Enhanced photocatalytic performance of cementitious material with TiO_2@Ag modified fly ash micro-aggregates

A TiO2 photocatalyst is coated on the surface of a zeolite fly ash bead（ZFAB） to improve its dispersability and exposure degree in a cement system.The application of Ag particles in TiO2/ZFAB modified cementitious materials is to further enhance the photocatalytic performance.Various Ag@TiO2/ZFAB modified cementitious specimens with different Ag dosages are prepared and the characteristics and photocatalytic performance of the prepared samples are investigated.It is observed that the multi-level pore structure of ZFAB can improve the exposure degree of TiO2 in a cement system and is also useful to enhance the photocatalytic efficiency.With an increment of the amounts of Ag particles in the TiO2/ZFAB modified cementitious samples,the photocatalytic activities increased first and then decreased.The optimal Ag@TiO2/ZFAB modified cementitious sample reveals the maximum reaction rate constant for degrading benzene（9.91×10^-3 min^-1）,which is approximately 3 and 10 times higher than those of TiO2/ZFAB and TiO2 modified samples,respectively.This suggests that suitable Ag particles coupled with a ZFAB carrier could effectively enhance the photocatalytic effects and use of TiO2 in a cement system.Thus,ZFAB as a carrier could provide a potential method for a high efficiency engineering application of TiO2 in the construction field.

Biomimetic“Nacre-like”Films Prepared via Layer-by-Layer Self-assembly of Mica,Polyvinyl Alcohol and Polymethyl Methacrylate

A film with“brick-and-mortar”structure was prepared by layer-by-layer(LBL)technique using polyvinyl alcohol(PVA)and polymethyl methacrylate(PMMA)as the flexible material or“mortar”and mica as the rigid material or“brick”.The film deposited on a glass slide after self-assembly cycles had a thickness of 3μm thick and an uneven,wavy surface.The film exhibits enhanced mechanical properties,i e,the hardness and indentation modulus values could reach 6.14 and 68.41 GPa,respectively.The hardness and elastic toughness were found to be depended on three factors,i e,the ratio of PVA to mica,the number of self-assembly cycles,and the pretreatment method of the mica suspension.The self-assembly process was driven by formation of the hydrogen bonds between the silanol groups of mica and the hydroxyl groups of PVA and carbonyl groups of PMMA.