Electrolytic Corrosion of Titanium Carbonitride Composites

The corrosion properties of TiCN, TiCN – AlN, and (TiCN – AlN) – (Fe – Cr) ceramics as well as those of the individual components TiN and TiC in a 3% NaCl solution have been investigated. The kinetics and the mechanism of anode dissolution of metals and oxidation of specimens have been studied by using polarization curves, chemical and x-ray phase analyses, Auger electron spectroscopy, and scanning electron microscopy (SEM). TiCN and TiCN – AlN composites have been found to be the most corrosion-resistant. The presence of a metallic binder in the titanium carbon nitride somewhat decreases the corrosion resistance of the ceramics. On the whole, however, the ceramics developed boast a significantly higher corrosion resistance than that of structural steel.     

Mathematical model of an industrial robot with articulated configuration and six degrees of freedom

This paper analyses the load influence on a d.c. drive motor servo system for all six degrees of freedom of industrial robots with an articulated configuration. Through the analyses, the analytical equations of total inertia and gravitation moments of an industrial robot servo system for external coordinate function were obtained. A mathematical model of an electro-mechanical industrial robot system was also developed.     

Robot-assisted wayfinding for the visually impaired in structured indoor environments

We present a robot-assisted wayfinding system for the visually impaired in structured indoor environments. The system consists of a mobile robotic guide and small passive RFID sensors embedded in the environment. The system is intended for use in indoor environments, such as office buildings, supermarkets and airports. We describe how the system was deployed in two indoor environments and evaluated by visually impaired participants in a series of pilot experiments. We analyze the system’s successes and failures and outline our plans for future research and development.     

Quantum computing with spin qubits in semiconductor structures

We survey recent work on designing and evaluating quantum computing implementations based on nuclear or bound-electron spins in semiconductor heterostructures at low temperatures and in high magnetic fields. General overview is followed by a summary of results of our theoretical calculations of decoherence time scales and spin-spin interactions. The latter were carried out for systems for which the two-dimensional electron gas provides the dominant carrier for spin dynamics via exchange of spin-excitons in the integer quantum Hall regime.     

Ion implantation effect on atomic structure of deformed Si, Ir, W, Ni and Cu

It has been revealed, that in Ir subjected to severe plastic deformation, an ultrafine grained structure (UFG) is formed (the grain size of 20-30 nm). Practically no defects have been detected within the grains, while, in the case of Ar⁺ implantation, the subgrain structure with characteristic sizes of about 3-5 nm is formed; defects have been detected within subgrains.The subgrain structure was also revealed in UFG Ni and Cu after severe plastic deformation (SPD) (subgrain size of 3-15 nm), but in the latter case the observed boundary region is broader and subgrain is highly disoriented.     

Compositions of Co – Cr – Mo Alloys Examined by Glow-Discharge Mass Spectrometry

A method has been developed for the quantitative elemental analysis of Co – Cr – Mo alloys which are used for making surgical implants, and which is done by glow-discharge mass spectrometry. There is a discussion of the effects of molecular ions and an estimate is made of the sensitivity limits in the detection of traces of toxic elements. A method has been devised for calculating the concentrations of molecular ions that increases the analysis reliability. It is shown that raising the argon pressure and discharge current substantially reduces the relative concentrations of molecular ions and allows one to raise the analysis sensitivity.     

Flux Jumps and H-T Diagram of Instability for MgB2

We present a study of magneto-thermal instabilities in polycrystalline MgB₂ superconductor, by magnetic hysteresis loop measurements and by investigations of magnetic flux dynamics with a miniature Hall probe. Temperature and magnetic field ranges where the flux jumps may be observed have been determined. On the basis of measurements of the magnetic flux dynamics, an average magnetic diffusivity describing the process of the flux jump is estimated. This parameter is compared with the thermal and magnetic diffusivities calculated on the basis of available data for thermal conductivity, heat capacity and resistivity. It is shown that the estimated value of the field of the first flux jump is influenced significantly by the field dependence of specific heat. In order to explain the observed phenomenon, the temperature reached by the sample during the flux jump at different magnetic fields is calculated.     

Synthesis of Boron Nitride by Self-Propagating Reactions at High Pressure

Peculiarities of the formation of BN in a self-propagating reaction between LiBF₄ and Li₃N have been studied under a wide range of p,T conditions within the region of thermodynamic stability of cBN. Boron nitride crystallized mainly in the form of highly ordered hBN (1700–2100 K), of mesographitic BN (2200–3000 K), or of turbostratic BN (>3000 K). Cubic boron nitride was obtained with a low yield (up to 14 vol%) as a result of precipitation from the metastable eutectic liquid in the BN-Li₃N system. These results give further evidence for an alternative metastable behavior in the BN phase formation under high pressures.     

GC/MS characterization of mate tea leaves extracts obtained from high-pressure CO2 extraction

This work presents a study concerning the chemical characteristics and analytical separation process of the essential oil obtained from high-pressure carbon dioxide extraction of Ilex paraguariensis. The experiments were performed in a laboratory-scale unit in the temperature range of 20–40 °C, from 100 to 250 bar. A blend of the I. paraguariensis extracts was percolated through a preparative chromatographic column, containing silica gel, and successively eluted with 150 mL of each of the following solvents: hexane, toluene, dichloromethane, ethyl acetate, acetone and methanol. The raw extract and its fractions were analyzed by gas chromatography coupled to mass spectrometry detection (GC/MS). The fractionation procedure showed to be a good clean up technique due to the isolation of different classes of compounds in each fraction. Chromatographic analyses allowed the identification of caffeine, fatty acids and esters, phytol, squalene, Vitamin E, stigmasterol derivatives and saturated hydrocarbons.