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This study deals with SrAl2O4: Eu2+, Dy3+ phosphor pigments prepared by an optimized perchlorate-assisted combustion synthesis and tested for developing glow-in-the-dark safety markings. Recipes with different oxidizer/fuel ratios were designed to create an in-situ reducing-reaction atmosphere and promote Eu3+ → Eu2+ reduction, which is responsible for the specific long-lasting, green emission of the pigments. The obtained data proved the efficiency of glycine-rich mixtures (up to 200% glycine excess), which led to improved optical features, as compared to the reference stoichiometric sample. The best results in terms of emission intensity and decay time were obtained in the case of 100% glycine excess. The sample with optimum emission characteristics was successfully tested in making glow-in-the-dark coatings applied to two different substrates and using pigment concentrations between 10 and 33% weight. [ABSTRACT FROM AUTHOR]

Palladium is a noble metal of the platinum group metals (PGMs) with a high value and major industrial applications. Due to the scarce palladium resources, researchers' attention is currently focused on Pd ions recovery from secondary sources. Regarding the recovery process from aqueous solutions, many methods were studied, amongst which adsorption process gained a special attention due to its clear advantages. Moreover, the efficiency and the selectivity of an adsorbent material can be further improved by functionalization of various solid supports. In this context, the present work aims at the synthesis and characterization of Mg3Al-LDH and its functionalization with ionic liquid (IL) (Methyltrialkylammonium chloride) to obtain adsorbent materials with high efficiency in Pd removal from aqueous solutions. The maximum adsorption capacity developed by Mg3Al-LDH is 142.9 mg Pd., and depending on the functionalization method used (sonication and co-synthesis, respectively) the maximum adsorption capacity increases considerably, qmax-Mg3Al IL-US = 227.3 mg/g and qmax-Mg3Al IL-COS = 277.8 mg/g. [ABSTRACT FROM AUTHOR]

Two series of magnetic nanopowders were synthesized at room temperature starting from a mixture of iron II and III precursors, FeSO4 and FeCl3, respectively. Precipitation agents, as KOH and NaOH were used. While the concentration of the added ferrous and ferric solutions ranged between 0.1 M and 0.0125 M, the hydroxide solution concentration was maintained constant (1 M). TEM images of the samples showed that the particles shape changes from quasi spherical to spherical. For both series the crystallite size decreases with iron concentration, from 9 to 2 nm for KOH series and from 10 to 3 nm for NaOH series. Moessbauer Spectroscopy was signaling only Fe3+ in the final spinel product. BET measurements revealed the material mesoporosity and fractal structure of maghemite nanoparticles that explain the unusual high surface area, ~240 m2/g. All the samples actually exhibit superparamagnetic behavior at room temperature with saturation magnetization up to 73 emu/g value closed to those of bulk maghemite. [ABSTRACT FROM AUTHOR]

Hot-dip galvanizing process is used worldwide to protect the steel or iron pieces from corrosion. This process is a large generator of waste, considered one of the so-called dirty industries. One of the important wastes, in terms of quantity, is zinc ash that contains a mixture of metallic zinc and zinc oxide with a total content of zinc between 70 and 90%. The aim of this study is the preparation and characterization of a series of ZnR-Al-CO3 (R = 2-4) layered double hydroxides (LDH) by using as zinc precursor the zinc chloride obtained after hydrochloric acid leaching of fine-grained zinc ash. Results presented herein clearly demonstrated that characteristics of the synthesized samples are close to those of similar materials synthesized starting from analytical grade reagents. At the same time, it was observed that impurities existent in the zinc chloride solution prepared by zinc ash leaching (Pb, Fe, Ca), are found at traces in the synthesized LDH materials; therefore, they have no significant influence on the obtained LDH structure and properties. By this approach, several important benefits may be simultaneously achieved: (1) preventing the pollution associated with hot-dip galvanizing process wastes, (2) obtaining of valuable products with minimized costs, keeping in mind that LDH have multiple utilizations at industrial scale, (3) saving energy and material costs, and (4) increase of product competitiveness with respect to the circular economy. [ABSTRACT FROM AUTHOR]

