Thin films and nanostructured coatings for eco-efficient buildings - Nanotechnology in Eco-efficient Construction - page 172

Vacuum pump

Deposition
chamber

Substrate Nozzle

Film

Transfer pipe

Evaporation pipe

Evaporation
chamber

Tungsten oxidation

Induction heating
generator

Tungsten pellet

Pedestal

Synthetic air

8.11 Schematic image of a unit for advanced gas deposition arranged
for making tungsten oxide nanoparticles. From Reyes et al. (2004).

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now used to mass-produce nanoparticles that can be collected for later use
or for coating directly onto substrates. The technique and its implementa-
tion are described in detail in a topic by Hayashi et al. (1997).
Figure 8.11 illustrates an AGD unit; as shown, it is arranged for tungsten
oxide nanoparticle production (Reyes et al. , 2004) but the technique can be
used reactively or non-reactively to make nanoparticles of a large variety
of pure metals, oxides, nitrides, etc. Evaporation takes place in the lower
chamber into a laminar gas fl ow surrounding the vapour source. The vapor-
ized species are then cooled via collisions with gas molecules so that they
form tiny nuclei that subsequently grow in the gas fl ow. A thin transfer pipe
collects nanoparticles in a region at a controlled distance from the vapour
source and transports them in a gas stream that ends in the upper deposi-
tion chamber, which is maintained at good vacuum. A separate evacuation