1. Rate Controlled Sintering - Application
in Advanced ceramic process
E .SIVANAGI REDDY
12ACPA02

2. OUTLINE 0F THE TALK
• Ceramics
• Sintering
• Types of sintering
• Process of sintering
• Consequence of sintering
• Rate controlled sintering
• Summary

3. ceramics
• A ceramic is an inorganic, non-metallic solid prepared by the
action of heat and subsequent cooling
• Ceramics that with minor exceptions have been developed
with in the last 50 years or so are called advanced ceramics.
• Advanced ceramics include ceramics for electrical, magnetic,
electronic, and optical applications

4. Sintering
• Sintering is the process by which a powder compact is
transformed to a strong, dense ceramic body upon heating.
• Sintering could eliminate most pores in porous green body and
compress residual pores, and bring grain growth and improve
binding among grains
• Driving force for sintering: Lowering of free energy
I. The curvature of particle surface
II. An extremely applied pressure
III. Chemical reaction

5. Stages of Sintering
Three stages:
1. Initial stage :
2. Intermediate Stage :
3. Final stage:

6. Factors effecting
sintering
• Temperature
• Time duration
• Green density
• Uniformity of green density
• Atmosphere
• Impurities
• Size distribution
• Particle size

7. FE-SEM micrograph of Mg/1 wt% HAp sintered at
different times, (a) 1 min, (b) 2 min, (c) 3 min and
(d) 4 min

8. Material transport mechanisms
Transport Material Material sink Related parameter
mechanism source
Lattice diffusion Grain Neck Lattice diffusivity, Df
boundary
Grain boundary Grain Neck Grain boundary
diffusion boundary diffusion, Db
Viscous flow Bulk grain Neck Viscosity, Ƞ
Surface diffusion Grain Surface Neck Surface diffusivity,
Ds
Lattice diffusion Grain Surface Neck Lattice diffusivity, D l
Gas phase
transport Gas surface Neck Vapour pressure
1. Evaporation/ difference Δp
condensation Gas surface Neck Gas diffusivity, Dg
2.Gas diffusion

9. Rate-Controlled Sintering
Rate – controlled sintering is done in two ways
I. controlling Heating rate
II. controlling temperature
SEM images of KNN sintered samples at: a) 1060, FE-SEM micrograph of Mg sintered at different
b) 1080, c) 1100 and d) 1120°C for 2 h heating rate, (a) 200 °C/min, (b) 400 °C/min,
(c) 500 °C/min and (d)1200 °C/min

10. Summary
• Sintering is the process by which a powder
compact is transformed to a strong, dense
ceramic body upon heating
• The driving force behind sintering is lowering of
free energy.
• Three stages of sintering depends of different
parameters.
• Rate controlled sintering basically done in
Temperature and heating rate controlling
methods.

11. References
• Suk-Joong L. Kang,
Sintering : Densification, Grain growth and Microstructure
Elsevier(2005)
• M.N Rahaman,
Ceramic processing and Sintering 2/e
CRC Press(2007)
• M.W Barsoum
Fundamentals of Ceramics
CRC Press(2003)