The recycling process toward the elimination of varistor wastes into new electro-active silicon composites has been investigated. We studied the dependence of the E-J characteristics on the aggregate content in the polymer matrix. Formulations with 40 vol.% metal oxide varistor aggregates in the 100-200m range exhibit reliable nonlinear behavior with a switching voltage of 280 +/- 30V/mm. The breakdown voltage of the composite decreases as both filler's diameter and filler's volume fraction increases in the 550-220V/mm and 440-280V/mm range, respectively. This paves the way for the valorization of varistors based zinc oxide (ZnO) ceramics.

Matériaux composites à base de silicone comprenant des charges non-linéaires

Recycling route toward electro-active silicone composites has been explored. We studied the dependence of the E-J characteristics on the aggregate content in the polymer matrix. Formulations with 35 vol.% MOV aggregates in the 200-375 µm range exhibit reliable nonlinear behavior with a switching voltage of 175 ± 30 V/mm. This opens a way to valorize varistors based on zinc oxide (ZnO) ceramics.

Thermo-mechanically durable industrial polymer nanocomposites have great demand as structural components. In this work, highly competent filler design is processed via nano-modified of micronic SiO2/Al2O3 particulate ceramics and studied its influence on the rheology, glass transition temperature, composite microstructure, thermal conductivity, mechanical strength, micro hardness, and tribology properties. Composites were fabricated with different proportions of nano-modified micro-composite fillers in epoxy matrix at as much possible filler loadings. Results revealed that nano-modified SiO2/Al2O3 micro-composite fillers enhanced inter-particle network and offer benefits like homogeneous microstructures and increased thermal conductivity. Epoxy composites attained thermal conductivity of 0.8 W/mK at 46% filler loading. Mechanical strength and bulk hardness were reached to higher values on the incorporation of nano-modified fillers. Tribology study revealed an increased specific wear rate and decreased friction coefficient in such fillers. The study is significant in a way that the design of nano-modified mixed-matrix micro-composite fillers are effective where a high loading is much easier, which is critical for achieving desired thermal and mechanical properties for any engineering applications. Copyright © 2016 John Wiley & Sons, Ltd.

Wet acid oxidation treatment methods have been widely reported as an effective method to purify and oxidize the surface of industrial multi-walled carbon nanotubes (MWCNT). This work examines the use of a concentrated HNO3/H2SO4 mixture in an attempt to optimize the purification procedure of industrial MWCNT with diameter distribution statistics. It is shown that acid treatments of several hours are enough to purify the nanotubes. The electrical and thermal conductivities of epoxy composites containing 0.05-0.25 wt. % of acid-treated MWCNT has been studied. The electrical conductivity of the composites decreases by more than three orders, whereas the thermal conductivity of the same specimen increases very modestly as a function of the filler content.

Polymers typically have intrinsic thermal conductivity much lower than other materials. Enhancement of this property may be obtained by the addition of conductive fillers. In this research, epoxy nanocomposites with exfoliated graphite nanoplatelets are prepared and characterized. The chosen approach requires no surface treatment and no sophisticated equipments allowing one to produce composites on a pilot scale. A significant increase of the thermal conductivity with the increasing of the graphite fillers content is nevertheless observed on 4 mm thick specimens. Our results viewed in the latest scientific findings suggest that the choice of resin is an important parameter to move towards composite materials with high thermal conductivity.

Tuning of Epoxy Dielectrics through Interfacial Engineering via Multifunctional Co-fillers