JP2019029199A - Method for manufacturing cathode electrode of ultraviolet sensor and ultraviolet sensor - Google Patents

Abstract

To provide an ultraviolet sensor in which a limit sensitivity wavelength is expanded to 280 nm or more.SOLUTION: Cupronickel is subjected to rolling treatment (S101). Copper is deposited on a surface of the cupronickel having been subjected to the rolling treatment (S102), and nickel in the cupronickel is diffused in copper (copper plating) having been deposited (S103). In this case, the copper has a smaller work function than that of nickel, so that electrons move from the copper to the nickel. As a result, an oozing-out amount of electrons of the copper at portions in contact with the nickel is decreased, and the barrier of electron emission from the copper is reduced, so that a work function becomes smaller. Accordingly, a limit sensitivity wavelength can be expanded to 280 nm or more.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a method of manufacturing a cathode electrode of an ultraviolet sensor that detects ultraviolet rays based on a current generated by discharge between an anode electrode and a cathode electrode, and the ultraviolet sensor.

  Conventionally, ultraviolet rays have been used as flame detection sensors for combustion safety devices in various industrial furnaces such as drying furnaces for painting lines of automobile bodies and parts, melting furnaces for die casting of aluminum and zinc, and heat treatment furnaces for quenching metal parts. A sensor is used.

  With reference to FIG. 15, the structure of the ultraviolet sensor used as a flame detection sensor is demonstrated (for example, refer patent document 1, 2).

  In FIG. 15, 11 is a glass package made of borosilicate glass. In the glass package 11, a special mixed gas (a mixed gas of Ne and H2) is sealed at a constant pressure in the internal space. In addition, a top plate 12 is provided on the upper surface of the glass package 11, and the top plate 12 is made of glass that can transmit ultraviolet rays. In addition, a disk-shaped cathode electrode 13 and an anode electrode 14 are provided in the glass package 11 with their surfaces (electrode surfaces) facing each other with a predetermined gap therebetween.

  One end of a plurality of conductive columns 15 (15-1 to 15-3) that support the anode electrode 14 from the direction in which the cathode electrode 13 is provided is laser-welded to the anode electrode 14. The other end of the sex support 15 (15-1 to 15-3) is drawn out of the glass package 11. The anode electrode 14 has a plurality of through holes 14a formed in a mesh shape.

  Similarly to the anode electrode 14, one end portions of a plurality of conductive columns 16 (16-1 to 16-3) that support the cathode electrode 13 are also laser-welded to the cathode electrode 13, and the conductive columns 16 ( The other end of 16-1 to 16-3) is drawn out of the glass package 11.

  In the ultraviolet sensor 1 configured in this way, when the ultraviolet light that has passed through the top plate 12 reaches the cathode electrode 13 through the through hole 14a of the anode electrode 14, electrons are emitted by the photoelectric effect, and then the enclosed gas / voltage As a result, avalanche occurs and discharge starts. That is, a current flows between the anode electrode 14 and the cathode electrode 13, and only the ultraviolet ray having a specific wavelength that has passed through the top plate 12 is transmitted to the ultraviolet sensor 1 based on the current flowing between the anode electrode 14 and the cathode electrode 13. Detected by.

  Note that the photoelectric effect refers to a phenomenon in which, when a substance absorbs light, internal electrons are excited and electrons are ejected accordingly. In this photoelectric effect, the energy required to extract one electron from the surface of the material is called a work function. The energy of incident light is hν, the work function is w, and the kinetic energy of the electrons jumping out of the material is E. In the case (see FIG. 16), E = hν−w.

JP 2012-255730 A JP2015-115228A

  In the conventional ultraviolet sensor, tungsten (W) is used as the electrode material of the cathode electrode. In this W electrode type ultraviolet sensor, there are fields (such as chemical plant reaction furnaces, refinery sulfur recovery furnaces, waste liquid treatment plants, etc.) where flames cannot be detected. In such a field, it is desired to change the electrode material of the cathode electrode to expand the limit sensitivity wavelength (cutoff wavelength), for example, 260 nm to 300 nm.

