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A series of Al2O3 nanoparticles with the sizes ranging from ~ 2 to 21 nm, according to XRD, HRTEM and BET, was obtained by vaporization of α-Al2O3 in flowing helium and argon at different pressures under the action of a cw CO2 laser. The particle size was changed by varying the composition of ambient gas (He, Ar) and its pressure in a vaporization chamber from 0.034 to 0.9 bar. The effect of the synthesis conditions on the properties of Al2O3 nanopowders is presented and discussed. Particles with the size smaller than 6–7 nm have a faceted shape, whereas the shape of larger particles is close to spherical. It was found that the resulting nanopowders consist of a mixture of transition aluminas, among which the γ-polymorph is dominant. Thermal analysis showed that for smaller nanoparticles the phase transition to α-Al2O3 occurs at a lower temperature. In nominally pure Al2O3 nanoparticles with different sizes, photoluminescence at RT and 80 K is determined by trace level concentrations (≤10–3 wt%) of uncontrolled impurities of 3d elements (Cr3+(Oh) and Fe3+(Td)), surface hydroxyl groups, and point defects represented mostly by F-type centers. The acquired experimental data indicate that manifestation of the size effect for Al2O3 nanoparticles has a boundary corresponding to 6–7 nm. Al2O3 nanoparticles with the dominant γ-Al2O3 structure obtained by the laser method can be promising in many chemical reactions, particularly as the supports of catalysts and sorbents, for which the high specific surface area is of special importance.

Some results on the mechanochemical synthesis of apatites with simultaneous substitutions of calcium by lanthanum and of phosphate by silicate are presented. The reagents of reaction mixtures are taken such that to synthesize the compounds containing equal concentrations of lanthanum and silicon. The synthesis is performed in an AGO-2 planetary mill. The complete conversion of initial reagents in the synthesis of substituted apatite takes a longer period as compared to the time required for the synthesis of unsubstituted apatite. The mechanochemical synthesis time must be 40 min to synthesize lanthanum-and-silicate substituted apatite with a degree of substitution of

Formic acid is well-recognized as safe and convenient hydrogen carrier. Development of active and cost-effective catalysts for formic acid to hydrogen conversion is important problem of hydrogen energy field. Herein, we report on new Co catalysts supported on oxidized multi-walled carbon nanotubes (MWCNTs), which demonstrate high efficiency in the gas-phase formic acid decomposition affording molecular hydrogen. Various parameters of the catalysts, Co loading, MWCNTs structure, and nanotubes treatment conditions, have been investigated in terms of their influence on the catalytic properties. The catalysts morphology has been characterized with a set of physicochemical methods. It is found that the catalytic activity of Co particles depends on their electronic state and location on the support. Co species located inside the MWCNTs channels are less active than Co species stabilized on the outer surface. An increase in the content of Co nanoparticles on the MWCNT outer surface leads to a higher catalytic activity.

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.

Chemical vapor deposition (CVD) along with thermal decomposition of monosilane (SiH4) in a fluidized bed of multiwalled carbon nanotubes (MWCNTs) is used to prepare MWCNT-Si composites containing silicon nanoparticles deposited on the nanotube surfaces. The structure of obtained Si nanoparticles in composites based on MWCNTs with different average diameters is studied by TEM, SEM, XRD, Raman spectroscopy, and FTIR spectroscopy of diffuse reflection. The size of Si particles varies from 3 nm to 45 nm and increases together with the MWCNT diameter. The major part of precipitated silica in the nanoparticles occurs in the amorphous state with small (below 3 nm in size) inclusions of nanocrystalline silicon. Specific discharge capacity of prepared composites used as the anode material for lithium-ion batteries is estimated.

Zinc-substituted hydroxyapatite samples with a preset degree of substitution (Са10 –хZnx(PO4)6(OH)2, x = 0.1–2.0) have been synthesized by a mechanochemical method. The composition of starting components ((Zn(H2PO4)2 ⋅ 2Н2О and ZnO) and water of crystallization have been shown to influence the apatite structure formation process and the degree of zinc substitution for calcium in the mechanochemical synthesis and annealing processes. When ZnO was used as a dopant, beta-tricalcium phosphate was observed to form as a reaction intermediate directly in the mill after 5–10 min of the reaction mixture milling and disappear after 20 min of milling. The final synthesis product—zinc-substituted hydroxyapatite—remains single-phase for x ≤ 0.8 in the case of Zn(H2PO4)2 ⋅ 2Н2О and x ≤ 0.25 in the case of ZnO. After annealing, the zinc-substituted hydroxyapatite is single-phase only in the case of zinc phosphate using at x ≤ 0.1.

A relationship is established between the structural and thermoanalytical characteristics of the decomposition of hydrogen maleates and phthalates of Fe(II), Co(II), Ni(II), Cu(II). The temperatures of the onset of the first and second stages of decomposition grow in the series of both hydrogen maleates Cu ≤ Fe < Co < Ni and phthalates Fe ≤ Co < Ni < Cu, while the lengths of M– $${{{\text{O}}}_{{{{{\text{H}}}_{2}}{\text{O}}}}}$$ and M–Oanion bonds shrink in these structures. At the third stage, the temperature of the onset of the decarboxylation of hydrogen maleates and phthalates falls in the order Fe > Co > Ni > Cu. The size of metal nanoparticles additionally contained in a polymer or graphene shell grows from 3.5 to 5 nm (Co) and from 4.5 to 7 nm (Ni) upon moving from composites obtained through the decomposition of hydrogen maleates to hydrogen phthalates. Polymeric conglomerates containing shell-less copper nanoparticles, the average size of which ranges from 7.5 to 50 nm, are incorporated into a polymer matrix of composites obtained via the thermolysis of Cu(II) hydrogen maleate and phthalate.

