Preparation method of nano silicon dioxide-carboxyl multi-walled carbon nanotube-cement fly ash composite foam material

Abstract

The invention discloses a preparation method of a nano-silica-carboxyl multi-walled carbon nanotube-cement fly ash composite foam material, and relates to the technical field of composite material preparation, and the preparation method comprises the following steps: S11, preparing a carboxyl multi-walled carbon nanotube; s12, preparing a carboxyl multi-walled carbon nanotube mixed solution; s13, preparing a nano silicon dioxide-carboxyl multi-walled carbon nanotube dispersion liquid; s21, mixing ordinary Portland cement and secondary fly ash 3; s22, adding a naphthalene water reducer and water; s23, introducing a nano silicon dioxide-carboxyl multi-walled carbon nanotube dispersion liquid; s24, adding H2O2 (hydrogen peroxide) and FeCl3 (ferric trichloride The carboxyl multi-walled carbon nanotube-nano silicon dioxide dispersion liquid is added into a traditional cement-fly ash foaming material, so that the cement grade can be reduced, the fly ash consumption can be increased, and the compressive strength and tensile strength of the carboxyl multi-walled carbon nanotube-cement-fly ash foaming material can be effectively improved.

Description

Technical Field

[0001] The invention relates to the technical field of composite material preparation, in particular to the technical field of cement and fly ash-based composite materials, and in particular to a method for preparing a nano-silicon dioxide-carboxyl multi-walled carbon nanotube-cement fly ash composite foaming material. Background Art

[0002] As a typical porous cement material, foamed cement has a pore diameter ranging from 1mm to 3mm, and its pore volume can account for more than 60% of the total volume of the material. Due to the large number of closed pores of different diameters inside, the density of foamed cement ranges from 200 kg / m 3 Up to 2000 kg / m 3 Foamed cement has the characteristics of light weight, thermal insulation, and low elastic modulus. It can be used as certain non-load-bearing wall materials and lightweight partitions, and can also be used as thermal insulation materials, sound insulation materials, etc.

[0003] Fly ash is tiny solid particles produced after coal combustion, with a particle size between 1-100μm. In my country, about 250~300kg of fly ash is produced for every ton of coal burned. A large amount of fly ash has a huge impact on the ecological environment.

[0004] Cement-fly ash composite foaming materials made from cement and fly ash as the main raw materials are used in building structures such as roofs, floors, walls, columns, and wall core fillings. Generally, they can reduce the weight of buildings by 30%-40%. At the same time, due to its good thermal and sound insulation properties, it has become an energy-saving and environmentally friendly material that is currently being developed. However, the main disadvantages of cement-fly ash composite foaming materials are low strength and large shrinkage in the later stage. These problems seriously restrict its application scope.

[0005] At present, polypropylene fiber, as a traditional millimeter-level fiber, is widely used in foam material reinforcement due to its wide source, low price, and uniform distribution in cement slurry. The average diameter of polypropylene fiber is 100μm, which is suitable for density of 800-1500kg / m 3 The foamed concrete has a significant effect in enhancing the compressive strength and flexural strength. Polypropylene fibers prevent the cracking of the cement matrix through fiber pulling and fiber bridging.

[0006] However, there are many macropores and micropores in foamed cement, with large diameters and thin pore walls. Therefore, polypropylene fibers cannot prevent the formation and expansion of nanoscale microcracks in foamed cement, especially on thin pore walls. Especially for ultra-light foamed cement with low density, even a small amount of microcracks inside will lead to cracking of the overall specimen in the later stage. Summary of the invention

