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Evolution of a Nanocrystalline (Co,Ni)Al 2 O 4 Spinel Phase from Quasicrystalline Precursor
Author(s) -
Yadav Thakur Prasad,
Tiwari Radhey Shyam,
Srivastava Onkar Nath,
Mukhopadhyay Nilay Krishna
Publication year - 2008
Publication title -
international journal of applied ceramic technology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.4
H-Index - 57
eISSN - 1744-7402
pISSN - 1546-542X
DOI - 10.1111/j.1744-7402.2008.02243.x
Subject(s) - materials science , crystallite , nanocrystalline material , spinel , ball mill , annealing (glass) , alloy , quasicrystal , transmission electron microscopy , metallurgy , analytical chemistry (journal) , chemical engineering , crystallography , nanotechnology , chemistry , chromatography , engineering
This work reports on the synthesis of a spinel phase from a thermodynamically stable decagonal quasicrystalline Al 70 Co 15 Ni 15 alloy. The Al 70 Co 15 Ni 15 alloy, synthesized through slow cooling of the molten alloy, was subjected to milling in an attritor ball mill at 400 rpm for 5, 10, 20, 30, and 40 h with a ball to powder ratio of 20:1 in the hexane medium. The differential thermal analysis, X‐ray diffraction, scanning, and transmission electron microscopy techniques have been used for characterization of milled as well as annealed powders. The Voigt function analysis has been used for calculation of the effective crystallite size and relative strain of ball‐milled samples. The crystallite size has been found to be ∼14 nm after 40 h of milling along with a lattice strain of 8.1%. The annealing experiments have been carried out under two different conditions: (i) in vacuum and (ii) in air. The results of the present investigation clearly revealed that the nano‐decagonal phase was stable in vacuum while annealing at 600°C for 40 h. However, during annealing under a similar condition in air, the formation of a nanospinel of (Ni,Co)Al 2 O 4 of size ∼60 nm was identified. The possible structural evolution of the spinel from the quasicrystalline phase has been discussed.