JP5976354B2 - Porous sintered metal and manufacturing method thereof - Google Patents

Description

  The present invention relates to a porous sintered metal and a method for producing the same.

  The raw material industry such as cast forging for processing ferrous or non-ferrous metals is an important industrial field for supplying machine parts and the like to the downstream machine assembly industry. Among these, porous metals are attracting attention as materials that can realize weight reduction of mechanical parts and the like, which are limited by dense metals, and in recent years, research and development of manufacturing techniques are being advanced. Porous metal not only realizes weight reduction, but also has a large specific surface area, and therefore is promising as a functional material having high energy absorption capacity, heat exchange capacity, heat insulation characteristics, sound absorption characteristics, and the like. At present, there are various structures and manufacturing techniques for porous metals, and various properties are expected accordingly. Therefore, it is desired to develop a porous structure control technique and processing technique suitable for the purpose of use.

  Porous metals not only have various mechanical, physical, thermal, and electrical characteristics depending on the type of metal, but also the structure, size, and number of pores influence their properties. For example, a porous metal having a large number of pores communicating with the inside and outside of the structure can increase the specific surface area, and therefore, the application development of energy absorbing materials, electrode materials, filter materials, etc. can be made by utilizing the characteristics. Be expected. In addition, with the realization of high functionality, if a porous metal with a thinner plate thickness is developed, it is considered that the range of use of the porous metal is expanded.

Porous metal is produced by various methods, but it is extremely difficult to produce a porous metal having an extremely thin thickness such as a desirable plate thickness of several tens of μm or less in applications such as solar cell electrodes and thin film filters. .
In addition, although it is conceivable to use, for example, a sponge metal or a metal nonwoven fabric for the above-mentioned use, it is necessary to produce a thin product as described above due to restrictions on the manufacturing process and the size of the fine metal wire constituting the nonwoven fabric. It is difficult.
Therefore, it is necessary to once manufacture a thick porous metal and reduce it to a desired thickness according to the application by cutting or polishing. However, it is technically very difficult to manufacture a thin-film porous metal without defects, such as the possibility that the structure of the pores may change due to the stress generated when the film is thinned.

For example, a covering made of a material different from the constituent material of the metal foil is formed on the carrier foil with a thickness of 0.001 to 1 μm, and the constituent material of the metal foil is electrodeposited thereon by electrolytic plating. The manufacturing method of the porous metal foil which forms metal foil is disclosed (patent document 1). The resulting porous metal foil has a large number of micropores having a diameter of 0.01 to 200 μm, a density of micropores of 5 to 10,000 / cm ² , a thickness of 1 to 100 μm, and a non-aqueous electrolyte. Used as a negative electrode for secondary batteries.
However, in this case, when the metal foil is peeled off from the carrier foil and the cover, the metal foil that is an ultrathin film lacks self-supporting property, in other words, lacks rigidity enough to hold the shape. On the other hand, the electroplating process is not always practical for obtaining a metal foil having a thickness that is self-supporting. In addition, it is difficult for a thin film formed by a technique of depositing atoms such as electroplating to achieve both a high porosity and a large porosity.

Further, for example, a titanium powder sintered body made of a plate-like porous body formed by sintering spherical gas atomized titanium powder and having a thickness of 500 μm or less is disclosed (Patent Document 2). ). The titanium powder sintered body has an average particle diameter of spherical gas atomized titanium powder of 150 μm or less and a porosity of the porous body of 35 to 55%, and is used for a cylindrical filter, a dispersion plate or the like by bending.
However, the titanium powder sintered body shown as an example has a thickness of 100 to 600 μm, which is understood to be a thickness necessary to have a certain strength for applications such as a cylindrical filter. At the same time, it is conceivable that a thin film of several tens of μm or less has extremely low mechanical strength and is difficult to produce. In particular, titanium is easily oxidized and nitrided, so that mechanical strength is particularly low.

