Showing papers by "Sylwester J. Rzoska published in 2022"

Pretransitional and premelting effects in menthol

Abstract: To canonic features of melting/freezing discontinuous phase transitions, one can encounter the lack of pretransitional effects in the liquids state and weak premelting effects with non-defined temperature evolutions in the crystalline state. This report shows the evidence for long-range and critical-like pretransitional effects in liquid menthol for electrooptic Kerr effect (EKE) and nonlinear dielectric effect (NDE). These methods are inherently associated with a strong electric field. The premelting effect, with well-defined temperature evolution, was evidenced in the crystalline state. Model explanations of these phenomena are proposed. For the premelting effect, the ‘reversed’ Mossotti-Catastrophe behavior is suggested.

The impact of ionic contribution to dielectric permittivity in 11CB liquid crystal and its colloids with BaTiO3 nanoparticles

Abstract: Abstract The report shows the temperature behavior of the real part of dielectric permittivity in the static (dielectric constant) and low-frequency (LF) domains in bulk samples of 11CB and its BaTiO 3 -based nanocolloids. The study covers the isotropic liquid (I), nematic (N), smectic A (SmA), and solid crystal (Cr) phases. For each phase, the dominance of pretransitional fluctuations, significantly moderated by nanoparticles, is shown. The authors consider separate focuses on the dielectric constant $$\varepsilon \left( {\varvec{T}} \right)$$ ε T evolution in the static domain, yielding mainly response from permanent dipole moment and its arrangement, and in the low-frequency (LF) domain $$\Delta \varepsilon^{\prime } \left( f \right) = \varepsilon^{\prime } \left( f \right) - \varepsilon$$ Δ ε ′ f = ε ′ f - ε (where $$\varepsilon^{\prime } \left( {\varvec{f}} \right)$$ ε ′ f is for the real part of dielectric permittivity in the LF domain), which is associated solely with ionic-related polarization mechanisms. All of these led to new experimental evidence concerning I–N, N–SmA, and SmA–solid transitions, focusing on the strength and extent of pretransitional effects, critical exponents, and phase transitions discontinuities. The strong evidence for pretransitional effects near the SmA–Cr transition is notable, particularly regarding $$\Delta \varepsilon^{\user2{^{\prime}}} \left( {{\varvec{f}},{\varvec{T}}} \right)$$ Δ ε ′ f , T . Studies are supplemented by the discussion of DC electric conductivity—a parameter also related to the LF domain. Finally, the validity of the relation $$\varepsilon^{\prime } \left( {\varvec{f}} \right) = {\varvec{Af}}^{ - 3/2} + \varepsilon$$ ε ′ f = Af - 3 / 2 + ε (where f stands for frequency, and A is a constant parameter), often used for discussing dielectric spectra in LC compound and its nanocolloids in the LF domain, is examined. Graphical abstract

New paradigm for configurational entropy in glass-forming systems

Abstract: We show that on cooling towards glass transition configurational entropy exhibits more significant changes than predicted by classic relation. A universal formula according to Kauzmann temperature [Formula: see text] is given: [Formula: see text], where [Formula: see text]. The exponent [Formula: see text] is hypothetically linked to dominated local symmetry. Such a behaviour is coupled to previtreous evolution of heat capacity [Formula: see text] associated with finite temperature singularity. These lead to generalised VFT relation, for which the basic equation is retrieved. For many glass-formers, basic VFT equation may have only an effective meaning. A universal-like reliability of the Stickel operator analysis for detecting dynamic crossover phenomenon is also questioned. Notably, distortions-sensitive and derivative-based analysis focused on previtreous changes of configurational entropy and heat capacity for glycerol, ethanol and liquid crystal is applied.

The fluctuation-driven dielectric properties of liquid crystalline 8OCB and its nanocolloids.

