Formation of textured WS2 thin films by van der Waals rheotaxy process and their photoactivity

369-373<span style="font-size: 16.0pt;mso-bidi-font-size:9.0pt;font-family:" times="" new="" roman","serif""="">Photoactive thin films of tungsten disulphide (WS<span style="font-size:13.0pt; mso-bidi-font-size:6.0pt;font-family:" times="" new="" roman","serif""="">2) have been prepared by sulphurization of tungsten tri oxide (WO3) thin films. WO3<span style="font-size:12.5pt;mso-bidi-font-size: 5.5pt;font-family:" times="" new="" roman","serif""=""> <span style="font-size: 16.0pt;mso-bidi-font-size:9.0pt;font-family:" times="" new="" roman","serif""="">films have been deposited in an inert atmosphere onto the pre-deposited Ni coated quartz substrates by using an ultrasonic spray pyrolysis technique (USP). Subsequently, the WO3 films have been treated at 700 °<span style="font-size:16.0pt;mso-bidi-font-size:9.0pt;font-family: " times="" new="" roman","serif""="">C in a scaled <span style="font-size: 16.0pt;mso-bidi-font-size:9.0pt;font-family:" times="" new="" roman","serif""="">quartz ampoule tilled with elemental sulphur and <span style="font-size:15.5pt; mso-bidi-font-size:8.5pt;font-family:" times="" new="" roman","serif""="">0.2 bar N2/H<span style="font-size:13.0pt;mso-bidi-font-size: 6.0pt;font-family:" times="" new="" roman","serif""="">2 forming gas for about 6 hr. The films have been investigated by using X-ray diffractometer (XRD), scanning electron microscopy (SEM), and optical absorption techniques. The photoactivity has been measured using time- resolved microwave conductivity (TRMC) technique. For comparison, the results of WS2 films grown on quartz substrates without pre-deposited nickel layer have been given. </span

Friction and wear behavior of WS2/Zr self-lubricating soft coatings in dry sliding against 40Cr hardened steel balls

WS[subscript 2] and WS[subscript 2]/Zr self-lubricating soft coatings were produced by medium-frequency magnetron sputtering, multi-arc ion plating and ion beam assisted deposition technique on the cemented carbide YT15 (WC+15%TiC+6%Co) substrates. Microstructural and fundamental properties of these coatings were examined. Sliding wear tests against 40Cr hardened steel using a ball-on-disk tribometer method were carried out with these coated materials. The friction coefficient and wear rates were measured with various applied loads and sliding speeds. The wear surface features of the coatings were examined using SEM. The results showed that the WS-1 specimen (with WS[subscript 2]/Zr composite coating) has higher hardness and coating/substrate critical load compared with that of the WS-2 specimen (only with WS2 coating). The friction coefficient of WS-1 specimen increases with the increase in applied load, and is quite insensitive to the sliding speed. The wear rate of the WS-1 specimen is almost constant under different applied loads and sliding speeds. The WS-1 specimen shows the smallest friction coefficient and wear rate among all the specimens tested under the same conditions. The WS-1 specimen exhibits improved friction behavior to that of the WS-2 specimen, and the antiwear lifetime of the WS2 coatings can be prolonged through adding Zr additives. The self-lubricating and wear mechanism of the WS[subscript 2]/Zr coating was also found from the sliding wear tests

Room Temperature Oxidation of Ethanol to Acetaldehyde over Pt/WO 3

Oxidation of ethanol to acetaldehyde is of relevance to synthetic chemistry and development of sensors for detection of gas phase ethanol. It is demonstrated by gas phase analysis and diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) that a Pt/WO3 composite shows significant activity in oxidative dehydrogenation of ethanol to acetaldehyde at room temperature. DRIFTS also demonstrates consecutive surface chemistry occurs, yielding predominantly ethyl acetate. The oxidation state of the most active Pt particles is determined to be Pt0, rather than PtO, by studying variations in catalyst preparation methodology, and characterization of various samples by X-ray photoelectron spectroscopy. Illumination has very little effect on surface reactivity and selectivity, but promotes formation of gas phase acetaldehyde

Microstructure and electrical transport in electrodeposited Bi films

The semimetal character of bismuth and its large photon absorbing power make of this element the most suitable absorber material for X-ray low temperature detectors. This application requires coatings of Bi with thicknesses and properties that only electrodeposition methods may achieve. Although there are studies on electrodeposition of bismuth for these detectors and other devices, the process is not straightforward and has not been sufficiently studied in terms of the desired final properties, neither the effect of different parameters is well known or easily reproduced. This work reports the influence of two different electrolytes, of the deposition method, and of heating and stirring on the structure, microstructure and transport properties of bismuth films. Typically, rhombohedral Bi is obtained upon electrodeposition with very good crystallinity, and some crystal preferential orientation, while significant empirical correlations are found among electrochemical parameters, microstructure, and resistivity. Such correlation allows the identification of the deposition parameters for coatings that yield the optimal functional properties.Work financed by the Spanish Ministerio de Economía y Competitividad-MINECO (projects ESP2014-53672-C3-2-P, ESP2016-76683-C3-2-R and ESP2014-59309-JIN), the European Space Agency-ESA (CTP Contract “Optimization of a European TES array”) and the European Commission (H2020 project AHEAD: “Integrated activities for the high energy astrophysics domain”). Personnel from ICMAB acknowledge financial support from MINECO, through the “Severo Ochoa” Programme for Centres of Excellence in R&D (SEV-2015-0496). RMJ wishes to thank MINECO for her FPI contract. We acknowledge also the help of Guillermo Antorrena (INA) on XPS data.Peer reviewe