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Seven binary mixed oxides of V2O5, MoO3, TiO2, B2O3, Bi2O3, In2O3, and Tm2O3, in which V2O5 is a permanent component, were prepared by the method of mechanochemical activation (MCA). All composites have been investigated using EPR spectroscopy, X-ray diffraction, BET analysis and EPR spectra calculations. The results obtained were compared with those for individual V2O5 powder. The kinetic of structural transformations occurring in these binary mixtures under MCA were quantitatively characterized using a developed program of EPR spectra analysis. These structural rearrangements are fitted well by the first-order rate constants. Influence of the oxide nature mixed with vanadium pentoxide, the ratio of the components and time of milling on these transformations are discussed.

Ln2O3 + HfO2 (Ln = Nd, Dy) powders and ceramics have been studied in an oxidizing (O2) and a mild reducing (He) atmosphere using differential scanning calorimetry (DSC), thermogravimetry, mass spectrometric analysis of released gases, X-ray diffraction, IR spectroscopy, and Raman spectroscopy. The results demonstrate that both a mechanically activated oxide mixture of appropriate composition and the powders and ceramics prepared by heat-treating the mixture contain carbon-containing compounds (basic rare-earth carbonates and hydroxycarbonates) and/or at least 0.2–0.5 wt % carbon (X-ray amorphous or crystalline). As a result, during heating in an oxidizing atmosphere all of the samples release CO2 in the same temperature ranges (250–600 and 750–1200°C), which is accompanied by exothermic peaks in their DSC curves. The CO2 release in the range 250–600°C is due to the onset of decomposition of the basic rare-earth carbonates and hydroxycarbonates, which are present in small amounts in the starting mixture, powders, and ceramics. The CO2 release in the range 750–1200°C is due to the burnout of strongly bonded carbon and thermally stable carbon-containing compounds (rare-earth dioxymonocarbonates, Ln2O2CO3). The exothermic peaks in the DSC curve are due to fluorite LnHfO4 – δ (Ln = Nd, Dy) crystallization processes. We believe that synthesis in air, involving the formation of X-ray amorphous (fine-particle and nanocrystalline) precursors containing rare-earth oxides, which tend to form basic rare-earth carbonates and hydroxycarbonates in air, will always yield high-temperature ceramics containing carbon compounds and at least 0.5 wt % X-ray amorphous carbon and/or graphite. The amount of carbon and carbon-containing compounds in the dysprosium-containing ceramics is markedly smaller (~0.2%) than that in the neodymium-containing ceramics. The crystallization of the rare-earth hafnates is a rather slow process that can begin at temperatures as low as 550°C. The formation of Nd2Hf2O7 with the pyrochlore structure involves fluorite NdHfO4 – δ formation as an intermediate step, and a single-phase product can only be obtained by high-temperature firing at ~1600°C. Phase-pure DyHfO4 – δ with the fluorite structure can be obtained by firing at 1200°C.

The regularities of mechanical activation (MA) and the reactivity of an high-energy 15Al + 85Bi2O3 (wt %) system have been studied with the use of X-ray diffraction analysis, synchronous thermal analysis, and the measurement of the ignition temperature upon the contact with a hot surface. For the nonactivated system, the intercomponent interaction has not been recorded upon their heating in a DSC cell up to 760°C. When MA is carried out, the reaction partly occurs directly in the course of grinding and upon the subsequent heating. In the course of heating at a rate of 10°C/min, the intercomponent interaction proceeds to yield Bi metal and amorphous Al2O3 in a temperature range of 350–800°C, with maxima being observed at 520 and 630°C. At temperatures below 480°C, the reaction occurs in nanolayers, as is evident from the position and shape of the melting curve obtained for formed bismuth. The effects of the duration of MA on the conversion of the components, reaction kinetics upon heating in the DSC cell, the temperature of ignition upon the contact of an activated sample with a hot surface, and the rate of mixture combustion have been determined. The optimal duration of MA, at which the ignition temperature is minimum, has been found.

Molecular complexes [Zn(caf)(H2O)I2] (I), [Zn(caf)(H2O)Cl2] (IV), and the polymeric ones {[Cd(H2O)2I2](caf).2H2O}n (II) and {[Cd(H2O)2Br2](caf).2H2O}n (III) consisting of infinite Cd-containing chains with bridging halide ions and water molecules in trans-position and connected with each other due to hydrogen bonding with participation of caffeine (caf) and water molecules, were prepared and characterized by the powder and single crystal X-ray diffraction, IR vibrational spectroscopy, 1H NMR, ESI-MS spectroscopy, thermal analysis and DFT calculations. It was found that the complexes (I) and (IV) are characterized by tetrahedral geometry, the caffeine molecule being coordinated by the central atom via its N9 atom. The preferability of complex formation was evaluated by quantum-chemical calculations. Cyto- and genotoxicity of the compounds have been investigated and discussed in comparison with that of [Zn(AP)2I2] (1) and [Cd(AP)6][Cd(AP)I3]2 (2). It was demonstrated that the prepared complexes, primarily that of cadmium iodide with caffeine (II), are the promising ones for further studies both in vitro and in vivo.

The regimes of non-explosive mechanical treatment of ammonium perchlorate (AP) in high-energy intensity planetary ball mill are found. The changes in the structure and reactivity of AP as a result of mechanical processing were studied by methods of synchronous thermal analysis with registration of mass spectra, x-ray diffraction, microscopy and elemental analysis. Mechanical treatment reduces the particle size from 1000 μm to a fraction of μm and leads to formation of agglomerates of submicron particles with sizes of 5–10 μm. X-ray diffraction analysis shows the absence of the formation of new phases and a substantial broadening of the diffraction lines. As a result of mechanical activation, the temperature of AP thermal decomposition decreases by more than 100 °C, accompanied by the rapid release of oxygen at temperatures of 250–260 °C, immediately after the phase transformation in AP. The results obtained make it possible to explain the phenomenon of a significant increase in the detonation ability of mechanically activated AP and its mixtures with Al.

