Many-particle charged-particle plasma simulations using spatial meshes for the electromagnetic field solutions, particle-in-cell (PIC) merged with Monte Carlo collision (MCC) calculations, are coming into wide use for application to partially ionized gases. The author emphasizes the development of PIC computer experiments since the 1950s starting with one-dimensional (1-D) charged-sheet models, the addition of the mesh, and fast direct Poisson equation solvers for 2-D and 3-D. Details are provided for adding the collisions between the charged particles and neutral atoms. The result is many-particle simulations with many of the features met in low-temperature collision plasmas; for example, with applications to plasma-assisted materials processing, but also related to warmer plasmas at the edges of magnetized fusion plasmas. >

Particle-in-Cell Charged Particle Simulations, plus Monte Carlo Collisions with Neutral Atoms, PIC-MCC

an introduction to electrospinning and nanofibers is available in our book collection an online access to it is set as public so you can download it instantly. Our book servers spans in multiple countries, allowing you to get the most less latency time to download any of our books like this one. Kindly say, the an introduction to electrospinning and nanofibers is universally compatible with any devices to read.

An Introduction To Electrospinning And Nanofibers

Textbook Of Polymer Science

Electrospinning with various machine configurations is being used to produce polymer nanofibers with different rates of output. The use of polymers with high viscosity and the encapsulation of nanoparticles for achieving functionalities are some of the limitations of the existing methods. A profiled multi-pin electrospinning (PMES) setup is demonstrated in this work that overcomes the limitations in the needle and needleless electrospinning like needle clogging, particle settling, and uncontrolled/uneven Taylor cone formation, the requirement of very high voltage and uncontrolled distribution of nanoparticles in nanofibers. The key feature of the current setup is the use of profiled pin arrangement that aids in the formation of spherical shape polymer droplet and hence ensures uniform Taylor cone formation throughout the fiber production process. With a 10 wt% of Polyvinyl Alcohol (PVA) polymer solution and at an applied voltage of 30 kV, the production rate was observed as 1.690 g/h and average fiber diameter obtained was 160.5 ± 48.9 nm for PVA and 124.9 ± 49.8 nm for Cellulose acetate (CA) respectively. Moreover, the setup also provides the added advantage of using high viscosity polymer solutions in electrospinning. This approach is expected to increase the range of multifunctional electrospun nanofiber applications.

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A Novel Profiled Multi-Pin Electrospinning System for Nanofiber Production and Encapsulation of Nanoparticles into Nanofibers

Electric field strength and polarity in electrospinning processes and their effect on process dynamics and the physical properties of as-spun fibers is studied. Using a solution of the neutral polymer such as poly(methyl methacrylate) (PMMA) we explored the electrospun jet motion issued from a Taylor cone. We focused on the straight jet section up to the incipient stage of the bending instability and on the radius of the disk of the fibers deposited on the collecting electrode. A new correlation formula using dimensionless parameters was found, characterizing the effect of the electric field on the length of the straight jet, L˜E~E˜0.55. This correlation was found to be valid when the spinneret was either negatively or positively charged and the electrode grounded. The fiber deposition radius was found to be independent of the electric field strength and polarity. When the spinneret was negatively charged, L˜E was longer, the as-spun fibers were wider. The positively charged setup resulted in fibers with enhanced mechanical properties and higher crystallinity. This work demonstrates that often-overlooked electrical polarity and field strength parameters influence the dynamics of fiber electrospinning, which is crucial for designing polymer fiber properties and optimizing their collection.

The Role of Electrical Polarity in Electrospinning and on the Mechanical and Structural Properties of As-Spun Fibers.

