Porous nickel and a method for producing the same

Abstract

The application 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 powder, a plasticizer and a toughening agent to obtain uniform powder; step 2: forming the powder obtained in step 1 to obtain a green body; and step 3: vacuum debinding and sintering the green body obtained in step 2 to obtain a finished product. The performance of the PMMA powder is improved by using the plasticizer and the toughening agent. The plasticizer improves the performance of the PMMA molecular layer, so that the flexibility of the PMMA molecular layer is enhanced and the PMMA molecular layer is easy to process. The toughening agent can enhance the toughness of the high-strength material. The special cooperation of the plasticizer and the toughening agent improves the pore forming effect, and realizes the continuous production of the porous nickel. In addition, the application further provides a porous nickel.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of metal materials, and particularly relates to a porous nickel and a preparation method thereof. BACKGROUND

[0002] Porous metal is a lightweight metal with structural and functional dual-acting metal materials. Due to its small 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, it is widely used in filtration, separation, sound reduction, catalysis, heat exchange and other related fields.

[0003] At present, the mainstream processes for preparing porous nickel include traditional powder metallurgy, template method, dealloying method, electrodeposition method, etc. The porous iron prepared by the traditional powder metallurgy process often has low porosity, uneven porosity, dispersed pore size, and residual pore-forming agent. The dealloying method requires the addition of acid or alkali for dealloying, which may cause environmental pollution. Moreover, these processes cannot be continuously produced and have low production efficiency.

[0004] Chinese Patent CN112872354B discloses a gradient porous metal material and a preparation method thereof. The preparation method comprises the following steps: putting metal powder and pore-forming agent in a ball mill for ball milling and mixing to obtain uniformly mixed powder, putting the powder into a mold, pressing the powder into a preform block by using a press, sintering the preform block in a sintering furnace, polishing the sintered block to be flat, ultrasonic cleaning, drying in a vacuum drying oven, and finally performing 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 low production efficiency.

[0005] Therefore, the technical problem to be solved by the present application is how to realize continuous production of porous nickel material. SUMMARY

[0006] The present application aims to provide a preparation method of porous nickel, which realizes continuous hot extrusion molding by using specific proportions of PMMA powder, plasticizer and toughening agent, achieves the effect of continuous production, and effectively improves the uniformity and homogeneity of the pores of the porous nickel by using the above-mentioned additives.

[0007] Meanwhile, the present application also discloses a porous nickel.

[0008] To achieve the above-mentioned purpose, the present application adopts the following technical solutions:

[0009] A preparation method of porous nickel, comprising the following steps:

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

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

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

[0013] The molding is continuous hot extrusion molding.

[0014] In the present application, the 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 larger area, cracking and collapse of the pore structure after cooling are prone to occur. In the present application, the performance of PMMA powder is improved by using plasticizers and toughening agents, so that it can be adapted to the continuous hot extrusion molding process. In particular, by using the two additives in combination, the pore forming and molding effect of PMMA powder can be effectively improved, and the pore uniformity and uniformity can be improved. The mechanism for achieving this purpose is that the use of plasticizers weakens the secondary bond between PMMA molecules, increases the mobility of PMMA molecular bonds, reduces the crystallinity of PMMA molecules, increases the plasticity of PMMA molecules, and makes them more flexible and easier to process. The use of toughening agents can reduce the problem of cracking of the extrudate during the continuous hot extrusion molding process. The above two can also improve the dispersibility and flowability of PMMA powder, thereby improving the pore forming effect.

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

[0016] In some preferred embodiments of the present application, the particle size of the above-mentioned nickel powder can be 5 um, 10 um, 15 um, 20 um, 25 um, 30 um, 35 um, 40 um or 45 um; the above-mentioned particle size can achieve the purpose of the present application; if the particle size is less than 5 um, the powder flow during extrusion will be affected, resulting in uneven thickness and porosity; if the particle size is greater than 45 um, the sintering effect will be affected, resulting in insufficient toughness of the finished product.

[0017] In some preferred embodiments of the present application, the particle size of the above-mentioned PMMA powder can be 20 um, 60 um, 100 um, 140 um, 180 um, 220 um, 260 um or 300 um; the above-mentioned particle size can achieve the purpose of the present application; if the particle size is less than 5 um, the low porosity ratio will cause the pores to close; if the particle size is greater than 45 um, the high porosity ratio will cause the green body to collapse during the debinding stage.

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

[0019] In some preferred embodiments of the present application, the volume ratio of the PMMA powder and the nickel powder is 40:60, 45:55, 50:50, 55:45, 60:40, 65:35, 70:30, 75:25, 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 forming temperature in step 2 is 110 to 170℃; the extrusion pressure is 5 to 40MPa, more preferably 10 to 30MPa.

[0022] In some preferred embodiments of the present application, the continuous hot extrusion forming temperature in step 2 is 110℃, 120℃, 130℃, 140℃, 150℃, 160℃, or 170℃.

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

[0024] Preferably, the vacuum debinding and sintering environment in step 3 is kept in vacuum throughout the process, and the vacuum degree is <10Pa.

