Showing 5 results for Composite
Vida Zaroushani, Ali Khavanin, Ahmad Jonidi Jafari, Seyed Bagher Mortazavi, Farahnaz Khajenasiri,
Volume 6, Issue 4 (12-2016)
Abstract
Introduction: Due to the importance of engineering controls for prevention of microwave exposure, this study was conducted to design and constract a novel electromagnetic shielding and also to examine the factors influencing shielding efficacy in X band frequency range.
Material and Method: This study used Resin Epoxy as matrix and nano-Nickel Oxide as filler to prepare the composite plates with three different thicknesses (2,4, and 6 mm) and four different weight percentages (5,7,9 and 11). The fabricated composites characterized using X-ray diffraction and Field Emission Scanning Electron microscopy. Shielding effectiveness, percolation depth, and percolation threshold were measured using Vector Network Analyzers. Thermal Gravimetric Analysis was conducted to study the temperature influence on weight loss for fabricated composites.
Result: A maximum shielding effectiveness value of 84.18% was obtained for the 11%-6mm composite at 8.01 GHz and the 7%-4mm composite exhibits a higher average of shielding effectiveness of 66.72% at X- band frequency range. The 4mm thickness was optimum and critical diameter for composite plates; and percolation depth was obtained greater than thickness of composites. However, increasing the nickel oxide content did not show noticeable effect on the shielding effectiveness. Thermal Gravimetric Analysis showed that the study shields were resistant to temperature up to 150 °C without experiencing weight loss. What is more, the results indicated that Nickel oxide Nano particles had desirable distribution and dispersion in epoxy matrix and percolation threshold was appeared in low content of nickel oxide nanoparticles.
Conclusion: A novel electromagnetic shield using low thickness and few content of nanoparticle with noticeable efficacy was properly designed and constructed in the field of occupational health. In addition, this shield has low cost, easy to manufacture, resistance to wet/corrosion, and low weight. Epoxy/nickel oxide composite can represents a new generation of electromagnetic shielding, which is considered as a promising candidate for occupational protection against microwave exposure. It is recommended that future studies improve the shielding effectiveness by decreasing the percolation depth and investigate the efficacy of the fabricated shield in the workplaces.
Hojatolla Kakaei, Mojtaba Beygzadeh, Farideh Golbabaei, Mohammad Reza Ganjali, Mehdi Jahangiri, Sayed Jamaleddin Shahtaheri,
Volume 9, Issue 4 (12-2019)
Abstract
Introduction: Hydrogen sulfide is one of the most important impurities in natural gas. Due to the fact that this gas is hazardous, toxic, corrosive and volatile, therefore, the removal of hydrogen sulfide has been studied using several methods. One of the most known procedures is the adsorption process. In the present study, activated carbon and activated carbon-based composite scaffolds (MOF-5) were used as a cartridge mask to remove hydrogen sulfide from respiratory air.
Methods and Materials: First, activated carbon (AC) was converted to powder form by ball mill, and AC / MOF-5 composite with 10%, 25%, and 40% MOF-5 to AC was synthesized from the MOF-5 metal-organic scaffold. Then, the rates of adsorption and breakthrough time using a designed setup were tested in two ranges of temperatures, humidities and concentrations. XRD, SEM and BET were used to determine the properties of composite absorbents. The Aeroqual S500 Direct-reading sensor with 0.01 ppm accuracy was used to measure the exact amount of hydrogen sulfide gas.
Results: The AC/MOF-5 composite showed higher adsorption and breakthrough time compare to the other adsorbents. The Specific surface area (BET), average pore diameter, and total pore volume of the adsorbent were 814 m2 /g, 1.6795 nm, and 0.342 cm3 /g, respectively. The isotherm diagram showed that, according to IUPAC, most of the pore size of this adsorbent was classified in the micro-porous group. The maximum adsorption (mg/gS) and breakthrough time (min) were related to AC/MOF-5(40 Wt. %) adsorbent with 60.41 mg/gS (SD = 1.08) and 56.26 min (SD =2.38) at a temperature of 15 ° C, a concentration of 9.88 ppm (SD = 0.70), a moisture content of 51.06% (SD = 0.15) and a pressure drop of 51.34 mm water. By adding more than 25% MOF-5 metal-metal scaffold to activated carbon, the amount of adsorption, breakthrough time and pressure drop were increased.
Conclusion: AC / MOF-5 composite adsorbent due to its porous structure, high specific surface area, and most importantly, having Zn-O-C groups increased the adsorption rate as well as the pollutant Breakthrough time. However, it showed a relatively higher pressure drop than commercial activated carbon (AC).
Reza Jafari Nodoushan, Mostafa Azimzadeh, Sahar Bagheri, Arefeh Dehghani Tafti,
Volume 11, Issue 4 (12-2021)
Abstract
Introduction: In recent years tend to use of natural fibers has increased in making sound absorbers. Fiber-based natural materials have low density, low production costs, and are biodegradable.
