Saturation Estimation with Complex Electrical Conductivity for Hydrate-Bearing Clayey Sediments:An Experimental Study

Clays have considerable influence on the electrical properties of hydrate-bearing sediments.It is desirable to understand the electrical properties of hydrate-bearing clayey sediments and to build hydrate saturation(S_(h))models for reservoir evaluation and monitoring.The electrical properties of tetrahydrofuran-hydrate-bearing sediments with montmorillonite are characterized by complex conductivity at frequencies from 0.01 Hz to 1 kHz.The effects of clay and Sh on the complex conductivity were analyzed.A decrease and increase in electrical conductance result from the clay-swelling-induced blockage and ion migration in the electrical double layer(EDL),respectively.The quadrature conductivity increases with the clay content up to 10%because of the increased surface site density of counterions in EDL.Both the in-phase conductivity and quadrature conductivity decrease consistently with increasing Sh from 0.50 to 0.90.Three sets of models for Sh evaluation were developed.The model based on the Simandoux equation outperforms Archie’s formula,with a root-mean-square error(E_(RMS))of 1.8%and 3.9%,respectively,highlighting the clay effects on the in-phase conductivity.The fre-quency effect correlations based on in-phase and quadrature conductivities exhibit inferior performance(E_(RMS)=11.6%and 13.2%,re-spectively)due to the challenge of choosing an appropriate pair of frequencies and intrinsic uncertainties from two measurements.The second-order Cole-Cole formula can be used to fit the complex-conductivity spectra.One pair of inverted Cole-Cole parameters,i.e.,characteristic time and chargeability,is employed to predict S_(h) with an E_(RMS) of 5.05%and 9.05%,respectively.

Alcohol-dispersed polymer complex as an effective and durable interface modifier for n-i-p perovskite solar cells

Abundant interfacial defects remain a significant challenge that hampers both the efficiency and stability of perovskite solar cells(PSCs).Herein,an alcohol-dispersed conducting polymer complex,denoted as PEDOT:F(Poly(3,4-ethylene dioxythiophene):Perfluorinated sulfonic acid ionomers),is introduced into the interface between perovskite and hole transporting layer in regular-structured PSCs.PEDOT:F serves as a multi-functional interface layer(filling grain boundaries and covering perovskite's grain-surface)to achieve a robust interaction with organic groups within perovskites,which could induce a structural transformation of PEDOT to increase its conductivity for the efficient hole-transport.Furthermore,the strong interaction between PEDOT and perovskites could promote an effective coupling of undercoordinated Pb~(2+)ions with the lone electron pairs near O&S atoms in PEDOT molecules,thereby enhancing defect passivation.Additionally,PEDOT:F with inherent hydrophobic properties prevents effectively moisture invasion into perovskites for the improved long-term stability of the PSCs.Consequently,the PEDOT:F-based PSCs achieved a champion efficiency of 24.81%,and maintained ca.92%of their initial efficiency after 7680 h of storage in a dry air environment,accompanied by the enhanced photothermal stability.

Parameter of dielectric loss distribution in the new model for complex conductivity based on Havriliak-Negami formula

This paper is focused on the comparison of the results of various approximation models describing the frequency dependences of the dielectric constanε'/ε_(0)(f)andε"/ε_(0)(f),the tangent of the loss angle tgδ(f)T and the electrical conductivityγ'(f)T andγ"(f)T of nonlinear dielectrics.The classic ferroelectric material of the PZT system with x=0.50 was chosen as the object of study.Based on the analysis of temperature-frequency dependences of the“empirical”parametersαandβ,a regularity has been revealed that allows them to be calculated.A new relationship has been established through the parameterα,which allows to relate the temperature and frequency dependences of the complex electrical conductivity asω→∞and asω→0 in the Havriliak-Negami approximation models and in the new model for the description of the complex electrical conductivityγ*.It is shown thatαis a parameter of the temperature-frequency distribution of dielectric losses.Using the obtained expressions,a new theoretical description of experimental spectra having a relaxation character was proposed.It has been proven that the use of the new model makes it possible to accurately describe the set of studied spectra,including the high and low frequencies,in the frequency range from 10^(-3) to 10^(8) Hz.

