2. Utilization of Advanced Capillary
Suspension Route to Prepare Structured
Ceramic
العالق طريقة أستخدام
لتحضير المتقدمة الشعيري
هيكلي سيراميك
3. Capillary suspension
3
Capillary suspension has been used to summarily describe “suspensions formed through
the addition of a secondary fluid to a classical particle suspension”, which includes
suspensions in both the pendular and capillary states.
It is ternary particle–liquid–liquid system composed of particles dispersed in two
immiscible liquids can form a variety of structures depending on the ratio and properties of
the three components.
(A) Mixing,
Forming,
and Bulk
Debinding
(B) Thermal
Debinding
and
Sintering
Principle processing steps for the production of
porous ceramics by capillary suspensions
4. Geopolymer as chemically bonded ceramics
4
Chemically bonded ceramics (CBCs) refers to the fact that they are produced through a chemical
reaction at low temperature.
The bonding present in such CBCs, is a mixture of ionic, covalent, and van der Waals bonding, with
the ionic and covalent dominating, like in ceramic materials.
Hydraulic cements, hydrogen bonds are formed by chemical reaction when water is added to the
powders. These bonds are distinct from the bond in ceramics in which high temperature interparticle
diffusion leads to consolidation of powders.
CBCs show some of the typical properties of ceramic materials such as hardness, chemical and
thermal stability, good resistance to acid attack and excellent corrosion resistance with the great
advantage to be obtained at low temperature.
6. Introduction
6
Geopolymers are inorganic, typically ceramic, alumino-silicate forming long-range,
covalently bonded, non-crystalline (amorphous) networks. Obsidian (volcanic glass)
fragments are a component of some geopolymer blends.
Commercially produced geopolymers may be used for fire- and heat-resistant
coatings and adhesives, medicinal applications, high-temperature ceramics, new
binders for fire-resistant fiber composites, toxic and radioactive waste encapsulation
and new cements for concrete.
7. Cont.
7
In this project, geopolymer is developed into cost-effective porous materials from meta-
kaolin to overcome such a problem. The porous structure could be developed using
several different methods.
such as combined direct foaming capillary suspension approach.
High strength and high porosity properties are opposite so it is not easy to get both of them
at the same time.
Geopolymer foam processing typically has many effective parameters; this is not easy for
making geopolymer foam simultaneously has high strength and high porosity.
The optimization of the synthesis conditions in the production of strong geopolymer foam
with high porosity and improving their properties are the keys to making Iraqi metakaolin-
based geopolymer foams competitive with expensive synthetic foams.
8. Mechanism of geopolymerization
8
Dissolution of the solid aluminosilicates source by alkaline hydrolysis (consuming
water), i.e. surface dissolution of Al and Si in a highly alkaline solution that produces
monomeric aluminate and silicate species;
Diffusion of the dissolved species through the solution and reorganization with fine
coagulated structures production;
Polycondensation (i.e. incorporation) of the Al and Si complexes with the added
silicate solution to produce gel phases of aluminosilicate as the oligomers in the
aqueous phase form large networks by condensation.
Hardening of the gel that results to the final geopolymeric product: The final 3-
dimensional geopolymer aluminosilicate network is obtained after reorganization and
rearrangement of the system, when the connectivity of the gel network increases.
10. Aim And Objectives
10
The current work aims to find the mixes, and their processing parameters, which are suitable
to produce Geopolymer foam with one of the following features: Highest compressive strength,
Highest porosity, Highest specific surface area and Utilizing various mechanisms in order to
produce a
What is the best molar fraction of K2O substitution that can improve
metakaolin-based geopolymer foam's required properties?
What is the effect of the free silica, water, OPC, foaming agent, and
stabilizing agent amount on the required characteristics of metakaolin-
based geopolymer foam?
Can a strong geopolymer foam with high porosity be synthesized by direct
foaming/capillary suspension combined route?
What is the effect of the different reinforcement types on the characteristics of the
synthesized metakaolin-based geopolymer foam?
