Bruggeman Model Research Articles

Thermal dynamics of nanoparticle aggregation in MHD dissipative nanofluid flow within a wavy channel: Entropy generation minimization

This paper examines how nanoparticle aggregation and a consistent magnetic field influence the peristaltic movement of a dissipative nanofluid, which is caused by the sinusoidal deformation of the boundary. The viscosity of TiO2/H2O nanofluids is accurately determined by the Krieger-Dougherty model with nanoparticle aggregation, while thermal conductivity (TC) is estimated through the Bruggeman model. The set of governing equations are modeled in a fixed frame by utilizing the conservation laws of energy, mass and momentum. Galilean transformation is utilized to transform the system of equations into a wave frame, which is then converted into a dimensionless form. The assumption of a small Reynolds number and long wavelength serve to further simplify the set of equations, which are subsequently addressed through the implementation of the differential quadrature method (DQM), a highly effective numerical technique. Quantities of interest, namely velocity, pressure gradient, temperature, trapping phenomena, heat transfer, and volumetric entropy generation are analyzed across a range of physical parameters, including the solid volume fraction (Φ=0.01−0.04), Eckert number (Ec=0.0−0.1), Hartman number (Mh=0.2−2.2), Grashof number (Gr=1.0−3.0) and temperature ratio parameter (θd=0.5−2.5). A comparative analysis is conducted between the scenario involving aggregation and the one without aggregation. It is observed that nanoparticle aggregation significantly alters these quantities.

Analysis of Polymer-Ceramic Composites Performance on Electrical and Mechanical Properties through Finite Element and Empirical Models.

Polymer and ceramic-based composites offer a unique blend of desirable traits for improving dielectric permittivity. This study employs an empirical approach to estimate the dielectric permittivity of composite materials and uses a finite element model to understand the effects of permittivity and filler concentration on mechanical and electrical properties. The empirical model combines the Maxwell-Wagner-Sillars (MWS) and Bruggeman models to estimate the effective permittivity using Barium Titanate (BT) and Calcium Copper Titanate Oxide (CCTO) as ceramic fillers dispersed in a Polydimethylsiloxane (PDMS) polymer matrix. Results indicate that the permittivity of the composite improves with increased filler content, with CCTO/PDMS emerging as the superior combination for capacitive applications. Capacitance and energy storage in the CCTO/PDMS composite material reached 900 nF and 450 nJ, respectively, with increased filler content. Additionally, increased pressure on the capacitive model with varied filler content showed promising effects on mechanical properties. The interaction between BT filler and the polymer matrix significantly altered the electrical properties of the model, primarily depending on the composite's permittivity. This study provides comprehensive insights into the effects of varied filler concentrations on estimating mechanical and electrical properties, aiding in the development of real-world pressure-based capacitive models.

Synthesis of aqueous NiFe2O4-Fe3O4 hybrid magnetic nanofluids and investigation on electrical conducting behaviour

Highly stable aqueous magnetic mono nanofluids of nickel ferrite (NiFe2O4), magnetite (Fe3O4), and hybrid magnetic nanofluids of NiFe2O4-Fe3O4 are synthesized through a two-step method. The structural analysis of the NiFe2O4 and Fe3O4 nanoparticles made through X-ray diffraction identifies their spinel cubic structure. The magnetic studies indicate their superparamagnetic nature, which is further confirmed through the Langevin fitting of the experimental data. The monodomain nature of nanoparticles is verified using the coupling constant, and a spherical morphology is observed using a transmission electron microscope. The surface charge of the nanoparticles is studied through zeta potential analysis. The electrical conductivity of the aqueous mono and hybrid magnetic nanofluids is measured for various concentrations and temperatures. The hybrid magnetic nanofluids show higher electrical conductivity values than those of both the mono nanofluids. For instance, NiFe2O4-Fe3O4 (1.2 vol%) hybrid nanofluid is found to have a conductivity value of 18.91 μS/cm that is 1.5 times enhanced than that of Fe3O4 mono nanofluid (12.87 μS/cm) and three times enhanced than that of NiFe2O4 (6.43 μS/cm) mono nanofluid of same volume percentage at 303 K. A Maximum enhancement of 136 % is obtained for 1.2 vol% hybrid nanofluid with respect to water at 303 K and this enhancement further increases to 196 % with the rise in temperature to 323 K. There is no theoretical model found in literature to explain the electrical conductivity of hybrid nanofluids. Maxwell, Bruggeman, Cruz, and Shen models are applied to explain the conductivity of hybrid magnetic nanofluids. Through a comparison of experimental values with theoretical values, it is found that the Shen model, if modified suitably, can explain the electrical conduction of hybrid magnetic nanofluids. Also, the electrical conduction mechanism in hybrid magnetic nanofluids is described in terms of electrophoretic charge transportation and the Brownian motion. In addition, the magneto-electrical conductivity study is performed by measuring the electrical conductivity by applying a magnetic field of various strengths. The electrical conductivity, magneto-electrical conductivity studies and an understanding of electrical conduction mechanism are highly significant for magnetically transportable electronic cooling and conducting applications of hybrid magnetic nanofluids.

