| We study on the diffusion and aggregation behaviors of silver atoms and clusters on charged silicone oil surfaces under high vacuum conditions. Based on the experimental results, the physical mechanism of the diffusion and aggregation process is studied by Monte Carlo simulation in this dissertation. As a result, a model of the nonequilibrium system containing atomic clusters with repulsive interactions on nonlattice substrates is established. The main conclusions obtained from the experiment are investigated by using the model. The simulation results are in good agreement with the experimental findings. At the same time, several physical phenomena, which are difficult to be observed in the experiment, are predicted and analyzed by the simulation model. This nonequilibrium model can also be used for other real systems, such as the environmental pollution control system etc.The influences on the sound absorption of the samples are measured and studied after perforated panels are covered with membranes (such as organic films, the compound films of the organic film and the metal nanofilms deposited on liquid substrates etc.), or shaped with burrs at the bottom of the holes, or penetrated with circular table-board holes. It is found that the metal nanofilms exhibit favorable characteristics of sound transmission. Futhermore, the perforated panels, covered with the compound films, possess some good qualities, such as dustproof, dampproof, anti-eroding, anti-ultraviolet radiation and anti-aging etc. In addition, our experimental results indicate that the sound absorption behavior of the samples at low frequency is improved obviously for the perforated panels with burrs at the bottom of the holes. If the diameter of the perforated holes is larger than 1mm, the sound absorption performance of the circular table-board holes is higher than that of the cylindrical holes. Otherwise, the average sound absorption coefficient of the latter is higher than that of the former. The new findings described above may be applied to the field of the noise control engineering.This dissertation is organized as following:In chapter 1, previous theoretical and experimental studies on the growth mechanism of the metal films on solid substrates are summarized in details. Firstly, the nucleation and aggregation phenomenon of atoms and atomic clusters is expatiated. Secondly, the diffusion mechanism of the clusters and its influences on the morphologies of the clusters are analyzed. Thirdly, the interactions between the clusters and substrates among the clusters and are discussed, then the simulative growth models of thin films are described systematically. Finally, we summarized the recent developments on metallic films deposited on liquid surfaces.In chapter 2, the process of the aggregation and diffusion of silver atoms on charged silicone oil surfaces has been studied through experiment. Experimental results show that, after deposition, compact Ag clusters with an average diameter of 1.2μm form first. Then the average distance between two clusters increases as the clusters diffuse towards the edge of the liquid substrate. The diffusion time t dependence of the clusters density n on the liquid substrate obeys an exponential decay, i.e, n= n0e-Oft, where Of is the time constant. In the central area of the substrate, the relative speed V between two clusters increases linearly with their distance L according to vfit= HL, where vfit is the linear fit speed of V and H is the slope of the linear fit. Both the experimental result and theoretical analysis indicate that H≈Of, which is ranged in the order of 2×10-4s-1. Due to the resolving limitation of the optical microscope, the growth process of the clusters with diameter d< 0.5μm can not be observed in our experiment. Our theoretical analysis foretells that the Ag atoms deposited on the substrate can not carry electrons, and they aggregated into clusters. When the radius of clusters is larger than a critical value, the clusters is charged, and then the charged clusters diffuse towards the sample edge, which results in the accumulation of clusters at the edge of the substrate.In chapter 3, a simulative model of the diffusion and aggregation of atomic clusters with repulsive interactions on nonlattice substrates is established and the aggregation process of the silver atoms on charged silicone oil surfaces is studied. It is found that, after the stable atomic clusters form, the number density of the atomic clusters decays with time exponentially and the time constant is Of, due to the repulsive interaction among the clusters. Statistically, the relative speed V between two clusters increases linearly with their distance L according to V=HL. We find that the constant H≈Of, which approaches zero with time t. At the early stage of the diffusion process, the average diameter of the silver atomic clusters is small. However, as the time goes on, it increases rapidly. As t≥2500 s, the diameters of all the clusters are quite similar and their average difference is less than 0.1μm. With the increase of the viscosity coefficient of the liquid substrates, the friction force increases and H decreases. A linear dependence between the friction force and H is found and the slope k≈-0.10±0.01. The critical radius r1 of the clusters, above which the atomic clusters start to carry charges, relates closely to the atomic affinity. It is found that H and Of increase slowly with r1 and their slopes are 1.2±0.3 and 1.6±0.6, respectively. Our simulation results are in good agreement with the experimental findings. It should be mentioned that the model for the nonequilrium atomic clusters system with repulsive interactions is very useful to study microscope film systems through utilizing the controllable interaction between clusters and substrates, particularily, the interaction between the atomic clusters and electricmagnetic fields. The model can also be applied to other research fields, such as the field of the environment pollution control system etc.In chapter 4, the influences on the sound absorption of the samples are measured and studied after perforated panels are covered with membranes (such as organic films, the compound films of the organic film and the metal nanofilms deposited on liquid substrates etc.), or shaped with burrs at the bottom of the holes, or penetrated with circular table-board holes. Experimental results indicate that, when the incidence orientation of sound wave is perpendicular to the perforated panel and its frequency is in the range of 100Hz to 2000Hz, the increment or decrease of the sound absorption coefficient is lower than 0.1 after the perforated panels are covered with the organic films, whose thicknesses are 0.1mm. The maximum difference among the sound absorption coefficients is less than 0.03 no matter whether the organic film is covered with the metal nanofilms. When the frequency of the sound wave is lower than 1000Hz, the sound absorption coefficient increases with the thickness of the metal nanofilms. For both the situations that the microperforated panels possess burrs at the bottom of the holes or not, they have the different sound absorption coefficients when the perforation ratio changes. As the perforation ratio decreases, the peak of the sound absorption coefficient shifts to lower frequency. For a fixed perforation ratio, the larger the depth of the cavum is, the lower the frequency at the peak of the sound absorption coefficient will be. Compared with the perforated panels with burrs at the bottom of the holes, the perforated panels without burrs exhibit the higher resonant frequency, and the sound absorption coefficient of the former is higher than that of the latter below the resonant frequency. Otherwise, the sound absorption coefficient of the former is lower than that of the latter. Theoretical analysis shows that the experimental findings are in aggrement with the theoretical resulsts of the perforated and microperforated panels.
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