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Abstract: To focus on the influence of the intermetallic compound—oxide interface of Pd-based intermetallic phases in methanol steam reforming (MSR), a co-precipitation pathway has been followed to prepare and subsequently structurally and catalytically characterize a set of nanoparticulate Ga2O3- and In2O3-supported GaPd2 and InPd catalysts, respectively. To study the possible promoting effect of In2O3, an In2O3-doped Ga2O3-supported GaPd2 catalyst has also been examined. While, upon reduction, the same intermetallic compounds are formed, the structure of especially the Ga2O3 support is strikingly different: rhombohedral and spinel-like Ga2O3 phases, as well as hexagonal GaInO3 and rhombohedral In2O3 phases are observed locally on the materials prior to methanol steam reforming by high-resolution transmission electron microscopy. Overall, the structure, phase composition and morphology of the co-precipitated catalysts are much more complex as compared to the respective impregnated counterparts. However, this induces a beneficial effect in activity and CO2 selectivity in MSR. Both Ga2O3 and In2O3 catalysts show a much higher activity, and in the case of GaPd2-Ga2O3, a much higher CO2 selectivity. The promoting effect of In2O3 is also directly detectable, as the CO2 selectivity of the co-precipitated supported Ga2O3-In2O3 catalyst is much higher and comparable to the purely In2O3-supported material, despite the more complex structure and morphology. In all studied cases, no deactivation effects have been observed even after prolonged time-on-stream for 12 h, confirming the stability of the systems.Graphical Abstract: The presence of a variety of distinct supported intermetallic InPd and GaPd2 particle phases is not detrimental to activity/selectivity in methanol steam reforming as long as the appropriate intermetallic phases are present and they exhibit optimized intermetallic-support phase boundary dimensions. [ABSTRACT FROM AUTHOR]

A new hexagonal polymorph of scandium fluoride (ScF3) has been synthesized and thoroughly characterized. The new phase displays two types of negative thermal expansion in a wide temperature range at normal pressure: a relatively weak isotropic negative thermal expansion at low temperatures and a strong anisotropic negative thermal expansion above 500 K. The thermal behavior is explained in part by a model of static structure distortions. [ABSTRACT FROM AUTHOR]

A new hexagonal polymorph of scandium fluoride (ScF3) has been synthesized and thoroughly characterized. The new phase displays two types of negative thermal expansion in a wide temperature range at normal pressure: a relatively weak isotropic negative thermal expansion at low temperatures and a strong anisotropic negative thermal expansion above 500 K. The thermal behavior is explained in part by a model of static structure distortions. [ABSTRACT FROM AUTHOR]

The amorphous Ti 40.7 Hf 9.5 Ni 44.8 Cu 5 melt-span ribbon samples were subjected to low-frequency vibrations (20 Hz) with an amplitude of 1 or 4 μm at room temperature to study the influence of the vibrations on the structural relaxation and the crystallization of amorphous alloy. The results obtained showed that the samples retained the amorphous structure after low-frequency vibrations but the resistivity decreased due to some structural relaxation. It was found that the low-frequency vibrations with an amplitude of 4 μm led to the formation of nanoclusters with ordered atomic position in the amorphous structure, but it hardly affected the crystallization temperatures. [ABSTRACT FROM AUTHOR]

Novel CVD precursors for SiBxCyNz film deposition such as HC≡CB[N(SiMe3)2]2, MeB[N(SiMe3)2]2 and Me3SiC≡CB[N(SiMe3)2]2 were synthesized. The structure and composition of the compounds were investigated with NMR, FTIR, Raman spectroscopies and CHN-analysis. Comparison of theoretical and experimental FTIR and Raman data was performed. Thermogravimetric analysis and the static tensimetry method with a glass membrane null manometer demonstrated that Me3SiC≡CB[N(SiMe3)2]2 is the most suitable CVD precursor. The formation of SiBxCyNz films was predicted using thermodynamic modelling at a temperature below 1600 K in the total pressure range of 0.27–1333 Pa. The films of chemical composition Si23.7B8.3C51.4N9.6O7 were deposited by low-pressure chemical vapour deposition (LPCVD) and their morphology and mechanical properties were investigated. The amorphous SiBxCyNz films with a smooth surface exhibited hardness, Young's modulus and elastic recovery equal to 17.5 ± 0.9 GPa, 176 ± 11 GPa and 61 ± 2%, respectively. [ABSTRACT FROM AUTHOR]

