Morphology and Eu3+ doping effect on structural and photoluminescence properties of tin dioxide nanoparticles obtained by co-precipitation and hydrothermal methods are reported and analyzed for the ...first time. The samples were characterized by means of transmission electron microscopy (TEM), powder X-ray diffraction (XRD), specific surface area (SSA) estimation. TEM, XRD and SSA analyses showed that in the case of co-precipitation method the nanoparticles were spherical. Hydrothermal treatment leads to formation of cubic nanoparticles. An average particle size increased from 3 to 5 nm and from 6 to 11 nm along with increase of Eu3+ concentration for spherical and cubic nanoparticles, respectively. Steady-state and kinetics photoluminescence properties of nanophophors with different morphology were studied and compared. Radiative and nonradiative decay rates and Judd-Ofelt parameters were calculated using the model of 4f–4f intensity theory. It was shown, that preferred positions of substitution in SnO2 host differ depending on Eu3+ doping concentration and particle morphology.
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•Spherical and cubic Eu3+-doped SnO2 NPs were synthesized via co-precipitation and hydrothermal methods.•Emission and excitation spectra consisted of narrow bands assigned to 4f-4f transitions.•Concentration quenching in SnO2:Eu3+ phosphors depended on morphology and nanoparticle size.•Radiative and nonradiative decay rates and Judd-Ofelt parameters were calculated.•DFT method showed different preferred Eu3+ positions for highly-doped spherical and cubic NPs.
Selective calcium chelator 1,2-Bis(2-aminophenoxy) ethane-N,N,N',N'-tetraacetic acid (BAPTA) is a common tool to investigate calcium signaling. However, BAPTA expresses various effects on ...intracellular calcium signaling, which are not related to its ability to bind Ca
. In patch clamp experiments, we investigated calcium chelation independent effects of BAPTA on endogenous calcium-activated chloride channels ANO6 (TMEM16F) in HEK293T cells. We have found that application of BAPTA to intracellular solution led to two distinct effects on channels properties. On the one hand, application of BAPTA acutely reduced amplitude of endogenous ANO6 channels induced by 10 μM Ca
in single channel recordings. On the other hand, BAPTA application by itself induced ANO6 channel activity in the absence of the intracellular calcium elevation. Open channel probability was enhanced by increasing the intracellular BAPTA concentration from 0.1 to 1 and 10 mM. Another calcium chelator EGTA did not demonstrate chelation independent effects on the ANO6 activity in the same conditions. Due to off-target effects BAPTA should be used with caution when studying calcium-activated ANO6 channels.
The electroflotation extraction of fine particles of TiO
2
and Ti(OH)
4
was studied. It was determined that in water solutions of electrolytes with pH = 2 – 12 electroflotation of TiO
2
proceeds ...inefficiently: the degree of extraction is 10 – 15%. The degree of extraction is 25 – 30% in the presence of surfactants and 90 – 95% in the presence of surfactants and the coagulant Fe
+5
. Electroflotation of Ti(OH)
4
proceeds efficiently: the degree of extraction at pH = 3 reaches 99%, the electroflotation time 5 – 10 min, and energy consumption 0.5 kW · h/m
3
of solution.
A technique for measuring the spatial heterogeneity of the light yield of a proton radiography scintillator has been developed. It is based on the recording of digital images formed during the ...passage of a proton beam through a scintillator and the approximation of the intensity distribution in the beam cross section by a two-dimensional Gaussian-like function. The results of the spatial calibration of the light yield of a lutetium silicate scintillator obtained using a magneto-optical proton microscope PUMA are presented. It is shown that accounting of the spatial heterogeneity of the scintillator makes it possible to describe the transverse beam intensity at each point of the proton radiographic image with a mean accuracy of about 0.7%. Experimental data on fluctuations in the position of the beam center, its size, and shape in the scintillator plane of PUMA microscope were obtained. The proposed technique eliminates optical artifacts in the radiographic image caused by operation of the optical recording system and artifacts caused by the electron-optical shutter, provided that the signal is proportional to the intensity of the beam. It also eliminates or strongly suppresses optical artifacts in radiographic images due to changes in the efficiency of a charge-coupled digital camera.
The work sets the task of determining the conditions for tribological testing of coatings in which the coating realizes its potential of physical, mechanical, and tribological properties regardless ...of the substrate. A standard method of tribological testing was used on a friction machine according to the pin–disk scheme with a circular motion of a spherical indenter pin. Experimental data are presented on the study of the structure and properties of vacuum ion-plasma nitride coatings of TiN, TiAlN, and CrAlSiN. The coatings had a thickness of 0.8–4.0 μm and were applied to plate steel samples intended for testing in a friction machine. The wear process of coatings is considered from the perspective of contact fracture mechanics and fatigue theories. A calculation and analytical model is proposed for quantitative assessment of contact and wear parameters during friction tests: the size of the contact area; the depth of contact approach; the depth of the plastic zone; stresses in the coating; fatigue limit; and critical thickness of the coating, which excludes its deflection. To assess the wear of coatings in this case, it is recommended to use fatigue failure models with the construction of a Woehler fatigue curve and determination of the fatigue limit based on the Murokami–Endo theory. The implementation of the recommended approach was carried out for the nitride coatings using a database of the authors’ experimental data.
