Additive Manufacturing of Ceramics Enabled by Flash Pyrolysis of Polymer Precursors with Nanoscale Layers

We show that a polymer‐based route to ceramics can be implemented into additive manufacturing by reducing the time for pyrolysis to about a second, which we call flash pyrolysis. Repetitive deposition of nanometer scale coatings of the ceramic, in this way, is employed to create defect‐free infiltrations of carbon fiber composites. The mechanical strength of the fibers is retained in the composite. Excellent wetting properties of the polymer precursor permits three‐dimensional, conformal coating through the three stages of infiltration: nanoscale coating of the single fibers, filling of interstitial spaces between the fibers, and a buildup of the coating over the entire composite. The flash pyrolysis method will enable a new genre of polymer‐derived ceramics made into net shape by this unusual method of additive manufacturing.     

Synthesis of nanostructured copper hexacyanidoferrate and its application in voltammeteric detection of salbutamol

Nanostructured copper hexacyanidoferrate has been synthesized and characterized using elemental analysis, atomic absorption spectroscopy, thermal and infrared spectral studies. The transmission electron microscopic studies of the synthesized material showed that it consisted of irregular oval and rod shaped particles with a size range 70–100 nm. Nanostructured copper hexacyanidoferrate modified glassy carbon electrode was characterized by cyclic voltammetery and nanostructured copper hexacyanidoferrate–carbon nanotube composite material modified glassy carbon electrode has been used for electrocatalytic oxidation of salbutamol. The electrode modified with composite material was found to reduce the peak potential of oxidation of salbutamol by nearly 90 mV.     

pH‐sensitive crosslinked guar gum‐based superabsorbent hydrogels: Swelling response in simulated environments and water retention behavior in plant growth media

Crosslinked guar gum‐g‐polyacrylate (cl‐GG‐g‐PA) superabsorbent hydrogels were prepared to explore their potential as soil conditioners and carriers. The hydrogels were prepared by in situ grafting polymerization and crosslinking of acrylamide onto a natural GG followed by hydrolysis. Microwave‐initiated synthesis under the chosen experimental conditions did not exhibit any significant improvement over the conventional technique. The optimization studies of various synthesis parameters, namely, monomer concentration, crosslinker concentration, initiator concentration, quantity of water per unit reaction mass, particle size of backbone, and concentration of alkali were performed. The hydrogels were characterized by wide‐angle X‐ray diffraction, scanning electron microscopy, Fourier transform infrared spectroscopy, and solid‐state ¹³C‐NMR spectroscopy. Swelling behavior of a candidate hydrogel [GG‐superabsorbent polymer (SAP)] in response to external stimuli, namely, salt solutions, fertilizer solutions, temperature, and pH, was studied. The GG‐SAP exhibited significant swelling in various environments. The effect of GG‐SAP on water absorption and the retention characteristics of sandy loam soil and soil‐less medium were also studied as a function of temperature and moisture tensions. The addition of GG‐SAP significantly improved the moisture characteristics of plant growth media (both soil and soil‐less), showing that it has tremendous potential for diverse applications in moisture stress agriculture. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 41060.     

Phase behaviour modelling of Athabasca bitumen for in situ combustion applications

Phase behaviour modelling of reservoir fluid is a fundamental step for reservoir simulation. Furthermore, as the complexity of the recovery process increases, the fluid model plays a more important role in the reliability of the simulation outputs. Although the in situ combustion enhanced oil recovery method (ISC) is one of the most complex recovery techniques available in the petroleum engineering literature, for most of the simulation jobs related to this elaborate process only simple and rudimentary fluid characterization layouts are considered. In this work, the principal fluid properties of Athabasca bitumen with regard to the ISC process are recognized, extracted from the literature, validated for consistency, and used for the development of an inclusive and accurate fluid model. Then the fluid model is fully developed while considering the ISC reaction kinetics so that the model has both accuracy, indispensable for phase behaviour modelling, and consistency, essential for the reactions definitions.     

Solid Yttria-Stabilized Zirconia Films by Pulsed Chemical Vapor Deposition from Metal-organic Precursors

A pulsed chemical vapor deposition from metal-organic precursors (MOCVD) system was used to produce solid zirconia, and yttria-stabilized zirconia (YSZ) films. A total of six candidate metal-organic precursors for zirconia and three for yttria were investigated. Three precursor solutions for YSZ proved suitable for pulsed-MOCVD processing. Layers were deposited on metal, alumina, and porous nickel cermet substrates. Under optimal deposition conditions, precursor conversion efficiency of 90% was achieved using a solution of 3.74 vol% zirconium 2-methyl-2-butoxide + 0.42% yttium methoxyethoxide in toluene. The film growth rate was 7.5 μm·h⁻¹ at 525°C deposition temperature. Two alkoxide precursors produced YSZ layers with material costs under $0.50/(μm·cm²).     