Research on material jetting fabrication and dielectric constant calculation of LTCC based on silica-borosilicate glass

Several material systems are available for low-temperature co-fired ceramics, and to achieve more efficient designs and applications using additive manufacturing (AM) techniques such as material jetting, the predictability of the dielectric constant of the sintered structure will significantly reduce the consumption of material development. In this work, the LTCC part was fabricated by 3D material jetting using silica-borosilicate glass LTCC ink and densified at 850°C. The borosilicate glass composition was derived from nanopowders prepared by radio frequency plasma spheronisation and configured as surface-grafted glass sols. Scanning electron microscopy results showed that silica particles were embedded in the glass matrix by a liquid phase sintering mechanism accompanied by several confined pores that were difficult to remove. A dielectric constant of around 3.78 was tested from room temperature to 100°C. Molecular dynamics sintering simulation was used to create sintered structures that matched the experimental values. The dipole moment fluctuation of the silica/glass bulk was counted to obtain an accurate value of the dielectric constant, and then the Bruggeman model based on the effective medium theory predicted the dielectric constant of the sintered body, with a prediction of 3.65, which is within 4 % difference from the measured value (3.78). The dielectric constant was predicted for different ceramic/glass compositions and sintering temperatures and found that 35 wt% and 60 wt% should be the upper and lower bounds for borosilicate glass additions to satisfy a stable structure with a relatively low dielectric constant range (3.38–4.42). In conclusion, an effective molecular dynamics approach to predict the dielectric constant of sintered bodies was developed to assist material design in LTCC AM fabrication.

Evaluation of thermal conductivity models and dielectric properties in metal oxide-filled poly(butylene succinate-co-adipate) composites

This study examines how various nanofillers impact thermal conductivity, dielectric characteristics, and electromagnetic interference (EMI) shielding potential of bio-based and biodegradable poly(butylene succinate-co-adipate) (PBSA). TiO2, NiFe2O4, Fe2O3, and Fe3O4 were selected as fillers for nanocomposites at 4–50 vol.% (12–81 wt.%). The nanocomposites were analyzed in three domains: structural (scanning electron microscopy, energy dispersive X-ray spectroscopy mapping, density, tensile testing), thermal (light flash analysis, literature models), and dielectric (AC conductivity, permittivity, EM shielding effectiveness (SE)). The investigated fillers showed good dispersion and compatibility with the PBSA matrix. LFA was analyzed according to literature models, where Bruggeman and Agari models showed the best fit at high concentrations. The dielectric analysis revealed that most of the nanocomposites did not reach percolation; thus, producing thermally conductive plastics that are electrically insulating. EMI shielding was limited to frequencies below 10 Hz, with the notable exception of Fe3O4 (100 nm and loading of > 25 vol.%), which showed shielding at frequencies up to 105 Hz. The investigated composites based on a biodegradable polyester and abundant metal oxide nanofillers are suitable for the production of cheap, ecological, and electrically insulating heat dissipation solutions required for modern and lightweight applications.

Electric response of a composite of topological insulator nanoparticles

The electric response of a composite of topological insulator (TI) nanoparticles is studied using approximate effective medium models focusing on the topological magneto-electric (TME) response of the system. Both the Maxwell-Garnett and the Bruggeman models are generalized to incorporate the axion coupling parameter. Such a response is studied in the electrostatic limit via a capacitor with the composite as the dielectric medium. Manifestation of the TME is highlighted to provide an alternative probing method of such an effect via electrostatics experiments.

