Magnetic metal composite microsphere as well as preparation method and application thereof

Abstract

The invention discloses a magnetic metal composite microsphere and a preparation method and application thereof. The structure of the composite microsphere comprises a hollow cavity, a magnetic metal spherical shell layer coating the hollow cavity, a carbon spherical shell layer coating the magnetic metal spherical shell layer, and a movable carbon core located in the hollow cavity; the carbon sphere shell layer is preferably made of amorphous carbon. According to the technical scheme, the problem that in a magnetic metal-carbon composite structure, it is difficult to control the synergistic effect in the aspects of structural stability and function enhancement of a composite system through the combination state of different forms of carbon materials and magnetic metal is well solved.

Description

Technical Field

[0001] The present invention relates to the technical field of powder materials, and more specifically, to a magnetic metal composite microsphere and a preparation method and application thereof. Background Art

[0002] In today's society, electromagnetic waves have become the fourth largest source of environmental pollution after water pollution, air pollution and noise pollution. The impact of electromagnetic wave radiation on the operation of precision equipment, signal transmission and human health has become the focus of people's attention. For the control of electromagnetic waves, the design and application of high-performance absorbing materials is the preferred solution. Currently, most of the absorbing materials used are composite materials, and the absorber is the key to the function of the absorbing composite material. Ferrites, metal powders, conductive polymers, functional ceramics, etc. with electromagnetic response characteristics are excellent candidates for high-performance absorbers. In order to convert the incident electromagnetic wave energy into heat energy or other forms of energy and dissipate it, high-performance absorbers usually need to reasonably combine multiple active components to form composite absorbers. The combination of heterogeneous components can not only bring multiple loss mechanisms and longer electromagnetic wave transmission and loss paths, but also provide the possibility of optimizing the impedance matching characteristics, dispersion, density and environmental stability of absorbers. Especially for micro-nanoscale absorbers, assembling small-sized assembly units into larger-sized composite assemblies can not only maintain the performance advantages of the assembly units, but also improve the poor stability caused by their small size.

[0003] Magnetic metals and carbon materials are two types of candidate absorber components that have received widespread attention. Magnetic metals have the advantages of strong composition and structural designability, and both electrical conductivity and magnetic response; while carbon materials have the advantages of wide sources, low density, high stability, and rich microstructure morphology. Therefore, the combination of magnetic metals and carbon materials has attracted much attention in the design of composite absorbers.

[0004] However, the magnetic metal-carbon composite structures reported so far still have the problem of difficulty in utilizing the combination state of carbon materials with different forms and magnetic metals to control the synergistic effect in the structural stability and functional enhancement of the composite system. It is urgent to design and develop new magnetic metal-carbon composite hollow structures based on the differentiated design of the component forms. Summary of the invention

[0005] Based on the above facts, the purpose of the present invention is to provide a magnetic metal composite microsphere and a preparation method and application thereof, so as to solve the problem that it is difficult to utilize the combination state of carbon materials in different forms and magnetic metals to control the synergistic effect in the structural stability and functional enhancement of the composite system.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions:

[0007] On the one hand, the present invention provides a magnetic metal composite microsphere, the structure of which includes a hollow cavity, a magnetic metal spherical shell layer covering the hollow cavity, a carbon spherical shell layer covering the magnetic metal spherical shell layer, and a movable carbon core located in the hollow cavity; the material of the carbon spherical shell layer is preferably amorphous carbon.

[0008] Furthermore, in the composite microspheres, the carbon core content is 15-40wt%, the magnetic metal shell content is 40-80wt%, and the carbon shell content is 4-30wt%, calculated by mass percentage.

[0009] Furthermore, the magnetic metal is selected from one or more of iron, cobalt and nickel.

[0010] Furthermore, the diameter of the composite microsphere is 3-12.2 μm.

[0011] Furthermore, the diameter of the carbon core of the composite microsphere is 2-10 μm; the thickness of the magnetic metal shell layer is 0.1-0.5 μm, the thickness of the carbon shell layer is 0.1-0.4 μm, and the distance between the carbon core and the magnetic metal shell layer is 0.21-0.25 μm.

[0012] In another aspect, the present invention provides a method for preparing the magnetic metal composite microspheres as described above, comprising the following steps:

[0013] The intermediate carbon microspheres were prepared by hydrothermal method;

[0014] Pretreating the intermediate carbon microspheres;

[0015] Directed auxiliary assembly of magnetic metal spherical shells on the surface of pretreated intermediate carbon microspheres;

[0016] The surface of the intermediate carbon microsphere assembled with the magnetic metal shell is coated with a phenolic shell and subjected to heat treatment to obtain the magnetic metal composite microsphere.

[0017] It is found in the preparation method of the present invention that only the intermediate carbon microspheres prepared by the hydrothermal method can shrink in volume after subsequent heat treatment to form a structure with a hollow cavity, and the obtained carbon core is located in the hollow cavity.

[0018] Furthermore, the method for preparing intermediate carbon microspheres by hydrothermal method comprises the following steps:

[0019] The carbon source aqueous solution is mixed with a surfactant, subjected to a hydrothermal reaction, filtered, washed and dried to obtain the intermediate carbon microspheres.

[0020] Furthermore, the carbon source is selected from one or more of glucose, fructose, sucrose, maltose, starch and citric acid, preferably glucose.

[0021] Furthermore, the concentration of the carbon source in the carbon source aqueous solution is 0.1-1 mol / L.

[0022] Furthermore, the surfactant is selected from cetyltrimethylammonium bromide (CTAB) and polyvinylpyrrolidone (PVP), preferably CTAB.

[0023] Furthermore, the temperature of the hydrothermal reaction is 170-210° C., and the time is 8-20 hours.

[0024] Furthermore, the pretreatment method comprises the following steps:

[0025] The intermediate carbon microspheres are subjected to surface coupling treatment, sensitization treatment and activation treatment in sequence to obtain the intermediate carbon microspheres.

