A method of preparing porous iron by impregnation of an organic foam and porous iron

Abstract

The application belongs to the field of metal materials, and discloses a method for preparing porous iron by impregnating organic foam, which comprises the following steps: step 1: impregnating slurry into a polyurethane foam template after roughening, to obtain a slurry-attached foam template; the slurry is an aqueous solution containing water-soluble resin, iron powder, ferric oxide, surfactant and thickening agent; the water-soluble resin contains a curing agent; step 2: performing rolling and drying operations on the slurry-attached foam template obtained in step 1, to obtain a green body; and step 3: performing combustion, reduction and sintering operations on the green body obtained in step 2. By using a foaming surfactant, the foaming effect of the foaming surfactant is utilized to solve the problem of closed pores and increase the porosity, and the water-soluble resin is used in combination, so that the material has certain toughness and tensile strength while the porosity is increased, and the porous iron material with high porosity and high strength is obtained. Meanwhile, the application also discloses a porous iron.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of metal materials, and particularly relates to a method for preparing porous iron by impregnating organic foam and porous iron. BACKGROUND

[0002] Porous metal material is a kind of porous material which has developed rapidly in recent years. Compared with dense metal material, porous metal has many excellent properties, such as large specific surface area, good energy absorption, high heat exchange and heat dissipation capacity, good machinability, etc. It can be applied in many fields, for example, it can be prepared into a filter, and also can be used to make a porous electrode, a catalyst, etc. Even it can be prepared into an artificial bone for medical field.

[0003] Foam porous iron is one of the porous metal materials. With the advantage of low price of base metal, it can replace other foam porous materials in some specific fields, such as replacing foam ceramic to make automobile exhaust catalyst carrier material, replacing foam nickel to make battery electrode, etc. The main production process of foam porous iron at present is electrodeposition, followed by powder metallurgy warm pressing process. The foam iron prepared by electrodeposition has the best comprehensive performance, especially in mechanical properties. However, the waste liquid production is large, and the environmental pollution is serious. The size of foam porous iron prepared by powder metallurgy warm pressing process is small, which is not suitable for producing strip materials.

[0004] Impregnation method has a wide application in preparing foam porous metal or alloy, ceramic material, etc. Its main advantage is low cost, which is suitable for batch production of strip materials. When foam template is selected for preparing foam porous iron material by impregnation method, low PPI is preferred. This is because under the influence of gravity, higher PPI has the risk of vertical direction closure. The higher the PPI is, the greater the risk of closure is. In addition, high PPI also increases the risk of horizontal direction closure, resulting in poor pore effect of the finished product.

[0005] Therefore, the technical problem to be solved by the present application is how to solve the problem of closure when preparing porous iron with high PPI foam template, so as to prepare foam porous iron with high PPI, large specific surface area and low plugging rate. SUMMARY

[0006] The present application aims to provide a method for preparing porous iron by impregnating organic foam. By adding foaming surfactant and water-soluble resin, the porosity is increased while the material maintains a certain strength.

[0007] Meanwhile, the present application also discloses porous iron obtained based on the above method.

[0008] In order to achieve the purpose of the present application, the following technical solutions are adopted:

[0009] A method for preparing porous iron by impregnating an organic foam, comprising the following steps:

[0010] Step 1: roughening a polyurethane foam template and then impregnating a slurry to obtain a slurry-impregnated foam template;

[0011] The slurry is an aqueous solution containing a water-soluble resin, iron powder, ferric oxide, a surfactant and a thickening agent; the water-soluble resin contains a curing agent;

[0012] Step 2: rolling and drying the slurry-impregnated foam template obtained in Step 1 to obtain a green body;

[0013] Step 3: burning, reducing and sintering the green body obtained in Step 2.

[0014] In the prior art, a defoaming agent is generally added when porous materials are prepared by impregnation, which aims to reduce the bubbles in the slurry and make the pore-forming agent more uniformly dispersed. This process can only make the pores uniform, but cannot increase the porosity or solve the problem of closed pores. In the present application, a foaming surfactant is innovatively used, which can physically foam to fill the slurry with bubbles. The material after impregnation and sintering is full of micropores on the edges of the pores, which not only increases the porosity, but also reduces the rate of blocked pores because the bubble shrinks to the edge of the pore after the bubble breaks.

