CN115160627A

CN115160627A - Modified laser-induced graphene material and preparation method thereof

Info

Publication number: CN115160627A
Application number: CN202210942519.6A
Authority: CN
Inventors: 赵楠; 解洪兴; 何新
Original assignee: Beijing Haisu Technology Co ltd
Current assignee: Beijing Haisu Technology Co ltd
Priority date: 2022-08-11
Filing date: 2022-08-11
Publication date: 2022-10-11
Anticipated expiration: 2042-08-11
Also published as: CN115160627B

Abstract

The invention provides a preparation method of a modified laser-induced graphene material, which is characterized in that a substrate layer containing cellulose and a precursor is converted into laser-induced graphene through laser, and the precursor is modified through various chemical reactions such as grafting, esterification and the like, so that the temperature resistance and char formation performance of the precursor can be enhanced. The invention also provides a modified laser-induced graphene material which comprises a substrate layer and a graphene functional layer, wherein the substrate layer contains a modified precursor. The problem that graphene functional layer and substrate layer combine not firm is overcome because of its special construction that possesses to modified laser induction graphite alkene material for graphite alkene can combine firm difficult droing with the substrate, and has realized characteristics such as excellent flexibility, weatherability, simultaneously, can also possess better temperature resistant, waterproof and pliability performance.

Description

Modified laser-induced graphene material and preparation method thereof

Technical Field

The invention relates to the technical field of graphene materials, in particular to a modified laser-induced graphene material and a preparation method thereof.

Background

Graphene, a graphene single-layer, is a single-atomic-layer two-dimensional crystal material in which carbon atoms form a honeycomb structure in an sp2 hybridization manner. Graphene is an important member of the carbon nanomaterial family, and has shown broad application prospects in electronic devices, energy storage, and electrochemical catalysis due to its unique physical properties, such as high surface area, high electrical conductivity, good mechanical strength, and stability.

In order to obtain high-quality graphene, a mechanical exfoliation method, a chemical vapor deposition method, a surface epitaxial growth method, a cutting nanotube method, a liquid phase exfoliation method, a redox method, and the like are available at present.

In the process of implementing the invention, the inventor finds that at least the following problems exist in the prior art: the mechanical stripping method and the epitaxial growth method have low preparation efficiency and are difficult to meet the large-scale requirement. The reduced graphene oxide method is applied more, but most reducing agents used in the preparation process have the defects of high toxicity, high pollution and the like, and the cost is increased for protective measures and waste liquid treatment in the preparation process. Although the chemical vapor deposition method can obtain a large-size continuous graphene film, new impurities may be introduced during the stripping process to affect the quality of the graphene, and the reaction conditions are harsh and strict. In addition, the common production methods also use graphite ore as a raw material, and the mineral resources are not recyclable and are not beneficial to the large-scale production of graphene. How to obtain high-quality and low-cost graphene by a low-cost, large-scale, nontoxic and environment-friendly preparation method with simple production steps becomes a research hotspot in the field.

Disclosure of Invention

The inventor finds that the traditional graphene production method has the defects of high graphene preparation cost, complex graphene manufacturing process and the like through a great deal of research. The laser induction method for preparing the graphene is a novel graphene preparation method, and the principle of the method is that laser induction is used for converting a precursor into the graphene, so that the method can be used for preparing the graphene material at low cost under the conditions of normal temperature and no protective atmosphere.

In the process of implementing the present invention, the inventors found that the laser-induced method is prone to have cracks and not flat enough when preparing laser-induced graphene (LIG), the substrate is prone to twist and break, the prepared LIG is not firmly combined with the substrate and is prone to fall off, and the like, and meanwhile, the electrical property of the laser-induced graphene, the flame retardant property of the substrate, the waterproof property of the substrate, and the flexibility of the substrate are all to be improved.

In the process of implementing the invention, the inventor providesA preparation method of a modified laser-induced graphene material is provided, and the method converts a substrate layer containing cellulose and a precursor into laser-induced graphene through laser. Through a great deal of research, the inventor finds that the temperature resistance and the char formation performance of the precursor can be enhanced by performing various chemical reactions such as oxidation, reduction, hydrolysis, alcoholysis, methoxy acidolysis, carboxyl group, photolysis, esterification, sulfonation, alkylation, halogenation, nitration, polycondensation, grafting, esterification, copolymerization and the like on the precursor. Through modification, the flame-retardant group can be grafted to the precursor, so that the flame-retardant property of the precursor is improved. Cellulose can also be added into the LIG substrate, in the process of laser-induced conversion, laser parameters are reasonably set, so that laser penetrates into the LIG substrate, a precursor is converted into laser-induced graphene, part of cellulose is converted into carbonized cellulose, meanwhile, the beam tube structure and the net structure of the carbonized cellulose are not damaged by the laser, the stability of the graphene functional layer and the connection between the substrate layer and the laser-induced graphene are maintained, the prepared laser-induced graphene is better attached to the surface of the substrate layer, the problem that the graphene functional layer and the substrate layer are not firmly combined is solved, the graphene and the substrate can be firmly combined and are not easy to fall off, and the characteristics of excellent flexibility, weather resistance and the like are realized. The laser used in the preparation method comprises a CO2 laser, a red laser, a blue laser, a femtosecond laser and the like. The wavelength range of the laser light that can be used may be 9.3-10.6. Mu.m, 625-740nm, 450-480nm, 1053nm. The laser intensity borne by the surface of the LIG substrate needs to be more than 3J/cm ² 。

In the process of implementing the present invention, the inventors further provide a modified laser-induced graphene material, which includes a substrate layer and a graphene functional layer. The graphene functional layer contains a laser-induced graphene component. The substrate layer contains a modified precursor. Preferably, the modified precursor has an epoxy group or an ester group attached thereto. Preferably, the modified laser-induced graphene material further contains cellulose, and the cellulose is dispersed in the substrate layer and the graphene functional layer. In the structure of the modified laser-induced graphene material, part of cellulose is connected with the substrate layer and the graphene functional layer, and the part of the cellulose entering the graphene functional layer is converted into carbonized cellulose; part of cellulose and carbonized cellulose molecules are mutually entangled to form a net structure, and part of the laser-induced graphene component is nested in the net structure. The problem that graphene functional layer and substrate layer combine not firm is overcome because of its special construction that possesses to modified laser induction graphite alkene material for graphite alkene can combine firm difficult droing with the substrate, and has realized characteristics such as excellent flexibility, weatherability, simultaneously, can also possess better temperature resistant, waterproof and pliability performance.

The modified laser-induced graphene material provided by the inventor can be applied to the fields of flexible sensors, intelligent heating devices, nano friction generators, self-cleaning filters, super capacitors and the like.

Embodiment 1. A modified laser-induced graphene material comprises a substrate layer and a graphene functional layer, wherein the substrate layer of the modified laser-induced graphene material contains a modified precursor, the modified precursor comprises one or a combination of a biomass material, a synthetic material and a mineral material, and the particle size of the modified precursor is 50-500nm; the modified laser-induced graphene material contains cellulose, the graphene functional layer comprises laser graphene, the cellulose is dispersed in the base material and the graphene functional layer, and all or part of the cellulose in the graphene functional layer is converted into carbonized cellulose.

Embodiment 2. The graphene material of embodiment 1, wherein the cellulose comprises cellulose at a transition region between the substrate layer and the graphene functional layer, the cellulose connects the substrate layer and the graphene functional layer, the cellulose comprises cellulose and carbonized cellulose, molecules of which are entangled with each other to form a network structure, and a portion of the laser graphene is nested in the network structure.

Embodiment 3. The graphene material of embodiments 1-2, wherein the precursor is a biomass-based material, and the components of the biomass-based material comprise one or a combination of lignin, tannic acid, polyphenols, and flavonoids; the synthetic material comprises one or the combination of photoresist, polyimide film, polyimide fiber paper, polyimide foam sponge, polysulfone polymer, teflon, phenolic resin, ABS plastic and polystyrene polymer; the mineral material comprises one or a combination of coal, carbon black, graphene oxide and graphite.

Embodiment 4. The graphene material of embodiments 1-3, wherein the modified precursor is a modified lignin having at least one of epoxy groups and lipid groups.

Example 5. The graphene material of examples 1-4, wherein the modified lignin is a product prepared by modification of one or a combination of Kraft lignin, alkali lignin, dealkalized lignin, lignin sulfate.

