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wanghaiju

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專業(yè): 應用有機化學

[求助] 高分子材料論文翻譯求助

Morphology of multilayer film
The morphology of each layer film was investigated
with AFM. The results are displayed in Fig. 1.
The Films have no microcracks and are individually
consistent in color. It is known that the titanium
dioxide film is achromatous and barium ferrite film is
brown. The consistent in color of each layer film shows
that the composite film is uniform. With the increase of
layer, the color of composite film becomes heavier. The
morphology of each layer film is different to others.
The one layer film is looked not very even. Some
cavities appear in it. The size of cavities changes from
60 to 180 nm. The grains in the one layer film are not
homogeneous. The size changes from 30 to 120 nm.
Compared with the one layer film, the surface of the
two and three layer film is bettered. The cavity is few,
and the grains are relative uniform in the two layer
film. The size of grains changes from 30 to 60 nm. In
the three layer film, some big grains appear, with the
maximum size of 240 nm. The substrate and layer
number are important factors to affect the growth of
films. The first layer film grows on the quartz glass
plate. The difference in structure makes the film to
grow difficultly. So the defects easily appear and grains
are unordered. However, the second layer film grows
on the base of the first layer film. The growth
conditions are improved for the second layer film. It
can grow better under the direction of the first layer
film. With the increase of layer number, some grains
have chance to grow big in three dimensions. In the
three layer film, some grains even grow to 240 nm.
Additionally, the TiO2and ferrite grains can not be
distinguished in the composite film.
Crystalline structure of multilayer film
In the course of preparing substituted BaFe12O19using
sol–gel method, the intermediate results including
Fe2O3, BaCO3and BaFe2O4will appear. If they react
heavy with TiO2during the formation of multilayer
film, the expected magnetic materials, substituted
barium ferrites will not form. XRD is used to inves-
tigate the crystalline structure of composite film and its
pattern is shown in Fig. 2. The composite film is
composed of rutile titanium dioxide and M-type
hexagonal barium ferrite. The diffraction peaks of
Al2O3and Cr2O3are not found on the pattern, which
shows that all of Al3+and Cr3+ions have entered the
lattice of BaFe12O19. It is concluded that the mixed sols
basically react into the substituted BaFe12O19and TiO2
during the calcination process. The substituted barium
ferrite can be synthesized via titanium dioxide as a
matrix using sol–gel method. In addition, there are two
unknown weak diffraction peaks on XRD pattern,
which can not be recognized by standard cards. Maybe,
a little part of Fe, Ti and O elements still reacted into
an unstoichiometric compound.
Microwave absorption property of multilayer film
Microwave attenuation materials are required to
absorb microwave energy in a broad frequency range.
Single material is not easy to realize it. Substituted
barium ferrites are selected to prepare composite
multilayer film with TiO2. These films are arranged
according to the frequencies of their microwave
absorption peaks. The absorption frequencies of
BaFe10.1Al1.9O19 are the highest, so the composite
layer containing BaFe10.1Al1.9O19is treated as the first
layer nearby the substrate. The absorption frequencies
of BaFe11.4Cr0.6O19 are the lowest, and then the
composite layer containing it is on the top. Theomposite layer containing BaFe10.5Al1.5O19is in the
middle. This arrangement can make more microwave
energy to enter the multilayer film and to be absorbed.
The microwave loss spectrum of composite multilayer
film is shown in Fig. 3. The microwave loss spectra
of BaFe10.1Al1.9O19, BaFe10.5Al1.5O19 and BaFe11.4
Cr0.6O19 powders are simultaneously displayed as a
comparison.
The microwave absorption property of the compos-
ite multilayer film is excellent. The largest loss
efficiency is close to –40 dB. The frequency range with
the loss above –10 dB is more than 7 GHz. It is an
ideal microwave absorption material. Because of the
variable absorption frequency, each layer film can
absorb microwave energy in different frequency band.
The multilayer film assembles the achievements of
each layer. Moreover, the compounding of ferrites with
TiO2is helpful for the microwave absorption. Barium
ferrite is a magnetic material, and TiO2is a nonmag-
netic material. After they are compounded together,
electromagnetic properties of magnetic material can be
changed. It is known that almost all of ferrites have
little dielectric loss. Now the compounding with TiO2
can improve the dielectric losses of substituted barium
ferrites. Additionally, the size of most grains in
multilayer film belongs to nanometer scope, which is
attributed to the surround of TiO2particles. The ferrite
grains with single magnetic domain structure can notgrow big and convert into multi-domain structure, due
to the block of TiO2particles, which also increase the
microwave absorbing.

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1樓 2014-04-08 23:59:23

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金蟲 (著名寫手)

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2樓2014-04-09 08:29:47