16 research outputs found
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Self-Combustion Synthesis of Novel Metastable Ternary Molybdenum Nitrides
Ternary metal nitrides are a promising class of functional materials, but their variety has been limited by the challenging nature of nitride synthesis. Here, we demonstrate a facile self-combustion synthesis route to novel ternary molybdenum nitrides. The room temperature mixing of NaNH2, MoCl4, and 3d transition metal chlorides, such as MnCl2, FeCl2, and CoCl2, initiates a highly exothermic metathesis reaction, which is thermodynamically driven by the formation of stable NaCl, N2, and NH3 byproducts. The rapid combustion reaction yields ternary rocksalt Îł-TMxMo1-xN0.5 nanoparticles (TM = Mn, Fe, Co) in just a few seconds. We calculate from DFT that these disordered ternary molybdenum nitrides are thermodynamically stable under the high-temperatures at which they form but are remnantly metastable when quenched to ambient conditions. Introduction of Mn, Fe, and Co into Îł-Mo2N is found to change its magnetic properties and to enhance its oxygen reduction catalytic activities. Our work demonstrates self-combustion synthesis as a simple but powerful route for the realization of novel ternary intermetallic nitrides with emergent functionality
Recommended from our members
Self-Combustion Synthesis of Novel Metastable Ternary Molybdenum Nitrides
Ternary metal nitrides are a promising class of functional materials, but their variety has been limited by the challenging nature of nitride synthesis. Here, we demonstrate a facile self-combustion synthesis route to novel ternary molybdenum nitrides. The room temperature mixing of NaNH2, MoCl4, and 3d transition metal chlorides, such as MnCl2, FeCl2, and CoCl2, initiates a highly exothermic metathesis reaction, which is thermodynamically driven by the formation of stable NaCl, N2, and NH3 byproducts. The rapid combustion reaction yields ternary rocksalt Îł-TMxMo1-xN0.5 nanoparticles (TM = Mn, Fe, Co) in just a few seconds. We calculate from DFT that these disordered ternary molybdenum nitrides are thermodynamically stable under the high-temperatures at which they form but are remnantly metastable when quenched to ambient conditions. Introduction of Mn, Fe, and Co into Îł-Mo2N is found to change its magnetic properties and to enhance its oxygen reduction catalytic activities. Our work demonstrates self-combustion synthesis as a simple but powerful route for the realization of novel ternary intermetallic nitrides with emergent functionality
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Selective metathesis synthesis of MgCr2S4 by control of thermodynamic driving forces
MgCr2S4 thiospinel is predicted to be a compelling Mg-cathode material, but its preparation via traditional solid-state synthesis methods has proven challenging. Wustrow et al. [Inorg. Chem., 2018, 57, 14] found that the formation of MgCr2S4 from MgS + Cr2S3 binaries requires weeks of annealing at 800 °C with numerous intermediate regrinds. The slow reaction kinetics of MgS + Cr2S3 â MgCr2S4 can be attributed to a miniscule thermodynamic driving force of ÎH = -2 kJ mol-1. Here, we demonstrate that the double ion-exchange metathesis reaction, MgCl2 + 2NaCrS2 â MgCr2S4 + 2NaCl, has a reaction enthalpy of ÎH = -47 kJ mol-1, which is thermodynamically driven by the large exothermicity of NaCl formation. Using this metathesis reaction, we successfully synthesized MgCr2S4 nanoparticles (<200 nm) from MgCl2 and NaCrS2 precursors in a KCl flux at 500 °C in only 30 minutes. NaCl and other metathesis byproducts are then easily washed away by water. We rationalize the selectivity of MgCr2S4 in the metathesis reaction from the topology of the DFT-calculated pseudo-ternary MgCl2-CrCl3-Na2S phase diagram. Our work helps to establish metathesis reactions as a powerful alternative synthesis route to inorganic materials that have otherwise small reaction energies from conventional precursors
The use of electrochemical techniques for the characterization of the corrosion behavior of sol-gel-coated metals
2nononenoneAndreatta, Francesco*; Fedrizzi, LorenzoAndreatta, Francesco; Fedrizzi, Lorenz