Abstract: Results of broadband dielectric spectroscopy studies in liquid crystalline octyloxycyanobiphenyl (8OCB) and its colloids with BaTiO3 nanoparticles (paraelectric, diameter d = 50 nm) are presented. Studies were carried out in isotropic liquid, nematic, smectic A and solid crystalline phases. They are supported by derivative-based and distortion-sensitive analyses, revealing a set of universal scaling patterns for temperature evolution of static and dynamic dielectric properties. All these yielded evidence for a pretransitional fluctuation impact on the dielectric constant, primary relaxation time, loss curve maximum and translational-orientational decoupling associated with anomalous values of the fractional Debye-Stokes-Einstein (DSE) exponent 0.2 < S < 2.2. The evidence for critical like changes in a distribution of relaxation times is shown. For mesophases, a tiny addition of nanoparticles causes permanent orientation of LC molecules, leading even to a 16% increase of the dielectric constant above a maximal value in pure 8OCB. A split of two regions, dominated by pre-isotropic and pre-smectic fluctuations, is evidenced. Model explanations for detected phenomena, particularly in the isotropic liquid phase, are presented. New evidence for a premelting effect in the solid phase is also shown.

Pretransitional of behavior of electrooptic Kerr effect in liquid thymol

Abstract: Abstract Melting/freezing are canonical examples of discontinuous phase transitions, for which no pretransitional effects in the liquid phase are expected. For the solid phase, weak premelting effects are evidenced. This report shows long-range, critical-like, pretransitional effects in liquid thymol detected in electrooptic Kerr effect (EKE) studies. Notably is the negative sign of EKE pretransitional anomaly. Studies are supplemented by the high-resolution dielectric constant temperature-related scan, which revealed a weak premelting effect in the solid phase. Both EKE and dielectric constant show a ‘crossover’ change in the liquid phase, ca, 10 K above the freezing temperature. It can be recognized as the hallmark of the challenging liquid–liquid transition phenomenon. Graphical abstract

Criticality-related fundamental bases for new generations of gas–liquid, liquid–liquid, and liquid (LE) extraction technologies

Abstract: The report presents experimental results, which can be considered as the reference for innovative generations of supercritical fluids (SCF), liquid-liquid (LL), and liquid (L) extraction technologies. They are related to implementations of Critical Phenomena Physics, for such applications not considered so far. For the gas-liquid critical point, the shift SuperCritical Fluids (SCF) ⇒ SubCritical Fluids, due to the additional exogenic impact of ultrasounds, is indicated. For LL technology, the possibility of increasing process effectiveness when operating near the critical consolute under pressure is indicated. Finally, the discovery of long-range precritical-type changes of dielectric constant in linseed oil, standing even 50 K above the melting temperature, is presented. It suggests that extraction processes linking 'SCF' and 'L' technologies features and exploring the natural carrier, such as linseed oil, are possible. The report recalls the fundamental base for extraction processes via Kirkwood and Noyes-Whitney relations and presents their implementations to 'critical conditions,' including pressure.

Pressure Evolution of Glass Transition Temperature in LiFePO4.

Abstract: LiFePO4 is an important base material for generation of new batteries. One of the important developments is its use in the form of a solid glass, which allows an increase in the electrical conductivity after the high-pressure process. Such a treatment allows full control of the vitrification and nanocrystallization processes as well. This report shows the basic reference for the pressure dependence of the glass transition temperature. The unique behavior has been proven with a maximum of Tg (P) already at moderate pressures. The protocol for depicting the resulting evolution is as follows: it enables a reliable extrapolation beyond the experimental domain. The importance of the presented results for the general topic of glass transition physics is also remarkable due to the scant evidence of the existence of systems with clearly inverted vitrification under compression.

