Magnetic Properties of Ferrite Ceramics Made from Wastes

authors	Pullar, RC; Hajjaji, W; Amaral, JS; Seabra, MP; Labrincha, JA
nationality	International
journal	WASTE AND BIOMASS VALORIZATION
author keywords	Industrial wastes; Waste valorisation; Ferrites; Magnetic ceramics
keywords	HEXAFERRITES; PIGMENTS
abstract	Iron-rich industrial waste sludge (62 % Fe2O3) was processed to produce recycled chromatic and magnetic materials. In this paper we report on combining the waste with stoichiometric amounts of oxides, which were then fired to produce SrM hexagonal ferrite (SrFe12O19) based ceramic powders. A series of powders were made from pure oxides for comparison. All samples were fired in air at 1,050-1,150 degrees C, and analysed by use of XRD (X-ray diffraction) and VSM (vibrating sample magnetometry). The firing of SrM stoichiometric mixtures derived from Fe-rich waste sludge did not result in a hard SrM ferrite product, but instead resulted in strongly magnetic but soft ferrites, which were a mixture of SrM and spinel phases, along with nonmagnetic alpha-Fe2O3. XRD and VSM data strongly suggested that the 21 % volatile organic fraction of the waste was burnt out during firing, reducing some of the Fe3+ to form magnetite, Fe3O4, which was then oxidised on cooling in air to form maghemite, gamma-Fe2O3, which is magnetically soft, with M-s and H-c values lower than those of SrM. The recycled waste magnetic materials had M-s values of 37-59 A m(2) kg(-1), and H-c values of 13-40 kA m(-1). Thus, a highly magnetic soft-magnet ceramic is made from the simple thermal remediation of these wastes.
publisher	SPRINGER
issn	1877-2641
year published	2014
volume	5
issue	1
beginning page	133
ending page	138
digital object identifier (doi)	10.1007/s12649-013-9207-1
web of science category	Environmental Sciences
subject category	Environmental Sciences & Ecology
unique article identifier	WOS:000347719300015