Material and Methods: In this study, the effect of nanoclay and the behavior of the nanocomposite specimens containing tea waste, polypropylene, and nanoclay in the sound absorption coefficient are investigated.
Results: The results showed the sound absorption coefficient increases by increasing the tea waste weight percent of the polypropylene. 60% increase in tea waste has a special role in the absorption of sound waves at a frequency of 1000 Hz and 2500 to 6300 Hz frequency range as the TW60 N5 sample has the sound absorption coefficient 0.94 and 0.84 in 1000 and 6300 Hz frequencies, respectively. Comparison of the sound absorption coefficient of composite and nanocomposite showed that sound absorptions increase by adding nanoclay to the 5%, at frequencies above 2000 Hz.
Conclusion: Tea waste-based sound absorbers can be used in noise control due to the high acoustic absorption and no harmful effects on human health.
Ehsan Rezaieyan, Ebrahim Taban, Seyyed Bagher Mortazavi, Ali Khavanin, Hasan Asilian, Elham Mahmoudi,
Volume 12, Issue 2 (6-2022)
Abstract
Introduction: Micro perforated panel (MPP) absorbents promise the next generation of sound absorbers as they have significant advantages over other porous adsorbents. In this study, we will investigate the acoustic performance of MPP absorbents made of biodegradable polylactic acid composite reinforced with natural corkwood fibers (PLA/Corkwood) by 3D printing technology.
Material and Methods: First, the effective dimensional characteristics of the parameters were determined, then, all of the samples were fabricated by the Zortrax M200 3D-Printer using the FDM method. The normal incidence sound absorption coefficient of the samples was measured using an acoustic impedance tube according to ISO 10534-2 in the frequency range of 64 to 1600 Hz. Then the effect of four geometric parameters, including hole diameter, panel thickness, perforation ratio, and air gap depth, on the absorption coefficient was studied.
Results: The findings show that the SL-MPP 12 absorbent has the highest average sound absorption coefficient (SACA) with a value of 0.28, so that at a frequency of 804 Hz it has the highest sound absorption equal to 0.91. The parametric study found that as the hole diameter increased, the values of peak adsorption and average absorption coefficient were decreased. Increasing the MPP thickness causes the absorption peak to move towards the lower frequency range. Decreasing the perforation ratio increases the peak absorption values and the average sound absorption, and the frequency with the highest absorption also moves towards the higher frequency range. The resonant frequency also depends on the depth of the air gap behind the screen. Changes in air gap depth from 30 mm to 70 mm reduced the resonant frequency by more than 35%.
Conclusion: Using 3D printing technology, sustainable MPP can be fabricated with more quality and in less time than traditional methods such as mixing and heat pressing.
Elnaz Rahimi, Saba Kalantary, Aziz Babapoor, Habibollah Dehghan, Anoshirvan Kazemnejad, Mohammadreza Monazzam Esmaeelpour,
Volume 15, Issue 2 (7-2025)
Abstract
Introduction: Wearable thermal management systems and phase change materials (PCMs) have emerged as effective solutions for regulating body temperature and storing thermal energy. This study focuses on synthesizing and thermal optimizing a sodium sulfate decahydrate-based nanocomposite incorporating various nanoparticles to improve its performance for personal thermal regulation applications.
Material and Methods: The composite was prepared using sodium sulfate decahydrate as the base PCM. Potassium chloride (KCl) was added to adjust the melting point, borax (STD) served as a nucleating agent, and sodium polyacrylate (SPA) was included as a thickening agent to suppress phase separation. To evaluate the effect of nanoparticle additives, 0.05 wt.% of aluminum oxide (Al₂O₃), iron oxide (Fe₂O₃), graphene oxide (GO), and titanium dioxide (TiO₂) were separately incorporated into the base formulation. A field emission scanning electron microscope (FESEM) was used to analyze the surface morphology of the resulting nanocomposites. Differential scanning calorimetry (DSC) assessed thermal properties, including phase transition temperatures (melting and freezing points) and latent heat.
Results: Differential scanning calorimetry (DSC) analysis indicated that sample S-5-5 comprising sodium sulfate decahydrate with 3 wt.% KCl, 5 wt.% STD and SPA exhibited a melting temperature of 29.5 °C and a latent heat of 120 J/g. This composition remained stable without phase separation. The incorporation of nanoparticles raised the melting point of the base PCM by 0.6 to 1.72 °C. Aluminum oxide (Al₂O₃) and iron oxide (Fe₂O₃) reduced the latent heat of fusion, whereas GO and TiO₂ increased it.
Conclusion: These findings confirm that the thermal properties of sodium sulfate decahydrate-based PCMs can be tailored by including specific additives and nanoparticles. Hydrated salt nanocomposites demonstrate strong potential as PCMs for wearable body temperature regulation.
