JP5402381B2 - Method for producing porous aluminum sintered body - Google Patents

Description

The present invention particularly relates to a method for producing an aluminum porous sintered body suitable for a current collector of a lithium ion secondary battery or an electric double layer capacitor.

  At present, an aluminum foil is generally used as a positive electrode current collector of a lithium ion battery or an electric double layer type capacitor. And in recent years, these batteries and capacitors have come to be used for electric vehicles, etc., and with such expansion of applications, higher output and higher energy density of electrode current collectors in batteries and capacitors are required, As shown in Patent Documents 1 and 2, an aluminum porous body having open pores having a three-dimensional network structure is becoming known as an electrode current collector.

  As a method for producing such an aluminum porous body, for example, as disclosed in Patent Document 3, after adding a thickener to molten aluminum to increase the viscosity, titanium hydride as a foaming agent is added. Thus, there is known a foaming and melting method in which molten aluminum is foamed and solidified using hydrogen gas generated by a thermal decomposition reaction of titanium hydride. However, the foamed aluminum obtained by this method had large closed pores of several mm.

  In addition, as a second method, there is a method of obtaining foamed aluminum having a sponge skeleton by press-fitting aluminum into a mold having sponge urethane as a core and filling aluminum into a cavity formed by burning out urethane. According to this method, a foamed aluminum having a pore size of 40 PPI or less, that is, a pore size of 40 cells or less per inch (a pore size of about 600 μm or more) is obtained.

  Furthermore, as disclosed in Patent Document 4, as a third method, aluminum alloy is pressed and infiltrated into a reinforcing material made of hollow ceramics to have closed pores having a pore diameter of 500 μm or less according to the size of the reinforcing material. There is also a method for obtaining foamed aluminum.

Further, as disclosed in Patent Document 5, as a fourth method, aluminum is foamed by decomposition of TiH ₂ powder by heating and rolling a mixed powder of AlSi alloy powder and TiH ₂ powder between aluminum plates. However, the foamed aluminum obtained by this method has a large pore diameter of several mm.

  Furthermore, as disclosed in Patent Document 6, as a fifth method, a metal whose eutectic temperature with aluminum is lower than the melting point of aluminum is mixed with aluminum, and is higher than the eutectic temperature and higher than the melting point of aluminum. Although there is a method of heating and firing at a low temperature, the foamed aluminum obtained by this method has a porosity as small as about 40% even if the pore diameter can be reduced. For this reason, the amount of the positive electrode active material and the negative electrode active material penetrating into the pores of the foamed aluminum as the current collector is small, and the desired high output and high energy density cannot be achieved.

  Therefore, among the above-mentioned foaming and melting methods and the second to fifth methods, sponge urethane is used as a method for producing foamed aluminum having fine open pores that can achieve the purpose of high output and high energy density. A second method of press-fitting aluminum into the core mold can be employed.

  However, even in this second method, in order to further reduce the pore diameter of the open pores, it is necessary to use fine sponge urethane, and the flow of aluminum becomes worse, making it impossible to press-fit or casting. Since the pressure becomes too high, it is difficult to produce foamed aluminum having a pore diameter smaller than 40 PPI.

  On the other hand, as a method for producing a foam metal having a high porosity having a small pore size / size open pores in which a large number of minute open pores are evenly arranged, as shown in Patent Document 7, There is a slurry foaming method in which a foamable slurry containing a foaming agent is foamed, dried and then sintered. According to this method, if a raw material powder that can be sintered is available, it is a high-porosity foam metal having dimensionally open pores having an arbitrary pore size ranging from about 10 PPI to about 500 PPI, that is, a pore size ranging from 2.5 mm to 50 μm. Can be easily manufactured. In the slurry foaming method, as described above, foaming is performed by containing a foaming agent, or foaming is performed by injecting gas or stirring to sinter the foamable slurry as described above in the foamed state. Means a method of obtaining foam metal.

However, conventionally, it has been difficult to produce foamed aluminum by the slurry foaming method.
The reason for this will be described. In this slurry foaming method, the metal powder is sintered by free sintering that is sintered without applying stress such as compression, to obtain a foam metal. However, the aluminum powder has a surface covered with a dense aluminum oxide film having a thickness of several nanometers to several tens of nanometers, which inhibits sintering regardless of a solid phase or a liquid phase. For this reason, it is difficult to sinter with free sintering, and therefore homogeneous foamed aluminum cannot be obtained by the slurry foaming method.

