scholarly journals Synthesis, Characterization and Ageing of MgB2

2001 ◽  
Vol 689 ◽  
Author(s):  
A. Serquis ◽  
R. Schulze ◽  
Y. T. Zhu ◽  
J. Y. Coulter ◽  
D. E. Peterson ◽  
...  
Keyword(s):  
Photoelectron Spectroscopy ◽  
Rietveld Analysis ◽  
Superconducting Transition ◽  
Superconducting Properties ◽  
Ambient Conditions ◽  
X Ray ◽  
Grain Sizes ◽  
Crystal Strain ◽  
Surface Decomposition ◽  
Meissner Fraction

ABSTRACTWe studied the influence of sample preparation and defects in the superconducting properties samples using atomic ratios of Mg:B=1:1 and Mg:B=1:2. Samples were characterized by SEM, and XRD, and the magnetization properties were examined in a SQUID magnetometer. The presence of Mg vacancies was determined by Rietveld analysis. Most of the samples exhibited sharp superconducting transitions with Tcs between 37–39 K.We found a strong correlation between the crystal strain and the Tc. This strain was related to the presence of Mg vacancies. In addition, results showed that some samples degraded with time when exposed to ambient conditions. In these samples the Tc did not change with time, but the superconducting transition became broader and the Meissner fraction decreased. This effect was only present in samples with poor connectivity between grains and smaller grain sizes. The degradation was related to a surface decomposition as observed by X-ray Photoelectron Spectroscopy. No correlation was found between this effect and the presence of Mg vacancies.

Processing Relationships in YBa2Cu3O7−x Superconductors

1987 ◽  
Vol 99 ◽  
Author(s):  
W. J. Heber ◽  
L. R. Pederson ◽  
G. D. Maupin ◽  
E. J. Leblanc
Keyword(s):  
Photoelectron Spectroscopy ◽  
Superconducting Transition ◽  
Superconducting Properties ◽  
Orthorhombic Structure ◽  
Transition Width ◽  
Slow Cooling ◽  
Pressure Oxidation ◽  
Atmosphere Pressure ◽  
X Ray ◽  
Complete Transformation

ABSTRACTSamples of YBa2Cu3O7−x were prepared by solid state reaction of Y2O3, BaO2, and CuO powders mixed in stoichiometric proportions. Powders reacted at 900°C-925°C in air were pressed at 35 MPa into rectangular bars and sintered at 950°C in air for six hours. Slow cooling at 50°C/hour promoted complete transformation to the orthorhombic structure. The effects of subsequent oxidation processing on superconducting properties were also investigated. Oxidation anneals at one atmosphere pressure in flowing O2over the temperature range from 300 to 550°C were performed. Results indicate that oxidation at 450°C optimized the superconducting transition temperature at 91K with a 2-degree transition width. Subsequent high-pressure oxidation (2000 psi O2) at 200°C for one week significantly degraded the superconducting characteristics. Results based on i udometric titration, thermogravimetric analysis, and x-ray photoelectron spectroscopy suggest that the copper valency is about 2.3 and oxygen stoi chiometry is 6.94 (x = 0.06) in samples processed to optimize superconducting properties.

scholarly journals Vis-Responsive Copper-Modified Titania for Decomposition of Organic Compounds and Microorganisms

Catalysts ◽  
2020 ◽  
Vol 10 (10) ◽  
pp. 1194
Author(s):  
Maya Endo-Kimura ◽  
Bariş Karabiyik ◽  
Kunlei Wang ◽  
Zhishun Wei ◽  
Bunsho Ohtani ◽  
...  
Keyword(s):  
Visible Light ◽  
Photoelectron Spectroscopy ◽  
Water Oxidation ◽  
Diffuse Reflectance Spectroscopy ◽  
Antimicrobial Properties ◽  
Localized Surface Plasmon ◽  
Intrinsic Activity ◽  
Ambient Conditions ◽  
Copper Species ◽  
X Ray

Seven commercial titania (titanium(IV) oxide; TiO2) powders with different structural properties and crystalline compositions (anatase/rutile) were modified with copper by two variants of a photodeposition method, i.e., methanol dehydrogenation and water oxidation. The samples were characterized by diffuse reflectance spectroscopy (DRS), X-ray powder diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS) and X-ray photoelectron spectroscopy (XPS). Although zero-valent copper was deposited on the surface of titania, oxidized forms of copper, post-formed in ambient conditions, were also detected in dried samples. All samples could absorb visible light (vis), due to localized surface plasmon resonance (LSPR) of zero-valent copper and by other copper species, including Cu2O, CuO and CuxO (x:1-2). The photocatalytic activities of samples were investigated under both ultraviolet (UV) and visible light irradiation (>450 nm) for oxidative decomposition of acetic acid. It was found that titania modification with copper significantly enhanced the photocatalytic activity, especially for anatase samples. The prolonged irradiation (from 1 to 5 h) during samples’ preparation resulted in aggregation of copper deposits, thus being detrimental for vis activity. It is proposed that oxidized forms of copper are more active under vis irradiation than plasmonic one. Antimicrobial properties against bacteria (Escherichia coli) and fungi (Aspergillus niger) under vis irradiation and in the dark confirmed that Cu/TiO2 exhibits a high antibacterial effect, mainly due to the intrinsic activity of copper species.

