Processing of amorphous nanosize boron powder

Abstract

This article presents natural resources, properties, allotropes and the different synthesis methods for elemental amorphous boron (B) in small and large quantities. The industrial production of elemental amorphous B is mainly based on Moissan process while the gas phase pyrolysis and Chemical vapor deposition (CVD) techniques are more or less restricted to semi-commercial use and research applications. Among all, only thermolysis of B hydrides performed in the temperature range of 500- 1000°C yields fully amorphous nanosize B powders. The properties the commercially amorphous B samples of different purity grades and sources were characterized by using powder X-ray diffraction, SEM, TEM and chemical analysis. The results show that nanosize B has superior properties with respect to purity, particle size, amorphousness and chemical reactivity. The use of reactive nanosize B powder as precursor decreases not only the reaction temperature but leads also to the formation of nanosized MgB2. These attitudes are well compatible with the outstanding performance reported for MgB2 wires manufactured from fully amorphous B powder (B-A9999).