Embodiment 6. The graphene material of any one of embodiments 1-5, wherein the modified precursor contains a flame retardant group, and the flame retardant group is one or a combination of a phosphoric acid group, a halogen group, and a silicon group.

Embodiment 7. A method for preparing modified graphene, wherein a laser is used to irradiate a laser-induced graphene substrate to prepare a modified laser-induced graphene material, the laser has a wavelength ranging from 9.3 to 10.6 μm, 625 to 740nm, 450 to 480nm, and 1053nm, the laser intensity borne by the surface of the laser-induced graphene substrate ranges from 3J/cm2 to 40J/cm2, the laser-induced graphene substrate contains a modified precursor, and the thickness of the laser-induced graphene substrate is 0.02 to 0.5mm.

Example 8. The method of making of examples 1-7, wherein modifying the precursor comprises one or a combination of oxidation, reduction, hydrolysis, alcoholysis, acid hydrolysis of methoxy, carboxyl, photolysis, esterification, sulfonation, alkylation, halogenation, nitration, polycondensation, grafting, esterification, and copolymerization.

Example 9. The preparation method according to example 1 to 8, wherein the modification precursor is modified in such a way that the modification precursor has an epoxy group and a lipid group.

Example 10. The preparation method of examples 1 to 9, wherein the laser-induced graphene base material further comprises cellulose, the cellulose having a diameter of less than 100nm and an aspect ratio of 1000 to 1500; or the cellulose has a diameter of 0.1-120um and a length of 0.1-5mm.

Example 11. The preparation method according to examples 1 to 10, wherein the modified precursor is modified lignin having a particle size of 10nm to 500nm.

Example 12. The preparation method of examples 1-11, wherein the modified lignin addition amount in the laser-induced graphene substrate is 0-34wt%.

Example 13. The preparation method of examples 1-12, wherein the modified lignin addition in the laser induced graphene substrate is 21wt%.

In some embodiments, during the preparation of the modified laser-induced graphene material, the modification of the precursor includes performing a plurality of chemical reactions, such as oxidation, reduction, hydrolysis, alcoholysis, methoxy acidolysis, carboxyl group, photolysis, esterification, sulfonation, alkylation, halogenation, nitration, polycondensation, grafting, esterification, and copolymerization, so as to enhance the temperature resistance and char formation of the precursor.

In some embodiments, a flame retardant group is grafted to the precursor, improving the flame retardant properties of the precursor.

In other embodiments, a certain amount of cellulose is added to the LIG substrate, and the power and wavelength of the laser are controlled, so that part of the cellulose entering the graphene functional layer is converted into carbonized cellulose, and part of the cellulose and carbonized cellulose molecules are mutually entangled to form a network structure, and part of the laser-induced graphene component is nested in the network structure. These celluloses can be more firm and connect the substrate layer and the graphene functional layer, and the problem that the graphene functional layer and the substrate layer are not firm in combination is overcome, so that the graphene and the substrate can be firmly combined and are not easy to fall off, and the characteristics of excellent flexibility, weather resistance and the like are realized.

Drawings

FIG. 1 is an electron microscope image of laser-induced graphene with laser power of 1.25W on a cellulose LIG substrate (left) and a cellulose LIG substrate (right) without the addition of cellulose

FIG. 2 is an electron microscope image of laser-induced graphene with laser power of 1.5W on a cellulose LIG substrate (left) and a cellulose LIG substrate (right) without the addition of cellulose

FIG. 3 SEM image of LIG made from a lignocellulosic LIG substrate

FIG. 4 TEM image of LIG made from a lignocellulosic LIG substrate

FIG. 5 XRD characteristic peaks of LIG prepared from Lignocellulosic LIG substrate

FIG. 6 Raman characteristic peaks of LIG prepared from Lignocellulosic LIG substrate

FIG. 7 XPS spectra of LIG prepared from lignocellulosic LIG substrates

FIG. 8 is a schematic view of a roll-to-roll LIG manufacturing process

FIG. 9 schematic diagram of modified laser-induced graphene material

FIG. 10 schematic diagram of modified laser-induced graphene material containing cellulose

FIG. 11 SEM images of pure cellulose paper (left), lignocellulose composite paper (middle) and LIG prepared based on lignocellulose composite paper (right)

FIG. 12 SEM images of lignocellulose LIG substrate (left), 1 scan based on lignocellulose LIG substrate (middle), 2 scans based on lignocellulose LIG substrate (right)

FIG. 13 schematic process for preparing LIG based on lignocellulosic LIG substrate

FIG. 14 SEM pictures of LIG prepared based on lignocellulosic LIG substrate (different laser intensities, (a) 50wt%, (b) 60wt%, (c) 70wt%, (d) 80wt%, full power 40W)

FIG. 15 TEM image of LIG prepared based on lignocellulosic LIG substrate

FIG. 16 TEM images of LIG prepared based on lignocellulosic LIG substrate (different lignin addition amounts, (a, b) 2wt%, (c, d) 9wt%, (e, f) 15wt%, (g, h) 21wt%, (i, j) 34 wt%)

FIG. 17 is a schematic diagram of a structure in which laser-induced graphene is nested in cellulose and cellulose carbide

FIG. 18 schematic of the epoxidation and acrylation process of lignin

FIG. 19FeNi ₃ Nanoparticles and oxides thereof (Fe) ₃ O ₄ ) Schematic representation of multilayer structures formed in LIG matrices

In the figure: 100-a substrate layer; 200-a graphene functional layer; 210-laser induced graphene; 310-lignin solution; 320-modifying solution; 330-cellulose; 340-carbonized cellulose; 410-a first roller unit; 420-a second roll unit; 430-a third roller unit; 510-a first laser; 520-second laser.

Detailed Description

Interpretation of terms

Graphene: graphene (Graphene) is sp ² The hybridized and connected carbon atoms are tightly packed into a new material with a single-layer two-dimensional honeycomb lattice structure.

Laser-induced graphene: laser Induced Graphene (LIG) is sp ² The hybridized and connected carbon atoms are tightly packed into a multi-layer (generally more than five layers) three-dimensional honeycomb lattice structure.

Precursor: the precursor is also called LIG precursor, and is a precursor material for generating laser-induced graphene.

Cellulose layered material: prepared from cellulose or nanocellulose, or mixtures thereof

Laser-induced graphene substrate: the laser-induced graphene substrate is also called an LIG substrate, and is a substrate for preparing laser-induced graphene by a laser method.

Basic scheme

One embodiment of the invention provides a preparation method of a modified laser-induced graphene material, which comprises the following specific steps:

s001. Modifying the precursor, wherein the method comprises the following steps,

the modification of the precursor comprises a plurality of chemical reactions such as oxidation, reduction, hydrolysis, alcoholysis, methoxy acidolysis, carboxyl, photolysis, esterification, sulfonation, alkylation, halogenation, nitration, polycondensation, grafting, esterification and copolymerization, and the temperature resistance and char formation performance of the precursor are enhanced. The particle size of the precursor is 50-500nm.

S002. Making laminated LIG base material

Preparing the modified precursor into an LIG substrate by the processes of film laying, hot press molding and the like, wherein the thickness of the LIG substrate is 0.02-0.5mm

S003, setting laser processing parameters to carry out laser irradiation on the LIG substrate, wherein the method comprises the following steps,

the laser wavelength can be 9.3-10.6 μm, 625-740nm, 505-566nm, 450-480nm, 10-450nm, 1053nm. The laser comprises a CO ₂ Lasers, red lasers, green lasers, blue lasers, femtosecond and picosecond lasers, and the like.

The preferred scheme (process: LIG substrate modification + cellulose, integration) one embodiment of the invention provides a preparation method of a modified laser-induced graphene material, which comprises the following specific steps:

s001, modifying a precursor, wherein the method comprises the following steps,

(1) Modifying the precursor, wherein the modification of the precursor comprises various chemical reactions such as oxidation, reduction, hydrolysis, alcoholysis, acid hydrolysis of methoxyl group, carboxyl group, photolysis, esterification, sulfonation, alkylation, halogenation, nitration, polycondensation, grafting, esterification, copolymerization and the like, and the temperature resistance and char formation performance of the precursor are enhanced. The modification occurs primarily at the phenolic hydroxyl groups in the precursor.

