Nitridation Reaction Research Articles

Effect of Residual Oxygen Concentration on the Lattice Parameters of Aluminum Nitride Powder Prepared via Carbothermal Reduction Nitridation Reaction.

Residual oxygen in wurtzite-type aluminum nitride (AlN) crystal, which significantly affects phonon transport and crystal growth, is crucial to thermal conductivity and the crystal quality of AlN ceramics. In this study, the effect of residual oxygen on the lattice of AlN was examined for as-synthesized and sintered samples. By controlling reaction time in the carbothermal reduction nitridation (CRN) procedure, AlN powder was successfully synthesized, and the amount of residual oxygen was systematically controlled. The evolution of lattice parameters of AlN with respect to oxygen conc. was carefully investigated via X-ray diffraction analysis. With increasing amounts of residual oxygen in the as-synthesized AlN, lattice expansion in the ab plane was induced without a significant change in the c-axis lattice parameter. The lattice expansion in the ab plane owing to the residual oxygen was also confirmed with high-resolution transmission electron microscopy, in contrast to the invariant lattice parameter of the sintered AlN phase. Micro-strain values from XRD peak broadening confirm that stress, induced by residual oxygen, expands the AlN lattice. In this work, the lattice expansion of AlN with increasing residual oxygen was elucidated via X-ray diffraction and HR-TEM, which is useful to estimate and control the lattice oxygen in AlN ceramics.

Novel in-situ constructing approach for vertically aligned AlN skeleton and its thermal conductivity enhancement effect on epoxy

As one of the key components of electronic devices, thermal management materials (TMMs) with high thermal conductivity are essential to ensure their safety and long service life. For polymer-based TMMs, AlN is one of the preferred fillers, but it has some drawbacks such as high cost and easy hydrolysis. Herein, a controllable and continuously oriented three-dimensional AlN skeleton (3D-AlNNS) was in-situ transformed from a low-cost 3D Al-containing skeleton (3D-AlNS) by combining the ice-templating and nitriding reaction sintering. Subsequently, AlN/epoxy composites were obtained by a vacuum infiltration. The composite containing 39.69 vol% AlN had the highest thermal conductivity of 4.29 W m−1·K−1, which was 21.45 times higher than that of pure epoxy. The composite substrates showed excellent heat dissipation performance in practical applications due to their high thermal conductivity. The continuous directional alignment of AlN powders in the 3D skeleton and intersection of AlN whiskers between the skeleton walls produced in-situ contributed to the formation of effective multichannel heat transferring paths and improvement in thermal conductivity. This novel approach has the advantages of low-cost, short processing time, simple operation and repeatability, and provides a new idea for developing heat-conducting polymer composites, which can also be extended to the preparation of similar TMMs.

Stochastic calibration of a carbon nitridation model from plasma wind tunnel experiments using a Bayesian formulation

In this work, we calibrate a carbon nitridation model for a broad span of surface temperatures from existing plasma wind tunnel measurements by accounting for experimental and parametric uncertainties. A chemical non-equilibrium stagnation line model is proposed to simulate the experiments and obtain recession rates and CN densities, the measured model outputs. First, we establish the influence of the experimental boundary conditions and nitridation parameters on the simulated observations through a sensitivity analysis. Results show that such quantities are mostly affected by the efficiency of nitridation reactions at the gas-surface interface. We then perform model calibrations for each experimental condition and compare them based on the experimental data used. This allows us to check the consistency of the experimental dataset. Using only the trustworthy experimental data, we perform a calibration of Arrhenius law parameters for nitridation efficiencies considering all available experimental conditions jointly, allowing us to compute nitridation efficiencies even for surface temperatures for which there are no reliable experimental data available. The stochastic Arrhenius law agrees well with most of the data in the literature. This result constitutes the first nitridation model extracted from plasma wind tunnel experiments with accurate uncertainty estimates.

Room‐Temperature Printing of Ultrathin Quasi‐2D GaN Semiconductor via Liquid Metal Gallium Surface Confined Nitridation Reaction (Adv. Mater. Technol. 11/2022)

Surface-Confined Nitridation Reaction In article number 2200733, Jing Liu and co-workers report a fundamental strategy for directly printing GaN semiconductor film with finest thickness of 1nm on the surface of liquid gallium at room temperature. The new chemical reaction was defined and experimentally demonstrated as N 2 + 2 Ga → plasma 2 GaN ${{\rm{N}}_2} + 2{\rm{Ga}}\xrightarrow{{{\rm{plasma}}}}2{\rm{GaN}}$ . Such 2D GaN film with large area, uniformity and controllable thickness can be deposited on various substrates. This opens the way for facilely printing GaN based electronic devices in the coming time.

