An ultralow thermal conductivity biological porous carbonized material, a preparation method and application thereof

Abstract

The present application relates to a kind of ultra-low thermal conductive organism porous carbonized material and its preparation method and application, with chitin-based exoskeleton is soaked in the mixed solvent of acetone, anhydrous ethanol, after drying, obtain porous carbonized raw material;Exoskeleton porous carbonized raw material is pyrolyzed in inert gas, then, the sample obtained is fully dissolved in acetic acid at room temperature, until the complete removal of calcium carbonate, obtain natural porous carbonized material;Final product is washed with deionized water (DI) sample, until the solution becomes neutral, dried under vacuum or protective gas overnight after forming ultra-low thermal conductive organism exoskeleton porous carbonized material.The present application improves the application performance of organism exoskeleton carbonized material in the field of medium-low temperature insulation by the high porosity of organism exoskeleton porous carbonized material, and by the ultra-low intrinsic thermal conductivity of chitin and the stability of its Bouligand structure.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of carbonization, and relates to an ultralow-thermal-conductivity biological porous carbonized material and a preparation method and application thereof. BACKGROUND

[0002] Carbonization is a process that usually forms a solid residue with increased carbon element content by pyrolysis of organic materials in an inert gas. The process of exposing organic matter or carbon materials to a high-temperature environment to convert them into carbon. This process usually occurs in the absence of oxygen to prevent the material from burning or oxidizing. The purpose of the thermal carbonization process is to generate high-purity carbon materials. Biological carbonized materials convert organic matter into carbon through a high-temperature heat treatment process, retaining the special structure and chemical composition of the original material. However, biological carbonized materials usually have low mechanical strength and high thermal conductivity. For example, the thermal conductivity of carbon nanotube sponge can exceed 7.27 W / (m·K). The preparation cost of certain biological carbonized materials is high, especially in the case of high-temperature treatment and special equipment, which limits their commercialized application. Therefore, there is still a large development space in the direction of reducing thermal conductivity and improving the heat insulation and cold insulation performance.

[0003] Exoskeleton carbonized material is a material made from arthropod exoskeletons rich in chitin after carbonization. It has attracted extensive attention in the fields of medicine, food packaging, and agriculture. Chitin is a natural biopolymer mainly composed of polysaccharides, and its molecular structure includes N-acetylglucosamine and glucosamine monomers. These functional groups provide the possibility for chemical reactions of chitin during high-temperature carbonization. The content of chitin can improve the carbon residue rate of the material, i.e., retain more carbon elements during the carbonization process, affecting the electrical conductivity and mechanical properties of the material. Compared with other types of biological carbonized materials (such as wood), arthropod exoskeletons rich in chitin contain a large amount of amino groups, and their nitrogen content is relatively high. Nitrogen doping can improve the electrical conductivity of carbon materials and increase their application potential in electrochemistry and electronic devices. At the same time, chitin molecules contain multiple active functional groups such as amino and hydroxyl groups. These functional groups can introduce different functional groups during carbonization, thereby increasing the diversity and functionality of carbon materials. This provides more possibilities for the directed design of the performance of carbon materials, such as surface chemical activity and biocompatibility. The structure of wood and other materials is relatively fixed, which may limit the structural design of wood carbonization products and make it difficult to meet certain specific application requirements. At the same time, chitin is mainly derived from the exoskeleton of aquatic organisms, and its natural biodegradability makes chitin carbonization products more environmentally friendly. The biodegradability of wood may weaken during the carbonization process. This may not be ideal in some applications that require long-term stability of carbon materials. Chitin usually has relatively low thermal conductivity, ranging from 0.2 to 0.6 W / (m·K), which makes chitin have potential in some insulation and thermal insulation applications. Its thermal expansion coefficient is usually low, which can reach 20-80 ppm / °C or even lower. This type of material with extremely low thermal conductivity can further reduce the thermal conductivity of the material after being prepared into biological porous exoskeleton carbonized material.

