Fabrication Of Dense Alumina Through Slip Casting Process.
FABRICATION OF DENSE ALUMINA THROUGH SLIP
CASTING PROCESS
SITI NORFAZNIE BT AHMAD NAJIB
UNIVERSITI TEKNIKAL MALAYSIA MELAKA
UNIVERSITI TEKNIKAL MALAYSIA MELAKA
FABRICATION OF DENSE ALUMINA THROUGH SLIP
CASTING PROCESS
This report submitted in accordance with the requirement of the Universiti Teknikal
Malaysia Melaka (UTeM) for the Bachelor Degree of Manufacturing Engineering
(Engineering Materials) with Honours.
by
SITI NORFAZNIE BT AHMAD NAJIB
FACULTY OF MANUFACTURING ENGINEERING
2008
ABSTRACT
Dense alumina products were prepared through slip casting method. Slips are prepared
at different alumina and ball clay content. The slips were prepared by mixing the
powders with water as solvent and dispersant at different composition of alumina and
ball clay content in each batch. Three different body formulated were prepared named as
batch A, B and C. The process sequence for ceramic forming by using slip casting are
started by setting the composition, followed by mixing the starting raw material as well
as slip preparation through roller milling to obtain the homogenous slip and casting by
using the plaster of Paris mold, drying of slip cast, into bisque formation and lastly the
specimen was sintered. Mechanical properties and microstructures of dense alumina
product were evaluated, analysis methods used in this project research are measure
degree of shrinkage, Scanning Electron Microscopy (SEM) for microstructural
observation, X-Ray Diffraction (XRD) for phase observation, three point bending test
for flexural strength measurement of the specimen. All the specimen from batch A with
the 0.1% ball clay addition have fracture during the drying stages. Batch C have higher
shrinkage and higher flexural strength compared other two batches. From the
microstructural image less pores for batch C specimen are reveal.
i
ABSTRAK
Spesimen alumina terpadat dihasilkan menggunakan teknik pengacuanan tuangan..
Bancuhan disediakan dengan menngunakan tiga campuran alumina dan tanah liat yang
berbeza. Bancuhan juga telah dicampur dengan air dan bahan serak. Terdapat tiga
bancuhan iaitu bancuhan A, B, dan C. Urutan proses menggunakan teknik pengacuan
tuangan adalah seperti berikut; komposisi bahan dicampur, bancuhan disediakn
menggunakan „roller milling‟untuk mendapatkan bancuhan yang sebati, bancuhan
dituangan ke dalam acuan, spesimen yang terbentuk dikeringkan dan akhir sekali
specimen dibakar pada suhu tinggi ditetapkan. Sifat-sifat mekanikal dan mikrostruktur
alumina terpadat dinilai. Sifat mekanikal dan mikrostruktur dinilai, kaedah yang
digunakan untuk menganalisis adalah dengan mengukur darjah pengecutan, Mikroskop
Imbasan Elektron iaitu untuk pemerhatian pada mikrostruktur, Pembelauan X-Ray iaitu
untuk pemerhatian pada fasa, ujian pelenturan tiga titik untuk mengukur kekuatan
pelenturan. Didapati semua spesimen daripada bancuhan A telah patah pada bahagian
tengah pada peringkat pengeringan dimana bancuhan ini mengandungi 99.9% alumina
dan 0.1% tanah liat. Bancuhan C mempunyai pegecutan dan kekuatan pelenturan yang
paling tinggi berbanding dengan dua bancuhan yang lain. Daripada gambaran
mikrostruktur spesimen C, ia menunjukkan kurang lubang.
ii
DEDICATION
For my beloved family and friends.
iii
ACKNOWLEDGEMENT
Bismillahirrahmanirrahim,
First of all, I am very grateful to Allah the Almighty for giving me the opportunity to
finish my Projek Sarjana Muda (PSM) technical report from the first word until end of
point. I would like to thank to my supervisor, Dr Azizah binti Shaaban for her support,
willingness to help and give lot of guidance and full commitment for my research
project. I would also thank to Mr Sivarao a/l Subramonian, the PSM Coordinator of
Faculty of Manufacturing Engineering of University Technical Malaysia Melaka that
had manage and guide me during my final year project . Finally, my sincere appreciation
is dedicated to my family and my fellow friends in UTeM who are willing to help me
even though they are also busy with their own PSM project.
iv
TABLE OF CONTENTS
ABSTRACT
i
ABSTRAK
ii
DEDICATION
iii
ACKNOWLEDGEMENT
iv
TABLE OF CONTENTS
v
LIST OF TABLES
viii
LIST OF FIGURES
x
LIST OF ABBREVATIONS, SYMBOLS & NOMENCLATURE
xiii
1. INTRODUCTION
1
1.1
Introduction to Ceramic
1
1.2
Type of Ceramic
2
1.2.1
Traditional Ceramic
3
1.2.2
Advanced Ceramic
3
1.2.3
Ceramic Based Composite
3
1.3
Application of Ceramic
1.4
Objectives
5
1.5
Scope
6
1.6
Problem Statement
6
2. LITERATURE REVIEW
8
2.1.
Advanced Ceramic Material
8
2.2
Alumina Ceramic
8
2.3
Properties of Alumina
9
2.4
Ceramic Forming
12
2.5
Slip Casting
13
2.5.1
Slip Preparations
14
v
2.6
Ceramic Sintering
20
3. METHODOLOGY
23
3.1.
Process Sequence
23
3.2.
