JP2011111643A - Hydrophilic metal foam body - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a hydrophilic metal foam body free from a degradation in hydrophilicity during long-term use. <P>SOLUTION: In the hydrophilic metal foam body, the porosity of the entire void of the metal foam consisting of Ti, Cu, Ni, Al, Ag, stainless steel or the like is 55-99 vol.%, the opening ratio of the void open to at least one outermost surface of the metal foam is 5-80 area%, and the opening ratio of the void open to the outermost surface is smaller than the cross-section opening ratio of the void in an optional cross-section inside the metal foam parallel to the outermost surface. The skeleton surface of the metal foam is covered by a mixture of titanium oxide particles and silica, and an aggregate consisting of a mixture of titanium oxide particles and silica is inserted into the inside of pores of the metal foam and held thereby. <P>COPYRIGHT: (C)2011,JPO&amp;INPIT

Description

  The present invention relates to a hydrophilic foamed metal body in which the hydrophilicity of the foamed metal body is remarkably improved and the deterioration of the hydrophilicity of the foamed metal body does not occur even after long-term use.

Porous metal bodies in which the surface of a porous metal skeleton such as foam metal is coated with silica include, for example, gas diffusion layers for fuel cells, fin materials for heat exchangers such as room air conditioners and car air conditioners, and semiconductor chip babies. Conventionally, it has been widely used as a chamber wick material in various technical fields (see Patent Documents 1 to 3).
In any of the above-described porous metal bodies coated with silica, improvement of the hydrophilicity of the porous metal body is considered as a major issue, and various contrivances have been made. It is known to improve hydrophilicity by coating a silica coating layer containing 0.5 to 15% by mass with the balance being silica (see Patent Document 4).

  As a method for producing a porous metal made of a foam metal, for example, a raw material powder, a water-soluble resin binder, a plasticizer, a foaming agent and water are mixed and kneaded to prepare a foam slurry, and this foam slurry is used as a carrier. Formed into a thin plate shape with a doctor blade or the like on the sheet, and foamed using the vapor pressure of the volatile organic solvent contained in the foaming slurry as a foaming agent and the foaming property of the surfactant in a constant temperature / high humidity tank, Further, it is known that a foamed green sheet is produced by drying in a drying tank, and the foamed green sheet is produced by degreasing and firing through a degreasing apparatus and a firing furnace. (See Patent Documents 4 and 5).

JP 2006-100155 A Japanese Patent No. 3818882 JP 2009-92344 A JP 2008-195016 A JP 2004-43976 A

The conventional silica-coated porous metal body in which silica is coated on the skeleton surface of the conventional porous metal gradually loses its hydrophilicity over time when used over a long period of time. Due to the decrease in hydrophilicity, for example, the power generation performance is reduced in the gas diffusion layer of the fuel cell. In the fin materials for heat exchangers such as room air conditioners and car air conditioners, the heat exchange characteristics are lowered, the water droplets are scattered, the noise is reduced. In addition, various problems such as a decrease in heat transport efficiency have occurred in the vacuum chamber wick material of the semiconductor chip.
Accordingly, an object of the present invention is to provide a hydrophilic foamed metal body in which the hydrophilicity of the foamed metal body is remarkably improved, and the deterioration of the hydrophilicity of the foamed metal body does not occur over a long period of use. To do.

The inventor of the present invention has greatly improved the hydrophilicity of the metal foam body, and as a result, has been researching to obtain a hydrophilic metal foam body that does not deteriorate the hydrophilicity of the metal foam body over a long period of use. As a result, the following knowledge was obtained.
First, as the structure of the foam metal, the porosity of the entire void of the foam metal is 55 to 99% by volume, and the opening ratio of the void opening to at least one outermost surface of the foam metal is 5 of the area of the outermost surface. -80% by area, and further, the aperture ratio of the void opening to the outermost surface is smaller than the sectional aperture ratio of the void in any cross section inside the foam metal parallel to the outermost surface,
The surface of the skeleton of the metal foam is coated with a mixture of fine particle titanium oxide having an average film thickness of 0.01 to 1 μm and silica, and at the same time, the pores of the metal foam are made of a mixture of fine particle titanium oxide and silica. When a hydrophilic foam metal body is formed by inserting and holding aggregates, silica exerts an action of fixing to the entire surface including pores inside the foam metal, and silica itself is hydrophilic. In addition, the hydrophilicity is synergistically improved by coexistence with titanium oxide, and the hydrophilicity is further improved because fine titanium oxide has a high specific surface area. Further, the photocatalytic function of titanium oxide further improves the hydrophilicity. It has been found that the hydrophilicity is maintained over a long period of time and the deterioration does not occur.

