CN109054741B - Preparation method of cobalt-nickel alloy particle/reduced graphene composite material with sandwich structure - Google Patents
Preparation method of cobalt-nickel alloy particle/reduced graphene composite material with sandwich structure Download PDFInfo
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Abstract
The invention belongs to the technical field of nano functional materials, and particularly relates to a preparation method of a cobalt-nickel alloy particle/reduced graphene composite material with a sandwich structure. According to the method, graphene oxide is selected as a carbon base for cobalt-nickel ion chelation growth, cobalt-nickel alloy particles with the size distribution of 0.2-1.2 mu m are prepared by changing the types of a chelating agent and a pH regulator and the concentration of a precursor solution, and are chelated and dispersed on the surface of reduced graphene; and then, obtaining the cobalt-nickel alloy/reduced graphene composite material with a sandwich structure through subsequent freeze drying treatment. The composite material shows excellent loss performance in the microwave absorption field, particularly when the average size of the cobalt-nickel alloy particles dispersed in the composite is 0.8 mu m, the maximum microwave loss can reach-54.4 dB (the secondary microwave absorption peak is-45.4 dB), the bandwidth is as high as 4 GHz, and the composite material is used as a novel microwave absorbing material for microwave absorption and has a wide application prospect.
Description
Technical Field
The invention belongs to the technical field of compound preparation, and particularly relates to a preparation method of a sandwich-shaped large-size adjustable cobalt-nickel alloy particle/reduced graphene compound and application of the compound in the field of microwave absorption.
Background
Recently, rapidly developed information science facilitates human life, and promotes the emergence of a large number of electronic technology products, such as network televisions, mobile phones, 3G/4G, wireless networks and the like. Electromagnetic technology has been applied to various fields in human social life, the most important of which is its application in the fields of national defense safety and military development. However, due to their wide spread, they also pose very serious problems of electromagnetic pollution[1]. Electromagnetic waves asA high-energy particle beam has serious influence on human health and environment, and the phenomenon of electromagnetic interference is common in human society for a long time. Moreover, the emergence of stealth materials has very important strategic significance for national defense of every country. All the reasons are compelling to lead scientists all over the world to start a hot research on wave-absorbing materials. Wave-absorbing materials are those that absorb electromagnetic waves and convert them into other forms of energy (primarily thermal energy) without reflection[2]. After the nano material is small to a certain extent, the periodic boundary conditions of the material are destroyed by quantum size effect, tunneling effect, small size effect, dielectric confinement effect and the like, so that the nano material has many different characteristics and performances compared with the conventional material series, such as: the physical properties (acousto-optic electromagnetic and thermodynamic characteristics) of the material are obviously changed along with the reduction of the size[3-5]. On the other hand, the specific surface area of the nano particle material is 3-4 orders of magnitude larger than that of the conventional coarse powder, and the absorptivity of the nano particle material to infrared light and electromagnetic waves is much larger than that of the conventional material, so that the intensity of reflected signals obtained by an infrared detector and a radar is greatly reduced, and a detection target is difficult to find to play a stealth role. Nano material has become one of the most potential wave-absorbing materials[6-9]。
