This Presentation enlists and describes most ceramic process and most parameters which affect these ceramic processing. A reader shall understand the basic of these presented process to fabricate unique ceramic materials

1. A Review on Advanced Ceramic
Processing Techniques
Seminar and Technical Writing September 2021
Presented By: Alokjyoti Dash
Roll No.: 518CR6009
Faculty advisor: Dr. Debasish Sarkar
Department Of Ceramic Engineering

2. Contents
• Introduction
• Difference between Traditional and Advanced ceramics
• Raw materials
• Structure
• Manufacturing process
• Function
• Fabrication of ceramic compounds
• Dry forming
• Powder injection molding
• Tape casting
• Slip casting
• Extrusion
• Gel casting
• Freeze casting
• Conclusion

3. Introduction
• Ceramic materials provide interesting product capabilities and functions
as compared to other materials, which includes thermal insulation,
lightweight, high specific surface area, thermal shock resistance and so
on.
• Ceramics are typically inorganic and non-metallic solids, having a
relatively high melting points and require high temperature for processing
and applications.
• Now-a-days, ceramics’ is considered as a new generation of materials
which impact day-to-day lives. Many industries like electronics,
computers, communications, aerospace rely on them for a number of
uses.
• Recent attempts have been made to divide it into two parts: traditional
ceramics and advanced ceramics for easy understanding.
References
• Otitoju, Tunmise Ayode, Patrick Ugochukwu Okoye, Guanting Chen, Yang Li, Martin Onyeka Okoye, and
Sanxi Li. "Advanced ceramic components: Materials, fabrication, and applications." Journal of industrial
and engineering chemistry 85 (2020): 34-65.

4. Difference between Traditional and Advanced ceramics
• Traditional ceramics bear a close relationship to those materials that have
been developed since the earliest civilizations of human history, which are
clay based structural products, pottery, clay based refractories, cement,
glasses etc.
• Whereas advanced ceramics are different from traditional ceramics by their
higher strength, tailorable properties, improved toughness, higher operating
temperatures, which make up modern ceramic components
.
• Traditional ceramics represent a major part of the ceramics industry, but the
interest in recent years has focused on advanced ceramics.
• Due to their features, advanced ceramics can be considered for
environmental uses and energy applications, as well as for use in bio
ceramics, composites, functionally graded materials, smart materials and so
on.
References
1. Prasad, S. E. "A review of:“INTRODUCTION TO THE PRINCIPLES OF CERAMIC PROCESSING” James S. Reed John Wiley &
Sons, New York, NY 485 pages, hardcover, 1988." MATERIAL AND MANUFACTURING PROCESS 5, no. 1 (1990): 133-134.

5. Traditional Ceramics Advanced Ceramics
Raw Materials Natural minerals such as clay,
feldspar, quartz.
Synthetic high-quality powders. These are
responsible for the provision of special
functions and
qualities.
Structure The structures are decided by the
composition of the clay. More
complicated chemical structures and
compositions with more impurities.
The chemical structures of advanced
ceramics are clear and simple
with high purity.
Manufacturing
Process
The minerals for traditional ceramics can
be directly used for wet
moldings. The green body requires no
further processing after sintering
with the temperature between 9000
C to
14000
C.
Mostly done by dry pressing, isostatic
pressing, injection moulding etc., which
may require additional post sintering
processes. Advanced methods like vacuum
sintering, protection atmosphere
sintering, hot pressed sintering, high
temperature isostatic pressing, reaction
sintering process, under a higher sintering
temperature from 12000
to 22000
can be
used.
Function Mainly produced for daily work or
use as building materials.
Great potential for use in sound,
magnetism, heat, electricity, light, biology,
high strength, corrosion resistance and so
Advantages and disadvantages of traditional and advanced ceramics

6. Fabrication of ceramic compounds
• The fabrication of ceramics can be done by several methods, some of which are
originated from earliest civilization.
• From favorable starting materials, ceramic components can be fabricated
accordingly into desired shapes like hollow fibers, films, monoliths and discs.
• The preparation involves heating of ceramic powders which must undergo special
handling to control the heterogeneity, chemical compositions, purity, particle
size, particle size distribution (PSD) and specific shape.
• Typically, it involves four stages; material preparation, processing, sintering and
finishing.
• There are varieties of methods involved to process ceramics components
including dry forming, wet forming, gel-casting, thixotropic casting, direct
foaming, freeze casting and phase inversion.
References
1. Otitoju, Tunmise Ayode, Patrick Ugochukwu Okoye, Guanting Chen, Yang Li, Martin Onyeka Okoye, and Sanxi Li.
"Advanced ceramic components: Materials, fabrication, and applications." Journal of industrial and engineering
chemistry 85 (2020): 34-65.