Here, the foam metal is formed by continuously forming a plurality of polyhedral voids whose sides are constituted by a skeleton of a sintered metal such as Ti, Cu, Ni, Al, Ag, and stainless steel. The void is formed such that a plurality of polyhedral pores (pores) whose sides are constituted by a skeleton are continuous with each other.
And, the volume ratio (porosity) of the entire voids occupied in the foam metal is Wp as the weight of the foam metal when the weight of the same metal material with the same outer dimensions is W,
Porosity (% by volume) = (W−Wp) / W × 100
Calculated by

The foam metal (sintered metal) of the present invention has a large number of void openings on the outermost surface, and the area ratio (opening ratio) of the voids opened on the outermost surface is 25 to 300 obtained by photographing the outermost surface. When observing and measuring the visual field area A and the area sum Ap of all the void openings on the outermost surface observed in this visual field, using a double micrograph
Opening ratio (area%) = Ap / A × 100
Can be calculated.

In addition, the area ratio (cross-sectional aperture ratio) of the void opening in the arbitrary cross section parallel to the outermost surface inside the foam metal (sintered metal) is taken as in the above calculation of the aperture ratio. Using the photomicrograph of 25 to 300 times, the cross-sectional visual field area Ac and the area sum Acp of all the gap openings observed in the cross-sectional visual field,
Cross-sectional aperture ratio (area%) = Acp / Ac × 100
Can be calculated.

This invention has been made based on the above findings,
“(1) The porosity of the entire void of the foam metal is 55 to 99% by volume, and the aperture ratio of the void opening to at least one outermost surface of the foam metal is 5 to 80 area of the area of the outermost surface. Further, the opening ratio of the voids that open to the outermost surface is a hydrophilic foam metal body that is smaller than the sectional opening ratio of the voids in an arbitrary cross section inside the foam metal parallel to the outermost surface,
The skeleton surface of the foam metal is coated with a mixture of fine particle titanium oxide and silica having an average film thickness of 0.01 to 1 μm, and the pores of the foam metal are made of a mixture of fine particle titanium oxide and silica. A hydrophilic foam metal body, characterized in that an agglomerate is inserted and held.
(2) The hydrophilicity according to (1) above, wherein the opening ratio of the voids that open to the outermost surface of the foam metal parallel to the flow direction of the hydrophilic fluid is 5 to 80% by area of the area of the outermost surface. Metal foam body.
(3) The hydrophilic foam metal body according to (1) or (2), wherein the skeleton of the foam metal is composed of any one of Ti, Cu, Ni, Al, Ag, and stainless steel. "
It has the characteristics.

The present invention will be described in detail below.
First, in the present invention, regarding the structure of the foam metal, “the porosity of the entire void of the foam metal is 55 to 99% by volume”, “the aperture ratio of the void opening to at least one outermost surface of the foam metal is the outermost surface. Further, the opening ratio of the voids that open to the outermost surface is smaller than the sectional opening ratio of the voids in an arbitrary cross section inside the foam metal parallel to the outermost surface ”. However, the reasons for specifying each are as follows.

Porosity:
First, the porosity of the entire void formed in the foam metal (= (W−Wp) / W × 100 (volume%), where Wp is the weight of the foam metal, W is the same metallic material with the same outer dimensions. Weight) is required to be 55 to 99% by volume.
That is, when the porosity of the entire void of the foam metal is less than 55% by volume, not only the void for inserting and holding the aggregate composed of the mixture of fine particle titanium oxide and silica is insufficient, but also in the hydrophilic foam metal body. Since the voids acting as capillaries are insufficient, the effect of improving hydrophilicity cannot be sufficiently exhibited. On the other hand, when the porosity exceeds 99% by volume, the strength as the hydrophilic foam metal body is insufficient, so the porosity Needs to be 55 to 99% by volume.

