Formation of micron-sized and nanometer-sized single crystal alumina whiskers by displacement reactions

We propose a general methodology for fabricating single crystal α-Al2O3 whiskers by displacement reactions. The methodology is based on studies in which Al-rich powder mixtures that contain different kinds of metal oxides (MOx) were sintered. In some sintered products, the in situ formed Al2O3 appeared as particulate while in other it appeared as whiskers. Some conclusions from this study are: growth of the whiskers involves the presence of MOx−1 vapor and Al2O vapor during sintering, and the dimension of the whiskers depends on the size of the initial MOx particles. Micron-sized whiskers were produced in Al–MoO3 and in Al–WO3, while nanorods were produced in Al–SiO2.