微纳结构超疏水表面的浸润性及防冰性能

以Ti合金为基体材料,通过超快激光加工微结构并复合纳米SiO₂/氟化聚氨酯涂料,获得微纳结构的涂层表面,并与涂料喷涂获得的纳米涂层表面和未处理的Ti合金表面进行对比分析。分别采用扫描电镜、超景深显微镜、接触角和冰结合力测量仪,研究分析未处理Ti合金表面、纳米结构表面、微纳结构表面的形貌、疏水性、防覆冰性能。结果表明:具有微纳结构的涂层表面具有最佳的超疏水性,接触角为158.9°;与未处理Ti合金表面、纳米结构表面相比,微纳结构表面冰结合力显著降低,表面冰结合强度约为410 kPa。      

Surface energy increase of oxygen-plasma-treated PET

Prosthetic composite is a widely used biomaterial that satisfies the criteria for application as an organic implant without adverse reactions. Polyethylene therephthalate (PET) fiber-reinforced composites have been used because of the excellent cell adhesion, biodegradability and biocompatibility. The chemical inertness and low surface energy of PET in general are associated with inadequate bonds for polymer reinforcements. It is recognized that the high strength of composites, which results from the interaction between the constituents, is directly related to the interfacial condition or to the interphase. A radio frequency plasma reactor using oxygen was used to treat PET fibers for 5, 20, 30 and 100 s. The treatment conditions were 13.56 MHz, 50 W, 40 Pa and 3.33×10⁻⁷ m³/s. A Ramé-Hart goniometer was used to measure the contact angle and surface energy variation of fibers treated for different times. The experimental results showed contact angle values from 47° to 13° and surface energies from 6.4×10⁻⁶ to 8.3×10⁻⁶ J for the range of 5 to 100 s, respectively. These results were confirmed by the average ultimate tensile strength of the PET fiber/ polymethylmethacrylate (PMMA) matrix composite tested in tensile mode and by scanning electron microscopy.     

UV‐Resistant and Thermally Stable Superhydrophobic CeO2 Nanotubes with High Water Adhesion

A novel type of sticky superhydrophobic cerium dioxide (CeO₂) nanotube material is prepared by hydrothermal treatment without any chemical modification. A water droplet on the material surface shows a static water contact angle of about 157° but the water droplet is pinned on the material surface even when the material surface is turned upside down. Interestingly, the as‐prepared CeO₂ nanotube material displays durable superhydrophobicity and enhanced adhesion to water under ultraviolet (UV) light irradiation. Importantly, this change in water adhesion can be reversed by heat treatment to restore the original adhesive value of 20 µL. Further, the maximum volume of the water droplet adhered on the material surface of CeO₂ nanotubes can be regulated without loss of superhydrophobicity during the heating treatment/UV‐irradiation cycling. Meanwhile, the superhydrophobic CeO₂ nanotube material shows remarkable thermal stability even at temperatures as high as 450 °C, long‐term durability in chemical environment, and air‐storage and good resistance to oily contaminant. Finally, the potential application in no‐loss water transportation of this sticky superhydrophobic CeO₂ material is demonstrated.     

Failure investigation of GFRP communication towers

The rapid growth in telecommunication system requires a large number of free-standing and guyed towers. Glass Fiber Reinforced Polymer (GFRP) material is corrosion resistant and light weight with specific gravity one-fourth of steel. In triangular based communication towers gusset plates can be avoided by using GFRP 60° angles for leg members. The failures encountered in the full-scale testing of a 24 m high triangular GFRP communication tower designed by the pultruded profile manufacturer purely based on the properties derived from tensile coupon test results is presented in this paper. The GFRP 60° angles as struts exhibited torsional-flexural buckling mode and the 90° angles failed by flexural buckling. ANSYS Shell 281 layered element used to model the GFRP struts predicted the failure loads closer to the experiments. The GFRP 60° angles as leg members have shown torsional-flexural buckling mode till failure but finally failed by de-bonding of layers in the case of angle sections made of stitched mat and by shearing of the cross section in angles with multi-axial technical fabrics. The 60° angles subjected to compression, exhibited higher strength at a component level compared to the leg member in tower restrained by secondary bracings. The strength and behaviour of GFRP angles with multi-axial technical fabrics (± 45°/90°) are superior compared to the angles with stitched mat.     

