CERAMICS DERIVED FROM POLYMERIC PRECURSORS
Most ceramics manufacturing processes involve the step of sintering to densify compacted powder samples (green bodies) to form a continuous 3D structure and thus to get ceramic pieces appropriate for the selected application. Sintering generally requires the use of extremely high temperatures (>>1000 oC) so that it is energy-intensive. Hence the production of ceramics from formulations that provide fabricated articles possessing excellent properties without requiring the use of such extremely high processing temperatures is an area at the frontiers of materials R&D.
One of the most promising general directions in this area of materials R&D is the exploration of the use of polymeric precursors that can be cured at much lower temperatures than the types of precursors used in conventional ceramics precursor formulations. Two approaches, both involving the use of polymeric precursors, being pursued by two highly innovative ceramics manufacturers, will be described in the remainder of this post.
Pyromeral Systems develops and manufactures advanced materials and composite parts for applications requiring resistance to high temperatures and/or a fire barrier. Its unique technologies based on innovative inorganic polymers and glass-ceramic matrices are designed for continuous exposure to temperatures as high as 1000 oC. These technologies provide convenient, lightweight, and durable solutions for industrial processes, motorsports, and aerospace applications. Pyromeral’s inorganic polymers and composite matrices do not use organic solvents and do not emit fumes. They are easy to store and discard, and safer to handle than most matrix systems for high-temperature composites.
- Composites with organic thermoset or thermoplastic matrices reinforced with glass fibers (GFRP) or with carbon fibers (CFRP) are widely used at temperatures below 300 o Furthermore, they are easy to process with well-known techniques, and with systems that rely on fairly low temperatures, from 100 oC to 350 oC.
- Carbon/carbon composites and other ceramic-matrix composites (CMC) deliver exceptional performance at very high temperatures (well above 1000 oC), but their complex processing and high costs have limited their use to niche markets and to specific applications where no other material could be used.
- The use of a new family of glass-ceramic matrices resulting from the polymerization of inorganic polymers is the foundation of Pyromeral’s materials. These inorganic polymers are derived from aluminosilicate-based geopolymeric systems, and, as such, differ significantly from both organic polymers and conventional ceramic matrices. Anyone interested in geopolymers is recommended to study Joseph Davidovits, Geopolymer Chemistry and Applications, 4th Edition, Geopolymer Institute (November 2, 2015).
- With this technology, Pyromeral’s composites bring a lightweight and convenient alternative to metals and other materials for heat shields, ducts, and other components exposed to temperatures between 300 oC and 1000 o Short-term exposure to temperatures above 1000 oC is also possible. These materials are also used when superior fire, smoke, and toxicity properties are needed. Pyromeral’s glass-ceramic matrix composites hence provide a level of mechanical properties generally comparable to those of CMCs, while they also offer much improved processing, as they are cured at low temperature (< 150 oC) with only one cure/postcure cycle to complete a part.
- This unique combination of a heat resistant structural composite fashioned with the classic carbon fiber composite processing explains why Pyromeral’s materials can be described as bridging the gap between CFRP and CMC.
- The images shown below are reproduced from the website of Pyromeral Systems.
Covaron Advanced Materials has developed PetraForge™, an environmentally sustainable, thermosetting, inorganic material that combines the performance benefits of a ceramic with the processability and formulation versatility of a two-part epoxy or two-part polyurethane.
- While in its green state, it may be cut, milled, sawed, ground, carved, tapped, prilled, sanded, or polished with ordinary steel tooling.
- It cures to its final form in a humidity-controlled environment below 200 oF (93 oC).
- It possesses unique characteristics that are beneficial for applications in:
- Foams (heat resistance, thermal insulation, and energy absorption).
- Adhesives (heat resistance, gas-tight seal, metal to ceramic bonding, and ceramic to ceramic bonding).
- Coatings (heat resistance, thermal insulation, low thermal emissivity, superior adhesion, hardness, chemical resistance, and wear resistance).
- Fiber-reinforced composites (heat resistance and chemical resistance).
- Covaron enables innovation of other technologies at the system and subsystem levels through optimization of the formulation performance based on application requirements.
- The targeted products include ceramic-matrix composites, ceramic-organic composites, and ceramic-fiber composites.
- The targeted industries include automotive and other transportation, energy, construction, coatings, and manufacturing.
- The images shown below are adapted or reproduced from the website of Covaron Advanced Materials.