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In this study, we report the adsorption process of Congo Red (CR) dye by calcined Layered Double Hydroxide (ZAC) at 550°C. The urea hydrolysis method was applied to produce highly crystalline Zn2Al-LDH. Samples characterisation was carried out by X-ray diffraction (XRD), Thermogravimetric/differential thermal analysis (TG/DTA), and Fourier transform infrared spectroscopy (FTIR). The results show that the adsorption of CR on calcined ZnAl-LDH was accompanied by the reconstruction of the layered structure. The ZAC showed higher adsorption efficiency versus other adsorbent under investigation and optimum conditions of contact time, adsorbent dose, pH and temperature were found to be 50 min, 0.02 g, 7 and 318 K, respectively. Isotherm studies show that the Langmuir isotherm model was appropriate to describe the CR adsorption data compared with Freundlich and Temkin isotherm models, with a higher correlation coefficient (R2 > 0.99) and maximum adsorption capacity of 406.5 mg/g. The thermodynamic parameters revealed that the adsorption process was spontaneous, endothermic, and governed by chemisorption. To further facilitate the recovery process in CR adsorption, we test the feasibility of applying ZnAl-LDH and its calcined product at 550°C entrapped in alginate beads. Experimental results indicate that alginate-coated ZAC beads, which exhibited remarkable adsorption performance, were more stable and require less effort to pull and separate than the alginate/ZnAl-LDH composite beads. [ABSTRACT FROM AUTHOR]

Because of their significant magnetocaloric properties, Ca and Pb-doped LaMnO3 can be employed in magnetic refrigeration systems. The partial substitution effect of Ca2+ by Pb2+ cations on the structural, magnetocaloric properties, and critical behavior of mixed valence perovskites La0.8Ca0.2−xPbxMnO3 (0 ≤ x ≤ 0.15), synthesized by the flash combustion route, was studied in this work. The presence of structural transformations of the prepared ceramics from an orthorhombic structure (Pbnm space group) for samples with x ≤ 0.05 to a rhombohedral system ( R 3 - c space group) for x ≥ 0.1 was detected by X-ray diffraction analysis, which is related to the A-site disorder. The field-cooled (FC) magnetization indicated a second-order ferromagnetic-paramagnetic transition for the investigated samples when the temperature was increased. Due to the change in the Mn3+/Mn4+ ratio, substituting Ca2+ with larger Pb2+ ions increases the Curie temperature (TC) by increasing Pb doping content from 90 K for x = 0 to 205 K for x = 0.15. The magnetization isotherms of all samples showing a second-order phase transition were studied, where an applied magnetic field of 5 T, the value of maximum magnetic entropy variation / Δ S M max / for the sample with x = 0.15 was estimated to be 2.73 Jkg−1 K−1. In addition, it has a significant relative cooling power of about 276 Jkg−1 under the same applied magnetic field strength. The critical behavior of the samples was investigated close to TC. The exponent values were identical to the mean-field method, indicating a large disorder of spin magnetic moments in the perovskite compounds. [ABSTRACT FROM AUTHOR]

Alginate-coated calcined layered double hydroxide and illite clay (Alg@CLDH@ Illite) composite beads were fabricated and tested for single and mixture dye adsorption from aqueous solution. Adsorption characteristics of the as-fabricated beads were assessed by using Methylene Blue (MB) and Congo Red (CR) as adsorbates. As-prepared samples were characterised by using X-ray diffraction (XRD), Thermogravimetry/Differential Scanning Calorimetry (TG–DSC), Fourier transform infrared spectroscopy (FTIR), and point of zero charge (pHpzc). The characterisations demonstrated that the incorporation of CLDH powder/clay mixture can not only enhance thermal stability but also can improve the adsorption performance. The adsorption kinetics of dyes onto composite beads followed the linear form of pseudo-second-order model and their equilibrium data were fitted well to the Freundlich model. The results showed that the Alg@CLDH@Illite composite is able to adsorb anionic and cationic dyes from a binary dye mixture with high sorption capacities in short time 50 min. [ABSTRACT FROM AUTHOR]

In this paper, a simple chemical method in the presence of glycine is described to fabricate the hierarchical structure of MgAl-based Layered Double Hydroxides (Gly-LDH), served as high-performance adsorbent for Methyl orange (MO). To elucidate the effect of glycine on the adsorption capacity, the MgAl-LDH intercalated with CO32- anions was also prepared by urea hydrolysis method (Ur-LDH). The as-synthesised nanostructures were characterised by X-ray diffraction (XRD), Thermogravimetry/Differential Scanning Calorimetry (TG–DSC), Fourier transform infrared spectroscopy (FTIR), and Scanning Electron Microscopy (SEM),. The results demonstrated that the glycine intercalated LDH exhibited high adsorption capacity for MO dye compared with MgAl-LDH obtained by urea hydrolysis method. Adsorption isotherm data for MO adsorption on Gly-LDH at 300 K and acidic pH fitted well to the Langmuir isotherm model with a maximum adsorption capacity of 800 mg/g. l. The sorption mechanism indicates that MO molecules could be sorbed onto Gly-LDH via electrostatic attraction, and ion exchange. [ABSTRACT FROM AUTHOR]