[0007] In response to the above problems, this study added fly ash and nano-fiber carboxyl multi-walled carbon nanotubes to the foamed cement slurry. By absorbing a large amount of solid waste raw material fly ash, it not only reduced the production cost of the product, but also opened up a new way for the comprehensive resource utilization of solid waste raw material fly ash, effectively solving the environmental pollution caused by fly ash and the high investment cost of enterprises. By adding nano-fiber carboxyl multi-walled carbon nanotubes to the cement-fly ash foaming material, the generation of microcracks in the matrix is ​​suppressed at the nanoscale, the compressive and flexural strength of the matrix is ​​improved, and the durability is improved, so it has certain economic benefits, social benefits and environmental benefits, as follows: A method for preparing a nano-silicon dioxide-carboxyl multi-walled carbon nanotube-cement fly ash composite foam material comprises the following steps: Step 1: Preparation of nano-silica-carboxyl multi-walled carbon nanotubes S11, taking carboxyl multi-walled carbon nanotubes for later use; S12, adding 50 ml of tap water into a beaker, adding 0.04 wt % of the carboxyl multi-walled carbon nanotubes prepared in step S11, and stirring evenly to obtain a carboxyl multi-walled carbon nanotube mixed solution; S13, placing the obtained carboxyl multi-walled carbon nanotube mixed solution into an SK 250LH ultrasonic cleaning machine, and adding 1-3 wt% of nano-silicon dioxide into the mixed solution, and performing ultrasonic dispersion for 20 min to obtain a nano-silicon dioxide-carboxyl multi-walled carbon nanotube dispersion; Step 2: Preparation of nano-silicon dioxide-carboxyl multi-walled carbon nanotube-cement fly ash composite foaming material S21, mix P.O42.5 ordinary Portland cement and secondary fly ash in a mass percentage of 3:7, pour into a mixing equipment, and stir for 5 minutes; S22, adding 3-3.5 wt% of naphthalene-based water reducer and 35-40 wt% of tap water in sequence, and stirring evenly for 3 min to form a cement-fly ash slurry; S23, introducing the nano-silica-carboxyl multi-walled carbon nanotube dispersion prepared in step S13 into the cement-fly ash slurry prepared in step S22, and stirring for 2 min; S24, adding 2.5-3 wt% H2O2 and 2-3 wt% FeCl3 in sequence, stirring for 30 s, to obtain a nano-silica-carboxyl multi-walled carbon nanotube-cement fly ash composite foaming material; the H2O2 and FeCl3 act together as a foaming agent, a foam stabilizer, and a catalyst.

[0008] Moreover, in the step S12, the specific method of stirring evenly is: stirring with a magnetic stirrer for 2 minutes.

[0009] Moreover, in step S13, the ultrasonic power of the ultrasonic cleaning machine is 300 W, the ultrasonic frequency is 53 kHz, water is used as the dispersion medium for ultrasonic dispersion, and the ultrasonic temperature is 30-40°C.

[0010] Moreover, in the step S21, the rotation speed of the stirring process is 60 rad / min.

[0011] Moreover, in step S22, the water temperature is 30-40°C.

[0012] Furthermore, in the step S23, stirring is performed at a speed of 60 rad / min for 2 min, and the water temperature is 30-40°C.

[0013] Furthermore, in the step S24, stirring is performed at a rotation speed of 80 rad / min for 30 s.

[0014] Compared with the prior art, the present invention has the following beneficial effects: 1. The present invention provides a new method and process for preparing nano-silicon dioxide-carboxyl multi-walled carbon nanotube-cement fly ash composite foaming material. By adding nano-silicon dioxide-carboxyl multi-walled carbon nanotube dispersion into the traditional cement-fly ash foaming material, the cement grade used can be reduced and the amount of fly ash used can be increased: (1) The conventional cement-fly ash foaming material uses P.O52.5 cement, while the cement used in the present invention is P.O42.5; (2) In conventional cement-fly ash foaming materials, the fly ash mass ratio is 30%, while the fly ash mass ratio used in the foaming material of the present invention can be increased to 42%; Moreover, after the present invention adopts P.O42.5 cement and 42% fly ash, its compressive strength can reach 0.65MPa and its tensile strength can reach 0.24MPa. The compressive strength and tensile strength are respectively increased by 62.5% and 84.6% compared with traditional cement-fly ash foaming materials.

