On the electropolishing and anodic oxidation of Ti-15Mo alloy

This paper presents research on modifying the surface of Ti-15Mo alloy using electropolishing and anodic passivation. The electropolishing process was carried out in solutions containing sulfuric acid, ethylene glycol, ammonium fluoride and oxalic acid. Whereas a voltage range from 20 to 100 V and a 1 M orthophosphoric acid solution were used during the anodic passivation. The influence of above mentioned processes parameters on the quality of the obtained oxide layer on Ti-15Mo alloy was investigated. The analysis of Ti-15Mo surface after modification was performed using scanning electron microscopy (SEM), atomic force microscopy (AFM), energy-dispersive X-ray spectroscopy (EDX), X-ray photoelectron spectroscopy (XPS), ellipsometry, and mechanical tests. Moreover, the corrosion resistance was investigated using a potentiostatic method in Ringer's solution. It was found that electropolishing leads to an increase in the surface homogeneity and to the form of an oxide layer, which consisted of TiO2 and MoO3. Whereas the oxide layers obtained during anodic passivation were characterized by different properties depending on the applied voltage. The anodic passivation at various voltages (20-100 V) increased the surface wettability (94.5°-87.6°) in comparison to the electropolished sample (97.5°). Moreover, the obtained oxide layer after anodization exhibited a high hardness. The electrolytic polishing and anodic passivation of Ti-15Mo also improved corrosion resistance of the alloy in contact with Ringer's solution. The sample anodized at 80 V presented the highest corrosion resistance by the smallest corrosion current density (1.4 nA cm-2) and the highest polarization resistance (37.4 MΩ cm2). © 2016 Elsevier Ltd. All rights reserved

Religious transformations in the Middle Ages: towards a new archaeological agenda

The study of religious change in Europe between the collapse of the Roman Empire and the Reformation forms one of the cornerstones of medieval archaeology but has been riven by period, denominational and geographical divisions. This paper lays the groundwork for a fundamental rethink of archaeological approaches to medieval religions, by adopting a holistic framework that places Christian, pagan, Islamic and Jewish case studies of religious transformation in a long-term, comparative perspective. Focused around the analytical themes of ‘hybridity and resilience’ and ‘tempo and trajectories’, our approach shifts attention away from the singularities of national narratives of religious conversion towards a deeper understanding of how religious beliefs, practices and identity were renegotiated by medieval people in their daily lives

Pd/V2_{2}O5_{5} fiber optic hydrogen gas sensor*

The paper presents an optical-fiber hydrogen sensor. The sensor utilizes a layered sensing structure. This structure is a layered Fabry-Perot interferometer and includes gasochromic vanadium pentoxide (V$_{2}$O$_{5})$. A structure is made at the end of multi-mode optical fiber as a sensing element. The sensor permits to detect and to measure the concentration of hydrogen in a gaseous medium. The optical H$_{2}$ gas sensor has a very short response time and a fast regeneration time at room temperature

Hydrogen detection by palladium and nickel oxide in surface acoustic wave sensor system

Przedstawiono badania nowej struktury warstwowej typu: tlenek niklu-pallad w sensorowym układzie z akustyczną falą powierzchniową pod kątem detekcji wodoru w powietrzu. Wykonano strukturę warstwową z tlenkiem niklu (NiOx) 60 nm w technologii reaktywnego rozpylania magnetronowego, pokrytą palladem o grubości 18 nm, wykonanym metodą naparowania próżniowego. Specjalnie zaprojektowany i wykonany układ elektroniczny umożliwia detekcję częstotliwości różnicowej (różnica częstotliwości toru ze strukturą warstwową oraz toru swobodnego bez pokrycia). Przeprowadzono badania oddziaływań takiej struktury z wodorem w powietrzu w zakresie średnich stężeń, nieprzekraczających wartości 2,5%. Dla stosowanej temperatury oddziaływania ok. 35°C stwierdzono maksymalną czułość struktury w zakresie stężeń wodoru pomiędzy 2 i 2,5% w powietrzu. Zmiana częstotliwości (będąca miarą oddziaływania) w tej temperaturze dla ww. stężeń wynosiła około 600 Hz.Presented are the investigations of a new layered structure: nickel oxide - palladium in a sensor system with surface acoustic wave, from the point of view of hydrogen detection in air. The layered sensor structure was prepared by means of reactive sputtering technology - nickel oxide 60 nm and vacuum deposition technology - palladium 10 nm. The specialised electronic circuit allows detection of the differential frequency (the difference between frequency with layered structure and the free ones). The investigations of such a structure with medium concentrations of hydrogen not exceeding a safety value 2.5% in air has been performed. The maximum sensitivity is detected at the interaction temperature of 35°C - the maximum change in frequency is on the level 600 Hz between 2 and 2.5% of hydrogen

Investigations of the polyaniline and nafion bilayer sensor structure in SAW system

