Stable Nitride Research Articles

High-throughput exploration of stable semiconductors using deep learning and density functional theory

Semiconductors can lead to new applications and technological innovations. In this work, we developed a computational pipeline to discover new semiconductors by combining deep learning and high-throughput first-principles calculations. We used a random strategy combined with group and graph theory to generate initial boron nitride polymorphs and developed a classifier based on graph convolutional neural network to screen semiconductors and study their stability. We found 26 new stable boron nitride polymorphs in Pc phase, of which 3 are direct bandgap semiconductors, and 10 are quasi-direct bandgap semiconductors. This discovery not only expands the library of known semiconductor materials but also provides potential candidates for high-performance electronic and optoelectronic devices, paving the way for future technological advancements.

Synthesis and Characterization of Titanium Nitride-Supported Iridium-Nickel Alloys as Highly Active Electrocatalysts for Hydrogen Evolution Reaction

Iridium serves as the active electrocatalyst in driving the hydrogen evolution reaction (HER), an important process in water-splitting technology for the production of green hydrogen. However, the expensive cost and limited durability of Ir-based catalysts have hindered the widespread application of HER. Thus, there is research interest in reducing the mass loading of Ir and enhancing long-term stability. In this work, we synthesized highly stable titanium nitride (TiN) to serve as the supporting material for low-loading Ir-Ni alloys (Ir-Ni/TiN) utilized in HER. The TiN was derived from the pyrolysis of titania nanotubes (TNT) with melamine, resulting in a higher surface area than commercial TiN. Additionally, varying percentages of Ni were employed to investigate the influence of alloy composition on Ir catalytic activity. Electrochemical tests conducted in both 0.5 M H2SO4 and 1.0 M KOH media demonstrated that Ir-Ni/TiN exhibited enhanced activity, with ultra-small overpotentials (η10) of 8 mV and 22 mV, respectively. Furthermore, the utilization of TiN substantially was illustrated to increase the long-term stability of the catalyst compared to carbon-support materials. Therefore, this study provides an effective strategy for improving the performance of Ir-based electrocatalysts in HER.

High-temperature oxidation resistance and wear properties of functionally graded CrHfNbTaTiN high-entropy nitride coating on Ti alloy

High-entropy nitrides have emerged as promising alternatives to traditional protective coatings due to their excellent comprehensive properties. However, there is still a long-standing technical challenge in the design and manufacture of hard and high-temperature stable high-entropy nitride coatings. This study utilized first-principles calculations to evaluate the thermodynamic stability between high-entropy nitrides and corresponding high-entropy metals, as well as titanium alloy substrates, confirming the rationality of the structural design of the functional gradient high-entropy ceramic coating. Subsequently, a double-glow plasma surface alloying technique were conducted to prepare a CrHfNbTaTiN functional gradient high-entropy ceramic coating on titanium alloy, followed by high-temperature cyclic oxidation experiments and high-temperature ball-on-disk wear tests. The research demonstrates that the gradient composition coating exhibits strong interfacial bonding, with an adhesion strength of around 40 N. It maintains excellent oxidation resistance in environments below 700 °C and displays good high-temperature wear resistance. This study contributes to providing insights and guidance for the further development of high-temperature, high-hardness, and wear-resistant materials.

Two-dimensional tetragonal carbon nitride semiconductors with fascinating electronic/optical properties and low thermal conductivity

Abstract Exploring two-dimensional (2D) tetragonal carbon nitride materials is significant for unlocking new physical properties beyond those offered by traditional hexagonal lattices. In this work, we propose three theoretically stable 2D carbon nitride monolayers with tetragonal lattices, namely T-C3N, P-C3N, and PH-C5N4. Electronic structure calculations indicate that all three monolayers exhibit semiconducting characteristics, with T-C3N showing interesting flat band features. Additionally, these three carbon nitrides exhibit anisotropic and high carrier mobilities and excellent light absorption capabilities in the visible-light and near-infrared regions. Meanwhile, the calculated thermal conductivity (κp) of PH-C5N4 is 63.9 Wm−1K−1 at room temperature, significantly outperforming T-C3N (12.2 Wm−1K−1) and P-C3N (18.9 Wm−1K−1). Phonon scattering rates and Grüneisen parameters confirm the origin for the relatively high κp in PH-C5N4. Our study proposes three tetragonal carbon nitride structures with novel physical properties, which lays a theoretical foundation for the multifunctional applications of 2D carbon nitride materials.