Solid-state synthesis of UV-plasmonic Cr2N nanoparticles.

Materials that exhibit plasmonic response in the UV region can be advantageous for many applications, such as biological photodegradation, photocatalysis, disinfection, and bioimaging. Transition metal nitrides have recently emerged as chemically and thermally stable alternatives to metal-based plasmonic materials. However, most free-standing nitride nanostructures explored so far have plasmonic responses in the visible and near-IR regions. Herein, we report the synthesis of UV-plasmonic Cr2N nanoparticles using a solid-state nitridation reaction. The nanoparticles had an average diameter of 9 ± 5nm and a positively charged surface that yields stable colloidal suspension. The particles were composed of a crystalline nitride core and an amorphous oxide/oxynitride shell whose thickness varied between 1 and 7nm. Calculations performed using the finite element method predicted the localized surface plasmon resonance (LSPR) for these nanoparticles to be in the UV-C region (100-280nm). While a distinctive LSPR peak could not be observed using absorbance measurements, low-loss electron energy loss spectroscopy showed the presence of surface plasmons between 80 and 250nm (or ∼5 to 15eV) and bulk plasmons centered around 50-62nm (or ∼20 to 25eV). Plasmonic coupling was also observed between the nanoparticles, resulting in resonances between 250 and 400nm (or ∼2.5 to 5eV).

Micro-nanostructured plasmonic TiN layer produced using rapid thermal nitridation of a nanoimprinted TiO2 sol-gel

Titanium nitride (TiN) is a very promising new plasmonic material to replace traditional plasmonic materials like gold and silver, especially thanks to its thermal and chemical stability. However, its chemical resistance and its hardness make TiN difficult to microstructure. An alternative approach is to micro-nanostructure a titanium dioxide (TiO2) coating and then to use a nitridation reaction to obtain a micro-nanostructured TiN coating. This is an easy, rapid and cost-effective structuring process. In this paper, we demonstrate that rapid thermal nitridation (RTN) can be combined with nanoimprint lithography (NIL) to rapidly micro-nanostructure a TiN layer. This innovative approach is applied to a micro-nanostructured TiN layer for plasmonic response in the near infrared range. Experimental and theoretical approaches are compared.

Microstructure and properties of Cr-AlN composite coating prepared by pack-cementation on the surface of Al-containing ODS steel

An Al-containing ODS steel was coated with a composite Cr-AlN layer by pack-cementation treatment. Constituent phases and microstructures of the coating layer were carefully characterized. The results show that the Cr-layer is a Cr-Fe solid solution with {Cr,Fe}2N1-x particles and Cr2C particles, while the AlN-layer is composed of AlN particles and α-Fe matrix. The formation of Cr2C and {Cr,Fe}2N1-x particles in the Cr-layer is due to the drag effect of the strong carbide-forming element Cr on the carbon in ODS steel and nitridation reaction of NH4Cl and Cr, Fe, respectively. During high-temperature pack-cementation, N atoms in the air diffuse into the ODS steel substrate and react with Al in the steel under the catalytic action of yttria, resulting in the formation of the AlN particles. Due to the limited diffusion depth of N and the high nitrogen concentration in the surface layer, the density and size of AlN particles are distributed in a gradient. The particle size is small and high on the side of the Cr-layer, while the particles on the side near the substrate are coarse and low in density. The composite coating greatly improves the surface hardness and friction resistance of the ODS steel.

Palladium-mediated base-free and solvent-free synthesis of aromatic azo compounds from anilines catalyzed by copper acetate

Abstract Herein, we report a new one-step direct synthesis of aromatic azo compounds from anilines under mild conditions. With the catalysis of copper acetate mediated by palladium salt, rapid conversion of anilines to aromatic azo compounds can be observed under the conditions of base-free along with solvent-free. Furthermore, the cross-coupling nitridation reaction based on this strategy was also studied. This research provides not only a new way for the synthesis of symmetrical and asymmetrical aromatic azo compounds but also a strategy and platform for exploring catalytic applications of transition metal compounds.

