Xinzhu Yan

One-step preparation of transparent superhydrophobic coatings using atmospheric arc discharge

In this letter, we report a fast, simple, and single step approach to the preparation of transparent super-hydrophobic coatings on a copper conductor via atmosphere pressure arc discharges. The preparation procedures, hydrophobic characteristics, anti-pollution capability, and transparency of the super-hydrophobic coating are presented. A dual micro- and nano-scale hierarchical structure is observed on the super-hydrophobic coating with a water contact angle greater than 150°. The coating is, thus, capable of removing a significant amount of contaminants with a small quantity of water droplets. Attenuated total reflection Fourier transform infrared spectroscopy indicates that hydrophobic methyl groups exist on the surface of the coating. The surface roughness measurement results prove that the super-hydrophobic surface obeys the Cassie-Baxter model and its light scattering is very weak. Results demonstrate the conceptual feasibility of production of optically transparent super-hydrophobic coating by arc spraying of polymers under the atmospheric pressure.

An OH-PDMS-modified nano-silica/carbon hybrid coating for anti-icing of insulators part ii: anti-icing performance

Icing on insulators affects seriously the operation safety of high voltage transmission lines. Super-hydrophobic and semi-conducting coatings show anti-icing potential for insulators on transmission lines. By combining super-hydrophobicity and electrothermal effects, a hydroxy-terminated polydimethylsiloxane (OH-PDMS)-modified nano-silica/carbon hybrid coating was developed to solve the problem of insulator icing. The anti-icing performance of insulators coated with OH-PDMS-modified nanosilica/ carbon hybrid coating were investigated. Leakage current, temperature distribution, ice morphology, icicle length, and flashover voltage of the insulators are presented. Both the electric and the thermal field distributions were analyzed to verify anti-icing performance of the coating. Experimental results show that the joule heat generated by the coating increases the insulator surface temperature, and the OHPDMS- modified nano-silica/carbon hybrid coating has a superior performance to super-hydrophobic coating in terms of reducing ice accretion and improving flashover voltage of insulators.

Droplet condensation on superhydrophobic surfaces with enhanced dewetting under a tangential AC electric field

In this Letter, the dewetting behavior of superhydrophobic condensing surfaces under a tangential AC electric field is reported. The surface coverage of condensed droplets only exhibits a negligible increase with time. The jumping frequency of droplets is enhanced. The AC electric field motivates the dynamic transition of droplets from stretch to recoil, resulting in the counterforce propelling droplet jumping. The considerable horizontal component of jumping velocity facilitates droplet departure from superhydrophobic surfaces. Both the amplitude and frequency of AC voltage are important factors for droplet departure and dewetting effect. Thereby, the tangential electric field provides a unique and easily implementable approach to enhance droplet removal from superhydrophobic condensing surfaces.

Fabrication of superhydrophobic surface with discarded silicone under arc exposure

Super-hydrophobic surfaces can be fabricated based on discarded silicone after arc exposure. Hydrophobicity, microstructural development, chemical composition, corrosive liquid resistance, and the microscopic process of contaminant elimination of the surface are presented. High temperature of the arc discharge plays a substantial role in the preservation of surface hydrophobicity.

Influence of nano boron nitride (BN) on electric corrosion of fluororesin based super hydrophobic coatings for insulators

Ice accumulation on transmission lines, caused by freezing rain, wet snow or frost, is one of major problems influencing safety of electric power system. Super hydrophobic coating on insulators is a kind of efficient way to solve the problem. Many kinds of super hydrophobic coatings are widely used in power system, especially fluororesin based coating which is cheap and has good outdoor weathering capabilities. However, after arc burning, fluororesin based super-hydrophobic coating would be destroyed due to partial temperature rising. Addition of high thermal conductive nanoparticles can increase thermal conductivity of coating and improve its arc resistant ability compared with undoped coating. In this paper, heat conductivity behaviors of super hydrophobic with BN particles is studied. The charge polarity, charging time and charging voltage also play an important role on arc electric erosion behaviors. Samples were prepared by dispersing BN nanoparticle into coating. DC arc test was performed using inclined plane test method.

