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

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 stopinj C or more and at adequate pressure of the water vapour. Predmet izuma so nanodelci anatasa in način njihove sinteze po gel-sol metodi iz natrijevega titanata, ki se proizvede iz metatitanove kisline v reakciji z NaOH. Molsko razmerje med NaOH in TiO2 za sintezo natrijevega titanata mora biti nizko, če je namen sintetizirati anatas in sicer med 1:3 do 1:1, če je namen sintetizirati rutil pa mora biti višje in sicer vsaj med 3:1 do 4:1. V gel- sol reakciji med natrijevim titanatom in kislino se tvorijo zelo majhni delci anatasa, ki so sferične morfologije,polikristalinični in prisotni v kisli suspenziji. Velikost kristalitov, ki sestavljajo delce anatasa je približno 5 nm, medtem ko so sami delci večji in sicer med 40 do 60 nm. Predmet izuma je tudi način stabilizacije kisle suspenzije nanodelcev, ki omogoča dvig vrednosti pH, ne da bi prišlo do prekomerne aglomeracije, kar je doseženo z uporabo ustreznega disperganta, citronske kisline. Predmet izuma je tudi hidrotermalna metoda, ki omogoča prekristalizacijo polikristaliničnih nanodelcev anatasa vmonokristalinično obliko pod hidrotermalnimi pogoji v avtoklavu pri temperaturi približno 130 stopinj C ali več in temu primernemu tlaku vodne pare.