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The effect of a magnetic field of two magnetic coils on the ion current density distribution in the setup for low-temperature plasma deposition is investigated. The substrate of 400 mm diameter is placed at a distance of 325 mm from the plasma duct exit, with the two magnetic coils mounted symmetrically under the substrate at a distance of 140 mm relative to the substrate centre. A planar probe is used to measure the ion current density distribution along the plasma flux cross-sections at distances of 150, 230, and 325 mm from the plasma duct exit. It is shown that the magnetic field strongly affects the ion current density distribution. Transparent plastic films are used to investigate qualitatively the ion density distribution profiles and the effect of the magnetic field. A theoretical model is developed to describe the interaction of the ion fluxes with the negative space charge regions associated with the magnetic trapping of the plasma electrons. Theoretical results are compared with the experimental measurements, and a reasonable agreement is demonstrated. [ABSTRACT FROM AUTHOR]

[Display omitted] • New approach for surface crack repair and insulation recovery of silicone rubber composites. • Plasma-electrified repair based on dissociation and re-assembly of alkoxysilane. • Better mechanical and electrical properties of composites after plasma repair. • More effective, sustainable and low-carbon compared to common repair methods. Polymer composites, widely used in aerospace and electrical power systems, are inevitably aged by environmental stress causing cracks on the material's surface, which weakens their mechanical and electrical properties. Addressing the issue requires significant effort and the use of hazardous chemicals. In this study, a novel plasma-electrified repair method based on the Ar/H 2 O/alkoxysilane (PMDMS) low temperature plasma is developed for the surface crack healing and insulation recovery of silicone rubber (SIR) composites. It is demonstrated that the plasma-enabled polymerization effectively repairs the cracked SIR, with a new fin-like insulating layer deposited on the crack surface. The mechanical and electrical properties of the cracked SIR are improved after the plasma repair, with the result clearly better than using the conventional coating method. Hydrolysis-condensation of PMDMS by plasma-enabled dissociation and re-assembly, surface activation of the crack by plasma modification and grafting-crosslinking in the crack account for the multiphase chemical reactions induced within the crack. Further analysis based on quantum chemistry calculations reveals that the plasma treatment both promotes the chemical reactivity of the SIR surface and reconstructs a dense repair phase in the crack with a wide forbidden gap and shallow taps, further confirming this effective crack healing process which improves the mechanical and electrical performances of the damaged SIR. Overall, this newly-developed plasma-electrified repair method for damaged SIR eliminates the environmental pollution caused by large scale and overused chemical coatings, and offers new possibilities for sustainable and low-carbon-emission material engineering for processing and restoration of composite materials. [ABSTRACT FROM AUTHOR]