In the present work, a mechanism of the destruction of amorphous tantalum oxide Ta2O5 on the tantalum anode surface is suggested based on high absorption properties of tantalum. The data of analysis of the morphological peculiarities of the defective areas of the surface layers show that the destruction of the amorphous film occurs due to the growth of a pyramid-shaped defect; the pyramidal defect is not coherent with amorphous surface Ta2O5, and it is not a product of its crystallization. The nucleation and growth of the “pyramid” occurs due to the directed movement of oxygen during the oxidation of the tantalum surface along the grain boundaries to the region of triple junctions of the tantalum matrix with the subsequent local formation of crystalline Ta2O5. The suggested mechanism offig destruction can be realized when high-purity tantalum powders are used.

Stacking faults in tantalum deposited in a helium environment on a copper substrate by chemical vapor deposition and their effect on the protective properties are studied using X-ray diffraction, scanning electron microscopy, glow-discharge emission spectroscopy, electrochemistry, and strength assessment. It is shown that the probability of the formation of stacking faults in deposited body-centered cubic (bcc) tantalum in the 112 planes is a sensitive parameter with respect to the deposition conditions (temperature and helium content). With an increase in the helium concentration from high to medium values, the sum of probabilities of the formation of deformation (α) and twinning (β) stacking faults 1.5α + β in α-Ta increases five times (from 0.025 to 0.13

Using X-ray diffraction, scanning electron microscopy, glow discharge emission spectroscopy, electrochemistry and strength assessment, stacking faults in tantalum deposited in a helium environment on a copper substrate by chemical vapor deposition and their effect on the protective properties have been studied. It is shown that the probability of formation of stacking faults in deposited bcc tantalum in the {112} planes is a sensitive parameter with respect to the deposition conditions (temperature and helium content). With an increase in helium concentration from high to medium values, the sum of the probabilities of the formation of deformation (α) and twinning (β) stacking faults 1.5α + β in α-Ta increases five times (from 0.025 to 0.13%), with a decrease in temperature from 800 to 750°C — 35 times (from 0.025 to 0.89%). A decrease in the probability of formation of stacking defects in deposited α-Ta tantalum is associated with a significant increase in corrosion resistance and adhesion strength of the coating to the substrate. A mechanism for the formation of metastable hcp phases of tantalum on stacking faults in α-Ta in the {112} planes is proposed.

Structural changes in FTW60 and FTW8000 tantalum capacitor powders after sintering at different temperatures are investigated by X-ray diffraction and scanning electron microscopy. Sintering is carried out in accordance with the current technological process used in the production of oxide–semiconductor capacitors. The anodes obtained as a result of sintering are bulk-porous bodies in the form of a rectangular parallelepiped with a wire lead. On the free surface of the bulk-porous anodes obtained by sintering the FTW60 powder at temperatures of 1800°C and 1920°C, the formation of a wavy relief is observed. No such relief is observed after sintering the FTW800 powder at 1250°C. After analyzing the structural state and the morphology of the initial powders and the anodes obtained as a result of sintering, a phenomenological model of the formation of such a relief is proposed based on collective recrystallization near the free surface during high-temperature exposure.

The structure and morphology of CVD molybdenum coatings in the MoCl5–Cd system on substrates made of copper, stainless steel (12Kh18N10T), and Inconel X750 and ZhS6U-VI high-temperature alloys were studied by X-ray diffraction, scanning electron microscopy, and using thermodynamic calculations by the Miedema model. A loose, porous, and thin (0.1 μm) coating was formed on the copper substrate, while uniform and continuous coatings were observed on Inconel X750, 12Kh18N10T, and ZhS6U-VI, which were 0.3, 0.7, and 1.0 μm thick, respectively. In the series of substrates M1–Inconel X750–12Kh18N10T–ZhS6U-VI, the deposition rate of molybdenum increases (from 0.1 to 1.0 μm/h), the size of its crystallites decreases to 50 nm, and lattice microdistortions increase to 0.16%. The rate of deposition of the molybdenum coating based on the MoCl5–Cd mixture is consistent with the negative enthalpy of formation of intermetallic compounds of the equiatomic composition MeMo (where Me is the substrate metal), calculated by the Miedema model. The differences observed in the series of M1–Inconel X750–12Kh18N10T–ZhS6U-VI in the deposition kinetics, morphology, structure, and substructure of the obtained coatings are explained from the standpoint of the enhancement of the adsorption interaction between the substrate and MoCl5 and the chemical affinity of the substrate and molybdenum.

