Cluster synthesis of monodisperse rutile-TiO₂nanoparticles and dielectric TiO₂–vinylidene fluoride oligomer nanocomposites

Abstract

The embedding of oxide nanoparticles in polymer matrices produces a greatly enhanced dielectric response by combining the high dielectric strength and low loss of suitable host polymers with the high electric polarizability of nanoparticles. The fabrication of oxide-polymer nanocomposites with well-controlled distributions of nanoparticles is, however, challenging due to the thermodynamic and kinetic barriers between the polymer matrix and nanoparticle fillers. In the present study, monodisperse TiO(2) nanoparticles having an average particle size of 14.4 nm and predominant rutile phase were produced using a cluster-deposition technique without high-temperature thermal annealing and subsequently coated with uniform vinylidene fluoride oligomer (VDFO) molecules using a thermal evaporation source, prior to deposition as TiO(2)-VDFO nanocomposite films on suitable substrates. The molecular coatings on TiO(2) nanoparticles serve two purposes, namely to prevent the TiO(2) nanoparticles from contacting each other and to couple the nanoparticle polarization to the matrix. Parallel-plate capacitors made of TiO(2)-VDFO nanocomposite film as the dielectric exhibit minimum dielectric dispersion and low dielectric loss. Dielectric measurements also show an enhanced effective dielectric constant in TiO(2)-VDFO nanocomposites as compared to that of pure VDFO. This study demonstrates for the first time a unique electroactive particle coating in the form of a ferroelectric VDFO that has high-temperature stability as compared to conventionally used polymers for fabricating dielectric oxide-polymer nanocomposites.

Prospects for nanoparticle-based permanent magnets

“…For example, directly ordered nanocomposites particles can be produced using the cluster-deposition process and subsequently be aligned with the easy axis of hard phase and coated with a thin non-magnetic layer, prior to deposition. The formation of a thin layer of non-magnetic material is possible by employing a sputtering or evaporation source between the cluster-formation and deposition chambers [57][58][59]. While the thin non-magnetic layer eliminates the inter-composite particle interactions and can enhance the amount of inclusion of soft phases compared with the hard phase without much reduction in coercivities, the magnetic alignment is expected produce an ideal square loop with M r /M s = 1.…”

Structure and performance of dielectric films based on self-assembled nanocrystals with a high dielectric constant

“…With the ever growing trend towards integration, versatility and miniaturization in electronic devices, discrete surface mounted passive components (capacitors, resistors and inductors, and the range of types therein) are assessed for their ability to become embedded in integrated circuit (IC) design [2,3]. Such embedded capacitors require dielectric thin films with stable and high dielectric constants over a wide frequency and temperature range, high dielectric strength, low dielectric loss, low leakage current and ideally a low processing temperature that is compatible with the fabrication techniques of an integrated device manufacturer (IDM) [8][9][10]16]. One such application is the design of capacitors for switched DC-DC power conversion, for which specialized operation is desired at high frequency and with low equivalent series resistance (ESR) [17,18].…”

Study on the Thermal and Dielectric Properties of SrTiO3/Epoxy Nanocomposites

“…Therefore, the thermal conductivity of the composites must be increased by modifying the surface of the particles [12][13][14][15][16][17]. A thermal analysis was conducted using the TG-DSC test to examine further the thermal stability of the dual-phase composite.…”