We report that efficient high dielectric polymer/ceramic composite materials can be optically printed into three-dimensional (3D) capacitor by the projection based stereolithography (SLA) method. ...Surface decoration of Ag on Pb(Zr,Ti)O3(PZT@Ag) particles were used as filler to enhance the dielectric permittivity. Polymer nanocomposites were fabricated by incorporating PZT@Ag particles into the photocurable polymer solutions, followed by exposure to the digitally controlled optical masks to generate 3D structures. The dielectric permittivity of Flex/PZT@Ag composite reaches as high as 120 at 100Hz with 18vol% filler, which is about 30 times higher than that of pure Flex. Furthermore, the dielectric loss is as low as 0.028 at 100Hz. The results are in good agreement with the effective medium theory (EMT) model. The calculated specific capacitance of our 3D printed capacitor is about 63Fg−1 at the current density of 0.5Ag−1. Cyclic voltammetry (CV) curves indicate 3D printed capacitors possess low resistance and ideal capacitive properties. These results not only provide a tool to fabricate capacitor with complex shapes but lay the groundwork for creating highly efficient polymer-based composites via 3D printing method for electronic applications.
High dielectric polymer/ceramic composite materials can be optically printed into different types of three-dimensional (3D) capacitor (b1–b4) by the projection based stereolithography (SLA) method. Polymer nanocomposites were fabricated by incorporating PZT@Ag particles (Surface decoration of Ag on Pb(Zr,Ti)O3) into photocurable polymer solutions, followed by exposure to digitally controlled optical masks to generate 3D structures (a). Charge–discharge curves (c) indicate 3D printed capacitors possess low resistance and ideal capacitive properties. These results not only provide a tool to fabricate capacitor with complex shapes but lay the groundwork for creating highly efficient polymer-based composites with complicated structures via 3D printing method for electronic applications.
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•We report that high dielectric polymer/ceramic composite materials can be printed into three-dimensional (3D) capacitor using the projection based stereolithography (SLA) method (Fig. 1).•The dielectric permittivity of Flex/PZT@Ag composite reaches as high as 120 at 100Hz with 18vol% filler, which is about 30 times higher than that of pure Flex.•Cyclic voltammetry (CV) curves indicate the 3D printed capacitors have low resistance and ideal capacitive properties (Fig. 5).•The effective permittivity in the PZT composites comes from the incorporation of Ag and the related increase in the average field of both polymer matrix and ceramic filler (Fig. 3).
The electron transfer and specific adsorption of a redox-active molecule are coupled in many important electrode reactions. Herein, we report a theoretical framework for the voltammetric ...discrimination of the concerted and non-concerted mechanisms of adsorption-coupled electron-transfer (ACET) reactions. In the concerted mechanism, an oxidant in the solution is simultaneously reduced and adsorbed to deposit a reductant on the electrode surface. Alternatively, electron-transfer and adsorption steps are mediated separately in the non-concerted mechanism. Our model involves the common adsorption step for both mechanisms to ensure consistent adsorption properties of the redox couple. For simplicity, we assumed a weak adsorption step that does not contribute to the current response. We predicted that not only a kinetically controlled adsorption step but also a chemically reversible electron-transfer step is required for the voltammetric identification of the reaction mechanism. High scan rates were required during cyclic voltammetry (CV) for the kinetic control of the adsorption step. Unique CV shapes, or characteristic changes therein, were expected for each mechanism during the reversible adsorption of oxidants or reductants. We modelled the reversible adsorption of both the oxidant and reductant for the reduction of benzyl chloride at a Ag electrode. The experimental CV of this chemically irreversible ACET reaction kinetically controlled the adsorption step but was consistent with either mechanism to quantitatively validate our model. A voltammetric discrimination of the concerted and non-concerted mechanisms has not been demonstrated, but it will be possible if both requirements are satisfied.
