Characterization and improved electrical conductivity of partially biodegradable polyaniline/poly(1,4‐butylene succinate) polymer composite films

Polyaniline/poly(1,4‐butylene succinate) (PANI/PBS) composites were prepared by the polymerization of aniline hydrochloride in the presence of different weight percentages of poly(1,4‐butylene succinate) biodegradable polymer by in situ deposition technique. The oxidative polymerization of aniline hydrochloride was performed by the drop wise addition of an aqueous ammonium persulfate solution. Fourier‐transform infrared spectroscopy, surface morphology, and thermogravimetric analyses indicated a strong interaction between PANI and PBS. The temperature‐dependent DC conductivity and biodegradable properties of PANI/PBS were also investigated. The results showed that both the conductivity and biodegradability of the composites was significantly increased by the addition of PBS. POLYM. COMPOS., 35:2010–2017, 2014. © 2014 Society of Plastics Engineers     

In situ-grown hexagonal silicon nanocrystals in silicon carbide-based films

Silicon nanocrystals (Si-NCs) were grown in situ in carbide-based film using a plasma-enhanced chemical vapor deposition method. High-resolution transmission electron microscopy indicates that these nanocrystallites were embedded in an amorphous silicon carbide-based matrix. Electron diffraction pattern analyses revealed that the crystallites have a hexagonal-wurtzite silicon phase structure. The peak position of the photoluminescence can be controlled within a wavelength of 500 to 650 nm by adjusting the flow rate of the silane gas. We suggest that this phenomenon is attributed to the quantum confinement effect of hexagonal Si-NCs in silicon carbide-based film with a change in the sizes and emission states of the NCs.     

Dieless drawing steel wires using a dielectric heating method and modeling the process dynamics

Modern industries require the production of multi-functional, inorganic, micron-sized metal wires. This study suggests a novel method that could potentially offer a highly efficient dieless drawing technology for manufacturing thin stainless steel fibers. The method is based on a hot-working principle, using microwaves as the heat source and SiC as the susceptor. Experimental trials with a laboratory rig showed that the new system worked effectively for drawing the stainless steel wires and should be able to realize the diameter attenuation with a diameter reduction of up to 21%. The theoretical model describing the deformation behavior of the stainless steel wires in the working zone along with the constitutive equation of Bingham model modified with a power law and Zener–Hollomon parameter turned out to match very good with the actual results of the experiment. The coefficient of variation of the drawn wire diameter increased, as the draw ratio increased, which could be attributed to the occurrence of the narrow necking zone.     

Seismic reliability of non-linear frames with PR connections using systematic RSM

An effective, efficient, and robust reliability analysis algorithm is proposed for non-linear structures, where seismic loading can be applied in the time domain. The method is developed specifically for steel frame structures considering all major sources of non-linearity, including geometry, material, and partially restrained (PR) connections. The non-linearity due to PR connections is modeled by moment-relative rotation curves using the four-parameter Richard model. For seismic excitation, the loading, unloading, and reloading behavior at PR connections is modeled using moment-relative rotation curves and the Masing rule. The proposed algorithm intelligently integrates the response surface method, the finite element method, the first-order reliability method, and an iterative linear interpolation scheme. The uncertainties in all the random variables including the four parameters of Richard model are considered. Two unique features of the proposed algorithm are that (1) actual earthquake time histories can be used to excite structures in the presence of major sources of non-linearity and uncertainty and (2) it is possible to estimate the risk corresponding to both the serviceability and strength limit states. The algorithm is verified using the Monte Carlo simulation technique. The verified algorithm is first used to study the reliability of a frame structure in the presence of PR connections with different degrees of flexibility. Then the algorithm is used to estimate the reliability of a frame structure excited by 13 actual recorded earthquake time histories, 12 of them recorded during the Northridge earthquake of 1994. As expected, the reliabilities of the frame are found to be quite different, when excited by several time histories of the Northridge earthquake.     