The kinetics and mechanisms of the hydrogen-free chemical-vapor-deposition (CVD) method for protective tantalum coatings in the TaBr5–Cd system on St3, tungsten, and copper substrates in the temperature range of 700–950°C are investigated by X-ray diffraction, scanning electron microscopy, glow-discharge optical emission spectroscopy, and polarization curves. The thickness of the coatings obtained on St3, tungsten, and copper is 2.8–15.7, 2.2–5.3, and 2.0 µm respectively. The calculated activation energy of the CVD process during deposition onto St3 and tungsten (68 and 28 kJ/mol, respectively) indicates a diffusion-limiting stage. In the series of copper-tungsten-St3 substrates, the deposition rate of the tantalum coating increases and agrees with the negative enthalpy of formation of intermetallic compounds ΔHMeTa (Me is the substrate metal), which is associated with an increase in the adsorption interaction between the substrate and TaBr5 in it. It is shown that dense α-Ta-based coatings are deposited onto St3 at T = 700–750°C, and loose coatings based on face-centered cubic (fcc) tantalum with an admixture of lamellar hexagonal close-packed (hcp) tantalum crystals are deposited at T = 800°C and higher. Accordingly, dense body-centered tetragonal (bct) β-Ta-based coatings are deposited onto tungsten at T = 700–750°С; at 800–900°С, loose α-Ta-based coatings are deposited. A coating consisting of a mixture of α and β phases is obtained on copper at 800°C. The sums of the probabilities of deformation (α) and twinning (β) stacking faults (SFs) (1.5α + β) in deposited bcc ({112} planes) and fcc ({111} planes) tantalum are calculated by the harmonic analysis of diffraction lines according to Warren, and they range from 0.04 up to 1.2 and from 0.03 to 2%, respectively. The discovered SFs are likely to be closely related to the formation mechanisms of nonequilibrium bct, fcc, and hcp tantalum phases. Additional annealing (1000°С) of the β-Ta-based coating (tungsten substrate) leads to the formation of α-Ta, while annealing of the α-Ta-based coating (St3 substrate) leads to the formation of fcc tantalum. The formation of fcc tantalum crystals on an St3 substrate at T ≥ 725°C during CVD or as a result of annealing is assumed to be due to the α → γ phase transition in St3. The obtained α-Ta-based coatings demonstrate high corrosion properties.

We obtain titanium carbohydrides by the high-energy ball milling (HEBM) of titanium in a planetary ball mill in toluene. Depending on the duration of HEBM, face-centered cubic (FCC) and hexagonal close packed (HCP) carbohydrides with different carbon and hydrogen contents are obtained. The structural-phase state and the thermal stability of the solid phase of the reaction mixture, during successive stages of mechanosynthesis, are investigated by means of X-ray diffraction, differential scanning calorimetry, thermal desorption, and scanning electron microscopy. At short milling times (50 min), the endothermic peak appears at a temperature of 430°C due to the α → β phase transformation in Ti in the presence of hydrogen. Hydrogen stabilizes β-Ti, reducing its formation temperature to 300°C. The exothermic peak, at about 530°C, corresponds to the deformation-energy release of the crushed Ti powder. Processing in the planetary mill for 5 h leads to the formation of an α-Ti (HCP) and Ti carbohydride (HCP and FCC) mixture. We state that for the HCP carbohydrides, a higher hydrogen desorption temperature is observed as compared to the FCC carbohydrides. The correlation of the thermal desorption peaks and the differential scanning calorimetry curves is discussed. We make assumptions concerning the mechanisms of the thermally stimulated structural-phase transformations of the carbohydrides.

