Note: Descriptions are shown in the official language in which they were submitted.
CA 02768933 2012-02-22
SURFACE-MODIFIED POLYCRYSTALLINE DIAMOND AND PROCESSING
METHOD THEREOF
FIELD OF INVENTION
[0001] The present disclosure relates to improvement of properties of
polycrystalline
diamonds, and more particularly, to a surface-modified polycrystalline diamond
and a
processing method thereof.
BACKGROUD OF INVENTION
[0002] Polycrystalline diamond compacts ( briefly called PDCs) are made from a
diamond powder incorporating a certain amount of sintering aids therein and a
cemented
carbide substrate , which are assembled together and then sintered on a
special diamond
hydraulic press at an high temperature under an ultra-high pressure. A PDC is
composed
of a polycrystalline diamond layer and the cemented carbide substrate .
Because the
polycrystalline diamond layer has high hardness and good wear resistance and
the
substrate is excellent in toughness and weldability, the PDCs are widely
applied in the
fields of oil drilling, geological drilling, coal field exploitation, cutting,
and so on.
[0003] When PDCs or integrated polycrystalline diamonds are manufactured,
cobalt,
nickel, or iron is usually used as the sintering aids to sinter the diamond
powder at an high
temperature under an ultra-high pressure. The most common catalyst metal is
cobalt or an
alloy thereof, and the common pressure for sintering at an high temperature
under an
ultra-high pressure is 4.5 GPa to 6 GPa. Under this condition, the aforesaid
sintering aids
need to be used so that the diamond particles can be directly sintered with
each other to
form a diamond-diamond (D-D) combination structure, thereby achieving a
polycrystalline diamond layer having excellent properties. The microstructure
of the
polycrystalline diamond consists of a diamond phase having frameworks
connected with
each other and a dispersed islet-shaped metal phase.
[0004] After the diamond particles are sintered into the frameworks, the
properties of
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the entire polycrystalline diamond totally depend on the combination of the
diamond
frameworks. The greater the diamond particles are combined with each other and
the
larger the combination area is, the better the strength and wear resistance of
the
polycrystalline diamond will be. The strength is substantially unrelated to
the metal phase
dispersed in interstices between the frameworks. On the contrary, existence of
iron group
metal phases is detrimental to the performance of the polycrystalline diamond,
including
causing thermal damage and stress damage to the performance of the
polycrystalline
diamond.
[0005] When the PDC operates as a tool, there is often very high operating
temperature
around the operating point where the PDC contacts with a workpiece, and the
temperature
may be about 700 C to 800 C, or even over 1000 C at some points. As shown by
researches, cobalt, nickel or iron, which is used as a catalyst metal for
catalyzing
transformation of graphite into the diamond under a high pressure, also
catalyzes
transformation of the diamond into graphite under the normal pressure.
Consequently, the
iron group metal phase in the PDC can degrade the wear resistance of the PDC
to some
extent depending on different high temperatures at operating points, thereby
causing a
thermal damage.
[0006] A thermal expansion coefficient of the diamond is only one tenth of
cobalt.
When the operating temperate is very high, the cobalt phase expands to an
extent much
greater than that of the diamond frameworks, thereby generating a thermal
stress. After
reaching a certain value, the thermal stress will destroy the diamond
frameworks to cause
cracks in the polycrystalline diamond, thereby leading to a stress damage.
[0007] Accordingly, the structure of the existing polycrystalline diamond body
and the
method of processing the polycrystalline diamond body in the art need further
improvement and enhancement.
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SUMMARY OF THE INVENTION
[0008] In view of the shortcomings of the prior art, an objective of the
present
disclosure is to provide a surface-modified polycrystalline diamond and a
processing
method thereof, in which a catalyst metal is removed from a polycrystalline
diamond body
to form holes and a non-catalyst metal having a high thermal conductivity is
embedded
into the holes. Thus, thermal damage and stress damage to the polycrystalline
diamond
body during operations at a high temperature are eliminated.
