Search Results (261)

Memristors with resistive switching capabilities are vital for information storage and brain-inspired computing, making them a key focus in current research. This study demonstrates non-volatile analog resistive switching behavior in Al/TiO_x/TiN/Si(n⁺⁺)/Al memristive devices. Analog resistive switching offers gradual, controllable conductance changes, which are essential for mimicking brain-like synaptic behavior, unlike digital/abrupt switching. The amorphous titanium oxide (TiO_x) active layer was deposited using the pulsed-DC reactive magnetron sputtering technique. The impact of increasing the oxide thickness on the electrical performance of the memristors was investigated. Electrical characterizations revealed stable, forming-free analog resistive switching, achieving endurance beyond 300 DC cycles. The charge conduction mechanisms underlying the current–voltage (I–V) characteristics are analyzed in detail, revealing the presence of ohmic behavior, Schottky emission, and space-charge-limited conduction (SCLC). Experimental results indicate that increasing the TiO_x film thickness from 31 to 44 nm leads to a notable change in the current conduction mechanism. The results confirm that the memristors have good stability (>1500 s) and are capable of exhibiting excellent long-term potentiation (LTP) and long-term depression (LTD) properties. The analog switching driven by oxygen vacancy-induced barrier modulation in the TiO_x/TiN interface is explained in detail, supported by a proposed model. The remarkable switching characteristics exhibited by the TiO_x-based memristive devices make them highly suitable for artificial synapse applications in neuromorphic computing systems. Full article

By introducing oxygen doping, the structure of an AlCrNbSiTiN coating was optimized, and its high-temperature oxidation resistance was improved. As the oxygen content incorporated increases, the coating changes from an FCC structure to an amorphous or spinel structure. Meanwhile, stress relaxation occurred, and the hardness of the coating dropped to 12 gpa. Oxygen-doped coatings exhibit excellent oxidation resistance; this is especially the case for oxidized coatings, whose structure remains stable up to 900 °C in an oxidizing environment. Full article

The Tuztaşı low-sulfidation epithermal Au–Ag deposit (Biga Peninsula, Türkiye) records a multi-stage hydrothermal history that can be interpreted through the trace and rare-earth-element (REE) chemistry of quartz. High-precision LA-ICP-MS analyses of five representative quartz samples (23 ablation spots; 10 analytically robust) reveal two fluid stages. Early fluids were cold, dilute meteoric waters (δ¹⁸O₍H₂O₎ ≈ −6.8 to +0.7‰), whereas later fluids circulated deeper, interacted with felsic basement rocks, and evolved in composition. Mineralized quartz displays marked enrichment in As (raw mean = 2854 ± 6821 ppm; filtered mean = 70 ± 93 ppm; one spot 16,775 ppm), K (498 ± 179 ppm), and Sb (57.8 ± 113 ppm), coupled with low Ti/Al (<0.005) and elevated Ge/Si (0.14–0.65 µmol mol⁻¹). Chondrite-normalized REE patterns show pronounced but variable LREE enrichment ((La/Yb)_n ≤ 45.3; ΣLREE/ΣHREE up to 10.8) and strongly positive Eu anomalies (δEu ≤ 9.3) with slightly negative Ce anomalies (δCe ≈ 0.29); negligible Ce–Eu covariance (r² ≈ 0.05) indicates discrete redox pulses. These signatures indicate chemically evolved, reducing fluids conducive to Au–Ag deposition. By contrast, barren quartz is characterized by lower pathfinder-element contents, less fractionated REE profiles, higher Ti/Al, and weaker Eu anomalies. A composite exploration toolkit emerges: As > 700 ppm, As/Sb > 25, Ti/Al < 0.005, Ge/Si > 0.15 µmol mol⁻¹, and δEu ≫ 1 reliably identify ore-bearing zones when integrated with δ¹⁸O data and fluid-inclusion microthermometry from earlier studies on the same vein system. This study provides one of the first systematic applications of integrated trace-element and REE analysis of quartz to a Turkish low-sulfidation epithermal system, offering an applicable model for vectoring mineralization in analogous settings worldwide. Full article

