Enhanced magnetocaloric effect in Fe-rich (NixFe1-x)70.5B17.7Si7.8Ti4 (x = 0.3 and 0.4) mechanically alloyed nanocrystalline powder

Recent research at Harbin Institute of Technology on the synthesis of nanocrystalline and untrafine grained materials by mechanical alloying is reviewed. Examples of the materials include aluminum alloy, copper alloy, Ti/Al composite, magnesium-based hydrogen storage material, and Nd2Fe14B/α-Fe magnetic nanocomposite. Details of the processes of mechanical alloying and consolidation of the mechanically alloyed nanocrystalline powder materials are presented. The microstructure characteristics and properties of the synthesized materials are addressed.

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The Magnetic and Photo-Catalytic Properties of Fe Doped TiO2 Nanocrystalline Powder Synthesized by Mechanical Alloying

Materials Science Forum ◽

10.4028/www.scientific.net/msf.534-536.229 ◽

2007 ◽

Vol 534-536 ◽

pp. 229-232 ◽

Cited By ~ 3

Author(s):

Young Rang Uhm ◽

S.H. Woo ◽

Min Ku Lee ◽

Chang Kyu Rhee

Keyword(s):

Mechanical Alloying ◽

Paramagnetic Phase ◽

Uv Absorption ◽

Spherical Particles ◽

Nanocrystalline Powders ◽

Ferromagnetic Phase ◽

Nanocrystalline Powder ◽

Mechanically Alloyed ◽

Doped Tio2 ◽

Average Grain Size

Fe-doped TiO2 nanocrystalline powders were prepared by mechanical alloying (MA) by varying Fe contents up to 8.0 wt.%. The TEM analyses were carried out to clarify morphologies and position of Fe within the mechanically alloyed powders. The Fe-doped powder consisted of spherical particles, and the average grain size was less than 10 nm. For the Fe-doped TiO2, the color of the powders changed from white to bright yellow with increasing concentration of Fe. The UVvis absorption showed that the UV absorption for the Fe-doped powder shifted to a longer wavelength (red shift) and the photo-efficiency was enhanced. The absorption threshold depends on the concentration of nano-sized Fe dopant. Mössbauer spectrum for 4 wt.% Fe showed the ferromagnetic phase (sextet) and paramagnetic phase (doublet). However, the only paramagnetic phase (doublet) was seen for 8 wt.% Fe. As the Fe concentration increased up to 4 wt.%, the UV-vis absorption and the magnetization were increased. The beneficial effect of Fe doping for photocatalysis and ferromagnetism was observed at the critical dopant concentration of 4 wt.%. Based on the UV absorption and magnetization, the dopant level was localized to the valence band of TiO2.

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SYNTHESIS AND CHARACTERIZATION OF TiB2 NANOCRYSTALLINE POWDER BY MECHANICAL ALLOYING

International Journal of Modern Physics Conference Series ◽

10.1142/s2010194512002036 ◽

2012 ◽

Vol 05 ◽

pp. 204-211 ◽

Cited By ~ 2

Author(s):

MAHBOOBEH MOALLEM ◽

MOHAMMAD HASAN ABBASI ◽

FATHOLLAH KARIM ZADEH

Keyword(s):

Grain Size ◽

Mechanical Alloying ◽

Ball Milling ◽

Lattice Strain ◽

Structural Evolution ◽

Nanocrystalline Powder ◽

Combustion Mechanism ◽

Mechanically Alloyed ◽

Xrd Patterns

In this investigation, TiB 2 nanocrystalline powder was synthesized by mechanical alloying of the elemental mixture of Ti and B powders in argon atmosphere. In order to study the structural evolution of the powder during ball milling, X-Ray diffraction (XRD) and scanning electron microscopy (SEM) were used. Adiabatic temperature calculations were performed for characterization of TiB 2 powder. Also, the effects of heat treatment on the structural evolution and thermal stability of mechanically alloyed powders were investigated. It was found from the XRD patterns that TiB 2 was formed via combustion mechanism. By increasing milling time, the grain size decreased while the lattice strain increased. SEM micrographs showed that TiB 2 particles were spherical. The grain size and lattice strain reached 24 nm and 1.8% respectively, after 60 hours ball milling.

