Effect of DC glow discharge treatment on the surface energy and surface resistivity of thin film of polypropylene

A change in the surface energy and surface resistivity of a thin film of polypropylene (PP) of thickness 100 μm was investigated, using direct current (DC) glow discharge. The thin film of the PP was treated for various discharge powers and treatment time and the modification in the surface energy and the surface resistivity was observed. To investigate the modification in the surface energy after DC glow discharge treatment, contact angle of two test liquids formamide and de‐ionized water over the surface of PP film was measured. By measuring the contact angle the change in surface energy and its two polar and dispersive components have been measured. It was observed that at a given power level of DC glow discharge surface energy and its polar component increases with increase of the treatment time, attains a maximum value, and then becomes almost constant. Correspondingly, with increase in surface energy, a decrease in surface resistivity was observed. Also, a change in surface morphology was observed by atomic force microscopy and by FT‐IR spectra generation of polar groups at the surface of PP film. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 767–772, 2007     

Cure characteristics,morphology, and mechanical properties of ethylene–propylene–diene–monomer rubber/acrylonitrile butadiene rubber blends

Blends based on ethylene–propylene–diene monomer rubber (EPDM) and acrylonitrile butadiene rubber (NBR) was prepared. Sulfur was used as the vulcanizing agent. The effects of blend ratio on the cure characteristics and mechanical properties, such as stress–strain behavior, tensile strength, elongation at break, hardness, rebound resilience, and abrasion resistance have been investigated. Tensile and tear strength showed synergism for the blend containing 30% of NBR, which has been explained in terms of morphology of the blends attested by scanning electron micrographs. A relatively cocontinuous morphology was observed for 70 : 30, EPDM/NBR blend system. The experimental results have been compared with the relevant theoretical models. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

A novel catalyst for the Knoevenagel condensation of aldehydes with malononitrile and ethyl cyanoacetate under solvent free conditions

A novel, efficient and eco-friendly MgO/ZrO₂ catalyst is put forward for the Knoevenagel condensation. The as synthesized catalyst MgO/ZrO₂ was characterized by elemental analysis, XRD, FTIR, particle size, SEM–EDXS, average pore diameter, BET surface area analysis, and thermal gravimetric analysis. The Knoevenagel condensation of several aldehydes with ethyl cyanoacetate and malononitrile was carried out at 60 °C on MgO/ZrO₂ catalyst in the absence of solvent.     

Investigations of Wear Response of Pure Mg and Mg-0.4 Ce-Y2O3/ZnO Nanocomposites Using a Single and Repeated Scratch Tests

ABSTRACT

This work examines the micrometer-scale wear behavior of pure Mg and its composites at various loads (100–500 mN) under single and multiple scratch conditions. The Mg-0.4Ce alloy reinforced with nanoparticles of zinc oxide (ZnO) and yttrium oxide (Y₂O₃) is investigated. The effect of reinforcement addition on wear characteristics and the coefficient of friction (COF) was evaluated. Moreover, the influence of number of scratches on wear quantification and wear mechanism was deduced at different loads. The results suggest that both the mechanical and tribological performance of ZnO-reinforced composite is significantly better than that of the Y₂O₃-reinforced composite, which can be attributed to a low COF and higher strengthening due to ZnO addition.     

Structural and optical properties of tin oxide branched nanostructures

Branched nanostructures of tin oxide (SnO2) have been synthesized by Vapor-Liquid-Solid (VLS) mechanism using a gold catalyst in the temperature range of 800-850 degrees C under an ambient gas flow of 200 sccm. The microstructural and the optical properties of the as prepared products have been studied by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), micro-Raman, and photoluminescence (PL) studies. SnO2 branches with a rutile phase are found to have a preferential orientation along (101). Typical lengths of these branches are found to be approximately 3-5 microm and diameters in the range of 50-100 nm. Selected area electron diffraction (SAED) pattern shows that the SnO2 branches have a tetragonal cross section with [101] crystal direction. A Raman line at 631 cm(-1) (Sn-O bond) is obtained in the micro Raman spectra. Low temperature PL spectrum shows a strong green emission band near 506 nm.     

