Surface roughness induced by plasma etching of Si-containing polymers

Interfacial properties of polymers and their control become important at submicrometer scales, as polymers find widespread applications in industries ranging from micro- and nanoelectronics to optoelectronics and others fields. In this work, we address the issue of controlled modification of surface topography of Si-containing polymers when subjected to oxygen-based plasma treatments. Treated surfaces were examined by atomic force microscopy to obtain surface topography and roughness of plasma-treated surfaces. Our experimental results indicate that an appropriate optimization of plasma chemistry and processing conditions allows, on one hand, small values of surface roughness, a result crucial for the potential use of these polymers for sub-100 nm lithography, and, on the other hand, desirable topography, applicable for example in sensor devices. Plasma processing conditions can be modified to result either in smooth surfaces (rms roughness < 1 nm) or in periodic structures of controlled roughness size and periodicity.     

Highly Hydrophobic Wood Surfaces Prepared by Treatment With Atmospheric Pressure Dielectric Barrier Discharges

Atmospheric dielectric barrier discharge (DBD) treatments of wood were done to attain water repellency on wood surfaces. A specially designed frequency controlled parallel-plate DBD reactor was utilized to produce the discharges. Ethylene, methane, chlorotrifluoroethylene and hexafluoropropylene were used as DBD reagents. Contact angle, water absorption, X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM) measurements on the modified surfaces were performed. For methane and ethylene, XPS data showed an increased surface atomic concentration of carbon from 72.7% on untreated samples up to 80.7 and 96%, respectively, whereas nearly 50% fluorine concentration was observed with fluorinated reagents. The C_1s spectrum of hexafluoropropylene-DBD-treated wood sample showed that the CF₃ group was introduced in a relative amount of 19%. AFM images showed distinct features for each of the DBD treatments, such as a deposit of a thin uniform film in the case of ethylene-DBD treatment, whereas the hexafluoropropylene-DBD treatment resulted in the nucleation of plasma-derived entities at the fiber surface and the subsequent growth of a film. Under optimized conditions the water contact angle was in the range of 139°–145°. The combination of depositing a low surface energy polymer on an already rough surface gave the surface-treated wood a highly hydrophobic character.     

Adhesion stability of rough elastic films in presence of quantum vacuum fluctuations

In this work the influence of vacuum fluctuations through the Casimir effect on the stability of an elastic film conformal onto to a self-affine rough substrate that is brought in close proximity with another parallel plate is studied. By considering the energy balance among adhesion, elastic and Casimir energies, it is shown that beyond certain parameter values (low roughness exponent H and/or high ω/ξ ratio with ω the rms roughness amplitude and ξ the lateral correlation length) the adhesion energy is counter-balanced by the elastic energy, allowing significant contributions in this regime by the Casimir energy. With increasing lateral correlation length ξ and/or decreasing roughness amplitude ω, leading to long wavelength smoothing, the regime of roughness exponents H where the contribution of vacuum fluctuations is significant shifts drastically to a lower value. This occurs so that the short wavelength roughening compensates for the effect of long wavelength smoothing that decreases predominantly the elastic and Casimir energies.     

Effect of intensities of ultrasound sonication on reduction of crack formation and surface roughness in iridium electrodeposits

Abstract

The effect of ultrasound sonication on the electroplating of iridium in an aqueous hexabromoiridate(III) is examined at several different ultrasound intensities. Ultrasound sonication is effective not only in inhibiting the crack formation in iridium deposits but also in decreasing the surface roughness of iridium electrodeposits. Those effects of ultrasound sonication are attributed to the enhancement of the amount and uniformity of mass transport caused by the thinning of diffusion layer due to the agitating action of sonication.     

The effects of surface roughness and bond thickness on the fatigue life of adhesively bonded tubular single lap joints

Since the surface roughness of adherends greatly affects the strength of adhesively bonded joints, the effect of surface roughness on the fatigue life of adhesively bonded tubular single lap joints was investigated analytically and experimentally by a fatigue torsion test. The stiffness of the interfacial layer between the adherends and the adhesive was modelled as a normal statistical distribution function of the surface roughness of the adherends. From the investigation, it was found that the optimum surface roughness of the adherends for the fatigue strength of tubular single lap joints was dependent on the bond thickness and applied load.     

