Search

CN-121990563-A - Preparation method of graphene/nano bacterial cellulose composite material

CN121990563ACN 121990563 ACN121990563 ACN 121990563ACN-121990563-A

Abstract

A preparation method of the graphene/nano bacterial cellulose composite material comprises the steps of (1) dispersing nano cellulose and graphene in an aqueous medium to form a uniform suspension, and (2) constructing a three-dimensional porous skeleton through freeze drying. The raw materials are green and low in cost, cellulose sources are wide (such as wood pulp and straw), and the carbonization process has no noble metal or high pollution reagent. Can be produced in large scale, is suitable for continuous carbonization (such as infrared radiation heating) from roll to roll, and is compatible with the existing carbon material production line.

Inventors

  • ZHENG XIAOTIAN
  • ZHANG GUIQIN
  • Mou Yirui
  • ZHOU JIALIN
  • LIU ZHAOPING

Assignees

  • 宁波石墨烯创新中心有限公司

Dates

Publication Date
20260508
Application Date
20251225

Claims (10)

  1. 1. The preparation method of the graphene/nano bacterial cellulose composite material is characterized by comprising the following steps: (1) Dispersing bacterial cellulose and graphene oxide in an aqueous medium to form a uniform suspension; (2) And (3) constructing a three-dimensional porous framework by freeze drying the suspension in the step (1) to obtain aerogel.
  2. 2. The preparation method of the graphene/nano bacterial cellulose composite material according to claim 1, wherein the specific operation process of the step (1) is as follows: Dispersing graphite oxide with the solid content of 42% in water to obtain a graphene oxide solution with the mass fraction of 1-3%, then adding NaOH or ammonia water to adjust the pH to be neutral, and then using a high-speed dispersing machine with the rotating speed of 1500-4000rmp and the stirring time of 10-50min to obtain a graphene oxide dispersion liquid; (1.2) freeze-drying the prepared graphene oxide dispersion liquid to obtain graphene oxide powder nano-sheets; (1.3) mixing bacterial cellulose with solid content of 8% with pure water, wherein the mass ratio of the bacterial cellulose to H 2 O is 0.5-0.8:1, and carrying out ultrasonic treatment for 30-60 min; and (1.4) adding the graphene oxide powder nano-sheets obtained in the step (1.2) into the solution obtained in the step (1.3), stirring and carrying out ultrasonic treatment for 60-120 min to obtain a uniform suspension.
  3. 3. The preparation method of the graphene/nano bacterial cellulose composite material is characterized in that the ultrasonic dispersion power is 50W-100W, the time is 15min-60min, and the mass ratio of the graphene oxide nano sheet to the solute in the bacterial cellulose solution is (1-3): 1.
  4. 4. The preparation method of the graphene/nano bacterial cellulose composite material according to claim 1, wherein the specific operation process of the step (2) is that the suspension obtained in the step (1) is poured into a polytetrafluoroethylene rectangular mold, then liquid nitrogen is added, so that a porous array structure is formed, the formed sample is removed from the mold after freezing for 0.5-2 hours, the freezing is continued for 0.5-2 hours, ice crystals are sublimated and removed in a vacuum and low-temperature environment, the porous structure is reserved, and the sublimation and ice crystal removal operation lasts for 24-72 hours, so that the aerogel is obtained.
  5. 5. The method for preparing graphene/nano bacterial cellulose composite material according to claim 4, wherein the vacuum is less than 10 Pa, the low temperature is-50 ℃ to-80 ℃, the mold is placed on a pre-frozen copper block, and meanwhile, a trapezoidal mica block is placed in a polytetrafluoroethylene mold to form a temperature gradient in the horizontal and vertical directions in the mold.
  6. 6. The preparation method of the graphene/nano bacterial cellulose composite material according to claim 4, wherein the prefreezing temperature of the copper block is close to-70 ℃, and the temperature after adding liquid nitrogen is-196 ℃.
  7. 7. The method for preparing the graphene/nano bacterial cellulose composite material according to claim 1, wherein the preparation method further comprises the step of (3) optionally performing gradient carbonization treatment, namely heating the aerogel obtained in the step (2) to 200-1200 ℃ at a temperature of 2-10 ℃ per min in an inert atmosphere, and preserving the heat for 1-5 hours to obtain the carbonized electromagnetic shielding material.
  8. 8. The method for preparing the graphene/nano bacterial cellulose composite material according to claim 7, wherein the temperature is raised to 300-600 ℃.
  9. 9. The preparation method of the graphene/nano bacterial cellulose composite material according to claim 7, wherein the specific operation process of the step (3) is as follows: (3.1) in the first stage, the room temperature is raised to 200-300 ℃, the temperature raising rate is 2-5 ℃ per minute, and the temperature is kept for 0.5-2 hours; (3.2) in the second stage, continuously heating to 300-600 ℃, heating at a temperature of 5-10 ℃ per minute, and preserving heat for 1-3 hours.
  10. 10. The preparation method of the graphene/nano bacterial cellulose composite material according to claim 7, wherein the specific operation process of the step (3) is that the room temperature is raised to 200-300 ℃, the temperature raising rate is 2-5 ℃ per minute, the temperature is kept for 0.5-2 hours, the carbonized GO/CNF electromagnetic shielding material is obtained, or the temperature is raised to 600 ℃ in stages at the rate of 2-10 ℃ per minute, and the temperature is kept for 0.5-2 hours, so that the carbonized GO/CNF electromagnetic shielding material is obtained.

