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Nanocomposites highly loaded with various iron oxides were obtained by thermal treatment of SBA-15 mesoporous silica soaked in concentrated freshly prepared ferric oxalate aqueous solution. Ultradispersed iron oxide particles appeared to cover external surface of the matrix as well as to be embedded into the depth of silica. We showed that CO evolving during the thermal decomposition of ferric oxalate added at the second impregnation stage is able to reduce the iron(III) oxide preliminary formed by oxidative thermolysis of the salt having been initially loaded.

Herein, β-Bi2O3 has been synthesized by a thermal decomposition of bismuth oxoformate (BiO)HCOO, oxoacetate (BiO)CH3HCOO and oxofumarate (BiO)2H2C4O4. It was shown that pseudomorphs of β-Bi2O3 with sheet-like, plate-like and spherical morphology were formed. The thermal stability, structure and morphology of the precursors and their products were characterized by differential thermal analysis (DTA), powder X-ray diffraction (XRD), in situ high temperature X-ray diffraction (HTXRD) and scanning electron microscopy (SEM). It was found that the Bi/β-Bi2O3 composite was obtained from (BiO)HCOO and (BiO)2H2C4O4 and transferred to β-Bi2O3.

In this article, we report the formation of ordered porous nanocrystalline ceria CeO2 during oxidative thermolysis of cerium formate Ce(HCOO)3. Ordering of the reaction product occurs due to the presence of similar structural elements in the CeO2 and Ce(HCOO)3 crystalline lattices. It was shown that the morphology and the structure of the products of thermal decomposition of Ce(HCOO)3 are greatly influenced by the composition of the gaseous atmosphere, in which the decomposition takes place. During thermal decomposition of Ce(HCOO)3 in an atmosphere of argon, no ordering of the synthesized CeO2 nanocrystals is observed. It was concluded that the presence of oxygen in the gaseous atmosphere is crucial for obtaining ordered nanocrystalline CeO2 from the Ce(HCOO)3 precursor.

A remarkable feature of organic salts is easy reorientation of organic groups, especially in high-temperature phases. It would be expected that the reorientational motion of organic groups promotes also ion transport processes within the crystal structure. In this work thermal and transport properties of solid organic salt (n-C4H9)4NI were investigated by methods of DSC, dilatometry, conductivity measurements and NMR spectroscopy. It was proposed that three low-temperature phases, II, III and IV, along to the high-temperature phase I appear in this salt after heat treatment. The conductivity and temperature stability range of the low-temperature phases depend on conditions of the heat treatment of the salt. Temperature intervals of stability of phases II and III considerably increases after prolonged heating in the melt. In parallel, the conductivity of all low-temperature phases increases in contrast to the conductivity of the phase I. These facts may be explained by the formation of extrinsic iodine vacancies as a result of the dissolution of tributylanine formed at partial thermal decomposition of the salt. According to 1H NMR data, in high-temperature phase TBA cations are mobile. No information on anionic diffusion in this phase was obtained due to a low intensity of 127I NMR spectra. The most mobile defects in low-temperature phases of (n-C4H9)4NI seem to be iodine vacancies.

Thermal properties and conductivity of the lithium bis(trifluoromethane)sulfonamide (LiTSFI) were studied in a temperature range of 60–270 °C by differential scanning calorimetry (DSC) and impedance spectroscopy methods. As shown by DSC technique, at the first heating, three endothermic effects associated with dehydration, phase transition, and melting were observed On subsequent cooling and heating, only the thermal effect due to the ionic salt melting was observed. These data were confirmed by conductivity measurements. On cooling the LiTSFI sample from the molten state an abrupt decrease in the conductivity due to crystallization into the high-temperature γ-phase was observed. Thus, according to the DSC and conductivity data, the high-temperature γ-phase may be easily quenched down to room temperature. The parameters of Arrhenius dependence of conductivity for γ-phase were estimated. It was shown that this phase has rather low ionic conductivity, below 10-6 S/cm near the melting point and cannot be regarded as orientationally disordered phase.

