Azizurrahaman Ansari
Abstract
In this work, the microwave dielectric properties of Cu and PEO based composite sheets are studied in the X-band. The desired composites sheets (thickness ~ 250 μm) are prepared via solution casting method, one of the best methods for sheet preparation. Various characterization techniques including ...
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In this work, the microwave dielectric properties of Cu and PEO based composite sheets are studied in the X-band. The desired composites sheets (thickness ~ 250 μm) are prepared via solution casting method, one of the best methods for sheet preparation. Various characterization techniques including the X-ray diffraction and Scanning Electron Microscopy are used to analyze the presence and uniform dispersion of Cu particles into polyethylene oxide (PEO) matrix. Vector Network Analyzer is employed to obtain the scattering parameters (S21/S11), which are then used to extract the dielectric permittivity of the samples using cavity perturbation technique in the X-band of microwave frequency. The real and imaginary parts (dielectric constant and dielectric loss) of the complex permittivity of synthesized composite sheets are found to be increased with the addition of copper contents (10, 20, and 30 wt %). This enhancement of the dielectric properties in the X-band of microwave frequency may be attributed to the interfacial polarization mechanism. Copyright © VBRI Press.
Yong Yu; Preston Yi Jie Ching; Yen Nee Tan
Abstract
Developing effective synthesis method for few-atom gold nanoclusters (AuNCs) with tunable emissions is vitally important to gain better understanding of their formation mechanism and provide more design flexibilities to suite for various applications such as multiplex cellular imaging and/or light-emitting ...
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Developing effective synthesis method for few-atom gold nanoclusters (AuNCs) with tunable emissions is vitally important to gain better understanding of their formation mechanism and provide more design flexibilities to suite for various applications such as multiplex cellular imaging and/or light-emitting diodes. This paper reports a fast method (<30 minutes) of preparing multicolour (red, orange, near infrared) emissive AuNCs via a microwave-assisted biotemplating synthesis approach. A series of analytical tools such as UV-vis and photoluminescence spectroscopies, transmission electron microscopy (TEM) and polyacrylamide gel electrophoresis (PAGE) have been utilized to characterize the resultant AuNCs and unravel the formation mechanism that lead to their multicolour emissive properties. It was found that the surface charge of the thiol-containing peptide reagent and the peptide-to-Au ratio are crucial factors to control the size and emission colour of the resultant AuNCs. By bringing the solution pH to near the isoelectric point of peptide ligand (~3), the red (lem = 725 nm) emissive AuNC which is initially stable at alkaline conditions (pH-12) tends to aggregate due to deficiency of surface charge, thus forming a larger and orange (lem = 640 nm) emissive AuNC. By further applying an even lower peptide-to-Au ratio to fine-tune the protection power of thiolate ligands, a near-infrared (lem = 846 nm) emissive AuNC has been synthesized. Compared to other microwave-assisted synthesis of AuNCs, current study is featured by its simplicity, rapidity, and versatility to tune the emission wavelength of resultant AuNCs in a much broader range (up to 206 nm).
Sandeep Kumar; Neetu Ahlawat; Navneet Ahlawat
Abstract
In the present work, the results of microstructure, dielectric and ferroelectric investigation of microwave sintered CaCu3Ti4O12 (CCTO) ceramic with different heating rate are presented. Scanning electron micrographs revealed that grain size decreases from 1.167 µm to 0.744 µm with increased ...
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In the present work, the results of microstructure, dielectric and ferroelectric investigation of microwave sintered CaCu3Ti4O12 (CCTO) ceramic with different heating rate are presented. Scanning electron micrographs revealed that grain size decreases from 1.167 µm to 0.744 µm with increased heating rate from 10ºC/min. to 50ºC/min which can be explained on the basis of phenomenological kinetic equation for grain growth. Dielectric response also found to influence by heating rate. The CCTO ceramic sintered with 50 ºC/min. exhibited highest dielectric constant (ɛr~3915) with nominal losses (0.10) at room temperature in broad frequency range from 10 2 Hz-10 5 Hz. Cole-Cole plots revealed the change in grain boundary resistivity mainly caused by the oxygen vacancy activities and affected by varying sintering heating rate. An anomaly observed for 50 ºC/min heating rate due to trapping of oxygen at grain boundaries. The remnant polarization and coercive field for CCTO ceramic sintered with 50ºC/min were 0.1 µC /cm 2 and 1.477 kV /cm respectively. Remnant polarization found to decrease while the coercive field increases with increasing heating rate applying these are micro-structural dependent.
