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The effect of mechanical activation on synthesis and properties of MgAl2O4 ceramics

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2019
Obradovic_ECERS2019.pdf (2.037Mb)
Authors
Obradović, Nina
Fahrenholtz, William G.
Filipović, Suzana
Kosanović, Darko
Dapčević, Aleksandra
Rogan, Jelena
Pavlović, Vladimir B.
Conference object (Published version)
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Abstract
Magnesium aluminate, MgAl2O4, and other alumina-based spinels are refractory ceramics with high hardness and resistance to chemical attack while also being possible microwave dielectrics. Pure MgAl2O4 can be optically transparent when fully dense. Spinels exhibit inversion, which results in disorder among occupancy of A and B site cations. The goal of this study was to examine the effects of mechanical activation and composition on the temperature required for spinel formation and the site occupancy in the resulting spinel. MgAl2O4 was produced by solid state reaction between MgO and alpha-Al2O3. The starting powders were mixed by ball milling to homogenize the powders 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 1500 °C with 2 h dwell time, to determine the amount of sp...inel 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 influence of milling and consolidation parameters were studied by electrical measurements and mechanical characterization. The main results of this study were that mechanical activation for 60 minutes initiated a mechano-chemical reaction, and resulted in spinel formation at much lower temperatures than within non-activated powders. Microstructures of ceramics sintered below 1400 oC indicated that final stage sintering started at much lower temperatures for activated samples than for non-activated samples. 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.

Keywords:
mechanical activation / sintering / spinel / magnesium aluminate / MgAl2O4
Source:
Abstract Book / XVI Conference and Exhibition of the European Ceramic Society XVI ECerS Conference, Torino, 16-20 June 2019, 2019, 262-262
Publisher:
  • Societa ceramica italiana
  • Politecnico di Torino
Funding / projects:
  • Directed synthesis, structure and properties of multifunctional materials (RS-172057)
[ Google Scholar ]
Handle
https://hdl.handle.net/21.15107/rcub_dais_7022
URI
https://dais.sanu.ac.rs/123456789/7022
Collections
  • ИТН САНУ - Општа колекција / ITS SASA - General collection
Institution/Community
Институт техничких наука САНУ / Institute of Technical Sciences of SASA
TY  - CONF
AU  - Obradović, Nina
AU  - Fahrenholtz, William G.
AU  - Filipović, Suzana
AU  - Kosanović, Darko
AU  - Dapčević, Aleksandra
AU  - Rogan, Jelena
AU  - Pavlović, Vladimir B.
PY  - 2019
UR  - https://dais.sanu.ac.rs/123456789/7022
AB  - Magnesium aluminate, MgAl2O4, and other alumina-based spinels are refractory ceramics with high hardness and resistance to chemical attack while also being possible microwave dielectrics. Pure MgAl2O4 can be optically transparent when fully dense. Spinels exhibit inversion, which results in disorder among occupancy of A and B site cations. The goal of this study was to examine the effects of mechanical activation and composition on the temperature required for spinel formation and the site occupancy in the resulting spinel. 
MgAl2O4 was produced by solid state reaction between MgO and alpha-Al2O3. The starting powders were mixed by ball milling to homogenize the powders 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 1500 °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 influence of milling and consolidation parameters were studied by electrical measurements and mechanical characterization. 
The main results of this study were that mechanical activation for 60 minutes initiated a mechano-chemical reaction, and resulted in spinel formation at much lower temperatures than within non-activated powders. Microstructures of ceramics sintered below 1400 oC indicated that final stage sintering started at much lower temperatures for activated samples than for non-activated samples. 
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.
PB  - Societa ceramica italiana
PB  - Politecnico di Torino
C3  - Abstract Book / XVI Conference and Exhibition of the European Ceramic Society XVI ECerS Conference, Torino, 16-20 June 2019
T1  - The effect of mechanical activation on synthesis and properties of MgAl2O4 ceramics
SP  - 262
EP  - 262
UR  - https://hdl.handle.net/21.15107/rcub_dais_7022
ER  - 
@conference{
author = "Obradović, Nina and Fahrenholtz, William G. and Filipović, Suzana and Kosanović, Darko and Dapčević, Aleksandra and Rogan, Jelena and Pavlović, Vladimir B.",
year = "2019",
abstract = "Magnesium aluminate, MgAl2O4, and other alumina-based spinels are refractory ceramics with high hardness and resistance to chemical attack while also being possible microwave dielectrics. Pure MgAl2O4 can be optically transparent when fully dense. Spinels exhibit inversion, which results in disorder among occupancy of A and B site cations. The goal of this study was to examine the effects of mechanical activation and composition on the temperature required for spinel formation and the site occupancy in the resulting spinel. 
MgAl2O4 was produced by solid state reaction between MgO and alpha-Al2O3. The starting powders were mixed by ball milling to homogenize the powders 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 1500 °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 influence of milling and consolidation parameters were studied by electrical measurements and mechanical characterization. 
The main results of this study were that mechanical activation for 60 minutes initiated a mechano-chemical reaction, and resulted in spinel formation at much lower temperatures than within non-activated powders. Microstructures of ceramics sintered below 1400 oC indicated that final stage sintering started at much lower temperatures for activated samples than for non-activated samples. 
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.",
publisher = "Societa ceramica italiana, Politecnico di Torino",
journal = "Abstract Book / XVI Conference and Exhibition of the European Ceramic Society XVI ECerS Conference, Torino, 16-20 June 2019",
title = "The effect of mechanical activation on synthesis and properties of MgAl2O4 ceramics",
pages = "262-262",
url = "https://hdl.handle.net/21.15107/rcub_dais_7022"
}
Obradović, N., Fahrenholtz, W. G., Filipović, S., Kosanović, D., Dapčević, A., Rogan, J.,& Pavlović, V. B.. (2019). The effect of mechanical activation on synthesis and properties of MgAl2O4 ceramics. in Abstract Book / XVI Conference and Exhibition of the European Ceramic Society XVI ECerS Conference, Torino, 16-20 June 2019
Societa ceramica italiana., 262-262.
https://hdl.handle.net/21.15107/rcub_dais_7022
Obradović N, Fahrenholtz WG, Filipović S, Kosanović D, Dapčević A, Rogan J, Pavlović VB. The effect of mechanical activation on synthesis and properties of MgAl2O4 ceramics. in Abstract Book / XVI Conference and Exhibition of the European Ceramic Society XVI ECerS Conference, Torino, 16-20 June 2019. 2019;:262-262.
https://hdl.handle.net/21.15107/rcub_dais_7022 .
Obradović, Nina, Fahrenholtz, William G., Filipović, Suzana, Kosanović, Darko, Dapčević, Aleksandra, Rogan, Jelena, Pavlović, Vladimir B., "The effect of mechanical activation on synthesis and properties of MgAl2O4 ceramics" in Abstract Book / XVI Conference and Exhibition of the European Ceramic Society XVI ECerS Conference, Torino, 16-20 June 2019 (2019):262-262,
https://hdl.handle.net/21.15107/rcub_dais_7022 .

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