Purification/annealing of graphene with 100-MeV Ag ion irradiation

Studies on interaction of graphene with radiation are important because of nanolithographic processes in graphene-based electronic devices and for space applications. Since the electronic properties of graphene are highly sensitive to the defects and number of layers in graphene sample, it is desirable to develop tools to engineer these two parameters. We report swift heavy ion (SHI) irradiation-induced annealing and purification effects in graphene films, similar to that observed in our studies on fullerenes and carbon nanotubes (CNTs). Raman studies after irradiation with 100-MeV Ag ions (fluences from 3 × 10¹⁰ to 1 × 10¹⁴ ions/cm²) show that the disorder parameter α, defined by I_D/I_G ratio, decreases at lower fluences but increases at higher fluences beyond 1 × 10¹² ions/cm². This indicates that SHI induces annealing effects at lower fluences. We also observe that the number of graphene layers is reduced at fluences higher than 1 × 10¹³ ions/cm². Using inelastic thermal spike model calculations, we estimate a radius of 2.6 nm for ion track core surrounded by a halo extending up to 11.6 nm. The transient temperature above the melting point in the track core results in damage, whereas lower temperature in the track halo is responsible for annealing. The results suggest that SHI irradiation fluence may be used as one of the tools for defect annealing and manipulation of the number of graphene layers.

PACS

60.80.x; 81.05.ue     

Highly Efficient Osmotic Energy Harvesting in Charged Boron-Nitride-Nanopore Membranes

Recent studies of the high energy-conversion efficiency of the nanofluidic platform have revealed the enormous potential for efficient exploitation of electrokinetic phenomena in nanoporous membranes for clean-energy harvesting from salinity gradients. Here, nanofluidic reverse electrodialysis (NF-RED) consisting of vertically aligned boron-nitride-nanopore (VA-BNNP) membranes is presented, which can efficiently harness osmotic power. The power density of the VA-BNNP reaches up to 105 W m⁻², which is several orders of magnitude higher than in other nanopores with similar pore sizes, leading to 165 mW m⁻² of net power density (i.e., power per membrane area). Low-pressure chemical vapor deposition technology is employed to uniformly deposit a thin BN layer within 1D anodized alumina pores to prepare a macroscopic VA-BNNP membrane with a high nanopore density, ≈10⁸ pores cm⁻². These membranes can resolve fundamental questions regarding the ion mobility, liquid transport, and power generation in highly charged nanopores. It is shown that the transference number in the VA-BNNP is almost constant over the entire salt concentration range, which is different from other nanopore systems. Moreover, it is also demonstrated that the BN deposition on the nanopore channels can significantly enhance the diffusio-osmosis velocity by two orders of magnitude at a high salinity gradient, resulting in a huge increase in power density.     

Friction-induced vibration and noise generation of instrument panel material pairs

This study investigated the effect of various parameters of the friction–velocity relationship on the friction-induced vibration of simulated instrument panel components. The effect of subsystem stiffness and damping on the system response was also studied. A simple discretized model was utilized with subsystem properties that were intended to realistically model values of low, medium, and high stiffness components. Specifically, the metric of mean squared velocity was used as an indicator of the noise generated during the stick–slip process. It was found that the difference between the static and the asymptotic kinetic value of friction was the most important friction parameter in determining the resulting behavior. As stiffness and damping are increased, the mean squared velocity decreases. Additionally, results from single excursion tests on a variety of instrument panel material pairs showed good correlation between mean squared velocity and the difference in static and kinetic friction.     

Biocomposite formation using β-cyclodextrin as a biomaterial in poly(acrylamide-<Emphasis Type="Italic">co</Emphasis>-acrylic acid): preparation,characterization, and salinity profile

