescence of nanocrystalline gallium nitride synthesized by a novel polymer pyrolysis route

    NASA Astrophysics Data System (ADS)

    Garcia, Rafael; Hirata, Gustavo A.; Thomas, Alan C.; Ponce, Fernando A.

    2006-10-01

    Thermal decomposition in a horizontal quartz tube reactor of a polymer [-(CH 6N 4O) 3Ga(NO 3) 3-] in a nitrogen atmosphere, yield directly nano-structured gallium nitride (GaN) powder. The polymer was obtained by the reaction between high purity gallium nitrate (Ga(NO 3) 3) dissolved in toluene and carbohydrazide as an azotic ligand. The powder synthesized by this method showed a yellow color and elemental analysis suggested that the color is due to some carbon and oxygen impurities in the as-synthesized powder. Electron microscopy showed that the as-synthesized powders consist of a mixture of various porous particles containing nanowires and nano-sized platelets. The size of the crystallites can be controlled by annealing processes under ammonia. Photoluminescence analysis at 10 K on as-synthesized powders showed a broad red luminescence around 668 nm under UV laser excitation (He-Cd laser, 325 nm). However after annealing process the red luminescence disappears and the typical band edge emission of GaN around 357 nm (3.47 eV) and the UV band were the dominant emissions in the PL spectra.

  12. Influence of temperature on AC conductivity of nanocrystalline CuAlO2

    NASA Astrophysics Data System (ADS)

    Prakash, T.

    2012-07-01

    Nanocrystalline CuAlO2 was synthesized by mechanical alloying of Cu2O and α-Al2O3 powders in the molar ratio of 1:1 for 20 h in toluene medium with tungsten carbide balls and vials using planetary ball mill. The ball milling was carried out at 300 rpm with a ball to powder weight ratio of 10:1 and then annealed at 1373 K in a platinum crucible for 20 h to get CuAlO2 phase with average crystallite size 45 nm. Complex impedance spectroscopic measurement in the frequency region 1 Hz to 10 MHz between the temperatures 333 to 473 K was carried out for nanocrystalline CuAlO2 sample. The obtained complex impedance data was analyzed for AC conductivities, DC and AC conductivities correlations and crossover frequencies ( f co ). The BNN (Barton, Nakajima and Namikawa) relation was applied to understand the correlation between DC and AC conductivities. The observed experimental results were discussed in the paper.

  13. Three-Dimensional Hierarchical Structure ZnO@C@NiO on Carbon Cloth for Asymmetric Supercapacitor with Enhanced Cycle Stability.

    PubMed

    Ouyang, Yu; Xia, Xifeng; Ye, Haitao; Wang, Liang; Jiao, Xinyan; Lei, Wu; Hao, Qingli

    2018-01-31

    In this work, we synthesized the hierarchical ZnO@C@NiO core-shell nanorods arrays (CSNAs) grown on a carbon cloth (CC) conductive substrate by a three-step method involving hydrothermal and chemical bath methods. The morphology and chemical structure of the hybrid nanoarrays were characterized in detail. The combination and formation mechanism was proposed. The conducting carbon layer between ZnO and NiO layers can efficiently enhance the electric conductivity of the integrated electrodes, and also protect the corrosion of ZnO in an alkaline solution. Compared with ZnO@NiO nanorods arrays (NAs), the NiO in CC/ZnO@C@NiO electrodes, which possess a unique multilevel core-shell nanostructure exhibits a higher specific capacity (677 C/g at 1.43 A/g) and an enhanced cycling stability (capacity remain 71% after 5000 cycles), on account of the protection of carbon layer derived from glucose. Additionally, a flexible all-solid-state supercapacitor is readily constructed by coating the PVA/KOH gel electrolyte between the ZnO@C@NiO CSNAs and commercial graphene. The energy density of this all-solid-state device decreases from 35.7 to 16.0 Wh/kg as the power density increases from 380.9 to 2704.2 W/kg with an excellent cycling stability (87.5% of the initial capacitance after 10000 cycles). Thereby, the CC/ ZnO@C@NiO CSNAs of three-dimensional hierarchical structure is promising electrode materials for flexible all-solid-state supercapacitors.

  14. Micro-structural analysis of NiFe2O4 nanoparticles synthesized by thermal plasma route and its suitability for BSA adsorption.

    PubMed

    Bhosale, Shivaji V; Kanhe, Nilesh S; Bhoraskar, Sudha V; Bhat, Suresh K; Bulakhe, Ravindra N; Shim, Jae-Jin; Mathe, Vikas L

    2015-08-01

    The paper presents the experimental studies pertaining to the adsorption of bovine serum albumin (BSA) on the nanoparticles of nickel ferrite (NiFe2O4) with a view of correlating the adsorption properties to their microstructure and zeta potentials. Physical properties of two kinds of nickel ferrites, one synthesized by thermal plasma route and the other by chemical co-precipitation method, are compared. Maximum adsorption (231.57 μg/mg) of BSA onto nickel ferrite nanoparticles, at body temperature (37 °C) was observed at pH-value of 5.58 for the thermal plasma synthesized particles showing its higher adsorption capacity than those synthesized by wet chemical means (178.71 μg/mg). Under the same physical conditions the value of zeta potential, obtained for the former, was higher than that of the latter over a wide range of pH values (3.64-9.66). This is attributed to the differences in the specific surface energies of the two kinds of nanoparticles arising from the degree of crystallinity. The paper presents the experimental evidence for the single crystalline nature of the individual nanoparticles, with mean size of 32 nm, for the thermal plasma synthesized particles as evidenced from the high resolution transmission electron microscopy and electron diffraction analysis. The measurements also reveal the poor crystalline morphology in the chemically prepared particles (mean size of 28 nm) although the X-ray diffraction patterns are not much different. The atomic force microscopy images confirm that the surfaces of plasma synthesized nanoparticles possesses higher surface roughness than that of chemically synthesized one. Presence of adsorbed protein was confirmed by vibrational spectroscopy. The Langmuir adsorption model is found to fit into the experimental data better than the Freundlich adsorption model.

  15. A novel approach to synthesize, studies of structural and electrical characteristic of Bi(Ni0.30Ti0.30Fe0.40)O3 nanoceramics

    NASA Astrophysics Data System (ADS)

    Kumar, Nitin; Shukla, Alok

    2018-03-01

    In this study, we report a novel approach to synthesize the Bi(Ni0.30Ti0.30Fe0.40)O3 [arbitration BNTF30/40] nanoceramics by standard ceramic method at an ambient temperature of 1013 K. Carbonates and oxides powder were utilised as a raw materials in an appropriate stoichiometric amounts. X-ray diffraction pattern assigned that the BNTF30/40 sample presents a single phase of orthorhombic symmetry. The crystallite size obtain from X-ray data suggests the formation of BNTF30/40 nanoceramics in the range between 20 to 45 nm. Bulk density of the prepared pallets were measured and found to be more than 94 percent. The basic characterization tools have been used respectively with Field Emission Scanning Electron Microscope and Spectroscopy based techniques to obtain the correlation between surface morphology and electrical characteristic of specimen sample. Electrical characteristic of the as- synthesized material was studied in the experimental temperature range between RT to 623 K at different operated frequency (25 kHz - 500 kHz).

  16. Superparamagnetic nanocrystalline ZnFe2O4 with a very high Curie temperature.

    PubMed

    Deka, Sasanka; Joy, P A

    2008-08-01

    Studies on the magnetic properties of nanocrystalline ZnFe2O4 synthesized by an autocombustion method are reported. Superparamagnetic behavior is observed for the nanocrystalline materials with particle sizes of 8 nm and 17 nm, with superparamagnetic blocking temperatures of 65 K and 75 K, respectively. Magnetic hysteresis with very large coercivities of 533 Oe and 325 Oe, respectively, are observed at 12 K. Studies on the temperature variation of the magnetization above room temperature indicate that the Curie temperature is as high as approximately 800 K when compared to the paramagnetic nature of bulk zinc ferrite at room temperature.

  17. Mesoporous NiCo2O4 nano-needles supported by 3D interconnected carbon network on Ni foam for electrochemical energy storage

    NASA Astrophysics Data System (ADS)

    Lu, Congxiang; Liu, Wen-wen; Pan, Hui; Tay, Beng Kang; Wang, Xingli; Liang, Kun; Wei, Xuezhe

    2018-05-01

    In this work, a three dimensional (3D) interconnected carbon network consisting of ultrathin graphite (UG) and carbon nanotubes (CNTs) on Ni foam is fabricated and employed as a novel type of substrate for mesoporous NiCo2O4 nano-needles. The successfully synthesized NiCo2O4 nano-needles/CNTs/UG on Ni foam has many advantages including facile electrolyte access and direct conducting pathways towards current collectors, which enable it to be a promising electrode material in battery-like electrochemical energy storage. Encouragingly, a high capacity of 135.1 mAh/g at the current density of 1 A/g, superior rate performance and also stable cycling for 1200 cycles at the current density of 5 A/g have been demonstrated in this novel material.

  18. Magnetic behavior of the nanophase of YbNi2 alloys

    NASA Astrophysics Data System (ADS)

    Ivanshin, V. A.; Gataullin, E. M.; Sukhanov, A. A.; Ivanshin, N. A.; Rojas, D. P.; Fernández Barquín, L.

    2017-04-01

    Variations in magnetic properties of the heavy-fermion YbNi2 alloy when milled in a high energy ball milling system have been investigated. The ferromagnetic transition ( T C = 10.4 K) in the initial sample almost vanishes after milling, which leads to the appearance of a magnetic transition at T* = 3.2 K in nanocrystallites. Before milling, processes of spin-lattice relaxation of the Orbach-Aminov type with the participation of the first excited Stark sublevel of the Yb3+ ion located at 75 K are dominating in the electron spin dynamics in the paramagnetic phase of the alloy. A comparative study of the temperature dependence of the magnetic properties and spectra of electron paramagnetic resonance in poly- and nanocrystalline samples indicates the existence of a magnetic inhomogeneity of the compound arising upon milling.

  19. Nanocrystalline ceramic materials

    DOEpatents

    Siegel, Richard W.; Nieman, G. William; Weertman, Julia R.

    1994-01-01

    A method for preparing a treated nanocrystalline metallic material. The method of preparation includes providing a starting nanocrystalline metallic material with a grain size less than about 35 nm, compacting the starting nanocrystalline metallic material in an inert atmosphere and annealing the compacted metallic material at a temperature less than about one-half the melting point of the metallic material.

  20. Ultrahigh hardness and high electrical resistivity in nano-twinned, nanocrystalline high-entropy alloy films

    NASA Astrophysics Data System (ADS)

    Huo, Wenyi; Liu, Xiaodong; Tan, Shuyong; Fang, Feng; Xie, Zonghan; Shang, Jianku; Jiang, Jianqing

    2018-05-01

    Nano-twinned, nanocrystalline CoCrFeNi high-entropy alloy films were produced by magnetron sputtering. The films exhibit a high hardness of 8.5 GPa, the elastic modulus of 161.9 GPa and the resistivity as high as 135.1 μΩ·cm. The outstanding mechanical properties were found to result from the resistance of deformation created by nanocrystalline grains and nano-twins, while the electrical resistivity was attributed to the strong blockage effect induced by grain boundaries and lattice distortions. The results lay a solid foundation for the development of advanced films with structural and functional properties combined in micro-/nano-electronic devices.

  1. DOE Office of Scientific and Technical Information (OSTI.GOV)

    Phumying, Santi; Labuayai, Sarawuth; Swatsitang, Ekaphan

    Graphical abstract: This figure shows the specific magnetization curves of the as-prepared MFe{sub 2}O{sub 4} (M = Ni, Co, Mn, Mg, Zn) powders obtained from room temperature VSM measurement. These curves are typical for a soft magnetic material and indicate hysteresis ferromagnetism in the field ranges of ±500 Oe, ±1000 Oe, and ±2000 Oe for the CoFe{sub 2}O{sub 4}, MgFe{sub 2}O{sub 4} and MnFe{sub 2}O{sub 4} respectively, whereas the samples of NiFe{sub 2}O{sub 4} and ZnFe{sub 2}O{sub 4} show a superparamagnetic behavior. Highlights: ► Nanocrystalline MFe{sub 2}O{sub 4} powders were synthesized by a novel hydrothermal method. ► Metal acetylacetonates andmore » aloe vera plant-extracted solution are used. ► This biosynthetic route is very simple and provides high-yield oxide nanomaterials. ► XRD and TEM results indicate that the prepared samples have only spinel structure. ► The maximum M{sub s} of 68.9 emu/g at 10 kOe were observed for the samples of MnFe{sub 2}O{sub 4}. - Abstract: Nanocrystalline spinel ferrite MFe{sub 2}O{sub 4} (M = Ni, Co, Mn, Mg, Zn) powders were synthesized by a novel hydrothermal method using Fe(acac){sub 3}, M(acac){sub 3} (M = Ni, Co, Mn, Mg, Zn) and aloe vera plant extracted solution. The X-ray diffraction and selected-area electron diffraction results indicate that the synthesized nanocrystalline have only spinel structure without the presence of other phase impurities. The crystal structure and morphology of the spinel ferrite powders, as revealed by TEM, show that the NiFe{sub 2}O{sub 4} and CoFe{sub 2}O{sub 4} samples contain nanoparticles, whereas the MnFe{sub 2}O{sub 4} and MgFe{sub 2}O{sub 4} samples consist of many nanoplatelets and nanoparticles. Interestingly, the ZnFe{sub 2}O{sub 4} sample contains plate-like structure of networked nanocrystalline particles. Room temperature magnetization results show a ferromagnetic behavior of the CoFe{sub 2}O{sub 4}, MnFe{sub 2}O{sub 4} and MgFe{sub 2}O{sub 4} samples

  2. Insights into the deformation behavior of the CrMnFeCoNi high-entropy alloy revealed by elevated temperature nanoindentation

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Maier-Kiener, Verena; Schuh, Benjamin; George, Easo P.

    A CrMnFeCoNi high-entropy alloy was investigated by nanoindentation from room temperature to 400 °C in the nanocrystalline state and cast plus homogenized coarse-grained state. In the latter case a < 100 >-orientated grain was selected by electron back scatter diffraction for nanoindentation. It was found that hardness decreases more strongly with increasing temperature than Young’s modulus, especially for the coarse-grained state. The modulus of the nanocrystalline state was slightly higher than that of the coarse-grained one. For the coarse-grained sample a strong thermally activated deformation behavior was found up to 100–150 °C, followed by a diminishing thermally activated contribution atmore » higher testing temperatures. For the nanocrystalline state, different temperature dependent deformation mechanisms are proposed. At low temperatures, the governing processes appear to be similar to those in the coarse-grained sample, but with increasing temperature, dislocation-grain boundary interactions likely become more dominant. Finally, at 400 °C, decomposition of the nanocrystalline alloy causes a further reduction in thermal activation. Furthermore, this is rationalized by a reduction of the deformation controlling internal length scale by precipitate formation in conjunction with a diffusional contribution.« less

  3. Cross-sectional transmission electron microscopic study of irradiation induced nano-crystallization of nickel in a W/Ni multilayer.

    PubMed

    Bagchi, Sharmistha; Lalla, N P

    2008-06-11

    The present study reports the cross-sectional transmission electron microscopic investigations of swift heavy ion-irradiation induced nano-size recrystallization of Ni in a nearly immiscible W/Ni multilayer structure. Multilayer structures (MLS) of [W(25 Å)/Ni(25 Å)](10BL) were grown on Si-(100) substrate by the ion-beam sputtering technique. The as-synthesized MLS were subjected to 120 MeV-Au(9+) ion-irradiation to a fluence of ∼5 × 10(13) ions cm(-2). Wide-angle x-ray diffraction studies of pristine as well as irradiated W/Ni multilayers show deterioration of the superlattice structure, whereas x-ray reflectivity (XRR) measurement reveals a nearly unaffected microstructure after irradiation. Analysis of the XRR data using 'Parratt's formalism' does show a significant increase of W/Ni interface roughness. Cross-sectional transmission electron microscopy (TEM) studies carried out in diffraction and imaging modes (including bright-field and dark-field imaging), show that at high irradiation dose the intralayer microstructure of Ni becomes nano-crystalline (1-2 nm). During these irradiation induced changes of the intralayer microstructure, the interlayer definition of the W and Ni layers still remains intact. The observed nano-recrystallization of Ni has been attributed to competition between low miscibility of the W/Ni interface and the ion-beam induced mixing kinetics.

  4. Capacity improvement by deficit of transition metals in inverse spinel LiNi1/3Co1/3Mn1/3VO4 cathodes

    NASA Astrophysics Data System (ADS)

    Kitajou, Ayuko; Yoshida, Jun; Nakanishi, Shinji; Matsuda, Yasuaki; Kanno, Ryoji; Okajima, Toshihiro; Okada, Shigeto

    2016-01-01

    Although inverse spinel materials have attracted attention because of their unusually high voltage characteristics, their rechargeable capacities are generally less than 50 mAh g-1, as a result of the coexistence of Li and transition metal ions at 16d octahedral sites. This work attempted to improve cathode functioning by optimizing the quantities of Li and transition metal ions residing at the 16d sites of LiNi1/3Co1/3Mn1/3VO4. The rechargeable capacity of the LiNi0.28Co0.28Mn0.26V0.80O4 synthesized in the present study was found to be above 120 mAh g-1, representing the largest capacity reported to date for an inverse spinel material. The results of in-situ XANES analysis demonstrated that the charge-discharge reactions of LiNi1/3Co1/3Mn1/3VO4 corresponds to the Mn2+/Mn4+ and Co2+/Co3+ redox couples, mainly.

  5. Nanocrystalline ceramic materials

    DOEpatents

    Siegel, R.W.; Nieman, G.W.; Weertman, J.R.

    1994-06-14

    A method is disclosed for preparing a treated nanocrystalline metallic material. The method of preparation includes providing a starting nanocrystalline metallic material with a grain size less than about 35 nm, compacting the starting nanocrystalline metallic material in an inert atmosphere and annealing the compacted metallic material at a temperature less than about one-half the melting point of the metallic material. 19 figs.

  6. Thermodynamic characterization of Ni3TeO6, Ni2Te3O8 and NiTe2O5

    NASA Astrophysics Data System (ADS)

    Dawar, Rimpi; Babu, R.; Ananthasivan, K.; Anthonysamy, S.

    2017-09-01

    Measurement of vapour pressure of TeO2(g) over the biphasic mixture Ni3TeO6 (s) + NiO(s) in the temperature range 1143-1272 K was carried out using transpiration-thermogravimetric technique (TTG). Gibbs energy of formation of Ni3TeO6 was obtained from the temperature dependence of vapour pressure of TeO2 (g) generated by the incongruent vapourisation reaction, Ni3TeO6 (s) → NiO(s) + TeO2 (g) + 1/2 O2 in the temperature range 1143-1272 K. An isoperibol type drop calorimeter was used to measure the enthalpy increments of Ni3TeO6, Ni2Te3O8 and NiTe2O5. Thermodynamic functions viz., heat capacity, entropy and Gibbs energy functions of these compounds were derived from the experimentally measured enthalpy increment values. Third-law analysis was carried out to ascertain absence of temperature dependent systematic errors in the measurement of vapour pressure of TeO2 (g). A value of -1265.1 ± 1.5 kJ mol-1 was obtained for Δ Hf,298K o (Ni3TeO6) using third-law analysis.

