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Participants: 1. Elmars Blums, Dr.habil.phys., Head 2. Gunars Kronkalns Dr. phys., senior researcher 3. Ansis Mezulis Dr. phys., senior researcher 4. Mihail Majorov, researcher 5. Vilnis Frishfelds Dr. phys., senior researcher 6. Dmitrijs Zablockis, engineer 7. Aija Dreimane, engineer 8. Guntis Lipsbergs, design engineer 9. Nikolajs Vedernikovs, technician

Lake Shore vibration sample magnetometer for measurements of colloid magnetization and magnetogranulometry analysis.

The aim of the project is performing basic and applied research on magnetic nanoparticles and colloids for new applications in thermal engineering and biomedicine. The research activities will be concentrated on increase of pyromagnetic properties of magnetic nanocolloids by preparing complex ferrite nanoparticles instead of commonly used magnetite. It is anticipated that new temperature sensitive ferrocolloids will allow realizing a principle of magnetically controlled thermosyphon for cooling systems. Second task of the project is performing experiments on dissipation processes in ferrocolloids under the effect of high frequency alternating magnetic field to investigate a possibility to use complex ferrite nanoparticles as a hyperthermia agent in biomedicine.

Main results

1. Synthesis of new magnetic fluids. There are obtained stable hydrocarbon based sterically stabilized ferrocolloids containing subdomain nanoparticles of magnetite and complex ferrites Mn_1-xZn_xFe₂O₄ , Fe₂Co_1-xZn_xO_{4, ,} Fe_1,9Gd_0,1Mn_0,54Zn_0,46O₄ of various phase ratio. The saturation magnetization varies in the range of 10-15 emu/g, the working temperature up to 100 C, the maximal pyromagnetic coefficient reaches 0.1 kA/mK.

2. Thermomagnetic convection and modelling the magnetic thermosyphons. Numerical calculations and experimental measurements are performed to evaluate the principle of magnetic thermosyphon for linear heat transfer. It is shown that if the heat source is located in region of maximal magnetic field, the augment of magnetoconvective heat transfer intensity reaches 200-300% in comparison with that of conventional gravitation convection.

3. Thermal dissipation of magnetic field energy in nanoparticles. Steady magnetization measurements in ferrofluids under constant field as well as complex magnetic susceptibility and magnetic field energy dissipation measurements in vide range of field frequencies (spectral range 10 Hz - 2 MHz) are performed. It is shown that employing colloids of magnetically hard cobalt ferrite nanoparticles it is possible to achieve effective heating of the sample that is quite enough to realize magnetic hyperthermia for biomedical applications.

The scientific results of the Project are published in scientific literature and presented in international conferences

Papers in scientific journals and proceedings

1.     A. Mezulis, E.Blums, G.Kronkalns, Magnetoconvective intensification of heat transfer from a cylinder in magnetic fluid, In: Advances in Heat Transfer, Proceedings. of the Baltic Heat Transfer Conference, September 19 - 21, 2007, Sankt-Petersburg, Russia, Publ. House of St.Petersburg State Polytechnical University 2, p. 184 - 191.

2.     D. Zablotsky, V. Frishfelds, E. Blums. Numerical study of thermomagnetic convection in cylinder under the magnetic field of a solenoid, In: Advances in Heat Transfer, Proceedings. of the Baltic Heat Transfer Conference, September 19 - 21, 2007, Sankt-Petersburg, Russia, Publ. House of St.Petersburg State Polytechnical University 2, p. 301 - 308.

3.     E.Blums, G.Kronkalns, M.M.Maiorov, Microconvection and mass transfer induced by spherical filter elements in non-isothermal ferrocolloids, In: Advances in Heat Transfer, Proceedings. of the Baltic Heat Transfer Conference, September 19 - 21, 2007, Sankt-Petersburg, Russia, Publ. House of St.Petersburg State Polytechnical University 2, p. 333 - 340.

4.        M. M. Maiorov, E. Blums, G. Kronkalns, Thermal dissipation of energy of low-frequency alternate magnetic field in magnetic fluid, In: Advances in Heat Transfer, Proceedings. of the Baltic Heat Transfer Conference, September 19 - 21, 2007, Sankt-Petersburg, Russia, Publ. House of St.Petersburg State Polytechnical University 2, p. 178 - 193.

5.        G. Kroņkalns, M.M.Maiorov, Magnetic fluid mass transfer through the porous media under the action of temperature gradient in a magnetic field, In: Advances in Heat Transfer, Proceedings. of the Baltic Heat Transfer Conference, September 19 - 21, 2007, Sankt-Petersburg, Russia, Publ. House of St.Petersburg State Polytechnical University 2, p.

6.        Vilnis Frishfelds; Elmars Blums, Drift of nonuniform ferrocolloid through cylindrical grid by magnetic force, Journal of Physics: Condensed Mater, 20 (2008) 204130 (5pp)

7.        D.Zablotsky, V. Frishfelds, E. Blums. Numerical investigation of thermomagnetic convection in heated cylinder under the magnetic field of a solenoid. Journal of Physics: Condensed Mater, 20 (2008) 204134 (5pp).