  The limit sensitivity wavelength of the ultraviolet sensor is determined by the work function of the cathode electrode, and the work function is determined by the material and surface orientation of the electrode. FIG. 17 shows the work function and the limit sensitivity wavelength determined for each metal type. Even for the same metal, the work function and the limit sensitivity wavelength are not one value but have a variation width.

  This has a plurality of metal surface orientations such as (200), (220), and (111), and takes a predetermined value in which the work function and the limit sensitivity wavelength differ for each surface orientation (see FIG. 18). Since (200) plane, (220) plane, (111) plane, etc. are randomly mixed in the metal, even if the same kind of metal, the mixing degree (distribution) of the plane orientation is different, resulting in different values. Because it becomes. In the plane orientations (200) and (220), the atomic density is the same as the plane orientations (100) and (110), and the work function and the limit sensitivity wavelength are the same values as the plane orientations (100) and (110). Become.

  Metals are classified into a body-centered cubic structure (W: tungsten, etc.) and a face-centered cubic structure (Cu, Ni: copper, nickel, etc.) depending on the crystal structure. The body-centered cubic structure metal and the face-centered cubic structure metal have different work function magnitudes on each of the (200) plane, (220) plane, and (111) plane. The work function magnitude relationship of (111) plane <(200) plane <(220) plane is the magnitude of the work function of the metal having a face-centered cubic structure, but the (220) plane <(200) plane < (111) plane.

  Further, when a strong process such as rolling is performed, the plane orientation of the metal is oriented to a specific plane orientation (see FIGS. 19A and 19B). This structure is called a rolling texture. The plane orientation of the rolled texture of Cu or Ni is (220). When heating is performed, recrystallization occurs, and the plane orientation is oriented to another plane orientation (see FIGS. 19B and 19C). This structure is called a recrystallized texture. The plane orientation of the recrystallized texture of Cu or Ni indicates (200).

  From the relationship shown in FIG. 18, if Cu is used as the electrode material of the cathode electrode and Cu is a rolling texture ((220) plane), the limit sensitivity wavelength can be set to 277 nm. However, there is a desire to further increase the limit sensitivity wavelength in chemical reactor reactors, refinery sulfur recovery furnaces, waste liquid treatment plants, and the like.

  The present invention has been made to solve such problems, and an object of the present invention is to provide an ultraviolet sensor capable of expanding the limit sensitivity wavelength to 280 nm or more.

  In order to achieve such an object, the present invention provides a method of manufacturing a cathode electrode of an ultraviolet sensor (1) that detects ultraviolet rays based on a current generated by discharge between an anode electrode (14) and a cathode electrode (13). A rolling process (S101) for rolling the first metal, and a second metal having a work function smaller than that of the first metal is formed on the surface of the first metal rolled by the rolling process. A film forming step (S102) for forming a film and a grain boundary diffusion step (S103) for diffusing the first metal into the second metal formed by the film forming step are described.

  In the present invention, for example, the first metal is nickel, and the second metal is copper. That is, copper is deposited on nickel. In this case, nickel diffuses into the deposited copper through the grain boundary diffusion step. When two substances having different work functions are brought into contact with each other, electrons move from a substance having a small work function to a substance having a large work function. In the case of copper and nickel, since copper has a smaller work function, electrons move from copper to nickel. As a result, the amount of copper leaching out of the portion in contact with nickel is reduced, the barrier for electron emission from copper is reduced, and the work function is reduced. As a result, the limit sensitivity wavelength can be expanded to 280 nm or more. Note that the first metal may be an alloy of nickel and copper (cupronickel), and the grain boundary diffusion step may cause the grain boundary diffusion of nickel in the cupronickel to the deposited copper. Cupronickel is easier to obtain than nickel.

  In the above description, as an example, constituent elements on the drawing corresponding to the constituent elements of the invention are indicated by reference numerals with parentheses.