[0015] 2. The nano-silica-carboxyl multi-walled carbon nanotube-cement fly ash composite foam material prepared by the present invention has good flame retardant properties despite the addition of materials such as nano-silica and carboxyl multi-walled carbon nanotubes. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 This is a comparison chart of the absorbance changes of the three dispersions in Experiment 1 over time; Figure 2 This is the TEM image of nano-silicon dioxide in Experiment 1; Figure 3 This is the TEM image of the nano-silica-carboxyl multi-walled carbon nanotube dispersion in Experiment 1; Figure 4 The compressive strength test results of the three materials are shown below; Figure 5 The tensile strength test results of the three materials are shown in Figure 2. Figure 6 This is the SEM image of nano-silica-carboxyl multi-walled carbon nanotube-cement fly ash composite foam material; Figure 7 This is the SEM image of carboxyl multi-walled carbon nanotube-cement-fly ash foaming. DETAILED DESCRIPTION

[0017] Example 1

[0018] A method for preparing a nano-silicon dioxide-carboxyl multi-walled carbon nanotube-cement fly ash composite foam material comprises the following steps: Step 1: Preparation of nano-silica-carboxyl multi-walled carbon nanotubes S11, taking carboxyl multi-walled carbon nanotubes for later use; S12, adding 50 ml of tap water into a beaker, adding 0.04 wt % of the carboxyl multi-walled carbon nanotubes prepared in step S11, and stirring evenly to obtain a carboxyl multi-walled carbon nanotube mixed solution; S13, placing the obtained carboxyl multi-walled carbon nanotube mixed solution into an SK 250LH ultrasonic cleaning machine, and adding 1 wt% of nano-silicon dioxide into the mixed solution, and performing ultrasonic dispersion for 20 min to obtain a nano-silicon dioxide-carboxyl multi-walled carbon nanotube dispersion; Step 2: Preparation of nano-silicon dioxide-carboxyl multi-walled carbon nanotube-cement fly ash composite foaming material S21, mix P.O42.5 ordinary Portland cement and secondary fly ash in a mass percentage of 3:7, pour into a mixing equipment, and stir for 5 minutes; S22, adding 3 wt% of naphthalene-based water reducer and 35 wt% of tap water in sequence, and stirring evenly for 3 min to form a cement-fly ash slurry; S23, introducing the nano-silica-carboxyl multi-walled carbon nanotube dispersion prepared in step S13 into the cement-fly ash slurry prepared in step S22, and stirring for 2 min; S24, add 2.5 wt% H2O2 and 2 wt% FeCl3 in sequence, stir for 30 s, and obtain nano-silica-carboxyl multi-walled carbon nanotube-cement fly ash composite foaming material.

[0019] Furthermore, in step S12, the specific method for stirring uniformly is: stirring with a magnetic stirrer for 2 minutes.

[0020] Furthermore, in step S13, the ultrasonic power of the ultrasonic cleaning machine is 300 W, the ultrasonic frequency is 53 kHz, water is used as the dispersion medium for ultrasonic dispersion, and the ultrasonic temperature is 30°C.

[0021] Furthermore, in step S21, the rotation speed of the stirring process is 60 rad / min.

[0022] Furthermore, in step S22, the water temperature is 30°C.

[0023] Furthermore, in step S23, stirring is performed at a speed of 60 rad / min for 2 min, and the water temperature is 30°C.

[0024] Furthermore, in the step S24, stirring is performed at a speed of 80 rad / min for 30 s.

