An ultrahigh-strength three-dimensional reticular graphene / amorphous carbon composite material and a preparation method thereof

Abstract

The application provides a super-high-strength three-dimensional net-shaped graphene / amorphous carbon composite material and a preparation method thereof, and belongs to the technical field of carbon materials.The preparation method comprises the following steps: using a two-step method, a hydrogel prepared from acrylamide, a water-soluble saccharide and N,N'-methylene bisacrylamide is sequentially subjected to pretreatment and sintering treatment, and finally, the super-high-strength novel carbon material is prepared; wherein the sintering treatment adopts discharge plasma sintering or hot-press sintering.Through the two-step method strategy, the bottleneck in the microstructure design of the traditional method is solved, the preparation period is significantly shortened, the production cost is reduced, the graphite-based carbon material with high strength and excellent mechanical properties is successfully prepared, and the further development of the graphite material in industrial applications is laid a foundation.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of carbon materials, and particularly relates to a super-high-strength three-dimensional network graphene / amorphous carbon composite material and a preparation method thereof. BACKGROUND

[0002] Graphite materials have been widely used in many fields due to their excellent performance, including high strength, high electrical conductivity, high temperature resistance and corrosion resistance, especially in high-end technical fields such as aerospace, electronics, metallurgy and nuclear industry, and have become important basic materials. In addition, graphite materials are also widely used in battery electrodes, heat-conducting materials, high-temperature-resistant components and catalyst carriers. With the progress of science and technology, the demand for graphite materials is growing, but the existing graphite material preparation process has many problems, which limits its further application.

[0003] At present, the preparation of traditional high-strength graphite block carbon materials has long cycle, high raw material cost and low material strength. Its preparation usually relies on coke and binder as starting materials, and goes through a complex and long carbonization and graphitization process, resulting in a long production cycle, and the control ability of the microstructure during the preparation process is limited, and the strength of the final material is also limited. Therefore, optimizing the structural design of graphite-based carbon materials and improving their performance are still the main challenges currently faced.

[0004] In order to improve the mechanical properties of graphite materials, traditional methods mainly improve the microstructure by purifying raw materials and introducing reinforcing agents. For example, using chemical methods to purify petroleum coke, or by introducing reinforcing agents such as sulfonated graphene to improve mechanical properties. In addition, through high-pressure methods or cold isostatic pressing technology, some studies have successfully controlled the transformation of graphite materials from sp 2 to sp 3 hybrid, further improving the bending and compressive strength of the material. However, these traditional processes still have bottlenecks in the design and control of microstructure, especially in how to effectively improve the strength of the material.

[0005] In recent years, the synthesis technology of carbon-based materials has made some progress, including the synthesis method of using fibers, aerogels and composites. However, these methods are prone to cracks and pores during the carbonization process due to significant shrinkage and stress of the material, making it difficult to prepare large block materials at a macroscopic size. Therefore, developing new preparation methods to solve these problems has become an important research direction in the field of carbon materials. SUMMARY

[0006] In order to solve the problems of complexity, long cycle, high cost of raw materials, poor mechanical properties and the like in the preparation process of the existing graphite block carbon material, the application provides a super-high-strength three-dimensional net-shaped graphene / amorphous carbon composite material and a preparation method thereof, that is, a new two-step strategy is adopted, a high-strength graphite / amorphous carbon composite material is synthesized by using polyacrylamide and a water-soluble saccharide hydrogel as starting materials, and the composite material has excellent mechanical properties, the compressive strength is up to 303 MPa, and the bending strength is up to 203 MPa, which is significantly better than that of traditional graphite-based materials.

[0007] In order to achieve the above object, the application provides the following technical scheme.

[0008] One of the technical schemes of the application is as follows:

[0009] A preparation method of a super-high-strength three-dimensional net-shaped graphene / amorphous carbon composite material, comprising the following steps:

[0010] The hydrogel prepared from acrylamide, a water-soluble saccharide and N,N'-methylene bisacrylamide is sequentially subjected to pretreatment and sintering treatment by adopting a two-step method, and finally the super-high-strength three-dimensional net-shaped graphene / amorphous carbon composite material is prepared.

