Deposition of various coatings on surface of engineering components with the aim to improve their performance concerning wear, corrosion, friction, and thermal protection is already a standard practice. In special cases, depositing metallic NiTi shape memory alloy coatings may be a viable alternative for hard ceramic coatings. NiTi coatings offer additional benefits originating from their unique functional thermomechanical properties. However, fabrication of thick NiTi coatings turned out to be difficult. Standard electroplating and laser cladding methods are not suitable for NiTi, the most widely used plasma spray methods tend to produce chemically inhomogeneous coatings that do not transform martensitically, cold sprayed NiTi coatings suffer from poor adhesion to the substrates. In this work, we report on first ever successful fabrication of thick NiTi coatings (100–300 μm) that display functional thermomechanical properties and simultaneously show very good adherence to the substrate. We used high velocity air fuel thermal spray method to fabricate NiTi coatings deposited on mild steel using four different sets of fabrication parameters. Chemical composition, porosity, microstructure, phase transformation and functional thermomechanical properties of the NiTi coatings were evaluated. Although the coatings contain inhomogeneous microstructure, voids, oxide particles, high density of dislocation defects and internal stress, they undergo martensitic transformation upon cooling and/or mechanical loading. As sprayed NiTi coatings need to be annealed to display functional thermomechanical properties. Despite their limited tensile strength, the coatings displayed thermal actuation in 3-point bending tests and shape memory effects in nanoindentation and scratch tests.

This study describes the successful growth of highly boron-doped epitaxial diamond layers on heteroepitaxy diamond substrates using linear antenna microwave plasma CVD technology. Detailed characterisation by X-ray and electron diffraction confirms that the grown boron-doped diamond layers sustain epitaxy, while Raman and van de Pauw characterisation confirms high B incorporation and electrical performance with single crystal diamond characteristics. Electrochemical investigation demonstrates that the boron-doped diamond layers function as high-quality electrodes, offering a scalable route toward producing wafer-scale single crystal diamond devices. By overcoming the size limitations of traditional single crystal diamond and limits in cavity-based microwave plasma CVD technology, the combination of scalable heteroepitaxy diamond substrates with large area linear antenna microwave plasma CVD could provide a bridge toward future applications. Novelty statement: In this work we report the growth of highly boron-doped epitaxial diamond layers on heteroepitaxy diamond substrates using linear antenna MW PECVD. Characterisation of samples confirms high boron incorporation with Hall mobility values higher than that expected for polycrystalline diamond. Epitaxy in the grown layer is confirmed by bulk (X-ray) and localised (electron) diffraction. Finally, the suitability of the grown layers for electrodes in electrochemistry is investigated and confirmed.

In this work, the effectivity of scaife polishing was evaluated for {110}-oriented single-crystal boron-doped diamond (SC-BDD) electrodes with varying boron doping levels, [B] from similar to 3x10(20) to similar to 7x10(20) atoms cm(-3). While the RMS surface roughness of the as-deposited SC-BDD reached up to 137 nm, after polishing it was reduced to <= 1.5 nm. Following scaife polishing, peak potential difference Delta Ep evaluated from cyclic voltammetry for both outer-sphere ([Ru(NH3)(6)](3+/2+), ferrocenemethanol(+/0)) and inner-sphere redox marker [Fe(CN)(6)](3-/4-) became relatively equal regardless of [B]. Notably, heterogenous electron transfer (HET) kinetics of [Fe(CN)(6)](3-)/(4-) improved significantly with the HET rate constant k0 increasing from 45.7x10- 5 to 171x10- 5 cm s- 1 with increasing [B]. These results were confirmed by electrochemical impedance spectroscopy measurements with [Fe(CN)(6)](3-/4-) , as charge transfer resistance (R-CT) significantly decreased after scaife polishing, whereas R-CT values gradually decreased with increasing [B]. Finally, scaife-polished SC-BDD electrodes with varying surface terminations (H- vs. O-termination) were compared with chemically-mechanically polished polycrystalline BDD electrodes in dopamine sensing utilising square-wave voltammetry. The limits of detection achieved on both types of polished surfaces are generally lower than 1 mu mol L-1. Obviously, a smooth BDD surface presumably possesses uniform surface conductivity, which contributes significantly to the improved analytical performance of the BDD electrodes.

