Nitridation Procedure Research Articles

Polyaniline-coated Ni3N microflowers as sulfur host for advanced Li–S battery

This paper presents novel polyaniline-coated Ni3N/S (Ni3N/S@PANI) microflowers as sulfur host for lithium–sulfur battery to solve the problems of cathode, such as poor electrical conductivity caused by sulfur and shuttle effect caused by multi-sulfide dissolution. Microflower-like Ni3N is synthesized using hydrothermal reaction followed by a nitridation procedure. The Ni3N/S@PANI microflowers are obtained by compounding the Ni3N microflowers with sulfur powder, followed by polyaniline coating. The as-prepared Ni3N/S@PANI microflowers exhibit the first capacity of 935 mAh/g at 0.5 A/g and retain 678 mAh/g after 200 cycles. The high electrochemical property is due mainly to the porous hierarchical structure of the Ni3N and the highly conductive polyaniline coating, which provide sufficient interspace to mitigate the volume expansion of sulfur and trap polysulfides, and inhibit the dissolution of polysulfides, respectively.

Controlling the size and density of InN quantum dots formed on sapphire substrate by droplet epitaxy

The growth of InN quantum dots (QDs) on c-plane sapphire by droplet epitaxy (DE) using radio frequency plasma-assisted molecular beam epitaxy is reported here. The QD growth process from liquid In droplets to the InN QDs is described with a focus on the effect ambient nitrogen from an active RF-plasma source has on the formation of In droplets as a function of substrate temperatures. The variation in the shape and size of InN QDs is explained in terms of the In atom surface diffusion and the migration of droplets. Additionally, two nitridation procedures were used to investigate the crystallization of In droplets. The droplet formation was determined to follow well known principles of nucleation theory with ripening. The resulting activation energy for In surface diffusion on sapphire was found to be 0.62 ± 0.07 eV in ultra-high vacuum, ∼10−10 Torr, and 0.57 ± 0.08 eV in ambient N2, ∼10−5 Torr. The growth of InN QDs using the DE method has many advantages over the classical Stranski–Krastanov technique, including the ability to control a wide range of QD shapes, sizes, and densities.

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.

Metallic-Bonded Pt-Co for Atomically Dispersed Pt in the Co4N Matrix as an Efficient Electrocatalyst for Hydrogen Generation.

Exploiting highly efficient electrocatalysts toward hydrogen evolution reaction (HER) has a significant role in the mass production of hydrogen energy through water electrolysis. Herein, ginkgo leaf-like Co4N coupled with trace Pt with metallic bond Pt-Co on nickel foam via solvothermal, tannic acid treated, and nitridation procedures for HER (T-Pt-Co4N) is developed. It only requires low overpotentials of 31 mV and 27 mV to achieve 10 mA cm-2 in alkaline and neutral electrolytes, respectively, surpassing the benchmark Pt/C and previously reported values. Moreover, it presents excellent long-term stability in the studied media and also can drive overall water splitting under the assistance of sustainable energies. The specific nanostructure favors the acceleration of the electrocatalytic process by exposing abundant active sites and providing numerous mass transport channels during the catalytic process. Moreover, experimental and theoretical calculation demonstrate that the atomic Pt coordinates with Co to form metallic bond Pt-Co also act as crucial role to boost the electrocatalytic performance by optimizing the reaction kinetics for HER.

Plasma Nitriding and Its Effect on the Corrosion Resistance of Stainless Steel 1.4006