ABSTRACT Nanocomposite fibers consisting of isotactic polypropylene (iPP) as a matrix filled with vapor grown carbon nanofibers (VGCF) have been prepared and their fine crystalline structure and mechanical properties characterized. The obtained results point out that the VGCF oriented along the fiber extrusion direction induce crystallization in the surrounding iPP matrix in a special way leading to the formation of oriented iPP α-transcrystallite layers. The VGCF content and the draw ratio (DR) affect the textural properties of the composite material and lead to the formation of an anisotropic structure. The improvements of the mechanical properties of the composite fibers in both undrawn and drawn states are attributed to the VGCF aligning effect during extrusion, which produces highly oriented iPP crystalline structure, rather than to the reinforcing effect of the nanofibers. A new detailed scheme explaining the changes in tensile strength from the structural point of view is proposed. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 41865. [ABSTRACT FROM AUTHOR]

The fibers based on thermoplastic partially crystalline polyetherimide R-BAPB modified by vapor grown carbon nanofibers (VGCF) were prepared by melt extrusion, exposed to orientational drawing, and crystallized. All of the samples were examined by scanning electron microscopy, X-ray scattering, and differential scanning calorimetry to study how the carbon nanofiller influences on the internal structure and crystallization behavior of the obtained R-BAPB fibers. The mechanical properties of the composite R-BAPB fibers were also determined. It was found that VGCF nanoparticles introduced into R-BAPB polyimide can act as a nucleating agent that leads, in turn, to significant changes in the composite fibers morphology as well as thermal and mechanical characteristics. VGCF are able to improve an orientation degree of the R-BAPB macromolecules along the fiber direction, accelerate crystallization rate of the polymer, and enhance the fiber stability during crystallization process. [ABSTRACT FROM AUTHOR]

Abstract: Microstructural characteristics of various real Cu/ZnO/Al2O3 catalysts for methanol steam reforming (MSR) were investigated by in situ X-ray diffraction (XRD), in situ X-ray absorption spectroscopy (XAS), temperature programmed reduction (TPR) and electron microscopy (TEM). Structure–activity correlations of binary Cu/ZnO model catalysts were compared to microstructural properties of the ternary catalysts obtained from in situ experiments under MSR conditions. Similar to the binary system, in addition to a high specific copper surface area the catalytic activity of Cu/ZnO/Al2O3 catalysts is determined by defects in the bulk structure. The presence of lattice strain in the copper particles as the result of an advanced Cu–ZnO interface was detected only for the most active Cu/ZnO/Al2O3 catalyst in this study. Complementarily, a highly defect rich nature of both Cu and ZnO has been found in the short-range order structure (XAS). Conventional TPR and TEM investigations confirm a homogeneous microstructure of Cu and ZnO particles with a narrow particle size distribution. Conversely, a heterogeneous microstructure with large copper particles and a pronounced bimodal particle size distribution was identified for the less active catalysts. Apparently, lattice strain in the copper nanoparticles is an indicator for a homogeneous microstructure of superior Cu/ZnO/Al2O3 catalyst for methanol chemistry. [Copyright &y& Elsevier]

Highlights: [•] Stability of bulk and surface of intermetallic Pd2Ga were investigated. [•] The bulk was found to be stable under moderate conditions relevant for catalysis. [•] The surface is highly sensitive towards a passivating oxidative decomposition. [•] Different surface states of the catalyst can be easily controlled by pre-treatments. [ABSTRACT FROM AUTHOR]

