0000000000282330
AUTHOR
Gunars Kronkalns
Structure, Composition and Magnetic Properties of Ferrofluid Nanoparticles after Separation / Feromagnētisko Šķidrumu Nanodaļiņu Struktūras, Sastāva un Magnētisko Īpašību Izmaiņas Pēc Separācijas
Abstract The structure, composition and magnetic properties of iron oxide nanoparticles are studied as dependent on the synthesis technology and method of separation in ferrofluids. The goal of the present study is to improve the magnetic properties of wet-synthesized nanoparticles and achieve a narrow nanoparticle size distribution. The results of measurements show that by varying the conditions of the chemical coprecipitation method, different compositions and structures of the nanoparticles could be obtained. The separation of ferrite nanoparticles of a polydisperse colloid by centrifugation as well as by HGMS provides the possibility to obtain a nanoparticle set with narrow size distrib…
Magnetite Nanoparticles Prepared By Spark Erosion
Abstract In the present research, we study a possibility of using the electric spark erosion method as an alternative to the method of chemical co-precipitation for preparation of magnetic nanoparticles. Initiation of high frequency electric discharge between coarse iron particles under a layer of distilled water allows obtaining pure magnetite nanoparticles.
Thermoosmotic transfer of sterically stabilized ferrofluid particles in non-isothermal capillary porous layer
Experiments on thermodiffusive transfer of ferrofluid nanoparticles in capillary porous layer are presented. The layer consists of a number of capillary filter sheets pressed between two plates of different temperatures. Steady profiles of particle concentration are detected after the experiment from magnetization of each filter sheet. It is shown that particle separation in porous layer is remarkably influenced by thermoosmotic forces. The observed effect is different for colloids of various surfactants and of various carrier liquids.
Non-isothermal separation of ferrofluid particles through grids: Abnormal magnetic Soret effect
Abstract Nanoparticle transport through thin non-isothermal ferrofluid layer between permeable walls is investigated. The transient mass flux is determined from measurements of particle concentration changes in two fluid chambers of different temperatures which are attached on both sides of the layer. Experiments are performed employing fluid samples of small ordinary magnetic Soret effect, which is detected by thermal grating technique. The separation measurements say that a magnetic field, aligned along a temperature gradient, causes a remarkable increase in the mass diffusion coefficient and a simultaneous decrease in particle thermodiffusion mobility. It is proposed that the observed ef…
Experimental research of surfaced nanoparticle thermal transport in a porous medium
Abstract Experimental research on thermally induced nanocolloid transport in a porous environment is presented. Addition of excess surfactant to a colloid with dispersed phase made of surfaced nanoparticles results in a decrease of effective Soret coefficient in a porous environment. It is shown that with sufficient amounts of surfactant added, this effect extends to a reversal of nanoparticle thermophoretic transport direction, and that the effect shows a tendency of saturation. A mechanism of thermal transport that involves slip velocity of surfactant molecules appearing near pore walls is evaluated as a possible cause of the decrease of Soret coefficient. Effects of temperature on partic…
Non-isothermal mass transfer of ferrocolloids through porous membrane
Abstract The present paper deals with transport properties of ferrofluid nanoparticles in non-isothermal capillary-porous layer. Experiment establishes that the temperature difference, which is applied across the layer, induces a thermoosmotic pressure gradient directed toward increasing temperature. The measurement results are interpreted in a frame of phenomenology of linear irreversible thermodynamics. The transport coefficients are evaluated comparing the measured separation curves with approximate solution of the corresponding mass transfer problem.