Williams Watts Research Articles

Electrical and room temperature multiferroic properties of polyvinylidene fluoride nanocomposites doped with nickel ferrite nanoparticles

The higher values of magneto-dielectric coupling is observed in flexible multiferroic polyvinylidene fluoride (PVDF) nanocomposites doped with nickel ferrite (NFO) nanoparticles.

TPU/PLA blend foams: Enhanced foamability, structural stability, and implications for shape memory foams

ABSTRACTA series of thermoplastic polyurethane (TPU)/poly(lactic acid) (PLA) blends are studied in terms of morphological, thermal, and rheological properties by scanning electron microscopy, differential scanning calorimetry, and rheometry. Using supercritical CO2 batch foaming, the foamability of the blends is systematically investigated. It is found that the 80/20 (wt %/wt %) TPU/PLA blend (TPU80%) shows vastly enhanced foamability over a wide range of foaming conditions to produce foams with a myriad of cellular morphology. The foamability enhancement results from the improved cell nucleation and growth, and the changes in the polymer microstructure. Compared to elastic TPU foams, the TPU80% retain their shapes 3.4 times better. Mechanism for the enhanced stability is proposed and verified using Kohlrausch–Williams–Watts model. The materials developed in the study and the mechanistic understanding of the shape fixation process may facilitate the advancement of elastomeric foams in conventional use as well as in novel shape memory applications. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 47416.

The role of self-trapped excitons in polaronic recombination processes in lithium niobate

Transient absorption and photoluminescence are experimentally investigated in the polaronic reference system lithium niobate, LiNbO (LN), with the aim to refine the microscopic model of small polaron dynamics in materials with strong electron–phonon coupling. As a unique feature, our study is performed by using two different spectroscopic methods, in crystals with dopants enhancing photorefraction or damage resistance, and over a broad temperature range from 15–400 K. Although being self-consistent for particular experimental conditions, the hitherto used microscopic polaronic models reveal inconsistencies when applied to this larger data set. We show that comprehensive modeling is unlocked by the inclusion of an additional type of polaronic state with the following characteristics: (i) strongly temperature- and dopant-dependent relaxation times, (ii) an absorption feature in the blue-green spectral range, and (iii) a Kohlrausch–Williams–Watts decay shape with a temperature-dependent stretching factor showing a behavior contrary to that of small, strong-coupling polarons. The hypothesis of self-trapped excitons (STEs, i.e. bound electron–hole pairs strongly coupled to Nb and O within a niobium-oxygen octahedron) and their pinning on defects as the microscopic origin of these characteristics is supported by a spectroscopic linkage of photoluminescence at low (15 K) and elevated (300 K) temperatures and explains the long-lifetime components in transient absorption as due to pinned STEs.

Structural and dielectric properties of BaTi0.5 (Co0.33 Mo0.17) O3 perovskite ceramic

The polycrystalline sample BaTi0.5 (Co0.33 Mo0.17) O3 was synthesized by the sol-gel method. The effect of replacing titanium by cobalt and molybdenum on the structural and electrical properties of our compound was investigated. The results of X-ray diffraction (XRD) at room temperature showed a pure tetragonal perovskite. The electrical response was studied by complex impedance spectroscopy over a broad frequency range (30–106 Hz) at different temperatures. The values of ac conductivity were fitted by Jonscher's law σ(ω)==σDC+Aωn and supported by the correlated barrier hopping (CBH) mechanism. Complex impedance analysis confirmed the existence of an electrical relaxation in the compound. The dielectric constant and the dielectric loss decreased with the increase in frequency. This behavior can be explained by the presence of the Maxwell–Wagner type of polarization responsible for the electric conduction. The modulus plots were characterized by the Havriliak–Negami (H-N) and the empirical Kohlrausch–Williams–Watts (K.W.W.) functions. The Normalized plot of the imaginary part of modulus indicates that the dynamical processes are temperature independent.

