Characterization of intergranular cuprous oxide in polycrystalline YBa2Cu3O7-x

1988 ◽  
Vol 46 ◽  
pp. 880-881
Author(s):  
Bradley L. Thiel ◽  
Chan Han R. P. ◽  
Kurosky L. C. Hutter ◽  
I. A. Aksay ◽  
Mehmet Sarikaya
Keyword(s):  
Grain Boundary ◽  
Cuprous Oxide ◽  
Room Temperature ◽  
Boundary Phase ◽  
Spectroscopic Techniques ◽  
Transition Width ◽  
Practical Applications ◽  
Thin Foils ◽  
Superconducting Oxides

The identification of extraneous phases is important in understanding of high Tc superconducting oxides. The spectroscopic techniques commonly used in determining the origin of superconductivity (such as RAMAN, XPS, AES, and EXAFS) are surface-sensitive. Hence a grain boundary phase several nanometers thick could produce irrelevant spectroscopic results and cause erroneous conclusions. The intergranular phases present a major technological consideration for practical applications. In this communication we report the identification of a Cu2O grain boundary phase which forms during the sintering of YBa2Cu3O7-x (1:2:3 compound).Samples are prepared using a mixture of Y2O3. CuO, and BaO2 powders dispersed in ethanol for complete mixing. The pellets pressed at 20,000 psi are heated to 950°C at a rate of 5°C per min, held for 1 hr, and cooled at 1°C per min to room temperature. The samples show a Tc of 91K with a transition width of 2K. In order to prevent damage, a low temperature stage is used in milling to prepare thin foils which are then observed, using a liquid nitrogen holder, in a Philips 430T at 300 kV.

scholarly journals Green Synthesis and Characterization of Gallium(III) Sulphide (α-Ga2S3) Nanoparicles at Room Temperature

Nano Hybrids ◽  
2014 ◽  
Vol 6 ◽  
pp. 37-46 ◽  
Author(s):  
Tansir Ahamad ◽  
Saad M. Alshehri
Keyword(s):  
Green Synthesis ◽  
Band Gap ◽  
Raman Spectra ◽  
Room Temperature ◽  
Optical Band Gap ◽  
Blue Shift ◽  
Synthesis And Characterization ◽  
Spectroscopic Techniques ◽  
Sodium Thiosulphate

Two different batches of Gallium (III) sulphide nanocrystals, (α-Ga2S3)1 and (α-Ga2S3)2 were synthesized at room temperature by the reaction of Gallium (III) chloride with sodium thiosulphate in water for 10 and 20 min respectively. The resultant nanoparticles were characterized by different spectroscopic techniques. TEM micrographs showed well-defined, close to hexagonal particles, and the lattice fringes in the HRTEM images confirmed their nanocrystalline nature. The sizes of (α-Ga2S3)1 and (α-Ga2S3)2 were 12 and 35 nm respectively with similar morphologies. Optical band gap energies (3.43 eV/3.41 eV) and photoluminescence peaks 635/641 nm (red shift) and 414/420 nm (blue shift) of the synthesized α-Ga2S3 nanocrystals suggest that they may be promising photocatalysts. Raman spectra for the α-Ga2S3, shows very sharp bands at 119, 135 and 148 cm-1 due to Ga-S2 scissoring.

Characterization of grain boundary phase of a lead-based relaxor by raman scattering spectroscopy

1996 ◽  
Vol 16 (11) ◽  
pp. 1157-1161 ◽  
Author(s):  
Hideyuki Kanai ◽  
Yohachi Yamashita ◽  
Masato Kakihana ◽  
Masahiro Yoshimura
Keyword(s):  
Grain Boundary ◽  
Raman Scattering ◽  
Boundary Phase ◽  
Raman Scattering Spectroscopy

Precipitation of copper in proeutectoid cementite in steel

1990 ◽  
Vol 48 (4) ◽  
pp. 916-917
Author(s):  
F. A. Khalid ◽  
M. Farooque ◽  
D. V. Edmonds
Keyword(s):  
Grain Boundary ◽  
Room Temperature ◽  
Previous Analysis ◽  
Ferritic Steels ◽  
Decomposition Reactions ◽  
Boundary Allotriomorphs ◽  
Solution Treated ◽  
Thin Foils ◽  
Austenite Grains ◽  
Parent Austenite

The morphology and mechanism of Cu precipitation in grain boundary allotriomorphs of proeutectoid cementite forming isothermally inaustenite in two Fe-10Mn-3Cu-0.8C and Fe-lOMn- lCu-0.8C (nominal wt%) alloys are being studied. These particular alloys can be partially decomposed to the proeutectoid and eutectoid phases recognisable in ferritic steels, but possess the advantage that unlike ferritic steels the parent austenite phase is retained after cooling to room temperature thus facilitating studies of the decomposition reactions.A 50 g ingot of each experimental alloy was argon arc melted using high purity materials and homogenised. Samples were rolled, swaged and machined to 3mm diameter rod, solution treated at 1200 °C for 1 hr and quenched in water. Specimens were then solutionised at 1200°C for 10 min and isothermally transformed at 615 °C for 4 hrs. Methods for the preparation of thin foils for TEM are given elsewhere.The heat treatment resulted in the formation of grain boundary allotriomorphs of cementite in austenite (Fig 1). TEM confirmed that the cementite allotriomorphs formed with the Pitsch orientation relationship to one of the austenite grains at the grain boundary (Fig 2c ) consistent with a previous analysis.

