Decomposition Of Metal Azides Research Articles

Carbon hollow nanobubbles on porous carbon nanofibers: An ideal host for high-performance sodium-sulfur batteries and hydrogen storage

One-dimensional (1D) carbon nanostructures have been intensively investigated because of their intriguing features and great potential for practical application in various fields. This paper reports the controllable fabrication of carbon hollow nanobubbles on porous carbon nanofibers (CHNBs@PCNFs) through a general electrospinning strategy, with metal azides serving as both a bubbling and a porogen reagent. The strong repulsive forces resulting from the intense release of N2 from the decomposition of metal azides upon carbonization leads to the uniform formation of porous carbon nanofibers (PCNFs), which could be facile tuned by heating rates and the amount of the bubbling reagent, simultaneously constructed with carbon hollow nanobubbles (CHNBs) on the surface. Density functional theory calculations reveal the strong interactions between terminal Na atoms in sodium polysulfides and N and O atoms doped into CHNBs@PCNFs, which could effectively alleviate the shuttle effect of Na-S batteries via adsorbing and trapping polysulfides. With strong adsorption capability of sodium polysulfides and high electrical conductivity, these CHNBs@PCNFs are demonstrated to be an ideal sulfur host in room-temperature sodium-sulfur batteries, which delivers a high reversible capacity of 256 mA h g−1 (specific energy density 384 W h kg−1) with a low decay rate of 0.044% per cycle at 2 C-rate. When CHNBs@PCNFs used as functional supports for MgH2 nanoparticles, a significantly enhanced hydrogen storage performance was achieved. The present work represents a critically important step in advancing the electrospinning technique for generating 1D carbon nanostructures in a facile and universal manner.

Low-temperature solvothermal synthesis of nanocrystalline indium nitride and Ga–In–N composites from the decomposition of metal azides

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.

Modeling of the Elementary Processes of Metal Azide Decomposition

An analysis of the available experimental data on the slow and explosive decomposition of metal azides demonstrates that the intermediate product of the reaction is N6. Based on quantum-chemical calculations, the most symmetrical stable N6 complexes with cyclic, linear, and previously undetected octahedral configurations are established. The energy balance of reactions is calculated. It is demonstrated that the activation energy of forming the cyclic complex is minimum, and the energy of forming the octahedral complex is maximum. Conditions of forming complexes inside the crystal matrix are discussed. An important role of metal in the formation of complexes from azide groups is demonstrated, in particular, the existence of the stable Me2N6 cluster is established.

PHYSICOCHEMICAL PROCESSES IN HEAVY-METAL AZIDES AND THE DISLOCATION STRUCTURE

The present paper gives new experimental results that allow slow decomposition of metal azides of different types (including radiolysis, photolysis, electrolysis, and thermolysis) to be analyzed in the context of the common reaction pathway. Filamentary crystals of silver and lead azides are investigated. It is demonstrated experimentally that the reaction goes on the vacancy cluster formed by an edge dislocation in the near-surface region of the crystal. The reaction produces nonequilibrium electrons and holes considered as reactants. In the bulk of the crystal, the reaction in the anionic sublattice forms an intermediate product, hypothetically, N6. Methods of controlling the defect crystal structure of metal azides are suggested. They allow the reactivity of metal azides to be preset.