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In this study, the simulation of the current density was carried out through COMSOL Multiphysics on surface-modified M2 high-speed tool steel. The results demonstrated that in the presence of the ...nitride layer on the surface of M2, the current density was increased remarkably in the nitride layer and M2 was immune, and consequently, it can be predicted that the corrosion resistance was increased. For verification, the surface modification through plasma nitriding was applied on the M2 steel corrosion resistance and was evaluated through polarization and electrochemical impedance spectroscopy (EIS) in the 3.5 wt% of NaCl solution. The results confirmed the simulation outcomes; therefore, optimization of the parameters was performed. The impression of the variation of the process parameter of plasma nitriding such as temperature (500, 550, and 600 °C), time (4, 6, and 8 h), and ratio of inserted gases (N2/H2: 1:3, 1:1, 3:1) on the growth of the diffusive layer was assessed by X-Ray Diffractometry (XRD). Outcomes illustrated that applying plasma nitriding causes the formation of the different nitride phases on the top surfaces of the M2 substrate and Fe3N is the dominant phase. The diffusive nitride layer has a higher current density based on simulation results. The microhardness of the surface increased remarkably and 2414 HV was reached as a maximum surface hardness. By considering the obtained results, 500 °C, 6 h, and a ratio of 1:1 of N2/H2 were chosen as optimum conditions of the plasma nitriding of M2 high-speed tool steel, and a corrosion rate of 1.62 mpy was calculated.
The frequency of failures in hanger pins of Pakistan Railway carriages has risen to an alarming level. Such as hanger pins have become the reason for the highest number of cases regarding failures of ...Carriage and Wagons in Pakistan. The pins have been failing after only 3 months while the intended life of these pins was supposed to be 6 months at least. Previously we have been using rectangular cross-section cotter pins in the hanger brackets. Studies have shown that instead a circular cross-section cotter pin can make a major contribution to the lower the value of these fatigue stresses. In this study, we compute and perform the stress and fatigue analysis on the hanger pin assembly using Findley criterion. Findley criterion was used as it most closely resembled in the properties needed to carry out our desired simulation. COMSOL model is used to compute the stresses as well as do the fatigue analysis on the said model. Fatigue usage factor has been used in the COMSOL. The first part contains the analysis on the already in-effect hanger pins of rectangular cross-sectional area. While the second half contains analysis done by changing the cross-section to modified circular shaped hanger cotter pins. The new proposed material proved to have decreased the stresses induced in the components thus increasing its life.
Electro-conductive nanomaterials are promising interfacial platforms to manipulate and electrically stimulate electroresponsive cells for tissue engineering proposes. The present study aimed to ...fabricate electro-conductive electrospun carbon nanofibers (CNFs) to be used as the substrate for bone cells electrical stimulation. The CNFs were derived from electrospun polyacrylonitrile (PAN) nanofibers by a two steps heat treatment, stabilization and carbonization. The seeded CNFs with Mg-63 cells (SCNFs) were exposed to DC electrical fields with the current intensities of 10, 50, 100, and 200 μA. COMSOL Multiphysics software was used to simulate the applied DC electric field applied in the fabricated electrical stimulation chamber in the presence of the SCNFs. The simulation study confirmed the efficacy of the fabricated electrical stimulation set-up. The growth of the seeded cells was significantly increased in the presence of the applied DC electric field and resulted in the highest proliferation level, 116.43 ± 4.76%, at 100 μA. The alkaline phosphatase (ALP) activity assay revealed increased osteogenic activity of cells, necessary for the enhanced bone healing process, as a result of the applied field. The present study indicates the efficiency of conductive CNFs for bone growth and that the electrical sensitivity of the substrate fabricated here might complement the piezoelectric characteristics of bone to further promote and facilitate bone growth and healing.
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•The electrical stimulation significantly enhanced the proliferation and the osteogenic activity of the bone cells.•The CNFs possess nanometric diameter with outstanding electrical properties.•The fabricated electrospun CNFs is cytocompatible and suitable for cell culture and proliferation.•The fabricated electrical stimulation chamber is excellent to deliver the electrical stimulus to cells.