Material
24
3.3.
Slip Preparation
25
3.3.1
Mixing
25
3.3.2 Slip Preparation through Ball Mill
25
3.3.3 Casting using Plaster of Paris Mold
26
3.3.4 Drying and Released Slip Casting Part
28
3.4
Bisque Process
28
3.5
Sintering
28
3.6
Finishing Operation
29
3.7
Analysis of Specimens
29
3.7.1
Shrinkages Test
29
3.7.2
Flexural Test
30
3.7.3
Scanning Electron Microscopy (SEM)
31
3.7.4
X-ray Distribution (XRD)
32
4. RESULT AND DISCUSSION
33
4.1.
Introduction
33
4.2.
Raw Material Analysis
33
4.2.1
Powder Morphology
33
4.2.2
Particle Size Analysis
34
4.2.3
Phase Analysis of Raw Materials
35
4.3
Analysis of Dense Alumina
37
4.3.1
Shrinkages Analysis
37
4.3.1.1 Shrinkage during Drying Process
37
4.3.1.2 Shrinkage during Bisque Process
42
4.3.1.3 Shrinkage during Sintering Process
44
4.3.2
47
Density of the Sintered Sample
vi
4.3.3
Flexural analysis
48
4.3.4
Microstructure Analysis
49
4.3.5
Phase Analysis of Sintered Alumina
52
5. CONCLUSION AND RECOMMENDATIONS
54
5.1.
Conclusion
54
5.2
Recommendations
54
6.
REFERENCES
7.
APPENDICES
A
Gantt Chart for PSM 1
B
Gantt Chart for PSM 2
56
vii
LIST OF TABLES
1.1
The example application of the traditional ceramic
5
1.2
The example application of the advanced ceramic
5
2.1
High alumina engineering eeramics (grades Al-A4, at least 99%
10
Al2O3) and their characteristic (Morell 1987).
2.2
Engineering alumina grades A6-A9 (80% ≤ Al2O3 ≤ 99% as
10
requirement) and their characteristic (Morrell 1987)
2.3
Mechanical properties of engineering alumina ceramics at ambient 11
temperature. Data originated from specimens with a cross-sectional
effective diameter of 3-15mm (Auerkari 1996)
2.4
Apparent viscosity of the Al2O3 slurries with various amounts of
16
polycarboxylate ammonium dispersant inclusions
2.5
Mechanical Properties of the Alumina Samples Sintered at Different 22
Temperatures (Kim 2008)
3.1
Example of Slip casting composition.
24
4.1
Data shrinkage of reference line for drying
38
4.2
Data shrinkage of reference line for biscuits process
42
4.3
Data shrinkage of reference line for sintering
44
4.4
Density of the sample
47
viii
LIST OF FIGURES
2.1
Step in slip casting. In (1) a porous mold is filled with slurry, (2) 14
casting, (3) after a period of casting, excess is drained from the mold
leaving a hollow cast and (4) separation from mold.
2.2
Particle size distributions for the Al2O3 slurries with 0, 0.2 and 2 mass% 16
of dispersants
2.3
Scanning electron micrographs of polished and thermally etched 17
surfaces of Al2O3 sintered bodies prepared from the dispersed
(dispersant 0.2 mass %) and the flocculated (dispersant 2 mass %)
slurries
2.4
Weibull's plots of the Al2O3 sintered bodies prepared from the
18
dispersed (dispersant 0.2 mass%) and the flocculated (dispersant 2
mass%) slurries; “P ” indicates the sample including the fracture
surface which a spherical ball-like pore is present at the fracture
origin in specimens.
2.5
Optical photomicrographs taken in the transmission mode of the
19
Al2O3 sintered bodies prepared from the dispersed (dispersant 0.2
mass %) and the flocculated (dispersant 2 mass %) slurries
2.6
Scanning electron micrographs of a fractured surface of the Al2O3
19
sintered body prepared from the flocculated (dispersant 2 mass %)
slurry
2.7
Microstructure of the alumina sintered at (a) 1550°C (b) 1600°C (c)
21
1650°C.
3.1
Flow chart of the fabrication of dense alumina through slip casting 23
ix
Process
3.2
Roller milling machine with alumina pot
26
3.3
Plaster mold of Paris for Solid Casting
26
3.4
Plaster of Paris for Drain Casting
27
3.5
Sintering profile
29
3.6
Sample position for 3 point bending test
30
3.7
Scanning Electron Microscope (SEM)
32
3.8
XRD machine
32
4.1
The Morphology of Alumina Powder using SEM
34
4.2
Distribution Particle Size of Alumina
35
4.3
Alumina powder.
36
4.4
Ball clay powder
36
4.5
Graph average length of reference line during drying process
39
4.6
Percentage of linear drying shrinkage for four day
39
4.7
Specimen bar fracture at the middle
40
4.8
Voids produced inside the specimen bar
41
4.9
Percentage of linear biscuit shrinkage.
43
4.10 Average percentage of linear shrinkage after biscuit
43
4.11 Crucibles after bisque process using drain casting technique with casting 44
time; 5 minutes, 10 minutes and 15 minutes (a) batch A (b) batch B (c)
batch C
4.12 Percentage of Linear Shrinkage after Sintering.
45
4.13 Average Percentage of Linear Shrinkage after Sintering
45
4.14 Comparison Average Linear Shrinkage
46
4.15 Cracking crucible after sintering process
46
4.16 Sample density vs. batch
47
4.17 Flexural strength vs. number of specimen
48
4.18 Comparison of flexural strength
48
x
4.19 Image microstructure of the sintered sample (a) batch A, (b) batch B and 51
(c) batch C. At the left and right the image microstructure obtain from
BSE and SEM test respectively.
