JP2011080130A - Diamond-coated electrode, and method for producing diamond-coated electrode - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a diamond-coated electrode superior in durability, into which a fluid intrudes little through the pin-hole. <P>SOLUTION: One layer of a diamond layer 24 has a film thickness Tc of 30-40 nm and is formed of ultramicro crystals, which reduces the size of the pin-hole itself, also enhances the water-repelling effect of the surface and suppresses the intrusion of the fluid such as an electrolytic solution. The production method includes coating a substrate with multiple layers of ultramicro crystals of diamond by repeating nucleation treatment to form a predetermined stacking number N(&ge;3) of the multilayer films 22a to 22n of diamond so as to be a predetermined film thickness Td. Accordingly, the multilayer films 22a to 22n of diamond acquire enhanced adhesiveness to each other, acquire enhanced film strength compared to such a case as to form a film having a target total film thickness Tt only by repeating simply seed crystal formation treatment and crystal growth treatment, suppresses the intrusion of the fluid through the pin-hole and acquire superior durability against exfoliation. It is also effective for the enhancement of the durability against the exfoliation to provide a graphite layer between the multilayer films 22a to 22n of diamond. <P>COPYRIGHT: (C)2011,JPO&amp;INPIT

Description

  The present invention relates to a diamond-coated electrode, and more particularly, to a diamond-coated electrode having excellent durability with less fluid penetration by a pinhole.

  A diamond-coated electrode in which a surface of a predetermined electrode base material is coated with a conductive diamond film has been proposed as a water treatment electrode that purifies industrial waste liquid or performs a predetermined electrolytic reaction, for example. Yes. However, since the crystal grains of the normal diamond film generally have a large particle diameter (maximum particle diameter) of 2 μm or more, for example, as shown in FIG. A relatively large gap is formed, and the gap becomes a pinhole (hole-like defect) so that the electrolyte or the like penetrates to the vicinity of the surface of the electrode substrate 100 as indicated by an arrow (→), and the diamond coating 102 is formed on the surface of the substrate. There was a problem that it was easy to peel off.

  On the other hand, by adjusting the diamond film formation conditions (gas pressure, gas concentration, etc.), a single-layer diamond film composed of microcrystalline diamond with a particle size of less than 1 μm can be formed, seed crystal generation treatment and crystal growth A technique for forming a diamond film having a multilayer structure with microcrystals by repeating the treatment has been proposed (see, for example, Patent Document 1). If such a microcrystalline diamond technology is applied to a diamond-coated electrode, not only the pinhole itself is reduced by microcrystallization, but also the infiltration of fluid such as an electrolyte is suppressed by the water repellent effect on the surface. Durability improvement against film peeling can be expected.

JP 2006-152423 A

  However, in the case of a diamond film with a single layer structure, it is inevitable that non-diamond carbon such as graphite is mixed, and durability may be impaired due to brittleness, etc. In any case, there was still room for improvement, such as a lack of good adhesion and the tendency to still peel off.

  The present invention has been made in the background of the above circumstances, and an object of the present invention is to provide a diamond-coated electrode excellent in durability with less intrusion of fluid by a pinhole.

  In order to achieve such an object, the first invention is a method for producing a diamond-coated electrode in which a surface of a predetermined electrode base material is coated with a conductive diamond film, and (a) a crystal grain size of 30 nm The following nucleation process for nucleating the surface using single crystal diamond, and (b) a seed crystal generation process for generating a diamond seed crystal and a crystal growth process for growing the seed crystal alternately. By repeating the above, a diamond multilayer film having a superfine crystal multilayer structure in which the film thickness Tc of one diamond layer provided by the crystal growth treatment is 200 nm or less and the entire film thickness Td is in the range of 400 nm to 3 μm is obtained. A microcrystalline diamond multi-layer coating process formed on the nucleated surface, and (c) the nucleating process and the microcrystalline diamond By repeating three times or more multi-layer coating process alternately, characterized in that the total film thickness Tt form a diamond coating in the range of 1.2μm~30μm on the surface of the electrode substrate.

  In the nucleation process, diamond particles and an alcohol liquid are placed in an ultrasonic device, and an electrode base material is inserted therein, and the surface of the base material or the surface of a diamond multilayer film provided on the base material surface is minute. The surface roughening treatment for providing irregularities improves the adhesion of the diamond multilayer film provided thereon.

  A second invention is a method for producing a diamond-coated electrode in which a surface of a predetermined electrode base material is coated with a conductive diamond film, comprising: (a) a seed crystal generation process for generating a diamond seed crystal; By alternately repeating the crystal growth process for crystal growth of the seed crystal, the diamond film thickness Tc of the single layer provided in the crystal growth process is an ultrafine crystal multilayer structure having a thickness of 200 nm or less, and the total film thickness Td is A microcrystalline diamond multilayer coating step for forming a diamond multilayer film in a range of 400 nm to 3 μm; and (b) a film thickness Tg on the diamond multilayer film in a range of 10 nm to 1 μm and from the film thickness Td. A graphite lamination process for forming a small graphite layer, and (c) the ultra-microcrystalline diamond multilayer coating process and the A graphite film having a total film thickness Tt in the range of 1.2 μm to 30 μm is formed on the surface of the electrode substrate by alternately repeating the graphite lamination process and forming the diamond multilayer film at least three times. It is characterized by that.

  According to a third aspect of the present invention, there is provided a method for producing a diamond-coated electrode according to the second aspect of the present invention, comprising: ) The nucleation process is performed in the nucleation step prior to forming the diamond multilayer film at least first in the ultra-microcrystalline diamond multilayer coating step.

  According to a fourth aspect of the present invention, there is provided a method for producing a diamond-coated electrode according to the second or third aspect of the invention, wherein the ultra-microcrystalline diamond multilayer coating step and the graphite laminating step are repeatedly performed. It is characterized in that it is carried out by the CVD method while being held at a temperature.

