Phase Formation, Stability and Superconducting Properties of Mechanically Alloyed Yttrium-Nickel-Borocarbides

1998 ◽  
Vol 547 ◽  
Author(s):  
L. Ledig ◽  
D. Hough ◽  
C.-G. Oertel ◽  
J. Eckert ◽  
W. Skrotzki
Keyword(s):  
Amorphous Phase ◽  
Amorphous State ◽  
Superconducting Properties ◽  
X Ray Diffraction ◽  
Mechanically Alloyed ◽  
X Ray ◽  
Milling Parameters ◽  
Transmission Electron ◽  
Nanocrystalline And Amorphous ◽  
Nickel Borocarbides

AbstractThe solid state reaction of YNi2B2C by mechanical alloying of elemental powders has been investigated by X-ray diffraction, transmission electron microscopy and susceptibility measurements. Depending on the ball milling parameters either nanocrystalline YNi2B2C or an amorphous phase can be produced. Crystallization of the amorphous phase by annealing at 893 K produces YNi2B2C as major and Ni2B as minor intermetallic compound. Superconductivity is only observed in the annealed state. However, the transition temperature is much lower than in arc-melted samples. This is discussed with respect to the nanocrystalline and amorphous state as well as deviations from stoichiometry produced by impurities introduced during milling.

Synthesis of Amorphous Ti50Al50 by Mechanical Alloying

2012 ◽  
Vol 531-532 ◽  
pp. 490-495
Author(s):  
Jun Hong Zhang ◽  
Guo Hui Xu ◽  
Ya Juan Xu ◽  
Yue Hui He
Keyword(s):  
Electron Microscope ◽  
Amorphous Phase ◽  
Critical Density ◽  
Host Lattice ◽  
X Ray Diffraction ◽  
Mechanically Alloyed ◽  
X Ray ◽  
Blended Elemental ◽  
Transmission Electron ◽  
Size Condition

Blended elemental powders with the nominal compositions (at%) of Ti50Al50, was mechanically alloyed in a planetary ball milling system for up to 100h, an amorphous Ti50Al50 phase was obtained in the process. The amorphization process as a function of time of milling was monitored by scanning electron microscope, X-ray diffraction and transmission electron microscope. It is shown that, as first, Al atoms diffuse into the host lattice of hexagonal Ti; subsequently, the milling accumulates a critical density of disorder that causes the Ti (Al) crystalline phase to collapse into an amorphous phase, it is suggested the grain size condition for formation of amorphous phase is 12nm. On the basis of thermodynamic models, the formation of the amorphous phase is discussed.

scholarly journals Structural Evolution in Wet Mechanically Alloyed Co-Fe-(Ta,W)-B Alloys

Metals ◽  
2021 ◽  
Vol 11 (5) ◽  
pp. 800
Author(s):  
Vladimír Girman ◽  
Maksym Lisnichuk ◽  
Daria Yudina ◽  
Miloš Matvija ◽  
Pavol Sovák ◽  
...  
Keyword(s):  
Structural Changes ◽  
Magnetic Measurements ◽  
Structural Evolution ◽  
High Energy ◽  
Control Agent ◽  
X Ray Diffraction ◽  
Mechanically Alloyed ◽  
X Ray ◽  
Transmission Electron ◽  
X Ray Absorption

In the present study, the effect of wet mechanical alloying (MA) on the glass-forming ability (GFA) of Co43Fe20X5.5B31.5 (X = Ta, W) alloys was studied. The structural evolution during MA was investigated using high-energy X-ray diffraction, X-ray absorption spectroscopy, high-resolution transmission electron microscopy and magnetic measurements. Pair distribution function and extended X-ray absorption fine structure spectroscopy were used to characterize local atomic structure at various stages of MA. Besides structural changes, the magnetic properties of both compositions were investigated employing a vibrating sample magnetometer and thermomagnetic measurements. It was shown that using hexane as a process control agent during wet MA resulted in the formation of fully amorphous Co-Fe-Ta-B powder material at a shorter milling time (100 h) as compared to dry MA. It has also been shown that substituting Ta with W effectively suppresses GFA. After 100 h of MA of Co-Fe-W-B mixture, a nanocomposite material consisting of amorphous and nanocrystalline bcc-W phase was synthesized.

Structural and superconducting properties of melt-grown Y–Ba–Cu–O superconductors

1996 ◽  
Vol 11 (10) ◽  
pp. 2406-2415 ◽  
Author(s):  
R. Gopalan ◽  
T. Rajasekharan ◽  
T. Roy ◽  
G. Rangarajan ◽  
V. Ganesan ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Strain Field ◽  
Crack Width ◽  
Growth Process ◽  
Critical Radius ◽  
Radius Of Curvature ◽  
Superconducting Properties ◽  
X Ray Diffraction ◽  
X Ray ◽  
Transmission Electron

YBa2Cu3O7 (123) samples with varying Y2BaCuO5 (211) concentrations (0 mol%, 20 mol%, 28 mol%, and 50 mol%) were synthesized by the melt-growth process. Microstructural characterizations were done using x-ray diffraction (XRD), optical microscopy, scanning electron microscopy, and transmission electron microscopy (TEM). It was found that 123 platelet width, crack width between the platelets, and 211 particle size decreased systematically with increasing 211 concentration. TEM study showed that there is a critical radius of curvature (rc ≤ 0.2 μm-0.3 μm) of the 123/211 interface where defects/contrasts of strain field start to appear, and these defects are believed to be responsible for pinning the magnetic flux. Microhardness measurements showed that Vickers hardness (VHN) increases with increasing 211 content. Critical current density (Jc) values obtained from magnetization measurements using a SQUID magnetometer were found to increase in melt-grown samples by the addition of 211 content.