The Effect of Cu Alloying on Al Alloy Thin Films: Microstructural Mechanisms That Enhance Electromigration Resistance

1993 ◽  
Vol 309 ◽  
Author(s):  
D. R. Frear ◽  
J. R. Michael ◽  
A. D. Romig
Keyword(s):  
Thin Films ◽  
Grain Boundary ◽  
Grain Boundaries ◽  
Room Temperature ◽  
Boundary Diffusion ◽  
Boundary Phase ◽  
Al Alloy ◽  
Cu Films ◽  
Isothermal Heat Treatments ◽  
Lower Temperature

AbstractThe microstructural evolution of unpatterned Al-2wt.%Cu thin films has been examined to elucidate the mechanism by which copper improves electromigration resistance. After annealing at 425°C and cooling to room temperature at a rate of approximately 1°C/min., the microstructure of the Al-Cu films consisted of 1 μm aluminum grains with θ-phase Al2Cu precipitates at grain boundaries and triple points. The grain size and precipitation distribution did not change with subsequent isothermal heat treatments in the temperature range of 200° to 400°C. Al-Cu thin films annealed at 400°C, a temperature just below the Al/Al+θ solvus, exhibited microstructures in which the aluminum grain boundaries were depleted in copper except for the presence of the pre-existing large, widely dispersed AI2Cu precipitates. Al-Cu thin films annealed at 200° to 300°C were enriched with copper at the aluminum grain boundaries. The large, widely dispersed Al2Cu precipitates remained after the lower temperature anneals. From these results, it is proposed that the presence of copper in aluminum thin films improves electromigration resistance due to the precipitation of a thin film of Al2Cu, or a substoichiometric precursor, along the grain boundaries. The grain boundary phase retards grain boundary diffusion in the thin films, thereby reducing total mass transport and improving electromigration resistance.

Effects of Chemical Preservatives and Storage on Constituents Used to Characterize Lemon Juice

1968 ◽  
Vol 51 (1) ◽  
pp. 6-10
Author(s):  
Carl E Vandercook ◽  
Henry C Guerrero
Keyword(s):  
Room Temperature ◽  
Total Phenolics ◽  
Chemical Characterization ◽  
Lemon Juice ◽  
Potassium Sorbate ◽  
Practical Applications ◽  
Regression Approach ◽  
And Storage

Abstract The effects of sulfur dioxide, sodium benzoate, and potassium sorbate preservatives on the analytical methods for chemically characterizing lemon juice were studied. None of the preservatives had any effects on the analyses for total acidity as citric acid, the l-malic acid, the UV absorbance at the 330 m/x peak (referred to as the total phenolics), or the formol determination of total amino acids (after expelling the S02 by boiling 1 min). The study was continued over storage periods of up to 17 weeks at room temperature and 6 weeks at 30 °C. The constituents measured remained relatively stable except for some small but statistically significant changes that were apparently a function of both the juice and, in the case of the total phenolics, the preservative used. For practical applications, the changes did not affect the multiple regression approach to the chemical characterization of lemon juice

Fabrication of Silicon Nitride Ceramics with Electrical Conductivity

2005 ◽  
Vol 486-487 ◽  
pp. 501-505 ◽  
Author(s):  
Yoon Ho Kim ◽  
Tohru Sekino ◽  
Hirokazu Kawaoka ◽  
Takafumi Kusunose ◽  
Tadachika Nakayama ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Electrical Conductivity ◽  
Grain Boundary ◽  
Room Temperature ◽  
Boundary Phase ◽  
Si3n4 Ceramic ◽  
Nitride Ceramics ◽  
Infinite Network ◽  
Fine Microstructure ◽  
Si3n4 Ceramics

The electrical conductivity was provided to structural ceramics by controlling the grain boundary phase. We focused on the grain boundary phase of Si3N4 ceramics, which can be considered as an infinite network for conducting paths. In this study, we investigated the correlationship of the microstructure, mechanical properties, and electrical conductivity of Si3N4 ceramics with V2O5 based glasses. The Si3N4 ceramic with V2O5 based glasses were successfully fabricated by controlling the composition of grain boundary phase. Fabricated materials by a PECS method indicated a very fine microstructure. The mechanical properties of Si3N4 ceramics with V2O5 based glasses were not good compared to those of conventional Si3N4. However, the values for the SNVB and the SNVBA were four or six orders of magnitude higher at room temperature and had excellent mechanical properties compared to pure V2O5 based glasses.

