Search Results (42)

Rebar is a critical material in concrete constructions like high-rise buildings and seismic-resistant structures. To enhance its properties, microalloying with nitrogen is employed, but traditional methods using micro alloy additives such as vanadium (FeV), niobium (FeNb), titanium (FeTi), and vanadium nitride (VN) face issues of high costs, reduced purity, and difficulty in controlling molten steel composition. This article presents a novel approach of injecting top-blown O₂–N₂ mixed gas to increase nitrogen content efficiently. Experiments simulated HRB400 steel samples, varying N₂ ratios (10%, 20%, 30%, 40%), temperatures (1500 °C, 1550 °C, 1600 °C), and blowing times (1, 2, 3 min). Results show that optimized parameters enable nitrogen content adjustment from 50 to 104 ppm, with nitrogen utilization improved to 5.4%. This method utilizes inexpensive N₂ gas, reduces impurities, and provides precise control, offering a cost-effective and sustainable solution for high-performance steel production by replacing costly alloys and meeting nitrogen requirements. Full article

This work shows an approach on the role of the gas mixture used in the pulsed DC plasma nitriding aiming to enhance the niobium cavitation erosion resistance through the formation of niobium nitride on the treated surfaces. For this purpose, nitriding was carried out at 1353 K (1080 °C) for 2 h, under a pressure of 1.2 kPa (9 Torr), and a 5 × 10⁻⁶ Nm³s⁻¹ (300 sccm) flow rate for three distinct gas mixtures, namely 30% N₂ + 50% H₂ + 20% Ar, 50% N₂ + 30% H₂ + 20% Ar, and 70% N₂ + 10% H₂ + 20% Ar. Surfaces were comparatively characterized before and after nitriding through scanning electron microscopy (SEM), X-ray diffractometry, 3D roughness, and nanoindentation hardness measurements. The cavitation erosion test was carried out in accordance with ASTM G32-09, obtaining the cumulative mass loss (CML) curve and the average (AER) and maximum (MER) erosion rate of the tested surfaces. Surfaces showed multiphase layers mainly constituted of ε-NbN and β-Nb₂N nitride phases, for the three distinct gas mixture conditions investigated. A CML of 25.0, 20.2, and 34.6 mg, and an AER of 1.56, 1.27, and 2.16 mg h⁻¹ was determined to the 960 min (16 h) cavitation erosion testing time, for NbN surfaces obtained at the 30% N₂, 50% N₂, and 70% N₂ gas mixture, respectively. In this case, the nominal incubation period (NIP) was 600, 650, 550 min, and the maximum erosion rate (MER) was 4.2, 3.4, and 5.1 mg h⁻¹, respectively. Finally, the enhancement of the cavitation erosion resistance, based on the NIP of the NbN surfaces, regarding the Nb substrates (with NIP of ≈100 min), was up ≈6 times, on average, thus significantly improving the cavitation erosion resistance of the niobium. Full article

Niobium nitride (NbN) thin films are crucial materials for various applications, including superconductivity and hard coatings. However, precisely controlling their microstructure and crystal orientation during synthesis remains a challenge. This study addresses this gap by systematically investigating the effect of sputtering particle energy on NbN film properties. This research aims to elucidate the relationship between sputtering particle energy and the resulting microstructure and crystal structure of NbN thin films synthesized by reactive magnetron sputtering. NbN thin films were deposited on Si (100) substrates using reactive magnetron sputtering. The effects of sputtering power, total sputtering pressure, and nitrogen partial pressure on the films’ preferred orientation, grain size, and crystallinity were characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), and atomic force microscopy (AFM). The preferred orientation of NbN films can be controlled by sputtering parameters. Increasing sputtering power leads to a texture transition from a single -phase (111) orientation to mixed (111) and (200) orientations. Sputtering pressure influences the energy of sputtering particles and can shift the preferred orientation from mixed (111) and (200) to single-phase (200). Higher nitrogen partial pressure affects the crystallinity of NbN films, potentially introducing defects that reduce crystallinity. This study demonstrates that sputtering particle energy significantly influences the microstructure and crystal orientation of NbN thin films. Precise control of sputtering parameters enables tailored film properties, which are crucial for optimizing NbN performance in diverse technological applications. Full article

