| 摘要 |
PROBLEM TO BE SOLVED: To provide hollow nanoparticles each composed of a low density silica shell, with which very low thermal conductivity is effectively obtained by mixing the hollow nanoparticles into a material such as a coating material, and to provide a method for producing the same. SOLUTION: After subjecting calcium carbonate 2 to crystal growth (S10), the grown calcium carbonate 2 is aged (S11) and dehydrated (S12) to obtain a solid fine powder. Then, the fine powder is dispersed (S13) in ethanol, and each particle of the powder is coated (S14) with silica by a sol-gel method comprising adding a silicon alkoxide and ammonia. Thus prepared silica-coated particles 3 are washed (S15) and dispersed (S16) in water. Thereafter, hydrochloric acid is added to the resulting dispersion to dissolve and flow out (S17) the calcium carbonate 2 included in each particle 3. Thereby, hollow nanoparticles 4 each composed of a cubic silica shell having flow-out holes are formed. After drying (S18) the formed hollow nanoparticles 4, the hollow nanoparticles 1 each composed of a low density silica shell are produced by heating the hollow nanoparticles 4 at 400°C to seal (S19) the flow-out holes in a heating process. COPYRIGHT: (C)2010,JPO&INPIT |
