Study of the effect of milling parameters on mechanosynthesis of hydroxyfluorapatite using the Taguchi method

Hydroxyfluorapatite Ca10(PO4)6(OH)F (HFA) powders were prepared by mechanosynthesis method using planetary ball milling with various parameters. X-ray Diffraction (XRD), Infrared (IR) and Raman spectroscopies, Energy Dispersive X-ray (EDX) and Brunauer-Emmett-Teller (BET) methods were employed to characterize the synthesized nanoparticles. Four factors (rotation speeds of disk, mass of balls, initial mass of powder and milling time) were investigated to understand their effect on the milling process and the formation of HFA nanocrystallite. Taguchi's design, with just 16 experiments (an L16 orthogonal array), was used to evaluate the impact of these parameters on six distinct properties, namely the crystallite size (nm), the percentage of crystallinity, the specific surface area (m2/g), the Ca/P atomic ratio, the percentages of the apatite and calcite phases. The average effects of the milling parameters and the signal-to-noise ratio (SN) were discussed. ANOVA analysis was used to determine the importance, the proportion of factor participation and also the influence of process parameters on responses. The Taguchi results indicated that the mass of balls and the rotation speed were found to be the most influential factors on the purity of compounds. The ball to powder weight ratio (BPR) was also introduced to study its effect on the synthesis process. Transmission Electron Microscopy (TEM), Scanning Electronic Microscopy (SEM) and Dynamic Light Scattering (DLS) revealed that milled HFA powders contained a nano-sized agglomerate.