4.20 XRD pattern for each composition (a) Composition 99.9% alumina and 53
0.1% ball clay. (b) Composition 99.5% alumina and 0.5% ball clay. (c)
Composition 99% alumina and 1% ball clay.
xi
LIST OF ABBREVATIONS, SYMBOLS & NOMENCLATURE
Al2O3
-
Alumina
MgO
-
Magnesium Oxide
+
-
Ammonia
NH4+-PMA
-
Salt of poly (methacrylic acid)
SiC
-
Silicon carbides
Si3N4
-
Silicon nitride
NH4
CaSO4.2H2O
-
Gypsum
˚C
-
Degree Celsius
%
-
Percent
Wt%
-
Weight percent
h
-
Hour
m
-
Meter
MPa
-
Mega Pascal
µm
-
Micrometer
SEM
-
Scanning electron microscopy
XRD
-
X-ray diffraction
ASTM
-
American Standard Testing Material
xii
CHAPTER 1
INTRODUCTION
1.1
Introduction to Ceramic
William (2003) state that the term „ceramic‟ comes from the Greek word keramikos
which means „burnt stuff‟ indicating that desirable properties of these materials are
normally achieve through a high temperature heat treatment process called firing.
Chemically ceramics are nonmetallic, inorganic compounds which are formed by the
action of heat.
Ceramic generally are characterized by high hardness, high compressive strength,
corrosion-resistant, low thermal expansion, high temperature resistant, good chemical
inertness, low density, and low thermal and electrical conductivity. On the other hand,
they are brittle and have low toughness and ductility. The properties possessed by most
ceramics due to differences of bonding. Most of ceramic materials have a mixed
bonding structure with various ratios between ionic and covalent character. The
percentage of ionic bonds can be estimated by using electronegativity determinations.
1.2
Type of Ceramic
Ceramics are classified in many ways. It is due to different in composition, properties
and its applications. Based on their composition, ceramics can be classified into Oxides,
Carbides, Nitrides, Sulfides, Fluorides and etc. Based on their specific applications,
ceramics are classified as glasses, clay products, refractories, abrasives, cements, and
1
advanced ceramics for special applications. According to Kalpakjian (2006) ceramic
classification is based on their engineering applications, ceramics are classified into two
groups as: traditional and advanced ceramics.
1.2.1
Traditional Ceramic
Traditional ceramics are most made-up of clay, silica and feldspar. Traditional ceramics
include objects made of clay and cements that have been hardened by heating at high
temperatures. Traditional ceramic products usually made in large quantities by efficient
and inexpensive manufacturing methods. The examples of traditional ceramic are such
as dinnerware, sanitary ware, pottery, tiles and refractory. Traditional ceramics are most
made up of clay, feldspar and silica.
Clay has been used in a wide range of ceramics product for thousands of years and
continues to be a major component in most ceramic bodies today. Clay is essential and
predominant component in most ceramic product.
Feldspar is the most common igneous rock mineral and the most plentiful mineral in the
earth's crust. Feldspar is a common raw material in the production of ceramics product.
In the fabrication of ceramic material, feldspar also serves as a flux to form a glassy
phase at low temperatures. It improves the strength, toughness, and durability of the
ceramic body and cements the crystalline phase of other ingredients.
Silica is a major ingredient in refractories and whitewares. Silica occurs commonly in
nature as sandstone, silica sand or quartzite. Silica is one of the most abundant oxide
materials in the earth's crust. Silica is a precursor to the fabrication of other ceramic
products and as a material on its own.
2
1.2.2
Advanced Ceramic
Advanced ceramic include ceramics for electrical, magnetic, electronic, and optical
application (sometimes referred to as functional ceramics) and ceramics for structural
applications at ambient as well as at elevated temperatures (structural ceramics).
Advance ceramics include carbides, such as silicon carbide (SiC); oxides, such as
aluminum oxide, (Al2O3) and zirconia (ZrO2); nitrides, such as silicon nitride (Si3N4);
silicates such as kaolinite (Al2Si2O5 (OH) 4) and mullite (Al6Si2O13) and many other
materials, including the mixed oxide ceramics that can act as superconductors.
Advanced ceramic requires modern processing techniques, and the development of these
techniques has led to advances in industry.
Advanced ceramics materials possess unique properties in chemical resistance, corrosion
resistance; wear resistance and dimensional stability at room temperature as well as at
elevated temperatures. Ceramic matrix composites are at the forefront of advanced
materials technology because of their light weight, high strength and toughness, high
temperature capabilities, and graceful failure under loading. Ceramic composites are
considered as enabling technology for advanced aero propulsion, space propulsion,
space power, aerospace vehicles, and space structures.
1.2.3
Ceramic Based Composites
Ceramic composites are being actively developed in many research establishments
primarily to improve either the toughness or hardness to be more suited to a particular
application. This group can be composed of a combination of oxide ceramics and nonoxide ceramics (granular, platy, whiskers, etc.), oxide and oxide ceramics, non-oxide
and non-oxide ceramics, ceramics and polymers, etc. an almost infinite number of
combinations are possible. Fiber, whisker or particulate reinforced composites can be
made tougher and stronger than traditional un-reinforced ceramics. Ceramic composites
3
offer the mechanical and physical properties unavailable in the past and provide the
opportunities to solve past material problems.