[0011] The sintering treatment adopts discharge plasma sintering or hot-press sintering.

[0012] Preferably, the preparation process of the hydrogel is as follows:

[0013] The acrylamide, the water-soluble saccharide and the N,N'-methylene bisacrylamide are mixed and dissolved in deionized water to form a uniform solution by stirring, and then drying is performed at 50-200 DEG C to obtain the hydrogel.

[0014] Preferably, according to the weight percentage, the acrylamide, the water-soluble saccharide and the N,N'-methylene bisacrylamide are 1-30%, 5-60% and 0.05-3% respectively, and the balance is deionized water.

[0015] Preferably, according to the weight percentage, the acrylamide, the water-soluble saccharide and the N,N'-methylene bisacrylamide are 7.39%, 24.65% and 0.18% respectively.

[0016] Preferably, the water-soluble saccharide includes one or more of glucose, fructose, galactose, maltose, sucrose, lactose or fructooligosaccharide.

[0017] Preferably, the pretreatment process is as follows:

[0018] The hydrogel is subjected to heat treatment in a muffle furnace, and then a pretreatment product A is obtained.

[0019] The pretreatment product A is heated to 400-1400 DEG C at a heating rate of 1-20 DEG C / min in an inert environment, and then is kept at the temperature for 1h to obtain pretreatment product B;

[0020] The pretreatment product B is crushed and is ball milled in a ball mill to obtain pretreatment powder.

[0021] Preferably, the conditions of the heat treatment process are as follows:

[0022] The temperature is raised to 140-350 DEG C at a heating rate of 0.1-20 DEG C / min, and is kept at the target temperature for 0.5-30h after reaching the target temperature.

[0023] Preferably, the conditions of the heat treatment process are as follows: the temperature is raised to 220 DEG C at a heating rate of 0.5 DEG C / min, and is kept at the target temperature for 2h after reaching the target temperature.

[0024] Preferably, the inert environment is vacuum or argon or nitrogen.

[0025] Preferably, the ball milling treatment conditions are as follows: the ball-to-material ratio is 1-20:1, the ball milling rotation speed is 100-600r / min, and the ball milling time is 6-48h.

[0026] Preferably, the ball milling treatment conditions are as follows: the ball-to-material ratio is 3:1, the ball milling rotation speed is 200r / min, and the ball milling time is 16h.

[0027] Preferably, the sintering process parameters are as follows: the heating rate is 5-300 DEG C / min, the sintering temperature is 1600-2800 DEG C, the applied pressure is 10-200MPa, and the holding time is 1-120min.

[0028] Preferably, the sintering process parameters are as follows: the heating rate is 150 DEG C / min, the sintering temperature is 2400 DEG C, the applied pressure is 60MPa, and the holding time is 10min.

[0029] The second technical scheme of the present application is as follows:

[0030] The above preparation method is used to prepare a super-high-strength three-dimensional net-shaped graphene / amorphous carbon composite material.

[0031] Compared with the prior art, the present application has the following advantages and technical effects:

[0032] The application discloses a kind of superhigh-strength three-dimensional net-shaped graphene / amorphous carbon composite material and preparation method thereof, using two-step method strategy, by acrylamide and glucose hydrogel as starting material, synthesis high-strength graphite / amorphous carbon composite material.Experiments show that acrylamide preferentially occurs graphitization reaction, forms internal network structure, and using the different graphitization tendency of acrylamide and glucose, three-dimensional net-shaped graphene / amorphous carbon composite material can be constructed.This new composite material shows excellent mechanical properties, compressive strength can be as high as 303MPa, bending strength can reach 203MPa, significantly better than traditional graphite-based materials.This method provides a new way for the development of high-strength graphite-based carbon materials.