Currently, the treatment of wastewater containing dye by the effective adsorbent attracts a great deal of interest. In this work, we report the removal of Congo Red (CR) dye from water using ZnAl-Layered Double Hydroxides (LDH) synthesised by the urea method. Samples characterisation was carried out by X-ray diffraction (XRD), Thermogravimetric/differential thermal analysis (TG/DTA), and Fourier transform infrared spectroscopy (FTIR).The results showed that well-crystallised layer material with uniform particle size was formed. Various parameters influencing the adsorption process, such as dye concentration, adsorbent dosage, contact time, pH and solution temperature were investigated. The adsorption kinetics were evaluated using the pseudo-first-order and second-order kinetic models. According to kinetics studies, the adsorption of CR was instantaneous and fast, which reflects a strong affinity of LDH for dye molecules and follow ideally the pseudo-second order model. Isotherm studies show that the Freundlich isotherm model was appropriate to describe the adsorption of CR onto ZnAl-LDH, with a maximum adsorption capacity of 591.80 mg/g at pH = 3. Based on adsorption study, the amount of CR uptake onto LDH increases with increasing initial dye concentration and temperature from 298 to 318 K. The thermodynamic parameters show that adsorption process of CR was spontaneous and endothermic in nature. Furthermore, we investigated ZnAl-LDH decomposition and structure regeneration based on "memory effect" from previous calcined sample. After rehydration, layer material with good crystallinity was achieved, revealing that the regeneration process was successfully conducted. [ABSTRACT FROM AUTHOR]

In this paper, we investigate the structural, magnetic, and magnetocaloric properties of La0.62Nd0.05Ba0.33Mn1-xCrxO3 manganites elaborated by sol gel process. X-ray diffraction analyses confirm that all elaborated samples are crystallized on the rhombohedral perovskite structure with R-3c space group. Magnetic measurements reveal the presence of a magnetic transition from paramagnetic (PM) to ferromagnetic (FM) phase in the vicinity of Curie temperature TC. However, as Cr concentration increases, we witness a decrease in TC from 285 K for x = 0 to 250 K for x = 0.20. This behavior can be explained by the double exchange interaction of Mn3+-O-Mn4+. The maximum entropy change (- Δ S m max ) at µ0H = 5 T is found to be 2.63, 1.88, and 1.76 J.kg−1.K−1 for x = 0, 0.10, and 0.20, respectively. However, our research underlines the enhancement of relative cooling power (RCP) by Cr doping, from 310 to 340 J.kg−1 as Cr concentration increases from x = 0 to 0.20. This finding suggests the usefulness of our samples as magnetic refrigeration material around room temperature. Furthermore, the analysis of the magnetocaloric effect (MCE) using the Landau theory shows a good agreement with the experimental results with a soft difference, indicating the importance of Jahn–Teller interactions on manganites perovskite. [ABSTRACT FROM AUTHOR]

In the recent decade, magnetic compounds have attracted a great deal of interest due to their magnetic behaviour allowing them to be a good candidate for catalytic and biomedical applications. However, the problem of these materials is their aggregation during the synthesis process, and then problems related to particle size. To overcome these problems, an efficient assembly of magnetic nanoparticles with layered double hydroxides compound systems (Fe-NPs@LDH and M/Fe-NPs@LDH; M = Mn, Zn) were prepared by simple co-precipitation process. Analytical tools including TG-dTG, XRD, FTIR, SEM/EDX and BET were used to investigate the thermal, morphological, structural and textural properties of the studied materials. The magnetic properties of the composite were investigated by mean 57Fe Mossbauer spectrometry. [ABSTRACT FROM AUTHOR]