scholarly journals A modified ionic liquid clay to remove heavy metals from water: investigating its catalytic activity

2019 ◽  
Vol 17 (4) ◽  
pp. 2043-2058
Author(s):  
S. Kakaei ◽  
E. S. Khameneh ◽  
M. H. Hosseini ◽  
M. M. Moharreri
Keyword(s):  
Heavy Metal ◽  
Catalytic Activity ◽  
Photoelectron Spectroscopy ◽  
Metal Ion ◽  
Kinetic Studies ◽  
Heavy Metal Ion ◽  
Ambient Conditions ◽  
X Ray ◽  
Metal Ion Adsorption ◽  
Map Analysis

Abstract The new clay modified with triazole and triazolium ligands was prepared in this research. These materials were applied as abundant and eco-friendly adsorbents for removal of heavy metal ions such as Pb(II), Co(II) and Zn(II) ions. The adsorption efficiency of these materials was calculated by relevant equations such as Langmuir and Freundlich as well as kinetic studies with pseudo-first-order and pseudo-second-order models. These adsorbents proved to be very active on heavy metal ion adsorption. The characterization of these new materials was carried out by various techniques such as X-ray diffraction, thermogravimetric analysis, scanning electron microscope (SEM), X-ray photoelectron spectroscopy and energy-dispersive X-ray spectroscopy as well as SEM-map analysis. Eventually, the catalytic activity of the adsorbents which treated with heavy metal ion solutions was studied in the reduction of nitroarenes to its corresponding amines. The prepared adsorbent–catalyst materials indicated efficient catalytic activity in the reduction of nitroarenes to amines in ambient conditions. Graphic abstract

Synthesis of YBa2Cu3O7−δ with clean grain boundaries by a modified aerosol decomposition process

1992 ◽  
Vol 7 (12) ◽  
pp. 3175-3184 ◽  
Author(s):  
Yuan-Liang Wang ◽  
Z.Q. Tan ◽  
Yimei Zhu ◽  
A.R. Moodenbaugh ◽  
M. Suenaga
Keyword(s):  
Grain Boundaries ◽  
Decomposition Method ◽  
Flow Reactor ◽  
Superconducting Transition ◽  
X Ray ◽  
Grain Sizes ◽  
Fine Grain ◽  
Precursor Powders ◽  
X Ray Absorption

A modified aerosol decomposition method was developed for producing sintered YBa2Cu3O7−δ (1-2-3) pellets having sharp superconducting transition Tc's at ∼90 K, fine grain sizes, and clean grain boundaries. This method used “precursor” powders, which were produced with an aerosol flow reactor at 550 °C, instead of in situ produced 1-2-3 powders commonly processed at 880–1000 °C. As determined by x-ray absorption and powder diffraction studies, the 1-2-3 powders produced by the modified route contain less cation disorders than the in situ produced powders. The disorder is speculated to be the cause of Tc-suppression and broadening. It cannot be removed unless high sintering temperatures were used (>950 °C), which resulted in large grains and impurities and cracks at grain boundaries.

scholarly journals Synthesis and Characterization of Strontium Titanate Nanoparticles as Potential High Temperature Oxygen Sensor Material

2006 ◽  
Vol 2006 ◽  
pp. 1-6 ◽  
Author(s):  
Florian Voigts ◽  
Tanja Damjanovic ◽  
Günter Borchardt ◽  
Christos Argirusis ◽  
Wolfgang Maus-Friedrichs
Keyword(s):  
High Temperature ◽  
Strontium Titanate ◽  
Photoelectron Spectroscopy ◽  
Oxygen Sensor ◽  
Ambient Conditions ◽  
X Ray ◽  
Sensor Material ◽  
Force Microscopy ◽  
Atomic Force

We present a simple and highly reproductive method for the preparation of thin films consisting of strontium titanate nanoparticles. The films are produced by spin coating of a sol on silicon targets and subsequent annealing under ambient conditions. Analysis by atomic force microscopy shows particles with typical sizes between 10 nm and 50 nm. X-ray photoelectron spectroscopy displays a stoichiometry of the films as anticipated from preliminary experiments with strontium titanate single crystals. Metastable-induced electron spectroscopy and ultraviolet photoelectron spectroscopy are used as tools to give evidence to the similar electronic properties of nanoparticle film and single crystal. These results support the prospect for an application of the nanoparticle films as high temperature oxygen sensor with superior properties.

