It is little work. May be you will get idea about the FOAM technology from this slide.

1. Development of Carbon Foam
and Silica Foam by Template
route
Name : Nikunj Patel
Parth M.Ka.patel
Sem. : 4th
Roll no.: 11,12
Department of Materials
science
Date : 16/4/2015
Guides : Dr.
(Miss)R.H.Patel
Mr. Milan Vyas

2. Outline
What is Foam ?
Two types of Foam:
1.Closed-cell Foam
2.Open-cell Foam
Basic terminologies of foams: strut, cell and pore
Types of Foam:
-Polymeric foam
-Metallic Foam
-Ceramic Foam
Various routes to fabricate the porous ceramics
(A)Replica method
(B)Direct foaming methods and
(C)Sacrificial template
Development of carbon foam
Development of silica foam
Characterization of Foam and Results
References

3.  What is Foam?
- A Foam is a substance that is formed by
trapping pockets of gas in a liquid or solid.
 Now carbon foam means a carbonaceous
porous solid having well connected network
of struts.
 Many modern day natural occurring porous
materials are being used for a long time, e.g.
wood, cork, bone, etc. in many applications in
day to day life by human beings.
 Having derived inspiration from nature,
several synthetic cellular materials have been
developed.
 e.g. polymeric foams for packaging,
metallic in crush protection and
ceramic for water purification. [1]

4. Two types of Foam
 The foams can be classified into two
types based on their pore structure:
 1.Open cell structured foams (also
known as reticulated foams i.e. like a
net) and 2.Closed cell foams shown in
figure.
1.Open cell 2.Closed cell foam

5. 1.Open cell structured Foam
 Open cell structured foams are relatively soft
as they contain pores that are connected to each
other and form an interconnected network.
 Open cell foams can be filled with whatever those
are surrounded with.
 i.e. If filled with air this could be a relatively good
insulator, but if the open cells are filled with water,
insulation properties would be reduced. The solid
component of reticulated foam may be an organic
polymer like polyurethane, a ceramic or a metal.
 These foams are used in wide range of
applications where high porosity and large
surface area are needed, including filters, catalyst
supports, fuel tank inserts, and loudspeaker

6. Close cell structured Foam
 Closed cell foams have isolated pores. Normally
closed cell foams have higher compressive
strength due to their structures.
 However, closed cell foams are also generally
denser, require more material, and consequently
are more expensive to produce.
 The closed cells can be filled with a specialized
gas to provide improved insulation.
 The closed cell structure foams have higher
dimensional stability, low moisture absorption
coefficients and higher strength compared to open
cell structured foams.
 All types of foam are widely used as core material
in sandwich structured composite materials.
 The disadvantage of the closed-cell foam is that it
is denser, requiring more material, and therefore,
more expensive.

7. Basic terminologies of foams
 Strut, cell and pore :
 The microstructure of foam in below figure
shows cells, pores and struts.
 The basic structure of foam is made up of
interconnected cells.
 The cells are made of pores and connected
through struts. Struts are also called ligaments.
In given foam, there are pores joined through
ligaments.
Pore
cell
strut

8. Types of Foam
 With specific application of foam,
foam of any material or composition
are being developed.
 e.g. Polymeric foam for room to low
temperature applications,
 Metallic foam for structural
applications and
 Ceramic foam for high
temperature insulation applications
etc.

9. Polymeric foam
 Polymer foams are made up of a solid and gas
phase mixed together to form a foam.
 Polymer foams can be divided into either
thermoplastics or thermosets, which are further
divided into rigid or flexible foams.
 Examples of different polymeric foams are given
in below figure.
 Polymer foams are used in a wide variety of
applications such as disposable packaging of
fast-food, the cushioning of furniture and
insulation material.
(i) PVC foam , (ii) polystyrene foam , (iii) polyethylene foam and
(iv) polyurethane foam

10. Metallic foams
 Metal foams are a new class of material.
 They are light and stiff, they have good energy-
absorbing characteristics (making them good
for crash-protection and packaging) and they
have attractive heat-transfer properties (used
to cool electronic equipment and as heat
exchangers in engines).
 Below Figure shows examples of metallic
foams such as 1.copper, 2. silicon, 3. gold
foam.
1.Copper 2. silicon 3. gold foams

11. Ceramic Foams
 Ceramic foam is usually manufactured by
impregnating open-cell polymer foams internally with
ceramic slurry and then firing in a kiln, leaving only
ceramic material.
 The foams may consist of several ceramic materials
such as aluminium oxide, silica etc .
 The foam is often used for thermal insulation, acoustic
insulation, adsorption of environmental pollutants,
filtration of molten metal alloys and as substrate for
catalysts requiring large internal surface area.
 Ceramic foams like zirconia (ZrO2), silicon carbide
(SiC), alumina foam (Al2O3) and carbon foam are
shown in below figure .

12. Various routes to fabricate
the porous ceramics
 The processing routes described have
been classified into
 (A)Replica method
 (B)Direct foaming methods and
 (C)Sacrificial template,
 Schematically illustrated in figure (A, B
& C).

