TY  - JOUR
AU  - Obradović, Nina
AU  - Filipović, Suzana
AU  - Fahrenholtz, William G.
AU  - Marinkovic, Bojan A.
AU  - Rogan, Jelena
AU  - Lević, Steva
AU  - Đorđević, Antonije
AU  - Pavlović, Vladimir B.
UR  - https://doiserbia.nb.rs/Article.aspx?ID=0350-820X2301001O
UR  - http://aspace.agrif.bg.ac.rs/handle/123456789/6372
AB  - Magnesium aluminate has the spinel structure along with good mechanical, chemical, and thermal properties. Magnesium aluminate has a wide range of applications including refractory ceramics, optically transparent ceramic windows, and armors. Its low dielectric permeability and low loss tangent enable its applications for integrated electronic devices, as well. In this paper, MgO and Al2O3 powders were mixed in a one-to-one molar ratio and calcined at temperatures ranging from 1500 to 1800o C to produce phase pure spinel. Thereafter, pellets were crushed and treated in a planetary ball mill for 60 min to obtain a fine powder. All powders were examined for phase composition, crystal structure, and morphology. The obtained results showed that by increasing the temperature, samples with higher density were synthesized. Milling for 1 h led to formation of larger particles, but finer powders after milling. XRPD and Raman spectroscopy showed disorder in the crystal structure after milling.
T2  - Science of Sintering, 55 (2023) 1-10
T1  - Morphological and structural characterization of MgAl2O4 spinel.
DO  - 10.2298/SOS2301001O
ER  - 

@article{
author = "Obradović, Nina and Filipović, Suzana and Fahrenholtz, William G. and Marinkovic, Bojan A. and Rogan, Jelena and Lević, Steva and Đorđević, Antonije and Pavlović, Vladimir B.",
abstract = "Magnesium aluminate has the spinel structure along with good mechanical, chemical, and thermal properties. Magnesium aluminate has a wide range of applications including refractory ceramics, optically transparent ceramic windows, and armors. Its low dielectric permeability and low loss tangent enable its applications for integrated electronic devices, as well. In this paper, MgO and Al2O3 powders were mixed in a one-to-one molar ratio and calcined at temperatures ranging from 1500 to 1800o C to produce phase pure spinel. Thereafter, pellets were crushed and treated in a planetary ball mill for 60 min to obtain a fine powder. All powders were examined for phase composition, crystal structure, and morphology. The obtained results showed that by increasing the temperature, samples with higher density were synthesized. Milling for 1 h led to formation of larger particles, but finer powders after milling. XRPD and Raman spectroscopy showed disorder in the crystal structure after milling.",
journal = "Science of Sintering, 55 (2023) 1-10",
title = "Morphological and structural characterization of MgAl2O4 spinel.",
doi = "10.2298/SOS2301001O"
}

Obradović, N., Filipović, S., Fahrenholtz, W. G., Marinkovic, B. A., Rogan, J., Lević, S., Đorđević, A.,& Pavlović, V. B..Morphological and structural characterization of MgAl2O4 spinel.. in Science of Sintering, 55 (2023) 1-10.
https://doi.org/10.2298/SOS2301001O

Obradović N, Filipović S, Fahrenholtz WG, Marinkovic BA, Rogan J, Lević S, Đorđević A, Pavlović VB. Morphological and structural characterization of MgAl2O4 spinel.. in Science of Sintering, 55 (2023) 1-10..
doi:10.2298/SOS2301001O .

Obradović, Nina, Filipović, Suzana, Fahrenholtz, William G., Marinkovic, Bojan A., Rogan, Jelena, Lević, Steva, Đorđević, Antonije, Pavlović, Vladimir B., "Morphological and structural characterization of MgAl2O4 spinel." in Science of Sintering, 55 (2023) 1-10,
https://doi.org/10.2298/SOS2301001O . .

