Epoxy-based anticorrosive coating developed with modified poly(<Emphasis Type="Italic">o</Emphasis>-anisidine) and depolymerized product of PET waste

Poly(o-anisidine) (POA) is used as a modifier in an epoxy system to enhance its anticorrosive properties. The modification of POA is done by aminosilane to introduce amine functionality on the surface. Through this functionality, it becomes part of the coating backbone during curing of an epoxy-polyaminoamide system. The concentration of poly(o-anisidine) has been varied as 1, 3, and 5 wt%. Depolymerized product of polyethylene terephthalate (PET) obtained from aminolysis of PET with ethylamine has amine functionality. Depolymerized product is added at concentrations of only 1 and 3 wt%. The same concentration is used with 5 wt% of silane-modified POA. The synthesized POA and silane-modified POA (Si-POA) have been characterized by FTIR, UV–Visible, and XRD analysis. The coating is characterized by mechanical properties and it is observed that pencil hardness and scratch hardness of the coating were enhanced to 6H and 3.5 kg from 2H and 2.5 kg of a plain epoxy system. The anticorrosive properties of Si-POA are better as compared to plain POA, but the addition of depolymerized product is unable to improve the anticorrosive performance of the coating. In EIS study, it is observed that 5% Si-POA system shows the highest impedance > 10 G (Ω) and it has a tendency to retain anticorrosive performance for longer duration.     

Some aspects of pulsed laser deposited nanocrystalline LaB(6) film: atomic force microscopy, constant force current imaging and field emission investigations

Nanocrystalline lanthanum hexaboride (LaB(6)) films have been deposited on molybdenum foil by the pulsed laser deposition (PLD) technique. The as-deposited films were characterized by x-ray diffraction (XRD), scanning electron microscopy (SEM) and atomic force microscopy (AFM). The XRD pattern shows the cubic crystallinity of the LaB(6) film. The AFM studies reveal that the conical shaped LaB(6) nanostructures have height 60?nm, base 800?nm, and a typical radius of curvature ～20?nm. A comparison of force and in situ current imaging AFM studies reveals that current contrast does not originate from the surface topography of the LaB(6) film. Field emission studies have been performed in the planar diode configuration. A current density of 4.4 × 10(-2)?A?cm(-2) is drawn from the actual emitting area. The Fowler-Nordheim plot is found to be linear, in accordance with the quantum mechanical tunneling phenomenon. The field enhancement factor is estimated to be 3585, indicating that the field emission is from LaB(6) nanocrystallites present on the emitter surface, as confirmed by the AFM. The emission current-time plots show current stability to the extent of 5% fluctuation about the average current over a period of 3?h.     

Chemical Vapor Deposition of B13C2 from BCl3-CH4-H2-Argon Mixtures

The deposition of boron carbide (B₁₃C₂) onto graphite substrates was accomplished by using a hot-wall chemical vapor deposition (CVD) reactor at a pressure of 10.1 kPa in the temperature range of 1000°–1400°C. A modified impinging-jet geometry was used to simplify the mass-transfer analysis. Coatings were characterized using X-ray diffractometry (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The surface morphology was composed of well-defined facets, the size of which was dependent on the growth rate and deposition time, as would be expected from a competitive growth mechanism. TEM micrographs of the coating showed long, columnar grains that emanated from a narrow nucleation zone. The growth rate could be adequately described by a first-order kinetic expression, with respect to the bulk gas phase boron chloride (BCl₃) concentration. The activation energy of the kinetic expression was estimated to be 93.1 kJ/mol. It was proposed that the deposition was limited by the adsorption of (BCl₃) onto the substrate surface.     

Poly(O‐methoxyaniline) thin films: Cyclic voltammetry study

Electrochemical polymerization of poly(O‐methoxyaniline) (POMA) thin films was carried out under cyclic voltammetric conditions. The cyclic voltammograms (CV) of the POMA films in the presence and absence of monomer in the aqueous solution of 1M H₂SO₄ were studied. The electrochemical degradation of the POMA films was investigated by cyclic voltammetry and UV‐visible spectroscopy. It was observed that the rate of degradation is strongly dependent on the applied potential. UV‐visible spectroscopy revealed no significant chemical modification or phase change from the degradation. The temperature dependence of the voltammetric response of the POMA films in the aqueous solution of 1M H₂SO₄ was also investigated. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 3009–3015, 1999     

