Ceramics

Topic 3:
Prof. Dr. H.Z. Harraz Presentation Ceramic Materials
Hassan Z. Harraz
hharraz2006@yahoo.com
2013- 2014

OUTLINE OF TOPIC 3:
 Properties of ceramics
 Classification of ceramics
 Ceramic raw material
 Fabricating and processing of ceramic
 Application of Ceramics
1) Glasses
2) Clay Products
2.1) Structural clay product
2.2) Whitewares
3) Refractories:
3.1) Fireclay
3.2) Silica
3.3) Basic refractories
3.4) Special refractories
4) Abrasives
5) Cements
6) Advanced Ceramics

CLASSIFICATION OF MATERIALS
21 November 2015 Prof. Dr. H.Z. Harraz Presentation 3

PROPERTIES OF CERAMICS
 Extreme hardness:
High wear resistance
Extreme hardness can reduce wear caused by friction
 Corrosion resistance
 Heat resistance:
Low electrical conductivity
Low thermal conductivity
Low thermal expansion
Poor thermal shock resistance
Low ductility:
Very brittle
High elastic modulus
 Low toughness:
Low fracture toughness
Indicates the ability of a crack or flaw to produce a catastrophic failure
 Low density:
Porosity affects properties
 High strength at elevated temperatures

Comparison metals v ceramics
CeramicsMetals

Definition
 Ceramic materials are inorganic, non-metallic materials and things made
from them.
 They may be crystalline or partly crystalline.
 They are formed by the action of heat and subsequent cooling.
 Most ceramics are compounds between metallic and nonmetallic elements for
which the interatomic bonds are either totally ionic bond or predominantly ionic
but having same covalent character.
 Clay was one of the earliest materials used to produce ceramics, but many
different ceramic materials are now used in domestic, industrial and building
products.
 A wide-ranging group of materials whose ingredients are clays, sand and
felspar.
The term “ Ceramics” comes from the Greek word keramikos, which
means “Burnt stuff or drinking vessel”, indicating that desirable
properties of these materials are normally achieve through a high-
temperature heat treatment process called Firing, but was later applied by
the Greeks to all fired clay products.
What is “Ceramic”?

SPECTRUM OF CERAMICS USES
http://www.ts.mah.se/utbild/mt7150/051212%20ceramics.pdf

Traditional Ceramics
Traditional Ceramics Advanced Ceramics
Older and more generally known types.
(porcelain, brick, earthenware, etc.)
have been developed over the past half century
Based primarily on Natural crude raw
materials of clay and silicates.
Include industrial inorganic chemicals (i.e,
artificial raw materials) that exhibit specialized
properties, require more sophisticated
processing.
Applications:
Building materials (brick, clay pipe, glass)
Household goods (pottery, cooking ware)
Manufacturing (abbrasives, electrical
devices, fibers)
Applications:
Applied as thermal barrier coatings to
protect metal structures, wearing surfaces.
Engine applications (Silicon nitride (Si3N4),
Silicon carbide (SiC), Zirconia (ZrO2), Alumina
(Al2O3)
1) Traditional and Advanced Ceramic Materials
CLASSIFICATION OF CERAMICS
Bioceramic implants

Comparison of the different aspects of traditional and
advanced ceramics
• Compares of the different aspects of traditional and advanced ceramics in terms of the type of raw materials used, the
forming and shaping processes, and the methods used for characterization

1) Traditional and Advanced Ceramic Materials

2) Amorphous and Crystalline Ceramics Materials
Amorphous Crystalline
Atoms exhibit only short-range
order
Atoms (or ions) are arranged in a
regularly repeating pattern in three
dimensions (i.e., they have long-
range order)
no distinct melting temperature
(Tm) for these materials as there
is with the crystalline materials
Crystalline ceramics are the
“Engineering” ceramics:
High melting points
Strong
Hard
Brittle
Good corrosion resistance
Na2O, CaO, K2O, …..etc Silicon nitride (Si3N4), Silicon carbide
(SiC), Zirconia (ZrO2), Alumina (Al2O3)

3) Type of Ceramic by Elements
 Aluminates - (11)
 Arsenides - (5)
 Borides - (20)
 Carbides - (17)
 Ferrites - (9)
 Niobates - (8)
 Nitrides - (24)
 Phosphide - (6)
 Silicides - (5)
 Titanates - (22)
 Tungstates - (14)
 Zirconates - (7)