Dynamic mechanical analysis and broadband electromagnetic interference shielding characteristics of poly (vinyl alcohol)-poly (4-styrenesulfonic acid)-titanium dioxide nanoparticles based tertiary nanocomposites

ABSTRACT

Novel tertiary nanocomposite films comprising of poly (vinyl alcohol) (PVA), poly (4-styrenesulfonic acid) (PSSA) and titanium dioxide (TiO₂) nanoparticles (NP_S) were prepared using simple solvent casting method. The structural, thermal, morphological, thermo-mechanical and electromagnetic interference (EMI) shielding properties of PVA/PSSA/TiO₂ nanocomposite films were investigated. The EMI shielding effectiveness (SE) of PVA/PSSA/TiO₂ nanocomposite films in the X and Ku band was found to be 12 dB and 13 dB respectively at 25 wt% TiO₂ NPs loading. These results demonstrate the possible applications of PVA/PSSA/TiO₂ nanocomposite films as low cost, lightweight and flexible material for EMI shielding.     

Elucidating the Effects of Cu‐Nanoparticles in a Porous Medium vis‐à‐vis Heat Transfer Phenomena

In this paper, a numerical simulation technique is developed to investigate the qualitative and quantitative behaviour of Cu‐nanoparticles in a porous medium vis‐a‐vis the heat transfer enhancements—buoyancy driven flow in a two‐dimensional square cavity, with moving walls is presented. The model utilizes the finite volume approach to solve the Brinkman–Darcy equations for Cu‐nanoparticles in a porous media. Discretization is carried out for convective and diffusive fluxes using Quadratic Upwind Interpolation for Convective Kinematics (QUICK) and central difference schemes, respectively. Tri‐Diagonal Matrix Algorithm is invoked to solve the set of algebraic equations. The Darcy number (Da), Prandtl number (Pr), and volume fraction (χ) are varied from 10^?3 to 10^?1, 3 to 7, and 0% to 20%, respectively. Insight into the cause of variations in isotherms, streamlines, Nusselt number (Nu), and mid‐plane velocities is explicated. The present numerical results are compared with the existing literature and found to be in good agreement. Even though nanoparticles slightly hinder the activity of the fluid, they can augment the average Nu by 90% for Pr = 7, Da = 0.1, and χ = 20% as compared to the absence of nanoparticles. Their efficacy is more prominent for flows with higher Da and Pr. Quantitative values for Nu were obtained for various combinations of Pr, Da, and χ.     

A green and facile one-pot synthesis of Ag–ZnO/RGO nanocomposite with effective photocatalytic activity for removal of organic pollutants

In this study, Ag–ZnO/reduced graphene oxide (Ag–ZnO/RGO) composite was synthesized by a green and facile one-step hydrothermal process. Aqueous suspension containing Ag and ZnO precursors with graphene oxide (GO) sheets was heated at 140 °C for 2 h. The morphology and structure of as-synthesized particles were characterized by field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), Raman spectroscopy, and Photoluminescence (PL) spectroscopy which revealed the formation of composite of metal, metal oxide and RGO. It was observed that the presence of Ag precursor and GO sheets in the hydrothermal solution could sufficiently decrease the size of ZnO flowers. The hybrid nanostructure, with unique morphology, obtained from this convenient method (low temperature, less time, and less number of reagents) was found to have good photocatalytic and antibacterial activity. The perfect recovery of catalyst after reaction and its unchanged efficiency for cyclic use showed that it will be an economically and environmentally friendly photocatalyst.     

rGO Sheets/ZnFe2O4 Nanocomposities as an Efficient Electro Catalyst Material for I3−/I− Reaction for High Performance DSSCs

In this paper, Reduced Graphene Oxide (rGO)/ZnFe₂O₄ (rZnF) nanocomposite is synthesized by a simple hydrothermal method and employed as a counter electrode (CE) material for tri-iodide redox reactions in Dye sensitized solar cells (DSSC) to replace the traditional high cost platinum (Pt) CE. X-ray diffraction analysis and High resolution Transmission electron microscopy, clearly indicated the formation of rZnF nanocomposite and also amorphous rGO sheets were smoothly distributed on the surface of ZnFe₂O₄ (ZnF) nanostructure. The rZnF-50 CE shows excellent electro catalytic activity toward I₃^? reduction, which has simultaneously been confirmed by cyclic voltammetry, electrochemical impedance spectroscopy and Tafel polarization measurements. A DSSC developed by rZnF-50 CE (η?=?8.71%) obtained quite higher than the Pt (η?=?8.53%) based CE under the same condition. The superior performances of rZnF-50 CE due to addition of graphene in to Spinel (ZnF) nanostructure results in creation of highly active electrochemical sites, fast electron transport linkage between CE and electrolyte. Thus it’s a promising low cost CE material for DSSCs.