[0033] By the two-step method strategy of the application, not only the bottleneck in the microstructure design of traditional methods is solved, but also the preparation period is significantly shortened, the production cost is reduced, and the graphite-based carbon material with high strength and excellent mechanical properties is successfully prepared, which lays a foundation for the further development of graphite materials in industrial applications. BRIEF DESCRIPTION OF DRAWINGS

[0034] The accompanying drawings, which form a part of this application, are included to provide a further understanding of the application and are incorporated in and constitute a part of this application. The embodiments of the application illustrated in the drawings are presented to explain the present application and should not be considered as posing limitations to the present application. In the drawings:

[0035] Figure 1 The bending strength curve diagram of the three-dimensional net-shaped graphene / amorphous carbon composite material prepared for Example 1;

[0036] Figure 2 The compressive strength curve diagram of the three-dimensional net-shaped graphene / amorphous carbon composite material prepared for Example 1;

[0037] wherein Figure 1 and Figure 2 1#, 2#, 3# of the three-dimensional net-shaped graphene / amorphous carbon composite material prepared for Example 1 are three tests of the same sample;

[0038] Figure 3 The microstructure diagram of the three-dimensional net-shaped graphene / amorphous carbon composite material prepared for Example 1;

[0039] Figure 4 The wear rate diagram of the three-dimensional net-shaped graphene / amorphous carbon composite material prepared for Example 1. DETAILED DESCRIPTION

[0040] Now, various exemplary embodiments of the present application will be described in detail, which should not be considered as limiting the present application, but should be understood as a more detailed description of certain aspects, characteristics and embodiments of the present application.

[0041] It is to be understood that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the present application. Additionally, for a range of values of, for example, concentrations, amounts, and other

[0042] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. Although methods and materials similar or equivalent to those described herein can be used in the practice or testing of the present application, preferred methods and materials are described. All publications mentioned herein are incorporated by reference to disclose and describe the methods and / or materials in connection with which the publications are cited. The citation of any reference is not an admission that it is prior art with respect to the present application.

[0043] Many modifications and variations of this application can be made in the light of the above teachings without departing from the spirit and scope thereof. Additional implementations of the application will be apparent to those skilled in the art from consideration of the specification and practice of the application disclosed herein. For example, one of ordinary skill in the art can readily combine the various aspects of the application without departing from the scope of the application. Therefore, the specification and examples should be regarded as illustrative rather than restrictive, and all such modifications are intended to be included within the scope of the application.

[0044] As used herein, the terms "comprise", "comprising", "include", "including", "have", "having" and the like are open-ended and do not exclude additional, unrecited elements or method steps.

[0045] The present application selects acrylamide and water-soluble saccharide as starting materials, and uses a two-step method to prepare high-strength graphite / amorphous carbon composite materials. The specific three-dimensional network graphene / amorphous carbon composite material preparation method comprises the following steps:

[0046] (1) Raw material weighing for standby: according to the weight percentage, acrylamide: water-soluble saccharide: N, N'-methylene bisacrylamide = (1-30%) : (5-60%) : (0.05-3%), and the rest is deionized water;

[0047] (2) Pretreatment process:

[0048] 21) Acrylamide, water-soluble saccharide and N, N'-methylene bisacrylamide are mixed and dissolved in deionized water, stirred to form a uniform solution; the solution is gelled and dried at 50-200°C to obtain a hydrogel; the hydrogel is then heat treated in a muffle furnace, and then a pretreatment product A is obtained;

[0049] 22) the pretreatment product A is treated in an inert environment at 400-1400°C for 1 hour to obtain a pretreatment product B;

[0050] 23) the pretreatment product B is crushed and ball-milled in a ball mill to obtain a pretreatment powder;

[0051] (3) the pretreatment powder is loaded into a C / C composite mold with a diameter of 10-100 mm and sintered by spark plasma sintering (SPS) or hot-pressing sintering.

[0052] In some preferred embodiments, the water-soluble sugar includes one or more of glucose, fructose, galactose, maltose, sucrose, lactose, or fructooligosaccharide.

[0053] In some preferred embodiments, the acrylamide: water-soluble sugar: N, N'- methylenebisacrylamide is 7.39%: 24.65%: 0.18% by weight percentage.

[0054] In some preferred embodiments, the temperature during the drying process in step (2) is 60°C.

[0055] In some preferred embodiments, the conditions of the heat treatment process in step 21) are:

[0056] The temperature is raised at a rate of 0.1-20°C / min to 140-350°C, and the temperature is maintained at the target temperature for 0.5-30 hours.