Dynamic compressive behaviour of unidirectional GFRP for various fibre orientations

The dynamic stress-strain behaviour of unidirectional glass-epoxy composite has been studied at an average strain rate of 265 s⁻¹ for fibre orientations of 0°, 10°, 30°, 45°, 60° and 90° with respect to loading axis, using the Kolsky pressure bars technique. GFRP (glass fibre reinforced plastic) is found to be strain rate sensitive for all fibre orientations. Compared to quasi-static, the dynamic ultimate strength increases almost 100% for 0°, 80% for 10° fibre orientations and about 45% for all other orientations. Failure occurs predominantly by tensile splitting in 0° specimens and by shear for all other orientations preserving the fibre direction in each case.     

Wear behavior of laser metal deposited 17-4 PH SS-W composite at varied tungsten powder flow rate

This research studies the wear behavior of laser metal deposition of 17-4 PH SS-W composite using a 6 mm alumina-stainless steel ball under a load of 10 N, for 16 minutes, 40 seconds and with acquisition rate of 100 Hz conducted at 25 °C. The effect of laser power of between 2600 W and 1500 W; and powder flow rate of between 0.5 min⁻¹ and 2.0 min⁻¹ on wear resistance is investigated. Other processing parameters are constant throughout the experiments. The results show that the 17-4 PH SS-W composite produced at a high laser power of 2600 W exhibits a higher wear resistance as compared to the 17-4 PH SS-W composite samples produced at low laser power of 1500 W. The 17-4 PH SS-W composite sample produced at high laser power of 2600 W with tungsten powder flow rate of 2.0 min⁻¹ has the highest wear resistance with wear volume of 0.0276 mm³ and wear rate of 8.8 ⋅ 10⁻⁵ mm³/N m while the 17-4 PH SS-W composite sample produced at a low laser power of 1500 W with tungsten powder flow rate of 1.0 min⁻¹ has the wear volume of 0.02834 mm³ and wear rate of 9.0 ⋅ 10⁻⁵ mm³/N m.     

Ice adhesion to pristine and eroded polymer matrix composites reinforced with carbon nanotubes for potential usage on future aircraft

In aircraft icing conditions, the accretion of super-cooled liquid droplets on to the surface of an aircraft is dependent on numerous factors. In particular the temperature, liquid water concentration and material properties are of crucial importance in this context. This article features results obtained upon accretion of impact ice on pristine and eroded polymeric matrix composites with and without carbon nanotube reinforcement, for potential use in aeronautical applications. Results are shown for ice shear strength of a selection of advanced materials at T = − 5 °C and T = − 10 °C for a liquid water concentration LWC ≅ 0.3 g·m^− 3, actualized in an icing tunnel. The effect of surface roughness is further examined on the considered specimens in relation to their ice shear strength characteristics.     

Mechanical properties of atmospheric ice

Mechanical properties of atmospheric ice obtained in a wind tunnel are measured. The ice is grown from supercooled droplets on a rotating aluminium cylinder of 31.5-mm diameter and 6.5-μm rugosity. Compressive strength is measured at two speeds of deformation (0.76 and 26 mm/min) for glaze and rime samples, as a function of air temperature for different atmospheric conditions (0.4 and 0.8 g/m³ liquid-water contents, 20 and 40 μm mean volume droplet diameters, and 4, 8, 15, and 20 m/s air velocities). These values of compressive strength are compared to the adhesive strength on aluminium, measured at a 26 mm/min speed of deformation. The ratio of compressive to adhesive strength has a maximum value of 135 for hard rime accreted at −10°C, with a wind velocity of 15 m/s, a liquid-water content of 0.8 g/m³ and a mean droplet diameter of 40 μm. The maximum compressive strength measured for the lower speed of deformation is 17395 kPa and 10745 kPa for the higher speed of deformation. The maximum adhesive strength measured is 181 kPa. On the other hand, compressive strengths measured at deformation speeds varying from 0.015 to 288 mm/min show that atmospheric ice has a ductile-brittle behaviour approaching that reported for snow ice and fine-grained lake ice.     