Opening ratio of void:
Next, the opening ratio (= Ap / A × 100 (area%)) of the voids that open to at least one outermost surface of the foam metal, preferably the outermost surface of the foam metal parallel to the fluid flow direction. Ap: the sum of the areas of all the void openings on the outermost surface observed in the visual field, and A: the visual field area A) must be 5 to 80% by area.
For example, in the gas diffusion layer of the fuel cell, the opening ratio of the voids that open to the outermost surface of the foam metal parallel to the flow direction of the liquid fluid such as methanol and the hydrophilic fluid such as generated water is 5 to 80 area%. To do.
In other words, when the opening ratio of the voids that open to at least one outermost surface of the foam metal is less than 5% by area, the agglomerates composed of a mixture of fine particle titanium oxide and silica can uniformly enter the pores of the foam metal. In addition, there are too few openings that serve as fluid inflow ports, preventing fluid absorption and movement. On the other hand, when the aperture ratio exceeds 80 area%, the relatively small aggregates fall out, and a sufficient amount of aggregates cannot be held inside the pores, and it becomes difficult to move the fluid against natural fall. Therefore, the opening ratio of at least one outermost surface of the foam metal, preferably the outermost surface of the foam metal parallel to the fluid flow direction, was set to 5 to 80 area%.

In the present invention, the opening ratio of the foam metal is smaller than the cross-sectional opening ratio (= Acp / Ac × 100 (area%)). However, the presence ratio of voids on the outermost surface of the foam metal and the foam metal By deliberately varying the abundance ratio of the voids in the internal cross section of the glass, a decrease in capillary force due to long-term use of the entire hydrophilic foam metal body is prevented, and hydrophilic deterioration is prevented.
That is, by making the opening ratio of the metal foam smaller than the opening ratio of the cross section, it is possible to prevent the agglomerates inserted and held inside the pores of the metal foam, and at the same time, draw the fluid by the capillary pressure difference. The force is increased and the moving speed of the fluid is increased.

Next, according to the present invention, in the foam metal body having the above structure, “coating with a mixture of fine particle titanium oxide having an average film thickness of 0.01 to 1 μm and silica” and “inside the pores of the foam metal, The agglomerates composed of a mixture of fine particle titanium oxide and silica are defined to be inserted / held ”for the following reason.
The surface of the foam metal is coated with a mixture of fine particle titanium oxide and silica with an average film thickness of 0.01 to 1 μm to increase the hydrophilicity, but the average of the mixture of fine particle titanium oxide and silica to be coated If the film thickness is less than 0.01 μm, the foam metal body cannot have sufficient hydrophilicity. On the other hand, if the average film thickness of the mixture of fine particle titanium oxide and silica exceeds 1 μm, cracks occur in the coating film. In this invention, the average film thickness of the mixture of fine-particle titanium oxide and silica coated on the surface of the foam metal skeleton is 0.01 to. 1 μm was determined.
The average film thickness of the coating can be calculated from the weight of the mixture of the coated fine particle titanium oxide and silica and the specific surface area of the foam metal.

Furthermore, in the present invention, an aggregate made of a mixture of fine particle titanium oxide and silica is inserted and held in the pores of the foam metal, for the following reason.
Silica, which is a component of the agglomerate, has an action of adhering and holding the agglomerates inserted inside the pores of the foam metal on the entire surface inside the pores, and the silica itself exhibits hydrophilicity, and at the same time, titanium oxide. And synergistically improve hydrophilicity. The fine particle titanium oxide, which is another component of the aggregate, is a hydrophilic powder having a high specific surface area, so that the hydrophilicity on the inner surface of the pores of the foam metal is increased, and further, the titanium oxide has a photocatalytic action. Further, the hydrophilicity is further improved, and the hydrophilicity is maintained over a long period of use, thereby preventing the deterioration of the hydrophilicity.

In the present invention, the mixture of fine particle titanium oxide and silica was mixed with, for example, 35% of tetraethoxysilane, 35% of ethanol and 30% of water. After preparing a silica sol-gel solution by adding 0.1% acetic acid to 99.9% of this mixed solution, 95% of the silica sol-gel solution and 5% of fine particle titanium oxide (for example, P25 manufactured by Nippon Aerosil Co., Ltd.) are mixed. It is produced by preparing a fine particle titanium oxide-dispersed silica sol-gel solution.
In the present invention, the aggregate made of a mixture of fine particle titanium oxide and silica inside the pores of the foam metal is obtained by, for example, immersing the foam metal in the fine particle titanium oxide-dispersed silica sol-gel solution. The agglomerates are inserted into the pores, fixed to the inner surfaces of the pores, and retained.
Further, in the present invention, the mixture of the fine particle titanium oxide and silica coated on the foam metal, and the fine particle titanium oxide and silica mixture (agglomerate) inserted, fixed and held on the pore inner surface of the foam metal. The ratio of the total amount to the entire hydrophilic foam metal body is not particularly limited. However, the greater the amount, the higher the hydrophilic sustaining effect, but the lack of voids capable of holding water. ~ 45 wt% is desirable.
here,
m _b : Weight of the mixture of fine particle titanium oxide and silica and weight before inserting the aggregate (g),
m _a : Weight (g) after coating of a mixture of fine particle titanium oxide and silica and insertion of an aggregate
If
Mixture ratio of fine particle titanium oxide and silica (wt%)
= (M _a -m _b ) / m _a × 100 (%)
It is.