Nickel-based superalloy Hastelloy C276 is widely used in high-performance industries due to its strength, corrosion resistance, and thermal stability. However, these same properties pose substantial challenges in machining, resulting in high tool wear, surface defects, and dimensional inaccuracies. This study investigates methods to enhance machining performance and surface quality by evaluating the tribological behavior of TiSiN/TiAlN-coated carbide inserts under six cooling and lubrication conditions: dry, MQL with coconut oil, Cryo-LN₂, Cryo-LCO₂, MQL–Cryo-LN₂, and MQL–Cryo-LCO₂. Open-slot finishing was performed at constant cutting parameters, and key indicators such as cutting zone temperature, tool wear, surface roughness, chip morphology, and microhardness were analyzed. The hybrid MQL–Cryo-LN₂ approach significantly outperformed other methods, reducing cutting zone temperature, tool wear, and surface roughness by 116.4%, 94.34%, and 76.11%, respectively, compared to dry machining. SEM and EDS analyses confirmed abrasive, oxidative, and adhesive wear as the dominant mechanisms. The MQL–Cryo-LN₂ strategy also lowered microhardness, in contrast to a 39.7% increase observed under dry conditions. These findings highlight the superior performance of hybrid MQL–Cryo-LN₂ in improving machinability, offering a promising solution for precision-driven applications. Full article

The impact of modulation periods on the microstructure, as well as the tribological and mechanical characteristics of the AlCrTiVNbN/TiSiN nano multilayer films, was investigated. The films were prepared with modulation periods ranging from 4 nm to 7 nm, and their properties were explored using X-ray diffraction (XRD), scanning electron microscope (SEM), nanoindentation, and a tribological tester. All nano multilayer films revealed a face-centered cubic (FCC) structure with a preferred planar direction of (200). As the modulation period increased, the XRD peak moved to higher angles, and the interplanar distance decreased. Also, the mechanical properties deteriorated, and the COF rose monotonically as a result. The nano multilayer film with a modulation period equal to 4 nm exhibited a smooth surface with minimal small particles, the highest hardness of 15.51 ± 0.16 GPa and elastic modulus of 182.89 ± 2.38 GPa, the highest values for the ratios of H/E and H³/E², the lowest average friction coefficient of 0.73, and a wear rate equal to (8.2 9 ± 0.18) × 10⁻⁸ mm³·N⁻¹·m⁻¹. The improvement in the properties of the film was ascribed to the coherent growth and alternating stress field between the AlCrTiVNbN and TiSiN layers. Full article

This work presents a multiscale, microstructure-aware framework for predicting fatigue strength distributions in additively manufactured (AM) alloys—specifically, laser powder bed fusion (L-PBF) AlSi10Mg and Ti-6Al-4V—by integrating density functional theory (DFT), instrumented indentation, and Bayesian inference. The methodology leverages principles common to all 3D printing (additive manufacturing) processes: layer-wise material deposition, process-induced defect formation (such as porosity and residual stress), and microstructural tailoring through parameter control, which collectively differentiate AM from conventional manufacturing. By linking DFT-derived cohesive energies with indentation-based modulus measurements and a MAP-based statistical model, we quantify the effect of additive-manufactured microstructural heterogeneity on fatigue performance. Quantitative validation demonstrates that the predicted fatigue strength distributions agree with experimental high-cycle and very-high-cycle fatigue (HCF/VHCF) data, with posterior modes and 95 % credible intervals of ${\widehat{\sigma }}_f^{\mathrm{AlSi}10\mathrm{Mg}}={86}_{-7}^{+8}\mathrm{MPa}$ and ${\widehat{\sigma }}_f^{\mathrm{Ti}–6\mathrm{Al}–4\mathrm{V}}={115}_{-9}^{+10}\mathrm{MPa}$, respectively. The resulting Woehler (S–N) curves and Paris crack-growth parameters envelop more than 92 % of the measured coupon data, confirming both accuracy and robustness. Furthermore, global sensitivity analysis reveals that volumetric porosity and residual stress account for over 70 % of the fatigue strength variance, highlighting the central role of process–structure relationships unique to AM. The presented framework thus provides a predictive, physically interpretable, and data-efficient pathway for microstructure-informed fatigue design in additively manufactured metals, and is readily extensible to other AM alloys and process variants. Full article