Further, it is made of a metal sintered body obtained by sintering metal powder, and has a plurality of pore portions dispersed and arranged therein, and the porosity thereof is 10% by volume or more and 50% by volume or less. A sintered metal sheet material for an electrochemical member is disclosed in which the average pore diameter is 1 μm or more and 30 μm or less, and a part of the plurality of pores is arranged to open to the surface. (Patent Document 3). The sintered metal sheet material for electrochemical members is obtained by sintering a material slurry formed into a green sheet, and is used as an electrochemical member such as an electrode or a current collector.
However, the above-described method for producing a sintered metal sheet material for electrochemical members that handles a green sheet seems to have a limit in obtaining a sheet material having an extremely thin thickness of several tens of μm or less.

JP 2005-129264 A JP 2002-317207 A JP 2011-099146 A

  The problem to be solved is that the conventional method for producing a porous metal has an extremely thin thickness of several tens of μm or less depending on the application, and it is not easy to obtain a porous metal having a desired porous structure. It is a point considered not to be.

  The porous sintered metal according to the present invention has a thickness of 5 to 30 μm, a porosity of 25 to 70%, an average pore diameter of 0.2 to 40 μm, and a through hole in which a large number of holes are connected isotropically. It is characterized by being.

  In the method for producing a porous sintered metal according to the present invention, a slurry-like composition containing a metal powder and a solvent is formed on a base material that is soluble in an acid to obtain a pre-sintered compact. Including a pre-sintered green body forming step, a sintering step of sintering the pre-sintered green body to obtain a sintered body, and a base material removing step of separating and removing the base material from the sintered body with an acid. Features.

  The method for producing a porous sintered metal according to the present invention is preferably characterized in that the base material is formed of Fe or an alloy containing Fe.

  Further, in the method for producing a porous sintered metal according to the present invention, preferably, the sintering step is performed in a substantially sealed container, and the standard free energy value of carbide and oxide is determined by sintering. In the temperature range, a metal having a value larger than that of the metal powder is disposed in the vicinity of the green body before sintering.

  The method for producing a porous sintered metal according to the present invention is preferably characterized in that the metal is one or more selected from Ti, Zr and Hf, or an alloy thereof.

  The method for producing a porous sintered metal according to the present invention is preferably characterized in that the pre-sintered compact is heat-treated in a gas containing oxygen atoms before the sintering step. .

The porous sintered metal according to the present invention has a thickness of 5 to 30 μm, a porosity of 25 to 70%, an average pore diameter of 0.2 to 40 μm, and a through hole in which a large number of holes are connected isotropically. Therefore, it is suitable for applications requiring a porous sintered metal that is a thin film and has an excellent porous structure.
In the method for producing a porous sintered metal according to the present invention, a slurry-like composition containing a metal powder and a solvent is formed on a base material that is soluble in an acid to obtain a pre-sintered compact. The present invention includes a pre-sintered green body forming step, a sintering step of sintering the pre-sintered green body to obtain a sintered body, and a base material removing step of separating and removing the base material from the sintered body with an acid. The porous sintered metal which concerns on can be obtained suitably.

FIG. 1 is a view showing an SEM photograph of a porous sintered metal according to this embodiment viewed from the main surface (surface). FIG. 2 is a view showing an SEM photograph of a cross section of the porous sintered metal according to the present embodiment.

  An embodiment of the present invention (hereinafter referred to as this embodiment) will be described below.

First, the porous sintered metal according to the present embodiment will be described.
The porous sintered metal according to the present embodiment has a thickness of 5 to 30 μm, a porosity of 25 to 70%, an average pore diameter of 0.2 to 40 μm, and a large number of pores communicating isotropically. Through hole. In addition, it goes without saying that the definition of terms is obvious, but the unit of porosity is volume%.
The porous sintered metal has a thickness of preferably 25 μm or less and a porosity of preferably 30% or more.