Based on composition of raw materials and type of ceramic materials:
a) Silicate ceramics:
compounds containing the anionic complex (SiO4) e.g. the silicate group.
 Porcelain
 Magnesium Silicates (MgO.SiO2)
 Mullite (or Porcelainite : 3Al2O3.2SiO2)
b) Advanced ceramics:
i) Oxide ceramics:
 Aluminum Oxide (Al2O3)
 Titanium Oxide (TiO2);
 Magnesium Oxide (MgO)
 Zirconium Oxide (ZrO2)
 Lead Zirconate Titanate (Pb(ZrxTi1-x)O3)
 Lead oxide (PbO)
 Aluminum Oxide -Titanium Oxide (Al2O3 . TiO2)
4) Type of ceramic materials
Boride ceramics
 Aluminum diboride (AlB2)
 Aluminum dodecaboride (AlB12)
 Calcium hexaboride (CaB6 )
 Gadolinium boride (GdB6)
 Hafnium boride (HfB2)
 Lanthanum boride (LaB6)
 Lanthanum hexaboride(LaB6)
 Magnesium boride (MgB)
 Nickel boride (Ni2B)
 Niobium diboride (NbB2)
 Niobium monoboride (NbB)
 Silicon tetraboride (SiB4)
 Tantalum boride (TaB)
 Tantalum boride (TaB2)
 Tungsten boride (WB)
 Vanadium boride (VB )
Nitride ceramics
 Aluminum nitride (AlN)
 Magnesium nitride (Mg3N2)
 Silicon aluminum oxynitride (Al6N6O2Si)
 Silicon nitride (Si3N4)
 Barium nitride (Ba3N2)
 Boron nitride (BN)
 Calcium nitride (Ca3N2)
 Gallium nitride (GaN)
 Germanium(III) nitride(Ge3N4)
 Indium(III) nitride (InN)
 Lithium nitride (Li3N)
 Strontium nitride (Sr3N2)
 Tantalum nitride(TaN)
 Titanium carbonitride (Ti2CN)
 Titanium nitride (TiN)
 Zirconium nitride (ZrN)
Carbide ceramics:
 Aluminum carbide (Al4C3)
 Silicon carbide (SiC)
 Boron carbide (CB4)
 Calcium carbide (CaC2)
 Chromium carbide (Cr3C2)
 Hafnium(IV) carbide (HfC)
 Molybdenum carbide (Mo2C)
 Niobium(IV) carbide (NbC)
 Tantalum(IV) carbide (TaC)
 Titanium carbide (TiC)
 Tungsten(IV) carbide (WC)
Silicide ceramics
 Calcium silicide technical ( CaSi2 )
 Magnesium silicide ( Mg2Si )
 Molybdenum disilicide ( MoSi2)
 Niobium silicide ( NbSi2)
 Tungsten silicide ( WSi2)
ii) Non-oxide ceramics: carbides and nitrides are the
most important compounds of this group.
 Carbide ceramics
 Nitride ceramics
 Boride ceramics
 Silicide ceramics

Titanium Oxide
TiO2 Zirconium Oxide
ZrO2
Aluminum Oxide
Titanium Oxide
Al2O3 . TiO2
Aluminum Oxide
Al2O3
Magnesium Oxide
MgO
Lead Zirconate
Titanate Pb(ZrxTi1-x)O3
Magnesium Silicates
MgO.SiO2
Mullite
3Al2O3.2SiO2Porcelain
Boron Carbide
(BC)
Silicon Carbide
(SiC)
Tungsten Carbide
(B4C)
Silicon Nitride
(Si3N4)
Aluminum Nitride
(AlN)
Silicon Aluminum
OxyNitride (SiAlON:
Al6N6O2Si)

Carbide Ceramics
Automotive Components in Silicon carbide (SiC)
Silicon carbide (SiC) is known under trade names Carborundum,
Crystalon, and carbolon
Chosen for its heat and wear resistance
Carbide ceramics
 Aluminum carbide (Al4C3)
 Boron carbide (CB4)
 Calcium carbide (CaC2)
 Chromium carbide (Cr3C2)
 Hafnium(IV) carbide (HfC)
 Molybdenum carbide (Mo2C)
 Niobium(IV) carbide (NbC)
 Silicon carbide (SiC)
 Tantalum(IV) carbide (TaC)
 Titanium carbide (TiC)
 Tungsten(IV) carbide (WC)

Molybdenum disilicide (MoSi2, or molybdenum silicide)
 An intermetallic compound, a silicide of molybdenum, is a refractory ceramic with primary use
in heating elements. It has moderate density, melting point 2030 °C, and is electrically conductive.
At high temperatures it forms a passivation layer of silicon dioxide, protecting it from further
oxidation. It is a gray metallic-looking material with tetragonal crystal structure (alpha-
modification); its beta-modification is hexagonal and unstable. It is insoluble in most acids but
soluble in nitric acid and hydrofluoric acid.
 While MoSi2 has excellent resistance to oxidation and high Young's modulus at temperatures above
1000 °C, it is brittle in lower temperatures. Also, at above 1200 °C it loses creep resistance. These
properties limits its use as a structural material, but may be offset by using it together with another
material as a composite material.
 Molybdenum disilicide (MoSi2) based materials are usually made by sintering. Plasma spraying can
be used for producing its dense monolithic and composite forms; material produced this way may
contain a proportion of β-MoSi2 due to its rapid cooling.
 Used:
Molybdenum disilicide heating elements can be used for temperatures up to 1800 °C, in
electric furnaces used in laboratory and production environment in production
of glass, steel, electronics, ceramics, and in heat treatment of materials.
In microelectronics as a contact material.
as a shunt over polysilicon lines to increase their conductivity and increase signal speed.

