Rapid synthesis of novel flowerlike K0.46Mn2O4(H2O)1.4 hierarchical architectures and their catalytic degradation of formaldehyde in aqueous solution

Novel flower-like birnessite type manganese oxide hierarchical architectures were hydrothermally synthesized from KMnO₄ solution using sodium fluorite as a reductant in sulfuric acid medium at low temperature. X-ray diffraction (XRD), Fourier transform infrared (FT-IR) and X-ray photoelectron (XPS) spectroscopes confirm that the composition of the as-fabricated product. Field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), selected area electron diffraction (SA-ED), high resolution transmission electron microscopy (HR-TEM) and N₂ adsorption–desorption isotherm reveal that the as-synthesized sample exhibits a microsized flower-like crystal with dense nanoleaves standing on their surfaces, polycrystalline, monoclinic phase structure and high BET surface area. On the basis of time-dependent experimental results, a possible mechanism for the formation of flowerlike structures is speculated. Their capability of catalytic degradation of formaldehyde solution with oxygen air bubbles were studied by using an acetylacetone calorimetric spectra, total organic carbon (TOC) method and turnover number (TON). In addition, the birnessite nanoflower is stable during the reaction and can be used repeatedly.     

AC impedance analysis of LaLiMo2O8 electroceramics

Complex impedance analysis of a new rare earth-based ceramic oxide, LaLiMo₂O₈, prepared by a standard solid-state reaction technique has been carried out. Material formation under the reported conditions has been confirmed by X- ray diffraction studies. A preliminary structural analysis indicates the crystal structure to be orthorhombic. Electrical properties of the material sample have been studied using AC impedance spectroscopy technique. Impedance spectrum results indicate that the electrical properties of the material are strongly dependent on temperature and it bears a good correlation with the sample microstructure (i.e. the presence of bulk, grain boundary, etc.) in different temperature ranges. Evidences of temperature-dependent electrical relaxation phenomena in the material have also been observed. The bulk resistance, evaluated from complex impedance spectrum has been observed to decrease with rise in temperature showing a typical negative temperature coefficient of resistance (NTCR)-type behavior like that of semiconductors. The DC conductivity shows typical Arrhenius behavior when observed as a function of temperature. The AC conductivity spectrum has provided typical signature of an ionically conducting system and is found to obey Jonscher's universal power law. Modulus analysis has indicated the possibility of hopping mechanism for electrical transport processes in the system with non-exponential-type conductivity relaxation.     

Co-RS-紧拓扑

A topoogy R(τ) is constructed from a given topology τ on a set X. R(τ) is coarser than τ, and the following are some results based on this topology:1. Continuity and RS-continuity are equivalent if the codomain is retopologized by R(τ).2. Each topological space has a coarser extremely disconnected topology.3. The class of semi-open sets with respect to R(τ) is a topology.4. T₂ and semi-T₂ properties are equivalent on a space whose topology is R(τ).5. Minimal R₀-spaces are RS-compact.6. Maximal a-compact spaces are RS-compact.