Lightweight and high-strength composite materials

Abstract

The present invention relates to a lightweight, high-strength composite material, which is a composite resin with a shell-like structure. Nanosheets are used as bricks in the bionic structure, which, on the one hand, provide the structural material with a strength higher than that of pure plastic. On the other hand, the "brick and mud" bionic structure greatly improves the material's toughness and crack propagation resistance. Highly oriented two-dimensional nanosheets can effectively improve the strength and toughness of the composite material. That is, by adding a small amount of inorganic matter, the strength and toughness are greatly improved, achieving lightness and high strength. The present invention simply realizes the rapid preparation, thickness control, and microstructure control of the composite resin with a shell-like structure, and realizes the preparation of nanosheet composite materials with various forms and functions.

Description

Technical Field

[0001] The present invention relates to new high-performance materials, in particular to lightweight and high-strength composite materials. Background Art

[0002] Structural materials characterized by lightness, high strength, and high toughness play a vital role in defense, aerospace, biomedicine, and other fields, and they also represent a major challenge in materials science research. It has been discovered that, through millions of years of selective evolution, many natural structural materials have achieved these properties. Despite being composed of relatively simple components, these natural structural materials achieve performance superior to synthetic materials due to their unique, multi-scale, complex and ordered internal structures.

[0003] Among numerous natural materials, mother-of-pearl (nacre) is particularly exceptional. Composed of 95% by volume of brittle calcium carbonate mineral flakes and 5% by volume of weaker organic matter, nacre possesses exceptional strength and toughness. This has attracted many scientists to mimic nacre's microstructure in an effort to create high-strength, high-toughness shell-like structural materials. Numerous methods have been developed to create these materials with diverse functionalities.

[0004] Traditional molding methods were the first to be used to prepare shell-like structural materials, initially used to improve the fracture toughness of laminated composites. However, because the thickness of the "bricks" in traditional molding methods is typically at the micrometer level, far exceeding the thickness of natural nacre flakes, the resulting composites lack mechanical properties compared to natural nacre. Layer-by-layer assembly methods for preparing shell-like structural composites allow for precise control of the microstructure and high loadings of inorganic phases, but the time-consuming preparation process and the difficulty of large-scale production have limited their practical application. Mechanical assembly methods allow for the rapid, economical, and large-scale preparation of thin films, thick films, and bulk materials. However, due to the inability to precisely control the microstructure, the resulting composites often struggle to surpass the strength, modulus, and toughness of natural nacre. While biomimetic mineralization methods can successfully replicate the macromorphology, microstructure, and crystallinity of natural nacre, they still cannot fully replicate the structural characteristics of shells, resulting in inferior mechanical properties of shell-like structural composites. Furthermore, this method also suffers from complex, time-consuming preparation processes and the inability to scale up. Shell-like structural composites prepared by 3D printing suffer from insufficient inorganic loading. The ice-templating method for preparing shell-like composite materials has long production cycles and is difficult to produce on large sizes and curved surfaces. Therefore, finding a method that can quickly produce high-performance composite materials with large sizes and complex shapes is of great significance and value. Summary of the Invention

[0005] The purpose of the present invention is to address the deficiencies of the existing technology and propose to use gel-induced assembly of two-dimensional nanomaterials to obtain a lightweight and high-strength composite material with a shell-like structure.

[0006] The objective of the present invention is achieved through the following technical solutions: a lightweight, high-strength composite material comprising a nanomaterial skeleton and a resin filled in the nanomaterial skeleton; the nanomaterial skeleton is prepared by the following simple, low-cost, and stable method: dispersing two-dimensional primitives and a gel component in water to form an assembly liquid, wherein the volume fraction of the two-dimensional primitives is less than 20 vol%; placing a substrate capable of releasing charged particles in the assembly liquid, and assembling the two-dimensional primitives along the surface of the substrate; removing the substrate and the gel component to obtain a nanomaterial skeleton composed of two-dimensional primitives, wherein the two-dimensional primitives are oriented along the surface of the substrate; wherein the two-dimensional primitives can form an electrostatic interaction with the charged particles; and the gel component can form a gel under the induction of the charged particles. In the present invention, the gel component can form a gel under the induction of the charged particles, which synchronizes the diffusion of the charged particles with the formation of the gel. The gel interface contains a large number of charged particles, making the interface electrically conductive, and the interface continuously attracts nanosheets of opposite charge to migrate toward the interface. When the nanosheets are parallel to the gel surface, they have the maximum contact area and reach the most stable state, so the nanosheets are oriented parallel to the gel interface. When the nanosheets are in contact with the gel interface and oriented, as the charged particles further diffuse, the nanosheets are fixed, and the charged particles continue to diffuse forward perpendicular to the substrate to continue to orient and fix the nanosheets behind them.