Ice nucleation in water droplets on glass surfaces: From micro- to macro-scale

Ice nucleation encountered in engineering systems is often induced by solid/water interfaces. When classical nucleation theory is used to analyze ice nucleation in such systems, the uniformity of interfaces that contribute to ice nucleation must be carefully considered, because classical nucleation theory cannot be directly applied to non-uniform interfaces. In this study, to discuss the uniformity of ice nucleating activity of solid/water interfaces, ice nucleation in water droplets prepared on glass surfaces was investigated for various droplet sizes from micrometer to sub-millimeter. When the interfacial area between water and the glass surface was smaller than 1 × 10⁻¹⁰ m², the ice nucleation temperature showed scatter of about 2 °C, suggesting uniformity of the interface. However, when the interfacial area was larger than 1 × 10⁻⁸ m², the ice nucleation temperature showed large scatter, suggesting the ice nucleating activity was no longer uniform.     

超疏水仿生水泥混凝土路面防覆冰技术及效能评价

通过微纳米路表构建与超疏水材料涂覆技术相结合,制备了超疏水仿生水泥混凝土路面模型试件;开展超疏水材料涂覆技术研究,分析总结其制备工艺;采用自行设计的"冰-路"附着强度测试装置进行防覆冰性能测试,同时开展接触角测量试验、路面表面能计算及耐久性试验,综合评价超疏水仿生水泥混凝土路面的疏水、防冰效能。结果表明:超疏水水泥混凝土试件表面冰的残留率为29.9%,是普通试件的1/3左右,间接反映了超疏水路面具有较好的疏冰性能;与普通试件的接触角0°相比,超疏水水泥混凝土试件的接触角为153.5°,达到超疏水状态;表面能计算表明超疏水材料的作用降低了路面表面能,仅为普通水泥路面的3.4%,进一步验证了超疏水水泥混凝土路面可显著降低"冰-路"附着强度;通过模拟轮胎与路面的摩擦作用,接触角依然在90°以上,表明超疏水路面耐久性良好。     

Measurement of shear strength of granular/discontinuous-columnar sea ice

A method of performing shear tests using asymmetrical four-point bending was applied to sea ice. The method leads to less uncertainty in the stress field created. The tests were performed on specimens of granular/discontinuous-columnar ice obtained from the Beaufort Sea. For a test temperature of $\text{?13 ± 2°C}$ and salinity of 4.2%, the average shear strength was 550 kPa with a standard deviation of 120 kPa.     

Laser material processing of nickel superalloy for improved erosion resistance

A nickel-based superalloy was laser surface treated, and its erosion behavior was evaluated. The laser power and scan speed were varied in different levels to impart variations in microstructure and mechanical properties. The microstructure of specimens exhibited fine equiaxed grains to columnar structure at different parameters. A high cooling rate improved the hardness of the laser-treated specimen up to 603?HV_0.3 compared to the base material hardness of 430?HV_0.3. The rate of erosion increased linearly from 30° to 60° impingement angle and decreased at 75° impingement angle. The accumulation of the erodent inside the crater and the consequent absorbtion of the incident kinetic energy might have caused this reduction. The laser surface treated specimens exhibited ～1.5 factor of improvement in high temperature erosion resistance. This was attributed to the minimized energy transfer from impinging particle to the substrate achieved through laser surface melting.     

Superhydrophobicity vs. Ice Adhesion: The Quandary of Robust Icephobic Surface Design

The mesoscale, multitier texture of the lotus leaf has served as an inspiration to fabricate surface designs with controllable superhydrophobic properties, targeting a broad range of applications. The choice of material for such designs is directly related to surface performance, in particular under adverse and realistic conditions. Due to its importance in many applications, here aluminium is employed as a material platform and identify key porous hierarchical textures, yielding extraordinary impalement‐resistant behavior: Droplet repellency is demonstrated consistently for water impact velocities up to 12 m s⁻¹ (extreme Weber number, We ≈ 3500). Despite impressive superhydrophobic behavior, if ice forms on such surfaces, ice adhesion is markedly stronger than on less hydrophobic alumina nanotube array structures. In a departure from the findings of the well‐accepted shear stress‐based ice adhesion criterion, a deviation between decreasing ice adhesion strength and increasing hydrophobicity is observed. This is explained with ice adhesion mechanism, depending strongly on the applied stress field orientation and the respective effective ice–substrate contact area. Our results indicate that ice adhesion criteria for the performance of icephobic surfaces should account for the simultaneous presence of shear and tensile stresses, instead of shear stresses alone.     

