Numerical simulation of resistive switching in heterostructures based on anisotropic oxide compounds

Numerical simulation is used to study the effect anisotropic electrical conductivity and anisotropic oxygen diffusion have on the bipolar resistive switching effect in oxide compounds.     

The Structure and the Properties of Polyphosphates Recieved by Gasophase Method on Polyoxides Surface

Abstract

The gasophase method of polyphosphate (PPh) synthesis through the reaction between gaseous P₄O₁₀ or mixture P₄O₁₀-activator and surface of polyoxides was developed. The methods of investigation were: IR- and Laser-mass-spectro-scopy, photocolorimetry, X-ray analyse, gravimetry, gel-sol-fraction, and others. The synthesis characteristics of the mono- or polyoxide (MgO, Al₂O₃, CaO, SiO₂, TiO₂, MnO₂ and other ceramics) systems have been investigated. The structure and physical properties of synthesis products, possibility of their modification by thermo- and photochemical influences, and surface anisotropy of composition have been evaluated. The reaction has diffusion nature. Anisotropy determines the peculiarities of the products properties and modification possibility. The results of the investigations allow us to consider the macromolecular structure of glasslike polyphosphates as chains, which consist of various regularly placed components (ROC), e.g. for Mg-, Al-, Mn- or Ti-PPh tetracyclophosphate is ROC as to Si-PPH-it is copolymer with structure ROC in the form of Si-pyropnosphate. PPh structure and the degree of PPh sewing synthesized on polyoxide ceramic surface have been determined mostly by the composition of ceramics. Thus PPh is presented by polytetracyclophosphate of aluminium and by pyrophosphate, of silicon on “Al₂O₃-ceramic” surface (Al₂0₃ + SiO₂). The chains sewing takes place by the mechanism of substitution (by atoms of Mg, Al, Si) or introduction (Ca, zn). The present method has been applied for protection of ceramics by thin films and other coatings, soldering and obtaining composite materials.     

The Use of a Novel Three-Electrode Impulse Underwater Discharge for the Synthesis of W-Mo Mixed Oxide Nanocomposites

Plasma Chemistry and Plasma Processing - The novel three-electrode underwater pulse discharge excited by two independent high-voltage sources was used for the synthesis of W-Mo mixed oxide...     

Transfer coefficients of cations and anions upon glow discharge-induced nonequilibrium vaporization of solutions of alkaline earth metal salts

Firing of atmospheric-pressure, electrolytic-cathode glow discharge leads to an effect that is similar to well-known cathode sputtering. This process can be called nonequilibrium vaporization of the solution. Unlike quasi-equilibrium vaporization, the nonequilibrium process entails the transfer of nonvolatile components of the solution to the gas phase. Previously, studying glow discharge with calcium and barium chloride solutions as the cathode, we have shown that the transfer of cations and anions via the nonequilibrium vaporization of the nonvolatile solutes is not necessarily stoichiometric [1].     

Diode pumped Nd:YAG laser with active Q-switching and mode locking for hole drilling

A diode-pumped Nd:YAG laser operating with active-passive Q-switch mode locking, has been developed. The acousto-optic repetition train was one kilohertz with generated pulse train widths 65 ns, single pulse widths 200 ps and an average power of 6.5 W. Improvement of efficiency of small diameter deep holes laser drilling in different materials was studied.     

Laser-induced microjet: wavelength and pulse duration effects on bubble and jet generation for drug injection

The expansion of the laser-induced bubble is the main mechanism in the developed microjet injector. In this study, Nd:YAG and Er:YAG lasers are used as triggers of the bubble formation. The impact of the laser parameters on the bubble dynamics is studied and the performance of the injector is evaluated. We found that the main cause of the differences in the bubble behavior comes from the pulse duration and wavelength. For Nd:YAG laser, the pulse duration is very short relative to the bubble lifetime making the behavior of the bubble close to that of the cavitation bubble, while in Er:YAG case, the high absorption in the water and long pulse duration change the initial behavior of the bubble making it close to a vapor bubble. The contraction and subsequent rebound are typical for cavitation bubbles in both cases. The results show that the laser-induced microjet injector generates velocity which is sufficient for the drug delivery for both laser beams of different pulse duration. We estimate the typical velocity within 30–80 m/s range and the breakup length to be larger than 1 mm suitable for trans-dermal drug injection.     

Production of carbon nanotubes by self-propagating high-temperature synthesis

Carbon nanotubes are prepared by the method of self-propagating high-temperature synthesis for the first time. The initial components for this synthesis are carboniferous materials (soda, limestone, and Teflon) and reducers (magnesium, lithium, and sodium) with addition of a nickel or iron catalyst. The morphology of the nanotubes (straight multiwall nanotubes apparently free of a catalyst, bent nanotubes completely filled with a catalyst, and carbon nanofibers) is similar to that of nanotubes grown by chemical methods. The nanotubes account for 2–4 wt % of the product synthesized.