Direct Comparison of Probe Reorientation and Linear Mechanical Measurements of Segmental Dynamics in Glassy Poly(methyl methacrylate)

Optical probe reorientation experiments and mechanical stress relaxation measurements in the linear response regime were performed on a polymer glass. Segmental dynamics of lightly cross-linked poly(methyl methacrylate) (PMMA) were monitored via both methods at temperatures between 9 and 24 K below the glass transition temperature (Tg) and over the course of 8 h of aging. Relaxation times from the two methods cover a range of ∼1.7 decades. Similar results were obtained from the two experiments other than a slight difference in the aging rate. A difference of ∼0.3 decades (a factor of ∼2) is observed between the optically and mechanically obtained relaxation times, related primarily to the size of the probe. Both experiments give a value near 0.3 for the Kohlrausch–Williams–Watts (KWW) β parameter. These results provide an important baseline for the interpretation of optical probe reorientation experiments during nonlinear deformation.

Rethinking the representation of Gustavus Adolphus: the case of William Watts and The Swedish Intelligencer, 1630–33

ABSTRACTBetween 1630 and 1633, English newsbooks resounded with tales of King Gustavus Adolphus of Sweden’s victories against the “popish” armies of Emperor Ferdinand II. Such literary praise has been widely associated with Calvinist disapprobation of Charles I’s pacific foreign policy. This article throws new light on the alternative, non-Calvinist sources of enthusiasm for Gustavus Adolphus in the newsbook, The Swedish Intelligencer, which portrayed the Swedish king as the figurehead of a broad, confessionally flexible, pan-Protestant cause. This has important implications for our understanding of the relationship between English and European Protestant nations in the context of the Thirty Years’ Wars. News from the military camp of the Lutheran King of Sweden offered a subtle way of promoting and normalising non-Calvinist forms of worship in England, and thus provides evidence that a range of Protestants were utilising the London news presses to advance their religious agenda in the early 1630s.

Mesomorphic glass-forming ionic complexes composed of a cholesterol phthalate and 1-Cn-3-methylimidazolium: phase transition and enthalpy relaxation behavior

Ionic complexes consisting of a mesogenic cholesterol derivative and 1-alkyl (Cn)-3-methylimidazolium (CnMim) (n = 6–18) were prepared from ethanol solutions containing an equimolar mixture of cholesterol hydrogen phthalate (CHP) and 1-Cn-3-methylimidazolium hydroxide; the imidazolium hydroxide was obtained by anion exchange of 1-Cn-3-methylimidazolium bromide. The complex samples, termed [CnMim][CHP], were examined to evaluate their thermal transition patterns. Excluding the two samples (n = 6, 8) that showed no definite ordered phase, the complexes with n ≥ 10 formed a cholesteric (n = 10, 12) or smectic (n = 14–18) mesophase in a considerably wide range of temperatures; this wide range reflects the additional thermotropic property of the salts of CnMim with longer alkyl chains. These fluid mesophases transformed into a mesomorphic vitreous solid without crystallization in a usual cooling process. For the glassy mesomorphic samples of selected complexes (n = 10, 18), the enthalpy relaxation behavior was followed as a function of the aging temperature and time, and the data were analyzed in terms of a Kohlrausch–Williams–Watts (KWW) type of stretched exponential equation. A very narrow distribution of relaxation times was observed for the “liquid crystalline glasses”, indicating the high uniformity of the relaxation mode. We prepared a series of ionic complexes, [CnMim][CHP] (n = 6–18), by neutralizing cholesterol hydrogen phthalate (CHP) with 1-alkyl (Cn)-3-methylimidazolium hydroxide ([CnMim][OH]) derived from [CnMim][Br]. The complexes of n ≥ 10 formed a thermotropic mesophase in each individual temperature range and solidified into a mesomorphic glass upon cooling, although two samples of n = 6 and 8 showed no ordered structure. Enthalpy relaxation behavior of the mesomorphic glasses (n = 10, 18) was also examined as a function of the aging temperature and time

