A kind of network glassy carbon and preparation method thereof

Abstract

The present invention discloses a reticular glassy carbon and a preparation method thereof. The reticular glassy carbon is prepared by the following method: (1) preparing a soft foam polyurethane material and treating the pores by a combustion and explosion method; (2) impregnating the soft foam polyurethane material in an impregnation liquid, drying it after taking it out and curing it at high temperature to obtain an intermediate product; the impregnation liquid includes phytic acid and resin; (3) pyrolyzing the intermediate product at 500-1700°C, and carbonizing the intermediate product after pyrolysis at 1700-3000°C after cooling. The present invention can obtain a reticular glassy carbon with a highly interconnected, three-dimensional porous, uniform pore structure and high strength by accurately controlling the foaming, combustion and explosion, impregnation, curing, pyrolysis and carbonization process of the soft foam polyurethane material, and can also obtain the required pore size. The preparation process is highly controllable, low in cost, good in product stability, and easy for large-scale industrial production.

Description

Technical Field

[0001] The invention relates to the technical field of carbon materials, and in particular to a network of glassy carbon and a preparation method thereof. Background Art

[0002] Reticulated vitreous carbon (RVC) is an open, porous mesh of glassy or amorphous carbon. Reticulated vitreous carbon provides a highly interconnected, three-dimensional porous, uniform pore structure, with the advantages of good chemical stability, high temperature resistance (3000°C in non-oxidizing atmosphere), high specific surface area, small density, adjustable pore size, adjustable electrical / thermal conductivity, high porosity, low thermal expansion coefficient and high structural strength. It is increasingly used in glassy carbon electrodes, battery current collectors, biomaterial scaffolds, water purification, catalyst carriers and filtration.

[0003] Research on reticulated glassy carbon started early abroad, and it has a history of nearly 60 years. Walter Ford of the United States took the lead in developing reticulated glassy carbon by pyrolysis of polymers in the 1960s. This foamed carbon material is a reticulated glassy structure composed of a carbon skeleton. In the 1990s, a new generation of foamed carbon materials appeared abroad, mainly using asphalt or coal to replace other precursor materials to prepare foamed carbon materials. In 1998, JWKlett, a carbon material researcher at the Oak Ridge National Laboratory (ORNL) in the United States, accidentally discovered a graphitized porous carbon material when preparing carbon materials with asphalt. This achievement has attracted great attention from many scientists around the world. China has only started to study foamed carbon materials in the past thirty years. From the current research status, the research on reticulated glassy carbon is still in the exploratory stage, but with the continuous improvement of my country's industrial and equipment levels, the demand for reticulated glassy carbon is becoming more and more urgent. Due to the limitations of the process, the existing reticulated glassy carbon has a large shrinkage rate during the preparation process, resulting in a low open porosity (less than 80%), and the pore size cannot be controlled. Therefore, a new preparation process for reticulated glassy carbon is urgently needed to be developed. Summary of the invention

[0004] The invention provides a mesh glassy carbon and a preparation method thereof, which are used to solve the technical problems of low opening rate, difficult control of pore size and high production cost of the existing mesh glassy carbon.

[0005] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0006] A method for preparing a network glassy carbon comprises the following steps:

[0007] (1) A soft polyurethane foam material is prepared, and the pores of the soft polyurethane foam material are treated by a combustion and explosion method.

[0008] (2) The soft foam polyurethane material is immersed in a resin impregnation liquid, taken out and dried and cured at high temperature to obtain an intermediate product; the impregnation liquid comprises phytic acid and resin; the resin comprises at least one of furan resin, furfuryl ketone resin, furfuryl alcohol resin, phenolic resin and epoxy resin.

[0009] (3) pyrolyzing the intermediate product at 500-1700° C., and then carbonizing the intermediate product at 1700-3000° C. after cooling, to obtain the network glassy carbon.

