Electrochemical corrosion of silicon carbide ceramics in sodium hydroxide

Electrochemical corrosion of silicon-infiltrated silicon carbide ceramics in aqueous solutions

“…6b, Spectrum 1). SiSiC yielded similar results and was hence additionally investigated after corrosion at a constant voltage of 1.6 V in 0.5 M H 2 SO 4 solution for one hour and in 1 M NaOH at 2 V for 1000 s. These conditions are comparable with those in the investigations carried out on the SSiC material described by Herrmann et al [8], Sydow et al [12] and Herrmann et al [15]. The current response to the applied potential in H 2 SO 4 was linear with two different slopes in the double-logarithmic plot (Fig.…”

“…Taking this into account, the lower etching rates have to be expected. These are much less than the etching rate observed for SSiC ceramics (approximately 30 nm/min in 1 M NaOH) [15] or for SiC crystals observed by Kato et al [19] (1-10 nm/min). On the other hand, the impurities existing in the initial Si are also incorporated into the formed SiC.…”

“…The local corrosion rate of the grains was found to be controlled by the local resistivity, depending mainly on the resistivity of the grain boundaries [8,15]. No correlation between the corrosion rate and the polytype or the crystallographic orientation was found in acids or alkaline solutions [8,15]. In LPS-SiC materials, with grains exhibiting a core-rim structure, the rim exhibited a higher corrosion rate.…”

“…Dissolution of the grains was found in alkaline solutions due to the formation of soluble silicates [12][13][14][15]. In contrast, formation of a SiO 2 layer was observed in acids.…”

“…The authors assumed that silicon was the reason for the stronger corrosion, but they did not proof this assumption by carrying out the associated microstructural investigations. For SiSiC ceramics, not only the described electrochemical dissolution of SiC [8,12,13,15], but also the electrochemical corrosion of Si in acid and alkaline solutions, has to be considered. The following half-reactions are involved:…”