Preparation and characterization of activated carbon from marine macro-algal biomass

Activated carbons prepared from two macro-algal biomass Sargassum longifolium (SL) and Hypnea valentiae (HV) have been examined for the removal of phenol from aqueous solution. The activated carbon has been prepared by zinc chloride activation. Experiments have been carried out at different activating agent/precursor ratio and carbonization temperature, which had significant effect on the pore structure of carbon. Developed activated carbon has been characterized by BET surface area (S(BET)) analysis and iodine number. The carbons, ZSLC-800 and ZHVC-800, showed surface area around 802 and 783 m(2)g(-1), respectively. The activated carbon developed showed substantial capability to adsorb phenol from aqueous solutions. The kinetic data were fitted to the models of pseudo-first-order, pseudo-second-order and intraparticle diffusion models. Column studies have also been carried out with ZSLC-800 activated carbon.     

Development of electromagnetic shielding materials from the conductive blends of polystyrene polyaniline-clay nanocomposite

Electromagnetic interference shielding composite materials were developed from the conductive blends of nanostructured polyaniline-clay composite (PANICN) and Polystyrene (PS) by a one step host matrix assisted emulsion polymerization of anilinium salt of 3-pentadecyl phenol-4-sulphonic acid (3-PDPSA) in clay. 3-PDPSA was derived from cashew nut shell liquid, a low cost renewable resource based product. These blends were characterized using Uv–visible and FT-IR spectroscopy, XRD, electrical conductivity, thermal property, dielectric property and electromagnetic shielding efficiency. The interactions between the primary particles and host matrix were elucidated from the studies made through spectroscopy and rheology. The key finding of the research is that this low cost PANICNPS blend with superior electrical conductivity (7.6 × 10^?1 S/m), excellent thermal stability and EMI SE of 10–20 dB at 8 GHz makes them as a promising candidate for application in EMI shielding and antistatic discharge matrix for the encapsulation of micro electronic devices.     

Nanoscale characterization of natural fibers and their composites using contact-resonance force microscopy

Contact-resonance force microscopy (CR-FM) has been used for the first time to evaluate the mechanical properties of the interphase in natural fiber-reinforced composites and of cell wall layers of natural fibers. With CR-FM, quantitative images of the spatial distribution in nanoscale elastic properties were acquired. The images were calibrated with nanoindentation values. From the modulus images, the average interphase width was found to be (49 ± 5) nm for composite without any treatment, and (139 ± 21) nm for one with a maleic anhydride polypropylene treatment. There was a gradient of modulus across the interphase that ranged between the values of fiber and the polymer. The average values of indentation modulus obtained for different cell wall layers within a fiber were 22.5–28.0 GPa, 17.9–20.2 GPa, and 15.0–15.5 GPa for the S₂ and S₁ layers and the compound middle lamellae, respectively.     

Zinc oxide epitaxial thin film deposited over carbon on various substrate by pulsed laser deposition technique

Zinc Oxide (ZnO) is a promising candidate material for optical and electronic devices due to its direct wide band gap (3.37 eV) and high exciton binding energy (60 meV). For applications in various fields such as light emitting diode (LED) and laser diodes, growth of p-type ZnO is a prerequisite. ZnO is an intrinsically n-type semiconductor. In this paper we report on the synthesis of Zinc Oxide-Carbon (ZnO:C) thin films using pulsed laser deposition technique (PLD). The deposition parameters were optimized to obtain high quality epitaxial ZnO films over a carbon layer. The structural and optical properties were studied by glazing index X-ray diffraction (GIXRD), photoluminescence (PL), optical absorption (OA), and Raman spectroscopy. Rutherford backscattering spectroscopy (RBS), scanning electron microscopy with energy dispersive spectroscopy (SEMEDS) and atomic force microscopy (AFM) were employed to determine the composition and surface morphology of these thin films. The GIXRD pattern of the synthesized films exhibited hexagonal wurtzite crystal structure with a preferred (002) orientation. PL spectroscopy results showed that the emission intensity was maximum at -380 nm at a deposition temperature of 573 K. In the Raman spectra, the E2 phonon frequency around at 438 cm(-1) is a characteristic peak of the wurtzite lattice and could be seen in all samples. Furthermore, the optical direct band gap of ZnO films was found to be in the visible region. The growth of the epitaxial layer is discussed in the light of carbon atoms from the buffer layer. Our work demonstrates that the carbon is a novel dopant in the group of doped ZnO semiconductor materials. The introduction of carbon impurities enhanced the visible emission of red-green luminescence. It is concluded that the carbon impurities promote the zinc related native defect in ZnO.     

Analysis of the Normal-State Magnetotransport in CeIrIn5

We present an analysis of the normal-state magnetotransport in the heavy-fermion superconductor CeIrIn₅. The Hall effect and the transverse magnetoresistance in this material do not appear to be uniquely correlated, as inferred from the field dependence of the current ratio (R _σ =σ _xy /σ _xx ² H). The Hall coefficient is seen to satisfy a scaling equation of the form R _H=f[H/(a+bT ^c )]. These results are compared to those observed earlier in CeCoIn₅, and are discussed in terms of the contrasting phase diagram which the CeIrIn₅ system exhibits in relation to its Co counterpart.     

