Plasma Spray Synthesis Of TiO₂ Nanoparticals And Study On Their Dispersing

The Synthesis of TiO2 Nanoparticals by the plasma spray equipment are explored in the atmosphere environment. The feeding system of liquid feedstock was equipped on the bases of general high energy plasma spray equipment. Two phases atomizing nozzle and parallel board electrostatic precipitator were designed. Ti02 powders were synthesized by plasma spraying with ethanol solution of butyl titanate as liquid feedstock on the optimized parameters. The factors effecting on TiO2 particles grain and phase compose are discussed. The detailed process of forming TiO2 particles are analyzed. In allusion to the agglomerates of TiO2 particles, dispersion process of the nanoparticle TiO2 in water was studied with mechanism whisk and dispersant, and the dispersing effects were measured by the methods of spectrophotometer. The parameters of dispersants was optimized and the factors affecting dispersing effects are analyzed. The operation mechanisms of the dispersants are discussed. By the methods of contrastive and orthogonal experiments, the excellent dispersants were found. This provids a theory base to the preparation of TiO2 nanoparticals. The diameter of atomizing gas duct and liquid feedstock duct and their crossing angle are vital elements in the design of two phases atomizing nozzle. Thevelocity of atomizing gas and the flux of liquid feedstock were accounted. The droplet size was found though the experience formulae and experience methods.The parallel board electrostatic precipitator was designed on the base of electrostatic collection theory. Through the normal temperature spray experiments, the factors affecting collection efficiency were obtained. They are as follows: powder types, electrode voltage and board space etc. and the optimized parameters obtained in the normal temperature spray experiments were applied in the thermal spray. The granularity and appearance of the powders collected in the spray experiments were characterized by scan electron microscope transmission and gravity sedimentation. Better results can be obtained when fine powders were collected by electrostatic precipitator. The TiO2 powders were characterized by scan electron microscope, transmission electron microscope and X-ray diffraction analysis. The synthesized Ti02 powders consist of anatase TiO2 and rutile TiO2 according to XRD patterns. Results show that the TiCfe particles show a mean grain size from 10nm to 50nm, and most of which present anatase. The content of anatase TiO2 decrease with the increase of arc powder. The collection velocity achieve 0. 8-1.2g/min, and collection efficiency achieve 8-10% under these parameters. Through the study on the dispersion process of the nanoparticle TiO2 in water, the author finds out that whisk time, dispersant types, dispersant concentration, dispersing time, pH value, temperature and electrolyte concentration have significant influence on dispersing effects. Through contrastive and orthogonal experiments, the author obtains that composite dispersants have better results than single dispersants. This results from the cooperation function of different kinds of dispersants. Three optimum dispersants for TiO2 nanoparticles are obtained on the basis of a great numberof experiments. They are as follows: (l)SDBS(0.2%), NaCl(0.5%), pH=5, T(temperature)=50℃; (2)Sorbitol (10. %), Sodium pyrophosphate(0. 1%), Sodium laurate(0. 2%), pH=ll, T=30℃; (3)Sodium pyrophosphate(0. 1%), Triethanola -mine (0.1%), SDBS(0. 1%), pH=9, T=40℃...