JP6593875B2 - Porous material and method for producing the same - Google Patents

Description

  The present invention relates to a porous material and a method for producing the same, and more particularly to a porous material having pores surrounded by an aluminum compound shell and a method for producing the porous material.

  A porous material having a large number of pores has a function that cannot be obtained with a dense body, and has attracted attention as a functional material. In particular, porous aluminum has lightness, sound absorption, shock absorption, and heat insulation, and is expected to be demanded not only in the environmental and energy fields but also in a wide range of fields. For example, it is used as a honeycomb material for automobile parts and aircraft, or as a sound absorbing material.

  Porous aluminum is conventionally produced by powder metallurgy, casting, chemical vapor deposition, and the like. In particular, the precursor method can be cited as the current main production method. The precursor method is a method in which aluminum powder and titanium hydride, which is a foaming auxiliary powder, are mixed, compression-molded, and sintered. During the sintering, the metal portion is in a semi-molten state, titanium hydride is decomposed and hydrogen gas is released, and pores are formed by this gas to obtain porous aluminum. Also, for example, Patent Document 1 proposes a method for producing an aluminum alloy foam that is lightweight and has a uniform cell structure and is used as an impact energy absorbing member. This technology increases the casting temperature of the molten aluminum alloy during casting by adding a thickener and a foaming agent to the molten aluminum alloy and stirring it higher than the solidus temperature of the aluminum alloy. At the same time, the temperature of the casting mold is equal to or higher than the liquidus temperature of the aluminum alloy and equal to or higher than the casting temperature to obtain foamed aluminum. These manufacturing methods require complicated equipment, use of a thickener and a foaming agent, and manufacturing conditions are also complicated.

  On the other hand, for example, Patent Document 2 proposes an aluminum solidification molding method that can easily obtain an aluminum solidification compact made of a porous body without melting or sintering the aluminum. In this technique, an aluminum material and water are placed in a container and stirred, and the aluminum and water are mixed while the container containing the mixture of aluminum and water is allowed to stand. And a solidification step of obtaining a solidified molded body made of a porous body integrated through alumina hydrate produced by reaction of aluminum and water. In this method, a porous body is formed by a large number of voids generated when aluminum powder is integrated through alumina hydrate, and complicated equipment and conditions such as conventional production of foamed aluminum are not required. There is an advantage of becoming.

  In recent years, regenerative treatment has attracted attention, and a scaffold for osteoblasts, which are cells that are particularly important for the treatment of fractures, is required. In order for osteoblasts to grow, pores of several tens of μm to several hundreds of μm need to be open. For example, Patent Document 3 proposes a medical material for preventing loosening or downgrowth that occurs when a hard medical device is embedded in bone or the like, and promoting the fixation of osteoblasts to the hard medical device. Has been. This medical material is a spacer that fills between the bone tissue and / or cartilage tissue and the rigid medical device, is not fixed to the rigid medical device, has a void structure, and is deformed according to pressure. The rigid medical device is fixed to bone tissue and / or cartilage tissue. As this medical material, metal fiber, metal coated fiber, inorganic coated fiber, synthetic polymer material-derived material, hydroxyapatite, titanium, titanium alloy, stainless steel, cobalt alloy, silver, titanium oxide, titanium nitride, titanium carbide, alumina It is described that non-absorbable materials such as zirconia can be used.

JP 2009-45655 A JP 2012-52223 A JP 2010-233860 A

  Since the above-described conventional production of porous aluminum is performed by a powder metallurgy method, a casting method, a chemical vapor deposition method, or the like, there is a difficulty in that the production apparatus is complicated and the cost is increased. In addition, the production of porous aluminum by the method of Patent Document 2 already proposed by the present inventor has an advantage that a complicated apparatus and conditions are unnecessary, but there is a demand for realizing a lighter weight. There is also a demand for use in medical materials such as osteoblast scaffolds.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a porous material that is easy to manufacture, is lightweight, and can be used as a medical material, and a method for manufacturing the same. It is in.

  (1) A method for producing a porous material according to the present invention for solving the above-described problems includes a step of reacting an aluminum material and water to form an aluminum compound on the aluminum material, and the aluminum material melts. And a step of pouring out the aluminum material by applying a temperature.

  According to the present invention, the aluminum compound is formed on the aluminum material and then heat-treated to flow out the aluminum material. Therefore, after the aluminum material flows, the aluminum compound shell remains, and a large number of pores constituted by the shell. Can be produced. As a result, it is possible to manufacture a porous material that does not require a sintering process, does not require a foaming agent, is easy to manufacture, is lightweight, and can be used as a medical material.

  In the method for producing a porous material according to the present invention, the aluminum compound is solidified by joining adjacent aluminum materials together.

  In the method for producing a porous material according to the present invention, the aluminum material is a particulate or fibrous fine raw material.

  In the method for producing a porous material according to the present invention, the aluminum compound is aluminum hydroxide and / or aluminum oxide, and the aluminum hydroxide and / or the aluminum oxide is boehmite or bayerite.