TY  - JOUR
AU  - Obradović, Nina
AU  - Fahrenholtz, William G.
AU  - Filipović, Suzana
AU  - Marković, Smilja
AU  - Blagojević, Vladimir A.
AU  - Lević, Steva
AU  - Savić, Slobodan
AU  - Djordjević, Antonije
AU  - Pavlović, Vladimir
PY  - 2020
UR  - http://aspace.agrif.bg.ac.rs/handle/123456789/5344
AB  - Solid-state mechanical activation of MgO and alpha-Al2O3 powders was used to produce MgAl2O4. The cation site occupancy in the resulting MgAl2O4 spinel was investigated using different methods. Differential thermal analysis and thermal gravimetry showed that mechanical activation reduced the spinel formation temperature by around 200 degrees C, and the corresponding activation energy by about 25%. In addition, characteristic temperatures for evaporation of physisorbed water and decomposition of Mg(OH)(2) shifted to lower values, and peaks were more pronounced. Raman spectra were used to characterize the degree of inversion as a function of the sintering temperature for all of the sintered specimens, indicating that the breaking point for ordering of the crystal structure was around 1500 degrees C for non-activated samples, and 1400 degrees C for activated samples.
PB  - Springer, Dordrecht
T2  - Journal of Thermal Analysis and Calorimetry
T1  - Formation kinetics and cation inversion in mechanically activated MgAl2O4 spinel ceramics
EP  - 107
IS  - 1
SP  - 95
VL  - 140
DO  - 10.1007/s10973-019-08846-w
ER  - 

@article{
author = "Obradović, Nina and Fahrenholtz, William G. and Filipović, Suzana and Marković, Smilja and Blagojević, Vladimir A. and Lević, Steva and Savić, Slobodan and Djordjević, Antonije and Pavlović, Vladimir",
year = "2020",
abstract = "Solid-state mechanical activation of MgO and alpha-Al2O3 powders was used to produce MgAl2O4. The cation site occupancy in the resulting MgAl2O4 spinel was investigated using different methods. Differential thermal analysis and thermal gravimetry showed that mechanical activation reduced the spinel formation temperature by around 200 degrees C, and the corresponding activation energy by about 25%. In addition, characteristic temperatures for evaporation of physisorbed water and decomposition of Mg(OH)(2) shifted to lower values, and peaks were more pronounced. Raman spectra were used to characterize the degree of inversion as a function of the sintering temperature for all of the sintered specimens, indicating that the breaking point for ordering of the crystal structure was around 1500 degrees C for non-activated samples, and 1400 degrees C for activated samples.",
publisher = "Springer, Dordrecht",
journal = "Journal of Thermal Analysis and Calorimetry",
title = "Formation kinetics and cation inversion in mechanically activated MgAl2O4 spinel ceramics",
pages = "107-95",
number = "1",
volume = "140",
doi = "10.1007/s10973-019-08846-w"
}

Obradović, N., Fahrenholtz, W. G., Filipović, S., Marković, S., Blagojević, V. A., Lević, S., Savić, S., Djordjević, A.,& Pavlović, V.. (2020). Formation kinetics and cation inversion in mechanically activated MgAl2O4 spinel ceramics. in Journal of Thermal Analysis and Calorimetry
Springer, Dordrecht., 140(1), 95-107.
https://doi.org/10.1007/s10973-019-08846-w

Obradović N, Fahrenholtz WG, Filipović S, Marković S, Blagojević VA, Lević S, Savić S, Djordjević A, Pavlović V. Formation kinetics and cation inversion in mechanically activated MgAl2O4 spinel ceramics. in Journal of Thermal Analysis and Calorimetry. 2020;140(1):95-107.
doi:10.1007/s10973-019-08846-w .

Obradović, Nina, Fahrenholtz, William G., Filipović, Suzana, Marković, Smilja, Blagojević, Vladimir A., Lević, Steva, Savić, Slobodan, Djordjević, Antonije, Pavlović, Vladimir, "Formation kinetics and cation inversion in mechanically activated MgAl2O4 spinel ceramics" in Journal of Thermal Analysis and Calorimetry, 140, no. 1 (2020):95-107,
https://doi.org/10.1007/s10973-019-08846-w . .

