4 — Silixon-PDC

Polymer-Derived Ceramic

What It Is

Silixon-PDC is Hardin Labs' proprietary polymer-derived ceramic material — the core structural and functional ceramic used across the entire Silixon product line. It belongs to the family of ceramics that are synthesized by pyrolyzing organic preceramic polymers under inert atmosphere rather than by sintering ceramic powders, a process that grants molecular-level control over composition, phase distribution, microstructure, and resulting properties. Hardin Labs' specific formulation augments conventional silicon oxycarbide chemistry with the chromene-derived carbon network from Silixon-HPDC and metalorganic dopants to produce a material with a unique combination of high thermal stability, intrinsic electrical conductivity, mechanical toughness, and chemical inertness.

Synthesis Route

The Silixon-PDC synthesis begins with blending Silixon-HPDC, polysiloxane monomers, and metalorganic crosslinkers — chosen for hafnium, zirconium, or boron content depending on the end application — into a homogeneous liquid precursor. This liquid is shaped by casting, injection molding, stereolithographic 3D printing, or filament extrusion into complex three-dimensional green bodies. The green body is thermally cross-linked at 150–300 °C, converting the liquid mixture into a solid polymer preform. The preform is then pyrolyzed under argon at temperatures between 1,000 °C and 1,800 °C in a controlled multi-stage ramp, driving off hydrogen, oxygen, and carbon in the form of gases while the remaining silicon, carbon, oxygen, and dopant metals reorganize into an amorphous or nanocrystalline ceramic network. The resulting material is chemically stable up to temperatures approaching 2,000 °C.

Key Properties

Silixon-PDC exhibits outstanding oxidation resistance and creep resistance at elevated temperatures — properties that set it apart from conventional powder-sintered ceramics. The carbon-rich phase inherited from the HPDC precursor gives the material a measurable electrical conductivity, making it suitable for use in conductive vias, RF-absorbing structural panels, and electrostatic shielding housings. Its low density (approximately 2.2–2.6 g/cm³ depending on dopant loading) combined with fracture toughness values above those of monolithic SiC makes it the preferred structural ceramic for weight-critical aerospace and bioid skeletal applications. Because the entire forming and shaping occurs in the polymer phase before pyrolysis, Silixon-PDC can be fabricated into geometrically complex forms — including the 524,288 sealed ceramic channels of the Silixon Cube — that would be impossible to machine from pre-sintered ceramic stock.