Publications by authors named "Sylwester J Rzoska"

41 Publications

Indentation Response of Calcium Aluminoborosilicate Glasses Subjected to Humid Aging and Hot Compression.

Materials (Basel) 2021 Jun 22;14(13). Epub 2021 Jun 22.

Department of Chemistry and Bioscience, Aalborg University, 9220 Aalborg, Denmark.

Aluminoborosilicate glasses find a wide range of applications, which require good mechanical reliability such as surface damage resistance. Calcium aluminoborosilicate (CABS) glasses have recently been found to exhibit so-called intermediate behavior in terms of their response to sharp contact loading. That is, these glasses deform with less shear than normal glass and less densification than anomalous glasses. This deformation mechanism is believed to give rise to high crack initiation resistance of certain CABS glasses. In order to further improve and understand the micromechanical properties of this glass family, we studied the indentation response of different CABS glasses subjected to two types of post-treatment, namely hot compression and humid aging. Upon hot compression, density, elastic moduli, and hardness increased. Specifically, elastic modulus increased by as much as 20% relative to the as-made sample, while the largest change in hardness was 1.8 GPa compared to the as-made sample after hot compression. The pressure-induced increase in these properties can be ascribed to the increase in network connectivity and bond density. On the other hand, the crack initiation resistance decreased, as the hot compression increased the residual stress driving the indentation cracking. Humid aging had only a minor impact on density, modulus, and hardness, but an observed decrease in crack initiation resistance. We discuss the correlations between hardness, density, crack resistance, and deformation mechanism and our study thus provides guidelines for tailoring the mechanical properties of oxide glasses.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.3390/ma14133450DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8269477PMC
June 2021

Pretransitional Effects of the Isotropic Liquid-Plastic Crystal Transition.

Molecules 2021 Jan 15;26(2). Epub 2021 Jan 15.

Condensed Matter Physics Department, Jožef Stefan Institute, Jamova 39, 1000 Ljubljana, Slovenia.

We report on strong pretransitional effects across the isotropic liquid-plastic crystal melting temperature in linear and nonlinear dielectric response. Studies were carried out for cyclooctanol (CHO) in the unprecedented range of temperatures 120 K < < 345 K. Such pretransitional effects have not yet been reported in any plastic crystals. Results include the discovery of the experimental manifestation of the Mossotti Catastrophe behavior, so far considered only as a hypothetical paradox. The model interpretations of experimental findings are proposed. We compare the observed pretransitional behavior with the one observed in octyloxycyanobiphenyl (8OCB), typical liquid crystal (LC), displaying a reversed sequence of phase transitions in orientational and translational degrees of order on varying temperature. Furthermore, in its nematic phase, we demonstrate first-ever observed temperature-driven crossover between regions dominated by isotropic liquid and smectic A pretransitional fluctuations. We propose a pioneering minimal model describing plastic crystal phase behavior where we mimic derivation of classical Landau-de Gennes-Ginzburg modeling of Isotropic-Nematic-Smectic A LC phase behavior.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.3390/molecules26020429DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7830473PMC
January 2021

Dynamics and Pretransitional Effects in C Fullerene Nanoparticles and Liquid Crystalline Dodecylcyanobiphenyl (12CB) Hybrid System.

Nanomaterials (Basel) 2020 Nov 26;10(12). Epub 2020 Nov 26.

Laboratory of Physics of Complex Systems, Faculty of Natural Sciences and Mathematics, University of Maribor, Koroška 160, 2000 Maribor, Slovenia.

The report shows the strong impact of fullerene C nanoparticles on phase transitions and complex dynamics of rod-like liquid crystal dodecylcyanobiphenyl (12CB), within the limit of small concentrations. Studies were carried out using broadband dielectric spectroscopy (BDS) via the analysis of temperature dependences of the dielectric constant, the maximum of the primary loss curve, and relaxation times. They revealed a strong impact of nanoparticles, leading to a ~20% change of dielectric constant even at = 0.05% of C fullerene. The application of the derivative-based and distortion-sensitive analysis showed that pretransitional effects dominate in the isotropic liquid phase up to 65 K above the clearing temperature and in the whole Smectic A mesophase. The impact of nanoparticles on the pretransitional anomaly appearance is notable for the smectic-solid phase transition. The fragility-based analysis of relaxation times revealed the universal pattern of its temperature changes, associated with scaling via the "mixed" ("activated" and "critical") relation. Phase behavior and dynamics of tested systems are discussed within the extended Landau-de Gennes-Ginzburg mesoscopic approach.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.3390/nano10122343DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7761475PMC
November 2020

High-pressure behavior of dielectric constant in a binary critical mixture.

Phys Rev E 2020 Oct;102(4-1):042610

Institute of High Pressure Physics, Polish Academy of Sciences (X-PressMatter Lab), ul. Sokołowska 29/37, 01-142 Warsaw, Poland.