Characteristic Exponent of Normal and Oblique Rolls in Homeotropically Aligned Nematic Liquid Crystal

Soft-mode turbulence (SMT) is one of an experimental example of spatiotemporal chaos, observed in electroconvection system of homeotropically aligned nematic liquid crystal (NLC), due to a non-linear interaction between Nambu-Goldstone mode denoted by the C(r)- director and the convective mode q(r). There are two types of stripe patterns in the SMT, namely normal rolls (NR) and oblique rolls (OR) which separated by a point of applied frequency, called the Lifshitz frequency (fL). We report a study of the phase transition from normal to oblique rolls by observing the patterns with an applied frequency below and beyond of fL. The temporal fluctuations of the pattern images had been analyzed using autocorrelation function. It fits with Kohlrausch Williams Watts (KWW) function, showing there is a dynamical glass-forming liquid in the transition of NR-OR regime. Also, we found a new type of defect in the NR regime which never been reported before, a dynamic defect which takes the shape of a ring first to a spot in the end.

In situ investigation of the kinetics and microstructure during photopolymerization by positron annihilation technique and NIR-photorheology.

The microstructural free volume evolution during a photopolymerization process was studied on a commercial photopolymer (SPOT LV) in situ by positron annihilation lifetime spectroscopy (PALS) and concomitant NIR-photorheology. Analysis of the positron lifetime spectra revealed a high sensitivity of the PALS technique to the different phases of photopolymerization associated with different reaction rates as well as to the evolution of microstructural free-volume shrinkage, which was described at the molecular level by the Kohlrausch–Williams–Watts equation. The in situ PALS study of microstructural changes in photopolymerization was related to the vitrification (gel point) accompanied by shrinkage stress registered via NIR-photorheology. The simultaneous NIR measurements yield information on the monomer conversion of SPOT LV, which can be correlated to the occurrence of the gel point and the evolution of the microstructural free volume. This combined study allows us to see deeper into the crosslinking process and its influence on the resulting material characteristics.

Electric modulus, scaling and ac conductivity of La2CuMnO6 double perovskite

A sample of La2CuMnO6 (LCM) was synthesized through the standard solid state reaction method. X-ray diffraction experiments and Rietveld analysis reveal that the material crystallizes in an orthorhombic structure. SEM image displayed well-defined regular shaped nearly spherical and unequal grains with grain-size lies between 2.5 and 3.0 μm ranges. Frequency dependence of dielectric, electric modulus and ac conductivity of LCM has been studied as a function of both frequency and temperatures. The conduction mechanism is explained using universal power law (σ (ω, T) = B ωn(T)). The Kohlrausch–Williams–Watts (KWW) model approaches were employed to fit frequency response curves of M′ and M″. The large asymmetry of M″(f) peaks were explained by stretched exponent parameter (β). Activation energy values suggest that the conduction mechanism and relaxation process have a different origin. The ε′ and ε″, as a function of normalized frequency, exhibit better master curves than M″ vs M′ data.

Characterization of the kinetic arrest of martensitic transformation in Ni45Co5Mn36.8In13.2 melt-spun ribbons

The kinetic arrest (KA) of martensitic transformation (MT) observed in Ni45Co5Mn36.8In13.2 melt-spun ribbons has been studied. These alloy ribbons show an ordered columnar-like grain microstructure with the longer grain axis growing perpendicular to ribbon plane and transform martensitically from a single austenitic (AST) parent phase with the L21-type crystal structure to a monoclinic incommensurate 6M modulated martensite (MST). Results show that the volume fraction of austenite frozen into the martensitic matrix is proportional to the applied magnetic field. A fully arrest of the structural transition is found for a magnetic field of 7T. The metastable character of the non-equilibrium field-cooled glassy state was characterized by introducing thermal and magnetic field fluctuations or measuring the relaxation of magnetization. The relaxation of magnetization from a field-cooled kinetically arrested state at 5 and 7T follows the Kohlrausch–Williams–Watts (KWW) stretched exponential function with a β exponent around 0.95 indicating the weak metastable nature of the system under the strong magnetic fields. The relationship between the occurrence of exchange bias and the frozen fraction of AST into the MST matrix was studied.