In FIG. 1, an example about the presence form of the space | gap of Ti foam metal is shown.
FIG. 1A is a microscopic image of the outermost surface of a Ti foam metal (thickness: 1.0 mm), and the aperture ratio obtained from this micrograph is 14 area%, and FIG. These are the microscope images in the cross section parallel to the thickness center part and outermost surface of the said Ti metal foam, The area ratio (cross-section opening ratio) of the opening space | gap which occupies for the thickness center partial cross section calculated | required by this micrograph Area%.
As illustrated in FIGS. 1 (a) and 1 (b), in the present invention, the existence ratio of voids on the outermost surface of the foam metal and the existence ratio of voids inside the foam metal are differently structured, and the capillary pressure The fluid pulling force due to the difference is increased, the fluid moving speed is increased, and the agglomerates inserted and held inside the foam metal pores are prevented from falling off.

  The foam metal body of the present invention having a porosity of 55 to 99% by volume, an aperture ratio of 5 to 80% by area, and an aperture ratio smaller than the cross-sectional aperture ratio can be produced by, for example, the following production method.

Foaming slurry making process:
First, a foamable slurry containing a metal powder and a foaming agent is prepared.
The foamable slurry is prepared by mixing a metal powder forming a skeleton, a binder (water-soluble resin binder), a foaming agent and water, and, if necessary, a surfactant and / or a plasticizer.
More specifically, a slurry containing a metal powder, a binder, and water is first prepared, and then a foaming agent is added to the slurry, followed by stirring with a stirring device such as a mixer. It does not specifically limit as metal powder, Ni, Cu, Ti, Al, Ag, stainless steel, etc. can be used.

  The metal powder preferably has an average particle size of 0.5 μm or more and 30 μm or less. Such a powder can be produced by an atomizing method such as a water atomizing method or a plasma atomizing method, a chemical process method such as an oxide reduction method, a wet reduction method, or a carbonyl reaction method.

  As the binder (water-soluble resin binder), methylcellulose, hydroxypropylmethylcellulose, hydroxyethylmethylcellulose, carboxymethylcellulose ammonium, ethylcellulose, polyvinyl alcohol, and the like can be used.

  The foaming agent is not particularly limited as long as it can generate gas and form bubbles in the slurry, and is a volatile organic solvent such as pentane, neopentane, hexane, isohexane, isopeptane, benzene, octane, toluene, etc. The water-insoluble hydrocarbon-based organic solvent can be used. The content of the foaming agent is preferably 0.1 to 5% by weight with respect to the foaming slurry.

  Surfactants include anionic surfactants such as alkylbenzene sulfonates, α-olefin sulfonates, alkyl sulfates, alkyl ether sulfates, alkane sulfonates, polyethylene glycol derivatives, polyhydric alcohol derivatives, etc. Nonionic surfactants and amphoteric surfactants can be used.

  The plasticizer is added to impart plasticity to a molded product obtained by molding a slurry. For example, polyhydric alcohols such as ethylene glycol, polyethylene glycol, and glycerin, fats and oils such as coconut oil, rapeseed oil, and olive oil, petroleum ether, etc. Ethers such as diethyl phthalate, di-N-butyl phthalate, diethyl hexyl phthalate, dioctyl phthalate, sorbitan monooleate, sorbitan trioleate, sorbitan palmitate, sorbitan stearate, and the like can be used.

Furthermore, an optional additive component may be added to improve the properties and moldability of the slurry. For example, a preservative can be added to improve the storage stability of the slurry, or a polymer compound can be added as a binding aid to improve the strength of the molded body.
From the foamable slurry thus prepared, a molding process and a foam drying process for forming a green sheet are performed using a molding apparatus.

Molding process:
The forming apparatus is an apparatus for forming a sheet using a doctor blade method, a hopper in which foamable slurry is stored, a carrier sheet for transferring the foamable slurry supplied from the hopper, a roller for supporting the carrier sheet, and a carrier sheet A blade (doctor blade) for forming the foamable slurry to a predetermined thickness, a constant temperature / high humidity tank for foaming the foamable slurry, and a drying tank for drying the foamed slurry are provided.
The lower surface of the carrier sheet is supported by a support plate.
In the above molding apparatus, first, the homogenized foaming slurry is put into a hopper, the foaming slurry is supplied from the hopper onto the carrier sheet, and the foaming slurry supplied onto the carrier sheet is the carrier sheet. It is formed into a thin plate shape by a blade while moving with it.

