Solvothermal Metal Azide Decomposition Routes to Nanocrystalline Metastable Nickel, Iron, and Manganese Nitrides

Mazumder B., Chirico P., Hector A.L.

Solvothermal reactions of TaCl5 with LiNH2 in benzene result in nanocrystalline Ta3N5 at 500 or 550 degrees C. The approximately 25 nm Ta3N5 particles have a band gap of 2.08-2.10 eV. The same reactions in mesitylene resulted in a higher crystallization temperature and large amounts of carbon incorporation due to solvent decomposition. Reactions of Ta(NMe2)5 with LiNH2 under the same conditions resulted in TaN. Rocksalt-type MN phases are obtained for Zr, Hf, or Nb when their chlorides (ZrCl4, HfCl4, or NbCl5) or dialkylamides (M(NEtMe)4, M = Zr, Hf) are reacted with LiNH2 under similar conditions. With the amides, there is some evidence for nitrogen-rich compositions (HfN >1), and carbon is incorporated into the products through pyrolysis of the dialkylamide groups.

Li R., Wang X., Liu T., Xu H., Zhao F., Wang Z., Gao S.

By utilizing suitable coligand endi (1,2-(tetrazole-1-yl)ethane)) with variable conformations, we synthesized three new azido-bridged Co(2+) compounds with molecular formulas Co(endi)(N3)2 (1, 3) and Co(endi)2(N3)2 (2) by tuning the stoichiometric ratio of ligand/metal and the concentration of the solution. All of the compounds have been characterized structurally and magnetically. In all three structures, the azide ions use the end-to-end mode to link the Co(2+) centers to the 1D chain (1) and 2D (4,4) layers (2 and 3). The endi coligands adopt a trans conformation in compound 1 and a gauche conformation in compounds 2 and 3. Linked by bridging endi, the 1D chains in compound 1 and 2D layers in compound 3 are extended, resulting in the final 2D layer for compound 1 and the 3D network for compound 3, whereas in compound 2, the endi acts as only a terminal ligand to separate the 2D layers. Compound 1 consists of dual end-to-end azido-bridged 1D Co(2+) chains that are linked by trans endi into a 2D layer and are further extended to a 3D framework through H bonds. Compound 2 is a 2D (4,4) layer that is connected by end-to-end azido ions. The gauche endi ligands act as terminal ligands to separate the neighboring layers thoroughly. Compound 3 has a (4,4) 2D layer that is similar to that of compound 2, and these layers are further extended to a 3D network through gauche endi. The magnetic investigation shows that compound 3 is antiferromagnetically coupled and compound 2 is a weak ferromagnet with a critical temperature of 22 K, which is quite high compared with that of the previously reported 2D azido-bridged Co(2+) compounds.

Mazumder B., Hector A.L.

Solvothermal reactions of TaCl5 with LiNH2 or Mg3N2 lead to amorphous products at temperatures up to 500 °C. Post-reaction annealing under nitrogen yields crystalline products with Ta3N5 (LiNH2) and TaN (Mg3N2) structures. When these reactions are carried out with LiNH2 in refluxing mesitylene, rods of Ta3N5-structured material are obtained. Using commercial LiNH2 these have dimensions of ∼5 × 200 nm but are contaminated with LiTaO3. With high purity LiNH2 a black oxide-free but carbon-containing material presents as rods of 20–50 nm length. Higher temperature reactions in an autoclave lead to isotropic nanocrystals of ca. 10 nm diameter of a nitrogen-deficient or carbide-substituted Ta3N5-type material. Carbon incorporation is attributed to solvent decomposition at the temperatures required for the reactions. The TaN derived from reactions with Mg3N2 consists of nanoparticles of 6–8 nm in diameter.

Han Y., Wang H., Zhang M., Su M., Li W., Tao K.

Iron nitride was prepared by a nitridation reaction in NH 3 using amorphous iron as precursor. The precursor was prepared at ambient temperature through the process of reducing ferrous sulfate by potassium borohydride, followed by the nitridation at different temperatures. The nitridation reaction occurred at 548 K, and -Fe 2-3N was formed at 573 K. The reaction temperature was much lower than that using crystallized iron because of the characteristics of the amorphous materials. The existence of a small quantity of boron (1.6 wt.%) improved the stability of the amorphous precursor, which guaranteed an amorphous iron precursor at nitriding temperatures in excess of 548 K.