[0015] In the present application, ferric oxide is used, which aims to improve the sintering strength and increase the toughness. The mechanism is that the microcrystalline surface formed by ferric oxide in the reduction stage has high surface activity, which can enhance the bonding strength between the grains.

[0016] Preferably, the slurry in Step 1 contains the following components by weight:

[0017] 10-30 parts of a water-soluble resin solution;

[0018] 40-60 parts of iron powder;

[0019] 0.01-0.3 parts of a surfactant;

[0020] 2-4 parts of ferric oxide;

[0021] 0.5-1 parts of a thickening agent;

[0022] Water is added to 100 parts;

[0023] The content of the water-soluble resin in the slurry is 0.5-1.5 parts;

[0024] The particle size of the iron powder is 5-45 um.

[0025] Preferably, the water-soluble resin in step 1 is selected from one or more combinations of methyl cellulose, gum arabic, carboxymethyl cellulose, polyvinyl alcohol, and epoxy resin.

[0026] Preferably, the thickening agent in step 1 is one or more combinations of acrylic, cellulose, and polyurethane corresponding to the water-soluble resin.

[0027] Preferably, the polyurethane foam template in step 2 is selected from a polyurethane foam template with a pore density of 60-130 PPI (pore density, i.e. the number of pores per inch length) and a thickness of 0.5-1.8 mm.

[0028] In some preferred embodiments of the present application, the pore density of the polyurethane foam template is 60 PPI, 70 PPI, 80 PPI, 90 PPI, 100 PPI, 110 PPI, 120 PPI, or 130 PPI.

[0029] The thickness of the polyurethane foam template is 0.5 mm, 0.6 mm, 0.7 mm, 0.8 mm, 0.9 mm, 1.0 mm, 1.1 mm, 1.2 mm, 1.3 mm, 1.4 mm, or 1.5 mm.

[0030] Preferably, in step 4, the drying temperature is 80-120°C and the time is 0.5-3h.

[0031] Preferably, in step 5, the combustion conditions are 300-350°C for 0.5-3h, 450-600°C for 0.5-3h, and the atmosphere is 5% oxygen and 95% nitrogen atmosphere.

[0032] The reduction conditions are 800-950°C for 1-5h and the atmosphere is pure hydrogen or carbon monoxide atmosphere.

[0033] The sintering conditions are 1050-1400°C for 2-5h and the atmosphere is inert gas atmosphere.

[0034] In addition, the present application also provides a porous iron prepared by the preparation method described above.

[0035] The beneficial effects of the present application are:

[0036] By using a foaming surfactant, the closed pore problem is solved by using its foaming effect, and the porosity is increased. In combination with the strengthening material effect of the water-soluble resin, the material has certain toughness and tensile strength while the porosity is increased, and a porous iron metal material with high porosity and high strength is obtained. BRIEF DESCRIPTION OF DRAWINGS

[0037] Figure 1SEM image of the product of Example 1;

[0038] Figure 2 SEM image of the product of Example 2;

[0039] Figure 3 SEM image of the product of Example 3;

[0040] Figure 4 SEM image of the product of Example 4;

[0041] Figure 5 SEM image of the product of Example 5;

[0042] Figure 6 SEM image of the product of Comparative Example 1. DETAILED DESCRIPTION

[0043] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by a person of ordinary skill in the art without creative labor fall within the protection scope of the present application.

[0044] Example 1

[0045] 1. Pulping:

[0046] The materials were weighed according to the following formula: 20 parts of PVA solution (5wt%), 50 parts by weight of 10um iron powder, 0.1 parts by weight of foaming surfactant, 2 parts by weight of ferric oxide powder, 0.5 parts by weight of acrylic thickening agent, and the balance of 27.4 parts by weight of water.

[0047] The foaming surfactant is alkyl glycoside, purchased from Zhonglian Chemical, model APG-0810;

[0048] The thickening agent is purchased from Zhonglian Federation, model C-012;

[0049] The water-soluble resin is purchased from Tianjin Zhonglian, model polyvinyl alcohol 2488;

[0050] First, the iron powder and ferric oxide were uniformly mixed, and the uniformly mixed powder was slowly added to the 5% PVA solution at a speed of 1000r / min, and stirring was continued for 1h. Then the foaming surfactant was added to the material, and stirring was continued for 30min, and then the thickening agent was added, and stirring was continued for 1h, to obtain a foaming body slurry, and the pulping was completed.

