Preparation and Growth Mechanism of Magnesium Borate Whiskers with High Aspect Ratio

Magnesium borate whiskers were prepared by molten salt method using MgCl2?6H2O and Na2B4O7?10H2O as raw materials,KCl and NaCl as fluxes.The lengths of the above whiskers varied from 200μm to 800 μm,and the maximum aspect ratio reached 250.The produced samples were characterized by X-ray diffraction(XRD),microscope and scanning electron microscope(SEM).The effects of n(Mg)/n(B),reaction temperature and reaction time on the whisker growth process and product quality were explored.It was found that the best operating parameters of n(Mg)/n(B),reaction temperature and reaction time were 3.0,900 ℃ and 6h,respectively.According to the XRD analysis,Mg3B7O13Cl is the intermediate product,and the growth of Mg2B2O5 whiskers needs a boron-enriched environment.The whisker growth process agrees to the liquid-solid(L-S) mechanism.