阅读说明：本技术 一种木质素/石墨烯基碳纤维的制备方法 (Preparation method of lignin/graphene-based carbon fiber ) 是由 文生平 林玙璠 于 2019-11-12 设计创作，主要内容包括：本发明公开了一种木质素/石墨烯基碳纤维的制备方法。该方法包括以下几个步骤：将石墨烯分散液与纯化后的木质素溶液按照一定比例混合搅拌得到纺丝液；采用聚电解质络合纺丝方法与壳聚糖溶液离子络合得到木质素/氧化石墨烯复合纤维；将复合纤维放置于管式炉中在氮气氛围下高温碳化得到木质素/石墨烯基碳纤维。本发明的有益效果如下：1、采用聚电解质络合纺丝方法制备石墨烯基复合纤维,与传统的湿法纺丝相比,没有涉及大量的有机凝固浴的使用,更加环保,纺丝液浓度低,更有利于纺丝；2、木质素的存在填充了石墨烯基碳纤维在碳化过程中产生的孔隙,赋予了碳纤维更高的力学性能和导电性能。(The invention discloses a preparation method of lignin/graphene-based carbon fibers. The method comprises the following steps: mixing and stirring the graphene dispersion liquid and the purified lignin solution according to a certain proportion to obtain a spinning solution; performing ion complexation with a chitosan solution by adopting a polyelectrolyte complexation spinning method to obtain lignin/graphene oxide composite fibers; and (3) putting the composite fiber into a tubular furnace, and carbonizing at high temperature in a nitrogen atmosphere to obtain the lignin/graphene-based carbon fiber. The invention has the following beneficial effects: 1. compared with the traditional wet spinning method, the polyelectrolyte complex spinning method is adopted to prepare the graphene-based composite fiber, and the use of a large amount of organic coagulation bath is not involved, so that the method is more environment-friendly, the concentration of the spinning solution is low, and the spinning is more facilitated; 2. the existence of the lignin fills the pores generated in the carbonization process of the graphene-based carbon fiber, and the carbon fiber is endowed with higher mechanical property and conductivity.)

1. A preparation method of lignin/graphene-based carbon fibers is characterized by comprising the following steps:

(1) mixing and stirring the graphene oxide dispersion liquid and the purified lignin solution to obtain a composite spinning solution;

(2) complexing the composite spinning solution with chitosan solution ions by adopting a polyelectrolyte complexing spinning method to obtain lignin/graphene oxide composite fibers, and drying the lignin/graphene oxide composite fibers at room temperature for several hours under the stretching action;

(3) and (3) putting the composite fiber into a tubular furnace, and carbonizing at high temperature in a nitrogen atmosphere to obtain the lignin/graphene-based carbon fiber.

2. The method for preparing lignin/graphene-based carbon fibers according to claim 1, wherein the composite spinning solution contains lignin in an amount of 0 to 40% by mass.

3. The method for preparing the lignin/graphene-based carbon fiber according to claim 1, wherein the mass percentage concentration of graphene oxide in the composite spinning solution is 1-5%.

4. The method for preparing lignin/graphene-based carbon fibers according to claim 1, wherein in the step (1), the lignin solution is purified by the following steps:

dispersing 50.0g of sodium lignosulfonate in 500ml of deionized water, and stirring until the sodium lignosulfonate is uniformly dispersed; adjusting the pH value of the suspension to 12 by using 1M NaOH solution; filtering the suspension to obtain supernatant, and removing insoluble impurities; adding 1M HCl solution into the supernatant until the pH value reaches 3; repeatedly centrifuging the supernatant at 10000rpm/min until the pH value of the filtrate reaches 5-6; the pH of the suspension obtained by centrifugation was adjusted to 12 by adding NaOH solution and then dialyzed to neutrality.

5. The method for preparing lignin/graphene-based carbon fibers according to claim 4, wherein the yield of purified lignin is 15% -25%.

6. The method for preparing lignin/graphene-based carbon fibers according to claim 1, wherein in the step (2), the chitosan solution is prepared by dissolving chitosan powder in 1% acetic acid aqueous solution, and the mass percentage concentration is 3% o to 1%.

