An Investigation on the Fatigue Fracture of P/M Al-SiC Nanocomposites

A tensile-compression fatigue response of Al matrix composites containing different amount of SiC nanoparticles (50 nm diameter) up to 6 vol. pct was studied. The nanocomposite powders were prepared by a powder metallurgy (P/M) route consisting of mechanical alloying, hot extrusion, and hot closed-die forging. The microstructure of the materials was evaluated by optical microscopy, scanning and transmission electron microscopies, and electron backscattered diffraction. A fine distribution of the nanoparticles in submicron and ultrafine grains was obtained. The low cycle fatigue behavior was examined in stress control mode under fully reversed tension-compression cycle at 1 Hz up to 1000 cycles. High cycle fatigue was conducted using a push-pull test up to 10⁷ cycles with the minimum to maximum stress ratio of 0.1 at a frequency of 40 Hz. Cyclic hardening was observed at a low cycle fatigue regime with an enhanced hardening rate in the presence of SiC nanocomposite. The fatigue endurance limit at 10⁷ cycles was also improved by nanoparticles. Fractographic studies revealed a mixture of ductile-brittle fracture modes with an increase in the ductile fracture mode at higher SiC fractions. The fatigue fracture mechanism was found to be local ductile deformation, microscopic void formation, and coalescence.     

Cavity Control of Prefoldin Nano Actuator (PNA) by Temperature and pH

Nano-Micro Letters - A molecular dynamics study to investigate the cavity control of Prefoldin based bio nano actuator is presented in this paper. Prefoldin is a molecular chaperone with a...     

One-pot synthesis of hematite-alumina hollow sphere composite by ultrasonic spray pyrolysis technique with high adsorption capacity toward PAHs

A hybrid nanocomposite of alumina and hematite was synthesized by ultrasonic spray pyrolysis technique. The study of microscopic images, mapping analysis, and XRD patterns revealed that the Al₂O₃ – Fe₂O₃ nanocomposite was composed of separated spherical particles with a thin layer ball-shaped structure that metal oxides are uniformly distributed in the wall of hollow sphere particles, led to a coherent and monotonous construction. A series of coefficients of equilibrium sorption of polycyclic aromatic hydrocarbons (PAHs) as hazardous materials were measured on the prepared composite material in a batch technique. The free or pure Al₂O₃ or Fe₂O₃ showed negligible removal efficiency for the mentioned analytes. The various significant variables, such as initial analyte concentration, solution pH, adsorbent dose, and contact time to remove analyte, were studied in the aqueous solutions. Adsorption data were modeled to Langmuir, Freundlich, and Temkin isotherms, and a good correlation found in the case of Langmuir isotherm and adsorption capacity for anthracene, phenanthrene, and naphthalene were 370, 333, and 322 mg g^?1, respectively. Investigation of the kinetic models proved a pseudo-second-order, and the prepared adsorbent can be reused more than 7 times without a significant decrease of adsorption performance.     

The Effects of One and Double Heat Treatment Cycles on the Microstructure and Mechanical Properties of a Ferritic–Bainitic Dual Phase Steel

Metallurgical and Materials Transactions A - In this study, samples with ferritic–bainitic dual phase structures consisting of 62 pct bainite were obtained from the AISI 4140 steel...     

Performance improvement of microbial fuel cell through artificial intelligence

The current work introduces an enhancement in the performance of the microbial fuel cell through estimating the optimal set of controlling parameters. The maximization of both power density (PD) and the percentage of chemical oxygen demand (COD) removal were considered as the enhancement in the cell's performance. Three main parameters in terms of performance as well as commercialization are the system's inputs; the Pt which takes the range of 0.1‐0.5 mg/cm², the degree of sulphonation in sulfonated‐poly‐ether‐ether‐ketone that changes in the range of 20‐80%, and the rate of aeration of cathode which varies between 10 and 150 mL/min. From the experimental dataset, two robust adaptive neuro‐fuzzy inference system models based on the fuzzy logic technique have been constructed. The comparisons between the models' outputs and the experimental data showed well‐fitting in both training and testing datasets. The mean squared errors of the PD model, for testing and whole datasets, were found 2.575 and 0.909 while for the COD model it showed 19.242 and 6.791, respectively. Then, based on the two fuzzy models, a Particle Swarm Optimization algorithm has been used to determine the best parameters that maximize both of the PD and the COD removal of the cell. The optimization process was utilized for single and multi‐object optimization processes. In the single optimization, the resulting maximums of the PD and the COD removal were found 62.844 (mW/m²) and 99.99 (%), respectively. Whereas, in the multi‐object optimization, the values of 61.787 (mW/m²) and 96.21 (%) were reached as the maximums for the PD and COD, respectively. This implies that, in both cases of optimization processes, the adopted methodology can efficiently enhance the microbial fuel cell performances than the previous work.     

