| Summary: | In this project, yolk-shell microspheres were fabricated as sound absorbing particles to be incorporated into paint and coating systems. The yolk-shell microspheres synthesis process consists of two major parts: (i) fabrication of polymer microspheres polystyrene copolymer poly4-vinylpyridine (PS-co-P4VP) as template for adsorption of metal ions, and (ii) fabrication of silica shell to obtain yolk-shell microspheres. Further two types of core metal nanoparticles were fabricated: Ag@SiO2 and iron oxides@SiO2. Morphology and structure of microspheres were characterized using scanning electron microscopy (SEM), transmission electron microscopy (TEM), thermogravimetric analysis (TGA), x-ray diffraction (XRD) and, dynamic mechanic analysis (DMA). While TGA was employed to evaluates the thermal properties.
The yolk-shell microspheres were incorporated into polyacrylic acid (PAA) matrix and casted to form thin films with thickness of ~50 μm. Sound impedance tube was used to measure the sound absorption coefficients of films in frequency range of 500 Hz to 6400 Hz. Results showed that Ag@SiO2 microspheres have an overall higher sound absorption coefficient compared to iron oxides@SiO2 microspheres. This was attributed to the easy mobility of Ag nanoparticles in the hollow microspheres, which converted sound energy to kinetic energy and subsequently heat energy. The total energy required for the nanoparticles to move in the hollow microspheres should be investigated in the future using atomic force microscopy (AFM).
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