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Novel methods were applied in this work to elucidate the structure evolution of Ln2-xCaxNiO4+δ oxides (Ln = La, Pr, Nd; x = 0, 0.3) and study their oxygen mobility. Relationship between cations state, structural, electrical, electrochemical and kinetic properties was revealed. In all doped materials the overall oxygen mobility characterized by Do declined by more than an order of magnitude due to decreasing the interstitial oxygen content and hampering cooperative mechanism of oxygen migration. For La nikelate additional slow diffusion channel appears with DO 5.4·10−14 cm2/s at 700 K. Correlation of electrochemical and oxygen transport properties was demonstrated. A high electrical conductivity (up to 120 S/cm at 700 K) in Ln1.7Ca0.3NiO4+δ (Ln = Pr, Nd) along with satisfactory oxygen mobility and electrochemical properties makes these materials promising for a wide row of electrochemical applications.

Materials with a layered Ruddlesden–Popper structure having high oxygen mobility are promising for SOFC cathodes and oxygen separation membranes. This work aims at studying structural and transport features of Pr2-xCaxNiO4+δ (x = 0–0.6) oxides synthesized by a modified co-precipitation method and sintered at 1250 °C. The samples were characterized by in situ XRD using synchrotron radiation, TGA, oxygen heteroexchange with C18O2 and dc four-probe method. The phase transitions Fmmm ↔ I4/mmm were observed for all samples caused both by the temperature increase and oxygen loss. The electronic conductivity increases with Ca doping, while ionic conductivity varies in a complex manner remaining rather high (~10−3–10−1 S/cm), thus ensuring high values of ambipolar conductivity attractive for the practical application. The best ambipolar conductivity values at high temperatures were demonstrated for the undoped sample as well as for those with a low (x = 0.1) or high (x = 0.3; 0.5) dopant content. The relationships between structural, thermomechanical and transport properties are discussed.

Calcium aluminate Ca12Al14O33 initially known as cement compound after a series of structural refinements presented a complex cubic structure. It demonstrates a surprising feature consisting of the occurrence of spherical cavities named as cages. After this, mayenite is regarded as a kind of anti-zeolite. An alternative representation of such compounds formulated as highly non-stoichiometric garnets is highlighted in the present study. Mayenite is described as non-stoichiometric garnet {Ca3–x□x}1[Ca, Al]2Al3O12–x using the Raman spectroscopy. The dependence of phase diagram Al2O3–CaO in the region near the mayenite composition on the oxygen activity is summarized regarding its structural deficiency. It is pointed that cage is the result of defects association whereas structural defects tend to interact with each other. The main consequence of such interaction is a spontaneous formation of a core–shell structure. It is evidenced by the presence of a near-surface layer of small thickness over a compact oxide. The local symmetry of the mayenite structure at room temperature in oxidized and reduced (electride) state was studied by Raman spectroscopy which revealed the presence of luminescence without the rare-earths’ doping.

The real/atomic structure of single phase homogeneous nanocrystalline Ce0.5Zr0.5O2±δoxides prepared by a modified Pechini route and Ni-loaded catalysts of methane dry reforming on their bases was studied by a combination of neutron diffraction, synchrotron X-ray diffraction, total X-ray scattering and X-ray absorption spectroscopy. The effects of sintering temperature and pretreatment in H2were elucidated. The structure of the mixed oxides corresponds to a tetragonal space group indicating a homogeneous distribution of Ce and Zr cations in the lattice. A pronounced disordering of the oxygen sublattice was revealed by neutron diffraction, supposedly due to incorporation of water into the structure when in contact with air promoted by the generation of anion vacancies in the lattice after reduction or calcination at high temperatures. However, such disordering has not resulted in any occupation of the oxygen interstitial positions in the bulk of the nanodomains.

The self-sustained kinetic oscillations in the catalytic oxidation of methane over Ni foil have been studied at atmospheric pressure using an X-ray diffraction technique and mass spectrometry. It has been shown that the regular reaction-rate oscillations appear under oxygen-deficient conditions and the period of oscillations varies between approximately 200 and 4000 s. The operando measurements have revealed a higher activity of metallic Ni in the reaction than NiO oxide and have unambiguously showed that the oscillations arise due to the reversible bulk oxidation of Ni to NiO.

This chapter reviews recent advances in developing intermediate-temperature solid oxide fuel cells; oxygen and hydrogen separation membranes; and methods for obtaining advanced oxide, nanocomposite, and nanostructured materials for such devices. All the materials were synthesized by novel methods and characterized by sophisticated techniques. High ionic conductivity and improved oxygen/protonic mobility and surface reactivity were demonstrated. A new approach to building the functional layers was developed. A high-power density of single-button fuel cells in the intermediate-temperature range was reached. Oxygen and hydrogen separation membranes demonstrated promising and stable performance due to fast ionic transport and high catalytic activity of the materials concerned.

