Yizhou Shen

Icephobic/anti-icing potential of superhydrophobic Ti6Al4V surfaces with hierarchical textures

The main purpose of this paper was to investigate the icephobic potential of hierarchical superhydrophobic surfaces, which were prepared by modifying micro-nanostructures (constructed by the combination of sand blasting and hydrothermal treatment) on the surfaces of Ti6Al4V alloy with fluoroalkylsilane (FAS-17). We previously reported that this hierarchical superhydrophobic surface displayed excellent non-wettability with apparent contact angle of 161° and sliding angle of 3°. Thus, the present study focused on the systematic characterizations and analyses of the icephobic potential of the superhydrophobic surfaces around three parameters, including icing-delay time, ice adhesion strength, and contact time of an impacting droplet on cold superhydrophobic surfaces. The results indicated that the icing-delay time of a droplet on the superhydrophobic surface was many times longer than that of a droplet on the smooth Ti6Al4V substrate, and the ice adhesion strength on superhydrophobic surface was greatly reduced, which was attributed to the Cassie wetting state of a droplet on the surface. Additionally, the dynamic droplet impact and rebound assay demonstrated that water droplets always bounced off of the superhydrophobic surfaces before freezing under subzero conditions.

In situ synthesis of two-dimensional leaf-like Cu2ZnSnS4 plate arrays as a Pt-free counter electrode for efficient dye-sensitized solar cells

Kesterite-structure Cu2ZnSnS4 (CZTS) has been proved to be a high-performance Pt-free counter electrode (CE) material for dye-sensitized solar cells (DSSCs). Herein, a green but powerful two-step method based on solvothermal treatment was proposed to synthesize semi-transparent two-dimensional (2D) leaf-like CZTS plate arrays (PLAr) in situ on a FTO glass substrate, without any post-treatments, such as annealing, toxic sulfurization, or coating with other ancillary materials. The growth mechanism of the 2D leaf-like CZTS PLAr based on solvothermal treatment was illustrated. A power conversion efficiency (PCE) of 7.09% was obtained by utilizing leaf-like CZTS PLAr as the CE. Surprisingly, the PCE increased to 8.67% assisted by a mirror reflection. The excellent performance of DSSCs could be attributed to the high catalytic surface area, fast photo-generated electron transport at the counter electrode/redox electrolyte interface, remarkable electrocatalytic activity for I3− reduction, low charge transfer resistance toward the reduction of I3− ions, and high diffusion coefficient of the I3−. This work provides a green and feasible approach to construct high-quality metal sulfide nanoarrays on arbitrary conductive substrates under mild conditions (i.e. low temperature, no annealing, green, speediness) and promotes the development of Pt-free sulfide materials for sustainable photovoltaic applications.

Superhydrophobic Ti6Al4V surfaces with regular array patterns for anti-icing applications

In this article, we present a route to fabricate a robust anti-icing superhydrophobic surface containing the hierarchical structures of microscale array patterns (built by micromachining) and nanohairs (prepared via hydrothermal growth) on a Ti6Al4V substrate. In particular, the superhydrophobic surfaces not only exhibited high non-wettability and water repellency, but also generated a tremendous anti-icing potential. The results of the measurements indicated that the apparent contact angle reached 160°, the contact angle hysteresis reduced to 2°, and the spreading and recoiling process of an impact droplet can be completed within 12 ms. Furthermore, it also caused a longer icing-delay time (approximately 765 s) to hinder the ice formation and growth at −10 °C, and the ice adhesion strength was also only 70 kPa.

Approaching the theoretical contact time of a bouncing droplet on the rational macrostructured superhydrophobic surfaces

The aim of this study is to reveal theoretically and experimentally a limited contact time of a bouncing droplet on superhydrophobic surfaces with the rationally designed macrostructures. During impacting, the water droplet hydrodynamics is properly altered under the assistance of the macrotextures. As a consequence, the retracting process of the impact water droplet can be completely integrated into the process of spreading out to the maximal deformation, resulting in a limited overall contact time of approximately 5.5u2009ms, i.e., the time required for spreading out to the maximal deformation.

Facile synthesis of single crystalline sub-micron Cu2ZnSnS4 (CZTS) powders using solvothermal treatment

Single crystalline sub-micron Cu2ZnSnS4 (CZTS) powders were successfully synthesized by a facile solvothermal method, using L-cysteine as sulfur precursor. It was confirmed that pure kesterite structured CZTS powders were synthesized at 400 °C after 5 h, with the irregular polygonal particle size being 500 nm to 1 μm. Interestingly, single crystalline CZTS particles were also obtained by simple solvothermal treatment without post annealing. The H2S released from L-cysteine had an impact on the growth of CZTS particles at high temperature. Further, the as-synthesized CZTS powders were used as counter electrode for dye-sensitized solar cells (DSSCs) and it is indicated that the CZTS counter electrode based DSSCs show a conversion efficiency of 4.243%.