  7. Basic molten salt process-A new route for synthesis of nanocrystalline Li 4Ti 5O 12-TiO 2 anode material for Li-ion batteries using eutectic mixture of LiNO 3-LiOH-Li 2O 2

    NASA Astrophysics Data System (ADS)

    Rahman, M. M.; Wang, Jia-Zhao; Hassan, Mohd Faiz; Chou, Shulei; Wexler, David; Liu, Hua-Kun

    A nanocrystalline Li 4Ti 5O 12-TiO 2 duplex phase has been synthesized by a simple basic molten salt process (BMSP) using an eutectic mixture of LiNO 3-LiOH-Li 2O 2 at 400-500 °C. The microstructure and morphology of the Li 4Ti 5O 12-TiO 2 product are characterized by means of X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), and transmission electron microscopy (TEM). The sample prepared by heat-treating at 300 °C for 3 h (S-1) reveals dense agglomerates of ultra-fine nanocrystalline Li 4Ti 5O 12; with heat treatment at 400 °C for 3 h (S-2), there is a duplex crystallite size (fine < 10 nm, and coarse > 20 nm) of Li 4Ti 5O 12-TiO 2; at 500 °C for 3 h (S-3), a much coarser and less-dense distribution of lithium titanate (crystallite size ∼15-30 nm) is observed. According to the results of electrochemical testing, the S-2 sample shows initial discharge capacities of 193 mAh g -1 at 0.2 C, 168 mAh g -1 at 0.5 C, 146 mAh g -1 at 1 C, 135 mAh g -1 at 2 C, and 117 mAh g -1 at 5 C. After 100 cycles, the discharge capacity is 138 mAh g -1 at 1 C with a capacity retention of 95%. The S-2 sample yields the best electrochemical performance in terms of charge-discharge capacity and rate capability compared with other samples. Its superior electrochemical performance can be mainly attributed to the duplex crystallite structure, composed of fine (<10 nm) and coarse (>20) nm nanoparticles, where lithium ions can be stored within the grain boundary interfaces between the spinel Li 4Ti 5O 12 and the anatase TiO 2.

  8. The impact of NiO on microstructure and electrical property of solid oxide fuel cell anode

    PubMed Central

    Li, Yan; Luo, Zhong-yang; Yu, Chun-jiang; Luo, Dan; Xu, Zhu-an; Cen, Ke-fa

    2005-01-01

    Ni-Ce0.8Sm0.2O1.9 (Ni-SDC) cermet was selected as anode material for reduced temperature (800 °C) solid oxide fuel cells in this study. The influence of NiO powder fabrication methods for Ni-SDC cermets on the electrode performance was investigated so that the result obtained can be applied to make high-quality anode. Three kinds of NiO powder were synthesized with a fourth kind being available in the market. Four types of anode precursors were fabricated with these NiO powders and Ce0.8Sm0.2O1.9 (SDC), and then were reduced to anode wafers for sequencing measurement. The electrical conductivity of the anodes was measured and the effect of microstructure was investigated. It was found that the anode electrical conductivity depends strongly on the NiO powder morphologies, microstructure of the cermet anode and particle sizes, which are decided by NiO powder preparation technique. The highest electrical conductivity is obtained for anode cermets with NiO powder synthesized by NiCO3·2Ni(OH)2·4H2O or Ni(NO3)2·6H2O decomposition technique. PMID:16252348

  9. Study on immobilization of yeast alcohol dehydrogenase on nanocrystalline Ni-Co ferrites as magnetic support.

    PubMed

    Shakir, Mohammad; Nasir, Zeba; Khan, Mohd Shoeb; Lutfullah; Alam, Md Fazle; Younus, Hina; Al-Resayes, Saud Ibrahim

    2015-01-01

    The covalent binding of yeast alcohol dehydrogenase (YADH) enzyme complex in a series of magnetic crystalline Ni-Co nanoferrites, synthesized via sol-gel auto combustion technique was investigated. The structural analysis, morphology and magnetic properties of Ni-Co nanoferrites were determined by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), vibrating-sample magnetometer (VSM), high resolution transmission electron microscopy (HRTEM) and Fourier transform infrared spectroscopy (FTIR). The comparative analysis of the HRTEM micrographs of bare magnetic nanoferrite particles and particles immobilized with enzyme revealed an uniform distribution of the particles in both the cases without undergoing change in the size which was found to be in the range 20-30 nm. The binding of YADH to Ni-Co nanoferrites and the possible binding mechanism have been suggested by comparing the FTIR results. The binding properties of the immobilized YADH enzyme were also studied by kinetic parameters, optimum operational pH, temperature, thermal stability and reusability. The immobilized YADH exhibits enhanced thermal stability as compared to the free enzyme over a wide range of temperature and pH, and showed good durability after recovery by magnetic separation for repeated use. Copyright © 2014 Elsevier B.V. All rights reserved.

  10. Superplastic Deformation Mechanisms of Superfine/Nanocrystalline Duplex PM-TiAl-Based Alloy

    PubMed Central

    Gong, Xuebo; Duan, Zhenxin; Pei, Wen; Chen, Hua

    2017-01-01

    In this paper, the equiaxed superfine/nanocrystalline duplex PM-TiAl-based alloy with (γ + α2) microstructure, Ti-45Al-5Nb (at %), has been synthesized by high-energy ball milling and vacuum hot pressing sintering. Superplastic deformation behavior has been investigated at 1000 °C and 1050 °C with strain rates from 5 × 10−5 s−1 to 1 × 10−3 s−1. The effects of deformation on the microstructure and mechanical behaviors of high Nb containing TiAl alloy have been characterized and analyzed. The results showed that, the ultimate tensile strength of the alloy was 58.7 MPa at 1000 °C and 10.5 MPa at 1050 °C with a strain rate of 5 × 10−5 s−1, while the elongation was 121% and 233%, respectively. The alloy exhibited superplastic elongation at 1000 and 1050 °C with an exponent (m) of 0.48 and 0.45. The main softening mechanism was dynamic recrystallization of γ grains; the dislocation slip and γ/γ interface twinning were responsible for superplastic deformation. The orientation relationship of γ/γ interface twinning obeyed the classical one: (001)γ//(110)γ. PMID:28925971

  11. High-performance transition metal-doped Pt 3Ni octahedra for oxygen reduction reaction

    DOE PAGES

    Huang, Xiaoqing; Zhao, Zipeng; Cao, Liang; ...

    2015-06-11

    Bimetallic platinum-nickel (Pt-Ni) nanostructures represent an emerging class of electrocatalysts for oxygen reduction reaction (ORR) in fuel cells, but practical applications have been limited by catalytic activity and durability. We surface-doped Pt 3Ni octahedra supported on carbon with transition metals, termed M-Pt 3Ni/C, where M is vanadium, chromium, manganese, iron, cobalt, molybdenum (Mo), tungsten, or rhenium. The Mo-Pt 3Ni/C showed the best ORR performance, with a specific activity of 10.3 mA/cm2 and mass activity of 6.98 A/mgPt, which are 81- and 73-fold enhancements compared with the commercial Pt/C catalyst (0.127 mA/cm 2 and 0.096 A/mg Pt). In conclusion, theoretical calculationsmore » suggest that Mo prefers subsurface positions near the particle edges in vacuum and surface vertex/edge sites in oxidizing conditions, where it enhances both the performance and the stability of the Pt3Ni catalyst.« less

  12. Cyanide bridged hetero-metallic polymeric complexes: Syntheses, vibrational spectra, thermal analyses and crystal structures of complexes [M(1,2-dmi)2Ni(μ-CN)4]n (M = Zn(II) and Cd(II))

    NASA Astrophysics Data System (ADS)

    Kürkçüoğlu, Güneş Süheyla; Sayın, Elvan; Şahin, Onur

    2015-12-01

    Two cyanide bridged hetero-metallic complexes of general formula, [M(1,2-dmi)2Ni(μ-CN)4]n (1,2-dmi = 1,2-dimethylimidazole and M = Zn(II) or Cd(II)) have been synthesized and characterized by vibrational (FT-IR and Raman) spectroscopy, single crystal X-ray diffraction, thermal analyses and elemental analyses. The crystallographic analyses reveal that the complexes, [Zn(1,2-dmi)2Ni(μ-CN)4] (1) and [Cd(1,2-dmi)2Ni(μ-CN)4] (2), have polymeric 2D networks. In the complexes, four cyanide groups of [Ni(CN)4]2- coordinated to the adjacent M(II) ions and distorted octahedral geometries of complexes are completed by two nitrogen atoms of trans 1,2-dmi ligands. The structures of 1 and 2 are similar and linked via intermolecular hydrogen bonding, C-H⋯Ni interactions to give rise to 3D networks. Vibration assignments are given for all the observed bands and the spectral features also supported to the crystal structures of heteronuclear complexes. The FT-IR and Raman spectra of the complexes are very much consistent with the structural data presented.

  13. YBa2Cu3O7 thin films on nanocrystalline diamond films for HTSC bolometer

    NASA Technical Reports Server (NTRS)

    Cui, G.; Beetz, C. P., Jr.; Boerstler, R.; Steinbeck, J.

    1993-01-01

    Superconducting YBa2Cu3O(7-x) films on nanocrystalline diamond thin films have been fabricated. A composite buffer layer system consisting of diamond/Si3N4/YSZ/YBCO was explored for this purpose. The as-deposited YBCO films were superconducting with Tc of about 84 K and a relatively narrow transition width of about 8 K. SEM cross sections of the films showed very sharp interfaces between diamond/Si3N4 and between Si3N4/YSZ. The deposited YBCO film had a surface roughness of about 1000 A, which is suitable for high-temperature superconductive (HTSC) bolometer fabrication. It was also found that preannealing of the nanocrystalline diamond thin films at high temperature was very important for obtaining high-quality YBCO films.

  14. Rationally-designed configuration of directly-coated Ni 3S 2/Ni electrode by RGO providing superior sodium storage

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Song, Xiaosheng; Li, Xifei; Bai, Zhimin

    Designing nanocomposite materials is an effective approach for enhancing the performance of sodium-ion batteries (SIBs), and understanding the synergy among components is critically important for new, better materials design. Here in this paper, a directly reduced graphene oxide (RGO) decorated anode electrode was designed and tested for SIBs, in which uniform RGO coating onto the Ni 3S 2/Ni electrode was realized using facile hydrothermal reactions. The results indicate that the RGO/Ni 3S 2/Ni electrode delivers a high reversible specific capacity of 448.6 mAh g -1, high capacity retention of 96.5% after 100 cycles, and excellent rate capability of 263.1 mAhmore » g -1 at 800 mA g -1. Compared with the Ni 3S 2/Ni electrode, the improved performance of the RGO/Ni 3S 2/Ni electrode benefits from RGO-promoted displacement reaction of Ni 3S 2 with sodium. DFT calculations reveal that the RGO layer can significantly improve the electron mobility of the RGO/Ni 3S 2 + Na structure, and the hybrid interaction between the extraneous p orbits of C and indigenous p and d orbits of Ni, as well as p orbits of S is the major reason for why RGO can improve the electrical transport properties.« less

  15. Rationally-designed configuration of directly-coated Ni 3S 2/Ni electrode by RGO providing superior sodium storage

    DOE PAGES

    Song, Xiaosheng; Li, Xifei; Bai, Zhimin; ...

    2018-02-28

    Designing nanocomposite materials is an effective approach for enhancing the performance of sodium-ion batteries (SIBs), and understanding the synergy among components is critically important for new, better materials design. Here in this paper, a directly reduced graphene oxide (RGO) decorated anode electrode was designed and tested for SIBs, in which uniform RGO coating onto the Ni 3S 2/Ni electrode was realized using facile hydrothermal reactions. The results indicate that the RGO/Ni 3S 2/Ni electrode delivers a high reversible specific capacity of 448.6 mAh g -1, high capacity retention of 96.5% after 100 cycles, and excellent rate capability of 263.1 mAhmore » g -1 at 800 mA g -1. Compared with the Ni 3S 2/Ni electrode, the improved performance of the RGO/Ni 3S 2/Ni electrode benefits from RGO-promoted displacement reaction of Ni 3S 2 with sodium. DFT calculations reveal that the RGO layer can significantly improve the electron mobility of the RGO/Ni 3S 2 + Na structure, and the hybrid interaction between the extraneous p orbits of C and indigenous p and d orbits of Ni, as well as p orbits of S is the major reason for why RGO can improve the electrical transport properties.« less

  16. Nanocrystalline high-entropy alloy (CoCrFeNiAl 0.3 ) thin-film coating by magnetron sputtering

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Liao, Weibing; Lan, Si; Gao, Libo

    High-entropy CoCrFeNiAl0.3 alloy thin films were prepared by magnetron sputtering technique. The thin film surface was very smooth and homogeneous. The synchrotron X-ray experiment confirmed that (111) type of texture existed in the thin film, and the structure was face-centered cubic nanocrystals with a minor content of ordered NiAl-type body-centered cubic structures. Interestingly, the elastic modulus of the thin film was nearly the same to the bulk single-crystal counterpart, however, the nanohardness is about four times of the bulk single-crystal counterpart. It was found that the high hardness was due to the formation of nanocrystal structure inside the thin filmsmore » and the preferred growth orientation, which could be promising for applications in micro fabrication and advanced coating technologies.« less

  17. Synthesis and magnetostrictive properties of Pr(Fe1.95B0.05)1.93 bulk nanocrystalline alloy

    NASA Astrophysics Data System (ADS)

    Shi, Y. G.; Hu, C. C.; Fan, J. Y.; Shi, D. N.; Lv, L. Y.; Tang, S. L.

    2012-11-01

    The structure, magnetic properties, and magnetostriction of Pr(Fe1.95B0.05)1.93 alloys prepared by annealing its precursor amorphous ribbons under high pressure were investigated. It was found that Pr(Fe1.95B0.05)1.93 single cubic Laves phase could be obtained only when the pressure is up to 3 GPa. The average grain size about 20 nm is found in the sample synthesized under 6 GPa. A large linear magnetostriction of 541 ppm at 3 kOe is observed in the Pr(Fe1.95B0.05)1.93 compound synthesized under 6 GPa, which is 25% larger than that under 3 GPa. The present work offers an effective method to obtain bulk nanocrystalline magnetostrictive compounds.

  18. Effect of surface properties of NiFe2O4 nanoparticles synthesized by dc thermal plasma route on antimicrobial activity

    NASA Astrophysics Data System (ADS)

    Bhosale, S. V.; Ekambe, P. S.; Bhoraskar, S. V.; Mathe, V. L.

    2018-05-01

    The present work reports the role of surface properties of NiFe2O4 nanoparticles on the antimicrobial activity. The NiFe2O4 nanoparticles were synthesized by gas phase condensation and chemical co-precipitation route. These nanoparticles were extensively investigated using X-ray diffraction, transmission electron microscopy, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy and electro-kinetic property measurements. The HRTEM was used to analyze surface morphology of nickel ferrite nanoparticles obtained by two different routes. Electro-kinetic properties of the nanoparticles under investigation were recorded, analyzed and correlated with the antimicrobial properties. It was observed that nickel ferrite nanoparticles synthesized by thermal plasma route (NFOTP) formed highly stable colloidal solution as compared to chemically synthesized (NFOCP), as the later tends to agglomerate due to low surface charge. The antimicrobial activity of NiFe2O4 nanoparticles were investigated on two Gram positive bacteria Staphylococcus aureus and Streptococcus pyogenes, two Gram negative bacteria Escherichia coli and Salmonella typhimurium and one fungal species Candida albicans. It was noted that the surface properties of NiFe2O4 particles have revealing effect on the antimicrobial activity. The NFOTP nanoparticles showed significant activity for gram negative E. coli bacteria however no activity was observed for other bacteria's and fungi under study. Moreover NFOCP particles did not show any significant activity for both bacteria's and fungi. Further, antimicrobial activity of nickel ferrite nanoparticles were studied even for different concentration to obtain the minimum inhibition concentration (MIC).

  19. Hydrogen Storage Performances of REMg11Ni (RE = Sm, Y) Alloys Prepared by Mechanical Milling

    NASA Astrophysics Data System (ADS)

    Zhang, Yanghuan; Cui, Songsong; Yuan, Zeming; Gao, Jinliang; Dong, Xiaoping; Qi, Yan; Guo, Shihai

    2018-01-01

    This study adopted mechanical milling to prepare Mg-based REMg11Ni (RE = Sm, Y) hydrogen storage alloys. The alloy structures were examined by X-ray diffraction and transmission electron microscopy. The isothermal hydrogenation thermodynamics and kinetics were determined by an automatic Sievert apparatus. The non-isothermal dehydrogenation performance of the alloys was tested by differential scanning calorimetry and thermogravimetry at different heating rates. The results showed a nanocrystalline and amorphous tendency for the alloys. The YMg11Ni alloy exhibited a larger hydrogen absorption capacity, faster hydriding rate, and lower temperature of onset hydrogen desorption than the SmMg11Ni alloy. The hydrogen desorption temperatures of the REMg11Ni (RE = Sm, Y) alloys were 557.6 K and 549.8 K (284.6 °C and 276.8 °C), respectively. The hydrogen desorption property of the RE = Y alloy was found superior to the RE = Sm alloy based on the time required to absorb 3 wt pct H2, i.e., the time needed by the RE = Y alloy was reduced to 1106, 456, 363, and 180 s, respectively, corresponding to the hydrogen desorption temperatures of 593 K, 613 K, 633 K, and 653 K (320 °C, 340 °C, 360 °C, and 380 °C), compared to 1488, 574, 390, and 192 s for the RE = Sm alloy under identical conditions. The dehydrogenation activation energies were 100.31 and 98.01 kJ/mol for the REMg11Ni (RE = Sm, Y) alloys, respectively, which agreed with those of the RE = Y alloy showing a superior hydrogen desorption property.

  20. Synthesis of MFe3S4 clusters containing a planar M(II) site (M = Ni, Pd, Pt), a structural element in the C-cluster of carbon monoxide dehydrogenase.

    PubMed

    Panda, Rashmishree; Berlinguette, Curtis P; Zhang, Yugen; Holm, Richard H

    2005-08-10

    Synthesis of an analogue of the C-cluster of C. hydrogenoformans carbon monoxide dehydrogenase requires formation of a planar Ni(II) site and attachment of an exo iron atom in the core unit NiFe(4)S(5). The first objective has been achieved by two reactions: (i) displacement of Ph(3)P or Bu(t)()NC at tetrahedral Ni(II) sites of cubane-type [NiFe(3)S(4)](+) clusters with chelating diphosphines, and (ii) metal atom incorporation into a cuboidal [Fe(3)S(4)](0) cluster with a M(0) reactant in the presence of bis(1,2-dimethylphosphino)ethane (dmpe). The isolated product clusters [(dmpe)MFe(3)S(4)(LS(3))](2-) (M = Ni(II) (9), Pd(II) (12), Pt(II) (13); LS(3) = 1,3,5-tris((4,6-dimethyl-3-mercaptophenyl)thio)-2,4,6-tris(p-tolylthio)benzene(3-)) contain the cores [MFe(3)(mu(2)-S)(mu(3)-S)(3)](+) having planar M(II)P(2)S(2) sites and variable nonbonding M...S distances of 2.6-3.4 A. Reaction (i) involves a tetrahedral --> planar Ni(II) structural change between isomeric cubane and cubanoid [NiFe(3)S(4)](+) cores. Based on the magnetic properties of 12 and earlier considerations, the S = (5)/(2) ground state of the cubanoid cluster arises from the [Fe(3)S(4)](-) fragment, whereas the S = (3)/(2) ground state of the cubane cluster is a consequence of antiferromagnetic coupling between the spins of Ni(2+) (S = 1) and [Fe(3)S(4)](-). Other substitution reactions of [NiFe(3)S(4)](+) clusters and 1:3 site-differentiated [Fe(4)S(4)](2+) clusters are described, as are the structures of 12, 13, [(Me(3)P)NiFe(3)S(4)(LS(3))](2-), and [Fe(4)S(4)(LS(3))L'](2-) (L' = Me(2)NC(2)H(4)S(-), Ph(2)P(O)C(2)H(4)S(-)). This work significantly expands our initial report of cluster 9 (Panda et al. J. Am. Chem. Soc. 2004, 126, 6448-6459) and further demonstrates that a planar M(II) site can be stabilized within a cubanoid [NiFe(3)S(4)](+) core.