We have studied interaction between the microwave activation product of gibbsite and an aqueous cobalt nitrate solution at room temperature, atmospheric pressure, and pH 8.0 ± 0.3. The results demonstrate that, under such conditions, the reaction in the near-surface region of the microwave-activated gibbsite particles leads to the formation of an aluminum cobalt oxyhydroxide with fragments of spinel structure and the composition Со2.3Al0.7O4, and a Со6 –xAl2 –x(OH)1.5 · 3.5H2O (0 ≤ x ≤ 1) nonstoichiometric hydrotalcite. The morphology of such compounds is determined by 2D nanoparticles in the form of bent sheets 2–5 nm in thickness and 500 nm or more in length. After calcination at 500°C, the composition of the reaction products corresponds to the aluminum cobalt oxide Со2.3Al0.7O4 with the spinel structure.

The Ni-containing catalysts based on ceria–zirconia doped with Ti and Ti+Nb were prepared by the solvothermal method in supercritical fluids. Ni deposition was carried out by incipient wetness impregnation and the one-pot technique. All materials were investigated by a complex of physicochemical methods (XRD, BET, TEM, H2-TPR). Samples catalytic properties were studied in methane dry reforming in the plug-flow reactor. Conversions of CH4 and CO2, H2/CO ratio, and CO and H2 yields were measured, and detailed kinetics analysis was carried out. The influence of Ni loading method and support modification on the catalytic behavior in the methane dry reforming process was studied. The preparation method of catalysts affects the textural characteristics. For one-pot samples, pore volume and surface area are lower than for impregnated samples. For catalysts on modified supports, strong metal–support interaction was shown to increase catalytic activity. A reduction pretreatment of samples was shown to have significant influence on their catalytic properties. The kinetic parameters such as reaction rate constant at 700 °C, effective activation energy, and TOF were estimated and analyzed.

A series of 5%Ni-CexZr1−xO2 (x = 0.3, 0.5, 0.7) catalysts has been prepared via one-pot solvothermal continuous synthesis in supercritical isopropanol and incipient wetness impregnation of CexZr1−xO2 obtained by the same route. The textural, structural, red-ox, and catalytic properties in methane dry reforming (MDR) of Ni-modified Ce-Zr oxides synthesized by two routes have been compared. It was shown by XRD, TEM, and Raman spectroscopy that the method of Ni introduction does not affect the phase composition of the catalysts, but determines the dispersion of NiO. Despite a high dispersion of NiO and near-uniform distribution of Ni within Ce-Zr particles observed for the one-pot catalysts, they have shown a lower activity and stability in MDR as compared with impregnated ones. This is a result of a low Ni concentration in the surface layer due to segregation of Ce and decoration of nickel nanoparticles with support species.

Reactivity of nanosized objects is a hot topic in modern solid-state chemistry and materials science. The present work is focused on the interaction between multi-walled carbon nanotubes (MWCNTs) and metallic titanium during high-energy ball milling and thermal explosion, a rapid temperature rise in a mixture caused by an exothermic reaction ignited by external heating and occurring throughout the sample volume. A fundamental property of the nanocomposite mixture—the ability of its components to react in the combustion mode—is explained; an analysis of the dependence of the combustion characteristics of the nanocomposites on the milling duration of powder mixtures is provided. The phase and structural transformations of the Ti-MWCNT mixtures have been analyzed using X-ray diffraction and transmission electron microscopy. It was found that the ball-milled powders contain nanostructured titanium, nanotube fragments, amorphous carbon and nanosized carbon-deficient titanium carbide TiCx. Within the nanocomposite powder particles, TiCx nanoparticles are covered with layers of amorphous carbon. Thermal explosion was observed in Ti-4mass%MWCNT mixtures milled for 1.5–7 min. Shorter milling times were apparently not sufficient for establishing a proper interfacial contact, while longer milling times led to the extensive formation of titanium carbide TiCx, which acted as a barrier lowering the heat release by the mixture upon ignition. Both the ignition temperature of Ti-4mass%MWCNT and the maximum temperature developed during thermal explosion decrease with the milling time. A comparison of the behavior of MWCNT with that of carbon black under conditions of thermal explosion in the mixtures with titanium is also presented.

We studied on the function of Pd species located in mesopores and inside zeolite channels (micropores) of the montmorillonite-modified zeolite catalyst for the hydrodesulfurization of diesel fraction with 350 ppm of sulfur as DBT, 4-MDBT, and 4,6-DMDBT. It was shown that the ex-dihydrogentetrachloropalladate impregnated catalyst as well as the ex-tetraamminepalladium(II) chloride ion-exchanged catalyst have high efficiency of sulfur removal from the diesel fuel in temperature range 280–300 оC. The sulfur tolerance of catalyst depended on the method of Pd adding. The catalyst prepared by ion-exchange with tetraamminepalladium chloride solution exhibited the highest sulfur tolerance. According to FTIR of adsorbed CO, this catalyst contains a small Pd metal atoms or cluster in electron-deficient state inside zeolite channels. They probably ensure sulfur tolerance due to hydrogen spillover. The montmorillonite addivite significantly modifies performance of the Pd-Zeolite catalyst in hydrotreating of diesel fraction. It leads to a decrease of cracking function, while those of hydrogenolysis of sulfurorganic molecules and hydrogenation of aromatic molecules are strengthened in comparison with the unmodified catalyst. This effect is explained by the change of acidic properties of the catalyst, limitations of diffusion of various molecules into the zeolite channels, and diffusion of Pd from the zeolite channels.