Effect of substrates on the chemical characteristics and evolving structures of an organic superhydrophobic coating

While recent research has used organic coatings to replace chromium-based coatings, the ability of a coating material to repeat its chemical properties on different substrates is still under investigation. The Repellix superhydrophobic compound was developed and deposited on three different substrates using the atomic layer deposition method under the same condition. The films were characterized using the scanning electron microscope, atomic force microscope, water contact angle, attenuated Fourier transform infrared, and x-ray diffractometer. The surface morphology revealed that microstructural evolutions and topologies are different. The roughness of the coating deposited on stainless steel is the highest at 38.39 nanometers, while mild steel substrate showed the least surface roughness at 28.66 nanometers. From observations, the roughness also contributed to the degree of superhydrophobicity of the films deposited on substrates. The multiple hydroxyl functional groups observed in the Fourier transform spectroscopy in the range 3200 cm⁻¹ to 4000 cm⁻¹ would aid the adhesion of deposited films to the substrates. The x-ray diffraction results showed that all substrates had chemical stability, and the Repellix compound is amorphous on all substrates. Stainless steel showed to be the most robust among the substrates considered.     

Vi-PDMS/S-SiO2超疏水聚酯纤维织物的制备及性能研究

目的 基于普通织物材料防水性较差的问题,制备一种具有超疏水涂层的聚酯纤维织物,并对其性能进行研究。方法 以聚酯纤维织物为基材,基于紫外光固化技术通过浸涂法,使用商用气相纳米SiO₂颗粒(S-SiO₂)、端乙烯基聚二甲基硅氧烷(Vi-PDMS)在织物表面构筑微纳粗糙结构,获得超疏水的织物。采用扫描电子显微镜、水接触角测量仪对其微观结构和疏水性能进行表征,并通过机械摩擦实验对其超疏水稳定性进行考察。结果 当Vi-PDMS和S-SiO₂质量比为1∶4时,选择交联剂为三羟甲基丙烷三丙烯酸酯(TMPTA)制备的聚酯纤维织物表面的水接触角可达到151°,滚动角可达9°;且经过40次循环摩擦后,其表面水接触角仍大于140°,具有一定的耐磨性。结论 基于紫外光固化技术,采用操作简便的浸涂法制备的聚酯纤维织物具有优异的超疏水性能和一定的耐磨性,为织物超疏水性能研究提供参考,有望应用于超疏水聚酯纤维织物领域。     

Parahydrophobic Surfaces by Electrodeposition of PEDOT Polymers with Aromatic Groups

We report the electropolymerization of five 3,4-ethylenedioxythiophene (EDOT) monomers containing different aromatic groups (phenyl, diphenyl, biphenyl, naphthalene, and pyrene). While with phenyl, diphenyl, biphenyl, and naphthalene the polymerization occurs on the EDOT moiety, with pyrene both the EDOT and the pyrene moieties polymerize. Their electrodeposition gives rise to different surface structures with parahydrophobic properties (water apparent contact angle θ > θ^Y, where θ^Y corresponds to the Young angle of the smooth surface of the same materials). The highest properties are obtained with PEDOT-BiPh (θ = 134.6° and extremely high water adhesion). The results are due to the combination of surface structures with intrinsically hydrophilic polymers (θ^Y of the smooth polymer <90°).     