• Titanium diboride (TiB2) is an extremely hard compound composed of titanium and boron which has excellent resistance
to mechanical erosion. TiB2 is also a reasonable electrical conductor, so it can be used as a cathode material in aluminium
smelting and can be shaped by electrical discharge machining
• Current use of TiB2 appears to be limited to specialized applications in such areas as impact resistant armor, cutting
tools, crucibles, neutron absorbers and wear resistant coatings.
• TiB2 is extensively used as evaporation boats for vapour coating of aluminium. It is an attractive material for the aluminium
industry as an inoculant to refine the grain size when casting aluminium alloys, because of its wettability by and low
solubility in molten aluminium and good electrical conductivity.
• Thin films of TiB2 can be used to provide wear and corrosion resistance to a cheap and/or tough substrate.
• Silicon borides (also known as boron silicides: SiB6 ) are lightweight ceramic compounds formed
between silicon and boron. Several stoichiometric silicon boride compounds, SiBn, have been reported: silicon triboride,
SiB3, silicon tetraboride, SiB4, silicon hexaboride, SiB6, as well as SiBn (n = 14, 15, 40, etc.). The n = 3 and n = 6 phases were
reported as being co-produced together as a mixture for the first time by Henri Moissan and Alfred Stock in 1900 by briefly
heating silicon and boron in a clay vessel. The tetraboride was first reported as being synthesized directly from the
elements in 1960 by three independent groups: Carl Cline and Donald Sands; Ervin Colton; and Cyrill Brosset and Bengt
Magnusson. It has been proposed that the triboride is a silicon-rich version of the tetraboride. Hence, the stoichiometry of
either compound could be expressed as SiB4 - x where x = 0 or 1. All the silicon borides are black, crystalline materials of
similar density: 2.52 and 2.47 g cm−3, respectively, for the n = 3(4) and 6 compounds. On the Mohs scale of mineral
hardness, SiB4 - x and SiB6 are intermediate between diamond (10) and ruby (9). The silicon borides may be grown from
boron-saturated silicon in either the solid or liquid state.
• The SiB6 crystal structure contains interconnected icosahedra (polyhedra with 20 faces), icosihexahedra (polyhedra with 26
faces), as well as isolated silicon and boron atoms. Due to the size mismatch between the silicon and boron atoms, silicon
can be substituted for boron in the B12 icosahedra up to a limiting stoichiometry corresponding to SiB2.89. The structure of
the tetraboride SiB4 is isomorphous to that of boron carbide (B4C), B6P, and B6O. It is metastable with respect to the
hexaboride. Nevertheless, it can be prepared due to the relative ease of crystal nucleation and growth.
• Both SiB4 - x and SiB6 become superficially oxidized when heated in air or oxygen and each is attacked by boiling sulfuric
acid and by fluorine, chlorine, and bromine at high temperatures. The silicon borides are electrically conducting. The
hexaboride has a low coefficient of thermal expansion and a high nuclear cross section for thermal neutrons.
• The tetraboride was used in the black coating of some of the space shuttle heat shield tiles.
Bromide

Zirconia
Silicon carbide cermic
foam filter (CFS)
Ceramic Matrix Composite (CMC) rotor
Oxide Ceramics Non-Oxide Ceramics Composite Ceramics
 Zirconia (ZrO2), Alumina (Al2O3) ….
etc
Carbides, Borides, Nitrides, Silicides Particulate reinforced,
combinations of oxides and non-
oxides (Silicon Aluminum
OxyNitride (Al6N6O2Si)
Oxidation resistant Low oxidation resistance Toughness
electrically insulating extreme hardness low and high oxidation resistance
(type related)
chemically inert chemically inert 
generally low thermal conductivity high thermal conductivityy variable thermal and electrical
conductivity
slightly complex manufacturing electrically conducting complex manufacturing processes
low cost for alumina
more complex manufacturing
higher cost for zirconia.
difficult energy dependent
manufacturing and high cost.
high cost.
5) Oxide and Non-oxide Ceramic

Chapter 13 -19
CERAMIC RAW MATERIAL
Ceramics are made from three basic ingredients: clay,
silica and feldspar
A mixture of components used
(50%) 1. Clay
(25%) 2. Filler – e.g. quartz (finely ground)
(25%) 3. Fluxing agent (Feldspar)
binds it together
aluminosilicates + K+, Na+, Ca+