  (2) A porous material according to the present invention for solving the above-mentioned problems has a void surrounded by a shell of an aluminum compound, and the adjacent shells are connected to form a porous structure. And

  According to this invention, the shells of aluminum compounds are connected to each other, and a characteristic porous structure having pores surrounded by the shells is obtained.

  In the porous material according to the present invention, the aluminum compound is aluminum hydroxide and / or aluminum oxide, and the aluminum hydroxide and / or aluminum oxide is boehmite or bayerite.

  According to the method for producing a porous material according to the present invention, a porous material having a large number of pores made of an aluminum compound shell can be produced, so that a sintering step is not required and a foaming agent is produced. In addition, a porous material that is easy to manufacture, lightweight, and usable as a medical material can be obtained. Moreover, according to the porous material which concerns on this invention, it is lightweight and can be used also as a medical material. The porous material according to the present invention can be used as a filter for biomaterials and liquids (chemicals and foods), and in particular, can be used as a scaffold for regenerative treatment.

It is an electron micrograph which shows an example of the porous material which concerns on this invention. It is an electron micrograph of a particulate aluminum material. 1 is a schematic diagram showing a mechanochemical reaction apparatus used in Example 1. FIG. It is typical sectional drawing of the solidification molded object when changing the applied pressure in a mechanochemical reaction apparatus. It is an electron micrograph which shows boehmite and bayerite. It is the X-ray diffraction pattern of the aluminum compound produced | generated as the mixture ratio of water 25% and 30%. It is the X-ray diffraction pattern of the aluminum compound produced | generated as the mixture ratio of water 40% and 50%. It is an electron micrograph of the surface of the solidification molding body after producing | generating an aluminum compound by a mechanochemical reaction and before a heating process. It is an appearance photograph which shows the solidified molded object (a) before a heating process, the molded object (b) after a heating process, and the molded object (c) after removing the outflow aluminum on the surface of a molded object after a heating process, respectively. FIG. 10 is an X-ray diffraction pattern on the surface of the molded body in FIG. 4 is an electron micrograph of particulate aluminum materials having different particle diameters used in Example 2. FIG. 2 is a schematic diagram showing a reaction apparatus used in Example 2. FIG. It is an external appearance photograph of the solidification molded object after producing | generating an aluminum compound on an aluminum material, and before a heating process, (a)-(d) is the average particle diameter of the aluminum material used as a raw material by 20 micrometers, 70 micrometers, and 120 micrometers, respectively. 275 μm. It is an electron micrograph of the surface of the solidification molding body after producing | generating an aluminum compound on an aluminum material and before a heating process. It is an electron micrograph of the cross section of the solidification molding body after producing | generating an aluminum compound on an aluminum material and before a heating process. It is the graph which showed the measurement result of the amount of hydrogen generated at the time of fabrication. The amount of hydrogen at this time is the result of measuring the total amount generated when the molding time is 32 hours. It is the graph which showed the generation amount of hydrogen per unit area of aluminum powder, and the total surface area of the powder calculated | required from the mass of aluminum powder with respect to the average particle diameter.

  The porous material and the method for producing the same according to the present invention will be described below. However, the scope of the present invention is not limited to the following embodiments, but includes the scope of the gist thereof.

  As shown in FIG. 1, the porous material according to the present invention has pores surrounded by shells of an aluminum compound, and adjacent shells are connected to form a porous structure. Such a porous material is made to react with an aluminum material and water to produce an aluminum compound on the aluminum material (aluminum compound production step), and to add the temperature at which the aluminum material melts to flow out the aluminum material. It can manufacture by the method which has a process (heating process).

  The obtained porous material has a characteristic porous structure in which a shell of an aluminum compound is bound and has pores surrounded by the shell, is lightweight, and can be used as a medical material. In addition, the production of the porous material does not require a sintering step, and no foaming agent is required, and the production is easy.

  Hereinafter, the constituent elements of the porous material and the manufacturing method thereof will be described in detail. First, a method for producing a porous material will be described, and then structural features of the produced porous material will be described.

  The method for producing a porous material includes a step of reacting an aluminum material with water to form an aluminum compound on the aluminum material (aluminum compound generation step), and adding a temperature at which the aluminum material melts to A flow-out step (heating step).

<Aluminum compound production process>
(Aluminum material)
The aluminum material may be pure aluminum or an aluminum alloy. Pure aluminum refers to aluminum having a purity of 99.00% or more, and examples thereof include A1100. Examples of the aluminum alloy include 2000 series aluminum to 8000 series aluminum. For example, an Al—Mg series aluminum alloy such as A5052 can be preferably exemplified. Of pure aluminum and aluminum alloys, pure aluminum is preferably applicable because of its good reaction with pure water.