Japanese Patent No. 3591055 JP 2009-43536 A Japanese Patent Application Laid-Open No. 08-209265 JP 2007-238971 A Special table 2003-520292 gazette Japanese Examined Patent Publication No. 61-48566 Japanese Patent No. 3535282

  Therefore, as a method of free sintering this aluminum powder, a method in which the slurry foaming method is combined with the above-mentioned fifth method is adopted, and copper powder which is a metal whose eutectic temperature with aluminum is lower than the melting point of aluminum is used. Even when foamed aluminum is mixed with foam and mixed with aluminum and heated and fired at a temperature higher than the eutectic temperature and lower than the melting point of aluminum, aluminum droplets ooze out on the surface and solidified. A hemispherical aluminum lump is formed. In particular, when the foamed aluminum is in the form of a thin plate, as shown in FIG. 4, formation of aluminum lumps was remarkable, and the desired homogeneous foamed aluminum could not be produced.

The present invention has been made in view of such circumstances, and aluminum porous sintering capable of obtaining a high porosity homogeneous foamed aluminum having fine and sized open pores having a pore diameter of 40 PPI or more, that is, 600 μm or less. It is an object to provide a method for manufacturing a body .

  When the sintering powder containing titanium is mixed with aluminum powder and heated and fired at a temperature within a predetermined range, the inventors of the present invention sintered without forming a lump of droplets even in free sintering. The present inventors have found that there are conditions that can be achieved, and have completed the present invention described in claim 1.

  That is, the invention described in claim 1 is a mixture of aluminum powder and a sintering aid powder containing titanium to form an aluminum mixed raw material powder. The aluminum mixed raw material powder is mixed with a water-soluble resin binder, water, A plasticizer composed of at least one of a monohydric alcohol, an ether and an ester is mixed to obtain a viscous composition, and the viscous composition is dried in a state where air bubbles are mixed to obtain the above-mentioned sintered compact, The temperature of Tm-10 (° C.) ≦ T ≦ 685 (° C.), where Tm (° C.) is the temperature at which the aluminum mixed raw material powder starts melting in a non-oxidizing atmosphere. It is characterized by heating at T (° C.) and firing.

  Here, the non-oxidizing atmosphere means an atmosphere that does not oxidize the aluminum mixed raw material powder, including an inert atmosphere or a reducing atmosphere. In addition, the above-described heating and firing temperature is not the temperature of the aluminum mixed raw material powder, that is, does not measure the reaction temperature of the aluminum mixed raw material powder, but means the holding temperature around the aluminum mixed raw material powder. .

  The method according to claim 1 discloses a method of free-sintering a novel aluminum powder, and the sintered body obtained thereby has a substantially uniform distribution of aluminum and titanium compounds, linear A porous sintered body having two or more holes per 100 μm length is obtained.

  In addition, the sintering method according to claim 1 is combined with a known slurry foaming method to produce a high porosity homogeneous foamed aluminum porous ceramic having fine and sized open pores smaller than a pore diameter of 600 μm. This has led to the completion of the invention of the method for producing a knot.

  That is, in the invention described in claim 1, the aluminum mixed raw material powder is mixed with a water-soluble resin binder, water, and a plasticizer made of at least one of polyhydric alcohol, ether and ester. The viscous composition is dried in a state where the bubbles are mixed with the viscous composition to form the pre-sintered compact, and then the pre-sintered compact is heated and fired.

  The said structure is the said aluminum mixed raw material powder being shape | molded by the known slurry foaming method, and making it a foaming molding before sintering, and sintering this and manufacturing an aluminum porous sintered compact, A porous body having two different types of pores, that is, pores surrounded by the formed sponge skeleton and pores formed in the sponge skeleton itself can be obtained.

  The invention according to claim 2 is characterized in that, in the method for producing a porous aluminum sintered body according to claim 1, the average particle diameter of the aluminum powder is 2 to 200 μm.

  The invention according to claim 3 is the method for producing an aluminum porous sintered body according to claim 1 or 2, wherein the average particle diameter of the sintering aid powder is r (μm) and the sintering aid is used. 1 (μm) ≦ r ≦ 30 (μm), 1 ≦ W ≦ 20 (mass%), and 0.1 ≦ W / r ≦ 2 when the blending ratio of the agent powder is W mass% It is characterized by that.

  Invention of Claim 4 is a manufacturing method of the aluminum porous sintered compact as described in any one of Claim 1 thru | or 3. WHEREIN: The said sintering auxiliary agent powder is titanium and / or titanium hydride. It is characterized by.

  Invention of Claim 5 is a manufacturing method of the aluminum porous sintered compact as described in any one of Claim 1 thru | or 4. WHEREIN: The water-insoluble hydrocarbon type | system | group of C5-C8 is added to the said viscous composition. It is characterized by adding an organic solvent.