  If the thickness of the porous sintered metal is significantly less than 5 μm, the number of particles present in the thickness direction is reduced, and the strength as a metal porous body may be impaired. On the other hand, if the thickness of the porous sintered metal greatly exceeds 25 μm and exceeds 30 μm, the flowability of a substance such as a fluid inside the porous sintered metal or between both surfaces deteriorates. Problems such as loss of properties, heavy porous sintered metal, large volume of porous sintered metal, and deterioration of applicability when porous sintered metal is used for desired materials May occur.

  As described above, the porosity of the porous sintered metal is 25 to 70%. When the porosity is significantly lower than 30% and less than 25%, the weight saving merit of the porous sintered metal is small. Moreover, there is a possibility that problems such as deterioration of the flowability of the substance inside or outside the porous sintered metal may occur. On the other hand, if the porosity is significantly higher than 70%, the strength of the porous sintered metal may be impaired. Moreover, when a porous sintered metal is a highly conductive metal, suitable conductivity cannot be obtained, and there is a possibility that it cannot be suitably used in applications such as electrodes.

  The average pore diameter of the porous sintered metal is 0.2 to 40 μm as described above. If the average pore diameter is much less than 0.2 μm, the flowability of the substance inside or outside the porous sintered metal is deteriorated, and for example, there is a possibility that the porous body is not suitable for use as a filter or an electrode. On the other hand, if the average pore diameter greatly exceeds 40 μm, the strength of the metal porous body may be impaired.

The porosity and the average pore diameter are values when measured by a mercury intrusion method. Using a mercury intrusion type pore distribution measuring device (Pascal I 140 and Pascal 440 manufactured by CARLOERBA INSTRUMENTS, measurable range: specific surface area 0.1 m ² / g or more, pore distribution 0.0034 to 400 μm), pressure range 0. In the range of 3 to 400 kPa and 0.1 to 400 MPa, the press-fitted volume is calculated as a side area according to the cylindrical pore model, integrated and measured.

  As described above, the numerous holes of the porous sintered metal are through holes that are isotropically communicated. Here, “isotropically communicating” means not only that a large number of pores communicate with each other only in the direction of the thickness of the porous sintered metal, that is, so as to have anisotropy, so that the through-holes are formed. The term “communication” means to communicate in a direction along the plane of the bonded metal so that it is isotropic in all directions in three dimensions. Accordingly, the substance penetrates more uniformly inside the porous sintered metal, and the substance diffuses more uniformly from the opening of the porous sintered metal. Therefore, performance is improved in applications such as filters and electrodes. In addition, for example, in energy absorber applications such as heat and sound, the number of internal echoes is large and the function becomes high.

The porous sintered metal preferably has an electric conductivity of 0.5 × 10 ³ Ω ⁻¹ · m ⁻¹ or more. Electrical conductivity can be measured by a four-probe method.

  The porous sintered metal is preferably self-supporting, that is, has a rigidity sufficient to maintain its shape, and can be suitably handled as a sheet body. However, a porous sintered metal is formed on an auxiliary substrate such as a glass fiber molded body, an inorganic porous body such as a porous alumina plate, an organic porous body such as a heat-resistant porous plastic, or a metal porous body. Also good. In this case, it is more preferable to use a glass fiber molded body from the viewpoints of flexibility, chemical resistance, and heat resistance.

  The porous sintered metal according to the present embodiment described above has excellent mechanical, chemical, thermal and electrical properties as a metal porous body, and is lightweight. For this reason, when using porous sintered metal for applications such as energy absorbers such as sound and heat, filters, or electrodes of fuel cells and dye-sensitized solar cells, it gives superior characteristics to existing ones. be able to.

Next, a method for manufacturing a porous sintered metal according to this embodiment, which can suitably obtain the porous sintered metal according to this embodiment, will be described.
In the method for producing a porous sintered metal according to the present embodiment, a slurry-like composition containing a metal powder and a solvent is formed on a base material having solubility with respect to an acid, and a pre-sintered compact ( Forming a pre-sintered compact to obtain a sintered precursor), a sintering process to obtain a sintered compact by sintering the pre-sintered compact, and a base material removing process to separate and remove the base material from the sintered compact by acid including.