Bonnet M., Aronica C., Chastanet G., Pilet G., Luneau D., Mathonière C., Clérac R., Robert V.

The reaction of a tridentate Schiff base LH (L-: 1,1,1-trifluoro-7-(dimethylamino)-4-methyl-5-aza-3-hepten-2-onato) with a Ni(II) salt in the presence of azide salt has led to a new alternating end-on (EO)/end-to-end (EE) azido-bridged Ni(II) chain of formula {[Ni2(micro1,1-N3)(micro1,3-N3)(L)2(MeOH)2]}n. Its originality lies in the presence of single EE and EO coordination modes for the azide. It crystallizes in the C2/c space group, a=21.570(7) A, b=10.79(1) A, c=16.154(5) A, beta=120.81(2) degrees, Z=4. The chain can be viewed as {Ni2(N3)(L)2(MeOH)2}+ dimeric units linked to each other in a zigzag pattern by the other azide. Magnetic susceptibility and magnetization measurements have been performed and revealed that the chain can magnetically be depicted as isolated {Ni2(N3)} units exhibiting antiferromagnetic interaction (JAF approximately -37 cm(-1)). Ab initio calculations confirmed the efficient magnetic coupling through the EE bridge and vanishingly small EO {Ni2(micro1,1-N3)} interactions.

Escuer A., Aromí G.

The synthesis of transition metal spin-clusters has become an important sub-discipline of coordination chemistry, especially since the discovery of single-molecule magnets (SMMs) in the early nineties. In this context, complexes with high spin-numbers and large anisotropy are particularly desired. The use of the azide ligand to act as a bridge and magnetic coupler within cages of paramagnetic ions has become increasingly common in this field, especially during the last five years, mainly because of the coordination versatility of this ligand, which is capable of bridging several metals in a variety of coordination modes, and its ability to induce ferromagnetic interactions. Several high-spin 3d metal aggregates have been prepared in this manner, a significant number of which behave as SMMs. This review covers the rapid progress made with this relatively recent synthetic approach by describing the structures and summarising the magnetic properties of the systems prepared in this manner. Some of the trends identified could serve as a privileged starting point for the further development of this promising area. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)

Choi J., Gillan E.G.

Nanocrystalline InN powders have been synthesized through metal azide decomposition in superheated toluene and refluxing hexadecane solvents near 280 °C. The metal azide intermediates were formed in situ through the metathesis reaction of InBr3 and NaN3. The InN products from toluene consist of ∼10 nm hexagonal (wurtzite) structured crystallites in aggregated arrangements. InN from hexadecane and lower temperature toluene reactions produced more poorly crystalline InN that appears to contain a cubic (zinc blende) component. Coordinating amine solvents led to decomposition of the nitride to indium metal. Several reactions were undertaken to produce mixed metal nitrides of the form Ga1−zInzN where z is 0.5 and 0.75. The mixed metal nitride products are analytically consistent with composite versus solid-solution formation, however some metal mixing is observed. Data from X-ray diffraction, electron microscopy, thermal analysis, elemental analysis, and several spectroscopic methods are combined to form a consistent picture of the bulk and surface structures for these nanocrystalline InN materials.

Liu Z.Q., Leineweber A., Mitsuishi K., Furuya K.

Annealed and quenched ɛ-Fe2-3N powders with an initially homogeneous composition of Fe3N1.0 were studied by transmission electron microscopy (TEM). TEM specimens were successfully prepared from the powder using a sandwiching technique. The superstructure in ɛ-powders was identified as ɛ′-Fe3N type (space group P6322), and no other type of superstructure was observed. γ′-Fe4N nitride precipitated from ɛ powders as individual grains during the annealing process, which is different from the typical fine lamellar structure observed in bulk iron-nitride samples. The observed orientation relationships between γ′ and ɛ grains are also different from that reported in the lamellar structure of bulk iron-nitride samples. This suggests that in the powder investigated by us there is no one specific orientation of the precipitated γ′ grains with respect to the parent ɛ grains.

Wu C., Li T., Lei L., Hu S., Liu Y., Xie Y.

In this paper, we present an effective synthetic protocol to produce high quality InN nanocrystals using indium iodide (InI3), one member of the family of indium halides, as the indium source at a low temperature of

Choi J., Gillan E.G.