  The invention according to claim 6 is the method for producing an aluminum porous sintered body according to any one of claims 1 to 5, wherein the water-soluble resin binder is about 0. 0 of the mass of the aluminum mixed raw material powder. It is characterized by being contained within a range of 5% to 7%.

  The invention according to claim 7 is the method for producing a porous aluminum sintered body according to any one of claims 1 to 6, wherein the aluminum mixed raw material powder has a mass of 0 of the aluminum mixed raw material powder. It is characterized by adding a surfactant in the range of 0.02 to 3%.

  The invention according to claim 8 is the method for producing a porous aluminum sintered body according to any one of claims 1 to 7, wherein the viscous composition is stretched to a thickness of 0.05 mm to 5 mm. Then, by drying, the pre-sintered compact is formed into a plate-shaped compact.

  According to the method for producing an aluminum porous sintered body according to claim 1, an aluminum mixed raw material powder obtained by mixing aluminum powder with a sintering aid powder containing titanium is Tm−10 (° C.) ≦ T ≦ 685 (° C. ) To obtain an aluminum porous sintered body having two or more openings per linear length of 100 μm.

  Here, the reason for limiting the heating and firing temperature to Tm-10 (° C) or higher is that the temperature at which the aluminum powder contained in the aluminum mixed raw material powder and the sintering aid powder containing titanium start the reaction is Tm-10 (° C). That's why. The melting point of aluminum is described as Tm because pure aluminum has a melting point of 660 ° C., but industrially used aluminum contains iron and silicon as impurities, so the melting point is lower than 660 ° C. . On the other hand, the reason for limiting the heating and firing temperature to 685 ° C. or less is that when heated and held at a temperature higher than that temperature, a liquid-like lump of aluminum is generated in the sintered body.

  At that time, the aluminum mixed raw material powder is mixed with a water-soluble resin binder, water and a plasticizer to form a viscous composition, and dried in a state in which bubbles are mixed in the viscous composition to form a pre-sintered compact. Then, when this pre-sintered compact is heated and fired in the above temperature range, the pre-sintered compact is a sponge skeleton structure (three-dimensional skeleton structure, foamed skeleton structure having open pores), and thus the obtained sintered body is obtained. The bonded body becomes an aluminum porous body having two different types of pores, a pore surrounded by the sponge skeleton and a pore formed in the sponge skeleton itself.

  In addition, the aluminum powder is viscous to such an extent that the viscous composition can be molded into a desired shape, and a molded body before sintering dried in a state where air bubbles are mixed with the viscous composition has a desired handling. It is prepared to have strength. That is, when the average particle size is reduced, the mass of the water-soluble resin binder needs to be increased by increasing the mass of the water-soluble resin binder relative to the mass of the aluminum powder. When the pre-sintered shaped body is heated and fired, the amount of carbon remaining in the aluminum increases and the sintering reaction is hindered. On the other hand, when the particle diameter of the aluminum powder is too large, the strength of the porous sintered body is lowered.

  Accordingly, as in the method for producing a porous aluminum sintered body according to claim 2, the sintering reaction is preferably inhibited by increasing the mass of the water-soluble resin binder preferably by setting the average particle diameter of the aluminum powder to 2 μm or more. And the strength of the porous sintered body is ensured to 200 μm or less. More preferably, the average particle diameter of the aluminum powder is 7 μm to 40 μm.

  Furthermore, the sintering aid powder has an average particle diameter r and a blending ratio W mass% of 1 (μm) ≦ r ≦ 30 (μm, as in the method for producing an aluminum porous sintered body according to claim 3. ), 0.1 (mass%) ≦ W ≦ 20 (mass%), and 0.1 ≦ W / r ≦ 2.

  This is because when the mixing ratio W of the sintering aid powder exceeds 20% by mass, the sintering aid powder has contact points in the aluminum mixed raw material powder, and the reaction heat of aluminum and titanium cannot be controlled. At the same time, a desired porous sintered body cannot be obtained, so 0.1 (mass%) ≦ W ≦ 20 (mass%).

  Further, even within the range of 0.1 (mass%) ≦ W ≦ 20 (mass%), the reaction heat of aluminum and titanium may become too large depending on the particle size of the sintering aid powder, In some cases, the temperature of the aluminum melted by heat is further increased, the viscosity is lowered, and droplets are generated.

  Therefore, from the results of observing specimens prepared under various conditions with an electron microscope, the surface layer with a substantially constant thickness from the exposed surface side of the titanium particles within a range in which the calorific value can be controlled by the blending amount and particle size of titanium. It was found that only the part reacted with aluminum. Thus, it was experimentally derived that it is desirable that 1 (μm) ≦ r ≦ 30 (μm) and 0.1 ≦ W / r ≦ 2 in order to prevent the generation of droplets.