TY  - CONF
AU  - Obradović, Nina
AU  - Fahrenholtz, William G.
AU  - Filipović, Suzana
AU  - Đorđević, Pavle
AU  - Rogan, Jelena
AU  - Pavlović, Vladimir
PY  - 2019
UR  - http://dais.sanu.ac.rs/123456789/7050
UR  - http://aspace.agrif.bg.ac.rs/handle/123456789/5757
AB  - Magnesium aluminate and other alumina-based spinels attract attention due to their high hardness, high mechanical strength, and low dielectric constant. MgAl2O4 was produced by solid-state reaction between MgO and a-Al2O3 powders. Mechanical activation was used to increase the reactivity of powders and decrease the sintering temperatures. Mechanical activation of mixed powders was performed in a high-energy planetary ball mill in air for 30, 60, 90, and 120 minutes. The resulting powders were characterized to determine the effect of activation on surface area, particle size, and crystallinity. Mechanical activation decreased particle size, increased surface area, and increased the width of peaks in x-ray diffraction. Dilatometry was used to monitor densification behavior up to 1500 °C. For non-activated powders, sintering started at approximately 1400 °C, while for activated powders, the onset temperature decreased to about 1340 °C. Mechanical activation is an efficient method to improve the densification behaviour of MgAl2O4 produced from mixed oxide powders.
PB  - The Ceramic Society of Japan
C3  - The 13th Pacific Rim Conference of Ceramic Societies (PACRIM13), October 27 - November 1, 2019, Okinawa Convention Center, Japan
T1  - Effect of Mechanical Activation on the Densification Behavior of MgAl2O4 Spinel
SP  - 30-B1C-S13-14
UR  - https://hdl.handle.net/21.15107/rcub_dais_7050
ER  - 

@conference{
author = "Obradović, Nina and Fahrenholtz, William G. and Filipović, Suzana and Đorđević, Pavle and Rogan, Jelena and Pavlović, Vladimir",
year = "2019",
abstract = "Magnesium aluminate and other alumina-based spinels attract attention due to their high hardness, high mechanical strength, and low dielectric constant. MgAl2O4 was produced by solid-state reaction between MgO and a-Al2O3 powders. Mechanical activation was used to increase the reactivity of powders and decrease the sintering temperatures. Mechanical activation of mixed powders was performed in a high-energy planetary ball mill in air for 30, 60, 90, and 120 minutes. The resulting powders were characterized to determine the effect of activation on surface area, particle size, and crystallinity. Mechanical activation decreased particle size, increased surface area, and increased the width of peaks in x-ray diffraction. Dilatometry was used to monitor densification behavior up to 1500 °C. For non-activated powders, sintering started at approximately 1400 °C, while for activated powders, the onset temperature decreased to about 1340 °C. Mechanical activation is an efficient method to improve the densification behaviour of MgAl2O4 produced from mixed oxide powders.",
publisher = "The Ceramic Society of Japan",
journal = "The 13th Pacific Rim Conference of Ceramic Societies (PACRIM13), October 27 - November 1, 2019, Okinawa Convention Center, Japan",
title = "Effect of Mechanical Activation on the Densification Behavior of MgAl2O4 Spinel",
pages = "30-B1C-S13-14",
url = "https://hdl.handle.net/21.15107/rcub_dais_7050"
}

Obradović, N., Fahrenholtz, W. G., Filipović, S., Đorđević, P., Rogan, J.,& Pavlović, V.. (2019). Effect of Mechanical Activation on the Densification Behavior of MgAl2O4 Spinel. in The 13th Pacific Rim Conference of Ceramic Societies (PACRIM13), October 27 - November 1, 2019, Okinawa Convention Center, Japan
The Ceramic Society of Japan., 30-B1C-S13-14.
https://hdl.handle.net/21.15107/rcub_dais_7050

Obradović N, Fahrenholtz WG, Filipović S, Đorđević P, Rogan J, Pavlović V. Effect of Mechanical Activation on the Densification Behavior of MgAl2O4 Spinel. in The 13th Pacific Rim Conference of Ceramic Societies (PACRIM13), October 27 - November 1, 2019, Okinawa Convention Center, Japan. 2019;:30-B1C-S13-14.
https://hdl.handle.net/21.15107/rcub_dais_7050 .

Obradović, Nina, Fahrenholtz, William G., Filipović, Suzana, Đorđević, Pavle, Rogan, Jelena, Pavlović, Vladimir, "Effect of Mechanical Activation on the Densification Behavior of MgAl2O4 Spinel" in The 13th Pacific Rim Conference of Ceramic Societies (PACRIM13), October 27 - November 1, 2019, Okinawa Convention Center, Japan (2019):30-B1C-S13-14,
https://hdl.handle.net/21.15107/rcub_dais_7050 .

