阅读说明：本技术 钛基多孔体及其制造方法 (Titanium-based porous body and method for producing same ) 是由 早川昌志 津曲昭吾 于 2018-03-19 设计创作，主要内容包括：提供一种钛基多孔体,该钛基多孔体具有较高的空隙率以保证作为电极和过滤器实际使用所需要的透气性和透水性,具有较大的比表面积以保证导电性以及与反应溶液或反应气体的足够的反应位点,从而显示出优异的反应效率,并且由于不使用有机物,所以含有较少的污染物。将平均粒径为10～50μm的不规则形钛基粉末不使用粘合剂在干燥体系中填充至厚度为4.0×10<Sup>-1</Sup>～1.6mm,在800～1100℃下烧结,获得具有特定的空隙率和高比表面积的钛基多孔体。(Provided is a titanium-based porous body which has a high porosity to ensure gas and water permeability required for practical use as an electrode and a filter, a large specific surface area to ensure electrical conductivity and sufficient reaction sites with a reaction solution or a reaction gas to exhibit excellent reaction efficiency, and contains less contaminants since organic substances are not used. Filling irregular titanium-based powder with average particle size of 10-50 μm in a drying system without using a binderTo a thickness of 4.0X 10 ‑1 1.6mm, and sintering at 800-1100 ℃ to obtain the titanium-based porous body with specific porosity and high specific surface area.)

1. A flaky titanium-based porous body characterized in that the specific surface area is 4.5X 10^-2～1.5×10^-1m²A porosity of 50-70%, a thickness of 4.0 × 10^-11.6mm and at least one surface having a surface roughness of 8.0 μm or less.

2. A method for producing a titanium-based porous body in the form of a sheet, characterized by:

placing irregular titanium-based powder having an average particle diameter of 10 to 50 μm, a D90 of less than 75 μm and an average roundness of 0.50 to 0.90 on a setter in a dry system without applying pressure, and

sintering the irregular titanium-based powder at 800-1100 ℃.

3. The method for producing a titanium base porous body in the form of a sheet as claimed in claim 2, wherein the material of the retainer is quartz.

4. An electrode comprising the sheet titanium-based porous body according to claim 1.

Technical Field

The present invention relates to a titanium-based porous body produced using a titanium-based powder as a raw material, the porous body being used in an electrode, a filter, or the like of a secondary battery or a fuel cell, and also relates to a method for producing the porous body.

Background

Recently, titanium-based porous bodies are considered for use in electrodes of secondary batteries and electrodes of fuel cells. It would be desirable to have a method for making titanium-based porous bodies having high porosity and electrical conductivity, which are desirable characteristics for battery electrodes.

Conventionally, a method has been known in which titanium fibers are sintered to produce a titanium-based porous body having a high porosity (for example, see patent document 1). However, the titanium-based porous body produced by sintering the fibers has a high porosity of 70 to 90%, but has a small specific surface area and a small area where the fibers are sintered together. Therefore, such a titanium-based porous body has a problem of low electrical conductivity. For example, when such a titanium-based porous body supports a catalyst thereon and is used as a carrier to cause a gas or liquid to react near the surface of the titanium-based porous body, such a small specific surface area causes a problem of lowering the reaction efficiency due to a reduction in the reaction sites between the titanium-based porous body and the reaction solution or reaction gas.

Further, there is known a method in which a paste-like binder is kneaded into titanium powder, which is then sintered to produce a titanium-based porous body having through holes and capable of allowing a liquid substance to flow from one side to the other side (for example, refer to patent document 2). However, in the method of kneading the binder and then sintering, the manufacturing steps are complicated, and the carbon content in the sintered body may increase. In addition, the porosity is as low as 10 to 50%, which causes a problem of deterioration in air permeability and water permeability.

Further, a titanium-based porous body is known which is produced by sintering gas-atomized titanium powder without using a paste (for example, see patent document 3). However, since titanium powder having a high volume density is used, a titanium-based porous body having a porosity of 55% or more cannot be produced, and therefore, there is a problem in that air permeability and water permeability are deteriorated.

Disclosure of Invention

Technical problem to be solved by the invention

The present invention has been made in view of the above circumstances. The problem to be solved by the present invention is to provide a titanium-based porous body having a high specific surface area to exhibit excellent reaction efficiency and a high porosity to secure air permeability and water permeability.

Means for solving the problems

The present inventors have made intensive studies to solve the above problems, and have completed the following inventions.

[1]A flaky titanium-based porous body characterized in that the specific surface area is 4.5X 10^-2～1.5×10^-1m²A porosity of 50-70%, a thickness of 4.0 × 10^-11.6mm and at least one surface having a surface roughness of 8.0 μm or less.

