Modified Silicon Nitride Nanopowder Coating and its Influence on the Dynamic Mechanical Property of Polymethyl Methacrylate Nanocomposite

In this study we modified nanoparticles to prepare Si ₃ N ₄ /PMMA nanocomposites. Surface modification of nano-Si ₃ N ₄ powder was carried out by using a suitable modification agent (NDZ-102) for improving nanoparticles dispersion stability. The surface properties of Si ₃ N ₄ nanoparticles were systematically investigated by Fourier transform infrared spectroscopy, thermogravimetric analysis, size distributions analyzer, surface free energy measurement and transmission electron microscopy (TEM). We concluded that 11% of NDZ-102 is the appropriate dosage of the coupling agent used to modify the surface of Si ₃ N ₄ nanoparticles. Based on TGA and the spectra of FTIR, our results indicate that the coupling agent molecules are linked to the nanoparticles by chemical bonds, and that the surface of nanoparticles were coated by an organic layer. On the basis of the surface free energy experiments, it can be seen that there is an obvious improvement in the nanoparticles hydrophobicity after modification. Particle size tests and TEM reveal that the average diameter of the modified nano-Si ₃ N ₄ is less than 100 nm and the nanoparticles have good dispersion in the solvent. It has also been found that the dynamic mechanical property of polymethyl methacrylate nanocomposite shows regular changes with an increasing powder content.