A complex of polyvinyl alcohol (PVA) with copper hydroxide was used as a precursor to obtain polymeric copper oxide through thermal decomposition. The absence of Cu(OH)2 crystalline phase was observed for the component ratio up to 1 Cu(OH)2 molecular unit to 3 PVA residuals. The formation of crystalline copper oxide was not observed after the dehydration of this material. UV–VIS and IR spectroscopy, and computational modeling were used to study the structure and properties of the obtained materials. A comparison with other similar materials was drawn. It was found that experimental data are in general accordance with the computations based on the polymeric model for copper hydroxide/oxide as a component of hybrid interpolymeric complex with PVA. A distinctive feature observed for polymeric copper oxide is strong broadening of the optical absorption band at 400 nm. It is suggested that this effect is caused by strong electron–phonon interaction, which is also responsible for superconductivity of copper oxide based systems.

The investigation of a structure of the complex of polyvinyl alcohol and boric acid was carried out by means of IR and Raman spectroscopy, X-ray diffraction and quantum mechanical calculations. The formation of inorganic polymeric chains ( O B(OH) )n within a hybrid interpolymeric complex with PVA is substantiated. Most convincingly this conclusion is supported by PVA-boric acid complex’s Raman spectrum. It consists of superposition of slightly changed PVA spectrum and strongly changed boric acid spectrum. It means that boric acid structure is changed significantly within the complex and PVA structure is not changed. Observed and calculated frequencies are in good agreement. Also the structural-sensitive theoretical neutron shielding ability of the complex is analyzed. It was found better than known one.

High-temperature powder sintering is an integral part of the dense ceramic manufacturing process. In order to find the optimal conditions for producing a ceramic product, the information about its behavior at high temperatures is required. However, the data available in the literature are very contradictory. In this work, the thermal stability of hydroxyapatite prepared by a solid-state mechanochemical method and structural changes occurring during sintering were studied. Stoichiometric hydroxyapatite was found to remain as a single-phase apatite structure with the space group P63/m up to 1300 °C inclusively. A further increase in the sintering temperature leads to its partial decomposition, a decrease in the crystallite size of the apatite phase, and the appearance of significant structural strains. It was shown that small deviations from stoichiometry in the Ca/P ratio upward or downward during the hydroxyapatite synthesis lead to a significant decrease in the thermal stability of hydroxyapatite. An apatite containing almost no hydroxyl groups, which is close to the composition of oxyapatite, was prepared. It was shown that the congruent melting of stoichiometric hydroxyapatite upon slow heating in a high-temperature furnace does not occur. At the same time, the fast heating of hydroxyapatite by laser radiation allows, under certain conditions, its congruent melting with the formation of a recrystallized monolayer of oxyhydroxyapatite. The data obtained in this study can be used when choosing sintering conditions to produce hydroxyapatite-based ceramics.

The present work was aimed to demonstrate the possibility of forming Fe66Cr10Nb5B19 metallic glass coatings by detonation spraying and analyze the coating formation process. A partially amorphous Fe66Cr10Nb5B19 powder with particles ranging from 45 &micro, m to 74 &micro, m in diameter was used to deposit coatings on stainless steel substrates. The deposition process was studied for different explosive charges (fractions of the barrel volume filled with an explosive mixture (C2H2 + 1.1O2)). As the explosive charge was increased from 35% to 55%, the content of the crystalline phase in the coatings, as determined from the X-ray diffraction patterns, decreased. Coatings formed at explosive charges of 55&ndash, 70% contained as little as 1 wt.% of the crystalline phase. In these coatings, nanocrystals in a metallic glass matrix were only rarely found, their presence was confined to some inter-splat boundaries. The particle velocities and temperatures at the exit of the barrel were calculated using a previously developed model. The particle temperatures increased as the explosive charge was increased from 35% to 70%, the particle velocities passed through maxima. The coatings acquire an amorphous structure as the molten particles rapidly solidify on the substrate, cooling rates of the splats were estimated. The Fe66Cr10Nb5B19 metallic glass coatings obtained at explosive changes of 55&ndash, 60% showed low porosity (0.5&ndash, 2.5%), high hardness (715&ndash, 1025 HV), and high bonding strength to the substrate (150 MPa).

