可切换润湿性超疏水表面制备方法及应用

目的 制备可切换润湿性的智能超疏水表面,并探索该表面潜在的应用前景。方法 利用模板法,基于热响应形状记忆聚合物（Shape Memory Polymer,SMP）制备具有条状微结构阵列的可切换润湿性智能超疏水表面,并对其润湿性可逆转换能力及循环使用稳定性进行测试。结果 通过扫描电子显微镜观察到所制备表面微结构完整且轮廓清晰,液滴接触角在该表面可达到（150±3）°。通过加热使该表面达到玻璃化转变温度,此时对其施加外载荷使表面上条状微结构向一侧倾倒,由于微结构形态的改变,SMP表面疏水性减弱、水黏附性增强,再通过简单加热就可以使表面形态恢复至原始状态。通过试验测得环氧SMP的形状固定率为98.8%、形状回复率为96.3%,均达到95%以上,由于其优异的形状记忆特性,条状微结构的形态可以在原始直立状态和受到外载荷时的倾倒状态之间产生热响应而自由转变,且这种润湿性转换循环10次以上后,该表面依然保持着相对良好的润湿性可逆转换能力。结论 基于形状记忆聚合物制备出的可切换润湿性智能超疏水表面具有良好的润湿性可逆转换能力和循环使用能力,且在液滴微反应器、生物检测、可重写液体图案、无损失液滴转移和芯...     

Functional characteristics of dragonfly wings and its bionic investigation progress

Dragonfly is one of the most excellent nature flyers,and its wings exhibit excellent functional characteristics through the coupling and synergy of morphology,configuration,structure and material.The functional characteristics presented by dragonfly wings provide an biological inspiration for the investigation and development of aerospace vehicles and bionics flapping aerocraft flapping-wing micro air vehicles.In resent years,some progresses have been achieved in the researches on the wings’ geometric structure,material characteristics,flying mechanism and the controlling mode.In this paper,the functional characteristics of the dragonfly wings including flying,self-cleaning,anti-fatigue,vibration elimination and noise reduction are introduced and the effects of their morphology,configuration,structure and material on the functional characteristics are described.Moreover,the current state of the bionic study on the functional characteristics of dragonfly wings is analyzed and its application prospect is depicted.     

Kinematics of Terrestrial Locomotion in Mole Cricket Gryllotalpa orientalis

The fore leg of mole cricket (Orthoptera: Gryllotalpidae) has developed into claw for digging and excavating. As the result of having a well-suited body and appendages for living underground, mole cricket still needs to manoeuvre on land in some cases with some kinds of gait. In this paper, the three-dimensional kinematics information of mole cricket in terrestrial walking was recorded by using a high speed 3D video recording system. The mode and the gait of the terrestrial walking mole cricket were investigated by analyzing the kinematics parameters, and the kinematics coupling disciplines of each limb and body were discussed. The results show that the locomotion gait of mole cricket in terrestrial walking belongs to a distinctive alternating tripod gait. We also found that the fore legs of a mole cricket are not as effective as that ofcommon hexapod insects, its middle legs and body joints act more effective in walking and turning which compensate the function of fore legs. The terrestrial locomotion of mole cricket is the result of biological coupling of three pairs of legs, the distinctive alternating tripod gait and the trunk locomotion.     

Wettability of a Biomimetic Non-smooth Coating by Water

Through the evolution of hundreds of millions of years,the living creature have superior structure and function such as the structure of non-smooth surfaces have a well water-repellent,drag reduction,adhesion reduction functions.This study chose a kind of widely used material gray cast iron as substrate,which the metal and nano-ceramic nanocomposite coatings by electrodepositon on gray cast iron surface were prepared.The 2-D and 3-D surface morphologies of composite coating were observed and the result indicated that 2-D and 3-D had a typical geometrical non-smooth character.Furthermore,the contact angles of coating were measured.The relation between coating morphology and wettability was analysed.Therefore,the water-repellent of the composite coating surface was due to the characteristic microstructure and content of coating.     