[0025] Example 2 A method for preparing a nano-silicon dioxide-carboxyl multi-walled carbon nanotube-cement fly ash composite foam material comprises the following steps: Step 1: Preparation of nano-silica-carboxyl multi-walled carbon nanotubes S11, taking carboxyl multi-walled carbon nanotubes for later use; S12, adding 50 ml of tap water into a beaker, adding 0.04 wt % of the carboxyl multi-walled carbon nanotubes prepared in step S11, and stirring evenly to obtain a carboxyl multi-walled carbon nanotube mixed solution; S13, placing the obtained carboxyl multi-walled carbon nanotube mixed solution into an SK 250LH ultrasonic cleaning machine, and adding 3 wt % of nano-silicon dioxide into the mixed solution, and performing ultrasonic dispersion for 20 min to obtain a nano-silicon dioxide-carboxyl multi-walled carbon nanotube dispersion; Step 2: Preparation of nano-silicon dioxide-carboxyl multi-walled carbon nanotube-cement fly ash composite foaming material S21, mix P.O42.5 ordinary Portland cement and secondary fly ash in a mass percentage of 3:7, pour into a mixing equipment, and stir for 5 minutes; S22, adding 3.5 wt% of naphthalene-based water reducer and 40 wt% of tap water in sequence, and stirring evenly for 3 min to form a cement-fly ash slurry; S23, introducing the nano-silica-carboxyl multi-walled carbon nanotube dispersion prepared in step S13 into the cement-fly ash slurry prepared in step S22, and stirring for 2 min; S24, add 3 wt% H2O2 and 3 wt% FeCl3 in sequence, stir for 30 s, and obtain nano-silica-carboxyl multi-walled carbon nanotube-cement fly ash composite foaming material.

[0026] Furthermore, in step S12, the specific method for stirring uniformly is: stirring with a magnetic stirrer for 2 minutes.

[0027] Furthermore, in step S13, the ultrasonic power of the ultrasonic cleaning machine is 300 W, the ultrasonic frequency is 53 kHz, water is used as the dispersion medium for ultrasonic dispersion, and the ultrasonic temperature is 40°C.

[0028] Furthermore, in step S21, the rotation speed of the stirring process is 60 rad / min.

[0029] Furthermore, in step S22, the water temperature is 40°C.

[0030] Furthermore, in step S23, stirring is performed at a speed of 60 rad / min for 2 min, and the water temperature is 30°C.

[0031] Furthermore, in the step S24, stirring is performed at a speed of 80 rad / min for 30 s.

[0032] Example 3 A method for preparing a nano-silicon dioxide-carboxyl multi-walled carbon nanotube-cement fly ash composite foam material comprises the following steps: Step 1: Preparation of nano-silica-carboxyl multi-walled carbon nanotubes S11, taking carboxyl multi-walled carbon nanotubes for later use; S12, adding 50 ml of tap water into a beaker, adding 0.04 wt % of the carboxyl multi-walled carbon nanotubes prepared in step S11, and stirring evenly to obtain a carboxyl multi-walled carbon nanotube mixed solution; S13, placing the obtained carboxyl multi-walled carbon nanotube mixed solution into an SK 250LH ultrasonic cleaning machine, and adding 2 wt% of nano-silicon dioxide into the mixed solution, and performing ultrasonic dispersion for 20 min to obtain a nano-silicon dioxide-carboxyl multi-walled carbon nanotube dispersion; Step 2: Preparation of nano-silicon dioxide-carboxyl multi-walled carbon nanotube-cement fly ash composite foaming material S21, mix P.O42.5 ordinary Portland cement and secondary fly ash in a mass percentage of 3:7, pour into a mixing equipment, and stir for 5 minutes; S22, adding 3.3 wt% of naphthalene-based water reducer and 38 wt% of tap water in sequence, and stirring evenly for 3 min to form a cement-fly ash slurry; S23, introducing the nano-silica-carboxyl multi-walled carbon nanotube dispersion prepared in step S13 into the cement-fly ash slurry prepared in step S22, and stirring for 2 min; S24, add 2.8 wt% H2O2 and 2.5 wt% FeCl3 in sequence, stir for 30 s, and obtain nano-silica-carboxyl multi-walled carbon nanotube-cement fly ash composite foaming material.

[0033] Furthermore, in step S12, the specific method for stirring uniformly is: stirring with a magnetic stirrer for 2 minutes.