An alternative design of the measurement capacitor for high-pressure studies of complex liquids or soft matter systems is presented. Subsequently, results for the precritical anomaly of dielectric constant in 1-nitropropane-octane critical mixture are reported. First, the pressure dependence of the critical consolute temperature T_{C} up to P=0.55GPa was determined and portrayed using the derivative-based analysis. Second, temperature and pressure evolutions of dielectric constant on approaching the critical consolute point at (T_{C}=304.1K and P_{C}=403MPa) were studied. They revealed that the pretransitional anomaly ɛ(P→P_{C}) is notably more pronounced than for ɛ(T→T_{C}). For both paths, the static domain extends even to as low frequency as f=100Hz, whereas for tests under atmospheric pressure, they require at least f=100kHz. The discussion of the impact of correction-to-scaling terms, including the unique case of the pressure paths, is also presented.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1103/PhysRevE.102.042610DOI Listing
October 2020

Impact of Pressure on Low-Molecular Weight Near-Critical Mixtures of Limited Miscibility.

ACS Omega 2020 Aug 5;5(32):20141-20152. Epub 2020 Aug 5.

Institute of High Pressure Physics, Polish Academy of Sciences, ul. Sokołowska 29/37, 01-142 Warsaw, Poland.

Near-critical mixtures of limited miscibility are significant for chemical physics, soft matter physics, and a variety of challenging applications. Their basic properties can be tuned by compressing or a systematic change of one of the components. This report addresses these issues, based on experimental studies in nitro-compound (nitrobenzene, -nitrotoluene, and 1-nitropropane) and -alkane (from pentane to eicosane) critical mixtures. Studies reveal new patterns for the evolution of the critical consolute temperature ( ) and concentration ( , mole fraction) within the tested homologous series: () ∼ and () ∼ . They also show two paths of the high-pressure impact: (i) d ()/d > 0 and overlapping of normalized () dependences and (ii) the crossover d ()/d < 0 → d ()/d > 0 with increasing -alkane length. The consistent parameterization of all () dependencies is introduced. Supplementary nonlinear dielectric effect studies indicate a possible molecular origin of the phenomenon. The coexistence curve under high pressure is in the agreement with the isomorphism postulate for critical phenomena but with a surprisingly strong distortion from the Cailletet-Mathias law of the rectilinear diameter. The new and reliable method for estimating the critical concentration and temperature is proposed. It explores the analysis of relative volumes occupied by coexisting phases.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1021/acsomega.0c01772DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7439374PMC
August 2020

Multifold pressure-induced increase of electric conductivity in LiFeVPO glass.

Sci Rep 2019 Nov 12;9(1):16607. Epub 2019 Nov 12.

Faculty of Physics, Warsaw University of Technology, Warsaw, Poland.

We investigated the impact of high pressure and high-temperature annealing on lithium-vanadium-iron-phosphate (LiFeVPO) glass materials, proposed for the use in cathodes for high-performance batteries. The treatment was carried out below the glass transition temperature (T ≈ 483 °C) at P = 1 GPa pressure, in an argon atmosphere. It led to the multifold electrical conductivity increase. Broadband dielectric spectroscopy (BDS) measurements before and after the process revealed the strong DC-conductivity increase across the whole studied frequency range by two orders of magnitude. The phenomenon is explained using Mott's theory of polaron hopping in disordered solids containing transition metal oxides. The pressure evolution of the glass transition temperature and the crystallisation temperature above T is shown.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1038/s41598-019-53232-zDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6851369PMC
November 2019

Polymer matrix ferroelectric composites under pressure: Negative electric capacitance and glassy dynamics.

Eur Phys J E Soft Matter 2019 Sep 9;42(9):118. Epub 2019 Sep 9.

State Key Laboratory of Solidification Processing, MIIT Key Laboratory of Radiation Detection Materials and Devices, NPU-QMUL Joint Research Institute of Advanced Materials and Structure, School of Material Science and Engineering, Northwestern Polytechnical University, 710072, Xi'an, China.

This report presents the results of high-pressure and broadband dielectric spectroscopy studies in polyvinylidene difluoride (PVDF) and barium strontium titanate (BST) microparticles composites (BST/PVDF). It shows that the Arrhenius behaviour for the temperature-related dynamics under atmospheric pressure is coupled to Super-Arrhenius/Super-Barus isothermal pressure changes of the primary relaxation time. Following these results, an explanation of the unique behaviour of the BST/PVDF composite is proposed. Subsequently, it is shown that when approaching the GPa domain the negative electric capacitance phenomenon occurs.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1140/epje/i2019-11876-9DOI Listing
September 2019

Revisiting the Dependence of Poisson's Ratio on Liquid Fragility and Atomic Packing Density in Oxide Glasses.

Materials (Basel) 2019 Jul 31;12(15). Epub 2019 Jul 31.

Department of Chemistry and Bioscience, Aalborg University, 9220 Aalborg East, Denmark.

