Heat treatment of Ni-P+TiO2+Ti composite layers
* Bożena Łosiewicz, * Antoni Budniok, * Katarzyna Wykpis, * Eugeniusz Łągiewka, * Edward Rówiński, ** Jerzy Cybo, ** Grzegorz Służałek * Uniwersytet Śląski, Instytut Fizyki i Chemii Metali, ul. Bankowa, 40-007 Katowice ** Uniwersytet Śląski, Katedra Materiałoznawstwa, ul. Śnieżna 2, 41-200 Sosnowiec
Annals 2 No. 3, 2002 pages 47-51
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abstract Amorphous Ni-P+TiO2+Ti composite layers were prepared by co-deposition of nickel with titanium dioxide (anatase) and titanium powder on a copper substrate from a solution in which TiO2 and Ti particles were suspended by stirring. In order to obtain composite Ni-P+TiO2+Ti layers the following nickel plating bath was prepared (g/dm3): 51 NiSO4 ⋅ 7H2O, 10,7 NH4Cl, 29 NaH2PO2 ⋅ H2O, 10 CH3COONa, 8 H3BO3 with addition of: 99 TiO2 and 10 Ti. The mean surface area of TiO2 and Ti grains were measured and calculated to be respectively: 12 and 25 μm2. Reagents from POCh Gliwice (Poland) and Merck (Germany) of analytical purity and deionized water were used for the solution. The suspension had a pH of 4.8÷5.1. The electrodeposition was carried out under galvanostatic conditions at the current density of j = 250 mA/cm2 at a temperature of 293 K. The vessel diameter was 8 cm. The copper plates of one-sided area 1 cm2 were placed parallel to the bottom of the vessel. Electrodeposition was conducted in the electrolytic cell containing 250 cm3 of the solution. The other side of the plates was covered with non-conducting resin. The distance between the plates and the surface of the solution was 5 cm. The counter electrode was made of platinum mesh with the geometric area of 1 dm2. Under these conditions the solution mixing rate of 300 rev/min was applied. For comparison the Ni-P layers were also obtained and investigated in the same manner. The thickness of the deposited layers was found to be about 100-250 μm. Heat treatment of the layers was carried out at a temperature of: 400°C for 8 h, 500°C for 10 h, 800°C for 12 h in argon atmosphere. X-ray diffractometer, Auger electrons spectrometer, atomic absorption spectroscope, metallographic and stereoscopic microscope, and surface analyser were used for physical and chemical characterization of the layers. It was found that the heat treatment of the composite Ni-P+TiO2+Ti layers leads to the production of Ni-P + titanium oxides layers with a new qualitative chemical composition. The layers obtained after heat treatment are of a compact composite structure and contain new phases as products of an amorphous nickel matrix crystallization, NiTi intermetallic compound and nonstoichiometric titanium oxides. There are nonstoichiometric titanium oxides after heat treatment at the temperature of: 400°C - Ti10O19, 500°C - Ti7O13 and 800°C - Ti4O7 in the layers. Under proposed conditions of the heat treatment of composite Ni-P+TiO2+Ti layers is possible to obtain composite materials containing different red-ox pairs as TiO2-Ti10O19, TiO2-Ti7O13 or TiO2-Ti4O7. Such pairs of titanium dioxide and nonstoichiometric titanium oxides can influence the electrolytic hydrogen evolution reaction.