  The shape of the aluminum material may be particulate as shown in FIG. 2 or may be fibrous (not shown), and is not particularly limited. The particle size of the particulate aluminum material varies depending on the presence or absence of compressive stress to be applied, and is not particularly limited. In Example 2, which will be described later, a solidified molded product can be obtained in the range of 20 μm to 275 μm in average particle size, but it is preferably in the range of 20 μm to 150 μm in average particle size. By using an aluminum material having an average particle diameter in this range, a porous material having many voids can be obtained. As the particulate aluminum material, those produced by various methods can be used. As an example, as shown in FIG. 2, a particulate aluminum material produced by centrifugal spraying can be used. The average particle size can be measured by reading a value where the integrated value of the particle size distribution is 50%.

  The fibrous aluminum material can be used without being limited to the aspect ratio (fiber length: fiber diameter). By using fibrous aluminum materials having different aspect ratios, the voids can be controlled. The fiber length is preferably in the range of 20 μm to 15 mm, and the fiber diameter is preferably in the range of 20 μm to 150 μm. As such a fibrous aluminum material, those produced by various methods can be used. As an example, a fibrous aluminum material produced by a coil cutting method can be used. The fiber length and fiber diameter can be measured from images taken using a field emission scanning electron microscope.

(water)
As water, pure water, ion exchange water, reverse osmosis membrane water, tap water, saline, water containing oil, and the like can be used, and there is no particular limitation as long as water (H ₂ O) is contained. Usually, pure water can be preferably used.

(Production reaction of aluminum compound)
The reaction is carried out by bringing an aluminum material into contact with water. By this contact, an aluminum compound is generated on the surface of the aluminum material. Examples of the aluminum compound include one or both of aluminum hydroxide and aluminum oxide. Among these, Al (OH) ₃ .nH ₂ O, which is a hydrate of aluminum hydroxide, is easily generated. Such an aluminum compound is produced without heating or sintering an aluminum material as in the prior art. The aluminum material formed on the surface of the aluminum compound becomes a solidified aluminum body. The solidified molded body is obtained as a form in which the adjacent granular or fibrous aluminum materials are bonded together by the aluminum compound on the surface and solidified.

The reaction between the aluminum material and water is represented by 2Al + 6H ₂ O → 2Al (OH) ₃ + 3H ₂ (1). Examples of the aluminum hydroxide produced by this reaction include boehmite (aluminum hydroxide monohydrate) and bayerite (aluminum hydroxide trihydrate). Which is produced depends on the reaction temperature, but usually boehmite is produced first on the surface of the aluminum material, and bayerite is produced after the boehmite is produced. The electron micrograph shown in FIG. 5 shows acicular boehmite and columnar bayerite. In addition, in the reaction of an aluminum material and water, in addition to aluminum hydroxide, aluminum oxide may also be generated. One (a simple substance) or both (mixture) of these aluminum hydroxide and aluminum oxide is used as an aluminum compound in the present application. It is called.

  Specifically, when the particulate aluminum material is immersed in water, aluminum hydroxide, which is an aluminum compound generated by the reaction of the formula (1), is deposited on the surface of the particulate aluminum material. Cover the surface. At this time, the aluminum compound covering the surface of the aluminum material is also filled in the gap with the surrounding aluminum material, and plays a role of connecting the particulate aluminum materials. Thus, the particulate aluminum material is bonded to each other via the film-like aluminum compound formed on the surface, and as a result, the aluminum material can be solidified and formed. Note that the generated hydrogen acts to cause vacancies in the coating film of the aluminum compound or to form gaps in the aluminum compound that connects adjacent aluminum materials.

  The thickness of the film-like aluminum compound is in the range of about 0.5 μm to 5 μm at the end of the reaction. The thickness of the aluminum compound depends on the environmental temperature during the reaction. Specifically, the thickness of the aluminum compound tends to increase as the environmental temperature during the reaction decreases. Although the environmental temperature at the time of reaction is not particularly limited, it is preferably within a range of 35 ° C. or higher and 70 ° C. or lower, and by reacting in this temperature range, the aluminum materials can be joined and joined together. Of aluminum compound can be produced. The relationship between the thickness of the aluminum compound and the reaction time is such that the film thickness of the aluminum compound increases as the reaction time increases.

  In this reaction, a container filled with an aluminum material and water is accommodated in an apparatus capable of temperature control and reacted in a constant temperature environment, whereby a solidified molded body can be obtained efficiently. The “solidified molded body” herein is a molded body in which an aluminum compound is formed in a film shape on the surface of an aluminum material, and the aluminum compound bonds and integrates adjacent aluminum materials. In the aluminum compound generation step, it is preferable to obtain a solidified molded body by applying mechanical energy to a container filled with them and utilizing a mechanochemical reaction. By this mechanochemical reaction, an aluminum compound is formed on the surface of the aluminum material in close contact with each other, so that the bonding state is further increased by the aluminum compound, and a solidified molded body having high strength can be obtained. As the mechanical energy, a method of applying pressure can be preferably exemplified.

