Note: Descriptions are shown in the official language in which they were submitted.
2058137
The present invention relates to an insulating
member such as a wire for high temperature operation, an
insulated lead wire or the like.
An insulating member such as an insulated wire is
generally applied to equipment such as heating equipment or
a fire alarm, which requires safety at high temperatures.
An insulated wire is also employed in an automobile under an
environment which is heated to a high temperature. Such an
insulated wire is generally formed by a conductor which is
coated with heat-resistant organic resin such as polyimide,
fluororesin or the like.
Such a resin-coated wire can normally withstand a
temperature of about 300C at the most. However, a wire
which is employed in a high vacuum apparatus must have high
heat resistance against baking etc., small emission
characteristics as to gas and water which are absorbed for
achieving and maintaining a high degree of vacuum, and small
gas emission caused by thermal decomposition. It is
impossible to satisfy such requirements for heat resistance
and non-outgassing property with the conventional wire which
is coated with an organic material.
When an insulated wire is applied to usage
requiring high heat resistance or employed under an
environment requiring a high degree of vacuum, it is
impossible to attain sufficient heat resistance or non-
outgassing property with only an organic coating. In this
case, therefore, an insulated wire comprising a conductor
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which passes through an insulator tube of ceramics, an MI
cable comprising a conductor which passes through a tube of
a heat-resistant alloy, such as a stainless steel alloy,
filled up with fine particles of a metal oxide such as
magnesium oxide, or the like is generally employed.
On the other hand, a glass braided tube insulated
wire employing an insulating member of glass fiber fabric or
the like is known as an insulated wire having heat
resistance and flexibility.
Further, wires coated with organic materials have
been studied, and there have been proposed an alumite-coated
wire prepared by alumite-working the surface of an aluminum
conductor for forming an Ae2O3 film on its surface, and a
wire which is formed by electroanalysis.
However, the aluminum-coated wire and the wire
which is formed by electroanalysis are inferior in heat
resistance to a wire employing a metal such as Cu, since the
material for the conductors thereof is restricted to
aluminum. Further, such conventional wires have only low
breakdown voltages and high gas emission characteristics due
to porous films.
In the case of the MI cable, on the other hand,
the overall diameter is increased as compared with the
conductor diameter leading to an inferior space factor.
Thus, it is impossible to feed a high current.
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In the glass braided tube insulated wire, further,
fine glass powder is generated and the conductor is
disadvantageously exposed due to mesh displacement.
An object of the present invention is to provide
an inorganic insulating member, which is excellent in heat
resistance and insulability.
The inorganic insulating member according to the
present invention comprises a conductor containing Ni or Ni
alloy at least in its outer surface, an oxide layer of Ni or
Ni alloy which is formed through oxidation treatment of the
outer surface of the conductor, and an insulating inorganic
compound layer which is formed on the oxide layer of Ni or
Ni alloy.
According to the present invention, the oxide
layer of Ni or Ni alloy may be formed through oxidation
treatment of Ni or Ni alloy forming the outer surface of the
conductor. Such oxidation treatment is preferably performed
in a vapor phase containing oxygen.
According to the present invention, the insulating
inorganic compound layer can advantageously be formed on the
oxide layer of Ni or Ni alloy by hydrolyzing and poly-
condensing metal alkoxide or metal carboxylic ester, for
example.
The insulating inorganic compound layer can
alternatively be formed by thermally decomposing an organic
metal polymer. According to this method, it is possible to
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form a metal oxide, a metal carbide, a metal nitride or a
composite thereof.
According to the present invention, the insulating
inorganic compound layer may contain fine particles of
ceramics.
The inorganic insulating member according to the
present invention is applied to a wire intended for high
temperature operation, such as an insulated lead wire or the
like. However, the present invention is not restricted to
such usage.
Embodiments of the present invention will now be
described, by way of example, with reference to the
accompanying drawings, in which:
Figure 1 is a sectional view of an inorganic
insulating member;
Figure 2 is a sectional view of another embodiment
of insulating member; and
Figure 3 is a sectional view of a further
embodiment of insulating member.
Referring now to the drawings, Figure 1 shows a
sectional view showing a first embodiment of the present
invention, in which an Ni oxide layer 2 is formed around an
Ni conductor 1, and an insulating inorganic compound layer
3 is formed around the Ni oxide layer 2.
Figure 2 is a sectional view showing a second
embodiment of the present invention. Referring to Figure 2,
an Ni alloy oxide layer 12 is formed around an Ni alloy
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,~`
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conductor 11. An insulating inorganic compound layer 13 is
formed around the Ni alloy oxide layer 12.
Figure 3 is a sectional view showing a third
embodiment of the present invention. Referring to Figure 3,
a diffusion preventing layer 24 of carbon, for example, is
provided around a Cu conductor 20. An Ni layer 21 is formed
around the diffusion preventing layer 24. An Ni oxide layer
22 is formed around the Ni layer 21, and an insulating
inorganic compound layer 23 is formed around the Ni oxide
layer 22.
According to the present invention, it is possible
to employ a metal having a higher heat resistance than Ae,
which is generally employed for a conductor. At least the
outer surface of a conductor employed in the present
invention is made of Ni or Ni alloy. Although the overall
conductor may be made of Ni or Ni alloy, such a material has
low conductivity. While Ae has a conductivity of 60% IACS,
those of Ni and Ni alloy are 25% IACS and not more than 25%
IACS, respectively. In order to improve conductivity,
therefore, the outer surface of a Cu conductor may be plated
or clad with Ni. When such an Ni-plated or Ni-clad Cu
conductor is used under high temperature for a long time,
however, mutual diffusion takes place between Ni and Cu, to
form an alloy layer and reduce the conductivity. In order
to cope with this, a diffusion preventing layer of BN or the
like may be provided in the interface between Ni and Cu, as
shown in Figure 3.