Simulation of the newtonian flow through an abruptly contracted tube using a mixed finite element method

The solutions of the Navier-Stokes equation for a Newtonian flow through a 4/1 contraction tube were obtained numerically using the Galerkin finite element method with the nine-node Lagrangian element which was believed to be one of the most accurate tools for mixed-type interpolating formulations. It was proved from this study that the vortex occurrence in the entrance corner region were confirmed but its size was gradually decreased with the increase of Reynolds numbers, and that the velocity profiles and pressure distributions along the applied mesh layers were in agreement with the experimental and the previously reported numerical results.     

Experiments on formation of the adiabatic shear band in sheet metal

Formation of the adiabatic shear band in sheet metal is investigated with experiments for high strength steel sheets, 60 C and 60 TRIP. Since the adiabatic shear band is formed as a result of adiabatic shear failure with a narrow band of concentrated shear strain, the adiabatic shear band plays an important role in the analysis of high speed deformation phenomena. For shear band experiments with a tension split Hopkinson bar, specimens are designed to induced large shear strain. The experimental results show that the shear deformation modes of two sheet metals, 60 TRIP and 60 C, are quite different from each other in that the adiabatic shear band is observed only in 60 C. The shear deformation in 60 TRIP is restrained by the abrupt increase of strength due to the plastic strain, which interferes with propagation of the shear crack. Instead, a tensile crack developed at the corner where the shear crack should have been initiated. As a result, the load-displacement curves show that the tensile load of 60 TRIP specimens becomes higher than that of 60 C at the same displacement.     

Nanoscale Investigation of Grain Growth in RF-Sputtered Indium Tin Oxide Thin Films by Scanning Probe Microscopy

This work studied the electronic characteristics of the grains and grain boundaries of indium tin oxide (ITO) thin films using electrostatic and Kelvin probe force microscopy. Two types of ITO films were compared, deposited using radiofrequency magnetron sputtering in pure argon or 99% argon + 1% oxygen, respectively. The average grain size and surface roughness increased with substrate temperature for the films deposited in pure argon. With the addition of 1% oxygen, the increase in the grain size was inhibited above 150°C, which was suggested to be due to passivation of the grains by the excess oxygen. Electrostatic force microscopy and Kelvin probe force microscopy (KPFM) images confirmed that the grain growth was defect mediated and occurred at defective interfaces at high temperatures. Films deposited at room temperature with 1% oxygen showed crystalline nature, while films deposited with pure argon at room temperature were amorphous as observed from KPFM images. The potential drop across the grain and grain boundary was determined by taking surface potential line profiles to evaluate the electronic properties.     

Synthesis of polyaniline-gold/graphene oxide composite and microwave absorption characteristics of the composite films

This paper describes the synthesis of polyaniline-gold nanocomposite by an in situ polymerization of aniline hydrochloride with graphene oxide using hydrogen tetrachloroaurate as an oxidant. The synthesized nanocomposites were characterized by FT-IR and UV–vis spectroscopy, and their surface morphology was studied by scanning and transmission electron microscopy. Microwave absorption property of the composite films was studied at 2–12 GHz, and the effects of sample thickness on the microwave absorption were investigated. The electromagnetic interference shielding effectiveness of PANI-GNP has been enhanced due to the inclusion of GO.     

Morphology-dependent antibacterial activities of Cu2O

Cubic and octahedral Cu₂O microcrystals were synthesized by the reduction of a copper-ligand complex solution with glucose under microwave irradiation using ethylenediaminetetraacetic acid (EDTA) and N,N,N′,N′-tetramethyl ethylenediamine (TMEDA) as ligands. Scanning electron microscopy (SEM) and X-ray diffraction (XRD) confirmed that the surfaces of the cubic and octahedral of Cu₂O microcrystals had {100} and {111} lattice planes. The antibacterial activity of the Cu₂O microcrystals against E. coli was examined using optical density (OD) methods. The antibacterial activity of the cubic Cu₂O crystals was superior to that of the octahedral Cu₂O crystals. The mechanism of the specific morphology-controlled synthesis of Cu₂O and their morphology-dependent antibacterial activity are discussed.