Hybrid reverse Monte Carlo simulations of the structure of Zr50Cu45Al5 bulk metallic glass incorporating medium-range structure from fluctuation electron microscopy data and short-range structure from an embedded atom potential produce structures with significant fractions of icosahedral- and crystal-like atomic clusters. Similar clusters group together into nanometer-scale regions, and relaxation transforms crystal-like clusters into icosahedral clusters. A model refined against only the potential does not agree with the fluctuation microscopy data and contains few crystal-like clusters.

No abstract

a b s t r a c tPerovskite-based materials (LaMnO 3 , Pd/LaMnO 3 , LaCoO 3 and Pd/LaCoO 3 ) were synthesized, characterized (via BET, XRD, Raman spectroscopy, XPS and TEM) and their NO x (x = 1,2) adsorption characteristics were investigated (via in-situ FTIR and TPD) as a function of the nature of the B-site cation (i.e. Mn vs Co), Pd/PdO incorporation and H 2 -pretreatment. NO x adsorption on of LaMnO 3 was found to be significantly higher than LaCoO 3 , in line with the higher SSA of LaMnO 3 . Incorporation of PdO nanoparticles with an average diameter of ca. 4 nm did not have a significant effect on the amount of NO 2 adsorbed on fresh LaMnO 3 and LaCoO 3 . TPD experiments suggested that saturation of fresh LaMnO 3 , Pd/LaMnO 3 , LaCoO 3 and Pd/LaCoO 3 with NO 2 at 323 K resulted in the desorption of NO 2 , NO, N 2 O and N 2 (without O 2 ) below 700 K, while above 700 K, NO x desorption was predominantly in the form of NO + O 2 . Perovskite materials were found to be capable of activating N-O linkages typically at ca. 550 K (even in the absence of an external reducing agent) forming N 2 and N 2 O as direct NO x decomposition products. H 2 -pretreatment yielded a drastic boost in the NO oxidation and NO x adsorption of all samples, particularly for the Cobased systems. Presence of Pd further boosted the NO x uptake upon H 2 -pretreatment. Increase in the NO x adsorption of H 2 -pretreated LaCoO 3 and Pd/LaCoO 3 surfaces could be associated with the electronic changes (i.e. reduction of B-site cation), structural changes (surface reconstruction and SSA increase), reduction of the precious metal oxide (PdO) into metallic species (Pd), and the generation of oxygen defects on the perovskite. Mn-based systems were more resilient toward B-site reduction. Pd-addition suppressed the B-site reduction and preserved the ABO 3 perovskite structure.

No abstract