This work presents the results from a study of the structure and transport properties of Ca-doped La2NiO4+δ. La2−xCaxNiO4+δ (x = 0–0.4) materials that were synthesized via combustion of organic-nitrate precursors and characterized by X-ray diffraction (XRD), in situ XRD using synchrotron radiation, thermogravimetric analysis (TGA) and isotope exchange of oxygen with C18O2. The structure was defined as orthorhombic (Fmmm) for x = 0 and tetragonal (I4/mmm) for x = 0.1–0.4. Changes that occurred in the unit cell parameters and volume as the temperature changed during heating were shown to be caused by the excess oxygen loss. Typical for Ruddlesden–Popper phases, oxygen mobility and surface reactivity decreased as the Ca content was increased due to a reduction in the over-stoichiometric oxygen content with the exception of x = 0.1. This composition demonstrated its superior oxygen transport properties compared to La2NiO4+δ due to the enhanced oxygen mobility caused by structural features. Electrochemical data obtained showed relatively low polarization resistance for the electrodes with a low Ca content, which correlates well with oxygen transport properties. © 2021 by the authors. Licensee MDPI, Basel, Switzerland. The materials synthesis as well as electrochemical study were performed in a framework of the budget task of the IHTE UB RAS with using the equipment of the shared access center “Composition of compounds”. The TGA and isotope exchange studies were supported by the Ministry of Science and Higher Education of the Russian Federation within the governmental order for Boreskov Institute of Catalysis (projects АААА‐А21‐121011390007‐7, АААА‐А21‐ 121011390009‐1). The SXRD experiments were performed at the shared research center SSTRC on the basis of the Novosibirsk VEPP‐3 complex at BINP SB RAS, using equipment supported by pro‐ ject RFMEFI62119X0022.

The presence of nitric oxide NO in the gas phase was shown to decrease the decomposition rate of the hydrotalcite-like Co–Al LDH phase in the catalysts prepared by co-precipitation or deposition on Al 2 O 3 under the condition of urea hydrolysis. The decrease in LDH decomposition rate is related to the formation of a more crystallized phase of the spinel-like Co–Al oxide due to the ability of nitric oxide to transfer oxygen in consecutive reactions of the oxidation to NO 2 and reduction to NO. The difference in the coherent scattering domain size of the catalyst samples precalcined in the presence of NO or in a pure inert gas is retained at all consecutive steps of the reductive heat treatment in hydrogen: after the formation of a cubic phase of the (Co, Al)O oxide and its reduction to metallic cobalt. The observed changes in the degree of crystallinity and dispersion of the active metal exert only a slight effect or even no effect on the activity of the catalysts in Fischer–Tropsch synthesis. Noteworthy are a lower selectivity for methane and a greater fraction of olefins in the products obtained on the catalysts precalcined in a flow of inert gas containing 3% NO.

The growth mechanisms of carbon nanofibers on Ni catalysts and nitrogen-doped carbon nanofibers on Ni and Ni-Cu catalysts were studied. The growth of both types of nanofibers was found to occur by a mechanism that included the formation of surface non-stoichiometric nickel carbide followed by the dissolution and diffusion of carbon, or carbon and nitrogen into the bulk of the catalyst particles.

Mixed nanocrystalline Ce-Zr-O oxides (Ce/Zr = 1 or 7/3) were prepared by modified Pechini route using ethylene glycol solutions of metal salts. Detailed characterization of their real structure and surface properties by X-ray diffraction on synchrotron radiation with the full-profile Rietveld analysis, high resolution electron microscopy with elemental analysis, Raman spectroscopy, UV-Vis and X-ray photoelectron spectroscopy revealed a high homogeneity of cations distribution in nanodomains resulting in stabilization of disordered cubic phase. This provides a high dispersion of NiO loaded on these mixed oxides by wet impregnation, a high reactivity and mobility of oxygen in these catalysts and strong interaction of Ni with support in the reduced state. This helps to achieve a high activity and coking stability of developed catalysts in CH4 dry reforming in feeds with CH4 concentration up to 15% and CH4/CO2 ratio =1.