[0051] 2. The 110 PPI, 1.2 mm thick foam template is pre-processed by roughening, placed in the slurry tank, slowly pulled out at one end and extruded by the roller to squeeze out excess slurry, and then dried at 110°C for 2h to obtain a green body.

[0052] 3. The green body is placed in an atmosphere furnace for combustion, reduction, and sintering.

[0053] Combustion: in an atmosphere of 5% oxygen and 95% nitrogen, 350°C for 2h, and 500°C for 2h.

[0054] Reduction: after the oxidation process, the atmosphere is changed to pure hydrogen, and 850°C is maintained for 2h;

[0055] Sintering: after the reduction process, the atmosphere is changed to nitrogen, and 1200°C is maintained for 3h, and the furnace is cooled to room temperature, and the furnace is taken out.

[0056] 4. Post-processing of the sintered sample, i.e. roller flattening, detection, cutting, and packaging;

[0057] Example 2

[0058] 1. Slurry preparation:

[0059] Prepare a 5% CMC aqueous solution; and weigh the materials according to the following formula: 20 parts by weight of CMC aqueous solution (5wt%), 50 parts by weight of 5um iron powder, 0.1 parts by weight of foaming surfactant, 2 parts by weight of ferric oxide powder, 0.5 parts by weight of cellulose thickener, and the balance of 27.4 parts by weight of water.

[0060] Among them, the foaming surfactant is BASF AES;

[0061] The thickener is purchased from Foshan Shenghui Chemical Co., Ltd., model N-0056;

[0062] The water-soluble resin is purchased from Henan Wanbang Industry, model ordinary type.

[0063] First, the iron powder and ferric oxide are uniformly mixed, and the uniform powder is slowly added to the 5% CMC aqueous solution at a speed of 1000r / min, and stirring is continued for 1h. Then the foaming surfactant is added to the material, and stirring is continued for 30min, and then the thickener is added, and stirring is continued for 1h to obtain a foaming body slurry, and the slurry preparation is completed.

[0064] 2. The 60 PPI, 1.8 mm thick foam template is pre-processed by roughening, placed in the slurry tank, slowly pulled out at one end and extruded by the roller to squeeze out excess slurry. Then dried at 120°C for 0.5h to obtain a green body.

[0065] 3. The green body is placed in an atmosphere furnace for combustion, reduction, and sintering.

[0066] Combustion: 5% oxygen and 95% nitrogen atmosphere, 350°C for 0.5h, 600°C for 0.5h.

[0067] Reduction: after the oxidation section process, the atmosphere is changed to pure hydrogen, 950°C for 1h;

[0068] Sintering: after the reduction section process, the atmosphere is changed to nitrogen, 1400°C for 2h, furnace cooling to room temperature, and then out of the furnace.

[0069] 4. Post-processing of the sintered sample, i.e. rolling, detection, cutting, and packaging.

[0070] Example 3

[0071] 1. Slurry preparation:

[0072] Prepare a 5% gum arabic solution; and weigh the materials according to the following formula: 20 parts by weight of gum arabic solution (5wt%), 50 parts by weight of 45um iron powder, 0.1 parts by weight of foaming surfactant, 2 parts by weight of ferric oxide powder, 0.5 parts by weight of polyurethane thickener, and the balance of 27.4 parts by weight of water.

[0073] Among them, the foaming surfactant is general type K12;

[0074] The thickener is purchased from Zhongli Federation, model C-040;

[0075] The water-soluble resin is purchased from Komiyu Reagent, AR grade.

[0076] First, mix the iron powder and ferric oxide uniformly, and slowly add the uniform powder to the gum arabic solution at a speed of 1000r / min, and continue to stir for 1h. Then add the foaming surfactant to the material, and continue to stir for 30min, and then add the thickener, and continue to stir for 1h, to obtain the foaming body slurry, and complete the slurry preparation.

[0077] 2. After roughening pretreatment, the 130PPI, 0.5mm thick foam template is placed in the slurry tank, slowly pulled out at one end and extruded by the roller to extrude the excess slurry. Then, 80°C drying for 3h, to obtain the green body.

[0078] 3. The green body is placed in the atmosphere furnace for combustion, reduction, and sintering.

[0079] Combustion: 5% oxygen and 95% nitrogen atmosphere, 300°C for 3h, 450°C for 3h.

[0080] Reduction: after the oxidation section process, the atmosphere is changed to pure hydrogen, 800°C for 5h;

[0081] Sintering: after the reduction section process, the atmosphere is changed to nitrogen, and the temperature is kept at 1050°C for 5h, and the furnace is cooled to room temperature, and the furnace is discharged.