Chapter 13 -
• In this chapter we briefly consider the nature of the starting materials, traditionally called raw
materials, that can be purchased from a vendor and received at a manufacturing site. These
materials can vary widely in nominal chemical and mineral composition, purity, physical and
chemical structure, particle size, and price.
Accordingly, a higher-quality and more expensive material may be acceptable for
microelectronics, coatings, fibers, and some high-performance products. But the average cost
of raw materials for building materials and traditional ceramics such as tile and porcelain must
be relatively low.
Categories of raw materials include:-
Common examples are listed in Table.
COMMON RAW MATERIALS
Category Purity (%) Materials
Crude materials variable
shale, clay, crude bauxite, crude kyanite,
natural Ball clay, Bentonite
Industrial minerals (Refined
crude materials)
85 -98
pyrophyllite, talc, feldspar, wollastonite,
spodumene, glass sand, kyanite, bauxite,
zircon, rutile, calcined kaolin, dolomite
Industrial inorganic chemicals 98 - >99.9
clacined alumina, calcined magnesia, fused
alumina, aluminum nitride, silicon carbide,
silicon nitride, barium carbonate, titania,
calcined titanates, calcined ferrites
Table 1.2: shows Starting raw materials for ceramics

 Non-uniform crude material from natural deposits.
 Many early ceramics industries were based near a natural deposit containing a combination of crude
minerals that could be conveniently processed into usable products.
 Some crude materials are of sufficient purity to be used in heavy refractories:
 Crude bauxite, a nonplastic ore containing hydrous alumina minerals, clay minerals, and mineral
impurities such as quartz and ferric oxides, is used in producing some refractories.
 Construction materials such as brick and tile and some pottery items are historical examples, and many
are still identified by the regional name.
 Today, however, most ceramics are produced from more refined minerals.
i) Crude materials
 Refined industrial minerals that have been beneficiated to remove mineral impurities to significantly increase
the mineral purity and physical consistency.
 Industrial minerals are used in large tonnages for producing construction materials, refractories, whitewares,
and some electrical ceramics.
 They are used extensively as additives in glazes, glass, and raw materials for industrial chemicals.
ii) Industrial minerals (Refined crude materials)
 High-tonnage industrial inorganic chemicals that have undergone extensive chemical processing and refinement
to significantly upgrade the chemical purity and improve the physical characteristics.
 Important industrial ceramic chemicals include tabular and calcined aluminas (Al2O3), magnesium oxide (MgO),
silicon carbide (SiC), silicon nitride, alkaline earth titanates soft and hard femtes, stabilized zirconia, and inorganic
pigments.
 Extensive chemical beneficiation reduces the content of accessary minerals and may increase the chemical purity
up to about 99.5.
 For many materials, the scale of operation is extremely large, which aids in lowering the unit processing costs and
selling price.
iii) Industrial inorganic chemicals

FABRICATING AND PROCESSING OF CERAMICS
Raw Material
properties
Microstructure
Final product
properties
Material Preparation
Forming, Shaping
Coasting
Drying
Glaze processes
Firing
Application
 Most traditional and technical ceramics
product are manufactured by
compacting powder or particles into
shapes which are heated to high
temperature.
 The basic steps in the processing of
ceramics are:
 Material Preparation
 Forming & Casting
 Thermal treatment by drying

THE MANUFACTURING PROCESS
• This consists of four basic stages: shaping, drying, firing and glazing.
• Sometimes the glaze is applied before firing (once-firing), and sometimes the item is fired, then the
glaze is applied and then the item is refired (twice-firing).
Step 1 – Shaping:
 The ingredients are mixed together and soaked in water. The excess water is squeezed out to make a
clay with a moisture content of about 20%, and the mixture is shaped appropriately. This is either done
by forcing the clay into a mould or by pressing a mould into the clay while it is spinning on a turn-table.
Processing techniques:-
 Tape casting
 Slip casting
 Injection molding
Step 2 – Drying:
• The items are dried slowly in an oven, during which stage they lose all of the water except that which is
bound up in crystal lattices.
 Before the ware can be fired to high temperatures it must first be dried to remove water.
 This results in a 3 - 7% volume reduction.
 Water is added to increase the plasticity of the clay; this water is still present in the body after it has
been formed, and can be removed only slowly as it must migrate through the spaces between the
particles of clay, silica and feldspar to evaporate from the surface.
 During the drying period the body will shrink by a significant amount. Shrinkage stops when the particles
come into contact. However, if drying is not uniform, stresses can build to the extent that the body warps
or possibly cracks.
 Castware is in the mould for 0.5 - 1 hour, where some drying occurs, and then air-dried for 1 - 4 days.
Jiggered-ware is dried at a little above ambient temperature for a little over an hour in a "mangle drier"
and then air-dried for 1 - 5 days.