[0004] The biological exoskeleton carbonization raw material mainly has a Bouligand structure. The inner cuticle of the biological exoskeleton carbonization raw material is overlapped by multiple layers of fibers, which are bounded by amorphous calcium bodies. The fiber layers form very dense, twisted plywood-like planes that gradually rotate around their normal, thus forming a Bouligand structure. Each layer of the structure contains a series of individual fiber bundles. The gaps between the fibers are filled with micrometer- and nanometer-sized proteins and biominerals. The fiber bundles in the same fiber layer are arranged along the same angle, resulting in the intersection of the fiber layer with the adjacent layer. Each group of fiber bundles is composed of many filamentous fibers with a helical twist structure. The cross-section of the fiber bundle shows tiny pores between the fibers. Therefore, these fibers are orderly interwoven into a crisscrossing cross-frame, which increases the toughness, stability, strength and porosity of the structure. Therefore, this makes it easier for pyrolysis gas to diffuse to the internal area during the carbonization process, promoting more uniform carbonization of the raw material, and improving the adsorption capacity of the carbonization product to the gas. This helps to reduce the local non-uniformity of the carbonization reaction and improve the uniformity of the product.

[0005] Now the preparation and application technology of biological exoskeleton carbonization material is mainly concentrated in the fields of adsorption, catalysis, energy storage system, electrode material preparation and electrochemical capacitor. There are relatively few preparation technologies of ultra-low thermal conductivity biological porous exoskeleton carbonization material. Most of them are mixed with chitin powder and KOH / urea solution at different concentrations to prepare high-performance and biodegradable chitin bioplastics, without fully utilizing the high porosity and low intrinsic thermal conductivity of the material itself. The characteristics of the biological exoskeleton carbonization product may limit its promotion in some application fields. For example, its high porosity and multiple functional groups may make it superior to other materials in some aspects, but it may not be as good as some specifically designed carbon materials in other aspects. The current research focus of carbonization technology may be more concentrated on other carbonization raw materials, limiting the in-depth study of biological exoskeleton carbonization technology. The lack of knowledge base leads to the relative lag of technology development. Therefore, the preparation of biological porous carbonization material from ultra-low thermal conductivity crustacean exoskeleton is a blank in the field of low thermal conductivity biological carbonization material. SUMMARY

[0006] Technical problems to be solved

[0007] In order to avoid the shortcomings of the prior art, the present application provides an ultra-low thermal conductivity biological porous carbonization material and its preparation method and application, which mainly solves the problem of preparing natural porous carbonization material from biological chitin with ultra-low intrinsic thermal conductivity without relying on other carbonization materials as the matrix skeleton. The ultra-low thermal conductivity biological exoskeleton porous carbonization material is lower than the traditional thermal insulation carbonization material.

[0008] The application provides an ultralow thermal conductivity exoskeleton porous carbonized material and a preparation method and application thereof. The method comprises the following steps: heating an exoskeleton mainly composed of chitin, then soaking the exoskeleton in a mixed solvent of acetone and anhydrous ethanol, and drying to obtain a porous carbonized raw material; pyrolyzing the exoskeleton porous carbonized raw material in an inert gas, then fully dissolving the obtained sample in acetic acid at room temperature until the calcium carbonate is completely removed to obtain a natural porous carbonized material; and finally washing the sample with deionized water (DI) until the solution becomes neutral, and drying the washed sample to obtain the ultralow thermal conductivity exoskeleton porous carbonized material. The high porosity of the exoskeleton and the ultralow intrinsic thermal conductivity of chitin, as well as the ultralow thermal conductivity and chemical stability after carbonization, improve the application performance of the carbonized material in the field of medium and low temperature insulation.