Field emission studies on electrochemically synthesized ZnO nanowires

Nanocrystalline zinc oxide (ZnO) films were synthesized using cathodic reduction of Zn foil in aqueous electrolyte of different molar concentrations containing ZnCl₂ and H₂O₂, followed by annealing at 400 °C in air. An X-ray diffractometer (XRD), scanning electron microscope (SEM) and transmission electron microscope (TEM) were used for characterization. The XRD patterns exhibited a set of well-defined diffraction peaks corresponding to the wurtzite phase of ZnO. SEM and TEM images clearly revealed the formation of randomly oriented ZnO nanowires having lengths of several microns and diameters less than 100 nm. From the field emission studies, the threshold field values, required to draw emission current density of ∼1 μA/cm² were found to be 1.44, 1.36 and 1.5 V/μm for nanowires synthesized using 0.002, 0.004 and 0.016 M electrolyte concentrations, respectively. All Folwer–Nordheim (F–N) plots showed non-linear behavior indicating semiconducting nature of the emitters. The ZnO nanowires exhibited good emission current stability at the pre-set value of ∼10 μA over a duration of 6 h. The simplicity of the synthesis route coupled with the promising emission properties made the electrochemically synthesized ZnO nanowires a suitable candidate for high-current density applications.     

Experimental platform for development and Evaluation of hybrid generation systems based on fuel cells

An experimental hybrid power generation platform for the design and assessment of advanced control systems has been developed. It is specifically intended as a flexible development tool for the implementation and refinement of real-time novel control algorithms, aimed to maximize energy efficiency and optimize the electrical power management of hybrid generation systems based on fuel cells. The platform consists of two generation modules and storage module. The main one is based on a PEM fuel cell stack. The second one, implemented with a programmable electronic source, allows to emulate an alternative energy module, particularly a wind energy generation system. The storage module is built with Supercapacitors. Finally, a variable electronic load represents the lumped energy demand, with profiles that can be programmed in accordance with the user requirements. All modules of the system are connected to a common DC bus through intermediary electronic converters, which are controlled by a dedicated digital signal processor. The complete system is supervised through a Personal Computer, resulting into a highly versatile platform. Experimental results are presented to validate the whole system performance.     

Conducting polyaniline based paints on low carbon steel for corrosion protection

Conducting polyaniline powder was synthesized chemically and paints containing conducting polyaniline powder were applied on low carbon steel samples. The conducting polyaniline powder was characterized by UV-Visible absorption spectroscopy and the morphology of paint coating on low carbon steel was studied by scanning electron microscopy. The corrosion protection performance of the coating was evaluated by using potentiodynamic polarization techniques and electrochemical impedance spectroscopy. It has been found that the 2 wt % polyaniline-hydrochloric acid based paint coating offers maximum corrosion protection to low carbon steel in chloride medium.     

Nanopatterned electrically conductive films of semiconductor nanocrystals

We present the first semiconductor nanocrystal films of nanoscale dimensions that are electrically conductive and crack-free. These films make it possible to study the electrical properties intrinsic to the nanocrystals unimpeded by defects such as cracking and clustering that typically exist in larger-scale films. We find that the electrical conductivity of the nanoscale films is 180 times higher than that of drop-cast, microscopic films made of the same type of nanocrystal. Our technique for forming the nanoscale films is based on electron-beam lithography and a lift-off process. The patterns have dimensions as small as 30 nm and are positioned on a surface with 30 nm precision. The method is flexible in the choice of nanocrystal core-shell materials and ligands. We demonstrate patterns with PbS, PbSe, and CdSe cores and Zn(0.5)Cd(0.5)Se-Zn(0.5)Cd(0.5)S core-shell nanocrystals with a variety of ligands. We achieve unprecedented versatility in integrating semiconductor nanocrystal films into device structures both for studying the intrinsic electrical properties of the nanocrystals and for nanoscale optoelectronic applications.     

UV radiation induces genome-mediated, site-specific cleavage in viral proteins

Much research has been dedicated to understanding the molecular basis of UV damage to biomolecules, yet many questions remain regarding the specific pathways involved. Here we describe a genome-mediated mechanism that causes site-specific virus protein cleavage upon UV irradiation. Bacteriophage MS2 was disinfected with 254 nm UV, and protein damage was characterized with ESI- and MALDI-based FT-ICR, Orbitrap, and TOF mass spectroscopy. Top-down mass spectrometry of the products identified the backbone cleavage site as Cys46-Ser47 in the virus capsid protein, a location of viral genome-protein interaction. The presence of viral RNA was essential to inducing backbone cleavage. The similar bacteriophage GA did not exhibit site-specific protein cleavage. Based on the major protein fragments identified by accurate mass analysis, a cleavage mechanism is proposed by radical formation. The mechanism involves initial oxidation of the Cys46 side chain followed by hydrogen atom abstraction from Ser47 C(α). Computational protein QM/MM studies confirmed the initial steps of the radical mechanism. Collectively, this study describes a rare incidence of genome-induced protein cleavage without the addition of sensitizers.