SOLID STATE AMORPHIZATION IN MECHANICALLY ALLOYED Al–Ti–Si NANOCOMPOSITES

2005 ◽  
Vol 04 (05n06) ◽  
pp. 1025-1028
Author(s):  
I. MANNA ◽  
P. NANDI ◽  
B. BANDYOPADHYAY ◽  
P. M. G. NAMBISSAN ◽  
K. GHOSHRAY ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Solid State ◽  
Amorphous Solid ◽  
Positron Annihilation Spectroscopy ◽  
Intermetallic Phases ◽  
X Ray Diffraction ◽  
Mechanically Alloyed ◽  
X Ray ◽  
Transmission Electron ◽  
State Amorphization

The microstructural evolution at different stages of milling of a ternary powder blend of Al 50 Ti 40 Si 10 composition was monitored by X-ray diffraction, high-resolution transmission electron microscopy, positron annihilation spectroscopy and 27 Al nuclear magnetic resonance. Ball-milling leads to alloying, nanocrystallization and partial solid state amorphization, either followed or accompanied by strain-induced nucleation of nanocrystalline intermetallic phases from an amorphous solid solution.

A structural and calorimetric study of the transformations in sputtered Al–Mn and Al–Mn–Si films

1990 ◽  
Vol 5 (9) ◽  
pp. 1871-1879 ◽  
Author(s):  
L. C. Chen ◽  
F. Spaepen ◽  
J. L. Robertson ◽  
S. C. Moss ◽  
K. Hiraga
Keyword(s):  
Isothermal Calorimetry ◽  
Amorphous State ◽  
Calorimetric Study ◽  
X Ray Diffraction ◽  
X Ray ◽  
Sputtered Films ◽  
Transmission Electron ◽  
Average Grain Size ◽  
Lattice Images ◽  
Si Films

Scanning and isothermal calorimetry, together with x-ray diffraction and high resolution transmission electron microscopy (TEM), have been used to characterize Al–Mn and Al–Mn–Si films sputtered onto substrates at 60 °C, 45 °C, and −100 °C. In the case of Al0.83Mn0.17, the monotonically decreasing isothermal calorimetric signal, characteristic of a grain growth process, has proved decisive in identifying the as-sputtered “amorphous” state as microquasicrystalline, with an average grain size of ∼ 20 Å, in agreement with an estimate of correlation range from the x-ray pattern. The TEM at 400 keV reveals well-defined atomic or lattice images in annealed films but only barely resolved grains (ordered clusters) in the as-sputtered films. The relation between the metallic glass and the microquasicrystalline state in these alloys is discussed.

Solid State Amorphization of Ti60Si40 Alloy via Mechanical Alloying

2021 ◽  
Vol 876 ◽  
pp. 7-12
Author(s):  
Petr Urban ◽  
Fátima Ternero Fernández ◽  
Rosa M. Aranda Louvier ◽  
Raquel Astacio López ◽  
Jesus Cintas Físico
Keyword(s):  
Electron Microscopy ◽  
Particle Size ◽  
Mechanical Alloying ◽  
Amorphous Phase ◽  
Milling Time ◽  
X Ray Diffraction ◽  
Mechanically Alloyed ◽  
Scanning Calorimetry ◽  
Transmission Electron ◽  
Heating Up

The effect of milling time on the microstructure evolution and formation of amorphous phase of Ti60Si40 alloy produced by mechanical alloying (MA) has been investigated. Laser diffraction, Scanning Electron Microscopy (SEM), X-ray Diffraction (XRD), Transmission Electron Microscopy (TEM) and Differential Scanning Calorimetry (DSC) were employed to characterize the particle size, morphology and structure of mechanically alloyed Ti60Si40. When the milling time is increased to 20 h, the particle size decreases from 23.7 to 4.7 μm, the shape of the particles changes to spherical and the crystalline structure is transformed into an amorphous phase. The amorphous Ti60Si40 alloy is stable when heating up to 750oC. Above this temperature, the cold crystallization of the intermetallic compounds Ti5Si3 and/or Ti5Si4 begins.