[0009] To achieve the aforesaid objective, the present disclosure provides the
following
technical solutions:
[0010] A surface-modified polycrystalline diamond, which comprises a
polycrystalline
diamond body, wherein holes are formed on the polycrystalline diamond body
after a
catalyst metal is removed, and the holes are embedded with a non-catalyst
metal.
[0011] The surface-modified polycrystalline diamond, wherein the non-catalyst
metal is
one of copper, silver, aluminum, and alloys thereof
[0012] The surface-modified polycrystalline diamond, wherein each of the holes
has a
depth of 0.1 mm to 1 mm.
[0013] The present disclosure further provides a method of processing a
surface-modified polycrystalline diamond, which comprises the following steps
of:
[0014] removing a catalyst metal from a surface of the polycrystalline diamond
body
and forming holes in the surface of the polycrystalline diamond body; and
[0015] embedding a non-catalyst metal into the holes.
[0016] The method of processing a surface-modified polycrystalline diamond,
wherein
the steps of removing the catalyst metal from the surface of the
polycrystalline diamond
body and forming the holes in the surface of the polycrystalline diamond body
comprise:
[0017] boiling the polycrystalline diamond body in an aqua regia for 20 to 60
hours;
and
[0018] taking the polycrystalline diamond body out of the aqua regia and
rinsing the
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polycrystalline diamond body until the polycrystalline diamond body becomes
neutral.
[0019] The method of processing a surface-modified polycrystalline diamond,
wherein
the steps of embedding the non-catalyst metal into the holes comprise:
[0020] putting a copper wheel rotating at a rotating speed of 1400 revolutions
per
second (rps) into contact with the surface of the polycrystalline diamond
body; and
[0021] feeding the copper wheel by 0.1 mm to 0.4 mm for strong friction so
that the
surface of the polycrystalline diamond body is covered by copper.
[0022] The method of processing a surface-modified polycrystalline diamond,
wherein
the polycrystalline diamond body is boiled in the aqua regia for 10 to 110
hours; and the
polycrystalline diamond body is taken out of the aqua regia and rinsed until
the
polycrystalline diamond body becomes neutral.
[0023] The method of processing a surface-modified polycrystalline diamond,
wherein
the step of embedding the non-catalyst metal into the holes comprises: placing
the
polycrystalline diamond body into a copper mould for electrodeposition, with
the mould
being used as a cathode, a copper sulfate solution being used as an
electrolyte, and a pure
copper plate being used as an anode.
[0024] The method of processing a surface-modified polycrystalline diamond,
wherein
the non-catalyst metal is one of copper, silver, aluminum, and alloys thereof.
[0025] The method of processing a surface-modified polycrystalline diamond,
wherein
each of the holes has a depth of 0.1 mm to 1 mm.
[0026] According to the surface-modified polycrystalline diamond and the
processing
method thereof provided in the present disclosure, the catalyst metal is
removed from the
polycrystalline diamond body, and the non-catalyst metal is embedded into the
holes
formed in the surface of the polycrystalline diamond after the catalyst metal
is removed.
Thus, thermal damage and stress damage to the polycrystalline diamond during
operations
at a high temperature are eliminated and, therefore, the service life of the
polycrystalline
diamond is prolonged.
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[0026a] In a first aspect of the invention, there is a surface-modified
polycrystalline diamond
for use in a polycrystalline diamond compact. The surface-modified
polycrystalline diamond
comprises a polycrystalline diamond body, the polycrystalline diamond body
having a surface
layer, wherein holes are formed in the surface layer by removing a catalyst
metal from only the
surface layer, and the holes are embedded with a non-catalyst metal.
[0026b] According to a feature of this first aspect of the invention, the
non-catalyst metal is
one of copper, silver, aluminum, and alloys thereof. According to another
feature, each of the
holes in the surface layer has a depth of 0.1 mm to 1 mm.
[0026c] In a second aspect of the invention, there is provided a method of
processing a
surface-modified polycrystalline diamond for use in a polycrystalline diamond
compact. The
method includes the steps of: a) removing a catalyst metal from only a surface
layer of the
polycrystalline diamond body, thereby forming holes in the surface layer of
the polycrystalline
diamond body; and b) embedding a non-catalyst metal into the holes.
