National Institute Of Materials Physics - Romania

To avoid the deleterious effects of dopant segregation, synthesis methods that facilitate a homogenous dopant distribution in the ceria lattice were employed. Though doping ceria by wet impregnation was also credited to induce a homogeneous solid solution even in the heavy regime (concentration >= 20%, A. Corma, P. Atienzar, H. Garcia and J. Chane-Ching, Nat. Mater., 2004, 3, 394-397), no follow up investigation has been reported. Herein, we investigated ceria nanoparticles (1% Tm-CeO2 and 1% Eu-CeO2) wetimpregnated with trivalent rare-earth (Yb, 20%), bivalent (Ca, 20%) and isovalent (Zr, 30%) metals, followed by annealing in air. Homogeneity of the solid solutions of Yb-impregnated ceria was confirmed by a two-feature characterization toolbox that included X-ray diffraction, Raman spectroscopy, transmission electron microscopy, as well as up-conversion emission as a probe tool. Since the up-conversion emission of Tm was not detectable in the absence of Yb while its efficiency depends on the average distance between Yb and Tm ions, the Yb incorporation and its migration from the surface to the lattice bulk sites in wet-impregnated ceria can be "visualized" and compared with that of the Yb bulk-doped counterpart. The use of Eu luminescence as a local probe confirmed the homogeneity of solid solutions of Ca and Zr-impregnated ceria and also sustained the opposite roles of Ca and Zr as the repeller and the scavenger of oxygen vacancies, respectively. All these results suggested that heavy doping of ceria by wet impregnation with metals with +2, +3 and +4 valencies represent a facile alternative to conventional doping approaches. Therefore, the effects of the amount and the type of metal dopant on the structural properties of CeO2 could be investigated in a more systematic and probably a more reproducible manner, which would significantly increase the potential of ceria in catalysis and other applications.

During conflict situations, the combat staff is exposed to a wide variety of aggressions, such as temperature and pressure variations and dynamic impacts (from ammunition or fragments). Textiles used in the manufacture of the military uniforms and devices have always played an important role in defending the military against these hazards, and an adequate level of individual protection equipment is required. In this respect, novel fibre-reinforced polymer composite materials for military application, such as reducing blunt trauma for ballistic protection equipment, have been studied in terms of thermal and mechanical properties and ballistic protection, obtaining very good results.

This work investigates the catalytic properties toward sulfide oxidation in wastewater for three composites which are functional materials obtained from red mud waste following its neutralization, chemical activation and functionalization of the iron by treatment with disodium salt of ethylenediaminetetraacetic acid, trisodium citrate or a combination of these two organic ligands. X-ray diffraction and diffuse reflectance Fourier transformed infrared spectroscopy characterizations indicated the coexistence of the corresponding iron chelates phases along with hematite the main crystallographic phase from red mud. The most active catalyst was the red mud-derived material obtained by functionalization with the mixture of ethylenediaminetetraacetate and citrate ligands. The results obtained after its testing in multiple reaction cycles showed that the decrease in conversion after 10 reaction cycles was less than 5%. Considering the results of diffuse reflectance ultraviolet visible narrow infrared spectroscopical analysis which revealed that this solid contains species with lower bond strength, it has been inferred that both the higher catalytic activity, as well as the enhanced stability, is directly related to the versatility of the active species.

Ceria materials doped by Gd and/or Pr were prepared by a precipitation route and calcined in air at 500 and 900 degrees C. The effects of doping and thermal treatment on the materials' surfaces were studied by X-ray photoelectron and Raman spectroscopies. The redox properties were investigated using temperature-programmed reduction experiments in H-2 and CH4 followed by temperature-programmed oxidation in O-2. The catalytic properties of these materials in CH4/H2O reaction in the absence/presence of H2S were evaluated at 750 degrees C in a large excess of CH4 with respect to H2O. The materials were classified by order of reactivity as follows: CPO > CGPO > CeO2 > CGO, which can be primarily related to the surface area variation. Comparing the activity per m(2) of various samples indicates that the catalytic activity is correlated with the Ce3+ concentration at the surface as measured by XPS. Gd-doped and undoped samples exhibit the highest surface Ce3+ concentration as well as the highest activity in SMR per m(2), while Pr-doped samples are the least active (activity per m(2)) with the lowest surface Ce3+ concentrations. H2S has a sharp promoting effect on the catalytic behavior of ceria-based materials, improving the production of H-2 by almost one order of magnitude.

Mixed manganese iron oxides (Mn/Fe/O) as heterogeneous catalysts were prepared by hydrothermal treatment and citrate methods to be tested in the oxidation of p-xylene (PX) using as oxidation agent molecular oxygen, hydrogen peroxide, and tert-butyl hydroperoxide. Preparation of mixed Mn-Fe oxide by the citrate method releases materials with smaller particle size and lower degree of crystallinity as compared with the hydrothermal one, which further leads to a higher activity toward the oxidation of PX. A conversion of PX of 98% and a yield in p-toluic acid of 93% were obtained in the presence of Mn/Fe/O prepared by the citrate method using tert-butyl hydroperoxide as an oxidizing agent. (C) 2017 Academie des sciences. Published by Elsevier Masson SAS. All rights reserved.

The catalytic methanolysis of the chemical warfare nerve agents soman, sarin, and VX was investigated by using Cu or Zn complexes. Although VX withstood decontamination, the decomposition yield being around 96%, the soman and sarin deposited on different surfaces were almost fully destroyed under ambient conditions. The catalytic tests performed on a wide range of contaminated surfaces confirm the activity of the investigated catalytic systems, these complexes being suitable, from an economical point of view, for use in the formulation of a possible decomposition kit with military or civilian applicability. (C) 2017 Academie des sciences. Published by Elsevier Masson SAS. All rights reserved.

This contribution concerns the catalytic activity of functional layered double hydroxides (LDHs) for 1,4-addition of n-octanol to 2-propenonitrile aiming to investigate the influence of the organic interlayer anion nature on their physico-chemical and catalytic performances. Two series of functional LDHs, e.g. Mg2.5Al, and Zn2.5Al respectively, were synthesized by co-precipitation at pH 9.5 using a metal nitrates M2+ (NO3)(2)center dot 6H(2)O (M2+ = Mg, Zn), Al(NO3)(3)center dot 9H(2)O solution, an organic acid sodium salt (e.g. sodium dodecyl sulfate (NaDS), sodium laurate (NaL), or sodium stearate (NaS)) and NaOH solution for pH adjustment. XRD, DRIFTS and DR-UV-Vis-NIR characterizations indicated a better intercalation of DS in the interlayer region compared to L or S. The catalytic activity of these solids was related to both their organophilic character and basicity, Mg2.5Al-DS samples, which were more basic, showed a higher activity than Zn2.5Al-DS.