JP2007031738A - Porous titanium body and manufacturing method therefor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a porous titanium body which has high porosity and shows excellent strength, and to provide a manufacturing method therefor. <P>SOLUTION: The method for manufacturing the titanium porous body comprises the steps of: preparing slurry; compacting it; foaming the compact; degreasing the foam; and calcining the degreased foam. In the slurry preparation step, the foaming slurry containing a titanium powder, a foaming agent, a binder of a water-soluble resin, a surface active agent and water is prepared so that a value Tc calculated in the following expression can be 0.5 or less: formula (1). In the foaming step, the foaming slurry is compacted to produce the compact. In the degreasing step, the foaming compact is degreased to produce the foaming degreased body. In the calcination step, the foaming degreased body is calcined to produce the porous titanium body 1. The titanium porous body has many cavities 12 in a structure made from titanium. The porous titanium body 1 contains 0.5 mass% or less carbon (C) by concentration. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a titanium porous body made of titanium and having a large number of pores, and a method for producing the same.

Conventionally, a metal porous body made of a porous metal has been widely used for a weight reduction member, an impact absorbing material, various filters, and the like. As the metal porous body, for the purpose of weight reduction and high functionality, a metal having a finer pore and a high porosity is desired.
In general, the metal porous body can be produced by forming a slurry containing metal powder, a foaming agent, a binder, water, and the like, and sintering the metal powder after foaming. At this time, a metal porous body with fine pores and high porosity can be produced by adjusting the composition of the slurry or adjusting the foaming conditions (see Patent Documents 1 and 2). .

  By the way, the use of the metal porous body has been increasingly widespread in recent years, and for example, it has been applied to a use in a severe corrosive environment such as a current collector of a secondary battery or a biomaterial. In applications where the corrosive environment is particularly severe, a titanium porous body using titanium having excellent corrosion resistance as a metal component is suitable.

However, when a metal porous body (titanium porous body) is manufactured by using the above-described conventional manufacturing method using titanium powder as a metal powder, the resulting titanium porous body tends to be brittle. Therefore, the conventional porous titanium body is easily broken by a slight deformation stress. Further, as described above, a metal porous body having a high porosity is desired, but a titanium porous body tends to become more brittle when the porosity is increased.
Therefore, it has been difficult to produce a porous titanium body having high porosity and excellent strength.

JP-A-9-87704 JP 7-331302 A

  This invention is made | formed in view of this conventional problem, Comprising: It aims at providing the titanium porous body which can exhibit the high intensity | strength with high porosity, and its manufacturing method.

A first invention is a method for producing a porous titanium body having a large number of pores inside a structure made of titanium,
A slurry adjustment step of preparing a foamable slurry by mixing titanium powder, a foaming agent, a water-soluble resin binder, a surfactant, and water;
A molding step of molding the foamable slurry to produce a molded body;
A foaming step of foaming the molded body to produce a foamed molded body;
A degreasing step of degreasing the foamed molded body to produce a foamed degreased body;
Firing the foamed degreased body to produce a titanium porous body,
In the slurry adjusting step, each of n kinds of components A _i (i is a natural number of 1 to n) other than the titanium powder constituting the foamable slurry was heated to a temperature of 500 ° C. at a temperature rising rate of 10 ° C./min. The ratio of the amount of the remaining residue is a _i (mass%), the carbon concentration in the titanium powder is α (mass%), and the ingredients A _i other than the titanium powder in the foamable slurry are mixed. When the amount is b _i (g) and the blending amount of the titanium powder in the foamable slurry is β (g), the value of Tc calculated by the following formula (1) is 0.5 or less. In the method for producing a porous titanium body, the foamable slurry is adjusted as described above.

In the method for producing a porous titanium body of the present invention, the slurry adjustment step, the molding step, the foaming step, the degreasing step, and the firing step are performed. In the present invention, it should be noted that the foamable slurry is adjusted in the slurry adjusting step so that the value of Tc calculated by the above formula (1) is 0.5 or less.
Therefore, in this invention, the carbon concentration in the said titanium porous body obtained after the said baking process can be reduced, and it can suppress that TiC produces | generates in the said titanium porous body. Therefore, the titanium porous body can exhibit excellent strength even when produced with a high porosity.