First-principles DFT study of SO2 and SO3 adsorption on 2PANI: a model for polyaniline response

Interaction of SO_x (x?=?2,3) molecules on active sites of dianiline (as a model for polyaniline, denoted here as 2PANI) was studied using density functional theory at the BLYP-D/6-31+G(d) level of theory. Natural population analysis was used to find out the charge distribution as well as the net transferred charge of SO_x upon adsorption on 2PANI and the result has been compared with Mulliken charge analysis to evaluate the sensing ability of 2PANI. The computed density of states point to the remarkable orbital hybridization between SO_x and 2PANI during the adsorption process. As a consequence, the results of UV–VIS confirm the sensing ability of 2PANI toward SO₂ and SO₃. Based on our results, it can be found that at proper configuration the SO₂ and SO₃ molecules can be adsorbed on 2PANI with adsorption energies (E_ads) of ?18.2 and ?62.9?kJ/mol (BSSE), respectively.     

Properties of PET/clay nanocomposite films

Polyethylene terephthalate (PET) nanocomposite films were prepared by cast extrusion followed by uniaxial stretching, using chill rolls. Transmission electron microscopy (TEM) and wide angle X‐ray diffraction (WAXD) showed that the clay layers were aligned in the machine direction (MD) in the PET/clay nanocomposite (PCN) films. Differential scanning calorimetry (DSC) showed that PCN films have higher crystallinity than the neat PET films, possibly due to the nucleating role of the silicate layers. The PCN films became hazier as the clay content increased, but the film transparency remained in the acceptable range. Oxygen permeability of the PCN films decreased by 23% compared to the neat PET film. This is comparable with predictions of models proposed in the literature. Silicate incorporation brought about 20% increase in the tensile modulus, while the puncture and tear propagation resistance were reduced, due to brittleness of the PCN films. The measured modulus (1.7 GPa) was somewhat smaller than the values predicted using the Pseudoinclusion model (2.1 GPa). POLYM. ENG. SCI., 2012. © 2011 Society of Plastics Engineers     

Graphene nanoplatelets dispersion in poly(<Emphasis Type="SmallCaps">l</Emphasis>-lactic acid): preparation method and its influence on electrical,crystallinity and thermomechanical properties

Poly(l-lactic acid) (PLLA)/graphene nanoplatelets (GnP) nanocomposites were prepared through solvent casting and coagulation methods. The better dispersion of graphene was achieved by ultrasounds and its effect on crystallinity, thermomechanical and electrical properties of PLLA were studied and compared in both methods. Differential scanning calorimetry (DSC) was used to investigate the crystallinity of PLLA and its composites. Field emission gun scanning electron microscope (FEG-SEM) and wide-angle X-ray scattering (WAXS) were employed to characterize the microstructure of PLLA crystallites. Dynamic mechanical thermal analysis (DMTA) was performed to study the thermomechanical properties of the nanocomposites. FEG-SEM images illustrated finer dispersion of GnP in samples obtained by coagulation method with respect to solvent casting method. Graphene imparted higher electrical conductivity to nanocomposites obtained by solvent casting under ultrasound due to better formation of graphene network. DSC thermograms and their resulting data showed positive effects of GnP on crystallization kinetics of PLLA in both methods enhanced by the nucleating effect of graphene particles. Meanwhile, the effect of GnP, as nucleating agent, was more prominent in samples produced by coagulation method without utilization of ultrasounds. WAXS patterns represented the same characteristic peaks of PLLA in nanocomposite specimens suggesting similar crystalline structure of PLLA in presence of graphene, and the intensified peaks of nanocomposites compared to neat PLLA confirmed the DSC results regarding its improved crystallinity. Graphene increased storage modulus in rubbery region and glass transition temperature of nanocomposites in the coagulation method due to restricted mobility of PLLA chains.     

Future directions in physiochemical modeling of the thermodynamics of polyelectrolyte coacervates

We review theories of polyelectrolyte (PE) coacervation, which is the spontaneous association of oppositely charged units of PEs and phase separation into a polymer-dense phase in aqueous solution. The simplest theories can be divided into “physics-based” and “chemistry-based” approaches. In the former, PEs are treated as charged, long-chain, molecules, defined by charge level, chain length, and chain flexibility, but otherwise lacking chemical identity, with electrostatic interactions driving coacervation. The “chemistry-based” approaches focus on the local interactions between the species for which chemical identity is critical, and describe coacervation as the result of competitive local binding interactions of monomers and salts. In this article, we show how these approaches complement each other by presenting recent approaches that take both physical and chemical effects into account. Finally, we suggest future directions toward producing theories that are made quantitatively predictive by accounting for both long range electrostatic and local chemically specific interactions.