Geopolymer as dielectric materials for ultra-wideband antenna applications: Impact of magnetite addition and humidity

Vlasceanu, Ioana Nicoleta; Gharzouni, Amine; Tantot, Olivier; Lalande, Michèle; Elissalde, Catherine; Rossignol, Sylvie

doi:10.1016/j.oceram.2020.100013

Cited by 12 publications

(9 citation statements)

References 29 publications

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“…Geopolymer is a cross-link long-chain inorganic polymer of AlO 4 and SiO 4 so that it requires charge balancing from alkali cations, such as Na + and K + . The dielectric constant ( ε ′) of the geopolymer paste and mortar at 24 h after mixing were found as 3.5 and 7–10, respectively [ 22 , 23 ]. At room temperature, the most important variables influencing the electrical conductivity and dielectric property of geopolymers are water molecules and hydroxide [ 24 ].…”

Section: Introductionmentioning

confidence: 99%

Mechanical and Dielectric Properties of Fly Ash Geopolymer/Sugarcane Bagasse Ash Composites

et al. 2022

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Fly ash (FA) and sugarcane bagasse ash (SCBA) are the wastes from lignite power plants and sugar industries, usually disposed of as landfills. In this research, these wastes were effectively utilized as a construction material, namely geopolymer. The effect of the SCBA (0–40 wt.%) addition to the FA geopolymers was investigated. The compressive strength of the FA geopolymers was reduced with the SCBA addition. The reduction was mainly due to the presence of the highly stable and non-reactive quartz (SiO2) phase in SCBA. The SCBA was not dissolved in the alkaline activated solution and hence did not contribute to the geopolymerization process. The unreacted SCBA particles remained in the geopolymer matrix but did not provide strength. However, if the amount of SCBA was about 10 wt.% or less, the impact on the characteristics and properties of FA geopolymers was minimal. Furthermore, this research also studied the dielectric properties of the FA geopolymer/SCBA composites. The relatively large dielectric constant (e’ = 3.6 × 103) was found for the pristine geopolymer. The addition of SCBA decreased the e¢ slightly due to high carbon content in SCBA. Nevertheless, the variation in e’ was mainly controlled by the geopolymerization process to form the aluminosilicate gel structure.

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Section: Introductionmentioning

confidence: 99%

Mechanical and Dielectric Properties of Fly Ash Geopolymer/Sugarcane Bagasse Ash Composites

et al. 2022

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“…Permittivity and loss tangent increase with relative humidity, but this phenomenon reverses. It was also shown that time does not affect the dielectric constant value [26].…”

Section: B Relative Humidity (Rh)mentioning

confidence: 99%

Development of a wearable resonator mask for breathing rate monitoring

Rahayu,

Kirana,

Soh

2023

J.INFOTEL

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As one of the processes of patient care, diagnosis, and monitoring are the most important steps in the medical field. Sleep apnea is a problem that affects about 25 million Americans, and 80% of them go untreated because it is not identified. Monitoring has a big role in making patient treatment decisions. So this research aims to produce a wearable resonator mask that can work as a breathing rate monitor. The proposed resonator will use the relative humidity generated during the respiration process. The resonator uses a textile jeans material that is flexible, comfortable, and fits on a mask. Testing is carried out in 3 different positions; lying down, sitting, and standing. There is a difference in the percentage of RH produced from each position based on the difference in the frequency range produced. The proposed resonator operates well at 3.9 GHz.

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“…It also was not expected that removal of the magnetic particles would affect the formation of reaction products, as previous studies have shown that magnetite does not participate in the polycondensation reactions during alkali activation [76][77][78]. Therefore, the results obtained from the NMR analysis of the alkali-activated mine tailings (demagnetized and with a water-to-tailings ratio of 0.4) were expected to describe comparable reaction products to the alkali-activated mine tailings used in the remainder of this study (the magnetic particles retained with a water-to-tailings ratio of 0.18).…”

Section: Institutional Review Board Statement: Not Applicablementioning

confidence: 99%

Improvements in Hydrolytic Stability of Alkali-Activated Mine Tailings via Addition of Sodium Silicate Activator

Clements,

Tunstall,

Bolanos Sosa

et al. 2024

Polymers

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Over 14 billion tons of mine tailings are produced throughout the world each year, and this type of waste is generally stored onsite indefinitely. Alkali activation is a promising strategy for the reuse of mine tailings to produce construction materials, converting this waste stream into a value-added product. One major problem with alkali-activated mine tailings is their low durability in water (i.e., low hydrolytic stability). In this article, the influence of a mixed sodium hydroxide/sodium silicate alkali activator on the compressive strength, hydrolytic stability, and microstructure of alkali-activated materials (AAMs) were systematically investigated. XRD, FTIR, NMR, and NAD were used to investigate microstructural changes, and a water immersion test was used to show improvements in hydrolytic stability. For gold mine tailings activated with pure sodium hydroxide, the compressive strength was 15 MPa and a seven-day water immersion test caused a strength loss of 70%. With an addition of 1 M sodium silicate in the activator, the AAMs achieved a compressive strength of over 30 MPa and strength loss of only 45%. This paper proposes a mechanism explaining why the strength and hydrolytic stability of AAMs are dependent on the dosage of soluble silicate. A high dosage of sodium silicate inhibits the depolymerization of the source material, which results in a sample with less amorphous aluminosilicate gel and, therefore, lower hydrolytic stability.

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Geopolymer as dielectric materials for ultra-wideband antenna applications: Impact of magnetite addition and humidity

Cited by 12 publications

References 29 publications

Mechanical and Dielectric Properties of Fly Ash Geopolymer/Sugarcane Bagasse Ash Composites

Mechanical and Dielectric Properties of Fly Ash Geopolymer/Sugarcane Bagasse Ash Composites

Development of a wearable resonator mask for breathing rate monitoring

Improvements in Hydrolytic Stability of Alkali-Activated Mine Tailings via Addition of Sodium Silicate Activator

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