TY  - JOUR
AU  - Obradović, Nina
AU  - Fahrenholtz, William G.
AU  - Filipović, Suzana
AU  - Kosanović, Darko
AU  - Dapčević, A.
AU  - Đorđević, Antonije
AU  - Balać, Igor
AU  - Pavlović, Vladimir
PY  - 2019
UR  - http://www.sciencedirect.com/science/article/pii/S0272884219306340
UR  - http://aspace.agrif.bg.ac.rs/handle/123456789/5761
AB  - 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.
PB  - Elsevier
T2  - Ceramics International
T1  - The effect of mechanical activation on synthesis and properties of MgAl2O4 ceramics
EP  - 12021
IS  - 9
SP  - 12015
VL  - 45
DO  - 10.1016/j.ceramint.2019.03.095
ER  - 

@article{
author = "Obradović, Nina and Fahrenholtz, William G. and Filipović, Suzana and Kosanović, Darko and Dapčević, A. and Đorđević, Antonije and Balać, Igor and Pavlović, Vladimir",
year = "2019",
abstract = "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.",
publisher = "Elsevier",
journal = "Ceramics International",
title = "The effect of mechanical activation on synthesis and properties of MgAl2O4 ceramics",
pages = "12021-12015",
number = "9",
volume = "45",
doi = "10.1016/j.ceramint.2019.03.095"
}

Obradović, N., Fahrenholtz, W. G., Filipović, S., Kosanović, D., Dapčević, A., Đorđević, A., Balać, I.,& Pavlović, V.. (2019). The effect of mechanical activation on synthesis and properties of MgAl2O4 ceramics. in Ceramics International
Elsevier., 45(9), 12015-12021.
https://doi.org/10.1016/j.ceramint.2019.03.095

Obradović N, Fahrenholtz WG, Filipović S, Kosanović D, Dapčević A, Đorđević A, Balać I, Pavlović V. The effect of mechanical activation on synthesis and properties of MgAl2O4 ceramics. in Ceramics International. 2019;45(9):12015-12021.
doi:10.1016/j.ceramint.2019.03.095 .

Obradović, Nina, Fahrenholtz, William G., Filipović, Suzana, Kosanović, Darko, Dapčević, A., Đorđević, Antonije, Balać, Igor, Pavlović, Vladimir, "The effect of mechanical activation on synthesis and properties of MgAl2O4 ceramics" in Ceramics International, 45, no. 9 (2019):12015-12021,
https://doi.org/10.1016/j.ceramint.2019.03.095 . .

TY  - CONF
AU  - Obradović, Nina
AU  - Fahrenholtz, William G.
AU  - Filipović, Suzana
AU  - Marković, Smilja
AU  - Blagojević, Vladimir A.
AU  - Lević, Steva
AU  - Đorđević, Antonije
AU  - Pavlović, Vladimir
PY  - 2019
UR  - http://dais.sanu.ac.rs/123456789/7020
UR  - http://aspace.agrif.bg.ac.rs/handle/123456789/5752
AB  - Magnesium aluminate and other alumina-based spinels are refractory ceramics with excellent properties, such as high hardness, high mechanical strength, and low dielectric constant, applicable in many modern industries. MgAl2O4 was produced by solid state reaction between MgO and alpha-Al2O3 powders. Mechanical activation represents a very efficient method for increasing the reactivity of powders, accelerating chemical reactions and decreasing the sintering temperatures. Mechanical activation of mixed powders was performed in a high-energy planetary ball mill in air for 60 minutes. Sintering was performed in air at temperatures ranging from 1200°C to 1600 °C with a 2 h dwell time. Initial powders and sintered samples were characterized using X-ray diffraction and scanning electron microscopy. Differential thermal analysis (DTA) and thermal gravimetry (TG) were used to determine the temperatures for synthesis reactions and phase transformations. Based on the DTA results, several different processes occured during heating, including evaporation of physisorbed water, decomposition of Mg(OH)2, and spinel formation. With mechanical activation, all characteristic temperatures shifted to lower values, and peaks were more pronounced. Raman spectra were used to characterize the degree of inversion as a function of sintering temperature for all of the sintered specimens.
PB  - Central and Eastern European Committee for Thermal Analysis and Calorimetry
C3  - Book of abstracts of the 5th Central and Eastern European Conference on Thermal Analysis and Calorimetry (CEEC-TAC5) and 14th Mediterranean Conference on Calorimetry and Thermal Analysis (Medicta2019)
T1  - Influence of mechanical activation on kinetics and formation of spinel monitored by DTA
EP  - 70
SP  - 70
UR  - https://hdl.handle.net/21.15107/rcub_dais_7020
ER  - 

