Optimization of Phase Formation and Superconducting Properties in MgB2 Prepared by Phase Transformation from MgB4

2012 ◽  
Vol 41 (4) ◽  
pp. 673-678 ◽  
Author(s):  
K. L. Tan ◽  
K. Y. Tan ◽  
K. P. Lim ◽  
A. H. Shaari ◽  
S. K. Chen
Keyword(s):  
Phase Transformation ◽  
Phase Formation ◽  
Superconducting Properties

Effect of V Additions on Bi2223 Phase Formation and Superconducting Properties of (Bi,Pb)2Sr2Ca2Cu3Oz

1998 ◽  
pp. 561-567
Author(s):  
H. Maeda ◽  
K. Kakimoto ◽  
M. Kikuchi ◽  
J. O. Willis ◽  
K. Watanabe ◽  
...  
Keyword(s):  
Phase Formation ◽  
Superconducting Properties

SUPERCONDUCTING PROPERTIES OF (Tl0.64Bi0.16Pb0.2)Ba2−xSrxCa3Cu4Oy BY LIQUID-GAS-SOLIDIFICATION PROCESSING

1991 ◽  
Vol 05 (26) ◽  
pp. 1735-1743
Author(s):  
H. CHOU ◽  
H.S. CHEN ◽  
E.M. GYORGY ◽  
A.R. KORTAN ◽  
L.C. KIMERLING ◽  
...  
Keyword(s):  
Phase Transformation ◽  
Solidification Process ◽  
Tetragonal Structure ◽  
Layer Formation ◽  
Superconducting Properties ◽  
Solidification Processing ◽  
Resistivity Measurements ◽  
Percolation Limit ◽  
Non Equilibrium

The effect of Sr substitution in (Tl0.64Bi0.16Pb0.2)Ba2−xSrxCa3Cu4Oy(x=0, 1, 2) superconductors is studied by liquid-gas-solidification process. (Tl0.64Bi0.16Pb0.2)Ba2−x SrxCa3Cu4Oy forms a tetragonal structure, with a c axis decreasing with Sr content. The substitution of Sr tends to suppress Cu-O layer formation. It also slows down the phase transformation from Tl-rich to Tl-poor phases which may be attributed to a phase equilibration of kinetic origin. The superconducting crystals grow under non-equilibrium and anisotropic conditions, and exhibit platelet and dentritic morphologies. The resistivity measurements indicate percolation effects with a percolation limit of just above 8% of the high Tc phase.

Enhancement of the phase formation and superconducting properties of HgRe1223 through fluorine addition

2000 ◽  
Vol 341-348 ◽  
pp. 513-514 ◽  
Author(s):  
N.M. Hamdan ◽  
P.V.P.S.S. Sastry ◽  
J. Schwatrz
Keyword(s):  
Phase Formation ◽  
Superconducting Properties

Role of Rare Earth Ions (Gd, Dy, Ho and Er) in Phase Formation and Superconducting Properties of Ba1-xLnxCuO3-yCompounds

1989 ◽  
Vol 28 (Part 1, No. 3) ◽  
pp. 324-329
Author(s):  
Shigetoshi Ohshima ◽  
Hiroyuki Ishida ◽  
Tokuo Wakiyama
Keyword(s):  
Rare Earth ◽  
Phase Formation ◽  
Rare Earth Ions ◽  
Superconducting Properties

Phase formation and superconducting properties of mechanically alloyed Nb3(Al1−xGex) system

2016 ◽  
Vol 29 (7) ◽  
pp. 075001 ◽  
Author(s):  
Pingyuan Li ◽  
Yongliang Chen ◽  
Liyuan Xu ◽  
Yun Zhang ◽  
Xifeng Pan ◽  
...  
Keyword(s):  
Phase Formation ◽  
Superconducting Properties ◽  
Mechanically Alloyed

Enhancement of Aurivillius Phase Formation Kinetics in SBT Thin Films using Nanoparticle Seeding

2003 ◽  
Vol 784 ◽  
Author(s):  
Yun-Mo Sung ◽  
Woo-Chul Kwak ◽  
Se-Yon Jung ◽  
Seung-Joon Hwang
Keyword(s):  
Thin Films ◽  
Activation Energy ◽  
Phase Transformation ◽  
Phase Formation ◽  
X Ray Diffraction ◽  
Aurivillius Phase ◽  
X Ray ◽  
Si Substrates ◽  
Formation Kinetics ◽  
Kinetics Of