Reduced‐order modeling of parameterized PDEs using time–space‐parameter principal component analysis

This paper presents a methodology for constructing low‐order surrogate models of finite element/finite volume discrete solutions of parameterized steady‐state partial differential equations. The construction of proper orthogonal decomposition modes in both physical space and parameter space allows us to represent high‐dimensional discrete solutions using only a few coefficients. An incremental greedy approach is developed for efficiently tackling problems with high‐dimensional parameter spaces. For numerical experiments and validation, several non‐linear steady‐state convection–diffusion–reaction problems are considered: first in one spatial dimension with two parameters, and then in two spatial dimensions with two and five parameters. In the two‐dimensional spatial case with two parameters, it is shown that a 7 × 7 coefficient matrix is sufficient to accurately reproduce the expected solution, while in the five parameters problem, a 13 × 6 coefficient matrix is shown to reproduce the solution with sufficient accuracy. The proposed methodology is expected to find applications to parameter variation studies, uncertainty analysis, inverse problems and optimal design. Copyright © 2009 John Wiley & Sons, Ltd.     

Effect of Processing of Sword Beans (Canavalia gladiata) on Physicochemical Properties of Starch

The effect of various processing methods on physico‐chemical properties of sword bean starch was studied. Seed grits and flour were cooked with and without soaking, wet‐autoclaved, and roasted. The changes in starch associated with these processing methods were studied by observing changes in granular structure, water solubility index, water absorption index, molecular size distribution and the degree of gelatinization estimated by differential scanning calorimetry. Intact, ungelatinized starch granules of raw and dry‐heat treated samples were observed under the light microscope. The starch granules were elliptical in shape and had an average length and breadth of 37–40 μm and 27 μm, respectively. Wet‐processed samples had the lowest water solubility, higher water absorption and lower gelatinization enthalpies than the raw bean flour, whereas the dry heat‐treated samples showed higher water solubility and higher gelatinization enthalpies. The starch molecular size distribution pattern showed a higher amount of high molecular size carbohydrates in dry heat‐treated samples and a large fraction of intermediate molecular size carbohydrates in the wet‐processed samples. The low molecular size carbohydrate content was low in wet‐processed samples where processing was done with excess water.     

Phase-pure two-dimensional FexGeTe2 magnets with near-room-temperature Tc

Two-dimensional(2D)ferromagnets with out-of-plane(OOP)magnetic anisotropy are potential candidates for realizing the next-generation memory devices with ultra-low power consumption and high storage density.However,a scalable approach to synthesize 2D magnets with OOP anisotropy directly on the complimentary metal-oxide semiconductor(CMOS)compatible substrates has not yet been mainly explored,which hinders the practical application of 2D magnets.This work demonstrates a cascaded space confined chemical vapor deposition(CS-CVD)technique to synthesize 2D FexGeTe₂ ferromagnets.The weight fraction of iron(Fe)in the precursor controls the phase purity of the as-grown FexGeTe2.As a result,high-quality Fe₃GeTe₂ and Fe₅GeTe₂ flakes have been grown selectively using the CS-CVD technique.Curie temperature(Tc)of the as-grown FexGeTe2 can be up to-280 K,nearly room temperature.The thickness and temperature-dependent magnetic studies on the Fe₅GeTe₂ reveal a 2D Ising to 3D XY behavior.Also,Terahertz spectroscopy experiments on Fe₅GeTe₂ display the highest conductivity among other FexGeTe₂ 2D magnets.The results of this work indicate a scalable pathway for the direct growth and integration of 2D ternary magnets on CMOS-based substrates to develop spintronic memory devices.     

Addition-fragmentation of 5-bromopenta-1,3-diene in free radical polymerization of methyl methacrylate

5-Bromopenta-1,3-diene (BPD) was examined as an addition-fragmentation chain transfer agent (AFCTA) in the free radical polymerization of methyl methacrylate (MMA). Studies of the kinetics of polymerization in the presence of this compound showed it to be a very effective chain transfer agent and that retardation was not significant, implying efficient reinitiation by the expelled Br radical. Analysis of the resulting polymers showed that the intermediate radical formed by the addition of the propagating radical to the C₁ carbon of BPD underwent exclusive fragmentation. However, addition on the C₄ carbon, with a relative probability of 0·6, led to its copolymerization with MMA. Kinetic studies showed BPD to be a better chain-end functionalization agent than its 5-t-butyl thio derivative for deriving pentadiene-functional macromonomer. © 1998 SCI.     

Physical and rheological characteristics of liquid natural rubber modified bitumen

Polymer modification of commercially available bitumen has been attempted by the incorporation of liquid natural rubber (LNR) of medium viscosity. Both soft and blown bitumens have been studied. Physical and rheological characteristics of the samples were investigated. Improvement in physical properties such as shear strength and ductility in the case of blown bitumen and resistance to flow in the case of soft bitumen were observed. It was also found that as a result of addition of LNR, the activation energy of flow increases in the case of soft bitumen and decreases in blown bitumen. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 68:53–61, 1998