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1.
表面润湿性对水润滑Al-Mg合金摩擦学特性的影响 总被引:1,自引:0,他引:1
通过自组装技术在Al-Mg合金表面制备自组装分子膜,采用接触角测量仪测定了自组装分子膜的水接触角,采用多功能摩擦磨损试验机对制备不同自组装分子膜的Al-Mg合金在3种润滑方式下进行摩擦磨损实验。结果表明,制备自组装分子膜可显著改变Al-Mg合金的表面润湿性,制备FDTS、FOTS、OTS自组装分子膜的表面呈疏水性,制备MPS、APS自组装分子膜的表面则呈亲水性,5种自组装分子膜接触角由大到小的顺序为FDTS>FOTS>OTS>MPS>APS。自组装分子膜的疏水性越强,Al-Mg合金的摩擦系数越小。同种自组装分子膜在干摩擦条件下摩擦系数最大,浸水润滑条件下摩擦系数有所下降,喷水润滑条件下摩擦系数最小。 相似文献
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基于位错刻蚀理论利用溶液浸泡处理A1-Mg-Si合金在其表面形成微观粗糙表面结构,采用自组装技术在此表面制备FDTS自组装分子膜.采用X射线衍射仪、扫描电子显微镜和表面粗糙度仪对试样表面形貌进行了表征;采用接触角测量仪对试样表面接触角进行了测量.结果表明,试样经溶液浸泡处理和沉积自组装分子膜后,其表面润湿性实现了由亲水到超亲水再到超疏水的转变;改变溶液浸泡时间得到具有不同微观结构的表面,沉积自组装分子膜后得到的超疏水表面具有不同的滚动接触角,其表面黏附力具有明显差异.分析认为,超疏水表面的获得是溶液浸泡处理得到的粗糙表面结构和低表面能物质FDTS自组装分子膜共同作用的结果;表面黏附力的差异是试样表面微观形貌的不同造成水滴在其表面所处状态的差异引发的. 相似文献
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通过自组装技术在Al-Mg合金表面制备自组装分子膜,采用接触角测量仪测定了自组装分子膜的水接触角,采用多功能摩擦磨损试验机对制备不同自组装分子膜的Al-Mg合金在3种润滑方式下进行摩擦磨损实验。结果表明,制备自组装分子膜可显著改变Al-Mg合金的表面润湿性,制备FDTS、FOTS、OTS自组装分子膜的表面呈疏水性,制备MPS、APS自组装分子膜的表面则呈亲水性,5种自组装分子膜接触角由大到小的顺序为FDTS>FOTS>OTS>MPS>APS。自组装分子膜的疏水性越强,Al-Mg合金的摩擦系数越小。同种自组装分子膜在干摩擦条件下摩擦系数最大,浸水润滑条件下摩擦系数有所下降,喷水润滑条件下摩擦系数最小。 相似文献
4.
复合SiO2粒子涂膜表面的超疏水性研究 总被引:4,自引:0,他引:4
采用溶胶-凝胶法制备不同粒径和形状的SiO2粒子,并利用氟硅氧烷的表面自组装功能制备了具有仿生类"荷叶效应"的超疏水涂膜.通过原子力显微镜、扫描电镜和水接触角的测试对膜结构及性能进行了表征,探讨了SiO2粒子的粒径和形状对材料微观结构,表面粗糙度和疏水性能的关系.结果表明,含单一粒径涂膜表面水接触角符合Wenzel模型;而复合粒子构成了符合Cassie模型的非均相界面,单纯的粗糙度因子不能反映水接触角的变化,复合粒子在膜表面的无规则排列赋予涂膜表面不同等级的粗糙度,使得水滴与涂膜表面接触时能够形成高的空气捕捉率和较小的粗糙度因子,这与在涂膜表面能形成自组装分子膜的氟硅氧烷共同作用赋予了涂膜超疏水性能. 相似文献
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以亲水性高分子聚乙烯醇(PVA)为基体,二氧化硅(SiO_2)纳米颗粒为无机填料,旋涂在玻璃表面后的PVA/SiO_2再经十七氟癸基三甲氧基硅烷(C_(13)H_(13)F_(17)O_3Si,FAS)修饰,制备了具有超疏水性能的PVA/SiO_2-FAS薄膜。考察了PVA与SiO_2复合的比例及FAS修饰对膜疏水性的影响。用傅里叶变换红外光谱、X射线能谱和扫描电子显微镜分别对超疏水表面进行了结构分析和形貌表征,用接触角测量仪观察了水滴在膜表面的润湿性。结果显示,当PVA/SiO_2体积比为1∶5时,氟化PVA/SiO_2膜表面具有较好的超疏水功能,静态接触角可达151.24°,滚动角约为4°。这主要是膜表面含有低表面能氟原子及具有纳米粗糙结构共同作用的结果。 相似文献
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通过扫描探针显微镜(SPM)直接观察沉积在基片表面的花生酸LB(Langmuir-Blodgett)薄膜不同范围尺度下的微观结构.研究在经过表面两亲性(亲水性或疏水性)处理的基片上,在相同的制膜条件下,改变其拉膜沉积方式,对花生酸LB膜样品的表面结构、薄膜均匀性和缺陷等的影响.结果显示,花生酸LB膜在不同拉膜沉积方式下,薄膜表面将形成不同的分子自组装形态;改变基片表面的亲水性强弱也直接影响LB膜的表面形貌的均匀性,可能通过选择恰当表面处理和沉积方式来获得平整度更高,缺陷更少的LB膜. 相似文献
10.
