Improving Anti-frosting Performance for Super-hydrophobic Nanocomposite Coatings

New super-hydrophobic nanocomposite coatings were formed from modified nano-sized CaCO3 particles and polyacrylate at weight ratio of 9/1-8/2. SEM and XPS analysis indicated that such hydrophobicity could be attributed to the surface nano-microstructure and the surface enrichment of fluorine atoms. As the surface hydrophobicity increased, longer time was required for formation the initial frost, which makes super-hydrophobic coatings suitable for anti-frosting purpose.

Rapid surface texturing to achieve robust superhydrophobicity,controllable droplet impact,and anti-frosting performances

Robust superhydrophobic surfaces with excellent capacities of repelling water and anti-frosting are of importance for many mechanical components.In this work,wear-resistant superhydrophobic surfaces were fabricated by curing a mixture of polyurethane acrylate(PUA)coating and 1H,1H,2H,2H-Perfluorodecyltrichlorosilane(HFTCS)on titanium alloy(TC4)surfaces decorated with micropillars pattern,thus,composite functional surfaces with PUA coating in the valleys around the micropillars pattern of TC4 were achieved.Apparent contact angle on fabricated surfaces could reach 167°.Influences of the geometric parameters of micropillars pattern on the apparent contact angle were investigated,and the corresponding wear-resistant property was compared.Droplet impact and anti-frosting performances on the prepared surfaces were highlighted.An optimized design of surface texture with robust superhydrophobicity,controllable droplet impact,and anti-frosting performances was proposed.This design principle is of promising prospects for fabricating superhydrophobic surfaces in traditional mechanical systems.

Review on Anti-Frost Technology Based on Microchannel Heat Exchanger

Frosting is an inevitable adverse phenomenon in many fields such as industrial refrigeration,cryo-genics,and heat pump air conditioning,which may influence the efficiency of the equipment and increase the energy consumption of the system.The complicated louvered-fin structure and fuid-channels arrangements of the microchannel heat exchanger(HEX)will affect the heat transfer performance and frosting characteristics.First,this article analyzes different factors such as refrigerant distribution,refrigerant fow pattern,and HEX surface temperature distribution.Further,combined with the features of the microchannel HEX,the existing anti-frosting technologies and various methods of surface treatment for anti-frosting are summarized.The review focuses on the preparation of superhydrophobic surfaces and their superior properties.Furthermore,the internal mechanism is analyzed in conjunction with the relevant research of our group.Superhydrophobic character has excellent anti-frosting performance and heat transfer performance,which is of great significance for improving energy-saving and system performance.Finally,the future development of superhydrophobic surface technology is analyzed and prospected.

Summary of research on frost heave for subgrade in seasonal frozen ground

The building of railways on seasonally frozen ground is inevitable as China pursues economic development and the improvement of its citizens'living standards.However,railway construction in seasonally frozen soil areas is often faced with frost heave,leading to uneven subgrades which seriously threaten traffic safety.This article summarizes extant research results on frost heave mechanism,frost heave factors,and anti-frost measures of railway subgrades in seasonally frozen soil areas.

Ultralow-adhesion icephobic surfaces:Combining superhydrophobic and liquid-like properties in the same surface

As a ubiquitous natural phenomenon,ice/frost formation on solid surfaces have adverse effects on many commercial and residential activities.Icephobic surfaces feature low ice adhesion strengths(<100 kPa)can passively retard ice formation and ease ice removal.Superhydrophobic surfaces and liquid-lubricating surfaces are two prevailing categories of icephobic surfaces.However,their long-term stability is relatively poor,and the ice adhesion strengths are not low enough for passive removal of small ice crystals(e.g.,frosts)from the surfaces.Herein,we combine the superhydrophobic and liquid-like properties in one surface to obtain durable icephobic surfaces with extremely low ice adhesion strengths(about 0.035 kPa).Ices and frosts can be removed from the surface under the action of gravity or gas purge.These surfaces are prepared based on surface nanoconical structure and covalently-grafted liquid-like perfluorinated polyether(PFPE)coating,which show synergy effects on suppressing icing and frosting by promoting expulsion of subcooled condensate droplets from the nanotexture and decreasing ice adhesion strengths.The icephobic surfaces show significantly better durability compared to lubricant-impregnated textured surfaces.Our results provide a new avenue to design passive anti-icing/anti-frosting surfaces for a wide range of applications where surfaces are exposed to humid and low-temperature environments.

Thermal Stability of Typical Superhydrophobic Surfaces

Two kinds of typical superhydrophobic surfaces, ZnO nanorods and porous nano-SiO2 coating were successfully prepared on nickel alloy plates using a wet chemical method for the ZnO nanorods and spraying for the nano-SiO2 coating. Thermal stability of each of the superhydrophobic surfaces was tested. Scanning Electron Microscopy （SEM） and energy dispersive spectrometry were used to analyze microstructures and compositions. Although both superhydrophobic surfaces show similar wettability with respect to water, the SiO2 Nanoparticles Superhydrophobic Coatings （SiO2-NSCs） has better thermal stability than the ZnO Nanorods Superhydrophobic Coatings （ZnO-NSCs）. The micro/nano structures of the two superhydrophobic surfaces can be destroyed during icing-melting cycles. In addition, at high temperature, the superhydrophobic properties of the surface can be destroyed because of the decomposition of fluorinated silane. The results can provide guidance for the practical cryogenic application of superhydrophobic surfaces.