Exsolution of Nickel Nanoparticles from Mixed-Valence Metal Oxides: A Quantitative Evaluation by Magnetic Measurements

A fast and accurate experimental method is demonstrated to assess the fraction of exsolved metallic nanoparticles using magnetic measurements. As a benchmark, nanometric metallic nickel exsolved from (La_1−xSr_x)(Cr_1−yNi_y)O_3−δ is used for its high relevance as a solid oxide fuel cell component. The method is based on the difference in the magnetic response of the exsolved metallic nickel (ferromagnetic) and Sr-doped lanthanum chromite ceramic matrix (paramagnetic). The exsolved nickel results in coherent nanoparticles pinned on the surface of the Sr-doped lanthanum chromite ceramic matrix, as evidenced by electron microscopy analyses. The results obtained indicate the procedure as a fast and sensitive method to study the exsolution of ferromagnetic nanoparticles.     

Thermal stability and thermodynamic properties of hybrid proton-conducting polyaryl etherketones

The thermal and structural stability of sulfonated cross-linked PEEK (polyether ether ketone) and its silicon-containing class II hybrid derivatives were characterized by combination of mass spectrometry, infrared spectroscopy, X-ray diffraction, thermogravimetric analysis, and differential scanning calorimetry. Thermodynamic properties of the hybrids were determined, including glass-transition temperature, degree of crystallinity, and thermal stability. The decomposition processes of the hybrid polymers could be consistently interpreted and their energetics quantitatively determined. The introduction of inorganic silanol moieties improves the thermal stability compared to sulfonated products.     

Lead removal and recovery from battery industry wastewaters by soluble starch xanthate

Treatment, removal and recovery of lead (3 mg/L) from battery industry wastewaters have been investigated utilising a chemical precipitation process with soluble starch xanthate (SX) at pH 5-6. A reactant ratio, i.e., SX/Pb(II) = 6 mol/mol, a reaction time of 15 min., the addition of 15 mg/L of a cationic polyelectrolyte and a final filtration gave residual lead concentrations in the liquid phase less than 0.2 mg/L, well below the maximum limit established by the EU Directive. Lead was extracted from the obtained sludge by oxidation with sodium hypochlorite or hydrogen peroxide solutions. The amounts of oxidant needed were quantified as 13.5 mol NaClO/mol Pb and one order of magnitude larger, for H2O2, the latter due to the competitive disproportion reaction of the oxidant. The metal extraction was quantitative using sodium hypochlorite; when hydrogen peroxide was used, the formation of insoluble PbSO4 (Anglesite) gave a 80% metal extraction. In both cases molar ratios between sulphate and lead ions in the extracted solutions were in the range 2.1-2.2, in agreement with the stoichiometries of the reactions. Lead can be quantitatively recovered from the extracted (NaClO) solutions, for reuse, after a chemical precipitation process with 1M NaOH at pH 9-9.5, in the form of hydrocerussite [Pb3(CO3)2(OH)2].     

Point estimate methods based on Taylor Series Expansion – The perturbance moments method – A more coherent derivation of the second order statistical moment

Point estimate methods (PEMs) have found their niche in application to geotechnical problems and a few other engineering fields, where their relative simplicity matches well with the need for quick and reliable estimates of the uncertainty in model results. In some cases, however, the simplicity of the PEMs has to come to terms with the physical meaning of the stochastic variables and with the non-linearity of the model function. In this study, a general review of PEMs is presented and an improved method is proposed that requires fewer model evaluations, but still provides meaningful results for non-linear problems. Two uncertainty analyses of the hydrologic response to a rainfall event are presented: for a small synthetic basin and for a small mountain basin in Italy. The results of three PEMs are evaluated – Rosenblueth’s method, Li’s method, and the proposed perturbance moments method (PMM), along with the computationally-intensive, Monte Carlo simulation (MCS) approach. It is shown that for the same computational requirements, the derivation of the PMM is more coherent and resolves the problem of the negative variance which can occur when using other PEMs derived from the Taylor Series Expansion. The method is also computationally efficient, both compared to MCS and to other PEMs.     

Investigation of a point-like and plane-wave excitation in 2D photonic bandgap microcavities using Green’s function method

We report on a new model for simulating wave propagation in two-dimensional photonic crystals (PhCs) by means of Green’s functions rearranged to fit on the geometrical and physical properties of the structure under investigation. The model can take into account physical effects occurring when the PhC is excited by either a point-like source, for the analysis of extended crystals with line and point defects, or a plane wave coming from infinite, to investigate mirrors and microlenses. The model has been used for studying a Fabry–Peròt cavity to evaluate its response in presence of a Hankel source or a plane wave excitation. A parametric investigation of the filter response as a function of the cavity length has been carried out and the best conditions to obtain an increase of quality factor of each resonant cavity mode have been determined.