Laser shock peening (LSP) can induce deep compressive residual stresses in AA7075; however, the maximum useful compressive residual stress and its dependence on laser shock pressure and pulse overlap remain insufficiently understood. This study identifies the maximum compressive residual stress limit in AA7075 and the optimal LSP processing window with reference to the Hugoniot elastic limit (HEL). A nanosecond Yb: YAG laser with pulse energies of 0.1 to 5 J was employed, corresponding to laser power densities of 0.25 to 12.5 GW/cm² and shock pressures of up to 3.36 GPa, applied with and without 50

Mechanical properties and dynamical mechanical analysis were performed on compact Spark Plasma Sinter samples. It has been observed that the sample with less porosity reflects the behavior of superelasticity response. Other samples show failure during first cycles that may be due to porosity. Compaction of metallic powder is one of the standard procedures in the field of powder metallurgy for the fabrication of bulk material. Consolidation of the sample as a function of sintering temperature plays a crucial role in the final compaction mechanism. However, the evolution of compaction, microstructure, phase transformation and mechanical properties as a function of sintering temperature is hardly disclosed. In this work, a correlation has been established between mechanical and microstructural properties of compact samples. The maximum compactness and the corresponding microstructure, porosity, texture, phase transformation, grain size, hardness, mechanical properties of compact samples were discussed. The research establishes mechanical properties-structure correlations for compaction of NiTi alloy in advanced engineering applications.

The influence of pulsed nitrogen gas flow on microstructure and nitrogen-vacancy (NV) center formation was systematically investigated in polycrystalline diamond layers synthesized by microwave plasma chemical vapor deposition. Compared with static flow, gas pulsing enabled precise control of nitrogen-related radicals and induced a transition from microcrystalline to nanocrystalline diamond, accompanied by variations in residual stress and NV emission. Under optimized nitrogen flow, a bimodal structure emerged, comprising (001)-oriented, flake-like microcrystalline grains embedded in nanocrystalline diamond. Confocal optical analysis revealed that negatively charged NV (NV-) centers were preferentially localized within highly crystalline grains, whereas neutral NV (NV0) centers predominated at grain boundaries, forming spatially separated NV--rich clusters. Relaxometry demonstrated that the longitudinal relaxation times of flake-like grains were comparable to those of high-quality single-crystal diamond. These findings demonstrate that pulsed nitrogen modulation provides an effective strategy for tailoring diamond microstructure and optimizing NV center formation, offering significant potential for quantum applications.

Laser Shock Peening (LSP) is an advanced surface treatment technique capable of inducing deep compressive residual stresses, thereby improving fatigue life, wear resistance, and stress corrosion cracking resistance in high-strength aluminium alloys. However, the maximum useful compressive residual stress that can be safely introduced in AA7075, and its dependence on laser shock pressure and overlap strategy, remain insufficiently understood. If laser power density is raised above a critical threshold, surface damage, stress relaxation, or reverse straining may occur, which could limit the effectiveness of LSP. Finding the maximum compressive residual stress limit in AA7075 and the optimal LSP processing window while taking the Hugoniot elastic limit (HEL) into account are the goals of this study. For LSP, a nanosecond Yb:YAG laser with pulse energies between 0.1 and 5 J was employed. This led to shock pressures of up to 3.36 GPa and laser power densities of 0.25–12.5 GW/cm². Two peening strategies, namely: no overlap and 50% overlap, were investigated. Samples treated with the laser power density 12.5 GW/cm2 with the 50% overlap strategy exhibit ~35.31% higher microhardness compared to the base material and a maximum compressive residual stress of -302 MPa at a depth of 0.2 mm. The results imply that cumulative strain from pulse overlaps within an optimal shock pressure range largely determines the effectiveness of laser shock peening in AA7075 rather than peak shock pressure alone. This provides a mechanistic foundation for selecting the LSP parameter window in order to maximize residual stress and minimize negative surface effects.

