Effective Medium Theory for Multi-Component Materials Based on Iterative Method

Nazarov, Ravshanjon; Zhang, Tianmiao; Khodzitsky, Mikhail K.

doi:10.3390/photonics7040113

Cited by 11 publications

(10 citation statements)

References 24 publications

(38 reference statements)

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“…The particle size distribution of the initial iron powder can be found in Figure 3 from [ 6 ]. Another calculation technique may be applied, which is first calculating the effective permeability of the paraffin and silicon shell, and then using that result as the environmental permittivity for the iron [ 37 ]. However, if the model applied in the manuscript may be derived rigorously with account for inclusion and shell shapes, another model is semi-empirical.…”

Section: Resultsmentioning

confidence: 99%

Deposition of a SiO2 Shell of Variable Thickness and Chemical Composition to Carbonyl Iron: Synthesis and Microwave Measurements

Dolmatov

Zezyulina²,

Osipov³

et al. 2021

Sensors

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Protective SiO2 coating deposited to iron microparticles is highly demanded both for the chemical and magnetic performance of the latter. Hydrolysis of tetraethoxysilane is the crucial method for SiO2 deposition from a solution. The capabilities of this technique have not been thoroughly studied yet. Here, two factors were tested to affect the chemical composition and the thickness of the SiO2 shell. It was found that an increase in the hydrolysis reaction time thickened the SiO2 shell from 100 to 200 nm. Moreover, a decrease in the acidity of the reaction mixture not only thickened the shell but also varied the chemical composition from SiO3.0 to SiO8.6. The thickness and composition of the dielectric layer were studied by scanning electron microscopy and energy-dispersive X-ray analysis. Microwave permeability and permittivity of the SiO2-coated iron particles mixed with a paraffin wax matrix were measured by the coaxial line technique. An increase in thickness of the silica layer decreased the real quasi-static permittivity. The changes observed were shown to agree with the Maxwell Garnett effective medium theory. The new method developed to fine-tune the chemical properties of the protective SiO2 shell may be helpful for new magnetic biosensor designs as it allows for biocompatibility adjustment.

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Section: Resultsmentioning

confidence: 99%

Deposition of a SiO2 Shell of Variable Thickness and Chemical Composition to Carbonyl Iron: Synthesis and Microwave Measurements

Dolmatov

Zezyulina²,

Osipov³

et al. 2021

Sensors

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show abstract

“…Detecting materials with powder by analyzing permittivity requires considering the contribution of air within the holder. In this regard, we employed effective medium theories (EMT) which provide effective dielectric properties of the inhomogeneous constituent materials [ 27 , 35 , 36 ]. Basically, the EMTs depend on the volume fraction of the components of the mixtures [ 27 , 35 ].…”

Section: Methodsmentioning

confidence: 99%

“…In this regard, we employed effective medium theories (EMT) which provide effective dielectric properties of the inhomogeneous constituent materials [ 27 , 35 , 36 ]. Basically, the EMTs depend on the volume fraction of the components of the mixtures [ 27 , 35 ]. Among various models including Maxwell-Garnet and Bruggeman model, the LLL model can be applied for our mixture powder samples which rely on not the shape, but the size of the constituent particles [ 37 , 38 , 39 , 40 , 41 , 42 ].…”

Section: Methodsmentioning

confidence: 99%

Detection of Microplastic in Salts Using Terahertz Time-Domain Spectroscopy

Goo

Kim

et al. 2021

Sensors

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We report on a prototypical study of the detection of microplastic embedded in table salts by using terahertz time-domain spectroscopy. In the experiment, high-density polyethylene (HDPE) of sizes from 150 to 400 μm are used as a representative microplastic and mixed with table salts. Analyzing terahertz transmittance with an effective medium model, we extract various optical properties such as refractive index, absorption coefficient, and real/imaginary parts of the dielectric constant of the mixture. Consequently, the optical properties exhibit volume-ratio-dependence in 0.1–0.5 THz regimes. Especially, the refractive index and the real part of the dielectric constant possess monotonic frequency dependence, meaning that the quantities can be relevant indicators for the detection of the microplastic in terms of practical applications. Our work proves that terahertz time-domain spectroscopy can pave a way to recognize microplastic mixed with salts and be expanded for detecting various micro-sized particles.

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“…The effect permittivity of GO can be calculated using the LLL effective medium theory 33,34 by incorporating the porosity into the model, as given by eq 7.…”

Section: Methodsmentioning

confidence: 99%

“…The effect permittivity of GO can be calculated using the LLL effective medium theory , by incorporating the porosity into the model, as given by eq . where ε 1 , ε 2 , and ε 3 are the permittivities of air, water, and GO, respectively, and f 1 , f 2 , and f 3 are volume fractions of air, water, and GO, respectively. The initial volume fractions of 11.5, 0, and 88.5% are fitted with the experimentally measured permittivity of the unetched GO at different RHs .…”

Section: Methodsmentioning

confidence: 99%

Numerical Study of a Capacitive Graphene Oxide Humidity Sensor with Etched Configuration

Mohammedture

Hashmi

et al. 2021

ACS Omega

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The geometrical dependence of humidity sensors on sensing performance has not been quantitatively outlined. Furthermore, the etching effect on humidity sensors is still elusive due to the difficulty in separating the effects of the geometrical change and etching-induced porosity on the overall performance. Here, we use COMSOL Multiphysics to perform a numerical study of a capacitive graphene oxide (GO) humidity sensor, with emphasis on the dimensions and etching effect on their sensing performance. GO is a useful and promising material in detecting humidity because of its selective superpermeability to water molecules. The mechanism of improved sensing performance of the etched humidity sensors is discussed in terms of the morphological profile and the effective permittivity including the etching-induced porosity effect. Our study shows that as compared to the unetched sensors, isotropic etching achieves the lowest response time of 1.011 s at 15.75% porosity, while vertical etching achieves the highest capacitance sensitivity of 0.106 fF/RH %.

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Effective Medium Theory for Multi-Component Materials Based on Iterative Method

Cited by 11 publications

References 24 publications

Deposition of a SiO2 Shell of Variable Thickness and Chemical Composition to Carbonyl Iron: Synthesis and Microwave Measurements

Deposition of a SiO2 Shell of Variable Thickness and Chemical Composition to Carbonyl Iron: Synthesis and Microwave Measurements

Detection of Microplastic in Salts Using Terahertz Time-Domain Spectroscopy

Numerical Study of a Capacitive Graphene Oxide Humidity Sensor with Etched Configuration

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