MHD nanofluid flow between porous convergent-divergent channel with velocity slip and nanoparticle aggregation

The aggregation of nanoparticles is a major phenomenon having broad consequences in many fields. In order to fully utilize the capabilities of nanoparticles in a variety of applications and to evaluate the effects that they will have on the environment and biological systems, it is crucial to comprehend and manage aggregation. To develop and improve nanoparticle-based technology, researchers are still learning more about the aggregation processes. Thus, the present study investigates the combined effects of velocity slip and nanoparticle aggregation on Heat transfer (HT) analysis of MHD nanofluid (i.e., TiO2-C2H6O2) flow between porous convergent, divergent channel. The modified Krieger–Dougarty and Maxwell–Bruggeman models were utilized for nanoparticle aggregation. The modeling is based on nonlinear PDEs such as continuity, momentum, and heat equations. These equations are transformed into a system of nonlinear ODEs using similarity transformations and then solved numerically and analytically. The analytical solution has been constructed using the ADM method. The present results in particular cases are compared to results obtained by the HAM- package and by the Runge- Kutta Fehlberg 4th–5th order (RKF-45) for validation. The effects of active parameters on the velocity, temperature, concentration, skin friction, and Nusselt numbers are investigated. It is found that nanoparticle aggregation can limit fluid velocity in converging channels by increasing flow resistance through aggregate formation. Individual nanoparticles generate friction and lower velocity, while aggregated nanoparticles boost fluid density and velocity. In addition, it is found that the magnetic field lowers skin friction and increases HT due to Lorentz force, while porosity increases friction and HT. Nanoparticle concentration inversely affects friction, increasing friction without aggregation and decreasing friction with aggregation, with the HT rate rising with increased nanoparticle concentrations.

Toward tailoring the mechanical and dielectric properties of short glass fiber‐reinforced epoxy composites

AbstractGlass fiber‐reinforced polymer‐matrix (GFRP) composites are used to manufacture devices such as radomes, electrical insulators, and radar‐absorbing structures, many of which are used in applications with strict mechanical and dielectric property requirements. As such, designs and properties of GFRP composite materials should be regularly improved to guarantee their safe operation and meet their constantly evolving application requirements. In this study, glass fiber (GF) particles and epoxy resin 128 (EP‐128) were used to manufacture high‐performance EP/GF‐X composites with GF particle contents ranging from 5% to 40%. An investigation into their mechanical and dielectric properties revealed that EP/GF‐20 composite specimens presented the best mechanical performance with their bending strength and modulus reaching 159.68 MPa and 6521.92 MPa, respectively, and an average dielectric constant of 4.862 within the 10–105 Hz frequency range. A theoretical analysis of the EP/GF‐X composite specimens' dielectric constants using classic dielectric models based on the Lichtenecker, Bruggeman, Jaysundere‐Smith, and Maxwell‐Garnett rule‐of‐mixture equations indicated that the dielectric model based on the Bruggeman rule‐of‐mixture equation provided the dielectric constants closest to the measured values with a maximum deviation of less than −0.321% for EP/GF‐40 composites. This study provides a feasible strategy to control the mechanical and dielectric properties of GFRP composites.Highlights Glass fiber (GF) particles and epoxy 128 (EP‐128) resin were used to manufacture high‐performance glass fiber‐reinforced epoxy (EP/GF‐X) composites. The composite manufacturing process was carefully controlled to ensure uniform distribution and orientation of GF particles in the EP‐128 resin. The mechanical and dielectric properties of the manufactured EP/GF‐X composites were effectively tailored by controlling the content and distribution of GF particles in the EP‐128 resin matrix. The dielectric constants of the EP/GF‐X composites were measured experimentally and predicted using various theoretical dielectric models. The Bruggeman model provided the dielectric constants of the EP/GF‐X composites closest to the measured values.

Fin field-effect-transistor engineered sensor for detection of MDA-MB-231 breast cancer cells: A switching-ratio-based sensitivity analysis.

