Coating Growth on Nanofibers: Multi-Scale Modeling, Simulations and Experiments (original) (raw)
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Modeling, simulation, and experiments of coating growth on nanofibers
Journal of Applied Physics, 2008
This work is a comparison of modeling and simulation results with experiments for an integrated experimental/modeling investigation of a procedure to coat nanofibers and core-clad nanostructures with thin film materials using plasma enhanced physical vapor deposition. In the experimental effort, electrospun polymer nanofibers are coated with metallic materials under different operating conditions to observe changes in the coating morphology. The modeling effort focuses on linking simple models at the reactor level, nanofiber level and atomic level to form a comprehensive model. The comprehensive model leads to the definition of an evolution equation for the coating free surface around an isolated nanofiber. This evolution equation was previously derived and solved under conditions of a nearly circular coating, with a concentration field that was only radially dependent and that was independent of the location of the coating free surface. These assumptions permitted the development of analytical expressions for the concentration field. The present work does not impose the above-mentioned conditions and considers numerical simulations of the concentration field that couple with level set simulations of the evolution equation for the coating free surface. Further, the cases of coating an isolated fiber as well as a multiple fiber mat are considered. Simulation results are compared with experimental results as the reactor pressure and power, as well as the nanofiber mat porosity, are varied.
Soft plasma polymer coatings based on atomic polymerization
Atomic polymerization (plasma polymerization) may be used to form soft polymer coatings of controlled physicochemical properties. Such coatings are utilized to construct functionally gradient and multilayered nanostructures of continuously or quasi-continuously varying physicochemical properties. Tailored nanostructures have high application potential for optical devices, photonic crystals, dielectric coatings, chemical sensors, separation membranes, biocompatible coatings, and polymer composites or nanocomposites of controlled interphase -composites without interfaces.
Polymer, 2013
Transmission electron micrograph images, made at high magnification, of electrospun nanofibers of polyvinylidene fluoride showed rows of dark dots, separated by about 0.24 nm, along segments of molecules. The thin fibers supported themselves across tiny holes, so there was no support material in the field of view. The dots were seen because the electron density of the CF 2 groups is three times that of the intervening CH 2 groups. The polymer nanofibers contained crystals with the polymer chains aligned predominately along the axis of the fiber. A significant degree of long-range translational symmetry, associated with the planar zigzag of backbone carbon atoms and the average lateral separation of the molecules, was maintained as the radiation gradually modified the polymer molecules. These high magnification images showed surprising persistence of the chain-like morphology and segmental motion. Primary radiation damage events were dominant. Many more numerous and damaging secondary radiation events that are encountered in thicker samples, or in support films were almost completely avoided, since the only nearby material where secondary radiation could be generated was in the very thin fiber. The nanofibers contained from 50 to a few hundred molecules in a typical cross section. Irradiation severed the molecules at slow rates until only two or three molecules remained in the fiber, and finally the fiber broke. Evidence was noted that irradiation with electrons also caused loss of fluorine atoms, cross-linking, and chain scission. The entire observed segments of the nanofibers were small enough for detailed comparison of images with calculated molecular models.
Physics and Chemistry of Nanofibers
NATO Science Series, 2004
The structure of HipCO single-wall carbon nanotubes was controlled by Raman scattering during the material heating in three ways: in a laser beam ("in situ"), in an optical oven ("in situ") and after a preliminary heating in the oven followed by Raman measurements. All experiments have demonstrated a diameterselective oxidative etching of the smallest nanotubes (8 -10 Å) at temperatures 400 -450 o C.
Plasma Enhanced CVD of Organosilicon Thin Films on Electrospun Polymer Nanofibers
Plasma Processes and Polymers, 2015
ABSTRACT Organosilicon plasma polymers were deposited on polyvinyl alcohol and polyamide 6 electrospun nanofibers from hexamethyldisiloxane/Ar mixtures in low pressure (LP) radio frequency (RF) discharges with capacitive coupling and by cold RF plasma multi-jets working at atmospheric pressure (AP). The chemistry of the films deposited at LP was significantly varied by changing the RF power and process pressure as studied by X-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy. Both the gas phase and surface processes contributed to the observed differences in the film properties. Significant variations in the nano/microstructure of the plasma polymers prepared by plasma processes at two different pressures were revealed by Atomic force microscopy and Scanning electron microscopy analysis. Modifications of the fibrous materials were investigated with respect to the wettability and structural properties. The values of the water contact angle were strongly influenced by both, the chemical composition of the deposited layers and the overall surface structure.
New Horizons in Modeling and Simulation of Electrospun Nanofibers: A Detailed Review
2014
Electrospinning is applied to create continuous fibers with nanometer diameters through jetting polymer solutions in high electric fields. A drawback of this method, however, is the unstable behavior of the liquid jet, which causes the fibers to be collected randomly. So a critical concern in this process is to achieve desirable control. Studying the dynamics of the electrospinning jet will be easier and faster, if it can be modeled and simulated, rather than doing experiments. This paper focuses on modeling and then simulating the electrospinning process as viewed by different approaches. In order to study the applicability of the electrospinning modeling equations, which have been discussed in detail in earlier parts of this review, an existing mathematical model, in which the jet is considered as a mechanical system, has been interconnected with viscoelastic elements and used to build a numeric method. The simulation features the possibility of predicting essential parameters of ...
Applied Physics Letters, 2003
Ultrathin films of polystyrene were deposited on the surfaces of carbon nanofibers using a plasma polymerization treatment. A small percent by weight of these surface-coated nanofibers were incorporated into polystyrene to form a polymer nanocomposite. The plasma coating greatly enhanced the dispersion of the nanofibers in the polymer matrix. High-resolution transmission-electron-microscopy ͑HRTEM͒ images revealed an extremely thin film of the polymer layer ͑ϳ3 nm͒ at the interface between the nanofiber and matrix. Tensile test results showed considerably increased strength in the coated nanofiber composite while an adverse effect was observed in the uncoated composites; the former exhibited shear yielding due to enhanced interfacial bonding while the latter fractured in a brittle fashion.
Ultrathin fibre coatings on nanofibrous nonwovens by plasma enhanced chemical vapor deposition
Current Directions in Biomedical Engineering, 2021
For the generation of tailor-made polymer coatings on nanofibrous nonwovens plasma enhanced chemical vapor (PECVD) is a promising process, even for complex geometries. The plasma coatings can greatly improve their suitability for biomedical applications by optimising biocompatibility to the local needs, especially for cardiovascular disease treatments. Therein, wound healing and endothelialisation are important steps which are connected by a complex interaction. The monomers allylamine and hexamethyldisiloxane, as well as different process conditions were studied for the coating of nanofibrous thermoplastic silicone polycarbonate polyurethane (TSPCU) nonwovens. Aim of this study was to investigate the feasibility of plasma polymer coating under preservation of the nanofibrous morphological structure. Beside characterization of the nonwoven, biological evaluation with endothelial and fibroblast cells was performed. The prepared nonwoven samples support the feasibility of plasma coati...