[0026d] According to a feature of this second aspect of the invention, the
step of removing
the catalyst metal from the surface layer includes: i) boiling the
polycrystalline diamond body
in an aqua regia for 20 to 60 hours; and ii) taking the polycrystalline
diamond body out of the
aqua regia and rinsing the polycrystalline diamond body until the
polycrystalline diamond body
becomes neutral. As a further feature, the step of embedding the non-catalyst
metal into the
holes includes putting a copper wheel rotating at a rotating speed of 1400
revolutions per
second (rps) into contact with the surface of the polycrystalline diamond
body; and feeding the
copper wheel by 0.1 mm to 0.4 mm for strong friction so that the surface of
the polycrystalline
diamond body is covered by copper.
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[0026e] According to another feature of this second aspect of the
invention, the step of
removing the catalyst metal from the surface layer includes: i) boiling the
polycrystalline
diamond body in an aqua regia for 10 to 110 hours; and ii) taking the
polycrystalline diamond
body out of the aqua regia and rinsing the polycrystalline diamond body until
the
polycrystalline diamond body becomes neutral. As a further feature, the non-
catalyst metal is
copper and the step of embedding the non-catalyst metal into the holes
includes placing the
polycrystalline diamond body into a copper mould for electrodeposition, with
the mould being
used as a cathode, a copper sulfate solution being used as an electrolyte, and
a pure copper
plate being used as an anode.
[0026f] According to yet another feature of this second aspect of the
invention, the non-
catalyst metal is one of copper, silver, aluminum, and alloys thereof.
[0026g] According to yet another feature of this second aspect of the
invention, each of the
holes has a depth of 0.1 mm to 1 mm.
[0026h] According to yet another feature of this second aspect of the
invention, the non-
catalyst metal is a metallic material having a melting point below 700 C. As a
further feature,
the non-catalyst metal is aluminum or an alloy thereof.
[0026i] In a third aspect of the invention, there is provided a
polycrystalline diamond
compact ("PDC"). The PDC comprises a carbide substrate, and a surface-modified
polycrystalline diamond attached to the carbide substrate, the surface-
modified polycrystalline
diamond having an exposed surface with a surface layer thereunder, wherein the
exposed
surface is modified by removing a catalyst metal from only the surface layer
to form holes in
the surface layer, and filling the holes with a non-catalyst metal.
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[0026j] According to a feature of this third aspect of the invention, the
non-catalyst metal is
one of copper, silver, aluminum, and alloys thereof.
[0026k] According to another feature of this third aspect of the invention,
the non-catalyst
metal is a metallic material having a melting point below 700 C. As a further
feature, the non-
catalyst metal is aluminum or an alloy thereof.
[00261] According to another feature of this third aspect of the
invention, each of the holes
has a depth of 0.1 mm to 1 mm.
[0026m] In a fourth aspect of the invention, there is provided a method of
making a
polycrystalline diamond compact ("PDC"). The PDC has a carbide substrate and a
surface-
modified polycrystalline diamond attached thereto. The surface-modified
polycrystalline
diamond has an exposed surface with a surface layer thereunder. The method
includes the steps
of: a) protecting the carbide substrate with an anticorrosion covering, b)
corrosively removing a
catalyst metal from only the surface layer to form holes in the surface layer,
and c) filling the
holes with a non-catalyst metal.
[0026n] According to a feature of this fourth aspect of the invention, the
step of corrosively
removing the catalyst metal from the surface layer includes: i) boiling the
polycrystalline
diamond body in an aqua regia; and ii) taking the polycrystalline diamond body
out of the aqua
regia and rinsing the polycrystalline diamond body until the polycrystalline
diamond body
becomes neutral.
[00260] According to another feature of this fourth aspect of the invention,
the non-catalyst
metal is one of copper, silver, aluminum, and alloys thereof.
[0026p] According to yet another feature of this fourth aspect of the
invention, the non-
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catalyst metal is a metallic material having a melting point below 700 C. As a
further feature,
the non-catalyst metal is aluminum or an alloy thereof.
