A carbon nanotube / silica nanofiber membrane prepared by a silica-free template electrospinning method and its preparation method

Abstract

The present invention belongs to the field of nanofiber membrane technology and provides a carbon nanotube / silica nanofiber membrane produced by a silica gel template-free electrospinning method and a preparation method thereof. The preparation method comprises the following steps: ultrasonically dispersing ethyl orthosilicate, anhydrous ethanol, and carbon nanotubes to obtain a dispersion; reacting the dispersion, hydrochloric acid, and water, and sequentially electrospinning and heat-treating the reaction solution. The silica nanofiber membrane of the present invention does not use polymers and their dispersants during the preparation process, and the added carbon nanotubes have the advantage of being used in a small amount. The prepared nanofiber membrane not only retains the original excellent properties of silica nanofiber membranes but also possesses many of the properties of carbon nanotubes. The combination of the two effectively compensates for the insufficient mechanical properties of silica nanofibers. The carbon nanotube / silica nanofiber membrane of the present invention has a breaking strength that is over 150% of the breaking strength of silica nanofiber membranes.

Description

Technical Field

[0001] The present invention relates to the technical field of nanofiber membranes, and in particular to a carbon nanotube / silicon dioxide nanofiber membrane produced by a silica gel template-free electrostatic spinning method and a preparation method thereof. Background Art

[0002] Silica nanofiber membranes are among the most important inorganic materials. Due to their small diameter, numerous micropores, large specific surface area, strong surface adsorption, high surface energy, and high chemical purity, they exhibit excellent properties in terms of thermal and electrical resistance, as well as excellent stability, reinforcement, thickening, and thixotropy. Consequently, they are widely used in numerous disciplines and fields. However, due to shortcomings such as the brittleness of silica nanofiber membranes, the poor potential bonding continuity of fibers spun using polymer-based electrospinning templates, and the relatively low inter-fiber adhesion, the mechanical properties of silica nanofiber membranes are limited, hindering their application in certain fields. Researchers have explored various approaches to enhance the mechanical properties of silica nanofiber membranes and expand their applications. Currently, most approaches have been to dope silica nanofibers with organic fibers. While this approach significantly improves mechanical properties, the organic fibers often suffer from poor high-temperature resistance, negating the inherent high-temperature resistance of the silica nanofibers.

[0003] Carbon nanotubes possess exceptionally high-temperature resistance. Doping silica nanofibers with carbon nanotubes effectively preserves the high-temperature resistance of the original silica nanofibers. Carbon nanotubes possess excellent mechanical properties, with a tensile strength of 50 to 200 GPa, 100 times that of steel, yet only one-sixth the density. Their elastic modulus can reach 1 TPa, comparable to that of diamond and approximately five times that of steel. While their structure is similar to that of polymers, theirs is significantly more stable. Carbon nanotubes possess the highest specific strength of any material currently available.

[0004] Therefore, it is of great significance to prepare a carbon nanotube / silica nanofiber membrane with good mechanical strength. Summary of the Invention

[0005] The purpose of the present invention is to provide a carbon nanotube / silica nanofiber membrane prepared by a silica gel template-free electrospinning method and a preparation method thereof in order to overcome the shortcomings of the prior art. The carbon nanotubes added by this method have the advantage of small usage, which solves the defect of low mechanical strength of silica nanofibers prepared by polymer template electrospinning method.

[0006] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0007] The present invention provides a method for preparing a carbon nanotube / silica nanofiber membrane by a silica gel template-free electrospinning method, comprising the following steps:

[0008] 1) ultrasonically dispersing ethyl orthosilicate, anhydrous ethanol, and carbon nanotubes to obtain a dispersion;

[0009] 2) reacting the dispersion, hydrochloric acid, and water, and sequentially subjecting the reaction solution to electrospinning and heat treatment to obtain a silica gel template-free electrospinning carbon nanotube / silica nanofiber membrane;

[0010] In step 1), the volume-to-mass ratio of the tetraethyl orthosilicate to the carbon nanotubes is 20-40 mL: 0.005-0.15 g.

