SiCN fibers

In the case of PSSZ a more extensive study was carried out. In particular, it was shown that the nitrogen content of the ceramic is in good correlation with the value of x when x < 0.75. For X > 0.5 Si-Si-Si sequences were hardly detected. A PSSZ prepared with equimolar amounts of Me2SiCl2 and (ClHMeSi)2NH was converted into PCSZ upon thermolysis (temperature of the bath 425 °C, 8h), cross-linked by y-irradiation, then pyrolyzed to afford SiCN-based material containing a very small amount of oxygen [4a]. In a preliminary study carried out at the Laboratoire des Composites Thermostructuraux, F-33600 Pessac, France (Prof R. Naslain), SiCN fibers were obtained (tensile strength 2 400 MPa Young s modulus 235 GPa). 

A summary of some of the polymer-derived SiCN fibers is presented in Table 1. This table includes the polymer precursor systems for these fibers, the compositional data, and the developing companies. Reliable elemental analyses of these fibers are often diflScult to obtain because of incomplete sample combustion. In addition, many of these fiber compositions are being changed as their development proceeds. 

The stability of these two amorphous materials compared with Si3N4 and SiCN at high temperatures (see Figure 5) suggests that in fiber form they would offer superior properties. Preliminary studies suggest that Si—B—N—C fibers with diameters of 10-12 pm offer... 

The earliest report of fibers containing silicon and nitrogen is by Verbeek (11). Chlorosilanes and amines are used to prepare polycarbosilazane polymers, which are converted into amorphous SiCN-containing ceramic fibers (equation 7). 

The synthesizing of this catalyst consists of three process steps which are construction of carbon nanotubes (CNTs) on carbon fibers support, coating of polymer-derived silicon carbonitride (SiCN) on CNTs and finally decoration of transition metal on surface. The rate of hydrogen generation has been reported as 75 L mim g" [100]. 

Coatings were applied to bend bars made from various commercial types of silicon nitride or silicon carbide, fiber-reinforced, silicon carbide matrix composites. In some cases the silicon nitride bend bars had as-processed surfaces, but in most cases the surfaces were machined and ground. The surfaces of the SiCf/SiCn, bend bars were cleaned prior to coating, but no other treatment was applied to them. 

To date, SiCN materials have been used to make coatings monolithic and extruded shapes, for binder applications" , fibers" " and composite processing" . Recently, photopolymerizable precursors have been considered for rapid prototyping applications . ... 

Saha, A., Shah, S. R., Raj, R. (2004). Oxidation behavior of SiCN-ZrOj fiber prepared from alkoxide-modified silazane. Journal of the American Ceramic Society, S7(8), 1556-1558. doi 10.1111/j.l551-2916.2004.01556.x. 

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