@conference{
author = "Obradović, Nina and Fahrenholtz, William G. and Filipović, Suzana and Marković, Smilja and Blagojević, Vladimir A. and Lević, Steva and Đorđević, Antonije and Pavlović, Vladimir",
year = "2019",
abstract = "Magnesium aluminate and other alumina-based spinels are refractory ceramics with excellent properties, such as high hardness, high mechanical strength, and low dielectric constant, applicable in many modern industries. MgAl2O4 was produced by solid state reaction between MgO and alpha-Al2O3 powders. Mechanical activation represents a very efficient method for increasing the reactivity of powders, accelerating chemical reactions and decreasing the sintering temperatures. Mechanical activation of mixed powders was performed in a high-energy planetary ball mill in air for 60 minutes. Sintering was performed in air at temperatures ranging from 1200°C to 1600 °C with a 2 h dwell time. Initial powders and sintered samples were characterized using X-ray diffraction and scanning electron microscopy. Differential thermal analysis (DTA) and thermal gravimetry (TG) were used to determine the temperatures for synthesis reactions and phase transformations. Based on the DTA results, several different processes occured during heating, including evaporation of physisorbed water, decomposition of Mg(OH)2, and spinel formation. With mechanical activation, all characteristic temperatures shifted to lower values, and peaks were more pronounced. Raman spectra were used to characterize the degree of inversion as a function of sintering temperature for all of the sintered specimens.",
publisher = "Central and Eastern European Committee for Thermal Analysis and Calorimetry",
journal = "Book of abstracts of the 5th Central and Eastern European Conference on Thermal Analysis and Calorimetry (CEEC-TAC5) and 14th Mediterranean Conference on Calorimetry and Thermal Analysis (Medicta2019)",
title = "Influence of mechanical activation on kinetics and formation of spinel monitored by DTA",
pages = "70-70",
url = "https://hdl.handle.net/21.15107/rcub_dais_7020"
}

Obradović, N., Fahrenholtz, W. G., Filipović, S., Marković, S., Blagojević, V. A., Lević, S., Đorđević, A.,& Pavlović, V.. (2019). Influence of mechanical activation on kinetics and formation of spinel monitored by DTA. in Book of abstracts of the 5th Central and Eastern European Conference on Thermal Analysis and Calorimetry (CEEC-TAC5) and 14th Mediterranean Conference on Calorimetry and Thermal Analysis (Medicta2019)
Central and Eastern European Committee for Thermal Analysis and Calorimetry., 70-70.
https://hdl.handle.net/21.15107/rcub_dais_7020

Obradović N, Fahrenholtz WG, Filipović S, Marković S, Blagojević VA, Lević S, Đorđević A, Pavlović V. Influence of mechanical activation on kinetics and formation of spinel monitored by DTA. in Book of abstracts of the 5th Central and Eastern European Conference on Thermal Analysis and Calorimetry (CEEC-TAC5) and 14th Mediterranean Conference on Calorimetry and Thermal Analysis (Medicta2019). 2019;:70-70.
https://hdl.handle.net/21.15107/rcub_dais_7020 .

Obradović, Nina, Fahrenholtz, William G., Filipović, Suzana, Marković, Smilja, Blagojević, Vladimir A., Lević, Steva, Đorđević, Antonije, Pavlović, Vladimir, "Influence of mechanical activation on kinetics and formation of spinel monitored by DTA" in Book of abstracts of the 5th Central and Eastern European Conference on Thermal Analysis and Calorimetry (CEEC-TAC5) and 14th Mediterranean Conference on Calorimetry and Thermal Analysis (Medicta2019) (2019):70-70,
https://hdl.handle.net/21.15107/rcub_dais_7020 .