7. The method for preparing lignin/graphene-based carbon fibers according to claim 1, wherein in the step (2), the lignin/graphene oxide composite fibers have a fiber diameter of 10-40um and a fiber length of 50-300 mm; the lignin/graphene oxide composite fiber comprises the following components in percentage by mass: 50-95% of graphene oxide, 0-40% of lignin and 5-15% of chitosan.

8. The method for preparing lignin/graphene-based carbon fibers according to claim 1, wherein in the step (2), the lignin/graphene oxide composite fibers are prepared by the following specific steps: allowing a lignin/graphene spinning solution to flow in from a main flow channel in the middle by using a spinning device, converging the lignin/graphene spinning solution with chitosan solutions of sheath flow channels at two sides at an outlet after the lignin/graphene spinning solution is stretched by a convergent flow channel, pulling out the lignin/graphene spinning solution from a complexing surface of the lignin/graphene spinning solution by using a pair of tweezers to form fibers, and forming the fibers by an ion complexing self-assembly effect; the spinning device comprises a die and a liquid adding device; the mold comprises two sheath runners, a main runner and an outlet channel; the diameter of the sheath flow channel and the outlet channel is 1.2 mm; the main runner consists of an inlet section and a convergence section, the cross section of the inlet section is larger than that of the convergence section, the diameter of the inlet section is 6mm, and the diameter of the convergence section is 1.2 mm; the liquid adding device is respectively connected with the three inlets of the die through pipelines; the adding device is a needle cylinder, and the flow rate is controlled to be 3mL/h of graphene oxide and 1mL/h of chitosan.

9. The preparation method of the lignin/graphene-based carbon fiber according to claim 1, wherein in the step (3), the carbonization step is that the fiber is placed in an ammonium chloride/ammonium sulfate solution to be soaked for 1-6h, taken out to be dried, placed in a tube furnace, heated to 220-260 ℃ in an air atmosphere at a heating rate of 0.2-2 ℃/min, and kept at the constant temperature for 2-4 h; then raising the temperature to 1000-1500 ℃ at the temperature raising rate of 1-5 ℃/min under the nitrogen atmosphere for carbonization, wherein the constant temperature time is 1-2 h; and cooling to room temperature at a cooling rate of 1-5 ℃/min to obtain the lignin/graphene-based carbon fiber.

10. The method of claim 9, wherein the fiber is fixed in a corundum boat and placed in a tube furnace, the fiber is adhered to the bottom of the corundum boat by a double-sided adhesive tape, and the double-sided adhesive tape and the fiber are fixed again by a phenolic resin solution, so that the fiber is always subjected to a tensile force during carbonization.

Technical Field

The invention relates to the technical field of carbon fiber preparation, and particularly relates to a preparation method of lignin/graphene-based carbon fiber.

Background

Graphene-based carbon fiber materials have been extensively studied in the scientific and industrial fields due to their excellent physical properties. How to embody the excellent microscopic properties of graphene in macroscopic materials still remains a challenge to us. In 2011, a super topic group firstly reports that GO fiber (CN 102534868A) is prepared by a wet spinning method by utilizing the liquid crystal behavior of GO, the tensile strength is 250MPa-500MPa, and the electric conductivity is more than 10000S/m. At present, the traditional wet spinning method is also the most common method for preparing the graphene-based carbon fiber, but the method needs a large amount of organic solvent coagulation bath for solvent replacement to obtain the fiber; the spinning solution has high concentration (more than 6 mg/ml) and poor fluidity, and is not beneficial to the high orientation of the graphene sheets. The polyelectrolyte complex spinning method is based on the spontaneous self-assembly process of two polyelectrolyte solutions or nanometer material suspensions with relative charges, and continuous fibers are formed at a complex interface through mechanical stretching. The method completely finishes spinning in a water phase without a large amount of organic solvent; the needed spinning solution has low concentration, and the obtained graphene-based carbon fiber has better mechanical property and electrical conductivity under the action of a stretching field of a spinning device.

