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ceramic fabrication process

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ceramic can be fabricate by varieties of method but these are most commonly used . these are principle methods CVD directed metal oxidation sol-gel etc. – PowerPoint PPT presentation

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Title: ceramic fabrication process


1
CERAMIC FABRICATION
BY GOURAV ACHARYA PREETI VYAS
2
DEFINATION
  • Methods to produce a solid product of desired
    shape such as a film, fiber or monolith with
    desired engineering properties from suitable
    starting materials.

3
IMPORTANCE
  • Carefully done fabrication processes are
    responsible for better production of ceramic
    products.
  • As the fabrication process govern the
    micro-structure of the product, being
    manufactured, with desired properties.

4
RELATION DIAGRAM
5
CLASSIFICATION
  • (A)GASEOUS PHASE
  • (B)LIQUID PHASE
  • (C)SOLID PHASE

6
(A)GASEOUS PHASE
  • Gaseous Phase as a starting material
  • The process can further be divided in to three
    groups.
  • 1. Gas Phase Reactions
  • 2. Gas to Liquid Reactions
  • 3. Gas to Solid Reactions

7
Fabrication processes of Gaseous Phase
Starting Materials Fabrication Method Type of Product
Between Gases Chemical vapor deposition (CVD) Films, Monoliths
Gas Liquid Directed metal oxidation Monoliths
Gas solid Reaction bonding Monoliths, mainly for production of Si3N4 Sic
8
FABRICATION METHODS
  • A.1. Chemical Vapor Deposition(CVD)
  • Reaction between the gases.
  • Production of thin, thick films or monoliths.
  • Endothermic reactions(surfaces deposited may be
    heated).
  • Heterogeneous precipitation for better
    densification.
  • Non-oxides as well as oxides are fabricated by
    CVD.

9
Table 2- Important fabrication processes through
CVD
Reaction Temperature 0C Application
SiCl4 2H2O? SiO24HCl 700 1300 Films for Semiconductor devices, optical fibers
TiCl4 O2? TiO2 2Cl2 1200 -1500 Films for electronics devices
3SiH4 4NH3? Si3N4 6H2 1000 1800 Films for Semiconductors devices
3SiCl4 4NH3? Si3N4 12HCl 1200 1800 Films for Semiconductors devices
CH3Cl3Si?SiC 3HCl 1200 -1500 Composites
NH3 BCl3? BN 3HCl 1000 1300 Monoliths
W(CO)6?WC CO2 4CO 600 -1100 Coatings
10
Reactors in CVD
11
A.2. Directed Metal Oxidation
  • Processes involving the reaction between the gas
    liquid.
  • Production of porous dense materials as well as
    composites.
  • Composites with matrices not only of the oxides
    but also of
  • nitrides,borides,carbides or titanates.
  • Reacted product usually forms a solid protective
    coating thereby separating reactants.

12
  • Schematic diagram of structure
  • (a)Formation of a matrix of oxide unreacted
    metal by
  • direct oxidation
  • (b)Oxidation in the presence of a filler.

13
ADVANTAGES OF D.M.O.
  • Includes matrices of
  • Al2O3/Al, AlN/Al etc. or fillers of SiC,TiN,
    ZrN etc.
  • The growth of the matrix involve little or no
    change in dimensions.
  • Problem of shrinkage during densification, is
    avoided.

14
A.3. Reaction Bonding
  • The process of chemical reactions between a gas
    and solid.
  • Mainly with the fabrication of
  • Si3N4 SiC bodies.
  • Very low shrinkage occurs during the bonding
    process.

15
FLOW DIAGRAM OF RBSN
16
(B)Liquid Precursor methods
  • Process of converting the solution of the metal
    compound into a solid body.
  • Two methods are
  • (a.) SOL-GEL PROCESS
  • (b.) POLYMER PYROLYSIS

17
(a) SOL-GEL PROCESS
  • A solution of metal compounds or a suspension of
    very fine particles in a liquid (referred to as
    Sol) is converted in to a semi-rigid mass (the
    gel).
  • simple or complex oxides are produced by this
    route.
  • Simple Oxides such as alumina (Al2O3), Zirconia
    (ZrO2) .
  • Complex Oxides other than Silicates such as
    Barium Titanate
  • HYDROLYSIS

Si(OR)4 H2O   gt   HO-Si(OR)3 R-OH
CONDENSATION
(OR)3Si-OR HOSi-(OR)3 gt (OR)3SiOSi(OR)3
R-OH
18
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20
(b) POLYMER-PYROLYSIS
Two polymerization routes are quite prominent in
use. (i) Polysilazanes with Si? N in the main
chain
(ii) Polycarbosilanes with CH2 groups separating
the Si atoms in the main chain.
21
ADVANTAGES OF POLYMER PYROLYSIS
  • The Pyrolysis is usually accompanied by an
    appreciable loss in mass or considerable
    shrinkage.
  • More suitable for the production of films or
    fibers.
  • The polymers are also being considered for use as
    binders in the injection moldings of ceramics and
    as matrices for ceramic composites.
  •  Used for the commercial production of SiC
    fibers.

22
(C) Fabrication from Powders
  • Production of the desired bodies from an compact
    of finely divided solids(i.e. powders) by the
    action of heat.
  • Divided in two most widely used methods.
  • MELT CASTING
  • FIRING OF COMPACTED POWDERS

23
C.(1) MELT CASTING
  • Melting a batch of powdered raw materials.
  • Followed by cooling and forming to produce a
    solid finished shape.
  • Limited to the fabrication of glasses.
  • COMMON PROBLEMS
  • Formation of non-equilibrium phases.
  • Retention of residual glassy phase due to
    incomplete crystallization.

24
PRODUCTION OF GLASS GLASS CERAMICS (MELT CASTING)
25
C.(2) FIRING OF COMPACTED POWDERS
  • Used for production of GLASSES (not more)
    POLYCRYSTALLINE CERAMICS.
  • Traditional ceramics.
  • Depends upon the physical properties of the
    starting materials.
  • Plastic flow properties(according to the of
    water in body mixes)

26
Production of polycrystalline ceramics
27
Fig-Pressure required for making a plastic body
mix to flow at different water percentage.
28
Table .- Consolidation processes according to
water percentages in body mix.
Sl.No. Condition of Body mix Water content or consistency Process
1. Liquid or thick slurry 25 to35 (a)Slip casting under gravity Drain Casting Solid Casting Drain-solid casting (b)Pressure casting High Pressure casting up to 4.0MPa Medium Pressure casting up to 0.35MPa Injection Molding Hot Molding Tape casting Electrophoresis casting
29
Continue..
2. Plastic 10 to 15 (a)Soft plastic shaping Hand building Hand pinch Coiling Slab method (b)Plastic shaping Hand throwing Jiggering Jollying Motorized Jigger- Jolly Semi- Fully automatic Jigger-Jolly Roller Head Machines (c)Extrusion (d)Turning (e)Squeeze Forming
3 Semi-dry Pressing 5 to 8 (a)Mechanical Pressing (b)Tamping
4 Dry Pressing 1 to 5 (a)Hydrostatic Pressing (b)Quasisostatic Pressing (c) Isostatic Pressing (d)Ram Pressing
30
? ANY QUERY
31
THANKS FOR YOUR KIND ATTENTION
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