Effect of film composition on the orientation of (Ba,Sr)TiO3 grains in (Ba,Sr)yTiO2+ythin films

1999 ◽  
Vol 14 (12) ◽  
pp. 4657-4666 ◽  
Author(s):  
Debra L. Kaiser ◽  
Mark D. Vaudin ◽  
Lawrence D. Rotter ◽  
John E. Bonevich ◽  
Igor Levin ◽  
...  
Keyword(s):  
Amorphous Phase ◽  
Composition Dependence ◽  
Compressive Strain ◽  
Chemical Vapor ◽  
Growth Conditions ◽  
X Ray Diffraction ◽  
Two Phase ◽  
Film Composition ◽  
X Ray ◽  
Transmission Electron

Thin films of composition (Ba,Sr)yTiO2+y with 0.43 ≤ y ≤; 1.64, were deposited by metalorganic chemical vapor deposition on (100) MgO substrates at various growth conditions. X-ray diffraction and transmission electron microscopy studies showed that the films were composed of epitaxial Ba1–xSrxTiO3 (x ≈0.06) grains and an amorphous phase. The orientation of the tetragonal Ba1–xSrxTiO3 grains (pure a axis, pure c axis, or a mix of the two) was found to be strongly dependent upon film composition. This composition dependence is explained for the majority of the Ti-rich films by an analysis of average strains in the two-phase films, assuming a compressive strain of ≈1% in the amorphous phase.

Formation of intermetallic nanocomposites in the Ti–Al–Si system by mechanical alloying and subsequent heat treatment

1998 ◽  
Vol 13 (5) ◽  
pp. 1198-1203 ◽  
Author(s):  
K. W. Liu ◽  
J. S. Zhang ◽  
J. G. Wang ◽  
G. L. Chen
Keyword(s):  
Amorphous Phase ◽  
Titanium Aluminides ◽  
Annealing Treatment ◽  
X Ray Diffraction ◽  
X Ray ◽  
Nanocrystalline Composites ◽  
Transmission Electron ◽  
Crystallization Reaction ◽  
Different Temperatures ◽  
20 Nm

Formation of nanocrystalline Al3Ti, TiAl, Ti3Al, and Ti5Si3 composites by mechanically alloying (MA) in the Ti–Al–Si system and subsequent annealing treatment are investigated. Microstructure development was monitored by x-ray diffraction, differential thermal analysis, and transmission electron microscopy. An amorphous phase could be generated through milling for 100 h. The results of annealing at different temperatures on this amorphous phase show that the formation of titanium aluminides (Al3Ti, TiAl, and Ti3Al, according to the initial relative amount of Ti and Al) and Ti5Si3 (the only silicide produced by the crystallization reaction) take place. Annealing produces nanocrystalline composites of Al3Ti, TiAl, Ti3Al, and Ti5Si3 with a grain size less than 20 nm. With increasing annealing temperature, the crystalline sizes of the phases increased.

Synthesis and Evaluations of Microstructure Properties on Al-(50, 60, 70 mass%)Si Systems by Mechanical Alloying

2004 ◽  
Vol 449-452 ◽  
pp. 249-252 ◽  
Author(s):  
Jung Il Lee ◽  
Tae Whan Hong ◽  
Il Ho Kim ◽  
Soon Chul Ur ◽  
Young Geun Lee ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Mechanical Alloying ◽  
Milling Time ◽  
Alloy System ◽  
Misfit Strain ◽  
X Ray Diffraction ◽  
Mechanically Alloyed ◽  
X Ray ◽  
Transmission Electron ◽  
Nanocrystalline Structures

High silicon Al-Si alloy powders having nanocrystalline structures have been produced by mechanical alloying process. Microstructures in mechanically alloyed Al-Si powders were investigated by scanning electron microscopy and transmission electron microscopy. X-ray diffraction analyses were also carried out to characterize lattice constant, crystallite size and misfit strain. Effective milling time for the formation of nanocrystalline microstructure was thought to be approximately 12 hours, and the sizes of Al and Si crystallites in mechanically alloyed powders after longer than 12 hours of milling were reduced to about 30nm and 70nm respectively, in Al-70 mass% Si alloy system. The misfit strains increased with milling time up to 240 hours, and saturated to 5.73×10-3 and 4.39×10-3 for Al and Si crystallites, respectively.

Effects of Milling Variables in Amorphous Phase Formation of Fe78Si9B13 Alloy Produced by Mechanical Alloying

2021 ◽  
Vol 876 ◽  
pp. 19-24
Author(s):  
Raquel Astacio López ◽  
Rosa M. Aranda Louvier ◽  
Petr Urban ◽  
Fátima Ternero Fernández ◽  
Juan Manuel Montes Martos
Keyword(s):  
Electron Microscopy ◽  
Mechanical Alloying ◽  
Amorphous Phase ◽  
Milling Time ◽  
Morphological Evolution ◽  
X Ray Diffraction ◽  
Transmission Electron ◽  
Nanocrystalline And Amorphous ◽  
Gas Atmosphere ◽  
Amorphous Phase Formation

In this study, amorphous Fe78Si9B13 alloy was successfully synthesized by mechanical alloying (MA) of pure elemental powders which were milled under an argon gas atmosphere. Effects of milling time on the phase transformation, microstructure and morphological evolution were studied by X-ray diffraction (XRD), laser diffraction (Granulometry), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Results showed that by increasing the milling time, the nanocrystalline and amorphous phase content increases and alloys with good properties are obtained at 100 h of milling.

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