[0034] Furthermore, in step S13, the ultrasonic power of the ultrasonic cleaning machine is 300 W, the ultrasonic frequency is 53 kHz, water is used as the dispersion medium for ultrasonic dispersion, and the ultrasonic temperature is 35°C.

[0035] Furthermore, in step S21, the rotation speed of the stirring process is 60 rad / min.

[0036] Furthermore, in step S22, the water temperature is 35°C.

[0037] Furthermore, in step S23, stirring is performed at a speed of 60 rad / min for 2 min, and the water temperature is 35°C.

[0038] Furthermore, in the step S24, stirring is performed at a speed of 80 rad / min for 30 s.

[0039] Experimental Section

[0040] Experiment 1 The ordinary multi-walled carbon nanotube dispersion, the carboxyl multi-walled carbon nanotube dispersion, and the nano-silica-carboxyl multi-walled carbon nanotube dispersion prepared in Example 3 of the present invention were scanned using a spectrophotometer, and the absorbance values ​​of the three dispersions at different times were recorded respectively, as shown in FIG. Figure 1 As shown, Figure 1 The present invention provides a comparison of the absorbance variation over time of a common multi-walled carbon nanotube dispersion, a carboxyl multi-walled carbon nanotube dispersion, and a nano-silica-carboxyl multi-walled carbon nanotube dispersion. As can be seen from the figure, the dispersibility and stability of the nano-silica-carboxyl multi-walled carbon nanotube dispersion prepared by the present invention are much higher than those of a common multi-walled carbon nanotube dispersion and a carboxyl multi-walled carbon nanotube dispersion. The dispersion with excellent stability and dispersibility provides a good experimental basis for further preparing a carboxyl multi-walled carbon nanotube-cement-fly ash foaming material with excellent performance.

[0041] The results of electron microscopy scanning of nano-silica and nano-silica-carboxyl multi-walled carbon nanotubes are as follows: Figure 2 , Figure 3 As shown, Figure 2 This is the TEM image of nano-silicon dioxide. Figure 3 TEM image of nano-silica-carboxyl multi-walled carbon nanotubes. Figure 2 It can be seen that nano-silicon dioxide is in agglomerated form due to surface effects and interactions between particles; Figure 3 It can be seen that in the nano-silica-carboxyl multi-walled carbon nanotubes, the nano-silica is tightly wrapped on the surface of the carboxyl multi-walled carbon nanotubes. There is a strong van der Waals force between the carbon nanotubes. When the nano-silica is attached to the surface of the carbon nanotubes, the van der Waals force will be destroyed, thereby improving the dispersibility of the carbon nanotubes. Therefore, the dispersibility and stability of the nano-silica-carboxyl multi-walled carbon nanotube dispersion are much higher than those of the ordinary multi-walled carbon nanotube dispersion and the carboxyl multi-walled carbon nanotube dispersion. This is consistent with Figure 1 The results are the same.

[0042] Experiment 2 Ordinary multi-walled carbon nanotubes, carboxyl multi-walled carbon nanotubes, and nano-silica-carboxyl multi-walled carbon nanotubes (the carboxyl multi-walled carbon nanotube contents were 0.01 wt%, 0.02 wt%, 0.03 wt%, 0.04 wt%, and 0.05 wt%, respectively) were made into two groups of standard test blocks, 100×100×100 mm and 100×100×400 mm, respectively, and placed in a standard curing room for 28 days. The compressive strength (100×100×100 mm test block) and tensile strength (100×100×400 mm test block) were measured respectively. The results are as follows Figure 4 , Figure 5 As shown, Figure 4 The compressive strength test results are Figure 5 The tensile strength test results.

[0043] like Figure 4 As shown, no matter which group of experiments, the compressive strength of nano-silica-carboxyl multi-walled carbon nanotubes is stronger than that of ordinary multi-walled carbon nanotubes and carboxyl multi-walled carbon nanotubes; compared with other groups, when the content of carboxyl multi-walled carbon nanotubes is 0.04wt%, the compressive strength of nano-silica-carboxyl multi-walled carbon nanotubes is the highest, which is 0.65MPa, which is 62.5% higher than that of ordinary multi-walled carbon nanotubes (compressive strength is 0.4MPa).

