Sylwester J. Rzoska

Bio: Sylwester J. Rzoska is an academic researcher from Polish Academy of Sciences. The author has contributed to research in topics: Dielectric & Liquid crystal. The author has an hindex of 33, co-authored 216 publications receiving 3570 citations. Previous affiliations of Sylwester J. Rzoska include University of Silesia in Katowice & Silesian University.

Indentation deformation mechanism of isostatically compressed mixed alkali aluminosilicate glasses

Abstract: Oxide glasses can be permanently densified through application of high pressure at room or elevated temperature. Such treatment allows for modification of macroscopic glass properties. However, the structural origins of the pressure-induced property changes are not yet fully understood. In this study, we investigate the ability of a glass network to resist densification under pressure at both ambient and elevated temperatures. We study the detailed deformation mechanisms (densification and shear flow) that occur during indentation of series of as-prepared and isostatically compressed mixed Na/K aluminosilicate glasses, which exhibit a pronounced nonlinear scaling in glass properties due to the mixed alkali effect. Following pressure treatment at elevated temperature, an increase in Vickers hardness is observed due to a significant decrease in densification under the indenter. In contrast, the volume of glass developed in the pileup regions due to shear flow is unaffected by the pressure treatment. This change in the relative contributions of these plastic deformation mechanisms can explain the decrease in crack resistance of the glasses induced by the isostatic compression treatment.

Fluidlike behavior of dielectric permittivity in a wide range of temperature above and below the nematic-isotropic transition.

Abstract: Singular behavior of the static dielectric permittivity of n-alkyloxycyanobiphenyls $({\mathrm{C}}_{n}{\mathrm{H}}_{2n+1}\mathrm{O}\ensuremath{-}\mathrm{P}\mathrm{h}\ensuremath{-}\mathrm{P}\mathrm{h}\ensuremath{-}\mathrm{C}\ensuremath{\equiv}N,$ $n=6,$ 7) was studied above and below the nematic clearing point ${(T}_{I\ensuremath{-}N}).$ On approaching the clearing point, the evolution of principal components of the nematic permittivity tensor, ${\ensuremath{\varepsilon}}_{\ensuremath{\parallel}}$ and ${\ensuremath{\varepsilon}}_{\ensuremath{\perp}},$ is described by the order parameter exponent $\ensuremath{\beta}\ensuremath{\approx}0.25.$ The mean value of the nematic permittivity ${\ensuremath{\varepsilon}}_{\mathrm{mean}}=({\ensuremath{\varepsilon}}_{\ensuremath{\parallel}}+2{\ensuremath{\varepsilon}}_{\ensuremath{\perp}})/3$ exhibits a singular behavior similar to that observed in the isotropic phase and that for the diameter of the coexistence curve in binary mixtures. The derivative of experimental data $d{\ensuremath{\varepsilon}}_{\mathrm{iso}}(T)/dT$ and $d{\ensuremath{\varepsilon}}_{\mathrm{mean}}(T)/dT$ shows the specific-heat-like behavior with universal exponents $\ensuremath{\alpha}={\ensuremath{\alpha}}^{\ensuremath{'}}\ensuremath{\approx}0.5.$ Results obtained confirm the hypothesis of the fluidlike, pseudospinodal, and tricritical behavior of the isotropic to nematic phase transition. [A. Drozd-Rzoska, Phys. Rev. E 59, 5556 (1999)].

Modifier field strength effects on densification behavior and mechanical properties of alkali aluminoborate glasses

Abstract: The constituents of oxide glasses are typically classified as network formers, which form the rigid backbone of glasses, and network modifiers, which tend to either charge stabilize tetrahedral network formers or depolymerize the network. Although it is well known that the properties of glasses depend on their degree of polymerization, little is known about the role of the type of elements used as network modifiers. Here, based on a series of aluminoborate glasses comprising varying alkali oxide modifiers, we show that the glasses' structural and mechanical properties are controlled by the field strength (ratio of charge to size) of the modifiers. Namely, we show that the stiffness, hardness, and toughness depend on a fine balance between the atomic bonding energy, the packing efficiency of the atoms, and the ability of the network to densify reversibly or irreversibly, with each of these features showing a different dependence on the modifier field strength. This opens a new degree of freedom in the optimization of glass properties.

Composition-Structure-Property Relations of Compressed Borosilicate Glasses

Abstract: Glass is ubiquitous, yet our understanding of its structure-function relationships remains far from complete and limits technology. For example, while compression is an important tool in the synthesis of crystalline materials, comparable breakthroughs in preparing bulk glasses are still largely lacking. This work reveals the striking linear dependence of the plastic compressibility of borosilicate glasses on both initial trigonal boron content and relative change in hardness with pressure, with important implications for manufacturing tailored damage-resistant glassy materials.

Comparative effect of supercritical carbon dioxide and high pressure processing on structural changes and activity loss of oxidoreductive enzymes

Abstract: Due to the CO2 specific characteristics, it has been used as supercritical (Sc) fluid for several applications, including enzyme inactivation. The influence of Sc-CO2 (10–65 MPa/10–30 min/35–65 °C) on mushroom polyphenol oxidase (PPO) and horseradish peroxidase (POD) was evaluated and the results were compared with those found using high pressure processing (HPP) (200–900 MPa/5–45 °C/1–15 min). The free ion concentration was also studied to compare the enzymatic activity and changes in electrical conductivity. Additionally both enzymes, untreated or treated using either Sc-CO2 or HPP, were used as additives in the CuCl2 crystallization method. The resulting additive-specific CuCl2 patterns were characterized based on different structural features. Sc-CO2 was found to have a significant influence on PPO and POD activities, and an increased reduction in the residual activity of both enzymes was observed when the Sc-CO2 pressure was increased. However, PPO was more resistant to temperature and pressure than POD. The D-value calculated for POD was in the range of 38.3 and 592.0 min, and 60.6 and 291.5 min, for HPP and Sc-CO2 treatments, respectively; whereas for PPO varied from 103.1 to 284.3 min under HPP and from 83.4 to 303.0 min using the Sc-CO2 treatment. It can be concluded that the application of Sc-CO2 could be an effective tool for inactivating PPO and POD enzymes. Moreover, both enzymes and treatments could be differentiated significantly based on the resulting CuCl2 crystallization patterns.

Classification of secondary relaxation in glass-formers based on dynamic properties.

Abstract: Dynamic properties, derived from dielectric relaxation spectra of glass-formers at variable temperature and pressure, are used to characterize and classify any resolved or unresolved secondary relaxation based on their different behaviors. The dynamic properties of the secondary relaxation used include: (1) the pressure and temperature dependences; (2) the separation between its relaxation time τβ and the primary relaxation time τα at any chosen τα; (3) whether τβ is approximately equal to the independent (primitive) relaxation time τ0 of the coupling model; (4) whether both τβ and τ0 have the same pressure and temperature dependences; (5) whether it is responsible for the “excess wing” of the primary relaxation observed in some glass-formers; (6) how the excess wing changes on aging, blending with another miscible glass-former, or increasing the molecular weight of the glass-former; (7) the change of temperature dependence of its dielectric strength Δeβ and τβ across the glass transition temperature Tg; ...

Supercooled dynamics of glass-forming liquids and polymers under hydrostatic pressure

Abstract: An intriguing problem in condensed matter physics is understanding the glass transition, in particular the dynamics in the equilibrium liquid close to vitrification Recent advances have been made by using hydrostatic pressure as an experimental variable These results are reviewed, with an emphasis in the insight provided into the mechanisms underlying the relaxation properties of glass-forming liquids and polymers