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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.

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.

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.

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.

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.

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).

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.

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.

Mechanical treatment of CeNi2Si2 with the CeGa2Al2-type structure in the presence of hydrogen (P < 1 atm) and at room temperature initiates hydrogenation of this material. Under our experimental conditions the maximum amount of dissolved hydrogen formally corresponds to stoichiometry of CeNi2Si2H0.46. The hydrogenation is followed by increases of interatomic distances and volume of the CeNi4Si pores.

Processes of CH 4 and C 2 H 6 formation during mechanical treatment of NiZrH x , ZrH x , NiZr, Zr, Ni, and Zr+Ni in the presence of CO + H 2 or CO atmosphere as well as the mechanochemical reaction of hydrides with carbon (graphite) have been investigated using X-ray, chemisorption, thermodesorption, mass-spectroscopy and chromatography. It was found that I) the rate of methane formation decreases when Ni is included into the systems, 2) 100% hydrogen of hydrides may be converted into methane in mixtures of the hydrides with carbon, 3) in the presence of CO the major part of hydrides hydrogen is evolved in a molecular form while only

The effect of mechanochemical treatment on the hydrogenation of CO and CO2 was studied using a flow milling vial as a catalytic reactor. Traditional catalysts for the methane formation (Ni, Zr, Zr-Ni-containing samples, Zr hydride and Zr-Ni hydrides of various genesis), as well as inactive NiO and ZrO2, were examined. The following features of the mechanically driven CO hydrogenation were observed: (i) Zr and Zr-Ni hydrides demonstrated the highest activity in the formation of CH4; (ii) the hydrogen present in the reaction mixture suppressed the formation of CH4; (iii) Ni was found to be ineffective in the formation of CH4 but active in the reaction of CO disproportionation; (iv) on the oxide samples, a small amount of CH4 was formed owing to the mechanical activation. Deep structural transformations of the metal and hydride samples under milling in the reaction mixture were found to be responsible for the changes in their catalytic activity. Only zirconium hydride exhibited catalytic activity for CO2 hydrogenation. In this case, no phase transformation was observed.