[0009] Technical scheme

[0010] A preparation method of an ultralow thermal conductivity exoskeleton porous carbonized material, characterized by the following steps:

[0011] Step 1: removing muscle fibers, grease and proteins from an exoskeleton mainly composed of chitin, then soaking the exoskeleton in a mixed solvent of acetone and anhydrous ethanol, and drying to obtain an exoskeleton porous carbonized raw material;

[0012] Step 2: pyrolyzing the exoskeleton porous carbonized raw material in an inert gas, then fully dissolving the obtained sample in acetic acid at room temperature until the calcium carbonate is completely removed to obtain a natural porous carbonized material;

[0013] Step 3: washing the natural porous carbonized material with deionized water (DI) until the solution becomes neutral, and drying to obtain the ultralow thermal conductivity exoskeleton porous carbonized material.

[0014] The method for removing muscle fibers, grease and proteins in step 1 is: preheating the exoskeleton at 80-120 DEG C for 30-100 minutes to preliminarily remove muscle fibers, grease and proteins.

[0015] The soaking time of the exoskeleton in the mixed solvent of acetone and anhydrous ethanol in step 1 is 6-24 hours, and the muscle fibers, grease and proteins are completely removed.

[0016] The method for pyrolyzing the exoskeleton porous carbonized raw material in an inert gas in step 2 is: heat treating the exoskeleton porous carbonized raw material at a temperature of 80-960 DEG C for 1-5 hours, and the inert gas can be nitrogen, helium or argon, and the exoskeleton is processed at high temperature to form the carbonized material.

[0017] The drying of the natural porous carbonized material in step 3 is carried out under vacuum or in a protective gas at a temperature of 80-100 DEG C for 6-24 hours.

[0018] The chitin-based exoskeleton raw material of step 1 is selected from the Malacostraca subphylum of the Malacostraca class of the Malacostraca class.

[0019] The molar ratio in the mixed solvent of acetone and anhydrous ethanol is 30-60:60-30; the purity of acetone and anhydrous ethanol is 99.99%.

[0020] The concentration of the acetic acid solution is 1 mol / L; the conductivity of the deionized water DI is less than 1.0 μs / cm.

[0021] The ultra-low thermal conductivity exoskeleton porous carbonized material prepared by the method has the characteristics of good physical properties, large porosity, and low thermal conductivity, and can exhibit better strength and toughness.

[0022] The application of the ultra-low thermal conductivity exoskeleton porous carbonized material prepared by the method is in the field of medium and low temperature insulation.

[0023] Advantages

[0024] The application provides an ultra-low thermal conductivity exoskeleton porous carbonized material, a preparation method and application thereof, and relates to the technical field of carbonization. The method comprises the following steps: heating chitin-based exoskeleton at 80-120 DEG C for 30-100 minutes, immersing the exoskeleton in a mixed solvent of acetone and anhydrous ethanol, and drying to obtain a porous carbonized raw material; pyrolyzing the exoskeleton porous carbonized raw material in an inert gas at 80-960 DEG C for 1-5 hours; then, fully dissolving the obtained sample in acetic acid at room temperature until the calcium carbonate is completely removed, to obtain a natural porous carbonized material; and finally, washing the product with deionized water (DI) until the solution becomes neutral, drying at 80-100 DEG C under vacuum or in a protective gas overnight to form an ultra-low thermal conductivity exoskeleton porous carbonized material. The application improves the application performance of the exoskeleton carbonized material in the field of medium and low temperature insulation, by virtue of the high porosity of the exoskeleton porous carbonized material, the ultra-low intrinsic thermal conductivity of chitin, and the stability of the Bouligand structure.

[0025] Compared with the prior art, the application has the following advantages:

[0026] The present application utilizes the exoskeleton of the crustacean subphylum Malacostraca, which is mainly composed of chitin, to remove muscle fibers, oils, and proteins and other impurities through a mixture of temperature and acetone, anhydrous ethanol, and then dried to form a porous carbonized raw material. Then, through the high-temperature pyrolysis of chitin, heterogeneous atoms are uniformly incorporated into the carbon ring, forming high-quality carbonized materials. Subsequently, using acetic acid to remove calcium carbonate from the material, a natural porous carbonized material is obtained. Finally, through drying means, the natural porous carbonized material is converted into an ultralow thermal conductivity exoskeleton porous carbonized material. Through experiments, as an exoskeleton carbonized material of living organisms, the thermal diffusivity coefficient is different due to the different types of raw materials, but it is within the range of low thermal conductivity. At the same time, PPMS is used to measure Cp to prove its low thermal conductivity characteristics.

