晶种和盐处理剂对煅烧过程中二氧化钛晶型转变的影响

Effects of crystal seeds and salt dopants on phase transformation of TiO2 in calcination process

为探究煅烧晶种及复合盐处理剂对硫酸法钛白粉生产过程中煅烧工序二氧化钛晶型转变的影响,采用热重-差热分析(TG-DTA)、X射线衍射(XRD)和扫描电镜(SEM)等检测手段对煅烧过程中脱水脱硫、相变、样品的晶型组成以及晶粒的形貌进行分析。结果发现:煅烧过程中偏钛酸需要先经历由无定型至锐钛晶型的晶化过程才能向金红石晶型转变;煅烧晶种与盐处理剂的加入使得相变区间由900~1000℃扩大至850~1050℃,其中煅烧晶种促进相变,使得相变温度起始点降低约50℃,盐处理剂在800~900℃表现为对晶粒尺寸的抑制,900℃后对生长的抑制作用弱化,表现为对相变区间的扩大和晶体形貌的调整,有效地调整了晶体的形貌,改善了粒度分布,从而降低了烧结程度。

In order to investigate the effect of crystal seeds and compound salt dopants on the phase transformation of TiO2 crystal forms in calcination process of the titanium dioxide production by sulfuric acid method,the dehydration and desulfation in calcination process,changes of phase,composition of crystal form and granule morphology were analyzed by using the means of thermogravimetry differential thermal analysis(TG-DTA),powder X-ray diffraction(XRD)and scanning electron microscopy(SEM).Results showed that the metatitanic acid(MTA)experienced crystallization process from amorphous to anatase in order to transform to rutile crystal.It was found that calcined crystal seeds and salt dopants can effectively expand the temperature range of phase transformation from the range of 900~1000℃to the range of 850~1050℃.The calcined crystal seeds promoted the phase transformation and reduced the starting point of phase transformation temperature by about 50℃.The salt dopants inhibited the size of crystal seeds at 800~900℃.After 900℃,the inhibition on the growth of crystal seeds was weakened.The phase transformation range was expanded and the crystal morphology was adjusted.It′s helpful in adjusting the crystal morphology,improving the particle size distribution and reducing the sinter ing degree.