  FIG. 3 is a schematic diagram showing an example of the mechanochemical reaction apparatus 10. The mechanochemical reaction apparatus 10 includes at least a reaction molding unit 11 and a pressure device 12 that applies pressure to the reaction molding unit 11. The reaction molding part 11 contains a mixed raw material of aluminum and water. The pressure device 12 can pressurize the mixed raw material and heat it as necessary. For example, a raw material filling space (reaction molding unit 11) surrounded by the under punch member 13A, the upper punch member 13B, and the cylinder 14 can be used. Have. In the example of FIG. 3, the upper punch member 13 </ b> B descends and applies pressure to the reaction molding portion 11. The reaction molding unit 11 can be heated by the heating device 15 and can be controlled to a predetermined temperature as required. Reference numeral 16 is a thermometer, reference numeral 17 is a pressure gauge, reference numeral 18 is an on-off valve, reference numeral 20 is a weighing cylinder, and reference numeral 21 is a trap water tank. The open / close valve 18 is a valve for discharging the generated gas (hydrogen) 22 generated by the mechanochemical reaction, and the discharged generated gas 22 is trapped through the plastic tube 19.

  In this mechanochemical reaction device, the pressure range that can be applied by the pressure device 12 is not particularly limited, but for example, it can be configured to be capable of being pressurized constantly or stepwise within a range of 0 to 100 MPa. Although the temperature which can be heated with the heating apparatus 15 is not specifically limited, For example, it can be set as the structure which can be heated constantly or in steps within the range of 35 degreeC or more and 70 degrees C or less.

  FIG. 4 is a schematic cross-sectional view of the solidified molded product when the applied pressure in the mechanochemical reaction apparatus is changed to increase in the order of (A), (B), and (C). As shown in FIG. 4, as the pressure is increased, the gap between the solidified molded bodies is reduced and the density is increased. As a result, as the pressure is increased, the density and strength of the solidified molded body are increased, but the formation of aluminum compounds tends to decrease. Therefore, the conditions are set in the mechanochemical reaction apparatus in consideration of these.

  In the production step of the aluminum compound, the blending ratio of the aluminum material and water affects the amount of aluminum compound produced and the amount of hydrogen generated. For example, as the blending ratio of water increases, the amount of aluminum compound produced increases, so that the thickness of the aluminum compound that covers the aluminum material increases and it becomes easier to bond adjacent aluminum materials together. In addition, since the generation of hydrogen increases, the voids due to the generation of hydrogen become large and large. Therefore, the aluminum compound itself becomes porous, the density is lowered, and the strength is also lowered.

  The proportion of aluminum material and water affects the amount of aluminum compound produced. Increasing the proportion of water increases the amount of aluminum compound produced, but when the amount of aluminum compound produced increases, the boehmite shown in FIG. And the amount of bayerite produced. That is, boehmite is acicular aluminum hydroxide that is initially formed on the surface of the aluminum material, and bayerite is columnar aluminum hydroxide that is subsequently formed, so in the production of aluminum hydroxide that is an aluminum compound. When the production amount is small, the aluminum compound is a boehmite-rich aluminum compound, but the boehmite does not tend to increase thereafter, and the proportion of bayerite relatively increases as the production amount increases.

  FIG. 6 is an X-ray diffraction pattern of an aluminum compound generated with water mixing ratios of 25% and 30%, and FIG. 7 is an X-ray diffraction pattern of an aluminum compound generated with water mixing ratios of 40% and 50%. It is a pattern. The blending ratio shown here represents the amount of water in which all the reactions of aluminum of the above formula (1) are performed as 100%. However, in practice, the aluminum compound is formed on the surface of the aluminum material with a predetermined thickness, so that a lot of water exists as surplus water. As the amount of water increases, the amount of aluminum compound formed from aluminum hydroxide increases, but as shown in FIGS. 6 and 7, the X-ray diffraction peak of bayerite increases and bayerite is generated. It can be seen that is increasing.

  FIG. 8 is an electron micrograph of the solidified molded body after the aluminum compound made of aluminum hydroxide is generated by a mechanochemical reaction and before the heating step. By the mechanochemical reaction, an aluminum compound is generated on the surface of the aluminum material, and the aluminum compound binds adjacent aluminum materials to form a solidified molded body.

  In the aluminum compound production step, a different material may be added in addition to the aluminum material and water in a range that does not inhibit the production of the porous material or promotes the production of the porous material. Examples of the different material include biocompatible materials. Among these, hydroxyapatite can be preferably added from the viewpoint of biocompatibility.

  According to such an aluminum compound production step, many steps such as kneading, molding, drying, and firing, which are essential in the conventional precursor method, are unnecessary, and further, an oxidation produced by the buyer method or the ammonia alum pyrolysis method. There is an advantage that an aluminum raw material is also unnecessary. Further, in the conventional method, heating at 1000 ° C. or higher is necessary for sintering, a lot of energy is required, and production costs are high and the burden on the environment is large. In the method for producing a material, the reaction can be carried out at a temperature of several tens of degrees Celsius, so that it does not have the above-mentioned difficulties.

