Mn Zn ferrite nanoparticles for ferrofluid preparation: Study on thermal magnetic properties

MnZnFe2O4ferrite nanoparticles were prepared by co-precipitation method using a microwave heating system at temperature of 100 °C. X-ray diffraction reveals the samples as prepared are pure ferrite nanocrystalline phase, transmission electron microscopy image analysis shows particles are in agglomeration state with an average size of about 10 nm, furthermore, crystal size of samples are increased with longer microwave heating.

https://link.springer.com/content/pdf/10.1007%2Fs11671-006-9027-3.pdf

Microwave assisted low temperature synthesis of MnZn ferrite nanoparticles

A convection-cooled electromagnetic device, such as a transformer, and methods of cooling that utilize a ferrofluid as a cooling medium The device's leakage magnetic field, which can be augmented by auxiliary magnets, draws the ferrofluid toward the device As the fluid approaches the device its temperature rises, resulting in loss of magnetic properties and a decrease in density The ferrofluid rises as its temperature approaches the Curie point, since the gravitational effect of density reduction begins to overcome the weakening magnetic attraction Movement of hot ferrofluid is strongly assisted by the attraction exerted by the device on cooler, more intensely magnetic ferrofluid, which displaces the hot ferrofluid The displaced ferrofluid cools as a result of movement from the heat source and through contact with the walls of the housing Preferably, the Curie temperature of the ferrofluid is close to or slightly higher than the operating temperature of the device

Ferrofluid-cooled electromagnetic device and improved cooling method

Magnetic properties of Co0.5Zn0.5Fe2O4 and Mn0.5Zn0.5Fe2O4 nanoparticles and preparation of temperature-sensitive magnetic fluid are discussed in this paper. Ferrofluids having Co0.5Zn0.5Fe2O4 and Mn0.5Zn0.5Fe2O4 fine particles were prepared by co-precipitation and by ball milling the precipitated fine particles. Ball milling technique was used for coating of the surfactant rather than size reduction. The final cation contents estimated from the prepared powder samples agree with the initial degree of substitution. The powder samples were characterized by XRD, VSM and Mossbauer studies. The precipitated particles were less than 10 nm size and showed FCC spinel structure. Mossbauer studies confirm the single domain nature of the fine particles. Temperature-sensitive ferrofluid having transformer oil as the carrier liquid was prepared by carrier exchange technique. Co0.5Zn0.5Fe2O4 particles can be used for the preparation of temperature-sensitive magnetic fluid with relatively large magnetic volume force.

Preparation and properties of temperature-sensitive magnetic fluid having Co0.5Zn0.5Fe2O4 and Mn0.5Zn0.5Fe2O4 nanoparticles

High field magnetization of the colloidal Mn–Zn ferrite

The magnetic properties of ferrofluids containing polydisperse chemically coprecipitated Mn-Zn ferrite nanoparticles of various composition, as well as the dispersion characteristics and structure of particles, are investigated. Results of the neutron-activation analysis of particles give a Mn, Zn and Fe ratio different from that of stoichiometrically predicted ones at precipitation. Magnetogranulometric analysis of ferrofluid samples performed by using the Langevin-type magnetization model of noninteracting subdomain particles shows that, instead of the usually observed log-normal particle size distribution curves, there exists a more complex distribution of magnetic moments of particles. Ultracentrifugal separation of samples allows the distribution of two fractions of particles having different magnetic moment values, which are not proportional to the particle mean volumes determined using X-ray diffraction spectra measurements. >

M.M. Maiorov

Papers

Thermomagnetic properties of ferrofluids containing chemically coprecipitated Mn-Zn ferrite particles