Investigation of the electric field driven self-propelled motion of water droplets on a super-hydrophobic surface

Super-hydrophobic coatings have recently drawn considerable attention in research and applications towards self-cleaning materials. This paper presents experiments and analysis of water droplet behaviors on glass, silicone rubber, and super-hydrophobic surface in an ac electric field applied parallel to the surface. Experimental results show that a water droplet tends to move on a super-hydrophobic surface while it tends to stretch or deform on glass and silicone rubber surfaces. A physical model of the water droplet deformation and motion mechanism is presented. An electrostatic force acting as the domain driving force plays a key role in water droplet motion on super-hydrophobic surface. The electrostatic stress acting along the external profile of a water droplet cross section was simulated using a surface integral of the Maxwell stress tensor. The simulation for surfaces with different wetting properties are in good agreement with the experimental results. Super-hydrophobic coating demonstrates a prospective electric field enhanced self-cleaning property.

An OH-PDMS-modified nano-silica/carbon hybrid coating for anti-icing of insulators part I: Fabrication and small-scale testing

Super-hydrophobic coatings have recently drawn a lot of attention in research and applications towards reduction of ice accumulation on insulators. This paper presents a new type of hybrid coating fabricated via self-assembly of a super-hydrophobic layer on a semi-conducting layer. Hydroxy-terminated polydimethylsiloxane (OH-PDMS) modified nano-silica is used for fabrication of the super-hydrophobic layer. Fabrication procedures, hydrophobic characteristics, and flashover performances of the hybrid coating are presented. Experimental results show that the hybrid coating has a dual micro- and nano-scale hierarchical structure and a water contact angle greater than 155°. Surface resistivity, volume resistivity, temperature rise, and surface flashover voltages of the hybrid coating are also presented. Temperature distribution on the hybrid coating is simulated for further analysis. The results show that the hybrid coating is capable of improving the electrical field and surface temperature along the surface of the coating.

Electrical driven rolling behavior of water droplet on a super hydrophobic surface

The paper aims at studying the electrical driven rolling behavior of water droplet on a super-hydrophobic surface under electrical field. Firstly, Parallel plate electrodes and super-hydrophobic surface (contact angle > 150°) are adopted. Experiments are conducted to investigate deformation and rolling behavior of water droplet on super-hydrophobic surface when A.C voltage is applied. Secondly, Electrical field distribution of water droplet on super-hydrophobic surface is simulated with Finite Element Method (FEM). Electrostatic stress that drives water droplet to roll is calculated by combing electrical field distribution results with Maxwell stress tensor. Simulation and calculation results indicated electrostatic force had a tendency to drive water droplet to roll.

Preparation of steel fiber/graphite conductive concrete for grounding in substation

In high soil resistivity regions, values of grounding resistance of substations are usually difficult to meet the requirements of working earthing and safety earthing. The common methods for reducing the grounding resistance are not practical. In order to solve this problem, a steel fiber/graphite conductive concrete is developed in this paper. Steel fiber and graphite are added as conductive fillers. Orthogonal experimental design is applied to formulation optimization. The resistivity, compressive strength and flexural strength of steel fiber/graphite conductive concrete are measured for obtaining the optimal formula. The results demonstrate that the steel fiber/graphite conductive concrete not only has the advantage of small resistivity, but also has excellent mechanical property and good material dispersion effect.

Ice bonding strength detection of the super-hydrophobic coating

The icing flashover is increasingly becoming a serious problem with the development of the extra-high voltage engineering. Reducing the bonding strength between the substrate and the ice by super-hydrophobic coating is a choice for the anti-icing. The bare insulator, RTV coated insulator and the super-hydrophobic insulator are chosen for comparing. The experimental facility is set up. The vertical bonding strength, the vertical fracture energy, the shear bonding strength and the shear fracture energy are detected after first ice glaciations and second one. Results show that bonding strength between the super-hydrophobic substrate and the ice is less than that of the RTV coated insulator and the ice. The deiced surface still shows good super-hydrophobicity and the small ice bonding strength keeps almost the same which show good prospect for the anti-icing and de-icing.