- Ceramic foams have
an interesting combination of properties, such as low weight, high
temperature stability. high permeability, high porosity, low thermal
conductivity and low heat capacity. These properties have lead to a
diverse field of applications, ranging from metal melt filtration,
ion-exchange filtration, heat exchangers, catalyst support, refractory
linings, thermal protection systems, diesel soot traps, flame rectifiers
and solar radiation collectors. Recently the bio-technology and
biomedical industries are employing ceramic foams made of hydroxyapatite,
which can simulate bone and bio-implants.
- Engineered foams
have cellular structures which are categorized as either open call or
closed cell foams. Foams consists of an assembly of irregularly shaped
prismatic or polyhedral cells connected to each other with solid edges
or faces. Engineered foams have been manufacturers from polymers,
metals, glasses and ceramics. Ceramic foams are porous brittle materials
with closed, fully open or partially interconnected porosity. Porous
ceramic materials are being used in many industries and continue to be
very active area of research for yet uncharted applications.
- Open cell ceramic
foams are used for a very wide range of applications. The excellent
thermal shock resistance facilities their use for metal melt filtration
and diesel engine exhaust filters. Ceramic foam filters improve molten
metal casting quality by removing non metallic inclusions.
- Open cell ceramic
foam manufacturing techniques can be classified into three general
categories: Sponge-replication, foaming agents or space holder method.
The Sponge replication was first developed in the early 1960s. It
consists of using natural sponge or polyurethane foam as a form, which
is infiltrated with ceramic slurry. The ceramic slurry is then fired to
form ceramic foam.
- The second
technique is based on gas bubbles in preceramic melts. Gas evolving
constituents are added to the melt. During the treatment bubbles are
generated, causing the material to foam . This process was introduced in
1973 by sunderman.
- The manufacturing
process for Hi‑Por relies on the gelation of an organic binder to
stabilise the foamed structure. It should not be confused with
reticulated foam, which is produced from a polyurethane skeleton. The
essential components of the process are ceramic powder, organic binders,
dispersing agents, a foaming agent and water.
ultra-light ceramic foams developed by Cellaris contain either
closed or open pores, 50-2000 micrometer in
diameter. The foams may have a very high void fraction of 94%-99%.
The closed and open cell materials are directed towards thermal
insulation and catalyst support, respectively. Thermal stability
is retained up to 1600øC - making the foams attractive for high
- Ceramic foam
burners are studied intensively at ECN, both experimentally and
computationally. The aim is to realise energy savings and to reduce NOx
emissions. A one-dimensional mathematical model has been developed that
incorporates a one-step chemical reaction, heat transfer between gas and
ceramic, radiation from the burner surface to the surroundings, and
radiative heat transfer within the ceramic foam. The CSE has been used
to steer those simulations.
- Ceramic foams have
so far been produced in a variety of materials with various cell sizes,
densities and degree of interconnectivity. Foams are usually produced
with densities between 10 and 40% of theoretical and pore sizes between
100 µm and 1 mm. The majority of the development work was carried out on
a fine grained α‑alumina, before moving on to alternative materials.
- The Exhaust
Systema of Military jet engines must be constructed using radar
absorbing ceramic materials that can withstand harsh thermal, chemical
and mechanical environments. Currently, these exhaust system structures
combine relativelt dense ceramic matrix composites and a lightweight,
non- structural porous ceramic in a prprietary configuration that is
heavy and that provides inadequate control over both radar and infrared
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