A method for preparing a heat-insulating nano-carbon composite material

Abstract

The present invention relates to the technical field of thermal insulation composite materials, and in particular to a method for preparing a thermal insulation nano-carbon composite material, comprising the following steps: (1) using a high-speed mixer to uniformly mix a nano-carbon material and a starch-containing expandable substance to obtain a mixed material; (2) adding water to the mixed material for infiltration; (3) using an expander to expand the infiltrated mixed material to obtain an expanded material; (4) transferring the expanded material to a post-processing device for high-temperature carbonization in an oxygen-free atmosphere; (5) cooling and collecting the carbonized material to obtain a thermal insulation nano-carbon composite material. The technical solution is simple to operate, easy to realize automated continuous preparation, and has high processing efficiency. By adjusting parameters such as moisture content and expansion temperature, controllable preparation of thermal insulation composite materials with different porosities, different shapes and appearances, and different thermal conductivity can be achieved.

Description

Technical Field

[0001] The invention relates to the technical field of thermal insulation composite materials, and in particular to a method for preparing a thermal insulation nano-carbon composite material. Background Art

[0002] As a one-dimensional nanomaterial, carbon nanotubes have excellent physical and mechanical properties. They are mainly coaxial circular tubes composed of several to dozens of layers of carbon atoms arranged in a hexagonal pattern. They have a very large aspect ratio, with a diameter usually between 1-100nm and a length between several microns and hundreds of microns. It is precisely because of their large aspect ratio that carbon nanotubes have excellent mechanical, electrical, and electrical and thermal conductivity properties. Due to their excellent properties, carbon nanotubes have broad potential application prospects in many fields such as semiconductor chips, catalyst carriers, rubber and plastic composites, electrochemical materials, and photoelectric sensors.

[0003] In 2013, the research group of Professor Gao Chao from the Department of Polymer Science and Engineering at Zhejiang University freeze-dried aqueous solutions containing two nanocarbon materials, graphene and carbon nanotubes, at low temperatures to remove moisture and retain the skeleton, and developed an ultra-light material. This solid material, called "full carbon aerogel", has a density of only 0.16 mg per cubic centimeter, which is one-sixth the density of air. It is also the lightest material in the world to date, with the characteristics of large specific surface area, low density, high strength and good thermal insulation performance. At present, full carbon aerogel still needs to be used in combination with a substrate. The full carbon aerogel can fully demonstrate its excellent performance advantages on the basis of good dispersion in the substrate. However, the traditional preparation process of aerogel-type thermal insulation materials prepared by nanocarbon materials is complicated, with low processing efficiency, high cost, and it is not easy to control the molding, and the resulting product has low strength. Summary of the invention

[0004] In view of the technical problems of complex preparation process, low processing efficiency and difficult to control molding of thermal insulation materials prepared by using nano-carbon materials, the present invention provides a method for preparing thermal insulation nano-carbon composite materials, and the specific technical scheme is as follows:

[0005] (1) using a high-speed mixer to evenly mix the nano-carbon material and the starch-containing expandable material to obtain a mixed material; (2) adding water to the mixed material to soak it; (3) using an expander to expand the soaked mixed material to obtain an expanded material; (4) transferring the expanded material to a post-processing device to perform high-temperature carbonization in an oxygen-free atmosphere; (5) cooling and collecting the carbonized material to obtain an insulating nano-carbon composite material.

[0006] The nano-carbon material is mixed with the expandable material containing starch, and then the starch gelatinization is completed under the combined effects of water, heat, mechanical shear, friction, kneading and pressure difference. When starch is mixed with steam and water, the starch particles begin to absorb water and swell. When the starch particles pass through the expansion chamber, the rapidly rising temperature and the kneading action of the spiral blades accelerate the water absorption of the net-shaped starch particles, and the starch crystal structure begins to disintegrate, the hydrogen bonds break, and it becomes a viscous melt. Then, due to the sudden drop in pressure at the outlet of the expander, the material loses a large amount of water instantly and expands into a preset shape.

[0007] Furthermore, the nano-carbon material includes one or more of vertical array carbon nanotubes, horizontal array carbon nanotubes, single-walled carbon nanotubes, clustered carbon nanotubes, and graphene, preferably vertical array carbon nanotubes.

[0008] Furthermore, the expandable material is one or more of corn particles, wheat particles, highland barley particles, buckwheat particles, and rice particles.

[0009] Furthermore, the mass ratio of the nano-carbon material to the expandable substance is 1:1-50.

