Nanotechnology Lect.7

Ceramic and glassy materials
Ceramic materials by definition are ionically bound; they are hard materials,
both electrically and thermally very stable. Included in this category are, for
example, Al2O3, Si3N4, MgO, SiO2, Na2O, CaO and ZrO2. Ceramics are
characterised by being hard yet brittle, therefore, in many cases, they are used
as composites where they are mixed with other materials (e.g. metals) to
increase their mechanical performance. Composite hard nanocoatings are
particularly important for cutting tools.
Ceramics exist both in a crystalline and non-crystalline form (e.g. the broad family
of ?glass‘). Nanostructures within the material have important consequences for
their properties.
? Porous alumina
Porous alumina membranes produced by anodic aluminium oxidation are
characterised by having hexagonally close-packed channels with diameters ranging
from 10 to 250 nm or greater. This material is often used as a template for the
synthesis of other materials.
? Zeolites
Zeolites are natural crystalline materials with pores having regular
arrangements (Figure 22). They are also often used in the template synthesis
of nanomaterial. They can also be used to prepare organised structures of a
certain material to confer new optical properties on it. For instance, selenium
can be incorporated into the channels of mordenite, a natural zeolite. The