Hierarchically Structured Composite Fibers for Real Nanoscale Manipulation of Carbon Nanotubes

Carbon nanotube (CNT)-reinforced polymer fibers have broad applications in electrical, thermal, optical, and smart applications. The key for mechanically robust fibers is the precise microstructural control of these CNTs, including their location, dispersion, and orientation. A new methodology is presented here that combines dry-jet-wet spinning and forced assembly for scalable fabrication of fiber composites, consisting of alternating layers of polyacrylonitrile (PAN) and CNT/PAN. The thickness of each layer is controlled during the multiplication process, with resolutions down to the nanometer scale. The introduction of alternating layers facilitates the quality of CNT dispersion due to nanoscale confinement, and at the same time, enhances their orientation due to shear stress generated at each layer interface. In a demonstration example, with 0.5 wt% CNTs loading and the inclusion of 170 nm thick layers, a composite fiber shows a significant mechanical enhancement, namely, a 46.4% increase in modulus and a 39.5% increase in strength compared to a pure PAN fiber. Beyond mechanical reinforcement, the presented fabrication method is expected to have enormous potential for scalable fabrication of polymer nanocomposites with complex structural features for versatile applications.     

Combustion synthesis and characterization of Ba<Subscript>2</Subscript>NdSbO<Subscript>6</Subscript> nanocrystals

Nanocrystalline Ba₂NdSbO₆, a complex cubic perovskite metal oxide, powders were synthesized by a self-sustained combustion method employing citric acid. The product was characterized by X-ray diffraction, differential thermal analysis, thermogravimetric analysis, Fourier transform infrared spectroscopy, transmission electron microscopy and scanning electron microscopy. The as-prepared powders were single phase Ba₂NdSbO₆ and a mixture of polycrystalline spheroidal particles and single crystalline nanorods. The Ba₂NdSbO₆ sample sintered at 1500°C for 4 h has high density (∼ 95% of theoretical density). Sintered nanocrystalline Ba₂NdSbO₆ had a dielectric constant of ∼ 21; and dielectric loss = 8 × 10⁻³ at 5 MHz.     

Linear Dichroism Conversion in Quasi‐1D Perovskite Chalcogenide

Anisotropic photonic materials with linear dichroism are crucial components in many sensing, imaging, and communication applications. Such materials play an important role as polarizers, filters, and waveplates in photonic devices and circuits. Conventional crystalline materials with optical anisotropy typically show unidirectional linear dichroism over a broad wavelength range. The linear dichroism conversion phenomenon has not been observed in crystalline materials. The investigation of the unique linear dichroism conversion phenomenon in quasi‐1D hexagonal perovskite chalcogenide BaTiS₃ is reported. This material shows a record level of optical anisotropy within the visible wavelength range. In contrast to conventional anisotropic optical materials, the linear dichroism polarity in BaTiS₃ makes an orthogonal change at an optical wavelength corresponding to the photon energy of 1.78 eV. First‐principles calculations reveal that this anomalous linear dichroism conversion behavior originates from the different selection rules of the parallel energy bands in the BaTiS₃ material. Wavelength‐dependent polarized Raman spectroscopy further confirms this phenomenon. Such a material, with linear dichroism conversion properties, could facilitate the sensing and control of the energy and polarization of light, and lead to novel photonic devices such as polarization‐wavelength selective detectors and lasers for multispectral imaging, sensing, and optical communication applications.     

3D numerical modeling of Quantum Dot using homotopy analysis

The 3D numerical modeling of nanoscale InGaAs quantum dot is developed and the characteristics of the device are presented. The exact potential and energy profile of the Quantum Dot are computed by obtaining the solution of 3D Poisson and Schrodinger equations using homotopy analysis. The dark current is estimated by considering the Quantum Dot density, applied voltage, length of quantum dot array, number of quantum dot array and temperature. The results obtained show that the dark current is strongly influenced by Quantum Dot density and applied voltage. The developed model is physics based one and overcomes the limitations of the existing analytical models. The model is validated by comparing the results obtained with the existing models.     

Effect of Morinda Tinctoria Leaves Extract on the Corrosion Inhibition of Mild Steel in Acid Medium

The Morinda tinctoria (MT) plant leaves extract was prepared in aqueous and hydrochloric acid media and was used as corrosion inhibitor for mild steel in hydrochloric acid medium. MT is found to be an efficient inhibitor at room temperature and the efficiency decreases with increase in temperature. Results from colorimetric studies predict the amount of iron present in the test solution and the percentage inhibition efficiency values calculated from this data fit well with the weight loss experiments. The AC impedance studies reveal that the mild steel surface is positively charged and the process of inhibition is through charge transfer. Polarisation studies indicate the mixed nature of the inhibitor. Thermodynamic parameters obtained predict that the process of inhibition is a spontaneous one.     