Catalytic performance of hexagonal boron Nitride@ APTS-SO3H as heterogeneous nanocatalyst for biodiesel production

In this study, the synthesis of a new stable hexagonal boron nitride (h-BN) is reported via the combustion of boric acid and urea using a pyrolysis method. The surface of hBN particles was modified and the physical/chemical properties of h-BN-APTS-SO3H were examined by different characterization, confirming the modification of h-BN. The effects of methanol/acid molar ratio, temperature, and amount of catalyst were investigated. The results showed that the optimal conditions for the esterification of palmitic acid were as follows: methanol to a palmitic acid molar ratio of 30:1, a temperature of 50 °C, a catalyst of 300 mg for 5 h, and a maximum yield of biodiesel of 90 % was achieved. Furthermore, the quality parameters of the biodiesel were made according to ASTM methods [ASTM D445: Kinematic viscosity, ASTM D445: Flash-point, ASTM D92: Ash content, ASTM D6751: Density]. Tests indicate that the quality parameters of the prepared biodiesel were within ASTM standards. Significantly, the h-BN@APTS-SO3H(1) catalyst showed excellent stability on repeated reuse and can be recycled several times without much activity loss.

Effect of Ti micro-addition on the hot tensile behaviour, microstructure and fractography of low-C high-manganese steels

The aim of the work was to determine the effect of Ti micro-addition on the hot tensile behaviour, microstructure and fractography of two low-C high-manganese steels with additions of Si and Al. The hot tensile tests were performed using the Gleeble 3800 thermomechanical simulator. Samples were stretched at a temperature range from 1050 ℃ to 1200 ℃ at a strain rate of 2.5·10 3 s−1. The microstructure of the tested high-manganese steels under conditions of hot deformation was influenced by strain hardening and simultaneous dynamic recrystallization, as well as precipitation processes-depending on the chemical composition of the alloy and plastic deformation parameters. The analysis of the curves registered in the hot tensile tests indicated that a decrease of strain hardening was the result of the dynamic recrystallization. Hot tensile curves of the Ti-micro-alloyed steel were characterized by higher yield stress compared to the Ti-free steel. The Ti micro-addition with a concentration of 0.075 wt.% guaranteeing stable TiN-type nitrides eliminated the possibility of precipitating AlN-type nitrides and complex MnS-AlN type non-metallic inclusions, which are harmful to hot ductility. Fracture modes of the Ti-free steel showed a mixed nature from 1050 ℃ to 1150 °C, i.e. ductile fracture and numerous cavities and voids were identified. As the deformation temperature increased to 1200 °C, the fracture character was brittle with numerous inter-crystalline cracks along austenite grain boundaries. The addition of Ti improved significantly the hot ductility behaviour characterized by higher values of flow stress and reduction in area as well as ductile fracture modes in the entire high deformation temperature range.

Theoretical exploration of ternary nitrides for high-efficiency ferroelectric photovoltaics

Although nitride materials hold great functional promise, ferroelectric photovoltaic nitrides remain relatively rare within the scientific community. In this study, high-throughput calculations have been employed to explore and predict novel stable ternary nitrides characterized by both high photoelectric conversion efficiency and robust ferroelectric polarization. Notable candidates, including Mg2CrN3, Mg2MnN3, MgVN2, ZnVN2, and X2BiN3 (where X represents Mg, Ca, and Sr), are anticipated to exhibit remarkable ferroelectric photovoltaic properties, with a particular emphasis on efficiently harnessing visible light. The incorporation of early 3d transition metals and bismuth (Bi) elements within ternary metal nitrides is highlighted as a key strategy for achieving high ferroelectric photovoltaic efficiency. Furthermore, these ferroelectric nitrides demonstrate relatively high carrier mobilities, which are conducive to facilitating the transport of photogenerated carriers driven by ferroelectricity. This research offers a selection of promising ternary nitride candidates with substantial potential for application in the field of ferroelectric photovoltaics.