  First, a pre-sintered green body forming step for obtaining a pre-sintered green body by forming a slurry-like composition containing a metal powder and a solvent on a base material that is soluble in acid will be described.

The type of metal powder that is a raw material of the porous sintered metal is not particularly limited, and metal powder produced by hydrodehydrogenation method, sponge metal powder, gas atomized metal powder, etc. can be applied, preferably necking between metal powders Metal powder produced by hydrodehydrogenation method with many sites is used. The metal species of the metal powder is preferably Ti, W, Mo, Rh, Pt, Ta, Ru, Pd, Ni or an alloy containing these from the viewpoint of adaptability to a filter, an electrode, etc. A powder, a titanium hydride powder or a mixed powder thereof is more preferable.
The average particle diameter (also referred to as average particle diameter) of the metal powder is preferably 1 μm to 50 μm in order to impart an appropriate viscosity and fluidity to the composition containing the solvent and to facilitate forming into a thin plate shape, And it is preferable to contain 50 vol% or more of particles having a particle diameter of 1 to 50 μm. As a result, a porous sintered metal having a more uniform film thickness, porosity, and pore diameter can be obtained. When the particle diameter is less than 1 μm, the thickness of the non-conductive coating with respect to the size of the particles increases during sintering, and a sufficient sintered body may not be obtained. Moreover, when metal powder is a highly conductive metal, there exists a possibility that the electroconductivity of the porous sintered metal after sintering may be impaired. On the other hand, when the particle diameter exceeds 50 μm, it becomes difficult to form the thickness of the porous sintered metal to 25 μm or less.

  As the solvent, water or an organic solvent such as ethanol, toluene, isopropanol, terpineol, butyl carbitol, cyclohexane, and methyl ethyl ketone can be used. The proportion of the solvent may vary depending on the type of solvent used, the type of metal powder, and the like, but is preferably 25 to 150 parts by mass with respect to 100 parts by mass of the metal powder.

Furthermore, a binder may be added. When the solvent is water or a water-soluble organic solvent, a methylcellulose-based, ethylcellulose-based, or polyvinyl alcohol-based binder can be used. When the solvent is a water-insoluble organic solvent, Acrylic, polyvinyl butyral, and ethyl cellulose binders can be used. However, if the ratio of the binder to the metal powder is too large, the ratio of oxygen, carbon, hydrogen, etc. contained in the sintered body increases, and the sintered body may be damaged due to embrittlement. For this reason, it is preferable that the ratio of a binder is 30 mass parts or less with respect to 100 mass parts of metal powders.
Furthermore, a plasticizer may be added. When the solvent is water or a water-soluble organic solvent, glycerin, ethylene glycol, polyethylene glycol or the like can be used. When the solvent is a water-insoluble organic solvent, phthalate ester or the like can be used. Can be used. However, if the ratio of the binder to the metal powder is too large, the leveling property at the time of drying the slurry becomes poor and the film thickness becomes non-uniform. There is a fear. For this reason, it is preferable that the ratio of a plasticizer is 2-30 mass parts with respect to 100 mass parts of metal powders.

The base material is soluble in acid, and has heat resistance at the sintering temperature of the metal powder and does not react with the metal powder.
The material type of the base material is not particularly limited as long as it has the above characteristics, but Zn, Fe, an alloy containing these, or an oxide containing them is suitable, and is composed of an alloy containing Fe or Fe Is particularly preferred.
The thickness of the substrate is not particularly limited, but is preferably thick enough to prevent warping in the sintering step, and can be, for example, about 100 μm or more.
The substrate may be a simple substance or may have a multilayer structure in which a release agent is surface-coated on the surface in contact with the sintered body.
In addition, it is possible to add a high-viscosity organic substance as a binder to the slurry composition without using a base material, and to form a pre-sintered molded body as a self-supporting film (green sheet). Residues are likely to remain, which is not preferable because carbides and oxides are formed in the sintering process and become a sintering inhibiting factor.