  1. Electrodeposition of Nanocrystalline Co-P Coatings as a Hard Chrome Alternative

    DTIC Science & Technology

    2009-09-02

    Electrodeposition  of Nanocrystalline Co‐P  Coatings as a Hard Chrome Alternative Report Documentation Page Form ApprovedOMB No. 0704-0188 Public reporting burden...AND SUBTITLE Electrodeposition of Nanocrystalline Co‐P Coatings as a Hard Chrome Alternative 5a. CONTRACT NUMBER 5b. GRANT NUMBER 5c...Defense Conference – 2 September 2009 Conventional  Electrodeposits Polycrystalline (10‐100 µm) Electrodeposited Nanocrystalline Materials Pulsed

  2. Ni nanoparticles@Ni-Mo nitride nanorod arrays: a novel 3D-network hierarchical structure for high areal capacitance hybrid supercapacitors.

    PubMed

    Ruan, Yunjun; Lv, Lin; Li, Zhishan; Wang, Chundong; Jiang, Jianjun

    2017-11-23

    Because of the advanced nature of their high power density, fast charge/discharge time, excellent cycling stability, and safety, supercapacitors have attracted intensive attention for large-scale applications. Nevertheless, one of the obstacles for their further development is their low energy density caused by sluggish redox reaction kinetics, low electroactive electrode materials, and/or high internal resistance. Here, we develop a facile and simple nitridation process to successfully synthesize hierarchical Ni nanoparticle decorated Ni 0.2 Mo 0.8 N nanorod arrays on a nickel foam (Ni-Mo-N NRA/NF) from its NiMoO 4 precursor, which delivers a high areal capacity of 2446 mC cm -2 at a current density of 2 mA cm -2 and shows outstanding cycling stability. The superior performance of the Ni-Mo-N NRA/NF can be ascribed to the metallic conductive nature of the Ni-Mo nitride, the fast surface redox reactions for the electrolyte ions and electrode materials, and the low contacted resistance between the active materials and the current collectors. Furthermore, a hybrid supercapacitor (HSC) is assembled using the Ni-Mo-N NRA/NF as the positive electrode and reduced graphene oxide (RGO) as the negative electrode. The optimized HSC exhibits excellent electrochemical performance with a high energy density of 40.9 W h kg -1 at a power density of 773 W kg -1 and a retention of 80.1% specific capacitance after 6000 cycles. These results indicate that the Ni-Mo-N NRA/NF have a promising potential for use in high-performance supercapacitors.

  3. New twinning route in face-centered cubic nanocrystalline metals.

    PubMed

    Wang, Lihua; Guan, Pengfei; Teng, Jiao; Liu, Pan; Chen, Dengke; Xie, Weiyu; Kong, Deli; Zhang, Shengbai; Zhu, Ting; Zhang, Ze; Ma, Evan; Chen, Mingwei; Han, Xiaodong

    2017-12-15

    Twin nucleation in a face-centered cubic crystal is believed to be accomplished through the formation of twinning partial dislocations on consecutive atomic planes. Twinning should thus be highly unfavorable in face-centered cubic metals with high twin-fault energy barriers, such as Al, Ni, and Pt, but instead is often observed. Here, we report an in situ atomic-scale observation of twin nucleation in nanocrystalline Pt. Unlike the classical twinning route, deformation twinning initiated through the formation of two stacking faults separated by a single atomic layer, and proceeded with the emission of a partial dislocation in between these two stacking faults. Through this route, a three-layer twin was nucleated without a mandatory layer-by-layer twinning process. This route is facilitated by grain boundaries, abundant in nanocrystalline metals, that promote the nucleation of separated but closely spaced partial dislocations, thus enabling an effective bypassing of the high twin-fault energy barrier.

  4. Electron beam induced green luminescence and degradation study of CaS:Ce nanocrystalline phosphors for FED applications

    NASA Astrophysics Data System (ADS)

    Kumar, Vinay; Mishra, Varun; Biggs, M. M.; Nagpure, I. M.; Ntwaeaborwa, O. M.; Terblans, J. J.; Swart, H. C.

    2010-01-01

    Green luminescence and degradation of Ce 3+ doped CaS nanocrystalline phosphors were studied with a 2 keV, 10 μA electron beam in an O 2 environment. The nanophosphors were synthesized by the co-precipitation method. The samples were characterized using X-ray diffraction, Transmission electron microscopy, Scanning electron microscopy/electron dispersive X-ray spectroscopy and Photoluminescence (PL) spectroscopy. Cubic CaS with an average particle size of 42 ± 2 nm was obtained. PL emission was observed at 507 nm and a shoulder at 560 nm with an excitation wavelength of 460 nm. Auger electron spectroscopy and Cathodoluminescence (CL) were used to monitor the changes in the surface composition of the CaS:Ce 3+ nanocrystalline phosphors during electron bombardment in an O 2 environment. The effect of different oxygen pressures ranging from 1 × 10 -8 to 1 × 10 -6 Torr on the CL intensity was also investigated. A CaSO 4 layer was observed on the surface after the electron beam degradation. The CL intensity was found to decrease up to 30% of its original intensity at 1 × 10 -6 Torr oxygen pressure after an electron dose of 50 C/cm 2. The formation of oxygen defects during electron bombardment may also be responsible for the decrease in CL intensity.

  5. Noble-metal-free g-C3N4/Ni(dmgH)2 composite for efficient photocatalytic hydrogen evolution under visible light irradiation

    NASA Astrophysics Data System (ADS)

    Cao, Shao-Wen; Yuan, Yu-Peng; Barber, James; Loo, Say Chye Joachim; Xue, Can

    2014-11-01

    We report an economic photocatalytic H2 generation system consisting of earth-abundant elements only by coupling graphitic carbon nitride (g-C3N4) with Ni(dmgH)2 sub-microwires that serve as effective co-catalysts for H2 evolution. This composite photocatalyst exhibits efficient hydrogen evolution under visible-light irradiation in the presence of triethanolamine as electron donor. The optimal coupling of 3.5 wt% Ni(dmgH)2 to g-C3N4 (5 mg composite) allows for a steady H2 generation rate of 1.18 μmol/h with excellent stability. This study demonstrates that the combination of polymeric g-C3N4 semiconductor and small proportion of transition-metal-based co-catalyst could serve as a stable, earth-abundant and low-cost system for solar-to-hydrogen conversion.

  6. Swift heavy ion irradiation effects in Pt/C and Ni/C multilayers

    NASA Astrophysics Data System (ADS)

    Gupta, Ajay; Pandita, Suneel; Avasthi, D. K.; Lodha, G. S.; Nandedkar, R. V.

    1998-12-01

    Irradiation effects of 100 MeV Ag ion irradiation on Ni/C and Pt/C multilayers have been studied using X-ray reflectivity measurements. Modifications are observed in both the multilayers at (dE/dx)e values much below the threshold values for Ni and Pt. This effect is attributed to the discontinuous nature of the metal layers. In both the multilayers interfacial roughness increases with irradiation dose. While Ni/C multilayers exhibit large ion-beam induced intermixing, no observable intermixing is observed in the case of Pt/C multilayer. This difference in the behavior of the two systems suggests a significant role for chemically guided defect motion in the mixing process associated with swift heavy ion irradiation.

  7. Effect of Ni Core Structure on the Electrocatalytic Activity of Pt-Ni/C in Methanol Oxidation

    PubMed Central

    Kang, Jian; Wang, Rongfang; Wang, Hui; Liao, Shijun; Key, Julian; Linkov, Vladimir; Ji, Shan

    2013-01-01

    Methanol oxidation catalysts comprising an outer Pt-shell with an inner Ni-core supported on carbon, (Pt-Ni/C), were prepared with either crystalline or amorphous Ni core structures. Structural comparisons of the two forms of catalyst were made using transmission electron microscopy (TEM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS), and methanol oxidation activity compared using CV and chronoamperometry (CA). While both the amorphous Ni core and crystalline Ni core structures were covered by similar Pt shell thickness and structure, the Pt-Ni(amorphous)/C catalyst had higher methanol oxidation activity. The amorphous Ni core thus offers improved Pt usage efficiency in direct methanol fuel cells. PMID:28811402

  8. Morphology controlled synthesis of 2-D Ni-Ni3S2 and Ni3S2 nanostructures on Ni foam towards oxygen evolution reaction

    NASA Astrophysics Data System (ADS)

    Chaudhari, Nitin Kaduba; Oh, Aram; Sa, Young Jin; Jin, Haneul; Baik, Hionsuck; Kim, Sang Gu; Lee, Suk Joong; Joo, Sang Hoon; Lee, Kwangyeol

    2017-03-01

    Catalysts for oxygen evolution reactions (OER) are at the heart of key renewable energy technologies, and development of non-precious metal catalysts with high activity and stability remain a great challenge in this field. Among various material candidates, metal sulfides are receiving increasing attention. While morphology-dependent catalytic performances are well established in noble metal-based catalysts, relatively little is known for the morphology‒catalytic performance relationship in metal sulfide catalysts. In this study, uniform spider web-like Ni nanosheets-Ni3S2 and honeycomb-like Ni3S2 structures are deposited on nickel foam (Ni3S2/NF) by a facile one-step hydrothermal synthetic route. When used as an oxygen evolution electrode, the spider web-like Ni-Ni3S2/NF with the large exposed surface area shown excellent catalytic activity and stability with an overpotential of 310 mV to achieve at 10 mA/cm2 and a Tafel slope of 63 mV/dec in alkaline media, which is superior to the honeycomb-like structure without Ni nanosheet. The low Tafel slope of the spider web-like Ni-Ni3S2/NF represents one of the best OER kinetics among nickel sulfide-based OER catalysts. The results point to the fact that performance of the metal sulfide electrocatalysts might be fine-tuned and optimized with morphological controls.

  9. Intrinsic ferromagnetism in nanocrystalline Mn-doped ZnO depending on Mn concentration.

    PubMed

    Subramanian, Munisamy; Tanemura, Masaki; Hihara, Takehiko; Soga, Tetsuo; Jimbo, Takashi

    2011-04-01

    The physical properties of Zn(1-x)Mn(x)O nanoparticles synthesized by thermal decomposition are extensively investigated by X-ray diffraction (XRD), Transmission Electron Microscopy (TEM), X-ray photoelectron spectroscopy (XPS), Raman light scattering and Hysteresis measurements. XRD and XPS spectra reveal the absence of secondary phase in nanocrystalline ZnO doped with 5% or less Mn; and, later confirms that the valance state of Mn to be 2+ for all the samples. Raman spectra exhibit a peak at 660 cm(-1) which we attribute to the intrinsic lattice defects of ZnO with increasing Mn concentration. Overall, our results demonstrate that ferromagnetic properties can be realized while Mn-doped ZnO obtained in the nanocrystalline form.

  10. On the existence of declared 9R phase in Fe–Ni invar alloy

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Kabanova, I. G.; Sagaradze, V. V., E-mail: vsagaradze@imp.uran.ru; Kataeva, N. V.

    2016-07-15

    An analysis of recently reported electron diffraction patterns suggests that metastable austenitic Fe–32Ni alloy subjected to α → γ transformation upon slow heating does not exhibit any signs of formation of the 9R phase; the conventional nanocrystalline γ phase with an fcc lattice is formed instead. Extended lamellae with a layered structure, erroneously identified as a new phase of the (3R + 9R) type in Fe–32Ni alloy, are conventional twinning (midrib) regions of each initial α crystal, in which γ-phase twin nanolamellae are formed upon heating.

  11. Secondary ion mass spectrometric investigation on ruthenium oxide systems: a comparison between poly- and nanocrystalline deposits

    PubMed

    Barison; Barreca; Daolio; Fabrizio; Piccirillo

    2000-01-01

    The influence of different RuO(2) crystallite sizes was investigated by secondary ion mass spectrometry (SIMS) on the oxide deposited on various support materials (Ni, Ti, Al(2)O(3), oxidized Si(100)). In order to examine the effect of an oxidic environment on the film structure, RuO(2) 20%-TiO(2) 80% at. mixed oxide was deposited on Ti. The polycrystalline coatings were prepared by heating the Ru (and Ti)-containing solution dropped on the supports.1 RuO(2) nanocrystalline coatings were grown by chemical vapor deposition (CVD) from Ru(COD)(eta(3)-allyl)(2).2 The identification of mixed oxide clusters showed the higher reactivity of Ni and Al(2)O(3) over the other substrates. Diffusion and migration characteristics were observed to be influenced by the nature of the support. The results are complementary to those of a previous SIMS investigation.3 Copyright 2000 John Wiley & Sons, Ltd.

  12. Facile preparation of 3D hierarchical coaxial-cable-like Ni-CNTs@beta-(Ni, Co) binary hydroxides for supercapacitors with ultrahigh specific capacitance.

    PubMed

    Zhang, Manyu; Ma, Xiaowei; Bi, Han; Zhao, Xuebing; Wang, Chao; Zhang, Jie; Li, Yuesheng; Che, Renchao

    2017-09-15

    A facile chemical method for Co doping Ni-CNTs@α-Ni(OH) 2 combining with an in situ phase transformation process is successfully proposed and employed to synthesize three-dimensional (3D) hierarchical Ni-CNTs@β-(Ni, Co) binary hydroxides. This strategy can effectively maintain the coaxial-cable-like structure of Ni-CNTs@α-Ni(OH) 2 and meanwhile increase the content of Co as much as possible. Eventually, the specific capacitances and electrical conductivity of the composites are remarkably enhanced. The optimized composite exhibits high specific capacitances of 2861.8F g -1 at 1A g -1 (39.48F cm -2 at 15mAcm -2 ), good rate capabilities of 1221.8F g -1 at 20A g -1 and cycling stabilities (87.6% of capacitance retention after 5000cycles at 5A g -1 ). The asymmetric supercapacitor (ASC) constructed with the as-synthesized composite and activated carbon as positive and negative electrode delivers a high specific capacitance of 287.7F g -1 at 1A g -1 . The device demonstrates remarkable energy density (96Whkg -1 ) and high power density (15829.4Wkg -1 ). The retention of capacitance remains 83.5% at the current density of 5A g -1 after 5000cycles. The charged and discharged samples are further studied by ex situ electron energy loss spectroscopy (EELS) analysis, XRD and SEM to figure out the reasons of capacitance fading. Overall, it is believable that this facile synthetic strategy can be applied to prepare various nanostructured metal hydroxide/CNT composites for high performance supercapacitor electrode materials. Copyright © 2017. Published by Elsevier Inc.

  13. Mass enhancement versus Stoner enhancement in strongly correlated metallic perovskites: LaNiO3 and LaCuO3

    NASA Astrophysics Data System (ADS)

    Zhou, J.-S.; Marshall, L. G.; Goodenough, J. B.

    2014-06-01

    Measurements of physical properties, including transport and magnetic properties, specific heat, and thermal conductivity, have been performed on high-quality samples of LaNiO3 and LaCuO3 synthesized under high pressure. Some measurements, such as thermoelectric power and magnetic susceptibility, have been made under high pressure. The availability of a complete set of data enables a side-by-side comparison between these two narrowband systems. We have demonstrated unambiguously the mass enhancement due to electron-electron correlations in both systems relative to the recent density functional theory results. Correlations in these narrowband systems also enhance the magnetic susceptibility. Ferromagnetic spin fluctuations give rise to a strong Stoner enhancement in the magnetic susceptibility in the quarter-filled LaNiO3. Although we are able to tune the bandwidth by either chemical substitutions or by applying hydrostatic pressure on LaNiO3, the Stoner enhancement does not lead to the Stoner instability.

  14. Synthesis and properties of nanocrystalline copper indium oxide thin films deposited by Rf magnetron sputtering.

    PubMed

    Singh, Mandeep; Singh, V N; Mehta, B R

    2008-08-01

    Nanocrystalline copper indium oxide (CuInO2) thin films with particle size ranging from 25 nm to 71 nm have been synthesized from a composite target using reactive Rf magnetron sputtering technique. X-ray photoelectron spectroscopy (XPS) combined with glancing angle X-ray diffraction (GAXRD) analysis confirmed the presence of delafossite CuInO2 phase in these films. The optical absorption studies show the presence of two direct band gaps at 3.3 and 4.3 eV, respectively. The resistance versus temperature measurements show thermally activated hopping with activation energy of 0.84 eV to be the conduction mechanism.

  15. Coexistence of short- and long-range ferromagnetic order in nanocrystalline Fe2Mn1-xCuxAl (x=0.0, 0.1 and 0.3) synthesized by high-energy ball milling

    NASA Astrophysics Data System (ADS)

    Thanh, Tran Dang; Nanto, Dwi; Tuyen, Ngo Thi Uyen; Nan, Wen-Zhe; Yu, YiKyung; Tartakovsky, Daniel M.; Yu, S. C.

    2015-11-01

    In this work, we prepared nanocrystalline Fe2Mn1-xCuxAl (x=0.0, 0.1 and 0.3) powders by the high energy ball milling technique, and then studied their critical properties. Our analysis reveals that the increase of Cu-doping concentration (up to x=0.3) in these powders leads to a gradual increase of the ferromagnetic-paramagnetic transition temperature from 406 to 452 K. The Banerjee criterion suggests that all the samples considered undergo a second-order phase transition. A modified Arrott plot and scaling analysis indicate that the critical exponents (β=0.419 and 0.442, γ=1.082 and 1.116 for x=0.0 and 0.1, respectively) are located in between those expected for the 3D-Heisenberg and the mean-field models; the values of β=0.495 and γ=1.046 for x=0.3 sample are very close to those of the mean-field model. These features reveal the coexistence of the short- and long-range ferromagnetic order in the nanocrystalline Fe2Mn1-xCuxAl powders. Particularly, as the concentration of Cu increases, values of the critical exponent shift towards those of the mean-field model. Such results prove the Cu doping favors establishing a long-range ferromagnetic order.