Tolerance Factor and Phase Stability of the KCoO2-Type AMN2 Nitrides.

In order to help understand the structural stability of KCoO2-type ternary nitrides AMN2, referring to perovskite structure, a tolerance factor t is proposed to describe the size effect on the phase/symmetry options of the experimentally accessible AMN2 nitrides. This leads to a range of t values above 0.946 for structurally stable KCoO2-type AMN2 nitrides with t values around 0.970 for the orthorhombic and tetragonal phase boundary. In contrast, most of AMN2 nitrides exhibit α-NaFeO2-type structure with t ∼ 0.898-0.946 and cations ordered or disordered rocksalt structure while t below 0.898. Employing the proposed criterion, the structure formation for other ternary AMN2 compositions with lanthanum and alkaline earth cations for the A sites were predicted, which was testified through the synthesis attempts and complemented by formation energy evaluations. The efforts to synthesize the ternary Lanthanide and alkaline earth-based AMN2 nitrides were unsuccessful, which could associate the structural instability with the large formation energies of lanthanide nitrides LaMN2 and the greater tolerance factor of 1.048 for BaTiN2. The experimentally already synthesized AMN2 nitrides could be categorized into three types with different tolerance factors, and scarce AMN2 nitrides with lower formation energies would be accessible using different synthetic routes beyond the traditional solid-state synthesis method.

Single-atom catalytic N2 fixation with integrated descriptors on a novel π-π conjugated graphitic carbon nitride (g-C13N15) platform obtained by self-doping design: Prediction of ultrahigh activity and desirable selectivity

Great enthusiasm in nitrogen reduction reaction (NRR) towards the robust design of efficient catalysts is being stimulated by a promising active moiety featured by metal-Nx, yet tackling the activity and selectivity dilemmas remains one of the most urgent and challenging tasks. Herein, based on a self-doping strategy and first-principles calculations, an emerging and stable graphitic carbon nitride, g-C13N15, is rationally proposed for the first time, and TM@g-C13N15 (TM = from Ti to Au) single-atom catalysts benefiting from delocalized π−π conjugated interactions between substituted C3N3 rings toward NRR are constructed. High-throughput “Four-Step” screening strategy helps Re@g-C13N15 stand out from 23 TM-centers quickly since the binding strength of the target *N2H and *NH2 adsorbates can be manipulated by Re to compromise. First-principles calculations reveal that Re@g-C13N15 possesses satisfactory selectivity and impressively, miserly energy consumption with a low limiting potential of −0.20/-0.31 V for side-on/end-on N2-adsorption. Also, good thermodynamic stability, large Re-diffusion barrier, outstanding electrochemical durability, and facile synthesis for Re@g-C13N15 ensure its implementations in ambient conditions. Particularly, good linear relationships between descriptors (ICOHP, Bader charge, bond length, d-band center, and spin moment) are established to describe/explain intrinsic activity trends/mechanism, bridging the relation between the intrinsic property and activity.

Microstructural characteristics of different heat-affected zones in welded joints of UNS S32304 duplex stainless steel using the GMAW process: analysis of the pitting corrosion resistance

Abstract The influence of specific microstructural characteristics on the properties of single-pass welding joints was assessed by optical processed images, transmission electron microscopy, microhardness measurements and corrosion tests conducted in various regions of the heat-affected zone (HAZ) in a lean duplex stainless steel. The welded joints were obtained with heat inputs of 1.5 and 2.5 kJ/mm using a gas metal arc welding (GMAW) process with a shielding gas enriched in Ar. Three selected regions in the HAZ showed different ferrite grain sizes and austenite fractions. The place in the welded joint where the HAZ was narrowest, and therefore experiences the highest cooling rate, is most prone to the formation of cubic CrN metastable nitrides. Conversely, the place where the HAZ was wider promotes the precipitation of stable Cr2N nitrides with more coalesced intragranular austenite (IGA) particles, where presumably random interfaces predominate. The HAZ region where the cooling rate was the highest presented more pitting corrosion resistance.

