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

Abstract

The invention discloses a magnetic metal hollow microsphere as well as a preparation method and application thereof. The structure of the magnetic metal consists of a hollow inner core and a magnetic metal spherical shell layer; wherein carbon microspheres are arranged in the hollow inner core. The movable carbon microsphere core in the magnetic metal hollow microsphere can controllably fill the hollow structure in the magnetic metal spherical shell, so that the effective scattering of incident electromagnetic waves is improved; the combination of electrical loss and magnetic loss is realized through the compounding of the carbon microsphere core and the magnetic metal spherical shell layer.

Description

Technical Field

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

[0002] In order to reduce the interference of electromagnetic waves on instruments and equipment and the impact on the health of organisms, electromagnetic wave absorbing materials are widely used for the absorption and shielding of electromagnetic waves. In scientific research and practical applications, many materials with electrical or magnetic response characteristics are used as candidate materials for electromagnetic wave absorbing materials. Among them, micro-nanoscale magnetic metal absorbers have attracted widespread attention. The reason is that on the one hand, magnetic metals have both magnetic response (ferromagnetism) and electrical response (conductivity), which can simultaneously dissipate the magnetic field and electric field energy in electromagnetic waves; on the other hand, magnetic metal materials have strong designability of chemical composition and physical structure, and can easily control their composition and (micro and macro) structure through the regulation of process parameters such as raw material system composition, synthesis conditions and post-treatment. In addition, for micro-nanoscale magnetic metal materials, their tiny size will also bring additional surface effects and size effects, thereby obtaining characteristics that large-size materials with the same composition do not have.

[0003] Although magnetic metals, especially their micro-nano-sized materials, have unique advantages in electromagnetic properties. However, their inherent high density is an important limiting factor affecting their application performance. Given that magnetic metal micro-nanoparticles usually need to be combined with matrix materials such as polymers to form composite materials when applied, researchers have designed a variety of different magnetic metal single-component special-shaped structures or multi-component composite structures to achieve the lightweight of magnetic metals. For example, designing magnetic metals into fiber or rod-shaped structures with different aspect ratios, or making them into large-area thin-sheet structures, can form electromagnetic functional networks at a lower addition ratio and reduce the overall density of the composite material. On the other hand, designing magnetic metal absorbers as loaded structures or hollow structures of low-density carriers can reduce the density of the absorber itself, and thus reduce the density of the composite material at the same volume fraction. Compared with anisotropic sheet or fiber structures, designing magnetic metals into hollow microspheres can reduce density while having the advantages of high dispersibility, which makes it possible to enhance the magnetic loss of performance composite materials by filling them at a large proportion. At the same time, the low density of the absorber itself can ensure that the density of the composite material is not significantly increased under high filling rates.

[0004] However, currently most magnetic metal hollow microspheres are formed by themselves or composited with preformed hollow carriers to form hollow structures with cavities of different sizes inside. The structure is relatively simple, and the cavity part is usually a gas with no electromagnetic response capability. It is impossible to utilize the coordinated design of the cavity and heterogeneous functional components to construct a composite structure and thereby enhance the loss capacity. Summary of the invention

[0005] Based on the above facts, the purpose of the present invention is to provide a magnetic metal hollow microsphere and a preparation method and application thereof to solve the above problems.

[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 hollow microsphere, wherein the structure of the magnetic metal consists of a hollow core and a magnetic metal shell layer; wherein carbon microspheres are arranged in the hollow core.

[0008] Furthermore, in the hollow microspheres, the content of carbon microspheres is 15-50wt%, and the content of magnetic metal spherical shells is 50-85wt%, 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 hollow microspheres is 2.6-11.5 μm, the diameter of the carbon microspheres is 2-10 μm; the thickness of the magnetic metal spherical shell is 0.1-0.5 μm, and the distance between the carbon microspheres and the magnetic metal spherical shells is 0.2-0.25 μm.