利用激光加工在铝合金表面进行微织构,通过自组装工艺在微织构表面修饰有机硅烷分子膜,制备得到具有疏水/超疏水性表面。利用扫描电镜、三维形貌仪、接触角测量仪对微织构表面微观形貌和润湿性进行表征。结果表明:激光微织构具有的微米级粗糙结构与自组装分子膜的共同作用对超疏水表面的构建具有重要作用;接触角随激光微织构加工间距(50~100μm)的减小而增大,且与微织构的形貌类型相关。漂浮承载实验表明,超疏水表面符合Cassie-Baxter状态模型,且可有效提高平台的漂浮承载能力。 相似文献
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This study investigated alkanethiolate self-assembled monolayers (SAMs) of varied chain lengths adsorbed upon novel Au-coated microelectrodes, of which the surface properties were quantitatively evaluated by surface characterization and 3T3 fibroblast cell adhesion, total impedance and cell detachment tests. Thin-film SAMs adsorbed upon Au/PI/Si provided a hydrophobic or passive surface with increased water contact angle and initial total impedance. From cell adhesion tests, we can observe that the film formed as a dense-packed spacer resulted in incomplete cell sealing of 3T3 cells upon the surface-modified microelectrode. Thus the decrease in cell coverage rate and in the slope in association with total impedance as a function of cell-surface reaction time can be found. To study the adhesion force of a comparable single cell attached upon varied modified surfaces, a cell detachment test using a triangular probe tip of a well defined cantilever was carried out in medium containing fibroblast cells. Overall, both the peak force and the work required to detach a comparable single cell from the anchoring domain corresponded well to the increased length of alkyl chains adsorbed upon Au/PI/Si. Both measurements on the SAM modified surfaces demonstrated much smaller values than those on the pristine Au/PI/Si surface. These results concluded that a cell-repulsive characteristic was clearly formed on the SAM modified microelectrode surface. The non-adhering properties of surface-modified microelectrodes should provide better sensitivity for neuromuscular stimulation as well as for the recording of infinitesimal neural signals in future applications of neural prostheses. 相似文献
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In this study, the well-ordered alkanethiolate self-assembled monolayers (SAMs) of varied chain lengths and tail groups were employed as examples for nano-characterization on their mechanical properties. A novel nano-indentation technique with a constant harmonic frequency was applied on SAMs chemically adsorbed on Au to explore their contact mechanics, and furthermore to interpret how SAM molecules respond to an infinitesimal oscillation force without pressing them. Experimental results demonstrated that the harmonic contact stiffness along with the measured displacement of SAMs/Au was distinguishable using a dynamic contact modulus with the distinct feature of phase angles. Phase angles resulted from the relaxing continuation of an applied harmonic frequency and mostly influenced by the outermost tail group of SAM molecules. The harmonic contact stiffness of SAM molecules obviously increased with the densely packed alkyl chains and relatively intense agglomeration of the head group at the anchoring site. As a consequence, the result of this work is relevant to contact mechanics at the surface contact level for the distinction of molecular substances attached on a solid surface. Furthermore it is particularly anticipated to identify biological molecules of variable qualities under a fluid-like micro-environment. 相似文献
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Molecular dynamics calculations have been used to investigate the behavior of overlayers of water or n-alkane fluids on solid surfaces formed from “self-assembled” monolayers of long-chain hydrocarbons. A microscopic analog of the wetting contact angle is used to measure the surface wetting characteristics. On a nonpolar surface, formed by close packed chains having -CH3 tailgroups, the water molecules aggregate to form a compact droplet. The calculated contact angle of the droplet is similar to experimental values for macroscopic water droplets. Contrary to intuition, the overlayers of hexadecane or decane form droplets with smaller contact angles on the same surface. However, the calculated contact angles are again in reasonable accord with experimental values. 相似文献
