Preparation of Hollow Silica by Spray Drying of Nano Silica Particles and Its Heat Transfer Property

Abstract

Hollow silica spheres were prepared by spray drying of precursor solution of colloidal silica. The precursor solution is composed of 10-20 nm colloidal silica dispersed in a water or ethanol-water mixture solvent with additives of tris hydroxymethyl aminomethane. The effect of pH and concentrations of the precursor and additives on the formation of hollow sphere particles was studied. The spray drying process parameters of the precursor feeding rate, inlet temperature, and gas flow rate are controlled to produce the hollow spherical silica. The mixed solvent of ethanol and water was preferred because it improved the hollowness of the spheres better than plain water did. It was possible to obtain hollow silica from high concentration of 14.3 wt% silica precursor with pH 3. The thermal conductivity and total solar reflectivity of the hollow silica sample was measured and compared with those values of other commercial insulating fillers of glass beads and TiO 2 for applications of insulating paint, in which the glass beads are representative of the low thermal conductive fillers and the TiO 2 is representative of infrared reflective fillers. The thermal conductivity of hollow silica was comparable to that of the glass beads and the total solar reflectivity was higher than that of TiO 2 .

Preparation of Spherical Granules of Dolomite Kiln Dust as Gas Adsorbent

“…2) Porosity here is known to be the major factor affecting physical interaction and chemical reactivity between matters. 3,4) To produce many spherical granules having a porous and hollow structure with a size of a few ten µm, various methods such as core-shell method, spray drying method, spray pyrolysis method, self-assembly method, smelting method, polymer sponge method, etc. have been reported.…”

“…have been reported. 3,5) Among these methods, the spray drying method has advantages of good scale-up properties and cost effectiveness, since the design is relatively simple, the particle size distribution is continuous and reproducible with a relatively low and uniform density accompanied by a high specific surface area, and no separate drying process is required. [6][7][8] As described in Fig.…”