Biomimetic composite material and preparation method thereof

Abstract

The present invention provides a biomimetic composite material, a nacreous layer-mimetic material, a biomimetic nacre material and preparation methods thereof. The biomimetic composite material comprises multiple composite film formed from biomass fibers and an inorganic nanomaterial, wherein an organic polymer material is arranged between the multiple composite film layers or in the composite base body. The invention combines a high-mechanical-performance shellfish structure with a wood fiberboard to overcome the original defects of the fiberboard, improve the fiberboard performances and endow it with new special performances, so that the prepared material has dual functions of the fiberboard and the nanomaterial at the same time.

Claims

1. A method for preparing a biomimetic nacre material, comprising the steps of: S1: pulverizing biomass fibers, and dissolving in distilled water together with an inorganic nanomaterial to form a nano suspension, and colloid milling at 2,500˜3,000 rpm for 5˜10 hours, and further treating in a disc mill at 2,500˜3,000 rpm for 5˜10 hours to obtain a nanomaterial-wood fiber composite suspension with a particle size of 50˜500 nm; S2: mixing the nano suspension with mixed salt solution composed of 3.632 g/L NaCl, 0.113 g/L Na.sub.2SO.sub.4, 0.332 g/L NaHCO.sub.3, 0.328 g/L MgCl.sub.2.6H.sub.2O, 0.284 g/L CaCl.sub.2 and 0.177 g/L KCl, reacting at 40˜60° C. for 36˜60 hours to obtain a mineralized nano wood fiber suspension, pre-cooling to 1˜5° C., freeze-casting in a liquid nitrogen environment at −196˜−30° C., and freeze-drying at −30˜20° C. under 10˜40 Pa for 12˜48 hours to obtain a layered nacre structure-imitating base body; and S3: soaking an organic polymer material in the suspension of the layered nacre structure-imitating base body obtained in step S2, and hot pressing at 100˜250° C. under 0.8˜20 MPa for 0.5˜24 hours to obtain a finished product containing the organic polymer material 1˜10 mass %, wherein: in step S1, a mass ratio of the biomass fibers, the inorganic nanomaterial and the distilled water is 1:(5×10−4˜0.2):20.

2. The method in claim 1, wherein the temperature gradually rises during the freeze-drying process in step S2.

3. The method in claim 2, wherein the biomass fibers are one of wood fibers, bamboo fibers, rice straws, wheat straws, corn stalks, cotton stalks, bagasse, reeds and Chinese silver grass.

4. The method in claim 3, wherein the inorganic nanomaterial is selected from one of CaCO.sub.3, TiO.sub.2, ZnO, Ag, SiO.sub.2, Al.sub.2O.sub.3, Fe.sub.3O.sub.4, Mg(OH).sub.2, Al(OH).sub.3, boron nitride, graphene, graphene oxide, nano montmorillonite, nano flaky calcium phosphate, nano mica sheets, carbon fibers and carbon nanotubes.

5. The method in claim 4, wherein the organic polymer material is selected from one of polyvinyl alcohol, polylactic acid, polyethylene, polypropylene, polyvinyl chloride, p-phenylenediamine, acrylic resin, polyetherimide, chitosan and polyester.

Description

BRIEF DESCRIPTION OF FIGURES

(1) Hereinafter, a brief introduction to the drawings required in the specific embodiments of the present invention or in prior arts will be given, so as to clearly illustrate the embodiments of the present invention or the technical solutions in prior arts. In all the drawings, similar elements or parts are generally marked by similar reference signs. Each element or part is not necessarily drawn according to the actual scale.

(2) FIG. 1 is an SEM image of the nacreous layer-mimetic material prepared in Example 1 of the present invention;

(3) FIG. 2 is an SEM image of the biomimetic nacre material prepared in Example 9 of the present invention;

(4) FIG. 3 is an SEM image of the layered base body of the biomimetic nacre material prepared in Example 9 of the present invention;

(5) FIG. 4 is a cross-sectional SEM image of the biomimetic nacre material prepared in Example 9 of the present invention;

(6) FIG. 5 is a comparison diagram of the bending stress-strain curves of the biomimetic nacre material prepared in Example 9 of the present invention and other related wood materials;

(7) FIG. 6 is a comparison diagram of the specific strength of the biomimetic nacre material prepared in Example 9 of the present invention and other materials; and

(8) FIG. 7 is a formaldehyde degradation curve of the biomimetic nacre material prepared in Example 11 of the present invention.

