The fate and role of in situ formed carbon in polymer-derived ceramics

A dream for
many scientists,
engineers and sci-fi
enthusiasts is of an aerospace
vehicle that can
take off from an airport,
fly through the atmosphere
and travel to the
other side of the earth
at hypersonic speeds,
and then return through
the atmosphere to the
same or another airport.
Thanks to programs
like DARPA’s Falcon
Hypersonic Technology
Vehicle 2 program
(Figure 1), the dream is
taking form.

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UHTC composites for hypersonic applications

Preparation and reactive applications of nanoporous silicon carbide membranes

Processing and properties of C/Si-B-C-N fiber-reinforced ceramic matrix composites prepared by precursor impregnation and pyrolysis

This review states recent developments in the preparation of ceramic fibers using a chemical procedure denoted as Pyrolysis of Preceramic Polymers. Synthesis strategies which are used to prepare Polymer‐Derived Ceramics (PDCs) fibers from molecular and polymeric precursors are presented by refering to the crystalline boron nitride (BN) fibers and amorphous silicoboron carbonitride (SiBCN) fibers as models. The influence of the structure of the molecular and polymeric precursors, in which specific functional groups and structural motifs are incorporated on the melt‐spinnability, polymer‐to‐ceramic conversion and fiber properties is discussed. A minimum cross‐linking degree combined with the presence of flexible structural patterns and plasticizing functional groups yield controlled melt‐viscoelastic properties and appropriate thermal stability at low temperature to produce high quality fine‐diameter endless green fibers in a stable melt‐spinning process. These structural motifs and functional groups are al...

Recent Developments in Polymer‐Derived Ceramic Fibers (PDCFs): Preparation, Properties and Applications – A Review

Preceramic polymers offer a unique method to fabricate ceramic matrix composites (CMC). Relatively large and complex shapes were fabricated using a polysilazane polymer and silicon carbide based reinforcements of CG Nicalon™ and HI-nicalon™ fibers. This paper summarizes a raw material system and the fabrication process used to prepare two-dimensional cloth reinforced composites. Typical tensile, shear and compressive properties of CMCs prepared with the two types of reinforcements are presented. Although CG Nicalon reinforced composites exhibit good mechanical stability at moderate stress levels at 1100°C, HI-Nicalon reinforced composites show improved creep behavior at 1200°C.

Polymer derived ceramic matrix composites

SYLRAMIC™ SiC fibers for CMC reinforcement

The elastic modulus and density of an amorphous, ceramic article derived from a resinous organosilicon polymer and having a composition consisting essentially of silicon, nitrogen and/or carbon are increased while substantially maintaining or improving tensile strength by heat treating the ceramic article at an elevated temperature under superatmospheric nitrogen pressure to increase its density while avoiding crystallization During heat treatment, at least some of the conditions of time, temperature, heating rate, cooling rate, pressure and atmosphere are controlled to minimize erosion of the article which could otherwise occur due to the loss to the surrounding atmosphere, as a gas or gaseous component, of at least one of nitrogen, silicon and carbon The heat treated, ceramic article is amorphous and non-crystalline and has a density substantially greater than 25 g/cc together with desirable values of tensile strength and elastic modulus

Method for densification of amorphous ceramic material

The invention relates to a method for increasing the density and elastic modulus of an article amorphous ceramic obtained from a resinous organosilicon polymer and having a composition consisting essentially of silicon, nitrogen and / or carbon, while maintaining or improving the tensile strength. the ceramic article, in particular a cable of ceramic fibers, is heat-treated at high temperature, in particular between 1400degre (s) to 1800 degree (s) C, under positive nitrogen pressure to increase its density while avoiding crystallization. During the heat treatment, at least some of the conditions of time, temperature, heating and cooling rates, pressure and atmosphere are adjusted to minimize the erosion of the article that might otherwise occur due to loss to the surrounding atmosphere, at least one nitrogen, silicon and carbon in the form of a gas or gaseous component. the invention applies to the manufacture ceramic products, including ceramic fibers and composite materials containing them.

Richard Eugene Jones

Papers

Polymer derived ceramic matrix composites

SYLRAMIC™ SiC fibers for CMC reinforcement

Method for densification of amorphous ceramic material

A method for increasing the density of an amorphous ceramic article, and ceramic article obtained by this method