A biocomposite of poly(acrylamide-co-acrylic acid) hydrogel with β-cyclodextrin as a biomaterial was prepared through one-pot synthesis in water as a green solvent. The formation of biocomposite was confirmed by advanced techniques such as FTIR spectroscopy, XRD, DSC, TGA, and FE-SEM. In this report, straight forward and efficient synthetic protocol for biocomposite formation responded without any environmental hazard. Swelling capacity of P(AM-co-AA) and biocomposite was studied by addition of different saline solutions including monovalent, divalent, and trivalent salts. By addition of β-cyclodextrin, the swelling and saline water-absorbing properties of the biocomposite hydrogel were significantly improved. In this regard, the possible formation mechanism of the composite hydrogel is also discussed. It is deduced that the biocomposite formation can be the result of intermolecular interactions between polymer and β-cyclodextrin. The water-soluble polymer seems to have entered into the inner cavity of β-cyclodextrin to form supramolecular biocomposite structure. The results indicate that the order of water uptake decreases with increase in valency of the salts. It is believed that this is an effective method to prepare supramolecular biocomposite hydrogel materials. Its applications can be extended in marine water industries as a basis for antifouling coating, waste water treatment, and even in medical field. Hence, the synthesized materials can be biodegradable, environment-friendly, and biocompatible inspired by the green chemistry concept.     

Schiff Based Silatranyl Compounds Exhibiting ‘Fe3+ and Mn2+ Fluorescence Dual Ion Sensing and Antibacterial Activity’

Silicon - The synthesis of different Schiff base substituted silatranes (1c–4c) was carried out from the corresponding organotrimethoxysilanes (OTMS) (1b–4b) under anhydrous atmospheric...     

Study of corrosive fatigue and life enhancement of low pressure steam turbine blade using friction dampers

The paper investigates the causes of failure of low pressure steam turbine blade of the last stage and suggests few techniques to overcome the failure causes is presented in this paper. The blade under investigation is made of chrome alloy steel. The fracture occurred at the airfoil region of the blade. The investigation included visual inspection, micro structural characterization, SEM-EDS microanalysis and spectroscopy test to identify the causes of failure. The paper also suggests the methods to reduce the blade fatigue subsequently through computation and to enhance the fatigue strength of the steam turbine blade. In order to reduce the blade fatigue susceptibility and to enhance the fatigue life of the steam turbine blade, the wedge shape friction damper is proposed.     

In-process prediction of surface roughness in turning of Ti–6Al–4V alloy using cutting parameters and vibration signals

In this work, an attempt has been made to use vibration signals for in-process prediction of surface roughness during turning of Ti–6Al–4V alloy. The investigation was carried out in two stages. In the first stage, only acceleration amplitude of tool vibrations in axial, radial and tangential directions were used to develop multiple regression models for prediction of surface roughness. The first and second order regression models thus developed were not found accurate enough (maximum percentage error close to 24%). In the second stage, initially a correlation analysis was performed to determine the degree of association of cutting speed, feed rate, and depth of cut and the acceleration amplitude of vibrations in axial, radial, and tangential directions with surface roughness. Subsequently, based on this analysis, feed rate and depth of cut were included as input parameters aside from the acceleration amplitude of vibrations in radial and tangential directions to develop a refined first order multiple regression model for surface roughness prediction. This model provided good prediction accuracy (maximum percentage error 7.45%) of surface roughness. Finally, an artificial neural network model was developed as it can be readily integrated into a computer integrated manufacturing environment.     

Plasmonic Au nanoparticles for enhanced broadband light absorption in inverted organic photovoltaic devices by plasma assisted physical vapour deposition

We use a low vacuum plasma assisted physical vapour deposition (PAPVD) method to deposit a Au nanoparticles (NPs) thin film onto the poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) layer in inverted poly(3-hexylthiophene):[6,6]-phenyl C61-butyric acid methylester (P3HT:PCBM) organic photovoltaic (OPV) devices. The Au NPs that incorporated into the PEDOT:PSS layer and reached to the active P3HT:PCBM layer can provide significant plasmonic broadband light absorption enhancement to the active layer. An approximately 50–90% improvement in short-circuit current density and in power convention efficiency has been achieved compared with those OPV devices without the plasmonic light absorption enhancement. This technique can be adopted and easily fit into most OPV device fabrication processes without changing other layers’ processing methods, morphologies, and properties.     

Damage micromechanisms in IMI-834 titanium alloy: Stress triaxiality effects

In the present investigation, tensile tests were performed with select interruptions on pre-polished specimens to study the effects of stress triaxiality on damage micromechanisms operative in IMI-834 titanium alloy.