[0026] In the preparation method of the present invention, the pretreatment method affects the structural stability and density of the magnetic metal shell assembled on the surface of the intermediate carbon microsphere, and further affects the electromagnetic properties of the obtained composite microsphere. Only by performing surface coupling treatment, sensitization treatment and activation treatment in sequence can composite microspheres with stable structure and good electromagnetic properties be obtained.

[0027] Furthermore, the surface coupling treatment is carried out in a surface treatment liquid, wherein the solute of the surface treatment liquid is a coupling agent, and the solvent is anhydrous ethanol and / or distilled water, more preferably a mixture of anhydrous ethanol and distilled water in a volume ratio of 1:1-1:5.

[0028] Furthermore, the temperature of the surface coupling treatment is 20-70°C, more preferably 30-50°C.

[0029] Furthermore, the sensitization treatment is carried out in a sensitizing solution, wherein the sensitizing solution is a stannous chloride aqueous solution with a concentration of 0.03-0.3 mol / L.

[0030] Furthermore, the activation treatment is carried out in an active solution, wherein the activation solution is a noble metal ion solution with a concentration of 0.002-0.2 mol / L, wherein the noble metal is preferably one or more of palladium, gold, platinum and rhodium.

[0031] Furthermore, the method also includes a reduction treatment step after the pretreatment to reduce the noble metal ions modified during the activation treatment to metals to impart catalytic activity. Exemplarily, the reduction treatment step includes the following steps: placing the pretreated intermediate carbon microspheres in a reducing solution (such as an aqueous solution of sodium hypophosphite, preferably with a concentration of 0.4 mol / L), stirring evenly at room temperature, filtering, and drying. Among them, the ratio of the pretreated intermediate carbon microspheres to the reducing solution is preferably 1 g / 20 mL.

[0032] Furthermore, the method for directional auxiliary assembly of magnetic metal spherical shells on the surface of pretreated intermediate carbon microspheres comprises the following steps:

[0033] The pretreated intermediate carbon microspheres are placed in an auxiliary deposition solution containing magnetic metal ions, stirred in a water bath, filtered, dried, and agglomerates are screened out to obtain the obtained product.

[0034] Furthermore, the auxiliary deposition solution comprises a magnetic metal ion source salt, a stabilizer, a reducing agent and a pH adjuster.

[0035] Furthermore, the magnetic metal ion source salt is selected from sulfates, chlorides or organic acid salts of magnetic metals, and the concentration is 20-60 g / L.

[0036] Furthermore, the stabilizer is selected from one or more of ammonium sulfate, potassium sodium tartrate and EDTA, and the concentration is 20-100 g / L.

[0037] Furthermore, the pH adjuster is selected from inorganic bases.

[0038] Furthermore, the reducing agent contained is an organic or inorganic reducing agent that can reduce the corresponding metal ions to metal elements.

[0039] Furthermore, the pH of the auxiliary deposition solution is 9-11.

[0040] Furthermore, the temperature of the water bath is 50-85°C.

[0041] Furthermore, the addition amount of the pretreated intermediate carbon microspheres is 0.0025-0.01 g / mL.

[0042] Furthermore, the method for coating the phenolic spherical shell comprises the following steps:

[0043] The intermediate carbon microspheres assembled with the magnetic metal shells are added to solution A, and then solution B is added dropwise to solution A, mixed evenly, reacted at 80° C. for 6 hours, filtered, and dried to obtain the product.

[0044] Furthermore, the solution A contains ethanol, deionized water, ammonia water, resorcinol and hexadecyltrimethylammonium bromide in a ratio of 400 mL: 60 mL: 20 mL: 5 g: 3 g.

[0045] Furthermore, the solution B contains formaldehyde solution, ethanol and water in a ratio of 11 g:40 mL:6 mL.

[0046] Furthermore, the volume of solution B is 12% of the volume of solution A.

[0047] Furthermore, the amount of the intermediate carbon microspheres assembled with magnetic metal spherical shells added to solution A is 0.01-0.1 g / mL.

[0048] Furthermore, the heat treatment is performed at a temperature of 600-900°C and for a time of 2-4 hours.

[0049] Furthermore, the heat treatment is performed in a mixed gas of N2 / Ar, nitrogen or Ar atmosphere.

[0050] In another aspect, the present invention provides a wave absorbing agent, which is prepared from a raw material comprising the magnetic metal composite microspheres as described above.

[0051] Furthermore, the absorbent can be used as one of the following materials: in the field of military stealth, electromagnetic radiation protection of radio and television transmitters, microwave darkroom materials, building absorbing materials or electromagnetic shielding materials in radio communication equipment.

[0052] In another aspect, the present invention provides use of the magnetic metal composite microspheres as described above in microwave absorption, catalysis, adsorption or wastewater treatment.

[0053] The beneficial effects of the present invention are as follows:

[0054] In the composite microsphere provided by the present invention, the movable carbon core in the hollow cavity cooperates with the hollow cavity structure, which can enrich the scattering interface of electromagnetic waves, thereby improving the maximum effective absorption band of the obtained composite material; the inner magnetic metal spherical shell layer brings magnetism and local high conductivity inside, and the outer amorphous carbon spherical shell layer gives controllable dielectric and conductivity losses, which can reduce the conductivity of the metal shell, which is conducive to improving the impedance matching characteristics of the material, and provides a wider effective absorption band of the material (for example, the maximum effective absorption band can be between 5.5-8GHz, and the frequency range of the maximum effective absorption band can be 7-15GHz). In addition, the frequency corresponding to the strongest reflection loss coefficient of the material can be 10.5-12GHz. In addition, the outer amorphous carbon spherical shell layer can also prevent the direct contact between the magnetic metal and the air, and prevent the magnetic metal from being oxidized; at the same time, an interface is generated between the amorphous carbon spherical shell layer and the magnetic metal spherical shell layer, and this interface will further promote electromagnetic wave loss and give the material better electromagnetic properties. BRIEF DESCRIPTION OF THE DRAWINGS

[0055] The specific implementation modes of the present invention are further described in detail below in conjunction with the accompanying drawings.