[0007] In the present invention, the substrate that releases charged particles can be: a metal that releases charged particles in situ through reaction (for example, a metal electrode plate that is energized), a hydrophilic material that adsorbs charged particles (including water-absorbing materials, hydrophobic materials after hydrophilic modification, such as plastics, etc.). Since the assembly elements are assembled under the action of charged particles released by the substrate, those skilled in the art can foresee that under the adsorption situation, the concentration of charged particles adsorbed on the substrate will affect the thickness of the oriented assembly. The higher the concentration of charged particles, the greater the thickness of the assembly; experiments have shown that ordered assembly can be achieved at a concentration of 0.1 mol / L. Those skilled in the art can regulate the concentration of charged particles adsorbed on the substrate according to the product thickness requirements. In a preferred embodiment of the present invention, the concentration of charged particles is above 1 mol / L.

[0008] Since the formation speed of the gel is directly related to the release speed of the charged particles of the substrate, it has been proved through experiments that when the formation speed of the gel is below 0.2 mm / min, the effective orientation induction of the gel for the assembly unit can be guaranteed. For example, for divalent calcium ions, under adsorption conditions, the concentration of the charged particles adsorbed by the substrate is set to below 5 mol / L, which can ensure that the speed of gel formation is below 0.2 mm / min; and for trivalent iron ions, under adsorption conditions, the concentration of the charged particles adsorbed by the substrate is set to below 1 mol / L to ensure that the speed of gel formation is below 0.2 mm / min. Those skilled in the art can regulate the concentration of the adsorbed charged particles by detecting the formation speed of the gel, or regulate the electrochemical reaction speed (such as the current size, for the metal that releases the charged particles in situ in the reaction), so as to achieve the best promoting effect of the gel.

[0009] Experiments have shown that the volume fraction of two-dimensional elements should be below 20 vol%. If the content is too high, the steric hindrance between the nanosheets will be relatively large, affecting the orientation of the nanosheets in space and reducing the degree of orientation. Based on the volume content requirement, those skilled in the art can conveniently and quickly measure the weight of the assembled elements by combining the formula weight = density × volume. In the embodiments of the present invention, all measurements are based on weight.

[0010] In the present invention, the content of the gel component is subject to the following prerequisites: ① The concentration cannot be too low, otherwise, gel formation cannot occur under the induction of the charged particles; as long as the concentration can form a gel, it can provide a force for the assembly of nanomaterials. ② The concentration cannot be too high, otherwise the viscosity of the assembly solution will be too high, resulting in orientation resistance; generally, the viscosity of the assembly solution should be below 500 mPa·s. It is common knowledge in the art to formulate the required concentrations of the various assembly solution components based on these two prerequisites.

[0011] In certain preferred embodiments of the present invention, the framework material is further compressed and densified to obtain a dense framework. Specifically, the framework material is placed in a mold and subjected to uniaxial compression (circumferential constraint) at gradient pressures of 1 MPa, 10 MPa, and 100 MPa for 30 minutes each to achieve framework densification. A dense framework increases the inorganic content of the composite material and enhances the mechanical strength of the composite resin.

[0012] Furthermore, the two-dimensional elementary boron nitride nanosheets, aluminum oxide nanosheets, glass sheets, mica sheets, clay sheets, graphene, molybdenum disulfide and the like are at least one.

[0013] Corresponding to the above-mentioned elements, the gel component is selected from carboxyl polyelectrolytes: sodium alginate, pectin, cellulose, carboxyl PU, carboxylated chitosan, sodium polygalacturonate, etc.