The lignin is a natural polymer material which is second to cellulose in quantity in nature, has the advantages of wide source, low price, environmental protection, renewability, high carbon content of 60 percent and the like, and is an ideal carbon material precursor. The lignin is applied to the preparation process of the graphene-based carbon fiber, so that the production cost is reduced, and in the high-temperature carbonization process, lignin carbon can chemically react with graphene sheets to generate new carbon-carbon chemical bonds, and tiny holes and the like generated by the carbonization of chitosan are filled, so that the carbon material with excellent physical properties is obtained.

Disclosure of Invention

Based on the defects of the background technology, the invention provides a preparation method of lignin/graphene-based carbon fibers. The method effectively prepares the graphene-based carbon fiber with excellent mechanical property and conductivity, is low in production cost, is green and environment-friendly, and avoids the use of a large amount of organic solvents.

The technical scheme adopted by the invention is as follows:

a preparation method of lignin/graphene-based carbon fibers comprises the following steps:

(1) mixing and stirring the graphene oxide dispersion liquid and the purified lignin solution to obtain a composite spinning solution;

(2) complexing the composite spinning solution with chitosan solution ions by adopting a polyelectrolyte complexing spinning method to obtain lignin/graphene oxide composite fibers, and drying the lignin/graphene oxide composite fibers at room temperature for several hours under the stretching action;

(3) and (3) putting the composite fiber into a tubular furnace, and carbonizing at high temperature in a nitrogen atmosphere to obtain the lignin/graphene-based carbon fiber.

In the method, the mass percent of the lignin in the composite spinning solution is 0-40%.

In the method, the mass percentage concentration of the graphene oxide in the composite spinning solution is 1-5 per mill.

In the method, in the step (1), the lignin solution is obtained by purifying the following steps:

dispersing 50.0g of sodium lignosulfonate in 500ml of deionized water, and stirring until the sodium lignosulfonate is uniformly dispersed; adjusting the pH value of the suspension to 12 by using 1M NaOH solution; filtering the suspension to obtain supernatant, and removing insoluble impurities; slowly adding 1MHCl solution into the supernatant until the pH value reaches 3; repeatedly centrifuging the supernatant at 10000rpm/min until the pH value of the filtrate reaches 5-6; the pH of the suspension obtained by centrifugation was adjusted to 12 by adding NaOH solution and then dialyzed to neutrality.

In the method, the yield of the purified lignin is 15-25%.

In the method, in the step (2), the chitosan solution is prepared by dissolving chitosan powder in 1% acetic acid water solution, and the mass percentage concentration is 3 per mill-1%.

In the method, in the step (2), the fiber diameter of the lignin/graphene oxide composite fiber is 10-40um, and the fiber length is 50-300 mm; the lignin/graphene oxide composite fiber comprises the following components in percentage by mass: 50-95% of graphene oxide, 0-40% of lignin and 5-15% of chitosan.

In the above method, in the step (2), the lignin/graphene oxide composite fiber method is specifically as follows: allowing a lignin/graphene spinning solution to flow in from a main flow channel in the middle by using a spinning device, converging the lignin/graphene spinning solution with chitosan solutions of sheath flow channels at two sides at an outlet after the lignin/graphene spinning solution is stretched by a convergent flow channel, pulling out the lignin/graphene spinning solution from a complexing surface of the lignin/graphene spinning solution by using a pair of tweezers to form fibers, and forming the fibers by an ion complexing self-assembly effect; the spinning device comprises a die and a liquid adding device; the mold comprises two sheath runners, a main runner and an outlet channel; the diameter of the sheath flow channel and the outlet channel is 1.2 mm; the main runner consists of an inlet section and a convergence section, the cross section of the inlet section is larger than that of the convergence section, the diameter of the inlet section is 6mm, and the diameter of the convergence section is 1.2 mm; the liquid adding device is respectively connected with the three inlets of the die through pipelines; the adding device is a needle cylinder, and the flow rate is controlled to be 3mL/h of graphene oxide and 1mL/h of chitosan.