[0056] Figure 1 A schematic diagram showing the structure of an exemplary magnetic metal composite microsphere of the present invention is shown in the figure.

[0057] Figure 2 A schematic diagram of an exemplary preparation process of magnetic metal composite microspheres according to the present invention is shown.

[0058] Figure 3 A low-magnification scanning electron microscope (SEM) image of the magnetic metal composite microspheres obtained in Example 3 is shown.

[0059] Figure 4 A high-magnification scanning electron microscope (SEM) image of the magnetic metal composite microspheres obtained in Example 3 is shown.

[0060] Figure 5 X-ray diffraction pattern of the magnetic metal composite microspheres obtained in Example 3. DETAILED DESCRIPTION

[0061] In order to more clearly illustrate the present invention, the present invention is further described below in conjunction with preferred embodiments and accompanying drawings. Similar components in the accompanying drawings are represented by the same reference numerals. It should be understood by those skilled in the art that the content specifically described below is illustrative rather than restrictive, and should not be used to limit the scope of protection of the present invention.

[0062] In the embodiment of the present invention, the schematic diagram of the structure of the exemplary magnetic metal composite microsphere is as follows Figure 1 shown.

[0063] An exemplary schematic diagram of the preparation process of the magnetic metal composite microspheres is shown in Figure 2 It should be noted here that although Figure 2 It is not shown in the figure, but the intermediate carbon microspheres are pre-treated before assembling the magnetic metal shells.

[0064] Example 1

[0065] The preparation of magnetic metal composite microspheres, the specific implementation scheme is as follows:

[0066] 1) Preparation of intermediate carbon microspheres: 20 g of glucose was dissolved in 250 mL of distilled water and stirred evenly, then 0.7 g of CTAB was added and stirred until all dissolved, and then the mixed solution was transferred to a hydrothermal reactor and reacted at 170° C. for 18 hours, then filtered, washed, and dried to obtain intermediate carbon microspheres;

[0067] 2) Surface treatment of the intermediate carbon microspheres: anhydrous ethanol, distilled water, and 3-aminopropyltriethoxysilane were mixed uniformly in a volume ratio of 10:10:1, and the intermediate carbon microspheres were added in a ratio of 5 g / 100 mL (5 g microspheres were added to every 100 mL solution), stirred in a water bath at 35° C. for 30 min, filtered, and dried for standby use;

[0068] 3) Sensitization treatment of intermediate carbon microspheres: the microspheres obtained in step 2) were treated in a 0.12 mol / L stannous chloride aqueous solution at a ratio of 1 g / 20 mL, stirred at 40° C., and filtered;

[0069] 4) Activation treatment of intermediate carbon microspheres: The microspheres obtained in step 3) are treated in a ratio of 1 g / 25 mL in a 0.015 mol / L palladium chloride solution, stirred at 40° C., and filtered;

[0070] 5) Reduction treatment of intermediate carbon microspheres: The microspheres obtained in step 4) are treated in a 0.4 mol / L sodium hypophosphite aqueous solution at a ratio of 1 g / 20 mL, stirred at room temperature, filtered, and dried for later use;

[0071] 6) Preparation of intermediate carbon microsphere-metal composite microsphere: The microspheres obtained in step 5) were treated in a mixed solution of metal ions containing 40 g / L cobalt sulfate, 50 g / L sodium hypophosphite, 100 g / L potassium sodium tartrate, 50 g / L ammonium sulfate, pH ≈ 9.5 (adjusted by ammonia water) at a ratio of 1 g / 120 mL, stirred in a water bath at 55° C. for 30 min, and filtered;

[0072] 7) First, 400 mL of ethanol, 60 mL of deionized water, 20 mL of ammonia water and 3 g of hexadecyltrimethylammonium bromide were mixed and mechanically stirred for 30 minutes, and then 5 g of resorcinol was added and stirred to dissolve to obtain solution A; secondly, 11 g of formaldehyde solution, 40 mL of ethanol and 6 mL of water were mixed and stirred to obtain solution B; finally, the microspheres obtained in step 6) were added to solution A at a ratio of 1 g / 37 mL and stirred to obtain solution B; solution B equivalent to 12% of the volume of solution A was taken and slowly added dropwise to solution A using a constant pressure funnel, reacted at 80° C. for 6 hours, filtered, dried and set aside;

[0073] 8) The microspheres obtained in step 7) were heat treated in an argon atmosphere at a temperature of 700° C., a heating rate of 10° C. / min, and a holding time of 3 h to obtain the target product.

[0074] The carbon core of the magnetic metal composite microspheres with a carbon core obtained in this embodiment has a diameter of 5.0 microns, a cavity spacing (the distance between the carbon core and the inner surface of the magnetic metal shell) of 0.23 microns, and the mass percentages of the carbon shell layer, the magnetic metal shell layer and the carbon core are 13.2%, 48.2% and 38.6% respectively.

[0075] Example 2

[0076] The preparation of magnetic metal composite microspheres, the specific implementation scheme is as follows:

[0077] 1) Preparation of intermediate carbon microspheres: 20 g of glucose was dissolved in 250 mL of distilled water and stirred evenly, then 0.7 g of CTAB was added and stirred until all dissolved, and then the mixed solution was transferred to a hydrothermal reactor and reacted at 170° C. for 18 hours, then filtered, washed, and dried to obtain intermediate carbon microspheres;

[0078] 2) Surface treatment of the intermediate carbon microspheres: anhydrous ethanol, distilled water, and 3-aminopropyltriethoxysilane were mixed uniformly in a volume ratio of 10:10:1, and the intermediate carbon microspheres were added in a ratio of 5 g / 100 mL (5 g microspheres were added to every 100 mL solution), stirred in a water bath at 35° C. for 30 min, filtered, and dried for standby use;

[0079] 3) Sensitization treatment of intermediate carbon microspheres: the microspheres obtained in step 2) were treated in a 0.12 mol / L stannous chloride aqueous solution at a ratio of 1 g / 20 mL, stirred at 40° C., and filtered;