Nonaqueous solvothermal chemical reactions have found extensive utility in the growth of inorganic non-oxide materials. This report describes the successful use of organic solvothermal environments to synthesize energetically unstable copper azide precursors that are then decomposed in situ to crystalline metastable copper nitride at temperatures below 200 degrees C. A comparison of Cu3N products formed from nonpolar (toluene) and coordinating (THF) solvents is described. The cubic Cu3N products are nanocrystalline with aggregated particle-like extended structures and were characterized by X-ray diffraction, electron microscopy, IR spectroscopy, and mass spectrometry. The thermal stability and composition of Cu3N was examined by thermogravimetric analysis and bulk elemental analysis. The particle surfaces contain bound residual solvent species that can be removed by heating. The poorly coordinating solvent, toluene, lead to a more crystalline product containing less residual organic content. Benchtop reactions were performed to follow the temporal formation and decomposition of metal azide intermediates. These studies provided more detailed information on the progression of metal azide to metal nitride materials in a solvothermal environment.

Cao M., Liu T., Sun G., Wu X., He X., Hu C.

We report the synthesis of Fe{sub 3}N nanodendrites directly by reduction-nitriding of {alpha}-Fe{sub 2}O{sub 3} nanopine dendrites in a mixed stream of H{sub 2}-NH{sub 3}. Fe{sub 3}N basically retains dendritic morphology of the starting material {alpha}-Fe{sub 2}O{sub 3.} It is found that nanorod branches of Fe{sub 3}N dendrites have relatively uniform diameters and are evenly distributed at both sides of the stem with a periodicity of about 50nm. The diameters of the nanorods are about 50nm, and their lengths range from 50 to 1000nm. Fe{sub 3}N nanodendrites show a rapid saturation of magnetization of 104emu/g at 300K, as expected for a magnet.

Xu Y., Hosein S., Judy J.H., Wang J.

Fe 16 N 2 has been reported to have a saturation magnetization as high as 2.8–3.0T based on molecular beam epitaxy deposited single crystal film. We report on Fe nitride nanoparticles prepared with a gas-aggregation nanocluster deposition technique, which could potentially generate pure metastable Fe16N2 phase nanoparticles. Nitrogen gas has been used to nitride the particles after they have been formed in the cluster source. X-ray diffraction patterns show a peak split of α-Fe (110) at 52.4° (2θ), which indicates the formation of Fe3N phase.

Lukashev P., Lambrecht W.R.

A full-potential linear muffin-tin orbital method is used to study the magnetic and electronic properties of Fe1−xInxN alloys in zino-blende-derived structures. The lattice constant is found to vary linearly with concentration and to become matched to GaN near x=0.25. The materials are found to exhibit a magnetic moment beyond a critical lattice constant.

Meyer F., Demeshko S., Leibeling G., Kersting B., Kaifer E., Pritzkow H.

Pyrazolate-based dinucleating ligands with thioether-containing chelate arms have been used for the synthesis of a family of novel tetranuclear nickel(II) complexes [L2Ni4(N3)3(O2CR)](ClO4)2 that incorporate three azido bridges and one carboxylate (R = Me, Ph). Molecular structures have been elucidated by X-ray crystallography in four cases, revealing Ni4 cores with a unique topology in which two of the azido ligands adopt an unusual mu3-1,1,3 bridging mode. The compounds were further characterized by mass spectrometry, IR spectroscopy, and variable-temperature magnetic susceptibility measurements. Magnetic data analyses indicate a combination of significant intramolecular ferromagnetic and antiferromagnetic exchange interactions that give rise to an overall S(T) = 0 ground state. The sign and the magnitude of the individual couplings have been rationalized in the framework of the common magnetostructural correlations for end-to-end and end-on azido linkages, suggesting that these correlations also remain valid for the respective fragments of multiply bridging mu3-1,1,3 azido ligands.

Hu J., Lu Q., Tang K., Yu S., Qian Y., Zhou G., Liu X.

