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High-purity films consisting of copper tungstate (CuWO 4) and sub-stoichiometric tungsten oxide (WO 3- x) were prepared by reactive sputter deposition. An original two-step deposition process was applied for their synthesis. First, a tungsten oxide thin film was deposited by dc magnetron sputtering from a W target in an Ar + O 2 gas mixture, afterward, rf sputtering of a Cu target in an Ar + O 2 gas mixture was employed to form a discontinuous CuWO 4 layer at the top. This results in a formation of nanostructured branched islands of the tungstate. Bilayers with various layer thicknesses were investigated for the sensitivity to hydrogen gas as a conductometric sensor. The sensitivity changes remarkably with the thicknesses of individual layers. The maximum sensitivity was observed for the films with a layer thickness ratio of 5 nm/20 nm. The response was enhanced more than eight times compared to a 20 nm-thick tungsten oxide alone film. An explanation based on the formation of nano-sized n - n junctions is provided. In addition, a microscopy study of the bilayer growth is presented in detail. Image 1 • Two-step reactive sputter deposition used for CuWO 4 /WO 3- x bilayer films synthesis. • Nanostructured CuWO 4 islands were formed on top of WO 3 thin film. • CuWO 4 /WO 3- x tested for the H 2 gas response for the first time. • Sensing mechanism based on the formation of nano-sized n - n junction is proposed. • Only dry techniques were employed for deposition → high-purity films were prepared. [ABSTRACT FROM AUTHOR]

Abstract High power impulse magnetron sputtering of a Ta target in various Ar + O 2 + N 2 gas mixtures was utilized to prepare amorphous tantalum oxynitride (Ta–O–N) films with a finely controlled elemental composition in a wide range. We investigate the effect of film annealing at 900 ° C in vacuum on structure and properties of the films. We show that the finely tuned elemental composition in combination with the annealing enables the preparation of crystalline Ta–O–N films exhibiting a single TaON phase with a monoclinic lattice structure, refractive index of 2.65 and extinction coefficient of 2.0 × 10 2 (both at the wavelength of 550 nm), optical band gap width of 2.45 eV (suitable for visible light absorption up to 505 nm), low electrical resistivity of 0.4 Ω cm (indicating enhanced charge transport in the material as compared to the as-deposited counterpart), and appropriate alignment of the band gap with respect to the redox potentials for water splitting. These films are therefore promising candidates for application as visible-light-driven photocatalysts for water splitting. [ABSTRACT FROM AUTHOR]

Abstract Magnetron-based gas aggregation cluster source (GAS) was used to prepare high-purity CuO (cupric oxide) nanoclusters on top of sputter-deposited thin film of tungsten trioxide (WO 3). The material was assembled as a conductometric hydrogen gas sensor and its response was tested and evaluated. It is demonstrated that addition of CuO clusters noticeably enhances the sensitivity of the pure WO 3 thin film. With an increasing amount of CuO clusters the sensitivity of CuO/WO 3 system rises further. When CuO clusters form a sufficiently thick and compact layer, the resistance response is reversed. Based on the sensorial behavior, conventional and near-ambient pressure X-Ray photoemission spectroscopies, and resistivity measurements, we propose that the sensing mechanism is based on the formation of nano-sized p - n junctions in between p -type CuO and n -type WO 3. The advantages of the GAS technique for preparing sensorial and/or catalytically active materials are emphasized. Graphical abstract Image 1 Highlights • Magnetron based gas aggregation cluster source was used for making a hydrogen gas sensor. • CuO nanocluster were combined with a WO 3 thin film. • Addition of CuO clusters noticeably enhances the sensitivity in comparison with a pure WO 3 thin film. • Sensing mechanism based on the formation of nano-sized p-n junction is proposed. • No noble metal was needed to enhance the WO 3 response. [ABSTRACT FROM AUTHOR]

This study deals with surface integrity expressed in terms of stress state as well as microstructure alterations after turning a duplex stainless steel. Residual stresses and the presence of strain-induced martensite are studied as functions of the rake angle. Residual stresses of surface and sub-surface layers were determined by the use of the X-ray diffraction and hole-drilling techniques. X-ray diffraction enables us to distinguish between residual stresses in each phase separately, which is not possible when the hole-drilling method is applied. Furthermore, alterations in the near surface region are also analysed by the use of the magnetic Barkhausen noise and metallographic observation. [ABSTRACT FROM AUTHOR]