This study investigates the fabrication, nanomechanical behavior, and tribological performance of nanostructured superlattice coatings (NSCs) composed of alternating TiAlSiNb-N/TiCr-CN bilayers. Deposited via High-Power Ion-Plasma Magnetron Sputtering (HiPIPMS) onto 100Cr6 steel substrates, the coatings achieved nanohardness values of ~25 GPa and elastic moduli up to ~415 GPa. A novel empirical method was applied to extract stress–strain field (SSF) gradient and divergence profiles from nanoindentation load–displacement data. These profiles revealed complex, depth-dependent oscillations attributed to alternating strain-hardening and strain-softening mechanisms. Fourier analysis identified dominant spatial wavelengths, DWL, ranging from 4.3 to 42.7 nm. Characteristic wavelengths WL1 and WL2, representing fine and coarse oscillatory modes, were 8.2–9.2 nm and 16.8–22.1 nm, respectively, aligning with the superlattice period and grain-scale features. The hyperfine structure exhibited non-stationary behavior, with dominant wavelengths decreasing from ~5 nm to ~1.5 nm as the indentation depth increased. We attribute the SSF gradient and divergence spatial oscillations to alternating strain-hardening and strain-softening deformation mechanisms within the near-surface layer during progressive loading. This cyclic hardening–softening behavior was consistently observed across all NSC samples, suggesting it represents a general phenomenon in thin film/substrate systems under incremental nanoindentation loading. The proposed SSF gradient–divergence framework enhances nanoindentation analytical capabilities, offering a tool for characterizing thin-film coatings and guiding advanced tribological material design. Full article

Micro-sandblasting pretreatment was applied to AlTiSiN-coated WC–Co tools to enhance cutting performance in 316 L stainless steel milling. An L₉(3³) Taguchi orthogonal array varied passivation pressure (0.1, 0.2, and 0.3 MPa), gun traverse speed (60, 80, and 100 m/min), and tool rotation speed (20, 30, and 40 r/min). Coating thickness varied only from 0.93 to 1.19 μm, and surface roughness remained within 0.044–0.077 μm, confirming negligible thickness and roughness effects. Under optimized conditions, coating adhesion strength and nano-hardness both exhibited significant improvements. A weighted-scoring method balancing these two responses identified the optimal pretreatment parameters as 0.1 MPa, 80 m/min, and 20 r/min. Milling tests at 85 m/min—using flank wear VBₘₐₓ = 0.1 mm as the failure criterion—demonstrated a cutting distance increase from 4.25 m (untreated) to 12.75 m (pretreated), a 200% improvement. Wear progressed through three stages: rapid initial wear, extended steady wear due to Al₂O₃ protective-film formation and Si-induced oxygen-diffusion suppression, and accelerated wear. Micro-sandblasting further prolonged the steady-wear phase by removing residual cobalt binder, exposing WC grains, and offsetting tensile residual stresses. These findings establish a practical, cost-effective micro-sandblasting pretreatment strategy that significantly enhances coating adhesion, hardness, and tool life, providing actionable guidance for improving the durability and machining performance of coated carbide tools in difficult-to-cut applications. Full article

Enhanced hard coatings with exceptional mechanical and thermal qualities have prompted substantial study into multicomponent nitride systems. TiAl(Si)N coatings have emerged as viable possibilities owing to their remarkable hardness, thermal stability, and oxidation resistance. This work involved the fabrication of thickness-varied TiAl(Si)N gradient coatings using reactive magnetron sputtering, employing a controlled modulation of aluminum and silicon content across the film thickness. Three samples, with thicknesses of ~400 nm, ~600 nm, and ~800 nm, were deposited under uniform Ar/N₂ gas flow ratios, and their microstructural, mechanical, and tribological characteristics were rigorously examined. SEM investigation demonstrated a significant change across thicknesses. XRD results validated the emergence of a predominant cubic TiAl(Si)N phase alongside a secondary hexagonal AlN phase, signifying partial phase segregation. The nanoindentation results indicated that Sample 2 exhibited the maximum hardness (~38 GPa) and Young’s modulus (~550 GPa) due to an optimized equilibrium between solid solution strengthening and nanocomposite production. Tribological testing revealed that Sample 1 displayed the lowest and most consistent friction coefficient, corresponding to its superior H/E and H3/E2 ratios, which signify improved elasticity and resistance to plastic deformation. The findings emphasize that the implementation of a compositional gradient, especially in the distribution of Si and Al, markedly affects the microstructure and performance of TiAl(Si)N coatings. Gradient structures enhance the microstructure, optimize hardness, and increase the friction coefficient. Ongoing refinement of gradient profiles and deposition parameters may further improve the characteristics of TiAl(Si)N coatings, facilitating their wider industrial use. Full article

