Preceramic polymer

The term preceramic polymer refers to one of various <a href="/facts/Polymer/eF32E50K"> polymeric compounds</a>, which through <a href="/facts/Pyrolysis/h1cEegI7">pyrolysis</a> under appropriate conditions (generally in the absence of oxygen) are converted to ceramic compounds, having high thermal and chemical stability. Ceramics resulting from the <a href="/facts/Pyrolysis/h1cEegI7">pyrolysis</a> of preceramic polymers are known as <a href="/facts/Polymer_derived_ceramics/S8d420ve">polymer derived ceramics</a>, or PDCs. Polymer derived ceramics are most often <a href="/facts/Silicon/cgWx0hdr">silicon</a> based and include <a href="/facts/Silicon_carbide/kQLVAYbr">silicon carbide</a>, silicon oxycarbide, <a href="/facts/Silicon_nitride/58X9QPQJ">silicon nitride</a> and silicon oxynitride. Such PDCs are most commonly amorphous, lacking long-range crystalline order. 
The field of preceramic polymers and polymer derived ceramics in general emerged from the requirements in aerospace industries for heat shield materials such as fiber reinforced ceramic / ceramic composite materials. The use of preceramic polymers allows for diverse processing techniques relative to conventional ceramic processing. For example, the spinning of fibres, casting of <a href="/facts/Thin_films/nSeoUT4Q">thin films</a> and the molding of complex shapes. Commonly used preceramic polymers include polycarbosilanes and <a href="/facts/Silicone/4AX8YA5m">polysiloxanes</a>, which transform through <a href="/facts/Pyrolysis/h1cEegI7">pyrolysis</a> to <a href="/facts/Silicon_carbide/kQLVAYbr"> SiC</a> and <a href="/facts/Silicon_oxycarbide/bXsDVeX2">SiOC</a> type ceramics respectively. 
A low-cost method of creating complex 3D shapes of ceramics components is to use <a href="/facts/3D_printing/lbvWU3t0">additive manufacturing</a> (AM) in a use a two-step process of first printing the artifact in polymer and then converting it to ceramic using pyrolysis to form polymer derived ceramics (PDCs). This process works with <a href="/facts/Fused_filament_fabrication/9g464H6S">fused filament fabrication</a> (FFF)-based 3-D printing to make fully dense cellular structures, which can be used for scaffolds for bone regeneration that need to be mechanically stable and have a 3D architecture with interconnected pores. Various other 3D printing techniques (e.g., <a href="/facts/Stereolithography/wIPeT3Wy">stereolithography</a>, <a href="/facts/Digital_Light_Processing/jxMs8emm">digital light processing</a>, and <a href="/facts/Multiphoton_lithography/QScbSQrA">two-photon polymerization</a>) that are compatible with this strategy have so far been widely investigated. For example, through photopolymerization methods, preceramic polymers can be used in stereolithography approaches, enabling the <a href="/facts/Additive_manufacturing/lbvWU3t0">additive manufacturing</a> of complex shaped ceramic objects. In such methods, by means of irradiation-driven cross-linking, liquid preceramic polymers transform into rigid thermoset polymers that preserve their shape through the following polymer-to-ceramic transformation that takes place in pyrolysis. In this transformation, polymers transform into glassy ceramic products.

Preceramic polymer open-in-new

Preceramic polymer