Preferably, the precursor is modified to attach an epoxy group or an ester group. Further, in the step of modifying the precursor, grafting and esterifying the precursor, grafting an epoxy group to a phenolic hydroxyl group of the precursor by a chemical catalysis method, and then carrying out esterification reaction with acrylic acid to prepare an epoxy precursor acrylate solution so as to improve the viscosity and the high-temperature ductility of the precursor.

S002. Preparation of cellulose reinforced modified precursor LIG base material, the method comprises the following steps,

(1) Preparing a mixed solution of a precursor and cellulose, namely adding cellulose or nano-cellulose into the precursor solution, stirring, performing ultrasonic treatment, and emulsifying to prepare the mixed solution of the precursor and the cellulose. The addition amount of the precursor is 0-41wt%, and the preferred addition amount of the precursor is 29wt%. Modified precursor/cellulose addition amount, modified precursor addition amount: 0-34wt%, and the preferable addition amount of the modified precursor is 21wt%. The preferred cellulose diameter is > 1000nm.

(2) And (3) paving a film, and preparing a precursor cellulose wet film from the precursor and cellulose mixed solution by a tape casting method or a vacuum filtration method.

(3) Hot-pressing and molding, curing the precursor cellulose wet film at 40-150 ℃ and 1-15MPa to form a film, and obtaining the precursor cellulose LIG substrate, wherein the preferred temperature is 50-110 ℃, and the preferred pressure is 5-10MPa.

S004, setting laser processing parameters to carry out laser irradiation on the LIG base material, wherein the method comprises the following steps,

the laser wavelength may be 9.3-10.6 μm, 625-740nm, 505-566nm, 450-480nm, 10-450nm, 1053nm. The laser comprises a CO ₂ Lasers, red lasers, green lasers, blue lasers, femtosecond and picosecond lasers, and the like. The LIG substrate surface is required to bear laser intensity of more than 3J/cm ² Less than 40J/cm ² The preferred laser intensity is 5.5-20J/cm ² . The same area of the LIG substrate may be irradiated a single time or multiple times with a laser of the above parameters.

By modifying the precursor in the LIG substrate, the quality of the laser-induced graphene prepared by the LIG substrate can be improved, such as the conductivity, hydrophobicity and the like of the laser-induced graphene. The precursor in the LIG substrate is modified, so that the strength and flexibility of the LIG substrate can be improved.

Preferred embodiment 1

s001, modifying a precursor, wherein the method comprises the following steps,

(1) And modifying the precursor, wherein in the step of modifying the precursor, a flame-retardant group is grafted to the precursor, and the flame-retardant group comprises a halogen group and a phosphorus group. The mass ratio of the flame-retardant group substance to the precursor is 0-10wt%, the mass ratio of the flame-retardant group substance to the precursor is 3-8wt%,

(1) Preparing a mixed solution of a precursor and cellulose, namely adding cellulose or nano-cellulose into the precursor solution, stirring, performing ultrasonic treatment, and emulsifying to prepare the mixed solution of the precursor and the cellulose. The addition amount of the precursor is 0-41wt%, and the preferred addition amount of the precursor is 29wt%. Modified precursor/cellulose addition amount, modified precursor addition amount: 0-34wt%, and the preferable addition amount of the modified precursor is 21wt%. The preferred cellulose diameter is > 1000nm. The precursor can be lignin, tannin, tea polyphenol, etc.

S004, setting laser processing parameters to carry out laser irradiation on the LIG substrate, wherein the method comprises the following steps,

the laser wavelength may be 9.3-10.6 μm, 625-740nm, 505-566nm, 450-480nm, 10-450nm, 1053nm. The laser comprises a CO ₂ Lasers, red lasers, green lasers, blue lasers, femtosecond and picosecond lasers, and the like. The laser intensity born by the surface of the LIG substrate needs to be more than 3J/cm ² Less than 40J/cm ² Preferably, the laser intensity is 5.5 to 20J/cm ² . The same area of the LIG substrate may be irradiated a single time or multiple times with a laser of the above parameters.

By modifying the precursor in the LIG substrate, the quality of the laser-induced graphene prepared by the precursor can be improved, such as the conductivity and hydrophobicity of the laser-induced graphene. The precursor in the LIG substrate is modified, so that the strength and flexibility of the LIG substrate can be improved.

Preferred embodiment 2

One embodiment of the invention provides a preparation method of a modified laser-induced graphene material, wherein a laser graphene precursor is lignin, and the preparation method specifically comprises the following steps:

s001, purifying and modifying lignin, wherein the method comprises the following steps,

(1) Acid washing, acid washing is carried out on lignin, and the used acid comprises hydrochloric acid, sulfuric acid or inorganic acid and the like.

(2) Sieving, and sieving lignin for 1-5 times, wherein the sieves are sequentially arranged from large to small.

(3) Extracting and grading lignin with organic solvent such as acetone, butanol, ethanol, etc., controlling molecular weight and particle size of lignin, removing non-functional components, increasing relative content of active groups, and enhancing processability of lignin.

(4) And (4) washing and drying, namely washing and drying the lignin.

S002, lignin modification, wherein the method comprises the following steps,

(5) Lignin is modified, wherein the lignin is modified by carrying out various chemical reactions such as oxidation, reduction, hydrolysis, alcoholysis, acid hydrolysis methoxy group, carboxyl group, photolysis, esterification, sulfonation, alkylation, halogenation, nitration, polycondensation, grafting, esterification, copolymerization and the like, and the temperature resistance and char formation performance of the lignin are enhanced. The modification occurs mainly on the phenolic hydroxyl groups in the lignin.

Further, in the lignin modification step, lignin is grafted and esterified, epoxy groups are grafted to phenolic hydroxyl groups of the lignin by a chemical catalysis method, and then an esterification reaction is carried out with acrylic acid to prepare an epoxy lignin acrylate solution, so that the viscosity and the ductility of the lignin at high temperature are improved.

Further, in the step of lignin modification, a flame-retardant group is grafted to lignin, and the flame-retardant group comprises a halogen group, a phosphorus group and a silicon group.

S003. Preparation of cellulose reinforced modified lignin LIG substrate, the method comprises the following steps,

(1) The preparation of the mixed solution of lignin and cellulose comprises the steps of adding cellulose or nano-cellulose into a lignin solution, stirring, carrying out ultrasonic treatment, and emulsifying to obtain the mixed solution of lignin and cellulose. The amount of added lignin is 0-41wt%, preferably 29wt%. Adding amount of modified lignin/cellulose, wherein the adding amount of the modified lignin is as follows: 0-34wt%, and the preferable addition amount of the modified lignin is 21wt%. The preferred cellulose diameter is > 1000nm.

(2) And (3) paving a film, and preparing the lignin cellulose wet film from the lignin and cellulose mixed solution by a tape casting method or a vacuum filtration method.

(3) Hot-pressing to form a lignocellulose LIG substrate, curing the lignocellulose wet film at 40-150 ℃ and 1-15MPa to form the lignocellulose LIG substrate, wherein the preferred temperature is 50-110 ℃, and the preferred pressure is 5-10MPa.

the laser wavelength may be 9.3-10.6 μm, 625-740nm, 505-566nm, 450-480nm, 10-450nm, 1053nm. The laser comprises a CO ₂ Lasers, red lasers, green lasers, blue lasers, femtosecond and picosecond laser lasers, and the like. The laser intensity born by the surface of the LIG substrate needs to be more than 3J/cm ² Less than 40J/cm ² The preferred laser intensity is 5.5-20J/cm ² . The same area of the LIG substrate may be irradiated a single time or multiple times with a laser of the above parameters.

In an embodiment of the invention, the epoxy value of the modified lignin can be changed by adjusting the addition amount of Epichlorohydrin (ECH) in the lignin modification process, and different epoxy values can correspond to different viscosities and flowabilities of lignin at high temperature, thereby affecting the quality of the prepared laser-induced graphene composite material.

By modifying lignin in the LIG substrate, the quality of the laser-induced graphene prepared by the LIG substrate can be improved, such as the conductivity and hydrophobicity of the laser-induced graphene. The strength and flexibility of the LIG base material can be improved by modifying lignin in the LIG base material.

TABLE 1 table of lignin epichlorohydrin addition and epoxy value

ECH addition per g lignin (g)	Epoxy value (mol/100 g) of Lignin epoxy acrylate
		0.5	1.39
1	2.08
		2	2.94

Preferred embodiment 3

s001. Purifying and modifying lignin, the method comprises the following steps,

(1) Acid washing, acid washing is carried out on the lignin, and the used acid comprises hydrochloric acid, sulfuric acid or inorganic acid and the like.

