Preceramics

Gate Keeper Prof. Paolo Colombo University of Padova (UniPD)  Department of Industrial Engineering   Via Marzolo 9 35131 Padova (ITALY) T: + 39 049 827 5825 F: + 39 049 827 5505 E-Mail: paolo.colombo@unipd.it

The materials

   
Preceramic polymers are a special class of inorganic polymers that can convert with a high yield into ceramic materials, or polymer-derived ceramics (PDCs), via high-temperature treatment in inert or oxidative atmospheres. The polymer-to-ceramic conversion occurs with gas release and shrinkage at 400°C–800°C. The most frequently used preceramic polymers contain silicon atoms in the backbone (e.g., polysiloxanes, polysilazanes, and polycarbosilanes), yielding SiOC, SiCN, or SiC ceramics after pyrolysis. However, aluminum- and boron containing polymers also are possible. In addition, preceramic polymers can be mixed with various fillers (either reactive or inert) to produce numerous advanced ceramic phases.

The particular attraction of preceramic polymers lies in the possibility of combining properties of a polymeric feedstock—very favorable for high-resolution additive buildup of parts—with the capability of transforming them into a ceramic. Manufacturers can use preceramic polymers to produce ceramic components in a range of compositions using a variety of additive manufacturing technologies. Preceramic polymers even can overcome some of the problems that are intrinsic to additive manufacturing in general.

Source: Colombo, P.; Schmidt, J.; Franchin, G.; Zocca, A.; Günster, J.: Additive manufacturing techniques for fabricating complex ceramic components from preceramic polymers.
American Ceramic Society Bulletin, 2017, 96 (3), pp. 16-23.1

 
 
3D Printing and Selective Laser Sintering
 

Post-infiltration of 3D printed green bodies with a liquid preceramic polymer to fill the porosity between ceramic particles (SiSiC lattice structures,2,3 ceramic-matrix composites).4
 
Raw materials for AM: they are readily soluble in several common organic solvents which can be used as printing liquids. Polymer particle surfaces are dissolved by the jetted solvent and, after evaporation, strong connecting necks form between particles.
When printing with a polysiloxane, parts are successively converted to a SiOC ceramic upon heat treatment in an inert atmosphere.
Siloxane resins can also be mixed with inert or reactive fillers for 3-D printing, resulting in silicates such as apatite–wollastonite bioglass–ceramic scaffolds.5

 
Printing binder: dissolution of siloxane in a printing solvent, to add SiO2 to the final composition of the ceramic (BAM, data not yet published).

SiOC coffee cup pyrolyzed at 1,200°C. Inset shows detail of the as-printed object before pyrolysis.1

 
References:

1. P. Colombo, J. Schmidt, G. Franchin, A. Zocca, and J. Günster. "Additive manufacturing techniques for fabricating complex ceramic components from preceramic polymers." ACerS Bulletin, 96 (3), 16 (2017).
2. Z. Fu, L. Schlier, N. Travitzky, and P. Greil. “Threedimensional printing of SiSiC lattice truss structures,” Mater. Sci. Eng. A., 560, 851 (2013).
3. L. Schlier, W. Zhang, N. Travitzky, and P. Greil. “Macrocellular silicon carbide reactors for nonstationary combustion under piston-engine-like conditions,” Int. J. Appl. Ceram. Technol., 8, 1237 (2011).
4. M. Singh, M.C. Halbig, and J.E. Grady, “Additive manufacturing of lightweight ceramic matrix composites for gas turbine engine applications,” Ceram Eng. Sci. Proc., 36 [6] 145 (2015).
5. A. Zocca, H. Elsayed, E Bernardo, C.M. Gomes, M. A. Lopez-Heredia, C. Knabe, P. Colombo, and J Günster, “3D-printed silicate porous bioceramics using a nonsacrificial preceramic polymer binder,” Biofabrication, 7, 025008 (2015).