[0080] 4) Activation treatment of intermediate carbon microspheres: The microspheres obtained in step 3) are treated in a ratio of 1 g / 25 mL in a 0.015 mol / L palladium chloride solution, stirred at 40° C., and filtered;

[0081] 5) Reduction treatment of intermediate carbon microspheres: The microspheres obtained in step 4) are treated in a 0.4 mol / L sodium hypophosphite aqueous solution at a ratio of 1 g / 20 mL, stirred at room temperature, filtered, and dried for later use;

[0082] 6) Preparation of intermediate carbon microsphere-metal composite microsphere: The microspheres obtained in step 5) were treated in a ratio of 1 g / 160 mL in a metal ion mixed solution containing 40 g / L cobalt sulfate, 50 g / L sodium hypophosphite, 100 g / L potassium sodium tartrate, 50 g / L ammonium sulfate, pH ≈ 9.5 (adjusted by ammonia water), stirred in a water bath at 55° C. for 30 min, and filtered;

[0083] 7) First, 400 mL of ethanol, 60 mL of deionized water, 20 mL of ammonia water and 3 g of hexadecyltrimethylammonium bromide were mixed and mechanically stirred for 30 minutes, and then 5 g of resorcinol was added and stirred to dissolve to obtain solution A; secondly, 11 g of formaldehyde solution, 40 mL of ethanol and 6 mL of water were mixed and stirred to obtain solution B; finally, the microspheres obtained in step 6) were added to solution A at a ratio of 1 g / 52 mL and stirred to obtain solution B; solution B equivalent to 12% of the volume of solution A was taken and slowly added dropwise to solution A using a constant pressure funnel, reacted at 80° C. for 6 hours, filtered, dried and set aside;

[0084] 8) The microspheres obtained in step 7) were heat treated in an argon atmosphere at a temperature of 650° C., a heating rate of 10° C. / min, and a holding time of 3 h to obtain the target product.

[0085] The carbon core of the magnetic metal composite microspheres with a carbon core obtained in this embodiment has a diameter of 5.0 microns, a cavity spacing (the distance between the carbon core and the inner surface of the magnetic metal shell) of 0.22 microns, and the mass percentages of the carbon shell layer, the magnetic metal shell layer and the carbon core are 17.2%, 52.3% and 30.5% respectively.

[0086] Example 3

[0087] The preparation of magnetic metal composite microspheres, the specific implementation scheme is as follows:

[0088] 1) Preparation of intermediate carbon microspheres: 20 g of glucose was dissolved in 250 mL of distilled water and stirred evenly, then 0.7 g of CTAB was added and stirred until all dissolved, and then the mixed solution was transferred to a hydrothermal reactor and reacted at 170° C. for 18 hours, then filtered, washed, and dried to obtain intermediate carbon microspheres;

[0089] 2) Surface treatment of the intermediate carbon microspheres: anhydrous ethanol, distilled water, and 3-aminopropyltriethoxysilane were mixed uniformly in a volume ratio of 10:10:1, and the intermediate carbon microspheres were added in a ratio of 5 g / 100 mL (5 g microspheres were added to every 100 mL solution), stirred in a water bath at 35° C. for 30 min, filtered, and dried for standby use;

[0090] 3) Sensitization treatment of intermediate carbon microspheres: the microspheres obtained in step 2) were treated in a 0.12 mol / L stannous chloride aqueous solution at a ratio of 1 g / 20 mL, stirred at 40° C., and filtered;

[0091] 4) Activation treatment of intermediate carbon microspheres: The microspheres obtained in step 3) are treated in a ratio of 1 g / 25 mL in a 0.015 mol / L palladium chloride solution, stirred at 40° C., and filtered;

[0092] 5) Reduction treatment of intermediate carbon microspheres: The microspheres obtained in step 4) are treated in a 0.4 mol / L sodium hypophosphite aqueous solution at a ratio of 1 g / 20 mL, stirred at room temperature, filtered, and dried for later use;

[0093] 6) Preparation of intermediate carbon microsphere-metal composite microsphere: The microspheres obtained in step 5) were treated in a metal ion mixed solution containing 40 g / L nickel sulfate, 50 g / L sodium hypophosphite, 85 g / L potassium sodium tartrate, 40 g / L ammonium sulfate, pH ≈ 9.0 (adjusted by ammonia water) at a ratio of 1 g / 160 mL, stirred in a water bath at 60° C. for 30 min, and filtered;

[0094] 7) First, 400 mL of ethanol, 60 mL of deionized water, 20 mL of ammonia water and 3 g of hexadecyltrimethylammonium bromide were mixed and mechanically stirred for 30 minutes, and then 5 g of resorcinol was added and stirred to dissolve to obtain solution A; secondly, 11 g of formaldehyde solution, 40 mL of ethanol and 6 mL of water were mixed and stirred to obtain solution B; finally, the microspheres obtained in step 6) were added to solution A at a ratio of 1 g / 31 mL and stirred to obtain solution B; solution B equivalent to 12% of the volume of solution A was taken and slowly added dropwise to solution A using a constant pressure funnel, reacted at 80° C. for 6 hours, filtered, dried and set aside;

[0095] 8) The microspheres obtained in step 7) were heat treated in an argon atmosphere at a temperature of 900°C, a heating rate of 10°C / min, and a holding time of 3 hours to obtain the target product. The low-magnification scanning electron microscope (SEM) image is as follows: Figure 3 As shown in the high magnification scanning electron microscope (SEM) image Figure 4 The X-ray diffraction pattern is shown in Figure 5 shown.

[0096] The carbon core of the magnetic metal composite microspheres with a carbon core obtained in this embodiment has a diameter of 4.9 microns, a cavity spacing (the distance between the carbon core and the inner surface of the magnetic metal shell) of 0.25 microns, and the mass percentages of the carbon shell layer, the magnetic metal shell layer and the carbon core are 11.3%, 57.6% and 31.2% respectively.

