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JPH0270193

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DESCRIPTION JPH0270193
[0001]
<Industrial field of application> The present invention is made by blending a piezoelectric
ceramic powder with a synthetic rubber or the like, and transmits an acoustic wave or an
ultrasonic wave in water, or receives an acoustic wave or an ultrasonic wave propagating in
water. 6. Piezoelectric composite material for hydrophones applicable as an underwater
microphone, etc. 6 <US technology in the US> A piezoelectric composite material formed by
mixing a piezoelectric ceramic powder such as lead titanate in synthetic rubber is a general sinter
piezoelectric material Since the sound velocity of sound waves propagating through the medium
is lower than that of porcelain and the sound velocity is small, good acoustic matching with water
is obtained, and because of its flexibility, the effect of water pressure is small even if immersed
deeply in water. And a piezoelectric composite material for hydrophones such as an underwater
microphone. <Problems to be Solved by the Invention> By the way, piezoelectric composite
materials for hydrophones are required to have high wave receiving sensitivity in water as much
as possible, but materials with high wave receiving sensitivity are dependent on hydrostatic
pressure of delivery sensitivity. It turned out that sex is easy to accompany. An object of the
present invention is to provide a material having high wave sensitivity and low hydrostatic
pressure dependency in this kind of piezoelectric composite material for hydrophone. <Means for
Solving the Problems> The present invention relates to a piezoelectric composite material for a
hydrophone obtained by mixing a piezoelectric ceramic powder with a vulcanizing agent in a
synthetic rubber, forming the mixture, and further polarizing it. Is characterized in that it
comprises a mixture of two or more kinds of powder materials having different average particle
sizes. <Function> The hydrostatic pressure dependency is considered to be due to the presence of
an air layer between the ceramic powders in the piezoelectric composite material. However,
when the piezoelectric ceramic powder mixes two or more types of powder materials having
different average particle sizes, particles having different particle sizes are mixed in a complex
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manner compared to a single powder material having the same average particle size. The packing
efficiency is improved, which reduces the air space between particles. For this reason, hydrostatic
pressure dependence falls. <Example> Commercially available PbO of 99% or more in purity
(average particle diameter 3 μm or less) and TiO □ of 99.5% or more in purity are compounded
under the composition formula of PbTi01, and 2.5 kg is weighed 1 Dry mixing was carried out
for 3 hours with alumina boulders (3, 5 Kg). At this time, the inner wall of the pot of the vibration
mill was lined with a urethane resin to prevent mixing of impurities. Next, use a mold to create
tablets of 47 mm in outer diameter, 5 mm in thickness, and press density of 4.5 g / am ′ ′ by
applying pressure of 350 kg / cm ′ ′, solid phase reaction for 2 hours at 1050 ° C. in high
alumina crucible Did.
Thereafter, the high-temperature lump was put into a cooling water tank to obtain fine particles
which did not cause quenching in water. Furthermore, stirring was performed for 5 hours or
more using a propeller stirrer to accelerate disintegration. The lead titanate powder thus formed
was drained and dried at 100 ° C. for 124 hours, and then passed through a sieve to fractionate
porcelain powders of two types (32 μm and 7 μm) of average particle size groups. Next, these
two types of powders were formulated so that the ratio of 32 μm / 7 μm was in the range of 0
to 100 (% by weight) to be every 25%, and mixed respectively to prepare a plurality of mixed
powder samples . And to each of these mixed powders, synthetic rubber made of neobrene
rubber as a synthetic rubber was mixed at various blending ratios. The mixing ratio of the lead
titanate mixed powder (piezoelectric ceramic powder) / synthetic rubber was prepared so as to
be every 5% in the range of 50 to 80% by volume. Furthermore, PbaO +, ZnO and dibenzothiazyl
disulfide (trade name: Nickseller DM) were mixed as vulcanizing agents. The compounding ratio
of the vulcanizing agent was PbaO 4: ZnO nickseller DM = 20 parts by weight: 5 parts by weight
2 0.5 parts by weight with respect to 100 parts by weight of the synthetic rubber. Furthermore,
it is roll-formed by a small-sized roll machine, crosslinked by a vulcanizing press under
conditions of a temperature of 170 ° C., a pressure of 140 kg / cm ′ ′ and a time of 15
minutes to form a sheet having a thickness of 1 mmt. A square electrode was formed on the front
and back surfaces by application of silver paste. Then, the sheet is immersed in an insulating
solution at 20 ° C., and application of a direct current voltage of 70 KV / cm is continued for 1
hour in the solution for one polarization treatment, thereby providing a piezoelectric rubber
sheet for a hydrophone (piezoelectric composite material Got). And the change of the wave
receiving sensitivity under predetermined hydrostatic pressure of each piezoelectric rubber sheet
was measured. This measurement used a receiving sensitivity measurement water tank using
Florinert solution. The hydrostatic pressure dependence measured the decrease value of the
receiving sensitivity when changing from 51 (g / cn + "to 150 / g / cm"). On the other hand, the
difference between the theoretical density and the actual density was measured for each
material. The density was determined by measuring the gravity in the air and the weight in the
Fluorinert liquid on a piezoelectric rubber sheet, and comparing the density of each raw material
with the theoretical density determined by the blending ratio. In addition, the Mt and the value,
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which are targets for ease of molding during vulcanization molding of the piezoelectric rubber,
were measured using a curastometer. Experimental Results> FIG. 1 shows the wave sensitivity of
the piezoelectric rubber sheet at each compounding ratio, and FIG. 2 shows the hydrostatic
pressure dependency of the wave sensitivity of the piezoelectric rubber sheet at each
compounding ratio.