[0025] Preferably, the vacuum debinding temperature in step 3 is 160 to 180℃, and the holding time is 1 to 3h, or 260 to 300℃, and the holding time is 1 to 3h.

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

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

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

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

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

[0031] The present application has the following advantages:

[0032] The present application improves the performance of PMMA powder by using plasticizers and toughening agents. The plasticizers improve the performance of the PMMA molecular layer, making it more flexible and easier to process. The toughening agents greatly enhance the toughness of the material. The special combination of plasticizers and toughening agents improves the porosity effect and realizes the continuous production of porous nickel. DETAILED DESCRIPTION

[0033] The technical solutions of the present application will be described clearly and completely below in combination with the embodiments of the present application. Obviously, the described embodiments are only some of the embodiments of the present application, but not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application. It should be noted that, in the embodiments, the specific conditions are not specified, and the conventional conditions or the conditions recommended by the manufacturer are used. The reagents or instruments used are not specified by the manufacturer, and are all conventional products that can be purchased on the market.

[0034] Embodiment 1

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

[0036] The PMMA powder has a molecular weight of 500-1000 million, and the manufacturer is Altuglas.

[0037] The toughening agent is ethyl acrylate, with a molecular formula of C5H8O2.

[0038] The plasticizer is dioctyl phthalate, with a molecular formula of C 24 H 38 O4.

[0039] Mixing: first, mix the PMMA powder and nickel powder mechanically for 10 minutes, then add the plasticizer and toughening agent and mix again for 30 minutes to obtain uniform powder,

[0040] Hot extrusion molding: place the uniform powder in the mold cylinder, heat the mold cylinder and extrusion head together to 160℃, and keep the temperature for 1 hour. Then, continuously extrude under the condition of maintaining back pressure of 20Mpa to obtain a green body.

[0041] Vacuum debinding and sintering: the green body is placed in a vacuum furnace, vacuumed to below 10 Pa, heated to 175°C, kept for 3 h, then heated to 280°C, kept for 3 h, and debinding is completed. Continue to heat to 1100°C, keep for 4 h, and cool in the furnace to obtain the finished product.

[0042] Example 2

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

[0044] The molecular weight of the PMMA powder is 500-1000 million, and the manufacturer is Arkema Altuglas;

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

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

[0047] Mixing: first, the PMMA powder and nickel powder are preliminarily mechanically mixed for 10 min, then the plasticizer and toughening agent are added for secondary mixing for 30 min, and uniform powder is obtained.

[0048] Hot extrusion molding: the uniform powder is placed in a mold cylinder, heated to 110°C together with the mold cylinder and extrusion head, kept for 3 h, then continuously extruded at a back pressure of 30 Mpa, and a green body is obtained.

[0049] Vacuum debinding and sintering: the green body is placed in a vacuum furnace, vacuumed to below 10 Pa, heated to 160°C, kept for 3 h, then heated to 300°C, kept for 1 h, and debinding is completed. Continue to heat to 1300°C, keep for 2 h, and cool in the furnace to obtain the finished product.

[0050] Example 3

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

[0052] The molecular weight of the PMMA powder is 500-1000 million, and the manufacturer is Arkema Altuglas;

[0053] The toughening agent is liquid nitrile rubber, and the manufacturer is Donglin Rubber and Plastic;

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

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

[0056] Hot extrusion molding: the uniform powder is placed in a die cylinder, which is heated to 170°C together with the die cylinder and extrusion head, and then the green body is continuously extruded under a back pressure of 10 MPa after 1 hour of heat preservation.

[0057] Vacuum degreasing and sintering: the green body is placed in a vacuum furnace, vacuumed to below 10 Pa, heated to 180°C, heat preserved for 2 hours, then heated to 260°C, heat preserved for 3 hours to complete degreasing. Continue to heat to 850°C, heat preserved for 5 hours, and then cool in the furnace to obtain the finished product.

[0058] Example 4

[0059] Generally the same as Example 1, except that the amount of toughening agent is 5wt%; the amount of plasticizer is 3wt%.

[0060] Example 5

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

[0062] Comparative Example 1

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

[0064] Among them, the molecular weight of PMMA powder is 500-100 million, and the manufacturer is Altuglas;

[0065] The toughening agent is liquid nitrile rubber, and the manufacturer is Donglin Rubber and Plastic;

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

[0067] Mixing: first, the PMMA powder and nickel powder are mechanically mixed for 10 minutes, then the plasticizer and toughening agent are added and mixed again for 30 minutes.

[0068] Mold pressing: the uniform powder is placed in a mold, cold pressed at 150 MPa first, heated to 150°C while maintaining the pressing force, and then heat preserved for 20 minutes to obtain the green body.

[0069] Vacuum degreasing, sintering: Put the green body into the vacuum furnace, vacuumize to 10 Pa or less, heat to 180 °C, keep for 2 h, then heat to 260 °C, keep for 3 h, complete degreasing. Continue to heat to 850 °C, keep for 5 h, cool with the furnace, and the finished product is obtained.