Description

Preparation method of graphene/nano bacterial cellulose composite material Technical Field The application belongs to the technical field of electromagnetic functional composite materials, and particularly relates to a preparation method of a graphene/nano bacterial cellulose composite material (electromagnetic functional material) with carbonization dependence and electromagnetic response characteristics. Background With the rapid development of 5G communication, internet of things and national defense stealth technologies, electromagnetic functional materials are required to meet various requirements. The multi-band compatibility comprises the wide-band response capability of covering low frequency (1-10 GHz, civil communication) to high frequency (10-40 GHz, radar wave band), functional adjustability, light weight and high strength, adaptation to the requirements of aerospace and wearable equipment on the light weight and mechanical reliability of materials, and environmental friendliness, wherein the same material needs to have the dual-mode functions of electromagnetic wave absorption, reflection reduction and electromagnetic shielding interference suppression under different scenes, and the problems of high energy consumption preparation or non-degradability of traditional materials are avoided. The prior art still has defects such as limitation of single-function electromagnetic materials, wherein the shielding materials in the prior art comprise metal-based materials which have high density, are easy to corrode and mainly reflect electromagnetic waves so as to cause secondary electromagnetic pollution, and conductive polymers which have poor high-frequency loss performance (shielding effectiveness suddenly drops when the high-frequency loss performance is more than 10 GHz) and insufficient thermal stability. The microwave absorbing material in the prior art comprises ferrite/magnetic particles which have high density and narrow frequency band (only cover 2-8 GHz) and are difficult to meet the light weight requirement, and graphene aerogel which has low density and high dielectric loss, but has high brittleness (strain <5% fracture) and is difficult to process and form. Besides single-function electromagnetic materials, the dual-function electromagnetic materials have defects at present, such as the increase of thickness of the dual-function electromagnetic materials or the complexity of control circuits due to the dependence of a multi-layer structure (such as an absorption layer and a shielding layer) or external stimulus (such as voltage/temperature), and secondly, the function switching of the dual-function electromagnetic materials is irreversible (such as the non-recovery after chemical modification), so that the repeated use of the dual-function electromagnetic materials is limited. Patent CN112341689A discloses graphene/nano bacterial cellulose aerogel, which is only used in the adsorption field and does not relate to electromagnetic performance regulation, patent US2018032757A1 adopts a chemical reduction method to prepare a conductive composite material, and a hydrazine toxic reducer is used in the process, so that the method does not accord with the green manufacturing trend. Disclosure of Invention In order to solve the technical problems, the application provides a preparation method of a graphene/nano bacterial cellulose composite material, which can realize that hydroxyl groups in Bacterial Cellulose (BC) molecular chains and Graphene (GO) oxygen-containing functional groups form a hydrogen bond network to form a local dielectric gradient to induce interfacial polarization loss, and can realize that amorphous Carbon (CNF) bridged graphene sheets are formed by cellulose pyrolysis to form a three-dimensional continuous conductive network in a carbonization state, and electromagnetic shielding is realized through free carrier movement. In order to solve the technical problems, the technical scheme adopted by the application is that the preparation method of the graphene/nano bacterial cellulose composite material comprises the following steps: (1) Dispersing bacterial cellulose (nanocellulose) and graphene oxide in an aqueous medium to form a uniform suspension; (2) And (3) constructing a three-dimensional porous framework by freeze drying the suspension in the step (1) to obtain aerogel. Further, the specific operation process of the step (1) is as follows: (1.1) dispersing graphite oxide with a solid content of 42% (the graphite oxide with the solid content of 42% is in a block shape in a wet state modified by ammonia water or sodium hydroxide solution, and the rest 58% is ammonia water or sodium hydroxide solution) in water to obtain a graphene oxide solution with a mass fraction of 1-3, then adding NaOH or ammonia water to adjust the pH to be neutral, and then using a high-speed dispersing machine with a rotating speed of 1500-4000rmp and stirring time of 10-50min to obtain a graphene