A slurry-like composition containing a metal powder and a solvent is applied onto a substrate to a thickness of 6 to 100 μm, for example, and molded.
Application method is doctor blade method, dip coating method, die coating method, comma coating method, bar coating method, screen printing method, offset printing method, gravure printing method, ink jet method, spray method, dispensing method, spin coating method, etc. This method can be used.

  The obtained pre-sintered molded body shape is preferably dried in order to remove the organic solvent and the like. Drying can be performed under normal pressure, reduced pressure, or increased pressure, but if the drying rate is too high, cracks and warpage may occur in the molded body before sintering. Select an appropriate temperature, pressure, air volume, etc. according to the physical properties. In addition, when drying under pressure, it will serve also as the press processing of the pre-sintering molded object demonstrated below.

  The pre-sintered compact is preferably pressed. Since the contact area between the metal powders increases due to the press treatment, the number of necking sites increases. Moreover, the higher the pressure of the press treatment, the higher the electrical conductivity, the lower the film thickness, and the lower the porosity. Therefore, it is necessary to select a pressure condition according to the application. However, if the pressing pressure is too low, the contact area between the metal powders does not increase, and if it is too high, the porosity falls outside an appropriate range, or the metal powder undergoes plastic deformation. Therefore, the preferable press pressure range is 0.1 to 100 MPa. Moreover, it is preferable to use a suitable cushion material in a press process. As the cushioning material, an appropriate material such as paper, metal foil, silicon, heat resistant plastic, rubber or the like can be used. The pressing method can be performed by an appropriate method such as a flat plate press, a roll press, or a vacuum laminator.

Next, a sintering process for producing a sintered body by sintering the green body before sintering will be described.
It is preferable to perform a degreasing treatment before the sintering step. The purpose of the degreasing treatment is to thermally decompose or evaporate and remove the solvent, binder and plasticizer (hereinafter collectively referred to as residual carbon component) contained in the green body before sintering. Usually, most of the remaining carbon component is removed at the time of temperature increase in the sintering process, but when the remaining carbon component remains in the pre-sintered molded body, Metals may react to form metal carbides. As a result, the mechanical strength of the sintered body is lowered and is easily damaged. In particular, when titanium is sintered, the remaining carbon component and titanium easily react at 800 ° C. or higher to form titanium carbide. For this reason, it is desirable to perform a degreasing process and to reliably remove residual carbon components.
For the degreasing treatment, methods such as heat treatment, plasma treatment, ozone treatment, and cleaning with a solvent can be used. In the case of heat treatment, the degreasing treatment and the sintering step can be performed continuously by lowering the rate of temperature rise or providing a holding time in the temperature raising step in the sintering step. The heating environment at this time can be appropriately selected depending on the type of metal powder, such as an inert gas such as argon or nitrogen, a gas containing oxygen atoms, an air current or an atmosphere, or a vacuum, but can effectively remove residual carbon components. Therefore, a gas containing oxygen atoms is preferable, and a gas containing 1% or more of oxygen atoms such as oxygen gas, air, a mixed gas of oxygen gas and inert gas is more preferable. Further, the heating temperature and the heating time can be appropriately selected depending on the type and amount of the binder and the gas type. In particular, when performed in a gas containing oxygen atoms, the oxidation of the green body before sintering is suppressed. In that respect, it is preferably 400 ° C. or lower, more preferably less than 350 ° C. The heating time is preferably 0.1 to 6 hours.

  Sintering conditions vary depending on the type of metal to be sintered. For example, in the case of titanium, oxides and nitrides are easily formed. Therefore, it is preferably performed in a vacuum or under an inert atmosphere of argon and kept at a temperature of 700 to 1100 ° C. for 0.1 to 6 hours, 750 It is more preferable to hold at ˜1000 ° C. for 0.5 to 4 hours. When the temperature is too low, the sintering is not sufficient, and when the temperature is too high, the metal porous body is warped, and the metal powder is melted so that the pores are blocked and the porous body may not be formed.