Reference 1 Capek J., Trojan K., Kec J., Cerny I., Ganev N., Nemecek S. On the Weldability of Thick P355NL1 Pressure Vessel Steel Plates Using Laser Welding. On the Weldability of Thick P355NL1 Pressure Vessel Steel Plates Using Laser Welding. The authors would like to add the following sentence to the "Funding" section of their article [[1]]: "Neutron diffraction measurements were carried out at the CANAM infrastructure of the NPI ASCR Rez supported through MEYS project No. LM2015056. [Extracted from the article]

Pipeline transport uses millions of kilometers of pipes worldwide to transport liquid or gas over long distances to the point of consumption. High demands are placed, especially on the transport of hazardous substances under high pressure (gas, oil, etc.). Mostly seamless steel pipes of various diameters are used, but their production is expensive. The use of laser-welded pipes could significantly reduce the cost of building new pipelines. However, sufficient mechanical properties need to be ensured for welded pipes to meet stringent requirements. Therefore, laser-welded 10 mm thick pressure vessel steel plates were subjected to various mechanical tests, including high-cycle fatigue tests. Furthermore, the microstructural parameters and the state of residual stresses were determined using X-ray and neutron diffraction, which could affect fatigue life, too. The critical areas for possible crack initialization, especially in and near the heat-affected zone, were found using different tests. The presented results outline the promising application potential of laser welding for the production of pipes for high-pressure pipelines. [ABSTRACT FROM AUTHOR]

Tungsten heavy alloys are composite materials containing spherical tungsten particles embedded in binder matrix. Their excellent mechanical properties can be further improved by rotary forging. This paper aims to gain deeper understanding of the forging process by investigating the local elastic modulus, hardness, and residual stress of individual phases in W6Ni3Co pseudo-alloy. The resulting global properties of the composite material such as stress-strain behavior, fracture toughness and fatigue crack growth rate behavior are also studied. The results show that sintered and quenched material consists of highly textured matrix containing nearly perfect single crystal spheres of pure W. The rotary forging leads to significant lattice deformations destroying the texture and significantly increasing the hardness of both WNiCo matrix and W particles and making residual stresses in W particles anisotropic with increased compression along the longitudinal axis of the forged part. [ABSTRACT FROM AUTHOR]

Three mechanically alloyed (MA) and spark plasma sintered (SPS) CoCrFeNiNbX (X = 5, 20, and 35 at.%) alloys with an addition of 5 at.% of SiC were investigated. The face-centered cubic (FCC) high-entropy solid solution, NbC carbides, and hexagonal Laves phase already developed during MA. In addition, the SPS compacting led to the formation of oxide particles in all alloys, and the Cr7C3 carbides in the Nb5 alloy. The fraction of the FCC solid solution decreased with increasing Nb concentration at the expense of the NbC carbide and the Laves phase. Long-term annealing at 800 °C led to the disappearance of the Cr7C3 carbide in the Nb5 alloy, and new oxides—Ni6Nb6O, Cr2O3, and CrNbO4—were formed. At laboratory temperature, the Nb5 alloy, containing only the FCC matrix and carbide particles, was relatively strong and very ductile. At a higher Nb content (Nb20 and Nb35), the alloys became brittle. After annealing for 100 h at 800 °C, the Nb5 alloy conserved its plasticity and the Nb20 and Nb35 alloys maintained or even increased their brittleness. When tested at 800 °C, the Nb5 and Nb20 alloys deformed almost identically (CYS ~450 MPa, UTS ~500 MPa, plasticity ~18%), whereas the Nb35 alloy was much stronger (CYS of 1695 MPa, UCS of 1817 MPa) and preserved comparable plasticity. [ABSTRACT FROM AUTHOR]

The use of specimen loss factor as fatigue damage indicator of Hastelloy-X substrates with different surface treatments was investigated together with other fatigue damage indicators, namely resonance frequency and crack mouth length. The tested surface treatments included grit-blasting and plasma spraying of NiCoCrAlY bond coat and yttria stabilized zirconia (YSZ) top coat. The loss factors of fatigue test specimens were measured repeatedly during the resonance bending fatigue test using the conventional free decay method. The analysis of the damping spectra, i.e. the model describing the relation of loss factor to maximum macroscopic specimen strain ε yy was drafted. The model is based on the combination of defect models developed by Göken and Riehemann (2004) and classical dislocation model of Granato and Lücke (1956). It appears, that the damping spectra can be well approximated as a combination of two defect peaks ( C 1 and C 2 ) and one dislocation peak ( D 1 ). The low strain defect peak (peak C 1 ) is sensitive to the presence of fatigue cracks. The second defect peak (peak C 2 ) can be attributed to the remaining substrate and coating defects such as embedded grit particles, coating porosity, surface roughness and sliding in the sample clamping area. The fatigue damage detection using the C 1 peak magnitude was performed and its results were related to the crack length obtained by digital image correlation (DIC) method. In the crack initiation stage I., the C 1 peak height shows different behavior than the resonance frequency and therefore provides new information. The underlying processes causing C 1 peak changes need to be found yet , however. In the crack growth stage II., both resonance frequency and peak height C 1 correlate with the measured fatigue crack size. [ABSTRACT FROM AUTHOR]

