Ehab Abdelhamid

Fabrication of flexible and self-standing inorganic–organic three phase magneto-dielectric PVDF based multiferroic nanocomposite films through a small loading of graphene oxide (GO) and Fe3O4 nanoparticles

Flexible inorganic-organic magneto-electric (ME) nanocomposite films (PVDF, PVDF-GO, PVDF-Fe3O4 and PVDF-GO-Fe3O4), composed of well-dispersed graphene oxide (GO 5 wt%) and magnetic Fe3O4 nanoparticles (5 wt%) embedded into a poly(vinylidene-fluoride) (PVDF) matrix, have been prepared by a solvent casting route. The magnetic, ferroelectric, dielectric, magneto-dielectric (MD) coupling and structural properties of these films have been systematically investigated. Magnetic (Ms = 2.21 emu g(-1)) and ferroelectric (P = 0.065 μC cm(-2)) composite films of PVDF-GO-Fe3O4 (PVDF loaded with 5% GO and 5% Fe3O4) with an MD coupling of 0.02% at room temperature (RT) showed a three times higher dielectric constant than that of the pure PVDF film, with a dielectric loss as low as 0.6. However, the PVDF-Fe3O4 film, which exhibited improved magnetic (Ms = 2.5 emu g(-1)) and MD coupling (0.04%) properties at RT with a lower dielectric loss (0.3), exhibited decreased ferroelectric properties (P = 0.06 μC cm(-2)) and dielectric constant compared to the PVDF-GO-Fe3O4 film. MD coupling measurements carried out as a function of temperature on the multi-functional PVDF-GO-Fe3O4 film showed a systematic increase in MD values up to 100 K and a decrease thereafter. The observed magnetic, ferroelectric, dielectric, MD coupling and structural properties of the nanocomposite films are attributed to the homogeneous dispersion and good alignment of Fe3O4 nanoparticles and GO in the PVDF matrix along with a partial conversion of nonpolar α-phase PVDF to polar β-phase. The above multi-functionality of the composite films of PVDF-Fe3O4 and PVDF-GO-Fe3O4 paves the way for their application in smart multiferroic devices.

Enhancement of dielectric, ferroelectric and magneto-dielectric properties in PVDF–BaFe12O19 composites: a step towards miniaturizated electronic devices

Highly flexible inorganic–organic composite films of barium hexaferrite (BHF) nanoparticles and a polyvinylidene fluoride (PVDF) polymer with small but appreciable magneto-dielectric coupling have been fabricated at room temperature. The films have been thoroughly characterized by using different techniques like X-ray Diffraction (XRD), Fourier Transform Infrared spectroscopy (FTIR) and Scanning Electron Microscopy (SEM). Coexistence of alpha and beta forms of PVDF has been established in undoped and doped PVDF. The amount of electro-active β phase of PVDF increases with an increase in filler (BHF) amount. Interestingly, dielectric permittivity of PVDF is enhanced up to eight times upon addition of the optimum amount of BHF. This increase in permittivity has been explained by the space charge polarization at the interfaces between the two phases of the composite and the formation of several micro-capacitors within the samples. The electrical and magnetic polarization measurements on the films confirm the composite materials are ferroelectric as well as ferromagnetic in nature. Subsequently, magneto-dielectric (MD) coupling measurements confirm the multiferroic nature of the composite films.

Multiferroic PVDF–Fe3O4 hybrid films with reduced graphene oxide and ZnO nanofillers

Flexible and self-standing polyvinylidene fluoride (PVDF) films loaded with nanofillers, reduced graphene oxide (RGO), zinc oxide (ZnO) and magnetic iron oxide (Fe3O4) nanoparticles, were prepared by a solvent casting method. The crystallinity, morphology and structure of these films were studied using XRD, SEM, FTIR and Raman spectroscopy. FTIR studies reveal a higher percentage of polar ferroelectric β-phase (∼80%) in both pristine PVDF and PVDF–RGO films, whereas the addition of nanofillers, Fe3O4 and ZnO, resulted in a reduced amount of β-phase (∼50%) in the films. Of all the films studied, PVDF–RGO shows an enhanced dielectric constant as well as maximum electric polarization. On the other hand, Fe3O4 loaded–PVDF composite films exhibit reduced values of both dielectric constant and electric polarization. A weak magneto-dielectric behavior is observed in Fe3O4 loaded PVDF nanocomposite films at room temperature with a coupling constant ∼0.04%.

Synthesis of colloidal MnSb nanoparticles: consequences of size and surface characteristics on magnetic properties

A solution phase methodology was developed for the formation of discrete colloidal MnSb nanoparticles using dimanganesedecacarbonyl and triphenylantimony as the main reaction components. Stoichiometric reactions result in significant Sb impurities, but these can be eliminated by the use of excess Mn reagent, limiting the reaction time, and using a lower temperature (280 °C) relative to that commonly employed for MnP or MnAs synthesis (330–360 °C). The resultant MnSb nanoparticles are, when evidenced by both powder X-ray diffraction and transmission electron microscopy, ca. 14 nm in diameter and exhibit low polydispersity (13 ± 1.7 nm). High Angle Annular Dark Field-Scanning Transmission Electron Microscopy and energy dispersive line scan data revealed that the as-synthesized MnSb nanoparticles are core–shell in nature, having a MnSb core and an amorphous manganese oxide shell. Evidence is presented supporting a pathway for decomposition of MnSb nanoparticles driven by formation of MnO2 and Sb due to reaction with adventitious O2. The MnSb nanoparticles are superparamagnetic at room temperature, and exhibit suppressed moments attributed to surface oxidation arising from the high surface area and intrinsic oxophilicity of Mn.