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•The more hydroxylated ZrO2 surface possesses the higher surface energy that leads to the higher surface hydrophilicity.•The direction of the photoinduced hydrophilic conversion of ...the ZrO2 surface can be controlled by changing the photoexcitation region.•ZrO2 thin film successfully degrades the stearic acid and E. coli strain under the light with λ>300 nm.
Here we focused on the fundamental study of self-cleaning properties of zirconium dioxide films, including photoinduced alteration of surface hydrophilicity, photocatalytic and photoinduced bactericidal activities. The accent was made on the factors influencing the photoinduced hydrophilic conversion such as surface acidity and spectral composition of light for the surface photoexcitation. The studies on photoinduced hydrophilic conversion of the ZrO2 thin film were carried out using the contact angle measurements and XPS method. The experimental data demonstrate the very different hydrophilic behavior of the hydrated surface depending on the spectral region of photoexcitation corresponding to intrinsic or extrinsic ZrO2 absorption. This is explained by the difference in the concentration of photoelectrons and photoholes which participate in the photo-induced surface processes. It is suggested that hole-trapping species such as surface hydroxyl groups and adsorbed water molecules play a crucial role in the photoinduced superhydrophilic transition. The effect of the electron-acceptor and electron-donor gas atmospheres on the aging of the surface superhydrophilicity is found to be in agreement with this conclusion. The photochemical activity of ZrO2 coatings was tested by photodegradation of stearic acid. The antibacterial properties are investigated against Escherichia coli. The ZrO2 thin films reveal self-cleaning properties and can be successfully used as biomedical or construction material.
In this work, the UV-stimulated processes in the TiO2–COg system were explored by in situ FTIR spectroscopy and photoelectron spectroscopy. Kinetic dependences of the total band intensity for ...adsorbed CO and background absorption, as well as the positions of the Fermi level in TiO2 before, during, and after UV irradiation of the system, were analyzed and compared. The observed reversible shift in the adsorption–desorption equilibrium was explained by changing the electronic state of the photocatalyst under UV irradiation. The proposed mechanism of photostimulated CO adsorption and CO re-adsorption in the TiO2–COg system is described in detail. A deflection of reversibility of molecular photodesorption–re-adsorption dynamics is caused by the side reaction of CO photooxidation and the formation of strongly bound surface carbonates.
The Globus-M2 spherical tokamak is the considerably upgraded Globus-M facility. Its technical parameters were increased as much as possible to achieve the promising range of physical parameters ...(sub-fusion temperatures and collisionality of much less than unity). These parameters will be achieved in a compact magnetic configuration similar to that of the Globus-M tokamak, the plasma current and toroidal magnetic field amounting to 0.5 MA and 1 T, respectively. The demand to increase the magnetic field and plasma current in the Globus-M2 resulted in the need for a complete redesign of the electromagnetic system because the plasma equilibrium requirements have changed and the mechanical and thermal loads have considerably increased as compared to the Globus-M. The vacuum vessel and the in-vessel components of the new Globus-M2 tokamak remain the same. Power supplies were upgraded to provide the required currents in the toroidal field coil and the central solenoid. The Globus-M2 tokamak was build up and preliminary tests were carried out. New auxiliary heating systems and diagnostics were developed and installed to be used in future experiments. Fist plasma was achieved at the Globus-M2 in April 2018.
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It is recognized that the filaments have a significant effect on the anomalous energy and particle transport in the tokamak periphery. They are actively investigated using various diagnostics in ...this regard. Recently studies of filaments using the Doppler backscattering method have been performed in the Globus-M and the ASDEX-Upgrade tokamaks. Backscattering from filaments manifests itself as a burst of quasi-coherent fluctuations of the signals of detectors. Such signals are easy to describe in the Born approximation using the diagnostic weighting function. However, the filaments in tokamaks differ noticeably in their size and intensity. With an increase in the amplitude of the filaments, it is necessary to consider the transition from linear scattering to nonlinear one and further up to the transition from backscattering to reflection from a moving filament. This problem can be solved only using a full wave code. Our simulation was carried out using the finite-difference time-domain code IPF-FD3D in slab geometry. We did not resort to using well-known non-linear MHD codes to determine filament parameters. In the simulation artificial filament-like perturbations were used, the parameters of which varied over a wide range. Modeling Doppler backscattering signal was focused on the identification of the influence of the amplitude of the filament and its size on the shape and the size of the Doppler backscattering output signal. The results obtained largely explain the similarity of the IQ detector data registered in different tokamaks.