The plasma nitriding (PN) technology was applied on the martensitic stainless steel 1.4006. The influence of PN on the corrosion resistance of selected material was investigated. The chemical composition of selected steel was verified using the Q4 TASMAN device. The PN process was performed using two stage nitriding procedure. After plasma cleaning procedure at 515 °C for 45 min in a nitriding atmosphere ratio 20H2:2N2 (l/h) was the first stage nitriding procedure performed at 520°C for 16 hours in a nitriding atmosphere ratio 25H2:5N2 (l/h) and followed by the second stage of nitriding procedure performed at 525°C for 4 hours in a nitriding atmosphere ratio 28H2:4N2 (l/h). The microstructure and mechanical properties of the nitride layers were studied using OES spectrometry, optical microscopy, and hardness testing. The depths of plasma nitride layers were also estimated using a cross-sectional microhardness profiles measurement. The corrosion resistance testing of PN stainless steel 1.4006 samples were carried out in a 5 % neutral sodium chloride solution (NSS) in accordance with ISO 9227 standard in the VLM GmbH SAL 400-FL corrosion chamber and visually evaluated. Microhardness and surface hardness of experimental samples were significantly increased, but the corrosion resistance remarkably decreased.

Steel Cruciform Sample with Nitrided Arms Achieves Higher Plastic Strain in the Gauge Region

This paper describes a novel solution to increase plastic strain in the gauge region of a cruciform sample during a forming limit test. A nitriding procedure was used to increase the strength of the arms of the specimen and at the same time enabled higher plastic deformation in the centre of the sample. DC 5 steel sheets were cut in bone-shape samples and subjected to the nitriding procedure. Uniaxial tensile tests were done to obtain the properties of both the raw and thermo-chemically treated material. Two shapes of the gauge region, partially protected against diffusion of nitrogen, were modelled with the use of Abaqus software and a numerical analysis of biaxial tensile tests were conducted. Based on the obtained numerical analysis results DC 5 steel cruciform samples were nitrided while keeping the same gauge region geometries and subsequently subjected to a biaxial tensile test. The obtained results prove the positive influence of the nitriding procedure on increasing the strength of the cruciform sample arms and at the same time the plastic strain in the centre of the sample. The test bench analysis showed almost six times higher plastic deformation, as compared to the raw specimen, however special attention should be paid to the nitriding process parameters and the shape of the protected gauge region.

Molybdenum and nickel-molybdenum nitride catalysts supported on MgO-Al2O3 for the dry reforming of methane

Molybdenum and nickel-molybdenum nitride catalysts supported on MgO-Al2O3 were synthesized and tested for methane dry reforming at temperatures of 760−840 °C. Two in-situ nitridation procedures involving heating the catalyst in NH3/N2 or H2/N2 gas at a space velocity of 44 s−1 and 5 °C/min heating rate, were assessed and compared with a conventional reduction procedure. The activity of the bimetallic nitride was much higher than that of molybdenum nitride, with a slightly better performance with H2/N2-treated catalysts. The nitrides showed deactivation and poor stability at atmospheric pressure. The nitride phase was shown to transition into an oxide/carbide phase during reaction. Furthermore, hydrogen/nitrogen treatment caused partial reduction to occur, which explains the activity improvement in bimetallic Ni-Mo nitrides. Whisker carbon was significantly decreased although carbon formation was observed. The basic support improves coking resistance by enhancing CO2 adsorption. Initial results indicate a unique activation site for both methane and CO2 through a Mars-Van Krevelen mechanism, with a phase transformation followed by a carbide-oxide redox cycle mechanism taking place.

Chemical vapor deposition of sp2-boron nitride on Si(111) substrates from triethylboron and ammonia: Effect of surface treatments

Thin films of the sp2-hybridized polytypes of boron nitride (BN) are interesting materials for several electronic applications such as UV devices. Deposition of epitaxial sp2-BN films has been demonstrated on several technologically important semiconductor substrates such as SiC and Al2O3 and where controlled thin film growth on Si would be beneficial for integration of sp2-BN in many electronic device systems. The authors investigate the growth of BN films on Si(111) by chemical vapor deposition from triethylboron [B(C2H5)3] and ammonia (NH3) at 1300 °C with focus on treatments of the Si(111) surface by nitridation, carbidization, or nitridation followed by carbidization prior to BN growth. Fourier transform infrared spectroscopy shows that the BN films deposited exhibit sp2 bonding. X-ray diffraction reveals that the sp2-BN films predominantly grow amorphous on untreated and pretreated Si(111), but with diffraction data showing that turbostratic BN can be deposited on Si(111) when the formation of Si3N4 is avoided. The authors accomplish this condition by combining the nitridation procedure with reactions from the walls on which BxC had previously been deposited.