<Heating process>
The heating step is a step of adding a temperature at which the aluminum material is melted and pouring out the aluminum material. In this step, as shown in FIG. 9, the solidified molded body (see FIG. 9 (a)) obtained in the aluminum compound generation step for forming an aluminum compound composed of aluminum hydroxide and / or aluminum oxide on an aluminum material is heat treated. And a step of pouring an aluminum material from the solidified molded body (see FIGS. 9B and 9C). FIG. 9 (b) shows a case where aluminum that has flowed out by heating remains on the surface of the molded body, and FIG. 9 (c) shows a case where aluminum remaining on the surface of the molded body is removed. ing. The aluminum on the surface of the molded body may or may not remain as shown in FIG.

  By this process, the aluminum material flows out of the solidified molded body, so that the aluminum compound generated on the surface of the aluminum material remains in a shell shape, and as a result, a porous material having many pores can be produced. it can. In the production of such a porous material, a sintering process is not required, a foaming agent is not necessary, and the production is easy, and the porous material that is lightweight and can be used as a medical material can be obtained.

  FIG. 10 is an X-ray diffraction pattern on the surface of the molded body in FIG. It can be seen that most of the aluminum flows out before and after the heating process. Moreover, it turns out that the aluminum compound which consists of aluminum hydroxide changed into aluminum oxide by heating.

  The heating temperature may be any temperature at which the aluminum material melts and flows. For example, when pure aluminum having a melting point of 660 ° C. is used, the temperature is preferably 700 ° C. or higher. In the case of pure aluminum, if it is less than 700 ° C., the aluminum material may not be sufficiently melted and may not flow out. In addition, although the upper limit of temperature is not specifically limited, From a viewpoint of melting | fusing point of aluminum oxide, it is preferable that it is 2049 degrees C or less. Even in an aluminum material other than pure aluminum, it is preferable that the temperature be such that the aluminum material melts and a film-like aluminum compound (aluminum hydroxide and / or aluminum oxide) remains as a shell. Such a temperature is usually a temperature higher by 50 ° C. to 200 ° C. than the melting point in many cases. It is also possible to melt and flow the aluminum material not by heating but by acid treatment or alkali treatment.

  After the aluminum material flows out, an aluminum compound such as aluminum hydroxide remains in a shell state as shown in FIG. Such a shape can be preferably used as a porous material because voids are present in portions where the aluminum material has flowed out. In particular, since the void shape is surrounded by the shell, for example, the adsorbed material can be specifically adsorbed on the inner surface of the shell.

  The shape of the void depends on the shape of the aluminum material constituting the solidified molded body. For example, when a particulate aluminum material is used as the aluminum material, for example, as shown in FIG. 1, the inside of the spherical shell is vacant, for example, when a fibrous aluminum material is used. The interior of the cylindrical shell is vacant (not shown).

  Two or more types of aluminum materials having different melting points may be combined, and a temperature at which one or more types of aluminum materials are melted and poured out may be added. By doing so, a part of the aluminum material in the solidified molded body is melted and removed, so that the porosity and the like can be arbitrarily adjusted. For example, a pure aluminum material that can be melted and removed at 660 ° C. and an A2014-based aluminum material that can be melted and removed at 550 ° C. are combined to form an aluminum compound (aluminum hydroxide and / or aluminum hydroxide) on the surface of each aluminum material through an aluminum compound generation step. If it is heated in an atmosphere of 650 ° C. after producing aluminum oxide or the like, only the pure aluminum can be melted and poured out, leaving the aluminum compound. As a result, it is possible to control the porosity within a specific range as compared to the case where all use pure aluminum material.

  As described above, according to the method for producing a porous material according to the present invention, a porous material having many pores composed of an aluminum compound shell can be produced. A porous material that is not required, does not require a foaming agent, is easy to manufacture, is lightweight, and can be used as a medical material can be obtained.

<Porous material>
As shown in FIG. 1, the porous material obtained by the above-described manufacturing method has pores surrounded by an aluminum compound shell made of aluminum hydroxide and / or aluminum oxide, and adjacent shells are connected to each other. And has a porous structure. The aluminum compound is produced by reacting an aluminum material and water by the above-described manufacturing method, and is formed on the surface of the aluminum material. As a result, the shells of the aluminum compound are connected to each other, and a characteristic porous structure having pores surrounded by the shells is obtained.

  According to the obtained porous material, it is lightweight and can be used as a medical material. Such a porous material can be used as a filter for biomaterials and liquids (drugs and foods), and in particular, can be used as a scaffold for regenerative treatment.

  The invention is explained in more detail by means of examples.

[Example 1]
(Aluminum material)
As a pure aluminum material used for solidification molding, pure aluminum powder (see FIG. 2) having a purity of 99.7% and a particle size of 63 μm to 75 μm prepared by centrifugal spraying was used. The aluminum powder used contains Si (0.019%), Fe (0.056%), Zn (0.002%), and others (0.0016%) as impurity components. A solidified molded body was produced using this aluminum material.