[0014] In certain embodiments of the present invention, gel components can directly serve as modifying groups on assembly units, modifying their surfaces. For example, sodium alginate, as a gel component, can be physically adsorbed onto alumina nanosheets, imparting a negative charge to the sheets. Chitosan, as a gel component, can be physically adsorbed onto alumina nanosheets, imparting a positive charge to the sheets.

[0015] Furthermore, the resin is obtained by injecting prepolymerized resin or high molecular monomer into the skeleton and then polymerizing it.

[0016] Furthermore, the prepolymer resin includes epoxy resin, acrylic resin, phenolic resin, urea-formaldehyde resin, etc.; the high molecular monomer includes methyl methacrylate, styrene, acrylonitrile, etc.

[0017] Furthermore, the substrate surface is flat or curved, or any other irregular shape. Its material includes wood, plastic, rubber, ceramic, metal, etc. Non-hydrophilic materials can be made hydrophilic by pre-treatment, including plasma treatment, commercial hydrophilic spray, polydopamine modification, etc.

[0018] Furthermore, methods for removing gel components include: physical high-temperature burning and chemical dissociation.

[0019] In certain specific embodiments of the present invention, the following steps are taken:

[0020] 1) adding 0.1-40 parts by weight of a two-dimensional element, 1-500 parts by weight of water, and 0.5-2 parts by weight of a polymer into a container, and stirring them uniformly to obtain a nanomaterial dispersion;

[0021] 2) taking a substrate material and adsorbing an ion solution on the substrate material;

[0022] 3) immersing the above-mentioned base material in the nanomaterial dispersion for a certain period of time;

[0023] 4) Proposing a substrate material with a nanomaterial gel adhered thereto;

[0024] 5) drying or freeze-drying the gel to remove the base material, thereby obtaining a nanomaterial skeleton or composite material;

[0025] 6) The nanomaterial skeleton can be selectively post-treated, including heat treatment to remove organic matter, chemical modification of the skeleton with a coupling agent, hot pressing and densification, etc.

[0026] 7) Filling the nanomaterial skeleton with prepolymerized resin or high molecular monomer, including impregnation with resin under vacuum conditions or normal pressure.

[0027] Compared with the prior art, the present invention has the following beneficial effects:

[0028] 1) In the shell-like composite resin, nanosheets serve as the bricks in the biomimetic structure, providing the structural material with greater strength than pure plastic. Furthermore, this "brick-and-mortar" biomimetic structure significantly improves the material's toughness and crack growth resistance.

[0029] 2) The highly oriented two-dimensional nanosheets can effectively improve the strength and toughness of composite materials. This means that by adding a small amount of inorganic matter, the strength and toughness are greatly improved, achieving lightweight and high strength.

[0030] 3) Gel-assisted assembly can quickly obtain highly oriented large-scale skeleton structures, achieving controllable preparation of materials with thickness ranging from nanometers to millimeters.

[0031] 4) Any shape and material can be used as a template to prepare composite structural materials with curved surface orientation. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 is the relationship between the nanosheet assembly time and the thickness of the dry sample.

[0033] Figure 2 Scanning electron microscope images of the skeleton structure prepared by the gel-induced assembly method (b) and the blending method (a).

[0034] Figure 3 The mechanical properties of composite resins prepared by gel-induced assembly and blending methods are shown in Figure 1. (a) is the bending stress-strain diagram, and (b) is the strength modulus bar graph.

[0035] Figure 4 The mechanical properties of the shell-like structure composite resin after the skeleton is hot-pressed and densified.

[0036] Figure 5 This is a scanning electron micrograph of a spherical substrate oriented along a curved surface. (a) shows the hydrogel grown on the curved surface, (b) shows the peelable skeleton after drying, (c) shows the cross-section of the skeleton after resin filling, and (d) shows the cross-sectional structure.

[0037] Figure 6 Optical images of composite resins with curved shell-like structures of different curvatures.

[0038] Figure 7 Mechanical properties of composite resins for curved shell-like structures with different curvatures.