[0010] The design idea of ​​the above technical solution is that the present technical solution firstly processes the polyurethane material by the explosion method, removes the closed pores inside it, greatly improves the open porosity of the polyurethane material, and then impregnates and solidifies the polyurethane material by the impregnating agent, so that the pore structure of the polyurethane material can be preserved and shaped, and finally obtains the mesh glass carbon material with a pore structure by pyrolysis and carbonization. At the same time, the present technical solution optimizes the type of impregnating agent. The traditional mesh glass carbon processing technology uses furfural (furfural / furan) resin to impregnate the soft foam polyurethane material, and uses sulfuric acid (or nitric acid, etc.) as a curing agent for curing. Due to the large amount of sulfuric acid (or nitric acid, etc.) curing agent, the lack of carbon, and the poor curing effect, the mesh glass carbon produced by it has low strength, large shrinkage, and it is difficult to effectively control the pore size.

[0011] The strength of the reticular glassy carbon depends on the following aspects: ① The thickness and density of the carbon beams in the cross-linked mesh structure. Under normal circumstances, under the same density, the thicker the beams in the reticular glassy carbon, the higher its strength, and the higher the overall strength of the reticular glassy carbon; under the same carbon content in the reticular glassy carbon beams, the higher its density (the thinner the beams), the higher its strength. The traditional method uses sulfuric acid (or nitric acid, etc.) as a curing agent. The acid dilutes the carbon content per unit volume of the impregnation solution. When the same mass of impregnation solution is used, the amount of carbon impregnated on the polyurethane soft foam by the traditional method is reduced, which will cause the beams in the carbonized sample to become thinner, loose and porous, and its strength is low. When sulfuric acid (or nitric acid, etc.) is used as a curing agent, due to its strong oxidizing property, it is easy to form excessive local oxidation after adding resin, and the overall viscosity of the impregnation liquid is uneven. During impregnation, it is impossible to effectively squeeze out the excess impregnation liquid, which will cause serious local sealing of the mesh glass carbon and reduce the overall open porosity after pyrolysis and carbonization; ② The graphitization rate of the cross-linked mesh structure carbon beams. Resin and polyurethane soft foam materials are both difficult to graphitize carbon materials. The graphitization rate of the former at high temperature is less than 0.5%, and the latter is even lower. Therefore, even if the mesh glass carbon produced by the traditional method is vitrified at 3000℃, the overall graphitization rate of the obtained mesh glass carbon is less than 0.5%. The technical solution uses inositol hexaphosphate as a curing agent and resin. On the one hand, it avoids the adverse effects of sulfuric acid (or nitric acid, etc.) as a curing agent, and on the other hand, it utilizes the properties of inositol hexaphosphate that is not difficult to graphitize carbon materials. After the cured sample is subjected to high-temperature pyrolysis and carbonization, the graphitization rate of the mesh glass carbon is improved to a certain extent, which effectively improves the overall strength of the mesh glass carbon. At the same time, several resin impregnating agents in the present technical solution also have obvious advantages over other resin impregnating agents: high carbon content, fast curing speed, high curing strength, etc. After curing, the shrinkage rate of the material during pyrolysis and carbonization is small, so that the final product can retain the high open porosity of the original polyurethane matrix material while ensuring that the pore size changes are small.

[0012] As a further preferred embodiment of the above technical solution, the impregnating agent includes a combination of at least one of furfural resin and furfural resin and phytic acid.

[0013] As a further preferred embodiment of the above technical solution, the specific operation of treating the soft foam polyurethane material by the explosion method in step (1) is to introduce an appropriate amount of hydrogen, oxygen and nitrogen into the pores of the soft foam polyurethane material and ignite them to remove the closed pores inside the soft foam polyurethane material.

[0014] As a further preferred embodiment of the above technical solution, in step (2), the soft foam polyurethane material is impregnated 3 to 5 times, and after each impregnation, the impregnation liquid in the soft foam polyurethane material is squeezed dry before the next impregnation.

