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TiO2 prepared by the sol–gel method and adding 30 wt.% of polyvinylpyrrolidone (PVP) has been proved to be efficient in the photodegradation of methylene red under ultraviolet (UV) light. The same powder was also found to be photoactive under sunlight in this research. TiO2 powders with various contents of added PVP were prepared and characterized by XRD, diffuse reflectance spectroscopy (DRS), etc. It was found that the presence of PVP in the sol–gel process can reduce the transformation temperature from anatase to rutile phase and the crystallite size of TiO2. At the same time, a unique coexistence structure of the anatase and rutile phases was obtained in these materials. [Copyright &y& Elsevier]

Abstract: Pure aluminum matrix composite reinforced with a high volume fraction of silicon particles (Al/Sip) was fabricated by gas-pressured infiltration. The results of four point flexural strength tests show that Al/Sip has low flexural strength. The analysis of the fractograph reveals the fracture mechanism of Al/Sip. The fracture of Al/Sip is primarily dominated by the fracture of brittle silicon particles and the subsequent link up of damage through the matrix. The pre-existent microcracks in silicon particles that were made during the process of compacting will also lower the flexural strength of Al/Sip composite. The hybrid particle reinforced pure aluminum matrix composite (Al/Sip+SiCp) was fabricated in the same way. Results show the flexural strength can be improved by 11.3% compared with Al/Sip when 6 vol.% silicon particles are replaced by silicon carbide particles with the same volume fraction and size. The reason is that SiCp with higher fracture stress and higher elastic modulus can prevent the rapid expansion of cracks through the composite and lower the stress in silicon particles. [Copyright &y& Elsevier]