Porous nickel and preparation method thereof

Abstract

The invention belongs to the field of metal materials, and discloses a preparation method of porous nickel, which comprises the following steps: step 1, mixing nickel powder, PMMA (polymethyl methacrylate) powder, a plasticizer and a flexibilizer to obtain uniform powder; step 2, molding the powder obtained in the step 1 to obtain a green body; 3, the green body obtained in the step 2 is subjected to vacuum degreasing and sintering, and a finished product is obtained. According to the invention, the performance of the PMMA powder is improved by using the plasticizer and the flexibilizer, the plasticizer improves the performance of a PMMA molecular layer, so that the flexibility of the PMMA molecular layer is enhanced, the PMMA molecular layer is easy to process, and the flexibilizer can greatly enhance the toughness of the material; through special cooperation of the plasticizer and the flexibilizer, the pore forming effect is improved, continuous production of the porous metal nickel is achieved, and meanwhile the invention further provides the porous nickel.

Description

Technical Field

[0001] The invention belongs to the field of metal materials, and in particular relates to porous nickel and a preparation method thereof. Background Art

[0002] Porous metal is a lightweight metal that has both structural and functional properties. It is widely used in filtration, separation, silencing, catalysis, heat exchange and other related fields due to its low density, large specific surface area, good energy absorption and shock absorption performance, excellent permeability, high temperature resistance, and the ability to process special-shaped parts.

[0003] At present, the mainstream processes for preparing porous nickel include traditional powder metallurgy, template method, dealloying method, electrodeposition method, etc.; the porous iron actually prepared by traditional powder metallurgy process often has low porosity, uneven pores, dispersed pore sizes and residual pore-forming agent; the dealloying method requires the addition of acid or alkali to dealloy, which is easy to cause environmental pollution; and these processes have the disadvantages of not being able to produce continuously and low production efficiency.

[0004] Chinese patent CN112872354B discloses a gradient porous metal material and its preparation method, wherein a certain ratio of metal powder and pore-forming agent are put into a ball mill for ball milling and mixing, a uniformly mixed powder is obtained and put into a mold, a press is used to press into a prefabricated block, and then put into a sintering furnace for sintering, and then polished with sandpaper for ultrasonic cleaning, and then put into a vacuum drying oven for drying, and finally laser surface treatment. The raw materials are only metal powder and pore-forming agent, and no other additives are added. Moreover, the molding method adopted is compression molding, which cannot achieve continuous production and has the problem of low production efficiency.

[0005] Therefore, the technical problem that needs to be solved in this case is: how to realize the continuous production operation of porous metal nickel materials. Summary of the invention

[0006] The purpose of the present invention is to provide a method for preparing porous nickel, by combining specific PMMA powder, plasticizer and toughening agent in a certain ratio, continuous hot extrusion molding is realized to achieve the effect of continuous production. At the same time, by using the above-mentioned auxiliary agents in combination, the pore uniformity and homogeneity of the porous nickel can be effectively improved.

[0007] Meanwhile, the invention also discloses porous nickel.

[0008] In order to achieve the purpose of the invention, the present invention adopts the following technical solutions:

[0009] A method for preparing porous nickel comprises the following steps:

[0010] Step 1: Mix nickel powder, PMMA powder, plasticizer and toughening agent to obtain uniform powder;

[0011] Step 2: forming the powder obtained in step 1 to obtain a green embryo;

[0012] Step 3: vacuum degreasing and sintering the green body obtained in step 2 to obtain a finished product.

[0013] Wherein, the forming is continuous hot extrusion forming.

[0014] In the present invention, a continuous hot extrusion molding process is innovatively used to prepare porous nickel. In the prior art, porous nickel is mostly prepared by a molding method. This process can only achieve the purpose of intermittent production, and when preparing materials with a large area, cracking and pore structure collapse after cooling are prone to occur. In the present invention, the performance of PMMA powder is improved by using plasticizers and toughening agents, so that it can be suitable for adapting to the continuous hot extrusion molding process. In particular, by combining the two additives, the pore forming effect of PMMA powder can be effectively improved, and the pore forming uniformity and uniformity can be improved. The mechanism for achieving this purpose is: by using a plasticizer to weaken the secondary bond between PMMA molecules, increase the mobility of PMMA molecular bonds, reduce the crystallinity of the resin molecule PMMA molecule, increase the plasticity of PMMA molecules, enhance its flexibility, and make it easy to process; by using a toughening agent to reduce the problem that the extrudate is easy to crack during continuous hot extrusion molding; the above two can also improve the dispersibility and fluidity of PMMA powder through toughening and plasticizing, thereby achieving an improvement in the pore forming effect.