[0010] Furthermore, the mass ratio of the mixture of the nano-carbon material and the expandable substance to water is 1:0.1-15, and the impregnation time is 3-24 hours.

[0011] Furthermore, the outlet of the puffing chamber of the puffing machine is connected to a discharging die, the gap of the discharging die is 0.1-5 mm, and the shape is one of cylindrical, annular, spring, and long strip.

[0012] Furthermore, the temperature in the puffing chamber of the puffing machine is 70-200°C, preferably 80-170°C.

[0013] Furthermore, the post-processing device is one of a microwave oven, a roller furnace, a mesh belt furnace, and a high-temperature oven; and the oxygen-free atmosphere is one of nitrogen, argon, or vacuum.

[0014] Furthermore, the temperature of the carbonization treatment is 150-600° C., preferably 160-300° C.; and the treatment time is 30-240 min.

[0015] Furthermore, the thermal conductivity of the heat insulating nano-carbon composite material is 0.02 to 0.07 W / (m·K), preferably 0.02 to 0.04 W / (m·K).

[0016] The beneficial effects of the present invention are:

[0017] The preparation method of the heat-insulating nano-carbon composite material provided by the present invention is to prepare an aerogel-type heat-insulating material by pre-mixing the nano-carbon material with the expandable substance, then quickly dispersing and expanding and shaping with controllable strength by means of an expander, and then combining the post-treatment process of high-temperature carbonization. The technical solution is simple to operate, easy to realize automatic continuous preparation, and has high processing efficiency. The controllable preparation of heat-insulating composite materials with different porosities, different shapes and appearances, and different thermal conductivity coefficients can be achieved by adjusting parameters such as moisture content and expansion temperature. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, for ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0019] Figure 1 This is a scanning electron microscope (SEM) image of the thermal insulation nano-carbon composite material prepared in Example 1 of the present application.

[0020] Figure 2 This is a scanning electron microscope (SEM) image of the thermal insulation nano-carbon composite material prepared in Example 2 of the present application. DETAILED DESCRIPTION

[0021] In order to enable those skilled in the art to better understand the technical solutions in the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present invention.

[0022] The test methods and standards for each test in the following examples are as follows:

[0023] 1. Specific surface area test: using specific surface area and pore size analyzer, test standard GB / T 10722-2003 "Determination of total surface area and external surface area of ​​carbon black - nitrogen adsorption method";

[0024] 2. Tap density test: using density tester, test standard GB / T 14853.1-2002 "Determination of pouring density of granulated carbon black";

[0025] 3. Thermal conductivity test: Use solid thermal conductivity meter, test standard GB / T 10294-2008 "Determination of steady-state thermal resistance and related properties of insulation materials - Guarded hot plate method".

[0026] Example 1

[0027] (1) Cobalt-based vertical array carbon nanotube powder and corn particles are weighed in a mass ratio of 1:10 and added into a high-speed mixer, and a high-speed motor is turned on to mix them evenly to obtain a mixed material.

[0028] (2) Add water to the mixture in a mass ratio of 1:2 and soak for 10 hours.

[0029] (3) Install a cylindrical discharging die with a gap of 2 mm at the outlet of the puffing chamber of the puffing machine, and start the puffing machine.

[0030] (4) Add the impregnated mixed material into the extruder through the hopper, control the temperature in the extrusion chamber to 150-160° C., and obtain a cylindrical extruded material.

[0031] (5) The expanded material is transferred into a roller furnace, and after nitrogen replacement, the temperature is controlled at 180-200°C and maintained for 90 minutes for carbonization treatment.

[0032] (6) Cooling and collecting the carbonized material to obtain a heat-insulating nano-carbon composite material.

[0033] After testing, the specific surface area of ​​the above thermal insulation nano-carbon composite material is 959m 2 / g, tap density is 0.033g / cm 3 The thermal conductivity is 0.036W / (m·K). The scanning electron microscope (SEM) image of the thermal insulation nano-carbon composite material is as follows: Figure 1 As shown, it can be seen that the carbon nanotubes are evenly dispersed in the matrix with less agglomeration.

[0034] Example 2

[0035] (1) Weighing iron-based vertical array carbon nanotube powder and corn starch in a mass ratio of 1:5, adding them into a high-speed mixer, turning on a high-speed motor to mix them evenly, and obtaining a mixed material.

[0036] (2) Add water to the mixture in a mass ratio of 1:2 and soak for 8 hours.

[0037] (3) Install a cylindrical discharging die with a gap of 1.5 mm at the outlet of the puffing chamber of the puffing machine, and start the puffing machine.

