Oleic acid as grinding aid and surface antioxidant for ultrafine zirconium hydride particle preparation

Highlights: • Wet ball milling of ZrH₂ in ethanol solution to produce ultrafine ZrH₂ particles. • D₅₀ value of the ground ZrH₂ reduced from 9.10 μm to 3.21 μm with oleic acid addition. • Surface oxygen content of ZrH₂ decreased from 21.65% to 13.11% with oleic acid addition. ZrH₂ is brittle and easy to grind into ultrafine particles, which can be further thermally dehydrogenated to produce fine metal zirconium powder. However, surface oxidation of ZrH₂ usually occurs during the grinding process. In this study, oleic acid was employed as a grinding aid and surface antioxidant for ultrafine ZrH₂ preparation by wet ball milling in ethanol solution. With the addition of oleic acid, the particle size (d₅₀) of ZrH₂ after milling was reduced from 9.10 to 3.21 μm, and the surface oxygen content decreased from 21.65% to 13.11%. The zeta potential of the ZrH₂ surface was positive and the oleate anion was adsorbed on the ZrH₂ surface by electrostatic adsorption. Oleic acid acted as a grinding aid, improving the grinding efficiency of ZrH₂, and also as a coating film protecting ZrH₂ from surface oxidation. Ultrafine ZrH₂ particles with high purity can be manufactured by the proposed wet ball milling process, which has great potential for practical industrial production. The approach based on surfactant addition to improve the grinding efficiency and surface protection could also be applied for the preparation of other ultrafine materials using wet ball milling.