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Domain studies on mechanically alloyed Fe-Zr-B-Cu-nanocrystalline powder

IEEE Transactions on Magnetics ◽

10.1109/20.538876 ◽

1996 ◽

Vol 32 (5) ◽

pp. 4383-4385 ◽

Cited By ~ 12

Author(s):

R. Schafer ◽

S. Roth ◽

C. Stiller ◽

J. Eckert ◽

U. Klement ◽

...

Keyword(s):

Nanocrystalline Powder ◽

Mechanically Alloyed

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Fine Microstructure of a Mechanically Alloyed Oxide Dispersion Strengthened Nickel-Base Superalloy

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100079012 ◽

1977 ◽

Vol 35 ◽

pp. 298-299

Author(s):

Jordi Marti ◽

Timothy E. Howson ◽

David Kratz ◽

John K. Tien

Keyword(s):

Solid Solution ◽

Volume Fraction ◽

Stress Rupture ◽

Oxide Dispersion Strengthened ◽

Solid Solution Alloy ◽

Oxide Dispersion ◽

Creep And Stress Rupture ◽

Mechanically Alloyed ◽

Fine Microstructure ◽

Nickel Base

The previous paper briefly described the fine microstructure of a mechanically alloyed oxide dispersion strengthened nickel-base solid solution. This note examines the fine microstructure of another mechanically alloyed system. This alloy differs from the one described previously in that it is more generously endowed with coherent precipitate γ forming elements A1 and Ti and it contains a higher volume fraction of the finely dispersed Y2O3 oxide. An interesting question to answer in the comparative study of the creep and stress rupture of these two ODS systems is the role of the precipitate γ' in the mechanisms of creep and stress rupture in alloys already containing oxide dispersoids.The nominal chemical composition of this alloy is Ni - 20%Cr - 2.5%Ti - 1.5% A1 - 1.3%Y203 by weight. The system receives a three stage heat treatment-- the first designed to produce a coarse grain structure similar to the solid solution alloy but with a smaller grain aspect ratio of about ten.

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Microstructure of mechanically alloyed and hot-pressed Al5CuZr2

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100177982 ◽

1990 ◽

Vol 48 (4) ◽

pp. 970-971

Author(s):

T. E. Mitchell ◽

P. B. Desch ◽

R. B. Schwarz

Keyword(s):

Mechanical Alloying ◽

Vickers Hardness ◽

Hot Pressing ◽

Rapid Quenching ◽

Hardened Steel ◽

Alloyed Powder ◽

Ion Milling ◽

Mechanical Grinding ◽

Mechanically Alloyed ◽

Steel Container

Al3Zr has the highest melting temperature (1580°C) among the tri-aluminide intermetal1ics. When prepared by casting, Al3Zr forms in the tetragonal DO23 structure but by rapid quenching or by mechanical alloying (MA) it can also be prepared in the metastable cubic L12 structure. The L12 structure can be stabilized to at least 1300°C by the addition of copper and other elements. We report a TEM study of the microstructure of bulk Al5CuZr2 prepared by hot pressing mechanically alloyed powder.MA was performed in a Spex 800 mixer using a hardened steel container and balls and adding hexane as a surfactant. Between 1.4 and 2.4 wt.% of the hexane decomposed during MA and was incorporated into the alloy. The mechanically alloyed powders were degassed in vacuum at 900°C. They were compacted in a ram press at 900°C into fully dense samples having Vickers hardness of 1025. TEM specimens were prepared by mechanical grinding followed by ion milling at 120 K. TEM was performed on a Philips CM30 at 300kV.

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