Chemical resistance of tantalum-boride films under the action of sulfuric acid solutions
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BRIEF COMMUNICATIONS CHEMICAL RESISTANCE OF TANTALUM-BORIDE FILMS UNDER THE ACTION OF SULFURIC ACID SOLUTIONS N. A. Klyakhina,1 D. M. Terpii,2 and B. A. Hru 3 We applied films, as in the previous works [1, 2], by sputtering a target, sintered of TaB2 powder, with the help of a high-frequency magnetron sputtering system. The thickness of the films was measured by the methods of radiography and multibeam microinterferometry (MII-4), and the change in their composition was determined by a DRON-3 X-ray diffractometer and a SPLAV 200 X-ray element analyzer. We deposited the films onto glass ceramic plates and steel substrates (40Kh). In the course of application, we controlled changes in the total electric resistance of the films, which were applied onto glass ceramic substrates of size 16 × 16 mm. During deposition, we changed the power of the high-frequency generator ( W ), the pressure of the working gas ( p ), the distance between the substrate and target ( d ), and the electric state of the substrate holder (grounded or insulated). The corrosion properties were determined by the standard procedures. All films obtained by the described technology have a TaB2 -type structure with columnar grains of size 10 to 15 nm. They are characterized by texturing in the direction 〈001 〉, which coincides with the direction of their growth, and by deviations from stoichiometry (to the side of a lesser amount of boron). Note that the degree of texturing is proportional to the growth rate of the film (or W ), which enables us to assume that the nature of texturing is growth-induced. We have also established that the grain size and the critical film thickness depend on the same parameter: with increase in W from 200 to 500 W, the average grain size changes from ∼10 to 15 – 20 nm, and the maximum thickness, on the contrary, decreases from ∼ 600 to ∼ 450 nm. The boron content in the films depends not on the power of the generator, but on the pressure of the working gas and the distance between the target and substrate. For corrosion tests, we took films deposited onto glass ceramic substrates at room temperature with different sputtering rates (or different W values) and different electric states of the substrate holder (grounded or insulated: we induced a negative potential of ∼ 25 – 40 V on the surface of insulated substrate holder). To measure the corrosion rate of the films, we held the specimens in 10% sulfuric acid for 2640 h at room temperature. Afterwards, we washed them with distilled water, dried, and weighed them on an ADV-200 analytical balance. Having determined the mass loss of specimens, we calculated the mass factor of corrosion rate as κ =
m0 − m , St
1 Rubizhne Branch of the Dal’ East-Ukrainian National University, Rubizhne. 2 Donbas State Machine-Building Academy, Kramators’k. 3 Scientific-Research and Design Institute “Khimtekhnologiya,” Severodonets’k.
Translated from Fizyko-Khimichna Mekhanika Materialiv, Vol. 42, No. 5, pp. 113 – 114, September – October, 2006. Original article submitted February 1, 2006. 1068
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