(3) Extracting and grading the lignin by using organic solvents such as acetone, butanol, ethanol and the like to obtain the lignin soluble in the organic solvents. The molecular weight and particle size of lignin can be controlled by organic solvent extraction and classification, non-functional components are removed, the relative content of active groups is increased, and the processability of lignin is enhanced.

10g of lignin was added to 100ml of acetone, stirred at room temperature for 60 minutes, and then sonicated in an ice bath for 60 minutes to extract soluble components in the lignin. Next, using vacuum filtration, the acetone solution was retained. Acetone soluble lignin is obtained by subsequent removal of acetone by rotary evaporation.

(4) And (4) washing and drying, and washing and drying the lignin. The obtained acetone soluble lignin was washed with water and subsequently vacuum dried in a vacuum oven at 50 ℃.

Ethanol or butanol may also be used to extract the lignin soluble in ethanol or butanol according to the same procedure.

S002, lignin modification, wherein the method comprises the following steps,

(5) And (3) lignin modification, wherein the lignin modification comprises grafting and esterification reaction, and the temperature resistance and char formation performance of the lignin are enhanced.

In the lignin modification step, lignin is grafted and esterified, epoxy groups are grafted to phenolic hydroxyl groups of the lignin by a chemical catalysis method, and then an esterification reaction is carried out with acrylic acid to prepare an epoxy lignin acrylate solution, so that the viscosity and the ductility of the lignin at high temperature are improved.

The organic solvent soluble lignin was dissolved in 100mL of dimethyl sulfoxide (DMSO) solution at different addition levels of 1, 3, 5, 10 and 20g, in proportions of 0.5, 1 and 2g of Epichlorohydrin (ECH) per 1g of lignin, respectively. 0.2g KOH solution (30%, w/w) was then added at 65 deg.C and after 2 hours of mixing with stirring, 0.2g KOH was added again and stirring was continued for 2 hours.

After cooling, the mixture is treated with 0.5mol/L NaH ₂ PO ₄ ·2H ₂ And O, neutralizing the pH value of the solution to 7.5-8.0, and finally obtaining the lignin-based epoxy resin through glycidation reaction.

Subsequently 0.2% of hydroquinone 0.2% of pyridine was added and the required amount of acrylic acid was added over 30 minutes at 80 ℃ in a proportion of 0.9 mole of acrylic acid per mole of epoxy group, finally obtaining lignin-based epoxy acrylate (LBEA).

(1) Preparing a mixed solution of modified lignin and cellulose, crushing the cellulose, sieving the crushed cellulose by a sieve of 2mm, adding 2g of the sieved cellulose into a lignin-based epoxy acrylate mixed system, and stirring the mixture at room temperature at 1000rpm overnight. The cellulose having adsorbed lignin-based epoxy acrylate was collected by centrifugation at 8000rpm for 20 minutes, washed with dimethyl sulfoxide to remove non-adsorbed lignin-based epoxy acrylate, and then washed with water to remove dimethyl sulfoxide.

(2) The cellulose adsorbed with lignin-based epoxy acrylate was dispersed in 200mL of deionized water and homogenized until a homogeneous suspension was obtained. And filtering 10ml of suspension to the surface of filter paper by vacuum filtration to obtain the wet lignocellulose composite paper.

(3) And (3) performing hot press molding, namely pressing the wet lignocellulose composite paper for 10 minutes under the load of 5kg at room temperature, and then performing hot press at 100 ℃ and 5MPa for 90 minutes to obtain the modified LIG substrate. The modified LIG substrates can be stored at 23 ℃ at 50% Relative Humidity (RH).

the laser wavelength may be 9.3-10.6 μm, 625-740nm, 505-566nm, 450-480nm, 10-450nm, 1053nm. The laser comprises a CO ₂ Lasers, red lasers, green lasers, blue lasers, femtosecond and picosecond laser lasers, and the like. The LIG substrate surface is required to bear laser intensity of more than 3J/cm ² Less than 40J/cm ² Preferably, the laser intensity is 5.5 to 20J/cm ² . The same area of the LIG substrate may be irradiated a single time or multiple times with a laser of the above parameters.

Preferably, the laser is also in the form of pulses with a pulse duration of 14 μ s, a maximum power of 40W, a grating lateral velocity of 23in/s, a focal length of 35mm and a laser beam size of about 100 μm.

Preferably, the laser scan rate may be 30% of its full speed, with laser intensities of 50%, 60%, 70% and 80% of full power.

In one embodiment of the invention, the laser can be focused or defocused for scanning (-3.0-3.0 mm) when irradiating the surface of the LIG substrate, the laser point is circular during the defocused scanning, each group of circles can be overlapped in the translation process of the laser head, and the overlapped area is equivalent to two times or more of scanning.

In one embodiment of the invention, the particle size of the precursor is 10nm-500nm, and the diameter of the cellulose is more than 1000nm.

In one embodiment of the invention, the addition amount of the precursor is more than 10wt%, which is beneficial to wrapping cellulose fibers, protecting the cellulose from carbonization in the laser scanning process, and maintaining the stability of the structure of the bundle tube of the cellulose, so that the finally generated graphene functional layer is better attached to the surface of the substrate layer. Too low addition of the precursor can result in too thin a precursor covering the surface of the cellulose, and the cellulose cannot be effectively protected from laser irradiation. And the flexibility of the modified laser-induced graphene material can be influenced by the excessively high addition amount of the precursor. The thickness of the LIG substrate is 0.02-0.5mm.

The lignin-based epoxy acrylate (LBEA) is synthesized by taking lignin as a raw material through epoxy resin and acrylic acid, then well crosslinked with cellulose in a DMSO system, and the high-strength, flexible and waterproof composite paper is obtained after hot pressing.

Example 1

One embodiment of the invention provides a modified laser-induced graphene material which comprises a substrate layer and a graphene functional layer, wherein the graphene functional layer is attached to the surface of the substrate layer. The graphene functional layer contains laser-induced graphene and has a three-dimensional pore structure. In the structure of the modified laser-induced graphene material, part of the laser-induced graphene is nested in the reticular structure. The base material layer also contains a modified precursor, and the further modified precursor is connected/grafted with a flame-retardant group, wherein the flame-retardant group comprises a halogen group and a phosphorus group. The further precursor is connected with epoxy group and ester group.

In one embodiment of the present invention, the ratio of graphene to laser-induced graphene in the graphene functional layer is 1 _G /I _D Is 0.5 to 5.0, I _2D /I _G Is 0.1 to 1.0, L _a Is 10-40mm. The surface resistance of the graphene functional layer is 2-33000 omega/square, and the omega/square is the same as omega/cm ² . The conductivity of the graphene functional layer is 8-5500S/cm. The specific surface area of the graphene functional layer is 10-350m ² (ii) in terms of/g. The aperture of the graphene functional layer is 0-750nm. The thickness of the graphene functional layer is 0.05-350 μm. The detection method of the ratio of the graphene to the laser-induced graphene is TEM detection. The thickness of the substrate layer is 0.02-0.5mm.

Example 2

One embodiment of the invention provides a preparation method of a modified laser-induced graphene material, which is characterized in that a cellulose composite LIG (laser induced gelation) substrate containing a precursor is irradiated by laser to prepare the modified laser-induced graphene material. The specific implementation method comprises the following steps:

(1) A cellulose-composited LIG substrate containing the precursor was prepared. The addition ratio of the precursor may be 2 to 45wt%, and the preferable addition ratio may be 15 to 25wt%. The precursor can be graphene oxide, polyimide and lignin. The LIG substrate contains cellulose.

(2) And setting laser processing parameters to carry out laser irradiation on the LIG substrate. The laser wavelength may be 9.3-10.6 μm, 625-740nm, 505-566nm, 450-480nm, 10-450nm, 1053nm. The laser comprises a CO ₂ Lasers, red lasers, green lasers, blue lasers, femtosecond and picosecond laser lasers, and the like. The LIG substrate surface is required to bear laser intensity of more than 3J/cm ² Less than 40J/cm ² Preferably, the laser intensity is 5.5 to 20J/cm ² . The same area of the LIG substrate can be irradiated with a laser of the above parameters, single or multiple times, with different laser intensity TEM results as shown in fig. 14.