A benzene–thermal reaction of TiCl4 and NaN3 at 350°–380°C was conducted for the preparation of nanocrystalline TiN. Powder X-ray diffractometry patterns indicated that the powder was cubic-phase TiN with a lattice constant a= 4.23656 A. Transmission electron microscopy images showed the TiN powders consisted of uniform spherical particles with an average diameter of 50 nm. The binding energies of Ti 2p3/2 and N 1s core levels at the positions of 454.85 and 397.1 eV, respectively, and the Ti:N atomic ratio of 1.08:1.00 were detected by X-ray photoelectron spectra. A possible formation mechanism of TiN was proposed.

Kwon H.R., Yang J.W., Jang H.W.

ABSTRACTMetal nitrides have emerged as promising materials for photoelectrochemical and electrochemical catalysis due to their unique electronic properties and structural versatility, offering high electrical conductivity and abundant active sites for catalytic reactions. Herein, we comprehensively explore the characteristics, synthesis, and application of diverse metal nitride catalysts. Fundamental features and catalytic advantages of metal nitrides are presented in terms of electronic structure and surface chemistry. We deal with synthetic principles and parameters of metal nitride catalysts in terms of nitrogen source, introducing synthesis strategies of metal nitrides with various morphologies and phases. Recent progress of metal nitride catalysts in (photo)electrochemical reactions, such as hydrogen evolution, oxygen evolution, oxygen reduction, nitrogen reduction, carbon dioxide reduction, and biomass valorization reactions, is discussed with their tailored roles. By providing future direction for remaining challenges, this review aims to guide the design of metal nitride catalysts from a materials point of view, contributing to expanding into energy and environmental technologies.

Zipkat M., Koldemir A., Block T., Ceniza C., Boyko T.D., Kläger S., Pritzl R.M., Moewes A., Pöttgen R., Rudel S.S., Schnick W.

AbstractNitrides represent a promising class of materials for a variety of applications. However, bulk synthesis remains a challenging task due to the stability of the N2 molecule. In this study, we introduce a simple and scalable approach for synthesizing nitride bulk materials. Moderate reaction temperatures are achieved by using reactive starting materials, slow and continuous mixing of the starting materials, and by dissipating heat generated during the reaction. The impact on the synthesis of using different starting materials as nitrogen source and the influence of a flux were examined. γ‐Sn3N4 was selected as the model compound. The synthesis of pure γ‐Sn3N4 bulk material on a large scale has still been a challenge, although a few synthesis methods were already described in the literature. Here we synthesized γ‐Sn3N4 by metathesis reaction of argon‐diluted SnCl4 with Li3N, Mg3N2 or Ca3N2 as nitrogen sources. Products were characterized by powder X‐ray diffraction, scanning and transmission electron microscopy, energy‐dispersive X‐ray spectroscopy, dynamic flash combustion analysis, hot gas extraction analysis, X‐ray photoelectron spectroscopy, Mössbauer spectroscopy and X‐ray absorption and emission spectroscopy. Additionally, single‐crystal diffraction data of γ‐Sn₃N₄, previously unavailable, were successfully collected.

Mikhailov Oleg V.

The review integrates and systematizes data published in the last 15 years on the physicochemical characteristics of specific chemical compounds formed by metal elements with nitrogen atoms containing three or more nitrogen atoms per metal atom. Most often, the total number of nitrogen atoms exceeds their greatest number allowed by the formal higher oxidation state of the metal atom present in the compound. The conceptual possibility of practical application of these compounds now and in the future is also discussed.The bibliography includes 230 references.

Mishra P.P., Panda R.N.