That is, in the titanium porous body obtained by the above-described conventional manufacturing method, a large amount of TiC is generated in the titanium porous body, and this TiC is a factor for reducing the strength of the titanium porous body. It was.
In the production method of the present invention, the foamable slurry adjusted so that the value of Tc represented by the formula (1) is 0.5 or less is used. And in this foaming slurry, the content rate of the carbon which can form TiC in the said titanium porous body in the said baking process, ie, the carbon which remains as a residue at the time of a heating, is very small. Therefore, after the baking step, carbon can be prevented from remaining in the titanium porous body and the residual carbon and Ti reacting to form TiC. Therefore, even if a high porosity titanium porous body is produced, the titanium porous body can be prevented from becoming brittle. Therefore, a porous titanium body having high porosity and excellent strength can be produced.

  Further, in general, the value of Tc represented by the above formula (1) is determined by heating at a relatively low temperature of 500 ° C. in the slurry adjustment step as compared with a firing step of heating at a high temperature of, for example, 1000 ° C. or higher. can do. Therefore, the determination of Tc in the slurry adjustment step can be performed with energy saving compared to the heating in the actual firing step.

A second invention is a titanium porous body having a large number of pores inside a structure made of titanium,
The titanium porous body is a titanium porous body characterized in that the carbon (C) concentration is 0.5 mass% or less.

The titanium porous body of the second invention has a carbon (C) concentration of 0.5 mass% or less.
That is, the titanium porous body has almost no TiC that causes a decrease in the strength of the titanium porous body.
Therefore, even if the said titanium porous body has high porosity, it can exhibit the outstanding intensity | strength.

Next, a preferred embodiment of the present invention will be described.
In the method for producing a porous titanium body of the present invention, the slurry adjustment step, the molding step, the foaming step, the degreasing step, and the firing step are performed.
In the slurry adjustment step, the foamable slurry is adjusted so that the value of Tc represented by the formula (1) is 0.5 or less.
When the value of Tc exceeds 0.5, a large amount of TiC is generated in the titanium porous body obtained after the firing step, and the strength of the titanium porous body may be reduced.

The above formula (1) will be described.
In the above formula (1), ai (a ₁ , a ₂ , a ₃ ,... A _i (i is a natural number of 1 to n)) is an n-type component other than the titanium powder constituting the foamable slurry. It is the ratio (mass%) of the residual amount produced when A _i (for example, a foaming agent, a water-soluble resin binder, a surfactant, a plasticizer, water, etc.) is heated.
Specifically, a _i is the amount of residue remaining when each component A _i is heated to a temperature of 500 ° C. at a rate of temperature increase of 10 ° C./min using, for example, a differential thermothermal gravimetric simultaneous measurement device (TG / DTA). A value obtained by dividing (g) by the amount of each component (A _i ) used for heating, expressed as a 100-percentage. For example, when 10 mg of the slurry component (A ₁ ) is heated as described above and 1 mg of the residue remains without being decomposed, the amount of the residue (a ₁ ) is 10 mass%.
b _i (g) is a blending amount of each component A _i in the foamable slurry.

In addition, the mathematical expression represented by the following expression (2) in the above expression (1) represents the sum of products of a _i and b _i, and specifically expressed as the following expression (3). Can do.

Further, “i” attached to the lower right of a _i and b _{i in} the above formula (1) is a natural number of 1 to n, and is determined by the type of slurry component. For example, a _i and b _i having the same number i such as a ₁ and b ₁ , a ₂ and b _2, etc., indicate the ratio (a _i ) and the blending amount (b _i ) of the residual amount for the same slurry component. To express. For example, if the proportion of the remaining amount of titanium powder (A ₁ ) is a ₁ among the components constituting the foamable slurry component, the blend amount b ₁ indicates the blend amount of the titanium powder (A ₁ ). Similarly, for example, when the remaining amount of the water-soluble resin binder (A ₂ ) is a ₂ , the blend amount b ₂ is the blend amount of the water-soluble resin binder (A ₂ ).
Further, a ₁ × b ₁ and a ₂ × b ₂ shows the product of the ratio and the amount of residue amounts for the same slurry components.