TY  - CONF
AU  - Obradović, Nina
AU  - Fahrenholtz, William G.
AU  - Filipović, Suzana
AU  - Kosanović, Darko
AU  - Dapčević, Aleksandra
AU  - Rogan, Jelena
AU  - Pavlović, Vladimir
PY  - 2019
UR  - http://dais.sanu.ac.rs/123456789/7022
UR  - http://aspace.agrif.bg.ac.rs/handle/123456789/5753
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
EP  - 262
SP  - 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",
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.. (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 V. 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, "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 .

TY  - CONF
AU  - Filipović, Suzana
AU  - Obradović, Nina
AU  - Fahrenholtz, William G.
AU  - Marinković, Bojan A.
AU  - Rogan, Jelena
AU  - Lević, S.
AU  - Pavlović, Vladimir
PY  - 2019
UR  - http://dais.sanu.ac.rs/123456789/6779
UR  - http://aspace.agrif.bg.ac.rs/handle/123456789/5743
AB  - Magnesium aluminate has spinel structure and very good mechanical, chemical, and thermal properties. Owing to these properties, it has a wide range of applications including refractory ceramics, optically transparent ceramic windows and armors. Its low dielectric permeability and low loss tangent enable its using for integrated electronic devices, as well. Furthermore, as a porous ceramic, magnesium aluminate has important application as humidity sensor, catalyst and filter for waste water purification. In this paper, synthesis and characterization of MgAl2O4 was performed. Stochiometric ratio of MgO and Al2O3powders was mixed and calcined within the temperatures range 1500-1800 oC to produce pure spinel phase. Thereafter pellets were crushed and treated in planetary ball mill for 60 minutes to obtained fine grain. All powders, calcined and milled, were examined for phase composition, crystal structure, and morphology. The obtained results showed that by increasing the temperature denser samples but more fragile have been synthesized. Milling for 1 hour leads to crumble of bigger particles and getting finer, single phase powders. XRPD and Raman spectroscopy showed disorder in crystal structure after milling.
PB  - Belgrade : Serbian Ceramic Society
C3  - Program and the Book of abstracts / Serbian Ceramic Society Conference Advanced Ceramics and Application VIII : New Frontiers in Multifunctional Material Science and Processing, Serbia, Belgrade, 23-25. September 2019
T1  - Morphological and structural characterization of spinel MgAl2O4
EP  - 32
SP  - 32
UR  - https://hdl.handle.net/21.15107/rcub_dais_6779
ER  - 

@conference{
author = "Filipović, Suzana and Obradović, Nina and Fahrenholtz, William G. and Marinković, Bojan A. and Rogan, Jelena and Lević, S. and Pavlović, Vladimir",
year = "2019",
abstract = "Magnesium aluminate has spinel structure and very good mechanical, chemical, and thermal properties. Owing to these properties, it has a wide range of applications including refractory ceramics, optically transparent ceramic windows and armors. Its low dielectric permeability and low loss tangent enable its using for integrated electronic devices, as well. Furthermore, as a porous ceramic, magnesium aluminate has important application as humidity sensor, catalyst and filter for waste water purification. In this paper, synthesis and characterization of MgAl2O4 was performed. Stochiometric ratio of MgO and Al2O3powders was mixed and calcined within the temperatures range 1500-1800 oC to produce pure spinel phase. Thereafter pellets were crushed and treated in planetary ball mill for 60 minutes to obtained fine grain. All powders, calcined and milled, were examined for phase composition, crystal structure, and morphology. The obtained results showed that by increasing the temperature denser samples but more fragile have been synthesized. Milling for 1 hour leads to crumble of bigger particles and getting finer, single phase powders. XRPD and Raman spectroscopy showed disorder in crystal structure after milling.",
publisher = "Belgrade : Serbian Ceramic Society",
journal = "Program and the Book of abstracts / Serbian Ceramic Society Conference Advanced Ceramics and Application VIII : New Frontiers in Multifunctional Material Science and Processing, Serbia, Belgrade, 23-25. September 2019",
title = "Morphological and structural characterization of spinel MgAl2O4",
pages = "32-32",
url = "https://hdl.handle.net/21.15107/rcub_dais_6779"
}

Filipović, S., Obradović, N., Fahrenholtz, W. G., Marinković, B. A., Rogan, J., Lević, S.,& Pavlović, V.. (2019). Morphological and structural characterization of spinel MgAl2O4. in Program and the Book of abstracts / Serbian Ceramic Society Conference Advanced Ceramics and Application VIII : New Frontiers in Multifunctional Material Science and Processing, Serbia, Belgrade, 23-25. September 2019
Belgrade : Serbian Ceramic Society., 32-32.
https://hdl.handle.net/21.15107/rcub_dais_6779