Generally speaking, we can classify wave-absorbing materials into two categories according to the loss mechanism of the material to electromagnetic waves: magnetic loss materials and dielectric loss materials. Magnetic loss materials refer to transition metals (cobalt, iron, nickel) and their oxides, such as: ferroferric oxide, cobalt-nickel alloys, and the like[10](ii) a The dielectric material refers to carbon nanotubes, molybdenum disulfide, titanium dioxide, and the like. They have good absorption capacity for electromagnetic waves[11]. However, according to the principle of wire transmission, the absorption performance of pure magnetic materials or pure dielectric materials for electromagnetic waves has a bottleneck as the matching principle is easier to be not satisfied: the absorption intensity is small, and the absorption frequency band is narrow. Many researchers have tried to combine dielectric and magnetically lossy materials to match impedances and use their synergistic effect to achieve strong absorption of electromagnetic waves, such as composite denier car-kernel ultrasoundThe subject group utilizes magnetic materials of ferroferric oxide, cobalt-nickel alloy and various dielectric materials (titanium dioxide, manganese dioxide and the like) to combine and absorb waves, obtains very superior wave absorption loss performance, and solves the problem that single-component materials are not strong in wave absorption capacity. At present, although small-sized cobalt-nickel alloy and graphene oxide are chelated for wave absorption, the application of the cobalt-nickel alloy in the field is severely limited due to the problems of poor dispersity, general wave absorption performance, narrow absorption band and the like. Based on the method, a series of large-size cobalt-nickel alloy particles/reduced graphene composites with sandwich structures are prepared. By changing the size of the magnetic particles, the saturation magnetization, the electromagnetic parameters and the internal structure of the composite become adjustable, thereby achieving better absorption of electromagnetic waves. The graphene is characterized in that the cobalt-nickel alloy provides strong magnetic loss (magnetic coupling effect caused by high-density cobalt-nickel alloy particles, irreversible magnetic domain motion, magnetic resonance, natural resonance, magnetic impedance behavior caused by magnetism and the like), the graphene provides dielectric loss (molecules with different series of polarizabilities, dipole polarization in the arrangement direction of functional groups, dipole relaxation process of dipoles, too many interfaces between cobalt-nickel metal and graphene, interface polarization, internal potential caused by the series of electron accumulation states between reduced graphene layers causes resistance loss and eddy current loss, and dipoles or resistance loss and the like caused by defects in the reduction process of the graphene. The composite almost simultaneously meets four requirements of being used as a microwave absorbing material, and has simple synthesis and low cost.
Disclosure of Invention
The invention aims to overcome the reported defects of the application of the ultra-small and single-size cobalt-nickel alloy and graphene chelate complex in the microwave absorption field, such as structural disorder[13]Agglomeration of particles[14]Poor performance[14]And the like, and provides a preparation method of the large-size adjustable submicron cobalt-nickel alloy particle/reduced graphene composite material with a sandwich structure.
According to the preparation method of the cobalt-nickel alloy particle/reduced graphene composite material with the sandwich structure, the size of the loaded cobalt-nickel alloy particle is changed by simultaneously changing the types of the PH regulator and the chelating agent and adjusting the concentration of the precursor solution, and the average particle size of the cobalt-nickel alloy in the prepared composite material is controlled to be 0.2-1.2 mu m. The method comprises the following specific steps:
(1) firstly, ultrasonically dispersing 40 +/-3 mg of graphene oxide in 20 +/-3 mL of ethylene glycol for 30 +/-5 min, adding 0.05 +/-0.03 g of cobalt acetate, stirring for dissolving, adding 0.2 +/-0.08 g of nickel acetate, and stirring to dissolve to obtain a solution A;
(2) slowly dripping 20 +/-3 mL of glycol solution in which 0.12 +/-0.05 g of citric acid is dissolved into the solution A; slowly dripping the solution at the speed of 8-15 seconds per drop, and then carrying out ultrasonic treatment on the solution for 40 +/-5 minutes to obtain a reaction solution;
(3) transferring the reaction solution into a reaction kettle, heating to 210 +/-10 ℃, and reacting for 12-15 h; after the hydrothermal kettle is cooled, washing the hydrothermal kettle for a plurality of times by using deionized water and absolute ethyl alcohol, and carrying out centrifugal separation to obtain a viscous cobalt-nickel/reduced graphene compound;
(4) and (4) placing the compound obtained in the step (3) in 20 +/-10 mL of deionized water, and carrying out freeze drying for 24 +/-1 h by using a freeze dryer to finally obtain the cobalt-nickel alloy particle/reduced graphene compound with the sandwich structure.
Generally, the average particle size of cobalt-nickel alloy particles in the composite obtained according to the above steps is 0.2 to 0.6 μm.