In the above formula (1), α (mass%) is the carbon concentration in the titanium powder, and β (g) is the blending amount of the titanium powder in the foamable slurry. α × β is the product of the carbon concentration and the blending amount of the titanium powder.
When the titanium powder having a high purity of, for example, a carbon content of 40 ppm or less is used as the titanium powder, the above formula (1) can be handled by setting α × β to 0.

Further, “× 59−0.017” in the above formula (1) indicates a correction value by temperature.
That is, in the slurry adjustment step, Tc is defined using the ratio (a _i ) of the residual amount obtained by heating to a temperature rising rate of 10 ° C./min and a temperature of 500 ° C. In the firing step, In many cases, firing is performed at a higher temperature than 1500 ° C., for example. Therefore, in reality, the residue generated by high-temperature heating becomes a problem. Thus, a large difference is likely to occur between the heating (firing) temperature in the firing step and the heating temperature when measuring the ratio (a _i ) of the remaining amount in the slurry adjusting step. Therefore, in the above formula (1), temperature correction is performed as described above. With this temperature correction, heating conditions (temperature increase rate of 10 ° C.) when measuring the ratio (a _i ) of the residual amount as in the case of firing at a temperature of 1 ° C./min up to 1500 ° C. in the firing step, for example. The above formula (1) can also be applied in the case of performing firing at a temperature history different from (heating to 500 ° C. at / min).

Moreover, when measuring the ratio (a _i ) of the residual amount in the slurry adjustment step, the atmospheric conditions such as the air atmosphere, vacuum atmosphere (oxygen-free atmosphere), and Ar atmosphere are set in the degreasing step and the firing step. The conditions can be the same as the atmospheric conditions, but can also be different.

Next, a specific example of calculating Tc by applying the above formula (1) will be described.
For example, pure titanium powder 28.9 (g) with a carbon concentration of 0.00 (mass%), a water-soluble resin binder 3.8 (g) with a residual quantity of 12.25 (mass%), and a residual quantity Is 7.67 (mass%) water-soluble resin binder 7.0 (g), the residual amount is 0.00 (mass%) plasticizer 2.7 (g), and the residual amount is 39.55 ( mass%) sodium laurylbenzenesulfonate 2.2 (g) is mixed with water to form a slurry, and the foaming slurry prepared by adding 1.1 g of a foaming agent having a residual amount of 0.00 mass% When (1) is applied, Tc can be calculated as in the following equation (4). In this case, Tc = 3.57 (mass%). Further, as in this example, a component such as water, for example, in which the remaining amount is clearly 0 can be excluded from the slurry component A _i applied to the above formula (1).

Further, as described above, the value of Tc is calculated by calculating the ratio (a _i ) and the blending amount (b _i ) of the residual amount for each component other than the titanium powder constituting the foamable slurry. It can be calculated by calculating the sum of (a _i × b _i ) and applying the formula (1), but simply, the ratio of the remaining amount of the foamable slurry other than titanium powder (a _i ) And the amount (b _i ) of the foamable slurry excluding the amount of titanium powder, and can be obtained by applying this to the part of the above formula (2) in the above formula (1).
That is, in this case, the remaining amount (g) other than the titanium powder produced by heating the foamable slurry to a temperature of 500 ° C. at a temperature rising rate of 10 ° C./min is the foamable slurry excluding the amount of the titanium powder. The product of the value represented by 100 percent divided by the amount (g) and the amount of foamable slurry excluding the amount of titanium powder is synonymous with the part of the above formula (2).

  Moreover, in the said slurry adjustment process, as said titanium powder, a thing with an average particle diameter of 0.3-200 micrometers is preferable. Titanium powder having an average particle size of less than 0.3 μm is difficult to obtain, process and manufacture. On the other hand, when the average particle diameter of the titanium powder exceeds 200 μm, it may be difficult to form uniform and fine pores.