[0011] Preferably, in step 1), the volume ratio of the ethyl orthosilicate to anhydrous ethanol is 20-40:10-25.

[0012] Preferably, the carbon nanotubes are carboxylated single-walled carbon nanotubes, carboxylated double-walled carbon nanotubes or carboxylated multi-walled carbon nanotubes.

[0013] Preferably, the ultrasonic dispersion time in step 1) is 5 to 20 minutes, and the ultrasonic dispersion power is 100 to 150W.

[0014] Preferably, the mass fraction of the hydrochloric acid in step 2) is 1-38%, and the volume ratio of the hydrochloric acid in step 2) to water and the tetraethyl orthosilicate in step 1) is 0.1-0.3:3.5-8.0:20-40.

[0015] Preferably, the reaction temperature in step 2) is 70-90° C., and the reaction time is 0.5-1 h.

[0016] Preferably, the temperature of the heat treatment in step 2) is 400-750° C., and the heat treatment time is 1-4 hours.

[0017] Preferably, the temperature of the electrospinning in step 2) is -40 to 30° C., the flow rate of the reaction liquid during the electrospinning process is 3 to 5 mL / h, the distance between the nozzle and the collector is 13 to 18 cm, and the high voltage static voltage is 15 to 25 kV.

[0018] The present invention also provides a carbon nanotube / silicon dioxide nanofiber membrane prepared by the silica gel template-free electrospinning method.

[0019] The beneficial effects of the present invention include:

[0020] 1) The present invention uses ethyl orthosilicate and carbon nanotubes to prepare a silica gel template-free electrospinning carbon nanotube / silica nanofiber membrane without using a polymer as a template agent. The silica gel template-free electrospinning carbon nanotube / silica nanofiber membrane has good mechanical strength and elongation at break, which greatly improves the performance of the silica nanofiber membrane and expands its application field.

[0021] 2) The present invention adds carbon nanotubes to the silica spinning solution, and utilizes an electrospinning reciprocating platform and a roller collection device to obtain a smooth and uniform carbon nanotube / silica nanofiber membrane. When the carbon nanotube / silica nanofiber silica molecular chains have not yet been completely cross-linked into a network structure, heat treatment is used to form a bond between -SiOH and the -COOH on the surface of the carbon nanotube to increase its adhesion points, thereby enhancing the mechanical properties of the carbon nanotube / silica nanofiber membrane. The silica nanofiber membrane of the present invention has the advantage of adding carbon nanotubes in a small amount. It not only retains the original excellent properties of silica nanofibers, but also has many properties of carbon nanotubes. The combination of the two effectively compensates for the shortcomings of the insufficient mechanical properties of silica nanofibers. The breaking strength of the carbon nanotube / silica nanofiber membrane of the present invention is more than 150% of the breaking strength of the silica nanofiber membrane. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 This is a photo of the carbon nanotube / silica nanofiber membrane produced by the silica gel template-free electrospinning method of Example 1;

[0023] Figure 2 This is a physical picture of the mechanical properties test of the carbon nanotube / silica nanofiber membrane produced by the silica gel template-free electrospinning method in Example 1;

[0024] Figure 3 This is an example diagram of the data of the fracture strength increase of the mechanical properties test of the carbon nanotube / silica nanofiber membrane produced by the silica gel template-free electrospinning method in Example 1 under different conditions. DETAILED DESCRIPTION

[0025] The present invention provides a method for preparing a carbon nanotube / silica nanofiber membrane by a silica gel template-free electrospinning method, comprising the following steps:

[0026] 1) ultrasonically dispersing ethyl orthosilicate, anhydrous ethanol, and carbon nanotubes to obtain a dispersion;

[0027] 2) reacting the dispersion, hydrochloric acid, and water, and sequentially subjecting the reaction solution to electrospinning and heat treatment to obtain a silica gel template-free electrospinning carbon nanotube / silica nanofiber membrane;

[0028] In step 1), the volume-to-mass ratio of the tetraethyl orthosilicate to the carbon nanotubes is 20-40 mL: 0.005-0.15 g.