[0015] As a further preferred embodiment of the above technical solution, the high temperature curing temperature in step (2) is 100-150°C, and the curing time is 3-5h. After the polyurethane material treated with the parameters of this preferred solution is initially shaped, it has high strength and extremely low shrinkage during pyrolysis and carbonization, and can effectively control the pore size of the network glassy carbon material to ensure the open porosity.

[0016] As a further preferred embodiment of the above technical solution, the operation of pyrolyzing the intermediate product in step (3) is as follows: first, the intermediate product is heated to 280-320°C and kept warm for 0.5-1.5h, with a heating rate of 7-9°C / min; then heated to 450-550°C and kept warm for 0.5-1.5h, with a heating rate of 2-3°C / min; finally heated to 1650-1750°C and kept warm for 2.5-3.5h, with a heating rate of 10-15°C / min. After curing, the resin impregnating agent still retains some double bonds (or epoxy bonds) or two-dimensional linear structures. Pyrolysis can initially break the double bonds or linear structures into carbon, and initially separate them from some H and O elements in the material, thereby ensuring the degree of carbonization.

[0017] As a further preferred embodiment of the above technical solution, the operation of carbonizing the intermediate product in step (3) is as follows: firstly, the intermediate product is heated to 1650-1750°C at a heating rate of 22-28°C / min; then the temperature is continuously raised to 2400-2600°C at a heating rate of 10-15°C / min; finally, the temperature is raised to 2800-3000°C and kept for 2-4 hours at a heating rate of 7-9°C / min. Carbonization is carried out according to the heating curve of this preferred solution, and the obtained product has high carbon content, high strength and a three-dimensional mesh dodecahedron structure.

[0018] As a further preferred embodiment of the above technical solution, the pyrolysis and carbonization operations in step (3) are carried out in a vacuum environment or a protective atmosphere, the absolute vacuum degree of the vacuum environment is less than 10000 Pa, and the protective atmosphere is a high-purity argon or high-purity nitrogen atmosphere.

[0019] As a further preferred embodiment of the above technical solution, the soft foam polyurethane material is prepared by mixing and foaming the following raw materials: polyether polyol, water, silicone oil, triethylenediamine, stannous octoate, toluene diisocyanate, chlorofluorocarbon and liquid CO2.

[0020] As a further preference of the above technical solution, based on the same technical concept, the present invention also provides a mesh glassy carbon prepared by the above preparation method, wherein the open porosity of the mesh glassy carbon is greater than 90% and the pore size is 100 to 1000 μm.

[0021] Compared with the prior art, the advantages of the present invention are:

[0022] The present invention can obtain a mesh glassy carbon with a highly interconnected, three-dimensional porous, uniform pore structure and high strength by precisely controlling the foaming, impregnation, curing, pyrolysis and carbonization processes of a soft foam polyurethane material and optimizing and designing an impregnation liquid. The mesh glassy carbon presents a three-dimensional mesh structure of a dodecahedron, and the beams are in a glassy state. The pores can be adjusted within the range of 100 to 1000 μm, the porosity is greater than 90%, and the yield strength is greater than 0.1 Mpa. At the same time, the preparation process has strong controllability, low cost, good product stability, and is easy for large-scale industrial production. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 This is a diagram of the internal structure of the mesh glassy carbon prepared in Example 1. DETAILED DESCRIPTION

[0024] The present invention is further described in detail below in conjunction with specific embodiments.