Foam drying process:
Next, the thin plate-like foaming slurry foams while moving in a constant temperature / high humidity tank under predetermined conditions (for example, temperature 30 ° C. to 40 ° C., humidity 75% to 95%) over 10 minutes to 20 minutes, for example. . Subsequently, the slurry foamed in the constant-temperature / high-humidity tank moves in a drying tank under a predetermined condition (for example, a temperature of 50 ° C. to 80 ° C.) over 10 to 20 minutes, for example, and is dried.
Thereby, a sponge-like green sheet is obtained.

Sintering process:
The green sheet thus obtained is degreased and sintered to form a thin plate-like sintered body.
Specifically, for example, after removing (degreasing) the binder (water-soluble resin binder) in the green sheet under vacuum at a temperature of 550 ° C. to 650 ° C. for 25 minutes to 35 minutes, Sintering is performed at 1200 to 1300 ° C. for 60 to 120 minutes.
In addition, it is possible to adjust to arbitrary thickness and porosity by rolling after sintering.
For example, after sintering, the porosity of 50 to 99% by volume of the present invention can be obtained by rolling at a rolling rate of 5 to 90%.
Here, the rolling rate is represented by [1- (plate thickness after rolling / plate thickness before rolling)] × 100.
In addition, regarding the adjustment of the aperture ratio and cross-sectional aperture ratio, the types of metal powder, the composition of the slurry, the surface state of the carrier sheet, the conditions of the constant temperature / high humidity tank (temperature, humidity, time, pressure, etc.), the conditions of the drying tank Although it varies depending on (temperature, time, pressure, etc.), specific conditions are as shown in the examples below.

  The hydrophilic foam metal body of the present invention can maintain and exhibit excellent hydrophilicity over a long period of time as compared with a conventional silica-coated foam metal body (porous metal body), and can be used for a long time. Capillary force can be sustained. Furthermore, by maintaining hydrophilicity, the effects of preventing surface contamination and maintaining water retention over a long period of time can be obtained.

The hydrophilic Ti foam metal body of the present invention (Example 1) shows a microscopic image of a foam before covering and coating the mixture of fine particle titanium oxide and silica, and (a) shows the outermost surface. A microscopic image (magnification: 250 times) of the open space (opening ratio 14%) is shown, and (b) is a microscopic image (magnification: 250 times) of the open space (cross-sectional open area ratio 83%) in the central section in the thickness direction. Indicates. The electron microscope image (magnification: 100 times) of the surface state of the hydrophilic Ti foam metal body of the present invention (Example 1) after covering with a mixture of fine particle titanium oxide and silica and inserting aggregates is shown. Microscope of coating of mixture of fine particle titanium oxide and silica and opening void (opening ratio of 77%) on the outermost surface of the foam before inserting the agglomerate for the hydrophilic Cu foam metal body of the present invention (Example 2) An image (magnification: 250 times) is shown.

The present invention will be described below using examples.
Here, a hydrophilic foam metal body obtained by coating a mixture of fine particle titanium oxide and silica and inserting an aggregate on a Ti foam metal body, a Cu foam metal body, and a Ni foam metal body. However, the present invention is not limited to these, and can also be applied to foamed metals such as Al, Ag, and stainless steel.

Production of Ti foam metal:
Ti powder with an average particle size of 10 μm as a metal powder, an aqueous solution containing 10% methylcellulose as a binder (water-soluble resin binder), ethylene glycol as a plasticizer, sodium alkylbenzene sulfonate as a surfactant, and neopentane as a foaming agent, These are blended so that the raw material powder is 20% by mass, the water-soluble resin binder is 10% by mass, the plasticizer is 1% by mass, the surfactant is 3% by mass, the foaming agent is 0.6% by mass, and the balance is water. Stir to produce a foamed slurry.
The obtained foamed slurry is molded on a carrier sheet by a doctor blade method with a blade gap of 0.5 mm, and supplied to a constant temperature / high humidity tank, where the temperature is 35 ° C. and the humidity is 90% in the constant temperature / high humidity tank for 20 minutes. And then moved in a drying tank at a temperature of 80 ° C. over 20 minutes to produce a sponge-like green sheet.
This green sheet is peeled off from the carrier sheet, placed on an alumina plate, degreased in a vacuum sintering furnace under the conditions of atmosphere 5 × 10 ⁻³ Pa, temperature 550 ° C., 180 minutes, and subsequently in a vacuum sintering furnace. Sintered and rolled under the conditions of atmosphere 5 × 10 ⁻³ Pa, temperature 1200 ° C., 1 hour holding, porosity 70%, thickness 2.0 mm, and opening on the surface A Ti foam metal having continuous voids continuous with the internal voids was prepared.
The obtained Ti foam metal was cut so as to have a length of 20 mm and a width of 20 mm to prepare a test piece.