DETAILED DESCRIPTION OF THE EMBODIMENTS

(9) Hereinafter, the present invention will be further described in detail in conjunction with the specific embodiments, and the examples are given only for clarifying the present invention, not for limiting the scope of the present invention.

(10) It should be noted that, unless otherwise stated, the technical terms or scientific terms used in this application should receive the ordinary meanings as understood by those skilled in the art to which the present invention belongs.

(11) Wood fibers used in the following examples are 40-mesh pine wood fibers with a water content of 10%, from Ningbo Dashijie Group Co., Ltd.

Example 1

(12) A nacreous layer-mimetic material is prepared by: S1-1: wood fiber pretreatment adding wood fibers 100 g into distilled water 4 L, stirring, adding flaky nano alumina 2.5 g, stirring, and colloid milling for 2 h to obtain wood fiber nanosheet suspension. S1-2: wood fiber-based film formation adding the wood fiber nanosheet suspension 200 g into a vacuum suction filtration device, performing suction filtration to obtain a nanosheet-loaded wood fiber film with a diameter of 150 mm and thickness of about 0.1 mm, and prepressing at 80° C. under 2.5 MPa for 5 min. S1-3: assembly spray-coating a thin layer of epoxy resin to the surface of the nanosheet-loaded wood fiber film, alternately laminating together with polymer films layer by layer to form a 30-layer laminate, and prepressing at a room temperature under 5 MPa for 5 min to obtain a board blank. S1-4: hot pressing hot pressing the board blank at 180° C. under 10 MPa for 10 min.

(13) FIG. 1 shows the SEM image of the nacreous layer-mimetic material prepared in this example. From FIG. 1, it can be seen that the material has a clear layered structure.

Example 2

(14) A nacreous layer-mimetic material is prepared by: S1-1: wood fiber pretreatment adding wood fibers 100 g into distilled water 4 L, stirring, adding nano boron nitride 5 g, stirring, and colloid milling for 6 h to obtain wood fiber nanosheet suspension. S1-2: wood fiber-based film formation adding the wood fiber nanosheet suspension 200 g into a vacuum suction filtration device, performing suction filtration to obtain a nanosheet-loaded wood fiber film with a diameter of 150 mm and thickness of about 0.1 mm, and prepressing at 80° C. under 2.5 MPa for 5 min. S1-3: assembly spray-coating a thin layer of epoxy resin to the surface of the nanosheet-loaded wood fiber film, alternately laminating together with polymer films layer by layer to form a 30-layer laminate, and prepressing at a room temperature under 5 MPa for 5 min to obtain a board blank. S1-4: hot pressing hot pressing the board blank at 180° C. under 10 MPa for 10 min.

(15) The SEM image shows that the material has a clear layered structure.

Example 3

(16) A nacreous layer-mimetic material is prepared by: S1-1: wood fiber pretreatment adding wood fibers 100 g into distilled water 4 L, stirring, adding nano graphene oxide 10 g, stirring, and colloid milling for 6 h to obtain wood fiber nanosheet suspension. S1-2: wood fiber-based film formation adding the wood fiber nanosheet suspension 200 g into a vacuum suction filtration device, performing suction filtration to obtain a nanosheet-loaded wood fiber film with a diameter of 150 mm and thickness of about 0.1 mm, and prepressing at 80° C. under 2.5 MPa for 5 min. S1-3: assembly spray-coating a thin layer of epoxy resin to the surface of the nanosheet-loaded wood fiber film, alternately laminating together with polymer films layer by layer to form a 30-layer laminate, and prepressing at a room temperature under 5 MPa for 5 min to obtain a board blank. S1-4: hot pressing hot pressing the board blank at 180° C. under 20 MPa for 5 min.

(17) The SEM image shows that the material has a clear layered structure.

Example 4

(18) A nacreous layer-mimetic material is prepared by: S1-1: wood fiber pretreatment adding wood fibers 100 g into distilled water 4 L, stirring, adding nano montmorillonite 5 g, stirring, and colloid milling for 4 h to obtain wood fiber nanosheet suspension. S1-2:wood fiber-based film formation adding the wood fiber nanosheet suspension 200 g into a vacuum suction filtration device, performing suction filtration to obtain a nanosheet-loaded wood fiber film with a diameter of 150 mm and thickness of about 0.1 mm, and prepressing at 80° C. under 2.5 MPa for 5 min. S1-3: assembly spray-coating a thin layer of epoxy resin to the surface of the nanosheet-loaded wood fiber film, alternately laminating together with polymer films layer by layer to form a 30-layer laminate, and prepressing at a room temperature under 5 MPa for 5 min to obtain a board blank. S1-4: hot pressing hot pressing the board blank at 200° C. under 5 MPa for 15 min.