[0057] In some preferred embodiments, the conditions of the heat treatment process in step 21) are: the temperature is raised at a rate of 0.5°C / min to 220°C, and the temperature is maintained at the target temperature for 2 hours.

[0058] In some preferred embodiments, the inert environment in step 22) is vacuum or argon or nitrogen.

[0059] In some preferred embodiments, the ball-milling process conditions in step 23) are: the ball-to-material ratio is 1-20:1, the ball-milling rotation speed is 100-600 r / min, and the ball-milling time is 6-48 hours.

[0060] In some preferred embodiments, the ball-milling process conditions in step 23) are: the ball-to-material ratio is 3:1, the ball-milling rotation speed is 200 r / min, and the ball-milling time is 16 hours.

[0061] In some preferred embodiments, the parameters of the sintering process are: the temperature raising rate is 5-300°C / min, the sintering temperature is 1600-2800°C, the applied pressure is 10-200 MPa, and the holding time is 1-120 minutes.

[0062] In some preferred embodiments, the parameters of the sintering process are: a heating rate of 150℃ / min, a sintering temperature of 2400℃, an applied pressure of 60MPa, and a holding time of 10min.

[0063] The bulk carbon material with high density prepared through the process not only has excellent mechanical properties, but also overcomes the complexity and long cycle of the traditional graphite bulk material preparation process, and realizes high strength and high wear resistance of the material.

[0064] The "room temperature" in the present application refers to 20-30℃ unless otherwise specified.

[0065] The "parts" in the present application refer to mass parts unless otherwise specified.

[0066] The raw materials used in the present application are commercially available.

[0067] The technical solutions of the present application are further described below through examples.

[0068] Example 1

[0069] A preparation method of a three-dimensional reticular graphene / amorphous carbon composite material, comprising the following steps:

[0070] The first step is a pretreatment step, 200g of glucose, 60g of acrylamide and 1.5g of N,N'-methylenebisacrylamide are mixed and dissolved in 550g of deionized water, and stirred for 60min to form a clear solution. Then the solution is placed in an oven at 60℃ for gelation and drying for 24h to obtain a hydrogel. The obtained hydrogel is heated to 220℃ at a heating rate of 0.5℃ / min in a muffle furnace, and kept at this temperature for 2h, and then cooled in the furnace to obtain a pretreated product PG-220. Then, the PG-220 sample is heated to 900℃ at a heating rate of 4℃ / min, and kept at this temperature for 1h to obtain the corresponding product PG-900. The pretreated PG-900 sample is crushed and ball milled under the condition of a ball-to-material ratio of 3:1, and the ball milling speed is 200r / min.

[0071] The second step is a sintering step, the ball milled sample powder is placed in a C / C composite material mold with a diameter of 20mm, and sintered by using a spark plasma sintering technology. The sintering parameters are a heating rate of 150℃ / min, a sintering temperature of 2400℃, a sintering pressure of 60MPa, and a holding time of 10min; and then cooled in the furnace. Through this sintering process, a dense high-strength bulk carbon material is finally obtained, Figure 1 and Figure 2 which is the carbon material prepared in Example 1.

[0072] Example 2

[0073] A preparation method of a three-dimensional network graphene / amorphous carbon composite material, the difference from Example 1 is that the water-soluble sugar glucose is replaced by sucrose, and the PG-220 sample is heated to 500℃ at a heating rate of 4℃ / min; other preparation conditions are the same as in Example 1.

[0074] Example 3

[0075] A preparation method of a three-dimensional network graphene / amorphous carbon composite material, the difference from Example 1 is that the sintering method is replaced from spark plasma sintering to hot-pressing sintering, and the specific condition parameters are: heating rate is 10℃ / min, sintering temperature is 2300℃, sintering pressure is 40MPa, and holding time is 120min. Other preparation conditions are the same as in Example 1.