[0097] Example 4

[0098] The preparation of magnetic metal composite microspheres, the specific implementation scheme is as follows:

[0099] 1) Preparation of intermediate carbon microspheres: Dissolve 20 g of glucose in 250 mL of distilled water and stir evenly, then add 0.7 g of CTAB and stir thoroughly until all dissolved, then transfer the mixed solution to a hydrothermal kettle, react at 170° C. for 18 hours, then filter, wash, and dry to obtain intermediate carbon microspheres. ;

[0100] 2) Surface treatment of the intermediate carbon microspheres: anhydrous ethanol, distilled water, and 3-aminopropyltriethoxysilane were mixed uniformly in a volume ratio of 10:10:1, and the intermediate carbon microspheres were added in a ratio of 5 g / 100 mL (5 g microspheres were added to every 100 mL solution), stirred in a water bath at 35° C. for 30 min, filtered, and dried for standby use;

[0101] 3) Sensitization treatment of intermediate carbon microspheres: the microspheres obtained in step 2) were treated in a 0.12 mol / L stannous chloride aqueous solution at a ratio of 1 g / 20 mL, stirred at 40° C., and filtered;

[0102] 4) Activation treatment of intermediate carbon microspheres: The microspheres obtained in step 3) are treated in a ratio of 1 g / 25 mL in a 0.015 mol / L palladium chloride solution, stirred at 40° C., and filtered;

[0103] 5) Reduction treatment of intermediate carbon microspheres: The microspheres obtained in step 4) are treated in a 0.4 mol / L sodium hypophosphite aqueous solution at a ratio of 1 g / 20 mL, stirred at room temperature, filtered, and dried for later use;

[0104] 6) Preparation of intermediate carbon microsphere-metal composite microsphere: The microspheres obtained in step 5) were treated in a metal ion mixed solution containing 40 g / L nickel sulfate, 50 g / L sodium hypophosphite, 85 g / L potassium sodium tartrate, 40 g / L ammonium sulfate, pH ≈ 9.0 (adjusted by ammonia water) at a ratio of 1 g / 340 mL, stirred in a water bath at 60° C. for 30 min, and filtered;

[0105] 7) First, 400 mL of ethanol, 60 mL of deionized water, 20 mL of ammonia water and 3 g of hexadecyltrimethylammonium bromide were mixed and mechanically stirred for 30 minutes, and then 5 g of resorcinol was added and stirred to dissolve to obtain solution A; secondly, 11 g of formaldehyde solution, 40 mL of ethanol and 6 mL of water were mixed and stirred to obtain solution B; finally, the microspheres obtained in step 6) were added to solution A at a ratio of 1 g / 40 mL and stirred to obtain solution B; solution B equivalent to 12% of the volume of solution A was taken and slowly added dropwise to solution A using a constant pressure funnel, reacted at 80° C. for 6 hours, filtered, dried and set aside;

[0106] 8) The microspheres obtained in step 7) were heat treated in an argon atmosphere at a temperature of 600° C., a heating rate of 10° C. / min, and a holding time of 3 h to obtain the target product.

[0107] The carbon core of the magnetic metal composite microspheres with a carbon core obtained in this embodiment has a diameter of 5.1 microns, a cavity spacing (the distance between the carbon core and the inner surface of the magnetic metal shell) of 0.21 microns, and the mass percentages of the carbon shell layer, the magnetic metal shell layer and the carbon core are 13.4%, 68.9% and 17.7% respectively.

[0108] Example 5

[0109] The preparation of magnetic metal composite microspheres, the specific implementation scheme is as follows:

[0110] 1) Preparation of intermediate carbon microspheres: 20 g of glucose was dissolved in 250 mL of distilled water and stirred evenly, then 0.7 g of CTAB was added and stirred until all dissolved, and then the mixed solution was transferred to a hydrothermal reactor and reacted at 170° C. for 18 hours, then filtered, washed, and dried to obtain intermediate carbon microspheres;

[0111] 2) Surface treatment of the intermediate carbon microspheres: anhydrous ethanol, distilled water, and 3-aminopropyltriethoxysilane were mixed uniformly in a volume ratio of 10:10:1, and the intermediate carbon microspheres were added in a ratio of 5 g / 100 mL (5 g microspheres were added to every 100 mL solution), stirred in a water bath at 35° C. for 30 min, filtered, and dried for standby use;

[0112] 3) Sensitization treatment of intermediate carbon microspheres: the microspheres obtained in step 2) were treated in a 0.12 mol / L stannous chloride aqueous solution at a ratio of 1 g / 20 mL, stirred at 40° C., and filtered;

[0113] 4) Activation treatment of intermediate carbon microspheres: The microspheres obtained in step 3) are treated in a ratio of 1 g / 25 mL in a 0.015 mol / L palladium chloride solution, stirred at 40° C., and filtered;

[0114] 5) Reduction treatment of intermediate carbon microspheres: The microspheres obtained in step 4) are treated in a 0.4 mol / L sodium hypophosphite aqueous solution at a ratio of 1 g / 20 mL, stirred at room temperature, filtered, and dried for later use;

[0115] 6) Preparation of intermediate carbon microsphere-metal composite microsphere: The microspheres obtained in step 5) were treated at a ratio of 1 g / 100 mL in a metal ion mixed solution containing 40 g / L nickel sulfate, 50 g / L sodium hypophosphite, 85 g / L potassium sodium tartrate, 40 g / L ammonium sulfate, pH ≈ 9.0 (adjusted by ammonia water), stirred in a water bath at 60° C. for 30 min, and filtered;

[0116] 7) First, 400 mL of ethanol, 60 mL of deionized water, 20 mL of ammonia water and 3 g of hexadecyltrimethylammonium bromide were mixed and mechanically stirred for 30 minutes, and then 5 g of resorcinol was added and stirred to dissolve to obtain solution A; secondly, 11 g of formaldehyde solution, 40 mL of ethanol and 6 mL of water were mixed and stirred to obtain solution B; finally, the microspheres obtained in step 6) were added to solution A at a ratio of 1 g / 83 mL and stirred to obtain solution B; solution B equivalent to 12% of the volume of solution A was taken and slowly added dropwise to solution A using a constant pressure funnel, reacted at 80° C. for 6 hours, filtered, dried and set aside;

[0117] 8) The microspheres obtained in step 7) were heat treated in an argon atmosphere at a temperature of 680° C., a heating rate of 10° C. / min, and a holding time of 3 h to obtain the target product.