Investigation on the Relationship between the Surface Chemistry and the Corrosion Resistance of Electrochemically Nitrided AISI 304 Stainless Steel

The relationship between the surface chemistry and the corrosion resistance of electrochemically nitrided AISI 304 stainless steel samples has been investigated. The nitriding treatment was carried out in HNO3 0.1 M and HNO3 0.1 M + KNO3 0.5 M at room temperature. Samples were subjected to the nitriding procedure for 30 minutes under a cathodic potential of -0.7 VAg/AgCl. The chemical composition of the nitrided layers was assessed by X-ray photoelectron spectroscopy (XPS). Depth profiles of the main elements present in the nitrided layers were also obtained by XPS by etching them with argon ions. The corrosion behavior of the nitrided samples was evaluated by potentiodynamic polarization. The results showed that the nitrided layers consisted of a mixture of chromium nitrides, chromium oxides, iron oxides/oxyhydroxides, and nickel oxide. The best corrosion resistance was obtained by electrochemical nitriding in the HNO3 0.1 M + KNO3 0.5 M solution. This result could be correlated with the composition and thickness of the nitrided layer.

The Corrosion Resistance of Turbocharger Stator after Plasma Nitriding Process

The plasma nitriding technology was applied on the turbocharger stator wheel. Martensitic stainless steel X12Cr13 was choosen for the experiment. The influence of plasma nitriding process on the corrosion resistance of selected steel was investigated. The chemical composition of selected steel was verified using the Q4 TASMAN device. After plasma cleaning procedure was plasma nitriding process performed using two stage nitriding procedure. The microstructure and mechanical properties of the nitride layers were studied using optical and laser confocal microscopy and hardness testing. The depths of plasma nitride layers were also estimated using cross-sectional microhardness profiles measuring. The corrosion resistance of plasma nitrided X12Cr13 steel samples were evaluated in a 5 % neutral sodium chloride solution (NSS) in accordance with ISO 9227 standard in the VLM GmbH SAL 400-FL corrosion chamber and visually verified. Microhardness and surface hardness of experimental samples were significantly increased, but the corrosion resistance significantly decreased.

Hydrothermal‐carbothermal synthesis of highly sinterable AlN nanopowders

AbstractAluminum nitride (AlN) nanopowders have been synthesized by a novel method which combines the hydrothermal and carbothermal techniques. The phase of the nitridation products can be controlled through adjusting the carbon content of precursor by adding different amount of urea (U). The nitridation product synthesized from the precursor (U/Al=2) was comprised of spherical and well‐distributed particles with sizes ranging from 50 to 100 nm. The nitridation procedure was investigated in detail withTG/DSC,XRD, andTEMmeasurements. It was found that the core‐matrix structured Al2O3/C mixture presents after pyrolysis, favoring the nitridation completed at low temperature, and brings in temperature independency for AlN grain size. Finally, the additive‐free AlN ceramic with 99.08% relative density has been achieved by pressureless sintering at 1850°C.

Cu/TiN nanofiber with tunable electrical conductivity for cost-efficient transparent electrode

Cu/TiN hybrid nanofibers were successfully fabricated by applying nitridation procedure to CuO/TiO2 nanofibers. Through modifying the nitridation temperature, the electrical conductivity of Cu/TiN nanofibers was tunable, which could achieve a high value of 320S/cm-approximately three times that of TiN nanofibers. The oxidation resistance property of the resulting Cu/TiN nanofibers was assessed. With the excellent chemical stability of TiN composition, hybrid Cu/TiN nanofibers possessed greatly enhanced thermostability. Moreover, by taking advantage of readily fiber patterning using electrospinning, Cu/TiN nanofiber networks were assembled as transparent electrodes, which reached an optoelectrical achievement of 34.4Ω/sq at 83.2% transparency. Given its low-cost, enhanced thermostability, together with considerable optoelectrical achievement, Cu/TiN nanofiber is therefore expected to offer a new platform for cost-efficient transparent electrode.

