The field of viscous liquid and glassy solid dynamics is reviewed by a process of posing the key questions that need to be answered, and then providing the best answers available to the authors and their advisors at this time. The subject is divided into four parts, three of them dealing with behavior in different domains of temperature with respect to the glass transition temperature, Tg , and a fourth dealing with ‘‘short time processes.’’ The first part tackles the high temperature regime T.Tg ,i n which the system is ergodic and the evolution of the viscous liquid toward the condition at Tg is in focus. The second part deals with the regime T;Tg , where the system is nonergodic except for very long annealing times, hence has time-dependent properties ~aging and annealing!. The third part discusses behavior when the system is completely frozen with respect to the primary relaxation process but in which secondary processes, particularly those responsible for ‘‘superionic’’ conductivity, and dopart mobility in amorphous silicon, remain active. In the fourth part we focus on the behavior of the system at the crossover between the low frequency vibrational components of the molecular motion and its high frequency relaxational components, paying particular attention to very recent developments in the short time dielectric response and the high Q mechanical response. © 2000 American Institute of Physics.@S0021-8979~00!02213-1#

https://lib.dr.iastate.edu/cgi/viewcontent.cgi?article=1065&context=mse_pubs

Relaxation in glassforming liquids and amorphous solids

Selected aspects of recent progress in the study of supercooled liquids and glasses are presented in this review. As an introduction for nonspecialists, several basic features of the dynamics and thermodynamics of supercooled liquids and glasses are described. Among these are nonexponential relaxation functions, non-Arrhenius temperature dependences, and the Kauzmann temperature. Various theoretical models which attempt to explain these basic features are presented next. These models are conveniently categorized according to the temperature regimes deemed important by their authors. The major portion of this review is given to a summary of current experimental and computational research. The utility of mode coupling theory is addressed. Evidence is discussed for new relaxation mechanisms and new time and length scales in supercooled liquids. Relaxations in the glassy state and significance of the “boson peak” are also addressed.

Supercooled Liquids and Glasses

We provide a new fit for the microwave complex dielectric constant of water in the salinity range between 0-40 ppt using two Debye relaxation wavelengths. For pure water, the fit is based on laboratory measurements in the temperature range between -20/spl deg/C and +40/spl deg/C including supercooled water and for frequencies up to 500 GHz. For sea water, our fit is valid for temperatures between -2/spl deg/C and +29/spl deg/C and for frequencies up to at least 90 GHz. At low frequencies, our new model is a modified version of the Klein-Swift model. We compare the results of the new fit with various other models and provide a validation using an extensive analysis of brightness temperatures from the Special Sensor Microwave Imager.

/pdf/the-complex-dielectric-constant-of-pure-and-sea-water-from-kbtsn5o4iw.pdf

The complex dielectric constant of pure and sea water from microwave satellite observations

The dynamics of solvation in polar liquids

The state-of-the-art polymer dielectrics have been limited to nonpolar polymers with relatively low energy density but ultralow dielectric losses for the past decades. With the fast development of power electronics in pulsed power and power conditioning applications, there is a need for next-generation dielectric capacitors in areas of high energy density/low loss and/or high temperature/low loss polymer dielectrics. Given limitations in further enhancing atomic and electronic polarizations for polymers, this Perspective focuses on a fundamental question: Can orientational polarization in polar polymers be utilized for high energy density and low loss dielectrics? Existing experimental and theoretical results have suggested the following perspectives. For amorphous polar polymers, high energy density and low loss can be achieved below their glass transition temperatures. For liquid crystalline side-chain polymers, dipole mobility is so high that they saturate at relatively low electric fields, and only li...

