Nitride Layer Research Articles

Distance Dependence of the Energy Transfer Mechanism in WS_{2}-Graphene Heterostructures.

We report on the mechanism of energy transfer in Van der Waals heterostructures of the two-dimensional semiconductor WS_{2} and graphene with varying interlayer distances, achieved through spacer layers of hexagonal boron nitride (h-BN). We record photoluminescence and reflection spectra at interlayer distances between 0.5 and 5.8nm (0-16 h-BN layers). We find that the energy transfer is dominated by states outside the light cone, indicative of a Förster transfer process, with an additional contribution from a Dexter process at 0.5nm interlayer distance. We find that the measured dependence of the luminescence intensity on interlayer distances above 1nm can be quantitatively described using recently reported values of the Förster transfer rates of thermalized charge carriers. At smaller interlayer distances, the experimentally observed transfer rates exceed the predictions and, furthermore, depend on excess energy as well as on excitation density. Since the transfer probability of the Förster mechanism depends on the momentum of electron-hole pairs, we conclude that, at these distances, the transfer is driven by nonrelaxed charge carrier distributions.

Surface nano crystallization and nitriding on microstructure and properties of 304J1 stainless steel

To improve the mechanical and antibacterial properties of 304J1 stainless steel, hybrid surface treatments, which include nitriding combined with shot peening operations, are used. Shot peening with different sizes of steel balls makes the material’s surface nanocrystalline, providing more diffusion channels for subsequent nitrogenating, and the nitriding efficiency is improved. Nitrogen cannot only improve the antibacterial property but also significantly enhance the strength of 304J1. The experimental results show that within a certain depth, the surface of 304J1 can be nanosized by shot peening for 20 min with a projectile diameter of 0.2 mm. The depth of the nitriding layer reaches 0.6 um, the surface hardness increases from 560 HV to 1100 HV, and the antibacterial property against Escherichia coli increases from 10% to 85%.

Diffusion Nitride Surface Layers on Aluminum Substrates Produced by Hybrid Method Using Gas Nitriding

While gas nitriding of steel is currently used in industry, nitriding of aluminum alloys remains an open challenge. The main obstacle is aluminum’s high susceptibility to passivation. The oxide film provides an effective barrier to nitrogen diffusion. Attempts to overcome this problem have mainly focused on glow discharge nitriding using cathode sputtering of an oxide layer. The produced AlN layers exhibit no diffusion zone and show limited performance properties. In this work, the effect of hybrid treatment aimed at producing diffusion layers of nitrides other than AlN on aluminum alloys was investigated on the model system of iron nitride–aluminum substrate. Hybrid treatment combines an electrochemical process involving the removal of the aluminum oxide layer from the substrate, its subsequent iron plating, and a further gas nitriding in high-purity ammonia. The obtained results prove that the hybrid treatment allows the production, at 530 °C/10 h, of diffusion layers of Fe3N iron nitrides on aluminum substrates with a nitrogen diffusion zone range in aluminum of ca. 12 µm. In alloys containing magnesium, its unfavorable effect on the nitrogen diffusion and the functional properties of the layers was observed. An interesting direction for further research is hybrid treatment of precipitation-hardened alloys without magnesium.

Effect of combined laser shock peening and nitrogen implantation on the microstructure and tribology of M50 bearing steel

The M50 bearing steel underwent a combined treatment of laser shock peening (LSP) and nitrogen ion implantation. The microstructure, surface mechanical properties and tribological behaviors were evaluated. Comparative analysis with the untreated sample revealed significant improvements in surface nano-hardness, increasing from 7.51 GPa to 11.35 GPa, 11.51 GPa, and 12.62 GPa for samples subjected to LSP, ion implantation, and combined strengthening, respectively. Correspondingly, surface compressive residual stress showed notable increases from −15.55 MPa to −1043.76 MPa, −451.34 MPa, and −1276.13 MPa, respectively. The improved surface mechanical properties observed in the combined strengthened sample are likely due to the synergistic effects of the combined strengthening. In friction tests, the combined strengthened sample exhibited the lowest friction coefficient, attributed to the presence of a metal nitride layer and a thicker amorphous layer. Wear mechanisms transitioned from fatigue spalling for the untreated specimen to slight wear and the formation of an oxidative adhesion layer after LSP and ion implantation. Remarkably, the surface of the combined strengthened specimen demonstrated minimal wear, with only an oxidative adhesion layer present.