1.3
Application of Ceramic
The applications for ceramics have found for a long time ago. Every day new and
different applications are being discovered. This truly makes ceramics have broad ranges
of functions and applications. Ceramic materials display a wide range of properties
which purpose in many different product areas to facilitate user.
Most people, when they hear the word of ceramics, they will think of art, dinnerware,
pottery, tiles, and brick. The above mentioned products are commonly referred to as
traditional ceramic that have been developed since the time of the earliest civilizations.
These traditional products have been and continue to be important and still represent a
major part of the ceramics industry although in recent year advanced material have been
successfully developed . These advanced ceramics are being used for applications such
as space shuttle tile, engine components, artificial bones and teeth, computers and other
electronic components, and cutting tools (Callister, 2003).
Examples of the wide range application of ceramics can be seeing as mention in the
following tables. The applications of ceramics can be simplifies into two major
categories which are traditional and advanced material as in the Table 1.1 and 1.2
respectively. For the traditional ceramic application it can be divided into five major
industries segment together with several examples. For the advanced ceramic it can be
classified into four categories which consists structural, electrical, coatings and lastly
chemical and environmental together with a few examples.
4
Table 1.1: The example application of the traditional ceramic
Industry Segment
Structural clay
products
Whitewares
Refractories
Glasses
Abrasives
Cements
Common Examples
Brick, sewer pipe, roofing tile, clay floor and wall tile (i.e.,
quarry tile), flue linings
Dinnerware, floor and wall tile, sanitary ware, electrical
porcelain, decorative ceramics
Brick and monolithic products are used in iron and steel, nonferrous metals, glass, cements, ceramics, energy conversion,
petroleum, and chemicals industries
Flat glass (windows), container glass (bottles), pressed and
blown glass (dinnerware), glass fibers (home insulation), and
advanced/specialty glass (optical fibers)
Natural (garnet, diamond, etc.) and synthetic (silicon carbide,
diamond, fused alumina, etc.) abrasives are used for grinding,
cutting, polishing, lapping, or pressure blasting of materials
Used to produce concrete roads, bridges, buildings, dams, and the
like
Table 1.2: The example application of the advanced ceramic
Industry Segment
Structural
Electrical
Coatings
Chemical and
environmental
1.4
Common Examples
Wear parts, bioceramics, cutting tools, and engine
components
Capacitors, insulators, substrates, integrated circuit
packages, piezoelectrics, magnets and superconductors
Engine components, cutting tools, and industrial wear parts
Filters, membranes, catalysts, and catalyst supports
Objective
The objectives of this project are listed as below:
i. To fabricate the bar specimens and crucibles of dense alumina by using slip casting
technique.
ii. To analyze the effect of different raw materials composition on the final properties
of dense alumina.
5
1.5
Scope
The project involved the theoretical study on the ceramic slip casting process and
fabricates the dense alumina through the slip casting process. The emphases are on the
preparation of slip with correct percentage of composition between alumina and ball
clay. Water are used until slip casting obtain the desired specific gravity ranges between
1.4-1.6. For this experiment, the raw materials used were alumina and ball clay with
different ratios of raw materials constituent. There are three different weight ratios of
powder mixture, which are 1:1000; 5:1000 and 10:1000. The ratio refers to ball clay:
alumina. The slip casting was prepared and was mixed using roll mill for three hour to
make sure all the chemical composition agglomerate homogenously. The ratio of
grinding media is ¼ raw materials. The slip is then casted into the plaster mold of Paris
by using solid and drain casting technique for bar specimens and crucibles respectively.
In this study the bar specimens will be done through the process drying at room
temperature and bisque at 900°C by using the heating rate 10°C/min. Then the green
body will be sintered at 1400°C. The samples dimensions were measured before and
after sinter to get the percent of shrinkage of sintered specimen. The finished specimens
were needed to prepare for testing and evaluations. The sintered specimens were tested
by using X-ray diffraction (XRD) to identify phase composition in every sample.
Scanning Electron Microstructure (SEM) is used to analyze the microstructures in each
sample. Other testing for specimens includes flexural test and shrinkage.
1.6
Problem Statement
Alumina is widely known as advanced ceramic materials which are used in a variety of
applications. High purity alumina (Al2O3 content > 99%) have high thermal
conductivity, low thermal expansion, corrosion resistance and high compressive strength
leads to good thermal shock resistance is ideal for high temperature applications such as
crucibles. Advanced ceramic typically used non-traditional techniques such as hot
6
pressing, vapor deposition, gel casting and injection molding to form ceramic materials
into a recognizable shape or product.
However considering the importance homogeneous distribution of the particles in the
production of ceramic crucibles is essential to obtain a high-density impervious product;
therefore the slip casting technique was chosen to produce the crucibles. Homogeneous
distribution of the particles can be obtained by using the slip casting technique although
it quit conventional to the industries.
Rak (2000) stated the problem in the slip casting contains about 30 wt% water and about
half of it must be absorbed by the plaster of Paris mould in order to reduce the liquid slip
to an acceptably firm body at the mold surface. This forms a dense cast with long
production time and the molds are easily damaged.
High purity alumina forming with slip casting technique produce parts that are fragile
and cannot easily be machined in the green body state. The composition of the purity
alumina ceramic body can be changed to enhance particular desirable material
characteristics by adding little additive. In this project, properties of the final body
ceramic alumina with the different composition of additive is then analyzed.
