“…All samples were accomplished by using a manual mixer with a metal tip for 10 min approximately or until obtaining a homogeneous wet mixing. Then, the coir paste was filled into the sample holder, a pressure of 0.5 kPa and heat were applied to dehydrate at 120 °C for 24 h to create coir-MWCNT as pills, whose dimensions were 2.8 cm in diameter and 0.6 cm thick 9 . Two vertical silver stripes were traced with a highly conductive pen (CW2200STP, Chemtronics) and used as electrodes, 2 cm long, 1.2 mm wide, and 1.5 cm apart, to each of the samples separately.…”
Section: Methodsmentioning
confidence: 99%
“…There are several types of materials that are commercially available as sound absorbers and heat insulators, these synthetic materials are hazardous to human health 5 . Agricultural wastes such as coir are non-hazardous natural sources of loss carbon that can be used to absorb electromagnetic waves 6 – 9 . Agricultural waste is formed by organic compounds from plants and whose main element is carbon, an element which is suitable for converting microwave energy into thermal energy.…”
A biomaterial made of coir and Multi-Walled Carbon Nanotubes (MWCNTs) is presented which exhibits a relatively high-Temperature Coefficient of Resistance (TCR) and thermal insulation properties. Bolometers usually offer acceptable thermal isolation, electrical resistance, and high TCR. Fibers from agricultural waste materials such as coir has a synergistic effect as thermal insulating material and noise reducer. Based on it, powdered coir pills were used as pilot samples, as well as 2 other samples with different dispersions of MWCNTs, sodium dodecyl benzene sulfonate (SDBS) and polyvinylpyrrolidone (PVP) solution. The 3 kinds of samples were thermo-electrically characterized to determine their bolometric performance. Thermal conductivity of k = 0.045 W/m K was obtained by solving the Fourier’s law substituting the data into the equation describing heat flux on the sample around room temperature. Results show that adding different concentrations of MWCNT to powdered coir will lead to films with lower electrical resistance, therefore the thermal conductivity increases while thermal resistance decreases. Finally, the bolometric performance shows a maximum peak with a relatively high TCR of − 40.4% at a temperature of 300.3 K, this synthesized material outperforms by almost 1 order of magnitude larger than commercial materials. Results in this work also indicate that it is possible to tune bolometric parameters of this kind of samples and to use them as thermal insulators in the construction industry, when building roofs and walls.
“…All samples were accomplished by using a manual mixer with a metal tip for 10 min approximately or until obtaining a homogeneous wet mixing. Then, the coir paste was filled into the sample holder, a pressure of 0.5 kPa and heat were applied to dehydrate at 120 °C for 24 h to create coir-MWCNT as pills, whose dimensions were 2.8 cm in diameter and 0.6 cm thick 9 . Two vertical silver stripes were traced with a highly conductive pen (CW2200STP, Chemtronics) and used as electrodes, 2 cm long, 1.2 mm wide, and 1.5 cm apart, to each of the samples separately.…”
Section: Methodsmentioning
confidence: 99%
“…There are several types of materials that are commercially available as sound absorbers and heat insulators, these synthetic materials are hazardous to human health 5 . Agricultural wastes such as coir are non-hazardous natural sources of loss carbon that can be used to absorb electromagnetic waves 6 – 9 . Agricultural waste is formed by organic compounds from plants and whose main element is carbon, an element which is suitable for converting microwave energy into thermal energy.…”
A biomaterial made of coir and Multi-Walled Carbon Nanotubes (MWCNTs) is presented which exhibits a relatively high-Temperature Coefficient of Resistance (TCR) and thermal insulation properties. Bolometers usually offer acceptable thermal isolation, electrical resistance, and high TCR. Fibers from agricultural waste materials such as coir has a synergistic effect as thermal insulating material and noise reducer. Based on it, powdered coir pills were used as pilot samples, as well as 2 other samples with different dispersions of MWCNTs, sodium dodecyl benzene sulfonate (SDBS) and polyvinylpyrrolidone (PVP) solution. The 3 kinds of samples were thermo-electrically characterized to determine their bolometric performance. Thermal conductivity of k = 0.045 W/m K was obtained by solving the Fourier’s law substituting the data into the equation describing heat flux on the sample around room temperature. Results show that adding different concentrations of MWCNT to powdered coir will lead to films with lower electrical resistance, therefore the thermal conductivity increases while thermal resistance decreases. Finally, the bolometric performance shows a maximum peak with a relatively high TCR of − 40.4% at a temperature of 300.3 K, this synthesized material outperforms by almost 1 order of magnitude larger than commercial materials. Results in this work also indicate that it is possible to tune bolometric parameters of this kind of samples and to use them as thermal insulators in the construction industry, when building roofs and walls.
“…This material is made from coconut shell-based activated carbon, where the 9.6mm sample has a minimum reflection loss of −17dB at 11.3 GHz. Due to their rich carbon source, which shows high shielding potential, agricultural residues are important materials that can be applied in manufacturing EM radiation absorbers [19,20]. However, the use of environmentally friendly biomaterials with potentially protective characteristics is still in its development phase, which is the reason for the significance of this research.…”
The aim of this research was to determine the efficiency of electromagnetic (EM) radiation absorbers based on biomaterials from harvest residues (soybean straw, wheat straw, and clover straw) for the additional protection and/or construction of residential buildings. To determine their protective properties, the transmission parameter S21 was measured through harvest residues in the frequency range from 300 MHz to 5 GHz. Important parameters of the tested samples included sample type, sample thickness, and humidity. The measurement results showed that the transmission parameters decreased with an increase in the sample thickness, moisture, and frequency. Regarding this type of substrate, soybean straw showed the lowest values of parameter S21 for all measurements except for the case of the highest amount of moisture (34.48%), for which clover straw showed the lowest value of the transmission parameter. The greatest reduction in the S21 transmission parameter was 43.80 dB for a soybean sample of 300 mm thickness at a frequency of 4.93 GHz. These tests were performed on samples that were not additionally structured (additives, pressing, additional shredding, etc.), so it was possible to optimize their structure and conduct further research.
“…Pure copper plate (99.9%) of 1 mm thickness has been used as a metal backing. The amount of carbon present in the dried corn husks is 79.11% as shown in Table 1, and its physicochemical properties [6] are shown in Tables 2 and 3, respectively. Fig.…”
Design and development of cheap and eco-friendly microwave absorber are one of the challenging and interesting topics for the scientific community nowadays. This paper proposes the design and fabrication of corn husk-based low cost, light-weight, and flexible microwave absorber treated as a promising eco-friendly microwave absorber. In this work, an extensive study on microwave absorption efficiency of corn husk at different thicknesses is performed in the frequency range of 1–20 GHz. The absorber at 5.21 mm thickness possesses a return loss (RL) of −32.72247 dB at 2.255 GHz. The measured RL values agree well with simulated ones, indicating the utility of proposed absorber for various practical microwave absorption applications.
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