[0027] See the table below:

[0028] Biological extracorporeal bone carbonization raw material types Thermal diffusivity (mm2 / s) Scylla paramamosain 0.34 Cancer pagurus 0.35 Paralithodes camtschaticus 0.16 Portunus trituberculatus 0.22 Chionoecetes opilio 0.20

[0029] In the present application, due to the use of exoskeleton carbonized raw materials with high chitin content and Bouligand structure, the Bouligand structure can be preserved to some extent during high-temperature carbonization, and the organic matter of the exoskeleton of living organisms is converted into carbon. Due to the hierarchical arrangement of the Bouligand structure, part of the structure can be preserved in the product, forming a certain multi-level ordered structure. At the same time, the carbonized product that retains the Bouligand structure can exhibit better strength and toughness, which depends on the degree of structure preservation during carbonization and the microstructure of the product. The hierarchical arrangement of fibers provides a template for the pore structure of the carbonized product. The volatilization and structural transformation of organic matter can lead to the formation of pores, and the presence of the Bouligand structure may affect the distribution and shape of the pores, thereby enhancing the pore structure of the carbonized product and finally reducing the thermal conductivity of the final product. Compared with other types of carbonized raw materials, the natural structure of chitin and the organic matter contained in the exoskeleton of living organisms can affect the pore structure of the carbonized product. The volatilization and structural transformation of organic matter can lead to the formation of pores. The special structure of chitin as a raw material can regulate the size and shape of the pores to some extent, thereby affecting the pore structure of the product. The natural biocompatibility of chitin makes the carbonized product have potential advantages in biomedical applications. The presence of high nitrogen content and multiple functional groups makes it more suitable for biomedical applications, such as drug carriers, tissue engineering scaffolds, etc.

[0030] The preparation process of the present application is simple, and advanced technologies of inert gas protection and temperature gradient control are used to ensure the uniformity and purity of the product in the high-temperature carbonization process, and to reduce the thermal conductivity of the material. The microwave-assisted technology is introduced to accelerate the carbonization process, improve the efficiency, control the pore structure of the product, and increase the surface area. It is suitable for mass production. The prepared ultra-low thermal conductivity exoskeleton porous carbonized material has good mechanical properties, low density, good quality, low thermal conductivity, and good heat preservation performance. As a new type of low thermal conductivity material, it has replaced the existing common heat preservation materials in performance. BRIEF DESCRIPTION OF DRAWINGS

[0031] Figure 1 The preparation process of the ultra-low thermal conductivity exoskeleton porous carbonized material provided for the examples is shown in the schematic diagram.

[0032] Figure 2 The Vickers hardness test results provided for Example 1 are shown in the table.

[0033] Figure 3 The micro-CT scan provided for Example 1 is shown in the figure.

[0034] Figure 4 The SEM electron microscope image with Bouligand structure provided for Example 1 is shown in the figure.

[0035] Figure 5 The nanoindentation hardness graph provided for Example 1 is shown in the figure.

[0036] Figure 6 The nanoindentation hardness graph provided for Example 1 is shown in the figure. DETAILED DESCRIPTION

[0037] The present application will be further described in conjunction with the examples and drawings:

[0038] In order to enable those skilled in the art to better understand the technical solutions of the present application and implement them, the present application will be further described in conjunction with specific examples and drawings, but the examples are not limiting the present application.

[0039] The purpose of the present application is to prepare a new type of exoskeleton porous carbonized material by virtue of the ultra-low intrinsic thermal conductivity and high porosity of biological chitin. By virtue of the high porosity and ultra-low intrinsic thermal conductivity of chitin and its low-temperature thermal stability, the application performance of the exoskeleton porous carbonized material in the low-temperature heat preservation field is further improved.