Additive manufacturing through laser powder bed fusion (LPBF) enables the production of geometrically complex nickel-based superalloy components. However, it results in poor surface quality, partially melted powder particles, and surface irregularities, that limits their performance in critical applications. This study investigates nanosecond laser polishing as an advanced post-processing technique for improving the surface quality of LPBFmanufactured Haynes 230, a high-temperature Ni-Cr-W superalloy. Eighteen LPBF-manufactured samples were polished using a nanosecond pulsed fiber laser while systematically varying laser power (25-170 W), pulse duration (2611420 ns), pulse frequency (150-400 kHz), and scanning speed (900-2400 mm/s) to establish a comprehensive processing window. Surface roughness parameters (arithmetic mean height Sa and maximum height Sz) were measured using confocal microscopy, while remelted layer thickness, microstructure, and microhardness were analyzed through metallographic observations and Vickers microhardness testing. Laser polishing significantly improved the surface finish, achieving a maximum reduction in Sa of 90.9%, decreasing from 18.98 & micro;m to 1.72 & micro;m under optimal parameters of 110 W, 150 kHz, 1420 ns, and 900 mm/s. The remelted layer thickness ranged from 24 to 129 & micro;m, increasing with higher laser power and lower scanning speeds. Excessive power levels (170 W) resulted in subsurface cracking and porosity, whereas optimal conditions produced a smooth, crack-free surface and average microhardness of remelted layer ranging approximately from 274 to 383 HV. This work provides the systematic investigation of nanosecond laser polishing of LPBFmanufactured Haynes 230 and establishes practical correlations between laser parameters, energy intensity, and resulting surface morphology. The findings provide valuable guidelines for optimizing laser-based surface finishing of nickel-based superalloys used in high-temperature applications.

NiTiHf high-temperature shape memory alloys (HTSMAs) fabricated via laser powder bed fusion (LPBF) suffer from poor tensile strength preventing their successful use in engineering applications. We managed to fabricate NiTiHf HTSMA showing tensile actuation under stresses up to 500 MPa in the temperature range 250-350 degrees C. A tensile strength of 821 MPa, an actuation strain 2.34 % under 300 MPa tensile stress with negligible irrecoverable plastic strain, and fracture upon cooling under 600 MPa tensile stress are the best values reported so far for LPBFfabricated NiTiHf HTSMAs in the literature. The enhanced tensile strength reaching half of the strength of the conventional cast and thermomechanically processed NiTiHf HTSMAs was attributed to the lack of micropores (porosity 0.02 %). The tensile actuation performance is claimed to be facilitated by the strengthening effect from homogeneously distributed oxide nanoparticles introduced naturally by the LPBF fabrication. The oxide nano-particles decrease the size of domains of (001) compound twinned martensite created by the forward martensitic transformation upon cooling under stress, which reduces actuation strain but also suppresses dislocation slip in martensite. This dimensional strengthening mechanism lowers actuation strain but increases cyclic stability of the actuation response of the LPBF NiTiHf HTSMA.

The ternary compound Co-Ni-Al was investigated by the X-ray Kossel microdiffraction as a member of this material class of ferromagnetic shape memory alloys for the first time. Thereby monocrystals with the nominal chemical composition Co38Ni33Al29 were initially studied in the austenitic phase, in order to contribute to a better understanding of the complex behaviour of this material by means of a further diffraction method with a high informational content. While in the present two phase structure the precipitates could be clearly identified and confirmed as face-centred cubic cobalt solid solution by the Kossel diffraction, whereas for the expected B2-structure only 2 of the needed 5 superstructure reflections could be proved by means of the Kossel technique. A possible explanation lies besides the reason of a weak reflection intensity in a very strong discrepancy of 21 % of the ideal stoichiometric composition of (Co, Ni)(50)Al-50 in the investigated (Co, Ni)(71)Al-29. As known from the literature to maintain the B2-structure under such conditions is only possible by the formation of an enormous number of so-called constitutional crystal defects, which could be used to explain the non-verified superstructure reflections. Moreover, the local lattice constant of the main crystal phase beta was determined to a = (0.2855 +/- 0,0002) nm by the Kossel technique.

Wire Arc Additive Manufacturing (WAAM) using aluminum alloys supports high deposition rates and the production of geometrically complex components, making it viable for aerospace components and rapid prototyping. Though, WAAM tends to introduce tensile residual stresses, porosity, and poor surface integrity, which compromise mechanical performance. In this study, laser shock peening without coating (LSPwC) was used as a post-processing method to overcome these drawbacks. LSPwC generated beneficial compressive residual stresses (>90 MPa to 1 mm), improved the microstructure, and decreased porosity by more than 50 % along with visible alterations in pore shape. Although surface roughness was enhanced by the lack of a protective layer during peening, surface hardness was found to improve. These findings prove the prospect of combining LSPwC with WAAM towards more efficient and durable production of high-performance aluminum parts.

