Nitride Layer Research Articles

High-temperature oxidation and diffusion studies on selected Al–Cr–Fe–Ni high-entropy alloys for potential application in thermal barrier coatings

In this work, the properties of two high-entropy alloys (HEAs) Al25Cr20Fe20Ni35 and Al20Cr20Fe20Ni40 (at.%) were compared for potential application as bond coats in thermal barrier coatings (TBCs). For this reason, both their oxidation resistance under isothermal and thermal shock conditions, as well as diffusion phenomena occurring at the substrate-HEA diffusion couple interface, were investigated. It was determined that both alloys demonstrate good phase stability and oxidation resistance during prolonged exposure to air atmosphere at 1000°C. In the initial 100 h period, selective aluminum oxidation is responsible for the protective scale growth on both materials under both isothermal and thermal shock conditions. However, only the Al20Cr20Fe20Ni40 high entropy alloy maintains a single Al2O3 layer for over 1000 h of oxidation with cyclic temperature changes. On the other hand, diffusion studies indicate that mainly iron and chromium travel between the ferritic steel substrate and the HEAs. Aluminum diffusion is seemingly limited by the unexpected formation of a thin aluminum nitride layer at the interface between the materials. From all these results it can be concluded that the Al20Cr20Fe20Ni40 alloy shows more promise for application in TBCs based on high entropy materials than Al25Cr20Fe20Ni35.

In-situ synthesis of dual-phase nitrides and multiple strengthening mechanisms in FeCoCrNiAl0.5 high entropy matrix composite coatings by laser cladding and plasma nitriding

To enhance the wear resistance of high entropy alloy (HEA) coatings and broaden their applications under extreme conditions, this study proposed an in-situ synthesis process of a dual-phase strengthened nitrides layer on laser cladded HEA coating. The microstructural evolution and mechanical properties of FeCoCrNiAl0.5 HEA coating by plasma nitriding were systematically investigated, revealing formation and strengthening mechanisms of nitrides. In comparison to the traditional nitrided substrate 38CrMoAl, the results showed that the nitrided HEA coating exhibited high hardness and wear resistance, characterized by dual-phase nitrides AlN+CrN due to the negative Gibbs free energy, negative nitride formation enthalpy and higher atomic specific surface areas. While only a single-phase iron nitride with lower hardness was obtained on the nitrided 38CrMoAl. The microhardness and wear mass loss of the nitrided HEA coating were 1167 HV and 0.435×10−6 mg/mm, respectively, which were 33.4% higher and 63.3% lower than those of the nitrided 38CrMoAl. The strengthening effects attributed to the refinement of dual-phase nitrides, interstitial solid solution by N atoms, dispersion strengthening by higher proportion of nitrides.

Supercapacitor Performance of MXene-Coated Carbon Nanofiber Electrodes

MXenes consisting of thin layers of transition metal carbides or nitrides are good candidates for electrode materials due to their excellent electrical conductivity and fast ion transfer. Electrospun carbon nanofibers are highly porous and electrically conductive, making them attractive for electrode materials. In this study, free-standing electrodes were prepared by the dip-coating of carbon nanofibers (CNFs) in the MXene (Ti3C2) colloidal solution, which was synthesized via the wet-etching of MAX (Ti3AlC2) phase, and their chemical structures were investigated by X-ray diffraction and Fourier transform infrared spectroscopy. In addition, scanning and transmission electron microscopy were used to investigate the morphological and crystallographic features of MXene-coated CNFs. Surface area and pore volumes were investigated by nitrogen adsorption/desorption measurements. Supercapacitor performance was studied by assembling a 3-electrode system with 1M aqueous sodium sulfate solution as an electrolyte. MXene-coated CNFs exhibited a maximum specific capacitance of 514 F/g at 0.5 A/g, with energy and power densities of 71.4 Wh/kg at 0.5 A/g and 2.3 kW/kg at 5 A/g, respectively, which are relevantly higher compared to the pristine CNFs due to the pseudocapacitive behavior of MXenes. They also showed comparable cyclic stability during 5000 cycles with the CNFs. This result indicates that MXene-coated carbon nanofibers can be effective electrode materials for electrochemical energy storage.