This work summarizes results of synchrotron radiation (SR) studies of the real/defect structure of nanocrystalline/nanocomposite oxide materials, which determines their functional properties in hydrogen energy field as catalysts and mixed ionic electronic conductors (cathodes and anodes of solid oxide fuel cells, oxygen separation membranes). For nanocrystalline ceria-zirconia mixed oxide prepared via modified Pechini route using ethanol solution of reagents, a high spatial uniformity of cations distribution between domains along with the oxygen sublattice deficiency revealed by full-profile Rietveld refinement of SR diffraction data provide structure disordering enhancing oxygen mobility. For PrNi 0.5 Co 0.5 O 3–δ – Ce 0.9 Y 0.1 O 2–δ nanocomposite extensive transfer of Pr cations into fluorite domains generates a new path of fast oxygen diffusion along chains of Pr 3+ – Pr 4+ cations as directly proved by analysis of the unit cell relaxation after changing pO 2 in perfect agreement with data obtained by oxygen isotope heteroexchange.

Mesoporous tungsten-silicates, W-MMM-E, have been prepared following evaporation-induced self-assembly methodology and characterized by elemental analysis, XRD, N2 adsorption, STEM-HAADF (high angle annular dark field in scanning-TEM mode), DRS UV-vis, and Raman techniques. DRS UV-vis showed the presence of two types of tungsten oxo-species in W-MMM-E samples: isolated tetrahedrally and oligomeric octahedrally coordinated ones, with the ratio depending on the content of tungsten in the catalyst. Materials with lower W loading have a higher contribution from isolated species, regardless of the preparation method. W-MMM-E catalyzes selectively oxidize of a range of alkenes and organic sulfides, including bulky terpene or thianthrene molecules, using green aqueous H2O2. The selectivity of corresponding epoxides reached 85–99% in up to 80% alkene conversions, while sulfoxides formed with 84–90% selectivity in almost complete sulfide conversions and a 90–100% H2O2 utilization efficiency. The true heterogeneity of catalysis over W-MMM-E was proved by hot filtration tests. Leaching of inactive W species depended on the reaction conditions and initial W loading in the catalyst. After optimization of the catalyst system, it did not exceed 20 ppm and 3 ppm for epoxidation and sulfoxidation reactions, respectively. Elaborated catalysts could be easily retrieved by filtration and reused several times with maintenance of the catalytic behavior.

Fine powders of Pr2 − xNiO4 + δ (PNO) oxides (x = 0 ÷ 0.3) synthesized by Pechini route were uniaxially pressed into pellets and sintered at 1300 °C under air. Chemical diffusion coefficients (Dchem.) and surface exchange constants (kchem.) were estimated by analysis of the weight and conductivity relaxations after step-wise change of pO2. In situ XRD studies were carried out in VEPP-3 facilities of the Siberian Center of Synchrotron Radiation using unique high-temperature camera and procedures. Analysis of dynamics of the cell volume expansion caused by oxygen loss with due regard for penetration depth of X-rays into the pellet allowed to estimate Dchem and kchem found to be close to those obtained by traditional methods. Isolated Pr vacancies appear to be the most important for fast oxygen diffusion and high surface reactivity providing the highest values of kchem and Dchem for Pr1.9NiO4 + δ composition.

Electrocatalytic activity for the oxygen reduction reaction (ORR) of the carbon-supported Pt catalysts obtained by chemical and electrochemical deposition has been studied in 0.10 M HClO 4 at 293 K in the expectation to gain new insights into the influence of the substructure of platinum on its catalytic properties for the ORR. Electron microscopy, XRD and electrochemical techniques have been employed to demonstrate that: (i) the ‘chemically’ synthesised Pt/C catalysts contain highly-dispersed isolated metal particles at intermediate metal loadings and both isolated crystallites and crystallite aggregates at higher loading; (ii) the electrodeposited Pt/C materials are ‘nanostructured’, i.e. contain large (up to ca 350 nm) aggregates with the deposition potential dependent morphology composed of comparatively small ( 2 , which further reduction occurs at the highly catalytically active Pt(1 1 1) facets. Structural defects present at an optimal concentration are concluded to promote the ORR catalytic activity of platinum, but excessive defectiveness of the Pt catalyst might hinder the kinetics of the oxygen electroreduction.

Changes of a 65Ni25Cu10Al 2 O 3 catalyst consisting of Ni-enriched and Cu-enriched alloys were investigated in the bulk and on the surface during the growth of nitrogen-doped carbon nanofibers (N-CNFs) by decomposition of a 50%C 2 H 4 /50%NH 3 mixture using in situ X-ray diffraction (XRD) analysis, ex situ X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM) techniques. It was shown that N-CNF growth at 450–650 °C is accompanied by dissolution of carbon and nitrogen in the Ni-enriched alloy, whereas Cu-enriched alloy remains inactive. A correlation between nickel and copper surface concentrations and properties of N-CNFs in relation to the nitrogen content was found. It was demonstrated that phase composition of the catalyst during N-CNF growth determines the type of N-CNFs structure.