The general aspects of the mechanical activation (MA) of Al/CuO thermite compositions based on micron-sized particles and nanopowders of the starting components have been analyzed using X-ray diffraction and hydrogen titration. The latter method has been employed to evaluate the amount of residual oxygen in CuO and Cu2O from the weight loss during heating in H2. The reactivity of the activated mixtures was assessed using DSC and TG in combination with mass spectrometric analysis. In addition, we have measured the ignition temperature, burning velocity, and brightness temperature of the reaction products. The results demonstrate that mechanical activation leads to the fragmentation of the components, mixture homogenization, and the formation of a composite, producing “weakly bound” oxygen in CuOn and causing partial reaction between the components. The total exothermic heat effect in DSC scans, burning velocity, and brightness temperature as functions of specific milling dose (D) have an extremum. The highest reactivity is observed near D = 2 kJ/g, where a sufficient defect density in the components and good mixture homogenization are ensured, but the degree of MA-induced conversion does not exceed 10%. The burning velocity then reaches 400–700 m/s, and the brightness temperature is 3400–3800 °C. The milling dose dependence of the self-ignition temperature has no extremum. The self-ignition temperature steadily decreases with increasing milling dose, even though the ignition knock “power” falls off. The use of nanoparticulate starting components does not appear reasonable.

An experimental and computational study of the formation of pure iron nanoparticles, carbon nanoparticles (soot), and binary carbon-coated iron nanoparticles during the pyrolysis of iron pentacarbonyl–argon, ethylene–argon, and iron pentacarbonyl–ethylene–argon mixtures, respectively, behind reflected shock waves is carried out. The shape and size distribution of these nanoparticles are examined on a Zeiss Ultra plus ultrahigh-resolution field-emission scanning electron microscope. The binary iron–carbon particles were also investigated by high-resolution transmission electron microscopy and high-angle annular dark-field imaging (HAADF STEM) on a FEI Osiris transmission electron microscope equipped with a Bruker SuperX detector. Detailed kinetic simulations of the formation of these three types of particles are performed, which predict the concentration, average size, and size distribution of particles.

The TiO2/MoO3 and TiO2/V2O5 thin-film nanoheterogeneous photocatalysts obtained by mechanochemical activation of oxides were studied by using the test reactions of probing dye photooxidation, EPR spectroscopy, X-ray diffraction, and atomic force microscopy. It was shown that mechanochemical synthesis yields nanoheterostructures of the oxide–oxide type, in which optimum conditions were created for photogeneration of charge carriers and their accumulation and thus opens up an opportunity of obtaining photocatalytic systems with prolonged oxidative activity.

In this review, the regularities of formation, structure and high reactivity of two types of energetic metal/solid oxidizer nanocomposites (Al(Mg)/X (X = MoO3, (–C2F4–) n )) prepared by mechanoactivation are examined. One reason for the high reactivity is an increase in contact surface between the components occurring after mechanoactivation. Two methods for determination of area of contact surface S C between the components are used, and the values of S C for all the systems are estimated. Considerable attention is paid to the role of highly reactive defects (grain sizes, dislocations and stacking faults, paramagnetic centers, “weakly bound” oxygen in MoO3, etc.), formed in the components under mechanical stress. For the Me/MeO3 systems, the formation of point defects in the oxide is an important factor. It was found that, after mechanoactivation, the evolution of O2 from MoO3 occurs at 230–450 °C. It is argued that this process is associated with the thermal destruction of “weak” Mo–O bonds in the “bridge” oxygen. It was suggested that the formation of defect structure in MoO3 and increasing of the oxygen mobility under heating give rise to a low-temperature peak in DSC curves and initiated self-ignition on the fuel–air mixture. For composites Mg/MoO3, self-ignition occurs at temperature 100 °C lower than that for Al/MoO3: The decreasing of temperature can be connected with larger S C in the first system. In the Mg/(–C2F4–) n system, the reactions of magnesium defects with (–C2F4–) n are accompanied by a weak heat evolution, too low to initiate ignition. In this case, the reaction is initiated by the thermal depolymerization of (–C2F4–) n , while a high values of S C provide a complete conversion. In the case of shock-wave initiation, defects in the components play only a minor role in the conversion, whereas the value of S C remains to be highly important.

The regularities of the thermal relaxation of structural defects (paramagnetic centers and microdistortions), as well as the sizes of coherent-scattering regions and the external surface, of mechanically activated МоО3 have been studied with the use of X-ray diffraction, electron paramagnetic resonance, and adsorption/desorption methods. It has been revealed that heating of activated samples at temperatures below 450°C is accompanied by the death of paramagnetic centers, annealing of microdistortions, and liberation of molecular oxygen. It has been assumed that oxygen results from the rupture of deformed Mo–O–Mo bridge bonds formed by its atoms. Above 450°C, recrystallization processes occur, which are accompanied by an increase in the sizes of the coherent-scattering regions and the MoO3 (monoclinic) → MoO3 (orthorhombic) phase transition. The thermal stability of the external particle surface depends on mechanical activation conditions. For samples activated at early stages of activation (fracture regime), the specific surface area decreases by more than an order of magnitude, when a temperature of 450°C is reached. At higher activation doses (friction regime), the sample is not sintered in the same temperature range.