A new 3D metallic, ductile, and porous boron nitride as a promising anode material for sodium-ion batteries.

We propose a new stable three-dimensional (3D) porous and metallic boron nitride anode material, named h-B10N12, with good ductility for sodium-ion batteries (SIBs). Based on first-principles calculations and a tight-binding model, we demonstrate that the metallicity originates from the synergistic contribution of the p-orbital of the sp2-hybridized B and N atoms, while the ductility is due to the unique configurations of B-B and N-N dimers in the structure. More importantly, this boron nitride allotrope exhibits a high reversible capacity of 582.21 mA h g-1 in gravimetric density and 663.72 mA h cm-3 in volumetric density, fast Na-ion transport dynamics with low energy barriers ranging from 0.06 to 0.12 eV, a small volume change of 2.77%, and a long cycle-life. This study not only expands the family of conventional boron nitride materials with new features, but also enriches the family of anode materials for SIBs with high performance.

Modifying the electronic and magnetic properties of the scandium nitride semiconductor monolayer via vacancies and doping.

In this work, the effects of vacancies and doping on the electronic and magnetic properties of the stable scandium nitride (ScN) monolayer are investigated using first-principles calculations. The pristine monolayer is a two-dimensional (2D) indirect-gap semiconductor material with an energy gap of 1.59(2.84) eV as calculated using the GGA-PBE (HSE06) functional. The projected density of states, charge distribution, and electron localization function assert its ionic character generated by the charge transfer from the Sc atoms to the N atoms. The monolayer is magnetized by a single Sc vacancy with a total magnetic moment of 3.00μB, while a single N vacancy causes a weaker magnetization with a total magnetic moment of 0.52μB. In both cases, the magnetism originates mainly from the atoms closest to the defect site. Significant magnetization is also reached by doping with acceptor impurities. Specifically, a total magnetic moment of 2.00μB is obtained by doping with alkali metals (Li and Na) in the Sc sublattice and with B in the N sublattice. Doping with alkaline earth metals (Be and Mg) in the Sc sublattice and with C in the N sublattice induces a value of 1.00μB. In these cases, either magnetic semiconducting or half-metallicity characteristics arise in the ScN monolayer, making it a prospective 2D spintronic material. In contrast, no magnetism is induced by doping with donor impurities (O and F atoms) in the N sublattice. An O impurity metallizes the monolayer; meanwhile, F doping leads to a large band-gap reduction of the order of 82%, widening the working regime of the monolayer in optoelectronic devices. The results presented herein may introduce efficient methods to functionalize the ScN monolayer for optoelectronic and spintronic applications.

Wide-direct-band-gap monolayer carbon nitride CN2: a potential metal-free photocatalyst for overall water splitting.

Two dimensional metal-free semiconductors with high work function have attracted extensive research interest in the field of photocatalytic water splitting. Herein, we have proposed a kind of highly stable monolayer carbon nitride CN2 with an anisotropic structure based on first principles density functional theory. The calculations of electronic structure properties, performed using the HSE06 functional, indicate that monolayer CN2 has a wide direct band gap of 2.836 eV and a high work function of 6.54 eV. And the suitable band edge alignment, high electron mobility (∼103 cm2 V-1 s-1) and visible-light optical absorption suggest that monolayer CN2 has potential on visible-light photocatalytic water splitting at pH ranging from 0 to 14. Moreover, we have observed that uniaxial strain can effectively control the electronic structure properties and optical absorption of monolayer CN2, which can further improve its solar to hydrogen efficiency from 9.6% to 16.02% under 5% uniaxial tension strain along the Y direction. Our calculations have not only proposed a new type of potential metal-free photocatalyst for water splitting but also provided a functional part with high work function for type-I and scheme-Z heterojunction applied in photocatalytic water splitting.

Searching for the Rules of Electrochemical Nitrogen Fixation.