Vibration analysis of a poroelastic composite hollow sphere

Vibrations in a poroelastic composite hollow sphere are investigated employing Biot’s theory of wave propagation in poroelastic media. A composite hollow poroelastic sphere consists of two concentric poroelastic spherical layers both of which are made of different poroelastic materials with each poroelastic material being homogeneous and isotropic. The boundaries of the composite hollow poroelastic sphere are free from stress. The frequency equations of both radial and rotatory vibrations are obtained each for pervious and impervious surfaces. The frequency equation of vibrations of a poroelastic composite hollow sphere with rigid core is derived as a particular case. The non-dimensional frequency for propagating modes is computed as a function of ratio of thickness to inner radius of core. The results are presented graphically for two types of poroelastic composite spheres and then discussed.     

Biocompatible glutathione capped gold clusters as one- and two-photon excitation fluorescence contrast agents for live cells imaging

The one- and two-photon excitation emission properties of water soluble glutathione monolayer protected gold clusters were investigated. Strong two-photon emission was observed from the gold clusters. The two-photon absorption cross section of these gold clusters in water was deduced from the z-scan measurement to be 189?740 GM, which is much higher compared to organic fluorescent dyes and quantum dots. These gold clusters also showed high photo-stability. The MTT assay showed that these gold clusters have low toxicity even at high concentrations. We have successfully demonstrated their applications for both one and two-photon excitation live cell imaging. The exceptional properties of these gold clusters make them a promising alternative for one- and two-photon bio-imaging and other nonlinear optical applications.     

Synthesis,characterization, and properties of flexible magnetic nanocomposites of cobalt ferrite–polybenzoxazine–linear low‐density polyethylene

A simple method for the preparation of magnetic nanocomposites consisting of cobalt ferrite (CF; CoFe₂O₄) nanoparticles, polybenzoxazine (PB), linear low‐density polyethylene (LLDPE), and linear low‐density polyethylene‐g‐maleic anhydride (LgM) is described. The composites were prepared by the formation of benzoxazine (BA)–CF nanopowders followed by melt blending with LLDPE and the thermal curing of BA. The composites were characterized by X‐ray diffraction, thermogravimetric analysis, differential scanning calorimetry, scanning electron microscopy, universal testing machine measurement, and vibrating sample magnetometry. The composites consisting of LLDPE, PB, and LgM (47.5L–47.5PB–5LgM) exhibited a higher tensile strength (23.82 MPa) than pure LLDPE and a greater elongation at break (6.11%) than pure PB. The tensile strength of the composites decreased from 19.92 to 18.55 MPa with increasing CF loading (from 14.25 to 33.25 wt %). The saturation magnetization of the composites containing 33.25 wt % CF was 18.28 emu/g, and it decreased with decreasing amount of CF in the composite. The composite films exhibited mechanical flexibility and magnetic properties. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

N and P metal oxide semiconductor field effect transistor characteristics of hafnium-doped SiO2 gate dielectrics

This work presents the interfacial properties of hafnium-doped SiO₂ films via N and P metal oxide semiconductor (MOS) materials, MOS-capacitor, and N and P metal oxide semiconductor field effect transistor (MOSFET) characterization. The results indicate that HfSi_xO_y films (a) have excellent transistor characteristics; (b) remain amorphous through high-temperature processing; (c) are compatible with N+ and P+ polysilicon electrodes; (d) have lower gate leakage than SiO₂ of the same equivalent oxide thickness (EOT); and (e) have a dielectric constant of ∼8. Therefore, the hafnium-doped SiO₂ films are at-tractive as a dielectric material and offer a technologically relevant gate-stack node for insertion, prior to deployment of high-K dielectrics.     

Repeat sequence proteins as matrices for nanocomposites

Recombinant protein–inorganic nanocomposites comprised of exfoliated Na⁺ montmorillonite (MMT) in a recombinant protein matrix based on silk-like and elastin-like amino acid motifs (silk elastin-like protein (SELP)) were formed via a solution blending process. Charged residues along the protein backbone are shown to dominate long-range interactions, whereas the SELP repeat sequence leads to local protein/MMT compatibility. Up to a 50% increase in room temperature modulus and a comparable decrease in high temperature coefficient of thermal expansion occur for cast films containing 2–10 wt.% MMT.