CN111286079A - A kind of preparation method of radar wave absorbing composite material with infrared stealth - Google Patents

Abstract

The invention discloses a method for preparing a radar wave absorbing composite material with infrared stealth. The chemical reaction between a substrate and metal ions is used to prepare a composite (BM-M) in which the substrate supports metal particles with absorbing properties. , and then use the hydrophobicity and porous structure characteristics of the substrate to load and store the phase change material PCM to prepare the product BM‑M/PCM. The composite material prepared by the invention has the characteristics of softness and high mechanical strength. Therefore, the leather that is compatible with radar wave stealth and infrared stealth prepared by using leather as the base material has the characteristics of being bendable and wearable.

Description

A kind of preparation method of radar wave absorbing composite material with infrared stealth

technical field

The invention belongs to the research field of functional materials, in particular to a preparation method of a radar wave absorbing composite material with infrared stealth.

Background technique

Multifunctional stealth materials have broad application prospects in the military field. Among them, dual-stealth materials with both radar stealth and infrared stealth are of great significance in the protection of important military targets and individual combat. However, radar stealth is based on the principle of absorption, that is, by absorbing radar waves to reduce the reflection of radar waves on the surface of the target object to achieve radar stealth, while infrared stealth mainly increases the reflectivity of the surface of the object and uses the principle of reflecting infrared rays Achieve infrared stealth. The contradiction in the realization principle of radar stealth and infrared stealth makes the preparation of radar and infrared stealth materials extremely challenging.

At present, multi-layer coating is mainly used at home and abroad to prepare radar and infrared dual stealth materials, that is, a coating with infrared stealth is coated on the surface of the radar wave absorbing coating. Radar wave absorbing coating is mainly composed of absorbing metal powder (metal particles, alloy powder, ferrite powder, carbon black, conductive fiber, etc.) and resin (polyurethane, polyacrylic acid, epoxy resin, silicone resin, etc.) ) is mixed and applied to the target, and the infrared stealth coating is a combination of metal powder with high infrared reflection characteristics, especially flake silver powder, flake copper powder, flake aluminum powder, etc., with resin (polyurethane, polyacrylic acid, epoxy resin) , polyamide resin, etc.) are mixed and coated on the surface of the wave-absorbing coating. It can be seen that a big problem of this coating-type dual-function stealth material is the reflection of the radar wave by the superimposed infrared stealth coating. The metal powder of the infrared coating will cause a large reflectivity to the radar wave, so that it cannot be incident on the radar wave absorbing layer, which is lost and reflected back, thus affecting the compatibility of the radar wave. Therefore, this coating type double stealth material has strict requirements on the thickness of the infrared stealth coating and the amount of metal powder, and the infrared stealth effect needs to be improved urgently.

To sum up, the previous dual stealth materials achieved infrared stealth by improving the reflectivity of the material, which contradicts the principle of radar stealth. To this end, if we can develop a method of absorption rather than reflection to jointly achieve infrared stealth and radar stealth performance, we can prepare radar wave absorbing materials that can have both infrared stealth and infrared stealth.

SUMMARY OF THE INVENTION

The patent of the present invention mainly aims at the above-mentioned problems, and prepares a radar wave absorbing composite material based on the absorption principle that can also have infrared stealth. It is characterized by using natural leather or foam made from the skin of livestock animals as the base material, and by loading metal particles with radar wave absorption properties and paraffin with phase change absorption ability, the leather is given radar stealth performance and infrared stealth performance, and The leather is bendable and wearable.

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

A preparation method of a radar wave absorbing composite material with infrared stealth, comprising the following steps:

(1) Using the chemical reaction between the substrate and metal ions to prepare a substrate composite (BM-M) in which the substrate supports metal particles with absorbing properties;

(2) The phase change material is supported on the substrate to prepare the product substrate-metal ion/phase change material.

Further, the chemical reaction between the substrate and the metal ion is any one of the following two methods:

(1) The substrate and metal ions react under mechanical action, and then a reducing agent is added to reduce the metal ions into nanoparticles;

(2) After the substrate reacts with the plant polyphenol under mechanical force, metal ions are added to continue the reaction, and finally a reducing agent is added to reduce the metal ions into nanoparticles.

