Theoretical And Experimental Research On Photoacoustic Effect Of Graphene Film

The sound of photoacoustic effect of the solid comes from the heat that is transferred from the solid to the surrounding medium after photo-thermal conversion.The low photoacoustic conversion efficiency is the main factor hindering the application of photoacoustic technology.In this paper,the graphene film was taken as the research object,and its photoacoustic effect mechanism was deeply studied.With the goal of improving the photoacoustic efficiency of thin films,the sound field characteristics of graphene films and their influencing factors were studied in depth.The heat transfer characteristics of the photoacoustic effect of graphene films were investigated,and the transient temperature rise law and steady-state temperature distribution were analyzed.The main research contents were as follows:(1)From the perspective of thermoelastic coupling,considering the film heat capacity and substrate heat dissipation,the sound pressure formulas of near-field and far-field for the photoacoustic effect of graphene films were derived.Using the acoustic modules(thermo-viscous acoustics and pressure acoustics)in the COMSOL Multiphysics simulation software,the photoacoustic field distribution of graphene film under different conditions was simulated to initially verify the correctness of the model.(2)An acoustic experiment platform was set up to perform photoacoustic experiments on graphene films with different substrates.The theoretical values of the photoacoustic effect agreed well with the experimental measurements,which effectively verified the correctness of the photoacoustic model.The graphene films had good high-frequency response performance,and the photoacoustic signal output by the film was linearly related to the incident laser power;the relationship between the photoacoustic sound pressure of the film in the far field is inversely proportional to the distance of the measuring point;The photoacoustic performance of graphene films with different substrates was different.The performance of graphene on aluminum is significantly better than graphene on PET and PDMS,whereas the performance of graphene on glass is worse than the first three(3)On the basis of verifying the correct photoacoustic model,by calculating the local sensitivity coefficients of the relevant parameters of the film,the influence degree of the relevant parameters on the photoacoustic efficiency of the film was analyzed.The research showed that as the film thickness increases in the range of 5-15nm,the sensitivity coefficient is less than 0.01;the sensitivity coefficient of the substrate Thermal effusivity remains at about 1.88;the sensitivity coefficients of thermal conductivity,density and specific heat of ambient gas were 0.97,1.09,and 0.9,respectively.(4)Based on the energy conservation equation,a photoacoustic effect heat transfer model for graphene films was established,and the expression of transient temperature rise on the surface of graphene films was derived.Temperature rise tests were performed on graphene films with different substrates.The research shows that the steady-state response time of the film was long,the steady-state temperature of the film is positively correlated with the ambient temperature at the beginning,while the steady-state temperature response time was independent of the ambient temperature,and the relationship between the input power and surface steady-state temperature was linear;The time to reach steady state temperature of the graphene film on PDMS substrate was much longer than the steady state response time of graphene film on PET substrate;the steady state temperature distribution of the film had regularity,and the surface temperature of the film reaches the maximum at the center point of the film,and it decays in a circle to the surroundings,the temperature difference between the edge of the film and the center of the film is large.