[0040] In order to achieve the above purpose, the present application obtains a porous carbonized raw material by soaking the chitin-based exoskeleton after heating in a mixed solvent of acetone and anhydrous ethanol, and drying; then, the exoskeleton porous carbonized raw material is pyrolyzed in an inert gas, and then the obtained sample is fully dissolved in acetic acid at room temperature until the calcium carbonate is completely removed, to obtain a natural porous carbonized material; finally, the product is washed with deionized water (DI) until the solution becomes neutral, and after drying, an ultra-low thermal conductivity exoskeleton porous carbonized material of living beings is formed. The specific process is as follows:

[0041] A preparation method of an ultra-low thermal conductivity exoskeleton porous carbonized material of living beings, comprising the following steps:

[0042] (1) The exoskeleton of living beings is washed with distilled water and placed in an oven for heating and keeping at 80-120℃ for 30-100 minutes.

[0043] (2) Acetone with a purity of 99.99% and 99.99% anhydrous ethanol are mixed in a ratio of 40:60 to form a mixed solvent system as a treatment solution for the porous carbonized raw material. The cleaned exoskeleton of living beings is fully soaked in the treatment solution for 6-24 hours to remove muscle fibers, grease and proteins, and a high-porosity exoskeleton porous raw material is obtained

[0044] (3) The exoskeleton porous raw material is placed in a high-temperature heat treatment furnace and heated to 80-960℃, and inert gas is introduced, and the pyrolysis time is 1-5 hours. The high-temperature pyrolysis of chitin causes heterogeneous atoms to be uniformly doped into the carbon ring, forming a high-quality carbonized material.

[0045] (4) After the furnace is cooled to room temperature, the carbonized sample is fully soaked in an acetic acid solution with a concentration of 1 mol / L, and after the complete reaction of calcium carbonate and acetic acid, a high-porosity natural porous carbonized material is formed.

[0046] (5) The sample is washed with deionized water (DI) with a conductivity less than 1.0 μs / cm until the solution becomes neutral.

[0047] (6) The sample is transferred to an oven and dried at 80-100℃ under vacuum or protective gas for 6-24h to form an ultra-low thermal conductivity exoskeleton porous carbonized material of living beings.

[0048] The present application provides a preparation method of an ultra-low thermal conductivity exoskeleton porous carbonized material of living beings.

[0049] The present application also provides an application of an ultra-low thermal conductivity exoskeleton porous carbonized material of living beings in the field of low-temperature thermal insulation.

[0050] It should be noted that the experimental method used in the present application is a conventional method unless otherwise specified; The reagents and materials used, unless otherwise specified, can be purchased on the market.

[0051] Example 1

[0052] A preparation method of an ultralow thermal conductivity exoskeleton porous carbonized material of a living body, see Figure 1 As shown, comprising the following steps:

[0053] Step 1, select blue crab exoskeleton material, use distilled water to clean the surface of the sample, then put it into a constant temperature oven and heat at 80°C for 100 minutes;

[0054] Step 2, mix 99.99% pure acetone and 99.99% anhydrous ethanol according to the ratio of 40:60 to form a mixed solvent system as a treatment solution for porous carbonized raw materials. Put the cleaned blue crab exoskeleton into the treatment solution and soak for 12 hours;

[0055] Step 3, after cleaning the residual solution on the surface of the blue crab exoskeleton sample, move the sample to a high-temperature heat treatment furnace, set the temperature to 300°C, use argon as a protective gas and heat for 4 hours;

[0056] Step 4, wait for the temperature of the high-temperature heat treatment furnace to drop to room temperature, prepare a 1 mol / L acetic acid solution and soak the high-temperature pyrolyzed blue crab sample in it, and after the calcium carbonate inside the sample is completely removed, get a high-porosity blue crab natural porous carbonized material.

[0057] Step 5, use deionized water (DI) with conductivity less than 1.0 μs / cm to wash the sample until the solution becomes neutral.