This study was carried out to evaluate the influence of high voltage polarity on a newly designed multi-pin upward electrospinning spinneret to produce poly (vinyl alcohol) nanofibers. Two different high voltage polarity configurations were applied to the spinneret and collector, namely collector charging configuration (configuration-1) and spinneret charging configuration (configuration-2). The outcomes demonstrated that the collector charging configuration is better in case of upward multi-pin electrospinning setup, to their conservative framework in terms of stable Taylor cone formation, smaller fiber diameter and less bead formation. Electrical field profile in the electrospinning zone was investigated using finite element modelling for both the configurations. No difference in electric field intensity norm (|E|) was observed near the tip of the pins for both the polarities (configurations). Although having the same magnitude, the dominant electrical field component, Ez for configuration -1 is found to be of opposite sign to that of configuration -2. The electrostatic simulations also suggested that all the pins were not at the same potential and that there was a minor difference in pin potentials. Also, optimizations of pin length to reduce the potential differences between the pins were theoretically estimated through COMSOL3D simulation software.

https://krishi.icar.gov.in/jspui/bitstream/123456789/34793/1/polymer%20research%20paper%20original%20download%20%281%29%20%283%29.pdf

Influence of high voltage polarity in multi-pin upward electrospinning system on the Fiber morphology of poly (vinyl alcohol)

A new computational model to understand the mechanism of discharges along the gas/solid interface at high voltage and high pressure is made based on the models of explosive electron emission, secondary emission, and neutral gas ionization by using finite-difference time domain-based particle-in-cell code. The charge particle movement at different durations is obtained at a pressure of 1 atmosphere. The profiles of phase space, the net charge density along the gap, and the effect of the dielectric on the characteristics of the gas discharge are presented. The ionization coefficient (α) and drift velocity (ve) calculated from simulation data closely match with the existing experimental results.

Particle-in-Cell Simulations of Discharge Along Gas–Solid Interface

An investigation of the reflex triode virtual cathode oscillator based on simulations with 3-D particle-in-cell code developed by ATK Mission Systems is done. The device model is based on an actual experimental setup with 15-mm anode–cathode gap. The obtained simulation results use a single-shot 200-kV, 300-ns pulse at anode. Numerical analysis is done to validate the results and to gain insight into the dynamics of the electrons emitted from the cathode surface and their movement between the cathode and the virtual cathode. The obtained single dominant microwave frequency for the model is 2.35 GHz with virtually no competing frequencies.

Modeling of Reflex Triode Virtual Cathode Oscillator

The objective of this paper is to report findings based on the particle-in-cell (PIC) modeling of the axial and coaxial virtual cathode oscillators in order to validate the experiments already performed on these devices over the years. In addition to this, observations regarding validation and similarities between the simulations and the experiments have been reported, with an emphasis on analysis of device parameters such as e-beam voltage, current density, and microwave power. Theoretical aspects of a virtual cathode oscillator (vircator) and some of the key experimental works have been revisited. Investigation is done on the power generated in a coaxial vircator, and various cavity modifications have been tested for the coaxial vircator using the MAGIC3D, PIC tools suite, in order to search for improvement in the device efficiencies. Also, the axial vircator has been modeled to comment on the particle energies, device design, and beam quality associated with it.

Particle-in-Cell Modeling of Axial and Coaxial Virtual Cathode Oscillators

An experimental S-band Relativistic Backward Wave Oscillator (RBWO) which uses Kilo Ampere Linear Injector (KALI) which is a 30GW system and for this system voltage pulse has been simulated using Particle-In-Cell (PIC) code. The motivation of this paper is to study the effect of replication of KALI input pulse and magnetic field profile, obtained from experimental data into the PIC simulations, which in turn will help in optimizing the design of the device. The actual KALI pulse of ~550kV peak voltage, 100ns duration and 20ns rise time is simulated as a temporal function of the voltage instead of a conventional dc pulse. The experimental magnetic field with peak value of ~0.5T is not constant and changes along the longitudinal axis (z). Hence, the same is expressed in the PIC code as a spatial function of the z-coordinate instead of a constant value. The output power from the PIC simulations with KALI input pulse is found to be in close agreement with the experimental results against the output power obtained from the PIC simulations with conventional dc pulse.

Ayush Saxena

Papers

Influence of high voltage polarity in multi-pin upward electrospinning system on the Fiber morphology of poly (vinyl alcohol)

Particle-in-Cell Simulations of Discharge Along Gas–Solid Interface

Modeling of Reflex Triode Virtual Cathode Oscillator

Particle-in-Cell Modeling of Axial and Coaxial Virtual Cathode Oscillators

Particle-in-cell simulation of a RBWO with experimental voltage input pulse and external magnetic field