X-ray diffraction and thermal analyses, microscopy, and specific surface area measurements are used to study the formation, structure, and reactivity of mechanoactivated Mg/MoO3 and Al/MoO3 nanocomposites during slow heating (10°C/min). The optimal mechanoactivation dose is determined. The mechanoactivated Mg/MoO3 composite is a dense mixture of two nanosized components with a contact surface of ~8 m2/g (upper estimate). The area of the contact surface between the components of the Al/MoO3 composite is less than 2 m2/g, with the sample consisting of micron-sized aluminum flakes coated with nanoparticles oxide nanoparticles. When heated, the Mg/MoO3 system explodes, with the temperature of explosion being determined by the heating conditions. The minimum temperature of conversion is ~250°C, close to the temperature of autoignition of fuel–air mixtures promoted by these additives. The Al/MoO3 system is characterized by a phased progress of the reaction in the temperature range of 200 to 1000°C. The reasons for the differences in the reactivity of the mixtures are discussed.

Samples of individual and mixed vanadium-molybdenum (V:Mo) oxides xV2O5:(1-x)MoO3, 0 ≤ x ≤ 1, were prepared by the method of mechanochemical activation (MCA). The samples have been characterized by X-ray diffraction (XRD) and X-band electron paramagnetic resonance (EPR) spectroscopy. Prolongation of the treatment duration time in mills led to considerable increase in the V(IV) paramagnetic centers content as well as after additional high temperature annealing at 600 °C. Paramagnetic Mo(V) centers were recorded only in the case of MCA of individual MoO3 oxide. Complexity of the composition of mechanically activated mixed oxides was confirmed with the XRD data. It is shown that in the case of all individual and mixed oxides the content of paramagnetic species increases noticeably with the increase in milling time. The annealing at 600 °C after MCA of mixed oxides forms a new mixed phase of MoV2O8 composition.

Using mechanochemical synthesis through milling of equiatomic multicomponent mixtures of Cr, Fe, Co, Ni, Al, Ti, Mo, and Nb metals in various combinations, we have synthesized powder alloys with different phase compositions: amorphous phase (AP), AP + BCC phase, AP + BCC phase + MO, and FCC + BCC phases. The FCC phase has been shown to be a Ni-based solid solution. The presence of aluminum in a starting mixture helps to stabilize the BCC phase owing to the formation of a disordered B2 phase. Al dissolves in both the BCC and FCC solid solutions, increasing their lattice parameters. In Al-free starting mixtures, Cr is responsible for the formation of the BCC solid solution. The formation of an AP during milling of multicomponent mixtures is favored by the presence of transition metals with a large atomic radius: Ti, Mo, and Nb.

Molecular complex [Zn(AP)2I2] (1) and the isomorphous ones [Cd(AP)6][Cd(AP)X3]2 consisting of octahedral complex cations [Cd(AP)6]2+ and the respective complex anions [Cd(AP)X3]− (AP – antipyrine, 2,3-dimethyl-1-phenyl-3-pyrazolin-5-one; X = I (2) or Br(3)) were prepared and characterized by single crystal X-ray diffraction, IR vibrational spectroscopy, thermal analysis and DFT calculations. It was found that antipyrine molecules are coordinated by the metal atom, in both zinc-containing molecular complex (1) and in the cadmium-containing complex cations and anions (compounds (2) and (3)), via an oxygen atom of the ligand carbonyl group. The experimental results confirm the calculated ones. Both zinc (cadmium) iodides and their antipyrine complexes demonstrate cytotoxic activity in vitro at 10−5–10−3 mol/L, and are promising ones for further investigations of their anticancer activity both in vitro and in vivo.

The properties of mechanoactivated energetic composites based on aluminum and potassium perchlorate with high rates of self-sustaining chemical reactions under conditions of combustion and detonation are examined. The results of experiments on studying the combustion, deflagration-to-detonation transition, and sensitivity to friction of these composites are reported. The activation duration and aluminum content in the mixture are varied. The experiments on the deflagration-to-detonation transition of mechanoactivated composites are supplemented by the results of numerical simulations. The calculations and experiments on the dynamics of development of a blast wave and on the steady detonation velocity are found to be in qualitative agreement. It is shown that the velocity of the observed process is significantly (by about 40%) lower than the normal detonation velocity obtained from thermodynamic calculations.

Ternary and quaternary alloys of the Nb-Al-Si and Nb-Al-Si-C systems have been produced by mechanochemical synthesis. Our results demonstrate that the milling of a 62Nb + 19Al + 19Si ternary mixture, whose composition corresponds to that of the intermetallic phase Nb10Al3Si3, leads to the formation of an amorphous phase, whereas the milling of a 86Nb + 9Al + 5Si mixture, corresponding to a solid solution, results in the formation of a two-phase mixture, consisting of an amorphous phase and a nanostructured (7 nm) bcc solid solution. The addition of graphite to the starting mixtures homogenizes the MS products and reduces their particle size to ≃2 nm. The milling of a mixture with the composition Nb10Al3Si3C10 causes no changes in phase composition. The milling of a 78Nb + 8Al + 5Si + 9C mixture leads to the formation of an additional phase: nanoparticulate niobium carbide. Using differential thermal analysis, we have identified the sequence of transformations underlying the transition of the MS alloys to an equilibrium state. After the compaction of the MS powders by hot isostatic pressing, the samples prepared from the graphite-containing mixtures were more homogeneous in the case of both the alloys based on the intermetallic phase and the Nb-based solid solutions. The carbide nanoparticles precipitating on grain boundaries increase the hardness HV of the alloys by almost 30%: from 12.75 to 18.13 GPa for the samples corresponding to the intermetallic phase and from 4.76 to 6.85 GPa for the samples corresponding to solid solutions.

