Technological Aspects of Lithium-Titanium Ferrite Synthesis by Electron-Beam Heating

Solid-phase synthesis of lithium-titanium ferrite by electron-beam heating of a Fe₂O₃-Li₂CO₃-TiO₂ initial reagents mixture with different history (powder, compact, mechanically activated mixture) was studied using X-ray diffraction, thermomagnetometric and specific saturation magnetization analyses. Ferrite was synthesized using an ILU-6 pulsed electron accelerator; it generated electrons with electron energy of 2.4 MeV to heat samples to temperatures of 600 and 750 °C. The isothermal holding time upon reaching the synthesis temperature was 0-120 min. The efficiency of ferrite synthesis by electron-beam heating was evaluated via comparison of the characteristics of the obtained samples with those synthesized by conventional ceramic technology under similar temperature-time conditions. It was found that the rate of ferrite formation depends on the heating method, temperature, synthesis time, density, and activity of the initial mixture. It was shown that sample compaction provides the preferential formation of unsubstituted lithium ferrite of Li_0.5Fe_2.5O₄ composition with a Curie temperature of at ca. 630 °C in both synthesis methods. High-energy electron-beam heating of the mechanically activated mixture significantly accelerates synthesis of Li_0.6Fe_2.2Ti_0.2O₄ substituted ferrite, for which the Curie temperature and specific saturation magnetization were recorded as 534 °C and 50 emu/g, respectively. Therefore, LiTi ferrites can be obtained at a lower temperature (750 °C) and with a shorter synthesis time (120 min) compared to traditional ceramic technology.

Synthesis, Structure, and Antimicrobial Performance of NixZn1−xFe2O4 (x = 0, 0.3, 0.7, 1.0) Magnetic Powders toward E. coli, B. cereus, S. citreus, and C. tropicalis

The active development of water purification functional materials based on multicomponent spinel ferrites makes it necessary to search for new efficient methods of obtaining initial nanostructured powders. In this study, a two-stage method for the synthesis of perspective pollutant absorption agents based on NixZn1−xFe2O4 (x = 0, 0.3, 0.7, 1.0) spinel ferrites are proposed and implemented. The approach is based on the synthesis of the initial powder using the solution combustion method and its subsequent thermal treatment in the air. It was found that synthesized samples are single-phase Ni-Zn ferrites with an average crystallite size of 41.4 to 35.7 nm and a degree of crystallinity of ~95–96%. The analysis of antimicrobial activity against four diverse test-cultures: Escherichia coli ATCC 11229 (non-spore-forming gram-negative), Bacillus cereus ATCC 10702 (spore-forming gram-positive), Staphylococcus citreus NCTC 9379 (non-spore-forming gram-positive), and Candida tropicalis ATCC 750 (yeast) showed that almost all of the synthesized powders exhibit an advanced ability to inhibit the growth of the microorganisms mentioned above. The compositions obtained can be a perspective basis for both natural and wastewater purificators with magnetic separation ability and can find biotechnological and biomedical applications as promising antimicrobial materials.

Multiferroic, Phonon and Optical Properties of Pure and Ion-Doped YFeO3 Nanoparticles

The magnetic, electric, phonon and optical properties of pure and ion-doped orthorhombic YFeO3 nanoparticles are studied for the first time theoretically. The spontaneous magnetization Ms in YFeO3 decreases with decreasing particle size. Ms is also shape dependent. The magnetization increases by Co and Er ion doping and decreases by Ti doping, which is caused by the different strain which appears in the nanoparticles and changes the exchange interaction constants in the doped states. The phonon energy for the Ag mode ω = 149 cm−1 and their damping decreases or increases with increasing temperature, respectively. Both show a kink near the Neel temperature, TN, which disappears by applying an external magnetic field. The influence of different ion doping on the band gap energy is also discussed. The doping effects can be used for different applications.

Simple Synthesis of NdFeO3 Nanoparticles By the Co-Precipitation Method Based on a Study of Thermal Behaviors of Fe (III) and Nd (III) Hydroxides

In this study, a nanostructured NdFeO3 material was synthesized via a simple process of the hydrolysis of Nd (III) and Fe (III) cations in hot water with 5% NaOH as a precipitating agent. According to the results of the thermal behaviors of each hydroxide, either containing Fe (III) or Nd (III), the perovskite type of neodymium orthoferrite NdFeO3 was simply synthesized by annealing a mixture of Fe (III) and Nd (III) hydroxides at 750 °C. The nanostructured NdFeO3 was obtained in spherical granules with diameters of around 30 nm. The magnetic properties of the material were a coercive force (Hc) of 136.76 Oe, a remanent magnetization (Mr) of 0.68 emu·g–1, and a saturation magnetization (Ms) of 0.79 emu·g–1.