  A fifth invention is a diamond-coated electrode in which a surface of a predetermined electrode base material is coated with a conductive diamond film, and (a) an ultrafine crystal having a film thickness Tc of one diamond layer of 200 nm or less A multi-layered diamond multilayer film having a total film thickness Td in the range of 400 nm to 3 μm; and (b) a graphite layer having a film thickness Tg in the range of 10 nm to 1 μm and smaller than the film thickness Td, And (c) the diamond multilayer film and the graphite layer are alternately and repeatedly laminated, and the diamond multilayer film is formed at least three times, so that the total film thickness Tt is in the range of 1.2 μm to 30 μm. A diamond coating is provided on the surface of the electrode substrate.

  In the method for producing a diamond-coated electrode according to the first invention, a nucleation step in which a single crystal diamond having a crystal grain size of 30 nm or less is used for nucleation, a seed crystal generation process for generating a diamond seed crystal, and its By alternately repeating the crystal growth treatment for crystal growth of the seed crystal, a diamond having an ultrafine crystal multilayer structure in which the film thickness Tc of one diamond layer is 200 nm or less and the entire film thickness Td is in the range of 400 nm to 3 μm A diamond film having a total film thickness Tt in the range of 1.2 μm to 30 μm is formed by alternately repeating the microcrystalline diamond multilayer coating process for forming a multilayer film three or more times. In that case, since the film thickness Tc of one diamond layer is 200 nm or less, the diamond crystal particles constituting the diamond layer also become ultrafine crystals having a particle diameter substantially equal to the film thickness Tc, and the pinhole itself is formed. Intrusion of fluid such as an electrolyte is suppressed by decreasing the surface and increasing the water-repellent effect on the surface.

  In addition, a nucleation process in which a nucleation process is performed using a single crystal diamond having a crystal grain size of 30 nm or less is repeated to perform a microcrystalline diamond multilayer coating process, and a diamond multilayer film having a predetermined film thickness Td is applied three or more times. As a result, the adhesion between the electrode substrate and the diamond multilayer film and between the diamond multilayer films is improved, and the seed crystal generation process and the crystal growth process are simply repeated in the polycrystalline diamond multilayer coating process. As compared with the case where the target total film thickness Tt is obtained, the coating strength is increased, and the durability against peeling is obtained in combination with the suppression of fluid penetration by the pinhole.

  In the ultra-microcrystalline diamond multi-layer coating process, an ultra-microcrystalline diamond multi-layer film is formed by alternately repeating seed crystal generation processing and crystal growth processing. The non-diamond carbon such as the above is suppressed, and also in this respect, the coating strength is improved, and further excellent durability against peeling of the coating can be obtained.

  The method for producing a diamond-coated electrode according to the second aspect of the present invention includes alternately repeating a seed crystal generation process for generating a diamond seed crystal and a crystal growth process for crystal growth of the seed crystal to thereby obtain a film thickness Tc of one diamond layer. Is an ultra-microcrystalline multilayer structure with a thickness of 200 nm or less, and an ultra-microcrystalline diamond multilayer coating process for forming a diamond multilayer film with an overall film thickness Td in the range of 400 nm to 3 μm, and a film thickness Tg on the diamond multilayer film A graphite laminating step for forming a graphite layer within a range of 10 nm to 1 μm and smaller than the film thickness Td, and repeatedly performing such a microcrystalline diamond multilayer coating step and a graphite laminating step alternately, and at least a diamond multilayer film Is formed three times or more, so that the total film thickness Tt is 1.2 μm to 30 μm. Forming a diamond coating in the range of on the surface of the electrode substrate. In other words, the point that the ultrafine diamond multilayer film is provided three or more times is the same as in the first invention. The pinhole itself is reduced, and when the outermost surface of the diamond film is this diamond multilayer film, the surface repellent property is reduced. By increasing the water effect, the intrusion of a fluid such as an electrolyte is suppressed. Further, when the outermost surface of the diamond coating is a graphite layer, the graphite layer is non-crystalline, so there are few pinholes and the infiltration of a fluid such as an electrolytic solution can be prevented more reliably.

  Further, in the present invention, since an amorphous graphite layer is provided between each diamond multilayer film, according to experiments by the present inventors, a seed crystal generation process and a crystal growth process are simply performed in a polycrystalline diamond multilayer coating process. As compared with the case where the target total film thickness Tt is obtained simply by repeating the above, it is possible to obtain more excellent durability against peeling. This is presumably because the graphite layer is non-crystalline, so that there are few pinholes and the infiltration of a fluid such as an electrolyte is more reliably prevented, and the adhesion is improved and the film strength is increased. Since the film thickness Tg of the graphite layer is smaller than the film thickness Td of the diamond multilayer film, it is possible to improve the film strength and prevent peeling while suppressing the weakening of the diamond film due to the provision of the graphite layer. it can.

  In addition, since the diamond multilayer film itself formed by the ultra-microcrystalline diamond multilayer coating process suppresses the mixing of non-diamond carbon such as graphite, it is compared with the microcrystalline diamond film having a single layer structure as in the first invention. As a result, excellent film strength can be obtained, and even better durability against film peeling can be obtained.

  Further, in the second invention, when the diamond multilayer film is provided three times or more, the graphite layer having a predetermined film thickness Tg is provided, so that it is not always necessary to perform the nucleation process one by one. For example, as in the fourth invention The repeated ultra-microcrystalline diamond multi-layer coating process and the graphite lamination process can be performed by the CVD method while holding the electrode base material in the reactor of the CVD apparatus, which facilitates the production of the diamond-coated electrode. it can.