  Moreover, as a foaming agent, a volatile organic solvent etc. can be used, for example. Specific examples include hydrocarbon organic solvents having 5 to 8 carbon atoms that are liquid at room temperature, and more specifically selected from, for example, pentane, neopentane, hexane, isohexane, isopentane, benzene, octane, and toluene. 1 or more types can be used. The foaming agent can form micelles by the action of the surfactant in the foamable slurry, and can be vaporized by heating, for example, to form bubbles during foaming.

The water-soluble resin binder can play a role of maintaining the shape of a molded body formed by molding the foamable slurry. It can also serve as a viscosity modifier that adjusts the viscosity of the foamable slurry.
As the water-soluble resin binder, for example, one or more selected from cellulose, methylcellulose, hydroxypropylmethylcellulose, hydroxyethylcellulose, carboxymethylcellulose ammonium, ethylcellulose, polyvinyl alcohol, and the like can be used.

  Moreover, the said surfactant forms the said foaming agent and a micelle in the said foamable slurry, and can stabilize the fine bubble (hole) produced in a foaming process. Examples of the surfactant include an anionic surfactant and a nonionic surfactant. Examples of the anionic surfactant include sodium lauryl benzene sulfonate, alkyl benzene sulfonate, α-olefin sulfonate, alkyl sulfate ester salt, alkyl ether sulfate ester salt, and alkane sulfonate salt. Examples of nonionic surfactants include polyethylene glycol derivatives and polyhydric alcohol derivatives.

  Moreover, in the said slurry adjustment process, content of the said titanium powder in the said foamable slurry is 20 to 80 weight%, content of the said foaming agent is 0.1 to 10 weight%, and the said water-soluble resin binder It is preferable to adjust the foamable slurry so that the content is 1 to 20% by weight, and the content of the surfactant is 0.1 to 10% by weight.

  When content of the said titanium powder in the said foamable slurry is less than 20 weight%, there exists a possibility that the intensity | strength of the said titanium porous body obtained after the said baking process may fall. On the other hand, if it exceeds 80% by weight, it may be difficult to increase the porosity of the titanium porous body. More preferably, the content of the titanium powder is 30% to 70% by weight, and more preferably 50% to 70% by weight.

  Moreover, when the content of the foaming agent is less than 0.1% by weight, it is difficult to sufficiently form pores in the foaming step, and it may be difficult to increase the porosity of the titanium porous body. There is. On the other hand, when it exceeds 10% by weight, the pores of the titanium porous body tend to be large. More preferably, the content of the foaming agent is 0.3 wt% to 5 wt%, and more preferably 0.3 wt% to 2 wt%.

When the content of the water-soluble resin binder is less than 1% by weight, the strength of the molded body, the foamed molded body, and the foamed degreased body after the molding step may be reduced and handling may be difficult. is there. On the other hand, when it exceeds 20% by weight, the viscosity becomes too high, and it may be difficult to form the foamable slurry into a desired shape. More preferably, the content of the water-soluble resin binder is 2 to 15% by weight, and more preferably 2.5 to 10% by weight.
If the surfactant content is less than 0.1% by weight, the formation of micelles of the foaming agent becomes unstable, and it may be difficult to form fine pores with uniform diameters. There is. On the other hand, even if added over 10% by weight, there is no particularly remarkable advantage, and there is a possibility that the cost is wasted. More preferably, the content of the surfactant is 0.3 to 5% by weight, and more preferably 0.5 to 2% by weight.

  Moreover, it is preferable that content of the water in the said foamable slurry is 15 to 60 weight%. When the water content is less than 15% by weight, the viscosity of the foamable slurry becomes too high, and it may be difficult to form the foamable slurry into a desired shape. On the other hand, if it exceeds 60% by weight, the viscosity of the foamable slurry becomes too low, and it may be difficult to form the desired shape in this case as well. More preferably, the water content is 25 to 50% by weight, and more preferably 25 to 40% by weight.

Moreover, in the said slurry adjustment process, it is preferable to mix a plasticizer so that it may become a density | concentration of 0.1 to 10 weight%.
In this case, the moldability of the foamable slurry can be further improved, and handling of the molded body after molding can be facilitated.
When the content of the plasticizer is less than 0.1% by weight, the above-described effects of improving moldability and handleability may not be sufficiently obtained. On the other hand, when it exceeds 10% by weight, the strength of the titanium porous body after the firing may be lowered. More preferably, the content of the plasticizer is 0.3 to 5% by weight.

