Polymer-to-ceramic

The polymer-to-ceramic conversion was performed in flowing ammonia to 1000°C (heating rate 25°C/h), then in flowing nitrogen to 1800°C (heating rate 100°C/h).29 30 Some of the properties of the final BN fibers are summarized in Table 4. 

The simplest way to follow the polymer-to-ceramic transformation process is by solid state MAS 29Si NMR spectroscopy. Thus, Figure 7 shows the MAS 29Si NMR spectra of samples of copolymer heated to selected temperatures in N2. Figure 8 provides an integration of the various species and how the relative amounts of each change on pyrolysis. 

B[C2H4Si(R)NH]3 is mainly a function of the silicon-bonded moiety R, whereas the reaction pathway applied does not significantly influence the polymer-to-ceramic conversion. 

One aspect of their elegant and extensive studies dealt with the pyrolysis of these polymers to ceramic powders, fibers, and film. 

In contrast, thermal stability is not necessarily a direct function of the molecular structure. However, simply reducing the nitrogen content by performing the reaction with excess chlorosilanes is not possible, since the released polymers possess undesired large amounts of chlorine which lead to uncontrollable reactions during the polymer-to-ceramic conversion. 

The following properties are desirable for conversion of polymers to ceramic fibers ... 

Polymer to Ceramic Transformation Processing of Ceramic Bodies and Thin Films... 

The use of polymer pyrolysis for the fabrication of bulk ceramics has been hindered mainly by the significant volume shrinkage (>50%) accompanying the polymer-to-ceramic conversion, often resulting in the formation of cracks which destroys the structural integrity of the ceramic component. 

J. C. Pivin and P. Colombo, Conversion of inorganic-organic polymers to ceramics by ion implantation, Nucl. Instr. Meth. Phys. Res. B, 1996, 120, 262-265. 

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