Abstract: An effective and versatile synthetic approach to produce well-dispersed supported intermetallic nanoparticles is presented that allows a comparative study of the catalytic properties of different intermetallic phases while minimizing the influence of differences in preparation history. Supported PdZn, Pd2Ga, and Pd catalysts were synthesized by reductive decomposition of ternary Hydrotalcite-like compounds obtained by co-precipitation from aqueous solutions. The precursors and resulting catalysts were characterized by HRTEM, XRD, XAS, and CO-IR spectroscopy. The Pd2+ cations were found to be at least partially incorporated into the cationic slabs of the precursor. Full incorporation was confirmed for the PdZnAl-Hydrotalcite-like precursor. After reduction of Ga- and Zn-containing precursors, the intermetallic compounds Pd2Ga and PdZn were present in the form of nanoparticles with an average diameter of 6nm or less. Tests of catalytic performance in methanol steam reforming and methanol synthesis from CO2 have shown that the presence of Zn and Ga improves the selectivity to CO2 and methanol, respectively. The catalysts containing intermetallic compounds were 100 and 200 times, respectively, more active for methanol synthesis than the monometallic Pd catalyst. The beneficial effect of Ga in the active phase was found to be more pronounced in methanol synthesis compared with steam reforming of methanol, which is likely related to insufficient stability of the reduced Ga species in the more oxidizing feed of the latter reaction. Although the intermetallic catalysts were in general less active than a Cu-/ZnO-based material prepared by a similar procedure, the marked changes in Pd reactivity upon formation of intermetallic compounds and to study the tunability of Pd-based catalysts for different reactions. [Copyright &y& Elsevier]

One of the main stumbling blocks in developing rational design strategies for heterogeneous catalysis is that the complexity of the catalysts impairs efforts to characterize their active sites. We show how to identify the crucial atomic structure motif for the industrial Cu/ZnO/Al2O3 methanol synthesis catalyst by using a combination of experimental evidence from bulk, surface-sensitive, and imaging methods collected on real high-performance catalytic systems in combination with density functional theory calculations. The active site consists of Cu steps decorated with Zn atoms, all stabilized by a series of well-defined bulk defects and surface species that need to be present jointly for the system to work. [ABSTRACT FROM AUTHOR]

Highlights: [•] Performance of Pd2Ga in hydrogenation of phenylacetylene was investigated. [•] Surface state, activity, and stability depend strongly on the pre-treatment. [•] Even at highly inert conditions, the surface is sensitive toward oxidation. [•] Reactivity is due to the decomposed and not due to the clean intermetallic surface. [ABSTRACT FROM AUTHOR]

The anisotropic crystallite sizes in high-performance LiFePO 4 powders were measured by XRD and compared with the particle sizes found by TEM image analysis. Lognormal particle size distribution functions were determined for all three main crystallographic axes. A procedure was developed to determine the fraction of the composite particles which consists of several crystallites and contains small- and large-angle boundaries. In a sample with the most anisotropic crystallites (ratio of volume-weighted mean crystallite sizes L̄ V [001] / L̄ V [010] = 1.41) the number of the composite particles was at least 30%., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

Nanocomposite fibers based on heat-resistant amorphous polyetherimide (PEI) were prepared by twin screw melt micro-extrusion. Vapor-grown carbon nanofibers (VGCFs) and single-wall carbon nanotubes (SWCNTs) were used as fillers which helped to achieve enhanced mechanical properties. The structure and mechanical properties of such nanocomposite fibers were studied. Electron microscopy and melt rheology data revealed a uniform distribution of the nanofillers throughout the volume of the fibers. Wide-angle X-ray scattering showed that the orientational drawing of the nanocomposite fibers led to an improved orientation of the filler particles along the fiber axis. VGCFs or SWCNTs increased the tensile strength and modulus (by ∼275 MPa and ∼5 GPa, respectively) in oriented nanocomposite fibers and decreased deformation at break. SWCNTs were found to be more effective reinforcers than VGCFs., Competing Interests: The authors declare no competing financial interest., (Copyright © 2020 American Chemical Society.)

