A method for preparing electromagnetic absorbing material

Abstract

The present invention belongs to the technical field of electromagnetic wave absorbing materials, and in particular relates to a method for preparing an electromagnetic wave absorbing material, comprising the following steps: mixing alkenylsilane, trichlorosilane, and propenyl magnesium chloride to perform alkenylation to obtain a multi-branched alkenylsilane compound containing three functional groups, performing hydroboration with 9-BBN, and then performing hydroboration with H2O2 / OH. ‑ Oxidation is performed to convert it into a dendritic carbon silane polyol; silica sphere sols of different particle sizes are selected according to needs and placed in two containers. A silane coupling agent and a dendritic carbon silane polyol are added under alkaline conditions for condensation reaction to respectively produce dendritic carbon (a small amount of silicon)-silica spheres and silicon carbide-silica sphere precursors, respectively. This solves the problems of carbon nanomaterials being extremely easy to agglomerate and difficult to disperse, which greatly limit their performance and cannot meet the requirements of "strong absorption, wide bandwidth, low density, and thin thickness" for absorbing materials. In addition, existing carbon-based absorbing materials have defects such as uncontrollable preparation and poor absorbing effect.

Description

Technical Field

[0001] The present invention belongs to the technical field of electromagnetic wave absorbing materials, and in particular relates to a method for preparing an electromagnetic wave absorbing material. Background Art

[0002] Electromagnetic absorbing materials (EMA) are materials that absorb or significantly attenuate electromagnetic wave energy received by their surface, thereby reducing electromagnetic interference. Electromagnetic absorbing materials can generally be divided into three categories: resistive loss, dielectric loss, and magnetic loss. They can also be categorized by the element used in the absorbing material, such as iron, carbon, ceramic, and other types.

[0003] With the advancement of modern science and technology, the impact of electromagnetic radiation on the environment is increasing. Flights can be delayed due to electromagnetic interference; in hospitals, mobile devices can interfere with the normal operation of various electronic diagnostic and treatment equipment. Therefore, combating electromagnetic pollution and finding materials that can absorb and attenuate electromagnetic radiation—absorbers—has become a major topic in materials science. In engineering applications, absorbing materials must not only have high electromagnetic wave absorptivity over a wide frequency band, but also be lightweight, heat-resistant, moisture-resistant, and corrosion-resistant. Electromagnetic waves enter the absorbing material and are dissipated through dielectric and magnetic loss mechanisms, or through the principle of destructive interference. This dissipation converts the electromagnetic energy into other forms of energy, such as heat. This fundamental absorption of electromagnetic waves prevents secondary pollution.

[0004] Carbon-based absorbing materials have attracted widespread attention due to their low density, high strength, and excellent chemical and environmental stability. However, carbon nanomaterials are prone to agglomeration and difficulty dispersing, significantly limiting their performance. They cannot meet the requirements of high absorption, wide bandwidth, low density, and thin thickness for absorbing materials. Therefore, the development of high-performance carbon-based absorbing materials is urgent. Summary of the Invention

[0005] (1) Technical issues to be resolved

[0006] The present invention aims to address the shortcomings of existing technologies by providing a method for preparing electromagnetic absorbing materials. This method addresses the problems of carbon nanomaterials, which are prone to agglomeration and difficulty in dispersion, significantly limiting their performance and failing to meet the requirements for "strong absorption, wide bandwidth, low density, and thin thickness" for absorbing materials. Furthermore, existing carbon-based absorbing materials suffer from uncontrollable preparation and poor absorbing performance.

[0007] (2) Technical solution

[0008] 1. A method for preparing an electromagnetic absorbing material, comprising the following steps:

[0009] S1. Alkenylsilane, trichlorosilane and propenyl magnesium chloride were mixed and olefinated to obtain a multi-branched alkenylsilane compound containing three functional groups, which was then hydroborated with 9-BBN and then hydrated with H2O2 / OH. - Oxidation is performed to convert it into a dendritic carbosilane polyol;

[0010] S2. Silica sphere sols of different particle sizes are selected as required and placed in two containers. A silane coupling agent and a dendritic carbosilane polyol are added thereto under alkaline conditions for condensation reaction to obtain silica sphere-dendritic carbosilane and silica sphere-silane coupling agent condensation products, respectively.