[0118] The carbon core of the magnetic metal composite microspheres with a carbon core obtained in this embodiment has a diameter of 5.0 microns, a cavity spacing (the distance between the carbon core and the inner surface of the magnetic metal shell) of 0.22 microns, and the mass percentages of the carbon shell layer, the magnetic metal shell layer and the carbon core are 25.7%, 41.2% and 33.2% respectively.

[0119] Example 6

[0120] The preparation of magnetic metal composite microspheres, the specific implementation scheme is as follows:

[0121] 1) Preparation of intermediate carbon microspheres: 20 g of glucose was dissolved in 250 mL of distilled water and stirred evenly, then 0.7 g of CTAB was added and stirred until all dissolved, and then the mixed solution was transferred to a hydrothermal reactor and reacted at 190° C. for 12 hours, then filtered, washed, and dried to obtain intermediate carbon microspheres;

[0122] 2) Surface treatment of the intermediate carbon microspheres: anhydrous ethanol, distilled water, and 3-aminopropyltriethoxysilane were mixed uniformly in a volume ratio of 10:10:1, and the intermediate carbon microspheres were added in a ratio of 5 g / 100 mL (5 g microspheres were added to every 100 mL solution), stirred in a water bath at 35° C. for 30 min, filtered, and dried for standby use;

[0123] 3) Sensitization treatment of intermediate carbon microspheres: the microspheres obtained in step 2) were treated in a 0.12 mol / L stannous chloride aqueous solution at a ratio of 1 g / 20 mL, stirred at 40° C., and filtered;

[0124] 4) Activation treatment of intermediate carbon microspheres: The microspheres obtained in step 3) are treated in a ratio of 1 g / 25 mL in a 0.015 mol / L palladium chloride solution, stirred at 40° C., and filtered;

[0125] 5) Reduction treatment of intermediate carbon microspheres: The microspheres obtained in step 4) are treated in a 0.4 mol / L sodium hypophosphite aqueous solution at a ratio of 1 g / 20 mL, stirred at room temperature, filtered, and dried for later use;

[0126] 6) Preparation of intermediate carbon microsphere-metal composite microsphere: The microspheres obtained in step 5) were treated in a ratio of 1 g / 350 mL in a metal ion mixed solution containing 25 g / L cobalt sulfate, 25 g / L nickel sulfate, 60 g / L sodium hypophosphite, 80 g / L potassium sodium tartrate, 60 g / L ammonium sulfate, pH ≈ 9.5 (adjusted by ammonia water), stirred in a water bath at 65°C for 30 min, and filtered;

[0127] 7) First, 400 mL of ethanol, 60 mL of deionized water, 20 mL of ammonia water and 3 g of hexadecyltrimethylammonium bromide were mixed and mechanically stirred for 30 minutes, and then 5 g of resorcinol was added and stirred to dissolve to obtain solution A; secondly, 11 g of formaldehyde solution, 40 mL of ethanol and 6 mL of water were mixed and stirred to obtain solution B; finally, the microspheres obtained in step 6) were added to solution A at a ratio of 1 g / 14 mL and stirred to obtain solution B; solution B equivalent to 12% of the volume of solution A was taken and slowly added dropwise to solution A using a constant pressure funnel, reacted at 80° C. for 6 hours, filtered, dried and set aside;

[0128] 8) The microspheres obtained in step 7) were heat treated in an argon atmosphere at a temperature of 650° C., a heating rate of 10° C. / min, and a holding time of 3 h to obtain the target product.

[0129] The carbon core of the magnetic metal composite microspheres with a carbon core obtained in this embodiment has a diameter of 5.1 microns, a cavity spacing (the distance between the carbon core and the inner surface of the magnetic metal shell) of 0.22 microns, and the mass percentages of the carbon shell layer, the magnetic metal shell layer and the carbon core are 4.7%, 80% and 15.3% respectively.

[0130] Example 7

[0131] The preparation of magnetic metal composite microspheres, the specific implementation scheme is as follows:

[0132] 1) Preparation of intermediate carbon microspheres: 20 g of glucose was dissolved in 250 mL of distilled water and stirred evenly, then 0.7 g of CTAB was added and stirred until all dissolved, and then the mixed solution was transferred to a hydrothermal reactor and reacted at 180° C. for 10 hours, then filtered, washed, and dried to obtain intermediate carbon microspheres;

[0133] 2) Surface treatment of the intermediate carbon microspheres: anhydrous ethanol, distilled water, and 3-aminopropyltriethoxysilane were mixed uniformly in a volume ratio of 10:10:1, and the intermediate carbon microspheres were added in a ratio of 5 g / 100 mL (5 g microspheres were added to every 100 mL solution), stirred in a water bath at 35° C. for 30 min, filtered, and dried for standby use;

[0134] 3) Sensitization treatment of intermediate carbon microspheres: the microspheres obtained in step 2) were treated in a 0.12 mol / L stannous chloride aqueous solution at a ratio of 1 g / 20 mL, stirred at 40° C., and filtered;

[0135] 4) Activation treatment of intermediate carbon microspheres: The microspheres obtained in step 3) are treated in a 0.015 mol / L palladium chloride solution at a ratio of 1 g / 25 mL, stirred at 40° C., and filtered. ;

[0136] 5) Reduction treatment of intermediate carbon microspheres: The microspheres obtained in step 4) are treated in a 0.4 mol / L sodium hypophosphite aqueous solution at a ratio of 1 g / 20 mL, stirred at room temperature, filtered, and dried for later use;