Study of the Wear Resistance Plasma Nitrided GGG60 by Optimization of Surface Treatment Conditions Using Response Surface Methodology

AbstractIn this study, the wear performance of spheroidal graphite cast iron subjected to plasma nitriding at different temperatures and treatment durations was investigated. The plasma nitriding parameters were optimized by response surface methodology (RSM) due to the output performance. Plasma nitriding was applied at three different temperatures (400, 450, 500 °C) and three different heat treatment durations (0.5, 2, 4 h). Wear tests were performed by ball-on-disk method for 60 minutes and for three different wear loads (10, 20, 30 N). The specimens were investigated for hardness, microstructure and wear performance. The RSM model was then created by using the wear resistance features. Plasma nitriding showed better wear performance than the untreated specimen for all treatment conditions. Hardness, nitrided layer thickness and wear performance remarkably improved with increasing temperature and process duration. The parameter that affects volume loss the most is wear load with 70.66% according to RSM modeling results. The most effective parameter in the wear rate change was found to be treatment duration at 42.85%. The model was able to predict the results with an error of 2.11% for volume loss and 9.14% for wear rate. The prediction results are very close to the experimental results. This clearly shows that the model can be used to determine the plasma nitriding parameters.

Study of the Effectiveness of Corrosion Resistance Growth by Application of Layered AlN–TiO2 Coatings

The work is devoted to the study of the use of AlN–TiO2 coatings as protective materials against corrosion and natural aging, as well as a rise in wear resistance of the steel surface under long-term mechanical influences. The choice of oxy-nitride coatings obtained by magnetron sputtering by layer-by-layer deposition of layers of aluminum nitride and titanium oxide with layer thicknesses of the order of 50 nm and 100 nm as objects of study is due to their high resistance to external influences, which can have a significant impact on growth in the resistance to degradation processes associated with hydrogenation during the operation of steel structures. During determination of the hydrophobicity/hydrophilicity of AlN–TiO2 coatings, it was found that the applied coatings, regardless of the conditions for their preparation, have hydrophobic properties (the contact angle is ~125–130°), which are preserved both during corrosion tests (except for TiO2 coatings, for which the change in the contact angle after corrosion tests is ∆ ~ 10°) and when modeling natural aging processes. During the tribological tests of coating samples, it was found that a growth in the number of spray layers (when alternating them) leads to a rise in wear resistance, both in the case of the initial samples and for samples subjected to corrosion in a model solution of 0.1 M NaCl and when simulating natural aging processes.

Interface stress analysis and bonding strengthening exploration of metal layer on the laser-activated copper-clad AlN

Aluminum nitride ceramics has excellent thermal conductivity and insulation property, making it a kind of excellent electronic packaging material. But enhancing the bonding strength between the metal layer and aluminum nitride (AlN) ceramic is a challenging problem. Especially regarding the lack of accurate data analysis on the stress between interfaces, enhancing adhesive strength still relies on blind attempts. By using the finite element method, this study reveals that the shear stress generated between the metal/ceramic interface is concentrated at the interface edge. Based on this finding, a method of inserting micro-pore arrays at the edge is proposed to enhance the interfacial bonding strength. The simulation results show that by inserting micro-pores with an appropriate density, the interface shear stress between metal and ceramic can be reduced obviously by 36 %. Finally, vertical peel-off verification experiments were designed. After inserting micro-pores to the interface, the bonding strength of the interface increased from 8.75 MPa to 11.69 MPa, and the performance was improved by 33.6 %. The experimental results were consist with the simulation results and indicated that the micro-pores had a significant effect on improving the bonding strength.