Example 3

One embodiment of the present invention provides a method for preparing a modified laser-induced graphene material, which converts a LIG substrate containing cellulose into graphene by laser, as shown in fig. 11. The specific implementation is that laser processing parameters are set to carry out laser irradiation on the surface of the LIG substrate, so that the precursor is converted into graphene.

In one embodiment of the invention, the laser may have a wavelength of 9.3-10.6 μm, 625-740nm, 450-480nm, 1053nm. The laser comprises a CO ₂ Lasers, red lasers, blue lasers, femtosecond lasers, and the like. The power of the laser is in the range of 0-50W. The laser intensity borne by the surface of the LIG substrate needs to be more than 3J/cm ² The preferred laser intensity is > 5.5J/cm ² . The same area of the substrate may be irradiated with a single or multiple passes as shown in fig. 12. The LIG substrate comprises a cellulosic component.

The LIG substrate contains a precursor, which can be a biomass material including paper and textiles, and the textiles can be silk, cotton, linen and the like. The biomass material comprises lignin (Kraft lignin, alkali lignin, dealkalized lignin, etc.), cellulose, tannin, polyphenol (such as tea polyphenol, chlorogenic acid, apple polyphenol, cocoa polyphenol, resveratrol, etc.), and flavonoid (such as flavonol, anthocyanin, flavonoid, etc.). The biomass material has the advantages of environmental friendliness, degradability and the like.

Cellulose belongs to semi-rigid molecules, molecular chains of the cellulose are flexible, the cellulose has high polymerization degree, good molecular orientation degree and strong chemical stability. The LIG substrate is added with cellulose, and a net structure is formed in a composite system by utilizing the advantage of the cellulose belonging to semi-rigid molecules, so that the LIG substrate has larger free space/pores. When the laser beam irradiates the surface of the LIG substrate, the laser beam can penetrate into the paper more easily, so that the paper can absorb more heat and the heat distribution is more uniform. The unique pore structure of cellulose can guide graphene to better fill the free space of paper when the surface of the paper grows, and the graphene is uniformly distributed on the surface of the paper instead of vertically growing downwards (disordered distribution). The surface of the formed graphene functional layer is smoother and smoother, and cracks are fewer. Generally, under laser scanning, a substrate is easily distorted or even broken due to high temperature, so that a graphene functional layer is easily separated from the substrate; in contrast, since cellulose molecules have polarity, the interaction force between molecular chains is strong, severe shape distortion is not easy to occur, graphene growing on the surface layer of paper can be firmly grasped, the overall mechanical stability of the modified laser-induced graphene material is improved, and TEM images of different lignin addition amounts are shown in fig. 16.

TABLE 2 substrate layer containing cellulose and lignin and LIG parameters

Adding amount of lignin	Mechanical tensile strength	Contact angle	Area resistance omega/square	I _D /I _G	I _G /I _2D	L _a
							0wt％	43Mpa	29.8°	Greater than 10000	-	-	-
2wt％	51Mpa	33.8°	23.4	1.34	8.97	28.8
							9wt％	57Mpa	45.3°	15.6	1.19	6.47	32.3
15wt％	90Mpa	65.3°	11.9	1.12	3.96	34.4
							21wt％	126Mpa	70.8°	6.9	0.63	2.5	60.9
34wt％	106Mpa	77.7°	3.1	0.55	1.96	69.8

TABLE 3 layer parameters containing cellulose and tannin base

The amount of tannic acid added	Mechanical tensile strength	Area resistance omega/square	I _D /I _G	I _G /I _2D	L _a
						0wt％	43Mpa	Greater than 10000	-	-	-
2wt％	48Mpa	69	1.63	4.65	23.5
						9wt％	54Mpa	48	1.51	3.02	25.4
15wt％	60Mpa	36	1.08	2.13	35.7
						21wt％	63Mpa	24	0.92	2.1	41.8
34wt％	66Mpa	13	0.88	1.99	43.7

TABLE 4 contains tea polyphenols and tea polyphenols substrate layer parameters

Example 4

One embodiment of the invention provides a preparation method of a modified laser-induced graphene material, which converts a LIG substrate containing cellulose into graphene by laser. The method comprises the following specific steps:

s001, purifying lignin, wherein the method for purifying the lignin comprises the following steps,

(1) Acid washing, acid washing is carried out on the lignin, and the used acid comprises inorganic acid such as hydrochloric acid, sulfuric acid and the like.

(3) And (4) washing and drying, namely washing and drying the lignin.

S002. Preparation of cellulose reinforced LIG substrate containing lignin, the method comprises the following steps,

(1) Preparing a lignin-cellulose mixed solution, namely adding cellulose into a lignin solution, stirring, performing ultrasonic treatment, and emulsifying to prepare the lignin-cellulose mixed solution. The amount of added lignin is 0-41wt%, preferably 29wt%. The preferred cellulose diameter is > 1000nm.

(3) Hot-pressing to form the lignocellulose LIG base material by curing the lignocellulose wet film at 40-150 ℃ and 1-15MPa, preferably at 50-100 ℃ and 5-10MPa.

S003, laser-induced scanning is carried out,

and irradiating the lignocellulose LIG substrate by using laser to generate a graphene functional layer on the surface of the lignocellulose LIG substrate. The laser wavelength may be 9.3-10.6 μm, 625-740nm, 450-480nm, 1053nm. The laser comprises a CO ₂ Lasers, red lasers, blue lasers, femtosecond lasers, and the like. Power of laserThe range is 0-50W. The laser intensity borne by the surface of the substrate needs to be more than 3J/cm ² The preferred laser intensity is > 5.5J/cm ² . The same area of the substrate may be irradiated with a single or multiple passes as shown in fig. 12. The substrate comprises a cellulosic component.

The nanocellulose can enhance the mechanical strength and the surface hydrophobicity of the composite paper, but because the nanocellulose is small in diameter and short in length, the surface of the formed composite paper is smooth, the porosity is small and is mostly microporous, so that laser cannot penetrate through the composite paper, energy (heat) cannot be uniformly and effectively conducted into the composite paper, the graphitization of lignin can be hindered, the energy consumption is high, and the formed LIG (Ligno glass) resistance is high.

TABLE 5 substrate layer parameters with cellulose and different lignin addition levels

Adding amount of lignin	Mechanical tensile strength	Contact angle
			3wt％	70Mpa	61°
7wt％	94Mpa	64°
			13wt％	135Mpa	66°
29wt％	202Mpa	69°
			41wt％	12Mpa	77°

The nano-cellulose added in the base material layer can enhance the mechanical tensile strength of the base material layer and improve the hydrophobic property of the base material layer.

TABLE 6 substrate layer parameters containing cellulose and different nano-lignin particle sizes

The nano lignin can be better wrapped on the surface of cellulose, and the nano cellulose is protected from being decomposed in the laser irradiation process. Meanwhile, nano lignin is converted into laser-induced graphene. Thereby improving the quality of the graphene functional layer.

Table 7 contains different cellulose diameter and nano lignin substrate layer parameters

Because lignin is a rigid macromolecule, it is highly hard but somewhat brittle; cellulose belongs to semi-rigid molecules, although the strength is poor, the molecular chain flexibility of the cellulose is superior to that of lignin, and the cellulose has high polymerization degree, good molecular orientation degree and strong chemical stability. The addition of cellulose in the lignin can combine the advantages of the lignin (hardness and flexibility) and form a net structure in a composite system, so that the lignin composite paper has larger free space/pores. When the laser beam irradiates the surface of the composite paper, the laser beam can penetrate into the paper more easily, so that the paper can absorb more heat and the heat distribution is more uniform. The unique pore structure of cellulose can guide graphene to better fill the free space of paper when the surface of the paper grows, and the graphene is uniformly distributed on the surface of the paper instead of growing vertically downwards (disordered distribution). The LIG formed at this time has a smoother and flatter surface and fewer cracks. Generally, under laser scanning, lignin is easily distorted or even broken due to high temperature, so that laser-induced graphene is easily dropped from a substrate layer; compared with the prior art, due to the fact that cellulose molecules have polarity, the interaction force between molecular chains is strong, severe shape distortion is not prone to occurring, graphene growing on the surface layer of paper can be firmly grasped, and the overall mechanical stability of the modified laser-induced graphene material is improved.