Poisson's ratio () defines a material's propensity to laterally expand upon compression, or laterally shrink upon tension for non-auxetic materials. This fundamental metric has traditionally, in some fields, been assumed to be a material-independent constant, but it is clear that it varies with composition across glasses, ceramics, metals, and polymers. The intrinsically elastic metric has also been suggested to control a range of properties, even beyond the linear-elastic regime. Notably, metallic glasses show a striking brittle-to-ductile (BTD) transition for ν-values above ~0.32. The BTD transition has also been suggested to be valid for oxide glasses, but, unfortunately, direct prediction of Poisson's ratio from chemical composition remains challenging. With the long-term goal to discover such high-ν oxide glasses, we here revisit whether previously proposed relationships between Poisson's ratio and liquid fragility () and atomic packing density () hold for oxide glasses, since this would enable and to be used as surrogates for . To do so, we have performed an extensive literature review and synthesized new oxide glasses within the zinc borate and aluminoborate families that are found to exhibit high Poisson's ratio values up to ~0.34. We are not able to unequivocally confirm the universality of the Novikov-Sokolov correlation between and and that between and for oxide glass-formers, nor for the organic, ionic, chalcogenide, halogenide, or metallic glasses. Despite significant scatter, we do, however, observe an overall increase in with increasing and , but it is clear that additional structural details besides or are needed to predict and understand the composition dependence of Poisson's ratio. Finally, we also infer from literature data that, in addition to high , high Young's modulus is also needed to obtain glasses with high fracture toughness.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.3390/ma12152439DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6696245PMC
July 2019

Nanoparticle-controlled glassy dynamics in nematogen-based nanocolloids.

Phys Rev E 2019 May;99(5-1):052703

Faculty of Natural Sciences and Mathematics, University of Maribor, Koroska 160, 2000 Maribor, Slovenia and Condensed Matter Physics Department, Jozef Stefan Institute, Jamova 39, 1000 Ljubljana, Slovenia.

Results of broad-band dielectric spectroscopy studies in liquid crystal (pentylcyanobiphenyl, 5CB)-based nanocolloids are presented. They reveal the strong impact of BaTiO_{3} nanoparticles on dynamics and uniaxial ordering. Studies were carried out in an extreme range of temperatures (∼150 K), including the supercooled nematic phase. For the latter, the unique "pretransitional" effect for dielectric constant on approaching solid state is reported. The distortion-sensitive analysis revealed super-Arrhenius dynamics but associated with critical-like behavior. In the isotropic phase, translational-orientational decoupling, unusual for the high temperature dynamic domain, was detected. It can be directly link to heterogeneities-prenematic fluctuations. The model linking the classical Landau-de Gennes approach with Imry-Ma arguments has been developed to discuss experimental results.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1103/PhysRevE.99.052703DOI Listing
May 2019

Unique dynamic crossover in supercooled x,3-dihydroxypropyl acrylate (x = 1, 2) isomers mixture.

Eur Phys J E Soft Matter 2018 Sep 20;41(9):108. Epub 2018 Sep 20.

Institute of High Pressure Physics, Polish Academy of Sciences, ul. Sokołowska 29/37, 01-142, Warsaw, Poland.

The previtreous dynamics in the glass-forming monomer, glycerol monoacrylate (GMA), was tested using the broadband dielectric spectroscopy (BDS). The measurements revealed a clear dynamic crossover at the temperature [Formula: see text] K and the time scale [Formula: see text] ns for the primary (structural) relaxation time and no hallmarks for the crossover for the DC electric conductivity [Formula: see text]. This result was revealed via the derivative-based and distortions-sensitive analysis [Formula: see text] vs. [Formula: see text] , where [Formula: see text] stands for the apparent activation energy. Subsequent tests of the fractional Debye-Stokes-Einsten relation [Formula: see text] showed that the crossover is associated with [Formula: see text] [Formula: see text] (for [Formula: see text]. The crossover coexists with the emergence of the secondary beta relaxation, which smoothly develops deeply into the solid amorphous phase below the glass temperature [Formula: see text].
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1140/epje/i2018-11714-8DOI Listing
September 2018

Structural Compromise between High Hardness and Crack Resistance in Aluminoborate Glasses.

J Phys Chem B 2018 06 31;122(23):6287-6295. Epub 2018 May 31.

Institute of High-Pressure Physics , Polish Academy of Sciences , Warsaw 01-142 , Poland.

Alkali aluminoborate glasses have recently been shown to exhibit a high threshold for indentation cracking compared to other bulk oxide glasses. However, to enable the use of these materials in engineering applications, there is a need to improve their hardness by tuning the chemical composition. In this study, we substitute alkaline earth for alkali network-modifying species at fixed aluminoborate base glass composition and correlate it with changes in the structure, mechanical properties, and densification behavior. We find that the increase in field strength (i.e., the charge-to-size ratio) achieved by substituting alkaline earth oxide from BaO to MgO manifests itself in a monotonic increase in several properties, such as atomic packing density, glass-transition temperature, densification ability, indentation hardness, and crack resistance. Although the use of alkaline earth oxides as modifier enables higher hardness values (increasing from 2.0 GPa for Cs to 5.8 GPa for Mg), their crack resistance is generally lower than that of the corresponding alkali aluminoborate glasses. We discuss the origin of this compromise between hardness and crack resistance in terms of the ability of the glass networks to undergo structural transformations and self-adapt under stress. We show that the extent of volume densification scales linearly with the number of pressure-induced coordination number changes of B and Al.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1021/acs.jpcb.8b02905DOI Listing
June 2018

Impact of ferroelectric and superparaelectric nanoparticles on phase transitions and dynamics in nematic liquid crystals.

