Iron compounds silicides

After many attempts with several anode materials we found a stable anode. Silicon carbide and iron silicide, etc. in a conducting form are stable towards chlorine. The chlorine formed on the anode then reacts with the solvent (THF) forming chlorinated organic compounds. 

Silicon carbide is comparatively stable. The only violent reaction occurs when SiC is heated with a mixture of potassium dichromate and lead chromate. Chemical reactions do, however, take place between silicon carbide and a variety of compounds at relatively high temperatures. Sodium silicate attacks SiC above 1300°C, and SiC reacts with calcium and magnesium oxides above 1000°C and with copper oxide at 800°C to form the metal silicide. Silicon carbide decomposes in fused alkalies such as potassium chromate or sodium chromate and in fused borax or cryolite, and reacts with carbon dioxide, hydrogen, air, and steam. Silicon carbide, resistant to chlorine below 700°C, reacts to form carbon and silicon tetrachloride at high temperature. SiC dissociates in molten iron and the silicon reacts with oxides present in the melt, a reaction of use in the metallurgy of iron and steel (qv). The dense, self-bonded type of SiC has good resistance to aluminum up to about 800°C, to bismuth and zinc at 600°C, and to tin up to 400°C a new silicon nitride-bonded type exhibits improved resistance to cryolite. 

Fig. 273. Iron bombs used in the preparation of alkali metal silicides and germanides . 4—bomb for preparation of Rb and Cs compounds 5—bomb for the Na and K compounds, b—Iron bomb h iron screw-on cap t/—corundum crucible —copper gasket I —iron cone.

Y.-C. Yang et al. (1993) claim that carbon substitution increases both saturation magnetization and magnetocrystalline anisotropy. This conclusion is confirmed by other authors (see table 22). One can see that the silicide carbides of light rare earths exist with a different crystal structure of the BaCdi i -type (I4i/amd space group) in which the carbon atoms fill octahedral vacancies formed by four iron and two lanthanide atoms, with an occupancy of 25%. These compounds exhibit Curie temperatures which are lower than for corresponding the ThMni2-type phases they lie between 390 and 460 K. The mean iron moment amounts to about 1.4 Ub at low temperature (Le Roy et al. 1987). 

In addition to the crystalline compounds, amorphous materials of UFeioM2-type with M=A1, Ti, y Cr, Ge, Sn and W have been prepared. They exhibit a much lower saturation magnetization than the corresponding crystalline silicide (H. Ratajczak, private communication) but unfortunately no detailed examination has yet been carried. The single exception is an investigation of the optical properties of UFeioGe2 (Beznosov et al. 1992). Relative to amorphous iron this material exhibits a markedly lower optical... 

Intermetallic compounds titanium aluminides [55-60], nickel aluminides [61-64], iron aluminides [65-68] and molybdenum silicides [69,70]. 

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