Novel Ferroelectric Polymers for High Energy Density and Low Loss Dielectrics

Dielectric spectra of some common solvents in the microwave region. Dipolar aprotic solvents and amides

A system of computer controlled transmission lines based on the method of traveling waves is presented, permitting the precise detn. of complex permittivities of medium to high loss liqs. at 8.5 to 90 GHz. It consists of a newly developed app. for the E-band region (60 ≤ v/GHz ≤ 90), which is described in detail, together with existing X- (8.5 ≤ v/GHz ≤ 12.4), Ku- (12.4 ≤ v/GHz ≤ 18), and A-band (26.4 ≤ v/GHz ≤ 40) set-ups now appropriately adapted for computer control. Consistency and accuracy of the equipment are evidenced with the help of permittivity data for water, methanol, N-methylformamide, DMF.

A computer-controlled system of transmission lines for the determination of the complex permittivity of lossy liquids between 8.5 and 90 GHz

Complex permittivity spectra in the frequency range 0.95≤v (GHz)≤89 for acetonitrile and its solutions of LiBr, NaI, NaClO4, and Bu4NBr at 25°C show one Debye equation for the neat solvent whereas the superposition of a Debye process for the solute and a Cole-Cole distribution for the solvent is necessary to account for the dielectric relaxation behavior of the solutions. The reorientation of bulk acetonitrile is diffusive and only weakly coupled to viscosity. The number of solvent molecules irrotationally bound to the electrolyte is in good agreement with conventional solvation numbers for all electrolytes, when kinetic depolarization is assumed to be negligible. The solute relaxation process is dominated by the formation kinetics and reorientation of contact ion pairs. There is evidence for solvent-shared ion pairs in dilute NaClO4 solutions.

Dielectric relaxation of electrolyte solutions in acetonitrile

The microwave dispersion and absorption spectra are discussed for various protic and aprotic electrolyte solns. and their solvents over large frequency ranges, in general 0.9-90 GHz. Wider frequency ranges are covered for water (0.9-409 GHz) and for methanol, N-methylformamide, and N,N-dimethylformamide (all 0.9-293 GHz). The role of insufficient frequency coverage is critically discussed. Permittivities and relaxation times of the underlying relaxation processes are compared for electrolyte solns. of the hydrogen-bonding solvents water, methanol and higher alcs., formamide, N-methylformamide, and the dipolar aprotic solvents acetonitrile, propylene carbonate, DMSO, and N,N-dimethylformamide. The hydrogen-bonding mode at τ ≃1 ps is not affected by the addn. of alkali metal and tetrabutylammonium salts, in contrast to the bulk and the internal relaxation of the H-bonded chains; NH4+ in methanol produces peculiar effects. For 1:1-electrolytes ion-pair formation is detectable in all solvents of static permittivity below 50; the concn. dependence of the corresponding relaxation time permits sepn. into rotational and kinetic modes of ion-pair formation and decompn.

/pdf/molecular-processes-in-electrolyte-solutions-at-microwave-49mv7kyw5m.pdf

Molecular processes in electrolyte solutions at microwave frequencies

Permittivity data from 0.9 to 40 GHz for acetonitrile and 0.05 to 1.4 molar acetonitrile solutions of Bu4NBr at 25°C are used to exemplify the behavior of ion pairs in high frequency electric fields. Measurements were excuted by the method of travelling waves with equipment known to produce data of high precision. Data analysis of the acetonitrile spectrum shows a single relaxation process at relaxation time of 3.5 ps for the solvent reorientation; the spectra of the salt solutions reveal two relaxation processes with relaxation times increasing from 3.5 to 6.8 ps for the solvent and decreasing from 120 to 70 ps for the ion pair [Bu4NBr]o at increasing salt concentration. The association constant of Bu4NBr in acetonitrile determined by permittivity measurements agrees well with that from conductance measurements. The concentration-dependence of the ion-pair relaxation times reveals the rate constants of ion-pair formation and decomposition.

M. Kleebauer

Papers

Dielectric spectra of some common solvents in the microwave region. Dipolar aprotic solvents and amides

A computer-controlled system of transmission lines for the determination of the complex permittivity of lossy liquids between 8.5 and 90 GHz

Dielectric relaxation of electrolyte solutions in acetonitrile

Molecular processes in electrolyte solutions at microwave frequencies

The behavior of ion pairs in high frequency electric fields exemplified by acetonitrile solutions of Bu4NBr