Biodegradation kinetic modeling of acrylic acid-grafted polypropylene during thermophilic phase of composting

Iranian Polymer Journal - This work aims at modelling and characterizing the kinetics of biodegradation of acrylic acid-grafted polypropylene. Different films of acrylic acid-grafted polypropylene...     

Machining Characteristics and Corrosion Behavior of Grain Refined AZ91 Mg Alloy Produced by Friction Stir Processing: Role of Tool Pin Profile

In the present study, influence of friction stir processing (FSP) tool pin profile on the microstructure evolution, corrosion and machining characteristics of the AZ91 magnesium alloy was investigated. Three different pin profiles namely simple taper, threaded taper and square taper were selected and FSP was carried out at 1400 rpm and 25 mm/min tool travel speed. Microstructural observations indicated grain refinement from a starting grain size of 166.5–7.9, 22.1 and 4.08 µm for FSPed samples processed by simple taper, threaded taper and square taper pins, respectively. In all the FSPed samples, decreased amount of secondary phase (Mg₁₇Al₁₂) was observed compared with that of the unprocessed sample. From the X-ray diffraction analysis, it was observed that the square taper pin tool had induced higher texture effect compared with the other two FSP tools. From the electrochemical studies, the corrosion resistance of the sample processed with square taper pin tool was observed to be more in comparison to that of the other samples; which could be attributed to the texture effect and decreased fraction of secondary phase. Machining behavior assessed by conducting drilling experiments showed a significant influence of grain refinement on the cutting forces.     

Influence of resonant Raman scattering in the elemental analysis using X-ray emission based techniques

A tabulation of characteristic X-ray energies across the periodic table are provided where those X-rays are expected to result in a significant fractional resonant Raman scattering (RRS) contribution to the X-ray attenuation from a particular shell/subshell of the same or another element. The tabulations can be considered as guideline so as to know what can be expected due to RRS in typical photon- and particle-induced X-ray emission spectrometry. The RRS contribution is not included in the available theoretical attenuation coefficients, which are generally used in estimation of the matrix corrections in routine quantitative elemental analysis based on various X-ray emission techniques. The radiative RRS peaks can also interfere with normal X-ray spectrum and influence the elemental analysis. The RRS cross-section depends upon the energy difference of the X-ray energy and the shell/subshell ionization threshold taken in the units of the shell/subshell energy width, density of available states near the Fermi level, and the band structure in case the element is in the solid form. Some aspects of the dependence of the RRS contribution on the chemical forms of the elements are also discussed.     

Evaluation of electromagnetic loads on various design options of the ITER diagnostic upper port plug during plasma disruptions

Electromagnetic (EM) loads due to eddy current and halo current during plasma disruptions are evaluated for the ITER diagnostic upper port plug. To reduce strong EM loads acting on the port plug fixed to the vacuum vessel like a cantilever beam, three design options have been considered: removal of the diagnostic first wall, slitting of the diagnostic shield module and recess of the port plug. The main focus of the present study is to examine the efficacy of these options in terms of EM loads on the upper port plug. It is found that making slits is more effective than removing the first wall. It is also shown that the upper port plug needs to be recessed to reduce the EM load induced by halo current.     

The Couette flow of a conducting Jeffrey fluid when the walls are lined with deformable porous material

The paper deals with the flow, past a deformable porous channel bounded by finite deformable porous layer with moving rigid parallel plates. Transverse magnetic field is also applied and incorporated in the momentum equation. The coupled nonlinear equations are transformed to ordinary differential equations (ODEs) with suitable choice of similarity transformation. Further, these sets of nonlinear ODEs are solved analytically and are used to get results for the flow phenomena. The effects of the porous layer thickness and the drag on the flow phenomena are discussed graphically. It is observed that rigid velocity decreases with increasing in the drag, whereas the decrease in the deformable is noted. It is clear to see that the retards in solid displacement are shown with enhancing viscosity parameter η.     

Effect of Constraint on Creep Behavior of 9Cr-1Mo Steel

The effect of constraint on creep rupture behavior of 9Cr-1Mo steel has been investigated. The constraint was introduced by incorporating a circumferential U-notch in a plain cylindrical creep specimen of 5 mm diameter. The degree of constraint was increased by decreasing the notch root radius from 5 to 0.25 mm. Creep tests were conducted on plain and notched specimens at stresses in the range of 110 to 210 MPa at 873 K (600 °C). The creep rupture life of the steel was found to increase under constrained conditions, which increased with the increase in degree of constraint and applied stress, and tended to saturate at a higher degree of constraint. The creep rupture ductility (pct reduction in area) of the steel was found to be lower under constrained conditions. The decrease in creep ductility was more pronounced at a higher degree of constraint and lower applied stresses. Scanning electron microscopic studies revealed a change in fracture behavior with stress and degree of constraint. The fracture surface appearance for relatively lower constrained specimens at higher stresses was predominantly transgranular dimple. Creep cavitation-induced intergranular brittle fracture near the notch root was observed for specimens having a higher degree of constraint at relatively lower stresses. The creep rupture life of the steel under constrained conditions has been predicted based on the estimation of damage evolution by continuum damage mechanics coupled with finite element analysis of the triaxial state of stress across the notch. It was found that the creep rupture life of the steel under constrained conditions was predominantly governed by the von-Mises stress and the principal stress became progressively important with increase in the degree of constraint and decrease in applied stress.     

Morphology,polymorphism, and metal ion adsorption studies of electrospun nanofibers based on PVDF and organically modified layered double hydroxide

Nonwoven nanofiber mats of polyvinylidene fluoride (PVDF) with modified layered double hydroxide (MLDH) were prepared by electrospinning. The fiber morphology was studied using scanning electron microscopy. X‐ray diffraction and FTIR spectroscopy was used to characterize the polymorphism in electrospun mats. Fibers of diameter in the range 80–800 nm with beads of about 2–3 µm size were observed for pure PVDF, while in case of PVDF/MLDH nanocomposites the number and size of beads were found to be significantly reduced. Uniform and fine nanofibers were obtained at lower content of MLDH, but slightly rough surface was seen for higher content. FTIR and X‐ray diffraction patterns signify various crystalline forms of electrospun PVDF. The content of polar β‐crystalline phase of PVDF, which exhibit piezo and ferroelectric properties was found to be enhanced significantly due to reinforcement of MLDH. Use of these nanofiber mats for heavy metal Cu (II) removal was explored. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 4508–4515, 2013     

Structural,vibrational, optical,magnetic and dielectric properties of Bi1−xBaxFeO3 nanoparticles

Bi_1−xBa_xFeO₃ (x=0.05, 0.10 and 0.15) nanoparticles were synthesized by the sol–gel method. X-ray diffraction and Raman spectroscopy results showed the presence of distorted rhombohedral structure of Bi_1−xBa_xFeO₃ nanoparticles. Rietveld refinement and Williamson–Hall plot of the x-ray diffraction patterns showed the increase in lattice parameters, unit cell volume and the particle size. Infrared spectroscopy and Raman analysis revealed the shifting of phonon modes towards the higher wavenumber side with increasing Ba concentration. These samples exhibited the optical band gap in the visible region (2.47–2.02 eV) indicating their ability to absorb visible light. Magnetic measurement showed room temperature ferromagnetic behavior, which may be attributed to the antiferromagnetic core and the ferromagnetic surface of the nanoparticles, together with the structural distortion caused by Ba substitution. The magnetoelectric coupling was evidenced by the observation of the dielectric anomaly in the dielectric constant and the dielectric loss near antiferromagnetic Neel temperature in all the samples.