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Chen W.,Key Laboratory of Silicate Materials Science and Engineering | Chen W.,Wuhan University of Technology | Brouwers H.J.H.,TU Eindhoven
Cement and Concrete Research | Year: 2010

The alkali-binding capacity of C-S-H in hydrated Portland cement pastes is addressed in this study. The amount of bound alkalis in C-S-H is computed based on the alkali partition theories firstly proposed by Taylor (1987) and later further developed by Brouwers and Van Eijk (2003). Experimental data reported in literatures concerning thirteen different recipes are analyzed and used as references. A three-dimensional computer-based cement hydration model (CEMHYD3D) is used to simulate the hydration of Portland cement pastes. These model predictions are used as inputs for deriving the alkali-binding capacity of the hydration product C-S-H in hydrated Portland cement pastes. It is found that the relation of Na+ between the moles bound in C-S-H and its concentration in the pore solution is linear, while the binding of K+ in C-S-H complies with the Freundlich isotherm. New models are proposed for determining the alkali-binding capacities of C-S-H in hydrated Portland cement paste. An updated method for predicting the alkali concentrations in the pore solution of hydrated Portland cement pastes is developed. It is also used to investigate the effects of various factors (such as the water to cement ratio, clinker composition and alkali types) on the alkali concentrations. © 2010 Elsevier Ltd. All rights reserved. Source


Hu Q.,Key Laboratory of Silicate Materials Science and Engineering | Liu B.,Key Laboratory of Silicate Materials Science and Engineering | Liu B.,Wuhan University of Technology | Zhang Z.,Key Laboratory of Silicate Materials Science and Engineering | And 2 more authors.
Journal Wuhan University of Technology, Materials Science Edition | Year: 2010

PTA sol was prepared using titanium tetrachloride (TiCl4), hydrogen peroxide (H2O2) and ammonia (NH 3·H2O), and then stable anatase-TiO2 hydrosol was synthesized by refluxing the PTA sol at 100 °. It was found that TiO2 hydrosol can efficiently photo-degrade methyl orange (MO) under UV-vis light irradiation. Photocatalytic reactions at the temperature of 38 to 100 ° all followed pseudo-first-order rate law, and the temperature had a great effect on the reaction rate. The rate constants increased by about 6 times from 3.52×10-4 to 2.17×10-3 min -1 when the temperature was adjusted from 38 to 100 °. Consequently, this photocatalytic course can be accelerated by using the infrared light of solar energy to increase the temperature of the photo-catalytic reaction, it should be a potential way to make full use of solar light in photocatalysis in practice. © Wuhan University of Technology and Springer-Verlag Berlin Heidelberg 2010. Source


Liu B.,Key Laboratory of Silicate Materials Science and Engineering | Liu B.,Wuhan University of Technology | Zhao X.,Key Laboratory of Silicate Materials Science and Engineering
Electrochimica Acta | Year: 2010

A model based on spherical TiO2 nanoparticles was developed to study heterogeneous photocatalysis based on TiO2 in the case of indirect interfacial charge transfer. In this model, the effect of light intensity (I0), grain size (r0), carrier lifetime (τp), and minority carrier diffusion coefficient (Dp) on the quantum yield (QY) of photocatalytic reactions was investigated in detail. Under conditions of sufficiently low incident-light intensity, the QY was found to be ∝I0, while it decreased rapidly with an increase in I0. In addition, the QY went to zero at a critically high light intensity. Furthermore, the QY was found to decrease with increasing r0 due to the bulk-recombination loss, and the effect of r0 on the QY became increasingly stronger with the increase in I0. The QY decreased with the decrease in τp and Dp, which was more apparent at the critically high I0. Under conditions of low [(RH2)aq], the QY increased with an increase in [(RH2)aq], while it remained nearly constant at high [(RH2)aq] due to the fact that the photoinduced electron interfacial transfer became the limiting step for photocatalytic reactions in the case of high [(RH2)aq]. © 2010 Elsevier Ltd. All rights reserved. Source


Liu B.,Key Laboratory of Silicate Materials Science and Engineering | Liu B.,Wuhan University of Technology | Wen L.,Wuhan University of Technology | Zhang H.,Key Laboratory of Silicate Materials Science and Engineering | Zhao X.,Key Laboratory of Silicate Materials Science and Engineering
Journal of the American Ceramic Society | Year: 2012

Using magnetron sputtering, followed by post calcination TiO 2, WO 3, and TiO 2/WO 3 layered films were prepared using magnetron sputtering and followed by post calcination. The film structures and morphologies were checked using XRD, Raman spectroscopy, FE-SEM, XPS, and UV-Vis spectroscopy. The TiO 2 and WO 3 films are of anatase and orthorhombic structures. The WO 3 underlayer of the TiO 2/WO 3 film grows in [002] direction, almost perpendicular to substrates. Compared with the TiO 2 film, the TiO 2/WO 3-layered film effectively absorbs near-UV light. The photocurrent of layered TiO 2/WO 3 film is much higher than that of TiO 2 film under UV light illumination. The photoelectrocatalytic activity of the films was evaluated in two-electrode photocatalytic reactor, which is assisted by bias voltage. It is seen that PEC activity of TiO 2/WO 3 film is almost four times higher than pure TiO 2 film. Summarily, the TiO 2/WO 3-layered film with dual-function of anti-UV light and high PEC activity was prepared using facile magnetron sputtering. © 2012 The American Ceramic Society. Source

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