Dielectric response and breakdown strength improvement of LDPE/TiO2 nanocomposites by using POSS as compatibilizing agent
In this paper, two types of nanocomposites were prepared by ball milling techniquee The first type consists of 5% untreated titanium dioxide (TiO2) incorporated into LDPE. For the second one, 5% commercial TiO2 chemically treated with trisilanol phenyl polyhedral oligomeric silsesquioxane (TSP-POSS) as dispersant was ball-milled with LDPE. The microscopic observation by Atomic Force Microscopy (AFM) showed a better dispersion into polymer matrix of the TiO2 treated with POSS as compared to untreated TiO2. It was found that LDPE/treated TiO2 nanocomposite exhibited lower relative permittivity and dielectric losses compared to LDPE/untreated TiO2. The surface treatment of LDPE/TiO2 by TSP-POSS also affects the dielectric strength. The LDPE/treated TiO2 revealed highest breakdown strength of 82 kV/mm, compared to 78 kV/mm and 71 kV/mm of LDPE neat and LDPE/untreated TiO2, respectively.
Surface and breakdown resistance of polyethylene-based nano-dielectrics containing graphene-like additives
In this work, nanopowders of graphene oxide (GO) and functionalized graphene (G*) have been mixed with low-density polyethylene (LDPE) to fabricate samples with low filler weight ratio. A peculiar fabrication method was utilized, which consisted of ball-milling followed by thermal pressing. Electrical properties like resistance to erosion due to partial discharge (PD), and breakdown values were detected and the results were compared with those obtained on the neat LDPE. It is highlighted that the addition of G*, in particular, improves significantly both resistance to PD activity and the electric strength of LDPE specimens.
Photoreflectance characterization of vanadium-doped GaAs layers grown by metalorganic vapor phase epitaxy
Abstract We characterized the vanadium-doped (GaAs:V) layers grown on GaAs substrate by metalorganic vapor phase epitaxy. The conductivity of the samples is checked by the Hall effect measurements, and it is n type with electrons concentration ranging from 2×10 13 to 2×10 17  cm −3 . We used the photoreflectance technique (PR) to study the effect of vanadium doping on the optical properties of GaAs. Our experimental results show that the built-in electric field F and the broadening parameter Γ 0 increase with V-doping concentration. Furthermore, the temperature dependence of the built-in electric field and the broadening parameter of GaAs:V samples have been investigated by PR. It has been observed that these parameters increase with increasing temperature. The decrease of the built-in electric field with decreasing temperature is due to the photovoltage effect.We characterized the vanadium-doped GaAs (GaAs:V) layers grown on GaAs substrate by metalorganic vapor phase epitaxy.