Ceramika

The anti-corrosive properties of most ceramics make them difficult to etch by standard metallographic etching techniques. Most useful etching techniques for ceramics include: thermal, molten salt and plasma etching. A good resouce for additional etchants can be found with the etchant database provided by PACE Technologies, http://www.metallographic.com/Consumables/Etch.htm

Sample Preparation: Ceramic materials must be properly prepared to reveal the true metallographic microstructure. A number of recommended procedures can be found at the following links:

http://www.metallographic.com/Procedures/Ceramic%20Description.htm

http://www.metallographic.com/Procedures/Engineer%20Ceramics%20Description.htm

http://www.metallographic.com/Brochures/Met-Manual-2b.pdf

CAUTION: Safety is very important when etching. Be sure to wear the appropriate protective clothing and observe all WARNINGS on chemical manufacturers SDS (Safety Data Sheets). Also review COMMENTS Section for each etchant.

Oxide Ceramics (e.g alumina, zirconia, etc.)

 Etchant Conc. Conditions Comments
Thermal etching in air Minutes to hours at 100-200°C below the sintering temperature AL2O3,
Al2O3-MgO
Molten Salt
Potassium hydrogen fluoride melt		 5-10 minutes in Pt crucible Al2O3,
Al2SiO5
Distilled water
Phosphoric acid		 15 ml
85 ml		 Boiling for 5 minutes to
2 hours		 Al2O3
Distilled water
Sulfuric acid		 50 ml
50 ml		 Boiling for 1-5 minutes ZrO2

Carbide Ceramics (e.g silicon carbide, tungsten carbide)

 Etchant Conc. Conditions Comments
Molten Salt
Sodium or potassium bicarbonate melt		 10 minutes in Pt crucible SiC
Hydrochloric acid
Hydrogen peroxide (30%)		 10 ml
10 ml		 Seconds to minutes WC

Nitride Ceramics (e.g. silicon nitride)

 Etchant Conc. Conditions Comments
Thermal etching in high purity nitrogen Several hours at 1600° C Si3N4
Molten Salt
Potassium hydroxide melt		 Seconds to minutes in Pt crucible Si3N4
Hydrofluoric acid 100% 10-15 minutes Si3N4

Boride Ceramics (e.g. zirconium boride, titanium boride)

 Etchant Conc. Conditions Comments
Latic acid
Nitric acid
Hydrofluoric acid		 30 ml
10 ml
10 ml		 Seconds to minutes ZrB2 ,TiB2