Filipović S, Obradović N, Fahrenholtz WG, Marinković BA, Rogan J, Lević S, Pavlović V. Morphological and structural characterization of spinel MgAl2O4. in Program and the Book of abstracts / Serbian Ceramic Society Conference Advanced Ceramics and Application VIII : New Frontiers in Multifunctional Material Science and Processing, Serbia, Belgrade, 23-25. September 2019. 2019;:32-32.
https://hdl.handle.net/21.15107/rcub_dais_6779 .

Filipović, Suzana, Obradović, Nina, Fahrenholtz, William G., Marinković, Bojan A., Rogan, Jelena, Lević, S., Pavlović, Vladimir, "Morphological and structural characterization of spinel MgAl2O4" in Program and the Book of abstracts / Serbian Ceramic Society Conference Advanced Ceramics and Application VIII : New Frontiers in Multifunctional Material Science and Processing, Serbia, Belgrade, 23-25. September 2019 (2019):32-32,
https://hdl.handle.net/21.15107/rcub_dais_6779 .

TY  - JOUR
AU  - Obradović, Nina
AU  - Fahrenholtz, William G.
AU  - Filipović, Suzana
AU  - Kosanović, Darko
AU  - Dapčević, A.
AU  - Đorđević, Antonije
AU  - Balać, Igor
AU  - Pavlović, Vladimir B.
PY  - 2019
UR  - http://www.sciencedirect.com/science/article/pii/S0272884219306340
UR  - http://dais.sanu.ac.rs/123456789/5272
UR  - http://aspace.agrif.bg.ac.rs/handle/123456789/5740
AB  - 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.
PB  - Elsevier
T2  - Ceramics International
T1  - The effect of mechanical activation on synthesis and properties of MgAl2O4 ceramics
EP  - 12021
IS  - 9
SP  - 12015
VL  - 45
DO  - 10.1016/j.ceramint.2019.03.095
ER  - 

@article{
author = "Obradović, Nina and Fahrenholtz, William G. and Filipović, Suzana and Kosanović, Darko and Dapčević, A. and Đorđević, Antonije and Balać, Igor and Pavlović, Vladimir B.",
year = "2019",
abstract = "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.",
publisher = "Elsevier",
journal = "Ceramics International",
title = "The effect of mechanical activation on synthesis and properties of MgAl2O4 ceramics",
pages = "12021-12015",
number = "9",
volume = "45",
doi = "10.1016/j.ceramint.2019.03.095"
}

Obradović, N., Fahrenholtz, W. G., Filipović, S., Kosanović, D., Dapčević, A., Đorđević, A., Balać, I.,& Pavlović, V. B.. (2019). The effect of mechanical activation on synthesis and properties of MgAl2O4 ceramics. in Ceramics International
Elsevier., 45(9), 12015-12021.
https://doi.org/10.1016/j.ceramint.2019.03.095

Obradović N, Fahrenholtz WG, Filipović S, Kosanović D, Dapčević A, Đorđević A, Balać I, Pavlović VB. The effect of mechanical activation on synthesis and properties of MgAl2O4 ceramics. in Ceramics International. 2019;45(9):12015-12021.
doi:10.1016/j.ceramint.2019.03.095 .

Obradović, Nina, Fahrenholtz, William G., Filipović, Suzana, Kosanović, Darko, Dapčević, A., Đorđević, Antonije, Balać, Igor, Pavlović, Vladimir B., "The effect of mechanical activation on synthesis and properties of MgAl2O4 ceramics" in Ceramics International, 45, no. 9 (2019):12015-12021,
https://doi.org/10.1016/j.ceramint.2019.03.095 . .