[0029] In the present invention, the volume ratio of the ethyl orthosilicate and anhydrous ethanol in step 1) is preferably 20-40:10-25, more preferably 25-35:12-22, and more preferably 28-32:15-18; the volume mass ratio of the ethyl orthosilicate and carbon nanotubes is preferably 25-35 mL:0.01-0.12 g, more preferably 28-32 mL:0.05-0.10 g.

[0030] In the present invention, the carbon nanotubes are preferably carboxylated multi-walled carbon nanotubes, and the purity of the carboxylated multi-walled carbon nanotubes is preferably ≥98%, more preferably ≥99%; the inner diameter of the carboxylated multi-walled carbon nanotubes is preferably 3-5 nm, more preferably 4 nm; the outer diameter of the carboxylated multi-walled carbon nanotubes is preferably 8-15 nm, more preferably 10-13 nm; the length of the carboxylated multi-walled carbon nanotubes is preferably 5-15 μm, more preferably 8-12 μm; the specific surface area of the carboxylated multi-walled carbon nanotubes is preferably ≥250 m 2 / g, more preferably ≥260m 2 / g; the density of the carboxylated multi-walled carbon nanotubes is preferably 0.09 to 0.11 g / cm 3 , more preferably 0.1 g / cm 3 The carboxyl content of the carboxylated multi-walled carbon nanotubes is preferably ≥1 mmol / g, and more preferably ≥1.2 mmol / g; the carboxylated multi-walled carbon nanotubes are preferably prepared by CVD method.

[0031] In the present invention, the ultrasonic dispersion time in step 1) is preferably 5 to 20 min, more preferably 8 to 16 min, and more preferably 10 to 14 min; the ultrasonic dispersion power is preferably 100 to 150 W, more preferably 110 to 140 W, and more preferably 120 to 130 W.

[0032] In step 1) of the present invention, preferably, ethyl orthosilicate and anhydrous ethanol are mixed and then carbon nanotubes are added for ultrasonic dispersion.

[0033] In the present invention, the mass fraction of the hydrochloric acid in step 2) is preferably 1-38%, more preferably 5-36%, and more preferably 15-25%; the volume ratio of the hydrochloric acid in step 2) to water and the ethyl orthosilicate in step 1) is preferably 0.1-0.3:3.5-8.0:20-40, more preferably 0.15-0.25:4.5-7.0:25-35, and more preferably 0.18-0.22:5.5-6.0:28-32.

[0034] In the present invention, the reaction temperature in step 2) is preferably 70-90° C., more preferably 75-85° C., and more preferably 80° C.; the reaction time is preferably 0.5-1 h, and more preferably 0.75 h.

[0035] In the present invention, the temperature of the heat treatment in step 2) is preferably 400-750°C, more preferably 450-700°C, and more preferably 500-600°C; the time of the heat treatment is preferably 1-4h, more preferably 1.5-3.5h, and more preferably 2-3h.

[0036] In the present invention, the temperature of the electrospinning in step 2) is -40 to 30°C, more preferably -20 to 20°C, and more preferably 0 to 10°C; the flow rate of the reaction liquid during the electrospinning process is preferably 3 to 5 mL / h, more preferably 3.5 to 4.5 mL / h, and more preferably 4 mL / h; the distance between the nozzle and the collector is preferably 13 to 18 cm, more preferably 14 to 17 cm, and more preferably 15 to 16 cm; the high voltage static voltage is preferably 15 to 25 kV, more preferably 17 to 22 kV, and more preferably 19 to 21 kV.

[0037] The present invention also provides a carbon nanotube / silicon dioxide nanofiber membrane prepared by the silica gel template-free electrospinning method.