7
CASTING PROCESS
SITI NORFAZNIE BT AHMAD NAJIB
UNIVERSITI TEKNIKAL MALAYSIA MELAKA
UNIVERSITI TEKNIKAL MALAYSIA MELAKA
FABRICATION OF DENSE ALUMINA THROUGH SLIP
CASTING PROCESS
This report submitted in accordance with the requirement of the Universiti Teknikal
Malaysia Melaka (UTeM) for the Bachelor Degree of Manufacturing Engineering
(Engineering Materials) with Honours.
by
SITI NORFAZNIE BT AHMAD NAJIB
FACULTY OF MANUFACTURING ENGINEERING
2008
ABSTRACT
Dense alumina products were prepared through slip casting method. Slips are prepared
at different alumina and ball clay content. The slips were prepared by mixing the
powders with water as solvent and dispersant at different composition of alumina and
ball clay content in each batch. Three different body formulated were prepared named as
batch A, B and C. The process sequence for ceramic forming by using slip casting are
started by setting the composition, followed by mixing the starting raw material as well
as slip preparation through roller milling to obtain the homogenous slip and casting by
using the plaster of Paris mold, drying of slip cast, into bisque formation and lastly the
specimen was sintered. Mechanical properties and microstructures of dense alumina
product were evaluated, analysis methods used in this project research are measure
degree of shrinkage, Scanning Electron Microscopy (SEM) for microstructural
observation, X-Ray Diffraction (XRD) for phase observation, three point bending test
for flexural strength measurement of the specimen. All the specimen from batch A with
the 0.1% ball clay addition have fracture during the drying stages. Batch C have higher
shrinkage and higher flexural strength compared other two batches. From the
microstructural image less pores for batch C specimen are reveal.
i
ABSTRAK
Spesimen alumina terpadat dihasilkan menggunakan teknik pengacuanan tuangan..
Bancuhan disediakan dengan menngunakan tiga campuran alumina dan tanah liat yang
berbeza. Bancuhan juga telah dicampur dengan air dan bahan serak. Terdapat tiga
bancuhan iaitu bancuhan A, B, dan C. Urutan proses menggunakan teknik pengacuan
tuangan adalah seperti berikut; komposisi bahan dicampur, bancuhan disediakn
menggunakan „roller milling‟untuk mendapatkan bancuhan yang sebati, bancuhan
dituangan ke dalam acuan, spesimen yang terbentuk dikeringkan dan akhir sekali
specimen dibakar pada suhu tinggi ditetapkan. Sifat-sifat mekanikal dan mikrostruktur
alumina terpadat dinilai. Sifat mekanikal dan mikrostruktur dinilai, kaedah yang
digunakan untuk menganalisis adalah dengan mengukur darjah pengecutan, Mikroskop
Imbasan Elektron iaitu untuk pemerhatian pada mikrostruktur, Pembelauan X-Ray iaitu
untuk pemerhatian pada fasa, ujian pelenturan tiga titik untuk mengukur kekuatan
pelenturan. Didapati semua spesimen daripada bancuhan A telah patah pada bahagian
tengah pada peringkat pengeringan dimana bancuhan ini mengandungi 99.9% alumina
dan 0.1% tanah liat. Bancuhan C mempunyai pegecutan dan kekuatan pelenturan yang
paling tinggi berbanding dengan dua bancuhan yang lain. Daripada gambaran
mikrostruktur spesimen C, ia menunjukkan kurang lubang.
ii
DEDICATION
For my beloved family and friends.
iii
ACKNOWLEDGEMENT
Bismillahirrahmanirrahim,
First of all, I am very grateful to Allah the Almighty for giving me the opportunity to
finish my Projek Sarjana Muda (PSM) technical report from the first word until end of
point. I would like to thank to my supervisor, Dr Azizah binti Shaaban for her support,
willingness to help and give lot of guidance and full commitment for my research
project. I would also thank to Mr Sivarao a/l Subramonian, the PSM Coordinator of
Faculty of Manufacturing Engineering of University Technical Malaysia Melaka that
had manage and guide me during my final year project . Finally, my sincere appreciation
is dedicated to my family and my fellow friends in UTeM who are willing to help me
even though they are also busy with their own PSM project.
iv
TABLE OF CONTENTS
ABSTRACT
i
ABSTRAK
ii
DEDICATION
iii
ACKNOWLEDGEMENT
iv
TABLE OF CONTENTS
v
LIST OF TABLES
viii
LIST OF FIGURES
x
LIST OF ABBREVATIONS, SYMBOLS & NOMENCLATURE
xiii
1. INTRODUCTION
1
1.1
Introduction to Ceramic
1
1.2
Type of Ceramic
2
1.2.1
Traditional Ceramic
3
1.2.2
Advanced Ceramic
3
1.2.3
Ceramic Based Composite
3
1.3
Application of Ceramic
1.4
Objectives
5
1.5
Scope
6
1.6
Problem Statement
6
2. LITERATURE REVIEW
8
2.1.
Advanced Ceramic Material
8
2.2
Alumina Ceramic
8
2.3
Properties of Alumina
9
2.4
Ceramic Forming
12
2.5
Slip Casting
13
2.5.1
Slip Preparations
14
v
2.6
Ceramic Sintering
20
3. METHODOLOGY
23
3.1.
Process Sequence
23
3.2.
Material
24
3.3.