Studying of dielectric spectra of YCu_(0.15)Mn_(0.85)O_(3)solid solution with the use of complex conductivity

This work presents the results of studying the electrophysical properties of the YCu_(0.15)Mn_(0.85)O_(3)solid solution in the range of temperatures of T=26-400°C and frequency range of f=102-105 Hz.A model description of the revealed dispersion of dielectric parameters in the material is made.The nonclassical modified Havriliak-Negami model written for complex electrical conduc-tivity was used as an approximation model.It is shown that the application of this model almost exactly describes the frequency behavior of the dielectric constantε′/ε0(f),the dielectric loss tangent tgδ(f)as well as the real and imaginary parts of complex conductivityγ′(f)andγ′′(f).The results of this work are an important step in identifying the opportunities and understanding the applications of this model.

Disorder effects in NbTiN superconducting resonators

Disordered superconducting materials like NbTiN possess a high kinetic inductance fraction and an adjustable critical temperature, making them a good choice for low-temperature detectors. Their energy gap(D), critical temperature(T_(c)),and quasiparticle density of states(QDOS) distribution, however, deviate from the classical BCS theory due to the disorder effects. The Usadel equation, which takes account of elastic scattering, non-elastic scattering, and electro–phonon coupling,can be applied to explain and describe these deviations. This paper presents numerical simulations of the disorder effects based on the Usadel equation to investigate their effects on the △, Tc, QDOS distribution, and complex conductivity of the NbTiN film. Furthermore, NbTiN superconducting resonators with coplanar waveguide(CPW) structures are fabricated and characterized at different temperatures to validate our numerical simulations. The pair-breaking parameter α and the critical temperature in the pure state T_(c)^(P) of our NbTiN film are determined from the experimental results and numerical simulations. This study has significant implications for the development of low-temperature detectors made of disordered superconducting materials.

CATIONIC CONDUCTION IN BLEND COMPLEX OF LITHIUM METHOXY OLIGO (OXYETHYLENE) SULFATE AND COMBLIKE POLYETHER

Two kinds of lithium methoxy oligo(oxyethylene) sulfate LiSAEO_8 and LiSAEO_(12) were synthesized. The blend complexes of the salts with P(MEO_(16)—AM) show high cationic conductivity, the transference numbers of lithium ion(t_+)in [P(MEO_(16)—AM)/LiSAEO_8] and [-P(MEO_(16)—AM)/LiSAEO_(12)] are 0.93 and 0.98 at 50℃, and their ambient conductivities are 1.4×10^(-5)/cm and 7.7×10^(-6)S/cm respectively.

IONIC CONDUCTIVITY OF POLY (β-ALKOXYCARBONYLETHYLMETHYLSILOXANE)-LiClO_4 CROSSLINKED FILMS

Poly (β-carboxyethylmethylsiloxane)-LiClO_4 and poly (β-alkoxylethylmethylsiloxane)-LiClO_4 crosslinked fllms have been prepared. The ionic conductivity of the films depends on the polymer species, concentration of lithium perchlorate, temperature and content of crosslinking agent. The effect of high polar organic solvent 1, 4-butyrolactone on the ionic conductivity and mechanical properties of poly (β-carhoxyethylmethylsiloxane )-LiClO_4 system was also investignied.

Monitoring lime and cement improvement using spectral induced polarization and bender element techniques

Spectral induced polarization(SIP)and bender element(BE)techniques show a high sensitivity to particle size,particle distribution and content of generated hydration products,which essentially govern the efficiency of ground improvement.In this context,both SIP and BE were integrated on a column setup to monitor the processes of lime and cement stabilization.A 5 mmol/L Na2CO3 solution was injected into the sand-lime mixture to produce CaCO3 precipitation,while deionized water was injected into the sandcement mixture to induce the hydration of cement.The average diameters of the precipitated particles or clusters were calculated from the relaxation time,which was a significant parameter of SIP signals,via the Schwarz equation.Two pairs of BE were used to demonstrate the heterogeneity of the product precipitation,which was probably caused by the location of the inflow and outflow on the SIP-BE column.SIP and BE showed the capability of nondestructively monitoring the spatiotemporal chemical evolution processes,which could be helpful for engineering applications.

