scholarly journals Electrical Transport and Lowered Percolation Threshold in YBa2Cu3O7−δ-Nano-YBa2ZrO5.5 Composites

2014 ◽  
Vol 2014 ◽  
pp. 1-7
Author(s):  
Pullanhiyodan Puthiyaveedu Rejith ◽  
Sukumariamma Vidya ◽  
Jijimon Kumpukattu Thomas
Keyword(s):  
Percolation Threshold ◽  
Electrical Transport ◽  
Composite System ◽  
Current Flow ◽  
Weak Link ◽  
Chemical Reactivity ◽  
X Ray Diffraction ◽  
X Ray ◽  
Combustion Route ◽  
Scanning Electron

We investigated the chemical reactivity and percolation characteristics of insulating nanocrystalline YBa2ZrO5.5 prepared by modified combustion route and the YBa2Cu3O7−δ superconductor composite system. Structural analysis was done by using X-ray diffraction technique, surface morphology of the samples was studied using scanning electron microscopy, and electrical transport measurements like critical transition temperatures (Tc) and self-field transport critical current (Jc) were done by using standard four-probe technique. It is found that, in YBa2Cu3O7−δ-nano-YBa2ZrO5.5 composite system, the superconductor and insulator materials coexist as separate phases without any noticeable chemical reaction even after sintering at high temperatures. Furthermore, percolation threshold and critical exponent are found to be VC=0.3, t=1.68, and u=2.7. And the analysis of the current flow in the polycrystalline samples reveals weak link behavior in the majority of grain connections.

CHARACTERISATION AND LUMINESCENCE INVESTIGATIONS OF Mn DOPED CaAl2O4 PHOSPHOR PREPARED BY COMBUSTION

2008 ◽  
Vol 22 (13) ◽  
pp. 2095-2101 ◽  
Author(s):  
VIJAY SINGH ◽  
V. NATARAJAN ◽  
DONG-KUK KIM
Keyword(s):  
Electron Microscopy ◽  
Green Emission ◽  
Combustion Products ◽  
X Ray Diffraction ◽  
X Ray ◽  
Prepared Material ◽  
Combustion Route ◽  
Photoluminescence Studies ◽  
Mn Doped ◽  
Scanning Electron

Manganese-doped calcium aluminate powder was prepared at furnace temperatures as low as 500°C using the combustion route without further calcining treatment. Powder X-ray diffraction, thermogravimetric analysis and scanning electron microscopy measurements were used to characterize the as-prepared combustion products, while the optical properties were studied using photoluminescence. Photoluminescence studies of Mn doped CaAl 2 O 4 showed green emission from Mn 2+ ions. EPR investigations also indicated the presence of Mn 2+ ions in the prepared material.

Effects of Nano-Sized NiF2 Addition in Bi1.4Pb0.6Sr2Ca2Cu3O10+δ Superconductor

2014 ◽  
Vol 895 ◽  
pp. 87-90 ◽  
Author(s):  
Muhammad Hafiz ◽  
Roslan Abd-Shukor
Keyword(s):  
Electron Microscope ◽  
Critical Temperature ◽  
Scanning Electron Microscope ◽  
Electrical Transport ◽  
Diffraction Method ◽  
X Ray Diffraction ◽  
X Ray ◽  
Average Size ◽  
20 Nm ◽  
Scanning Electron

The effects of NiF2addition on the superconducting and transport properties of Bi1.4Pb0.6Sr2Ca2Cu3O10+δ(Bi-2223) were studied. Bi-2223 superconductor samples were prepared via conventional nitrate coprecipitation method, and 0.01 wt% - 0.05 wt% of NiF2nanoparticles with average size of 20 nm were added into the samples. The critical temperature (Tc) of each sample was measured by using the four-point probe method. Furthermore, phase formation and the microstructure of the samples were identified using x-ray diffraction method (XRD) and scanning electron microscope (SEM) respectively. The optimumTcwas observed for the sample with 0.04 wt% addition of NiF2. Results of electrical transport measurement are presented.