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We studied four trialkoxysilane thin films, fabricated via self-assembly by casting neat silane reagents onto hydrophilic SiOx/Si substrates in the ambient. This drop-casting method is simple, yet rarely studied for the production of silane self-assembled monolayers (SAMs). Various ex-situ techniques were utilized to systematically characterize the growth process: Ellipsometry measurements can monitor the evolution of film thickness with silanization time; water droplet contact angle measurements reveal the wettability; the change of surface morphology was followed by Atomic Force Microscopy; the chemical identity of the films was verified by Infrared-Visible Sum Frequency Generation spectroscopy. We show that the shorter carbon chain (propyl-) or branched (2-(diphenylphosphino)ethyl-) silane SAMs exhibit poor ordering. In contrast, longer carbon chain (octadecyl and decyl) silanes form relatively ordered monolayers. The growth of the latter two cases shows Langmuir-like kinetics and a transition process from lying-down to standing-up geometry with increasing coverage. 相似文献
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Silicon surface hydrophobicity has been varied by using silane treatments on silicon pyramid surfaces generated by KOH anisotropic etching. Results demonstrated that by altering the surface hydrophobicity, the apparent contact angle changed in accord with the Wenzel equation for surface structures with inclined side walls. Hierarchical structures were also constructed from Si pyramids where nanostructures were added by Au-assisted electroless HF/H2O2 etching. Surface hydrophobicity and superhydrophobicity were achieved by surface modification with a variety of silanes. Stability of the Cassie state of superhydrophobicity is described with respect to the Laplace pressure as indicated by the water droplet meniscus in contact with the hierarchical structures. The contact angle hysteresis observed is also discussed with respect to water/substrate adhesion. 相似文献
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Rahul Bhure Anil Mahapatro Carl Bonner Tarek M. Abdel-Fattah 《Materials science & engineering. C, Materials for biological applications》2013,33(4):2050-2058
Surface modification of cobalt chromium (Co–Cr) alloy is being investigated as a possible solution to the biomedical challenges arising from its usage. Self assembled monolayers (SAMs) of organophosphonic octadecylphosphonic acid (ODPA) were formed on the oxide surface of Co–Cr alloy by chemisorption using the solution deposition technique. High quality and well-ordered SAMs were formed which were characterized using Fourier transform infrared spectroscopy-attenuated total reflectance (FTIR-ATR), X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), contact angle measurements and ellipsometry. The resulting monolayers were then exposed to in vitro conditions using phosphate buffered saline (PBS) solution. The samples were analyzed for a period of 1, 3, 7 and 14 days. The resulting samples were characterized using XPS, AFM and Contact angle measurements. XPS atomic concentrations and detailed high energy elemental scans gave an insight into the trends of elemental concentrations over the duration of the study. SAMs were found to be strongly bound to the oxide surface after PBS exposure. AFM gave the topographic details of SAMs presence by island formation before and after SAM formation and also over the duration of the PBS exposure. Contact Angle Measurements confirmed the hydrophobicity of the surface after SAM formation and indicated a slight disorder of the SAM alkyl chain upon exposure to PBS. Thus, ODPA SAMs were successfully coated on Cobalt Chromium (Co–Cr) alloy surface and were found to be stable and strongly bound after PBS exposure. 相似文献
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Surfaces functionalized with a self-assembled monolayer (SAM) formed from a mixture of two alkylsilanes with different chain lengths have been designed to simultaneously improve the liquid crystal (LC) wettability and promote homeotropic anchoring of the LC. Most chemically functionalized surfaces (e.g., long alkyl chain SAMs) that promote homeotropic alignment of LC possess low surface energy and result in poor LC wettability, inhibiting LC infiltration into microstructured surfaces and sometimes resulting in LC dewetting from the surface. However, a surface modified with a mixed SAM of octadecyltriethoxysilane (C18) and ethyltriethoxysilane (C2) exhibited very low LC contact angle while providing homeotropic anchoring. Ellipsometry was used to correlate the bulk concentration of C18 in the deposition