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Search Results: 1 - 10 of 120152 matches for " Jiadao Wang "
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Research progress on the ultra hydrophobic surface topography effect
Jiadao Wang,Ying Yu,Darong Chen
Chinese Science Bulletin , 2006, DOI: 10.1007/s11434-006-2129-6
Abstract: Ultra hydrophobic surfaces take on better hydrophobicity and exhibit a water contact angle larger than 150°. In this paper the ultra hydrophobicity is analyzed and common fabrication methods are summarized in detail. The applications of micro topography in both the fabrication of hydrophobic surface and the experiments of drag reduction are addressed. Finally, the development trend and foreground of ultra hydrophobic surface are discussed.
Progress of marine biofouling and antifouling technologies
Shan Cao,JiaDao Wang,HaoSheng Chen,DaRong Chen
Chinese Science Bulletin , 2011, DOI: 10.1007/s11434-010-4158-4
Abstract: Adhesion of marine fouling organisms on artificial surfaces such as ship hulls causes many problems, including extra energy consumption, high maintenance costs, and increased corrosion. Therefore, marine antifouling is an important issue. In this review, physical and biochemical developments in the field of marine biofouling, which involves biofilm formation and macro-organism settlement, are discussed. The major antifouling technologies based on traditional chemical methods, biological methods, and physical methods are presented. The chemical methods include self-polishing types such as tributyltin (TBT) self-polishing copolymer coatings, which despite its good performance has been banned since 2008 because of its serious environmental impact. Therefore, other methods have been encouraged. These include coatings with copper compounds and biocide boosters to replace the TBT coatings. Biological extracts of secreted metabolites and enzymes are anticipated to act as antifoulants. Physical methods such as modification of surface topography, hydrophobic properties, and charge potential have also been considered to prevent biofouling. In this review, most of the current antifouling technologies are discussed. It is proposed that the physical antifouling technologies will be the ultimate antifouling solution, because of their broad-spectrum effectiveness and zero toxicity.
Water erosion mechanism of mild carbon steels induced by micro-particles
WanLi Xu,Li Qin,JiaDao Wang,HaoSheng Chen,DaRong Chen
Chinese Science Bulletin , 2009, DOI: 10.1007/s11434-009-0589-1
Abstract: To clarify the water erosion mechanism of the mild carbon steels, the water erosion experiments were performed by using deionized water as steam source. The results showed that under the damage threshold velocity of liquid impact, the material surface would not be destroyed. However, when the micro-particles were added into the steam, the pits appeared on the surface soon. By comparison, it is found that the pits are quite different from those induced by micro-particles impact without steam, but similar to those induced by cavitation erosion. The results indicated that the water erosion mechanism was similar to that of cavitation erosion under the damage threshold velocity. The micro-particles carry the micro-bubbles to approach the surface of the material, and the micro-bubbles collapse and generate micro-jet to impinge vertically on the surface, which lead to the produce of pits.
Key roles of micro-particles in water on occurrence of cavitation-erosion of hydro-machinery
JiaDao Wang,HaoSheng Chen,Li Qin,YongJian Li,DaRong Chen
Chinese Science Bulletin , 2008, DOI: 10.1007/s11434-008-0089-8
Abstract: It has been believed for about one hundred years that the cavitation directly induces the cavitation erosion. It is proposed in this research that cavitation is only the necessary condition but not the sufficient condition of the cavitation erosion. The experiment performed on the rotary disk cavitation system shows that the micro-particles in the fluid play indispensable roles in the cavitation erosion process, and the generation of the erosion pits on the steel surface is also affected by the particles’ size. These cracks and deformations on the sample surface indicate that the erosion is the result of the mechanical behavior. Numerical calculations are also provided to support this mechanism.
Fabrication of a micro-structured surface based on interfacial convection for drag reduction
ZhaoLiang Dou,JiaDao Wang,Feng Yu,DaRong Chen
Chinese Science Bulletin , 2011, DOI: 10.1007/s11434-011-4378-2
Abstract: Based on interfacial convection in the presence of solvent evaporation, a novel method for the fabrication of a micro-structured surface is proposed to facilitate drag reduction. A mixture was coated on a substrate through a specially developed spray-painting system. Micron scale pits formed spontaneously in the coated surface because of interfacial convection and deformation driven by the gradient of the interfacial tension. Experimental results indicated that particles in the mixture played a crucial role in pit formation, and with a suitable selection of particle size and dosage, the characteristic parameters of the pitting could be controlled. The drag reduction experiments were first performed in a water tunnel, and the results showed that the micro-structured surface had a remarkable drag reduction performance over a great range of flow speeds.