Conditions of synthesis are optimized and XRD and thermoanalytical studies are performed for normal maleate [Zn(H2O)2(C4H2O4)] and acid maleate [Zn(H2O)4(C4H3O4)2], along with acid Co(II)–Zn(II), Ni(II)–Zn(II) maleates. It is shown that when solid solutions thermally decompose in acidic maleate systems, the kinetically less stable component causes the temperature of decomposition of the more stable component to fall. It is established that the solid residue of Zn(II) maleate after heating to 500°C in a He atmosphere is a composite containing Zn oxide whose reduction to metal begins at 675°C. The decomposition of [(Co0.1Zn0.9)(H2O)4(С4H3O4)2] leads to the oozing of metallic cobalt atoms embedded in the channels of the ZnO structure that act as a catalyst for the spontaneous growth of uniform carbon nanotubes on the surface of the composite. After thermal decomposition of the samples in a system of acid Ni(II) maleate–acid Zn(II) maleate, only the bimetallic phase is observed in the composites, and there is no zinc oxide.

New results of an investigation of NH3BH3 dehydrogenation with supplying a limited quantity of aqueous solution of a catalyst precursor to a solid-state bed of the hydride particles with subsequent external heating at 40–90 °C are presented. Measurements of the reaction layer temperature and the amount of the evolved hydrogen have shown that at external heating temperature higher than 85°С there was acceleration of the first stage of the process, the highly exothermic catalytic hydrolysis of a portion of ammonia borane, which resulted in a stronger heating of the reaction layer and the start of NH3BH3 thermolysis. This type of process is referred to as hydrothermolysis. A TEM, ATR FTIR, and XRD investigation has shown that in the reaction medium the metal chlorides become reduced to an amorphous catalytically active phase. During this process, ammonia reacts with chlorides to form NH4Cl. All of this leads to increased rate of hydrogen generation and hydrogen yield. Gravimetric hydrogen capacity of 7.6 wt% and the average rate of H2 evolution of 39 ml·gcomp.−1min−1 have been achieved at molar ratios of NH3BH3/MCl2 = 50 (M = Co, Ni) and H2O/NH3BH3 = 2 and at external heating of 85°С.

The cobalt-boron composition by reduction of cobalt chloride in an aqueous solution of sodium borohydride is an amorphous ferromagnetic black powder consisting of spherical particles covered with a shell. Transformations of cobalt-boron composition upon its heat treatment from 20 to 1000 °С in an inert atmosphere have been studied by thermal analysis, magnetic susceptibility and HR TEM. On the basis of the obtained results the heating process was divided into five temperature intervals characterized by considerable changes in the structure of cobalt-boron composition. The end products of chemical and structural transformations are cobalt metal and cobalt borates – Co 2 B 2 O 5 , Co 3 BO 5 , Co 3 (BO 3 ) 2 . In our study it was shown for the first time that the metallic phase with a face-centered cubic lattice forms from the amorphous core while the cobalt borates form as a result of transformation of an oxygen-containing shell under an inert atmosphere. The study of the effect of physicochemical properties of the calcined cobalt-boron composition on the rate of NaBH 4 hydrolysis has shown that it decreases with decline specific surface area of the sample and its phase composition determines the rate of formation of the catalytic active component in the reaction medium.

The structure of a cobalt-boron catalyst obtained by reduction of cobalt chloride in an aqueous solution of sodium borohydride at ambient temperature has been investigated by TEM HR, XPS, EXAFS and X-ray diffraction method. It was found that nanoparticles of the forming catalyst consisted of a core and a shell. The oxygen-containing compounds (cobalt hydroxide and cobalt borates) mainly reside in the shell. In spite of the amorphous state of the catalyst the EXAFS and X-ray diffraction analysis indicated the presence of ferromagnetic clusters with the shortest Co Co distance of about 2.5 A and coordination number of 2.7 which are regularly distributed within the core with average separations of 5.8 A. The presence in the catalyst of the Co B bonds, a short Co Co distance and the absence of long Co Co distances (4.3 and 4.8 A) as well as the presence of boron bound to hydrogen allows suggestion to be made that stabilization of the cobalt tetramers occurs due to the presence of a boron-hydrogen structure formed by BH 4 − ions upon the reduction of cobalt chloride. To substantiate the above model of the active phase of the cobalt-boron catalyst the DFT method with a PBE functional in the plane-wave basis has been employed which showed that the ferromagnetic tetramers may exist within a boron-hydrogen matrix isolated from the surrounding medium by an oxygen-containing shell.

Regularities of the thermolysis of acidic salts of unsaturated (maleic) [M(H2O)4(C4H3O4)2] and aromatic (ortho-phthalic) [M(H2O)6](C8H5O4)2 (M = Fe(II), Co(II), and Ni(II)) acids are established. The thermolysis of both maleates and phthalates can conventionally be divided into three stages. The onset decomposition temperature of the maleates is insignificantly higher than that of the phthalates for the salts of similar metals. The onset dehydration temperature increases in the series of the acidic transition metal maleates and phthalates Fe Co > Ni. Composites consisting of a metal, an organic polymer, and amorphous carbon are the thermolysis products of both maleates and phthalates in a helium flow. The composites with iron and cobalt in the polymer contain nanosized metal particles and oxide nanoparticles, whose content increases in the composites obtained by the decomposition of phthalates, whereas only metal nanoparticles are observed in the composite with nickel. The compositions and structures of the carbon/polymer matrix differ in these composites.