[0038] In the present invention, the thickness of the carbon nanotube / silica nanofiber membrane is preferably 120 to 230 μm, more preferably 150 to 200 μm.

[0039] The technical solutions provided by the present invention are described in detail below with reference to the embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0040] Example 1

[0041] 20 mL of ethyl orthosilicate and 10.5 mL of anhydrous ethanol were mixed, and the mixed solution was mixed with 0.032 g of carboxylated multi-walled carbon nanotubes (purity of 98.5%, inner diameter of 4 nm, outer diameter of 10 nm, length of 10 μm, specific surface area of 255 m 2 / g, density is 0.1g / cm 3, carboxyl content of 1.1 mmol / g) and ultrasonically dispersed at 120 W for 10 minutes to obtain a dispersion. The dispersion was then heated in a water bath at 80°C for 0.75 hours with 0.1 mL of hydrochloric acid (10% by mass) and 3.865 mL of water. The reaction solution was then electrospun using a silica gel template-free electrospinning method (electrospinning temperature of 25°C, high voltage of 20 kV, distance between nozzle and roller collection device of 15 cm, and reaction solution flow rate of 4 mL / h) to produce a nanofiber membrane. The nanofiber membrane was then heat-treated at 600°C for 2 hours to obtain a silica gel template-free electrospinning carbon nanotube / silica nanofiber membrane.

[0042] The actual picture of the carbon nanotube / silica nanofiber membrane produced by the silica gel template-free electrospinning method in this embodiment is as follows: Figure 1 As shown, the thickness of the nanofiber membrane is 129.7 μm.

[0043] The mechanical properties test of the carbon nanotube / silica nanofiber membrane produced by the silica gel template-free electrospinning method in this embodiment is shown in the figure below. Figure 2 As shown in the figure, the performance test used the ZQ-990-5 electric tensile testing machine.

[0044] Comparative Example 1

[0045] 20 mL of ethyl orthosilicate, 10.5 mL of anhydrous ethanol, 0.1 mL of hydrochloric acid (the mass fraction of hydrochloric acid is 10%) and 3.865 mL of water were heated in a water bath at 80°C for 0.75 h, and the reaction solution was prepared into a silica nanofiber membrane by a silica gel template-free electrospinning method (the electrospinning temperature was 25°C, the high voltage static voltage was 20 kV, the distance between the nozzle and the roller collection device was 15 cm, and the flow rate of the reaction solution was 4 mL / h).

[0046] The mechanical properties of the carbon nanotube / silica nanofiber membrane prepared by the silica gel template-free electrospinning method in this embodiment were tested. The data of the fracture strength increase part (relative to the silica nanofiber membrane in comparative example 1) are shown in the figure below. Figure 3 The maximum breaking force is 6.681N and the breaking strength is 2.575N / mm. 2 , the elongation at break is 7.502%; the maximum force for breaking the silica nanofiber membrane of Comparative Example 1 is 1.991N, and the breaking strength is 0.809N / mm 2 The elongation at break was 4.521%. The breaking strength of the carbon nanotube / silica nanofiber membrane produced by the silica template-free electrospinning method was 320% of that of the silica nanofiber membrane.

[0047] Example 2

[0048] 35 mL of ethyl orthosilicate and 22 mL of anhydrous ethanol were mixed, and the mixed solution was mixed with 0.12 g of carboxylated multi-walled carbon nanotubes (purity of 98.2%, inner diameter of 3.5 nm, outer diameter of 11 nm, length of 8 μm, specific surface area of 253 m 2 / g, density is 0.1g / cm 3 , carboxyl content of 1.05 mmol / g) and ultrasonically dispersed at 130 W for 7 minutes to obtain a dispersion. The dispersion was then heated in a 75°C waterbath with 0.25 mL of hydrochloric acid (6% by mass) and 6 mL of water for 0.5 h. The reaction solution was then electrospun using a silica gel template-free electrospinning method (electrospinning temperature of 30°C, high voltage of 23 kV, distance between nozzle and roller collection device of 16 cm, and reaction solution flow rate of 3.5 mL / h) to produce a nanofiber membrane. The nanofiber membrane was then heat-treated at 500°C for 3.5 h to obtain a silica gel template-free electrospinning carbon nanotube / silica nanofiber membrane.

