Nanotubular TiOxNy-Supported Ir Single Atoms and Clusters as Thin-Film Electrocatalysts for Oxygen Evolution in Acid Media

A versatile approach to the production of cluster- and single atom-based thin-film electrode composites is presented. The developed TiOxNy–Ir catalyst was prepared from sputtered Ti–Ir alloy constituted of 0.8 ± 0.2 at % Ir in α-Ti solid solution. The Ti–Ir solid solution on the Ti metal foil substrate was anodically oxidized to form amorphous TiO2–Ir and later subjected to heat treatment in air and in ammonia to prepare the final catalyst. Detailed morphological, structural, compositional, and electrochemical characterization revealed a nanoporous film with Ir single atoms and clusters that are present throughout the entire film thickness and concentrated at the Ti/TiOxNy–Ir interface as a result of the anodic oxidation mechanism. The developed TiOxNy–Ir catalyst exhibits very high oxygen evolution reaction activity in 0.1 M HClO4, reaching 1460 A g–1Ir at 1.6 V vs reference hydrogen electrode. The new preparation concept of single atom- and cluster-based thin-film catalysts has wide potential applications in electrocatalysis and beyond. In the present paper, a detailed description of the new and unique method and a high-performance thin film catalyst are provided along with directions for the future development of high-performance cluster and single-atom catalysts prepared from solid solutions

Modification of multilayered TiAlN/TiN coating by nanosecond and picosecond laser pulses

A multilayered TiAlN/TiN coating deposited on H11 work-steel was irradiated by a TEA CO(2) laser (ns pulses) and a Nd:YAG laser (ps pulses), and the effects compared. The coating was 2.17 mu m thick and consisted of 45 layers. The laser-induced modifications showed dependence on laser pulse duration, pulse count and laser wavelength. The conditions for coating ablation in both cases were determined. The experiment has revealed laser-induced periodic surface structures (LPSS) on nanometre and micrometre scales, depending on the laser wavelength used. Sample surfaces were characterized before and after laser irradiation by an optical microscope, scanning electron microscope (SEM), focused ion beam (FIB) microscope and profilometry

Theoretical lidar point density for topographic mapping in the largest scales

When ordering LiDAR data, LiDAR point density per surface unit is important information with decisive influence on the price of the LiDAR survey. The paper first deals with the theoretical calculation of the minimum LiDAR point density, necessary for the acquisition of topographic data of the largest scales. For this purpose the sampling theorem is used. However, since topographic objects (roads, water bodies, etc.) and phenomena represented on topographic maps and in topographic bases are in many cases located under vegetation, also the rate of laser beam penetration through vegetation for the area where the topographic data are to be gathered has to be known. In a research on a test case conducted in the area of the town Nova Gorica we calculated the rate of laser beam penetration for four different vegetation types: scarce Mediterranean vegetation, thick thermophilic deciduous forest, mixed vegetation (meadows, orchards and forest) and built-up area. By connecting the theoretic minimum LiDAR point density with the rate of penetration, we defined the minimum LiDAR point density for the needs of data acquisition on topographic maps of the largest scales or in topographic bases of comparable detail (from 1 : 1000 to 1 : 10,000)

A simplified analytical model for a priori Lidar point positioning error estimation and a review of Lidar error sources

Although various rigorous lidar error models already exist and examples of a-posteriori studies of lidar data accuracies verified with field-work can be found in the literature, a simple measure to define a-priori error sizes is not available. In this paper, the lidar error contributions are described in detail: the basic systematic error Sources, the flight-mission-related error sources, and the target-characteristic-related error sources. A review of the different error-source sizes is drawn from the literature in order to define the boundary conditions for each error size. Schenk's geolocation equation is used as a basis for deriving a simplified error model. This model enables a quick calculation and gives a-priori plausible values for the average and maximum error size, independent of the scan and heading angles as well as being independent of any specific lidar system's characteristics. Additionally, some notes are provided for assistance when ordering lidar data, to enable easier a-posteriori quality control

