Abstract. A novel Al-Er master alloy has been prepared through situ metallothermic reactions of NaErF 4 and aluminium melts. The compound NaErF 4 is formed as a result of the interaction of NaF and ErF 3 in the melt medium KCl. The metallothermic reactions produce erbium, which through low solubility in molten aluminium and forms intermetallic compound Al 3 Er. The microstructures of the Al-Er master alloy with different contents of the alloying metal has been investigated. The results showed that the Al-Er master alloy mainly consisted of phases of α-Al and Al 3 Er, that confirmed by the results of X-ray diffraction. Backscattered electron imaging of the Al-Er master alloy under a scanning electron microscope (SEM) revealed the presence of phase Al 3 Er, which crystallized in the eutectic composition [Al+Al 3 Er]. The observed microstructure is explained according to the eutectic reaction in an Al-Er phase diagram. The preparation of Al-Er master alloy by the metallothermic reduction method will allow to reduce energy consumption for master alloy production and to reduce the cost of aluminium alloys alloyed with Er through the novel master alloy.
Titanium dioxide has a special feature: anatase, to rutile transformation which was considered in our investigations. It is especially important to keep anatase form of titanium dioxide for photocatalytic materials, different ceramics with tribo-chemical properties, self-cleaning coatings and self-sterilizing coatings. For that only one of the titanium dioxide forms is more suitable – anatase, which is more active but not stable, because it transforms to rutile during the time or with the temperature increase loses its activity. Different methods of stabilising anatase have been considered in the paper. Several doping agents have been determined and it was chosen fluorine ion to modify titanium dioxide. Stabilization of anatase is achieved by preparing the reaction mixture by a sol-gel method with hydrofluoric acid. It has shown thermodynamic data, results of experiment, temperatures of anatase to rutile transformation of non-doped and doped titanium dioxide, its X-Ray diffraction and TGA. It is proved that titanium dioxide doped by fluorine ion keeps anatase form till the temperature is more than 1000 °C.
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