[0076] Comparative Example 1

[0077] This comparative example uses the preparation process of CN 115849362A to prepare carbon materials, and the specific steps are:

[0078] Step one, preparation of mixed solution, initiation of gel and preliminary dehydration:

[0079] Take 1.2g of analytical pure N,N'-methylene bisacrylamide into a beaker, add 90g of deionized water, stir to dissolve and clarify, then heat and stir in a 60℃ water bath, slowly add 180g of analytical pure glucose monohydrate, dissolve to clarify, then naturally cool to 40℃, slowly add 36g of analytical pure acrylamide, continue to stir until the solution is clear, to obtain a mixed solution; add 0.6g of 10wt% concentration ascorbic acid aqueous solution and 5wt% concentration hydrogen peroxide aqueous solution into the mixed solution, respectively, stir quickly and uniformly, then pour into a mold and wait for gelation, take out after the heat release of the gel is over, to obtain a hydrogel block, cut into pieces and place in a 100℃ oven for drying and dehydration for 48h, to obtain a dry gel;

[0080] Step two, gel heat treatment and powder preparation:

[0081] A large amount of free water removed xerogel is placed in the inner liner of the reaction kettle, and analytical pure acetone is poured to the 2 / 3 of the volume, and is tightly covered and sealed in the outer liner. The sealed reaction kettle is placed in the oven, and the program is set to 200℃ for 8h. After the heat preservation is completed, it is cooled to room temperature. The block material in the reaction kettle is taken out, and the surface liquid is dried. The block material taken out is mechanically crushed, and particles below 20 meshes are screened out. Two parts are evenly divided and poured into two 1L planetary ball mills. The material ball ratio is 1:1, and the matching zirconia ball milling beads account for 1 / 3 of the volume. The ball milling medium is zirconia beads with particle sizes of 5mm, 10mm and 15mm, and the mass ratio of zirconia beads with particle sizes of 5mm, 10mm and 15mm is 5:3:2. The parameter setting of the planetary ball mill is as follows: first run at 500r / min for 10min, then adjust to 360r / min and continue to run for 6h, then stop. The ground powder is sieved through a 100 mesh sieve and stored to prevent moisture. About 76g of powder raw material can be screened in each tank.

[0082] Step three, warm compaction, carbonization and graphitization:

[0083] 32g of the prepared raw powder is weighed and loaded into a Φ50mm graphite mold for warm compaction. Slowly load and heat at a rate of 3℃ / min while uniaxially pressing, and heat at 180℃, 220℃, 260℃ and the highest temperature of 300℃ for 30min respectively, then reduce to 220℃ at a rate of 2℃ / min, and then naturally cool to room temperature. The preform is obtained. The pressure reaches a peak of 8 tons before 260℃ heat preservation, and slowly decreases to 6 tons before 300℃ heat preservation. No additional load is applied during the cooling stage. The temperature is unloaded when it drops below 200℃. After cooling to room temperature, the compacted blank is taken out. The mass of the blank is about 27g at this time.

[0084] The compacted blank is placed in a 1000℃ argon atmosphere tube furnace for 1h to obtain a carbonized block. The heating rate is 3℃ / min, and the cooling rate is 2℃ / min. The temperature is naturally cooled to 400℃. The carbonized block is then subjected to a graphitization treatment at 3000℃ for 10h, and finally cooled to room temperature to obtain a graphitized block. From the compacted block to the graphitized block.

[0085] The compressive strength of the carbon material prepared according to the above steps is 112MPa; the bending strength is 57MPa. By comparing the mechanical effect data of the three samples in Example 1, it can be seen that the mechanical strength of the carbon material prepared in Comparative Example 1 is much lower than that of the three-dimensional net-like graphene / amorphous carbon composite material prepared in Example 1.

[0086] Figure 1 The bending strength curve of the three-dimensional net-like graphene / amorphous carbon composite material of Example 1;

[0087] Figure 2 A compression strength curve of the three-dimensional reticular graphene / amorphous carbon composite material prepared in Example 1 is shown in the following figure:

[0088] Figure 3 A microstructure of the three-dimensional reticular graphene / amorphous carbon composite material prepared in Example 1 is shown in the following figure:

[0089] Figure 4 A wear rate of the three-dimensional reticular graphene / amorphous carbon composite material prepared in Example 1 is shown in the following figure. During the friction and wear test, the pure carbon block sample was contacted with the alumina ball by linear reciprocating motion at room temperature, the load was set to 5 N, the friction speed was 0.1 m / s, the stroke was 2.5 mm, and the friction lasted for 60 minutes. Figure 4 As can be seen from the figure, the volume wear rate of the three-dimensional reticular graphene / amorphous carbon composite material prepared in Example 1 is 2.63 x 10 -8 mm 3 / (Nm), which proves that the three-dimensional reticular graphene / amorphous carbon composite material prepared by the present application has high wear resistance.

