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The material chiefly used as
a photocatalyst is "Titanium dioxide".
What kind of material is this "Titanium dioxide"? |
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 Titanium
dioxide... |
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Titanium dioxide is a
harmless substance widely applied in various fields
such as cosmetics, toothpaste and paints. For these
uses, titanium dioxide
has been used as the white paints. Most of titanium
dioxide that are manufactured also in the present
are used as the paint. Titanium
dioxide that is spent on the photocatalyst is
still not a lot.
Titanium dioxide that is
used as the photocatalyst is mainly anatase-type
crystal structure.
There are 3 kinds crystal structure of titaniumu dioxide,
| Rutile type ( the
high temprature type ) [Tetragonal-type ] |
| Anatase type ( the
low temprature type) |
| Brookite type [orthorhombic
type]. |
Generally rutile type is used for pigment of paint.
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Unit Lattice Figure
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Rutile
type
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Anatase
type
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| How should I use
the titanium dioxide as a photocatalyst? |
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| How
to prepare... |
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In the case the powder of titanium dioxide is used as
the photocatalyst, it's nessesary to stick powder on the
substance. The methods to stick powder are as follows. There
are the following methods of the fixation, |
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Methods of the titanium dioxide
coating
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Slurry
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The one that is dispersed the powder
of titanium dioxide to water etc.
However the coated film with this is very fragile
and this durability is low. |
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Organic binder
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In the case that an organic
binder is used, the binder itself is decomposed and
powder of titanium dioxide comes off it. Therefore
the use of the organic binder is not appropriate. |
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Inorganic binder
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In the case that an inorganic binder
is used, decomposition of binder doesn't happen and
the durability is good. Therefore the efficienncy
is bad, because only powder of titaniumu dioxide that
is out in a surface can work as the photocatalyst.
This means that a lot of powder of titanium dioxide
become necessary. |
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There are good respect and bad
respect in fixation as stated above. How should I do to
use the titanium dioxide efficiently as a photocatalyst?
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| The
thin-film of the photocatalyst |
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In collaboration with National
Industrial Research Institute of Nagoya, we
succeded in developing the coating technology of photocatalytric
thin-film that can cover all surface only with TiO2, instead
of using powdery TiO2 to solve the problem of photocatalyst
film that was made by the method that was showed above
" Methods of titanium dioxide coating "
Our thin-film coating of the photocatalyst is prepared
with titanium alkoxide as a stating materials by using
" Sol-Gel
Method ".
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Difference of the fixation
method of titanium dioxide coating film
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Binder
fixation coating film
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Our
coating film
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The thin film photocatalyst
is made by the Sol-Gel Method.
What is the Sol-Gel Method?
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| Sol-Gel
Method |
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It is defined in the following manner with Sol-Gel
method.
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| Method |
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This method, called the Sol-Gel method,
uses titanium alkoxide as a starting materials.
And the solution, that is dispersed the small
particle of metal oxide or hydroxide by the
hydrolysis and the polymerization of the compound
in the solution, is called Sol.
The noncrystalline porous gel after the gelation
of the further reaction is heated to be crystallite. |
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Sol-Gel
Dip Coater |
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When the principle of Sol-Gel maethod is applied to the
production of the titanium film, alkoxide of titanium, that
is the organic compound of titanium, become titanium sol
through the process of the hydorolysis that is dispersed
the small particle of hydroxide of titanium.
The sol is sintered along with the substrate to be crystallized,
and thus the film of titanium dioxide is formed. |
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