[0011] In another aspect, the present invention provides a method for preparing the magnetic metal hollow microspheres as described above, comprising the following steps:

[0012] Precursor carbon spheres were prepared by hydrothermal method;

[0013] Pretreating the precursor carbon spheres;

[0014] Directed auxiliary assembly of magnetic metal spherical shells on the surface of pretreated precursor carbon spheres;

[0015] The magnetic metal hollow microspheres are obtained by heat treatment under a reducing or inert atmosphere.

[0016] Furthermore, the method for preparing precursor carbon spheres by hydrothermal method comprises the following steps:

[0017] The carbon source aqueous solution is mixed with a surfactant, subjected to a hydrothermal reaction, filtered, washed and dried to obtain the precursor carbon sphere.

[0018] Furthermore, the carbon source is selected from one or more of glucose, fructose, sucrose, maltose, starch and citric acid.

[0019] Furthermore, the concentration of the carbon source in the carbon source aqueous solution is 0.1-1 mol / L.

[0020] Furthermore, the surfactant is selected from one of cetyltrimethylammonium bromide and polyvinylpyrrolidone.

[0021] Furthermore, the temperature of the hydrothermal reaction is 170-200° C., and the time is 8-12 hours.

[0022] In the preparation method of the present invention, 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 core of the obtained carbon microspheres is located in the hollow cavity.

[0023] Furthermore, the pretreatment method comprises the following steps:

[0024] The precursor carbon spheres are subjected to surface coupling treatment, sensitization treatment and activation treatment in sequence to obtain the obtained carbon spheres.

[0025] 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 hollow microsphere. Only by performing surface coupling treatment, sensitization treatment and activation treatment in sequence can the hollow microsphere with stable structure and good electromagnetic properties be obtained.

[0026] 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.

[0027] Furthermore, the temperature of the surface coupling treatment is 20-70°C, more preferably 30-50°C.

[0028] 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.

[0029] 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.

[0030] Furthermore, the method also includes a reduction treatment step after 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 precursor carbon spheres 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 precursor carbon spheres to the reducing solution is preferably 1 g / 20 mL.

[0031] Furthermore, the method for directional auxiliary assembly of magnetic metal spherical shells on the surface of the pretreated precursor carbon spheres comprises the following steps:

[0032] The pretreated precursor carbon spheres are treated in an auxiliary deposition solution containing magnetic metal ions, stirred in a water bath, filtered, dried, and agglomerates are screened out to obtain the product.

[0033] Furthermore, the auxiliary deposition solution comprises a magnetic metal ion source salt, a stabilizer, a reducing agent and a pH adjuster.

[0034] Furthermore, the magnetic metal ion source salt is selected from sulfates, chlorides or organic acid salts of magnetic metals, and the concentration is 5-60 g / L.

[0035] 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.

[0036] Furthermore, the pH adjuster is selected from inorganic bases.

[0037] Furthermore, the pH of the auxiliary deposition solution is 9-11.

[0038] Furthermore, the temperature of the water bath is 50-85°C.

[0039] Furthermore, the addition amount of the pretreated intermediate carbon microspheres is 0.0025-0.01 g / mL.

[0040] Furthermore, the heat treatment temperature is 550-900°C and the time is 2-4h.

[0041] Furthermore, the atmosphere is a hydrogen / argon mixed gas, nitrogen or argon atmosphere.

[0042] In another aspect, the present invention provides a wave absorbing agent, which is prepared from the raw materials of the magnetic metal hollow microspheres as described above.

[0043] Furthermore, the application of the absorbing material can be used as one of the following materials: military stealth field, electromagnetic radiation protection of radio and television transmitters, microwave darkroom materials, building absorbing materials or electromagnetic shielding materials in radio communication equipment.

[0044] In another aspect, the present invention provides use of the magnetic metal hollow microspheres as described above in microwave absorption, catalysis, adsorption or wastewater treatment.

[0045] The beneficial effects of the present invention are as follows:

[0046] The movable carbon microsphere core in the magnetic metal hollow microsphere provided by the present invention can controllably fill the hollow structure inside the magnetic metal shell to improve the effective scattering of incident electromagnetic waves; the composite of the carbon microsphere core and the magnetic metal shell layer realizes the combination of electrical loss and magnetic loss.