The effect of the cooling rate on the structure and properties of hypoeutectic Nb–Si–Al alloys obtained by aluminothermy in an argon atmosphere studied by scanning electron microscopy, X-ray phase analysis, and energy-dispersive analysis. The indentation method is used to measure the mechanical properties of the obtained alloys: the fracture toughness and hardness. The cooling rate of the alloy is regulated by replacing the crucible material: the cooling rates of the alloy differ by almost an order of magnitude. The difference in the cooling rates does not affect the phase composition of the obtained alloys: in all cases, a solid solution of silicon and aluminum in niobium (Nbss) and β-Nb5Si3 silicide are formed. The microstructures of the obtained alloys are similar, but differ in dispersion. The formation of a finer structure led to an increase in the mechanical properties of the alloy compared to those of the alloy with a lower degree of structure dispersion.

The combination of various extreme influences (ultrahigh pressures, torsion under pressure and equal channel angular pressing, ultralow and ultrahigh temperatures, strong electric and magnetic fields, ultrafast cooling from the melt) allows us to significantly expand the region of metastable states and to obtain materials with different structural hierarchy: amorphous, quasiand nanocrystalline. The key extreme parameter in the work is high pressure. High pressure phases are thermodynamically stable at high pressures. The methods of X-ray diffraction analysis and electron microscopy were used to study the structure, elemental, and phase composition of the hypereutectic Al86Ni6Gd4Tb2Er2 (hereinafter, at.%) alloy during solidification of the melt at a rate of 1000 deg / s under ultrahigh pressure of 3 and 7 GPa. Samples for research were obtained in a high-pressure chamber of the toroid type. The alloy was heated and melted by passing alternating current through the sample. The structure of all the obtained samples is homogeneous, dense, without shrinkage shells. Solidification of the melt under pressure of 3 and 7 GPa leads to a change in the phase composition of the alloy, the alloy remains hypereutectic. At a pressure of 7 GPa, metastable crystalline phases were obtained. The combination of high solidification rate and mechanical compaction made it possible to obtain alloys with a crushed structure and high density. The average microhardness of samples obtained under pressure is ~4 times higher than the microhardness of the initial sample due to solid-solution and dispersion hardening. Despite the fact that the alloy is glass-forming, amorphous phases were not detected under the selected solidification conditions.

The influence of domestic nitrogen-containing corrosion inhibitors of the VNKh-L type on corrosion regularities of a zinc coating on steel in neutral media is investigated. This work is aimed at studying the surface structure of a corroding zinc coating, as well as the influence of conditions simulating the degradation of inhibitors during real operation on their protective properties. Mechanical activation in a ball planetary mill is used to simulate the deformation and thermal operational conditions of inhibitors. Corrosion of a zinc coating on steel is carried out in a sulfate–chloride medium simulating atmospheric corrosion and in a borate buffer solution. The concentration of inhibitors in the corrosion media was 0.2 wt %. The morphology of a corroded surface of a zinc coating is studied using a Philips SEM-515 scanning electron microscope (at an accelerating voltage of 10 kV) with an X-ray microprobe. Studies of the corrosion rate of zinc coating on St 08 are carried out by the indirect measurement of corrosion resistance with the help of a MONIKOR-1 corrosion meter. A borate buffer solution (Na 2 B 4 O 7 + H 3 BO 3 , pH 6.6) and a solution simulating atmospheric corrosion (NaCl + Na 2 SO 4 , pH 6.0) are used as corrosion media. The corrosion rate of samples in corrosive media without an inhibitor is accepted 1. The exposure time of each sample in corrosive media is 3 h. The chemical composition of corrosion products is studied by the mirror reflection in the IR range. The IR spectra of the metal plate surface are recorded using an FSM-1202 IR Fourier spectrometer in a wavelength range of 450–4000 cm –1 with a resolution of 2 cm –1 and an accumulation of 100 scans. To record the reflection spectra, a mirror-reflection attachment with a 10° angle of incidence is used. The corrosion rate of zinc coating in sulfate–chloride and solvent media in the presence of inhibitors based on benzotriazole and cyclohexylamine is practically not decreased when compared with the corrosion rate in the same media without inhibitors. The addition of both initial and mechanically activated inhibitors based on morpholine and benzotriazole to the corrosion medium decreases the corrosion rate of iron when compared with the corrosion in the same media without inhibitors. The pitting corrosion of a zinc coating is observed in the presence of initial and mechanically activated inhibitors of both types in studied corrosion media. Herewith, the pitting depth is smaller than the zinc-coating thickness under these conditions.

