Melting temperature of metal polycrystalline nanowires electrochemically deposited into the pores of anodic aluminum oxide.

The arrays of metallic nanowires are considered as promising precursors for 1D semiconductor nanostructures after appropriate treatment at temperatures close to the melting point. Therefore the melting behaviour of the metallic structures in oxide templates is a key parameter for the subsequent conversion process. The present paper focuses on understanding of the effect of mechanical stress generated during heating on the melting point of the metal nanowires deposited into the pores of anodic alumina. Extremely high local compressive stress appears due to the difference in the thermal coefficients of the oxide template and nanowires inside the pores. The effect of the composite structural parameter that may be related to the concentration of nanowires on the melting temperature has been investigated. A numerical model predicting the melting point has been developed for composites with indium, tin, and zinc nanowires. The simulation results obtained using the suggested model were compared with the experimental data.

Effects during the cathode polarization of porous silicon.

The large inner surface of porous silicon (pSi) not only provides unique opportunities for introducing various foreign materials into the open pores, but is also responsible for a lot of processes during the pSi cathode polarization. PSi surface and contact effects are considered in the article. The space charge layer induced by both the surface states and the double electrical layer in the solution is shown to have a decisive influence on the electrical conductivity of the silicon skeleton in the pSi layer. Depending on the depletion degree of the pSi skeleton, the electrochemical deposition of metals is possible either on the entire pSi surface or pore filling from the bottom. The erbium hydroxide formation in the process of the cathode polarization of pSi in the solution of erbium salt is shown to have a chemical nature and is stimulated by the alkalization of the cathode space. The formation of erbium-containing deposits occurs by the following mechanism. First, hydrogen is electrochemically reduced at the cathode. This causes the ion imbalance and leads to the alkalinization in the space near the cathode. The alkaline medium creates conditions for the chemical process of the erbium hydroxide formation. Formed as a gel, erbium hydroxide is physically adsorbed on the cathode surface as a film. The components of the solution are necessarily included in the deposit composition. The accompanying oxidation and dehydrogenation effects during the cathode pSi polarization are considered. Moreover, during the pSi oxidation, the solid phase extends in the pore increases the steric factor, which is essential for the formation of internal oxygen bonds. These effects are characteristic features of any pSi cathode treatment. These formation rules are true for any lanthanide. The obtained results open wide prospects for practical application of Er-filled pSi as a promising material for practical biomedical application as prospective electrodes.

Peculiarities of the microwave properties of hard-soft functional composites SrTb0.01Tm0.01Fe11.98O19-AFe2O4 (A = Co, Ni, Zn, Cu, or Mn).

Herein, we investigated the correlation between the chemical composition, microstructure, and microwave properties of composites based on lightly Tb/Tm-doped Sr-hexaferrites (SrTb0.01Tm0.01Fe11.98O19) and spinel ferrites (AFe2O4, A = Co, Ni, Zn, Cu, or Mn), which were fabricated by a one-pot citrate sol-gel method. Powder XRD patterns of products confirmed the presence of pure hexaferrite and spinel phases. Microstructural analysis was performed based on SEM images. The average grain size for each phase in the prepared composites was calculated. Comprehensive investigations of dielectric properties (real (ε') and imaginary parts (ε'') of permittivity, dielectric loss tangent (tan(δ)), and AC conductivity) were performed in the 1-3 × 106 Hz frequency range at 20-120 °C. Frequency dependency of microwave properties were investigated using the coaxial method in frequency range of 2-18 GHz. The non-linear behavior of the main microwave properties with a change in composition may be due to the influence of the soft magnetic phase. It was found that Mn- and Ni-spinel ferrites achieved the strongest electromagnetic absorption. This may be due to differences in the structures of the electron shell and the radii of the A-site ions in the spinel phase. It was discovered that the ionic polarization transformed into the dipole polarization.

Evolution of poled state in P(VDF-TrFE)/(Pb,Ba)(Zr,Ti)O3 composites probed by temperature dependent Piezoresponse and Kelvin Probe Force Microscopy.

Polarized states of polymer/inorganic inclusion P(VDF-TrFE)-(Pb,Ba)(Zr,Ti)O3 composites are studied at the nanoscale using both piezoresponse force microscopy (PFM) and Kelvin probe force microscopy (KPFM). It has been shown that inorganic inclusions can be visualized using KPFM due to a discontinuity of the surface potential and polarization at the interface between the inclusions and the polymer matrix. The temperature evolution of the PFM and KPFM signal profiles is investigated. Softening of the polymer matrix on approaching the Curie temperature limits application of the contact PFM method. However non-contact KPFM can be used to probe evolution of the polarization at the phase transition. Mechanisms of the KPFM contrast formation are discussed.