  In the third invention, since the nucleation process is performed in the nucleation process prior to the formation of the diamond multilayer film at least first in the ultra-microcrystalline diamond multilayer coating process, Adhesion is enhanced and the peeling of the diamond coating is more effectively suppressed.

  The fifth aspect of the invention is an ultra-microcrystalline multilayer structure in which the thickness Tc of one diamond layer is 200 nm or less, the diamond multilayer film having a total film thickness Td in the range of 400 nm to 3 μm, and the film thickness Tg of 10 nm to 1 μm. And the diamond multilayer film and the graphite layer are alternately and repeatedly laminated, and at least the diamond multilayer film is formed at least three times. Is a diamond-coated electrode in which a diamond film having a total film thickness Tt in the range of 1.2 μm to 30 μm is provided on the surface of the electrode substrate, and is manufactured using the manufacturing method of the first invention or the second invention. can do. In such a diamond-coated electrode, the microcrystalline diamond multilayer film is provided three or more times, so that the pinhole itself becomes smaller and the surface water-repellent effect is enhanced, so that the ingress of fluid such as an electrolyte is suppressed. Is done. Moreover, since a graphite layer having a predetermined film thickness Tg is provided between each diamond multilayer film, as in the case of the second invention, the film strength is improved while preventing the diamond film from becoming brittle, and peeling is appropriately prevented. can do. Furthermore, since the ultra-microcrystalline diamond multilayer film itself is suppressed from mixing non-diamond carbon such as graphite, an excellent film strength can be obtained compared to a single-layer microcrystalline diamond film, Even better durability can be obtained with respect to film peeling and the like.

BRIEF DESCRIPTION OF THE DRAWINGS It is a figure explaining an example of the diamond covering electrode manufactured according to the manufacturing method of 1st invention, (a) is an expanded sectional view of the surface layer part in which the diamond film was provided, (b) is one diamond in a diamond film FIG. 5 is an image diagram conceptually showing how the diamond crystal particles C are arranged by further enlarging the multilayer film. It is a schematic block diagram explaining an example of the microwave plasma CVD apparatus suitably used when coating a diamond film. It is a flowchart explaining the procedure at the time of coating the diamond film of FIG. 1 according to 1st invention using the apparatus of FIG. It is a figure explaining the result of having investigated durability about the some test article containing the product of this invention manufactured according to the film-forming procedure of FIG. It is a figure explaining an example of the diamond covering electrode by which the diamond multilayer film and the graphite layer were provided alternately, and is an expanded sectional view of the surface layer part in which the diamond film was provided, and is a figure corresponding to (a) of FIG. is there. It is a flowchart explaining an example of the procedure at the time of coating the diamond film of FIG. 5 according to 2nd invention using the apparatus of FIG. It is a figure explaining the result of having investigated durability about the some test article containing this invention product manufactured according to the film-forming procedure of FIG. It is a flowchart explaining another example of the procedure at the time of coating the diamond film of FIG. 5 according to 2nd invention. It is a flowchart explaining an example of the procedure at the time of coating the diamond film of FIG. 5 according to 1st invention, 2nd invention. It is an image figure explaining the path | route at the time of a predetermined fluid infiltrating from the pinhole produced between particle | grains to the surface vicinity of an electrode base material in the diamond film comprised by the conventional normal diamond crystal grain (crude crystal).

  The present invention is preferably applied to a diamond-coated electrode for water treatment that purifies industrial waste liquid or causes a predetermined electrolytic reaction, but is similarly applied to a diamond-coated electrode used in other fields. obtain. As an electrode base material, metals such as copper, cemented carbide and titanium are preferably used, but other conductive materials such as graphite can also be adopted. The shape of the electrode substrate is appropriately determined such as a plate shape or a rod shape. Although diamond is an electrical insulator by nature, it can be given conductivity by doping impurities such as boron (boron; B) when the crystal is grown. The doping amount is appropriately determined depending on the kind of impurities. For example, in the case of boron, the range of 0.05 to 5 atomic% is appropriate, and the range of 0.5 to 1 atomic% is desirable.

  The diamond used for the nucleation treatment may have a crystal grain size of 30 nm or less, but is preferably 20 nm or less. For example, a commercially available artificial single crystal of about 5 to 20 nm is preferably used.

  A CVD (chemical vapor deposition) method is preferably used for the execution of the ultra-microcrystalline diamond multi-layer coating process in which the seed crystal generation process and the crystal growth process are performed, and the microwave plasma CVD method is particularly preferable. Alternatively, other CVD methods such as a high-frequency plasma CVD method can be used. In carrying out the graphite laminating step of the second invention, it is possible to form a graphite layer using the above-mentioned CVD method, and supply the electrode substrate while holding the electrode substrate in the reactor of the CVD apparatus as in the fourth invention. The microcrystalline diamond multilayer coating process and the graphite laminating process can be performed continuously by switching the reaction gas to be used.

  The film thickness Tc of one diamond layer of the diamond multilayer film may be 200 nm or less, preferably 100 nm or less, and more preferably 50 nm or less. The film thickness Tc may be constant, but can be continuously changed or changed stepwise within a range of 200 nm or less.

  The diamond multilayer film may be formed directly on the surface of the electrode base material, but another base layer may be provided as necessary to improve adhesion, and the diamond multilayer film may be formed thereon. good. In the first invention, the diamond multilayer films formed three or more times may be directly stacked so as to be in contact with each other, but a graphite layer is provided between the diamond multilayer films as in the second invention. It is also possible to provide other intermediate layers. When a graphite layer having a predetermined film thickness Tg is provided between the diamond multilayer films, the obtained diamond-coated electrode is an embodiment of the fifth invention. When an intermediate layer such as a graphite layer is provided on the diamond multilayer film, the surface of the intermediate layer may be nucleated, and the diamond multilayer film may be formed on the surface subjected to the nucleation process.