This paper presents results of a detailed study of fundamental aspects of the formation of 2D and 3D nanostructured YSZ:Yb3+ ceramics with a cubic structure through a key synthesis step in aqueous solutions of zirconium-containing hydroxy nanoparticles (1–2 nm) modified by Y3+ and Yb3+ ions, with the use of a sol–gel method and subsequent calcination of the resultant xerogels at temperatures above 350°C. As starting chemicals for the synthesis of ceramic powders, we used zirconyl, yttrium, and ytterbium nitrates and chlorides and aqueous ammonia. Using mixed solutions of these salts and a procedure developed by us, we synthesized sols, gels, and xerogels. To examine the effect of temperature on solid-state transformations, the xerogels were calcined according to a predetermined program in a muffle furnace at temperatures in the range from 350 to 1350°C (rarely, up to 1650°C). We focused primarily on ceramic powders close in composition to 0.86ZrO2 · 0.10Y2O3 · 0.04Yb2O3. The ceramics were characterized by high-resolution transmission electron microscopy, electron microdiffraction, electronic diffuse reflectance spectroscopy, energy dispersive X-ray microanalysis, and X-ray fluorescence analysis.

The paper presents a comparative study of the activity of magnetite (Fe3O4) and copper and cobalt ferrites with the structure of a cubic spinel synthesized by combustion of glycine-nitrate precursors in the reactions of ammonia borane (NH3BH3) hydrolysis and hydrothermolysis. It was shown that the use of copper ferrite in the studied reactions of NH3BH3 dehydrogenation has the advantages of a high catalytic activity and the absence of an induction period in the H2 generation curve due to the activating action of copper on the reduction of iron. Two methods have been proposed to improve catalytic activity of Fe3O4-based systems: (1) replacement of a portion of Fe2+ cations in the spinel by active cations including Cu2+ and (2) preparation of highly dispersed multiphase oxide systems, involving oxide of copper.

Europium doped Gd2O3 sphere-like nanoparticles with dm = 9.3 ± 3.5 nm were synthesized by cw CO2 laser vaporization technique in a flowing mixture of argon and oxygen. According to XRD data, the Eu:Gd2O3 nanoparticles crystallize in the monoclinic symmetry class (C2/m space group). High-resolution luminescence spectroscopy study showed that the ultra-narrow 5D0 → 7F0 transition of Eu3+ demonstrates only two peaks corresponding to two inequivalent Cs positions of Eu3+ ion in monoclinic Gd2O3 lattice that is explained by the peculiarities of local environment of Eu3+ ion at these sites. The hypersensitive transition 5D0 → 7F2 dominates in the spectrum and is expanded to the red part of the spectrum in comparison with cubic Eu:Gd2O3 due to intense transitions terminating at higher-lying components of the crystal-field-split 7F2 state. In the luminescence spectrum, an additional weak band with the maximum at 407 nm corresponding to the electronic transitions 4f65 d1(7FJ) → 4f7(8S7/2) of Eu2+ was detected. The obtained values of chromaticity coordinates and absolute quantum yield are (0.644; 0.325) and ca. 1%, respectively. The phase transformations have been investigated using differential scanning calorimetry and thermogravimetry (50–1400 °C). After annealing in air at 700 °C, the monoclinic symmetry class of the Eu:Gd2O3 nanoparticles is preserved and the particle size increases to dm = 17.8 ± 6.1 nm. After annealing, the chromaticity coordinates (0.659; 0.334) and absolute quantum yield (ca. 4%) can be obtained using red phosphor based on monoclinic Gd2O3:Eu3+. The lifetime of the excited 5D0 state of Eu3+ in the annealed nanoparticles is longer than that in the as-synthesized nanoparticles, due to the suppression of nonradiative decay after annealing.

Catalysts with the Mo1V0.3Te0.23Nb0.12Bi0-0.05 compositions were prepared via spray-dry method and tested in ethane oxidative dehydrogenation (ODE) reaction. The catalysts were characterized by XRD, HRTEM, SEM and XPS. A strong effect of the bismuth content on physicochemical and catalytic properties was observed. At low Bi concentrations (Bi/Mo = 0.004–0.075) the M1/M2 ratio, morphology and dispersity of the M1 phase changed resulting in a decrease of the catalytic activity. The maximum activity, selectivity to ethylene and stability in reaction conditions were obtained at intermediate Bi concentrations (Bi/Mo = 0.015–0.025). These samples had the highest M1 amount among modified samples. Hindering of Te segregation along six-membered channels of the M1 phase preventing the Te loss was detected. Bi incorporation in such channels and its possible participation in active ensembles are assumed to be responsible both for the stability and enhanced catalytic properties of the M1 phase. A further increase of the bismuth content (Bi/Mo = 0.05) was accompanied by a decrease of the M1 particle size and structural disordering. Suppression of the M1 phase crystallization and formation of less active and selective M2 and M5O14 phases (M-Mo,V,Nb) were observed at the maximum bismuth content.