  16. Effect of milling methods on performance of Ni-Y 2O 3-stabilized ZrO 2 anode for solid oxide fuel cell

    NASA Astrophysics Data System (ADS)

    Cho, Hyoup Je; Choi, Gyeong Man

    A Ni-YSZ (Y 2O 3-stabilized ZrO 2) composite is commonly used as a solid oxide fuel cell anode. The composite powders are usually synthesized by mixing NiO and YSZ powders. The particle size and distribution of the two phases generally determine the performance of the anode. Two different milling methods are used to prepare the composite anode powders, namely, high-energy milling and ball-milling that reduce the particle size. The particle size and the Ni distribution of the two composite powders are examined. The effects of milling on the performance are evaluated by using both an electrolyte-supported, symmetric Ni-YSZ/YSZ/Ni-YSZ cell and an anode-supported, asymmetric cell. The performance is examined at 800 °C by impedance analysis and current-voltage measurements. Pellets made by using high-energy milled NiO-YSZ powders have much smaller particle sizes and a more uniform distribution of Ni particles than pellets made from ball-milled powder, and thus the polarization resistance of the electrode is also smaller. The maximum power density of the anode-supported cell prepared by using the high-energy milled powder is ∼850 mW cm -2 at 800 °C compared with ∼500 mW cm -2 for the cell with ball-milled powder. Thus, high-energy milling is found to be more effective in reducing particle size and obtaining a uniform distribution of Ni particles.

  17. Phase Decomposition in the Fe-rich Fe-Ni-S System from 900 Degrees C to 300 Degrees C--Application to Meteoritic Metal

    NASA Astrophysics Data System (ADS)

    Ma, L.; Williams, D. B.; Goldstein, J. I.

    1995-09-01

    It has been observed that metal particles in ordinary chondrites contain essentially no P and that the tetrataenite rim of the metal particles is much wider than that in other types of meteorites, especially when the taenite rim abuts troilites (FeS) [1]. It is possible that S plays an important role in the formation of the zoned tetrataenite at low cooling temperatures. Most of the studies of the Fe-Ni-S system have concentrated on high temperature and high Ni-high S part of the ternary diagram [2][3]. In this study we have systematically investigated the microstructure and microchemistry of the Fe-rich Fe-Ni-S system in regions where meteoritic metal forms from 900 degrees C down to 300 degrees C. High spatial resolution electron probe microanalysis (EPMA) and analytical electron microscopy (AEM) techniques were employed. The two and three phase boundaries at high temperatures (900 degrees C to 600 degrees C) are consistent with previous studies. However, at 500 degrees C, an Fe-Ni phase with 51.6 +/- 1.4 wt.% Ni was observed to form along some of the g/g and g/FeS boundaries. The size of this Fe-Ni phase is as large as 10 micrometers in width. AEM analysis indicates that this Fe-Ni phase may have even higher Ni content, 56 wt.%. In addition, the phase has a FCC structure and is disordered. Because the composition of this phase is very close to the stoichiometric composition of FeNi, it is very likely that the phase is tetrataenite. High Ni precipitates with similar morphology were also observed in the Fe-Ni-S alloy aged at 400 degrees C. However, the Ni content is 60.9 +/- 4.0 wt.% measured with EPMA, which is much higher than that in the corresponding 500 degree C sample. The fact that all the high Ni precipitates formed at boundaries of g/g or g/FeS indicates the boundaries are favorable energy nucleation sites. Such a high Ni phase with a Ni content over 60 wt.% has not been observed in the Fe-Ni and Fe-Ni (P) systems above 400 degrees C. The tetrataenite

  18. Solid state consolidation nanocrystalline copper-tungsten using cold spray

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Hall, Aaron Christopher; Sarobol, Pylin; Argibay, Nicolas

    It is well known that nanostructured metals can exhibit significantly improved properties compared to metals with conventional grain size. Unfortunately, nanocrystalline metals typically are not thermodynamically stable and exhibit rapid grain growth at moderate temperatures. This severely limits their processing and use, making them impractical for most engineering applications. Recent work has shown that a number of thermodynamically stable nanocrystalline metal alloys exist. These alloys have been prepared as powders using severe plastic deformation (e.g. ball milling) processes. Consolidation of these powders without compromise of their nanocrystalline microstructure is a critical step to enabling their use as engineering materials. Wemore » demonstrate solid-state consolidation of ball milled copper-tantalum nanocrystalline metal powder using cold spray. Unfortunately, the nanocrystalline copper-tantalum powder that was consolidated did not contain the thermodynamically stable copper-tantalum nanostructure. Nevertheless, this does this demonstrates a pathway to preparation of bulk thermodynamically stable nanocrystalline copper-tantalum. Furthermore, it demonstrates a pathway to additive manufacturing (3D printing) of nanocrystalline copper-tantalum. Additive manufacturing of thermodynamically stable nanocrystalline metals is attractive because it enables maximum flexibility and efficiency in the use of these unique materials.« less

  19. One-pot synthesis of LaFeO3-NiFe2O4 nanocomposite ceramic by egg-white method and its magnetic and dielectric properties

    NASA Astrophysics Data System (ADS)

    Muthu, K. Sudalai; Lakshminarasimhan, N.; Perumal, P.

    2017-10-01

    A facile, one-pot synthesis of nanocomposite of LaFeO3-NiFe2O4 was demonstrated by using egg-white method. The same method was adopted to synthesize the individual component oxide nanoparticles of LaFeO3 (LFO) and NiFe2O4 (NFO). The phase formation of individual components and the nanocomposite was confirmed using powder X-Ray diffraction (XRD) technique. The measured room temperature magnetic properties of LFO, NFO and LFO-NFO nanoparticles revealed an enhancement in the properties of the nanocomposite. The dielectric behaviours of LFO, NFO and LFO-NFO pellets sintered at different temperatures such as 800, 900 and 1000 °C were investigated and correlated with the microstructures.

  20. Two isotypic diphosphates LiM{sub 2}H{sub 3}(P{sub 2}O{sub 7}){sub 2} (M=Ni, Co) containing ferromagnetic zigzag MO{sub 6} chains

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Yang Tao; Yang Sihai; Liao Fuhui

    2008-06-15

    Two new isotypic phosphates LiNi{sub 2}H{sub 3}(P{sub 2}O{sub 7}){sub 2} (1) and LiCo{sub 2}H{sub 3}(P{sub 2}O{sub 7}){sub 2} (2) have been hydrothermally synthesized and structurally characterized by the single-crystal X-ray diffraction technique. They crystallize in the monoclinic space group C2/c with the lattice: a=10.925(2) A, b=12.774(3) A, c=8.8833(18) A, {beta}=123.20(3){sup o} for 1 and a=10.999(2) A, b=12.863(3) A, c=8.9419(18) A, {beta}=123.00(3){sup o} for 2. The transition metal atoms are octahedrally coordinated, whereas the lithium and phosphorus atoms are all tetrahedrally coordinated. As the lithium-induced derivatives of MH{sub 2}P{sub 2}O{sub 7} (M=Ni, Co), 1 and 2 possess the same structure withmore » MH{sub 2}P{sub 2}O{sub 7} in terms of topology, comprising the MO{sub 6} zigzag chains and P{sub 2}O{sub 7} as the interchain groups. The magnetisms of 1 and 2 could be interpreted by adopting a quasi-one-dimensional (1D) zigzag chain model as that in their parent compounds: both 1 and 2 have ferromagnetic (FM) NiO{sub 6}/CoO{sub 6} chains; 1 shows a FM cluster glass behavior at low temperatures, which is originated from the possible antiferromagnetic (AFM) next-nearest-neighbour intrachain interactions; 2 shows a AFM ordering at T{sub N}=2.6 K and a metamagnetic transition at H{sub C}=4.2 kOe at 1.8 K. - Graphical abstract: LiNi{sub 2}H{sub 3}(P{sub 2}O{sub 7}){sub 2} (1) and LiCo{sub 2}H{sub 3}(P{sub 2}O{sub 7}){sub 2} (2) have been hydrothermally synthesized and structurally characterized. The MO{sub 6} octahedra share edges forming zigzag chains with P{sub 2}O{sub 7} as the interchain groups. Both of them are quasi-one-dimensional magnets and have ferromagnetic MO{sub 6} chains; 1 is a ferromagnet, whereas 2 is a metamagnet.« less

  1. Microstructural evolution during quenching and partitioning of 0.2C-1.5Mn-1.3Si steels with Cr or Ni additions

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Pierce, Dean T.; Coughlin, D. R.; Clarke, Kester D.

    Here, the influence of Cr and Ni additions and quench and partition (Q&P) processing parameters on the microstructural development, including carbide formation and austenite retention during Q&P, was studied in two steels with a base composition of 0.2C-1.5Mn-1.3Si wt.% and additions of 1.5 wt.% Cr (1.5Cr) or Ni (1.5Ni). Additions of 1.5 wt.% Cr significantly slowed the kinetics of austenite decomposition relative to the 1.5Ni alloy at all partitioning temperatures, promoting greater austenite retention, lower retained austenite carbon (C) contents, and reduced sensitivity of the retained austenite amounts to processing variables. In the 1.5Cr alloy after partitioning at 400 °Cmore » for 300 s, η-carbides were identified by transmission electron microscopy (TEM) and atom probe tomography (APT) revealed no significant enrichment of substitutional elements in the carbides. In the 1.5Ni alloy after partitioning at 450 °C for 300 s, both plate-like and globular carbides were observed by TEM. APT analysis of the globular carbides clearly revealed significant Si rejection and Mn enrichment. Mössbauer effect spectroscopy was used to quantify the amount of carbides after Q&P. In general, carbide amounts below ~0.3% of Fe were measured in both alloys after partitioning for short times (10 s), irrespective of quench or partitioning temperature, which corresponds to a relatively small portion of the bulk C. With increasing partitioning time, carbide amounts remained approximately constant or increased, depending on the alloy, quench temperature, and/or partitioning temperature.« less

  2. Microstructural evolution during quenching and partitioning of 0.2C-1.5Mn-1.3Si steels with Cr or Ni additions

    DOE PAGES

    Pierce, Dean T.; Coughlin, D. R.; Clarke, Kester D.; ...

    2018-03-08

    Here, the influence of Cr and Ni additions and quench and partition (Q&P) processing parameters on the microstructural development, including carbide formation and austenite retention during Q&P, was studied in two steels with a base composition of 0.2C-1.5Mn-1.3Si wt.% and additions of 1.5 wt.% Cr (1.5Cr) or Ni (1.5Ni). Additions of 1.5 wt.% Cr significantly slowed the kinetics of austenite decomposition relative to the 1.5Ni alloy at all partitioning temperatures, promoting greater austenite retention, lower retained austenite carbon (C) contents, and reduced sensitivity of the retained austenite amounts to processing variables. In the 1.5Cr alloy after partitioning at 400 °Cmore » for 300 s, η-carbides were identified by transmission electron microscopy (TEM) and atom probe tomography (APT) revealed no significant enrichment of substitutional elements in the carbides. In the 1.5Ni alloy after partitioning at 450 °C for 300 s, both plate-like and globular carbides were observed by TEM. APT analysis of the globular carbides clearly revealed significant Si rejection and Mn enrichment. Mössbauer effect spectroscopy was used to quantify the amount of carbides after Q&P. In general, carbide amounts below ~0.3% of Fe were measured in both alloys after partitioning for short times (10 s), irrespective of quench or partitioning temperature, which corresponds to a relatively small portion of the bulk C. With increasing partitioning time, carbide amounts remained approximately constant or increased, depending on the alloy, quench temperature, and/or partitioning temperature.« less

  3. Grain Nucleation and Growth in Deformed NiTi Shape Memory Alloys: An In Situ TEM Study

    NASA Astrophysics Data System (ADS)

    Burow, J.; Frenzel, J.; Somsen, C.; Prokofiev, E.; Valiev, R.; Eggeler, G.

    2017-12-01

    The present study investigates the evolution of nanocrystalline (NC) and ultrafine-grained (UFG) microstructures in plastically deformed NiTi. Two deformed NiTi alloys were subjected to in situ annealing in a transmission electron microscope (TEM) at 400 and 550 °C: an amorphous material state produced by high-pressure torsion (HPT) and a mostly martensitic partly amorphous alloy produced by wire drawing. In situ annealing experiments were performed to characterize the microstructural evolution from the initial nonequilibrium states toward energetically more favorable microstructures. In general, the formation and evolution of nanocrystalline microstructures are governed by the nucleation of new grains and their subsequent growth. Austenite nuclei which form in HPT and wire-drawn microstructures have sizes close to 10 nm. Grain coarsening occurs in a sporadic, nonuniform manner and depends on the physical and chemical features of the local environment. The mobility of grain boundaries in NiTi is governed by the local interaction of each grain with its microstructural environment. Nanograin growth in thin TEM foils seems to follow similar kinetic laws to those in bulk microstructures. The present study demonstrates the strength of in situ TEM analysis and also highlights aspects which need to be considered when interpreting the results.

  4. Observation of Superconductivity in the LaNiO3/La0.7Sr0.3MnO3 Superlattice.

    PubMed

    Zhou, Guowei; Jiang, Fengxian; Zang, Julu; Quan, Zhiyong; Xu, Xiaohong

    2018-01-17

    In the pursuit of high-temperature superconductivity like that in cuprates, artificial heterostructures or interfaces have attracted tremendous interest. It has been a long-sought goal to find similar unconventional superconductivity in nickelates. However, as far as we know, this has not yet been experimentally realized. To approach this objective, we synthesized a prototypical superlattice that consists of ultrathin LaNiO 3 and La 0.7 Sr 0.3 MnO 3 layers. Both zero resistance and the Meissner effect are observed using resistive and magnetic measurements of the superlattice. These are experimental indicators for superconductivity in new superconductors. X-ray linear dichroism causes the NiO 2 planes to develop electron-occupied x 2 -y 2 orbital order similar to that of cuprate-based superconductors. Our findings demonstrate that artificial interface engineering is suitable for investigating novel physical phenomena, such as superconductivity.

  5. Electrochemical performance of LiNi0.4Co0.2Mn0.4O2 prepared by different molten salt flux: LiNO3-LiCl and LiNO3-KNO3

    NASA Astrophysics Data System (ADS)

    Satyanarayana, M.; James, Joseph; U. V., Varadaraju

    2017-10-01

    LiNi0.4Co0.2Mn0.4O2 material synthesized at different temperatures by using LiNO3-LiCl and LiNO3-KNO3 molten salt as a reaction medium. The phase purity of the samples obtained by powder X-ray diffraction measurement which suggests layered α-NaFeO2 type is obtained at 800-900 °C using LiNO3-LiCl flux and at 750-850 °C using LiNO3-KNO3 flux. The surface morphology change with flux media at different temperature are obtained by scanning electron microscopy analysis. The galvanostatic cycling results show that the high stable reversible discharge capacity of 155 (±3) mAh g-1 obtained for treated compound at 900 °C for 1 h (using LiNO3-LiCl) with coloumbic efficiency of 99%. The reversible discharge capacity of 140 and 130 (±3) mAh g-1 obtained for treated compound at 750 and 850 °C, respectively (using LiNO3-KNO3).

  6. One-pot synthesis of NiO/Mn2O3 nanoflake arrays and their application in electrochemical biosensing

    NASA Astrophysics Data System (ADS)

    Wang, Yao; Cui, Jiewu; Luo, Lan; Zhang, Jingcheng; Wang, Yan; Qin, Yongqiang; Zhang, Yong; Shu, Xia; Lv, Jun; Wu, Yucheng

    2017-11-01

    The exploration of novel nanomaterials employed as substrate to construct glucose biosensors is still of significance in the field of clinical diagnosis. In this work, NiO/Mn2O3 nanoflake arrays were synthesized by hydrothermal approach in combination with calcination process. As-prepared NiO/Mn2O3 nanoflake arrays were utilized to construct electrochemical biosensors for glucose detection. NiO/Mn2O3 nanoflake arrays were investigated systematically by scanning electron microscopy (SEM), X-ray diffractionmeter (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and energy dispersive X-ray spectroscopy, the formation mechanism of NiO/Mn2O3 nanoflake arrays was proposed. As-prepared glucose biosensors based on NiO/Mn2O3 nanoflake arrays were characterized by cyclic voltammgrams and chronoamperometry. The results indicated that glucose biosensors based on optimized NiO/Mn2O3 nanoflake arrays exhibited a high sensitivity of 167.0 μA mM-1 Cm-2 and good anti-interference ability, suggesting the NiO/Mn2O3 nanoflake arrays are an attractive substrate for the construction of oxidase-based biosensors.

  7. Template-free approach to synthesize hierarchical porous nickel cobalt oxides for supercapacitors

    NASA Astrophysics Data System (ADS)

    Chang, Jie; Sun, Jing; Xu, Chaohe; Xu, Huan; Gao, Lian

    2012-10-01

    Nickel cobalt oxides with various Ni/Co ratios were synthesized using a facile template-free approach for electrochemical supercapacitors. The texture and morphology of the nanocomposites were characterized by powder X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and Brunauer-Emmett-Teller analysis (BET). The results show that a hierarchical porous structure assembled from nanoflakes with a thickness of ~10 nm was obtained, and the ratio of nickel to cobalt in the nanocomposites was very close to the precursors. Cyclic voltammetry (CV) and galvanostatic charge and discharge tests were carried out to study the electrochemical performance. Both nickel cobalt oxides (Ni-Co-O-1 with Ni : Co = 1, Ni-Co-O-2 with Ni : Co = 2) outperform pure NiO and Co3O4. The Ni-Co-O-1 and Ni-Co-O-2 possess high specific capacities of 778.2 and 867.3 F g-1 at 1 A g-1 and capacitance retentions of 84.1% and 92.3% at 10 A g-1, respectively. After full activation, the Ni-Co-O-1 and Ni-Co-O-2 could achieve a maximum value of 971 and 1550 F g-1 and remain at ~907 and ~1450 F g-1 at 4 A g-1, respectively. Also, the nickel cobalt oxides show high capacity retention when fast charging.Nickel cobalt oxides with various Ni/Co ratios were synthesized using a facile template-free approach for electrochemical supercapacitors. The texture and morphology of the nanocomposites were characterized by powder X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and Brunauer-Emmett-Teller analysis (BET). The results show that a hierarchical porous structure assembled from nanoflakes with a thickness of ~10 nm was obtained, and the ratio of nickel to cobalt in the nanocomposites was very close to the precursors. Cyclic voltammetry (CV) and galvanostatic charge and discharge tests were carried out to study the electrochemical performance. Both nickel cobalt oxides (Ni-Co-O-1 with Ni : Co = 1, Ni-Co-O-2 with Ni

  8. Synthesis of nanocrystalline rare earth oxides by glycothermal method

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Hosokawa, Saburo; Iwamoto, Shinji; Inoue, Masashi

    2008-11-03

    The reaction of yttrium acetate hydrate in 1,2-propanediol at 300 deg. C yielded a product containing acetate groups and glycol moieties. From this product, Y{sub 2}O{sub 3} was directly crystallized at 400 deg. C without the formation of a carbonate oxide phase. The thus-obtained Y{sub 2}O{sub 3} samples had a small crystallite size (2.2 nm) and significantly large surface area (280 m{sup 2}/g). Other nanocrystalline rare earth (Gd-Yb) oxides were also obtained by this method.

  9. Synthesis of novel amperometric urea-sensor using hybrid synthesized NiO-NPs/GO modified GCE in aqueous solution of cetrimonium bromide.