Low-temperature (

In the area of metal matrix composites, novel reinforcing options are currently being evaluated. Particles of amorphous alloys present an interesting possibility to reinforce soft metals. In the present work, the interaction between Fe66Cr10Nb5B19 metallic glass and aluminum during spark plasma sintering (SPS) was studied for the first time. In order to trace the phase and microstructural changes upon sintering, mixtures containing 20 vol% and 50 vol% of metallic glass were subjected to SPS at 500–570 °C. After SPS at 500 °C, no reaction layer between the metallic glass particles and aluminum was observed. After SPS at 570 °C, a reaction layer containing Fe2Al5 and FeAl3 formed around the Fe-based cores. The Vickers hardness of composites obtained from mixtures containing 20 vol% Fe66Cr10Nb5B19 at 540 °C was 75 HV and increased to 280 HV after sintering at 570 °C due to the formation of thicker reaction layers at the interface. The hardness of the composite sintered from the mixture containing 20 vol% Fe66Cr10Nb5B19 at 570 °C was between the values predicted by Reuss and Voigt models. Comparison of results of SPS of the powder mixtures with those of SPS of a pre-compacted pellet and electric current-free annealing suggests that local heating at the interface caused by interfacial resistance may be an important factor influencing the reaction advancement at the interface and the formation of Al-containing intermetallics.

We report the formation and development of the interface between diamond and nickel in partially densified compacts obtained from powder mixtures by Spark Plasma Sintering, hot pressing and conventional sintering at 700 and 900 °C – temperatures, which are well below the melting point of nickel and even below that of the nickel–graphite eutectic. The nickel particles sintered among themselves and formed joints with facets of the diamond crystals. Most of these joints fractured cohesively leaving Ni-containing patches on the diamond facets. The microstructure of the patches adhered to the diamond surface in compacts sintered at 900 °C and their geometry and orientation relative to the edges of the diamond facets suggest that the formation and development of the nickel/diamond interface are associated with melting and solidification of the melt according to certain directions of the diamond crystalline lattice. A possible explanation of the formation of a liquid at such a low temperature is contact melting of a metastable eutectic between nickel and diamond.

Hybrid materials of polyvinyl alcohol-hydroxides/oxides of Be, Mg, Zn, Cd, B, Al, Cr, and Fe have been obtained. The studies have been carried out by the methods of optical spectroscopy, X-ray diffraction, and synchronous thermal analysis. Interpretation of experimental data is presented, presuming that, in systems with zinc, boron, aluminum, chromium, and iron hydroxides/oxides, interpolymeric complexes of polyvinyl alcohol with corresponding polymeric inorganic compounds are formed. They belong to a new class of materials with unusual structure containing chains of inorganic polymers isolated in the organic matrix.

Hybrid materials polyvinyl alcohol (PVA)-stannic acid and PVA-SnO2 were produced in the form of transparent films. Their investigations by means of optical spectroscopy, X-ray analysis, thermo-gravimetry, and mass-spectrometry were carried out as well as electrical measurements. The model is discussed where the polymeric chains of inorganic constituent are linked by coordinative bonds with carbon polymeric chains. Photoconductivity of PVA-SnO2 was discovered.

Under mechanical milling (MM) in a planetary ball mill the FeSn intermetallic decomposes with the formation of the Fe5Sn3 and FeSn2 phases, and the Fe2Ge3 decomposes into FeGe (B20) and FeGe2. These processes were investigated using X-ray diffraction (XRD), and magnetization measurements in order to assess whether or not local melting upon impact by milling balls, or low-temperature solid-state processes are responsible for decomposition. Fe2Ge3 decomposes completely after a relatively short milling period, while the amount FeSn decomposed reaches a steady state, depending on milling conditions, after prolonged milling. Particle sizes of the decomposition products (Fe5Sn3 and FeGe) determined from the XRD and magnetization data remain approximately constant during MM. These peculiarities are in good accordance with local melting as a mechanism of the mechanical decomposition of FeSn and Fe2Ge3.

