New rotation-corrosion dispergation method for obtaining of iron-oxygen nanoparticles

New rotation-corrosion dispergation method for the obtaining of iron-oxygen particles bases on the simple electrochemical process of iron dissolution and oxygen depolarization is received. The metered oxygen delivery and the agglomeration of ferrous iron on the steel - dispersion medium - air interface and permanent change of the physicochemical condition when the iron-oxygen seed-structures are formed take place due to creating of interrupted contact of the steel surface with air and water solution. Variable particles contact with thin film saturated by hydroxyl, ferrous iron and other disperse medium species and provide for controlled component delivery into the reaction area and create the specific condition for heterogeneous growth of the Green Rust seed particles and the products of it phase transformation. As primary particles registered on the steel surface are Fe(II)-Fe(III) layered double hydroxides and ferrihydrite. The peculiar micelle species are formed in the reaction area and they take place in the formation of Fe(II)-Fe(III) layered double hydroxides (LDH) layer on steel surface. Such structures transform in magnetite particles by contact-recrystallization mechanism. The essence of such process lies in the accumulation of the primary magnetite particles on the surface of Fe(II)-Fe(III) LDH, where they form aggregates and prove the recrystallization process. The primary ferrihydrite particles form the structured film of near surface layer. Ferric and ferrous aquahydroxoforms from the reaction area take part in the formation of ferric oxyhydroxides in the near surface layer (NSL). The phase transformation into NSL leads to formation of needle like lepidocrocite γ-FeOOH particles on its inner side and goethite α-FeOOH particles on its outer side. The probable mechanism of the well crystallized α-FeOOH and γ-FeOOH micro particles formatiion are the solution-reprecipitation or reconstructive transformation. According to such mechanism the phase transformation of Fe(II)-Fe(III) LDH in water medium occurs in two stages: the ferrous oxidation into Green Rust lattice with partial solution (destruction) of its nanosized particles and the second precipitation of the well-ordered microsized oxyhydroxide particles. When the mineral phases are formed on iron (steel) surface and in its near electrode layer the iron-oxygen nanoparticles entered in water medium from the reaction area spontaneously form weak-concentrated sols. Usage of stabilizer species applying the rotation-corrosion dispergation (RCD) method of the iron-oxygen nanoparticles obtaining could change of sedimentative and aggregative stability of water sols as well as iron oxyhydroxide mineral particles and aggregates formation. According to experimental investigation we found the optimum physicochemical condition for the formation of nanosized iron-oxygen particle such as lepidocrocite, goethite, magnetite, spinel ferrites. As the most important parameters for obtaining nanoparticles during rotation-corrosion dispergation process chemical composition and pH value of dispersion medium, temperature and oxidation condition were pointed out. (author)