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Content available remote Neutron diffraction study of porous glasses structure
Naberezhnov A., Antropova T., Glavatsky I., Seregin M., Drozdova I.
Optica Applicata
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2012
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Vol. 42, nr 2
271-280
EN
Microscopic structure of three types of porous glasses with the average pore diameter of 5, 7 and 140 nm obtained by chemical etching was studied by neutron diffraction. The analysis of diffraction patterns has shown that in these glasses, besides an amorphous phase forming a weakly structured background, there are microscopic crystalline inclusions of sassolite with a diffraction size of 26š3 nm and of ?-quartz with a characteristic size of 6š1 nm. Microcrystalline inclusions sizes do not depend on the average pore size diameter. It is shown that in these samples a tridymite phase does not make a significant contribution to observed scattering and a relative sassolite contribution decreases substantially with the average pore size increasing from 5 to 140 nm.
2
Content available remote Dielectric properties of two-phase and porous ferriferous glasses
Koroleva E., Burdin D., Antropova T., Porechnaya N., Naberezhnov A., Anfimova I., Pschenko O.
Optica Applicata
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2012
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Vol. 42, nr 2
287-294
EN
In the present contribution we have studied the dielectric properties of two-phase sodium borosilicate glasses doped by iron oxide and of porous media based on them. The temperature dependences of dielectric permittivity and conductivity for all samples have been obtained, and the impedance spectroscopy analysis for porous magnetic glasses has been done. The obtained data allow us to estimate the values of activation energies for porous samples.
3
Content available remote Effect of restricted geometry on structural phase transitions in KH2PO4 and NH4H2PO4 crystals
Tarnavich V., Korotkov L., Karaeva O., Naberezhnov A., Rysiakiewicz-Pasek E.
Optica Applicata
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2010
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Vol. 40, nr 2
305--309
EN
The dielectric response of crystalline NH4H2PO4 and KH2PO4–SiO2 and NH4H2PO4–SiO2 composites prepared by embedding salts into porous glasses with the average pore diameter of 320 nm has been studied at the temperature range of 85–300 K. An increase of the structure phase transition temperatures in embedded salts has been observed, which is supposedly due to tensile deformations of embedded crystalline particles. The antiferroelectric phase transition in confined ADP particles becomes diffuse in the temperature region around 10 K.
4
Content available remote Dynamical heterogeneity of NaNO2 confined within porous glasses
Dvornikov V., Korotkov L., Naberezhnov A., Fokin A., Korotkova T.
Optica Applicata
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2008
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Vol. 38, nr 1
25-29
EN
Frequency dependences of imaginary part of the dielectric response e(f) of SiO2-NaNO2 nanocomposite, prepared by embedding of sodium nitrite into porous glasses with 7 nm average pore diameter, have been studied within a temperature range of 360-520 K. It has been found that the spectrum S(omega) = e(f)/f contains the component ~1/f alfa where alfa is a coefficient indicating the dynamical heterogeneity of dipoles. Peculiarities of the temperature dependence of alfa are discussed.
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