The growth of nitrogen-doped carbon nanofibers (N-CNFs) by the decomposition of ethylene–ammonia mixtures on a Ni–Cu catalyst was studied using in situ X-ray diffraction analysis. The catalyst consists of the Ni-enriched (Ni0.85Cu0.15) and Cu-enriched (Cu0.95Ni0.05) alloys. It was found that the growth of N-CNFs, similar to the growth of carbon nanofibers, proceeds on the Ni-enriched alloy, whereas the Cu-enriched alloy remains inactive. During the N-CNF growth, carbon dissolves in the Ni0.85Cu0.15 alloy with the formation of a oversaturated solid solution, but without formation of bulk nickel carbide. It was supposed that nitrogen also dissolves in this alloy, but the driving force is the primary dissolution of carbon.

Structural changes in a 65Ni–25Cu–Al2O3 catalyst during the decomposition of a C2H4/NH3 mixture at different stages of nitrogen-containing carbon nanofiber (N-CNF) synthesis were studied by X-ray diffraction (XRD) analysis, X-ray diffraction using anomalous scattering effect and extended X-ray absorption fine structure (EXAFS) spectroscopy. The N-CNF growth over a catalyst particle was supposed to proceed via the formation of an oversaturated solid solution of carbon and nitrogen in a nickel-enriched alloy “NiCuxCyNz”. The latter resulted in an increase of the alloy lattice parameter to abnormally large values а = 3.616–3.706 A without destruction of its cubic structure. The formation of the “NiCuxCyNz” phase and its presence in the system coincide with the optimum time for the synthesis of N-CNFs with the highest nitrogen concentration and maximum values of specific surface area and total pore volume.

Iron-containing mesoporous mesophase materials Fe,Al-MMM-2 have been synthesized according to a sol-mesophase route under mild acidic conditions (pH 2.3–4.4) using Keggin type cation [FeAl12O4(OH)24(H2O)12]7+ (FeAl127+) as Al and Fe sources. Effect of pH of the synthetic solution on structural and physicochemical properties of Fe,Al-MMM-2 has been evaluated by means of small- and wide-angle XRD, FTIR, DR-UV–vis, and N2-adsorption/desorption analysis. It has been established that deviation of stability of FeAl127+ cation at various pH determines Al/Fe ratio in the resulting material as 12/1 (material synthesized at pH 4.4), and 6/1 (pH 2.4 and 3.3). Correlation between incorporation of Al and Fe in different forms and resulting materials texture is discussed. Fe,Al-MMM-2 materials have been tested as catalysts for wet phenol oxidation with H2O2. Insertion of Al species into the framework of the silicate matrix increases the activity comparing to a reference Fe,Al-pillared clay due to both higher surface acidity and lower diffusion limitations that correspond to Fe,Al-MMM-2.

The phase stability of SrCo0.8Fe0.2O3−d perovskite doped with niobium was studied by in situ high-temperature X-ray diffraction in the temperature range of 30–1000 °C and oxygen partial pressure 0.2–10−5 atm. The stability of the cubic perovskite structure in a wide range of oxygen partial pressures is the main advantage of SrCo0.8−xFe0.2NbxO3−d (x = 0.1–0.3) system in comparison with SrCo0.8Fe0.2O3−d. It is suggested that equilibrium of the thermal expansion with changes of the oxygen non-stoichiometry leading to the same lattice parameters in the oxidizing and reducing environments at the catalytic temperatures is a necessary requirement for stable operation of perovskite as an oxygen-conducting membrane. In the case of SrCo0.8−xFe0.2NbxO3−d perovskite this condition is met at x = 0.2. This makes the SrCo0.6Fe0.2Nb0.2O3−d composition promising for application as oxygen-conducting membrane.

Perovskite SrCo0.6Fe0.2Nb0.2O3-z attracts attention as a promising material with high oxygen conductivity. The sample was investigated by means of high-temperature X-ray powder diffraction and thermogravimetry. Phase transition was detected near 400 °C and accompanied with significant mass loss. The phase transition affects oxygen mobility, important for the synthesis of oxygen permeable membranes. The unit cell parameters are proved to change with temperature after two effects (1) reversible conventional thermal expansion and (2) irreversible contraction-expansion due to the changes in the oxygen content. In situ high-temperature X-ray diffraction experiments allowed us to separate the contributions and to measure them as a function of temperature.