[0047] In the preparation method of the magnetic metal hollow microspheres provided by the present invention, the functionality can be regulated by the composition and structural design of the metal spherical shell; by designing the internal cavity of the magnetic metal hollow microspheres, the specific structure is formed by the contraction of the forming template (carbon microspheres) and the self-supporting effect of the metal spherical shell. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] The specific implementation modes of the present invention are further described in detail below in conjunction with the accompanying drawings.

[0049] Figure 1 A schematic diagram showing the structure of an exemplary magnetic metal hollow microsphere of the present invention is shown in the figure.

[0050] Figure 2 A schematic diagram of an exemplary preparation process of magnetic hollow metal microspheres according to the present invention is shown.

[0051] Figure 3 A low-magnification scanning electron microscope (SEM) image of the magnetic metal hollow microspheres obtained in Example 1 is shown.

[0052] Figure 4 A high-magnification scanning electron microscope (SEM) image of the magnetic metal hollow microspheres obtained in Example 1 is shown.

[0053] Figure 5 X-ray diffraction pattern of the magnetic metal hollow microspheres obtained in Example 1. DETAILED DESCRIPTION

[0054] 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.

[0055] In the embodiment of the present invention, the schematic diagram of the structure of an exemplary magnetic metal hollow microsphere is as follows: Figure 1 shown.

[0056] An exemplary schematic diagram of the preparation process of the magnetic metal hollow microspheres is shown in Figure 2 shown. Figure 2 In the figure, A and B are hydrothermal treatments, C is magnetic metal assembly, and D is sulfidation treatment. Figure 2 It is not shown in the figure, but the precursor carbon spheres are pre-treated before assembling the magnetic metal shells.

[0057] Example 1

[0058] The preparation of magnetic metal hollow microspheres is as follows:

[0059] 1) Preparation of precursor carbon spheres: 14 g of glucose was dissolved in 140 mL of distilled water and stirred evenly, then 0.5 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 precursor carbon spheres;

[0060] 2) Surface treatment of the precursor carbon spheres: mix anhydrous ethanol, distilled water, and 3-aminopropyltriethoxysilane in a volume ratio of 30:10:2, add the precursor carbon spheres in a ratio of 5 g / 100 mL (5 g microspheres per 100 mL solution), stir in a water bath at 45° C. for 40 min, filter, dry and set aside;

[0061] 3) Precursor carbon sphere sensitization treatment: the microspheres obtained in step 1) are treated in a 0.1 mol / L stannous chloride aqueous solution at a ratio of 1 g / 20 mL, stirred at room temperature, and filtered;

[0062] 4) Activation treatment of precursor carbon spheres: The microspheres obtained in step 3) were treated in a ratio of 1 g / 30 mL in a 0.01 mol / L palladium chloride solution, stirred at room temperature, and filtered;

[0063] 5) Reduction treatment of precursor carbon spheres: 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;

[0064] 6) Preparation of precursor carbon sphere-metal composite microspheres: The microspheres obtained in step 5) were treated in a mixed solution of metal ions containing 36 g / L cobalt sulfate, 40 g / L sodium hypophosphite, 80 g / L potassium sodium tartrate, 40 g / L ammonium sulfate, pH ≈ 9.5 (adjusted by ammonia water) at a ratio of 1 g / 225 mL, stirred in a water bath at 65°C for 30 min, and filtered;

[0065] 7) The microspheres obtained in step 6) were placed in a flowing hydrogen-argon mixed atmosphere (hydrogen content 5%), heated to 700° C. at 10° C. / min, and kept at this temperature for 3 h, and then naturally cooled to room temperature.

[0066] The carbon microspheres in the inner core of the magnetic metal hollow microspheres obtained in this example have a diameter of 5.0 micrometers, and the cavity spacing (the distance between the carbon microspheres and the inner surface of the magnetic metal shell) is 0.23 micrometers; the mass percentages of the metal and carbon inner core are 69.1% and 30.9% respectively.

