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JPS57171899

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DESCRIPTION JPS57171899
Specification -1, the title of the invention
Method of manufacturing boron diaphragm
3. Detailed Description of the Invention The present invention relates to a method of
manufacturing a boron diaphragm, and it is an object of the present invention to obtain an
acoustic boron diaphragm which is lightweight and has a high specific elastic modulus. Boron
has been noted especially as an acoustic constituent material in recent years because it is
characterized by a very high specific modulus (elastic modulus / density) and very high.
However, it is boron. It is difficult to carry out processing such as casting and rolling as it is
alone. Therefore, boron has been complexly formed on a substrate made of a material other than
boron by PVD (vacuum evaporation, ion plating, sputtering), CVD (chemical vapor deposition) or
the like. For example, according to the pvn method, a diaphragm is obtained by forming a boron
layer in a composite manner on titanium foil or aluminum foil at a relatively low temperature. on
the other hand. Since the CVD method is performed at a high temperature of about 1000 to
1200 ° C., the sample has cracks in the cooling process unless the high melting point material
whose difference in thermal expansion coefficient is as small as possible between the substrate
and the film forming material is selected. Partially peeled off. For this reason, conventionally, a
boron coating has been obtained using a heat-resistant metal such as tantalum, molybdenum,
tungsten or tungsten or the like as a substrate. However, these heat resistant metals require
much time to remove the substrate with hydrofluoric acid and EndPage: 1 and boron diffuses
into the heat resistant metal during CVD to form a boride layer, It becomes difficult to dissolve
and remove the substrate. Also, in the case of graafite, selective etching of gravaite against boron
is difficult. Therefore, in the past, it was the fact that it was very difficult to beat the vibration
plate of boron alone. The present invention forms a thin layer of boride on a sintered zinc oxide
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substrate, forms a boron layer on the substrate by chemical vapor deposition, and dissolves away
the zinc oxide, thereby eliminating the above-mentioned drawbacks. The present invention
provides a method of manufacturing a boron diaphragm. A simple diaphragm having a high
mechanical strength and a high specific elastic modulus can be obtained by a simple etching
operation. Hereinafter, the production method of the present invention will be specifically
described. Zinc oxide is an inexpensive, abundant and safe substance and is an amphoteric oxide
that can be dissolved with dilute acid and concentrated alkali. In addition, zinc oxide powder is
compression molded, and zinc oxide sintered at 1100 to 1400 ° C. in air exhibits a pale yellow
to light brownish brown color, and its linear expansion coefficient is 4. It is a heat resistant round
bar having OX 10 '/ ° C. First, as a boride to be formed on a sintered zinc oxide substrate, the
thermal expansion coefficient (4,0 × 10 10) of zinc oxide (2 nO) is to withstand rapid heat and
rapid cooling at boron cvn and to prevent peeling of the boride layer. / ° C) and matched
titanium boride (TiB2: 4. 6 × 10 / ° C), zirconium boride (ZrB2: 5-9 X 1 o '/ ° C) is desirable
○, while vanadiumium boride (VB 2: 7) .6 x 10 / l ?,).
The difference in thermal expansion coefficient between j'7 tall boride (TaB2 '8.2 x 10 / ° C)
and chromium boride (CrB 2: 1 0.6 x 10 / ° C) etc. is too large, so zinc oxide and these borides
Peel at the interface of the layers. When there is no boride layer, boron peels off and breaks at
cvn. Moreover, the reason for limiting the film thickness of the boride layer to 0.1 to 2 μm is
because it is necessary to avoid the accumulation of internal stress and to reduce the difference
in thermal expansion coefficient as much as possible. Further details will be described in the
examples. <Example 1> Zinc oxide powder (commercial special grade product) is compression
molded into a disc shape with a diameter of 2QWLX and a thickness of 1.6 g with a pressure of
300 Kl /, 4 and several sheets are stacked and placed in a high purity alumina boat And sintered
in air at 11O 0 C to 1 400 ° C for 1 hour. The temperature elevation rate was 200 ° C./hτ,
and the sampling was performed at 300 ° C. or less. Using a RF magnetron sputtering apparatus
(Nippon Vacuum @) on this sintered zinc oxide substrate, the substrate is heated by 300 to 450 C
to form a titanium boride (TiB2) 6D film thickness of 0.1.1.1.2 , 4 μ rn varied in film deposition.
Next, the film deposition sample was held at a temperature of 1100 ° C. in a CVD reaction
vessel using an infrared condensing lamp. In this state, a mixed gas of 1 part by volume of boron
trichloride (jcc5) and 3 parts by volume of hydrogen (B2) was flowed into the reaction vessel at a
rate of 11 minutes per minute for 6 minutes. At this time, the pressure in the reaction vessel was
controlled to 1 QTorr by a rotary pump and pulp operation. As a result, an amorphous boron
layer of about 80 μm in thickness is formed. The sample thus obtained was cut 7111 into a disk
of 15 & j directly by laser light, and then zinc oxide was removed by hydrochloric acid to obtain a
boron thin plate. The various characteristics of the boron thin plate obtained here are
summarized in the following table as samples 1, 2, 3 and 4. Hereinafter, the seed species of
boride is changed to zirconium boride (ZrB2), vanadium boride (VB2), tantalum boride v (TaBz)
and chromium boride (CrB2), and samples 6 shown in the following table in the same manner as
described above 9 are produced, and the effect of the present invention is shown together with
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the reference example. EndPage: As is apparent from the results of 2 or more, according to the
method of the present invention, the zinc oxide substrate is dissolved and removed by simple
etching to obtain a diaphragm made of boron alone having a high specific modulus 1 % Can be
used for the diaphragm of the speaker to improve the high frequency of its shoulder wave
number characteristics. Name of Agent Attorney Nakao and 1 other EndPage:
3
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