Magnetic Properties and SAR for Gadolinium-Doped Iron Oxide Nanoparticles Prepared by Hydrothermal Method

This study is an attempt to produce gadolinium-doped iron oxide nanoparticles for the purpose of utilization in magnetic fluid hyperthermia (MFH). Six gadolinium-doped iron oxide samples with varying gadolinium contents ( were prepared using the hydrothermal method and high vapor pressure to incorporate gadolinium ions in the iron oxide structure. The samples were indexed as , with varying from 0.0 to 0.1. The results reveal that gadolinium ions have a low solubility limit in the iron oxide lattice (x = 0.04). The addition of gadolinium caused distortion in the produced maghemite phase and formation of other phases. Based on X-ray diffraction (XRD) analysis and photoelectron spectroscopy (XPS), it was observed that gadolinium mostly crystalized as gadolinium hydroxide, for gadolinium concentrations above the solubility limit. The measured magnetization values are consistent with the formed phases. The saturation magnetization values for all gadolinium-doped samples are lower than the undoped sample. The specific absorption rate (SAR) for the pure iron oxide samples was measured. Sample GdIO/0.04, pure iron oxide doped with gadolinium, showed the highest potential to produce heat at a frequency of 198 kHz. Therefore, the sample is considered to hold great promise as an MFH agent.

Biocompatible Magnetic Fluids of Co-Doped Iron Oxide Nanoparticles with Tunable Magnetic Properties

Magnetite (Fe3O4) particles with a diameter around 10 nm have a very low coercivity (Hc) and relative remnant magnetization (Mr/Ms), which is unfavorable for magnetic fluid hyperthermia. In contrast, cobalt ferrite (CoFe2O4) particles of the same size have a very high Hc and Mr/Ms, which is magnetically too hard to obtain suitable specific heating power (SHP) in hyperthermia. For the optimization of the magnetic properties, the Fe2+ ions of magnetite were substituted by Co2+ step by step, which results in a Co doped iron oxide inverse spinel with an adjustable Fe2+ substitution degree in the full range of pure iron oxide up to pure cobalt ferrite. The obtained magnetic nanoparticles were characterized regarding their structural and magnetic properties as well as their cell toxicity. The pure iron oxide particles showed an average size of 8 nm, which increased up to 12 nm for the cobalt ferrite. For ferrofluids containing the prepared particles, only a limited dependence of Hc and Mr/Ms on the Co content in the particles was found, which confirms a stable dispersion of the particles within the ferrofluid. For dry particles, a strong correlation between the Co content and the resulting Hc and Mr/Ms was detected. For small substitution degrees, only a slight increase in Hc was found for the increasing Co content, whereas for a substitution of more than 10% of the Fe atoms by Co, a strong linear increase in Hc and Mr/Ms was obtained. Mössbauer spectroscopy revealed predominantly Fe3+ in all samples, while also verifying an ordered magnetic structure with a low to moderate surface spin canting. Relative spectral areas of Mössbauer subspectra indicated a mainly random distribution of Co2+ ions rather than the more pronounced octahedral site-preference of bulk CoFe2O4. Cell vitality studies confirmed no increased toxicity of the Co-doped iron oxide nanoparticles compared to the pure iron oxide ones. Magnetic heating performance was confirmed to be a function of coercivity as well. The here presented non-toxic magnetic nanoparticle system enables the tuning of the magnetic properties of the particles without a remarkable change in particles size. The found heating performance is suitable for magnetic hyperthermia application.

Comparative study of low-grade banded iron ores for iron recovery

Two low-grade banded iron ores are evaluated as a potential source for meeting the iron/steel demand due to the scarcity of high-grade iron ores. The present study investigates the processing and enrichment of banded iron ores and their comparison with pure iron oxide and synthetic mixture. The feasibility of physical beneficiation, microwave processing, and carbothermal reduction is thoroughly investigated. A trace amount of magnetite in BHJ ore leads to an improved response of microwave exposure compared to pure iron oxide and mixture. Physical beneficiation was found futile in recovering iron values. The energy consumed during the microwave processing is calculated as 405.2 kWh/ton, whereas for conventional reduction is 223.7 kWh/ton. Significant iron enrichment was achieved through structural alteration of the ore. The microwave processing offered faster reduction kinetics and ferrite formation in a short duration. BHJ sample was found suitable for extracting iron values compared to BHQ using carbothermal reduction.

Characterization of 3 mol% Fe from Different Source Doped 8YSZ Ceramics

Pure 8 mol% yttria stabilized zirconia (YSZ) and 3mol % of Fe-doped YSZ electrolyte from different source of Fe (p)in oxide form (pure iron oxide powders, Fe2O3) and Fe(s) source from salt (iron nitrate, Fe(NO3)3) were prepared and sintered at 1550°C for 2 hours. The effect of Fe dopant from different source of Fe to the crystal structure and ionic conductivity of 8YSZ samples were investigated. The addition of 3 mol % Fe from iron nitrate source (sample 3Fe(s)YSZ) greatly enhanced the growth of monoclinic phase as compared to 8YSZ sintered samples while the addition of 3 mol % Fe from pure iron oxide powder source (sample 3Fe(s)YSZ) enhanced the crystallization of cubic phase and decrease the monoclinic phase. The addition of Fe significantly enhanced the ionic conductivity of 8YSZ sample for both source of Fe. However, 3Fe(p)8YSZ has smaller grain resistivity and thus has higher conductivity compared to 3Fe(s)YSZ.