Superconductor-substrate interactions of the Y–Ba–Cu oxide

1989 ◽  
Vol 4 (1) ◽  
pp. 1-15 ◽  
Author(s):  
C. T. Cheung ◽  
E. Ruckenstein
Keyword(s):  
Chemical Reactivity ◽  
Oxide Superconductor ◽  
Reaction Products ◽  
X Ray Diffraction ◽  
Metallic Substrates ◽  
X Ray ◽  
Qualitative And Quantitative ◽  
Unknown Phase ◽  
Flowing Oxygen ◽  
Scanning Electron

The chemical interactions between the YBa2Cu3O7−x high Tc superconductor and various substrates (Si, Al2O3, ZrO2, SrTiO3, MgO, Ag, Cu, and Nb) were studied. Powders of the orthorhombic YBa2Cu3O7−x (123) phase and each of the various substrates were mixed, pressed into pellets, and subjected to either one of the following heat treatments in flowing oxygen: 600 °C for 11 h, 800 °C for 10 h, 945 °C for 5 h, and 945 °C for 17 h. The reacted samples were characterized by qualitative and quantitative x-ray diffraction, scanning electron microscopy with EDAX, electrical resistivity, and magnetic susceptibility measurements. For all substrates studied, the extent of reaction is much more significant at 945 °C than at 800 °C and 600 °C. The reaction products, in general, are some Ba compounds, CuO (and Cu2O), and the Y2BaCuO5 (211) phase. The reaction with Si results in a morphology of layers of 123/211/Ba2SiO4/CuO/Si. Reactions with Al2O3 and ZrO2 result in similar products and morphologies. Reaction with SrTiO3 results in the replacement of Ba by Sr and the formation of a Ba–Ti–Y–Cu unknown phase. With MgO, the chemical reaction results in the enrichment of MgO with Cu and the formation of an apparently glassy Ba–Cu phase. With the metallic substrates Ag, Cu, and Nb, Ag shows no interaction at all, Cu results in the formation of CuO (and Cu2O), whereas the Nb samples completely disintegrated. By comparing the percentage of remaining 123 phase in samples reacted at 945 ° for 17 h, a reactivity scale in decreasing order was obtained as Nb > Si > ZrO2  Al2O3 > SrTiO3 > MgO  Cu > Ag. It is suggested that the chemical reactivity of the Y–Ba–Cu oxide superconductor is mostly controlled by the highly electropositive Ba2+ ions.

Preparation and Characterization of Cement-TiO2 Composites

2015 ◽  
Vol 804 ◽  
pp. 133-136
Author(s):  
Noosara Kaewgabkam ◽  
Nittaya Jaitanong ◽  
Suparut Narksitipan
Keyword(s):  
Composite System ◽  
Low Cost ◽  
High Photocatalytic Activity ◽  
Chemical Compositions ◽  
Hydration Reaction ◽  
X Ray Diffraction ◽  
X Ray ◽  
Powder Content ◽  
Scanning Electron

Titanium dioxide (TiO2) is the most widely used photocatalyst because of its high photocatalytic activity and reasonably low cost. Moreover, TiO2 has strong chemical stability in a large variety of environmental conditions. The combination of TiO2 with cementatious materials has been widely investigated, and the effects of the TiO2 contents (10-40% by weight) were studied in this research. The crystalline structures and chemical compositions were analyzed using x-ray diffraction (XRD) and energy dispersive x-ray spectroscopy (EDS), respectively. Moreover, its microstructure was investigated by scanning electron microscopy (SEM). It was found that the intensity of CS and CH decreased with an increase in the TiO2 powder content. This was because when adding more TiO2 powder to the composite system, more water was needed to add to the hydration reaction.