Interfacial mechanisms of novel laser-irradiated L10-based nanocomposite magnets

In melt-spun FePtB-based ribbons, the addition of Ag has been proven to decrease the temperature of phase transformation from the A1 fcc FePt phase to the hard magnetic tetragonal L10 phase. Alloys with 6 and 9 at.% Ag added to the initial FePtB have been synthesized by rapid solidification from the melt. The samples have been laser irradiated and submitted to nitriding procedure. This procedure has been proven beneficial for inducing complete transformation of A1 to L10 phase and a strong (001) texturing. Ag segregation combined to mechanisms of creation of vacancies and diffusion of N give rise to the formation of an intergranular disordered region and due to an improved interfacial coupling between FePt grains, enhanced coercivity and two-phase magnetic behavior is obtained.

Influence of Nitrocarburizing Process Parameters on the Development of Surface Roughness and Layer Formation

Nitriding of tools and engineering components is a well-established surface modification procedure in many industries to ensure operational efficiency. The focus of this work is laid on understanding the influence of nitriding processing technology on the resulting surface properties which strongly dominate its tribological performance. Therefore, nitriding layers based on salt bath and plasma procedure were realised using 31CrMoV9 substrate. The surface roughness before nitriding was set to a Ra value of ~0.16 μm which corresponds to at technically fine grinded surface. 3D measurements as well as SEM micrographs of the nitrided surfaces were compared to the original surface prior to the nitriding procedure. Additionally, cross-section microscopy and hardness depth profiles were done to describe nitriding layer structure and nitriding hardness depth (NHD). Results show a correlation of nitriding processing parameters with the resulting compound layer formation and nitriding hardening depth (NHD). An increase of surface roughness during nitriding can be correlated with the growth of ɛ-nitrides on top of the surface.

Surface polariton spectroscopy of AlN films grown by ammonia MBE on (0001) Al2O3 substrate

AbstractSurface polariton (SP) spectra of nitridated sapphire and rather thick (1 µm) AlN films on sapphire have been measured using attenuated total reflection technique. The high sensitivity of SP allows to see the sapphire spectra change after nitridation of sapphire and even variations parameters of the nitridation procedure. SP dispersion curves depend on degree of conversion of an initial sapphire surface layer into crystalline AlN during the nitridation procedure. The TO frequencies of formed AlN films are higher than the frequency reported for the AlN single crystal indicating the increase of the lattice constant. (© 2015 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Influence of substrate nitridation temperature on epitaxial alignment of GaN nanowires to Si(111) substrate

An arrangement of self-assembled GaN nanowires (NWs) grown by plasma-assisted molecular beam epitaxy on a Si(111) substrate is studied as a function of the temperature at which the substrate is nitridized before GaN growth. We show that the NWs grow with the c-axis perpendicular to the substrate surface independently of nitridation temperature with only a slight improvement in tilt coherency for high nitridation temperatures. A much larger influence of the substrate nitridation process on the in-plane arrangement of NWs is found. For high (850 °C) and medium (450 °C) nitridation temperatures angular twist distributions are relatively narrow and NWs are epitaxially aligned to the substrate in the same way as commonly observed in GaN on Si(111) planar layers with an AlN buffer. However, if the substrate is nitridized at low temperature (∼150 °C) the epitaxial relationship with the substrate is lost and an almost random in-plane orientation of GaN NWs is observed. These results are correlated with a microstructure of silicon nitride film created on the substrate as the result of the nitridation procedure.

