The variation of the physical properties of different carbon nanofibers, CNFs, based-polymer nanocomposites processed by twin-screw extrusion , TSE, was investigated. Nanocomposites fabricated with CNFs with highly graphitic outer layer revealed electrical isolation-to-conducting behaviour as function of CNFs´content. Nanocomposites fabricated with CNFs with an outer layer consisting on a disordered pyrolitically stripped layer, in contrast, revealed better mechanical performance and enhanced thermal stability. Further, CNFs´ incorporation to the polymer matrix increased the thermal stability and the degree of crystallinity of the polymer, independently on the filler content and type. In addition, dispersion of the carbon nanofibers´ clusters in polypropylene composites was analysed by transmitted light optical microscopy, LOM, and greyscale analysis, GSA. The results showed a correlation between the filler concentration and the variance, a parameter which measures quantitatively the dispersion, for all composites. This method indicated a value of 1.4 vol % above which large clusters of CNFs cannot be dispersed effectively and as a consequence only slight changes in mechanical performance are observed. Finally, this study establishes that the physical properties of carbon nanofiber based-polymer nanocomposites can be tailored as function of both adequate CNFs´ structure and content.

The ferroelectric (FE) betaine arsenate (BA) and the antiferroelectric (AF) betaine phosphate (BP) are structurally very closely related and mixed crystals of BA(x)BP(1-x) can be grown over the whole concentration range. The concentration (x)-temperature (T)-pressure (P) phase diagram of the system is characterized by a transition from an AF to a FE phase along with the appearance of some mixed regions upon changing concentration. Depending on concentration, one or two relaxation processes appear in the low-temperature region of the phase diagram. Measurement of the hysteresis loops and the current curves have been carried out along the (x-T-P)-phase diagram of this system. Multiple loops have been observed in various regions of the phase diagram. The correlation of the different contributions of the polarization and the temperature behavior of their critical fields with the main features of the temperature- and frequency-dependent dielectric constant enables clarification of the rich phase diagram obtained in this mixed compound in terms of the ferro- and/or antiferroelectric interactions.

The first book on this topic provides a comprehensive and well-structured overview of the fundamentals, synthesis and emerging applications of magnetoelectric polymer materials. Following an introduction to the basic aspects of polymer based magnetoelectric materials and recent developments, subsequent chapters discuss the various types as well as their synthesis and characterization. There then follows a review of the latest applications, such as memories, sensors and actuators. The book concludes with a look at future technological advances. An essential reference for entrants to the field as well as for experienced researchers.

Carbon nanotubes / poly(vinylidene fluoride) composites were prepared using CNT with different oxidation and thermal treatments. The oxidation procedure leads to CNT with the most acidic characteristics that lower the degree of crystallinity of the polymer and contribute to a large increase of the dielectric constant. The surface treatments, in general, increase percolation threshold and decrease conductivity, but, on the other hand, are able to promote the nucleation of the electroactive phase of the polymer, which is suitable for the use of PVDF in sensors, actuators and other smart materials applications. Finally, the surface treatments do not seem to affect CNT interaction among them, reaching similar degrees of dispersion in all cases, as shown by the SEM results. The maximum value of the dielectric constant is ~630. It is demonstrated that the composite conductivity can be attributed to a hopping mechanism that is strongly affected by the surface treatment of the CNT.

Neutron diffraction was used to study the paraelectric (PE) to antiferroelectric (AFE) phase transition in a deuteron glass crystal Rb-0.5(ND4)(0.5)D(2)ASO(4) (DRADA-50). Coexistence of AFE and PE phases was proven in a temperature range 7-12 K wide.

The ferroelectric (FE) betaine arsenate (BA) and the antiferroelectric (AF) betaine phosphate (BP) are structurally very closely related and mixed crystals of BAxBP1-x can be grown over the whole concentration range. The concentration (x) – temperature (T) – pressure (P) phase diagram of the system is characterized by a transition from an AF to a FE phase along with the appearance of some mixed regions on changing concentration. Depending on concentration, one or two relaxation processes appear in the low temperature region of the phase diagram. Measurement of the hysteresis loops and the current curves have been carried out along the (x-T-P)-phase diagram of this system. Multiple loops have been observed in various regions of the phase diagram. The correlation of the different contributions of the polarization and the temperature behavior of their critical fields with the main features of the temperature and frequency dependent dielectric constant enables clarification of the rich phase diagram obtained in this mixed compounds in terms of the ferro- and/or antiferroelectric interactions.

Ferroelectric (FE) betaine arsenate (BA) and antiferroelectric (AF) betaine phosphate (BP) are structurally very closely related and mixed crystals BA(x)BP(1-x) can be grown over the full concentration range. This system exhibits interesting pressure-temperature-concentration phase diagrams in which the transition in concentration from an AF to a FE phase can be observed with a concentration-dependent appearance of some mixed regions. At low temperatures different relaxation processes have been observed that might be related to the transition from a domain state to an orientational glass depending on concentration. In some regions of the phase diagram different phases coexist. The origin of the different transitions and relaxation processes is still unclear and recent x-ray-diffraction studies reveal that the peculiar behavior of the mixed crystals cannot be explained from the structural point of view. We have performed Raman and infrared investigation of samples across the whole (x, T) phase diagram, at various hydrostatic pressures, in order to shed light on the structural origin of the different processes. It is concluded that the FE or AF character of the ordered phase is related to the degrees of freedom of the AsO4 and PO4 tetrahedra. In the same way these units determine the type and the modes triggering the phase transitions for each concentration. The latter seems to occur together with a participation of the betaine molecule, especially of the methyl and buthyl groups.

Temperature and frequency dependent hysteresis loop measurements have been carried out along the phase diagram of ferroelectric (FE) betaine at-senate (BA) and antiferroelectric (AF) betaine phosphate (BP) mixed crystal system (BA(x)BP(1-x)). Coexistence regions characterized by competing ferro- and/or antiferroelectric interactions are detected by multiple hysteresis loops.

Films of semicrystalline poly(vinylidene fluoride) (PVDF) in the β-phase have been studied by means of dielectric measurements and Fourier Transform Infrared Spectroscopy (FTIR). The main goal of the study was to compare the dielectric relaxations of α- and β-PVDF and to improve the understanding of the structural changes that occur in β-PVDF during a mechanical deformation process and their impact in the electromechanical properties of the polymer. A reorientation of the chains and a decrease in the degree of crystallinity with increasing deformation was observed.

Two different types of carbon nanofibers (CNF) were incorporated in the same polypropylene (PP) matrix by twin-screw extrusion. The electrical characterization of both CNFs / PP composites as a function of volume fraction show different electrical performance: conducting and non-conducting. The objective of this work is to study the rheological behaviour of both composites with the aim of relating it to the electrical behaviour. The results indicate that the rheological behaviours are different, suggesting that rheology differentiates the microstructural variations responsible for the electrical performance. Furthermore, the main rheological parameters were correlated to the electrical conductivity. The results show that G´/ G´´ and G´ are the most sensitive parameters when compared to the onset of electrical percolation. Finally, in spite of the intrinsic measuring differences between electrical and rheological analysis, the two calculated thresholds are very similar: ~ 0.5 for the rheological and ~ 0.4 for the electrical.