  Examples of the plasticizer include polyhydric alcohols, fats and oils, ethers, and esters. Examples of the polyhydric alcohol include ethylene glycol, polyethylene glycol, and glycerin. Examples of the oil include sardine oil, rapeseed oil, and olive oil. Examples of the ester include diethyl phthalate, di-N-butyl phthalate, diethyl-hexyl phthalate, di-N-octyl phthalate, sorbitan monooleate, sorbitan trioleate, sorbitan palmitate, and sorbitan stearate.

Next, in the molding step, the foamable slurry is molded to produce a molded body.
The foamable slurry can be formed by, for example, a doctor blade method, extrusion, roll rolling, or the like.

In the foaming step, the molded body is foamed to produce a foamed molded body.
Foaming of the molded body can be performed, for example, by volatilizing the foaming agent. More specifically, it can be carried out, for example, by heating the molded body or putting it in a low pressure state.

Next, in the degreasing step, the foamed degreased body is produced by degreasing the foamed molded body by heating or the like.
By performing this degreasing process, the organic substance contained in the said foaming molding can be removed. As a result, it is possible to obtain a foamed degreased body while maintaining the pore shape.

Moreover, it is preferable to perform the drying process which dries the said foaming molding between the said foaming process and the said degreasing process.
In this case, it is possible to prevent the voids (bubbles) contained in the foamed molded body from being destroyed. Therefore, in this case, the shape and diameter of the pores of the titanium porous body obtained after the firing step can be made more uniform.

  Next, in the firing step, the foamed degreased body is fired to produce a titanium porous body. In the firing step, the titanium porous body can be produced by sintering the titanium powder contained in the foamed degreased body.

In the firing step, the foamed degreased body can be fired at a temperature of 1000 to 1600 ° C. If the temperature is lower than 1000 ° C., the titanium powder may not be sufficiently sintered. On the other hand, firing at a temperature exceeding 1600 ° C. has almost no effect on the improvement of the sinterability of the resulting porous titanium body, and there is a possibility that the manufacturing cost may be increased. Further, if the firing temperature exceeds 1600 ° C., titanium may be melted.
Even when firing in the temperature range of 1000 to 1500 ° C. as described above, TiC is generated in the fired titanium porous body by adjusting the value of Tc in the slurry adjustment step to 0.5 or less. It is possible to produce a titanium porous body with high porosity and excellent strength. More preferably, the firing temperature in the firing step is 1300 to 1500 ° C.

The titanium porous body preferably has a porosity of 60% or more.
In this case, the titanium porous body can be reduced in weight and functionality. Further, in this case, the above-described effect of the present invention that exhibits high strength even at a high porosity can be exhibited more remarkably. When the porosity is less than 60%, the titanium porous body cannot be sufficiently reduced in weight, and the titanium porous body may not fully exhibit the advantages as a porous body. More preferably, the porosity is 70% or more.
The porosity is adjusted, for example, by adjusting the blending of the foamable slurry in the adjusting step, changing the foaming conditions such as temperature and humidity in the foaming step, the heating conditions and the atmospheric conditions in the degreasing step and the firing step, and the like. Can be adjusted.

Next, in the second invention, the titanium porous body has a carbon concentration (carbon atom content) of 0.5 mass%.
When the carbon concentration exceeds 0.5 mass%, the content of TiC increases and the strength of the titanium porous body may be reduced.

Preferably, the carbon (C) concentration of the porous titanium body is 0.3 mass% or less.
In this case, the strength of the titanium porous body can be further improved.

Moreover, it is preferable that the said titanium porous body of the said 2nd invention is manufactured by the manufacturing method as described in any one of Claims 1-3 (Claim 6).
In this case, the titanium porous body having a carbon concentration of 0.5 mass% or less can be easily produced.

Example 1
Next, examples of the present invention will be described.
In this example, a titanium porous body having a large number of pores inside a structure made of titanium is manufactured. In the manufacturing method of this example, a slurry adjustment process, a molding process, a foaming process, a degreasing process, and a firing process are performed.