The meaning of 0.1 ≦ W / r ≦ 2 will be described below when titanium is used as the sintering aid powder. The average particle diameter of titanium is r, the number of titanium particles is N, and the titanium Assuming that the added mass is w, the specific gravity of titanium is D, and the amount of decrease in the titanium particle size due to the reaction with aluminum is d, the amount of heat of reaction Q is proportional to the volume of the reacted titanium, so Q∝4πr ² dN. Furthermore, since the addition amount of the titanium particles is calculated by the product of the average volume of one titanium particle and the number of titanium particles, w = 4 / 3πr ³ DN. Therefore, when the latter equation is substituted into the former equation, Q∝3wd / rD is obtained. Here, Q∝w / r from the observation result that 3 / D is a constant and d is substantially constant regardless of the sintering conditions. Therefore, by experimentally determining the range of W / r in which no droplets are generated and limiting it as described above, the generation of droplets due to excessive reaction heat between aluminum and titanium is prevented.

  In addition, titanium hydride as a sintering aid powder has a titanium content of 95% by mass or more and is dehydrogenated at 470 to 530 ° C. to become titanium. And titanium. For this reason, like the invention of Claim 4, reaction efficiency with aluminum powder can be improved by using titanium and / or titanium hydride as sintering auxiliary agent powder.

  Further, as in the invention described in claim 5, the viscous composition can be foamed by adding a water-insoluble hydrocarbon organic solvent having 5 to 8 carbon atoms to mix bubbles.

  Further, when the water-soluble binder is contained in excess of 7% of the mass of the aluminum mixed raw material powder, the amount of carbon remaining in the pre-sintered molded body during heating and firing is increased, and the sintering reaction is caused. Be inhibited. On the other hand, if it is less than 0.5%, the handling strength of the green body before sintering cannot be ensured. For this reason, it is preferable to be contained within the range of 0.5% to 7% of the mass of the aluminum mixed raw material powder as in the invention described in claim 6.

  In addition to this, by adding a surfactant to the aluminum mixed raw material powder as in the invention described in claim 7, it is possible to effectively generate bubbles, and the amount of the surfactant added is mixed with aluminum. By making it 0.02% or more of the mass of the raw material powder, the effect due to the addition of the above-mentioned surfactant can be obtained, and by making it 3% or less, the amount of carbon remaining in the pre-sintered molded body increases. This can prevent the sintering reaction from being hindered.

  Further, as in the invention described in claim 8, by forming the viscous composition to a thickness of 0.05 mm to 5 mm and making the pre-sintered molded body into a plate-shaped molded body, By sintering the body, an aluminum porous sintered body suitable as a current collector for a lithium ion secondary battery or an electric double layer capacitor can be obtained.

2 is a SEM photograph of foamed aluminum of Example 1. It is a partially expanded SEM photograph figure of FIG. 2 is an SEM photograph of foamed aluminum of Comparative Example 1. It is the photograph of the foamed aluminum obtained by the method which combined the slurry foaming method with the 5th method in the prior art as a method of free sintering aluminum powder.

Hereinafter, an embodiment of a method for producing an aluminum porous sintered body according to the present invention will be described.
The method for producing an aluminum porous sintered body of the present embodiment includes an aluminum mixed raw material powder preparation step in which aluminum and titanium hydride are mixed with aluminum powder to obtain an aluminum mixed raw material powder, and the aluminum mixed raw material powder is water-soluble. A viscous composition preparation step of preparing a viscous composition by mixing a water-soluble resin binder, water and a plasticizer, and drying in a state where bubbles are mixed in the viscous composition to obtain a pre-sintered molded body. A pre-sintering step, and a sintering step in which the pre-sintered compact is heated and fired in a non-oxidizing atmosphere at Tm-10 (° C.) ≦ heating and firing temperature T ≦ 685 (° C.). Tm (° C.) is a temperature at which the aluminum mixed raw material powder starts to melt.

  In this aluminum mixed raw material powder preparation step, aluminum powder having an average particle size of 2 to 200 μm is used. This is because when the average particle size becomes small, a large amount of a water-soluble resin binder is added to the aluminum powder so that the viscous composition is viscous enough to be molded into a desired shape, and before sintering. It is necessary for the body to have handling strength. However, when a large amount of the water-soluble resin binder is added, the amount of carbon remaining in the aluminum is increased when the pre-sintered molded body is heated and fired, thereby inhibiting the sintering reaction. On the other hand, when the particle diameter of the aluminum powder is too large, the strength of the foamed aluminum is lowered. Therefore, as the aluminum powder, those having an average particle diameter in the range of 2 to 200 μm, more preferably in the range of 7 to 40 μm are used as described above.