[0137] 6) Preparation of intermediate carbon microsphere-metal composite microsphere: The microspheres obtained in step 5) were treated in a ratio of 1 g / 240 mL in a metal ion mixed solution containing 20 g / L cobalt sulfate, 30 g / L ammonium ferrous sulfate, 50 g / L sodium hypophosphite, 80 g / L potassium sodium tartrate, 50 g / L ammonium sulfate, pH ≈ 10 (adjusted by ammonia water), stirred in a water bath at 80°C for 30 min, and filtered;

[0138] 7) First, 400 mL of ethanol, 60 mL of deionized water, 20 mL of ammonia water and 3 g of hexadecyltrimethylammonium bromide were mixed and mechanically stirred for 30 minutes, and then 5 g of resorcinol was added and stirred to dissolve to obtain solution A; secondly, 11 g of formaldehyde solution, 40 mL of ethanol and 6 mL of water were mixed and stirred to obtain solution B; finally, the microspheres obtained in step 6) were added to solution A at a ratio of 1 g / 12 mL and stirred to obtain solution B; solution B equivalent to 12% of the volume of solution A was taken and slowly added dropwise to solution A using a constant pressure funnel, reacted at 80° C. for 6 hours, filtered, dried and set aside;

[0139] 8) The microspheres obtained in step 7) were heat treated in an argon atmosphere at a temperature of 670° C., a heating rate of 10° C. / min, and a holding time of 3 h to obtain the target product.

[0140] The carbon core of the magnetic metal composite microspheres with a carbon core obtained in this embodiment has a diameter of 5.0 microns, a cavity spacing (the distance between the carbon core and the inner surface of the magnetic metal shell) of 0.22 microns, and the mass percentages of the carbon shell layer, the magnetic metal shell layer and the carbon core are 4.6%, 69.1% and 26.3% respectively.

[0141] Example 8

[0142] The preparation of magnetic metal composite microspheres, the specific implementation scheme is as follows:

[0143] 1) Preparation of intermediate carbon microspheres: 20 g of glucose was dissolved in 250 mL of distilled water and stirred evenly, then 0.7 g of CTAB was added and stirred until all dissolved, and then the mixed solution was transferred to a hydrothermal reactor and reacted at 200° C. for 15 hours, then filtered, washed, and dried to obtain intermediate carbon microspheres;

[0144] 2) Surface treatment of the intermediate carbon microspheres: anhydrous ethanol, distilled water, and 3-aminopropyltriethoxysilane were mixed uniformly in a volume ratio of 10:10:1, and the intermediate carbon microspheres were added in a ratio of 5 g / 100 mL (5 g microspheres were added to every 100 mL solution), stirred in a water bath at 35° C. for 30 min, filtered, and dried for standby use;

[0145] 3) Sensitization treatment of intermediate carbon microspheres: the microspheres obtained in step 2) were treated in a 0.12 mol / L stannous chloride aqueous solution at a ratio of 1 g / 20 mL, stirred at 40° C., and filtered;

[0146] 4) Activation treatment of intermediate carbon microspheres: The microspheres obtained in step 3) are treated in a ratio of 1 g / 25 mL in a 0.015 mol / L palladium chloride solution, stirred at 40° C., and filtered;

[0147] 5) Reduction treatment of intermediate carbon microspheres: The microspheres obtained in step 4) are treated in a 0.4 mol / L sodium hypophosphite aqueous solution at a ratio of 1 g / 20 mL, stirred at room temperature, filtered, and dried for later use;

[0148] 6) Preparation of intermediate carbon microspheres-metal composite microspheres: The microspheres obtained in step 5) were treated in a ratio of 1 g / 230 mL in a metal ion mixed solution containing 20 g / L nickel sulfate, 30 g / L ammonium ferrous sulfate, 50 g / L sodium hypophosphite, 80 g / L potassium sodium tartrate, 50 g / L ammonium sulfate, pH ≈ 10 (adjusted by ammonia water), stirred in a water bath at 75°C for 30 min, and filtered;

[0149] 7) First, 400 mL of ethanol, 60 mL of deionized water, 20 mL of ammonia water and 3 g of hexadecyltrimethylammonium bromide were mixed and mechanically stirred for 30 minutes, and then 5 g of resorcinol was added and stirred to dissolve to obtain solution A; secondly, 11 g of formaldehyde solution, 40 mL of ethanol and 6 mL of water were mixed and stirred to obtain solution B; finally, the microspheres obtained in step 6) were added to solution A at a ratio of 1 g / 34 mL and stirred to obtain solution B; solution B equivalent to 12% of the volume of solution A was taken and slowly added dropwise to solution A using a constant pressure funnel, reacted at 80° C. for 6 hours, filtered, dried and set aside;

[0150] 8) The microspheres obtained in step 7) were heat treated in an argon atmosphere at a temperature of 680° C., a heating rate of 10° C. / min, and a holding time of 3 h to obtain the target product.

[0151] The carbon core of the magnetic metal composite microspheres with a carbon core obtained in this embodiment has a diameter of 5.0 microns, a cavity spacing (the distance between the carbon core and the inner surface of the magnetic metal shell) of 0.22 microns, and the mass percentages of the carbon shell layer, the magnetic metal shell layer and the carbon core are 11.8%, 63.9% and 24.3% respectively.

[0152] Comparative Example 1

[0153] The other steps are the same as in Example 1, except that commercial carbon microspheres are used instead of carbon intermediate microspheres synthesized by hydrothermal method. The microspheres do not have volume shrinkage and no cavities are generated during the heat treatment process.

[0154] Comparative Example 2

[0155] The other steps are the same as those of Example 1, except that in step 1), the carbon intermediate microspheres synthesized by the hydrothermal method are first subjected to heat treatment and then subjected to subsequent treatment. The microspheres do not have volume shrinkage during the subsequent heat treatment, and the obtained microspheres do not generate cavities.

[0156] Comparative Example 3

[0157] The rest is the same as in Example 1, except that no sensitization treatment is performed (i.e., step 3) "sensitization treatment of the intermediate carbon microspheres" is not performed).