21 November 2015 Prof. Dr. H.Z. Harraz Presentation
Feldspar Groups
24

Schematic of the jaw, rotary,
crushing rollers, and hammermill
crushing equipment and ball mill
(grinding) equipment.
Hammermill
Rotary crusherJaw crusher Crushing rollers
Typical ball mill (grinding)
Crushing & Grinding
(to get ready ceramic
powder for shaping)

Sinter
and
Serve
Slip Casting
Slip casting: Forming a hollow ceramic part by
introducing a pourable slurry into a mold.
Tape casting: A process for making thin sheets of
ceramics using a ceramic slurry consisting of
binders, plasticizers, etc. The slurry is cast with
the help of a blade onto a plastic substrate.
Figure showing Schematic of a tape casting machine.
Figure shows Steps in slip casting of ceramics
pour slip
into mold
Assemble
mold
Remove
mold
Trim
Drain residue

 Raw materials are mixed with resin to provide the necessary fluidity degree.
 Then injected into the molding die
 The mold is then cooled to harden the binder and produce a "green" compact part (also
known as an unsintered powder compact).
http://global.kyocera.com/fcworld/first/process06.html
Injection Molding

Step 3 – Firing: The item is heated to temperatures up to 1170oC, during which time the clay
undergoes some chemical changes and the silica and feldspar undergo physical changes. The
reactions of the clay can be summarised as follows:
6Al2Si2O5(OH)4 → 6Al2Si2O7 → 3Al4Si3O12 → 2Al6Si2O13
kaolinite metakaolinite silicon spinel mullite
Silica and water (from the crystal lattice) are also expelled during firing, resulting in a further 5
- 7% volume reduction. This silica mixes with the silica already present and melts to form a
glass. It is this glass, which also includes metallic ions from the feldspar, that makes the
ceramic item non-porous and water-tight.
 Once drying is complete the body is ready for firing. All unglazed articles and many glazed
ones are fired using the "once-firing" method. However, a small number of articles are fired
twice in a method whereby the glaze is applied after the first, biscuit, firing and is fixed on
by a second, glost, firing. In this method the dried articles pass through the first, biscuit (or
"bisque"), firing at a slow rate. For hollow-ware, such as cups, the total time from cold
through the kiln and back to cold is about 26 hours, while for other articles it is 44 hours,
although modern kiln design is able to significantly decrease both these times. After this
the glaze is applied and the ware is fired again. The maximum temperature in both kilns is
1170oC.
 To understand this process it necessary to consider what happens to the individual
components of the body when they are heated to high temperatures.

Step 3 >1100oC
5SiO2 + 2Al6Si2O13
silica glass mullite
Step 2 925oC
3SiO2 + 3Al4Si3O12
silica glass silicon spinel
Al2Si2O5(OH)4
kaolinite
Step 1 500oC
12 H2O + 6Al2Si2O7
metakaolinite
Chemical reactions of clay
 When heated to 1100oC, kaolinite decomposes by first order
kinetics (i.e., This means that the reaction rate is proportional to
the concentration of the substances reacting) according to the
following sequence of steps:
 Step 1 is a very important step, and the temperature must be
carefully controlled as the clay decomposes. The water given off
by this reaction is not water remaining between the particles, but
water bound into the mineral lattice. The loss of this water causes
the lattice and hence the clay particles and therefore the clay body
to shrink. If this step is not carefully controlled, the body can be
destroyed by thermal stresses and by the rapidly escaping steam.
 The weight loss during Step 1 is about 14%, which means that the
volume of steam evolved at 550oC from a 3 kg lump of clay would
be ~ 2 m3 at S. T. P. Large masses of clayware being fired in a kiln
must be well ventilated.
 Steps 2 and 3 illustrate that the mineral undergoes further solid
state reactions where the parent crystal is rearranged and silica is
rejected in the form of a glass. Finally, at about 1250oC, mullite
and silica glass remain.

Chemical reactions of silica
• Silica will not decompose at the temperature encountered in firing kilns and
melts at 1725oC.
Chemical reactions of feldspar
• Pure feldspar grains begin to melt at about 1140oC to form a solid and a viscous
liquid; as the temperature is raised the solid decomposes to form more liquid.
Combined chemical reaction
• When a clay body consisting of the above components (clay, silica and feldspar) is heated
sufficiently, all of the above reactions occur as well as several others. These other
reactions are between the components themselves.
• Illustrated in Step 1 in the decomposition of kaolinite reaction. This is then followed by
Step 2, the decomposition of metakaolinite to form silicon spinel, and then between 1000 -
1100oC mullite crystals form and SiO2 glass begins to form (Step 3). The mullite crystals
remain in the vicinity of the clay particles.
• At 1140oC, feldspar grains smaller than about 10m have completely disappeared by
reaction with the surrounding clay. The alkali metal ions diffuse out of the feldspar and the
remaining solid decomposes to form mullite and a silica-rich liquid.
• If the body is fired to about 1250oC the alkali metal ions, Na+ and K+ dissolve on to the
outer layers of the quartz particles in a silica glass containing alkali metal ions. This glass
cements the whole structure together and makes it non-porous and water tight.

