Synthesis and electrorheological characteristics of titanate nanotube suspensions under oscillatory shear

In this study, titanate nanotubes (TNTs) were synthesized by hydrothermal treatment of TiO₂ powders (P25) in a NaOH solution. The as-synthesized TNTs exhibit high surface area and large aspect ratio. Rheological properties of TNTs suspensions were then investigated under oscillatory shear. The TNTs fluid shows the viscoelastic behavior and the dynamic moduli (G′, G″) increase significantly by about 4 orders of magnitude as the electric field strength is up to 2.0 kV/mm. Transient response under dynamic shear reveals different changes in the microstructure of TNTs fluid from steady shear. The complex modulus of TNTs fluids is sensitive to temperature while that of P25 fluid become insensitive at higher temperature. Dynamic viscoelastic behavior suggests that structure of P25 to TNTs transition merits the enhancement of ER activity of TNTs fluid.     

Fouling control in sugarcane juice ultrafiltration with surface modified polysulfone and polyethersulfone membranes

Commercial 50 and 100 kD polyethersulfone (PES) and polysulfone (PS) ultrafiltration membranes were surface modified by UV photografting of poly(ethylene glycol) methacrylate (PEGMA) monomer. The modified membranes were characterized by the degree of grafting, water flux and molecular weight cutoff (MWCO) rating. The flux and fouling of the modified and unmodified membranes were examined with sugarcane juice and its polysaccharide fraction. Under the conditions of this study, the modified membranes displayed a low degree of grafting (26-36 μg/cm²), which was independent of the UV exposure duration; however, both membrane water flux and MWCO rating were affected by the irradiation time. In the best case, the modified membranes exhibited lower fouling with sugarcane juice; furthermore, the propensity to foul also decreased. More significantly, juice flux recovery was almost complete for successive UF-cleaning cycles.     

Nanoclay‐reinforced syntactic foams: Flexure and thermal behavior

Syntactic foams containing 60 vol% of hollow glass microballoons in epoxy matrix are modified with untreated nanoclays using combined mechanical and ultrasonication methods. Effects of nanoclays on flexure and thermal behavior of syntactic foams are investigated by adding different amount of nanoclays in the range of 1–3% by weight. Microscopic examinations and physical property characterization are performed to determine the interactions among constituent materials and the void formation during fabrication. It is found that the syntactic foams with 2 wt% nanoclays show the highest improvement in flexural properties (∼42% strength and ∼18% modulus) and dynamic mechanical properties (∼30% storage modulus and ∼28% loss modulus) properties. Thermal decomposition temperature is found to be unaffected by the addition of nanoclays, whereas a continuous reduction in the coefficient of thermal expansion (CTE) is observed. An examination of failure surface indicates that the failure is initiated on the tension side of the flexure sample due to fracturing of microballoons. POLYM. COMPOS., 31:1332–1342, 2010. © 2009 Society of Plastics Engineers     

Effect of Change in Strain Path During Cold Rolling on the Evolution of Microstructure and Texture in Al and Al-2.5%Mg

The effect of change in strain path during cold rolling on the evolution of microstructure and texture is investigated. For this purpose, high purity aluminum and Al-2.5%Mg alloy are deformed (~90% reduction in thickness) by unidirectional and cross cold rolling. Irrespective of the alloy system, copper-type texture is observed in unidirectional processed materials, while strong brass ({011}〈112〉) texture is developed during cross rolling. Unidirectionally rolled aluminum showed higher HAGB fraction, but similar HAGB spacing as compared to the cross-rolled aluminum after 90% reduction in thickness. At the same time, the internal misorientation in the cross-rolled 2N-Al is higher than in the unidirectionally rolled material. In contrast, Al-2.5% Mg alloy processed differently in both ways shows similar HAGB fraction, spacing, and internal misorientation distribution. These observations indicate that microstructure evolution due to strain path change is more strongly affected by dynamic recovery as compared to texture evolution.     

Minimization of exit burr in face milling of medium carbon steel by exit edge beveling

Elimination, or reduction, of burrs formed during machining is drawing focus of manufacturers and researchers since long or suppressing a burr regarding its formation or removal of it through a suitable deburring process. Deburring is an extra process often required to undertake, and it involves additional time and cost. Presence of burr may cause several problems, such as difficulty in assembly, dimensional inaccuracy, injury to the operator, etc. Like other industries, avoidance of burr on milled component surfaces in railways is of concern. In the present investigation, formation of burr in face milling is tried to reduce by beveling the exit edge of blocks of medium carbon steel (45C8) which is widely used in railways for manufacture of different components. Cutting conditions are also varied to observe the effect on burr formation. It is observed that at an exit edge bevel angle of 15°, negligible burr is formed at most of the cutting conditions undertaken, and hence, recommended.     