Recycling the diamond-wire saw silicon powder for preparing the regulable Si3N4 materials by non-catalytic nitridation

In this paper, the diamond-wire saw silicon powder (DWSSP) solid waste in the photovoltaic industry was recycled to prepare silicon nitride through the nitridation method. Nitridation dynamics and reaction mechanisms of DWSSP were investigated in detail. The results showed that the kinetic model of nitriding DWSSP was more suitable for the grain model controlled by the combination of diffusing through the product layers and accumulation pores. Meanwhile, two paths to destroy the dense silicon oxides shell covered on the surface of DWSSP were illustrated during the nitridation process. They were the indirect nitridation to generate the silicon oxynitride fibers and the direct nitridation to form the silicon oxynitride granules, respectively. Morphology and composition of products were mainly determined by the nitriding temperature and time. The pure silicon nitride powder was obtained from DWSSP nitrided at 1550 °C for 10 h. Interestingly, a core-shell structure particle of silicon nitride as core and silicon oxynitride as the shell was prepared at 1450 °C for 10 h, which possible could be a pretty raw material for fabricating the silicon nitride-based composite ceramics with special performances.

Preparation of Al/AlN composites by in-situ reaction in the nitridation-induced self-forming process

Recently, we developed and reported an easy and cost-effective process called nitridation-induced self-forming Al composites (NISFAC) for manufacturing aluminum matrix composites from Al powder. In this process, AlN is formed by an in situ reaction between Al powder and nitrogen gas, and Al/AlN composites are self-sintered at temperatures below the melting point of aluminum because of the thermal energy released by the nitridation reaction of the Al powder. Because AlN is formed by an in situ reaction in the Al matrix, it is not only chemically stable, but also beneficial in terms of its wettability with the matrix. In this study, we prepared Al/AlN composites using the NISFAC process by increasing the amount of ex-situ added AlN reinforcement. The coefficient of thermal expansion (CTE) was effectively reduced by increasing the volume fraction of AlN, which was significantly lower than the theoretically expected value; a CTE of ∼10.8 × 10−6/°C could be achieved by adding only 20 vol.% of AlN. This demonstrates that the in situ formation of AlN during the NISFAC process may help reduce the CTE of Al/AlN composites.

Improved the Wear Resistance of Ti/Cu Multilayer Film by Nitriding

In this study, Ti/Cu multilayer film was deposited by magnetron sputtering and then nitrided at 800 and 900 °C in N2. The microstructure and wear performance were studied. The deposited Ti/Cu multilayer film mainly consisted of Ti and Cu phases. After nitriding, the film mainly consisted of Cu4Ti3, CuTi, and TiN phases, indicating the interface reaction and nitriding reaction occurring. The surface microstructure of the Ti/Cu multilayer film became denser after nitridation. The wear resistance of the Ti/Cu multilayer film improved after nitriding. After nitriding at 900 °C for 2 h, the maximum wear track depth of the multilayer film was ~0.73 μm, which is just 65% of the deposited Ti/Cu multilayer film. The wear mechanism of the Ti/Cu multilayer film before and after nitriding was abrasive and adhesive wear.

Room‐Temperature Printing of Ultrathin Quasi‐2D GaN Semiconductor via Liquid Metal Gallium Surface Confined Nitridation Reaction

AbstractOutstanding wide‐bandgap semiconductor material such as gallium nitride (GaN) has been extensively utilized in power electronics, radiofrequency amplifiers, and harsh environment devices. Due to its quantum confinement effect in enabling desired deep‐ultraviolet emission, excitonic impact, and electronic transport features, 2D or ultrathin quasi‐2D GaN semiconductors have been one of the most remarkable candidates for future growth of microelectronic devices. Here, for the first time, the authors report a large area, wide bandgap, and room‐temperature quasi‐2D GaN synthesis and printing strategy through introducing the plasma medicated liquid metal gallium surface‐confined nitridation reaction mechanism. The developed direct fabrication and compositional process is consistent with various electronics manufacturing approaches and thus opens an easy going way for cost‐effective growth of the third‐generation semiconductor. In particular, the fully printed field‐effect transistors relying on the GaN thus made show p‐type switching with an on/off ratio greater than 105, maximum field‐effect hole mobility of 53 cm2 V−1 s−1, and a small sub‐threshold swing. As demonstrated, the present method allows to produce at room temperature the GaN with thickness spanning from 1 nanometer to nanometers. This basic method can be further extended, generalized, and utilized for making various electronic and photoelectronic devices in the coming time.