Hetero-Single-Atom F and P-Doped Layered Graphitic Carbon Nitride Nanosheets for Electrochemical Quantification of Vanillin in Food Samples

Hetero-Single-Atom F and P-Doped Layered Graphitic Carbon Nitride Nanosheets for Electrochemical Quantification of Vanillin in Food Samples

Production and Mechanical Characterization of Steel/Al-B4C Layered Circular Hybrid Composite Materials

This study aimed to develop a layered circular metal composite that would combine high strength, low density, and developable surface properties. The outer part of this composite material called the sheath was made of AISI 4140 steel, and the inner part, as the core, was composed of Al/B4C (boron carbide) mixed metal matrix composite. Al/B4C powder mixing ratios were determined by volume rate as 5, 15, and 25% B4C. Al2024 powder with an average particle size of 40 µm and B4C with particle sizes of 5, 17, and 58 µm were used. Composite materials were produced by forming the pre-products obtained by compressing Al/B4C powder mixtures into steel tubes using the drawing method. The drawing process was carried out at room temperature, 250 °C, and 400 °C, and with three different deformation extents (16, 30, and 37%). In the composite materials produced under all temperature conditions, increasing of the deformation extent increased the compression strength of the materials. Compression strength also increased with B4C reinforcement at all temperature conditions, but it decreased when the ratio of reinforcement passed over 15%. The gas nitriding process was applied to the produced composites to improve their surface properties. Strength values showed improvement after the nitriding process, and a thicker nitride layer was obtained on the steel sheath in highly deformed materials. As a result, the study presented the production of a composite with different sheath-core materials by rod drawing method and the effect of production variables on the material's mechanical properties. In addition, it was shown that the desired surface quality can be obtained by the gas nitriding process at low temperatures.

A Study on the Aging Behavior of Nitrided W18Cr4V Steel in High-Temperature Sodium

The loading and unloading elevators are the primary equipment in the refueling system, used for transferring fuel assemblies in the sodium-cooled fast reactors. The guideway friction pairs are the critical components of these elevators in the refueling system. With the excellent hardness and wear resistance in air, nitrided W18Cr4V steel is a promising material for the guideway friction pairs. In order to assess the feasibility of using nitrided W18Cr4V steel, it is essential to understand the aging behavior of nitrided W18Cr4V steel in high-temperature sodium. Aging tests were conducted on nitrided W18Cr4V steel in sodium and in argon environments at various temperatures for different exposure times. The results showed that the nitrogen atoms in the nitrided layer exhibited bidirectional diffusion behavior in the sodium or argon environment at 540 °C. Compared to the argon environment, cracks formed within the nitrided layer and the diffusion of nitrogen into the sodium was accelerated in the nitrided layer. As a significant number of nitrogen atoms had diffused into the sodium, there was little difference in the hardness between nitrided W18Cr4V steel and non-nitrided W18Cr4V steel after long-term exposure to 540 °C sodium.

ADJUSTABLE NITROOXIDATION TECHNOLOGY FOR LOW ALLOY STEEL

The article discusses the production of a surface diffusion nitride-oxide layer on low-alloy structural steel with specified structures and properties. To develop a controlled technology for nitro-oxidation of low-alloy carbon steel, the dependences of the composition and structure of the nitrided and oxide layer on the chemical composition of the steel and the technological parameters of the process were studied. Technical iron was used as a model alloy and samples of industrial steel grades 40X, P6M5 and steel 45 were processed. Saturation temperatures were studied in the ranges above and below the eutectoid temperature for the “Fe-N” system and, accordingly, for the “Fe-O” system and it was found that the best structures are at saturation temperatures below the eutectoid

Photo‐Induced Electrical Gating with the Inserting of an Interfacial Carrier Blocking Layer for Organic/Graphene Phototransistors

AbstractAlthough ultrahigh photoconductive gain is achieved in organic semiconductor‐sensitized graphene phototransistors, the response speed is limited by the photo‐induced carrier injection at the organic/graphene interface. In this work, an insulating hexagonal boron nitride layer is inserted between the organic heterostructure and graphene to block the interfacial carrier transport. Above the h‐BN layer, the organic heterostructure is adopted as the light‐absorbing layer, and the photoresponse of graphene is realized through electrical gating of the atop h‐BN dielectric layer, by the accumulated carriers in the organic heterostructure. Under this “photo‐induced electrical gating” mechanism, the recombination of nonequilibrium carriers takes place only within the organic heterostructure. Furthermore, monolayer perylene‐3,4,9,10‐tetracarboxylic dianhydride (PTCDA) is deposited on graphene before transfer of the h‐BN, by which the interfacial encapsulated bubbles are effectively reduced. As a step further, the trap states are pre‐filled with background light illumination, then the carrier recombination follows the band‐to‐band pathway. Finally, the response time of the organic/h‐BN/graphene phototransistor is reduced to 7.15 ms, and a high photoresponsivity is achieved even though the carrier multiplication is sacrificed, which is reconciled by the improvement of the device quantum efficiency.