Phys Rev E 2017 Aug 9;96(2-1):022705. Epub 2017 Aug 9.

Condensed Matter Physics Department, Jozef Stefan Institute, Jamova 39, 1000 Ljubljana, Slovenia and Faculty of Natural Sciences and Mathematics, University of Maribor, Koroska 160, 2000 Maribor, Slovenia.

Results of broadband dielectric spectroscopy (BDS) studies of pure liquid crystalline (4-pentyloxy-4-biphenylcarbonitryle) 5OCB and its nanocolloids with BaTiO_{3} nanoparticles (NPs) under varying pressure and temperature are presented. The notable impact of NPs on phase transitions and dynamics was found. Particularly strong impact on pretransitional behavior was observed for relatively low concentrations of NPs, which can be related to the NPs-induced disorder. There are also notable differences between pressure and temperature paths of studies for nanocomposites, absent for the pure LC compound. For instance, tests focused on the translational orientational decoupling via the fractional Debye-Stokes-Einstein relation yielded S=0.71 and S=0.3 for the temperature and pressure paths, respectively: S=1 is for the complete coupling. The possible theoretical frame of observed phenomena is also proposed.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1103/PhysRevE.96.022705DOI Listing
August 2017

Dissolution Kinetics of Hot Compressed Oxide Glasses.

J Phys Chem B 2017 09 14;121(38):9063-9072. Epub 2017 Sep 14.

Department of Chemistry and Bioscience, Aalborg University , 9220 Aalborg, Denmark.

The chemical durability of oxide glasses is an important property for a wide range of applications and can in some cases be tuned through composition optimization. However, these possibilities are relatively limited because around 3/5 of the atoms in most oxide glasses are oxygens. An alternative approach involves post-treatment of the glass. In this work, we focus on the effect of hot compression on dissolution kinetics because it is known to improve, for example, elastic moduli and hardness, whereas its effect on chemical durability is poorly understood. Specifically, we study the bulk glass dissolution rate of phosphate, silicophosphate, borophosphate, borosilicate, and aluminoborosilicate glasses, which have been compressed at 0.5, 1.0, and 2.0 GPa at the glass transition temperature (T). We perform weight loss and supplementary modifier leaching measurements of bulk samples immersed in acid (pH 2) and neutral (pH 7) solutions. Compression generally improves the chemical durability as measured from weight loss, but the effect is highly composition- and pressure-dependent. As such, we show that the dissolution mechanisms depend on the topological changes induced by permanent densification, which in turn are a function of the changes in the number of nonbridging oxygens and the network cross-linking. We also demonstrate a direct relationship between the chemical durability and the number of chemical topological constraints per atom (n) acting within the molecular network.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1021/acs.jpcb.7b04535DOI Listing
September 2017

Accessing Forbidden Glass Regimes through High-Pressure Sub-T Annealing.

Sci Rep 2017 04 18;7:46631. Epub 2017 Apr 18.

Department of Chemistry and Bioscience, Aalborg University, Aalborg 9220, Denmark.

Density and hardness of glasses are known to increase upon both compression at the glass transition temperature (T) and ambient pressure sub-T annealing. However, a serial combination of the two methods does not result in higher density and hardness, since the effect of compression is countered by subsequent annealing and vice versa. In this study, we circumvent this by introducing a novel treatment protocol that enables the preparation of high-density, high-hardness bulk aluminosilicate glasses. This is done by first compressing a sodium-magnesium aluminosilicate glass at 1 GPa at T, followed by sub-T annealing in-situ at 1 GPa. Through density, hardness, and heat capacity measurements, we demonstrate that the effects of hot compression and sub-T annealing can be combined to access a "forbidden glass" regime that is inaccessible through thermal history or pressure history variation alone. We also study the relaxation behavior of the densified samples during subsequent ambient pressure sub-T annealing. Density and hardness are found to relax and approach their ambient condition values upon annealing, but the difference in relaxation time of density and hardness, which is usually observed for hot compressed glasses, vanishes for samples previously subjected to high-pressure sub-T annealing. This confirms the unique configurational state of these glasses.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1038/srep46631DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5394531PMC
April 2017

Volume and structural relaxation in compressed sodium borate glass.

Phys Chem Chem Phys 2016 Nov 19;18(43):29879-29891. Epub 2016 Oct 19.

Department of Chemistry and Bioscience, Aalborg University, Aalborg, Denmark.