[0049] The thickness of the carbon nanotube / silica nanofiber membrane produced by the silica gel template-free electrospinning method in this embodiment is 152.3 μm.

[0050] Example 3

[0051] 30 mL of ethyl orthosilicate and 17 mL of anhydrous ethanol were mixed, and the mixed solution was mixed with 0.08 g of carboxylated multi-walled carbon nanotubes (purity 98.7%, inner diameter 4.5 nm, outer diameter 13 nm, length 12 μm, specific surface area 257 m 2 / g, density is 0.1g / cm 3 , carboxyl content of 1.08 mmol / g) and ultrasonically dispersed at 150 W for 16 minutes to obtain a dispersion. The dispersion was then heated in a water bath at 85°C for 1 hour with 0.15 mL of hydrochloric acid (12% by mass) and 4.5 mL of water. The reaction solution was then electrospun using a silica gel template-free electrospinning method (electrospinning temperature: -10°C, high voltage: 17 kV, distance between nozzle and roller collection device: 13 cm, flow rate of reaction solution: 3 mL / h) to produce a nanofiber membrane. The nanofiber membrane was then heat-treated at 700°C for 1.5 hours to obtain a silica gel template-free electrospinning carbon nanotube / silica nanofiber membrane.

[0052] The thickness of the carbon nanotube / silica nanofiber membrane produced by the silica gel template-free electrospinning method in this embodiment is 213.5 μm.

[0053] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as within the scope of protection of the present invention.

Claims

1. A method for preparing carbon nanotube / silica nanofiber membrane by silica gel template-free electrospinning method, characterized in that: The following steps are included: 1) Ultrasonic dispersion of ethyl orthosilicate, anhydrous ethanol, and carbon nanotubes to obtain a dispersion; 2) reacting the dispersion, hydrochloric acid, and water, and sequentially subjecting the reaction solution to electrospinning and heat treatment to obtain a silica gel template-free electrospinning carbon nanotube / silica nanofiber membrane; Step 1) The volume-to-mass ratio of the tetraethyl orthosilicate to the carbon nanotubes is 20-40 mL: 0.005-0.15 g; Step 1) The volume ratio of the tetraethyl orthosilicate to anhydrous ethanol is 20-40:10-25; The mass fraction of the hydrochloric acid in step 2) is 1-38%, and the volume ratio of the hydrochloric acid in step 2) to water and the ethyl orthosilicate in step 1) is 0.1-0.3:3.5-8.0:20-40.

2. The preparation method according to claim 1, characterized in that The carbon nanotubes are carboxylated single-walled carbon nanotubes, carboxylated double-walled carbon nanotubes or carboxylated multi-walled carbon nanotubes.

3. The preparation method according to claim 2, characterized in that The ultrasonic dispersion time in step 1) is 5-20 min, and the ultrasonic dispersion power is 100-150 W.

4. The preparation method according to claim 3, characterized in that Step 2) The reaction temperature is 70-90° C., and the reaction time is 0.5-1 h.

5. The preparation method according to claim 4, characterized in that Step 2) The heat treatment temperature is 400-750° C., and the heat treatment time is 1-4 hours.

6. The preparation method according to claim 5, characterized in that Step 2) The electrospinning temperature is -40-30°C, the flow rate of the reaction solution during the electrospinning process is 3-5 mL / h, the distance between the nozzle and the collector is 13-18 cm, and the high voltage static voltage is 15-25 kV.

7. Carbon nanotube / silica nanofiber membrane prepared by the preparation method according to any one of claims 1 to 6 using a silica gel template-free electrospinning method.

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