Molybdenum disulfide is a 2D material with excellent lubricant properties, resulting from weak van der Waals forces between lattice layers and shear-induced crystal orientation. The low forces needed to shear the MoS₂ crystal layers grant the tribological system low coefficients of friction (COF). However, film oxidation harms its efficacy in humid atmospheres, leading to an increased COF and poor surface adhesion, making its use preferable in dry or vacuum conditions. To overcome these challenges, doping MoS₂ with elements such as Nb, Ti, C, and N emerges as a promising solution. Nevertheless, the adhesion of these coatings to a steel substrate presents challenges and strategies involving the reduction in residual stresses and increased chemical affinity to the substrate by using niobium-based materials as interlayers. In this study, Nb-doped MoS₂ films were deposited on H13 steel and silicon wafers using the pulsed direct current balanced magnetron sputtering technique. Different niobium-based interlayers (pure Nb and NbN) were deposited to evaluate the adhesion properties of Nb-doped MoS₂ coatings. Unlubricated scratch tests, conducted at room temperature and relative humidity under a progressive load, were performed to analyze the COF and adhesion of the coating. Instrumented indentation tests were conducted to assess the hardness and elastic modulus of the coatings. The microstructure of the coatings was obtained by Scanning Electron Microscopy (SEM), Scanning Transmission Electron Microscopy (STEM), and Transmission Electron Microscopy (TEM), with Energy-Dispersive X-Ray Spectroscopy (EDS). Results indicated that niobium doping on MoS₂ coatings changes the structure from crystalline to amorphous. Additionally, the Nb concentration of the Nb:MoS₂ coating changed the mechanical properties, leading to different cohesive failures by different loads during the scratch tests. Results have also indicated that an NbN interlayer optimally promoted the adhesion of the film. This result is justified by the increase in hardness led by higher Nb concentrations, enhancing the load-bearing capacity of the coating. It is concluded that niobium-based materials can be used to enhance the adhesion properties of Nb-doped MoS₂ films and improve their tribological performance. Full article

Coupling superconducting (SC) contacts to light-emitting layers can lead to remarkable effects, as seen in inorganic quantum-well LEDs with superconducting contacts, where an enhancement in radiative recombination was observed. Additional dramatic effects were theorized if both electrodes are SC, such as correlated emission and 2-photon entanglement. Motivated by this and by the question of whether proximity induced SC is possible in organic light-emitting materials, we studied the electronic properties of stacked SC–organic–SC devices. Our structures consisted of Nb (bottom) and NbN (top) SC electrodes and a spin-coated light-emitting semiconductor polymer, MEH-PPV. Sputtering the SC directly on the polymer causes pinholes, which we prevent by ultra-slow deposition of a 5 nm aluminum film, before depositing the top SC in situ. The Al protects the organic film from damage and pinhole formation, while preserving SC in the top electrodes due to the proximity effect between Al and NbN. Electrical transport measurements of the completed junctions indicate that indeed, the top and bottom contacts are superconducting and the protected MEH-PPV layer is pinhole-free, as supported by HR-TEM and EDS. Most importantly, we find that as the temperature is decreased below the critical temperature of the SCs, the device shows evidence for the proximity effect in the MEH-PPV. Full article

Titanium (Ti) is widely used in structural, maritime, aerospace, and biomedical applications because of its outstanding strength-to-weight ratio, superior corrosion resistance, and excellent biocompatibility. However, the lower surface hardness and inferior wear resistance of the Ti and Ti alloys limit their industrial applications. Coating Ti surfaces can initiate new possibilities to give unique characteristics with significant improvement in the Ti component’s functionality. The current research designed and synthesized titanium nitride (TiN), titanium carbide (TiC), titanium carbonitride (TiCN), tantalum nitride (TaN), and niobium nitride (NbN) ceramic coating layers (400 µm) over a Ti substrate using a spark plasma sintering process (SPS). The coatings on the Ti substrate were compact and consolidated at an SPS temperature of 1500 °C, pressure of 50 MPa, and 5 min of holding time in a controlled argon atmosphere. Microstructure investigation revealed a defect-less coating-substrate interface formation with a transition/diffusion zone ranging from 10 µm to 20 µm. Among all of the ceramic coatings, titanium carbide showed the highest improvement in surface hardness, equal to 1817 ± 25 HV, and the lowest coefficient of friction, equal to 0.28 for NbN. Full article

The recent advancements in the field of superconductivity have been significantly driven by the development of nitride superconductors, particularly niobium nitride (NbN). Multicomponent nitrides offer a promising platform for achieving high-temperature superconductivity. Beyond their high superconducting transition temperature (Tc), niobium-based compounds are notable for their superior superconducting and mechanical properties, making them suitable for a wide range of device applications. In this work, machine learning is used to identify ternary and quaternary nitrides, which can surpass the properties of binary NbN. Specifically, Nb_0.35Ta_0.23Ti_0.42N shows an 84.95% improvement in Tc compared to base NbN, while the ternary composition Nb_0.55Ti_0.45N exhibits a 17.29% improvement. This research provides a valuable reference for the further exploration of high-temperature superconductors in diversified ternary and quaternary compositions. Full article

