D. F. Cui

Robust Prototypical Anti-icing Coatings with a Self-lubricating Liquid Water Layer between Ice and Substrate

A robust prototypical anti-icing coating with a self-lubricating liquid water layer (SLWL) is fabricated via grafting cross-linked hygroscopic polymers inside the micropores of silicon wafer surfaces. The ice adhesion on the surface with SLWL is 1 order of magnitude lower than that on the superhydrophobic surfaces and the ice formed atop of it can be blown off by an action of strong breeze. The surface with self-lubricating liquid water layer exhibits excellent capability of self-healing and abrasion resistance. The SLWL surface should also find applications in antifogging and self-cleaning by rainfall, in addition to anti-icing and antifrosting.

Superhydrophobic surfaces cannot reduce ice adhesion

Understanding the mechanism of ice adhesion on surfaces is crucial for anti-icing surfaces, and it is not clear if superhydrophobic surfaces could reduce ice adhesion. Here, we investigate ice adhesion on model surfaces with different wettabilities. The results show that the superhydrophobic surface cannot reduce the ice adhesion, and the ice adhesion strength on the superhydrophilic surface and the superhydrophobic one is almost the same. This can be rationalized by the mechanical interlocking between the ice and the surface texture. Moreover, we find that the ice adhesion strength increases linearly with the area fraction of air in contact with liquid.

Anti-icing Coating with an Aqueous Lubricating Layer

In this paper, an anti-icing coating with an aqueous lubricating layer is reported. This anti-icing coating can be directly applied to various substrates, and the ice adhesion strength on the coated surfaces can be lowered greatly as compared to uncoated substrates. We demonstrate for the first time that the formed ice on this anti-icing coating can be blown off by a wind action in the wind tunnel with a controlled temperature and wind velocity. Moreover, the low ice adhesion of the anti-icing coating can be maintained even when the temperature is lowered to -53 °C. The robustness and durability of the anti-icing coating are proved by the icing/de-icing experiments. The results show that the anti-icing coating with an aqueous lubricating layer is of great promise for practical applications.

Hierarchical Porous Surface for Efficiently Controlling Microdroplets' Self‐Removal

Removing condensed water from a cold surface can improve the surface heat-exchange coeffi cient by at least one order of magnitude, compared with the case of condensed water staying on the surface, [ 1–3 ] which is very important for all cooling systems due to increasing energy concerns nowadays. Because of their excellent water-repellent properties, superhydrophobic surfaces with low adhesion to water are promising candidates for effi cient removal of condensed water microdroplets. [ 4–7 ] It has been reported that coalescing microdroplets can self-remove from superhydrophobic surfaces when powered by the released surface energy, [ 8 , 9 ] which has aroused interest. [ 10–13 ] Though the self-removal of condensed microdroplets is energy saving, its effi ciency depends on the growth rate and the coalescing frequency of condensed droplets. Generally, faster growth and more frequent coalescence will lead to higher self-removal effi ciency of condensed droplets. However, though hydrophilic surfaces are favorable for the quick nucleation and growth of condensed water, they are unfavorable for the self-removal of condensed microdroplets. [ 1 , 14 , 15 ] While the high nucleation energy barrier on hydrophobic or superhydrophobic surfaces slows down the growth of condensed droplets, [ 16 ] the uncontrollable distance between condensed microdroplets decreases the coalescing frequency, resulting in a low self-removal effi ciency. Thus, how to control the condensation and coalescence processes and accelerate the self-removal of condensed microdroplets remains a great challenge for developments of new antifogging, anti-icing materials and heat exchangers. Herein, inspired by the peculiar hydrophilic/hydrophobic structures on a beetle’s elytra, [ 14 , 17 , 18 ] a micro-/nanoporous superhydrophobic surface modifi ed with hydrophilic polymer was designed for effi ciently controlling microdroplet self-removal. The hierarchical micro-/nanoporous structure was fabricated on aluminum by integrating microcontact printing [ 19 , 20 ] and chemical bath deposition. [ 11 , 21 ] After modifying the bottom of

Hierarchically structured porous aluminum surfaces for high-efficient removal of condensed water

Hierarchically structured porous aluminum surfaces for the high efficient removal of condensed water microdroplets are prepared via simply immersing aluminum sheets in hot water followed by modification with a low surface energy chemical. A correlation between the work of adhesion with the self-removal of condensed water microdroplets is established.