Density functional theory (DFT) study of ozone adsorption on dehydrated nanocrystalline TiO2 is presented. Singlet and triplet binding modes of ozone to the oxide’s titanium cations are considered. ...In both the modes, monodentate and bidentate ozone complexes are formed. According to DFT, the triplet monodentates are the most stable species. The formation of monodentate ozone adsorption complexes is in-line with an earlier interpretation of infrared (IR) spectroscopic data on ozone adsorption on an anatase surface. However, the computed difference in the fundamental vibrational frequencies (ν1 – ν3) of ozone in the triplet monodentates is significantly larger than the corresponding IR value. This discrepancy is resolved by demonstrating that the triplet monodentates readily decompose, realizing molecular oxygen that is consistent with published experimental data. The predicted energy barrier of the dissociative adsorption is less than 2 kcal/mol. In contrast, the computed difference in the fundamental vibrational frequencies (ν1 – ν3) of adsorbed ozone in the singlet bidentates perfectly agrees with the experiment.
Geodesic acoustic mode (GAM) observations in TUMAN-3M tokamak show that in ohmic discharges with low plasma density GAM have intermittent character; transition to high confinement regime ...(LH-transition) is usually preceded by a short (up to 5 ms) GAM burst series with distinctive frequency drop, or there exists long (up to 30 ms) GAM burst series evolution with several characteristic timescales and varying amplitude. To determinate the effect of GAM temporal parameters on the possibility of LH-transition initiation numerical modeling of plasma density profile evolution under the effect of GAM burst sequence with varying frequency and amplitude was carried out.
We investigate vibrations of the pyridinium cation PyH
= C
H
NH
in one-dimensional lead halide perovskites PyPbX
and pyridinium halide salts PyHX (X
= I
, Br
), combining infrared absorption and ...Raman scattering methods at room temperature. Internal vibrations of the cation were assigned based on density functional theory modeling. Some of the vibrational bands are sensitive to perovskite or the salt environment in the solid state, while halide substitution has only a minor effect on them. These findings have been confirmed by
H,
C and
Pb solid-state nuclear magnetic resonance (NMR) experiments. Narrower vibrational bands in perovskites indicate less disorder in these materials. The splitting of NH-group vibrational bands in perovskites can be rationalized the presence of nonequivalent crystal sites for cations or by more exotic phenomena such as quantum tunneling transition between two molecular orientations. We have shown how organic cations in hybrid organic-inorganic crystals could be used as spectators of the crystalline environment that affects their internal vibrations.
During modernization of the Globus-M tokamak, toroidal magnetic field and plasma current were increased, and a number of diagnostics were upgraded, which made it possible to study phenomena ...associated with the excitation of Alfvén waves in a spherical tokamak in a wider range of plasma parameters. In the experiments with neutral beam injection, the dependences of fast particle losses initiated by the toroidal Alfvén eigenmodes (TAE) on their magnitude in the magnetic field range of 0.4 - 0.7 T and currents of 180 - 330 kA were acquired. Resulting dependences confirm previously obtained results and indicate a decrease in losses with increasing magnetic field and plasma current. At the same time, a number of new phenomena, that have never been observed on Globus-M were detected. In experiments with neutral beam injection at the current ramp up stage, Alfvén cascades (AC) in the frequency range of 100 - 300 kHz were observed for the first time. By means of the Doppler backscattering diagnostics (DBS), it was shown that ACs are localized closer to magnetic axis unlike TAE. Also, during low hybrid wave current drive (LHCD) experiments, global Alfvén eigenmodes (GAE) were detected at a frequency close to 1 MHz, apparently driven in the resonance with runaway electron beam. Detected global eigenmodes are also able to arise in ohmic discharges, however, their magnitude is lower.
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