Example 5

s001. Purifying lignin, wherein the method for purifying lignin comprises the following steps,

(3) And (4) washing and drying, and washing and drying the lignin.

S002, preparing the cellulose-reinforced LIG substrate containing lignin, wherein the method comprises the following steps,

(1) The preparation method comprises the steps of adding conventional cellulose or nano-cellulose into a lignin solution, stirring, performing ultrasonic treatment, and emulsifying to obtain a mixed solution of the lignin and the cellulose. The amount of added lignin is 0-41wt%, preferably 29wt%. The preferred cellulose diameter is > 1000nm.

(3) Hot-pressing to form a lignocellulose LIG substrate, curing the lignocellulose wet film at 40-150 ℃ and 1-15MPa to form a lignocellulose LIG substrate, wherein the preferred temperature is 50-100 ℃, and the preferred pressure is 5-10MPa.

S003, laser-induced scanning is carried out,

and irradiating the lignocellulose LIG substrate by using laser to generate laser-induced graphene on the surface of the lignocellulose LIG substrate. The laser wavelength may be 9.3-10.6 μm, 625-740nm, 450-480nm, 1053nm. The laser comprises a CO ₂ Lasers, red lasers, blue lasers, femtosecond lasers, and the like. The power of the laser is in the range of 0-50W. The laser intensity borne by the surface of the substrate needs to be more than 3J/cm ² The preferred laser intensity is > 5.5J/cm ² . The same area of the substrate may be irradiated with a single or multiple times. The substrate comprises a cellulosic component.

Table 8 lignin addition plain cellulose vs. nanocellulose

Parameter(s)	Adding conventional cellulose into base material	Adding nano-cellulose into base material
			Diameter of cellulose	0.1-120μm	＜100nm
Length of cellulose	0.5-5mm	0.1-1um
			I _G /I _D	0.5-3.0	0.5-3.0
I _2D /I _G	0.1-1.0	0.1-0.8
			L _a	25-150mm	25-150
Surface resistance omega/square	2-20	5-50

Conventional cellulose, namely cellulose with larger diameter and length, is added into the LIG substrate, the conventional cellulose fiber is thicker, pores formed in the LIG substrate are larger, laser can better penetrate into the LIG substrate in a deeper layer, and then LIG with higher quality is formed, and the surface resistance of the LIG is lower. Nanocellulose, namely cellulose with smaller size, is added into the LIG substrate, and the cellulose with smaller size can enable the modified laser-induced graphene material to be more compact, so that the tensile strength, the waterproof performance and the like of the material are improved.

Example 6

s001.LIG substrate preparation, the method comprises the following steps,

(1) Impregnating a cellulose layered material with a lignin solution to prepare an LIG substrate, wherein the LIG substrate contains cellulose; the mass percent of the lignin solution is 2-25 wt%.

(2) And (3) drying and curing the LIG substrate impregnated with the lignin solution by using a hot-pressing curing method. The curing temperature is 40-150 ℃, and the curing pressure is 1-15MPa; the preferred temperature is 50-100 deg.C and the preferred pressure is 5-10MPa.

S002, laser-induced scanning is carried out,

and irradiating the LIG substrate impregnated with the lignin by using laser to generate laser-induced graphene on the surface of the LIG substrate. The laser wavelength may be 9.3-10.6 μm, 625-740nm, 450-480nm, 1053nm. The laser comprises a CO2 laser, a red laser, a blue laser, a femtosecond laser and the like. The power of the laser is in the range of 0-50W. The laser intensity borne by the surface of the substrate needs to be more than 3J/cm ² The preferred laser intensity is 8-50J/cm ² . The same area of the LIG substrate may be irradiated with a single or multiple times. The LIG substrate contains a cellulosic component.

Because lignin is a rigid macromolecule, it is highly hard but somewhat brittle; cellulose belongs to semi-rigid molecules, although the strength is poor, the molecular chain flexibility of the cellulose is superior to that of lignin, and the cellulose has high polymerization degree, good molecular orientation degree and strong chemical stability. The lignin is introduced into the substrate containing cellulose, so that the advantages (hardness and flexibility) of the two materials can be combined, and a net structure is formed in a composite system, so that the substrate has larger free space/pores. When the laser beam irradiates the surface of the LIG substrate, the laser beam can penetrate into the paper more easily, so that the LIG substrate absorbs more heat and the heat is distributed more uniformly. The unique pore structure of cellulose can guide graphene to better fill the free space of paper when the surface of the paper grows, and the graphene is uniformly distributed on the surface of the paper instead of vertically growing downwards (disordered distribution). The surface of the graphene functional layer formed at the moment is smoother and flatter, and cracks are fewer. Generally, under laser scanning, lignin is easily distorted or even broken due to high temperature, so that laser-induced graphene is easily dropped; compared with the prior art, the cellulose has polarity, so that the interaction force between molecular chains is strong, the serious shape distortion is not easy to occur, the graphene growing on the surface layer of the paper can be firmly grasped, and the overall mechanical stability of the modified laser-induced graphene material is improved.

Example 7

s001, preparing a LIG base material layer containing cellulose and lignin, wherein the lignin content of the LIG base material layer is 21wt%, the particle size of the lignin is more than 500nm, and the diameter of the cellulose is 15-30um.

And S002, scanning the LIG substrate layer by laser, and inducing the surface of the LIG substrate layer to generate a graphene functional layer. The laser used is CO ₂ The laser intensity is 20-32W, the laser moving speed is 175mm/s, and the laser focal length is 0. The specific parameters and parameters of the laser-induced graphene are as follows.

TABLE 9 comparison of laser-induced graphene parameters at different laser intensities

Example 8

One embodiment of the invention provides a preparation method of a modified laser-induced graphene material, which converts a substrate containing cellulose into graphene by laser. The method comprises the following specific steps:

s001, preparing an LIG substrate containing cellulose and lignin, wherein the lignin content of the LIG substrate is 21wt%, the grain diameter of the lignin is more than 500nm, and the diameter of the cellulose is 15-30um.

And S002, scanning the LIG substrate by laser to induce the surface of the LIG substrate to be converted into a graphene functional layer. The laser used was a CO2 laser with a laser intensity of 32W, a laser movement rate of 175mm/s and a laser focal length of 0.5-2.5mm. Specific parameters and parameters of laser-induced graphene are as follows.

TABLE 10 comparison of laser-induced graphene parameters at different laser focal lengths

Example 9

s001. Purifying and modifying lignin, the method comprises the following steps,

(3) Extracting and grading with organic solvent such as acetone, butanol, and ethanol, controlling lignin molecular weight and particle size, removing non-functional components, increasing relative content of active groups, and enhancing lignin processability.

(4) And (4) washing and drying, and washing and drying the lignin.

(5) Lignin is modified, wherein the lignin modification comprises multiple chemical reactions such as oxidation, reduction, hydrolysis, alcoholysis, acid hydrolysis methoxy group, carboxyl group, photolysis, esterification, sulfonation, alkylation, halogenation, nitration, polycondensation, grafting, esterification, copolymerization and the like, and the temperature resistance and char formation performance of lignin are enhanced.

S002.LIG base material preparation and flame-retardant treatment, the method comprises the following steps,

(3) Hot pressing to form wet lignocellulose film at 40-150 deg.c and 1-15MPa to form LIG base material, preferably at 50-100 deg.c and 5-10MPa.

(4) And (3) performing flame retardant treatment, namely spraying a flame retardant on the surface of the lignocellulose LIG substrate, or infiltrating the lignocellulose LIG substrate by using the flame retardant. The flame retardant can be organic flame retardant and inorganic flame retardant, and the inorganic flame retardant can be ferric chloride solution, ferric nitrate solution, phosphoric acid, boric acid and the like; the flame retardant may be a halogen flame retardant or a non-halogen flame retardant, and the halogen flame retardant may be an organic chloride or an organic bromide.

After the LIG base material is subjected to flame retardant treatment, the LIG base material has a flame retardant effect and high temperature resistance, the ignition point of the LIG base material is improved, and the LIG base material is simulated to burn under laser. In addition, the LIG substrate does not need protective gas in the laser scanning process, and the cost and the equipment complexity are reduced. Meanwhile, the laser power can be increased, the scanning speed can be improved, and the production efficiency can be increased. After the flame retardant is added, the sheet resistance of the biomass LIG is reduced from 2000 omega/square to 80 omega/square.