Experimental Study on Turbine Blade Material

This experimental study investigates the nitriding effects on microstructure of wrought 17-4 PH stainless steel. Nitriding was carried out at 560 °C for 2 hours, resulting in significant improvements in hardness. Nitriding improves the hardness on the surface of the 17-4 PH steel and remains constant in the core. As a result of nitriding the harness increased 3.5 times the hardness of the wrought alloy. Microstructural analysis of both untreated and nitrided samples using a scanning electron microscope (SEM) equipped with energy-dispersive X-ray spectroscopy (EDS) revealed the formation of a nitride layer. The results show a relationship between nitriding temperature and nitride layer thickness, with higher temperatures leading to thicker layers.

Microstructure, mechanical and corrosion behavior of CrNx/Al2O3 multilayer films deposited by magnetron sputtering

A novel design was adopted to improve corrosion resistance of 2024 Al alloys by magnetron sputtering CrNx based multilayer films with Al2O3 intercalation. The multilayer films were composed of inhomogeneous structure, i.e., thick CrNx transition layer (∼2 μm) + CrNx/Al2O3 multilayer (∼1 μm). The effect of Al2O3 interlayer and modulation period on microstructure and performance of multilayer films were investigated. The nitride layer was dominated by Cr2N and CrN with minor Cr, while the Al2O3 layer displayed in the amorphous form. The intercalation of Al2O3 blocked the columnar growth in CrNx layers and refined the grains. As the period increased, the cluster particle size decreased and the mechanical properties increased, with the maximum hardness and modulus at CN-8 (19.13 GPa and 282.2 GPa). In addition, the multilayer structure enhanced the bonding between the film and the substrate, and has an improvement on the hard and brittle properties of the film. The multilayer films showed improved corrosion resistance than the CrNx mono-layer in 3.5 wt% NaCl solution. The film with CrNx-top layer showed superior corrosion resistance than the film with Al2O3-top layer. The increasing period also enhanced corrosion resistance, showing an excellent corrosion potential and corrosion current density (Ecorr=-0.538 V, icorr=0.96 μA·cm−2) at CN-8.

Improved tribological behaviour of super duplex stainless steel through plasma nitriding at ultra-low temperature without prior polishing

Super duplex stainless steels (SDSS), widely used in industries such as offshore oil and gas, offer a unique combination of high strength and corrosion resistance. However, surface hardening treatments are crucial to enhance their performance and extend service life. This work investigates the effect of plasma nitriding on the tribological behaviour of SDSS SAF 2507. Samples are treated without prior polishing (as received, AR) at ultra-low temperatures (250 and 300 °C) aiming to avoid detrimental CrN precipitation. Comprehensive microstructural characterization, corrosion studies, and tribological tests (scratch and ball-on-disc) are conducted on samples that do not present CrN (PN). Results indicate that the hardness of PN samples nearly doubles that of AR samples due to the presence of expanded austenite. Corrosion tests show improvements in passivity for PN samples. In scratch tests, while the AR material undergoes progressive plastic deformation, in PN material the nitrided layer breaks down only after reaching a critical load. In ball-on-disc test, wear rates are remarkably lower for PN condition compared to AR condition. Wear mechanism is tribo-oxidative and abrasive for the AR condition. Wear of PN samples is characterized by asperity break-off and ratcheting. The nitrided layer in PN samples exhibits an enhanced load-bearing capacity that improves wear resistance in both tests.

