Dynamic adhesion due to fluid infusion

The resistance of fluid infusion inside a thin film that separates an opening gap leads to viscous adhesion. Viscous adhesion can be detrimental for some mechanical devices such as valves or during additive manufacturing processes. On the other hand, it is also a mechanism found in nature for dynamic reversible adhesion. In this article we review analysis and measurements of viscous adhesion. In particular, we give conditions where viscous adhesion dominates over other surface forces. We also describe how characteristics of the solid surfaces such as roughness and elasticity, as well as the compliance of the load cell can be incorporated in the analysis. Finally, we discuss the knowledge gaps and scientific areas where a better understanding of viscous adhesion could be beneficial.     

A novel method for improving the adhesion strength of the electrodeposited Ni films in MEMS

Adhesion performance of MEMS materials is increasingly important with the widely use of miniaturized devices. This paper proposed a novel method for improving adhesion performance between electrodeposited Ni multi-layers. The new method is to treat the Ni substrate in nickel chloride plating solution by pulse reverse current technique before electrodeposition. The dense oxide film of Ni substrate can be removed effectively by this electrochemical method, meanwhile, the proper roughness of Ni substrate is in favor of epitaxial growth during electrodeposition. Moreover, the Ni film is electrodeposited by the new method with low stress and coarse crystal grain. Consequently, the adhesion performance of Ni films is improved dramatically. The experimental results show that the adhesion performance of Ni film electrodeposited by the new method is about 3 times that of by traditional method.     

Influence of adhesion of silica and ceria abrasive nanoparticles on Chemical-Mechanical Planarization of silica surfaces

We report on a direct measurement of adhesion between abrasive nanoparticles of irregular shape, which are used in semiconductor industry in the process of Chemical-Mechanical Planarization (CMP), and silica surface. The adhesion of ceria and silica nanoparticles to silica surface is measured in multiple chemistries of different CMP slurries using a specially developed atomic force microscopy (AFM) method. Using this method, we study the influence of adhesion on the main parameters of CMP, removal rate and defectivity, scratches. While being plausible to expect correlation between these parameters and adhesion, it has not been systematically studied as of yet. We observed direct correlation between adhesion and removal rate. Comparing the measured defectivity and adhesion, we observe the presence of some correlation between these parameters. We conclude that both adhesion and shape of abrasive particles influence defectivity, micro-scratches. Direct measurements of the adhesion between abrasive nano-particles and surface can be used in the screening of new slurries as well as various modeling related to wearing of the surfaces.     

Influence of superalloy substrate roughness on adhesion and oxidation behavior of magnetron-sputtered NiCoCrAlY coatings

The present study has been conducted in order to determine the influence of superalloy substrate roughness on adhesion and oxidation behavior of magnetron-sputtered NiCoCrAlY coatings. Six types of coating samples with different substrate roughness were tested. The surface roughness and real surface area of both the substrates and coatings were studied by atomic force microscopy (AFM) techniques. The scratch tests performed at progressive loads were employed to evaluate the adhesion of the coatings. Cyclic oxidation tests were performed at 1100 °C in air for 50 cycles, each cycle consisting of 1 h heating in the tube furnace followed by 15 min cooling in the open air. The AFM measurements exhibit that the surface roughness of the sputtered NiCoCrAlY coating increases with the increasing of the superalloy substrate roughness. The NiCoCrAlY coatings present slightly lower roughness than the corresponding superalloy substrate. The scratch adhesion tests indicate that the coatings on substrates with a smoother surface possess better adhesion than on those with a rougher surface. Both the real surface area and oxidation weight gain of the coatings decrease with the decreasing of the superalloy substrate roughness. The NiCoCrAlY coating sputtered on the superalloy substrate with lower roughness provides relatively higher antioxidant protection than that provided by the coating with rougher substrate.     

Synthesis of titanium nitride thin films deposited by a new shielded arc ion plating

Thin films of titanium nitride (TiN) were deposited on stainless steel substrates by a modified deposition technique, double-layered shielded arc ion plating with vicarious circular holes (DL-SAIP). The results show that the TiN film with the distance of 10 mm between the double-layered shield plates had the least droplets. The deposition rate of the films prepared with the new technique was more homogeneous than that of all the other shielded arc ion plating. The film/substrate adhesion and microhardness values of the TiN films were higher than 40 N and 18 GPa, respectively. Thus such TiN thin films can be expected in applications.     