[0067] Example 2

[0068] The preparation of magnetic metal hollow microspheres is as follows:

[0069] 1) Preparation of precursor carbon spheres: 14 g of glucose was dissolved in 140 mL of distilled water and stirred evenly, then 0.5 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 precursor carbon spheres;

[0070] 2) Surface treatment of the precursor carbon spheres: mix anhydrous ethanol, distilled water, and 3-aminopropyltriethoxysilane in a volume ratio of 30:10:2, add the precursor carbon spheres in a ratio of 5 g / 100 mL (5 g microspheres per 100 mL solution), stir in a water bath at 45° C. for 40 min, filter, dry and set aside;

[0071] 3) Precursor carbon sphere sensitization treatment: the microspheres obtained in step 1) are treated in a 0.1 mol / L stannous chloride aqueous solution at a ratio of 1 g / 20 mL, stirred at room temperature, and filtered;

[0072] 4) Activation treatment of precursor carbon spheres: The microspheres obtained in step 3) were treated in a ratio of 1 g / 30 mL in a 0.01 mol / L palladium chloride solution, stirred at room temperature, and filtered;

[0073] 5) Reduction treatment of precursor carbon spheres: 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;

[0074] 6) Preparation of precursor carbon sphere-metal composite microspheres: The microspheres obtained in step 5) were treated in a mixed solution of metal ions containing 30 g / L cobalt sulfate, 40 g / L sodium hypophosphite, 80 g / L potassium sodium tartrate, 40 g / L ammonium sulfate, pH ≈ 9.5 (adjusted by ammonia water) at a ratio of 1 g / 200 mL, stirred in a water bath at 70°C for 30 min, and filtered;

[0075] 7) The microspheres obtained in step 6) were placed in a flowing hydrogen-argon mixed atmosphere (hydrogen content 5%), heated to 650° C. at 10° C. / min, and kept at this temperature for 3 h, and then naturally cooled to room temperature.

[0076] The carbon microspheres in the inner core of the magnetic metal hollow microspheres obtained in this example have a diameter of 5.1 microns, and the cavity spacing (the distance between the carbon microspheres and the inner surface of the magnetic metal shell) is 0.22 microns; the mass percentages of the metal and carbon inner core are 63.1% and 36.9% respectively.

[0077] Example 3

[0078] The preparation of magnetic metal hollow microspheres is as follows:

[0079] 1) Preparation of precursor carbon spheres: 14 g of glucose was dissolved in 140 mL of distilled water and stirred evenly, then 0.5 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 precursor carbon spheres;

[0080] 2) Surface treatment of the precursor carbon spheres: mix anhydrous ethanol, distilled water, and 3-aminopropyltriethoxysilane in a volume ratio of 30:10:2, add the precursor carbon spheres in a ratio of 5 g / 100 mL (5 g microspheres per 100 mL solution), stir in a water bath at 45° C. for 40 min, filter, dry and set aside;

[0081] 3) Precursor carbon sphere sensitization treatment: the microspheres obtained in step 1) are treated in a 0.1 mol / L stannous chloride aqueous solution at a ratio of 1 g / 20 mL, stirred at room temperature, and filtered;

[0082] 4) Activation treatment of precursor carbon spheres: The microspheres obtained in step 3) were treated in a ratio of 1 g / 30 mL in a 0.01 mol / L palladium chloride solution, stirred at room temperature, and filtered;

[0083] 5) Reduction treatment of precursor carbon spheres: 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;

[0084] 6) Preparation of precursor carbon sphere-metal composite microspheres: 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, 40 g / L ammonium sulfate, pH ≈ 9.5 (adjusted by ammonia water) at a ratio of 1 g / 250 mL, stirred in a water bath at 65°C for 30 min, and filtered;

[0085] 7) The microspheres obtained in step 6) were placed in a flowing hydrogen-argon mixed atmosphere (hydrogen content 5%), heated to 900° C. at 10° C. / min, and kept at this temperature for 3 h, and then naturally cooled to room temperature.

[0086] The carbon microspheres in the inner core of the magnetic metal hollow microspheres obtained in this example have a diameter of 4.8 micrometers, and the cavity spacing (the distance between the carbon microspheres and the inner surface of the magnetic metal shell) is 0.25 micrometers; the mass percentages of the metal and carbon inner core are 73.7% and 26.3% respectively.