  In the second invention, it is sufficient that the diamond multilayer film is formed at least three times, and the uppermost layer of the diamond coating may be a diamond multilayer film or a graphite layer. It can be appropriately selected according to the field of use or required performance of the diamond-coated electrode. The same applies to the diamond-coated electrode of the fifth invention. In implementing the first invention, it is possible to provide a graphite layer or the like as the uppermost layer as necessary.

  The graphite layer has a film thickness Tg in the range of 10 nm to 1 μm and smaller than the film thickness Td of the diamond multilayer film in order to suppress the weakening of the diamond film due to the presence of the graphite layer. 5 μm or less is desirable, or it is desirable to be 1/2 or less of the film thickness Td of the diamond multilayer film.

  In the third invention, the nucleation process is performed in the nucleation process prior to the formation of the diamond multilayer film at least in the ultra-microcrystalline diamond multilayer coating process. The diamond multilayer film is formed in the ultra-microcrystalline diamond multilayer coating process. Prior to this, the nucleation process can always be performed in the nucleation process. In carrying out the second invention, such a nucleation process is not necessarily required, and only the ultra-microcrystalline diamond multilayer coating process and the graphite lamination process may be repeated to form a diamond film.

  In the fourth invention, the microcrystalline diamond multilayer coating process and the graphite laminating process, which are repeatedly performed, are performed by the CVD method while the electrode base material is held in the reaction furnace of the CVD apparatus. The electrode substrate is held in the reaction furnace of the CVD apparatus, and the ultra-microcrystalline diamond multilayer coating process and the graphite laminating process are performed to form a diamond multilayer film and a graphite layer for one lamination period, and then the electrode substrate is reacted once. After taking out from the furnace, for example, after performing the nucleation process and the like, it may be set in the reaction furnace again to perform the next ultra-microcrystalline diamond multilayer coating process and graphite lamination process.

  The diamond-coated electrode of the fifth invention is preferably produced using the production method of the first invention or the second invention, but is not necessarily limited to these production methods, and is produced by other production methods. There is no problem.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
FIG. 1 is a diagram for explaining an example of a diamond-coated electrode manufactured according to the method of the present invention (first invention). (A) is an enlarged sectional view of a surface layer portion provided with a diamond coating 20, and (b) is diamond. FIG. 3 is an image diagram conceptually showing how diamond crystal particles C are arranged by further enlarging one diamond multilayer film 22a in a coating 20; The diamond-coated electrode 10 is obtained by coating the surface 14 of the electrode substrate 12 with the diamond coating 20 according to the flowchart of FIG. 3 using the microwave plasma CVD apparatus 30 of FIG. It is comprised with metal plate materials, such as copper.

  The diamond coating 20 is composed of a large number of diamond multilayer films 22a, 22b,... 22n (hereinafter simply referred to as the diamond multilayer film 22 unless otherwise distinguished). The film thickness Td is substantially constant in the range of 400 nm to 3 μm, and the total film thickness Tt is in the range of 1.2 μm to 30 μm. The number of diamond multilayer films 22, that is, the number N of laminated layers is 3 or more, and is appropriately determined according to the film thickness Td so that the target total film thickness Tt is obtained. In addition, as shown in FIG. 1 (b), the diamond multilayer film 22 has a large number of diamond layers 24a, 24b,... 24m (hereinafter simply referred to as the diamond layer 24 unless otherwise distinguished). The film thicknesses Tc of the diamond layers 24 are substantially the same and are in the range of 30 to 40 nm (for example, target value 35 nm), and the grain size of the diamond crystal particles C is substantially equal to the film thickness Tc. It has a multilayer structure of ultrafine crystals.

  The microwave plasma CVD apparatus 30 of FIG. 2 includes a reaction furnace 32, a microwave generator 34, a source gas supply device 36, a vacuum pump 38, and an electromagnetic coil 40. A table 42 is provided in the cylindrical reaction furnace 32, and a plurality of electrode substrates 12 to be coated with the diamond coating 20 are set (arranged) in a predetermined posture. The microwave generator 34 is an apparatus that generates a microwave of, for example, 2.45 GHz. The microwave base 34 is heated by introducing the microwave into the reaction furnace 32, and the microwave generator 34 is also used. The heating temperature is adjusted by controlling the electric power.

The source gas supply device 36 is for supplying source gases such as methane (CH ₄ ), hydrogen (H ₂ ), and carbon monoxide (CO) into the reaction furnace 32, and controls the gas cylinders and flow rates thereof. In this embodiment, in order to dope boron, for example, a liquid obtained by dissolving boron oxide in methanol can be mixed with the raw material gas and supplied into the reaction furnace 32. It is like that. The vacuum pump 38 is for sucking and depressurizing the gas in the reaction furnace 32, so that the pressure value in the reaction furnace 32 detected by the pressure gauge 46 becomes a predetermined pressure value determined in advance. The motor current of the vacuum pump 38 is feedback controlled. The electromagnetic coil 40 is arranged in an annular shape on the outer peripheral side of the reaction furnace 32 so as to surround the inside of the reaction furnace 32.

  The coating process of the diamond film 20 using such a microwave plasma CVD apparatus 30 is performed according to the procedure shown in the flowchart of FIG. In step S1 of FIG. 3, prior to disposing the electrode substrate 12 in the reaction furnace 32, a nucleation process is performed using an artificial single crystal of diamond having a crystal grain size of 5 to 20 nm. This nucleation process is a surface roughening process in which diamond particles and an alcohol liquid are placed in an ultrasonic device, an electrode substrate 12 is inserted therein, and minute irregularities are formed on the surface thereof. Although the attaching process is performed, the second and subsequent nucleation processes performed when the determination in step S3 is NO (No) are performed on the diamond multilayer film 22 provided on the surface 14 of the electrode base 12. . This step S1 is a nucleation step, and can be performed manually by an operator using an ultrasonic device, for example. As the artificial single crystal of diamond having a crystal grain size of 5 to 20 nm, for example, a commercially available product may be purchased.