    PubMed

    Parsaee, Zohreh

    2018-06-01

    In this study NiO nanostructures were synthesized via combinational synthetic method (ultrasound-assisted biosynthesis) and immobilized on the glassy carbon electrode (GCE) as a highly sensitive and selective enzyme-less sensor for urea detection. NiO-NPs were fully characterized using SEM, EDX, XRD, BET, TGA, FT-IR, UV-vis and Raman methods which revealed the formation of NiO nanostructures in the form of cotton like porous material and crystalline in nature with the average size of 3.8 nm. GCE was modified with NiO-NPs in aqueous solution of cetrimonium bromide(CTAB). Highly adhesive NiO/CTAB/GO nanocomposite membrane has been formed on GCE by immersing NiO/CTAB modified GCE in GO suspension. CTAB has a major role in the production and immobilization of the nanocomposites on the GCE surface and the binding NiO nanoparticles on GO plates. In addition, CTAB/GO composition made a highly adhesive surface on the GCE. The resulting NiO/CTAB/GO/GCE contains potently sensitive to urea in aqueous environments. The response of as developed amperometric sensor was linear in the range of 100-1200 µM urea with R 2 value of 0.991 and limit of detection (LOD), 8 µM. The sensor responded negligibly to various interfering species like glucose, uric acid and ascorbic acid. This sensor was applied successfully for determining urea in real water samples such as mineral water, tap water and river water with acceptable recovery. Copyright © 2018 Elsevier B.V. All rights reserved.

  10. Low-temperature synthesis of nanocrystalline ZrC coatings on flake graphite by molten salts

    NASA Astrophysics Data System (ADS)

    Ding, Jun; Guo, Ding; Deng, Chengji; Zhu, Hongxi; Yu, Chao

    2017-06-01

    A novel molten salt synthetic route has been developed to prepare nanocrystalline zirconium carbide (ZrC) coatings on flake graphite at 900 °C, using Zr powder and flake graphite as the source materials in a static argon atmosphere, along with molten salts as the media. The effects of different molten salt media, the sintered temperature, and the heat preservation time on the phase and microstructure of the synthetic materials were investigated. The ZrC coatings formed on the flake graphite were uniform and composed of nanosized particles (30-50 nm). With an increase in the reaction temperature, the ZrC nanosized particles were more denser, and the heat preservation time and thickness of the ZrC coating also increased accordingly. Electron microscopy was used to observe the ZrC coatings on the flake graphite, indicating that a "template mechanism" played an important role during the molten salt synthesis.

  11. Bimetallic CoNiSx nanocrystallites embedded in nitrogen-doped carbon anchored on reduced graphene oxide for high-performance supercapacitors.

    PubMed

    Chen, Qidi; Miao, Jinkang; Quan, Liang; Cai, Daoping; Zhan, Hongbing

    2018-02-22

    Exploring high-performance and low-priced electrode materials for supercapacitors is important but remains challenging. In this work, a unique sandwich-like nanocomposite of reduced graphene oxide (rGO)-supported N-doped carbon embedded with ultrasmall CoNiS x nanocrystallites (rGO/CoNiS x /N-C nanocomposite) has been successfully designed and synthesized by a simple one-step carbonization/sulfurization treatment of the rGO/Co-Ni precursor. The intriguing structural/compositional/morphological advantages endow the as-synthesized rGO/CoNiS x /N-C nanocomposite with excellent electrochemical performance as an advanced electrode material for supercapacitors. Compared with the other two rGO/CoNiO x and rGO/CoNiS x nanocomposites, the rGO/CoNiS x /N-C nanocomposite exhibits much enhanced performance, including a high specific capacitance (1028.2 F g -1 at 1 A g -1 ), excellent rate capability (89.3% capacitance retention at 10 A g -1 ) and good cycling stability (93.6% capacitance retention over 2000 cycles). In addition, an asymmetric supercapacitor (ASC) device based on the rGO/CoNiS x /N-C nanocomposite as the cathode and activated carbon (AC) as the anode is also fabricated, which can deliver a high energy density of 32.9 W h kg -1 at a power density of 229.2 W kg -1 with desirable cycling stability. These electrochemical results evidently indicate the great potential of the sandwich-like rGO/CoNiS x /N-C nanocomposite for applications in high-performance supercapacitors.

  12. Effects of Nd-, Pr-, Tb- and Y-doping on the structural, textural, electrical and N2O decomposition activity of mesoporous NiO nanoparticles

    NASA Astrophysics Data System (ADS)

    Abu-Zied, Bahaa M.; Bawaked, Salem M.; Kosa, Samia A.; Ali, Tarek T.; Schwieger, Wilhelm; Aqlan, Faisal M.

    2017-10-01

    Recently, nickel oxide, NiO, promoted with various dopants showed an interesting activity behavior in N2O direct decomposition. In this paper, the activity of a series of rare earth (Nd, Pr, Tb and Y) doped NiO catalysts was investigated for this reaction. These catalysts have been prepared by the calcination of their corresponding oxalate mixtures, which have been synthesized via the microwave-assisted precipitation route using oxalic acid as precipitant. Characterization of the obtained catalysts was carried out by using various physico-chemical techniques including TGA, FT-IR, XRD, FE-SEM, TEM, TPR, XPS and electrical conductivity. The results obtained revealed the nanocrystalline nature of the prepared catalysts. Moreover, the presence of the various dopants has led to a noticeable decrease of the NiO crystallites size, mesoporosity development and an increase of its surface area and pore volume. There is a substantial activity increase upon doping NiO with the various rare earth oxides. Such activity increase is associated with the structural modifications as well as the electrical conductivity increase of these catalysts.

  13. The Influence of NiO Addition in TiO2 Structure and Its Photoactivity

    NASA Astrophysics Data System (ADS)

    Wahyuningsih, S.; Ramelan, A. H.; Purwanti, P. D.; Munawaroh, H.; Ichsan, S.; Kristiawan, Y. R.

    2018-03-01

    The synthesis of TiO2 together with the TiO2-NiO composite using various annealing temperatures has been studied. The synthesis of TiO2 was performed by sol gel method using Titanium Tetra Isopropoxide (TTIP) precursor, whereas the synthesis of TiO2-NiO composite was done by wet impregnation method using NiNO3.6H2O precursor. This study aims to determine the influence of NiO addition in its structure and photoactivity. The diffraction of synthesized TiO2 at 400 °C temperature shows anatase TiO2 peak at 2θ = 25.35 °. The addition of NiO dopant to the synthesis of TiO2 process is carried out by annealing at 300 °C, 400 °C, 500 °C, 600 °C, and 700 °C, respectively. The TiO2-NiO composite has been prepared and shows the diffraction peak of NiO at 2θ=43° about 33.08 to 36.68%. The optimum result of Rhodamine B photodegradation with TiO2 was 43.15%, while the optimum result of Rhodamine B degradation with TiO2-NiO composite was 92.85%.

  14. Effects of P/Ni ratio and Ni content on performance of γ-Al2O3-supported nickel phosphides for deoxygenation of methyl laurate to hydrocarbons

    NASA Astrophysics Data System (ADS)

    Zhang, Zhena; Tang, Mingxiao; Chen, Jixiang

    2016-01-01

    γ-Al2O3-supported nickel phosphides (mNi-Pn) were prepared by the TPR method and tested for the deoxygenation of methyl laurate to hydrocarbons. The effects of the P/Ni ratio (n = 1.0-2.5) and Ni content (m = 5-15 wt.%) in the precursors on their structure and performance were investigated. Ni/γ-Al2O3 was also studied for comparison. It was found that the formation of AlPO4 in the precursor inhibited the reduction of phosphate and so the formation of nickel phosphides. With increasing the P/Ni ratio and Ni content, the Ni, Ni3P, Ni12P5 and Ni2P phases orderly formed, accompanying with the increases of their particle size and the amount of weak acid sites (mainly due to P-OH group), while the CO uptake and the amount of medium strong acid sites (mainly related to Ni sites) reached maximum on 10%Ni-P1.5. In the deoxygenation reaction, compared with Ni/γ-Al2O3, the mNi-Pn catalysts showed much lower activities for decarbonylation, Csbnd C hydrogenolysis and methanation due to the ligand and ensemble effects of P. The conversion and the selectivity to n-C11 and n-C12 hydrocarbons achieved maximum on 10%Ni-P 2.0 for the 10%Ni-Pn catalysts and on 8%Ni-P2.0 for the mNi-P2.0 catalysts, while the turnover frequency (TOF) of methyl laurate mainly increased with the P/Ni ratio and Ni content. We propose that TOF was influenced by the nickel phosphide phases, the catalyst acidity and the particle size as well as the synergetic effect between the Ni site and acid site. Again, the hydrodeoxygenation pathway of methyl laurate was promoted with increasing P/Ni ratio and Ni content, ascribed to the phase change in the order of Ni, Ni3P, Ni12P5 and Ni2P in the prepared catalysts.

  15. Electromigration effect upon the Sn-0.7 wt% Cu/Ni and Sn-3.5 wt% Ag/Ni interfacial reactions

    NASA Astrophysics Data System (ADS)

    Chen, Chih-ming; Chen, Sinn-wen

    2001-08-01

    This study investigates the effect of electromigration upon the interfacial reactions between the promising lead-free solders, Sn-Cu and Sn-Ag, with Ni substrate. Sandwich-type reaction couples, Sn-0.7 wt% Cu/Ni/Sn-0.7 wt% Cu and Sn-3.5 wt% Ag/Ni/Sn-3.5 wt% Ag, were reacted at 160, 180, and 200 °C for various lengths of time with and without the passage of electric currents. Without passage of electric currents through the couples, only one intermetallic compound Ni3Sn4 with ˜7 at. % Cu solubility was found at both interfaces of the Sn-0.7 wt% Cu/Ni couples. With the passage of an electric current of 500 A/cm2 density, the Cu6Sn5 phase was formed at the solder/Ni interface besides the Ni3Sn4 phase. Similar to those without the passage of electric currents, only the Ni3Sn4 phase was found at the Ni/solder interface. Directions of movement of electrons, Sn, and Cu atoms are the same at the solder/Ni interface, and the growth rates of the intermetallic layers were enhanced. At the Ni/solder interface, the electrons flow in the opposite direction of the Sn and Cu movement, and the growth rates of the intermetallic layers were retarded. Only the Ni3Sn4 phase was formed from the Sn-3.5 wt% Ag/Ni interfacial reaction with and without the passage of electric currents. Similar to the Sn-0.7 wt% Cu/Ni system, the movement of electrons enhances or retards the growth rates of the intermetallic layers at the solder/Ni and Ni/solder interfaces, respectively. Calculation results show the apparent effective charge za* decreases in magnitude with raising temperatures, which indicates the electromigration effect becomes insignificant at higher temperatures.

  16. Characterization of nanocrystalline ZnO:Al films by sol-gel spin coating method

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Gareso, P. L., E-mail: pgareso@gmail.com; Rauf, N., E-mail: pgareso@gmail.com; Juarlin, E., E-mail: pgareso@gmail.com

    2014-09-25

    Nanocrystalline ZnO films doped with aluminium by sol-gel spin coating method have been investigated using optical transmittance UV-Vis and X-ray diffraction (X-RD) measurements. ZnO films were prepared using zinc acetate dehydrate (Zn(CH{sub 3}COO){sub 2}@@‡2H{sub 2}O), ethanol, and diethanolamine (DEA) as a starting material, solvent, and stabilizer, respectively. For doped films, AlCl{sub 3} was added to the mixture. The ZnO:Al films were deposited on a transparent conductive oxide (TCO) substrate using spin coating technique at room temperature with a rate of 3000 rpm in 30 sec. The deposited films were annealed at various temperatures from 400°C to 600°C during 60 minutes.more » The transmittance UV-Vis measurement results showed that after annealing at 400°C, the energy band gap profile of nanocrystalline ZnO:Al film was a blue shift. This indicated that the band gap of ZnO:Al increased after annealing due to the increase of crystalline size. As the annealing temperature increased the bandgap energy was a constant. In addition to this, there was a small oscillation occurring after annealing compared to the as–grown samples. In the case of X-RD measurements, the crystalinity of the films were amorphous before annealing, and after annealing the crystalinity became enhance. Also, X-RD results showed that structure of nanocrystalline ZnO:Al films were hexagonal polycrystalline with lattice parameters are a = 3.290 Å and c = 5.2531 Å.« less

  17. Enhancement of electrochemical performance by simultaneous substitution of Ni and Mn with Fe in Ni-Mn spinel cathodes for Li-ion batteries

    NASA Astrophysics Data System (ADS)

    Kiziltas-Yavuz, Nilüfer; Yavuz, Murat; Indris, Sylvio; Bramnik, Natalia N.; Knapp, Michael; Dolotko, Oleksandr; Das, Bijoy; Ehrenberg, Helmut; Bhaskar, Aiswarya

    2016-09-01

    LiNi0.5-xFe2xMn1.5-xO4 (x = 0, 0.1, 0.15, 0.2) spinel cathode materials are synthesized using citric acid-assisted sol-gel method with final calcination temperature of 1000 °C. The structure and morphology of the materials are characterized by using synchrotron and neutron powder diffraction as well as scanning electron microscopy. Different from the parent LiNi0.5Mn1.5O4 (LNMO) material, the Fe-doped spinels do not contain a rock-salt type impurity phase. However, they contain additional layered (C2/m) and spinel Fe3O4 (Fd 3 bar m) phases in small amounts. The substitution of Fe into the spinel structure has been confirmed by Mössbauer spectroscopy. The Fe-doped spinels exhibit improved cycling stability (with a C/2 charge-discharge rate) and rate capability compared to the parent LNMO at room temperature in a voltage range 3.5-5.0 V. Among all these samples, the composition LiNi0.4Fe0.2Mn1.4O4 shows the best room temperature cycling stability (capacity retention of 92% after 300 cycles) as well as the highest initial discharge capacity (134 mAh g-1). The delivered capacities at high C-rates (especially at 10C and 20C) with respect to the capacity delivered at C/2 are higher for all Fe-doped samples compared to the parent LNMO. Furthermore, Fe-doping improves the thermal stability of the Ni-Mn spinels in the delithiated state.

  18. a Study on Microstructure Characteristics of IN SITU Formed TiC Reinforced Composite Coatings

    NASA Astrophysics Data System (ADS)

    Liu, Peng; Guo, Wei; Luo, Hui

    2012-04-01

    In situ synthesized TiC reinforced composite coating was fabricated by laser cladding of Al-Ni-Cr-C powders on titanium alloys, which can greatly improve the surface performance of the substrate. In this study, the Al-Ni-Cr-C laser-cladded composite coatings have been researched by means of X-ray diffraction, scanning electron microscope (SEM) and electron probe micro-analyzer (EPMA). There was a metallurgical combination between the Al-Ni-Cr-C laser-cladded coating and the Ti-6Al-4V substrate, and the micro-hardness of the Al-Ni-Cr-C laser-cladded coating was in the range of 1200-1450 HV0.2, which was 3-4 times higher than that of Ti-6Al-4V substrate. Furthermore, the reinforcement of theAl-Ni-Cr-C laser-cladded coating were mainly contributed to the action of the TiC, Ti3Al, Cr7C3, Al8Cr5 phases and the solution strengthening.

  19. Analysis of Distribution of Polyvinyl Alcohol Hydrogel Nanocrystalline by using SAXS Synchrotron

    NASA Astrophysics Data System (ADS)

    Sunaryono; Taufiq, A.; Mufti, N.; Hidayat, N.; Rugmai, S.; Soontaranon, S.; Putra, E. G. R.; Darminto

    2017-05-01

    Polyvinyl alcohol (PVA) hydrogel has been successfully synthesized through freezing-thawing (F-T) process by using time-variation. This work is aimed to investigate the distribution of nanocrystalline from the hydrogel. Fourier Transform Infrared (FTIR) Spectroscopy, Differential Thermal Analysis/Thermogravimetric (DTA/TG), and Synchrotron Small-Angle X-ray Scattering (SAXS) were used as the instruments in characterizing the PVA hydrogel, respectively to observe the frequency of absorption, thermal degradation, and structural dimensions. The functional groups which represent the PVA polymer chains were verified on the wavenumber of 1450-1480 cm-1 and 850-870 cm-1 which is in accordance with the stretching of -CH2 vibration mode. The absorption band of PVA polymer chains was also found on the wavenumber of 1090-1150 cm-1 which is in accordance with the stretching of carboxyl vibration mode (CO), and this wavenumber gave a contribution towards the crystallinity of PVA polymer. Furthermore, the PVA polymer only interacted with the distilled water in the sample of PVA hydrogel without experiencing any chemical interactions between the PVA polymer and other substances. Meanwhile, the graphic of PVA hydrogel thermal degradation shows three thermal decompositions which are indicated by three areas in which there was sample weight loss. The second decomposition with sample weight loss was equivalent to 61.62%-73.04% occurred at the temperature of 282-376 °C which became the highest sample weight loss due to polymer chain degradation. Teubner-Strey and Beaucage models were used to analyze the characterization of structural dimension and distribution of PVA Hydrogel nanocrystalline with SAXS Synchrotron. With a high compatibility between the model data and the experiment, the average structural dimension of PVA hydrogel nanocrystalline is the equivalent of 3.96 nm, with an inter-crystalline average distance of 16.9 nm. These results indicate that PVA hydrogel is very

  20. Remediation of arsenic and lead with nanocrystalline zinc sulfide.

    PubMed

    Piquette, Alan; Cannon, Cody; Apblett, Allen W

    2012-07-27

    Nanocrystalline (1.7 ± 0.3 nm) zinc sulfide with a specific surface area up to 360 m(2) g(-1) was prepared from the thermal decomposition of a single-source precursor, zinc ethylxanthate. Zinc ethylxanthate decomposes to cubic zinc sulfide upon exposure to temperatures greater than or equal to 125 °C. The resulting zinc sulfide was tested as a water impurity extractant. The target impurities used in this study were As(5+), As(3+), and Pb(2+). The reaction of the nanocrystalline ZnS with Pb(2+) proceeds as a replacement reaction where solid PbS is formed and Zn(2+) is released into the aqueous system. Removal of lead to a level of less than two parts per billion is achievable. The results of a detailed kinetics experiment between the ZnS and Pb(2+) are included in this study. Unlike the instance of lead, both As(5+) and As(3+) adsorb on the surface of the ZnS extractant as opposed to an ion-exchange process. An uptake capacity of > 25 mg g(-1) for the removal of As(5+) is possible. The uptake of As(3+) appears to proceed by a slower process than that of the As(5+) with a capacity of nearly 20 mg g(-1). The nanocrystalline zinc sulfide was extremely successful for the removal of arsenic and lead from simulated oil sand tailing pond water.