Under mechanical milling (MM) in a planetary ball mill the FeSn intermetallic decomposes with formation of the Fe5Sn3 and FeSn2 phases, which have the highest density among the phases of the Fe–Sn system. This process was investigated using conventional X-ray diffraction, DSC, magnetization and alternative current susceptibility measurements. If the amount of decomposition of FeSn is relatively small (

Prolonged mechanical alloying of elemental blends and mechanical milling of individual intermetallics of the same chemical composition in the Fe–Ge system lead to the same steady state. The phase composition of this steady state was investigated in the entire composition range using a conventional XRD technique. A map reflecting the steady-state phase composition for the different chemical composition was constructed. Mechanical alloying and grinding form products of the following composition (in sequence of increasing Ge content): α (α 1 ) bcc solid solution, α+β-phase (Fe 2− x Ge), β-phase, β+FeGe(B20), FeGe(B20), FeGe(B20)+FeGe 2 , FeGe 2 , FeGe 2 +Ge, Ge. The incongruently melting intermetallics Fe 6 Ge 5 and Fe 2 Ge 3 decompose on milling. Fe 6 Ge 5 produces a mixture of the β-phase and FeGe(B20) while Fe 2 Ge 3 produces a mixture of the FeGe(B20) and FeGe 2 phases. These facts are in good agreement with a model that implies local melting as mechanism for new phase formation during mechanical alloying. The stability of the FeGe(B20) phase, which is also an incongruently melting compound, is explained as a result of the highest density of this phase in the Fe–Ge system.

Mechanically driven decomposition of intermetallics during mechanical milling(MM 1 was investigated. This process for Fe-Ce and Fe-Sn system was studied using conventional XRD, DSC, magnetization and alternative current susceptibility measurements. Mechanical alloying and milling form products of the following composition (in sequence of increasing Gecontent): () bcc solid solution, +-phase (), -phase, +FeGe(B20), FeGE(B20), FeGe(B20)+,,+Ge, Ge. Incongruently melting intermetallics and decompose under milling. produces mixture of -phase and FeGe(B20), produces mixture of FeGe(B20) and phases. These facts are in good agreement with the model that implies local melting as a mechanism of new phase for-mation during medchanical alloying. Stability of FeGe(B20) phase, which is also incongruently melting compound, is explained as a result of highest density of this phase in Fe-Ge system. Under mechanical milling (MM) in planetary ball mill, FeSn intermetallic decomposes with formation and phases, which have the biggest density among the phases of Fe-Sn system. If decomposition degree of FeSn is relatively small( phase determined from fitting parameters are in good agreement with crystalline sizes determined from XRD data and remiain approximately chageless during MM. The decomposition of FeSn is attributed to the effects of local temperature and local pressure produced by ball collisions.

A simple calorimetric technique was used to estimate the temperature of balls during mechanical alloying (MA) in an AGO-2 planetary ball mill. Temperatures up to 600 °C were realized for balls in the case that compact layers of milled powder are formed on the surface of the balls and the wall of the vial. Though free powders in the vial would decrease the temperature of the balls, it was found that a difference in temperature between the balls and the vial still exists. This should be taken into account in the analysis of temperature effects during MA. An influence of the temperature of the balls on the MA process of Mg67Ni33 and Ni50Al50 powder blends was demonstrated.

Polyethylene was irradiated with intensive electron beam with different doses. Structure changes after irradiation ex situ and in situ during heating up to its melting point were studied using synchrotron radiation X-Ray diffraction and thermal analysis.

The structure of the product in mechanical alloying depends both on the elemental composition and the milling conditions. An increase of ball energy led to more pronounced crystallinity of the product. Mechanical alloying at small ball energy leads to the formation of amorphous alloys for Zr-Co and Cu-Ti systems. Demixing of Ti3Cu4 into crystalline TiCu and TiCu4 and demixing of Zr50Co50 into Zr3Co and ZrCo2 was found. The results are explained on the basis of the concept of tribochemical equilibrium.