Transition metal nitrides are technologically important because of their unique physical and chemical properties. Research on metal nitrides is scanty, due to their synthetic difficulty. Also, the stability of the metal nitrides is a matter of concern, as most nitrides are sensitive to oxygen and form oxides in the air atmosphere. Therefore, studies on metal nitrides are not explored much. This chapter deals with a general introduction to transition metal nitrides including their classification, crystal structure and bonding. The current chapter investigates novel synthesis and magnetic properties study of various binary and ternary transition metal nitrides such as: ε-CoxFe3-xN (0 ≤ x ≤ 0.4), γ′-NixFe4-xN (x = 0.2, 0.4, 0.6, 0.8), γ-Mo2N, γ-CoxMo2-xN (x = 0.25), FeMoN2, β-W2N and CoWN2. A general discussion on magnetism in bulk and nano form has been presented. Various novel synthesis routes have been developed and adopted to obtain the above-mentioned nitrides as pure-phase nano-structures. The observed properties have been correlated to the size, shape and structure of the materials. Size and surface effects become predominant at nano scale leading to variation in intrinsic properties, which is evident in our research findings. ε-Fe3N and γ′-Fe4N materials have been synthesized via the citric acid-assisted sol–gel method. The effect of Co substitution on the structural and magnetic properties of ε-phase iron nitride has been studied in detail. With a gradual increase of Co content (x) to 0.2 at wt%, the ε-Fe3N phase was stabilized. However, with further increase of Co content (x) to 0.3 and 0.4 at wt%, a small amount of α-Fe precipitation in the nitride product as an impurity was observed. The values of saturation magnetization, Ms and coercivity, Hc, of ε-CoxFe3-xN (0 ≤ x ≤ 0.4) system of nitrides were found to be in the range of 8–39 emu/g and 199–219 Oe, respectively. The values of Ms are found to increase with a slight initial decrease with a progressive increase in Co content. The effect of Ni substitution on the structural and magnetic properties of γ′-Fe4N nitrides has been investigated. Insertion of Ni atoms into the host lattice expands the lattice due to nano size and strain effect, dominantly. A maximum value of Ms, i.e. 181 emu/g, was obtained for γ′-Ni0.6Fe3.4N material. The observed values of Hc are in the range of 76–109 Oe. γ-Mo2N and γ-Co0.25Mo1.75N have been synthesized by using various precursor routes and using solid urea and gaseous ammonia as nitridation agents. Hydrazine and potassium borohydride have been used for the synthesis of precursors of γ-Mo2N and γ-Co0.25Mo1.75N, respectively for the nitridation using the ammonia route. Ethylenediamine has been used as an organic source for the precursor synthesis of γ-Mo2N obtained via the urea route. M versus H hysteresis study indicates weak ferromagnetic behaviour of γ-Mo2N and γ-Co0.25Mo1.75N (ammonia route) and γ-Mo2N (urea route) materials having coercivity values of 2838 Oe, 296 Oe and 880 Oe, respectively. Pure phase β-W2N and ternary CoWN2 materials have been synthesized using the citric acid-based sol–gel method followed by nitridation using urea and ammonia route, respectively. The values of saturation magnetization, Ms and coercivity, Hc, are estimated to be 0.031 emu/g and 759 Oe, respectively for crystalline β-W2N synthesized at 750 °C. The values of Ms and Hc of CoWN2 synthesized at 750 °C are estimated to be 1.71 emu/g and 375Oe, respectively.

Ahmed I., Jhung S.H.

Catalytic oxidation reactions, one of typical examples of environmental catalysis, can be effectively carried out with transition metal nitrides (TMNs) that are recently advanced much. TMNs are more advantageous compared to their counterpart, traditional metal oxides, due to their better electronic configuration, enhanced redox properties, lower operating temperatures, and resistance to sintering. They can be also used as a replacement for expensive noble metal catalysts. Considering their advantageous applications, a review about the preparation of the TMNs and their applications in oxidation catalysis is required. At the beginning of the review, the advantages of the TMNs over metal oxides were introduced. Next, the preparation methods of TMNs were discussed. Then, the application of TMNs in catalytic oxidation reactions, including oxidative desulfurization and denitrogenation of fuel, was discussed in detail. Finally, the contents were summarized and prospects were given for the future study of TMNs.

Yang Z., Xu H., Shuai T., Qi-Ni Z., Zhi-Jie Z., Huang K., Dai C., Li G.

Transition metal nitrides (TMNs) have become usable substitutes for precious metals such as Pt and Ir in the field of electrocatalysis because of their high electrocatalytic performance, high conductivity, good corrosion resistance and stability.

Mikhailov Y.M., Aleshin V.V., Zhemchugova L.V., Bakeshko A.V.

It has been shown experimentally that the flameless combustion of RDX mixtures with iron precursors, nitrogen-containing additives, and a polymer binder can lead to the formation of iron nitrides. Nanosized particles of iron nitride (Fe3N) were obtained by optimizing the ratio of initial components and the conditions of flameless combustion of RDX. The method developed for obtaining iron nitrides in this way can be used to obtain nanosized particles of nitrides of other elements.

Luo Q., Lu C., Liu L., Zhu M.

