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21.
N.?Yu.?Koval’koEmail author M.?V.?Kalinina A.?N.?Malkova S.?A.?Lermontov L.?V.?Morozova I.?G.?Polyakova O.?A.?Shilova 《Glass Physics and Chemistry》2017,43(4):368-375
The technology of liquid-phase synthesis of mesoporous xerogels and aerogels based on ZrO2–Y2O3–CeO2 is developed. Xerogels are obtained by the coprecipitation of hydroxides, while aerogels are obtained in accordance with the sol–gel technology: the average pore size is 1.5–17.2 nm and the specific surface area is 120–878 m2/g. Aerogels are characterized by a high degree of porosity: the pore volume attains 1–4 cm3/g. Based on precursor xerogels, nanopowders of a tetragonal solid solution of the (ZrО2)0.92(Y2О3)0.03(CeО2)0.05 composition with a particle size of 5–9 nm and S spec = 74 m2/g were fabricated. Due to the high values of their specific surface area, the synthesized xerogels and aerogels are promising as sorbents, catalysts, or catalyst supports. 相似文献
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Polina Vakuliuk Anatoliy Burban Victorya Konovalova Mihailo Bryk Marina Vortman Nina Klymenko Valeriy Shevchenko 《Desalination》2009,235(1-3):160-169
Microbiological contamination of polymeric membranes in the process of their exploitation is an essential problem of membrane technology. It results in the increase of manufacturing costs, destruction of membranes, operating life reduction and secondary contamination of water by the metabolism products of microorganisms. For the purpose of reduction of membrane biofouling and biodegradation investigation of adsorption of the guanidine containing oligomers on the surface of PET track membranes was conducted and their influence on the selectivity and antibacterial properties of the membranes was investigated. It was established that modified membranes have substantially higher resistance to biofouling. 相似文献
27.
The possibility of controlling the aerodynamic characteristics of lifting airfoils by means of local periodic pulsed energy
supply in transonic flight regimes has been studied. Using a numerical solution of two-dimensional nonstationary equations
of gasdynamics, a change in the flow structure near a symmetric airfoil is determined as dependent on the amount of energy
supplied to the lower side of the airfoil in a range of attack angles. 相似文献
28.
A study has been made of the influence of the pulse-periodic supply of energy that is equal to the energy released in the
combustion of hydrogen in air on the structure of supersonic flow in a channel of variable cross section, modeling the duct
of a ramjet engine. The flow has been modeled on the basis of two-dimensional nonstationary gas-dynamic equations. Different
flow regimes have been obtained depending on the configuration of the zones of energy supply and the excess-air coefficients.
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Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 81, No. 3, pp. 464–469, May–June, 2008. 相似文献
29.
The formation of a response signal in the presence of a layer of trapping centers in semiconductor SiC ionizing radiation detectors is considered on the basis of a new model. Since the trapping layer is situated near the detector surface, nuclear particles that possess long tracks partly generate a charge behind this layer. Under certain conditions, the proposed model leads to a paradoxical situation, in which the signal decreases with increasing bias voltage. The application of the model to results obtained using ion-doped 4H-SiC detectors provides a qualitative explanation for the experimentally observed increase in the signal with the temperature in the region of saturation with respect to the bias voltage (i.e., under the conditions of total charge transfer), which were previously unclear. 相似文献
30.
Anton A. Kovalchuk Vitaliy G. Shevchenko Alexander N. Shchegolikhin Polina M. Nedorezova Alla N. Klyamkina Alexander M. Aladyshev 《Journal of Materials Science》2008,43(22):7132-7140
Isotactic polypropylene (iPP) and syndiotactic polypropylene (sPP) nanocomposites containing 0.1–3.5 wt.% multi-wall carbon
nanotubes (MWCNTs) have been synthesized via in situ polymerization method with the use of C2- and Cs- symmetry zirconocenes activated by methylaluminoxane (MAO) in liquid propylene medium. Fracture morphology studies by SEM
reveal different MWCNT dispersion efficiency in various polymer matrices, which arises from the catalytic peculiarities of
the composite synthesis. Considerable Young’s modulus enhancement of iPP and sPP (25–66%) takes place even at low MWCNT loadings
(below 0.5 wt.%). The obtained nanocomposites can find use as efficient electromagnetic shielding materials and microwave
absorbing filters due to relatively low permittivity values and considerable dielectric losses in microwave range. Calorimetry
data demonstrate that MWCNTs exert evident influence as nucleating agents causing the rise of iPP and sPP crystallization
temperature. Considerable retardation effect on iPP thermal oxidative degradation has been observed: the temperature of maximal
weight loss rate rises by ~52 °C upon incorporating only 1.4 wt.% MWCNTs. 相似文献