The structure and properties of glass can be modified through compression near the glass transition temperature (T), and such modified structure and properties can be maintained at ambient temperature and pressure. However, once the compressed glass undergoes annealing near T at ambient pressure, the modified structure and properties will relax. The challenging question is how the property relaxation is correlated with both the local and the medium-range structural relaxation. In this paper, we answer this question by studying the volume (density) and structural relaxation of a sodium borate glass that has first been pressure-quenched from its T at 1 GPa, and then annealed at ambient pressure under different temperature-time conditions. Using B MAS NMR and Raman spectroscopy, we find that the pressure-induced densification of the glass is accompanied by a conversion of six-membered rings into non-ring trigonal boron (B) units, i.e. a structural change in medium-range order, and an increase in the fraction of tetrahedral boron (B), i.e. a structural change in short-range order. These pressure-induced structural conversions are reversible during ambient pressure annealing near T, but exhibit a dependence on the annealing temperature, e.g. the ring/non-ring B ratio stabilizes at different values depending on the applied annealing temperature. We find that conversions between structural units cannot account for the pressure-induced densification, and instead we suggest the packing of structural units as the main densification mechanism.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1039/c6cp06341aDOI Listing
November 2016

Pretransitional behavior of the nonlinear dielectric effect for the liquid-solid transition in nitrobenzene.

Phys Rev E 2016 06 20;93(6):062131. Epub 2016 Jun 20.

Karol Lipinski Academy of Music in Wrocław, Plac Jana Pawła II 2, 50-043 Wrocław, Poland.

The nonlinear dielectric effect describes changes of dielectric permittivity induced by the strong electric field. This report shows the evidence for the critical-like pretransitional behavior for the liquid-solid transition in the supercooled nitrobenzene. Hallmarks of such behavior extend even above the melting temperature. A method for the analysis of pretransitional effects, avoiding the biasing impact of the noncritical background contribution, is proposed.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1103/PhysRevE.93.062131DOI Listing
June 2016

The super- and sub-critical effects for dielectric constant in diethyl ether.

J Chem Phys 2016 Jun;144(22):224506

Institute of High Pressure Physics Polish Academy of Sciences, ul. Sokołowska 29/37, 01-142 Warsaw, Poland.

Results of dielectric constant (ε) studies in diethyl ether for the surrounding of the gas - liquid critical point, TC - 130 K < T < TC + 50 K, are presented. The analysis recalls the physics of critical phenomena for portraying ε (T) evolution along branches of the coexistence curve, along its diameter (d(T)) and in the supercritical domain for T > TC. For the ultrasound sonicated system, the split into coexisting phases disappeared and dielectric constant approximately followed the pattern of the diameter. This may indicate the possibility of the extension of the "supercritical technology" into the ultrasound "homogenized" subcritical domain: the "strength" and the range of the precritical effect of d(T) are ca. 10× larger than for ε (T > TC).
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1063/1.4953616DOI Listing
June 2016

Unique effects of thermal and pressure histories on glass hardness: Structural and topological origin.

J Chem Phys 2015 Oct;143(16):164505

Institute of High Pressure Physics, Polish Academy of Sciences, Warsaw 01-142, Poland.

The properties of glass are determined not only by temperature, pressure, and composition, but also by their complete thermal and pressure histories. Here, we show that glasses of identical composition produced through thermal annealing and through quenching from elevated pressure can result in samples with identical density and mean interatomic distances, yet different bond angle distributions, medium-range structures, and, thus, macroscopic properties. We demonstrate that hardness is higher when the density increase is obtained through thermal annealing rather than through pressure-quenching. Molecular dynamics simulations reveal that this arises because pressure-quenching has a larger effect on medium-range order, while annealing has a larger effect on short-range structures (sharper bond angle distribution), which ultimately determine hardness according to bond constraint theory. Our work could open a new avenue towards industrially useful glasses that are identical in terms of composition and density, but with differences in thermodynamic, mechanical, and rheological properties due to unique structural characteristics.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1063/1.4934540DOI Listing
October 2015

Dielectric Spectroscopy of Pressurized .

Food Biophys 2015;10(3):229-234. Epub 2014 Sep 17.

University of Berne, Freiestrasse 3, Berne, CH-3012 Switzerland.

Results of broadband dielectric spectroscopy (BDS) in (baker's yeast), as the function of pressure are presented. They show a clear evidence of a threshold to the new pattern of the pressure evolution of the static dielectric permittivity and DC electric conductivity already for  ≈ 200 at  = 5 and  ≈ 300 at  = 25 . BDS monitoring versus pressure tests up to  = 400 revealed particularly notable changes of properties after 30 minutes of compressing. Finally, the correlation between the amount of the spectrophotometric maximum absorbance and the DC electric conductivity was found. All these indicate significance of BDS as the tool for testing of pressure properties of cells assemblies, model foods etc., under high pressures.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1007/s11483-014-9367-yDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4512274PMC
September 2014

Fractional Debye-Stokes-Einstein behaviour in an ultraviscous nanocolloid: glycerol and silver nanoparticles.