The present study describes the utilization of a gallium-arsenide gate-stack gate-all-around (GaAs-GS-GAA) fin field-effect transistor (FinFET) to accomplish the electrical identification of the breast cancer cell MDA-MB-231 by monitoring the device switching ratio. The proposed sensor uses four nanocavities carved beneath the gate electrodes for enhanced detection sensitivity. MDA-MB-231 (cancerous) and MCF-10A (healthy) breast cells have a distinct dielectric constant, and it changes when exposed to microwave frequencies spanning across 200 MHz and 13.6 GHz, which modifies the electrical characteristics, allowing for early diagnosis. First, a percentage shift in the primary DC characteristics is presented to demonstrate the advantage of GS-GAA FinFET over conventional FinFET. The sensor measures the switching-ratio-based sensitivity, which comes out to be 99.72% for MDA-MB-231 and 47.78% for MCF-10A. The sensor was tested for stability and reproducibility and found to be repeatable and sufficiently stable with settling times of 55.51, 60.80, and 71.58 ps for MDA-MB-231 cells, MCF-10A cells, and air, respectively. It can distinguish between viable and nonviable cells based on electrical response alterations. The possibility of early detection of cancerous breast cells using Bruggeman's model is also discussed. Further, the impact of biomolecule occupancy and frequency variations on the device sensitivity is carried out. This study also explains how to maximize the sensing performance by adjusting the fin height, fin width, work function, channel doping, temperature, and drain voltage. Lastly, this article compared the proposed breast cancer cell detectors to existing literature to evaluate their performance and found considerable improvement. The findings of this research have the potential to establish GaAs-GS-GAA FinFET as a promising contender for MDA-MB-231 breast cancer cell detection.

Influence of NH2-MOF addition into PVDF and estimation of CO2 gas transport through membrane

Polyvinylidene fluoride (PVDF) had been vastly utilised for CO2/CH4 gas separation application. Nevertheless, pure polymeric membranes always suffer from a trade-off between permeability and selectivity as proven by Robeson in upper bound curves developed in gas separation applications. Thus, alternative modification like incorporating filler into polymer matrix to develop mixed matrix membranes (MMMs) is required. Besides, estimation of CO2 permeance of MMMs via unsuitable theoretical models would result in mismatch between experimental and predicted CO2 permeance data, subsequently causing troubles in membrane separation system designation. In the current work, PVDF hollow fiber mixed matrix membranes (HFMMMs) had been developed using NH2-MIL-125 (Ti) loadings of 1, 1.5, 2.5, and 3 wt%. The synthesized NH2-MIL-125 (Ti) and spun NH2-MIL-125 (Ti)/PVDF HFMMMs were characterized using Fourier transform infrared (FTIR). Furthermore, the Maxwell, Pal, modified Pal, Lewis–Nielson, Bruggeman and Bottcher model, were utilised to estimate the CO2 permeance of developed membranes. The additional FTIR peaks appeared at around 3440, 3358, 1478, 1430 cm−1 for developed HFMMMs when compared with pure PVDF indicate the presence of NH2-MIL-125 (Ti) in the HFMMMs. CO2 permeance estimation of 1.5 wt% PVDF HFMMM using all selected models yields around 1 absolute average relative error percent (AARE%). The remaining membranes displayed a high deviation, with an AARE% exceeding ± 5. AARE% obtained in the current work suggested that all the selected models can fit 1.5 wt% PVDF HFMMM.

Nanoparticle aggregation effect on nonlinear convective nanofluid flow over a stretched surface with linear and exponential heat source/sink

