SYNTHESIS METHOD FOR OBTAINING ANATASE NANOPARTICLES OF HIGH SPECIFIC SURFACE AREA AND SPHERICAL MORPHOLOGY

摘要

The subject of the invention is anatase nanoparticles and ways of the synthesis thereof by a gel- sol method from sodium titanate, which is produced from metatitanic acid in a reaction with NaOH. The molar ratio between NaOH and TiO₂ must be low for a synthesis of sodium titanate, if the goal is to synthetize anatase, i. e. is between 1 :3 to 1 : 1. If the goal is to synthetize rutile, the molar ratio must be higher, at least between 3: 1 to 4: 1. In the gel-sol reaction between sodium titanate and acid very small anatase particles are formed that are of spherical morphology, polycrystalline and present in the acidic suspension. The size of crystallites that constitute the anatase particles is approximately 5 nm, wherein the particles themselves are bigger, somewhere between 40 to 60 nm. The subject of the invention is also a manner of stabilising the acidic suspension of nanoparticles, which allows an increase in pH value without causing excessive agglomeration, which is achieved by the use of an suitable dispersant, citric acid. A further subject of the invention is a hydrothermal method, which allows re-crystallisation of polycrystalline anatase nanoparticles into a monocrystalline form under hydrothermal conditions in an autoclave at a temperature about 130 °C or more and at adequate pressure of the water vapour.