Condensation mode determines the freezing of condensed water on solid surfaces

A series of surfaces with the similar morphology but different surface free energy were fabricated to achieve surfaces with distinct condensation modes. It was found that the freezing of condensed water formed via filmwise condensation occurred much more quickly and at a higher temperature than that of condensed water formed via dropwise condensation.

Sb-doped SrTiO3 transparent semiconductor thin films

Optically transparent Sb-doped SrTiO3 thin films with a transmittance higher than 95% in most of the visible region have been grown on SrTiO3 (001) substrate by pulsed laser deposition. The films behave as an n-type semiconductor between 10 K and room temperature. The carrier concentration and mobility of the films at room temperature are ∼5.8×1017 cm−3 and ∼6.4 cm2/V s, respectively. X-ray photoelectron spectroscopy measurement reveals that the delocalized electrons from the Sb dopants give rise to deep impurity levels within the band gap of the parent compound, which are responsible for the electrical conduction observed. The wide band gap and low density of states in the conduction band account for transparency of the films.

In situ reflection high-energy electron diffraction observation of epitaxial LaNiO3 thin films

Epitaxial LaNiO3 (LNO) thin films were grown on (001) SrTiO3 substrates by laser molecular-beam epitaxy. The growth process of the LNO films was monitored by in situ reflection high-energy electron diffraction (RHEED). Clear RHEED patterns and the intensity oscillation of RHEED were observed during the epitaxial growth process. The morphology of the films was studied by atomic force microscopy. The results show that the films grown by this method have a nanoscale smooth surface with the root-mean-square surface roughness smaller than 7 nm on an area of 1×1 μm2. X-ray diffraction patterns indicate that the crystalline LNO films exhibited preferred (00l) orientation. The resistivity of the thin film is 0.28 mΩ cm at 278 K and 0.06 mΩ cm at 80 K, respectively.

Large area, low microwave surface resistance thin films of YBa2Cu3O7 prepared by pulsed laser ablation

YBa2Cu3O7 (YBCO) superconducting thin films were deposited on (100)LaAlO3 substrates 35 mm in diameter by pulsed laser ablation. The substrates were heated resistively during deposition by a single-crystal Si heater and the laser beam was scanned on the rotating YBCO target. The films exhibited a thickness variation of +/- 3.7%, with zero resistance temperature T-c0 = 90.6 +/- 0.6 K, critical current density J(c) = 2.9 +/- 0.9 X 10(6) A/cm(2) at 77 K, and at 10 GHz a surface microwave resistance of < 250 mu Omega at 77 K. The above-mentioned properties showed that high-quality YBCO thin films over a large substrate area can be obtained with this laser ablation system.

Microstructure and properties of YBa2Cu3O7−δ thin films with BaO precipitates

BaO precipitates with sizes between 10–100 nm in laser ablated YBa2Cu3O7−δ (YBCO) thin films on Y‐stabilized Zirconia substrates have been identified by x‐ray diffraction and transmission electron microscopy. The precipitates exhibit equiaxed shapes and grow epitaxially inside and on the surface of the YBCO films, with (001)BaO plane parallel to the a,b plane of YBCO. Some of these smaller precipitates and BaO/YBCO boundaries probably provide potential pinning sites for magnetic flux lines, which might contribute to the observed increase of critical current density with magnetic field B under B≤500 G in the case of B perpendicular to the c axis of the film.