[0025] Embodiment 1:

[0026] The internal structure of the mesh glassy carbon of this embodiment is shown in the figure below. Figure 1 As shown, it is prepared by the following steps:

[0027] (1) 100 g of polyether polyol, 3 g of water, 0.8 g of silicone oil, 0.14 g of triethylenediamine, 0.2 g of stannous octoate, 0.41 g of toluene diisocyanate (TDI), and an appropriate amount of chlorofluorocarbon (CFC) (or liquid CO2) are rapidly mixed in a foaming box in a certain order, and foamed in a one-step method for 110 seconds. The mixture is then cooled to room temperature and aged for 24 hours to obtain a soft foam polyurethane material. The order in which the raw materials are mixed in the foaming box is: polyether polyol, water, an appropriate amount of chlorofluorocarbon (CFC) (or liquid CO2), silicone oil, triethylenediamine, stannous octoate, and finally toluene diisocyanate (TDI).

[0028] (2) Then, hydrogen, oxygen and nitrogen with a volume ratio of 2:1:3 are introduced into the pores of the prepared soft foam polyurethane material, and the closed pores in the pores of the soft foam polyurethane material are removed by a combustion and explosion method.

[0029] (3) Cut the above-mentioned soft foam polyurethane material into soft foam polyurethane material blocks of 100mm*100mm*100mm, and then impregnate the soft foam polyurethane material blocks with impregnation liquid for 3 times, squeezing out the impregnation liquid each time, the impregnation liquid uses furfural resin and phytic acid with a mass ratio of 10:1, dry the impregnated soft foam polyurethane material blocks in dry air, and then cure the dried soft foam polyurethane material blocks at 150°C for 3h to obtain an intermediate product.

[0030] (4) The intermediate product is pyrolyzed in an atmosphere pyrolysis furnace, wherein the atmosphere gas is high-purity argon; during the pyrolysis process, the temperature is first raised to 280°C and kept at this temperature for 1.2 hours, wherein the heating rate is controlled at 7°C / min, and then the temperature is continued to be raised to 520°C and kept at this temperature for 0.8 hours, wherein the heating rate is controlled at 3°C / min, and then the temperature is continued to be raised to 1100°C and kept at this temperature for 3 hours, wherein the heating rate is controlled at 5-6°C / min.

[0031] (5) The intermediate material after pyrolysis is carbonized in an atmosphere carbonization furnace, wherein the atmosphere gas is high-purity argon. During the carbonization process, the temperature is first raised to 900°C, wherein the heating rate is controlled at 28°C / min, then the temperature is further raised to 2400°C, wherein the heating rate is controlled at 10°C / min, then the temperature is further raised to 3000°C, and the temperature is maintained for 3 hours, wherein the heating rate is controlled at 9°C / min, and then the atmosphere carbonization furnace is cooled to room temperature to obtain a network glassy carbon having the following morphology: Figure 1 shown.

[0032] The performance test of the mesh glassy carbon of the present application showed that the open porosity was 96% and the yield strength was 0.10 MPa.

[0033] Embodiment 2:

[0034] The reticular glassy carbon of this embodiment is prepared by the following steps:

[0035] (1) 100 g of polyether polyol, 3 g of water, 0.8 g of silicone oil, 0.14 g of triethylenediamine, 0.2 g of stannous octoate, 0.41 g of toluene diisocyanate, and an appropriate amount of chlorofluorocarbon (or liquid CO2) are rapidly mixed in a foaming box in a certain order, and foamed in a one-step method for 110 seconds. The mixture is then cooled to room temperature and aged for 24 hours to obtain a soft foam polyurethane material. The order in which the raw materials are mixed in the foaming box is: polyether polyol, water, an appropriate amount of chlorofluorocarbon (or liquid CO2), silicone oil, triethylenediamine, stannous octoate, and finally toluene diisocyanate.

[0036] (2) Then, hydrogen, oxygen and nitrogen with a volume ratio of 2:1:3 are introduced into the pores of the prepared soft foam polyurethane material, and the closed pores in the pores of the soft foam polyurethane material are removed by a combustion and explosion method.