  1. Phase stability, crystal structure and magnetism in (U1-xNbx)2 Ni21B6 and (UyNb1-y)3Ni20B6

    NASA Astrophysics Data System (ADS)

    Provino, Alessia; Bhattacharya, Amitava; Dhar, Sudesh K.; Pani, Marcella; Gatti, Flavio; Paudyal, Durga; Manfrinetti, Pietro

    Ternary phases with composition T2M21X6 and T3M20X6 (T = transition metal; M = 3 d metal; X = B, C, P) are reported to crystallize with the W2Cr21C6-type and Mg3Ni20B6-type, respectively (ternary ordered derivatives of the cubic Cr23C6-type, cF116). They attract interest due to their refractory, mechanical, and peculiar magnetic properties. Literature data on these compounds only concern apparently stoichiometric 2:21:6 and 3:20:6 phases. Often only nominal composition has been reported, with few structural refinements and no measurements of physical properties. Lack of detailed stoichiometry and crystallographic data does not allow sufficient understanding of the crystal chemistry and properties of these compounds. We studied stability, crystal structure and magnetism of (U1-xNbx)2 Ni21B6 and (UyNb1-y)3Ni20B6; stable phases are U2Ni21B6 and Nb3Ni20B6, as also confirmed by theoretical calculations. The two pristine compounds solubilize Nb and U, respectively, up to a given extent. The substitution of U by Nb leads to a structural change from the W2Cr21C6- to the Mg3Ni20B6-type. While U2Ni21B6 is a Pauli paramagnet (itinerant non-magnetic state of U-5 f electrons), in agreement with literature, magnetization data for (UyNb1-y)3 Ni20B6 show itinerant ferromagnetism with TC >300 K.

  2. Synthesis and characterization of homoleptic group 10 dithiocarbamate complexes and heteroleptic Ni(II) complexes, and the use of the homoleptic Ni(II) for the preparation of nickel sulphide nanoparticles

    NASA Astrophysics Data System (ADS)

    Bobinihi, Felicia F.; Onwudiwe, Damian C.; Hosten, Eric C.

    2018-07-01

    A series of new dithiocarbamate complexes of Ni(II), Pd(II) and Pt(II) of the form [NiL2], [PdL2] and [PtL2] (where L = N-ethyl-N-ethanoldithiocarbamate) have been synthesized and characterized by elemental analysis, FTIR, and 1H and 13C NMR spectroscopy. The nickel complex was utilized to prepare heteroleptic complexes bearing triphenylphosphino (PPh3) and isothiocyanate (sbnd NCS) or isocyanide (sbnd NC) molecules. Furthermore, the structures of the palladium complex and the heteroleptic nickel with PPh3 and NC molecules have been confirmed by X-ray diffraction. The Pd(II) complex indicated a trans arrangement with a distorted square planar geometry around the Pd atom, while the Ni(II) complex revealed a highly distorted geometry with another molecule of triphenylphosphine moiety, held by hydrogen bonding, within the crystal structure. The thermal stability studies of all the complexes conducted by using thermogravimetric analyser (TGA) showed they all have good stability above 200 °C. The nanoparticles synthesized using the homoleptic nickel complex yielded platelets of pure Heazlewoodite phase of Ni3S2 with average size of 7.60 nm. The optical properties of the nanoparticles studied by using UV-vis spectroscopy showed band gap energy of 4.0 eV (355 nm), which was a blue shift of 1.90 eV compared to the bulk and a consequence of quantum confinement effect.

  3. Ni2C surface carbide to catalyze low-temperature graphene growth

    NASA Astrophysics Data System (ADS)

    Martinez-Gordillo, Rafael; Varvenne, Céline; Amara, Hakim; Bichara, Christophe

    2018-05-01

    The possibility to grow a graphene layer using the chemical-vapor-deposition technique over a Ni2C /Ni (111 ) substrate has been identified experimentally, with the advantage of having a lower processing temperature (T <500 ∘C ), compared to standard growth over a Ni (111 ) surface. To understand the role of the metal carbide/metal catalyst, we first perform a static study of the Ni2C /Ni (111 ) structure and of the binding and removal of a carbon atom at the surface, using both a tight-binding (TB) energetic model and ab initio calculations. Grand-canonical Monte Carlo TB simulations then allow us (i) to determine the thermodynamic conditions to grow graphene and (ii) to separate key reaction steps in the growth mechanism explaining how the Ni2C /Ni (111 ) substrate catalyzes graphene formation at low temperature.

  4. Construction of New Coordination Polymers from 4'-(2,4-disulfophenyl)- 3,2':6'3"-terpyridine: Polymorphism, pH-dependent syntheses, structures, and properties

    NASA Astrophysics Data System (ADS)

    Zhang, Li; Li, Chao-Jie; He, Jia-En; Chen, Yin-Yu; Zheng, Sheng-Run; Fan, Jun; Zhang, Wei-Guang

    2016-01-01

    Nine new coordination compounds, namely, [Co(HDSPTP)2(H2O)4]·4H2O (H2DSPTP=4'-(2,4-disulfophenyl)-3,2':6'3"-terpyridine, 1 and 2), {[Ni(DSPTP)(H2O)4]·3H2O}n (3), {[Cu(HDSPTP)2(H2O)3]·8H2O}n (4), {[Cu(HDSPTP)2(H2O)3]·6H2O}n (5), {[Cu(DSPTP)(H2O)2]·H2O}n (6), {[Zn(DSPTP)(H2O)2]·2H2O}n (7), {[Cd(DSPTP)(H2O)2]·2H2O}n (8), and [Ag2(DSPTP)(H2O)]n (9), were constructed based on a new ligand containing both terpyridyl and sulfo groups. The reactions of H2DSPTP with Co(NO3)2.6H2O resulted in two mononuclear complexes (compounds 1 and 2). They are polymorphisms that display different hydrogen bonding networks. They are selectively synthesized by altering the added alkalis. The reaction of H2DSPTP with Ni(NO3)2·6H2O resulted in a 1D "S-shaped" coordination chain (compound 3). The reactions of Cu(II) with H2DSPTP at different pH value resulted in the following three compounds: two kinds of 1D chains obtained at pH 3.0 and 4.0 for compounds 4 and 5, respectively, and a 3D framework based on binuclear ring units with 4-connected sra topology (Compound 6). The reactions of H2DSPTP with ds-block ions resulted in the following three compounds: a Zn(II) (compound 7) and a Cd(II) (compound 8) 3D frameworks with structures similar to that in compound 6, and a 3D framework based on tetranuclear Ag(I) SBUs with binodal (4,8)-connected flu type 3D framework topology. The structural diversity is mainly attributed to the rich coordination modes (from monodentate to μ7-mode) and conformations (cis-cis and cis-trans) of HDSPTP-/DSPTP2- ligands and the metal center and can be controllable synthesized by altering the alkalis, and pH value. Thermal stability of all compounds was performed, and the thermal behaviors of compounds 6 and 8 were further explored by PXRD. Compound 6 exhibits low thermal stability and undergo a crystalline-crystalline-amorphous phase transition as temperature increases from 25 °C to 200 °C, and show amorphous-crystalline phase transition when rehydrated

  5. EFFECT OF HEAT TREATMENT ON (Cr, Fe)7C3/γ-Fe COATINGS IN SITU SYNTHESIZED BY VACUUM ELECTRON BEAM IRRADIATION

    NASA Astrophysics Data System (ADS)

    Lu, Binfeng; Chen, Yunxia; Xu, Mengjia

    (Cr, Fe)7C3/γ-Fe composite layer has been in situ synthesized on a low carbon steel surface by vacuum electron beam VEB irradiation. The synthesized samples were then subdued to different heat treatments to improve their impaired impact toughness. The microstructure, impact toughness and wear resistance of the heat-treated samples were studied by means of optical microscope (OM), X-ray diffraction (XRD), scanning electron microscope (SEM), microhardness tester, impact test machine and tribological tester. After heat treatment, the primary and eutectic carbides remained in their original shape and size, and a large number of secondary carbides precipitated in the iron matrix. Since the Widmanstatten ferrite in the heat affected zone (HAZ) transformed to fine ferrite completely, the impact toughness of the heat-treated samples increased significantly. The microhardness of the heat-treated samples decreased slightly due to the decreased chromium content in the iron matrix. The wear resistance of 1000∘C and 900∘C heat-treated samples was almost same with the as-synthesized sample. While the wear resistance of the 800∘C heat-treated one decreased slightly because part of the austenite matrix had transformed to ferrite matrix, which reduced the bonding of carbides particulates.

  6. Generalizable, Electroless, Template-Assisted Synthesis and Electrocatalytic Mechanistic Understanding of Perovskite LaNiO3 Nanorods as Viable, Supportless Oxygen Evolution Reaction Catalysts in Alkaline Media.

    PubMed

    McBean, Coray L; Liu, Haiqing; Scofield, Megan E; Li, Luyao; Wang, Lei; Bernstein, Ashley; Wong, Stanislaus S

    2017-07-26

    The oxygen evolution reaction (OER) is a key reaction for water electrolysis cells and air-powered battery applications. However, conventional metal oxide catalysts, used for high-performing OER, tend to incorporate comparatively expensive and less abundant precious metals such as Ru and Ir, and, moreover, suffer from poor stability. To attempt to mitigate for all of these issues, we have prepared one-dimensional (1D) OER-active perovskite nanorods using a unique, simple, generalizable, and robust method. Significantly, our work demonstrates the feasibility of a novel electroless, seedless, surfactant-free, wet solution-based protocol for fabricating "high aspect ratio" LaNiO 3 and LaMnO 3 nanostructures. As the main focus of our demonstration of principle, we prepared as-synthesized LaNiO 3 rods and correlated the various temperatures at which these materials were annealed with their resulting OER performance. We observed generally better OER performance for samples prepared with lower annealing temperatures. Specifically, when annealed at 600 °C, in the absence of a conventional conductive carbon support, our as-synthesized LaNiO 3 rods not only evinced (i) a reasonable level of activity toward OER but also displayed (ii) an improved stability, as demonstrated by chronoamperometric measurements, especially when compared with a control sample of commercially available (and more expensive) RuO 2 .

  7. Generalizable, Electroless, Template-Assisted Synthesis and Electrocatalytic Mechanistic Understanding of Perovskite LaNiO 3 Nanorods as Viable, Supportless Oxygen Evolution Reaction Catalysts in Alkaline Media

    DOE PAGES

    McBean, Coray L.; Liu, Haiqing; Scofield, Megan E.; ...

    2017-07-17

    We present that the oxygen evolution reaction (OER) is a key reaction for water electrolysis cells and air-powered battery applications. However, conventional metal oxide catalysts, used for high-performing OER, tend to incorporate comparatively expensive and less abundant precious metals such as Ru and Ir, and, moreover, suffer from poor stability. To attempt to mitigate for all of these issues, we have prepared one-dimensional (1D) OER-active perovskite nanorods using a unique, simple, generalizable, and robust method. Significantly, our work demonstrates the feasibility of a novel electroless, seedless, surfactant-free, wet solution-based protocol for fabricating “high aspect ratio” LaNiO 3 and LaMnO 3more » nanostructures. As the main focus of our demonstration of principle, we prepared as-synthesized LaNiO 3 rods and correlated the various temperatures at which these materials were annealed with their resulting OER performance. In addition, we observed generally better OER performance for samples prepared with lower annealing temperatures. Specifically, when annealed at 600 °C, in the absence of a conventional conductive carbon support, our as-synthesized LaNiO 3 rods not only evinced (i) a reasonable level of activity toward OER but also displayed (ii) an improved stability, as demonstrated by chronoamperometric measurements, especially when compared with a control sample of commercially available (and more expensive) RuO 2.« less

  8. The effect of pH on the corrosion behavior of intermetallic compounds Ni{sub 3}(Si,Ti) and Ni{sub 3}(Si,Ti) + 2Mo in sodium chloride solutions

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Priyotomo, Gadang, E-mail: gada001@lipi.go.id; Nuraini, Lutviasari, E-mail: Lutviasari@gmail.com; Kaneno, Yasuyuki, E-mail: kaneno@mtr.osakafu-u.ac.id

    The corrosion behavior of the intermetallic compounds, Ni{sub 3}(Si,Ti) (L1{sub 2}: single phase) and Ni{sub 3}(Si,Ti) + 2Mo (L1{sub 2} and (L12 + Ni{sub ss}) mixture region), has been investigated using an immersion test, electrochemical method and surface analytical method (SEM; scanning electron microscope and EDAX: Energy Dispersive X-ray) in 0.5 kmol/m{sup 3} NaCl solutions at various pH. The corrosion behavior of nickel alloy C-276 was studied under the same experimental conditions as a reference. It was found that the uniform attack was observed on Ni{sub 3}(Si,Ti) for the immersion test at lower pH, while the pitting attack was observedmore » on this compound for this test at neutral solution. Furthermore, Ni{sub 3}(Si,Ti)+2Mo had the preferential dissolution of L1{sub 2} compared to (L1{sub 2} + Ni{sub ss}) mixture region at lower pH, while pitting attack occurred in (L1{sub 2} + Ni{sub ss}) mixture region at neutral solution. For both intermetallic compounds, the magnitude of pitting and uniform attack decrease with increasing pH of solutions. From the immersion test and polarization curves, the corrosion resistance of Ni{sub 3}(Si,Ti)+2Mo is lower than that of Ni{sub 3}(Si,Ti), while the nickel alloy C-276 is the highest one at various pH of solutions. On the other hand, in the lower pH of solutions, the corrosion resistance of tested materials decreased significantly compared to those in neutral and higher pH of solutions.« less

  9. Synthesis of H/Bentonite and Ni/Al2O3-bentonite and its application to produce biogasoline from nyamplung seed (Calophyllum inophillum Linn) oil by catalytic hydrocracking

    NASA Astrophysics Data System (ADS)

    Marini, A. T.; Wijaya, K.; Sasongko, N. A.

    2018-03-01

    Hydrocracking process of Nyamplung (Calophyllum inophillum Linn) seed oil to produce biogasoline using H/bentonite and Ni/Al2O3-bentonite that pillared by Al2O3 as catalyst had been conducted. Bentonite was activated by acidification using HF 1% and H2SO4 0.5 M. Ni metal was impregnated into bentonite with two steps reaction; therewas intercalation with Al2O3kegging ion and Ni metal impregnation using NiCl2 metal salt. Catalysts were characterized by infrared spectrophotometer (FTIR), X-ray diffraction (XRD), X-ray fluorescence (XRF), BET, TEM and ammonia adsorption. Hydrocracking reaction was variated by Ni/Al2O3-bentonite and H/bentonite with ratio catalyst/oil 1:100. Biocrude was prepared by extraction by using ethanol 96%. Hydrocracking oil products were further analyzed by GC-MS. The results show that the acidity of bentonite by activation using HF 1% and H2SO4 0.5 M has been increased from 62.58 to 64.62 mmol/g. Impregnation process also increased the acidity of bentonite from 62.58 to 64.89 mmol/g. Activation using HF 1% and H2SO4 0.5 M, intercalation by Al2O3 and impregnation by Ni metal were increasing the crystallinity, surface area, total volume pore and average pore size of bentonite. These techniques were also causeddealumination of bentonite. The hydrocracking process successfully synthesized hydrocarbons with a number of carbon chain between C5-C20 which include bio-gasoline group compounds. Moreover, catalytic processes by H/bentonite and Ni/Al2O3-bentonite also successfully produced 39.83% and 60.37% of biogasoline yields, respectively.

  10. 3D structured Mo-doped Ni3S2 nanosheets as efficient dual-electrocatalyst for overall water splitting

    NASA Astrophysics Data System (ADS)

    Wu, Chengrong; Liu, Bitao; Wang, Jun; Su, Yongyao; Yan, Hengqing; Ng, Chuntan; Li, Cheng; Wei, Jumeng

    2018-05-01

    Searching for a cost-effective, high efficient and stable bifunctional electrocatalyst for overall water-splitting is critical to renewable energy systems. In this study, three-dimensional (3D) curved nanosheets of Mo-doped Ni3S2 grown on nickel foam were successfully synthesized via a one-step hydrothermal process. The hydrogen-evolution reaction (HER) and the oxygen-evolution reaction (OER) in alkaline environment of this 3D catalyst are investigated in detail. The results show that it possesses lower overpotential, high current densities and small Tafel slopes both in OER and HER. For HER, the catalysts show excellent electrochemical performance, demonstrating a low over-potential of 212 mV at 10 mA cm-2 with a large decrease of 127 mV compared to the undoped Ni3S2. And it also shows a lower overpotential of 260 mV at 10 mA cm-2 which decreases 30 mV for OER. In addition, it is only need 1.67 V for the overall water splitting at 10 mA cm-2 which is 70 mV. It found that the Mo element would change the morphology of Ni3S2 and induce much more active sites for HER and OER. The as-prepared Mo-doped Ni3S2 bi-functional electrocatalyst could act as the promising electrode materials for water splitting.

  11. Synthesis, characterization, and biological activity of some novel Schiff bases and their Co(II) and Ni(II) complexes: A new route for Co3O4 and NiO nanoparticles for photocatalytic degradation of methylene blue dye

    NASA Astrophysics Data System (ADS)

    Nassar, Mostafa Y.; Aly, Hisham M.; Abdelrahman, Ehab A.; Moustafa, Moustafa E.

    2017-09-01

    Six novel Co(II) and Ni(II)-triazole Schiff base complexes have been successfully synthesized by refluxing the prepared triazole Schiff bases with CoCl2·6H2O or NiCl2·6H2O. The Schiff base ligands were prepared through condensation of 3-R-4-amino-5-hydrazino-1,2,4-triazole with dibenzoylmethane [Rdbnd H, CH3, and CH2CH3; namely, L1, L2, and L3, respectively]. The prepared Co(II) and Ni(II) complexes have been identified using elemental analysis, FT-IR, UV-Vis, magnetic moment, conductivity, and thermal analysis. On the basis of the conductance results, it was concluded that all the prepared complexes are nonelectrolytes. Interestingly, the prepared Co(II) and Ni(II) complexes were employed as precursors for producing of Co3O4 and NiO nanoparticles, respectively. The produced nanostructures have been identified by XRD, HR-TEM, FT-IR and UV-Vis spectra. The produced nanoparticles revealed good photocatalytic activity for the degradation of methylene blue dye under UV illumination in presence of hydrogen peroxide. The percent of degradation was estimated to be 55.71% in 420.0 min and 90.43% in 360.0 min for Co3O4 and NiO, respectively. Moreover, the synthesized complexes, nano-sized Co3O4, and NiO products have been examined, employing modified Bauer- Kirby method, for antifungal (Candida albicans and Aspergillus flavus) and antibacterial (Staphylococcus aureus and Escherichia coli) activities.

  12. Nanoscale morphology of Ni{sub 50}Ti{sub 45}Cu{sub 5} nanoglass

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Śniadecki, Z., E-mail: sniadecki@ifmpan.poznan.pl; Institute of Nanotechnology, Karlsruhe Institute of Technology, Hermann-von-Helmholtz-Platz 1, D-76344 Eggenstein-Leopoldshafen; Wang, D.

    2016-03-15

    Nanoglasses are noncrystalline solids with a granular nano-/microstructure. In contrast to their nanocrystalline analogs, typically constituted of grains and grain boundaries, nanoglasses consist of glassy regions with a structure corresponding to melt-quenched glasses and amorphous interfaces characterized by a reduced density. Their unique properties can be controlled by modifying size and chemical composition of the granular and interfacial regions. Ni{sub 50}Ti{sub 45}Cu{sub 5} amorphous films were obtained by magnetron sputtering and analyzed to determine their nanoscale morphology and the formation mechanisms. The nanoglasses were noted to have a hierarchical nano-columnar structure with the smallest Ni-rich (Ni:Ti ratio of ca. 5:3)more » amorphous columns with diameters of about 8 nm and Ti-rich glassy interfacial regions with a substantially lower density. The results were obtained utilizing X-ray diffraction and different microscopic methods, e.g., atomic force microscopy and transmission electron microscopy. A detailed analysis indicates the complexity of the formation mechanisms of topologically and chemically distinguishable structural units with curvature driven surface diffusion, surface mobility, self-shadowing and internal stresses as the most important parameters. Common and simple synthesis method and the possibility for easy modification of the morphology and, consequently, the physical properties offer an opportunity for intensive studies of this new class of materials, opening the way towards possible applications. - Highlights: • Ni{sub 50}Ti{sub 45}Cu{sub 5} thin film nanoglasses were synthesized by magnetron sputtering. • Ti amorphous interfacial phase with reduced density is observed. • Stabilization of interfaces by specific local thermodynamic conditions.« less

  13. Structural morphology, upconversion luminescence and optical thermometric sensing behavior of Y2O3:Er(3+)/Yb(3+) nano-crystalline phosphor.

