Correction: One-Step Synthesis, Structure, and Band Gap Properties of SnO2 Nanoparticles Made by a Low Temperature Nonaqueous Sol–Gel Technique

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One-Step Synthesis, Structure, and Band Gap Properties of SnO2 Nanoparticles Made by a Low Temperature Nonaqueous Sol–Gel Technique

American Chemical Society. Because of its electrically conducting properties combined with excellent thermal stability and transparency throughout the visible spectrum, tin oxide (SnO2) is extremely attractive as a transparent conducting material for applications in low-emission window coatings and solar cells, as well as in lithium-ion batteries and gas sensors. It is also an important catalyst and catalyst support for oxidation reactions. Here, we describe a novel nonaqueous sol-gel synthesis approach to produce tin oxide nanoparticles (NPs) with a low NP size dispersion. The success of this method lies in the nonhydrolytic pathway that involves the reaction between tin chloride and an oxygen donor, 1-hexanol, without the need for a surfactant or subsequent thermal treatment. This one-pot procedure is carried out at relatively low temperatures in the 160-260 °C range, compatible with coating processes on flexible plastic supports. The NP size distribution, shape, and dislocation density were studied by powder X-ray powder diffraction analyzed using the method of whole powder pattern modeling, as well as high-resolution transmission electron microscopy. The SnO2NPs were determined to have particle sizes between 3.4 and 7.7 nm. The reaction products were characterized using liquid-state13C and1H nuclear magnetic resonance (NMR) that confirmed the formation of dihexyl ether and 1-chlorohexane. The NPs were studied by a combination of13C,1H, and119Sn solid-state NMR as well as Fourier transform infrared (FTIR) and Raman spectroscopy. The13C SSNMR, FTIR, and Raman data showed the presence of organic species derived from the 1-hexanol reactant remaining within the samples. The optical absorption, studied using UV-visible spectroscopy, indicated that the band gap (Eg) shifted systematically to lower energy with decreasing NP sizes. This unusual result could be due to mechanical strains present within the smallest NPs perhaps associated with the organic ligands decorating the NP surface. As the size increased, we observed a correlation with an increased density of screw dislocations present within the NPs that could indicate relaxation of the stress. We suggest that this could provide a useful method for band gap control within SnO2NPs in the absence of chemical dopants

Processing clinker from wastes: A new raw material source for a global change

The final destination of the wastes generated in the manufacture of pulp paper is one of the growing concerns in this sector since the European regulations are becoming stricter in regard to their landfill. So it is urgent to seek ways for their valorization through incorporation in other product as, although not usually dangerous, the quantities generated are substantial. In this work the residues used were: (i) a calcareous sludge generated in the chemical recovery circuit of the production process; (ii) a biological sludge generated in the secondary wastewater treatment step and (iii) a fly ash from the combustion of biomass in the cogeneration operation. The first stage of was the waste characterization and then different blends were prepared and submitted to distinct firing cycles to obtain Portland clinker, the main component of the ordinary cement. Using only wastes in adjusted proportions and a tuned firing cycle, it was possible to obtain ecological Portland clinker. Moreover, it was possible to reduce, by about 50 C, the firing temperature in relation to the value used in cement industry, which results in economical and procedural benefits. © (2016) Trans Tech Publications

Effect of nano-SiO\u3csub\u3e2\u3c/sub\u3e and nano-TiO\u3csub\u3e2\u3c/sub\u3e addition on the rheological behavior and the hardened properties of cement mortars

\u3cp\u3eThis paper reports on the use of nano-SiO\u3csub\u3e2\u3c/sub\u3e (nS) and nano-TiO\u3csub\u3e2\u3c/sub\u3e (nT) in cement pastes and mortars. Samples with 0-3wt.% nS, 0-12wt.% nT and 0.5 water/binder weight ratio were prepared. Rheological and flow table measurements were carried out. In addition, the design of experiments was applied to validate the results found. The temperature of hydration and compressive strength with 28 days was also determined. In general, mortars exhibited noticeable differences in the rheological behavior, but less evident in temperature of hydration and compressive strength. The values of torque, yield stress and plastic viscosity of mortars with nanoadditives increased significantly, reducing the open testing time in rheology tests. Meanwhile, the flow table values reduced. In addition, spread on table and initial yield stress exhibited a power correlation, while the spread on table and plastic viscosity did not show any special relationship. The results of kinetics of hydration followed the same tendency found by rheology, in which samples with higher amounts of nS and nT showed remarkable changes in relation to the samples without nanoadditives. Mechanical properties were not significantly affected by nanoparticles in the range considered in this work.\u3c/p\u3