The Effect of Different Surface Pretreatment Methods on Nano-adhesive Application in High Strength Steel and Aluminum Bonding

Epoxy adhesives (single and two components) modified with SiO₂ nano-particles were used in this investigation to glue aluminum alloy and also two types of high strength steel (dip-galvanized steel DP 600 and micro-alloyed steel ZStE340). To improve the adhesion between metal surfaces and adhesives, the metal surfaces were pretreated with: a self-indicating pretreatment (SIP^*); corundum blasting; corundum blasting + a SIP coating; and a Pyrosil^® treatment + SurALink^® primer (PG 15 for epoxy adhesive). A single-lap shear tension test, done in accordance to DIN EN 1465, was used to determine the adhesive strength. Scanning Electron Microscopy (SEM) and Energy Dispersive X-ray spectroscopy (EDX) analysis were used to analyze fractures that took place in the samples. The results showed that the adhesion strength of glued samples, containing the nano-particles modified adhesive, had significantly higher strength than unmodified ones. Pretreatment of the metal surfaces affected the adhesion, using nano-adhesives, only slightly. The adhesive strength values for single component epoxy resins were higher than those for two component epoxy resins. It was found that steel samples fractured adhesively at the steel surfaces. Aluminum treated samples indicated after pretreatment an increase in adhesive strength and the fracture occurred adhesively at the aluminum surfaces. Aluminum glued with two-component adhesives and pretreated with corundum blasting plus a SIP coating showed a mixed fracture mode; adhesively at the aluminum surface and cohesively in the adhesive layer.     

Acid–base properties of polymer-coated paper

The wetting behavior of a series of polymer-coated papers has been studied. Different ways of determining the acid–base properties of the polymers are presented. The well-known van Oss–Chaudhury–Good (vOCG) bi–bi polar model is compared with more simplified mono–bi polar and mono–mono polar models. The effect of surface roughness on the wetting was also studied with atomic force microscopy. The overall wetting of each probe liquid was evaluated by calculating the work of adhesion to the polymer surfaces. It is shown that ethylene glycol and water may be considered as mono polar liquids, which simplifies the original vOCG-model. It is also shown that in most cases the surface energy values are in the same range when using both the complex bi–bi polar approach and the simpler mono–mono polar approach. The different polymers used are found to be of a predominating basic character.     

Effect of Surface Roughness on the Adhesive Strength of the Heat-Resistant Adhesive RTV88

Heat-resistant adhesive RTV88 is a hyper-elastic material and so far there have been little research on using RTV88 in adhesive joints. In this study, the effect of surface roughness on the adhesive strength of RTV88 was examined. Aluminum adherends were first sandblasted in order to generate rough surfaces, and then tensile–shear tests on Al/RTV88 single lap joints were performed. The shear strength was shown to be influenced by surface roughness. Peel failure was dominant when the surface roughness was at a low level. However, cohesive failure was the major type of failure when the surface roughness was at a high level. Effective area, peel failure area, and cohesive failure area were introduced to explain the effects of surface roughness on the adhesive strength. An empirical relation for the failure force was proposed, based on these parameters. Tensile tests of the RTV88 bonding was performed in order to obtain the necessary data. Finally, the empirical relation for the failure force was verified by tensile–shear test results.     

Bessemer Lecture and Metals Technology Masterclass 2005

Abstract

Stuart Pettifor, recently retired Chief Operating Officer of Corus Group, presented the 3rd Sir Henry Bessemer Lecture of the Steel Division of the Institute of Materials, Minerals and Mining on 27 September. The Lecture at the Institute's London headquarters was followed by the Division's Annual Dinner and preceded by a masterclass aimed at young managers and researchers in the steel industry on the theme 'Technology profiting business'.     

Surface characterization of pre-treated copper foil used for PCB lamination

Properly micro-roughened electrodeposited copper foil is used in the conventional lamination process in order to improve its bond strength. In this investigation other treatments, including pumice scrubbing, chemical etching and brush scrubbing methods, were employed in order to obtain strong bonding. The effects of these treatments are investigated in terms of copper surface morphology using optical profilometry (OP), scanning electron microscopy (SEM) and atomic force microscopy (AFM). The microstructure of the electrodeposited copper foil surface and its bonding properties are discussed in terms of various experimental results, in order to compare it with rolled annealed copper foil. Various surface morphologies of copper foil corresponding to different treatments are observed. The pumice scrubbing showed the largest increase in copper surface roughness, which leads to the highest improvement in bonding properties. The bond strength between copper and FR-4 resin substrate was analyzed by peel strength measurements, and based on this, the optimized process to treat the copper surface is proposed.