Defect structure of mechanically activated MoO3 has been studied with the use of X-ray diffraction, Raman spectroscopy, electron paramagnetic resonance, laser granulometry, and adsorption methods. Two stages of mechanical activation have been distinguished. At mechanical activation doses below 1 kJ/g, the fracture of oxide particles is the main process. At this stage, MoO3 particle sizes decrease from 30 μm to 60 nm and specific surface area linearly increases to 30 m2/g, the sizes of coherent-scattering regions decrease to 18 nm, paramagnetic centers are accumulated, and the Raman spectral bands corresponding to three different types of Mo-O bonds widen and shift. At doses above 1 kJ/g, the main process consists in the friction and aggregation of particles, which is accompanied by some reduction in the specific surface area and an increase in the particle sizes. At the stage of friction, the phase transition from an orthorhombic modification to a monoclinic modification of MoO3 occurs seemingly due to a shift of one layer of the material in plane (100). The shift is accompanied by the accumulation of lattice microstrains in the same plane, formation of “stressed” Mo-O-Mo bridge bonds, and a substantial rise in the concentration of Mo5+ radicals. The maximum total concentration of paramagnetic centers is 1 × 1018 g−1. It may be assumed that the radicals are formed due to the rupture of the most stressed molybdenum-oxygen bridge bonds.

Energy parameters (dose D and the work of surface formation) have been determined for the formation of a defective structure as a result of mechanical activation of graphite. Graphite activation has been shown to be a two-stage process: at low doses (D ≤ 20 kJ/g), the disruption and shift of graphite particles are the main processes, which are accompanied by a reduction in particle size, formation of meso- and micropores, and a rise in the BET specific surface area to 450–550 m2/g predominantly due to the development of a slitlike mesoporosity. At the same time, the crystalline structure of graphite is transformed into a turbostrate one with a concomitant increase in the lattice parameter and a decrease in the sizes of coherentscattering regions. The shape of diffraction lines can be described under the assumption that several fractions with greatly different degrees of defectiveness coexist in graphite. At higher doses, turbostrate graphite is transformed into X-ray amorphous carbon with a concomitant decrease in the specific surface area and meso- and microporosity. The defects resulting from the mechanical activation cannot be completely annealed at 2800°C. The main parameter of mechanical activation is the dose of supplied energy D = Jgt (Jg is the specific power consumption, and t is the duration of the activation). The curves describing accumulation of different defects can be represented in the form of a unified dependence on the dose for the Jg and, accordingly, t values varied by more than an order of magnitude (Jg = 1.7–22 W/g).

Mechanical activation has been employed to produce highly reactive energy-saturated Mg/(-C2F4-)n composites, chemical transformations in which are initiated by either heating or shock-wave loading. The structure and reactivity of these composites have been analyzed with the use of X-ray diffraction, microscopy, thermogravimetry, calorimetry, and the measurement of combustion and detonation velocities. Mechanical activation is accompanied by the formation of a magnesium/fluoroplastic composite structure with the intercomponent contact area as large as 6 m2/g and accumulation of chaotically arranged dislocations to concentrations as high as 6 × 1010 cm−2, basal and prismatic deformation stacking faults (the maximum probabilities of their formation are 2.1 and 1.4%, respectively), and boundaries of coherent-scattering regions in magnesium. In fluoroplastic, disordering and partial amorphization of the structure take place. Mechanical activation leads to a dramatic increase in the propagation velocity of Mg + (-C2F4-)n → MgF2 + C chemical reaction in the explosive combustion regime (to 400 m/s) and the development of knocking combustion, in which the reaction propagates at a velocity as high as 1100 m/s. The optimal dose of mechanical activation (7–8 kJ/g), at which the maximum velocity of reaction propagation is reached, has been determined. The use of a “slow” heating in the cell of a calorimeter in combination with the mass-spectral analysis of evolved gases has made it possible to distinguish processes of three types in the thermally activated interaction between magnesium and fluoroplastic. The formation of MgF2 at temperatures below 300°C seems to be due to the interaction between defects in magnesium (dislocations and stacking faults) and macromolecules. The reaction occurring at 300–420°C with a slight thermal effect is caused by the solid-phase interaction between magnesium and fluoroplastic brought in contact with one another. The main contribution to the conversion is made by the processes that take place at temperatures above 420°C and are relevant to the thermal depolymerization of fluoroplastic. The layered structure of the composite and the large area of the intercomponent contact ensure the penetration of gaseous products of depolymerization into the bulk of magnesium particles and the completeness of the interaction.

The genesis of a defective structure (particle size, size of coherent scattering regions (CSRs), dislocation concentrations, and two types of deformation and twin stacking defects (SDs)) of magnesium during its mechanical activation in a vibrating mill in the presence of liquid additions was studied by X-ray diffraction (XRD) analysis, microscopy, and adsorption (BET) method. The dynamic mechanical properties were checked for the activated samples using a K-44-2 vertical impact machine. The ability of magnesium to be oxidized in air was checked by heating it in the cell of a differential scanning calorimeter. At mechanical activation doses of less than 5 kJ/g, the accumulation of chaotically arranged dislocations and deformation SDs was accompanied by an increase in the plasticity of the material. At higher doses, polygonization of dislocations led to a drastic decrease in the CSR size and dislocation run, leading to embrittlement of the material. The changes in the mechanical properties were confirmed by symbatic changes in the outer particle size and showed themselves on the pressure oscillograms during the impulse loading of pressed Mg layers. Mechanical activation led to an increase in the level of oxidation of magnesium with oxygen, but did not affect the temperature of the start of oxidation. A method for activating magnesium with additions was suggested and led to the formation of highly disperse magnesium samples with the oxidation temperature lowered by 150°C.