[2] A method for producing a titanium-based porous body in the form of a sheet, characterized in that an irregularly shaped titanium-based powder having an average particle diameter of 10 to 50 μm, a D90 of less than 75 μm and an average roundness of 0.50 to 0.90 is placed on a setter in a dry system without applying pressure, and the irregularly shaped titanium-based powder is sintered at 800 to 1100 ℃.

[3] The method for producing a titanium base porous body in the form of a sheet as recited in [2], wherein the material of the retainer is quartz.

[4] An electrode comprising the sheet-like titanium-based porous body according to [1 ].

Effects of the invention

The present invention can provide a titanium-based porous body that can maintain good electrical conductivity, air permeability and water permeability while maintaining the bending strength required for practical use by controlling the specific surface area and porosity of the titanium-based porous body.

Detailed Description

The following detailed description will describe specific embodiments of the present invention.

< specific surface area, void ratio, surface roughness >

The titanium-based porous body of the present invention has a specific surface area of 4.5X 10^-2～1.5×10^-1m²(iii) a porosity of 50 to 70%, and a surface roughness of one surface of 8.0 [ mu ] m or less.

First, the titanium-based porous body preferably has a specific surface area of 5.0X 10^-2～1.3×10^-1m²A porosity of 55 to 68%, preferably a specific surface area of 7.0X 10^-2～1.1×10^-1m²A porosity of 60 to 66% based on the total amount of the composition. By setting the numerical value within the above range, it is possible to maintain good electrical conductivity, air permeability and water permeability while maintaining the bending strength required for practical use. The specific surface area of the present invention is measured by the BET method according to JIS Z8831: 2013. Krypton was used as the measurement gas.

Next, the surface roughness of at least one surface is 8.0 μm or less. The lower limit of the surface roughness is not limited, but is preferably 0.1 μm or more. The surface roughness in the present invention is the arithmetic average roughness Ra measured in accordance with JIS B0601-2001.

In addition, the porosity in the present invention means a void ratio per unit volume of the titanium-based porous body, expressed as a percentage. The porosity may be based on the volume V (cm) of the titanium-based porous body³) Mass M (g) of the titanium-based porous body and true density D (g/cm) of the titanium-based material³) (for example, in the case of pure titanium, the true density is 4.51g/cm³) Calculated according to the following formula.

Void ratio (%) ((M/V)/D) × 100 (a)

< carbon concentration >

The carbon concentration of the titanium-based porous body of the present invention is 0.05 wt% or less, preferably 0.03 wt% or less. Due to such low carbon concentration in the porous body, the titanium-based porous body of the present invention is advantageously free from a decrease in strength and an increase in electrical resistance which may be caused by the influence of impurity contamination.

< thickness >

The titanium-based porous body of the present invention has a thickness of 4.0X 10^-11.6 mm. The thickness is more preferably 4.0X 10^-1About 1.0mm, more preferably about 4.0X 10^-1～6.0×10^-1mm. Within this range, the size of the final product can be reduced while maintaining the bending strength required for practical use. When the thickness of the titanium-based porous body is less than 4.0X 10^-1mm, the uniformity of voids in the titanium-based porous body decreases, resulting in a decrease in the bending strength of the titanium-based porous body. When the thickness of the titanium-based porous body is thicker than 1.6mm, the porous body is difficult to be used in secondary batteries that are increasingly miniaturized.

< materials >

The titanium-based porous body of the present invention is composed of a composite material of pure titanium, a titanium alloy, pure titanium or a titanium alloy coated with titanium nitride or titanium silicide, or a combination thereof, or the like. Pure titanium is titanium composed of metallic titanium and other unavoidable impurities. The titanium alloy is an alloy of titanium and any metal (e.g., Fe, Sn, Cr, Al, V, Mn, Zr, Mo, etc.), and specific examples thereof include: ti-6-4(Ti-6Al-4V), Ti-5Al-2.5Sn, Ti-8-1-1(Ti-8Al-1Mo-1V), Ti-6-2-4-2(Ti-6Al-2Sn-4Zr-2Mo-0.1Si), Ti-6-6-2(Ti-6Al-6V-2Sn-0.7Fe-0.7Cu), Ti-6-2-4-6(Ti-6Al-2Sn-4Zr-6Mo), SP700(Ti-4.5Al-3V-2Fe-2Mo), Ti-17(Ti-5Al-2Sn-2Zr-4Mo-4Cr), beta-CEZ (Ti-5Al-2Sn-4Zr-4Mo-2 Cr-) 1Fe), TIMETAL 555, Ti-5553(Ti-5Al-5Mo-5V-3Cr-0.5Fe), TIMETAL 21S (Ti-15Mo-2.7Nb-3Al-0.2Si), TIMETAL LCB (Ti-4.5Fe-6.8Mo-1.5Al), 10-2-3(Ti-10V-2Fe-3Al), Beta C (Ti-3Al-8V-6Cr-4Mo-4Cr), Ti-8823(Ti-8Mo-8V-2Fe-3Al), 15-3(Ti-15V-3Cr-3Al-3Sn), Beta III (Ti-11.5Mo-6Zr-4.5Sn) and Ti-13V-11Cr-3 Al.