A nanofluid flow (TiO2/Ethylene Glycol) over a stretched surface caused by the considerable nonlinear convection is investigated with the nanoparticle aggregation effect in the presence of quadratic thermal radiation. The modified Maxwell model and Bruggeman model are utilized, which depict the nanoparticle aggregation effect. In addition, the system employs two separate variable heat sources i.e., linear heat source and exponential heat source. The similarity transformations are utilized to convert the basic governing PDEs to ODEs. The “bvp4c function” in MATLAB is used to numerically handle the resultant nonlinear system. The impact of the involved parameters is explored on the non-dimensional fields of velocity boundary layer patterns, velocity, streamlines, temperature, and heat transfer rate. Graphs compare and display the control of pertinent parameters on the distinct flow properties. A comparison of the behavior of the solution profiles with and without the influence of nanoparticle aggregation is illustrated. The nanoparticle aggregates significantly enhance the velocity and heat transmission mechanism. Furthermore, the influence of varied heat sources (linear and exponential) aids in growing the thermal boundary layer. Nanofluid flow with nanoparticle aggregation has a 5.36% higher Nusselt number value in comparison to flow without aggregation effect when the volume fraction of nanoparticles is varied from 0 to 0.1. The results of the study will be helpful in the fields where applications of a continuously stretching/shrinking surface are used like in many engineering processes and industries, glass-fiber production, aerodynamic extrusion of plastic sheets, and manufacturing of paper and rubber sheets.

Effects of scattering on optical parameters of terahertz time-domain spectroscopy of coal based on effective medium model

The optical parameters measured by terahertz time-domain spectroscopy (THz-TDS) are directly analyzed without considering the scattering effect, which is a common issue in the quantitative analysis of coal using THz-TDS. In this study, the optical parameters, microstructure, and true density of the samples were measured using THz-TDS, Scanning Electron Microscopy (SEM), and true density meter. The effective permittivity of a pure high-density polyethylene (HDPE) tablet sample was determined using the Maxwell-Garnett (MG), Bruggeman (BR), Landau-Lifshitz-Looyenga (LLL), and linear absorption (LA) models. The discrepancies between the effective permittivity and the true permittivity of HDPE were compared, leading to the determination that the LA model is the optimal approach. The irregular morphology of particles and the significant difference in permittivity between HDPE and coal are responsible for larger discrepancies observed in other effective medium models. The amplitude of the sample is inversely proportional to the size of coal particles in the time-dependent THz signal spectra. The effective absorbance and the extinction coefficient of coal are increased by scattering as the size of particles increases. Larger coal particles tend to agglomerate, resulting in a greater error in the effective refractive index. A quadratic function can be utilized to model the correlation between coal's absorbance caused by scattering and relative size. The results have demonstrated the validity of the LA model in calculating effective permittivity in tablet samples and provided guidance for minimizing scattering errors in THz-TDS.

Dielectric relaxation and hydrogen bonding studies of chlorobutane-dioxane mixtures using a time domain technique

Complex permittivity spectra have been computed for the binary mixtures of Chlorobutane (CLB) with 1, 4-Dioxane (DX) using Time Domain Reflectometry (TDR) for different concentrations and temperatures in the frequency range from 10 MHz to 30 GHz. The static dielectric permittivity and relaxation time have been obtained by fitting complex permittivity spectra to the Debye relaxation using least squares fit method. The Kirkwood correlation factor have been determined at various concentrations of 1, 4-dioxane. The Bruggeman model for the non-linear case has been fitted to the dielectric data for the mixtures.

Three-Dimensional Swirling Flow of Nanofluid with Nanoparticle Aggregation Kinematics Using Modified Krieger–Dougherty and Maxwell–Bruggeman Models: A Finite Element Solution

The current study explores a three-dimensional swirling flow of titania–ethylene glycol-based nanofluid over a stretchable cylinder with torsional motion. The heat transfer process is explored subject to heat source/sink. Here, titania–ethylene glycol–water-based nanofluid is used. The Maxwell–Bruggeman models for thermal conductivity and modified Krieger–Dougherty models for viscosity are employed to scrutinize the impact of nanoparticle aggregation. A mathematical model based on partial differential equations (PDEs) is developed to solve the flow problem. Following that, a similarity transformation is performed to reduce the equations to ordinary differential equations (ODEs), which are then solved using the finite element method. It has been proven that nanoparticle aggregation significantly increases the temperature field. The results reveal that the rise in Reynolds number improves the heat transport rate, whereas an increase in the heat source/sink parameter value declines the heat transport rate. Swirling flows are commonly found in many industrial processes such as combustion, mixing, and fluidized bed reactors. Studying the behavior of nanofluids in these flows can lead to the development of more efficient and effective industrial processes.

