Search

Because the agglomerated silica fume can’t realize its filling effect, hydration nucleation effect and pozzolanic effect in cement-based composites, a new dispersing method on silica fume aiming to dispersing it fully is introduced. The influence of physical and chemical properties of the modified silica fume on performance of cement-based materials was investigated. In view of the presence of silanol groups and negative charges of silica fume surface, the zeta potential of silica fume surface becomes positive after reaction of silanol groups on silica fume surface and calcium ions in modification solution. The change of zeta potential generates stronger adsorption force to anionic polycarboxylate copolymer. This paper discusses in detail the effect of the modified solution with different concentrations and pH values on adsorption amount of calcium ions on the surface of silica fume, thereby the optimal modified system was determined. The optimized dispersion of the modified silica fume was characterized by infrared spectra and comparing with the result of the commercial silica fume. The performance of modified silica fume in the simulated cement pore solution was evaluated by zeta potential and adsorption amount of polycarboxylate copolymers on silica fume particles surface. Besides, laser particle distribution and SEM photos help us clarify the difference between the particle size distribution and microstructure of the modified silica fume and the commercial silica fume. Results show that zeta potential, adsorption amount of polycarboxylate copolymers on modified silica fume surface increases obviously, the homogeneous dispersion fraction of the modified silica fume in the simulated cement pore solution increases significantly. Furthermore, influence of modified silica fume on the performance of cement-based materials was evaluated. Results showed that the effects of modified silica fume on fluidity, mechanical properties, hydration heat, non-evaporable water, hydration products, pore structure and morphology of cement-based materials are optimizer than the commercial silica fume. And the Ca/Si ratio of the C-S-H gel of cement-based material containing modified silica fume is lower than that of cement-based material containing commercial silica fume.

An optimized approach is applied to realize the transfer printing of an In0.2Ga0.8As/GaAs/In0.2Ga0.8As trilayer nanomembrane (NM) onto a plastic substrate with high quality. Bendable metal-oxide-semiconductor capacitors (MOSCAPs) are fabricated on the transferred NM. A detailed COMSOL simulation study is conducted to investigate the mechanical bending behavior induced tri-principle stress of the NM on flexible substrates. The electrical characteristics of the fabricated MOSCAPs exhibit almost no hysteresis voltage of only 0.03 V, an extremely low gate leakage of 10-6 to 10-7 A/cm2, and low accumulation frequency dispersion, thus indicating the possibility of achieving high performance III-V MOS transistor operation. The impact of mechanical strains on the flatband voltages has been carefully investigated from the capacitance-voltage (C-V) measurements. The corresponding accumulation capacitance shows good robustness under tensile bending conditions. The results indicate an important step toward the realiz...

A series of three dimensional (3D) porous TiO2–graphene (TGR) hydrogel samples with different mass ratio of graphene to TiO2 were obtained using a one-step hydrothermal method. Their microstructure, mechanical properties, and photocatalytic activity were investigated. The TGR samples exhibited well defined interconnected 3D porous network microstructure and good mechanical strength. Moreover, the pore size and the compressive strength could be easily adjusted by changing the content of TiO2, showing a decreasing tendency with the increase of the relative content of TiO2. The results of the photodegradation of methylene blue indicated that the photocatalytic activity of the TGR samples can be significantly enhanced, compared to the pure TiO2 nanoparticles. The TGR sample also showed good durability and reusability. The mechanisms resulting in the improvement of photocatalytic activity were investigated with DRS, PL spectra, and adsorption experiment under dark conditions. It was found that adsorption is the dominant factor for the enhanced photocatalytic activity.