In particular, since the electrical resistance can be reduced when used in an electrode, a titanium-based porous body composed of a composite material of pure titanium, pure titanium coated with titanium nitride or titanium silicide, or a combination thereof is preferable, and a titanium-based porous body composed of pure titanium is further preferable.

< method for producing titanium-based porous body >

< Properties of titanium powder >

The titanium-based powder used for producing the titanium-based porous body of the present invention is an irregular titanium-based powder having (1) an average particle diameter (D50 by volume) of 10 to 50 μm, (2) D90 of less than 75 μm, and (3) an average roundness of 0.50 to 0.90. These characteristics will be described below.

(1) Average particle diameter (D50)

When the average particle diameter is larger than 50 μm, the specific surface area of the sintered body is less than 4.5X 10^-2m²(ii) in terms of/g. On the other hand, when the average particle diameter is less than 10 μm, the titanium-based powder is difficult to handle. The average particle diameter used herein means a particle diameter D50 (median particle diameter) of a particle diameter distribution (by volume) obtained by a laser diffraction scattering method.

(2)D90

An irregular titanium-based powder having a particle size distribution (by volume) of less than 75 μm in D90 is preferred. When D90 is less than 75 μm, a sintered body having high strength can be produced.

Further, the surface roughness of the titanium-based porous body depends on the particle diameter D90, and the smaller the D90, the lower the surface roughness, and the higher the strength of the titanium-based porous body. D90 indicates a particle diameter corresponding to a volume distribution integrated value of 90% when the particle diameter distribution is measured by a laser diffraction scattering method.

(3) Irregular titanium-based powder with average roundness of 0.50-0.90

The irregular titanium-based powder is a titanium-based powder containing primary particles that do not have a perfect spherical shape or a perfect spheroidal shape and have an average roundness of 0.50 to 0.90. Examples of the irregular titanium-based powder include titanium-based powder produced by the HDH method and titanium-based powder produced by the milling method, and titanium-based powder which is a blend thereof. The titanium-based powder obtained by the above-mentioned manufacturing method is irregular in shape and non-spherical. When a titanium-based powder having a primary particle average roundness ratio of 0.90 or more is used, the specific surface area of the titanium-based porous body in the form of a sheet is less than 4.5X 10^-2m²(ii) a void fraction of less than 50% in terms of the total weight of the composition.

The roundness described herein is defined as follows: when the circumferential length (a) of the projected area of the particle is measured with an electron microscope or an atomic microscope, and the circumferential length of a circle having the same area as the projected area is taken as (B), B/a is calculated as the circularity. Further, the average circularity is obtained, for example, as follows: the particles are made to flow through the cell together with the carrier liquid, images of a large number of particles are taken with a CCD camera, the circumferential length (A) of the projected area of each particle and the circumferential length (B) of a circle having the same area as the projected area are measured in the images of 1000 to 1500 particles to calculate the circularity, and the average circularity of the particles is calculated as the circularity of the particles. The closer the shape of the particle is to the perfect sphere, the larger the circularity value, and the circularity of the particle having the perfect sphere is 1. Conversely, the further the shape of the particle is from a perfect sphere, the less the roundness.

The titanium-based powder used in the present invention is a pure titanium powder, a titanium alloy powder, a hydrogenated pure titanium powder or a titanium alloy powder, or a pure titanium powder or a titanium alloy powder coated with titanium nitride or titanium silicide. The pure titanium powder is a titanium powder composed of metallic titanium and other inevitable impurities. The same example as above can be applied to the titanium alloy of the titanium alloy powder. In particular, a composite of pure titanium powder, hydrogenated pure titanium powder, pure titanium powder coated with titanium nitride or titanium silicide, or a combination thereof is preferred, and pure titanium powder is particularly preferred.

In the method for producing a titanium-based porous body of the present invention, an irregular titanium-based powder having an average particle diameter of 10 to 50 μm, a D90 of less than 75 μm, and an average roundness of 0.50 to 0.90 is placed on a setter in a dry system without applying pressure. Since the powder is packed more densely than the powder alone, it is difficult to produce a titanium-based porous body having a porosity of 70% or more.