[0038] (4) Add the impregnated mixed material into the extruder through the hopper, control the temperature in the extrusion chamber to 160-165° C., and obtain a cylindrical extruded material.

[0039] (5) The expanded material is transferred into a microwave oven, and after nitrogen replacement, the temperature is controlled at 200-210° C. and maintained for 60 minutes for carbonization treatment.

[0040] (6) Cooling and collecting the carbonized material to obtain a heat-insulating nano-carbon composite material.

[0041] After testing, the specific surface area of ​​the above thermal insulation nano-carbon composite material is 1187m 2 / g, tap density is 0.025g / cm 3 The thermal conductivity is 0.026W / (m·K). The scanning electron microscope (SEM) image of the thermal insulation nano-carbon composite material is as follows: Figure 2 As shown, it can be seen that the carbon nanotubes are evenly dispersed in the matrix with less agglomeration.

[0042] Example 3

[0043] (1) Cobalt-based vertical array carbon nanotubes, graphene and buckwheat starch are weighed in a mass ratio of 0.8:0.2:8, added into a high-speed mixer, and the high-speed motor is turned on to mix uniformly to obtain a mixed material.

[0044] (2) Add water to the mixture in a mass ratio of 1:6 and soak for 12 hours.

[0045] (3) Install a strip-shaped discharging die with a gap of 1.3 mm at the outlet of the puffing chamber of the puffing machine, and start the puffing machine.

[0046] (4) Add the impregnated mixed material into the extruder through the hopper, control the temperature in the extrusion chamber to 140-150° C., and obtain long strips of extruded material.

[0047] (5) The expanded material is transferred into a high-temperature oven, and after argon gas replacement, the temperature is controlled at 200-210°C and maintained for 100 minutes for carbonization treatment.

[0048] (6) Cooling and collecting the carbonized material to obtain a heat-insulating nano-carbon composite material.

[0049] After testing, the specific surface area of ​​the above thermal insulation nano-carbon composite material is 1271m 2 / g, tap density is 0.021g / cm 3 , the thermal conductivity is 0.022W / (m·K).

[0050] Although the present invention has been described in detail by referring to the accompanying drawings and in combination with the preferred embodiments, the present invention is not limited thereto. Without departing from the spirit and essence of the present invention, a person skilled in the art may make various equivalent modifications or substitutions to the embodiments of the present invention, and these modifications or substitutions shall be within the scope of the present invention. Any person skilled in the art who is familiar with the present technical field can easily think of changes or substitutions within the technical scope disclosed by the present invention, and they shall be within the scope of protection of the present invention.

Claims

1. A method for preparing a heat-insulating nano-carbon composite material, characterized in that: The following steps are involved: (1) using a high-speed mixer to evenly mix the nano-carbon material and the starch-containing expandable material to obtain a mixed material; (2) adding water to the mixed material to infiltrate it; (3) using an expander to expand the infiltrated mixed material to obtain an expanded material; (4) transferring the expanded material to a post-processing device for high-temperature carbonization in an oxygen-free atmosphere; (5) cooling and collecting the carbonized material to obtain a heat-insulating nano-carbon composite material; the nano-carbon material is a cobalt-based vertical array carbon nanotube or an iron-based vertical array carbon nanotube.

2. The preparation method according to claim 1, characterized in that The expandable material is one or more of corn particles, wheat particles, highland barley particles, buckwheat particles and rice particles.

3. The preparation method according to claim 1, characterized in that: The mass ratio of the nano-carbon material to the expandable substance is 1:1~50.

4. The preparation method according to claim 1, characterized in that: The mass ratio of the mixture of the nano-carbon material and the expandable substance to water is 1:0.1-15, and the impregnation time is 3-24 hours.

5. The preparation method according to claim 1, characterized in that: The outlet of the puffing chamber of the puffing machine is connected with a discharging die, the gap of the discharging die is 0.1-5 mm, and the shape is one of cylindrical, annular, spring, and long strip.

6. The preparation method according to claim 1, characterized in that: The temperature inside the puffing chamber of the puffing machine is 70~200℃.

7. The preparation method according to claim 1, characterized in that: The post-processing device is one of a microwave oven, a roller furnace, a mesh belt furnace, and a high-temperature oven; and the oxygen-free atmosphere is one of nitrogen, argon, or vacuum.

8. The preparation method according to claim 1, characterized in that: The temperature of carbonization treatment is 150~600℃, and the treatment time is 30~240min.

9. The preparation method according to claim 1, characterized in that: The thermal conductivity of the insulating nanocarbon composite material is 0.02~0.07W / (m·K).

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