[0044] like Figure 5 As shown, no matter which group of experiments, the tensile strength of nano-silica-carboxyl multi-walled carbon nanotubes is stronger than that of ordinary multi-walled carbon nanotubes and carboxyl multi-walled carbon nanotubes; relative to other groups, when the content of carboxyl multi-walled carbon nanotubes is 0.04wt%, the tensile strength of nano-silica-carboxyl multi-walled carbon nanotubes is the highest, which is 0.24MPa, which is 84.6% higher than that of ordinary multi-walled carbon nanotubes (tensile strength is 0.13MPa).

[0045] Experiment 3 The nano-silica-carboxyl multi-walled carbon nanotube-cement fly ash composite foam material test and cement-fly ash foam material of the present invention were prepared into standard test blocks of 100×50×20 mm, respectively, and placed in a standard curing room for curing for 28 days. According to the provisions of the "Test Method for Non-combustibility of Building Materials" (GB / T 5464-2010), a high vacuum pit furnace (Shanghai Institute of Optics and Precision Mechanics) was used to test the combustion levels of the two test blocks, respectively. The results are shown in Table 1.

[0046] Table 1 Combustion level test results

[0047] As can be seen from Table 1, the combustion grade of the nano-silica-carboxyl multi-walled carbon nanotube-cement fly ash composite foam material test block is the same as that of the cement-fly ash foam material test block, both of which are A1 level. Although the nano-silica-carboxyl multi-walled carbon nanotube-cement fly ash composite foam material prepared by the present invention adds materials such as nano-silica and carboxyl multi-walled carbon nanotubes, its combustion grade is not affected.

[0048] Experiment 4 Take the standard test block of Experiment 3, and according to the provisions of the national standard GB / T 10294-2008, use the QTM-700 thermal conductivity meter (produced by Kyoto Electronics, Japan) to test the thermal conductivity of the test block. The power supply used by the thermal conductivity meter is DC 24V, 5A, the operating frequency is 50 / 60Hz, the ambient temperature is 30℃, and the humidity is lower than 85%RH during the test. The measurement is carried out using the hot wire method, 12-06753-01 box probe sensor, the measurement range is 0.03-12 W / (m·K), the measurement time is 60s, and the chromium-aluminum thermocouple. The test results are shown in Table 2 below.

[0049] Table 2 Thermal conductivity test results

[0050] It can be seen from Table 2 that the thermal conductivity of the nano-silica-carboxyl multi-walled carbon nanotube-cement fly ash composite foam material test block is not significantly reduced compared with the cement-fly ash foam material test block. Although the nano-silica-carboxyl multi-walled carbon nanotube-cement fly ash composite foam material prepared by the present invention is added with materials such as nano-silica and carboxyl multi-walled carbon nanotubes, its heat insulation effect is not affected.

[0051] Experiment 5 The nano-silicon dioxide-carboxyl multi-walled carbon nanotube-cement fly ash composite foamed material prepared by the present invention and the conventional carboxyl multi-walled carbon nanotube-cement-fly ash foamed material were subjected to electron microscope scanning. Figure 6 , 7 As shown, Figure 6This is a SEM image of the nano-silicon dioxide-carboxyl multi-walled carbon nanotube-cement fly ash composite foam material prepared by the present invention. Figure 7 It is a SEM image of carboxyl multi-walled carbon nanotube-cement-fly ash foaming. As can be seen from the figure, there are a large number of cracks in the traditional carboxyl multi-walled carbon nanotube-cement-fly ash foaming. Compared with the traditional carboxyl multi-walled carbon nanotube-cement-fly ash foaming, the nano-silicon dioxide-carboxyl multi-walled carbon nanotube-cement fly ash composite foaming material prepared by the present invention has almost no millimeter-level microcracks, and millimeter-level cracks are the main reason for the cracking of the specimen, and the nano-silicon dioxide-carboxyl multi-walled carbon nanotube-cement fly ash composite foaming material prepared by the present invention is mainly based on micron-level and nanometer-level cracks, and its crack resistance is significantly improved. Moreover, the nano-silicon dioxide-carboxyl multi-walled carbon nanotube-cement fly ash composite foaming material prepared by the present invention is mostly closed pores, and closed pores are an important factor in determining strength; while the traditional cement-fly ash foaming material is mostly composed of closed pores and semi-closed pores, or there are a large number of holes on the pore walls of the closed pores, which will reduce the strength of the foaming material.

