| The rutile Ti O2 is often used as dielectric constant regulator in the preparation of high frequency and microwave substrate materials for its high dielectric constant. The direct use of micron grade Ti O2 will lead to the waste of titanium resources. In this thesis, the Ba SO4/rutile Ti O2 composite particles were synthesized by thermal hydrolysis method under low calcination temperature using Ti C l4 as raw material and Ba SO4 as core, which maximized the utilization of resources. This method has the advantages of cheap materials, simple process and low production energy. All of these advantages may offer theoretical and practical basis for the industrial production of rutile Ti O2 compounds. The main contents are shown as follows:(1) The synthesis of micron grade spherical Ba SO4 core with narrow particle size distribution.Firstly, the Ba SO4 particles were separately synthesized by direct precipitation method, homogeneous precipitation method and complexing precipitation method using Ba C l2 and various precipitator as raw materials. The impacts of reaction temperature, reactant concentration, p H value, feed rate and aging time on the particle morphology and particle size were investigated by single factor experiment. SEM and grading analysis showed that only the particles prepared by H2SO4 process and complexing precipitation method could basically meet the requirement of application. However, the former Ba SO4 had some deficiencies in terms of morphology and particle size distribution. In contrast, the complexing precipitation method can control those two aspects effectively. The optimal reaction conditions were as follows: reaction temperature was 25 oC, p H value was 8, conc entration of Ba C l2 was 0.20 mol/L, complex-ratio was 1, concentration of Na2SO4 was 0.25 mol/L, feed rate of precipitator was 5 m L/min and reaction time was 1 h. Spherical Ba SO4 precipitates with narrow particle size distribution were obtained under the above-mentioned reaction conditions without aging process. The average particle size of Ba SO4 was 1.2 μ m. Secondly, composite Ti O2 were obtained under the same coating technology using different Ba SO4 as core materials, and the coating effects were studied by means of SEM. Results showed that the particles synthesized by complexing precipitation method were more easily for cladding than the one prepared by H2SO4 process. In consideration of the coating effects, the former Ba SO4 were chosen to be the core material of composite Ti O2.(2) The synthesis of rutile composite Ti O2.Firstly, the effecting factors of crystal form, including initial p H value, hydrolysis temperature, SO42- and calcination temperature were investigated. The technology of thermal hydrolysis method for the preparation of rutile Ti O2 was determined. Secondly, composite Ti O2 were synthesized using Ba SO4 particles which were prepared under the optimal reaction conditions by complexing precipitation method as core materials. The influences of hydrolysis time, hydrolysis temperature, dosage of Ti C l4 and concentration of Ti4+ on the coating effects were studied. The optimum hydrolysis conditions of the preparation of Ba SO4/rutile Ti O2 were determined as follows: initial p H of the hydrolysis system was 0.1, concentration of Ti4+ was 0.20 mol/L, n(Ti C l4) : n(Ba SO4) was 2, hydrolysis temperature was 80 oC, hydrolysis time was 1.5 h, calcination temperature was 500 oC and calcination time was 2 h. The obtained composite particles were fully covered by a dense and homogeneous rutile Ti O2 coating layer. In addition, the spherical Ba SO4/rutile Ti O2 composite particles had good dispersion. |
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