[0090] In summary, the above results show that the two-step strategy adopted by the present application successfully prepares the graphite / amorphous carbon composite material with excellent mechanical properties. By using polyacrylamide and water-soluble sugar hydrogel as starting materials, the prepared composite material has a compressive strength of up to 303 MPa and a bending strength of up to 203 MPa (Example 1), which is significantly better than traditional graphite-based carbon materials and the carbon material prepared in Comparative Example 1. That is, the present application effectively solves the problems of traditional graphite block carbon materials, such as complex preparation process, long cycle, high raw material cost, poor mechanical properties, etc. At the same time, by simplifying the process flow, the production cost is reduced, the preparation cycle is shortened, and the bottleneck of the prior art in the design of material microstructure is broken through. The high strength and high performance of the composite material lay a foundation for the wide application of graphite-based materials in the industrial field, especially in the fields of aerospace, electronics, metallurgy, etc. have great application potential. Therefore, the present application not only has significant technical advantages, but also has high economic and social benefits.

[0091] The above merely provides the preferred specific embodiments of the present application, but the protection scope of the present application is not limited thereto, and any changes or replacements within the technical scope disclosed by the present application can be easily thought of by those skilled in the art, which should be covered within the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims.

Claims

1. A method for preparing an ultra-high strength three-dimensional network graphene / amorphous carbon composite material, characterized in that, Includes the following steps: A two-step method was used to pretreat and sinter the hydrogel prepared from acrylamide, water-soluble sugars, and N,N'-methylenebisacrylamide in sequence, and finally the ultra-high strength three-dimensional network graphene / amorphous carbon composite material was prepared. The sintering process is performed by discharge plasma sintering or hot pressing sintering. The preprocessing process is as follows: The hydrogel is subjected to heat treatment to obtain pretreated product A; the conditions of the heat treatment process are: heating to 140-350℃ at a heating rate of 0.1-20℃ / min, and holding at the target temperature for 0.5-30h after reaching the target temperature. The pretreated product A was heated to 900°C in an inert environment at a heating rate of 1~20°C / min, and then kept at this temperature for 1 hour to obtain the pretreated product B. The pretreated product B is crushed and ball-milled to obtain pretreated powder; the ball milling conditions are: ball-to-material ratio 1-20:1, ball milling speed 100-600 r / min, and ball milling time 6-48 h. The parameters for the sintering process are: heating rate 5-300℃ / min, sintering temperature 1600-2800℃, applied pressure 10-200MPa, and holding time 1-120min.

2. The method for preparing an ultra-high strength three-dimensional network graphene / amorphous carbon composite material according to claim 1, characterized in that, The preparation process of the hydrogel is as follows: The acrylamide, water-soluble sugars, and N,N'-methylenebisacrylamide were mixed and dissolved in deionized water and stirred until homogeneous; then dried at 50-200°C to obtain a hydrogel.

3. The method for preparing an ultra-high strength three-dimensional network graphene / amorphous carbon composite material according to claim 1, characterized in that, The acrylamide, water-soluble sugars, and N,N'-methylenebisacrylamide are used in amounts of 1-30%, 5-60%, and 0.05-3% by weight, respectively, with the remainder being deionized water.

4. The method for preparing an ultra-high strength three-dimensional network graphene / amorphous carbon composite material according to claim 3, characterized in that, The amounts of acrylamide, water-soluble sugars, and N,N'-methylenebisacrylamide, by weight percentage, are 7.39%, 24.65%, and 0.18%, respectively.

5. The method for preparing an ultra-high strength three-dimensional network graphene / amorphous carbon composite material according to claim 1, characterized in that, The inert environment is a vacuum, argon, or nitrogen.

6. A high-strength three-dimensional network graphene / amorphous carbon composite material, characterized in that, It is prepared according to any one of claims 1-5.

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