The invention further replaces the step (2) with the following steps: (2) slowly dripping 20 +/-3 mL of diglycol solution in which 0.12 +/-0.05 g of sodium hydroxide is dissolved into the solution A; slowly dripping liquid at the speed of 8-15 seconds per drop, then carrying out ultrasonic treatment on the solution for 40 +/-5 minutes to obtain a reaction liquid, and finally obtaining the cobalt-nickel alloy particle/reduced graphene composite with the sandwich structure by the same other steps.
Typically, the average particle size of the cobalt-nickel alloy particles in the composite thus obtained is 0.3 to 0.6 μm.
The invention further replaces the step (2) with the following steps: (2) slowly dripping 20 plus or minus 3 mL of glycol solution dissolved with 0.12 plus or minus 0.05 g into the solution A; slowly dripping liquid at the speed of 8-15 seconds per drop, then carrying out ultrasonic treatment on the solution for 40 +/-5 minutes to obtain a reaction liquid, and finally obtaining the cobalt-nickel alloy particle/reduced graphene composite with the sandwich structure by the same other steps.
Generally, the average particle size of cobalt-nickel alloy particles in the composite obtained by the method is 0.8-1.2 mu m.
The preparation method provided by the invention can be used for obtaining the cobalt-nickel alloy particle/reduced graphene composite material with a sandwich structure, and the size of the loaded cobalt-nickel alloy particle is adjustable. By changing the pH regulator citric acid, the chelating agent diethylene glycol and the concentration of the precursor solution, the average particle size of the prepared cobalt-nickel alloy is 0.2-1.2 mu m (for example, 0.2 mu m, 0.5 mu m, 0.8 mu m and 1.2 mu m respectively).
The invention can change the size of the magnetic particles to adjust the saturation magnetization, electromagnetic parameters and internal structure of the compound, thereby achieving better absorption of electromagnetic waves. The graphene is characterized in that the cobalt-nickel alloy provides strong magnetic loss (magnetic coupling effect caused by high-density cobalt-nickel alloy particles, irreversible magnetic domain motion, magnetic resonance, natural resonance, magnetic impedance behavior caused by magnetism and the like), the graphene provides dielectric loss (molecules with different series of polarizabilities, dipole polarization in the arrangement direction of functional groups, dipole relaxation process of dipoles, too many interfaces between cobalt-nickel metal and graphene, interface polarization, internal potential caused by the series of electron accumulation states between reduced graphene layers causes resistance loss and eddy current loss, and dipoles or resistance loss and the like caused by defects in the reduction process of the graphene. The composite almost simultaneously meets four requirements of being used as a microwave absorbing material, and has simple synthesis and low cost.
Particularly, when the average size of the cobalt-nickel alloy particles dispersed in the composite is 0.8 mu m, the maximum microwave loss can reach-54.4 dB (the secondary microwave absorption peak is-45.4 dB), the bandwidth is as high as 4 GHz, and the composite is used as a microwave absorbing material with a better effect.
The cobalt-nickel alloy/reduced graphene composite material with the sandwich structure prepared by the invention can be used for microwave absorption, and comprises the following specific steps: dispersing the adjustable large-size cobalt-nickel alloy particles/reduced graphene compound in paraffin according to the mass fraction of 1:6 (compound: paraffin), pouring the mixture into an aluminum template, pressing the mixture into a sample with the inner diameter of 3 mm and the outer diameter of 7 mm and the thickness of 2 mm, and then putting the sample into a network vector instrument to measure the reflection loss of the sample.
The shape and the size of the material are characterized by a scanning electron microscope (SEM, Hitachi FE-SEM S-4800 operated at 1 kV); and (3) characterization by using a transmission electron microscope (TEM, JEOL JEM-2100F operated at 200 kV), Selected Area Electron Diffraction (SAED), energy loss spectroscopy (EDS) and microstructure information. The X-ray diffraction spectra were measured on a Bruker D8X-ray diffractometer (Germany) with Ni-filter Cu KR radiation operated at 40 kV and40 mA.