Presented here are the preliminary results concerning an investigations of a novel bilayer sensor structure of polyaniline and Nafion as a toxic gas sensors in a Surface Acoustic Wave system. The investigations were performed with different concentrations of the various toxic gases like SO$_{2}$, CO, H$_{2}$S and ammonia (NH$_{3}$) in synthetic dry air. The prototype polyaniline and nafion bilayer structure has been manufactured by two deposition technologies: 180 nm of PANI by PVD technology and thin Nafion film by spin coating technology and specific process of annealing. A good interaction with various concentrations of ammonia for the bilayer structure (PANI film with Nafion) has been observed

The multichannel, optoelectronic gas sensor system based on interferometric nanostructures with gasochromic thin films

W pracy przedstawiono nowatorski wielokanałowy, optoelektroniczny system pomiarowy i sposób pomiaru stężenia gazów przemysłowych i toksycznych. Mierzony analit gazowy może być różny w zależności od zastosowanej interferencyjnej nanostruktury sensorowej. Pomiar odbywa się w gazowym środowisku pomiarowym. Niniejsze rozwiązanie optoelektronicznego, gazowego systemu pomiarowego wykorzystuje interferencyjne, optyczne nanostruktury sensorowe zawierające w swej konstrukcji cienkie warstwy receptorowe z optycznie czynnych materiałów. Zatem, optyczna głowica sensorowa zmienia swoje parametry optyczne w wyniku oddziaływania z badanym analitem gazowym.In the paper the multichannel, optoelectronic gas sensor system based on interferometric, gasochromic nanostructures is presented. The silicon colour sensor TCS230 detects the intensity and change of colour coordinates RGB of an optical signal resulting from exposure of the sensing structure to a specific type of gas. Using multichannel measurement, one can simultaneously detect different gas or analyte molecules in the sample by immobilizing different optical receptor thin films (nanostructures) at different channels. Each optical sensing channel consists of three parts: the input port which includes a broadband light source: "warm" white LED, multi-layered sensing nanostructure: interferometric and gasochromic, the output port including a silicon colour sensor TCS230 detecting the intensity and change of colour coordinates RGB of an optical signal resulting from the sensing structure exposure to a specific type of gas. At the sensing window, on the glass substrate there are immobilized nanostructures being chemo-optical, gasochromic and interferometric transducer receptors, which can selectively interact with a specific type of gas molecules present in the gas mixture. When a physical-chemical binding process takes place on the sensing window of the measuring channel, an interferometric colour of the sensing element (nanostructure) changes and colour coordinates of the measured optical signal change as well. The change of the colour coordinates is proportional to the change of the effective refractive index of the receptor structure (particularly refractive index of the resonance cavity). By measuring the intensity change of the optical signal RGB, the refractive index change ?n taking place in the measuring window can be calculated and the concentration of a specific gas in the gas mixture can be measured

Bilayer Structures of NiOxNiO_{x} and Pd in Surface Acoustic Wave and Electrical Gas Sensor Systems

A bilayer sensor structure of nickel oxide $NiO_x$ ( ≈ 60 nm) with a very thin film of palladium (Pd ≈ 18 nm) on the top, has been studied for gas-sensing application at relatively low temperatures of about 30°C and 60°C. The bilayer structure was obtained by rf sputtering and by vacuum deposition (first the $NiO_{x}$ and then the Pd film) onto a $LiNbO_{3}$ Y-cut Z-propagating substrate, making use of the surface acoustic wave method, and additionally (in the same technological processes) onto a glass substrate with a planar microelectrode array for simultaneous monitoring of the planar resistance of the layered structure. Such a bilayer structure was investigated in a low concentration range (from 50 ppm to 400 ppm in air) of nitrogen dioxide $(NO_{2})$, carbon monoxide (CO) and ammonia $(NH_{3})$ in a dry and wet air atmosphere and in a medium hydrogen concentration (1-2.5%) in dry air. The $NiO_{x}$ and Pd bilayer structure interact rather weakly with $NO_{2}$ molecules but with CO and $NH_{3}$ this interaction is much greater, especially at higher temperature ( ≈ 60°C). The hydrogen sensitivity is on the medium level, not exceeding 600 Hz (relative change in the differential frequency of ≈ 2.3%) at interaction temperature of 35°C

SAW sensor for detection of hydrocarbons. Numerical analysis and experimental results

The paper presents the results of numerical analyses of the SAW gas sensor in the steady and non-steady state. The effect of SAW velocity changes vs. the surface electrical conductivity of the sensing layer is predicted. The conductivity of the porous sensing layer above the piezoelectric waveguide depends on the profile of the diffused gas molecule concentration inside the layer. Knudsen's model of gas diffusion was used. Numerical results for the gases CH4, C2H4, C3H8, C6H6 in the steady state and CH4 in the non-steady state in the WO3 sensing layer have been shown. The results of numerical analyzes allow to select the sensor design conditions, including the morphology of the sensor layer, its thickness and operating temperature. Some numerical results were verified in experimental studies concerning methane