The microstructures of a commercial aluminum foil and an aluminum foil alloyed by 0.001 wt % scandium are studied before and after electrochemical etching. The strength properties, the capacitance, and the weldability of the foils subjected to electrochemical etching are investigated. We are the first to show that the alloying of aluminum by such a low amount of scandium affects the microstructure of a foil and is sufficient for increasing the strength properties, the capacitance, and the weldability of the aluminum foil used for capacitors.

The authors have performed a comparative study of the structures of the hypereutectic Al87Ni8Y5 alloy (hereinafter indicated at.%) obtained by rapid cooling from the liquid phase during crystallization under pressure (from 1.8 to 2.2 GPa and 7 GPa), subject to temperature changes (from 1200 to 1800 degrees C) of the melt, through durametry, X-ray structural analysis and optical and electron microscopy. It is shown that under all the considered conditions of crystallization and the cooling rate of the melt of 103 K/sec, there are formed crystalline phases in the alloy. Dense homogeneous structures of the alloy with dispersed primary ternary aluminides Ni and Y of variable composition (with different contents of Ni and Y) or anomalously oversaturated alpha-Al-solid solution and modified eutectic, which have high hardness, are obtained.

The influence of domestic VNKh-L type nitrogen-containing corrosion inhibitors on the corrosion patterns of zinc coating on steel in a neutral environment was investigated. The paper aims to study the structure of the corroding zinc coating surface, as well as the influence of conditions simulating the degradation of inhibitors under actual application conditions on their protective properties. Mechanical activation in a ball planetary mill was used to simulate the thermal and deformation conditions of inhibitors. Zinc coating corrosion on steel was carried out in a sulfate-chloride environment simulating atmospheric corrosion and in borate buffer solution. The concentration of inhibitors in corrosion environments was 0,2 wt.%. The corroded surface morphology of the zinc coating was studied using the Philips SEM-515 scanning electron microscope (at an accelerating voltage of 10 kV) with an X-ray micro probe. Studies of the zinc coating corrosion rate on St 08 were carried out by the indirect measurement of corrosion resistance using the MONIKOR-1 corrosion meter. Borate buffer solution (Na2B4O7 + H3BO3, pH = 6,6) and the solution simulating atmospheric corrosion (NaCl + + Na2SO4, pH = 6,0) were used as corrosive environments. The corrosion rate of samples in corrosive environments without inhibitors was taken as 1. Exposure time of each sample in corrosive environments was 3 h. The chemical composition of corrosion products was studied by mirror reflection in the IR range. The IR spectra of metal plate surfaces were recorded on the FSM-1202 IR Fourier spectrometer in a wavelength range of 450–4000 cm–1 with a resolution of 2 cm–1 and an accumulation of 100 scans. A mirror reflection attachment with a 10° angle of incidence was used to obtain reflection spectra. The zinc coating corrosion rate in sulfate-chloride and borate environments in the presence of inhibitors based on benzotriazole and cyclohexylamine was virtually not reduced compared to the corrosion rate in the same environments without inhibitors. When both initial and mechanically activated inhibitors based on morpholine and benzotriazole are added to the corrosion environment, the iron corrosion rate decreases compared to the corrosion rate in the same environments without inhibitors. In the presence of initial and mechanically activated inhibitors of both groups, pitting corrosion of the zinc coating in the studied corrosion environments is observed. At the same time, the pitting depth under corrosion conditions is less than the zinc coating thickness.

Using the methods of durametry, X-ray structural analysis, optical and electronic microscopy, we have compared the structures of the Al90Y10 hypereutectic alloy (hereinafter at.% is given) obtained at the atmospheric pressure and that produced with quick cooling under pressure of 9 GPa. It has been demonstrated that, in both cases, the crystalline phases of alpha-Al and Al3Y get formed.(1) Using high pressure, we have provided a dense homogeneous alloy structure with abnormally alpha-Al-supersaturated solid solution and finely divided aluminides in metastable eutectics with high hardness.