[0015] Preferably, the nickel powder in step 1 is spherical with a particle size of 5 to 45 um, and the PMMA powder is spherical with a particle size of 20 to 300 um.

[0016] In some preferred embodiments of the present invention, the particle size of the nickel powder can be 5um, 10um, 15um, 20um, 25um, 30um, 35um, 40um or 45um; the above particle sizes can all achieve the purpose of the present invention; if the particle size is lower than 5um, it is not conducive to the flow of powder during extrusion, resulting in uneven thickness and porosity; if the particle size is higher than 45um, it is not conducive to the sintering effect and will result in insufficient toughness of the finished product.

[0017] In some preferred embodiments of the present invention, the particle size of the PMMA powder can be 20um, 60um, 100um, 140um, 180um, 220um, 260um or 300um; the above particle sizes can all achieve the purpose of the present invention; if the particle size is lower than 5um, the low porosity ratio will lead to pore closure, and if the particle size is higher than 45um, the high porosity ratio will easily lead to green body collapse during the degreasing stage.

[0018] Preferably, the volume ratio of the PMMA powder to the nickel powder is 40-80:20-60.

[0019] In some preferred embodiments of the present invention, the volume ratio of PMMA powder to nickel powder is 40:60, 45:55, 50:50, 55:45, 60:40, 65:35, 70:30, 75:25, or 80:20.

[0020] Preferably, the plasticizer is equivalent to 2.5% to 3% of the weight of the PMMA powder, and the plasticizer is equivalent to 4% to 5% of the weight of the PMMA powder.

[0021] Preferably, the continuous hot extrusion molding temperature in step 2 is 110-170° C.; the extrusion pressure is 5-40 MPa, more preferably 10-30 MPa.

[0022] In some preferred embodiments of the present invention, the continuous hot extrusion molding temperature in step 2 is 110°C, 120°C, 130°C, 140°C, 150°C, 160°C or 170°C;

[0023] In some preferred embodiments of the present invention, the extrusion pressure in step 2 is 5MPa, 10MPa, 15MPa, 20MPa, 25MPa, 30MPa, 35MPa or 40MPa;

[0024] Preferably, the vacuum degreasing and sintering environment described in step 3 are kept in vacuum throughout the process, and the vacuum degree is less than 10Pa.

[0025] Preferably, the vacuum degreasing temperature in step 3 is 160-180° C., the insulation time is 1-3 h, and 260-300° C., the insulation time is 1-3 h.

[0026] Preferably, the sintering temperature in step 3 is 850° C. to 1300° C., and the holding time is 2 h to 5 h.

[0027] In some preferred embodiments of the present invention, the sintering temperature in step 3 is 850°C, 900°C, 9850°C, 1000°C, 1050°C, 1100°C, 1150°C, 1200°C, 1250°C or 1300°C;

[0028] In some preferred embodiments of the present invention, the insulation time in step 3 is 2 h, 3 h, 4 h or 5 h.

[0029] Preferably, the plasticizer is one or more combinations of dioctyl phthalate, tributyl citrate, trioctyl trimellitate, and dioctyl terephthalate; the toughening agent is one or more combinations of ethyl acrylate, butyl acrylate, liquid nitrile rubber, and styrene-butadiene emulsion.

[0030] In addition, a porous nickel is also disclosed, which is prepared by the preparation method as described above.

[0031] The beneficial effects of the present invention are:

[0032] The present invention improves the performance of PMMA powder by using plasticizers and toughening agents. The plasticizer improves the performance of PMMA molecular layers to enhance its flexibility and facilitate processing, while the toughening agent can greatly enhance the toughness of the material. The porosity effect is improved by special matching of the plasticizer, toughening agent, plasticizer and toughening agent, thereby realizing the continuous production of porous nickel metal. DETAILED DESCRIPTION

[0033] Below in conjunction with the embodiment of the present invention, technical solution of the present invention will be clearly and completely described, it is obvious that the described embodiment is only a part of the present invention, rather than all embodiments. Based on the embodiment in the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative work premise belong to the scope of protection of the present invention. It should be noted that, in the embodiment, those who do not indicate specific conditions, are carried out according to the conditions recommended by normal conditions or manufacturers. Reagents used or instruments that do not indicate manufacturers are conventional products that can be obtained by commercial purchase.