The sintering process is performed in a substantially hermetically sealed container, and the standard free energy values of carbides and oxides in the vicinity of the green body before sintering are larger than the sintered metal powder in the sintering temperature range. It is preferable to perform by arranging a metal having the following (hereinafter referred to as a getter material).
The substantially sealed container is, for example, a vacuum baking furnace whose opening is closed by a door.
Sintering in a container with a getter material prevents oxygen from being mixed outside the container, and oxygen in the container is preferentially reacted and consumed by the getter material, so that oxidation of the sintered body is suppressed More preferable. The material of the getter material varies depending on the type of metal to be sintered. For example, when the metal powder is titanium, the getter material is preferably Ti, Zr or Hf. One kind or two or more kinds selected from Ti, Zr and Hf, or an alloy of one or more kinds of these metals is used.

Finally, the base material removal step of separating and removing the base material from the sintered body with an acid will be described.
The substrate removing method using an acid is preferable from the viewpoint of peeling efficiency. The type of acid is not particularly limited as long as the base material is peeled off, such as inorganic acid such as hydrochloric acid, sulfuric acid, nitric acid, aqua regia, organic acid such as phosphoric acid, carboxylic acid, etc., but the sintered body dissolves. Acids that do not react and those that do not chemically react with the sintered body are preferred. Specifically, nitric acid and sulfuric acid are preferably used. The substrate removal method using an acid is not particularly limited, and a method of immersing the sintered body in an acid solution or a method of spraying the acid solution onto the sintered body may be used. After the substrate is peeled off, it is quickly washed to remove the acid remaining in the sintered body. The cleaning liquid can be used without limitation as long as it dissolves acid, such as water or an organic solvent.

  According to the method for producing a porous sintered metal according to the embodiment described above, the thickness is 5 to 25 μm, the porosity is 30 to 70%, the average pore diameter is 0.2 to 40 μm, and many The porous sintered metal according to the present embodiment, which is a through hole in which the holes are isotropically communicated, can be suitably obtained. In addition, a porous sintered metal having a thickness of more than 25 μm and not more than 60 μm can be suitably obtained, and can be used for applications such as electrodes of fuel cells and dye-sensitized solar cells.

  EXAMPLES Hereinafter, although this invention is demonstrated more concretely based on an Example and a comparative example, this invention is not limited to this Example.

Example 1
Titanium powder (average particle size 10 μm) produced by hydrodehydrogenation method and ethyl cellulose binder (EC-200FTD manufactured by Nisshin Kasei Co., Ltd.) with a blending ratio of 60% by mass of titanium powder and binder 40 A slurry-like composition was prepared by mixing to a mass%. The binder is composed of about 80% by mass of terpineol and about 20% by mass of ethyl cellulose.
Next, this slurry-like composition is applied onto an iron foil having a thickness of 20 μm × 40 mm and a thickness of 100 μm by a squeegee method (screen printing method) using a metal mask having a thickness of 50 μm and an opening of 10 mm × 30 mm, This was dried under reduced pressure at a temperature of 150 ° C. under a pressure of 30 kPa for 1.5 hours to obtain a molded body before firing. Then, the green body before firing was pressed at a pressure of 68.6 MPa.

Then, this pre-fired shaped body was put together with the iron foil in a vacuum firing furnace and heated at 300 ° C. under atmospheric pressure for 1 hour for degreasing treatment. Furthermore, after covering the entire upper surface of the pre-sintered compact in a vacuum firing furnace with a titanium foil, it was fired at a temperature of 800 ° C. for 2 hours under a pressure of 3 × 10 ⁻³ Pa, and fired. A sintered body was obtained.