[0011] S3, placing the silicon ball-dendritic carbon silane in a high-temperature reaction vessel and calcining it under high-temperature conditions under inert atmosphere to obtain silicon dioxide core-dendritic carbon shell beads; similarly, calcining the silicon ball-silane coupling agent condensation product under high-temperature vacuum (2000° C., 1 Torr) to obtain silicon dioxide core-silicon carbide shell beads;

[0012] S4. The prepared silicon sphere-dendritic carbon silane of different particle sizes is doped and mixed with the silicon sphere-silane coupling agent condensation product to obtain an electromagnetic absorbing material, which can achieve good absorption and dissipation effects on electromagnetic waves of different bands and bandwidths.

[0013] As a preferred technical solution, the alkenylsilane in step S1 is tetrapropylenesilane.

[0014] As a preferred technical solution, the reaction molar ratio of alkenylsilane, trichlorosilane, and propenylmagnesium chloride in step S1 is 1:4:12, the conditions are catalyst and heating, and the catalyst is nickel oxide.

[0015] As a preferred technical solution, the order of adding materials in step S1 is to first add alkenylsilane and trichlorosilane into the reactor and stir and mix them for reaction, and then slowly add allylmagnesium chloride.

[0016] As a preferred technical solution, the trichlorosilane and allylmagnesium chloride in step S1 can be changed according to the spatial length and branching degree.

[0017] As a preferred technical solution, the three functional groups in step S1 are double bond alkenyl, halosilane, and haloolefin.

[0018] (3) Beneficial effects

[0019] The beneficial effects of the present invention are:

[0020] (1) Different halogenated silanes can adjust the branching degree of dendritic carbosilane polyols. The dendritic carbosilane polyols prepared by trichlorosilane have a high degree of branching, strong adhesion to silica spheres, and the carbon spheres are relatively stable after sintering.

[0021] (2) Using allyl magnesium chloride to alkenylate halogenated silanes, the spatial length of the dendritic carbosilane polyol is increased, providing alkenyl functional groups that can be alcoholized.

[0022] (3) The present invention can produce different target products by selecting different intermediate reactants under controllable experimental conditions. The particle size, branching degree, spatial length, etc. of the product can be controlled, and the experimental repeatability is high.

[0023] (4) The product obtained by the present invention has excellent theoretical performance, and the reaction process can be controlled according to different needs, resulting in a variety of products and applications. The dendritic carbosilane condensed on the silica sphere solves the problem of poor adhesion of the carbon shell of the electromagnetic wave absorber, reduces the material density, increases the electromagnetic wave loss path, and improves the electromagnetic wave loss capacity of the material. The resulting composite absorber has an adjustable absorption frequency, a bandwidth of 0 to 4.1 GHz with a reflection loss of <10 dB, and a minimum reflection coefficient of 42.2 dB. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0025] Figure 1 It is the chemical formula structural formula diagram of the product of the present invention. DETAILED DESCRIPTION

[0026] The present invention is further described with reference to the accompanying drawings. The present invention is further described in detail with reference to the embodiments below:

[0027] As shown in the accompanying drawings: A method for preparing an electromagnetic absorbing material comprises the following steps:

[0028] S1. Alkenylsilane, trichlorosilane and propenyl magnesium chloride were mixed and olefinated to obtain a multi-branched alkenylsilane compound containing three functional groups, which was then hydroborated with 9-BBN and then hydrated with H2O2 / OH. - Oxidation is performed to convert it into a dendritic carbosilane polyol.

[0029] S2. Silica sphere sols of different particle sizes are selected as required and placed in two containers. A silane coupling agent and a dendritic carbosilane polyol are added thereto under alkaline conditions for condensation reaction to obtain silica sphere-dendritic carbosilane and silica sphere-silane coupling agent condensation products, respectively.

[0030] S3. Place the silicon ball-dendritic carbon silane in a high-temperature reaction vessel and calcine it under high-temperature conditions under inert atmosphere protection to obtain silicon dioxide core-dendritic carbon shell beads; similarly, calcine the silicon ball-silane coupling agent condensation product under high-temperature vacuum (2000°C, 1 Torr) to obtain silicon dioxide core-silicon carbide shell beads.

[0031] S4. The prepared silicon sphere-dendritic carbon silane of different particle sizes is doped and mixed with the silicon sphere-silane coupling agent condensation product to obtain an electromagnetic absorbing material, which can achieve good absorption and dissipation effects on electromagnetic waves of different bands and bandwidths.

