Ferromagnetic ceramics

We have a specific interest in the self-assembled structures formed by poly(ferrocenylsilane) block copolymers, such as poly(ferrocenyldimethylsilane-Z -dimethyl-siloxane) (PFS-PDMS) and (ferrocenyldimethylsilane-Z>-isoprene) (PFS-PI). The PFS block contains an iron atom in the main chain repeat unit. These polymers are particularly promising for novel applications, since they can be used as charge-transport materials and, by pyrolysis, as precursors to ferromagnetic ceramics [4-6], Moreover, they can by synthesized with a very narrow molar mass distribution, with excellent control over chain length and composition [7], An important feature of PFS is that the polymers bearing two methyl groups on the silane unit are crystalline, whereas polymers with two different substituents on each silane (methyl, ethyl methyl, phenyl) are atactic and remain amorphous. This feature of the polymer composition has a strong influence on the type of self assembled structures that these poly-... 

Chromium dioxide (CrOi) is at present the most important ferromagnetic ceramic. It is used as magnetic media in audio and video recording tapes. In this application, the Cr02 is not in the pure form but is usually doped to improve its properties. 

Ikenaga, M., Ohura, K., Yamamuro, T., Kotoura, Y., Oka, M., and Kokubo, T. (1993). Localized hyperthermic treatment of experimental bone tumors with ferromagnetic ceramics. J. OrAop. Res. 11 849-833. 

Finally, in ferroelectric and ferromagnetic ceramics, it is possible to obtain the phase transitions by changing the temperature, leading to the development of paraelectric-ferroelectric or paramagnetic-ferromagnetic... 

For microwave welding, it is also possible to preferentially heat the interface by placing a susceptor at the joint interface, where the susceptor may include conductive polymer, carbon particles, ferromagnetic ceramic particles or other materials that heat in an alternating electromagnetic field. 

FERROELECTRIC MATERIALS. The dielectric analogs of ferromagnetic materials. Their uses parallel those of ferromagnetic materials in such applications as magnetostriclive transducers, magnetic amplifiers, and magnetic information storage devices. Rochelle salt was the first ferroelectric material to be discovered and the barium titanale ceramics arc materials of this type... 

For the CDA experiments described below a PERKIN-ELMER TGS-1 system was used with a cylindrical furnace on alumina ceramic, 6 mm i.d., with bifilar Pt windings as sketched in Fig. lb. The sample, 4x4 mm and 1.5-3 mm thick, was suspended from a fused silica hang-down wire and rested on a fused silica loop below the rim of the furnace. A Ni electrode 3 x 5 mm was introduced sidewise above the furnace, parallel to the sample surface at a distance of <0.5 mm. The temperature (T) was calibrated by means of the Curie points of ferromagnetic alloys. During the runs the balance was... 

Scheme 31 Upper panel-. Complex formation between acetylenes and cobalt carbonyls. Lower panel Formation of polymer complexes 81 and 82 via metal complexation and transformation of the complexes into soft ferromagnetic materials 83 and 84 by pyrolytic ceramization...

Certain ferromagnetic materials, notably iron, steels, and some ceramics (ferrites), are far more receptive ( lOOx) to magnetic flux than is air. Permeability is a measure of the receptiveness of the material to having magnetic flux set up in it [15],... 

---