XRD phase analysis and thermal analysis are used to confirm the formation of a continuous series of solid solutions in which one cation is substituted for another in the systems Co(II) hydrogen maleate–Ni(II) hydrogen maleate; Fe(II) hydrogen maleate–Co(II) hydrogen maleate; and Fe(II) hydrogen maleate–Ni(II) hydrogen maleate. The unit cell volume of these solid solutions is shown to depend linearly on their composition. The linear character of changes in the initial temperatures of dehydration and thermal decomposition is established. Using the example of the first of these systems, it is shown that when heated, bimetallic nanoparticles embedded in the polymeric matrix of composites obtained via the thermal decomposition of solid solutions of hydrogen maleates undergo a second-order phase transition, resulting in decomposition of the solid solutions of metals at the Curie temperature.

The applicability of Cu/C catalysts is limited by sintering of Cu leading to deactivation in catalytic reactions. We show that the problem of sintering could be resolved by N-doping of the carbon support. Cu nanocatalysts with 1 at% of metal were synthesized by Cu acetate decomposition on N-free and N-doped (5.7 at% N) mesoporous carbon supports as well as on thermally expanded graphite oxide. Catalytic properties of these samples were compared in hydrogen production from formic acid decomposition. The N-doping leads to a strong interaction of the Cu species with the support providing stabilization of Cu in the form of clusters of less than 5 nm in size and single Cu atoms, which were observed in a significant ratio by atomic resolution HAADF/STEM even after testing the catalyst under harsh conditions of the reaction at 600 K. The mean size of the obtained Cu clusters was by a factor of 7 smaller than that of the particles in the N-free catalyst. The N-doped Cu catalyst possessed good stability in the formic acid decomposition at 478 K for at least 7 h on-stream and a significantly higher catalytic activity than the N-free Cu catalysts. The nature of the strongly interacting Cu species was studied by XPS, XRD and other methods as well as by DFT calculations. The presence of single Cu atoms in the N-doped catalysts should be attributed to their strong coordination by pyridinic nitrogen atoms at the edge of the graphene sheets of the support. We believe that the N-doping of the carbon support will allow expanding the use of Cu/C materials for different applications avoiding sintering and deactivation.

The phase and chemical compositions, size and morphology of Pt particles, manganese oxides, and alumina in the binary Pt–MnOx–alumina catalysts have been studied and compared with Redox behaviors and catalytic properties in butane oxidation. X-ray diffraction, high-resolution transmission electron microscopy, and chemical differentiating dissolution were used for the catalysts characterization. Temperature-programmed reduction by hydrogen was employed to study the Redox properties. The catalyst Pt–MnOx–alumina has been shown to possess synergetic effects in the catalytic butane oxidation activity and reducibility by hydrogen as compared to alone Pt–alumina and MnOx–alumina samples. These effects were shown to be associated with modification of the imperfect Al3+-doped β-Mn3O4 nanoscale particles and the Mn3+-doped alumina crystals by platinum ions as well as the intimate contact of 1–2 nm sized PtO2 particles with β-Mn3O4 and manganese–alumina particles. It was found that Pt-precursors (such as H2PtCl6, H2[Pt(OH)6], Pt(NO2)2(NH3)2, [Pt(NH3)4]Cl2), alumina phase type (γ and χ) and temperature of the manganese–alumina activation (500 and 900 °C) had a strong effect on the unique properties of the Pt–MnOx–alumina in butane oxidation and its reducibility.

An interest in NiMoО4–SiO2 reduction stems from its promising use as catalysts for hydrodeoxygenation and hydrodesulfurization processes. The work exploits in situ X-ray diffraction to investigate phase transformations during NiMoO4–SiO2 reduction with hydrogen in a temperature range of 30-700°C. The α-NiMoО4 reduction is shown to proceed in two stages. In the first stage, at 400-500°C, an intermediate state (Ni,Mo,□)O mixed oxide and Ni1–x Mo x form. In the second stage, above 650°C, two solid solutions based on the Mo and Ni structures form. The structure of the intermediate state is refined by the Rietveld method. It is demonstrated that the Ni–Mo mixed oxide forms based on the NiO structure, which contains a certain number of cation vacancies.

The activity of cobalt–boron catalysts in sodium borohydride hydrolysis has been correlated with change of structure in the active component of the catalysts upon their thermal treatment. It was shown that at temperatures to 300 °C there takes place loss of water and hydrogen from the catalysts without noticeable changes in activity. At temperatures above 300 °C the amorphous cobalt boride particles undergo crystallization to produce metallic cobalt with a hexagonal structure and this is seemingly the cause of the substantial fall in the rate of hydrogen generation in the presence of cobalt–boron catalysts.

Studies of the thermolysis of ortho-[Ni(H2O)2(C8H4O4)](H2O)2, [Cu(H2O)(C8H4O4)], and acid [M(H2O)6](C8H5O4)2 (M(II) = Fe(II), Co(II), and Ni(II)), [Cu(H2O)2(C8H5O4)2] phthalates reveal that the solid products of their decomposition are composites with nanoparticles embedded in carbon–polymer matrices. Metallic nanoparticles with oxide nanoparticle impurities are detected in iron/cobalt polymer composites, while nickel/copper composites are composed of only metallic particles. It is found that nickel nanoparticles with the diameters of 6–8 nm are covered with disordered graphene layers, while the copperbased composite matrix contains spherical conglomerates (50–200 nm) with numerous spherical Cu particles (5–10 nm).