Slip Preparation
25
3.3.1
Mixing
25
3.3.2 Slip Preparation through Ball Mill
25
3.3.3 Casting using Plaster of Paris Mold
26
3.3.4 Drying and Released Slip Casting Part
28
3.4
Bisque Process
28
3.5
Sintering
28
3.6
Finishing Operation
29
3.7
Analysis of Specimens
29
3.7.1
Shrinkages Test
29
3.7.2
Flexural Test
30
3.7.3
Scanning Electron Microscopy (SEM)
31
3.7.4
X-ray Distribution (XRD)
32
4. RESULT AND DISCUSSION
33
4.1.
Introduction
33
4.2.
Raw Material Analysis
33
4.2.1
Powder Morphology
33
4.2.2
Particle Size Analysis
34
4.2.3
Phase Analysis of Raw Materials
35
4.3
Analysis of Dense Alumina
37
4.3.1
Shrinkages Analysis
37
4.3.1.1 Shrinkage during Drying Process
37
4.3.1.2 Shrinkage during Bisque Process
42
4.3.1.3 Shrinkage during Sintering Process
44
4.3.2
47
Density of the Sintered Sample
vi
4.3.3
Flexural analysis
48
4.3.4
Microstructure Analysis
49
4.3.5
Phase Analysis of Sintered Alumina
52
5. CONCLUSION AND RECOMMENDATIONS
54
5.1.
Conclusion
54
5.2
Recommendations
54
6.
REFERENCES
7.
APPENDICES
A
Gantt Chart for PSM 1
B
Gantt Chart for PSM 2
56
vii
LIST OF TABLES
1.1
The example application of the traditional ceramic
5
1.2
The example application of the advanced ceramic
5
2.1
High alumina engineering eeramics (grades Al-A4, at least 99%
10
Al2O3) and their characteristic (Morell 1987).
2.2
Engineering alumina grades A6-A9 (80% ≤ Al2O3 ≤ 99% as
10
requirement) and their characteristic (Morrell 1987)
2.3
Mechanical properties of engineering alumina ceramics at ambient 11
temperature. Data originated from specimens with a cross-sectional
effective diameter of 3-15mm (Auerkari 1996)
2.4
Apparent viscosity of the Al2O3 slurries with various amounts of
16
polycarboxylate ammonium dispersant inclusions
2.5
Mechanical Properties of the Alumina Samples Sintered at Different 22
Temperatures (Kim 2008)
3.1
Example of Slip casting composition.
24
4.1
Data shrinkage of reference line for drying
38
4.2
Data shrinkage of reference line for biscuits process
42
4.3
Data shrinkage of reference line for sintering
44
4.4
Density of the sample
47
viii
LIST OF FIGURES
2.1
Step in slip casting. In (1) a porous mold is filled with slurry, (2) 14
casting, (3) after a period of casting, excess is drained from the mold
leaving a hollow cast and (4) separation from mold.
2.2
Particle size distributions for the Al2O3 slurries with 0, 0.2 and 2 mass% 16
of dispersants
2.3
Scanning electron micrographs of polished and thermally etched 17
surfaces of Al2O3 sintered bodies prepared from the dispersed
(dispersant 0.2 mass %) and the flocculated (dispersant 2 mass %)
slurries
2.4
Weibull's plots of the Al2O3 sintered bodies prepared from the
18
dispersed (dispersant 0.2 mass%) and the flocculated (dispersant 2
mass%) slurries; “P ” indicates the sample including the fracture
surface which a spherical ball-like pore is present at the fracture
origin in specimens.
2.5
Optical photomicrographs taken in the transmission mode of the
19
Al2O3 sintered bodies prepared from the dispersed (dispersant 0.2
mass %) and the flocculated (dispersant 2 mass %) slurries
2.6
Scanning electron micrographs of a fractured surface of the Al2O3
19
sintered body prepared from the flocculated (dispersant 2 mass %)
slurry
2.7
Microstructure of the alumina sintered at (a) 1550°C (b) 1600°C (c)
21
1650°C.
3.1
Flow chart of the fabrication of dense alumina through slip casting 23
ix
Process
3.2
Roller milling machine with alumina pot
26
3.3
Plaster mold of Paris for Solid Casting
26
3.4
Plaster of Paris for Drain Casting
27
3.5
Sintering profile
29
3.6
Sample position for 3 point bending test
30
3.7
Scanning Electron Microscope (SEM)
32
3.8
XRD machine
32
4.1
The Morphology of Alumina Powder using SEM
34
4.2
Distribution Particle Size of Alumina
35
4.3
Alumina powder.
36
4.4
Ball clay powder
36
4.5
Graph average length of reference line during drying process
39
4.6
Percentage of linear drying shrinkage for four day
39
4.7
Specimen bar fracture at the middle
40
4.8
Voids produced inside the specimen bar
41
4.9
Percentage of linear biscuit shrinkage.
43
4.10 Average percentage of linear shrinkage after biscuit
43
4.11 Crucibles after bisque process using drain casting technique with casting 44
time; 5 minutes, 10 minutes and 15 minutes (a) batch A (b) batch B (c)
batch C
4.12 Percentage of Linear Shrinkage after Sintering.
45
4.13 Average Percentage of Linear Shrinkage after Sintering
45
4.14 Comparison Average Linear Shrinkage
46
4.15 Cracking crucible after sintering process
46
4.16 Sample density vs. batch
47
4.17 Flexural strength vs. number of specimen
48
4.18 Comparison of flexural strength
48
x
4.19 Image microstructure of the sintered sample (a) batch A, (b) batch B and 51
(c) batch C. At the left and right the image microstructure obtain from
BSE and SEM test respectively.
