Preparation Of Oxide Porous Microspheres And Lithium Based Ceramic Pebbles By Sol-gel Method

Spherical particles are widely used in separation, adsorption, filtration, catalysis and other fields due to its excellent properties such as good fluidity and filling characteristic. On the basis of comprehensive discussion about the research status of oxide porous microspheres and lithium base ceramic pebbles, ZrO2 porous microspheres were prepared by sol-gel method combined with phase separation, Li2TiO3 and Li2ZrO4 pebbles were prepared by sol-gel method combined with micro fluid control technology. Reflective insulation coatings were prepared in the presence of ZrO2 porous microspheres as reflecting pigment. The effects of ZrO2 powder、 ZrO2 solid microspheres and ZrO2 porous microspheres as fillers on the optical properties and thermal insulation properties of the coatings were analyzed. The main contents and results of this paper are as follows:(1) With zirconium propoxide as precursor, PVP as phase separation agent and EAA as chelating agent, ZrO2 microspheres with independent closed pore structure were prepared by sol-gel method combined with phase separation. The addition of EAA, surfactant Span 80, OP-10 and PVP has great influences on the structure of the porous microspheres. When the content of EAA, Span 80 and OP-10 is 2.377,0.571 and 8 g, the ZrO2 microspheres possesses excellent porous structure. The pore size increases with the increase of PVP content. When the shear rate is 1000 and 1500rpm, the microspheres possesses smooth surface structure and excellent dispersity. ZrO2 microspheres possess excellent thermal stability. ZrO2 microspheres still retain smooth spherical surface and internal porous structure after heat treatment at 900℃.(2) With tetrabutyl titanate, zirconyl chloride and citric acid as raw materials, titanium citrate and zirconium citrate were prepared as precursor. Li2TiO3 and Li1ZrO3 pebbles were prepared by sol-gel method combined with micro fluid control technology. When the molar ratio of tetrabutyl titanate, citric acid and lithium hydroxide is 1:1:2, the obtained gel pebbles possesses higher sphericity and good dispersibility after heat treatment. The obtained Li2TiO3 pebbles have higher sphericity when choose acetone as dehydration medium. The Li2TiO3 pebbles all has high sphericity prepared with different viscosities sols after heat treatment. With optimized heat treatment plan, the density of Li2TiO3 ceramic pebbles is greatly improved, the spherical degree is 0.913, the diameter is 0.898 mm and the density is 1.47 g/cm3. When the molar ratio of zirconium oxychloride, citric acid and lithium hydroxide is 3:4:6, Li2ZrO3 pebbles possess good surface structure, high sphericity and good dispersibility after heat treatment.(3) With silicone acrylate emulsion as base material, reflective insulation coatings were prepared in the presence of ZrO2 powder, ZrO2 solid microspheres and ZrO2 porous microspheres as reflecting pigment. The optical performance and heat insulation properties of coatings were investigated. With ZrO2 porous microspheresas reflecting pigment, coatings have excellent barrier properties in the range of ultraviolet, visible and near infrared light. After half hour irradiation of iodine-tungsten lamp, coatings without addition reach to 88.5℃, coatings with 5 wt.% ZrO2 powder reach to 86.3℃, coatings with 5 wt.% ZrO2 solid microspheres reach to 71.9℃, coatings with 5 wt.%ZrO2 porous microspheres reach to 56.5℃.