The series of size-adjustable cobalt-nickel alloy particles/reduced graphene composites with sandwich structures are used in microwave absorption or electromagnetic shielding devices, and are good in absorption effect and low in cost.
Drawings
FIGS. 1 a-d are SEM images of a series of different size distributions of cobalt-nickel alloys synthesized by a one-step hydrothermal method under otherwise identical conditions without addition of graphene oxide.
FIGS. 2 a-d are size tunable cobalt nickel alloy particles/reduced graphene composites rGO/CN with sandwich structure4Scanning Electron Micrograph (SEM) of-x, it can be seen that the series of composites has graphene/CoNi4graphene/CoNi4A sandwich structure which is arranged and covered in a multilayer way.
FIG. 3 shows a size-adjustable cobalt-nickel alloy particle/reduced graphene composite rGO/CN with a sandwich structure4The X-ray diffraction (XRD) pattern of the X can reflect the information of the crystalline phase, the purity, the crystallinity and the like of the product more accurately.
FIG. 4 shows a size-adjustable cobalt-nickel alloy particle/reduced graphene composite rGO/CN with a sandwich structure4Characterization of the magnetic properties of x at 300K. Can be reflected quite clearly in: as the size of cobalt-nickel alloy particles increases, their magnetic properties change accordingly.
FIG. 5 shows a size-adjustable cobalt-nickel alloy particle/reduced graphene composite rGO/CN with a sandwich structure4X curve of the maximum reflection loss at the corresponding thickness, the abscissa representing the frequency of the electromagnetic wave and the ordinate representing the reflection loss.
Detailed Description
Example 1:
(1) size-adjustable cobalt-nickel alloy particle/reduced graphene composite rGO/CN with sandwich structure4-0.2：
First, 40 mg of graphene oxide was ultrasonically dispersed in 20 mL of ethylene glycol at room temperature for 30 minutes, then 0.05 g of cobalt acetate and 0.2 g of nickel acetate were added in this order and dissolved, respectively, and then 20 mL of ethylene glycol (PH-sensitive) in which 0.125 g of citric acid was dissolved was slowly dropped at a rate of 10 seconds per drop. Pouring the solution into a reaction kettle, heating to 210 ℃, and reacting for 13 h;
after the hydrothermal kettle is cooled, washing the hydrothermal kettle for a plurality of times by using deionized water and absolute ethyl alcohol, performing centrifugal separation, and then performing cold drying on the hydrothermal kettle for 24 hours in a freeze dryer to finally obtain cobalt-nickel alloy particles with a sandwich structure, wherein the average size of the particles is 0.2 mu m, and the reduced graphene composite rGO/CN4-0.2。
Example 2:
(2) size-adjustable cobalt-nickel alloy particle/reduced graphene composite rGO/CN with sandwich structure4-synthesis of 0.5:
firstly, 40 mg of graphene oxide is ultrasonically dispersed in 10 mL of ethylene glycol and 10 mL of monoethylene glycol at room temperature for 30 min, then 0.05 g of cobalt acetate and 0.2 g of nickel acetate are sequentially added and respectively dissolved, and then a mixed solution of 10 mL of ethylene glycol and 10 mL of monoethylene glycol (pH is alkaline) in which 0.12 g of sodium hydroxide is dissolved is slowly dropped, wherein the dropping speed is 10 s/drop. Pouring the solution into a reaction kettle, heating to 210 ℃, and reacting for 13 h;
after the hydrothermal kettle is cooled, washing the hydrothermal kettle for a plurality of times by deionized water and absolute ethyl alcohol, centrifugally separating, and then carrying out freeze drying on the hydrothermal kettle for 24 hours in a freeze dryer to finally obtain the product with the molecular weight of IIICobalt-nickel alloy particles/reduced graphene composite rGO/CN with average particle size of about 0.5 mu m for a Mingzhi structure4-0.5 complex.