And S003, performing laser induction scanning, namely irradiating the lignocellulose LIG substrate by using laser to convert a precursor in the lignocellulose LIG substrate into laser-induced graphene. The laser wavelength may be 9.3-10.6 μm, 625-740nm, 450-480nm, 1053nm. The laser comprises a CO ₂ Lasers, red lasers, blue lasers, femtosecond lasers, and the like. The power range of the laser is 30W, and the irradiation power may be 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, 100%. The laser intensity borne by the surface of the LIG substrate needs to be more than 3J/cm ² The preferred laser intensity is > 5.5J/cm ² . The same area of the LIG substrate, including the cellulose component, may be irradiated with a single or multiple timesAnd (4) dividing. During laser-induced scanning, the LIG substrate is exposed to a protective gas, which may be a reducing and inert gas, such as H ₂ 、Ar、N ₂ 、 SF ₆ Or a mixture of several gases.

Reducing or inert gas is used as protective gas, so that the hydrophobicity of the surface of the graphene functional layer can be effectively enhanced, and the flame-retardant treatment step of the biomass LIG substrate can be replaced; at SF ₆ And scanning in the atmosphere, and depositing fluorine element in the graphene functional layer to modify the graphene functional layer.

Example 10

An embodiment of the present invention provides a modified laser-induced graphene material, which includes a substrate layer and a graphene functional layer, wherein the graphene functional layer is attached to a surface of the substrate layer, as shown in fig. 9 and 10. The graphene functional layer contains laser-induced graphene and has a three-dimensional pore structure. In the structure of the modified laser-induced graphene material, part of cellulose is connected with the substrate layer and the graphene functional layer, and the part of the cellulose entering the graphene functional layer is converted into carbonized cellulose; molecules of part of cellulose and carbonized cellulose are intertwined with each other to form a net structure, and the laser-induced graphene is nested in the net structure, wherein the nested structure is shown in fig. 17.

The substrate layer contains cellulose and also contains one or more other precursors which are easy to be graphitized by laser induction, such as bio-based materials including paper and textiles, wherein the textiles can be silk, cotton, linen and the like; synthetic materials including photoresist, polyimide (PI), PI fiber paper, PI foam sponge, polysulfone polymers (such as PES), teflon (such as PTFE, FEP, PFA, ETFE), phenolic resin, ABS plastic, polystyrene polymers, etc.; mineral materials including coal, carbon black, graphene Oxide (GO), graphite.

In one embodiment of the invention, the proportion of the precursor in the substrate layer is 2wt% to 40wt%, preferably 10wt% to 30wt%. The precursor type in the base layer may be a bio-based material, preferably the bio-based material is lignin, the lignin having a particle size of 10nm to 500nm. The cellulose diameter in the base layer was > 1000nm and TEM results for different lignin addition levels are shown in FIG. 16.

The laser-induced graphene production method is characterized in that a precursor containing carbon is radiated by laser, local instant high temperature (more than 1000 ℃) is generated on the surface of the precursor, and carbon atoms are led to finish sp reaction ³ To sp ² Forming 3D porous graphene with a honeycomb structure. In the laser scanning process, carbon-carbon single bonds, carbon-carbon double bonds, and the like are broken, and elements other than carbon in the carbon precursor are volatilized at high temperature (in an air atmosphere). The cellulose in the precursor can be graphitized without being destroyed and decomposed by high temperature under the irradiation of laser with proper intensity, so that carbonized cellulose is formed, the specific beam tube structure of the cellulose is maintained, and the cellulose (including the carbonized cellulose) can still maintain a net-shaped framework structure after laser scanning.

In one embodiment of the invention, the addition amount of the precursor is more than 10wt%, which is beneficial to wrapping the cellulose fiber, protecting the cellulose from carbonization in the laser scanning process, and maintaining the stability of the structure of the bundle tube of the cellulose, so that the finally generated laser-induced graphene is better attached to the surface of the substrate layer. Too low addition of the precursor can result in too thin a carbon source layer covering the surface of the cellulose, and the cellulose cannot be effectively protected from laser irradiation. And the flexibility of the modified laser-induced graphene material can be influenced by the excessively high addition amount of the precursor.

Example 11

One embodiment of the invention provides a preferred bio-based modified laser-induced graphene material, which comprises a substrate layer and a graphene functional layer, wherein the graphene functional layer is attached to the surface of the substrate layer. The substrate layer comprises a precursor. The addition ratio of the precursor may be 2 to 45wt%, and the preferable addition ratio may be 15 to 25wt%. The precursor can be graphene oxide, polyimide and lignin. The particle size of the precursor is 10nm-500nm. The diameter of the cellulose is more than 1000nm. The preferred precursor may be lignin, graphene oxide, or polyimide.

In an embodiment of the invention, the graphene functional layer contains laser-induced graphene and has a three-dimensional pore structure. In the structure of the modified laser-induced graphene material, part of cellulose is connected with the substrate layer and the graphene functional layer, and the part of the cellulose entering the graphene functional layer is converted into carbonized cellulose; part of cellulose (containing carbon chemical cellulose) molecules are intertwined with each other to form a net structure, and part of laser-induced graphene is nested in the net structure.

Example 12

In an embodiment of the invention, the invention provides a preferred bio-based modified laser-induced graphene material, which comprises a substrate layer and a graphene functional layer, wherein the graphene functional layer is attached to the surface of the substrate layer. The graphene functional layer contains laser-induced graphene and has a three-dimensional pore structure. In the structure of the modified laser-induced graphene material, part of cellulose is connected with the substrate layer and the graphene functional layer, and part of the cellulose entering the graphene functional layer is converted into carbonized cellulose; part of cellulose (containing carbonized cellulose) molecules are mutually entangled to form a net structure, and part of laser-induced graphene is nested in the net structure.

In one embodiment of the present invention, the substrate layer contains a precursor, and the precursor can be a biomass material, including paper and textile, and the textile can be silk, cotton, linen and the like. The biomass material comprises lignin (Kraft lignin, alkali lignin, dealkalized lignin, etc.), cellulose, tannin, polyphenol (such as tea polyphenol, chlorogenic acid, apple polyphenol, cocoa polyphenol, resveratrol, etc.), and flavonoid (such as flavonol, anthocyanin, flavonoid, etc.). The biomass material has the advantages of environmental friendliness, degradability and the like.

In one embodiment of the invention, the lignin may be nano-sized, such as nano-lignin particles, having a particle size in the range of 50-500nm, which may serve as a better pore filler for occupying the intermediate nanopores.

Example 13

One embodiment of the invention provides a modified laser-induced graphene material which comprises a base material layer and a graphene functional layer, wherein the graphene functional layer is attached to the surface of the base material layer. The graphene functional layer contains laser-induced graphene and has a three-dimensional pore structure. In the structure of the modified laser-induced graphene material, part of the laser-induced graphene is nested in the net structure.

In one embodiment of the present invention, the ratio of the graphene in the graphene functional layer to the laser-induced graphene is 1 _G /I _D Is 0.5 to 5.0 _2D /I _G Is 0.1 to 1.0, L _a Is 10-40mm. The surface resistance of the graphene functional layer is 2-33000 omega/square, and the omega/square is the same as omega/cm ² . The conductivity of the graphene functional layer is 8-5500S/cm. The specific surface area of the graphene functional layer is 10-350m ² (ii) in terms of/g. The aperture of the graphene functional layer is 0-750nm. The thickness of the graphene functional layer is 0.05-350 μm. The detection method of the ratio of the graphene to the laser-induced graphene is TEM detection. The thickness of the base material layer is 0.02-0.5mm.

Example 14

One embodiment of the invention provides a modified laser-induced graphene material which comprises a substrate layer and a graphene functional layer, wherein the graphene functional layer is attached to the surface of the substrate layer. The graphene functional layer contains laser-induced graphene and has a three-dimensional pore structure. In the structure of the modified laser-induced graphene material, part of cellulose is connected with the substrate layer and the graphene functional layer, and part of the cellulose entering the graphene functional layer is converted into carbonized cellulose; part of cellulose (containing carbon chemical cellulose) molecules are intertwined with each other to form a net structure, and part of laser-induced graphene is nested in the net structure.

