Grants:
J. METALLURGY AND MAGNETISM
Around 33 at.% Si, a metastable Fe-Si nanocrystalline phase was prepared with the B2 structure which exhibited good soft magnetic behaviour (saturation Js=0.6 T, coercivity Hc~100 A/m, resistivity ρ=200 µΩ·cm). This brittle and easy-to-powderize material is a promising substitute for ferrite type cores.
Temperature-modulated thermomagnetometry. — The combination of thermal analysis with other measurement techniques is very fruitful for the interpretation of the behaviour of the investigated physical system during heating or cooling. In cooperation with the Technical University of Koszalin (Poland), a thermoanalyser apparatus has been developed and built which permits the following kinds of measurement: differential thermal analysis (DTA), thermal dilatometry (TD), and thermomagnetometry (TM). In the last year, the thermoanalyser was modified to have a new feature: temperature modulation. The importance of temperature-modulated DTA lies in the possibility of the deconvolution of the response of the analysed sample to the temperature modulation, which yields information on reversible effects. The modification extends the measurement capabilities to perform a simultaneous analysis of specific heat changes as well and enables the separation of reversible and irreversible processes during phase transitions. Besides thermal analysis, the temperature-modulated thermomagnetometry enables a more detailed observation of the crystallization processes even in amorphous alloys with a crystallization temperature higher than the Curie temperature. The method is significantly new and further potential applications are under study.
E-Mail:
Attila Kákay attilak@power.szfki.kfki.hu Pawel Kamasa kamasa@power.szfki.kfki.hu Géza Konczos konczos@power.szfki.kfki.hu Antal Lovas lovas@kgtt.bme.hu
József Pádár padar@power.szfki.kfki.hu Lajos Pogány pogany@ power.szfki.kfki.hu Ferenc I. Tóth ftoth@power.szfki.kfki.hu Béla Varga varga@kgtt.bme.hu
István Varga vargai@power.szfki.kfki.hu Lajos K. Varga varga@power.szfki.kfki.hu
Grants
OTKA T020891 Study of intracellular element distribution in soil microorganisms (L. Pogány, 1996-1999)
GE-TUNGSRAM: Contract for materials research by SEM (L. Pogány, 1999) AGMI (Material Testing and Quality Control Co.): Contract for design and
construction of eddy-current probe for non-destructive testing of high-pressure chemical reactor walls at Tisza Chemical Works (TVK) (P. Kamasa, 1999)
MTA SZBK (Biological Research Centre of Szeged, HAS): Contract for the reconstruction of laserbeam scanning electron microscope (P.
Kamasa, 1999)
NATO Science for Peace Project 97/1930: Magnetic nanocomposites for transformer cores and magnetic refrigeration (L.K. Varga, 1999-2003) OMFB grant “NATO 00002/99”: Matching fund to NATO SfP Project 97/1930 (L.K.
Varga, 1999-2002)
Publications
Articles
J.1. P. Kamasa, P. Myśliński*, B. Varga, Z. Jurasz*: Investigation of the oxidation process in rod and foil iron samples by thermomagnetic measurements. acta phys. slovaca 48, 857-860 (1998)
J.2. A. Sólyom*, P. Marko*, P. Petrovič*, D. Matisová*, G. Konczos: Rapidly quenched microcrystalline Fe-Si-Co alloys. acta phys. slovaca 48, 711-714 (1998)
J.3. I. Bakonyi, E. Tóth-Kádár, J. Tóth, T. Becsei*, T. Tarnóczi, P. Kamasa:
Magnetic and electrical transport properties of electrodeposited Ni-Cu alloys and Ni81Cu19/Cu multilayers. J. Phys. Cond. Matter 11, 963-973 (1999) (see also I.2.)
J.4. Á. Cziráki*, I. Gerőcs*, L.K. Varga, A. Lovas, I. Bakonyi: Structural differences between the nanocrystalline Fe86Zr7B6Cu1 and Fe73.5Si13.5B9Nb3Cu1 alloys.
Nanostruct. Mater. 12, 1109-1112 (1999) (see also I.3.)
J.5. D. García*, G.V. Kurlyandskaya*, M. Vázquez*, F.I. Tóth, L.K. Varga:
Influence of field annealing on the hysteretic behaviour of the giant magneto-impedance effect of Cu wires covered with Ni80Fe20 outer shells. J. Magn.
