Robust SrTiO3 Passivation of Silicon Photocathode by Reduced Graphene Oxide for Solar Water Splitting

Development of a robust photocathode using lowcost and high-performing materials, e.g., p-Si, to produce clean fuel hydrogen has remained challenging since the semiconductor substrate is easily susceptible to (photo)corrosion under photoelectrochemical (PEC) operational conditions. A protective layer over the substrate to simultaneously provide corrosion resistance and maintain efficient charge transfer across the device is therefore needed. To this end, in the present work, we utilized pulsed laser deposition (PLD) to prepare a high-quality SrTiO3 (STO) layer to passivate the p-Si substrate using a buffer layer of reduced graphene oxide (rGO). Specifically, a very thin (3.9 nm ∼10 unit cells) STO layer epitaxially overgrown on rGO-buffered Si showed the highest onset potential (0.326 V vs RHE) in comparison to the counterparts with thicker and/or nonepitaxial STO. The photovoltage, flat-band potential, and electrochemical impedance spectroscopy measurements revealed that the epitaxial photocathode was more beneficial for charge separation, charge transfer, and targeted redox reaction than the nonepitaxial one. The STO/rGO/Si with a smooth and highly epitaxial STO layer outperforming the directly contacted STO/Si with a textured and polycrystalline STO layer showed the importance of having a well-defined passivation layer. In addition, the numerous pinholes formed in the directly contacted STO/Si led to the rapid degradation of the photocathode during the PEC measurements. The stability tests demonstrated the soundness of the epitaxial STO layer in passivating Si against corrosion. This study provided a facile approach for preparing a robust protection layer over a photoelectrode substrate in realizing an efficient and, at the same time, durable PEC device

Structural and Functional Picosecond Laser Modification of the Nimonic 263 Superalloy in Different Environmental Conditions and Optimization of the Irradiation Process

In this experimental study, picosecond laser treatment was performed on a nickel-based superalloy Nimonic 263, aiming to investigate the surface effects induced by irradiation in different atmospheric conditions and, concerning changes in surface composition, regarding the possibility for improvement of its functionality. Besides the varying laser parameters, such as a number of pulses and pulse energy, environmental conditions are also varied. All surface modifications were carried out in standard laboratory conditions and a nitrogen- and argon-rich atmosphere. The resulting topography effects depend on the specific laser treatment and could be categorized as increased roughness, crater formation, and formation of the laser-induced periodic surface structures (LIPSS). Changes in the chemical surface composition are distinguished as the potential formation of the protective oxides/nitrides on the sample surface. Numerous characterization techniques analyse the resulting effects on the topography and surface parameters. The multi-response parametric optimization of the picosecond laser process was performed using an advanced statistical method based on Taguchi’s robust parameter design. Finally, the optimal parameter conditions for Nimonic 263 modification are suggested

Plasma–wall interaction studies within the EUROfusion consortium : progress on plasma-facing components development and qualification

The provision of a particle and power exhaust solution which is compatible with first-wall components and edge-plasma conditions is a key area of present-day fusion research and mandatory for a successful o peration of ITER and DEMO. The work package plasma-facing components (WP PFC) within the European fusion programme complements with laboratory experiments, i.e. in linear plasma devices, electron and ion beam loading f acilities, the studies performed in toroidally confined magnetic devices, such as JET, ASDEX Upgrade, WEST etc. The connection of both groups is done via common physics and engineering studies, including the qualificat ion and specification of plasma-facing components, and by modelling codes that simulate edge-plasma conditions and the plasma–material interaction as well as the study of fundamental processes. WP PFC addresses these c ritical points in order to ensure reliable and efficient use of conventional, solid PFCs in ITER (Be and W) and DEMO (W and steel) with respect to heat-load capabilities (transient and steady-state heat and particle lo ads), lifetime estimates (erosion, material mixing and surface morphology), and safety aspects (fuel retention, fuel removal, material migration and dust formation) particularly for quasi-steady-state conditions. Alter native scenarios and concepts (liquid Sn or Li as PFCs) for DEMO are developed and tested in the event that the conventional solution turns out to not be functional. Here, we present an overview of the activities with an emphasis on a few key results: (i) the observed synergistic effects in particle and heat loading of ITER-grade W with the available set of exposition devices on material properties such as roughness, ductility and m icrostructure; (ii) the progress in understanding of fuel retention, diffusion and outgassing in different W-based materials, including the impact of damage and impurities like N; and (iii), the preferential sputtering of Fe in EUROFER steel providing an in situ W surface and a potential first-wall solution for DEMO.Peer reviewe

