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A comparison is made of the thermoanalytical characteristics and the composition and structure of solid products of the thermal decomposition of ortho-phthalates [Cu(H2O)2(C8H4O4)], [CuNi(H2O)4(C8H4O4)2], and [Ni(H2O)2(C8H4O4)](H2O)2. It is found that the thermal decomposition of these compounds upon heating to 500°C in a He atmosphere can be conditionally divided into two stages: dehydration and decarboxylation. Polymer conglomerates containing uncoated Cu nanoparticles as large as 75 nm are embedded into the polymer matrix of the composite obtained via the thermal decomposition of [Cu(H2O)2(C8H4O4)]. Three types of nanoparticles with sizes of 40–85, 15–25, and 10–15 nm are embedded in the polymer matrices of composites. The particles are Cux/Ni1−x solid solutions of different compositions, obtained via the thermolysis of [CuNi(H2O)4(C8H4O4)2]. It is found that the onset temperature of [CuNi(H2O)4(C8H4O4)2] decarboxylation at the third part of the second stage with the formation of a three-phase region correlates with the temperature of decomposition of Cux/Ni1 – x solid solutions in the binary metal system, due apparently to the quantum size effect.

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

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.

The conductivity of three types of composites prepared by mechanical melt mixing from polyethylene (PE) and multi-walled carbon nanotubes (MWCNTs) with an average diameter of 9.8 nm and an aspect ratio of ∼3000, 112, 36 is studied. The structure of these composites is investigated by optical and scanning electron microscopies and powder X-ray analysis. Cyclic measurements of current-voltage (I–V) characteristics and the use of a 3-point measurement scheme showed that the current density through the composite is nonlinearly increasing with increasing voltage or upon sequential measurements of I–V characteristics with the same voltage. The results of I–V measurements were used to determine concentration dependences of conductivity and their changes for each type of MWCNTs. It is shown that the percolation threshold determined from the third I–V measurement for MWCNTs in composites prepared by mechanical melt mixing decreases with decreasing aspect ratio of nanotubes from 3000 to 36.

Formation features of mono- (Fe, Co, Ni), bi- (Fe-Co, Fe-Ni, Co-Ni), and trimetallic (Fe-Co-Ni) catalysts for the synthesis of multiwalled carbon nanotubes (MWCNTs) prepared by the method of polymerized complex precursors are revealed. It is shown that initial bimetallic and trimetallic catalysts occur in a wide range of phases with spinel structure consisting of different mixed metal oxides (Me(II)Me(III)2O4). The influence of the active component composition and the catalyst activation conditions on their activity in the reaction of MWCNT synthesis is determined. MWCNTs with specific structural characteristics, a narrow diameter distribution and a relatively low degree of defectiveness, can be obtained by varying the composition of the catalyst active component.

The effect of the residual catalyst for the synthesis of multi-walled carbon nanotubes (MWCNTs) on the electrophysical properties of MWCNT–polyethylene composites produced by melt mechanical mixing was studied. The residual catalyst content was varied by changing the MWCNTs synthesis time. The nanotubes used in the work were characterized using transmission and scanning electron microscopy, atomic emission analysis, X-ray phase analysis, and magnetic permeability measurements. The structure of the synthesized composites was studied using optical and scanning electron microscopy. The dependences of the specific magnetization on the applied magnetic field, bulk electrical conductivity on the volumetric content of the filler in the composite, and the frequency dependences of the reflection, transmission, and absorption of electromagnetic radiation in the range 0.01–18 GHz were obtained. It was established that the obtained composites are characterized by a uniform distribution of nanotubes in the polymer matrix, and the dependence of the bulk electrical conductivity on the content of MWCNTs in the composite has a percolation character. Variation in the synthesis time of nanotubes allows producing MWCNTs with a high content of ferromagnetic particles, which are an alloy close in stoichiometry to the composition of the active component of the catalyst. It was shown that the use of composites modified with MWCNTs with a high content of residual catalyst is more effective for absorbing electromagnetic radiation due to an increase in their magnetic losses.

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.