仿生超疏水聚丙烯/二氧化钛复合薄膜的构筑及性能研究

采用简便的相分离法制备出超疏水PP/TiO2复合薄膜。该复合薄膜表面与水的接触角为169°,滚动角小于4°。pH值为1~14的水溶液在其表面都具有很高的接触角,均大于160°。对其表面进行扫描电子显微镜分析可知,该薄膜具有类花瓣二元微纳米复合微观结构,这种结构可捕获空气,形成水与基底之间的气垫,对表面超疏水性的产生起到了关键作用。用Cassie理论对其表面超疏水进行分析,结果表明,约2.7%的面积是水滴和基体接触,而有约97.3%的面积是水滴和空气接触。     

Highly Thermoconductive,Thermostable, and Super-Flexible Film by Engineering 1D Rigid Rod-Like Aramid Nanofiber/2D Boron Nitride Nanosheets

Polymer-based thermal management materials have many irreplaceable advantages not found in metals or ceramics, such as easy processing, low density, and excellent flexibility. However, their limited thermal conductivity and unsatisfactory resistance to elevated temperatures (<200 °C) still prevent effective heat dissipation during applications with high-temperature conditions or powerful operation. Therefore, herein highly thermoconductive and thermostable polymer nanocomposite films prepared by engineering 1D aramid nanofiber (ANF) with worm-like microscopic morphologies into rigid rod-like structures with 2D boron nitride nanosheets (BNNS) are reported. With no coils or entanglements, the rigid polymer chain enables a well-packed crystalline structure resulting in a 20-fold (or greater) increase in axial thermal conductivity. Additionally, strong interfacial interactions between the weaved ANF rod and the stacked BNNS facilitate efficient heat flux through the 1D/2D configuration. Hence, unprecedented in-plane thermal conductivities as high as 46.7 W m⁻¹ K⁻¹ can be achieved at only 30 wt% BNNS loading, a value of 137% greater than that of a worm-like ANF/BNNS counterpart. Moreover, the thermally stable nanocomposite films with light weight (28.9 W m⁻¹ K⁻¹/10³ (kg m⁻³)) and high strength (>100 MPa, 450 °C) enable effective thermal management for microelectrodes operating at temperatures beyond 200 °C.     

PVDF/SiO2/PDMS涂层超疏水纺织品性能

目的 针对普通纺织品材料防水性和防污性较差的问题,制备具有自清洁功能的超疏水涂层纺织品,并研究其性能.方法 以涤纶织物为基材,通过非溶剂诱导相分离法,使用聚偏氟乙烯和疏水纳米二氧化硅复合液在纺织品表面构筑微纳粗糙结构,采用聚二甲基硅氧烷对其进行疏水化处理,获得自清洁超疏水涂层纺织品.采用扫描电子显微镜、X射线能量散射光谱和视频光学接触角测量仪等对其结构和性能进行表征,并通过机械摩擦、洗涤、酸/碱/盐溶液浸渍和紫外光照等方法对其表面超疏水稳定性进行考察.结果 当聚偏氟乙烯质量分数为2％,疏水纳米二氧化硅质量分数为0.4％,聚二甲基硅氧烷质量分数为1％时,制备的纺织品的表面接触角可达(162.2°±0.8°),滚动角达(2.0°±0.4°),具有优异的超疏水自清洁效应;经72 h酸/碱/盐溶液浸渍、196 h紫外光照、2500次摩擦和120次家庭水洗后,其表面接触角仍大于150°,表现出优异的超疏水稳定性.结论 采用简便的非溶剂相分离法制备的涂层纺织品具有优异的自清洁性能,并且其超疏水性能具有机械耐久性和化学稳定性,有望应用于纺织材料包装领域.     

Comparative strengths of fresh water ice

In order to gain a quantitative comparison among the various mechanical properties of ice, a series of tests was performed on fresh water ice in which several of the mechanical properties were tested under identical experimental conditions. In particular, the tests were standardized with respect to ice growth conditions, ice type, grain size and orientation, sample size, test temperature and strain rate. The average results of the test were: flexural strength ? cantilever beam = 770 ± 150 kPa; flexural strength ? simple beam (top tension) = 2200 ± 320 kPa; flexural strength ? simple beam (bottom tension) = 1770 ± 190 kPa; $\text{fracture toughness}\text{= 83 ± 7}\text{kPa m}{}^{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}$; shear strength = 500 ± 220 kPa; compressive strength (horizontal loading) = 4400 ± 700 kPa and strain modulus ? cantilever beam = 1.6 ± 0.4 GPa. Since most of the tests were performed using a portable compression test machine, the strength values can serve as baseline values for comparison with field results.