Li-mediated ammonia synthesis is, thus far, the only electrochemical method for heterogeneous decentralized ammonia production. The unique selectivity of the solid electrode provides an alternative to one of the largest heterogeneous thermal catalytic processes. However, it is burdened with intrinsic energy losses, operating at a Li plating potential. In this work, we survey the periodic table to understand the fundamental features that make Li stand out. Through density functional theory calculations and experimentation on chemistries analogous to lithium (e.g., Na, Mg, Ca), we find that lithium is unique in several ways. It combines a stable nitride that readily decomposes to ammonia with an ideal solid electrolyte interphase, balancing reagents at the reactive interface. We propose descriptors based on simulated formation and binding energies of key intermediates and further on hard and soft acids and bases (HSAB principle) to generalize such features. The survey will help the community toward electrochemical systems beyond Li for nitrogen fixation.

Synthesis and magnetic properties of [formula omitted]-Fe16N2 nanofibers prepared by an electrospinning method

Although the iron-nitride α″-Fe16N2 phase exhibits excellent magnetic properties, its poor thermal and phase stability pose challenges in the fabrication of bulk-type samples. In particular, the low nitriding temperature, below 200 °C, increases possibility of forming the stable nitride phase with higher nitrogen content on the surface due to the slow diffusion rate of nitrogen atoms. To overcome this problem, it is crucial that the α-Fe precursors are small in size, well-dispersed, and that the post-heat treatment is conducted below 200 °C. In this study, we successfully demonstrated the fabrication of α″-Fe16N2 nanofibers through electrospinning process and a two-step heat treatment procedure involving hydrogen reduction at 290 °C for 2 h, followed by nitration at 160 °C for 12 h in an ammonia gas flow rate of 1.5 L/min. Furthermore, these α″-Fe16N2 nanofibers exhibited a saturation magnetization (M2.5T) of 182 emu/g, a residual magnetization (Mr) of 76.1 emu/g, and a coercivity (Hc) of 1.29 kOe.

Template-free synthesis of water-vapor stable porous 3D boron nitride

Due to its high thermal stability, dipolar structure, and easy synthesis porous boron nitride is a promising material in adsorption, catalysis, and gas storage. However, recent investigations showed that micro-mesoporous boron nitride is highly water-susceptible and reacts quickly with water to boron oxide and ammonia. Key parameters such as boron oxide content, crystallinity, and porosity primarily influence the water stability. Previous studies indicate that the synthesis of boron nitride without any microporosity could lead to a water-vapor stable product. Thus, this work pursues the template-free synthesis of solely meso-macroporous boron nitride. In order to achieve this, the influence of different nitrogen flow rates on the porosity of boron nitride was investigated. In addition, a pre-heating step was introduced which led to the successful synthesis of a meso-macroporous material. By varying the precursor ratio up to urea to boric acid 4–1, the porosity of the product was increased up to a BET surface area of 361 m2 g-1. To analyse the water stability, water-vapor adsorption was used. This enabled us to demonstrate the successful synthesis of highly water-vapor stable porous boron nitride.

Study on Hot Corrosion of Low-Nickel Cladding Metals Containing Nitrogen in K2SO4-MgSO4 Binary Molten Salt

Molten salt is usually used as the energy storage medium for solar energy heat storage pipes, and 40wt% K2SO4 + 60wt% MgSO4 is very suitable for use as a heat storage material for solar thermal power generation in tower and butterfly parabolic systems. The demand for high-temperature thermal energy storage systems has prompted research on low-cost alloys for use in high-temperature and corrosion-resistant environments. The 44% Ni-24% Cr-0.18N nitrogen-containing low-nickel flux-cored welding wire designed in this article has a corrosion resistance of up to 900 °C after welding repair, which is better than the repair ability of Inconel 625 flux-cored welding wire. Using the high-temperature static immersion corrosion method, the corrosion behavior of two deposited metals immersed in molten salt for 60 h at 900 °C was assessed. The corrosion product phase composition, corrosion morphology, and elemental distribution of the two deposited metals were systematically studied using X-ray diffraction (XRD) and a Gemini SEM 300 (Zeiss thermal field scanning electron microscope). The results showed that the corrosion weight loss of the deposited metals showed the same trend at 900 °C, with corrosion occurring slowly from 0 h to 10 h and increasing after 10 h to 60 h. It was found that 10 h was the boundary point for corrosion behavior, and the corrosion resistance of the low-nickel nitrogen-containing deposited metal is better than that of the Inconel 625 deposited metal. This was because the addition of N energy elements allowed the formation of a stable composite nitride layer to suppress corrosion.