[0026q] According to yet another feature of this fourth aspect of the
invention, the non-
catalyst metal is copper and the step of filling the holes includes: i)
putting a rotating copper
wheel into contact with the surface of the polycrystalline diamond body, and
ii) forcefully
feeding the copper wheel toward the surface of the polycrystalline diamond
body for strong
friction so that the surface of the polycrystalline diamond body is covered by
copper. As a
further feature, the rotating copper wheel rotates at a rotating speed of 1400
revolutions per
second (rps) and the copper wheel is forced toward the surface of the
polycrystalline diamond
body for 0.1 mm to 0.4 mm.
[0026r] According to yet another feature of this fourth aspect of the
invention, the non-
catalyst metal is copper and the step of embedding the non-catalyst metal into
the holes
includes: placing the polycrystalline diamond body into a copper mould for
electrodeposition,
with the mould being used as a cathode, a copper sulfate solution being used
as an electrolyte,
and a pure copper plate being used as an anode.
[0026s] According to yet another feature, each of the holes has a depth of
0.1 mm to 1 mm.
[0026t] In other aspects, the invention provides various combinations and
subsets of the
aspects and features described above and as further described in detail
herein.
4d
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BRIEF DESCRIPTION OF THE DRAWINGS
[0027] Fig. 1 is a schematic structural view of a polycrystalline diamond
according to
an embodiment of the present disclosure;
[0028] Fig. 2 is a schematic structural view of the polycrystalline diamond
according to
an embodiment of the present disclosure after a catalyst metal is removed
therefrom; and
[0029] Fig. 3 is a flowchart diagram of a method of processing the
polycrystalline
diamond according to an embodiment of the present disclosure.
DETAILED DESCRIPTION
[0030] The present disclosure provides a surface-modified polycrystalline
diamond and
a processing method thereof. To make the objectives, technical solutions, and
efficacies of
the present disclosure clearer, the present disclosure will be further
described hereinbelow
with reference to the attached drawings and embodiments thereof It shall be
understood
that, the embodiments described herein are only intended to illustrate but not
to limit the
present disclosure.
[0031] Referring to Fig. 1 and Fig. 2, a surface-modified polycrystalline
diamond
according to an embodiment of the present disclosure comprises a
polycrystalline diamond
body 11 installed on a cemented carbide matrix 21. A plurality of holes 111
are formed on
the polycrystalline diamond body 11 after a catalyst metal is removed
therefrom, and the
holes 111 are embedded with a non-catalyst metal.
[0032] The catalyst metal is one of iron, cobalt, and nickel, and the non-
catalyst metal
is one of copper, silver, aluminum, and alloys thereof Each of the holes 111
preferably
has a depth of 0.1 mm to 1 mm; that is, only the catalyst metal at the depth
of 0.1 mm to 1
mm from a surface of the polycrystalline diamond body 11 is removed in the
present
disclosure. According to the present disclosure, the holes 111 are formed in
the surface of
the polycrystalline diamond body 11 after iron, cobalt, or nickel is removed;
and then
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copper, silver, or aluminum is embedded into the holes 111. In this way, the
heat
resistance of the polycrystalline diamond is improved and, thus, the service
life of the
polycrystalline diamond is prolonged.
100331 None of copper, silver, and aluminum is a catalyst metal of the
synthetic
diamond and can catalyze reverse transformation of the diamond into graphite.
Copper has
a thermal conductivity of 397 W/mK, silver has a thermal conductivity of 429
W/mK,
aluminum has a thermal conductivity of 217 W/mK, and cobalt has a thermal
conductivity
of only 96 W/mK. Replacing cobalt, nickel, or iron with one of copper, silver,
aluminum,
and alloys thereof is beneficial to improvement of the overall thermal
conductivity of the
polycrystalline diamond, and this makes it easier to dissipate heat from the
surface of the
polycrystalline diamond body 11 so that the operating temperature at the
operating point
of the polycrystalline diamond body 11 can be reduced.
[0034] In this embodiment, although the thermal conductivity of silver is
slightly higher
than that of copper, silver is much expensive than copper. Therefore, copper
or an alloy
thereof is preferably used in the present disclosure to replace cobalt.
