A method of obtaining a stable suspension of graphene oxide nanoparticles and carbon nanotubes

Abstract

A method for obtaining a stable suspension of graphene oxide nanoparticles and carbon nanotubes. The method comprises: preparing graphene nanoparticles of size 70-150 nm, graphene oxide nanoparticles, in the process 0.7 g of potassium dichromate is added to 2 g of 96-98% sulfuric acid, 1 g of graphene nanoparticles is introduced, washed with water to a pH of 5.5; the graphene oxide nanoparticle suspension is dispersed in an ultrasonic disperser for 1 minute, 0.5 ml of ethanol is added to the carbon nanotubes, the resulting mixture is introduced into the graphene oxide nanoparticle suspension and dispersed for 5 minutes. In the method, the suspension contains graphene oxide nanoparticles at a concentration of 0.02 g / L or 0.03 g / L; the mixture containing 0.75 g of carbon nanotubes is introduced into the graphene oxide nanoparticle suspension at a concentration of 0.02 g / L, and the mixture containing 0.5-1 g of carbon nanotubes is introduced into the graphene oxide nanoparticle suspension at a concentration of 0.03 g / L.

Description

Technical Field

[0001] This invention belongs to the field of materials science. Carbon nanotubes and graphene nanoparticles are promising functional elements for manufacturing composite materials, used for purposes such as shielding electromagnetic radiation, preventing radio interference, developing antistatic and anti-friction coatings, and manufacturing temperature, pressure, and humidity sensors. Carbon nanotube-containing polymer composites only possess stable properties when the components are uniformly distributed within the composite material. Background Technology

[0002] In a dry state, carbon nanotubes exist as aggregates, which must be deagglomerated before being introduced into composite materials. In industrial and laboratory conditions, ball mills, planetary vibratory mills, jet mills, and pulverizers are commonly used to disperse carbon nanotubes, and chemical modification of carbon nanotubes is also prevalent. The brittleness of carbon nanotubes under mechanical action makes the deagglomeration process challenging. Ultrasonic dispersion in a surfactant solution is an energy-efficient and convenient method for treating suspensions, allowing for varying degrees of dispersion depending on the power and time, preventing the agglomeration of dispersed particles. However, the surfactant used as the medium is typically a polymer with low electrical conductivity. The dispersed carbon nanotube and graphene nanoparticle suspension remains stable in the surfactant solution for extended periods without separating into individual fractions, but impurities negatively impact the further incorporation of carbon nanotubes into the composite material.

[0003] The prototype chosen was patent RU№2662484, published on July 26, 2021, publication number №21, which describes a method for preparing aerogels based on graphene oxide and carbon nanotube composite materials. This method includes steps such as chemically synthesizing graphene, obtaining graphene oxide, mixing graphene and nanotubes in a colloidal solution, obtaining a hydrogel, drying, and obtaining an aerogel. A common feature of both the prototype and this invention is the use of graphene oxide and carbon nanotubes to oxidize graphene, obtaining an intermediate product in suspension. The prototype's disadvantages include the extensive use of strong inorganic acids and other precursors, as well as the inherent complexity of the technology. Summary of the Invention

[0004] The objective of this invention is to develop a method for producing a highly conductive carbon nanotube suspension that can remain stable for an extended period of time without the presence of a surfactant.

[0005] The solution to this problem is to use graphene oxide nanoparticles to obtain stable carbon nanotube suspensions.

[0006] Graphene nanoparticles are prepared by an electrochemical method: a graphite tape (anode) is placed in a potassium hydroxide electrolyte solution (pH9) tank, the electric field strength of the electrolytic cell is 20V / cm, the membrane is divided into anode and cathode spaces, the anode space is separated by a porous filter plate, allowing the graphene nanoparticle suspension to pass through and intercepting the coarsely dispersed graphite suspension.

[0007] The flow rate of the potassium hydroxide electrolyte solution was controlled by adjusting the optical density of the resulting graphene suspension. The foil made of thermally expanded graphite powder had a bulk density of 1.5-2.0 g / dm³. After the potassium hydroxide aqueous solution was poured into the container and the reactor was filled to a predetermined level, a voltage with an electric field strength of 20 V / cm and a direct current density of 12 mA / cm² were supplied using a power supply unit.

[0008] The resulting graphene nanoparticle suspension most likely contains graphene nanoparticles with a size of 70-150 nm, which can be determined by laser correlation spectroscopy. Graphene nanoparticles can also be obtained through another method, provided that the specified size can be achieved.

[0009] The oxidation of graphene nanoparticles was carried out chemically. 0.7 g of potassium dichromate was added to 2 g of sulfuric acid (96-98%), and 1 g of graphene nanoparticles were introduced. The exothermic reaction proceeded vigorously, and the reaction rate was then slowed down by diluting the solution with water to 15% N₂SO₄. The suspension of oxidized graphene nanoparticles was washed several times with water to achieve an acidity level of 5.5 pH.

