Study on spheroidization and the growth mechanism of eutectic boron in Cu–B alloys

Abstract

In this work, a method of preparing boron nanoparticles using copper–boron alloy is presented, and the growth mechanism of boron nanoparticles is analyzed. It was found that sharp eutectic boron in copper–boron alloy can be spheroidized through adjustment of the cooling rate. By comparing three elements Al, Mg and Si, Mg can further control the morphology of eutectic boron and achieve further spheroidization of eutectic boron by limiting the emergence and growth of dendrites. Boron spheres as well as amorphous boron spheres were obtained by extracting the Cu–B alloy which had been spheroidized. The growth mechanism of eutectic boron and boron spheres has been analyzed by HRTEM. Solid boron spheres with curved lattice fringes and obvious crystal defects can be observed. Lattice puckering can be seen in amorphous boron spheres. Moreover, we also report a simple method to prepare hollow boron spheres which consist of multiple crystals and these crystals can form perfect coherent interfaces through twins. Twins and dislocations play an important role in the globular growth of boron.