骨髓基质干细胞在等离子体处理PEGDA基凝胶表面的黏附和增殖

通过低温等离子体技术对聚乙二醇双丙烯酸酯(PEGDA)/甲基丙烯酸β-羟乙酯(HEMA)共聚物水凝胶生物材料进行表面改性,以骨髓基质干细胞(BMSc)为细胞模型,考察了细胞在等离子体表面改性前后的水凝胶材料的黏附和增值行为,材料的表面性能通过 X 射线光电子能谱、接触角和扫描电镜进行表征.研究结果表明,材料表面经氩等离...     

The preparation and tribological characteristics of phosphorylated 3-aminopropyltriethoxysilane self-assembled film

Thin films deposited on the phosphonate 3-aminopropyltriethoxysilane (APTES) self-assembled monolayer (SAM) were prepared on the hydroxylated silicon substrate by self-assembling process from specially formulated solution. Chemical compositions of the films were detected by X-ray photoelectron spectrometry (XPS). The thickness of the films was determined with an ellipsometer, and the morphologies and nanotribological properties of the samples were analyzed by means of atomic force microscopy (AFM). As a result, the target film was obtained and the thin films were deposited on the silicon substrate. It was also found that the thin films showed the lowest friction and adhesion followed by APTES-SAM and phosphorylated APTES-SAM, while silicon substrate showed high friction and adhesion. Microscale scratch/wear studies clearly showed that thin films were much more scratch/wear resistant than the other samples. The superior friction reduction and scratch/wear resistance of thin films were attributed to low work of adhesion of non-polar terminal groups and the strong bonding strength between the films and the substrate.     

Surface modification of an epoxy resin with polyamines via cyanuric chloride coupling

The presence of polyamine groups on the surface of dielectric resins potentially improves the adhesion with electrochemically deposited metals. In this article, first cyanuric chloride is covalently bound to the surface hydroxyl groups of the epoxy resin. The remaining reactive sites on the coupled cyanuric chloride molecule are then used to anchor polyamines. New data on the triazine coupling is presented. The surface reactions are monitored and characterized by means of ATR-IR, SEM-EDS, XPS and ToF-S-SIMS.     

The effects of organoclay on the morphology and mechanical properties of PAI/clay nanocomposites coatings prepared by the ultrasonication assisted process

In this research, solvent based polyamide – imide (PAI)/clay nanocomposites were prepared successfully using the solution dispersion technique. With the assistance of the ultrasonic wave, the effect of the ultrasonic wave time on the microstructure of 3 wt% PAI/C20A nanocomposite (NC) was investigated. Then, the best ultrasonic parameters were selected and the effects of the concentration of Cloisite 20A (C20A) (1, 3 and 5 wt% C20A) on the microstructure and mechanical properties (adhesion, hardness, flexibility, wear and impact) of NCs were investigated. The PAI, C20A and nanocomposites (NC)s were characterized by Fourier transform infrared spectroscopy (FTIR), field emission scanning electron microscopy (FE-SEM), energy dispersive X-ray analysis (EDX), and Wide-angle X-ray diffraction (WAXD). The results showed that the sample with 1 and 3 wt% C20A had better mechanical properties, as compared to the pure PAI and the 5 wt% NC.     

Scattering of guided waves by defective adhesive bonds in multilayer anisotropic plates

We introduce an analytic-numerical method to simulate the interaction between ultrasonic guided waves and defective adhesive bonds in multilayer structures. We replace the thin adhesive layer by equivalent continuous distribution of normal and transversal springs and locally reduce the corresponding spring constants to model localized defects. We then formulate the resulting scattering problem as a linear least squares problem and solve it accordingly. The developed formulation is easy to implement and equally well suited to treating anisotropic as well as isotropic constituent layers. We illustrate the application of the proposed method through the simulation of ultrasound inspection of a three-layer isotropic plate and a sixteen-layer anisotropic plate used in the aeronautical industry, indicating in the simulations the guided modes that will most strongly interact with interfacial defects and computing the scattering resulting from the interaction of these modes with localized defects. We believe that the proposed method will serve both to aid in the design of interface inspections and as a basis for solving inverse scattering problems.