The study characterizes the effects of intensive plastic deformation, realized by the rotary swaging method, on the deformation behavior of WNiCo tungsten heavy alloy samples. To assess the differences in the deformation behaviors of the samples, evaluated via uniaxial compression tests (UCT), and characterize the microstructures, i. e. occurrence and development of hardening/softening processes, two different temperatures of swaging (900 °C and 1200 °C), and two different uniaxial compression testing temperatures (1100 °C and 1200 °C), were used. A relatively high strain rate of 10 s −1 was chosen for the testing because of the typical use of the tungsten heavy alloy for kinetic penetrators. The achieved results indicate that the development of softening processes, especially dynamic recrystallization, can occur within the swaged material, depending on the processing/testing conditions. Swaging at the lower temperature of 900 °C introduced significant work hardening and accumulation of strain, which promoted the development of dynamic recrystallization during the subsequent hot temperature testing. Swaging at 1200 °C, on the other hand, facilitated dynamic recrystallization and relaxation (especially within the nickel‐cobalt matrix) already during processing, which consequently increased the activation energy necessary for the development of recrystallization during the hot testing.

This study delves into investigation of the growth, electrical, and optical properties of epitaxial boron-doped diamond oriented on the {115} crystallographic plane, with varying boron concentrations. Epitaxial diamond layers with boron concentration between 10(17) and 10(20) cm(-3), as determined by Raman spectroscopy and secondary ion mass spectroscopy, were obtained. Resistivity varies significantly with the boron concentration. The resistivity was controlled between 313 and 4.37 Omega.cm by changing the B/C ratio from 0 to 250 ppm. The presence of oxygen in the process gas reduces the boron incorporation rate and controls boron incorporation in low doped layers. The resistivity of the boron-doped layer was controlled between 313 and 503 Omega.cm with the addition of oxygen for a ratio of [O-2/CH4](gas) = 0.001. Specific contact resistance R-Csp was measured using c-TLM structures after different annealing stages at high temperatures. The lowest value for specific contact resistance reached 1.28 x 10(-5) Omega.cm(2). These findings underscore the potential for a more streamlined and feasible approach in the creation of vertical devices, such as high-power Schottky diodes, through the growth of high quality, thick (similar to 200 mu m) {115}-oriented epitaxial layers characterized by high boron concentrations (similar to 10(20) cm(-3)), and low resistivity (3 Omega.cm) than those utilizing conventional {100} or {111} oriented epitaxial layers.

Contactless, laser-based resonant ultrasound spectroscopy was utilized to monitor changes in elastic properties in single-crystalline NiTi shape memory alloy. It was observed that the elastic behavior of the temperature-induced B19′ martensite, which is formed by a fine mixture of variants, adopts the symmetry elements of the parent austenite phase and thus, the changes over the transformation temperature can be represented by the temperature evolution of three cubic elastic coefficients. The experiments confirm that the transition during the cooling run is preceded by pronounced softening of the c44 elastic coefficient, which leads to nearly complete vanishing of elastic anisotropy prior to the transition. Below the transition, this coefficient remains soft, and the character of anisotropy switches from c44/c′ > 1 to c44/c′ < 1. We rationalize this behavior from the mechanical instability of the B19′ lattice with respect to shears along the (001)B19′ plane, which is known from first-principles calculations.

Epitaxially grown full Heusler alloy Rh2MnSb thin films were prepared for the first time using DC magnetron sputtering. The films were deposited on MgO [001] substrates at deposition temperatures of 600 degrees C, 700 degrees C, and 800 degrees C. We report on the structural, morphological, optical, magneto-optical, and magnetic properties of these films, which had a nominal thickness of 200 nm. The film grown at 600 degrees C was nearly stoichiometric and exhibited the almost perfect L21 ordering typical of Heusler alloys. The single-phase Rh2MnSb film possessed a tetragonal structure with lattice parameters close to the bulk material. X-ray photoelectron spectroscopy revealed the metallic character of the contamination-free film. The tetragonal films displayed discernible regular twinning, where most twin domains oriented with their c-axis perpendicular to the surface, attributed to substrate constraint. Twin formation was investigated using atomic force microscopy, transmission electron microscopy, and X-ray diffraction. Magnetic measurements of the film prepared at 600 degrees C revealed a Curie temperature (TC) of approximately 220-275 K and a saturation magnetization of around 55 emu/g at 10 K, both values close to the bulk material's. Magneto-optical Kerr effect measurements confirmed paramagnetic behavior at room temperature. These observed properties highlight the need for further studies of Rh2MnSb's thin films, focusing on compositional and structural control.