Closed-form internal impedance model and characterization of mixed carbon nanotube bundles for three-dimensional integrated circuits

Based on the complex effective conductivity method, a closed-form expression for the internal impedance of mixed carbon nanotube （CNT） bundles, in which the number of CNTs for a given diameter follows a Gaussian distribution, is proposed in this paper. It can appropriately capture the skin effect as well as the temperature effect of mixed CNT bundles. The results of the closed-form expression and the numerical calculation are compared with various mean diameters, standard deviations, and temperatures. It is shown that the proposed model has very high accuracy in the whole frequency range considered, with maximum errors of 1% and 2.3% for the resistance and the internal inductance, respectively. Moreover, by using the proposed model, the high-frequency electrical characteristics of mixed CNT bundles are deeply analyzed to provide helpful design guidelines for their application in future high-performance three-dimensional integrated circuits.

Temperature dependence of heat conduction coefficient in nanotube/nanowire networks

Studies on heat conduction are so far mainly focused on regular systems such as the one-dimensional（1D） and twodimensional（2D） lattices where atoms are regularly connected and temperatures of atoms are homogeneously distributed.However, realistic systems such as the nanotube/nanowire networks are not regular but heterogeneously structured, and their heat conduction remains largely unknown. We present a model of quasi-physical networks to study heat conduction in such physical networks and focus on how the network structure influences the heat conduction coefficient κ. In this model,we for the first time consider each link as a 1D chain of atoms instead of a spring in the previous studies. We find that κ is different from link to link in the network, in contrast to the same constant in a regular 1D or 2D lattice. Moreover, for each specific link, we present a formula to show how κ depends on both its link length and the temperatures on its two ends.These findings show that the heat conduction in physical networks is not a straightforward extension of 1D and 2D lattices but seriously influenced by the network structure.

Characterizing temperature dependent complex electrical impedance analysis of LaFe_(1−x)Zn_(x)O_(3)(x=0.03,0.05,and 0.07)ceramics

followed by sintering-annealing treatments to form the bulk-phase.X-ray diffraction analysis revealed that all ceramics were crystallized in the orthorhombic perovskite structure with Pbnm symmetry.Grain size distribution and morphological characteri-stics were investigated by scanning electron microscopy.Specific surface area was analyzed through BET-BJH methods.Electrical impedance analysis was investigated as a function of frequency at various temperatures.It was found that the electrical behavior is dominated by grain boundary contribution,i.e.,electrical conductivity.The frequency dependence of the complex conductivity was analyzed through Joncher’s power law and the dominance of translational motion with a sudden hopping mechanism in the electrical conduction mechanism increased with increasing Zn content.Activation energy decreased with increasing Zn content.

Dielectric and piezoelectric properties of modified lead-free NaNbO_(3)-KNbO_(3)/PVDF composite ceramics

This work presents the results of study of the electrophysical properties of composite polymer ceramics(1−x)[KNN-LTSN]-xPVDF at x=25 vol.%and x=50 vol.%in the temperature range of T=20-160℃and frequency range of f=2×10^(1)-2×10^(6)Hz.The concentration dependence of piezomodules of the studied materials has been analyzed as a function of temperature.X-ray measurements have also been carried out.A model of description of revealed dielectric parameters dispersion in the material is presented.The nonclassical modified Havriliak-Negami model written for complex electrical conductivity has been used to describe the temperature-frequency properties.It is shown that the dielectric spectra of the studied composites include three relaxation processes in the temperature ranges of 40-80℃,80-120℃and 120-150℃,which were confirmed by the dynamics of changes in the dependences of g′(f),tgδ(f),M′(f),M″(f)and M″(M′).All three processes are almost exactly described by this model and well correlated with the studies by other researchers of the composites based on PVDF.The results of this work show that the use of such experimental model is suitable for describing the complex dielectric spectra of any nonlinear dielectrics including composite materials.