Preparation of fine particle titanium oxide dispersed silica sol-gel solution:
By weight percent, 35% tetraethoxysilane, 35% ethanol, and 30% water were mixed. A silica sol-gel solution is prepared by adding 0.1% acetic acid to 99.9% of this mixed solution, and 95% of this silica sol-gel solution and 5% of fine-particle titanium oxide (P25 manufactured by Nippon Aerosil Co., Ltd.) are mixed to oxidize the fine particles. A titanium-dispersed silica sol-gel solution was prepared.

Preparation of foamed metal body made of hydrophilic Ti:
The Ti foam metal test piece is immersed in the fine particle titanium oxide-dispersed silica sol-gel solution, and heat-treated in the atmosphere at 80 ° C. for 60 minutes to form fine particles on the surface of the Ti foam metal skeleton. The mixture of titanium oxide and silica is coated with a film thickness of 0.1 μm, and an aggregate made of a mixture of fine particle titanium oxide and silica is inserted and held inside the pores of the Ti foam metal. A hydrophilic Ti foam metal body (referred to as Example 1) was produced.

Table 1 shows the porosity (volume%), the opening ratio (area%), the cross-sectional opening ratio (area%) at the central portion in the thickness direction, and the mixture ratio of fine particle titanium oxide and silica (measured and calculated for Example 1). = (M _a -m _b ) / m _a × 100).

FIG. 1A shows a microscopic image (magnification: 250 times) of the open space (opening ratio: 14%) on the outermost surface of the Ti foam metal of Example 1, and FIG. 1 shows a microscopic image (magnification: 250 times) of an open space (cross-sectional aperture ratio 83%) in the central cross section of No. 1;
FIG. 2 is an electron microscopic image (magnification: 100 times) showing the surface state of the hydrophilic Ti foam metal body of Example 1 after coating with a mixture of fine particle titanium oxide and silica and inserting aggregates, and in the pores The presence of agglomerates (whitish part) is observed.

Production of Cu foam metal:
Cu powder with an average particle size of 8 μm as a metal powder, an aqueous solution containing 10% methylcellulose as a binder (water-soluble resin binder), ethylene glycol as a plasticizer, sodium alkylbenzene sulfonate as a surfactant, and neopentane as a foaming agent, These are blended so that the raw material powder is 20% by mass, the water-soluble resin binder is 10% by mass, the plasticizer is 1% by mass, the surfactant is 6% by mass, the foaming agent is 3% by mass, and the balance is water. A foaming slurry was prepared.
The obtained foamed slurry was formed on a carrier sheet by a doctor blade method with a blade gap of 0.05 mm, and supplied to a constant temperature / high humidity tank, where the temperature was kept at 35 ° C. and a humidity of 90% for 20 minutes. And then moved in a drying bath at a temperature of 80 ° C. over 20 minutes to produce a sponge-like green sheet.
The green sheet is peeled off from the carrier sheet, placed on an alumina plate, degreased under the condition of holding in the air at a temperature of 450 ° C. for 180 minutes, and subsequently sintered in a hydrogen atmosphere at a temperature of 900 ° C. for 1 hour. Then, by rolling, a Cu foam metal having a porosity of 93%, a thickness of 0.2 mm, and having continuous voids open to the surface and continuous to the internal voids was produced.
The obtained Cu foam metal was cut so as to have a length of 20 mm and a width of 20 mm to prepare a test piece.

Preparation of foamed metal body made of hydrophilic Cu:
The Cu foam metal is immersed in the fine particle titanium oxide-dispersed silica sol-gel solution prepared in Example 1, and heat-treated in the atmosphere at 80 ° C. for 60 minutes to form a surface of the Cu foam metal skeleton. The present invention covers a mixture of fine particle titanium oxide and silica with a thickness of 0.1 μm, and inserts and holds an aggregate composed of a mixture of fine particle titanium oxide and silica inside the pores of the foam metal made of Cu. A hydrophilic Cu foam metal body of the invention (referred to as Example 2) was prepared.