This study investigates the effect of duo-ceramic zirconia and silicon nitride (ZrO₂-Si₃N₄) particles and their reinforcement proficiencies on a Ti6Al4V alloy, consolidated using the spark plasma sintering (SPS) technique. The selected sintering parameters are, viz., 900 °C temperature, 50 MPa pressure, 10 min of holding time, and 100 °C/min of sintering rate. SEM/EDS and XRD equipment were used to disclose the microstructural evolution and phase identification of created composites. The mechanical characteristics of the resulting composites were determined using the nanoindentation technique. All consolidated sintered composites showed excellent densification, with sample relative densities reaching 96.65%. Significant improvements were also made in their nanomechanical characteristics; among the composite samples with different volume fractions, the ceramics with the lowest volume percentage had the best mechanical characteristics, whereas the sintered samples with the highest ceramic volume percentage showed a decrease in mechanical proficiencies and relative density. Composite S1, with the lowest volume fraction of the duo-ceramic particles, was seen to have a significant mechanical property improvement better than other composites, S2 and S3, in terms of measured Vickers microhardness, elastic modulus, and nano hardness values at a sintering temperature of 900 °C. Consequentially, composite specimens S2 and S3’s mechanical characteristics and relative densities dropped as the volume fractions of the duo-ceramic particles increased. Full article

This study investigates the nanomechanical and tribological behavior of multilayered nitride/carbonitride nanostructured superlattice type coatings (NTCs) composed of alternating TiAlSiNb-N and TiCr-CN sublayers, deposited via high-power ion-plasma magnetron sputtering (HiPIPMS) technique. Reinforced with refractory elements Cr and Nb, the NTC samples exhibit high nanohardness (39–59 GPa), low friction, and excellent wear resistance. A novel analytical approach was introduced to extract stress–strain field (SSF) gradients and divergences from nanoindentation data, revealing alternating strain-hardening and strain-softening cycles beneath the incrementally loaded indenter. The discovered oscillatory behavior, consistent across all samples under the investigation, suggests a general deformation mechanism in thin films under incremental loading. Fourier analysis of the SSF gradient oscillatory pattern revealed a variety of characteristic dominant wavelengths within the length-scale interval (0.84–8.10) nm, indicating multi-scale nanomechanical responses. Additionally, the NTC samples display an anisotropic coating morphology exhibited as unidirectional undulating surface roughness waves, potentially attributed to atomic shadowing, strain-induced instabilities, and limited adatom diffusion. These findings deepen our understanding of nanoscale deformation in advanced PVD coatings and underscore the utility of SSF analysis for probing thin-film mechanics. Full article

The gate reliability issues in SiC-based devices with a gate dielectric formed through heat oxidation are important factors limiting their application in power devices. Aluminum oxide (Al₂O₃) and titanium dioxide (TiO₂) were combined using the ALD process to form a composite AlTiO gate dielectric on a 4H-SiC substrate. TDMAT and TMA were the precursors selected and deposited at 200 °C, and the samples were Ar or N₂ annealed at temperatures ranging from 300 °C to 700 °C. An XPS analysis suggested that the AlTiO film had been deposited with a high overall quality and the involvement of Ti atoms had increased the interfacial bonding with the substrate. The as-deposited MOS structure had band shifts of ΔE_C = 1.08 eV and ΔE_V = 2.41 eV. After annealing, the AlTiO bandgap increased by 0.85 eV at most, and better band alignment was attained. Leakage current and breakdown voltage characteristic investigations were conducted after Al electrode deposition. The leakage current density and electrical breakdown field of an MOS capacitor structure with a SiC substrate were ~10⁻³ A/cm² and 6.3 MV/cm, respectively. After the annealing process, both the measures of the JV performance of the MOS capacitor had improved to ~10⁻⁶ A/cm² and 7.2 MV/cm. The interface charge N_eff of the AlTiO layer was 4.019 × 10¹⁰ cm⁻². The AlTiO/SiC structure fabricated in this work proved the feasibility of adjusting the properties of single-component gate dielectric materials using the ALD method, and using a suitable thermal annealing process has great potential to improve the performance of the compound MOS dielectric layer. Full article

