Microwave-assisted Chemical Method Research Articles

Tunable dielectric and memory features of ferroelectric layered perovskite Bi4Ti3O12 nanoparticles doped nematic liquid crystal composite

Herein, we report the synthesis of ferroelectric layered perovskite Bi4Ti3O12 (BT4) nanoparticles (NPs) and the temperature-dependent dielectric and electro-optical (especially memory effect) properties of 4-pentyl-4′-cyanobiphenyl (5CB) nematic liquid crystal (NLC) doped with 1 wt% BT4 NPs (i.e. 5CB-BT4 composite) using polarising optical microscopy and frequency-dependent dielectric spectroscopy techniques. BT4 NPs were synthesised via a microwave-assisted chemical method and characterised using various instrumental techniques, which confirmed the formation of a non-stoichiometric and oxygen-deficient orthorhombic crystal phase. The agglomeration-free and uniform dispersion of BT4 NPs in the 5CB matrix was confirmed by optical textures. The optical memory studied by bias voltage-dependent (ON-OFF) optical textures is decreased by ∼ 2.6 times in the 5CB-BT4 composite compared with 5CB. Moreover, dielectric parameters such as dielectric permittivity, dielectric loss, loss tangent, conductivity, and activation energy of 5CB and composite (5CB-BT4) are estimated using dielectric spectroscopy. The dielectric anisotropy is decreased, whereas no shift in the clearing temperature is observed in the 5CB-BT4 composite compared to the 5CB sample. Also, the DC conductivity of 5CB-BT4 composite is found to be increased by approximately four times compared to the 5CB. Our studies clearly demonstrate the tunability of the dielectric and optical memory features of NLC (5CB) matrix by dopant BT4 NPs, without significantly affecting the molecular alignment of the NLC molecules. Such composites would certainly be useful in the fabrication of NLC based tunable devices such as optical memory and conductivity switches.

Doping-induced changes in the structural, optical, magnetic and thermal properties of Ni:ZnS nanoparticles prepared by microwave-assisted chemical method

Doping-induced changes in the structural, optical, magnetic and thermal properties of Ni:ZnS nanoparticles prepared by microwave-assisted chemical method

Size-controlled, single-crystal CuO nanosheets and the resulting polyethylene–carbon nanotube nanocomposite as antimicrobial materials

In this study, size-controlled single-crystal copper oxide nanosheets (CuO NSs) were fabricated by a microwave-assisted chemical method. Next, their nanocomposites with high-density polyethylene (HDPE) were fabricated. These nanocomposites were further reinforced with carbon nanotubes (CNTs) of oil fly ash. The produced CuO NSs along with their polymer nanocomposites were evaluated as antimicrobial agents against Escherichia coli, Bacillus subtilis, and yeast Saccharomyces cerevisiae. Significant microbial-growth inhibition was observed. This inhibition correlated with oxygen defects, free Cu2+ ion release, and a change in the lattice constant c. These factors were found to increase with the increased molar ratio of the precursors and might be responsible for formation of additional reactive oxygen species. Moreover, adding 1 wt% of CuO NSs and 0.5 wt% of CNTs enhanced the mechanical properties of HDPE by ~ 20%. These results indicate that it is possible to design polymer nanocomposites that have both antimicrobial and enhanced mechanical properties for various applications, mainly in the healthcare sector.

Development of a low cost and green microwave assisted approach towards the circular carbon fibre composites

In this study, we have developed a rapid, cost-effective, environmentally green, and yet efficient approach for the complete reclamation of the carbon fibre composites through a microwave assisted chemical method. It was found that in a catalyst-free and one-step process using microwave irradiation, a mixture of hydrogen peroxide (H2O2) and tartaric acid (TA) can initiate decomposition of the epoxy matrix up to 95% yield, leaving behind CFs with ~92% tensile strength and ~94% strain-to-failure retentions compared to the original CFs. Less than 2 min microwave irradiation was used which makes this approach considerably promising for the fast reclamation of the carbon fibre composites. The repetition of reclamation for the second and third times, which have been performed on the composite laminates re-manufactured using the reclaimed CFs, indicated that further reductions in the CFs mechanical performance are typically less than 5% after first reclamation process. Our proposed reclamation process changed surface properties of the reclaimed CFs compared to original CFs, which led to a significant increase in interfacial performance of the recycled CFs-epoxy composites. Moreover, the re-manufactured composite laminates using the reclaimed CFs showed highly comparable flexural strength and modulus, compared to its original composite laminates.

