Gravimetry, resistometry, and Fourier-transform infrared spectroscopy for monitoring the corrosivity of the atmosphere with the use of an iron-oxide nanocomposite sensor layer

The properties of a heterophase nanostructured metal-oxide layer produced by reactive sputtering in a vacuum followed by exposing to an oxidizing air environment at different evacuation degrees at 25°C are monitored with the use of diffuse reflectance Fourier transform infrared spectroscopy, resistometry, and gravimetry. According to the data of atomic force microscopy and infrared spectroscopy, as a result of the application of a metal to a glass substrate and subsequent oxidation, a metal-oxide nanocomposite film composed of metal-oxide nanoparticles with sizes of 20–30 nm covered with magnetite-hematite oxide shells is formed. It is shown that a metal-oxide nanocomposite layer can be used as a sensor in oxidizing environments. Gravimetric and resistometric sensor responses (the integral degree of oxidation) are almost proportional to the logarithmic rarefaction, which enables one to use metal-oxide sensors in broad ranges of pressure and rarefaction of the monitored atmosphere. Results of gravimetry and resistometry showed that the low-temperature oxidation of freshly sputtered iron films is accompanied by their partial oxide compaction. For overall monitoring of the formation of magnetite and its transformation into hematite, the above methods should be supplemented with a spectral method, such as Fourier-transform infrared spectroscopy.