[0032] Furthermore, the alkenylsilane in step S1 is tetrapropylenesilane.

[0033] It should be noted that the spatial length and branching degree of the dendritic carbosilane polyol produced in step S1 can be controlled by selecting intermediate reactants with different chain lengths and different halogenated hydrocarbons.

[0034] Furthermore, in step S1, the reaction molar ratio of tetrapropylene silane, trichlorosilane, and propenyl magnesium chloride is 1:4:12, the conditions are catalyst and heating, and the catalyst is nickel oxide.

[0035] Furthermore, the order of adding materials in step S1 is to first add tetrapropylene silane and trichlorosilane into the reactor and stir and mix them for reaction, and then slowly add propenyl magnesium chloride.

[0036] It should be noted that different halogenated silanes can adjust the branching degree of the dendritic carbosilane polyol. The dendritic carbosilane polyol prepared by trichlorosilane has a high branching degree, strong adhesion to silica spheres, and the carbon spheres after sintering are relatively stable.

[0037] Furthermore, the trichlorosilane and allylmagnesium chloride in step S1 can be changed according to the spatial length and branching degree, for example, they can be replaced with dichlorosilane and vinylmagnesium halide. If replaced, the molar ratio must be recalculated.

[0038] Furthermore, the three functional groups in step S1 are double bond alkenyl, halosilane, and haloolefin.

[0039] It should be noted that the product produced by this invention has excellent theoretical performance, and the reaction process can be controlled according to different needs, resulting in a variety of products and applications. The dendritic carbosilane condensation onto silica spheres solves the problem of poor adhesion of the carbon shell of the electromagnetic wave absorber, reduces material density, increases electromagnetic wave loss pathways, and improves the material's electromagnetic wave loss capability. The resulting composite absorber has adjustable absorption frequency, with a frequency band of 0 to 4.1 GHz where reflection loss is less than 10 dB, and a minimum reflection coefficient of 42.2 dB.

[0040] The above embodiments are merely descriptions of preferred implementations of the present invention and are not intended to limit the concept and scope of the present invention. Without departing from the design concept of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary persons in the art should fall within the scope of protection of the present invention. The technical contents for which protection is sought in the present invention are all recorded in the claims.

Claims

1. A method for preparing an electromagnetic absorbing material, characterized in that: The following steps are involved: S1. Alkenylsilane, trichlorosilane and propenyl magnesium chloride are mixed for alkenylation. The reaction molar ratio of alkenylsilane, trichlorosilane and propenyl magnesium chloride is 1:4:

12. The conditions are catalyst and heating. The catalyst is nickel oxide. A multi-branched alkenylsilane compound containing three functional groups is obtained. The compound is hydroborated with 9-BBN and then treated with H2O2 / OH. - Oxidation is performed to convert it into a dendritic carbosilane polyol; S2. Silica sphere sols of different particle sizes are selected as required and placed in two containers. Dendritic carbosilane polyol and silane coupling agent are added respectively under alkaline conditions for condensation reaction to obtain silica sphere-dendritic carbosilane and silica sphere-silane coupling agent condensation products, respectively. S3, placing the silicon ball-dendritic carbon silane in a high-temperature reaction vessel and calcining it under high-temperature conditions under inert atmosphere protection to obtain silicon dioxide core-dendritic carbon shell beads; similarly, calcining the silicon ball-silane coupling agent condensation product under high-temperature vacuum conditions, i.e., 2000° C., 1 Torr, to obtain silicon dioxide core-silicon carbide shell beads; S4. The prepared silicon sphere-dendritic carbon silane of different particle sizes is doped and mixed with the silicon sphere-silane coupling agent condensation product to obtain an electromagnetic absorbing material, which can achieve good absorption and dissipation effects on electromagnetic waves of different bands and bandwidths.

2. The method for preparing an electromagnetic absorbing material according to claim 1, wherein: The alkenylsilane in step S1 is tetrapropylenesilane.

3. The method for preparing an electromagnetic absorbing material according to claim 1, wherein: The order of adding materials in step S1 is to first add alkenylsilane and trichlorosilane into the reactor and stir and mix them for reaction, and then slowly add allylmagnesium chloride.

4. The method for preparing an electromagnetic absorbing material according to claim 1, wherein: The three functional groups in step S1 are double bond alkenyl, halosilane, and haloolefin.

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