Electrospinning of polyvinylidene difluoride-based nanocomposite fibers

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J.J. Mack Teledyne Scientific Company, Thousand Oaks, California 91360

D.R. Clarke Materials Department, College of Engineering, University of California, Santa Barbara, California 93106-5050 (Received 14 March 2007; accepted 20 September 2007)

Polyvinylidene difluoride fibers and composite fibers with Ni–Zn ferrite nanoparticles and rutile nanoparticles were prepared by electrospinning dimethyl formamide (DMF) solutions. To prevent agglomeration, the ferrite nanoparticles were coated with silica, allowing the formation of a stable ferrofluid in DMF as well as the formation of homogeneous fibers. The rutile nanoparticles could be spun with a uniform distribution within the fiber without silica coating. The effects of various solution properties (viscosity and solids loading for composite fibers) and processing parameters (flow rate and voltage) on fiber morphology and diameter were studied to identify a processing window that resulted in the formation of smooth, defect-free fibers. Of the variables examined, fiber diameter was found to be the most strongly dependent on the viscosity of the electrospinning solution. Infrared spectroscopy revealed that the inclusion of well-dispersed nanoparticles in the electrospun fibers enhanced the presence of the ferroelectric phase in the composite fibers.

I. INTRODUCTION

It has been known for many years that certain properties of materials are mutually exclusive. For instance, there are no materials that have both a high dielectric permittivity and a high magnetic permeability. An explanation for this incompatibility between high permittivity and high permeability in a single compound has recently been given by Hill.1 However, several years ago Van Suchtelen2 proposed that these, and other property combinations, could be achieved by a composite approach. He described two types of composites, series and product composites. The former are composites whose properties are a weighted average of those of the constituent phases, whereas the latter are composites whose properties are a result of a coupling between the phases and are not exhibited by the individual phases themselves. For instance, as he demonstrated, a composite having both magnetic and ferroelectric properties could be achieved by combining a piezoelectric and a magnetostrictive

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Address all correspondence to this author. e-mail: [email protected] DOI: 10.1557/JMR.2008.0003 J. Mater. Res., Vol. 23, No. 1, Jan 2008

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phase with elastic coupling between the two phases. Recent work on these multiferroic composites has focused on both multilayer and nanoscale morphologies of magnetostrictive and piezoelectric oxides.3–5 This article describes the first step in developing a novel multiferroic composite material consisting of a ferroelectric polymer matrix with a high dielectric and/or ferrimagnetic nanoparticle inclusion phase. The focus of this article is to describe the processing conditions for electrospinning polymer composite nanofibers with these prop