High-energy-density cubic gauche nitrogen successfully synthesized at atmospheric pressure

A research group led by Prof. Wang Xianlong from the Hefei Institutes of Physical Science of the Chinese Academy of Sciences, has successfully synthesized high-energy-density materials cubic gauche nitrogen (cg-N) at atmospheric pressure by treating potassium azide (KN₃) using the plasma-enhanced chemical vapor deposition technique (PECVD).

The research is published in Science Advances.

Cg-N is a pure nitrogen material consisting of nitrogen atoms bonded by N-N single bonds, resembling the structure of diamond. It has attracted attention because it has a high-energy-density and produces only nitrogen gas when it decomposes. The development of efficient and safe synthesis methods under atmospheric pressure is an important issue.

Since 2020, the research team has employed first-principles calculations as a theoretical guide to simulate the stability of the cg-N surface under various saturated states, pressures, and temperatures. The results revealed that surface instability led to the cg-N decomposition at low-pressures. They proposed that saturating the surface suspension bonds and transferring the charge could stabilize cg-N up to 750 K at atmospheric pressure.

In this research, choosing KN₃ with lower toxicity and explosiveness as a precursor due to the strong electron transfer capacity of potassium, the team successfully synthesized cg-N using PECVD technology without relying on the carbon nanotube-limiting effect.

Thermogravimetric-differential scanning calorimetry (TG-DSC) measurements confirmed that the synthesized cg-N exhibits thermal stability up to 760 K, followed by rapid and intense thermal decomposition.

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