PERCOLATION STUDIES IN SmBa2SbO6–YBa2Cu3O7−δ COMPOSITE SYSTEM

1995 ◽  
Vol 09 (10) ◽  
pp. 585-590 ◽  
Author(s):  
P. R. S. WARIAR ◽  
J. KOSHY ◽  
J. KURIAN ◽  
Y. P. YADAVA ◽  
A. D. DAMODARAN
Keyword(s):  
Percolation Threshold ◽  
Transport Properties ◽  
Normal State ◽  
Composite System ◽  
Threshold Values ◽  
X Ray Diffraction ◽  
Normal State Resistivity ◽  
X Ray ◽  
Resistivity Measurements ◽  
Percolation Behavior

Percolation behavior of normal state resistivity and superconductivity of SmBa 2 SbO 6– YBa 2 Cu 3 O 7−δ have been studied. The normal state and superconducting percolation threshold values of the composite are both found to be around 22% of YBa 2 Cu 3 O 7−δ in the system. The X-ray diffraction and resistivity measurements on the above percolation system have shown that there is no detectable reaction between SmBa 2 SbO 6 ceramic and YBa 2 Cu 3 O 7−δ superconductor even when the two substances are mixed thoroughly and sintered at 1020°C. The values of exponent 't' and 'u' describing the transport properties of the system are found to be 1.66 and 0.66 which agree with the theoretically expected value for a perfect composite system. The implications of the results are discussed.

The Use of Advanced Analytical Techniques for Characterization of the Chemical, Physical, and Crystallographic Nature of a Surface

1973 ◽  
Vol 31 ◽  
pp. 132-133 ◽  
Author(s):  
R. E. Herfert
Keyword(s):  
Surface Characterization ◽  
Analytical Techniques ◽  
X Ray Diffraction ◽  
Depth Of Penetration ◽  
X Ray ◽  
The Past ◽  
Transmission Electron ◽  
Scanning Electron

Studies of the nature of a surface, either metallic or nonmetallic, in the past, have been limited to the instrumentation available for these measurements. In the past, optical microscopy, replica transmission electron microscopy, electron or X-ray diffraction and optical or X-ray spectroscopy have provided the means of surface characterization. Actually, some of these techniques are not purely surface; the depth of penetration may be a few thousands of an inch. Within the last five years, instrumentation has been made available which now makes it practical for use to study the outer few 100A of layers and characterize it completely from a chemical, physical, and crystallographic standpoint. The scanning electron microscope (SEM) provides a means of viewing the surface of a material in situ to magnifications as high as 250,000X.

Identification of calcium oxalate crystals in dried or fixed tobacco leaf

1984 ◽  
Vol 42 ◽  
pp. 288-289
Author(s):  
Vicki L. Baliga ◽  
Mary Ellen Counts
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Calcium Oxalate ◽  
Growth And Development ◽  
Polarized Light ◽  
Calcium Oxalate Crystals ◽  
X Ray Diffraction ◽  
X Ray ◽  
Transmission Electron ◽  
Scanning Electron

Calcium is an important element in the growth and development of plants and one form of calcium is calcium oxalate. Calcium oxalate has been found in leaf seed, stem material plant tissue culture, fungi and lichen using one or more of the following methods—polarized light microscopy (PLM), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and x-ray diffraction.Two methods are presented here for qualitatively estimating calcium oxalate in dried or fixed tobacco (Nicotiana) leaf from different stalk positions using PLM. SEM, coupled with energy dispersive x-ray spectrometry (EDS), and powder x-ray diffraction were used to verify that the crystals observed in the dried leaf with PLM were calcium oxalate.