[0039] Figure 8 Schematic diagram of the gelation process for nanosheet orientation. The long rectangles in the figure represent negatively charged one- or two-dimensional assembly units; the small dots represent calcium ions; the dotted line represents the gel interface; and the left side of the dotted line represents the gel formation induced by calcium ions. DETAILED DESCRIPTION

[0040] The present invention provides a method for orderly assembly of nanomaterials. The method is based on the electrostatic interaction between an assembly substrate and assembly primitives and gel induction to achieve orderly assembly of assembly primitives.

[0041] In order to further illustrate the technical means and effects adopted by the present invention to achieve the predetermined purpose of the invention, the specific implementation methods, structures, features and effects of the present invention are described in detail below in conjunction with the accompanying drawings and preferred embodiments.

[0042] Since the concentration of the assembly units, the viscosity of the assembly liquid, and the concentration of charged particles in the solution adsorbed on the substrate can all be adjusted according to needs through simple experiments, in the following embodiments, unless otherwise specified, the concentration of the assembly units is calculated to be 0-20 vol%, the viscosity of the assembly liquid is tested to be below 500 mPa·s, the concentration of charged particles adsorbed on the substrate is above 1 mol / L, and the gel speed is ensured to be below 0.2 mm / min. Example 1

[0043] 1) Add 50 parts by weight of alumina flakes, 100 parts by weight of water, and 2 parts by weight of sodium alginate to a container and stir them evenly to obtain an alumina dispersion; the concentration of the alumina flakes is approximately 12 vol%, and the viscosity of the assembled solution is below 500 mPa·s.

[0044] 2) Take filter paper and adsorb enough 5 mol / L calcium chloride solution on the filter paper;

[0045] 3) Immerse the filter paper in the alumina dispersion for 10 minutes;

[0046] 4) Remove the filter paper with the alumina gel and place it in clean water for 24 hours to remove excess calcium ions;

[0047] 5) Remove the filter paper and burn at high temperature to remove the gel to obtain the alumina skeleton. The thickness of the dry skeleton is related to the assembly time. Figure 1 shown.

[0048] 6) The alumina skeleton was surface-modified by silane coupling with KH-560, ie, immersed in a solution containing KH-560: ethanol: water = 1:95:5 by mass ratio at 50° C. for 24 hours.

[0049] 7) by vacuum filling epoxy resin (100 parts by weight of bisphenol F, 100 parts by weight of methyl hexahydrophthalic anhydride, 1 part by weight of 2,4,6-tris(dimethylaminomethyl)phenol), 100°C

[0050] After curing, a lightweight, high-strength composite resin is prepared for structural parts in the aerospace field.

[0051] Comparative Example 1:

[0052] Blending method: The composite material was prepared by blending the nanosheets with epoxy resin prepolymer, where the volume fraction of aluminum oxide was 20 vol%, and the same curing conditions were used;

[0053] like Figure 2 , the nanosheets are completely disordered; in contrast, the gelation effect caused by calcium ions can achieve a high degree of orientation of the nanosheets over a long range. Figure 3 The three-point bending test shows that the shell-like structure composite resin prepared by the gel-assisted orientation method has a bending strength of nearly 200 MPa, which is 2.6 times that of the disordered blended composite resin, and has obvious mechanical advantages. Example 2

[0054] 1) Add 50 parts by weight of aluminum oxide flakes, 100 parts by weight of water, and 2 parts by weight of sodium alginate into a container, and stir them evenly to obtain an aluminum oxide dispersion;

[0055] 2) Take filter paper and adsorb enough 5 mol / L calcium chloride solution on the filter paper;

[0056] 3) Immerse the filter paper in the alumina dispersion for 10 minutes;

[0057] 4) Remove the filter paper with the alumina gel and place it in clean water for 24 hours to remove excess calcium ions;

[0058] 5) Remove the filter paper and burn at high temperature to remove the gel to obtain the alumina skeleton.

[0059] 6) The alumina skeleton is subjected to gradient cold pressing treatment (10 MPa, 50 MPa, 100 MPa for 30 minutes each) to obtain a densified alumina skeleton.

[0060] 7) The densified alumina skeleton was surface-modified by silane coupling with KH-560, ie, immersed in a solution containing KH-560: ethanol: water = 1:95:5 by mass ratio at 50° C. for 24 hours.

