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. Developing efficient and safe synthesis method under atmospheric pressure is important.

Since 2020, WANG's team has simulated the stability of the cg-N surface in different saturated states and at different pressures and temperatures, with first-principles calculations as a theoretical guide. The simulation results revealed that surface instability causes the cg-N decomposition at low-pressure. Researchers 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, research team chose KN3 as a precursor and synthesized cg-N by using PECVD technology without the help of carbon nanotube-limiting effect, because potassium is less electronegative than sodium. KN3 has a stronger electron transfer capacity and low toxicity and low explosiveness.

Thermogravimetric-differential scanning calorimetry (TG-DSC) measurements showed that synthesized cg-N exhibits thermal stability up to 760 K following with a rapid and intense thermal decomposition.

The study provides an efficient and convenient way to cg-N synthesis at atmospheric pressure, and also new ideas for the development of future high-energy-density materials.