[0034] Example 1

[0035] Prepare the raw materials according to the porosity of 40%: 40% vol. PMMA powder with a particle size of 250um, 60% vol. nickel powder with a particle size of 20um, a toughening agent equivalent to 2% of the total weight of PMMA powder, and a plasticizer equivalent to 3% wt of the total weight of PMMA powder.

[0036] Among them, the molecular weight of PMMA powder is 500,000 to 1 million, and the manufacturer is Arkema Altuglas;

[0037] The toughening agent is ethyl acrylate, with the molecular formula of C5H8O2;

[0038] The plasticizer is dioctyl phthalate, with the molecular formula C 24 H 38 O4;

[0039] Mixing: First, perform preliminary mechanical mixing of PMMA powder and nickel powder for 10 minutes, then add plasticizer and toughening agent and mix again for 30 minutes to obtain uniform powder.

[0040] Hot extrusion molding: Place the uniform powder in the die barrel, heat it together with the die barrel and extrusion head to 160°C, keep it warm, and after 1 hour, maintain the back pressure of 20Mpa for continuous extrusion to obtain the green billet.

[0041] Vacuum degreasing and sintering: Place the green body in a vacuum furnace, evacuate to below 10Pa, heat to 175℃, keep warm for 3h, then heat to 280℃, keep warm for 3h to complete degreasing. Continue to heat to 1100℃, keep warm for 4h, cool with the furnace, and get the finished product.

[0042] Example 2

[0043] Prepare the raw materials according to the porosity of 80%: 80% vol. PMMA powder with a particle size of 20um, 20% vol. nickel powder with a particle size of 5um, a toughening agent equivalent to 2% of the total weight of PMMA powder, and a plasticizer equivalent to 3% of the total weight of PMMA powder.

[0044] Among them, the molecular weight of PMMA powder is 500,000 to 1 million, and the manufacturer is Arkema Altuglas;

[0045] The toughening agent is butyl acrylate, with the molecular formula of C7H 12 O2;

[0046] The plasticizer is tributyl citrate, with the molecular formula C 18 H 32 O7;

[0047] Mixing: First, PMMA powder and nickel powder are preliminarily mechanically mixed for 10 minutes, and then plasticizer and toughening agent are added and mixed again for 30 minutes to obtain uniform powder.

[0048] Hot extrusion molding: Place the uniform powder in the die barrel, heat it together with the die barrel and the extrusion head to 110°C, keep it warm, and after 3 hours, maintain the back pressure at 30 MPa for continuous extrusion to obtain the green material.

[0049] Vacuum degreasing and sintering: Place the green body in a vacuum furnace, evacuate to below 10Pa, heat to 160℃, keep warm for 3h, then heat to 300℃, keep warm for 1h to complete degreasing. Continue to heat to 1300℃, keep warm for 2h, cool with the furnace, and get the finished product.

[0050] Example 3

[0051] Prepare the raw materials according to the porosity of 65%: 65% vol. PMMA powder with a particle size of 300um, 35% vol. nickel powder with a particle size of 45um, a toughening agent equivalent to 2% wt of the total weight of PMMA powder, and a plasticizer equivalent to 3% of the total weight of PMMA powder.

[0052] Among them, the molecular weight of PMMA powder is 500,000 to 1 million, and the manufacturer is Arkema Altuglas;

[0053] The toughening agent is liquid nitrile rubber, produced by Donglin Rubber & Plastic;

[0054] The plasticizer is trioctyl trimellitate, with the molecular formula C33 H 54 O6;

[0055] Mixing: First, PMMA powder and nickel powder are preliminarily mechanically mixed for 10 minutes, and then plasticizer and toughening agent are added and mixed again for 30 minutes to obtain uniform powder.

[0056] Hot extrusion molding: Place the uniform powder in the die barrel, heat it together with the die barrel and extrusion head to 170°C, keep it warm, and after 1 hour, maintain the back pressure of 10Mpa for continuous extrusion to obtain the green material.