[0058] Step 6, transfer the sample to an oven and dry it under vacuum at 100°C for 12 hours to obtain an ultralow thermal conductivity exoskeleton porous carbonized material of a living body.

[0059] Example 2

[0060] A preparation method of an ultralow thermal conductivity exoskeleton porous carbonized material of a living body, see Figure 1 As shown, comprising the following steps:

[0061] Step 1, select snow crab exoskeleton material, use a diamond wire cutting machine to divide the raw material into 3.5 cm x 3.5 cm square pieces, then put it into a constant temperature oven and heat at 100°C for 60 minutes;

[0062] Step 2, 99.99% pure acetone and 99.99% anhydrous ethanol are mixed in a ratio of 30:70 to form a mixed solvent system as a treatment solution for porous carbonized raw materials. The cleaned snow crab exoskeleton material is soaked in the treatment solution for 12 hours;

[0063] Step 3, after cleaning the residual solution on the surface of the king crab exoskeleton sample, the sample is moved to a high-temperature heat treatment furnace, the temperature is set to 423°C, helium gas is used as the protective gas and the temperature is kept for 4 hours;

[0064] Step 4, wait for the temperature of the high-temperature heat treatment furnace to drop to room temperature, prepare an acetic acid solution with a concentration of 1 mol / L, and soak the high-temperature pyrolyzed snow crab sample in it. After the calcium carbonate inside the sample is completely removed, a high-porosity snow crab natural porous carbonized material is obtained.

[0065] Step 5, use deionized water (DI) with a conductivity less than 1.0 μs / cm to wash the sample until the solution becomes neutral.

[0066] Step 6, transfer the sample to an oven and dry it under vacuum at 80°C for 12 hours to obtain an ultra-low thermal conductivity biological exoskeleton porous carbonized material.

[0067] Example 3

[0068] A method for preparing an ultra-low thermal conductivity biological exoskeleton porous carbonized material, as shown in Figure 1 , comprising the following steps:

[0069] Step 1, select a bread crab exoskeleton material, wash the surface of the sample with distilled water, and then place it in a constant temperature oven at 100°C for 100 minutes;

[0070] Step 2, 99.99% pure acetone and 99.99% anhydrous ethanol are mixed in a ratio of 30:70 to form a mixed solvent system as a treatment solution for porous carbonized raw materials. The cleaned snow crab exoskeleton material is soaked in the treatment solution for 12 hours, and after drying, a part of the bread crab exoskeleton material is placed in a ball mill at a speed of 300 rpm / min for 5 minutes, and then the powder is mixed into the ethylene;

[0071] Step 3, place the bread crab exoskeleton material in a plasma CVD as a substrate material, and use ethylene gas mixed with bread crab powder as a precursor gas. The temperature of the reaction chamber is set to 800°C, and after the precursor gas is pyrolyzed, it is deposited on the surface of the substrate to form a thin film of carbonized material;

[0072] Step 4, after the deposition is completed, the temperature is lowered and other atmosphere gases are gradually introduced to cool and stabilize the carbonized film. An acetic acid solution with a concentration of 1 mol / L is prepared and the carbonized film is fully immersed therein, and after the calcium carbonate inside the sample is completely removed, a high-porosity natural porous carbonized material of Portunus sanguinolentus is obtained.

[0073] Step 5, the sample is washed with deionized water (DI) with a conductivity less than 1.0 μs / cm until the solution becomes neutral.

[0074] Step 6, the sample is transferred to an oven and dried at 100°C under vacuum for 12h, and then taken out to obtain an ultralow thermal conductivity exoskeleton porous carbonized material.

