1 Nanostructured Functional Coatings of Iron Family Metals with Refractory. . .
7
The chemical composition of the coatings was determined by energy-dispersive
X-ray spectroscopy (EDS) on an Oxford INCA Energy 350 electron probe microanalysis integrated into the system of the SEM. The X-rays were excited by exposure
of the samples to a beam of 15 keV electrons. The surface morphology of the
deposits was studied with a Zeiss EVO 40XVP scanning electron microscope
(SEM). Images were recorded by the registration of secondary electrons (SEs) via
scanning with an electron beam; this mode made it possible to study the topography
with a high resolution and contrast ratio.
The surface morphology of thin films was studied by an atomic force microscopy
(AFM) using a NT-206 scanning probe microscope. The tapping mode was conducted to measure sample surface morphologies. Scanning was performed by using
the contact probe CSC-37 with a cantilever lateral resolution of 3 nm [33]. The scan
area sizes were fixed at different scopes, namely, 39.9 × 39.9 μm, 20.0 × 20.0 μm,
10.0 × 10.0 μm, and 5.0 × 5.0 μm, and the height of the surface relief was recorded
at the resolution of 256 × 256 pixels. For each sample, a variety of scans were
obtained at random locations on the surface of thin films. In order to analyze the
AFM images, all image data were converted into Surface Explorer software.
The structure of the deposits was examined by X-ray diffraction analysis using
a diffractometer (DRON-2.0) in the emission of iron (cobalt) anode and CuKα
radiation. X-ray patterns were recorded in discrete mode with a step 2θ = 0.1 ◦ with
the exposure at each point for 20 s; the operating voltage was 35 kV and current,
20 mA.
Magnetic characteristics of the Fe-Co-W(Mo) thin films were measured using
the vibration magnetometer for the fields up to 1600 kA·m −2 . The coercive force
H c and the saturation field H s were defined by hysteresis loops measured in the
fields applied to the coating plane. The saturation magnetization I s and the saturation
induction B s were estimated by hysteresis loops obtained for the magnetization of
specimens by the film plane normal.
Corrosion tests of coated samples were carried out in a model media of 1 M
sodium sulfate with the addition of sulfuric acid to pH 3 or potassium hydroxide to
pH 11 and in 3% potassium chloride (pH 7). The corrosion current was determined
by the polarization resistance technique using digital analysis of anodic and cathodic
plots in Tafel coordinates within the range of 200–300 mV from open circuit
potential [34]. The potentiostat IPC-Pro controlled by PC was used for voltammetry
measurements with scan rate of 1 mV/s. Corrosion depth index k h (mm per year)
was converted from corrosion current:
k h = (8.76k e i cor ) /ρ,
where k e is the electrochemical equivalent of alloy, kg·C −1 ; i cor the corrosion current
density, A/m 2 ; and ρ the density of the alloy, kg/m 3 . Electrochemical equivalent
k e and density ρ of the alloys were determined considering their quantitative
composition [35].
7
The chemical composition of the coatings was determined by energy-dispersive
X-ray spectroscopy (EDS) on an Oxford INCA Energy 350 electron probe microanalysis integrated into the system of the SEM. The X-rays were excited by exposure
of the samples to a beam of 15 keV electrons. The surface morphology of the
deposits was studied with a Zeiss EVO 40XVP scanning electron microscope
(SEM). Images were recorded by the registration of secondary electrons (SEs) via
scanning with an electron beam; this mode made it possible to study the topography
with a high resolution and contrast ratio.
The surface morphology of thin films was studied by an atomic force microscopy
(AFM) using a NT-206 scanning probe microscope. The tapping mode was conducted to measure sample surface morphologies. Scanning was performed by using
the contact probe CSC-37 with a cantilever lateral resolution of 3 nm [33]. The scan
area sizes were fixed at different scopes, namely, 39.9 × 39.9 μm, 20.0 × 20.0 μm,
10.0 × 10.0 μm, and 5.0 × 5.0 μm, and the height of the surface relief was recorded
at the resolution of 256 × 256 pixels. For each sample, a variety of scans were
obtained at random locations on the surface of thin films. In order to analyze the
AFM images, all image data were converted into Surface Explorer software.
The structure of the deposits was examined by X-ray diffraction analysis using
a diffractometer (DRON-2.0) in the emission of iron (cobalt) anode and CuKα
radiation. X-ray patterns were recorded in discrete mode with a step 2θ = 0.1 ◦ with
the exposure at each point for 20 s; the operating voltage was 35 kV and current,
20 mA.
Magnetic characteristics of the Fe-Co-W(Mo) thin films were measured using
the vibration magnetometer for the fields up to 1600 kA·m −2 . The coercive force
H c and the saturation field H s were defined by hysteresis loops measured in the
fields applied to the coating plane. The saturation magnetization I s and the saturation
induction B s were estimated by hysteresis loops obtained for the magnetization of
specimens by the film plane normal.
Corrosion tests of coated samples were carried out in a model media of 1 M
sodium sulfate with the addition of sulfuric acid to pH 3 or potassium hydroxide to
pH 11 and in 3% potassium chloride (pH 7). The corrosion current was determined
by the polarization resistance technique using digital analysis of anodic and cathodic
plots in Tafel coordinates within the range of 200–300 mV from open circuit
potential [34]. The potentiostat IPC-Pro controlled by PC was used for voltammetry
measurements with scan rate of 1 mV/s. Corrosion depth index k h (mm per year)
was converted from corrosion current:
k h = (8.76k e i cor ) /ρ,
where k e is the electrochemical equivalent of alloy, kg·C −1 ; i cor the corrosion current
density, A/m 2 ; and ρ the density of the alloy, kg/m 3 . Electrochemical equivalent
k e and density ρ of the alloys were determined considering their quantitative
composition [35].