Applications Of Carbon Nanocomposites In Anticorrosive Coatings And Flexible Sensors

Graphene and carbon nanotubes,with amazing comprehensive properties,have been hot materials for research since discovery,arousing great interest in both scientific research and industrial applications.Due to the continuous development of usability,carbon nanomaterials have been identified as an ideal reinforcement for composite materials,which have been applied in the fileds of metal matrix composites,anti-corrosion coatings and flexible sensors,and certain research results have been achieved.However,there are still some problems that need to be solved in this research.Carbon nanomaterials have great application prospects as reinforcing phases of metal composites.At present,most of them prepared by powder metallurgy methods,which may form oxides during high temperature heating and reduce the purity of the material.There are few studies on the preparation of metal-graphene composite coatings by electroless plating.In addition,the dispersion of carbon nanomaterials in plating solution is also the focus of research.Due to the excellent mechanical properties and barrier properties,graphene and carbon nanotubes have a good enhancement effect on anti-corrosion coatings.It is well known that the dispersibility of the reinforcing phase in the polymer coating is very important,which is a necessary prerequisite for improving its performance.The good dispersion of carbon nanomaterials in the coating is also an urgent problem to be solved.Modification of carbon nanomaterials is a common method,which may reduce the inherent properties of carbon nanomaterials,and increase the complexity of the preparation process.Therefore,the development of nano-reinforced phases with good dispersibility will promote the further development of corrosion resistant coatings.Carbon nanomaterials also have shown great potential in the field of flexible strain sensors,but the contradiction between high sensitivity and large sensing range has not been completely solved,and the challenge of high performance and simplicity and economy is still the focus of exploration and research and development.Based on the hot issues and stratedies discussed above,this paper conducts relevant research.Metal-graphene composite coatings were prepared by electrodeposition and chemical deposition methods,and the performance of the composite coatings and the enhancement of graphene were systematically studied.Taking advantage of the synergy between carbon nanomaterials,a kind of GO+CNTs hybrid reinforcement phase with good dispersibility was prepared,which was used as an anti-corrosion coating.Taking advantage of the excellent electrical conductivity and length-diameter ratio of carbon nanotubes,together with nanocarbon black,superhydrophobic conductive polymers with good mechanical properties were prepared and used for wearable flexible sensors.The full text consist of eight chapters,the main contents are as follows:In the first chapter,the basic properties of carbon nanomaterials represented by graphene and carbon nanotubes,the research on metal-graphene composite coatings,carbon nanomaterials reinforced polymer anticorrosion coatings,and progress of carbon nanocomposite based flexible sensors are introduced.At the same time,the background of the topic,research sources and the main work of this thesis are briefly described.The second chapter is the experimental part,which introduces the main experimental materials,instruments,preparation techniques and characterization methods involved in this thesis.Mainly include copper-graphene and zinc-nickel alloy-graphene composite coating,graphene oxide+carbon nanotube synergistically enhanced hydrophobic polyurethane coating,PDMS/（CB+CNTs）/TPU and PDMS/（CB+CNTs）/EB conductive composites.The characterization methods mainly include the microstructure and composition of the samples,mechanical properties,corrosion resistance,hydrophobicity,sensing properties of conductive materials,durability,and detection of human motion.In the third chapter,the Cu-Gr composite coating was prepared by using electroless plating.The surface morphologies,microstructures and properties of the coatings were evaluated by different techniques and characterization methods.The co-deposited Gr is evenly distributed in the coating,resulting in grain refinement and surface morphology change.When the addition amount of GO in the electroless plating solution was 60 mg/L,the optimal value,the hardness and elastic modulus of the Cu-Gr composite coating reached the best values of 3.46 GPa and 96.2 GPa.The E_corr,i_corr and corrosion