The morphological and structural properties of Pd–CeO2/Al2O3 catalytic compositions annealed at 100, 500, and 1000°С are studied, along with thereof coatings deposited on metallic foil via cold gas dynamic spraying. The influence of the preparation technique of the initial catalytic composition and introducing active component into a coating on their phase states, particle sizes, and activitites is elucidated. It is shown that introducing active components via impregnation into preliminarily sprayed alumina layer ensures the uniform distribution of Pd and Ce in the support profile, the formation of nanosized PdO particles, and the phase of interaction between the components of the catalyst and support. The impregnated catalyst shows the highest activity in the reaction of methane oxidation. The technique for preparing coatings has no limitations when scaled up and can find application in manufacturing full-size catalysts on metallic foil for different types of power engineering devices.

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.

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.

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.

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 synthesis conditions of multi-walled carbon nanotubes (MWCNTs) indirectly determine their application potential through the decisive role in the characteristics of individual tubes: diameter distribution, structure and defectiveness of graphene walls, the amount of metal impurities and amorphous carbon. In the present work, we have studied the influence of the catalyst composition and synthesis conditions on the diameter distribution and the structure of nanotube walls. We have observed the influence of the particle size for MWCNT synthesis (i.e. size effect) on catalytic activity by ex situ and in situ techniques: in situ X-ray diffraction on synchrotron radiation (SRXRD), gas chromatography, and ex situ transmission electron microscopy. The data obtained by in situ SRXRD are in agreement with the results collected using laboratory tubular fix-bed catalytic reactor allowing thereby extending the applicability of the approach. For the first time we have shown the increase of the fraction of graphene walls in the total MWCNT diameter with time.

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.

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).

Comparison was made for the structural, IR spectral, and thermoanalytical characteristics of normal [M1(H2O)2(C4H2O4)](H2O) (M1 = Co(II) and Ni(II)) and acid maleates [M2(H2O)4(C4H3O4)2] (M2 = Mn(II), Fe(II), Co(II) and Ni(II)). Only structures of acid maleates contain intramolecular asymmetric hydrogen bond whose asymmetry increases in the series of transition metal salts. Thermal decomposition of Co(II), Ni(II) normal maleates, and Mn(II), Fe(II), Co(II), Ni(II) acid maleates proceeds in three stages. Onset decomposition temperatures for the first and second stages decreases in the series of normal maleates Co(II) ≥ Ni(II) and increases in the series of acid maleates Fe(II) Ni(II) and acid maleates Mn(II) > Fe(II) > Co(II) > Ni(II).

The structure of X-ray amorphous precursors of MoVTeO and MoVTeNbO oxide catalysts and their conversion at high-temperature treatment and under exposition in the reaction medium is studied by analytical transmission electron microscopy (TEM) in combination with the local energy dispersive X-ray (EDX) microanalysis of the elemental composition. At thermal treatment in the range of 300–450 °C the presence of both true amorphous phases and nanosized crystallites of the orthorhombic M1 and pseudohexagonal M2 phases is detected in the MoVTe(Nb)O catalysts. An increase in the annealing temperature results in the formation of well-crystallized particles of the M1 and M2 phases in the MoVTeNbO catalyst. The four-component M1 phase is stable at 550 °C and it is maintained under the reaction conditions. At an increase in the temperature of thermal treatment the successive crystallization of nanosized particles occurs in the three-component MoVTeO system with the formation of mainly the M2 phase. The nanostructured three-component M1 phase formed at low temperatures cannot crystallize into the full M1 phase in the absence of Nb and decomposes with the formation of the M2 phase that is inactive in the conversion of propane. The calculation procedure for EDX, which was developed specially for these catalysts, enabled the refinement of the chemical composition of separate phases.

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.

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.

The replacement of expensive propylene by propane, which requires the development of catalysts for the direct oxidation of propane into acrylonitrile, is an important and insufficiently studied problem. Multicomponent Mo m V n Te k Nb x oxide systems are promising in one-stage ammoxidation of propane to acrylonitrile. Despite considerable attention of various authors to the preparation methods for these catalysts, the reproducibility of their physicochemical and catalytic properties is low. To optimize the technology of catalyst synthesis, we studied the effect of drying method (evaporation or spray drying) for the aqueous suspension of the initial compounds on the formation of the Mo1V0.3Te0.23(Nb0.12) oxide catalyst. It is shown that the method of drying determines the chemical and phase composition of solid catalyst precursors and the phase composition of the final catalyst in high-temperature treatment. The use of spray drying provides the required physicochemical characteristics of the catalyst (the specific surface area and the phase composition) that determine the high activity and selectivity in the selective conversion of propane. These catalysts contain two crystalline phases: orthorhombic M1 and hexagonal M2 in an optimal ratio of 3: 1.