The effect of hole doping on the crystal and electronic structure of La1−xSrxCo1−yNbyO3 (y=0.0–0.25) at the x=0.0; 0.2; 0.5 has been studied by neutron diffraction and X-ray absorption spectroscopy at the Co K and L2,3-edges. The preliminary analysis of the Co K and L2,3-edges X-ray absorption near edge structure (XANES) in La1−xSrxCo1−yNbyO3 series suggests that upon niobium doping, an increase of the intermediate Co3+ spin state and a decrease of low spin Co4+ states contributions occur. The possible explanation of the observed changes of crystal and electronic structure in these cobaltites is discussed.

International audience; A combined high-resolution Co K-edge extended x-ray absorption fine structure (EXAFS) and high-resolution X-ray powder diffraction (XRD) study has been performed to clarify the detail of anomalous behavior of temperature-dependent magnetic susceptibility curve on the LaCoO3 across the spin-state (similar to 120 K) transition. According to XRD analysis, the Debye-Waller factor of Co-O bond exhibit rapid growth below 20 K whereas the temperature dependence of the average Co-O bond length shows linear behavior from 10 K to 400 K. The EXAFS data show an anomalous decrease of the Co-O bond lengths with respect to those obtained by XRD. No local distortion of CoO6 octahedral as temperature increases up to 400 K has been detected

We report the effect of pulsed electron beam irradiation on the long-range and short-range atomic structure, as well as on the Raman phonon modes, of perovskite (Pb1−xLax)(Zr0.65Ti0.35)O3, x = 0.04 and 0.09 (PLZT 4/65/35 and 9/65/35) ferroelectric ceramics. X-ray powder diffraction (XRD) spectra from the single-pulse-irradiated PLZT 9/65/35 samples reveal transformation of the cubic Pm3m ( Z = 1 ) into the orthorhombic Pmmm ( Z = 1 ) structure. This symmetry change is however not observed for 10-pulse irradiation performed under the same conditions: here only an increase in the coherent scattering regions, lattice volume, and the Zr–O distance distribution is observed, as revealed by XRD and X-ray absorption spectroscopy at Zr K-edge. Raman scattering from PLZT 9/65/35 ceramics is in agreement with the symmetry reduction after single-pulse irradiation and reveals significant Raman signal intensity decrease after multiple-pulse irradiation. On the contrary, no significant structural changes could be detected in PLZT 4/65/35 ceramics after single- or multiple-pulse irradiation. Possible mechanisms of pulsed electron irradiation effects in PLZT 4/65/35 and 9/65/35 ceramics are discussed.

The effect of pulsed electron irradiation on the long- and short-range order in the La0.7Sr0.3CoO3 ceramics is reported. Neutron and X-ray powder diffraction reveal that the unit cell symmetry and single-phase state of single and multiple irradiated La0.7Sr0.3CoO3 are preserved, while the oxygen atoms coordination changes towards the La0.5Sr0.5CoO3 structure. X-ray absorption data confirm this observation and further reveal the details of the shift and splitting of the Co 3+ t2g and eg atomic orbitals. Possible mechanisms of pulsed electron irradiation effect in La0.7Sr0.3CoO3 are discussed.

Physical and chemical properties of TSEFLAR™-treated gibbsite/hydrargillite (centrifugal thermal activation) CTA HG were studied with X-ray analysis, TA, EM, BET and IRS. CTA HG product obtained at the temperature range of 330–580 °C and contact time ∼1 s is the one with a transitional non-equilibrated layered hydroxide structure with partly lost hydroxide groups. The CTA HG structure does not correspond to the produced chemical composition Al 2 O 3 ·(0.4–2)H 2 O and, therefore, the products reveal a higher reactivity. Such products are already readily hydrated at room temperature in water and aqueous ammonia to form eventually the stable bayerite-like hydroxide structure.

Coprecipitated Fe-Al 2 O 3 , Fe-Co-Al 2 O 3 and Fe-Ni-Al 2 O 3 catalysts is shown to be very efficient in carbon deposition during methane decomposition at moderate temperatures (600–650 °C). The carbon capacity of the most efficient bimetallic catalysts containing 50–65 wt.% Fe, 5–10 wt.% Co (or Ni) and 25–40 wt.% Al 2 O 3 is found to reach 145 g/g cat . Most likely, their high efficiency is due to specific crystal structures of the metal particles and formation of optimum particle size distribution. According to the TEM data, catalytic filamentous carbon (CFC) is formed on them as multiwall carbon nanotubes (MWNTs). The phase composition of the catalysts during methane decomposition is studied using a complex of physicochemical methods (XRD, REDD, Mossbauer spectroscopy and EXAFS). Possible mechanisms of the catalyst deactivation are discussed.