Abstract: To focus on the influence of the intermetallic compound-oxide interface of Pd-based intermetallic phases in methanol steam reforming (MSR), a co-precipitation pathway has been followed to prepare and subsequently structurally and catalytically characterize a set of nanoparticulate Ga 2 O 3 - and In 2 O 3 -supported GaPd 2 and InPd catalysts, respectively. To study the possible promoting effect of In 2 O 3 , an In 2 O 3 -doped Ga 2 O 3 -supported GaPd 2 catalyst has also been examined. While, upon reduction, the same intermetallic compounds are formed, the structure of especially the Ga 2 O 3 support is strikingly different: rhombohedral and spinel-like Ga 2 O 3 phases, as well as hexagonal GaInO 3 and rhombohedral In 2 O 3 phases are observed locally on the materials prior to methanol steam reforming by high-resolution transmission electron microscopy. Overall, the structure, phase composition and morphology of the co-precipitated catalysts are much more complex as compared to the respective impregnated counterparts. However, this induces a beneficial effect in activity and CO 2 selectivity in MSR. Both Ga 2 O 3 and In 2 O 3 catalysts show a much higher activity, and in the case of GaPd 2 -Ga 2 O 3 , a much higher CO 2 selectivity. The promoting effect of In 2 O 3 is also directly detectable, as the CO 2 selectivity of the co-precipitated supported Ga 2 O 3 -In 2 O 3 catalyst is much higher and comparable to the purely In 2 O 3 -supported material, despite the more complex structure and morphology. In all studied cases, no deactivation effects have been observed even after prolonged time-on-stream for 12 h, confirming the stability of the systems., Graphical Abstract: The presence of a variety of distinct supported intermetallic InPd and GaPd 2 particle phases is not detrimental to activity/selectivity in methanol steam reforming as long as the appropriate intermetallic phases are present and they exhibit optimized intermetallic-support phase boundary dimensions.

A Cu-based methanol synthesis catalyst was obtained from a phase pure Cu,Zn,Al hydrotalcite-like precursor, which was prepared by co-precipitation. This sample was intrinsically more active than a conventionally prepared Cu/ZnO/Al2O3 catalyst. Upon thermal decomposition in air, the [(Cu0.5Zn0.17Al0.33)(OH)2(CO3)0.17]⋅mH2O precursor is transferred into a carbonate-modified, amorphous mixed oxide. The calcined catalyst can be described as well-dispersed "CuO" within ZnAl2 O4 still containing stabilizing carbonate with a strong interaction of Cu(2+) ions with the Zn-Al matrix. The reduction of this material was carefully analyzed by complementary temperature-programmed reduction (TPR) and near-edge X-ray absorption fine structure (NEXAFS) measurements. The results fully describe the reduction mechanism with a kinetic model that can be used to predict the oxidation state of Cu at given reduction conditions. The reaction proceeds in two steps through a kinetically stabilized Cu(I) intermediate. With reduction, a nanostructured catalyst evolves with metallic Cu particles dispersed in a ZnAl2 O4 spinel-like matrix. Due to the strong interaction of Cu and the oxide matrix, the small Cu particles (7 nm) of this catalyst are partially embedded leading to lower absolute activity in comparison with a catalyst comprised of less-embedded particles. Interestingly, the exposed Cu surface area exhibits a superior intrinsic activity, which is related to a positive effect of the interface contact of Cu and its surroundings., (© 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

A technique of contact angle measurement was applied to the nano-scale oxide-supported metal particles. For Cu supported on ZnO and ZrO2 the angles were found to increase and the work of adhesion to decrease with increasing particle size. Such a trend is interpreted as an effect of negative contact line tension of 2.1 x 10(-9) J m(-1) and 1.0 x 10(-9) J m(-1) in the Cu/ZnO and Cu/ZrO2 system, correspondingly. For the small-sized Cu particles the apparent work of adhesion on ZnO support is higher than that on ZrO2.