Surface modification of the Cr-based coatings by the pulsed TEA CO2 laser

The interaction of a transversely excited atmospheric (TEA) CO2 laser with chromium oxynitride (CrON) coating deposited on a AISI 304 steel substrate was considered. The results have shown that CrON was surface-modified by the laser beam of 45 J/cm(2) energy density. The energy absorbed from the TEA CO2 laser beam was partially converted into thermal energy, which has generated a series of effects such as melting, vaporization of the molten material, and shock waves in the vapor and in the solid. Morphological manifestations on the CrON coating surface can be summarized as follows: non-uniform features with ablation and appearance of crater-like form (central zone of interaction); appearance of three damaged areas and presence of hydrodynamic effects with resolidified droplets (periphery zone of interaction). In case of applied energy density the interaction of laser radiation with CrON has been always followed by plasma creation in front of the coating

DC-sputtering of yttria-stabilised zirconia films for solid oxide fuel cell applications

Yttria-stabilised zirconia (YSZ) thin films were dc-sputtered and investigated with respect to surface morphology, microstructure and film-substrate interface interaction. The films were deposited under argon/oxygen atmospheres on NiO/YSZ substrates heated to between 500 and 700 degreesC. Dense and crack-free coatings were obtained in the thickness range of 1 to 10 mum. The film morphology varied from columnar to crystalline structure depending on the oxygen pressure and the substrate temperature. Whereas the coated films consisted of YSZ with cubic and tetragonal crystal structure under low oxygen atmospheres, the same deposition experiments on Al2O3 substrates revealed highly disordered layers of cubic YSZ. The formation of oxide layers on the NiO/YSZ substrates is due to a film-substrate redox interaction. The NO grains close to the coating interface are partially reduced and serve as an oxygen source for the oxidation of the film. An exponential decay of the gas leakage vs. coating thickness was found. (C) 2001 Elsevier Science Ltd. All rights reserved

Pulsed carbon-dioxide laser ablation: profilometric analysis

Pulsed carbon-dioxide (TEA CO2) laser, among other, is suitable for ablation of hard ceramic coatings (HCC). HCC, deposited on steel substrate, can be used for tools and machine parts protection. The roughness and thickness of HCC are commonly measured by a profilometer. Data obtained with diamond tip usually give real 2D surface profile. A 3D topography of the surface can be obtained with this procedure, too. The results of profilometric analysis including 3D visualization, using a Taylor-Hobson Talysurf 2 profilometer, of laser ablated area (especially craters) are presented in this work. The following HCC were studied: TiN, CrN, CrON, as well as stainless steel wafer; all of them were surface ablated by pulsed TEA CO2 laser. The applied profilometer analysis describes effects of laser ablation well and it would be supplement to the results obtained by microscopic analysis.SFKM 2004 : September 20–23, 2004, Sokobanja

Laser irradiation of 10x(Ni/Ti)/Si multilayers at different wavelengths

A study of the effects of laser irradiation on the morphology and composition of Ni/Ti multilayers induced by nanosecond laser pulses at different wavelengths is reported. Irradiation of complex 109(Ni/Ti)/Si sample was done by a Nd:YAG laser which operate at a 1064 nm wavelength, frequency doubled wavelength (532 nm) and dual-wavelength (1064 and 532 nm). The following surface morphological changes were observed: (1) ablation of the thin film during the first laser pulse and (2) appearance of some nanostructures (mosaic structure) in the irradiated region. After action of one pulse, the boundary of damage area was relatively sharp at low pulse energy, whereas it was diffuse after irradiation with higher energy per pulse. The results obtained show that laser irradiation induced mixing between Ni and Ti layers which creates conditions for the formation of intermetallic compounds. A numerical model was used to predict ablation depths and temperatures inside the material during the time. The model prediction shows a close agreement with experimental data