In the slurry adjustment step, a titanium powder, a foaming agent, a water-soluble resin binder, a surfactant, and water are mixed to produce a foamable slurry. In the slurry adjustment step, each of n kinds of components A _i (i is a natural number of 1 to n) other than titanium powder constituting the foamable slurry was heated to a temperature of 500 ° C. at a temperature rising rate of 10 ° C./min. The ratio of the amount of the remaining residue is a _i (mass%), the carbon concentration in the titanium powder is α (mass%), and the amount of each component A _i other than the titanium powder in the foamable slurry Where b _i (g) and the blending amount of the titanium powder in the foamable slurry are β (g), the value of Tc calculated by the following formula (1) is 0.5 or less. The foamable slurry is adjusted as described above.

In the molding step, the foamable slurry is molded to produce a molded body.
In the foaming step, the molded body is foamed to produce a foamed molded body.
In the degreasing step, the foamed degreased body is produced by degreasing the foamed molded body.
Moreover, in a baking process, the said foaming degreased body is baked and a titanium porous body is produced.

Hereinafter, the manufacturing method of this example will be described in detail.
First, as a titanium powder, a low-oxygen titanium powder having a carbon concentration of 0.00 mass% and an average particle diameter of 20 μm (Titanium, Low, Oxigen, and TILOP) was prepared. Moreover, hexane was prepared as a foaming agent, and methylcellulose and hydroxypropyl methylcellulose (HPMC) were prepared as water-soluble resin binders. Furthermore, as a surfactant, ST221 manufactured by Nippon Oil & Fats Co., Ltd. was prepared, and glycerin was prepared as a plasticizer.

Next, seven types of ingredients, titanium powder (TILOP), hexane, methylcellulose, HPMC, ST221, glycerin, and water are mixed to prepare an effervescent slurry.
In preparing the foamable slurry, first, a certain amount of each component other than the titanium powder was heated to a temperature of 500 ° C. at a rate of temperature increase of 10 ° C./min using a differential thermothermal gravimetric simultaneous measurement device (TG / DTA) The amount of residue to be measured was measured. Next, the obtained residual amount was divided by the amount of the component used for the measurement, and the ratio (a _i ) of the residual amount was calculated by setting it to 100 fraction.
As a result, when the hexane with component A _1, the left amount a ₁ was 0mass%. Similarly, the residual amount a ₂ of methylcellulose (A ₂ ) is 12.25 mass%, the residual amount a ₃ of HPMC (A ₃ ) is 7.67 mass%, and the residual amount a ₄ of ST221 (A ₄ ) is 2.24 mass%. the amount a ₅ residue of glycerine (a ₅₎ is 0Mass%, the amount a ₆ residue of water (a ₆₎ was 0mass%. As described above, the carbon concentration α of the titanium powder is 0.00 mass%.

By applying the residual amount ratio of each component and the carbon concentration of the titanium powder to the above formula (1), titanium powder, hexane, methylcellulose, HPMC, ST221, glycerin, and water are added so that Tc is 0.5 or less. Mix to prepare a foaming slurry. Specifically, 75.3 g (β = 75.3) of titanium powder, 0.6 g (b ₁ = 0.6) of hexane, 1.9 g (b ₂ = 1.9) of methylcellulose, 3 HPMC 0.5 g (b ₃ = 3.5), 1.1 g of ST221 (b ₄ = 1.1), 1.4 g of glycerin (b ₅ = 1.4), and 36.6 g of water (b ₆ = 36) .6) A foamable slurry having a Tc value of 0.392 (mass%) was prepared by mixing.
The formula for calculating Tc of the foamable slurry of this example is shown in the following formula (5), and the composition of the foamable slurry of this example and the value of Tc are shown in Table 1 described later.

Subsequently, the foamable slurry thus obtained was molded into a plate shape by a doctor blade method to produce a molded body. Next, the molded body was foamed under conditions of a temperature of 40 ° C. and a humidity of 90% to produce a foamed molded body, and then dried using a far infrared dryer set at a temperature of 45 ° C.
The foamed molded body after drying was degreased by holding in air at a temperature of 500 ° C. for 30 minutes to obtain a foamed degreased body.
Next, this foamed degreased body was fired to produce a titanium porous body.
Firing was performed under the condition that the temperature was raised to 1500 ° C. at a temperature raising rate of 1 ° C./min and the temperature was held at 1500 ° C. for 2 hours.
Thus, a titanium porous body made of titanium and having a large number of pores was obtained.