Further, titanium and / or titanium hydride are mixed with the aluminum powder. In this method, titanium is mixed with aluminum powder, and the pre-sintered compact is heated and fired at Tm-10 (° C.) ≦ heating and firing temperature T ≦ 685 (° C.), thereby generating droplets. This is because free sintering of aluminum without any metal becomes possible. Further, titanium hydride (TiH ₂ ) has a titanium content of 47.88 (molecular weight of titanium) / (47.88 + 1 (molecular weight of hydrogen) × 2) and is 95% by mass or more, and 470 to 530. Since it is dehydrogenated at titanium and becomes titanium, it is thermally decomposed by the above-mentioned heating and baking to become titanium. Accordingly, free sintering of aluminum is possible without generating droplet lumps even when titanium hydride is mixed.

  At that time, when the average particle diameter of titanium or titanium hydride is r (μm), the mixing ratio when the mixing ratio of titanium or titanium hydride is W mass% is 1 (μm). ≦ r ≦ 30 (μm), 0.1 (mass%) ≦ W ≦ 20 (mass%), and 0.1 ≦ W / r ≦ 2. That is, in the case of titanium hydride powder having an average particle diameter of 4 μm, the compounding ratio W is 0.4 ≦ 8% by mass because 0.1 ≦ W / 4 ≦ 2, and the titanium powder having an average particle diameter of 20 μm In this case, the compounding ratio W is 2 to 40% by mass because 0.1 ≦ W / 20 ≦ 2, but 2 to 20% by mass from 0.1 (% by mass) ≦ W ≦ 20 (% by mass). %.

  The average particle diameter of titanium hydride is 0.1 (μm) ≦ r ≦ 30 (μm), more preferably 4 (μm) ≦ r ≦ 20 (μm). If it is 1 μm or less, there is a risk of spontaneous ignition. On the other hand, if it exceeds 30 μm, the titanium hydride becomes titanium particles coated with a compound of aluminum and titanium after sintering. This is because the compound phase of aluminum and titanium is easily peeled off from the titanium particles, and desired strength is obtained in the sintered body.

  Further, 0.1 (mass%) ≦ W ≦ 20 (mass%) is set when the sintering aid powder is mixed in the aluminum mixed raw material powder when the blending ratio W of the sintering assistant powder exceeds 20 mass%. This makes it possible to have a contact, so that the reaction heat between aluminum and titanium cannot be controlled, and a desired porous sintered body cannot be obtained.

  Further, even within the range of 0.1 (mass%) ≦ W ≦ 20 (mass%), the reaction heat of aluminum and titanium may become too large depending on the particle size of the sintering aid powder, In some cases, the temperature of the aluminum melted by heat is further increased, the viscosity is lowered, and droplets are generated.

  Therefore, from the results of observing specimens prepared under various conditions with an electron microscope, the surface layer with a substantially constant thickness from the exposed surface side of the titanium particles within a range in which the calorific value can be controlled by the blending amount and particle size of titanium. It was found that only the part reacted with aluminum. Thus, it was experimentally derived that it is desirable that 1 (μm) ≦ r ≦ 30 (μm) and 0.1 ≦ W / r ≦ 2 in order to prevent the generation of droplets.

Regarding the meaning of 0.1 ≦ W / r ≦ 2, the case where titanium is used for the sintering aid powder will be described. The average particle diameter of titanium is r, the number of titanium particles is N, and the added mass of titanium is Assuming that w, the specific gravity of titanium is D, and the amount of decrease in the titanium particle size due to the reaction with aluminum is d, the amount of reaction heat Q is proportional to the volume of the reacted titanium, so that Q∝4πr ² dN. Furthermore, since the addition amount of the titanium particles is calculated by the product of the average volume of one titanium particle and the number of titanium particles, w = 4 / 3πr ³ DN. Therefore, when the latter equation is substituted into the former equation, Q∝3wd / rD is obtained. Here, Q∝w / r from the observation result that 3 / D is a constant and d is substantially constant regardless of the sintering conditions. Therefore, by experimentally determining the range of W / r in which no droplets are generated and limiting it as described above, the generation of droplets due to excessive reaction heat between aluminum and titanium is prevented.

  Next, in the viscous composition preparation step, at least one of polyvinyl alcohol, methylcellulose and ethylcellulose is used as the water-soluble resin binder, and polyethylene glycol, glycerin and di-N-phthalate are used as the plasticizer. While adding at least one of butyl, distilled water and alkylbetaine as a surfactant are added.