Sem and X-Ray Analysis of Renal and Biliary Calculi

1976 ◽  
Vol 34 ◽  
pp. 306-307
Author(s):  
R. J. Narconis ◽  
G. L. Johnson
Keyword(s):  
Chemical Constituents ◽  
Natural State ◽  
X Ray Diffraction ◽  
Chemical Methods ◽  
X Ray ◽  
Additional Dimension ◽  
Biliary Calculi ◽  
Calculus Formation ◽  
Scanning Electron

Analysis of the constituents of renal and biliary calculi may be of help in the management of patients with calculous disease. Several methods of analysis are available for identifying these constituents. Most common are chemical methods, optical crystallography, x-ray diffraction, and infrared spectroscopy. The application of a SEM with x-ray analysis capabilities should be considered as an additional alternative.A scanning electron microscope equipped with an x-ray “mapping” attachment offers an additional dimension in its ability to locate elemental constituents geographically, and thus, provide a clue in determination of possible metabolic etiology in calculus formation. The ability of this method to give an undisturbed view of adjacent layers of elements in their natural state is of advantage in determining the sequence of formation of subsequent layers of chemical constituents.

Environmental scanning electron microscopy of fresh human gallstones reveals new morphologies of precipitated calcium salts

1992 ◽  
Vol 50 (2) ◽  
pp. 1322-1323
Author(s):  
Howard S. Kaufman ◽  
Keith D. Lillemoe ◽  
John T. Mastovich ◽  
Henry A. Pitt
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Environmental Scanning Electron Microscopy ◽  
Environmental Scanning ◽  
X Ray Diffraction ◽  
Calcium Salts ◽  
Cholesterol Gallstones ◽  
X Ray ◽  
Ca Carbonate ◽  
Scanning Electron

Gallstones contain precipitated cholesterol, calcium salts, and proteins. Calcium (Ca) bilirubinate, palmitate, phosphate, and carbonate occurring in gallstones have variable morphologies but characteristic windowless energy dispersive x-ray (EDX) spectra. Previous studies of gallstone microstructure and composition using scanning electron microscopy (SEM) with EDX have been limited to dehydrated samples. In this state, Ca bilirubinates appear as either glassy masses, which predominate in black pigment stones, or as clusters, which are found mostly in cholesterol gallstones. The three polymorphs of Ca carbonate, calcite, vaterite, and aragonite, have been identified in gallstones by x-ray diffraction, however; the morphologies of these crystals vary in the literature. The purpose of this experiment was to study fresh gallstones by environmental SEM (ESEM) to determine if dehydration affects gallstone Ca salt morphology.Gallstones and bile were obtained fresh at cholecystectomy from 6 patients. To prevent dehydration, stones were stored in bile at 37°C. All samples were studied within 4 days of procurement.

Photocatalytic activity of TiO2 synthesized by anodization and anodic spark deposition

MRS Advances ◽  
2020 ◽  
Vol 5 (61) ◽  
pp. 3141-3152
Author(s):  
Alma C. Chávez-Mejía ◽  
Génesis Villegas-Suárez ◽  
Paloma I. Zaragoza-Sánchez ◽  
Rafael Magaña-López ◽  
Julio C. Morales-Mejía ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Photocatalytic Activity ◽  
Surface Characteristics ◽  
Amorphous Solids ◽  
X Ray Diffraction ◽  
X Ray ◽  
Catalytic Activities ◽  
Anodic Spark Oxidation ◽  
Porous Surfaces ◽  
Scanning Electron

AbstractSeveral photocatalysts, based on titanium dioxide, were synthesized by spark anodization techniques and anodic spark oxidation. Photocatalytic activity was determined by methylene blue oxidation and the catalytic activities of the catalysts were evaluated after 70 hours of reaction. Scanning Electron Microscopy and X Ray Diffraction analysis were used to characterize the catalysts. The photocatalyst prepared with a solution of sulfuric acid and 100 V presented the best performance in terms of oxidation of the dye (62%). The electric potential during the synthesis (10 V, low potential; 100 V, high potential) affected the surface characteristics: under low potential, catalyst presented smooth and homogeneous surfaces with spots (high TiO2 concentration) of amorphous solids; under low potential, catalyst presented porous surfaces with crystalline solids homogeneously distributed.

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