Calderón Ortiz, Eric R.

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    Composition- and size-controlled synthesis of Mn-Zn ferrite nanocrystals for potential magnetocaloric applications
    (2008) Calderón Ortiz, Eric R.; Perales Pérez, Oscar J.; College of Arts and Sciences - Sciences; Rinaldi, Carlos; Román Velázquez, Félix R.; Romañach, Rodolfo; Department of Chemistry; Gutiérrez, Gustavo
    There are presently many applications using nanofluids in thermal engineering. Some examples include the use of nanoparticles in conventional coolants to enhance heat transfer rate by increasing its thermal conductivity. Other applications include the sealing of bearing cases and sealing of rotary shafts. Even at low weight concentration, thermal conductivity increases significantly. In biotechnology, magnetic nanoparticles have been proposed for thermal treatment of tumor using nanoshells and alternating magnetic fields to generate heat in localized points. This work evaluates the use of nanoparticles composed of MnxZn1-xFe2O4 ferrite for cooling applications in the room temperature range. The use of ferrimagnetic nanoparticles in a fluid, for cooling applications represents an encouraging alternative to traditional methods; the fact that the fluid with ours nanoparticles, can be pumped with no moving mechanical parts, using the magnetocaloric effect, can be a great advantage for many applications where maintenance or power consumption are undesirable. The magnetic material for this specific application has to have certain specific properties, like low Curie temperature (Tc), high saturation magnetization (Ms), low viscosity and high specific heat. The selection of this type of ferrite is made based on these properties. The synthesis of the ferrite nanoparticles was carried out by chemical precipitation and the process is described further on. Magnetic characterization of MnxZn1-xFe2O4 nanoparticles includes the determination of MS as a function of composition at 300K and the dependence of Ms with temperature for a specific ‘x’ value. Both types of measurements were carried out by using SQUID (Superconducting Quantum Interference Device) magnetometer and VSM (Vibrating System Measurement).