(Experimental device)
FIG. 3 is a schematic view of the mechanochemical reaction apparatus used. This mechanochemical reaction apparatus is a mold using a split mold made of SUS304 and having a cylinder shape (cylindrical shape) having an inner diameter of 20 mm and a height of 50 mm. A mixed raw material of the aluminum powder and pure water was put into a mold and filled. Thereafter, compressive stress was applied to the mold. As a pressure gauge, a strain gauge (KFG-2-120-C1-11, manufactured by Kyowa Denki Co., Ltd.) is used, and it is attached by an active dummy method (4 gauge method), and a bridge box (DB-120S3, Kyowa Co., Ltd.). The strain and compression stress at the time of molding were measured using a strain measuring instrument (CDV-700A, manufactured by Kyowa Denki Co., Ltd.). The molding temperature was measured using a K-type thermocouple and fed back to the heater via a digital temperature controller (TR-K, manufactured by ASONE Corporation). When measuring the compressive stress and the temperature at the time of molding, a data logger (midi LOGGER GL220, manufactured by Graphtec Corporation) was used. Furthermore, the amount of hydrogen generated by the mechanochemical reaction between the aluminum powder and pure water is collected in a weighing cylinder using the water displacement method with the configuration shown in FIG. 3 and photographed every hour by a web camera. It was measured.

(Production of aluminum compounds)
13 g of prepared aluminum powder and 1.56 g of pure water were mixed and filled in the reaction molding unit 11 of the mechanochemical reaction apparatus 10 shown in FIG. 3, and a compressive stress σ _F was applied by the punch members 13A and 13B. The compressive stress σ _F was changed to 0, 10, 30, 50, 60, 70, 80, 90, and 100 MPa. The molding temperature was set to 313 K (about 40 ° C.), which is the condition in which the most aluminum hydroxide was produced, by solidification molding of the aluminum porous material by a chemical reaction between aluminum powder and pure water, and was maintained for 24 hours.

(Removal of aluminum outflow by heating)
In this example, a molded body produced with a compressive stress σ _F = 10 MPa was employed as a sample for removing aluminum outflow by heating. The reason for using this molded body is that the total amount of hydrogen generated is the largest among all σ _F , so that it is thought that the aluminum hydroxide of boehmite and bayerite contained in the molded body is the largest. . The compact was heated using a small electric furnace (FT-101FM, manufactured by Fulltech Co., Ltd.) under the conditions of an argon gas atmosphere, a holding temperature of 1073 K (about 800 ° C.), and a holding time of 7 hours.

[result]
(Appearance of molded body)
An appearance photograph of the heated molded body is shown in FIG. Although aluminum did not come out on the surface of the molded body before heating, it was confirmed that aluminum was flowing out from various places of the molded body after heating. This is because heating of 1073 K (about 800 ° C.) melts the aluminum inside the molded body, and water vapor generated when the aluminum hydroxide, which is an aluminum compound, is heated and dehydrated. It is thought that aluminum has come out. This is presumably because molten aluminum was pushed out to the outside by the generated water vapor during the transformation from aluminum hydroxide by heating to γ-alumina (aluminum oxide).

(X-ray diffraction results)
In order to confirm that the formed aluminum hydroxide is transformed into aluminum oxide by heating the molded body, X-ray diffraction was performed using the molded body from which the aluminum on the surface was removed after the heating shown in FIG. 9 (c). went. The result of X-ray diffraction is shown in FIG. From FIG. 10 (a), it was confirmed that the formed body was composed of aluminum, bayerite, and boehmite before heating. From FIG. 10 (b), it was confirmed that the formed body after heating was composed of aluminum, γ-alumina and δ-alumina. Boehmite contained in the green body before heating changes to γ-alumina at 773 K (about 500 ° C.), and γ-alumina changes to δ-alumina at 1073 K (about 800 ° C.). It is thought that alumina was detected.

  As described above, the following was clarified as a result of heating the solidified molded body in a state where aluminum powder and pure water were mixed and compressive stress was applied. By heating the compact that was solidified and formed by reacting aluminum powder and pure water with a compressive stress applied, the contained aluminum melted and flowed out of the compact. By heating, the aluminum hydroxide contained in the compact was transformed into aluminum oxide. From these results, the aluminum hydroxide contained in the porous material is transformed into aluminum oxide by heating to produce a porous material that is a composite material of aluminum oxide and aluminum that cannot be completely discharged. I was able to.

[Example 2]
Next, several types of aluminum powder having different average particle diameters were used, and a solidified molded body in which an aluminum compound was generated on an aluminum material was formed using a chemical reaction with water. In Example 2, the production state and bonding state of the aluminum compound were examined.