[0087] Example 4

[0088] The preparation of magnetic metal hollow microspheres is as follows:

[0089] 1) Preparation of precursor carbon spheres: 14 g of glucose was dissolved in 140 mL of distilled water and stirred evenly, then 0.5 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 precursor carbon spheres;

[0090] 2) Surface treatment of the precursor carbon spheres: mix anhydrous ethanol, distilled water, and 3-aminopropyltriethoxysilane in a volume ratio of 30:10:2, add the precursor carbon spheres in a ratio of 5 g / 100 mL (5 g microspheres per 100 mL solution), stir in a water bath at 45° C. for 40 min, filter, dry and set aside;

[0091] 3) Precursor carbon sphere sensitization treatment: the microspheres obtained in step 1) are treated in a 0.1 mol / L stannous chloride aqueous solution at a ratio of 1 g / 20 mL, stirred at room temperature, and filtered;

[0092] 4) Activation treatment of precursor carbon spheres: The microspheres obtained in step 3) were treated in a ratio of 1 g / 30 mL in a 0.01 mol / L palladium chloride solution, stirred at room temperature, and filtered;

[0093] 5) Reduction treatment of precursor carbon spheres: 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;

[0094] 6) Preparation of precursor carbon sphere-metal composite microspheres: The microspheres obtained in step 5) were treated in a metal ion mixed solution containing 35 g / L nickel sulfate, 45 g / L sodium hypophosphite, 80 g / L potassium sodium tartrate, 40 g / L ammonium sulfate, pH ≈ 8.5 (adjusted by ammonia water) at a ratio of 1 g / 390 mL, stirred in a water bath at 50°C for 40 min, and filtered;

[0095] 7) The microspheres obtained in step 6) were placed in a flowing hydrogen-argon mixed atmosphere (hydrogen content 5%), heated to 550° C. at 10° C. / min, and kept at this temperature for 3 h, and then naturally cooled to room temperature.

[0096] The carbon microspheres in the inner core of the magnetic metal hollow microspheres obtained in this example have a diameter of 5.2 micrometers, and the cavity spacing (the distance between the carbon microspheres and the inner surface of the magnetic metal shell) is 0.21 micrometer; the mass percentages of the metal and carbon inner core are 79.5% and 20.5% respectively.

[0097] Example 5

[0098] The preparation of magnetic metal hollow microspheres is as follows:

[0099] 1) Preparation of precursor carbon spheres: 14 g of glucose was dissolved in 140 mL of distilled water and stirred evenly, then 0.5 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 precursor carbon spheres;

[0100] 2) Surface treatment of the precursor carbon spheres: mix anhydrous ethanol, distilled water, and 3-aminopropyltriethoxysilane in a volume ratio of 30:10:2, add the precursor carbon spheres in a ratio of 5 g / 100 mL (5 g microspheres per 100 mL solution), stir in a water bath at 45° C. for 40 min, filter, dry and set aside;

[0101] 3) Precursor carbon sphere sensitization treatment: the microspheres obtained in step 1) are treated in a 0.1 mol / L stannous chloride aqueous solution at a ratio of 1 g / 20 mL, stirred at room temperature, and filtered;

[0102] 4) Activation treatment of precursor carbon spheres: The microspheres obtained in step 3) were treated in a ratio of 1 g / 30 mL in a 0.01 mol / L palladium chloride solution, stirred at room temperature, and filtered;

[0103] 5) Reduction treatment of precursor carbon spheres: 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 precursor carbon sphere-metal composite microspheres: The microspheres obtained in step 5) were treated in a metal ion mixed solution containing 30 g / L nickel sulfate, 40 g / L sodium hypophosphite, 80 g / L potassium sodium tartrate, 40 g / L ammonium sulfate, pH ≈ 9.0 (adjusted by ammonia water) at a ratio of 1 g / 150 mL, stirred in a water bath at 65°C for 30 min, and filtered;

[0105] 7) The microspheres obtained in step 6) were placed in a flowing hydrogen-argon mixed atmosphere (hydrogen content 5%), heated to 700° C. at 10° C. / min, and kept at this temperature for 3 h, and then naturally cooled to room temperature.

