scholarly journals Effects of Mo Concentration on the Structural and Corrosion Properties of Cu–Alloy

Metals ◽  
2019 ◽  
Vol 9 (12) ◽  
pp. 1307
Author(s):  
Oscar Hernández ◽  
Claudio Aguilar ◽  
Ariosto Medina
Keyword(s):  
Mechanical Alloying ◽  
Load Transfer ◽  
High Energy ◽  
Corrosion Properties ◽  
Transmission Electron Microscopy Analysis ◽  
X Ray ◽  
Electrochemical Tests ◽  
Cu Alloy ◽  
Transmission Electron ◽  
Electron Microscopy Analysis

Mechanical Alloying (MA) has the ability to extend the solubility limits of immiscible alloys in a solid state. In this work, a Cu-10 wt% Mo alloy was synthesized by mechanical alloying, using a high-energy mill type SPEX. The X-ray diffraction and Rietveld results show a crystallite size of 24 and 22 nm of Cu and Mo, respectively, with an occupation value of Mo inside the Cu structure of 27%, which was identificated by Energy Dispersive X-ray Spectroscopy and High-Resolution Transmission Electron Microscopy analysis. After that, the alloy was sinterized in an oven, heating the alloy to 1000 °C—close to the melting point of Cu (1085 °C). Electrochemical tests were carried out under a saline environment of synthetic seawater. The results show that the polarization curve of the alloy showed a pitting corrosion at about 134.83 mV, as well as a repasivation phenomenon (Erp = 241.47 mV) in the cathodic branch. Finally, three time constants were observed in the Nyquist diagrams: formation of a corrosion product film, load transfer, and diffusion, indicating that the corrosion properties in this alloy were improved compared with other Cu–alloys.

scholarly journals Purification and Characterization of the [NiFe]-Hydrogenase of Shewanella oneidensis MR-1

2011 ◽  
Vol 77 (16) ◽  
pp. 5584-5590 ◽  
Author(s):  
Liang Shi ◽  
Sara M. Belchik ◽  
Andrew E. Plymale ◽  
Steve Heald ◽  
Alice C. Dohnalkova ◽  
...  
Keyword(s):  
Methyl Viologen ◽  
Shewanella Oneidensis ◽  
Tris Buffer ◽  
Transmission Electron Microscopy Analysis ◽  
Content Type ◽  
X Ray ◽  
Hepes Buffer ◽  
Transmission Electron ◽  
Genes Encoding ◽  
Electron Microscopy Analysis

ABSTRACTShewanella oneidensisMR-1 possesses a periplasmic [NiFe]-hydrogenase (MR-1 [NiFe]-H2ase) that has been implicated in H2production and oxidation as well as technetium [Tc(VII)] reduction. To characterize the roles of MR-1 [NiFe]-H2ase in these proposed reactions, the genes encoding both subunits of MR-1 [NiFe]-H2ase were cloned and then expressed in an MR-1 mutant withouthyaBandhydAgenes. Expression of recombinant MR-1 [NiFe]-H2ase intransrestored the mutant's ability to produce H2at 37% of that for the wild type. Following purification, MR-1 [NiFe]-H2ase coupled H2oxidation to reduction of Tc(VII)O4−and methyl viologen. Change of the buffers used affected MR-1 [NiFe]-H2ase-mediated reduction of Tc(VII)O4−but not methyl viologen. Under the conditions tested, all Tc(VII)O4−used was reduced in Tris buffer, while in HEPES buffer, only 20% of Tc(VII)O4−was reduced. The reduced products were soluble in Tris buffer but insoluble in HEPES buffer. Transmission electron microscopy analysis revealed that Tc precipitates reduced in HEPES buffer were aggregates of crystallites with diameters of ∼5 nm. Measurements with X-ray absorption near-edge spectroscopy revealed that the reduction products were a mixture of Tc(IV) and Tc(V) in Tris buffer but only Tc(IV) in HEPES buffer. Measurements with extended X-ray adsorption fine structure showed that while the Tc bonding environment in Tris buffer could not be determined, the Tc(IV) product in HEPES buffer was very similar to Tc(IV)O2·nH2O, which was also the product of Tc(VII)O4−reduction by MR-1 cells. These results shows for the first time that MR-1 [NiFe]-H2ase catalyzes Tc(VII)O4−reduction directly by coupling to H2oxidation.

scholarly journals (Al,Mg)3La: a new phase in the Mg–Al–La system

2018 ◽  
Vol 74 (4) ◽  
pp. 370-375 ◽  
Author(s):  
Charlotte Wong ◽  
Mark J. Styles ◽  
Suming Zhu ◽  
Dong Qiu ◽  
Stuart D. McDonald ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Powder Diffraction ◽  
Dark Field ◽  
Transmission Electron Microscopy Analysis ◽  
X Ray ◽  
Transmission Electron ◽  
Scanning Transmission ◽  
Annular Dark Field ◽  
Electron Microscopy Analysis

During an investigation of the Mg-rich end of the Mg–Al–La system, a new ternary phase with the composition of (Al,Mg)3La was identified. The crystal structure of this phase was determined by conventional X-ray powder diffraction and transmission electron microscopy analysis and refined using high-resolution X-ray powder diffraction. The (Al,Mg)3La phase is found to have an orthorhombic structure with a space group of C2221 and lattice parameters of a = 4.3365 (1) Å, b = 18.8674 (4) Å and c = 4.4242 (1) Å, which is distinctly different from the binary Al3La phase (P63/mmc). The resolved structure of the (Al,Mg)3La phase is further verified by high-angle annular dark-field scanning transmission electron microscopy.