  As described above, according to the present invention, the first metal is rolled, and the second metal having a work function smaller than that of the first metal is formed on the surface of the rolled first metal. Then, since the first metal is allowed to diffuse into the formed second metal at the grain boundary, for example, when the first metal is nickel and the second metal is copper, nickel is added to the copper. It is possible to reduce the barrier of electron emission from copper and to expand the limit sensitivity wavelength to 280 nm or more by performing field diffusion.

FIG. 1 is a process diagram for explaining an embodiment of a method for producing a cathode electrode of an ultraviolet sensor according to the present invention. FIG. 2 is a diagram showing the X-ray diffraction measurement result of the cupro-nickel that has been rolled. FIG. 3 is a diagram showing a cross-sectional image of cupronickel that has been rolled. FIG. 4 is a diagram showing the results of X-ray diffraction measurement of the surface of copper-plated cupronickel. FIG. 5 is a diagram showing a cross-sectional image of copper-plated cupronickel. FIG. 6 is a diagram showing the work function and limit sensitivity wavelength of the plane orientation (111) of copper. FIG. 7 is a diagram showing a result of X-ray diffraction measurement of the surface of copper-plated cupronickel after the heat treatment. FIG. 8 is a diagram showing a cross-sectional image of copper-plated cupronickel after the heat treatment. FIG. 9 is a diagram showing the work function and critical sensitivity wavelength of the plane orientation (200) of copper. FIG. 10 is a diagram schematically showing a state in which nickel in cupronickel diffuses into the copper plating at grain boundaries. FIG. 11 is a diagram for explaining the movement of electrons from copper plating to nickel. FIG. 12 is a diagram for explaining how electrons are exuded from the surface of a metal. FIG. 13 is an image diagram of a change in the amount of electron leakage in a state where nickel (Ni) is diffused into copper (Cu) at grain boundaries. FIG. 14 is a diagram showing the spectroscopic measurement results of the present application and a Cu electrode having a (220) plane. FIG. 15 is a perspective view showing a main part of the ultraviolet sensor. FIG. 16 is a diagram for explaining the relationship between the kinetic energy of electrons jumping out by the photoelectric effect, the energy of incident light, and the work function. FIG. 17 is a diagram illustrating a work function and a limit sensitivity wavelength that are determined for each type of metal. FIG. 18 is a diagram exemplifying a work function and a limit sensitivity wavelength that each plane orientation of each metal material takes. FIG. 19 is a diagram showing a change in crystal structure from the untreated state to the rolled texture and the recrystallized texture.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  In this embodiment, as shown in FIG. 1, cupronickel (nickel-copper alloy (in this example, nickel (30%), copper (70%)) is rolled as the first metal (step S101). Next, copper is deposited as a second metal having a work function smaller than that of cupronickel on the surface of the rolled cupronickel (step S102). ), The grain boundary diffusion of nickel in cupronickel is performed (step S103).

  In the present embodiment, the first metal is cupro-nickel, but it may be nickel. In this embodiment, cupro-nickel is used as the first metal because it is easier to obtain than nickel.

  In step S101, when cupronickel is rolled, the plane orientation of cupronickel is oriented to (220). In FIG. 2, the X-ray-diffraction measurement result of the cupro nickel which carried out the rolling process is shown. As can be seen from the X-ray diffraction measurement results, (220) is the maximum in the plane orientation of the rolled cupronickel.

  FIG. 3 shows a cross-sectional image of the rolled cupronickel. In this figure, the rolled cupronickel is indicated by reference numeral 21. Note that the cupronickel rolling process may be performed before the cupronickel is delivered. That is, it may be performed on the manufacturer side supplying cupronickel.

  In step S102, copper plating (10 μm) is applied to the surface of the rolled cupronickel 21. FIG. 4 shows the results of X-ray diffraction measurement of the surface of copper-plated cupronickel. As can be seen from the X-ray diffraction measurement results, the surface orientation of the copper-plated cupronickel has a maximum of (111). FIG. 5 shows a cross-sectional image of copper-plated cupronickel. In this figure, the copper plating applied to the surface of cupronickel 21 is indicated by reference numeral 22.