Influence of SnO2 nanoparticles on the relaxation dynamics of the conductive processes in polyaniline

The effect of stannic oxide (SnO2) nanoparticles on the electrical conductivity relaxation and distribution of relaxation times within the 4-Dodecylbenzenesulfonic acid (DBSA) doped polyaniline (Pani) was investigated using electrical impedance spectroscopy. A temperature dependent Kohlrausch–Williams–Watts (KWW) type temporal relaxation function in the time domain was generated from the analysis of the frequency dependence of the dielectric modulus (imaginary component). The thermal evolution of the characteristics parameters of the KWW function was evaluated and using these parameters the temperature dependent average conductivity relaxation time and associated macroscopic conductivity of different samples were estimated. The study revealed that SnO2 nanoparticles within the polyaniline matrix induced faster relaxation of charge carriers that essentially enhanced the conductivity of the nanocomposite. The observed phenomena were well supported by the observed improvement of the localization length of the charge carriers within the nanocomposite.

Wealth distribution, Pareto law, and stretched exponential decay of money: Computer simulations analysis of agent-based models

We study by Monte Carlo simulations a kinetic exchange trading model for both fixed and distributed saving propensities of the agents and rationalize the person and wealth distributions. We show that the newly introduced wealth distribution – that may be more amenable in certain situations – features a different power-law exponent, particularly for distributed saving propensities of the agents. For open agent-based systems, we analyze the person and wealth distributions and find that the presence of trap agents alters their amplitude, leaving however the scaling exponents nearly unaffected. For an open system, we show that the total wealth – for different trap agent densities and saving propensities of the agents – decreases in time according to the classical Kohlrausch–Williams–Watts stretched exponential law. Interestingly, this decay does not depend on the trap agent density, but rather on saving propensities. The system relaxation for fixed and distributed saving schemes are found to be different.

Lithium ion conductivity and dielectric relaxation in dendritic nanostructured LiTaO3 glass–nanocrystal composites

Lithium tantalate in single-crystalline and coarse-grained configurations is a poor ionic conductor and does not qualify as a solid electrolyte for lithium-based batteries. In this work, ionic conductivity was sought to be enhanced by the use of nanocrystals of LiTaO3 embedded in a borate-based glass matrix. Glasses of composition 3Li2O–4B2O3–Ta2O5 were formed by melt-quenching. The crystallization process was described by using isothermal crystallization kinetics, invoking the Johnson–Mehl–Avrami–Kolmogorov equation, which indicated a three-dimensional growth with an Avrami exponent of 3.5 and an effective activation energy for crystallization of 735 ± 65 kJ mol–1. Heat treatment of the as-quenched glasses was performed between 530 and 560 °C, and the evolution of LiTaO3 phase was studied by X-ray powder diffraction, scanning electron microscopy, and transmission electron microscopy. The heat treatment yielded coalesced LiTaO3 nanocrystals of 18–32 nm size, forming dendritic structures in the glass matrix. Impedance analyses of the as-quenched and heat-treated glasses showed a dramatic improvement in dc conductivity (σdc), with a maximum around 3 × 10–3 S m−1 at 200 °C (σdcT = 1.5 S m−1 K) and activation energy of 0.54 eV for 530 °C/3 h heat-treated glasses. The values of σdc of the as-quenched glasses and of the 530 °C/3 h and 540 °C/3 h heat-treated glasses were about seven orders of magnitude higher than those of the single crystalline LiTaO3. Furthermore, the effect of heat treatment on lithium ion dynamics in the 40–200 °C temperature range was investigated by modulus formalism invoking the stretched exponential Kohlrausch–Williams–Watts function. The 7Li magic angle spinning NMR was used to investigate lithium self-diffusion in the nanostructured glass nanocrystal composites as a function of temperature between −10 °C and 60 °C.

