Silver nanoparticles as a key feature of a plasma polymer composite layer in mitigation of charge injection into polyethylene under dc stress

Laurent Millière (1) , Kremena Makasheva (2) , Christian Laurent (3) , Bernard Despax (1) , Laurent Boudou (3) , G. Teyssedre (3)

1 LAPLACE - LAboratoire PLasma et Conversion d'Energie
2 LAPLACE-MPP - Matériaux et Procédés Plasmas
3 LAPLACE-DSF - Diélectriques Solides et Fiabilité

The aim of this work is to limit charge injection from a semi-conducting electrode into low density polyethylene (LDPE) under DC field by tailoring the polymer surface using a silver nanoparticles-containing layer. The layer is composed of a plane of silver nanoparticles embedded in a semi-insulating organosilicon matrix deposited on the polyethylene surface by a plasma process. Size, density and surface coverage of the nanoparticles are controlled through the plasma process. Space charge distribution in 300 m-thick LDPE samples is measured by the pulsed-electroacoustic technique following a short term (step-wise voltage increase up to 50 kV/mm, 20 min in duration each, followed by a polarity inversion) and a longer term (up to 12 hours under 40 kV/mm) protocols for voltage application. A comparative study of space charge distribution between a reference polyethylene sample and the tailored samples is presented. It is shown that the barrier effect depends on the size distribution and the surface area covered by the nanoparticles: 15 nm (average size) silver nanoparticles with a high surface density but still not percolating form an efficient barrier layer that suppress charge injection. It is worthy to note that charge injection is detected for samples tailored with (i) percolating nanoparticles embedded in organosilicon layer; (ii) with organosilicon layer only, without nanoparticles and (iii) with smaller size silver particles (<10 nm) embedded in organosilicon layer. The amount of injected charges in the tailored samples increases gradually in the samples ranking given above. The mechanism of charge injection mitigation is discussed on the basis of complementary experiments carried out on the nanocomposite layer such as surface potential measurements. The ability of silver clusters to stabilize electrical charges close to the electrode thereby counterbalancing the applied field appears to be a key factor in explaining the charge injection mitigation effect.

Mots clés: polyethylene; nanocomposites; silver nanoparticles; plasma processes; HVDC; charge injection; space charge mitigation

Domaines: Sciences de l'ingénieur [physics]; Plasmas

Laurent Millière, Kremena Makasheva, Christian Laurent, Bernard Despax, Laurent Boudou, et al.. Silver nanoparticles as a key feature of a plasma polymer composite layer in mitigation of charge injection into polyethylene under dc stress. Journal of Physics D: Applied Physics, 2016, 49 (1), pp.015304. ⟨10.1088/0022-3727/49/1/015304⟩. ⟨hal-02448489⟩