Laser vaporized xCr/Al2O3 nanopowders with the particle size of ca. 15 nm were studied by XRF, EDX, HRTEM, XRD, DD, BET, TGA, UV–Vis DRS, Raman and PL spectroscopy methods as a catalytic system in dehydrogenation of isobutane. The nanopowders were found to contain not only the Cr6+ ions located on the surface of nanoparticles, but also two different types of Cr3+ sites as components of the γ-Al2O3 solid solution. One type consists of the bulk Cr3+b sites in a strong crystal field. Another type is represented by the Cr3+s sites residing near the surface of xCr/Al2O3 nanoparticles. Such sites are in a weak crystal field. It was shown that catalytic activity of the nanostructured xCr/Al2O3 system is provided by the high content of surface Cr3+s sites. The results obtained make it possible to propose the nanopowders obtained by laser synthesis as a promising catalytic system that can be used in the development of highly active catalysts for dehydrogenation of alkanes with the decreased chromium content.

Europium doped Y2O3spherical nanoparticles with the diameter ~10 nmobtained via cw laser vaporization are shown to crystallize in monoclinic symmetry class (C2/m space group). The size of nanoparticles established via HRTEM coincides with coherent scattering region established by XRD. Luminescence spectrum in the vicinity of ultranarrow transition demonstrates three peaks consistent with three inequivalent positions of Eu3+ ion in monoclinic Y2O3 lattice. Hypersensitive transition dominates in the spectrum, admitting the lack of inversion symmetry at Cs sites occupied by Eu3+. The spectrum of hypersensitive transition is expanded to the red part of spectrum due intense transitions terminating at higher-lying components of crystal-field-split 7F2 energy level. Obtaining chromaticity coordinates (0.669, 0.331)and absolute quantum yield (~21%) is possible using red phosphor based on monoclinic Y2O3:Eu3+.

The effect of potassium and bismuth doping on the morphology and structure of M1 phase, which determines the activity of MoVTeNbO catalysts in the oxidative conversion of ethane to ethylene, was studied. According to XRD, HRTEM and XPS data, the introduced K and Bi enter the M1 phase and do not form individual compounds. The addition of potassium is accompanied by anisotropic growth of the M1 phase particles: an increase in potassium content enhances the growth of particles along the [0 0 1] direction. The insertion of bismuth does not change the morphology of M1 phase but produces structural features (extended defects, disorientation of the crystal structure) that increase the fraction of accessible surface formed by {0 0 1} faces. Along with the structural and morphological transformations, the both additives affect the ratio of V5+/V4+ and Mo6+/Mo5+ cations and the enrichment of the catalyst surface with tellurium. The observed changes in physicochemical characteristics of the promoted catalysts correlate with changes in the catalytic properties.

Laser evaporation of an Al2O3 target by a continuous wave CO2 laser was used to obtain nanostructured Al2O3 condensates with a mean crystallite size of 6 nm, one nominally pure and another doped with chromium at a concentration of 0.2 wt%. Photoluminescence of Cr3+ was observed in all the samples of the Al2O3 condensate. In all the Al2O3 condensates the α-Al2O3 phase, undetectable by XRD and HRTEM, was revealed by Cr3+ probing. Photoluminescence studies with the use of Cr3+ as a probe also revealed the θ- and (γ + δ)-crystal phases of Al2O3; this finding was supported by XRD and HRTEM data.

The structure of copper oxide species in Cu/ZrO2 catalysts with monoclinic zirconia as a support was studied. The catalysts with various copper loadings (3–40 wt % of Cu) prepared by impregnation technique were characterized using N2O titration, X-ray diffraction (XRD) analysis, radial distribution function (RDF) of electron density, and high-resolution transmission electron microscopy (HRTEM). It was established that the Cu/ZrO2 catalysts contained highly dispersed CuO particles along with the large ones. Geometrical similarity between the CuO and ZrO2 monoclinic structures favors stabilization of the highly dispersed CuO particles on the support with low specific surface area.

Obtaining stable metal nanoparticles is of high interest for various applications such as catalysis, batteries, supercapacitors and electro-magnetic devices. Cobalt/multi-walled carbon nanotubes (MWCNT) hybrids with an original set of magnetic and electric properties were formed by casting Co nanoparticles (3 – 5 nm) of high aspect ratios within the internal space of MWCNTs. The Co particles localization and size were analyzed by transmission electron microscopy and synchrotron x-ray diffraction. The magnetism of the cobalt nanoparticles was probed by 59Co internal field nuclear magnetic resonance (IF NMR) and their electrical behavior by dielectric spectroscopy. The majority of Co particles were fully metallic. They resisted sintering up to 550 °C. Below 7.5 wt%, the Co was exclusively embedded inside the MWCNT. At higher loading, they coexisted with larger Co outside particles. While nanometer size particles are normally superparamagnetic at room temperature, the confinement of Co within MWCNTs resulted in a ferromagnetism revealed by 59Co IF NMR. This spectroscopy provided original information about the structure, size, and shape anisotropy of the nanoparticles. Finally, the MWCNT modification by Co metal nanoparticles improved the electrical conductivity of polyethylene based composite thus extending the useful frequency band of Co/MWCNT/PE composites for applications requiring light-weight conduction or energy absorption.

