CVI and TAV Vacuum Furnaces
Giorgio Valsecchi presented this blog on Linkedin, which really interested me.
What does the abbreviation CVI stand for and what is it for? Chemical Vapor Infiltration (CVI) technology is an advanced method for producing high-performance ceramic matrix composites (CMC) and carbon/carbon (C/C) composites. CVI allows the infiltration of the porous fiber structure (preform) with gaseous precursors, which decompose at high temperatures and create a matrix inside the structure, without damaging the fibers.
The process takes place in specialized vacuum furnaces, where the gaseous precursor infiltrates the porous preform (e.g. carbon or SiC fibers) and decomposes at high temperatures (> 900 °C), creating a solid matrix. A description of the process can be found at https://en.wikipedia.org/wiki/Chemical_vapor_infiltration
What interested me about it? Mainly the applications.
- C/C composites (Carbon/Carbon): Brake discs for aircraft and high-speed trains, rocket nozzles.
- SiC/SiC (Ceramics/Ceramics): Aero engine components, hot sections of turbines, nuclear applications (high temperature resistance).
All positives. And those terms?
The word precursor in chemistry refers to a compound that participates in a chemical reaction that produces another compound. And what precursors are they talking about in relation to CVI? The most common examples:
Generally, these are toxic, corrosive, flammable and explosive substances.
- CH₄, BCl₃, NH₃ = gases
- CH₃SiCl₃, TiCl₄, SiCl₄ = liquids
- AlCl₃ = solid (subliming)
And the term preform? It is an input material, with a porous structure, made of carbon or ceramic fibers.
- 3D woven/braided structures (3D woven/braided): Most often used for high demands on strength in various directions, minimizing delamination.
- Needled preforms (needle felts): The fibers are combed into a mesh (mesh) and then needled in the Z axis, which ensures good strength even in the third dimension.
- Carbon cloth laminates: Unidirectional or woven carbon cloth is laid layer by layer, often with a fiber orientation of 0/0/90/90° for brake discs.
- Short fiber (Short fiber molded): A mixture of short carbon fibers with resin, which is then molded.
and the most common layers that are applied to these preforms using the CVI method?
- Carbon: C
- Carbides: SiC, B4C, and TiC
- Nitrides: BN and Si3N4
- Borides: TiB2
- Oxides: Al2O3 and ZrO
What’s so special about it? It’s a technology that allows us to fly to space and back, or to exceed hypersonic speeds of over Mach 5. For today’s technology, it’s really very appropriate.
So my admiration for TAV and Giorgio.
Jiří Stanislav
February 11, 2026