(19) The SEM image shows that the material has a clear layered structure.

Example 5

(20) A nacreous layer-mimetic material is prepared by: S1-1: wood fiber pretreatment adding wood fibers 100 g into distilled water 4 L, stirring, adding flaky nano calcium phosphate 5 g, stirring, and colloid milling for 8 h to obtain wood fiber nanosheet suspension. S1-2: wood fiber-based film formation adding the wood fiber nanosheet suspension 200 g into a vacuum suction filtration device, performing suction filtration to obtain a nanosheet-loaded wood fiber film with a diameter of 150 mm and thickness of about 0.1 mm, and prepressing at 80° C. under 2.5 MPa for 5 min. S1-3: assembly spray-coating a thin layer of epoxy resin to the surface of the nanosheet-loaded wood fiber film, alternately laminating together with polymer films layer by layer to form a 30-layer laminate, and prepressing at a room temperature under 5 MPa for 5 min to obtain a board blank. S1-4: hot pressing hot pressing the board blank at 220° C. under 10 MPa for 10 min.

(21) The SEM image shows that the material has a clear layered structure.

Example 6

(22) A nacreous layer-mimetic material is prepared by: S1-1: wood fiber pretreatment adding wood fibers 100 g into distilled water 4 L, stirring, adding nano mica sheets 10 g, stirring, and colloid milling for 8 h to obtain wood fiber nanosheet suspension. S1-2: wood fiber-based film formation adding the wood fiber nanosheet suspension 200 g into a vacuum suction filtration device, performing suction filtration to obtain a nanosheet-loaded wood fiber film with a diameter of 150 mm and thickness of about 0.1 mm, and prepressing at 80° C. under 2.5 MPa for 5 min. S1-3: assembly spray-coating a thin layer of epoxy resin to the surface of the nanosheet-loaded wood fiber film, alternately laminating together with polymer films layer by layer to form a 30-layer laminate, and prepressing at a room temperature under 5 MPa for 5 min to obtain a board blank. S1-4: hot pressing hot pressing the board blank at 220° C. under 20 MPa for 15 min.

(23) The SEM image shows that the material has a clear layered structure.

(24) Performance Test

(25) The physical mechanical performances of the boards prepared in Examples 1-6 and common fiberboards are tested in reference to the national standard GB/T 17657-2013 Test Methods of Evaluating the Properties of Wood-Based Panels and Surface Decorated Wood-based Panels. The test results are shown in Table 1.

(26) TABLE-US-00001 TABLE 1 Example Example Example Example Example Example Test items Fiberboard 1 2 3 4 5 6 Density (g/cm.sup.3) 0.8 1.04 1.14 1.20 1.01 1.19 1.24 Static bending 25 48.41 67.41 58.60 52.60 56.60 61.60 strength (MPa) Modulus (MPa) 2500 4390 5720 5800 4800 5500 6000

(27) As shown in Table 1, all the materials prepared in Examples 1-6 have densities higher than that of a common fiberboard, and have greatly-improved mechanical strength. The density and mechanical performance of the inventive materials can be adjusted by adjusting the amounts and kinds of the nanoparticles added. Moreover, the material prepared in Example 2 exhibits excellent mechanical performance under the condition of low density.

Example 7

(28) A biomimetic nacre material is prepared from wood fibers by the following steps: S1: pulverizing the wood fibers, and dissolving in distilled water together with nano CaCO.sub.3 to form suspension, wherein the mass ratio of the wood fibers, the nano CaCO.sub.3 and the distilled water is 1:5×10.sup.−4:20; and colloid milling at 2,500 rpm for 10 h, and further treating in a disc mill at 2,500 rpm for 10 h to obtain nanomaterial-wood fiber composite suspension with a particle size of 50-500 nm; S2: mixing the nano suspension with mixed salt solution composed of 3.632 g/L NaCl, 0.113 g/L Na.sub.2SO.sub.4, 0.332 g/L NaHCO.sub.3, 0.328 g/L MgCl.sub.2.6H.sub.2O, 0.284 g/L CaCl.sub.2) and 0.177 g/L KCl, reacting at 40° C. for 60 h to obtain mineralized nano wood fiber suspension, pre-cooling to 1° C., freeze-casting in a liquid nitrogen environment at −196° C., and freeze-drying at −30-20° C. (the temperature gradually rises during the freeze-drying process, the same below) under 40 Pa for 24 h to obtain a layered nacre structure-imitating base body; S3: soaking organic polymer PMMA in the suspension of the layered nacre structure-imitating base body obtained in the step S2, and hot pressing at 100° C. under 0.8 MPa for 24 h to obtain a finished product containing the organic polymer material 1 mass %.