A study of optical absorption and dielectric properties in lithium chromium diphosphate compound

The optical properties of diphosphate LiCrP2O7 compound prepared by the classic ceramic method were recorded at room temperature. Absorption spectrum shows the presence of five characteristics bands related to the octahedral transitions of Cr3+ from ground term 4A2g to excited terms. Crystal field strength and inter electronic repulsion Racah parameters were deduced. The calculated value of direct $$ {E}_g^{\mathrm{direct}} $$ =1.62 eV energy gap has been found using Tauc’s procedure. Besides, the dielectric properties were carried out by impedance spectroscopy at different temperatures (460–700 K). The frequency and temperature dependent of the real e ′ and imaginary e ″ parts of the dielectric constant were discussed. The variation of the frequency power law of the imaginary part of dielectric constant was analyzed in terms of two different conduction mechanisms. Furthermore, the modulus plots can be characterized by the empirical Kohlrausch–Williams–Watts (K.W.W.) function and the obtained values of activation energies deduced from relaxation frequency are in order of E a (I) = 0.49 eV and E a (II) = 0.87 eV.

Dielecric relaxation and conduction mechanism of dysprosium doped barium bismuth titanate Aurivillius ceramics

In this report, we present the structure, electrical properties and optical study of dysprosium doped bismuth layer-structured BaBi4Ti4O15 (BBT) with a general formula Ba(Bi1−xDyx)4Ti4O15 (BDBT), prepared by solid state reaction route. The X-ray diffraction study shows a single phase orthorhombic structure with a space group A21 am in all compositions. The relaxation and conduction mechanism was studied by frequency and temperature dependent impedance spectroscopy. Impedance studies show a non-Debye type relaxation, and relaxation frequency shift to the higher side with an increase in temperature indicating conduction in material and favouring the long range motion of mobile charge carriers. The Nyquist plot shows overlapping semicircles, for grain and grain boundary of Dy doped BBT ceramics. The Kohlrausch–Williams–Watts function is used to explain the modulus analysis and confirms the coexistence of grain and grain boundary effects. The frequency dependent AC conductivity at different temperatures indicates that the conduction process is thermally activated and the spectra follow the universal power law. The variation of DC conductivity confirms that the BDBT ceramics exhibit negative temperature coefficient of resistance behaviour in high temperature. Activation energies are obtained from the Arrhenius fitting of impedance and conductivity plots.

Impedance spectroscopy and photocatalysis water splitting for hydrogen production with cerium modified SrBi2Ta2O9 ferroelectrics

A pure phase cerium modified bismuth layer based Aurivillius type SrBi2-xCe3x/4Ta2O9 (x = 0–0.1) ferroelectric ceramics are synthesized by solid state route. X-ray diffraction patterns are well-indexed with orthorhombic (A21am) according to the JCPDS card no. 49-0609. Impedance analysis revealed that the non-debye type nature and corresponding resistance-capacitance values are calculated. An existence of grain effect at high temperature is identified by modulus spectrum using Kohlrausch–Williams–Watts (KWW) function. The diffusive reflectance spectrum estimated the bandgap of cerium modified SrBi2Ta2O9 ferroelectrics and the values are increased by increasing the substitution concentration. The conduction band of these photocatalysts composed of hybridization with Ta5d + Bi6p(Ce4f)+O2p orbitals and the valence bands composed of Ta5d + Bi6s(Ce4d)+O2p orbitals. The water splitting photocatalytic activity is investigated under UV-light irradiation and indicated that these photocatalysts showed photocatalytic activity for H2 and O2 evolution from aqueous solutions containing sacrificial reagents (methanol and Ag+). The correlation of electrical and photocatalytic properties are explained clearly.