[0075] Example 4

[0076] A method for preparing an ultralow thermal conductivity exoskeleton porous carbonized material, as shown in Figure 1 , comprises the following steps:

[0077] Step 1, select Portunus sanguinolentus exoskeleton material, wash the surface of the sample with distilled water, and then place it in a constant temperature oven at 100°C for 100 minutes;

[0078] Step 2, mix acetone with a purity of 99.99% and 99.99% anhydrous ethanol according to a ratio of 50:50 to form a mixed solvent system as a treatment solution for the porous carbonized raw material. The cleaned Portunus sanguinolentus exoskeleton is immersed in the treatment solution for 6 hours;

[0079] Step 3, after cleaning the residual solution on the surface of the Portunus sanguinolentus exoskeleton sample, the sample is moved to a high-temperature heat treatment furnace, the temperature is set to 900°C, argon is used as a protective gas, and the sample is kept at this temperature for 5 hours;

[0080] Step 4, wait for the temperature of the high-temperature heat treatment furnace to drop to room temperature, prepare an acetic acid solution with a concentration of 1 mol / L, and fully immerse the Portunus sanguinolentus sample after high-temperature pyrolysis in the solution, and after the calcium carbonate inside the sample is completely removed, a high-porosity natural porous carbonized material of Portunus sanguinolentus is obtained.

[0081] Step 5, the sample is washed with deionized water (DI) with a conductivity less than 1.0 μs / cm until the solution becomes neutral.

[0082] Step 6, the sample is transferred to an oven and dried at 100°C under vacuum for 6h, and then taken out to obtain an ultralow thermal conductivity exoskeleton porous carbonized material.

[0083] In order to illustrate the related properties of the exoskeleton porous carbonized material prepared by the method provided by the present application, the exoskeleton porous carbonized material is described in combination with the drawings.

[0084] Figure 2 The Vickers hardness map of the blue crab exoskeleton carbonized raw material provided for Example 1 is provided. A relatively smooth platform is obtained by polishing the surface of the sample, and pre-preparation of the Vickers indentation is carried out on the HVC-10A1 type Vickers hardness tester, the pressure used is 9.8N, and the pressure holding time is 15s. The indentation length is measured under the VK9700 type 3D laser scanning microscope, and the hardness of the sample is calculated by the formula Hv = 1.854(F / d^2). Through the indentation of the blue crab exoskeleton carbonized raw material, the hardness is good. Figure 2

[0085] Figure 3 The micro-CT map of the blue crab exoskeleton carbonized raw material provided for Example 1 is provided. The blue crab exoskeleton carbonized raw material is scanned and imaged by X-ray analysis. Among them, the dark area is the structure of the blue crab exoskeleton mainly composed of chitin, and the light area is the pore structure. From the micro-CT map of the blue crab exoskeleton carbonized raw material provided for Example 1, it can be directly observed that the blue crab exoskeleton carbonized raw material has a high level of porosity. At the same time, the excellent mechanical properties can make the exoskeleton raw material still maintain a relatively high level after carbonization, and the high porosity can make an outstanding contribution to reducing the thermal conductivity. Figure 3

[0086] Figure 4 The comparison chart of the blue crab exoskeleton carbonized material provided for Example 1 and other types of low thermal diffusion coefficient materials. The fungus foam material made of fungus carbon has been widely used as thermal insulation material in the fields of building insulation and production heat insulation. The thermal insulation material made of carbon fiber can be applied to automobile and ship manufacturing, and also can be applied to aerospace field. From the chart, it can be seen that the thermal diffusion coefficient of the crab exoskeleton carbonized material is much lower than that of graphene at room temperature. According to the experimental data of the prior art, the thermal diffusion coefficient of graphite at room temperature is 3.6mm2 / s. According to the test results of the present patent, the thermal diffusion coefficient of the crab exoskeleton carbonized material reaches 0.35mm2 / s at room temperature. It shows that the biological porous exoskeleton carbonized material has good competitiveness, and the lower thermal conductivity brings better thermal insulation effect.

[0087] Figure 5 The blue crab cross-sectional layered micro-Bouligand structure provided for Example 1. During the process of using crab shell as carbonized raw material, the Bouligand structure can be preserved to a certain extent. During the high-temperature carbonization process, the organic matter of the crab shell is converted into carbon, and due to the hierarchical arrangement of the Bouligand structure, part of the structure can be preserved in the product, forming a certain multi-level ordered structure. In some cases, the carbonized product which preserves the Bouligand structure can exhibit better strength and toughness, which depends on the structure preservation degree in the carbonization process and the microstructure of the product.