Hardness is one of the most crucial mechanical properties, serving as a key indicator of a material’s suitability for specific applications and its resistance to fracturing or deformation under operational conditions. Machine learning techniques have emerged as valuable tools for swiftly and accurately predicting material behavior. In this study, regression methods including decision trees, adaptive boosting, extreme gradient boosting, and random forest were employed to forecast Vickers hardness values based solely on scanned monochromatic images of indentation imprints, eliminating the need for diagonal measurements. The dataset comprised 54 images of D2 steel in various states, including commercial, quenched, tempered, and coated with Titanium Niobium Nitride (TiNbN). Due to the limited number of images, non-deep machine learning techniques were utilized. The Random Forest technique exhibited superior performance, achieving a Root Mean Square Error (RMSE) of 0.95, Mean Absolute Error (MAE) of 0.12, and Coefficient of Determination ($R^2$) ≈ 1, surpassing the other methods considered in this study. These results suggest that employing machine learning algorithms for predicting Vickers hardness from scanned images offers a promising avenue for rapid and accurate material assessment, potentially streamlining quality control processes in industrial settings. Full article

The use of 3D-printed highly porous titanium acetabular cups in total hip arthroplasty (THA) is increasing. The porosity and mechanical properties of such highly porous titanium structures mimic those of natural cancellous bone, possibly allowing biological implant fixation to be improved. Recently, a 3D-printed highly porous Dual Mobility (DM) monobloc construct fully manufactured using Ti6Al4V alloy, with a titanium–niobium nitride (TiNbN) ceramic coating on the articular side to allow articulation against the mobile liner by improving the titanium vs. polyethylene tribological behavior, was introduced in THA. To the best of our knowledge, this is the first highly porous titanium monobloc DM implant on the market. The reasons for using a Ti alloy highly porous DM are multifarious: to prevent any possible adverse reactions due to the corrosion of Cobalt–Chromium–Molybdenum Alloy (CoCrMo) and Stainless Steel (SS) implants and to improve implant primary and secondary stability, particularly in cases of poor bone quality. Finally, with the introduction of an inner TiNbN ceramic coating surface, it was possible to overcome the poor tribological quality of titanium. Another interesting characteristic is this material’s higher implant radiolucency, which might facilitate the radiographic assessment of cup orientation, which can, in turn, facilitate the detection of any intraprosthetic dislocation (IPD) and the measurement of polyethylene wear, which is very important in the study of the durability of THA. Full article

Bipolar Plates (BPPs) play a critical role in Polymer Electrolyte Membrane Water Electrolysers (PEMWEs) for effective hydrogen generation. The performance and longevity of the system can be considerably impacted by choosing the suitable material for these components. Polymer electrolyte membrane water electrolysis technology relies on cost-effective and corrosion-resistant BPPs. Tantalum, niobium, and titanium are low-cost, easy-to-machine materials that have good electrical and thermal conductivity; however, they exhibit low corrosion resistance. Noble metal and metal nitride coatings are usually investigated to minimize corrosion and interfacial contact resistance. Because of its performance-to-cost ratio, Stainless Steel (SS) based materials are among the most popular materials for BPP development. This study recommends material and operating parameters to improve PEMWE systems for sustainable hydrogen production’s efficiency, durability, and economic viability. Full article

The search for biocompatible, non-toxic, and wear-resistant materials for orthopedic implant applications is on the rise. Different materials have been investigated for this purpose, some of which have proved successful. However, one challenge that has proven difficult to overcome is the balance between ductility and hardness of these materials. This study employed ab initio calculations to investigate the structural and mechanical properties of niobium nitride (NbN) alloyed with hafnium, indium, and zirconium, with the aim of improving its hardness. The calculations made use of density function theory within the quantum espresso package’s generalized gradient approximation, with Perdew–Burke–Ernzerhof ultrasoft pseudopotentials in all the calculations. It was found that addition of the three metals led to an improvement in both the shear and Young’s moduli of the alloys compared to those of the NbN. However, both the bulk moduli and the Poisson’s ratios reduced with the introduction of the metals. The Young’s moduli of all the samples were found to be higher than that of bone. The Vickers hardness of the alloys were found to be significantly higher than that of NbN, with that of indium being the highest. The alloys are therefore good for wear-resistant artificial bone implants in ceramic acetabulum, and also in prosthetic heads. Full article

