In this paper we report of obtaining novel nanocomposite structures based on isotactic polypropylene and nanoparticles of titanium. The distribution of titanium nanoparticles in the polymer matrix was studied by optical (Zeiss Axio Imager A2m) and scanning electron microscopy (SEM, Jeol JSM-767F). The IR spectra reveal that after the introduction of titanium nanoparticles in the polypropylene matrix there is a significant decrease in the intensity of the band at 2950 cm-1 and 2839 cm-1 which indicate on weakening CH stretching vibrations in the spectrum of polypropylene. SEM studies of polypropylene (PP) and nanocomposites based on PP+Ti showed that the introduction of nanoparticles in polypropylene leads to change of the supramolecular structure of the polymer and forming of a relatively ordered structure with the introduction of 1% of titanium nanoparticles in the polymer. It has been also shown that the dielectric permittivity of the nanocomposite not changed as the frequency increases, and this is explained by lack of polarization processes. It was found that the temperature dependence of the resistivity of the nanocomposite has three areas. On the first and third areas the resistivity of the nanocomposite decreases linearly with temperature, on the second-decreases abruptly. The first area of depending of ρ on the temperature is conditioned by the increase of the electrical conductivity of the nanoparticles. At reaching the melting point of the polymer, due to the transition from the crystalline to the amorphous phase, the volume of the nanocomposite sample increases dramatically at a narrow temperature range, which leads to an abrupt increase in resistivity. The third area corresponds to a sharp increase of conductivity of the polymer matrix.

The structure and dielectric measurements made on the nanocom-posites based on PP polypropylen and TiO 2 nanoparticles are reported in this paper. It has been defined that, the incorporation of TiO 2 nanoparticles to the PP matrix enhances the dielectric constant of nanocomposites in comparison with the pristine polypropylene. The dependence of dielectric permittivity of nanocomposites of different volume contents of titanium dioxide (TiO 2) nanoparticles changes with an extremum, for 1% content of TiO 2 nanoparticles in polypropylene matrix the dielectric permittivity (er') reaches at its peak and then gradually decreaseMoreover the posistor effect is observed for nanocomposites based on PP/TiO 2. Thermal properties of PP/TiO 2 nanocomposites were also studied. With the addition of nanoparticles with the volume content of 1% the degradation temperature for nanocomposites shifts to relatively higher temperatures (54 C) as compared to the pure polymer. At lower concentrations, nanoparticles play the role of structurant, which in turn leads to the enhancement of electrophysical and thermal properties of these nanocomposites. ARTICLE HISTORY

IOP Conference Series: Materials Science and Engineering, 2015

In this paper, we present the synthesis of poly vinyl pyrrolidone (PVP) / titanium dioxide nanocomposites via sol-gel technique. The structural and dielectric properties of the samples were also analysed in this work. PVP doped with varying concentrations of TiO 2 are prepared by the sol-gel route. The prepared composites were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM) and impedance spectroscopy. XRD and TEM confirm the presence of TiO 2 nanoparticles in the composites. The dielectric response and the AC electrical conductivity of the samples are investigated for the frequency range 1 kHz-2MHz at room temperature. The dielectric studies show low values for dielectric constant and loss at high frequencies.

2020 IEEE 3rd International Conference on Dielectrics (ICD), 2020

This study focuses on the influence of polar and unpolar surface functionalization of silica on the dielectric performance of PP/POE (polypropylene/poly(ethylene-cooctene)) nanocomposites. The silica fillers were surface-modified with unpoalr trimethylethoxysilane (TMES) or polar 3aminopropyl triethoxysilane (APTES). Fourier-Transform Infrared Spectroscopy and Thermogravimetric analysis were performed and confirmed qualitatively and quantitatively the successful silica-silane modification. Silica/PP/POE nanocomposite films were prepared using a mini-extruder. Scanning Electron Microscope images showed good dispersion of the modified silica in the PP/POE matrix. However, the polar silica cluster size (300 nm) is slightly larger than the one of the unpolar silica (100 nm). Thermally Stimulated Depolarization Current (TSDC) characterization data showed that the polar silica introduced deeper charge traps than the unpolar one, which also showed higher trap density. The apparent conductivity measured during the TSDC poling phase indicated that the polar silica filled nanocomposites featured very fast polarization to reach the saturation state, while the unpolar silica had a rather slow polarization rate. From Pulsed Electroacoustic Analysis it was obvious that the space charge is suppressed by addition of the polar silica, but increased by the presence of the unpolar silica.

Japanese Journal of Applied Physics, 2012

A poly(methyl methacrylate)-doped titanium dioxide (PMMA:TiO 2) nanocomposite film was obtained by spin coating the nanocomposite solution onto a silicon substrate. The nanocomposite solutions were prepared by dissolving the PMMA and TiO 2 nanopowder in three different types of organic solvent, namely, toluene, tetrahydrofuran (THF), and acetone. We found that the dielectric properties of the PMMA:TiO 2 nanocomposite are dependent on the type of solvent used. The dielectric properties measured at a frequency of 1 kHz showed that acetone gives the highest dielectric constant and capacitance compared with toluene and THF. Toluene gives the lowest dielectric loss among the three. The topography and roughness of the PMMA:TiO 2 nanocomposite indicate that a particular solvent results in a different kind of surface morphology.