8.        E. Blums, A. Mezulis, G. Kronkalns. Magnetoconvective heat transfer from a cylinder under the effect of a non-uniform magnetic field. Journal of Physics: Condensed Mater 20 (2008) 204128 (5pp)

9.        M.M.Maiorov, E Blums, G. Kronkalns. The heat generation by an alternating magnetic field of low frequency in a ferrofluid: the dependence of energy dissipation on temperature, Magnetohydrodynamics, 44 (2008), No. 1, pp. 27-32

10.    G. Kroņkalns, A. Dreimane, M.M. Maiorov. The effect of thermal treatment on the magnetic properties of spinel ferrite nanoparticles in magnetic fluids, Magnetohydrodynamics, 44 (2008), No. 1, pp. 3-10

11.    E. Blums, G. Kronkalns, M. Maiorov. Thermoosmotic Transfer of Ferrocolloids through a Capillary Porous Layer in the Presence of Transversal Magnetic Field, In:, Thermal Nonequilibrium, 7th International Meeting on Thermodiffusion, Lecture notes, Eds. S. Wiegand, W. Kohler, J.K.G. Dhont, Forschungcentrum Julich GmbH, 2008, p. 169 - 174.

12.    25. Elmars Blums, Gunars Kronkalns and Michail Maiorov, Thermoosmosis in magnetic fluids in the presence of a magnetic field, In: Proc. 7th International PAMIR Conference on Fundamental and Applied MHD, Presqu'Ile de Giens, France, 2008, Vol. 2, 667-272.

13.    D. Zablotsky, V. Frishfelds, E. Blums, Investigation of heat transfer efficiency of thermomagnetic convection in ferrofluids, In: Proc. 7th International PAMIR Conference on Fundamental and Applied MHD, Presqu'Ile de Giens, France, 2008, Vol. 2, 715-720.

14.   A. Mezulis, E. Blums and G. Kronkalns, Magnetoconvective intensification of heat transfer based on permanent magnets, In: Proc. 7th International PAMIR Conference on Fundamental and Applied MHD, Presqu'Ile de Giens, France, 2008, Vol. 2, 803-808.

15.   M. M. Maiorov, G. Kronkalns, E. Blums. Complex Magnetic Susceptibility of Cobalt Ferrite Ferrofluid: Influence of Carrier Viscosity and Particle Concentration, In: Proc. 7th International PAMIR Conference on Fundamental and Applied MHD, Presqu'Ile de Giens, France, 2008, Vol. 2, 725-730.

Participation in conferences: digests and abstracts

1.      A. Mezulis, E. Blums, G. Kronkalns, Magnetoconvective heat transfer from a cylinder under the effect of a nonuniform magnetic field, 11^th International Conference on Magnetic Fluids, Košice, Slovakia, July 23 - 27, 2007, abstracts, paper 4P12.

2.      D.Zablotsky, V. Frishfelds, E. Blums, Numerical investigation of thermomagnetic convection in heated cylinder under the magnetic field of a solenoid, 11^th International Conference on Magnetic Fluids, Košice, Slovakia, July 23 - 27, 2007, abstracts, paper 4P5.

3.      M.M.Maiorov, E. Blums, G. Kronkalns, The heat generation by an alternating magnetic field of low freqency in a ferrofluid: the dependence of energy dissipation on temperature, 11^th International Conference on Magnetic Fluids, Košice, Slovakia, July 23 - 27, 2007, abstracts, paper 2P22.

4.      V. Frishfelds, E. Blums, Drift of nonuniform ferrocolloid through cylindrical grid by magnetic force, 11^th International Conference on Magnetic Fluids, Košice, Slovakia, July 23 - 27, 2007, abstracts, paper 4O3.

5.      A. Mezulis, E. Blums, G. Kronkalns, Magnetoconvective intensification of heat transfer from a heated body in magnetic fluid, In: International Baltic Sea Region conference "Functional materials and nanotechnologies-2007, Institute of Solid State Physics, University of Latvia, April 2-4, Riga 2007, p. 35.

6.      E. Blums, G. Kronkalns, M. M. Maiorov, The heater with cobalt ferrite nanoparticles utilizing a low frequency magnetic field, , In: International Baltic Sea Region conference "Functional materials and nanotechnologies-2007, Institute of Solid State Physics, University of Latvia, April 2-4, Riga 2007, p. 108.

7.      E. Blums, G. Kronkalns, M. Maiorov. Thermoosmotic transfer of ferrocolloids through a capillary porous layer in the presence of transversal magnetic field. Abstracts, 7th International Meeting on Thermodiffusion, Bonn, June 2008, p. 56 - 57.

8.      D. Zablockis, V. Frishfelds, E. Blums. Numerical Investigation of Heat Transfer in Magnetic Nanocolloids under Inhomogeneous Magnetic Field, Abstracts, International Baltic Sea Region conference "Functional materials and nanotechnologies", Institute of Solid State Physics, April 1 - 3, 2008, Riga.

9.      M. Maiorov, G. Kronkalns, E. Blums. The Magnetic Susceptibility Spectrum of Cobalt Ferrite Ferrofluid, Abstracts, International Baltic Sea Region conference "Functional materials and nanotechnologies", Institute of Solid State Physics, April 1 - 3, 2008, Riga.

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