Plasma-wall interaction studies within the EUROfusion consortium: Progress on plasma-facing components development and qualification

This work has been carried out within the framework of the EUROfusion Consortium and has received funding from the Euratom research and training programme 2014-2018 under grant agreement No 633053. The views and opinions expressed herein do not necessarily reflect those of the European Commission.The provision of a particle and power exhaust solution which is compatible with first-wall components and edge-plasma conditions is a key area of present-day fusion research and mandatory for a successful operation of ITER and DEMO. The work package plasma-facing components (WP PFC) within the European fusion programme complements with laboratory experiments, i.e. in linear plasma devices, electron and ion beam loading facilities, the studies performed in toroidally confined magnetic devices, such as JET, ASDEX Upgrade, WEST etc. The connection of both groups is done via common physics and engineering studies, including the qualification and specification of plasma-facing components, and by modelling codes that simulate edge-plasma conditions and the plasma-material interaction as well as the study of fundamental processes. WP PFC addresses these critical points in order to ensure reliable and efficient use of conventional, solid PFCs in ITER (Be and W) and DEMO (W and steel) with respect to heat-load capabilities (transient and steady-state heat and particle loads), lifetime estimates (erosion, material mixing and surface morphology), and safety aspects (fuel retention, fuel removal, material migration and dust formation) particularly for quasi-steady-state conditions. Alternative scenarios and concepts (liquid Sn or Li as PFCs) for DEMO are developed and tested in the event that the conventional solution turns out to not be functional. Here, we present an overview of the activities with an emphasis on a few key results: (i) the observed synergistic effects in particle and heat loading of ITER-grade W with the available set of exposition devices on material properties such as roughness, ductility and microstructure; (ii) the progress in understanding of fuel retention, diffusion and outgassing in different W-based materials, including the impact of damage and impurities like N; and (iii), the preferential sputtering of Fe in EUROFER steel providing an in situ W surface and a potential first-wall solution for DEMO.European Commission; Consortium for Ocean Leadership 633053; Institute of Solid State Physics, University of Latvia as the Center of Excellence has received funding from the European Union’s Horizon 2020 Framework Programme H2020-WIDESPREAD-01-2016-2017-TeamingPhase2 under grant agreement No. 739508, project CAMART

How to decide which oblique image has the highest mapping potential for monoplotting method: a case studies on river erosion and floods

When studying the development of different geomorphic processes, floods, glaciers or even cultural heritage through time, one cannot rely only on regular photogrammetrical procedures and metrical images. In a majority of cases the only available images are the archive images with unknown parameters of interior orientation showing the object of interest in oblique view. With the help of modern high resolution digital elevation models derived from aerial or terrestrial laser scanning (lidar) or from photogrammetric stereo-images by automatic image-matching techniques even single nonmetric high or low oblique image from the past can be applied in the monoplotting procedure to enable 3D-data extraction of changes through time. The first step of the monoplotting procedure is the orientation of an image in the space by the help of digital elevation model (DEM). When using oblique images tie points between an image and DEM are usually too sparse to enable automatic exterior orientation, still the manual interactive orientation using common features can resolve such shortages. The manual interactive orientation can be very time consuming. Therefore, before the start of the manual interactive orientation one should be certain if one can expect useful results from the chosen image. But how to decide which image has the highest mapping potential before we introduce a certain oblique image in orientation procedure? The test examples presented in this paper enable guidance for the use of monoplotting method for different geoscience applications. The most important factors are the resolution of digital elevation model (the best are the lidar derived ones), the presence of appropriate common features and the incidence angle of the oblique images (low oblique images or almost vertical aerial images are better). First the very oblique example of riverbank erosion on Dragonja river, Slovenija, is presented. Than the test example of September 2010 floods on Ljubljana moor is discussed. Finally, case study from November 2012 floods is presented. During November 2012 floods an initiative was launched to gather as much non-metrical images of floods as possible from casual observers (volunteered image gathering). From all gathered images the guidelines presented before helped to pick out 21% images which were used for monoplotting

