The Effect of SiO2 Content and Shape on Mechanical Properties of Al Matrix Composites

Abstract

Physical properties and processing parameters of the reinforcing phase such as shape and content can dramatically influence the mechanical properties of the composites. In this project, the effect of different shapes of silicon dioxide or silica (SiO2) reinforcement including nanoparticle and nanotube as well as their weight percent (1, 3, 5 and 10 wt %) on the mechanical properties of aluminum (Al) composite were investigated. The silica nanotubes (SNTs) were prepared by hydrothermal methods. In order to achieve a good dispersion, Al powders were coated by cetyl trimethyl ammonium bromide (CTAB) to obtain a surface positive charge. Then, SiO2–Al powders were obtained by electrostatic self-assembly to realize the homogeneous adsorption of SiO2 nano reinforcement on Al powders. Finally, SiO2-reinforced Al matrix composites were fabricated by powder metallurgy. Characterization of composites was carried out by transmission electron microscopy (TEM), field emission scanning electron microscopy (FESEM) and Fourier transform infrared spectroscopy (FTIR). For determination of the mechanical properties of the composite, the compressive strength and density were investigated.Results showed a significant reduction in the relative density from 98% to 84% for composites containing 0 to 10 wt % of SiO2. The compressive strength exhibited a moderate increase by adding SNTs while in samples containing SiO2 nanoparticles, the mechanical properties improved and reached a peak value of 225 MPa at 5 wt % SiO2 nanoparticles (~40% increase compared to pure Al). However, a further increase in nanotubes content resulted in a considerable reduction in compressive strength. This can be attributed to the increase in porosity and agglomeration of nano reinforcement in the composite.