Mechanochemical activation was used in the synthesis of CuO-CeO2 catalysts for the preferential oxidation of CO in the presence of excess H2. Catalysts similar in properties to supported CuO/CeO2 systems were prepared from mixtures of copper oxide (5 or 10 wt % CuO) and cerium dioxide with the use of mechanochemical activation. It was found that the time of mechanochemical activation influences the catalytic properties: a maximum conversion of CO into CO2 (97%) at 140°C was achieved with a sample of 10 wt % CuO-90 wt % CeO2 after mechanochemical activation in a ball mill for 90 min. Changes in the phase compositions of the catalysts depending on mechanochemical activation time and reaction mixture composition were studied by X-ray diffraction. The interaction of the oxides of copper and cerium in the process of mechanochemical activation with the formation of new Cu-O-Ce surface structures, which, supposedly constitute active sites for CO oxidation, was found using differential scanning calorimetry and differential thermogravimetric analysis.

An amorphous-crystalline two-phase (amorphous phase + BCC solid solution) powder alloy has been produced by mechanochemical synthesis (MS): by grinding an equiatomic mixture of Cr, Fe, Co, Ni, Al, and Ti metals in a Fritsch (P-7) ball mill at a powder-to-ball weight ratio of 1: 8. Using X-ray diffraction, X-ray microanalysis, and scanning electron microscopy, we have determined the sequence of reaction steps during milling of the mixture. In the early stages of milling (2 h), we observed the formation of an ordered phase (B2), Al + Ni → NiAl, and the CoHCP → CoFCC polymorphic transformation. Milling for 3 h led to the formation of a BCC solid solution. Further milling produced an amorphous phase (AP). In the range 6–25 h of milling, the percentage of the AP increased and that of the BCC solid solution decreased. The phase transformations induced by heating the alloy to 1200°C after MS have identified using differential thermal analysis and X-ray diffraction: \(MS (FCC + AP)\xrightarrow{{450^ \circ C}}(B2)\xrightarrow{{650^ \circ C}}(L2_1 + BCC)\xrightarrow{{850^ \circ C}}L2_1 + \sigma - phase\) (FeCr structure). Prolonged milling has been shown to stabilize the metastable BCC solid solution at temperatures of ≃650°C.

We have compared (Ln 2- x Zr x )Zr 2 O 7 + x/2 (Ln = Nd, Sm) pyrochlorelike solid solutions with interstitial oxide ion conduction and Ln2(Zr 2- xLnx)O 7- δ (Ln = Nd, Sm) pyrochlorelike solid solutions with vacancymediated oxide ion conduction in the symmetric systems Nd2O3-ZrO2 (NdZrO) and Sm2O3- ZrO2 (SmZrO). We have studied their structure, microstructure, and transport properties and determined the excess oxygen content of the (Sm 2- xZrx)Zr2O7 + x/2 (x = 0.2) material using thermal analysis and mass spec� trometry in a reducing atmosphere (H 2 /Ar-He). The Ln 2 ± x Zr 2 ± x O 7 ± x/2 (Ln = Nd, Sm) solid solutions have almost identical maximum oxygen vacancy and interstitial conductivities: (3-4) × 10 -3 S/cm at 750°C. The lower oxygen vacancy conductivity of the Ln2(Zr 2- xLnx)O 7- δ (Ln = Nd, Sm; 0 < x ≤ 0.3) solid solutions is due to the sharp decrease in it as a result of defect association processes, whereas the interstitial oxide ion con� ductivity of the (Ln 2- xZrx)Zr2O 7+ x/2 (Ln = Nd, Sm; 0.2 ≤ x < 0.48) pyrochlorelike solid solutions is essen� tially constant in a broad range of Ln 2 O 3 concentrations.

Solid solutions Ni(Al, Mo, C) are formed via milling the Ni2.8Al1Mo0.2 and Ni3Al0.8Mo0.2 and graphite-containing Ni2.8Al1Mo0.2C(0.25, 0.5) and Ni3Al0.8Mo0.2C(0.25, 0.5) mixtures. In this case, some amount of Mo remains beyond the solid solution. Graphite added to a starting mixture decreases the Mo solubility and favors the amorphization of solid solutions. The complete amorphization was found for the mixture with the 5 at % C and 5 at % Mo, which was added instead of Ni. The heating of mechanically synthesized (MS) powder alloys leads to the ordering of carbon-free and carbon-containing solid solutions with the formation of the L12 and E21 structure, respectively. In the course of the ordering of the Ni(Al, Mo, C) solid solutions, Mo and carbon precipitate in the form of the molybdenum carbide (Mo2C) second phase. The hardness of the MS three-phase Ni-Al-Mo-C solid solutions subjected to hot isostatic pressing is determined by the mass fraction of the formed Mo2C carbide. It is shown that the carbon content in the multicomponent antiperovskite can be estimated by analyzing the ratio of integral intensities of superlattice reflections I(100)/I(110).

