418
E. A. Koblova et al.
PEO-coatings and interrelationships between the surfaces and catalytic properties. A
number of Ni- and/or Cu-containing coatings formed by PEO have been investigated
by the method of X-ray photoelectron spectroscopy (XPS) [5–7]. It was determined
that the main components of the surface layers of these coatings are a variety of
oxide structures of the base and electrolyte elements – oxides of aluminum, nickel,
copper, and more complicated composite structures. In this chapter, we introduce
our recent experimental results on surface coatings on aluminum.
11.2 Composition and Electronic State of Surface Metal
Oxide Structure
11.2.1 Experimental Details
The coatings were formed on aluminum (A7 grade) by PEO in water electrolytes
containing the basic components (Na 3 PO 4 , Na 2 ¥ 4 O 7 , Na 2 WO 4 ) [8] and nickel and
copper acetates in various ratios. A detailed description of the coatings and the
process of their formation are in Ref. [5].
The XPS spectra were measured by an ultra-vacuum spectrometer (Specs, Germany) equipped with a 150 mm electrostatic hemispherical Phoibos-150 analyzer
[4]. To excite the spectra, we used nonmonochromatized Mg K α (1253.6 eV)
radiation. The vacuum in the analyzer chamber (when measuring the spectra) was
about 5·10 −7 PÃ. The transmission energy of the analyzer was set to 50 eV (which
caused the resolution of the spectra in the C 1s band about 1.8 eV). The spectra
of the initial surface of the samples (the upper layers of 3–5 nm thickness) and the
underlying near-surface layers exposed by ion etching were measured. To remove
the upper layer (∼3 nm thick), ion etching was used by scanning the sample surface
for 5 min at an Ar + energy of 5000 eV and current I total = 20 μA. According to
our estimation, the etching rate of the studied materials was about 0.1 Å/s. The
spectra were calibrated using the hydrocarbon C1s lines whose energy was taken to
be 285.0 eV.
11.2.2 Experimental Results
According to our previous results [5–7], PEO-coatings have the complicated
composition and structure due to the peculiarities of their formation processes.
Oxidation of the initial pure aluminum in the base electrolyte (PBW) leads to the
oxidation of upper layer metal-base and to the integration of components from
electrolyte: Na, P, and W (see Fig. 11.1). Here, as follows from the photoelectron
spectra (see Table 11.1), the surface layer of the Al-PBW coating contains not
only aluminum oxide and phosphate but also sodium phosphate Na 3 PO 4 , tungsten
E. A. Koblova et al.
PEO-coatings and interrelationships between the surfaces and catalytic properties. A
number of Ni- and/or Cu-containing coatings formed by PEO have been investigated
by the method of X-ray photoelectron spectroscopy (XPS) [5–7]. It was determined
that the main components of the surface layers of these coatings are a variety of
oxide structures of the base and electrolyte elements – oxides of aluminum, nickel,
copper, and more complicated composite structures. In this chapter, we introduce
our recent experimental results on surface coatings on aluminum.
11.2 Composition and Electronic State of Surface Metal
Oxide Structure
11.2.1 Experimental Details
The coatings were formed on aluminum (A7 grade) by PEO in water electrolytes
containing the basic components (Na 3 PO 4 , Na 2 ¥ 4 O 7 , Na 2 WO 4 ) [8] and nickel and
copper acetates in various ratios. A detailed description of the coatings and the
process of their formation are in Ref. [5].
The XPS spectra were measured by an ultra-vacuum spectrometer (Specs, Germany) equipped with a 150 mm electrostatic hemispherical Phoibos-150 analyzer
[4]. To excite the spectra, we used nonmonochromatized Mg K α (1253.6 eV)
radiation. The vacuum in the analyzer chamber (when measuring the spectra) was
about 5·10 −7 PÃ. The transmission energy of the analyzer was set to 50 eV (which
caused the resolution of the spectra in the C 1s band about 1.8 eV). The spectra
of the initial surface of the samples (the upper layers of 3–5 nm thickness) and the
underlying near-surface layers exposed by ion etching were measured. To remove
the upper layer (∼3 nm thick), ion etching was used by scanning the sample surface
for 5 min at an Ar + energy of 5000 eV and current I total = 20 μA. According to
our estimation, the etching rate of the studied materials was about 0.1 Å/s. The
spectra were calibrated using the hydrocarbon C1s lines whose energy was taken to
be 285.0 eV.
11.2.2 Experimental Results
According to our previous results [5–7], PEO-coatings have the complicated
composition and structure due to the peculiarities of their formation processes.
Oxidation of the initial pure aluminum in the base electrolyte (PBW) leads to the
oxidation of upper layer metal-base and to the integration of components from
electrolyte: Na, P, and W (see Fig. 11.1). Here, as follows from the photoelectron
spectra (see Table 11.1), the surface layer of the Al-PBW coating contains not
only aluminum oxide and phosphate but also sodium phosphate Na 3 PO 4 , tungsten