[0037] (3) Cut the above-mentioned soft foam polyurethane material into soft foam polyurethane material blocks of 100mm*100mm*100mm, and then impregnate the soft foam polyurethane material blocks with impregnation liquid for 5 times, squeezing out the impregnation liquid each time, the impregnation liquid adopts furfural resin, and the impregnated soft foam polyurethane material blocks are dried in dry air, and then the dried soft foam polyurethane material blocks are cured at 100°C for 5h to obtain an intermediate product.

[0038] (4) The intermediate product is pyrolyzed in an atmosphere pyrolysis furnace, wherein the atmosphere gas is high-purity argon; during the pyrolysis process, the temperature is first raised to 320°C and kept at this temperature for 1 hour, wherein the heating rate is controlled at 9°C / min, and then the temperature is continued to be raised to 450°C and kept at this temperature for 1.5 hours, wherein the heating rate is controlled at 3°C / min, and then the temperature is continued to be raised to 1000°C and kept at this temperature for 2.5 hours, wherein the heating rate is controlled at 5°C / min.

[0039] (5) The intermediate material obtained by the pyrolysis is carbonized in an atmosphere carbonization furnace, wherein the atmosphere gas is high-purity argon. During the carbonization process, the temperature is first raised to 1100°C, wherein the heating rate is controlled at 28°C / min, and then the temperature is continued to be raised to 2600°C, wherein the heating rate is controlled at 15°C / min, and then the temperature is continued to be raised to 3200°C, and kept at this temperature for 3 hours, wherein the heating rate is controlled at 9°C / min, and then the atmosphere carbonization furnace is cooled to room temperature to obtain a network of glassy carbon.

[0040] The performance test of the mesh glassy carbon of the present application showed that the open porosity was 97% and the yield strength was 0.11 MPa.

[0041] Comparative Example 1:

[0042] The network glassy carbon of this comparative example is prepared by the following steps:

[0043] (1) 100 g of polyether polyol, 3 g of water, 0.8 g of silicone oil, 0.14 g of triethylenediamine, 0.2 g of stannous octoate, 0.41 g of toluene diisocyanate (TDI), and an appropriate amount of chlorofluorocarbon (CFC) (or liquid CO2) are rapidly mixed in a foaming box in a certain order, and foamed in a one-step method for 110 seconds. The mixture is then cooled to room temperature and aged for 24 hours to obtain a soft foam polyurethane material. The order in which the raw materials are mixed in the foaming box is: polyether polyol, water, an appropriate amount of chlorofluorocarbon (CFC) (or liquid CO2), silicone oil, triethylenediamine, stannous octoate, and finally toluene diisocyanate (TDI).

[0044] (2) Then, hydrogen, oxygen and nitrogen with a volume ratio of 2:1:3 are introduced into the pores of the prepared soft foam polyurethane material, and the closed pores in the pores of the soft foam polyurethane material are removed by a combustion and explosion method.

[0045] (3) Cut the above-mentioned soft foam polyurethane material into soft foam polyurethane material blocks of 100mm*100mm*100mm, and then impregnate the soft foam polyurethane material blocks with impregnation liquid for 3 times, squeezing out the impregnation liquid each time, the impregnation liquid uses furfural resin and sulfuric acid with a mass ratio of 10:1, dry the impregnated soft foam polyurethane material blocks in dry air, and then cure the dried soft foam polyurethane material blocks at 150°C for 3h to obtain an intermediate product.

[0046] (4) The intermediate product is pyrolyzed in an atmosphere pyrolysis furnace, wherein the atmosphere gas is high-purity argon; during the pyrolysis process, the temperature is first raised to 280°C and kept at this temperature for 1.2 hours, wherein the heating rate is controlled at 7°C / min, and then the temperature is continued to be raised to 520°C and kept at this temperature for 0.8 hours, wherein the heating rate is controlled at 3°C / min, and then the temperature is continued to be raised to 1100°C and kept at this temperature for 3 hours, wherein the heating rate is controlled at 5-6°C / min.