    PubMed

    Joshi, C; Dwivedi, A; Rai, S B

    2014-08-14

    Infrared-to-visible upconverting rare earths Er(3+)/Yb(3+) co-doped Y2O3 nano-crystalline phosphor samples have been prepared by solution combustion method followed by post-heat treatment at higher temperatures. A slight increase in average crystallite size has been found on calcinations verified by X-ray analysis. Transmission electron microscopy (TEM) confirms the nano-crystalline nature of the as-prepared and calcinated samples. Fourier transform infrared (FTIR) analysis shows the structural changes in as-prepared and calcinated samples. Upconversion and downconversion emission recorded using 976 and 532 nm laser sources clearly demonstrates a better luminescence properties in the calcinated samples as compared to as-prepared sample. Upconversion emission has been quantified in terms of standard chromaticity diagram (CIE) showing a shift in overall upconversion emission of as-prepared and calcinated samples. Temperature sensing behaviour of this material has also been investigated by measurement of fluorescence intensity ratio (FIR) of various signals in green emission in the temperature range of 315 to 555 K under 976 nm laser excitation. Copyright © 2014 Elsevier B.V. All rights reserved.

  14. High Energy Density Asymmetric Supercapacitor Based on NiOOH/Ni3S2/3D Graphene and Fe3O4/Graphene Composite Electrodes

    PubMed Central

    Lin, Tsung-Wu; Dai, Chao-Shuan; Hung, Kuan-Chung

    2014-01-01

    The application of the composite of Ni3S2 nanoparticles and 3D graphene as a novel cathode material for supercapacitors is systematically investigated in this study. It is found that the electrode capacitance increases by up to 111% after the composite electrode is activated by the consecutive cyclic voltammetry scanning in 1 M KOH. Due to the synergistic effect, the capacitance and the diffusion coefficient of electrolyte ions of the activated composite electrode are ca. 3.7 and 6.5 times higher than those of the Ni3S2 electrode, respectively. Furthermore, the activated composite electrode exhibits an ultrahigh specific capacitance of 3296 F/g and great cycling stability at a current density of 16 A/g. To obtain the reasonable matching of cathode/anode electrodes, the composite of Fe3O4 nanoparticles and chemically reduced graphene oxide (Fe3O4/rGO) is synthesized as the anode material. The Fe3O4/rGO electrode exhibits the specific capacitance of 661 F/g at 1 A/g and excellent rate capability. More importantly, an asymmetric supercapacitor fabricated by two different composite electrodes can be operated reversibly between 0 and 1.6 V and obtain a high specific capacitance of 233 F/g at 5 mV/s, which delivers a maximum energy density of 82.5 Wh/kg at a power density of 930 W/kg. PMID:25449978

  15. Structural, morphological and electrical properties of Sn-substituted Ni-Zn ferrites synthesized by double sintering technique

    NASA Astrophysics Data System (ADS)

    Ali, M. A.; Uddin, M. M.; Khan, M. N. I.; Chowdhury, F.-U.-Z.; Haque, S. M.

    2017-02-01

    The Sn-substituted Ni-Zn ferrites, (0.0≤x≤0.30), have been synthesized by the standard double sintering technique from the oxide nanopowders of Ni, Zn, Fe and Sn. The structural and electrical properties have been investigated by the X-ray diffraction (XRD), scanning electron microscopy (SEM), DC resistivity and dielectric measurements. From XRD data, the single cubic spinel phase has been confirmed for x≤0.1, whereas for x>0.1 an extra intermediate phase has been detected along with the cubic spinel phase of Ni-Zn ferrite. The grain size is increased due to Sn substitution in Ni-Zn ferrites. DC resistivity as a function of temperature has been measured by two probe method. The semiconducting nature has been found operative in the samples. The DC resistivity was found to decrease whilst the dielectric constant increased with increasing Sn content in Ni-Zn ferrites. The unusual behavior of the dielectric loss factor of the ferrites was explained by the Rezlescu model. The electrical relaxation of the ferrites has been studied in terms of electric modulus formalism and the time for dielectric relaxation was calculated. The contribution of grain resistance has been studied from the Cole-Cole plot. The suitability to use the as prepared samples in the miniaturized memory devices based capacitive components or energy storage principles are confirmed from the values of dielectric constant.

  16. Preparation of nanocrystalline TiN coated cubic boron nitride powders by a sol-gel process.

    PubMed

    Park, Hee S; Umer, M Adeel; Ryu, Ho J; Hong, Soon H

    2011-01-01

    Cubic boron nitride (cBN) particles coated with 20 wt% nanocrystalline TiN were prepared by coating the surface of cBN particles with TiO2, followed by nitridation with NH3 gas at 900 degrees C. Coating of TiO2 on cBN powders was accomplished by a sol-gel process from a solution of titanium (IV) isopropoxide and anhydrous ethanol. An amorphous TiO(x) layer of 50 nm thickness was homogenously formed on the surface of the cBN particles by the sol-gel process. The amorphous layer was then crystallized to an anatase TiO2 phase through calcination in air at 400 degrees C. The crystallized TiO2 layer was 50 nm in thickness, and the size of TiO2 particles comprising the layer was nearly 10 nm. The TiO2 on cBN surfaces was completely converted into nanocrystalline TiN of uniform particles 20 nm in size on cBN particles by nitridation under flowing NH3 gas.

  17. Nanocrystalline Iron-Ore-Based Catalysts for Fischer-Tropsch Synthesis.

    PubMed

    Yong, Seok; Park, Ji Chan; Lee, Ho-Tae; Yang, Jung-Il; Hong, SungJun; Jung, Heon; Chun, Dong Hyun

    2016-02-01

    Nanocrystalline iron ore particles were fabricated by a wet-milling process using an Ultra Apex Mill, after which they were used as raw materials of iron-based catalysts for low-temperature Fischer-Tropsch synthesis (FTS) below 280 degrees C, which usually requires catalysts with a high surface area, a large pore volume, and a small crystallite size. The wet-milling process using the Ultra Apex Mill effectively destroyed the initial crystallite structure of the natural iron ores of several tens to hundreds of nanometers in size, resulting in the generation of nanocrystalline iron ore particles with a high surface area and a large pore volume. The iron-ore-based catalysts prepared from the nanocrystalline iron ore particles effectively catalyzed the low-temperature FTS, displaying a high CO conversion (about 90%) and good C5+ hydrocarbon productivity (about 0.22 g/g(cat)(-h)). This demonstrates the feasibility of using the iron-ore-based catalysts as inexpensive and disposable catalysts for the low-temperature FTS.

  18. Transformation characteristics of TiNi/TiNi alloys synthesized by explosive welding

    NASA Astrophysics Data System (ADS)

    Li, Juntao; Zheng, Yanjun; Cui, Lishan

    2007-10-01

    Effects of severe deformation and heat treatment on the transformation behaviors of explosively welded duplex TiNi/TiNi shape memory alloys (SMAs) were investigated by the differential scanning calorimeter (DSC). The explosively welded duplex TiNi/TiNi plate of 0.7 mm in thickness was cold-rolled at room temperature to the extent of 60% reduction in thickness and then annealed at different temperatures (573-973 K) for different time (15 min-10 h). Low temperature (623-723 K) heat treatment led to amorphous crystallization. At higher temperature (873 K), the re-crystallization took place in the specimens. Analysis showed that the change of internal stresses is just the root cause of the change of transformation temperature. The relationships between the transformation behaviors and the heat treatment were discussed in the present report.

  19. Structural and thermal stabilities of layered Li(Ni 1/3Co 1/3Mn 1/3)O 2 materials in 18650 high power batteries

    NASA Astrophysics Data System (ADS)

    He, Yan-Bing; Ning, Feng; Yang, Quan-Hong; Song, Quan-Sheng; Li, Baohua; Su, Fangyuan; Du, Hongda; Tang, Zhi-Yuan; Kang, Feiyu

    The structural and thermal stabilities of the layered Li(Ni 1/3Co 1/3Mn 1/3)O 2 cathode materials under high rate cycling and abusive conditions are investigated using the commercial 18650 Li(Ni 1/3Co 1/3Mn 1/3)O 2/graphite high power batteries. The Li(Ni 1/3Co 1/3Mn 1/3)O 2 materials maintain their layered structure even when the power batteries are subjected to 200 cycles with 10 C discharge rate at temperatures of 25 and 50 °C, whereas their microstructure undergoes obvious distortion, which leads to the relatively poor cycling performance of power batteries at high charge/discharge rates and working temperature. Under abusive conditions, the increase in the battery temperature during overcharge is attributed to both the reactions of electrolyte solvents with overcharged graphite anode and Li(Ni 1/3Co 1/3Mn 1/3)O 2 cathode and the Joule heat that results from the great increase in the total resistance (R cell) of batteries. The reactions of fully charged Li(Ni 1/3Co 1/3Mn 1/3)O 2 cathodes and graphite anodes with electrolyte cannot be activated during short current test in the fully charged batteries. However, these reactions occur at around 140 °C in the fully charged batteries during oven test, which is much lower than the temperature of about 240 °C required for the reactions outside batteries.

  20. Effect of Biaxial Isothermal Quasi-Continuous Deformation on Structure and Shape Memory Properties of Ti-Ni Alloys

    NASA Astrophysics Data System (ADS)

    Khmelevskaya, I.; Komarov, V.; Kawalla, R.; Prokoshkin, S.; Korpala, G.

    2017-08-01

    Severe plastic deformation (SPD) of Ti-50.0 at.% Ni alloy was carried out using the multi-axial deformation MaxStrain module of Gleeble system at 400, 370, 350 and 330 °C with accumulated true strains from e = 3.5 to 9.5. Kinetics of martensitic transformations was studied by DSC method, the structure features by x-ray diffraction and TEM. The recoverable strain was studied using a bending mode for strain inducing. A mixed nanocrystalline and nanosubgrained structure with average grain/subgrain size below 100 nm has been formed in a bulk sample as a result of SPD at as low as 330 °C. The resulting nanostructure provides an obvious advantage in the completely recoverable strain (9.3%) as compared to SPD at 350-400 °C (7-8%), and to reference treatment (2.5%). That correlates with Vickers hardness changes versus SPD strain.

  1. Microstructural and optical properties of Co doped NiO nanoparticles synthesized by auto combustion using NaOH as fuel

    NASA Astrophysics Data System (ADS)

    Parveen, Azra; Agrawal, Shraddha; Azam, Ameer

    2018-05-01

    The nanoparticles of 5% Co doped NiO were synthesized by auto-combustion method in aqueous medium using NaOH as a fuel. The obtained particles were characterized using X-ray diffraction studies XRD. The results of structural characterization shows the formation of Co doped Nickel oxide nanoparticles in single phase without any impurity. The optical absorption spectra of Co doped NiO sample recorded by UV-VIS spectrophotometer in the range of 200 to 800 nm have been presented. The variation of dielectric constant and dielectric loss has been studied as function of frequency. Co doping affects the optical properties and band gap. NiO can potentially be used in optical, electronic, catalytic materials, antimicrobial agent and super-paramagnetic devices.

  2. Mixed nickel-gallium tellurides Ni{sub 3−x}GaTe{sub 2} as a matrix for incorporating magnetic cations: A Ni{sub 3−x}Fe{sub x}GaTe{sub 2} series

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Kuznetsov, Alexey N., E-mail: alexei@inorg.chem.msu.ru; N.S. Kurnakov Institute of General and Inorganic Chemistry, RAS, Leninsky pr. 31, GSP-1, 119991 Moscow; Stroganova, Ekaterina A.

    Using a high-temperature ampoule technique, a series of mixed nickel-iron-gallium metal-rich tellurides with layered structures, Ni{sub 3-x}Fe{sub x}GaTe{sub 2}, were prepared and characterized based on X-ray powder diffraction, energy-dispersive spectroscopy, and {sup 57}Fe Mössbauer spectroscopy data. These compounds may be regarded as a result of partial substitution of nickel by iron in the recently reported ternary Ni{sub 3-x}GaTe{sub 2} series, which are based on NiAs/Ni{sub 2}In type of structure. The compositional boundary for the substitution was found to be at x~1. According to the Mössbauer spectroscopy data, the substitution is not statistical, and iron atoms with the increase in xmore » tend to preferentially occupy those nickel positions that are partially vacant in the initial ternary compound. Magnetic measurements data for the Ni{sub 3-x}Fe{sub x}GaTe{sub 2} series show dramatic change in behavior from temperature-independent paramagnetic properties of the initial matrix to a low-temperature (~75 K) ferromagnetic ordering in the Ni{sub 2}FeGaTe{sub 2}. - Graphical abstract: Ordered substitution of nickel by iron in the Ni{sub 3−x}GaTe{sub 2} series leading to ferromagnetic ordering. - Highlights: • A series of Ni{sub 3−x}Fe{sub x}GaTe{sub 2} compounds were synthesized. • They adopt the NiAs/Ni{sub 2}In type of structure with ordered iron distribution. • The distribution of iron was studied using {sup 57}Fe Mössbauer spectroscopy. • An increase in iron content leads to the strong ferromagnetic coupling.« less

  3. Optimization of the electrochemical performance of a Ni/Ce0.9Gd0.1O2-δ-impregnated La0.57Sr0.15TiO3 anode in hydrogen

    NASA Astrophysics Data System (ADS)

    Xia, Tian; Brüll, Annelise; Grimaud, Alexis; Fourcade, Sébastien; Mauvy, Fabrice; Zhao, Hui; Grenier, Jean-Claude; Bassat, Jean-Marc

    2014-09-01

    A-site deficient perovskite La0.57Sr0.15TiO3 (LSTO) materials are synthesized by a modified polyacrylamide gel route. X-ray diffraction pattern of LSTO indicates an orthorhombic structure. The thermal expansion coefficient of LSTO is 10.0 × 10-6 K-1 at 600 °C in 5%H2/Ar. LSTO shows an electrical conductivity of 2 S cm-1 at 600 °C in 3%H2O/H2. A new composite material, containing the porous LSTO backbone impregnated with small amounts of Ce0.9Gd0.1O2-δ (CGO) (3.4-8.3 wt.%) and Ni/Cu (2.0-6.3 wt.%), is investigated as an alternative anode for solid oxide fuel cells (SOFCs). Because of the substantial electro-catalytic activity of the fine and well-dispersed Ni particles on the surface of the ceramic framework, the polarization resistance of 6.3%Ni-8.3%CGO-LSTO anode reaches 0.73 Ω cm2 at 800 °C in 3%H2O/H2. In order to further improve the anodic performance, corn starch and carbon black are used as pore-formers to optimize the microstructure of anodes.

  4. Characterization of Nanocrystalline Aluminum Alloy 5083 Powders Produced by Cryogenic Attrition

    DTIC Science & Technology

    2014-11-01

    Characterization of Nanocrystalline Aluminum Alloy 5083 Powders Produced by Cryogenic Attrition by Tiffany Ngo ARL-TN-0643...November 2014 Characterization of Nanocrystalline Aluminum Alloy 5083 Powders Produced by Cryogenic Attrition Tiffany Ngo Weapons and...3. DATES COVERED (From - To) August 2014 4. TITLE AND SUBTITLE Characterization of Nanocrystalline Aluminum Alloy 5083 Powders Produced by

  5. The impedance spectroscopic study and dielectric relaxation in A(Ni1/3Ta2/3)O3 [A=Ba, Ca and Sr

    NASA Astrophysics Data System (ADS)

    Hoque, Md M.; Dutta, A.; Kumar, S.; Sinha, T. P.

    2012-09-01

    We present the results of impedance spectroscopic study with its analytical interpretations in the framework of electric modulus formalism for Barium Nickel Tantalate Ba(Ni1/3Ta2/3)O3 (BNT), Calcium Nickel Tantalate Ca(Ni1/3Ta2/3)O3 (CNT) and Strontium Nickel Tantalate Sr(Ni1/3Ta2/3)O3 (SNT) synthesized by the solid-state reaction technique. The results of powder X-ray diffraction study reveal that BNT and SNT crystallize in cubic structure with lattice parameter a=4.07 Å and 3.98 Å respectively, whereas CNT crystallizes in monoclinic structure having lattice parameters, a=5.71 Å, b=13.45 Å and c=5.47 Å with β=118.3°. The logarithmic angular frequency dependence of the real part of complex dielectric permittivity and loss tangent as a function of temperature indicate significant dielectric relaxation in the samples, which have been explained by the Debye theory. The frequency dependence of the loss peak and the imaginary part of electrical modulus are found to obey the Arrhenius law. The relaxation mechanism of these samples is modeled by the Cole-Cole equation. This confirms that the polarization mechanism in BNT, CNT and SNT is due to the bulk effect arising in semiconductive grains. The scaling behavior of imaginary part of electric modulus M″ suggests that the relaxation describes the same mechanism at various temperatures but relaxation frequency is strongly temperature dependent. The normalized peak positions of tan δ/tan δm and M″/M″m versus log ω for BNT, CNT and SNT do not overlap completely and are very close to each other. These indicate the presence of both long-range and localized relaxation. Due to their high dielectric constant and low loss tangent, these materials may find several technological applications such as in capacitors, resonators, filters and integrated circuits.

  6. A scanning tunnelling microscopy study of C and N adsorption phases on the vicinal Ni(100) surfaces Ni(810) and Ni(911)

    NASA Astrophysics Data System (ADS)

    Driver, S. M.; Toomes, R. L.; Woodruff, D. P.

    2016-04-01

    The influence of N and C chemisorption on the morphology and local structure of nominal Ni(810) and Ni(911) surfaces, both vicinal to (100) but with [001] and [ 01 1 bar ] step directions, respectively, has been investigated using scanning tunnelling microscopy (STM) and low energy electron diffraction. Ni(911) undergoes substantial step bunching in the presence of both adsorbates, with the (911)/N surface showing (411) facets, whereas for Ni(810), multiple steps 2-4 layers high are more typical. STM atomic-scale images show the (2 × 2)pg 'clock' reconstruction on the (100) terraces of the (810) surfaces with both C and N, although a second c(2 × 2) structure, most readily reconciled with a 'rumpling' reconstruction, is also seen on Ni(810)/N. On Ni(911), the clock reconstruction is not seen on the (100) terraces with either adsorbate, and these images are typified by protrusions on a (1 × 1) mesh. This absence of clock reconstruction is attributed to the different constraints imposed on the lateral movements of the surface Ni atoms adjacent to the up-step edge of the terraces with a [ 01 1 bar ] step direction.

