Experimental investigation on flow improvement in compressor cascades

There is no general rule in the literature to help choose a correct flow control device for any given case of turbomachinery applications. This suggests individual optimization of flow control devices for each specific case. The objective of this study is to prove experimentally the benefits of passive control methods in improving the compressor performance. This allows to reduce the fuel consumption, leading to energy saving and reduction of atmospheric pollution. Two features have been controlled in this study: flow separation over the blade surfaces and the secondary flow over the cascade endwalls. Vortex generator ribs are tested on the blade suction side for flow reattachment on the blade surfaces, and low‐profile vortex generators are tested on the side walls of the compressor cascade against secondary flow losses. Different vortex generator designs are compared for total pressure recovery, flow turning, boundary layer characteristics, and pressure distributions over the endwalls. Copyright © 2016 John Wiley & Sons, Ltd.     

Study on the behavior of the trace metal and macro minerals in Mytilus galloprovincialis as a bioindicator species: the case of Marmara Sea, Turkey

Sea food is a major source of animal protein. Marine foods are very rich sources of mineral components. The total content of minerals in the raw flesh of marine fish and invertebrates is in the range of 0.6–1.5% wet weight. The contents of Na, K, Ca, Mg and P are up to 1 mg/100 g, whereas those of Fe, Zn, I are less than 1 mg/100 g. Mussels (Mytilus galloprovincialis) were investigated for macro and trace element composition throughout the year. Ranges of moisture, ash, protein and fat contents were 79.76–87.46 g/100 g, 1.06–2.06 g/100 g, 7.28–12.65 g/100 g and 0.33–3.49 g/100 g, respectively. While the highest protein and fat values were found in the summer (July–August), the highest moisture and ash contents were found in the winter (December–January). The contents of highest Na, K, Ca were found in the summer. Cadmium, lead and copper were found to be below the legislative limits throughout year. High levels of mercury were found in January and October. It should be discussed whether mussel may provide an alternative source of mineral for healthy nutrition.     

Effects and modelling of ultrasonic waste‐activated sludge disintegration

Sonication is a well‐known sludge pretreatment technique with the advantages of simple operation and high efficiency. However, it is an energy‐intensive process. Hence, it is very important to predetermine its sludge disintegration efficiency at varying pretreatment conditions in order to minimize the ultrasonic energy consumption. In this study, it was found that the ultrasonic sludge disintegration occurred in two stages: rapid and subsequent slow disintegration stages. For this reason, it was aimed to develop a simple and accurate mathematical model to describe the two‐stage sludge disintegration as a function of pretreatment conditions. Sludge concentration and ultrasonic density along with sonication period were involved in this model as independent variables. It was determined that the mathematical model can predict accurately the degree of sludge disintegration. Thus, the proposed model was seen to be very useful for evaluating the disintegration efficiency and/or for process design using the operating parameters under different conditions.     

Novel colloidal nanofiber electrolytes from PVA‐organoclay/poly(MA‐alt‐MVE), and their NaOH and Ag‐carrying polymer complexes

Novel multifunctional polymer nanofiber electrolytes with covalence crosslinked structures from various solution blends of reactive intercalated poly(vinyl alcohol)/octadecylamine montmorillonite (as a matrix polymer), poly(maleic anhydride‐alt‐methyl vinyl ether) (as a partner polymer) and their NaOH‐absorbing and Ag‐carrying polymer complexes were fabricated via electrospinning. Chemical, physical, morphological, and electrical properties of nanofiber structures were investigated by FTIR, XRD, SEM, and electrical analysis methods. Ag precursors in fiber composites significantly improved phase separation processing, fiber morphologies, diameter distributions, and electrical properties of the fibers. In situ generation of Ag nanoparticles and their distribution on nanofiber surfaces during fiber formation occurred via complex formation between silver cations and electronegative functional groups from both matrix and partner polymers as stabilizing/reducing agents. Electrical resistance and conductivity strongly depended on matrix/partner polymer ratios and absorption time of NaOH solution on nanofibers. Addition of NaOH changed the electrical properties of fiber structures from almost dielectric state to excellent conductivity form. The fabricated unique nanofiber electrolytes are promising candidates for applications in power and fuel cell nanotechnology, electrochemical, and bioengineering processes as reactive semiconductive platforms. POLYM. ENG. SCI., 56:204–213, 2016. © 2015 Society of Plastics Engineers     

Stabilized electrospinning of heat stimuli/in situ crosslinkable nanofibers and their self‐same nanocomposites