Laser annealing represents a powerful method for tailoring the properties of silver nanofilms on quartz substrates, offering advantages in terms of precision, scalability, and functionalization. ...Continued research efforts are expected to deepen our understanding and broaden the applications of this promising technology in diverse fields. In this work, laser annealing of silver nanofilms deposited on quartz substrates was performed and investigated. RF CO2 laser of variable power in the range 1–20 W with beam quality of 1.1 was used to anneal silver nanofilms. AFM analysis emphasized that nanocrystal sizes of 60 nm were obtained for silver nanofilms. Furthermore, the optimum absorbance peak occurred at about 449 nm for smaller film thickness. Thermal simulation and analysis of the annealing process were also conducted using COMSOL Multiphysics software. It was observed that optimal temperature of 729 K was achieved when 10 W laser power and 2 mm/s scanning speed were used to anneal 20 nm silver film thickness. Design of expert analysis was also used to better understand the laser annealing process of silver nanofilms since convolution of several process parameters affect the process output.
The human kidney is one of the most important organs in the human body. It performs many functions and has a great impact on the work of the rest of the organs. Artificial and implantable kidneys ...become a promising and potential technology to compensate damaged kidneys. In this paper, we are presenting a prototype model of an implantable kidney that is designed using Solidworks. The proposed prototype device enables us to conduct a particle separation using electrophoresis with an external electrical field. The final prototype is fabricated using 3d printing and an In Vitro experiment of particle separation is conducted using a saline solution, in addition to numerical simulation of solution flow under influence of an electrical field using COMSOL Multiphysics. In vitro results illustrate that electric potential can be used to separate the charged ions under the influence of the electric bias forces to the opposite poles to charge them. The numerical simulation of the proposed design and separation method using COMSOL Multiphysics was able to show a difference in particle trajectories with and without applied electrical field.
In the current paper, a numerical model was designed using COMSOL Multiphysics software based on experimental results to predict Nusselt number of TiO2, ZnO and Ag water-based nanofluids in helical ...coil under isothermal boundary conditions. All Nusselt number data extracted from the model were compared with experimental data to validate the model and the results showed that the model gives good accuracy and the model could be used to predict non-experimental data. Root Mean Square Error (RMSE) was calculated to evaluate model accuracy and the results were 4.35, 2.40 and 2.53 for TiO2/water, Ag/water and ZnO/water respectively. The model was used to predict non-experimental data and the results were logically predicted compared with experimental data and the model was proven to be sufficient for predicting non-experimental data. Model results were compared with two types of artificial neural networks predicting Nusselt number Feed Forward Neural Network (FFNN) and Generalized Regression Neural Network (GRNN). The deviation between predicted data and experimental data was calculated and the results indicated that GRNN network has the highest accuracy with maximum deviations of +0.02% & −0.3% while the COMSOL model has a maximum deviation of +4.5% & −5.9% and finally FFNN network +8.9% & −5.7%.
The coupling effects of geostress and multi-attribute corrosion environments are the major causes of damage and rupture of prestressed cable bolts in deep underground environments. To determine ...impacts of different environmental factors on stress corrosion cracking of cable bolts in underground conditions, the accelerated stress corrosion tests and finite element numerical simulations were carried out. By implementing the material diffusion theory and appreciating the hydrogen induced lattice expansion effects, the diffusion and aggregation behavior of hydrogen in cable bolts were simulated. The influences of stress intensity and hydrogen concentration on failure mechanisms of cable bolts were studied by considering the hydrogen induced expansion strain. The failure only occurred in the environments where sufficient hydrogen concentration existed. The hydrogen diffusion flux and distribution were consistent with stress concentration distribution. The prestress accelerated the hydrogen diffusion to stress concentrated position leading to a greater strain in the stressed areas, which consequently induced hydrogen expansion stress and decreased cohesion strength of lattice near crack tip. The fractographic features of failed specimen were analysed and hydrogen assisted fracture was confirmed to be one of the main failure mechanisms leading to stress corrosion failures. The methodologies proposed could be used to study the diffusion and distribution of hydrogen in metals and the obtained results improved the understanding failure mechanism of hydrogen assisted SCC.
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