Further, the sintered body was immersed in a 3N sulfuric acid aqueous solution for 1 hour to dissolve the iron foil portion in contact with the sintered body, and the iron foil was peeled off from the sintered body.
The obtained sintered body was washed repeatedly with distilled water and detergent water to remove sulfuric acid, and then dried by heating to obtain porous titanium (porous sintered metal) having a thickness of 27 μm.
1 and 2 show SEM photographs of porous titanium. FIG. 1 is a view of porous titanium as viewed from the main surface (surface) side. In the figure, reference numeral 10 indicates a porous sintered metal (porous titanium), reference numeral 12 indicates a metal portion, and reference numeral 14. Indicates holes. FIG. 2 is a view of porous titanium as viewed from the cross section side. In the figure, reference numeral 16 indicates a main surface, and reference numeral 18 indicates a cross section.

  The thickness, porosity, average pore diameter, and electrical conductivity of the obtained porous titanium were measured. The obtained results are shown in Table 1 together with the particle size of the titanium powder.

(Example 2)
Titanium powder (average particle size 10 μm) produced by the hydrodehydrogenation method and ethyl cellulose binder (EC-200FTD manufactured by Nisshin Kasei Co., Ltd.), titanium powder 60 mass%, binder 40 mass % To prepare a slurry composition. The binder is composed of about 80% by mass of terpineol and about 20% by mass of ethyl cellulose.
Next, this slurry-like composition was applied onto a base material of 60 mm × 70 mm and 100 μm thick iron foil using a Baker type applicator (manufactured by Hosen Co., Ltd.) having a coating thickness of 75 μm, and this was applied to 30 kPa. Under reduced pressure, it was dried under reduced pressure at a temperature of 150 ° C. for 1.5 hours to obtain a molded body before sintering.

Then, the green compact before sintering was put into a siliconit furnace together with the iron foil, and heated at 300 ° C. under atmospheric pressure for 1 hour to perform a degreasing treatment. Next, the degreased pre-sintered compact was placed in a vacuum firing furnace and covered with a titanium foil so as to cover the entire upper surface of the pre-sintered compact, and then at 800 ° C. under a pressure of 3 × 10 ⁻³ Pa. Was heated for 2 hours to obtain a sintered body.

Further, the sintered body was immersed in a 3N sulfuric acid aqueous solution for 1 hour to dissolve the iron foil portion in contact with the sintered body, and the iron foil was peeled off from the sintered body.
The obtained sintered body is pickled with 3N sulfuric acid, washed repeatedly with distilled water and detergent water to remove sulfuric acid, and then dried by heating to obtain porous titanium (porous sintered metal) having a thickness of 23 μm. Obtained.
1 and 2 show SEM photographs of porous titanium. FIG. 1 is a view of porous titanium as viewed from the main surface (surface) side. In the figure, reference numeral 10 indicates a porous sintered metal (porous titanium), reference numeral 12 indicates a metal portion, and reference numeral 14. Indicates holes. FIG. 2 is a view of porous titanium as viewed from the cross section side. In the figure, reference numeral 16 indicates a main surface, and reference numeral 18 indicates a cross section.

  The thickness, porosity, average pore diameter, and electrical conductivity of the obtained porous titanium were measured. The obtained results are shown in Table 1 together with the particle size of the titanium powder.

(Example 3)
Porous titanium was obtained in the same manner as in Example 1 except that the green compact was pressed at 294 MPa. The thickness, porosity, average pore diameter, and electrical conductivity of the obtained porous titanium were measured. The obtained results are shown in Table 1 together with the particle size of the titanium powder.

Example 4
Porous titanium was obtained in the same manner as in Example 1 except that titanium particles having an average particle diameter of 17 μm were used, and the slurry-like composition was applied by a squeegee method using a metal mask having a thickness of 50 μm and an opening of 10 × 30 mm. . The thickness, porosity, average pore diameter, and electrical conductivity of the obtained porous titanium were measured. The obtained results are shown in Table 1 together with the particle size of the titanium powder.

(Example 5)
A slurry composition containing 30% by mass of titanium particles having an average particle size of 10 μm, 30% by mass of titanium hydride particles having an average particle size of 6 μm, and 40% by mass of an ethylcellulose binder is 50 μm in thickness and has an opening of 10 × 30 mm. A porous titanium was obtained in the same manner as in Example 1 except that the metal mask was applied by the squeegee method. The thickness, porosity, average pore diameter, and electrical conductivity of the obtained porous titanium were measured. The obtained results are shown in Table 1 together with the particle size of the titanium powder.

