Sub-µm-and nano-technologies for transparent components exhibiting highest strength, hardness and wear resistance together with an extreme thermal and chemical stability

Known "transparent" alumina ceramics exhibit low mechanical parameters and a low in-line transmission of unscattered light (< 15 %) because of coarse micro-structures (> 20 µm); in fact, they are optically not clear and rather translucent than transparent. The new sub-µm corundum ceramics (a-Al₂O₃, Fig. 1), avoid these shortcomings and can be manufactured with very complex shapes.

Fig. 1: Transparent components of sintered corundum with sub-µm microstructure. 4-point bending strength 650-700 MPa (3-pt: ~800 MPa), hardness HV10 > 2000. The transparency of the hollow component is demonstrated by a central wire and the XXX-marker on the backside.

• In-line transmission (wave length = 640 nm, aperture = 0.57 °) > 50 % at thickness 0.8 mm (Fig. 2).
• Same high infrared transmission as sapphire in the 3-5 µm range (Fig. 4).
• Extremely high strength (600-850 MPa), hardness (Fig. 4), scratch and wear resistance.
• High chemical stability in acids, bases, and agressive gases.
• Flexible shaping by casting (discs, tiles, complex hollow shapes); technology to be used also for other materials.

• Development of high-strength transparent ceramics, e.g. on the basis of corundum (a-Al₂O₃) with sub-µm/ nano microstructures.
• Alternative developments with commercial or with nanoscale raw materials.
• Technological investigations for upscaling supporting the development of new products; screening of raw materials and shaping approaches.
• Investigations of the technical performance in various applications.