Genesis of the composition and structure of the active component of coprecipitated iron containing catalysts (Fe-Al 2 O 3 , Fe-Co-Al 2 O 3 , Fe-Ni-Al 2 O 3 ) with high metal loadings (>50 wt.%) for methane decomposition at moderate temperatures (600–650 °C) has been investigated by XRD, EXAFS, radial electron density distribution (REDD), TEM, FTIR and Mossbauer spectroscopy. The main stages of the catalyst genesis during drying, thermal decomposition and reduction have been studied. For bimetallic systems (Fe-Co-Al 2 O 3 , Fe-Ni-Al 2 O 3 ) intermediate spinel phases with a composition (M II , Fe) 3 O 4 (M=Co, Ni) have been shown to form during heat treatment and reduction. This leads to a decrease of the reduction temperature for iron oxides. Reduced bimetallic catalysts (Fe-Co-Al 2 O 3 , Fe-Ni-Al 2 O 3 ) are composed of alloys. The structure and parameters of their crystal lattices depend on the type and concentration of the added metal. Alumina has been shown to behave as a structural promoter. A model of the reduced catalysts consisting of highly dispersed (20–50 nm) metal and alumina particles with a spinel phase at their interface has been suggested.

Hexagonally packed mesostructured titanosilicates of the SBA-15 type have been prepared in moderately acidic aqueous media starting from sodium disilicate Na 2 Si 2 O 5 , TiOSO 4 , and olefin oxide co-polymer of the Pluronic type (P123) as a template. Structure–texture parameters of the synthesised materials were characterised by using X-ray diffraction and nitrogen adsorption techniques. The titanium state in the silicate matrix was characterised by DR-UV, IR, Raman spectroscopy, and XPS. The catalytic properties of the new titaniumsilicates were tested in oxidation reactions with aqueous H 2 O 2 using methyl phenyl sulfide and 2,3,6-trimethylphenol as model substrates and compared with the catalytic properties of TS-1 and Ti-MMM (titaniumsilicate of the MCM-41 type). The structure of the Ti-SBA-15 materials, by contrast to Ti-MMM catalysts, was proved to be hydrolytically stable towards aqueous H 2 O 2 . The catalytic activity of Ti-SBA-15 is considerably lower than that of Ti-MMM, most likely due to a lower titanium dispersion and higher wall thickness of the former material, which makes part of titanium sites unavailable for the reactants.

Silicon carbonitride films were synthesised in a remote plasma chemical vapour deposition process using novel single-source precursors w(CH ) HSiNHN(CH ) and (CH ) SiwNHN(CH ) x , which are silyl derivatives of 1,1-dimethylhydrazine. The films 32 3 2 3 2 3 2 2 were characterised by X-ray photoelectron (XPS), Fourier transform infrared (FTIR) and UV–Vis absorption spectroscopy. The microstructure of the films was examined by scanning electron microscopy and diffraction of synchrotron radiation methods. XPS and FTIR spectroscopic studies showed the Si–C and Si–N to be the basic bonds for the films deposited in the system with excited hydrogen, whereas the C–N and Si–N bonds are mainly peculiar to the films synthesised in the system with excited helium. The films were found to be predominately amorphous with a number of crystallites embedded in an unstructured matrix. The crystalline phase can be indexed in tetragonal cell with lattice parameters as9.6 A and cs6.4 A. Appearance of the crystals, ˚˚ their dimensions and crystal forms did not depend on the substrate temperature. We hypothesised the crystallisation to be occurring either in the gas phase during deposition or in the solid as a result of the increase in mechanical stress with increasing film thickness. The FTIR and XPS data demonstrate the chemical bonding and the atomic local order in the amorphous matrix to be much more complicated than those of Si N –SiC or Si N –C N mixtures. This novel material has an optical band gap varying 34 3 4 3 4 within the energy range from 2.0 to 4.7 eV. The films obtained were highly resistant to thermal degradation. 2003 Elsevier Science B.V. All rights reserved.

The model of structure and structural transformation of the mesostructured carbon material CMK-1 was established by X-ray powder diffraction (XRD) and transmission electron microscopy (TEM) investigations. The investigations showed that the enantiomeric carbon subframeworks formed within the pores of the MCM-48 mesoporous template used for the material synthesis displaced with respect to one another without significant distortions after the dissolution of the silica wall of the template. The model proposed agrees well with TEM images observed. The XRD structural modeling of CMK-1 done using the continuous density function technique allowed perfect fit of the calculated to the experimental powder diffraction pattern and provided geometric characteristics of the material texture. The structural characteristics obtained agreed fairly well with TEM analysis and with previously reported adsorption data.