Effect of spheroidized microstructure on the impact toughness and electrochemical performance of a high-carbon steel

The influence of cementite spheroidization on the impact toughness and electrochemical properties of a high-carbon steel has been thoroughly investigated in this study. Heavy warm rolling, followed by 2 h of annealing, has resulted in near-complete spheroidization, leading to a microstructure consisting of nano-cementite globules dispersed in the ultrafine-grained ferritic matrix. The Charpy impact test exhibited superior impact toughness with increased spheroidization. It is validated by the presence of abundant dimples in the fractographs of spheroidized specimens, in contrast to the as-received one that experienced a brittle failure due to its lamellar pearlitic structure. Potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) carried out in a 3.5% NaCl solution revealed that the corrosion resistance of the alloy gets improved with the increase in the degree of spheroidization. This is attributed to the lower susceptibility of the spheroidized specimen to microgalvanic corrosion owing to the minimum area of contact between nano-spheroidized cementite and ferrite, as elucidated with the help of EIS results aided by equivalent electrical circuit model.     

Augmenting the performance of acrylonitrile–butadiene–styrene plastics for low‐noise dynamic applications

The main objective of this study was to enhance the performance of acrylonitrile–butadiene–styrene (ABS) plastics for dynamic structural applications, including those of automobile relevance. First, ABS was modified by blending with maleic anhydride grafted styrene–ethylene–butadiene–styrene block copolymer (MA‐g‐SEBS) in various proportions. Squeaking noise characteristics were evaluated by measurement of the frictional behavior in an in‐house fabricated friction testing apparatus, and the results are explained on the basis of the change in surface energy upon modification. Detailed dynamic mechanical analyses (strain, frequency, and temperature sweep) revealed significant improvements in the damping characteristics of the modified ABS, especially that modified with 10 wt % MA‐g‐SEBS, without much sacrifice in its mechanical strength. The modulus values predicted with Kerner's model of the blends were well correlated with the morphological changes upon modification. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Removal of 17β-oestradiol and 17α-ethinyl oestradiol from water by activated carbons and hypercrosslinked polymeric phases

There has been growing concern about man-made and naturally occurring chemicals in the environment in recent years. These chemicals interfere with the hormone (or endocrine) system, suggesting far-reaching effects on reproduction and development in current and future man and wildlife generations. Recent research has highlighted the existence of these substances in sewage and industrial effluents and their potential for recycling back into the environment, including drinking water, through point and non-point sources. 17β-Oestradiol (E2) and 17α-ethinyl oestradiol (EE2) are amongst the compounds of concern since they were found to cause adverse effects to fish even at low concentration levels.In this work, the adsorption of E2 and EE2 onto several granular activated carbons and Macronet polymers was investigated by batch experiments after a low level detection system was developed using Gas Chromatography Mass Spectrometry (GC/MS). Equilibrium experiments were carried out for all adsorbents to quantify the sorption capacity for E2 and EE2 and the data were correlated using conventional theoretical treatments. For better assessment of the sorbents, their physical properties including surface area, average pore diameter and micropore volume and chemical structure were characterised by N₂ adsorption experiments. Further characterisation was performed with scanning electron microscopy (SEM), FTIR spectroscopy, sodium capacity determination, pH titration, development of proton-binding curves and zeta potential measurements. Kinetic experiments were performed at different size ranges of adsorbents and the results were analysed by applying a particle diffusion model. This study demonstrates the potential of these adsorbents for the removal of endocrine-disrupting compounds from aqueous solution.     

Nano fibrillated cellulose-based foam by Pickering emulsion: Preparation,characterizations, and application as dye adsorbent

An ecofriendly and biodegradable porous structure was prepared from drying aqueous foams based on nano fibrillated cellulose (NFC), extracted from softwood pulp by subcritical water/CO₂ treatment (SC-NFC). The primary aim of this work was to use the modified SC-NFC as stabilizer for a water-based Pickering emulsion which upon drying, yielded porous cellulosic materials, a good dye adsorbent. In order to exploit the carboxymethylated SC-NFC (CMSC-NFC, with a degree of substitution of 0.35 and a charge density of 649 μeqv/g) as a stabilizer for water-based Pickering emulsion in subsequent step, an optimized quantity of octyl amine (30 mg/g of SC-NFC) was added to make them partially hydrophobic. A series of dry foam structures were prepared by varying the concentrations of treated CMSC-NFCs and 4 wt% was found to be the optimum concentration to yield foam with high porosity (99%) and low density (0.038 g/cc) along with high compression strength (0.24 MPa), superior to the conventionally extracted NFC. The foams were applied to capture as high as 98% of methylene blue dyes, making them a potential green candidate for treating industrial effluent. In addition, the dye adsorption kinetics and isotherms were found to be well suited with second order kinetics and Langmuir isotherm models.