The effect of size, morphology and crystallinity of seed crystals on the nucleation and growth of Y–Ba–Cu–O single-grain superconductors

2004 ◽  
Vol 18 (1) ◽  
pp. 64-72 ◽  
Author(s):  
E Sudhakar Reddy ◽  
N Hari Babu ◽  
K Iida ◽  
T D Withnell ◽  
Y Shi ◽  
...  
Keyword(s):  
Nucleation And Growth ◽  
Seed Crystals ◽  
Single Grain

Fabrication of a good-quality single grain YBCO sample through the control of seed crystals

1999 ◽  
Vol 35 (5) ◽  
pp. 4070-4072
Author(s):  
Chan-Joong Kim ◽  
Gye-Won Hong ◽  
Y.A. Jee ◽  
Young-Hee Han ◽  
Sang-Chul Han ◽  
...  
Keyword(s):  
Seed Crystals ◽  
Ybco Sample ◽  
Single Grain

CAFE Modeling of Segregation and Structure in Levitated Droplets

2010 ◽  
Vol 649 ◽  
pp. 237-242 ◽  
Author(s):  
Salem Mosbah ◽  
Michel Bellet ◽  
Charles-André Gandin
Keyword(s):  
Finite Element ◽  
Mushy Zone ◽  
Mass Exchange ◽  
Nucleation And Growth ◽  
Fe Model ◽  
Back Diffusion ◽  
Two Dimensional ◽  
Spherical Domain ◽  
Levitated Droplets ◽  
Single Grain

The coupled two dimensional (2D) Cellular Automaton (CA) Finite Element (FE) model has been extended based on the recent work by Guillemot et al. [1]. Extensions concern i microsegregation at the scale of the CA cells ii macrosegregation at the scale of the FE mesh based on a remeshing technique. The model is applied to segregation taking place upon single grain nucleation and growth from the centre of a spherical domain. The simulation retrieves the prediction of Heringer et al. [2]. Application to solidification of a spherical Al-4wt%Cu droplet demonstrates its capability to deal with mass exchange by diffusion outside the grain envelope defined by the mushy zone together with back diffusion in the solid [3].

Mg-doped Nd-Ba-Cu-O generic seed crystals for the top-seeded melt growth of large-grain (rare earth)-Ba-Cu-O bulk superconductors

2006 ◽  
Vol 21 (6) ◽  
pp. 1355-1362 ◽  
Author(s):  
Y. Shi ◽  
N. Hari Babu ◽  
K. Iida ◽  
D.A. Cardwell
Keyword(s):  
Rare Earth ◽  
Volume Fraction ◽  
Seed Crystal ◽  
Superconducting Properties ◽  
Seed Crystals ◽  
Bulk Superconductors ◽  
Wide Range ◽  
Single Grain ◽  
Basic Characteristics ◽  
Mg Doped

We report the fabrication of Mg-doped NdBCO generic seed crystals, which have been developed recently for the fabrication of any rare earth (RE) based (RE)-Ba-Cu-O single-grain superconductor, with a wide range of Nd1+xBa2-xCu3-yMgyO7-δ compositions. Three basic characteristics of the seed crystals required for effective seeding of bulk (RE)BCO materials were studied in detail. We report the chemical, crystallographic, microstructural, and superconducting properties of the seeds and demonstrate clearly their potential to process various (RE)BCO superconductors in single-grain form. The melting point, volume fraction of Mg-rich inclusions in the bulk microstructure, and the chemical composition of the Nd1+xBa2-xCu3-yMgyO7-δ superconducting matrix of the seed crystals were studied as a function of initial MgO content. Finally, the suitable range of MgO-content within the generic seed crystal that controls effectively the orientation of the seeded grain without compromising its superconducting properties relative to those of the Mg-free compound is identified based on the wide range of seed crystal compositions investigated.

Martensite Spread: Analytical Modeling and Computer Simulation

2014 ◽  
Vol 783-786 ◽  
pp. 2182-2187 ◽  
Author(s):  
Paulo Rangel Rios ◽  
Gustavo da Silva Drumond ◽  
Tiago Neves ◽  
José Roberto Costa Guimarães
Keyword(s):  
Computer Simulation ◽  
Analytical Methods ◽  
Martensite Transformation ◽  
Stochastic Geometry ◽  
Analytical Modeling ◽  
Nucleation And Growth ◽  
Nucleation Event ◽  
Growth Processes ◽  
Formal Kinetics ◽  
Single Grain

In bulk polycrystals, the first nucleation event in a single grain may induce transformationin neighboring grains, resulting in a cluster of partially transformed grains. This cluster of partiallytransformed grains is normally designated as a ‘spread event’. The collection of these single spreadevents can be defined as the ‘spread’or ‘martensite spread’. In this paper we show how the martensitespreadmay be well described by formal kinetics. Spread taking place as a result of athermalmartensitetransformation, isothermal martensite transformation and even martensite burst are analyzed with thehelp of such a methodology. Formal kinetics is essentially based on a stochastic geometry approach ofthe transformations considered as nucleation and growth (or birth-and-growth ) processes. Therefore,the success of such an analysis strongly suggests the possibility of a computer simulation of the spreadentirely based on probabilistic considerations. Such a simulation has been carried out and the resultsare discussed in this paper with reference to the results obtained by the analytical methods.