[0057] Vacuum degreasing and sintering: Place the green body in a vacuum furnace, evacuate to below 10Pa, heat to 180℃, keep warm for 2h, then heat to 260℃, keep warm for 3h to complete degreasing. Continue to heat to 850℃, keep warm for 5h, cool with the furnace, and get the finished product.

[0058] Example 4

[0059] The method is substantially the same as Example 1, except that the amount of the toughening agent is 5 wt % and the amount of the plasticizer is 3 wt %.

[0060] Example 5

[0061] The method is substantially the same as Example 1, except that the amount of toughening agent used is 4 wt %; the amount of plasticizer used is 2.5 wt %.

[0062] Comparative Example 1

[0063] Prepare the raw materials according to the porosity of 65%: 65% vol. PMMA powder with a particle size of 300um, 35% vol. nickel powder with a particle size of 45um, a toughening agent equivalent to 2% of the total weight of the PMMA powder, and a plasticizer equivalent to 3% of the total weight of the PMMA powder.

[0064] Among them, the molecular weight of PMMA powder is 500,000 to 1 million, and the manufacturer is Arkema Altuglas;

[0065] The toughening agent is liquid nitrile rubber, produced by Donglin Rubber & Plastic;

[0066] The plasticizer is trioctyl trimellitate, with the molecular formula C 33 H 54 O6;

[0067] Mixing: PMMA powder and nickel powder were initially mechanically mixed for 10 min, and then plasticizer and toughening agent were added and mixed again for 30 min.

[0068] Compression molding: Place uniform powder in a mold, first cold press at 150MPa, maintain the pressing force, heat to 150℃, and keep warm for 20min to obtain a green body.

[0069] Vacuum degreasing and sintering: Place the green body in a vacuum furnace, evacuate to below 10Pa, heat to 180℃, keep warm for 2h, then heat to 260℃, keep warm for 3h to complete degreasing. Continue to heat to 850℃, keep warm for 5h, cool with the furnace, and get the finished product.

[0070] Comparative Example 2

[0071] Prepare the raw materials according to the porosity of 40%: 40% vol, 250um PMMA powder, 60% vol, 20um nickel powder, and plasticizer equivalent to 3% of the total weight of PMMA powder.

[0072] Among them, the molecular weight of PMMA powder is 500,000 to 1 million, and the manufacturer is Arkema Altuglas;

[0073] The plasticizer is dioctyl phthalate, with the molecular formula C 24 H 38 O4;

[0074] Mixing: First, perform preliminary mechanical mixing of PMMA powder and nickel powder for 10 minutes, then add plasticizer and mix again for 30 minutes to obtain uniform powder.

[0075] Hot extrusion molding: Place the uniform powder in the die barrel, heat it together with the die barrel and extrusion head to 160°C, keep it warm, and after 1 hour, maintain the back pressure of 20Mpa for continuous extrusion to obtain the green billet.

[0076] Vacuum degreasing and sintering: Place the green body in a vacuum furnace, evacuate to below 10Pa, heat to 175℃, keep warm for 3h, then heat to 280℃, keep warm for 3h to complete degreasing. Continue to heat to 1100℃, keep warm for 4h, cool with the furnace, and get the finished product.

[0077] Comparative Example 3

[0078] Prepare the raw materials according to the porosity of 40%: 40% vol. PMMA powder with a particle size of 250 um, 60% vol. nickel powder with a particle size of 20 um, and a toughening agent equivalent to 2% of the total weight of the PMMA powder.

[0079] Among them, the molecular weight of PMMA powder is 500,000 to 1 million, and the manufacturer is Arkema Altuglas;

[0080] The toughening agent is ethyl acrylate, with the molecular formula of C5H8O2;

[0081] Mixing: First, perform preliminary mechanical mixing of PMMA powder and nickel powder for 10 minutes, then add toughening agent and mix again for 30 minutes to obtain uniform powder.

[0082] Hot extrusion molding: Place the uniform powder in the die barrel, heat it together with the die barrel and extrusion head to 160°C, keep it warm, and after 1 hour, maintain the back pressure of 20Mpa for continuous extrusion to obtain the green billet.

[0083] Vacuum degreasing and sintering: Place the green body in a vacuum furnace, evacuate to below 10Pa, heat to 175℃, keep warm for 3h, then heat to 280℃, keep warm for 3h to complete degreasing. Continue to heat to 1100℃, keep warm for 4h, cool with the furnace, and get the finished product.

