Controlled synthesis of Ultra large diameter K₂Ti₆O₁₃ micro-rods via spherical agglomeration mechanism

Potassium hexatitanate whiskers (PHWs, K₂Ti₆O₁₃) are generally slender, with diameters of about 1 μm, which falls under the category of inhalable particles. Producing large-diameter rod-shaped K₂Ti₆O₁₃ is necessary to prevent the environmental and human health threats posed by inhalable fibers. We report a new synthesis approach, via spherical agglomeration, which separates the nucleation stage from the nuclei agglomeration and growth stages of the calcination process resulting in the growth of the K₂Ti₆O₁₃ micro-rods with large diameter. From thermogravimetric analysis, we deduced the critical temperature for generating K₂Ti₆O₁₃ nuclei in the melt phase to be around 800 °C; this was referred to as the nucleation stage. The absorption of K₂O on different facets of the growing crystal nuclei was used to control the nuclei agglomerate in a subsequent step. K₂O acted as a binding agent to agglomerate the nuclei in the melt phase and transforms the finer agglomerate nuclei into large diameter micro-rods similar to the bridging agents employed in spherical agglomeration technique. K₂Ti₆O₁₃ micro-rods with large diameters of up to 8.3 μm were produced.