This study explores the feasibility of deposition of composite films based on nanoparticles (NPs) using a magnetron-based gas aggregation source of NPs. First, we investigate the deposition conditions and properties of the individual components of the composite films, namely, NPs prepared using Cu and W targets. We thoroughly discuss that the generation of NPs might be more efficient in the Ar atmosphere in the case of W target due to an enhanced direct emission of NP seeds from the target and/or a longer lifetime of the seeds in the plasma. To operate reasonable fluxes of NPs for both targets, O 2 was added into the gas mixture. Lower O 2 flow rates promote enhanced seed formation of NPs, while higher flow rates exhibit a dominant target poisoning effect, reducing the flux of NPs. We demonstrate that a fine-tuning of O 2 flow rate allows us to control the resulting crystal structure of the NPs. Fully oxidized NPs were produced at O 2 flow rates of 1.30 sccm and 1.50 sccm for Cu and W targets, respectively. Subsequently, CuO/WO 3 composite films were prepared using our in-house-built software as alternating NPs-based layers. To demonstrate the capabilities of the deposition technique, three different CuO/WO 3 multilayers were prepared, each with a specific thickness of the individual layers (80 nm, 40 nm, and 10 nm, which corresponds to a monolayer of NPs). Scanning electron microscopy imaging shows well-defined layers with the intended thickness. In addition, XRD analysis confirms that all three multilayers exhibit practically identical patterns, indicating the same volumetric ratio of CuO and WO 3 NPs in the investigated films. • Mastering sputter-deposition process of nanoparticles-based composite films. • Enhancement of deposition rate of nanoparticles by oxygen admixture. • Tuning elemental and phase composition of nanoparticles by oxygen flow rate. • Controlled deposition of well-defined CuO/WO 3 multilayers for improved gas sensing. [ABSTRACT FROM AUTHOR]

We have determined the local plasma parameters using the Langmuir probe measurements with a sub-microsecond time resolution during positive voltage pulses of a bipolar high-power impulse magnetron sputtering discharge using an unbalanced magnetron with a titanium target. The effects of the positive voltage pulse amplitude and the delay between the negative voltage pulse end and the positive voltage pulse initiation are investigated as well as the spatial dependence of the plasma parameters at three distances from the target. From the results, the values of the average energy flux of ions during the positive voltage pulse to the substrate are estimated. We have found that the time evolution of the plasma parameters has similar developments which are independent of the positive voltage pulse parameters and the distance from the target, although the values of the plasma parameters are different. During the initial part of the positive voltage pulse, a large difference (up to 200 V) between the plasma and the floating potential accompanied by a high electron temperature (up to 150 eV) and a significant decrease of electron density (up to one order of magnitude) is registered. After this part, the difference of the potentials and the electron temperature are low (<2 V and ≲1 eV, respectively). The short delays between the negative voltage pulse end and the positive voltage pulse initiation as well as the higher positive voltage amplitudes have a beneficial effect on the average energy flux of ions during the positive voltage pulse to the grounded and insulated substrates. [ABSTRACT FROM AUTHOR]

A bipolar HiPIMS discharge with a rectangular positive voltage pulse (with controllable amplitude, delay after the main negative pulse and positive pulse length) was systematically investigated by mass spectroscopy. The time-averaged spectra of ions measured at the substrate position exhibit a prominent high-energy peak. It is shown that the position of the peak can be varied by the positive pulse amplitude, its magnitude scales with the pulse length and its width can be slightly influenced by the length of the delay interval. Measurements of the plasma potential at the mass spectrometer position and time-resolved mass spectroscopy clearly show that the high-energy peak is formed by ions accelerated by the elevated plasma potential during the positive pulse. In addition, fine details of the ion energy distribution functions related to the plasma potential transients at the start of the positive pulse are identified. The presented results are beneficial for the optimisation of the parameters of the positive pulse in experiments implementing the bipolar HiPIMS technology. [ABSTRACT FROM AUTHOR]