  Thereafter, the electrode substrate 12 is set in the reaction furnace 32, and a microcrystalline diamond multilayer coating process is performed in step S2 by a microwave plasma CVD method. This ultra-microcrystalline diamond multilayer coating process is for forming the diamond multilayer film 22, and is performed by alternately repeating the seed crystal generation process in step S2-1 and the crystal growth process in step S2-2.

The seed crystal generation process in step S2-1 is for generating a seed crystal while suppressing the crystal growth of diamond. Specifically, the flow rate of methane and hydrogen is adjusted so that the concentration of methane becomes a set value determined within a range of 10% to 30%, and the surface temperature of the electrode base 12 is 700 ° C. to 900 ° C. The microwave generator 34 is adjusted so that the set temperature is determined within the range, and the gas pressure in the reaction furnace 32 is determined within the range of 2.7 × 10 ² Pa to 2.7 × 10 ³ Pa. The vacuum pump 38 is operated so as to reach the set pressure, and the state is continued for 0.1 to 2 hours. As a result, a large number of seed crystals serving as starting points for crystal growth of diamond are generated and deposited on the surface 14 of the electrode substrate 12 on which the nucleation process has been performed. Further, in the second and subsequent seed crystal generation processes performed after step S2-3, on the surface of the diamond layer 24 composed of a large number of diamond crystal particles C grown by the crystal growth process of step S2-2, Newly produced seed crystals are deposited in layers.

In the crystal growth process in step S2-2, the seed crystal attached in the seed crystal generation process in step S2-1 is grown. Specifically, the flow rate of methane and hydrogen is adjusted so that the methane concentration becomes a set value determined within a range of 1% to 4%, and the surface temperature of the electrode base 12 is 800 ° C to 900 ° C. adjust the microwave generator 34 so as to set the temperature defined in the range of the gas pressure in the reactor 32 is defined within the range of ^{1.3 × 10 3 Pa~6.7 × 10 3} Pa The vacuum pump 38 is operated so that the set pressure is set, and the state is determined for a predetermined time that the film thickness of the diamond layer 24 becomes Tc, specifically, the crystal length of the diamond crystal particles C. This is continued for a predetermined processing time when the length dimension in the crystal growth direction becomes the film thickness Tc.

  Subsequent to step S2-2, step S2-3 is executed to determine whether or not the diamond multilayer film 22 has reached a predetermined target film thickness Td. Specifically, the number of processing times of the seed crystal generation processing in step S2-1 and the crystal growth processing in step S2-2 is determined by the set number of times determined according to the film thickness Td and the film thickness Tc of the diamond layer 24 ( It is determined whether or not (Td / Tc) has been reached. Steps S2-1 and S2-2 are repeatedly executed until the set number is reached, and step S3 is executed when the set number is reached.

  In the ultra-microcrystalline diamond multi-layer coating process in step S2, when a raw material gas such as hydrogen is supplied, a liquid obtained by dissolving boron oxide in methanol is mixed with the raw material gas, and the reaction gas is supplied to the reactor 32 at a predetermined flow rate. By supplying, the diamond layer 24 and further the diamond multilayer film 22 are doped with boron. The doping amount (content) of boron can be adjusted by changing the supply flow rate of the liquid in which boron oxide is dissolved, and boron is doped at a ratio of, for example, 0.5 to 1 atomic% so that predetermined conductivity is obtained. To be set.

  This step S2 is an ultra-microcrystalline diamond multilayer coating process. When the diamond multilayer film 22 reaches the target film thickness Td and the determination in step S2-3 becomes YES (positive), step S3 is executed. The ultra-microcrystalline diamond multilayer coating process in step S2 can be automatically performed by controlling the operation of the microwave plasma CVD apparatus 30 by a control device using a computer, for example.

  In step S3, whether or not the diamond multilayer film 22 has reached a predetermined target number N of layers, that is, whether or not the number of executions of the ultra-microcrystalline diamond multilayer coating process in step S2 is the same as the number N of layers. It is determined whether or not, and steps S1 and S2 are repeated until the number of stacks is equal to N. When steps S1 and S2 are repeatedly executed as many times as the number N of layers, the target diamond film 20 in which the diamond multilayer film 22 is stacked by the number N of layers is formed, and the determination in step S3 is YES, A series of diamond coating film forming processes for manufacturing the diamond-coated electrode 10 is completed.

  As described above, in this embodiment, the nucleation process in step S1 in which a single crystal diamond having a crystal grain size of 5 to 20 nm is used, and the seed crystal generation process in which a seed crystal is generated (step S2-1). ) And the crystal growth treatment (step S2-2) for crystal growth of the seed crystal are alternately repeated, so that the entire film can be obtained in an ultrafine crystal multilayer structure in which the film thickness Tc of one diamond layer 24 is 30 to 40 nm. By repeating the ultra-microcrystalline diamond multilayer coating process of step S2 for forming the diamond multilayer film 22 having a thickness Td in the range of 400 nm to 3 μm alternately by the same number of times as the number N of layers (≧ 3), the total film thickness is obtained. A target diamond film 20 having a Tt in the range of 1.2 μm to 30 μm is formed. In that case, since the film thickness Tc of one diamond layer 24 is 30 to 40 nm, the diamond crystal particles C constituting the diamond layer 24 are also ultrafine crystals having a particle diameter substantially equal to the film thickness Tc. As the pinhole itself becomes smaller and the water-repellent effect on the surface becomes higher, the intrusion of fluid such as an electrolyte is suppressed.