Another choice is to
use aluminum or an alloy thereof. Specifically, aluminum has a low melting
point, so it is
easier to embed aluminum into the holes 111; and additionally, at the
operating point
under a temperature above 700 C, the molten aluminum will overflow from the
surface,
thereby achieving the purpose of heat dissipation through "sweating".
Therefore, in this
embodiment of the present disclosure, the non-catalyst metal having a high
thermal
conductivity is adopted to replace cobalt, nickel, and iron so as to eliminate
thermal
damage and stress damage to the polycrystalline diamond.
[0035] Correspondingly, an embodiment of the present disclosure further
provides a
method of processing a surface-modified polycrystalline diamond. Referring to
Fig. 3, the
processing method comprises the following steps of:
[0036] S110: coating an anticorrosion paint on the cemented carbide matrix of
the
polycrystalline diamond compact (PDC);
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[0037] S210: removing a catalyst metal from a surface of the polycrystalline
diamond
body and forming holes in the surface the polycrystalline diamond body;
[0038] S310: embedding the non-catalyst metal into the holes; and
[0039] S410: sanding the surface of the polycrystalline diamond body by using
an
abrasive paper or an abrasive cloth so as to remove a redundant part of the
non-catalyst
metal from the surface of the polycrystalline diamond body.
[0040] In the step S210, the catalyst metal is iron, cobalt, or nickel, which
is corroded
from the surface of the polycrystalline diamond body mainly by an acid boiling
method;
however, the diamond has strong acid and alkali resistance and, thus, will not
change after
being treated with an acid or an alkali. After the catalyst metal is removed
from the surface
of the polycrystalline diamond body, the microstructure of the polycrystalline
diamond
body comprises a single diamond phase and dispersed holes.
[0041] In the step S310, the non-catalyst metal is one of copper, silver,
aluminum, and
alloys thereof. Copper, silver, or aluminum is only filled in the holes that
are formed after
iron, cobalt, or nickel is removed, and is particularly flexible and only
located in the
surface. Therefore, there can be very small thermal stress generated due to a
difference
between a thermal expansion coefficient of copper, silver or aluminum and that
of the
diamond during operations at a high temperature, thereby eliminating thermal
damage and
stress damage.
[0042] The step S410 is optional, and may be executed by using a mechanical
polishing
method to polish the polycrystalline diamond until the surface thereof is
exposed. In this
case, it can be observed by means of a microscope that the microscopic holes
in the
surface of the polycrystalline diamond body have been filled by copper,
silver, or
aluminum. In practical implementations, a surface grinder of model M7132 may
be
adopted, in which a 240/270 fine diamond grinding wheel is slowly fed to grind
off the
surface of the polycrystalline diamond body by a thickness of about 0.01 mm,
thereby
grinding the surface into a polished surface. If there is no requirement on
the appearance
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of the polycrystalline diamond body but much attention is paid to the use
effect of the
polycrystalline diamond body, it is advantageous to maintain the copper layer
in the
surface of the polycrystalline diamond body.
[0043] As shown by researches, the larger the depth in the surface of the
polycrystalline
diamond body by which cobalt is removed and copper is filled is, the better
the effect of
the polycrystalline diamond body in practical applications will be and, thus,
the longer the
service life of the polycrystalline diamond will become. However, in case the
depth by
which cobalt is removed is over 0.5 mm, both the speed of removing cobalt and
that of
filling copper will be remarkably reduced, and this will significantly
increase the
manufacturing cost. Accordingly, in this embodiment of the present disclosure,
the depth
by which cobalt is removed is 0.1 mm to 1 mm, and preferably 0.3 mm to 0.5 mm.
[0044] Hereinafter, the method of processing the surface-modified
polycrystalline
diamond according to this embodiment of the present disclosure will be
described in detail
with reference to examples thereof.
