Molybdenum - metalised layer on Al₂O₃

Tip

The cutting process described in the preparation table is also to be understand as a tip how better results can be achieved. Should this not be done, a separation of the Molybdenum layer can occur.

Should shrink-free Demotec 15 embedding material not be available, a fissure-free embedding can also be achieved with Demotec 10 and the "puddle technique". One mixes a small amount of Demotec 10 and fills the embedding mould to a maximum depth of 2 mm into which the sample is dipped several times in order to prevent the formation of bubbles and then left to harden and to cool. The sample is then filled with newly-mixed Demotec 10 in the embedding mould already used up to the desired height.

In dealing with open-pore ceramics and in order to avoid larger fractures it is often better to perform the sanding on SiC - paper rather than on a diamond disc.

	Picture 1 The interference contrast picture shows a good optical separation of the true Molybdenum layer of 5 to 6 µm and the diffusion layer of 24 to 27 µm. The blue marking in the picture serves as a scale for 30 µm.
	Picture 2 The light-field picture shows the transitional area between the metallised end surface and the outer shell of the ceramic section. The blue marking in the picture serves as a scale for 50 µm.

Preparation table

Cutting procedure

Before firmly clamping the sample, the sensitive metal layer was protected by a sheet of cork 4 mm thick. A metal-bonded diamond cutting-blade with a low diamond concentration 130 mm diameter, 0.4 mm thickness) was used. Only slight pressure was applied and the cutting direction went through the cork and the metal layer into the ceramic section, such that any pulling on the metallic layer was avoided.

Embedding

Cold embedding medium - 1.25 inches sample DEMOTEC 10.

Semi-automatic sanding

ECOMET 4 together with AUTMET 3 on nickel-bonded diamond disc, grain-size 30 µm at a speed of 160 RPM until the sample is level.

Semi-automatic polishing

ECOMET 4 together with AUTMET 3

Polishing medium	Grain-size	Base	Trial pressure [N]	Speed [RPM]	Time [min]
Color-diamond suspension	15µm	Ceramant	23	160 in reverse	15
Color-diamond suspension	6µm	Silkoflex	15	160 in reverse	8
Color-diamond suspension	3µm	Silkoflex	15	160 in reverse	8
Color-diamond suspension	1µm	Silkoflex	13	160 in reverse	6
SiO2 suspension	0,05µm	Mikromant® studded	11	160 in reverse	3