  Further, the nucleation process of step S1 in which the nucleation process is performed using single crystal diamond having a crystal grain diameter of 5 to 20 nm is repeated, and the ultrafine crystal diamond multi-layer coating process of step S2 is performed to obtain a predetermined film thickness Td. Since the diamond multilayer film 22 is formed three times or more, the adhesion between the electrode substrate 12 and the diamond multilayer film 22 and between the diamond multilayer films 22 is improved, and the polycrystalline diamond in step S2 is simply obtained. By simply repeating the seed crystal generation process and the crystal growth process in the multilayer coating process, the film strength is increased compared to the case where the target total film thickness Tt is obtained, and the intrusion of fluid by the pinhole is suppressed as described above. In combination with this, excellent durability against peeling can be obtained.

  Further, in the ultra-fine diamond multi-layer coating process in step S2, the ultra-fine diamond multi-layer film 22 is formed by alternately repeating the seed crystal generation process (step S2-1) and the crystal growth process (step S2-2). Therefore, in comparison with a microcrystalline diamond film having a single-layer structure, mixing of non-diamond carbon such as graphite is suppressed, and also in this respect, the film strength is improved and further excellent durability against film peeling is obtained. It becomes like this.

  In this connection, five types of test products No1 to No5 having different numbers of layers N and total film thickness Tt were prepared, and subjected to predetermined water treatment to examine the durability against peeling of the diamond coating 20, as shown in FIG. Results were obtained. The electrode substrate 12 is a cemented carbide plate, and the dimensions (mm) are width × thickness × height = 10 × 1 × 30.

  In FIG. 4, test products No1 and No2 are comparative products with the number of stacked layers N = 1 and 2, and the total film thickness Tt is somewhat thick, but in both cases, the diamond coating 20 peeled off early and the electrode life was reached. On the other hand, the test products No3 to No5 having a lamination number N of 3 or more were the products of the present invention, and the diamond coating 20 did not peel off even when used for 240 hours. From this, the nucleation process of step S1 in which nucleation processing is performed using diamond having a predetermined crystal grain size is repeated, and the ultrafine-crystal diamond multi-layer coating process of step S2 is performed, and the diamond multilayer film 22 is stacked in a predetermined layer. The formation of only a few N (≧ 3) improves the adhesion of the diamond multilayer film 22 and increases the film strength. Simply, seed crystal generation processing (step S2-1) and crystal growth processing (step S2-2) are performed. It can be seen that, as compared with the case where the predetermined total film thickness Tt is obtained simply by repeating (), it greatly contributes to improving the durability against peeling.

  Next, another embodiment of the present invention will be described. In the following embodiments, parts that are substantially the same as those in the first embodiment are denoted by the same reference numerals, and detailed description thereof is omitted.

  The diamond-coated electrode 50 shown in FIG. 5 has graphite layers 54a, 54b,... 54n (hereinafter not particularly distinguished) on the large number of diamond multilayer films 22 as compared with the diamond-coated electrode 10 shown in FIG. Is simply referred to as a graphite layer 54). The film thicknesses Tg of the respective graphite layers 54 are substantially the same and are in the range of 10 nm to 1 μm, and are smaller than the film thickness Td of the diamond multilayer film 22. The diamond multilayer film 22 is configured in the same manner as in the first embodiment. As shown in FIG. 1 (b), the diamond multilayer film 22 has an ultrafine crystal multilayer structure in which the film thickness Tc of many diamond layers 24 is 30 to 40 nm. The film thickness Td is in the range of 400 nm to 3 μm. The total film thickness Tt of the diamond coating 52 including the graphite layer 54 is also in the range of 1.2 μm to 30 μm, similarly to the first embodiment. In this embodiment, the diamond multilayer film 22 and the graphite layer 54 are stacked as many as the number of stacks N (≧ 3) with one stacking cycle. However, the uppermost graphite layer 54n can be omitted. This diamond-coated electrode 50 is an embodiment of the fifth invention.

  Such a diamond-coated electrode 50 is manufactured by forming the diamond film 52 according to the procedure shown in the flowchart of FIG. 6 using the microwave plasma CVD apparatus 30 of FIG. Steps R1, R2, and R4 in FIG. 6 are the same as steps S1, S2, and S3 in FIG. 3, and steps R2-1 to R2-3 in step R2 are also the same as steps S2-1 to S2-3. However, the difference is that the graphite laminating process of step R3 is executed following step R2, and the steps after step R4 are executed following step R4. Step R3 is a graphite lamination process, and the manufacturing procedure according to the flowchart of FIG. 6 is one embodiment of the second invention.

  The graphite laminating process in step R3 is performed continuously with the microcrystalline diamond multilayer coating process in step R2 while holding the electrode substrate 12 in the reaction furnace 32 of the microwave plasma CVD apparatus 30. Specifically, by stopping the supply of hydrogen gas and supplying only methane gas, the crystal growth of diamond crystal particles C is stopped, and an amorphous graphite layer 54 is formed. Further, the processing time is determined in advance according to the film thickness Tg of the graphite layer 54. In the next step R4, it is determined whether or not the number of laminations with the diamond multilayer film 22 and the graphite layer 54 as one lamination period has reached the same number as the predetermined number N (≧ 3). Steps R2 and R3 are repeated until the same number of times. In the present embodiment, steps R2 and R3 are repeatedly performed as many times as the number N of layers while holding the electrode substrate 12 in the reaction furnace 32 of the microwave plasma CVD apparatus 30. As a result, the target diamond film 52 is formed by laminating the diamond multilayer film 22 and the graphite layer 54 by the number N, and the determination in step R4 is YES, and a series for manufacturing the diamond-coated electrode 50 is performed. The diamond film forming process is completed. The ultra-microcrystalline diamond multilayer coating process in step R2, the graphite laminating process in step R3, and the judgment process in step R4 are automatically performed by controlling the operation of the microwave plasma CVD apparatus 30 by a control device using a computer, for example. Can be made.

