Solid State Phenomena Vol. 245

Abstract: Influence of the polarizing signal parameter used during plasma electrolytic oxidation (PEO) on the composition, morphology and properties of protective coatings formed on aluminum alloy in tartrate-containing electrolyte has been presented. It was established, that using of the short-pulse bipolar polarizing signal (τ=5 μs) facilitates the reduction of porosity and roughness of the formed PEO-layers. This, in turn, increases wearproof and protective corrosion characteristics of the treated alloy surface. Increasing the duty cycle (D) affects on the chemical composition and the thickness of the obtained coatings.

Abstract: The paper presents the results of the study of electrochemical and mechanical properties of PVDF/PEO-coatings formed on magnesium alloy MA8 by plasma electrolytic oxidation (PEO) and subsequent application of polyvinylidene fluoride (PVDF) on the PEO-layer. The oxide coatings were formed using a 300 Hz bipolar signal with duty cycle (D) 0.50. The analysis of electrochemical data has showed a decrease of corrosion currents by 3 orders of magnitude (down to 6.0·10^-9 А·сm^-2) and an increase of the polarization resistance by 3 orders of magnitude (up to 5.3·10⁶ Оhm·сm²) for the coatings formed by triple dipping (x3) of the PEO-layers into PVDF solution. Evaluation of the tribological properties of the (x3) PVDF/PEO-coatings has showed a significant increase of the wear resistance (the number of abrasion cycles resulting in complete destruction of the coating increased in 25 times) as compared to the base PEO-layer.

Abstract: The developed methods of formation and results of the study of the hydrophobic layers on aluminum alloy, previously subjected to plasma electrolytic oxidation (PEO), boiling in bidistilled water, and additional treatment (either in ethanol solution or under UV-radiation in the presence of ozone plasma) with subsequent deposition of the hydrophobic agent (methoxy-{3-[(2,2,3,3,4,4,5,5,6,6,7,7,8,8,8-pentadecafluoroctyl) oxy] propyl}-silane solution in decane) have been described. It was found, that the formed composite layers possess hydrophobicity (contact angle higher 155o) and high anticorrosion properties (the impedance modulus (|Z|_{f = 0.01 Hz}) ranges from 1.5·10⁸ to 1.7·10⁸ Оhm·cm² depending on treatment procedure).

Abstract: Plasma electrolytic oxidation (PEO) of commercially pure titanium VT1-0 was performed in phosphate electrolyte. High-frequency 200 kHz bipolar signal at a duty cycle D=0.1 was used to form the oxide coatings. Polymer-containing anticorrosion coatings were formed by applying polyvinylidene fluoride (PVDF) on the base PEO-coating. The results of electrochemical tests have showed a decrease of corrosion current density by 2 orders of magnitude (down to 1.5∙10^-10 А∙сm^-2) and the corresponding increase of the polarization resistance (up to 1.9∙10⁸ Оhm∙сm²) in comparison with the metallic substrate.

Abstract: Two-phase Al(OH)₃–PbSnF₄ composites (concentrations of aluminum hydroxide are equal to 5 wt.%, 15 wt.% and 30 wt.%) has been prepared by high-energy ball-milling method. The materials were employed as anodes in Li-ion batteries. It was established that PbSnF₄-based systems yield high initial capacity of 800–1100 mAh g^–1. The reversible specific capacity of Al(OH)₃–PbSnF₄ (aluminum hydroxide – 15 wt.%) after 10-fold charge–discharge cycling in the range of 2.5–0.005 V attains 120 mAh g^–1, while the specific capacity of pure PbSnF₄ is equal only to 20 mAh g^–1. It has been shown that the deviation from 15 wt.% concentration of Al (OH)₃ decreases cycling stability of lead fluorostannate (II).

Abstract: The high-tech method of creating anticorrosion calcium phosphate coating on the magnesium alloy MA8 (MgMnCe) has been developed. As was demonstrated by the volumetry method the sealing of the layer formed on the surface of Mg alloy using plasma electrolytic oxidation by superdispersed polytetrafluoroethylene substantially reduced the rate of the corrosion process. Here, the surface of the calcium phosphate layer containing hydroxyapatite (Ca/P = 1.61) remains biologically active. Studies of architectonics of the surface of innate immune cells have been performed in vitro.

Abstract: Investigated systems including solid solutions K_(1–x)Li_xSn₂F₅ (0 ≤ x ≤ 7.5) and 0.95KSn₂F₅–0.05Al₂O₃ synthesized through high-energy ball milling and characterized by XRD and DSC techniques. The values of the dc conductivity and activation energies estimated in the temperature range from 298 K to 473 K by impedance spectroscopy. It was established that conductivity at ambient temperature increases for K_0.975Li_0.025Sn₂F₅ and K_0.95Li_0.05Sn₂F₅ samples as compared to pure KSn₂F₅. The role of cation substitution influencing on conductivity values, phase transitions and activation energies in the given systems discussed.

Abstract: A new concept for synthesis of the nanostructured transition metal oxides had been proposed. In particular, the method of pulsed high-voltage discharge was adopted for synthesis of α-MoO₃ nanostructure with orthorhombic crystal lattice. The as-prepared α-MoO₃ was investigated as anode for Li-ion battery. The 30-fold charge–discharge cycling has shown that material specific capacity (approximately 90 mAh g^–1) is not high, however excellent reversibility was achieved (the Coulombic efficiency equals to 99.9%). Thus the method opens new ways for the synthesis of nanomaterials with stable reversible capacities for Li-ion batteries.

Abstract: Layered oxide coatings containing europium ferrite multiferroic have been synthesized on titanium plates through plasma electrolytic oxidation and extraction pyrolysis. The composites have weak ferromagnetic properties: the coercive force attains 45–78 Oe in the temperature range 3–340 K. Their luminescence properties are typical of inorganic materials with europium ions.

Abstract: The nanotubular titanium dioxide structures were prepared using anodic oxidation. The structural features of surface have been investigated by scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and energy-dispersive spectroscopy (EDS) techniques. These nanotubular titanium dioxide structures can be used as a sensor in potentiometric indication components of different types of chemical reactions.