A quartet of researchers from Italy and Germany have published an fascinating overview of polymer-derived ceramics in the most recent edition of JACerS. Paolo Colombo, Gabriela Mera, Ralf Riedel and Gian Domenico Sorarù write in “Polymer-Derived Ceramics: 40 Years of Research and Innovation in Advanced Ceramics” (free access), that:
“The polymer precursors represent inorganic/organometallic systems that provide ceramics with a tailored chemical composition and a closely defined nanostructural organization by proper thermal treatment (curing and thermolysis processes) under a controlled atmosphere. The PDCs route is an emerging chemical process as attested by the increasingly commercial development of pre-ceramic polymers to produce near-net shapes in a way not known from other techniques. Moreover, PDCs are additive-free ceramic materials possessing excellent oxidation and creep resistance up to exceptionally high temperatures.”
It’s easy to understand the growing interest in PDCs because, at least In principle, the pre-ceramic polymers can be produced and shaped using familiar techniques such as injection molding, coating from solvent and extrusion. The pre-ceramic polymers still have to be converted to a true ceramic, something that is accomplished by components by heating to a temperature that that it consolidate the elements contained in the polymer structure to a ceramic. PDCs also have excellent oxidation and creep resistance.
Over the years, PDCs have grown from binary systems, such as Si3N4, SiC, BN, and AlN, to ternary systems that include SiCN, SiCO and BCN, and quaternary systems, such as SiCNO, SiBCN, SiBCO, SiAlCN, and SiAlCO.
Regarding applications, the authors sum up the remarkable evolution of PDCs:
“Initially the research on PDCs was focused mainly on dense bulk materials and fibers for mechanical applications at high temperatures. Nowadays, nano powders and porous PDCs with pore sizes in the range between several microns and few nanometers for applications such as catalyst support and for liquid and (hot) gas separation processes are gaining increasingly importance. Moreover, the polymer-to-ceramic transformation is a suitable technology to produce a broad spectrum of ceramic-based composite materials with adjusted chemical, mechanical, and physical properties. PDCs can also be processed to thin films for optoelectronic applications and to thick films, e.g. for hard coatings, environmental barrier coatings, and others. The great flexibility in terms of processing and forming of pre-ceramic polymers into shaped-ceramic components has also enabled them to play an important role in several other applications.”
They also discuss how PDCs are being used in cutting-edge areas such as anode material for solid oxide fuel cells (SiCN), glow plugs, temperature and pressure sensors, high-temperature brake pads (to compliment the new ceramic composite brake disks) and space mirror mock-ups.