Example 8

(29) A biomimetic nacre material is prepared from wood fibers by the following steps: S1: pulverizing the wood fibers, and dissolving in distilled water together with nano CaCO.sub.3 to form suspension, wherein the mass ratio of the wood fibers, the nano CaCO.sub.3 and the distilled water is 1:20:20; and colloid milling at 3,000 rpm for 5 h, and further treating in a disc mill at 3,000 rpm for 5 h to obtain nanomaterial-wood fiber composite suspension with a particle size of 50-500 nm; S2: mixing the nano suspension with mixed salt solution composed of 3.632 g/L NaCl, 0.113 g/L Na.sub.2SO.sub.4, 0.332 g/L NaHCO.sub.3, 0.328 g/L MgCl.sub.2.6H.sub.2O, 0.284 g/L CaCl.sub.2) and 0.177 g/L KCl, reacting at 60° C. for 36 h to obtain mineralized nano wood fiber suspension, pre-cooling to 5° C., freeze-casting in a liquid nitrogen environment at −30° C., and freeze-drying at −30-20° C. under 40 Pa for 36 h to obtain a layered nacre structure-imitating base body; S3: soaking organic polymer PMMA in the suspension of the layered nacre structure-imitating base body obtained in the step S2, and hot pressing at 250° C. under 20 MPa for 0.5 h to obtain a finished product containing the organic polymer material 10 mass %.

Example 9

(30) A biomimetic nacre material is prepared from wood fibers by the following steps: S1: pulverizing the wood fibers, and dissolving in distilled water together with nano CaCO.sub.3 to form suspension, wherein the mass ratio of the wood fibers, the nano CaCO.sub.3 and the distilled water is 1:0.02:20; and colloid milling at 2,880 rpm for 6 h, and further treating in a disc mill at 2,880 rpm for 6 h to obtain nanomaterial-wood fiber composite suspension with a particle size of 50-500 nm; S2: mixing the nano suspension with mixed salt solution composed of 3.632 g/L NaCl, 0.113 g/L Na.sub.2SO.sub.4, 0.332 g/L NaHCO.sub.3, 0.328 g/L MgCl.sub.2.6H.sub.2O, 0.284 g/L CaCl.sub.2) and 0.177 g/L KCl, reacting at 50° C. for 48 h to obtain mineralized nano wood fiber suspension, pre-cooling to 4° C., freeze-casting in a liquid nitrogen environment at −90° C., and freeze-drying at −30-20° C. under 20 Pa for 36 h; S3: soaking organic polymer PMMA in the suspension of the layered nacre structure-imitating base body obtained in the step S2, and hot pressing at 168° C. under 5 MPa for 1 h to obtain a finished product containing the organic polymer material 5 mass %.

Example 10

(31) A biomimetic nacre material is prepared from bamboo fibers by the following steps: S1: pulverizing the bamboo fibers, and dissolving in distilled water together with nano SiO.sub.2 to form suspension, wherein the mass ratio of the bamboo fibers, the nano SiO.sub.2 and the distilled water is 1:0.02:20; and colloid milling at 2,880 rpm for 6 h, and further treating in a disc mill at 2,880 rpm for 6 h to obtain nanomaterial-bamboo fiber composite suspension with a particle size of 50-500 nm; S2: mixing the nano suspension with mixed salt solution composed of 3.632 g/L NaCl, 0.113 g/L Na.sub.2SO.sub.4, 0.332 g/L NaHCO.sub.3, 0.328 g/L MgCl.sub.2.6H.sub.2O, 0.284 g/L CaCl.sub.2) and 0.177 g/L KCl, reacting at 50° C. for 48 h to obtain mineralized nano bamboo fiber suspension, pre-cooling to 4° C., freeze-casting in a liquid nitrogen environment (−90° C.), and freeze-drying at −30-20° C. under the vacuum condition of 20 Pa for 36 h; S3: soaking organic polymer PE in the suspension of the layered nacre structure-imitating base body obtained in the step S2, and hot pressing at 168° C. under 5 MPa for 1 h to obtain a finished product containing the organic polymer material 5 mass %.