solution to the surface coverage of C18 in the mixed monolayer; these bulk and surface concentrations were found to be equal within experimental uncertainty. The LC contact angle was found to depend nonmonotically with the surface coverage density, with a minimum (14.4 ± 0.1°) at a C18 surface coverage of 0.26 ± 0.08. Homeotropic LC anchoring was achieved at a C18 surface coverage of ≥0.11 ± 0.04, in the regime where a minimum in the LC contact angle was observed. The practical application of this approach to surface modification was demonstrated using a micropillar array sensor substrate. When the array was functionalized with a conventional C18 SAM, the LC did not infiltrate the array and exhibited a contact angle of 47.4 ± 0.5°. However, the LC material successfully infiltrated and wetted the same microstructured substrate when functionalized with a C18/C2 mixed SAM, while still exhibiting the desired homeotropic anchoring. 相似文献
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Cheng-Da Wu Li-Min Kuo Shiang-Jiun Lin Te-Hua Fang Shy-Feng Hsieh 《Computational Materials Science》2012,53(1):25-30
The wetting properties of water nanodroplets on a gold substrate are studied using molecular dynamics (MD) simulations. The effects of temperature, droplet size, and surface roughness are evaluated in terms of molecular trajectories, internal energy, dynamic contact angle, and the radial distribution function. The simulation results show that the wetting ability and spreading speed of water greatly increases with increasing temperature. The dynamic contact angle of water on the gold substrate decreases with increasing temperature and decreasing droplet size and surface roughness, which leads to an increase in wetting ability. The compactness of a water droplet increases with decreasing temperature and droplet size, and slightly increases with degree of roughness. The internal energy of a water droplet decreases with increasing surface roughness, indicating that droplets form more stably on a rough surface. 相似文献
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High-temperature sessile-drop wettability tests were conducted on unpolished C–C and SiC–SiC composite substrates using commercial
braze alloys Palco (Pd-35Co), Palni (Pd-40Ni), Cusil-ABA (63Ag–35.3Cu–1.75Ti), and Ticusil (68.8Ag–26.7Cu–4.5Ti). Observations
revealed non-uniform, anisotropic spreading, copious braze infiltration of the composite substrates, particularly C–C composite,
and Ti enrichment at the composite/braze interface together with dissolution of Si (from SiC–SiC composite) in braze and diffusion
of Co (from Palco) in the composite. The droplet/composite contact region near the droplet center revealed intimate and microstructurally
sound bonding. However, inter-laminar shear cracking within the SiC–SiC composite in contact with Ticusil, Palco, and Palni,
and partial substrate/droplet de-cohesion near the edge of the droplet were also observed. In Palco and Palni droplets, fiber
tows in the contact region de-laminated from the main body of the composite via inter-laminar shear cracking resulting in
fiber flotation, segregation, and surface degradation. The study is one of the first empirical enquiries into the complex
wetting and spreading behavior of brazes on commercial C–C and SiC–SiC composites. 相似文献
20.
Hydrophilicity of Graphene in Water through Transparency to Polar and Dispersive Interactions
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Liubov A. Belyaeva Pauline M. G. van Deursen Kassandra I. Barbetsea Grégory F. Schneider 《Advanced materials (Deerfield Beach, Fla.)》2018,30(6)
Establishing contact angles on graphene‐on‐water has been a long‐standing challenge as droplet deposition causes free‐floating graphene to rupture. The current work presents ice and hydrogels as substrates mimicking water while offering a stable support for graphene. The lowest water contact angles on graphene ever measured, namely on graphene‐on‐ice and graphene‐on‐hydrogel, are recorded. The contact angle measurements of liquids with a range of polarities allow the transparency of graphene toward polar and dispersive interactions to be quantified demonstrating that graphene in water is hydrophilic. These findings are anticipated to shed light on the inconsistencies reported so far on the wetting properties of graphene, and most particularly on their implications toward rationalizing how molecules interact with graphene in water. 相似文献