4.20 XRD pattern for each composition (a) Composition 99.9% alumina and 53
0.1% ball clay. (b) Composition 99.5% alumina and 0.5% ball clay. (c)
Composition 99% alumina and 1% ball clay.
xi
LIST OF ABBREVATIONS, SYMBOLS & NOMENCLATURE
Al2O3
-
Alumina
MgO
-
Magnesium Oxide
+
-
Ammonia
NH4+-PMA
-
Salt of poly (methacrylic acid)
SiC
-
Silicon carbides
Si3N4
-
Silicon nitride
NH4
CaSO4.2H2O
-
Gypsum
˚C
-
Degree Celsius
%
-
Percent
Wt%
-
Weight percent
h
-
Hour
m
-
Meter
MPa
-
Mega Pascal
µm
-
Micrometer
SEM
-
Scanning electron microscopy
XRD
-
X-ray diffraction
ASTM
-
American Standard Testing Material
xii
CHAPTER 1
INTRODUCTION
1.1
Introduction to Ceramic
William (2003) state that the term „ceramic‟ comes from the Greek word keramikos
which means „burnt stuff‟ indicating that desirable properties of these materials are
normally achieve through a high temperature heat treatment process called firing.
Chemically ceramics are nonmetallic, inorganic compounds which are formed by the
action of heat.
Ceramic generally are characterized by high hardness, high compressive strength,
corrosion-resistant, low thermal expansion, high temperature resistant, good chemical
inertness, low density, and low thermal and electrical conductivity. On the other hand,
they are brittle and have low toughness and ductility. The properties possessed by most
ceramics due to differences of bonding. Most of ceramic materials have a mixed
bonding structure with various ratios between ionic and covalent character. The
percentage of ionic bonds can be estimated by using electronegativity determinations.
1.2
Type of Ceramic
Ceramics are classified in many ways. It is due to different in composition, properties
and its applications. Based on their composition, ceramics can be classified into Oxides,
Carbides, Nitrides, Sulfides, Fluorides and etc. Based on their specific applications,
ceramics are classified as glasses, clay products, refractories, abrasives, cements, and
1
advanced ceramics for special applications. According to Kalpakjian (2006) ceramic
classification is based on their engineering applications, ceramics are classified into two
groups as: traditional and advanced ceramics.
1.2.1
Traditional Ceramic
Traditional ceramics are most made-up of clay, silica and feldspar. Traditional ceramics
include objects made of clay and cements that have been hardened by heating at high
temperatures. Traditional ceramic products usually made in large quantities by efficient
and inexpensive manufacturing methods. The examples of traditional ceramic are such
as dinnerware, sanitary ware, pottery, tiles and refractory. Traditional ceramics are most
made up of clay, feldspar and silica.
Clay has been used in a wide range of ceramics product for thousands of years and
continues to be a major component in most ceramic bodies today. Clay is essential and
predominant component in most ceramic product.
Feldspar is the most common igneous rock mineral and the most plentiful mineral in the
earth's crust. Feldspar is a common raw material in the production of ceramics product.
In the fabrication of ceramic material, feldspar also serves as a flux to form a glassy
phase at low temperatures. It improves the strength, toughness, and durability of the
ceramic body and cements the crystalline phase of other ingredients.
Silica is a major ingredient in refractories and whitewares. Silica occurs commonly in
nature as sandstone, silica sand or quartzite. Silica is one of the most abundant oxide
materials in the earth's crust. Silica is a precursor to the fabrication of other ceramic
products and as a material on its own.
2
1.2.2
Advanced Ceramic
Advanced ceramic include ceramics for electrical, magnetic, electronic, and optical
application (sometimes referred to as functional ceramics) and ceramics for structural
applications at ambient as well as at elevated temperatures (structural ceramics).
Advance ceramics include carbides, such as silicon carbide (SiC); oxides, such as
aluminum oxide, (Al2O3) and zirconia (ZrO2); nitrides, such as silicon nitride (Si3N4);
silicates such as kaolinite (Al2Si2O5 (OH) 4) and mullite (Al6Si2O13) and many other
materials, including the mixed oxide ceramics that can act as superconductors.
Advanced ceramic requires modern processing techniques, and the development of these
techniques has led to advances in industry.
Advanced ceramics materials possess unique properties in chemical resistance, corrosion
resistance; wear resistance and dimensional stability at room temperature as well as at
elevated temperatures. Ceramic matrix composites are at the forefront of advanced
materials technology because of their light weight, high strength and toughness, high
temperature capabilities, and graceful failure under loading. Ceramic composites are
considered as enabling technology for advanced aero propulsion, space propulsion,
space power, aerospace vehicles, and space structures.
1.2.3
Ceramic Based Composites
Ceramic composites are being actively developed in many research establishments
primarily to improve either the toughness or hardness to be more suited to a particular
application. This group can be composed of a combination of oxide ceramics and nonoxide ceramics (granular, platy, whiskers, etc.), oxide and oxide ceramics, non-oxide
and non-oxide ceramics, ceramics and polymers, etc. an almost infinite number of
combinations are possible. Fiber, whisker or particulate reinforced composites can be
made tougher and stronger than traditional un-reinforced ceramics. Ceramic composites
3
offer the mechanical and physical properties unavailable in the past and provide the
opportunities to solve past material problems.