Boron doped diamond electrodes brought a new potential in bioanalytical chemistry including studies of structure and interactions of nucleic acids. Herein, deposition conditionswere optimized to produce a set of polycrystalline BDD electrodes with comparable boron concentration in solid phase of (1.8 - 2.1) · 1021 cm-3 akin to metallic-type conductivity but with increasing sp2carbon content. Increase of[CH4]/[H2]from 0.25 % to 2.0 % during deposition led to an obvious decrease in grain size from ca.300 nm (BDD0.25) to < 100 nm (BDD2.0). Adsorption of oligodeoxynucleotides and their structural changes in the presence of K+ and Li+ ions were evaluated through enzyme-linked DNA hybridization assay in which oxidizable 1-naphthol was released from its phosphoesterbystreptavidin-alkaline phosphatase conjugate upon successful hybridization of the target oligodeoxynucleotide with a biotinylated complementary probe. With increasing sp2carbon content, the hybridization assay showed improved discrimination between a target forming guanine quadruplex (stabilized by K+ ions), yielding by 40 % - 60 % lower hybridization signal with the complementary probe, compared to the same but unstructured target oligodeoxynucleotide in the presence of Li+ions that don't stabilize the quadruplex structure. Such behaviour was observed also for commercial BDD electrode with surface roughness < 10 nm.

Phosphorus-doped diamond (PDD) offers significant potential for innovative applications, yet traditional growth techniques face difficulties in achieving high levels of phosphorus incorporation. This study presents a novel growth process to enhance phosphorus incorporation into diamond layers through transient plasma conditions under CH4 gas pulsing. Unlike conventional approaches, heavily PDD layers ([P] similar to 3 x 10(20) atoms/cm(3)) are obtained at low phosphine concentrations by utilizing phosphorus contamination as the primary source of PH radicals. Time-resolved optical emission spectroscopy analysis reveals that, when the CH4 gas flow is turned off, the distinct relaxation dynamics of CH and PH radicals promote a non-equilibrium plasma state in which sufficient quantities of both radicals coexist. Additionally, the enhanced hydrogen etching process leads to the formation of faceted crystalline grains with reduced nucleation density and fewer non-diamond compounds. In contrast to the fine grains typically observed in conventional heavily PDD nanocrystalline layers, the phosphorus concentration exhibits a proportional trend with grain size, suggesting that phosphorus is primarily incorporated within the diamond grains rather than at grain boundaries. These findings pave the way for achieving heavily PDD layers with precise microstructural control, supporting the development of advanced devices.

Coating Inconel tiles by tungsten is a necessary step towards the full tungsten first wall coverage of the COMPASS-U tokamak. Thin tungsten coatings on Inconel based on physical vapor deposition were successfully produced consequently to a programme of R&D within the COMPASS Upgrade project by three different suppliers. This contribution presents the qualification phase of these tungsten coatings under COMPASS-U relevant high heat fluxes (50 cycles at 10 MW/m2, 100 cycles at 30 MW/m2) in the neutral beam test facility GLADIS. The behavior of the different tungsten coatings during exposures and the main conclusions from the post-mortem analysis are presented. The most important result is that under COMPASS-U relevant heat fluxes, no damage was observed on the front face of all samples, proving the practicability of such coatings for fusion application.

Homoepitaxially grown single crystal boron-doped diamond (BDD) electrodes with {100} surface were nano-structured using dip-coated silica nanospheres (400 nm in diameter) as a template for microwave plasma-enhanced chemical vapour deposition. Co-doping of BDD with Si atoms was confirmed as a result of SiO2 etching during the deposition process. Electrochemical properties of the nanostructured electrodes with hemispherical cavities were thoroughly investigated using cyclic voltammetry and electrochemical impedance spectroscopy, and were compared with smooth {100} BDD surfaces. Heterogeneous electron transfer kinetics rates for the [Fe(CN)6]3-/4-redox marker were notably higher than literature-reported values for {100} BDD and were further increased up to two orders of magnitude by the nanostructuring. Similar increase in the electron transfer rate was observed for dopamine. Such enhancement can be caused by exposure of more reactive surfaces with other crystallographic orientations due to nanostructuring. Further, surface area analysis revealed the electroactive surface increase factor up to 2.44 upon nanostructuring, exceeding the theoretical estimate of 1.91 derived from geometrical considerations. This discrepancy may indicate nanoscale roughness of the surface of the hemispherical cavities' walls. Overall, the results demonstrate that the applied nanostructuring approach preserves the spa carbon character of the material while improving its electrochemical properties. These findings uncover the potential of nanostructured BDD surfaces for applications in electrochemical sensors, spatially distributed surface modification, and particle entrapment.