In this example, the ratio (a _i ) of the residual amount was measured and applied to the above formula (1) for all of the components constituting the foamable slurry, but the residue was left by heating such as water. Constituent components that are almost never generated can be excluded from the component A _{i for} which the ratio (a _i ) of the residual amount is measured. That is, in the slurry adjusting step, the formula (1) can be applied to the constituent component A _i that can generate a residue by heating among the constituents of the foamable slurry.

(Examples 2-5 and Comparative Examples 1-6)
Next, ten types of foamable slurries with different blendings from the foamable slurry of Example 1 were prepared.
The blending of foamable slurries and Tc values of Examples 2 to 5 are shown in Table 1 below, and the blending of foamable slurries and Tc values of Comparative Examples 1 to 6 are shown in Table 2 below. In addition, a porous titanium body was produced in the same manner as in Example 1 using each foamable slurry.

(Experimental example)
Next, about 11 types of titanium porous bodies produced in Examples 1-5 and Comparative Examples 1-6, C (carbon) density | concentration and porosity were measured, the bending test was done, and the intensity | strength was investigated.

“Measurement of C concentration”
The C concentration (mass%) of the titanium porous body was measured as follows.
That is, first, each titanium porous body is heated and melted in oxygen. Thereby, carbon (C) and oxygen contained in each titanium porous body are reacted to generate gas (CO and CO ₂ ). The amount of gas was quantified by comparing with the blank state by an infrared absorption method to obtain a C concentration (oxygen combustion infrared absorption method).
The results are shown in Tables 1 and 2.

"Porosity"
The porosity (%) of the titanium porous body was measured by the Archimedes method using paraffin.
That is, first, the titanium porous body was cut into a certain size (30 mm × 30 mm × 0.3 mm), and its weight (W ₁ [g]) was measured. After the measurement, the sample was immersed in melted paraffin, the pores were closed, and the weight (W ₂ [g]) was measured again. Next, the weight of the porous titanium body (W ₃ [g]) was measured in water.
Here, assuming that the density of water is ρ ₀ [g / cm ³ ] (in this example, ρ ₀ = 1), the apparent density (ρ [g / cm ³ ]) of the titanium porous body is expressed as ρ = Ρ ₀ · W ₁ / (W ₂ −W ₃ ) The porosity (x [%]) is x = 100 × (1) where the density of titanium (Ti) is ρ ₁ [g / cm ³ ] (in this example, ρ ₁ = 4.5). -Ρ / ρ ₁ ).
The results are shown in Tables 1 and 2.

"Bending test"
The bending test of the titanium porous body was performed as follows.
That is, each titanium porous body produced in each example and comparative example was formed into a plate shape having a thickness of 0.5 mm, a width of 30 mm, and a length of 200 mm, and this was wound around a round bar of φ70 mm. Further, the wound titanium porous body was removed from the round bar, and its shape was returned to the original plate shape. At this time, the presence or absence of cracks or cracks was visually observed. The results are shown in Tables 1 and 2.

  As is known from Table 1 and Table 2, in the porous titanium body prepared using the foamable slurry of Examples 1 to 5 adjusted so that Tc is 0.5 mass% or less, the C concentration is 0.5 mass. % Or less. Therefore, despite having a relatively high porosity of 70% or more, the titanium porous bodies produced in Examples 1 to 5 were free from cracks and cracks in the bending test, and were excellent in strength.

On the other hand, in the titanium porous body manufactured using the foamable slurry of Comparative Examples 1 to 6 adjusted so that Tc exceeded 0.5 mass%, the C concentration exceeded 0.5 mass%. Therefore, the titanium porous body produced in Comparative Examples 1 to 5 was produced under the same conditions as in Examples 1 to 5, and cracks and cracks occurred in the bending test despite having the same porosity. The strength was low.
Moreover, as known from Table 1 and Table 2, in Examples 1 to 5 and Comparative Examples 1 to 6, the value of Tc obtained in the slurry adjustment step is the carbon concentration of the titanium porous body after actual firing. It can be seen that the values are almost the same.