Transition metal nitrides (TMN) have recently grabbed immensely appealing as ideal active materials in energy storage and catalysis fields on account of their remarkable electrical conductivity, excellent chemical stability, wide band gap and tunable morphology. Both pure TMN and TMN-based materials have been extensively studied concerned with their preparation approaches, nanostructures, and favored performance in various applications. However, the processes towards synthesis of TMN are numerous and complex. Choosing appropriate method to obtain target TMN with desired structure is crucial, which further affects its practical application performance. Herein, this review offers a timely and comprehensive summary of the synthetic ways to TMN and their application in energy related domains. The synthesis section is categorized into in-situ and ex-situ based on where the N element in TMN origins from. Then, overviews on the energy related applications including energy storage, electrocatalysis and photocatalysis are discussed. In the end, the problems to be solved and the development trend of the synthesis and application of transition metal nitrides are prospected. This review summarized the synthetic approaches toward metal nitride nanostructures by categorizing these methods into in-situ and ex-situ ones and presented their energy-related applications including energy storage, electrocatalysis and photocatalysis. • We innovatory categorized the synthesized methods into in-situ and ex-situ ones, which are discussed in the paper. • The energy-related applications of metal nitride nanostructures, including energy storage, electrocatalysis, and photocatalysis were summarized systematically. • Some challenges and prospects of this topic were outlined.

Franceschini F., Taurino I.

Nickel-based catalysts are currently the subject of intensive study in the search for novel electrode materials for non-enzymatic glucose sensing. Their strong activity towards glucose electrooxidation and intrinsic resistance to chloride poisoning makes these catalysts ideal candidates for the development of affordable and stable glucose sensors. In this review, the mechanism of glucose electrooxidation at Ni electrodes is described, clarifying the effect of the different phases of Ni on their catalytic activity. Moreover, a brief background on chloride poisoning is provided, supplemented by computational studies. Furthermore, this article details the most intriguing compounds of Ni (selenides, sulfides, nitrates) and the analytical performance of the respective sensors. Additional focus points of this work are multimetallic nanosystems where Ni is a component, and the growing field of conductive metal organic frameworks with Ni centers. This review will be beneficial for researchers who aim at delving deeper into the potential of Ni-based materials for glucose sensing.

Ali H.T., Tanveer Z., Javed M.R., Mahmood K., Amin N., Ikram S., Ali A., Shah Gilani M.R., Sajjad M.A., Yusuf M.

Thin films of copper nitride (Cu 3 N) were successfully synthesized by thermal evaporation method. The Cu powder was evaporated on glass substrate ina horizontal glass tube furnace having central temperature 1000 °C under a vacuum of 10 −2 m Torr for 25 mints. After evaporation of Cu powder, the temperature of tube furnace was set as 300 °C and nitrogen gas was flown into a tube furnace at a rate of 100 sccm for different time durations of 2–8 h respectively. XRD data demonstrated that only one XRD peak (53.916°) of Cu 3 N phase was observed for sample prepared using nitrogen gas flow time duration 2 h. But as we increased the time duration for nitrogen flow, three diffraction peaks at 2theta 23.005°, 32.9° and 38.228° were observed, which are related due to the (100), (111) and (200) planes of Copper Nitride. The intensity of Cu 3 N related diffraction peaks was found to be increased with increasing the time duration which suggested that good crystal quality was observed in the sample having the time duration of 8 h. We argued that for large time durations of nitrogen gas flow, the surface diffusion of the adatom is increased causes the nitrogen atoms react with free Cu atoms to form Cu 3 N thin films. Raman spectroscopy data demonstrated peaks of Cu 3 N structure at 487 and 608 cm −1 for samples prepared using 6 and 8 h time duration. SEM data further confirmed our XRD and Raman data that sample prepared using 8 h time duration has best crystal quality. The XPS and FTIR measurements were also performed on 8 h annealed sample to further justified the presence of Cu 3 N structure.

Ma T., Yin Y., Hong F., Zhu P., Yu X.