The retainer may be made of any material that hardly reacts with the titanium-based porous body, such as quartz or BN. As for the shape, a flat plate-shaped positioner or a flat plate-shaped positioner provided with a counterbore may be used, with a flat plate-shaped positioner provided with a counterbore being particularly preferred. As used herein, a counterbore refers to a portion having an aperture with an edge around it that does not extend through the plate, or a portion surrounded by a separator. The bottom of the counterbore may be flat and the shape of the counterbore is more preferably the same as the shape of the final product.

When a flat plate-shaped retainer is used, the placement method of the titanium-based irregular powder includes the following (1) and (2), and the like.

(1) A method of dropping the irregular titanium-based powder naturally from above the retainer to place the powder on the retainer; and

(2) a method of placing a frame-like powder-filling jig of a product size on a setter, dropping an irregular-shaped titanium-based powder naturally from above the setter, and filling the powder-filling jig with the irregular-shaped titanium-based powder without pressurizing the irregular-shaped titanium-based powder.

When using positioners provided with counterbores, there are

(3) Placing titanium-based irregular powder into a counterbore in a natural falling mode, and smoothing powder overflowing from the counterbore by using a plate-shaped clamp under the condition of not pressurizing the titanium-based irregular powder.

In particular, the methods of (2) and (3) are preferred because the powder left in the jig or in the counterbore itself defines the size of the product.

The portion (the surface of the retainer or the bottom surface of the counterbore) on which the titanium-based irregularly shaped powder is placed preferably has a surface roughness of 1.5 μm or less. Within this range, the surface roughness of at least one surface of the sheet-like titanium-based porous body may be 8.0 μm or less.

< Placement of titanium-based powder >

By placing the titanium-based powder without applying pressure (without pressurization), bridging inside the titanium-based powder occurs in a natural state, and a sintered body of the titanium-based porous body having a porosity of 50 to 70% can be obtained. As used herein, "not to pressurize" refers to a state in which any stress is not intentionally applied to the surface of the titanium powder after filling, and the stress applied to the surface of the titanium powder during powder filling is only a stress related to the leveling of the powder in a direction parallel to the retainer. Further, "bridging" as used herein refers to the formation of arcuate voids from the powder.

Furthermore, the filling with titanium-based powder is preferably carried out in a dry system. Filling with the powder in a dry system can lead to bridging within the powder in the natural state to provide a sintered body with high porosity. As used herein, "in a dry system" refers to a state in which the powder is not intentionally mixed with water or an organic solvent. When the titanium-based powder is filled in a wet system, the titanium-based powder is anisotropically deposited by the resistance of the fluid, and it is difficult to achieve a high porosity. In addition, when an organic solvent is used, the carbon concentration becomes as high as 0.1% by weight or more, and the strength of the sintered body of the titanium-based porous body may be reduced and the electric resistance may be increased due to contamination with impurities.

< sintering of titanium-based powder >

Sintering the obtained titanium-based powder accumulation body at 800-1100 ℃. If a quartz positioner is used, the sintering is preferably carried out at 800 to 1000 ℃. By performing sintering at a temperature within this range, a sintered body having strength required for practical use and a smooth surface can be produced. The sintering time is preferably 1 to 3 hours.

When hydrogenated pure titanium powder or titanium alloy powder is used as the raw material of the irregularly shaped titanium-based powder, a method may be proposed in which, prior to the sintering step, the powder is temporarily held at 400 to 600 ℃ to perform a dehydrogenation step for eliminating hydrogen contained in the powder, thereby producing a porous body having higher flexural strength comparable to that of a porous body produced using HDH powder as the raw material.

< summary of titanium-based powder production method >

As described above, the titanium-based powder having a specific average particle diameter and shape can be used and subjected to shaping and calcination under specific conditions to obtain the sheet-like titanium-based porous body of the invention.

For example, as the average particle diameter of the titanium-based powder increases, the specific surface area of the sheet-like titanium-based porous body decreases and the porosity increases. Further, as the circularity of the titanium-based powder increases, the porosity of the sheet-like titanium-based porous body decreases. The tendency of the roundness of the titanium-based powder to the specific surface area of the titanium-based porous body in the form of a sheet shows a peak change in a certain value. As the sintering temperature increases, the specific surface area and the porosity of the sheet-like titanium-based porous body decrease. By controlling these parameters, the specific surface area and the porosity of the titanium-base sheet porous body can be adjusted.

The thickness of the sheet-like titanium-based porous body can be adjusted by the thickness of the titanium-based irregular powder placed, the height of the jig, or the depth of the counterbore. Further, the surface roughness of one surface of the sheet-like titanium-based porous body can be adjusted by the surface roughness of the bottom surface of the jig or the counterbore on which the titanium-based powder is placed.