Table 1 shows the porosity (volume%), the aperture ratio (area%), the cross-sectional aperture ratio (area%) in the central portion in the thickness direction, and the mixture ratio of fine particle titanium oxide and silica (measured and calculated for Example 2). = (M _a -m _b ) / m _a × 100).

  FIG. 3 shows a microscopic image (magnification: 250 times) of the open space (opening ratio 77%) on the outermost surface of the Cu foam metal of Example 2.

Preparation of Ni foam metal:
Ni powder with an average particle diameter of 5 μm as a metal powder, an aqueous solution containing 10% methylcellulose as a binder (water-soluble resin binder), ethylene glycol as a plasticizer, sodium alkylbenzenesulfonate as a surfactant, and neopentane as a foaming agent, These are blended so that the raw material powder is 20% by mass, the water-soluble resin binder is 10% by mass, the plasticizer is 1% by mass, the surfactant is 3% by mass, the foaming agent is 1% by mass, and the balance is water. A foaming slurry was prepared.
The obtained foamed slurry was formed on a carrier sheet by a doctor blade method with a blade gap of 0.3 mm, and supplied to a constant temperature / high humidity tank, where the temperature inside the constant temperature / high humidity tank at 35 ° C. and 90% humidity was maintained for 20 minutes. And then moved in a drying bath at a temperature of 80 ° C. over 20 minutes to produce a sponge-like green sheet.
This green sheet is peeled off from the carrier sheet, placed on an alumina plate, degreased in a vacuum sintering furnace under the conditions of atmosphere 5 × 10 ⁻³ Pa, temperature 550 ° C., 180 minutes, and subsequently in a vacuum sintering furnace. Sintered and rolled under conditions of atmosphere 5 × 10 ⁻³ Pa, temperature 1000 ° C., 1 hour holding, having a porosity of 93%, a thickness of 0.2 mm, and opening on the surface Then, a Ni foam metal having continuous voids continuous with the internal voids was produced.
The obtained Ni foam metal was cut so as to have a length of 20 mm and a width of 20 mm to prepare a test piece.

Production of hydrophilic Ni foam metal body:
The Ni foam metal is immersed in the fine particle titanium oxide-dispersed silica sol-gel solution prepared in Example 1 and heat-treated in the atmosphere at 80 ° C. for 60 minutes to form the Ni foam metal skeleton surface. The present invention covers a mixture of fine particle titanium oxide and silica with a thickness of 0.1 μm, and inserts and holds an aggregate made of a mixture of fine particle titanium oxide and silica inside the pores of the Ni foam metal. A hydrophilic Ni foam metal body of the invention (referred to as Example 3) was produced.

Table 1 shows the porosity (volume%), the opening ratio (area%), the cross-sectional opening ratio (area%) at the center in the thickness direction, and the mixture ratio of fine particle titanium oxide and silica (measured and calculated for Example 3). = (M _a -m _b ) / m _a × 100).

For comparison, silica coating is performed on a Ti foam metal by a method described in Patent Document 4 (Japanese Patent Laid-Open No. 2008-195016), and silica-coated porous Ti1 to 3 (Comparative Examples 1 to 3) of a comparative example are applied. Produced).
That is, after a Ti foam metal specimen was prepared in the same manner as in Example 1, the Ti foam metal specimen was diluted with 10-fold ethanol with a silane coupling agent (3-mercaptopropyltrimethoxysilane). (Comparative Example 1) Or immersed in a solution diluted with 50-fold ethanol (Comparative Example 2) or 100-fold ethanol (Comparative Example 3), and kept at 50 ° C. for 10 minutes in an air dryer It dried on the conditions of. Thereafter, this was baked in the atmosphere at a temperature of 400 ° C. for 10 minutes to form a silica coating layer on the surface of the skeleton, thereby producing silica-coated porous Ti of Comparative Examples 1 to 3.

  For reference, a sintered Ti metal foam test piece without silica coating was used as Reference Example 1.

