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REPLICATION TECHNIQUE

AIM

To prepare a ceramic product with controlled macro-porosity by

replication technique.

REQUISITES

Polymer Foam, Beaker, Fireclay slurry.

PRINCIPLE

Replication involves coating a flexible, open-cell polymer foam with

ceramic slurries. After removal of the excess slip by squeezing and subsequent

drying, the polymer is burned out and the ceramic sintered in a single step. It is

a simple technique to produce a ceramic with controlled macro-porosity.

PROCEDURE

A Polymer foam was selected, may be of polyurethane or polyvinyl

chloride. The Ceramic slurry was prepared with fireclay and china clay (binder)

such that fireclay-70%, china clay-30% and required amount of water was

added, to make a suitable suspension with appropriate rheological properties.

Flocculating agents were also added to improve the adherence of the slurry to

the polymer material. The polymer foam was then dipped into the slurry and

squeezed such that the polymer was able to absorb the slurry and should burn

out completely on firing. The excess slip was squeezed out, dried, fired to burn

out organics and finally it was sintered to get a ceramic with controlled

macroporosity.

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FLOWCHART

RESULT

Thus, a ceramic product with controlled macro-porosity was prepared by

replication technique.

Polymer Foam

Dipped in Ceramic

Dried

Squeezed

(to remove excess slurry)

Fired

(to burn out organics)

Ceramic Product

(with controlled macro-

orosit )

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Plasticiser (PEG)

Mixed with Water & Stirred

Suspension

Shaped into a Thin Coat

Dried

Binder (PVA) Zirconia Powder

Coated over a glass plate

(coated with releasing agent)

Removed from Glass

plate using Doctor Blade

Zirconia Tapes

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100 parts of 4.5 %AlCl3Solution

75.3 parts of 10.9 %

Na2CO3Solution

Dried in Air Bath

Washed & Filtered

Aged

Alumina Gel

Mixed in Ma netic Stirrer

Dr Gel

Dis ersed in Water

Alumina Gel Slurry

(10 % Al2O3)

Nano Al2O3 Powder

Resultant is Ground

Hydrothermal Treatment in

Autoclave

Acetic Acid

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Zirconium Oxy-chloride

Mixed

Distilled Water

Continuous Stirring

White gelatinous

precipitates

Thick Gel

Filtered & Washed

Ammonia

Oven Dried

Milled

Calcined

Zirconia Powder

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AIM

To prepare zirconia powder by precipitation technique

APPARATUS REQUIRED

Beaker, China dish, Magnetic stirrer, Drier, Furnace, pH meter

REAGENTS REQUIRED

Zirconium Oxy-chloride, Distilled Water, Ammonia

PROCEDURE

A saturated solution of Zirconium Oxy-chloride (ZrOCl2.8H2O) was

prepared with distilled water. The solution was well mixed in magnetic stirrer

and . Adequate quantity of ammonia was added to the solution drop by drop

until the pH was around 10 - 10.5. The pH of the solution was monitored

frequently. This hydrolysis yielded while gelatinous precipitates which were

filtered and washed with distilled water. The precipitate was then oven dried at

110C for 12 hours. Later, the dried precipitate was calcined at around 400 -

700C. The calcined precipitate was then ground to get the zirconia powders.

The Flow sheet for the process has been given below:

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RESULT

The Zirconia powder was prepared successfully by precipitation

technique.