Soft Matter 2015 Jul;11(27):5554-62

Silesian Intercollegiate Center for Education and Interdisciplinary Research & Institute of Physics, University of Silesia, ul. 75 Pułku Piechoty 1A, 41-500 Chorzów, Poland.

One of the major features of glass forming ultraviscous liquids is the decoupling between translational and orientational dynamics. This paper presents studies of this phenomenon in glycerol, an accepted molecular glass former, concentrating on the impact of two exogenic factors: high pressures (P) up to the extreme 1.5 GPa and silver (Ag) nanoparticles (NPs). The analysis is focused on the fractional Debye-Stokes-Einstein (FDSE) relationship: σ(T,P)(τ(T,P))(S) = const, linking DC electric conductivity (σ) and primary (alpha, structural) relaxation time (τα). In glycerol and its nanocolloid (glycerol + Ag NPs) at atmospheric pressure only negligible decoupling (S ∼ 1) was detected. However, in the compressed nanocolloid, a well-defined transformation (at P = 1.2 GPa) from S ∼ 1 to the very strongly decoupled dynamics (S ∼ 0.5) occurred. For comparison, in pressurized 'pure' glycerol the stretched shift from S ∼ 1 to S ∼ 0.7 took place. This paper also presents the general discussion of FDSE behavior in ultraviscous liquids, including the new link between the FDSE exponent, fragility and the apparent activation enthalpy and volume.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1039/c5sm00266dDOI Listing
July 2015

Fragility and basic process energies in vitrifying systems.

Sci Rep 2015 Feb 9;5:8314. Epub 2015 Feb 9.

Science and Technology Division, Corning Incorporated, Corning, New York 14831, USA.

The concept of 'fragility' constitutes a central point of the glass transition science serving as the 'universal' metric linking previtreous dynamics of qualitatively distinct systems. Finding the fundamental meaning of fragility is the 'condicio sine qua' for reaching the long expected conceptual breakthrough in this domain. This report shows that fragility is determined by the ratio between two fundamental process energies, viz. the activation enthalpy and activation energy. The reasoning, avoiding any underlying physical model, is supported by the experimental evidence ranging from low molecular weight liquids and polymers to plastic crystals and liquid crystals. All these lead to the new general scaling plot for dynamics of arbitrary glass former. The limited adequacy of broadly used so far semi-empirical relationships between fragility and the activation energy is shown. Results presented remain valid for an arbitrary complex system and collective phenomena if their dynamics is described by the general super-Arrhenius relation.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1038/srep08314DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4321169PMC
February 2015

Germination and Inactivation of Alicyclobacillus acidoterrestris Spores Induced by Moderate Hydrostatic Pressure.

Pol J Microbiol 2015 ;64(4):351-9

Given the importance of spoilage caused by Alicyclobacillus acidoterrestris for the fruit juice industry, the objective of this work was to study the germination and inactivation of A. acidoterrestris spores induced by moderate hydrostatic pressure. Hydrostatic pressure treatment can induce the germination and inactivation of A. acidoterrestris spores. At low pH, spore germination of up to 3.59-3.75 log and inactivation of 1.85-2.04 log was observed in a low pressure window (200-300 MPa) applied at 50 degrees C for 20 min. Neutral pH suppressed inactivation, the number of spores inactivated at pH 7.0 was only 0.24-1.06 log. The pressurization temperature significantly affected spore germination and inactivation. The degree of germination in apple juice after pressurization for 30 min with 200 MPa at 20 degrees C was 2.04 log, with only 0.61 log of spores being inactivated, while at 70 degrees C spore germination was 5.94 log and inactivation 4.72 log. This temperature strongly stimulated germination and inactivation under higher (500 MPa) than lower (200 MPa) pressure. When the oscillatory mode was used, the degree of germination and inactivation was slightly higher than at continuous mode. The degree of germination and inactivation was inversely proportional to the soluble solids content and was lowest in concentrated apple juice.
View Article and Find Full Text PDF

Download full-text PDF

Source
May 2016

Nonlinear dielectric effect in supercritical diethyl ether.

J Chem Phys 2014 Sep;141(9):094907

Department of Biochemistry, University of Berne, Freiestrasse 3, Berne CH-3012, Switzerland.

Nonlinear dielectric effect (NDE) describes changes of dielectric permittivity induced by a strong electric field in a liquid dielectric. The most classical finding related to this magnitude is the negative sign of NDE in liquid diethyl ether (DEE), recalled by Peter Debye in his Nobel Prize lecture. This article shows that the positive sign of NDE in DEE is also possible, in the supercritical domain. Moreover, NDE on approaching the gas-liquid critical point exhibits a unique critical effect described by the critical exponent ψ ≈ 0.4 close to critical temperature (T(C)) and ψ ≈ 0.6 remote from T(C). This can be linked to the emergence of the mean-field behavior in the immediate vicinity of T(C), contrary to the typical pattern observed for critical phenomena. The multi-frequency mode of NDE measurements made it possible to estimate the evolution of lifetime of critical fluctuations. The new way of data analysis made it possible to describe the critical effect without a knowledge of the non-critical background contribution in prior.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1063/1.4893979DOI Listing
September 2014

Pressure-induced changes in interdiffusivity and compressive stress in chemically strengthened glass.