Step 4 - Glazing
 Glaze is a thin layer of glass or glass and crystals that adheres to the surface of the clay body.
 It provides a smooth, non-absorbent surface that can be coloured and textured in a manner not possible
on the clay body itself.
 Glazes are composed of various oxides combined in proportions that will yield the desired properties.
 Silica, SiO2, and boric oxide, B2O3, are the glass formers, but oxides such as Na2O, K2O, CaO, PbO
and Al2O3 must be present in the stoichiometric sense to give the desired properties. These include, for
example, lowering the viscosity of the molten glass so that the glaze will flow smoothly over the surface
of the clay body at the temperature at which the glaze is fired.
 The glaze is either applied before firing or between a first and second firing. Glazes are glassy
substances used to provide a smooth surface on the item (which can then be textured if necessary) and
to colour the ceramic surface.
Glaze application
 If a plain coloured article is being produced, the glaze is either applied by dipping or
spraying.
 For patterns, the pattern is printed on, on a special machine, one colour at a time, with a
maximum of three colours.
 Some patterns are hand painted. When the glaze is applied the articles go through a
second glazing kiln, taking up to twelve hours cold to cold to go through and reaching a
maximum temperature of 1050oC.
 Some patterns are put on after glazing by a transfer process, and these articles then go
through another oven at a temperature of 720oC.

21.11.2015 33
Some of the substances commonly used in forming glazes are listed below in Table
Colour Chemical(s)
Blue Cobalt. When Co2+ ions are in a tetrahedral environment a blue colour results. In
Matte blue, cobalt is present as a cobalt aluminate. Royal blue, mazarine and willow
are Co2+ in tetrahedral environments in silica glazes.
Green Many green glazes contain Cr2O3, with Cr3+ in an octahedral environment. As
Cr2O3 is not soluble in most glazes, the glazes are opaque.
Virtually all complexes and compounds of Cu2+ are blue or green. CuO (green)
dissolves in boric oxide (B2O3) glaze, giving transparent green shades. If SnO2 is
added to this glaze it becomes opaque and if alkalis, e.g. Na2O or K2O, are added,
a blue colour may be produced.
Red Many red coloured glazes contain the red oxide Fe2O3 where the ferric ion, Fe3+, is
held in an octahedral environment. This is achieved by dissolving Fe2O3 in Al2O3 to
form a solid solution, particles of this solid being suspended in the glaze. If Fe2O3 is
dissolved directly into a silica containing glaze, the red colour is lost because the
two components react to give an iron silicate that is brown.
Black A combination of CoO (blue), Cr2O3 (green) and MnO (black).
Yellow Lead chromate, PbCrO4
Colours of glazes

Figure Shows Different techniques for
processing of advanced ceramics.

Application of Ceramics
Taxonomy of Ceramics
Glasses Clay
Products
Refractories
Glass
Glass-ceramics
Abrasives Advance
Ceramics
Structural clay
products
Whiteware
Fireclay
Silica
Basic
Special
Sandpaper
Cutting
Polishing
Cement

APPLICATION AND PROCESSING OF
CERAMICS
1) Glasses
2) Clay Products
2.1) Structural clay product
2.2) Whitewares
3) Refractories:
3.1) Fireclay
3.2) Silica
4) Abrasives
5) Cements

2) Clay Products
 Ceramic products intended for use in building
construction.
 Typical structural clay products are building brick, paving
brick, terra-cotta facing tile, roofing tile, and drainage
pipe.
 These objects are made from commonly occurring
natural materials, which are mixed with water, formed
into the desired shape, and fired in a kiln in order to give
the clay mixture a permanent bond.
 Finished structural clay products display such essential
properties as load-bearing strength, resistance to wear,
resistance to chemical attack, attractive appearance, and
an ability to take a decorative finish.
2.1) Structural clay product :

2.2) Whitewares
Any of a broad class of ceramic products that are
white to off-white in appearance and frequently
contain a significant vitreous, or glassy, component.
Including products as diverse as
Fine china dinnerware
Crockery
Floor and wall tiles
Sanitary-ware (lavatory sinks and toilets)
Dental implants
Electrical porcelain (spark-plug insulators)
Decorative ceramics
All depend for their utility upon a relatively small set
of properties: imperviousness to fluids, low
conductivity of electricity, chemical inertness, and
an ability to be formed into complex shapes.
These properties are determined by the mixture of
raw materials chosen for the products, as well as by
the forming and firing processes employed in their
manufacture.
Whiteware: Bathrooms

3) Refractories
 Firebricks for furnaces and ovens.
 Have high Silicon or Aluminium oxide content.
 Brick products are used in the manufacturing plant for iron and steel, non-
ferrous metals, glass, cements, ceramics, energy conversion, petroleum,
and chemical industries.
 Used to provide thermal protection of other materials in very high
temperature applications, such as steel making (Tm=1500°C),
metal foundry operations, etc.
 They are usually composed of alumina (Tm=2050°C) and silica
along with other oxides: MgO (Tm=2850°C), Fe2O3, TiO2, etc.,
and have intrinsic porosity typically greater than 10% by volume.
Refractory Brick

