Polymer-to-ceramic conversion

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. 

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. 

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 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. 

It has been confirmed that the presence of bridge-type bonds in such poly (B-alkylaminoborazines) confers flexibility and an inaeased melt-spirmability, thus leading to the conclusions that melt-spinnability inaeases from 1- to 4-daived polymers. In addition, the ceramic yield is reduced with the increased proportion of -NlCHj) in the B-(alkylamino)borazine leading to important shrinkages during the furlha- polymer-to-ceramic conversion of green fibers derived therefrom. Hence, it is relevant to assume... 

Polymer derived ceramic nanocomposites PDC-NCs are promising materials for structural and functional applications. They can be synthesized via polymer-to-ceramic conversion of suitable single-source precursors, leading in a first step to amorphous single-phase ceramics, which subsequently undergo phase separation processes to furnish bi- or multiphase ceramic nanocomposites (lonescu, 2012a). 

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