Zhongning Guo

A Rapid One-Step Process for Fabrication of Biomimetic Superhydrophobic Surfaces by Pulse Electrodeposition

Inspired by some typical plants such as lotus leaves, superhydrophobic surfaces are commonly prepared by a combination of low surface energy materials and hierarchical micro/nano structures. In this work, superhydrophobic surfaces on copper substrates were prepared by a rapid, facile one-step pulse electrodepositing process, with different duty ratios in an electrolyte containing lanthanum chloride (LaCl3·6H2O), myristic acid (CH3(CH2)12COOH), and ethanol. The equivalent electrolytic time was only 10 min. The surface morphology, chemical composition and superhydrophobic property of the pulse electrodeposited surfaces were fully investigated with SEM, EDX, XRD, contact angle meter and time-lapse photographs of water droplets bouncing method. The results show that the as-prepared surfaces have micro/nano dual scale structures mainly consisting of La[CH3(CH2)12COO]3 crystals. The maximum water contact angle (WCA) is about 160.9°, and the corresponding sliding angle is about 5°. This method is time-saving and can be easily extended to other conductive materials, having a great potential for future applications.

Application of Powder Metallurgy Methods for Production of a Novel Cu‐Based Composite Frictional Train Brake Material

A novel Cu-based composite frictional train brake material composed of several elements such as Al, SiO2, Fe, graphite, Sn, Mn and SiO2 re-enforced with other elements was treated under Powder Metallurgy (P/M) route. The materials were sintered at three different temperatures (850 C, 900 C and 950 C) at a constant pressure. The tribological behavior of these materials was analyzed by pad-on-disk tests without lubrication and the coefficient of friction, wear rate and wear number were studied in order to identify the effects of the sintering temperature on the base materials composition. The pores in the sintered material were mainly solid lubricants such as graphite and other low melting elements. This resulted in poor hardness and mechanical properties, which were compensated by its ability to reduce seizure. The wear mechanisms that were generated are as follows; delamination, plowing and abrasive wear. The abrasive wear were dominant and found on samples sintered at 850 C and 900 C, it is seen to be responsible for high wear rates. The friction coefficient under high pressure (3.13MPa) dry conditions had average values of 0.404, 0.343, and 0.336, at 950 C, 900 C and 850 C respectively. The investigation of worn surface was assessed by using x-ray defractory and scanned electron microscope.

Fabrication of a Metal Micro Mold by Using Pulse Micro Electroforming

Microfluidic devices have been widely used for biomedical and biochemical applications. Due to its unique characteristics, polymethyl methacrylate (PMMA) show great potential in fabricating microfluidic devices. Hot embossing technology has established itself as a popular method of preparing polymer microfluidic devices in both academia and industry. However, the fabrication of the mold used in hot embossing is time-consuming in general and often impractical for economically efficient prototyping. This paper proposes a modified technology for preparing metal micro molds by using pulse micro electroforming directly on metallic substrate, which could save time and reduce costs. In this method, an additive was used to avoid surface defect on deposited nickel. A chemical etching process was performed on the metallic substrate before the electroforming process in order to improve the bonding strength between the deposited structure and substrate. Finally, with the aim of obtaining a metal micro mold with high surface quality (low surface roughness), an orthogonal experiment was designed and conducted to optimize the electroforming parameters. Additionally, metal micro molds with different structures were well prepared by using the optimized parameters.