  7. Understanding micro-diffusion bonding from the fabrication of B4C/Ni composites

    NASA Astrophysics Data System (ADS)

    Wang, Miao; Wang, Wen-xian; Chen, Hong-sheng; Li, Yu-li

    2018-03-01

    A Ni-B4C macroscopic diffusion welding couple and a Ni-15wt%B4C composite fabricated by spark plasma sintering (SPS) were used to understand the micro-scale diffusion bonding between metals and ceramics. In the Ni-B4C macroscopic diffusion welding couple a perfect diffusion welding joint was achieved. In the Ni-15wt%B4C sample, microstructure analyses demonstrated that loose structures occurred around the B4C particles. Energy dispersive X-ray spectroscopy analyses revealed that during the SPS process, the process of diffusion bonding between Ni and B4C particles can be divided into three stages. By employing a nano-indentation test, the room-temperature fracture toughness of the Ni matrix was found to be higher than that of the interface. The micro-diffusion bonding between Ni and B4C particles is quite different from the Ni-B4C reaction couple.

  8. High Temperature Oxidation Behavior of gamma-Ni+gamma'-Ni3Al Alloys and Coatings Modified with Pt and Reactive Elements

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Mu, Nan

    2007-12-01

    Materials for high-pressure turbine blades must be able to operate in the high-temperature gases (above 1000 C) emerging from the combustion chamber. Accordingly, the development of nickel-based superalloys has been constantly motivated by the need to have improved engine efficiency, reliability and service lifetime under the harsh conditions imposed by the turbine environment. However, the melting point of nickel (1455 C) provides a natural ceiling for the temperature capability of nickel-based superalloys. Thus, surface-engineered turbine components with modified diffusion coatings and overlay coatings are used. Theses coatings are capable of forming a compact and adherent oxide scale, which greatly impedesmore » the further transport of reactants between the high-temperature gases and the underlying metal and thus reducing attack by the atmosphere. Typically, these coatings contain β-NiAl as a principal constituent phase in order to have sufficient aluminum content to form an Al 2O 3 scale at elevated temperatures. The drawbacks to the currently-used {beta}-based coatings, such as phase instabilities, associated stresses induced by such phase instabilities, and extensive coating/substrate interdiffusion, are major motivations in this study to seek next-generation coatings. The high-temperature oxidation resistance of novel Pt + Hf-modified γ-Ni + γ-Ni 3Al-based alloys and coatings were investigated in this study. Both early-stage and 4-days isothermal oxidation behavior of single-phase γ-Ni and γ'-Ni 3Al alloys were assessed by examining the weight changes, oxide-scale structures, and elemental concentration profiles through the scales and subsurface alloy regions. It was found that Pt promotes Al 2O 3 formation by suppressing the NiO growth on both γ-Ni and γ'Ni 3Al single-phase alloys. This effect increases with increasing Pt content. Moreover, Pt exhibits this effect even at lower temperatures (~970 C) in the very early stage of oxidation. It was

  9. Fabrication and characterization of He-charged ODS-FeCrNi films deposited by a radio-frequency plasma magnetron sputtering technique

    NASA Astrophysics Data System (ADS)

    Song, Liang; Wang, Xianping; Wang, Le; Zhang, Ying; Liu, Wang; Jiang, Weibing; Zhang, Tao; Fang, Qianfeng; Liu, Changsong

    2017-04-01

    He-charged oxide dispersion strengthened (ODS) FeCrNi films were prepared by a radio-frequency (RF) plasma magnetron sputtering method in a He and Ar mixed atmosphere at 150 °C. As a comparison, He-charged FeCrNi films were also fabricated at the same conditions through direct current (DC) plasma magnetron sputtering. The doping of He atoms and Y2O3 in the FeCrNi films was realized by the high backscattered rate of He ions and Y2O3/FeCrNi composite target sputtering method, respectively. Inductive coupled plasma (ICP) and x-ray photoelectron spectroscopy (XPS) analysis confirmed the existence of Y2O3 in FeCrNi films, and Y2O3 content hardly changed with sputtering He/Ar ratio. Cross-sectional scanning electron microscopy (SEM) shows that the FeCrNi films were composed of dense columnar nanocrystallines and the thickness of the films was obviously dependent on He/Ar ratio. Nanoindentation measurements revealed that the FeCrNi films fabricated through DC/RF plasma magnetron sputtering methods exhibited similar hardness values at each He/Ar ratio, while the dispersion of Y2O3 apparently increased the hardness of the films. Elastic recoil detection (ERD) showed that DC/RF magnetron sputtered FeCrNi films contained similar He amounts (˜17 at.%). Compared with the minimal change of He level with depth in DC-sputtered films, the He amount decreases gradually in depth in the RF-sputtered films. The Y2O3-doped FeCrNi films were shown to exhibit much smaller amounts of He owing to the lower backscattering possibility of Y2O3 and the inhibition effect of nano-sized Y2O3 particles on the He element.

  10. Cavitation resistance of surface composition "Steel-Ni-TiNi-TiNiZr-cBNCo", formed by High-Velocity Oxygen-Fuel spraying

    NASA Astrophysics Data System (ADS)

    Blednova, Zh. M.; Dmitrenko, D. V.; Balaev, E. U. O.

    2018-01-01

    The object of the study is a multilayered surface composition "Steel - a Multicomponent material with Shape Memory Effect - a wear-resistant layer" under conditions of cavitation effects in sea water. Multicomponent TiNi-based coatings with addition of alloying elements such as Zr in an amount up to 10% mass, allow to create a composite material with a gradient of properties at the interface of layers, which gives new properties to coatings and improves their performance significantly. The use of materials with shape memory effect (SME) as surface layers or in the composition of surface layered compositions allows to provide an effective reaction of materials to the influence of external factors and adaptation to external influences. The surface composite layer cBN-10%Co has high hardness and strength, which ensures its resistance to shock cyclic influences of collapsing caverns. The increased roughness of the surface of a solid surface composite in the form of strong columnar structures ensures the crushing of vacuum voids, redistributing their effect on the entire surface, and not concentrating them in certain zones. In addition, the gradient structure of the multilayer composite coating TiNi-Ti33Ni49Zr18-cBN-10%Co Co makes it possible to create conditions for the relaxation of stresses created by the variable impact load of cavitation caverns and the manifestation of compensating internal forces due to thermo-elastic martensitic transformations of SME materials. The cavitation resistance of the coating TiNi-Ti33Ni49Zr18-cBN-10%Co according to the criterion of mass wear is 15-20 times higher than that of the base material without coating and 10-12 times higher than that of the TiNi-TiNiZr coating. The proposed architecture of the multifunctional gradient composition, "steel-Ni-TiNi- Ti33Ni49Zr18-cBN-10%Co", each layer of which has its functional purpose, allows to increase the service life of parts operating under conditions of cavitation-fatigue loading in

  11. Preparation and Characterization of NiMo/Al2O3Catalyst for Hydrocracking Processing

    NASA Astrophysics Data System (ADS)

    Widiyadi, Aditya; Guspiani, Gema Adil; Riady, Jeffry; Andreanto, Rikky; Chaiunnisa, Safina Dea; Widayat

    2018-02-01

    Hydrocracking is a chemical process used in petroleum refineries for converting high boiling hydrocarbons in petroleum crude oils to more valuable lower boiling products such as gasoline, kerosene, and diesel oil that operate at high temperature and pressure. Catalyst was used in hydrocracking to reduce temperature and pressure. Hydrocracking catalyst are composed of active components and support. Alumina is widely used in hydrocracking process as catalyst support due to its high surface area, high thermal stability, and low prices. The objective of this research was preparated NiMo/Al2O3 catalyst that used as hydrocracking catalyst. Catalyst was synthesized by wetness impregnation method and simple heating method with various kind of Al2O3. The physicochemical properties of catalyst were investigated by X-ray diffraction (XRD) to determine type of crystal and scanning electron microscopy (SEM) to determine morphology of the catalyst. The NiMo/Al2O3 catalyst prepared by aluminium potassium sulfate dodecahydrate exhibited the highest crystallinity of 90.23% and it is clear that MoO3 and NiO crystallites are highly dispersed on the NiMo/Al2O3 catalyst which indicates as the best catalyst. The catalytic activity in hydrocracking process was successfully examined to convert fatty acid into hydrocarbon.

  12. Electrocatalytic performances of LaNi1-xMgxO3 perovskite oxides as bi-functional catalysts for lithium air batteries

    NASA Astrophysics Data System (ADS)

    Du, Zhenzhen; Yang, Peng; Wang, Long; Lu, Yuhao; Goodenough, J. B.; Zhang, Jian; Zhang, Dawei

    2014-11-01

    Mg-doped perovskite oxides LaNi1-xMgxO3 (x = 0, 0.08, 0.15) electrocatalysts are synthesized by a sol-gel method using citric acid as complex agent and ethylene glycol as thickening agent. The intrinsic oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) activity of as-prepared perovskite oxides in aqueous electrolyte are examined on a rotating disk electrode (RDE) set up. Li-air primary batteries on the basis of Mg-doped perovskite oxides LaNi1-xMgxO3 (x = 0, 0.08, 0.15) and nonaqueous electrolyte are also fabricated and tested. In terms of the ORR current densities and OER current densities, the performance is enhanced in the order of LaNiO3, LaNi0.92Mg0.08O3 and LaNi0.85Mg0.15O3. Most notably, partially substituting nickel with magnesium suppresses formation of Ni2+ and ensures high concentration of both OER and ORR reaction energy favorable Ni3+ (eg = 1) on the surface of perovskite catalysts. Nonaqueous Li-air primary battery using LaNi0.92Mg0.08O3 and LaNi0.85Mg0.15O3 as the cathode catalysts exhibit improved performances compared with LaNiO3 catalyst, which are consistent with the ORR current densities.

  13. Analyzing and Modelling the Corrosion Behavior of Ni/Al2O3, Ni/SiC, Ni/ZrO2 and Ni/Graphene Nanocomposite Coatings

    PubMed Central

    Saeed, Adil; Braun, Wolfgang; Bajwa, Rizwan; Rafique, Saqib

    2017-01-01

    A study has been presented on the effects of intrinsic mechanical parameters, such as surface stress, surface elastic modulus, surface porosity, permeability and grain size on the corrosion failure of nanocomposite coatings. A set of mechano-electrochemical equations was developed by combining the popular Butler–Volmer and Duhem expressions to analyze the direct influence of mechanical parameters on the electrochemical reactions in nanocomposite coatings. Nanocomposite coatings of Ni with Al2O3, SiC, ZrO2 and Graphene nanoparticles were studied as examples. The predictions showed that the corrosion rate of the nanocoatings increased with increasing grain size due to increase in surface stress, surface porosity and permeability of nanocoatings. A detailed experimental study was performed in which the nanocomposite coatings were subjected to an accelerated corrosion testing. The experimental results helped to develop and validate the equations by qualitative comparison between the experimental and predicted results showing good agreement between the two. PMID:29068395

  14. Spectroscopic features of Ni(2+) ion in PbO-Bi2O3-SiO2 glass system.

    PubMed

    Suresh, B; Srinivasa Reddy, M; Siva Sesha Reddy, A; Gandhi, Y; Ravi Kumar, V; Veeraiah, N

    2015-04-15

    Glasses of the composition (30-x)PbO-5Bi2O3-65SiO2: xNiO (with x ranging from 0 to 1.0 mol%) were synthesized. A variety of spectroscopic studies, viz., IR, Raman optical absorption and luminescence properties of these glasses have been carried out as a function of NiO concentration. The analysis of results of all these studies has indicated that the nickel ions occupy both octahedral and tetrahedral positions. However, with the increase of NiO concentration the octahedral occupancy of Ni(2+) ions prevailed over the tetrahedral ions. The luminescence spectra of these glasses have exhibited a broad NIR emission band in region 1100-1500 nm. This band is identified as being due to (3)T2(3F)→(3)A2(3F) octahedral transition of Ni(2+) ions. The luminescence efficiency and cross section have been found to be the highest for the glass containing the highest concentration of NiO. The reasons for such high luminescence efficiency have been discussed in the light of structural variations taking place in the host glass network. Copyright © 2015 Elsevier B.V. All rights reserved.

  15. Selective oxidation of cube textured Ni and Ni-Cr substrate for the formation of cube textured NiO as a component buffer layer for REBa 2Cu 3O 7+ x (REBCO) coated conductors

    NASA Astrophysics Data System (ADS)

    Lockman, Z.; Goldacker, W.; Nast, R.; deBoer, B.; MacManus-Driscoll, J. L.

    2002-08-01

    Thermal oxidation of cube textured, pure Ni and Ni-Cr tapes was undertaken under different oxidation conditions to form cube textured NiO for the use as a first component of buffer layer for the coated conductor. Cube textured NiO was formed on pure Ni after oxidising for more than 130 min in O 2 at 1250 °C. The oxide thickness was >30 μm. Much shorter oxidation times (20-40 min, NiO thickness of ∼5 μm) and lower temperature (1050 °C) were required to form a similar texture on Ni-Cr foils. In addition, NiO formed on Ni-13%Cr was more highly textured than Ni-10%Cr. A Cr 2O 3 inner layer and NiO outer layer was formed on the Ni-Cr alloys.

  16. Morphological evolution of Bi2Se3 nanocrystalline materials synthesized by microwave assisted solvothermal method

    NASA Astrophysics Data System (ADS)

    Bera, Sumit; Behera, P.; Mishra, A. K.; Krishnan, M.; Patidar, M. M.; Singh, D.; Gangrade, M.; Venkatesh, R.; Deshpande, U. P.; Phase, D. M.; Ganesan, V.

    2018-04-01

    Structural, morphological and spectroscopic properties of Bi2Se3 nanoparticles synthesized by microwave assisted solvothermal method were investigated systematically. A controlled synthesis of different morphologies by a small variation in synthesis procedure is demonstrated. Powder X-ray diffraction (XRD) confirmed the formation of single phase. Crystallite and particle size reductions were studied with XRD and AFM (Atomic Force Microscopy). Different morphologies such as hexagonal nanoflakes with cross section of around˜6µm, nanoflower and octahedral agglomerated crystals of nearly ˜60 nm size have been observed in scanning electron microscope while varying the microwave assisted synthesis procedures. A significant blue shift observed in diffuse reflectance spectroscopy evidences the energy gap tuning as a result of morphological evolution. The difference in morphology observed in this three fast, facile and scalable synthesis is advantageous for tuning the thermoelectric figure of merit and for probing the surface states of these topological insulators. Low temperature resistivity remains similar for all three variants depicting a 2D character as evidenced by a -lnT term of localization.

  17. Metal-Insulator Transition of strained SmNiO3 Thin Films: Structural, Electrical and Optical Properties

    PubMed Central

    Torriss, B.; Margot, J.; Chaker, M.

    2017-01-01

    Samarium nickelate (SmNiO3) thin films were successfully synthesized on LaAlO3 and SrTiO3 substrates using pulsed-laser deposition. The Mott metal-insulator (MI) transition of the thin films is sensitive to epitaxial strain and strain relaxation. Once the strain changes from compressive to tensile, the transition temperature of the SmNiO3 samples shifts to slightly higher values. The optical conductivity reveals the strong dependence of the Drude spectral weight on the strain relaxation. Actually, compressive strain broadens the bandwidth. In contrast, tensile strain causes the effective number of free carriers to reduce which is consistent with the d-band narrowing. PMID:28098240

  18. Divergent Total Syntheses of (-)-Huperzine Q, (+)-Lycopladine B, (+)-Lycopladine C, and (-)-4-epi-Lycopladine D.

    PubMed

    Hong, Benke; Hu, Dachao; Wu, Jinbao; Zhang, Jing; Li, Houhua; Pan, Yingming; Lei, Xiaoguang

    2017-07-04

    We report herein our synthetic efforts towards the divergent syntheses of (-)-huperzine Q (1), (+)-lycopladine B (2), (+)-lycopladine C (3), and (-)-lycopladine D (4). The 10-step total synthesis of (-)-huperzine Q (1) and the first total syntheses of (+)-lycopladines B (2) and C (3) were accomplished through a series of cascade reactions. Our approach involved a Michael addition/aldol/intramolecular C-alkylation sequence to forge the 6/9 spirocycle ring, and this was followed by an ethylene-accelerated carbonyl-olefin metathesis to construct the common 6/5/9 ring system. Finally, late-stage enamine bromofunctionalization enabled us to access (-)-huperzine Q (1), (+)-lycopladine B (2), and (+)-lycopladine C (3), and a tandem C4-epimerization/retro-Claisen condensation furnished (-)-4-epi-lycopladine D (63). © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  19. Influences of neodymium doping on magnetic and electrochemical properties of Li3V2(PO4)3/C synthesized via a sol-gel method

    NASA Astrophysics Data System (ADS)

    Liu, Liying; Qiu, Yongbin; Mai, Yongzhi; Wu, Qibai; Zhang, Haiyan

    2015-11-01

    A series of neodymium doped Li3V2-xNdx(PO4)3/C cathode materials have been successfully synthesized by a citric acid assisted sol-gel method. Nd doped samples (x ≤ 0.10) have well developed monoclinic structure of Li3V2(PO4)3 with enlarged unit cell volume. All samples present typical characteristics of paramagnetism in 4 < T ≤ 300 K, but the magnetic susceptibilities of Nd doped samples increase with Nd content (except for x = 0.15). Nd doped composites show better electrochemical property than that of the undoped one. Among them, the Li3V1.95Nd0.05(PO4)3/C displays the highest capacity and best cycle stability. The Li3V1.95Nd0.05(PO4)3/C presents the first discharge capacity of 129.2 mAh g-1 at 1 C rate in the voltage range of 3.0-4.3 V, 21.7% higher than that of Li3V2(PO4)3/C. And no capacity loss occurs after 100 cycles. The high structural stability, low charge-transfer resistance and rapid Li+ diffusion due to the presence of Nd3+ are mainly responsible for the superior electrochemical performance of Nd doped Li3V2(PO4)3/C cathode materials.

  20. Thermal conductivity of amorphous and nanocrystalline silicon films prepared by hot-wire chemical-vapor deposition

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Jugdersuren, B.; Kearney, B. T.; Queen, D. R.

    We report 3..omega.. thermal conductivity measurements of amorphous and nanocrystalline silicon thin films from 85 to 300 K prepared by hot-wire chemical-vapor deposition, where the crystallinity of the films is controlled by the hydrogen dilution during growth. The thermal conductivity of the amorphous silicon film is in agreement with several previous reports of amorphous silicon prepared by a variety of deposition techniques. The thermal conductivity of the as-grown nanocrystalline silicon film is 70% higher and increases 35% more after an anneal at 600 degrees C. They all have similarly weak temperature dependence. Structural analysis shows that the as-grown nanocrystalline siliconmore » is approximately 60% crystalline, nanograins and grain boundaries included. The nanograins, averaging 9.1 nm in diameter in the as-grown film, are embedded in an amorphous matrix. The grain size increases to 9.7 nm upon annealing, accompanied by the disappearance of the amorphous phase. We extend the models of grain boundary scattering of phonons with two different non-Debye dispersion relations to explain our result of nanocrystalline silicon, confirming the strong grain size dependence of heat transport for nanocrystalline materials. However, the similarity in thermal conductivity between amorphous and nanocrystalline silicon suggests the heat transport mechanisms in both structures may not be as dissimilar as we currently understand.« less