Here we report on the results of an in situ X-ray diffraction study of phase transformations during catalytic graphitisation of amorphous carbon. It is demonstrated that there is unusual change of iron catalyst reflection intensity at low temperature ∼640°C. This unusual intensity change may possibly be caused by the transition of some part of metal into liquid state at low temperature. It was also shown by electron microscopy that although no graphite reflections were detected 80–90% of amorphous carbon becomes graphite after sample heating in a high temperature vacuum chamber.

Honeycomb structure model was applied for describing surface properties in the MCM-41 and SBA-15 types of highly ordered silicas and aluminosilicates with different nominal mesopore diameters: about 4 nm and about 10 nm. As shown, calculations of internal specific surface area A me require a heterogeneity of this surface to be taken into account, the latter being quantified by the roughness coefficient β . These calculations at the condition β =1.0 will allow to estimate the lower limit of specific surface area of the materials only, which will correspond to the perfectly smooth walls of mesopores. This description seems to be valid for the MCM-41 type systems, for which β is about 1.1–1.2. On the contrary, β is found to exceed 1.5 for the SBA-15 type materials. This fact is probably due to an essential non-smoothness of the mesopore surface in these systems and may be associated with their synthesis conditions.

Well-organized Ti- and V-containing silicate mesoporous mesophase materials (MMM) were synthesized using C 16 H 33 N(CH 3 ) 3 Br and characterized by elemental analysis, IR, DRS-UV, XRD, and N 2 adsorption. Catalytic properties of these materials in alkene and thioether oxidations with aqueous H 2 O 2 were examined. The structure–activity study was performed for the C16-(Ti,Si)-MMM catalysts with the Si/Ti atomic ratio ranged from 19 to 166. The samples with the Si/Ti atomic ratio in the range of 49–124 showed the highest catalytic activities. Both structure perfection of the silicate matrix and degree of isolation of titanium ions in it appeared to be crucial factors determining catalytic activity of C16-(Ti,Si)-MMM in alkene oxidation. For efficient oxidation of more nucleophilic substrates (thioethers) the structural perfection of the C16-(Ti,Si)-MMM catalysts was less important. No titanium leaching occurred even in 1.1 M H 2 O 2 solution at 353 K, whereas vanadium leaching was already pronounced at [H 2 O 2 ]=0.05 M and room temperature. The oxidation processes proved to be true heterogeneous for C16-(Ti,Si)-MMM and mostly homogeneous for C16-(V,Si)-MMM.

Rietveld’s technique in combination with a continuous electron density representation was applied to structural modeling of highly ordered pure siliceous mesoporous mesophase material C16-SiO 2 -MMM of the MCM-41 type prepared by hydrothermal synthesis in the presence of C 16 H 33 N(CH 3 ) 3 Br. Several important characteristics of the material in both as-synthesized and calcined forms were revealed. In particular, it was found that mesopores in the materials are of true hexagonal shape, and the wall electron density seems to be not continuous.

Structural and textural characteristics as well as coordination states of aluminium and some catalytic properties are studied for highly-ordered (with very narrow XRD reflections) aluminosilicate mesoporous mesophase materials ((Si,Al)-MMM) prepared with different aluminium concentrations by hydrothermal synthesis in the presence of C 16 H 33 N(CH 3 ) 3 Br. As shown, all physico-chemical parameters measured for these systems including their structural hydrostability are strongly influenced by the aluminium content. Based on analysis of the results obtained, a description of probable transformations during formation of mesoporosity in the C16-(Si,Al)-MMM is considered.

Some examples illustrating the use of the method based on the radial distribution function (RDF) of electronic density for investigation metal and oxide catalysts are reported. Using monoatomic unsupported metal catalysts with crystallite sizes D =40–450 A, it was shown that the areas of coordination peaks in RDF directly define the absolute values of coordination numbers Z and depend on crystallite sizes. The investigation of the phase composition and local structure of supported metal catalysts revealed that the interaction between the active component and the support was responsible for the thermal stability of small supported metal particles. The local structure of ceria with different crystallite sizes was investigated.

