Optimization of preparation parameters and characterization of the Mn0.5Zn0.5Fe2O4 thermal-sensitive magnetic ferrofluid prepared by the hydro-thermal method
The bare magnetic Mn<inf>0.5</inf>Zn<inf>0.5</inf>Fe<inf>2</inf>O<inf>4</inf> nanoparticles were prepared by the hydro-thermal method. The optimized preparation conditions were obtained by the orthogonal experiment. Crystal structure and the grain diameter of the particles were observed by X-ray Diffraction (XRD) and Transmission Electron Microscope (TEM), and the Curie temperature of the bare particles and the performance of the magnetic moment of the particles at different temperatures were characterized by the Vibrating Sample Magnetometer (VSM). The bare particles were modified by the oleic acid, and the modification effect was verified by the Infrared Test (IR). Mn<inf>0.5</inf>Zn<inf>0.5</inf>Fe<inf>2</inf>O<inf>4</inf> thermal-sensitive magnetic ferrofluid with excellent performance were prepared by dissolving the modified particles in the kerosene carrier. The saturation magnetization could reach up to 278Gs and the Curie temperature is confirmed to be 322K, which indicates that the quality of the Mn<inf>0.5</inf>Zn<inf>0.5</inf>Fe<inf>2</inf>O<inf>4</inf> thermal-sensitive ferrofluid is better than other Mn<inf>0.5</inf>Zn<inf>0.5</inf>Fe<inf>2</inf>O<inf>4</inf> thermal-sensitive ferrofluids prepared by the coprecipitation method previously reported (Saturation magnetization: 150Gs, Curie temperature: 340K[1]).
Mn–Zn ferrite nanoparticles for ferrofluid preparation: Study on thermal–magnetic properties
Abstract Mn1−xZnxFe2O4 (with x varying from 0.1 to 0.5) ferrite nanoparticles used for ferrofluid preparation have been prepared by chemical co-precipitation method and characterized. Characterization techniques like elemental analysis by atomic absorption spectroscopy and spectrophotometry, thermal analysis using simultaneous TG-DTA, XRD, TEM, VSM and Mossbauer spectroscopy have been utilized. The final cation contents estimated agree with the initial degree of substitution. The Curie temperature ( T c ) and particle size decrease with the increase in zinc substitution. In the case of particles with higher zinc concentration, both ferrimagnetic nanoparticles and particles exhibiting superparamagnetic behavior at room temperature are present. In addition, some of the results obtained by slightly altering the preparation condition are also discussed. The precipitated particles were used for ferrofluid preparation. The fine particles were suitably dispersed in heptane using oleic acid as the surfactant. The volatile nature of the carrier chosen helps in altering the number concentration of the magnetic particles in a ferrofluid. Magnetic properties of the fine particles and ferrofluids are discussed. Ferrofluids having Mn0.5Zn0.5Fe2O4 particles can be used for the energy conversion application utilizing the magnetically induced convection for thermal dissipation.
Anomalous Annealing Behavior of Arsenic Implanted Silicon as a Function of Dose and Energy
Anomalous annealing behavior of damage in As implanted Si has been investigated by channeling effect measurements. Room temperature As implants with doses from 1014 to 2 × 1016cm-2 at energies ranging from 50 to 250 keV into Si were annealed over the range of 600°C to 1100°C. Anneal temperatures ≥ 950°C reduce the disorder for ion doses of 0.5 to 1 × 1016 cm-2 at energies between 50 and 250 keV. Anomalously high residual disorder was found for the intermediate doses of 2 × 1014 to 2 × 10/cm2 implanted above 100 keV. For this intermediate dose, annealing of implants performed at liquid nitrogen temperatures did not show significant reduction in this damage. However implants at 200° to 300°C indicate a lower amount of damage compared to the room temperature implants.