Electron Microscopy Studies of Potassium Sodium Niobate Ceramics

2005 ◽  
Vol 11 (6) ◽  
pp. 572-580 ◽  
Author(s):  
Darja Jenko ◽  
Andreja Benčan ◽  
Barbara Malič ◽  
Janez Holc ◽  
Marija Kosec
Keyword(s):  
Electron Microscopy ◽  
Secondary Phase ◽  
Nominal Composition ◽  
Potassium Sodium Niobate ◽  
Transmission Electron Microscopy Analysis ◽  
X Ray ◽  
Transmission Electron ◽  
Ferroelectric Domains ◽  
Electron Microscopy Analysis ◽  
Microscopy Analysis

Using electron microscopy, K0.5Na0.5NbO3 (KNN) ceramics sintered at 1030°C for 8 h and 1100°C for 2 and 24 h was studied. The scanning electron microscopy and X-ray spectrometry revealed that the materials consisted of a matrix phase in which the (Na+K)/Nb ratio corresponded closely to the nominal composition and a small amount of Nb-rich secondary phase. A bimodal microstructure of cube-shaped grains was revealed in the fracture and thermally-etched surfaces of the KNN. In the ceramics sintered at 1100°C, the larger grains (up to 30 μm across), contained angular trapped pores. The transmission electron microscopy analysis revealed that the crystal planes of the grains bordering the intragranular pore faces were of the {100} family with respect to the simple perovskite cell. Ferroelectric domains were observed in the grains of this material.

Investigation of Grain Boundaries in an Al-Mg-Si-Cu Alloy

2014 ◽  
Vol 794-796 ◽  
pp. 951-956 ◽  
Author(s):  
Jon Holmestad ◽  
Martin Ervik ◽  
Calin D. Marioara ◽  
John Charles Walmsley
Keyword(s):  
Electron Microscopy ◽  
Heat Treatment ◽  
Transmission Electron Microscopy ◽  
Grain Boundaries ◽  
Solution Heat Treatment ◽  
High Angle ◽  
Corrosion Properties ◽  
X Ray ◽  
Cu Alloy ◽  
Transmission Electron

The grain boundaries of a fibrous Al-Mg-Si-Cu alloy have been investigated with Transmission Electron Microscopy. The compositions have been mapped by Energy Dispersive X-ray Spectroscopy. The alloy has been aged for 12 hours at 155°C after solution heat treatment and is in a slightly underaged condition. The precipitates nucleated on the high angle grain boundaries are coarse, while the precipitates on the low angle grain boundaries are smaller and more numerous. The precipitates on both types of grain boundaries has been identified as Q'-type. Copper is segregated to both the low and high angle grain boundaries. The effect of this segregation will be discussed with regards to the corrosion properties of the alloy.

FORMATION OF TWO LAYERS IN Pr1-xCaxBa2Cu3O7-y(0≤x≤0.5) THIN FILMS DEPOSITED AT DIFFERENT TEMPERATURES

2000 ◽  
Vol 14 (16) ◽  
pp. 1651-1657
Author(s):  
J. A. DÍAZ ◽  
O. CONTRERAS ◽  
J. M. SIQUEIROS
Keyword(s):  
Thin Films ◽  
X Ray Diffraction ◽  
Stabilized Zirconia ◽  
Transmission Electron Microscopy Analysis ◽  
X Ray ◽  
Cell Parameters ◽  
Transmission Electron ◽  
Electron Microscopy Analysis ◽  
Different Temperatures ◽  
Microscopy Analysis

We have grown epitaxial Pr 1-x Ca x Ba 2 Cu 3 O 7-y(0≤x≤0.5) thin films on SrTiO 3 and Yttrium stabilized zirconia (YSZ) substrates by pulsed laser deposition at different temperatures. X-ray diffraction and transmission electron microscopy analysis revealed epitaxial growth on YSZ substrates for x=0 along the a and c axis directions for T=570° C , where first the film grows oriented along a-axis and afterward, it undergoes a shift in the orientation, growing in the c-axis direction from then on. The cell parameters were c=1.166 nm and a~b=0.386 nm .

Growth and Characterization of C-Axis Oriented YBa2Cu3O7-x/PrBa2Cu3O7-x Bilayers

1999 ◽  
Vol 13 (09n10) ◽  
pp. 1005-1010 ◽  
Author(s):  
C. Beneduce ◽  
F. Bobba ◽  
M. Boffa ◽  
M. C. Cucolo ◽  
A. M. Cucolo ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
X Ray Diffraction ◽  
Transmission Electron Microscopy Analysis ◽  
X Ray ◽  
Resistivity Measurements ◽  
Transmission Electron ◽  
High Oxygen Pressure ◽  
Electron Microscopy Analysis ◽  
Microscopy Analysis

We report on the preparation and characterization of YBa 2 Cu 3 O 7-x/ PrBa 2 Cu 3 O 7-x bilayers onto (100) SrTiO 3 substrates. The samples have been prepared by sequential dc sputtering processes in high oxygen pressure from stoichiometric targets. The structural characterization of the YBa 2 Cu 3 O 7-x and PrBa 2 Cu 3 O 7-x films and of the bilayers has been performed by means of X-ray diffraction. The Scanning Electron Microscopy analysis has showed that the film surfaces are flat and free of precipitates. A detailed study of the interfaces has been performed by Transmission Electron Microscopy analysis. The electrical resistivity measurements showed for the YBa 2 Cu 3 O 7-x films sharp superconducting transitions at 91.5 K and critical current density of about 106 A/cm 2 at 77 K, while for the PrBa 2 Cu 3 O 7-x films a semiconductor-like behavior has been observed.

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