The Transformation of Green Rusts on the Surface of Portland Cement Hydration Materials

Ordinary Portland cement (OPC) is widely used building material, and its hydration products can be recycling as low-cost absorbents. The loading of iron oxide is helpful to further improve their adsorption performance. In view of the fact that green rusts are frequently occurrence intermediate products in the co-precipitation of iron salt and prone to be oxidized into stable iron minerals. This study simulated co-precipitation to carry out iron-modification on hydration OPC. The results demonstrate that as the carrier materials, hydration OPC behaves excellent affinity with green rusts. Under the conditions of high temperature (70 oC) and high alklinity (pH=11), green rusts mainly transformed into feroxydrate, and a minor part are into magnetite. The enrichment and transformation of green rust can be regarded as an efficient approach for immobilization of iron oxide (oxyhydroxide).

The Catalytic Oxidation of Formaldehyde by FeOx-MnO2-CeO2 Catalyst: Effect of Iron Modification

A series of FeOx-MnO2-CeO2 catalysts were synthesized by the surfactant-templated coprecipitation method and applied for HCHO removal. The influence of Fe/Mn/Ce molar ratio on the catalytic performance was investigated, and the FeOx-MnO2-CeO2 catalyst exhibited excellent catalytic activity, with complete HCHO conversion at low temperatures (40 °C) when the molar ratio of Fe/Mn/Ce was 2/5/5. The catalysts were characterized by N2 adsorption and desorption, XRD, H2-TPR, O2-TPD and XPS techniques to illustrate their structure–activity relationships. The result revealed that the introduction of FeOx into MnO2-CeO2 formed a strong interaction between FeOx-MnO2-CeO2, which facilitated the improved dispersion of MnO2-CeO2, subsequently increasing the surface area and aiding pore development. This promotion effect of Fe enhanced the reducibility and produced abundant surface-active oxygen. In addition, a great number of Oα is beneficial to the intermediate decomposition, whereas the existence of Ce3+ favors the formation of oxygen vacancies on the surface of the catalyst, all of which contributed to HCHO oxidation at low temperatures.

Electromagnetic Performance due to Tooth-tip Design in Fractional-slot PM Brushless Machines

Permanent Magnet (PM) machines are favorable as an alternative to other machine topologies due to simpler construction and high torque density. However, it may result hight torque ripple due to an influence of cogging torque and electronic commutation. In this paper, comparisons of phase back-emf, static torque and cogging torque due to influence of tooth-tip asymmetry in 12-slot/10-pole double-layer and 12-slot/10-pole single layer winding machines are carried out using 2D Finite-Element Analysis. At rated condition, the stator asymmetry has great influence on the torque performance as there is significant reduction of torque ripple in 12-slot/10-pole mahine equipped with single layer winding than one equipped with double layer winding machine. It si confirmed that an optimum torque performance is desirable via stator iron modification in PM machines.