40
 Refractories - A group of ceramic materials capable of
withstanding high temperatures for prolonged periods of time.
 Acid Refractories: Common acidic refractories include
silica, alumina, and fireclay (an impure kaolinite).
 Basic Refractories: A number of refractories are based
on MgO (magnesia, or periclase).
 Neutral Refractories: These refractories, which include
chromite and chromite-magnesite, might be used to
separate acid and basic refractories, preventing them
from attacking one another.
Special Refractories: Other refractory materials include
zirconia (ZrO2), zircon (ZrO2 · SiO2), and a variety of
nitrides, carbides (SiC), and borides, mullite, and graphite with
low porosity are also used.
3) Refractories

Figure shows the Mg2SiO4-Fe2SiO4 phase
diagram, showing complete solid solubility.

• Need a material to use in high temperature furnaces.
• Consider the Silica (SiO2) - Alumina (Al2O3) system.
• Phase diagram shows:
Mullite (or porcelainite: 3Al2O3.2SiO2), Alumina, and Crystobalite as
candidate refractories.
Adapted from Fig. 12.27,
Callister 7e. (Fig. 12.27
is adapted from F.J. Klug
and R.H. Doremus,
"Alumina Silica Phase
Diagram in the Mullite
Region", J. American
Ceramic Society 70(10),
p. 758, 1987.)
Figure shows a simplified SiO2-Al2O3 phase diagram, the
basis for alumina silicate refractories.

 It is a type of clay which is used in the production of heat resistant
clay items, such as the crucibles used in metals manufacturing.
 This type of clay is commonly mined from areas around coal mines,
although other natural deposits are also available as potential
sources, with many nations having deposits of clays suitable for use in
high temperature applications.
 Fireclay can also be refined and treated to make it suitable for
specialty applications.
3.1) Fireclay:

 They are made from quartzites and silica
gravel deposits with low alumina and alkali
contents.
 They are chemically bonded with 3 to 3.5%
lime.
 Silica refractories have good load resistance
at high temperatures, are abrasion-
resistant, and are particularly suited to
containing acidic slags.
 Of the various grades coke-oven quality,
conventional, and super-duty the super-
duty, which has particularly low impurity
contents, is used in the superstructures of
glass-melting furnaces.
3.2) Silica

 Advanced ceramic materials have been developed over the past half century
Include industrial inorganic chemicals (i.e, artificial raw materials) that exhibit
specialized properties, require more sophisticated processing.
 Engine applications are very common for this class of material which
includes (Silicon nitride (Si3N4), Silicon carbide (SiC), Zirconia (ZrO2), Alumina
(Al2O3)
 Heat resistance and other desirable properties have lead to the development
of methods to toughen the material by reinforcement with fibers and
whiskers opening up more applications for ceramics
 Structural: Applied as thermal barrier coatings to protect metal structures,
wearing surfaces, Wear parts, , or as integral components by
themselves; bioceramics, engine components, armour.
 Electrical: Capacitors, insulators, integrated circuit packages, piezoelectrics,
magnets and superconductors
 Coatings: Engine components, cutting tools, and industrial wear parts
 Chemical and environmental: Filters, membranes, catalysts, and catalyst
supports

Kryocera Si3N4 gas turbine rotor
BORIDE Inc WC blast nozzle
Kundan MgO refractory bricks
(furnace liners)
Application of advanced ceramics
Structural Al2 O3
parts (Reed, 1995)
Rotor (Alumina)
Gears (Alumina)
Engine Components

47
Applications: Advanced Ceramics
Electronic Packaging
• Chosen to securely hold microelectronics & provide heat transfer
• Must match the thermal expansion coefficient of the microelectronic chip & the
electronic packaging material. Additional requirements include:
 good heat transfer coefficient
 poor electrical conductivity
• Materials currently used include:
• Boron nitride (BN)
• Silicon Carbide (SiC)
• Aluminum nitride (AlN)
 thermal conductivity 10x that for Alumina
 good expansion match with Si
Heat Engines
 Possible parts – engine block,
piston coatings, jet engines
Ex: Si3N4, SiC, & ZrO2
DisadvantagesAdvantages
 Brittle Run at higher temperature
 Too easy to have voids-
weaken the engine
 Excellent wear &
corrosion resistance
 Difficult to machine Low frictional losses
 Ability to operate
without a cooling system
 Low density

Ceramic Armour
• Typical ceramic materials used in armour systems include: Alumina (Al2O3), Boron carbide (B4C), Silicon
carbide (SiC), and Titanium diboride (TiB2).
 Extremely hard materials:
 shatter the incoming projectile
 energy absorbent material underneath
 Ceramic armour is armor used by armored vehicles and in personal armor.
• Ceramic armour systems are used to protect military personnel and equipment.
• Advantage: low density of the material can lead to weight-efficient armour systems.
• The ceramic material is discontinuous and is sandwiched between a more ductile outer and inner skin.
The outer skin must be hard enough to shatter the projectile. Most of the impact energy is absorbed by
the fracturing of the ceramic and any remaining kinetic energy is absorbed by the inner skin, that also
serves to contain the fragments of the ceramic and the projectile preventing severe impact with the
personnel/equipment being protected.
• Alumina ceramic/Kevlar composite system in sheets ~20mm thick are used to protect key areas of
aircraft (cockpit crew/instruments and loadmaster station).
• This lightweight solution provided an efficient and removable/replaceable armour system. Similar
systems used on Armoured Personnel Carrier’s.