[0106] The carbon microspheres in the inner core of the magnetic metal hollow microspheres obtained in this example have a diameter of 5.0 micrometers, and the cavity spacing (the distance between the carbon microspheres and the inner surface of the magnetic metal shell) is 0.22 micrometers; the mass percentages of the metal and carbon inner core are 55.4% and 44.6% respectively.

[0107] Example 6

[0108] The preparation of magnetic metal hollow microspheres is as follows:

[0109] 1) Preparation of precursor carbon spheres: 14 g of glucose was dissolved in 140 mL of distilled water and stirred evenly, then 0.5 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 precursor carbon spheres;

[0110] 2) Surface treatment of the precursor carbon spheres: mix anhydrous ethanol, distilled water, and 3-aminopropyltriethoxysilane in a volume ratio of 30:10:2, add the precursor carbon spheres in a ratio of 5 g / 100 mL (5 g microspheres per 100 mL solution), stir in a water bath at 45° C. for 40 min, filter, dry and set aside;

[0111] 3) Precursor carbon sphere sensitization treatment: The microspheres obtained in step 1) were treated in a 0.1 mol / L stannous chloride aqueous solution at a ratio of 1 g / 20 mL, stirred at room temperature, and filtered.

[0112] 4) Activation treatment of precursor carbon spheres: The microspheres obtained in step 3) were treated in a ratio of 1 g / 30 mL in a 0.01 mol / L palladium chloride solution, stirred at room temperature, and filtered;

[0113] 5) Reduction treatment of precursor carbon spheres: 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;

[0114] 6) Preparation of precursor carbon sphere-metal composite microspheres: 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 40 min, and filtered;

[0115] 7) The microspheres obtained in step 6) were placed in a flowing hydrogen-argon mixed atmosphere (hydrogen content 5%), heated to 700° C. at 10° C. / min, and kept at this temperature for 2 h, and then naturally cooled to room temperature.

[0116] The carbon microspheres in the inner core of the magnetic metal hollow microspheres obtained in this example have a diameter of 5.0 microns, and the cavity spacing (the distance between the carbon microspheres and the inner surface of the magnetic metal shell) is 0.23 microns; the mass percentages of the metal and carbon inner core are 83.2% and 16.8% respectively.

[0117] Example 7

[0118] The preparation of magnetic metal hollow microspheres is as follows:

[0119] 1) Preparation of precursor carbon spheres: 14 g of glucose was dissolved in 140 mL of distilled water and stirred evenly, then 0.5 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 precursor carbon spheres;

[0120] 2) Surface treatment of the precursor carbon spheres: mix anhydrous ethanol, distilled water, and 3-aminopropyltriethoxysilane in a volume ratio of 30:10:2, add the precursor carbon spheres in a ratio of 5 g / 100 mL (5 g microspheres per 100 mL solution), stir in a water bath at 45° C. for 40 min, filter, dry and set aside;

[0121] 3) Precursor carbon sphere sensitization treatment: the microspheres obtained in step 1) are treated in a 0.1 mol / L stannous chloride aqueous solution at a ratio of 1 g / 20 mL, stirred at room temperature, and filtered;

[0122] 4) Activation treatment of precursor carbon spheres: The microspheres obtained in step 3) were treated in a ratio of 1 g / 30 mL in a 0.01 mol / L palladium chloride solution, stirred at room temperature, and filtered;

[0123] 5) Reduction treatment of precursor carbon spheres: 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;

[0124] 6) Preparation of precursor carbon sphere-metal composite microspheres: The microspheres obtained in step 5) were treated in a ratio of 1 g / 235 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;

[0125] 7) The microspheres obtained in step 6) were placed in a flowing hydrogen-argon mixed atmosphere (hydrogen content 5%), heated to 650° C. at 10° C. / min, and kept at this temperature for 3 h, and then naturally cooled to room temperature.

