MULTIFERROFLEX
DESIGN OF NEW FLEXIBLE POLYMER BASED FILMS EXHIBITING MAGNETOELECTRIC PROPERTIES THROUGH THE TAILORING OF THE HYBRID INTERFACE
The miniaturization and the availability of new syntheses and characterization techniques have allowed the preparation of a large variety of interesting nanoscale materials, leading to new magnetic properties and a great interest in various research topics ranging from high density magnetic storage to biomedical applications. Besides scientific interest in their physical properties, multiferroics have potential for many applications such as actuators, magnetic field sensors or new types of electronic memory devices.
Even if ME effect was first observed in inorganic single crystals, their use on device applications was not successful since these materials exhibit weak ME effect. In order to overcome these limitations, the use of composite materials is appealing and promising. In this project, we focus on organic-inorganic materials and more precisely on magnetic polymer based free-standing films for possible multiferroic applications.
MultiFerroFlex project deals with the synthesis and characterization of flexible artificial multiferroic (MF) materials constituted of ferroelectric polymer (poly(vinylidene fluoride), PVDF) and inorganic ferromagnetic nanoparticles, exhibiting magnetoelectric (ME) effect. We aim at focusing on the relationships between the hybrid interface (controlled by the synthesis route) and the resulting magneto-electric coupling (coupled magnetic and dielectric properties).
First, we propose to study the influence of the functionalization of magnetic ferrite nanoparticles (NPs) (by fluorinated molecules or telomers) in order to tailor the hybrid interface when preparing magneto-electric (ME) films. Indeed, such functionalized NPs can exhibit better miscibility and dispersion in hydrophobic PVDF and strongly influence the PVDF crystallization. We plan to define the key-parameters promoting the crystallization of PVDF in its β-phase (e.g. size and content of NPs, temperature of the ultrasonic bath, how long NPs have to be stirred in the polymer solution, surface chemistry).
Then, the stress-induced self-crystallization of piezoelectric polymer phase will be achieved by coupling tensile tests to X-ray diffraction (for monitoring the crystalline phase modifications). This new synthetic pathway appears promising for optimizing the ME coupling since the flexibility of the polymer allows the transmission of interfacial strains without modifying the structure of the NPs.
Finally, coupled properties will be measured by near-field techniques to assess the potential of these materials for future ME devices.
ABOUT MULTIFERROFLEX
Project
The purpose of MultiFerroFlex project is to synthesize, by a chemical route, new polymer-based hybrid materials exhibiting a magneto-electric effect. Few studies describe such chemically made materials from magnetic nanoparticles and organic compounds (e.g. ferroelectric liquid crystals, metal-organic frameworks) and the weak mechanical properties of these systems are still drawbacks for future devices in magnetic recording. Thus, the polymer route appears appealing to develop new and promising materials for real applications since flexible devices can be produced.
We aim at focusing on the relationships between the hybrid interface (controlled by the synthesis route) and the resulting magnetic, dielectric and mechanical properties to increase significantly the ME coefficient.
Skills and facilities
Preliminary results could be obtained in 2013 on the feasibility of the project in the framework of the Laboratory of Excellence “Science and Engineering for Advanced Materials and devices” (LabEx SEAM). We bought the adapter between tensile tester and XRD, both being available at Paris Diderot and to sponsor the 6 months internship of Ms Sofia Marchesini (MSc student in Materials Engineering in Padova, Italy).
I developed neat PVDF and hybrid 6 nm superparamagnetic CoFe2O4 NPs / PVDF flexible films in order to define the scientific procedures to be used for each characterization technique (mainly IR, SEM, XRD, SAXS, DSC, PFM and tensile tests).
I identify how to get β-PVDF tuning the processing temperature.
First PFM measurements made by Silvana Mercone, allowed us to measure the local piezoelectric response.
One current downside could be mentioned regarding the XRD results: performing XRD on PVDF is not always so easy and we improved this characterization during MultiFerroFlex.