Effects of the surface-adsorption of boron-doped diamond electrode on its electrochemical behavior
Fengbin Liu,Xuemin Li,Jiadao Wang,Bing Liu,Darong Chen
Chinese Science Bulletin , 2006, DOI: 10.1007/s11434-006-2024-1
Abstract: To elucidate the effects of the hydrogenation and oxygenation of the boron-doped diamond (BDD) electrode on its electrochemical behaviors, the surface morphologies and phases of the two surface-adsorption BDD films have been investigated and the cyclic voltammograms and AC impedance spectra have been measured at these two BDD electrodes. The results indicate that compared with the hydrogen-adsorption BDD film, oxygen-adsorption BDD film is less conductive, and has a larger surface roughness and a lower sp3/sp2 ratio. The oxygenated BDD film electrode possesses a wider electrochemical window, larger diamond film resistance and capacitance and a larger polarization resistance than hydrogenated BDD electrode. In addition, the effect mechanism of the surface-adsorption of BDD electrode on its electrochemical behaviors has been discussed.
Electronic structures of the oxygenated diamond (100) surfaces
Fengbin Liu,Jiadao Wang,Bing Liu,Xuemin Li,Darong Chen
Chinese Science Bulletin , 2006, DOI: 10.1007/s11434-006-2139-4
Abstract: By means of first principles method on the basis of density functional theory (DFT), the equilibrium geometries and density of states (DOS) of the two oxygenated diamond (100) surfaces, bridging model and on-top model are calculated. The results indicate that there are no surface states located in the band gap of the bridging model of oxygenated diamond (100) surface, and the occupied surface states in the valence band are attributed to the non-bonded O 2p orbital, O 2p and C 2p bonding orbitals, and C 2p and H 1s bonding orbitals. By contrast, for the on-top model of oxygenated diamond (100) surface, the unoccupied surface states exist in the band gap, which originate from non-bonded C 2p and O 2p orbitals. In addition, the occupied surface states in the valence band are induced by non-bonded O 2p orbital and the C=O π bond.
Effect of microparticle properties on erosion in solid-steam mixtures
WanLi Xu,JiaDao Wang,Wei Zhao,DaRong Chen
Chinese Science Bulletin , 2011, DOI: 10.1007/s11434-011-4385-3
Abstract: Based on a custom-built experimental apparatus, irregular microparticles of different sizes and microparticles of the same size but of different shape were added to wet steam, and erosion experiments were performed on polished medium carbon steel specimens. After the experiments, the eroded surfaces were analyzed by scanning electron microscopy and the degree of damage was evaluated by area loss. The results indicated that microparticle size significantly affects the degree of erosion damage. With an increase in size, variations in the method of damage mainly cause different degrees of damage on an eroded surface. Microparticle shape hardly affects the number of craters. Compared with spherical microparticles, irregular microparticles cause indentations more easily and result in more severe abrasion on the material’s surface.
Equilibrium geometric structure and electronic properties of Cl and H2O co-adsorption on Fe (100) surface
Wei Zhao,JiaDao Wang,FengBin Liu,DaRong Chen
Chinese Science Bulletin , 2009, DOI: 10.1007/s11434-009-0199-y
Abstract: Based on the first principles density functional theory, the equilibrium geometric structure and surface electronic properties of Cl and H2O co-adsorption on the Fe (100) surface are investigated. The results indicate that the optimal adsorption site for Cl and H2O co-adsorption on the Fe (100) surface is the location of Cl at the bridge site and H2O at the top site. Compared with the Fe (100)/H2O adsorption system, remarkable changes in geometric structure and electronic properties occur, owing to the presence of Cl in the Fe (100)/(H2O+Cl) adsorption system. The analysis of equilibrium geometric structure and surface electronic properties shows that the presence of Cl in the Fe (100)/(H2O+Cl) adsorption system unstablizes the Fe surface, making it easy to lose electrons.
Affected zone generated around the erosion pit on carbon steel surface at the incipient stage of vibration cavitation
HaoSheng Chen,Jiang Li,ShiHan Liu,DaRong Chen,JiaDao Wang
Chinese Science Bulletin , 2008, DOI: 10.1007/s11434-008-0105-z
Abstract: The characteristics of erosion pits on a carbon steel surface were investigated at the incipient stage of cavitation erosion. After a 5-minute experiment performed in an ultrasonic vibration system, needle-like erosion pits appeared on the polished steel surface, and a specially affected zone was formed around the pit. The shape of the pit and the plastic deformation of the affected zone indicate that the mechanical impaction on the surface is the main reason for the cavitation damage. On the other hand, the iridescent color, the decreased surface hardness and the precipitated carbides on the affected zone prove that the affected zone has experienced a tempering process with the temperature higher than 300°C. The lack of oxygen in the affected zone also proves that it is not a chemical oxygen result. A special phenomenon that a carbon ring forms in the affected zone is explained as a result of the toroidal bubbles’ heating effect at the final stage of the bubble collapse.
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