We sintered bulk trigonal ε-Fe2N (space group: P312) with the high-pressure and high-temperature method. Structural refinements by the Rietveld method result in a trigonal unit cell with parameters of a = 4.7767(1) Å and c = 4.4179(3) Å. ε-Fe2N is ferromagnetic with a Curie temperature of ∼250 K, a saturation magnetization (Ms) value of up to 1.2 μB/formula units (f.u.), and comparatively low coercive field. The Vickers hardness was measured, and the results showed that the asymptotic hardness of bulk ε-Fe2N is about 6.5 GPa with a load of 1000 g. Thermogravimetric (TG) analysis shows that ε-Fe2N is thermally stable below 670 K. ε-Fe2N exhibits good metal conductivity, and the electron transport measurements show that the resistivity of it is 172 μΩ cm at room temperature. The theoretical calculations suggest that the conducting states are mainly derive from Fe-3d states.

Kadzutu-Sithole R., Machogo-Phao L.F., Kolokoto T., Zimuwandeyi M., Gqoba S.S., Mubiayi K.P., Moloto M.J., Van Wyk J., Moloto N.

To study the effect of time on the colloidal synthesis of Cu3N nanoparticles, copper(ii) nitrate was thermally decomposed at 260 °C for up to 60 min in octadecylamine as a stabilizing ligand.

Liu Z., Fan C., Chen C., Ming Z., Liu A., Yang C., Lin S., Wang L.

The nitrides were added to the molten pool to optimize the microstructure and mechanical properties of high nitrogen stainless steel weld. The nitrides of the alloy element that promote the nitrogen dissolution were selected. The alloy element and nitrogen element were thereby simultaneously added to the weld. MnN was selected from TiN, VN, CrN and MnN because the nitrogen content of the autogenous tungsten inert gas weld that brushed the MnN powder was the highest and manganese is an austenite forming element. And then MnN was filled into the gas metal arc welding molten pool as the way of bypass MnN-cored wire. The proportion of ferrite of the weld reduced by 51.4 %, the tensile strength of the joint increased by 7.4 % and the impact toughness of the weld increased by 28.1 %. The action mechanism of MnN during the welding was discussed. MnN was decomposed under the high temperature of the arc and the nitrogen and manganese entered the molten pool respectively. Nitrogen escape occurred along with the mass transfer process.

Sun W., Bartel C.J., Arca E., Bauers S.R., Matthews B., Orvañanos B., Chen B., Toney M.F., Schelhas L.T., Tumas W., Tate J., Zakutayev A., Lany S., Holder A.M., Ceder G.

Exploratory synthesis in new chemical spaces is the essence of solid-state chemistry. However, uncharted chemical spaces can be difficult to navigate, especially when materials synthesis is challenging. Nitrides represent one such space, where stringent synthesis constraints have limited the exploration of this important class of functional materials. Here, we employ a suite of computational materials discovery and informatics tools to construct a large stability map of the inorganic ternary metal nitrides. Our map clusters the ternary nitrides into chemical families with distinct stability and metastability, and highlights hundreds of promising new ternary nitride spaces for experimental investigation—from which we experimentally realized seven new Zn- and Mg-based ternary nitrides. By extracting the mixed metallicity, ionicity and covalency of solid-state bonding from the density functional theory (DFT)-computed electron density, we reveal the complex interplay between chemistry, composition and electronic structure in governing large-scale stability trends in ternary nitride materials. High-throughput computation is especially useful for materials screening where synthesis is challenging. Here, it is used to construct a stability map of ternary nitrides, allowing discovery of stable compounds and providing insight into principles that govern nitride stability.

Rounaghi S.A., Vanpoucke D.E., Esmaeili E., Scudino S., Eckert J.

Nanostructured epsilon iron carbonitride (e-Fe3CxN1-x, x ∼ 0.05) powder with high purity (>97 wt%) was synthesized through a simple mechanochemical reaction between metallic iron and melamine. Various characterization techniques were employed to investigate the chemical and physical characteristics of the milling intermediates and the final products. The thermodynamic stability of the different phases in the Fe-C-N ternary system, including nitrogen and carbon doped structures were studied through density functional theory (DFT) calculations. A Boltzmann-distribution model was developed to qualitatively assess the stability and the proportion of the different milling products vs. milling energy. The theoretical and experimental results revealed that the milling products mainly comprise the e-Fe3CxN1-x phase with a mean crystallite size of around 15 nm and a trace of amorphous carbon material. The thermal stability and magnetic properties of the milling products were thoroughly investigated. The synthesized e-Fe3CxN1-x exhibited thermal stabilities up to 473 K and 673 K in air and argon atmospheres, respectively, and soft magnetic properties with a saturation magnetization of around 125 emu/g.