Preparation of Mono-dispersed Ultrafine TiO<TEX>$_2$</TEX> Crystalline Powders by Homogeneous Spontaneous Precipitation from Aqueous TiOCl<TEX>$_2$</TEX> Solution

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J. Korean Ceram. Soc. > Volume 35(11); 1998 > Article

Journal of the Korean Ceramic Society 1998;35(11): 1212.

TiOCl$_2$ 수용액으로부터 자발적으로 일어나는 균일침전에 의한 결정상 TiO$_2$ 단분산 초미분체의 제조

김선재, 박순동, 전치중¹, 김경호, 이희균

한국원자력연구소 원자력기술개발팀
¹한양대학교 재료공학과

Preparation of Mono-dispersed Ultrafine TiO$_2$ Crystalline Powders by Homogeneous Spontaneous Precipitation from Aqueous TiOCl$_2$ Solution

ABSTRACT

The mono-dispersed {{{{ { TiO}_{2 } }} ultrafine particles with the diameters of 40nm-400nm were obtained from aqueous {{{{ {TiOCl }_{2 } }} solution with 0.67M Ti4+ concentration prepared diluting TiCl4 using homogeneous spon-taneous precipitation process. The process was carried out under the conditions to protect H2O evaporation completely or to make it freely in the ranges of 17$^{circ}C$~100~ and to protect it completely in the ranges of 10$0^{circ}C$~23$0^{circ}C$ With the spontaneous hydrolysis of TiOCl2 which means the natural decrease of pH value in the aqueous {{{{ {TiOCl }_{2 } }} solutions all the mono-dispersed precipitates were crystallized with anatase or rutile TiO2 phase during the reaction regardless of various conditions. TiO2 precipitate with rutile phase was fully formed at the temperatures blow $65^{circ}C$ which were not involved in the evaporation of H2O and above 155$^{circ}C$ which were possible to obtain by suppressing it TiO2 precipitate with rutile phyase including small amount of anatase phase started to be formed in the intermediate temperatures above 7$0^{circ}C$ showing the full formation of anatase above 95$^{circ}C$ under the free evaporation of H2O However in the case of completely suppressing H2O evaporation TiO2 precipitate with anatase phase that had been already formed by rapid reaction at the higher temperatures was fully transformed into the precipitate with rutile phase. These cry-stallization behaviors of TiO2 precipitates with the reaction temperature would be caused due to the ex-istences of the capillary pressure between the agglomerated needle-shaped particles or the ultrafine clusters the reaction rate and the vapor pressure of H2O

Key words: Rutile, Anatase, TiO$_2$, Homogeneous precipitation, TiOCl$_2$