Scratch Response of Hollow Cathode Radiofrequency Plasma-Nitrided and Sintered 316L Austenitic Stainless Steel

Low-temperature plasma nitriding is a thermochemical surface treatment that promotes surface hardening and wear resistance enhancement without compromising the corrosion resistance of sintered austenitic stainless steels. Hollow cathode radiofrequency (RF) plasma nitriding was conducted to evaluate the influence of the working pressure and nitriding time on the microstructure and thickness of the nitrided layers. A group of samples of sintered 316L austenitic stainless steel were plasma-nitrided at 400 °C for 4 h, varying the working pressure from 160 to 25 Pa, and the other group was treated at the same temperature, varying the nitriding time (2 h and 4 h) while keeping the pressure at 25 Pa. A higher pressure resulted in a thinner, non-homogeneous nitrided layer with an edge effect. Regardless of the nitriding duration, the lowest pressure (25 Pa) promoted the formation of a homogenously nitrided layer composed of nitrogen-expanded austenite that was free of iron or chromium nitride and harder and more scratching-wear-resistant than the soft steel substrate.

Investigation on the optimal ultra-precision machining of nitriding mold steel by in-situ laser assisted diamond cutting

S136 (STAVAX ESR) mold steel is an advanced material for the optical mold industry. The precisely machined surface quality is essential for guaranteeing the excellent performance of molds. Diamond cutting is a high-efficiency machining technique in optical mold manufacturing. However, the chemical wear of diamond tool is a huge challenge in precisely machining steel mold due to the reaction between atoms C and Fe. In this study, the hybrid machining technique which combined the in-situ laser assisted diamond cutting (LADC) and plasma nitriding was used to machine S136 mold steel. Furthermore, the impact of the various machining conditions on the machined workpiece surface roughness Sa was comprehensively investigated by the Taguchi method (TM) and Response surface methodology (RSM). The experimental results of material characterization indicated that a 90 μm nitride layer was generated on the workpiece surface by plasma nitriding. Analysis of variance (ANOVA) results demonstrated that the feed rate and laser power had an important impact on the machined surface roughness Sa. According to the RSM, a precise mathematical model was developed which is explored by experimental investigations. The results showed that the optimal machining parameter combination by RSM generated the better surface quality of 6.393 nm in in-situ LADC of nitriding steel. This study provides a reference for mold steel ultra-precision machining technique and parameter optimization method for surface integrity.

Design and study of a new QPQ combined with ultrasonic roller pressing method for gear surface strengthening

This study investigates a hybrid surface enhancement technique that combines Quench Polish Quench (QPQ) with ultrasonic rolling to augment the durability of 42CrMo gears against wear and fatigue. Analysis reveals that post-treatment, the composite nitride layer on the gear surface maintains its original phase composition, evidenced by the absence of new diffraction peaks in X-ray diffraction (XRD) patterns. Nevertheless, a noticeable broadening in these peaks suggests grain refinement and the presence of microstrain due to the rolling process. Incremental static pressures improve the mechanical characteristics of the surface, with the layer treated at 0.6 MPa exhibiting the lowest wear rate (3.15 × 10−8 mm3N−1 m−1). Oxidative wear increases at elevated temperatures (100 °C), yet under lubricated conditions, Coefficient Of Friction (COF) of the treated layer significantly reduces. The predominant wear mechanisms include mild abrasive wear, oxidative wear, and adhesion. Excessive impact force, particularly at 0.6 MPa, risks surface cracking and subsequent degradation in fatigue resistance. Optimal fatigue performance is achieved with a static pressure of 0.4 MPa, corresponding to a surface strength of 2300 MPa and a fatigue life of 3.23 × 106 cycles.