Can the RSM technique optimize the production process parameters of MK-based geopolymer foam?
11. Methodology
11
Kaolin
SH, SS, PH, PS, Silica gel
Alkaline solution
MK-750
Hybrid Geopolymer Paste (HGP)
Modified Hybrid Geopolymer
Foam (MHGF)
Tested by: (XRD, Chemical Analysis,
FTIR, PZA, and DTA)
Tested by: (XRD, FTIR, and PZA)
Addition of OPC
Addition of H2O2 and Olive Oil
Hybrid Geopolymer Foam (HGF)
Tested by: (CS, Physical tests, FTIR,
BET, and SEM-EDX) composition
Optimizing by RSM
Tested by: (XRD, FTIR, PZA, and
TEM) composition
Modification by CNT, GO, Graphite,
and PVA
Tested by: Compressive strength, Physical
tests, FTIR, BET, and SEM-EDX.
Firing at 750 °C for 3 hrs
Pouring
Dissolving in water
Mechanical mixing
12. Hybrid Geopolymer Foams (HGPFs)
1
(n): the number of moles of SiO2 in the geopolymers' formula.
(m): the number of moles of K2O in the geopolymer formula
m K2O. (1-m) Na2O. Al2O3. n SiO2. x H2O
The HGPFs have been produced in the following way. Initially, the metakaolin (MK-750)
and (0, 5, 10, 15, and 20 wt%) ordinary Portland cement (OPC) were mixed.
13. Chemical formula
and purity of
materials used in
work
Table
Materials Chemical formula Purity (%) Manufacturer
Sodium silicate Na2SiO3.5H2O 97.98 Thomas Baker, India
Sodium hydroxide NaOH 97.99 Thomas Baker, India
Potassium hydroxide KOH 97.99 Thomas Baker, India
Silica gel SiO2 98.99 Thomas Baker, India
Hydrogen peroxide H2O2 30 w/v Thomas Baker, India
Carbon nanotube C > 75 Jinzhou Hancheng, China
Graphene oxide C140H42O20 > 95 Soochow Hengqiu, China
Poly (vinyl alcohol)
(PVA)
[CH2CH(OH)] n 99 Sigma-Aldrich, Germany
Olive Oil - 99 ZER, Turkey
14. Preparation of Geopolymer Samples
14
• The alkaline liquid utilized in this investigation was a mixture of hydroxide salts,
involving potassium hydroxide (PH) and sodium hydroxide (SH), and silicate
salts including sodium silicate (SS) and potassium silicate (PS).
Alkaline solution
• After the alkaline solution is cooled to room temperature, the metakaolin (MK-
750) was added to the solution and mixed using an Electronic overhead stirrer at
a fixed speed of (1000 rpm) desired to mix time.
Geopolymer cement
paste
• The GPFs have been produced in the following way. Initially, the metakaolin (MK-
750) and alkaline solution were mixed; geopolymer paste will be formed.
• After allowing the paste to set for a bit, hydrogen peroxide (H2O2) has been
introduced as a foaming agent, followed by olive oil as a stabilizing agent.
Preparation of
geopolymer foams
(GPFs)
17. The affected
parameters of the
manufacture of
the geopolymer
Table N
H2O (ml)/10.73
MK-750
OPC powder
(wt%)
Foaming
agent (wt%)
Stabilizing
agent (wt%)
3.2 8 0 0 0
3.4 9 5 1 1
3.6 10 10 2 2
3.8 11 15 3 3
4.0 12 20 4 4
18. 18
The specimen of geopolymer cement
paste after curing 24 h at 25 °C.
Geopolymer Foam Strengthed by
Carbon nanotube
19. Modification of Hybrid Geopolymer Foams
1
According to the reinforcement types, there are four formulations of modified
hybrid geopolymer foam (MHGPF).
