| Nanometer TiO2 has attracted wide attention of people to its preparation owing to its excellent physical performance, chemical properties and widely application prospects. In this paper, nano-TiO2, whose grain size is small and crystalline phase is controllable , is prepared by Hydrothermal method and Boiling- Reflux method. This paper studied the influence of [Ti4+] of precursors, condition of preparation, aged time, cladded by surfactant and adulterated by cation on the grain size and crystalline phase through XRD, TG-DTA, TG-DSC and TEM technique. The apparent activation enthalpy of nanocrystalline growth and phase transfrmation are obtained by analysing XRD of nano-TiO2 calcinated at various temperature for various time.The raw material that is used in this paper is cheaper and operation is easier than other method. Pure anatase, anatase/rutile mixtures, and 100% rutile can be obtained by adding various [H+].The step of preparation of sol is one of most important steps to preparation of nano-TiO2. To obtain good sol, peptization of the resultant white preciptitates is conducted by dispersing the precipitates into aqueoussolutions of HC1 or HNO3 whose concentration is in scope of 0.5mol/L to 2mol/L at scope of 40℃ to 80℃.In hydrothermal method, studies shown that the smallest size of nano- particle is obtained when the reaction temperature is closed to the temperature of vapor liquid equilibrium (190癈 in this system) and the reaction time is 8h.The crystallinity of nano-TiO2 prepared by Boiling- Reflux method is worse and the grain size of nano-TiO2 prepared by Boiling-Reflux methodis smaller than those of nano-TiO2 prepared by hydrothermal method. After the precursor is aged for 4days, the crystallinity of nano-TiO2 is improved while the grain size of nano-TiO2 is not largen.Comparaed with the particle prepared by Boiling- Reflux method, the the content of TiO2 of the particle prepared by hydrothermal method is higer and the density is closed to the density of TiO2. When [Ti4+]=0.5mol/L and the reaction temperature is 230癈, portion of nuclei are transferred from anatase to rutile. But the reaction temperature of Boiling- Reflux methodis can not reach so high temperature. So we think that nano-TiO2 prepared by hydrothermal method is better than that of prepared by Boiling- Reflux method.After calcined at hige temperature, phase transformation is occurred. The course of Anatase→Rutile is made up of two successivephase transformation: Anatase→Brookite and Anatase→Rutile.The apparent activation energy of titania nanocrystalline growth was EA(Anatase) = 18.76 KJ/mol and ER(Rutile)=38.49 KJ/mol, respectively, when the temperature was below 500℃; and EA(Anatase)= 70.76 KJ/mol and ER(Rutile)= 75.66 KJ/mol, respectively, when the temperature was above 500℃. The temperature (T>500℃) was favorable for the growth of rutlle nanocrystalline compared with temperature (T<500 ℃). The apparent activation energy of Phase transformation from anatase to rutile is 63.444\0.391 KJ/mol?After cladded by surfactant, degree of dispersion of nano-TiO2 is improved. The optimum addition level is [surfactant]:[Ti4+] = 1:10. But because of cladded by surfactant, the temperture of phase transformation is higher.The adulteration of various anion and cation has an important role in the phase transformation. In various cation, [H+],[Sn4+]and[In2+] favor the formation of rutile. [H+],[Sn4+]and[In2+] can induce anatase nuclei to rutile nuclei. Along with the [cation] being improved, content of rutile phase is increased. When [H+]=6mol/L or [Sn4+]:[Ti4+]≥1:5, pure rutile can be obtained. The existence of [Cl~] will be hindered the occurrence of anatase→rutile.
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