[0061] 8) Vacuum-filling an epoxy resin (100 parts by weight of bisphenol F, 100 parts by weight of methylhexahydrophthalic anhydride, and 1 part by weight of 2,4,6-tris(dimethylaminomethyl)phenol) and curing at 100°C for 12 hours to produce a lightweight, high-strength composite resin for aerospace structural components.

[0062] like Figure 4 The three-point bending test showed that the dense shell-like structure composite resin had a bending strength of 200 MPa and a modulus of 25 GPa. Example 3

[0063] 1) Add 50 parts by weight of aluminum oxide flakes, 100 parts by weight of water, and 2 parts by weight of sodium alginate into a container, and stir them evenly to obtain an aluminum oxide dispersion;

[0064] 2) Preparation of ellipsoids (acrylate) with different curvatures by 3D printing;

[0065] 3) The curved plastic ball (acrylate) is subjected to plasma treatment to make the surface hydrophilic;

[0066] 4) Add enough 5 mol / L ferric chloride solution onto the plastic ball;

[0067] 5) Immerse the plastic balls in the alumina dispersion for 10 minutes;

[0068] 6) Producing plastic balls adhered with alumina gel;

[0069] 7) Dry the gel and remove the plastic balls to obtain a curved alumina skeleton, such as Figure 5 As shown, a curved alumina skeleton oriented along the spherical surface was successfully prepared.

[0070] 8) The gel was removed by high-temperature burning, and then the alumina skeleton was surface-modified by silane coupling with KH-560, namely, immersed in a solution containing KH-560: ethanol: water = 1:95:5 by mass ratio at 50° C. for 24 hours.

[0071] 9) Vacuum filling epoxy resin (100 parts by weight of bisphenol F, 100 parts by weight of methylhexahydrophthalic anhydride, and 1 part by weight of 2,4,6-tris(dimethylaminomethyl)phenol) is performed, and then taken out after full immersion, and cured at 100° C. for 12 hours to obtain a curved, lightweight, high-strength composite resin.

[0072] like Figure 6 As shown in Figure 3, ellipsoidal alumina composites with different curvatures were successfully prepared. Figure 7 As shown in the figure, the curvature of the ellipsoidal alumina composite material is positively correlated with the hardness. The high curvature material shows obvious mechanical advantages. For a curved surface with b / a of 1.5, it can withstand a pressure of nearly 2000N. Example 4

[0073] 1) Add 50 parts by weight of aluminum oxide flakes, 100 parts by weight of water, and 2 parts by weight of sodium alginate into a container, and stir them evenly to obtain an aluminum oxide dispersion;

[0074] 2) Take filter paper and adsorb enough 5 mol / L calcium chloride solution on the filter paper;

[0075] 3) Immerse the filter paper in the alumina dispersion for 10 minutes;

[0076] 4) Remove the filter paper with the alumina gel and place it in clean water for 24 hours to remove excess calcium ions;

[0077] 5) Dry the gel and remove the filter paper to obtain an alumina skeleton.

[0078] 6) The gel was removed by high-temperature burning, and then the alumina skeleton was surface-modified by silane coupling with KH-570, that is, immersed in a solution containing KH-570:ethanol = 1:100 by mass ratio at 50°C for 24 hours.

[0079] 7) The skeleton was immersed in a monomer solution (100 parts by weight of methyl methacrylate and 0.5 parts by weight of azobisisobutyronitrile) and cured at 50° C. for 48 hours to obtain a lightweight and high-strength composite resin. Example 5

[0080] 1) Add 50 parts by weight of boron nitride sheets, 100 parts by weight of water, and 2 parts by weight of sodium alginate into a container, and stir them evenly to obtain an aluminum oxide dispersion;

[0081] 2) Take filter paper and adsorb enough 2 mol / L calcium chloride solution on the filter paper;

[0082] 3) Immerse the filter paper in the alumina dispersion for 10 minutes;

[0083] 4) removing the filter paper with the boron nitride gel adhered thereto and placing it in clean water for 24 hours to remove excess calcium ions;

[0084] 5) Remove the filter paper and burn at high temperature to remove the gel to obtain the boron nitride skeleton.

[0085] 6) The boron nitride skeleton was surface-modified by silane coupling with KH-560, ie, immersed in a solution containing KH-560: ethanol: water = 1:95:5 by mass ratio at 50° C. for 24 hours.