Studying of Nonlinear Optical Properties of Binary Bi2S3 and Bi2Te3/PMMA Nanocomposite Films by Z-Scan Technique

For measuring the nonlinear refraction index n2 and absorption index β, we have used modified Z-scan technique with the single laser beam. The media is a nanocomposite films made from the binary (Bi2S3 and Bi2Te3) with PMMA. The material is prepared via the microwave-assisted chemical method. The Characterization of the nanocomposite films was carried out using X-ray diffraction (XRD), and U-V spectroscopy. The band gaps of Bi2S3 and Bi2Te3 are 2.6ev and 2.38ev respectively. XRD shows that Bi2S3 and Bi2Te3 have orthorhombic and trigonal (hexagonal axes) structures respectively. The optical non-linearity is intensity dependent. The nanocomposite films exhibit self-defocusing nonlinearity beneath the empirical conditions. Both samples exhibit a large negative nonlinear refractive index and good nonlinear absorption coefficient with increasing laser input power. The spotted nonlinear refraction and absorption are related to thermal in nature and reverse Saturable absorption, respectively. The obtained results indicate that the nanocomposite films may open several new possibilities of using these materials in all-optical element devices.

Controllable synthesis and photocatalytic activity of ZnO nanorods

ABSTRACTZnO nanorods were successfully synthesized by a microwave-assisted chemical method. The as-prepared ZnO particles were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), high resolution TEM, X-ray photoelectron spectra (XPS), and X-ray diffraction (XRD). It is found that ZnO nanorods with diameters around 20–30 nm and lengths in the range of 60–80 nm were synthesized. The products showed good photocatalytic performance under UV light irradiation. The ZnO nanorods also showed excellent photostability and reusability under UV-visible light irradiation.

Microwave-Assisted Chemical Preparation of ZnO Nanoparticles and Its Application on the Improving Grain Yield, Quantity and Quality of Safflower (Carthamus Tinctorius L.)

ZnO nanoparticles were synthesized by a microwave-assisted chemical method. ZnO nanostructures were synthesized via a fast reaction between zinc acetate and ammonia at presence citric acid and other effective agents in chemical procedure. Nanostructures were characterized by X-ray diffraction , scanning electron microscopy. Seed yield and seed quality of safflower grown under drought stress. The test includes control treatments priming with distilled water, priming with zinc sulphate in the amount of 300 mg per ml, priming with sulfate of zinc to 600 mg per liter, priming with Nano priming on the amount of 300 mg per liter, with Nano on priming rate of 600 mg per liter, priming with zinc sulphate in the amount of 300 mg/l zinc sulphate along with spraying the amount of 300 mg, zinc sulfate with priming to the amount of 600 mg/l zinc sulphate along with spraying the amount of 600 mg, priming with Nano over the amount of 300 mg per liter plus the foliar application of nano on the amount of 300 mg, priming with Nano over the amount of 600 mg per liter plus the foliar application to nano on 600 mg, zinc sulfate to foliar application with the amount of 300 mg per liter, foliar application with Nano over the amount of 300 Mg/l, respectively.

Microwave Synthesis, Characterization, and Photoluminescence Properties of Nanocrystalline Zirconia

We report synthesis of ZrO2 nanoparticles (NPs) using microwave assisted chemical method at 80°C temperature. Synthesized ZrO2 NPs were calcinated at 400°C under air atmosphere and characterized using FTIR, XRD, SEM, TEM, BET, and EDS for their formation, structure, morphology, size, and elemental composition. XRD results revealed the formation of mixed phase monoclinic and tetragonal ZrO2 phases having crystallite size of the order 8.8 nm from most intense XRD peak as obtained using Scherrer formula. Electron microscope analysis shows that the NPs were less than 10 nm and highly uniform in size having spherical morphology. BET surface area of ZrO2 NPs was found to be 65.85 m2/g with corresponding particle size of 16 nm. The band gap of synthesized NPs was found to be 2.49 eV and PL spectra of ZrO2 synthesized NPs showed strong peak at 414 nm, which corresponds to near band edge emission (UV emission) and a relatively weak peak at 475 and 562 nm.

High Yield Preparation of Macroscopic Graphene Oxide Membranes

Graphene oxide membranes up to 2000 microm(2) in size can be synthesized with 90% yield in bulk quantities through a microwave-assisted chemical method. Membranes are readily visualized on an oxidized silicon substrate, which enables efficient fabrication of electronic devices and sensors. Field effect transistors made of the membrane show ambipolar behavior, and their conductivity is significantly higher than previously reported values.