Structural and Optical Properties of Aluminium Nitride Thin Films Fabricated Using Pulsed Laser Deposition and DC Magnetron Sputtering on Various Substrates

Abstract Aluminium nitride thin films were fabricated using pulsed laser deposition and DC magnetron sputtering. Different technological parameters and the effects of different substrates on the optical and structural parameters of AlN samples were studied. An X-ray diffraction study was performed for the layer deposited on the Si3N4 substrate. A high-energy electron diffraction study was also carried out for the layer deposited on a KCl substrate. Transmission spectra of layers on quartz, sapphire, and glass substrates were obtained. An evaluation of the optical band gap of the obtained layers was carried out (Eg form 3.81 to 5.81 eV) and the refractive index was calculated (2.58). The relative density of the film (N1TN-AlN sample) is 1.26 and was calculated using the Lorentz-Lorentz relationship. Layers of aluminium nitride show an amorphous character with a polycrystalline region. It was shown that the properties of AlN films strongly depend on the method, growth conditions, and substrate used.

АНАЛИЗ ВЛИЯНИЯ ПРЕДВАРИТЕЛЬНОЙ И ЦИКЛИЧЕСКОЙ ПЛАСТИЧЕСКОЙ ДЕФОРМАЦИИ НА ХИМИКО-ТЕРМИЧЕСКУЮ ОБРАБОТКУ КОНСТРУКЦИОННЫХ СТАЛЕЙ

The subject of the study was thermodiffusion nitrided and silicified layers on steels obtained after plastic deformation. The influence of preliminary plastic deformation on the low-temperature nitriding process and cyclic plastic deformation on the high-temperature silicification process is studied. The results obtained are of interest for accelerating the production processes of chemical-thermal treatment of steels. It is established that preliminary surface plastic deformation contributes to the intensification of the process of ion-plasma nitriding of structural steel. The presence of high-temperature cyclic plastic deformation ensures the intensification of diffusion processes during the resorption of the diffusion silicified layer on structural steel.

A Review of Nanostructures in Electrowetting-on-dielectric Systems: From Nanostructured Dielectric Layers to Nanofluids

Abstract: The extensive interest in electrowetting-on-dielectric (EWOD) as a key in advancing the efficiency and controllability of fluid-based microelectromechanical and actuator systems has resulted in a deluge of technological research, especially in the area of microfluidics, liquid lenses, and fluid-based lab-on-chips. More recently, the integration of nanostructures into EWOD-driven devices has shown promising improvement in these devices’ performance, design, and miniaturization. Due to the exceptional properties, availability, versatility, and tunability of nanostructures, they are being utilized as components of EWOD systems for various applications. Utilization ranges from fabricating nanodimensional dielectric layers to incorporating nanoparticles in fluid droplets. With the current trend in improving the performance and functionality of EWOD-driven devices at low voltage operations, it is timely to revisit the fundamental principle of EWOD phenomena and how it is extended experimentally using nanostructures. In this paper, we present the different nanostructures investigated as dielectric materials in various EWOD experiments focusing on metal oxide and silicon nitride layers. Notes on the structure of these dielectric layers are also presented. Furthermore, various EWOD experiments employing nanofluid droplets are also described. This paper provides a clear picture of nanostructures’ diverse impact on the advancement of EWOD technology. The insights presented in this paper may also serve as a guidepost for future exploration and development of the role of nanostructures in EWOD-driven devices.

The Effect of La on the Surface Properties of Plasma Nitrided CoCrCuFeNi High-Entropy Alloys at 440 Degrees Celsius

