The unique properties and numerous applications of nanocrystalline titanium dioxide (TiO2) are stimulating research on improving the existing and developing new titanium dioxide synthesis methods. In this work, we demonstrate for the first time the possibilities of the extraction–pyrolytic method (EPM) for the production of nanocrystalline TiO2 powders. A titanium-containing precursor (extract) was prepared by liquid–liquid extraction using valeric acid C4H9COOH without diluent as an extractant. Simultaneous thermogravimetric analysis and differential scanning calorimetry (TGA–DSC), as well as the Fourier-transform infrared (FTIR) spectroscopy were used to determine the temperature conditions to fabricate TiO2 powders free of organic impurities. The produced materials were also characterized by X-ray diffraction (XRD) analysis and transmission electron microscopy (TEM). The results showed the possibility of the fabrication of storage-stable liquid titanium (IV)-containing precursor, which provided nanocrystalline TiO2 powders. It was established that the EPM permits the production of both monophase (anatase polymorph or rutile polymorph) and biphase (mixed anatase–rutile polymorphs), impurity-free nanocrystalline TiO2 powders. For comparison, TiO2 powders were also produced by the precipitation method. The results presented in this study could serve as a solid basis for further developing the EPM for the cheap and simple production of nanocrystalline TiO2-based materials in the form of doped nanocrystalline powders, thin films, and composite materials.
In this work, stoichiometric separate bismuth selenide (Bi 2 Se 3 ) nanoplates and continuous Bi 2 Se 3 coatings are synthesized on graphene substrate by catalystfree vapor-solid deposition method. The orientation of synthesized nanoplates relative to the substrate surface varies from heteroepitaxial (planar) to oriented under different angles (non-planar). The non-planar growth of the nanoplates was achieved for the first time by short-term carrier inert gas flow in certain temperature interval of the synthesis process. The crystallographic growth directions of non-planar nanoplates were determined from HRTEM images as well as estimated from the slope angles of non-planar nanoplates. Bi 2 Se 3 coatings consisting of combination of planar and non-planar nanoplates exhibit significantly enhanced in comparison with coating consisting of only planar coalescent Bi 2 Se 3 nanoplates thermoelectric properties. Demonstrated graphene/Bi 2 Se 3 /graphene devices may find applications in thermoelectric and photo-detection sensors.
Tungsten (W) and tungsten diboride (WB2) materials can be used to fabricate electron emission layers in field emission microelectronic devices. The characterization and quality assurance of synthesized films is crucial for the good performance of the devices. W and WB2 nanofilms with a thickness of 150 nm and 200 nm were deposited on the Si-SiO2 substrate by the magnetron sputtering technique. The synthesized layers were thermally treated in a thermal analysis device under various gas flow conditions (varying Ar; N2; synthetic air; air with O2, N2, and moisture (further in this text – laboratory air)) and after oxidation, FTIR (Fourier transform infrared spectrometry) spectra were registered. FTIR spectra of the as-deposited layers showed weak peaks related to Si-O and Si-O-Si bonds from the substrate and considered for the analysis of the layers. Several new peaks occur in the spectra of the thermally treated layers. Of the oxidation layers, new peaks related to nanolayers, were observed W-O bonds, it is noticeable that the spectra vary with each other with signal intensity and offsets. In each experimental environment with various gas flow conditions, there were W=O bonds observed, also in every environment except in laboratory air with the flow, B-O bond was detected for about 1300 – 1350 cm-1 range. It was shown that thermal oxidation of W and WB2 layers can be applied for the analysis of W and WB2 layers on SiO2 substrate by forming W and B oxides using treatment in high temperature and detection of their bonds by FTIR.
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