Further, the amount of the metal ions is 5-30% of the mass of the substrate.

Further, the base material is one of leather or foam.

Further, when the base material is leather, the phase change material loaded on the leather is prepared by the following method: the prepared Leather-M is dehydrated in an anhydrous ethanol solution, and then the phase change material is added to carry out physical adsorption to prepare. The product leather-metal ion/phase change material composite (leather-M/PCM).

Further, the metal ions are silver ions.

Further, the reducing agent is sodium borohydride NaBH ₄ .

Further, the leather is a powdered collagen fiber prepared by removing the non-collagen interstitium from animal skins or scraps according to a tanning pretreatment process, or a commercially available leather commodity or semi-finished product mainly consisting of collagen fibers.

Further, when the base material is foam, the foam is added to the bayberry tannin solution to carry out the adsorption reaction, then the metal ion solution is added to continue the adsorption reaction, and finally the reducing agent reduces the metal ions to prepare the intermediate product Foam-M. The obtained product was immersed in PDMS solution (5wt%, dodecane as solvent) for 0.5h, and after drying, the phase change material was added, and finally the composite material of foam-metal ion/phase change material (foam-metal ion/phase change material) was obtained after cooling. M/PCM).

It can be seen that, compared with the above-mentioned compatible radar wave stealth and infrared stealth coated composite materials, the present invention uses leather as the base material, and the radar wave stealth leather (MISL) with both infrared stealth prepared has the following advantages:

1. MISL does not have a strong reflective coating, which avoids the reflection problem of infrared coating on radar waves;

2. MISL has a unique multi-level fiber weaving structure, which has strong multi-level diffuse reflection and scattering characteristics for incident radar waves, which can enhance the multi-level diffuse reflection and scattering loss of nano metal particles to radar waves, and realize radar wave stealth;

_3. Leather is mainly formed by a high degree of weaving of skin _collagen fibers. A variety of chemical reactions occur with metal ions. It can be seen that when leather is used as a substrate to prepare radar wave absorbing materials, the active groups of skin collagen fibers or skin collagen fibers modified with plant polyphenols provide chemical support for their metal particles. foundation, and the metal particles can be dispersed evenly;

4. The thermal conductivity of the natural leather base material is poor, and its interior contains at least 12% moisture, and the specific heat capacity of water is large, so when the infrared stealth material prepared with natural leather as the base material covers high-temperature objects, the natural leather is blocked by A large amount of heat from radiation and convection of high-temperature objects, and its body temperature does not increase significantly, thereby effectively reducing the infrared heat radiation intensity of high-temperature objects and achieving infrared stealth effect of high-temperature objects;

5. Nano metal particles are metal particles with low reflectivity. When loaded in CF, they can effectively reduce the infrared emissivity of MISL, reduce the infrared radiation intensity of MISL, and enhance its infrared stealth performance;

6. Although MISL absorbs the infrared light waves incident on its interior, the phase change material PCM inside it can absorb a lot of heat through phase change, thereby delaying the temperature change of MISL. Therefore, even if MISL absorbs a lot of infrared radiation Light, its own temperature changes relatively slowly, or even does not change, to achieve infrared stealth;

7. When MISL covers the high temperature target surface, its internal phase change material can effectively absorb the heat conducted by the target through the phase change process, thereby further reducing the target surface temperature, reducing its infrared thermal radiation energy, and achieving infrared stealth effect;

8. Leather is mainly from cattle, sheep, pigs and other animal furs. It is woven from collagen fibers and has the characteristics of high porosity. Its unique porous structure provides a good structural basis for the adsorption and storage of phase change materials. Moreover, The collagen molecules of collagen fibers contain a large number of hydrophobic regions, which can adsorb and store a large amount of phase change materials, and can effectively prevent the leakage of phase change materials after phase change;

9. Leather is mainly a solid material with multi-level fiber structure formed by highly woven skin collagen fibers, which has the characteristics of softness and high mechanical strength. Therefore, radar stealth leather with infrared stealth and infrared stealth is prepared by using leather as the base material. , has the characteristics of being bendable and wearable.