Effect of Morphology on the Permeability of CO<sub>2</sub> Across PSF/FCTF-1 Mixed Matrix Membranes

This reaserch examines different analytical models based on the ideal case membrane structure that can use to evaluate gas penetration into mixed-matrix membranes (MMMs) loaded with non-partial fillers. Many models predicted CO2 permeance over PSF/FCTF-1(MMMs) and were compared to experimental results. The models were compared using standard criteria for validating models, such as the difference in penetrant permeability between the two phases ( and the absolute average relative error percentage. A comparison of those models was carried out based on the widely used model validation criteria, including a convenient measure of penetrant permeability difference between the two phases and absolute average relative error percent. Based on the typical values of morphological characteristics, it was determined that the following models fitted the data in the best order: Lewis‐Nielsen model< Pal model<Higuchi< Bruggeman model< Chiew and Gland < Maxwell model having AARE% values of 6.79, 8.45, 8.53, 10.23, 13.10, and 14.33, respectively. A scanning electron microscopy (SEM) examination of the cross-sectional image confirmed that the fillers were really ellipsoids scattered inside the matrix. The Maxwell-Wagner-Sillar model and the Lewis-Nielsen model were then used to evaluate the prolate effect, and the optimization curves of maximum packing () and shape factor (n) produced the least deviations. The AAR% variation was determined to be in the order of 0.01n 0.3, indicating the significance of the shape factor parameter in determining the accurate CO2 permeance. Key words: polysulfone, Mixed matrix membrane, the permeability of CO2, theoretical models

Insight into the significance of nanoparticle aggregation and non-uniform heat source/sink on titania–ethylene glycol nanofluid flow over a wedge

The properties of nanoparticles in the working fluid are affected by many external factors and it further influences the effective properties of the resulting nanofluid. To study the heat transference mechanism in nanofluids, the inclusion of such factors is quite important as it provides the exact illustration of the mechanism. One such factor is the nanoparticle aggregation effect. Authors have studied the titania–ethylene glycol nanofluid (TiO2/EG NF) flow over a wedge with nanoparticle aggregation effect. Through this communication, authors have attempted to make a development on the Falkner-Skan problem. The flow is developed in the presence of the suction/injection effects, mixed convection, thermal radiation, porous medium, and non-uniform heat source/sink. To account for the influence of nanoparticle aggregation, revised forms of the Maxwell and Bruggeman models and the Krieger-Dougherty model are employed to estimate the effective thermal conductivity and viscosity of TiO2/EG NF, respectively. The aforementioned modified models developed for TiO2/EG NF gave a soundly close agreement with the experimental data. The governing equations are numerically solved employing the “bvp4c function in MATLAB”. The effect of the primary relevant parameters on the velocity, temperature, and heat transmission rate is depicted graphically. The heat transmission rate at the surface is higher with aggregated nanoparticles in comparison to its absence. The higher NPs volume fraction and the aggregation effect enhance the effective viscosity, the fluid becomes denser, and as a result, the velocity decreases. The outcomes of this study will be useful in many fields that utilize applications of flow over wedge such as in raw oil extraction, storage of nuclear waste, insulating heat exchangers, etc.

Theoretical models for gas separation prediction of mixed matrix membranes: effects of the shape factor of nanofillers and interface voids

Abstract In this work, a new model is developed by modifying the existing Maxwell–Wagner–Sillars (MWS) model to predict the gas separation properties of mixed matrix membranes (MMMs). The new modified MWS model, for the first time, provides the simultaneous exploration of the role of nanofillers/matrix interface voids and the exact geometrical shape of nanofillers in predicting the gas separation properties of MMMs. To unveil the crucial role of nanofillers/matrix interface voids, a mixed matrix membrane is considered a three-component system composed of the polymer matrix as the continuous component, nanofillers as the dispersed component and the interface voids between the two components. Moreover, the new model elucidates the role of the exact ellipsoidal shape of nanofillers within the membrane on the gas separation of MMMs by considering the shape factor of nanofillers. The newly developed modified MWS model is accurately able to predict the gas permeation of MMMs with a lower average absolute relative error (%AARE) of around 8% compared with the around 30% for conventional models such as the Maxwell model, Bruggeman model, Lewis–Nielsen model and Pal model and even compared with the modified Maxwell model (∼24%).