  Thus, by using polyvinyl alcohol, methyl cellulose, or ethyl cellulose as the water-soluble resin binder, a relatively small amount is sufficient. For this reason, the addition amount is set within the range of 0.5% to 7% of the mass of the aluminum mixed raw material powder. If the content of the aluminum mixed raw material powder exceeds 7%, the amount of carbon remaining in the pre-sintered molded body during heating and firing is increased, and the sintering reaction is inhibited. It is because the handling intensity | strength of the molded object before sintering is not ensured that it is less than.

  In addition, 0.02% to 3% of the mass of the aluminum mixed raw material powder is added to the alkylbetaine. This is because by making 0.02% or more of the mass of the aluminum mixed raw material powder, bubbles are effectively generated when mixing the water-insoluble hydrocarbon organic solvent described later, and by making it 3% or less. Inhibition of the sintering reaction due to an increase in the amount of carbon remaining in the pre-sintered compact or the like is prevented.

  And after kneading these, it is made to foam by mixing a C5-C8 water-insoluble hydrocarbon-type organic solvent, and the viscous composition with which the bubble was mixed is adjusted. As this water-insoluble hydrocarbon organic solvent having 5 to 8 carbon atoms, at least one of pentane, hexane, heptane and octane can be used.

  Next, in the pre-sintering process, the viscous composition is stretched to a thickness of 0.05 mm to 5 mm on the surface of the strip-shaped polyethylene sheet, and the ambient temperature and humidity are controlled for a certain period of time. After air bubbles are sized, they are dried at a temperature of 70 degrees with an air dryer. At that time, the viscous composition is applied by a doctor blade method, a slurry extrusion method, a screen printing method, or the like.

  And the viscous composition after drying is peeled off from a polyethylene sheet, and if necessary, it cuts out into predetermined shapes, such as a circle with a diameter of 100 mm, and the molded object before sintering is obtained.

  Next, in the sintering step, the above-mentioned pre-sintered compact is placed on an alumina setter on which zirconia powder is spread, and heated and held at 520 ° C. for 1 hour in an argon atmosphere with a dew point of −20 ° C. or lower. Pre-baking is performed. This removes the binder solution of the water-soluble resin binder component, plasticizer component, distilled water and alkylbetaine of the pre-sintered molded body, and when titanium hydride is used as the sintering aid powder. Is dehydrogenated.

Thereafter, the pre-sintered molded body after the preliminary firing is heated and fired at Tm-10 (° C.) ≦ heating and firing temperature T ≦ 685 (° C.) to obtain foamed aluminum.
Although it is considered that the reaction between aluminum and titanium starts by heating the pre-sintered compact to the melting temperature Tm (° C.), it is actually a eutectic such as Fe or Si as an impurity in aluminum. This is because the alloy element is contained in a very small amount and the melting point is lowered, so that it is considered that the reaction between aluminum and titanium starts by heating to Tm-10 (° C.) to form foamed aluminum. Actually, while the melting point of aluminum is 660 ° C., the melting start temperature is around 650 ° C. for atomized powder having a purity of about 98% to 99.7% distributed as pure aluminum powder.

  On the other hand, the peritectic temperature of aluminum and titanium is 665 ° C., and further, when the latent heat of fusion is input, the sintered body of aluminum melts, so it is necessary to keep the furnace atmosphere temperature at 685 ° C. or lower.

  In addition, in order to suppress the growth of the oxide film of the aluminum particle surface and the titanium particle surface, it is necessary to perform the heat baking in the sintering process in a non-oxidizing atmosphere. However, if the heating temperature is kept at 400 ° C. or lower for about 30 minutes, the oxide film on the aluminum particle surface and the titanium particle surface does not grow so much even if heated in air. After debinding by heating and holding at 300 ° C. to 400 ° C. for about 10 minutes in air, it may be fired at a predetermined temperature in an argon atmosphere.

  The foamed aluminum thus obtained has a metal skeleton having a three-dimensional network structure made of a porous metal sintered body, and has pores between the metal skeletons. Further, the Al—Ti compound is dispersed in the perforated metal sintered body, 20 or more pores are formed per 1 cm of the linear length, and the total porosity is 70 to 90%. It is suitably used as a current collector for secondary batteries and electric double layer type capacitors.

  The present invention is not limited to the above-described embodiment. For example, a sintering aid powder other than titanium or titanium hydride may be used, and sintering including titanium as a sintering aid element. An auxiliary powder may be used.

  According to the method for producing foamed aluminum of this embodiment, an aluminum mixed raw material powder in which titanium and / or titanium hydride is mixed with aluminum powder as a sintering aid powder in the aluminum mixed raw material powder preparation step is prepared as a viscous composition. By foaming in the process and heating and firing at Tm-10 (° C.) ≦ T ≦ 685 (° C.) in the sintering process, the pores with a pore diameter of less than 600 μm surrounded by the sponge skeleton and the sponge skeleton itself A high-porosity and homogeneous foamed aluminum having pores with two different forms of two or more micropores per 100 μm of linear length to be formed can be obtained. At that time, the titanium hydride has a titanium content of 95% by mass or more and is dehydrogenated at 470 to 530 ° C. to be titanium, so that it is thermally decomposed by the above-mentioned heating and baking to become titanium. Therefore, it is considered that titanium hydride contributes to the production of foamed aluminum by the above-described heating and firing, as is the case with titanium.

