Classifications

• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C14/00—Alloys based on titanium
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22F—CHANGING THE PHYSICAL STRUCTURE OF NON-FERROUS METALS AND NON-FERROUS ALLOYS
  • C22F1/00—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working
  • C22F1/16—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working of other metals or alloys based thereon
  • C22F1/18—High-melting or refractory metals or alloys based thereon
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22F—CHANGING THE PHYSICAL STRUCTURE OF NON-FERROUS METALS AND NON-FERROUS ALLOYS
  • C22F1/00—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working
  • C22F1/16—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working of other metals or alloys based thereon
  • C22F1/18—High-melting or refractory metals or alloys based thereon
  • C22F1/183—High-melting or refractory metals or alloys based thereon of titanium or alloys based thereon
• • C25B11/0431—
• • C—CHEMISTRY; METALLURGY
  • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
  • C25B—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR
  • C25B11/00—Electrodes; Manufacture thereof not otherwise provided for
  • C25B11/04—Electrodes; Manufacture thereof not otherwise provided for characterised by the material
  • C25B11/051—Electrodes formed of electrocatalysts on a substrate or carrier
• • C—CHEMISTRY; METALLURGY
  • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
  • C25B—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR
  • C25B11/00—Electrodes; Manufacture thereof not otherwise provided for
  • C25B11/04—Electrodes; Manufacture thereof not otherwise provided for characterised by the material
  • C25B11/051—Electrodes formed of electrocatalysts on a substrate or carrier
  • C25B11/055—Electrodes formed of electrocatalysts on a substrate or carrier characterised by the substrate or carrier material
  • C25B11/057—Electrodes formed of electrocatalysts on a substrate or carrier characterised by the substrate or carrier material consisting of a single element or compound
  • C25B11/061—Metal or alloy
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22F—CHANGING THE PHYSICAL STRUCTURE OF NON-FERROUS METALS AND NON-FERROUS ALLOYS
  • C22F1/00—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working

Definitions

• the present disclosure relates to a titanium alloy sheet for electrode, that is used for an electrode of an electrolytic cell in electrolysis such as soda electrolysis, water electrolysis, or industrial electrolysis accompanied by generation of oxygen, chlorine or the like.
• anode using titanium as a base material has been widely used.
• an electrode material for anode in which a base material made of pure titanium (titanium sheet) is processed into a shape having many holes, such as an expanded metal or a punched perforated sheet, and then an electrode catalyst layer containing an electrode catalyst component composed of platinum group metal and an oxide thereof is formed on a surface thereof.
• an oxide film existing between a surface of pure titanium and the electrode catalyst layer acts as a resistance, thus degrading electrolysis efficiency. If this electric resistance can be reduced, the electrolysis efficiency can be improved, thus enabling reduction in electricity consumption and reduction in costs.
• Patent Document 1 discloses an anode capable of improving properties such as energy consumption by using, as a base material, a titanium alloy containing at least one element selected from the first group consisting of aluminum, niobium, chromium, manganese, molybdenum, ruthenium, tin, tantalum, vanadium and zirconium and at least one element selected from the second group consisting of nickel, cobalt, iron and copper, and palladium.
• a titanium alloy containing at least one element selected from the first group consisting of aluminum, niobium, chromium, manganese, molybdenum, ruthenium, tin, tantalum, vanadium and zirconium and at least one element selected from the second group consisting of nickel, cobalt, iron and copper, and palladium.
• Patent Document 2 discloses a method for producing an electrode for electrolysis in which performances of the electrode are not degraded even if the amount of an electrode catalyst component used is decreased by using a base material containing at least one metal selected from titanium, tantalum, niobium, zirconium, hafnium and nickel or an alloy thereof, and an electrode catalyst component with a predetermined composition, and applying the electrode catalyst component under predetermined conditions.
• the embodiment of the present invention has been made in view of the foregoing circumstances, and it is an object thereof to provide a sheet material for electrode, that can be used as a base material for electrode and enables reduction in electric resistance when an electrode catalyst layer is formed on a surface, thus enabling realization of high electrolysis efficiency of an electrode using this base material.
• the titanium alloy sheet for electrode according to the embodiment of the present invention can be used as a base material for electrode.