[0010] The method for preparing a stable suspension is as follows:

[0011] The graphene nanoparticle suspension was dispersed in an ultrasonic disperser (UZIN-A) for 1 minute. 0.5 ml of ethanol was added to the carbon nanotubes, and the resulting mixture was introduced into the graphene nanoparticle suspension and dispersed for 5 minutes.

[0012] Visually assess the stability of the suspension every 60 minutes for the first 5 hours after dispersion, then twice daily thereafter. A suspension that remains stable for more than three days is considered successful.

[0013] The following equipment and materials are required to implement this technology:

[0014] – Foil material, made of thermally expanded graphite TU U 26.8-34743542-002:2011;

[0015] –Analytical grade or pure grade potassium hydroxide GOST 24363-80;

[0016] – A 0.5 mm thick membrane made of polypropylene fabric, GOST R ISO 9001:2015;

[0017] –Carbon nanotubes TU U 03291669-009:2000

[0018] –GOST Sulfuric Acid 2184-2013

[0019] Potassium dichromate GOST 2652-78

[0020] – Distilled water GOST 6709-72

[0021] – Ethanol GOST 5962-2013 Detailed Implementation

[0022] Example 1: A 100ml suspension of graphene oxide nanoparticles containing 0.001g of graphene oxide nanoparticles was dispersed in an ultrasonic disperser (UZIN-A) for 1 minute. 0.5ml of ethanol was added to 0.01g of carbon nanotubes, and the resulting mixture was added to the graphene oxide nanoparticle suspension and dispersed for 5 minutes. The inventive task remains unsolved.

[0023] Example 2: Similar to Example 1, the content of graphene oxide nanoparticles was changed to 0.002 grams and the mass of carbon nanotubes was changed to 0.05 grams, but the invention task was not solved.

[0024] Example 3: Similar to Example 1, the content of graphene oxide nanoparticles is changed to 0.002 grams, and the mass of carbon nanotubes is changed to 0.75 grams. Invention Task

[0025] Example 4: Similar to Example 1, the content of graphene oxide nanoparticles was changed to 0.003 grams and the mass of carbon nanotubes was changed to 0.5 grams, thus solving the invention problem.

[0026] Example 5: Similar to Example 1, the content of graphene oxide nanoparticles was changed to 0.003 grams and the mass of carbon nanotubes was changed to 1 gram, thus solving the invention problem.

[0027] Example 6 (similar to Example 1). The stability of the suspension is not described.

[0028] The content and stability of the obtained suspension are shown in Table 1.

[0029] Table 1

[0030] Serial Number Carbon nanotube content, g Graphene oxide nanoparticle content, g Suspension stability, hours Example 1 0.01 0.001 10 Example 2 0.05 0.002 60 Example 3 0.75 0.002 80 Example 4 0.5 0.003 280 Example 5 0.1 0.003 600 Example 6 - - -

[0031] As can be seen from the data in the table, the method for preparing a stable carbon nanotube suspension described in this invention is effective for 600 hours in the absence of surfactants.

[0032] Therefore, the above examples demonstrate that the present invention has achieved technical results.

Claims

1. A method for obtaining a stable suspension of graphene oxide nanoparticles and carbon nanotubes, characterized in that, Includes the following steps: (a) Preparation of graphene nanoparticles with a size of 70-150 nm: A graphite tape was placed as the anode in a potassium hydroxide electrolyte solution with a pH of 9 using an electrochemical method. The electric field strength of the electrolytic cell was 20 V / cm, and the current density was 12 mA / cm². 2 The anode space is separated by a porous filter partition. The optical density of the graphene suspension is controlled to adjust the flow rate of the potassium hydroxide electrolyte solution, thus obtaining a graphene nanoparticle suspension. (b) Preparation of graphene oxide nanoparticles: 0.7g of potassium dichromate was added to 2g of sulfuric acid with a weight percentage of 96-98%, and then 1g of graphene nanoparticles obtained in step (a) were introduced to carry out an exothermic reaction. The reaction rate was then slowed down by adding water to dilute to a concentration of 15% H2SO4. The nanoparticles were washed several times with water until the acidity was pH 5.5 to obtain a suspension of graphene oxide nanoparticles. (c) Dispersion step: The graphene oxide nanoparticle suspension obtained in step (b) is dispersed in an ultrasonic disperser for 1 minute, then 0.5 mL of ethanol is added to the carbon nanotubes, and the resulting mixture is added to the graphene oxide nanoparticle suspension and dispersed for another 5 minutes. The suspension contains graphene oxide nanoparticles at a concentration of 0.02 g / L or 0.03 g / L. A mixture containing 0.75 g of carbon nanotubes was introduced into a graphene oxide nanoparticle suspension with a concentration of 0.02 g / L, and a mixture containing 0.5-1 g of carbon nanotubes was introduced into a graphene oxide nanoparticle suspension with a concentration of 0.03 g / L. The mass ratio of graphene oxide nanoparticles to carbon nanotubes is 1:166.7 to 1:375.