7. Dry Forming
• In this method, ceramic materials are prepared from processing of dry powders. It
depends upon two factors, method of material preparation, size and shape of the
material to be formed.
• Two types of pressing are most commonly used. Uniaxial die pressing and Cold isostatic
pressing.
• Uniaxial die pressing is a simple and most common method for fabrication of relatively
simple shaped ceramic compacts at a higher volume of production.
• Cold isostatic pressing has better advantages against uniaxial die pressing, as it can
provide more complex shapes with precision.
• Ceramic powders are fed into a uniaxial hollow die with one or more punches
(according to the shape) in case of uniaxial while liquid pressure is used for pressing
action in cold isostatic pressing.

8. Fig. Schematic illustration of uniaxial die pressing and cold isostatic pressing

9. Powder Injection Molding
• Powder injection molding (PIM) is an ideal process to manufacture complex
shapes, functional parts with a high precision.
• It basically involves four steps, feedstock preparation, injection molding, debinding
process and sintering.
• Ceramic injection molding is similar to plastic injection molding. Basically, the
same equipment that is used for polymers can be used for ceramic components.
• The feedstock is prepared by the mixture of ceramic powders and polymeric or
organic binders (about 40 wt.%).
• There are two key issues of great significance associated with PIM in ceramics
including wall thickness and draft angle as there is a risk of cracking of walls of the
material during debinding process.

10. Fig. Ceramic injection molding process
Fig. Schematic illustration of injection molding

11. Tape Casting
• Tape casting was first introduced by Glen N. Howatt in the mid-1940s for the
production of thin piezoelectric materials.
• It is a versatile approach for fabricating thin sheet like materials. It is also called as
scraper method or doctor-blade method.
• It involves three basic steps; slurry preparation (non-aqueous slurry with additives
and binder), tape casting to form films, drying, binder removal and sintering of
films.
• The tape-casting is a process of feeding the slurry through a micro screed referred
to as the doctor blade, which screeds the slurry into a thin layer of fixed
thickness, and then is rapidly dried via evaporation.
• According to the solvent nature of the slurries, tape casting is divided into two
categories such as non-aqueous and aqueous tape casting.

12. Fig. Tape casting process

13. Slip Casting
• Slip casting is specifically for making hollow components/shapes, which is low cost
and combines shape simplicity with complexity as compared to other component
processing techniques.
• Slip-casting involves the process of filling a porous mold, usually a mold, with a
ceramic slurry.
• When a certain thickness of the cast is produced, the extra amount of slip is taken
out and the cast is dried at room temperature. After it is fully dried, the binder is
burnt out via sintering of the casted product.
Fig. Slip casting process

14. • The most common material used as mold in slip casting is Gypsum (CaSO4.2H2O) which is
formed from the reaction of plaster of paris and water.
• The mechanics of slip casting is mainly based on the flow of liquid through the porous
consolidated layers.
• The flow of liquid into the pores follows Darcy’s law which is described as,
J=
𝐾(
𝑑𝑝
𝑑𝑥
)
ƞ𝐿
J = Flux of liquid
K = Permeability of the porous medium
dp/dx = pressure gradient in the liquid (it arises due to the capillary action of the porous
medium)
Ƞ L = viscosity of the liquid
• Thorough observation should be taken care of during the preparation of slurry, as the
ceramic powders are not well dissolved in water.

15. • As the liquid flow occurs through porous consolidated layers, the resistance of the
mold to the liquid flow is neglected.
• In this case, an application of Darcy’s law leads to a parabolic relation for the
increase in the thickness of the cast with time. Which is,
𝐿𝐶
2
=
2𝐾𝐶𝑝𝑡
ƞ𝐿(
𝑉𝐶
𝑉𝑆
−1)
• The rate of consolidation decreases with time, and this limits the slip casting
process to a certain thickness of the cast.
• Also the capillary suction pressure plays a vital role in the flow of liquid into the
pores. It can be expressed as,
p= Δpc+ Δpm
Δpc = pressure difference in cast.
Δpm = pressure difference in mold.

16. Extrusion
• Extrusion is another forming method where the ceramic slurry is extruded via a die and
produces articles of semi-infinite length with fixed cross-section.
• The main difference from injection molding is that there is no die cavity in extrusion,
which allows forming parts with unlimited length.
• Before the process, two important factors should be verified first for an efficient
extrusion process. Those are, the ceramic-polymer mixture must flow above a certain
yield stress and strength of the shaped material must be strong enough to retain its
shape despite of gravitational effect or in handling process.
• It is commonly used for the manufacturing of bricks, pipes, as well as ceramic tubing.
• Generally, two types of extruder are used, piston (plunger) type and screw (auger)
type. The design of piston extruder is simple whereas the screw extruder has a
complex one.

17. Fig. Schematic of extrusion process.
• The extrusion process involves five steps, (a) Blending, (b) Pugging, (c) Extrusion, (d)
Cutting and drying and (e) Sintering .
• In order to control the rheology of the suspension, additives are used; for example,
surfactants, coagulants, binder, deflocculants, plasticizer.