scholarly journals Synthesis and structural analysis of polynuclear silver(I) complexes with 4,7-phenanthroline

2019 ◽  
Vol 84 (7) ◽  
pp. 689-699 ◽  
Author(s):  
Ivana Stanojevic ◽  
Nada Savic ◽  
Aurélien Crochet ◽  
Katharina Fromm ◽  
Milos Djuran ◽  
...  
Keyword(s):  
Solid State ◽  
Room Temperature ◽  
Volume Ratio ◽  
Spectroscopic Techniques ◽  
X Ray Diffraction ◽  
X Ray ◽  
Bridging Ligand ◽  
Coordination Sites ◽  
Hydrolysis Of

New polynuclear silver(I) complexes, [Ag(CF3SO3)(4,7-phen)(CH3CN)]n (1) and [Ag(PO2F2)(4,7-phen)]n (2), were synthesized by the reaction of 4,7-phenanthroline (4,7-phen) and the corresponding AgX salt (X = CF3SO3 - and PF6 -) in 1:2 mole ratio, respectively, in methanol/acetone (1:1 volume ratio) at room temperature. The characterization of the complexes was established on the basis of elemental microanalysis, IR and NMR (1H and 13C) spectroscopic techniques, while their crystal structures were determined by single-crystal X-ray diffraction analysis. The results of spectroscopic and crystallographic analyses revealed that in these complexes, 4,7-phen behaves as a bridging ligand between two metal ions, while the remaining coordination sites of the Ag(I) ions are occupied by the oxygen atom of CF3SO3 - and an acetonitrile nitrogen atom in 1 or by two oxygen atoms from two PO2F2 -, formed after hydrolysis of PF6 -, in 2. In the solid state, both complexes are coordination polymers in which the geometry around the Ag(I) ions is distorted tetrahedral.

Analytical TEM study of a yttria stabilized zirconia/glass composite

1988 ◽  
Vol 46 ◽  
pp. 572-573
Author(s):  
Yung-Jen Lin ◽  
Peter Angelini ◽  
Martha L. Mecartney
Keyword(s):  
Grain Size ◽  
Grain Boundary ◽  
Grain Growth ◽  
Room Temperature ◽  
Tetragonal Zirconia ◽  
Yttria Stabilized Zirconia ◽  
Boundary Phase ◽  
Stabilized Zirconia ◽  
High Toughness ◽  
M Phase

Yttria stabilized zirconia is a versatile ceramic material. It can be used for structural components or as a solid electrolyte. Its properties (such as high toughness) are strongly affected by the microstructure. In partially stabilized zirconia, the high toughness is mainly due to the toughening effect of a tetragonal (t) to monoclinic (m) phase transformation in the vicinity of a crack. Retention of tetragonal zirconia at room temperature is important for fabricating transformation toughened materials. To completely retain tetragonal zirconia at room temperature the grain size of the material must be less than a critical size. In yttria stabilized zirconia this critical grain size depends on the yttria concentration. Grain growth of yttria stabilized zirconia is also influenced by the amount of yttria in the grains. These previous studies, however, have focused on the behavior of materials with minimal glassy grain boundary phases. In contrast, in commercial polycrystalline zirconia often a significant amount of glassy grain boundary phase is present. This current research seeks to elucidate the effects of these grain boundary phases on the grain growth in yttria stabilized zirconia ceramics.

Thermal conductivity of AlN ceramic with a very low amount of grain boundary phase at 4 to 1000 K

2002 ◽  
Vol 17 (11) ◽  
pp. 2940-2944 ◽  
Author(s):  
Koji Watari ◽  
Hiromi Nakano ◽  
Kazuyori Urabe ◽  
Kozo Ishizaki ◽  
Shixun Cao ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Grain Boundary ◽  
Single Crystal ◽  
Room Temperature ◽  
Phonon Scattering ◽  
Amorphous Film ◽  
Boundary Phase ◽  
Temperature Conductivity ◽  
Room Temperature Conductivity ◽  
Significant Difference

An AlN ceramic fired at 2173 K for 100 h under a reduced N2 atmosphere with carbon possessed a room-temperature conductivity of 272 Wm−1K−1, slightly lower than the value for high-purity, single-crystal AlN. However, the thermal conductivity of the ceramic at temperatures below 100 K was much lower than that of single crystal. This is mainly due to phonon scattering by grain junctions that possess an amorphous film with a thickness of under 1 nm. At 500 to 1000 K, no significant difference in the conductivity was observed between the ceramic and the single crystal.

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