inhibition efficiency of the coatings were optimized.Compared with 6.45 mil/a of pure Cu coating,the minimum corrosion rate of Cu-Gr composite coating is only 0.05 mil/a,indicating that it can effectively inhibit the corrosion of chloride ions.This method is simple and safe to operate,without external power supply and has broad application prospect.In the fourth chapter,the Zn-Ni alloy-Gr composite coating was prepared by using pulsed-reverse electrodeposition.The evenly distributed Gr increases the nucleation sites for metal ion reduction,resulting in grain refinement and dense structure.The microhardness of the composite coating increased from 1.97 of pure Zn coating and 2.02 GPa of Zn-Ni alloy coating to 4.68 GPa,and elastic modulus increased by 39%and 57%,respectively.The corrosion resistance of the coating in simulated seawater was tested by the electrochemical methods.The corrosion rates of pure Zn coating and the Zn-Ni alloy are 109 mil/a and 37.66 mil/a,while the lowest corrosion rate of the Zn-Ni alloy-Gr composite coating is only 1.30 mil/a,indicating that the corrosion resistance of Zn-Ni alloy-Gr composite coating in chloride solution can be improved effectively,and the effect of Gr on coating morphology,permeability resistance and barrier effect is explained.In the fifth chapter,a method for preparing hydrophobic（GO+CNTs）-HPU composite coating via a two-step process is introduced.Firstly,a well dispersed GO+CNTs synergistic reinforcement was prepared by usingπ-πbonding between GO and CNTs,which was used in polyurethane coatings.Then the micro-nano structure imitating the lotus leaf surface was constructed on the coating by using nano casting technology.The contact angle of the hydrophobicity coating is increased from70°of the original PU to 121°.The fracture morphology also changed obviously,the fracture cross-section of the composite coating presented many tearing ridge and dimples,indicating that the fracture mode has changed from brittle fracture to ductile fracture.The corrosion inhibition efficiency of（GO+CNTs）-HPU coating remained98.35%compared with 35.64%of pure PU coating after 20 days of immersion in simulated seawater.This work provides a kind of environment-friendly and simple process for preparing hydrophobic composite PU coating.In the sixth chapter,the thermoplastic polyurethane fiber film was used as polymer matrix,nanocarbon black and carbon nanotubes as conductive nanofillers,and then modified with low surface energy PDMS to prepare superhydrophobic conductive polymer PDMS/（CB+CNTs）/TPU.On the one hand,the modification of carbon nanomaterials endows TPU fiber good electrical conductivity,and on the other hand,leads to the increases of surface roughness and hydrophobicity,and its static contact angle reached up to 152°.The tensile strength of composite was increased from 5.88 of original TPU to 8.88 MPa,while the elongation at break maintained at the level of 385%.The flexible strain sensor prepared by the PDMS/（CB+CNTs）/TPU composite is light and comfortable,convenient,and has excellent sensing performance.The highest GF value could reach 49863.5,with excellent repeatability and durability in cyclic stretch-release test（50%strain）,and which could be used to detect subtle body movement monitoring including breathing,coughing,and speaking.In the seventh chapter,a superhydrophobic conductive polymer PDMS/（CB+CNTs）/EB was prepared by swelling method using a common elastic band as polymer matrix,and carbon nanomaterials as conductive nanofillers.Compared with pristine EB,the elastic modulus and tensile strength of the PDMS/（CB+CNTs）/EB composite were increased by 37.5%and 59.2%,respectively,and the superelasticity of EB was preserved,with a maximum strain range of 996.5%.The PDMS/（CB+CNTs）/EB composite based strain sensor has excellent sensing performance,the sensitivity could reach 648.82 in the strain range of 979.9-996.5%.Moreover,theΔR/R₀ value increased monotonically in the entire strain range,and the conductive network is not completely disconnected.After 3000 cyclic stretch-release tests（100%strain）,it still output a stable sensing signal,which could be used to monitor human body motions including large and subtle body movements,exhibiting great application and development prospects.The eighth chapter summarizes the main content of the full thesis.In the latter part,the research achievements,including published papers and applied patents,academic conferences and awards during the graduate period are introduced.At the end of the thesis is the acknowledgement to tutor,fimily,and students of the research group,as well as the author’s resume.