Influence of the high energy ball milling on structure and reactivity of the Ni+Al powder mixture

•We use high – energetic planetary ball mill to activate Ni+Al powder mixtures.•Temperature of the reaction initiation decreases depending on the activation mode.•Nanocrystalline and amorphous phases, non-detectable by XRD, found by HR TEM.•Formation of the nano-structures are responsible for increa...

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Bibliographic Details
Published in:Journal of alloys and compounds 2013-11, Vol.577, p.600-605
Main Authors: Rogachev, A.S., Shkodich, N.F., Vadchenko, S.G., Baras, F., Kovalev, D.Yu, Rouvimov, S., Nepapushev, A.A., Mukasyan, A.S.
Format: Article
Language:English
Subjects:
Aluminum
Atomic scale structure
Atomic structure
Ball milling
Intermetallics
Mechanical alloying
Microstructure
Nanocomposites
Nanocrystals
Nanomaterials
Nanostructure
Nickel
Nuclei
Phases
Transmission electron microscopy
X-ray diffraction
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Summary:•We use high – energetic planetary ball mill to activate Ni+Al powder mixtures.•Temperature of the reaction initiation decreases depending on the activation mode.•Nanocrystalline and amorphous phases, non-detectable by XRD, found by HR TEM.•Formation of the nano-structures are responsible for increasing reactivity.•A model explaining dependence of reactivity on microstructure is proposed. Investigation of the micro- and atomic structures for the planetary ball-milled Ni+Al mixtures has revealed existence of intermediate nano-crystalline and amorphous phases, which are not detectable by XRD analysis, but can be observed by means of HRTEM. Annealing of the milled mixtures at moderate temperature, 205–280°C, transforms the nano-phases into crystal state and makes them XRD-detectable. These nano-scale structures may serve as nucleus for the intermetallic phases produced via reaction between Ni and Al and, therefore, decrease the activation energy of this reaction and diminish the temperature of the reaction initiation. Apparently, the active nano-phases are formed due to sliding of Al and Ni layers during the ball milling. The simple model is suggested, which allows non-contradictory explanations of the nucleus formation and their influence on the reactivity of the mixture.
ISSN:0925-8388
1873-4669
DOI:10.1016/j.jallcom.2013.06.114