Preparation And Properties Of Fractal-Structured Silver Particle Conductive Paper

With the rapid development of science and technology,traditional electronic products are gradually unable to meet the needs of people's daily lives.Flexible electronic products have attracted the attention of scientific researchers due to their excellent flexibility,conductivity,and portability,and are widely used in many fields such as flexible sensors,supercapacitors,solar cells,and flexible electrodes.Among them,conductive paper has received extensive attention due to its green substrate,degradability,flexibility,and good biocompatibility.As the core part of building flexible electronic products,conductive paper not only requires excellent conductivity and mechanical properties,but also maintains good stability when subjected to cyclic stress.However,based on the current research,the electrical conductivity and mechanical properties of conductive paper need to be improved.Herein,cellulose with abundant reserves,low price,degradable and high mechanical strength was selected as the flexible electronic substrate.Fractal structure silver particles(FSSPs)were used as the conductive material to prepare conductive paper.The conductive paper with high conductivity,mechanical properties and stability was prepared by adjusting the interaction between FSSPs and fiber,the morphology of FSSPs,exploring the influence of morphology and addition amount of FSSPs on paper conductivity and mechanical properties.The specific research contents of this paper are as follows:(1)A physical blending method was used to prepare FSSPs/cotton fiber conductive paper and apply it to flexible circuits.Firstly,FSSPs with different morphologies were prepared by liquid-phase reduction method,and then conductive paper was prepared by physical blending method.The effects of the molar ratio of silver nitrate solution to hydroxylamine solution and the flow rate of the solution on the morphology and crystallization properties of FSSPs in the process of liquid phase reduction,and the changes of the properties of conductive paper with different mass ratios of cotton fiber to FSSPs in the process of physical blending were investigated.Through a variety of analysis and characterization methods,it was confirmed that the prepared FSSPs with three morphologies all had three-dimensional structure and good crystal structure.When the mass ratio of the second-order morphology FSSPs(FSSPs-2)to the cotton fiber was 2:1,the electrical conductivity can reach 90.1 S·cm-1,and the mechanical performance is 2.4 MPa.When the mass ratio of the third-order morphology FSSPs(FSSPs-3)to the cotton fiber was 2:1,the electrical conductivity can reach 79.5 S·cm-1,and the mechanical performance was 2.0 MPa.The prepared conductive paper was applied to a flexible circuit,and the result showed that the prepared conductive paper still had good conductivity after bending and folding.(2)To further improve the binding force between the FSSPs and the fiber,a new method of in-situ reduction of FSSPs on the surface of cotton fiber was developed.In this method,the cotton fiber surface was chemically modified,and then silver ions were absorbed on the fiber surface for in-situ reduction.The growth mechanism of FSSPs on the fiber surface,the change of morphology of FSSPs and the change of conductivity and mechanical properties of conductive paper with different mass ratio of silver to cellulose were explored.The results showed that when the mass ratio of silver to cellulose was 1.5:1,the conductive paper showed excellent conductivity(sheet resistance was 0.02 ?·sq-1,conductivity was 1041.33 S·cm-1)and certain mechanical properties(3.08 MPa).At the same time,after 1000 bending cycles,the sheet resistance of the conductive paper only increased by 0.004 ?·sq-1 compared with the initial value,showing excellent mechanical stability;after 31 days in the air,the sheet resistance didn't change significantly;finally,by immersing the conductive paper in the simulated human sweat environment for 8 hours,the sheet resistance only increased by 0.001 ?·sq-1 compared with the initial value.It was proved that the conductive paper had excellent mechanical cycle stability,oxidation resistance and conductivity stability in simulated human sweat environment,which can be applied in the field of flexible wearable.(3)In order to improve the mechanical properties of conductive paper,a new method of preparing conductive paper by in situ deposition of FSSPs on the surface of filter paper was developed.In the process of experiment,the surface of filter paper was chemically modified,and the FSSPs were deposited in situ after the adsorption of silver ions on the surface.The changes of surface elements and functional groups before and after the filter paper modification were studied,and the influence of different deposition time on the morphology of FSSPs on the surface of filter paper,the conductivity and mechanical properties of the paper were studied.The results showed that when the deposition time was 30 min(the mass ratio of silver to cellulose was about 0.58:1),the conductive paper had good conductivity and excellent mechanical properties(the sheet resistance was 1.47 ?·sq-1,and the mechanical property of the paper was 6.17 MPa).At the same time,after 500 bending cycles,the sheet resistance of conductive paper only increased by 0.06 ?·sq-1,indicating that the conductive paper had good mechanical stability.The results showed that the sheet resistance of conductive paper increased by 0.04 ?·sq-1 after 15 days in air,which had excellent antioxidant property.