Atikah Ali; Rubia Idris
Abstract
In this study, the low-cost activated carbon from pistachio shell waste was sought through experiments using rapid synthesis of microwave-induced pyrolysis. The effect parameters of activating agents and microwave power on the surface area and carbon yield were studied. The results revealed that, well-grown ...
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In this study, the low-cost activated carbon from pistachio shell waste was sought through experiments using rapid synthesis of microwave-induced pyrolysis. The effect parameters of activating agents and microwave power on the surface area and carbon yield were studied. The results revealed that, well-grown pore structures with the highest surface area (681.2 m 2 g -1 ) and the highest carbon yield (70.3%) were produced using K2CO3 as an activating agent and 600 W power level exposed to 15-minute irradiation. The activated carbon with the highest porosity (AC600) was subsequently utilized in the tungsten carbide (WC) preparation which employed a facile method of mechanical milling. Finally, a high-thermal treatment under inert conditions was performed to completely convert W into WC. The physicochemical properties of the catalyst were evaluated by N2 adsorption-desorption, XRD, FESEM and TEM. It was observed that, the tungsten carbide produced was small and uniform spherical nanoparticles with average diameters of 60 to 100 nm. High porosity and high surface area of catalyst support were identified as factors leading to a homogeneous distribution of metal catalyst. Therefore, the nanoparticles of WC produced were attributed to activated carbon with high porosity (AC600) due to well distribution of the tungsten crystal phase.
V. M. Gaikwad; S. A. Acharya
Abstract
Field cooled (FC) and zero field cooled (ZFC) magnetization measurements of Bismuth Ferrite (BiFeO3) multiferroic obtained by microwave-assisted gel combustion method are reported. The structural investigation of sythesized and calcined sample is done by XRD and the obtained data is well fitted with ...
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Field cooled (FC) and zero field cooled (ZFC) magnetization measurements of Bismuth Ferrite (BiFeO3) multiferroic obtained by microwave-assisted gel combustion method are reported. The structural investigation of sythesized and calcined sample is done by XRD and the obtained data is well fitted with Rietveld refinement using full-pro software suite. M-H hysterisis shows that BFO nanoparticles exhibit ferromagnetic properties at room temperature, which is unusally observed in BFO. The M -T plot at H = 1 and 2 kOe shows that the FC and ZFC magnetization curve start to differ at below 331K and 236 K respectively with sharp cusp around 124 K revealing spin glass behaviour of BiFeO3. Both ferromagnetic properties and spin-glass-like behavior are observed in BFO nanoparticles. Ferromagnetic behavior is attributed to a partial destruction in nanoparticles of the long-wavelength cycloid spin structure expected in bulk BFO. Spin-glass-like behavior is assigned to diffusion of domain walls, with possible contributions from pinning of the cycloid spin structure at the nanoparticle surface.
Oman Zuas; Harry Budiman; Nuryatini Hamim
Abstract
The ZnO nanoparticles (ZnO NPs) were synthesized by co-precipitating method followed by calcining at 500 o C for 4 h. The characterization data show that the synthesized ZnO NPs were present in hexagonal wurtzite structure and space group P63mc with high purity and good crystalline nature. The synthesized ...
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The ZnO nanoparticles (ZnO NPs) were synthesized by co-precipitating method followed by calcining at 500 o C for 4 h. The characterization data show that the synthesized ZnO NPs were present in hexagonal wurtzite structure and space group P63mc with high purity and good crystalline nature. The synthesized ZnO NPs were tested for decolorization of congo red (CR) dye under microwave irradiation using microwave induced catalytic (MIC) method. The investigation results showed that the microwave induced ZnO NPs process could effectively decolorize the CR dye with the efficiency approaches 90.63% in a short contact time under given condition of 10 mg/l CR dye, 300 watt of microwave power, 3 min of contact time, and 3 g/l of catalyst dosage. Since the microwave-induced catalytic process in this study is noticeable, the microwave technology coupled with ZnO NPs as catalyst may have synergistic effects on the decolorization of CR dye giving high degradation ratio in short reaction time. Therefore, the microwave technology can be used as an alternative option to enhance the catalytic activity of metal nanoparticles dealing with removal of various industrial dyes containing wastewater.