Biomaterials
• Biomaterials, defined as synthetic or natural materials used
in contact with biological systems, are enabling tools for
many advances in biomedical research. The field of
biomaterials is interdisciplinary and includes aspects
of materials science, chemistry, biology, and medicine.
• Here you will find biocompatible materials, including
biocompatible metals and ceramics
Microelectromechanical System (MEMS)
Mechanical parts and electronic circuits
combined to form miniature devices,
typically on a semiconductor chip, with
dimensions from tens of micrometers to a
few hundred micrometers (millionths of a
meter). Common applications for MEMS
include sensors, actuators, and process-
control units.

• A ball bearing is a type of rolling-element bearing that uses
balls to maintain the separation between the moving parts
of the bearing.
• The purpose of a ball bearing is to reduce rotational friction
and support radial and axial loads. It achieves this by using at
least two races to contain the balls and transmit the loads
through the balls. Usually one of the races is held fixed. As
one of the bearing races rotates it causes the balls to rotate
as well. Because the balls are rolling they have a much lower
coefficient of friction than if two flat surfaces were rotating
on each other.
Ceramic ball bearings
• Optical fibers - is a thin, flexible,
transparent fiber that acts as a
waveguide, or "light pipe", to
transmit light between the
two ends of the fiber.

REFERENCES
Cardarelli, F., 2005, Materials Handbook: A Concise Desktop Reference. 2nd edn, Springer Verlag London Limited,
London, 848p.
Bourne, H.L., 1994, Glass raw materials: in Carr, D.D. and others, eds., Industrial minerals and rocks (6th edition):
Littleton, CO, Soc. for Mining, Metallurgy and Exploration, Inc., p. 543-550.
Kauffman, R.A. and Van Dyk, D., 1994, Feldspars: in Carr, D.D. and others, eds., Industrial minerals and rocks (6th
edition): Littleton, CO., Soc. for Mining, Metallurgy, and Exploration, Inc., p. 473-481.
Lesure, F.G., 1968, Mica deposits of the Blue Ridge in North Carolina: U.S. Geol. Sur. Prof. Paper 577, 129 p.
Potter, M.J., 1991, Feldspar, and Nepheline Syenite, and Aplite: Annual Report, US Dept. of Interior, US Bureau of Mines.
Potter, M.J., 1996, Feldspar and Nepheline Syenite: Minerals Yearbook, US Dept. of Interior, US Geological Survey;
(//minerals.er.usgs.gov/minerals).
Potter, M.J., 1997, Feldspar: Mineral Commodity Summaries, US Dept. of Interior, US Geological Survey;
(//minerals.er.usgs.gov/minerals).
USM 1993, Short Course on : Industrial Processing of Kaolin, quartz/silica sand and Feldspar, 20th-22nd. April 1993,
School of Materials and Mineral Resources Engineering in Collaboration with The Department of Mining and
Metallurgical Engineering, University of Queensland, Australia.
http://www.azom.com/details.asp?ArticleID=2123
www.accuratus.com/materials.html
http://global.kyocera.com/fcworld/charact/heat/thermaexpan.html
http://www.keramverband.de/brevier_engl/5/4/5_4.htm
http://www.ts.mah.se/utbild/mt7150/051212%20ceramics.pdf
http://www.virginia.edu/bohr/mse209/chapter13.htm
http://ceramics.org/learn-about-ceramics/structure-and-properties-of-ceramics/
http://www.keramverband.de/brevier_engl/5/5_1.htm
http://me.queensu.ca/courses/MECH270/documents/Lecture20CeramicsA.pdf
http://www.tarleton.edu/~tbarker/2033/Notes_Handouts/Powerpoint_notes/Ceramic_Materials_Module_7.pdf
http://users.encs.concordia.ca/~mmedraj/mech221/lecture%2018.pdf
http://media-2.web.britannica.com/eb-media/85/1585-004-168972D1.gif
http://global.kyocera.com/fcworld/first/process06.html

Ceramics

Recommandé

Recommandé

Contenu connexe

Tendances

Tendances (20)

En vedette

En vedette (20)

Similaire à Ceramics

Similaire à Ceramics (20)

Plus de Geology Department, Faculty of Science, Tanta University

Plus de Geology Department, Faculty of Science, Tanta University (20)

Dernier

Dernier (20)

Ceramics