Fine-grained dense graphites of different manufacturers were tested and studied for the purpose of predicting their lifetimes at high (∼2000°C) temperatures. The tests consisted in sample heating by electric current to a destruction temperature. The study included a set of electron microscopy, X-ray diffraction, and electrical methods. X-ray diffraction data for initial samples were compared with data for domestic MPG graphite. Scanning electron microscopy was applied to both initial and heated samples. The lifetime prediction was based on the Zhurkov classical formula. It was shown that CGD, Carbone Lorraine, and MPG graphite composites can differ appreciably in both structural characteristics and high-temperature lifetimes.

The reduction of nanocrystalline cobalt oxide samples (single-phase and supported on γ-Al2O3) was studied using in situ X-ray diffraction (XRD) analysis. The atomic structures of single-phase and supported Co3O4 samples were refined, and the occurrence of cationic vacancies was demonstrated. A set of methods (XRD, temperature-programmed reduction, and differential dissolution) was used to find that the reduction of supported and unsupported model cobalt oxide was considerably different. The single-phase sample was reduced in undiluted hydrogen to cobalt metal with a hexagonal closely packed structure. The reduction of the supported sample (unlike the single-phase sample) occurred through the formation of a crystalline CoO phase to the formation of cobalt metal with a face-centered cubic structure. Interaction of cobalt oxide with the γ-Al2O3 support, which hinders the reduction to cobalt metal, was detected.

We have observed the phenomenon of photoinduced transparency in a suspension of onion-like carbon (OLC) nanoparticles in N,N-dimethylformamide (DMF) under the action of high-power laser radiation (λ = 1064 nm). The OLC particles were prepared from detonation nanodiamonds (NDs) by means of high-temperature annealing in vacuum and then ultrasonically dispersed in DMF. Upon exposure to laser radiation, the optical density of the suspension significantly decreases in the visible and near-infrared range, but increases in the range of wavelengths below 400 nm.

The formation of an active phase in V-Mo-Nb oxide catalysts for the selective oxidation and ammoxidation of ethane during thermal treatment in air and in helium was studied using high-temperature in situ and ex situ X-ray diffraction analysis, transmission electron microscopy, IR spectroscopy, and the differential dissolution method. It was found that, in thermal treatment below 500°C, the formation occurred through the same irreversible steps with the formation of a unidimensionally ordered layered compound with structure elements like Mo5O14 regardless of the calcination atmosphere. Above 500°C, the formation of crystalline phases took place; the composition and structure of these phases depended on the atmosphere of thermal treatment. The unidimensionally ordered V-Nb-Mo oxide with structure elements like Mo5O14 exhibited the best catalytic properties.

Nitrogen-containing catalytic filamentous carbon (N-CFC) of chemical composition NC18-NC104 has been synthesized by the decomposition of pyridine (Py) from gaseous mixtures with argon or H2 at 550–800°C on Ni/Al2O3 (Ni) and Ni-Cu/Al2O3 (Ni-Cu) high-percentage catalysts. The activity of the Ni-Cu catalyst in Py decomposition in mixtures with H2 is about one order of magnitude higher than its activity in Py/Ar mixtures (more than 70 g N-CFC per metal gram in 4.5 h at 750°C), which is interpreted as arising from the nickel-catalyzed hydrogenation of Py. The formation and growth of carbon fibers occurs through the decomposition of Py (from Ar/Py mixtures) and/or Py hydrodenitrification products (from H2/Py mixtures). The carbon material has been characterized by elemental analysis, low-temperature nitrogen adsorption, high-resolution transmission electron microscopy (HRTEM), and X-ray photoelectron spectroscopy (XPS). The effect of the noncatalytic reactions of Py and its transformation products on the composition and texture of N-CFC is discussed.