[0084] Performance Testing

[0085] Aperture test method: German Zeiss sigma300 field emission electron scanning electron microscope;

[0086] Porosity test method: Test according to GB / T21650.3-2011;

[0087] For specific test data on porosity, pore size and molding effect, please refer to Table 1

[0088] Table 1 Test data of each sample

[0089]

[0090]

[0091] Result analysis:

[0092] It can be concluded from the sample data of Examples 1 to 3 that the products with different porosities prepared by the technical solution of the present invention have measured porosities that are very close to the set porosities. The difference in Example 1 is only 0.8%, proving that there is almost no pore-forming agent residue in the product. The pore size of each product is as high as 230um to 240um, with excellent porosity effect. In addition, the products obtained by continuous hot extrusion molding of the present invention are flat and firm after cooling, without cracking or collapse.

[0093] Based on Example 1, Examples 4 to 5 adjust the dosage of plasticizer and toughening agent. It can be seen that within the dosage range of plasticizer and toughening agent set in the present invention, porous nickel products with good pore forming effect and complete and strong structure can be prepared.

[0094] Comparison of the data of Comparative Example 1 and Example 3 shows that the use of compression molding instead of continuous hot base molding can also have a good porosity, but its pore size is very small, only 142um, which is 61% of the sample in Example 3.

[0095] Comparative Examples 2 and 3 respectively eliminated the toughening agent and plasticizer on the basis of Example 1. From the corresponding data comparison, it can be concluded that the porosity and pore size effects of the products prepared after eliminating the toughening agent and plasticizer can be maintained, but the products without using the toughening agent have shrinkage warping at the edges after cooling, and the products without using the plasticizer have fish scale cracks during the extrusion process and local collapse after cooling.

[0096] It will be apparent to those skilled in the art that the invention is not limited to the details of the exemplary embodiments described above and that the invention can be implemented in other specific forms without departing from the spirit or essential features of the invention. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description, and it is intended that all variations within the meaning and scope of the equivalent elements of the claims be included in the invention. Any marking in a claim should not be considered as limiting the claim to which it relates.

Claims

1. A method for preparing porous nickel, characterized in that: The specific steps include: Step 1: Mix nickel powder, PMMA powder, plasticizer and toughening agent to obtain uniform powder; Step 2: forming the powder obtained in step 1 to obtain a green embryo; Step 3: vacuum degreasing and sintering the green embryo obtained in step 2 to obtain a finished product; Wherein, the forming is continuous hot extrusion forming.

2. The preparation method according to claim 1, characterized in that: The nickel powder is spherical and has a particle size of 5-45um, and the PMMA powder is spherical and has a particle size of 20-300um.

3. The preparation method according to claim 1, characterized in that: The volume ratio of the PMMA powder to the nickel powder is 40-80:20-60.

4. The preparation method according to claim 1, characterized in that: The plasticizer is equivalent to 2.5% to 3% of the weight of the PMMA powder, and the toughening agent is equivalent to 4% to 5% of the weight of the PMMA powder.

5. The preparation method according to claim 1, characterized in that: The continuous hot extrusion molding temperature described in step 2 is 110-170° C.; the extrusion pressure is 5-50 MPa.

6. The preparation method according to claim 1, characterized in that: The vacuum degreasing and sintering environment described in step 3 are kept in vacuum throughout the process, and the vacuum degree is less than 10Pa.

7. The preparation method according to claim 1, characterized in that: The vacuum degreasing temperature described in step 3 is 160-180° C. for 1-3 hours, and 260-300° C. for 1-3 hours.

8. The preparation method according to claim 1, characterized in that: The sintering temperature described in step 3 is 850° C. to 1300° C., and the holding time is 2 h to 5 h.

9. The preparation method according to claim 1, characterized in that: The plasticizer is one or more combinations of dioctyl phthalate, tributyl citrate, trioctyl trimellitate, and dioctyl terephthalate; the toughening agent is one or more combinations of ethyl acrylate, butyl acrylate, liquid nitrile rubber, and styrene-butadiene emulsion.

10. A porous nickel, characterized in that: The porous nickel is prepared by the method for preparing the porous nickel as described in any one of claims 1 to 9.

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