Platinum- and/or palladium-containing silica-based supports were applied for the selective catalytic reduction of NO_x with hydrogen (H₂-SCR-DeNO_x). To obtain enhanced activity and N₂ selectivity below 150 °C, we varied the type and loading of noble metals (Pt and Pd both individually and paired, 0.1–1.0 wt.-%), silica-containing supports (ZrO₂/SiO₂, ZrO₂/SiO₂/Al₂O₃, Al₂O₃/SiO₂/TiO₂), as well as the H₂ concentration in the feed (2000–4000 ppm). All of these contributed to enhancing N₂ selectivity during H₂-SCR-DeNO_x over the (0.5 wt.-%)Pt/Pd/ZrO₂/SiO₂ catalyst in the presence of 10 vol.-% of O₂. H₂ was completely consumed at 150 °C. A comparison of the catalytic results obtained during H₂-SCR-DeNO_x,(H₂-)NH₃-SCR-DeNO_x, as well as stop-flow H₂-SCR-DeNO_x and temperature-programmed studies, revealed that in the temperature range between 150 and 250 °C, the continuously coupled or overlaying mechanism of NO reduction by hydrogen and ammonia based on NH₃ formation at lower temperatures, which is temporarily stored at the acid sites of the support and desorbed in this temperature range, could be postulated. Full article

In this study, we propose a neuromorphic computing system based on a 3D-NAND flash architecture that utilizes analog input voltages applied through wordlines (WLs). The approach leverages the velocity saturation effect in short-channel MOSFETs, which enables a linear increase in drain current with respect to gate voltage in the saturation region. A NAND flash array with a TANOS (TiN/Al₂O₃/Si₃N₄/SiO₂/poly-Si) gate stack was fabricated, and its electrical and reliability characteristics were evaluated. Output characteristics of short-channel (L = 1 µm) and long-channel (L = 50 µm) devices were compared, confirming the linear behavior of short-channel devices due to velocity saturation. In the proposed system, analog WL voltages serve as inputs, and the summed bitline (BL) currents represent the outputs. Each synaptic weight is implemented using two paired devices, and each WL layer corresponds to a fully connected (FC) layer, enabling efficient vector-matrix multiplication (VMM). MNIST pattern recognition is conducted, demonstrated only a 0.32% accuracy drop for the short-channel device compared to the ideal linear case, and 0.95% degradation under 0.5 V threshold variation, while maintaining robustness. These results highlight the strong potential of 3D-NAND flash memory, which offers high integration density and technological maturity, for neuromorphic computing applications. Full article

The creation of coatings by the cathodic arc evaporation method has outstanding advantages: these coatings are highly durable and wear-resistant, especially since the method has an intense ionization process and the atoms can penetrate deep into the surface substrates, resulting in excellent adhesion. Furthermore, this approach provides precise control over the chemical composition and thickness of the coating, ensuring consistent quality across the entire surface. However, uneven evaporation and ejection of molten metal droplets from the cathode during cathode arc deposition produce particles and droplets, resulting in an uneven coating surface. This study presents a new design for a magnetically controlled cathode arc source to effectively reduce particles and droplets during the cathodic arc deposition of multi-component alloy targets for nitride-based hard coatings. The study compares the performance of a new source with a conventional magnetic-controlled arc source for depositing TiAlNbSiN and AlCrSiN films. In the conventional source, the magnetic field is generated by a permanent magnet (PM), whereas in the new source, it is generated and controlled using an electromagnet (EM). Both films are produced using multi-component alloy targets (TiAlNbSi and AlCrSi) with identical composition ratios. The plasma characteristics of the two different arc sources are investigated using an optical emission spectrometer (OES), and the surface morphology, structural characteristics, deposition rate, uniformity, and surface roughness (Sa) are examined using scanning electron microscopy (SEM). When the EM was applied to have high plasma density, the hardness of the TiAlNbSiN film deposited with the novel arc source measured 31.2 ± 1.9 GPa, which is higher than that of the PM arc source (28.3 ± 1.4 GPa). In contrast, the AlCrSiN film created using a typical arc source exhibited a hardness of only 25.5 ± 0.6 GPa. This lower hardness may be due to insufficient ion kinetic energy to enhance stress blocking and increase hardness, or the presence of the h-AlN phase in the film, which was not detected by XRD. The electromagnet arc source, with its adequate ion bombardment velocity, facilitated a complementary effect between grain growth and stress blocking, leading to a remarkable hardness of 32.6 ± 0.5 GPa. Full article