Thermodynamic modeling of amorphous Si–C–N ceramics derived from polymer precursors

Thermodynamic Analysis of Isothermal Crystallization of Amorphous Si-C-N Ceramics Derived from Polymer Precursors

“…7 To understand this unique thermal stability, recently a thermodynamic model was presented in which the amorphous Si-C-N domain was considered as a separate phase namedéam-SICNê . 8 This phase has been described as a solution of compounds with stoichiometry SiC i4 N 4 i 3 i 0-4 which have been introduced in agreement with the short range ordered atomic configurations of the SiC j N 4 j j 0-4 tetrahedra manifested in the structure of the amorphous Si-C-N ceramics. 4 ,5 Consequently, a thermodynamic effect of mixed SiC j N 4 j tetrahedra j 1-3 has been implied to explain the characteristic resistance of the am-SICN phase to crystallization.…”

“…Thus, in analogy with crystallization of conventional amorphous materials, 15 ,16 the structural changes observed during isothermal heat treatment of an originally amorphous Si-C-N matrix have been interpreted as nuclea- 19 ,20 With the thermodynamic model recently presented, 8 this domain has been considered as a solution phase build of atomic compounds having compositions SiC i4 N 4 i 3 i 0-4 . These compounds have been assumed to account for the short range ordered structures of simple tetrahedra SiN 4 and SiC 4 and the mixed SiC j N 4 j tetrahedra j 1-3 as revealed via NMR experiments.…”

“…To derive the functions DG ex for nanocrystalline Si 3 N 4 and SiC NASIN and NASIC phases the constant energy values of 9.8 kJmol atoms and 27.5 kJmol atoms have been used as recently estimated for the energy differences G am G cr of Si 3 N 4 and SiC respectively. 8 Consequently the Gibbs energies derived for the NASIN and NASIC phases are direct functions of the normalized nanocrystallites dimension.…”

“…Using the previous model of amorphous Si-C-N ceramics, 8 this Gibbs energy Eq. 12 has been computed as the function of composition f SiN for different temperatures.…”

Oxidation behavior of amorphous Si-(B)-C-N ceramic in ambient air

“…Jerzy A. Golczewski and Fritz Aldinger developed a thermodynamic model to rationalize the enhanced persistence of amorphous Si-C-N polymer derived ceramics (PDCs) [13], which offered an exemplification for us to deal with the oxidation mechanism using thermodynamic calculation qualitatively. That is, using the available thermodynamic parameters of the phases SiC and Si 3 N 4 and additional assumptions concerning Si-N, Si-C, Si-O and so on atomic bonds in the phase constituents, then the Gibbs energy before and after oxidation can be determined and compared qualitatively.…”