Magn. Mater. 203, 208-210 (1999)
J.6. P. Kamasa, P. Myśliński*: Study of the thermal effects during microstructural changes of metastable alloys by means of temperature-modulated thermomagnetometry. Thermochimica Acta 337, 51-54 (1999)
J.7. K. Lázár*, H.K. Beuer*, G. Onyestyák*, B.J. Jönsson*, L.K. Varga, S. Pronier*: Iron nanoparticles in X and Y zeolites. Nanostruct. Mater. 12, 155-158 (1999) J.8. V.T. Lebedev*, G.P. Gordeev*, A.I. Sibilev*, V.V. Klyubin*, Gy. Török, L. Cser,
Gy. Káli, L.K. Varga, A. Brulet*: Neutron spin echo study of low-Tc ferrofluid.
J. Magn. Magn. Mater. 201, 80-83 (1999) (see also K.13.)
J.9. P. Myśliński*, P. Kamasa, J. Vandlik*: Analysis of alloys using DTA and TD methods with simultaneous thermomagnetic studies. J. Therm. Anal. Calorim.
56, 233-238 (1999)
J.10. L. Takács*, A. Mossion*, K. Lázár*, L.K. Varga, M. Pardavi-Horváth*, A.
Bakhshai*: ZnO-Fe nanocomposites via ball milling and annealing. Nanostruct.
Mater. 12, 245-248 (1999)
J.11. L.K. Varga, K.V. Rao*: Thermomagnetic study of metastable nanograin in soft magnetic nanocrystalline alloys. Nanostruct. Mater. 12, 1157-1160 (1999) J.12. V. Franco*, C.F. Conde*, A. Conde*, B. Varga, A. Lovas: Thermomagnetic study
of Fe73.5-xCrxSi13.5B9Cu1Nb3 (x=1, 3, 5, 10) alloys. J. Magn. Magn. Mater., accepted for publication
J.13. S.N. Kane*, S. Sarabhai*, A. Gupta*, L.K. Varga, T. Kulik*: Effect of quenching rate on crystallization in Fe73.5Si13.5B9Cu1Nb3 alloys. J. Magn. Magn. Mater., accepted for publication
J.14. A. Lovas, L.F. Kiss, I. Balogh: Low-temperature saturation magnetization in the early stage of amorphous-nanocrystalline transformation. J. Magn. Magn.
Mater., accepted for publication (see also D.8.)
J.15. F. Mazaleyrat*, L.K. Varga: Ferromagnetic nanocomposites. J. Magn. Magn.
Mater., accepted for publication
J.16. J. Olszewski*, L.K. Varga, J. Zbroszczyk*, W.H. Ciurzyńska*, M. Hasiak*, A.
Błachowicz*: Magnetic behaviour of the amorphous and nanocrystalline Fe92-xZr7Cu1Bx (x = 2 or 6) alloys. J. Magn. Magn. Mater., accepted for publication)
J.17. B. Varga, A. Lovas, F. Ye*, X.J. Gu*, K. Lu*: Pressure dependence of nanocrystallization in amorphous Fe86B14 and Fe85Cr1B14 alloys. Mater. Sci.
Eng. A, accepted for publication
J.18. L.K. Varga, F. Mazaleyrat*, J.Kováč*, F. Alves*, A. Kákay: Soft magnetic properties of nanocrytalline Fe100-xSix (15 < x < 34) alloys obtained by rapid quenching. J. Magn. Magn. Mater., accepted for publication
J.19. L.K. Varga, F. Mazaleyrat*, J. Kováč*, F. Alves*, A. Kákay: Magnetic properties of rapidly quenched Fe100-xSix (15<x<34) alloys. Mater. Sci. Eng. A, accepted for publication
J.20. L.K. Varga, L. Novák*, F. Mazaleyrat*: Effective magnetic anisotropy and and internal demagnetization investigations in soft magnetic nanocrystalline alloys.
J. Magn. Magn. Mater., accepted for publication Conference proceedings
J.21. B. Varga: On the rate of α↔β transformation in Fe-rich Fe-Ni alloys. In: Proc.
of Scientific Conf. of the Fac. of Electrical Engineering and Informatics, Eds.:
B. Zagyi, M. Kovaliková, J. Ziman, Technical University of Kosice, Slovakia, 1999, pp. 157-160.
J.22. B. Varga, É. Zsoldos*, G. Gerencsér*, A. Lovas: Study of phase transformation in Fe100-xNixrapidly quenched alloys using thermomagnetic measurements. In:
Proc. 16th Int. Coll. on Advanced Manufacturing Technologies in Vehicle Industry, Balatonfüred, 1999, Techn. Univ. of Budapest, pp. 49-54.
Book
J.23. G. Konczos, I. Bársony*, P. Deák*: Introduction to Materials Science and Technology (Textbook of the Technical University of Budapest for Ph.D.
students in physics, 1998).
Others
J.24. L.K. Varga, F.I. Tóth, T. Kemény, P. Bánki: Method for the preparation of nanocrystalline magnetic powder for non-destructive crack testing. Hungarian Patent No. (1999)