ACS Appl Mater Interfaces 2014 Jul 17;6(13):10436-44. Epub 2014 Jun 17.

Section of Chemistry, Aalborg University , Aalborg 9000, Denmark.

Glass exhibits a significant change in properties when subjected to high pressure because the short- and intermediate-range atomic structures of glass are tunable through compression. Understanding the link between the atomic structure and macroscopic properties of glass under high pressure is an important scientific problem because the glass structures obtained via quenching from elevated pressure may give rise to properties unattainable under standard ambient pressure conditions. In particular, the chemical strengthening of glass through K(+)-for-Na(+) ion exchange is currently receiving significant interest due to the increasing demand for stronger and more damage-resistant glass. However, the interplay among isostatic compression, pressure-induced changes in alkali diffusivity, compressive stress generated through ion exchange, and the resulting mechanical properties are poorly understood. In this work, we employ a specially designed gas pressure chamber to compress bulk glass samples isostatically up to 1 GPa at elevated temperature before or after the ion exchange treatment of a commercial sodium-magnesium aluminosilicate glass. Compression of the samples prior to ion exchange leads to a decreased Na(+)-K(+) interdiffusivity, increased compressive stress, and slightly increased hardness. Compression after the ion exchange treatment changes the shape of the potassium-sodium diffusion profiles and significantly increases glass hardness. We discuss these results in terms of the underlying structural changes in network-modifier environments and overall network densification.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1021/am5019868DOI Listing
July 2014

Divergent dynamics and the Kauzmann temperature in glass forming systems.

Sci Rep 2014 Jun 4;4:5160. Epub 2014 Jun 4.

Science and Technology Division, Corning Incorporated, Corning, New York 14831, USA.

In the last decade the challenging analysis of previtreous behavior of relaxation time (τ(T)) in ultraviscous low molecular weight liquids led to the conceptual shift of the glass transition physics toward theories not predicting a "finite-temperature" divergence. This "breakthrough" experimental finding was strengthened by the discovery that "dynamic" (i.e. from τ(T) fitting) and "thermodynamic" estimations of the "ideal glass" (Kauzmann) temperature do not match, what in fact questioned its existence. In this report, due to the novel way of analysis based on the transformation of τ(T) experimental data to the activation energy temperature index form, the clear prevalence of the "finite-temperature" divergence is proved. The obtained "dynamic" singular temperatures clearly coincide with "thermodynamic" estimations of the Kauzmann temperature, thus solving also the second mystery. The comprehensive picture was obtained due to the analysis of 55 experimental data-sets, ranging from low molecular weight liquids and polymers to liquid crystal and plastic crystals.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1038/srep05160DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5381491PMC
June 2014

Mixed alkaline earth effect in the compressibility of aluminosilicate glasses.

J Chem Phys 2014 Feb;140(5):054511

Science and Technology Division, Corning Incorporated, Corning, New York 14831, USA.

The mixed modifier effect (MME) in oxide glasses manifests itself as a non-additive variation in certain properties when one modifier oxide species is substituted by another one at constant total modifier content. However, the structural and topological origins of the MME are still under debate. This study provides new insights into the MME by investigating the effect of isostatic compression on density and hardness of mixed MgO/CaO sodium aluminosilicate glasses. This is done using a specially designed setup allowing isostatic compression of bulk glass samples up to 1 GPa at elevated temperature. A mixed alkaline earth effect is found in the compressibility and relative change of hardness, viz., a local maximum of density as a function of Mg/Ca ratio appears following compression, whereas a local minimum of hardness in the uncompressed glasses nearly disappears after compression. Moreover, the densification of these glasses is found to occur at temperatures much below the glass transition temperature, indicating that a non-viscous mechanism is at play. This is further supported by the fact that density relaxes in a stretched exponential manner upon subsequent annealing at ambient pressure with an exponent of ∼0.62. This is close to the Phillips value of 3/5 for relaxation in three dimensions when both short- and long-range interactions are activated.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1063/1.4863998DOI Listing
February 2014

Distortion-sensitive insight into the pretransitional behavior of 4-n-octyloxy-4'-cyanobiphenyl (8OCB).

J Phys Condens Matter 2013 Jun 29;25(24):245105. Epub 2013 May 29.

Institute of Physics, University of Silesia, Katowice, Poland.