  Further, between the viscous composition preparation step and the sintering step, the viscous composition is stretched and applied to a thickness of 0.05 mm to 5 mm on the stripping surface of the strip-shaped polyethylene sheet. By having a pre-sintering process to form a pre-sintered shaped body, and obtaining a post-sintering process, depending on the application such as a current collector of a lithium ion secondary battery or an electric double layer capacitor Foamed aluminum can be obtained.

(Examples 1 to 16)
Next, an Al powder having an average particle size of 2.1 μm, 9.4 μm, 24 μm, 87 μm and 175 μm, a Ti powder having an average particle size of 9.8 μm, 24 μm and 42 μm, an average particle size of 4.2 μm, 9.1 μm and A 21 μm TiH ₂ powder is prepared. Then, according to the above embodiment, the raw aluminum mixed powder 10 obtained by mixing Ti powder and / or TiH ₂ powder to Al powder at a ratio shown in Table 1 were prepared, a binder solution 1 the formulation composition shown in Table 2 To 5 were prepared, and these and the water-insoluble hydrocarbon-based organic solvent were kneaded in the proportions shown in Table 3 to produce viscous compositions of Examples 1 to 16.

  Next, the viscous compositions of Examples 1 to 16 were stretched and applied to a polyethylene sheet coated with a release agent by the doctor blade method, and the temperature and humidity were controlled to be maintained for a certain period of time to regulate bubbles. After sizing, it is dried at a temperature of 70 ° C. in an air dryer. Table 3 shows the application thickness of the viscous composition and the temperature, humidity and holding time. And the viscous composition after drying is peeled off from a polyethylene sheet, it cuts out into a circle with a diameter of 100 mm, and the molded object before sintering of Examples 1-16 is obtained.

  Then, the pre-sintered compacts of Examples 1 to 16 were placed on an alumina setter on which zirconia powder was spread, and after debinding in an argon airflow atmosphere or in the air, heating and firing were performed. Thus, foamed aluminum is obtained. Table 3 also shows the heating and baking temperature and the heating and holding time at that time.

  Next, the shrinkage | contraction rate and porosity of the foamed aluminum of Examples 1-16 obtained by this were computed. In addition, the number of three-dimensional vacancies and the number of skeletal holes from a scanning electron microscope (SEM) photograph are measured from a stereomicrograph, and the presence or absence of droplet solidification is confirmed by the SEM photograph. The presence or absence of an Al-Ti compound was confirmed on the surface of the skeleton of the foamed aluminum by surface analysis using a microanalyzer (EPMA). The results are shown in Table 5, and a SEM photograph of the foamed aluminum of Example 1 is shown in FIG. 1, and a partially enlarged photograph thereof is shown in FIG.

  Next, each of the foamed aluminums of Examples 1 to 16 was subjected to a roll rolling test at a rolling reduction of 20%, and after confirming the presence or absence of cracks, was cut out into a rectangular shape of 20 mm × 50 mm and between the opposing corners. The electrical resistance of was measured. Next, these rectangular aluminum foams were respectively wound around the outer periphery of a cylindrical body having a diameter of 5 mm, and the presence or absence of cracks was visually confirmed. The results are shown in Table 5.

(Comparative Examples 1-9)
Next, the comparative aluminum mixed raw material powders 1 to 5 prepared by preparing the same Al powder, Ti powder and TiH ₂ powder as in the examples were used together with the aluminum mixed raw material powders 1 to 9, and the binder solution 1 shown in Table 2 The foamed aluminum of Comparative Examples 1 to 9 was produced in the same manner as in the Examples except that the water-insoluble hydrocarbon-based organic solvent was kneaded at a ratio shown in Table 4 according to -5. And while evaluating the foamed aluminum of Comparative Examples 1-9 by the method similar to an Example and showing in Table 5, the SEM photograph of the foamed aluminum of Comparative Example 1 was shown in FIG.

  As can be seen from Table 5, the foamed aluminum of Examples 1 to 16 has 2 to 4 holes per 100 μm of the skeleton length of the porous metal sintered body, and 1 three-dimensional void between the metal skeletons. There are 52 or more per inch, that is, 20 or more per 1 cm. Further, no droplet-like lump was formed in the foamed aluminum, the electric resistance was low, and there was no cracking due to the winding test. Therefore, it is suitable for a positive current collector of a battery or a capacitor that requires high output and high energy density.