1. MHGPF with single-walled carbon nanotubes (SWCNTs)
2. MHGPF with graphite:
3. MHGPF with graphene oxide (GO):
4. MHGPF with poly vinyl alcohol (PVA):
20. 20
Experiments Design
The experiments design using the full factorial method. The above
set of process parameters requires a large number of samples, up to
3125 samples (LP= 55), and the efforts, time, and high cost.
Response Surface Methodology (RSM) was used to overcome
these drawbacks.
RSM suggested 52 experiments for each geopolymer mix (HGPF1,
HGPF2, HGPF3).
22. Results And Analysis Of Groundwater Modeling
FTIR Results
SEM Images
Physical Properties
23. 23
FTIR spectrum of HGP3.
FTIR spectrum of GP3.
FTIR spectrum of HGPF1.
FTIR spectrum of HGPF3.
24. 24
Surface SEM micrographs
of HGPF1 sample
Surface SEM micrographs
of HGPF1 sample
Surface SEM micrographs
of MHGPF-SWCNT
Surface SEM micrographs
of MHGPF-Graphite sample
Surface SEM micrographs
of MHGPF-GO sample
Surface SEM micrographs
of MHGPF-PVA sample
25. EDX results
of the current
work samples
Table
Sample
Elements of GPs (atomic wt%.) Si/Al
atomic
ratio
Na(K)/Al
atomic
ratio
O Al C Si K Na Ca
GP3 53.73 11.78 8.90 19.78 2.87 2.95 1.04 1.67 0.25(0.24)
HGP3 49.37 10.03 14.56 18.43 3.28 1.85 2.49 1.83 0.18(0.32)
GPF3 50.89 13.26 6.96 24.65 2.68 1.07 0.48 1.85 0.08(0.20)
HGPF1 51.20 10.59 4.29 24.10 0.44 2.95 5.74 2.27 0.27(0.04)
HGPF3 51.93 11.05 10.61 20.78 3.63 2.01 - 1.88 0.18(0.32)
MHGPF-
CNT
52.83 8.27 13.24 17.91 3.81 0.94 1.51 2.16 0.11(0.46)
MHGPF-
Grap.
51.24 7.11 19.44 16.68 3.16 0.85 1.53 2.34 0.11(0.44)
MHGPF-GO 47.77 8.53 15.95 19.56 4.27 1.97 1.28 2.29 0.23(0.50)
MHGPF-
PVA
46.08 8.45 17.20 19.71 5.22 0.81 1.82 2.33 0.09(0.61)
26. The Results of
Surface area and
mean pore size
Test.
Table
Sample
Code
SBET
(m2/g)
V total
(cm3/g)
PD Mean
(nm)
Langmuir
(m2/g)
V micro
(cm3/g)
V meso
(cm3/g)
D Pore
(nm)
GP3 30.976 0.2214 28.593 37.832 0 0.2240 7.99
HGP3 24.735 0.2317 37.464 25.511 0 0.2339 1.21
GPF 53.133 0.2609 19.642 69.963 0 0.2622 7.99
HGPF1 43.214 0.1893 17.526 55.046 0 0.1970 4.61
HGPF3 43.677 0.3654 33.459 54.959 0 0.3688 7.99
CNT 46.766 0.1844 15.773 57.568 0 0.1892 4.61
Graphite 45.167 0.2321 20.557 59.289 0 0.2356 9.23
GO 31.352 0.1769 22.570 43.863 0 0.1815 10.65
PVA 41.006 0.1287 12.551 59.516 0 0.1359 4.61
27. The Results
of Physical
tests of GP3.
Table Sample
code
Density
(g/cm3)
Porosity (%) Water Absorption (%) I.S.T.
(min.)
F.S.T.
(min.)
