Research on the improvement of mixed titania and Co(Mn) oxide nano-composite coatings

Abstract

Abstract. The structure and the properties of the oxide films formed on titanium in the diphosphate based electrolytes by means of plasma electrolytic oxidizing at direct current density of 2-2.5 A· dm −2 have been studied. Oxide layers of different composition and content of alloying elements were obtained by modification of electrolytes and variation in current density. The interelectrode voltage during PEO, chemical and phase composition, topography and microstructure of the formed layers depend on the electrolyte composition and applied current density. The spark-discharge regime was shown to be reached at inter-electrode voltage 100 to 130 V depending on the composition of electrolyte. The effect of chemical composition and surface morphology formed mixed oxide films on the corrosion resistance and catalytic activity has been discussed. IntroductionTitanium is the most common oxide in heterogeneous catalysis and photo-catalysis for the purification gas and liquid media from toxicant [1,2]. This fact is attributed to the fairly high chemical stability under different operating conditions, no toxicity, and relatively low cost of this material. At the same time it was found that, in most cases, catalyst materials based on mixed two or three component oxide systems exhibit high activity and selectivity not only in heterogeneous red-ox reactions [3-5] but also in photo-catalytic ones [6][7][8]. Synthesis of nano-composite catalytic disperse systems based on titania is carried out by various methods, including sol-gel processes [6,9,10].The formation different kind of oxide layers has been achieved by the anodic oxidation and plasma surface treatment in the sparking regime (plasma electrolytic oxidizing PEO) seems to be the very promising since it does not need the sophisticated facilities, allows to form various types of titania and to incorporate different species into the layer by modification of electrochemical parameters and of electrolyte chemistry [11][12][13][14].Titania layers containing manganese oxides obtained by PEO in acetate-borate electrolyte was noted to be catalytic active in CO conversion to CO 2 [15]. Cobalt-containing oxide coatings on titanium are obtained from a silicate electrolyte with cobalt acetate addition [16]. However, the increase in the catalytic activity of above materials in CO oxidation reaction was achieved by additional impregnation followed by annealing. In [17] catalytic materials on titanium and aluminum doped with transition metal oxides (Mn, Fe, Co, Ni) were obtained in one stage by the PEO method,

Corrosion and Mechanical Properties of the Fe‐W‐Wo2 and Fe‐Mo‐MoO2 Nanocomposites

“…% were obtained at temperature of 60°C and direct current density of 50 mA/cm 2 from ammonia-citrate electrolytes based on Fe (III). It was shown in [10] ammonia-citrate baths to possess the required buffer capacity for the electrodeposition of nanocrystalline and smooth Co-W and Fe-W. A qualitative study of the mechanical behavior of electrodeposited Co-W and Fe-W alloys was performed by different methods.…”

“…Smoother and crack-free Fe-Mo coatings with molybdenum content of 54 wt. % were electrodeposited from a highly saturated ammonium acetate bath at current density of 30 mA/cm 2 [10]. It was considered that the coatings to be catalysts for the hydrogen evolution reaction.…”