Development and Testing of Pt/Al2O3 Catalysts for Hydrogen Peroxide Decomposition

Supported Pt/Al2O3 and Pt/SiC catalysts for hydrogen peroxide (HP) decomposition have been prepared by means of two innovative implantation techniques on spheres and granules of several alumina-based carriers (lanthanum-doped alumina, bimodal delta –alumina and theta –alumina, silicon carbide and alpha–alumina) with BET surface areas between 4 and 200 m2/g. In order to evaluate the chemical activity and thermal shock resistance of the supporting pellets, two focused sets of experiments have been carried out in a specifically-designed test bench. Scanning electron microscopy (SEM) measurements of the platinum load on the supporting surface have been used to assess the effectiveness of the deposition and monitor the degradation induced by hydrogen peroxide decomposition. Two of the Pt/α−Al2O3 catalysts showed excellent activity, high thermo-mechanical strength, and negligible loss of platinum after repeated cycles of hydrogen peroxide decomposition. In addition, h..

Nanoscale assembly of lanthanum silica with dense and porous interfacial structures

This work reports on the nanoscale assembly of hybrid lanthanum oxide and silica structures, which form patterns of interfacial dense and porous networks. It was found that increasing the molar ratio of lanthanum nitrate to tetraethyl orthosilicate (TEOS) in an acid catalysed sol-gel process alters the expected microporous metal oxide silica structure to a predominantly mesoporous structure above a critical lanthanum concentration. This change manifests itself by the formation of a lanthanum silicate phase, which results from the reaction of lanthanum oxide nanoparticles with the silica matrix. This process converts the microporous silica into the denser silicate phase. Above a lanthanum to silica ratio of 0.15, the combination of growth and microporous silica consumption results in the formation of nanoscale hybrid lanthanum oxides, with the inter-nano-domain spacing forming mesoporous volume. As the size of these nano-domains increases with concentration, so does the mesoporous volume. The absence of lanthanum hydroxide (La(OH)(3)) suggests the formation of La2O3 surrounded by lanthanum silicate

Dynamic behavior of impurities and native components in model LSM microelectrodes on YSZ

Energy conversion materials exhibit complex dynamic behavior when subjected to elevated temperatures and polarization.</p

Synthesis and Evaluation of ABO3 Perovskites (A=La and B=Mn, Co) with Stoichiometric and Over-stoichiometric Ratios of B/A for Catalytic Oxidation of Trichloroethylene

In this contribution, perovskite catalysts (ABO3) were probed that site A and site B were occupied by lanthanum and transition metals of manganese or cobalt, respectively, with stoichiometric ratios as well as 20 % over-stoichiometric ratios of B/A. The perovskite samples were synthesized using a gel-combustion method and characterized by BET, XRD, SEM and O2-TPD analyses. After mounting in a fixed bed reactor, the catalysts were examined in atmospheric pressure conditions at different temperatures for oxidation of 1000 ppm trichloroethylene in the air. Evaluation of over-stoichiometric catalysts activity showed that the increased ratio of B/A in the catalysts compared to the stoichiometric one led to BET surface area, oxygen mobility, and consequently catalytic performance improvement. The lanthanum manganite perovskite with 20 % excess manganese yielded the best catalytic performance among the probed perovskites.

Synthesis and Characterization of Highly Fluorescent Multi-Coloured Upconversion Nanomaterials

The current research project work essentially deals with the synthesis of highly bright fluorescent nanoparticles which have the ability to emit wavelength shorter than that of the pumped wavelength. The synthesis was carried out using thermal decomposition method to dope lanthanide ions into the host lattice using lanthanum oxides as precursors. The Upconversion NPs formed were either capped by oleylamine or oleic acid, yielding their dispersibility in organic solvents and preventing them from agglomeration. We developed UCNPs having varied colours which can prove useful for barcoding and imaging purposes. Further, we functionalised our NPs with silica using reverse micro-emulsion technique. These bifunctional nanocomposites increase the stability of upconversion materials and prevent the escape of rare earth ions from the lattice. The characterization for all the particles was carried out using XRD, EDAX, FTIR, DLS and Zeta potential analysis

Sumari

Sumar

Combinatorial synthesis of oxysulfides in the lanthanum-bismuth-copper system

Establishing synthesis methods for a target material constitutes a grand challenge in materials research, which is compounded with use-inspired specifications on the format of the material. Solar photochemistry using thin film materials is a promising technology for which many complex materials are being proposed, and the present work describes application of combinatorial methods to explore the synthesis of predicted La–Bi–Cu oxysulfide photocathodes, in particular alloys of LaCuOS and BiCuOS. The variation in concentration of three cations and two anions in thin film materials, and crystallization thereof, is achieved by a combination of reactive sputtering and thermal processes including reactive annealing and rapid thermal processing. Composition and structural characterization establish composition-processing-structure relationships that highlight the breadth of processing conditions required for synthesis of LaCuOS and BiCuOS. The relative irreducibility of La oxides and limited diffusion indicate the need for high temperature processing, which conflicts with the temperature limits for mitigating evaporation of Bi and S. Collectively the results indicate that alloys of these phases will require reactive annealing protocols that are uniquely tailored to each composition, motivating advancement of dynamic processing capabilities to further automate discovery of synthesis routes

Corrigendum: Selective catalytic and kinetic studies on oxydehydrogenation of ethane with CO2 over lanthanide metal catalysts

This note corrects an issue that has been identified in the article in Comptes Rendus Chimie with the above title. It was published online on 6th June 2020 in Volume 23, Issue 1, 2020, pages 33–46, https://doi.org/10.5802/crchim.4

Transmission electron microscopy of oxide dispersion strengthened (ODS) molybdenum: effects of irradiation on material microstructure

Oxide dispersion strengthened (ODS) molybdenum has been characterized using transmission electron microscopy (TEM) to determine the effects of irradiation on material microstructure. This work describes the results-to-date from TEM characterization of unirradiated and irradiated ODS molybdenum. The general microstructure of the unirradiated material consists of fine molybdenum grains (&lt; 5 {micro}m average grain size) with numerous low angle boundaries and isolated dislocation networks. 'Ribbon'-like lanthanum oxides are aligned along the working direction of the product form and are frequently associated with grain boundaries, serving to inhibit grain boundary and dislocation movement. In addition to the 'ribbons', discrete lanthanum oxide particles have also been detected. After irradiation, the material is characterized by the presence of nonuniformly distributed large ({approx} 20 to 100 nm in diameter), multi-faceted voids, while the molybdenum grain size and oxide morphology appear to be unaffected by irradiation