Nanogrooved carbon microtubes for wet three‐dimensional printing of conductive composite structures

Recent advances in three‐dimensional (3D) printing have enabled the fabrication of interesting structures which are not achievable using traditional fabrication approaches. The 3D printing of carbon microtube composite inks allows fabrication of conductive structures for practical applications in soft robotics and tissue engineering. However, it is challenging to achieve 3D printed structures from solution‐based composite inks, which requires an additional process to solidify the ink. Here, we introduce a wet 3D printing technique which uses a coagulation bath to fabricate carbon microtube composite structures. We show that through a facile nanogrooving approach which introduces cavitation and channels on carbon microtubes, enhanced interfacial interactions with a chitosan polymer matrix are achieved. Consequently, the mechanical properties of the 3D printed composites improve when nanogrooved carbon microtubes are used, compared to untreated microtubes. We show that by carefully controlling the coagulation bath, extrusion pressure, printing distance and printed line distance, we can 3D print composite lattices which are composed of well‐defined and separated printed lines. The conductive composite 3D structures with highly customised design presented in this work provide a suitable platform for applications ranging from soft robotics to smart tissue engineering scaffolds. © 2019 Society of Chemical Industry     

Effect of epitaxial realignment on the leakage behavior of arsenic-implanted,as-deposited polycrystalline Si-on-single crystal Si diodes

When dopants are indiffused from a heavily implanted polycrystalline silicon film deposited on a silicon substrate, high thermal budget annealing can cause the interfacial “native” oxide at the polycrystalline silicon-single crystal silicon interface to break up into oxide clusters, causing epitaxial realignment of the polycrystalline silicon layer with respect to the silicon substrate. Anomalous transient enhanced diffusion occurs during epitaxial realignment and this has adverse effects on the leakage characteristics of the shallow junctions formed in the silicon substrate using this technique. The degradation in the leakage current is mainly due to increased generation-recombination in the depletion region because of defect injection from the interface.     

Analysis of time-dependent flow-sensitive PC-MRI data

Many flow visualization techniques, especially integration-based methods, are problematic when the measured data exhibit noise and discretization issues. Particularly, this is the case for flow-sensitive phase-contrast magnetic resonance imaging (PC-MRI) data sets which not only record anatomic information, but also time-varying flow information. We propose a novel approach for the visualization of such data sets using integration-based methods. Our ideas are based upon finite-time Lyapunov exponents (FTLE) and enable identification of vessel boundaries in the data as high regions of separation. This allows us to correctly restrict integration-based visualization to blood vessels. We validate our technique by comparing our approach to existing anatomy-based methods as well as addressing the benefits and limitations of using FTLE to restrict flow. We also discuss the importance of parameters, i.e., advection length and data resolution, in establishing a well-defined vessel boundary. We extract appropriate flow lines and surfaces that enable the visualization of blood flow within the vessels. We further enhance the visualization by analyzing flow behavior in the seeded region and generating simplified depictions.     

One-dimensional axial simulation of electric double layer overlap effects in devices combining micro- and nanochannels

This paper presents a numerical steady-state model of ion transport in micro- and nanofluidic devices with widely varying geometric scale, such as transitions between micro- and nanochannels. Finite element or finite volume simulation of such problems is challenging, due to the number of elements needed to produce a satisfactory mesh. Here, only the lengthwise channel dimension is meshed; standard analytical approximations are used to incorporate cross-channel properties. Singularly perturbed cases are built up by continuation. The method is shown to reproduce our previously reported measurements of electric double-layer effects on conductivity, ion concentration, and ion enhancement and depletion. Comparison with 2-D simulations reported in the literature shows that effects on accuracy due to the 1-D approximation are small. The model incorporates analytical models of surface charge density taken from the literature. This enables predictive simulation with reasonable accuracy using published parameter values, or these values may be tuned based on experiment to give improved results. Use of the model for iterative design and parameter estimation is demonstrated.     

Corrosion of Mg alloys EV31A,WE43B,and ZE41A in chloride- and sulfate-containing solutions saturated with magnesium hydroxide

This study studied corrosion in 0.1 M Na₂SO₄, 0.1 M NaCl, and 0.6 M NaCl, all saturated with Mg(OH)₂, using weight loss, hydrogen evolution, and electrochemical measurements. Corrosion was similar in all cases. Nevertheless, the corrosion rates were alloy-dependent, were somewhat lower in 0.1 M Na₂SO₄ than in 0.1 M NaCl, and increased with NaCl concentration. The corrosion damage morphology was similar for all solutions; the extent correlated with the corrosion rate. The corrosion rates evaluated by the electrochemical methods were lower than those evaluated from hydrogen evolution, consistent with the Mg corrosion mechanism involving the unipositive Mg⁺ ion.     

Electrical,electrochemical and photo-electrochemical studies on the electrodeposited n-type semiconductor hexagonal crystalline CdS thin film on nickel substrate

Electrodeposited cadmium sulfide (CdS) on nickel substrate of new properties from aqueous solutions of Cd²⁺ and S₂O₃ ^2? at 313 K has been obtained using cyclic voltammetric and potentiostatic techniques. The mechanism of the electrode reactions for the electrodeposition of CdS has been evaluated and proposed. Energy dispersive X-ray florescence elemental analysis and X-ray diffraction investigations demonstrate that, the electrodeposited CdS is pure and hexagonal polycrystalline in nature, at our optimal conditions. Furthermore, the electrodeposited CdS is of n-type semiconductor was investigated and confirmed by Mott–Schotky test. Donor concentration (N_D) was determined to be 1.0 × 10¹⁷ cm^?3. In this research we discovered that, the electrodeposited semiconductor CdS on Ni substrate has low resistivity and magnetic properties (became as a strong magnet) at the mentioned conditions. The photoelectrochemical measurements of the electrodeposited CdS on nickel electrode had been investigated at room temperature and under illumination giving good results.     

Varistor effect in polymer-semiconductor composites

The formation mechanism of the varistor effect in composites based on polar (polyvinylidene fluoride) and nonpolar (polyethylene, polypropylene) polymers and semiconductors (silicon and germanium) is studied. It is shown that the varistor effect in polymer-semiconductor composites is caused by carrier tunneling transport through the barrier at the phase interface, the parameters of which depend on the voltage, temperature, volume concentration and dispersion of semiconductor particles, and permittivity of composite components.     

Organic Carbon and Trace Metal Distribution in the Gökçesu Shale: Eocene Basin,Bolu-Turkey

Abstract

Samples collected from the bituminous shales in the Eocene Tokmaklar formation are the material of this study. Distribution of organic material and trace metals in the shale samples and their concentration levels and correlations were evaluated. Organic carbon content of the bituminous shales is between 0.59 and 15.89% (averaging as 4.86%). The type of organic material is 100% amorphous material (kerogen type is Type I and Type II) and it has a potential to produce oil. Trace metal enrichment levels were determined on the basis of average shale concentration in the earth crust. These levels are divided into two groups. Mo (1.98–2.64), Cu (1.27), As (1.59–8.83), and Sr (2.58–2.75) in bituminous rocks show enrichment character while Pb, Zn, Ba, and Co metals do not display any enrichment. Moreover, comparison with the average values of these metals in seawater and living organisms yield enrichment coefficients of 86.17–386.000 (with respect to seawater) and 4.59–1,723.5 (with respect to living organisms).     

Prospects of two-contour geothermal power plant construction

Technologycal scheme of electric energy obtaining on the basis of thermal water is suggested. The method of optimal regime calculation is presented. Some parametries of Daghestan Geothermal power plant are presented.