[0047] (5) The intermediate material obtained by the pyrolysis is carbonized in an atmosphere carbonization furnace, wherein the atmosphere gas is high-purity argon. During the carbonization process, the temperature is first raised to 900°C, wherein the heating rate is controlled at 28°C / min, and then the temperature is continued to be raised to 2400°C, wherein the heating rate is controlled at 10°C / min, and then the temperature is continued to be raised to 3000°C, and kept at this temperature for 3 hours, wherein the heating rate is controlled at 9°C / min, and then the atmosphere carbonization furnace is lowered to room temperature to obtain a network of glassy carbon.

[0048] The performance of the reticulated glassy carbon of this comparative example was compared with that of the reticulated glassy carbon of Example 1, and the results are shown in Table 1.

[0049] Table 1: Comparative results of the performance test of the mesh glassy carbon of Comparative Example 1 and Example 1

[0050] The above is only a preferred embodiment of the present invention, and the protection scope of the present invention is not limited to the above embodiments. For those skilled in the art, improvements and changes obtained without departing from the technical concept of the present invention should also be regarded as the protection scope of the present invention.

Claims

1. A method for preparing a network glassy carbon, characterized in that: The following steps are involved: (1) preparing a soft foam polyurethane material, and treating the pores of the soft foam polyurethane material by a combustion and explosion method; (2) dipping the soft foam polyurethane material into an impregnation liquid, taking it out, drying it, and curing it at high temperature to obtain an intermediate product; The impregnation solution comprises phytic acid and a resin; the resin comprises at least one of a furan resin, a furfural resin, a furfuryl alcohol resin, a phenolic resin and an epoxy resin; (3) pyrolyzing the intermediate product at 500-1700° C., and then carbonizing the intermediate product at 1700-3000° C. after cooling, to obtain the network glassy carbon.

2. The method for preparing network glassy carbon according to claim 1, characterized in that: The specific operation of treating the soft foam polyurethane material by the explosion method in step (1) is to introduce hydrogen, oxygen and nitrogen into the pores of the soft foam polyurethane material and ignite them to remove the closed pores inside the soft foam polyurethane material.

3. The method for preparing network glassy carbon according to claim 1, characterized in that: In step (2), the soft foam polyurethane material is impregnated 3 to 5 times, and after each impregnation, the impregnation liquid in the soft foam polyurethane material is squeezed dry before the next impregnation.

4. The method for preparing network glassy carbon according to claim 1, characterized in that: The high temperature curing temperature in step (2) is 100-150° C., and the curing time is 3-5 hours.

5. The method for preparing network glassy carbon according to claim 1, characterized in that: The operation of pyrolyzing the intermediate product in step (3) is as follows: first, the intermediate product is heated to 280-320° C. and kept warm for 0.5-1.5 h, with a heating rate of 7-9° C. / min; then heated to 450-550° C. and kept warm for 0.5-1.5 h, with a heating rate of 2-3° C. / min; and finally heated to 1650-1750° C. and kept warm for 2.5-3.5 h, with a heating rate of 10-15° C. / min.

6. The method for preparing network glassy carbon according to claim 1, characterized in that: The operation of carbonizing the intermediate product in step (3) is as follows: first, the intermediate product is heated to 1650-1750°C at a heating rate of 22-28°C / min; then the temperature is continued to be heated to 2400-2600°C at a heating rate of 10-15°C / min; finally, the temperature is heated to 2800-3000°C and kept warm for 2-4h at a heating rate of 7-9°C / min.

7. The method for preparing network glassy carbon according to any one of claims 1 to 6, characterized in that: The pyrolysis and carbonization operations in step (3) are carried out in a vacuum environment or a protective atmosphere.

8. The method for preparing network glassy carbon according to any one of claims 1 to 6, characterized in that: The soft foam polyurethane material is prepared by mixing and foaming the following raw materials: polyether polyol, water, silicone oil, triethylenediamine, stannous octoate, toluene diisocyanate, chlorofluorocarbon and liquid CO2.

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