13. Replica method
 In this method ceramic suspension or precursor
solution that contain ceramic is impregnated in
cellular structure and after sintering it turns into
a macroporous ceramic exhibiting replica of
original porous material. Figure(A) shows
schematic of sacrificial replica foam method.
Figure(A)

14. Direct foaming of liquid slurry
 Direct foaming consists in generation of
bubbles inside liquid slurry containing
ceramic powders or inside a ceramic
precursor solution to create foam which then
needs to be set without collapsing obtained
porous network before heating to high
temperature. (figure (B))
Figure(B)

15. Sacrificial template method
 The sacrificial template technique usually
consists of the preparation of a biphasic
composite comprising a continuous matrix of
ceramic particles or ceramic precursors and
dispersed pore former phase that was initially
homogeneously distributed throughout matrix
and was ultimately extracted to generate pores
within the material.
 The schematic diagram of burn-out pore former
fugitive method is shown in figure(C).
Figure (C)

16. Conti….
 A wide variety of materials had been
used as pore formers, including
compound of natural and synthetic
organics, liquids, ceramics, metals,
polymers, proteins, etc. which
decompose or degrade or dissolve
leaving behind the porous structure
depending upon pore former used and
removal method.

17.  All method discussed above viz. replica method or direct
foaming method or burn-out of fugitive pore former offers
possibility to develop ceramic foams with wide range of
morphology and properties.
 Selection of processing technique basically depends on type
of application aimed and thus microstructural
characteristics.
 Porous ceramics obtained with the sponge replica method
can gives open porosity within the range 40%–95% and was
characterized by a reticulated structure of highly
interconnected pores with sizes between 200 mm and 3
mm.
 Replication technique is a well established method to
prepare ceramic foams in the range of 100 micron to 3 mm
or more.
 Direct foaming method yield porous ceramic foam with pore
size in range of 10 micron to 1.2 mm. Incorporation of pore
former fugitive method produce ceramic foams with pore

18. Development of Carbon foam
 Carbon foams were developed by using
template route. Commercially available open
cell polyurethane (PU) foam was used as
template and phenolic resin was used as
carbon precursor.
 PU foams were impregnated with phenolic
resin solution and cured.
 Carbonization of cured foam was carried out
up to 700 °C in an inert atmosphere to make
carbon foam.
 Materials used:
 Commercially available open cell
polyurethane foams
 Phenolic resin,
 Gas: Nitrogen.

19. Characteristics of
Polyurethane foam:
 Open cell polyurethane (PU) foams,
commercially available were collected having
different densities shown in below figure.
There were of different colours.
 Open cell PU foams used were characterized
for their density. The densities of different
foams were calculated and table-1 gives
density of different types of foam. The density
varies from 0.02 to 0.04 g/cc.
Figure: PU Foam having
different densities

20. Table I: Density of different PU foams
No. Colour PU foam density, (gm/cc)
i White 0.020
ii Dark grey 0.026
iii Yellow 0.030
v Pink 0.040
Preparation of resin solution:
=122 ml Phenol
=122 ml
Formaldehyde(HCHO)
=7.300 ml NaOH
solution
Resole
Color is Reddish Brown

21. Experimental work:
 Cleaned PU foam was impregnated with phenolic resin.
 The open cell PU foams having density of 0.04 g/cc were
selected for development of foam.
 The foams were washed in distilled water and dried in oven at
100 °C.
 The colour of PU foam was pink. Cleaned PU foams were cut
into small rectangular and square pieces.
 Dimensions of PU foam pieces were taken using vernier
callipers and mass by using electronic balance
 For that PU foam was dipped into beaker filled with phenolic
resin.
 The excess resin was removed from time to time to achieve
uniform impregnation.
 Drying and curing of foams:
 Drying of resin impregnated foam was carried out in oven at
between 60-70 °C over night and then after one day at 140 °C.
 To enhance the degree of cross linking between phenolic
chains, impregnated PU foams were cured at 150 °C
overnight.
 The change in color of foam appeared to be dark brown as
shown in figure

22. Carbonization:
The cured foams were carbonized at 700 °C in
nitrogen atmosphere.
The carbonization assembly used for making carbon
foam is shown in figure (A).
Carbonization was carried out in carbonization
reactor having gas outlet and inlet on same side.
The reactor was made up of stainless steel
material.
The S.S. container was placed in a muffle furnace
which was heated electrically.
Heating and cooling rate of the furnace was
controlled by temperature programmer.
The temperature of furnace was measured using
thermocouple and temperature
programmer/controller was used to maintain the
temperature of furnace.
High purity Nitrogen gas was used during

23. Figure (A): Set up for
carbonization
Figure (B):
Schematic
diagram for
development
of carbon
foam
Phenolic
resin

24. Development of silica foam:
 Cleaned PU foam was impregnated with silica sol
 The open cell PU foams having density of 0.03g/cc and 0.04 g/cc were
selected for development of silica foam.
 The foams were washed in distilled water and dried in oven at 100 °C.
 The colour of PU foam was yellow and pink. Cleaned PU foams were cut
into small rectangular and square pieces.
 Dimensions of PU foam pieces were taken using vernier callipers and
mass by using electronic balance
 For that PU foam was dipped into beaker filled with silica sol.
 The excess silica-sol was removed from time to time to achieve uniform
impregnation.
 Drying and curing of foams:
 Drying of resin impregnated foam was carried out in oven at between 60-
70 °C over night and then after one day at 100 °C.
 To enhance the degree of cross linking between silica-sol, impregnated PU
foams were cured at 100 °C.
 Then placing this bulk foam in the furnace in air for sintering.
Continue…..work..