New insight into 3-picoline—deuterium oxide (D2O) mixtures of limited miscibility with the lower critical consolute temperature

Abstract: Abstract Coexistence curves in mixtures of limited miscibility with the lower critical consolute temperature (LCT), of 3-picoline with deuterium oxide (D 2 O), and D 2 O/H 2 O have been determined. They were tested with respect to the order parameter, the diameter of the binodal, and coordinates of the critical consolute point (critical temperature $${T}_{\mathrm{C}}$$ T C and critical concentration $${\phi }_{\mathrm{C}}$$ ϕ C ). Studies were carried out using the innovative method based on the analysis of relative volumes occupied by coexisting phases, yielding high-resolution data. The clear violation of the Cailletet-Mathew law of rectilinear diameter for the LCT mixtures of limited miscibility is evidenced. For the order parameter, the new distortion-sensitive analysis method yielded the evidence for the model-value of the order parameter critical exponent $$\beta =0.326\pm 0.003$$ β = 0.326 ± 0.003 , up to ca. 1 K from $${T}_{\mathrm{C}}$$ T C . Finally, the simple & easy method for determining the critical concentration by testing relative volumes of coexisting phases (or alternatively fractional meniscus heights, h ) is presented. The significance of the invariant value $${h}_{\mathrm{C}}=h\left({T}_{\mathrm{C}},{\phi }_{\mathrm{C}}\right)=1/2$$ h C = h T C , ϕ C = 1 / 2 is highlighted. The appearance of the milky & bluish critical opalescence is also shown. Graphical abstract

Novel High-Pressure Nanocomposites for Cathode Materials in Sodium Batteries

Abstract: A new nanocomposite material was prepared by high pressure processing of starting glass of nominal composition NaFePO4. Thermal, structural, electrical and dielectric properties of the prepared samples were studied by differential thermal analysis (DTA), X-ray diffraction (XRD) and broadband dielectric spectroscopy (BDS). It was demonstrated that high-pressure–high-temperature treatment (HPHT) led to an increase in the electrical conductivity of the initial glasses by two orders of magnitude. It was also shown that the observed effect was stronger than for the lithium analogue of this material studied by us earlier. The observed enhancement of conductivity was explained by Mott’s theory of electron hopping, which is more frequent in samples after pressure treatment. The final composite consisted of nanocrystalline NASICON (sodium (Na) Super Ionic CONductor) and alluaudite phases, which are electrochemically active in potential cathode materials for Na batteries. Average dimensions of crystallites estimated from XRD studies were between 40 and 90 nm, depending on the phase. Some new aspects of local dielectric relaxations in studied materials were also discussed. It was shown that a combination of high pressures and BDS method is a powerful method to study relaxation processes and molecular movements in solids. It was also pointed out that high-pressure cathode materials may exhibit higher volumetric capacities compared with commercially used cathodes with carbon additions.

Critical-like behavior of ionic-related, low-frequency dielectric properties in compressed liquid crystalline 8OCB and its nanocolloid

Abstract: The report presents pressure-related broadband dielectric spectroscopy (BDS) studies in liquid crystalline octyloxycyanobiphenyl (8OCB) and its nanocolloid with BaTiO 3 nanoparticles, focused on the ionic-related low-frequency (LF) domain and the influence of pretransitional fluctuations. Hence, basic exogenic (pressure) and endogenic (nanoparticles) impacts on the dielectric properties are addressed. The innovative derivative-based analysis revealed functional ‘critical-like’ descriptions of ionic- contributions to dielectric permittivity and electric conductivity. The supplementary dielectric constant scan, yielding insight into the preferable dipole-dipole arrangements, is also presented. Studies cover the puzzling case of complex liquid (Smectic A) – Solid crystal phase transition, revealing relatively strong, critical-like, premelting effects, which have hardly been observed for the discontinuous ‘melting transition’ so far.

New scaling of Adam-Gibbs relation in glass-forming systems

Abstract: In this letter we introduced a new scaling method based on Adam-Gibbs model. Moreover, generalised critical-like expression of configurational entropy SC(T) = S0 (1 − TK T ) n is used. Obtained values of pseudocritical exponent n seem to be universal for studied systems and corresponds well with thermodynamic data. Relation between dynamic portrayal represented by primary relaxation time and thermodynamic (specific heat capacity) is in a good agreement. In our last paper [1] we introduced a critical-like relation for configurational entropy. It based on calculations of specific heat capacities between supercooled liquid and glassy state. Parametrised relation may be expressed as follows: SC (T) = S0 (1 − TK T ) n ,

