Hydrothermal Synthesis Of K₂TiO₃ Nano-fiber And The Further Hydrothermal Reaction

In this paper, hydrothermal method was adopt at 150℃for 24 h with fill factor 68%. We study the influence on the synthesis of titanate by adding different mineralizer (KOH) with different concentration by using TiO₂ as the precursor. Conclusions are as follows: only a part of TiO₂ change to potassium titanate nano-fiber when the concertration of KOH is 10 mol/L,when the concertration of KOH is 15 mol/L,almost all TiO₂ are corroded ,and fibers with diameters of 20nm and lengths of 1 3μm are formed.TiCl₃ as the precursor under hydrothermal condition at 180℃for 24h with fill factor 68%, adjusting the PH value of the aqueous solution by adding certain concentration of HCL and KOH. Analyzing the influence of solution with different PH value to the phase of potassium titanate. In the acidic solution, the concentration of K⁺ is low, TiCl₃ hydrolysis to rutile TiO₂.In the alkaline solution, the concentration of K⁺ is high, the formed TiO₂ are corroded to potassium titanate nano-fiber with diameters of 5¹0nm,lengths up to 1μm。The potassium titanate prepared by hydrothermal method as the precursor, adjusting the PH value of the solution by adding certain concentration of HCl and KOH,proceed a further hydrothermal reaction at 180℃for 24h with fill factor 68%. In strong acidic solution, the potassium titanate which was not washing by HCl was transformed to granular rutile and anatase TiO₂ nanocrystals, whereas anatase TiO₂ nanocrystals are formed in weak acidic solution. Under strong alkali condition, the product remains its former structure as potassium titanate fiber. In acidic solution, the potassium titanate which was washing by HCl was transformed to anatase TiO₂ nanocrystalsThe potassium titanate nanofibers prepared by hydrothermal method as precursor, proceed a further steam hydrothermal method. The original long fibrous structures are damaged, transformed into many messy short fibers with granular anatase TiO₂ crystals in their surfaces. Use steam hydrothermal method to further treat the potassium titanate nanofiber which was washing by HCl, diamond anatase TiO₂ crystals are formed.Experimental results showed: the hydrothermal stability of potassium titanate is relevant to the pH value of the solution, when solution is strong acidic, fibers corrode fast, and stable rutile nanocrystals are formed. When the solution is weak acidic, anatase TiO₂ crystallized faster than fiber's dissolution velocity, so anatase TiO₂ nanocrystals are formed. During the pickling process, K⁺ of the potassium titanate and the H⁺ in HCl solution exchanged, forming H₂TiO₃. If the temperature is high, the structure of the formed H2TiO3 is very unstable, after slow dissolution and phase transformation, dehydration to anatase TiO₂ nanocrystals .