Description of drawings

Fig. 1 is a graph of the reflection loss RL performance of the leather-Ag _5% prepared in Example 1 to radar waves under different thicknesses;

Figure 2 is a graph of the reflection loss RL performance of the leather-Ag _10% prepared in Example 2 to radar waves under different thicknesses;

Figure 3 is a graph of the reflection loss RL performance of the leather-Ag _30% prepared in Example 3 to radar waves under different thicknesses;

Fig. 4 SEM images (a, b) and TEM images (c, d) of leather-Ag _20% /PCM prepared in Example 4, the inset in Fig. d is the selection of leather-Ag _20% /PCM nanofibers (d) Area electron diffraction SAED pattern;

Fig. 5 is a graph of the reflection loss RL performance of the leather-Ag _20% /PCM prepared in Example 4 to radar waves under different thicknesses;

Fig. 6 DSC diagram of leather-Ag _20% /PCM prepared in Example 4;

The measured radar wave reflection loss RL performance diagram of the foam-Ag/PCM prepared in Fig. 7 Example 5;

Fig. 8 Variation curve of surface infrared radiation temperature with time when the foam-Ag/PCM prepared in Example 5 is placed on a heating plate of ~40°C.

Detailed ways

The present invention will be specifically described below by means of examples. It is necessary to point out here that this embodiment is only used to further illustrate the present invention, and should not be construed as a limitation on the protection scope of the present invention.

Example 1

Get 100g leather and 5g nano silver ion, in 100mL secondary water, carry out adsorption reaction under strong mechanical force (stirring) at room temperature, after 4h, add reducing agent sodium borohydride (molar ratio Ag ⁺ : NaBH ₄ =1: 1) Reducing silver ions, washing and drying to obtain a composite material of leather-loaded nano-silver particles (leather-Ag _5% ). As shown in Figure 1, leather-Ag _5% has a strong absorption effect on radar waves, where the maximum RL can reach -10dB.

Example 2

Take 100g of leather and 10g of nano-silver ions, put them in 100mL of secondary water, and carry out adsorption reaction under strong mechanical force at room temperature. After 4h, add reducing agent sodium borohydride (molar ratio Ag ⁺ : NaBH ₄ =1:1) to reduce Silver ions, after washing and drying, the composite material of leather loaded with nano silver particles (leather-Ag _10% ) can be obtained. As shown in Figure 2, leather-Ag _10% has a strong absorption effect on radar waves, and the maximum RL can reach -22dB.

Example 3

Take 100g of leather and 30g of nano silver ions, put them in 100mL of secondary water, and carry out adsorption reaction under strong mechanical force at room temperature. After 4h, add reducing agent sodium borohydride (molar ratio Ag ⁺ : NaBH ₄ =1:1) to reduce Silver ions, after washing and drying, the composite material of leather loaded with nano silver particles (leather-Ag _30% ) can be obtained. As shown in Fig. 3, the maximum RL of leather-Ag _10% to radar wave can reach -17dB. And by testing its infrared emissivity at 8-14μm outside 0.77.

Example 4

Take 100g of leather and 20g of nano-silver ions, put them in 200mL of secondary water, and carry out adsorption reaction under strong mechanical force at room temperature. After 4h, add reducing agent sodium borohydride (molar ratio Ag ⁺ : NaBH ₄ =1:1) to reduce Silver ions, after washing and drying, the composite material (CF-Ag _20% ) of leather loaded with nano-silver particles can be obtained. After dehydration with absolute ethanol, 30 g of paraffin was added at 50°C, and under strong mechanical force, the paraffin was uniformly penetrated to form a leather-metal ion/phase change material (leather-Ag _20% /PCM) composite material. As shown in Fig. 4, the leather-Ag _20% /PCM retained the original woven structure of the skin collagen fibers, and the PCM was uniformly physically adsorbed on the surface of the leather-Ag _20% /PCM nanofibers. At the same time, the Ag nanoparticles were also successfully loaded. on the surface of leather-Ag _20% /PCM nanofibers. It can be seen from Fig. 5 that the reflection loss value RL of leather-Ag _20% /PCM to radar wave is as high as -39dB. By DSC test (Fig. 6), leather-Ag _20% /PCM showed an endothermic peak at ~31°C and an exothermic peak at ~23°C. It can be seen that when the leather-Ag _20% /PCM covers the high-temperature target, it can absorb a large amount of heat, slow down the rise of its own temperature, suppress the infrared heat radiation intensity on the surface of the high-temperature target, and achieve a good infrared stealth effect. And by testing its infrared emissivity at 8-14μm outside 0.78.