Fabricating carbon quantum dots of graphitic carbon nitride vis ultrasonic exfoliation for highly efficient H2O2 production

A promising and sustainable approach for producing hydrogen peroxide is the two-electron oxygen reduction reaction (2e– ORR), which uses very stable graphitic carbon nitride (g-C3N4). However, the catalytic performance of pristine g-C3N4 is still far from satisfactory. Here, we demonstrate for the first time the controlled fabrication of carbon quantum dots (CQDs)-modified graphitic carbon nitride carbon (g-C3N4/CQDs-X) by ultrasonic stripping for efficient 2e– ORR electrocatalysis. HRTEM, UV–vis, EPR and EIS analyses are in good consistent which prove the in-situ generation of CQDs. The effect of sonication time on the physical properties and ORR activity of g-C3N4 is discussed for the first time. The g-C3N4/CQDs-12 catalyst shows a selectivity of up to 95% at a potential of 0.35 V vs. RHE, which is much higher than that of the original g-C3N4 catalyst (88%). Additionally, the H2O2 yield is up to 1466.6 mmol g−1 in 12 h, which is twice as high as the original g-C3N4 catalyst. It is discovered that the addition of CQDs through ultrasonic improves the g-C3N4 catalyst's electrical conductivity and electron transfer capability in addition to its high specific surface area and distinctive porous structure, speeding up the reaction rate. This research offers a green method for enhancing g-C3N4 activity.

Photochemical Acceleration of Ammonia Production by Pt1-Ptn-TiN Reduction and N2 Activation.

Stable metal nitrides (MN) are promising materials to fit the future "green" ammonia-hydrogen nexus. Either through catalysis or chemical looping, the reductive hydrogenation of MN to MN1-x is a necessary step to generate ammonia. However, encumbered by the formation of kinetically stable M-NH1─3 surface species, this reduction step remains challenging under mild conditions. Herein, we discovered that deleterious Ti-NH1─3 accumulation on TiN can be circumvented photochemically with supported single atoms and clusters of platinum (Pt1-Ptn) under N2-H2 conditions. The photochemistry of TiN selectively promoted Ti-NH formation, while Pt1-Ptn effectively transformed any formed Ti-NH into free ammonia. The generated ammonia was found to originate mainly from TiN reduction with a minor contribution from N2 activation. The knowledge accrued from this fundamental study could serve as a springboard for the development of MN materials for more efficient ammonia production to potentially disrupt the century-old fossil-powered Haber-Bosch process.

Controllable preparation of boron nitride microspheres and their epoxy-based thermoconductive composites

How to prepare spherical boron nitride (BN) particle with different size is an extremely challenging work. In this paper, the controllable preparation of spherical BN particle from nanospheres to microsphere was realized by changing the synthesis temperature of trimethyl borate (B(OMe)3) and ammonia. The spherical precursor (SP) with high oxygen content was obtained first, and then it was heated under flowing ammonia atmosphere to form stable boron nitride microspheres (BNMS). The BNMS exhibits onion-like cavitation structure with a diameter of 0.8–3.4 μm. The effects of the lower reaction temperature (700–825 °C) and gas flow rate on the spherical precursor are discussed. A possible mechanism is proposed to explain the formation of precursors and the appearance of onion-like structure. It is believed that the formation of microsphere is due to the deposition and growth of BO species during the flow process of nanosphere. In addition, the effect of the addition of BNMS on the thermal conductivity of epoxy resin (EP) composites was investigated.