[0158] Performance Testing:

[0159] The electromagnetic properties of the products prepared in the above embodiments were tested. The test method is: the hollow microspheres prepared in the embodiments are mixed with paraffin, the volume fraction of the hollow microspheres in the obtained mixture is 50%-70%, and coaxial rings are prepared, the inner diameter of the ring is 3mm, the outer diameter is 7mm, and the thickness is 2mm. Then, the electromagnetic parameters are tested by a vector network analyzer to analyze the electromagnetic properties. The results are shown in Table 1.

[0160] Table 1

[0161]

[0162]

[0163] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not limitations on the implementation methods of the present invention. For ordinary technicians in the relevant field, other different forms of changes or modifications can be made based on the above description. It is impossible to list all the implementation methods here. All obvious changes or modifications derived from the technical solution of the present invention are still within the protection scope of the present invention.

Claims

1. A magnetic metal composite microsphere, It is characterized in that The structure of the composite microsphere includes a hollow cavity, a magnetic metal spherical shell layer covering the hollow cavity, a carbon spherical shell layer covering the magnetic metal spherical shell layer, and a movable carbon core located in the hollow cavity; the material of the carbon spherical shell layer is preferably amorphous carbon.

2. The magnetic metal composite microsphere according to claim 1, It is characterized in that In the composite microspheres, the content of the carbon core is 15-40wt%, the content of the magnetic metal shell is 40-80wt%, and the content of the carbon shell is 4-30wt%, calculated by mass percentage.

3. The magnetic metal composite microsphere according to claim 1, It is characterized in that The magnetic metal is selected from one or more of iron, cobalt and nickel.

4. The method for preparing the magnetic metal composite microspheres according to any one of claims 1 to 3, It is characterized in that The steps include: The intermediate carbon microspheres were prepared by hydrothermal method; Pretreating the intermediate carbon microspheres; Directed auxiliary assembly of magnetic metal spherical shells on the surface of pretreated intermediate carbon microspheres; The surface of the intermediate carbon microsphere assembled with the magnetic metal shell is coated with a phenolic shell and subjected to heat treatment to obtain the magnetic metal composite microsphere.

5. The preparation method according to claim 4, It is characterized in that The method for preparing intermediate carbon microspheres by hydrothermal method comprises the following steps: The carbon source aqueous solution is mixed with a surfactant, subjected to a hydrothermal reaction, filtered, washed and dried to obtain the intermediate carbon microspheres; Preferably, the carbon source is selected from one or more of glucose, fructose, sucrose, maltose, starch and citric acid; Preferably, the concentration of the carbon source in the carbon source aqueous solution is 0.1-1 mol / L; Preferably, the surfactant is selected from one of cetyltrimethylammonium bromide and polyvinylpyrrolidone; Preferably, the temperature of the hydrothermal reaction is 170-210° C., and the time is 8-20 h.

6. The preparation method according to claim 4, It is characterized in that The pretreatment method comprises the following steps: The intermediate carbon microspheres are sequentially subjected to surface coupling treatment, sensitization treatment and activation treatment to obtain; Preferably, the surface coupling treatment is carried out in a surface treatment liquid, wherein the solute of the surface treatment liquid is a coupling agent, and the solvent is anhydrous ethanol and / or distilled water, more preferably a mixture of anhydrous ethanol and distilled water in a volume ratio of 1:1-1:5; Preferably, the temperature of the surface coupling treatment is 20-70°C, more preferably 30-50°C; Preferably, the sensitization treatment is carried out in a sensitizing solution, wherein the sensitizing solution is an aqueous solution of stannous chloride with a concentration of 0.03-0.3 mol / L; Preferably, the activation treatment is carried out in an active solution, wherein the activation solution is a noble metal ion solution with a concentration of 0.002-0.2 mol / L.

7. The preparation method according to claim 4, It is characterized in that The method for directional auxiliary assembly of magnetic metal spherical shells on the surface of pretreated intermediate carbon microspheres comprises the following steps: The pretreated intermediate carbon microspheres are treated in an auxiliary deposition solution containing magnetic metal ions, stirred in a water bath, filtered, dried, and agglomerates are removed by screening to obtain; Preferably, the auxiliary deposition solution comprises a magnetic metal ion source salt, a stabilizer, a reducing agent and a pH adjuster; Preferably, the magnetic metal ion source salt is selected from sulfates, chlorides or organic acid salts of magnetic metals, with a concentration of 20-60 g / L; Preferably, the stabilizer is selected from one or more of ammonium sulfate, potassium sodium tartrate and EDTA, and the concentration is 20-100 g / L; Preferably, the pH adjuster is selected from inorganic bases; Preferably, the pH of the auxiliary deposition solution is 9-11; Preferably, the temperature of the water bath is 50-85°C; Preferably, the addition amount of the pretreated intermediate carbon microspheres is 0.0025-0.01 g / mL.

8. The preparation method according to claim 4, It is characterized in that The method for coating the phenolic spherical shell comprises the following steps: The intermediate carbon microspheres assembled with magnetic metal shells are added to solution A, and then solution B is added dropwise to solution A, mixed, reacted at 80° C. for 6 hours, filtered, and dried to obtain; Preferably, the solution A contains ethanol, deionized water, ammonia water, resorcinol and hexadecyltrimethylammonium bromide in a ratio of 400 mL: 60 mL: 20 mL: 5 g: 3 g; Preferably, the solution B contains formaldehyde solution, ethanol and water in a ratio of 11 g: 40 mL: 6 mL; Preferably, the volume of solution B is 12% of the volume of solution A; Preferably, the intermediate carbon microspheres assembled with magnetic metal spherical shells are added in an amount of 0.01-0.1 g / mL in solution A; Preferably, the heat treatment is carried out at a temperature of 600-900° C. and for a time of 2-4 hours.

9. A wave absorbing agent, It is characterized in that The microspheres are prepared from raw materials comprising the magnetic metal composite microspheres as described in any one of claims 1 to 3.

10. Use of the magnetic metal composite microspheres according to any one of claims 1 to 3 in microwave absorption, catalysis, adsorption or wastewater treatment.

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