[0070] Comparative Example 2

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

[0072] The molecular weight of the PMMA powder is 500-1000 million, and the manufacturer is Arkema Altuglas;

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

[0074] Mixing: first, mechanically mix the PMMA powder and nickel powder for 10 min, then add the plasticizer and mix again for 30 min to obtain uniform powder,

[0075] Hot extrusion molding: place the uniform powder in the mold cylinder, heat the mold cylinder and extrusion head together to 160 °C, keep for 1 h, then continuously extrude under a back pressure of 20 MPa to obtain the green body.

[0076] Vacuum degreasing, sintering: Put the green body into the vacuum furnace, vacuumize to 10 Pa or less, heat to 175 °C, keep for 3 h, then heat to 280 °C, keep for 3 h, complete degreasing. Continue to heat to 1100 °C, keep for 4 h, cool with the furnace, and the finished product is obtained.

[0077] Comparative Example 3

[0078] Prepare raw materials according to 40% porosity: 40% vol, 250um PMMA powder, 60% vol, 20um nickel powder, and 2% toughener corresponding to the total weight of PMMA powder.

[0079] The molecular weight of the PMMA powder is 500-1000 million, and the manufacturer is Arkema Altuglas;

[0080] The toughener is ethyl acrylate, and the molecular formula is C5H8O2;

[0081] Mixing: first, mechanically mix the PMMA powder and nickel powder for 10 min, then add the toughener and mix again for 30 min to obtain uniform powder,

[0082] Hot extrusion molding: the uniform powder is placed in the mold cylinder, which is heated to 160℃ together with the mold cylinder and extrusion head, and after 1h of heat preservation, continuous extrusion is carried out at a back pressure of 20Mpa, and the green body is obtained.

[0083] Vacuum debinding and sintering: the green body is placed in a vacuum furnace, vacuumed to below 10Pa, heated to 175℃, and heat preserved for 3h, then heated to 280℃, and heat preserved for 3h to complete debinding. Continue to heat to 1100℃, heat preserved for 4h, and cool down with the furnace to obtain the finished product.

[0084] Performance detection

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

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

[0087] Pore size, pore size, and molding effect specific detection data refer to Table 1

[0088] Table 1: Sample detection data table

[0089]

[0090]

[0091] Result analysis:

[0092] From the sample data of Examples 1-3, it can be concluded that the products with different porosities prepared by the technical scheme of the application have a very close actual porosity to the set porosity. The difference of Example 1 is only 0.8%, which proves that there is almost no pore former residue in the product, and the pore diameter of each product is as high as 230um-240um, which has excellent pore effect. In addition, the product obtained by continuous hot extrusion molding of the application is flat and solid after cooling, without cracking and collapse.

[0093] Examples 4-5 adjust the amount of plasticizer and toughening agent based on Example 1. It can be seen that within the range of plasticizer and toughening agent amount set by the application, porous nickel products with good pore forming effect and complete structure can be prepared.

[0094] Comparing the data of Comparative Example 1 and Example 3, it can be concluded that using compression molding instead of continuous hot basic molding can also have good porosity, but the pore diameter is very small, only 142um, which is 61% of the sample of Example 3.

[0095] Comparative Example 2 and Comparative Example 3 respectively cancel the toughening agent and the plasticizer on the basis of Example 1, from the corresponding data comparison, it is concluded that the product prepared after canceling the toughening agent and the plasticizer can keep the porosity and pore size effect, but the product without using the toughening agent has edge shrinkage and warping after cooling, and the product without using the plasticizer has fish scale cracks during extrusion and local collapse after cooling.

[0096] 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 thereof. 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 limitation is intended to the scope of the claims by the presence of any marked section.

Claims

1. A method for producing porous nickel, characterized by, Specifically comprising the following steps: Step 1: mixing 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 body; Step 3: vacuum debinding and vacuum sintering the green body obtained in step 2 to obtain a finished product; The forming is continuous hot extrusion forming; The volume ratio of the PMMA powder to the nickel powder is 40-80:20-60; The plasticizer is 2.5-3% of the weight of the PMMA powder, and the toughening agent is 4-5% of the weight of the PMMA powder; The continuous hot extrusion forming temperature in step 2 is 110-170℃, and the extrusion pressure is 5-50 MPa; The plasticizer is one or a combination of dioctyl phthalate, tributyl citrate, trioctyl trimellitate and dioctyl terephthalate; and the toughening agent is one or a combination of ethyl acrylate, butyl acrylate, liquid butyl nitrile rubber and styrene-butadiene emulsion.

2. The production method according to claim 1, characterized by, 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 vacuum debinding and sintering environment in step 3 is kept in vacuum all the time, and the vacuum degree is <10Pa.

4. The method of claim 1, wherein, The vacuum debinding temperature in step 3 is 160-180℃ for 1-3h, and 260-300℃ for 1-3h.

5. The preparation method according to claim 1, characterized in that, The vacuum sintering temperature in step 3 is 850-1300℃, and the holding time is 2-5h.

6. A porous nickel characterized by, The porous nickel is prepared by the method of any one of claims 1-5.

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