[0082] 4. Post-processing of the sintered sample, i.e. rolling, detection, cutting and packaging.

[0083] Example 4

[0084] 1. Pulping:

[0085] Prepare a 5% PVA solution; and weigh the materials according to the following formula: 10 parts by weight of PVA solution (5wt%), 40 parts by weight of 10um iron powder, 0.01 parts by weight of foaming surfactant, 2 parts by weight of ferric oxide powder, 0.5 parts by weight of acrylic thickener, and the balance 47.49 parts by weight of water.

[0086] Among them, the foaming surfactant is alkyl polyglycoside, purchased from Zhonglian Chemical, model APG-0810;

[0087] The thickener is purchased from Zhonglian Federation, model C-012;

[0088] The water-soluble resin is purchased from Tianjin Zhonglian, model polyvinyl alcohol 2488;

[0089] First, the iron powder and ferric oxide are uniformly mixed, and the uniform powder is slowly added to the 5% PVA solution at a speed of 1000r / min, and continues to stir for 1h. Then the foaming surfactant is added to the material, and continues to stir for 30min, and then the thickener is added, and continues to stir for 1h, to obtain the foaming body slurry, and the pulping is completed.

[0090] 2. After roughening pretreatment, the 110PPI, 1.2mm thick foam template is placed in the slurry tank, one end is slowly pulled out and the excess slurry is squeezed out by roller extrusion. Then 110°C drying for 2h, to get the green body.

[0091] 3. The green body is placed in the atmosphere furnace for combustion, reduction and sintering.

[0092] Combustion: in 5% oxygen and 95% nitrogen atmosphere, 350°C for 2h, 500°C for 2h.

[0093] Reduction: after the oxidation section process, the atmosphere is changed to pure hydrogen, and the temperature is kept at 850°C for 2h;

[0094] Sintering: after the reduction section process, the atmosphere is changed to nitrogen, and the temperature is kept at 1200°C for 3h, and the furnace is cooled to room temperature, and the furnace is discharged.

[0095] 4. Post-processing of the sintered sample, i.e. rolling, detection, cutting and packaging.

[0096] Example 5

[0097] 1. Slurry preparation:

[0098] Prepare 5% PVA solution; and weigh the materials according to the following formula: 30 parts by weight of PVA solution (5wt%), 50 parts by weight of 10um iron powder, 0.3 parts by weight of foaming surfactant, 4 parts by weight of ferric oxide powder, 1 part by weight of acrylic thickening agent, and the balance of 14.7 parts by weight of water.

[0099] The foaming surfactant is alkyl glycoside, purchased from Zhonglian Chemical, model APG-0810;

[0100] The thickening agent is purchased from Zhonglian Federation, model C-012;

[0101] The water-soluble resin is purchased from Tianjin Zhonglian, model polyvinyl alcohol 2488;

[0102] First, mix the iron powder and ferric oxide uniformly, and slowly add the homogenized powder to the 5% PVA solution at a speed of 1000r / min, and continue stirring for 1h. Then add the foaming surfactant to the material, and continue stirring for 30min, and then add the thickening agent, and continue stirring for 1h, to obtain the foam slurry, and complete the slurry preparation.

[0103] 2. After roughening pretreatment, the 110PPI, 1.2mm thick foam template is placed in the slurry tank, one end is slowly pulled out and the excess slurry is squeezed out by the roller. Then dry at 110℃ for 2h to obtain the green body.

[0104] 3. Place the green body in the atmosphere furnace for combustion, reduction, and sintering.

[0105] Combustion: in an atmosphere of 5% oxygen and 95% nitrogen, heat at 350℃ for 2h, and at 500℃ for 2h.

[0106] Reduction: after the oxidation process, change the atmosphere to pure hydrogen, and heat at 850℃ for 2h;

[0107] Sintering: after the reduction process, change the atmosphere to nitrogen, and heat at 1200℃ for 3h, and cool to room temperature in the furnace, and then take out of the furnace.

[0108] 4. Post-treatment of the sintered sample, i.e. roller flattening, detection, cutting, and packaging.

[0109] Comparative Example 1

[0110] The specific experimental steps refer to Example 1, except that no water-soluble resin is added during slurry preparation, and the balance is replaced with water.