  As shown in FIG. 6, the copper plane orientation (111) has a work function of 4.94 and a limit sensitivity wavelength of 252 nm. The expansion of the wavelength cannot be expected.

  In step S103, nickel in the cupronickel 21 is diffused into the copper plating 22 at a grain boundary, and heat treatment is performed before the grain boundary diffusion to make the cupronickel 21 a recrystallized texture. This heat treatment is performed at 1000 ° C. for 0 minute. That is, it is rapidly cooled to room temperature after rapid heating at 1000 ° C. for 0 minute.

  By this heat treatment, the plane orientation of cupronickel 21 is oriented to (200), and the copper plating 22 can have a plane orientation (200) due to the influence. FIG. 7 shows the result of X-ray diffraction measurement of the surface of the copper-plated cupronickel after the heat treatment. FIG. 8 shows a cross-sectional image of copper-plated cupronickel after the heat treatment.

  Next, in step S <b> 103, the heat-treated cupro-nickel 21 and the copper plating 22 are reheated by discharge treatment or heat treatment to diffuse the nickel in the cupro-nickel 21 into the copper plating 22 at grain boundaries.

  When this reheating is performed by the discharge treatment, the sputtered particles adhering to the discharge are (111), but tend to adhere to the grain boundaries, and (200) made by the heat treatment remains, so the surface of the copper plating 22 remains. The work function is dominant (200). When the work function of the surface of the copper plating 22 is (200), as shown in FIG. 9, the work function is 4.59 and the limit sensitivity wavelength is 271 nm.

  Further, the diffusion of nickel into the copper plating 22 is promoted at the plasma temperature (about 500 ° C.) by this discharge. FIG. 10 schematically shows a state in which nickel in cupronickel 21 has diffused into the copper plating 22 at grain boundaries. In FIG. 10, nickel that has diffused grain boundaries into the copper plating 22 is indicated by reference numeral 23.

  When two substances having different work functions are brought into contact with each other, electrons move from a substance having a small work function to a substance having a large work function. In the state shown in FIG. 10, since the copper plating 22 has a work function smaller than that of the nickel 23, electrons move from the copper plating 22 to the nickel 23 (see FIG. 11). As a result, the amount of electron oozing out of the copper plating 22 in the portion in contact with the nickel 23 is reduced, and the barrier for electron emission from the copper plating 22 is reduced.

  FIG. 12 shows a state where electrons are oozing out from the metal surface. In FIG. 12, the left figure shows the electron distribution in the cross section from inside the solid to the vacuum across the surface, and the right figure is a graph of the positive charge of the nucleus and the electron charge density in the cross section. Unlike the bulk, electrons near the surface are weakly attracted to positively charged nuclei and ooze out into the vacuum. Since electrons ooze out from the surface into the vacuum, positive electric dipoles are generated on the solid side and negative on the vacuum side. Since this electric dipole interacts with the electrons emitted from the material, the work function is affected by the electronic state of the surface. Since the exuding electrons become a barrier when extracting internal electrons, the work function increases when the amount of exudation is large, and decreases when the amount of exudation is small.

  FIG. 13 shows an image diagram of the change in the amount of electron leakage in a state where nickel (Ni) is diffused into the copper (Cu) grain boundary. Since the exuding electrons are pulled by Ni, the amount of Cu exuding in the portion in contact with Ni is reduced, and the barrier for electron emission from Cu is reduced.

  In this way, in the present embodiment, the nickel 23 in the cupronickel 21 is diffused into the copper plating 22 at the grain boundary, so that the amount of the electron plating of the copper plating 22 in the portion in contact with the nickel 23 is reduced. The barrier for electron emission from the copper plating 22 is reduced, and the work function is reduced. An electrode obtained by diffusing nickel 23 in cupronickel 21 into the copper plating 22 at the grain boundary is used as the cathode electrode (Cu electrode) 13 of the ultraviolet sensor 1 shown in FIG. By enlarging, it becomes possible to make it 280 nm or more.

