Measuring the Complex Permittivities of Plastics in Irregular Shapes

Chao, Hsien-Wen; Chen, Hua-Hsuan; Chang, Tsun-Hsu

doi:10.3390/polym13162658

Cited by 6 publications

(7 citation statements)

References 29 publications

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“…For PEAD is observed a small variation between the values calculated for each sample of different thickness. This variation can be considered within the tolerance limits (2.3–2.45) that are usually specified by the manufacturers and several authors 18 . However, for the Nylon samples, the calculated dielectric constant resulted in values substantially close to 3.1, which is its commercially specified value and reported on the literature (3.09–3.21) 18 .…”

Section: Methodsmentioning

confidence: 99%

“…This variation can be considered within the tolerance limits (2.3–2.45) that are usually specified by the manufacturers and several authors 18 . However, for the Nylon samples, the calculated dielectric constant resulted in values substantially close to 3.1, which is its commercially specified value and reported on the literature (3.09–3.21) 18 . Therefore, according to these results, we can see that it is possible to use the designed and fabricated resonant cavity for dielectric properties characterization of different materials.…”

Section: Methodsmentioning

confidence: 99%

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Characterization of dielectric properties of residual ashes obtained from rice husk and annoni grass

Pereira,

Heckler,

Vasconcellos

et al. 2023

Sci Rep

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This paper presents a study about the characterization of dielectric properties (dielectric constant $${\varepsilon }_{r}$$ ε r and dielectric-loss constant $$\mathrm{tan}\delta$$ tan δ ) of samples derived from two different biomass types: rice husk ash (RHA) and annoni grass ash (AGA).The procedure is carried out using the resonant cavity method along with a vector network analyzer. For this purpose, four different ashes were produced, by burning rice husk and annoni grass at two different temperatures and burning times: 400 °C/30 min (RHA40030 and AGA40030) and 800 °C/5 h (RHA8005h and AGA8005h). These ashes were combined with Bakelite to produce cylindrical samples with diameter of 30 mm and thickness of 4.5 mm, which were characterized considering the frequency in the test band for 5G technologies ($${f}_{o}=3.5$$ f o = 3.5 GHz). Experimental results showed that the samples burnt at high temperature showed very high $$\mathrm{tan \delta }$$ tan δ when compared to the samples burnt at low temperature, mainly for AGA8005h. These values are $$\mathrm{tan \delta }=$$ tan δ = 0.1690 and 1.4900 for RHA8005h and AGA8005h, respectively. The resulting dielectric constants are $${\varepsilon }_{r}$$ ε r = 3.87 for RHA8005h and $${\varepsilon }_{r}$$ ε r = 15.14 for AGA8005h). These very high dielectric loss tangent, indicate that these materials exhibit formidable properties for electromagnetic energy absorption, hence allowing the application as radiation-absorbent material (RAM).

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Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Characterization of dielectric properties of residual ashes obtained from rice husk and annoni grass

Pereira,

Heckler,

Vasconcellos

et al. 2023

Sci Rep

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“…7 Different materials can have widely varying values for their relative permittivity at MR relevant frequencies. For example, air has a relative permittivity of 1.00058 on average, 11 plastics have values typically below 10, 12 and distilled water has a value of approximately 80. 13 Human tissues have varying electrical properties as well, with relative permittivities between 5 and 120, depending mostly on water content, 14 as illustrated in Figure 2.…”

Section: Dielectric Materials Characterizationmentioning

confidence: 99%

A review of recent developments and applications of high‐permittivity dielectric shimming in magnetic resonance

Jacobs,

Brink,

Reddy

2024

NMR in Biomedicine

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We present a review outlining the basic mechanism, background, recent technical developments, and clinical applications of aqueous dielectric padding in the field of MRI. Originally meant to be a temporary solution, it has gained traction as an effective method for correcting B1+ inhomogeneities due to the unique properties of the calcium titanate and barium titanate perovskites used. Aqueous dielectric pads have used a variety of high‐permittivity materials over the years to improve the quality of MRI acquisitions at 1.5 and 3 T and more recently for 7 T neuroimaging applications. The technical development and assessment of these pads have been advanced by an increased use of mathematical modeling and electromagnetic simulations. These tools have allowed for a more complete understanding of the physical interactions between dielectric pads and the RF coil, making testing and safety assessments more accurate. The ease of use and effectiveness that dielectric pads offer have allowed them to become more commonplace in tackling imaging challenges in more clinically focused environments. More recently, they have seen usage not only in anatomical imaging methods but also in specialized metabolic imaging sequences such as GluCEST and NOEMTR. New colossally high‐permittivity materials have been proposed; however, practical utilization has been a continued challenge due to unfavorable frequency dependences as well as safety limitations. A new class of metasurfaces has been under development to address the shortcomings of conventional dielectric padding while also providing increased performance in enhancing MRI images.

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“…The extrapolated data to 100% of the loaded volume are depicted in dashed lines. The dielectric constant and loss tangent of powder can be determined by the extrapolated method and the HFSS simulation curve [ 13 , 17 , 18 ].…”

Section: Sample Preparation and Measurement Proceduresmentioning

confidence: 99%

“…( b ) A modified (effective) model was used in the simulation. The modified model employed a block sample to represent the effects [ 17 ].…”

Section: Figurementioning

confidence: 99%

Percolation Effect on the Complex Permittivities of Polymer Blends

Chao,

Lai,

Chang

2023

Polymers

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This study focuses on the measurement and analysis of the complex permittivities of polymer blends using the field enhancement method (FEM). The blends, consisting of air-powder or solvent–solute mixtures, are placed in a Teflon holder and inserted into the FEM cavity to determine the complex permittivity. The resonant frequency and quality factor of the FEM cavity coupled with the samples provide information on the blends’ dielectric constant and loss tangents. To extract the complex permittivities of three specific samples of DC-840, MCL-805, and MCL-Siloxane, we employ effective medium theories and the high-frequency structure simulator (HFSS) together with the measured data. The results reveal that when the volume fraction of the DC-840 solute in the xylene solvent surpasses a specific threshold, the dielectric constants and the loss tangents experience a notable increase. This phenomenon, known as percolation, strongly correlates with the viscosity of polymer blends. The observed percolation effect on the dielectric behavior is further elucidated using the generalized dielectric constant and the Debye model. By employing these models, the percolation effect and its impact on the dielectric properties of the blends can be explained.

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Measuring the Complex Permittivities of Plastics in Irregular Shapes

Cited by 6 publications

References 29 publications

Characterization of dielectric properties of residual ashes obtained from rice husk and annoni grass

Characterization of dielectric properties of residual ashes obtained from rice husk and annoni grass

A review of recent developments and applications of high‐permittivity dielectric shimming in magnetic resonance

Percolation Effect on the Complex Permittivities of Polymer Blends

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