ABSTRACTPt/Ti/SiO2/Si substrates seeded by SBT nanoparticles (∼60–80 nm) were used to enhance the phase formation kinetics of Sr0.7Bi2.4Ta2O9 (SBT) thin films. The volume fractions of Aurivillius phase formation obtained through quantitative x-ray diffraction (Q-XRD) analyses showed highly enhanced kinetics in seeded SBT thin films. The Avrami exponents were determined as ∼1.4 and ∼0.9 for unseeded and seeded SBT films, respectively, which reveals different nucleation modes. By using Arrhenius–type plots the activation energy values for the phase transformation of unseeded and seeded SBT thin films were determined to be ∼264 and ∼168 kJ/mol, respectively. This gives a key reason to the enhanced kinetics in seeded films. Microstructural analyses on unseeded SBT thin films showed formation of randomly oriented needle-like crystals, while those on seeded ones showed formation of domains comprised of directionally grown worm-like crystals.

An investigation on thermodynamics and kinetics of η phase formation in Nb-modified iron-nickel base A286 superalloy

2020 ◽  
Vol 118 (1) ◽  
pp. 105
Author(s):  
Reza Soleimani Gilakjani ◽  
Seyed Hossein Razavi ◽  
Masoumeh Seifollahi
Keyword(s):  
Heat Treatment ◽  
Phase Transformation ◽  
Phase Formation ◽  
Volume Fraction ◽  
Treatment Time ◽  
Diffusion Activation Energy ◽  
Phase Volume Fraction ◽  
Titanium Nickel ◽  
Nickel Base ◽  
Microstructural Studies

In this study, precipitation of η phase (Ni3Ti) in conventional and Nb-modified (Nb-A286) A286 superalloys was evaluated at different aging times and temperatures. The TTP curve of the η phase formation was plotted using thermodynamic analyses, kinetics and microstructural studies. Depending on temperature and heat treatment, the η phase precipitated at the grain boundaries or twin sites, as a result of the γ′ phase or matrix austenite transformation. Heat treatment of conventional A286 superalloy and Nb-A286 was performed within a temperature range of 650 to 900 °C for 2 to 30 h. The η phase transformation was evaluated by scanning electron microscope (SEM) which is equipped to energy dispersive X-ray spectroscopy (EDS) and optical microscopy (OM). In the analyses based on thermodynamic calculations, the interaction of the Gibbs free energy of η phase formation and the diffusion activation energy of the elements, especially titanium and niobium, was considered. The microstructural studies showed that increasing the heat treatment time results in increasing the volume fraction of the η phase. By increasing the aging temperature to 840 and 860 °C for conventional A286 superalloy and Nb-A286 superalloy, respectively, the η phase volume fraction increased, however, further increase led to volume fraction decrease. The results of the thermodynamic analyses showed the tip of the TTP diagrams at temperatures of 860 and 820 °C for the A286 and Nb-A286 alloys, respectively. Investigation of kinetics calculations showed that η phase transformation depends on the diffusion of titanium, nickel, and niobium.

scholarly journals X-Ray Powder Diffraction Studies of Mechanically Milled Cobalt

2012 ◽  
Vol 626 ◽  
pp. 913-917
Author(s):  
W.S. Yeo ◽  
Z. Nur Amirah ◽  
H.S.C. Metselaar ◽  
T.H. Ong
Keyword(s):  
Grain Size ◽  
Phase Transformation ◽  
Surface Energy ◽  
Phase Formation ◽  
Rietveld Method ◽  
High Energy ◽  
Cubic Phase ◽  
X Ray Diffraction ◽  
Structure Defects ◽  
X Ray

The allotropic phase transformation of cobalt powder prepared by high-energy ball milling was investigated as a function of milling time. Measurement of crystallite size and micro-strain in the powder systems milled for different times were conducted by X-ray diffractometry. The X-ray diffraction (XRD) peaks were analyzed using the Pearson VII profile function in conjunction with Rietveld method. X-ray diffraction line broadening revealed that allotropic transformation between face-centred-cubic phase (fcc) and hexagonal close-packed phase (hcp) in cobalt is grain size dependent and also on the accumulation of structure defects. The results showed that the phase formation of cobalt depends on the mill intensity that influences of both the grain size and the accumulation of structure defects. However, this theory alone is not adequate to explain the effects in this work. It was found that the total surface energy (Ω) theory satisfactorily explains the phase transformation behavior of cobalt. The smaller value of surface energy (Ω) of the fcc crystal than the hcp phase when size decreases may alter the qualitative aspects of the phase formation.

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