Example 3:
(3) size-adjustable cobalt-nickel alloy particle/reduced graphene composite rGO/CN with sandwich structure4-synthesis of 0.8:
firstly, 40 mg of graphene oxide is ultrasonically dispersed in 20 mL of ethylene glycol at room temperature for 30 min, then 0.02 g of cobalt acetate and 0.08 g of nickel acetate are respectively added and dissolved in sequence, and then 20 mL of ethylene glycol (pH is alkaline) in which 0.12 g of sodium hydroxide is dissolved is slowly added dropwise at a dropping speed of 10 s/drop. Pouring the solution into a reaction kettle, heating to 210 ℃, and reacting for 13 h;
after the hydrothermal kettle is cooled, washing the hydrothermal kettle for a plurality of times by using deionized water and absolute ethyl alcohol, performing centrifugal separation, and then performing freeze drying on the hydrothermal kettle for 24 hours in a freeze dryer to finally obtain the cobalt-nickel alloy particles/reduced graphene composite rGO/CN with a sandwich structure and the average particle size of about 0.8 mu m4-0.8。
Example 4:
(3) size-adjustable cobalt-nickel alloy particle/reduced graphene composite rGO/CN with sandwich structure4-synthesis of 1.2:
first, 40 mg of graphene oxide was ultrasonically dispersed in 20 mL of ethylene glycol at room temperature for 30 minutes, then 0.05 g of cobalt acetate and 0.2 g of nickel acetate were added in this order and dissolved, respectively, and then 20 mL of ethylene glycol (PH-sensitive alkaline) in which 0.12 g of sodium hydroxide was dissolved was slowly dropped at a rate of 10 seconds per drop. Pouring the solution into a reaction kettle, heating to 210 ℃, and reacting for 13 h;
after the hydrothermal kettle is cooled, washing the hydrothermal kettle for a plurality of times by deionized water and absolute ethyl alcohol, performing centrifugal separation, and then performing cold drying on the hydrothermal kettle for 24 hours in a freeze dryer, wherein the cobalt-nickel alloy particles/reduced graphene composite rGO/CN with a sandwich structure and particle size of about 1.2 mu m4-1.2。
Size-adjustable cobalt-nickel alloy particle with sandwich structureParticle/reduced graphene complex rGO/CN4The morphology and size of the synthesis of-x are characterized by scanning electron microscopy (SEM, Hitachi FE-SEM S-4800 operated at 1 kV) and is made by spraying the oven dried sample powder directly onto a conductive gel. The Selected Area Electron Diffraction (SAED), energy loss spectroscopy (EDS) and microstructure information of the composite series are characterized by a transmission electron microscope (TEM, JEOL JEM-2100F operated at 200 kV), and a sample of the TEM is prepared by mixing graphene/CoNi4graphene/CoNi4The layered composite coated with the @ graphene multilayer arrangement was dispersed in an ethanol solution, and then 6 μ L of the solution was dropped onto a carbon-supported copper mesh. The X-ray diffraction spectra were measured on a Bruker D8X-ray diffractometer (Germany) with Ni-filter Cu KR radiation operated at 40 kV and40 mA.
FIGS. 1 a-d are SEM images of a series of sizes of cobalt-nickel particles synthesized by a one-step hydrothermal method, wherein a is a cobalt-nickel particle hydrothermally synthesized by using citric acid as a pH regulator, and the average size of the cobalt-nickel particle is about 0.2 mu m; if half of the reducing solvent is diethylene glycol, cobalt and nickel with the particle size uniformly distributed about 0.5 mu m can be synthesized by us as shown in a figure b; cobalt and nickel with the content of about 0.8 mu m can be obtained by correspondingly reducing the content of cobalt acetate and nickel acetate, as shown in a figure c; d, cobalt acetate and nickel acetate are 0.05: 0.2, 1.2 mu m cobalt nickel synthesized by using ethylene glycol as a solvent. From the a-d graphs, we can see that CoNi with different size distributions is synthesized4The alloy has uniform particle size and better particle size distribution.