Claims

1. A method for preparing a nano-silicon dioxide-carboxyl multi-walled carbon nanotube-cement fly ash composite foam material, characterized in that: The steps include: Step 1: Preparation of nano-silica-carboxyl multi-walled carbon nanotubes: S11, taking carboxyl multi-walled carbon nanotubes for later use; S12, taking 50 ml of tap water, adding 0.04 wt% of the carboxyl multi-walled carbon nanotubes prepared in step S11, and stirring evenly to obtain a carboxyl multi-walled carbon nanotube mixed solution; S13, adding 1-3 wt% of nano-silicon dioxide to the carboxyl multi-walled carbon nanotube mixed solution obtained in step S12, and performing ultrasonic dispersion for 20 min to obtain a nano-silicon dioxide-carboxyl multi-walled carbon nanotube dispersion; Step 2: Preparation of nano-silicon dioxide-carboxyl multi-walled carbon nanotube-cement fly ash composite foam material: S21, mix P.O42.5 ordinary Portland cement and secondary fly ash in a mass percentage of 3:7, pour into a mixing device, and stir for 5 minutes; S22, adding 3-3.5 wt% of naphthalene-based water reducer and 35-40 wt% of tap water in sequence, and stirring evenly for 3 min to form a cement-fly ash slurry; S23, introducing the nano-silica-carboxyl multi-walled carbon nanotube dispersion prepared in step S13 into the cement-fly ash slurry prepared in step S22, and stirring for 2 min; S24, adding 2.5-3 wt% H2O2 and 2-3 wt% FeCl3 in sequence, stirring for 30 s, to obtain a nano-silica-carboxyl multi-walled carbon nanotube-cement fly ash composite foaming material.

2. The method for preparing a nano-silicon dioxide-carboxyl multi-walled carbon nanotube-cement fly ash composite foam material according to claim 1, characterized in that: In the step S12, the specific method for stirring uniformly is: stirring with a magnetic stirrer for 2 minutes.

3. The method for preparing a nano-silicon dioxide-carboxyl multi-walled carbon nanotube-cement fly ash composite foam material according to claim 1, characterized in that: In step S13, the ultrasonic power is 300 W, the ultrasonic frequency is 53 kHz, water is used as the dispersion medium for ultrasonic dispersion, and the ultrasonic temperature is 30-40°C.

4. The method for preparing a nano-silicon dioxide-carboxyl multi-walled carbon nanotube-cement fly ash composite foam material according to claim 1, characterized in that: In the step S21, the rotation speed of the stirring process is 60 rad / min.

5. The method for preparing a nano-silicon dioxide-carboxyl multi-walled carbon nanotube-cement fly ash composite foam material according to claim 1, characterized in that: In step S22, the temperature of the tap water is 30-40°C.

6. The method for preparing a nano-silicon dioxide-carboxyl multi-walled carbon nanotube-cement fly ash composite foam material according to claim 1, characterized in that: In the step S23, stirring is performed at a speed of 60 rad / min for 2 min, and the water temperature is 30-40°C.

7. The method for preparing a nano-silicon dioxide-carboxyl multi-walled carbon nanotube-cement fly ash composite foam material according to claim 1, characterized in that: In the step S24, stirring is performed at a rotation speed of 80 rad / min for 30 s.

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