• 4 specimen types tested in push–pull cyclic loading to show the size effect impact. • The experiment focused on high-cycle fatigue response of 42CrMo4 + QT. • The effect of surface roughness was evaluated. • The effect of non-homogenous hardness of the semi-product could be neglected. • The effect of compressive residual stresses could be neglected in the comparison. The influence of the size effect is investigated experimentally on unnotched 42CrMo4 + QT fatigue specimens of four configurations with different critical volumes. An investigation of external factors present during experiments is also carried out. The paper shows how complicated it is to analyze a single effect in fatigue experiments. The effects of uneven surface roughness, semi-product hardness across its cross-section or of residual stresses on the fatigue life of the specimens are discussed. [ABSTRACT FROM AUTHOR]

High entropy alloys (HEAs) are materials of great application potential and which have been extensively studied during the last two decades. As the number of possible element combinations is enormous, model materials representing certain groups of HEAs are used for the description of microstructure, properties, and deformation mechanisms. In this study, the microstructure and mechanical properties of the so-called Cantor alloy composed of Co, Cr, Fe, Mn, and Ni in equiatomic ratios prepared by various techniques (casting, melt-spinning, spark plasma sintering) were examined. The research focused on the indentation measurements, namely, the indentation size effect describing the evolution of the hardness with penetration depth. It was found that the standard Nix–Gao model can be used for this type of alloy at higher penetration depths and its parameters correlate well with microstructural observations. The Nix–Gao model deviates from the measured data at the submicrometer range and the applied modification affords additional information on the deformation mechanism. [ABSTRACT FROM AUTHOR]

Nanocrystalline MBCN (M = Ti, Zr, Hf) films were deposited onto Si substrates using pulsed magnetron co-sputtering of a single B 4 C-M target (at a fixed 45% fraction of M in the target erosion area) with a repetition frequency of 10 kHz, voltage pulse duration of 85 μs and a fixed target power. The substrate temperature was adjusted to 450 °C during the depositions on the substrates at a floating potential. The total pressure of 95% Ar + 5% N 2 gas mixture was 0.5 Pa for TiBCN and ZrBCN, but it had to be increased up to 1.7 Pa for HfBCN to decrease very high compressive stress in the films resulting in their delamination from the substrate. Energy-resolved mass spectroscopy was used to correlate the energy of Ar+ ions bombarding the growing films with high positive voltage overshoots after the negative voltage pulses. Monte-Carlo simulations were carried out to estimate the energy and flux of sputtered M atoms and backscattered Ar atoms at the substrate. It was found that the energy and flux of the backscattered Ar atoms increase significantly with the mass of the M atoms in the target. The MBCN films with 41–46 at.% of M, 25–31 at.% of B, 7–10 at.% of C and 14–22 at.% of N exhibit a high hardness (18–37 GPa), high elastic recovery (69–85%), high H/E⁎ ratio (0.10–0.14) and low electrical resistivity (1.7–2.7 μΩm) at a low internal stress (less than 0.8 GPa). • Pulsed magnetron sputtering of hard conductive MBCN (M = Ti, Zr, Hf) films. • Voltage overshoot leads to bombardment by energetic ions. • Metal-dependent backscattering leads to bombardment by energetic Ar atoms. • Low compressive stress achieved by metal-dependent working pressure. • Relationships between metal-dependent bombardment and film characteristics. [ABSTRACT FROM AUTHOR]

This paper reports on an investigation treating a hard-milled surface as a surface undergoing severe plastic deformation at elevated temperatures. This surface exhibits remarkable magnetic anisotropy (expressed in term of Barkhausen noise). This paper also shows that Barkhausen noise emission in a hard-milled surface is a function of tool wear and the corresponding microstructure transformations initiated in the tool/machined surface interface. The paper discusses the specific character of Barkhausen noise bursts and the unusually high magnitude of Barkhausen noise pulses, especially at a low degree of tool wear. The main causes can be seen in specific structures and the corresponding domain configurations formed during rapid cooling following surface heating. Domains are not randomly but preferentially oriented in the direction of the cutting speed. Barkhausen noise signals (measured in two perpendicular directions such as cutting speed and feed direction) indicate that the mechanism of Bloch wall motion during cyclic magnetization in hard-milled surfaces differs from surfaces produced by grinding cycles or the raw surface after heat treatment. [ABSTRACT FROM AUTHOR]