Efficiency Evaluation of ZrB₂ Incorporation in the MgB₂ Matrix Phase Using High-Energy Milling

Abstract

The present study suggests the use of high energy ball milling to mix (to dope) the phase MgB2 with the AlB2 crystalline structure compound, ZrB2, with the same C32 hexagonal structure than MgB2, in different concentrations, enabling the maintenance of the crystalline phase structures practically unaffected and the efficient mixture with the dopant. The high energy ball milling was performed with different ball-to-powder ratios. The analysis of the transformation and formation of phases was accomplished by X-ray diffractometry (XRD), using the Rietveld method, and scanning electron microscopy. As the high energy ball milling reduced the crystallinity of the milled compounds, also reducing the size of the particles, the XRD analysis were influenced, and they could be used as comparative and control method of the milling. Aiming the recovery of crystallinity, homogenization and final phase formation, heat treatments were performed, enabling that crystalline phases, changed during milling, could be obtained again in the final product.

Effect of the Process Parameters on the Energy Transfer during the Synthesis of the 2LiBH4-MgH2 Reactive Hydride Composite for Hydrogen Storage

“…An essential parameter is represented by the yield coefficient ϕ b , which reflects mainly the percentage of filling. In their work, Burgio et al [34] assumed a primitive cubic packing of the spheres inside of the milling vial. Even avoiding a formal evaluation of the reliability of this consideration, it is possible to observe through practical trials that the obtained number differs significantly from the actual number of spheres that can be fitted in a vial.…”

“…The milling process provides a refined microstructure of reactants: reduced particle and crystallite sizes [34], which increase the reaction rate of hydrogen with the host material, mostly due to a greater specific surface and a higher number of paths of diffusion through the crystallite and phase boundaries [35]. It is hypothesized that the particles and crystallites sizes, and consequently the kinetic characteristics, depend on the transfer of energy to the powder material by milling.…”

Influence of milling parameters on the sorption properties of the LiH–MgB2 system doped with TiCl3

“…Another alternative is to add transition metal halides to increase significantly the sorption kinetics. The impact of transition metal halides has been studied extensively [16][17][18][19]. Their addition to the system reduces particle and crystallite size of the powders, and increases the number of lattice defects and grain boundaries.…”

The Influence of Milling Time and <inline-formula> <tex-math notation="TeX">$\hbox{ZrB}_{2}$</tex-math></inline-formula> Addition on the Superconducting Properties of <inline-formula> <tex-math notation="TeX">$\hbox{MgB}_{2}$</tex-math></inline-formula>

“…In our preliminary work [18], the efficiency of ZrB 2 incorporation in the MgB 2 matrix using high-energy ball milling and heat treatment at high temperature and long time (1000 • C/24 h) was studied, in an attempt to promote a higher densification and connectivity. The crystallographic and microstructural characterizations were performed, showing that the addition of ZrB 2 had no influence on the MgB 2 particle behavior.…”