The Effect of Mechanical Activation on Synthesis and Properties of MgAl₂O₄ Ceramics
Magnesium aluminate, MgAl2O4 and other alumina-based spinels are ceramics with high hardness, high melting point and mechanical strenght. Spinels can also be used as dielectrics in microwave applications. The goal of this study was to examine the effects of mechanical activation and sintering temperatures on physico-chemical properties of spinel.
MgAl2O4 was produced by solid state reaction between MgO and α-Al2O3 . The starting powders were mixed by ball milling to homogenize without significant particle size reduction. Mechanical activation of mixed powders was performed in a high-energy planetary ball mill in air for 1 h. Powders were compacted at 300 MPa. Heat treatments were performed in air, at temperatures ranging from 1200 to 1600 °C with 2 h dwell time, to determine the amount of spinel formation as a function of temperature. Phase composition and microstructure of initial powders and heated samples were determined by means of X-ray diffraction, particle size analysis, and scanning electron microscopy. The influences of milling and consolidation parameters were studied by electrical measurements and mechanical characterization.
The main conclusion of this study was that mechanical activation for 60 min initiated a mechano-chemical reaction, resulted in spinel formation at much lower temperatures than within non-activated powders, and indicated that final sintering stage started at much lower temperatures for activated powders. Changes in microstructure parameters, as a consequence of mechanical treatment and subsequent heating of investigated powder mixtures, strongly affect electrical and mechanical properties of the final ceramics.
N. Obradovic et al., "The Effect of Mechanical Activation on Synthesis and Properties of MgAl₂O₄ Ceramics," Ceramics International, vol. 45, no. 9, pp. 12015 - 12021, Elsevier Ltd, Jun 2019.
The definitive version is available at https://doi.org/10.1016/j.ceramint.2019.03.095
Materials Science and Engineering
Keywords and Phrases
Electrical properties; Mechanical activation; Mechanical properties; Microstructure; Sintering; Spinel
International Standard Serial Number (ISSN)
Article - Journal
© 2019 Elsevier Ltd and Techna Group S.r.l. , All rights reserved.
01 Jun 2019