Recently, a research group led by Prof. WANG Xianlong from the Hefei Institutes of Physical Science of the Chinese Academy of Sciences, synthesized high-energy-density materials cubic gauche nitrogen (cg-N) at atmospheric pressure by treating potassium azide (KN3) with the plasma-enhanced chemical vapour deposition technique (PECVD).
The research results were published in Science Advances.
Cg-N is a pure nitrogen material consisting of nitrogen atoms bonded together by N-N single bonds, with a structure similar to that of diamond. It has attracted attention because it has a high-energy-density and produces only nitrogen gas when it decomposes. In this field, developing efficient and safe synthesis method under atmospheric pressure is an important issue.
Since 2020, the research team using first-principles calculations as a theoretical guide, has simulated the stability of the cg-N surface in different saturated states and at different pressures and temperatures. The simulation results revealed that surface instability causes the cg-N decomposition at low-pressure, and it is proposed that saturating the surface suspension bonds and transferring the charge can stably cg-N up to 750 K at atmospheric pressure.
Based on this, because potassium is less electronegative than sodium, the research team chose KN3, which has a stronger electron transfer capacity and low toxicity and low explosiveness, as a precursor and successfully synthesized cg-N by using PECVD technology without the help of carbon nanotube-limiting effect. Thermogravimetric-differential scanning calorimetry (TG-DSC) measurements show that synthesized cg-N show thermal stability up to 760 K following with a rapid and intense thermal decomposition.
The study provides an efficient and convenient way to synthesis cg-N at atmospheric pressure, and also new ideas for the development of future high-energy-density materials.