Precision X-ray diffractometry with synchrotron radiation and transmission electron microscopy are used to show that the extent of hexagonal distortion of the perovskite cell of the (La1−x, Sr x )CoO3−δ system decreases and the microstructure of the samples changes when La is substituted by Sr; these changes are due to increased microstrains in the structure and subsequent formation of microunits. The microunit structure of particles in the region of the morphotropic transition 0.3≤x≤0.4, which is a consequence of the metastable state of the system, may be the reason for the high catalytic activity of the samples which we found previously.

The real structure of silver supported catalysts for ethylene epoxidation (Ag/α-Al2O3) was investigated using precision X-ray diffraction on synchrotron radiation, in situ high-temperature X-ray diffraction, and transmission electron microscopy. Stacking faults and intergrain boundaries were found to be main types of defects in the structure of silver microcrystals. In situ study revealed that under reaction conditions the intergrain boundaries remain unchanged, whereas stacking faults are annealed. We found a correlation between the reaction rate of ethylene epoxidation and parameters responsible for the relationship among the regular and defect regions in the bulk structure of silver particles.

Using Differential Anomalous X-ray Scattering (DAXS) method the structure and phase composition of Pt-containing particles of standard catalyst EuroPt-1 has been investigated. It has been demonstrated that EuroPt-1 catalyst consists of metal platinum and platinum oxide PtO. About 60% Pt is oxidized in fresh sample. No metal-support interaction has been detected.

Structure refinement of defect MgO containing acetate and carbonate groups has been performed. The experiment was carried out on high resolution powder diffractometer in Siberian Synchrotron Radiation Center, Novosibirsk. The results demonstrated possibility of admixtures to insert into the structure of MgO by two different ways. The reliability of both models has been estimated. These models provided the decrease of R-factor down to 2.0–2.2% in contrast to the ideal MgO structure R-factor (9.5%).

The structure of MCM-48 mesoporous silicate materials has been fully characterized from X-ray diffraction data by applying recently developed methods of mesostructure analysis and full-profile refinement. The pore wall thickness of both as-made and calcined MCM-48 was determined with high precision to be 8.0(1) Angstrom. No regular variations of the wall thickness were detected, but its density was found to be ca. 10% higher in the low-curvature regions. The surfactant density in the pores was assessed around 0.6-0.7 g/cm(3) and was found to have a distinct minimum in the pore center similar to that detected previously in MCM-41. A new extended model function of the density distribution in MCM-48 is proposed on the basis of the structural features that were revealed.

A continuous density function technique has been developed for X-ray diffraction (XRD) structural investigations of mesostructured materials. The technique is designed for the analysis of the density distribution in materials exhibiting nanoscale (2-50 nm) ordering of structural elements without atomic long-range order. The results of structure investigations of a series of silicate, metallosilicate and carbon mesostructured materials with hexagonal and cubic symmetry are presented.

Publisher Summary This chapter discusses a comparative study of the wall properties in highly ordered silicate and aluminosilicate mesostructured materials of the MCM-41 and SBA-15 types. X-ray diffraction (XRD) structural modeling based on a continuous electron density representation and textural analyses by the combined XRD-adsorption method is applied to quantify distinctions in the wall structure of the MCM-41 and SBA-15 types of mesostructured materials.

Rietveld profiles, Moessbauer spectra and x-ray absorption fine structure (XAFS) were analyzed through the structural phase transition at Ts = 355 K in HoBaCo4O7. Excess of the oxygen content over O7 was avoided via annealing the samples in argon flow at 600 degree C. Space groups (S.G.) Pbn21c and P63mc were used to refine the structure parameters in the low- and high-temperature phases, respectively. Additionally, the Cmc21 symmetry was considered as a concurrent model of structure of the low-temperature phase. In the high-temperature phase, severe anisotropy of thermal motion of the major part of the oxygen atoms was observed. This anisotropic motion turns to be quenched as the sample is cooled below Ts. The variation of quadrupole splitting near Ts is not similar to a steplike anomaly frequently seen at the charge-ordering transition. We observe instead a dip-like anomaly of the average quadrupole splitting near Ts. Narrow distribution of the electric field gradient (EFG) over different cobalt sites is observed and explained on the basis of point-charge model. XAFS spectra show no evidence of significant difference between YBaCo4O7 (T > Ts) and HoBaCo4O7 (T < Ts). The origin of the transition at Ts is ascribed to the condensation of the libration phonon mode associated with the rigid-body rotational movements of the starlike tetrahedral units, the building blocks of kagome network. It is shown that the condensation of the libration mode is not compatible with translation symmetry for the hexagonal S.G., but compatible for the orthorhombic S.G. The orthorhombic lattice parameters and EFG components (Vxx, Vyy, Vzz) vary smoothly with temperature at approaching Ts and closely follow each other., 13 figures