The thermal, structural and magnetocaloric properties of La1−xLixMn1−yFeyO3 (x = 0.1, 0.2 and y = 0, 0.1) powders were investigated in this study for application in magnetic refrigeration systems, using thermogravimetric analysis, X-ray diffraction analysis and superconducting quantum interference device magnetometer. All samples were synthesized by flash combustion method using glycine as fuels and nitrates as precursors. The Li and Fe doped samples exhibited a rhombohedral structure and an R 3 ¯ c space group. The increase of Li concentration to 20%, leads to the formation of LiMn2O4 spinel phase as a secondary phase. The ferromagnetic–paramagnetic transition was inferred from the temperature dependence of the magnetization. The magnetic entropy change (−ΔSM) has been calculated using the magnetization isotherms data. However, the increase of La substitution by Li from 10 to 20% leads to a decrease of the Curie temperature TC from 215 to 75 K accompanied with a maximum magnetic entropy change / - Δ S M max / from 3.63 to 1.52 J.Kg−1 K−1 under a magnetic field change of 5 T. Moreover, by the 10% Fe doping, there is a clear trend of decreasing the Curie temperature, the magnetic entropy change and the relative cooling efficiency. Therefore, in the vicinity of TC, (−ΔSM) reached a maximum value of 1.54 J.Kg−1 K−1 for La0.9Li0.1Mn0.9Fe0.1O3 and 0.96 J.Kg−1 K−1 for La0.8Li0.2Mn0.9Fe0.1O3. According to the Arrott plots results, a second-order ferromagnetic–paramagnetic transition was found for all the doped samples. [ABSTRACT FROM AUTHOR]

Mesoporous silicas are among the most suitable high-surface area solids to support small-sized metal clusters and nanoparticles. Unfortunately, the instability of silica in water constitutes a serious impediment for its widespread use and large implementation as a catalytic support for fine chemical synthesis and for biomass upgrading in the context of biorefineries. While end cupping silanols provides a way for delaying framework degradation, further investigations are needed to design more robust, water-resistant supports. Prompted by the success of polydimethylsiloxane (PDMS) in surface coating and water-repellent technologies, we herein explore the transformation of triethoxysilyl-functionalized polymethylethylsiloxane – a sol–gel analogue of PDMS – into a hydrophobic disordered mesoporous MCM-41-type siloxane framework. The concomitant addition of a soluble gold precursor during the mesophase formation followed by surfactant removal resulted in the entrapment and growth of gold nanoparticles inside. Thermally induced evolution of the PDMS-like siloxane framework was further investigated both under inert and open air atmospheres. Gold accessibility was ascertained during the transformation of nitrophenol, a harmful water pollutant, into aniline as a valuable amine-based precursor. Owing to the virtues of the PDMS-like framework for slowing down water and oxygen diffusion, the catalysts preserve their activity even after 18 months of storage under an open air atmosphere. [ABSTRACT FROM AUTHOR]

Abstract: In this paper, we present the synthesis and characterizations of NaSICON-type ionic conducting ceramics of the general formula Na1+x M1.775Si x −0.9P3.9−x O12 with 1.8≤ x ≤2.2 and M=Zr or Hf. The effect of the total substitution of zirconium by hafnium on electric properties has been studied. The various compositions were prepared by using the sol–gel method and the synthesized precursors were characterized by coupled DTA–TG. The oxides obtained after pyrolysis of the precursors were identified by X-ray diffraction. A sintering study by thermodilatometry permits to select the best thermal cycle adapted to our ceramics. Furthermore, the electric conductivity of the sintered ceramic samples was characterized by complex impedance spectroscopy. These results show that ceramics containing Zr synthesized by soft method, present a higher total conductivity than those obtained in literature (to be around 10−4 Scm−1). The total substitution of Zr by Hf still improves this conductivity for some compositions. [Copyright &y& Elsevier]

Abstract: In this work, we present the synthesis and the characterization of ionic conducting ceramics of NaSICON-type (Natrium super ionic conductor). The properties of this ceramic make it suitable for use in electrochemical devices. These solid electrolytes can be used as sensors for application in the manufacturing of potentiometric gas sensors, for the detection of pollutant emissions and for environment control. The family of NaSICON that we studied has as a general formula Na2.8Zr2-ySi1.8-4yP1.2+4yO12 with 0y0.45. The various compositions were synthesized by produced using the sol–gel method. The electric properties of these compositions were carried out by impedance spectroscopy. The results highlight the good conductivity of the Na2.8Zr1.775Si0.9P2.1O12 composition. [Copyright &y& Elsevier]

In this paper, we investigate the structural, magnetic, and magnetocaloric properties of La0.62Nd0.05Ba0.33Mn1-xCrxO3 manganites elaborated by sol gel process. X-ray diffraction analyses confirm that all elaborated samples are crystallized on the rhombohedral perovskite structure with R-3c space group. Magnetic measurements reveal the presence of a magnetic transition from paramagnetic (PM) to ferromagnetic (FM) phase in the vicinity of Curie temperature TC. However, as Cr concentration increases, we witness a decrease in TC from 285 K for x = 0 to 250 K for x = 0.20. This behavior can be explained by the double exchange interaction of Mn3+-O-Mn4+. The maximum entropy change (- Δ S m max ) at µ0H = 5 T is found to be 2.63, 1.88, and 1.76 J.kg−1.K−1 for x = 0, 0.10, and 0.20, respectively. However, our research underlines the enhancement of relative cooling power (RCP) by Cr doping, from 310 to 340 J.kg−1 as Cr concentration increases from x = 0 to 0.20. This finding suggests the usefulness of our samples as magnetic refrigeration material around room temperature. Furthermore, the analysis of the magnetocaloric effect (MCE) using the Landau theory shows a good agreement with the experimental results with a soft difference, indicating the importance of Jahn–Teller interactions on manganites perovskite. [ABSTRACT FROM AUTHOR]