• the titanium alloy sheet for electrode is a titanium alloy sheet including at least one of 0.1 to 1.0% by mass of Al and 0.1 to 1.0% by mass of Si, the total content of Al and Si being 0.2 to 1.0% by mass, wherein the balance is composed of Ti and inevitable impurities and an average grain size is 5 to 20 ⁇ m.
• the titanium alloy substrate for electrode according to the embodiment of the present invention has an oxide film containing at least one of Al and Si on a surface thereof, and the total content of Al and Si in the oxide film is 0.08 to 0.55% by mass.
• the titanium alloy sheet for electrode according to the embodiment of the present invention can be used as a base material for electrode and enables reduction in electric resistance when an electrode catalyst layer is formed on a surface thereof. Therefore, when using for an electrode, high electrolysis efficiency can be obtained.
• titanium is metal having extremely high activity, even if an oxide film existing on a surface of pure titanium or a titanium alloy sheet is removed, new oxide film is immediately formed. Therefore, when pure titanium or a titanium alloy is used as a base material and an electrode is produced by providing an electrode catalyst layer on a surface thereof, it is difficult to avoid that an oxide film is interposed between the metal portion of the pure titanium or titanium alloy of the base material and a contact layer.
• the inventors of the present invention have intensively studied a method of reducing electric resistance (e.g., contact resistance) between a base material and an electrode catalyst layer when the electrode catalyst layer is formed on a surface of the base material, on the premise that an oxide film exists on a surface of the base material.
• electric resistance e.g., contact resistance
• composition and the average grain size in this way, a certain amount of at least one of Al and Si exists in an oxide film formed on a surface, thus making it possible to suppress the growth of the oxide film and improving the adhesion between the oxide film and the electrode catalyst layer, leading to reduction in electric resistance.
• the total content of Al and Si in the oxide film is preferably 0.08 to 0.55% by mass.
• the titanium alloy sheet for electrode according to the embodiment of the present invention will be described in detail below.
• titanium alloy sheet is a concept including the embodiment in which an oxide film is formed on the surface.
• the composition mentioned below is the composition of the metal portion excluding the oxide film on the surface.
• the thickness of the oxide film formed on the surface is, for example, about 20 nm or less, and the amount of the oxide film is overwhelmingly smaller than that of the metal portion. Therefore, the results of composition analysis performed using a bulk sample with an oxide film formed thereon may be regarded as the composition of a titanium alloy sheet. For example, it is possible to use a method that is generally used for composition analysis such as ICP emission spectroscopy.
• composition of raw materials used for blending When the composition of raw materials used for blending is clear, values calculated from the composition of raw materials and amounts may be used.
• the titanium alloy sheet for electrode according to the embodiment of the present invention includes at least one of 0.1 to 1.0% by mass of Al and 0.1 to 1.0% by mass of Si.
• the total content of Al and Si is 0.2 to 1.0% by mass.
• the content of Al becomes 0.2% by mass or more in order to satisfy 0.2% by mass that is the lower limit of the total content of Al and Si.
• the Si content becomes 0.2% by mass or more in order to satisfy 0.2% by mass that is the lower limit of the total content of Al and Si.
• the balance is composed of Ti and inevitable impurities.
• Al content is less than 0.1% by mass, sufficient Al does not exist in the oxide film, and it is impossible to sufficiently obtain the effect of suppressing the growth of the oxide film and improving the adhesion to the electrode catalyst layer by Al.
• Si content is less than 0.1% by mass, sufficient Si does not exist in the oxide film, and it is impossible to sufficiently obtain the effect of suppressing the growth of the oxide film and improving the adhesion to the electrode catalyst layer by Si.
• the electrode catalyst layer a layer made of a platinum group metal and/or an oxide thereof.
• the titanium alloy sheet for electrode is usually used after being processed into a shape having many holes, such as an expanded metal or a punched perforated sheet. However, it becomes difficult to process into such a shape.
• the titanium alloy sheet for electrode includes at least one of 0.3 to 0.5% by mass of Al and 0.3 to 0.5% by mass of Si, and the total content of Al an Si is 0.6 to 0.9% by mass.
• the titanium alloy substrate for electrode according to the embodiment of the present invention has an average grain size of 5 ⁇ m or more and 20 ⁇ m or less.