Abstract: Single-phase LaAlO3 was prepared by a simple combustion synthesis procedure, which relies on using urea and β-alanine fuel mixture, instead of a single fuel. The aqueous solution of La(NO3)3, Al(NO3)3, urea and β-alanine underwent a strong exothermic reaction at 281°C, thus enabling the formation of single-phase LaAlO3 directly from the combustion reaction—without the need of supplementary annealing. The combustion synthesized LaAlO3 had an average crystallite size of 46nm and a BET surface area of 3.0m2/g. The addition of NaCl to the reaction mixture decreased the combustion temperature, promoting an increase of the BET surface area (8.5m2/g). At the same time the LaAlO3 crystallite size decreased to 36nm. After sintering at 1500°C for 5h, LaAlO3 pellets developed a fine microstructure, reaching 94% of the theoretical density. [Copyright &y& Elsevier]

Abstract: In order to achieve BaAl2O4 formation via combustion synthesis, two types of recipes were designed: single fuel recipes (urea, glycine, β-alanine or hexamethylenetetramine) and innovative fuel mixture recipes (urea+glycine, urea+β-alanine and urea+hexamethylenetetramine respectively). No combustion reactions were noticed in the case of single fuel recipes based on urea or hexamethylenetetramine. The only crystalline phase present in the case of the powders obtained in such a way was unreacted Ba(NO3)2. Glycine and β-alanine generated smoldering reactions, leading to the formation of black powders, which consist of Ba(NO3)2, BaCO3 and traces of BaAl2O4 (in the case of β-alanine). Fuel mixture recipes proved to be better than single fuel recipes, yielding BaAl2O4 as main crystalline phase. The specific surface area of the resulted powders ranges between 2.0 and 3.9m2/g. The urea and glycine fuel mixture was the most efficient yielding BaAl2O4 with an average crystallite size of 60nm. [Copyright &y& Elsevier]

The paper presents the obtained results in the synthesis of some thermoresistant pink pigments with different structures, such as: corundum (Al2- xCrxO3), spinel (ZnAl2-xCrxO4, MgAl2-xCrxO4) and perovskite (LaAl1-xCrxO3). An unconventional synthesis method has been used in order to increase the substitution of Al3+ with Cr3+. The method used is based on the thermal decomposition of organic complex combinations containing as ligand the glyoxylate dianion, (C2H2O4 2-). The evolution of the crystalline phases with temperature has been investigated by XRD. The colorimetric characterization of the obtained pigments has been studied by diffuse reflectance spectrophotometry. [ABSTRACT FROM AUTHOR]

The influence of urea, β-alanine and glycine on combustion synthesized Y2O3 powders was studied. Standard enthalpies of reactions suggested that the heat released from combustion reactions increases from urea (-1778 kJ/mol) to glycine (-1934 kJ/mol) and then to β-alanine (-1995 kJ/mol). Since the heat released during combustion reactions is generated at different rates, we suggested the use of a new concept - heat generation velocity - in order to explain the different characteristics of Y2O3 powders. Urea had the smallest heat generation velocity (0.4 kJ/s), therefore the resulted powder was amorphous. In the case of β-alanine, the higher heat generation velocity (0.7 kJ/s) led to the formation of nanocrystalline (5 nm) Y2O3 having a surface area of 36 m²/g. Glycine triggered the combustion reaction with the highest heat generation velocity (3.9 kJ/s). Therefore the resulted Y2O3 had the largest crystallite size (21 nm) and the smallest surface area (19 m²/g). [ABSTRACT FROM AUTHOR]

Highlights: [•] Large surface area ZnAl2O4 powder was prepared using a new combustion technique. [•] Basically, this new technique relies on using zinc acetate instead of zinc nitrate. [•] The nanocrystalline (6nm) ZnAl2O4 powder had a specific surface area of 127m2/g. [•] The addition of NH4NO3 increased even more the specific surface area to 201m2/g. [•] At the same time, the average crystallite size of ZnAl2O4 decreased to 2nm. [Copyright &y& Elsevier]

Zinc aluminate powders with tuned surface area were prepared by solution combustion synthesis, using different oxidizer-fuel ratios. As the amount of urea increased, standard heat of reaction and standard Gibbs free energy decreased, whilst adiabatic temperature increased. The larger amount of energy released during combustion facilitated grain growth and sintering, causing the decrease of specific surface area from 156 to 27 m 2 g −1 . The particle size estimated from TEM increased from 8 to 40 nm. The adsorption capacity of zinc aluminate powders with respect to methyl orange was highly dependent on the specific surface area. For an adsorbent dose of 3 g L −1 the removal efficiency of methyl orange was much larger (86 versus 18%) in the case of the sample with larger surface area. The adsorption kinetics followed a pseudo-second-order model and the equilibrium data were correlated with the Freundlich isotherm. [ABSTRACT FROM AUTHOR]