Grain size effects on dynamics of Li-ions in Li3V2(PO4)3 glass-ceramic nanocomposites

Li3V2(PO4)3 glass-ceramic nanocomposites, based on 37.5Li2O-25V2O5-37.5P2O5 mol% glass, were successfully prepared via heat treatment (HT) process. The structure and morphology were investigated by X-ray diffraction (XRD) and scanning electron microscope (SEM). XRD patterns exhibit the formation of Li3V2(PO4)3 NASICON type with monoclinic structure. The grain sizes were found to be in the range 32–56 nm. The effect of grain size on the dynamics of Li+ ions in these glass-ceramic nanocomposites has been studied in the frequency range of 20 Hz–1 MHz and in the temperature range of 333–373 K and analyzed by using both the conductivity and modulus formalisms. The frequency exponent obtained from the power law decreases with the increase of temperature, suggesting a weaker correlation among the Li+ ions. Scaling of the conductivity spectra has also been performed in order to obtain insight into the relaxation mechanisms. The imaginary modulus spectra are broader than the Debye peak-width, but are asymmetric and distorted toward the high frequency region of the maxima. The electric modulus data have been fitted to the non-exponential Kohlrausch–Williams–Watts (KWW) function and the value of the stretched exponent β is fairly low, suggesting a higher ionic conductivity in the glass and its glass-ceramic nanocomposites. The advantages of these glass-ceramic nanocomposites as cathode materials in Li-ion batteries are shortened diffusion paths for Li+ ions/electrons and higher surface area of contact between cathode and electrolyte.

Intrinsic correlation between β-relaxation and spatial heterogeneity in a metallic glass.

β-relaxation has long been attributed to localized motion of constituent molecules or atoms confined to isolated regions in glasses. However, direct experimental evidence to support this spatially heterogeneous scenario is still missing. Here we report the evolution of nanoscale structural heterogeneity in a metallic glass during β-relaxation by utilizing amplitude-modulation dynamic atomic force microscopy. The successive degeneration of heterogeneity during β-relaxation can be well described by the Kohlrausch–Williams–Watts equation. The characteristic relaxation time and activation energy of the heterogeneity evolution are in accord with those of excess enthalpy release by β-relaxation. Our study correlates β-relaxation with nanoscale spatial heterogeneity and provides direct evidence on the structural origins of β-relaxation in metallic glasses.

Durkheim, the Durkheimians, and the Arts. Edited by Alexander Riley, W. S. F. Pickering, and William Watts Miller. New York: Berghahn Books, 2013. Pp. viii+309. $95.00.

Previous articleNext article No AccessBook ReviewDurkheim, the Durkheimians, and the Arts. Edited by Alexander Riley, W. S. F. Pickering, and William Watts Miller. New York: Berghahn Books, 2013. Pp. viii+309. $95.00.Terry Nichols ClarkTerry Nichols ClarkUniversity of Chicago Search for more articles by this author PDFPDF PLUSFull Text Add to favoritesDownload CitationTrack CitationsPermissionsReprints Share onFacebookTwitterLinkedInRedditEmail SectionsMoreDetailsFiguresReferencesCited by American Journal of Sociology Volume 121, Number 6May 2016 Article DOIhttps://doi.org/10.1086/685771 Views: 112Total views on this site Citations: 1Citations are reported from Crossref For permission to reuse a book review printed in the American Journal of Sociology, please contact [email protected]PDF download Crossref reports the following articles citing this article:Wu Changzhi FORMS OF SYNTHESIS OF ARTS OF CHINESE ARCHITECTURE, Municipal economy of cities 4, no.164164 (Oct 2021): 58–64.https://doi.org/10.33042/2522-1809-2021-4-164-58-64