18. Gel Casting
• Gel casting is a promising forming process developed to overcome some of the
limitations of other complex shape techniques like slip casting and injection
molding.
• This process does not shrink the powder compact in the mold or remove any
component. Rather, dispersing the medium is either solidified via polymerization or
via trapping voids or molecules within the particle system.
• In gel casting, the essential components of the process are reactive organic
monomers that can be polymerized. The monomer solution is composed of a
solvent (typically water), a monomer that forms a polymer chain, a cross-linking
monomer, and a free-radical initiator.
• This process has evolved into an attractive ceramic forming process to manufacture
large-sized, near-net-shape, complex ceramic parts, high-quality with defined
threshold strength.
• However, before processing, it is required to determine the optimum gelation
speed to produce a desired complex structure. Also the rheology of the slurry has
to be specified according to the complexity of shapes.

19. Fig. Schematic illustration of gel casting process of porous ceramic
• The ceramic slurry is prepared by using a monomer as a solvent. The particle packing should
be high enough to maintain a certain handling stress of the green body.
• So the slurry should have a good particle concentration along with accurate rheological
property for a better flowability.

20. Freeze Casting Process
• Freeze casting is a solidification route capable to produce functionalized ceramic
components with highly-tunable porosity and has attracted a lot of consideration
due to its versatility, environmentally friendly character, and simplicity.
• Freeze casting involves physical interactions rather than chemical interactions, and
the freeze cast microstructure is not strongly dependent on the materials’ chemical
composition.
• The freeze casting (ice templating) process involves four essential steps which is
depicted in the following image.
• Slurry preparation.
• Solidification of the slurry.
• Sublimation of the solvent.
• Sintering.

21. • Freeze casting uses directional freezing of, generally, ceramic suspensions. The negative
replica of the ice template the architecture of the scaffolds which result in a layered
porous material.
• The porosity during the process may be tuned via a change in the suspension
characteristics (such as particle fraction, additives, fluid type) and solidification
conditions (such as freezing components material, mold design, freezing component
temperature, and solidification technique).
• In summary, freeze-casting starts with preparing the stable aqueous or non-aqueous
colloidal suspension, pouring the suspension into the mold, molded suspension freezing,
sublimating the solidified phase under reduced pressure, and sintering to consolidate a
porous structure.
Fig. Schematic illustration of gel casting process of porous ceramic

22. Fig Particle entrapment by the ice crystals during freeze casting process
• The particles accumulate in the space between the crystals, leading to the
formation of a lamellar material.
• The thickness of lamellae is controlled by ice growing characteristics of ice crystal
and particle moving speed.
• Different types of solvents are used for certain purposes. For example, to fabricate
layered pores water is the best choice whereas for randomly oriented pores
camphene is used as the solvent.

23. Conclusion
• Various shapes and dimensions of ceramics can be fabricated by following the
processing routes like slip casting, gel casting, powder injection molding, cold isostatic
pressing, freeze casting, extrusion process.
• Bulk products (3D structures) can be manufactured with slip casting, freeze casting
process, whereas gel casting, powder injection molding are useful for producing disc
like shapes (or tube shapes for electrical purpose).
• However, the post processing of the ceramic green body (drying, binder burn out,
sintering temperature), takes an important role in maintaining the strength, porosity,
crystal or grain growth of the ceramic body.
• Apart from other conventional methods of fabrication (solid state, sol gel process),
these advanced routes have the advantage of producing highly tuned materials with
better functionality.

24. Reference
1. Otitoju, Tunmise Ayode, Patrick Ugochukwu Okoye, Guanting Chen, Yang Li, Martin
Onyeka Okoye, and Sanxi Li. "Advanced ceramic components: Materials, fabrication,
and applications." Journal of industrial and engineering chemistry 85 (2020): 34-65.
2. Jabbari, M., Regina Bulatova, A. I. Y. Tok, C. R. H. Bahl, E. Mitsoulis, and Jesper Henri
Hattel. "Ceramic tape casting: a review of current methods and trends with emphasis
on rheological behaviour and flow analysis." Materials Science and Engineering: B 212
(2016): 39-61.
3. Studart, Andre R., Esther Amstad, and Ludwig J. Gauckler. "Colloidal stabilization of
nanoparticles in concentrated suspensions." Langmuir 23, no. 3 (2007): 1081-1090.
4. Hubadillah, Siti Khadijah, Mohd Hafiz Dzarfan Othman, Takeshi Matsuura, A. F. Ismail,
Mukhlis A. Rahman, Zawati Harun, Juhana Jaafar, and Mikihiro Nomura. "Fabrications
and applications of low cost ceramic membrane from kaolin: A comprehensive
review." Ceramics International 44, no. 5 (2018): 4538-4560.
5. Ruys, Andrew. "Processing, structure, and properties of alumina ceramics." Alumina
ceramics: Biomedical and clinical applications, Woodhead Publishing (2019): 71-121.
6. Deville, Sylvain. "Freeze‐casting of porous ceramics: a review of current achievements
and issues." Advanced Engineering Materials 10.3 (2008): 155-169.
7. S. Deville, Ice-templating and freeze-casting: control of the processes, microstructures,
and architectures, in: Freezing Colloids: Observations, Principles, Control, and Use,
Springer, Cham, 2017, pp. 351–438.

25. THANK YOU