[0086] 7) A lightweight, high-strength composite resin with high thermal conductivity is obtained by vacuum filling an epoxy resin (100 parts by weight of bisphenol F, 100 parts by weight of methylhexahydrophthalic anhydride, and 1 part by weight of 2,4,6-tris(dimethylaminomethyl)phenol) and curing at 100° C. for 12 hours. Example 6

[0087] 1) Add 100 parts by weight of water to a container, add a certain amount of glass sheets so that the volume content of the glass sheets is about 20 vol%, and slowly add carboxyl chitosan while monitoring the viscosity in real time. When the viscosity of the assembly solution is about 500 mPa·s, stop adding carboxyl chitosan to complete the preparation of the assembly solution.

[0088] 2) Take filter paper and adsorb enough 1 mol / L ferric chloride solution onto the filter paper so that the gel formation rate is about 0.2 mm / min;

[0089] 3) Immerse the filter paper in the alumina dispersion for 10 minutes;

[0090] 4) Remove the filter paper with aluminum oxide attached;

[0091] 5) Remove the filter paper and burn at high temperature to remove the gel to obtain the oriented glass sheet skeleton.

[0092] 6) Vacuum-filling an epoxy resin (100 parts by weight of bisphenol F, 100 parts by weight of methylhexahydrophthalic anhydride, and 1 part by weight of 2,4,6-tris(dimethylaminomethyl)phenol) and curing at 100°C for 12 hours. After curing, a lightweight, high-strength composite resin is prepared for use in aerospace structural components.

[0093] The above description is merely a preferred embodiment of the present invention and does not constitute any form of limitation to the present invention. Although the present invention has been disclosed as above in terms of a preferred embodiment, it is not intended to limit the present invention. Any person skilled in the art can, without departing from the scope of the technical solution of the present invention, make some changes or modifications to equivalent embodiments using the technical contents disclosed above. However, any brief modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention are still within the scope of the technical solution of the present invention.

Claims

1. Lightweight and high-strength composite material, characterized by: The nanomaterial skeleton comprises a nanomaterial skeleton and a resin filled in the nanomaterial skeleton; the nanomaterial skeleton is prepared by the following method: dispersing two-dimensional primitives and gel components in water to form an assembly liquid, wherein the volume fraction of the two-dimensional primitives is less than 20 vol%; Placing a substrate that releases charged particles in an assembly solution, and assembling two-dimensional primitives along the surface of the substrate; removing the substrate and the gel component to obtain a nanomaterial skeleton composed of two-dimensional primitives, wherein the two-dimensional primitives are oriented along the surface of the substrate; wherein the two-dimensional primitives form an electrostatic interaction with the charged particles; and the gel component can form a gel under the induction of the charged particles; The two-dimensional element is one or more of boron nitride nanosheets, aluminum oxide nanosheets, glass sheets, mica sheets, clay sheets, graphene, and molybdenum disulfide.

2. The composite material according to claim 1, characterized in that The resin is obtained by injecting prepolymerized resin or high molecular monomer into the nano material skeleton and then polymerizing it.

3. The composite material according to claim 2, characterized in that The prepolymer resin includes epoxy resin, acrylic resin, phenolic resin and urea-formaldehyde resin; the high molecular monomer includes methyl methacrylate, styrene and acrylonitrile.

4. The composite material according to claim 1, characterized in that The charged particles are selected from cations including: Na + , Ca 2+ 、Zn 2+ 、Ba 2+ 、Cu 2+ 、Fe 3+ 、Al 3+ 、Zr 4+ .

5. The composite material according to claim 1, characterized in that The gel component is selected from carboxyl polyelectrolyte: sodium alginate, pectin, cellulose, carboxyl PU, carboxylated chitosan, sodium polygalacturonate.

6. The composite material according to claim 1, characterized in that The substrate surface is a plane or a curved surface, or any other irregular shape.

7. The composite material according to claim 1, characterized in that Methods for removing gel components include: physical high-temperature burning and chemical dissociation.

8. The composite material according to claim 1, characterized in that The method also includes compressing and densifying the skeleton material to obtain a dense skeleton.

Images