25. Characterization of foams:
 Physical properties:
 Volume shrinkage
 The reduction in length, breadth and thickness
during carbonization and sintering was measured
by measuring dimensions both before and after
heat treatment using vernier callipers. The
shrinkage in all direction was calculated by using
formula:
 where,
 L.before – Length before heat treatment, cm
 L.after – Length after heat treatment, cm
 Likewise, shrinkage in breadth and thickness was
determined by above formula.

26.  Carbon yield, (%):
 Carbon yield was calculated from the initial weight of
materials (W1) before carbonization and final weight of
carbon (W2) obtained after carbonization using
following relation.
 Density Measurement:
 Bulk density of the samples was theoretically
calculated. Geometric volume of sample was calculated
by measuring length, breadth and thickness of foam
with the help of vernier callipers.
 Volume of sample (V) = l * b * t
 Where, l = length of the sample
 b = breadth of the sample
 t = thickness of the sample
 Density of sample was determined using following
formula:

27.  Density = mass of sample(W)
Volume of sample(V)
 Kerosene porosity:
 The kerosene pick-up method was used for
determination of open porosity of developed carbon and
silica foams.
 Figure(1) shows set-up used for determination of
kerosene porosity of foams.
 It consists of a glass flask connected to a kerosene
reservoir and vacuum system with stopcocks.
 One stopcock was joined in between flask and
kerosene reservoir and the second stop cork was joined
in between flask and vacuum system.
 A small piece of foam of known measured dimensions
was taken and weighed. It was placed in the round
bottom flask.
 Flask was connected with vacuum system by opening
stopcock 2.
 The sample was evacuated at 10-3 torr for one hour
with the help of vacuum pump to clean the sample.

28.  The stopcock -2 was closed after evacuation for
one hour and kerosene was allowed to flow by
opening stopcock- 1. Kerosene was allowed to
flow into open pores of sample. After equilibrium
was attained, sample was taken out and excess of
kerosene was wiped out. Sample was weighed
using electronic balance. The density of kerosene
was determined using specific gravity bottle. The
kerosene porosity of sample was calculated using
following reaction.
 % porosity=[Wb-Wa]
Vs * Dk
 Where,
 Wa = weight of sample before adding
kerosene/water
 Wb = weight of sample after adding
kerosene/water
 Vs = volume of sample
 Dk = Density of Kerosene/water

29. Figure (1): Set up for measurement of kerosene
porosity

30. Results
 Volume shrinkage:
 % shrinkage in length= 4.66%
 %shrinkage in breath=12.4%
 %shrinkage in thickness=9.5%
 Carbon yield= 74.93%
 Density of bulk Carbon Foam
=0.682gm/cm³
 Kerosene Porosity =41.59%

31. Other tests:
 SEM
I. SEM image of dried PU Foam impregnated with Phenolic resin
 SEM micrographs showed that pores get fractured during sample preparation or
machining. At higher temperatures it is also possible that small pore walls collapse
and create new bigger pores. The formation of these types of pores may be due to
trapping of air between the surface of PU struts and phenolic resin. The presence
of these types of pore may reduce mechanical properties of carbon foam.
 Compressive test
 TGA

32. References:
[1]Kalpesh patel,S.m.manocha& L.m. manocha,(oct.2010)
“Development of carbon foam from phenolic resin via templet
route” pp.338-342
[2]Ashida kanetoshi(2006), “polyurethane and related foams
chemistry and technology” CRP press, pp 333-342
[3]louis-philippe lefebvre,john Banhart,(2008) “porous metals
and metallic foams: current status and recent
developments”pp-775-787
[4]sulfizar ahmad,Marziana abdoll latif ,(2013),
“ceramic foam fabrication technique for water treatment
application”pp-5-8
[5]H.Schmidt, D.Koch, g.Grathwohl, P.Colombo, “Micro and
macroporous ceramics from preceramic precursors”,
J.Am.Ceram.Soc.84(2001)pp-2252-2255
[6]W.p.Minnear, Processing of foamed ceramics, in:M.J.Cima
(Ed.), Ceramic transactions, forming science and technology
for ceramics,Am.Cerami.Soc.,(1992)pp.149-156
[7]P.Sepulveda, Gelcasting of foams for porous ceramics,
J.Am.Ceram. Soc. 76(1997)pp.61-65

33. THANK YOU