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According to the present invention, as hereinabove
described, the insulating inorganic compound layer can be
prepared from a metal oxide which is obtained by hydrolyzing
and polycondensing metal alkoxide or metal carboxylic ester.
Examples of such a metal oxide are sio2, Ae2O3, MgO, ZrO2 and
composites thereof. Such metal oxides are extremely dense
and have smooth surfaces, whereby the same have high
insulability and small gas emission.
Further, a metal oxide such as sio2, a metal
carbide such as SiC and metal nitrides such as Si3N4, AeN and
BN, which are obtained by thermally decomposing organic
metal polymers, or composites thereof also have high
insulability and small gas emission.
An insulating inorganic compound layer of such a
material has only small affinity with the Ni or Ni alloy
forming the outer surface of the conductor. When this layer
is directly applied, therefore, it is impossible to attain
high adhesion and the layer is easily separated. Thus, the
member cannot be bent.
According to the present invention, Ni or Ni alloy
forming the outer surface of the conductor is subjected to
oxidation treatment for forming an oxide layer of Ni or Ni
alloy oxide, so that the insulating inorganic compound layer
is formed on this oxide layer. The oxide layer is in
extremely close contact with the conductor surface, and has
excellent adhesion to the insulating inorganic compound
layer. According to the present invention, therefore, the
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insulating inorganic compound layer is hardly separated, and
excellent flexibility is attained when the inventive
insulating member is applied to a wire, for example.
Conductors of
(1) an Ni wire of 0.5 mm in wire diameter,
(2) Ni - 15 wt.% Cr alloy wire of 0.32 mm in wire
diameter, and
(3) Ni/BN/Cu clad wire, comprising a Cu wire of
0.38 mm in diameter being clad with an Ni layer of 50 ~m in
thickness through a carbon layer of 10 ~m in thickness,
serving as a diffusion preventing layer, were employed to
prepare inorganic insulating members according to the
present invention.
The conductors (1) and (2) were heat treated in
the atmosphere at 800C for 30 minutes for oxidation of the
surfaces, thereby forming oxide layers. The conductor (3)
was subjected to plasma oxidation treatment in Ar - 10% Oz of
10 mTorr for 30 minutes, for forming an oxide layer.
The oxidation-treated conductors (1) to (3) were
used to prepare the wires of Examples 1 to 5.
Example 1
Tetrabutyl orthosilicate was hydrolyzed and
polycondensed in isopropyl alcohol as solvent, to prepare a
coating solution A. The solution A was applied to the
oxidation-treated conductor (3) and heated in the atmosphere
at 500C, to form an insulating inorganic compound layer of
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.~.
sioz. This SiO2 insulating layer was about 5 ~m in
thickness.
Example 2
Polysilazane was thermally decomposed and
polycondensed in an autoclave at a temperature of 460C, to
obtain polycarbosilane. A coating solution B was prepared
from this polycarbosilane, applied to the oxidation-treated
conductor (2) and heated in N2 gas at 600C, to form an SiC
layer of 5 ~m in thickness.
Example 3
Methylchlorodisilane was reacted with hexa-
methylene disilazane at 275C, to obtain polysilazane. A
coating solution C was prepared from this polysilazane,
applied to the conductor (1) and heated in NH3 gas at 700C,
to form an Si3N4 layer of 7 ~m in thickness.
Example 4
Ae(NO3)3 in an amount of 8% was added to the
coating solution A, which in turn was applied onto the
conductor (1) and heated at 500C, to form an Sio2-Ae2o3
composite layer of 6 ~m in thickness.
Example 5
20 percent by weight of SiO2 particles of 1 ~m in
particle diameter were dispersed in the coating solution B,
which in turn was applied onto the conductor (1) and heated
in N2 ~ 0.3 vol.% 2 gas at 600C. This conductor was
further coated with the solution C, and heated in NH3 gas at
700C to form an insulating inorganic compound layer. This
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.
inorganic compound layer, which was formed by an Si3N4 layer
and a partially oxidized SiC layer containing sio2 particles,
had an overall thickness of about 10 ~m.
Table 1 shows breakdown voltages and flexibility
values of the as-formed wires of Examples 1 to 5. The
flexibility values were evaluated in terms of diameter
ratios, by winding the wires on circular cylinders of a
prescribed diameter and measuring the minimum diameters
causing no separation of the insulating inorganic compound
layers.
The Comparative Example was prepared from an
alumite wire, which was obtained by forming an Ae2O3 layer of
10 ~m in thickness around a conventional aluminum wire.
Table 1
Breakdown
Voltage Flexibility
Example 1 600 V S D
Example 2 500 V 8 D
Example 3 900 V 3 D
Example 4 700 V 5 D
Example 5 1200 V 4 D
Comparative
Example 300 V 50 D
As clearly evident from Table 1, the wires of
Examples 1 to 5 according to the present invention are
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higher in breakdown voltage than and superior in flexibility
to the alumite wire of the Comparative Example.
As hereinabove described, the inorganic insulating
member according to the present invention has an insulating
inorganic compound layer which is hardly separated, and is
excellent in heat resistance and insulability.
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