  In the present embodiment, a diamond layer of one layer is obtained by alternately repeating the seed crystal generation process of Step R2-1 for generating a diamond seed crystal and the crystal growth process of Step R2-2 for crystal growth of the seed crystal. An ultra-microcrystalline diamond multi-layer coating process of step R2 for forming a diamond multi-layer film 22 having a total film thickness Td in the range of 400 nm to 3 [mu] m with an ultra-microcrystalline multi-layer structure having a film thickness Tc of 24 or less of 200 nm, and the diamond A graphite laminating step of step R3 for forming a graphite layer 54 having a film thickness Tg in the range of 10 nm to 1 μm and smaller than the film thickness Td on the multilayer film 22, and repeating these steps R2 and R3R3 And forming the diamond multilayer film 22 at least three times, the total film thickness Tt is A diamond coating 52 in the range of 1.2 μm to 30 μm is formed on the surface 14 of the electrode substrate 12. That is, when the diamond multilayer film 22 having a predetermined film thickness Td is formed three times or more in the ultra-microcrystalline diamond multilayer coating process of Step R2 as compared with the diamond film 20 of Example 1, nucleation is performed in Step R1 one by one. The difference is that instead of performing the treatment outside the furnace, a graphite layer 54 having a predetermined film thickness Tg is provided.

  Therefore, the point that the ultra-microcrystalline diamond multilayer film 22 is provided three times or more is the same as in Example 1, and the pinhole itself is reduced, and when the outermost surface of the diamond coating 52 is the diamond multilayer film 22, By increasing the water-repellent effect on the surface, the infiltration of fluid such as an electrolyte is suppressed. Further, when the outermost surface is the graphite layer 54 as in the present embodiment, since the graphite layer 54 is non-crystalline, there are few pinholes and the intrusion of fluid such as an electrolytic solution can be prevented more reliably.

  Further, since the amorphous graphite layer 54 is provided between the diamond multilayer films 22, according to the experiments by the present inventors, the seed crystal generation process (step S2) is performed in the polycrystalline diamond multilayer coating process of step R2. Compared to the case where the target total film thickness Tt is obtained simply by repeating R2-1) and the crystal growth treatment (step R2-2), it is possible to obtain more excellent durability against peeling. The reason is considered that the graphite layer 54 is amorphous, so that there are few pinholes and the infiltration of a fluid such as an electrolytic solution is prevented more reliably, and the adhesion is improved and the film strength is increased. . Since the film thickness Tg of the graphite layer 54 is smaller than the film thickness Td of the diamond multilayer film 22, the weakening of the diamond film 52 resulting from the provision of the graphite layer 54 is suppressed, and the film strength is improved and peeling is performed. It can be prevented appropriately.

  Further, since the diamond multilayer film 22 itself formed in the ultra-microcrystalline diamond multilayer coating process of Step R2 is prevented from mixing non-diamond carbon such as graphite, the single crystal structure microcrystals are the same as in the first embodiment. Excellent film strength can be obtained as compared with the diamond film, and more excellent durability against film peeling can be obtained.

  Further, in Example 2, when the diamond multilayer film 22 is provided three times or more, the graphite layer having a predetermined film thickness Tg is provided, so that it is not always necessary to perform the nucleation process in Step R1 outside the furnace one by one. In this embodiment, the ultra-microcrystalline diamond multilayer coating process in step R2 and the graphite lamination process in step R3 are repeated by the CVD method while the electrode substrate 12 is held in the reaction furnace 32 of the microwave plasma CVD apparatus 30. Therefore, the diamond coating 52 can be formed and the diamond-coated electrode 50 can be easily manufactured.

  Further, in this embodiment, the nucleation process of Step R1 is performed prior to the formation of the diamond multilayer film 22 in the ultra-microcrystalline diamond multilayer coating process of Step R2, and the nucleus 14 is formed on the surface 14 of the electrode substrate 12. Since the attaching process is performed, the adhesion between the electrode substrate 12 and the diamond coating 52 is enhanced by the nucleating process, and the peeling of the diamond coating 52 is more effectively suppressed.

  In this connection, six types of test products No1 to No6 having different numbers of layers N, total film thickness Tt, and the like were prepared, the durability of the diamond coating 52 was examined by performing predetermined water treatment, and the results shown in FIG. was gotten. The electrode substrate 12 is a cemented carbide plate, and the dimensions (mm) are width × thickness × height = 10 × 1 × 30. In addition, “3.5” described in the column of the number N of layers of test product No. 4 was formed four times for the diamond multilayer film 22, but the graphite layer 54 was three times and the outermost layer was the diamond multilayer film 22. Means that. In the other test products No1 to No3, No5, and No6, the diamond multilayer film 22 and the graphite layer 54 are laminated the same number of times, and the outermost layer is the graphite layer 54.

  In FIG. 7, the test product No. 1 is a comparative product with the number of stacked layers N = 2, and the diamond coating 52 peeled off at an early stage and the electrode life was reached. Test product No. 5 is a comparative product in which the number of layers N = 2 and the film thickness Tg of the graphite layer 54 is larger than the film thickness Td of the diamond multilayer film 22, and the test product No. 6 has the number of layers N = 3 but the graphite layer 54. The diamond film 52 was peeled off in about 7 minutes or 15 minutes, respectively, in a comparative product having a film thickness Tg greater than the film thickness Td of the diamond multilayer film 22. On the other hand, the test products No2 to No4 are products of the present invention in which the number of stacked layers N is 3 or more and the film thickness Tg of the graphite layer 54 is smaller than the film thickness Td of the diamond multilayer film 22. The diamond coating 52 was not peeled off, and excellent durability was obtained.