Surface Nitriding Enables Improved Intercalation Pseudocapacitance of T−Nb2O5 for Lithium‐Ion Batteries

AbstractThe low electrical conductivity limits the application of T−Nb2O5 as anode materials for practical applications. The large‐grain T−Nb2O5 nanowires with nitrogen doping are obtained by simple hydrothermal and annealing treatments. After nitriding with ammonia, an amorphous layer of NbON as an intermediate is formed and then the new crystalline NbN is generated with the deepening of the nitriding degree, causing homogeneous pores on the surface of the T−Nb2O5 and thus increasing the specific surface area. Meanwhile, the formation of the nitriding layer enhances the electrical conductivity, inducing a pseudo‐capacitance mechanism. Therefore, the N−T−Nb2O5 nanowire demonstrates superior electrochemical performance. Specifically, the 45N−T−Nb2O5 nanowires delivered a first reversible specific capacity of 238.33 mAh g−1 at 0.1 C, higher than of theoretical capacity (201.6 mAh g−1). However, the excessive nitride will be completely converted into NbN, reducing the initial lithium storage of the material due to the lack of a lithium storage site, which has not been previously discussed. Besides, at the high rate of 100 C, with the deepening of nitride degree of the T−Nb2O5, the higher the rate performance. Therefore, to find the balance between the high rate performance and the initial lithium storage amount, the nitride degree should be strictly controlled.

Highly Thermally Conductive Flexible Biomimetic APTES-BNNS/BC Nanocomposite Paper by Sol-Gel-Film Technology.

Owing to the evolution of 5G technology, new energy vehicles, flexible electronics, miniaturization and integration of microelectronic devices, high-frequency and high-power devices, and thermal management of materials must consider additional limitations such as electrical insulation, excellent transverse heat transfer, flexibility, and weight. Boron nitride nanosheets (BNNSs) are ideal insulating materials with high thermal conductivity. However, the problem of the 3D thermal conductivity pathway and toughness strength of nanocomposite paper loaded with inorganic thermal conductivity fillers remains a huge challenge. In this study, we propose a new method for preparing ultrathin, large, and uniformly thick BNNS for quantitative production. Bulk hexagonal boron nitride (hBN) layers were exfoliated using a simple and low-cost hydrothermal reaction, and large-scale fewer-layered BNNSs were efficiently prepared by ball milling with a high yield (up to 80%). Based on the aforementioned step, a flexible insulating composite film with high thermal conductivity and a natural "brick-mud" shell structure was constructed via the sol-gel-film conversion method. After prestretching and hot-pressing treatment, the hydrogels became denser, and the modified BNNS formed a three-dimensional (3D) network structure with an ordered orientation and interconnections in the bacterial cellulose (BC) matrix. After 100 folding cycles, the tensile strength of the nanofiber composite film reached 53 MPa, and the strength retention rate exceeded 42%. By optimizing the modified BNNS content, the thermal conductivity reached 24 W/(m·K). This simple approach has wide application potential in the next-generation electronic devices, providing options for designing thermal interface materials with excellent electrical insulation, high thermal stability, and flexibility.

Effect of PVD deposition method on indentation and friction wear characteristics with hydrogen embrittlement of CrN coated stainless steel for electric vehicle hydrogen valves

In this investigation, a chromium nitride layer was deposited on general austenite stainless steel (UNS S31603) by means of the physical vapor deposition coating method to improve the hardness, wear resistance, and hydrogen embrittlement resistance. Accordingly, the purpose of this investigation is to study the effect of different physical deposition methods on mechanical characteristics due to hydrogen embrittlement. Both the indentation and friction characteristics of the chromium nitride layer with in response to hydrogen embrittlement were examined. The ion beam-assisted deposition (IBAD) and arc ion plating (AIP) methods were used to densely deposit the coating layer with a thickness of approximately 2.0∼2.5 μm, and the hardness increased by around 1180.9 HV and 1638.6 HV, respectively, when compared with the base material (292.6 HV). In terms of the coating layer deposited using the IBAD method, all the base material was exposed after hydrogen embrittlement for 3 h, whereas in the case of the coating deposited using the AIP method, the base material began to be exposed locally following hydrogen embrittlement for 12 h. For the IBAD- and AIP-deposited coatings, the average friction coefficient was calculated as 0.52 and 0.34, respectively. In the case of the coating layer deposited using the IBAD method, the average friction coefficient increased by 0.29 after hydrogen embrittlement for 3 h, whereas the average friction coefficient of the coating layer deposited using the AIP method increased by 0.04 after hydrogen embrittlement for 48 h. Therefore, it can be seen that the AIP method is significantly better than IBAD in terms of mechanical characteristics with hydrogen embrittlement.

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