In the method, in the step (3), the step of carbonization is that the fiber is placed in an ammonium chloride/ammonium sulfate solution to be soaked for 1-6h, taken out and aired, then placed in a tubular furnace, heated to 220-260 ℃ in the air atmosphere at the heating rate of 0.2-2 ℃/min, and kept at the constant temperature for 2-4 h; then raising the temperature to 1000-1500 ℃ at the temperature raising rate of 1-5 ℃/min under the nitrogen atmosphere for carbonization, wherein the constant temperature time is 1-2 h; and cooling to room temperature at a cooling rate of 1-5 ℃/min to obtain the lignin/graphene-based carbon fiber.

In the method, the fiber is fixed in a corundum boat and placed in a tube furnace, the fiber is stuck to the bottom of the corundum boat by adopting double faced adhesive tape, and the double faced adhesive tape and the fiber are fixed again by using phenolic resin solution, so that the fiber is always under the action of tensile force in the carbonization process.

Compared with the prior art, the invention has the advantages that:

1) the method is based on the spontaneous self-assembly process of two polyelectrolyte solutions or nano material suspensions with relative charges, the preparation process completely finishes spinning in a water phase, and a large amount of organic solvents are not needed; the needed spinning solution has low concentration, and the obtained graphene-based carbon fiber has better mechanical property and conductivity under the action of a stretching field of a spinning device;

2) when the lignin is applied to the preparation process of the graphene-based carbon fiber, the production cost is reduced, and in the high-temperature carbonization process, lignin carbon can chemically react with graphene sheets to generate new carbon-carbon chemical bonds, and tiny holes and the like generated by the carbonization of chitosan are filled, so that the carbon material with excellent physical properties is obtained.

3) Compared with the traditional wet spinning method, the polyelectrolyte complex spinning method is adopted to prepare the graphene-based composite fiber, and the use of a large amount of organic coagulation bath is not involved, so that the method is more environment-friendly, the concentration of the spinning solution is low, and the spinning is more facilitated;

4) the existence of the lignin fills pores generated in the carbonization process of the graphene-based carbon fiber, so that the carbon fiber is endowed with higher mechanical property and conductivity;

5) the lignin is low in price, wide in source, green and renewable, has the carbon content as high as 60 percent, and is a high-quality carbon-based material precursor.

Drawings

FIG. 1 is a schematic diagram of the structure of a die in an apparatus for polyelectrolyte complex spinning of lignin/graphene-based carbon fibers;

FIG. 2 is a scanning electron micrograph of lignin/graphene-based carbon fibers showing a dense fiber internal structure;

fig. 3 is a tensile strength-elongation at break graph of 30% lignin/graphene-based carbon fiber, demonstrating the excellent tensile strength of the carbon fiber.

Detailed Description

In the following examples, the lignin solution was purified by the following steps: dispersing 50.0g of sodium lignosulfonate in 500ml of deionized water, and stirring until the sodium lignosulfonate is uniformly dispersed; adjusting the pH value of the suspension to 12 by using 1M NaOH solution; filtering the suspension to obtain supernatant, and removing insoluble impurities; slowly adding 1M HCl solution into the supernatant until the pH value reaches 3; repeatedly centrifuging the supernatant at 10000rpm/min until the pH value of the filtrate reaches 5-6; the pH of the suspension obtained by centrifugation was adjusted to 12 by adding NaOH solution and then dialyzed to neutrality.

The spinning device comprises a die and a liquid adding device; as shown in fig. 1, the mold includes two sheath flow channels, a primary flow channel, and an outlet channel; the diameter of the sheath flow channel and the outlet channel is 1.2 mm; the main runner consists of an inlet section and a convergence section, the cross section of the inlet section is larger than that of the convergence section, the diameter of the inlet section is 6mm, and the diameter of the convergence section is 1.2 mm; the liquid adding device is respectively connected with the three inlets of the die through pipelines; the adding device is a needle cylinder, and the flow rate is controlled to be 3mL/h of graphene oxide and 1mL/h of chitosan. FIG. 1 is a schematic diagram of a mold structure, wherein a, b, c are inlet ports, and d is an outlet port; the chitosan solution enters from inlets on two sides, namely inlets b and c, the graphene oxide spinning solution enters from an inlet a, and the final lignin/graphene oxide composite fiber is discharged from an outlet d. The liquid adding device in the invention can also adopt a CTN-W300 syringe pump of Beijing Tong Shiyida medical science and technology limited company.