• the average grain size By setting the average grain size at 20 ⁇ m or less, it is possible to improve the adhesion between the oxide film on the surface and the electrode catalyst layer. One reason is that the surface roughness tends to decrease if the average grain size is 20 ⁇ m or less. In addition to this, the other reason is that, by setting the average grain size at 20 ⁇ m or less, at least one of Al and Si can be contained in the oxide film in the greater amount even with the same composition.
• Si and Al tend to be easily concentrated in grain boundaries.
• Si and Al in grains do not enter the oxide film but to be expelled to the metal portion.
• Si and Al in the grain boundary tend to be incorporated into the oxide film. Therefore, by decreasing the average grain size thereby increasing the grain boundary and concentrating a greater amount of Si and Al in the grain boundary, a sufficient amount of Si and/or Al can be contained in the oxide film, thus enabling an improvement in adhesion between the oxide film and the electrode catalyst layer. Containing a sufficient amount of Si and/or Al in the oxide film also has the effect of suppressing the growth of the oxide film. This makes it possible to reduce the electric resistance and to improve the electrolysis efficiency.
• the titanium alloy sheet for electrode is usually used after being processed into a shape having many holes, such as an expanded metal or a punched perforated sheet. However, it becomes difficult to process into such a shape.
• the average grain size is preferably 10 ⁇ m or more and 15 ⁇ m or less.
• the average grain size can be determined by a section method using the results of structure observation with an optical microscope.
• the oxide film formed on the surface of the titanium alloy sheet according to the embodiment of the present invention preferably contains at least one of Al and Si, and the total content of Al and Si is 0.08 to 0.55% by mass.
• the content of Al in the oxide film is preferably 0.08 to 0.55% by mass.
• the content of Si in the oxide film is preferably 0.08 to 0.55% by mass.
• the oxide film contains Al and Si the total content of Al and Si in the oxide film is preferably 0.08 to 0.55% by mass. This makes it possible to more surely obtain the effect of suppressing the growth of the oxide film and the effect of improving the adhesion between the oxide film and the electrode catalyst layer. As a result, it is possible to more surely reduce the electrical resistance between the base material and the electrode catalyst layer, thus enabling an improvement in electrolysis efficiency.
• the total content of Al and Si is more than 0.55% by mass, the hardness of the oxide film may increase and the abrasion of the tool or the like may be accelerated in the case of processing into a shape having many holes, such as an expanded metal or a punched perforated sheet. Therefore, the total content of Al and Si is preferably 0.55% by mass or less.
• the oxide film contains at least one of Al and Si, and the total content of Al and Si is 0.10 to 0.40% by mass.
• the Al content and the Si content in the oxide film can be measured by performing composition analysis using EDS attached to TEM during TEM observation.
• a cast billet such as bloom or slab with a desired composition is obtained by melting and forging as needed. It is possible to use a method that is commonly used for melting a titanium alloy, such as VAR (vacuum arc remelting). A small amount of a sample may be obtained by button arc melting or the like.
• VAR vacuum arc remelting
• the thus obtained cast billet such as bloom or slab is heated to 750° C. to 850° C. and then subjected to hot-rolling to obtain a hot-rolled sheet.
• Heating may be performed in the atmosphere, for example, by open flame of burners disposed in upper and lower portions of a heating furnace.
• As an example of the finish thickness of hot-rolling 3 mm to 5 mm can be exemplified.
• annealing is performed to remove processing strain.
• oxidation scale and an oxygen diffusion layer exist on the surface due to heating of hot-rolling and annealing. If the oxidation scale and the oxygen diffusion layer remain, the electric resistance increases, thus degrading the electrolysis efficiency when used as an electrode. During cold-rolling, they can cause flaws. Therefore, there is a need to remove the oxide scale and oxygen diffusion layer. For example, they can be removed by pickling.
• the thickness (total thickness) L (m) of the oxidation scale and oxygen diffusion layer depends on the heating temperature T (K) and the heating time t (second) and can be determined by the following equation (1):
• the removal amount (pickling amount) are required to exceed L.
• Pickling can be performed using fluonitric acid or the like.
• the hot-rolled sheet After removing the amount exceeding L from the surface by pickling or the like, the hot-rolled sheet is rolled to a predetermined thickness by a cold-rolling step.
• the cold-rolled sheet is placed in a furnace to conduct an annealing treatment in the atmosphere.
• the heating temperature is set to 780 to 830° C., it is possible to control the average grain size within a predetermined range.