GP3 1.6 11.2 7.16 105 205
HGP3 2.0 ~9.5 6.5 75 120
28. R2, R2
adj., and R2
pred.
test for responses full
quadratic regression
model of HGPF1
Table Response characteristic R2 (%) R2
adj.(%) R2
pred.(%)
Compressive strength 94.26 90.19 77.24
Apparent porosity 97.50 95.73 88.33
Water absorption 97.04 94.94 87.98
Total porosity 95.80 92.82 81.77
Bulk density 94.37 90.37 72.42
True density 96.85 94.62 86.31
R2, R2
adj., and
R2
pred. test for
responses full
quadratic
regression
model of HGPF2
Response characteristic R2 (%) R2
adj.(%) R2
pred.(%)
Compressive strength 95.88 92.95 82.49
Apparent porosity 98.69 97.75 93.74
Water absorption 98.22 96.95 93.39
Total porosity 96.85 94.61 85.83
Bulk density 98.35 97.18 92.94
True density 95.69 92.64 82.37
R2, R2
adj., and
R2
pred. test for
responses full
quadratic
regression
model of HGPF3
Response characteristic R2 (%) R2
adj.(%) R2
pred.(%)
Compressive strength 92.61 87.36 74.22
Apparent porosity 99.48 99.11 97.46
Water absorption 93.44 88.79 77.04
Total porosity 94.76 91.04 76.38
Bulk density 97.08 95.00 85.82
True density 95.10 91.62 77.05
29. The optimum
output results
of the (HGPFs).
Table Optimum output
HGPF-batches
HGPF1 HGPF2 HGPF3
Compressive strength (MPa) 23.49 32.00 33.86
Apparent porosity (%) 81.75 87.75 83.78
Water absorption (%) 89.67 96.67 93.33
Total porosity (%) 71.74 76.11 73.33
Bulk density (g/cm3) 0.27 0.24 0.23
True density (g/cm3) 2.66 2.39 2.04
30. Multi-Response
optimal points
and experimental
validation.
Table
HGPF1-Batch
Optimum input setting N W C F S
3.2 10.46 0.1 4 0.1
Responses C.S. A.P. W.A. T.P. B.D. T.D.
Predicted 23.49 81.75 89.67 71.74 0.27 2.66
Experiment 23.31 81.62 89.71 71.86 0.26 2.64
Relative error (%) - 0.77
-0.16 0.04 0.17 -3.84 -0.75
HGPF2-Batch
Optimum input setting
N W C F S
3.2 12 8.51 3.84 4
Responses C.S. A.P. W.A. T.P. B.D. T.D.
Predicted 32.00 87.75 96.67 76.11 0.24 2.39
Experiment 31.87 87.88 95.89 76.92 0.23 2.38
Relative error (%) -0.4 0.14 -0.81 1.05 -4.34 -0.42
HGPF3-Batch
Optimum input setting
N W C F S
3.2 11.15 0.2 0.53 2.20
Responses C.S. A.P. W.A. T.P. B.D. T.D.
Predicted 33.86 83.78 93.33 73.33 0.23 2.04
Experiment 33.84 83.81 93.25 73.66 0.22 2.01
31. Conclusions
Response Surface Methodology is a useful technique to
experiments design and optimize the process of hybrid geopolymer
foam synthesis.
In general, the K-ions substitution of Na-ions improves the
compressive strength and increases the porosity of the produced
foam.
Regulating the content of silica, water, OPC, H2O2, and olive oil
is necessary to produce hybrid geopolymer foam with highest
compressive strength and highest porosity.
The capillary suspension/ direct foaming combined method is
suitable strategy to produce hybrid geopolymer foams having
pores within micro and macro sizes.
The modification of the optimized samples with SWCNT,
graphite, GO, and PVA is a suitable choice to strengthen the
mechanical properties.
32. Recommendations
Investigating the synthesizing of hybrid geopolymer foam by
capillary suspension utilizing the pendular state.
Using solid part inert with respect to the two immiscible
solutions through the capillary state in the solution.
Studying the effect of higher mole fraction of K-ions
substitution on the final characteristics of the hybrid
geopolymer foam.
Evaluation of the possibility of HGPF and MHGPF to serve as a
catalyst support via examine the catalytic activity.
Characterize the thermal and acoustic properties of the
prepared HGPF and MHGPF.