(Aluminum material)
As the aluminum material used for solidification molding, pure aluminum powder (see FIG. 11) having a purity of 99.7% and an average particle diameter (d _Al ) of 20 μm, 70 μm, 120 μm, and 275 μm prepared by centrifugal spraying was used. The aluminum material used contains Si (0.019%), Fe (0.056%), Zn (0.002%), and others (0.0016%) as impurity components, as in Example 1. A solidified molded body was formed using this aluminum material. FIG. 11 is SEM images obtained by observing various aluminum materials having different average particle sizes with a field emission scanning electron microscope (FE-SEM, model: JSM-7000, manufactured by JEOL Ltd.).

(Formation of experimental apparatus and molded body)
FIG. 12 is a schematic diagram showing the reaction apparatus 30 used in Example 2. The reactor 30 is a cylindrical polyacetal cylinder 32 having an outer diameter of 20 mm, an inner diameter of 10 mm, and a height of 60 mm. A mixed raw material of 3 g of the above-described aluminum powder and 0.72 g of pure water was charged in the reaction molding portion 31 of the cylindrical mold 32. The temperature of the water bath 34 was adjusted with a thermometer (thermocouple) 36, a heating device 35, and a controller 37, and the temperature was maintained at a molding temperature of 313 K (about 40 ° C.) for 32 hours. An upper molding member 33B made of a rubber plug was attached to the upper part of the mold, a tube 38 was attached to the upper molding member 33B, and the generated hydrogen 41 was recovered in the graduated cylinder 40 by a water displacement method. Note that no compression stress was applied to the solidified molded body obtained at this time (σ _F = 0 MPa). In addition, the code | symbol 33A is an undermolding member (stainless steel member), and the code | symbol 39 is a water tank.

(Appearance of molded body)
FIG. 13 is an appearance photograph of the solidified molded body after the aluminum compound is formed on the aluminum material and before the heating step. FIGS. 13 (a) to (d) are external photographs of those obtained when the average particle diameter of the aluminum material used as a raw material is 20 μm, 70 μm, 120 μm, and 275 μm, respectively. As shown in FIGS. 13A to 13C, the compacts obtained using aluminum materials having an average particle diameter of 20 μm, 70 μm, and 120 μm could be solidified. On the other hand, as shown in FIG.13 (d), the molded object obtained using the aluminum material with an average particle diameter of 275 micrometers showed the location which is not partially solidified. As a result, it was presumed that a solidified molded body that can be a porous material after the heating step can be formed although there is a difference in degree even when using an aluminum material having any average particle diameter.

(Surface of molded body)
FIG. 14 is an electron micrograph of the surface of the solidified molded body after the aluminum compound is formed on the aluminum material and before the heating step. The surface observation of the solidified molded body was also performed by the above-described FE-SEM in the same manner as the aluminum powder. FIGS. 14A to 14D are electron micrographs of the aluminum particles obtained as raw materials having average particle diameters of 20 μm, 70 μm, 120 μm, and 275 μm, respectively. As shown in FIGS. 14 (a) to (d), as a result of observing the bonding state between the powders of the solidified molded body, in any of the solidified molded bodies having different average particle diameters, adjacent powders are made of aluminum hydroxide. It was confirmed that they were combined. However, as shown in FIG. 14 (a), a lot of spongy boehmite was confirmed on the surface of the solidified molded article having an average particle diameter of 20 μm, whereas it is shown in FIGS. 14 (b) to (d). As described above, columnar bayerite was confirmed on the surface of the solidified molded body having an average particle diameter of 70 μm, 120 μm, and 275 μm, and the bonding state was different.

FIG. 15 is an electron micrograph of a cross section of the solidified molded body after the aluminum compound is formed on the aluminum material and before the heating step. This cross-sectional observation is a result of observing the central portion in the longitudinal direction of the sample. It was confirmed that the aluminum compound covering the surface of the aluminum powder was boehmite, and the aluminum compound deposited and covered on the boehmite was bayerite. The chemical reaction formula of boehmite is represented by 2Al + 4H ₂ O → 2AlO (OH) + 3H ₂ , and the chemical reaction formula of bayerite is represented by 2Al + 6H ₂ O → 2Al (OH) ₃ + 3H ₂ . Comparing both formulas, it can be seen that when the same amount of pure water is used, the amount of hydrogen generated during the production of boehmite is greater than the amount of hydrogen generated during the production of bayerite.

