High‐Temperature Creep Behavior ofSiOCGlass‐Ceramics: Influence of Network Carbon Versus Segregated Carbon

Abstract

Three silicon oxycarbide samples with different carbon contents are analyzed in the present study with respect to their hightemperature creep behavior. The tests were performed in compression at 1100°C, 1200°C, and 1300°C; in this temperature range the mechanism of creep relies on viscoelastic flow within the samples and has been modeled with the Jeffreys viscoelastic model. After the release of the applied mechanical stress, a viscoelastic recovery behavior was observed in all samples. The creep behavior of the investigated samples indicates two rheological contributions in SiOC: (i) a high viscous answer, coming from the silica-rich network, and (ii) an elastic response from the segregated carbon phase within the samples. Furthermore, two distinct effects of the carbon phase on the HT creep behavior of SiOC were identified and are discussed in the present paper: the effect of the carbon presence within the SiOC network (the "carbidic" carbon), which induces a significant increase in the viscosity and a strong decrease in the activation energy for creep, as compared to vitreous silica; and the influence of the segregated carbon phase (the "free" carbon), which has been shown to affect the viscosity and the activation energy of creep and dominates the creep behavior in phase-separated silicon oxycarbides.

Thermomechanical properties of a spark plasma sintered ZrC–SiC composite obtained by a precursor derived ceramic route

“…Papendorf et al [50] and Ionescu et al [51] have recently studied the compression creep behaviour at high temperatures (i.e. 1100-1300°C) of dense silicon oxycarbide-based ceramics obtained by the PDC route.…”

Tape casting of preceramic polymers toward advanced ceramics: A review

“…For the PDC route, specific rheological investigations are limited to a few PCP systems . Even less frequent are rheological studies with direct correlations to common shaping processes, such as extrusion or melt spinning .…”

“…109 For the PDC route, specific rheological investigations are limited to a few PCP systems. 56,[110][111][112][113] Even less frequent are rheological studies with direct correlations to common shaping processes, such as extrusion or melt spinning. 114 To the best of our knowledge, no specific investigation on mechanical properties of cross-linked PCPs before pyrolysis was performed so far.…”

“…In the forthcoming years, there has been much activity worldwide in the PDCs field, and the organosilicon precursor chemistry remained the highest active contributor to this topic, as illustrated in a majority of references. 36,[53][54][55][56][57][58][59][60][61][62][63][64][65][66][67][68][69] Organosilicon precursors, such as halogenosilanes, made an increasingly important contribution to the research development and manufacture of PDCs. For instance, chlorosilanes have been investigated for the synthesis of polysiloxanes by hydrolysis of Si-Cl bonds followed by subsequent condensation of the Si-OH intermediates to form Si-O-Si groups in polysiloxanes ( Figure 2).…”

Precursor derived SiOC/MoSi₂-composites for diesel glow plugs: preparation and high temperature properties

“…The viscous silica continuous phase and the elastic carbon network have different influence on the activation energy. Ionescu et al 37) found that the carbon network decreases the activation energy and that at higher temperatures the viscous silica phase dominates the creep behaviour. The activation energy for the SiOC/MoSi 2 -composites was higher; 206 and 220 kJ/mol for 17 and 30 vol.-percent MoSi 2 , respectively.…”