This paper investigates the effect of the element La on plasma nitriding of the CoCrCuFeNi high-entropy alloy (HEA) at 440 °C for 8, 16, and 24 h. The phase composition, morphology, and hardness distribution of the nitrided layer are characterized using XRD, optical microscopy, and a microhardness tester. Furthermore, the corrosion resistance is tested using an electrochemical workstation. The study evaluated the friction and wear performance using a testing machine and scanning electron microscope. The thickness of the effective hardening layer after 16 h of treatment with La was similar to that after 24 h of treatment without La. The addition of La significantly increased the growth rate constant of the effective hardening layer from 0.53 × 10−14 m2/s to 0.72 × 10−14 m2/s. In addition, an expanded FCC phase with greater interplanar spacing can be formed on the surface of the sample by introducing La into the plasma nitriding process. This indicates that the expanded FCC phase, with a higher concentration of interstitial nitrogen atoms, can effectively improve the corrosion resistance of the specimen surface. The corrosion rate of the specimen surface was reduced by 27.5% and the wear rate was reduced by 41.7% after 16 h of treatment with the addition of La compared to 24 h of nitriding without the addition of La. It has been shown that the addition of La to the plasma nitriding process results in a higher quality nitrided layer in a shorter time and also demonstrates that La has the potential to optimize the surface properties of plasma nitrided HEAs.

Revealing the mechanism of interfacial adhesion enhancement between the SiO2 film and the GaAs substrate via plasma pre-treatments

The formation mechanism of a highly adherent silicon dioxide (SiO2) film on gallium arsenide (GaAs) substrate by plasma enhanced chemical vapor deposition (PECVD) is proposed. Ar, N2, and NH3 were used as pre-treatment gas to improve the interfacial adhesion. The interfacial adhesion was measured by the cross-cut tape test. By the measurement of spectroscopic ellipsometry and x-ray photoelectron spectroscopy (XPS), it is revealed that nitrogen plasma pre-treatment had formed a very thin GaN transition layer on the surface, which was responsible for the improvement of interfacial adhesion. XPS depth-profiling further confirmed various pre-treatment gases generate plasma mixtures and form thin film layers with different compositions on the GaAs surface. These layers have a significant impact on the adhesion of the subsequently prepared SiO2 film. The primary mechanism for improving interfacial adhesion is the renovation of the substrate composition via plasma pre-treatment by PECVD, which forms a transition layer of nitrides that eliminates the negative effects of oxides on adhesion. This study reveals the mechanism of interfacial adhesion enhancement between SiO2 film and GaAs substrate, which is of significant importance in fabricating high-performance and reliable semiconductor devices.

Novel high-efficiency plasma nitriding process utilizing a high power impulse magnetron sputtering discharge

Lifetime and biocompatibility of orthopedic implants are crucial in meeting the new challenges brought about by the fall in the patient age and the aging population. The high-load surfaces in contact with the biological environment must display enhanced tribological properties, biocompatibility, and reduced metal ion release in long-term clinical performance. Surface modification techniques such as nitriding can significantly improve the in-service behavior of the medical-grade alloys in current use. We report on a novel approach for nitriding of CoCrMo alloys using high power impulse magnetron sputtering (HIPIMS) discharge. The new nitriding process has been successfully carried out at the National HIPIMS Technology Centre at Sheffield Hallam University, UK, in an industrial size Hauzer 1000-4 system enabled with HIPIMS technology. While the nitriding ion flux is controlled by the HIPIMS magnetron plasma source, the ion energy can be independently set via the substrate bias. Implementing the HIPIMS source allows reducing the operational pressure by one order of magnitude compared to conventional dc plasma nitriding (DCPN). Plasma analyses have identified significantly enhanced production of ions of molecular nitrogen (N2+), atomic nitrogen (N+), and N2H+ radicals in the HIPIMS discharge compared to DCPN. Because of the low pressure of operation of the HIPIMS process, the energy of ions is similar to the bias voltage, whereas the high pressures used in DCPN cause severe losses in ion energy due to scattering collisions within the sheath. The high flux and high ion energy are primarily responsible for achieving a fourfold increase in process productivity as compared to state-of-the-art plasma nitriding processes. The nitrided surface layers exhibit excellent mechanical and tribological properties, which bring about significant improvements in hardness, fracture toughness, and wear. The protective function of the nitrided layer against corrosion in the aggressive environments of simulated body fluid is remarkably augmented. The barrier properties of the nitrided layer have been demonstrated through a reduction in metal ion release by as much as a factor of 2, 4, and 10 for Co, Cr, and Mo, respectively.