Nanosized Eu/γ- and/or η-Al2O3 ([Eu2О3] = 0.00, 0.02, 0.45 and 0.92 wt%) powders with the particle size from

For the first time, silicate-substituted hydroxyapatites have been prepared from mixtures containing different amounts of silicon (0.2–2 mol per mol of apatite unit cell) by dry mechanochemical synthesis at room temperature in a planetary ball mill. The XRD, FTIR, TEM, and NMR spectroscopic data show that the product of the mechanochemical synthesis is a single-phase nanocrystalline apatite containing different amounts of carbonate and silicate ions and adsorbed water. In the annealed samples, three silicon concentration subranges can be distinguished, each of which is characterized by specific evolution of the lattice parameters. The formation mechanism of the silicate-substituted hydroxyapatite obtainable by this method is discussed. The studies indicate that the silicon substitution limit in the silicate-substituted lattice achievable by the dry mechanochemical synthesis followed by heat treatment is 1.2 mol per mol of apatite unit cell.

A procedure has been proposed for the preparation of copper/polymer composites through Cu(C4H4O4) · H2O succinate thermolysis. Three types of copper nanoparticles have been incorporated into a fibrous carbon-polymer matrix of the composite: cubic (350 × 350 nm) and needle-like (40–80 nm in diameter and 4.5–5.5 μm in length) crystals and spherical copper particles (5 to 45 nm). We have compared copper succinate and copper maleate decomposition processes. The composites obtained through thermolysis have been shown to differ drastically.

Nanostructured carbon-silica composite materials are prepared from different compounds in one-pot. They are characterized by BET, transmission electron microscopy, X-ray diffraction, and small-angle X-ray scattering. An effective method of the quantitative analysis of the structural dispersed characteristics of the template phase of silica in these composites is proposed.

Porous nitrogen-doped and nitrogen-free carbon materials possessing high specific surface areas (400−1000 m2 g−1) were used for deposition of Ni by impregnation with nickel acetate followed by reduction. The nitrogen-doped materials synthesized by decomposition of acetonitrile at 973, 1073, and 1173 K did not differ much in the total content of incorporated nitrogen (4−5 at%), but differed in the ratio of the chemical forms of nitrogen. An X-ray photoelectron spectroscopy study showed that the rise in the synthesis temperature led to a strong growth of the content of graphitic nitrogen on the support accompanied by a reduction of the content of pyrrolic nitrogen. The content of pyridinic nitrogen did not change significantly. The prepared nickel catalysts supported on nitrogen-doped carbons showed by a factor of up to two higher conversion of formic acid as compared to that of the nickel catalyst supported on the nitrogen-free carbon. This was related to stabilization of Ni in the state of single Ni2+ cations or a few atoms clusters by the pyridinic nitrogen sites. The nitrogen-doped nickel catalysts possessed a high stability in the reaction at least within 5 h and a high selectivity to hydrogen (97%).

The mechanochemical method is used to synthesize samples of hydroxyapatite (HA) with substitution of the phosphate ion by silicate and zirconate ions, and substitution of calcium ions by copper ions. In the process of mechanochemical synthesis, carbonate ions and water molecules are incorporated into the structure of HA due to interaction of components of the reaction mixture with air. Intrusion of carbonate into the structure of HA is a competing process with modification of apatite by silicate and zirconate anions; therefore, the composition of the product during synthesis differs from the prescribed one. After annealing of the samples, the composition of the anion-modified HA can be described by the formula Са10(РО4)6–х (АО4) х (ОН)2–х , where (АО4)4– is the modifying anion. Substitution of calcium by copper ions localized at the Са1 position has been detected. Silver ions are not incorporated into the structure of HA, but are distributed in the apatite matrix in the form of nanocrystals of metallic silver.

Metal-polymer composites have been prepared through the thermolysis of the [M1(H2O)2(C4H2O4)] · H2O (M1 = Co(II), Ni(II)) neutral maleates and [M2(H2O)4(C4H3O4)2] (M2 = Fe(II), Co(II), Ni(II)) acid maleates. In the polymer matrix of the Fe-containing composite, we identified metal, Fe2O3, and Fe3O4 particles, with slight densification of the matrix around them. The polymer matrix of the cobalt maleate-derived composite contained four types of nanoparticles: α-Co, β-Co, and CoO in polymer shells and Co3O4 with no polymer shell. The decomposition of the nickel maleates yielded homogeneous nickel nanoparticles (4–5 nm) covered with two to five graphene layers. The Co-containing composite was found to be a dielectric. The Ni-containing composite exhibited variable range hopping conduction in the range T ≤ 50 K.

The thermal decomposition of neutral ([Cu(H2O)(C4H2O4)]) and acidic ([Cu(H2O)4](C4H3O4)2) maleates can conventionally be divided into four stages: (1) dehydration, (2) polymerization, (3) isomerization of the maleate ion to the trans form with the simultaneous reduction Cu(II) → Cu(I), and (4) decarboxylation of copper(I) fumarate. The third and fourth stages of the decomposition of these salts coincide. The residue after the thermolysis of copper(II) maleates in a He flow is a composite consisting of aggregates from 50 nm to several microns in size. Spherical conglomerates (50–200 nm) containing many spherical Cu particles (5–10 nm) are incorporated into the organic polymer matrix of these aggregates.

This work reviews results of research aimed at design and characterization of mixed ionic–electronic conducting perovskite–fluorite nanocomposite oxide ceramics. Nanocrystalline oxides were prepared via Pechini route, nanocomposites – via ultrasonic dispersion of their mixture in organic solvents with addition of surfactants. Genesis of the real structure of nanocomposites at sintering by conventional as well as advanced (microwave or e-beam treatment) techniques was studied in details by structural methods. Applied preparation procedures ensured nano-sizes of perovskite/fluorite domains even in dense ceramics and a high spatial uniformity of their distribution. Redistribution of elements between perovskite and fluorite domains without formation of new phases was revealed. Characterization of nanocomposite transport properties by oxygen isotope heteroexchange and conductivity or weight relaxation demonstrated that perovskite–fluorite interfaces are paths for fast oxygen diffusion. Best perovskite–fluorite combinations tested as cathode layers or dense oxygen separation layers in asymmetric supported membranes demonstrated performance promising for the practical application.