[0111] Comparative Example 2

[0112] The specific experimental steps refer to Example 1, except that no surfactant is added during pulping.

[0113] Performance detection

[0114] Micro-morphology test method: German Zeiss sigma300 field emission scanning electron microscope;

[0115] Porosity test method: GB / T21650.3-2011;

[0116] The finished products prepared in each example and comparative example are detected according to the above method, and the specific detection data are referred to Table 1.

[0117] Table 1: Sample detection data

[0118]

[0119] Conclusion analysis:

[0120] From the data analysis of Examples 1-5, it can be concluded that the porous iron prepared by the technical scheme of the present application has very high porosity, among which the porosity of Example 5 is as high as 86.7%, and through the SEM image, it can be seen that the porosity of each product is very uniform, and there is no closed pore problem. This is because the foaming surfactant can be physically foamed, so that the inside of the slurry is full of bubbles, and the material after impregnation and sintering is full of micropores on the pore ridge, which not only increases the porosity, but also reduces the pore blocking rate because the bubble shrinks to the pore ridge position after the bubble breaks.

[0121] Comparative Example 1 cancels the use of water-soluble resin on the basis of Example 1. The role of water-soluble resin is to make the green body into a mold, so that the material has certain toughness and tensile strength, which is convenient for winding and prevents cracking due to shrinkage during heat treatment. Ultimately, the experiment fails and the porous iron product cannot be prepared.

[0122] Comparative Example 2 cancels the use of surfactant on the basis of Example 1, which results in the failure to play the role of the above-mentioned surfactant, and the porosity of the porous iron product is only 58.3%, which is 27.1% less than that of Example 1. Further observation of the SEM image shows that there are almost no small pores on the pore ridge of the sintered material, and the porosity effect is very poor.

[0123] In summary, when preparing porous iron by using the technical scheme of the present application, it is necessary to add foaming surfactant and water-soluble resin in combination, and both are indispensable.

[0124] It will be apparent to those skilled in the art that the application is not limited to the details of the above-exemplified embodiments and that the present application can be implemented in other particular forms without departing from the spirit or essential characteristics of the present application. The embodiments should therefore be considered in all respects as illustrative and not restrictive, the scope of the application being indicated by the appended claims rather than by the above description, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein. No reference signs in the claims should be considered as limiting the scope of the claims with respect to the figures of the patent document.

Claims

1. A method of preparing porous iron by impregnation of an organic foam, characterized in that, It comprises the following steps: Step 1: roughening the polyurethane foam template and then dipping it in the slurry to obtain a slurry-attached foam template; The slurry is an aqueous solution containing water-soluble resin, iron powder, ferric oxide, surfactant and thickening agent; the water-soluble resin contains a curing agent; Step 2: rolling and drying the slurry-attached foam template obtained in Step 1 to obtain a green body; Step 3: burning, reducing and sintering the green body obtained in Step 2; The slurry of Step 1 contains the following components by weight fraction: Water-soluble resin solution 10-30 parts; Iron powder 40-60 parts; Surfactant 0.01-0.3 parts; Ferric oxide 2-4 parts; Thickening agent 0.5-1 part; Water is added to the total weight of the slurry to 100 parts; The content of water-soluble resin in the slurry is 0.5-1.5 parts; The particle size of the iron powder is 5-45 um; The surfactant is a foaming surfactant; The polyurethane foam template of Step 1 is selected from polyurethane foam templates with 60-130 PPI and a thickness of 0.5-1.8 mm; In Step 2, the drying temperature is 80-120℃ and the time is 0.5-3h; In Step 3, the burning conditions are 300℃-350℃ for 0.5-3h, 450℃-600℃ for 0.5-3h, and the atmosphere is 5% oxygen and 95% nitrogen atmosphere; The reduction conditions are 800℃-950℃ for 1-5h, and the atmosphere is pure hydrogen or carbon monoxide atmosphere; The sintering conditions are 1050℃-1400℃ for 2-5h, and the atmosphere is inert gas atmosphere.

2. The method of claim 1, wherein, The water-soluble resin of Step 1 is selected from one or more combinations of methyl cellulose, ethyl cellulose, carboxymethyl cellulose, polyvinyl alcohol and epoxy resin.

3. The method of claim 1, wherein, The thickening agent of Step 1 is one or more combinations of acrylic, cellulose and polyurethane.

4. A porous iron, characterized by, It is prepared by the method of any one of claims 1-3.

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