An Exfoliation Approach For Industrial-scale Production Of Graphene Sheets And High Performan Graphene Sound Source Devices

Graphene is a new type of carbon material.It has a single-layer graphitic structure of carbon atoms that are tightly arranged in a two-dimensional honeycomb lattice.Because it has excellent characteristics(e.g.,high electrical conductivity,excellent room temperature thermal conductivity,high optical transmittance,and high strength)and is ultra-thin and ultra-light,graphene is useful for a wide variety of applications and has huge development prospective.As a new high-performance material,graphene can be widely used in new energy vehicles,electronic information systems,high-performance composite materials,biomedicine materials,and aerospace materials and so on.Since being discovered in 2004,graphene has attracted much attention from academic and industrial researchers.However,since the realization of practical graphene-based applications requires high-quality materials,the large-scale preparation of high-quality graphene materials remains a challenge,and the use of graphene in practical applications should be explored in the future.As described in this thesis,a series of studies were performed,focusing on the use of graphene in acoustics,the mass preparation of graphene powder through nondestructive methods,and the use of copper foils to synthesize large-area graphene films.This thesis is divided into five parts,which have different themes.The first chapter is the introduction,which introduces the basic structure,properties,and categories of graphene while describing common characterization methods and applications of graphene.The introduction also describes the state of research in this field and the contents of this thesis.The second chapter discusses the use of copper foil for the preparation of large-scale graphene,which was realized using a positive-pressure annealing method.The third chapter covers the preparation of macroscopic quantities of graphene using a mechanical exfoliation method and suggests a potential large-scale preparation approach.The fourth chapter describes the preparation of a graphene woven fabrics and its application in the field of acoustics.The fifth chapter is a summary of the entire work and provides an outlook for future research directions.The specific contents of chapters two through four include:Chapter Two.In this chapter,a positive-pressure annealing method was proposed employing a variety of copper foil substrates for the preparation of large-area graphene thin films.The copper substrates annealed under positive-pressure conditions were sensitive to annealing pressure and time during the processing of the large-area graphene films.The annealing temperature,gas ratio,temperature,and growth pressure can be adjusted within a relatively wide range,allowing the process to be universall)applicable to different needs.This work overcomes the limitation of copper foil used in the preparation of large-area graphene on copper substrates.Meanwhile,the cleanliness of the adhesive was improved by adding photoresist to the PMMA/methyl ether solution.The smoothness of the graphene synthesized on the copper substrates was also improved by replacing the frosted quartz tube with a smooth quartz tube.Roll-to-roll transfer of large-area graphene films was also achieved through the combination of a computer screen film and a molding machine.Chapter three.In the past 12 years,graphene has attracted great interest from basic-science researchers and those pursuing potential commercial applications,because of the many unprecedented intrinsic characteristics of graphene.In order to satisfy the increasing demand for high-quality graphene sheets,the industrial-scale development of graphene through a reliable,environmentally friendly,and low cost process is crucially needed.In this chapter,a new stone-grinding exfoliation process is introduced that enabled a size-controlled mechanical exfoliation method for the mass production of a few layers of defect-free graphene flakes.The exfoliated graphene sheets exhibited no defects.The method for the mechanical exfoliation of graphite presented in this chapter allowed the controlled preparation of hundreds of liters of graphene dispersions,leading to proposed approaches for industrial graphene production.The size of the prepared graphene sheets was controlled by adjusting the size of the original graphite materials and the filtering conditions,allowing the different requirements of diverse applications to be met.Chapter four.Chemical vapor deposition was used to prepare a graphene woven fabrics composed of multiple overlapping graphene ribbons.The raphene woven fabrics produced sound when excited with an electric field.This phenomenon was caused by the thermo-acoustic effect.Because of the very low heat capacity per unit area of the raphene woven fabrics,the sound source device performed similarly to a single layer of graphene.Moreover,the graphene woven fabrics could be placed on high porosity substrates,which are inaccessible to single-layer graphene.This reduced heat loss and improved the thermo-acoustic effect.Because of the transparency,flexibility,and mechanical and biological compatibility of the prepared graphene woven fabrics,the sound source can be used in a wide variety of applications.In this thesis,the thermo-acoustic effect of the graphene woven fabrics was tested on various substrates.Chapter five:we have summaried the entire work of this thesis and provides an outlook for future research directions.