In addition, a Ti metal foam body that was not included in the porosity, aperture ratio, and cross-sectional aperture ratio defined in the present invention was produced as Reference Example 2.
The preparation procedure of the Ti foam metal body of Reference Example 2 is as follows.
First, Ti powder having an average particle diameter of 20 μm as metal powder, methyl cellulose as binder (water-soluble resin binder), ethylene glycol as plasticizer, sodium alkylbenzenesulfonate as surfactant, 20% by mass of raw material powder, water-soluble resin 7 mass% binder, 1 mass% plasticizer, 0.1 mass% surfactant, and the balance: water were blended and stirred for 30 minutes to prepare a foamed slurry.
The obtained foamed slurry was molded on a carrier sheet by a doctor blade method with a blade gap of 0.5 mm, and supplied to a constant temperature / high humidity tank where the temperature was kept at 35 ° C. and a humidity of 90% for 5 minutes. And then moved in a drying tank at a temperature of 110 ° C. over 5 minutes to produce a sponge-like green sheet.
This green sheet is peeled off from the carrier sheet, placed on an alumina plate, degreased in a vacuum sintering furnace under the conditions of atmosphere 5 × 10 ⁻³ Pa, temperature 550 ° C., 180 minutes, and subsequently in a vacuum sintering furnace. Sintered and rolled under the conditions of atmosphere 5 × 10 ⁻³ Pa, temperature 1200 ° C., 1 hour holding, having a porosity of 45%, a thickness of 0.8 mm, and opening on the surface A Ti foam metal having continuous voids continuous with the internal voids was prepared.
The obtained Ti foam metal was cut so as to have a length of 20 mm and a width of 20 mm to prepare a test piece.
This test piece was immersed in the fine particle titanium oxide-dispersed silica sol-gel solution prepared in Example 1 and heat-treated in the atmosphere at 80 ° C. for 60 minutes, and the Ti foam metal skeleton surface and pores inside The Ti foam metal body of Reference Example 2 was produced by performing a coating treatment consisting of a mixture of fine particle titanium oxide and silica.

Table 1 shows the porosity (volume%), the opening ratio (area%), and the cross-sectional opening ratio (area%) at the center in the thickness direction, measured and calculated for Comparative Examples 1 to 3 and Reference Examples 1 and 2, Further, for Comparative Examples 1 to 3, the content ratio of silica is shown, and for Reference Example 2, the mixture ratio of fine particle titanium oxide and silica (= (m _a −m _b ) / m _a × 100) is shown.

Hydrophilic evaluation test:
For Examples 1 to 3, Comparative Examples 1 to 3, and Reference Examples 1 and 2, a hydrophilicity evaluation test was performed under the following conditions in order to evaluate the quality of hydrophilicity under long-term use conditions.
That is, it was immersed in running water at room temperature of 20 mL / min for 1 hour and then dried in air at 150 ° C. for 2 to 12 hours. Using this sample, 0.005 ml of distilled water was dropped with a dropper, and distilled water was used. The presence or absence of hydrophilicity was determined by observing whether or not the water was sucked or remained as a droplet.
This operation was repeated until the liquid droplets remained in the liquid droplets until it was determined that there was no hydrophilicity. Table 1 shows the number of times the hydrophilicity was maintained.

From the results of the hydrophilicity evaluation test shown in Table 1, with respect to Examples 1 to 3 of the present invention, the hydrophilicity retention times are 100 times or more, so that excellent hydrophilicity is provided under long-term use conditions. Is clear.
On the other hand, in Comparative Examples 1 to 3 and Reference Examples 1 and 2, the hydrophilicity retention frequency is 53 or less at most, which is far inferior in hydrophilicity under long-term use conditions as compared with the present invention. I understand that.

  The hydrophilic foam metal body of the present invention maintains excellent hydrophilicity under long-term use conditions, and also has effects such as sustained capillary force, long-term surface contamination prevention, and water coercivity. Therefore, for example, gas diffusion layers for fuel cells, fin materials for heat exchangers such as room air conditioners and car air conditioners, and Baber chamber wick materials for semiconductor chips, etc. that require stable characteristics over a long period of time The application to the field of can be greatly expected.

Claims (3)

The porosity of the entire void of the foam metal is 55 to 99% by volume, and the aperture ratio of the void opening to at least one outermost surface of the foam metal is 5 to 80% by area of the area of the outermost surface. Further, the opening ratio of the void opening to the outermost surface is a hydrophilic foam metal body smaller than the sectional opening ratio of the void in an arbitrary cross section inside the foam metal parallel to the outermost surface,
The skeleton surface of the foam metal is coated with a mixture of fine particle titanium oxide having an average film thickness of 0.01 to 1 μm and silica, and the pores of the foam metal are formed from a mixture of fine particle titanium oxide and silica. A hydrophilic foam metal body, characterized in that an aggregate is formed and held.   2. The hydrophilic foam metal body according to claim 1, wherein an opening ratio of voids opened to the outermost surface of the foam metal parallel to the flow direction of the hydrophilic fluid is 5 to 80 area% of the area of the outermost surface.   The hydrophilic foam metal body according to claim 1 or 2, wherein the skeleton of the foam metal is composed of any one of Ti, Cu, Ni, Al, Ag, and stainless steel.

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