scholarly journals Effect of Sol-Gel Synthesized BiFeO3 Nanoparticle Addition in YBa2Cu3O7–δ (Y123) Superconductor Synthesized by Standard Solid State Reaction Method

2019 ◽  
Vol 290 ◽  
pp. 245-251
Author(s):  
Abdalla Bahboh ◽  
Abdul Halim Shaari ◽  
Hussein Baqiah ◽  
Soo Kien Chen ◽  
Mohd Mustafa Awang Kechik ◽  
...  
Keyword(s):  
Sol Gel ◽  
Solid State Reaction Method ◽  
Superconducting Transition ◽  
Secondary Phases ◽  
Superconducting Properties ◽  
Orthorhombic Structure ◽  
X Ray Diffraction ◽  
Scanning Electron Micrograph ◽  
X Ray ◽  
Pure Ybco

The effects of the multiforric BiFO3 nanoparticles addition on the structure and superconducting properties of YBa2Cu3O7–δ (Y123) with different concentrations were systematically investigated using X-ray diffraction (XRD), field emission scanning electron micrograph (FESEM), EDX and four point probe measurement. It was found that the added samples were predominant by Y-123 phase beside small amount of Y-211 and unreacted BiFeO3 secondary phases. Samples with less (wt.%) BFO added YBCO precursor powder preserved the orthorhombic structure similar to the pure YBCO, while samples with higher wt% addition show orthorhombic-to-tetragonal transition tendency. The samples became more porous and their grain size slightly decreased with addition of BiFeO3. The addition of nanoBiFeO3 disturbed the grain growth of Y123, thus resulting in the degradation of superconducting properties of the samples. The superconducting transition temperature (Tc onset) of samples decreased from 92 K for x=0.0 to 44 K for x=10.0 wt. %, which could be attributable to oxygen vacancy disorder.

STRUCTURAL AND SUPERCONDUCTING PROPERTIES OF La2CuO4+δ OXIDIZED BY KMnO4 UNDER HYDROTHERMAL CONDITIONS

2001 ◽  
Vol 15 (26) ◽  
pp. 1171-1179 ◽  
Author(s):  
Q. Y. TU ◽  
B. K. MA ◽  
X. L. CHEN ◽  
Y. C. LAN ◽  
Y. X. XU ◽  
...  
Keyword(s):  
Thermal Conditions ◽  
Excess Oxygen ◽  
Superconducting Transition ◽  
Orthorhombic Distortion ◽  
Hydrothermal Conditions ◽  
X Ray ◽  
Grain Sizes ◽  
Selected Area Electron Diffraction ◽  
Before And After ◽  
Incommensurate Modulation

A series of samples of La2CuO4+δ chemically oxidized in KMnO 4 solution under hydro-thermal conditions have been prepared. A large orthorhombic distortion and the increased unit cell volume of the oxidized sample have been observed by means of X-ray powder diffraction, compared with that of the starting material. Selected-area electron diffraction investigations reveal that two kinds of incommensurate modulation structures exist in the oxidized samples. Magnetic susceptibility measurements indicate that the oxidized samples are multiphase with two superconducting phases, one is dominant with onset of superconducting transition temperature at 43 K or 40 K, and the other at 19 K. Up to now, a T c of 43 K is the highest value achieved in KMnO 4-treated samples. The excess oxygen content determined by iodometric titration increases with the oxidation temperature. Average grain sizes observed by scanning electron microscope have no obvious changes for the samples before and after oxidation.

Deposition of Superconducting Thin Films of Magnesium Di-Boride on Various Substrates by Electroless Plating Process

2010 ◽  
Vol 654-656 ◽  
pp. 1840-1843
Author(s):  
Susil K. Putatunda ◽  
Khurpa S. Vijayaragavan ◽  
Gavin Lawes
Keyword(s):  
Thin Films ◽  
Electroless Plating ◽  
Magnesium Diboride ◽  
Superconducting Thin Films ◽  
Superconducting Transition ◽  
Superconducting Properties ◽  
X Ray Diffraction ◽  
Temperature Dependent ◽  
X Ray ◽  
Gold Silver

Superconducting thin films of magnesium diboride (MgB2) has been synthesized on various substrates such as gold, silver, copper and silicon using a novel electroless plating technique. The microstructures and the superconducting properties of these films have been characterized using X-ray diffraction, scanning electron microscopy and temperature dependent magnetometry. X-ray diffraction measurements confirm that the films are crystalline magnesium diboride with some impurity phases. Clear evidence for a superconducting transition in the magnetization measurements was observed.

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