Preparation of two-dimensional mesoporous Ta3N5 by utilizing a biological template for enhanced photocatalytic hydrogen production

The design and development of efficient nitride photocatalysts have attracted much attention. Herein, two-dimensional mesoporous Ta3N5 is successfully synthesized through a simple sol-gel process with filter paper as a biological template and a combination of vacuum nitriding reactions. The prepared Ta3N5 shows a wide light response range up to the near infrared (NIR) region due to the nitrogen vacancies generated from substitution of N3− for O2− ions during vacuum nitridation. Significantly, such a narrow bandgap (∼1.99 eV) still satisfies the redox potential of water splitting in thermodynamics. The experimental results show that the Ta3N5 photocatalyst exhibits an enhanced hydrogen production rate of 34.6 μmol h−1 g−1, which is 3.9 and 2.1 times higher than that of Ta2O5 and partial nitridation of Ta2O5 (N–Ta2O5), respectively. This enhanced photocatalytic performance could be attributed to the high specific surface area to provide reactive active sites, substitution of N3− for O2− ions to optimize the band structure, and special two-dimensional mesoporous structure to shorten the charge transfer distance. This work provides a new perspective for the preparation of two-dimensional nitride materials by a biological template method combining vacuum nitriding with enhanced photocatalytic performance.

Competitive Hydrogen Migration in Silicon Nitride Nanoclusters: Reaction Kinetics Generalized from Supervised Machine Learning.

The rate coefficients for 52 hydrogen shift reactions for silicon nitrides containing up to 6 atoms of silicon and nitrogen have been calculated using the G3//B3LYP composite method and statistical thermodynamics. The overall reaction of substituted acyclic and cyclic silylenes to their respective silene and imine species by a 1,2-hydrogen shift reaction was sorted by three different types of H shift reactions using overall reaction thermodynamics: (1) endothermic H shift between N and Si:, (2) endothermic H shift between Si and Si:, and (3) exothermic H shift between Si and Si:. Endothermic H shift reactions between Si atoms have one dominant activation barrier where the exothermic H shift reaction between Si atoms has two barriers and a stable intermediate. The rate-determining step was determined to be from the intermediate to the substituted silene, and then kinetic parameters for the overall reaction were calculated for the two-step pathway. The single event pre-exponential factors, Ã, and activation energies, Ea, for the three different classes of hydrogen shift reactions of silicon nitrides were computed. The hydrogen shift reaction was explored for acyclic and cyclic monofunctional silicon nitrides, and the type of hydrogen shift reaction gives the most significant influence on the kinetic parameters. Using a supervised machine learning approach, the models for predicting the energy barrier of three different hydrogen shift reactions were generalized and suggested based on selected descriptors.

Large Area Ultrathin InN and Tin Doped InN Nanosheets Featuring 2D Electron Gases.

Indium nitride (InN) has been of significant interest for creating and studying two-dimensional electron gases (2DEG). Herein we demonstrate the formation of 2DEGs in ultrathin doped and undoped 2D InN nanosheets featuring high carrier mobilities at room temperature. The synthesis is carried out via a two-step liquid metal-based printing method followed by a microwave plasma-enhanced nitridation reaction. Ultrathin InN nanosheets with a thickness of ∼2 ± 0.2 nm were isolated over large areas with lateral dimensions exceeding centimeter scale. Room temperature Hall effect measurements reveal carrier mobilities of ∼216 and ∼148 cm2 V-1 s-1 for undoped and doped InN, respectively. Further analysis suggests the presence of defined quantized states in these ultrathin nitride nanosheets that can be attributed to a 2D electron gas forming due to strong out-of-plane confinement. Overall, the combination of electronic and plasmonic features in undoped and doped ultrathin 2D InN holds promise for creating advanced optoelectronic devices and functional 2D heterostructures.

TiN porous ceramics with excellent electrochemical properties prepared by freeze-drying and in-situ nitridation reaction

Porous ceramics have attracted extensive attention because of their high porosity, low thermal conductivity, large specific surface area and good corrosion resistance. In this work, TiN porous ceramics with high porosity are successfully prepared via the combination of freeze-drying and in-situ nitridation reaction method using Ti powder and chitosan as raw materials. The influence of the solid content of Ti powder, the concentration of chitosan/acetic acid solution and the nitridation temperature on the morphologies and physical properties of as-prepared TiN porous ceramics are fully investigated. The sample with high porosity of 92.8% and low bulk density of 0.27 g/cm3 can be obtained through optimal parameters (the solid content of Ti powder is 9.6 wt%, the concentration of chitosan/acetic acid solution is 5 wt%, and the nitridation temperature is 1473 K). Particular emphasize is that the as-prepared TiN porous ceramics can be used as sulfur host material for lithium-sulfur batteries (LSBs). Good rate performance and cycle stability of TiN/S electrodes are achieved by electrochemical performance tests. The initial discharge capacity of TiN/S electrodes is 778 mAh g−1 at 0.5C, and the capacity retention rate is 94% after 200 cycles.