Mechanochemical synthesis (MS) of Ni70Al25Mo5 (composition 1) and Ni75Al20Mo5 (composition 2) mixtures, in which 5 at % Mo substitutes for the equal amount of Ni or Al, leads to the formation of Ni-based nanocrystalline (coherent domains are ∼7–12 nm in size) solid solutions; in this case, some amount of molybdenum remains free. A comparison of the lattice parameters of solid solutions, which were determined experimentally, with the magnitudes determined theoretically using Vegard law and Bozollo-Ferrante simulation, which takes into account volume modules of elasticity of elements, showed an increase in interactions between atoms composed the solid solution and the formation of regions characterized by short-range order. The heating of mechanically synthesized three-component Ni(Al, Mo) solid solutions to 720°C in a calorimeter chamber forms the ordered γ′ phase (L12) at T ∼ 450°C. An analysis of the ratio of relative intensities of superlattice and fundamental reflections showed that, whatever the composition of initial mixture, Mo atoms always occupy positions in the Al sublattice. This arrangement of Mo atoms was confirmed by calculations of coefficients of concentrational variations of the lattice parameters. When molybdenum is added to Ni3 Al, Mo atoms, rather than Ni atoms, complete the Al sublattice. In this case, vacancies compensate for the lack of atoms in the Ni sublattice.

Ni(Al, C) mixed (substitutional and interstitial) solid solutions have been synthesized by mechanical alloying; the atomic ratio of Ni and Al was constant at 3: 1, but the concentration of carbon was varied. A carbide-forming element CE (Ti, Nb, or Hf) was added to the formed solid solutions with nanocrystalline substructures; the size D of coherent scattering regions was 4–6 nm. These mixtures Ni(Al, C) + CE were subjected to mechanical activation (short-term milling) and subsequent hot isostatic pressing. According to X-ray phase analysis, compacted samples exhibited three phases: Ni3AlCx antiperovskit, Ni(Al) solid solution with D = 50–100 nm and corresponding metal monocarbides (TiC, NbC, or HfC; D ≈ 7 nm) located at boundaries. These results were confirmed by scanning electron and optical microscopy. Thus, we obtained the analog of the conventional high-temperature γ/γ′ alloys hardened by grain-boundary nanoscale carbides, which prevent recrystallization.

The regularities of the formation of a solid solution in a Ni-Cr(20 at %) system are studied using X-ray diffraction, optical microscopy, and particle-size distribution analysis within the framework of an energetical approach to the analysis of the kinetics of mechanochemical synthesis. It is established that the curves of the consumption of chromium atoms and the formation of the reaction product (a solid solution of chromium in nickel) coincide with each other. The rate-limiting step of the reaction is the formation of a contact surface between chromium and nickel, while the “stirring” of chromium atoms in nickel matrix has a very high rate. The rate of the formation of the contact surface in the mixture of brittle chromium and plastic nickel is determined by the rate of chromium particle disintegration. To a conversion of about 60%, the reaction kinetics is described by a quadratic dependence on the dose (D) of the mechanical treatment (N ∼ D 2).

Nanocrystalline mixed (substitutional/interstitial) solid solutions have been prepared by milling four-component mixtures with the overall compositions (Ni2.8AlCr0.2)C0.5 and (Ni3Al0.8Cr0.2)C0.5. Analysis of X-ray diffraction data indicates that the formation of the solid solutions is accompanied by an increase in deformation stacking fault probability, which is directly related to the amount of dissolved carbon. Our results demonstrate that the heating-induced ordering of the solid solutions occurs in several steps. Nucleation of the antiperovskite phase E21 occurs through spinodal decomposition of the Ni(Al,Cr,C) solid solution starting at 400°C. Heating to higher temperatures leads to partial Cr precipitation from the ordered phase and the formation of the chromium carbide Cr3C2, which reduces the carbon content of the antiperovskite phase.

The method for the mechanical alloying of Ni-Al-C and Ni3Al-C mixtures was used to obtain nonequilibrium solid Ni(Al,C) solutions in which the carbon content varies from 2.9 to 8.5 at %. The relationship between carbon dissolution and the probability of appearance of deformation-induced stacking faults (SFs) in the formation of mixed (substitutional and interstitial) solid Ni(Al,C) solutions has been found based on an analysis of the diffraction spectra. SFs are assumed to serve as pathways of carbon penetration in nickel-based solid solutions. The effective carbon radius was found to be about 0.0616 nm in the formation of an antiperovskite phase Ni3AlC x . The method of calculating the amount of interstitial carbon was proposed based on the experimental lattice parameters of fcc solid Ni(Al,C) solutions and ordered phases L12 Ni3Al and E21 (Ni3AlC x ). The temperature stability of the nonequilibrium solid Ni(Al,C) solutions was established. It was shown that the decomposition of the solid solutions proceeded according to a spinodal mechanism at a temperature of 400°C with separation into two phases, i.e., an antiperovskite carbide (Ni3AlC x ) and Ni(Al,C). At higher temperatures (600–800°C), carbon precipitates from these phases with the formation of an antiperovskite Ni3AlC0.16, solid Ni(Al) solution, and nanocrystalline graphite.

Different procedures for analysis of particle sizes by the X-ray diffraction method are compared by the example of nanoparticles of nickel and iron(3+) oxide (Fe2O3). A modified Warren-Averbach method is proposed for the analysis of the X-ray diffraction line profile based on the approximation by the Voigt function, which yields stable solutions, and the efficiency of the method is shown. The analysis within the frame-work of the Warren-Averbach method makes it possible to restore the distribution function of nanoparticles (crystallites) over true diameters, which satisfactorily correlates with electron microscopy data. The applicability of the Warren-Averbach method to the estimation of crystallite sizes by the analysis of a single diffraction line is substantiated. The range of the applicability of the Scherrer, Williamson-Hall, Warren-Averbach, and modified Warren-Averbach methods to the substructure analysis by the X-ray diffraction is determined as depending on the method of nanostructure formation.