  Next, the cross section of the porous titanium body of Example 4 and the porous titanium body of Comparative Example 4 was observed with an electron microscope. The micrographs are shown in FIGS. FIG. 1 shows a cross section of the titanium porous body of Example 4, and FIG. 2 shows a cross section of the titanium porous body of Comparative Example 4.

As shown in FIGS. 1 and 2, the porous titanium bodies 1 and 2 of Example 4 and Comparative Example 4 both have a large number of pores 12 and 22 inside, and around the pores 12 and 22. Were arranged such that the sintered body of titanium formed the pore walls 11 and 21.
As can be seen from FIG. 1, in the porous titanium body 1 of Example 4, almost no TiC was formed in the pore walls 11.
On the other hand, as can be seen from FIG. 2, in the porous titanium body 2 of Comparative Example 4, TiC was generated in the pore wall 21 made of a sintered titanium body. This TiC is a cause of a decrease in strength of the porous titanium body of Comparative Example 4 (see Table 2). In FIG. 2, in order to clearly show a portion where TiC is generated, the portion is shown surrounded by a dotted line.

  As described above, the value of Tc in the slurry adjustment step and the C concentration of the titanium porous body obtained after the firing step show substantially the same value. By reducing Tc to 0.5 or less, the C concentration becomes 0 A titanium porous body of 5 or less can be obtained. And it turns out that the titanium porous body whose C density | concentration is 0.5 or less can exhibit high intensity | strength even if it is a high porosity.

The photograph substitute figure which shows the cross-sectional structure | tissue of the titanium porous body of Example 4 concerning an experiment example. The photograph substitute figure which shows the cross-sectional structure | tissue of the titanium porous body of the comparative example 4 concerning an experiment example.

Explanation of symbols

1 Titanium porous body 11 Porous wall 12 Porous

Claims (6)

In a method for producing a titanium porous body having a large number of pores inside a structure made of titanium,
A slurry adjustment step of preparing a foamable slurry by mixing titanium powder, a foaming agent, a water-soluble resin binder, a surfactant, and water;
A molding step of molding the foamable slurry to produce a molded body;
A foaming step of foaming the molded body to produce a foamed molded body;
A degreasing step of degreasing the foamed molded body to produce a foamed degreased body;
Firing the foamed degreased body to produce a titanium porous body,
In the slurry adjusting step, each of n kinds of components A _i (i is a natural number of 1 to n) other than the titanium powder constituting the foamable slurry was heated to a temperature of 500 ° C. at a temperature rising rate of 10 ° C./min. The ratio of the amount of the remaining residue is a _i (mass%), the carbon concentration in the titanium powder is α (mass%), and the ingredients A _i other than the titanium powder in the foamable slurry are mixed. When the amount is b _i (g) and the blending amount of the titanium powder in the foamable slurry is β (g), the value of Tc calculated by the following formula (1) is 0.5 or less. A method for producing a porous titanium body, wherein the foamable slurry is adjusted so as to be.
  In Claim 1, In the said slurry adjustment process, content of the said titanium powder in the said foamable slurry is 20 to 80 weight%, Content of the said foaming agent is 0.1 to 10 weight%, The said water-soluble resin A method for producing a porous titanium body, comprising adjusting the foamable slurry so that the content of the binder is 1 to 20% by weight and the content of the surfactant is 0.1 to 10% by weight. .   3. The method for producing a porous titanium body according to claim 1, wherein in the slurry adjustment step, a plasticizer is mixed so as to have a concentration of 0.1 to 10 wt%. A titanium porous body having a large number of pores inside a structure made of titanium,
The titanium porous body has a carbon (C) concentration of 0.5 mass% or less.   The titanium porous body according to claim 4, wherein the titanium porous body has a carbon (C) concentration of 0.3 mass% or less.   The titanium porous body according to claim 4 or 5, wherein the titanium porous body is manufactured by the manufacturing method according to any one of claims 1 to 3.