• the thickness L of the oxidation scale and oxygen diffusion layer is determined by the equation (1), and the surface is removed by pickling or the like by the amount exceeding L thus obtained. Pickling can be performed using fluonitric acid or the like.
• titanium is metal that is active with oxygen
• an oxide film is formed on a surface of a titanium alloy sheet immediately after pickling.
• Al and Si existing near the surface are incorporated into the oxide film.
• Al and Si are hardly incorporated into the oxide film due to interference of oxygen, thus failing to contain a sufficient amount of Al and/or Si in the oxide film.
• the titanium alloy sheet for electrode according to the embodiment of the present invention can be obtained.
• Test materials were fabricated in the following way.
• Ingot of titanium alloys with each composition shown in Table and having a size of about 40 mm in diameter ⁇ 20 mm in height was manufactured using button arc melting.
• the ingot was heated to 1,000° C. and subjected to forging to fabricate the forged material with a size of 10 mm in thickness ⁇ 35 mm in width ⁇ 75 mm in length. After surface grinding and heating at 850° C. for 120 minutes, hot-rolling was performed to obtain a sheet with a size of 3.5 mm in thickness ⁇ 35 mm in width ⁇ 165 mm in length. Thereafter, annealing at 750° C. for 20 minutes was performed in the atmosphere.
• each thickness L of an oxidation scale and an oxygen diffusion layer determined by the equation (1) was about 80 ⁇ m.
• the removal amount (pickling amount) by pickling was set at 120 ⁇ m on one side (240 ⁇ m on both sides).
• this sheet was annealed in the atmosphere at 800° C. for 2 minutes.
• each thickness L of an oxidation scale and an oxygen diffusion layer determined by the equation (1) was about 6 ⁇ m.
• the removal amount (pickling amount) by pickling was set at 10 ⁇ m on one side (20 ⁇ m on both sides).
• the test material thus obtained was cut into a predetermined size and cross-sectional observation (at a magnification of 100,000 times) was performed using a transmission electron microscope (TEM). Using the thus obtained micrograph (TEM image), after selecting five positions where the thickness of the oxide film is considered to be representative, the thickness of the oxide film in this point was measured and the average thereof was taken as the thickness of the oxide film. The results are shown in Table 1.
• the average grain size was measured at one field of view having an area of 520 ⁇ m ⁇ 860 ⁇ m by a section method using the results of structure observation with an optical microscope (at a magnification of 100 times). The results are shown in Table 1.
• Vickers hardness (load of 10 kgf) was measured at five positions near the center in the thickness direction of the cross section and the average was taken as hardness. The results are shown in Table 1.
• test materials of Examples 1 to 7 and Comparative Example 1 exhibit hardness (Hv) of less than 200 and have excellent processability. Meanwhile, the test material with excess Si content of Comparative Example 2 and the test material with excess Al content of Comparative Example 3 exhibit hardness of 200 or more and have insufficient processability.
• a catalyst layer-forming solution prepared by mixing a ruthenium chloride acid solution, an iridium chloride acid solution and titanium chloride was applied to a surface of each sample after subjecting to shot blasting and pickling, placed in a dryer (inside temperature: 75° C.) and dried for 2 minutes. The dried sample was placed in an atmosphere heat treatment furnace set at a furnace temperature of 475° C., held for 10 minutes and then taken out. Lamination was performed by repeating the operation from application of the catalyst layer-forming solution to heat treatment (holding) five times. Finally, a heat treatment was performed at 500° C. for 60 minutes to form an electrode catalyst layer.
• the contact resistance of the sample on which the electrode catalyst layer was formed was measured.
• the sample after formation of the catalyst layer was interposed between gold sheets, and two gold sheets between which the sample was interposed was further interposed between two copper electrodes under a load of 10 kgf so that the contact area became 1 cm 2 .
• a current was applied between two copper electrodes and the voltage at that time was measured by a voltmeter disposed between two gold sheets.
• the contact resistance was determined from the current applied and the measured voltage.

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• 2016
  • 2016-08-24 JP JP2016163915A patent/JP6789035B2/ja active Active
• 2017
  • 2017-08-21 WO PCT/JP2017/029820 patent/WO2018038061A1/ja unknown
  • 2017-08-21 RU RU2019108098A patent/RU2719233C1/ru active
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