Control of chaos in SEPIC DC-DC converter

DC-DC converters are widely used in power electronic systems where there is a need for stabilizing a given dc voltage to a desired value. It has been reported that DC-DC converters exhibit different non-linear phenomena including bifurcations, quasi-periodicity and chaos under both voltage mode and current mode control schemes. In this work, current mode controlled SEPIC converter operating in continuous conduction mode is considered and by varying the reference current I_ref, the converter exhibits chaos. It has been observed that the system changes from a stable buck-like operation to an unstable boost-like operation by varying I_ref. Bifurcation diagram is plotted for control signal and capacitor voltage with I_ref as bifurcation parameter. Resonant parametric perturbation control technique has been applied to suppress chaos. Effects of phase shift and frequency mismatch are also analyzed. With phase shift, control power required for suppressing chaos has been reduced. Also intermittent chaotic stages are suppressed with the effect of frequency mismatch at the expense of increasing control power. The stability analysis in SEPIC converter is performed by means of discrete model and is validated through the simulated and experimental results.     

Regulation of Phosphor's Color Gamut Area Using Mesoporous Silicate Source—A New Paradigm for the Solid‐State Lighting Segment

The inception of phosphors provoked the need of highly efficient lighting sources for the conceivable next generation applications. In this regards, a striking characteristic material namely the mesoporous silica (MPS) and their series that are quite distinct to each other in their physical properties have been synthesized by adopting a cooperative self‐assemble strategy. Utilizing it, the development of high‐performance Sr_1?xCa_1?yEu_x+ySiO₄ phosphor was traversed using a simple wet‐solid phase process. Systematic investigations on morphological, structural, and few other physical properties were carried out. The derived results are intriguing with a crystal clear alteration in the phosphor morphology when MPS has been used as a silicate source. Subsequent luminescence studies displayed its efficient yellow‐emitting property covering the red spectral components, along with good thermal luminescence stability. Perhaps, the designed prototype LEDs yielded a color correlation temperature (CCT) < 5000 K and color rendering index (CRI) > 80. Therefore, it directs the way for the fabrication of potential warm white LEDs with a long‐lived emission efficacy and high thermal luminescence stability.     

Microbial mediated dimerization of fattyacids of sunflower oil: An effective role of lipase and biosurfactant

This study emphasizes microbial mediated transformation of sunflower oil to an adhesive product and characterization in detail. Marine bacterial isolates Bacillus (MTCC 5514), when grown in mineral medium, releases both hydrolytic enzymes and surface‐active components during the log phase of growth. When this species was grown in the presence of sunflower oil at an optimized concentration of 5% (w/v) under room temperature, enzymatic hydrolysis of oil proceeds with the release of fatty acids and glycerol. Further, on increasing the incubation period, the presence of surface‐active components, lipase and glycerol, influence the dimerization of the fatty acids, which further, transformed to a polymerized product sunflower oil‐based adhesive product with adhesive nature. Liquid chromatography‐mass spectrometry (electrospray ionization) analysis further authenticates the presence of dimeracids. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40555.     

Effect of indirubin‐3‐monoxime against lung cancer as evaluated by histological and transmission electron microscopic studies

The aim of this study is to evaluate the antitumor effect of indirubin‐3‐monoxime and its mode of action in benzo(α)pyrene [B(α)P] induced lung cancer in A/J mice. Light microscopic examination of lung sections of [B(α)P] induced lung cancer mice revealed the presence of adenocarcinoma characterized by extensive proliferation of alveolar epithelium and loss of alveolar spaces. The control lung tissue showed a normal architecture with clear alveolar spaces. Interestingly the indirubin‐3‐monoxime treated groups showed the reduced adenocarcinoma with appearance of alveolar spaces. Transmission Electron Microscopic (TEM) studies of lung sections of [B(α)P] induced lung cancer mice showed the presence of phaemorphic cells with dense granules and increased mitochondria. The lung sections of mice treated with indirubin‐3‐monoxime showed the presence of shrunken, fragmented, and condensed nuclei implying apoptosis. The effects were dose dependent and prominent in 10 mg/kg/5 d/week groups suggesting the therapeutic role of indirubin analogue against this deadly human malignancy. Here, our results indicate that indirubin‐3‐monoxime brings antitumor effect against [B(α)P] induced lung cancer by its apoptotic action in A/J mice. Microsc. Res. Tech. 73:1053–1058, 2010. © 2010 Wiley‐Liss, Inc.