  FIG. 8 shows a case where the diamond film 52 shown in FIG. 5 is formed by a film forming method different from that shown in FIG. 6. Steps Q1 to Q3 are the same as steps R2 to R4, respectively. The difference is not provided. That is, without performing the nucleation process, the electrode base material 12 is set in the reaction furnace 32 of the microwave plasma CVD apparatus 30 from the beginning, and the ultra-microcrystalline diamond multilayer coating process in step Q1 and the graphite lamination process in step Q2 are performed. In the case where the diamond film 52 is formed by repeatedly performing the same number of times as the number N of layers, the diamond film 52 can be completely formed in the reaction furnace 32 of the microwave plasma CVD apparatus 30. The film forming procedure of FIG. 8 is an embodiment of the second invention.

  FIG. 9 shows that compared with the second embodiment of FIG. 6, when the determination in step R4 is NO (No), the process returns to step R1 to perform the nucleation process outside the furnace, and then the microwave plasma CVD apparatus. The ultra-microcrystalline diamond multilayer coating process of step R2 and the graphite lamination process of step R3 are performed in the reactor 32 of 30. That is, not only the substrate surface 14 but also the surface of the graphite layer 54 is subjected to a nucleation process to provide minute irregularities on the surface, and the diamond multilayer film 22 is formed thereon. As a result, the coating strength is further improved, and the durability of the diamond coating 52 is further improved. The film forming procedure of FIG. 9 is an embodiment of the first invention and the second invention.

  As mentioned above, although the Example of this invention was described in detail based on drawing, these are one embodiment to the last, and this invention is implemented in the aspect which added the various change and improvement based on the knowledge of those skilled in the art. be able to.

DESCRIPTION OF SYMBOLS 10, 50: Diamond coating electrode 12: Electrode base material 14: Surface 20, 52: Diamond coating 22a ... 22n: Diamond multilayer film 24a ... 24m: Diamond layer 30: Microwave plasma CVD apparatus (CVD apparatus) 32 : Reactor 54: Graphite layer C: Diamond crystal particle Tt: Total film thickness Tc: Film thickness of diamond layer Td: Film thickness of diamond multilayer film Tg: Film thickness of graphite layer Step S1, R1: Nucleation process step S2, R2, Q1: Ultra-microcrystalline diamond multilayer coating process step S2-1, R2-1, Q1-1: Seed crystal generation process step S2-2, R2-2: Q1-2: Crystal growth process step R3, Q2: Graphite Lamination process

Claims (5)

A method for producing a diamond-coated electrode in which a surface of a predetermined electrode substrate is coated with a conductive diamond film,
A nucleation step of performing nucleation treatment on the surface using a single crystal diamond having a crystal grain size of 30 nm or less;
By alternately repeating a seed crystal generation process for generating a diamond seed crystal and a crystal growth process for crystal growth of the seed crystal, the film thickness Tc of one diamond layer provided in the crystal growth process is 200 nm or less. A microcrystalline diamond multilayer coating process in which a diamond multilayer film having an ultrafine crystal multilayer structure and an overall film thickness Td in the range of 400 nm to 3 μm is formed on the nucleated surface; In addition, a diamond film having a total film thickness Tt in the range of 1.2 μm to 30 μm is formed on the surface of the electrode base material by alternately repeating the nucleation step and the microcrystalline diamond multilayer coating step three times or more. A method for producing a diamond-coated electrode. A method for producing a diamond-coated electrode in which a surface of a predetermined electrode substrate is coated with a conductive diamond film,
By alternately repeating a seed crystal generation process for generating a diamond seed crystal and a crystal growth process for crystal growth of the seed crystal, the film thickness Tc of one diamond layer provided in the crystal growth process is 200 nm or less. A microcrystalline diamond multi-layer coating process for forming a diamond multi-layer film having an ultra-microcrystalline multi-layer structure and an overall film thickness Td in the range of 400 nm to 3 μm;
And a graphite laminating step for forming a graphite layer having a film thickness Tg in the range of 10 nm to 1 μm and smaller than the film thickness Td on the diamond multilayer film, and the microcrystalline diamond multilayer coating process and By alternately repeating the graphite lamination process and forming the diamond multilayer film at least three times, a diamond film having a total film thickness Tt in the range of 1.2 μm to 30 μm is formed on the surface of the electrode substrate. A method for producing a diamond-coated electrode, comprising: Having a nucleation step of nucleating the surface using a single crystal diamond having a crystal grain size of 30 nm or less,
The diamond-coated electrode according to claim 2, wherein the nucleation process is performed in the nucleation step prior to forming the diamond multilayer film at least first in the ultra-microcrystalline diamond multilayer coating step. Method. 4. The ultra-microcrystalline diamond multilayer coating step and the graphite laminating step that are repeatedly performed are performed by a CVD method while the electrode base material is held in a reaction furnace of a CVD apparatus. 5. Of producing a diamond-coated electrode. A diamond-coated electrode in which a surface of a predetermined electrode substrate is coated with a conductive diamond film,
A diamond multi-layer structure having an ultra-microcrystalline multi-layer structure in which a film thickness Tc of one diamond layer is 200 nm or less, and a total film thickness Td in a range of 400 nm to 3 μm;
A graphite layer having a film thickness Tg in the range of 10 nm to 1 μm and smaller than the film thickness Td, and the diamond multilayer film and the graphite layer are alternately and repeatedly laminated so that at least the diamond multilayer film is 3 A diamond-coated electrode, wherein a diamond film having a total film thickness Tt in the range of 1.2 μm to 30 μm is provided on the surface of the electrode substrate by being formed more than once.

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