Manganese monoxide/titanium nitride composite as high performance anode material for rechargeable Li-ion batteries

To develop new anode materials for Li-ion batteries, manganese monoxide/titanium nitride (MnO/TiN) composite was prepared by a facile nitridation procedure. Through the analysis of XRD, TEM, EDS and XPS data, it is found that MnO is homogenously mixed with TiN. Due to that TiN in the composite offers a conducting network and acts as a barrier to effectively buffer the volume expansion/contraction of MnO during the Li+ insertion/extraction process, the MnO/TiN electrode exhibits superior lithium storage properties than pristine MnO electrode. As a result, the Li-ion battery with MnO/TiN composite as anode displays a high and reversible specific capacity of 656mAhg−1 after the 140th cycle at 200mAg−1, and it still delivers a capacity of 210mAhg−1 at 2Ag−1.

Nitrogen-Doped Graphene Nanosheets as Metal-Free Catalysts for Aerobic Selective Oxidation of Benzylic Alcohols

This work demonstrates the molecular engineering of active sites on a graphene scaffold. It was found that the N-doped graphene nanosheets prepared by a high-temperature nitridation procedure represent a novel chemical function of efficiently catalyzing aerobic alcohol oxidation. Among three types of nitrogen species doped into the graphene lattice—pyridinic N, pyrrolic N, and graphitic N—the graphitic sp2 N species were established to be catalytically active centers for the aerobic oxidation reaction based on good linear correlation with the activity results. Kinetic analysis showed that the N-doped graphene-catalyzed aerobic alcohol oxidation proceeds via a Langmuir–Hinshelwood pathway and has moderate activation energy (56.1 ± 3.5 kJ·mol–1 for the benzyl alcohol oxidation) close to that (51.4 kJ·mol–1) proceeding on the catalyst Ru/Al2O3 reported in literature. An adduct mechanism was proposed to be different remarkably from that occurring on the noble metal catalyst. The possible formation of a sp2 N–...

Preparation of visible light responsive N doped TiO2 via a reduction–nitridation procedure by nonthermal plasma treatment

A visible light responsive N-doped TiO2 was prepared via a reduction–nitridation procedure by nonthermal plasma treatment. X-ray diffraction, N2 adsorption, UV–vis spectroscopy, photoluminescence, and X-ray photoelectron spectroscopy were used to characterize the prepared TiO2 samples. The plasma treatment did not change the phase composition and particle sizes of TiO2 samples, but extended its absorption edges to the visible light region. The photocatalytic activities were tested in the degradation of an aqueous solution of a reactive dyestuff, methylene blue, under visible light. The photocatalytic activities of TiO2 prepared by reduction–nitridation procedure were much higher than that of samples prepared by simple nitridation treatment. The enhanced activity was ascribed to the substitutional N-doping and appropriate concentration of oxygen vacancies. TOHN10 prepared by reduction–nitridation procedure exhibited excellent photocatalytic stability. A possible mechanism for the photocatalysis was proposed.

The influence of preparation method, nitrogen source, and post-treatment on the photocatalytic activity and stability of N-doped TiO 2 nanopowder

NH 3 plasma, N 2 plasma, and annealing in flowing NH 3 were used to prepare N doped TiO 2, respectively. XRD, UV–vis spectroscopy, N 2 adsorption, FT-IR, Zeta-potential measurement, and XP spectra were used to characterize the prepared TiO 2 samples. The nitridation procedure did not change the phase composition and particle sizes of TiO 2 samples, but extended its absorption edges to the visible light region. The photocatalytic activities were tested in the degradation of an aqueous solution of a reactive dyestuff, methylene blue, under visible light. The photocatalytic activity and stability of TiO 2 prepared by NH 3 plasma were much higher than that of samples prepared by other nitridation procedures. The visible light activity of the prepared N doped TiO 2 was improved by increasing the lattice-nitrogen content and decreasing adsorbed NH 3 on catalyst surface. The lattice-nitrogen stability of N-doped TiO 2 samples improved after HCl solution washing. The possible mechanism for the photocatalysis was proposed.