1.3
Application of Ceramic
The applications for ceramics have found for a long time ago. Every day new and
different applications are being discovered. This truly makes ceramics have broad ranges
of functions and applications. Ceramic materials display a wide range of properties
which purpose in many different product areas to facilitate user.
Most people, when they hear the word of ceramics, they will think of art, dinnerware,
pottery, tiles, and brick. The above mentioned products are commonly referred to as
traditional ceramic that have been developed since the time of the earliest civilizations.
These traditional products have been and continue to be important and still represent a
major part of the ceramics industry although in recent year advanced material have been
successfully developed . These advanced ceramics are being used for applications such
as space shuttle tile, engine components, artificial bones and teeth, computers and other
electronic components, and cutting tools (Callister, 2003).
Examples of the wide range application of ceramics can be seeing as mention in the
following tables. The applications of ceramics can be simplifies into two major
categories which are traditional and advanced material as in the Table 1.1 and 1.2
respectively. For the traditional ceramic application it can be divided into five major
industries segment together with several examples. For the advanced ceramic it can be
classified into four categories which consists structural, electrical, coatings and lastly
chemical and environmental together with a few examples.
4
Table 1.1: The example application of the traditional ceramic
Industry Segment
Structural clay
products
Whitewares
Refractories
Glasses
Abrasives
Cements
Common Examples
Brick, sewer pipe, roofing tile, clay floor and wall tile (i.e.,
quarry tile), flue linings
Dinnerware, floor and wall tile, sanitary ware, electrical
porcelain, decorative ceramics
Brick and monolithic products are used in iron and steel, nonferrous metals, glass, cements, ceramics, energy conversion,
petroleum, and chemicals industries
Flat glass (windows), container glass (bottles), pressed and
blown glass (dinnerware), glass fibers (home insulation), and
advanced/specialty glass (optical fibers)
Natural (garnet, diamond, etc.) and synthetic (silicon carbide,
diamond, fused alumina, etc.) abrasives are used for grinding,
cutting, polishing, lapping, or pressure blasting of materials
Used to produce concrete roads, bridges, buildings, dams, and the
like
Table 1.2: The example application of the advanced ceramic
Industry Segment
Structural
Electrical
Coatings
Chemical and
environmental
1.4
Common Examples
Wear parts, bioceramics, cutting tools, and engine
components
Capacitors, insulators, substrates, integrated circuit
packages, piezoelectrics, magnets and superconductors
Engine components, cutting tools, and industrial wear parts
Filters, membranes, catalysts, and catalyst supports
Objective
The objectives of this project are listed as below:
i. To fabricate the bar specimens and crucibles of dense alumina by using slip casting
technique.
ii. To analyze the effect of different raw materials composition on the final properties
of dense alumina.
5
1.5
Scope
The project involved the theoretical study on the ceramic slip casting process and
fabricates the dense alumina through the slip casting process. The emphases are on the
preparation of slip with correct percentage of composition between alumina and ball
clay. Water are used until slip casting obtain the desired specific gravity ranges between
1.4-1.6. For this experiment, the raw materials used were alumina and ball clay with
different ratios of raw materials constituent. There are three different weight ratios of
powder mixture, which are 1:1000; 5:1000 and 10:1000. The ratio refers to ball clay:
alumina. The slip casting was prepared and was mixed using roll mill for three hour to
make sure all the chemical composition agglomerate homogenously. The ratio of
grinding media is ¼ raw materials. The slip is then casted into the plaster mold of Paris
by using solid and drain casting technique for bar specimens and crucibles respectively.
In this study the bar specimens will be done through the process drying at room
temperature and bisque at 900°C by using the heating rate 10°C/min. Then the green
body will be sintered at 1400°C. The samples dimensions were measured before and
after sinter to get the percent of shrinkage of sintered specimen. The finished specimens
were needed to prepare for testing and evaluations. The sintered specimens were tested
by using X-ray diffraction (XRD) to identify phase composition in every sample.
Scanning Electron Microstructure (SEM) is used to analyze the microstructures in each
sample. Other testing for specimens includes flexural test and shrinkage.
1.6
Problem Statement
Alumina is widely known as advanced ceramic materials which are used in a variety of
applications. High purity alumina (Al2O3 content > 99%) have high thermal
conductivity, low thermal expansion, corrosion resistance and high compressive strength
leads to good thermal shock resistance is ideal for high temperature applications such as
crucibles. Advanced ceramic typically used non-traditional techniques such as hot
6
pressing, vapor deposition, gel casting and injection molding to form ceramic materials
into a recognizable shape or product.
However considering the importance homogeneous distribution of the particles in the
production of ceramic crucibles is essential to obtain a high-density impervious product;
therefore the slip casting technique was chosen to produce the crucibles. Homogeneous
distribution of the particles can be obtained by using the slip casting technique although
it quit conventional to the industries.
Rak (2000) stated the problem in the slip casting contains about 30 wt% water and about
half of it must be absorbed by the plaster of Paris mould in order to reduce the liquid slip
to an acceptably firm body at the mold surface. This forms a dense cast with long
production time and the molds are easily damaged.
High purity alumina forming with slip casting technique produce parts that are fragile
and cannot easily be machined in the green body state. The composition of the purity
alumina ceramic body can be changed to enhance particular desirable material
characteristics by adding little additive. In this project, properties of the final body
ceramic alumina with the different composition of additive is then analyzed.
7