Permittivity and permeability studies of multiferroic nanocomposites: Comparison of experimental results with theoretical models

Multiferroic nanocomposites of two different series with ferrite and ferroelectric phases were developed successfully. The permittivity and the permeability studies were performed in the range 100 kHz–1.8 GHz frequency band, for all nanocomposites. The experimental results of effective permittivity and effective permeability of all nanocomposite samples were compared with the theoretical models of Maxwell Garnett, Lichtenecker and Bruggeman models. The deviations of experimentally determined values from Maxwell Garnett and Lichtenecker models are found to be slightly more. However, it was found that the experimental results of effective permittivity and effective permeability at 1 MHz for nanocomposite samples, were very close to the computed values of Bruggeman effective medium theory confirming that the composites obey homogeneous mixing rule.

Optical and temperature dependent electrical properties of poly (vinyl chloride)/copper alumina nanocomposites for optoelectronic devices

Abstract The practical applications of poly (vinyl chloride) have been constrained due to its poor thermal stability, low dielectric constant and inability to shield against ultraviolet (UV) radiation. In this study, we tried to improve the optical properties, thermal stability, temperature-dependent electrical conductivity and dielectric constant using copper alumina (Cu–Al2O3) nanoparticles reinforced poly (vinyl chloride) (PVC). Optical absorption measured with an ultraviolet-visible (UV-visible) spectrometer emphasises the blueshift in absorption edges and decreasing bandgap energies of PVC/Cu–Al2O3 nanocomposites compared to PVC. The presence of Cu–Al2O3 in PVC and its interaction with the polymer were confirmed by FTIR spectroscopy. Thermogravimetric analysis (TGA) demonstrates that nanocomposites have higher thermal stability than PVC, and that thermal stability increases with filler loading. Scanning electron microscopy (SEM) indicates the homogeneous dispersion of nanosized Cu–Al2O3 in the polymer matrix. The activation energy determined by the Arrhenius equation revealed that AC conductivity increases with the addition of nanoparticles up to a specific loading. The dielectric constant increases as a function of temperature and decreases with frequency. The magnitude of AC conductivity and dielectric constant were highest for 7 wt% loaded nanocomposites. The dielectric constant predicted by the Bruggeman and Maxwell-Garnet models were in good agreement with the experimental permittivity. The semiconducting nature of nanocomposites was investigated by impedance analysis. The semi-circular nature of Cole-Cole plots manifests the combination of parallel capacitance with low bulk resistance. The enhanced optical, thermal, electrical and dielectric properties of PVC/Cu–Al2O3 nanocomposites can be utilized in fabricating optoelectronic devices with excellent charge-storing ability.

A Dual-Parameter Measurement Method for Oil–Water Flow Based on a Venturi Embedded With Microwave Transmission Line Sensor

Accurate and real-time measurement of water cut (WC) and flowrate of oil–water flow is a critical factor in achieving intelligent digital oil field. In this article, a dual-parameter (WC and water flowrate) measurement method for oil–water flow is proposed based on a Venturi embedded with microwave transmission line sensor (V&MS). Dynamic experiments of horizontal fine dispersed oil–water flow are conducted. A two-dimensional finite element simulation model for V&MS under the fine dispersed flow is developed to simulate microwave phase outputs at 0%–100% WC. The simulation results agree with the experiments, providing a low-cost alternative to expensive oil–water dispersed flow tests. Furthermore, it is found that the flow patterns for 0%–10% WC and 40%–100% WC are water-in-oil and oil-in-water flows, respectively, but the flow patterns for 10%–40% WC are dispersions of water-in-oil and oil-in-water flow, and 20% WC is the transition point of the dominant continuous phase. When the water phase is continuous, V&MS has a higher sensitivity to phase signals. Finally, a WC prediction model (40%–100%) is developed by combining a modified Bruggeman model with microwave transmission line theory. Then, a discharge coefficient model is developed and the water flowrate is obtained by combining the pressure drop and the predicted WC. The absolute average relative deviation (AARD) of the predicted WC and water flowrate is 1.49% and 1.54%, respectively. The results suggest that appropriate sensing technology integration can offer a powerful solution for accurate and real-time determination of dual-parameter in oil–water flow systems.