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CERAMIC, Similarities & Differences - Coggle Diagram
CERAMIC
CHAPTER 5 - GLASS & CERAMICS
1. Glass
Definition
inorganic solid material
Natural & abundant raw materials :
limestone
soda ash
sand
silica main component
Properties
hard but brittle
chemically inert
Not permeable :
gas
liquid
Resistance to :
heat
electricity
Types
a) Fused Glass
Properties
Chemical durability
High softening point
Expensive
High purity & optical transparency
Low coefficient thermal expansion
Application
Telescope mirrors
Optical fibers
Laboratory glasses
Lenses
b) Soda Lime Glass
heating silica with sodium oxide + calcium oxide
Properties
Low softening point
- different shapes produced
High thermal coefficient of expansion
Low chemical resistance
Application
Bottles
Glass containers
Light bulbs
Window panes
c) Borosilicate Glass
Boron oxide + soda-lime glass
Properties
Hogh softening point
Thermal shock resistance
Low thermal expansion coefficient
Chemiially resistance
Application
Lab glassware
Glass containers
Cookware
d) Lead Crystal Glass
made by
lead oxide
potassium oxide
Properties
High density
Attractive appearence
High reflective index
Application
Prism
Decorations
Decanters
Chandeliers
2. Ceramics
Definition
inorganic non-metallic solid compound
contains metallic & non-metallic element
aluminosilicate as main component
Properties
Hard & strong but brittle
High melting point
Heat & electrical insulator
Chemically inert
Opaque & porous
Application
Construction Materials
bricks
sinks & toilets bowls
roof tiles
Electrical Insulators
Medical Fields
dentures
posthetic limbs
Decorative Items
potteries
vases
wall tiles
Composite materials
3. Glass-Ceramics
Introduction
Produced by :
i) glass formed by glass-manufacturing process (heating & forming)
ii) glass cooled down & reheated to cause dense network cystal nuclei
glass partly crystallizes
nucleation agent added to control crystallization process
nucleation started, heat treatment continue at higher temperature to cause growth of crystalline
high density nucleation inhibits grain growth, leads to fine grain
no pressing & sintering
no pores
ceramic material produced by conversion of glass into polycrystalline through heat treatment
grain formation via phase transformation
grain size ; 0.1 - 1.0 micrometer
same chemical composition with glass, but typically crystalline range between 90-98% than glass, remainder unconverted vitreous materials
Properties
high thermal shock resistance
good dielectric properties
low coefficient thermal expansion
good biological properties
special properties of ceramic
low porosity
hermetic sealing properties
special optical properties
Application
Construction materials :
tale tops, interior & exterior wall
Electronic components :
photovoltaic substrates, ferroelectrics
Medical fields :
orthopedic, dental application
Consumer goods :
kitchenware, bakeware, cookware
Engineering components
CHAPTER 7 : CERAMIC PROCESSING ADDITIVES
Introduction
Purpose
control feed materials characteristics
achieve designed shape
control greenbody packing before firing
Features
added at low percentage except solvents
mostly organics, removed by sintering
inorganic additives leave residual
Types
1. Solvent / Dispersion Mediium
provide viscous mideum
enable fluidity
dissolve additional additives to achieve certain mechanical
disperse particle uniformly
Water :
low cost, safe, environmental friendly
mostly used (good solvent for polar & non-polar)
recycled when possible
Organic Solvents
Uses :
to achieve high solid loading
industrial trend
for requirement of :
i) higher boiling point
ii) better wetting
iii) require fast drying
iv) avoid contamination
Disadvantages :
flammable / even explosive
volatile
toxic, difficult to dispose
expensive
2. Dispersants
to help disperse ceramic particles in solvents & stabilize slurry against flocculation / sedimentation
Mechanism :
electrostatic
steric
electrosteric
Simple inorganic ions & molecules
For aqueous suspension :
simple ions & molecules can be effective dispersants
Formation (dissolution of electrolytes) :
preferred adsorption of certain ions on ceramic particle surfaced coupled with formation of diffuse layer of counter ions lead to electrostatic stabilization
Surfactants
have one polar head group and non-polar organaic tail that help dispersion of one phase (solid/liquid) in another liquid phase
Nonpolar tail :
repels water/other polar substances while attracts non-polar molecules
Polar head :
attracts water/polar solvents while repels non-polar solvents
Features
Nonionic surfactant
Anionic surfactant
Cationic surfactant
Amphoteric surfactant
Low to medium molecular weight polymer
molecular weight of hundreds to thousands
Types :
non-ionic
ionic (polyelectrolytes)
Features :
i) solubility depends on chain side group
ii) adsorb on particle surface via Van der Waals / coordination
iii) may use as binders
3. Binders
improve strength of the as-formed product to provide strength for handling before product is densified by firing
Classification
Colloidal
Molecular
Selection
Burnout Characteristics :
temperature
inorganic residual
atmosphere
volume change
Compatibility with dispersant :
binder should not displace dispersants
suspension becone flocculated
Molecular Weight :
impacts viscosity
Glass Trasition Temperature :
too high : rigid
too low : soft
Solubility in solvent
Cost
Additional Effects
Plasticity :
enable plastic deformation
Flocculation :
interaction between particles with adsorbed polymer binder