Fig. 2 is a low-magnification SEM image of a size-tunable cobalt-nickel alloy particle/reduced graphene composite with a sandwich structure. Wherein, (a) can be seen in rGO/CN4In the-0.2 complex, about 0.2 μm cobalt-nickel alloy particles are completely wrapped inside the reduced graphene layer, and the particle size distribution is good, but the aggregation phenomenon is severe. The edge part of the composite is the graphene in a folded state, the surface of the composite has more curved surfaces, and the structure can increase the scattering of electromagnetic waves and is beneficial to the absorption of the electromagnetic waves; (b) middle complex rGO/CN4A morphology of 0.5, which better demonstrates the sandwich structure of the complex: specifically 0.5 mu mCobalt nickel particles with the size of m are uniformly dispersed in the folded graphene, and the distribution state of layers is obvious; (c) then the complex rGO/CN is displayed4A micro-topography of 0.8, indicating that its trimodal structure can be perfectly preserved with increasing size; however, when the size of the alloy particles is increased to 1.2 μm, the special sandwich structure is partially destroyed due to the strong magnetic action, and the alloy particles begin to agglomerate on the surface layer of the reduced graphene (as shown in a D compound rGO/CN)4Morphology of-1.2).
Fig. 3 is an X-ray diffraction (XRD) pattern of a size-tunable cobalt-nickel alloy particle/reduced graphene composite having a sandwich structure. The XDR can accurately reflect the information of the crystal phase, the purity, the crystallinity and the like of the product. In the figure, XRD curves of cobalt-nickel alloy, graphene oxide, and a tunable large-sized cobalt-nickel alloy particle/reduced graphene composite having a sandwich structure are shown by curves of series of colors, respectively. Then, it can be seen that the adjustable large-size cobalt-nickel alloy particle/reduced graphene composite with the sandwich structure is 44.5o，51.8o，76.7oThree strong peaks respectively appear, which are consistent with XRD diffraction peaks of cobalt-nickel alloys, which correspond to (111), (200), (220) planes of face-centered cubic structure cobalt-nickel alloys, respectively. Because the peak of the pure graphene is at 10.2oThe peak of pure reduced graphene is at 27.6oHowever, the composite product has a weak intensity peak between the two, which proves that the graphene oxide with the group is only partially reduced into the reduced graphene, the order is only partially destroyed, and the order degree is retained. Moreover, we can speculate that: during the reaction, Co2+And Ni2+It will react catalytically with graphene oxide and will also be more graphitized. Overall, the XRD patterns demonstrate the correctness of the composite material and the incorporation of impurities.
FIG. 4 shows a size-adjustable cobalt-nickel alloy particle/reduced graphene composite rGO/CN with a sandwich structure4-characterization of the magnetic properties at 300K for x. As can be seen from (c), rGO/CN4The hysteresis loops of the-x series all exhibiting SShape, which illustrates the successful loading of cobalt nickel alloys to give the composite ferromagnetic properties corresponding to cobalt nickel alloys. Furthermore, from (d) (magnified view of local magnetic field strength), rGO/CN4The hysteresis loops of the x-series composites have different areas and the saturation magnetization increases in turn as the size of the cobalt-nickel alloy particles increases. The composite has different dielectric behavior, magnetic behavior and different structural characteristics due to the change of the particle size, and the series of composites show extremely excellent and adjustable microwave absorption performance. This demonstrates that the microwave absorption properties of the composite material can be controllably adjusted by the size of the alloy particle size.
