Mechanochemical synthesis of SrFe12O19 from recycled mill scale: Effect of synthesis time on phase formation and magnetic properties

• Published in: Journal of alloys and compounds 2021-08, Vol.873, p.159787, Article 159787
• Main Authors: İÇİN, Kürşat, ÖZTÜRK, Sultan, ÇAKIL, Damla Dilara, SÜNBÜL, Sefa Emre
• Format: Article
• Language: English
• Subjects: Annealing; Coercivity; Magnetic properties; Mechanochemical synthesis; Mill scale; Phase ratio; Scale (corrosion); Strontium; Strontium carbonate; Strontium hexaferrite; Synthesis
• ISSN: 0925-8388; 1873-4669
• DOI: 10.1016/j.jallcom.2021.159787

•Strontium hexaferrite powders are successfully produced using a recycled mill scale.•The mechanochemical synthesis time of 16 h is crucial process parameter to produce high performance strontium hexaferrite.•The coercivity value of the hexaferrite powders increased up to 5.5 kOe.•The change in the phase ratio of the SrFe12O19 and lattice parameters affected the magnetic properties.•After annealing at, all of C─O bonds in SrCO3 were not visible and Sr─O and Fe─O bonds in SrFe12O19 were strengthened. [Display omitted] In the present study, the strontium hexaferrite (SrFe12O19) has been successfully produced from recycled mill scale and strontium carbonate (SrCO3) powders with stoichiometric ratio (SrCO3/Fe2O3) of 1:6 by mechanochemical synthesis process, followed by annealing at 975 °C temperature. As the mechanochemical synthesis time increased, the phase ratio of hard magnetically SrFe12O19 in the structure increased after the annealing, according to the XRD analysis. The SrFe12O19 phase formation temperature decreased from 851 °C to 762 °C with increasing mechanochemical synthesis time. Also, FTIR analysis showed that The C═O bond peaks are only visible for a 2 h synthesis time at 854 cm−1 wavenumbers. Magnetic properties have changed according to particle size, activation energy, and phase ratios. The best magnetic properties were obtained with the application of 16 h of synthesis time. The coercivity values of 3.3, 3.6, 4.6, 5.5, 5,4, and 3.7 kOe were obtained for 2, 4, 8, 16, 32, and 64 h of mechanochemical synthesis times, respectively. The residual magnetization density (Br) values under 1 T magnetic field for the same synthesis times were obtained as 168, 221, 292, 347, 314, 258 mT, respectively.