We present a strategy for stabilizing the morphological integrity of electrospun polymeric nanofibers by heat stimuli in situ crosslinking. Amorphous polymer nanofibers, such as polystyrene (PS) and its co‐polymers tend to lose their fiber morphology during processing at temperatures above their glass transition temperature (T_g) typically bound to happen in nanocomposite/structural composite applications. As an answer to this problem, incorporation of the crosslinking agents, phthalic anhydride (PA) and tributylamine (TBA), into the electrospinning polymer solution functionalized by glycidylmethacrylate (GMA) copolymerization, namely P(St‐co‐GMA), is demonstrated. Despite the presence of the crosslinker molecules, the electrospinning polymer solution is stable and its viscosity remains unaffected below 60 °C. Crosslinking reaction stands‐by and can be thermally stimulated during post‐processing of the electrospun P(St‐co‐GMA)/PA‐TBA fiber mat at intermediate temperatures (below the T_g). This strategy enables the preservation of the nanofiber morphology during subsequent high temperature processing. The crosslinking event leads to an increase in T_g of the base polymer by 30 °C depending on degree of crosslinking. Crosslinked nanofibers are able to maintain their nanofibrous morphology above the T_g and upon exposure to organic solvents. In situ crosslinking in epoxy matrix is also reported as an example of high temperature demanding application/processing. Finally, a self‐same fibrous nanocomposite is demonstrated by dual electrospinning of P(St‐co‐GMA) and stabilized P(St‐co‐GMA)/PA‐TBA, forming an intermingled nanofibrous mat, followed by a heating cycle. The product is a composite of crosslinked P(St‐co‐GMA)/PA‐TBA fibers fused by P(St‐co‐GMA) matrix. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 44090.     

Specific heavy metal ion recovery with ion‐imprinted cryogels

In this study, the functional monomers, N‐methacryloyl‐l ‐aspartic acid and N‐methacryloyl‐l ‐cysteine were synthesized through a reaction between appropriate amino acids and methacryloyl chloride. Then, Pb(II) or Cd(II) ion‐imprinted 2‐hydroxyethyl methacrylate based cryogels were prepared by free radical polymerization method under partially frozen conditions. Following the characterization of matrices, adsorption of heavy metal ions was examined in batch mode from aqueous solution considering several parameters affecting the adsorption performance. The actual adsorption capacities were 44.5, 65.3, and 86.7 mg/g for Cd‐1, Cd‐2, and Cd‐3 cryogels meanwhile those were 41.9, 86.3, and 122.7 mg/g for Pb‐1, Pb‐2, and Pb‐3 cryogels, respectively at optimum pH: 5.5. By increasing temperature, adsorption capabilities of both cryogels were inhibited because of the electrostatic nature of coordinated covalent bonds and collapsing of coordination spheres. The adsorption process was very fast, the equilibrium adsorption was achieved in about 60 min, which was directly related to macroporous structure and interconnected flow‐channels of cryogels. Kinetics and adsorption isotherms were also studied. Langmuir isotherms and pseudo‐second order kinetic model were well suited to adsorption data, which also indicated that the process occurred without any diffusion restrictions or steric hindrances. Finally, the competitive adsorption studies were performed using multi‐ion containing synthetic wastewater to show whether the cryogels developed are suitable for specific heavy metal recycling or not. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43095.     

Pt nanoparticles synthesized with new surfactants: improvement in C1–C3 alcohol oxidation catalytic activity

Platinum electrocatalysts were prepared using PtCl₄ as a starting material and 1-decylamine, N,N-dimethyldecylamine, 1-dodecylamine, N,N-dimethyldodecylamine, 1-hexadecylamine, and 1-octadecylamine as surfactants. These surfactants were used for the first time in this synthesis to determine whether the primary and/or tertiary structure and/or chain length of the surfactants, affects the size and/or activity of the catalysts in C₁–C₃ alcohol electro-oxidation reactions. Electrochemical measurements (cyclic voltammetry and chronoamperometry) indicated that the highest electrocatalytic performance was observed for the Pt nanocatalysts that were stabilized by N,N-dimethyldecylamine, and this has a tertiary amine structure with a short chain length (R = C₁₀H₂₁). The high performance may be due to the high electrochemical surface area, Pt(0)/Pt(IV) ratio, %Pt utility, and roughness factor (R _f). X-ray photoelectron spectroscopy, X-ray diffraction, atomic force microscopy, and transmission electron microscopy were used to determine the parameters that affect the catalytic activities.     

Hybrid dual-curable cyanate ester/boron phosphate composites via sequential thiol-ene photopolymerization and thermal polymerization

The aim of this study was to improve hybrid dual-curable cyanate ester/boron phosphate composites via sequential thiol-ene photopolymerization and thermal polymerization for high performance applications such as aerospace and electronic devices. A novel 2,2′-diallylbisphenol A dicyanate ester (DA-BADCy) which is the allyl group containing cyanate ester was synthesized and characterized. DA-BADCy, silicon containing monofunctional thiol compound, trifunctional thiol compound and boron phosphate were cured using both ultraviolet (UV) and thermal methods. Using thiol-ene system, cyanate ester formulations, which are normally prepared at high temperatures, were prepared at room temperature. This study maintains ease of application for cyanate esters. Thermal stability, flammability and thermal conductivity of the samples were evaluated by thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), limiting oxygen index (LOI) and laser flash method, respectively. The samples were characterized with the following analysis; gel content, water absorption capacity and stress–strain test. Hydrophobicity of the samples was determined by the contact angle measurements. Moreover, the surface morphology of the samples was investigated by a scanning electron microscopy (SEM–EDS). The obtained results prove that the composites have good thermal and mechanical properties and with the help of easier preparation techniques, they can be used in many applications such as aerospace, electronic devices, materials engineering.