β-titanium (β-Ti) alloys are used in various biomedical applications, especially for orthopedic implants, due to their superior biocompatibility, excellent corrosion resistance, and enhanced mechanical properties. However, the inferior tribological properties of β-Ti alloys lead to fretting wear and a strong tendency to seize, which is a major concern in orthopedic applications involving continuous friction. This work aims to address this issue by incorporating biocompatible nitrides in Ti-Nb-Zr-Ta (TNZT) β-Ti alloys. TNZT composites comprising 2 wt.% of biocompatible nitrides (TiN, NbN, ZrN, and TaN) were prepared using high-energy ball milling followed by spark plasma sintering. All the nitrides improved the hardness and wear resistance of TNZT alloys and showed excellent biocompatibility. TNZT-2 wt.% TiN showed the average highest hardness of 311.8 HV and the lowest coefficient of friction of 0.659, suggesting the highest efficiency of TiN in improving the tribological performance of TNZT alloys. The underlying mechanisms behind the superior performance of nitride-reinforced TNZT composites are discussed in detail. The effect of TiN concentration was also studied by preparing TNZT composites with 5 and 10 wt.% TiN, which showcased a higher hardness of 388.5 HV and 444.3 HV, respectively. This work will aid in producing superior β-Ti alloys for advanced orthopedic applications. Full article

One of the most popular methods for ranking duplex stainless steels (DSSs) and predicting their corrosion properties is the calculation of the pitting resistance equivalent number (PREN). However, since DSSs are two-phase materials with a significant fraction of secondary phases and precipitates, the application of the PREN can be highly limited. This article attempted to use a new approach to describe the corrosion resistance of these steels. The corrosion resistance of two DSSs of the same class was investigated. Under identical solution heat treatments in the temperature range of 1050–1200 °C, the crevice corrosion resistance of one steel increased, while that of the other decreased. It was demonstrated that the amounts of austenite and ferrite changed similarly in these steels, and the different corrosion resistances were associated with the behaviors of secondary phases: niobium carbonitride and chromium nitride. SEM-EDS analysis was conducted to analyze the redistribution of elements between phases in both cases, showing good agreement with the thermodynamic modeling results. The PREN was calculated for each phase depending on the treatment temperature, and a method for calculating the effective PREN (PREN_eff), accounting for phase balance and secondary phases, was proposed. It was shown that this indicator described corrosion properties better than the classical PREN calculated for the average steel composition. This study demonstrated how the calculation of critical temperatures (the temperature of equal amounts of ferrite and austenite, the temperature of the beginning of chromium nitride formation, and the temperature of the beginning of σ-phase formation) could describe the corrosion resistance of DSSs. Maximum possible deviations from these temperatures were defined, allowing the attainment of the required corrosion properties for the steels. Based on the conducted research, an approach for selecting new compositions of DSSs was proposed. Full article

Yttrium nitride (YN) is a hard and refractory material with a high melting point. It is a semiconductor that has been investigated for its potential applications in the field of semiconductor technology, including as a material for electronic devices. It is also of interest for its optical properties and its potential for use in optoelectronics. However, investigating its mechanical properties for a possible application in optical coatings has not been completed. This study involved the exploration of the mechanical properties of YN alloyed with niobium (Nb) and zirconium (Zr) for possible application in optical coatings using a first-principles approach. The result showed that the addition of Nb and Zr into the YN matrix had a profound effect on the mechanical properties of the modeled structures, with the Y-N-Nb (CYN_5) sample having the best mechanical properties. The bulk modulus was the most affected, with an increase of 26.48%, while the Vickers hardness had the smallest increase of 6.128% compared with those of pure YN. The modeled structures were thus found to be ideal alternative materials for optical coatings due to their improved mechanical properties. Full article

An NbN coating was produced on AISI 316L steel using reactive DC magnetron sputtering. The effects of oxidation of the NbN coating in air on the microstructure, mechanical properties, corrosion resistance, contact angle and bioactivity were investigated. Phase composition was determined using X-ray diffraction (XRD), the coatings’ cross-sectional microstructure and thickness including surface morphology using a scanning electron microscope (SEM), microhardness via the Vickers method, corrosion by means of a potentiodynamic polarisation test in Ringer’s solution and bioactivity by observation in an SBF solution, while the contact angle was studied using a goniometer. The NbN coating and the oxidised coating were shown to demonstrate a Ca/P ratio close to that of hydroxyapatite, as well as increased microhardness and corrosion resistance. The best combination of mechanical, corrosion, bioactivity and hydrophilic properties was demonstrated by the air oxidised NbN coating, which featured an orthorhombic Nb₂O₅ structure in the top, surface layer. Full article