AEM analysis of crystallization in Ti-based amorphous alloys

1983 ◽  
Vol 41 ◽  
pp. 270-271
Author(s):  
A.R. Pelton ◽  
A.F. Marshall ◽  
Y.S. Lee
Keyword(s):  
Magnetic Properties ◽  
Amorphous Alloys ◽  
Amorphous Materials ◽  
Isothermal Annealing ◽  
Amorphous Matrix ◽  
Nucleation And Growth ◽  
Current Interest ◽  
Amorphous Films ◽  
Electrical And Magnetic Properties

Amorphous materials are of current interest due to their desirable mechanical, electrical and magnetic properties. Furthermore, crystallizing amorphous alloys provides an avenue for discerning sequential and competitive phases thus allowing access to otherwise inaccessible crystalline structures. Previous studies have shown the benefits of using AEM to determine crystal structures and compositions of partially crystallized alloys. The present paper will discuss the AEM characterization of crystallized Cu-Ti and Ni-Ti amorphous films.Cu60Ti40: The amorphous alloy Cu60Ti40, when continuously heated, forms a simple intermediate, macrocrystalline phase which then transforms to the ordered, equilibrium Cu3Ti2 phase. However, contrary to what one would expect from kinetic considerations, isothermal annealing below the isochronal crystallization temperature results in direct nucleation and growth of Cu3Ti2 from the amorphous matrix.

Observations oh Nucleation and Growth of Voids in Nickel

1970 ◽  
Vol 28 ◽  
pp. 414-415
Author(s):  
J. L. Brimhall ◽  
H. E. Kissinger ◽  
B. Mastel
Keyword(s):  
High Purity ◽  
Growth Stage ◽  
Elevated Temperatures ◽  
Early Growth ◽  
Nucleation And Growth ◽  
Pure Nickel ◽  
Different Temperatures ◽  
Total Fluence ◽  
Neutron Exposure ◽  
Growth Of Voids

Some information on the size and density of voids that develop in several high purity metals and alloys during irradiation with neutrons at elevated temperatures has been reported as a function of irradiation parameters. An area of particular interest is the nucleation and early growth stage of voids. It is the purpose of this paper to describe the microstructure in high purity nickel after irradiation to a very low but constant neutron exposure at three different temperatures.Annealed specimens of 99-997% pure nickel in the form of foils 75μ thick were irradiated in a capsule to a total fluence of 2.2 × 1019 n/cm2 (E > 1.0 MeV). The capsule consisted of three temperature zones maintained by heaters and monitored by thermocouples at 350, 400, and 450°C, respectively. The temperature was automatically dropped to 60°C while the reactor was down.

Electrochemical nucleation and growth of copper on iron and aluminum: A TEM study of industrial copper cementation

1978 ◽  
Vol 36 (1) ◽  
pp. 454-455
Author(s):  
L.E. Murr ◽  
V. Annamalai
Keyword(s):  
Metal Surface ◽  
Copper Deposit ◽  
Nucleation And Growth ◽  
16Th Century ◽  
Electrochemical Reactions ◽  
Mine Shaft ◽  
De Re ◽  
Copper Precipitation ◽  
Electrochemical Nucleation ◽  
Interesting System

Georgius Agricola in 1556 in his classical book, “De Re Metallica”, mentioned a strange water drawn from a mine shaft near Schmölnitz in Hungary that eroded iron and turned it into copper. This precipitation (or cementation) of copper on iron was employed as a commercial technique for producing copper at the Rio Tinto Mines in Spain in the 16th Century, and it continues today to account for as much as 15 percent of the copper produced by several U.S. copper companies.In addition to the Cu/Fe system, many other similar heterogeneous, electrochemical reactions can occur where ions from solution are reduced to metal on a more electropositive metal surface. In the case of copper precipitation from solution, aluminum is also an interesting system because of economic, environmental (ecological) and energy considerations. In studies of copper cementation on aluminum as an alternative to the historical Cu/Fe system, it was noticed that the two systems (Cu/Fe and Cu/Al) were kinetically very different, and that this difference was due in large part to differences in the structure of the residual, cement-copper deposit.

Fundamental Research into Thin Films in a Developing Country

1972 ◽  
Vol 30 ◽  
pp. 500-501
Author(s):  
J.A. Eades ◽  
E. Grünbaum
Keyword(s):  
Thin Films ◽  
Growth Process ◽  
Empirical Process ◽  
Nucleation And Growth ◽  
Research Groups ◽  
Film Research ◽  
Fundamental Research ◽  
Controlled Deposition ◽  
The One ◽  
The University

In the last decade and a half, thin film research, particularly research into problems associated with epitaxy, has developed from a simple empirical process of determining the conditions for epitaxy into a complex analytical and experimental study of the nucleation and growth process on the one hand and a technology of very great importance on the other. During this period the thin films group of the University of Chile has studied the epitaxy of metals on metal and insulating substrates. The development of the group, one of the first research groups in physics to be established in the country, has parallelled the increasing complexity of the field.The elaborate techniques and equipment now needed for research into thin films may be illustrated by considering the plant and facilities of this group as characteristic of a good system for the controlled deposition and study of thin films.

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