The structural evolution and mechanical properties of a Zr-based bulk metallic glass during superplastic gas pressure forming

The structural evolution and mechanical properties of a Zr-based bulk metallic glass during superplastic gas pressure forming were investigated by differential scanning calorimetry (DSC), transmission electron microscopy (TEM) and nanoindentation measurements at the optimum temperature of 676 K under different stress states. It was found that the crystallized volume fraction of the deformed specimens with die aspect ratios of 1:1 and 3:2 are estimated to be 15% and 25%, respectively. The high resolution TEM results show that more particles at the nanometer level exist in the deformed specimen with the aspect ratio of 3:2. The nanoindentation tests further illustrate that the Young’s modulus and hardness of the deformed specimens have increased, and the deformed sample with the aspect of 1:1 shows slightly smaller modulus and hardness. The nano-scale crystalline structure induced by gas pressure forming process is considered to be the main reason for the change of the mechanical properties, and in addition to thermal and strain energy. In addition, the structural evolution is also affected by the stress state in the process of gas pressure forming.     

Performance of experimental carbon blacks in aqueous supercapacitors

Four samples of carbon black were synthesised for use in aqueous supercapacitors. They were designed to have different surface areas and pore size distributions. The objectives were to identify the attributes that are necessary to obtain a high specific capacitance and to attempt to correlate different physical characteristics of the carbon electrodes with their capacitance. A fifth carbon was obtained from another laboratory for comparison. Carbon electrodes were analysed using both acidic and alkaline electrolytes. Their capacitance was measured at room temperature and at −40 °C, using slow sweep cyclic voltammetry. Electrochemical impedance spectroscopy was also performed on the carbon electrodes using the same electrolytes and temperatures. The results from these measurements are discussed in terms of the surface areas and pore size distributions of the samples, which were measured using the BET technique.     

Effect of postcrosslinking modification with glutaraldehyde on the properties of thermoplastic starch/poly(vinyl alcohol) blend films

Thermoplastic starch (TPS)/poly(vinyl alcohol) (PVA) blend films were modified by crosslinking through soaking the films in glutaraldehyde aqueous solution and then heating in an oven. The effects of the concentration of the glutaraldehyde aqueous solution, soaking time, reaction temperature, and time on the crosslinking reaction were investigated. The moisture absorption and mechanical properties of the films were measured to characterize the influence of the crosslinking modification. It was found that the crosslinking modification significantly reduced the moisture sensitivity of the TPS/PVA blend films and increased the tensile strength and Young's modulus but decreased the elongation at break of the TPS/PVA blend films. The described method could be used for posttreating TPS/PVA‐based products to optimize their properties. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Dry Sliding Friction and Wear Mechanism of TiC-TiB2 Particulate Locally Reinforced Mn-Steel Matrix Composite from a Cu-Ti-B4C System via a Self-Propagating High-Temperature Synthesis (SHS) Casting Route

An Mn-steel matrix composite locally reinforced with in situ TiC-TiB₂ ceramic particulates was successfully fabricated via a self-propagating high-temperature synthesis (SHS) casting route in a Cu-Ti-B₄C system with various Cu contents. The effect of the Cu content on wear behavior, wear surface, and wear mechanism of the composite was investigated against an AISI H13 mating disc in similar testing conditions at various applied loads and sliding velocities. Moreover, the phase identification and microstructure of the composite were examined. With the increase in Cu content, the wear resistance of the Mn-steel matrix composite decreases first and then increases. Impressively, the composite with 30 wt% Cu content has the highest wear resistance. The enhanced wear resistance can be attributed to the combination of size of ceramic particulates, number of pores, and strength of the interfacial bonding. The dominant wear mechanisms of the TiC-TiB₂ ceramic particulate–reinforced Mn-steel matrix are ploughing grooves and delamination wear associated with more abrasion and adhesion.