Embodiment 1
[0045] First step: enclosing the cemented carbide matrix of the
polycrystalline diamond
body with an anticorrosion fixture;
[0046] second step: boiling the polycrystalline diamond body in an aqua regia
for 20 to
60 hours, and removing cobalt from the surface of the polycrystalline diamond
body by a
depth of 0.3 mm to 0.4 mm;
[0047] third step: after the aqua regia is cooled, taking the polycrystalline
diamond
body out of the aqua regia and rinsing the polycrystalline diamond body until
the
polycrystalline diamond body becomes neutral;
[0048] fourth step: putting a copper wheel rotating at a rotating speed of
1400
revolutions per second (rps) into contact with the surface of the
polycrystalline diamond
body;
[0049] fifth step: feeding the copper wheel by 0.1 mm to 0.4 mm for strong
friction so
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-4
that the surface of the polycrystalline diamond body is covered by copper; and
[0050] sixth step: sanding the surface of the polycrystalline diamond body by
using a
common No. 180 abrasive cloth or abrasive paper to remove the redundant
purplish red
copper layer until the surface of the black polycrystalline diamond body layer
is exposed.
[0051] In practical implementations, given that a red copper wheel is used as
an
abrasion wheel on a surface grinder, the copper wheel rotating at a rotating
speed of 1400
rps is put into contact with the surface of the polycrystalline diamond that
has been treated
with an acid, and then fed by 0.2 mm for strong friction until the entire
surface of the
polycrystalline diamond is covered by the copper layer.
Embodiment 2
[0052] First step: coating an anticorrosion paint on the cemented carbide
matrix of the
polycrystalline diamond body;
[0053] second step: boiling the polycrystalline diamond body in an aqua regia
for 10 to
110 hours, and removing cobalt from the surface of the polycrystalline diamond
body by a
depth of 0.4 mm to 0.6 mm;
[0054] third step: taking the polycrystalline diamond body out of the aqua
regia and
rinsing the polycrystalline diamond body until the polycrystalline diamond
body becomes
neutral;
[0055] fourth step: placing the polycrystalline diamond body into a copper
mould for
electrodeposition, with the mould being used as a cathode, a copper sulfate
solution being
used as an electrolyte, and a pure copper plate being used as an anode; and
[0056] fifth step: sanding the surface of the polycrystalline diamond body by
using a
common No. 180 abrasive cloth or abrasive paper to remove the redundant
purplish red
copper layer until the surface of the black polycrystalline diamond body layer
is exposed.
[0057] In the process of plating copper in an electrodeposition device, the
polycrystalline diamond body is placed into a copper mould for
electrodeposition, with the
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mould being used as a cathode, a copper sulfate solution being used as an
electrolyte, and
a pure copper plate being used as an anode. The electrolyte consists of 250
g/L of copper
sulfate (CuSO4-5H20) and 0.1 g/L of polyethylene glycol solution. In practical
implementations, after the polycrystalline diamond body is placed into the
electrolyte, the
electrolyte is supplied with a current of 10 A/dm and is stirred at a speed of
150 r/min for
electrodeposition of 20 hours at the normal temperature (i.e., 25 C).
Embodiment 3
[0058] This embodiment differs from the second embodiment only in that, copper
is
filled into the holes by using an electroless copper plating method in the
fourth step,
wherein the electroless copper plating is accomplished by reducing copper ions
under the
action of a reducing agent on a surface having a catalytically active
material, so that a
copper plated layer is formed in the surface of the polycrystalline diamond
body, with the
solution being a CuSO4 solution or a CuC12 solution.
Embodiment 4
[0059] This embodiment differs from the second embodiment only in that, copper
is
evaporated into vapor by using a vacuum evaporation method in the fourth step
so that a
copper film is plated in the surface of the polycrystalline diamond body.
[0060] According to the above descriptions, in the surface-modified
polycrystalline
diamond and the processing method thereof provided in the present disclosure,
the catalyst
metal is removed from the polycrystalline diamond body, and the non-catalyst
metal is
embedded into the holes that are formed in the surface of the polycrystalline
diamond after
the catalyst metal is removed. Thus, thermal damage and stress damage to the
polycrystalline diamond during operations at a high temperature are eliminated
and,
therefore, the service life of the polycrystalline diamond is prolonged.
[0061] It can be understood that, for those skilled in the art, equivalents or
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modifications can be made on basis of the technical solution and the inventive
concept
provided in the present disclosure, and any of these equivalents and
modifications shall
also fall within the scope of the present disclosure.
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