Results of studies of the static and dynamic dielectric properties in rod-like 4-n-octyloxy-4'-cyanobiphenyl (8OCB) with isotropic (I)-nematic (N)-smectic A (SmA)-crystal (Cr) mesomorphism, combined with measurements of the low-frequency nonlinear dielectric effect and heat capacity are presented. The analysis is supported by the derivative-based and distortion-sensitive transformation of experimental data. Evidence for the I-N and N-SmA pretransitional anomalies, indicating the influence of tricritical behavior, is shown. It has also been found that neither the N phase nor the SmA phase are uniform and hallmarks of fluid-fluid crossovers can be detected. The dynamics, tested via the evolution of the primary relaxation time, is clearly non-Arrhenius and described via τ(T) = τ(c)(T-T(C))(-φ). In the immediate vicinity of the I-N transition a novel anomaly has been found: Δτ is proportional to 1/(T - T*), where T* is the temperature of the virtual continuous transition and Δτ is the excess over the 'background behavior'. Experimental results are confronted with the comprehensive Landau-de Gennes theory based modeling.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1088/0953-8984/25/24/245105DOI Listing
June 2013

A universal description of ultraslow glass dynamics.

Nat Commun 2013 ;4:1823

Department of Chemistry and Biochemistry, University of Berne, Freiestrasse 3, Berne CH-3012, Switzerland.

The dynamics of glass is of importance in materials science but its nature has not yet been fully understood. Here we report that a verification of the temperature dependencies of the primary relaxation time or viscosity in the ultraslowing/ultraviscous domain of glass-forming systems can be carried out via the analysis of the inverse of the Dyre-Olsen temperature index. The subsequent analysis of experimental data indicates the possibility of the self-consistent description of glass-forming low-molecular-weight liquids, polymers, liquid crystals, orientationally disordered crystals and Ising spin-glass-like systems, as well as the prevalence of equations associated with the 'finite temperature divergence'. All these lead to a new formula for the configurational entropy in glass-forming systems. Furthermore, a link to the dominated local symmetry for a given glass former is identified here. Results obtained show a new relationship between the glass transition and critical phenomena.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1038/ncomms2797DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3674245PMC
December 2013

The new insight into dynamic crossover in glass forming liquids from the apparent enthalpy analysis.

J Chem Phys 2012 Aug;137(6):064501

Department of Chemistry and Biochemistry, University of Berne, Freiestrasse 3, CH-3012 Berne, Switzerland.

One of the most intriguing phenomena in glass forming systems is the dynamic crossover (T(B)), occurring well above the glass temperature (T(g)). So far, it was estimated mainly from the linearized derivative analysis of the primary relaxation time τ(T) or viscosity η(T) experimental data, originally proposed by Stickel et al. [J. Chem. Phys. 104, 2043 (1996); J. Chem. Phys. 107, 1086 (1997)]. However, this formal procedure is based on the general validity of the Vogel-Fulcher-Tammann equation, which has been strongly questioned recently [T. Hecksher et al. Nature Phys. 4, 737 (2008); P. Lunkenheimer et al. Phys. Rev. E 81, 051504 (2010); J. C. Martinez-Garcia et al. J. Chem. Phys. 134, 024512 (2011)]. We present a qualitatively new way to identify the dynamic crossover based on the apparent enthalpy space (H(a)(') = dlnτ/d(1/T)) analysis via a new plot lnH(a)(') vs. 1∕T supported by the Savitzky-Golay filtering procedure for getting an insight into the noise-distorted high order derivatives. It is shown that depending on the ratio between the "virtual" fragility in the high temperature dynamic domain (m(high)) and the "real" fragility at T(g) (the low temperature dynamic domain, m = m(low)) glass formers can be splitted into two groups related to f < 1 and f > 1, (f = m(high)∕m(low)). The link of this phenomenon to the ratio between the apparent enthalpy and activation energy as well as the behavior of the configurational entropy is indicated.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1063/1.4739750DOI Listing
August 2012

Does the characteristic value of the discontinuity of the isotropic-mesophase transition in n-cyanobiphenyls exist?

J Phys Condens Matter 2012 Sep 27;24(37):375101. Epub 2012 Jul 27.

Institute of High Pressure Physics PAS Unipress, Warsaw, Poland.

Results of the extended Landau-de Gennes model analysis and experimental studies of the isotropic-nematic (I-N) and isotropic-smectic-A (I-SmA) phase transitions in rod-like liquid crystalline n-alkylcyanobiphenyls are presented. Experiments were carried out as a function of temperature and pressure using the static dielectric permittivity and its 'nonlinear' (strong electric field related) counterpart-the low-frequency nonlinear dielectric effect. Precise estimations of the values of the discontinuity of the isotropic-mesophase transitions (ΔT) for nCB from n = 3-14 have been obtained. It is suggested that for each nCB a unique, characteristic minimal value of ΔT, associated with the I-N-SmA triple point, exists. For 'shorter' nCBs it can be hidden in the negative pressures domain. The possibility of the extension of the 'melting curve' into the negative pressures region as well as the appearance of the 'melting inversion' at high enough pressures is indicated.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1088/0953-8984/24/37/375101DOI Listing
September 2012
-->