Mechanochemical processing of elemental mixtures with the compositions Ni75Al25, Ni70Al25Cr5, and Ni75Al20Cr5 (5 at % Cr in the mixtures instead of the equivalent amount of Ni or Al) leads to the formation of nanocrystalline nickel-based solid solutions (crystallite size in the range ≃ 7–12 nm). Comparison of experimentally determined lattice parameters of the solid solutions with Vegard’s law values and with the lattice parameters evaluated using the Bozzolo-Ferrante rule, which takes into account the bulk moduli of constituent elements, suggests that the atoms in the solid solutions are bonded more strongly. Heating the synthesized ternary solid solutions in a calorimeter to 1000°C leads to the formation of an ordered γ′-phase (L12). Analysis of the relative intensity ratio of superlattice and fundamental reflections indicates that the Cr atoms always reside in the Al sublattice, independent of the composition of the starting mixture. When 5 at % Cr is incorporated instead of Ni, the chromium atoms force out aluminum from the Al sublattice, and the Ni deficiency in the Ni sublattice is compensated by the Al atoms. The ordered phases remain nanocrystalline (crystallite size in the range ≃ 40–70 nm).

A method for production of mechanically activated energetic compositions consisting of nanosil� icon and solid inorganic oxidizers is developed. For the compositions prepared, both highspeed burning and detonation are observed. The propagation of the reaction is accompanied by a high energy release, compara� ble to the heat of explosion of aluminized high explosives. The compositions are highly sensitive to thermal stimuli and capable of rapid deflagrationtodetonation transition. The results obtained in the work suggest that nanosiliconbased formulations as promising ener getic materials for a wide range of applications, from initiating compositions in blasting caps to compositions for small charges in microsystem devices.

The methods of X-ray diffraction analysis, scanning electron microscopy, synchronous thermal analysis, and adsorption are used to study the mechanochemical synthesis of silicon carbide through the reaction Si + C → β-SiC. The reaction is found to take place in several stages. At the first stage, i.e., at activation doses below approximately 5 kJ/g, the powders of the components are independently ground to increase the specific surface area of the mixture to 145 m2/g, graphite is amorphized, and the sizes of the coherent-scattering regions of silicon drastically diminish. At the second stage (doses of 5–15 kJ/g), dense Si/C aggregates are formed and two fractions (coarse and fine) with different particle sizes arise in silicon crystallites. As the activation dose is enhanced, the amount of the fine fraction rises, while the sizes of coherent-scattering regions decrease to 2–3 nm. When samples are heated at 800°C, the fine fraction of silicon interacts with carbon to yield silicon carbide with crystallite sizes of 3–4 nm, whereas the coarse fraction of silicon recrystallizes. At the third stage, i.e., at doses of higher than 15 kJ/g, the mechanochemical synthesis of SiC occurs through the following scheme: fine fraction Si + C → amorphous SiC → crystallization of SiC.

The regularities of the mechanical activation of hexagonal boron nitride are analyzed using the X-ray diffraction, IR spectroscopy, transmission electron microscopy, dynamic light scattering, and adsorption methods. At the initial state of mechanical activation, the main process is material destruction. At this stage, the specific surface area increases to 400 m2/g and crystallographically oriented nanosized needles are formed. At the same time, boron nitride crystal structure is disordered with an increase in interplanar distance d(002). The disordering is assumed to be due to a shift along planes (001). At a specific dose of supplied mechanical energy above 6–8 kJ/g, the disordering processes dominate and the material is amorphized. At this stage, the specific surface area of samples decreases.

Mechanical activation makes boron nitride chemically reactive with respect to water. The fact of the reaction proceeding, which is accompanied by a change in the structure of boron nitride, is confirmed by the data of IR spectroscopy, X-ray diffraction, transmission electron microscopy, differential thermal analysis, adsorption, and gravimetry. It is established that the most defective amorphous part of the material is primarily hydrolyzed. The reaction takes place at room temperature, with the conversion increasing to values of higher than 50% with the dose of mechanical energy supplied during the mechanical activation. In addition to ammonia, hydrolysis gives rise to the formation of ammonium pentaboride, NH4B5O6(OH)4 · 2H2O. After the reaction products are removed, residual boron nitride, which is dried at T ≤ 100°C, crystallizes to form nanosized rods.

The processes of mechanical activation of a hexagonal boron nitride (h-BN) and its reactivity upon interaction with hydrogen and water were investigated using X-ray, TEM, Microdiffraction, Dynamic Light Scattering, FTIR-spectroscopy, adsorption (BET). Initial h-BN samples were monocrystalline plates 70–80 nm thick. Mechanical treatment of h-BN is accompanied by plate splitting and formation of crystallographically oriented “rods.” The rod thickness gradually diminishes to less than 5 nm. Specific surface area of the rods (400 m2/g), is found to be equal to the outer geometrical surface of rods. As nanocrystallites form “c” parameter of h-BN increases. When nanocrystallites are less than several nanometers in size, mechanical treatment results in BN amorphization; in this case specific surface of the system begins to decrease. Splitting of BN plates in the atmosphere of hydrogen is accompanied by the material hydrogenation and formation of B H and N H bonds. The amount of adsorbed hydrogen corresponds to monolayer filling. The amorphous part of activated BN interacts with water even at room temperature.

Mechanochemical synthesis in mixtures of light metals (Al, Mg, Ti) with hexagonal boron nitride under ball milling was studied. Well-pronounced stage behavior of the synthesis process was established and described in terms of dose of mechanical energy supplied to the material under milling (energy approach). At the initial stage the porous composite with nanometer-sized metal crystallites and high specific surface forms. The composite exhibits high reactivity with respect to external reactants, such as atmosphere and water. Mechanical activation also strongly facilitates the solid-state reaction between components, decreasing the temperature required for its initiation down to 450 °C. Solid-state reaction under milling takes place only after prolonged milling and results in formation of poorly crystallized metal borides and nitrides.