  FIG. 16 is a graph showing measurement results of the amount of hydrogen generated during molding. The amount of hydrogen is the result of measuring the total amount generated when the molding time is 32 hours. As shown in FIG. 16, the amount of hydrogen generated when aluminum powder having an average particle size of 20 μm is used is 362 mL, the amount of hydrogen generated when the average particle size is 70 μm is 329 mL, and the average particle size is 120 μm. The amount of hydrogen generated at 296 was 296 mL, and the amount of hydrogen generated when the average particle size was 275 μm was 206 mL. From this result, it was found that the amount of hydrogen generated was maximized when the average particle size was 20 μm, and decreased as the average particle size increased. The reason for this is that, from the electron micrographs of the surface and cross section of FIGS. 14 and 15, a large amount of boehmite was confirmed on the surface of the solidified molded body when the average particle size was 20 μm. It is thought that the total generation amount of

FIG. 17 is a graph showing the total surface area of the aluminum powder obtained from the mass of the aluminum powder and the amount of hydrogen generated per unit area of the aluminum powder with respect to the average particle diameter. If the mass of the aluminum powder was the same, the surface area increased as the aluminum powder had a smaller average particle size. Specifically, as shown in FIG. 17, the surface area when an aluminum powder having an average particle diameter of 20 μm is used is 3.3 × 10 ¹⁷ mL, and the surface area when the average particle diameter is 70 μm is 9.5 ×. a 10 ¹⁶ mL, the surface area when the average particle diameter of 120μm is 5.6 × ¹⁰ 16 mL, an average particle size of the surface area when the 275μm was 2.46 × ¹⁰ 16 mL. In addition, as shown in FIG. 17, the amount of hydrogen generated per unit area is 1.1 × 10 ⁻¹⁵ m ² at the minimum when the average particle size is 20 μm, and 3.5 when the average particle size is 70 μm. In the case of × 10 ⁻¹⁵ m ² , the average particle size of 120 μm was 5.3 × 10 ⁻¹⁵ m ² , and the average particle size of 275 μm was 8.5 × 10 ⁻¹⁵ m ² .

  In the reaction of aluminum powder and water, first, aluminum ions and water molecules react to generate boehmite, and then further, aluminum ions and water react to generate bayerite. However, as described above, the smaller the average particle size of the aluminum powder, the larger the surface area. Therefore, when the amount of pure water is constant relative to the mass of the aluminum powder, much of the pure water is consumed in the formation of boehmite. As a result, the amount of pure water required to generate bayerite is reduced. As a result, it is considered that bayerite was not sufficiently generated. On the other hand, in order to increase the bonding strength between aluminum powders, bayerite generated later is required rather than boehmite. Therefore, in order to increase the bonding strength and increase the mechanical strength, a large amount of bayerite must be generated. It has been found that this requires a lot of water.

  As described above, in Example 2, the average particle size of the aluminum powder was changed to form a solidified molded body, and the influence of the production state and the bonding state of the aluminum compound was examined. As a result, a molded body using aluminum powder having an average particle diameter of 20 μm to 120 μm could be solidified, but a molded body using aluminum powder having an average particle diameter of 275 μm could only be partially solidified. Met. In addition, as for aluminum hydroxide, which is an aluminum compound, a large amount of boehmite can be confirmed in a solidified molded body using an aluminum powder having an average particle diameter of 20 μm, and in a solidified molded body using an aluminum powder having an average particle diameter of 70 μm to 275 μm. Many buyer lights were confirmed. From these results, it was found that a solidified molded body capable of forming a porous material can be produced even if the average particle diameter of the aluminum powder is changed. Moreover, when the quantity of the pure water to add was constant, it turned out that the bonding state of powder differs with the average particle diameter of aluminum powder.

DESCRIPTION OF SYMBOLS 10 Mechanochemical reaction apparatus 11 Reaction shaping | molding part 12 Pressure apparatus 13A Under punch member 13B Upper punch member 14 Cylinder 15 Heating apparatus 16 Thermometer 17 Pressure gauge 18 Valve 19 Plastic tube 20 Weighing cylinder 21 Tube 22 Generated gas 30 Reactor 31 Reaction molding Part 32 Tube 33A Under molding member 33B Upper molding member 34 Water bath 35 Heating device 36 Thermometer 37 Controller 38 Tube 39 Water tank 40 Measuring cylinder 41 Generated gas (hydrogen)

Claims (6)

  A porous material comprising: a step of reacting an aluminum material with water to produce an aluminum compound on the aluminum material; and a step of pouring the aluminum material by applying a temperature at which the aluminum material melts. Manufacturing method.   The method for producing a porous material according to claim 1, wherein the aluminum compound is formed by solidifying the adjacent aluminum materials.   The manufacturing method of the porous material of Claim 1 or 2 whose shape of the said aluminum material is a particulate or fibrous fine raw material.   The method for producing a porous material according to any one of claims 1 to 3, wherein the aluminum compound is aluminum hydroxide and / or aluminum oxide. A porous material having pores surrounded by an aluminum compound shell, the adjacent shells being joined together to form a porous structure ;
The shell of the aluminum compound is left after the internal aluminum material flows out by heat treatment, and the size of the pores is the same as the spherical pores remaining when the aluminum material is a particulate aluminum material. Is within the range of 20 μm to 275 μm in average particle diameter, and when the aluminum material is a fibrous aluminum material, the remaining fiber holes have a fiber diameter of 20 μm to 15 mm and a fiber diameter of 20 μm to 150 μm. A porous material characterized in that it is within a range . The porous material according to claim 5, wherein the aluminum compound is aluminum hydroxide and / or aluminum oxide.