Using volunteered geographical information to map the November 2012 floods in Slovenia

Volunteered geographical information represents a promising field in the monitoring and mapping of natural disasters. The contributors of volunteered geographical information have the advantage that they are at the location of the natural disaster at exactly the time when the disaster happened. Therefore, they can provide the most complete account of the extent of the damage. This is not always possible when applying photogrammetric or remote-sensing methods, as prior to the data acquisition an order to carry out the measurements has to be made. On 5 and 6 November 2012 almost half of Slovenia was badly affected by floods. The gathering of volunteered geographical information in the form of images and videos of these floods is presented. Two strategies were used: (1) a public call for volunteered contributions and (2) a web search for useful images and their authors. The authorship of these images was verified with every contributor. In total, 15 contributors provided 102 terrestrial and aerial images and one aerial video, with 45% classified as potentially useful. For actual flood mapping 22 images and 12 sequences from video were used. With the help of the volunteered images 12% of the most severely affected river sections were mapped. Altogether, 1195.3 ha of flooded areas outside of the usual river beds along a total river length of 48 km were mapped. The results are compared with those from satellite mapping of the same floods, which successfully covered 18% of the most affected river sections

Determination of Tritium-Helium-3 differential cross-section in the energy range between 0.6 MeV and 3.3 MeV for tritium depth profiling in solids

The differential cross-section for the 3He+3H nuclear reaction was measured in a thin tritiated PdTi film that was deposited on a Si wafer. The sample was loaded with 3H2 gas at a temperature of 300 °C and at a pressure of 1.8 bar. The total activity of the sample, measured by the liquid scintillation technique, was found to be 395 MBq. Two peaks were observed in the spectrum of the thick Si detector, corresponding to the 3H(3He,d)4He and 3H(3He,p)5He reaction channels. The differential cross-section was determined for the energy range of the 3He beam from 0.6 to 3.4 MeV, at three scattering angles of 125, 135 and 155°. The differential cross-section for the first channel remained almost constant within the measured energy range, while the cross-section for the second channel increased with energy. In both cases, the cross-sections reached their maximum value at the lowest scattering angle measured. The differential cross-sections were verified using a thick solid tritiated tungsten target. For assessing the tritium depth profile, only the reaction channel 3H(3He,d)4He can be utilized

Wear behavior and cutting performance of nanostructured hard coatings on cemented carbide cutting tools in hard milling

The influence of nanolayer AlTiN/TiN and multilayer nanocomposite TiAlSiN/TiSiN/TiAlN hard coatings on the wear behavior and cutting performance of carbide cutting tools was investigated in face milling of hardened AISI O2 cold work tool steel (∼58 HRC) at dry conditions. Characterization of the coatings was performed using nanoindentation, scratch test, reciprocating multi-pass wear test. The chips forming during cutting process were also analyzed. Results showed that abrasive and oxidation wear are dominant tool failures. The nanolayer AlTiN/TiN coating gives the best adhesion to the substrate, the best wear resistance in machining and thus provides the longest lifetime with carbide inserts. © 2013 Elsevier Ltd