In this work the Raman spectroscopy abilities for diagnostics of carbon onions synthesized from nanodiamonds have been analyzed. Several series of nanodiamonds transformed into onion-like carbon by heating at 1000–1900 K in vacuum were characterized with Raman spectroscopy. A high resolution transmission electron microscopy (HRTEM) was used to estimate the average size of nanodiamonds in the series synthesized by different methods. Each series consisted of a pristine nanodiamond powder and materials appeared after its heat treatment at different temperatures in vacuum. The changes corresponding to the nanodiamond crystal transformation into the onion-like carbon (via the stage of diamond cores enveloped by a few layer graphene) have been revealed in Raman spectra. The basic attention has been paid to behavior of D (disorder-induced), G (graphite) and 2D (two-phonon scattering)-bands in the Raman spectra.

To study the effect of nanoscale titanium dioxide (TiO2) on cell responses, we synthesized four modifications of the TiO2(amorphous, anatase, brookite, and rutile) capable of keeping their physicochemical characteristics in a cell culture medium. The modifications of nanoscale TiO2were obtained by hydrolysis of TiCl4and Ti(i-OC3H7)4(TIP) upon variation of the synthesis conditions; their textural, morphological, structural, and dispersion characteristics were examined by a set of physicochemical methods: XRD, BET, SAXS, DLS, AFM, SEM, and HR-TEM. The effect of synthesis conditions (nature of precursor, pH, temperature, and addition of a complexing agent) on the structural-dispersion properties of TiO2nanoparticles was studied. The hydrolysis methods providing the preparation of amorphous, anatase, brookite, and rutile modifications of TiO2nanoparticles 3–5 nm in size were selected. Examination of different forms of TiO2nanoparticles interaction with MDCK cells by transmission electron microscopy of ultrathin sections revealed different cell responses after treatment with different crystalline modifications and amorphous form of TiO2. The obtained results allowed us to conclude that direct contact of the nanoparticles with cell plasma membrane is the primary and critical step of their interaction and defines a subsequent response of the cell.

Three types of carbon multi-walled nanotubes (MWNT) with different morphology and mean diameter (7.5, 10.5, 22 nm) were used to produce polymethylmetacrylate-based composites (MWNT/PMMA) with variable MWNT loading (0.5–5wt%). The electrophysical properties of produced composites and electromagnetic response in frequency range of 2–12 GHz were investigated. Electrical conductivity of composites depends on the MWNT type increasing with lowering of the nanotube diameter and loading in composite. Reflectance and transmittance coefficients were calculated from dielectric permittivity data and found to correlate with electrical conductivity. The highest level of EM reflection was obtained for 7.5 nm MWNT-based composites and makes the value of 0.65–0.7, whereas 22 nm MWNT/PMMA composites are more transparent for EM radiation with reflection coefficient 0.3–0.4 for the highest MWNT loading. Thus MWNT/PMMA composites demonstrate high EM shielding properties.

Here multi-walled carbon nanotubes (MWNT) of different average diameters with ppm level purity were produced by a low temperature C2H4 pyrolysis on Fe-Co type catalysts combined with forthcoming graphitization at 2200–2800 °C in argon flow. Annealed nanotubes were characterized with X-ray fluorescent analysis, BET surface measurements, HR TEM, X-ray diffraction, DTA analysis, and measurements of temperature and magnetic field dependences of conductivity. The graphitization of MWNT results in removal of residual catalyst metal impurities, reduction of the wall defects, and closure of nanotube tips. It was found that extent of these effects depends on MWNT diameters. It was proposed that the graphitization is caused by a significant thermal displacement and diffusion of carbon atoms at temperatures higher the Debye temperature.

Raman spectroscopy study of multi-wall carbon nanotubes (MWNTs) of different diameters (with a small controllable number of walls) produced using Fe–Co catalyst with a variable size of the same active component has been performed. We have characterized as produced MWNTs with different diameters (series 1) and two types of tubes with fixed mean diameters (∼10 and 20 nm) heated in a flow of pure argon at various temperatures (2200, 2600 and 2800 °C – series 2). The Raman spectra of MWNTs have been registered in three spectral regions, corresponding to D (disorder-induced), G (graphite) and 2D (two-phonon scattering) bands. A ratio of intensities I2D/ID for tubes of series 1 has demonstrated almost a linear dependence on the nanotube diameter. After heating (series 2), D (disorder-induced) Raman band has shown a substantial decrease in intensity. The variation of the Raman spectra parameters is discussed in terms of defectiveness of nanotubes.

Apatite-type lanthanum silicates (ATLS) doped by Fe were prepared by using mechanical activation, and the effect of the nature of the dopant raw materials on the formation of ATLS was considered. Genesis of the formation of apatite was studied by XRD, IR, HRTEM, and Mossbauer and UV/ Vis electron spectroscopy. The possibility of a partial substitution of Si in the apatite with a dopant and the mechanism of formation of ATLS in the course of mechanical activation depend on the dopant parent compound. The structural compatibility of La2O3, La(OH)3, and apatite was shown to favor