Example 11

(32) A biomimetic nacre material is prepared from rice straw fibers by the following steps: S1: pulverizing the rice straw fibers, and dissolving in distilled water together with nano TiO.sub.2 to form suspension, wherein the mass ratio of the rice straw fibers, the nano TiO.sub.2 and the distilled water is 1:0.02:20; and colloid milling at 2,880 rpm for 6 h, and further treating in a disc mill at 2,880 rpm for 6 h to obtain nanomaterial-rice straw fiber composite suspension with a particle size of 50-500 nm; S2: mixing the nano suspension with mixed salt solution composed of 3.632 g/L NaCl, 0.113 g/L Na.sub.2SO.sub.4, 0.332 g/L NaHCO.sub.3, 0.328 g/L MgCl.sub.2.6H.sub.2O, 0.284 g/L CaCl.sub.2) and 0.177 g/L KCl, reacting at 50° C. for 48 h to obtain mineralized nano rice straw fiber suspension, pre-cooling to 4° C., freeze-casting in a liquid nitrogen environment (−120° C.), and freeze-drying at −30-20° C. under 20 Pa for 36 h; S3: soaking organic polymer PVA in the suspension of the layered nacre structure-imitating base body obtained in the step S2, and hot pressing at 168° C. under 5 MPa for 1 h to obtain a finished product containing the organic polymer material 5 mass %.

Example 12

(33) A biomimetic nacre material is prepared from bagasse fibers by the following steps: S1: pulverizing the bagasse fibers, and dissolving in distilled water together with nano Fe.sub.3O.sub.4 to form suspension, wherein the mass ratio of the bagasse fibers, the nano Fe.sub.3O.sub.4 and the distilled water is 1:0.02:20; and colloid milling at 2,880 rpm for 6 h, and further treating in a disc mill at 2,880 rpm for 6 h to obtain nanomaterial-bagasse fiber composite suspension with a particle size of 50-500 nm; S2: mixing the nano suspension with mixed salt solution composed of 3.632 g/L NaCl, 0.113 g/L Na.sub.2SO.sub.4, 0.332 g/L NaHCO.sub.3, 0.328 g/L MgCl.sub.2.6H.sub.2O, 0.284 g/L CaCl.sub.2) and 0.177 g/L KCl, reacting at 50° C. for 48 h to obtain mineralized nano bagasse fiber suspension, pre-cooling to 4° C., freeze-casting in a liquid nitrogen environment (−150° C.), and freeze-drying at −30-20° C. under the vacuum condition of 20 Pa for 36 h; S3: soaking organic polymer PMMA in the suspension of the layered nacre structure-imitating base body obtained in the step S2, and hot pressing at 168° C. under 5 MPa for 1 h to obtain a finished product containing the organic polymer material 5 mass %.

Comparative Example 1

(34) In this comparative example, a random CaCO.sub.3/wood fiber composite board, for comparison with the inventive biomimetic nacre material, is prepared from wood fibers by the following steps: 1. Pulverizing the wood fibers, and directly mixing with nano CaCO.sub.3 and organic polymer PMMA while heating, wherein the mass ratio of the wood fibers, nano CaCO.sub.3 and PMMA is 1:0.02:0.05; 2. Hot pressing at 168° C. under 5 MPa for 1 h.

(35) Characterization and Test

(36) 1. Morphological Features

(37) FIG. 2 is an SEM image of the CaCO.sub.3/wood fiber composite material prepared in Example 9, and reflects that the wood fibers undergo a mechanical and chemical grinding stage to get split, broken and refined at a nanometer scale, and at the same time CaCO.sub.3 is combined with the surfaces of the wood fibers under the actions of electrostatic adsorption and Van der Waals force.

(38) FIG. 3 is an SEM image of the nacre layered structure-imitating base body prepared in Example 9. During freeze-casting where an ice crystal induced assembly process is adopted, part of the CaCO.sub.3/wood fiber composite material is excluded out of the ice crystals grown in layers to get sandwiched between the adjacent ice crystals, thereby forming a continuous network and having the structure determined by an ice crystal template. Finally, an ordered layered structure is formed by freeze-drying after ice crystal sublimation.

(39) FIG. 4 is a cross-sectional SEM image of the biomimetic nacre material prepared in Example 9. An organic polymer soft material is filled in the ordered layered base body after freeze-drying to form a hard CaCO.sub.3/wood fiber composite material-soft organic polymer laminate structure, which enables stress to transfer and dissipate between the layers in a stress process to avoid stress concentration.