[0126] The carbon core of the magnetic metal hollow microspheres with a carbon core obtained in this example has a diameter of 5.0 microns and a cavity spacing (the distance between the core and the inner surface of the magnetic metal shell) of 0.22 microns; the mass percentages of the metal and carbon core are 72.2% and 27.8% respectively.

[0127] Example 8

[0128] The preparation of magnetic metal hollow microspheres is as follows:

[0129] 1) Preparation of precursor carbon spheres: 14 g of glucose was dissolved in 140 mL of distilled water and stirred evenly, then 0.5 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 precursor carbon spheres;

[0130] 2) Surface treatment of the precursor carbon spheres: mix anhydrous ethanol, distilled water, and 3-aminopropyltriethoxysilane in a volume ratio of 30:10:2, add the precursor carbon spheres in a ratio of 5 g / 100 mL (5 g microspheres per 100 mL solution), stir in a water bath at 45° C. for 40 min, filter, dry and set aside;

[0131] 3) Precursor carbon sphere sensitization treatment: the microspheres obtained in step 1) are treated in a 0.1 mol / L stannous chloride aqueous solution at a ratio of 1 g / 20 mL, stirred at room temperature, and filtered;

[0132] 4) Activation treatment of precursor carbon spheres: The microspheres obtained in step 3) were treated in a ratio of 1 g / 30 mL in a 0.01 mol / L palladium chloride solution, stirred at room temperature, and filtered;

[0133] 5) Reduction treatment of precursor carbon spheres: 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;

[0134] 6) Preparation of precursor carbon sphere-metal composite microspheres: 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;

[0135] 7) The microspheres obtained in step 6) were placed in a flowing hydrogen-argon mixed atmosphere (hydrogen content 5%), heated to 650° C. at 10° C. / min, and kept at this temperature for 4 h, and then naturally cooled to room temperature.

[0136] The carbon microspheres in the inner core of the magnetic metal hollow microspheres obtained in this example have a diameter of 5.0 microns, a cavity spacing (the distance between the inner core and the inner surface of the magnetic metal shell) of 0.22 microns, and the mass percentages of the metal and carbon inner cores are 72.4% and 27.6%, respectively.

[0137] Comparative Example 1

[0138] Same as Example 8, but without the heat treatment in step 7), no cavity is generated; the mass percentages of metal and precursor carbon spheres are 67.2% and 32.8% respectively.

[0139] Comparative Example 2

[0140] The other conditions are the same as those in Example 8, 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.

[0141] Comparative Example 3

[0142] The other conditions are the same as those in Example 8, except that the precursor carbon spheres synthesized by the hydrothermal method are first subjected to heat treatment, and then subjected to subsequent heat treatment and metal coating. The microspheres do not shrink in volume during the final heat treatment and do not generate cavities.

[0143] Performance Test:

[0144] 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 35%-50%, 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.

[0145] Table 1

[0146]

[0147] 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 hollow microsphere, It is characterized in that The structure of the magnetic metal consists of a hollow core and a magnetic metal spherical shell layer; wherein carbon microspheres are arranged in the hollow core.

2. The magnetic metal hollow microspheres according to claim 1, It is characterized in that In the hollow microspheres, the content of carbon microspheres is 15-50wt%, and the content of magnetic metal spherical shells is 50-85wt%, calculated by mass percentage.

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

4. A method for preparing magnetic hollow metal microspheres according to any one of claims 1 to 3, It is characterized in that The steps include: Precursor carbon spheres were prepared by hydrothermal method; Pretreating the precursor carbon spheres; Directed auxiliary assembly of magnetic metal spherical shells on the surface of pretreated precursor carbon spheres; The magnetic metal hollow microspheres are obtained by heat treatment under a reducing or inert atmosphere.

5. The preparation method according to claim 4, It is characterized in that The method for preparing precursor carbon spheres 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 precursor carbon spheres; 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 170-200° C. and the time is 8-12 h.

6. The preparation method according to claim 4, It is characterized in that The pretreatment method comprises the following steps: The precursor carbon spheres 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 precursor carbon spheres comprises the following steps: The pretreated precursor carbon spheres 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 5-60 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 heat treatment temperature is 550-900°C and the time is 2-4h.

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

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

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