Controlled titanium alkoxide mineralization in the presence of phosphonated, dendrimeric nano-building blocks provides a new family of hierarchically porous dendrimer-bridged titanium dioxide materials. [ABSTRACT FROM AUTHOR]

Review: 143 refs. [ABSTRACT FROM AUTHOR]

Abstract: The synthesis of electrode materials with controlled microstructural characteristics and high conductivity over 1000Scm−1 is a key factor in improving the performance of fuel cells. In this work, we propose an alternative route to the partial sintering of a powder mixture to control the porosity of a ceramic–metal composite currently used as an anode material in Protonic Ceramic Fuel Cells working at 400–600°C. This new method is based on the use of nanopowdered cermet materials and starch in gelling form for the elaboration of Ni–BaCe0.9Y0.1O3 (Ni–BCY) cermets. The microstructure and the electrical properties have been investigated with respect to the initial starch content. A porous microstructure consisting of homogenously distributed Ni and BCY phases is observed. It is shown that the degree of open porosity and the electrical conductivity of the cermets are sensitive to the starch content. Anodes elaborated from initial compositions comprising 10 and 20wt.% of starch offer sufficient mechanical strength and an open porosity >30vol.%. The measured conductivities vary with the composition, from 1000 to 3000Scm−1 at 600°C. The use of starch in gelled form as porogen allows the engineering of the porosity and the control of pore shape and distribution. [Copyright &y& Elsevier]

Due to their relatively large magnetocaloric effect, Ba and K doped LaMnO 3 can be used in magnetic cooling systems. In this study, La 1-x Ba x MnO 3 (x = 0.1; 0.2) and La 0.9 K 0.1 MnO 3 powders were synthesized by the flash combustion method using glycine as a fuel and chelating agent. A subsequent calcination at 1000 °C was performed. Different characterization tools were used to carry out a detailed study of the structural, morphological, thermal, electrical, and magnetic behaviors of the doped materials. The structure of un-doped and doped samples was examined by X-ray Diffraction. According to magnetic data, La 0.9 K 0.1 MnO 3 exhibits a ferromagnetic-paramagnetic phase transition at 271 K and a magnetic entropy variation under a magnetic induction of 4 T /ΔS M / = 5.33 J kg−1K−1. On the other hand, the Curie temperature of La 1-x Ba x MnO 3 increases with the Ba content from 157 K for x = 0.1 to 200 K for x = 0.2, whereas /ΔS M / decreases from 2.56 J kg−1K−1 to 2.07 J kg−1K−1, respectively. Accordingly, it has been proven that the highest cooling performance corresponds to the K doped compound. The evolution from ferromagnetic to paramagnetic state was also determined with electron paramagnetic resonance spectroscopy. The temperature dependence of the resistivity shows a semiconductor character in La 0.9 Ba 0.1 MnO 3 and 2 maxima of metal-insulator (M-I) transitions in the K doped sample. Enhanced magnetoresistance effects have been observed in La 0.9 K 0.1 MnO 3 close to the ferromagnetic-paramagnetic transition temperature. Image 1 • La 1-x A x MnO 3 (A = K; Ba) samples were synthesized by flash combustion. • La 0.9 K 0.1 MnO 3 exhibits a large magnetocaloric effect in the vicinity of room temperature. • Enhanced magnetoresistance was found for La 0.9 K 0.1 MnO 3. • Magnetic entropy variation of La 0.9 K 0.1 MnO 3 is 5.33 J kg−1K−1 at 4T. [ABSTRACT FROM AUTHOR]

This review reports on the recent advances in the synthesis and physico-chemical properties of palladium-containing perovskites. Initially, the perovskite structure is briefly reviewed, then palladium-containing perovskites synthesis and physico-chemical properties are detailed. The applications of palladium-containing perovskites in catalysis; namely, NO reduction, methane combustion, methanol as well as ethanol oxidation, are briefly highlighted. The involvement and the important contribution of palladium-containing perovskites in cross-coupling reactions, especially Suzuki-Miyaura, Sonogashira, Ulmann and Grignard, are discussed.