(Example 6)
In the sintering step, porous titanium was obtained in the same manner as in Example 1 except that the entire upper surface of the molded body before sintering was covered with a zirconium foil. The thickness, porosity, average pore diameter, and electrical conductivity of the obtained porous titanium were measured. The obtained results are shown in Table 1 together with the particle size of the titanium powder.

(Example 7)
Porous in the same manner as in Example 1 except that the slurry composition was applied by a squeegee method using a metal mask having a thickness of 50 μm and an opening of 10 × 30 mm, and degreasing was performed under 1 × 10 ⁻¹ Pa. Titanium was obtained. The thickness, porosity, average pore diameter, and electrical conductivity of the obtained porous titanium were measured. The obtained results are shown in Table 1 together with the particle size of the titanium powder.

(Example 8)
The slurry composition was applied by a squeegee method using a metal mask having a thickness of 50 μm and an opening of 10 × 30 mm, the degreasing treatment was performed under 1 × 10 ⁻¹ Pa, and the substrate removal step was performed with 3N nitric acid. In the same manner as in Example 1, porous titanium was obtained. The thickness, porosity, average pore diameter, and electrical conductivity of the obtained porous titanium were measured. The obtained results are shown in Table 1 together with the particle size of the titanium powder.

(Comparative Example 1)
Except for using Ti as a base material, when trying to obtain porous titanium in the same manner as in Example 1, the base material and the sintered body could not be peeled off, and the intended porous titanium was obtained. There wasn't.

(Comparative Example 2)
Porous titanium was obtained in the same manner as in Example 1 except that PET was used as the base material and the pre-sintered compact was mechanically peeled off from the base material before firing. The body was cracked and the intended porous titanium could not be obtained.

(Comparative Example 3)
A porous titanium was obtained in the same manner as in Example 1 except that a Teflon sheet was used as a base material and the green body before sintering was mechanically peeled from the base material before firing. The molded body was cracked, and the intended porous titanium could not be obtained.

(Comparative Example 4)
Except for setting the application thickness of the Baker type applicator to 10 μm, an attempt was made to obtain porous titanium in the same manner as in Example 1, but the slurry-like composition could not be applied on the substrate.

DESCRIPTION OF SYMBOLS 10 Porous sintered metal 12 Metal part 14 Hole part 16 Main surface 18 Cross section

Claims (6)

The metal is Ti or Ti alloy , the thickness is 5 to 30 μm, the porosity is 25 to 70%, the average pore diameter is 0.2 to 40 μm, and many holes are isotropic through holes. A porous sintered metal characterized by that. A pre-sintered green body forming step for forming a pre-sintered green body by forming a slurry-like composition containing a metal powder that is Ti or a Ti alloy and a solvent on a substrate that is soluble in acid, look containing a substrate removal step of separating and removing the substrate a sintered preform by sintering step and acid to obtain a sintered sintered body from the sintered body, the thickness of the porous sintered metal obtained A method for producing a porous sintered metal, comprising 5 to 30 μm, a porosity of 25 to 70%, and an average pore diameter of 0.2 to 40 μm .   3. The method for producing a porous sintered metal according to claim 2, wherein the base material is formed of Fe or an alloy containing Fe.   The sintering step is performed in a substantially sealed container, and a metal as a getter material having a standard free energy value for formation of carbides and oxides that is larger than the metal powder in the sintering temperature range. 3. The method for producing a porous sintered metal according to claim 2, wherein the porous sintered metal is disposed in the vicinity of the green body before sintering.   5. The method for producing a porous sintered metal according to claim 4, wherein the metal as the getter material is one or more selected from Ti, Zr and Hf, or an alloy thereof.   The method for producing a porous sintered metal according to claim 2, wherein the pre-sintered compact is heat-treated in a gas containing oxygen atoms before the sintering step.

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