Civil Engineering Reference
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superhydrophilic properties. In 2001 Pilkington started to develop photo-
catalytic glass, which has been available in the market since then. The
Pilkington Activ was successfully trialled in many countries such as the UK,
Ireland and North America. The product is currently available worldwide
and is applied in many commercial and private buildings. This is one of the
most successful photocatalytic products available in the market. The coating
is composed of a 15 nm layer of titanium dioxide deposited by chemical
vapour methods.
Saint Gobain Glass's Bioclean is another signifi cant photocatalytic glass
product available in the market. These glasses were produced by coating a
transparent layer of photocatalytic or hydrophilic material on the glass. An
Italian manufacturer, Gambarelli, has developed photocatalytic tiles using
titanium dioxide ceramic particles.
TOTO's (Japan) HYDROTECT tiles, with a photocatalytic antibacterial
function, has been available since 1993. HYDROTECT fi nds applications
in TOTO's own tile building materials, paints, and coatings. They also
licensed the technology to over 100 companies in Japan and overseas. About
270 patents have been registered in the photocatalytic technology domain
by TOTO Ltd.
42
Their representative products are white ceramic tiles for
exterior walls and home environments. They are fabricated by spraying a
liquid suspension containing TiO
2
powder or gel on the surface and then
heated to 600-800°C. Through the heat treatment, the TiO
2
is sintered and
strongly attached to the tile surface, forming a micrometer thick layer.
43
Turkish-based ceramic tile manufacturer VitrA has launched a photoac-
tive tile (http://www.vitratilescpd.com/faq/whats-photoactivity-2) to inhibit
bacterial growth and eliminate microorganisms through oxidation. Air pol-
lutants such as oxides of nitrogen and sulphur can also be removed using
this technology.
14.2 Important production parameters
14.2.1 Temperature stability of the photocatalyst
One of the key issues with using titanium dioxide as a photocatalytic mate-
rial in tiles and glass is the transition of the photocatalytically active phase,
anatase, to the non-photocatalytically active phase, rutile, which typically
occurs at 600-700°C. This is 300°C below the typical processing tempera-
tures for tiles.
The retention of a high stable anatase phase with visible light active
photocatalytic properties up to a temperature as high as
1000°C has not
yet been published or patented. Many proposed innovative and commercial
applications for photocatalytically active stable titania-coated materials
such as bathroom tiles, sanitary wares, and self-cleaning glass for the control
≥
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