Precursor-derived ceramics

Ceramics obtained from polymeric precursors are usually amorphous. Since substantial thermal activation is required for nucleation and crystallization, precursor-derived ceramics (PDCs) frequently remain amorphous or nanocrystalUne up to rather high temperatures. For example, crystallization of a number of quaternary Si-B-C-N ceramics is retarded even up to 1800°C, resulting in excellent thermomechanical properties. Nevertheless, crystalline materials are of great interest because their microstructure formation can be controlled during devitrification, providing a means for stabilizing nanosized morphologies. 

Fig. 25a, b. Concentration sections in the Si-B-C-N system at constant boron content (10 at.%) and temperatures. Composition of some high-temperature stable precursor-derived ceramics are indicated [272, 273]. (a) T = 1673 K, (b) T = 2273 K... 

Bill J, Wakai F, Aldinger F (eds) (1999) Precursor-derived ceramics. Wiley-VCH,... 

Kleebe HJ, Suttor D, Muller H, Ziegler G (1998) J Am Ceram Soc 81 2971 Seifert HJ, Peng J, Aldinger F (2001) J Alloys and Compounds 320 251 Rassaerts H, Schmidt A (1966) Planseeberichte fiir Pulvermetallurgie 14 110 Seifert HJ, Aldinger F (1999) Thermodynamic calculations in the system Si-B-C-N-O. In Bin J, Wakai F, Aldinger F (eds) Precursor-Derived Ceramics. Wiley-VCH, Weinheim, New York, p 165... 

During their genesis all precursor derived ceramics pass through an amorphous state which in certain cases is stable up to the respective decomposition temperature. The propensity to crystaUize is strongest for the binary silicon and boron nitrides and carbides, while in particular quaternary materials out of the Si/B/N/C system show the strongest resistance towards crystallization. It is interesting to note that in any case investigated, so far, the amorphous multinary ceramics decompose into the binary border phases upon crystallization - crystalline ternary silicon boron nitrides or carbides are not known to date cf. [9]. 

The issue of thermal stability is important for these phases, because precursor-derived ceramics are amorphous and have stoichiometries where detrimental structural and chemical changes may occur on crystallization. The highest temperatures recorded so far come from phases in the system Si-B-C-N (2000°C [166]). 

We are not aware of hot corrosion testing of precursor-derived ceramics. A prediction rests upon the argument that for those which contain boron a top scale compositions in the Na-B-Si-O-system should form, that is a classical glass forming system with low melting points and viscosities [176]. Apart from the hot corrosion degradation by itself it is completely unknown whether this will induce crystallization of the amorphous precursor-derived ceramics. 

J. Bill and F. Aldinger, Precursor-derived covalent ceramics, in Precursor-Derived Ceramics, J. Bill, F. Wakai, and F. Aldinger (Eds.), Wiley-VCH, Weinheim, 1999, pp. 33 51. 

J. Bill, F. Wakai, F. Aldinger Precursor-Derived Ceramics... 

Self-diffusion studies of Si in amorphous precursor-derived ceramics (Si3BC4 3N2 and Si2.6C4.i N2.3) were carried out in order to compare the atomic transport properties of B-containing and B-free material in the Si... 

Butchereit, E. Nickel, K. G. (2000). Oxidation behaviour of precursor derived ceramics in the system Si-(B)-C-N. Engineering Ceramics Multifunctional Properties - New Perspectives, 175-1, 69-77. 

Iwamoto, Y. (2007). Precursors-derived ceramic membranes for high-temperature separation of hydrogen. Journal of the Ceramic Society of Japan, 775(1348), 947-954. doi 10.2109/jcersj2.115.947. 

Muller, A., Gerstel, P, Butchereit, E., Nickel, K. G., Aldinger, F. (2004). Si/B/C/N/ Al precursor-derived ceramics Synthesis, high temperature behaviour and oxidation resistance. Journal of the European Ceramic Society, 24(12), 3409-3417. doi 10.1016/j.jeurceramsoc.2003.10.018. 

Schutz, A., Gunthner, M., Motz, G., Greissl, O., Glatzel, U. (2012). Characterisation of novel precursor-derived ceramic coatings with glass filler particles on steel substrates. Surface and Coatings Technology, 207, 319-327. doi 10.1016/j. surfcoat.2012.07.013. 

---