FIG. 5 shows a size-adjustable cobalt-nickel alloy particle/reduced graphene composite rGO/CN with a sandwich structure4X reflection loss curve at the corresponding thickness. Wherein, the compound rGO/CN4-0.2 maximum reflection loss at a thickness of 2 mm of-15.04 dB; complex rGO/CN40.5 maximum reflection loss of-34.98 dB at a sample thickness of 2.5 mm; complex rGO/CN40.8 maximum reflection loss at a sample thickness of 3.5 mm of-54.44 dB; complex rGO/CN4-1.2 the maximum reflection loss is-24.38 dB at a sample thickness of 2.5 mm. With pure graphene or pure CoNi4Maximum reflection loss comparison of alloy particles, composite rGO/CN4The-x series simultaneously meets the requirements of low thickness, wide frequency, strong absorption, low density and the like. Furthermore, the complex rGO/CN4And the maximum reflection loss of-0.8 is-54.44 dB when the thickness of a sample is 3.5 mm, and the capacity of the sample to loss of electromagnetic waves is several times that of the conventional wave-absorbing materials.
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Claims (2)
1. a preparation method of a cobalt-nickel alloy particle/reduced graphene composite material with a sandwich structure is characterized in that the size of a loaded cobalt-nickel alloy particle is changed by simultaneously changing the types of a pH regulator and a chelating agent and adjusting the concentration of a precursor solution; the preparation method comprises the following specific steps:
(1) firstly, ultrasonically dispersing 40 +/-3 mg of graphene oxide in 20 +/-3 mL of ethylene glycol for 30 +/-5 min, adding 0.05 +/-0.03 g of cobalt acetate, stirring for dissolving, adding 0.2 +/-0.08 g of nickel acetate, and stirring to dissolve to obtain a solution A;
(2) dripping 20 +/-3 mL of glycol solution in which 0.12 +/-0.05 g of citric acid is dissolved into the solution A; dripping the liquid at the speed of 8-15 seconds per drop, and then carrying out ultrasonic treatment on the solution for 40 +/-5 minutes to obtain a reaction solution;
(3) transferring the reaction solution into a reaction kettle, heating to 210 +/-10 ℃, and reacting for 12-15 h; after the hydrothermal kettle is cooled, washing the hydrothermal kettle for a plurality of times by using deionized water and absolute ethyl alcohol, and carrying out centrifugal separation to obtain a viscous cobalt-nickel/reduced graphene compound;
(4) and (4) placing the compound obtained in the step (3) in 20 +/-10 mL of deionized water, and carrying out freeze drying for 24 +/-1 h by using a freeze dryer to finally obtain the cobalt-nickel alloy particle/reduced graphene compound with the sandwich structure.
2. The method of claim 1, wherein step (2) is replaced with: dripping 20 +/-3 mL of diethylene glycol solution dissolved with 0.12 +/-0.05 g of sodium hydroxide into the solution A; dripping the liquid at the speed of 8-15 seconds per drop, and then carrying out ultrasonic treatment on the solution for 40 +/-5 minutes to obtain a reaction solution; the other steps are the same, and finally the cobalt-nickel alloy particle/reduced graphene composite with the sandwich structure is obtained.
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| CN103117389A (en) * | 2013-01-25 | 2013-05-22 | 浙江大学 | Nickel-cobalt oxide/graphene composite material as well as preparation method and application thereof |
| CN105295832A (en) * | 2014-07-25 | 2016-02-03 | 南京理工大学 | Preparation method for reduced graphene oxide/Ni-Co ternary composite wave-absorbing material |
| CN105390676A (en) * | 2015-11-02 | 2016-03-09 | 北京师范大学 | Quick preparation method for graphene base metal or metal oxide with sandwich structure |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN103117389A (en) * | 2013-01-25 | 2013-05-22 | 浙江大学 | Nickel-cobalt oxide/graphene composite material as well as preparation method and application thereof |
| CN105295832A (en) * | 2014-07-25 | 2016-02-03 | 南京理工大学 | Preparation method for reduced graphene oxide/Ni-Co ternary composite wave-absorbing material |
| CN105390676A (en) * | 2015-11-02 | 2016-03-09 | 北京师范大学 | Quick preparation method for graphene base metal or metal oxide with sandwich structure |
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