In an embodiment of the invention, the ratio of graphene to laser-induced graphene in the graphene functional layer is 1-1. In Raman spectrum, I _G /I _D Is 1.0 to 3.3 _2D /I _G Is 0.4 to 0.8, L _a Is 20-45mm. The area resistance of the graphene functional layer is 18-150 omega/square. The conductivity of the graphene functional layer is 50-200S/cm. The specific surface area of the graphene functional layer is 10-350m ² (iv) g. The aperture of the graphene functional layer is 0-750nm. The thickness of the graphene functional layer is 0.05-35 μm. The relative content of C in the graphene functional layer is 85wt%93wt%, a relative content of O of 5wt% to 10wt%, and a relative content of N of 2wt% to 5wt%, as shown in FIGS. 3 to 7.

In one embodiment of the present invention, the substrate layer may be a cellulose reinforced polyimide, wherein the mass ratio of cellulose to polyimide is 4. The cellulose forms a mutually staggered net-shaped structure in the base material layer, the polyimide is attached to the fiber surface of the cellulose, the liquid polyimide can also permeate into the fiber surface of the cellulose in the preparation process of the base material layer, and the polyimide fiber paper reinforced by the cellulose after the polyimide is cured has larger free space/pore compared with a polyimide film. The air permeability of the polyimide fiber paper substrate layer is 1700-2200 mL. Mm. (cm) ² ·h·mmAq) ^-1 . Tensile index of polyimide fiber paper: > 40 N.m/g, tear index: > 30mM m ² ,/g, electrical constant: 1.5-2.0, dielectric loss factor: 3.1X 10 ^-3 -6.5×10 ^-3 。

Example 15

One embodiment of the invention provides a preferred bio-based modified laser-induced graphene material, which comprises a substrate layer and a graphene functional layer, wherein the graphene functional layer is attached to the surface of the substrate layer. The graphene functional layer contains laser-induced graphene and has a three-dimensional pore structure. In the structure of the modified laser-induced graphene material, part of cellulose is connected with the substrate layer and the graphene functional layer, and part of the cellulose entering the graphene functional layer is converted into carbonized cellulose; part of cellulose (containing carbon chemical cellulose) molecules are intertwined with each other to form a net structure, and part of laser-induced graphene is nested in the net structure. The substrate comprises lignin and cellulose. In Raman spectrum of graphene functional layer, I _G /I _D Is 0.5 to 3.4 _2D /I _G Is 0.2-0.8, L _a Is 10-40mm.

In one embodiment of the invention, the substrate layer is a lignocellulosic blended composite paper: the tensile strength is 30-130MPa, and the contact angle is 30-80 degrees. Laser-induced graphene I of lignocellulose blended composite paper _G /I _D 0.5-3.0，I _2D /I _G 0.1-1.0，L _a 25-150mm, and the surface resistance is 2-20 omega/square.

In one embodiment of the invention, the substrate layer is a lignin nanocellulose blend composite paper: tensile strength is 50-250MPa, and contact angle is 50-90 degrees. Laser-induced graphene I of lignin nano-cellulose blended composite paper _G /I _D 0.5-3.0，I _2D /I _G 0.1-0.8，L _a 25-150mm, and the surface resistance is 5-50 omega/square.

In an embodiment of the present invention, the nanocellulose may enhance the mechanical strength and the surface hydrophobicity of the composite paper, but because the nanocellulose has a small diameter and a short length, the surface of the formed composite paper is smooth, the porosity is small and mostly micropores, which makes it difficult for laser to penetrate, energy (heat) cannot be uniformly and effectively conducted into the composite paper, which may hinder the graphitization of lignin, resulting in high energy consumption and high LIG resistance.

Example 16

One embodiment of the invention provides a preferred bio-based modified laser-induced graphene material, which comprises a substrate layer and a graphene functional layer, wherein the graphene functional layer is attached to the surface of the substrate layer. The graphene functional layer contains laser-induced graphene and has a three-dimensional pore structure. In the structure of the modified laser-induced graphene material, part of cellulose is connected with the substrate layer and the graphene functional layer, and part of the cellulose entering the graphene functional layer is converted into carbonized cellulose; part of cellulose (containing carbon chemical cellulose) molecules are intertwined with each other to form a net structure, and part of laser-induced graphene is nested in the net structure. The substrate comprises lignin and cellulose. The substrate layer is processed by hot pressing at 100MPa and 100 ℃. The substrate layer is scanned by laser, the laser scanning speed is 175mm/s, the laser intensity is 32W, and the laser focal length is 0, namely, the laser is focused on the surface of the substrate layer. The diameter of the cellulose in the substrate layer is 15-30um, and the particle size of the lignin is more than 500nm.

The diameter of the cellulose also affects the mechanical strength of the substrate layer, as well as the water resistance (contact angle). The cellulose added in the base material layer is nano-cellulose, the diameter of the nano-cellulose is less than 100nm, and the particle size of the lignin is more than 500nm. The base material layer is processed by hot pressing at 100MPa and 100 ℃.

The nano-cellulose added to the substrate layer can enhance the mechanical tensile strength of the substrate layer and improve the hydrophobic property of the substrate layer.

Claims

1. A modified laser-induced graphene material comprises a substrate layer and a graphene functional layer, and is characterized in that the substrate layer of the modified laser-induced graphene material contains a modified precursor, the modified precursor comprises one or a combination of a biomass material, a synthetic material and a mineral material, and the particle size of the modified precursor is 50-500nm; the modified laser-induced graphene material contains cellulose, the graphene functional layer comprises laser graphene, the cellulose is dispersed in the base material and the graphene functional layer, and all or part of the cellulose in the graphene functional layer is converted into carbonized cellulose.

2. The graphene material of claim 1, wherein the cellulose comprises cellulose at a transition region between the substrate layer and the graphene functional layer, the cellulose connects the substrate layer and the graphene functional layer, the cellulose comprises cellulose and carbonized cellulose, molecules of which are entangled with each other to form a network structure, and a part of the laser graphene is nested in the network structure.

3. The graphene material of claim 2, wherein the precursor is a biomass-based material, and the components of the biomass-based material comprise one or a combination of lignin, tannic acid, polyphenols, and flavonoids; the synthetic material comprises one or the combination of photoresist, polyimide film, polyimide fiber paper, polyimide foam sponge, polysulfone polymer, teflon, phenolic resin, ABS plastic and polystyrene polymer; the mineral material comprises one or a combination of coal, carbon black, graphene oxide and graphite.

4. The graphene material of claim 3, wherein the modified precursor is a modified lignin having at least one of epoxy groups and lipid groups.

5. The graphene material of claim 4, wherein the modified lignin is a product prepared by modification of one or a combination of Kraft lignin, alkali lignin, dealkalized lignin, lignin sulfate.

6. The graphene material according to any one of claims 1 to 5, wherein the modified precursor contains a flame retardant group, and the flame retardant group is one of a phosphoric acid group, a halogen group, a silicon group, or a combination thereof.

7. The preparation method of the modified graphene is characterized in that a laser is used for irradiating a laser-induced graphene substrate to prepare the modified laser-induced graphene material, the wavelength range of the laser is 9.3-10.6 microns, 625-740nm, 450-480nm and 1053nm, the laser intensity range borne by the surface of the laser-induced graphene substrate is 3J/cm & lt 2 & gt-40J/cm & lt 2 & gt, the laser-induced graphene substrate contains a modified precursor, and the thickness of the laser-induced graphene substrate is 0.02-0.5mm.

8. The method of claim 7, wherein the modifying step comprises one or a combination of oxidation, reduction, hydrolysis, alcoholysis, methoxy acidolysis, carboxyl group, photolysis, esterification, sulfonation, alkylation, halogenation, nitration, polycondensation, grafting, esterification and copolymerization.

9. The method according to claim 8, wherein the modification of the modification precursor is carried out by modifying the modification precursor so that the modification precursor has an epoxy group and a lipid group.

10. The method of claim 9, wherein the laser-induced graphene substrate further comprises cellulose, wherein the cellulose has a diameter of less than 100nm and an aspect ratio of 1000 to 1500; or the cellulose has a diameter of 0.1-120um and a length of 0.1-5mm.

11. The method according to claim 10, wherein the modified precursor is a modified lignin having a particle size of 10nm to 500nm.

12. The method of claim 11, wherein the modified lignin is added to the laser-induced graphene substrate in an amount of 0 to 34wt%.

13. The method of claim 12, wherein the modified lignin is added to the laser-induced graphene substrate in an amount of 21wt%.