Papers by Keyword: Adhesion

Abstract: The failure characteristics of silicon nitride thin film deposited on GaAs substrate were investigated by use of nanoscratch. It was found that the film started to failvia delamination or buckling, which should beattributed to interfacial shear stress. The cracks were then formed and propagated around the edge of the delaminated film before it was chipped away by the moving tip. A normal load of 6.5 mN, corresponding to a depth of 150 nm, was found to be the critical threshold for theinterfacial failure. The fracture energy release rateof the film/substrate interface, or the work of adhesion, was calculated as 2.90 J/m2.

Abstract: With the advantage of simplicity and low cost, ink jet printing has the potential to replace the traditional chemical and physical deposition technology in thin film fabrication. In this work, silver conductive thin films are deposited on glass and polyimide substrates by ink jet printing, where some major characteristics of the printed thin films are investigated and compared to those deposited by sputtering. The micro texture and residual stresses of the thin films are measured with X-ray diffractometry (XRD). Using thin film scratch tester, the adhesion of thin films deposited by both ink jet printing and sputtering is studied. Further observations on electric and optical performance by using visible wavelength photospectrometry, four-point probe, and surface profiler are also discussed. The result shows that the micro texture of the printed thin film behaves as good as the sputtered thin film. Furthermore, the micro scratch result illustrates that the adhesion of the printed thin film is even better than the sputtered thin film. It emphasizes that, after certain baking process, the ink jet printing has the possibility to replace sputtering in thin film deposition, especially for the polymer substrates.

Abstract: The paper analyses possibilities to use new materials having a high degree of adhesion for designing vacuum gripping elements with a view to increase the radial capacity and at the same time to preserve the compressed air consumption or the vacuum level. Structural modification of the suction cup is presented with a bearing supporting plate having a material with an adhesion layer on the contact boundary and allowing the down-pressure to be regulated depending on mechanical properties of the object kept. In conclusion the results achieved are summarized illustrating a marked increase of the radial load capacity with regard to the defined vacuum level and the degree of shifting in the contact profile compared with the standard suction cups with a similar geometrical diameter in relation to the contact surface.

Abstract: Atomic layer deposition (ALD) is utilized to grow high performance zinc oxide (ZnO) thin films, where the effects of ALD process temperature on the thin film properties are also studied in this work. Some major properties of the ALD ZnO films are characterized and compared with those of sputtered ZnO films. Significant differences are observed that the electrical resistances of the ALD ZnO films are largely improved, while the optical transmittances also increase. Nevertheless, the adhesion and mechanical properties of the ALD films are worse than the sputtered films because of the weak bonding in the ALD process. For various substrate temperatures, the ALD ZnO films with 200°C behave the best performance.

Abstract: Micromachine service life is often shortened by excessive adhesion and friction forces arising during fabrication or operation. SiC film is a possible choice for MEMS surfaces because of its favorable friction and wear properties. In this study, biocompatibility SAMs film (OTS), in advance, was used to decrease the adhesion force and extend the lifetime of MEMS devices for the different SiC topography. Experimental results show that OTS can increase the contact angle of SiC surfaces for the different roughness values and roughness directions. Small roughness value of OTS surfaces has a smaller friction coefficient than that of large roughness value surfaces.

Abstract: Mechanical properties of biocompatible diamond like carbon (DLC) and titanium dioxide (TiO2) films were tested using micro and macro methods. Microhardness was evaluated by AFM head and by Hysitron nanoindenter. Micro-hardness (H) from 27.0 GPa to 30.5 GPa (for DLC/Si) and from 11.7 GPa to 15.3 GPa (for DLC on Ti alloy) was measured. H for TiO2/Si was in range of 1.2 to 5.4 GPa. Macro Adhesion was tested by CSM Revetest. The critical force (FC) was from 6.5 to 13 N for DLC/Si resp. 3.5 to 10.8 N for DLC/Ti. For TiO2 the FC from 1 to more than 15 N was found. Micro adhesion was tested by AFM head and by Hysitron For DLC films the force FC from 4.3 to more than 75 mN resp. 1.1 to 1.5 mN and for TiO2.from 15 to 39 mN resp. 0.5 to 0.8 mN was achieved. Biocompatible DLC and TiO2 films were prepared by PLD on silicon or titanium alloy substrates. The advantage, disadvantage and comparison of methods and results obtained from micro and macro mechanical measurements are discussed.

Abstract: L-3, 4-Dihydroxyphenylalanine(DOPA) has a unique catechol moiety found in adhesive proteins in marine organisms, such as mussels and polychaete, which results in strong adhesion in aquatic conditions. Conventional efforts incorporating DOPA into polymer is grafting methacrylate anhydride. For this reason, we synthesized the new catechol intermediate N-methacryloyl 3,4-dihydroxyl-phenylamine and analyzed the surface morphology and thermal stability of it.

Abstract: PVD method is used to deposit (Ti,Al)N coatings on the surface of W6Mo5Cr4V2 steels. The value of bias voltage changes from -100V to -400V. X-ray diffraction (XRD), Scanning electron microscope(SEM) and UNMT-1 were employed to analysis the microstructure and mechanical properties of (Ti,Al)N coatings. The research results showed that the microstructure and mechanical properties of coatings became better when the value of bias voltage was -400V. The size and quantity of particles on coatings both decreased obviously. The adhesion between coatings and substrates increase to 54.6N. The hardness of (Ti,Al)N coatings rise to 39.7N.

Abstract: Bonding strength of the interface of film-substratum is an important factor and key problem that influence the reliability and usage of film-substratum system. The new technology of pulsed-laser shock detection method which analyzes the mechanism and mathematical model of film separation under the action of pulsed-laser shock,. With the example of measuring the adhesion strength of TiN/SKD11 film system, the surface was respectively impacted with pulsed-laser at the range of 650~1000mJ. To observe the surface topography of Impact points by scanning electron microscope, and to identify TiN film failure threshold by the reflected signal detection. By analyzing the experimental result, it was suggested that film/substrate interfacial adhesion strength was 4.954GW/cm2.

Abstract: The weak interfacial transition zone between new and old concrete is always paid much attention and controls many properties of repaired concrete, The present work reports a study on the influence of the silica fume on the adhesion of reactive powder concrete (RPC), as a concrete restoration material, with the ordinary concrete (OC) substrate. The results showed that, the silica fume presence in the interfacial transition zone significantly enhances the adhesion strength between RPC and OC substrate. Furthermore, the silica fume particles consume calcium hydroxide, which is in attendance in the interfacial transition zone, and make the zone more dense, uniform and tough.