Pressure-driven relaxation processes in nanocomposite ionic glass LiFe0.75V0.10PO4

Abstract: This paper presents results for systems formed in a solid glassy state after nanocrystallization process above the glass temperature. We analyze electric conductivity and relaxation processes after such treatment under high temperature (HT) and high pressure (HP-HT) as well. The latter leads to ca. 8% increase of density, two decades (100) increase of electric conductivity as well as qualitative changes in relaxation processes. The previtreous-type changes of the relaxation time on cooling is analyzed by the use of critical-like and the 'critical-activated' description. Presented results correspond well with obtained for this material and shown in ref. [8]. The evidence for pressure evolution of the glass and crystallization temperatures, indicating the unique possibility of maxima and crossovers is also reported.

Continuous Isotropic-Nematic transition in compressed rod-like based nanocolloid

Abstract: Landau-de Gennes mean-field model predicts the discontinuous transition for the isotropic – nematic (I-N) transition, associated with uniaxial ordering and a quadrupolar order parameter in three dimensions. This report shows pressure-related dielectric studies for rod-like nematogenic pentylcyanobiphenyl (5CB) and its nanocolloids with BaTiO 3 nanoparticles. The scan of dielectric constant revealed the continuous I-N phase transition in the compressed nanocolloid with a tiny amount of nanoparticles ( x = 0.1%). For the nematic phase in 5CB and its x =1% nanocolloid the enormous values of dielectric constant and the bending–type, long-range pretransitional behavior were detected. The ‘shaping’ influence of prenematic fluctuations was also noted for the ionic-related contribution to dielectric permittivity in the isotropic liquid phase. For the high-frequency relaxation domain, this impact was tested for the primary relaxation time pressure evolution and the translational– orientational decoupling.

Strong pretransitional anomaly near glass transition

Abstract: In this report we present the first ever results of strong pretransitional effect observed for the maximum of absorption peak εmax ′′ (T) in supercooled liquid-crystalline systems near the glass transition temperature. This anomaly may be described by critical-like relation with critical exponent α = 0.5, which corresponds well with previous results for static electric permittivity εs(T). Such a behaviour may suggest thermodynamic character of glass transition. The description of the glass transition as a typical phase transition is still a subject of academic debate [1-4]. On the one hand, it is believed that the glass transition is a continuous transition, which begins at the temperature Tg and ends only around the Kauzmann temperature. There is still insufficient experimental evidence to unambiguously define its character. Colby and Erwin found that the dynamics of the transition to the glass state is related to the critical point (Tc) below Tg [5,6]. Then Tanaka [7] created a model in which he assumed that in each liquid there is a tendency to local aggregation of the bond-ordering and / or density

History-dependent phase transition character

Abstract: Abstract We consider history-dependent behavior in domain-type configurations in orientational order that are formed in configurations reached via continuous symmetry-breaking phase transitions. In equilibrium, these systems exhibit in absence of impurities a spatially homogeneous order. We focus on cases where domains are formed via (i) Kibble-Zurek mechanism in fast enough quenches or by (ii) Kibble mechanism in strongly supercooled phases. In both cases, domains could be arrested due to pinned topological defects that are formed at domain walls. In systems exhibiting polar or quadrupolar order, point and line defects (disclinations) dominate, respectively. In particular, the disclinations could form complex entangled structures and are more efficient in stabilizing domains. Domain patterns formed by fast quenches could be arrested by impurities imposing a strong enough random-field type disorder, as suggested by the Imry-Ma theorem. On the other hand, domains formed in supercooled systems could be also formed if large enough energy barriers arresting domains are established due to large enough systems’ stiffness. The resulting effective interactions in established domain-type patterns could be described by random matrices. The resulting eigenvectors reveal expected structural excitations formed in such structures. The most important role is commonly played by the random matrix largest eigenvector. Qualitatively different behavior is expected if this eigenvector exhibits a localized or extended character. In the former case, one expects a gradual, non-critical-type transition into a glass-type structure. However, in the latter case, a critical-like phase behavior could be observed. Graphical abstract