Thickening & Rheological Control :
increase viscosity
Liquid Retention :
reduce liquid migration
4. Plasticizers
small liquid molecules added in small amount to plastics or ceramics paste which causes polymer binder to pack less densely & reduce Van der Waals forces that binds polymer together
Features :
liquid with low vapor pressure at molding temperature
can be combined with water or other solvents
increase water absorption
Other
Antifoaming agent
Foaming agents
Lubricants
Coagulents
CHAPTER 6 : CERAMIC FABRICATION PROCESS
Gas-Phase Reaction
2. Directed Metal Oxidation
reaction between liquid (molten metal) and gas : directed oxidation of molten metal
Fabrication :
Liquid metal oxidizes :
contact with oxygen, forming thinlayer of ceramic
Phase of Products
Unreacted products
Oxidation products
3. Reaction Bonding
Types
Reaction Bonded Aluminium Oxide (RBAO)
mixture of aluminium and zirconia is milled, dried and compacted to green body
during heat treatment, aluminium oxidizes to nanosized and undergo phase transformation
oxidation of Al is used to partially copensate for shrinkage due to sintering
Reaction Bonded Silicon Carbide (RBSC)
reaction between solid and liquid
mixture of silicon carbide formed into green body by pressing/extrusion/injection molding
binder burned off to microporous carbon by pyrolysis
reaction product crystallizes on SiC grains and bonds together
infiltration and reaction process occur simultaneously
Reaction Bonded Silicone Nitride (RBSN)
silicon powder consolidated by variety of methods to form billet
preheated in argon after which can be machined to required component shape
component undergoes nitridation
Porous ceramic preform become dense covalent ceramic by reacting with gas/liquid
1. Chemical Vapor Deposition
vapor phase reactive molecules that contains required constituent are chemically reacted at surface to form high purity, high performance solid film
reactant gases chosen to react and produce specific film
Advantages :
low reaction temperature
Disadvantages :
slow deposition rate
limit for formation of thin film & coating
not suitable for mixture of materials
Process :
transport of reactants by forced convection into deposition region
transport of reactants by diffusion from main gas stream thru boundary level to water surface
adsorption of reactants
Surface processes (chemical decomposition, surface migration to attachment site)
desorption of by-products
transport of by-products by diffusion back to gas stream
transport of by-products by forced convection away from deposition region
Solid & Liquid Phase Reaction
Solid-Phase Reaction
Melt Casting
melting a batch of raw materials followed by forming into shape by one of several methods (csting, rolling, pressing, blowing, spinning)
Glass Ceramic Route :
raw materials melted and formed into shape in glassy state by conventional glass fabrication method and crystallized usiing heat treatment
lower temperature to hold induce nucleation of crystals
one or more higher temperature hold to promote growth of crystal throughout glass
Advantages :
economical fabrication
improved properties of glass ceramics
Firing of Compacted Powders
Process :
powder
mixing
consolidation
debinding
shaped powder form
firing
dense polycrystalline product
Consolidation
dry / semi-dry pressing of powder in die
mixing of powder with water / organic polymer to produce plastic mass by pressing
casting from concentrated suspension
Sintering
Firing
definition : when process occur during heating stage are fairly complex
green body heated to produce desired microstructure
reduction in surface free energy of consolidated mass of particles
Liquid-Phase Reactions
Sol-Gel Processing
Advantage :
high purity materials can be produced (ease of purification)
good chemical homogenity can be produced (mixing of constituents occur at molecular level)
lower densification temperature
Disadvantage :
expensive starting materials
difficulties of conventional drying
solution of metal compounds or suspension of very particles in liquid (sol) converted to highly viscous mass (gel)
Process :
Polymer Pyrolysis
Advantage :
ease of processing
low conversion temperature to non-oxide ceramics
degraded toxic components by use of high temperature
reduction of water volume
produce gases as fuel (limit supply of external fuel)
Disadvantage :
high operational and investment cost
expensive preceramic polymers
air purification installation is necessary
produce dangerous waste
pyrolytic decomposition of metal organic polymeric compounds by high temperature to produce ceramics
Silicone Carbide :
polycarbosilane dissolve in organic solvent
melt is spun into fiber
fiber undergo rigidization step
pyrolysis to produce SiC
ceramic yield increase to 80% wt
Silicone Nitride :
preceramic polymer prepared by ammonolyis of methylchlorosilanes, followed by polymerization of silazane product catalyzed by potassium hydride
Similarities & Differences
(i) Similarities
Do not corrode
Chemical resistance
Good electrical & heat insulator
Can withstand compression
Hard but brittle
(ii)Differences
Atomic Structure :
Glass : non-crystalline
Ceramic : crystalline, semi-crystalline, non-crystalline
Glass Transition :
Glass : :check:
Ceramic :red_cross:
Processing :
Glass : can be melted & remoulded
Ceramic : cannot be melted & remoulded
Melting Point :
Glass : no melting point
Ceramic : high melting point
Appearence :
Glass : trasparent
Ceramic : mostly opaque
Cost :
Glass : cheap
Ceramic : mostly expensive