Detonation-like regimes in mechanoactivated energetic composites (MAECs) were experimentally studied. The test MAECs consisted of layers of a metal (Al, Mg) and Teflon mixed at the submicron and nano levels. The systems reacted to form solid final products. MAECs are appreciably superior to ordinary mixtures in chemical transformation rate. The burning of MAECs occurs in an explosive regime at a velocity of 300–400 m/s, with the temperature of the products being as high as 4000 K. When initiated with a HE charge, porous MAECs detonate in the steady regime. Depending on the composition and density of the samples, the detonation velocity varies from 700 to 1300 m/s, values markedly higher than the speed of sound in the initial mixture. Detonation is controlled by a hot spot mechanism, more specifically, by relay reaction propagation by jets of products.

The sequence and crystallization kinetics of the amorphous phase have been analyzed by differential scanning calorimetry and X-ray diffraction for mechanochemically activated Ni80Ta20 and Ni80Nb20 samples. The formation of equilibrium products from the amorphous phase occurs through the formation of metastable products of the A3 type. The kinetic parameters (activation energy and reaction order) and thermodynamic characteristics of this process are determined. Crystallization of the amorphous phase for the Ni80Ta20 and Ni80Nb20 systems occurs due to the growth of existing nuclei through the polymorphic and eutectic mechanisms, respectively. The thermal effects of the synthesis of equilibrium products from a mechanochemically activated mixture of components are identified.

The mechanical activation of thermal synthesis of aluminum carbide Al4C3 in Al-15 wt % C and Al-30 wt % C mixtures is studied with differential scanning calorimetry, X-ray diffraction, and transmission electron microscopy. It is found that the mechanical treatment of powders results in an essential reduction in the temperature of carbide synthesis. A correlation between the temperature of the onset of synthesis and size L of the coherent scattering region of aluminum is established. When the doses of absorbed mechanical energy exceed 15–20 kJ/g and, as a result, the L value decreases to 20 nm, the synthesis proceeds by a solid-phase mechanism at a temperature significantly lower than the melting point of aluminum and the synthesis temperature reduces by 800°C. The particle size of the formed aluminum carbide and unreacted aluminum after heating to 900°C is 20–40 nm. At doses D = 50–80 kJ/g, the heat of the formation of carbide from activated samples is about two times lower compared to the standard value. The possible sources of this discrepancy are discussed.

The kinetics of mechanochemical synthesis of aluminum carbide Al4C3 from elements was studied with X-ray diffraction analysis, low-temperature argon adsorption, laser granulometry, chemical analysis, X-ray photoelectron spectroscopy, and electron scanning microscopy. The conversion was presented as a function of energy consumption (dose) upon the mechanical treatment of mixtures of aluminum and graphite powders with the composition Al-15 wt % C and Al-30 wt % C. A multistage mechanism of the mechanochemical reaction was revealed, and the following stages were separated and characterized: (i) independent grinding and mixing of reagents, (ii) formation of molecular-dense Al/C composites based on nanosized aluminum particles, (iii) chemical interaction of components with the formation of interatomic Al-C bonds, and (iv) crystallization of Al4C3 carbide. The formation of amorphous nuclei of aluminum carbide occurs on the contact surface of aluminum nanoparticles with carbon.

Two regimes of oxidation by water are revealed for nanocrystalline aluminum prepared by the mechanical activation of its mixture with graphite and distributed in the matrix of amorphous carbon. At the temperatures 50°C < T < 90°C, nanosized aluminum particles interact with water under quasi-isothermal conditions. The main products are hydrogen and pseudoboehmite AlOOH; a low content of bayerite Al(OH)3 is also formed. After the induction period, the kinetics of interaction can be satisfactorily described by the law of a diminishing sphere. The effective activation energy of the reaction is equal to 61 ± 10 kJ/mol and is identical for the samples of submicron aluminum prepared by different procedures. At temperatures above 90–95°C, the oxidation of mechanically activated aluminum by water is transformed into a thermally self-accelerated explosion process. Under these conditions, the oxidation of aluminum to α-Al2O3 is accompanied by an exothermal reaction between the metal and the carbon matrix during which aluminum carbide Al4C3 is formed.

Detonation in an aluminum-fluoroplastic-4 (Teflon) mixture is studied experimentally. To increase reactivity, the initial mixture is pretreated in a mechanochemical activator. As a result, a mechanically activated composite is obtained in the form of thin aluminum layers in a Teflon matrix. The action of a shock wave on a composite sample initiates the steady detonation regime, in which the initial and final substances are in the condensed state. Depending on the percentage composition and density of the mixture, the detonation velocity varies from 700 to 1300 m/s for the speed of sound below 100 m/s in the initial composition. The steady detonation velocity changes insignificantly when sample pores are filled with helium instead of air. The results prove that it is possible in principle to reach the steady detonation regime in reactive condensed mixtures forming final reaction products in the solid state.

The structure of active Al/C composite prepared by the mechanochemical method from aluminum and graphite powders (10–30 wt % C) is studied by scanning and transmission electron microscopies, atomic force microscopy, local elemental analysis, X-ray diffraction, as well as by adsorption and sedimentation measurements. It is established that the particles of chemically active Al/C composite represent porous plate-like aggregates with a mean size smaller than 2.5–5 μm and composed of nanocrystalline aluminum blocks with a size of 15–60 nm distributed in a loose amorphous carbon. Single aluminum particles with a size of up to 10 nm are also observed; however, their weight fraction is small.