[0088] ​​Figure 6 A nanoindentation hardness plot for Example 1 is provided for the blue crab. The average hardness of the test results was 2.5 GPa, which has entered the range of superhard materials.

[0089] The preferred embodiments are described herein, including the best mode known to the inventors of practicing the application. Of course, variations on the preferred embodiments will occur to those of ordinary skill and are encompassed within the spirit and scope of the application as defined by the claims. Accordingly, the application is not limited to the preferred embodiments described herein, but is intended to cover any and all modifications and equivalents of the limiting claims.

[0090] While the application has been illustrated and described in the context of the preferred embodiments, it will be understood by those of ordinary skill that various changes, modifications, alternatives, and variations can be made thereto without departing from the spirit and scope of the application, which are defined by the claims and their equivalents. Modifications, alternatives, and variations,

Claims

1. A method for preparing an ultralow thermal conductivity exoskeleton porous carbonized material of living beings, characterized by The steps are as follows: Step 1: remove muscle fibers, oil and protein from the chitin-based exoskeleton, then soak in a mixed solvent of acetone and anhydrous ethanol, and dry to obtain exoskeleton porous carbonized raw materials; Step 2: pyrolyze the exoskeleton porous carbonized raw materials in an inert gas, then fully dissolve in acetic acid at room temperature until the calcium carbonate is completely removed, and obtain a natural porous carbonized material; Step 3: wash the natural porous carbonized material with deionized water DI until the solution becomes neutral, and dry to obtain an ultra-low thermal conductivity biological exoskeleton porous carbonized material.

2. The method of claim 1, wherein the method further comprises: The method of removing muscle fibers, oil and protein in step 1 is to pretreat the exoskeleton at 80-120°C for 30-100 minutes to initially remove muscle fibers, oil and protein. ​ 3. The method of claim 1, wherein the method further comprises: The soaking time in the mixed solvent of acetone and anhydrous ethanol in step 1 is 6-24 hours to completely remove muscle fibers, oil and protein. ​ 4. The method of claim 1, wherein the method further comprises: The method of pyrolyzing the exoskeleton porous carbonized raw materials in an inert gas in step 2 is to heat treat the exoskeleton porous carbonized raw materials at a temperature of 80-960°C for 1-5 hours, and the inert gas can be nitrogen, helium or argon. The exoskeleton is processed at high temperature to form a carbonized material. ​ 5. The method of claim 1, wherein the method further comprises: The drying of the natural porous carbonized material in step 3 is carried out under vacuum or protective gas at a temperature of 80-100°C for 6-24h. ​ 6. The method of claim 1, wherein the method further comprises: The exoskeleton raw material in step 1 is selected from the Arthropoda Crustacea Malacostraca.

7. The method of claim 1, wherein the method further comprises: The molar ratio of acetone to anhydrous ethanol in the mixed solvent is 30-60:60-30; the purity of acetone and anhydrous ethanol is 99.99%. ​ 8. The method of claim 1, wherein the method further comprises: The concentration of the acetic acid solution is 1 mol / L; the conductivity of the deionized water DI is less than 1.0 μs / cm. ​ 9. The ultralow thermal conductivity biocompatible exoskeleton porous carbonized material prepared by the method of any one of claims 1-8, wherein: The ultra-low thermal conductivity biological exoskeleton porous carbonized material is prepared by the above steps, and the heterogeneous atoms are uniformly doped into the carbon ring of the porous carbonized raw material to form a carbonized material. The hierarchical arrangement of Bouligand structure forms a multi-level ordered structure, which has the characteristics of good physical properties, high porosity and low thermal conductivity, and can exhibit better strength and toughness.

10. Use of the ultralow thermal conductivity biocompatible exoskeletal porous carbonized material produced by the method according to any one of claims 1 to 8, characterized in that: Application in the field of medium and low temperature insulation.

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