Composites Part A: Applied Science and Manufacturing, 2015

TiO 2 /epoxy nanocomposites were prepared at different filler concentrations varying from 3 to 12 phr (parts per hundred resin per weight). The dispersion of TiO 2 was examined by Scanning Electron Microscopy and proved to be adequate. Differential Scanning Calorimetry was implemented to determine the glass to rubber transition temperature of the polymer matrix. The dielectric analysis was performed via Broadband Dielectric Spectroscopy in a wide frequency and temperature range. Five different mechanisms were observed in the spectra of the examined composites which are identified, in terms of increasing temperature at constant frequency, as c, b, Intermediate Dipolar Effect (IDE), a and Interfacial Polarization (IP) relaxation modes. The activation energies of all relaxation modes were calculated. Finally, the dielectric response of the TiO 2 nanocomposites compared to that of the TiO 2 microcomposites reveals that the former exhibit significantly higher energy storage efficiency even at lower TiO 2 concentration than the corresponding of the microcomposites.

Dielectrics and …, 2005

The incorporation of silica nanoparticles into polyethylene increased the breakdown strength and voltage endurance significantly compared to the incorporation of micron scale fillers. In addition, dielectric spectroscopy showed a decrease in dielectric permittivity for the nanocomposite over the base polymer, and changes in the space charge distribution and dynamics have been documented. The most significant difference between micron scale and nanoscale fillers is the tremendous increase in interfacial area in nanocomposites. Because the interfacial region (interaction zone) is likely to be pivotal in controlling properties, the bonding between the silica and polyethylene was characterized using Fourier Transformed Infra-red (FTIR) spectroscopy, Electron Paramagnetic Resonance (EPR), and X-ray Photoelectron Spectroscopy (XPS) The picture which is emerging suggests that the enhanced interfacial zone, in addition to particle-polymer bonding, plays a very important role in determining the dielectric behavior of nanocomposites.

MATERIALE PLASTICE

iPP/TiO 2 samples containing various amount of nanofiller (5, 10, 15, 20 and 30 %) are investigated in the γradiation field. Thermal stability and electrical properties (permittivity, dielectric loss and volume resistivity) were assessed for the evaluation of the effects of compounding on the functional performances of basis polymer material. The improvement in the thermal stability has been emphasized. The correlation between the presence of TiO 2 nanoparticles at various levels of concentration and electrical behavior is discussed.

Owing to the high surface to volume ratio of nanoparticles, nanoparticle-modified polymers promise to exhibit properties exceeding bounds predicted by effective media approaches, where the effective response is not solely dependent on inherent nanoparticle properties but rather dominated by nature and volume content of interface. This study is focused on 1) investigating impact of surface treatment and thermal processing of nanoTiO2-modified-PVDF on dielectric and mechanical properties of resulting nanocomposites, and 2) highlighting a unique dielectric behavior of nanoparticle-reinforced polymers where an initial increase in dielectric permittivity is seen at very low content followed by a decrease resulting from nanoparticle-polymer interaction. X-Ray Photoelectron Spectroscopy (XPS) and Fourier Transform Infrared spectroscopy (FT-IR) confirm efficient particle surface modification by showing the presence of atoms from coupling agent molecules on the particle's surface. Scanning Electron Microscopy (SEM) of TiO2/PVDF nanocomposites verifies that surface porosity was removed by a post annealing process. Dynamic Mechanical Analysis (DMA) results demonstrate an increase in storage modulus in the glassy region from 67 to 108% as compared to the pristine PVDF for TiO2 contents varying from 5 to 20 wt% (2.3 to 10 vol%) as a result of adding functionalization and thermal treatment. Based on Dielectric Spectroscopy measurements, a 74% increase in permittivity is observed at 0.1 Hz and a 30% increase at 1 kHz, both at relatively low volume content (2.3 vol%), owing to the good dispersion, high interfacial volume content and strong interaction. A further increase of TiO2 content decreases the dielectric permittivity as a result of dipolar confinement. Contributions of the study are two-fold: firstly, compared to the current literature, this increase in the value of dielectric permittivity at such a low volume content using TiO2 nanoparticles is unprecedented and has not been reported so far; and secondly, the study brings to light a unique nanodielectric behavior where the initial increase in permittivity is followed by a decrease owing to dipolar confinement resulting from particle/polymer interaction

Advances in Condensed Matter Physics, 2016

TiO2/polypyrrole composites with high dielectric constant have been synthesized byin situpolymerization of pyrrole in an aqueous dispersion of low concentration of TiO2, in the presence of small amount of HCl. Structural, optical, surface morphological, and thermal properties of the composites were investigated by X-ray diffractometer, Fourier transform infrared spectroscopy, field-emission scanning electron microscopy, and thermogravimetric analysis, respectively. The data obtained from diffractometer and thermal gravimetric analysis confirmed the crystalline nature and thermal stability of the prepared composites. The dielectric constant of 5 wt% TiO2increased with filler content up to 4.3 × 103at 1 kHz and then decreased to 1.25 × 103at 10 kHz.