ceramic powder forming

V.M. Sglavo – CerSciTech - UNITN 2011

Forming technologies from powders pressing!

-!

granulated powder!

extrusion, injection moulding!

-!

ceramic paste!

tape casting, slip casting!

-!

ceramic suspension!

water, organic solvent

powder

solvent formability

additives deflocculant, binder,! plasticizer, lubricant

V.M. Sglavo – CerSciTech - UNITN 2011

Granulation • direct granulation (pellettization)

water jet powder

granules

500 µm

Principles of ceramics processing, 2nd ed., J.S. Reed, J. Wiley & sons, 1995!

[mm/h]

V.M. Sglavo – CerSciTech - UNITN 2011

Introduction to the principles of ceramic forming, J.G. Heinrich, CFI, 2004!

V.M. Sglavo – CerSciTech - UNITN 2011

• spray drying

Principles of ceramics processing, 2nd ed., J.S. Reed, J. Wiley & sons, 1995!

V.M. Sglavo – CerSciTech - UNITN 2011

Granules shape

ΔT

ΔT

ΔT

ΔT

0% binder

deformability!

1% binder

ΔT

4% binder

ΔT

V.M. Sglavo – CerSciTech - UNITN 2011

Example: alumina granules

counter-current drying air

dispersant = citric acid (0.25 wt%) binder = PVA (1 wt%)

J. Ceram. Sci. Tech., 02 [02] 75-88 (2011)!

V.M. Sglavo – CerSciTech - UNITN 2011

granule 1

J. Ceram. Sci. Tech., 02 [02] 75-88 (2011)!

granule 2

granule 3

V.M. Sglavo – CerSciTech - UNITN 2011

Pressing

punch! filling shoe!

mould!

p = 20-100 MPa

ease of filling

Principles of ceramics processing, 2nd ed., J.S. Reed, J. Wiley & sons, 1995!

V.M. Sglavo – CerSciTech - UNITN 2011

Principles of ceramics processing, 2nd ed., J.S. Reed, J. Wiley & sons, 1995!

V.M. Sglavo – CerSciTech - UNITN 2011

additives

granules

Principles of ceramics processing, 2nd ed., J.S. Reed, J. Wiley & sons, 1995!

V.M. Sglavo – CerSciTech - UNITN 2011

Pressing & porosity!

duttile!

Principles of ceramics processing, 2nd ed., J.S. Reed, J. Wiley & sons, 1995!

Introduction to the principles of ceramic forming, J.G. Heinrich, CFI, 2004!

V.M. Sglavo – CerSciTech - UNITN 2011

Principles of ceramics processing, 2nd ed., J.S. Reed, J. Wiley & sons, 1995!

V.M. Sglavo – CerSciTech - UNITN 2011

Pressure distribution! without lubricant p = 8.83 MPa

p = 200 MPa

132

pressione (MPa)

densitĂ (%)

Introduction to the principles of ceramic forming, J.G. Heinrich, CFI, 2004!

Principles of ceramics processing, 2nd ed., J.S. Reed, J. Wiley & sons, 1995!

V.M. Sglavo – CerSciTech - UNITN 2011

D

density gradients: • • • •

A

absence of lubricant (B, C) uneven filling (B) L/D >2 (A, B) too high compaction (sping-back) (A, B, C)

B

L

OK

C Principles of ceramics processing, 2nd ed., J.S. Reed, J. Wiley & sons, 1995!

V.M. Sglavo – CerSciTech - UNITN 2011

Isostatic pressing!

flexible mould (rubber)

p ≤ 100 MPa

p ≤ 500 MPa

flexible cylinder (rubber)

liquid (oil)

é limited pressure gradients! ê limited geometric shapes!

Principles of ceramics processing, 2nd ed., J.S. Reed, J. Wiley & sons, 1995!

V.M. Sglavo – CerSciTech - UNITN 2011

dry bag!

Introduction to the principles of ceramic forming, J.G. Heinrich, CFI, 2004!

V.M. Sglavo – CerSciTech - UNITN 2011

wet bag!

Introduction to the principles of ceramic forming, J.G. Heinrich, CFI, 2004!