Next, a lithium cobaltate (LiCoO ₂ ) powder as an active material, polyvinylidene fluoride (PVdE) as a binder, and artificial graphite powder as a conductive material are mixed in a weight ratio of 86: 6: 8 to obtain a positive electrode agent. A positive electrode active material slurry was prepared by mixing N-methyl-2pyrrolidone as a solvent with this positive electrode agent.

  Next, in this positive electrode active material slurry, the foamed aluminum of Examples 1 to 16 and the foamed aluminum of Conventional Example 1 were immersed for 10 minutes, taken out and dried, then rolled and rolled into Examples 1 to 5 having a thickness of 0.5 mm. Sixteen lithium ion battery positive electrodes were prepared.

  In addition, as the foamed aluminum of Conventional Example 1, 30 PPI foamed aluminum produced by press-fitting aluminum into a mold having sponge urethane as a core, which is the second method of the prior art, was used. Further, the packing density of the positive electrode active materials of the foamed aluminum of Examples 1 to 16 and the foamed aluminum of Conventional Example 1 is shown in Table 5.

  Next, cylindrical bodies having diameters of 1 mm, 1.5 mm, 2 mm, 2.5 mm, 3 mm, 3.5 mm, 4 mm, 4.5 mm, and 5 mm were prepared, and the lithium ion batteries of Examples 1 to 16 and Conventional Example 1 were prepared. Each of the positive electrodes was wound, and whether or not the active material was peeled was visually observed. Table 5 shows the minimum diameter where no peeling was observed.

As a result, as can be seen from Table 5, the positive electrodes of the lithium ion batteries of Examples 1 to 16 did not peel off the active material even when wound around a cylindrical body having a diameter of 1.5 mm to 2.5 mm. In the positive electrode of Conventional Example 1, the active material was peeled off when it was wound around a cylindrical body having a diameter of 3 mm. Furthermore, the positive electrode of the lithium ion batteries of Examples 1 to 16 has an active material packing density of 4.1 g / cm ³ or more, whereas the positive electrode of Conventional Example 1 has an active material packing density of 3 It was as small as 84.1 g / cm ³ .

  In addition to being used as a method for producing foamed aluminum, it can be used as a method for producing a current collector of a lithium ion secondary battery or an electric double layer capacitor.

Claims (8)

  A sintering aid powder containing titanium is mixed with aluminum powder to obtain an aluminum mixed raw material powder, and this aluminum mixed raw material powder is mixed with water-soluble resin binder, water, at least one of polyhydric alcohol, ether and ester. A plasticizer consisting of seeds is mixed to obtain a viscous composition, and the viscous composition is dried in a state where air bubbles are mixed to form the pre-sintered molded body. In an atmosphere, when the temperature at which the aluminum mixed raw material powder starts melting is Tm (° C.), it is fired at a temperature T (° C.) of Tm−10 (° C.) ≦ T ≦ 685 (° C.). The manufacturing method of the aluminum porous sintered compact characterized by these.   2. The method for producing a porous aluminum sintered body according to claim 1, wherein the aluminum powder has an average particle diameter of 2 to 200 μm.   When the average particle size of the sintering aid powder is r (μm) and the blending ratio of the sintering aid powder is W mass%, 1 (μm) ≦ r ≦ 30 (μm), 1 ≦ W ≦ It is 20 (mass%) and it is 0.1 <= W / r <= 2, The manufacturing method of the aluminum porous sintered compact of Claim 1 or 2 characterized by the above-mentioned.   The method for producing an aluminum porous sintered body according to any one of claims 1 to 3, wherein the sintering aid powder is titanium and / or titanium hydride.   The method for producing a porous aluminum sintered body according to any one of claims 1 to 4, wherein a water-insoluble hydrocarbon-based organic solvent having 5 to 8 carbon atoms is added to the viscous composition.   The aluminum according to any one of claims 1 to 5, wherein the water-soluble resin binder is contained within a range of 0.5% to 7% of a mass of the aluminum mixed raw material powder. A method for producing a porous sintered body.   7. The surfactant according to claim 1, wherein a surfactant within a range of 0.02 to 3% of the mass of the aluminum mixed raw material powder is added to the aluminum mixed raw material powder. 8. A method for producing an aluminum porous sintered body.   The said viscous composition is made into the plate-shaped molded object by extending | stretching the said viscous composition to the thickness of 0.05 mm-5 mm, and drying it, The said molded object before sintering is any one of Claim 1 thru | or 7 characterized by the above-mentioned. The method for producing an aluminum porous sintered body according to one item.