  In FIG. 14, the spectroscopic measurement result of this application and Cu electrode made into (220) plane is shown. In FIG. 14, the horizontal axis indicates the wavelength (nm), the vertical axis indicates the number of discharges, I indicates the spectroscopic measurement result of the Cu electrode of the present application, and II indicates the spectroscopic measurement result of the Cu electrode having the (220) plane. In the Cu electrode having the (220) plane, the limit sensitivity wavelength is 277 nm, but in the Cu electrode of the present application, the limit sensitivity wavelength is 280 nm or more.

  Note that the grain boundary diffusion treatment (heat treatment + reheating) in step S103 may be performed in a state in which the cupro-nickel 21 to which the copper plating 22 is applied is incorporated as the cathode electrode of the ultraviolet sensor 1. It is good also as what is performed in the state before incorporating.

[Extension of the embodiment]
The present invention has been described above with reference to the embodiment. However, the present invention is not limited to the above embodiment. Various changes that can be understood by those skilled in the art can be made to the configuration and details of the present invention within the scope of the technical idea of the present invention.

  DESCRIPTION OF SYMBOLS 1 ... Ultraviolet sensor, 11 ... Glass package, 13 ... Cathode electrode (Cu electrode), 14 ... Anode electrode, 21 ... Rolled cupro nickel, 22 ... Copper plating, 23 ... Nickel.

Claims (6)

A method of manufacturing a cathode electrode of an ultraviolet sensor that detects ultraviolet rays based on a current generated by a discharge between an anode electrode and a cathode electrode,
A rolling process for rolling the first metal;
A film forming step of forming a second metal having a work function smaller than that of the first metal on the surface of the first metal rolled by the rolling step;
A method for producing a cathode electrode of an ultraviolet sensor, comprising: a grain boundary diffusion step of diffusing the first metal into the second metal formed by the film formation step. In the manufacturing method of the cathode electrode of the ultraviolet sensor according to claim 1,
The grain boundary diffusion step includes
A method for producing a cathode electrode of an ultraviolet sensor, wherein a heat treatment is performed before grain boundary diffusion of the first metal into the second metal to make the first metal a recrystallized texture. In the manufacturing method of the cathode electrode of the ultraviolet sensor according to claim 2,
The grain boundary diffusion step includes
A cathode electrode of an ultraviolet sensor, wherein the heat-treated first metal and the second metal are reheated to diffuse grain boundaries of the first metal into the second metal. Production method. In the manufacturing method of the cathode electrode of the ultraviolet sensor according to claim 3,
The first metal is an alloy of nickel and copper;
The second metal is copper;
The heat treatment is rapidly cooled to room temperature after rapid heating at 1000 ° C. for 0 minute,
The reheating is performed at about 500 ° C.,
The grain boundary diffusion step includes
A method for producing a cathode electrode of an ultraviolet sensor, characterized in that nickel in the first metal is diffused into the second metal at grain boundaries. In the manufacturing method of the cathode electrode of the ultraviolet sensor according to claim 3,
The first metal is an alloy of nickel and copper;
The second metal is copper;
The heat treatment is rapidly cooled to room temperature after rapid heating at 1000 ° C. for 0 minute,
The reheating is performed at about 500 ° C.
The grain boundary diffusion step includes
A method for producing a cathode electrode of an ultraviolet sensor, characterized in that nickel in the first metal is diffused into the second metal at grain boundaries. An ultraviolet sensor that detects ultraviolet rays based on a current generated by a discharge between an anode electrode and a cathode electrode,
The cathode electrode is
It is manufactured with the manufacturing method of the cathode electrode of the ultraviolet sensor described in any one of Claims 1-5. The ultraviolet sensor characterized by the above-mentioned.

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