Synthesis of nanocrystalline Spinel phase by Mechanical Milling of Al-Cu-Fe and Al-Cu-Cr-Fe Quasicrystalline alloys

TL;DR

This study demonstrates low-temperature synthesis of nanocrystalline spinel phases from quasicrystalline alloys through mechanical milling and annealing, revealing phase transformations and optical properties of the resulting nanospinels.

Contribution

It introduces a novel low-temperature method for synthesizing nanocrystalline spinel phases from quasicrystalline alloys using mechanical milling and controlled annealing.

Findings

Spinel phases formed at 500°C after milling.

Nanospinel grains sized 20-40 nm confirmed by microscopy.

Optical absorption properties characterized by UV-Vis spectroscopy.

Abstract

In the present study, low-temperature synthesis of (Cu Fe)Al2O4 and (Cu Cr Fe)Al2O4 spinels from the quasicrystalline phases was investigated with the variation of process parameters during milling and annealing. The milling of the quasicrystalline materials was carried out in an attritor mill at 400 rpm for 40 hours with ball to powder ratio of 40:1 in hexane medium. Subsequently, annealing was performed in an air ambience for 10, 20, and 40 h at 400, 500, 600 and 700 C in side a furnace in order to oxidize the mechanically milled quasicrystalline phase for the possible formation of the spinel phase. It was found that after annealing at higher temperature (500 C), mechanically milled quasicrystalline alloy transformed to spinel phase whereas annealing at lower temperature (500 C) it led to the formation of B2 phase as a major one along with minor amount of oxide phase. The X-ray diffraction and transmission electron microscopy of the annealed samples confirmed the formation of spinel phase with an average grain size of 20-40 nm. It is interesting to note that the nanospinel phases showed the different colors during various annealing time and temperature. The optical properties of nanospinel materials, investigated employing UV visible spectrometer exhibited absorption characteristics.