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Attempts to solve interrelated tasks by specifying materials for coatings and developing a methodology for monitoring the friction unit operation have been tried previously. The importance and ...originality of this study is that it examines the distribution of elements in the CrAlSiN coating, as well as their comparative physical, mechanical, and tribological properties. Besides, we have found that surface modification with a coating of the CrAlSiN system increases the strength and resistance to plastic deformation, which ensures high-quality deposition of thin vacuum ion-plasma coatings and leads to an increase in wear resistance. To control friction units with such coatings, it was decided to develop a monitoring technology using a dimensionless damping coefficient of friction-mechanical bonds in sub-octave band frequency ranges of forced vibrations. It makes it possible to identify natural vibration frequencies, which manifest the properties of the coatings and modifiers used for friction or anti-friction purposes. Our findings should make a significant contribution to tribology. Alongside observations of variations in the elastic-dissipative and inertial properties of the interaction between contact surfaces, the analysis of the generalized dynamic criteria on heavily loaded friction units that operate in the boundary lubrication mode allowed determining adhesion stability of contact friction bodies for friction subsystems. Furthermore, we have defined the effectiveness of lubricants, transition to boundary friction, and non-lubricated friction for antifriction subsystems. The use of the technologies developed by the authors for heavy-loaded tribosystems makes it possible to increase the wear resistance, reliability, and safety of operation of railway and air transport.
TiN coatings have been deposited using cathodic arc deposition at various nitrogen pressures and deposition temperatures. The structure and elemental coating composition are analyzed using a scanning ...electron microscope and an energy dispersive spectrometer. The mechanical properties and adhesion strength of the coating are measured using nanoindentation and scratch testing. The degree of wear is investigated with a tribometer using the ball-on-disk test method. The analysis of the results is carried out by the methods of two-factor orthogonal experiment planning with optimization elements. The results show that the coating structure has a columnar (fibrous) morphology, the composition is close to stoichiometric. The moment of coating destruction, when determining the adhesive strength, occurs at a load of about 600 mN. On the basis of the obtained regression equations for the optimized values of hardness, plasticity index and wear degree, the values of the process parameters of deposition should be in intervals
T
= 350–430°С and
P
= 0.065–0.075 Pa.
Abstract
In this work, we show the route to obtain thermoplastic based composites with an enhanced thermal conductivity that was achieved by using exfoliated hexagonal boron nitride (hBN) particles ...as a filler material. Reports on composites with bulk or nano hBN showed, that while increasing the filler load improves thermal properties it could aggravate the composite melt rheology and mechanical properties. On the other hand, exfoliated hBN particles compared to bulk or nanopowder hBN could provide even better thermal properties with no degradation in composite mechanics, which was shown for epoxy. Taking into account the above, we obtained exfoliated hBN particles by ultrasound treatment in isopropyl alcohol and then used them as a filler in polypropylene based composites to increase the thermal conductivity. The composites with 29% wt. of exfoliated hBN showed a thermal conductivity of 0.721 W m
−1
K
−1
which is 4 times higher than for pristine polypropylene.
This study discusses CrAlSiN coatings obtained by vacuum arc plasma deposition. The structural and compositional parameters that are responsible for the most essential coating properties are ...identified. The structural morphology, elemental distribution, and phase composition of the coatings are investigated. The physicomechanical, adhesive and tribological characteristics are determined. Coatings were deposited on substrates of nitrided and carburized structural steels widely used in mechanical engineering. The coating properties are determined and compared with the corresponding surface properties of the standard uncoated specimen. The coating thickness for the experimental specimens was 0.82–1.18 µm. A comparative analysis of the coating phase composition is carried out using X-ray photoelectron spectroscopy (XPS) and thermodynamic calculations with Termo-Calc software. It is shown and proved experimentally that ion plasma coatings are nonequilibrium. In addition, CrAlSiN coatings significantly increase the mechanical characteristics of the material, such as hardness and resistance to elastic and plastic deformation, and adhere well to the substrate surface. In tribological tests, CrAlSiN coatings reduce the wear rate by a factor of 2–4 compared to nitrided steel and by an order of magnitude compared to carburized steel. These high properties are also attributed to the nonequilibrium structural-phase state of the coating. The obtained results indicate that vacuum arc plasma CrAlSiN coatings can be used as wear resistant protective coatings, including under friction conditions.
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