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.     

Fe and N co-doped carbon derived from melamine resin capsuled biomass as efficient oxygen reduction catalyst for air-cathode microbial fuel cells

Cathode oxygen reduction reaction (ORR) performance is crucial for power generation of microbial fuel cells (MFCs). The current study provides a novel strategy to prepare Fe/N-doped carbon (Fe/N/C) catalyst for MFCs cathode through high temperature pyrolyzing of biomass capsuling melamine resin polymer. The obtained Fe/N/C can effectively enhance activity, selectivity and stability toward 4 e^– ORR in pH neutral solution. Single chamber MFC with Fe/N/C air cathode produces maximum power density of 1166 mW m⁻², which is 140% higher than AC cathode. The improved performance of Fe/N/C can be attributed to the involvement of nitrogen and iron species. The excellent stability can be attributed to the preferential structure of the catalyst. The moderate porosity of the catalyst facilitates mass transfer of oxygen and protons and prevents water flooding of triple-phase boundary where ORR occurs. The biomass particles encapsulated in the catalyst act as skeletons, which prevents catalyst collapse and agglomeration.     

Thermal stresses of a wind turbine blade made of orthotropic material

This study is to investigate the thermal stress of a wind turbine blade made of wood composite material. First, the governing partial differential equation on heat conduction is stated, then, a finite element procedure using a variational approach is employed for the solution of the governing equation. Thus, the temperature field throughout the blade is determined. Next, based on the temperature field, a finite element procedure using potential energy approach is applied to determine the thermal stress field. A set of results is obtained through the use of a computer, which is considered to be satisfactory.     

An expert system for optimum water management in power production

This paper describes a software system (EPA) designed by A.I.TEC. Applied Information Technologies to plan production of electricity from hydroelectric power plants belonging to SELM (Servizi Elettrici Montedison). The main purpose of the system is to provide short term scheduling of water releases in order to optimize production, while complying with several constraints. This is achieved using expert system techniques to implement heuristic based optimization. We describe the problem, EPA architecture and heuristics used. A qualitative performance evaluation of the system is also given.     

Organic light-emitting diodes based on multilayer structures

We study various organic structures and explain the obtained improvements by the use of protective layer or hole transport layer in multilayer OLEDs based on Alq₃ as emitter.     

Functionally graded materials produced by laser cladding

AlSi40 functionally graded materials (FGMs) were produced by a one-step laser cladding process on cast Al-alloy substrate as a possible solution for interfacial problems often present in laser coatings. The microstructure of the FGMs consists of a large amount of silicon primary particles surrounded by α-Al dendritic halos and by Al/Si eutectic. The Si particles exhibit a continuous increase in both size and volume fraction, from 8.5 μm and 22.7% at the bottom to 52 μm and 31.4% at the top of the FGM layer, respectively. The morphology of the Si particles changes accordingly from a small polygonal shape to a coarsely branched equi-axial shape. The α-Al halos and eutectic areas show less change over the same distance. From an analysis of the temperature field of the laser pool, Si particles heterogeneously nucleate on incompletely melted Si particles. The number density of Si particles is most likely being controlled by the non-homogeneous temperature field of the pool that determines the decomposition of the original Si phase in the AlSi40 powder. The growth rate and time available at different depths of the laser pool mainly affect the final size of Si particles.