Example 5

Take 210*210*20mm foam, dissolve 10g of bayberry tannin in 150mL of secondary deionized water, add 300mL of absolute ethanol, mix well and pour it on the foam, and squeeze the foam under the action of external force to make the foam completely absorbed. Then, 50 mL of secondary deionized water containing 23.59 g of silver nitrate was poured onto the foam, and the foam was squeezed under the action of external force to be completely absorbed. Finally, after dissolving 5.26 g of sodium borohydride in 50 mL of secondary deionized water, invert the foam, squeeze the foam under the action of external force to make the solution completely absorbed and dry. A foam loaded with silver nanoparticles (foam-Ag) can be obtained. The obtained foam-Ag was soaked in 40mL PDMS solution (5wt%, dodecane as solvent) for 0.5h, then 40mL paraffin liquid was added, and after natural cooling and solidification, a foam with both radar wave absorption and infrared stealth performance was obtained ( Foam-Ag/PCM). As shown in Figure 7, the foam-Ag/PCM has good absorption and loss performance for radar waves, and when placed on a high temperature heat source (~40 °C), it can be seen by infrared thermal imager observation that after 60 minutes, the foam-Ag/PCM The surface temperature of the PCM still remained at 14.4°C, which was much lower than the heat source temperature (Fig. 8). Therefore, the foam-Ag/PCM can effectively suppress the infrared thermal radiation intensity of the heat source and realize the infrared stealth of the heat source.

Claims (10)

1. A preparation method of a radar wave absorption composite material with infrared stealth is characterized by comprising the following steps:

firstly, preparing a composite (BM-M) of a base material loaded with metal particles with absorption performance by utilizing a chemical reaction between the base material and metal ions;

and then continuously loading and storing the Phase Change Material (PCM) by utilizing the hydrophobicity and the porous structure characteristics of the base material, and finally preparing the product base material-metal particle/phase change material (BM-M/PCM).

2. The method according to claim 1, wherein the chemical reaction between the substrate and the metal ion is any one of two methods:

(1) reacting a base material with metal ions under a mechanical action force, and then adding a reducing agent to reduce the metal ions into nano particles; or

(2) The base material reacts with plant polyphenol under mechanical action, then metal ions are added for continuous reaction, and finally a reducing agent is added to reduce the metal ions into nano particles.

3. The method of claim 1, wherein the substrate is one of leather or foam.

4. The method of claims 1 to 3, wherein when the substrate is leather, the leather composite (leather-M) loaded with metal particles is dehydrated in an absolute ethanol solution, and then a Phase Change Material (PCM) is added for physical adsorption, thereby finally preparing the leather-metal ion/phase change material composite (leather-M/PCM).

5. A method for preparing according to claim 1 or 3, characterized in that said Phase Change Material (PCM) is paraffin (P).

6. The method according to claim 1, wherein the metal ion is used in an amount of 5 to 30% by mass based on the mass of the base material.

7. The method according to claim 1, 2 or 6, wherein the metal ion is silver ion.

8. The method according to claim 1 or 2, wherein the reducing agent is sodium borohydride NaBH₄。

9. The method according to claim 4, wherein the leather is a powdered collagen fiber obtained by removing non-collagenous substances from skins or scraps of livestock animals by a tanning pretreatment process, or a commercially available commercial or semi-finished leather product mainly comprising collagen fibers.

10. The method according to claim 3, wherein when the substrate is a foam, the foam is added into the myricetin solution to perform an adsorption reaction, then a metal ion solution is added to continue the adsorption reaction, and finally a reducing agent is used to reduce the metal ions to prepare an intermediate product loaded with a metal particle foam composite (foam-M) with absorption properties; and soaking the obtained composite in a PDMS solution (5 wt% with dodecane as a solvent) for 0.5h, drying, and adding a phase-change material to obtain the foam-metal ion/phase-change material composite (foam-M/PCM).

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