(40) The characterizations of the morphological features of the biomimetic nacre materials prepared in Examples 7, 8, 10 and 12 show the same result as that in Example 9, so no more detail is provided herein.

(41) 2. Performance Test

(42) 1) Bending strength: FIG. 5 is a comparison diagram of the bending stress-strain curves of the biomimetic nacre material prepared in Example 9 of the present invention and other related wood materials. In FIG. 5, Line A represents the bending stress-strain curve of a pure wood fiberboard; Line B represents the bending stress-strain curve of the biomimetic nacre material prepared in Example 9 of the present invention; and Line C represents the bending stress-strain curve of a random CaCO.sub.3/wood fiber composite board (prepared in the Comparative Example 1).

(43) From FIG. 5, it can be seen that the bending strength (Line B) of the biomimetic nacre material is higher than that (Line C) of the random CaCO.sub.3/wood fiber composite board, which is higher than the bending strength (Line A) of the pure wood fiberboard. The interaction between the organic polymer and two CaCO.sub.3/wood fiber composite layers plays the role in synergistic toughening of the biomimetic nacre material. If the organic polymer is absent, the CaCO.sub.3/wood fiber composite layer is more likely to aggregate, and the anionic interaction between the two CaCO.sub.3/wood fiber composite layers is relatively weak. In addition, the CaCO.sub.3/wood fiber composite material has a high rigidity.

(44) 2) Specific strength: FIG. 6 is a comparison diagram of the specific strength of the biomimetic nacre material prepared in Example 9 of the present invention and other materials, wherein 1. Concrete; 2. Glass; 3. Copper alloy; 4. Natural Sinanodonta woodiana shell; 5. Synthetic shell; 6. Polyurethane; 7. Al.sub.2O.sub.3/polyacrylic acid composite material; 8. Aluminum alloy; 9. Polystyrene; 10. Epoxy resin; 11. Quartz glass; 12. The inventive biomimetic nacre material; 13. Ferroalloy; 14. Natural California red abalone shell; 15. Cristaria plicata shell; 16. Natural nacre; 17. Nylon; 18. Al.sub.2O.sub.3 material; 19. Silicon carbide material.

(45) The comparison results of the bending strength and the specific strength between the biomimetic nacre material prepared in Examples 7, 8, 10 and 12 and other materials are similar to those in Example 9, so no more detail is provided herein.

(46) Since the wood fiber contains low-molecular-weight C, H and 0 as its constituents, it has lower density than other inorganic materials such as metal products and metal oxides. Therefore, the inventive biomimetic nacre material has higher specific strength and specific toughness than various alloys and composite materials thereof.

(47) 3) Exemplary Illustration of Functional Groups

(48) In order to effectively characterize the photocatalytic effect of the inventive biomimetic nacre material, a strip composite material (prepared in Example 11, with a dimension of 20 mm×7 mm×5 mm) is soaked in formaldehyde water solution (0.15 mmol/L) and then exposed to ultraviolet (UV) light.

(49) FIG. 7 is a formaldehyde degradation curve of the biomimetic nacre material prepared in Example 11 of the present invention. As shown in FIG. 7, from the formaldehyde degradation curve after UV irradiation for 360 min, it can be seen that formaldehyde is gradually degraded over time, the formaldehyde concentration changes little after 300 min, and the biomimetic nacre material has degraded about 44.5% of formaldehyde after 360 min. Such a result shows that the inventive biomimetic nacre material has a remarkable degrading effect on formaldehyde under UV irradiation when using a functional nano inorganic material.

(50) Therefore, the preparation method of the present invention can introduce various functional groups of nanoparticles such as CaCO.sub.3, TiO.sub.2 and ZnO into a wood material, to endow the inventive biomimetic nacre material with various new functions, e.g. photocatalytic performance, wear resistance, antibacterial performance and magnetism, thereby greatly expanding the application fields of the composite material.

(51) Unless otherwise stated specifically, the numerical values set forth in these examples do not limit the scope of the present invention. In the examples shown and described herein, unless otherwise specified, any specific value should be interpreted as merely exemplary, but not as a limitation, and therefore other examples of exemplary embodiments may have different values.

(52) Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, not to limit them. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can be made on the technical solutions recorded in the foregoing embodiments, or equivalent replacements can be made on some or all of the technical features. These modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present invention, and should be covered by the scope of the claims and the specification of the present invention.