Due to these, the receiving sensitivity is low at -205 to -206 dB until the compounding ratio of
piezoelectric ceramic powder / synthetic rubber is 60%, but the hydrostatic pressure dependency
is also small at 1 dB or less, and the receiving ratio is further increased It can be seen that the
hydrostatic pressure dependence becomes thicker (proportionally proportional). For example,
when the piezoelectric ceramic powder / synthetic rubber compounding ratio = 65% and the
powder particle size compounding ratio = 100% at which the wave sensitivity is the highest, the
sensitivity is highest at −198, 4 dB, but the hydrostatic pressure dependency is also 5. It is the
highest at 3 dB. On the other hand, the piezoelectric ceramic powder / synthetic rubber
compounding ratio = 70% and the powder particle diameter compounding ratio = 0%, which
show the second highest wave receiving sensitivity, but -201 and 1 dB, but the hydrostatic
pressure dependency is 2.7 dB And relatively small. Next, FIG. 3 shows ε 33 T / ε with respect
to the ratio of piezoelectric ceramic powder / synthetic rubber. Changes in the measured density
and the theoretical density of the piezoelectric rubber sheet, and the hydrostatic pressure
dependence of the receiving sensitivity. The deviation between the measured density of the
piezoelectric rubber sheet and the theoretical density is approximately + 3% between the
piezoelectric ceramic powder / synthetic rubber compounding ratio = 60%, but it gradually
decreases when it exceeds this, especially When the powder particle diameter compounding ratio
is 0%, it sharply decreases in the region exceeding the piezoelectric ceramic powder / synthetic
rubber compounding ratio = 75%. In this area, it is estimated that an air layer is contained in the
piezoelectric rubber sheet. Here, ε 33 T / ε. In the range of more than 75%, the straight line
decreases, and the agreement between the measured density and the theoretical density is good.
Is showing. In theory, in the case of PVDF containing porous PZT and an air layer, hydrostatic
pressure dependence is shown, and it is reported that the air layer and hydrostatic pressure
dependence are closely related. In addition, about receiving sensitivity and hydrostatic pressure
dependence, deviation of actual density and theoretical density and ε 337 / ε. The causal
relationship with the change of is not shown in the figure. From this, it is suggested that although
the air layer and hydrostatic pressure dependence are related, other factors should be
quantitatively introduced and examined. Thus, according to FIG. 3, the composition in which the
ratio of piezoelectric ceramic powder / synthetic rubber is 65 to 75 (volume%) and the
composition of two kinds of powder particle size is more than that of single average particle size.
It was found that the static pressure dependency was low without losing the receiving sensitivity.
FIG. 4 shows the difference between the measured density of the piezoelectric rubber sheet and
the theoretical density with respect to the powder particle diameter compounding ratio, the
curastometer ML value, and the hydrostatic pressure dependency of the receiving sensitivity,
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whereby the powder particle diameter compounding ratio = Each value shows maximum and
minimum at around 50%, that is, the one with the powder particle diameter of 32μm and the
one with 7μm blended in 50% each has a larger density (becomes the density of Curast than the
one with 32μm and 7μm alone). It can be seen that the meter ML value is smaller, the
formability is better (and the hydrostatic pressure dependency can be reduced).
This is considered to be because the amount of the air layer can be reduced by increasing the
filling effect by mixing different particle sizes of the piezoelectric ceramic powder. In the abovementioned experiment, although the powder material of two average particle sizes of 32 μm and
7 μm is mixed, the filling efficiency can be enhanced and the hydrostatic pressure dependency
can be reduced also by mixing two or more types. it is conceivable that. <Effects of the Invention>
The present invention is produced by mixing piezoelectric ceramic powder with two or more
powder materials having different average particle sizes, and has a low hydrostatic pressure
dependency, which is why the present invention The piezoelectric composite material has
excellent effects such as being able to obtain a stable output even if there is a change in
hydrostatic pressure.
[0002]
Brief description of the drawings
[0003]
Fig. 1 is a graph showing the wave sensitivity of the piezoelectric rubber sheet at each
composition ratio, Fig. 2 is a graph showing the hydrostatic pressure dependence of the wave
sensitivity of the piezoelectric rubber sheet at each composition ratio, and Fig. 3 is piezoelectric
Ε33 / ε relative to the porcelain powder / synthetic rubber blend ratio.
Of the density of the piezoelectric rubber sheet and the theoretical density of the piezoelectric
rubber sheet, and the hydrostatic pressure dependency of the wave sensitivity, FIG. 4 shows the
measured density of the piezoelectric rubber sheet and the theoretical density with respect to the
powder particle size blending ratio. It is a graph which shows a hydrostatic pressure dependence
of a deviation, curastometer ML value, and receiving sensitivity.
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