Superhydrophilic molybdenum nitride nanoplate arrays enable rapid cerium reaction kinetics

The cerium-based redox flow batteries (RFBs) have great potential for efficient energy storage applications, so the development of highly active and cheap catalysts has become an indispensable work due to the sluggish kinetics of cerium redox reactions. In this work, we prepare a superhydrophilic molybdenum nitride (MoN) nanoplate arrays (NPAs) decorated graphite felt (GF) electrode (MNGF) for cerium-based RFBs by a generalized and high-yield route in terms of scalable impregnation method and facile nitriding reaction. Interestingly, the 3D micro-nano hierarchical NPAs with open and ordered structure ensure entirely exposing active sites toward cerium electrolyte and contribute to the direct and complete contact of every nanoplate with cerium electrolyte. Moreover, in the contact angle measurements, the electrolyte droplet instantaneously soaked into the surface of MNGF in a very short time (within 0.3 s) and the electrolyte solution contact angle of MNGF is ultrasmall, even near 0°, as compared to 102.6° for MoO2 decorated GF (MOGF), 113.4° for air-oxidized GF (AGF), and 121.9° for pristine GF, suggesting that MNGF is superhydrophilic. The highly catalytic MoN NPAs with ingenious open and ordered structure and superhydrophilicity enable the MNGF to possess excellent catalytic activity toward Ce4+/Ce3+ electrochemical reactions. When applied to the cerium-zinc RFBs, the energy efficiency of MNGF is increased by 46.8% relative to pristine GF at 40 mA cm−2. The viable strategy proposed here, for the first time, applies the superhydrophilic materials concept into catalyst design for RFBs and provides a new perspective on the performance boost of RFBs.

Preparation of nano-TiN powders by Ni-catalysed carbothermal reduction nitridation

TiN nanoparticles were prepared at 900–1100 °C by Ni-catalysed carbothermal reduction nitridation from sol-gel using tetrabutyl titanate, citric acid monohydrate and nickel chloride hexahydrate as starting materials. The catalytic effects of nickel on the carbothermal reduction nitridation of xerogels were investigated. Ni has a crucial promoting effect on the carbothermal reduction reaction of the xerogels and visibly enhanced carbothermal reduction and nitridation reactions. The dry gel with 5% NiCl2 was added to obtain nano-TiN at 900 °C. The transmission electron microscopy analysis and Materials Studio simulation results showed that the facilitating effect of Ni on carbothermal reduction nitridation reaction was ascribed to the provision of heterogeneous nucleation sites for amorphous titania, promoting crystallisation and adsorption of N2, resulting in its smooth dissociation into highly active N atoms and consequently enhancing the carbothermal reduction nitridation.

New functionalisation reactions of graphitic carbon nitrides: Computational and experimental studies

The functionalisation of two-dimensional materials is key to modify their properties and facilitate assembly into functional devices. Here, new reactions have been proposed to modify crystalline two-dimensional carbon nitrides of polytriazine imide structure. Both amine alkylation and aryl-nitrene-based reactions have been explored computationally and with exploratory synthetic trials. The approach illustrates that alkylation is unfavourable, particularly at basal-plane sites. In contrast, while initial trial reactions were inconclusive, the radical-addition of nitrenes is shown to be energetically favourable, with a preference for functionalising sheet edges to minimise steric effects.

Controllable synthesis of Mo2C with different morphology and application to electrocatalytic hydrogen evolution reaction

In order to evaluate the effect of precursors and synthesis strategies on catalytic ability of Mo2C in the hydrogen evolution reaction (HER), four kinds of Mo2C were synthesized using two kinds of MoO3 by two strategies. Compared with the one-step direct carbonization strategy, Mo2C with a large special surface area and a better performance could be synthesized by the two-step strategy composed of a nitridation reaction and a carbonization reaction. Additionally, the as-prepared porous Mo2C nanobelts (NBs) exhibit good electrocatalytic performance with a small overpotential of 165 mV (0.5 M H2SO4) and 124 mV (1 M KOH) at 10 mA cm−2, as well as a Tafel slope of 58 mV dec−1 (0.5 M H2SO4) and 59 mV dec−1 (1 M KOH). The excellent catalytic activity is ascribed to the nano crystallites and porous structure. What’s more, the belt structure also facilitates the charge transport in the materials during the electrocatalytic HER process. Therefore, the two-step strategy provides a new insight into the structural design with superior performance for electrocatalytic HER.