TY  - CONF
AU  - Obradović, Nina
AU  - Fahrenholtz, William G.
AU  - Filipović, Suzana
AU  - Đorđević, Pavle
AU  - Marković, Smilja
AU  - Rogan, Jelena
AU  - Vulić, Predrag J.
AU  - Pavlović, Vladimir
PY  - 2019
UR  - http://dais.sanu.ac.rs/123456789/6980
UR  - http://aspace.agrif.bg.ac.rs/handle/123456789/5748
AB  - Single crystalline phase MgAl2O4 is made from the predetermined composition of MgO-Al2O3 powder mixture by using ball-milling. Mixtures of MgO and Al2O3 are treated in planetary ball mill for 30, 60, 90 and 120 minutes, in air. The aim of this experiment was to examine phase composition, microstructure, and densification behavior of all sintered samples and to find out which sample has the best features for further use. After sintering in dilatometer at 1500 °C, XRD patterns and SEM images were recorded. The results show that mechanical activation is an efficient method to improve the densification behavior of MgAl2O4 sintered specimens. With the prolonged milling time, densities increased, reaching the maximum value of 2.8 g/cm3 for sample activated 120 minutes.
PB  - Belgrade : Serbian Ceramic Society
C3  - Program and the Book of abstracts / Serbian Ceramic Society Conference Advanced Ceramics and Application VIII : New Frontiers in Multifunctional Material Science and Processing, Serbia, Belgrade, 23-25. September 2019
T1  - Characterization of MgAl2O4 sintered ceramics
EP  - 54
SP  - 54
UR  - https://hdl.handle.net/21.15107/rcub_dais_6980
ER  - 

@conference{
author = "Obradović, Nina and Fahrenholtz, William G. and Filipović, Suzana and Đorđević, Pavle and Marković, Smilja and Rogan, Jelena and Vulić, Predrag J. and Pavlović, Vladimir",
year = "2019",
abstract = "Single crystalline phase MgAl2O4 is made from the predetermined composition of MgO-Al2O3 powder mixture by using ball-milling. Mixtures of MgO and Al2O3 are treated in planetary ball mill for 30, 60, 90 and 120 minutes, in air. The aim of this experiment was to examine phase composition, microstructure, and densification behavior of all sintered samples and to find out which sample has the best features for further use. After sintering in dilatometer at 1500 °C, XRD patterns and SEM images were recorded. The results show that mechanical activation is an efficient method to improve the densification behavior of MgAl2O4 sintered specimens. With the prolonged milling time, densities increased, reaching the maximum value of 2.8 g/cm3 for sample activated 120 minutes.",
publisher = "Belgrade : Serbian Ceramic Society",
journal = "Program and the Book of abstracts / Serbian Ceramic Society Conference Advanced Ceramics and Application VIII : New Frontiers in Multifunctional Material Science and Processing, Serbia, Belgrade, 23-25. September 2019",
title = "Characterization of MgAl2O4 sintered ceramics",
pages = "54-54",
url = "https://hdl.handle.net/21.15107/rcub_dais_6980"
}

Obradović, N., Fahrenholtz, W. G., Filipović, S., Đorđević, P., Marković, S., Rogan, J., Vulić, P. J.,& Pavlović, V.. (2019). Characterization of MgAl2O4 sintered ceramics. in Program and the Book of abstracts / Serbian Ceramic Society Conference Advanced Ceramics and Application VIII : New Frontiers in Multifunctional Material Science and Processing, Serbia, Belgrade, 23-25. September 2019
Belgrade : Serbian Ceramic Society., 54-54.
https://hdl.handle.net/21.15107/rcub_dais_6980

Obradović N, Fahrenholtz WG, Filipović S, Đorđević P, Marković S, Rogan J, Vulić PJ, Pavlović V. Characterization of MgAl2O4 sintered ceramics. in Program and the Book of abstracts / Serbian Ceramic Society Conference Advanced Ceramics and Application VIII : New Frontiers in Multifunctional Material Science and Processing, Serbia, Belgrade, 23-25. September 2019. 2019;:54-54.
https://hdl.handle.net/21.15107/rcub_dais_6980 .

Obradović, Nina, Fahrenholtz, William G., Filipović, Suzana, Đorđević, Pavle, Marković, Smilja, Rogan, Jelena, Vulić, Predrag J., Pavlović, Vladimir, "Characterization of MgAl2O4 sintered ceramics" in Program and the Book of abstracts / Serbian Ceramic Society Conference Advanced Ceramics and Application VIII : New Frontiers in Multifunctional Material Science and Processing, Serbia, Belgrade, 23-25. September 2019 (2019):54-54,
https://hdl.handle.net/21.15107/rcub_dais_6980 .